DE10133315A1 - Workpiece measuring apparatus uses an image-processing device, especially for use in determining the position of contact pins, etc. on integrated circuits where the effects of scattered light have to be combated - Google Patents

Abstract

Device for measuring workpieces (1) has an image processing arrangement with optically transparent supports (3, 4) for positioning the workpiece with respect to an image-recording device. A scatter element (7) produces largely homogeneous diffuse illumination. The amount (V) by which the image-recording device extends beyond the side surfaces of the scatter device is so small that required measurement accuracy can be obtained without using shutter elements.

Description

The invention relates to a device for measuring Workpieces with an image processing system according to the Preamble of claim 1.

When measuring workpieces with a The image processing system is usually the one to be checked Workpiece placed on a support, illuminated there and with Watched with the help of a camera. In the case of a black and white Accordingly, the camera is digital at certain points Image information in the form of gray values.

For example, a solder pin at a certain test point of a chip socket in its shape or position to the chip housing is often measured, the front edge of the chip housing, the rests on the carrier, taken as the reference edge and the Height of the measuring point recognizable in the picture, for example the Center of the lower edge of a solder pin, above this Reference edge by appropriate evaluation of the Image coordinates determined.

With previous devices, carriers are already used, which essentially consist of transparent, clear  Material exist and on the aligned to the test specimen Side a scattering element to produce a homogeneous diffuse Lighting is provided (DE 199 37 326 A1). A disadvantage of the previous carriers, however, is that of diffuse Scattering element reflections obliquely on rounded edges, such as contact pins, for example, so that the Reflections on the contact pin lead to measurement inaccuracies can lead by these reflections towards the camera are reflected and thus a "smaller" contact pin to pretend.

To avoid correspondingly adverse reflections according to DE 199 37 326 A1 one or more panels for Hide the lighting in certain areas provided, these as black inserts in Workpiece carriers are executed. The manufacture or the Attaching appropriate panels is, however, with a comparatively high design and manufacturing technical effort connected.

In contrast, the object of the invention is a device to propose an exact measurement for rounded test edges of the workpiece to be measured possible is and the effort compared to the prior art is reduced becomes.

This task is based on a device of type mentioned in the introduction, by the characteristic features of claim 1 solved.

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

Accordingly, one according to the invention is distinguished Device characterized in that at least one over the  Projecting protrusion of a workpiece in the direction of the recording the image acquisition unit transversely arranged side surface of the Scattering elements is so small that a given one Measuring accuracy of the workpiece without the use of Aperture elements can be reached.

With the help of a correspondingly small projection the side surface of the scattering element can disadvantageous or disturbing reflections, especially on rounded test edges or test points of the workpiece are prevented, d. H. Reflections of the stray light falling at an angle Scattering element on the side facing away from the scattering element section of the workpiece to be measured and the direction the image acquisition unit are reflected.

The scattering element preferably projects in particular perpendicular to the Recording direction of the image recording unit is only insignificant over the test edge to be measured or the one to be measured Check point of the workpiece. This makes one exactly measuring contrast edge or a precisely measured contrast generated between the workpiece and the scattering element, whereby the measuring accuracy of devices according to the invention is increased becomes.

In addition, a correspondingly small dimensioned projection of the side surface of the scattering element the use of bezels to hide the lighting in certain areas avoidable, which makes the constructive and manufacturing expenditure corresponding measuring devices significantly reduced. This also leads to economical production corresponding measuring devices.

Furthermore, this is mainly due to the scatter element Reaching crystal clear, transparent material Illumination intensity of the lighting means with clearly  less scattering losses brought to the test specimen. This allows the lighting means to be more advantageous Are dimensionally smaller. At the same time ensures that the contrast between the scattering element and Test object is reinforced compared to the state of the art, which also affects the measurement of the workpiece or the evaluation has an advantageous effect.

In a special development of the invention, an in Direction of recording of the image recording unit arranged distance from a section of the workpiece to be measured to Scattering element greater than / equal to the protrusion of the side surface of the Scattering element. For example, the distance from to measuring section of the workpiece to the scattering element at least three times the protrusion of the side surface of the scatter element.

These measures ensure that adverse Reflections are largely prevented. Thus only the side facing the diffusing element is illuminated, whereby the contour of the portion of the workpiece to be measured can be detected almost exactly by the image recording unit can or within the tolerable, predetermined Measuring accuracy of the workpiece.

The protrusion is advantageously less than 5/10 mm. With a corresponding supernatant is a comparative one easily achievable manufacturing accuracy of the diffuser to realize with relatively high measuring accuracy.

The protrusion is preferably less than 3/10 mm. Herewith becomes the realizable measuring accuracy of the workpiece additionally improved. For example, with a appropriately dimensioned projection of the side surface of the Scattering element contact pins or solder pins of chip bases be measured particularly precisely.  

In an advantageous embodiment of the invention at least two holders for upper and lower positioning of the workpiece in front of the image acquisition unit. This makes it possible to use the two holders a particularly exact positioning of the workpiece in front of the Image acquisition unit can be realized. Furthermore, can both the upper holder and the lower holder for Generation of a reference plane for measuring the workpiece be used.

For example, one of the holders according to the prior art Technology at least one reference point, especially one Marking such as an insert, ball or the like, for determining the coordinates of the Workpiece and / or a defined contact surface for the Workpiece whose coordinates refer to the marking at least partially in the image processing system are saved.

At least one of the holders advantageously serves in particular the supply of the corresponding test specimens for the actual measuring process. Presses during the measuring process for example a lower ejector Workpiece carrier made of light-conducting material with a comparatively thin, diffuse upper scattering layer or a supernatant according to the invention is equipped to testing workpiece from the through the workpiece carrier predetermined position upwards. For example, the Ejector or ejector the workpiece against one Hold-down device, which in turn essentially consists of light-guiding Material with a lower diffuse, thin top layer, i.e. H. the diffusing element according to the invention is equipped.

During the entire measurement process, the testing body preferably between the two elements  above the workpiece carrier plate respectively Form palette kept. Here, the two enable Scattering layers, d. H. scattering elements according to the invention, a high-contrast optical image of the object to be measured Test edges such as contact pins or the like. These measures allow both top and bottom at the same time lower test points or test edges of the Workpiece are measurable.

For example, depending on the test specimen, both the Hold-down device as well as the ejector a reference plane, Reference edge or contact edge of the test specimen exhibit. This makes it particularly flexible Device according to the invention can be implemented, which to numerous variable test specimen is customizable.

According to the invention, the diffuse cover layer, ie. H. the Scatter element, hold-down device, ejector or the like a high-contrast reference edge respectively Generated reference line so that this together with the high-contrast image of the section to be measured, for example the contact pins can be measured.

At least one of the holders advantageously comprises at least one damping element to adjust the Positioning on different workpieces. This measure enables manufacturing-related deviations from workpieces to be measured by means of an appropriate Damping element or several damping elements balance and thus an advantageous positioning appropriate workpieces in front of the image acquisition unit realize.

The hold-down device preferably has damping elements, such as for example springs or the like, so that in particular this is able to deal with the  Test specimens even in the event of shape-related deviations to adapt and the test specimens for the measuring process exactly holders.

In a special embodiment, the hold-down device has this at least two damping elements, such as two springs or the like, so that at least two Test specimen simultaneously, d. H. in one step, can be measured. As a result, the Measurement of numerous test specimens, for example at industrial surveying, can be significantly accelerated.

In a special variant of the invention, at least one of the holders as a workpiece holder for holding and transport the workpiece to the area in front of the Image acquisition unit trained. this makes possible for example positioning the workpiece on the Workpiece carrier, while measuring the Workpiece can be performed. So in particular an advantageous industrial measurement of workpieces realizable.

In this variant of the invention, this is preferably Workpiece or the workpieces are not by means of of an appropriate ejector raised, but lie during the measuring process directly on the workpiece carrier.

Fixed in appropriate variants of the invention for example, the hold-down the test specimen during the Measurement process and, if necessary, defines the reference plane over the specified contact surface of the hold-down device. As an alternative to this, however, the reference level can also be set via the Workpiece carriers can be defined. Here in particular a reproducible position of the workpiece carrier testing part guaranteed.  

In general, both a workpiece carrier with only one Workpiece as well as be used with several workpieces. The first variant is particularly comparative large workpieces advantageous, so that a more detailed Image section of the workpiece from the image acquisition unit is detectable.

In a special development of the invention at least the workpiece carrier as a guide rail trained on which the workpieces or test specimens become. This advantageously creates a dynamic Measurement, d. H. continuous measurement, feasible. In particular, U-shaped test specimens are placed on a for example, metallic guide rail continuously transported.

Preferably press or lock one or several essentially made of light-conducting material existing hold-down device with an inventive Scattering element, d. H. a diffuse scattering layer with a relatively small projection on the workpiece Side of the workpieces to be checked, for example from above against the guide rail. This in turn becomes a Contrast increase in the area of the test points to be measured or test edges, such as contact pins or the like, implementable. So the diffuse Cover layer of the or the hold-down device the measurement of upper test points or test edges of the workpiece.

The upper hold-down device (s) preferably has one or more damping elements, so that an advantageous Adaptation to the workpieces can be guaranteed. In particular is an adjustment of the contact pressure of the hold-down device adjustable so that u. a. the friction of the workpieces lengthways the guide rail is changeable.  

It is advantageously below the guide rail arranged at least one bar, which in turn consists of light-conducting material with an upper, diffuse, comparatively small top layer, d. H. one scattering element according to the invention is produced. hereby enables in particular lower test points or test edges of the workpiece are measurable.

In this variant, there is preferably at least one Image acquisition unit provided, which is generally pro Holds several, for example six workpieces records and by a corresponding evaluation unit evaluates. The time interval between two recordings is especially with the speed with which the workpieces transported on the guide rail are coordinated. This advantageously ensures that the Workpieces, for example, continuously over the Guide rail are moved and the receiving unit here all workpieces recorded.

A workpiece carrier coding is preferably carried out. With the aid of the carrier coding, the evaluation unit of the Image acquisition system without additional separate input Use multiple carriers to identify which carrier the part to be tested is placed so that corresponding (Calibration) data from the image processing data memory plant, e.g. B. according to the prior art can.

The carrier coding is preferably via inserts accomplished. This has the advantage that a Insert is designed to be wear-resistant and sensitive to dirt can be and accordingly also after multiple Cleaning the coding is clearly recognizable. Furthermore forms the use of inserts for coding in Connection with inserts as a marking, the  Reference level has the advantage that the coding in one Work step with the marking of the carrier can be made can, which enables economically favorable production.

The use of is particularly useful for carrier coding Balls as insert z. B. by the simple introduction in a corresponding hole is an advantage. A carrier coding can be realized, for example, in such a way that two Inserts are used for coding. Accordingly can by inserting or omitting the two inserts what four numbers are represented in the binary system especially with a 4-step Working with four carriers is advantageous.

For example, a measurement of workpieces or Test specimens possible in four steps. If applicable loading the carrier with test specimens in step 1, wherein through appropriate positioning means and special Embodiments of the carrier an exact positioning of the Test body is guaranteed on the carrier. In step 2 For example, the test specimen is measured, with a corresponding evaluation unit, u. a. by means of a programmable data storage, the test specimen in one classified "good" or "bad" body. In For example, step 3 becomes a "bad" body discarded. Finally, in step 4, if necessary the "good" body for the further processing of one taken from the corresponding test arrangement.

The test arrangement 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 rotating the For example, the turntable is 90 degrees described 4-step measurement of corresponding workpieces realizable.  

The positioning aids for positioning the carrier are preferably designed as an insert. Here is in particular, the insert is designed as a ball. through the positioning aid is a defined one Mounting position of the carrier on a holding device intended. This is precisely reproducible assembly position required to take the measures listed above achievable accuracy is not due to a too large error in the mounting position deteriorate again.

The positioning aids can, for example, on the Bottom of the carrier can be arranged 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, since this is only in corresponding holes relatively simple and also regardless of the angular orientation of the insert exact positioning of the carrier on the holding device is feasible. It should be noted that the Assembly of these inserts does not improve the later measurement accuracy must be observed. The finished carrier is on the Holding device in the appropriate test facility with the help of a calibration body, so that corresponding fluctuations in the position of these inserts during calibration taken into account and accordingly in the evaluation of the Measurement results can be compensated.

Another advantage in using bullets as Auxiliary positioning elements is the relatively light and reliable centering in a corresponding countersink the holding device on which the carrier is mounted. The Reproducibility of the position in the calibration is thereby improved. Especially at Signs of wear on the wearer or at Cleaning work, the carrier from the holding device  must be removed is a comparatively simple one Then position the carrier back in can be realized in an advantageous manner. this makes possible for example, an exchange of the workpiece carrier at too great wear or excessive abrasion, so that the new workpiece carrier in turn exactly at the specified one Position is aligned and a complex readjustment of the Measuring arrangement can be omitted.

Furthermore, positioning by means of balls allows Exchange of workpiece carriers for different test objects. The workpiece carrier is preferably aligned the holding device by means of two balls, so that one particularly exact positioning is feasible.

If necessary, in a further development of the invention one or more inserts for coding at the same time as Marking for determining a reference point in the Image evaluation recorded during the calibration and its Coordinates are saved.

For a good reproducibility of the measurement results is one precise positioning of the part to be measured on the Carrier or the guide rail necessary. In particular, the two-sided contact surfaces must be good be joined together. To be in fully automatic operation to ensure a relatively accurate position advantageously, if necessary, suction channels in the carrier provided that open into the contact surface and through the the part to be tested using reduced pressure can be sucked in.

An image evaluation unit is preferably without an optical one The depth of field can be adjusted so that a less complex and less expensive image acquisition unit, for example without a complex and expensive lens system  can be provided.

An embodiment of the invention is in the drawing shown and will be explained in more detail below with reference to the figures explained.

Show in detail

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

Fig. 2 is a schematic side view of the first embodiment,

Fig. 3 is a schematic side view of a second embodiment of the invention with mold pallet,

Fig. 4 is a schematic side view of a third embodiment of the invention with a sheet metal support and

Fig. 5 is a side view and plan view of the sheet metal carrier in accordance with Fig. 4.

In Fig. 1 a first embodiment of the present invention is shown with a detailed view schematically. Workpieces 1 to be measured are guided on a guide rail 2 . A first diffuser strip 3 is arranged below the guide rail 2 . A second diffuser strip 4 is arranged above the workpiece 1 . In a manner not shown, the upper diffuser strip 4 is flexibly supported by means of spring elements, so that deviations in the dimensions of the workpieces 1 caused by production can be compensated for.

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

In the right part of FIG. 1, an enlarged section of the arrangement described above is shown. The configuration of the scattering element 7 according to the invention can be seen from this detailed illustration, light rays 9 striking the scattering element 7 and generating lateral reflections 10 . As an example, only a reflection beam 10 is shown, which emerges at the boundary line between the scattering element 7 and the transparent light guide 6 . The reflection beam 10 strikes the pin 8 and is in turn reflected by it, so that it is at least partially emitted in a direction opposite to a direction y and therefore cannot be detected by the camera.

Further, the detailed cut-away view is shown in FIG. 1 refer to a distance H as a horizontal line, wherein the distance H is the distance from the apex of the measurement pins 8 to the spreading member 7. In addition, an overhang V can be seen as the vertical of FIG. 1, the overhang V of the overhang V projecting beyond the workpiece 1 or the pin 8 to be measured of a side surface 11 of the camera which is arranged transversely to the recording direction X, -X of the camera (not shown in more detail) Scattering element is.

For comparison, a beam path or configuration of the scattering element 7 is shown in FIG. 1. Here, hypothetical light beams 12 meet a hypothetical boundary line of a diffusion element according to the invention and a transparent light guide not according to the invention, so that reflection beams 13 according to the invention would strike the pin 8 and be reflected by it in the -X direction. These light beams reflected in the -X direction strike the camera, not shown in detail, so that a faulty measurement of the pins 8 with respect to the Y direction would be carried out.

In FIG. 2 the first embodiment of the present invention with the guide rail 2 1 is shown in FIG. Schematically shown in side view. Four workpieces 1 are shown by way of example, the pins 8 of which are measured by means of the scattering element 7 according to the invention. For backlighting the upper pins 8 , a diffuser strip 3 with LEDs 5 is provided, a transparent light guide 6 guiding light to the scattering element 7 according to the invention. Compared to FIG. 1, a connecting line 14 of the diffuser strip 3 is additionally shown. In addition, a backlight 15 is shown to generate transmitted light. The backlighting 15 arranged behind the workpieces 1 with respect to the sheet plane causes a camera arranged in front of the workpieces 1 with respect to the sheet plane to perceive the outlines of the workpieces 1 .

In Fig. 3 a second embodiment of this invention is illustrated. Here, a form pallet 16 comprises a scattering element 7 which, in the region of the workpieces 1, has a projection according to the invention with respect to the workpieces 1 in a manner not shown. Outside the area of the workpieces 1 , the scattering element 7 can be designed as desired. In a manner not shown, the light guide 6 is illuminated by means of lighting, so that the diffusion element 7 enables diffuse backlighting of the lower pins 8 .

During the measuring process, the diffuser strip 3 lowers onto the workpiece 1 , so that the scattering element 7 of the diffuser strip 3 forms an overhang according to the invention.

As an example, the form pallet 16 has two areas for positioning the workpiece 1 . The form pallet 16 performs a movement in the X or -X direction to measure the two workpieces 1 it holds, so that the diffuser strip 3 only needs to perform a movement in the Y or -Y direction.

In FIG. 4 a third embodiment according to the invention is shown with a sheet metal support 17. The sheet metal carrier 17 is shown in a top view and in a side view in FIG. 5. The sheet metal support 17 advantageously consists of three sheets welded together. If appropriate, the upper sheet has insertion bevels 18 , in particular for the introduction of the workpiece 1 . The middle plate preferably has the positioning or fixing of the workpiece 1 . In particular, the lower plate prevents the falling of the workpiece 1, if appropriate by means of corresponding ribs 19, so that for example a below the sheet support 17 arranged ejector 20 can lift the workpieces 1 during the measuring process in a simple manner on the sheet metal carrier 17th Here, the ejector 20 has scattering elements 7 according to the invention for measuring the pins 8 . To illuminate the workpieces 1 , the ejector 20 has LEDs 5 in the area of a transparent light guide 6 , with which the scattering element 7 is illuminated.

Correspondingly, a hold-down device 21 has LEDs 5 , which in turn illuminates the diffusing element 7 of the hold-down device 21 .

A camera unit (not shown in more detail), which is arranged above the hold-down device 21 and views the workpiece 1 in plan view, is provided with lighting 22 for generating transmitted light.

The workpieces 1 shown in the figures essentially relate to chip holders 1 , which are generally used in radio telephones for receiving the chip card for activation. The chip holder 1 is soldered to a corresponding circuit board with its soldering pins 8 . In order to ensure perfect soldering, it is necessary that the soldering pins 8 are precisely aligned and in particular lie in one plane.

LIST OF REFERENCE NUMBERS

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

down device

22

lighting
H horizontal
V vertical
X direction
Y direction

Claims (9)

1. Device for measuring workpieces ( 1 ) with an image processing system, which has an at least partially optically transparent holder ( 2 , 3 , 4 , 16 , 17 , 20 , 21 ) for positioning the workpieces ( 1 ) in front of the image recording unit with a scattering element ( 7 ) for generating a largely homogeneous diffuse illumination, has an image recording unit and an evaluation unit, characterized in that at least one protrusion (V) protruding beyond the workpiece ( 1 ) of a side surface ( 11 ) arranged transversely to the recording direction (X, -X) of the image recording unit ) of the scattering element ( 7 ) is so small that a predetermined measuring accuracy of the workpiece ( 1 ) can be achieved without the use of aperture elements. 2. Device according to claim 1, characterized in that a distance (H) arranged in the recording direction (X, -X) of the image recording unit from a section ( 8 ) of the workpiece ( 1 ) to the scattering element ( 7 ) to be measured is greater than or equal to the projection ( V) of the side surface ( 11 ) of the scattering element ( 7 ) is (H ≧ V). 3. Device according to one of the preceding claims, characterized in that the distance (H) from the portion to be measured ( 8 ) of the workpiece ( 1 ) to the scattering element ( 7 ) is at least three times as large as the protrusion (V) of the side surface ( 11 ) of the scattering element ( 7 ) is (H ≧ 3 × V). 4. Device according to one of the preceding claims, characterized in that the supernatant (V) is less than is five tenths of a millimeter (H <5/10 mm). 5. Device according to one of the preceding claims, characterized in that the supernatant (V) is less than is three tenths of a millimeter (H <3/10 mm).   6. Device according to one of the preceding claims, characterized in that at least two holders ( 3 , 4 , 20 , 21 ) for upper and lower positioning of the workpiece ( 1 ) are provided in front of the image recording unit. 7. Device according to one of the preceding claims, characterized in that at least one of the holders ( 3 , 4 , 20 , 21 ) comprises at least one damping element for adapting the positioning to different workpieces ( 1 ). 8. Device according to one of the preceding claims, characterized in that at least one of the holders ( 2 , 16 , 17 ) is designed as a workpiece carrier ( 2 , 16 , 17 ) for receiving and transporting the workpiece ( 1 ) in the area in front of the image recording unit , 9. Device according to one of the preceding claims, characterized in that at least the workpiece carrier ( 2 ) is designed as a guide rail ( 2 ).