CN117589079A - Optical testing device - Google Patents

Abstract

An optical test device (2) for testing a planar test object (6) comprises a holder (4) for the test object (6) and two optical sensors (8, 10) for detecting a three-dimensional surface topography of the test object (6). According to the invention, the support (4) is formed at least in a partial region and serves as a test standard, and the support (4) is arranged relative to the sensors (8, 10) such that the sensors (8, 10) can scan the test object (6) from opposite sides, and the support (4) is detected as a test standard at least in a partial region when the test object (6) is detected.

Description

Optical testing device

Technical Field

The present invention relates to an optical test device for testing a planar test object.

Background

In the detection of planar test objects, the test object is usually detected and measured by an optical test device from only one side. For this purpose, contour projectors can be used to detect, for example, the shape and position of both sides of the test object. The distortions caused by the manufacturing process of the test object are only minor here.

Distortion of a test object plays an important role if the test object has a precise and well-toleranced surface topography that can be detected by a 3D measurement system. For fixing the test object on the measurement plane during the test, a holder which works with magnetic or vacuum techniques can be used. After one side of the object to be measured is detected or measured, the clamping must be re-applied to detect or measure the other side. This not only wastes time, but also significantly reduces the measurement accuracy.

Patent document DE 10 2015 205 461 A1 discloses a correction device for an optical measuring device, in which a light-transmitting graduation is arranged in the path of the measuring beam.

Disclosure of Invention

The object of the present invention is to provide an optical test device for testing a planar test object, which device enables a fast and reliable test with high measurement accuracy.

This problem is solved by the invention detailed in claim 1.

The invention provides an optical test device for testing a planar test object, which comprises a support for the test object. According to the invention, the test device comprises two optical sensors for detecting the three-dimensional surface topography of the test object. According to the invention, the support is formed at least in a partial region and is used as a test standard, and the support is arranged in a position relative to the sensor such that the sensor scans the test object from the opposite side, and the support is also detected as a test standard at least in a partial region when detecting the test object.

The basic idea of the invention is to perform a geometric test on the front and back of a planar test object during a common measurement process, and to form a support at least in some areas and to perform the test as a test standard also during the test of the surface of the component. The geometry of the test criterion is precisely determined or known in advance, so that the geometry of the test criterion detected during the measurement forms a reference for the measurement.

By means of the reference provided by the test standard, on the one hand, the measured values of the sensors representing opposite sides of the test object can be correlated.

On the other hand, alignment errors between the sensors can be compensated.

For example, in particular, the holder may form a frame similar to a frame with a window-shaped recess, and the holder may comprise a support structure on which the test objects are arranged, for example in the form of projections spaced apart from each other along the circumference of the recess.

In the test process, the three-dimensional morphology of the surface of the test object is detected by detecting the three-dimensional morphology by optical sensors from both sides of the test object. According to the invention, the surface of the support is also detected as a test criterion at least in a partial region in order to detect the position of the test object in three-dimensional space unambiguously. Thus, no prior mechanical or computational alignment of the test object is required.

Therefore, when the three-dimensional shape of the surface of the test object is determined, the test of the corresponding test object is simplified, and the measurement accuracy is improved.

A particular advantage of the invention is that both sides of the test object are detected simultaneously and that the position of the test object does not change during the test. This significantly increases the test speed and avoids measurement errors that may occur when the test object position must be changed (e.g., by re-clamping) during the test.

The present invention results in a relatively simple test device structure by designing and using a holder (which is present anyway) for a test object as a test standard.

An advantageous further development of the invention is to design the support as a frame. The test object in the frame can be optically detected from both sides and can thus be scanned by the sensor.

The design of the frame may be chosen within a wide range according to the respective requirements and conditions. A further development is advantageous in that the frame is designed as a circumferential closed frame with window-shaped recesses. In this embodiment, the circumferentially closed frame ensures a high mechanical stability of the holder, wherein both side surfaces of the test object can be optically detected by the recess and scanned by the sensor.

Another advantageous further development of the invention is that the frame comprises a support structure on which the test object can be loosely arranged. In this embodiment, the test object is loosely arranged on the support structure of the stand in a particularly simple manner.

The support structure may be formed in a variety of ways depending on the respective requirements and conditions, and may be composed of a transparent material, for example. For example, the support structure can also be designed as a screw thread and extend over a recess in the support.

A further development of the invention is that the support structure comprises protrusions spaced apart from each other in the circumferential direction of the frame. In this respect, it is sufficient and advisable to provide three projections spaced apart from each other in the circumferential direction of the frame or on recesses in the frame in the sense of static certainty.

The stent may be designed in a variety of ways depending on the respective requirements and conditions. In order to achieve a particularly simple construction, a further development is advantageous in that the support is designed as a parallel planar plate. The plate is adapted to the respective test object or series of test objects according to the thickness and size of its recess. The material of the plate may be chosen according to the respective application, for example aluminium for relatively low precision measurement tasks and Zerodur for high precision measurement tasks.

Another advantageous further development of the invention is that the stent is at least partially coated. By coating, the desired or necessary surface properties in the sense of the optical sensor used can be produced in the surface area of the support, which is used as a test standard surface for the test standard. However, this can also be accomplished by machining methods.

Depending on the respective requirements and conditions, different optical sensors may be used, wherein the sensors may be selected depending on, for example, the surface properties of the test object, its aspect ratio, the required cycle time and the tolerance of the test object. With regard to the formation of the sensor, an advantageous further development of the invention is that the at least one optical sensor is formed and configured for planar detection of the test object. Because of the planar detection of the test object, no relative movement between the support and the sensor is required during the test. For example, a planar white light sensor or a holographic sensor may be used for planar detection of the test object.

A further advantageous further development of the invention with respect to the sensor selection is that the at least one optical sensor is formed and configured for linear detection of the test object, wherein a feed device for a relative movement of the support with respect to the sensor is also provided, so that the test object is scanned by the sensor during the feed. For example, a laser triangulation sensor or a photogrammetry sensor may be used as the corresponding sensor.

Furthermore, suitable optical sensors are generally known to those skilled in the art and, therefore, are not explained in detail herein.

In order to detect both sides of the test object simultaneously during the test, according to the invention it is basically sufficient that two sensors are assigned to each side of the test object. However, two or more sensors may be assigned to each side of the test object, depending on the respective requirements and conditions.

The sensor of the test device according to the invention can be identical in terms of structure, in the case of identical or similar surface properties on both sides of the test object and thus identical or similar measurement tasks with respect to the sensor. However, for test subjects with different surface properties on both sides, different sensors may also be used.

A very advantageous further development of the invention is that the holder comprises two preferably plate-shaped individual parts, each having a window-shaped recess for receiving the test object in a reference plane, the individual parts being formed as test standard surfaces on their surfaces facing one another, wherein the individual parts are connected together offset relative to one another in the reference plane, so that in each case the test standard surface of one of the individual parts can be scanned or contacted by one of the sensors through the recess of the other individual part. In this embodiment it is sufficient to finish the contact surface of the stand-alone component only to a very flat surface. Meanwhile, the measurement accuracy is improved by reducing the influence of the test standard geometric deviation on the measurement result.

A further advantageous further development of the test device according to the invention is that the holder is arranged on at least one test standard surface, the surface properties of which can be detected by the sensor. For example, the corresponding surface properties may form a scale, by means of which the feed movement of the feed device can be detected accurately. However, a corresponding scale may also be used to detect defects of the sensors used and take this into account when evaluating the test results.

In claim 12, a method for testing a planar test object is specified, wherein a test device according to the invention is used.

In particular, as provided by an advantageous further development of the method according to the invention, the test object may be a bipolar plate or a cell foil of a fuel cell.

Drawings

The invention will be described in more detail below using embodiments with reference to the attached, highly schematic drawings. It is obvious to the person skilled in the art that the individual features of the examples of embodiments in each case further develop the examples of embodiments themselves, i.e. independently of the further features. It is therefore also obvious to a person skilled in the art that all the described, shown in the drawings and claimed features, whether taken alone and in any technically useful combination, form the subject matter of the invention, whether they are summarized in the patent claims and their references, or whether they are specifically described or represented in the drawings. The subject matter and disclosure of the present application also includes combinations of the features of the apparatus claims and the features of the method claims. The subject matter and disclosure of the present application also includes combinations of features of one embodiment with features of another embodiment. The subject matter and disclosure of the present application also includes sub-combinations of the claims, wherein at least one feature of the claims is omitted or replaced by another feature.

As shown in the figure:

fig. 1 is a perspective view of an optical test device according to a first embodiment of the present invention.

Fig. 2 is a schematic side view of the test apparatus of fig. 1 during a test.

Fig. 3 is a schematic side view of a rack of a testing device according to a second embodiment of the invention.

Fig. 4 is a top view of the bracket of fig. 3.

Detailed Description

Hereinafter, examples of embodiments of the test device according to the present invention are explained in more detail with reference to fig. 1 to 4.

Fig. 1 shows a first embodiment of an optical test device 2 according to the invention for testing planar test objects, which device comprises a holder 4 for a test object 6, the test object 6 being formed in this embodiment by a bipolar plate of a fuel cell.

The test device 2 according to the invention comprises two optical sensors 8, 10 for detecting the three-dimensional surface topography of the test object 6. The sensors 8, 10 are arranged opposite one another with respect to their measuring direction, so that they scan the test object 6 from two sides opposite one another.

According to the invention, the support 4 is formed at least in a partial region and serves as a test standard, and the support 4 is arranged relative to the sensors 8, 10 such that the sensors 8, 10 scan the test object 6 from opposite sides to one another, and during the detection of the test object 6 the support 4 is also detected as a test standard.

In the embodiment shown, the support 4 consists of parallel planar plates and forms a frame 12. In the embodiment, as shown in fig. 1, the frame is formed to be closed in the circumferential direction and to have a middle window-shaped recess 14. The frame 14 comprises a support structure at its recess, on which the test object 6 is loosely arranged. The support structure may comprise, for example, protrusions spaced apart from each other in the circumferential direction of the frame.

As can be seen from fig. 1, the holder 4 and the sensors 8, 10 are arranged opposite each other such that the frame 12 is at least partially also detected when the test object 6 is detected by the sensors 8, 10. By using the detection frame also as a test criterion, the position of the test object 6 in space is clearly defined, so that the measured values of the sensors 8, 10 can be correlated without the need for prior mechanical or computational alignment of the test object.

In the embodiment shown, the sensors 8, 10 are formed identically and are designed and configured for linear detection of a test object. For scanning the test object 6, the support 4 is moved in the X-direction by the feeding device. The construction of the respective feeding means is generally known to the person skilled in the art and will therefore not be explained in detail here. For simplicity of illustration, the feeding device is also not shown.

Suitable sensors are generally well known to those skilled in the art and, therefore, are not explained in detail herein.

At least part of the support 4 is subjected to fine machining, which parts are also inspected during inspection of the surface of the test object 6 and thus form a test standard surface, so that the geometry of the support is precisely determined and known in advance at least in these parts, so that the support 4 functions as a test standard or measurement standard according to the invention.

In the data transmission connected to the sensors 8, 10, the evaluation device evaluates the measured values obtained during the scanning of the test object 6 by the sensors 8, 10, so that at the end of the test procedure the actual geometry of the test object 6 can be regarded as test result or measurement result.

According to the invention, the geometric test of the test object can be performed without prior mechanical or computational alignment, and therefore, the test of the test object becomes quick and simple.

Since it is not necessary to change the position of the test object 6 to test both sides of the test object 6, measurement errors are avoided and measurement accuracy is improved.

Fig. 2 shows a side view of the embodiment according to fig. 1, wherein the measuring or scanning direction of the sensors 8 and 10 is ideally perpendicular to a measuring plane in which the test object 6 is placed on the support 4. In fig. 1, the alignment error of the sensor 8 is represented by the inclination opposite to the measurement plane.

The alignment error can be corrected after measurement as follows:

the sensor 8 detects measured values of the upper surface of the test object 6 in a first sensor coordinate system SKS 1. In the evaluation device, a plane is calculated using the measured value of the upper surface of the support 4 as a test standard, and the measured value of the surface of the test object 6 is subjected to coordinate transformation by the normal vector of the plane. By evaluating previously selected features of the upper surface, such as edges, the plane in the first sensor coordinate system SKS1 is rotated about the normal vector VN 1 into the coordinate system of the test object 6 (workpiece coordinate system WKS). Thus, measured values of the upper side of the test object 6 can be obtained in the workpiece coordinate system.

The sensor 10 detects the measured values of the underside surface of the support 4 in a corresponding manner, calculates a plane from this and performs a coordinate transformation of the measured values of the surface of the test object 6 by means of the normal vector of this plane. Similar to the sensor 8, a plane is calculated by selecting the previously selected underside surface feature (e.g., edge) and the plane of the sensor coordinate system SKS2 is rotated about its normal vector to the workpiece coordinate system WKS. The measurements may then be converted to a workpiece coordinate system.

In summary, the upper and lower surfaces of the test object 6 are detected in a common coordinate system, and further evaluation can be performed.

In addition, corrections can be made in the Y/Z plane during measurement. In this case, a direct reference of the reference plane is constructed for each measurement line xi in order to compensate for the path error in the Z direction during the X-direction movement. The deviation of the path in the Y direction can be determined, for example, by evaluating the edges of the stent 4 and compensating accordingly.

The data obtained by the sensors 8, 10 may be taken as an image that has undergone image processing (e.g. artifact detection in gray images) if needed or desired.

Fig. 3 shows a second exemplary embodiment of a test device 2 according to the invention, which differs from the first exemplary embodiment in the design of the support 4.

In the second embodiment example, the stand 4 includes two rectangular plate-like independent members 4',4″ formed as identical members, each member 4, 4' having a rectangular window-shaped recess 14, '14 ' for accommodating the test object 6 on the reference plane, the independent members 4',4″ being formed as test standard surfaces on surfaces thereof facing each other. The individual parts 4',4 "are connected offset to one another in the reference plane, so that one of the sensors 8, 10 scans or can scan the test standard surface of the other individual part 4' or 4" via the recess 14 "or 14" in the one individual part 4 "or 4".

As shown in fig. 4, the offset of the individual parts 14',14 "and the design of the contact surface between the individual parts 14',14" as a test standard surface 2 results in a surface that is visible from both sides (upper and lower side) and can be scanned or detected by the sensors 8, 10. The two surfaces lie in one plane, thus defining a zero plane, avoiding measurement errors due to parallelism tolerances and thickness variations of the support 4. This reliably prevents deviations between the geometry of the support 4 as a test standard and the specified or desired geometry from entering the measurement results.

Claims (14)

1. An optical test device (2) for testing a planar test object (6), comprising:

-a support (4) for the test object (6); and

at least two optical sensors (8, 10) for detecting a three-dimensional surface topography of the test object (6),

wherein the holder (4) is formed at least in a partial region and serves as a test standard, and wherein the holder (4) is arranged relative to the sensors (8, 10) such that the sensors (8, 10) scan the test object (6) from opposite sides, and wherein the holder (4) is detected as a test standard at least in a partial region during detection of the test object (6).

2. Testing device according to claim 1, wherein the rack (4) is formed as a frame (12).

3. Testing device according to claim 2, wherein the frame (12) is formed as a circumferentially closed frame with a window-shaped recess.

4. A test device according to claim 2 or 3, wherein the frame (12) comprises a support structure on which the test object (6) is loosely arrangeable.

5. The test device according to claim 4, wherein the support structure comprises protrusions spaced apart from each other in the circumferential direction of the frame (12).

6. Testing device according to any of the preceding claims, wherein the rack (4) is formed as a parallel planar plate.

7. Testing device according to any of the preceding claims, wherein the stent (4) is at least partially coated.

8. The test device according to any of the preceding claims, wherein at least one optical sensor (8, 10) is formed and configured for planar detection of the test object (6).

9. Test device according to any one of claims 1 to 7, wherein at least one optical sensor (8, 10) is formed and configured for linear detection of the test object (6), wherein a feeding device for relative movement of the support (4) with respect to the sensor (8, 10) is provided such that during the feeding the sensor scans the test object (6).

10. Test device according to any one of the preceding claims, wherein the stand (4) comprises two preferably plate-shaped individual parts (4 ',4 "), each individual part (4', 4") having a window-shaped recess (14 ',14 ") for accommodating the test object (6) in a reference plane, the individual parts (4', 4") being formed as test standard surfaces on their surfaces opposite to each other, wherein the individual parts (4 ',4 ") are connected together offset relative to each other on the reference plane such that one of the sensors (8, 10) scans or can scan the test standard surface of the other individual part (4', 4") through the recess (14 "or 14 ') in one of the individual parts (14", 14').

11. The test device according to any of the preceding claims, wherein the holder (6) is arranged on at least one test standard surface, wherein the at least one test standard surface has a surface property that can be detected by at least one sensor (8, 10).

12. A method for testing a planar test object, wherein a test device according to any of the preceding claims is used.

13. The method of claim 12, wherein the test object is a bipolar plate of a fuel cell.

14. The method of claim 12, wherein the test object is a battery foil.