阅读说明：本技术 包括厚介质的虚拟现实、增强现实和混合现实系统及相关方法 (Virtual reality, augmented reality, and mixed reality systems including thick media and related methods ) 是由 P·圣西莱尔 于 2017-09-07 设计创作，主要内容包括：本公开涉及包括厚介质的虚拟现实、增强现实和混合现实系统及相关方法。头戴式成像系统包括被配置为产生光束的光源。该系统还包括光导光学元件,其具有在0.1mm和1.5mm之间的厚度,并且被配置为通过全内反射传播光束的至少一部分。该系统还包括光导光学元件的进入部分和离开部分,其被配置为基于光的入射角、光的曲率半径和/或光的波长选择性地允许访问离开部分的光离开光导光学元件。(The present disclosure relates to virtual reality, augmented reality, and mixed reality systems including thick media and related methods. The head-mounted imaging system includes a light source configured to generate a light beam. The system also includes a light guide optical element having a thickness between 0.1mm and 1.5mm and configured to propagate at least a portion of the light beam by total internal reflection. The system also includes an entry portion and an exit portion of the light guide optical element configured to selectively allow light accessing the exit portion to exit the light guide optical element based on an angle of incidence of the light, a radius of curvature of the light, and/or a wavelength of the light.)

1. A head-mounted imaging system, comprising:

a light source configured to generate a light beam;

a light-guiding optical element having a thickness between 0.1mm and 1.5mm and comprising an entry portion and an exit portion,

wherein the light guide optical element is configured to propagate at least a portion of the light beam by total internal reflection.

2. The system of claim 1, wherein the light guide optical element allows multiplexing of light having multiple angles of incidence through the light guide optical element.

3. The system of claim 1 or 2, wherein the light guide optical element allows multiplexing of light having a plurality of wavelengths through the light guide optical element.

4. The system of any of claims 1 to 3, wherein the light guide optical element allows multiplexing of light having a plurality of radii of curvature through the light guide optical element.

5. The system of any of claims 1-4, wherein the exit portion comprises an out-coupling grating corresponding to a particular depth plane.

6. The system of any of claims 1-5, further comprising:

a variable focus element configured to adjust a curvature of the light beam by adjusting at least one focal point before the light beam enters the light guide optical element through the entry portion.

7. The system of any of claims 1-6, wherein a portion of the light beam is selected to exit the light guide optical element based at least on a thickness of the light guide optical element or in-coupling grating.

Background

Modern computing and display technologies have facilitated the development of systems for so-called "mixed reality" (MR), "virtual reality" (VR), and "augmented reality" (AR) experiences. This may be accomplished by the head mounted display presenting a computer generated image to the user. The image creates a sensory experience that immerses the user in the simulated environment. VR scenes typically involve only the presentation of computer-generated images, and not actual real-world images as well.

AR systems typically supplement the real world environment with simulation elements. For example, the AR system may provide a view of the surrounding real-world environment to the user via the head-mounted display. However, computer-generated images may also be presented on the display to augment the real-world environment. Such computer-generated images may include elements that are contextually relevant to the real-world environment. These elements may include simulated text, images, objects, and the like. MR systems also introduce simulated objects into the real-world environment, but these objects are often characterized by a greater degree of interactivity than AR systems. The elements of the simulation can often interact in real time. The human visual perception system is very complex, and it is therefore challenging to develop VR/AR/MR techniques that facilitate comfortable, natural-feeling, rich presentation of virtual images in other virtual or real-world image elements. The visual center of the brain derives valuable perceptual information from the movement of the two eyes and their components relative to each other. Vergence movement of the two eyes relative to each other (i.e., rolling movement of the pupils toward or away from each other to focus on an object with converging eye lines) is closely related to the focusing (or "accommodation") of the eye's lens. Under normal circumstances, changing the focus of the eye lens to accommodate the eye to focus on objects at different distances will automatically cause matching changes in vergence to the same distance under a relationship known as "accommodation-vergence reflex". Also, under normal circumstances, a change in vergence will cause a matching change in accommodation. As with most conventional stereoscopic VR/AR/MR configurations, countering such reflections is known to produce eye strain, headaches, or other forms of discomfort in the user.

Stereoscopic wearable glasses typically have two displays for the left and right eye, configured to display images with slightly different element presentations so that the human visual system perceives a three-dimensional viewing angle. Such a configuration has been found to be uncomfortable for many users because there is a mismatch between vergence and accommodation ("vergence-accommodation conflict") that must be overcome to perceive the image in three dimensions. Indeed, some users cannot tolerate stereoscopic configurations. These limitations apply to VR, AR and MR systems. Thus, most conventional VR/AR/MR systems are not best suited to present a rich binocular three-dimensional experience in a manner that is comfortable and maximally useful to the user, in part because existing systems fail to address some of the fundamental aspects of the human perception system, including vergence-accommodation conflicts.

The VR/AR/MR system must also be able to display virtual digital content at various perceived locations and distances relative to the user. The design of VR/AR/MR systems also introduces many other challenges, including the speed at which the system provides the virtual digital content, the quality of the virtual digital content, the eye relief of the user (resolving the vergence-accommodation conflict), the size and portability of the system, and other system and optical challenges.

One possible approach to solving these problems, including vergence-accommodation conflicts, is to project light to the user's eye using multiple light guide optical elements, such that the light and the image rendered by the light appear to originate from multiple depth planes. The light guide optical element is designed to incouple virtual light corresponding to a digital or virtual object and propagate it by total internal reflection ("TIR"), and then to outcouple the virtual light in order to display the digital or virtual object to the user's eye. In AR/MR systems, the light guide optical element is also designed to be transparent to light from (e.g., reflect) the actual real world object. Thus, in an AR/MR system, a portion of the light guide optical element is designed to reflect virtual light for propagation via TIR while being transparent to real world light from real world objects.

To implement multiple light guide optical element systems, light from one or more sources must be controllably distributed to each light guide optical element system. One approach is to project an image using a large number of optical elements (e.g., light sources, prisms, gratings, filters, scanning optics, beam splitters, mirrors, half mirrors, shutters, eyepieces, etc.) with a sufficient number (e.g., six) of depth planes. The problem with this approach is that the use of a large number of components in this manner necessarily requires a larger than desired form factor and limits the extent to which the system size can be reduced. The large number of optical elements in these systems also results in a longer optical path over which the light and the information contained therein will be clipped. These design problems result in cumbersome power hungry systems. The systems and methods described herein are configured to address these challenges.

Disclosure of Invention

Embodiments of the present invention provide improved systems configured to incouple and outcoupling light having a narrow range of light curvatures, directions, and/or wavelengths to achieve selectivity in incident angle, radius of curvature, and/or wavelength by using a single thick (e.g., about 0.1 millimeters to about 1.5 millimeters or "mm" thick) light guide optical element (e.g., a waveguide). Due to the large dynamic range of materials, waveguides allow multiplexing of multiple focal planes and/or wavelengths. Since the thickness of the material forming the light-guiding optical element facilitates the selectivity of angle or/and wavelength, only a part of the light propagating along the waveguide is outcoupled. Thus, light beams corresponding to a narrow range of angles and field curvatures and/or a narrow range of wavelengths will be outcoupled from the waveguide. The waveguide facilitates the formation of incoupling and outcoupling gratings that preserve angle and wavefront curvature, which allows precise control of the position and direction of the individual rays used for incoupling and outcoupling. Thus, multiple viewing planes can be multiplexed using a single thick lightguide optical element with multiple out-coupling gratings in a single polymer layer.

In one embodiment, a head-mounted imaging system includes a light source configured to generate a light beam. The system also includes a light guide optical element having a thickness between 0.1mm and 1.5 mm. The light guide optical element includes an entry portion and an exit portion. The light guide optical element is configured to propagate at least a portion of the light beam by total internal reflection. The exit portion of the light guide optical element is configured to selectively allow light accessing the exit portion to exit the light guide optical element based on an angle of incidence of the light.

In another embodiment, a head-mounted imaging system includes a light source configured to generate a light beam. The system also includes a light guide optical element having a thickness between 0.1mm and 1.5 mm. The light guide optical element includes an entry portion and an exit portion. The light guide optical element is configured to propagate at least a portion of the light beam by total internal reflection. The exit portion of the light guide optical element is configured to selectively allow light accessing the exit portion to exit the light guide optical element based on a wavelength of the light.

In yet another embodiment, a head-mounted imaging system includes a light source configured to generate a light beam. The system also includes a light guide optical element having a thickness between 0.1mm and 1.5 mm. The light guide optical element includes an entry portion and an exit portion. The light guide optical element is configured to propagate at least a portion of the light beam by total internal reflection. The exit portion of the light guide optical element is configured to selectively allow light accessing the exit portion to exit the light guide optical element based on a radius of curvature of the light.

In one or more embodiments, the light guide optical element allows multiplexing of light having multiple focal planes through the light guide optical element. The light guide optical element may allow light having multiple wavelengths to be multiplexed by the light guide optical element. The light guide optical element may allow light having multiple radii of curvature to be multiplexed through the light guide optical element. The exit portion may comprise an out-coupling grating corresponding to a particular depth plane.

In one or more embodiments, the system further includes a variable focus element configured to adjust the curvature of the light beam by adjusting at least one focal point before the light beam enters the light guide optical element through the entrance portion. Based at least on the thickness of the light guide optical element or the in-coupling grating, a portion of the light beam may be selected to exit the light guide optical element.

Further details of aspects, objects and advantages of the invention are described below in the detailed description, drawings and claims. The foregoing general description and the following detailed description are exemplary and explanatory and are not intended to limit the scope of the invention.

Drawings

The drawings illustrate the design and utility of various embodiments of the present invention. It should be noted that the figures are not drawn to scale and that elements of similar structure or function are represented by like reference numerals throughout the figures. In order to better appreciate how the above-recited and other advantages and objects of various embodiments of the present invention are obtained, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered to be limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings, in which:

FIG. 1 is a detailed schematic diagram of an optical system according to one embodiment.

FIG. 2 illustrates angular multiplexing using a single thick optical element, according to one embodiment.

Figure 3 illustrates curvature multiplexing using a single thick optical element, according to one embodiment.

FIG. 4 illustrates spectral multiplexing using a single thick optical element, according to one embodiment.

FIG. 5 is a schematic diagram depicting a focal plane of an optical system, in accordance with one embodiment.

FIG. 6 is a detailed schematic diagram of a light guide optical element of an optical system according to one embodiment.

FIG. 7 is a detailed perspective view of a light guide optical element of an optical system according to one embodiment.

Detailed Description

Various embodiments will now be described in detail with reference to the drawings, which are provided as illustrative examples of the invention so as to enable those skilled in the art to practice the invention. It is noted that the following figures and examples are not meant to limit the scope of the present invention. Where certain elements of the present invention can be partially or fully implemented using known components (or methods or processes), only those portions of such known components (or methods or processes) that are necessary for an understanding of the present invention will be described, and detailed descriptions of other portions of such known components (or methods or processes) will be omitted so as not to obscure the invention. Furthermore, the various embodiments encompass current and future known equivalents to the components referred to herein by way of illustration.

Various embodiments will now be described in detail with reference to the drawings, which are provided as illustrative examples of the invention so as to enable those skilled in the art to practice the invention. It is noted that the following figures and examples are not meant to limit the scope of the present invention. Where certain elements of the present invention can be partially or fully implemented using known components (or methods or processes), only those portions of such known components (or methods or processes) that are necessary for an understanding of the present invention will be described, and detailed descriptions of other portions of such known components (or methods or processes) will be omitted so as not to obscure the invention. Furthermore, the various embodiments encompass current and future known equivalents to the components referred to herein by way of illustration.

The optical system described herein may be implemented independently of a VR/AR/MR system, but is for illustrative purposes only, and many of the embodiments below are described with respect to a VR/AR/MR system.

Problem and solution

An optical system for generating images at various depths includes an increasing number of many optical components (e.g., light sources, prisms, gratings, filters, scanning optics, beam splitters, mirrors, half mirrors, shutters, oculars, etc.), so as the quality of the 3D experience/scene (e.g., the number of imaging planes) and the image quality (e.g., the number of image colors) increase, the complexity, size, and cost of VR/AR/MR systems increase. As 3D scene/image quality improves, the size of the optical system increases, which limits the size of the VR/AR/MR system, resulting in a cumbersome system with reduced optical efficiency.

To implement a multiple light guide optical element head mounted imaging system, light from one or more sources must be controllably distributed. Conventional solutions involve the use of systems that utilize various light distribution systems (including various system components and designs) to reduce the size of the optical system while selectively distributing light from one or more light sources to multiple light guide optical elements (e.g., planar waveguides) needed to render a high quality VR/AR/MR scene. A problem with these multiple-lightguide optical element type systems is that the thin diffractive element has little spectral and angular selectivity in the diffraction of light propagating along the waveguide. This limits the ability of a single waveguide to provide multiple view planes and/or primary colors.

Thus, in conventional solutions, multiple waveguides are required to provide multiple view planes and primary colors. Conventional systems create multiple depth planes by using stacked light guide optical element ("LOE") assemblies, each LOE configured to display an image that appears to originate from a particular depth plane. It should be noted that the stack may include any number of LOEs. However, at least N stacked LOEs are required to generate N depth planes. Furthermore, N, 2N, or 3N stacked LOEs may be used to generate RGB color images at N depth planes. However, the use of multiple waveguides creates a number of problems, such as requirements for a multi-planar switching element, difficulty in aligning layers, thickness of the resulting eyepiece, and scattering effects from multiple surface reflections.

The following disclosure describes various embodiments of systems and methods for creating 3D perception using a single thick lightguide optical element that solves the above-described problems by providing an optical system with fewer parts and higher efficiency. In particular, the systems described herein utilize a single thick lightguide optical element to reduce the number of optical system components while selectively distributing light from one or more light sources to lightguide optical elements needed to render a high quality VR/AR/MR scene based on the angle of incidence, radius of curvature, and wavelength of the light.

Illustrative optical system

Before describing the details of embodiments of the light distribution system, the present disclosure will now provide a brief description of an illustrative optical system. Although embodiments may be used with any optical system, a specific system (e.g., a VR/AR/MR system) is described to illustrate the underlying technology of the embodiments.

To present 3D virtual content to a user, the VR/AR/MR system projects images of the virtual content into the user's eyes such that they appear to originate from respective depth planes in the Z-direction (i.e., orthogonally away from the user's eyes). In other words, the virtual content may not only change in the X and Y directions (i.e., in a 2D plane orthogonal to the central visual axis of the user's eyes), but it may also appear to change in the Z direction, such that the user may perceive the object as being very close or at an infinite distance or any distance therebetween. In other embodiments, a user may perceive multiple objects at different depth planes simultaneously. For example, the user may see that a virtual dragon appears from infinity and runs towards the user. Alternatively, the user may see a virtual bird 3 meters away from the user and a virtual coffee cup about 1 meter from the user's arm length at the same time.

The multi-plane focusing system creates a perception of variable depth by projecting images on some or all of a plurality of depth planes located at respective fixed distances in the Z direction from the user's eyes. Referring now to fig. 5, it should be appreciated that a multi-plane focusing system typically displays frames at fixed depth planes 502 (e.g., the six depth planes 502 shown in fig. 5). Although the VR/AR/MR system may include any number of depth planes 502, one exemplary multi-plane focusing system has six fixed depth planes 502 in the Z-direction. As the six depth planes 502 generate one or more virtual content, a 3D perception is created such that the user perceives one or more virtual objects at different distances from the user's eyes. Assuming that the human eye is more sensitive to objects that appear farther away than objects that are closer together, a plurality of depth planes 502 are generated closer to the eye, as shown in FIG. 5. In other embodiments, the depth planes 502 may be placed at equal distances from each other.

Depth plane location 502 is typically measured in diopters, which is a unit of power equal to the reciprocal of the focal length measured in meters. For example, in one embodiment, depth plane 1 may be 1/3 diopters, depth plane 2 may be 0.3 diopters, depth plane 3 may be 0.2 diopters, depth plane 4 may be 0.15 diopters, depth plane 5 may be 0.1 diopters, and depth plane 6 may represent infinity (i.e., 0 diopters). It should be understood that other embodiments may generate the depth plane 502 at other distances/diopters. Thus, the user is able to perceive a three-dimensional virtual object when generating virtual content at the strategically placed depth plane 502. For example, when displayed in depth plane 1, the user may perceive a first virtual object as being close to him, while another virtual object appears at infinity at depth plane 6. Alternatively, the virtual object may be displayed first at depth plane 6, then at depth plane 5, and so on until the virtual object appears very close to the user. It should be appreciated that the above examples are significantly simplified for illustrative purposes. In another embodiment, all six depth planes may be centered at a particular focal distance away from the user. For example, if the virtual content to be displayed is a coffee cup half a meter away from the user, all six depth planes may be generated at various cross-sections of the coffee cup, providing the user with a highly granular 3D view of the coffee cup.

In one embodiment, the VR/AR/MR system can be used as a multi-plane focusing system. In other words, a single LOE 190 is illuminated such that images that appear to originate from six fixed depth planes are generated simultaneously with the light source that rapidly passes image information to the LOE. For example, a portion of a desired image including an image of the sky at optical infinity may be injected at time 1, and a LOE 190 (e.g., depth plane 6 of fig. 5) that maintains collimation of the light may be utilized. Then, an image of the closer branches may be injected at time 2, and the LOE 190 configured to create an image that appears to originate from a depth plane 10 meters away (e.g., depth plane 5 of fig. 5) may be utilized; next, an image of the pen may be injected at time 3, and a LOE configured to create an image that appears to originate from a depth plane 1 meter away may be utilized. This type of paradigm can be repeated in a fast time sequential (e.g., 360Hz) fashion, such that the user's eyes and brain (e.g., visual cortex) perceive the input as all of the same image.

Some VR/AR/MR systems project (i.e., by diverging or converging beams) images that appear to originate from various locations (i.e., depth planes) along the Z-axis to generate images for a 3D experience. As used in this application, a "beam" of light or "line" of light includes, but is not limited to, a directional projection of light energy (including visible and invisible light energy) radiated from a light source. Generating images that appear to originate from various depth planes conforms to the vergence and accommodation of the images by the user's eyes and minimizes or eliminates vergence-accommodation conflicts.

One possible approach to implementing a VR/AR/MR system is to use a single thick-volume phase hologram, or light-guide optical element ("LOE") embedded with gratings corresponding to different depth plane information, to generate images that appear to originate from the various depth planes. In other words, a diffractive pattern or diffractive optical element ("DOE") can be embedded within or imprinted on the LOE such that when light is substantially totally internally reflected along the LOE, it intersects the diffractive pattern at a plurality of locations and exits toward the user's eye. The DOE is configured such that light emerging therethrough from the LOE is edged (verse) such that they appear to originate from a particular depth plane.

A thick LOE also allows the DOE (e.g., in-coupling and out-coupling gratings) to maintain the curvature of the wavefront over the entire wavelength. This allows the light to be focused before entering the LOE, thereby minimizing the thickness of the display by moving the variable focal length element ("VFE") away from the "lens" of the glasses. In this manner, controlling the direction and curvature of the light coupled into the eyepiece will correspond directly to the direction and curvature of the individual rays that will emerge from the "lens" of the eyeglasses.

The eyepiece (i.e., LOE) applies the principle of edge-illuminated holography by using an edge-introduced reference beam for recording and a similar illumination beam for display to allow for a simplified display configuration. Such displays integrate a hologram (i.e., LOE), its supporting display structure, and an illumination source into a compact device.

Traditionally, reflection holograms and transmission holograms are considered to be of different types, each having its own unique optical characteristics. A key difference between reflection holograms and transmission holograms is the geometric orientation of their fringes. The direct reason is the different directions of their respective reference beams, since the transmission type propagates perpendicular to the plane of the hologram and the reflection type propagates parallel to the plane of the hologram.

The system also uses Kogelnik's coupled wave theory to exploit diffraction in volume gratings and holograms. The theory of Kogelnik assumes that only two plane waves propagate inside and outside the finite thickness grating. Kogelnik's coupled-wave theory is a successful approach to understanding diffraction in sinusoidal volume gratings and to provide an analytical formula for calculating diffraction efficiency. The first wave is assumed to be the illumination "reference" wave and the second "signal" wave is the response of the hologram. The duplex wave assumption is based on the following assumptions: coupling to higher order modes is negligible.

FIG. 1 depicts a basic optical system 100 for projecting an image at a single depth plane. System 100 includes an optical source 120 and a LOE 190, LOE 190 having an in-coupling grating 192 ("ICG") and an out-coupling grating 198 ("OCG"). Light source 120 may be any suitable imaging light source including, but not limited to, DLP, LCOS, LCD, and fiber optic scanning displays. Such a light source may be used with any of the systems 100 described herein. ICG192 and OCG 198 may be any type of diffractive optical element, including volume or surface relief. ICG192 and OCG 198 may be reflective mode aluminized portions of LOE 190. Alternatively, ICG192 and OCG 198 may be transmissive diffractive portions of LOE 190. When system 100 is in use, virtual light beam 210 from light source 120 enters LOE 190 via ICG192, propagates along LOE 190 by substantial total internal reflection ("TIR") and exits LOE 190 via OCG 198 for display to the user's eye. The beam 210 is virtual in that it encodes an image or a portion thereof according to the instructions of the system 100. It should be understood that although only one beam is shown in FIG. 1, multiple beams of encoded images may enter the LOE 190 from a wide range of angles through the same ICG192 and exit through one or more OCGs 198. Light beams that "enter" or are "admitted" into the LOE include, but are not limited to, light beams that interact with the LOE so as to propagate along the LOE by substantial TIR. The system 100 depicted in fig. 1 may include various light sources 120 (e.g., LEDs, OLEDs, lasers, and masked broad area/broadband emitters). Light from the light source 120 may also be transmitted to the LOE 190 via a fiber optic cable (not shown).

Thick media for EDGE

Fig. 2 depicts angular multiplexing using a single thick lightguide optical element 190. In some embodiments, the thick optical element has a thickness between about 0.1mm to about 1.5 mm. In other embodiments, the thickness of the thick optical element is about 0.5 mm. Thick holographic optical elements enable more precise selectivity in the angle, radius of curvature and wavelength of light directed therethrough. By controlling the direction and curvature of the light coupled into the waveguide, the system can control the direction and curvature of the individual rays to be coupled out of the waveguide. The system can also produce very efficient holograms (i.e., images that appear to originate from different depth planes) with small modulation indices. The hologram is formed by modulating the refractive indices of the bulk material and the grating in very small proportions.

A thick LOE selects light according to various properties (e.g., wavelength, radius of curvature, and/or in-coupling angle), allowing the system to control light output through the waveguide. Due to the large dynamic range of the material, multiple focal planes and wavelengths (e.g., colors) are allowed to be multiplexed by a single element. In some embodiments, the material dynamic range is 0.01 modulation, so that more holograms can be multiplexed for a given diffraction efficiency multiplex. The advantage of using a single thick holographic optical element is that only one waveguide is required due to the high selectivity of angle and wavelength and the preservation of wave curvature throughout the waveguide.

Both reflection (in which diffracted light exits from the same side as the incident ray) and transmission (in which diffracted light exits from the opposite side as the incident ray) geometric holograms can be implemented using waveguides. As described by Kogelnik's coupled wave theory, reflection holograms are preferably used to achieve wavelength selectivity.

As shown in fig. 2, only light rays corresponding to a very narrow range of angles and radii of curvature are coupled out of the waveguide. By controlling the range of angles of incidence, the range of wavelengths, and the range of radii of curvature of the light generated by the light source, the system can control the direction and curvature of each light ray 203 that will be outcoupled from the waveguide. Only a few rays are diffracted out because the selectivity of the beam is determined by the thickness of the material forming the light guide optical element 190 and the optical elements formed therein.

The LOE may be selective over the entire range of light propagation within the waveguide. The range of radii of curvature for which the LOE is selective depends on the thickness of the polymer layer 205 in which the grating is formed. For example, for a thick LOE having a 1mm thick polymer layer, the radius of curvature of the LOE may range from about 1 m. The wavelength selectivity of the LOE depends on whether the LOE is used in a transmissive mode or a reflective mode, and the curvature of the hologram. In the reflective mode, the wavelength selectivity can be as small as a few nanometers. The sensitivity of the LOE to differences in incident angle, radius of curvature, and wavelength depends on the geometry of the LOE and can affect each other.

As described above, the position and direction of each outgoing ray 203 can be controlled because the waveguide maintains angle and wavefront curvature, allowing the position and direction of each outgoing ray to be selectively controlled by controlling the input light. Thus, multiple viewing plane pupils can be multiplexed at multiple grating positions to achieve pupil expansion.

The system may also change the depth plane by controlling the curvature (i.e., radius of curvature) of the light of the spherical rays diffracted by the hologram. In prior art systems, the plane wave (i.e., of collimated light) does not have any curvature. However, this system allows the curvature of a particular wavefront to be matched to particular rays entering different directions.

Grating 207 may be written into polymer layer 205 based on an interference beam that produces an interference pattern. The grating 207 may diffract the respective beams into multiple places, one place, or not at all, depending on various characteristics of the input beams. Each grating 207 diffracts a set of light beams from a predetermined input direction to another predetermined selectable output direction. Thus, only a narrow beam will be diffracted by the grating 207 in the polymer layer 205. Light interacting with a volume within the entire depth of the polymer material allows the beam components to add constructively. The polymeric material may have a thickness of about 0.1mm to about 1.5 mm. Only first order in-coupling and first order out-coupling of the beam is allowed here. In addition, the system may utilize the superposition of the LOE and the polymer layer 205 in which the grating 207 is formed to extend the viewing angle of transmitted or reflected light outside the hologram based on the input of the light.

Multiplexing allows the system to generate images at various depth planes using a single eyepiece, thereby changing the apparent depth of the virtual object. In some embodiments, the system will include a Variable Focusing Element (VFE) capable of adjusting the wavefront curvature of the light being incoupled into the waveguide. The VFE may be configured to change the focus (i.e., wavefront curvature) of the projected light and deliver the light to the user's eye. Also as described above, the input grating may be programmed such that only light of a particular angle and wavelength is in-coupled. Angular multiplexing also enables compensation of distortions of the input objective lens.

Figure 3 depicts curvature multiplexing using a single thick optical element 301. The volume hologram is thick enough to preserve the wavefront curvature of the light incoupled into the waveguide 301. In some embodiments, the system can control the curvature of each light ray 303 that will be outcoupled from the waveguide 301 by controlling the range of angles of incidence, the range of wavelengths, and the range of radii of curvature of the light generated by the light source based on the pattern of the grating. In some embodiments, the individual light rays 305 will not be outcoupled from the waveguide 301 due to the selected angle of the grating. Only a few selectable curvature rays (e.g., 303) are outcoupled based on, for example, selectivity of beam angle.

In some embodiments, the system will multiplex multiple depth planes in a single eyepiece/waveguide. However, the system cannot use only existing waveguides and gratings because they only accept straight waves (i.e., collimated beams) that will be diffracted in parallel. This way no depth is created using a single waveguide. In another aspect, the disclosed system matches an output wavefront curvature to an input wavefront curvature. The hologram may be configured to diffract a piece of light only if the light has a predetermined direction, angle, and curvature into the eyepiece.

As described above, since the waveguide is selectable in both angle and wavefront curvature, the position and curvature of each exiting ray 303 can be controlled, allowing selective control of the position and curvature of each exiting ray by controlling the range of angles of incidence of the input ray and the range of radii of curvature of the input ray. Thus, multiplexing of curvatures can be maintained at multiple grating positions.

Fig. 4 depicts spectral multiplexing using a single thick optical element. Volume holograms are particularly sensitive to spectra. In some embodiments, this allows multiplexing of the R401, G403, and B405 color components in a single layer waveguide. In other embodiments, dispersion compensation may allow for the use of a wider bandwidth light source, such as a superluminescent light emitting diode ("SLED or SLD") or a chaotic laser, to reduce speckle.

Pupil expander

As shown in FIG. 6, portions of the LOE 190 described above may be used as an exit pupil expander 196 ("EPE") to increase the numerical aperture of the light source 120 in the Y direction, thereby increasing the resolution of the system 100. Because the light source 120 produces light of a small diameter/spot size, the EPE196 expands the apparent size of the pupil of the light exiting the LOE 190, thereby increasing the system resolution. In addition to EPE196, VR/AR/MR system 100 may also include an orthogonal pupil expander 194 ("OPE") to expand the light in the X-direction (OPE) and the y (EPE) directions. Further details regarding EPE196 and OPE 194 are described in the above-referenced U.S. utility patent application serial No. 14/555,585 and U.S. utility patent application serial No. 14/726,424, the contents of which have been previously incorporated herein by reference.

FIG. 7 depicts another optical system 100 that includes a LOE 190 with an ICG192, an OPE 194, and an EPE 196. The system 100 also includes a light source 120 configured to direct a virtual light beam 210 into the LOE 190 via the ICG 192. As described above with respect to fig. 6, beam 210 is split into beamlets 210' by OPE 194 and EPE 196. In addition, as beamlets 210 'propagate through EPE196, they also exit LOE 190 via EPE196 toward the user's eye. For clarity, only selection beam 210 and beamlet 210' are labeled.

The VR/AR/MR systems described above are provided as examples of various optical systems that may benefit from more selectively reflective optical elements. Thus, use of the optical system described herein is not limited to the disclosed VR/AR/MR system, but is applicable to any optical system.

Various example embodiments of the invention are described herein. Reference is made to these examples in a non-limiting sense. Examples are provided to illustrate more broadly applicable aspects of the present invention. Various changes may be made and equivalents may be substituted for elements thereof without departing from the true spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation, material, composition of matter, process action or steps, to the objective, spirit or scope of the present invention. Further, as will be appreciated by those of skill in the art, each of the individual variations described and illustrated herein has individual components and features which may be readily separated from or combined with the features of any of the other several embodiments without departing from the scope and spirit of the present invention. All such modifications are intended to be within the scope of the claims associated with this disclosure.

The invention includes methods that may be performed using a subject device. The method may include the act of providing such a suitable device. Such provisioning may be performed by the end user. In other words, the act of "providing" requires only the obtaining, accessing, processing, locating, setting, activating, powering on, or other act of the end user to provide the necessary means in the method. The methods described herein may be performed in any order of events that is logically possible and in the order of events described.

Example aspects of the invention and details regarding material selection and fabrication have been described above. Additional details of the invention can be found in conjunction with the above-referenced patents and publications and as generally known or understood by those skilled in the art. The same is true with respect to the method-based aspects of the invention, in respect of additional actions as commonly or logically employed.

Furthermore, while the invention has been described with reference to several examples that optionally include various features, the invention is not limited to being described or shown as contemplated for each variation of the invention. Various changes may be made to the invention described and equivalents (whether set forth herein or otherwise included for the purpose of brevity) may be substituted without departing from the true spirit and scope of the invention. Further, if a range of values is provided, it is understood that each intervening value, between the upper and lower limit of that range and any other intervening value in that stated range, is encompassed within the invention.

Furthermore, it is contemplated that any optional feature of the described inventive variations may be set forth and claimed independently or in combination with any one or more of the features described herein. Reference to a singular item includes a plural of the same item that may be present. More specifically, as used herein and in the appended claims, the singular forms "a," "an," and "the" include plural referents unless the content clearly dictates otherwise. In other words, in the above description and in the claims relating to the present disclosure, use of the article allows "at least one" of the target item. It is also noted that such claims may be drafted to exclude any optional element. Accordingly, this statement is intended to serve as antecedent basis for use of such exclusive terminology as "solely," "only," and the like, or use a "negative" limitation in connection with the recitation of claim elements.

The term "comprising" in the claims relating to the present disclosure should be allowed to include any other elements irrespective of whether a given number of elements are listed in such claims, or the added features may be considered to transform the nature of the elements recited in the claims, without using such exclusive terms. Unless specifically defined herein, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this invention belongs.

The present invention is not limited to the examples provided and/or this specification, but is only limited by the scope of the claim language associated with this disclosure.

In the foregoing specification, the invention has been described with reference to specific embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention. For example, the processes described above are described with reference to a particular order of process actions. However, the order of many of the described process actions may be varied without affecting the scope or operation of the invention. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.