DE10133315B4 - Device for testing the dimensional accuracy of workpieces with an image processing system - Google Patents

Abstract

contraption for testing the dimensional stability of workpieces (1) with an image processing system with image acquisition unit and Evaluation device and a holder (2, 3, 4, 16, 17, 20, 21) for Positioning of the workpiece (1), which at the same time lighting means for generating a largely homogeneous diffuse illumination light comprises, which consists of a transverse to the receiving direction of the image pickup unit extending side surface of a Spreading elements (7) emerges and partially shaded by the workpiece (1) arrives at the image recording unit, characterized in that the Scattering element (7) at one reaching to the scattering element (7) transparent light guide element (6) arranged for light supply is, no aperture element limits the light emission, and the extension the interface in the recording direction between the light guide element (6) and scattering element (7) with only a very small supernatant (V) on the workpiece (1) passes by.

Description

The The invention relates to a device for testing the dimensional accuracy of workpieces an image processing system according to the preamble of the claim 1.

at the survey of workpieces with an image processing system is usually the workpiece to be checked on a carrier hung up, lit there and watched with the help of a camera. In the case of a black and white camera Accordingly, pointwise digital picture information results in the form of gray values.

Around a specific checkpoint for example, a solder pin to measure a chip socket in its shape or location to the chip package, becomes common the leading edge of the chip package, the on the carrier rests, taken as a reference edge and the height of the recognizable in the picture Measuring point, for example, the center of the lower edge of a soldering pin, above this Reference edge determined by appropriate evaluation of the image coordinates.

In previous devices carriers are already used, which consist essentially of transparent, clear material and on the side facing the test body provided a scattering element for generating a homogeneous diffuse illumination ( DE 199 37 326 A1 ). A disadvantage of the previous carriers, however, is that reflections from the diffuse scattering element can obliquely strike rounded edges, such as contact pins, so that the reflections on the contact pin can lead to measurement inaccuracies by reflecting these reflections towards the camera and thus producing a "smaller "Pretend contact pin.

To avoid corresponding adverse reflections are in accordance with DE 199 37 326 A1 one or more apertures provided to hide the lighting in certain areas, these being performed as black inserts in the workpiece carrier. However, the production or, the attachment of appropriate panels is associated with a comparatively high design and manufacturing effort.

Publication WO 98/04882 A1 discloses an apparatus for measuring workpieces with an image processing system which has an at least partially optically transparent holder for positioning the workpieces in front of the image recording unit with a scattering element for producing a largely homogeneous diffuse illumination, an image recording unit and an evaluation unit wherein a projecting beyond the workpiece supernatant of a receiving direction of the image pickup unit transversely arranged lateral surface of the scattering element is small and has no aperture elements. A comparable device is also from the document US 5,043,589 known.

task the invention it is in contrast, a Propose device in which a precise measurement even at rounded test edges of the workpiece to be measured possible is and the effort is opposite the prior art is reduced.

These Task is, starting from a device of the introduction mentioned Art, solved by the characterizing features of claim 1.

By in the subclaims mentioned measures are advantageous embodiments and further developments of the invention possible.

Accordingly a device according to the invention is characterized characterized in that the scattering element at one to the scattering element reaching transparent light guide element arranged for light supply is, no aperture element limits the light emission, and the extension the interface in the recording direction between the light guide element and scattering element with only a very small supernatant on the workpiece passes by.

With Help of a correspondingly small protrusion of the side surface of the Spill element can adverse or disturbing Reflections especially on rounded test edges or test points of the workpiece be prevented, i. Reflections of obliquely incident stray light of the Scattering on the side facing away from the scattering element to measuring section of the workpiece and the direction of the Image capture unit to be reflected.

It protrudes the scattering element in particular perpendicular to the receiving direction the image pickup unit only slightly above the test edge to be measured or the test point to be measured of the workpiece out. As a result, a contrast edge to be measured exactly or a precisely measured contrast between the workpiece and the Generating scattering element, whereby the measurement accuracy of inventive devices elevated becomes.

In addition, the use of apertures to hide the illumination in certain areas can be avoided by a correspondingly small-sized projection of the side surface of the scattering element, whereby the constructive so how production cost of corresponding measuring devices significantly reduced. This also leads to an economically favorable production of corresponding measuring devices.

Farther is mainly due to the reaching to the scattering element crystal clear, transparent material with the illumination intensity of the lighting means significantly less scattering losses brought to the test specimen. This makes possible, that the illumination means advantageously smaller dimensioned are. At the same time it ensures that the contrast between scattering element and test object compared to the State of the art is reinforced, which is additional on the measurement of the workpiece or the evaluation has an advantageous effect.

In a particular embodiment of the invention is a receiving direction the image pickup unit arranged distance from a to be measured Section of the workpiece greater or equal to the scattering element the supernatant the side surface of the spreading element. For example, the distance to be measured Section of the workpiece to the scattering element at least three times as large as the projection of the side surface of the Scattering element.

With these measures will ensure that adverse reflections are largely prevented. Consequently only the side facing the diffuser is illuminated, whereby the contour of the part of the workpiece to be measured almost can be detected exactly by the image pickup unit or within the tolerable, predetermined measurement accuracy of the workpiece is.

advantageously, is the supernatant less than 5/10 mm. With a corresponding supernatant is a comparatively easily achievable manufacturing accuracy of the scattering element to realize a relatively high measuring accuracy.

Preferably is the supernatant less than 3/10 mm. This is the feasible measurement accuracy of the workpiece additionally improved. For example, you can with a suitably dimensioned projection of the side surface of the Spreader contact pins or solder pins of chip sockets especially be measured exactly.

In an advantageous embodiment at least two holders for the upper and lower are provided by the invention Positioning of the workpiece provided in front of the image pickup unit. This will enable that by means of the two holders a particularly accurate positioning of the workpiece can be realized in front of the image acquisition unit. In addition, can both the upper holder and the lower holder for generating a reference plane of the measurement of the workpiece can be used.

For example has one of the holders according to the state the technique at least one reference point, in particular a marker such as an insert, ball or the like, for the determination the coordinates of the workpiece and / or a defined bearing surface for the workpiece, whose Coordinates regarding the marking at least partially in the image processing system are stored.

advantageously, serves at least one of the holder in particular the supply of corresponding test specimen for the actual Measurement. For example, a lower one presses during the measuring process Ejector or ejector a workpiece carrier, the made of light-conducting material with a comparatively thin, diffuse upper litter layer or a supernatant according to the invention equipped to be tested workpiece from the predetermined by the workpiece carrier Position upwards. For example, the ejector or ejector jammed the workpiece against a hold-down, which in turn essentially made of light-conducting material with a lower diffuse, thin Topcoat, i. the scattering element according to the invention equipped is.

Preferably is during the entire measuring process, the body to be tested between the two elements preferably above the workpiece carrier plate or form palette held. Enable this the two scattering layers, i. Inventive scattering elements, a high-contrast optical recording of the test edges to be measured such as Contact pins or the like. These measures allow both upper as well as lower checkpoints at the same time or test edges of the workpiece measurable are.

For example may vary depending on the specimen the hold-down and the ejector a reference plane, reference edge or bearing edge of the test specimen have. hereby a particularly flexible device according to the invention can be realized, which can be adapted to numerous variable test specimens is.

According to the invention the diffuse cover layer, i. the scattering element, the hold-down, the ejector or the like a high-contrast reference edge or reference line generated so that this together with the high-contrast recording of the section to be measured, for example the contact pins, can be measured.

Advantageously, at least one of the holders comprises at least one damping element for adapting the positioning to different ones Workpieces. This measure makes it possible, for example, to compensate for production-related deviations from workpieces to be measured by means of a corresponding damping element or a plurality of damping elements and thus to realize an advantageous positioning of corresponding workpieces in front of the image recording unit.

Preferably the hold-down has damping elements, such as springs or the like, so that in particular this is able to the test specimens even with production-related To adapt shape deviations and the test specimens for the measuring process exactly holders.

In a particular embodiment the hold-down has this at least two damping elements, such as two springs or the like, so that at least two test specimens simultaneously, i.e. in one work step, can be measured. As a result, if necessary the measurement of numerous test specimens, for example at industrial survey, significantly accelerated.

In a particular variant of the invention is at least one of Holder as workpiece carrier for Pick up and transport the workpiece in the area in front of the Image recording unit formed. This allows for example a Positioning of the workpiece on the workpiece carrier, where at the same time the measurement of the workpiece are carried out can. Thus, in particular, an advantageous industrial survey of workpieces realizable.

Preferably In this variant of the invention, the workpiece or become the workpieces not raised by means of a corresponding ejector, but lie during that Measuring process directly on the workpiece carrier.

at corresponding variants of the invention fixed, for example, the Hold down the test specimen during the Measuring process and defines if necessary the reference plane over the given contact surface the hold-down. Alternatively, however, the reference plane also over Defines the workpiece carrier become. This is in particular on the workpiece carrier a ensures reproducible position of the part to be tested.

As a general rule can use both a workpiece carrier only one workpiece as well as with several workpieces be used. The first variant is in particular at comparatively huge workpieces advantageous, so that a more detailed image section of the workpiece of the image acquisition unit is detectable.

In a particular embodiment of the invention is at least the Workpiece carrier as guide rail formed, on which the workpieces or Test body are performed. This advantageously provides a dynamic measurement, i. continuous Measurement, feasible. In particular, U-shaped specimens are on an example metallic guide rail transported continuously.

Preferably to press or arrest one or more essentially light-conducting material existing hold-down with a scattering element according to the invention, i.e. a diffuse litter layer with a relatively small projection, on the to the workpiece located side to be tested workpieces for example, from above against the guide rail. This will again a contrast increase in the area of the test points to be measured or test edges, such as contact pins or the like, feasible. So allows the diffuse cover layer of the blank or the measuring of upper checkpoints or test edges of the workpiece.

Preferably In this case, the upper downholder (s) has one or more damping elements, so that an advantageous adaptation to the workpieces can be ensured is. In particular, an adjustment of the contact pressure of the blank holder adjustable, so that u.a. the friction of the workpieces along the guide rail changeable is.

In Advantageously, at least one below the guide rail Rail arranged, in turn, made of photoconductive material an upper, diffused, relatively small cover layer, i. a scattering element according to the invention, is made. This makes it possible in particular lower checkpoints or test edges of workpiece are measurable.

Preferably is provided in this variant, at least one image pickup unit, in general, each recording more in each case, for example six workpieces receives and evaluates by a corresponding evaluation. The time interval between two shots is above all with the speed with which the workpieces on the guide rail be transported coordinated. This will be advantageous Guaranteed manner that the workpieces for example, continuously over the guide rail be moved and the recording unit here detects all workpieces.

Preferably, a workpiece carrier coding is performed. With the help of the carrier coding, the evaluation unit of the image acquisition Systems without further separate input when using multiple carriers recognize on which carrier the part to be tested is placed so that corresponding (calibration) data from the data memory of the image processing system, eg according to the prior art, can be retrieved.

Preferably becomes the carrier coding over inserts accomplished. This results in the advantage that an insert wear and dirt sensitive can be formed and accordingly even after multiple cleaning the coding is easily recognizable. About that addition, the use of inserts for coding forms in Connection with inserts as marking, the reference plane the Advantage that the coding in one operation with the mark the carrier can be made, which allows an economical production.

Especially for the carrier encoding the use of balls as insert is e.g. by the simple Insertion into a corresponding bore of advantage. A carrier coding For example, can be realized in such a way that two inserts be used for coding. Accordingly, by Insertion or omission of the two inserts in the binary system four numbers are displayed, which in particular at a subsequent explained 4-step operation with four carriers is advantageous.

For example is a measurement of workpieces or specimens in four steps possible. Possibly the loading of the carrier takes place with test specimens in Step 1, wherein by appropriate positioning means as well as special Embodiments of the carrier ensures an exact positioning of the specimen on the carrier becomes. In step 2, for example, the specimen is measured, with a corresponding evaluation unit, i.a. by means of a programmable Data storage, the test specimen in classified a "good" or "bad" body. In step 3, for example, a "bad" body discarded. Finally, it will in step 4, if necessary, the "good" body for the further Machining taken from a corresponding test arrangement.

The test set advantageously comprises a turntable with, for example, four Holding devices on each of which a workpiece carrier or a form pallet with corresponding positioning auxiliary elements is held. By rotation the turntable by 90 ° degrees For example, the described 4-step measurement of corresponding workpieces can be realized.

The Positioning aids for positioning the carrier are preferably formed as an insert. This is in particular the insert formed as a ball. By means of positioning auxiliary elements is a defined mounting position of the carrier on a holding device intended. This precise reproducible mounting position is required to work with the above activities achievable accuracy not by a too large error in the mounting position to worsen again.

The Positioning auxiliary elements can for example, be arranged on the underside of the carrier and as support elements on a holding surface of a holding device serve the test arrangement. The spherical shape is especially for the assembly advantageous because this only in corresponding holes relatively easy and besides independently from the angular orientation of the insert accurate positioning of the carrier can be realized on the holding device. Please note that during assembly of these inserts not the later measurement accuracy must be complied with. The finished carrier is placed on the holder in the appropriate test facility calibrated with the aid of a calibration body, so that appropriate fluctuations in the location of these inserts taken into account during the calibration and compensated accordingly in the evaluation of the measurement results can be.

One Another advantage in the use of balls as Positionierhilfselemente is the relatively easy and reliable centering in one corresponding countersinking of the holding device on which the carrier is mounted becomes. The reproducibility of the position in the calibration is thereby improved. Especially with signs of wear of the carrier or in cleaning operations, with the carriers removed from the fixture Need to become, is a comparatively simple positioning of the carrier then again realized in an advantageous manner. This allows, for example, a replacement the workpiece carrier at too much wear, respectively too big Abrasion, leaving the new workpiece carrier turn is aligned exactly at the predetermined position and a complex Re-adjustment of the measuring arrangement can be omitted.

Farther allows the positioning by means of balls exchanging workpiece carriers for different Examinees. The orientation of the workpiece carrier preferably takes place on the holding device by means of two balls, so that a particularly exact positioning is feasible.

Optionally, in one embodiment of the invention, one or more inserts for coding at the same time detected as a marker for determining a reference point in the image analysis during the calibration and their coordinates abge stores.

For a good Reproducibility of the measurement results is a precise positioning of the part to be measured on the carrier or the guide rail necessary. In particular, need the mutual bearing surfaces well put together become. To be in fully automatic operation, a relatively accurate position to ensure, Suction channels are optionally provided in the carrier, if appropriate, which open out in the support surface and by means of reduced pressure, the part to be tested can be sucked.

Preferably If an image evaluation unit can be realized without optical adjustment of the depth of field, so that a less expensive and less costly image acquisition unit, For example, provided without a complex and expensive lens system can be.

One embodiment The invention is illustrated in the drawing and is based on the Figures in more detail below explained.

in the Show individual

1 a schematic front view of a first embodiment of the invention with guide rail, including a detailed view,

2 a schematic side view of the first embodiment,

3 a schematic side view of a second embodiment of the invention with form pallet,

4 a schematic side view of a third embodiment according to the invention with a sheet metal carrier and

5 a side view and top view of the sheet metal carrier according to 4 ,

In 1 is schematically shown a first embodiment of the invention with a detailed view. These are workpieces to be measured 1 on a guide rail 2 guided. Below the guide rail 2 is a first diffuser strip 3 arranged. Above the workpiece 1 is a second diffuser strip 4 arranged. In a manner not shown, the upper diffuser bar 4 flexibly mounted by means of spring elements, so that production-related deviations of the dimensions of the workpieces 1 can be compensated.

The diffuser strips 3 . 4 have lighting elements 5 , in particular light-emitting diodes (LED). The light of the LEDs 5 is by means of a transparent light guide 6 to a scattering element 7 supplied according to the invention. The scattering element 7 is made of diffuse plastic, for example, so that the sections to be measured, in particular pins 8th , are backlit with respect to camera units not shown. The camera units are each on the side of the scattering element 7 opposite side of the pins 8th arranged, ie laterally in the X or -X direction.

In the right part of the 1 an enlarged section of the arrangement described above is shown. This detail is the inventive design of the scattering element 7 to be taken, with light rays 9 on the scattering element 7 meet and lateral reflections 10 to generate. Exemplary is only a reflection beam 10 shown at the borderline between the scattering element 7 and the transparent light guide 6 exit. The reflection beam 10 meets the pin 8th and is in turn reflected by this, so that it is at least partially emitted in a direction opposite to a direction y direction and thus can not be detected by the camera.

Furthermore, the detailed sectional view according to 1 to take a distance H as a horizontal, wherein the distance H, the distance from the apex of the pins to be measured 8th to the scattering element 7 is. In addition, a supernatant V as vertical of 1 can be seen, wherein the supernatant V over the workpiece 1 or the pin to be measured 8th projecting supernatant V of the recording direction X, -X of the camera not shown in detail laterally disposed side surface 11 of the scattering element is.

For comparison, a non-inventive beam path or configuration of the scattering element 7 in 1 shown. Here are hypothetical light rays 12 to a hypothetical boundary line of a non-inventive scattering element and a non-inventive transparent light guide, so that non-inventive reflection rays 13 on the pin 8th would be reflected and reflected by this in -X direction. These light beams reflected in the -X direction strike the camera, which is not shown in more detail, so that a measurement of the pins which is erroneous with respect to the Y direction 8th would be performed.

In 2 is the first embodiment of the invention with the guide rail 2 according to 1 shown schematically in side view. Exemplary are four workpieces 1 represented, whose pins 8th by means of the scattering element 7 be measured according to the invention. To backlight the upper pins 8th is a diffuser strip 3 with LEDs 5 provided, wherein a transparent light guide 6 Light to the scattering element 7 according to the invention passes. Across from 1 is additionally a connection cable 14 the diffuser strip 3 shown. In addition, to generate a transmitted light, a backlight 15 shown. The with respect to the sheet plane behind the workpieces 1 arranged backlight 15 causes one with respect to the sheet plane in front of the workpieces 1 arranged camera the outlines of the workpieces 1 perceives.

In 3 a second, inventive embodiment is shown. This includes a form palette 16 a scattering element 7 in the area of workpieces 1 in a manner not shown a supernatant according to the invention with respect to the workpieces 1 having. Outside the range of workpieces 1 is the scattering element 7 freely configurable. In a manner not shown, the light guide 6 illuminated by means of illumination, so that the scattering element 7 a diffuse backlighting of the lower pins 8th allows.

During the measuring process, the diffuser bar lowers 3 on the workpiece 1 down, leaving the scattering element 7 the diffuser strip 3 forms a supernatant according to the invention.

The shape palette is an example 16 two areas for positioning the workpiece 1 on. The shape palette 16 leads to the measurement of the two workpieces held by her 1 a movement in X- or -X-direction, so that the diffuser bar 3 only needs to perform a movement in the Y- or Y-direction.

In 4 is a third embodiment according to the invention with a sheet metal carrier 17 shown. The sheet metal carrier 17 is in plan view as well as in side view in 5 shown in more detail. Advantageously, the sheet metal carrier 17 from three welded together sheets. Optionally, the upper sheet introduction chamfers 18 on, in particular for the introduction of the workpiece 1 , The middle plate preferably has the positioning or fixation of the workpiece 1 on. In particular, the lower plate prevents the falling through of the workpiece 1 optionally by means of appropriate webs 19 so that, for example, one below the sheet metal carrier 17 arranged ejector 20 the workpieces 1 during the measuring process in a simple manner over the sheet metal carrier 17 can lift. Here, the ejector 20 scatterbars 7 according to the invention for measuring the pins 8th on. For lighting the workpieces 1 points the ejector 20 LEDs 5 in the range of a transparent light guide 6 on, bringing the scattering element 7 is illuminated.

Accordingly, has a hold-down 21 LEDs 5 on, which in turn the scattering element 7 the hold-down 21 is illuminated.

A camera unit, not shown, above the hold-down 21 is arranged and the workpiece 1 viewed in plan view, is a lighting 22 provided for generating a transmitted light.

The workpieces shown in the figures 1 essentially concern chip holders 1 , which are generally used in radio telephones for receiving the chip card for activation. The chip holder 1 will with his soldering pins 8th soldered to a corresponding board. To ensure proper soldering, it is necessary that the solder pins 8th are precisely aligned and in particular lie in one plane.

1

workpiece

2

guide rail

3

diffuser bar

4

diffuser bar

5

LED

6

optical fiber

7

scattering element

8th

Pin code

9

light rays

10

reflection beam

11

side surface

12

light rays

13

reflection beams

14

connecting cable

15

backlighting

16

shape range

17

Blechträgerbrücke

18

slope

19

web

20

ejector

21

Stripper plate

22

lighting

H

horizontal

V

vertical

X

direction

Y

direction

Claims (9)

Device for checking the dimensional accuracy of workpieces ( 1 ) with an image processing system with image acquisition unit and evaluation device and a holder ( 2 . 3 . 4 . 16 . 17 . 20 . 21 ) for positioning the workpiece ( 1 ), which at the same time comprises illumination means for generating a substantially homogeneous diffuse illumination light, which consists of a lateral surface of a scattering element extending transversely to the direction of picking up of the image acquisition unit ment ( 7 ) and from the workpiece ( 1 ) partially shaded passes to the image recording unit, characterized in that the scattering element ( 7 ) on one to the scattering element ( 7 ) reaching transparent light guide element ( 6 ) is arranged to supply light, no aperture element restricts the light exit, and the extension of the interface in the receiving direction between light guide element ( 6 ) and scattering element ( 7 ) with only a very small projection (V) on the workpiece ( 1 ) passes by. Device according to Claim 1, characterized in that a spacing (H) arranged in the recording direction (X, -X) of the image recording unit is determined by a section ( 8th ) of the workpiece ( 1 ) to the scattering element ( 7 ) greater than the supernatant (V) of the side surface ( 11 ) of the spreading element ( 7 ) is (H ≥ V). Device according to claim 2, characterized in that the distance (H) from the section to be measured ( 8th ) of the workpiece ( 1 ) to the scattering element ( 7 ) at least three times as large as the supernatant (V) of the side surface ( 11 ) of the spreading element ( 7 ) is (H ≥ 3 × V). Device according to one of the preceding claims, characterized characterized in that the supernatant (V) less than five Tenths of a millimeter (H <5/10 mm) is. Device according to claim 4, characterized in that that the supernatant (V) is less than three tenths of a millimeter (H <3/10 mm). Device according to one of the preceding claims, characterized in that at least two holders ( 3 . 4 . 20 . 21 ) for the upper and lower positioning of the workpiece ( 1 ) are provided in front of the image pickup unit. Device according to one of the preceding claims, characterized in that at least one of the holders ( 3 . 4 . 20 . 21 ) at least one damping element for adjusting the positioning of different workpieces ( 1 ). Device according to one of the preceding claims, characterized in that at least one of the holders ( 2 . 16 . 17 ) as a workpiece carrier ( 2 . 16 . 17 ) for picking up and transporting the workpiece ( 1 ) is formed in the area in front of the image pickup unit. Device according to one of the preceding claims, characterized in that at least the workpiece carrier ( 2 ) as a guide rail ( 2 ) is trained.