Device and method for determining the image quality of at least one image for a test specimen

Abstract

Device (100) for determining the image quality of at least one image for a test specimen (105), wherein the device (100) has the following features: - at least one projection unit (115) for emitting light (120) in the direction of the test object (105) in order to project at least one luminous and / or illuminated object structure (300) onto the test object (105); - optical receiving unit (110) for receiving light rays (130) of the light (120) transmitted through or by the test object (105) or reflected, which represent at least one image of the projected object structure (300), wherein the receiving unit (110) comprises an optical device (135) and an optical detector (140) and wherein the receiving unit (110) is adjustable or variable in its spectral sensitivity; - a mounting unit (145) for holding the test specimen (105), wherein the mounting unit (145) is arranged between the projection unit (115) and the optical receiving unit (110); and - a computing unit (150) for simultaneously evaluating a first light parameter (825), representing at least one optical light parameter, and a second light parameter (830), representing at least one colorimetric and / or photometric light parameter, of light rays (130) of the light (120) transmitted through or on the test object (105) and received using the receiving unit (110), in order to determine the image quality of the at least one image for the test object (105), wherein the computing unit (150) is connected to the projection unit (115), the receiving unit (110) and / or the mounting unit (145).

Description

State of the art

[0001] The invention relates to a device and a method for determining the image quality of at least one image for a test specimen according to the preamble of the independent claims. The present invention also relates to a computer program.

[0002] US Patent 11 029 206 B2 describes a device for measuring and characterizing the performance of augmented and virtual reality waveguide structures using glass substrates.

[0003] Publication WO 2016 / 169 890 A1 discloses a lithographic process and a corresponding device.

[0004] Publication WO 2023 / 018 554 A1 discloses a full-field measuring device for waveguide combiners and meta-surfaces.

[0005] Against this background, the approach presented here introduces an improved device and an improved method for determining the image quality of at least one image for a test specimen, furthermore a computing unit that uses this method, and finally a corresponding computer program according to the main claims. Advantageous further developments and improvements of the device specified in the independent claim are possible through the measures listed in the dependent claims.

[0006] The approach presented here offers a way to reliably determine the properties of a test object. For example, the device itself can be used as a measuring device. This can advantageously improve the quality of the test object and thus, for example, of a near-eye display (NED), such as those used in conjunction with smart glasses, augmented reality (AR), or virtual reality (VR). For instance, images can be displayed sharply, which can have a positive impact on the health of the end user.

[0007] Advantageously, both imaging colorimeters and imaging photometers, as well as systems for measuring optical parameters, can be used to achieve color measurement and an improvement of the systems for measuring optical parameters simultaneously.

[0008] A device for determining the image quality of at least one image of a test object is presented, wherein the device comprises at least one projection unit for emitting light towards the test object in order to project at least one luminous and additionally or alternatively illuminated object structure onto the test object. Furthermore, the device comprises an optical receiving unit for receiving light rays transmitted through or reflected by the test object, representing at least one image of the projected object structure. The receiving unit includes an optical device and an optical detector.Furthermore, the device includes a holding unit for the test specimen, the holding unit being arranged between the projection unit and the optical receiving unit, and a processing unit for simultaneously evaluating a first light parameter, representing at least one optical light parameter, and a second light parameter, representing at least one colorimetric or photometric light parameter, of light rays transmitted through or reflected by the test specimen and received using the receiving unit, in order to determine the image quality of the at least one image for the test specimen. The processing unit is connected to the projection unit, the receiving unit, and additionally or alternatively to the holding unit.

[0009] The device can be, for example, a measuring device for augmented reality (AR) or virtual reality (VR) systems, which can also be referred to simply as AR / VR, used to measure the properties of the device under test. The device under test can, for example, be a lens for smart glasses or an AR / VR device, also known as a near-eye display (NED), on or around which images can be projected. Furthermore, the device under test can also be a complete system for which the image quality can be determined. For this purpose, it is advantageous to define the image properties beforehand. The device under test can therefore be an optical system to be tested, a waveguide, a combination of waveguides, or alternatively, a module that may include a lighting unit and a waveguide.The module can be capable of generating a self-illuminating object structure that can be detected by the receiving unit. Advantageously, the object structure can represent a pattern, image, or symbol to be displayed on the test object.

[0010] The projection unit can advantageously include a light source, for example, a light-emitting diode (LED). Furthermore, the projection unit can be directed towards the test object so that the light can be transmitted through or reflected from the test object. Advantageously, the light can either be transmitted directly through the test object or enter the test object at an entry point and be reflected, for example, from opposite surfaces of the test object until an exit point is reached. The exit point can advantageously be in line with the receiving unit so that the transmitted or reflected light rays can be received by the receiving unit. The receiving unit can advantageously include the optical device, which can, for example, include lenses or other optical elements, and the detector.The detector can advantageously also comprise a plurality of components by means of which the light beams and additionally or alternatively transmitted information can be detected. The processing unit can advantageously be designed as a control unit or control device configured to process this information. The information can be transmitted and processed based on the light parameters, which in turn enable a conclusion or calculation of the image quality. In order to obtain a meaningful result, the device can include a mounting unit to which the test specimen can be attached. The mounting unit can advantageously be designed to be movable or adjustable, so that the image quality can be determined with respect to different positioning of the test specimen using the processing unit.The holding unit can advantageously be designed as a multi-axis linear stage, which allows free positioning of the test specimen in space and can therefore be moved once or repeatedly along an x, y or z axis, for example.

[0011] According to one embodiment, the detector of the receiving unit can have a plurality of spectral channels and at least one image sensor. The spectral channels can be implemented, for example, using a filter unit. Advantageously, the filter unit can be designed as a filter wheel with a plurality of optical filters. Such filters can, for example, be designed as a glass or plastic disc of optical quality that can be inserted into the beam path of the receiving unit, e.g., swiveled, to obtain a defined wavelength spectrum in the image. Alternatively, the spectral channels can be implemented using several image sensors, each with a spectral filter. In both variants, the spectral filters can additionally be combined with neutral density filters to uniformly attenuate the incident optical intensity on the image sensor, thereby preventing possible sensor overload.The detector can therefore be implemented, for example, as a sensor unit. It is also conceivable that the detector of the receiving unit is implemented as a focusable camera.

[0012] Furthermore, the receiving unit can include the optical device, which can be diffraction-limited for the entire detectable field angle. The optical device can advantageously include at least one lens, and in particular a plurality of lenses, which can be configured to direct the light rays to the detector. The resolution of optical instruments, in this case the optical device, can be limited by diffraction in conjunction with the field angle. The field angle can, for example, be a characteristic parameter for the field of view of the receiving unit, i.e., related to a detection range.

[0013] The optical device can have interchangeable components and at least one adjustable optical aperture diaphragm, which can be configured to adapt the geometric properties of the incident beams, in particular their diameter. For example, the optical device can be designed similarly to a conoscope. The adjustable aperture diaphragm can be used, for example, to simulate the iris diameter of the human eye. Advantageously, the optical aperture diaphragm can be physically or virtually adjustable and, additionally, can be shaped, for example, as an opening through which the light rays can be received. By adjusting the optical aperture diaphragm, it is advantageous to determine how much light is received, thus ensuring optimal lighting conditions.

[0014] According to one embodiment, the projection unit can be configured as a focusable or non-focusable collimator, which can, in particular, have at least one monochromatically and additionally or alternatively polychromatically illuminated or illuminable line element. The receiving unit accordingly has an imaging telescope to project the image generated by the collimator from infinity onto the sensor. A collimator can be configured to generate light with an approximately parallel beam path from a divergent source. This advantageously allows the light to be directed in a specific direction. Monochromatic can, for example, refer to light emission in a very narrow wavelength range. Polychromatic can therefore refer to multicolored light that comprises a mixture of different colors and can thus be spectrally broadband and exhibit different wavelengths.The line element can advantageously also be referred to as a line plate or reticle.

[0015] Furthermore, the projection unit can have at least one line element with a plurality of different object structures. Alternatively, the projection unit can have a switching mechanism for sequentially introducing different line elements with different object structures into a light beam path. In particular, the object structures can represent large-area elements, sharp edges, and additionally or alternatively, lines. The line element with the plurality of different object structures can, for example, be referred to as a multi-feature reticle. The object structures can therefore be, for example, patterns that have curved or straight contours or lines. The object structures can thus be implemented, among other things, as a circle, square, or cross, which can, for example, be displayed on or by the test object.

[0016] According to one embodiment, the object structures can be generated or generated using a self-illuminating element. Additionally or alternatively, the projection unit can have an adjustable projection aperture diaphragm. The object structures can advantageously be implemented as virtual structures. To enable their representation, the projection unit can, for example, have the projection aperture diaphragm, which, similar to an optical aperture diaphragm, can be shaped as an opening through which light can be emitted. The projection aperture diaphragm can advantageously be implemented physically or virtually and can be additionally or alternatively adjusted to limit the diameter of the beam exiting the projection unit. Furthermore, the projection unit can optionally have an additional projection field diaphragm, which in turn can be optionally adjusted to adapt the field angle of the exiting beams.

[0017] The device can also include a movable first goniometer, which may be connected to the projection unit, and a movable second goniometer, which may be connected to the receiving unit. The first and second goniometers can be configured to move the projection unit and the receiving unit independently of each other about a defined point of rotation in at least two different directions. In particular, the first goniometer and, additionally or alternatively, the second goniometer can be movable translationally relative to the test specimen in at least three spatial directions. The goniometer(s) can, for example, also be referred to as protractors, which can, for instance, measure an angle between the projection unit and the receiving unit. This means that the goniometers can be connected to each other and each connected at a free end to the projection unit or the receiving unit, respectively.The projection unit and the receiving unit can be connected. This allows the projection unit and the receiving unit to be advantageously moved in different directions in order to measure and determine the image quality of the test object from different positions and thus from different light sources. The goniometers can also be pivoted.

[0018] Furthermore, a method for determining the image quality of at least one image for a test object using a device in a previously mentioned variant is presented, wherein the method includes a step of emitting light using the projection unit in order to be able to project at least one luminous and additionally or alternatively illuminated object structure onto the test object.Furthermore, the method comprises a step of receiving light rays transmitted through or reflected by the test object using the receiving unit, which represent at least one image, and a step of simultaneously evaluating a first light parameter, representing at least one optical light parameter, and a second light parameter, representing at least one colorimetric or photometric light parameter, of light rays transmitted through or reflected by the test object in order to determine the image quality of the at least one image using the computing unit.

[0019] This method advantageously allows the determination of the image quality of the test specimen, which can be used, for example, in conjunction with smart glasses or AR / VR systems. Determining the image quality advantageously allows the sharpness of the images to be ascertained or verified. In the output step, the light can, for example, be emitted for a duration that can advantageously be adjustable.

[0020] According to one embodiment, in the receiving step, further light rays transmitted through or reflected by the test object can be received, which can represent at least one further image. In the evaluation step, a further first light parameter, which can represent at least one further optical light parameter, and a further second light parameter of the further light rays, which can represent at least one further colorimetric or photometric light parameter, can be evaluated simultaneously in order to determine the image quality of the further image. In particular, the image and the further image can each be acquired at different exposure times. The exposure time for emitting the light can be, for example, the same for the images or, alternatively, different.

[0021] The process can further include a step of combining the image and the subsequent image into a single overall image after the evaluation step. Advantageously, if the exposure times for the images differ, the combined image can be generated as a high-dynamic-range (HDR) image, meaning an image with large differences in brightness. Alternatively, the images can be combined using different spectral settings of the light rays to create a single color image. These parameters can be optionally defined for individual images or for the combined image.

[0022] According to one embodiment, the method can also include a step of compensating for imaging errors using predefined calibration data prior to the evaluation step. This compensation step advantageously corrects imaging errors to improve image quality before the light parameters are evaluated to determine the image quality. The calibration data can advantageously be stored on a memory unit.

[0023] This process can be implemented, for example, in software or hardware, or in a hybrid form of software and hardware, for example in a control unit.

[0024] The approach presented here further creates a computing unit designed to execute, control, and implement the steps of a variant of the method presented here in appropriate devices. This embodiment of the invention, in the form of a computing unit implemented as a control device, also allows the underlying problem of the invention to be solved quickly and efficiently.

[0025] For this purpose, the processing unit for signals or data can include 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 can be, for example, a signal processor, a microcontroller, or the like, and the storage unit can be flash memory or a magnetic storage device.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.

[0026] In this context, a computing unit can be understood as an electrical device that processes sensor signals and outputs control and / or data signals accordingly. The computing unit can have an interface, which may be implemented in hardware and / or software. In the case of a hardware-based interface, the interfaces can, for example, be part of a so-called system ASIC, which incorporates various functions of the device. However, it is also possible that the interfaces are separate integrated circuits or at least partially comprised of discrete components. In the case of a software-based interface, the interfaces can be software modules, which, for example, are present on a microcontroller alongside other software modules.

[0027] Examples of the approach presented here are shown in the drawings and explained in more detail in the following description. It shows: Fig. 1 a schematic representation of a device according to an exemplary embodiment; Fig. 2 a schematic representation of an exemplary embodiment of a device; Fig. 3 a schematic representation of an exemplary embodiment of an object structure for a device; Fig. 4 a schematic representation of an exemplary embodiment of an object structure for a device; Fig. 5 a schematic representation of an exemplary embodiment of an object structure for a device; Fig. 6 a schematic representation of an exemplary embodiment of an object structure for a device; Fig. 7 a flowchart of an exemplary embodiment of a method for determining the image quality of an image for a test specimen; and Fig. 8 a block diagram of a computing unit according to an exemplary embodiment of a device.

[0028] 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.

[0029] 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.

[0030] Fig. Figure 1 shows a schematic representation of a device 100 according to an exemplary embodiment. The device 100 is, for example, implemented as a measuring device designed to determine the image quality of at least one image for a test specimen 105. Accordingly, different optical systems can be arranged in or on the device 100, the image quality of which is to be measured or determined. The test specimen 105 is, for example, designed as a waveguide, as a combination of waveguides, or as a module that is designed as a combination of an illumination unit and a waveguide. The module is, for example, capable of generating a self-illuminating object structure that can be detected by a receiver unit 110 of the device 100.

[0031] The device 100 therefore comprises at least one projection unit 115 for emitting light 120 towards the test object 105 in order to project at least one luminous and / or illuminated object structure onto the test object 105. The projection unit 115 optionally includes an illumination unit, i.e., a light source 125, which generates the light 120. The previously mentioned optical receiving unit 110 is also part of the device 100. The receiving unit 110 is configured to receive light rays 130 of the light 120 transmitted through or reflected by the test object 105. The light rays 130 represent at least one image of the projected object structure. Furthermore, the receiving unit 110 comprises an optical device 135 and a detector 140.The detector 140, for example, has a plurality of spectral channels 141, an image sensor 142, and at least one filter unit 143, for example, a filter wheel with color filters (e.g., V(Lambda) filter) and an additional optional neutral density (ND) filter. The optical device 135 is diffraction-limited for an entire detectable field angle. Furthermore, the optical device 135 has interchangeable components and at least one physically or virtually adjustable optical aperture diaphragm 144, which is configured to adjust the diameter of the beams incident on the optical device. The optical device can also, for example, be designed like a conoscope.

[0032] According to this embodiment, both the projection unit 115 and the receiving unit 110 are movably and, in particular, pivotably arranged. Furthermore, according to this embodiment, they are arranged lying on a common line, which here corresponds, for example, to the path of the light 120 and the light rays 130. The test specimen 105 is arranged between the projection unit 115 and the receiving unit 110. More precisely, the device 110 has a mounting unit 145, which is shaped to hold the test specimen 105. According to this embodiment, the mounting unit 145 is also movably shaped to move the test specimen 105 in the x, y, and z directions of a coordinate system.For example, according to this embodiment, the device 100 comprises a movable first goniometer 146, also referred to as a protractor, which is connected to the projection unit 115, and a movable second goniometer 147, which is connected to the receiving unit 110. The first goniometer 146 and the second goniometer 147 are configured, for example, to move the projection unit 115 and the receiving unit 110 independently of each other about a defined point of rotation in at least two different directions. In particular, the first goniometer 146 and / or the second goniometer 147 is or are movable translationally relative to the test specimen 105 in at least three spatial directions.

[0033] The device 100 further comprises a processing unit 150 configured to simultaneously evaluate a first light parameter, representing at least one optical light parameter, and a second light parameter, representing at least one colorimetric or photometric light parameter, of the light rays 130 of the light 120 transmitted through or reflected by the test object 105 and received using the receiving unit 110, in order to determine the image quality of the at least one image for the test object 105. The processing unit 150 is connected to the projection unit 115, the receiving unit 110, and / or the mounting unit 145. According to this embodiment, the test object 105 (which here consists of or comprises an AR module) additionally comprises a waveguide with a further projection unit 155, which is also connected to the processing unit 150.The projection unit 115 and the further projection unit 155 are arranged, or can be arranged, offset from each other. The projection unit 115 is, for example, arranged such that the light 120 is transmitted in a straight line through the test object 105. According to this embodiment, the further projection unit 155 is arranged such that, for example, further light 160 enters the test object 105 at an entry point 165, which is also referred to as the entry pupil of the test object 105, and is reflected from surfaces of the test object 105 until it reaches an exit point 170, which is also referred to as the exit pupil of the test object 105. At the exit point 170, the light rays 130 and / or reflected further light rays 171 of the further light 160 emerge according to this embodiment and are then received by the receiving unit 110.The additional projection unit 155 also has a further light source 175 for emitting the additional light 160.

[0034] In other words, according to this embodiment, a system and in Fig. 7. A method for the simultaneous measurement of a total modulation transfer function (MTF), color MTF, and colorimetric or photometric parameters is then presented. The device 100 is thus realized as an all-in-one system that enables a customer, for example, for near-eye display (NED) systems, such as in the AR / VR field, to measure all essential light parameters, i.e., the optical and colorimetric quality of these systems, with a single measuring device.

[0035] The approach presented in general terms in this description therefore relates to a method and a device 100 for the simultaneous measurement of optical parameters, such as MTF, and colorimetric or photometric parameters for components and modules of NED systems. The device 100 includes, by way of example, a sensor described here in conjunction with the receiving unit 110, in front of which at least one filter wheel is arranged. The filter wheel comprises filters that, individually or in combination, filter the incident light rays 130 in their total quantity and spectrally, for example, with the weighting of the color perception of the human eye.Furthermore, the receiving unit 110 includes an optical system described as an optical device 135, which is mounted in front of the filter wheel and has a physical aperture 144 as its first element on one side of the test specimen. The diameter of this aperture can be changed manually or automatically by replacement or by some kind of adjustment. A key feature of the optical device 135 is its design as diffraction-limited for the entire detectable field angle. The optical device 135 can have either a small field of view (FOV) or an FOV corresponding to that of a conoscope.

[0036] For measuring colorimetric, photometric, and optical parameters, such as MTF, a target is used that is characterized by the presence of both large-area homogeneous elements and sharp edges or lines as its object structure. In addition to a target exhibiting both features, various targets with one feature each can also be used. The target can optionally be generated and projected by a self-illuminating display element that is part of the test specimen 105, or by a target projector that projects the target through the test specimen 105. For targets with only one feature, the projection occurs, for example, sequentially during the process. An optional additional projection unit 155, for instance, has another light source 175 that can generate either different individual wavelengths or polychromatic light of varying spectral widths.In this embodiment, the projection unit 155 is part of the test specimen 105 and can be implemented, for example, as an LCD or LCOS element. The projection unit 115 has a projection aperture diaphragm 180, also referred to as the exit aperture, which is located externally on the side facing the test specimen 105. Furthermore, the projection unit 115 has a homogeneously illuminated target template 182. The projection unit 115 can be technically similar to the other projection unit 155. The light 120, 160 is directed to an entrance pupil of the test specimen 105. The projection aperture diaphragm 180 can be implemented physically or virtually.

[0037] To measure optical and colorimetric or photometric parameters, the projection of a described target by the test object 105 is performed, for example, using the target projector or by projection using the test object 105 itself. Data acquisition is carried out by taking sequential images with the described system, each image being captured using different filtering through the filter wheel. The image acquisition can include one image per filter position or multiple images, even with different exposure times. For measuring optical and colorimetric parameters, the acquired data is forwarded to the processing unit 150 and processed.The processing includes, for example, not only combining images with different exposure times to create so-called high-dynamic-range images, combining images with different color weights to create color images, and / or correcting distortions in individual and composite images. The processing also optionally includes correcting the acquired data using calibration datasets and calculating optical and colorimetric parameters. The colorimetric parameters are determined using large-area structures as an example, while optical parameters, such as MTF, are determined in parallel using edges and lines.

[0038] Furthermore, the device 100 has at least one goniometer 146, 147; more precisely, the projection unit 115 and the receiver unit 110 can each be arranged on a goniometer 146, 147, which enables independent two-axis rotation of both elements about respective rotation points. The rotation points of the respective systems are located, for example, at the location of respective apertures of, for example, the test specimen or the projection or receiver unit, whereby any other position is also possible. According to this embodiment, both goniometers 146, 147 have the capability to be moved manually or automatically once or repeatedly, at least in the X and Y directions, and optionally also in the Z direction.The task of the goniometers 146, 147 is to independently position the receiving unit 110 and the projection unit 115 relative to the test object 105, such that at least one optical aperture diaphragm 144 of the receiving unit 110 can be adjusted at a defined measurement location and at a defined angle to the test object 105. If required, an exit pupil of the target object can also be aligned relative to the entrance pupil according to the defined position and angle. Furthermore, the test object 105 can be moved at least in the X and Y directions within a plane by means of the mounting unit 145. Depending on the receiving unit 110, the measurement of a test object 105 can therefore be achieved by adjusting the positioning systems or by sequential positioning, recording, and measurement at different locations and angles. The locations of the system and any projection unit 115 are defined by the mounting unit 145.The necessary target projectors are located, for example, either on opposite sides of the test specimen 105 or alternatively on the same side of the test specimen 105. Test specimens 105 are designed as individual or a combination of waveguides or light-guiding elements, modules consisting of several identical or different components, or complete systems.

[0039] This means that the device 100 and an associated method are presented, with which it is possible to perform a simultaneous measurement of optical imaging parameters as well as colorimetric and photometric parameters of optical components or modules of near-eye displays (NEDs). In this context, the term NED refers to devices that are worn by a user, for example, in the form of glasses, and which are capable of either projecting virtual images into the user's field of vision, such as through augmented, mixed, or extended reality, or creating a virtual environment, which is referred to as virtual reality.

[0040] Optical imaging or light parameters are quantities that characterize the image quality of an optical system, such as the MTF (Maximum Telemetry Factor), the degree of distortion, and the principal beam angle. Colorimetric and photometric light parameters are quantities that characterize color perception through an optical system, such as the transmitted color component or the color representation in a color space. Photometric parameters are quantities that provide information about the emission characteristics or the amount of light transmitted or reflected by the test object. These include, for example, the transmitted luminous flux or the luminous intensity. For the specific definitions of these and / or other parameters, please refer to the IEC 63145 and ISO 9241 standards.

[0041] The described approach enables simultaneous measurement of the aforementioned parameters, which is applicable, for example, to individual components of NEDs as well as pre-assembled modules or complete systems.

[0042] In other words, here is a first one, in the Fig. Figure 1 illustrates and describes a more detailed embodiment of the device 100, and its operation is schematically explained. According to this embodiment, the device 100 to be tested or measured (Device under Test - DUT) is an assembly of a NED. This assembly consists of an internal projection unit 155, which includes an illuminated LCD element and, for example, a waveguide designed to provide the image generated by the internal projection unit 155 to a viewer in a suitable manner. The device 100 is mounted in a mechanical holder, such as a multi-axis linear stage, which allows free positioning of the device 105 in space. More precisely, the device 105 can be moved once or repeatedly along an x-, y-, and z-axis of a coordinate system using the stage. According to the illustration in the Fig. In the embodiment shown and described in Figure 2, the projection unit 115 is implemented as a collimator. This collimator has, for example, a fixed or variable focus. The projection unit 115 generally comprises the light source 125, a line element 182, referred to as a reticle or grid plate, on which a structured object pattern is applied, and an optical system 184, such as a lens, which has a real or virtual exit aperture 180. The line element 182 is preferably connected to a diffuser to ensure homogeneous illumination of the object pattern. If the projection unit 115 is designed as a focusable collimator, the line element 182 can be moved relative to the collimator's optics, for example, by means of a linear encoder, in order to simulate different object distances.

[0043] According to this embodiment, the structured object pattern advantageously includes both large-area, homogeneous elements and sharp edges or lines. Both types of structure can be located on the line element 182, which is thus realized, or can be realized, as a so-called multi-feature reticle. Alternatively, a mechanical exchange mechanism can be provided by which different line elements 182 with different structures can be introduced into the beam path of the projection unit 115. Alternatively, line structures can be used for both partial measurements. In this case, a correction factor is used in the colorimetric and photometric evaluation to account for the limited area fraction of the luminous structure. When using, for example, a double cross or a ring, the optical magnification is optionally also determined metrologically and individually considered in the calculation.Examples of object structures to be projected are in the . Fig. 3 to 6 are shown.

[0044] For example, the light source 125 of the projection unit 115 is polychromatic, and a suitable mechanism may be provided to limit or adjust the spectral bandwidth. The light source 125 is implemented, for example, as a single polychromatic LED with appropriate spectral filtering or as a combination of several monochromatic light sources. Alternatively, the projection unit can also be designed to generate a virtual object structure via a self-illuminating element, such as a display.

[0045] The device 100 also includes the optical receiving unit 110, which is arranged on the opposite side from the projection unit 115. If the test specimen 105 is measured in reflection, the projection unit 115 and the receiving unit 110 can be arranged on the same side. In the configuration shown here... Fig. Figure 1 shows an example of measurement in transmission. However, the approach works equally well for measurement in reflection.

[0046] The receiving unit 110 comprises an optical system described as an optical device 135 and an image sensor, which can be implemented as a multispectral detector 140, meaning a detector with multiple spectral channels. Other configurations include monochromatic detectors with filter units or separate channels for spectrometric evaluations. In other words, the spectral sensitivity of the image sensor is variable. The image sensor is thus able to spectrally weight and / or filter incident light rays. For example, this allows the sensor's spectral sensitivity to be adapted to that of the human eye. In one embodiment, such a detector 140 can be implemented using a combination of at least one filter wheel with a V (lambda) filter and an additional ND filter.In this embodiment, the optical device 135 is arranged in front of the detector 140 and is designed to produce a diffraction-limited image for its entire detectable field of view (FOV). Furthermore, the optical device 135 has one or more interchangeable components, making it possible to adapt the FOV of the optical device 135 to different measurement requirements. For example, at a maximum FOV setting, the design of the optical system corresponds to that of a conoscope, where the first optical element is always an adjustable optical aperture diaphragm 144, as shown in the figure. Fig. 1 or the Fig. Figure 2 is shown. This is preferably implemented as a physical aperture, but alternatively also as a virtual pupil.

[0047] Both the projection unit 115 and the receiver unit 110 according to the one described in the Fig. 1 and Fig. In the embodiment shown in Figure 2, each projection unit is attached to a goniometer 146, 147, which can be pivoted or moved laterally independently of one another, either once or repeatedly. The axes about which the projection and receiving units can be pivoted run, for example, approximately parallel to the respective optical axis and / or intersect the respective entrance or exit pupil centrally. To achieve a lateral offset, each goniometer 146, 147 can also be mechanically connected to a multi-axis linear stage. Pivoting and / or moving the projection unit 115 is necessary to illuminate the test specimen 105 at different positions and / or under different object angles, or to provide the object pattern at different positions or under different object angles. An application example is shown below. Fig. 2 shown.

[0048] In other words and / or to summarize, this embodiment presents the device 100 for measuring the image quality of optical systems or modules of NED systems, wherein the device 100 comprises the projection unit 115, a mounting unit 145 (also referred to as a mechanical mount for the optical system or module or the test specimen 105 under test), which is movable translationally in three spatial directions, the optical receiving unit 110, and the processing unit 150. The device 100 is capable of simultaneously determining optical and photometric or colorimetric measurement parameters of the optical system or module 105 under test, wherein the optical receiving unit 110 consists of an optical imaging system, previously described as an optical device 135, and an optical detector 140 with a plurality of spectral channels 141.The optical detector 140 can be implemented, for example, by combining an image sensor 142 with at least one filter element 143, such as a front-mounted filter wheel with a V(Lambda) filter and an optional additional ND filter. According to this embodiment, the optical receiving unit 110 has an optical system 135 which is diffraction-limited for the entire detectable field angle. The optical system, meaning the optical device 135 of the receiving unit 100, also optionally has interchangeable components and at least one physically or virtually adjustable optical aperture diaphragm 144, so that it is possible to limit the diameter of the incident beams, for example, to simulate the size of the human iris. The optical system 135 can also be designed like a conoscope.

[0049] According to this embodiment, the projection unit 115 is optionally implemented as a focusable or non-focusable collimator with a monochromatically and / or polychromatically illuminated reticle element 182 and also features a physical or virtual aperture diaphragm, previously described as the exit aperture 180. The aperture diaphragm can optionally be adjustable to limit the diameter of the beams incident on the test object. Furthermore, the projection unit 115 can include an adjustable field diaphragm 181, which can also be implemented physically or virtually. This diaphragm serves to adjust the field angles of the exiting beams. Such adjustment may be necessary for some test objects to precisely match the coupling angle into a waveguide under test.The reticle element 182 optionally includes different object structures (multi-feature reticle) or is designed such that reticle plates with different object structures can be sequentially introduced into the beam path of the projection unit 115 using a changing mechanism. The object structures can be implemented, for example, as large-area elements as well as sharp edges or lines, which are generated as virtual structures using a self-illuminating element.In other words, the projection unit 115 comprises at least one line element 182 with a plurality of different object structures or a switching mechanism for sequentially introducing different line elements, for example, reticles, with different object structures into a beam path of light 120, in particular wherein the object structures represent large-area elements, sharp edges and / or lines that are, for example, curved or straight. The object structures are generated or can be generated as virtual structures using a self-illuminating element. Additionally or alternatively, the projection unit 115 comprises a physical or virtual projection aperture diaphragm 180 and an optional physical or virtual projection field diaphragm 181.

[0050] According to this embodiment, the projection unit 115 is designed to illuminate the test specimen 105 in reflection or transmission. For this purpose, the projection unit 115 is, for example, arranged on the first goniometer 146 and the receiving unit 110 on the second goniometer. This allows both units 110, 115 to be pivoted about a defined rotation point in at least two directions. Each of the goniometers 146, 147 is therefore translationally movable relative to the test specimen 105 in three spatial directions. The goniometers are not strictly necessary for the device to function. In such a case, the receiving unit would be implemented as a conoscope, and the projection unit would have an adjustable aperture and field stop to adapt the diameter and field angles of the light beams to the test specimen.Overall, the test specimen is designed, for example, as a waveguide, a combination of waveguides, or a module consisting of a combination of a lighting unit and a waveguide, wherein the module is able to generate a self-illuminating object structure which can be detected by the receiving unit 110 of the device 100.

[0051] Fig. Figure 2 shows a schematic representation of an embodiment of a device 100. The device 100 shown here is similar to the one described in Fig. The device 100 described in Section 1. According to this embodiment, the device 100 shown here comprises, in addition to the receiving unit 110, the processing unit 150, and the mounting unit 145 holding the test specimen 105, the projection unit 115. The test specimen shown here does not have an independent, active illumination or projection element 155. According to this embodiment, the light 120 enters the test specimen 105 via the entry point 165 and is reflected off the surfaces of the test specimen 105 until it reaches the exit point 170 and the light rays 130 are output to the receiving unit 110. Also according to this embodiment, the projection unit 115 is implemented as a focusable or non-focusable collimator, which in particular has at least one monochromatically and / or polychromatically illuminated or illuminable line element 182 (reticle).It is also conceivable that the (image) sensor 142 can be focused accordingly. A collimator is designed to generate light with an approximately parallel beam path from a divergent source. This collimation often serves to give the light a specific direction.

[0052] In the Fig. In other words, as shown in Figure 1, the device 100 is used to measure the image quality of the test specimen 105, for example, a single waveguide. The projection unit 115 is positioned such that the object pattern is projected into the entrance pupil 165. The object pattern can also be projected into other areas of a waveguide of an NED module. For example, in a module for AR glasses, the projection unit 115 simulates a real object from the user's environment. In this application, the exposure unit of the NED module also optionally generates a self-illuminating structured object pattern, which is captured by the receiver unit 110 in addition to or as an alternative to the object pattern of the projection unit 115. Swiveling the receiver unit 110 is necessary, for example, to capture an image of the object pattern at different field angles.In other words, axial and off-axis image quality is determined in this way. Using a lateral method of the receiving unit 110, the optical, photometric, and colorimetric parameters of the optical system or NED module being measured are determined at different positions within an eye box.

[0053] The device 100 also includes the computing unit 150, which electronically controls both the projection unit 115 and the receiving unit 110. The computing unit 150 is configured, for example, to control the projection unit 115 in order to introduce various object patterns into the beam path if a corresponding reticle-changing mechanism is used. Large-area structures are used for determining colorimetric or photometric parameters, and structures with sharp lines or edges are used for determining optical imaging parameters.

[0054] The processing unit 150 processes images recorded by the sensor of the receiving unit 110 and calculates the desired optical, colorimetric, or photometric imaging parameters of the test object 105 from these recorded images. The processing unit 150 controls the image sensor, for example, so that it sequentially records images of the object structure projected by the test object 105 for each of the available spectral channels. The sensor's exposure time is also variable. For example, using a filter wheel, changing a spectral channel changes its filter position. For each filter position, one or more images are recorded and forwarded to the processing unit 150.

[0055] The optical, colorimetric, or photometric parameters are determined, for example, for each individual recorded image or for any combination of individual images. For instance, sequentially recorded images with different exposure times can be combined to create one or more high-dynamic-range (HDR) images. Alternatively, sequentially recorded images with different spectral weightings can be combined to create one or more color images. When examining complete NED systems or modules, the processing unit 150 is also additionally or alternatively connected to the test object 105. In such a case, the projection unit 115, or the additional projection unit of the test object 105 (not shown here), is activated to display a self-illuminating object structure.An example of such a self-illuminating object structure would be a crosshair pattern or a ring, which are merely displayed as examples by an LCD or LED display. The processing unit 150 also optionally has calibration data for the measuring device, which was read in prior to the measurement. This data helps to correct imaging errors, such as a degree of distortion, in the projection unit 115.

[0056] The optics used in receiver unit 110 can be subtracted from the subsequent measurement data.

[0057] Fig. Figure 3 shows a schematic representation of an embodiment of an object structure 300 for a device, as exemplified in at least one of the Fig. 1 to 2. The object structure 300, for example, is designed as one that is used to determine the image quality of a test specimen.

[0058] According to this embodiment, the object structure 300 has a dark area 305 and a light area 310, which are sharply separated from each other. The object structure 300 is shaped like a cross. Furthermore, according to this embodiment, the object structure 300 has a polygonal contour.

[0059] Fig. Figure 4 shows a schematic representation of an embodiment of an object structure 300 for a device, as exemplified in at least one of the Fig. 1 to 2. The object structure 300, for example, is designed as one that is used to determine the image quality of a test specimen.

[0060] According to this embodiment, the object structure 300 has a dark area 305 and a light area 310, which are sharply separated from each other. The object structure 300 is shaped as a circle, in particular as a ring, so that, according to this embodiment, the object structure 300 has a further dark area 400. Furthermore, according to this embodiment, the object structure 300 has a polygonal contour.

[0061] Fig. Figure 5 shows a schematic representation of an embodiment of an object structure 300 for a device, as exemplified in at least one of the Fig. 1 to 2. The object structure 300, for example, is designed as one that is used to determine the image quality of a test specimen.

[0062] According to this embodiment, the object structure 300 has a dark area 305 and a light area 310, which are sharply separated from each other. According to this embodiment, the object structure 300 is shaped as a square. Furthermore, according to this embodiment, the object structure 300 has a polygonal contour.

[0063] Fig. Figure 6 shows a schematic representation of an embodiment of an object structure 300 for a device, as exemplified in at least one of the Fig. 1 to 2. The object structure 300, for example, is designed as one that is used to determine the image quality of a test specimen.

[0064] According to this embodiment, the object structure 300 has a dark area 305 and a light area 310, which are sharply separated from each other. Additionally, according to this embodiment, the object structure 300 has a further dark area 400 and a further light area 600. According to this embodiment, the light areas 310, 600 and the dark areas 305, 400 are arranged diagonally to each other, such that all areas 305, 310, 400, 600 meet at a common center point 605 of the object structure 300. Furthermore, according to this embodiment, the object structure 300 has a round contour.

[0065] Fig. Figure 7 shows a flowchart of an embodiment of method 700 for determining the image quality of an image for a test specimen. Method 700 can be carried out, for example, by a computing unit for a device such as those found in one of the Fig. As described in sections 1 to 2. The computing unit is, for example, designed as a control unit.

[0066] Method 700 therefore comprises a step 705 of emitting light using the projection unit, for example for an adjustable duration, to project at least one luminous and / or illuminated object structure onto the test object. Method 700 further comprises a step 710 of receiving light rays transmitted through or reflected by the test object using the receiving unit, which represent at least one image, and a step 715 of simultaneously evaluating a first light parameter and a second light parameter of light rays transmitted through or reflected by the test object.The first light parameter represents at least one optical light parameter, and the second light parameter represents at least one colorimetric or photometric light parameter, in order to simultaneously determine the image quality of at least one image using the processing unit. Only optionally, in step 710 (receiving), are further light rays transmitted through or reflected by the test object received, representing at least one further image. This means that in step 715 (evaluation), another first light parameter, representing at least one further optical light parameter, and another second light parameter, representing at least one further colorimetric light parameter, are simultaneously evaluated from these further light rays to determine the image quality of the further image.In particular, the image and the subsequent image were each captured at different exposure times.

[0067] Additionally, but optionally, the method 700 according to this embodiment includes a step 720 for compensating and thus correcting image errors, such as distortion, using predefined calibration data before step 715 of evaluation, and / or a step 725 for combining the image and the subsequent image into a complete image after step 715 of evaluation. This occurs, for example, when the exposure time differs for the overall HDR image, or when different spectral settings are used for a complete color image. Parameters are determined for individual images or for the complete image.

[0068] In other words, method 700 describes the measurement of the image quality of optical systems or modules of NED systems, wherein in step 705, the output, a luminous and / or illuminated object structure is projected, which is transmitted by or reflected from the optical system or module under test. In step 710, the receive, one or more images of the transmitted or reflected object structure are received by the receiving unit at different spectral settings of the detector. In step 715, the evaluation, one or more optical, colorimetric, or photometric parameters of the optical system or module under test are simultaneously determined from the one or more images using the processing unit.The detector's exposure time is optionally adjustable, allowing multiple images, each captured at a different exposure time, to be combined into a single HDR image using the processing unit. Furthermore, in step 725 of the combining process, images captured at different spectral settings are combined into a single image using the processing unit. The optical, colorimetric, and photometric parameters can be determined optionally for each individual image and / or for combined images.

[0069] Fig. Figure 8 shows a block diagram of a computing unit 150 according to an embodiment of a device such as those found, for example, in at least one of the Fig. As described in sections 1 to 2. The computing unit 150 is therefore, for example, designed to control and / or execute a procedure for determining the image quality of at least one image for a test specimen, as is described, for example, in Fig. As described in section 7, the computing unit 150 comprises an output unit 800, a read unit 805, and an evaluation unit 810. Optionally, the computing unit 150 may also include a balancing unit 815 and / or a combining unit 820.

[0070] The output unit 800 is configured to emit light using the projection unit in order to project at least one luminous and / or illuminated object structure onto the test specimen. The input unit 805 is configured, for example, to read in light rays received by the receiving unit of the device, which were transmitted through or reflected by the test specimen; this means, for example, reading in a first light parameter 825 and a second light parameter 830 of the light rays.The evaluation unit 810 is designed to simultaneously evaluate the first light parameter 825, which represents at least one optical light parameter, and the second light parameter 830, which represents at least one colorimetric or photometric light parameter, of light rays transmitted or reflected through or on the test object in order to simultaneously determine the image quality of the at least one image.The receiving unit 805 is optionally further configured to read additional light beams received by the receiving unit of the device, which are transmitted through or reflected by the test specimen. This includes, for example, an additional first light parameter 831, representing at least one further optical light parameter, and an additional second light parameter 832, representing at least one further colorimetric or photometric light parameter. Consequently, the evaluation unit 810 is configured to simultaneously evaluate the additional first light parameter 831 and the additional second light parameter 832 of the additional light beams in order to determine the image quality of the additional image, in particular where the image and the additional image were each acquired at different exposure times.

[0071] The compensation unit 815 is also optionally configured to compensate for or correct imaging errors using predefined calibration data 835. The combination unit 820, for example, is configured to combine the image and an optional additional image to obtain a complete image.

[0072] In summary, regarding the type of optical systems to be tested, it should be noted that the intended application of the device to be patented is modules for AR / VR systems. Specifically, these can be individual waveguides or waveguides with their own projector (e.g., for AR glasses). The measuring system itself only has, for example, a projection device and a receiving device. Both can, for example, be swiveling or movable. Specifically, the second projection unit is not a standard component of the measuring system. It is only present when a NED module is being measured, as is the case, for example, in the Fig. 1 is described. In the case of the following Fig. In a fully developed system, this would be an application example where one can use measurement technology to examine how well the waveguide transmits the images generated by the NED projector (e.g., in AR glasses) compared to the representation of the real environment.

[0073] Regarding the comparison between spectral filters and ND filters, it should be noted that a distinction should be made between two types of filters for the receiving unit. Spectral filters allow a desired wavelength range to be set, particularly for colorimetric measurements. Examples include V(Lambda) filters for matching the spectral sensitivity of the human eye or Beyer patterns (weighted distribution of RGB filters) in CCD cameras. ND filters reduce light intensity, regardless of the spectrum. Both types of filters can be used in practice.

[0074] Regarding the adjustment of field angles and beam cross-sections, it should be noted that on the receiving side, for example, no adjustment of the field angle of the light rays is necessary. Here, optics with a suitable FOV are selected, e.g., a conoscope for large field angles. However, adjusting the beam cross-section is helpful, e.g., when simulating the iris of the human eye; hence the adjustable aperture diaphragm 144. On the projection side, it may be necessary to adjust both the beam cross-section and its field angle. Hence the proposed field diaphragm 181. Fig.1. (The field aperture is depicted as a hatch.) Adjusting the beam cross-section is helpful to prevent the test object from being overexposed and to avoid potentially interfering effects, such as stray light. The field angle should be adjustable to achieve a desired coupling angle into the waveguide, as not every possible total internal reflection is necessarily desirable.

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