CA2287242C - Sensor unit, process and device for inspecting the surface of an object - Google Patents
Sensor unit, process and device for inspecting the surface of an object Download PDFInfo
- Publication number
- CA2287242C CA2287242C CA002287242A CA2287242A CA2287242C CA 2287242 C CA2287242 C CA 2287242C CA 002287242 A CA002287242 A CA 002287242A CA 2287242 A CA2287242 A CA 2287242A CA 2287242 C CA2287242 C CA 2287242C
- Authority
- CA
- Canada
- Prior art keywords
- light
- sensor unit
- deflecting element
- mirror
- guided
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
- G01N21/88—Investigating the presence of flaws or contamination
- G01N21/89—Investigating the presence of flaws or contamination in moving material, e.g. running paper or textiles
- G01N21/892—Investigating the presence of flaws or contamination in moving material, e.g. running paper or textiles characterised by the flaw, defect or object feature examined
- G01N21/898—Irregularities in textured or patterned surfaces, e.g. textiles, wood
- G01N21/8986—Wood
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
- G01N21/88—Investigating the presence of flaws or contamination
- G01N21/89—Investigating the presence of flaws or contamination in moving material, e.g. running paper or textiles
- G01N21/8901—Optical details; Scanning details
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
- G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
- G02B26/10—Scanning systems
- G02B26/12—Scanning systems using multifaceted mirrors
- G02B26/125—Details of the optical system between the polygonal mirror and the image plane
- G02B26/126—Details of the optical system between the polygonal mirror and the image plane including curved mirrors
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
- G01S17/06—Systems determining position data of a target
- G01S17/46—Indirect determination of position data
- G01S17/48—Active triangulation systems, i.e. using the transmission and reflection of electromagnetic waves other than radio waves
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/481—Constructional features, e.g. arrangements of optical elements
- G01S7/4817—Constructional features, e.g. arrangements of optical elements relating to scanning
Abstract
The invention concerns a sensor unit (50), a device and a process for the inspection of the surface (10', 10") of an object (10) for the purpose of identifying surface characteristics, such as structural defects. The device contains an emitting module (51), which emits at least one beam bundle (6, 6', 6"), and a receiving module (52 ) with at least one light receiver (15, 16, 20). In the focal point of a parabolic mirror (1) a rotating polygonal mirror wheel (2) is located, on to which the beam bundle (6) of the laser (3, 4) is directed by means of a telecentric lens, which guides th e emitter -and receiver beam on the same optical axis, whereby the parabolic mirror (1) guides the deflected beam bundle (6, 6', 6") under a constant angle relative to the symettry axis (7) of the parbolic minor (1) along a scanning line (23, 24) over the object (10) and the diffusely reflected beam bundle after its deflection out of the comm on beam path impinges on the processing unit (5).
Description
P1339 PCT Os.10.99 s PROCESS AND DEVICE FOR INSPECTING THE SURFACE OF
AN OBJECT
to The invention concerns a device and a process for the inspection of the surface of an object in accordance v.~ith the generic terms of the independent claims.
is Known with respect to the surface inspection of materials is the scannin~l of the respective surface with CCD - line - or matrix cameras as well as with laser scanners and the analyzing of the grey-scale value or colour pictures with image processing means.
In the case of the processing of woods, for example in door and window building or in the fabrication of veneer sheets, it is necessary to investigate the woods to be processed with regard to their quality. In doing so, it has to, e.g., be determined, 2s whether the woods have shakes, fissures, knot holes or protrusions or indentations or whether they are affected by blue stain or red ring rot, which make them unsuit-able for the foreseen purpose. Up until now, therefore such inspections of woods are to the greatest extent carried out by people. It is in particular up to now prcatically not possible to automatically eliminate or to classify woods which are affected P1339 PCT 05.10.99 by blue stain or red ring rot. Furthermore, there are a number of technical problems, which generally are associated with the great depth of focus and the simultaneously high resolution called for by the process as well as with the transportation speed of the wood. For this, relatively elaborate illumination equipment with a very high per S formance is necessary.
When illuminating wood by means of a laser beam, the so-called scatter effect oc-curs, which signifies, that a part of the light is dispersed into the wood fibres and I O there is scattered in the vicinity of the surface in function of the local density distri-bution. In the case of an undisturbed fibre orientation, a characteristic dipole distri-bution in the spatial intensity distribution of the dii'fusely reflected light is manifest, whereby the (1/e) - drop, the integral intensity as well as the actual structure of the maxima of the emissions are dependent on the type of material and on the structure of 15 the defect. Through SE-A-7500465-S, a process and a device utilizing a helium-neon laser has become known, where the scatter effect is indirectly exploited for the evaluation.
20 Through EP-0 I98 037 B1, a process for measuring the fibre angles in a fibrous material, such as wood, has become known, where an area on the surface of the ma-terial is illuminated with an impinging ray of light and photo-sensitive devices are spatially arranged in such a manner, that they measure the light reflected by the il-luminated area. The fibre angle is measured relative to three reference axes vertical 25 to one another (x, y, z) and any point on the surface of the material is defined as the point of origin of the axes. The illuminated area encompasses the point of origin and has a diameter, which is at least ten times the size of the average fibre diameter of the substance to be measured. A majority of the photo-sensitive devices is posi-tioned in a manner to be able to assess the azimuthal angular positions around the 30 point of origin of the intensity maximum of the reflected light.
Furthermore, a num-P 1339 PCT 05.10.99 ber of arbitrary points in transverse and longitudinal direction of an area on the surface of the material are staked out, in order to be in a position to assess the azimuthal angular positions of the intensity maxima at each of the points. By means of the relationship between the azimuthal angular position of the refected light maxima and the fibre angle, for every measuring point the corresponding fibre angle is cal-culated relative to all three axes, in order to indicate the complete pattern of the fibre angles within the measured area of the fibrous material. For carrying out this proc ess, a highly elaborate installation is necessary, in order to on the one hand measure the radiated beam proportion of the reflected light and on the other hand the propor tion of the diffusely reflected light.
By DE-A-196 04 076.0, a device for the inspection of the surface of woods for the purpose of determining surface characteristics has been proposed, consisting of an opto-electronic sensor, an electronic and / or optical processing unit, a computer capable of real-time operation, whereby the wood can be moved relative to the sen-sor, as ~.vell as an incremental position transducer, which synchronizes the sensor with the speed of the wood. The sensor consists of a colour laser scanner with at least two beam bundles of differeing wave lengths and a receiver with two channels with onopto-electrical receiving element each, whereby the channels are formed by beam splitting of the reflected beam bundle and at least in one of the channels a lens for creating an intermediate image plane is located. After the lens, within one of the channels there is an optical graduated filter, which is capable of modulating the passing light current to the opto-electrical receiving element belonging to it inde-pendent of the position. The signals of the receiving element of the one channel without the graduated filter are converted into a colour image in the computer and those of the other channel, the light current of which has been modulated independ-ent of the position, into a profile image of the surface.
P1339 PCT 05.10.99 -3a-It is, for example, known from the documents US-4,286,880 or JP 59 040 149 A, that wood surfaces can be investigated by scanning with a light beam. These two documents divulge a rotating mirror, which is located in the focal point of a para-bolic mirror, light is emitted on to the rotating mirror from a light sowce and from there distributed by reflection on the parabolic mirror along a scanning line on the wood surface. In US-4,286,880, the subject is an improvement of work stations for the localization of wood defects, in the case of which work stations are operating person has to find the defects. The operating person marks the defects and the marks are detected by an optical sensor with a binary output signal. The object of 149 A is the detecting of live knots by means of asymmetrically scattered light. For the solution of this problem, a wood surface is scanned by a light beam anti light scat-tered from the wood surface is directly detected by two detectors arranged symmetri-cally with respect the the scanning beam.
From the state of the technology, optical distance sensors are also known. The dis-tance sensor divulged in the document EP-0 387 521 A2 is based on a triangulation process. A beam of light is focussed on the surface to be measured by means of a lens. Light scattered by the surface is collected by the same lens and focussed on position-sensitive detectors by a concave mirror. The components are positioned in such a manner relative to an optical axis, that a high light sensitivity is assured by a small angle of incidence. Another distance sensor is divulged in document WO
93/11403. It contains a rotating polygonal mirror, which distributes light emitted from a light source on to a scanning line on the surface to t;c measured. A
scanning lens projects the point-shaped light sowce on to the surface. The light reflected by the surface is projec,~ted on to a point-shaped detector by means of the same scanning lens and a further lens; this construction is designated as "confoc al". Only when the object is in the focal plane of the sca~uiing lens and the detector is simultaneously in the focal plane of the further lens, does a maximum light intensity impinge on the detector. The detected light intensity is therefore a measure for the dista:nee of the ob P1339 PCT 05.10.99 -3b-jest from the scanning lens. The construction can be refined by foreseeing several de-tectors, which supply maximum signals at differing object distances.
P1339 PCT 05.10.99 The invention is based on the objective of indicating a device and a process for the dynamic inspection of the surfaces of objects such as woods, tiles, textiles or glasses, for the identification of surface characteristics, by means of which an auto-matic inspection of the surface can be carried out continuously and with a high speed and by means of which characteristics such as shakes, fissures, cracks, knot holes, protrusions, indentations, in the case of wood also bhte stain or red ring rot can be identified with certainty by the exploitation of the scatter effect. In particular, simultaneously the position-dependent diffuse reflection of a surface, the distance of the surface as urell as the deviation of the diffuse reflection characteristic in function of the position can be detected by a Lambert projector at processing speeds of several metres per second in real time. Apart from this, the device shall be of a simple con-struction and should be able to be manufactured ax a low cost.
IS The objective is achieved by the device in accordance with the invention and by the process in accordance with the invention, as these are defined in the independent Maims.
The device in accordance with the invention for the inspection of the surface of an object for the purpose of the identification of surface characteristics contains a sen-sor unit according to the invention, whereby in preference the lens can be moved relative to the sensor unit. The device furthermore contains a scanning device, to which light is transmitted from the sensor unit, whereby the scanning device com-prises a concave mire or, in the focal point of which a light deflecting element illu-minated by the sensor unit with a deflection angle dependent on time is located, so that the light transmitted by the sensor unit can be guided over the object along a scanning line and light from the scanning device diffusely reflected by the object impinges on the sensor unit.
P1339 PCT 05.10.99 A preferred embodiment of the device in accordance with the invention is charac-terized by a parabolic mirror, in the focal point of which a rotating polygonal mirror is located, on to which the beam bundle of the laser is directed by means of a tele-S centric lens, which guides the transmitter and receiver beam along the same optical axis, whereby the parabolic mirror guides the deflected beam bundle over the object along a scanning line under a constant angle relative to the symmetry axis of the parabolic mirror and guides the beam bundle diffusely reflected by the object back along the same path, and whereby it (the beam bundle) after being reflected out of the common beam path impinges on the processing unit.
The device is based on the fact of the so-called Tracheid effect (scatter effect) , which occurs with density changes on the surface in the case of a number of materi-als with a point-shaped, in preference coherent illumination. In doing so, light enters into the material through the surface and is guided inside the material, whereby the guidance of the Light and its damping are determined by the stnzcture of the material.
The device and the process are in a position to exploit the scatter effect for the evaluation of surface anomalies and to carry out an assessment of surface defects like this under real time conditions.
T.~. the beam path between the laser and the polygonal mirror wheel, in preference there is a mirror with an aperture or with a hole, through which the irradiated beam bundle impinges on the polygonal mirror wheel, whereby the mirror deflects the diffusely reflected bem bundle on to a lens under a given angle, in the focal plane of which the optical detectors and the electronic processing unit, in preference includ-ing a computer capable of real time operation, are situated. After the lens and in front of its focal plane, by beam splitting two beam bundles and preferably at least P1339 PCT 05.10.99 two channels are created, which are evaluated separately. A high precision of exe-cution is important for the functioning of the device.
5 I1; for example, the material to be inpsected is wood, then around the intensive light spot of the direct irradiation two light cones are formed aligned to the direction of the fibres, which diminish corresponding to the dipole characteristic and which join the direct light spot of the impinging beam. In correspondence with the change of the surface structure and the direction of the fibres, these two light cones change 10 with respect to their length, brightness and direction. The brightness, length and di-rection are dependent on the local defect and its shape as well as on the direction of the fibres. The inventors have in particular discovered, that through the scatter effect for the first time in the case of woods just starting blue stain or red ring rot can be made visible, long before the attack can be identified by the unaided eye, but can 15 solely be detected by means of chemical analyses or microscopic viewing.
Equally on the basis of the scatter effect defects in the wood, such as, for example, knot holes, compression wood or blue stain become visible, which lead to a diminuition of the quality of the corresponding wood.
In order to obtain a surface profile (3D - profile) by means of a triangulation proc-ess, at least one one light beam emitted from the sensor unit can be guided on to the object. Light diffusely reflected from the object under a finite angle relative to the impinging beam can be guided back to the sensor unit in such a manner, that the 25 impinging and the returned light beam are essentially in coincidence in a plane par-allel to the surface of the object. In an alternative version, also several, in preference two, laser beams can be guidable by means of verious mirrors offset ralative to one another in such a manner, that the individual laser beams are in coincidence in the horizontal plane, while in the vertical object plane a constant angle is given, in order 30 to measure the surface profile by means of the vertical deposition of the diffusely P1339 PCT 05.10.99 reflected laser light with a position-sensitive opto-electrical receiving element, which is in particular a PSD sensor element capable of high speed.
In a preferred embodiment of the invention, at least one leaser beam is focussed on the surface of the object in order to obtain a 3D surface profile by triangulation. The vertical deposit of the diffusely reflected laser light is measured through an addi-tional guidable mirror under a constant angle by means of a position-sensitive re-ceiving element (PSD) capable of high speed.
The process for the inspection of the surface of an object for the purpose of the identification of surface characteristics in accordance with the invention utilizes a sensor unit according to the invention which emits light to a scanning device, whereby in preference the object is moved relative to the sensor unit. The emitted light is focussed on the object by means of a telecentric projection and guided over the object along a scanning line under a constant angle relative to the object to be scanned and relative to the vertical line of the transportation surface. Light diffusely reflected by the object is guided back in to the sensor unit along the same beam path as the emitted light.
In a preferred embodiment of the process in accordance with the invention, the laser beam is focussed on the object by means of a telecentric projection, which guides the emitted and receiver beam along the same optical axis focusses it on the object and guides it along a scanning line always under a constant angle relative to the object to be scanned and relative to the vertical line of the transportation surface ~f the object, which can be the most effectively achieved by the arrangement of a para-bolic mirror, in the focal point of which a polygonal mirror wheel is located, so that in this case the angle of the laser beam is constant with respect to the symmetry axis P1339 PCT 05.10.99 _g_ of the parabolic mirror. In doing so, the spatial resolution is limited solely by the focussing ability of the laser light. The telecentric beam bundle of the moving laser light spot, the measuring point, along a scanning line, does not have to impinge or-thogonally on the surface to be scanned, the angle of impingement can rather more S be any one within wide ranges, it must, however, be constant relative to the normal line of the transportation surface of the object. In doing so, the diffusely reflected light is guided back to the detector through the same projection system.
In accordance with the process, in preference with the utilization of parallel proces-sors, various surface characteristics can be measured in real time, namely in par-ticular:
a) the intensity distribution of the diffusely reflected laser light and / or b) the distribution of the intensity of the laser light scattered by local density variations (Tracheid effect), which is observed through spacial filters in the scatter channel and / or c) the elevation profile (3D channel) of the surface, which is measured by means of a triangulation process and I or d) double refi~action characteristics, which are measured by means of detection processes dependent on polarization, for example by means of an analyser par allel and anti-parallel to the surface direction.
After the lens and in front of the image plane of it, at least two channels are formed by beam splitting into two partial beam bundles, which are assessed. On principle it is even possible to detect all characteristics mentioned above with only one laser, which can be implemented by a modification of the receiving module. For splitting-up the diffusely reflected Iaser radiation into partial radiation bundles according to their differing wave lengths, a dichroic minor is positioned in the beam path, whereby from the partial beam bundles of differing wave lengths various surface P1339 PCT 0.10.99 characteristics, such as in particular the elevation profile in the 3D
channel, the re-flectivity in a red light channel as well as the Tracheid effect in the mentioned scat-ter channel are simultaneously recorded with a high repetition rate. One of the par-tial radiation bundles formed by the dichroic mirror, in preference the red light pro-s portion of the diffusely reflected laser beams, is preferably once again split-up into two channels, in preference by means of a semi-transparent mirror, in which in ac-cordance with the diffusely reflected laser light sensitive sensors are located, whereby within one channel the image of the directly diffusely reflected light point, or spot on the object is evaluated and the image of the light cones of the scatter effect is blanked out and from the image of the laser point or spot a grey-scale image is obtained, while inside the other channel (scatter channel) by means of special spatial filters the directly diffusely reflected light point or spot is blanked out and only the image of the remaining light cones is evaluated. The blanking out is carried out by means of special spatial filters. .
The Tracheid - scattered laser light (scatter channel), which, for example, in the case of wood serves for the evaluation of the image of the remaining light cones, is de-tected in a real time process for making visible density dependent surface anomalies, such as shakes, cracks, fissures, structure defects, by means of a four-quadrant process, for example by means of dichroic mirrors or a four-quadrant diode, position- dependent in the form (Sx +Sy)/S and in the direction arctan (SX
/Sy), if necessary in combination with the triangulation process in the 3D channel also in function of the elevation, the spatial resolution of which is only limited by the focussing ability of the laser light.
In the following, the invention is explained in detail on the basis of the Figures. In these are schematically illustrated:
..
P1339 PCT 05.10.99 Figure 1 a cross section through a first embodiment of the sensor unit in accor-dance with the invention, Figure 2 a cross section through a second embodiment of the sensor unit in accor-dance with the invention, Figure 3 a cross section through a third embodiment of the sensor unit in accor-dance with the invention, Figure 4 a top view of a defecting element of the sensor unit of Fig. 3, Figure 5 a schematic layout of the device in accordance with the invention in top view, Figure 6 a top view of a technical embodiment of the device in accordance with the invention, in which the beam path is folded in order to achieve a small depth of the construction, Figure 7 a side view of the device of Fig. 6, Figure 8 a view of a receiving module with a spatial filter vertical to the parabolic mirror in the scatter channel and Figure 9 a view of the receiving module of Fig. 8 with the same spatial filter par-allel to the parabolic mirror in the scatter channel.
Figure 1 shows a schematic cross section through the first embodiment of the sensor unit SO in accordance with the invention. The sensor unit 50 serves to emit light to a scanning device 60 (not illustrated in Fig. 1), which is situated in the direction of an P1339 PCT 05.10.99 arrow 61, and for receiving light impinging from the scanning device 60. The sensor unit 50 contains a light-emitting sender module 51 and a light receiving receiver module 52. The emitting module 51 contains at least one light source 3; this can be a laser, a light-emitting diode (LED) or another light source. In front of the light sour-s ce 3, if necessary there can be a (not illustrated), e.g., focussing optical system. The receiving module 52 contains at least one light receiver 20, e.g., a photo-diode, a CCD camera, a position-sensitive receiving element (PSD), etc. An optical system 13, e.g., a focussing lens or a multi-element lens can project an object (not illustrated in Fig. 1) on to the light receiver 20.
The sensor unit SO apart from this also has an optical deflection element 9.
If light from the direction of the scanning device 60 were to impinge on the sensor unit 50, then it would be split-up by the deflecting element 9 into two light paths 53, 54 dif fering from one another. A first beam path 53 is defined by a first spatially limited part 55 of the light and a second beam path 54 is defined by a second spatially limi-ted part of the light 56. The first beam path 53 has a smaller cross sectional area than the second beam path 54. The emitting module 51 is located in the first beam path 53 and the receiving module 52 in the second beam path 54. In this embodiment the deflection element 9 is designed as a plane mirror with an aperture 25 and arranged in such a manner, that light travelling to the deflection element 9 is to a greater ex-tent left to pass through to the scanning device 60 through the aperture 25.
Light emanating from the scanning device 60 outside the first beam path 53 is in contrast to a greater extent reflected to the receiving module 52. The surface shell, which surrounds the aperture 25 in the deflection element 9, is in preference parallel to the direction of diffusion of the emitted light 53.
In Figure 2, a different embodiment of the sensor unit in accordance with the inven-tion 50 is schematically illustrated. Here the deflection element 9 is designed as a PI339 PCT 05.10.99 small mirror and arranged in such a manner, that Iight 53 travelling from the emitter module 51 to the deflection element 9 is to a greater extent reflected to the (not illu strated in Fig. 2) scanning device 60. Light 54 emanating from the scanning device outside the first beam path 53 is in contrast to a greater extent allowed to pass through to the receiving module 52.
Figure 3 schematically illustrates a further embodiment of the sensor unit in accor-dance with the invention 50. The deflection element 9 corresponds to that of Fig. 1.
This embodiment contains two light sources 3, 4, for example, two lasers. A
first laser 3 emits red light in the wave Length range between 620 nm and 770 nm, e.g., 680 nm, and a second laser 4 emits infrared light in the wave length rangle above 770 nm, e.g., 830 nm. The two laser beams are joined by n>eans of a mirror 12 and a beam splitter 11. The receiving module 52 contains two light receivers 15, 20 and a I 5 beam splitter I4, by means of which light 54 impinging on the receiving module 52 is split-up on to the light receivers 15, 20. The beam splitter 14 can have dichroic characteristics, i.e., its reflection to transmission ratio can be dependent on the wave length.
Figure 4 schematically illustrates a top view of the mirror 9 with aperture 25 of Fig.
3 along the line IV - IV. Light 54 emanating from the scanning device 60, which exactly coincides with the light 53 travelling to the scanning device 60, does not impinge on the receiving module 52. This way a "cross-talk" is efl:iciently preven øed.
In accordance with Figure 5, the fundamental principle of the device in accordance with the invention consists of a concave mirror 1, which is in preference cut out of a paraboloid as a narrow strip I and which has the length 1 and the height h.
Preferred P1339 PCT OS.10.99 as a concave mirror is a parabolic minor, beacuse it provides an ideal, practically aberration-free image. Within the focal point of the parabolic mirror 1 is a polygonal mirror wheel 2, which is rotated by a motor 27 at a high speed, with one of its poly-gon surfaces arr4 ~~ged in such a manner, that preferably at an angle of 4S
degrees of S the normal line of the polygon surface of the mirror wheel to the optical axis 7 (symmetry axis) of the parabolic mirror 1, the centre of the polygon surface comes to lie exactly in t'~e focal point of the parabolic mirror 1. Two lasers 3, 4 each gene-rate a laser beam, whereby one laser in preference operates in the wave length range of approx. 680 r:n, therefore in the red light range, and the other laser preferably in the wave length range of 830 nm, therefore in the infrared light range. The laser be-ams are deflected through mirrors 11, 12 and brought together to a common beam 6.
For this purpose, the mirror 11 illustrated in Figure 1 is transparent for the laser be-am of the lase_- 3 situated behind it. The combined laser beams 6 pass through a further mirror 7 through a hole 2S in it and impinge on one of the plane polygon 1 S surfaces of the rotating polygonal mirror wheel 2. Dependent on the design of the polygonal mirror wheel 2 and on the centre distance of it from the parabolic mirror 1, the polygonal mirror wheel. 2 guides the laser beams 6, 6', 6" at a certain prede-fined horizontal image field angle a over the parabolic mirror 1 in its longitudinal expanse 1, as can be seen in Figure S.
The horizontal image field angle a is limited by the laser beams 6', 6". The laser beam 6"' respectively reflected by the parabolic minor ~ is guided parallel to itself over the longitudinal expanse 1 of the parabolic mirror 1 and forms the scanning line. The reflected laser beam 6"' is guided to an inclined mirror and impinges on the 2S surface 10' of an object to be scanned 10, for example a piece of wood travelling with the speed v relative to the laser. In this manner, the laser beams 6 from the lasers 3, 4, which are focussed on the abject 10, are guided under a constant angle relative to the symmetry axis 7 of the parabolic mirror 1, i.e., to the normal line of the transportation surface of the object 10 to the object 10 to be P1339 PCT 05.10.99 scanned, along the scanning line 23, 24. The object surface is projected on to the light receiver contained in the receiving module as a telecentric image.
The laser light diffusely reflected in the point of impingement is guided back along the same path, so that arriving beam and diffusely reflected beam in essence coin-cide. The polygonal mirror wheel 2 projects the diffusely reflected beam bundle on to the mirror 9, which deflects it and guides it to a processing unit 5, which evaluates the diffusely reflected beam bundle optically and electric< lly, to which a computer capable of real time operation also belongs.
In the Figures 6 and 7, a technical embodiment of the device is illustrated.
The t~No lasers 3, 4 genera to laser beams 6, which are brought together through mirrors 1 l, 12 and are projected on to the rotating polygonal mirror wheel driven by a motor 27, rotating at high speed, through a hole 25 within the mirror 9, which once again is located in the fecal point range - this time relative to a longish, plane mirror 17 - of the parabolic minor 1. The two laser beams 6 are projected on to the mirror 17 by the polygonal mirror wheel 2, which deflects the laser beams on to the parabolic mirror 1, so that the folded beam path illustrated in Figures 6 and 7 is produced. The parabolic mirror 1 now has the effect, that the laser beams reflected by it can be guided parallel to one another and therefore under a constant angle relative to its symmetry axis 7, relative to a normal line 19 of the transportation surface 10' of the object 10 on to the surface 10'.
To do this, in the beam path after the parabolic minor 1 in accordance with Figure 7 there are two plane mirrors 18, 19 aligned transverse to the surface to be scanned 10' of the object to be scanned 10, which guide the laser beams travelling parallel in one another along a scanning line 23 over the surface 10'. Two mirrors 18, 19 are used, P1339 PCT 05.10.99 in order with respect to the evaluation in the triangulation process to be able to ob-tain a 3D depiction of the image. If the information in the direction of the vertical axis can be made do without, then on principle one mirror 19 is sufficient for the construction of the device and for carrying out the process.
In the following, on the basis of Figure 7 beam paths for the case without triangula-tion process and for the case with triangulation process are discussed. The light be-am emitted by the sensor unit 50 and reflected by the parabolic minor 1 impinges on 10 the object 10 through mirror 19. In this, preferably the angle of impingement (3 rela-tive to the normal line 29 on to the object surface 10' is greater than zero, i.e., the light impingement on to the surface 10' is not vertical. As a consequence, light di-rectly reflected from the surface 10' does not fall back on to the mirror 19;
therefore diffuse reflection on the surface 10' is measured. In the case without triangulation 15 process, light is measured, which returns to the sensor unit SO under the same angle of reflection J3 through the mirror 19 on the same path as the impinging light. If a triangulation process is to be utilized, then the vertical deposition of light is measu-red, which is diffusely reflected under a constant angle A relative to the impinging light and which falls back into the sensor unit 50 through a further mirror 18. Also in 20 this case, the light in essence travels along the same path back to the sensor unit 50 as the impinging light. In this, the angle B determines the resolution of the 3D mea-surement. The greater the angle 8, the more sensitively the 3D profile can be measu-red. A preferred value for the angle 8 is A = 15.5° t 1.5°. In an alternative version of the process, light can be beamed on to the object 10 both through mirror 19 as well 25 as through mirror 18 - or even on more than two light paths - , and the respective diffusely reflected light portions detected.
Two further mirrors 21, 22, which in the top view are arranged laterally from the 30 mirrors 18, 19 and if necessary in different planes, serve to simultaneously guide the P1339 PCT 05.10.99 laser beams over a side surface 10" of the object 10 along a further scanning line 24 and to obtain an image - also as a 3d image -, so that simultaneously two planes 10', 10" inclined relative to one another at a given angle can be scanned, which in the example illustrated are inclined at 90 degrees to one another. The diffusely reflected light beams travel back along the same path and impinge on the mirror 9 under the horizontal image field angle a, from where they are deflected towards a lens 13.
Located in the beam path of the lens 13 there is a dichroic min or 14, which is trans-parent for the infrared radiation of the diffusely reflected laser light, but deflects the diffusely reflected red light radiation of the other laser. After the mirror 14, in the image field plane of the lens 13 there is a receiver 20, the received signals of which are utilized as 3D information. With this information, a relief image can be calcu-fated in the computer, which enables the identification of depth changes of the object 1 S to be inspected. Used in preference as sensor element 20 for the 3D
channel, is a position-sensitive, opto-electrical receiving element, in particular a PSD
sensor ele-ment capable of high speed, which detects the positional deviation of the laser beam ~~elative to the zero position, which has been guided through the mirror 18 and 21.
'The red light proportion of the diffusely reflected laser beams is deflected through the dichroic mirror 14 and impinges on to a splitter mirror 26, which once again splits-up this beam proportion into two channels, in which light-sensitive sensors 15, 16 are located. One channel is operated as a so-called direct red sensor and provides a grey-scale image, whereby here the image of the direct light point or spot on the object is evaluated. For this purpose, by means of a diaphragm the light cones of the scatter effe ct are blanked out. The other channel is the so-called scatter channel and serves to evaluate the actual scatter image and thus in the case of wood the light cones, which adjoin the direct light spot. To do this, the centre point or centre spot, -Nhich is of course evaluated in the other channel, is blanked out be means of special spacial filters 30 in the scatter channel and the image of the remaining light cones, for example, projected on to a four-quadrant diode. From the relationship of P1339 PCT 05.10.99 the two light cones to one another, their position relative to one another and relative to the direction of transport can be calculated and therefore in the case of wood, for example, the fibre direction or places affected with blue stain or red ring rot can be identified. The evaluation of the diffusely reflected laser radiation is therefore car-ried out in such a manner, that the energetic and / or the positional distribution of the diffusely reflected radiation is converted into different electrical signals.
By means of a computer capable of real time operation, subsequently the channels can be evaluated and the images generated displayed on a monitor. It is equally pos-sible to convert the signals from the three channels into colour values, in order to thus also generate a colour image.
It is also conceivable to transmit the diffusely reflected laser radiation to a CCD
camera for evaluation.
The figures 8 and 9 on the one hand show a view of the receiving module 15 with a spatial filter 30 vertical to the parabolic mirror 1 in the scatter channel with lens 13 and mirror 14, and on the other hand- a view of the same receiving module 15 with the same spatial filter 30 parallel to the parabolic minor in the. scatter channel. 'One can make out the spatial blanking out on the one hand of the centre spot by a central plate 31, whereby the light cones impinge on the light receiver 15 through slits 32, 33.
The device and the process are in particular suitable for assessing the surface of an object, in particular of flat objects such as woods, tiles, textiles, glasses, plastic sur-faces, foils, silicium wafers, cardboards and others for the purpose of identifying P1339 PCT 05.10.99 surface characteristics such as shakes / cracks, holes, protrusions or indentations, and to evaluate them according to quality criteria. The device and the process are in particular suitable for the application of the inspection of woods, because they are for the first time capable of directly evaluating the scatter effect in the case of wood - 5 and they provide a selective optical contrast enhancement in the case of the most diverse surface defects or enable a differentiation of woods with saw roughness.
Equally,. blue stain as well as dirt contamination or damage done by worms or cracks / shakes are made very well visible. The usefulness of the invention consists in particular of the fact, that with it in real time various surface characteristics can be measured, such as a) the intensity distribution of the diffusely reflected laser light and / or b) the distribution of the intensity of the laser light scattered by local density varia-tions (Tracheid effect), which is observed through spatial filters in the scatter channel and 7 or c) the elevation profile (3D channel) of the surface, which is measured by means of a triangulation process and / or d) double refraction characteristics, which are measured by detection processes dependent on polarization, for example by means of an analyser parallel and anti-parallel to the surface direction.
AN OBJECT
to The invention concerns a device and a process for the inspection of the surface of an object in accordance v.~ith the generic terms of the independent claims.
is Known with respect to the surface inspection of materials is the scannin~l of the respective surface with CCD - line - or matrix cameras as well as with laser scanners and the analyzing of the grey-scale value or colour pictures with image processing means.
In the case of the processing of woods, for example in door and window building or in the fabrication of veneer sheets, it is necessary to investigate the woods to be processed with regard to their quality. In doing so, it has to, e.g., be determined, 2s whether the woods have shakes, fissures, knot holes or protrusions or indentations or whether they are affected by blue stain or red ring rot, which make them unsuit-able for the foreseen purpose. Up until now, therefore such inspections of woods are to the greatest extent carried out by people. It is in particular up to now prcatically not possible to automatically eliminate or to classify woods which are affected P1339 PCT 05.10.99 by blue stain or red ring rot. Furthermore, there are a number of technical problems, which generally are associated with the great depth of focus and the simultaneously high resolution called for by the process as well as with the transportation speed of the wood. For this, relatively elaborate illumination equipment with a very high per S formance is necessary.
When illuminating wood by means of a laser beam, the so-called scatter effect oc-curs, which signifies, that a part of the light is dispersed into the wood fibres and I O there is scattered in the vicinity of the surface in function of the local density distri-bution. In the case of an undisturbed fibre orientation, a characteristic dipole distri-bution in the spatial intensity distribution of the dii'fusely reflected light is manifest, whereby the (1/e) - drop, the integral intensity as well as the actual structure of the maxima of the emissions are dependent on the type of material and on the structure of 15 the defect. Through SE-A-7500465-S, a process and a device utilizing a helium-neon laser has become known, where the scatter effect is indirectly exploited for the evaluation.
20 Through EP-0 I98 037 B1, a process for measuring the fibre angles in a fibrous material, such as wood, has become known, where an area on the surface of the ma-terial is illuminated with an impinging ray of light and photo-sensitive devices are spatially arranged in such a manner, that they measure the light reflected by the il-luminated area. The fibre angle is measured relative to three reference axes vertical 25 to one another (x, y, z) and any point on the surface of the material is defined as the point of origin of the axes. The illuminated area encompasses the point of origin and has a diameter, which is at least ten times the size of the average fibre diameter of the substance to be measured. A majority of the photo-sensitive devices is posi-tioned in a manner to be able to assess the azimuthal angular positions around the 30 point of origin of the intensity maximum of the reflected light.
Furthermore, a num-P 1339 PCT 05.10.99 ber of arbitrary points in transverse and longitudinal direction of an area on the surface of the material are staked out, in order to be in a position to assess the azimuthal angular positions of the intensity maxima at each of the points. By means of the relationship between the azimuthal angular position of the refected light maxima and the fibre angle, for every measuring point the corresponding fibre angle is cal-culated relative to all three axes, in order to indicate the complete pattern of the fibre angles within the measured area of the fibrous material. For carrying out this proc ess, a highly elaborate installation is necessary, in order to on the one hand measure the radiated beam proportion of the reflected light and on the other hand the propor tion of the diffusely reflected light.
By DE-A-196 04 076.0, a device for the inspection of the surface of woods for the purpose of determining surface characteristics has been proposed, consisting of an opto-electronic sensor, an electronic and / or optical processing unit, a computer capable of real-time operation, whereby the wood can be moved relative to the sen-sor, as ~.vell as an incremental position transducer, which synchronizes the sensor with the speed of the wood. The sensor consists of a colour laser scanner with at least two beam bundles of differeing wave lengths and a receiver with two channels with onopto-electrical receiving element each, whereby the channels are formed by beam splitting of the reflected beam bundle and at least in one of the channels a lens for creating an intermediate image plane is located. After the lens, within one of the channels there is an optical graduated filter, which is capable of modulating the passing light current to the opto-electrical receiving element belonging to it inde-pendent of the position. The signals of the receiving element of the one channel without the graduated filter are converted into a colour image in the computer and those of the other channel, the light current of which has been modulated independ-ent of the position, into a profile image of the surface.
P1339 PCT 05.10.99 -3a-It is, for example, known from the documents US-4,286,880 or JP 59 040 149 A, that wood surfaces can be investigated by scanning with a light beam. These two documents divulge a rotating mirror, which is located in the focal point of a para-bolic mirror, light is emitted on to the rotating mirror from a light sowce and from there distributed by reflection on the parabolic mirror along a scanning line on the wood surface. In US-4,286,880, the subject is an improvement of work stations for the localization of wood defects, in the case of which work stations are operating person has to find the defects. The operating person marks the defects and the marks are detected by an optical sensor with a binary output signal. The object of 149 A is the detecting of live knots by means of asymmetrically scattered light. For the solution of this problem, a wood surface is scanned by a light beam anti light scat-tered from the wood surface is directly detected by two detectors arranged symmetri-cally with respect the the scanning beam.
From the state of the technology, optical distance sensors are also known. The dis-tance sensor divulged in the document EP-0 387 521 A2 is based on a triangulation process. A beam of light is focussed on the surface to be measured by means of a lens. Light scattered by the surface is collected by the same lens and focussed on position-sensitive detectors by a concave mirror. The components are positioned in such a manner relative to an optical axis, that a high light sensitivity is assured by a small angle of incidence. Another distance sensor is divulged in document WO
93/11403. It contains a rotating polygonal mirror, which distributes light emitted from a light source on to a scanning line on the surface to t;c measured. A
scanning lens projects the point-shaped light sowce on to the surface. The light reflected by the surface is projec,~ted on to a point-shaped detector by means of the same scanning lens and a further lens; this construction is designated as "confoc al". Only when the object is in the focal plane of the sca~uiing lens and the detector is simultaneously in the focal plane of the further lens, does a maximum light intensity impinge on the detector. The detected light intensity is therefore a measure for the dista:nee of the ob P1339 PCT 05.10.99 -3b-jest from the scanning lens. The construction can be refined by foreseeing several de-tectors, which supply maximum signals at differing object distances.
P1339 PCT 05.10.99 The invention is based on the objective of indicating a device and a process for the dynamic inspection of the surfaces of objects such as woods, tiles, textiles or glasses, for the identification of surface characteristics, by means of which an auto-matic inspection of the surface can be carried out continuously and with a high speed and by means of which characteristics such as shakes, fissures, cracks, knot holes, protrusions, indentations, in the case of wood also bhte stain or red ring rot can be identified with certainty by the exploitation of the scatter effect. In particular, simultaneously the position-dependent diffuse reflection of a surface, the distance of the surface as urell as the deviation of the diffuse reflection characteristic in function of the position can be detected by a Lambert projector at processing speeds of several metres per second in real time. Apart from this, the device shall be of a simple con-struction and should be able to be manufactured ax a low cost.
IS The objective is achieved by the device in accordance with the invention and by the process in accordance with the invention, as these are defined in the independent Maims.
The device in accordance with the invention for the inspection of the surface of an object for the purpose of the identification of surface characteristics contains a sen-sor unit according to the invention, whereby in preference the lens can be moved relative to the sensor unit. The device furthermore contains a scanning device, to which light is transmitted from the sensor unit, whereby the scanning device com-prises a concave mire or, in the focal point of which a light deflecting element illu-minated by the sensor unit with a deflection angle dependent on time is located, so that the light transmitted by the sensor unit can be guided over the object along a scanning line and light from the scanning device diffusely reflected by the object impinges on the sensor unit.
P1339 PCT 05.10.99 A preferred embodiment of the device in accordance with the invention is charac-terized by a parabolic mirror, in the focal point of which a rotating polygonal mirror is located, on to which the beam bundle of the laser is directed by means of a tele-S centric lens, which guides the transmitter and receiver beam along the same optical axis, whereby the parabolic mirror guides the deflected beam bundle over the object along a scanning line under a constant angle relative to the symmetry axis of the parabolic mirror and guides the beam bundle diffusely reflected by the object back along the same path, and whereby it (the beam bundle) after being reflected out of the common beam path impinges on the processing unit.
The device is based on the fact of the so-called Tracheid effect (scatter effect) , which occurs with density changes on the surface in the case of a number of materi-als with a point-shaped, in preference coherent illumination. In doing so, light enters into the material through the surface and is guided inside the material, whereby the guidance of the Light and its damping are determined by the stnzcture of the material.
The device and the process are in a position to exploit the scatter effect for the evaluation of surface anomalies and to carry out an assessment of surface defects like this under real time conditions.
T.~. the beam path between the laser and the polygonal mirror wheel, in preference there is a mirror with an aperture or with a hole, through which the irradiated beam bundle impinges on the polygonal mirror wheel, whereby the mirror deflects the diffusely reflected bem bundle on to a lens under a given angle, in the focal plane of which the optical detectors and the electronic processing unit, in preference includ-ing a computer capable of real time operation, are situated. After the lens and in front of its focal plane, by beam splitting two beam bundles and preferably at least P1339 PCT 05.10.99 two channels are created, which are evaluated separately. A high precision of exe-cution is important for the functioning of the device.
5 I1; for example, the material to be inpsected is wood, then around the intensive light spot of the direct irradiation two light cones are formed aligned to the direction of the fibres, which diminish corresponding to the dipole characteristic and which join the direct light spot of the impinging beam. In correspondence with the change of the surface structure and the direction of the fibres, these two light cones change 10 with respect to their length, brightness and direction. The brightness, length and di-rection are dependent on the local defect and its shape as well as on the direction of the fibres. The inventors have in particular discovered, that through the scatter effect for the first time in the case of woods just starting blue stain or red ring rot can be made visible, long before the attack can be identified by the unaided eye, but can 15 solely be detected by means of chemical analyses or microscopic viewing.
Equally on the basis of the scatter effect defects in the wood, such as, for example, knot holes, compression wood or blue stain become visible, which lead to a diminuition of the quality of the corresponding wood.
In order to obtain a surface profile (3D - profile) by means of a triangulation proc-ess, at least one one light beam emitted from the sensor unit can be guided on to the object. Light diffusely reflected from the object under a finite angle relative to the impinging beam can be guided back to the sensor unit in such a manner, that the 25 impinging and the returned light beam are essentially in coincidence in a plane par-allel to the surface of the object. In an alternative version, also several, in preference two, laser beams can be guidable by means of verious mirrors offset ralative to one another in such a manner, that the individual laser beams are in coincidence in the horizontal plane, while in the vertical object plane a constant angle is given, in order 30 to measure the surface profile by means of the vertical deposition of the diffusely P1339 PCT 05.10.99 reflected laser light with a position-sensitive opto-electrical receiving element, which is in particular a PSD sensor element capable of high speed.
In a preferred embodiment of the invention, at least one leaser beam is focussed on the surface of the object in order to obtain a 3D surface profile by triangulation. The vertical deposit of the diffusely reflected laser light is measured through an addi-tional guidable mirror under a constant angle by means of a position-sensitive re-ceiving element (PSD) capable of high speed.
The process for the inspection of the surface of an object for the purpose of the identification of surface characteristics in accordance with the invention utilizes a sensor unit according to the invention which emits light to a scanning device, whereby in preference the object is moved relative to the sensor unit. The emitted light is focussed on the object by means of a telecentric projection and guided over the object along a scanning line under a constant angle relative to the object to be scanned and relative to the vertical line of the transportation surface. Light diffusely reflected by the object is guided back in to the sensor unit along the same beam path as the emitted light.
In a preferred embodiment of the process in accordance with the invention, the laser beam is focussed on the object by means of a telecentric projection, which guides the emitted and receiver beam along the same optical axis focusses it on the object and guides it along a scanning line always under a constant angle relative to the object to be scanned and relative to the vertical line of the transportation surface ~f the object, which can be the most effectively achieved by the arrangement of a para-bolic mirror, in the focal point of which a polygonal mirror wheel is located, so that in this case the angle of the laser beam is constant with respect to the symmetry axis P1339 PCT 05.10.99 _g_ of the parabolic mirror. In doing so, the spatial resolution is limited solely by the focussing ability of the laser light. The telecentric beam bundle of the moving laser light spot, the measuring point, along a scanning line, does not have to impinge or-thogonally on the surface to be scanned, the angle of impingement can rather more S be any one within wide ranges, it must, however, be constant relative to the normal line of the transportation surface of the object. In doing so, the diffusely reflected light is guided back to the detector through the same projection system.
In accordance with the process, in preference with the utilization of parallel proces-sors, various surface characteristics can be measured in real time, namely in par-ticular:
a) the intensity distribution of the diffusely reflected laser light and / or b) the distribution of the intensity of the laser light scattered by local density variations (Tracheid effect), which is observed through spacial filters in the scatter channel and / or c) the elevation profile (3D channel) of the surface, which is measured by means of a triangulation process and I or d) double refi~action characteristics, which are measured by means of detection processes dependent on polarization, for example by means of an analyser par allel and anti-parallel to the surface direction.
After the lens and in front of the image plane of it, at least two channels are formed by beam splitting into two partial beam bundles, which are assessed. On principle it is even possible to detect all characteristics mentioned above with only one laser, which can be implemented by a modification of the receiving module. For splitting-up the diffusely reflected Iaser radiation into partial radiation bundles according to their differing wave lengths, a dichroic minor is positioned in the beam path, whereby from the partial beam bundles of differing wave lengths various surface P1339 PCT 0.10.99 characteristics, such as in particular the elevation profile in the 3D
channel, the re-flectivity in a red light channel as well as the Tracheid effect in the mentioned scat-ter channel are simultaneously recorded with a high repetition rate. One of the par-tial radiation bundles formed by the dichroic mirror, in preference the red light pro-s portion of the diffusely reflected laser beams, is preferably once again split-up into two channels, in preference by means of a semi-transparent mirror, in which in ac-cordance with the diffusely reflected laser light sensitive sensors are located, whereby within one channel the image of the directly diffusely reflected light point, or spot on the object is evaluated and the image of the light cones of the scatter effect is blanked out and from the image of the laser point or spot a grey-scale image is obtained, while inside the other channel (scatter channel) by means of special spatial filters the directly diffusely reflected light point or spot is blanked out and only the image of the remaining light cones is evaluated. The blanking out is carried out by means of special spatial filters. .
The Tracheid - scattered laser light (scatter channel), which, for example, in the case of wood serves for the evaluation of the image of the remaining light cones, is de-tected in a real time process for making visible density dependent surface anomalies, such as shakes, cracks, fissures, structure defects, by means of a four-quadrant process, for example by means of dichroic mirrors or a four-quadrant diode, position- dependent in the form (Sx +Sy)/S and in the direction arctan (SX
/Sy), if necessary in combination with the triangulation process in the 3D channel also in function of the elevation, the spatial resolution of which is only limited by the focussing ability of the laser light.
In the following, the invention is explained in detail on the basis of the Figures. In these are schematically illustrated:
..
P1339 PCT 05.10.99 Figure 1 a cross section through a first embodiment of the sensor unit in accor-dance with the invention, Figure 2 a cross section through a second embodiment of the sensor unit in accor-dance with the invention, Figure 3 a cross section through a third embodiment of the sensor unit in accor-dance with the invention, Figure 4 a top view of a defecting element of the sensor unit of Fig. 3, Figure 5 a schematic layout of the device in accordance with the invention in top view, Figure 6 a top view of a technical embodiment of the device in accordance with the invention, in which the beam path is folded in order to achieve a small depth of the construction, Figure 7 a side view of the device of Fig. 6, Figure 8 a view of a receiving module with a spatial filter vertical to the parabolic mirror in the scatter channel and Figure 9 a view of the receiving module of Fig. 8 with the same spatial filter par-allel to the parabolic mirror in the scatter channel.
Figure 1 shows a schematic cross section through the first embodiment of the sensor unit SO in accordance with the invention. The sensor unit 50 serves to emit light to a scanning device 60 (not illustrated in Fig. 1), which is situated in the direction of an P1339 PCT 05.10.99 arrow 61, and for receiving light impinging from the scanning device 60. The sensor unit 50 contains a light-emitting sender module 51 and a light receiving receiver module 52. The emitting module 51 contains at least one light source 3; this can be a laser, a light-emitting diode (LED) or another light source. In front of the light sour-s ce 3, if necessary there can be a (not illustrated), e.g., focussing optical system. The receiving module 52 contains at least one light receiver 20, e.g., a photo-diode, a CCD camera, a position-sensitive receiving element (PSD), etc. An optical system 13, e.g., a focussing lens or a multi-element lens can project an object (not illustrated in Fig. 1) on to the light receiver 20.
The sensor unit SO apart from this also has an optical deflection element 9.
If light from the direction of the scanning device 60 were to impinge on the sensor unit 50, then it would be split-up by the deflecting element 9 into two light paths 53, 54 dif fering from one another. A first beam path 53 is defined by a first spatially limited part 55 of the light and a second beam path 54 is defined by a second spatially limi-ted part of the light 56. The first beam path 53 has a smaller cross sectional area than the second beam path 54. The emitting module 51 is located in the first beam path 53 and the receiving module 52 in the second beam path 54. In this embodiment the deflection element 9 is designed as a plane mirror with an aperture 25 and arranged in such a manner, that light travelling to the deflection element 9 is to a greater ex-tent left to pass through to the scanning device 60 through the aperture 25.
Light emanating from the scanning device 60 outside the first beam path 53 is in contrast to a greater extent reflected to the receiving module 52. The surface shell, which surrounds the aperture 25 in the deflection element 9, is in preference parallel to the direction of diffusion of the emitted light 53.
In Figure 2, a different embodiment of the sensor unit in accordance with the inven-tion 50 is schematically illustrated. Here the deflection element 9 is designed as a PI339 PCT 05.10.99 small mirror and arranged in such a manner, that Iight 53 travelling from the emitter module 51 to the deflection element 9 is to a greater extent reflected to the (not illu strated in Fig. 2) scanning device 60. Light 54 emanating from the scanning device outside the first beam path 53 is in contrast to a greater extent allowed to pass through to the receiving module 52.
Figure 3 schematically illustrates a further embodiment of the sensor unit in accor-dance with the invention 50. The deflection element 9 corresponds to that of Fig. 1.
This embodiment contains two light sources 3, 4, for example, two lasers. A
first laser 3 emits red light in the wave Length range between 620 nm and 770 nm, e.g., 680 nm, and a second laser 4 emits infrared light in the wave length rangle above 770 nm, e.g., 830 nm. The two laser beams are joined by n>eans of a mirror 12 and a beam splitter 11. The receiving module 52 contains two light receivers 15, 20 and a I 5 beam splitter I4, by means of which light 54 impinging on the receiving module 52 is split-up on to the light receivers 15, 20. The beam splitter 14 can have dichroic characteristics, i.e., its reflection to transmission ratio can be dependent on the wave length.
Figure 4 schematically illustrates a top view of the mirror 9 with aperture 25 of Fig.
3 along the line IV - IV. Light 54 emanating from the scanning device 60, which exactly coincides with the light 53 travelling to the scanning device 60, does not impinge on the receiving module 52. This way a "cross-talk" is efl:iciently preven øed.
In accordance with Figure 5, the fundamental principle of the device in accordance with the invention consists of a concave mirror 1, which is in preference cut out of a paraboloid as a narrow strip I and which has the length 1 and the height h.
Preferred P1339 PCT OS.10.99 as a concave mirror is a parabolic minor, beacuse it provides an ideal, practically aberration-free image. Within the focal point of the parabolic mirror 1 is a polygonal mirror wheel 2, which is rotated by a motor 27 at a high speed, with one of its poly-gon surfaces arr4 ~~ged in such a manner, that preferably at an angle of 4S
degrees of S the normal line of the polygon surface of the mirror wheel to the optical axis 7 (symmetry axis) of the parabolic mirror 1, the centre of the polygon surface comes to lie exactly in t'~e focal point of the parabolic mirror 1. Two lasers 3, 4 each gene-rate a laser beam, whereby one laser in preference operates in the wave length range of approx. 680 r:n, therefore in the red light range, and the other laser preferably in the wave length range of 830 nm, therefore in the infrared light range. The laser be-ams are deflected through mirrors 11, 12 and brought together to a common beam 6.
For this purpose, the mirror 11 illustrated in Figure 1 is transparent for the laser be-am of the lase_- 3 situated behind it. The combined laser beams 6 pass through a further mirror 7 through a hole 2S in it and impinge on one of the plane polygon 1 S surfaces of the rotating polygonal mirror wheel 2. Dependent on the design of the polygonal mirror wheel 2 and on the centre distance of it from the parabolic mirror 1, the polygonal mirror wheel. 2 guides the laser beams 6, 6', 6" at a certain prede-fined horizontal image field angle a over the parabolic mirror 1 in its longitudinal expanse 1, as can be seen in Figure S.
The horizontal image field angle a is limited by the laser beams 6', 6". The laser beam 6"' respectively reflected by the parabolic minor ~ is guided parallel to itself over the longitudinal expanse 1 of the parabolic mirror 1 and forms the scanning line. The reflected laser beam 6"' is guided to an inclined mirror and impinges on the 2S surface 10' of an object to be scanned 10, for example a piece of wood travelling with the speed v relative to the laser. In this manner, the laser beams 6 from the lasers 3, 4, which are focussed on the abject 10, are guided under a constant angle relative to the symmetry axis 7 of the parabolic mirror 1, i.e., to the normal line of the transportation surface of the object 10 to the object 10 to be P1339 PCT 05.10.99 scanned, along the scanning line 23, 24. The object surface is projected on to the light receiver contained in the receiving module as a telecentric image.
The laser light diffusely reflected in the point of impingement is guided back along the same path, so that arriving beam and diffusely reflected beam in essence coin-cide. The polygonal mirror wheel 2 projects the diffusely reflected beam bundle on to the mirror 9, which deflects it and guides it to a processing unit 5, which evaluates the diffusely reflected beam bundle optically and electric< lly, to which a computer capable of real time operation also belongs.
In the Figures 6 and 7, a technical embodiment of the device is illustrated.
The t~No lasers 3, 4 genera to laser beams 6, which are brought together through mirrors 1 l, 12 and are projected on to the rotating polygonal mirror wheel driven by a motor 27, rotating at high speed, through a hole 25 within the mirror 9, which once again is located in the fecal point range - this time relative to a longish, plane mirror 17 - of the parabolic minor 1. The two laser beams 6 are projected on to the mirror 17 by the polygonal mirror wheel 2, which deflects the laser beams on to the parabolic mirror 1, so that the folded beam path illustrated in Figures 6 and 7 is produced. The parabolic mirror 1 now has the effect, that the laser beams reflected by it can be guided parallel to one another and therefore under a constant angle relative to its symmetry axis 7, relative to a normal line 19 of the transportation surface 10' of the object 10 on to the surface 10'.
To do this, in the beam path after the parabolic minor 1 in accordance with Figure 7 there are two plane mirrors 18, 19 aligned transverse to the surface to be scanned 10' of the object to be scanned 10, which guide the laser beams travelling parallel in one another along a scanning line 23 over the surface 10'. Two mirrors 18, 19 are used, P1339 PCT 05.10.99 in order with respect to the evaluation in the triangulation process to be able to ob-tain a 3D depiction of the image. If the information in the direction of the vertical axis can be made do without, then on principle one mirror 19 is sufficient for the construction of the device and for carrying out the process.
In the following, on the basis of Figure 7 beam paths for the case without triangula-tion process and for the case with triangulation process are discussed. The light be-am emitted by the sensor unit 50 and reflected by the parabolic minor 1 impinges on 10 the object 10 through mirror 19. In this, preferably the angle of impingement (3 rela-tive to the normal line 29 on to the object surface 10' is greater than zero, i.e., the light impingement on to the surface 10' is not vertical. As a consequence, light di-rectly reflected from the surface 10' does not fall back on to the mirror 19;
therefore diffuse reflection on the surface 10' is measured. In the case without triangulation 15 process, light is measured, which returns to the sensor unit SO under the same angle of reflection J3 through the mirror 19 on the same path as the impinging light. If a triangulation process is to be utilized, then the vertical deposition of light is measu-red, which is diffusely reflected under a constant angle A relative to the impinging light and which falls back into the sensor unit 50 through a further mirror 18. Also in 20 this case, the light in essence travels along the same path back to the sensor unit 50 as the impinging light. In this, the angle B determines the resolution of the 3D mea-surement. The greater the angle 8, the more sensitively the 3D profile can be measu-red. A preferred value for the angle 8 is A = 15.5° t 1.5°. In an alternative version of the process, light can be beamed on to the object 10 both through mirror 19 as well 25 as through mirror 18 - or even on more than two light paths - , and the respective diffusely reflected light portions detected.
Two further mirrors 21, 22, which in the top view are arranged laterally from the 30 mirrors 18, 19 and if necessary in different planes, serve to simultaneously guide the P1339 PCT 05.10.99 laser beams over a side surface 10" of the object 10 along a further scanning line 24 and to obtain an image - also as a 3d image -, so that simultaneously two planes 10', 10" inclined relative to one another at a given angle can be scanned, which in the example illustrated are inclined at 90 degrees to one another. The diffusely reflected light beams travel back along the same path and impinge on the mirror 9 under the horizontal image field angle a, from where they are deflected towards a lens 13.
Located in the beam path of the lens 13 there is a dichroic min or 14, which is trans-parent for the infrared radiation of the diffusely reflected laser light, but deflects the diffusely reflected red light radiation of the other laser. After the mirror 14, in the image field plane of the lens 13 there is a receiver 20, the received signals of which are utilized as 3D information. With this information, a relief image can be calcu-fated in the computer, which enables the identification of depth changes of the object 1 S to be inspected. Used in preference as sensor element 20 for the 3D
channel, is a position-sensitive, opto-electrical receiving element, in particular a PSD
sensor ele-ment capable of high speed, which detects the positional deviation of the laser beam ~~elative to the zero position, which has been guided through the mirror 18 and 21.
'The red light proportion of the diffusely reflected laser beams is deflected through the dichroic mirror 14 and impinges on to a splitter mirror 26, which once again splits-up this beam proportion into two channels, in which light-sensitive sensors 15, 16 are located. One channel is operated as a so-called direct red sensor and provides a grey-scale image, whereby here the image of the direct light point or spot on the object is evaluated. For this purpose, by means of a diaphragm the light cones of the scatter effe ct are blanked out. The other channel is the so-called scatter channel and serves to evaluate the actual scatter image and thus in the case of wood the light cones, which adjoin the direct light spot. To do this, the centre point or centre spot, -Nhich is of course evaluated in the other channel, is blanked out be means of special spacial filters 30 in the scatter channel and the image of the remaining light cones, for example, projected on to a four-quadrant diode. From the relationship of P1339 PCT 05.10.99 the two light cones to one another, their position relative to one another and relative to the direction of transport can be calculated and therefore in the case of wood, for example, the fibre direction or places affected with blue stain or red ring rot can be identified. The evaluation of the diffusely reflected laser radiation is therefore car-ried out in such a manner, that the energetic and / or the positional distribution of the diffusely reflected radiation is converted into different electrical signals.
By means of a computer capable of real time operation, subsequently the channels can be evaluated and the images generated displayed on a monitor. It is equally pos-sible to convert the signals from the three channels into colour values, in order to thus also generate a colour image.
It is also conceivable to transmit the diffusely reflected laser radiation to a CCD
camera for evaluation.
The figures 8 and 9 on the one hand show a view of the receiving module 15 with a spatial filter 30 vertical to the parabolic mirror 1 in the scatter channel with lens 13 and mirror 14, and on the other hand- a view of the same receiving module 15 with the same spatial filter 30 parallel to the parabolic minor in the. scatter channel. 'One can make out the spatial blanking out on the one hand of the centre spot by a central plate 31, whereby the light cones impinge on the light receiver 15 through slits 32, 33.
The device and the process are in particular suitable for assessing the surface of an object, in particular of flat objects such as woods, tiles, textiles, glasses, plastic sur-faces, foils, silicium wafers, cardboards and others for the purpose of identifying P1339 PCT 05.10.99 surface characteristics such as shakes / cracks, holes, protrusions or indentations, and to evaluate them according to quality criteria. The device and the process are in particular suitable for the application of the inspection of woods, because they are for the first time capable of directly evaluating the scatter effect in the case of wood - 5 and they provide a selective optical contrast enhancement in the case of the most diverse surface defects or enable a differentiation of woods with saw roughness.
Equally,. blue stain as well as dirt contamination or damage done by worms or cracks / shakes are made very well visible. The usefulness of the invention consists in particular of the fact, that with it in real time various surface characteristics can be measured, such as a) the intensity distribution of the diffusely reflected laser light and / or b) the distribution of the intensity of the laser light scattered by local density varia-tions (Tracheid effect), which is observed through spatial filters in the scatter channel and 7 or c) the elevation profile (3D channel) of the surface, which is measured by means of a triangulation process and / or d) double refraction characteristics, which are measured by detection processes dependent on polarization, for example by means of an analyser parallel and anti-parallel to the surface direction.
Claims (26)
1. A device for inspecting a surface of an object to determine surface characteristics of the object, said device comprising:
a scanning device, and an optical sensor unit comprising:
a sending module for emitting light to the scanning device, a receiving module for receiving light incident from the scanning device, and an optical deflecting element that is operable to split light incident from the scanning device into a first beam path and a second beam path, said first beam path being different than said second beam path, said first beam path being defined by a first spatially limited part of the incident light and said second beam path being defined by a second spatially limited part of the incident light, and where the first spatially limited part has a cross sectional area that is smaller than a cross sectional area of the second spatially limited part, wherein the scanning device includes:
a light deflecting element, said light deflecting element having a time-dependent deflection angle, and a concave mirror having a focal point and an axis of symmetry, wherein said light deflecting element is located in said focal point so that light emitted from the sensor unit can be guided into the sensor unit under a constant angle relative to the symmetry axis of the concave mirror along a scanning line over the object and so that light diffusely scattered from the object emanating from the scanning device can be guided into the sensor unit along a path identical to the emitted light, and wherein the concave mirror is disposed relative to the object surface and the receiving module such that the surface can be telecentrically projected into the receiving module and the light deflecting element acts as an aperture diaphragm, said receiving module further comprising at least one light receiver with a special filter or a diaphragm designed and positioned in a manner that directly diffusely scattered light is blanked out for said of least one light receiver, in order to detect tracheid scattered light.
a scanning device, and an optical sensor unit comprising:
a sending module for emitting light to the scanning device, a receiving module for receiving light incident from the scanning device, and an optical deflecting element that is operable to split light incident from the scanning device into a first beam path and a second beam path, said first beam path being different than said second beam path, said first beam path being defined by a first spatially limited part of the incident light and said second beam path being defined by a second spatially limited part of the incident light, and where the first spatially limited part has a cross sectional area that is smaller than a cross sectional area of the second spatially limited part, wherein the scanning device includes:
a light deflecting element, said light deflecting element having a time-dependent deflection angle, and a concave mirror having a focal point and an axis of symmetry, wherein said light deflecting element is located in said focal point so that light emitted from the sensor unit can be guided into the sensor unit under a constant angle relative to the symmetry axis of the concave mirror along a scanning line over the object and so that light diffusely scattered from the object emanating from the scanning device can be guided into the sensor unit along a path identical to the emitted light, and wherein the concave mirror is disposed relative to the object surface and the receiving module such that the surface can be telecentrically projected into the receiving module and the light deflecting element acts as an aperture diaphragm, said receiving module further comprising at least one light receiver with a special filter or a diaphragm designed and positioned in a manner that directly diffusely scattered light is blanked out for said of least one light receiver, in order to detect tracheid scattered light.
2. The device according to claim 1, wherein the deflecting element is a mirror with an aperture and is positioned such that a major portion of light traveling from the emitting module to the deflecting element passes through the aperture to the scanning unit.
3. The device according to claim 1, wherein the deflecting element is a mirror and is positioned such that a major portion of light traveling from the sending module to the deflecting element is reflected to the scanning device by the mirror.
4. The device according to any one of claims 1 to 3, wherein the emitting module includes a plurality of light sources that produce light having different wave lengths.
5. The device according to claim 4, wherein said plurality of light sources includes at least a first light source and a second light source, said first light source emits light having a wave length between about 620 nm and 770 nm, and said second light source emits light having a wave length above 770 nm.
6. The device according to any one of claims 1 to 5, wherein the receiving module includes an optical system, the optical system being positioned between said deflecting element and said at least one light receiver such that the at least one light receiver is disposed in the focal plane of the optical system.
7. The device according to claim 6, wherein the receiving module includes several light receivers and at least one beam splitter, whereby by means of said at least one beam splitter, light impinging on the receiving module can be split up among the light receivers.
8. The device according to claim 7, wherein the at least one beam splitter has a wave length dependent reflection to transmission ratio.
9. The device according to any one of claims 7 and 8, wherein a further spatial filter or diaphragm is positioned ahead of a light receiver for blanking out light cones from a scatter effect.
10. The device according to any one of claims 1 to 9, including two light receivers, each of said two light receivers having a spatial filter or diaphragm arranged in a manner that directly diffusely scattered light is blanked out, said spatial filters being positioned orthogonally relative to one another to measure directional dependence of tracheid scattered light.
11. The device according to any one of claims 1 to 10, wherein the receiving module includes at least one CCD camera or at least one position-sensitive receiving element.
12. The device according to any one of claims 1 to 11, wherein the light deflecting element is a rotating polygonal mirror wheel.
13. The device according to any one of claims 1 to 12, wherein the concave mirror is a strip having parallel cut edges out of a paraboloid.
14. The device according to any one of claims 1 to 13, wherein, for obtaining a 3D profile by a triangulation process, at least one light beam emitted from the sensor unit can be guided on to the object and light diffusely scattered from the object under a constant angle relative to the incident beam can be guided back to the sensor unit such that the incident beam and the guided back beam are coincident in a plane parallel to the surface of the object.
15. The device according to claim 14, wherein, for obtaining a telecentric 3D profile by means of a triangulation process, the sensor unit includes a position-sensitive receiving element capable of high speed, in order to measure the surface profile by deposition of the diffusely scattered light vertically to the object surface by means of telecentric projection.
16. The device according to any one of claims 1 to 15, wherein the object is movable relative to the sensor unit.
17. A process for inspecting a surface of an object to determine surface characteristics thereof, wherein light emitted from a sensor unit is transmitted to a scanning device and the emitted light is guided to and deflected by a deflecting element wherein the light deflected by the deflecting element is focused on the object by a concave mirror having a focal point and a symmetry axis, the light deflecting element being positioned at said focal point, said deflected light being guided under a constant angle relative to the symmetry axis of the concave mirror along a scanning line over the object, and light diffusely reflected from the object is generally guided back to the sensor unit along the same path as the emitted light, wherein the object surface is telecentrically projected into the sensor unit by the concave mirror, whereby the light deflecting element acts as an aperture diaphragm and wherein additionally the intensity of tracheid scattered light guided back to the sensor unit is measured by a receiver, the directly diffusely scatted light being blanked out for the receiver.
18. The process according to claim 17, wherein the tracheid scattered light is measured by two receivers, each of said two receivers comprising a spatial filter for blanking out the directly diffusely scattered light point, the spatial filters being positioned orthogonally relative to one another to measure directional dependence of tracheid scattered light.
19. The process according to any one of claims 17 and 18, wherein for obtaining a 3D profile by a triangulation process, at least one light beam emitted by the sensor unit is guided on to the object and light directly diffusely scattered from the object under a constant angle relative to the incident beam is guided back to the sensor unit such that the incident beam and the guided back beam are coincident in a plane parallel to the surface of the object.
20. The process according to any one of claims 17 to 19, wherein various surface characteristics are measured in real time using parallel processors.
21. The process according to any one of claims 17 to 20, further comprising separating light portions of differing wave length impinging on the sensor unit from one another, and instantaneously recording, from the light portions, with a high repetition rate, various surface characteristics, said surface characteristics including elevation profile in a 3D channel, reflectivity in a red light channel, and tracheid effect in a scatter channel.
22. The process according to claim 21, comprising splitting up light impinging on the sensor unit into first and second light portions, and guiding the first and second light portions to two light receivers, said first light portion having an image of light cones of the scatter effect blanked out, the image of the directly diffusely reflected light point on the object is evaluated and from grey-scale image is obtained, and in the case of the second light portion, the directly diffusely reflected light point is blanked out by special spatial filters and only an image of remaining light cones is evaluated by said receiver.
23. The process according to claim 22, comprising the further steps of separating light portions of differing wave length impinging on the sensor unit from one another, whereby, with a first light portion in a triangulation process, 3D information is measured by means of a position sensitive receiving element and, with a second light portion, the intensity distribution of the object as well as the surface characteristics are measured with opto-electrical sensor elements.
24. The process according to any one of claims 17 to 23, wherein light impinging on the sensor unit makes density-dependent surface anomalies visible and, by means of a four-quadrant process, which is a function of position (S x + S y)/ S and direction arctan (S x + S y).
25. The process according to claim 19, wherein light impinging on the sensor unit makes density-dependent surface anomalies visible and, by means of a four-quadrant process, which is a function of position (S x + S y)/ S and direction arctan (S x + S y) and, if necessary, in combination with the triangulation process in a 3D channel, which is a function of elevation, is detected in a real time process, a spatial resolution of which is limited only by a focusing ability of the light.
26. The process according to any one of claims 17 to 24, further comprising moving the object relative to the sensor unit.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19717488A DE19717488C2 (en) | 1997-04-25 | 1997-04-25 | Device for inspecting the surface of objects |
| DE19717488.4 | 1997-04-25 | ||
| PCT/IB1998/000614 WO1998049545A1 (en) | 1997-04-25 | 1998-04-23 | Sensor unit, process and device for inspecting the surface of an object |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2287242A1 CA2287242A1 (en) | 1998-10-25 |
| CA2287242C true CA2287242C (en) | 2007-01-16 |
Family
ID=7827728
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002287242A Expired - Fee Related CA2287242C (en) | 1997-04-25 | 1998-04-23 | Sensor unit, process and device for inspecting the surface of an object |
Country Status (8)
| Country | Link |
|---|---|
| US (1) | US6449036B1 (en) |
| EP (1) | EP0977982B1 (en) |
| AT (1) | ATE227843T1 (en) |
| AU (1) | AU6848798A (en) |
| CA (1) | CA2287242C (en) |
| DE (2) | DE19717488C2 (en) |
| RU (1) | RU2186372C2 (en) |
| WO (1) | WO1998049545A1 (en) |
Families Citing this family (50)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6661506B2 (en) * | 2000-08-24 | 2003-12-09 | Og Technologies, Inc. | Engine bearing inspection system |
| US6624883B1 (en) * | 2000-09-28 | 2003-09-23 | National Research Council Of Canada | Method of and apparatus for determining wood grain orientation |
| JP2003029201A (en) * | 2001-07-11 | 2003-01-29 | Canon Inc | Picture projecting device and picture correcting method |
| EP1345024A1 (en) * | 2002-03-11 | 2003-09-17 | Centre National De La Recherche Scientifique | Method and device for polarimetric measurement of the Mueller matrix coefficients of a sample in the far ultraviolet to visible spectral range |
| US6795175B2 (en) * | 2002-05-21 | 2004-09-21 | The Boeing Company | System and method for imaging contamination on a surface |
| US20070020321A1 (en) * | 2003-01-16 | 2007-01-25 | Redding Bruce K | Method for enhancing attenuation characteristic of absorbent materials useful with dermal and transdermal substance delivery systems |
| AT413452B (en) * | 2003-11-18 | 2006-03-15 | Riegl Laser Measurement Sys | DEVICE FOR RECORDING AN OBJECT ROOM |
| WO2006091783A1 (en) * | 2005-02-25 | 2006-08-31 | Accent Optical Technologies, Inc. | Apparatus and method for enhanced critical dimension scatterometry |
| DE102005025009A1 (en) | 2005-05-29 | 2006-11-30 | Massen Machine Vision Systems Gmbh | Characterization and quality control of at least partially optically translucent and internally optically scattering products |
| WO2006133283A2 (en) * | 2005-06-06 | 2006-12-14 | Infocus Corporation | Mirror-based light path combination for light sources |
| US7397553B1 (en) * | 2005-10-24 | 2008-07-08 | Kla-Tencor Technologies Corporation | Surface scanning |
| WO2007072794A1 (en) | 2005-12-19 | 2007-06-28 | International Frontier Technology Laboratory, Inc. | Card which can be authenticated by hologram chip |
| ES2302599B1 (en) * | 2006-01-28 | 2009-05-08 | Universidade De Vigo | METHOD FOR THE IDENTIFICATION OF MARISCO. |
| US7545502B2 (en) * | 2006-09-27 | 2009-06-09 | Weyerhaeuser Nr Company | Methods for detecting compression wood in lumber |
| US20080224041A1 (en) * | 2007-03-16 | 2008-09-18 | Cannamela John J | Method and apparatus for subsurface anomaly detection and image projection |
| DE102008012635A1 (en) * | 2008-03-05 | 2009-09-10 | Carl Zeiss Microlmaging Gmbh | Method and arrangement for time-resolved spectroscopy |
| CA2738396C (en) * | 2011-04-28 | 2013-12-24 | Denis Lessard | Optical inspection apparatus and method |
| NO336441B1 (en) | 2012-01-24 | 2015-08-17 | Tomra Sorting As | Apparatus, system and method for optical detection of matter |
| JP5906115B2 (en) * | 2012-03-29 | 2016-04-20 | 川崎重工業株式会社 | Optical scanning apparatus and laser processing apparatus |
| JP6289450B2 (en) | 2012-05-09 | 2018-03-07 | シーゲイト テクノロジー エルエルシーＳｅａｇａｔｅ Ｔｅｃｈｎｏｌｏｇｙ ＬＬＣ | Surface feature mapping |
| US9212900B2 (en) | 2012-08-11 | 2015-12-15 | Seagate Technology Llc | Surface features characterization |
| US9297751B2 (en) | 2012-10-05 | 2016-03-29 | Seagate Technology Llc | Chemical characterization of surface features |
| US9297759B2 (en) | 2012-10-05 | 2016-03-29 | Seagate Technology Llc | Classification of surface features using fluorescence |
| US9377394B2 (en) | 2012-10-16 | 2016-06-28 | Seagate Technology Llc | Distinguishing foreign surface features from native surface features |
| US9217714B2 (en) | 2012-12-06 | 2015-12-22 | Seagate Technology Llc | Reflective surfaces for surface features of an article |
| DE102013003744B4 (en) * | 2013-03-06 | 2021-02-11 | Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. | Method and device for determining a density distribution in a wood-based panel |
| US9217715B2 (en) | 2013-05-30 | 2015-12-22 | Seagate Technology Llc | Apparatuses and methods for magnetic features of articles |
| US9201019B2 (en) | 2013-05-30 | 2015-12-01 | Seagate Technology Llc | Article edge inspection |
| US9274064B2 (en) | 2013-05-30 | 2016-03-01 | Seagate Technology Llc | Surface feature manager |
| US9513215B2 (en) | 2013-05-30 | 2016-12-06 | Seagate Technology Llc | Surface features by azimuthal angle |
| CA2928878C (en) * | 2013-11-04 | 2020-06-23 | Tomra Sorting Nv | Inspection apparatus |
| RU2579817C1 (en) * | 2014-10-16 | 2016-04-10 | Открытое Акционерное общество "Ростовский оптико-механический завод" | Optical range finder system |
| RU2621469C1 (en) * | 2015-12-11 | 2017-06-06 | Акционерное общество "Концерн радиостроения "Вега" | Surface controlling method |
| CN107270813A (en) * | 2017-06-27 | 2017-10-20 | 中国航空工业集团公司北京长城航空测控技术研究所 | One kind scanning lens device |
| US20190017878A1 (en) * | 2017-07-12 | 2019-01-17 | Radiant Innovation Inc. | Non-contact temperature measuring device |
| DE102017214715A1 (en) * | 2017-08-23 | 2019-02-28 | Robert Bosch Gmbh | Optical arrangement for a LiDAR system, LiDAR system and working device |
| WO2019117301A1 (en) * | 2017-12-15 | 2019-06-20 | 株式会社堀場製作所 | Surface characteristic inspection device and surface characteristic inspection program |
| RU182588U1 (en) * | 2017-12-27 | 2018-08-23 | Федеральное государственное автономное образовательное учреждение высшего образования "Уральский федеральный университет имени первого Президента России Б.Н. Ельцина" | PRODUCT SURFACE GEOMETRIC CONTROL DEVICE |
| RU182109U1 (en) * | 2017-12-27 | 2018-08-03 | Федеральное государственное автономное образовательное учреждение высшего образования "Уральский федеральный университет имени первого Президента России Б.Н. Ельцина" | Optoelectronic sensor |
| EA035636B1 (en) * | 2017-12-27 | 2020-07-20 | Федеральное государственное автономное образовательное учреждение высшего образования "Уральский федеральный университет имени первого Президента России Б.Н. Ельцина" | Device for control of geometric parameters of a product surface |
| US20210025986A1 (en) * | 2018-03-15 | 2021-01-28 | Pioneer Corporation | Scanning device and measuring device |
| FR3089642A1 (en) * | 2018-12-11 | 2020-06-12 | Safran Electronics & Defense | MULTI-SPECTRAL HARMONIZATION DEVICE FOR ALIGNING THE OPTICAL TRACKS OF AN OPTRONIC SYSTEM |
| WO2020177076A1 (en) * | 2019-03-05 | 2020-09-10 | 深圳市大疆创新科技有限公司 | Detection apparatus initial-state calibration method and apparatus |
| CN110068288A (en) * | 2019-05-28 | 2019-07-30 | 西南科技大学 | A kind of whole field projection of laser scanning composite coding striped and acquisition device |
| EP3745081B1 (en) * | 2019-05-28 | 2023-03-22 | Tecan Trading Ag | Position detector and method for 3d positioning |
| CN110230988B (en) * | 2019-07-15 | 2021-08-03 | 河北科技大学 | Wheel hub detection device |
| DE102020003850A1 (en) * | 2020-06-26 | 2021-12-30 | Baumer Inspection Gmbh | Device for determining a height profile of an object |
| EP3985455A1 (en) * | 2020-10-16 | 2022-04-20 | The Swatch Group Research and Development Ltd | Device for measuring the degree of relative humidity inside a watch case |
| CN113358070B (en) * | 2021-07-07 | 2023-03-28 | 苏州鑫睿益荣信息技术有限公司 | Automobile brake pad flatness and pin height detection system and detection method thereof |
| CN115145020A (en) * | 2022-06-16 | 2022-10-04 | 北京遥感设备研究所 | Optical adjusting system and method for enabling laser propagation direction to be parallel to optical platform |
Family Cites Families (21)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1488841A (en) | 1974-01-18 | 1977-10-12 | Plessey Co Ltd | Optical detection apparatus |
| JPS6010284B2 (en) * | 1976-09-03 | 1985-03-16 | キヤノン株式会社 | scanning optical system |
| US4286880A (en) | 1979-07-30 | 1981-09-01 | The Bendix Corporation | Scanning light beam lumber defect position system and method of using same |
| JPS5940149A (en) * | 1982-08-31 | 1984-03-05 | Matsushita Electric Works Ltd | Apparatus for detecting live knot |
| JPS6019117A (en) * | 1983-07-13 | 1985-01-31 | Nec Corp | Plane scanning mechanism |
| DE3408106A1 (en) * | 1984-03-05 | 1985-09-12 | Erwin Sick Gmbh Optik-Elektronik, 7808 Waldkirch | Optical roughness scanner |
| US4606645A (en) * | 1984-10-29 | 1986-08-19 | Weyerhaeuser Company | Method for determining localized fiber angle in a three dimensional fibrous material |
| US4744663A (en) * | 1984-12-14 | 1988-05-17 | Nippon Kogaku K.K. | Pattern position detection apparatus using laser beam |
| US5177511A (en) * | 1986-11-08 | 1993-01-05 | G. Rodenstock Instruments Gmbh | Apparatus for producing images of an object and in particular for observing the rear portions of the eye |
| EP0387521A3 (en) | 1989-02-28 | 1991-02-06 | Siemens Aktiengesellschaft | Optical distance-sensor |
| DE3920669A1 (en) * | 1989-06-23 | 1991-01-10 | Sick Optik Elektronik Erwin | Optical scanning arrangement for rapidly moving material - contains laser, anamorphotic propagator, deflector, scanning lens and receiver arrangement |
| DE3923788C1 (en) | 1989-07-18 | 1991-01-10 | Erwin Sick Gmbh Optik-Elektronik, 8000 Muenchen, De | |
| JP2511391B2 (en) * | 1991-12-04 | 1996-06-26 | シーメンス アクチエンゲゼルシヤフト | Optical distance sensor |
| JP3214944B2 (en) * | 1992-03-17 | 2001-10-02 | 株式会社リコー | Optical scanning device |
| SE501650C2 (en) * | 1994-03-08 | 1995-04-03 | Soliton Elektronik Ab | Device and method for detecting defects in wood |
| NZ270892A (en) | 1994-08-24 | 1997-01-29 | Us Natural Resources | Detecting lumber defects utilizing optical pattern recognition algorithm |
| JP3335258B2 (en) * | 1994-10-27 | 2002-10-15 | 旭光学工業株式会社 | Reflective scanning optical device |
| US5953120A (en) * | 1996-01-04 | 1999-09-14 | Sandia Corporation | Optical probe |
| DE19703596C2 (en) * | 1996-01-31 | 2000-12-14 | Asahi Optical Co Ltd | Scanner and polygon mirror cover |
| US5847400A (en) * | 1996-02-01 | 1998-12-08 | Molecular Dynamics, Inc. | Fluorescence imaging system having reduced background fluorescence |
| DE19604076C2 (en) | 1996-02-05 | 1998-02-19 | F & O Electronic Systems | Device for inspecting the surface of wood for the determination of surface features and method therefor |
-
1997
- 1997-04-25 DE DE19717488A patent/DE19717488C2/en not_active Expired - Fee Related
-
1998
- 1998-04-23 DE DE59806277T patent/DE59806277D1/en not_active Expired - Lifetime
- 1998-04-23 EP EP98913977A patent/EP0977982B1/en not_active Expired - Lifetime
- 1998-04-23 RU RU99122593/28A patent/RU2186372C2/en not_active IP Right Cessation
- 1998-04-23 WO PCT/IB1998/000614 patent/WO1998049545A1/en active IP Right Grant
- 1998-04-23 US US09/403,735 patent/US6449036B1/en not_active Expired - Fee Related
- 1998-04-23 AU AU68487/98A patent/AU6848798A/en not_active Abandoned
- 1998-04-23 CA CA002287242A patent/CA2287242C/en not_active Expired - Fee Related
- 1998-04-23 AT AT98913977T patent/ATE227843T1/en active
Also Published As
| Publication number | Publication date |
|---|---|
| DE59806277D1 (en) | 2002-12-19 |
| EP0977982A1 (en) | 2000-02-09 |
| RU2186372C2 (en) | 2002-07-27 |
| US6449036B1 (en) | 2002-09-10 |
| CA2287242A1 (en) | 1998-10-25 |
| WO1998049545A1 (en) | 1998-11-05 |
| DE19717488C2 (en) | 2003-05-15 |
| DE19717488A1 (en) | 1998-10-29 |
| AU6848798A (en) | 1998-11-24 |
| ATE227843T1 (en) | 2002-11-15 |
| EP0977982B1 (en) | 2002-11-13 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA2287242C (en) | Sensor unit, process and device for inspecting the surface of an object | |
| US4899041A (en) | Light sensor for detecting an object in a certain distance | |
| US11255767B2 (en) | Method for measuring light field distribution and device therefor | |
| CN1662808B (en) | Optical technique for detecting buried defects in opaque films | |
| US10955531B2 (en) | Focal region optical elements for high-performance optical scanners | |
| US4004152A (en) | Apparatus for monitoring a moving web of material for faults | |
| EP0182471B1 (en) | Inspection apparatus with a scanning beam of radiation | |
| RU99122593A (en) | SENSOR UNIT FOR SURFACE SURFACE CONTROL AND METHOD FOR IMPLEMENTING THIS CONTROL | |
| US4116527A (en) | Device for concentrating light from a linear field on to a receiver | |
| US4522497A (en) | Web scanning apparatus | |
| US4728196A (en) | Arrangement for determining a surface structure, especially for roughness | |
| US4330205A (en) | Optical apparatus for measuring the size and location of optical in an article | |
| US7466403B2 (en) | Grain angle sensor | |
| EP0244102B1 (en) | Inspection apparatus | |
| CN115917299A (en) | Foreign matter/defect inspection device, image generation device in foreign matter/defect inspection, and foreign matter/defect inspection method | |
| CN115803608A (en) | Foreign matter/defect inspection device, image generation device in foreign matter/defect inspection, and foreign matter/defect inspection method | |
| CA2017031A1 (en) | Apparatus for the measurement of aerosols and dust or the like distributed in air | |
| JPH04151502A (en) | Photosensor device | |
| CN207541269U (en) | All band three-dimensional EO-1 hyperion laser radar | |
| WO1995002179B1 (en) | Misalignment detection apparatus for transmissometer with underfilled reflector | |
| JPH04110707A (en) | Device for measuring three-dimensional shape | |
| JP2796906B2 (en) | Foreign matter inspection device | |
| JPH04110706A (en) | Device for taking three-dimensional form data | |
| JPS61140802A (en) | Light wave interference device preventing reverse surface reflected light | |
| CN213657775U (en) | Symmetrical double-receiving direct-injection type laser triangular displacement sensor |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |