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

Abstract

A flatness standard (1) for determining the performance of an optical 3D coordinate measuring machine is described. The flatness standard (1) has a flat surface (2) coated with a paint layer (3). The paint layer (3) diffusely reflects visible light, and the cured paint layer (3) is deformation-resistant when contacted by a tactile coordinate measuring machine. The coated flat surface (2) has a form deviation of less than 100 µm.

Description

The invention relates to a flatness standard for determining the performance of a 3D optical coordinate measuring machine.The invention further relates to a method for producing such a flatness standard.Optical 3D coordinate measuring machines are widely used in industrial metrology. In contrast to tactile coordinate measuring machines, the objects to be measured are detected in a contactless manner. The optical 3D coordinate measuring machine is equipped for this purpose with at least one camera and an associated objective. To determine the 3D coordinates of the object, methods of photogrammetry are usually used, for example photogrammetric forward section. For this purpose, a measurement image of the object must be recorded from two different points of view. The images are preferably taken by two cameras at the same time. However, it is also possible for only one camera to be used and for the images to be recorded at two separate times. In order 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 is required, which corresponds to the mapping from the same object point in each case.In practice, pattern projection methods have become established in manufacturing metrology. In this case, one or more patterns are projected onto the object to be measured by means of a projector. At least one camera captures the pattern backscattered from the object. The at least one projected pattern generates a texture on the object, which texture is advantageously used for identifying homologous image points. The projector can also be used as an inverse camera for determining the homologous image points. Equally, at least two cameras can also be used which record the pattern backscattered from the object from two different points of view 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.When a coordinate measuring machine is to be sold from a manufacturer to a customer, a so-called acceptance check is usually performed. In this case, a standardized test checks whether the coordinate measuring machine complies with defined specifications for one or more characteristic variables. For each characteristic variable, at least one deviation value is determined with the coordinate measuring machine to be checked and compared against the limit value defined by the manufacturer of the coordinate measuring machine taking into account the check value uncertainty. If all deviations are smaller than or equal to the associated limit value, taking into account the test value uncertainty, the coordinate measuring machine has successfully passed the acceptance test.To carry out the acceptance test, test specimens are required which contain geometric shapes such as, for example, balls or even planes. These geometric shapes must be manufactured with high precision so that they have the smallest possible shape deviations. In the standardized acceptance test, these geometric shapes are measured. In order to ensure identical standards for manufacturers of coordinate measuring machines and in particular also to enable the comparison for customers, the international standardization organization "International Organization for Standardization" (ISO) introduced the series of standards ISO 10360. This defines how the acceptance and confirmation checking of coordinate measuring machines is to be carried out. Since there are different measurement principles in industrial metrology in order to measure objects three-dimensionally, it was and is the goal of ISO to create a separate sheet per measurement principle within the scope of the ISO 10360 series for an established measurement principle.A known characteristic variable 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, which include a percentile of all data measured in the test plane." Expressed in simplified form, it describes how great the deviation of the measurement points, measured with the coordinate measuring machine to be tested, from the ideal shape of the plane. The smaller the value of the inspection variable flatness deviation or the smaller the associated limit value of the coordinate measuring machine detected in the context of the acceptance test is, the more exactly the tested coordinate measuring machine can determine shape deviations of planes in the later measurement use.ISO 10360-13:2021 describes the acceptance and confirmation testing of 3D optical coordinate measuring machines. To carry out this acceptance test, several different test specimens are required. In order for the respective test body to be able to be measured with the optical coordinate measuring machine, it must have a so-called optical cooperative surface. This means that the light / pattern projected onto the test specimen is reflected as diffusely as possible on the surface of the flatness standard, the degree of absorption is as small as possible and no volume scattering occurs (that is to say the light does not penetrate into the test specimen and is absorbed / reflected at various depths).In order for the test specimen to be able to be used in the context of the acceptance test, it must be calibrated beforehand. This is generally done by an independent laboratory which is as cold-redited as possible for this measurement task according to ISO 17025. Almost without exception, the accredited method involves the calibration of the test specimen with a tactile coordinate measuring machine. This has the result that the test specimen can also be measured tactilely. That is, the surface must be hard enough that it is not deformed during probing by the tactile coordinate measuring machine.The characteristic of the flatness deviation is determined according to ISO 10360-13:2021 as follows. A flatness standard is measured in six (6) defined positions in the sensor measurement volume. As already stated, it is a prerequisite that the flatness standard is calibrated. This means that the variation in flatness of the normal to the flatness and the associated measurement uncertainty must be known from an external calibration. In addition, it is absolutely necessary for the flatness standard to have an optical cooperative surface.The shape deviation of the flatness standard, which is determined during calibration, must be small in relation to the limit value for the characteristic of the flatness deviation of the 3D optical coordinate measuring machine to be tested. Likewise, the measurement uncertainty of the dimensional deviation in relation to the limit value for the characteristic quantity of the flatness deviation of the optical 3D coordinate measuring machine to be tested must be as small as possible. Both requirements are elementary, since the variation in flatness occurring in the measurement result is to be a quality characteristic of the sensor to be tested and not an expression of the imperfections of the test specimen. From the shape deviation of the flatness standard and the associated measurement uncertainty, the test value uncertainty is calculated, which must always be taken into account in the evaluation of whether the coordinate measuring machine complies with the permissible limit value.If the limit value of the coordinate measuring machine to be checked is large, the requirement for the flatness standard with respect to the perfectness of the plane (=form deviation of the plane) but also the requirement for the external calibration laboratory with respect to the obtained measurement uncertainty of the form deviation of the plane are lower. Thus, in the case of very large limit values to be checked, a flatness standard can also be used which, for example, has greater flatness deviations due to production and / or costs. Just as, a calibration laboratory can be ordered whose smallest measurement uncertainty that can be achieved is possibly somewhat greater, but which carries out the calibration more cost-effectively for this purpose. However, if the limit value of the coordinate measuring machine to be checked is small, the requirements for the quality of the test body and the calibration laboratory charged with the calibration increase.Previously known flatness standards often consist of natural stone, e.g. gritite. They are used, for example, as a test normal in the context of acceptance testing for 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 in a tactile manner. However, they do not have an optically cooperative surface. For example, such natural stones are frequently too dark and thus have a relatively high degree of absorption. In general, they also have texture because various minerals are present in the natural stone. This texture can lead to measurement errors during the optical measurement of the surface. In addition, natural stones frequently have so-called microcracks. That is, the stone has small holes and pockets, which are usually significantly smaller than 1 mm. Microcracks are the result of genesis of natural stones. In previous uses, such as a measuring table plate, this is irrelevant. When used as test means for the acceptance test of optical coordinate measuring machines, however, they are disruptive, since the microcracks lead to shape deviations in the measurement result, which, however, do not originate from the coordinate measuring machine itself, but from the imperfections of the test specimen.Alternatively, flatness standards made of ceramic are also known in the art. They are frequently referred to by the respective manufacturer as suitable optical standards. However, this is not generally valid, since volume scattering occurs in the case of the material ceramic depending on the respective optical measuring device, in particular on the wavelength of the projection unit used for the measurement. This means that the projected light penetrates into the ceramic surface and is refracted due to the transition into another optical medium. The light is then reflected at various depths of the ceramic to be refracted again at the transition between ceramic and air. This leads to measurement errors which are reflected in an increased shape deviation. Thus, the performance of the optical coordinate measuring machine cannot be evaluated objectively, since an optically non-cooperative material is used in the test body.It is an object of the invention to provide an improved flatness standard which is measurable optically and tactilely, and a method for producing such a flatness standard.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 the use of the flatness standard according to claim 13. Advantageous embodiments are described in the dependent claims.It is proposed that in the case of a flatness standard which has a flat surface, wherein this flat surface is partially or completely coated with a color layer by means of a suitable machine method, and wherein the color used for the color layer is selected such that visible light is diffusely reflected and the color, after curing, is hard enough to be tactilely probed by a tactile coordinate measuring machine. The dimensional deviation of the coated planar surface is less than 100 μm.The surface is configured with the aid of the at least one color layer such that it reflects optically diffusely. For this purpose, the degree of reflection is sufficiently high and is designed such that no volume scattering occurs or only a small volume scattering occurs depending on the requirement. The surface of the cured color layer is designed such that it is hard enough not to deform during a tactile measurement, i.e. not to be damaged by scratches, compaction and the like, for example.By means of the coating of the planar surface with a paint layer, it is possible in a simple and reliable manner to create a highly accurate planar normal which has a planar surface which is sufficiently uniform, diffusely reflecting and protected from damage for the optical measurement.As a result of the coating, microcracks which may be present in the uncoated normal to flatness can be closed, as a result of which a reduction in the dimensional deviation of the normal to flatness can be achieved. Thus, for example, materials for the flatness standard can also be used that would not be usable without coating. Materials with microcracks can thus likewise be used for producing the uncoated flatness standard.The indefinite term "a" is to be understood as such and not as a numerical word unless expressly stated otherwise from the context. Further features are thus not excluded, so that the term should be interpreted in the sense of "at least one".In this respect, the flatness standard can also have more than one planar surface and / or more than one color layer.A suitable machine method for coating the planar surface with the at least one color layer is in particular the screen printing method. The ink to be applied is pressed through a screen onto the surface to be printed. The process is distinguished in that a very constant ink layer thickness can generally be applied. When a flatness standard is printed by screen printing, the dimensional deviation generally only marginally increases. Depending on the size and condition of the flatness standard, the deviation in shape of the ink layer itself is in some cases significantly below 10 μm. It is thus possible that the flatness standard after the coating process and subsequent calibration can be used without further aftertreatment as a flatness standard for optical but also tactile coordinate measuring machines.However, it is also conceivable that a plurality of colored layers of the same color are applied one above the other on the planar surface and a planar deviation of the planar surface occurring in the process is reduced by machining the cured colored layers. With such a post-processing, for example by lapping, an extremely uniform planar surface can be produced and the thickness variations, possibly occurring during the application of ink, for example by streaks, can be eliminated.If the 3D optical coordinate measuring machine to be tested has a very small limit value for the flatness deviation, the shape deviation (and thus the directly related test value uncertainty) of a single-coated flatness standard can be too large. In such a case, a possible solution is that the flatness standard is coated multiple times with the suitable machine coating method. Thus, for example, a flatness standard can be repeated, for example. 10x are successively screen printed with the selected ink. Between the coating processes, it is ensured that the respective applied color layer is sufficiently dried and solid. As a result of the repeated coating, the total ink layer thickness is significantly greater than in the case of a single coating with only one ink layer. The distortion of the multiple coated plane is generally greater than in single coated planes. However, the shape deviation is significantly smaller than the total ink layer thickness. It is thus possible to remachine the multiple-coated flatness standard using a suitable machining method. Thus, for example, it is possible by the machining process lapping to significantly reduce the dimensional deviation of the coated plane. In this case, care should be taken that the material removal is significantly less than the original ink layer thickness, so that the entire original-coated region is still coated with ink after lapping. Otherwise, at least one further color layer must be applied again, if necessary after the machining, which may then be remachined again.Such a flatness standard can be produced by producing a planar surface of a carrier element and simply or multiple coating of the planar surface of the carrier element with a paint layer such that the deviation in shape of the planar surface coated with the paint layer is less than 100 μm and the paint layer diffusely reflects visible light and the cured paint layer is deformation-resistant, in particular scratch-resistant, when tactilely probed by a tactile coordinate measuring machine.It is advantageous to apply a plurality of colored layers of the same color to the planar surface one above the other, for example by screen printing, and to process the cured colored layers by machining in order to reduce the variation in flatness of the planar surface.The determination of the characteristic variable "flatness deviation" according to ISO 10360-13:2021 takes place together both for each of the six (6) individual measurements (single view) and also for the six (6) individual measurements (multiple view) registered in a common coordinate system. In order to be able to perform this registration, fixed measurement marks relative to the normal to flatness are advantageous. To calculate the transformation parameters for transforming each individual measurement into a common coordinate system, at least three measurement marks (for example circle marks) are required. The measurement marks must not lie on a line.In an advantageous embodiment, a link element, which is equipped with at least three measurement marks, is therefore arranged in a fixed position with respect to the normal to flatness. These measurement marks can now be measured in each of the six (6) individual measurements in addition to the planar surface. On the basis of the measurement marks, the measurement data of the flatness standard from each individual measurement can be transformed into a superordinate coordinate system.The gate element can have a rectangular basic shape and have a window in the inner region. The window is surrounded by a frame on which the measurement marks are advantageously attached. The link element is arranged relative to the normal to the flatness in such a way that the window leaves a defined partial region of the coated planar surface of the normal to the flatness or the entire coated planar surface of the normal to the flatness visible. Thus, the visible coated surface of the flatness standard can be measured with the optical coordinate measuring machine to be checked. Likewise, three or more measurement marks can be measured by the optical coordinate measuring machine to be checked and then used for registering the measurement data.It is advantageous if the flatness standard is stored and transported in a transport case or comparable body. The transport case protects the flatness standard from damage and dirt.It is advantageous if the transport case comprises at least one fixing unit which makes it possible to firmly connect the flatness standard to the transport case. This fixing unit can advantageously also be used to firmly align the link element with the normal to flatness. The fixation can be effected in different ways. For example, a form-fit and / or force-fit fastening, such as for example a fixing of the flatness standard on the transport case by screwing, is conceivable. For this purpose, the flatness standard and / or the link element have corresponding bores, which make it possible to screw to the fixing unit in the transport case.In a further advantageous embodiment, the link element can be fixed in a fixed position relative to the normal to flatness by magnetic force. For this purpose, a magnetic holder can be present as a fixing unit, for example, in the transport case. The link element has a matching counterpart, so that the link element can be connected to the fixing unit by magnetic force. This also enables the use of several different link elements, which can then be easily exchanged with one another.A set of flatness standard and gate element with measurement marks, which is designed for the fixed arrangement relative to the flatness standard, can advantageously have a plurality of gate elements which are different from one another and can each be selected for the fixed arrangement relative to the flatness standard.Optical coordinate measuring machines are frequently supplied with sensor measurement volumes of different sizes. A separate acceptance test is carried out for each sensor measurement volume. To carry out the acceptance test according to ISO 10360-13:2021, it is absolutely necessary for at least three measurement marks to be measured in addition to the planar surface in each individual measurement of the flatness standard. With small sensor measurement volumes, it is possible for a first link element to have an excessively large window, such that the normal to flatness in the region of the window and the measurement marks cannot be measured simultaneously. In such a case, a second gate element with a smaller window is advantageously used, in which the measurement marks can also be placed closer to one another. It is thus possible to check very many different sensor measurement volumes using a single normal to flatness of uniform size and two or more different gate elements. Thus, not many different sizes of flatness standards need to be stored, since 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 allows a great saving of effort and money, since in principle a single size of the flatness standard is sufficient. In addition, the calibration costs are also lower, since in the ideal case only one flatness standard has to be calibrated and not a plurality of different flatness standards of different dimensions. Thus, the size of the coated region of the flatness standard is advantageously determined by the largest sensor measurement volume of the measurement device manufacturer to be tested, taking into account the requirements with regard to the length and width 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 for all sensor measurement volumes to be checked that a sufficiently large partial region of the coated surface with respect to the requirements of ISO 10360-13:2021 is measurable and at least three measurement marks on the frame can likewise be measured.In this respect, the use of the above-described flatness standard for acceptance or confirmation testing of an optical coordinate measuring machine is advantageous, which is carried out in particular according to the specifications of the standard ISO 1030-13:2021.A further advantage of using one or more link elements with windows which enable the measurement capability of a defined partial region of the coated surface of the flatness standard is the use of a separate shape deviation and a separate measurement uncertainty for the respective partial region if these are specified in the calibration note of the flatness standard. Assuming that a flatness standard large in its dimension (length and width of the coated surface) is used, a comparatively large flatness deviation as a result of calibration is to be expected. This is because as the size of the normal increases, it becomes technically more difficult to ensure a defined maximum variation in flatness than in the case of a normal of smaller size. At the same time, the measurement uncertainty of the dimensional deviation also generally deteriorates, since the accuracy of the measurement method for determining the dimensional deviation decreases as the size of the normal increases. As already stated, the dimensional deviation determined by the calibration laboratory and the associated measurement uncertainty result in the check value uncertainty. The goal must always be that the test value uncertainty is small in relation to the limit value of the coordinate measuring machine to be tested.If the position and size of the windows of the at least one link element relative to the normal to flatness are known, it can be agreed with the laboratory when the calibration of the normal is ordered that the associated calibrated deviation in shape and the associated measurement uncertainty are identified for each field of view of the normal to flatness per window. The shape deviation of the flatness standard tends to decrease as the calibrated range of the flatness standard is smaller. Likewise, under certain circumstances, a smaller measurement uncertainty can also be achieved by the calibration laboratory if, for example, a more accurate measuring device is used for a partial region of the flatness standard than for the entire coated surface of the flatness standard. The smaller the window size, the smaller will generally also be the check value uncertainty if the associated shape deviation and the measurement uncertainty are specified for the respective window size by the calibration laboratory. This is advantageous above all from the aspect that smaller sensor measurement volumes to be checked generally also have smaller limit values of the flatness deviation. In this respect, it is advantageous if the uncertainty of the test value is as small as possible.The invention is explained in more detail below with reference to exemplary embodiments with the attached drawings. The following are shown: FIG. 1 shows a sketch of a perspective view of a flatness standard; FIG. 2 shows a sketch of a flatness standard with a link element screwed into a transport case; FIG. 3 shows a sketch of a flatness standard with magnet holders screwed into a transport case; FIG. 4 shows a sketch of a link element with integrated magnets; FIG. 5 shows a sketch of a flatness standard with a first magnetically fixed link element in a transport case; FIG. 6 shows a sketch of a flatness standard with a second magnetically fixed link element in a transport case.FIG. 1 shows a perspective view of a sketch of a first exemplary embodiment of a flatness standard 1 coated according to the invention, which is configured as a test body for optical coordinate measuring machines according to ISO 10360-13:2021. The flatness standard 1 can, however, also be used as a test body for other coordinate measuring machines, in particular for tactile coordinate measuring machines.The flatness standard 1 may be formed of a natural stone as a support member, such as from garnet. However, other types of stone may also be used. These include natural stones as well as artificial stones. An example of a flatness standard 1 made of a artificial stone is a molded part made of concrete. It is also possible for the flatness standard 1 to be formed from a ceramic. It is also conceivable to use another suitable material, such as metal, glass or plastic.The flatness standard 1 is, for example, rectangular parallelepiped-shaped and has a surface which has been mechanically machined in such a way that a flat surface 2 with a small flatness deviation is present. The edges of each surface of the flatness standard 1 may be chamfered as in this embodiment. The surface formed as a planar surface 2 can be, for example, the surface of the upper side shown in FIG. 1 and / or the longitudinal side surfaces and / or end side surfaces and / or also the lower side surface for an application rotated through 180°.The variation in flatness of the planar surface 2 is less than 100 μm and should advantageously be significantly less than 100 μm, for example less than 10 μm. With suitable machining methods, deviations in flatness of less than 5 μm can be easily achieved. The size of the planar surface 2 (length, width) should be dimensioned in accordance with the specific measurement environment such that the specifications of ISO 10360-13:2021 with respect to the sensor measurement volume to be tested of the 3D optical coordinate measuring machine are complied with.The planar surface 2 of the normal to flatness is coated with a white paint layer 3. The paint is applied to the flatness standard 1 by a suitable machine coating method. This can be effected, for example, by a screen printing method.The white color is selected so that visible light emitted from the 3D optical coordinate measuring machine is diffusely reflected. Moreover, after drying, the ink is so resistant to pressure and scratching that it resists slight mechanical stress, such as manual grip and cleaning, and remains dimensionally stable when measured with a tactile coordinate measuring machine. For this purpose, the color should be sufficiently scratch-resistant.A two-component lacquer made of polyurethane and / or acrylic is suitable, for example. As the hue, for example, RAL 9010 is suitable for achieving a sufficient diffusely reflecting effect.The flatness standard 1 can have a respective embedded thread 4 on the two end sides. This can be implemented, for example, by a metal bushing glued into the artifact, i.e. into the carrier element. With the aid of the thread 4, the flatness standard 1 can be screwed into a transport case 6 (not shown in FIG. 1 ). In addition, the flatness standard 1 can have a marking 5, for example in the form of a bore, on at least one of the two end face surfaces. This marking 5 marks the adjacent flat surface and ensures that the desired side is also coated during the coating process.FIG. 2 shows a flatness standard 1 in an opened transport case 6.U-shaped metal brackets 7 are integrated in the transport case 6. For this purpose, two metal brackets 7 can be arranged spaced apart from one another at a distance corresponding to the length of the flatness standard 1. The metal brackets 7 are arranged in the case 6 in such a way that the flatness standard 1 can be placed with its front sides lying opposite one another in the longitudinal direction between a pair of metal brackets 7. The flatness standard 1 can be fastened to the metal brackets 7 by means of screws 8, respectively.In the transport case 6, a link element 9 can also be arranged. The link element 9 is designed such that it has a window in its center which is slightly larger than the planar surface 2 of the normal to flatness 1. The link element 9 can likewise be fixed to the metal brackets 7 by means of the screws 8. Thus, the normal 1 for flatness and the sliding element 9 are arranged stationary with respect to one another. Also in the case of a movement of the transport case 8, the relative position of the link element 9 and the flatness standard 1 remains unchanged.The slide element 9 has at least three measurement marks 10 on its upper side. Advantageously, there are clearly more than three measurement marks 10, which ideally also have different diameters or mutually different shapes. Depending on the spatial resolution of the system to be checked, for example, only measurement 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 slide element 9 for different optical coordinate measuring machines to be tested having different sensor measurement volumes.FIG. 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 opened transport case 6 by means of the holders 7 fixedly installed in the case and two screws 8 with a star grip, by screwing the flatness standard 1 on the mutually opposite end sides to a holder 7 in each case by means of the screws 8.In the transport case 6, there are magnetic holders 11 which are fixedly installed in the case 6. Alternatively, the magnet holders 11 can also be loose elements which are fixed together with the flatness standard 1 by the screws 8 in the case 6.FIG. 4 shows a link element 9 in a front and rear view. On the front side, various measurement marks 10 of different diameters are arranged in the vicinity of the window. On the rear side, a magnet 12 is installed at each of the four corners of the link element 9.Analogously to the link element 9 skied in FIG. 4, further link elements can be present, which however each have windows of different sizes to the link element 9 illustrated in FIG. 4. In particular, the window can be significantly smaller, so that only a very limited region of the normal 1 for flatness is visible. The measurement marks 10 are usually arranged close to the respective window of the gate element 9.FIG. 5 shows the flatness standard 1 in the transport case 6 from FIG. 3. A first link element 9 (see FIG. 4 ) with integrated magnets 12 is placed on the magnet holders 11 fixedly arranged in the transport case 6. In this embodiment, the gate element 9 has a window which is smaller than the planar surface 2 of the normal 1 to be level coated with the ink layer 3. The size of the window of the gate element 9 and the arrangement of the measurement marks 10 are designed such that one or more sensor measurement volumes of the optical 3D coordinate measuring machine to be checked can measure the plane in the window and at least three surrounding measurement marks 10 in each of the six (6) test positions.Assuming that the test is to be carried out for a sensor measurement volume whose size is significantly smaller than the window of the gate element 9 in FIG. 5, this configuration cannot be used for the acceptance test according to ISO 10360-13:2021. Advantageously, however, a different link element 9 with a significantly smaller window can then be used. The size of the window is advantageously oriented to 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.FIG. 6 again shows the flatness standard 1 in the transport case 6 from FIG. 3. A second link element 9 with integrated magnets 12 is placed on the magnet holders 11 fixedly arranged in the transport case 6. This link element 9 has a significantly smaller window than the link element 9 from FIG. 5. The smaller window results in a significantly smaller region of the normal 1 for flatness, which is visible and can be measured.According to the embodiment, further link elements 9 with in turn different window sizes can be kept available. It is thus possible that a uniform flatness standard 1 can be used with the aid of the link elements 9 that differ from one another due to different window sizes for a very large number of different sensor measurement volumes with significantly different sizes. In principle, it is thus sufficient if only one artifact or type of flatness standard 1 is stored, the size of which is oriented to the greatest sensor measurement volume and the specifications of ISO 10360-13:2021. The windows of the various link elements 9 and the diameters of the measurement marks 10 are then oriented toward the smaller sensor measurement volume and, in turn, the specifications of ISO 10360-13:2021. Thus, high costs for the construction, production and calibration of many different artifacts of flatness standards 1 can be saved.List of reference characters1 Flatness standard 2 Planar surface 3 Color layer 4 Thread 5 Marking 6 Transport case 7 U-shaped metal bracket 8 Screws 9 Link element 10 Measurement mark 11 Magnet holder 12 MagnetReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Cited Non-Patent LiteratureDIN EN ISO 10360-13:2023-11 (German version of ISO 10360-13:2021

[0007] Standard ISO 1030-13:2021

[0036] according to ISO 10360-13:2021

[0057]

Claims

A flatness standard (1) for determining the performance of an optical 3D coordinate measuring machine, characterized in that - the flatness standard (1) has a planar 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 tactilely probed by a tactile coordinate measuring machine, and in that - the coated planar surface (2) has a shape deviation of less than 100 μm.The normal (1) for flatness according to claim 1, characterized in that the ink layer (3) is applied to the flat surface (2) by screen printing.The normal (1) for flatness according to claim 1 or 2, characterized in that the flat surface (2) is coated with a plurality of paint layers (3) applied one above the other.The flatness standard (1) according to claim 3, characterized in that a plurality of paint layers (3) of the same color are applied on the flat surface (2) one above the other, and the flatness deviation of the flat surface (2) is reduced by machining the cured paint layers (3).Flatness standard (1) according to one of the preceding claims, characterized in that a link element (9) with measurement marks (10) is arranged in a fixed position with respect to the flatness standard (1).Flatness standard (1) according to Claim 5, characterized in that the link element (9) can be fixed in a fixed position with respect to the flatness standard (1) by magnetic force.The flatness standard (1) according to claim 5 or 6, characterized in that a plurality of mutually different link elements (9) are arranged in a fixed manner with respect to the flatness standard (1).The flatness standard (1) according to any one of the preceding claims, characterized in that the flatness standard (1) has a plurality of planar surfaces (2).Set of flatness standard (1) according to one of the preceding claims and gate element (9) with measurement marks (10) which is designed for the fixed arrangement with respect to the flatness standard (1), characterized in that the set has a plurality of gate elements (9) which are different from one another and which can each be selected for the fixed arrangement with respect to the flatness standard (1).Method for producing a normal (1) for flatness according to one of the preceding claims, characterized by - producing a planar surface (2) of a carrier element; - coating the planar surface (2) of the carrier element with a paint layer (3) in such a way that the shape deviation of the planar surface (2) coated with the paint layer (3) is less than 100 μm and the paint layer (3) diffusely reflects visible light and the cured paint layer (3) is deformation-resistant when tactile probing by a tactile coordinate measuring machine.Method for producing a planar standard (1) according to Claim 10, characterized by coating the planar surface (2) with a colour layer (3) by screen printing.Method according to claim 10 or 11, characterised by coating several paint layers (3) of the same paint onto the flat surface (2) one above the other and machining the cured paint layers (3) to reduce the variation in flatness of the flat surface (2).Use of a flatness standard according to one of Claims 1 to 9 for acceptance or confirmation checking of an optical coordinate measuring machine.

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