Perspective near-eye display device and its crystal waveguide

Abstract

A see-through near-eye display device includes an image source configured to emit light carrying an image, a one-dimensional waveguide made of a crystal material that is transmissive to visible light and arranged to receive and guide the light emitted by the image source, and a first grating disposed on or in the waveguide. The first grating is configured to out-couple at least a portion of the light from the image source after it has been guided by the waveguide to the first grating. Several particularly advantageous crystal waveguide materials are disclosed that exhibit high refractive index and high transparency in the visible spectrum. In one class of embodiments, the crystal waveguide material is based on a bismuth germanate crystal or a bismuth silicate crystal, optionally with substitution and / or doping. The crystal waveguide material can be in the form of a boule, with or without additional dopants.

Description

Technical Field

[0001] This disclosure generally relates to a see-through near-eye display device for use in augmented reality (AR) glasses. Specifically, this disclosure relates to a waveguide for relaying virtual content into the user's field of view (FOV). Background Technology

[0002] AR glasses overlay electronically generated virtual content onto the real-world scene observed by the user, creating a hybrid visual experience that combines real-world images with virtual ones. Overlaying virtual content onto a real-world image requires merging the light carrying the virtual content into the light path from the real-world scene. For widespread user adoption, it is preferable that the user's observation and perception of the real-world scene is enhanced without being impaired. Widespread adoption also requires AR glasses to be aesthetically pleasing and, for example, resemble ordinary glasses. Furthermore, an immersive experience is desired, where the virtual image can cover a large portion of the user's field of view (FOV).

[0003] An AR glasses pair comprises one or two see-through near-eye displays, i.e., one device per eye, or a single device for only the left or right eye. At a basic level, a see-through near-eye display comprises: (a) a virtual image source, such as a digital display device or scanning laser projector that emits light carrying the virtual image; and (b) relay and combining optics that relay the virtual image light to the user's field of view (FOV) and deflect the virtual image light into the light path propagating from the real scene toward the eye. Designing non-bulky relay and combining optics capable of producing a large FOV virtual image with high quality and minimal degradation of the real-world image is a challenging task critical to user experience. An early type of AR glasses suspended prisms in the corners of the user's FOV to deflect light from the digital display device toward the user's eye. The result was a virtual image superimposed on a real-world image at a relatively peripheral location. This type of AR glasses had limited functionality and did not achieve commercial success.

[0004] By comparing such systems with some aspects of this disclosure as set forth in the remainder of this disclosure with reference to the accompanying drawings, further limitations and disadvantages of conventional and traditional methods will become apparent to those skilled in the art. Summary of the Invention

[0005] Waveguide-based see-through near-eye displays are becoming the dominant technology, offering a more immersive experience, improved see-through performance, and a form factor similar to ordinary eyeglasses. In these waveguide-based devices, a one-dimensional waveguide relays virtual image light to the user's field of view (FOV), and a grating on the waveguide couples the virtual image light from the waveguide to the user's eye. The waveguide can be shaped like a lens in ordinary eyeglasses with zero optical power, and the virtual image source can be integrated into the temples of the glasses. Waveguide transmission is based on total internal reflection. Therefore, the waveguide material can transmit visible light from the real scene while simultaneously acting as a light guide for visible light from the virtual image source.

[0006] This paper discloses a waveguide-based see-through near-eye display device with a crystal waveguide. The crystal waveguide material has several potential advantages, including: (a) high transparency across the entire visible spectrum, which helps to minimize the darkening of the real-world image and minimize spectral distortion, while achieving low-loss transmission of virtual image light; (b) high refractive index, which enables the creation of a large FOV virtual image; (c) isotropic optical and mechanical properties, which ensure high optical quality for both the real-world image and the virtual image; and (d) high mechanical strength and stiffness.

[0007] Several crystalline materials have been identified as particularly advantageous material choices for waveguides in the see-through near-eye display devices of this disclosure. These crystalline materials exhibit high refractive indices, such as 2.0 or higher, across the entire visible spectrum. These materials also exhibit very low absorption across the entire visible spectrum. In one type of embodiment, the crystalline waveguide material is based on bismuth germanate or bismuth silicate crystals, optionally with substitution and / or doping. For example, the crystalline material may exhibit… In this type of embodiment, the crystal waveguide material may or may not contain additional dopants. In another type of embodiment, the crystal waveguide material is based on cubic zirconia. In this type of embodiment, the crystal material may be in the form of… In the form of , where A is Ca or Y, with or without additional dopant.

[0008] In one aspect of this disclosure, a see-through near-eye display device includes: an image source configured to emit light carrying an image; a one-dimensional waveguide made of a crystalline material that transmits visible light and arranged to receive and guide the light emitted by the image source; and a first grating disposed on or in the waveguide. The first grating is configured to couple at least a portion of the light from the image source out of the waveguide after it has been guided to the first grating by the waveguide.

[0009] These and other advantages, aspects, and novel features of this disclosure, as well as the details of the illustrative embodiments thereof, will be more fully understood through the following description and accompanying drawings. Attached Figure Description

[0010] The accompanying drawings, which are incorporated in and constitute a part of this specification, schematically illustrate embodiments of the present disclosure and, together with the general description given above and the detailed description of embodiments given below, serve to explain the principles of the present disclosure.

[0011] Figure 1 An AR glasses pair according to one embodiment is illustrated, which includes two see-through near-eye display devices based on one-dimensional crystal waveguides.

[0012] Figure 2 A portion of a crystal waveguide-based near-eye display device according to one embodiment is shown, which implements two gratings for diffracting virtual image light into and out of the crystal waveguide.

[0013] Figure 3 An exemplary light propagation in a crystal planar waveguide-based near-eye display device according to one embodiment is illustrated schematically in cross-sectional view.

[0014] Figure 4 This is a cross-sectional view of another crystal waveguide-based perspective near-eye display device according to one embodiment, the perspective near-eye display device being configured with a non-planar one-dimensional waveguide.

[0015] Figure 5 Drawings for formable Figures 1 to 4 The curve showing the refractive index of certain crystal materials in the crystal waveguide of any see-through near-eye display device as a function of wavelengths from 400 nanometers (nm) to 800 nm. Detailed Implementation

[0016] Now refer to the accompanying drawings, in which the same parts are labeled with the same numbers. Figure 1 An AR glasses 100 is illustrated, comprising a left-eye see-through near-eye display 102L and a right-eye see-through near-eye display 102R, each based on a one-dimensional crystal waveguide. Each of the display devices 102L and 102R includes a waveguide 110 for transmitting visible light, a grating 130, and a virtual image source 150. The virtual image source 150 may be integrated into the frame 120 of the AR glasses 100. The virtual image source 150 emits virtual image light carrying a virtual image to be formed in the user's eye. For this purpose, each virtual image source 150 may include (a) a digital display configured with a collimating lens or (b) a scanning laser projector.

[0017] Waveguide 110 is incorporated into AR glasses 100 as a left "lens" and a right "lens". Typically, the "lens" formed by waveguide 110 has zero optical power. However, without departing from the scope of this disclosure, one or both of waveguides 110 may have non-zero optical power, for example, according to a user's ophthalmological prescription. Each waveguide 110 is a one-dimensional waveguide that confines guided light in a lateral dimension. In one example, each waveguide 110 is a planar waveguide having two parallel planar surfaces. Light is guided in the planar waveguide by total internal reflection between these two parallel planar surfaces, provided that the direction of light propagation is incident on these surfaces at an angle of incidence exceeding the critical angle for total internal reflection.

[0018] In operation, the user wears AR glasses 100 and observes the real scene through the AR glasses 100, i.e., through the "lens" formed by waveguide 110. More specifically, light from the real scene is transmitted through grating 130 and waveguide 110, but not guided by waveguide 110. One or both of display devices 102L and 102R superimpose a virtual image onto the real scene observed by the user through AR glasses 100. In each of display devices 102L and 102R, this process requires coupling light emitted by virtual image source 150 into waveguide 110. Such coupling of virtual image light into waveguide 110 can occur outside the user's field of view (FOV) and / or in a location concealed by frame 120. Waveguide 110 then guides the virtual image light to the location of grating 130. Grating 130 is disposed on or within waveguide 110. The grating 130 diffracts at least a portion of the virtual image light away from the waveguide 110 in the direction toward the user's eye, thereby superimposing the virtual image originating from the virtual image source 150 onto the real-world image observed by the user.

[0019] Figure 2 A portion of a crystal waveguide-based near-eye display device 200 is shown, which implements two gratings for diffracting virtual image light into and out of the one-dimensional crystal waveguide. The display device 200 is an example of either display device 102L or display device 102R of AR glasses 100. The display device 200 includes a waveguide 110, a grating 130, an additional grating 240, and a virtual image source 150. Figure 2 (Not shown in the image). When the display device 200 is implemented in the AR glasses 100, the grating 240 can be implemented in a portion of the waveguide 110 that is hidden in the frame 120.

[0020] In operation of the display device 200, virtual image light 290 from virtual image source 150 is incident on waveguide 110 at the location of grating 240. Grating 240 diffracts the virtual image light 290 into waveguide 110. This coupled virtual image light 290 propagates within waveguide 110 at a propagation angle exceeding the critical angle for total internal reflection at the surface of waveguide 110. Waveguide 110 then guides the virtual image light 290 to grating 130, whereby grating 130 diffracts the guided virtual image light 290 away from waveguide 110. Each of grating 130 and grating 240 may be a surface relief grating or a holographic grating.

[0021] Figure 3 An exemplary light propagation in a crystal planar waveguide-based near-eye display device 300 is illustrated in cross-sectional view. Specifically, Figure 3 An example demonstrates the effect of the waveguide's refractive index on the achievable field of view (FOV) of the virtual image perceived by the user. Display device 300 can be implemented in AR glasses 100 as either display device 102L or display device 102R. Display device 300 includes a crystal planar waveguide 310, gratings 330 and 340, and a virtual image source 350.

[0022] Waveguide 310 has two planar surfaces 312 and 314, which work together through a total internal reflection mechanism to achieve one-dimensional waveguide transmission. The thickness 364 of waveguide 310 between surfaces 312 and 314 is, for example, in the range of 0.5 mm to 2 mm. Gratings 330 and 340 can be similar to those referenced above. Figure 2 The gratings 130 and 240 are discussed. Gratings 340 and 330 are separated from each other by a non-zero distance 360. The distance 360 ​​is, for example, in the range of 10 mm and 50 mm. Figure 3 An example is depicted where gratings 330 and 340 are located at surface 312 of waveguide 310, specifically on the surface of waveguide 310 opposite to the user's eye 390. Alternatively, one or both of gratings 330 and 340 may be located at surface 314 or embedded within waveguide 310. In the depicted embodiment, virtual image source 350 and eye 390 are located on the same side of waveguide 310. Alternatively, although generally disadvantageous for packaging purposes, virtual image source 350 and eye 390 may be located on opposite sides of waveguide 310.

[0023] In operation, grating 340 diffracts light from virtual image source 350 into waveguide 310, which then guides the virtual image light in a direction toward grating 330. Grating 330 then diffracts at least a portion of the guided virtual image light toward eye 390. This diffraction of the guided virtual image light toward eye 390 superimposes it onto light 380 propagating from the real scene toward eye 390.

[0024] exist Figure 3 In the illustrated embodiment, the virtual image source 350 includes a digital display 352 and a collimating lens 354. Alternatively, the virtual image source 350 may take different forms and, for example, include a scanning laser projector. In either case, the virtual image source 350 emits light with a series of propagation angles. In operation, the display device 300 relays this virtual image light to the eye 390, where the eye 390's focusing of the virtual image light maps each propagation angle to a position on the retina of the eye 390. In other words, image information is encoded in the propagation angles of the light emitted by the virtual image source 350.

[0025] For simplicity and without loss of generality, the following discussion of the display device 300 assumes that the virtual image source 350 includes a digital display 352 and a collimating lens 354. In this embodiment, the digital display 352 displays an image. The collimating lens 354 and the lens of the eye 390 cooperate to form an imaging system that images the displayed image onto the retina of the eye 390. The magnification (reduction) of this imaging system may be related to... Figure 3 The differences are shown. Consider three beams of light emanating from three different positions on the digital display 352: beam 358C emanating from the center of the digital display 352, and two beams 358A and 358B emanating from two peripheral positions on the digital display 352. Each of beams 358A, 358B, and 358C is collimated by collimating lens 354. For each of beams 358A, 358B, and 358C, Figure 3 Two external rays and one central ray are shown.

[0026] Grating 340 diffracts beams 358A, 358B, and 358C to propagate within waveguide 310. Beams 358A, 358B, and 358C are incident on surfaces 312 and 314 of waveguide 310 at three distinct incident angles relative to the normals of surfaces 312 and 314. For each of beams 358A, 358B, and 358C, the incident angle on surfaces 312 and 314 exceeds the critical angle for total internal reflection, thereby confining these beams between surfaces 312 and 314 by waveguide 310. Figure 3 An incident angle 318 is indicated for a selected ray of beam 358A, which is incident on surfaces 312 and 314 at an angle closest to the critical angle for total internal reflection.

[0027] Although Figure 3Although not shown, a portion of the light emitted by the virtual image source 350 may be diffracted by the grating 340, thus propagating in the waveguide 310 at an angle smaller than the critical angle for total internal reflection. This light will not undergo total internal reflection and therefore will not be guided by the waveguide 310. This light can be considered lost and is ignored in the present discussion. However, to minimize the generation of stray light, it is preferable to configure the virtual image source 350 to emit only the light rays guided by the waveguide 310 from the grating 340 to the grating 330.

[0028] A virtual image generated on the retina of eye 390 from light originating from virtual image source 350 spans an FOV angle 370. The FOV angle 370 is limited by the range of permissible propagation angles of light guided in waveguide 310. This is from... Figure 3 It is evident that the FOV angle 370 is defined by the angular difference in propagation between the collimated rays of beam 358A and beam 358B. While the angular difference in propagation between the collimated rays of beams 358A and 358B emitted by the virtual image source 350 could be increased, these rays would only be guided by waveguide 310 if they propagated at an angle greater than the critical angle for total internal reflection. As shown, beam 358A is incident on surfaces 312 and 314 at the smallest angle of incidence, and is therefore closer to the critical angle than beams 358B and 358C. Extending the FOV angle 370 would require reducing the angle of incidence of beam 358A, but the critical angle for total internal reflection limits how much this angle can be reduced (if possible). However, the critical angle for total internal reflection is a decreasing function of the refractive index of waveguide 310. Therefore, the embodiment of waveguide 310 with a relatively high refractive index is able to guide light incident on surfaces 312 and 314 at a relatively small incident angle, thereby allowing a relatively large FOV angle 370.

[0029] Figure 4 This is a cross-sectional view of another perspective near-eye display device 400 based on a crystal waveguide, which is configured with a non-planar one-dimensional waveguide. Display device 400 is similar to display device 300, except that a curved one-dimensional waveguide 410 is implemented instead of a planar waveguide 310. Waveguide 410 can be a curved “lens” (with or without optical power) of an AR pair of glasses (such as AR glasses 100). Despite being curved, waveguide 410 still guides light incident on the surface of waveguide 410 at an angle of incidence greater than the critical angle for total internal reflection. Light propagation in display device 400 is schematically illustrated by a single ray 458. The discussion of light propagation in display device 300 can easily be extended to display device 400. As in the case of display device 300, the achievable field of view of the virtual image generated in display device 400 is limited by the critical angle for total internal reflection.

[0030] The above discussion of light propagation in display devices 300 and 400 demonstrates that the high refractive index of the waveguide material allows for the creation of a large FOV virtual image in waveguide-based near-eye display devices. Furthermore, from... Figure 3 It is evident that the high refractive index of waveguide materials allows the virtual image source to be positioned closer to the waveguide, which may be beneficial for packaging purposes.

[0031] Certain crystalline materials are advantageous material choices for use as waveguides in any of waveguide-based near-eye display devices, such as waveguides 110, 310, and 410. For optimal optical performance, the crystalline waveguide can be made of a single crystal. In one embodiment, the waveguide is made of a crystalline material with a refractive index of at least 2.0 over the entire wavelength range of 430 nm to 760 nm or over the entire wavelength range of 400 nm to 800 nm, to facilitate the creation of a large field-of-view (FOV) virtual image. To transmit virtual image light with low loss and transmit real scene light with minimal dimming and spectral distortion, the crystalline material may be characterized by a low absorption coefficient in the visible spectrum. For example, the absorption coefficient may be less than [value missing] over the entire wavelength range of 430 nm to 760 nm or over the entire wavelength range of 400 nm to 800 nm. or even smaller .

[0032] Two types of materials have been identified that simultaneously exhibit high refractive index and low absorption in the visible spectrum, meeting the aforementioned specifications: so-called BGO / BSO-based crystals and cubic zirconia. The BGO / BSO-based crystal category includes crystals based on bismuth, germanium, and oxygen, as well as crystals based on bismuth, silicon, and oxygen. BGO / BSO-based crystals in the form of (where 0 ≤ x ≤ 1 and 0 ≤ y ≤ 0.2) possess particularly advantageous properties. Each BGO / BSO-based crystal can be further doped with boron, aluminum, gallium, and / or indium. Molar doping concentrations can be as high as 5%, for example, in the range between 0.5% and 5%. Doping can help improve optical properties such as absorption, and boron and / or aluminum doping is expected to produce the best results. Cubic zirconia crystals typically contain... Alternatively, CaO can be used to stabilize the cubic structure. Therefore, cubic zirconia crystals can exhibit... The form is , where A is yttrium or calcium. Alternatively, the cubic zirconia crystal contains additional dopants. It can be added at a molar concentration of 10% to 25%, while CaO can be added at a molar concentration of 5% to 20%.

[0033] BGO / BSO-based crystals can be grown using growth processes known in the art, such as the Czochralski, Bridgman, or hydrothermal growth methods. Cubic zirconia crystals can be grown using the cold crucible fused-shell method. Dopants and substitutions discussed above can be present at the start of the growth process. Crystals can be grown with high purity (e.g., at least 99.995% purity) to ensure low absorption. Furthermore, when dopants are included, the growth process can be optimized to achieve dopant homogenization. Dopant homogenization improves the optical quality of the crystal. Crystals can be stoichiometric or non-stoichiometric. For example, doped or undoped BGO / BSO-based crystals may contain excess bismuth. In this case, the starting mixture used for crystal growth can be Where 0 ≤ t ≤ 0.15, or more specifically, 0 ≤ t ≤ 0.07. The mixture may further contain additional dopants. The crystal can be grown in cubic or cylindrical form. In the case of cylindrical crystals, due to the crystal structure, the crystal may exhibit slightly faceted surfaces, and the crystal diameter may exceed 160 mm. Waveguides can be cut from the grown crystal using sawing, milling, drilling, grinding, and / or polishing.

[0034] Figure 5 The refractive index of some of the crystalline waveguide materials discussed above varies with wavelengths from 400 nanometers (nm) to 800 nm, as plotted: BGO crystal. BSO crystals and cubic zirconia crystals Each of these materials has a high refractive index, exceeding 2.0 in the range between 400 nm and 800 nm. and It has an exceptionally high refractive index, approximately 2.5 or higher in the range of 400 nm to 800 nm. For comparison, Figure 5 Titanium dioxide crystals were also drawn. The curve of the ordinary refractive index. ordinary light refractive index and and quite.

[0035] Based on their refractive index Figure 5 All the crystal compositions in these materials are good waveguide materials, which can facilitate the creation of large FOV virtual images in waveguide-based perspective near-eye display devices. However, It exhibits significantly higher performance in the visible spectrum than , And the absorption of cubic zirconia, at least when the latter types of crystals are manufactured in high purity. Therefore, Less than ideal. , Both cubic zirconia and zirconia will guide virtual image light with very little loss and transmit real scene light with minimal loss and minimal spectral distortion.

[0036] In addition to high refractive index and low absorption, BGO / BSO-based crystals and cubic zirconia can also possess highly isotropic optical and mechanical properties, high mechanical strength, and hardness suitable for waveguide manufacturing and use.

[0037] As used herein, “and / or” means any one or more items in a list connected by “and / or”. For example, “x and / or y” means any element in the set of three elements {(x), (y), (x, y)}. In other words, “x and / or y” means “one or both of x and y”. Similarly, “x, y and / or z” means any element in the set of seven elements {(x), (y), (z), (x, y), (x, z), (y, z), (x, y, z)}. In other words, “x, y and / or z” means “one or more of x, y and z”. As used herein, the term “exemplary” means used as a non-limiting example, instance, or illustration. As used herein, the term “for example” introduces a list of non-limiting examples, instances, or illustrations. As used herein, a circuit, component, or device is “operable” to perform a function, provided that the circuit, component, or device includes the hardware and code (if required) or other elements necessary to perform that function, regardless of whether the performance of that function is disabled or not enabled (e.g., through user-configurable settings, factory adjustments, configurations, etc.).

[0038] The present disclosure has been described above with reference to various embodiments. However, the invention is not necessarily limited to the embodiments described and depicted herein. Rather, the invention is limited only by the appended claims.

Claims

1. A perspective-type near-eye display device, the perspective-type near-eye display device comprising: An image source, configured to emit light carrying an image; A one-dimensional waveguide, which is made of a crystalline material that transmits visible light and is arranged to receive and guide the light emitted by the image source; A first grating is disposed on or in the waveguide, and the first grating is configured to couple at least a portion of the light from the image source out of the waveguide after it has been guided to the first grating by the waveguide.

2. The apparatus according to claim 1, wherein the crystal material is a single crystal.

3. The apparatus according to claim 2, wherein the single crystal contains bismuth, germanium and oxygen.

4. The apparatus of claim 2, wherein the single crystal is doped or undoped. Crystals, in which .

5. The apparatus according to claim 4, wherein... The crystal is doped with one or more of boron, aluminum, gallium and indium.

6. The apparatus according to claim 4, wherein... The crystal is doped with only one or both of boron and aluminum.

7. The apparatus according to claim 5, wherein... The crystal is characterized by a doping concentration of less than 5%.

8. The apparatus of claim 2, wherein the single crystal is doped or undoped. .

9. The apparatus of claim 2, wherein the single crystal is doped or undoped. .

10. The apparatus of claim 2, wherein the single crystal is cubic zirconium oxide.

11. The apparatus of claim 2, wherein the single crystal is used... Stabilized cubic zirconia.

12. The apparatus of claim 2, wherein the single crystal is used... Stabilized cubic zirconia.

13. The apparatus of claim 1, wherein the crystal material has a refractive index of at least 2.0 over the entire wavelength range of 430 nm to 760 nm.

14. The apparatus of claim 13, wherein the crystal material has a wavelength of less than 430 nm over the entire wavelength range of 760 nm. The absorption coefficient.

15. The apparatus of claim 1, wherein the crystal material has a refractive index of at least 2.0 over the entire wavelength range of 400 nm to 800 nm.

16. The apparatus of claim 15, wherein the crystal material has a wavelength of less than 400 nm over the entire wavelength range of 400 nm to 800 nm. The absorption coefficient.

17. The apparatus of claim 1, wherein the waveguide has a first surface and a second surface facing away from each other, and total internal reflection of the light at the first surface and the second surface results in one-dimensional waveguide transmission of the light.

18. The apparatus of claim 17, wherein the first grating is located at one of the first surface and the second surface.

19. The apparatus of claim 1, further comprising a second grating disposed on or in the waveguide, the second grating being configured to couple the light from the image source into the waveguide such that the light is guided by the waveguide to the first grating.

20. The apparatus of claim 19, wherein the first grating and the second grating are separated from each other by a non-zero distance.

Images