Optical lens for augmented reality display

Abstract

An optical lens for an augmented reality display comprises an optical diffuser and an optical combiner (50) having a first side (51) and a second side (52) opposite the first side (51). The optical combiner (50) is operable to transmit ambient light incident on the first side (51) and to collimate image light incident on the second side (52). The optical diffuser is operable to diffuse the collimated image light exiting the optical combiner (5) so as to form diffused image light. The optical diffuser includes a hologram (40) and the optical combiner (50) includes a polarizer (54). The hologram (40) and / or the polarizer (54) has a curved profile.

Description

Technical Field

[0001] The present invention relates to an optical lens for an augmented reality display, an optical system for an augmented reality display, and a wearable augmented reality display. Background Art

[0002] An off-axis retinal display is a type of display used for virtual reality and augmented reality (or AR) applications, such as for wearable heads-up displays. This type of display is designed to allow the user to see projected content in their field of view (FOV) while viewing the external environment. The display works by projecting an image onto the user's retina using a projector fixed to the user's head, which allows the user to see the displayed content floating in the space in front of them.

[0003] The projector is attached to the side (i.e. off-axis) of a wearable frame, such as a headset or eyeglass frame with eyepieces. Each eyepiece is provided with a holographic combiner illuminated by the projector. The illuminated holographic combiner causes the image to be projected through the user's pupil and onto their retina.

[0004] As is known in the art, in near-eye optical devices such as ORSD (short for "off-axis retinal scanning display"), the term "eye box" refers to the volume of space relative to the ORSD in which the user must position his eye to be able to correctly see the complete projected image. If the ORSD has a small eye box, the range of eye positions at which the user can correctly see the complete image is small. If the ORSD has a large eye box, the range of eye positions at which the user can correctly see the complete image is larger, which therefore provides a better user experience. If the user moves his eye position outside the eye box, he will only see a portion of the projected image, or not at all. This is because only in the eye box can the user's pupil and therefore the retina be correctly aligned with the optical path of the light projected by the ORSD. It is well known that the user's gaze direction can affect whether the user's pupil is aligned with the optical path of the light projected by the ORSD, especially in the case where the eye box is small and only covers the user's eye position looking straight ahead.

[0005] Recently, designs of optical lenses for augmented reality displays have been developed, such as reflective pancake lenses, that allow the exit pupil of an image generator to be replicated at multiple locations in the plane of the user's eye, or to form an extended version of the exit pupil of the image generator in the plane of the user's eye, thereby extending the eye box of the optical system to a large enough size to make it practical, while also reducing the physical thickness of the eyepiece including the optical lens, resulting in a more compact eyepiece and a more compact optical system for AR displays (AR is short for "augmented reality").

[0006] The design of the optical lens suggests an optical lens consisting of an optically powered reflector plus a flat hologram / polarized reflector. This configuration provides sharp on-axis performance, but has a large field curvature. This means that the user needs to adjust his focus to bring the off-axis field point into focus. While adjustment is usually allowed in visual instruments (such as telescopes), the problem of divergent adjustment conflict may arise in binocular near-eye displays. Therefore, it is desirable to find an optical design for a reflective pancake type that improves field resolution without the need for adjustment.

[0007] An object of the present disclosure is to provide an optical lens and an optical system for an augmented reality display, and a wearable augmented reality display, which features improved resolution of a light field without requiring user adjustment.

[0008] These objects are achieved by the subject-matter of the independent claims. Further developments and embodiments are described in the dependent claims. Summary of the invention

[0009] The following relates to improved concepts in the field of optical lens design, for example for augmented reality displays. One aspect relates to allowing curvature of one or more optical components of an optical lens. For example, the holographic material and / or the polarizer can have a curved profile. By doing so, the improved concepts provide degrees of freedom for the optical design, which allows for improved optical performance of the display path (e.g., field modulation transfer function MTF). In order to increase the degrees of freedom, for example, the optical element closest to the eye can be curved. For example, the hologram and the reflective polarizer can be arranged in this element, which opens up several design options: keep one of the two flat (e.g., buried in the optical element) or both curved. For example, a larger curvature can be allowed to achieve improved performance (e.g., in the display light path).

[0010] In at least one embodiment, an optical lens for an augmented reality display includes an optical diffuser and an optical combiner. The optical combiner has a first side and a second side opposite the first side. The optical diffuser includes a hologram, and the optical combiner includes a polarizer. The hologram and / or the polarizer have a curved profile.

[0011] The optical combiner is operable to transmit ambient light incident to the first side and collimate image light incident to the second side. The optical diffuser is operable to diffuse the collimated image light exiting the optical combiner to form diffuse image light. For example, the optical diffuser can be configured to transmit and diffuse image light in the optical system to form diffuse image light, or to reflect and diffuse image light to form diffuse image light.

[0012] Allowing the curved profile of the hologram and / or polarizer opens up greater freedom for designing optical lenses for their desired purposes, such as components of optical systems for augmented reality displays. This leads to significant improvements in optical quality (such as off-axis resolution). More specifically, for example, the improved concept allows the use of curved polarizers, or the use of curved holograms and polarizers. This adds freedom to the optical design, which allows the optical performance of the display path to be improved (such as field MTF). Since optical lenses are generally required to be perspective, there are constraints on the optical design, that is, the refractive index should be zero during perspective, with low aberration (blur, distortion). In order to increase the degree of freedom, the optical element closest to the user's eyes can be curved. Since the hologram and reflective polarizer can be arranged in this element, there is a choice: keep one of the two flat (buried in the element) or both curved. Further, a larger curvature is allowed to achieve improved performance (display light path).

[0013] In the following, a curved profile is at least partially convex, concave, cylindrical, spherical or aspherical. The term "profile" refers to the curvature of one or more optical surfaces. In contrast, for example, a curved profile may have one or more convex or concave parts compared to a curved profile, a linear profile indicates that one or more optical surfaces are flat, i.e. the surface is planar. In general, a curved profile can be described by any mathematical function, for example as an aspherical optical surface, which is neither spherical nor cylindrical. A curved profile can be represented by a continuous function. In general, a curved profile can be defined segment by segment, for example, each segment is represented by a continuous function. Thus, the optical design can change the curved profile individually and segment by segment, thereby providing further degrees of freedom.

[0014] An optical diffuser can have several optical properties. For example, an optical diffuser is configured to transmit ambient light without diffusing the ambient light. An optical diffuser can be configured to transmit ambient light with substantially no aberration of the ambient light. An optical diffuser can include an optical fan-out component, a beam expander, or an optical diffuser. An optical diffuser may have no optical power or be light driven.

[0015] In at least one embodiment, the optical combiner is configured to transmit ambient light with substantially no aberrations of the ambient light. The term "substantially no aberrations" relates to no or negligible aberrations of the ambient light, for example when the optical lens is integrated into an optical system. Aberrations may include all common optical distortions such as blur, distortion, chromatic aberration, astigmatism, etc. The term "substantially" also indicates that aberrations may be noticeable to a certain extent, which is irrelevant to the desired application or can be explained with the help of image or video processing.

[0016] Despite the constraint of being essentially aberration-free, the proposed optical design provides an additional degree of freedom, allowing for improved off-axis optical performance (eg, on-field modulation transfer function MTF) of the display path.

[0017] In at least one embodiment, the total refractive index (perspective) of the optical lens including the optical diffuser and the optical combiner is 0. For example, in a lens design where only the optical diffuser and the optical combiner are present, these combined optical elements may result in a total refractive index of zero.

[0018] The "see-through" requirement may be relevant to the use case of the proposed concept, such as an optical system for an augmented reality display, but imposes strong constraints on the optical design, for example, the refractive index should be zero, or at least close to zero, in see-through, with low aberrations such as blur, distortion, etc. Despite these constraints, the proposed optical design provides additional degrees of freedom, allowing for improved off-axis optical performance of the display path (e.g., on-field modulation transfer function MTF).

[0019] In at least one embodiment, the optical combiner is or includes a reflective pancake type optical combiner. The reflective pancake type provides a low profile and thus may require less space in the optical system of the augmented reality display.

[0020] In at least one embodiment, the hologram is or comprises a volume phase hologram VPH.

[0021] For example, the VPH includes one or more VPH gratings. These gratings have no or no surface grooves. One or more surfaces of the (one or more) VPH gratings may be curved according to a curved profile or a segment thereof. For the VPH gratings, diffraction may occur when incident light passes through a film with a periodic refractive index modulation sealed between continuous substrates.

[0022] For example, a volume phase hologram includes an active optical structure. In particular, the active optical structure of the volume phase hologram has only a Bragg diffraction effect on the incident / passing light.

[0023] In at least one embodiment, the optical lens further comprises at least one lens body, and the hologram and / or polarizer is buried in the lens body and / or arranged on the surface of the lens body. For example, the hologram and / or polarizer may comprise a dielectric, which may be formed to have optical power and may be buried in the material forming the lens body.

[0024] In at least one embodiment, the optical lens further comprises a plurality of lenses, each lens comprising a respective lens body, and the lenses form a double lens, a triple lens or a multi-lens and / or a catadioptric system.

[0025] For example, one or more optical elements can be implemented as mirrors. Therefore, the entire lens can be regarded as a catadioptric system. Furthermore, the optical lens can include any number of additional lenses or lens groups, thus forming a multi-lens and / or catadioptric system.

[0026] In at least one embodiment, the optical lens further comprises a first lens and a second lens forming a double lens. The front side of the optical combiner is or is arranged on the surface of the first lens. In particular, the front side of the optical combiner is the first side of the optical combiner. The rear side of the optical combiner is or is arranged on the surface of the second lens. In particular, the rear side of the optical combiner is the second side of the optical combiner. The hologram and / or the polarizer are buried in the lens body of the second lens or are arranged on the surface of the lens body of the second lens. For example, the hologram and / or the polarizer may be arranged in or on the optical element or lens, and in use, the optical element or lens may be located closest to the user's eyes.

[0027] In at least one embodiment, the polarizer is or includes a polarization dependent reflector.

[0028] In at least one embodiment, the polarizer is configured to reflect only light of a predetermined polarization state. Additionally or alternatively, the polarizer is configured to reflect only light having wavelengths in one or more narrow spectral bands, each spectral band being arranged around the wavelength of the image light. Additionally or alternatively, the polarizer is configured to reflect only light of a predetermined linear polarization. Additionally or alternatively, the polarizer comprises a polarizer.

[0029] In at least one embodiment, the optical combiner includes a light-driven reflector and the polarizer and the light-driven reflector define an optical cavity, wherein the retarder is located in the optical cavity.

[0030] In at least one embodiment, the optical combiner includes a light driven reflector, a retarder including or configured to function as a quarter wave plate, and / or a circular polarizer for circularly polarizing ambient light before the ambient light is incident on the first side of the optical combiner.

[0031] For example, the circular polarizer is arranged to circularly polarize the ambient light before the ambient light is incident on the first side of the optical combiner, for example, wherein the circular polarizer is disposed on an outer surface of the light driven reflector.

[0032] In at least one embodiment, the polarizer and the light-driven reflector define an optical cavity, and wherein the retarder is located in the optical cavity.

[0033] For example, the optical cavity includes air or is filled with air. A solid transparent member or a solid transparent material may be located in the optical cavity. Alternatively, the optical cavity may be filled with a solid transparent material, such as a polymer material or a glass material.

[0034] In at least one embodiment, the light-driven reflector includes at least one of the following: a curved mirror, a Fresnel reflector, or a diffraction mirror, such as a volume phase hologram or a polarization volume grating. The light-driven reflector is configured to reflect light in one or more narrow spectral bands, each spectral band is arranged around the wavelength of the image light, and the light-driven reflector is configured to have a reflectivity of 90% or greater, 95% or greater, or 99% or greater in each spectral band.

[0035] For example, the light-driven reflector includes a light-driven dichroic reflector. Additionally, or alternatively, the light-driven reflector includes a transparent substrate and a dichroic reflective coating disposed on one surface of the transparent substrate. Additionally, or alternatively, the light-driven reflector is configured to partially reflect the image light, for example, wherein the light-driven reflector is configured to reflect 50% of the image light. Additionally, or alternatively, the light-driven reflector includes a light-driven partial reflector. Additionally, or alternatively, the light-driven reflector includes a transparent substrate and a partially reflective coating disposed on one surface of the transparent substrate, such as a semi-silvered partially reflective coating.

[0036] Furthermore, an optical system for an augmented reality display is proposed. The optical system comprises an optical lens according to one or more aspects above. Furthermore, the optical system comprises an image generator operable to generate image light.

[0037] The optical lens is to be located in the field of view of the user of the optical system between the user and the scene. Then, if ambient light from the scene is incident on the first side, the light is transmitted towards the eyes of the user. Image light from the image generator is incident on the second side and passes through the optical combiner several times and leaves the optical combiner from the second side towards the eyes of the user as collimated image light, while ambient light passes through the optical combiner only once. For example, the image generator is configured to focus the image light to a focal plane, and the optical diffuser is located at the focal plane.

[0038] In at least one embodiment, the optical combiner is configured to reflect the image light and control the divergence of the image light so that the image light passes through the optical combiner four times and exits the optical combiner from a second side of the optical combiner as collimated light, while the ambient light passes through the optical combiner only once.

[0039] Furthermore, a wearable augmented reality display is proposed. The wearable augmented reality display comprises an optical system according to one or more aspects above. A support frame is arranged to mount the optical system on a user so that the optical lens is located within the user's field of view.

[0040] Based on the above-described embodiments of the optical lens and the optical system for an augmented reality display, further embodiments of a wearable augmented reality display will be apparent to readers skilled in the art, and vice versa. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The following description of the various figures may further illustrate and explain aspects of optical lenses and optical systems for augmented reality displays, as well as aspects of wearable augmented reality displays. Components and parts of optical lenses that are functionally the same or have the same effect are designated by the same reference symbols. Identical or effectively identical components, parts, and steps of the method may be described only with respect to the figure in which they first appear. Their descriptions are not necessarily repeated in the descriptions of consecutive figures.

[0042] In each figure:

[0043] Figure 1 A schematic diagram of a head mounted AR display is shown,

[0044] Figure 2 shows an example embodiment of an optical lens for an augmented reality display,

[0045] Figure 3 Another example embodiment of an optical lens for an augmented reality display is shown,

[0046] Figure 4 Another example embodiment of an optical lens for an augmented reality display is shown, and

[0047] Figure 5 Another example embodiment of an optical lens for an augmented reality display is shown. DETAILED DESCRIPTION

[0048] Figure 1 A schematic illustration of a head mounted AR display 2 is shown. The wearable AR display 2 comprises a support frame 4 having a central axis 6 and an optical system 10 in the form of an off-axis retinal scanning display mounted on the support frame 4. The optical system 10 comprises an image generator in the form of a scanning laser projector 12 and an eyepiece 14. The projector 12 is offset from the central axis 6.

[0049] In use, when the support frame 4 is mounted on the head of a user with the eyepiece 14 positioned in the user's field of view, the eyepiece 14 transmits ambient light from a scene 16 located in front of the eyepiece 14 through the eyepiece 14 to the user's eye 20 located behind the eyepiece 14, and the scanning laser projector 12 projects linearly polarized image light 18 defining an image through the eyepiece 14 toward the user's eye 20. The linearly polarized image light 18 may include one or more wavelengths, such as one or more of red, green, or blue light.

[0050] The eyepiece 14 includes one or more optical lenses for an augmented reality display that replicates the image defined by the projected image light 18 several times at multiple locations in a plane 22 at the user's eye 20 to extend the eye box of the wearable AR display 2. In particular, the plane 22 is the focal plane of the user's eye. For example, in use, the scanning laser projector 12 projects the linearly polarized image light 18. The optical system 10 replicates the image defined by the linearly polarized principal rays at different locations in the plane 22 at the user's eye 20 to provide an extended eye box in the plane 22 of the user's eye 20 for each principal ray of the projected image light 18.

[0051] The following discussion discloses several example embodiments of an optical lens for an augmented reality display. To better describe the optical function, the optical lens is shown between the user's eye 20 and the scene 16. The optical lens includes at least an optical diffuser 59 and an optical combiner 50. Additional optical elements may be present, which will be discussed in further detail below.

[0052] The optical combiner 50 has a first side 51 and a second side 52 opposite to the first side 51. In the embodiments discussed below, both the optical diffuser 59 and the optical combiner 50 are configured to transmit the ambient light 32 without or with negligible aberration of the ambient light 32. In other words, the optical design of the optical lens has a "see-through" constraint, which imposes strong constraints on the optical design, that is, the refractive index in see-through should be zero, or at least close to zero, with low aberrations such as blur, distortion, etc. Despite these constraints, the proposed optical design provides additional degrees of freedom, allowing for improved off-axis optical performance (e.g., field modulation transfer function MTF) of the display path. Although the "see-through" requirement may be relevant to the use case of the proposed concept, it should by no means be interpreted as limiting. In fact, the optical design may allow for a certain degree of aberration, which in turn can be explained with the help of image or video processing. Optical power can also be added to allow for the user's lens prescription (nearsightedness, hyperopia, etc.).

[0053] Figure 2 Example embodiments of optical lenses for augmented reality displays are shown. This first design shows an optical lens with a flat hologram 40 and a curved polarized reflector 54. The optical diffuser 59 is implemented in the form of a transmissive volume phase hologram (VPH) 40. In the optical system 10, the VPH is operable to fan out the projected image light 18 to form diffused image light. The optical lens also includes an optical combiner 50 in the form of a "reflective pancake-type" optical combiner. In the optical system 10, the optical combiner 50 is operable to collimate the diffused image light and reflect the collimated light back through the VPH 40 to form collimated light that propagates to the plane 22 at the user's eye 20 to provide an extended eye box in the plane 22 of the user's eye 20.

[0054] The VPH 40 may be configured to selectively diffuse or fan out light incident on the VPH 40 depending on the angle of incidence of the light incident on the VPH 40. For example, the VPH 40 may be configured to diffuse or fan out image light 18 incident on the VPH 40 at a higher angle of incidence, but transmit ambient light 32 from the scene 16 without diffusing or fanning out ambient light 32 from the scene 16.

[0055] In the exemplary embodiment, VPH 40 has a flat or linear profile. The term "profile" refers to the curvature of one or more optical surfaces. A linear profile indicates that VPH 40 is flat, i.e., it has a planar optical surface, as opposed to a curved profile, e.g., a curved profile having one or more convex or concave optical surfaces. In general, a curved profile can be described by any mathematical function, e.g., as an aspherical optical surface, which is neither spherical nor cylindrical.

[0056] The optical combiner 50 includes one or more optical elements. In this embodiment, the optical combiner includes a first lens 55 and a second lens 56, and thus forms an optical objective. The optical combiner 50 has a first side 51 or front side 51 that can be disposed toward the scene 16 and a second side 52 or back side 52 that can be disposed toward the VPH 40. For example, the front side 51 can be considered to be on the surface of the first lens 55, and the back side 52 can be considered to be on the surface of the second lens 56. The lenses 55, 56 include a curved transparent body or substrate (e.g., glass or a transparent polymer, such as PMMA or OKP4 polymer, for a higher refractive index). The lenses 55, 56 in this embodiment are biconvex lenses, such as seen from the scene 16, i.e., have a positive radius of curvature (ROC) toward the user's eyes. The two lenses 55, 56 can be monocentric or non-monocentric. The lenses 55, 56 can have a common center of curvature (or exit pupil).

[0057] The first lens 55 is supplemented by a dichroic reflector 58. In particular, the dichroic reflector 58 is a light-driven reflector. In this exemplary embodiment, the dichroic reflector 58 includes a convex dielectric that is buried in the transparent body of the first lens 55. The dichroic reflector 58 can be configured to be highly reflective in one or more narrow spectral bands, each narrow spectral band being arranged around a corresponding wavelength of the image light 18, but transmitting light of other wavelengths. The dichroic reflector 58 is, for example, a dichroic reflective reflector. For example, the dichroic reflective reflector 58 can be configured to have a reflectivity of 90% or greater, 95% or greater, or 99% or greater in each spectral band. The dichroic reflective reflector 58 can be configured to reflect ambient light 32 having a wavelength within one or more narrow spectral bands, but transmit ambient light 32 having a wavelength outside of the one or more narrow spectral bands.

[0058] For example, the optical combiner 50 further includes a polarization-dependent reflector 54 or a polarizer, which is arranged in the second lens 56 or on the surface of the second lens 56. The polarizer 54 is curved, i.e., an optical surface having a curved profile. In this embodiment, the curved profile is defined by the curvature of the second lens 56, i.e., is convex.

[0059] The optical combiner 50 typically includes additional optical elements, which are not shown for easier representation. For example, the optical combiner 50 includes a retarder 60, such as a quarter wave plate. The retarder 60 can be another separate optical element, or it can be curved and added to or incorporated into the polarizing reflector 54.

[0060] The polarization dependent reflector 54 and the dichroic reflector 58 define an optical cavity 61 in which the retarder 60 is located. In addition, the polarization dependent reflector 54 and the dichroic reflector 58 are arranged such that the polarization dependent reflector 54 is located in the optical path between the VPH 40 and the dichroic reflector 58. The retarder 60 and the dichroic reflector 58 are typically separated by an air gap 64.

[0061] Optical lenses can be implemented in Figure 1 In the optical system 10 of the wearable AR display 2 shown. For example, two such optical lenses are provided for the eyepiece 14 for the augmented reality display. The eyepiece 14 also includes an optional circular polarizer (not shown), which can be disposed on the dichroic reflector 58.

[0062] In use, the optical combiner 50 effectively combines ambient light 32 incident on a first side 51 of the optical combiner 50 with collimated light exiting a second side 52 of the optical combiner 50. For example, the circular polarizer 70 imparts circular polarization to the ambient light 32, and the circularly polarized ambient light 32 is incident on the first side 51 of the optical combiner 50 defined by the dichroic reflector 58. The dichroic reflector 58 transmits wavelengths of the circularly polarized ambient light 32 toward the retarder 60 that fall outside of one or more narrow spectral bands that are highly reflected by the dichroic reflector 58. The retarder 60 converts the circularly polarized ambient light 32 transmitted by the dichroic reflector 58 into linearly polarized ambient light 32 having a linear polarization aligned with the polarization transmission axis of the polarization-dependent reflector 54, so that the polarization-dependent reflector 54 transmits the linearly polarized ambient light 32 toward the eye box. The use of the circular polarizer 70 at least partially suppresses reflection of the ambient light 32 from the polarization-dependent reflector 54, thereby at least partially suppressing any ghost images of the scene 16 from forming at the eye box.

[0063] It has been found that the proposed optical lens can have improved optical performance relative to prior art lenses, including a larger field of view, higher resolution and / or a larger eye box. Still further, another aspect relates to a reduction in thickness for a desired focal length.

[0064] An example parameter set may be as follows. The lenses 55, 56 in this embodiment may be 6-base lenses or dual 4-base lenses, with a lens diameter of approximately 40 mm, and a TTL, such as a distance of 7 mm between lenses 55, 56. The first lens 55 may have a thickness of approximately 2 mm, and the second lens 56 is approximately 1.5 mm. Optical element calculations show that the design exhibits improved resolution across the light field, such as supporting a full FOV of 50 degrees, with good MTF over a variety of wavelengths over at least 20 degrees without refocusing. Barrel distortion may be kept low at around 5.5%. Calculations indicate that there is no significant axial chromatic aberration. Lateral color may be corrected by software if desired. The example parameter set is for illustrative purposes only, and leaves room for further improvement. The design may be limited only by parameters defined by the application at hand, such as form factor and perspective quality.

[0065] Figure 3 Another example embodiment of an optical lens for an augmented reality display is shown. This second design shows an optical lens with a curved hologram 40 and a curved polarizing reflector as a polarizer 54. Since this design builds on Figure 2 of the designs shown, therefore only some differences are highlighted.

[0066] The optical diffuser 59 is implemented in the form of a curved transmission volume phase hologram (VPH) 40. In the optical system 10, the VPH 40 is operable to fan out the projected image light 18 to form a diffused image light. For example, both the curved hologram 40 and the curved polarizing reflector 54 are implemented inside the second lens 56, or on the surface of the second lens 56. The curved hologram 40 and the curved polarizing reflector 54 are curved, i.e., optical surfaces with a curved profile. In this embodiment, the curved profile is defined by the curvature of the second lens 56, i.e., it is convex.

[0067] The optical lens also includes an optical combiner 50 in the form of a "reflective pancake" optical combiner. In the optical system 10, the optical combiner 50 is operable to collimate the diffuse image light 18 and reflect the collimated light back through the VPH 40 to form collimated light that propagates to the plane 22 at the user's eye 20 to provide an extended eye box in the plane 22 at the user's eye 20. In this example, the dichroic reflector 58 includes a conical aspheric dielectric that is buried in the transparent body of the first lens 55. The two lenses 55, 56 can be monocentric or non-monocentric.

[0068] This lens design has improved optical performance relative to prior art lenses, namely, a larger field of view, higher resolution and / or a larger eye box. An example parameter set may be as follows. The lenses 55, 56 in this embodiment may be 2.5 base lenses with a lens diameter of approximately 40 mm. The first lens 55 may have a thickness of approximately 2.5 mm, and the second lens 56 may have a thickness of approximately 1.0 mm, and a TTL, such as a distance of 6.5 mm between lenses 55, 56. Optical element calculations show that the design shows improved resolution over the light field, such as supporting a full FOV of 30 degrees with excellent performance. Above 50 degrees, barrel distortion may be kept low at approximately 7%. The optical lens is characterized by a quality equivalent to a 3.5 mm thick lens. The design includes only spherical surfaces, except for the buried dichroic reflector 58, which is a conical aspherical surface. Optical properties include good perspective, low distortion, aberrations, and 12 mm eye relief. The design was calculated using a 50mm ROC VPH and 12mm diameter and a 50mm ROC polarizing reflector and 18mm diameter.

[0069] Figure 4 Another example embodiment of an optical lens for an augmented reality display is shown. Figure 3 , i.e., the design is based on a curved hologram 40 and a curved polarizing reflector 54. However, Figure 3 Differently, this design uses a flatter radius of curvature with a higher refractive index.

[0070] The first lens 55 is a 2-base lens and may have a thickness of about 2.0 mm with a ROC of 265 mm. The second lens 56 is a 6-base lens and may have a thickness of about 1.5 mm. The TTL, specifically the distance between the lenses 55, 56, is set to 6.5 mm center thickness. Optical element calculations show that the design can be fine-tuned by adjusting the radius of curvature and the refractive index.

[0071] Figure 5 Another example embodiment of an optical lens for an augmented reality display is shown. This design is also based on the previous design. However, the first lens 55 is a flat lens, rather than a convex lens. In fact, the first lens 55 has two flat surfaces. Compared to the previous design, this change allows a still larger field of view to be achieved.

[0072] In this design, the first lens 55 is a 3 mm thick flat lens with a dichroic reflector 58 buried therein. The second lens 56 is a 1.5 mm thick 88 mm ROC lens (6 base). The TTL is set to a center thickness of 8.5 mm.

[0073] This application claims the priority of German application DE 102022126674.5, the disclosure content of which is incorporated herein by reference.

[0074] The designs discussed herein are used as examples to highlight the improved optical performance that can be achieved. It is also apparent that various parameters have an impact on the overall performance. Those skilled in the art will readily appreciate that the optical combiner can include lenses of many more various shapes. The lenses can have a variety of curvatures or flat elements, which can be used as variable parameters of the lens design. Further, the dichroic reflector 58 may not necessarily be buried in the lens body, but can be a separate optical element or a surface feature of the lens (e.g., a coating).

[0075] Although this specification contains many details, these details should not be interpreted as limitations on the scope of the invention or what may be claimed, but rather as descriptions of specific features of specific embodiments of the invention. Certain features described in this specification in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, the various features described in the context of a single embodiment may also be implemented individually or in any suitable sub-combination in multiple embodiments. In addition, although the above-mentioned features may be described as functioning in the form of certain combinations, and even initially claimed as such, in some cases, one or more features from the combination may be deleted from the claimed combination, and the claimed combination may point to a sub-combination or a variant of a sub-combination.

[0076] Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that the operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed to achieve desired results. In some situations, multitasking and parallel processing may be advantageous.

[0077] Features recited in individual dependent claims may advantageously be combined. Furthermore, reference signs used in the claims are not to be construed as limiting the scope of the claims.

[0078] Furthermore, as used herein, the term "comprising" does not exclude other elements. In addition, as used herein, the articles "a" and "an" are intended to include one or more than one components or elements, and are not limited to being interpreted as referring to only one.

[0079] refer to

[0080] 2 Wearable augmented reality display; 4 Support frame; 6 Central axis of support frame; 10 Optical system; 12 Scanning laser projector; 14 Eyepiece; 16 Scene; 18 Image light; 20 User eye; 22 Plane at user eye; 30 Collimated light; 32 Ambient light; 40 Transmission volume phase hologram (VPH); 50 Optical combiner; 51 First side / front side of optical combiner; 52 Second side / back side of optical combiner; 54 Polarization-dependent reflector, polarizer, polarized reflector; 55 First lens; 56 Second lens; 58 Light-driven reflector, dichroic (reflective) reflector; 59 Optical diffuser; 60 Retarder; 61 Optical cavity; 64 Air gap; 70 Circular polarizer; TTL Distance between first lens and second lens.

Claims

1. An optical lens for an augmented reality display, the optical lens comprising an optical diffuser (59) and an optical combiner (50), the optical combiner having a first side (51) and a second side (52) opposite to the first side (51), wherein: - the optical combiner (50) is operable to transmit ambient light (32) incident on the first side (51) and to collimate image light (18) incident on the second side (52), - the optical diffuser (59) is operable to diffuse the collimated image light (18) exiting the optical combiner (50) so as to form diffuse image light; and wherein - the optical diffuser (59) comprises a hologram (40), and the optical combiner (50) comprises a polarizer (54), and - the hologram (40) and / or the polarizer (54) has a curved profile, - the optical combiner (50) comprises a light-driven reflector (58), - the polarizer (54) and the light driven reflector (58) define an optical cavity (61), and - The retarder (56) is located in the optical cavity (61).

2. The optical lens according to claim 1, wherein: The curved profile may be at least partially convex, concave, cylindrical, spherical or aspherical.

3. The optical lens according to claim 1, wherein: The optical combiner (50) is configured to transmit the ambient light (32) substantially without aberrations of the ambient light (32).

4. The optical lens according to any one of claims 1 to 3, wherein: The total refractive index (perspective) of the optical lens including the optical diffuser (59) and the optical combiner (50) is zero.

5. The optical lens according to any one of claims 1 to 4, wherein: The optical combiner (50) is or includes a reflective pancake-type optical combiner.

6. The optical lens according to any one of claims 1 to 5, wherein: The hologram (40) is or comprises a volume phase hologram.

7. The optical lens according to any one of claims 1 to 6 comprises at least one lens body, and the hologram (40) and / or the polarizer (54) are buried in the lens body and / or are arranged on the surface of the lens body.

8. The optical lens according to any one of claims 1 to 7, comprising a plurality of lenses, each lens comprising a respective lens body, and the lenses forming a double lens, a triple lens or a multi-lens and / or a catadioptric system.

9. The optical lens according to claim 8, comprising a first lens (55) and a second lens (56) forming a doublet, wherein - the first side (51) of the optical combiner (50) is or is arranged on the surface of the first lens (55), - the second side (52) of the optical combiner (50) is or is arranged on a surface of the second lens (56), and The hologram (40) and / or the polarizer (54) are embedded in the lens body of the second lens (56) or are arranged on the surface of the lens body of the second lens (56).

10. The optical lens according to claims 1 to 9, wherein the polarizer (54) is or comprises a polarization dependent reflector.

11. The optical lens according to any one of claims 1 to 10, wherein: The optical combiner (50) comprises: - a circular polarizer (70) for circularly polarizing the ambient light (32) before the ambient light (32) is incident on the first side (51) of the optical combiner (50).

12. An optical system for an augmented reality display, the optical system comprising: - An optical lens according to any one of the preceding claims, and an image generator (12) operable to generate said image light (18), wherein: - the optical lens is to be located in the field of view of the user of the optical system between the user and the scene (16), - ambient light (32) from the scene (16) incident on the first side (51) is transmitted towards the eyes (20) of the user, - image light (18) from the image generator (12) incident on the second side (52) passes through the optical combiner (50) several times and leaves the optical combiner (50) from the second side (52) towards the eye (20) of the user as the collimated image light, while the ambient light (32) passes through the optical combiner (50) only once.

13. The optical system according to claim 12, wherein: The optical combiner (50) is configured to reflect the image light (18) and control the divergence of the image light (18) so that the image light (18) passes through the optical combiner (50) four times and exits the optical combiner (50) from the second side (52) of the optical combiner (50) as collimated light, while the ambient light (32) passes through the optical combiner (50) only once.

14. A wearable augmented reality display comprising: - an optical system (10) according to any of the preceding claims, and - a support frame (4) for mounting the optical system (10) on a user so that the optical lens is within the user's field of view.

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