Projection unit for projecting a test pattern, test device, and method for testing sharpness characteristics of an optical test object

Abstract

The invention relates to a projection unit (110) for projecting a test pattern (140). Sharpness characteristics of an optical test object (X) can be tested by using the test pattern (140). The projection unit (110) comprises a diffractive optical element, which is designed to produce a plurality of virtual test objects (142, 143) as the test pattern (140) in response to different excitation lights (125, 135) coupled into the projection unit (110) at the same time from one or more light sources (120, 130). In this case, different test objects (142, 143) are arranged in different focal planes and at different solid angles from the point of view of the test object (X).

Description

[0001] R. 413255

[0002] - 1 -

[0003] Description

[0004] title

[0005] Projection unit for projecting a test pattern, test device and method for testing the sharpness properties of an optical test piece

[0006] State of the art

[0007] The invention relates to a device or a method according to the preamble of the independent claims. The present invention also relates to a computer program.

[0008] In the production of automotive cameras, imaging performance is typically measured, for example, using the MTF (Modulation Transfer Function), across the camera's field of view (FOV) to enable 3D alignment, i.e., a joining step for connecting the lens and sensor. The alignment and joining process, in which the sensor and lens are adjusted and fixed relative to each other, conventionally comprises two stages.

[0009] In a first stage, a focus scan can be performed in which either the sensor or the lens is moved along the Z-axis while the other component remains fixed. This can be achieved, for example, using nine collimators, which are adjusted and aligned so that each projects a measurement target, such as a cross, which is then imaged by the lens onto a specific point on the sensor. It is advantageous if the measurement points are distributed across the image field. The number of measurement points in this conventional arrangement may be limited by the installation space, since the collimators are positioned next to each other. By gradually bringing the joining partners closer together, a value can be generated for each measurement point. Each measurement point may exhibit optimal sharpness at a different Z-position, as shown in R. 413255.

[0010] - 2 - This is due to the fact that the sensor surface and the wavefront of greatest sharpness are at different distances from each other. A target value can be achieved by changing the position and orientation of one of the components in space so that the optima coincide. This position can be calculated from the previously measured values ​​and, for example, approached by manipulation using a hexapod.

[0011] In a second stage, the lens can be fixed to the sensor, for example, using adhesives, rivets, or clamps. Finally, the result of the joining process should be checked again, which conventionally requires traversing the focus planes once more. This can be done using tunable collimators set to different distances.

[0012] The number of measuring points can be limited by the space required for the collimators used simultaneously. For example, using five to nine collimators can be practical; beyond that, the measuring apparatus becomes increasingly unwieldy and expensive. Adjusting the collimators relative to each other can also be complex and should be repeated relatively frequently, especially when tolerances need to be met. Furthermore, moving or repositioning a component, such as the lens or sensor of the test piece, across approximately 20 measuring points to obtain sufficient support locations for measurement can be time-consuming, impacting the production cycle time. In-situ monitoring of the entire work area during the joining process is not practical, as checking all object distances would require moving the components or the collimation optics.

[0013] Disclosure of the invention

[0014] Against this background, the approach presented here comprises a projection unit for projecting a test pattern, a test device for testing the sharpness properties of an optical test piece, a method for testing the sharpness properties of an optical test piece, a device which uses this method, and finally an R. 413255.

[0015] - 3 - A corresponding computer program according to the main claims is presented. Advantageous further developments and improvements of the device specified in the independent claim are possible through the measures listed in the dependent claims.

[0016] According to embodiments, a diffractive element or a volume hologram can be used, in particular, to project targets or test patterns from virtually different distances and image them onto the sensor of an optical test object via its optics. Advantageously, a pattern can be generated that allows for standard evaluation, e.g., the application of the established "slanted edge" method. In other words, a projection unit can provide a target or test pattern that can simultaneously image a large number of measurement points or test objects, for example, significantly more than nine, in different focal planes, so that no or significantly fewer traverse steps of a test optic are required to measure, for example, a sharpness performance (MTF, SFR, e-SFR, etc.) over different object distances with a very high number of support points. An alignment process or...This allows for faster and more cost-effective alignment processes and MTF checks during camera manufacturing. Furthermore, it enables in-situ monitoring of the entire working area of ​​the optics, rather than just a single operating point.

[0017] A projection unit for projecting a test pattern is presented, wherein the sharpness properties of an optical test object can be tested using the test pattern, wherein the projection unit comprises a diffractive optical element shaped to generate a plurality of virtual test objects as the test pattern in response to different excitation light coupled into the projection unit from one or more light sources simultaneously, wherein different test objects are arranged in different focal planes and in different solid angles from the viewpoint of the test object.

[0018] The optical test object may be a camera, in particular a vehicle camera intended for installation in a vehicle. (See R. 413255)

[0019] - 4 - The optical test object can also be an imager module for a camera or vehicle camera. The test object can be aligned and arranged relative to the projection unit in a predefined test pose. The test pattern can contain multiple virtual test objects. The virtual test objects can be generated by the projection unit at different virtual distances or in different virtual focal planes relative to the predefined test pose. A test object can, for example, be a cross, a dot, or a slanted-edge structure. The projection unit can be formed as a single diffractive optical element. Thus, a single light source may be sufficient to make several targets appear at virtually different distances.

[0020] According to one embodiment, the diffractive optical element can be a holographic-optical element configured as a transmission hologram or a reflection hologram. The diffractive optical element can be a volume optical element. The diffractive optical element can be multilayered. Such an embodiment offers the advantage that the test objects of the test pattern can be generated or projected precisely and reliably in response to the excitation light.

[0021] The diffractive optical element can also have multiple projection zones. Each projection zone can be shaped to generate a predefined number of test objects in a predefined focal plane in response to excitation light of a type specifically predefined for that projection zone. The projection zones can be formed within a volume of the diffractive optical element. Such an embodiment offers the advantage that at least one test object per predefined focal plane can be projected in a simple and accurate manner.

[0022] Different types of excitation light can differ with respect to their wavelength spectrum and additionally or alternatively with respect to their coupling direction. Such an embodiment offers the advantage that a reliably and unambiguously distinguishable projection of the one described in R. 413255 is possible.

[0023] - 5 - different focus planes can be achieved with test objects arranged at different focal planes.

[0024] Furthermore, the diffractive optical element can be shaped to generate the test objects distributed across the entire field of view of the test specimen. Such an embodiment offers the advantage of enabling a thorough and comprehensive examination of the sharpness properties of the optical test specimen with minimal examination time.

[0025] A test device for testing the sharpness properties of an optical test specimen is also presented, wherein the test device has the following features: an embodiment of a projection unit presented herein; and one or more light sources for coupling the excitation light into the projection unit.

[0026] In conjunction with the test device, an embodiment of a projection unit presented herein can be advantageously employed or used to project the test pattern onto the coupled excitation light. The at least one light source can be implemented as a laser light source. This can be a particularly advantageous implementation.

[0027] According to one embodiment, the one or more light sources can be configured to couple the excitation light with different wavelength spectra and, additionally or alternatively, with different coupling directions into the projection unit. Additionally or alternatively, several light sources can be spatially separated from one another and, additionally or alternatively, arranged at different distances from the projection unit. Such an embodiment offers the advantage that activation or generation of the required test objects can be carried out in an application-specific, targeted, and precisely defined manner. R. 413255

[0028] - 6 -

[0029] Furthermore, a method for testing the sharpness properties of an optical test specimen is presented, wherein the method comprises the following steps:

[0030] Arranging the test specimen in a test pose with respect to an embodiment of a projection unit or test device mentioned herein;

[0031] Coupling the excitation light into the projection unit by means of one or more light sources in order to project the test pattern; and

[0032] Evaluation of image data representing the projected test pattern, recorded by the test subject in the test pose, with regard to sharpness properties.

[0033] The method can therefore be carried out in conjunction with an embodiment of a projection unit or test device mentioned herein. In the positioning step, the test specimen can be positioned such that the projection unit lies within the test specimen's field of vision.

[0034] According to one embodiment, in the arrangement step, parts of the test specimen that are movable relative to each other can be brought into a positional relationship. The method can include a step for fixing the parts in this positional relationship if the image data meets a predefined evaluation criterion. Such an embodiment offers the advantage that the alignment and fixing of parts of the test specimen that are movable relative to each other can be carried out under reliable and precise control of the optical parameters of the test specimen, thereby accelerating and simplifying the manufacturing process.

[0035] Optionally, the arranging, coupling, and evaluation steps can be repeated with the fixed parts of the test specimen. In the evaluation step, correction parameters can be determined based on a comparison of an evaluation result with at least one expected value. Optionally, the method can also include a step for storing the correction parameters in a memory location of the test specimen. Such an embodiment offers the advantage that R. 413255

[0036] - 7 - additional correction parameters for safe and accurate operation of the optical test object during manufacturing can be determined easily and precisely.

[0037] This method can be implemented, for example, in software or hardware, or in a hybrid form of software and hardware, for example in a control unit or device.

[0038] The approach presented here further provides a device designed to perform, control, and implement the steps of a variant of the method presented herein in appropriate facilities. This embodiment of the invention, in the form of a device, also allows the underlying problem to be solved quickly and efficiently. A further advantage is that the described device can be significantly smaller than a conventional arrangement with multiple collimators.

[0039] For this purpose, the device may have at least one processing unit for processing signals or data, at least one storage unit for storing signals or data, at least one interface to a sensor or actuator for reading sensor signals from the sensor or for outputting data or control signals to the actuator, and / or at least one communication interface for reading or outputting data embedded in a communication protocol. The processing unit may, for example, be a signal processor, a microcontroller, or the like, and the storage unit may be flash memory or a magnetic storage unit.The communication interface can be configured to read or output data wirelessly and / or via wired connections, whereby a communication interface that can read or output wired data can, for example, read this data electrically or optically from or output it into a corresponding data transmission line.

[0040] In this context, a device can be understood to be an electrical device that processes sensor signals and, depending on them, controls R. 413255

[0041] - 8 - and / or outputs data signals. The device may have an interface, which can be implemented in hardware and / or software. In the case of a hardware implementation, the interfaces may, for example, be part of a so-called system ASIC, which incorporates a wide variety of the device's functions. However, it is also possible for the interfaces to be separate integrated circuits or at least partially composed of discrete components. In the case of a software implementation, the interfaces may be software modules, which, for example, are located on a microcontroller alongside other software modules.

[0042] Also advantageous is a computer program product or computer program with program code that can be stored on a machine-readable carrier or storage medium such as a semiconductor memory, a hard disk memory or an optical memory and is used to carry out, implement and / or control the steps of the method according to one of the embodiments described above, in particular if the program product or program is executed on a computer or device.

[0043] According to embodiments, a reduction in measurement time and equipment costs for alignment and focus control can be advantageously achieved during the manufacturing of the optical test object, for example, in camera production. Furthermore, the joining process of optics and sensor can be optimized, for example, during the production of imager modules or cameras as optical test objects. The focal plane or spherical cap generated by the optics of the test object can, for example, be aligned as centrally and symmetrically as possible with a surface of a sensor of the test object and maintain application-specific focus limits for various object distances. Another embodiment can be to adjust the wavefront of the optics at a controlled tilt relative to the sensor surface in order to generate a focal plane inclined to the sensor normal, for example, in a Scheimpflug arrangement, in order to, for example, image objects on a road surface sharply over a large distance range.Thanks to a shortened manufacturing time, an accelerated production cycle is also possible, without the frequent measuring and travel times required for the output of an alignment- R. 413255, as is the case with conventional systems.

[0044] - 9 -

[0045] The system would be similar to other systems. Thanks to reduced setup costs, depreciation costs can also be lowered through high throughput and lower investment costs. Furthermore, reduced maintenance costs allow for extended service intervals and reduced susceptibility to malfunctions.

[0046] Advantageously, the projection unit, also known as a test pattern projection device, can project a multitude of objects or test objects across the entire field of view of the device under test, distributed over virtually any number of different distances. A camera manufacturing system equipped with the projection device or projection unit presented here, or in other words, with this pattern projector, allows for image quality measurements (e.g., MTF) to be performed across an expanded object distance range with just one image acquisition, without needing to vary the device under test, camera, projection unit, or target. This enables in-situ measurement. Multiple measurements on several images can be used to reduce noise components of the measurement signal. This can accelerate the alignment process by several factors, and the alignment target, e.g.,Weighted sharpness across multiple depth levels can be varied as needed without requiring any retooling or modification of the production equipment. This eliminates setup times and allows alignment to be performed in a single step (one-pass alignment). The measurement density across the image field can be increased compared to a conventional collimator solution, enabling the detection of local anomalies in image quality and the early identification of degradation that would otherwise only be apparent in the field. The pattern generator or projection unit can also be used by system integrators (OEMs) to verify compliance with optical sharpness limits in a single step after mounting a test object or camera, for example, behind a vehicle's windshield.

[0047] Examples of the approach presented here are shown in the drawings and explained in more detail in the following description. It shows: R. 413255

[0048] - 10 -

[0049] Fig. 1 shows a schematic representation of an embodiment of a test device with an embodiment of a projection unit;

[0050] Fig. 2 shows a schematic representation of a test pattern projected by an embodiment of a projection unit;

[0051] Fig. 3 shows a schematic representation of a test pattern projected by an embodiment of a projection unit;

[0052] Fig. 4 shows a flowchart of a process according to an exemplary embodiment;

[0053] Fig. 5 shows a flowchart of a process according to an exemplary embodiment; and

[0054] Fig. 6 shows a flowchart of a process according to an exemplary embodiment.

[0055] In the following description of favorable embodiments of the present invention, the same or similar reference numerals are used for the elements shown in the various figures and acting similarly, without repeating these elements.

[0056] Fig. 1 shows a schematic representation of an embodiment of a test device 100 with an embodiment of a projection unit 110. The test device 100 is designed to test the sharpness properties of an optical test specimen X. The test device 100 comprises a projection unit 110 and one or more light sources 120, 130.

[0057] The test object X is a camera or an imager module for a camera, in particular a vehicle camera for installation in a vehicle. Test object X is assigned a field of view Y. The field of view Y has, for example, an opening angle of ±30 degrees around the optical axis. R. 413255

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[0059] The projection unit 110 is at least partially located within the field of view Y.

[0060] The projection unit 110 is configured to project a test pattern 140, using which at least one sharpness property of the optical test object X can be tested. The projection unit 110 comprises a diffractive optical element. The diffractive optical element is designed to generate a plurality of virtual test objects 142, 143 as the test pattern 140 in response to different excitation light 125, 135 coupled simultaneously into the projection unit 110 from one or more light sources 120, 130. Different of the test objects 142, 143 are arranged at different focal planes or sharp planes or virtual distances from the perspective of the test object X.

[0061] For example, the diffractive optical element is a holographic-optical element configured as a transmission hologram or a reflection hologram. In particular, the diffractive optical element is a multilayer transmission hologram. According to one embodiment, the diffractive optical element is shaped to generate the test objects 142, 143 distributed across the entire field of view Y of the test specimen X. Additionally or alternatively, according to one embodiment, the diffractive optical element comprises a plurality of projection zones, each shaped to generate a predefined number of test objects 142 / 143 in a predefined focal plane in response to excitation light 125 / 135 of a type specifically predefined for the projection zone. Different types of excitation light 125, 135 differ with respect to a wavelength spectrum and / or a coupling direction.

[0062] The light sources 120, 130 are configured to couple the excitation light 125, 135 into the projection unit 110. For example, the light sources 120, 130 are configured to couple the excitation light 125, 135 into the projection unit 110 with different wavelength spectra and / or coupling directions. Additionally or alternatively, the light sources 120, 130 are spatially separated from each other and / or arranged at different distances from the projection unit 110. R. 413255

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[0064] Figure 1 shows only two light sources 120 and 130 as examples. According to exemplary embodiments, the test device 100 can also have a different number of light sources, in particular only one. A first light source 120 is configured to couple first excitation light 125 into the projection unit 110. A second light source 130 is configured to couple second excitation light 135 into the projection unit 110. The light sources 120 and 130 are configured to couple the excitation light 125 and 135 into the projection unit 110 with at least different coupling directions. In addition, the light sources 120 and 130 are both spatially separated from each other and arranged at different distances from the projection unit 110.

[0065] The projection unit 110 is designed to generate a first test object 142 in response to the first excitation light 125 and a second test object 143 in response to the second excitation light 135. The test objects 142 and 143 of the test pattern 140 are arranged at different focal planes relative to the test specimen X. In the illustration of Fig. 1, the first test object 142 is shown, for illustrative purposes only, at a greater distance from the test specimen X than the second test object 143.

[0066] Fig. 2 shows a schematic representation of a test pattern 140 projected by an exemplary embodiment of a projection unit. The projection unit corresponds to or is similar to the projection unit from Fig. 1. The test pattern 140 also corresponds to or is similar to the test pattern from Fig. 1. The test pattern 140 comprises a plurality or multiple of test objects in several virtual focus planes, here in six virtual focus planes 251, 252, 253, 254, 255, and 256. A predefined number of test objects are arranged in each of the focus planes 251, 252, 253, 254, and 255. The test objects have, for example, a cross-shaped contour.

[0067] A first focal plane 251 corresponds, for example, to a virtual focus of -3m, a second focal plane 252 corresponds, for example, to a virtual focus of -5m, and a third focal plane 253 corresponds, for example, to R. 413255

[0068] - 13 - virtual focus of -11 m, a fourth focus plane 254 corresponds, for example, to a virtual focus of -80 m, a fifth focus plane 255 corresponds, for example, to a virtual focus of -200 m, and a sixth focus plane 256 corresponds, for example, to a virtual focus of -10,000 m. For focus planes 251, 252, 253, 254, 255, and 256, any other virtual distances can be selected, depending on the specific implementation.

[0069] The test pattern 140 with the test objects in the focus planes 251 , 252, 253, 254, 255 is constructed according to a distributed fractal pattern 260, which appears from the viewpoint of the test subject in recombined or composite form 265, with each segment representing a different distance or a different focus plane.

[0070] Fig. 3 shows a schematic representation of a test pattern 140 projected by an embodiment of a projection unit. The test pattern shown here corresponds to the test pattern from Fig. 2, with a combined view of the same. The majority of test objects 341, 342, 343, 344, 345, and 346 from the different focal planes are combined to form the test pattern 140. The focal planes are shown here in a composite or superimposed form. Of the test objects in the test pattern 140, one from each of the six focal planes is explicitly labeled.

[0071] A first test object 341 is arranged in the first focal plane with a virtual focus of -3m, a second test object 342 is arranged in the second focal plane with a virtual focus of -5m, a third test object 343 is arranged in the third focal plane with a virtual focus of -11m, a fourth test object 344 is arranged in the fourth focal plane with a virtual focus of -80m, a fifth test object 345 is arranged in the fifth focal plane with a virtual focus of -200m and a sixth test object 346 is arranged in the sixth focal plane with a virtual focus of -10000m.

[0072] According to one embodiment, the test objects 341, 342, 343, 344, 345, and 346 are arranged distributed over a plan view of the test pattern 140 that fills the field of view of the test specimen. Test objects assigned to a specific focal plane are, for example, arranged via the R. 413255

[0073] - 14 -

[0074] The floor plan of the test pattern 140 is arranged scattered across the area. From the perspective of the test subject, test objects 341, 342, 343, 344, 345, 346 can thus appear adjacent to each other from different focal planes, also with respect to the floor plan.

[0075] Fig. 4 shows a flowchart of a method 400 according to an exemplary embodiment. The method 400 can be carried out to test the sharpness properties of an optical test specimen. It is a method 400 for testing the sharpness properties of an optical test specimen. The testing method 400 can be carried out in conjunction with the projection unit and / or the test device from Fig. 1 or a similar projection unit and / or test device. The testing method 400 comprises a step 401 of arranging, a step 403 of coupling, and a step 405 of evaluating.

[0076] In step 401 of the arrangement process, the test specimen is positioned in a test pose relative to a projection unit and / or test fixture such as that shown in Fig. 1. This involves positioning the test specimen, optionally with its own adjustment pattern, for example, a crosshair.

[0077] In step 403 of the coupling process, the excitation light is coupled into the projection unit using one or more light sources to project the test pattern. This activates a test pattern, for example, from virtually different distances and solid angles. If required, recursion can also be performed, as symbolically indicated in Fig. 4, allowing different test patterns to be projected successively.

[0078] Subsequently, in step 405 of the evaluation process, image data representing the projected test pattern, captured by the test subject in the test pose, are evaluated with regard to sharpness characteristics. This involves an assessment of image quality, for example, by weighting the measurements taken over different solid angles and distances. R. 413255

[0079] - 15 -

[0080] The application of the projection unit or test system according to Method 400 allows for accelerated measurement, testing, and calibration processes in various applications related to the manufacturing of optical test objects, such as image sensor modules or cameras. The projection unit or test system can be used according to Method 400 to measure the image quality of a fully assembled sensor and optics module with regard to optical performance. A particular advantage is that the measurement can be performed in a single step at multiple locations within the image field and for multiple object distances, without the need for mechanical tuning processes. Multiple wavelengths can also be tested.

[0081] Fig. 5 shows a flowchart of a method 400 according to an exemplary embodiment. The method 400 can be carried out to test the sharpness properties of an optical test specimen. It is a method 400 for testing the sharpness properties of an optical test specimen. The testing method 400 can be carried out in conjunction with the projection unit and / or the test device from Fig. 1 or a similar projection unit and / or test device. The testing method 400 in Fig. 5 comprises the steps of the testing method from Fig. 4 or a similar method. In other words, Fig. 5 shows a further exemplary embodiment of the method from Fig. 4.

[0082] In step 401 of the arrangement process, movable parts of the test specimen are also placed in a positional relationship to one another. The inspection procedure 400 further includes step 507 of fixing the parts in their positional relationship if the image data meets a predefined evaluation criterion, as determined in step 506 of the verification process. In step 506 of the verification process, it is determined whether a target sharpness distribution has been achieved or whether a deviation is too large. If the target sharpness distribution has been achieved, step 507 of the verification process is executed, for example, an evaluation of an adhesive. If the deviation is too large, a recursion occurs as needed, and the process returns to step 401 of the arrangement process. R. 413255

[0083] - 16 -

[0084] Measurement and alignment can be performed by executing method 400 for testing according to the embodiment shown here. When manufacturing actively aligned imager modules or similar test pieces, if the typical focus profile across the focus area is known (e.g., recorded using a sample), a travel path to a target position can be calculated based on a single measurement or a single execution of method 400 for testing. After executing the corresponding movement of one of the joining partners, or even during the movement, the deviation from a target function can be measured. If the termination criterion is met, the joining partners can be fixed in step 507 of the fixing process. It may be advantageous to include a settling allowance. Verification after successful fixing can be performed as described in Fig. 4.

[0085] Fig. 6 shows a flowchart of a method 400 according to an exemplary embodiment. The method 400 can be carried out to test the sharpness properties of an optical test specimen. It is a method 400 for testing the sharpness properties of an optical test specimen. The testing method 400 can be carried out in conjunction with the projection unit and / or the test device from Fig. 1 or a similar projection unit and / or test device. The testing method 400 in Fig. 6 comprises the steps of the testing method from Fig. 5 or a similar method. In other words, Fig. 6 shows a further exemplary embodiment of the method from Fig. 5.

[0086] Following step 507 of fixing, at least the coupling step and the evaluation step, and optionally the arrangement step, are repeated with the fixed parts of the test specimen. Repeated executions of steps 403 and 405 are exemplified by step 603 of activating a parameter evaluation pattern, for example, a dot matrix, and step 605 of determining correction parameters. In the repeated execution of step 405 (evaluation) or step 605 (determination), the correction parameters are determined based on a comparison of an evaluation result with at least one expected value. R. 413255

[0087] - 17 -

[0088] This involves, for example, measuring the deviation at different grid points and calculating intermediate values, for example by bilinear interpolation.

[0089] Optionally, the method 400 for testing according to the embodiment shown here also includes a step 609 of storing the correction parameters specific to the test object, preferably in a memory of the test object.

[0090] By performing method 400 for testing according to the embodiment shown here, measurement, alignment, and determination of correction parameters can be carried out. If the application of the test specimen or system requires correction of the residual error, or if reconvolution is even desired to achieve improved imaging performance, a repeat measurement with the same or a different test pattern, e.g., a dot matrix, is possible. This pattern is generated by the same volume hologram, possibly from a different excitation source at a different illumination angle or frequency. Correction values ​​can be determined from the difference in measured values ​​at discrete points distributed across the entire field of view, representing virtual objects at various distances. These correction values ​​can then be used to adjust the real image of the imager module.The test object can be transformed so that it more closely approximates the expected value. The re-folding is successful if a subsequent image quality test on the processed image yields a better quality assessment even after repositioning. It is advantageous to smooth the (point-specific) parameters determined in this way for the re-folding by applying bilinear interpolation between adjacent values. Storing the correction parameters in the test object allows for subsequent online correction calculations and serves to correct any remaining errors using software.

[0091] With reference to the figures described herein, exemplary embodiments and their advantages are briefly explained again in other words and summarized below. R. 413255

[0092] - 18 -

[0093] The optical volume element of the projection unit 110, operating in transmission or reflection mode for generating the virtual test target or test pattern 140, comprises a multitude of zones distributed across the image field or field of view Y, each contributing to the generation of a test target element or test object 142, 143; 341, 342, 343, 344, 345, 346 – e.g., a cross, a dot, or a slanted-edge structure. From the observer's perspective, here the image sensor of the test object X, a target or test object 142, 143 appears through the superposition of wavefronts diffracted at the density-modulated zones of the optical volume element of the projection unit 110; 341, 342, 343, 344, 345, 346 from a discrete distance, whereby each individual test object or group of test objects appears virtually from a different distance. It is advantageous to have targets orTest objects 142, 143; 341, 342, 343, 344, 345, 346 are illuminated from a discrete distance by a narrowband illumination element or a narrowband light source 120, 130 from a suitable solid angle, and several illumination units or light sources 120, 130 are spatially and, if necessary, spectrally separated. The concept is cascadable, since the volume hologram of the projection unit 110 appears transparent to light from a different direction or wavelength and does not create a virtual object or test object from the perspective of the camera or the test object X. This makes it possible to inscribe several different test patterns 140 for alignment and correction parameter determination into the hologram volume and to make them visible to the test object X by illumination from different excitation directions or with different excitation spectra.

[0094] A time saving by avoiding "through focus scans" is, for example, in the range of a factor of 10 when using an embodiment of the present invention. Investment costs for the projection unit 110 are approximately 50 percent of those of a pattern projection unit equipped with actuable collimators; the impact on manufacturing costs can be in the range of 5 percent; a positive impact on cash flow is achieved through lower and less frequent reinvestments during a production ramp-up. If the technology is also used by OEMs, field returns and the associated costs and reputational losses due to unfavorable conditions can be avoided. R. 413255

[0095] - 19 -

[0096] The camera-lens pairing effect is reduced in vehicle cameras used as test objects X. This effect may increase significantly with future higher-resolution cameras.

[0097] A possible core element of the projection unit 110 is, for example, a volume hologram operated in transmission mode to generate an image of test patterns or test objects 142, 143; 341, 342, 343, 344, 345, 346 onto a camera module as the test object X. The generated test pattern 140 contains structures that make objects appear at different distances. These patterns or test objects 142, 143; 341, 342, 343, 344, 345, 346 can be multiple and spatially distributed across the detection area to simultaneously scan the entire field of view Y of the camera or test object X with test patterns or test objects 142, 143; to cover 341, 342, 343, 344, 345, 346. It is advantageous if groups of test objects 142, 143; 341, 342, 343, 344, 345, 346 are located at the same virtual distance or focal plane 251, 252, 253, 254, 255, 256.The test objects 142, 143; 341, 342, 343, 344, 345, 346 are excited by illuminating the volume hologram from different directions and can be activated simultaneously without interfering with each other. Narrowband illumination is preferred to improve the image quality of the test patterns and test objects 142, 143; 341, 342, 343, 344, 345, 346.

[0098] Ideally, a test pattern 140 used for measurement consists of several segments that are virtually located at different distances, e.g. as shown in Fig. 2.

[0099] The spatially distributed arrangement of such segmented patterns or test patterns 140 allows evaluation for multiple object distances and field angles based on a single recorded image. Maintenance of the system or test device 100 or projection unit 110 is significantly simpler, since, unlike an approach with multiple tunable collimators, calibration is performed during the production of the hologram in a monolithic body, and the adjustment of the excitation lighting sources 120, 130 can also be carried out in a single step, as the target or projection unit 110 R. 413255

[0100] - 20 - covers several distances or focus planes 251 , 252, 253, 254, 255, 256 and field angles simultaneously.

[0101] The measurement on the test specimen X by executing procedure 400 for testing is used, for example, either to carry out a quality assessment of an already fully connected imager module as test specimen X, whereby a quality measure is based, for example, on an evaluation of sharpness performance in different solid angles and distances, or to control an alignment system for aligning test specimens X with distance- or solid-angle-weighted parameters in such a way that the sharpness distribution approximates a target distribution that is complexly varied over field angle and object distance, or to parameterize a refolding matrix, for example, toto enable a distance- or field-angle-weighted refolding of the camera image, or first to achieve a target distribution by continuous multi-axis alignment and to use the measurement of the residual deviation to parameterize a refolding matrix for the correction of the residual deviation in such a way that an even higher optical resolution performance is achieved.

[0102] By executing procedure 400 for testing or using projection unit 110 or testing device 100, an alignment and sharpness testing process can be performed even within the production cycle, for example, in 8 seconds. This eliminates the need for parallelization of the measuring device, thus saving costs. Implementing procedure 400 for testing or using projection unit 110 or measuring device 100 allows for the measurement of sharpness performance across the entire application distance range in a single setup with only one image, i.e., for example, in 1 / 30 of a second plus calculation latency. If the sharpness calculation is not time-limited, the feed rate of the parts feeder would become the limiting factor.The deployment of an alignment system with such a projection unit 110, also referred to as a pattern generator, can even be used as an alignment station for several camera production lines. The implementation of the test fixture 100 can, if necessary, be carried out by a test equipment supplier. This allows for a space-saving and rapid production setup and, instead of collimators, can utilize a diffractive optic or R. 413255.

[0103] - 21 - a target projection device or projection unit 110 with hologram capability and the test objects 142, 143; 341 , 342, 343, 344, 345, 346 can be optimally imaged in different focus points or focus planes 251 , 252, 253, 254, 255, 256.

[0104] If an embodiment includes an “and / or” connection between a first feature and a second feature, this is to be read as meaning that the embodiment according to one embodiment has both the first feature and the second feature, and according to another embodiment either only the first feature or only the second feature.

Claims

R. 413255 - 22 - Claims 1. Projection unit (110) for projecting a test pattern (140), wherein the sharpness properties of an optical test object (X) can be tested using the test pattern (140), wherein the projection unit (110) comprises a diffractive optical element shaped to generate a plurality of virtual test objects (142, 143; 341, 342, 343, 344, 345, 346) as the test pattern (140) in response to different excitation light (125, 135) coupled into the projection unit (110) simultaneously from one or more light sources (120, 130), wherein different test objects (142, 143; 341 , 342, 343, 344, 345, 346) are arranged in different focal planes (251 , 252, 253, 254, 255, 256) from the viewpoint of the test subject (X).

2. Projection unit (110) according to claim 1, wherein the diffractive optical element is a holographic-optical element configured as a transmission hologram or as a reflection hologram.

3. Projection unit (110) according to one of the preceding claims, wherein the diffractive optical element has a plurality of projection zones, each of the projection zones being shaped to generate a predefined number of test objects (142, 143; 341 , 342, 343, 344, 345, 346) in a predefined focal plane (251 , 252, 253, 254, 255, 256) in response to excitation light (125, 135) of a type specifically predefined for the projection zone.

4. Projection unit (110) according to claim 3, wherein different types of excitation light (125, 135) differ with respect to a wavelength spectrum and / or a coupling direction. R. 413255 - 23 - 5. Projection unit (110) according to one of the preceding claims, wherein the diffractive optical element is shaped to generate the test objects (142, 143; 341 , 342, 343, 344, 345, 346) distributed over an entire field of view (Y) of the test object (X).

6. Test device (100) for testing the sharpness properties of an optical test specimen (X), wherein the test device (100) has the following features: a projection unit (110) according to one of the preceding claims; and the one or more light sources (120, 130) for coupling the excitation light (125, 135) into the projection unit (110).

7. Test device (100) according to claim 6, wherein the one or more light sources (120, 130) are configured to couple the excitation light (125, 135) with different wavelength spectra and / or coupling directions into the projection unit (110), and / or wherein several light sources (120, 130) are spatially separated from each other and / or arranged at different distances from the projection unit (110).

8. Method (400) for testing the sharpness properties of an optical test specimen (X), wherein the method (400) comprises the following steps: Arranging (401) the test specimen (X) in a test pose with respect to the projection unit (110) according to one of claims 1 to 5 or with respect to the test device (100) according to one of claims 6 to 7; Coupling (403) of the excitation light (125, 135) into the projection unit (110) by means of one or more light sources (120, 130) in order to project the test pattern (140); and R. 413255 - 24 - Evaluating (405) image data recorded by the test subject (X) in the test pose, representing the projected test pattern (140), with regard to sharpness properties.

9. Method (400) according to claim 8, wherein in step (401) of arranging relative to each other movable parts of the test specimen (X) are brought into a positional relationship relative to each other, wherein the method (400) includes a step (507) of fixing the parts in the positional relationship when the image data meet a predefined evaluation criterion.

10. Method (400) according to claim 9, wherein the step (401) of arranging, the step (403; 603) of coupling and the step (405; 605) of evaluating are repeated with the fixed parts of the test specimen (X), wherein in the step (405; 605) of evaluating correction parameters are determined depending on a comparison of an evaluation result with at least one expected value.

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