Method and device for determining an imaging quality of an optical system to be tested

Abstract

A method for determining an imaging quality of an optical system (102) to be tested is presented, wherein the method comprises a step of capturing an optical wavefront profile (107) in a measurement plane behind an exit pupil of the optical system (102), a step of ascertaining a partial optical wavefront profile for each subaperture of a plurality of subapertures of the measurement plane using the wavefront profile (107), and a step of determining a partial optical imaging quality for each of the subapertures using the ascertained partial optical wavefront profiles.

Description

[0001] Method and device for determining an imaging quality of an optical system to be tested

[0002] State of the art

[0003] The invention is based on a method and a device for determining an imaging quality of an optical system to be tested according to the preamble of the independent claims.

[0004] For applications and systems in the fields of augmented reality (AR) and virtual reality (VR), the image quality within an eyebox, i.e., within the range of movement of an eye, is an important quality parameter. The eyebox can be understood as a three-dimensional volume in which the eye's center of rotation must be located in order for it to be able to fully perceive a displayed image solely through eye movements or rotation.

[0005] US 10 277 893 B1 describes a camera system that is placed behind a VR headset under test. A measurement task is solved by mechanically moving a measuring device, such as a camera positioned behind the exit pupil of the test object. The camera system mechanically simulates the user's eye movements.

[0006] Against this background, the approach presented here provides an improved method and an improved device for determining the imaging quality of an optical system under test according to the main claims. The measures listed in the dependent claims enable advantageous refinements and improvements of the device specified in the independent claim.

[0007] The approach presented here represents a simple and time-efficient way of determining the imaging quality of an optical system to be tested, without, for example, using a scanning process or a mechanical grid. Instead, a plurality of measurement parameters can advantageously be obtained from a single measurement, which can also, for example, result in a low susceptibility to errors. A method for determining the imaging quality of an optical system to be tested is presented, wherein the method comprises a step of detecting an optical wavefront profile in a measurement plane behind an exit pupil of the optical system, a step of splitting orSegmentation of the measurement plane into a plurality of sub-apertures, a step of determining an optical partial wavefront profile for each sub-aperture of a plurality of sub-apertures of the measurement plane using the wavefront profile, a step of determining an optical partial image quality for each of the sub-apertures using the determined optical partial wavefront profiles, whereby a statement can be made about the distribution of the image quality over the entire measurement plane.

[0008] The optical system to be tested can, for example, be implemented as data glasses, as the optics of data glasses, or as a spectacle lens, which can be implemented in conjunction with an ARA / R device that is usually worn close to the human eye. The method can advantageously measure and check the imaging quality of the optical system to be tested within an eye box. For example, corresponding measurement results can be used to check or improve the optical system. The optical wavefront profile can represent a profile of the optical wavefront in the measurement plane or an image of optical waves on the measurement plane. The optical waves can propagate from the exit coil of the optical system towards the measurement plane.The wavefront profile can depend on a structure of the optical system to be tested, which can, for example, influence a beam path of the optical system to be tested. The imaging quality of the optical system to be tested can therefore be determined from a characteristic of the wavefront profile. The imaging quality can relate to at least one parameter of an optical transfer function of the optical system to be tested. The subapertures can, for example, be designed as segment surfaces of the measuring plane, which together can form the measuring plane or a section of the measuring plane located within the eye box. There is a possibility that the subapertures partially overlap, since, particularly in optical systems for ARA / R applications, the generally large exit pupil is generated by multiplying the generally small entrance pupil.Thus, the partial wavefront profiles together, i.e., viewed as a whole, can form the recorded wavefront profile of the measurement plane. Thus, the partial wavefront profiles of the subapertures can be determined by segmenting the wavefront profile. The subapertures can, for example, have dimensions of less than 10 mm. 2For example, the sub-apertures can be rectangular, circular, or square. The sub-apertures can be the same size. The dimensions of the sub-apertures can be on the order of magnitude of a human eye pupil. The partial imaging qualities can relate to at least one parameter of an optical transfer function of a section of the optical system to be tested that can be assigned to the respective sub-apertures. Advantageously, the method can be used to determine the imaging quality at each position of the eye pupil within the eye box with a so-called one-shot measurement, which can significantly reduce the time required for measurement. For example, the imaging qualities of the sub-apertures within the measurement plane can be used to make a statement about how the imaging quality parameter is distributed across the measurement plane.

[0009] Alternatively, the method described here can also be applied to other near-eye optical systems outside the field of application of virtual or augmented reality. Examples of such systems would be bifocal contact lenses or progressive lenses. Such optics have the property that the exit aperture is divided into different zones, each of which can be assigned a different refractive power. Thus, the distribution of image quality can also be determined for such near-eye optical systems using the method described here. The subapertures, which can be assigned to the zones of different refractive power, can have different dimensions and do not have to be evenly distributed across the measurement plane.

[0010] An example of a bifocal contact lens is disclosed in US20210382323 A1. The lens described in this document has a zone for distance vision located in the upper lens area and a zone for near vision located in the lower lens area. Furthermore, the lens has an outer ring structure for stabilization while the eye is moving. The use of the near and far vision zones of the contact lens is achieved by offsetting the contact lens relative to the eye pupil. According to one embodiment, this can be metrologically simulated by differently positioned subapertures.

[0011] According to one embodiment, the wavefront profile in the measurement plane can be detected in the detection step using a wavefront sensor. The wavefront sensor can be implemented, for example, as part of a test device with which the method can be carried out. Advantageously, the wavefront sensor can detect light rays guided through the optical system to be tested and provide the detected light rays for evaluation. The wavefront sensor can be implemented, for example, as a known Shack-Hartmann sensor.

[0012] A division rule used in the division step to divide the measurement plane into a plurality of subapertures can be specified for the measurement plane. Advantageously, the division step allows the image quality to be easily determined at different positions within the eyebox, whereby the individual subapertures can partially overlap. Furthermore, mechanical rasterization or scanning of the measurement plane can be dispensed with.

[0013] Furthermore, the method may include a step of defining a measurement volume prior to the acquisition step, wherein the measurement plane may represent a cross-sectional area of ​​the measurement volume. The size of the measurement volume may correspond to the size of an eye box used. By defining a suitably sized and appropriately positioned measurement volume, the imaging quality of a section of the optical system to be tested can be determined, which is relevant for a planned subsequent application of the optical system to be tested.

[0014] According to one embodiment, the method can further comprise a step of determining a further optical partial image quality for each further subaperture of a plurality of further subapertures of a further measurement plane behind the exit pupil of the optical system. In this case, in the determining step, the image quality can further be determined using the further partial image qualities. Advantageously, the measurement plane and the further measurement plane can be linearly spaced along an optical axis of the optical system to be tested. For example, the optical system to be tested can have a plurality of measurement planes whose distances from one another can, for example, be uniformly realized. Advantageously, the further partial image qualities can be determined with a single measurement. The further measurement plane can be composed of the plurality of further subapertures, i.e., subsurfaces.This means that each of the additional subapertures can be formed as a segment of the additional measurement plane. Analogously, the additional wavefront profile can be composed of the plurality of additional partial wavefront profiles of the additional subapertures. Furthermore, the method can comprise a step of detecting an additional optical wavefront profile in the additional measurement plane and a step of determining an additional optical partial wavefront profile for each additional subaperture of the plurality of additional subapertures of the additional measurement plane using the additional wavefront profile. Advantageously, the additional wavefront profile can also be detected using a wavefront sensor.

[0015] As an alternative to measuring, the at least one further wavefront profile in the further measurement plane can be calculated in a calculation step using the wavefront profile of the measurement plane. Furthermore, in a determination step, a further optical partial wavefront profile can be determined for each further subaperture of the plurality of further subapertures of the further measurement plane using the further wavefront profile. This means that the further wavefront profile can be derived from already existing data regarding the wavefront profile.

[0016] According to one embodiment, in the calculation step, the further wavefront profile in the second measurement plane can be calculated using a known ray tracing algorithm. The ray tracing algorithm, also referred to as a ray tracing algorithm, can represent an algorithm based on the emission of rays for calculating their path, by which a spatial path of the light rays from a specific point in space can be determined. Advantageously, the algorithm can be implemented in advance so that it can, for example, use previously acquired and additionally or alternatively determined data regarding the optical system to be tested to calculate the further wavefront profile. Alternatively, the calculation step can be carried out on the mathematical basis of wave-optical models.

[0017] According to one embodiment, a size of the plurality of subapertures can differ from a size of the plurality of further subapertures. This means, for example, that the dimensions of the subapertures and the further subapertures can differ. Furthermore, the measurement plane and, additionally or alternatively, the further measurement plane can be divided between multiple evaluation iterations.Furthermore, a device for determining an imaging quality of an optical system to be tested is presented, wherein the device has a recording device for recording the optical system to be tested, a further optical system for detecting an optical wavefront profile in a measuring plane behind an exit pupil of the optical system to be tested and an evaluation device for dividing the measuring plane into a plurality of sub-apertures, for determining an optical partial wavefront profile for each sub-aperture of a plurality of sub-apertures of the measuring plane using the wavefront profile, and for determining an optical partial imaging quality for each of the sub-apertures using the determined optical partial wavefront profiles.

[0018] The device can be implemented, for example, as a measuring device that can be used, for example, in connection with the manufacture or testing of optical systems, such as data glasses or general systems for the ARA / R sector. The recording device can be implemented, for example, as a holder, such as a gripper arm or holding arm, or simply as a recording area. The further optical system can be implemented, for example, as a sensor unit, for example a wavefront sensor. The evaluation device can also be referred to as a computing unit that can be connected to the further optical system. The device can advantageously be designed to carry out image quality characterization of, for example, AR / VR headsets, components of such headsets, or ophthalmic instruments as optical measurement technology.The described approach thus enables a fast, virtual evaluation of image quality for multiple measurement positions and different apertures within an eyebox, for example, for ARA / R measurement technology and generally for measurement technology for ophthalmic optical systems, such as binoculars, eyeglasses, or corrective lenses. The characterization of so-called near-eye displays is also possible. Advantageously, the image quality can be determined for different positions of the eye pupil within the eyebox. The device can advantageously be designed to perform this using a one-shot measurement with only a single measurement in the range between 1 and 3 seconds. This advantageously reduces the complexity of the device and thus saves costs.

[0019] According to one embodiment, the device may comprise a light source for illuminating the optical system to be tested when the optical system to be tested is received by the receiving device. The light source may be configured, for example, as a light-emitting diode (LED) or, for example, as a laser light source. The light source is configured to emit light and thereby illuminate the optical system to be tested.

[0020] An additional optical system for collimating the light rays emanating from the light source can be arranged downstream of the light source. The optical system for collimating the light rays emanating from the light source can advantageously be implemented as a projector unit, which can, for example, comprise at least one optical lens.

[0021] Furthermore, the additional optical system can be pivoted at an angle to an optical axis of the optical system to be tested. This pivotability advantageously allows the additional optical system to be pivoted such that one or more partial image qualities can be determined in at least one off-axis field angle position.

[0022] According to one embodiment, the further optical system for detecting the optical wavefront profile can comprise a telescope and a Shack-Hartmann sensor. The telescope and the Shack-Hartmann sensor can advantageously be enclosed in a common housing and referred to as components of the further optical system. Within the housing, the components can, for example, be arranged fixedly, i.e., stationary relative to one another, so that objects at a fixed distance from the housing are imaged onto the sensor.

[0023] Examples of the approach presented here are shown in the drawings and explained in more detail in the following description. It shows:

[0024] Fig. 1 is a schematic representation of an embodiment of a device for determining an imaging quality of an optical system to be tested;

[0025] Fig. 2 is a schematic representation of an embodiment of a device for determining an imaging quality of an optical system to be tested;

[0026] Fig. 3 is a diagrammatic representation of an exemplary embodiment of a section of a measurement plane with a three-dimensional wavefront profile; Fig. 4 is a diagrammatic representation of an exemplary embodiment of a three-dimensional representation of a partial wavefront profile;

[0027] Fig. 5 is a flowchart of an embodiment of a method for

[0028] Determining the imaging quality of an optical system to be tested;

[0029] Fig. 6 is a flowchart of an embodiment of a method for

[0030] Determining the imaging quality of an optical system to be tested;

[0031] Fig. 7 is a schematic representation of an operating arrangement of an optical system to be tested according to an embodiment; and

[0032] Fig. 8 shows a representation of a measuring plane according to an embodiment.

[0033] In the following description of advantageous embodiments of the present invention, the same or similar reference numerals are used for the elements shown in the various figures and having a similar effect, whereby a repeated description of these elements is omitted.

[0034] Fig. 1 shows a schematic representation of an embodiment of a device 100 for determining the image quality of an optical system 102 to be tested. The device 100 can also be referred to, for example, as a measuring device or testing device. The optical system 102 is implemented, for example, as a spectacle lens, as a waveguide, or as another element that is used, for example, in conjunction with data glasses or in the field of augmented reality (AR) or virtual reality (VR) as ARA / R glasses. For this purpose, the device 100 has a receiving device 104 for receiving the optical system 102 to be tested. The shape of the receiving device 104 is shown here merely as an example. The receiving device 104 can be implemented, for example, as a gripping arm or holding arm, which optionally further holds the optical system 102 on at least one system edge.The device 100 further comprises a further optical system 106 for detecting an optical wavefront profile 107 in a measurement plane behind an exit pupil of the optical system 102 to be tested. The further optical system 106 can also be referred to, for example, as a sensor device, since according to this exemplary embodiment it comprises a sensor unit 108 designed as a wavefront sensor or Shack-Hartmann sensor. Optionally, the optical system 106 according to this exemplary embodiment comprises a telescope 110.The device 100 further comprises an evaluation device 112 connected to the further optical system 106, which is designed to determine an optical partial wavefront profile for each subaperture of a plurality of subapertures of the measurement plane using the wavefront profile 107, to further determine an optical partial image quality for each of the subapertures using the determined optical partial wavefront profiles, and thereby to make a statement about the spatial distribution of the image quality in the selected measurement plane using the partial image qualities. The evaluation device 112 is accordingly also to be understood as a computing unit designed to control and / or carry out a method for determining the image quality for the optical system 102 to be tested. A corresponding method is described in more detail below with reference to Figures 5 to 6.According to one embodiment, the further optical system 106 additionally comprises a housing 114 designed to protect the telescope 110 and the sensor unit 108 from external influences. Only optionally, the further optical system 106 is pivotable about an optical axis 116 of the optical system 102 to be tested, for example, in at least two opposite directions 118.

[0035] The device 100 optionally comprises a light source 120 configured to illuminate the optical system 102 to be tested when the optical system 102 to be tested is received by the recording device 104. For this purpose, the light source 120, according to this exemplary embodiment, emits light beams 122 with predetermined light parameters in the direction of the optical system 102 to be tested. The light beams 122 penetrate the optical system 102 to be tested, and light beams exiting the optical system 102 to be tested are detected by the sensor unit 108.

[0036] In other words, the approach presented here deals with measuring the imaging quality of optical systems 102 that are worn close to the eye. In addition to spectacle lenses, these include, in particular, waveguides in augmented or virtual reality (AR / VR) devices. In such applications, electronically generated images are projected into the field of vision of a viewer. For unrestricted perception by the user, sufficiently good imaging quality in the range of movement of the eye is important. This area is referred to as the so-called eye box. The eye box is understood to be a three-dimensional volume in which the center of rotation of the eye must be located so that it is able to perceive the entire image exclusively through eye movements. According to this exemplary embodiment, the further optical system 106 is arranged in the area of ​​the eye box.

[0037] The imaging quality within the eye box is an important quality parameter and can be advantageously verified using the approach presented here. For example, the imaging quality, expressed by the modulation transfer function (MTF) and optionally by various other parameters, is measured at each eye position, more precisely at each pupil position, within the eye box. Only optionally does the proposed approach enable a complete verification of the entire volume enclosed by the eye box, which in the context of this approach is understood as the measurement volume. The measurement volume typically has an extent of 25 x 25 x 25 mm. Based on the measurement data determined with the wavefront sensor 108, other characteristic parameters such as the intensity distribution within the eye box can optionally also be determined.

[0038] According to one embodiment, the device 100 comprises the light source 120, which optionally has optics for beam shaping, depending on whether the optical system 102, also referred to as the test object, is to be illuminated collimated or divergently. For example, with afocal optical systems 102, such as waveguides for ARA / R glasses, collimated illumination of the optical system 102 is required. Behind the optical system 102, which is fastened in a suitable holder, the recording device 104, is the further optical system 106, with the aid of which the wavefront profile 107 is measured. In the example shown here, this optionally comprises a Shack-Hartmann sensor as the sensor unit 108 with a telescope 110. The telescope 110 is designed, according to this embodiment, to adapt the beam cross-section such that the detection area of ​​the sensor unit 108 is sufficiently illuminated.The detection area of ​​a Shack-Hartmann sensor typically has dimensions in the range of 7 x 7 mm to 15 x 15 mm. The telescope 110 and the sensor unit 108 are, for example, installed in the shared housing 114. According to this exemplary embodiment, the measurement results are evaluated in the evaluation device 112, referred to as the computing unit, such as a PC. Furthermore, the housing 114 and thus the further optical system 106 can be pivoted by a defined angle so that the wavefront profile 107 can also be measured for field angles greater than 0°. Instead of a Shack-Hartmann sensor, the sensor unit 108 can also be implemented as a wavefront sensor based on a different measuring principle.

[0039] Fig. 2 shows a schematic representation of an embodiment of a device 100 for determining the imaging quality of an optical system 102 to be tested. The device 100 shown here is similar to the device 100 described in Fig. 1. According to this embodiment, an additional optical system 200 for collimating the light beams emanating from the light source 120 is arranged downstream of the light source 120. The additional optical system 200 has, for example, one or more lenses for guiding light. The light source 120 and the additional optical system 200 are implemented, for example, in their entirety as a projector unit 202.

[0040] According to this exemplary embodiment, light emanating from the projector unit 202 strikes an entrance pupil 204 of the optical system 102 to be tested, which lies on a common axis 205. The optical system 102 further has an exit pupil 206, via which collimated light rays 122 are ultimately output in the direction of the eye box 208, within which wavefront profiles of the light rays are recorded at several measuring planes, for example a measuring plane 210 and at least one further measuring plane 211. By way of example, according to this exemplary embodiment, four measuring planes 210, 211 are shown, which are arranged at regular intervals from one another and can each have a curvature. Furthermore, the recording of a wavefront profile 213 for the entire measuring plane 210 is shown as an example. In addition, the recording of a partial wavefront profile 215 is shown.

[0041] Furthermore, Fig. 2 highlights a section 212 of an eye box 208, which is described in more detail in at least one of the figures described below using a diagrammatic representation. Section 212 represents, for example, a specific eye position and subaperture.

[0042] Fig. 3 shows a diagrammatic representation of an exemplary embodiment of a wavefront profile 213 in a measurement plane 210. The wavefront shown here corresponds, for example, to the wavefront within the measurement plane 210 mentioned in Fig. 2 and thus shows a result of a wavefront measurement across the entire measurement plane 210. The wavefront profile 213 of the measurement plane 210 includes a subaperture 212 of the measurement plane 210 within the eyebox 208, using the example of waveguides for AR applications, for example. The subaperture 212 has, for example, a partial wavefront profile 215, which is illustrated as an example in a diagram in the following figure.

[0043] According to this embodiment, the wavefront profile 213 in the measurement plane 210 is represented as a three-dimensional plot in an xyz diagram, with the axes omitted for improved visibility. The eye box itself typically has dimensions of, for example, 25 x 25 x 25 mm.

[0044] Fig. 4 shows a diagrammatic representation of an embodiment of a partial wavefront profile 215. The partial wavefront profile 215 corresponds, for example, to the partial wavefront profile 215 from the sub-aperture 212 mentioned in Fig. 3 and is merely shown enlarged. For example, the partial wavefront profile 215 corresponds to the usual dimensions of 3 mm in diameter for positioning the eye pupil in the eye box. The imaging quality for such a region is determined by the method as described in at least one of Figures 5 to 6. Because the entire wavefront profile 213 in the measurement plane 210 is known, partial wavefront profiles can be determined for any number of sub-apertures 212, whereby a virtual scan is carried out in the x,y direction. A virtual z-positioning is calculated, for example, using ray tracing.A measurement time is, for example, between 1 and 3 seconds and requires only a relatively simple measuring device.

[0045] Fig. 5 shows a flowchart of an embodiment of a method 500 for determining the imaging quality of an optical system to be tested. Method 500 is carried out, for example, using a device such as that described in at least one of Figures 1 to 2.The method 500 comprises a step 502 of detecting an optical wavefront profile in a measurement plane behind an exit pupil of the optical system, a step 504 of determining a partial optical wavefront profile for each subaperture of a plurality of subapertures of the measurement plane using the wavefront profile, a step 506 of determining an optical partial image quality for each of the subapertures using the determined optical partial wavefront profiles, and an optional step 508 of determining the distribution of the image quality in the measurement plane using the partial image qualities, as was presented merely by way of example in at least one of Figures 3 to 4. The method 500 further comprises a step 510 of dividing the measurement plane into the plurality of subapertures. According to this exemplary embodiment, the dividing step 510 is performed before the determining step 504.For example, a size of the majority of subapertures differs from a size of a plurality of optional further subapertures of a further measurement plane.

[0046] According to this exemplary embodiment, the wavefront profile in the measurement plane is detected in step 502 of detecting using a wavefront sensor. In step 504 of determining, an individual partial wavefront profile is further determined for each subaperture from the plurality of subapertures using the wavefront profile in the measurement plane, so that in step 506 of determining, the partial image quality for each of the subapertures is determined using the determined partial wavefront profile associated with it.

[0047] Optionally, the method 500 additionally comprises further steps, such as a determination step 509, which is performed before the acquisition step 502 and in which a measurement volume is determined. The measurement plane represents, for example, a cross-sectional area of ​​the measurement volume.

[0048] According to one embodiment, the method 500 further comprises a step 512 of detecting a further optical wavefront profile in the further measurement plane, for example using a further wavefront sensor or using the wavefront sensor used to detect the first wavefront. In a step 514 of determining, a further optical partial wavefront profile is determined for each further subaperture of the plurality of further

[0049] Subapertures of the further measuring plane using the further

[0050] Wavefront profile is determined. Prior to this, step 510 of splitting is also applied to the further measurement plane.

[0051] According to this exemplary embodiment, method 500 comprises a step 516 of determining a further optical partial image quality for each further subaperture of the plurality of further subapertures of the further measurement plane behind the exit pupil of the optical system, so that in the optional step 508 of determining, the distribution of the image quality is computationally determined using the further partial image qualities. The measurement plane and the further measurement plane are linearly spaced along an optical axis of the optical system, whereby the calculated partial image qualities are distributed within a volume.

[0052] Further optionally, the method 500 comprises a step 518 of calculating the further wavefront profile in the further measurement plane using the wavefront profile of the measurement plane. The step 518 of calculating is to be understood as an embodiment variant or in addition to the step 512 of detecting the further optical wavefront profile. According to this exemplary embodiment, the second wavefront profile in the second measurement plane is calculated, for example, using a ray tracing algorithm. If the step 518 of calculating is carried out, in step 514 of determining the further optical partial wavefront profile, the further optical partial wavefront profile is determined for each further subaperture of the plurality of further subapertures of the further measurement plane using the calculated further wavefront profile.

[0053] In a corresponding manner, further wavefront profiles can be determined for even further measurement planes and used to determine the imaging quality.

[0054] Fig. 6 shows a flowchart of an embodiment of a method 500 for determining an imaging quality of an optical system to be tested. The method 500 corresponds, for example, to the method 500 described in Fig. 5 and differs only in the representation of the flowchart. According to this embodiment, the method 500 also comprises step 509 of defining for defining the measurement volume before step 502 of detecting, as well as step 510 of dividing the measurement plane into the plurality of sub-apertures before step 504 of determining. According to this embodiment, individual steps can be performed repeatedly, so that, for example, after step 508 of determining the distribution of the imaging quality using the previously determined partial imaging qualities, step 502 of detecting is performed again for a further measurement plane.

[0055] Alternatively, the further wavefront profile in the further measurement plane is calculated in step 518 using the wavefront profile of the measurement plane, and thus the imaging quality in the further measurement plane is determined using previously acquired data. In other words, in a first method step 502, the profile of the optical wavefront in a first measurement plane, which lies behind the exit pupil of the optical system to be tested, is measured. As an example, the use of a Shack-Hartmann wavefront sensor is mentioned here. Of course, other methods, such as interferometric methods, for optical wavefront measurement are conceivable. For this purpose, the measurement plane comprises, for example, the size of a cross-section of the entire exit pupil, or the eye box, the test object, or a section thereof. Optionally, the desired measurement volume is defined in the preparatory step 509.

[0056] In the next step 510, the measurement plane is divided into a plurality of small sub-apertures or sub-areas. The extent of the individual sub-apertures is on the order of magnitude of a human eye pupil, i.e., for example, 2.5 mm in diameter. This setting can also optionally be adjusted in a preparatory step. In other words, the entire wavefront of the measurement plane is divided or segmented into a plurality of partial wavefronts in the division step 510. Subsequently, the wavefront profile for each of the individual sub-apertures is determined from the wavefront profile of the entire measurement plane in the determination step 504. From each of the partial wavefronts, for example, a local parameter for the local imaging quality of the test object within the sub-aperture is determined in the determination step 506.Such a parameter is, for example, the modulation transfer function (MTF) or an aberration such as coma or astigmatism.

[0057] Since the image quality for each subaperture within the measurement plane is now known, a further step 508 can be used to determine how the image quality parameter (e.g., the MTF) is distributed across the measurement plane. For example, a statement can be made about the eye positions at which the MTF exceeds or falls below a specified threshold. This enables a detailed evaluation of the MTF distribution in the measurement plane without having to explicitly measure the wavefront at every possible eye position, thereby reducing the overall measurement time. For this purpose, a corresponding threshold comparison can be performed in step 508, for example.

[0058] In order to determine the imaging quality in the entire measurement volume, according to this exemplary embodiment, the course of the optical wavefront along the optical axis of the test object is determined in the following method step 518. More precisely, the profile of the wavefront is determined computationally in at least one further measurement plane located at a defined distance z from the first measurement plane, which is carried out in Fig. 5 in the optional calculation step. The calculation of the wavefront profile is achieved, for example, using ray tracing algorithms if the profile of the wavefront has been measured at a first z-position. According to this exemplary embodiment, the imaging quality for each pupil position of the eye is also determined from the computationally determined wavefront. This step 518 can be repeated for any number of planes in the entire measurement volume.

[0059] Alternatively, optionally, after completing step 508 of determining the image quality distribution in one measurement plane, the wavefront profile is measured in another measurement plane by repeating step 502 of measuring for the additional measurement plane, for example, by moving the wavefront sensor along the z-axis. Step 502 can also be repeated for any number of measurement planes. A combination of steps 502 and 518 is also possible.

[0060] Fig. 7 shows a schematic representation of an operating arrangement 700 of an optical system 102 to be tested according to an exemplary embodiment. The optical system 102 corresponds, for example, to the optical system 102 described in one of Figures 1 or 2 and, according to this exemplary embodiment, is arranged in the ready-to-operate state. According to this exemplary embodiment, the projector unit 202 is aligned in the direction of the optical system 102, wherein the projector unit 202 is at least similar to the projector unit 202 described in Fig. 2. The operating arrangement 700 shown here also corresponds to the structure of the device described in Fig. 2. Only, according to this exemplary embodiment, an eye 702 of a viewer is shown, whose eye pupil 704 is schematically positioned in the region of the three-dimensional eye box 208 in a schematic representation of waveguides for AR applications.

[0061] Fig. 8 shows a representation of a measurement plane 210 according to an exemplary embodiment. The measurement plane 210 is plotted in a diagram with an x-axis and a y-axis, each indicating a spatial extent of the measurement plane 210 in millimeters. The measurement plane 210 represents a cross-section of the eye box. By way of example, the measurement plane 210 is shown as square and divided into a plurality of, by way of example, 16 square segments 812. Each of the segments 812 corresponds to an eye position. For each of the segments 812, there is a subaperture 212. Adjacent subapertures 212 can have an overlapping area. Each subaperture 212 and thus each eye position is assigned, by way of example, an MTF value as partial image quality 820. For example, the subapertures 212 shown have MTF values ​​between 0.2 and 0.9.

Claims

Patent claims 1. Method (500) for determining the image quality of an optical system (102) to be tested, wherein the method (500) comprises the following steps: Acquisition (502) of an optical wavefront profile (107; 213) in a Measurement plane (210) behind an exit pupil (206) of the optical system (102); Dividing (510) the measurement plane (210) into a plurality of sub-apertures (212); Determine (504) an optical partial wavefront profile (215) for each sub-aperture (212) of the plurality of sub-apertures (212) of the measurement plane (210) using the wavefront profile (107; 213); and Determining (506) an optical partial imaging quality (820) for each of the sub-apertures (212) using the determined optical partial wavefront profiles (215).

2. Method (500) according to claim 1, wherein in step (502) of the detection the Wavefront profile (107; 213) in the measurement plane (210) is detected using a wavefront sensor.

3. Method (500) according to one of the preceding claims, comprising a step (509) of defining a measurement volume prior to the step (502) of sensing, wherein the measurement plane (210) represents a cross-sectional area of ​​the measurement volume.

4. Method (500) according to one of the preceding claims, comprising a step (512) of acquiring a further optical wavefront profile in a further measurement plane (211), and a step (514) of determining a further optical sub-wavefront profile (215) for each further sub-aperture of a plurality of further sub-apertures of the further measurement plane (211) using the further wavefront profile. Method (500) according to any one of claims 1 to 3, comprising a step (518) of calculating at least one further wavefront profile in a further measurement plane (211) using the wavefront profile (107; 213) of the measurement plane (210), and comprising a step (514) of determining a further optical partial wavefront profile (215) for each further sub-aperture of a plurality of further sub-apertures of the further measurement plane (211) using the further wavefront profile. Method (500) according to claim 4 or 5, comprising a step (516) of determining a further optical partial image quality (820) for each further sub-aperture of the plurality of further sub-apertures of the further measurement plane (211) behind the exit pupil (206) of the optical system (102) Method (500) according to claim s, wherein in the step (518) of calculation the further wavefront profile in the further measurement plane (211) is calculated using a ray tracing algorithm.Method (500) according to any one of claims 4 to 7, wherein the size of a plurality of sub-apertures (212) differs from the size of a plurality of further sub-apertures. Device (100) for determining the image quality of an optical system (102) to be tested, wherein the device has the following features: a receiving device (104) for receiving the optical system (102) to be tested; a further optical system (106) for acquiring an optical wavefront profile (107; 213) in a measuring plane (210) behind a. Exit pupil (206) of the optical system (102) to be tested; and an evaluation device (112) for dividing (510) the measurement plane (210) into a plurality of sub-apertures (212), for determining an optical partial wavefront profile (215) for each sub-aperture (212) of the plurality of sub-apertures (212) of the measurement plane (210) using the wavefront profile (107; 213), and for determining an optical partial image quality (820) for each of the sub-apertures (212) using the determined optical partial wavefront profiles (215).

10. Device according to claim 9, comprising a light source (120) for illuminating the optical system (102) to be tested when the optical system (102) to be tested is received by the receiving device (104).

11. Device (100) according to claim 10, wherein an additional optical system (200) for collimating the light rays (122) emanating from the light source (120) is arranged downstream of the light source (120).

12. Device (100) according to one of claims 9 to 11, wherein the further optical system (106) is pivotable at an angle to an optical axis (116) of the optical system (102) to be tested.

13. Device (100) according to one of claims 9 to 12, wherein the further optical system (106) for detecting the optical wavefront profile (107; 213) comprises a telescope (110) and a Shack-Hartmann sensor.

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