Flatness standard for determining the performance of an optical 3D coordinate measuring device, and method for producing a flatness standard of this kind

Abstract

The invention relates to a flatness standard (1) for determining the performance of an optical 3D coordinate measuring device. The flatness standard (1) has a flat surface (2) which is coated with a colour layer (3), wherein the colour layer (3) diffusely reflects visible light and the cured colour layer (3) is deformation-resistant when touched by a tactile coordinate measuring device. The coated flat surface (2) has a shape deviation of less than 100 μm.

Description

[0001] Flatness standard for determining the performance of an optical 3D coordinate measuring machine and method for producing such a flatness standard

[0002] The invention relates to a flatness standard for determining the performance of an optical 3D coordinate measuring machine.

[0003] The invention further relates to a method for producing such a flatness standard.

[0004] Optical 3D coordinate measuring machines are widely used in industrial metrology.

[0005] In contrast to tactile coordinate measuring machines, the objects to be measured are captured without contact. The optical 3D coordinate measuring machine is equipped with at least one camera and an associated lens. To determine the 3D

[0006] Photogrammetric methods are typically applied to determine the object's coordinates, such as photogrammetric forward sectioning. This requires a measurement image of the object from two different viewpoints. The images are preferably taken by two cameras at the same time. However, it is also possible to use only one camera and take the images at two separate times. To calculate the photogrammetric forward section, so-called homologous image points must be identified in both measurement images. This means that the position in the respective camera image corresponding to the image of the same object point is required.

[0007] In practice, pattern projection methods have become established in production metrology. A projector projects one or more patterns onto the object to be measured. At least one camera records the pattern backscattered by the object. The at least one projected pattern creates a texture on the object, which is advantageously used to identify homologous pixels. The projector can also be used as an inverse camera to determine the homologous pixels. Likewise, at least two cameras can be used to capture the pattern backscattered by the object from two different viewpoints at the same time. A widely used pattern projection method is fringe projection, in which periodic fringe patterns are projected onto the object to be measured in different phase positions.

[0008] When a manufacturer sells a coordinate measuring machine to a customer, a so-called acceptance test is usually performed. This involves a standardized test to determine whether the coordinate measuring machine complies with defined specifications for one or more parameters. For each parameter, at least one deviation value is determined using the coordinate measuring machine to be tested and compared against the limit value defined by the manufacturer of the coordinate measuring machine, taking into account the test value uncertainty. If all deviations are less than or equal to the corresponding limit value, taking into account the test value uncertainty, the coordinate measuring machine has successfully passed the acceptance test.

[0009] Acceptance testing requires test pieces containing geometric shapes such as spheres or planes. These geometric shapes must be manufactured with high precision to ensure minimal deviations. These geometric shapes are measured in the standardized acceptance test. To ensure consistent standards for manufacturers of coordinate measuring machines and, in particular, to enable comparability for customers, the International Organization for Standardization (ISO) introduced the ISO 10360 series of standards. This series defines how the acceptance and confirmation testing of coordinate measuring machines should be conducted.Since there are various measuring principles in industrial metrology for measuring objects three-dimensionally, the aim of ISO was and is to create a separate sheet for each measuring principle within the ISO 10360 series for an established measuring principle.

[0010] A well-known parameter is the flatness deviation, which is defined according to DIN EN ISO 10360-13:2023-11 (German version of ISO 10360-13:2021) as follows: "Minimum distance between two parallel planes enclosing one percentile of all data measured in the test plane." Simply put, it describes the deviation of the measurement points measured with the coordinate measuring machine under test from the ideal shape of the plane. The smaller the value of the flatness deviation test parameter, or the smaller the corresponding limit value of the coordinate measuring machine verified during acceptance testing, the more accurately the tested coordinate measuring machine can determine shape deviations of planes in subsequent measuring applications.

[0011] ISO 10360-13:2021 describes the acceptance and confirmation testing of optical 3D coordinate measuring machines. Several different test specimens are required to perform this acceptance test. In order for the respective test specimen to be measured with the optical coordinate measuring machine, it must have a so-called optically cooperative surface. This means that the light / pattern projected onto the test specimen is reflected as diffusely as possible from the surface of the flatness standard, the absorption coefficient is as low as possible, and no volume scattering occurs (i.e., the light does not penetrate the test specimen and is absorbed / reflected at different depths).

[0012] Before the test piece can be used in the acceptance test, it must first be calibrated. This is generally performed by an independent laboratory, ideally accredited for this measurement task according to ISO 17025. Almost without exception, the accredited procedure includes calibrating the test piece with a tactile coordinate measuring machine. This requires that the test piece also be capable of tactile measurement. This means that the surface must be hard enough that it is not deformed when contacted by the tactile coordinate measuring machine.

[0013] The flatness deviation parameter is determined according to ISO 10360-13:2021 as follows. A flatness standard is measured at six (6) defined positions within the sensor measurement volume. As already explained, the flatness standard must be calibrated. This means that the flatness deviation of the flatness standard and the associated measurement uncertainty must be known from an external calibration. Furthermore, it is imperative that the flatness standard has an optically cooperative surface.

[0014] The form deviation of the flatness standard, which is determined during calibration, must be small in relation to the limit value for the flatness deviation parameter of the optical 3D coordinate measuring machine under test. Likewise, the measurement uncertainty of the form deviation must be as small as possible in relation to the limit value for the flatness deviation parameter of the optical 3D coordinate measuring machine under test. Both requirements are fundamental, as the flatness deviation occurring in the measurement result should be a quality characteristic of the sensor under test and not an expression of the imperfection of the test specimen. The test value uncertainty is calculated from the form deviation of the flatness standard and the associated measurement uncertainty. This uncertainty must always be taken into account when assessing whether the coordinate measuring machine complies with the permissible limit value.

[0015] If the limit value of the coordinate measuring machine to be tested is high, the requirements for the flatness standard with regard to the perfection of the plane (= form deviation of the plane) and also the requirements for the external calibration laboratory with regard to the achieved measurement uncertainty of the form deviation of the plane are lower. Therefore, for very high limit values ​​to be tested, a flatness standard can also be used which, for example, has larger flatness deviations due to manufacturing and / or cost reasons. Likewise, a calibration laboratory can be commissioned whose smallest achievable measurement uncertainty may be somewhat higher, but which performs the calibration more cost-effectively. However, if the limit value of the coordinate measuring machine to be tested is low, the demands on the quality of the test specimen and the calibration laboratory commissioned with the calibration increase.

[0016] Previously known flatness standards are often made of natural stone, such as granite. They are used, for example, as test standards in the acceptance testing of tactile coordinate measuring machines. They are also installed as measuring plates in tactile coordinate measuring machines. Flatness standards made of natural stone can be measured easily by touch. However, they do not have an optically cooperative surface. Such natural stones are often too dark and thus have a relatively high absorption coefficient. They generally also have a texture due to the various minerals present in the natural stone. This texture can lead to measurement errors during optical measurement of the surface. In addition, natural stones often have so-called microcracks. This means that the stone has small holes and pockets that are usually significantly smaller than 1 mm. The microcracks are a result of the genesis of the natural stone. For previous uses, such as measuring table plates, this is irrelevant.However, when used as test equipment for the acceptance testing of optical coordinate measuring machines, they are disruptive because the microcracks lead to shape deviations in the measurement result, which do not originate from the coordinate measuring machine itself, but from the imperfection of the test specimen.

[0017] Alternatively, flatness standards made of ceramic are also known. They are often described by the respective manufacturer as suitable optical standards. However, this is not generally true, since volume scattering occurs with ceramic materials depending on the respective optical measuring device, in particular the wavelength of the projection unit used for the measurement. This means that the projected light penetrates the ceramic surface and is refracted due to the transition to another optical medium. The light is then reflected at various depths in the ceramic, only to be refracted again at the transition between the ceramic and air. This leads to measurement errors, which are reflected in an increased form deviation. Thus, the performance of the optical coordinate measuring machine cannot be objectively assessed because an optically uncooperative material is used in the test specimen.

[0018] The object of the invention is to provide an improved flatness standard which can be measured optically and tactilely, and a method for producing such a flatness standard.

[0019] The object is achieved by the flatness standard having the features of claim 1, by a set of flatness standard and link elements according to claim 9, by the method having the features of claim 10, and by the use of the flatness standard according to claim 13. Advantageous embodiments are described in the subclaims.

[0020] It is proposed that a flatness standard which has a flat surface, wherein this flat surface is partially or completely coated with a layer of paint by means of a suitable mechanical process, and wherein the paint used for the paint layer is selected such that visible light is diffusely reflected and the paint is hard enough after curing to be tactilely probed by a tactile coordinate measuring machine. The shape deviation of the coated flat surface is less than 100 pm. The surface is designed with the aid of the at least one layer of paint such that it reflects optically diffusely. For this purpose, the degree of reflection is sufficiently high and designed such that no volume scattering occurs, or only a slight one depending on the requirements. The surface of the cured layer of paint is such that it is hard enough not to deform during tactile measurement, i.e. not, for example,to be damaged by scratches, compaction and the like.

[0021] By coating the flat surface with a layer of paint, it is possible to create a high-precision flatness standard in a simple and reliable way, which has a flat surface that is sufficiently uniform, diffusely reflective and protected from damage for optical measurement.

[0022] The coating can close any microcracks present in the uncoated flatness standard, thereby reducing the flatness standard's shape deviation. This allows materials to be used for the flatness standard that would be unsuitable without the coating. Materials with microcracks can therefore also be used to produce the uncoated flatness standard.

[0023] The indefinite term "a" is to be understood as such and not as a number, unless the context explicitly indicates otherwise. This does not exclude further characteristics, so the term is to be interpreted as "at least one."

[0024] In this respect, the flatness standard can also have more than one flat surface and / or more than one layer of paint.

[0025] A particularly suitable mechanical process for coating the flat surface with at least one layer of ink is screen printing. The ink to be applied is pressed through a screen onto the surface to be printed. This process is characterized by the fact that a very consistent ink layer thickness can generally be applied. When a flatness standard is screen printed, the form deviation generally increases only marginally. Depending on the size and nature of the flatness standard, the form deviation of the ink layer itself can sometimes be well below 10 pm. This means that after the coating process and subsequent calibration, the flatness standard can be used as a flatness standard for optical and tactile coordinate measuring machines without any further treatment.

[0026] It is also conceivable, however, for several layers of the same color to be applied one above the other on the flat surface, and for any resulting deviation in the flatness of the flat surface to be reduced by machining the cured paint layers. This type of post-processing, for example, by lapping, can create an extremely uniform, flat surface and eliminate any thickness variations that may occur during the paint application, such as streaks.

[0027] If the optical 3D coordinate measuring machine to be tested has a very small limit value for flatness deviation, the form deviation (and thus the directly related test value uncertainty) of a single-coated flatness standard may be too large. In such a case, one possible solution is to coat the flatness standard multiple times using a suitable mechanical coating process. For example, a flatness standard can be coated multiple times, e.g., 10 times in succession, with the selected color using screen printing. Between coating processes, it is ensured that each applied layer of paint is sufficiently dry and solid. Due to multiple coatings, the total paint layer thickness is significantly greater than with a single coating with only one layer of paint. The form deviation of the multiply coated plane is generally greater than with single-coated planes.However, the form deviation is significantly smaller than the total paint layer thickness. This makes it possible to rework the multi-coated flatness standard using a suitable machining process. For example, it is possible to significantly reduce the form deviation of the coated surface using lapping. Care should be taken to ensure that the material removal is significantly smaller than the original paint layer thickness, so that after lapping, the entire originally coated area is still coated with paint. Otherwise, at least one additional coat of paint may have to be applied after machining, which may then be reworked using another machining process.

[0028] The production of such a flatness standard can be carried out by producing a flat surface of a carrier element and coating the flat surface of the carrier element once or multiple times with a layer of paint in such a way that the shape deviation of the flat surface coated with the layer of paint is less than 100 pm and the layer of paint diffusely reflects visible light and the cured layer of paint is resistant to deformation, in particular scratch-resistant, when tactilely probed by a tactile coordinate measuring device.

[0029] It is advantageous to apply several layers of the same color on top of each other on the flat surface, for example using a screen printing process, and to machine the hardened layers of paint to reduce the flatness deviation of the flat surface.

[0030] The "flatness deviation" parameter is determined according to ISO 10360-13:2021 both for each of the six (6) individual measurements (single view) and for the six (6) individual measurements registered in a common coordinate system (multiple view). To perform this registration, stationary reference marks are advantageous for the flatness standard. At least three reference marks (e.g., circular marks) are required to calculate the transformation parameters for transforming each individual measurement into a common coordinate system. The reference marks must not lie on the same line.

[0031] In an advantageous embodiment, a guide element equipped with at least three measuring marks is arranged in a fixed position relative to the flatness standard. These measuring marks can then be measured in each of the six (6) individual measurements in addition to the flat surface. Using the measuring marks, the measurement data of the flatness standard from each individual measurement can be transformed into a higher-level coordinate system.

[0032] The guide element can have a rectangular basic shape and a window in its inner area. The window is enclosed by a frame, on which the measuring marks are advantageously attached. The guide element is arranged in relation to the flatness standard such that the window leaves a defined portion of the coated flat surface of the flatness standard or the entire coated flat surface of the flatness standard visible. This allows the visible coated surface of the flatness standard to be measured with the optical coordinate measuring machine to be tested. Likewise, three or more measuring marks can be measured by the optical coordinate measuring machine to be tested and then used to record the measurement data. It is advantageous if the flatness standard is stored and transported in a carrying case or similar device. The carrying case protects the flatness standard from damage and contamination.

[0033] It is advantageous if the transport case includes at least one fixing unit that allows the flatness standard to be firmly connected to the transport case. This fixing unit can also advantageously be used to firmly align the guide element to the flatness standard. Fixing can be achieved in various ways. For example, a positive and / or non-positive fastening is conceivable, such as fixing the flatness standard to the transport case by screwing. For this purpose, the flatness standard and / or the guide element have corresponding holes that enable screwing to the fixing unit in the transport case.

[0034] In a further advantageous embodiment, the guide element can be fixed in place to the flatness standard by magnetic force. For this purpose, a magnetic holder can be included in the carrying case, for example, as a fixing unit. The guide element has a matching counterpart, so that the guide element can be connected to the fixing unit by magnetic force. This also allows the use of several different guide elements, which can then be easily interchanged.

[0035] A set of flatness standard and link element with measuring marks, which is designed for fixed arrangement to the flatness standard, can advantageously have several different link elements, each of which can be selected for fixed arrangement to the flatness standard.

[0036] Optical coordinate measuring machines are often delivered with sensor measurement volumes of varying sizes. A separate acceptance test is performed for each sensor measurement volume. To perform the acceptance test according to ISO 10360-13:2021, it is mandatory that at least three measurement marks are measured in addition to the flat surface in each individual measurement of the flatness standard. With small sensor measurement volumes, it is possible that a first guide element has a window that is too large, meaning that the flatness standard in the area of ​​the window and the measurement marks cannot be measured simultaneously. In such a case, it is advantageous to use a second guide element with a smaller window, which also allows the measurement marks to be placed closer together. This makes it possible to test a very large number of different sensor measurement volumes using a single flatness standard of uniform size and two or more different guide elements.This eliminates the need to maintain a large number of different flatness standard sizes, as the effectively usable size of the flatness standard can be controlled by the dimensions of the window in the gate element or adapted to the available sensor volume. This can save considerable effort and money, as a single flatness standard size is generally sufficient. Furthermore, calibration costs are also lower, as ideally only one flatness standard needs to be calibrated, rather than several different flatness standards of different dimensions. The size of the coated area of ​​the flatness standard is advantageously determined by the largest sensor measurement volume to be tested by the measuring device manufacturer, taking into account the length and width requirements of the flatness standard according to ISO 10360-13:2021.Furthermore, one or more different gate elements are designed in such a way that it is ensured that for all sensor measuring volumes to be tested, a sufficiently large portion of the coated surface can be measured with regard to the requirements of ISO 10360-13:2021 and at least three measuring marks on the frame can also be measured.

[0037] In this respect, the use of the flatness standard described above is advantageous for the acceptance or confirmation test of an optical coordinate measuring machine, which is carried out in particular in accordance with the provisions of the ISO 1030-13:2021 standard.

[0038] A further advantage of using one or more gate elements with windows, which enable the measurement capability of a defined sub-area of ​​the coated surface of the flatness standard, is the application of a separate form deviation and measurement uncertainty for each sub-area, if these are specified in the flatness standard's calibration certificate. Assuming that a flatness standard with large dimensions (length and width of the coated surface) is used, a comparatively large flatness deviation can be expected as a result of the calibration. This is because the larger the standard, the more technically difficult it becomes to guarantee a defined maximum flatness deviation than with a smaller standard.At the same time, the measurement uncertainty of the form deviation also generally decreases, as the accuracy of the measurement method for determining the flatness deviation decreases with increasing size of the standard. As already explained, the test value uncertainty results from the form deviation determined by the calibration laboratory and the associated measurement uncertainty. The goal must always be to keep the test value uncertainty small relative to the limit value of the coordinate measuring machine being tested.

[0039] If the position and size of the windows of at least one of the splitter elements for the flatness standard are known, it can be agreed with the laboratory when commissioning the calibration of the standard that the corresponding calibrated form deviation and the corresponding measurement uncertainty are specified for each window for each viewing area of ​​the flatness standard. The form deviation of the flatness standard tends to decrease the smaller the calibrated area of ​​the flatness standard is. Likewise, under certain circumstances, a smaller measurement uncertainty can also be achieved by the calibration laboratory if, for example, a more precise measuring device is used for a partial area of ​​the flatness standard than for the entire coated area of ​​the flatness standard. In general, the smaller the window size, the smaller the test value uncertainty will be if the calibration laboratory specifies the corresponding form deviation and the measurement uncertainty for the respective window size.This is particularly advantageous given that smaller sensor measurement volumes to be tested generally also have smaller limit values ​​for flatness deviation. Therefore, it is advantageous to keep the test value uncertainty as small as possible.

[0040] The invention is explained in more detail below using exemplary embodiments and the accompanying drawings. They show:

[0041] Fig. 1 - Sketch of a perspective view of a flatness standard;

[0042] Fig. 2 - Sketch of a flatness standard with a link element screwed into a transport case;

[0043] Fig. 3 - Sketch of a flatness standard with magnetic holders screwed into a carrying case;

[0044] Fig. 4 - Sketch of a link element with integrated magnets;

[0045] Fig. 5 - Sketch of a flatness standard with a first magnetically fixed link element in a transport case;

[0046] Fig. 6 - Sketch of a flatness standard with a second magnetically fixed link element in a transport case.

[0047] Figure 1 shows a perspective view of a sketch of a first embodiment of a flatness standard 1 coated according to the invention, which is configured as a test specimen for optical coordinate measuring machines according to ISO 10360-13:2021. However, the flatness standard 1 can also be used as a test specimen for other coordinate measuring machines, in particular for tactile coordinate measuring machines.

[0048] The flatness standard 1 can be made of a natural stone as a supporting element, such as granite. However, other types of stone can also be used. This includes both natural and artificial stones. An example of a flatness standard 1 made of artificial stone is a molded concrete part. It is also possible for the flatness standard 1 to be made of ceramic. The use of another suitable material, such as metal, glass, or plastic, is also conceivable.

[0049] The flatness standard 1 is, for example, cuboid-shaped and has a surface that has been mechanically machined to produce a flat surface 2 with a slight flatness deviation. The edges of each surface of the flatness standard 1 can be chamfered, as in this exemplary embodiment. The surface formed as a flat surface 2 can, for example, be the surface of the top side shown in Figure 1 and / or the longitudinal side surfaces and / or end faces and / or, for an application rotated by 180°, also the underside surface.

[0050] The flatness deviation of the flat surface 2 is less than 100 pm and should ideally be significantly smaller than 100 pm, for example, less than 10 pm. With suitable machining processes, flatness deviations of less than 5 pm are easily achievable. The size of the flat surface 2 (length, width) should be dimensioned according to the specific measurement environment to ensure compliance with the specifications of ISO 10360-13:2021 with regard to the sensor measurement volume of the optical 3D coordinate measuring machine to be tested.

[0051] The flat surface 2 of the flatness standard is coated with a white ink layer 3. The ink is applied to the flatness standard 1 by a suitable mechanical coating process. This can be done, for example, by a screen printing process.

[0052] The white paint is selected to diffusely reflect visible light emitted by the optical 3D coordinate measuring machine. Furthermore, once dry, the paint is so pressure- and scratch-resistant that it can withstand light mechanical stress, such as manual handling and cleaning, and remains dimensionally stable when measured with a tactile coordinate measuring machine. For this purpose, the paint should be sufficiently scratch-resistant. A two-component paint made of polyurethane and / or acrylic is suitable, for example. RAL 9010, for example, is suitable for achieving sufficient diffuse reflection.

[0053] The flatness standard 1 can have a recessed thread 4 on each of its two end faces. This can be achieved, for example, by a metal bushing glued into the artifact, i.e., the support element. Using the thread 4, the flatness standard 1 can be screwed into a transport case 6 (not shown in Figure 1). Additionally, the flatness standard 1 can have a marking 5, for example, in the form of a hole, on at least one of the two end faces. This marking 5 marks the adjacent flat surface and ensures that the desired side is also coated during the coating process.

[0054] Figure 2 shows a flatness standard 1 in an open transport case 6. The lid of the transport case 6 is not shown in the sketch.

[0055] U-shaped metal brackets 7 are integrated into the transport case 6. For this purpose, two metal brackets 7 can be arranged at a distance from each other corresponding to the length of the flatness standard 1. The metal brackets 7 are arranged in the case 6 such that the flatness standard 1 can be placed between a pair of metal brackets 7 with its longitudinally opposite end faces. The flatness standard 1 can be attached to each of the metal brackets 7 using screws 8.

[0056] A guide element 9 can also be arranged in the transport case 6. The guide element 9 is designed such that it has a window in its center that is slightly larger than the flat surface 2 of the flatness standard 1. The guide element 9 can also be fixed to the metal brackets 7 using the screws 8. Thus, the flatness standard 1 and the guide element 9 are arranged stationary relative to each other. Even if the transport case 8 moves, the relative position of the guide element 9 and the flatness standard 1 remains unchanged.

[0057] The guide element 9 has at least three measuring marks 10 on its upper side. Advantageously, there are significantly more than three measuring marks 10, which ideally also have different diameters or different shapes. Depending on the spatial resolution of the system to be tested, for example, only measuring marks 10 of a diameter matching the spatial resolution of the system can be used. By using different diameters, a flatness standard 1 can be used in combination with the associated guide element 9 for various optical coordinate measuring machines to be tested with different sensor measurement volumes.

[0058] Figure 3 shows another embodiment of the fastening of the flatness standard 1 in a transport case 6. The flatness standard 1 is fixed in an open transport case 6 by means of the holders 7 permanently installed in the case and two screws 8 with star grip, in that the flatness standard 1 is screwed to a holder 7 on each of the opposite end faces using the screws 8.

[0059] The transport case 6 contains magnetic holders 11 that are permanently installed in the case 6. Alternatively, the magnetic holders 11 can also be loose elements that are fixed in the case 6 together with the flatness standard 1 by the screws 8.

[0060] Figure 4 shows a gate element 9 in a front and rear view. On the front, various measuring marks 10 of different diameters are arranged near the window. On the back, a magnet 12 is installed at each of the four corners of the gate element 9.

[0061] Analogous to the guide element 9 sketched in Figure 4, further guide elements may be present, each of which, however, has a window of different size than the guide element 9 shown in Figure 4. In particular, the window may be significantly smaller, so that only a very limited area of ​​the flatness standard 1 is visible. The measuring marks 10 are generally arranged close to the respective window of the guide element 9.

[0062] Figure 5 shows the flatness standard 1 in the transport case 6 from Figure 3. A first guide element 9 (see Figure 4) with integrated magnets 12 is placed on the magnetic holders 11 fixedly arranged in the transport case 6. In this embodiment, the guide element 9 has a window that is smaller than the flat surface 2 of the flatness standard 1 coated with the paint layer 3. At least three, but advantageously significantly more, measuring marks 10 are arranged on the guide element 9. The size of the window of the guide element 9 and the arrangement of the measuring marks 10 are designed such that one or more sensor measuring volumes of the optical 3D coordinate measuring machine to be tested can measure the plane in the window as well as at least three surrounding measuring marks 10 in each of the six (6) test positions.

[0063] Assuming that the test is to be performed for a sensor measurement volume whose size is significantly smaller than the window of the gate element 9 in Figure 5, this design cannot be used for acceptance testing according to ISO 10360-13:2021. However, a different gate element 9 with a significantly smaller window can then advantageously be used. The size of the window is advantageously based on the size of the sensor measurement volume, so that the plane and at least three surrounding measurement marks 10 can be measured in each of the six (6) measurement positions.

[0064] Figure 6 again shows the flatness standard 1 in the transport case 6 from Figure 3. A second guide element 9 with integrated magnets 12 is mounted on the magnetic holders 11 fixed in the transport case 6. This guide element 9 has a significantly smaller window than the guide element 9 from Figure 5. The measuring marks 10 are arranged close to the window, i.e., as close as possible to the window frame surrounding the window. The smaller window results in a significantly smaller area of ​​the flatness standard 1 that is visible and can be measured.

[0065] Depending on the design, additional gate elements 9 with different window sizes can be provided. This makes it possible for a uniform flatness standard 1 to be used for a wide variety of sensor measurement volumes with significantly different sizes, using gate elements 9 that differ from one another due to their different window sizes. In principle, it is sufficient to maintain only one artifact or type of flatness standard 1, the size of which is based on the largest sensor measurement volume and the specifications of ISO 10360-13:2021. The windows of the various gate elements 9 and the diameters of the measurement marks 10 are then based on the smaller sensor measurement volumes and, in turn, the specifications of ISO 10360-13:2021. This saves the high costs of designing, manufacturing, and calibrating many different flatness standard 1 artifacts.

[0066] 1 flatness standard

[0067] 2 flat surface 3 layer of paint

[0068] 4 threads

[0069] 5 Marking

[0070] 6 transport cases

[0071] 7 U-shaped metal bracket 8 screws

[0072] 9 backdrop element

[0073] 10 measuring marks

[0074] 11 Magnetic holder

[0075] 12 Magnet

Claims

Patent claims:

1. Flatness standard (1) for determining the performance of an optical 3D coordinate measuring machine, characterized in that - the flatness standard (1) has a flat surface (2) coated with a layer of paint (3), wherein the layer of paint (3) diffusely reflects visible light and the cured layer of paint (3) is resistant to deformation when tactilely probed by a tactile coordinate measuring device, and that; - the coated flat surface (2) has a shape deviation of less than 100 pm.

2. Flatness standard (1) according to claim 1, characterized in that the ink layer (3) is applied to the flat surface (2) by screen printing.

3. Flatness standard (1) according to claim 1 or 2, characterized in that the flat surface (2) is coated with several layers of paint (3) applied one above the other.

4. Flatness standard (1) according to claim 3, characterized in that several paint layers (3) of the same color are applied one above the other on the flat surface (2) and the flatness deviation of the flat surface (2) is reduced by machining the hardened paint layers (3).

5. Flatness standard (1) according to one of the preceding claims, characterized in that a link element (9) with measuring marks (10) is arranged stationary relative to the flatness standard (1).

6. Flatness standard (1) according to claim 5, characterized in that the link element (9) can be fixed in position to the flatness standard (1) by magnetic force.

7. Flatness standard (1) according to claim 5 or 6, characterized in that several mutually different link elements (9) are arranged in a fixed position relative to the flatness standard (1).

8. Flatness standard (1) according to one of the preceding claims, characterized in that the flatness standard (1) has several flat surfaces (2).

9. Set comprising a flatness standard (1) according to one of the preceding claims and a link element (9) with measuring marks (10), which is designed for stationary arrangement relative to the flatness standard (1), characterized in that the set has a plurality of mutually different link elements (9), each of which can be selected for stationary arrangement relative to the flatness standard (1).

10. Method for producing a flatness standard (1) according to one of the preceding claims, characterized by - producing a flat surface (2) of a support element; - Coating the flat surface (2) of the carrier element with a layer of paint (3) such that the shape deviation of the flat surface (2) coated with the layer of paint (3) is less than 100 pm and the layer of paint (3) diffusely reflects visible light and the cured layer of paint (3) is deformation-resistant when tactilely probed by a tactile coordinate measuring device.

11. A method for producing a flatness standard (1) according to claim 10, characterized by coating the flat surface (2) with a layer of color (3) using a screen printing process.

12. Method according to claim 10 or 11, characterized by applying several layers of paint (3) of the same color on the flat surface (2) one above the other and machining of the hardened paint layers (3) to reduce the flatness deviation of the flat surface (2).

13. Use of a flatness standard according to one of claims 1 to 9 for the acceptance or confirmation test of an optical coordinate measuring machine.

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