Projector architecture incorporating artifact mitigation

An eyepiece unit with optical filters includes a set of waveguide layers including a first waveguide layer and a second waveguide layer. The first waveguide layer is disposed in a first lateral plane and includes a first incoupling diffractive element disposed at a first lateral position, a first waveguide, and a first outcoupling diffractive element. The second waveguide layer is disposed in a second lateral plane adjacent to the first lateral plane and includes a second incoupling diffractive element disposed at a second lateral position, a second waveguide, and a second outcoupling diffractive element. The eyepiece unit also includes a set of optical filters including a first optical filter positioned at the first lateral position and operable to attenuate light outside a first spectral band and a second optical filter positioned at the second lateral position and operable to attenuate light outside a second spectral band.

BACKGROUND OF THE INVENTION

Modern computing and display technologies have facilitated the development of systems for so-called “virtual reality” or “augmented reality” experiences, wherein digitally produced images or portions thereof are presented in a wearable device to a user in a manner wherein they seem to be, or may be perceived as, real. A virtual reality, or “VR,” scenario typically involves presentation of digital or virtual image information without transparency to other actual real-world visual input; an augmented reality, or “AR,” scenario typically involves presentation of digital or virtual image information as an augmentation to visualization of the actual world around the user.

Despite the progress made in these display technologies, there is a need in the art for improved methods and systems related to augmented reality systems, particularly, display systems.

SUMMARY OF THE INVENTION

The present disclosure relates generally to methods and systems related to projection display systems including wearable displays. More particularly, embodiments of the present disclosure provide methods and systems for eyepiece units with one or more integrated polarizers and improved system performance. In other embodiments, a white light source is used in conjunction with an LCOS-based projector and a shutter operating in synchronization with the LCOS-based projector. The disclosure is applicable to a variety of applications in computer vision and image display systems.

In some projection display systems, light from a projector can be coupled into an eyepiece, which, in turn, projects images to a viewer's eye. In addition to light from the projector that is intended for the viewer's eye, light originating from sources other than the projector, for example, light from overhead lights near the viewer and/or light from unintended reflections from components within the projector, may be coupled into/within the eyepiece, thereby creating artifacts that are presented to the viewer.

Accordingly, in order to reduce the impact of such artifacts, embodiments of the present disclosure utilize optical elements, for example, a circular polarizer disposed in the optical path of the projection display to reduce the intensity of artifacts. In some embodiments, a split pupil design incorporating color filters is utilized that enables spectral filtering at sub-pupil locations of a distributed pupil system to mitigate artifacts.

In some embodiments, an eyepiece is provided that includes one or more optical filters for color separation between different waveguides of the eyepiece. The eyepiece may also utilize spatial positioning of the optical filters to reduce wavelength cross-coupling. Moreover, in some embodiments, a projection display utilizes a white light source, a liquid crystal on silicon (LCOS)-based projector, and a shutter operating in synchronization with the LCOS-based projector to reduce or eliminate artifacts. The disclosure is applicable to a variety of applications in computer vision and image display systems.

Numerous benefits are achieved by way of the present disclosure over conventional techniques. For example, embodiments of the present disclosure provide methods and systems that reduce or eliminate artifacts including ghost images in projection display systems. Additionally, embodiments of the present disclosure reduce eye strain, reduce artifacts due to stray light, and improve resolution, dynamic range, color accuracy, ANSI contrast, and general signal to noise of the displayed images or videos.

In some embodiments, methods and systems are provided that reduce wavelength cross-coupling, resulting in enhanced brightness and contrast. Further, some embodiments of the present disclosure provide methods and systems that can reduce stray light to achieve improved contrast. Moreover, in some embodiments, improved color saturation of images can be achieved using more saturated color filters.

In some embodiments, LCOS-based wearable display systems are provided that are characterized by high fill factors and bright images, thereby, improving the user experience. Further, some embodiments provide a larger pupil size, which can provide better image resolution and quality. Moreover, embodiments of the present disclosure can also provide flexibility of using a white LED or RGB LEDs as elements of a projection system as well as providing ghost mitigation. These and other embodiments of the disclosure along with many of its advantages and features are described in more detail in conjunction with the text below and attached figures.

DETAILED DESCRIPTION

The Figures (FIGS.) and the following description relate to various embodiments by way of illustration only. It should be noted that from the following discussion, alternative embodiments of structures and methods disclosed herein will be readily recognized as viable alternatives that can be employed without departing from the principles discussed herein. Reference will now be made in detail to several embodiments, examples of which are illustrated in the accompanying figures.

FIG. 1schematically illustrates light paths in a viewing optics assembly (VOA) that may be used to present a digital or virtual image to a viewer, according to some embodiments. The VOA includes a projector101and an eyepiece100that may be worn around a viewer's eye102. In some embodiments, the projector101may include a group of red LEDs, a group of green LEDs, and a group of blue LEDs. For example, the projector101may include two red LEDs, two green LEDs, and two blue LEDs. The eyepiece100may include one or more eyepiece layers. In some embodiments, the eyepiece100includes three eyepiece layers, one eyepiece layer for each of the three colors, red, green, and blue. In some embodiments, the eyepiece100may include six eyepiece layers, i.e., one set of eyepiece layers for each of the three colors configured for forming a virtual image at one depth plane, and another set of eyepiece layers for each of the three colors configured for forming a virtual image at another depth plane. In some embodiments, the eyepiece100may include three or more eyepiece layers for each of the three colors for three or more different depth planes. Each eyepiece layer includes a planar waveguide and may include an incoupling grating107, an orthogonal pupil expander (OPE) region108, and an exit pupil expander (EPE) region109.

Still referring toFIG. 1, the projector101projects image light onto the incoupling grating107in an eyepiece layer. The incoupling grating107couples the image light from the projector101into a planar waveguide propagating the image light in a direction toward the OPE region108. The planar waveguide propagates the image light in the horizontal direction by total internal reflection (TIR). The OPE region108of the eyepiece layer includes a diffractive element that couples and redirects a portion of the image light propagating in the waveguide toward the EPE region109. The EPE region109includes a diffractive element that couples and directs a portion of the image light propagating in the planar waveguide in a direction approximately perpendicular to the plane of the eyepiece layer toward the viewer's eye102. In this fashion, an image projected by the projector101may be viewed by the viewer's eye102.

As described above, image light generated by the projector may include light in the three colors, blue (B), green (G), and red (R). Such image light can be separated into the constituent colors, so that image light in each constituent color may be coupled to a respective waveguide in the eyepiece.

FIG. 2is a schematic diagram illustrating a projector, according to some embodiments. Projector200includes a set of spatially displaced light sources205(e.g., LEDs, lasers, etc.) that are positioned in specific orientations with a predetermined distribution as discussed below, for example, in relation toFIGS. 5A-5C. The light sources205can be used by themselves or with sub-pupil forming collection optics, such as, for example, light pipes or mirrors, to collect more of the light and to form sub-pupils at an end of the light pipes or collection mirrors. For purposes of clarity, only three light sources are illustrated. In some embodiments, quasi-collimation optics225are utilized to quasi-collimate the light emitted from the light sources205such that light enters a polarizing beam splitter (PBS)210in a more collimated like manner so that more of the light makes it to a display panel207. In other embodiments, a collimating element (not shown) is utilized to collimate the light emitted from the light sources205after propagating through portions of the PBS210. In some embodiments, a pre-polarizer may be between the quasi-collimating optics225and the PBS210to polarize the light going into the PBS210. The pre-polarizer may also be used for recycling some of the light. Light entering the PBS210reflects to be incident on the display panel207, where a scene is formed. In some embodiments, a time sequential color display can be used to form color images.

Light reflected from the display panel207passes through the PBS210and is imaged using a projector lens215, also referred to as imaging optics or a set of imaging optics, to form an image of the scene in a far field. The projector lens215forms roughly a Fourier transform of the display panel207onto or into an eyepiece220. The projector200provides sub-pupils in the eyepiece220that are inverted images of the sub-pupils formed by the light sources205and the collection optics. As illustrated inFIG. 2, the eyepiece220includes multiple layers. For example, the eyepiece220includes six layers or waveguides, each associated with a color (e.g., three colors) and a depth plane (e.g., two depth planes for each color). The “switching” of colors and depth layers is performed by switching which of the light sources205is turned on. As a result, no shutters or switches are utilized in the illustrated system to switch between colors and depth planes.

Additional discussion related to the projector200and variations on architectures of the projector200are discussed herein.

FIG. 3is a schematic diagram illustrating a projector, according to some embodiments.FIG. 2illustrates a projector300. A display panel320is a liquid crystal on silicon (LCOS) panel, but the disclosure is not limited to this implementation. Other display panels, including frontlit LCOS (FLCOS), DLP, and the like may be utilized. In some embodiments, a color sequential LCOS design is utilized as discussed in relation to the time sequential encoding discussed in relation toFIG. 6, although other designs can be implemented in which all colors (e.g., RGB) are displayed concurrently. As color filters improve in performance and pixel sizes are decreased, system performance will improve and embodiments of the present disclosure will benefit from such improvements. Thus, a number of reflective or transmissive display panels can be utilized in conjunction with the distributed sub-pupil architecture disclosed herein. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

Light emitted by light sources310, in some embodiments including collection optics, and polarized by a pre-polarizer325propagates through a polarizing beam splitter (PBS)330, passes through a quarter waveplate327, and impinges on a collimator332, which can be implemented as, for example, a mirrored lens, a reflective lens, or curved reflector. A spatial separation between the light sources310enables a distributed sub-pupil architecture. The collimator332, which is a reflective collimator in some embodiments, quasi-collimates or collects the light emitted by the light sources310and directs the collimated light back through the quarter waveplate327again into the PBS330with a polarization state changed to direct the light onto the display panel320.

As the collimated light propagate through the PBS330, it is reflected at an interface331and directed towards the display panel320. The interface331can be implemented using polarizing films, wire grid polarizers, dielectric stacked coatings, combinations thereof, and the like. The display panel320forms a scene or a series of scenes that can be subsequently imaged onto an eyepiece. In some embodiments, time sequential image formation for different colors and depth planes is accomplished by sequentially operating the light sources310in conjunction with operation of the display panel320. In some embodiments, a compensation element is placed at the PBS330or attached to the display panel320to improve the performance of the display panel320. After reflection from the display panel320, the light enters the PBS330at side303, propagates through the interface331, and exits the PBS330at side304. Optical lens340, also referred to as projector lens340, is then utilized to form a Fourier transform of the display and in conjunction with the collimator332to form an inverted image of the sub-pupils of the light sources310at or into the eyepiece.

According to some embodiments, a projector assembly is provided. The projector assembly includes a PBS (e.g., the PBS330). The projector assembly also includes a set of spatially displaced light sources (e.g., the light sources310) adjacent the PBS330. The light sources310can be different color LEDs, lasers, or the like. In some embodiments, the light sources310are adjacent a first side301of the PBS330. The PBS330passes the light emitted by the light sources310during a first pass.

The collimator332, which can be a reflective mirror, is disposed adjacent the PBS330and receives the light making a first pass through the PBS330. The collimator332is adjacent a second side302of the PBS330, which is opposite the first side301adjacent the light sources310. The collimator332collimates and collects the emitted light and directs the collimated light back into the second side302of the PBS330.

The projector assembly also includes the display panel320adjacent a third side303of the PBS330positioned between the first side301and the second side302. The display panel320can be an LCOS panel. During a second pass through the PBS330, the collimated light reflects from the interface331in the PBS330and is directed toward the display panel320due to its change in polarization states caused by double passing the quarter waveplate327.

The projector assembly further includes the projector lens340adjacent a fourth side304of the PBS330that is positioned between the first side301and the second side302and opposite to the third side303. The position of the projector lens340between the PBS330and the eventual image formed by the projection display assembly denotes that the illustrated system utilizes the PBS330at the back of the projector assembly.

The projector assembly forms an image of the sub-pupils and a Fourier transform of the display panel320at an image location. An incoupling interface to an eyepiece is positioned near the image location. Because light emitted by the light sources310propagates through different paths in the projector assembly, the images associated with each light source of the light sources310are spatially displaced at the image plane of the system, enabling coupling into different waveguides making up the eyepiece.

FIG. 4is a schematic diagram illustrating multiple colors of light being coupled into corresponding waveguides using an incoupling element disposed in each waveguide, according to some embodiments. A first waveguide410, a second waveguide420, and a third waveguide430are positioned adjacent each other in a parallel arrangement. In an example, the first waveguide410can be designed to receive and propagate light in a first wavelength range401(e.g., red wavelengths), the second waveguide420can be designed to receive and propagate light in a second wavelength range402(e.g., green wavelengths), and the third waveguide430can be designed to receive and propagate light in a third wavelength range403(e.g., blue wavelengths).

Light in all three wavelength ranges401,402, and403are focused due to the Fourier transforming power of a projector lens440onto roughly the same plane but displaced in the plane by roughly the spacing of the sub-pupils in a light module and the magnification, if any, of an optical system. Incoupling elements412,422, and432of the respective waveguides410,420, and430are placed in the path that corresponds to the correct color sub-pupil so as to capture and cause a portion of the light to couple into the respective waveguides410,420, and430.

The incoupling elements412,422, and432, which can be incoupling gratings, can be elements of incoupling diffractive optical elements (DOEs). When a given light source is turned on, the light from that light source is imaged at the corresponding plane (e.g., red LED #1, first waveguide410at a first depth plane). This enables switching between colors by merely switching the light sources off and on.

In order to reduce the occurrence and/or impact of artifacts, also referred to as ghost images or other reflections, some embodiments of the present disclosure utilize absorptive color filters. The filters may be used in single pupil systems.

FIGS. 5A-5Care top views of distributed sub-pupil architectures, according to some embodiments. The distributed sub-pupils can be associated with different sub-pupils and are associated with different light sources (e.g., LEDs or lasers) operating at different wavelengths and in different positions (i.e., different lateral positions). Referring toFIG. 5A, this first arrangement has six sub-pupils associated with two depth planes and three colors per depth plane. For example, two sub-pupils510and512associated with a first color (e.g., red sub-pupils), two sub-pupils514and516associated with a second color (e.g., green sub-pupils), and two sub-pupils518and520associated with a third color (e.g., blue sub-pupils). These sub-pupils correspond to six light sources that are spatially offset in an emission plane. The illustrated six sub-pupil embodiment may be suitable for use in a three-color, two-depth plane architecture. Additional description related to distributed sub-pupil architectures is provided in U.S. Patent Application Publication No. 2016/0327789, published on Nov. 10, 2016, the disclosure of which is hereby incorporated by reference in its entirety for all purposes.

As an example, if two light sources are positioned opposite each other with respect to an optical axis (i.e., opposite about the optical axis), it is possible that light from one of the light sources (i.e., a first light source) can propagate through the optical system, reflect off of the eyepiece, for example, an incoupling grating or other surface of the eyepiece, and propagate back through the optical system and then reflect again at the display panel to reappear at the location opposite the original light source image with respect to the optical axis. This double reflection appearing in a location of another sub-pupil will create a ghost image since the light was originally emitted by the first light source. Accordingly, in the arrangement illustrated inFIG. 5A, since sub-pupils510/512,514/516, and518/520are not positioned opposite each other with respect to a center of an optical axis and a sub-pupil distribution, light from these sets of sub-pupils will not be coupled to the other sub-pupils in the set after propagation through the optical system. Accordingly, this sub-pupil layout partially prevents artifact formation, also referred to as ghost image formation.

InFIG. 5A, the color and depth plane associated with each sub-pupil is illustrated as follows: red wavelengths at first and second depth planes: R1/R2; green wavelengths at first and second depth planes: G1/G2; and blue wavelengths at first and second depth planes: B1/B2. Diffractive optical elements can be placed at these sub-pupil locations as discussed in relation toFIG. 4. Although diffraction gratings, referred to as incoupling gratings, are discussed herein, embodiments of the present disclosure are not limited to diffraction gratings and other diffractive optical elements can be utilized, including binary diffractive elements, stepped diffractive elements, and other suitable diffraction-based structures. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

Referring toFIG. 5B, a nine sub-pupil embodiment is illustrated, which would be suitable for use in a three-color, three-depth plane architecture. In this embodiment, a first set of sub-pupils including sub-pupils540,542, and544associated with a first color (e.g., red sub-pupils) are positioned at 120° with respect to each other. A second set of sub-pupils including sub-pupils550,552, and554associated with a second color (e.g., green) are positioned at 120° with respect to each other and the distribution is rotated 60° from the first set of sub-pupils. Accordingly, if light from sub-pupil440is reflected in the system and reappears at sub-pupil554opposite to sub-pupil540, no overlap in color will be present. A third set of sub-pupils including sub-pupils560,562, and564associated with a third color (e.g., blue) are positioned inside the distribution of the first and second sub-pupils and positioned 120° with respect to each other.

FIG. 5Cillustrates a six sub-pupil arrangement in which sub-pupils570and572associated with a first color (e.g., red) are positioned at two corners of the sub-pupil distribution, sub-pupils580and582associated with a second color (e.g., green) are positioned at the other two corners of the sub-pupil distribution, and sub-pupils590and592associated with a third color (e.g., blue) are positioned along sides of the rectangular sub-pupil distribution. Thus, sub-pupil arrangement, as illustrated inFIGS. 5B-5C, can be utilized to reduce the impact from ghost images. Alternative sub-pupil arrangements may also be utilized, such as, for example, sub-pupil arrangements in which sub-pupils of different colors are opposite each other across the optical axis. Ghosting can be reduced by using color selective elements (e.g., a color selective rotator) or color filters at each respective incoupling grating.

FIG. 6is a schematic diagram illustrating time sequential encoding of colors for multiple depth planes, according to some embodiments. As illustrated inFIG. 6, depth planes (three in this illustration) are encoded into least significant bit (LSB) per pixel via a shader. The projector assembly discussed herein provides for precise placement of pixels for each color in a desired depth plane. Three colors are sequentially encoded for each depth plane—(R0, G0, B0for plane0)602, (R1, G1, B1for plane1)604, and (R2, G2, B2for plane2)606. Illumination of each color for 1.39 ms provides an illumination frame rate608of 720 Hz and a frame rate for all three colors and three depth planes610of 80 Hz (based on 12.5 ms to refresh all colors and planes). In some embodiments, a single color for a single depth plane per frame may be used by only using light sources associated with that particular color for that particular depth plane.

In some embodiments, multiple depth planes can be implemented through the use of a variable focus lens that receives the sequentially coded colors. In these embodiments, there may be three eyepiece layers and the incoupling gratings may be spaced further apart such that incoupling gratings are not positioned directly across from one another about the optical axis. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

FIG. 7Ais a schematic diagram illustrating a projector assembly, according to some embodiments.FIG. 7Bis an unfolded schematic diagram illustrating the projector assembly shown inFIG. 7A. As illustrated inFIG. 7A, a projector architecture700includes an illumination source710, which can emit a collimated set of light beams, such as, for example, lasers. In this embodiment, since light from the illumination source710is already collimated, a collimator can be omitted from the optical design. The illumination source710can emit polarized, unpolarized, or partially polarized light. In the illustrated embodiment, the illumination source710emits light712polarized with a p-polarization. A first optical element715(e.g., a pre-polarizer) is aligned to pass light with p-polarization to a polarizing beam splitter (PBS)720. Initially, light passes through an interface722(e.g., a polarizing interface) of the PBS720and impinges on a spatial light modulator (SLM)730. The SLM730, also referred to as a display panel, impresses a spatial modulation on the light to provide an image. In an on state, the SLM730modulates input light from a first polarization state (e.g., p-polarization state) to a second polarization state (e.g., s-polarization state) such that a bright state (e.g., white pixel) is shown. The second polarization state may be the first polarization state modulated (e.g., shifted) by 90°. In the on state, the light having the second polarization state is reflected by the interface722and goes downstream to projector lens740. In an off state, the SLM730does not rotate the input light from the first polarization state, thus a dark state (e.g., black pixel) is shown. In the off state, the light having the first polarization state is transmitted through the interface722and goes upstream to the illumination source710. In an intermediate state, the SLM730modulates the input light from the first polarization to a certain elliptical polarization state. In the intermediate state, some of the light having the elliptical polarization state (e.g., p-polarization state) is transmitted through the interface722and goes upstream to the illumination source710and some of the light having the elliptical polarization state (e.g., s-polarization state) is reflected by the interface722goes downstream to projector lens740.

After reflection from the SLM730, reflected light714is reflected from the interface722and exits the PBS720. The emitted light passes through the projector lens740and is imaged onto an incoupling grating750of an eyepiece (not shown).

FIG. 7Billustrates imaging of light associated with a first sub-pupil711of the illumination source710onto the incoupling grating750of the eyepiece. Light associated with the first sub-pupil is collected before entry into the PBS720, reflects from the SLM730, enters the PBS720and exits the PBS720after reflecting off the interface722(not shown), passes through the projector lens740, and is relayed onto the incoupling grating750. An optical axis705is illustrated inFIG. 7B.

FIG. 8Ais a schematic diagram illustrating artifact formation resulting from reflections from an in-coupling grating element or substrate surfaces of an eyepiece in a projection display system, according to some embodiments.FIG. 8Bis an unfolded schematic diagram illustrating artifact formation resulting from reflections from the in-coupling grating or substrate surfaces of the eyepiece in the projection display system shown inFIG. 8A. In some embodiments, the projector assembly800illustrated inFIG. 8Amay include a circular polarizer between the PBS720and the projector lens740.

Referring toFIG. 8A, in a manner similar to the operation of the projector assembly700inFIG. 7A, light802with a s-polarization state from the SLM730, also referred to as a display panel, is reflected at the interface722inside the PBS720. It should be noted that the tilting of the rays after reflection from interface722are merely provided for purposes of clarity. Most of the light emitted from the PBS720passes through projector lens740and is relayed by the projector lens740to provide an image of the sub-pupil at the incoupling grating750of the eyepiece.

A portion of the light incident on the incoupling grating750is reflected by the incoupling grating750. As illustrated inFIG. 8A, although the light incident on the incoupling grating750can be in a single polarization state (e.g., s-polarization state), the light reflected from the incoupling grating750can have a mixture of polarization states (A*s+B*p)804, where A and B are coefficients between zero and one. For diffractive optical incoupling gratings with steps that are in a plane of the eyepiece, the reflections are of mostly flipped circular polarizations. However, if the incoupling gratings steps are slanted out of the plane of the eyepiece, then other polarization states will be reflected. The reflected light804passes through projector lens740and emerges with a mixture of polarizations (C*s+D*p)806as it propagates back toward the PBS720, where C and D are coefficients between zero and one. Generally, A>C and B>D as a result of the characteristics of the incoupling grating750and/or the projector lens740.

Light in the upstream path that is properly aligned with the polarization of interface (C*s)808reflects from the interface722, the SLM730, the interface722, passes through projector lens740, and is imaged by projector lens740to provide an image at a second incoupling grating752of the eyepiece having a single polarization state (E*s)812. Since the source of light at both incoupling gratings750and752is the same, the light at incoupling grating752appears to be originating in the SLM730, thereby producing an artifact or ghost image.

Referring toFIG. 8B, the symmetry around the optical axis705is demonstrated by the imaging at the incoupling grating750after the first pass through the PBS720and projector lens740and the imaging at the incoupling grating752after the reflected light804is reflected from SLM730.

FIG. 9is a schematic diagram illustrating reflections from an in-coupling grating element, according to some embodiments. The eyepiece can include a cover glass910and an incoupling grating920. Incoming light is illustrated as left hand circularly polarized (LHCP) input light901. Although input light with circular polarization is illustrated, embodiments of the present disclosure are not limited to circularly polarized light and the input light can be elliptically polarized with predetermined major and minor axes. The reflections from the eyepiece can include a reflection903from a front surface912of the cover glass910as well as a reflection905from a back surface914of the cover glass910. Additionally, reflection907from the incoupling grating920is illustrated. In this example, reflections903and905are right hand circularly polarized (RHCP) and reflection907is LHCP. The sum of these reflections results in a mixed polarization state propagating upstream toward the PBS720. Accordingly, inFIG. 8A, the reflection from incoupling grating750is illustrated as A*s+B*p, but it will be evident to one of ordinary skill in the art that the polarization state of the reflected light is not limited to combinations of linear polarization, but can include elliptical polarizations as well. In particular, when diffractive elements of the incoupling grating750include blazed grating features, the polarization state of the reflected light is characterized by complex elliptical polarizations. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

FIG. 10Ais a schematic diagram illustrating a projector assembly with artifact reduction using color filters, according to some embodiments. The projector assembly illustrated inFIG. 10Ashares some common elements with the projector assembly illustrated inFIG. 8Aand the description provided inFIG. 8Ais applicable to the projector assembly inFIG. 10Aas appropriate. As described herein, color filters with spectral properties selected based on spectral properties of incoupling gratings are positioned adjacent incoupling gratings to block light with substantially different spectral characteristics from incoupling into incoupling gratings. As illustrated inFIG. 10A, embodiments of the present disclosure reduce optical artifacts that result from specular reflections associated with operation of reflective-display projectors, slab waveguides, and/or incoupling diffractive optical elements.

The projector assembly with artifact prevention1000includes an illumination source1010, which can emit a collimated set of light beams, such as, for example, lasers. The illumination source1010can emit polarized, unpolarized, or partially polarized light. In the illustrated embodiment, the illumination source1010emits light polarized with a p-polarization. A first optical element1015(e.g., a pre-polarizer) is aligned to pass light with p-polarization to a polarizing beam splitter (PBS)1020. Initially, light passes through an interface1022of the PBS1020and impinges on a spatial light modulator (SLM)1030. The SLM1030, also referred to as a display panel, impresses a spatial modulation on the light to provide an image. After reflection from the SLM1030and changing of the polarization to the s-polarization, the reflected light is reflected from interface1022and exits the PBS1020. The emitted light passes through projector lens1040and is imaged onto an incoupling grating1050of the eyepiece (not shown).

Although only two incoupling gratings1050and1052are illustrated inFIG. 10A, embodiments of the present disclosure are not limited to this number and other numbers of incoupling gratings can be utilized, for example, six incoupling gratings for two depth planes and three colors (e.g., red, green, and blue). Accordingly, if, for example, green light is specularly reflected back from the in-coupling grating1050, this light traverses the optical system and becomes blocked when a filter1072that attenuates green light, which can be referred to as a green reject filter, such as a red or blue color filter, is positioned adjacent an incoupling grating1052, thus mitigating the inverted ghost. Additionally, although incoupling gratings1050and1052are illustrated inFIG. 10A, embodiments of the present disclosure are applicable to other structures that can reflect light back into the optical system, eventually resulting in the reflected light propagating downstream toward the structures that produced the reflection. It should be noted that although some filters are illustrated as filters that pass a first set of one or more colors and attenuate a second set of one or more other colors, other embodiments can pass the first set of one or more colors (e.g., pass blue and green colors) and attenuate the second set of one or more colors (e.g., red colors). For example, in one embodiment, a filter may pass green and may attenuate blue and red. For example, in one embodiment, a filter may pass blue light and red light and may attenuate green light.

A portion of the incident light will reflect off of the incoupling grating1050and propagate back toward the projector lens1040. As illustrated inFIG. 10A, although the light incident on the incoupling grating1050can be in a single polarization (e.g., s-polarization), the light reflected from the incoupling grating1050can have a mixture of polarizations (A*s+B*p)1062, where A and B are coefficients between zero and one. The reflected light passes through projector lens1040and emerges with a mixture of polarizations (C*s+D*p)1064as it propagates back toward the PBS1020, where C and D are coefficients between zero and one. Generally, A>C and B>D as a result of the characteristics of projector lens1040.

Light in the upstream path that is properly aligned with the polarization of interface (C*s)1066reflects from the interface1022, the SLM1030, the interface1022, passes through the projector lens1040.

Spectral filters (e.g., absorptive optical filters) are placed in the optical path between the projector lens1040and the incoupling gratings1050and1052of the eyepiece. As illustrated, for example, inFIG. 11A, the spectral filters are patterned to overlap the incoming light path for a corresponding incoupling grating. The spectral filters may be reflective (e.g., dielectric coatings) and/or absorptive. Absorptive filters may be fabricated with inks, dyes, acrylics, photoresist, or using technologies such as retarder filter stacks. Spaces between spectral filters may be coated with an absorptive (e.g., black) material for further artifact reduction. As examples, Dimatix ultraviolet curable ink available from Kao Collins, Inc., of Cincinnati, Ohio and INXFlex™ UV Flexographic Inks and INXCure™ UV/EB Inks, available from INX International Ink Co., of Schaumberg, Ill., can be utilized according to embodiments of the present disclosure.

Referring back toFIG. 10A, absorptive color filters1070,1072are disposed adjacent the incoupling gratings1050,1052, respectively. Thus, the absorptive color filter1070is inserted in the optical path between the projector lens1040and the incoupling grating1050. In a similar manner, the absorptive color filter1072is inserted in the optical path between the projector lens1040and the incoupling grating1052. AlthoughFIG. 10Aillustrates color filters1070,1072placed adjacent the incoupling gratings1050,1052, the color filters1070,1072can be placed at other positions between the projector lens1040and the incoupling gratings1050,1052. Preferably, the color filters1070,1072are positioned near a beam focus so that the color filters1070,1072can be physically separated and located in distinct areas. Placement of the color filter1070,1072in the optical path upstream of the incoupling gratings1050,1052enables reflected light to be blocked or attenuated, whether the color filters1070,1072are disposed as an array in a single plane or at different planes.

In the absence of color filters1070,1072, the light (E*s)1068passing through the projector lens1040would be imaged at a second incoupling grating1052of the eyepiece. However, the presence of the color filter1072attenuates or eliminates the image at the second incoupling grating1052from the reflection from the incoupling grating1052, thereby reducing or preventing formation of the artifact or ghost image.

FIG. 10Bis an unfolded schematic diagram illustrating the projector assembly shown inFIG. 10A. Light from the illumination source1010is collimated by the first optical element1015, propagates through the PBS1020, reflects off the SLM1030, makes another pass through the PBS1020, reflects off interface1022(not shown), and passes through the projector lens1040. The light in the downstream path passes through the color filter1070, and is imaged at the incoupling grating1050.

Reflected light passes through the color filter1070, passes through the projector lens1040, passes through the PBS1020, reflects off the interface1022(not shown), and reflects off the SLM1030. The light passes through the PBS1020, reflects off the interface1022, propagates in the downstream path through the projector lens1040and is blocked or attenuated by the color filters1072.

The spectrally diverse nature of the sets of color filters enables blue/green/red imagery addressed to the corresponding sub-pupil to pass through the blue/green/red filter implemented at that location, but block the higher diffraction orders of the blue/green/red imagery from entering other sub-pupils. Light diffracted from the SLM1030that impinges between sub-pupils is absorbed by the dark or black matrix surrounding the sub-pupils, thus enhancing contrast in the final image.

As illustrated inFIG. 11A, one of the possible layouts for the color filters is shown. In general, a set of design rules can be followed in defining the layout of the color filters. For high efficiency in a small package, it is desirable to have all zero-order imagery projected within a super-pupil1110. In some embodiments, it is also preferable to have a complimentary color filter (i.e., a color filter that does not have the same spectral band) opposed symmetrically across the optical axis, to avoid zeroth order specular reflections from entering the image through an incoupling grating, which is operable to diffract light inside the spectral band, positioned across the optical axis. In some embodiments, it is preferable to minimize the area of overlap between higher orders of one type of color imagery and a different sub-pupil of the same color. This is discussed in additional detail in relation toFIG. 15. If the transmission profile for different color filters has regions of overlap in the spectrum (e.g., a green filter transmits some light at 500 nm while a blue filter also has some finite transmission at 500 nm), then it is preferable to locate filters and incoupling gratings such that the higher orders of the green imagery and the higher orders of the blue imagery overlap the spectrally adjacent color sub-pupils as little as possible within the super-pupil1110. For higher optical efficiency, the sizes of the color filters should be large enough to pass a significant portion of the beam energy (e.g., >90%). The color filters may also be used in conjunction with optical isolators, such as a circular polarizer, to further enhance the artifact mitigation. The color filters, and/or the surrounding glass substrate, can be coated with anti-reflection optical layers to enhance optical efficiency and further improve image contrast and reduce ghosting. The absorptive material in the area between the sub-pupils can block stray light from entering the eyepiece layers.

FIG. 11Bis a transmission plot for red, green, and blue color filters, according to some embodiments. The transmission spectra of the color filters is selected to produce high transmission values in the spectral band and little or a minimum overlap in the transmission spectra between two spectrally adjacent color filters. As an example, embodiments can be implemented to provide a predetermined minimum overlap between spectrally adjacent colors, with blue/green and green/red being spectrally adjacent. As an example, the spectral overlap between adjacent colors can be a predetermined percentage of the peak transmission value. For instance, the transmission values at the wavelength at which adjacent spectra overlap may be less than 10% of the maximum transmission value.

Referring toFIG. 11B, color filter B1/B2is characterized by high transmission (e.g., 80%) at the peak of the spectral band, which can be aligned with the wavelength of the corresponding light source, and minimal spectral overlap with the color filter G1/G2, which is the spectrally adjacent color filter. As illustrated inFIG. 11B, the minimal overlap can be, for example, less than 10% at certain wavelengths and/or the filter overlap can be less than 10% at the crossing point of the two spectra.

Although color filters with generally Gaussian transmission profiles can be utilized, high pass or low pass filters can be used for the color filters. As an example, inFIG. 11B, color filter R1/R2is a high pass filter that has high transmission at wavelengths greater than ˜550 nm and low transmission at wavelengths less than ˜550 nm. It should be noted that although the transmission profile for color filter R1/R2increases at wavelengths less than ˜450 nm, the incoupling gratings for the waveguides supporting green wavelengths are characterized by poor diffraction efficiency for red wavelengths.

FIG. 11Cis a top view of color filters used in conjunction with a distributed sub-pupil architecture, according to some embodiments. In this embodiment, two sets of spectrally adjacent colors are opposed to each other across the optical axis1105: G2/R1and B2/G1. Note that R2/B1are not spectrally adjacent colors.

FIG. 12is a top view of illustrating spatial arrangement of color filters and sub-pupils, according to some embodiments. In this embodiment, both the color filters, which are shaped as portions of a circle, and the incoupling gratings for the waveguides supporting the corresponding wavelengths (IGR1/IGR2:IGG1/IGG2:IGB1/IGB2) are illustrated. Embodiments are provided in which the color filters overlap more than one sub-pupil. It will be appreciated that the color filters are disposed in one more planes extending out of the plane of the figure and the incoupling gratings are disposed in planes extending into the plane of the figure. The optical axis1105is positioned at the intersection of the color filters in this embodiment.

FIG. 13is a cross sectional view illustrating integration of color filters with eyepiece waveguide layers, according to some embodiments. In some embodiments, the color filters can be placed in a single plane between the projection lens1040and the incoupling gratings1050/1052as illustrated inFIG. 10A. In some embodiments, the color filters can be placed between the waveguide layers of the eyepiece as illustrated inFIG. 13. In this embodiment, the eyepiece is illustrated by three waveguide layers1310,1320, and1330, which can be associated with three different colors, green, blue, and red, respectively. Light incident on a red incoupling grating1332passes through a red color filter1334that is positioned (e.g., printed) on a backside of the waveguide layer1320. As light propagates toward the incoupling grating1332, it passes through the waveguide layers1310and1320. Wavelengths of light that are outside a transmission band of the red color filter1334are blocked or attenuated by the red color filter1334. Referring toFIG. 13, the position of the color filters as measured along the x-axis and the y-axis (i.e., the x-y position) can be referred to as a lateral position. The position of the color filters with respect to the cover glass (i.e., cover plate)1305as measured along the z-axis (i.e., the z position) can be referred to as a longitudinal position.

Similarly for the other colors, light incident on a blue incoupling grating1322passes through a blue color filter1324that is positioned (e.g., printed) on a backside of the waveguide layer1310. As light propagates toward the blue incoupling grating1322, it passes through the waveguide layer1310. Wavelengths of light that are outside a transmission band of the blue color filter1324are blocked or attenuated by the blue color filter1324.

Since a green incoupling grating1312is disposed on the first waveguide layer1310, no color filter for green wavelengths is utilized in this embodiment although a green color filter can be implemented between a projection lens and the green incoupling grating1312, for example, printed on a front surface of waveguide layer1310or printed on a cover glass1305adjacent the waveguide layer1310. It should be appreciated that the color filters can be implemented on multiple surfaces, including a frontside and/or a backside of the cover glass as well as on a frontside and/or a backside of the waveguide layers, as well as combinations thereof. In some embodiments, the color filters can be implemented (e.g., printed) on a projector lens (e.g., the projector lens340). For example, the color filters can be printed on an element or surface of the projector lens340that is closest to the eyepiece, and particularly to the incoupling gratings. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

In an alternative embodiment, additional color filters can be added to increase the attenuation of colors outside the spectral band of the filters. For example, an optional (e.g., red) filter1336may be positioned on the backside of waveguide layer1310to provide for additional attenuation of blue and green artifacts. Moreover, such additional filters can have different spectral properties than the corresponding filters. As an example, optional filter1336can be a “yellow” filter, blocking blue wavelengths. It should be noted that although uniform thickness color filters are illustrated inFIG. 13, color filters can be differing thicknesses can be utilized to achieve the desired absorption properties. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

FIG. 14Ais a top view of color filters used in conjunction with a subset of distributed sub-pupils, according to some embodiments. In this top view, four color filters, R1, R2, G1, and B1are illustrated. In this implementation, color filters for the light intended for the second green and blue depth planes (B2and G2) are optional and are represented with dashed lines. As illustrated, the color filters in this sub-pupil layout are arranged such that color filters opposing each other, represented by line1410oriented between opposing color filters, attenuate light propagating through the optical system after reflection from the incoupling gratings. Light reflected from the incoupling grating adjacent optional color filter G2couples to opposing color filter R1. Similarly, light reflected from the incoupling grating adjacent optional color filter B2couples to opposing color filter R2. Light reflected from the incoupling gratings adjacent color filters G1and B1couple to the opposing color filters (B1and G1). As illustrated, filters passing the same color are not positioned opposite each other across the optical axis. Accordingly, G1and B1are opposed and R1and R2are adjacent each other. Accordingly, if green light passing through the incoupling grating for green is reflected through the optical system to impinge on the blue color filter B1, this green light will be attenuated by the blue color filter B1.

FIG. 14Bis a cross sectional view illustrating integration of the color filters illustrated inFIG. 14Awith eyepiece waveguide layers, according to some embodiments. In this cross sectional view, the layout of the color filters in a top view is superimposed for clarity. Only color filters R2and B1are illustrated in the cross sectional view since they are closest to the foreground surface of the eyepiece, but it will be appreciated that color filters R1and G1are present, but at positions extending into the plane of the figure. In this embodiment, the color filters are disposed on the backside surface of cover glass1430although they can be positioned in other locations. The color filters can have a thickness equal to the gap between adjacent waveguide layers. An additional cover glass1432is also illustrated. A high transparency adhesive1440that is preferably index matched can be utilized between waveguide layers to reduce Fresnel reflections as light propagates through the waveguide layers.

Light intended for the red waveguide layer1450passes through red color filter R2and the other waveguide layers until it is incident on incoupling grating1452, where it is diffracted into the plane of the waveguide layer1450. Light intended for the blue waveguide layer1460passes through blue color filter B1and the other waveguide layers until it is incident on incoupling grating1462, where it is diffracted into the plane of the waveguide layer1460. In this embodiment, the low coupling efficiency of red light into the blue and green incoupling gratings enables a design in which no color filters are positioned adjacent these incoupling gratings as represented by the optional G2/B2color filters.

FIG. 14Cis a top view of color filters used in conjunction with another subset of distributed sub-pupils, according to some embodiments. In this embodiment, spectrally adjacent colors are positioned opposite each other (G1/B1and R1/G2). Since red and blue wavelengths are at opposing ends of the optical spectrum, and, as a result, the incoupling efficiency of red light by the blue incoupling grating is low, no B2color filter is utilized in this implementation. In other embodiments, six filters are utilizing including the B2filter opposing the R2filter. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

FIG. 14Dis a cross sectional view illustrating integration of the color filters illustrated inFIG. 14Cwith eyepiece waveguide layers, according to some embodiments. In this cross sectional view, the layout of the color filters in a top view is superimposed for clarity. Only color filters R2, B1, and G2are illustrated in the cross sectional view since they are closest to the foreground surface of the eyepiece, but it will be appreciated that color filters R1and G1are present, but at positions extending into the plane of the figure. In this embodiment, the color filters are disposed on the backside surface of cover glass1430although they can be positioned in other locations. The color filters can have a thickness equal to the gap between adjacent waveguide layers. An additional cover glass1432is also illustrated.

Light intended for a red waveguide layer1450passes through red color filter R2and the other waveguide layers until it is incident on incoupling grating1452, where it is diffracted into the plane of the waveguide layer1450. Light intended for the blue waveguide layer1460passes through blue color filter B1and the other waveguide layers until it is incident on incoupling grating1462, where it is diffracted into the plane of the waveguide layer1460. Light intended for the green waveguide layer1470passes through green color filter G2and the other waveguide layers until it is incident on incoupling grating1472, where it is diffracted into the plane of the waveguide layer1470.

In some embodiments, a single color filter may be disposed over two incoupling gratings, for example, replacing R1and R2with a single color filter that overlaps with more than one incoupling grating. Thus, although circular color filters are illustrated inFIGS. 14A and 14C, other geometries can be utilized in other embodiments. In some embodiments, the color filters may be a same shape as concentrators used to collect light from light sources (e.g., the light sources205). For example, the color filters may be octagonal to match a shape of compound parabolic concentrators used to collect light from light sources.

As images are projected to a super-pupil, in order to control the depth and color of imagery sent through the waveguide during any one field period, it is desirable to only have light enter only one incoupling grating at a time. Although the optical system may have a high diffraction efficiency, higher diffraction orders may still be present in the projected pupil of the optical system. These higher order images can couple to an unintended incoupling grating and create an artifact.

FIG. 15is a top view of diffracted orders in a distributed sub-pupil architecture, according to one embodiment. A super-pupil1505includes six sub-pupils, B1, B2, G1, G2, R1, and R2. Zeroth order light is incident on sub-pupil R2for imaging after passing into a red incoupling grating as the sub-pupil R2overlaps the red incoupling grating. Higher order diffraction orders are also illustrated, with first order diffractive orders surrounding the zeroth order and second order diffractive orders surrounding the first order diffractive orders. For example, as illustrated inFIG. 15, a third order diffracted order1510can overlap with sub-pupil B1. If light in this higher order were coupled into the eyepiece by the blue incoupling grating, an artifact that is shifted and upright would be present in the imagery extracted from the waveguide.

Accordingly, embodiments of the present disclosure align the color filters such that the higher order diffraction orders have little to no overlap with filters of the same color or with filters of spectrally adjacent colors. In particular, embodiments position the color filters to account for the locations of the first order diffractive orders and/or the second order diffractive orders. Thus, the arrangement of the color filters is selected as a function of wavelength, the position of the diffractive orders, the location of the incoupling gratings, and the location of the optical axis of the lens.

FIG. 16Ais a side view of an eyepiece with an optical filter, according to some embodiments. Eyepiece1600illustrated inFIG. 16Acan be an element of the VOA illustrated inFIG. 1and used to project an image to the viewer's eye (e.g., the viewer's eye102). The eyepiece1600includes a first planar waveguide1610positioned in a first lateral plane. In this example, the first lateral plane extends into the plane ofFIG. 16Aand can be considered as the x-y plane. Light incident on the eyepiece1600along the z-direction will impinge normal to the lateral plane. As described herein, the various optical elements are disposed at predetermined positions in the lateral plane to achieve the performance provided by the methods and systems described herein.

The first planar waveguide1610includes a first diffractive optical element (DOE)1618disposed at a first lateral position (i.e., an x-y coordinate position). The first planar waveguide1610has a first surface1614and a second surface1616opposite to the first surface1614. Light is incident on the first planar waveguide1610in a first region1605to the left of divider1601. The first region1605includes the first lateral position and the diffractive optical elements associated with each of the planar waveguides. The first region1605is configured to receive image light incident on the eyepiece, for example, the first surface1614of the first planar waveguide1610. The image light includes image light in one or more wavelengths, for example, three wavelength ranges associated with red (600 nm-700 nm), green (500 nm-600 nm), and blue (400 nm-500 nm). The present disclosure is not limited to these wavelength ranges or three colors and other ranges and more than three colors (e.g., RBGY) or less than three colors. Thus, these wavelength ranges are just exemplary and can be modified as appropriate to the particular application.

The first planar waveguide1610also includes a second region1607to the right of the divider1601. Light incident on the first region1605is diffracted into the plane of the first planar waveguide1610and is guided toward the second region1607of the first planar waveguide1610. Accordingly, a portion of the image light is transmitted through the first planar waveguide1610. Referring toFIG. 16A, a green incident beam1642is incident on first DOE1618. A portion of the green incident beam1642is diffracted and is guided into the second region1607of the first planar waveguide1610as illustrated by guided rays1619.

A second planar waveguide1620positioned in a second lateral plane adjacent to the first lateral plane. In the example illustrated inFIG. 16A, the second lateral plane lies in the x-y plane at a location having a smaller z-dimension value than the first lateral plane. The second planar waveguide1620includes a second DOE1628disposed at a second lateral position (i.e., an x-y coordinate position).

The description provided in relation to the first planar waveguide1610is applicable to the second planar waveguide1620as appropriate. For example, the second planar waveguide1620has a first surface1624and a second surface1626opposite to the first surface1624. The second planar waveguide1620has a first region1605including the second lateral position and a second region1607. Like the first planar waveguide1610, the first region1605is configured to receive the image light. The image light impinging on the second planar waveguide1620, illustrated by incident beam1644includes light in a second wavelength range (e. g., blue light). The second planar waveguide1620also includes a second DOE1628that is configured to diffract image light in the second wavelength range into the second planar waveguide1620to be guided toward the second region1607of the second planar waveguide1620. The light guided in the second region1607is represented by guided rays1629.

A third planar waveguide1630is positioned in a third lateral plane adjacent to the second lateral plane. In the example illustrated inFIG. 16A, the third lateral plane lies in the x-y plane at a location having a smaller z-dimension value than the second lateral plane. The third planar waveguide1630includes a third DOE1638disposed at a third lateral position (i.e., an x-y coordinate position), which can be different from both the first lateral position and the second lateral position. In the embodiment illustrated inFIG. 16A, the first lateral position is different from the second lateral position and the third lateral position, and the second lateral position is different from the first lateral position and the third lateral position, providing independent access to each of the DOEs for incident beams1642,1644,1646, and1648. The description provided in relation to the first planar waveguide1610and second planar waveguide1610is applicable to the third planar waveguide1630as appropriate.

As illustrated inFIG. 16A, the third planar waveguide1630has a first surface1634and a second surface1636opposite to the first surface1634. The third planar waveguide1630has a first region1605including the third lateral position and a second region1607. The first region1605is configured to receive the image light in a third wavelength range (e.g., a red wavelength range). A third DOE1638associated with the third planar waveguide1630is configured to diffract image light in the third wavelength range (e.g., red light), represented by incident beam1648into the third planar waveguide1630to be guided toward the second region1607of the third planar waveguide1630. The light guided in the second region1607is represented by guided rays1639.

Referring toFIG. 16A, an optical filter1650(e.g., a dichroic filter or an absorption filter) is positioned between the second planar waveguide1620and the third planar waveguide1630. The optical filter1650is disposed at the third lateral position such that it is aligned with the third DOE1638.

As described herein, the optical filter1650improves system performance by reducing wavelength cross-coupling. Wavelength cross-coupling can occur when incoming light is reflected by a DOE (e.g., incoupling grating). Referring toFIG. 1, the projector101projects image light from an LCOS onto the incoupling grating107in an eyepiece layer of the eyepiece100. Some of the image light can be reflected by the incoupling grating107. The reflected light can illuminate the LCOS. In some cases, pixels in the LCOS can act like a mirror and reflect the light back to the incoupling grating107without polarization state changes. The reflected light can cause ghosting. An absorption type optical filter1650can filter (e.g., reflect) unwanted light to eliminate or reduce ghosting. For example, if optical filter1650is a dichroic filter, it can reflect blue light. In this case, the blue color DOE and the red color DOE can be disposed in line. In this arrangement, the blue light can be recycled, as described further in connection withFIG. 18A. Placing DOEs (e.g., incoupling gratings) in line can allow more pupils or depths inside a specific super pupil size. In some cases, DOE diffraction can generate ghosting images, which can be absorbed by color filters.

As illustrated inFIG. 16A, the third DOE1638is designed to diffract light in the third wavelength range (e.g., red light) into the third planar waveguide1630. In practice, the third DOE1638may also diffract (i.e., cross-couple) an amount (e.g., a small amount) of light of other colors (e.g., blue light or green light) into the third planar waveguide1630. Such cross-coupling can adversely impact the user experience if this cross-coupled light is subsequently directed to the user along with the desired light in the third wavelength range.

InFIG. 16A, the light incident on the third DOE1638includes not only incident beam1648, which is in the third wavelength range and is intended to be coupled into the third planar waveguide1630, but also incident beam1646, which is not in the third wavelength range. This example illustrates how light in the first wavelength range and/or the second wavelength range can be incident on the third DOE1638. In order to block light from the first wave length range and/or the second wavelength range from being cross-coupled into the third planar waveguide1630, embodiments of the present disclosure utilize the optical filter1650to reflect or absorb light at undesired wavelengths.

FIG. 16Bis a plot illustrating a transmittance/reflectance curve of an optical filter, according to some embodiments. The dichroic properties illustrated inFIG. 16Bare applicable to one or more of the optical filters described herein. In the embodiment illustrated inFIG. 16A, the optical filter is a long pass filter that is operable to transmit light in the third wavelength range (e.g., red wavelengths such as 600 nm to 700 nm) and reflect light in the second wavelength range (e.g., blue wavelengths such as 400 nm-500 nm). The optical filter can also reflect wavelengths in the first wavelength range (e.g., green wavelengths such as 500 nm to 600 nm).

The design of the eyepiece illustrated inFIG. 16Aprovides spatial separation in the lateral direction between the green input beam and the red input beam, enabling the filter design to be optimized for red and blue wavelengths, which are opposing ends of the visible spectrum. Accordingly, spatial separation can be used in conjunction with one or more optical filters to reduce or prevent cross-coupling. Transmittance at the wavelength range associated with the third DOE and the third planar waveguide can be approximately 90% or greater, for example 95% or higher and up to 100%. Reflectance at the first wavelength range associated with the second DOE and the second planar waveguide can be approximately 10% or less, for example, 5%, 4%, 3%, 2%, 1% or less.

Although reflective optical filters can be utilized in some embodiments, other embodiments can utilize absorptive optical filters to provide for wavelength selectivity. As an example, optical filter1650can be a long pass filter operable to transmit light in the third wavelength range and absorb light at wavelengths less than the third wavelength range.

As illustrated inFIG. 16A, the optical filter1650is disposed on the first surface1634of the third planar waveguide1630and the third DOE1638is disposed on the second surface1636of the third planar waveguide1630. However, this arrangement is not required by the present disclosure and other arrangements can be utilized, including placing the optical filter1650on the first surface1614or the second surface1616of the first planar waveguide1610or the first surface1624or the second surface1626of the second planar waveguide1620. Although the first DOE1618is disposed on the second surface1616of the first planar waveguide1610and the second DOE1628is disposed on the second surface1626of the second planar waveguide1620, and the third DOE1638is disposed on the second surface1636of the third planar waveguide1630, this is not required and the DOEs can be positioned at different positions along the z-axis with respect to the respective waveguide.

FIG. 17Ais a side view of an eyepiece with absorption color filters, according to some embodiments. Eyepiece1700for projecting an image to an eye of a viewer is illustrated. The eyepiece includes a substrate1710positioned in a substrate lateral plane. A set of color filters including a first color filter1712, a second color filter1714, and a third color filter1716(e.g., absorption color filters) are disposed on the substrate1710. The first color filter1712is disposed at a first lateral position that is operable to pass a first wavelength range (e.g., blue light, i.e., 400 nm-500 nm), the second color filter1714is disposed at a second lateral position that is operable to pass a second wavelength range (e.g., red light, i.e., 600 nm to 700 nm), and the third color filter1716is disposed at a third lateral position that is operable to pass a third wavelength range (e.g., green light, i.e., 500 nm to 600 nm).

The eyepiece1700also includes a first planar waveguide1720positioned in a first lateral plane adjacent the substrate lateral plane. The first planar waveguide1720includes a first diffractive optical element (DOE)1713disposed at the first lateral position below the first color filter1712. The eyepiece1700also includes a second planar waveguide1730positioned in a second lateral plane adjacent to the first lateral plane, and a third planar waveguide1740positioned in a third lateral plane adjacent to the second lateral plane. The second planar waveguide1730includes a second DOE1715disposed at the second lateral position below the second color filter1714, and the third planar waveguide1740includes a third DOE1717disposed at the third lateral position below the third color filter1716.

In some embodiments, the color filters are fabricating using photoresists, which can be formed on the substrate1710using photolithographic processes, for example, similar to those used in the fabrication of liquid crystal displays. The thickness of the color filters can be on the order of a few microns. As an example, the first color filter1712may be formed using a first photoresist operable to transmit the first wavelength range and attenuate the second wavelength range and the third wavelength range; the second color filter1714may be formed using a second photoresist operable to transmit the second wavelength range and attenuate the first wavelength range and the third wavelength range; and the third color filter1716may be formed using a third photoresist operable to transmit the third wavelength range and attenuate the first wavelength range and the second wavelength range.

The color filters can be positioned on either side of the substrate1710. In one embodiment, the substrate1710has a first side1705and a second side1707, with the second side1707of the substrate1710facing the first planar waveguide. The set of color filters can be disposed on the first side1705of the substrate1710as illustrated inFIG. 17A. In some embodiments, the set of color filters are disposed on the second side1707of the substrate1710facing the first planar waveguide1720.

In addition to photoresist, other appropriate color filters using absorption can be used, including ultraviolet ink. The ink can fill the gap for index matching and reduce Fresnel reflection. In addition to absorbing color filters, reflective color filters, for example, based on multilayer coatings can also be used in the embodiments described herein.

FIG. 17Bis a plan view of the eyepiece1700illustrated inFIG. 17A. As illustrated in the plan view ofFIG. 17B, the different color filters can be positioned opposite each other, for example, across an optical axis. InFIG. 17B, the red and green absorption color filters are positioned opposite each other so that light reflected back through the system, which can be mirrored to the opposite side of the optical system, will be absorbed. As an example, light reflected from the green DOE will be incident on the red color filter and will be absorbed and not coupled into the red DOE. In this embodiment, the color filters are positioned above the DOEs associated with the particular color passed by the color filter. Thus, as illustrated inFIG. 17B, embodiments of the present disclosure correlate the lateral positions of the color filters with the lateral positions of the associated DOEs so that light intended for the waveguide layers passes through the color filter and is coupled into the waveguide. Light in other wavelength ranges, which would otherwise (partially) couple into the DOE, is absorbed. If light in the desired wavelength range is reflected from the DOE, then after passing through the optical system and returning to the eyepiece1700, this light will be absorbed when it impinges on an opposing color filter that absorbs the desired wavelength range. In some embodiments, filters of the same color, for example, two blue color filters can be opposing each other. This arrangement may help with reducing the ghosting images. The incoupling grating reflection will pass through blue filters twice, which degrades the reflection intensity (i.e. ghost intensity) slightly.

Embodiments of the present disclosure provide eyepieces with multiple depth planes. In these embodiments, the eyepiece1700also includes a fourth color filter disposed on the substrate at a fourth lateral position and operable to pass the second wavelength range and a fifth color filter disposed at a fifth lateral position and operable to pass the third wavelength range. In a plan view, the second color filter can be positioned opposite the fourth color filter. The eyepiece can also include a fourth planar waveguide positioned in a fourth lateral plane adjacent the third lateral plane, a fifth planar waveguide positioned in a fifth lateral plane adjacent to the fourth lateral plane, and a sixth planar waveguide positioned in a sixth lateral plane adjacent to the fifth lateral plane. The fourth planar waveguide includes a fourth DOE disposed at the fourth lateral position, the fifth planar waveguide includes a fifth DOE disposed at the fifth lateral position, and the sixth planar waveguide includes a sixth DOE disposed at the sixth lateral position. Optionally, the eyepiece can include a sixth color filter disposed at a sixth lateral position and operable to pass the first wavelength range. Because of the low level of coupling of red light into blue DOEs, this sixth color filter can be optional. If a sixth color filter is used, the fifth color filter can be positioned opposite the sixth color filter in a plan view.

FIG. 17Cis a side view of an eyepiece with absorption color filters, according to some embodiments. In this embodiment, the color filters1712,1714, and1716are formed on one of the planar waveguide layers (e.g., the first planar waveguide1720) rather than on the substrate1710, which can be implemented using a cover glass. Variations are included within the scope of the present disclosure, including positioning one or more color filters on the substrate and one or more color filters on one or more of the planar waveguides. In embodiments, in which the color filters are positioned between the planar waveguides, maintenance of the total internal reflection properties of the waveguides is desirable. Additionally, multiple substrates (i.e., cover glass layers) can be used, with the color filters positioned between the substrates. Such arrangements can facilitate index matching to reduce the Fresnel reflection. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

FIG. 18Ais a side view of an eyepiece with aligned diffractive optical elements and optical filters, according to some embodiments.FIG. 18Bis a perspective view of an element of the eyepiece illustrated inFIG. 18A. InFIGS. 18A and 18B, an eyepiece is illustrated that utilizes aligned DOEs. The eyepiece illustrated inFIGS. 18A and 18Bshares some similarities with the eyepiece illustrated inFIG. 16Aand the description provided in relation toFIG. 16Ais applicable toFIGS. 18A and 18Bas appropriate.

Eyepiece1800, which can be used to project an image to a viewer's eye, includes a first planar waveguide1810positioned in a first lateral plane (i.e., at a first longitudinal position). The first planar waveguide1810includes a first diffractive optical element (DOE)1812disposed at a first lateral position (i.e., a first x-y coordinate position). A first optical filter1814is coupled to the first planar waveguide1810at a second lateral position (i.e., a second x-y coordinate position) that is different from the first lateral position. The first DOE1812is associated with a first wavelength range and the first optical filter1814can be implemented as an absorption filter that is operable to absorb wavelengths outside the first wavelength range. As a result, if the first DOE1812is operable to diffract green light into the first planar waveguide1810, but also couples a portion of the incident blue and red light into the first planar waveguide1810, the first optical filter1814can absorb diffracted blue and red light, improving the color performance of the first planar waveguide1810. Depending on the color configuration of the waveguide layers, the first optical filter1814can be a short pass filter if the first planar waveguide1810is designed to propagate blue light or a long pass filter if the first planar waveguide1810is designed to propagate red light. In the illustrated embodiment, with green/blue/red waveguides, the first color filter is a notch filter.

The first optical filter1814can be disposed inside a second region1807of the first planar waveguide1810so that it absorbs light propagating in the first planar waveguide1810from a first region1805. Additionally, the first optical filter1814can be disposed in a cavity inside the first planar waveguide1810or disposed on a first surface (e.g., top surface) or on a second surface (e.g., bottom surface) of the first planar waveguide1810.

The eyepiece1800also includes a second planar waveguide1820positioned in a second lateral plane (i.e., at a second longitudinal position) adjacent to the first lateral plane. The second planar waveguide1820includes a second DOE1822disposed at the first lateral position below the first DOE1812. The eyepiece1800also includes a third planar waveguide1830is positioned in a third lateral plane (i.e., at a third longitudinal position) adjacent to the second lateral plane. The third planar waveguide1830includes a third DOE1832disposed at the first lateral position below the first DOE1812and the second DOE1822and aligned along a longitudinal direction (i.e., aligned with the z-axis). In some embodiments, the third DOE1832may be a reflective grating with mirror coating for a higher diffraction efficiency, and the first DOE1812and the second DOE1822may be transmission type gratings.

A second optical filter1840is positioned between the second planar waveguide1820and the third planar waveguide1830. The second optical filter1840is disposed at the first lateral position.

Although all three DOEs (e.g., the first DOE1812, the second DOE1822, and the third DOE1832) are aligned in the embodiment illustrated inFIG. 18A, this is not required by the present disclosure and the DOEs can be spatially separated at different lateral positions. As an example, the first DOE1812(e.g., to diffract green light) can be spatially separated from the second DOE1822and the third DOE1832, which can be aligned. In this example, since green light is in the middle of the visible spectrum, it is spatially separated from the blue and red light, which are not strongly diffracted in the DOEs for the other color, enabling the blue and red DOEs (e.g., the second DOE1822and the third DOE1832) to be spatially aligned. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

Embodiments of the present disclosure utilize one or more dichroic reflectors to recycle light that can result in brighter images. Referring toFIG. 18A, a third input beam1802(e.g., a red input beam) is not strongly coupled into the second DOE1822(e.g., a DOE configured to diffract blue light). Accordingly, the third input beam1802passes through the second DOE1822with little loss due to diffraction. Image light in a second input beam1804(e.g., a blue input beam) that is not diffracted by the second DOE1822, is reflected from the second optical filter1840and impinges a second time on the second DOE1822, this time from the opposite direction of the first impingement by blue light on the second DOE1822. The second DOE1822can diffract the image light in the second wavelength range that is reflected by the second optical filter1840into the second planar waveguide1820to be guided toward the second region1807of the second planar waveguide1820, thereby improving brightness for the user.

FIG. 19is a side view of an eyepiece with optical filters integrated into waveguides of the eyepiece, according to some embodiments. In the embodiments illustrated inFIG. 19, color filters having a thicker profile than the separation distance between the substrate and the waveguides, which is typically on the order of 30 μm, can be utilized to provide for color selectivity.

Referring toFIG. 19, eyepiece1900can be used for projecting an image to a viewer's eye and includes a cover glass1910and a substrate1920positioned in a substrate lateral plane. The substrate1920includes a first color filter1922(e.g., a long pass filter operable to pass red light) disposed at a first lateral position and operable to pass a first wavelength range. The first color filter in this embodiment is operable to transmit the first wavelength range and attenuate the second wavelength range and the third wavelength range. The substrate1920also includes a second color filter1924(e.g., a notch filter operable to pass green light) disposed at a second lateral position and operable to pass a second wavelength range. The second lateral position is different from the first lateral position. The second color filter1924is operable to transmit the second wavelength range and attenuate the first wavelength range and the third wavelength range.

The substrate1920can include a first recess in which the first color filter1922is disposed and a second recess in which the second color filter1924is disposed.

The eyepiece1900also includes a first planar waveguide1930positioned in a first lateral plane adjacent the substrate lateral plane. The first planar waveguide1930includes a first diffractive optical element (DOE)1932disposed at the first lateral position below the first color filter1922. The first DOE1932is operable to diffract light in the first wavelength range into the first planar waveguide1930. The first planar waveguide1930also includes a third color filter1934(e.g., a short pass filter operable to pass blue light) disposed at a third lateral position and operable to pass a third wavelength range. The third lateral position is different from the first lateral position and the second lateral position. The first planar waveguide1930can include a recess in which the third color filter1934is disposed. The third color filter1934is operable to transmit the third wavelength range and attenuate the first wavelength range and the second wavelength range.

The eyepiece1900also includes a second planar waveguide1940positioned in a second lateral plane adjacent to the first lateral plane and a third planar waveguide1950positioned in a third lateral plane adjacent to the second lateral plane. The second planar waveguide1940includes a second DOE1942disposed at the third lateral position below the third color filter1934and the third planar waveguide1950includes a third DOE1952disposed at the second lateral position below the second color filter1924. In the illustrated embodiment, the first planar waveguide1930couples and propagates red light (i.e., the first wavelength range includes 600 nm to 700 nm), the second planar waveguide1940couples and propagates blue light (i.e., the third wavelength range includes 400 nm-500 nm), and the third planar waveguide1950couples and propagates green light (i.e., the second wavelength range includes 500 nm to 600 nm). In a plan view, the second color filter1924can be positioned opposite the third color filter1934.

In some embodiments, at least one of the first color filter1922, the second color filter1924, or the third color filter1934are cut from color filter sheets or plates and they can be laminated onto the substrate1920or the planar waveguides (e.g., the first planar waveguide1930, the second planar waveguide1940, and/or the third planar waveguide1950), can be dropped into recesses formed in the substrate1920or the planar waveguides, or the like. Since the color filters (e.g., the first color filter1922, the second color filter1924, and/or the third color filter1934) can have a thickness on the order of several hundred microns, which can be greater than the separation distance between the substrate1920and/or the planar waveguides (e.g., on the order of less than 50 μm), recesses or apertures can be formed in the substrate1920or the planar waveguides to accommodate the thicker color filters. The recesses can extend a fraction of the thickness of the substrate1920or the planar waveguides and the apertures can pass completely through the substrate1920or the planar waveguides. By recessing the color filters in the substrate1920and/or the planar waveguides or positioning the color filters in apertures passing through the substrate1920and/or the planar waveguides, the separation distance between the substrate1920and/or the planar waveguides can be maintained at a desired value.

In order to provide a second depth plane, the eyepiece1900can include a fourth color filter disposed at a fourth lateral position and operable to pass the first wavelength range and a fifth color filter disposed at a fifth lateral position and operable to pass the second wavelength range. In a plan view, the fourth color filter can be positioned opposite the fifth color filter. The eyepiece1900can also include a fourth planar waveguide positioned in a fourth lateral plane adjacent the third lateral plane, a fifth planar waveguide positioned in a fifth lateral plane adjacent to the fourth lateral plane, and a sixth planar waveguide positioned in a sixth lateral plane adjacent to the fifth lateral plane. The fourth planar waveguide includes a fourth DOE disposed at the fourth lateral position, the fifth planar waveguide includes a fifth DOE disposed at the fifth lateral position, and the sixth planar waveguide includes a sixth DOE disposed at the sixth lateral position. In some implementations, a sixth color filter can be disposed at a sixth lateral position that is operable to pass the third wavelength range, for example, a blue filter that can block red light, which is not strongly coupled into a blue DOE. The sixth color filter can be positioned opposite the first color filter.

FIG. 20is a perspective view of an eyepiece with shaped waveguides, according to some embodiments. Eyepiece2000reduces the intensity of Fresnel reflections from eyepiece surfaces, thereby decreasing ghost reflections that can occur in the optical system. The eyepiece2000can be used for projecting an image to a viewer's eye and includes one or more planar waveguides. A first planar waveguide2010is positioned in a first lateral plane. The first planar waveguide2010includes a first diffractive optical element (DOE)2012disposed at a first lateral position. The first planar waveguide2010has a first boundary2014that encloses a first surface area measured in the lateral plane.

A second planar waveguide2020is positioned in a second lateral plane adjacent to the first lateral plane. The second planar waveguide2020includes a second DOE2022that is disposed at a second lateral position outside the first boundary. The second planar waveguide2020has a second boundary2024that encloses a second surface area measured in the lateral plane. Since the second DOE2022is positioned outside the first boundary2014associated with the first planar waveguide2010, light incident on the second DOE2022does not interact with the first planar waveguide2010and does not reflect off of the first planar waveguide2010.

A third planar waveguide2030is positioned in a third lateral plane adjacent to the second lateral plane. The third planar waveguide2030includes a third DOE2032that is disposed at a third lateral position outside the first boundary2014and outside the second boundary2024. Since the third DOE2032is positioned outside the first boundary2014associated with the first planar waveguide2010and the second boundary2024associated with the second planar waveguide2020, light incident on the third DOE2024does not interact with the first planar waveguide2010or the second planar waveguide2020and does not reflect off of either the first planar waveguide2010or the second planar waveguide2020.

The first DOE2012is disposed at a peripheral region of the first boundary2014, which can include one or more peripheral cutouts on either side of the first DOE2012. In some embodiments, the first boundary2014can include one or more central orifices through which light directed to the second planar waveguide2020and the third planar waveguide2030can pass. Thus, various methods of enabling the light intended for each waveguide to reach the appropriate DOE without passing through portions of the other waveguides is provided by embodiments of the present disclosure by removing portions of the other waveguides that would otherwise reflect incident light intended for each waveguide. AlthoughFIG. 20illustrates the DOEs positioned on peninsula shaped projections from a central area of the eyepiece2000, this is not required by the present disclosure and other waveguide shapes are included within the scope of the present disclosure.

FIG. 21is a flowchart illustrating a method of operating an eyepiece including one or more planar waveguides, according to some embodiments. Method2100provides the ability to couple light into an eyepiece including one or more planar waveguides. The method2100includes directing a first beam including first wavelengths to impinge on the eyepiece (2110) and coupling at least a portion of the first beam into a first planar waveguide of the one or more planar waveguides (2112). The method2100also includes directing a second beam including second wavelengths to impinge on the eyepiece (2114) and coupling at least a portion of the second beam into a second planar waveguide of the one or more planar waveguides (2116). The method2100further includes directing a third beam including third wavelengths to impinge on the eyepiece (2118), passing a transmitted portion of the third beam through an optical filter (2120), and coupling at least a portion of the transmitted portion of the third beam into a third planar waveguide of the one or more planar waveguides (2122).

It should be appreciated that the specific steps illustrated inFIG. 21provide a particular method of operating an eyepiece including one or more planar waveguides, according to some embodiments. Other sequences of steps may also be performed according to alternative embodiments. For example, alternative embodiments may perform the steps outlined above in a different order. Moreover, the individual steps illustrated inFIG. 21may include multiple sub-steps that may be performed in various sequences as appropriate to the individual step. Furthermore, additional steps may be added or removed depending on the particular applications. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

FIG. 22is a flowchart illustrating a method of operating an eyepiece, according to some embodiments. Method2200enables light to be coupled into an eyepiece including one or more planar waveguides having a diffractive optical element associated with each of the one or more planar waveguides. The method2200includes directing a first beam including first wavelengths, a second beam including second wavelengths, and a third beam including third wavelengths to impinge on the eyepiece at a first lateral position (e.g., input port) (2210). The method2200also includes coupling at least a portion of the first beam, at least a portion of the second beam, and at least a portion of the third beam into a first planar waveguide of the one or more planar waveguides (2212) and attenuating the at least a portion of the second beam and the at least a portion of the third beam (2214).

The method2200further includes coupling at least a second portion of the second beam into a second planar waveguide of the one or more planar waveguides (2216), passing a transmitted portion of the third beam through an optical filter (2218), and coupling at least a portion of the transmitted portion of the third beam into a third planar waveguide of the one or more planar waveguides (2220).

According to some embodiments, each of the diffractive optical elements associated with each of the one or more planar waveguides is aligned at the first lateral position. The method2200can include reflecting a reflected portion of the third beam from the optical filter. The method2200can additionally include coupling at least a portion of the reflected portion of the third beam into the second planar waveguide.

It should be appreciated that the specific steps illustrated inFIG. 22provide a particular method of operating an eyepiece according to some embodiments. Other sequences of steps may also be performed according to alternative embodiments. For example, alternative embodiments may perform the steps outlined above in a different order. Moreover, the individual steps illustrated inFIG. 22may include multiple sub-steps that may be performed in various sequences as appropriate to the individual step. Furthermore, additional steps may be added or removed depending on the particular applications. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

FIG. 23is a schematic diagram illustrating a side view of an eyepiece, according to some embodiments.FIG. 23is similar toFIG. 16A. As shown inFIG. 23, eyepiece2300can be an element of the VOA illustrated inFIG. 1and used to project an image to a viewer's eye. The eyepiece2300includes a first planar waveguide layer2310positioned in a first lateral plane. In this example, the first lateral plane extends into the plane ofFIG. 23and can be considered as the x-y plane. Light incident on the eyepiece2300along the z-direction will impinge normal to a lateral plane. As described herein, the various optical elements are disposed at predetermined positions in a lateral plane to achieve the performance provided by the methods and systems described herein.

The first planar waveguide layer2310includes a first diffractive optical element (DOE)2318disposed at a first lateral position (i. e., an x-y coordinate position). The first planar waveguide layer2310has a first surface2314and a second surface2316opposite to the first surface2314. Light is incident on the first planar waveguide layer2310in a first region2305to the left of divider2301. The first region2305includes the first lateral position and the diffractive optical elements (DOEs) associated with each of planar waveguide layers. The first region2305is configured to receive image light incident on the eyepiece2300, for example, the first surface2314of the first planar waveguide layer2310. The image light includes image light in one or more wavelengths, for example, three wavelength ranges associated with red (600 nm-700 nm), green (500 nm-600 nm), and blue (400 nm-500 nm). The present disclosure is not limited to these wavelength ranges or three colors and other ranges and more than three colors (e.g., RBGY) or less than three colors. Thus, these wavelength ranges are just exemplary and can be modified as appropriate to the particular application.

The first planar waveguide layer2310also includes a second region2307to the right of divider2301. Light incident on the first region2305is diffracted into the plane of the first planar waveguide layer2310and is guided toward the second region2307of the first planar waveguide layer2310. Accordingly, a portion of the image light is transmitted through the first planar waveguide layer2310. A green incident beam2342is incident on first DOE2318. A portion of the green incident beam2342is diffracted and is guided into the second region2307of the first planar waveguide layer2310as illustrated by guided rays2319.

A second planar waveguide layer2320positioned in a second lateral plane adjacent to the first lateral plane. In the example illustrated inFIG. 23, the second lateral plane lies in the x-y plane at a location having a smaller z-dimension value than the first lateral plane. The second planar waveguide layer2320includes a second DOE2328disposed at a second lateral position (i. e., an x-y coordinate position). In the embodiment illustrated inFIG. 23, the second lateral position is different from the first lateral position, providing independent access to each of the DOEs for incident beams2342,2344, and2348.

The description provided in relation to the first planar waveguide layer2310is applicable to the second planar waveguide layer2320as appropriate. For example, the second planar waveguide layer2320has a first surface2324and a second surface2326opposite to the first surface2324. The second planar waveguide layer2320has a first region2305including the second lateral position and a second region2307. Like the first planar waveguide layer2310, the first region2305is configured to receive the image light. The image light impinging on the second planar waveguide layer2320, illustrated by incident beam2344includes light in a second wavelength range (e.g., blue light). The second planar waveguide layer2320also includes a second DOE2328that is configured to diffract image light in the second wavelength range into the second planar waveguide layer to2320be guided toward the second region2307of the second planar waveguide layer2320. The light guided in the second region2307is represented by guided rays2329.

A third planar waveguide layer2330is positioned in a third lateral plane (at a position at a smaller z-dimension than the second lateral plane). The third planar waveguide layer2330includes a third DOE2338disposed at a third lateral position, which can be different from both the first lateral position and the second lateral position. The description provided in relation to the first planar waveguide layer2310and the second planar waveguide layer2320is applicable to the third planar waveguide layer2330as appropriate.

As illustrated inFIG. 23, the third planar waveguide layer2330has a first surface2334and a second surface2336opposite to the first surface2334. The third planar waveguide layer2330has a first region2305including the third lateral position and a second region2307. The first region2305is configured to receive the image light in a third wavelength range (e.g., a red wavelength range). A third DOE2338associated with the third planar waveguide layer2330is configured to diffract image light in the third wavelength range, represented by incident beam2348into the third planar waveguide layer2330to be guided toward the second region2307of the third planar waveguide layer2330. The light guided in the second region2307is represented by guided rays2339.

FIG. 24Ais a schematic diagram illustrating an LCOS-based (Liquid Crystal on Silicon-based) image projector, according to some embodiments. Image projector2400includes a light source2410, a first lens2420, an LCOS (Liquid Crystal on Silicon) device2430, optical elements2440, and a second lens2450.FIG. 24Bis a schematic diagram illustrating an expanded view of the optical path in LCOS-based image projector2400to unfold the optical path.FIG. 24Ais similar toFIG. 7AandFIG. 24Bis similar toFIG. 7B.

The image projector2400may include light in the three primary colors, namely blue (B), green (G), and red (R). Such image light can be separated into the constituent colors, so that image light in each constituent color may be coupled to a respective waveguide layer in an eyepiece. In some embodiments, the light source2410may include a group of red LEDs, a group of green LEDs, and a group of blue LEDs. For example, the light source2410may include one red LED, one green LED, and one blue LED according to the embodiment shown inFIGS. 24A and 24B. In other embodiments, the light source2410may include two red LEDs, two green LEDs, and two blue LEDs for images to be presented on two depth planes. Each of the LEDs can have an associated CPC (Compound Parabolic Concentrator) or similar optical elements for transferring LED light radiation to a target. InFIGS. 24A and 24B, the image projector2400includes a red LED2411, a green LED2412, and a blue LED2413, each one including a respective CPC. The front surface of the LED light source2410at a plane2401is referred to herein as the CPC plane.

The image projector2400includes first lens2420, LCOS device2430, optical elements2440, and a second lens2450. The optical elements2440can include prisms and mirrors, and the like, which are configured to direct incoming light to the LCOS device2430and to direct light reflected from the LCOS device2430to the output of the image projector2400. The LCOS device2430is configured to deliver color sequential image light to a pupil plane2460in pupil plane2451. The pupil2460includes three sub-pupils, sub-pupil2461for the image in red color, sub-pupil2462for the image in green color, and sub-pupil2463for the image in blue color. For example, in a frame of colored image, in a first time period, light2415from the red LED2411is turned on, and the LCOS device2430selects a subset of pixels in an image frame to receive the red light. In a second time period, light2415from green the LED2412is turned on, and the LCOS device2430selects another subset of pixels to receive the green light. Similarly, in a third time period, light2415from the blue LED2413is turned on, and the LCOS device2430selects yet another subset of pixels to receive the blue light. The colored image light is delivered to the sub-pupils2461,2462, and2463in a color sequential manner.

The image projector2400is configured to project image light to an eyepiece2490. Similar to the eyepiece2300inFIG. 23, eyepiece2490includes three planar waveguide layers, each waveguide layer having a respective diffractive optical element (DOE)2491,2492, and2493, which can function as incoupling gratings (ICGs) to receive image light. Therefore, the terms DOE and ICG will be used interchangeably. As shown inFIG. 24B, the red, green, and blue colored image light delivered respectively to the sub-pupils2461,2462, and2463is received by a DOE in a corresponding waveguide layer in eyepiece2490. The eyepiece2490also includes an OPE2495and an EPE2497in each of the waveguide layer for delivering a colored image to the user.

Similar to the DOE2318,2328, and2338inFIG. 23, the three sub-pupils2461,2462, and2463inFIG. 24Bdisposed on separate waveguide layers and are also spatially displaced reduce interference of incoming image light directed to each waveguide layer in the eyepiece2490.

FIGS. 25A-25Bare diagrams illustrating an LED light sources, according to some embodiments.FIG. 25Ais similar toFIG. 5A.FIG. 25Aillustrates light illumination from a light source with six LED sources for six waveguide layers in an eyepiece for two depth planes. There are two red LEDs, two green LEDS, and two blue LEDs. The light illumination is shown on a CPC plane (e.g., the plane2401inFIG. 24B), or in front of LED light sources (e.g., the LEDs2411,2412,2413). Alternatively,FIG. 25Acan also represent light illumination in an output pupil (e.g., the pupil plane2460inFIG. 24B). It can be seen that the light sources illustrated inFIG. 25Autilize about 36% of the available space. In other words, this light source arrangement has a fill factor of approximately 36%.

FIG. 25Billustrates light illumination from another light source with nine LED sources for three waveguide layers in an eyepiece for three depth planes. There are three red LEDs, three green LEDS, and three blue LEDs. Again, the light illumination is shown on the CPC plane (e.g., the plane2401inFIG. 24B), or in front of the LED light sources (e.g., the LEDs2411,2412,2413). This arrangement also exhibits a limited light source fill factor.

FIGS. 26A-26Care schematic diagrams illustrating LED light sources, according to some embodiments.FIG. 26Aillustrates light illumination from a light source2610with three LED sources for two waveguide layers in an eyepiece for two depth planes. There is one red LED light source2611, one green LED light source2612, and one blue LED light source2613. Each LED light source is rectangular, and the three LED light sources2611,2612,2613are disposed adjacent to one another. The light illumination is shown on the plane2401(e.g., a CPC plane) inFIG. 24B, or in front of the LED light sources2611,2612,2613. Alternatively,FIG. 26Acan also represent light illumination in the pupil plane2460inFIG. 24B. It can be seen that the LED light sources2611,2612,2613utilize substantially 100% of the available space. In other words, this LED light source arrangement has a fill factor of approximately 100%. The higher fill factor can provide bright image light in the display. In light source2610, each LED light source can include one or more LED dies and a light concentrator, for example, a CPC. In some embodiments, the light source2610may include other types of light sources. In these embodiments, the LED light sources2611,2612, and2613may be other types of light sources.

FIG. 26Billustrates light illumination from a light source2620with six LED sources for two waveguide layers in an eyepiece for two depth planes. There are two red LED light sources2621and2625, two green LED light sources2622and2624, and two blue LED light sources2623and2626. The light illumination is shown on the plane2401inFIG. 24B, or in front of the LED light sources. Alternatively,FIG. 26Bcan also represent light illumination in the pupil plane2460inFIG. 24B. InFIG. 26B, the six LED light sources2621,2622,2623,2624,2625,2626are disposed, respectively, in six sectors of the circular-shaped light source2620. Each LED light source has a wedge-like or pie-like shape. It can be seen that the light sources2621,2622,2623,2624,2625,2626utilizes substantially 100% of the available space. In other words, this light source arrangement has a fill factor of approximately 100%. The higher fill factor can provide bright image light in the display. In light source2620, each LED light source can include one or more LED dies and a light concentrator, for example, a CPC.

FIG. 26Cillustrates light illumination from a light source2630with six LED sources for two waveguide layers in an eyepiece for two depth planes. There are two red LED light sources2631and2633, two green LED light sources2632and2635, and two blue LED light sources2634and2636. The light illumination is shown on the plane2401inFIG. 24B, or in front of the LED light sources. Alternatively,FIG. 26Ccan also represent light illumination in the pupil plane2460inFIG. 24B. InFIG. 26C, the six rectangular LED light sources2631,2632,2333,2634,2635,2636are disposed, respectively, in six regions of the rectangular-shaped light source2630. It can be seen that the light sources2631,2632,2333,2634,2635,2636utilizes substantially 100% of the available space. In other words, this light source arrangement has a fill factor of approximately 100%. The higher fill factor can provide bright image light in the display. In light source2630, each LED light source can include one or more LED dies and a light concentrator, for example, a CPC.

The geometric shapes illustrated inFIGS. 26A-26Care not intended to limit embodiments of the disclosure, but merely to provide examples of LED geometries that can be utilized according to some embodiments. In some embodiments, other geometric shapes including square, triangular, hexagonal, and the like can be utilized to increase the fill factor while providing sources suitable for use with one or more depth planes. Other geometry of RGB LED layouts can also be arbitrary, which may require the corresponding ICGs layout to match the geometry of the light source. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

FIG. 27Ais a schematic diagram illustrating an image display system, according to some embodiments. Image display system2700includes a white light source2710and an LCOS-based (Liquid Crystal on Silicon-based) image projector2701. The white light source2710may be a white LED light source2710. The image projector2701includes a first lens2720, an LCOS (Liquid Crystal on Silicon) device2730, optical elements2740, and a second lens2721. Similar toFIG. 24B,FIG. 27Ais a schematic diagram illustrating an expanded view of the optical path in LCOS-based image projector to unfold the optical path.

In some embodiments, the white light source2710can include one or more white LED light emitters. In some embodiments, each white LED light emitter can include a blue LED chip coated with a yellow phosphor layer for emitting white light. In some embodiments, a white LED light emitter can have a combinations of red, green, and blue for emitting white light. The white light source2710may also have a concentrator, such as a CPC for delivering the white light. In some embodiments, the white light source2710is configured in a square or rectangular shape, although other geometric shapes can be used depending on the application. A front surface of the white light source2710is at a plane2711is referred to herein as the CPC plane2711.

The image display system2700includes the first lens2720, the LCOS device2730, the optical elements2740, and the second lens2721. The optical elements2740may include prisms, mirrors, and the like, which are configured to direct incoming light to the LCOS device2730and to direct light reflected from the LCOS device2730to the output of the image projector2701. The LCOS device2730is configured to deliver time sequential image light to a pupil2750on a super pupil plane2751. The pupil2750includes a gray scale image light sequentially for each of the three fundamental colors. For example, in a first time period, light2715from the white light source2710is turned on, and the LCOS device2730is configured to select a subset of pixels in an image frame for the red light. In a second time period, light2715from the white light source2710is turned on, and the LCOS device2730is configured to select another subset of pixels for the green light. Similarly, in a third time period, light2715from the white light source2710is turned on, and the LCOS device2730is configured to select yet another subset of pixels for the blue light. The gray scale image light is delivered to the pupil2750, which is also referred to as a super pupil, in a color sequential manner.

In some embodiments, the image display system2700may also include a shutter2760and color filters (CFs)2770for projecting colored image light in a color sequential manner through a sub-pupils2780to an eyepiece2790. In the embodiment ofFIG. 27A, the image display system2700is configured for a single depth plane. Similar to the eyepiece2300inFIG. 23, eyepiece2790inFIG. 27Aincludes three planar waveguide layers, and each waveguide layer has a respective diffractive optical element (DOE), which can function as incoupling gratings to receive image light. InFIG. 27A, to simplify the drawing, only one waveguide layer is labeled with a DOE2791, an orthogonal pupil expander (OPE)2795, and an exit pupil expander (EPE)2797.

FIGS. 27B-27Dare schematic diagrams illustrating the operations of the shutter2760and the color filters2770in the image display system2700inFIG. 27A. In some embodiments, the shutter2760may be a liquid crystal shutter. As shown inFIG. 27B, for a display system with a single depth plane, the shutter2760includes three regions, a first shutter region2761, a second shutter region2762, and a third shutter region2763. Similarly, the color filters2770includes three regions, a first filter region2771for the red color, a second filter region2772for the blue color, and a third filter region2773for the green color. Each color filter region is aligned with a respective shutter region. Further, pupil, or super pupil,2780, includes three sub-pupils,2781,2782, and2783.

The shutter2760and the color filters2770are configured to present each of the primary colors in a time sequential manner. For example, as shown inFIG. 27B, in a first time period T1, the white light2715from the white light source2710is turned on, and the LCOS device2730is configured to select a subset of pixels in an image frame for the red light. The gray scale image from the LCOS device2730is projected in the pupil2750. During time period T1, the first shutter region2761is open, and the second shutter region2762and the third shutter region2763are closed, allowing the gray scale image light to reach the first filter region2771of filter2770. As a result, a red image light is present in the sub-pupil2781, which is projected to a corresponding ICG or DOE in a waveguide layer for the red image.

As shown inFIG. 27C, in a second time period T2, the white light2715from the white light source2710is turned on, and the LCOS device2730is configured to select a second subset of pixels for the green light. The gray scale image from the LCOS device2730is projected in the pupil2750. During time period T2, the second shutter region2762is open, and the first shutter region2761and the third shutter region2763are closed, allowing the gray scale image light to reach the second filter region2772of filter2770. As a result, a blue image light is present in the sub-pupil2782, which is projected to a corresponding ICG or DOE in a waveguide layer for the blue image.

Similarly, as shown inFIG. 27D, in a third time period T3, the white light2715from the white light source2710is turned on, and the LCOS device2730is configured to select a third subset of pixels for the blue light. The gray scale image light from the LCOS device2730is delivered to the pupil2750. During time period T3, the third shutter region2763is open, and the first shutter region2761and the second shutter region2762are closed, allowing the gray scale image light to reach the third filter region2773of filter2770. As a result, a green light image light is present in the sub-pupil2783, which is projected to a corresponding ICG or DOE in a waveguide layer for the green image.

As described above, in the image display system2700, the shutter2760and the colors filter2770are configured to operate in synchronization with LCOS device2730to present red, green, and blue colored image light respectively to the sub-pupils2781,2782, and2793. The colored image light is received by an ICG or DOE2791in a corresponding waveguide layer in the eyepiece2790for delivering a colored image to the user. The sub-pupils2781,2782, and2783are spatially displaced to be aligned with respective ICGs or DOEs2791in the eyepiece2790. Further, the sub-pupils2781,2782, and2783are configured to fill up the sub-pupil2780, with a fill factor substantially at 100%.

FIG. 28is a schematic diagram illustrating an operation of image light coupled into a waveguide layer in the image display system2700ofFIG. 27, according to some embodiments.FIG. 28illustrates a waveguide layer2800in a side view2810and a top view2820. The waveguide layer2800can be one of the waveguide layers in the eyepiece2790in the image display system2700inFIG. 27. An output pupil from an LCOS image projector is shown as2830, which includes sub-pupils2831,2832, and2832. After passing through a shutter and color filters a sub-pupil is selected, similar to the sub-pupil2780inFIG. 27A, and is coupled into the waveguide layer2800by diffractive optical element (DOE) or an input coupling grating (ICG)2805. As shown in the side view2810, image light2803is incoupled into the waveguide layer2800and propagates by total internal reflection (TIR) in the x-direction2809of the waveguide layer2800.

As shown in the top view2820of the waveguide layer2800, ICG2805is configured in a rectangular shape to match the shape of image light provided in the sub-pupils2831,2832,2833. It can be seen that ICG2805is elongated and extends in the direction that is perpendicular to the direction of propagation2809of the image light in the waveguide layer2800. Therefore, the elongated ICG2805can incouple a greater amount of image light into the waveguide layer2800for brighter display. If the ICG2805has an extended dimension along light propagation, then some light undergoing TIR may impinge on the ICG2805and diffract out of the waveguide layer2800, causing a loss of light intensity. As can be seen inFIG. 28, ICG2805is narrow in the direction of propagation2809. Therefore, it does not diffract the light undergoing TIR, which can cause light loss. Further, the elongated ICG2805can receive more light intensity.

FIG. 29Ais a photographic image illustrating higher order diffraction by the LCOS in an image display system. InFIG. 29A, the image is taken at the super pupil plane2751inFIG. 27A, in which a green light2910, a red light2920, and a blue light2930can represent LED light sources. Alternatively, they can also represent a placement of corresponding ICGs on respective waveguide layers of an eyepiece.FIG. 29Ashows higher order diffraction images2911,2912, and2913, and the like (not all labeled), of the green light2910by the LCOS device. It can be seen that the higher order diffraction images are aligned in horizontal and vertical directions from the light source. In the eyepiece, the higher order diffraction images from the green color can impinge on ICGs for the red and blue colors, which can cause interference, also known as ghosting.FIG. 29Ais similar toFIG. 15.

FIG. 29Bis a schematic diagram illustrating a method for arranging the incoupling gratings (ICGs) in an image display system, according to some embodiments. In a left portion ofFIG. 29B, the ICGs for the green, red, and blue colors are aligned vertically to match the RGB LED layout, which, as illustrated inFIG. 29A, can cause interference, because high order diffraction from the LCOS tends to be along the vertical or horizontal directions. Therefore, in some embodiments, the ICGs are arranged in a staggered or rotated manner, as shown in the right portion ofFIG. 29B, to avoid interference caused by LCOS higher order diffraction. Accordingly, embodiments of the present disclosure utilize a liquid crystal shutter and the spatial rotation of the ICGs by a predetermined angle to reduce the level of ghosting resulting from diffraction by the LCOS.

FIG. 29Cis a schematic diagram illustrating another method for arranging the incoupling gratings (ICGs) in an image display system, according to some embodiments. In the left portion ofFIG. 29C, six ICGs for the green, red, and blue colors are disposed in a symmetric arrangement, in which a green ICG and a blue ICG are aligned vertically, which, as illustrated inFIG. 29A, can cause interference. Therefore, in some embodiments, the pattern of the ICGs is tilted, e. g., by 15°, as shown in the right portion ofFIG. 29B, to avoid interference and or cross-talk caused by LCOS higher order diffraction.

FIG. 30is a schematic diagram illustrating another image display system, according to some embodiments. Image display system3000is similar to image display system2700inFIG. 27Aand discussion provided in relation toFIG. 27Ais applicable toFIG. 30as appropriate. As described above in connection toFIG. 27A-27D, the image display system2700is configured to provide three color images to three waveguide layers of an eyepiece for a single depth plane. In contrast, image display system3000is configured to provide six color images to six waveguide layers of an eyepiece for two depth planes.

As shown inFIG. 30, the image display system3000includes a white light source3010and a Liquid Crystal on Silicon-based (LCOS-based) image projector3001, according to some embodiments. The image projector3001includes a first lens3020, a Liquid Crystal on Silicon (LCOS) device3030, optical elements3040, and a second lens3021. Similar toFIG. 27A,FIG. 30is a schematic diagram illustrating an expanded view of the optical path in the LCOS-based image projector3001to unfold the optical path.

In image display system3000, the white light source3010, the first lens3020, the optical elements3040, and the second lens3021are similar to corresponding components in the image display system2700inFIG. 27A. The optical elements3040may include prisms and mirrors, and the like, which are configured to direct incoming light to the LCOS device3030and to direct light reflected from the LCOS device3030to the output of the image projector3001. The LCOS device3030is configured to deliver time sequential image light to a pupil3050on a pupil plane3051. The image projector3001is configured to project sequentially six gray scale or black-and-white images at the pupil3050. Each image is configures to select pixels for each of the three fundamental colors. For example, in a first time period, light3015from the white LED light source3010is turned on, and the LCOS device3030is configured to select a subset of pixels in an image frame for the red light for a first depth plane. In a second time period, light3015from the white LED light source3010is turned on, and the LCOS device3030is configured to select another subset of pixels for the green light for the first depth plane. Similarly, in a third time period, light3015from the white LED light source3010is turned on, and the LCOS device3030is configured to select yet another subset of pixels for the blue light for the first depth plane. Similarly, in the fourth, fifth, and sixth time periods, the LCOS device3030is configured to a subset of pixels for the red, the green, and the blue light, respectively, for a second depth plane. Thus, the gray scale image light is delivered to pupil3050, in a color sequential manner.

In some embodiments, the image display system3000also includes a shutter3060and color filters3070for projecting colored image light in a color sequential manner through a sub-pupils3080for projecting to an eyepiece (not shown). In the embodiment ofFIG. 30, the image display system3000is configured for an eyepiece having two depth planes. Therefore, the eyepiece includes six planar waveguide layers, and each waveguide layer has a respective diffractive optical element (DOE), which can function as incoupling gratings to receive image light. InFIG. 30, to simplify the drawing, the eyepiece is not shown.

For a display system with two depth planes, the shutter3060includes six regions, each region has a shutter for one of the colors. Similarly, the color filters3070includes six regions, each region has a filter for one of the colors. Each filter region is aligned with a respective shutter region. Further, the pupil3050and/or the sub-pupil3080, includes six sub-pupils.

As describe above, in the image display system3000, the shutter3060and the color filter3070are configured to operate in synchronization with the LCOS device3030to present red, green, and blue colored image light respectively to one of six sub-pupils. The colored image light is received by an ICG or DOE in a corresponding waveguide layer in the eyepiece for delivering a colored image to the user.

FIGS. 31A-31Care schematic diagrams illustrating another image display system, according to some embodiments. As shown inFIG. 31A, image display system3100is similar to image display system2700inFIG. 27A. As described above in connection toFIG. 27A-27D, the image display system2700is configured with a single white light source2710. In contrast, the image display system3100is configured with multiple white light sources.

As shown inFIG. 31A, the image display system3100includes a white light source3110and a Liquid Crystal on Silicon-based (LCOS-based) image projector3101according to some embodiments. The image projector3101includes a first lens3120, a Liquid Crystal on Silicon (LCOS) device3130, optical elements3140, and a second lens3121. Similar toFIG. 27A,FIG. 31Ais a schematic diagram illustrating an expanded view of the optical path in LCOS-based image projector to unfold the optical path.

In the image display system3100, the first lens3120, the optical elements3140, and the second lens3121are similar to corresponding components in the image display system2700inFIG. 27. In an embodiment, the white light source3110includes two LED white light sources,3111and3112. The optical elements3140can include prisms and mirrors, and the like, which are configured to direct incoming light to the LCOS device3130and to direct light reflected from the LCOS device3130to the output of the image projector3101. The LCOS device3130is configured to deliver time sequential image light to a pupil3150on a pupil plane3151. The image projector3101is configured to project sequentially gray scale or black-and-white images at the pupil3150. Each image is configures to select pixels for each of the three fundamental colors. In this embodiment, LED white light sources,3111and3112are turned on sequentially.

In some embodiments, the image display system3100also includes a shutter3160and color filters (CFs)3170for projecting colored image light in a color sequential manner through a sub-pupils3180to an eyepiece3190. Depending on the embodiments, different combinations of shutter and color filters can be used in the image display system. For example,FIG. 31Billustrate part of an image projector having two white LED light sources3111and3112, and a single shutter have three shutter regions. Further, color filters3171can have color regions for red, blue, and green colors aligned for each LED light sources. In contrast, in color filters3172, the red, blue, and green color filters can be staggered, which can result in less ghosting due to diffraction. In some embodiments, as shown inFIG. 31C, an image projector having two white LED light sources3111and3112, and two shutters3162and3163, each with three shutter regions. Further, color filters3173can have color regions for red, blue, and green colors aligned for each LED light sources3111,3112. In contrast, in color filters3174, the red, blue, and green color filters can be staggered.

As described above, the image display system3100can be configured to provide either three sub-pupils for a single depth plane or to provide six sub-pupils for two depth planes for the eyepiece3190. Therefore, the eyepiece3190can include either three waveguide layers for a signal depth plane or six waveguide layers for two depth planes. To simplify the drawing, only one waveguide layer is shown with a diffractive optical element (DOE)3191, an OPE3195, and an EPE3197.

FIG. 32is a schematic diagram illustrating another image display system, according to some embodiments. Image display system3200is similar to the image display system2700inFIG. 27A. As described above in connection toFIG. 27A-27D, the image display system2700is configured with a white light source and an image projector with a color-sequential LCOS device. In contrast, the image display system3200is configured with a white light source and an image projector with a non-color-sequential LCOS device.

As shown inFIG. 32, the image display system3200includes a white light source3210and a Liquid Crystal on Silicon-based (LCOS-based) image projector3201, according to some embodiments. The image projector3201includes a first lens3220, a non-color-sequential Liquid Crystal on Silicon (LCOS) device3230, optical elements3240, and a second lens3221. Similar toFIG. 27A,FIG. 32is a schematic diagram illustrating an expanded view of the optical path in LCOS-based image projector to unfold the optical path.

Certain components in the image display system3200are similar to the corresponding components in image display system2700inFIG. 27A, including the white light source3210, the first lens3220, the optical elements3240, and the second lens3221. However, the non-color-sequential LCOS device3230is non-color-sequential LCOS device that is configured to receive a white illumination light and project a full color image at a pupil3250on a pupil plane3251. In some embodiments, the non-color-sequential LCOS device3230is configured with color filters to process images in the three primary colors and provide a combined full color image. In some embodiments, the non-color-sequential LCOS device3230may include three LCOS panels to process images in the three primary colors and provide a combined full color image. In some embodiments, the non-color-sequential LCOS device3230may include a single integrated LCOS panel to process images in the three primary colors and provide a combined full color image.

In some embodiments, the image display system3200also includes a shutter3260and color filters (CFs)3270for receiving the full color images at pupil3250and projecting colored image light in a color sequential manner through a sub-pupils3280to an eyepiece3290. In the embodiment ofFIG. 32, the image display system3200is configured for a single depth plane. However, the system can also be applied to multiple depth planes. Similar to the eyepiece2790inFIG. 27A, eyepiece3290inFIG. 32includes three planar waveguide layers, and each waveguide layer has a respective diffractive optical element (DOE), which can function as incoupling gratings to receive image light. InFIG. 32, to simplify the drawing, only one waveguide layer is labeled with a DOE3291, an OPE (orthogonal pupil expander)3295, and an EPE (exit pupil expander)3297.

In some embodiments, the shutter3260can be a liquid crystal shutter. As shown inFIG. 32, for a display system with a single depth plane, the shutter3270includes three shutter regions. Similarly, the color filters3270includes three filter regions, a first filter region for a red color, a second filter region for a blue color, and a third filter region for a green color. Each filter region is aligned with a respective filter region. Further, pupil, or super pupil,3250, includes three sub-pupils, with only one sub-pupil3280shown inFIG. 32.

The shutter3260and the color filters3270are configured to receive the full color image at pupil3250and present images of each of the primary colors in a time sequential manner to the eyepiece3290. For example, in a first time period, the shutter region aligned to the red filter region is open, allowing the red image in the full color image to pass through forming a sub-pupil of red image, which is received in a DOE of a waveguide layer for the red color. In a second time period, the shutter region aligned to the green filter region is open, allowing the green image in the full color image to pass through forming a sub-pupil of green image, which is received in a DOE of a waveguide layer for the green color. Similarly, in a third time period, the shutter region aligned to the blue filter region is open, allowing the blue image in the full color image to pass through forming a sub-pupil of blue image, which is received in a DOE of a waveguide layer for the blue color. As described above, the ICGs in each waveguide layers may be spatially displaced. Therefore, ghost imaging from ICG reflection may be reduced.

As describe above, in the image display system3200, the shutter3260and the color filters3270are configured to operate in synchronization with the non-color-sequential LCOS device3230to receive a full color image from the LCOS device3230present red, green, and blue colored image light respectively. The colored image light is received by an ICG or DOE3291in a corresponding waveguide layer in the eyepiece3290for delivering a colored image to the user. Thus, each full color image provided by the LCOS device3230is projected into the eyepiece3290in a color-sequential manner of three single-color images in red, green, and blue, respectively. In this embodiment, the frame rate of the LCOS device3230, for example, 180 frames per second, can be fully utilized in the eyepiece3290. In contrast, in image display systems based on color-sequential LCOS device described above, a duration of three frames of the LCOS device is used to project a single frame in an eyepiece. As a result, only one-third of the frame rate of the LCOS device, for example, 60 frames per second, can be utilized in the projected images in the eyepiece.

Although the above has been illustrated in terms of specific hardware features, it would be recognized that many variations, alternatives, and modifications can exist. For example, any of the hardware features can be further combined, or even separated. The features can also be implemented, in part, through software or a combination of hardware and software. The hardware and software can be further integrated or less integrated depending upon the application. Further details of certain methods according to the present disclosure can be found throughout the present specification and more particularly below.

FIG. 33is a flowchart illustrating a method for displaying an image, according to some embodiments. Method3300for displaying an image includes providing a white light source and an image projector (3310). An example of white light source is shown inFIG. 27A, in which white light source2710can include one or more white LED light emitters. Each white LED light emitter may include a blue LED chip coated with a yellow phosphor layer for emitting white light. Alternatively, a white LED light emitter may have a combinations of red, green, and blue for emitting white light. The white light source2710may also have a concentrator, such as a CPC for delivering the white light. In some embodiments, the white LED light source is configured in a square or rectangular shape. The front surface of the white LED light source at the plane2711is referred to herein as the CPC plane.

In some embodiments, the image projector2701is an LCOS-based image projector2701. The image projector2701has the LCOS device2730and various optical components to direct incoming light to the LCOS device2730and to direct light reflected from the LCOS device2730to the output of the image projector2701.

The method3300also includes receiving white light from the white light source at the image projector (3320) and projecting sequentially gray scale images in an optical pupil (3330). The LCOS device2730is configured to deliver time sequential image light to the pupil2750on the pupil plane2751. The pupil2750includes a gray scale image light sequentially for each of the three fundamental colors. Each gray scale image configured for selecting pixels for each of three colors (e.g., primary colors).

The method3300also includes providing a shutter and color filters for dividing the optical pupil into three sub-pupils for the three primary colors (3340). In some embodiments, the shutter2760can be a liquid crystal shutter. As shown inFIG. 27B, for a display system with a single depth plane, the shutter2760includes three regions, a first shutter region2761, a second shutter region2762, and a third shutter region2763. Similarly, the color filters2770includes three regions, a first filter region2771for the red color, a second filter region2772for the blue color, and a third filter region2773for the green color. Each filter region is aligned with a respective filter region. The shutter regions and the filter regions are aligned to divide the pupil2750(e.g., super pupil), into three sub-pupils,2781,2782, and2783, for the three primary colors, red, green, and blue.

The method3300further includes synchronizing the shutter and color filters with the gray scale images from the LCOS-based image projector sequentially project images in each of the three primary colors in a corresponding sub-pupil (3750). As illustrated inFIG. 27B, in a first time period T1, light2715from the white light source2710is turned on, and the LCOS device2730is configured to select a subset of pixels in an image frame for the red light. The gray scale image from the LCOS device2730is projected in the pupil2750. During time period T1, the first shutter region2761is open, and the second shutter region2762and the third shutter region2763are closed, allowing the gray scale image light to reach the first filter region2771of the color filter2770. As a result, a red image light is present in the sub-pupil2781.

As shown inFIG. 27C, in a second time period T2, light2715from the white light source2710is turned on, and the LCOS device2730is configured to select a second subset of pixels for the green light. The gray scale image from the LCOS device2730is projected in the pupil2750. During time period T2, the second shutter region2762is open, and the first shutter region2761and the third shutter region2763are closed, allowing the gray scale image light to reach the second filter region2772of the color filter2770. As a result, a blue image light is present in the sub-pupil2782.

Similarly, as shown inFIG. 27D, in a third time period T3, light2715from the white light source2710is turned on, and the LCOS device2730is configured to select a third subset of pixels for the blue light. The gray scale image light from the LCOS device2730is delivered to the pupil2750. During time period T3, the third shutter region2763is open, and the first shutter region2761and the second shutter region2762are closed, allowing the gray scale image light to reach the third filter region2773of the color filter2770. As a result, a green light image light is present in the sub-pupil2783.

The method3300also includes providing an eyepiece having three waveguide layers (3360). For example, as shown inFIG. 27A, the eyepiece2790includes three planar waveguide layers, and each waveguide layer has a respective diffractive optical element (DOE), which can function as incoupling gratings to receive image light. InFIG. 27A, to simplify the drawing, only one waveguide layer is labeled with a DOE2791, an orthogonal pupil expander (OPE)2795, and an exit pupil expander (EPE)2797. Each waveguide layer is configured to display an image in one of the three colors (e.g., primary colors).

The method3300also includes sequentially receiving images in each of the three colors (e.g., primary colors) in a corresponding waveguide layer for projecting an image to a viewer (3370). Referring back toFIGS. 27B-27D, during time T1, a red image light is present in the sub-pupil2781, which is projected to a corresponding ICG or DOE in a waveguide layer for the red image. During time T2, a blue image light is present in the sub-pupil2782, which is projected to a corresponding ICG or DOE in a waveguide layer for the blue image. During time T3, a green light image light is present in the sub-pupil2783, which is projected to a corresponding ICG or DOE in a waveguide layer for the green image. The eyepiece2790with three waveguide layers are configured to display a color image to the view.

FIG. 34is a flowchart illustrating another method for displaying an image, according to some embodiments. Method3400for displaying an image includes providing a white light source and an image projector (3410), receiving white light from the white light source at the image projector (3420), projecting images in an optical pupil (3430), providing a shutter and color filters for dividing the optical pupil into a plurality of sub-pupils (3440), synchronizing the shutter and color filters with the images from the image projector and sequentially project images in each of the three primary colors in a corresponding sub-pupil (3450), providing an eyepiece having multiple waveguide layers (3460), and sequentially receiving images in each of the three primary colors in a corresponding waveguide layer for projecting an color image to a viewer (3470).

The method3400includes steps that are similar to the method3300described above in connection withFIG. 33. However, the method3400includes additional features. For example, as illustrated inFIGS. 27A-32, the white light source in step3410may include one or more white light sources either separately controlled or integrated. Further, the image projector in step3410may include a color-sequential LCOS-based image projector for projecting gray scale or black-and-white images to an optical pupil. In some embodiments, the image projector can be a non-color-sequential LCOS-based image projector for projecting full color images to the optical pupil. Further, the optical pupil is not limited to three sub-pupils. Depending on the embodiments, the optical pupil can be divided into three sub-pupils for an eyepiece having a single depth plane, six sub-pupils for an eyepiece having two depth planes, or nine sub-pixels for an eyepiece having thee depth planes, or more sub-pixels for eyepieces having more than three depth planes. Depending on the eyepiece and the number of sub-pixels, the shutter can have a corresponding number of shutter regions, and the color filter can have a corresponding number of filter regions. The shutter and color filters are configured to synchronize with either color-sequential or non-color-sequential LCOS-based projectors.

It should be appreciated that the specific steps illustrated inFIGS. 33 and 34provide a particular method of operating an eyepiece, according to some embodiments. Other sequences of steps may also be performed, according to some embodiments. For example, some embodiments may perform the steps outlined above in a different order. Moreover, the individual steps illustrated inFIGS. 33 and 34may include multiple sub-steps that may be performed in various sequences as appropriate to the individual step. Furthermore, additional steps may be added or removed depending on the particular applications. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

According to an aspect of the present disclosure, an eyepiece unit including optical filters is provided. The eyepiece unit includes a set of waveguide layers including a first waveguide layer and a second waveguide layer. The first waveguide layer is disposed in a first lateral plane and includes a first incoupling diffractive element disposed at a first lateral position, a first waveguide optically coupled to the first incoupling diffractive element, and a first outcoupling diffractive element optically coupled to the first waveguide. The second waveguide layer is disposed in a second lateral plane adjacent to the first lateral plane and includes a second incoupling diffractive element disposed at a second lateral position, a second waveguide optically coupled to the second incoupling diffractive element, and a second outcoupling diffractive element optically coupled to the second waveguide. The eyepiece also includes a set of optical filters including a first optical filter and a second optical filter. The first optical filter is positioned at the first lateral position and is operable to attenuate light outside a first spectral band and the second optical filter is positioned at the second lateral position and is operable to attenuate light outside a second spectral band.

In an aspect, the set of waveguide layers includes a third waveguide layer and the set of optical filters includes a third optical filter. The third waveguide layer is disposed in a third lateral plane and includes a third incoupling diffractive element disposed at a third lateral position, a third waveguide optically coupled to the third incoupling diffractive element, and a third outcoupling diffractive element optically coupled to the third waveguide. The third optical filter is positioned at the third lateral position and is operable to attenuate light outside a third spectral band.

In an aspect, the first spectral band includes red wavelengths, the second spectral band includes green wavelengths, and the third spectral band includes blue wavelengths. The first optical filter can transmit at least one of green wavelengths or blue wavelengths, the second optical filter can transmit at least one of red wavelengths or blue wavelengths. The set of optical filters can be disposed on a surface of a cover plate disposed in a third lateral plane adjacent to the first lateral plane.

The cover plate can include a low transmittance media between the set of optical filters. The first optical filter can be disposed between a cover plate and the first waveguide layer. The cover plate can be disposed in a third lateral plane adjacent the first lateral plane. The second optical filter can be disposed between the first waveguide layer and the second waveguide layer. The first lateral position and the second lateral position can be a same lateral position. The eyepiece unit can be disposed adjacent a projection lens and the set of optical filters can be disposed between the projection lens and the set of waveguide layers. The first lateral position can be displaced laterally with respect to the second lateral position. The first incoupling diffractive element can be configured to incouple light in the first spectral band. The second incoupling diffractive element can be configured to incouple light in the second spectral band.

According to an aspect of the present disclosure, an artifact mitigation system is provided. The artifact mitigation system includes a projector assembly, a set of imaging optics optically coupled to the projector assembly, and an eyepiece optically coupled to the set of imaging optics. The eyepiece includes an incoupling interface. The artifact mitigation system also includes a set of optical filters including a first optical filter operable to attenuate light outside a first spectral band, a second optical filter operable to attenuate light outside a second spectral band, and a third optical filter operable to attenuate light outside a third spectral band.

In an aspect, the first spectral band includes red wavelengths, the second spectral band includes green wavelengths, and the third spectral band includes blue wavelengths. The incoupling interface can include a plurality of incoupling diffractive elements arrayed around an optical axis. The projector assembly can further include a polarization beam splitter (PBS), a set of spatially displaced light sources disposed adjacent to the PBS, and a display panel disposed adjacent to the PBS. The set of imaging optics can be disposed adjacent to the PBS.

The projector assembly can further include a polarization beam splitter (PBS), a set of spatially displaced light sources disposed adjacent to a first side of the PBS, a collimator disposed adjacent to a second side of the PBS, and a display panel disposed adjacent to a third side of the PBS. The set of imaging optics can be disposed adjacent a fourth side of the PBS. The fourth side can be positioned between the first side and the second side and opposite to the third side. The display panel can include at least one of a reflective display or an LCOS display. The set of imaging optics can be configured to form an image at the incoupling interface. The incoupling interface can include at least one of polarizing films, wire grid polarizers, or dielectric stacked coatings.

According to an aspect of the present disclosure, an eyepiece for projecting an image to an eye of a viewer is provided. The eyepiece includes a first planar waveguide positioned in a first lateral plane. The first planar waveguide includes a first diffractive optical element (DOE) disposed at a first lateral position. The eyepiece also includes a second planar waveguide positioned in a second lateral plane adjacent to the first lateral plane. The second planar waveguide includes a second DOE disposed at a second lateral position different from the first lateral position. The eyepiece further includes a third planar waveguide positioned in a third lateral plane adjacent to the second lateral plane. The third planar waveguide includes a third DOE disposed at a third lateral position different from the first lateral position and the second lateral position. The eyepiece additionally includes an optical filter positioned between the second planar waveguide and the third planar waveguide. The optical filter is disposed at the third lateral position.

The optical filter can include a long pass filter operable to transmit a first wavelength range and reflect a second wavelength range less than the first wavelength range. In an aspect, the first wavelength range includes 600 nm to 700 nm and the second wavelength range includes 400 nm-500 nm. The transmittance at the first wavelength range can be approximately 90% or greater. The reflectance at the second wavelength range can be approximately 10% or less. The optical filter can include a long pass filter operable to transmit a first wavelength range and absorb a second wavelength range.

In an aspect, the first planar waveguide has a first surface and a second surface opposite to the first surface, the first planar waveguide having a first region including the first lateral position and a second region, the first region configured to receive image light incident on the first surface thereof, the image light including image light in a first wavelength range. The the first DOE can be disposed in the first region and configured to diffract image light in the first wavelength range into the first planar waveguide to be guided toward the second region of the first planar waveguide. A portion of the image light can be transmitted through the first planar waveguide.

The second planar waveguide can have a first surface and a second surface opposite to the first surface. The second planar waveguide can have a first region including the second lateral position and a second region, the first region configured to receive image light in a second wavelength range. The second DOE can be disposed in the first region and can be configured to diffract the image light in the second wavelength range into the second planar waveguide to be guided toward the second region of the second planar waveguide.

In an aspect, the third planar waveguide has a first surface and a second surface opposite to the first surface, the third planar waveguide having a first region including the third lateral position and a second region, the first region configured to receive image light in a third wavelength range. The third DOE can be disposed in the first region and can be configured to diffract the image light in the third wavelength range into the third planar waveguide to be guided toward the second region of the third planar waveguide. The optical filter can be disposed on the first surface of the third planar waveguide. The third DOE can be disposed on the second surface of the third planar waveguide. The optical filter can be disposed on the first or second surface of the first planar waveguide or the first or second surface of the second planar waveguide.

According to an aspect of the present disclosure, an eyepiece for projecting an image to an eye of a viewer is provided. The eyepiece includes a substrate positioned in a substrate lateral plane and a set of color filters disposed on the substrate. The set of color filters include a first color filter disposed at a first lateral position and operable to pass a first wavelength range, a second color filter disposed at a second lateral position and operable to pass a second wavelength range, and a third color filter disposed at a third lateral position and operable to pass a third wavelength range. The eyepiece also includes a first planar waveguide positioned in a first lateral plane adjacent the substrate lateral plane. The first planar waveguide includes a first diffractive optical element (DOE) disposed at the first lateral position. The eyepiece further includes a second planar waveguide positioned in a second lateral plane adjacent to the first lateral plane. The second planar waveguide includes a second DOE disposed at the second lateral position. The eyepiece additionally includes a third planar waveguide positioned in a third lateral plane adjacent to the second lateral plane. The third planar waveguide includes a third DOE disposed at the third lateral position.

The first color filter can include a first photoresist operable to transmit the first wavelength range and attenuate the second wavelength range and the third wavelength range. The second color filter can include a second photoresist operable to transmit the second wavelength range and attenuate the first wavelength range and the third wavelength range. The third color filter can include a third photoresist operable to transmit the third wavelength range and attenuate the first wavelength range and the second wavelength range. At least one of the first color filter, the second color filter, or the third color filter can include ultraviolet ink. In an aspect, in a plan view, the first color filter can be positioned opposite the third color filter about an optical axis.

In an aspect, the substrate has a first side and a second side, the set of color filters can be disposed on the first side of the substrate, and the second side of the substrate faces the first planar waveguide. In another aspect, the substrate has a first side and a second side, the set of color filters can be disposed on the second side of the substrate, and the second side of the substrate faces the first planar waveguide.

The eyepiece can further include a fourth color filter disposed on the substrate at a fourth lateral position and operable to pass the second wavelength range and a fifth color filter disposed at a fifth lateral position and operable to pass the third wavelength range. In a plan view the second color filter can be positioned opposite the fourth color filter about an optical axis. Additionally, the eyepiece can include a fourth planar waveguide positioned in a fourth lateral plane adjacent the third lateral plane, a fifth planar waveguide positioned in a fifth lateral plane adjacent to the fourth lateral plane, and a sixth planar waveguide positioned in a sixth lateral plane adjacent to the fifth lateral plane. The fourth planar waveguide can include a fourth diffractive optical element (DOE) disposed at the fourth lateral position, the fifth planar waveguide can include a fifth DOE disposed at the fifth lateral position, and the sixth planar waveguide can include a sixth DOE disposed at the sixth lateral position.

The eyepiece can further include a sixth color filter disposed at a sixth lateral position and operable to pass the first wavelength range. In a plan view, the fifth color filter can be positioned opposite the sixth color filter about an optical axis. In an aspect, the first wavelength range includes 400 nm-500 nm (blue), the second wavelength range includes 600 nm to 700 nm (red) and the third wavelength range includes 500 nm to 600 nm (green).

According to an aspect of the present disclosure, an eyepiece for projecting an image to an eye of a viewer is provided. The eyepiece includes a first planar waveguide positioned in a first lateral plane. The first planar waveguide includes a first diffractive optical element (DOE) disposed at a first lateral position. The eyepiece also includes a first optical filter coupled to the first planar waveguide at a second lateral position different from the first lateral position and a second planar waveguide positioned in a second lateral plane adjacent to the first lateral plane. The second planar waveguide includes a second DOE disposed at the first lateral position. The eyepiece further includes a third planar waveguide positioned in a third lateral plane adjacent to the second lateral plane. The the third planar waveguide includes a third DOE disposed at the first lateral position. Additionally, the eyepiece includes a second optical filter positioned between the second planar waveguide and the third planar waveguide. The second optical filter is disposed at the first lateral position.

In an aspect, the first DOE is configured to diffract light with a first wavelength range and the first optical filter includes an absorption filter operable to absorb wavelengths outside the first wavelength range. The first optical filter can include a filter configured to transmit light in a first wavelength range and to absorb at least a portion of the light outside the first wavelength range. The first optical filter can be further configured to absorb at least a portion of the light in a third wavelength range. The second optical filter can include a dichroic reflector. The second DOE can be configured to diffract light with a second wavelength range and the second optical filter can be configured to reflect light with the second wavelength range toward the second DOE for diffraction into the second planar waveguide.

The first DOE can be disposed in a first region disposed at the first lateral position and the first optical filter can be disposed in a second region of the first planar waveguide. The first optical filter can be disposed in a cavity inside the first planar waveguide. The first optical filter can be disposed on a first surface of the first planar waveguide. The first DOE can be configured to diffract light in a first wavelength range including 400 nm to 500 nm (green), the second DOE can be configured to diffract light in a second wavelength range including 400 nm-500 nm (blue), and the third DOE can be configured to diffract light in a third wavelength range including 600 nm to 700 nm (red).

According to an aspect of the present disclosure, an eyepiece for projecting an image to an eye of a viewer is provided. The eyepiece includes a substrate positioned in a substrate lateral plane. The substrate includes a first color filter disposed at a first lateral position and operable to pass a first wavelength range and a second color filter disposed at a second lateral position and operable to pass a second wavelength range. The substrate can further include a fourth color filter disposed at a fourth lateral position and operable to pass the first wavelength range and a fifth color filter disposed at a fifth lateral position and operable to pass the second wavelength range. In a plan view the fourth color filter can be positioned opposite the fifth color filter.

The eyepiece also includes a first planar waveguide positioned in a first lateral plane adjacent the substrate lateral plane. The first planar waveguide includes a first diffractive optical element (DOE) disposed at the first lateral position and a third color filter disposed at a third lateral position and operable to pass a third wavelength range. The eyepiece further includes a second planar waveguide positioned in a second lateral plane adjacent to the first lateral plane. The second planar waveguide includes a second DOE disposed at the third lateral position. The eyepiece additionally includes a third planar waveguide positioned in a third lateral plane adjacent to the second lateral plane. The third planar waveguide includes a third DOE disposed at the second lateral position.

In an aspect, the substrate includes a first recess in which the first color filter can be disposed and a second recess in which the second color filter can be disposed. The first planar waveguide can include a recess in which the third color filter can be disposed. The first color filter can be operable to transmit the first wavelength range and attenuate the second wavelength range and the third wavelength range. The second color filter can be operable to transmit the second wavelength range and attenuate the first wavelength range and the third wavelength range. The third color filter can be operable to transmit the third wavelength range and attenuate the first wavelength range and the second wavelength range.

In an aspect, at least one of the first color filter, the second color filter, or the third color filter includes an absorptive color filter. In a plan view, the second color filter can be positioned opposite the third color filter about an optical axis. The eyepiece can further include a fourth planar waveguide positioned in a fourth lateral plane adjacent the third lateral plane, a fifth planar waveguide positioned in a fifth lateral plane adjacent to the fourth lateral plane, and a sixth planar waveguide positioned in a sixth lateral plane adjacent to the fifth lateral plane. The fourth planar waveguide can include a fourth diffractive optical element (DOE) disposed at the fourth lateral position, the fifth planar waveguide can include a fifth DOE disposed at the fifth lateral position, and the sixth planar waveguide can include a sixth DOE disposed at the sixth lateral position. The eyepiece can also include a sixth color filter disposed at a sixth lateral position and operable to pass the third wavelength range. In a plan view, the sixth color filter can be positioned opposite the first color filter about an optical axis. The first wavelength range can include 600 nm to 700 nm, the second wavelength range can include 500 nm to 600 nm, and the third wavelength range can include 400 nm-500 nm.

According to an aspect of the present disclosure, an eyepiece for projecting an image to an eye of a viewer is provided. The eyepiece includes a first planar waveguide positioned in a first lateral plane. The first planar waveguide includes a first diffractive optical element (DOE) disposed at a first lateral position and defines a first boundary enclosing a first surface area. The eyepiece also includes a second planar waveguide positioned in a second lateral plane adjacent to the first lateral plane. The second planar waveguide includes a second DOE disposed at a second lateral position outside the first boundary. The second planar waveguide defines a second boundary enclosing a second surface area. The eyepiece further includes a third planar waveguide positioned in a third lateral plane adjacent to the second lateral plane. The third planar waveguide includes a third DOE disposed at a third lateral position outside the first boundary and outside the second boundary. The first DOE can be disposed at a peripheral region of the first boundary. The first boundary can include one or more peripheral cutouts. The first boundary can include one or more central orifices.

According to an aspect of the present disclosure, a method of coupling light into an eyepiece including a plurality of planar waveguides is provided. The method includes directing a first beam including first wavelengths to impinge on the eyepiece, coupling at least a portion of the first beam into a first planar waveguide of the plurality of planar waveguides, directing a second beam including second wavelengths to impinge on the eyepiece, and coupling at least a portion of the second beam into a second planar waveguide of the plurality of planar waveguides. The method also includes directing a third beam including third wavelengths to impinge on the eyepiece, passing a transmitted portion of the third beam through an optical filter, and coupling at least a portion of the transmitted portion of the third beam into a third planar waveguide of the plurality of planar waveguides.

According to an aspect of the present disclosure, a method of coupling light into an eyepiece including a plurality of planar waveguides having a diffractive optical element associated with each of the plurality of planar waveguides is provided. The method includes directing a first beam including first wavelengths, a second beam including second wavelengths, and a third beam including third wavelengths to impinge on the eyepiece at a first lateral position, coupling at least a portion of the first beam, at least a portion of the second beam, and at least a portion of the third beam into a first planar waveguide of the plurality of planar waveguides, and attenuating the at least a portion of the second beam and the at least a portion of the third beam. The method also includes coupling at least a second portion of the second beam into a second planar waveguide of the plurality of planar waveguides, passing a transmitted portion of the third beam through an optical filter, and coupling at least a portion of the transmitted portion of the third beam into a third planar waveguide of the plurality of planar waveguides.

In an aspect, each of the diffractive optical elements associated with each of the plurality of planar waveguides is aligned at the first lateral position. The method can further include reflecting a reflected portion of the third beam from the optical filter. The method can also include coupling at least a portion of the reflected portion of the third beam into the second planar waveguide.

According to an aspect of the present disclosure, an image display system is provided. The image display system includes a single white light source for providing illumination white light, an LCOS (Liquid Crystal on Silicon) image projection device configured to receive the illumination white light and to sequentially project gray scale images at an optical pupil. Each gray scale image is configured for selecting pixels for each of three colors. The image display system also includes a shutter having three shutter regions configured for dividing the optical pupil into three sub-pupils for the three colors and a filter having three filter regions aligned to the three shutter regions. Each filter region has a color filter for one of the colors. The shutter and the filter can be synchronized with the LCOS image projection device to sequentially project an image in each of the three colors at a corresponding sub-pupil. The image display system further includes an eyepiece having three waveguide layers, each waveguide layer including a diffractive optical element (DOE) aligned to a corresponding sub-pupil and configured for receiving image light in one of the colors, wherein the eyepiece can be configured for projecting a colored image to a viewer.

In an aspect, the single white light source can include a white light emitting diode (LED) light source. The single white light source can be configured to project square or rectangular illumination light beams. The shutter can include a liquid crystal (LC) shutter. The three shutter regions can be rectangular regions adjacent to one another. The three filter regions can be rectangular regions adjacent to one another. The three sub-pupils can be rectangular regions adjacent to one another.

The DOE in each waveguide layer can be configured to receive image light in one of the colors and to diffract the image light into the waveguide layer to propagate in the waveguide layer in a propagation direction by total internal reflection (TIR). The DOE in each waveguide layer can be aligned to a corresponding sub-pupil for receiving the image light in one of the colors. The DOEs in the waveguide layers can be spatially displaced from one another. The DOE in each waveguide layer has a rectangular shape, elongated in a direction perpendicular to the propagation direction.

According to an aspect of the present disclosure, an image display system is provided. The image display system includes a light source for providing color sequential illumination. The light source has a plurality of colored LED light sources. The image display system also includes an LCOS (Liquid Crystal on Silicon) image projection device configured to receive the illumination from the plurality of colored LED light sources and to project sequentially colored image light in an optical pupil for each of three colors. The optical pupil is characterized by a pupil area and includes a plurality of non-overlapping sub-pupils. Each of the plurality of non-overlapping pupils is characterized by a sub-pupil area. Each of the plurality of LED light sources can be configured to illuminate one of the plurality of non-overlapping sub-pupils. A sum of the sub-pupil areas can be substantially equal to the pupil area. The sum of the sub-pupil areas can be equal to the pupil area.

In an aspect, the optical pupil has a circular shape and each of the plurality of LED light sources can be configured to illuminate a sub-pupil that can be a circular sector of the optical pupil. In an aspect, the optical pupil has a square or rectangular shape and each of the plurality of LED light sources can be configured to illuminate a sub-pupil that can be a rectangular portion of the optical pupil. In an aspect, the optical pupil has a square or rectangular shape, the plurality of LED light sources can include a red LED, a blue LED, and a green LED, and each LED can be configured to illuminate a sub-pupil that can be a rectangular portion of the optical pupil. In an aspect, the optical pupil has a circular shape, the plurality of LED light sources can include two red LEDs, two blue LEDs, and two green LEDs, and each LED can be configured to illuminate a sub-pupil that can be a circular sector of the optical pupil. In an aspect, the optical pupil has a square or rectangular shape, the plurality of LED light sources can include two red LEDs, two blue LEDs, and two green LEDs, and each LED can be configured to illuminate a sub-pupil that can be a rectangular portion of the optical pupil.

The three colors can be three primary colors and the plurality of LED light sources comprise one or more LED light sources in each of the three primary colors. Each of the plurality of LED light sources can include an LED chip and a concentrator, for example, a compound parabolic concentrator (CPC).

According to an aspect of the present disclosure, an image display system is provided. The image display system includes a light source for providing color sequential illumination, the light source having a plurality of LED light sources and an LCOS (Liquid Crystal on Silicon) image projection device configured to receive the illumination from the plurality of colored LED light sources and to project sequentially colored image light in an optical pupil for each of three colors. The optical pupil includes a plurality of non-overlapping sub-pupils corresponding to the plurality of LED light sources. The image display system also includes an eyepiece having a plurality of waveguide layers. Each waveguide layer includes a diffractive optical element (DOE) aligned to a corresponding sub-pupil for receiving the image light from a corresponding LED light source. The LCOS image projection device generates high order of diffractions from each of the plurality of LED light sources and the DOE in each waveguide is disposed in a location displaced from images from the high order of diffractions.

According to an aspect of the present disclosure, an image display system is provided. The image display system includes a white light source for providing an illumination white light, an LCOS (Liquid Crystal on Silicon) image projection device configured to receive the illumination white light and to project sequentially gray scale images in an optical pupil for each of three colors, and a shutter having a plurality of shutter regions configured for dividing the optical pupil into a corresponding plurality of sub-pupils, one for each of the colors. The image display system also includes a filter having a plurality of filter regions. Each filter region has a color filter for one of the colors, each of plurality of filter regions being aligned to a corresponding one of the plurality of shutter regions. The shutter is synchronized with the LCOS image projection device sequentially project an image in each of the three colors in one of the plurality of sub-pupils.

The white light source can include a single white light source. The shutter can include six shutter regions and the filter can include six filter regions, the shutter and filter being aligned to form six sub-pupils. The image display system can further include an eyepiece having six waveguide layers, each waveguide layer including a diffractive optical element (DOE) aligned to a corresponding sub-pupil for receive image light in one of the colors. The eyepiece can be configured for projecting colored images in two depth planes.

According to an aspect of the present disclosure, an image display system is provided. The image display system includes a plurality of white LED light sources for providing illumination white light and an LCOS (Liquid Crystal on Silicon) image projection device configured to receive the illumination white light and to project sequentially gray scale images in an optical pupil for each of three colors. The image display system also includes a shutter device having a plurality of shutter regions configured for dividing the optical pupil into a corresponding plurality of sub-pupils, one for each of the colors. The image display system further includes a filter having a plurality of filter regions, each filter region having a color filter for one of the colors. Each of plurality of filter regions is aligned to a corresponding one of the plurality of shutter regions. The shutter is synchronized with the LCOS image projection device sequentially project an image in each of the three colors in one of the plurality of sub-pupils.

The plurality of white LED light sources can include a first white LED light source and a second white LED light source. The shutter device can have three shutter regions. The filter can have six color filter regions: two red color filter regions, two green color filter regions, and two blue color filter regions. A first red color filter region, a first green color filter region, and a first blue color filter region can be configured to receive light from the first white LED light source. A second red color filter region, a second green color filter region, and a second blue color filter region can be configured to receive light from the second white LED light source. The optical pupil can include three sub-pixels. The optical pupil can include six sub-pixels. The first and second red color filter regions can be aligned to two different shutter regions, the first and second green color filter regions can be aligned to two different shutter regions, and the first and second blue color filter regions can be aligned to two different shutter regions.

The plurality of white LED light sources can include a first white LED light source and a second white LED light source. The shutter device can have a first shutter and a second shutters, each shutter including three shutter regions. In an aspect, the filter has six color filter regions: two red color filter regions, two green color filter regions, and two blue color filter regions. A first red color filter region, a first green color filter region, and a first blue color filter region can be configured to receive light from the first white LED light source. A second red color filter region, a second green color filter region, and a second blue color filter region can be configured to receive light from the second white LED light source. The optical pupil can include three sub-pixels. The optical pupil can include six sub-pixels. The first and second red color filter regions can be aligned to two different shutter regions, the first and second green color filter regions can be aligned to two different shutter regions, and the first and second blue color filter regions can be aligned to two different shutter regions.

According to an aspect of the present disclosure, an image display system is provided. The image display system includes a single white light source for providing an illumination white light and an LCOS (Liquid Crystal on Silicon) image projection device configured to receive the illumination white light and to project full color images in an optical pupil. The image display system also includes a shutter having three shutter regions configured for dividing the optical pupil into three sub-pupils. Each of the three sub-pupils is associated with one of three colors. The image display system further includes a filter having three filter regions, each filter region having a color filter for one of the three colors, the three filter regions being aligned to the three shutter regions, respectively. The image display system is configured to sequentially project an image in each of the three colors in a respective sub-pupil.

In an aspect, the image display system further includes an eyepiece having three waveguide layers. Each waveguide layer includes a diffractive optical element (DOE) aligned to a corresponding sub-pupil for receive image light in one of the colors. The eyepiece can be configured for projecting a colored image to a viewer. The single white light source can be configured to project square or rectangular illumination light beams. The three shutter regions can be rectangular regions adjacent to one another. The LCOS image projection device can include three LCOS panels to process images in the three colors and provide an combined full color image.

According to an aspect of the present disclosure, an image display system is provided. The image display system includes a white light source for providing illumination white light, an LCOS (Liquid Crystal on Silicon)-based image projection device configured to receive the illumination white light and to project images in an optical pupil, and a shutter having a plurality of shutter regions configured for dividing the optical pupil into a plurality of sub-pupils, one for each of a plurality of colors. The image display system also includes a filter having a plurality of filter regions, each filter region having a color filter for one of the plurality of colors, each of plurality of filter regions being aligned to a corresponding one of the plurality of shutter regions. The shutter is synchronized with the LCOS image projection device to sequentially project an image in each of the plurality of colors in one of the plurality of sub-pupils.

The plurality of sub-pupils can be configured to fill up optical pupil. The image display system can further include an eyepiece having a plurality waveguide layers, each waveguide layer including a diffractive optical element (DOE) aligned to a corresponding sub-pupil for receive image light in one of the plurality of colors. The eyepiece can be configured for projecting a colored image to a viewer. The plurality of colors can be three primary colors and the LCOS image projection device can be configured to receive the illumination white light and to project sequentially gray scale images in an optical pupil for each of the three primary colors. The LCOS image projection device can include three LCOS panels, each of the three LCOS panels being associated with one of three primary colors. The LCOS image projection device can be configured to receive the illumination white light and to project full color images in an optical pupil.

According to an aspect of the present disclosure, a method for displaying an image is provided. The method includes providing a white light source and an image projector, receiving white light from the white light source at the image projector, and projecting sequentially gray scale images in an optical pupil. Each gray scale image is configured for selecting pixels for a corresponding one of three colors. The method also includes providing a shutter and color filters for dividing the optical pupil into three sub-pupils for the three colors, synchronizing the shutter and color filters with the gray scale images and sequentially project images in each of the three colors in a corresponding sub-pupil, providing an eyepiece having three waveguide layers, and sequentially receiving images in each of the three colors in a corresponding waveguide layer for projecting an image to a viewer.

In an aspect, the white light source includes a single white LED light source. The method can further include using an LCOS (Liquid Crystal on Silicon) image projection device to receive the white light and to project sequentially gray scale images in the optical pupil. The shutter can include a liquid crystal (LC) shutter having three shutter regions for dividing the optical pupil into three sub-pupils. The color filters can include three filter regions, each filter region includes a color filter for one of the three colors.

According to an aspect of the present disclosure, a method for displaying an image is provided. The method includes providing a white light source and an image projector, receiving white light from the white light source at the image projector, and projecting images in an optical pupil. The method also includes providing a shutter and color filters for dividing the optical pupil into a plurality of sub-pupils, synchronizing the shutter and color filters with the images from the image projector and sequentially projecting images in each of three colors in a corresponding sub-pupil, providing an eyepiece having multiple waveguide layers, and sequentially receiving images in each of the three colors in a corresponding waveguide layer for projecting an color image to a viewer.

The image projector can be configured to project sequentially gray scale images in the optical pupil, each gray scale image configured for selecting pixels for each of the three colors. In an aspect, synchronizing the shutter with color filters with the gray scale images can include projecting a single-color image for a sub-pixel for each gray scale image. The image projector can be configured to project full color images in the optical pupil. In an aspect, synchronizing the shutter and color filters with the images from the image projector can include projecting three single-color images for three corresponding sub-pixel for each full color image from the image projector.

Upon reading this disclosure, those of skill in the art will appreciate still additional alternative structural and functional designs for a system and a process for motion-based content navigation through the disclosed principles herein. Thus, while particular embodiments and applications have been illustrated and described, it is to be understood that the disclosed embodiments are not limited to a precise construction and components disclosed herein. Various modification, changes and variations, which will be apparent to those skilled in the art, can be made in the arrangement, operation and details of the method and apparatus disclosed herein without departing from the spirit and scope defined in the appended claims.