WO2007128316A1 - A method and apparatus for transilluminating objects - Google Patents

A method and apparatus for transilluminating objects Download PDF

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Publication number
WO2007128316A1
WO2007128316A1 PCT/DK2007/000219 DK2007000219W WO2007128316A1 WO 2007128316 A1 WO2007128316 A1 WO 2007128316A1 DK 2007000219 W DK2007000219 W DK 2007000219W WO 2007128316 A1 WO2007128316 A1 WO 2007128316A1
Authority
WO
WIPO (PCT)
Prior art keywords
light
transillumination
objects
light source
detector
Prior art date
Application number
PCT/DK2007/000219
Other languages
French (fr)
Inventor
Arne Holm Carlsen
Hjalti Joensen
Páll FAGRABERG
Original Assignee
Tórshavnar Skipasmiðja P/F
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Tórshavnar Skipasmiðja P/F filed Critical Tórshavnar Skipasmiðja P/F
Publication of WO2007128316A1 publication Critical patent/WO2007128316A1/en

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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
    • G01N21/896—Optical defects in or on transparent materials, e.g. distortion, surface flaws in conveyed flat sheet or rod
    • 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
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/59—Transmissivity
    • 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
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/02—Food
    • G01N33/12—Meat; fish
    • 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
    • G01N2021/845—Objects on a conveyor
    • 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
    • G01N21/86—Investigating moving sheets
    • G01N2021/8609—Optical head specially adapted
    • G01N2021/8627—Optical head specially adapted with an illuminator over the whole width
    • 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
    • G01N21/8806—Specially adapted optical and illumination features
    • G01N2021/8835—Adjustable illumination, e.g. software adjustable screen
    • 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
    • G01N2021/8908—Strip illuminator, e.g. light tube
    • 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
    • G01N21/86—Investigating moving sheets
    • 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
    • G01N21/93—Detection standards; Calibrating baseline adjustment, drift correction
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2201/00—Features of devices classified in G01N21/00
    • G01N2201/12—Circuits of general importance; Signal processing
    • G01N2201/124—Sensitivity

Definitions

  • the invention relates to a method and apparatus for transillu- minating objects, in which the objects are illuminated on one side with transillumination light by means of a transillumination light source, and transmitted transillumination light is received on the other side of the objects by means of a light detector or by an operator, where the transillumination light source emits a transillumination light bundle having a narrow, elongate cross section, and the light source and the objects are moved relative to each other in a direction approximately transverse to the propagation direction of the transillumination light and approximately transverse to the longitudinal direction of the cross section, whereby the objects and the bundle of transillumination light pass each other in such a way that the objects are successively transilluminated in their entire extension, and where the extension of the transillumination light source in the longitudinal direction of the cross section is generally greater than the extension of the objects in the same direction.
  • the object may e.g. be an inhomogeneous, translucent object such as a fish fillet which is to be processed locally, and that the area of the object to be processed is to be localised on the basis of the inner structure of the object. Such processing may only be performed if an overview or a description of the inner structure of the object is available.
  • the objective of the invention is to provide, on the above- mentioned background, the possibility of improved display, recording and/or detection of the inner structure, etc., in a translucent object in connexion with transillumination of the object.
  • a method of the type mentioned at the outset is characteristic in that the local intensity of the transillumination light source is controllable along the longitudinal direction of the cross section, and that it is controlled in dependency of the extension of the objects in the same direction, for the attainment of a lower variation of the intensity of the transillumination light incident onto the light detector.
  • a transillumination light source which is elongate in a direction trans- versely to the direction of conveyance of the objects, where the transillumination light source is able to emit light with different intensities in different portions, such that the intensity of the light emitted from a certain portion of the light source along its longitudinal direction may be controlled independently of the light emitted from other portions of the light source.
  • the portion of the transillumination light that is not incident onto the object and thus flow around the object without transilluminating it may selectively be damped or, preferably, switched off.
  • the light detector will not become illuminated by this light, which naturally will have a high intensity relative to the light passing through the object, and hereby it may be avoided that the light detector be overloaded or saturated by light flowing around the object. If the object is being watched by an operator, similar advantages are obtained, as the operator may avoid being stressed by a relatively strong light flowing round the object and towards the eyes of the operator.
  • the contour of the objects is being detected by means of a first photo detector utilising detection light having wavelengths different from the wavelengths of the transillumination light.
  • the first photo detector has the form of a first light barrier having a narrow, elongate cross section.
  • the local intensity of the light source is further controlled in dependency of the local trans- lucency of the object, for the attainment of a reduced variation of the intensity of the transmitted light incident onto the light detector.
  • the variation of the intensity of the transmitted light flowing towards the light detector or the operator, respectively, after having passed through the object may be controlled, e.g. reduced.
  • the range of variation or dynamic range of the transmitted light is narrowed, and even a detector having a limited dynamic range will capable of making a reliable detection of the variations in the transmitted light which are caused by the variations in the inner structure, etc., of the object.
  • the local translucency of the objects is de- tected by a second photo detector which utilises detection light having wavelengths different from the wavelengths of the transillumination light.
  • the second photo detector preferably has the form of a second light barrier having a narrow, elongate cross section.
  • the local translucency of the objects is detected by means of the first photo detector.
  • the transillumination light source and the light detector are stationary and the objects are being moved, preferably that the latter are being conveyed on a conveyor belt.
  • the utilised light barriers are each preferably divided into two light sub-barriers, each having a narrow, elongate cross section, and the distance between these light sub-barriers is preferably dependent on a pitch of the conveyor belt.
  • conveyor belts in particular in the food-processing industry, may be structured from mechanically interconnected links, including chains or similar, non-translucent and/or non-transparent portions may be present in the belt.
  • the disadvantages caused hereby in respect of reliable transillumination and reliable detection of the types mentioned above may be prevented or considerably reduced by thus dividing light barriers, etc., and arranging the light sub- barriers with such interspacing that the elements of the conveyor belt do not shade all of the light sub-barriers at any one time.
  • a camera preferably a line camera, as light detector.
  • detection with a suitable content of image detail is attained in a convenient and reliable way, thereby ena- bling the performing of a more qualified signal processing of the information content in the detected light.
  • apparatus for transilluminating objects comprising: a transillumination light source for illuminating the objects on one side with a bundle of transillumination light having a narrow, elongate cross section, a light detector for receiving transmitted transillumination light - or a control station for an operator for observing transmitted transillumination light - as well as moving means for moving the light source and the objects relative to each other in a direction approximately transverse to the direction of propagation of the transillumination light and approximately transverse to the longitudinal direction of the cross section, whereby the objects and the transillumination light bundle pass each other in such a way that the objects are successively transilluminated in their entire extension, is according to the invention characteristic in that the local intensity of the transillumination light source along the longitudinal direction of the cross section is controllable in dependency of the extension of the objects in the same direction, for the attainment of a reduced variation of the intensity of the transillumination light incident on the light detector.
  • the transillumination light source is preferably built from a number of light sources which are individually controllable and which are preferably arranged in one or more rows.
  • an elongated light source is provided in an advantageous and simple way, the intensity of which is locally controllable, that is, by controlling the intensity of each individual light source.
  • the contour of the objects is detected by means of a first photo detector which utilises detection light having wavelengths that are different from the wavelengths of the transillumination light.
  • the first photo detector preferably has the form of a first light barrier with a narrow, elongate cross section.
  • the apparatus comprises detector means connected to the first light barrier and adapted to detecting the extension of the object on the basis of signals from the first light barrier, as well as computing means for calculating a desired distribution of the transillumination light in dependence of the extension of the object, and control means for controlling an intensity distribution for the transillumination light source in accordance therewith.
  • the apparatus comprises a second photo detector for detecting the local translucency of the objects by means of detection light having wavelengths that are different from the wavelengths of the transillumination light.
  • the second photo detector has preferably the form of a second light barrier having a narrow, elongate cross section.
  • the apparatus comprises detector means connected to the second light barrier and adapted to detecting the local translucency of the object on the basis of signals from the second light barrier, as well as computing means for calculating a desired intensity distribution of the transillumination light in de- pendency of the local translucency of the object, and control means for controlling a desired intensity distribution for the transillumination light source in accordance therewith.
  • the first photo detector and the second photo detector are constituted by one and the same photo detector.
  • the transillumination light source and the light detector, or the operator control station, respectively are stationary and that the apparatus comprises a conveying means such as a conveyor belt for conveying the objects past the transillumination light source and the light detector, or the operator control station, respectively.
  • the light barrier is divided into two light sub-barriers, each having a narrow, elongate cross section, and the distance between these two light sub-barriers is chosen in dependency of a pitch in the conveyor belt.
  • the light detector is a camera, preferably a line camera.
  • a machine for boning and trimming fish fillets is characteristic in comprising apparatus according to the invention for transilluminating objects.
  • Fig. 1 shows a schematic diagram of a machine according to the invention, for boning and trimming fish fillets
  • Fig. 2 shows a schematic side view of part of the contents of a transillumination station in Fig. 1;
  • Figs 3-5 show consecutive moments during the introduction of the leading end of a fish fillet into a transillumination station in apparatus according to the invention.
  • slaughtering and processing fish for consumption is to a large extent performed in automatic plants.
  • Plants for processing fish fillets are known, and are generally structured around a conveyor belt, on which the fillets are conveyed.
  • a preferred embodiment of the invention is thus mounted on a machine comprising such a conveyor belt, please refer to Fig. 1.
  • Fish fillets 1 are conveyed on a conveyor belt 3 in a direction of conveyance 2.
  • a number of stations 4 for sorting out, sorting, boning, trimming, etc., of the fish fillets 1 are present in ways known per se. These stations and similar facilities will not be further dealt with in the present application.
  • a transillumination station 7 where transillumination according to the invention takes place.
  • the transillumination station 7 as well as the rest of the stations 4 mentioned is connected to a control unit 6 by means of signal cables 5 or in other suitable ways.
  • the control unit 6 may be structured, and may function, in any suitable way, most often according to principles known per se. Accordingly, the control unit 6 will generally comprise one or more computers, and will, besides this, not be considered any further in the present application. According to the invention, there is in the transillumination station 7 performed transillumination of the fillets and detecting and recording of the properties of every single fillet, that is, of the properties which are of importance in the subsequent sorting and processing of the fillet in the stations 4.
  • Fig. 2 illustrates the principle of an arrangement of transillumination light (light for illumination of the fillets by transillumination) and detection light (light for detection of the location, etc., of the fillets) in the transillumination station 7.
  • a transillumination light source 10 has been mounted below the conveyor belt 3, the transillumination light source 10 emitting light in the form of a light bundle 14 in the direction towards a light detector 11, which is mounted above the conveyor belt 3.
  • the conveyor belt 3 is translucent, e.g. by being made from wire mesh or as links in a chain forming the conveyor belt.
  • the conveyor belt 3 may alternatively be made from a translucent material.
  • the bundle 14 of light from the transillumination light source 10 thus penetrate the fish fillet 1 and flow on towards the light detector 11.
  • the fish fillet 1 will probably diffuse the light rather much, but sufficient light will still be incident onto the light detector 11. If the light detector 11 is imaging, e.g. by being made as a camera or a line camera, a well exposed image of the fish fillet 1 will be created in any case, the fillet being illuminated efficiently by the transmitted light 14.
  • the transillumination light source 10 is elongate in a direction orthogonal to the plane of the paper in Fig.
  • a band of the fish fillet 1 is thus illuminated, the band extending transversely to the plane of the paper and transversely to the direction of conveyance 2.
  • a scanning of the fish fillet 1 takes place in its entire extension, as the fish fillet 1 is conveyed in the direction 2, the latter thus being orthogonal to the extension of the transillumination light source 10.
  • the transillumination light source 10 is according to the invention switched off when no fish fillet 1 is present above the transillumination light source 10.
  • the transillumination light source 10 has to be switched off temporally, that is, until the fish fillet 1 reaches the transillumination light source 10 and after the fish fillet 1 has passed the light source, and locally, that is, the portions of the transillumination light source 10 extending outside the extension of the fillet must be switched off; these will in general be a portion at each of the ends of the elongate transillumination light source. In this way, exactly those portions of the transillumination light source 10, which are at any given moment located beneath the fish fillet 1, will become switched on, whereby the light detector 11 will not at any time be exposed to direct lighting from the transillumination light source 10.
  • An appropriate structuring of such a transillumination light source 10 may according to the invention be to divide the transillumina- tion light source 10 into a series of light sources which may be switched on and off separately. This may e.g. be attained by structuring the transillumination light source 10 as a row of closely spaced light emitting diodes which may be switched on and off separately, controlled by a suitable control device.
  • the control device must thereby control the switch- ing of the individual light sources in dependency of the extension of the fish fillet 1 and its conveyance on the conveyor belt 3 in the direction of conveyance 2.
  • a detection light source 12 is arranged above the conveyor belt 3, and this light source emits detection light in a bundle 15 directed towards approximately the same place on the conveyor belt 3 as is illuminated by the transillumination light source 10.
  • a first photo detector 13 is arranged below the conveyor belt 3, to receive the detection light bundle 15 from the detection light source 12. All of the detection light source 12, the first photo detector 13 and the bundle 15 of detection light have corresponding extensions in the transverse direction of the conveyor belt 3 (that is, transversely to the plane of the paper in Fig. 2) as have the transillumination light source 10 and the light detector 11.
  • the bundle 15 of detection light hereby constitutes a first light barrier, that is, a barrier which consists of light and which may thus be interrupted by an object or a body, and where a reaction may be trigged as the barrier is interrupted.
  • a barrier is often informally mentioned as a 'photo cell', the expression 'light barrier' traditionally designating light source, light bundle and photo detector together.
  • the detection light it is preferred to utilise infra-red light outside the visible spectrum as detection light.
  • the detection light will not disturb the light detector or the light detectors used for the transillumination, and will likewise not disturb possible human operators.
  • the skilled person will be able to make other suitable choices, such as light of different colours.
  • the detection light source 12 emits detection light constantly, in order to being ready all the time for detecting arriving fish fillets 1.
  • the first photo detector 13 is adapted to local detection of interruption of the detection light, that is, the first photo detector 13 is able to detect through which portions and for which length, transversely to the direction 2 of conveyance, the detection light has been inter- rupted, and is thus able to detect the extension, transversely to the direction 2 of conveyance, of a fish fillet 1 which is interrupting the rays of the detection light.
  • An appropriate structuring of such a first photo detector 13 may according to the invention be to divide the first photo detector 13 into a series of detectors, each of which are able to detect presence or absence of the detection light from the detection light source 12. This may e.g. be attained by structuring the first photo detector 13 as a row of closely spaced photo diodes, each of which is sending a signal to a suit- able control device.
  • the control device to record in which fraction of the width of the conveyor belt 3 the detection light is being interrupted by a fish fillet 1 being conveyed on the conveyor belt 3, and to switch on light emitting diodes in the transillumination light source 10, corresponding to the same width. If the fish fillet 1 may be split, or fish fillets are conveyed in more than one row on the belt, the control device, etc., may be adapted to switching on light emitting diodes in more than one width interval, corresponding to the width intervals in which the rays of the detection light has been interrupted. Fig.
  • a conveyor belt 3 which is to be utilised in the food processing industry with the consequent requirements to cleaning and hygiene and which must be able to be trans- illuminated for use with the invention, may be structured as a form of chain in the desired width and with links interconnected by hinges. In such a conveyor belt, it may be difficult to avoid interruptions of the light flows involved. In a particular embodiment, which is shown in Figs 3-5, means are provided for avoiding this disadvantage.
  • the conveyor belt 3 is seen to contain transversely extending shafts 20 which are placed in the belt at a fixed pitch 21.
  • a shaft 20 will be able to interrupt the bundle 15 of detection light (Fig. 2), and in order to avoid this disadvantage, the detection light is in the embodiment in Fig. 3 divided into two bundles 22 and 23 intersecting the plane of the conveyor belt 3 with an interspace 24 which differs substantially from an integer multiple of the pitch 21, e.g. by constituting Vi or Vh times the magnitude of the pitch 21.
  • the first light barrier which is constituted by the detection light, is thus divided into two light sub-barriers 22 and 23 in Figs 3-5.
  • the bundle 22 of detection light is emitted by a detection light source 25 and received by a photo detector 26, and the bundle 23 of detection light is emitted by a detection light source 27 and received by a photo detector 28. If one of these light sub-barriers is interrupted, it will in general be due to a shaft 20 in the conveyor belt 3, whereas both light sub-barriers 22, 23 will be interrupted if a fish fillet 1 is present on the conveyor belt 3.
  • Fig. 4 a fish fillet 1 which is conveyed in the direction 2 of conveyance (from the right in Fig. 3-5) has interrupted the bundle 23 of detection light, but not the bundle 22 of detection light.
  • Fig. 5 the fish fillet 1 has interrupted both bundles 22, 23 of detection light, whereby its presence will be detected by the control device in the control unit 6.
  • a transillumination light source 29 has been positioned, in the embodiment of Figs 3-5, which is able to emit a light bundle vertically upwards towards the fish fillet 1, through this and further towards a light detector in the form of a camera 30.
  • the camera may be a line camera, by which is to be understood in the present context a camera which does perform a proper imaging, but only of a narrow, elongate area - in this connexion a narrow band of the fish fillets 1 in the transverse direction of the conveyor belt 3.
  • the field of sight of the camera 30 is illustrated in Fig. 3 by the angle 32.
  • the control device When the presence of a fish fillet 1 has been detected as de- scribed above, the control device accordingly induces that the portion of a transillumination light source 29, situated below the fish fillet 1, lights up, as is illustrated in Fig. 5.
  • An upward directed bundle 31 of light is hereby emitted from the transillumination light source 29 in the direction towards the fish fillet 1.
  • Part of the light flows through the fish fil- let 1 and further towards the camera 30, or, more specifically, the fish fillet 1 is illuminated by the transillumination light, and the camera 30 photographs ("sees") the thus illuminated, narrow band of the fish fillet 1.
  • the transillumination light source 29 lights up only along those portions in its longitudinal direction, which are situated below portions of the fish fillet 1.
  • the longitudinal direction of the light source is hereby orthogonal to the plane of the paper in Figs 3-5.
  • the images recorded by the camera or line camera 30 are sent along to the control unit 6 as image data.
  • image data may be created in the control unit, representing the whole of the fish fillet 1, and these image data will be suitable for forming the basis for the desired processing of the fish fillet, in ways which are known per se.
  • the control unit may e.g. create process- ing instructions from image data, and pass on these to the stations 4, for sorting out, sorting, boning, trimming, etc., of the fish fillets 1.
  • the detection light is utilised as well for detecting the translucency of the fish fillets 1.
  • the detection light sources 12, 25, 27 and the photo detectors 13, 26, 28 are in this embodiment adapted to being able to transilluminate the fish fillets 1 completely or partly, the detection light must i.a. have a sufficient intensity for being receivable and detectable on the other side of the fish fillets 1.
  • the photo detectors 13, 26, 28 must be suitable for detecting the intensity of the detection light transmitted through the fillets, and for delivering a translucency signal in dependency of the translucency of the fish fillets 1. According to the invention, this translucency signal as well will vary in accordance with the local translucency along the extension of the detection light sources in the di- rection of the transverse direction of the conveyor belt 3.
  • the transillumination light source 10, 9 is adapted to being controllable for emitting transillumination light with a variable intensity, controlled by a control signal.
  • the intensity is controllable in time as well as in place, that is, the intensity must be controlla- ble in time, in dependency of the momentary translucency signal from the photo detectors, and in place, that is, for every spot or width interval across the width of the fish fillets 1, the intensity must be variable in dependency of the momentary, local translucency.
  • the system is preferably controlled in such a way that areas where the fish fillets 1 have a low translucency, will be illuminated with transillumination light having a higher intensity, and conversely: areas where the fish fillets 1 have a high translucency are being illuminated with transillumination light having a lower intensity.
  • the intensity variation of the transmitted transillumination light incident onto the light detector 11, or the camera 30, respectively may be kept within other limits than the variation of the translucency of the fish fillets 1.
  • the system is thus adjustable to reduce the intensity variation, to keep the lowest occurring intensity of the transmitted transillumination light incident onto light detector or camera above a certain value, and to keep the highest occurring intensity below another, certain value.
  • the apparatus according to the invention may be manufac- tured with light detectors or cameras having limited intensity ranges, and nevertheless provide a fully satisfying imaging of the translucency variation of the fish fillets, even if light detector or camera is not able to process such large variation.
  • the camera 30 delivers a continuous flow of image data, which are suitable for being assembled in the circuits of the control unit into complete image data for each individual fish fillet.
  • the apparatus according to the invention creates these complete image data in such a way that there is an unambiguous correspondence between the structure of the fish fillets and the contents of the image data, in quantity as well as in quality.
  • fish bones do not give rise to detectable shadows or translucency variations, and they are thus not directly detectable.
  • detection is according to the invention preferably performed by detecting those translucency variations that are manifestations of the course of groups of muscles and other structures in the interior of the fillets.
  • the positions of the bones may subsequently be estimated.
  • the invention will give excellent satisfaction by providing a tailored and purposeful transilluminating of the object, where the operator will not be subjected to the relatively strong light which would otherwise flow around the objects, and not be subjected to the relatively strong light which would otherwise flow through the most translucent portions of the objects.
  • lighting that is, transillumination

Abstract

In a method for transilluminating objects, the objects are illuminated and transmitted light is being received by a light detector. The objects are illuminated by a light bundle having an elongate cross section, and light source and objects are moved relative to each other, whereby the objects are successively transilluminated. The local intensity of the transillumination light source along the longitudinal direction of the cross section is preferably controllable, and it is preferably controlled in dependency of the extension of the objects for the attainment of reduced variation of the intensity of the transillumination light incident onto the light detector.

Description

A METHOD AND APPARATUS FOR TRANSILLUMINATING OBJECTS
The invention relates to a method and apparatus for transillu- minating objects, in which the objects are illuminated on one side with transillumination light by means of a transillumination light source, and transmitted transillumination light is received on the other side of the objects by means of a light detector or by an operator, where the transillumination light source emits a transillumination light bundle having a narrow, elongate cross section, and the light source and the objects are moved relative to each other in a direction approximately transverse to the propagation direction of the transillumination light and approximately transverse to the longitudinal direction of the cross section, whereby the objects and the bundle of transillumination light pass each other in such a way that the objects are successively transilluminated in their entire extension, and where the extension of the transillumination light source in the longitudinal direction of the cross section is generally greater than the extension of the objects in the same direction.
It is known to watch inhomogeneous, translucent objects such as fish fillets in transmitted light (light passing through the object), whereby the inner structure of the object may be judged in more detail, cf. e.g. WO 03/034049, where this is disclosed as prior art in connexion with Fig. 1 in that document.
From the same document, it is further known to convey fish fillets on a conveyor belt, whereby a band of the belt, transverse to the direction of movement of the belt, is illuminated from below with light illuminating the fish fillets, and the fillets are being photographed from above with a camera. The fillets may at the same time be illuminated with slanting light from above by means of a laser or similar.
From US 6,604,991, it is known to illuminate the fish fillets in a similar configuration with slanting light from above by means of more than one light source, one of the light sources being partly screened with a shading element, whereby a light-shadow transition in the slanting, partly screened light may reproduce the thickness of the fillets as variations in the light-shadow transition, as seen from above. It is a disadvantage of the thus known art that illumination conditions cannot be provided with the disclosed means and teachings, which enable a sufficiently detailed overview of the inner structure of an inhomogeneous, translucent object for performing mechanical handling, processing and similar of the object with a satisfactory result.
The object may e.g. be an inhomogeneous, translucent object such as a fish fillet which is to be processed locally, and that the area of the object to be processed is to be localised on the basis of the inner structure of the object. Such processing may only be performed if an overview or a description of the inner structure of the object is available.
The objective of the invention is to provide, on the above- mentioned background, the possibility of improved display, recording and/or detection of the inner structure, etc., in a translucent object in connexion with transillumination of the object.
For the purpose of meeting this objective, a method of the type mentioned at the outset is characteristic in that the local intensity of the transillumination light source is controllable along the longitudinal direction of the cross section, and that it is controlled in dependency of the extension of the objects in the same direction, for the attainment of a lower variation of the intensity of the transillumination light incident onto the light detector.
According to the invention, there is in other words provided a transillumination light source which is elongate in a direction trans- versely to the direction of conveyance of the objects, where the transillumination light source is able to emit light with different intensities in different portions, such that the intensity of the light emitted from a certain portion of the light source along its longitudinal direction may be controlled independently of the light emitted from other portions of the light source.
Hereby, it is attained that the portion of the transillumination light that is not incident onto the object and thus flow around the object without transilluminating it, may selectively be damped or, preferably, switched off. In this way, the light detector will not become illuminated by this light, which naturally will have a high intensity relative to the light passing through the object, and hereby it may be avoided that the light detector be overloaded or saturated by light flowing around the object. If the object is being watched by an operator, similar advantages are obtained, as the operator may avoid being stressed by a relatively strong light flowing round the object and towards the eyes of the operator.
It is preferred that the contour of the objects is being detected by means of a first photo detector utilising detection light having wavelengths different from the wavelengths of the transillumination light. Preferably, the first photo detector has the form of a first light barrier having a narrow, elongate cross section.
By detecting the contour of the object with a photo detector or a light barrier, respectively, a convenient and efficient detection of the contour of the object is attained, and by letting this detector or barrier function with light having a wavelength or wavelengths different from wavelength(s) of the transillumination light, a considerably diminished risk is attained of the functioning of the detector or barrier being dis- turbed by the light from the transillumination light source.
In a particularly preferred embodiment, the local intensity of the light source is further controlled in dependency of the local trans- lucency of the object, for the attainment of a reduced variation of the intensity of the transmitted light incident onto the light detector. Hereby, it is attained that the variation of the intensity of the transmitted light flowing towards the light detector or the operator, respectively, after having passed through the object, may be controlled, e.g. reduced.
In particular in the case of objects of natural origin, such as fish fillets or fish meat in general, it is frequently a problem that the trans- lucency of the object varies relatively greatly along the extension of the object. This may cause problems in detecting (or observing) the transmitted light, if the dynamic range or the effective intensity range of the detector is less than the actual variation of the intensity of the transmit- ted light. This condition is notoriously often present and gives rise to saturation phenomena in the detection, and such phenomena almost certainly lead to uncertain detection of either very translucent or very little translucent portions of the object. By controlling the local intensity of the transillumination light source as mentioned, it may be attained that very translucent portions of the object are illuminated with a relatively dim light, and not very translucent portions of the object are illuminated with a relatively intense light. In this way, the range of variation or dynamic range of the transmitted light is narrowed, and even a detector having a limited dynamic range will capable of making a reliable detection of the variations in the transmitted light which are caused by the variations in the inner structure, etc., of the object.
It is preferred that the local translucency of the objects is de- tected by a second photo detector which utilises detection light having wavelengths different from the wavelengths of the transillumination light. The second photo detector preferably has the form of a second light barrier having a narrow, elongate cross section.
In this way, similar advantages are attained as explained above with reference to detecting the contour of the objects.
In a simplified, preferred embodiment, the local translucency of the objects is detected by means of the first photo detector.
By thus utilising the same photo detector for both detections, an advantageous simplifying of the method of the invention is obtained. It is preferred that the transillumination light source and the light detector (or the operator, respectively) are stationary and the objects are being moved, preferably that the latter are being conveyed on a conveyor belt.
This entails a reliable structure with limited movable masses, and the method of the invention in this embodiment is very efficiently incorporated into a production plant or similar, where objects are being moved through the plant during manufacturing or preparation.
In this connexion, the utilised light barriers are each preferably divided into two light sub-barriers, each having a narrow, elongate cross section, and the distance between these light sub-barriers is preferably dependent on a pitch of the conveyor belt.
Since conveyor belts, in particular in the food-processing industry, may be structured from mechanically interconnected links, including chains or similar, non-translucent and/or non-transparent portions may be present in the belt. According to the invention, the disadvantages caused hereby in respect of reliable transillumination and reliable detection of the types mentioned above, may be prevented or considerably reduced by thus dividing light barriers, etc., and arranging the light sub- barriers with such interspacing that the elements of the conveyor belt do not shade all of the light sub-barriers at any one time.
Finally, it is preferred to use a camera, preferably a line camera, as light detector. In this way, detection with a suitable content of image detail is attained in a convenient and reliable way, thereby ena- bling the performing of a more qualified signal processing of the information content in the detected light.
Further, for the purpose of meeting the objective of the invention, apparatus for transilluminating objects and comprising: a transillumination light source for illuminating the objects on one side with a bundle of transillumination light having a narrow, elongate cross section, a light detector for receiving transmitted transillumination light - or a control station for an operator for observing transmitted transillumination light - as well as moving means for moving the light source and the objects relative to each other in a direction approximately transverse to the direction of propagation of the transillumination light and approximately transverse to the longitudinal direction of the cross section, whereby the objects and the transillumination light bundle pass each other in such a way that the objects are successively transilluminated in their entire extension, is according to the invention characteristic in that the local intensity of the transillumination light source along the longitudinal direction of the cross section is controllable in dependency of the extension of the objects in the same direction, for the attainment of a reduced variation of the intensity of the transillumination light incident on the light detector. Hereby, similar advantages are attained as explained above with reference to the method of the invention.
The transillumination light source is preferably built from a number of light sources which are individually controllable and which are preferably arranged in one or more rows.
In this way, an elongated light source is provided in an advantageous and simple way, the intensity of which is locally controllable, that is, by controlling the intensity of each individual light source.
By arranging the light sources in several rows, taking into ac- count a pitch of a conveyor belt, corresponding advantages may be attained as explained above with reference to the method of the invention.
It is preferred that the contour of the objects is detected by means of a first photo detector which utilises detection light having wavelengths that are different from the wavelengths of the transillumination light. The first photo detector preferably has the form of a first light barrier with a narrow, elongate cross section.
By these measures, corresponding advantages are attained as explained above with reference to the method of the invention. In this connexion, it is preferred that the apparatus comprises detector means connected to the first light barrier and adapted to detecting the extension of the object on the basis of signals from the first light barrier, as well as computing means for calculating a desired distribution of the transillumination light in dependence of the extension of the object, and control means for controlling an intensity distribution for the transillumination light source in accordance therewith.
In this way, a particularly simple and advantageous control of the intensity variation of the transillumination light according to the invention is attained. In addition, it is preferred that the apparatus comprises a second photo detector for detecting the local translucency of the objects by means of detection light having wavelengths that are different from the wavelengths of the transillumination light. The second photo detector has preferably the form of a second light barrier having a narrow, elongate cross section.
By these measures, corresponding advantages are attained as explained above with reference to the method of the invention. In this connexion, it is preferred that the apparatus comprises detector means connected to the second light barrier and adapted to detecting the local translucency of the object on the basis of signals from the second light barrier, as well as computing means for calculating a desired intensity distribution of the transillumination light in de- pendency of the local translucency of the object, and control means for controlling a desired intensity distribution for the transillumination light source in accordance therewith.
In this way, a particularly simple and advantageous control of the intensity variation of the transillumination light according to the in- vention is attained.
In a preferred and particularly simple embodiment, the first photo detector and the second photo detector are constituted by one and the same photo detector.
Experiments have shown that by utilising one photo detector, a reliable control of the transillumination light in dependency of the extension of the objects as well as the local translucency of the objects is attainable, and that the simplification thus obtained of the apparatus does contribute to lower costs and increased reliability.
It is generally preferred that the transillumination light source and the light detector, or the operator control station, respectively, are stationary and that the apparatus comprises a conveying means such as a conveyor belt for conveying the objects past the transillumination light source and the light detector, or the operator control station, respectively. By these measures, corresponding advantages are attained as explained above with reference to the method of the invention.
In a particular embodiment, the light barrier is divided into two light sub-barriers, each having a narrow, elongate cross section, and the distance between these two light sub-barriers is chosen in dependency of a pitch in the conveyor belt.
It is further preferred that the light detector is a camera, preferably a line camera. By these measures, corresponding advantages are attained as explained above with reference to the method of the invention.
Finally, for the purpose of meeting the above-mentioned objective, a machine for boning and trimming fish fillets is characteristic in comprising apparatus according to the invention for transilluminating objects.
It has surprisingly appeared that by basing detecting of appearances of fish bone and of various imperfections in fish fillets on the method and the apparatus of the invention, in connexion with machine processing of fish meat into consumer goods such as in particular fish fillets, a considerably improved detection and localising of bones and imperfections in the meat, and thereby an increased probability for such bones and imperfection being removable in a reliable and efficient way by subsequent machine processing of the fish meat or the fish fillets, respectively. According to the invention, it is preferred to utilise light outside the visible spectrum, preferably infra-red light, as detection light. Hereby, it is attained that the detection light will not interfere with the light detector or the light detectors utilised for the transillumination, and will not disturb possible human operators either. The invention will now be explained in more detail below with reference to the drawings, in which:
Fig. 1 shows a schematic diagram of a machine according to the invention, for boning and trimming fish fillets;
Fig. 2 shows a schematic side view of part of the contents of a transillumination station in Fig. 1; and
Figs 3-5 show consecutive moments during the introduction of the leading end of a fish fillet into a transillumination station in apparatus according to the invention. In present days, slaughtering and processing fish for consumption is to a large extent performed in automatic plants. As in many other automated processes of this nature, it has so far not been possible to reach fully satisfactory quality of the processing as compared to the re- suits attainable by letting operators perform the processing the traditional way.
In this connexion, it has in particular been difficult to attain satisfactory detection of fish bone and of defects and imperfections such as parasites or other in the meat. Even quite small bones, which most of- ten may have optical properties differing astonishingly little from those of the surrounding fish meat, will constitute an annoyance for the consumer, and it is thus of utmost importance for manufacturers of fish for consumption that all bones, etc., are efficiently removed from fish meat to be sold as e.g. fillets. While carved fish fillets with bones have optical properties which in themselves render satisfactory detection of bones, etc., difficult, carved fillets vary quite much in size and shape, depending on species and size of the fish of origin. It is thus disproportionately difficult to perform automatic boning and trimming of fish fillets, based on their size and shape.
Plants for processing fish fillets are known, and are generally structured around a conveyor belt, on which the fillets are conveyed. A preferred embodiment of the invention is thus mounted on a machine comprising such a conveyor belt, please refer to Fig. 1. Fish fillets 1 are conveyed on a conveyor belt 3 in a direction of conveyance 2. In a downstreams portion of the conveyor belt 3, a number of stations 4 for sorting out, sorting, boning, trimming, etc., of the fish fillets 1 are present in ways known per se. These stations and similar facilities will not be further dealt with in the present application. In an upstreams portion of the conveyor belt 3, there is according to the invention provided a transillumination station 7, where transillumination according to the invention takes place. The transillumination station 7 as well as the rest of the stations 4 mentioned is connected to a control unit 6 by means of signal cables 5 or in other suitable ways. The control unit 6 may be structured, and may function, in any suitable way, most often according to principles known per se. Accordingly, the control unit 6 will generally comprise one or more computers, and will, besides this, not be considered any further in the present application. According to the invention, there is in the transillumination station 7 performed transillumination of the fillets and detecting and recording of the properties of every single fillet, that is, of the properties which are of importance in the subsequent sorting and processing of the fillet in the stations 4. These properties are recorded as data related to the location of every single fillet on the conveyor belt 3, so that the fillet may subsequently be processed only on the basis of data for the conveying of the conveyor belt 3 and data for the positions of the recorded properties in the transverse direction of the conveyor belt 3. The skilled person will be able to indicate suitable methods and techniques for this, on the basis of the present specification.
Fig. 2 illustrates the principle of an arrangement of transillumination light (light for illumination of the fillets by transillumination) and detection light (light for detection of the location, etc., of the fillets) in the transillumination station 7. A transillumination light source 10 has been mounted below the conveyor belt 3, the transillumination light source 10 emitting light in the form of a light bundle 14 in the direction towards a light detector 11, which is mounted above the conveyor belt 3. The conveyor belt 3 is translucent, e.g. by being made from wire mesh or as links in a chain forming the conveyor belt. The conveyor belt 3 may alternatively be made from a translucent material.
As the conveyor belt 3 is conveying a fish fillet 1 in the direction 2, as shown in Fig. 2, the bundle 14 of light from the transillumination light source 10 thus penetrate the fish fillet 1 and flow on towards the light detector 11. The fish fillet 1 will probably diffuse the light rather much, but sufficient light will still be incident onto the light detector 11. If the light detector 11 is imaging, e.g. by being made as a camera or a line camera, a well exposed image of the fish fillet 1 will be created in any case, the fillet being illuminated efficiently by the transmitted light 14. The transillumination light source 10 is elongate in a direction orthogonal to the plane of the paper in Fig. 2, and with the arrangement shown, a band of the fish fillet 1 is thus illuminated, the band extending transversely to the plane of the paper and transversely to the direction of conveyance 2. In this way, a scanning of the fish fillet 1 takes place in its entire extension, as the fish fillet 1 is conveyed in the direction 2, the latter thus being orthogonal to the extension of the transillumination light source 10.
In order to avoid overdriving or saturating the light detector 11, the transillumination light source 10 is according to the invention switched off when no fish fillet 1 is present above the transillumination light source 10. In order to efficiently avoid overdriving, the transillumination light source 10 has to be switched off temporally, that is, until the fish fillet 1 reaches the transillumination light source 10 and after the fish fillet 1 has passed the light source, and locally, that is, the portions of the transillumination light source 10 extending outside the extension of the fillet must be switched off; these will in general be a portion at each of the ends of the elongate transillumination light source. In this way, exactly those portions of the transillumination light source 10, which are at any given moment located beneath the fish fillet 1, will become switched on, whereby the light detector 11 will not at any time be exposed to direct lighting from the transillumination light source 10.
An appropriate structuring of such a transillumination light source 10 may according to the invention be to divide the transillumina- tion light source 10 into a series of light sources which may be switched on and off separately. This may e.g. be attained by structuring the transillumination light source 10 as a row of closely spaced light emitting diodes which may be switched on and off separately, controlled by a suitable control device. The control device must thereby control the switch- ing of the individual light sources in dependency of the extension of the fish fillet 1 and its conveyance on the conveyor belt 3 in the direction of conveyance 2.
For the purpose of enabling such a control, there is according to the invention provided means for detecting the extension of the fish fil- lets 1, e.g. in the way illustrated in Fig. 2. A detection light source 12 is arranged above the conveyor belt 3, and this light source emits detection light in a bundle 15 directed towards approximately the same place on the conveyor belt 3 as is illuminated by the transillumination light source 10. Below the conveyor belt 3, a first photo detector 13 is arranged to receive the detection light bundle 15 from the detection light source 12. All of the detection light source 12, the first photo detector 13 and the bundle 15 of detection light have corresponding extensions in the transverse direction of the conveyor belt 3 (that is, transversely to the plane of the paper in Fig. 2) as have the transillumination light source 10 and the light detector 11.
The bundle 15 of detection light hereby constitutes a first light barrier, that is, a barrier which consists of light and which may thus be interrupted by an object or a body, and where a reaction may be trigged as the barrier is interrupted. Such a barrier is often informally mentioned as a 'photo cell', the expression 'light barrier' traditionally designating light source, light bundle and photo detector together.
According to the invention, it is preferred to utilise infra-red light outside the visible spectrum as detection light. Hereby, it is at- tained that the detection light will not disturb the light detector or the light detectors used for the transillumination, and will likewise not disturb possible human operators. The skilled person will be able to make other suitable choices, such as light of different colours.
The detection light source 12 emits detection light constantly, in order to being ready all the time for detecting arriving fish fillets 1.
The first photo detector 13 is adapted to local detection of interruption of the detection light, that is, the first photo detector 13 is able to detect through which portions and for which length, transversely to the direction 2 of conveyance, the detection light has been inter- rupted, and is thus able to detect the extension, transversely to the direction 2 of conveyance, of a fish fillet 1 which is interrupting the rays of the detection light.
An appropriate structuring of such a first photo detector 13 may according to the invention be to divide the first photo detector 13 into a series of detectors, each of which are able to detect presence or absence of the detection light from the detection light source 12. This may e.g. be attained by structuring the first photo detector 13 as a row of closely spaced photo diodes, each of which is sending a signal to a suit- able control device.
Following this, it is the task of the control device to record in which fraction of the width of the conveyor belt 3 the detection light is being interrupted by a fish fillet 1 being conveyed on the conveyor belt 3, and to switch on light emitting diodes in the transillumination light source 10, corresponding to the same width. If the fish fillet 1 may be split, or fish fillets are conveyed in more than one row on the belt, the control device, etc., may be adapted to switching on light emitting diodes in more than one width interval, corresponding to the width intervals in which the rays of the detection light has been interrupted. Fig. 2 hints that the transillumination light and the detection light flow in each their plane, the directions of which differ from the vertical, whereby the planes intersect in the plane of the conveyor belt 3. This is only one among many possible arrangements for meeting the requirement that space must be provided for both light sources 10, 12 and both detectors 11, 13, while at the same time both types of light must be directed towards substantially the same portion of the conveyor belt 3.
Even if the detection light is showed as flowing downwards from above in Fig. 2, nothing will prevent that the opposite direction be cho- sen. Another arrangement of transillumination light and detection light is mentioned below, and the skilled person will be able to indicate further arrangements on the background of the explanations in the present specification.
As it is mentioned briefly above, a conveyor belt 3, which is to be utilised in the food processing industry with the consequent requirements to cleaning and hygiene and which must be able to be trans- illuminated for use with the invention, may be structured as a form of chain in the desired width and with links interconnected by hinges. In such a conveyor belt, it may be difficult to avoid interruptions of the light flows involved. In a particular embodiment, which is shown in Figs 3-5, means are provided for avoiding this disadvantage.
In Figs 3-5, the conveyor belt 3 is seen to contain transversely extending shafts 20 which are placed in the belt at a fixed pitch 21. Such a shaft 20 will be able to interrupt the bundle 15 of detection light (Fig. 2), and in order to avoid this disadvantage, the detection light is in the embodiment in Fig. 3 divided into two bundles 22 and 23 intersecting the plane of the conveyor belt 3 with an interspace 24 which differs substantially from an integer multiple of the pitch 21, e.g. by constituting Vi or Vh times the magnitude of the pitch 21. The first light barrier, which is constituted by the detection light, is thus divided into two light sub-barriers 22 and 23 in Figs 3-5.
The bundle 22 of detection light is emitted by a detection light source 25 and received by a photo detector 26, and the bundle 23 of detection light is emitted by a detection light source 27 and received by a photo detector 28. If one of these light sub-barriers is interrupted, it will in general be due to a shaft 20 in the conveyor belt 3, whereas both light sub-barriers 22, 23 will be interrupted if a fish fillet 1 is present on the conveyor belt 3.
The former of these situations is illustrated in Fig. 4; a fish fillet 1 which is conveyed in the direction 2 of conveyance (from the right in Fig. 3-5) has interrupted the bundle 23 of detection light, but not the bundle 22 of detection light. The latter situation is illustrated in Fig. 5; here, the fish fillet 1 has interrupted both bundles 22, 23 of detection light, whereby its presence will be detected by the control device in the control unit 6.
Between the two photo detectors 26, 28, a transillumination light source 29 has been positioned, in the embodiment of Figs 3-5, which is able to emit a light bundle vertically upwards towards the fish fillet 1, through this and further towards a light detector in the form of a camera 30. Advantageously, the camera may be a line camera, by which is to be understood in the present context a camera which does perform a proper imaging, but only of a narrow, elongate area - in this connexion a narrow band of the fish fillets 1 in the transverse direction of the conveyor belt 3. The field of sight of the camera 30 is illustrated in Fig. 3 by the angle 32.
When the presence of a fish fillet 1 has been detected as de- scribed above, the control device accordingly induces that the portion of a transillumination light source 29, situated below the fish fillet 1, lights up, as is illustrated in Fig. 5. An upward directed bundle 31 of light is hereby emitted from the transillumination light source 29 in the direction towards the fish fillet 1. Part of the light flows through the fish fil- let 1 and further towards the camera 30, or, more specifically, the fish fillet 1 is illuminated by the transillumination light, and the camera 30 photographs ("sees") the thus illuminated, narrow band of the fish fillet 1.
According to the invention, and as has been explained above, the transillumination light source 29 lights up only along those portions in its longitudinal direction, which are situated below portions of the fish fillet 1. The longitudinal direction of the light source is hereby orthogonal to the plane of the paper in Figs 3-5.
The images recorded by the camera or line camera 30 are sent along to the control unit 6 as image data. On the basis of those continuous image data, image data may be created in the control unit, representing the whole of the fish fillet 1, and these image data will be suitable for forming the basis for the desired processing of the fish fillet, in ways which are known per se. The control unit may e.g. create process- ing instructions from image data, and pass on these to the stations 4, for sorting out, sorting, boning, trimming, etc., of the fish fillets 1.
In a particularly preferred embodiment, the detection light is utilised as well for detecting the translucency of the fish fillets 1. The detection light sources 12, 25, 27 and the photo detectors 13, 26, 28 are in this embodiment adapted to being able to transilluminate the fish fillets 1 completely or partly, the detection light must i.a. have a sufficient intensity for being receivable and detectable on the other side of the fish fillets 1. Further, the photo detectors 13, 26, 28 must be suitable for detecting the intensity of the detection light transmitted through the fillets, and for delivering a translucency signal in dependency of the translucency of the fish fillets 1. According to the invention, this translucency signal as well will vary in accordance with the local translucency along the extension of the detection light sources in the di- rection of the transverse direction of the conveyor belt 3.
In this embodiment, the transillumination light source 10, 9 is adapted to being controllable for emitting transillumination light with a variable intensity, controlled by a control signal. The intensity is controllable in time as well as in place, that is, the intensity must be controlla- ble in time, in dependency of the momentary translucency signal from the photo detectors, and in place, that is, for every spot or width interval across the width of the fish fillets 1, the intensity must be variable in dependency of the momentary, local translucency.
According to the invention, the system is preferably controlled in such a way that areas where the fish fillets 1 have a low translucency, will be illuminated with transillumination light having a higher intensity, and conversely: areas where the fish fillets 1 have a high translucency are being illuminated with transillumination light having a lower intensity. Upon suitable adjustment of the sensibility and amplification of the system, it will hereby be attainable that the intensity variation of the transmitted transillumination light incident onto the light detector 11, or the camera 30, respectively, may be kept within other limits than the variation of the translucency of the fish fillets 1. The system is thus adjustable to reduce the intensity variation, to keep the lowest occurring intensity of the transmitted transillumination light incident onto light detector or camera above a certain value, and to keep the highest occurring intensity below another, certain value. In this way, the apparatus according to the invention may be manufac- tured with light detectors or cameras having limited intensity ranges, and nevertheless provide a fully satisfying imaging of the translucency variation of the fish fillets, even if light detector or camera is not able to process such large variation. When the apparatus according to the invention is working, the camera 30 delivers a continuous flow of image data, which are suitable for being assembled in the circuits of the control unit into complete image data for each individual fish fillet. It is essential that the apparatus according to the invention creates these complete image data in such a way that there is an unambiguous correspondence between the structure of the fish fillets and the contents of the image data, in quantity as well as in quality. As mentioned above, fish bones do not give rise to detectable shadows or translucency variations, and they are thus not directly detectable. Because of this, detection is according to the invention preferably performed by detecting those translucency variations that are manifestations of the course of groups of muscles and other structures in the interior of the fillets. On the basis of knowledge of the correspondence be- tween the course of such muscle groups and the occurrence of bone in fish fillets, the positions of the bones may subsequently be estimated.
It has surprisingly turned out that estimates on that basis provide a very satisfactory determination of the position of the bones in a fish fillet, and that there may thus on this basis be provided processing data, on the basis of which processing means in processing stations 4 may be controlled in such a way that the bones may be cut from the fillets with automatic machinery, and it is to be noted that this automated cutting is performed with an absolute minimum of waste of fish meat.
Even if above, only the use of the invention in connexion with processing of fish has been described, there is nothing to prevent its use for transilluminating other forms of translucent objects, as has been noted at the outset, whether the objects be of regular or irregular nature.
Even if above, only the use of the invention has been described with respect to automatic detection and recording of image data from the transillumination, there is nothing to prevent the use of the invention in plants where watching and recording of the objects are performed by an operator. In that case, the invention will give excellent satisfaction by providing a tailored and purposeful transilluminating of the object, where the operator will not be subjected to the relatively strong light which would otherwise flow around the objects, and not be subjected to the relatively strong light which would otherwise flow through the most translucent portions of the objects. As mentioned above, lighting (that is, transillumination) will in those cases preferably be provided of the fish fillet along a considerably longer portion of the conveyor belt 3.

Claims

C L A I M S
1. A method for transilluminating objects, in which the objects are illuminated on one side with transillumination light by means of a transillumination light source, and transmitted transillumination light is received on the other side of the objects by means of a light detector or by an operator, where the transillumination light source emits a transillumination light bundle having a narrow, elongate cross section, and the light source and the objects are moved relative to each other in a direction approximately transverse to the propagation direction of the transillumination light and approximately transverse to the longitudinal direction of the cross section, whereby the objects and the bundle of transillumination light pass each other in such a way that the objects are successively transilluminated in their entire extension, and where the extension of the transillumination light source in the longitudinal di- rection of the cross section is generally greater than the extension of the objects in the same direction, characterised in that the local intensity of the transillumination light source is controllable along the longitudinal direction of the cross section, and that it is controlled in dependency of the extension of the objects in the same direction, for the attainment of a lower variation of the intensity of the transillumination light incident onto the light detector.
2. A method according to claim 1, characterised in that the controlling comprises that the portions of the transillumination light source, which are in a given moment lying outside the contour of the objects, are being switched off.
3. A method according to claim 2, characterised in that the contour of the objects is being detected by means of a first photo detector utilising detection light having wavelengths different from the wavelengths of the transillumination light, preferably infra-red light.
4. A method according to claim 3, characterised in that the first photo detector has the form of a first light barrier having a narrow, elongate cross section.
5. A method according to any preceding claim, characterised in that the local intensity of the light source is further controlled in dependency of the local translucency of the object, for the attainment of a reduced variation of the intensity of the transmitted light incident onto the light detector.
6. A method according to claim 5, cha racterised in that the controlling comprises that the local intensity of the light source is being increased in areas where the translucency of the object is reduced.
7. A method according to claim 6, cha racterised in that the local translucency of the objects is being detected by a second photo detector which utilises detection light having wavelengths different from the wavelengths of the transillumination light, preferably infrared light.
8. A method according to claim 7, cha racterised in that the second photo detector has the form of a second light barrier having a narrow, elongate cross section.
9. A method according to claim 5 or 8, cha racterised in that the local translucency of the objects is being detected by means of the first photo detector.
10. A method according to any preceding claim, characterised in that the transillumination light source and the light detector, or the operator, respectively, are stationary and the objects are being moved.
11. A method according to any preceding claim, characterised in that the objects are being conveyed on a conveyor belt
12. A method according to claim 4 or 8, cha racterised in that the light barrier is divided into two light sub-barriers, each having a narrow, elongate cross section, and that the distance between these light sub-barriers is dependent on a pitch of the conveyor belt.
13. A method according to any preceding claim, characterised in that a camera, preferably a line camera, is being used as the light detector.
14. Apparatus for transilluminating objects and comprising: a transillumination light source for illuminating the objects on one side with a bundle of transillumination light having a narrow, elongate cross section, a light detector for receiving transmitted transillumination light - or a control station for an operator for observing transmitted transillumination light - as well as moving means for moving the light source and the objects relative to each other in a direction approximately transverse to the direction of propagation of the transillumination light and approximately transverse to the longitudinal direction of the cross section, whereby the objects and the transillumination light bundle pass each other in such a way that the objects are successively transillumi- nated in their entire extension, characterised in that the local intensity of the transillumination light source along the longitudinal direction of the cross section is controllable in dependency of the exten- sion of the objects in the same direction, for the attainment of a reduced variation of the intensity of the transillumination light incident onto the light detector.
15. Apparatus according to claim 14, characterised in that the transillumination light source is built from a number of light sources which are individually controllable and which are preferably arranged in one or more rows.
16. Apparatus according to claim 14 or 15, characterised in comprising a first photo detector for detecting the contour of the objects by means of detection light having wavelengths that are dif- ferent from the wavelengths of the transillumination light, preferably infra-red light.
17. Apparatus according to claim 16, characterised in that the first photo detector has the form of a first light barrier with a narrow, elongate cross section.
18. Apparatus according to claim 17, characterised in comprising detector means connected to the first light barrier and adapted to detecting the extension of the object on the basis of signals from the first light barrier, as well as computing means for calculating a desired distribution of the transillumination light in dependence of the extension of the object, and control means for controlling an intensity distribution for the transillumination light source in accordance therewith.
19. Apparatus according to any of claims 14-18, cha ract- e r i s e d in comprising a second photo detector for detecting the local translucency of the objects by means of detection light having wavelengths that are different from the wavelengths of the transillumination light, preferably infra-red light.
20. Apparatus according to claim 19, cha racterised in that the second photo detector has the form of a second light barrier having a narrow, elongate cross section.
21. Apparatus according to claim 20, characterised in comprising detector means connected to the second light barrier and adapted to detecting the local translucency of the object on the basis of signals from the second light barrier, as well as computing means for calculating a desired intensity distribution of the transillumination light in dependency of the local translucency of the object, and control means for controlling a desired intensity distribution for the transillumination light source in accordance therewith.
22. Apparatus according to any of claims 19-21, characterised in that the first photo detector and the second photo detector are constituted by one and the same photo detector.
23. Apparatus according to any of claims 14-22, cha racterised in that the transillumination light source and the light detec- tor, or the operator control station, respectively, are stationary and that the apparatus comprises a conveying means such as a conveyor belt for conveying the objects past the transillumination light source and the light detector, or the operator control station, respectively.
24. Apparatus according to claim 17 or 20, character- i s e d in that the light barrier is divided into two light sub-barriers, each having a narrow, elongate cross section, and the distance between these two light sub-barriers is dependent on a pitch in the conveyor belt.
25. Apparatus according to any of claims 14-24, characterised in that the light detector is a camera, preferably a line camera.
26. Machine for boning and trimming fish fillets and comprising apparatus according to any of claims 14-25.
PCT/DK2007/000219 2006-05-08 2007-05-08 A method and apparatus for transilluminating objects WO2007128316A1 (en)

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DKPA200600645 2006-05-08
DKPA200600645 2006-05-08

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
IT201800003091A1 (en) * 2018-02-27 2019-08-27 Milan Fish S R L METHOD AND APPARATUS FOR THE INSPECTION OF FOOD PRODUCTS, IN PARTICULAR FISH PRODUCTS

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH06222014A (en) * 1993-01-22 1994-08-12 Sunx Ltd Inspection system for translucent sheet material
US20010001576A1 (en) * 1999-03-24 2001-05-24 Haque Md M. Light sensor for web-guiding apparatus
US20010054680A1 (en) * 2000-04-06 2001-12-27 Peter Lindner Process and system for the optical inspection of transparent containers
WO2003034049A1 (en) * 2001-10-16 2003-04-24 Baader-Canpolar Inc. Automatic inspection apparatus and method for detection of anomalies in a 3-dimensional translucent object
US6604991B1 (en) * 1998-07-31 2003-08-12 Nordischer Maschinenbau Rud. Baader Gmbh + Co Kg Device and method for processing meat

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH06222014A (en) * 1993-01-22 1994-08-12 Sunx Ltd Inspection system for translucent sheet material
US6604991B1 (en) * 1998-07-31 2003-08-12 Nordischer Maschinenbau Rud. Baader Gmbh + Co Kg Device and method for processing meat
US20010001576A1 (en) * 1999-03-24 2001-05-24 Haque Md M. Light sensor for web-guiding apparatus
US20010054680A1 (en) * 2000-04-06 2001-12-27 Peter Lindner Process and system for the optical inspection of transparent containers
WO2003034049A1 (en) * 2001-10-16 2003-04-24 Baader-Canpolar Inc. Automatic inspection apparatus and method for detection of anomalies in a 3-dimensional translucent object

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
IT201800003091A1 (en) * 2018-02-27 2019-08-27 Milan Fish S R L METHOD AND APPARATUS FOR THE INSPECTION OF FOOD PRODUCTS, IN PARTICULAR FISH PRODUCTS
EP3531126A1 (en) 2018-02-27 2019-08-28 Milan Fish S.R.L. Method and apparatus for the inspection of packaged fish products

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