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EP-4735946-A1 - METHOD FOR DEFINING THE FOCAL PLANE OF A VIRTUAL IMAGE FROM AN OPTICAL ARRANGEMENT WHICH CAN BE WORN IN FRONT OF THE EYES

EP4735946A1EP 4735946 A1EP4735946 A1EP 4735946A1EP-4735946-A1

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).

Inventors

  • BUEHREN, TOBIAS
  • BERNER, ANDREA
  • WIEDEMANN, Doreen
  • MUENZ, HOLGER
  • HAGE, Till-Hendrik

Assignees

  • Carl Zeiss AG

Dates

Publication Date
20260506
Application Date
20240618

Claims (15)

  1. 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 astigmatism of a person (52), - based on the determined angle-related visual impairment, 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), the second focus distance (42) having a higher value in diopters than the first focus distance (41), the focus distance between the first focus distance (41) and the second focus distance (42) corresponding to the determined depth of field (43) and the first focus distance (41) being 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 focal distance (41) and the second focal distance (42).
  2. 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 defined by the curve of the minimum relative vergence (11 ) and a curve of maximum relative vergence (12) is limited (54), and an area (44) within the determined zone of clear binocular single vision (18) is determined in the vergence accommodation diagram, which is limited by the first focus distance (41 ) and the second focus distance (42) on the axis of the focus distance.
  3. 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) in diopters has a maximum value of the determined accommodation amplitude.
  4. 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. 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. 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 established based on the determined angle-related visual impairment or is determined by measurement.
  7. 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. 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. 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. 10. Method (60) according to claim 9, characterized in that the at least one parameter is a parameter for setting the position and/or the angular position of the focal plane (40).
  11. 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. 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. 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. 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. 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.

Description

Method for determining the focal plane of a virtual image of an optical arrangement worn in front of the eyes 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. Head-mounted displays (HMD), 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. The light waves used to create a virtual image are usually guided to a decoupling point after being coupled in an optical fiber by means of total reflection. If a user looks through a head-mounted display, e.g. "augmented reality glasses" or "AR glasses" for short, he sees a coupled or reflected "virtual image" superimposed on his image of the real world ("real image"). This superposition is achieved by the optical waveguide or beam combiner, which is transparent to the ambient light on the one hand, and on the other hand directs a beam of rays generated by an external imager into an eyebox in which the eye of a user can be located. The eye perceives this beam of rays as a virtual image. In connection with the present invention, an imaging path is defined to describe the beam path of the image of the real environment and the coupled virtual image. In this case, an imaging path is the path of the light from the object, e.g. an object in the real environment, or from the image generator/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 the context of augmented reality (AR), the environment visible to a user is expanded by adding digital elements to a live view of the environment, i.e. an image path of the real environment. In the context of virtual reality (VR), only virtual images can be perceived by a user. The image path of a real environment is therefore replaced by an image path of a virtual environment (simulated environment). 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 means of total 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 can be visually perceived by a user is also called an 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 aberrations are generated that impair the image quality. 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 affecting the image of the real environment (push lens). It has now become clear that the continuous use of AR glasses, for example, over a longer period of time is associated with many technological and physiological challenges. Many users complain of symptoms when viewing through HMDs, which can be divided into two can be classified into different categories: extraocular complaints induced by the musculoskeletal system and ocular complaints caused by mechanisms of the eye and during vision. Extraocular symptoms include, for example, headaches caused by incorrect seating of the glasses on the head or neck pain caused by incorrect head and body posture during use. Ocular complaints include headaches originating from the eye, dry eyes, double vision and blurred vision. This is described, 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)]. Many of the symptoms mentioned have their origin in the so-called vergence-accommodation conflict (VAC), which arises from an incorrect interaction between the vergence and accommodation of the eyes. Vergence is a specific, basic type of opposing eye movement in which the two lines of sight in front of the eyes overlap when the eyes are parallel. This form of movement is essential for viewing objects close up without causing double image perception. Accommodation refers to the change in the refractive power of the lens of the eye in order to focus on objects from 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 neuron