Method for defining the focal plane of a virtual image from an optical arrangement which can be worn in front of the eyes

Abstract

The invention relates to a method (50) for defining the focal plane (40) of a stereoscopic virtual image from an optical arrangement (20) which can be worn in front of the eyes (1) and which has at least one optical device (25) for radiating a stereoscopic virtual image. The method comprises the following steps: ascertaining the heterophoria of a person (52); based on the ascertained heterophoria, ascertaining a dependency (9) between the vergence distance and the focus distance (53); ascertaining a curve of the minimum relative vergence (11) (54); determining a depth-of-field region (43) (55); ascertaining a first focus distance (41) and a second focus distance (42), wherein the second focus distance (42) has a higher value in dioptres than the first focus distance (41), wherein the focus distance between the first focus distance (41) and the second focus distance (42) corresponds to the determined depth-of-field region (43) and wherein the first focus distance (41) is defined such that it forms an intersection point with the curve of the minimum relative vergence (11), said intersection point having a vergence value of at most 1 dioptre (56); and defining the focal plane (40) (57) of the stereoscopic virtual image in a region between the second focus distance (42) and the first focus distance (41).

Description

[0001] Method for determining the focal plane of a virtual image of an optical arrangement worn in front of the eyes

[0002] The present invention relates to a method for determining the focal plane of a virtual image of an optical arrangement worn in front of the eyes, a method for producing an optical element of an optical arrangement worn in front of the eyes, an optical element and an optical arrangement.

[0003] Head-mounted displays (HMDs), for example in the form of data glasses or AR headsets (AR - Augmented Reality) or VR headsets (VR - Virtual Reality) or MR headsets (MR - Mixed Reality) or AR or VR or MR glasses or VR or MR helmets, are used in numerous contexts. In these cases, the light waves used to generate a virtual image are usually guided by total internal reflection after being coupled into an optical fiber to an output. When a user looks through a head-mounted display, e.g. "augmented reality glasses" or "AR glasses" for short, they see a coupled-in or reflected "virtual image" superimposed on their image of the real world ("real image").This superposition is achieved by the optical fiber, also called a beam combiner, which is transparent to the ambient light on the one hand and directs a beam of rays generated by an external imager into an eyebox, in which the user's eye can be located, on the other. The eye perceives this beam of rays as a virtual image. In the context of the present invention, an imaging path is defined to describe the beam path of the image of the real environment and the coupled-in virtual image. In this case, an imaging path is understood to be the path of the light from the object, e.g. an object in the real environment, or from the imager / projector that emits the virtual image to be coupled in, to the location where the image is created or perceived, e.g. the eye of a user or the eyebox.In augmented reality (AR), the environment visible to a user is enhanced by adding digital elements to a live view of the environment, i.e., a mapping path of the real environment. In virtual reality (VR), users only perceive virtual images. Thus, the mapping path of a real environment is replaced by a mapping path of a virtual environment (simulated environment).

[0004] In a head-mounted display, e.g. in AR headsets, the image generated by an imaging unit or a display is coupled into the optical fiber, reflected once or several times within the optical fiber by total internal reflection, and finally coupled out so that a user of the head-mounted display can see a virtual image. The spatial area from which the virtual image is visually perceptible to a user is also referred to as the eyebox. The two outer surfaces of the optical fiber are often designed as parallel flat surfaces so that neither optical refractive power is introduced within the optical fiber, nor are aberrations that impair image quality created. Furthermore, head-mounted displays, e.g. AR headsets, can comprise an optical fiber and one or more additional lenses (push-pull lens principle) per eye.This one lens or these several additional lenses serve to correct the ametropia (refractive error) or presbyopia (age-related farsightedness) of the eye (pull lens) and / or to make the virtual image appear focused at a desired distance (pull lens) without impairing the image of the real environment (push lens).

[0005] It has now become apparent that the continuous use of AR glasses, for example, over an extended period of time is associated with many technological and physiological challenges. Many users complain of symptoms when viewing through HMDs, which can be classified into two different categories: extraocular discomfort induced by the musculoskeletal system, and ocular discomfort caused by mechanisms of the eye and during viewing. Extraocular symptoms include, for example, headaches caused by the glasses not fitting properly on the head or neck pain caused by incorrect head and body posture during use. Ocular discomfort includes headaches originating from the eye, dry eyes, double vision, and blurred vision. This is discussed, among others, in Kaur et al. [Kaur, K., Gurnani, B., Nayak, S. et al.: Digital Eye Strain - A Comprehensive Review.Ophthalmol Ther 11 , 1655-1680 (2022)].

[0006] Many of the symptoms mentioned have their origin in the so-called vergence-accommodation conflict (VAC), which arises from an incorrect interaction between vergence and accommodation of the eyes. Vergence is understood to be a specific, basic type of opposing eye movement in which, from the parallel position of the eyes, the two lines of vision in front of them intersect. This form of movement is essential for viewing close objects without triggering double vision. Accommodation refers to the change in the refractive power of the eye lens in order to focus objects at different distances. The lens is elastic and can adjust its radius of curvature so that the light rays are focused on the retina.Both mechanisms are crucial for stereoscopic vision and are neuronally linked; they form the accommodation-vergence reflex of the eyes. Under normal conditions, the human visual system expects the vergence distance and the accommodation distance to be the same. When viewing most artificial 3D images, the vergence and accommodation distances are not aligned. As a result, the brain receives inconsistent signals of vergence and accommodation, resulting in the VAC. The VAC is illustrated in Figure 1. The natural coupling between vergence and accommodation can be described in a vergence-accommodation diagram, which is shown in Figure 2 based on Shibata et al. [Takashi Shibata, Joohwan Kim, David M. Hoffman, Martin S. Banks: The zone of comfort: Predicting visual discomfort with stereo displays. Journal of Vision 2011 ;11 (8):11 ].In the vergence-accommodation diagram, the vergence or vergence distance in diopters (D) is shown on the abscissa, and the focus distance or focus distance in diopters (D) is shown on the ordinate. The dashed "natural viewing line" graph, marked with reference number 10, represents the distance-independent, idealized behavior of accommodation and vergence to natural stimulation at various viewing distances of an orthophoric, non-squinting subject. Also shown are the minimum relative vergence (labeled with reference number 11) and maximum relative vergence (labeled with reference number 12), which form the boundaries of the zone of clear single binocular vision (ZCSBV). The zone of clear single binocular vision is marked with reference number 18.It represents the area of ​​decoupling of vergence and accommodation, in which the symptoms described above do not occur or only occur to a small extent.

[0007] The basis of such a diagram is the determination of the subjective distance refraction of test subjects using the values ​​of sphere, cylinder and axis. Based on this, heterophoria (latent squint), i.e. the deviation of the eye fixation lines from the "natural viewing line" or natural line of sight, is tested for various test distances (e.g. 6.0 m / 0.5 m / 0.25 m). In the simplest case, this is only done for one test distance in the distance, assuming that the deviation is constant across the different test distances. By switching off the so-called fusion, it is possible to separate the visual impressions of the right and left eye. In general, fusion is understood to be the totality of all motor and sensory processes which lead to a merging of the image impressions from both eyes in the brain. If there is a deviation from the ideal line, the test subjects experience, for example, subpression or double vision.This deviation can be compensated for by adding prisms, which again creates a simple binocular image. The value(s) determined during the heterophoria measurement are plotted on the abscissa for the respective test distance (ordinate). By parallel shifting the natural line of sight toward one of the values ​​and / or by connecting the individually determined points, a so-called phoria line is created.

[0008] Based on this determined phoria line, it is also possible to determine the fusion widths, i.e., the minimum relative vergence and the maximum relative vergence. For this purpose, additional prisms are added to the subject in the base direction, both inside and outside, based on the previously determined prism values, so that the image is no longer clearly visible to the subject, but is perceived as blurred. Based on these values, the maximum accommodation success (AAmax) and the near point of convergence (NPC) can be determined. AAmax is the shortest distance at which clear vision is still possible. The NPC is the closest point at which an object can just be seen binocularly, regardless of whether it is sharp or blurred. The zone of clear binocular single vision can be determined from the totality of these values.

[0009] According to Shibata et al., the ZCSBV merely describes a region of the vergence space as "comfortable" and everything outside this region as "uncomfortable." Such a description is an oversimplification. Vergence accommodation conflicts that lie just outside the nominal comfort zone are less problematic than conflicts that lie far outside this zone. Furthermore, some conflicts within the nominal zone are less comfortable than others. To reflect these properties, it is more meaningful to describe the comfort zone as continuous. Therefore, based on the ZCSBV, a continuous zone of comfortable vision ("Continuous Zone of Comfort") is derived, which is shown in Figure 3 based on Shibata et al. The variation in visual comfort for different vergences and focal lengths or focus distances is plotted in diopters.Areas 13 to 17 represent the visual comfort of an orthophoric subject, with the areas closer to the natural line of sight 10, e.g. areas 13 to 15, indicating more comfortable combinations of vergence and focal length than the areas further away from the natural line of sight 10, e.g. areas 16 and 17.

[0010] A further effect is that with increasing age up to about 40 years, the response curve to the accommodative stimulus slowly declines, before rapidly declining from the age of 40 onwards, approaching complete presbyopia. This is shown in Figure 4, which is taken from Mordi et al. [JA Mordi & KJ Ciuffreda. Static aspects of accommodation: age and presbyopia. Vision Research 38 (1998) 1643-1653]. The reduced amplitude of accommodation and the associated accommodative effort can be taken into account when designing stereo displays in AR glasses with prescription lenses.

[0011] Lightguide-based monocular or binocular headsets, such as AR glasses, can comprise a lightguide and one or more additional lenses (“push and / or pull lenses”) per eye. This is shown as an example in Figure 5. The one or more lenses serve to either correct the visual impairment of the eye and / or to make the focus of the virtual image generated by the stereo display appear at a desired distance (pull lens) without influencing the image of the real environment (push lens). The goal is to minimize the impact of VAC by setting the accommodation plane. The accommodative effort should be equal to or less than the focal length of the information content of the stereo display. Despite these efforts, a significant proportion of users experience potential negative effects of digital eye strain even after wearing the headset, e.g., AR glasses, for a short time.There is therefore a need for appropriate optical arrangements, especially AR glasses, that are suitable for comfortable all-day wear without digital eye strain. Currently, static push / pull lens concepts do not take into account individual fluctuations in the comfort zone, such as those caused by phoria in combination with changes in accommodative effort with age and the associated changes in the ratio of accommodative convergence to accommodation (AC / A). A common approach in the specialist literature, according to Kress [Kress, Bernard C., Optical architectures for augmented-, virtual-, and mixed-reality headsets. Bellingham, Washington State: Society of Photo-Optical Instrumentation Engineers, (2020)], is to use the pull lens to set the focal plane of the stereo display to a range between 1.5 meters and 3 meters, i.e., between 0.67D and 0.33D (see Figure 6).

[0012] Document US 7,857,444 B2 describes lightweight, ergonomic AR glasses with stereo displays. They feature a fixed focal plane of the virtual image to enable the optimal position for a person's accommodative reserve based on the amplitude of accommodation. This approach specifically addresses the residual accommodation that occurs with increasing age (presbyopia as described in Figure 3). This is reflected in the adjusted, angulated or truncated comfort zone (see Figure 7). The focal plane of the virtual image is to be displayed in an age-dependent manner so that the accommodative effort is equal to or lower than the focal plane of the information content of the stereo display.

[0013] Against the background described, it is the object of the present invention to provide an advantageous method for determining the focal plane, in particular an individualized focal plane, of a virtual image of an optical arrangement worn in front of the eyes, as well as a method for producing an optical element of an optical arrangement worn in front of the eyes, an optical element and an optical arrangement.

[0014] The stated objects are achieved by a method for determining the focal plane of a virtual image of an optical arrangement wearable in front of the eyes according to patent claim 1, a method for producing an optical element of an optical arrangement wearable in front of the eyes according to patent claim 8, an optical element according to patent claim 12, and an optical arrangement according to patent claim 13. The dependent claims contain further advantageous embodiments of the invention.

[0015] The method according to the invention for determining the focal plane of a stereoscopic virtual image, in particular the distance of the virtual image from an eyebox or from the eyes of a person, of an optical arrangement worn in front of the eyes relates to an optical arrangement which comprises at least one optical device for radiating a stereoscopic virtual image. The at least one optical device can, for example, comprise one or more optical waveguides and / or one or more lenses in a classic refractive or pancake or birdbath arrangement. The optical arrangement can, in particular, be designed to radiate or couple a virtual image into an imaging path of a real environment or in the direction of an eyebox.

[0016] The method according to the invention comprises the following steps: The angle-related visual impairment, e.g. heterophorias and / or heterotropias, of a person is determined, for example recorded or measured or read from a database which contains corresponding data of the person.

[0017] Based on the determined astigmatism, a relationship, preferably a linear relationship, is determined between the vergence distance (vergence) or the vergence distance and the focus distance (focal distance) or the focus distance. The relationship can be determined, for example, in a vergence-accommodation diagram, i.e. in a diagram that depicts the relationship between the vergence distance and the focus distance. A curve of the minimum relative vergence is then determined. Preferably, a zone of clear binocular single vision (comfort zone) is determined in the vergence-accommodation diagram, which zone is bounded by the curve, preferably a line, of the minimum relative vergence and a curve, preferably a line, of the maximum relative vergence.

[0018] In a further step, which can be performed before, after, or simultaneously with the previously described steps, a depth of field is determined, e.g., fixed, measured, or selected from predefined ranges. This can, in particular, be in the range from + / - 0.4 D to + / - 0.65 D. The measurement of the depth of field is described, for example, in the document Fan Yi, D. Robert Iskander, Michael J. Collins; Estimation of the depth of focus from wavefront measurements. Journal of Vision 2010;10(4):3.

[0019] In a next step, a first focus distance, e.g. a minimum focus distance in diopters, and a second focus distance, e.g. a maximum focus distance in diopters, are determined. In particular, an area, e.g. an area, within the optionally determined zone of clear binocular single vision (comfort zone) can be determined in the vergence-accommodation diagram, which is delimited by the first focus distance and the second focus distance on the axis of the focus distance. The second focus distance has a higher value in diopters than the first focus distance. The first focus distance is set such that it forms an intersection point with the curve of the minimum relative vergence, which has a vergence value of a maximum of 1 diopter, preferably a maximum of 0.5 diopters, in particular a maximum of 0.2 diopters, e.g. 0 diopters.Preferably, the first focus distance is set such that it forms an intersection point with the curve of the minimum relative vergence, which has a vergence value of 0 diopters. The configuration in which the first focus distance is set such that it forms an intersection point with the curve of the minimum relative vergence, which has a vergence value greater than 0 diopters, enables a flexible setting of the focal plane adapted to the respective use, for example in connection with HUDs for enclosed spaces or workplaces.

[0020] The focal distance between the first focal distance and the second focal distance corresponds to the determined depth of field. In a further step, the focal plane of the stereoscopic virtual image is set in a range between the first focal distance and the second focal distance, preferably midway between the first and second focal distances.

[0021] The method according to the invention makes it possible to individually define the focal plane of coupled stereoscopic virtual images of an optical arrangement worn in front of the eyes, in particular adapted to the individual zone of clear binocular single vision and the individual's astigmatism and / or accommodation ability. This allows the VAC described above to be minimized or avoided, and associated physical discomfort can be reduced.

[0022] Optionally, the accommodation amplitude (presbyopia) of the person, e.g. a user, is determined, in particular by measurement or from a database containing the person's corresponding data. In other words, the minimum distance from the eye of the person's binocular simple vision, i.e. from infinity to a minimum distance in front of the eye or from 0 diopters to the value in diopters corresponding to the minimum distance, is determined, in particular. This step can be carried out before, after or simultaneously with the step for determining the astigmatism described above. The second focus distance can have a maximum value in diopters equal to the value of the determined accommodation amplitude. This ensures that the focal plane lies in the individual comfort range while fully utilizing the depth of field and taking the person's presbyopia into account.

[0023] In one embodiment, the focal plane of the stereoscopic virtual image between the second, in particular maximum in dioptres, focus distance and the first, in particular minimum in dioptres, focus distance can be set such that it deviates from the mean value of the first focus distance and the second focus distance by a maximum of 0.3 dioptres, preferably by a maximum of 0.2 D.

[0024] The determination of the accommodative amplitude (presbyopia) and / or the angle-related visual impairment can be carried out using methods known from ophthalmology.

[0025] A person's astigmatism can be determined using a single focal distance, i.e., a single fixed focal distance, or multiple focal distances. The first option allows for a quick, cost-effective, and simple determination of astigmatism. For example, a phoria line running parallel to the natural line of sight can be assumed. The second option offers a more precise determination of astigmatism, allowing for an individual tilt of the phoria line to be determined and subsequently taken into account, preferably through a linear regression through the majority of measurement points.

[0026] The curve, preferably the line, of minimum relative vergence and / or the curve, preferably the line, of maximum relative vergence can be determined based on the determined phoria line or by measurement. Determination can be made according to the literature, e.g., according to Shibata et al.

[0027] Determining the amplitude of accommodation and / or the angle-closure error and / or the curve of minimum relative vergence and / or the curve of maximum relative vergence and / or the zone of clear binocular single vision and / or the depth of field can be performed using methods known from ophthalmology, as well as using an optical device or the aforementioned optical device worn in front of the eyes. The required measurements can be performed using a head-mounted display equipped with a camera.

[0028] The inventive method for producing an optical element of an optical arrangement that can be worn in front of the eyes, e.g., an HMD, AR glasses, VR glasses, or MR glasses, which comprises at least one optical device, e.g., an optical waveguide, for radiating a stereoscopic virtual image, wherein the optical element is designed to adjust the focal plane of the stereoscopic virtual image, is characterized in that the optical element is designed to project the radiated virtual image onto the focal plane determined according to a previously described inventive method. The inventive method for producing an optical element, which may, for example, be a pull lens, has the features and advantages already described above.

[0029] Within the scope of the method for producing the optical element, at least one parameter for adjusting, i.e., for generating or realizing, the focal plane of the stereoscopic virtual image can be determined, e.g., defined, based on the defined focal plane of the stereoscopic virtual image. The at least one parameter can be a parameter for adjusting the position of the focal plane, i.e., the distance of the focal plane from an eyebox in the direction of an optical axis, and / or the angular position of the focal plane, i.e., the direction in which a virtual image is projected. In particular, the at least one parameter for adjusting the focal plane of the stereoscopic virtual image can be the refractive power of at least one optical correction element, e.g., a pull lens, etc., and / or at least one prism parameter and / or at least one parameter of the optical device for radiating the stereoscopic virtual image, e.g. the optical waveguide.

[0030] The optical element according to the invention of a wearable optical arrangement comprising an optical waveguide for radiating a stereoscopic virtual image is manufactured according to a previously described method according to the invention and / or configured to project an irradiated virtual image onto a focal plane determined according to a method according to the invention. The optical element according to the invention has the features and advantages already described above.

[0031] The optical arrangement according to the invention, which is designed to be worn in front of the eyes and which comprises at least one optical device, e.g., an optical waveguide, for radiating a stereoscopic virtual image, comprises at least one optical element according to the invention as described above. The at least one optical element is preferably arranged in the beam path between the at least one optical device, e.g., the optical waveguide, and an eyebox or a fixed eye position. The optical arrangement can be configured as an HMD, AR glasses, VR glasses, or MR glasses. The optical arrangement according to the invention has the features and advantages already described above.

[0032] In summary, the present invention offers a solution that takes into account the individual variations described above that lead to digital eye strain. This is achieved by determining the comfort zone for a stereo display, taking into account the depth of field of the human eye and / or the individual phoria line and / or the individual accommodation capacity of a person.

[0033] The invention will be explained in more detail below using exemplary embodiments with reference to the accompanying figures. Although the invention is illustrated and described in more detail by the preferred embodiments, the invention is not limited to the disclosed examples, and other variations may be derived therefrom by those skilled in the art without departing from the scope of the invention.

[0034] The figures are not necessarily detailed or to scale and may be enlarged or reduced to provide a better overview. Therefore, the functional details disclosed herein are not to be interpreted in a limiting sense, but merely as an illustrative basis for teaching one skilled in the art how to variously employ the present invention.

[0035] As used herein, the term "and / or," when used in a series of two or more elements, means that any of the listed elements may be used alone, or any combination of two or more of the listed elements may be used. For example, if a composition is described containing components A, B, and / or C, the composition may contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination.

[0036] Fig. 1 shows schematically the vergence-accommodation conflict (VAC).

[0037] Fig. 2 shows a schematic vergence-accommodation diagram.

[0038] Fig. 3 shows schematically a continuously described comfort zone.

[0039] Fig. 4 shows schematically the dependence of the accommodation amplitude on the age of a person.

[0040] Fig. 5 schematically shows an optical arrangement for projecting a stereoscopic virtual image. Fig. 6 shows a vergence-accommodation diagram for a non-presbyopic, orthophoric user with focal planes according to the prior art.

[0041] Fig. 7 shows a vergence accommodation diagram for a presbyopic user with a focal plane according to the state of the art.

[0042] Fig. 8 shows a first embodiment using a vergence accommodation diagram.

[0043] Fig. 9 shows a second embodiment using a vergence accommodation diagram.

[0044] Fig. 10 shows a variant with convergence excess using a vergence-accommodation diagram.

[0045] Fig. 11 shows a third embodiment using a vergence accommodation diagram.

[0046] Fig. 12 shows a fourth embodiment using a vergence accommodation diagram.

[0047] Fig. 13 shows a fifth embodiment using a vergence accommodation diagram.

[0048] Fig. 14 shows schematically a method according to the invention for determining the focal plane of a stereoscopic virtual image in the form of a flow chart.

[0049] Fig. 15 schematically shows a method according to the invention for producing an optical element of an optical arrangement worn in front of the eyes in the form of a flowchart. Figure 1 illustrates the vergence-accommodation conflict (VAC). For this purpose, in the two images shown, the eyes 1 of a person are directed at an object 2. The image shown on the left shows an object in the person's real environment, and the image shown on the right shows an object displayed on a stereoscopic display 3 of a VR headset. In the image shown on the right, the person thus perceives a virtual image of the object 2.

[0050] The accommodation or focusing of object 2 by eyes 1 is marked by rays 4, which illustrate the accommodation. Vergence, i.e. the respective direction of gaze of eyes 1, is illustrated by lines 5. Furthermore, the respective vergence distance is marked by arrows 6 and the accommodation distance by arrows 7. While when viewing object 2 in the real environment, vergence distance 6 and accommodation distance 7 are identical, when viewing object 2 using a stereoscopic screen or display 3, a difference occurs between accommodation distance 7 and vergence distance 6. This leads to the VAC described at the beginning.

[0051] Figure 2 schematically shows a vergence-accommodation diagram according to Shibata et al., which describes the natural coupling between vergence and accommodation. In the diagram, the vergence V in diopters (D) is shown on the abscissa, and the focal distance F in D is shown on the ordinate. The natural viewing line 10 represents the distance-independent, idealized behavior of accommodation and vergence to natural stimulation at various viewing distances of an orthophoric, non-squinting person. Also shown are the minimum relative vergence 11 and maximum relative vergence 12, which form the boundaries of the zone of clear single binocular vision 18 (ZCSBV). This represents the area of ​​decoupling of vergence and accommodation, in which the symptoms described above do not occur.

[0052] Figure 3 schematically shows a continuously described comfort zone of an orthophoric person according to Shibata et al., where the visual comfort decreases continuously from area 13 to area 17.

[0053] Figure 4 shows schematically the dependence of the accommodation amplitude A in D on the age Y in years J of a subject according to Mordi et al.. It is evident that with increasing age up to about 40 years, the response curve of the accommodation stimulus 19 slowly decreases, before the curve 19 decreases rapidly from the age of 40 onwards and approaches complete presbyopia.

[0054] Figure 5 schematically shows an optical arrangement 20, which can also be an optical arrangement according to the invention, which is designed to radiate a stereoscopic virtual image into an imaging path of a real environment or in the direction of an eyebox, e.g., AR glasses. The optical arrangement 20 is constructed such that, by means of at least one optical device, e.g., an optical fiber 25, a virtual image can be radiated in the direction of an eyebox 22 or an eye 1 of a person. In other words, digitally generated content that is visually perceptible as virtual images is radiated into a person's field of vision. In the present example, the dimensions of the eyebox 22 are indicated by an arrow 21. The field of view (FOV) for displayed virtual images realized by means of the optical arrangement 20 is indicated by an arrow 23.

[0055] The optical arrangement 20 has an optical axis 28. An optical element 26 in the form of a pull lens is arranged along the optical axis 28 in the beam path extending from the eyebox 22 in front of the optical device, e.g., the optical waveguide 25. The optical element 26 is designed to make the focus of the generated stereoscopic virtual image appear at a desired distance from the eyebox 22 or the eyes 1 of a person. In addition, the optical element 26 can also be designed to correct ametropia. A further optical element 27 in the form of a push lens is arranged along the optical axis 28 in the beam path downstream of the optical waveguide 25 extending from the eyebox 22. The optical element 27 is designed to correct aberrations in an image of the real environment caused by the optical waveguide and / or by the optical element 26 and / or by ametropia.

[0056] In the following, with reference to Figures 6 and 7, prior art approaches for taking into account changes in accommodative effort with age in the design of optical arrangements, e.g., an optical arrangement 20 shown in Figure 5, are explained. Figure 6 schematically shows a vergence-accommodation diagram in which the region of the focal plane of a stereo display according to Kress et al., realized using a pull lens 26, is plotted. The focal plane of the stereo display or the stereoscopic virtual image is then placed in a range between 1.5 meters and 3 meters, i.e., between 0.67D and 0.33D. The corresponding focal planes are marked by lines 30 and 31.

[0057] Figure 7 illustrates the solution according to US Pat. No. 7,857,444 B2, according to which the focal plane 32 is fixed at the value of 2D. Figure 7 shows a vergence-accommodation diagram for a presbyopic person with a residual accommodation of 2D. The arrows 33 symbolize a possible age-related reduction in the focal plane range.

[0058] In the following, examples are explained with reference to Figures 8 to 13, which illustrate the solution according to the invention using vergence accommodation diagrams.

[0059] Figure 8 shows a first exemplary embodiment. Determining the astigmatism and optionally the accommodation amplitude results in a range 8 of clear binocular single vision of a virtual image from infinity to 38.5 cm in front of the eye (0D-2.6D) for a person with orthophoric vision (i.e., normal vision and no heterophoria, without presbyopia) after setting the focal plane 40 of the display to 1.35D. The accommodation amplitude determines the maximum value on the y-axis (axis of the focus distance) for determining the range to be considered.

[0060] To determine the focal plane 40 of a stereoscopic virtual image, starting from the determined zone of clear binocular single vision 18 and a defined depth of field 43, the area 44 within the zone of clear binocular single vision 18 in the vergence-accommodation diagram, which is delimited by a first focus distance 41 and a second focus distance 42 on the axis of the focus distance, is first determined. The second focus distance 42 has a higher value in diopters than the first focus distance 41, and the distance between the first focus distance 41 and the second focus distance 42 corresponds to the determined depth of field 43. The first focus distance 41 is set such that it forms an intersection point with the curve of the minimum relative vergence 11, which in the example shown has a vergence value of 0 diopters.Subsequently, the focal plane 40 of the stereoscopic virtual image is set in a range between the first focus distance 41 and the second focus distance 42.

[0061] In order to generate an optimally distributed, smallest possible VAC, in the present example the virtual image plane is set to 1.35D according to a method according to the invention and within the framework of an optical arrangement 20 according to the invention, e.g. using a push-pull lens concept 26, 27, the virtual image plane is projected to 1.35D. In contrast to the prior art, the depth of field 43 of the human eye is now also taken into account, which is typically + / - 0.4D for a 5mm pupil and + / - 0.65D for a 3.5mm pupil. The focal plane 40 is here placed in the area to be taken into account 44 in the vergence-accommodation diagram in such a way that the entire depth of field 43 can be optimally utilized. The depth of field 43 to be taken into account can be fixed or determined individually.

[0062] According to the invention, the optimal focal plane of the virtual image 40 is determined and implemented such that the area 44 of the zone of clear binocular single vision 18, i.e., the comfort zone, results within the limits 41 and 42 of the determined or specified depth of field 43. Ideally, i.e., with the exception of workplace applications (see Figure 13), this area begins on the vergence axis at 0D, see the intersection of the lower limit of the depth of field 41 with the focus axis (ordinate). The lower limit of the depth of field is thus at infinity. This creates a focus distance for distance from infinity to 38.5 cm for close-up, with the comfort zone (ZCSBV) 18 centered on the natural line of sight 10.

[0063] Figure 9 shows a second embodiment for a 1D esophoric person (latent inward squinting) without presbyopia, resulting in a zone of clear binocular single vision 18 from infinity to 38 cm in front of the eye (0D-2.6D). Due to the person's 1D esophoria in this example, the person's vergence deviates from the natural line of sight 10 by exactly this value. The resulting phoria line is identified by reference number 9. The setting of the continuous comfort range 18 is centered on the individual phoria line 9, not on the natural line of sight 10.

[0064] To generate an optimally distributed, smallest possible VAC, the virtual image plane 40 is projected to 0.4D, e.g., using a push-pull lens concept, taking into account the depth of field 43 of the human eye. The optimal focal plane of the virtual image is implemented such that the greatest possible coverage 44 of the comfort zone 18 results within the boundaries 41 and 42 of the depth of field 43. Ideally, this zone begins at 0D, i.e., at a lower limit of the depth of field lying at infinity. This creates a focus distance for distance from infinity to 38 cm for close-up, with the comfort zone ZCSBV 18 centered on the individual phoria line 9.

[0065] In addition to the second embodiment shown in Figure 9, Figure 10 shows a variant in which a so-called convergence excess results in a different rise of the phoria line 9 compared to the natural line of sight 10, which in turn individually changes the covered comfort range 44. In the example shown here, the range of clear binocular single vision of a virtual image 8 is therefore from infinity to 41 cm in front of the eye (0D-2.4D). These individual fluctuations in the rise of the phoria line 9 also occur in cases of convergence insufficiency, divergence insufficiency, and divergence excess. Within the scope of the present invention, these can advantageously be taken into account when determining the focal plane 40.

[0066] Figure 11 shows a third embodiment using a vergence-accommodation diagram. This results in a range 8 of clear binocular single vision of a virtual image from infinity to 55 cm in front of the eye (0D - 1.8D) for a 1D exophoric person (latent outward squinting) without presbyopia. Due to the person's 1D exophoria in this example, the person's vergence deviates by exactly this value from the natural line of sight 10, resulting in the individual phoria line 9. The setting of the continuous comfort range 18 is centered on the individual phoria line 9, not on the natural line of sight 10.

[0067] To generate an optimally distributed, smallest possible VAC, the virtual image plane is projected to 1.5D, taking into account the depth of field 43, e.g., using a push-pull lens concept. The optimal focal plane of the virtual image 40 is determined and implemented such that the greatest possible coverage of the comfort zone 18 by the zone 44 results within the limits of the depth of field 43. Ideally, this zone begins at 0D (the lower limit of the depth of field is at infinity). This creates a focus distance for distance from infinity to 55 cm for close-up, with the comfort zone ZCSBV centered on the individual phoria line 9.

[0068] Figure 12 shows a fourth embodiment using a vergence-accommodation diagram for a 1D exophoric, presbyopic person with residual accommodation of 1.6D. These values ​​result in a zone of clear binocular single vision from infinity to 71 cm in front of the eye (0D - 1.4D). If the accommodation amplitude of 1.6D is plotted on the vergence axis, there is no focus value for this vergence value within the area of ​​the zone of clear binocular single vision 18, which is additionally limited by the presbyopia on the focus axis. Due to the person's 1D exophoria in this example, the resulting area 8 of clear binocular single vision of a virtual image lies in the range from 0 to 1.4D. The setting of the continuous comfort zone is centered on the individual phoria line 9, not on the natural line of sight 10.In addition, as already mentioned, the person's presbyopia results in a limitation of the continuous comfort zone 18 on the focus axis to a residual accommodation of 1.6D.

[0069] In order to generate an optimally distributed, smallest possible VAC, the virtual image plane is projected to 1.1 D, e.g., using a push-pull lens concept. This takes into account the depth of field 43 of the human eye, in this case + / -0.4 D. The optimal focal plane 40 of the virtual image is implemented in such a way that the greatest possible coverage 44 of the comfort zone 18 is achieved. Ideally, this zone begins at 0 D (the lower limit of the depth of field is at infinity). This creates a focus distance for distance from infinity to 71 cm for close-up, with the comfort zone (ZCSBV) 18 centered on the individual phoria line 9. Figure 13 shows a fifth exemplary embodiment.By determining the angle-related visual acuity and optionally the accommodation amplitude, a region of the zone of clear binocular single vision 18 from infinity to 38.5 cm in front of the eye (0D-2.6D) results for an orthophoric person, i.e., one who is normal-sighted and does not exhibit heterophoria, without presbyopia. In contrast to the example shown in Figure 8, in this case, for a workplace application, the region 44 to be considered within the determined zone of clear binocular single vision 18 is selected in the vergence-accommodation diagram such that the first, i.e., minimum, focus distance 41 is set such that it forms an intersection point with the curve of minimum relative vergence 11, which has a vergence value of 0.5 diopters. When the depth of field 43 is fully utilized, in the present example the focal plane 40 of the stereoscopic virtual image is set at a focus distance of 2D.

[0070] Figure 14 schematically shows, in the form of a flowchart, a method 50 according to the invention for determining the focal plane 40 of a stereoscopic virtual image of an optical arrangement 20 that can be worn in front of the eyes and comprises an optical fiber 25 for radiating a stereoscopic virtual image. In an optional step 51, the accommodation amplitude (presbyopia) of a person is determined. This can be done using methods known from ophthalmology, e.g., in a conventional manner or using manual or electronic phoropters or using active optics, liquid crystals, or light field displays. Lenses and / or test charts and / or moving objects and / or AR displays and / or VR displays can be used.

[0071] In step 52, the person's astigmatism is determined. This can also be done using methods known from ophthalmology, e.g., conventionally or using manual or electronic phoropters, or using virtual or digital refraction systems, voice-assisted subjective refraction systems, light-field displays, or holograms. Individual eye covers, prisms, filters such as Maddox filters or polarization filters, and projections onto the right and / or left eye, e.g., using VR or AR displays, can be used. The astigmatism can be determined for just one focus distance or for multiple focus distances.

[0072] In step 53, based on the determined astigmatism, a relationship between the vergence distance and the focus distance is determined, e.g., in a vergence-accommodation diagram, preferably in the form of an individual phoria line 9. If the astigmatism was determined for only one focus distance, the individual phoria line 9 can be set to run parallel to the natural line of sight. If the astigmatism was determined for a plurality of focus distances, a possible tilt of the individual phoria line 9 relative to the natural line of sight 10 can also be taken into account (see example in Figure 10). This enables a higher degree of customization.

[0073] In step 54, a curve of the minimum relative vergence 11 is determined. Preferably, a zone of clear binocular single vision (comfort zone) 18 is determined in the vergence-accommodation diagram, which is bounded by the curve, e.g., a line, of the minimum relative vergence 11 and a curve, e.g., a line, of the maximum relative vergence 12. The curves of the minimum relative vergence 11 and the maximum relative vergence 12 can be defined based on values ​​or ranges preferred in the literature. Alternatively, the curves can be determined individually for the person, preferably measured. Methods known from ophthalmology for measuring the fusion width can be used here.

[0074] Optionally, the phoria line can also be determined from accommodative convergence and accommodation. This involves measuring the "voluntary" convergence of the other eye—that is, the convergence without a fusion stimulus—depending on different accommodative stimuli presented to only one eye. This measurement can be performed using a camera and an AR and / or VR display. The results are recorded in a vergence-accommodation diagram, as in step 53.

[0075] In step 55, a depth of field range 43 is determined, e.g., fixed or measured, or selected from a plurality of predefined ranges. This is preferably in the range of + / -0.4D to + / -0.65D. Steps 51, 52, and 55 can be performed in any order or simultaneously.

[0076] In step 56, a first focus distance 41 and a second focus distance 42 are determined. Preferably, an area, e.g., an area 44 within the determined zone of clear binocular single vision 18 is determined in the vergence-accommodation diagram, which area is delimited by the first focus distance 41 and the second focus distance 42 on the focus distance axis. The second focus distance 42 has a higher value in diopters than the first focus distance 41, wherein the distance between the first focus distance 41 and the second focus distance 42 corresponds to the determined depth of field 43. The first focus distance 41 is set such that it forms an intersection point with the curve of the minimum relative vergence 11, which has a vergence value of a maximum of 1 diopter, preferably a maximum of 0.5 diopters. Optionally, the second focus distance 42 can correspond to a maximum of the value of the determined accommodation amplitude.

[0077] In step 57, the focal plane 40 of the stereoscopic virtual image is set in a range between the maximum focal distance 42 and the minimum focal distance 41. The focal plane 40 can be set to the mean value between the second focal distance 42 and the first focal distance 41 or can deviate from the mean value by a maximum of 0.3D, preferably a maximum of 0.2D. Optionally, when setting the focal plane 40 of the stereoscopic virtual image, the optionally determined ratio of phoria and accommodation amplitude or of accommodative convergence and accommodation can also be taken into account, e.g., by setting the focal plane 40 below a line of sight adapted to the ratio. The procedure here is the same as in step 57, except that the phoria line determined from the accommodative convergence and accommodation is used as the basis.

[0078] Figure 15 schematically shows a method 60 according to the invention for producing an optical element of a wearable optical arrangement in the form of a flowchart. The optical element can be a pull lens 26 shown in Figure 5 or an optical waveguide. The optical arrangement 20 comprises an optical waveguide 25 for radiating a stereoscopic virtual image. The optical element 26 is designed for fixedly adjusting the focal plane 40 of the stereoscopic virtual image.

[0079] Within the scope of the method for producing the optical element 60, the focal plane 40 of the virtual image, i.e. in particular the distance of the focus from the eyebox 22, is first defined in step 61, e.g., according to a method 50 shown in Figure 14. Subsequently, in step 62, the optical element, for example the pull lens 26, is designed to project a virtual image onto the defined focal plane. Optionally, the angular position and the position of the focus of the virtual image can be designed so that they can be permanently adjusted using the optical element. In particular, the individual pupil distance can be taken into account here. The optical element can, for example, comprise at least one prism and / or have a refractive power suitable for projecting the virtual image onto the defined focal plane.Disparities between both eyes can be taken into account when designing the optical element according to the invention.

[0080] An optical element according to the invention, for example a pull lens 26, is manufactured according to a previously described method 60 and / or designed to project an irradiated virtual image onto a focus distance determined according to a method 50 according to the invention. An optical arrangement according to the invention, for example an arrangement 20 shown in Figure 5, is designed to be worn in front of the eyes 1 of a person. This can be AR glasses, VR glasses, or MR glasses. The optical arrangement 20 according to the invention comprises an optical waveguide 25 for irradiating a stereoscopic virtual image and at least one optical element 26 according to the invention.

[0081] List of reference symbols:

[0082] 1 eyes of a person

[0083] 2 objects

[0084] 3 stereoscopic display

[0085] 4 Accommodation, Focus

[0086] 5 Vergence

[0087] 6 Vergence distance

[0088] 7 Accommodation distance, focus distance

[0089] 8 Area of ​​clear binocular single vision of a virtual image

[0090] 9 Phoria line

[0091] 10 natural line of sight

[0092] 11 minimum relative vergence

[0093] 12 maximum relative vergence

[0094] 13 Zone in the Vergence-Accommodation Diagram

[0095] 14 Zone in the Vergence Accommodation Diagram

[0096] 15 Zone in the Vergence-Accommodation Diagram

[0097] 16 Zone in the Vergence Accommodation Diagram

[0098] 17 Zone in the Vergence-Accommodation Diagram

[0099] 18 Zone of clear binocular single vision, comfort zone

[0100] 19 Reaction curve of the accommodation stimulus

[0101] 20 optical arrangement

[0102] 21 Dimensions of the Eyebox

[0103] 22 Eyebox

[0104] 23 Dimension of the field of view (FOV)

[0105] 24 Field of View (FOV)

[0106] 25 optical device, optical fiber

[0107] 26 optical element, pull lens

[0108] 27 optical element, push lens

[0109] 28 optical axis

[0110] 30 Focal plane 31 Focal plane

[0111] 32 focal plane

[0112] 33 possible age-related reduction of the focal plane area

[0113] 40 Focal plane of the virtual image

[0114] 41 Lower limit of the depth of field, first or minimum focus distance

[0115] 42 Upper limit of the depth of field, second or maximum focus distance

[0116] 43 Depth of field

[0117] 44 Area within the zone of clear binocular single vision

[0118] 50 Methods for determining the focal plane of a stereoscopic virtual image

[0119] 51 Determining a person’s accommodation amplitude

[0120] 52 Determine the person’s astigmatism

[0121] 53 Determining a dependency between the vergence distance and the focus distance

[0122] 54 Determining a curve of minimum relative vergence / Determining a zone of clear binocular single vision

[0123] 55 Determining a depth of field

[0124] 56 Determining a first focus distance and a second focus distance / Determining an area within the determined zone of clear binocular single vision in the vergence accommodation diagram, which is limited by a first focus distance and a second focus distance on the axis of the focus distance

[0125] 57 Setting the focal plane of the stereoscopic virtual image in a range between the maximum focus distance and the minimum focus distance

[0126] 60 Method for producing an optical element

[0127] 61 Setting the focal plane of a virtual image

[0128] 62 Design of the optical element for projecting a virtual image onto the specified focal plane

[0129] A Accommodation amplitude

[0130] F Focus distance V Vergence

[0131] Y Age

Claims

Patent claims 1 . Method (50) for determining the focal plane (40) of a stereoscopic virtual image of an optical arrangement (20) which can be worn in front of the eyes (1) and which comprises at least one optical device (25) for irradiating a stereoscopic virtual image, characterized in that the method comprises the following steps: - Determining the angle-related visual impairment of a person (52), - based on the determined angle deviation, determining a dependency (9) between the vergence distance and the focus distance (53), - Determination of a curve of minimum relative vergence (11 ) (54), - Determining a depth of field (43) (55), - Determining a first focus distance (41) and a second focus distance (42), wherein the second focus distance (42) has a higher value in diopters than the first focus distance (41), wherein the focus distance between the first focus distance (41) and the second focus distance (42) corresponds to the determined depth of field (43), and wherein the first focus distance (41) is set such that it forms an intersection point with the curve of the minimum relative vergence (11), which has a vergence value of a maximum of 1 diopter (56), - Setting the focal plane (40) (57) of the stereoscopic virtual image in a range between the first focus distance (41) and the second focus distance (42).

2. Method (50) according to claim 1, characterized in that based on the determined angle-related visual impairment, the dependency (9) between the vergence distance and the focus distance is determined in a vergence-accommodation diagram (53), a zone of clear binocular single vision (18) is determined in the vergence-accommodation diagram, which zone is determined by the curve of the minimum relative vergence (11) and a curve of maximum relative vergence (12), and a region (44) within the determined zone of clear binocular single vision (18) is determined in the vergence-accommodation diagram, which region is delimited by the first focus distance (41) and the second focus distance (42) on the axis of the focus distance.

3. Method (50) according to claim 1 or claim 2, characterized in that the accommodation amplitude of the person is determined (51) and the second focus distance (42) has a maximum value in dioptres of the determined accommodation amplitude.

4. Method (50) according to one of claims 1 to 3, characterized in that the focal plane (40) of the stereoscopic virtual image between the second focus distance (42) and the first focus distance (41) is set such that it deviates from the mean value of the second focus distance (42) and the first focus distance (41) by a maximum of 0.3 diopters.

5. Method (50) according to one of claims 1 to 4, characterized in that the person's astigmatism is determined at one focus distance or at a plurality of focus distances.

6. Method (50) according to one of claims 1 to 5, characterized in that the curve of the minimum relative vergence (11) and / or the curve of the maximum relative vergence (12) is determined based on the determined angle-related ametropia or is determined by measurement.

7. Method (50) according to one of claims 1 to 6, characterized in that the determination of the accommodation amplitude and / or the angle deviation and / or the curve of the minimum relative vergence (11) and / or the curve of the maximum relative vergence (12) and / or the zone of clear binocular single vision (18) and / or the depth of field range (43) is carried out by means of the optical arrangement worn in front of the eyes.

8. Method (60) for producing an optical element (26) of an optical arrangement (20) which can be worn in front of the eyes (1) and which comprises at least one optical device (25) for irradiating a stereoscopic virtual image, wherein the optical element (26) is designed to adjust the focal plane (40) of the stereoscopic virtual image, characterized in that the optical element (26) is designed to project the irradiated virtual image onto the focal plane (40) defined according to a method according to one of claims 1 to 7.

9. The method (60) according to claim 8, characterized in that based on the defined focal plane (40) of the stereoscopic virtual image, at least one parameter for adjusting the focal plane (40) of the stereoscopic virtual image is determined.

10. Method (60) according to claim 9, characterized in that the at least one parameter is a parameter for adjusting the position and / or the angular position of the focal plane (40).

11. Method (60) according to claim 9 or 10, characterized in that the at least one parameter for adjusting the focal plane (40) of the stereoscopic virtual image is the refractive power of at least one optical correction element (26) and / or at least one prism parameters and / or at least one parameter of the optical waveguide (25).

12. Optical element (26) of an optical arrangement (20) which can be worn in front of the eyes and which comprises an optical device (25) for irradiating a stereoscopic virtual image, characterized in that the optical element (26) is manufactured according to a method (60) according to one of claims 8 to 11 and / or the optical element (26) is designed such that it projects an irradiated virtual image onto a focal plane (40) defined according to a method (50) according to one of claims 1 to 7.

13. Optical arrangement (20) which is designed to be worn in front of the eyes and which comprises at least one optical device (25) for irradiating a stereoscopic virtual image, characterized in that the optical arrangement (20) comprises at least one optical element (26) according to claim 12.

14. Optical arrangement (20) according to claim 13, characterized in that the at least one optical element (26) is arranged in the beam path between the at least one optical device (25) and an eyebox (22).

15. Optical arrangement (20) according to claim 13 or 14, characterized in that the optical arrangement (20) is designed as AR glasses or VR glasses or MR glasses.

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