Method and system for wide field of view displays using scanning reflectors

Abstract

To provide a favorable method and system for large field-of-view display with a scanning reflector.SOLUTION: An image display system includes an optical subsystem configured to emit a first light beam and a second light beam, where the first light beam illuminates a first portion of a composite field of view and the second beam illuminates a second portion of the composite field of view. A scanning mirror is positioned to intercept and reflect the first light beam and the second light beam. The system also has a waveguide with at least one input coupling optical element for receiving the first light beam and the second light beam in the waveguide. The waveguide also has an output coupling optical element for projecting a plurality of output light beams derived from the first light beam and the second light beam from the waveguide to illuminate the composite field of view.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. Provisional Patent Application No. 62 / 414,484, filed October 28, 2016, U.S. Provisional Patent Application No. 62 / 532,968, filed July 14, 2017, and U.S. Provisional Patent Application No. 62 / 545,243, filed August 14, 2017, the contents of all of which are incorporated herein by reference for all purposes. [Background technology]

[0002] Modern computing and display technology has facilitated the development of systems for so-called "virtual reality" or "augmented reality" experiences in which digitally reproduced images, or portions thereof, are presented to a user on a wearable device in a manner that appears or can be perceived as real. Virtual reality, or "VR," scenarios typically involve the presentation of digital or virtual image information without transparency to other actual, real-world visual input, while augmented reality, or "AR," scenarios typically involve the presentation of digital or virtual image information as an extension of the user's visualization of the real world around them.

[0003] The wearable device may include augmented and / or virtual reality glasses. Images can be displayed using image frames or raster-scanned images. In a scanning image display system, each light beam defines a pixel of the image. A two-dimensional field of view (FOV) can be created by scanning a mirror in two orthogonal axes. Images can be projected onto the lenses of glasses, which may include other optical elements such as waveguide-based eyepieces and optical fibers. An image display system can be mounted on each of the left and right sides of the glasses frame. Summary of the Invention [Means for solving the problem]

[0004] Conventional scanning image displays in wearable devices for virtual reality or augmented reality applications often have a limited field of view because the scanning mirror has a limited range of scanning motion and design constraints on the arrangement of optical elements. However, this arrangement can lead to a larger device size, which may be undesirable. Embodiments of the present invention provide a scanning image display system with a wide field of view while maintaining a small device form factor. In some embodiments, the wider field of view can be achieved by simultaneously scanning multiple incident light beams and combining the individual fields of view into a wider composite field of view.

[0005] Embodiments of the present invention generally relate to image display systems. According to some embodiments of the present invention, the image display system includes a scanning mirror for receiving two or more incident light beams and providing multiple reflected light beams. Each of the multiple reflected light beams is configured to provide an image within a separate field of view. The image display system also includes a waveguide having an input coupling optical element and an output coupling optical element. The input coupling optical element is configured to couple the multiple reflected light beams into the waveguide. The output coupling optical element is configured to project the multiple output light beams from the waveguide to form a projected image within the combined field of view.

[0006] According to some embodiments of the present invention, an image display system includes an optical subsystem configured to emit a first light beam and a second light beam, where the first light beam illuminates a first portion of a composite field of view and the second light beam illuminates a second portion of the composite field of view. A scanning mirror is positioned to capture and reflect the first light beam and the second light beam. The system also has a waveguide with at least one input coupling optical element for receiving the first light beam and the second light beam into the waveguide. The waveguide also has an output coupling optical element for projecting multiple output light beams derived from the first light beam and the second light beam from the waveguide to illuminate the composite field of view.

[0007] In some embodiments, the image display system also includes two or more RGB (red, blue, green) combiners positioned on opposite sides of the waveguide from the scanning mirror. The RGB combiners are configured to provide two or more incident light beams having different angles of incidence. The input coupling optical element is configured to allow the incident light beams to pass through the waveguide and reach the scanning mirror. The input coupling optical element is also configured to couple a reflected light beam into the waveguide.

[0008] In some embodiments of the image display system, two or more RGB combiners are positioned at different angles relative to the scanning mirror to provide two or more incident light beams with different angles of incidence.

[0009] In an alternative embodiment, the two or more RGB combiners are positioned at the same angle relative to the scanning mirror, and the image display system further includes a reflective optical element for providing two or more light beams having different angles of incidence.

[0010] In some embodiments, the input coupling optical element is a polarization-sensitive diffractive input coupling grating (ICG).

[0011] In some embodiments, the image display system also includes a polarization control element disposed between the scanning mirror and the waveguide to convert the incident beam into a polarized light that is transmissive to the input coupling element.

[0012] In some embodiments, the image display system also includes a polarization control element disposed between the waveguide and the two or more RGB combiners. The polarization element is configured to convert the incident light beam to a first polarization state, and the scanning mirror is configured to convert the first circular polarization state to a second circular polarization state. The polarization-sensitive input coupling optical element is configured to allow light of the first circular polarization state to pass through and is configured to couple light of the second circular polarization state into the waveguide.

[0013] In some embodiments, the image display system also includes two or more RGB combiners positioned on the same side of the waveguide with respect to the scanning mirror. The two or more RGB combiners provide two or more incident light beams having different angles of incidence. The image display system also includes a quarter-wave plate positioned adjacent to the scanning mirror and a polarization-sensitive beam splitter positioned between the quarter-wave plate and the waveguide. The polarization-sensitive beam splitter is configured to direct the two or more incident light beams from the RGB combiners through the quarter-wave plate toward the scanning mirror, and a light beam reflected from the scanning mirror is configured to propagate through the quarter-wave plate and the polarization-sensitive beam splitter and is coupled into the waveguide by an input coupling optical element.

[0014] According to some embodiments of the present invention, an image display system includes an image-modulating light source that outputs a collimated incident light beam including multiple components distinguished by wavelength and / or polarization. The image display system also includes a scanning mirror with a diffractive surface for receiving the collimated incident light beam and angularly separating the beam components by diffraction. Each of the multiple reflected and diffracted beam components is configured to provide an image within a separate field of view. The image display system also includes a waveguide having an input coupling optical element for coupling the multiple reflected light beams into the waveguide and an output coupling optical element for projecting the multiple output light beams from the waveguide to form a projected image with a composite field of view.

[0015] According to some embodiments of the present invention, a method for displaying an image includes impinging two or more input light beams on a scanning mirror at two or more angles. The method includes scanning the two or more input light beams and providing a plurality of reflected light beams. Each of the plurality of reflected light beams is configured to provide an image within a respective field of view (FOV). The plurality of reflected light beams are received within a waveguide, which projects a plurality of output light beams from the waveguide to form a projected image within the combined field of view (FOV). In some embodiments of the method, the combined field of view is wider than the FOV provided by each of the two or more input light beams. The image within the combined FOV can be a tiled image including an image from each of the input light beams.

[0016] Additional features, benefits, and embodiments are described below in the detailed description, drawings, and claims. The present specification also provides, for example, the following items: (Item 1) 1. An image display system, comprising: an optical subsystem configured to emit a first image-modulated light beam and a second image-modulated light beam, the first image-modulated light beam illuminating a first portion of a composite field of view (FOV) and the second image-modulated light beam illuminating a second portion of the composite field of view; a scanning mirror positioned to capture and reflect the first image-modulated light beam and the second image-modulated light beam; A waveguide, at least one input coupling optical element for receiving the first image-modulated light beam and the second image-modulated light beam into the waveguide; an output coupling optical element for projecting a plurality of output light beams derived from the first image-modulated light beam and the second image-modulated light beam from the waveguide to illuminate the composite field of view; a waveguide having An image display system comprising: (Item 2) Item 2. The image display system of item 1, wherein the optical subsystem is positioned on the opposite side of the waveguide from the scanning mirror. (Item 3) Item 3. The image display system of item 2, wherein the input coupling element is positioned between the optical subsystem and the scanning mirror so that the first image-modulated light beam and the second image-modulated light beam emitted from the optical subsystem pass through the input coupling element before reaching the scanning mirror. (Item 4) Item 4. The image display system of item 3, further comprising a polarization control element, the polarization control element being positioned between the optical subsystem and the input coupling element such that the first image-modulated light beam and the second image-modulated light beam pass through the polarization control element before reaching the input coupling element. (Item 5) Item 5. The image display system of item 4, wherein the input coupling element is a polarization selective device. (Item 6) Item 6. The image display system of item 5, wherein the optical subsystem is configured to generate the first image-modulated light beam and the second image-modulated light beam in linear polarization states, the polarization control element comprises a wave plate configured to convert the first image-modulated light beam and the second image-modulated light beam into at least one circular polarization state, and the input coupling element is polarization-selective in that the input coupling element is selective based on the handedness of circular polarization. (Item 7) Item 6. The image display system of item 5, wherein the input coupling element comprises a diffraction grating including a cholesteric liquid crystal. (Item 8) 8. The image display system of claim 7, wherein the input coupling element further comprises an alignment layer that establishes a periodic lateral variation in the alignment direction of the cholesteric liquid crystal. (Item 9) The optical subsystem includes: a first three-color channel modulated light source configured to generate the first image-modulated light beam; a second three-color channel modulated light source configured to generate the second image-modulated light beam; and Item 1. An image display system according to item 1, comprising: (Item 10) the first three-color channel modulated light source comprises a first red laser, a first green laser, and a first blue laser; the second three-color channel modulated light source comprises a second red laser, a second green laser, and a second blue laser; Item 10. The image display system according to item 9. (Item 11) the first three-color channel modulated light source comprises a first dichroic beam combiner optically coupled to the first red laser, the first green laser, and the first blue laser; the second three-color channel modulated light source comprises a second dichroic beam combiner optically coupled to the second red laser, the second green laser, and the second blue laser; Item 11. The image display system according to item 10. (Item 12) Item 1, an image display system according to item 1, wherein the optical subsystem is configured to emit the first image-modulated light beam at a first angle and the second image-modulated light beam at a second angle. (Item 13) Item 13. The image display system of item 12, wherein the optical subsystem is configured to emit the first image-modulated light beam along a first path and emit the second image-modulated light beam along a second path that intersects the first path at the scanning mirror. (Item 14) Item 1. The image display system of item 1, wherein the optical subsystem is configured to emit the first image-modulated light beam collinear with the second image-modulated light beam. (Item 15) Item 1, further comprising a polarizer and a wave plate, wherein the optical subsystem and the scanning mirror are arranged on a common side of the waveguide together with the polarizer and the wave plate, a first optical path section from the optical subsystem to the scanning mirror extends from the optical subsystem to the polarizer and from the polarizer through the wave plate, and a second optical path section from the scanning mirror to the input coupling optical element traverses the wave plate and the polarizer. (Item 16) Item 1, an image display system according to item 1, wherein the input coupling optical element comprises a first input coupling grating and a second input coupling grating. (Item 17) Item 1, wherein the first portion of the composite field of view is interleaved with the second portion of the composite field of view. (Item 18) a light source for providing a collimated incident light beam, the collimated incident light beam comprising a plurality of components; a scanning mirror with a diffractive surface for receiving the collimated incident light beam and for providing a plurality of reflectively diffracted light beams having different diffraction angles, each of the plurality of reflectively diffracted light beams configured to illuminate a portion of a field of view (FOV); A waveguide, an input coupling optical element for receiving the plurality of reflectively diffracted light beams into the waveguide; an output coupling optical element for projecting a plurality of output light beams from the waveguide to form a projected image with a compound field of view (FOV), the plurality of output light beams being derived within the waveguide from the plurality of reflectively diffracted light beams; a waveguide having An image display system comprising: (Item 19) Item 19. The image display system of item 18, wherein the plurality of components include components having different wavelengths. (Item 20) Item 19. The image display system of item 18, wherein the plurality of components includes components having different polarizations. (Item 21) Item 19. The image display system of item 18, wherein the plurality of components includes a plurality of sets of red, green, and blue components. (Item 22) 21. The image display system of claim 20, wherein the input coupling optical element is polarization state selective. (Item 23) the scanning mirror is disposed on an opposite side of the waveguide from the light source; the input coupling optical element of the waveguide is configured to allow the collimated incident light beam to pass through the input coupling element and the waveguide, and the input coupling optical element is configured to couple the multiple reflectively diffracted light beams into the waveguide by diffracting the reflectively diffracted beams at an angle greater than a critical angle for the waveguide. Item 19. The image display system according to item 18. (Item 24) 1. A method for providing a compound field of view, comprising: directing at least two input light beams to a scanning mirror; reflecting the at least two input light beams using the scanning mirror to provide at least two reflected beams, each of the reflected beams providing a portion of the composite field of view; receiving the at least two reflected beams in an eyepiece waveguide; outputting a plurality of output light beams from the eyepiece waveguide to form a projected image within the compound field of view, the plurality of output light beams being derived from the at least two reflected light beams; A method comprising: (Item 25) providing at least two red-blue-green combiners positioned on opposite sides of the eyepiece waveguide from the scanning mirror and configured to direct the at least two input light beams at different angles of incidence on the scanning mirror; directing the at least two input light beams to the scanning mirror includes directing the at least two light beams through the eyepiece waveguide. Item 25. The method according to item 24. (Item 26) providing an input coupling optical element on the eyepiece waveguide; directing the at least two input light beams to the scanning mirror includes directing the at least two light beams through the input coupling element; receiving the at least two reflected beams in the eyepiece waveguide includes receiving the at least two reflected beams through the input coupling element; Item 26. The method according to item 25. (Item 27) Item 25. The method of item 24, wherein directing at least two input light beams to a scanning mirror includes reflecting at least one of the at least two input light beams and introducing an angular difference between the at least two input light beams. (Item 28) Item 25. The method for providing a composite field of view of item 24, wherein directing at least two input light beams to a scanning mirror comprises passing the at least two input light beams through a quarter-wave plate. (Item 29) 1. A method for providing a compound field of view (FOV), comprising: providing an incident collimated light beam comprising a plurality of components; providing a scanning mirror with a diffractive surface for receiving the collimated incident light beam and for separating the plurality of components into a plurality of reflected light beams having different diffraction angles, each of the plurality of reflected light beams configured to provide a portion of the composite field of view; receiving the plurality of reflected light beams in an eyepiece waveguide; outputting a plurality of output light beams from the eyepiece waveguide to form a projected image within the compound field of view, the plurality of output light beams being derived from the plurality of reflected light beams; A method comprising: (Item 30) 30. The method of claim 29, wherein the plurality of components comprises components distinguished by wavelength. (Item 31) 30. The method of claim 29, wherein the plurality of components includes components distinguished by polarization states. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a simplified schematic diagram illustrating an image display system according to some embodiments of the present invention. [Figure 2] 2A-2C are simplified schematic diagrams illustrating image display systems according to some embodiments of the present invention. [Figure 3] FIG. 3 is a simplified schematic diagram illustrating an image display system for providing a compound field of view (FOV), according to some embodiments of the present invention. [Figure 4] FIG. 4 is a simplified schematic diagram illustrating a compound field of view (FOV), according to some embodiments of the present invention. [Figure 5] FIG. 5 is a simplified schematic diagram illustrating another image display system for providing a compound field of view (FOV), according to some embodiments of the present invention. [Figure 6A] FIG. 6A is a simplified schematic diagram illustrating another image display system for providing a compound field of view (FOV), according to some embodiments of the present invention. [Figure 6B] FIG. 6B is a simplified schematic diagram illustrating a portion of the image display system 600 of FIG. 6A. [Figure 7] FIG. 7 is a simplified schematic diagram illustrating another image display system for providing a compound field of view (FOV), according to some embodiments of the present invention. [Figure 8] Figure 8 is a schematic diagram of a display system that uses a scanning mirror with multiple layers of polarized and spectrally selective liquid crystal material to angularly separate independently modulated beam components to separately illuminate quadrants of the full field of view. [Figure 9] FIG. 9 is a simplified schematic diagram illustrating an image display system according to some embodiments of the present invention. [Figure 10] FIG. 10 is a simplified schematic diagram illustrating another image display system according to some embodiments of the present invention. [Figure 11] FIG. 11 is a simplified schematic diagram illustrating another image display system according to some embodiments of the present invention. [Figure 12] FIG. 12 is a simplified flowchart illustrating a method for displaying an image. [Figure 13] FIG. 13 is a schematic diagram of a light engine, according to one embodiment of the present invention. [Figure 14] FIG. 14 is a schematic diagram of a light engine according to another embodiment of the present invention. [Figure 15] FIG. 15 is a front view of the light engine shown in FIG. [Figure 16] FIG. 16 is a top view of a four-channel light engine according to a further embodiment of the present invention. [Figure 17] FIG. 17 is a cross-sectional view of a portion of the light engine shown in FIG. [Figure 18] FIG. 18 is a partial view of a waveguide display system according to one embodiment of the present invention. [Figure 19] FIG. 19 is a cross-sectional elevation view through the blue AR coating, blue ICG, and blue waveguide of the waveguide display system shown in FIG. [Figure 20] FIG. 20 is a schematic plan view of a first alignment layer used in one of the input coupling gratings shown in FIG. 19, according to an embodiment of the present invention. [Figure 21] FIG. 21 is a top view of a photonic chip-based 2RGB color channel combiner and associated lenses according to one embodiment of the present invention. [Figure 22]FIG. 22 is a top view of a photonic chip-based 2RGB color channel combiner and associated lenses according to another embodiment of the present invention. [Figure 23] FIG. 23 is a front view of a four RGB channel light engine including two of the combiners shown in FIG. 21 and / or FIG. 22, according to one embodiment of the present invention. [Figure 24] FIG. 24 is a top view of a 4RGB channel light engine according to one embodiment of the present invention. [Figure 25] FIG. 25 is a partial cross-sectional elevation view of a portion of the 4 RGB channel light engine shown in FIG. 24 of the present invention. [Figure 26] FIG. 26 is a top view of a 4RGB channel light engine according to another embodiment of the present invention. [Figure 27] FIG. 27 is a schematic diagram of a waveguide display system that may be used in augmented reality glasses, according to an embodiment of the present invention. [Figure 28] FIG. 28 includes a three-space Cartesian coordinate system along with a representation of the scanning mirror and input coupling grating used in the system shown in FIG. 27, according to one embodiment of the present invention. [Figure 29] FIG. 29 is a schematic diagram of a six-layer polarization-responsive liquid crystal grating that may be used on a scanning mirror in the system shown in FIG. 27, according to one embodiment of the present invention. [Figure 30] Figure 30 is a graph including scan angles in two regions, each resulting from different polarization states, generated by the system shown in Figure 27 using the multilayer selective liquid crystal grating shown in Figure 29, according to one embodiment of the present invention. [Figure 31] FIG. 31 is a schematic diagram of a waveguide display system that may be used in augmented reality glasses, according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] Embodiments of the present invention are directed to image display systems and methods for wearable devices that can provide a wider field of view (FOV) than conventional display systems.

[0019] FIG. 1 is a simplified schematic diagram illustrating an image display system according to some embodiments of the present invention. In this example, image display system 100 is a scanning display system including a scanning mirror that projects an image. Image display system 100 can be part of an eyepiece in a wearable device, such as a waveguide-based eyepiece. As shown in FIG. 1, image display system 100 includes a light source 110 and a scanning mirror 130 configured to form a raster-scanned image. Light source 110 can emit light that is image-modulated based on image data to form image-modulated light. Light source 110 is configured to emit a light beam, such as beam 120, toward scanning mirror 130, which is configured to scan reflected light 140 across surface 150 and project the image. For example, reflected light beam 140 is scanned across surface 150 in two dimensions, such as in the X and Y directions, to form an image or project an image onto surface 150. Surface 150 can be a surface for displaying an image or a virtual projection surface. For simplicity, other components, such as the control system and lens system, are not shown in FIG.

[0020] In some embodiments, a light beam is image-modulated by adjusting the intensity of each color component of the light beam during each of a series of time periods to a value based on the pixel color component value of a particular pixel in the series of pixels. Each pixel in the series has a corresponding angular coordinate (similar to the Cartesian coordinates of an LCD display panel). Simultaneously, while the image light modulation beam is modulated based on the particular pixel color component value, the beam is deflected to the pixel's angular coordinate. The light will emerge from the eyepiece and propagate toward the user's eye at an angle based on the angular coordinate.

[0021] In some embodiments of the present invention, light source 110 is configured to provide two or more light beams, e.g., beams 120 and 121, at different angles of incidence. Second incident light beam 121 and reflected light beam 141 are shown by dashed lines. In this case, image display system 100 is configured to provide light beam 120 to a first image in first field of view (FOV) 161 and light beam 121 to a second image in second field of view (FOV) 162. Image display system 100 can thus provide a composite field of view that includes images associated with multiple input light beams.

[0022] 2A-2C are simplified schematic diagrams illustrating image display systems according to some embodiments of the present invention. Figures 2A-2B illustrate an image display system 200 including a scanning mirror 230 and a waveguide 250. The scanning mirror 230 is configured to receive two or more incident light beams and provide multiple reflected light beams, each of the multiple reflected light beams configured to provide an image within a separate field of view (FOV).

[0023] 2A, first reflected light beam 241 is shown scanned across input coupling optical element 252 for coupling reflected light beam 241 into waveguide 250. After undergoing total internal reflection (TIR), light beam 241 reaches output coupling optical element 254 for projecting the light beam from the waveguide and forming a first image within first field of view FOV-1 (261).

[0024] The input coupling optical element 252 and the output coupling optical element 254 can be diffraction gratings. In some embodiments, the input light enters the waveguide through an input coupling diffractive optical element (DOE) or input coupling grating (ICG), such as a nano-grating structure with dimensions and relief patterns configured to diffract light of a particular wavelength or polarization while allowing light of other wavelengths or polarizations to transmit through the input coupling diffractive optical element (DOE). Similarly, the output coupling optical element can include an output coupling grating (OCG).

[0025] 2B, the second reflected light beam 242 is shown scanned across input coupling optical element 252 for coupling the reflected light beam 242 into waveguide 250. After undergoing total internal reflection (TIR), light beam 242 reaches output coupling optical element 254 for projecting the light beam from the waveguide and forming a second image within a second field of view FOV-2 (262).

[0026] In FIG. 2C , first reflected light 241 and second reflected light beam 242 are shown scanned across input coupling optical element 252, which couples reflected light beams 241 and 242 into waveguide 250. After undergoing total internal reflection (TIR), light beams 241 and 242 reach output coupling optical element 254, which projects the light beams from the waveguide and forms a projected image within composite field of view 266. In some embodiments, the image display system may also include optical element 280, such as an eyepiece, that directs the image to a user's eye 290. In some embodiments, the projected image within the composite field of view may be a tiled image, including images projected by multiple light beams to provide an expanded field of view. In some embodiments, overlap between each sub-FOV from individual beams may result in smoother transitions within the tiled image. In some embodiments, the projected image may include an interleaved image, including alternating odd and even regions from different light beams, which may provide a higher density of image pixels and improve resolution.

[0027] The image display system can also include a scanning controller for controlling the formation of a projected image within the composite field of view. The image display system can include a 2-D XY scanner for forming an image from multiple light sources, such as an RGB combiner (red, green, blue combiner). Each RGB combiner provides overlapping red, blue, and green collimated laser beams for forming the image. The controller can include timing and matching mechanisms, such as a feedback loop and a synchronization module.

[0028] FIG. 3 is a simplified schematic diagram illustrating an image display system for providing a compound field of view (FOV), according to some embodiments of the present invention. The image display system can be part of a wearable imaging system for a user to view a virtual image. As shown in FIG. 3 , the image display system 300 includes an image-modulated light source 310, which in this example includes four RGB (red-green-blue) laser combiners 310. The image-modulated light beams 320 emitted by the laser combiner 310 are separated from each other by a fixed angle. The image display system 300 also includes a scanning mirror 330 and a waveguide 350. Note that only two of the four light beams are visible in the perspective view of FIG. 3 because the remaining two beams would be directly behind those visible in FIG. 3 . The scanning mirror 330 can be a MEMS (microelectromechanical systems) reflector / scanner for projecting an image into the waveguide 350, which couples the light to the user's eye. Display system 300 also includes a waveplate 370, such as a quarter waveplate (QWP), that converts the linearly polarized light output by laser combiner 310 into circularly polarized light.

[0029] As shown in FIG. 3 , a light source 310, e.g., an RGB combiner 310, is configured to provide multiple incident light beams 320 having different angles of incidence. In this embodiment, a scanning mirror 330 and a polarizing element 370 are located on the opposite side of the waveguide 350 from the light source 310. This configuration has many advantages over alternative arrangements. For example, locating the mirror and light source on opposite sides of the waveguide allows for a compact configuration and achieves a smaller form factor for the image display device. This configuration allows the scanning mirror to be close to the input coupling element, thus allowing for a small light cone and a compact form factor for the system. The small form factor makes it suitable for wearable eyepiece imaging devices.

[0030] An input coupling grating (ICG) 352 (a form of input coupling element) is disposed on the lower surface 353 of the waveguide 350. The ICG 352 may be polarization-selective in that it allows light having the linear polarization emitted by the RGB combiner 310 to pass through and reflectively diffracts light having a linear polarization perpendicular to that emitted by the RGB combiner 310. Thus, the incident light beam 320 from the RGB combiner 310 passes through the ICG 352, the waveguide 350, and the wave plate 370 before reaching the scanning mirror 330. In transmitting the light, the wave plate 370 converts the polarization state of the light from the linear polarization state emitted by the RGB combiner 310 to circularly polarized light of a first handedness (e.g., RH or LH). Upon reflection by the scanning mirror 330, the handedness of the circularly polarized light is changed to a second handedness (e.g., LH or RH). Now, when light of the second handedness passes through waveplate 370 a second time, its polarization state is changed to a linear polarization state that is perpendicular to the linear polarization state emitted by RGB combiner 310. ICG 352's interaction depends on the orientation of the linear polarization of the light incident on it, and it is configured to reflectively diffract light that is reflected back from scanning mirror 330 through waveplate 370, rotating its polarization as described above. Light reflectively diffracted by ICG 352 will be diffracted at angles exceeding the critical angle for total internal reflection (TIR) of waveguide 350 and therefore will be coupled into a guided mode of waveguide 350. Waveguide 350 also has output coupling optical element 354 for projecting multiple output light beams 346 from the waveguide to form a projected image within a composite field of view (FOV) 366.

[0031] FIG. 4 is a simplified schematic diagram 400 illustrating a composite field of view (FOV) according to some embodiments of the present invention. In this example, the entire image is scanned simultaneously by four RGB beams in four quadrants. In some embodiments, each quadrant is a VGA (video graphic array) image, but the entire stitched image is full HD (high definition) with a double field of view. Referring to FIG. 3 , the MEMS reflector / scanner 330 has an optical scanning range of 20×20 degrees. Multiple RGB (red, green, blue) laser input beams 320 are separated by a 10-degree angle theta θ. The light beams 320 pass through an input coupling grating 352 and a quarter-wave plate 370 before reaching the scanning mirror 330. The scanning mirror 330 reflects the light beams at different angles (due to different angles of incidence) to cover different fields of view. For example, in some embodiments, image display system 300 can use two or four light beams to provide a resulting scanned image with a double field of view (40x40 degrees) and resolution that meets high-resolution 40x40 degree specifications, and the final image can have a 50 degree diagonal for high-resolution displays.

[0032] FIG. 5 is a simplified schematic diagram illustrating another image display system for providing a compound field of view (FOV), according to some embodiments of the present invention. Image display system 500 is similar to image display system 300 of FIG. 3 described above, and the same reference numerals are used to designate corresponding components in both FIG. 3 and FIG. 5 . As shown in FIG. 5 , image display system 500 includes a light source 510 having multiple RGB (red-green-blue) laser combiners. Unlike laser combiner 310 of FIG. 3 , which outputs beams 320 separated from each other by a fixed angle, two laser combiners 510 of FIG. 5 output parallel light beams 511 and 512. Mirrors 516, 517, and 518 are used to redirect the light beams and provide incident light beams 320 with different angles of incidence relative to scanning mirror 330.

[0033] Other than the light source, the components and functions of image display system 500 may be similar to those of image display system 300. Thus, the description provided in connection with FIG. 3 is applicable to FIG. 5, where appropriate. Image display system 500 also includes a scanning mirror 330 and a waveguide 350. Scanning mirror 330 can be a MEMS (microelectromechanical system) reflector / scanner for projecting an image within waveguide 350 for directing the image to a user's eye. Display system 500 also includes a polarization control element 370, such as a quarter-wave plate (QWP).

[0034] 5, the RGB combiner 510 is located on the opposite side of the waveguide 350 from the scanning mirror 330. Locating the mirror and light source on opposite sides of the waveguide allows for a compact configuration and enables a smaller form factor for the image display device. Incident light beams 320 having different angles of incidence are directed to a polarization-sensitive input coupling optical element 352. The input coupling optical element 352 is also configured to reflectively diffract the light beams reflected by the scanning mirror 330 into the waveguide.

[0035] Light is emitted from the RGB combiner 510 in a first linear polarization state. The input coupling optical element 352 is configured to transmit the light in the first linear polarization state without substantially polarizing the light (i.e., by diffraction). After passing through the input coupling optical element 352, the light traverses the waveguide 350 and subsequently traverses the polarization control element 370. Upon passing through the polarization control element 370, the polarization of the light is converted from the first linear polarization state to a first circular polarization state (e.g., LH or RH). The light is then reflected by the scanning mirror 330. The reflection changes the light to a second circular polarization state (e.g., RH or LH). The light then passes through the polarization control element 370 and is converted to linearly polarized light, polarized in a direction perpendicular to the polarization of the light emitted by the RGB combiner 510. The input coupling optical element 352 is configured to selectively reflectively diffract only the polarization of the light achieved after the second pass through the polarization control element. The light is diffracted by input coupling optical element 352 to an angle above the critical angle for total internal reflection (TIR) within waveguide 350. Inside waveguide 350, an optical path 345 of light beam 340 is obtained due to TIR. Waveguide 350 also has output coupling optical element 354 for projecting multiple output light beams 346 from the waveguide to form a projected image within a composite field of view (FOV) 366. The composite field of view includes portions produced by each of the multiple RGB combiners.

[0036] FIG. 6A is a simplified schematic diagram illustrating another image display system for providing a compound field of view (FOV), according to some embodiments of the present invention. Image display system 600 is similar to image display system 300 of FIG. 3 described above, and the same reference numerals are used to designate corresponding components in both FIGs. 3 and 6 . As shown in FIG. 6A , image display system 600 includes a light source 310 having multiple RGB (red-green-blue) laser combiners that provide incident light beams 320 with different angles of incidence. Unlike system 300 of FIG. 3 , in which a quarter-wave plate 370 is disposed between scanning mirror 330 and waveguide 350, image display system 600 shown in FIG. 6A has a quarter-wave plate 670 disposed between RGB combiner 310 and waveguide 350. In some embodiments, the incident light beam 320 emerging from the quarter-wave plate 670 may have a circular polarization of a first handedness (e.g., RH or LH), and the reflected light beam 340 reflected from the scanning mirror 330 may have a circular polarization of a second handedness (e.g., LH or RH). In this embodiment, the input coupling optical element 352 is polarization-sensitive. For example, the input coupling optical element 352 (e.g., an ICG) can be configured to allow the incident light beam 320 with circular polarization of the first handedness to pass through and to couple the reflected light beam 340 with circular polarization of the second handedness into the waveguide 350. The input optical element 352 can reflectively diffract light with circular polarization of the second handedness at an angle greater than the critical angle for total internal reflection with respect to the waveguide 350. The reflected light beam 340 is configured to project a tiled image. Inside the waveguide 350, the light beam 340 undergoes total internal reflection (TIR). Waveguide 350 also has output coupling optics 354 for projecting multiple output light beams 346 from the waveguide to form a projected image within a composite field of view (FOV) 366 .

[0037] A first anti-reflective layer 602 is formed on an outer surface 606 of the input optical coupling element. A second anti-reflective layer 604 is formed on a surface 608 of the waveguide 350 opposite the input coupling element, facing the scanning mirror 330. The anti-reflective layers 602, 604 can be single- or multi-layer optical interference coatings or surface-relief structured layers that include subwavelength-sized tapered structures that effectively provide a gradual transition in refractive index, thereby reducing or substantially eliminating reflections. The anti-reflective layers 602, 604 serve to avoid unintended bright spots in the field of view of the system 300 associated with Fresnel reflections at the surface 608 of the waveguide 350.

[0038] FIG. 6B is a simplified schematic diagram illustrating a portion of the image display system 600 of FIG. 6A . In some embodiments, the incident light beam 320 can include a first incident light beam and a second incident light beam having different angles of incidence. As a result, the reflected light beam 340 can include a first reflected light beam 341 from the first incident light beam and a second reflected light beam 342 from the second incident light beam. In some embodiments, the input coupling element 352 can include two separate ICGs, e.g., ICG1 and ICG2, for the two reflected light beams. In alternative embodiments, the two reflected light beams can be combined by different portions of a single input coupling optical element. In some embodiments, the first reflected light beam 341 and the second reflected light beam 342 can also have different polarizations. In this case, ICG1 and ICG2 can have different polarization responses.

[0039] FIG. 7 is a simplified schematic diagram illustrating another image display system for providing a composite field of view (FOV), according to some embodiments of the present invention. As shown in FIG. 7 , image display system 700 includes a light source 710, which in this example may have multiple RGB (red-green-blue) laser combiners, e.g., four combiners. Light source 710 provides incident light beams 720 with different angles of incidence. Each light beam 720 is image-modulated based on image data from a portion of the full field of view. The multiple light beams 720 are used together to display the full field of view. Similar to the image display systems described above, image display system 700 also includes a scanning mirror 730 and a waveguide 750. Unlike the display systems of FIGS. 3, 5, and 6A, in which the light source and scanning mirror are located on opposite sides of the waveguide, in image display system 700, light source 710 and scanning mirror 730 are located on the same side of waveguide 750. To enable the scanning mirror 730 to scan the incident light beam 720 toward the waveguide 750, the image display system 700 includes a polarization-sensitive beam splitter (PBS) 780 that directs the incident light beam 720 toward the scanning mirror 730 through a quarter-wave plate 770. The polarization-sensitive beam splitter (PBS) 780 also allows the reflected light beam 740 to pass through to reach the input coupling grating 752. The PBS 780 includes a reflective polarizer 781 (e.g., a wire grid) along its diagonal. A first optical path segment extends from the RGB combiner 710 to the polarizer 781, then through the quarter-wave plate 770 to the scanning MEMS mirror 730.

[0040] The second optical path segment extends from the scanning MEMS mirror 730 through the polarizer 781 to the input coupling grating 752. The RGB combiner 710 can output linearly polarized light with a polarization orientation that is reflected by the polarizer 781. The quarter-wave plate 770 converts the linearly polarized light reflected by the polarizer 781 into circularly polarized light with a certain handedness (e.g., RH or LH). Upon reflection by the scanning MEMS mirror 730, the handedness of the circularly polarized light is reversed (to RH if originally LH, and to LH if originally RH). The circularly polarized light with reversed handedness then passes through the quarter-wave plate 770 and, in doing so, is converted to a linear polarization state perpendicular to that emitted by the RGB combiner 710, and thus passes through the polarizer 781. In this case, the input coupling grating 752 is polarization insensitive and couples the reflected light beam 740 into the waveguide 750. Inside the waveguide 750, the light beam 740 undergoes total internal reflection (TIR). The waveguide 750 also has an output coupling grating 754 for projecting multiple output light beams 746 from the waveguide to form a projected image within a composite field of view (FOV) 766.

[0041] In image display system 700, the input coupling optical element or ICG 752 is not polarization sensitive. It is configured to couple the incident light beam into the waveguide but not allow the incident light beam to pass through the waveguide. Therefore, in these embodiments, the light source 710 is located on the same side of the waveguide as the scanning mirror, and a beam splitter 780 is used to direct the incident light beam to the scanning mirror. In some embodiments, the incident light beam is configured to be perpendicular to the scanning mirror. For simplified schematic illustration, only one incident light beam 720 is shown in FIG. 7. Using multiple incident light beams, an expanded field of view can be obtained, as described above in connection with FIG. 4. Depending on the embodiment, either multiple ICGs or a single ICG can be used.

[0042] Figure 8 is a schematic diagram of a display system 800 that uses scanning mirrors with multiple layers of polarization- and spectrally selective liquid crystal material to angularly separate independently modulated beam components to separately illuminate quadrants of the entire field of view. The system includes twelve laser diodes 801-810 (only ten of which are visible in Figure 8) logically organized into four sets of three laser diodes. The first set includes a first red laser diode 801, a first green laser diode 802, and a first blue laser diode 803. The second set includes a second red laser diode 804, a second green laser diode 805, and a second blue laser diode (not visible in Figure 8). The third set includes a third red laser diode 806, a third green laser diode 807, and a third blue laser diode 808. The fourth set includes a fourth red laser diode (not visible in FIG. 8), a fourth green laser diode 809, and a fourth blue laser diode 810. A second blue laser diode (not visible in FIG. 8) is located below the first blue laser diode 803, and a fourth red laser diode (not visible in FIG. 8) is located below the third red laser diode 806. Each of the four sets of three laser diodes includes a red laser diode, a green laser diode, and a blue laser diode such that by controlling the relative drive currents, and thereby the relative power outputs, of the three laser diodes in each set, the chromaticity coordinates of the combined output of the three lasers in each set can be controlled within a color gamut.

[0043] The first set of laser diodes 801, 802, and 803 are optically coupled to a first dichroic combiner cube 811, which combines the outputs of the three laser diodes 801, 802, and 803 into a single beam. Similarly, a second red laser diode 804, a second green laser diode 805, and a second blue laser diode (not visible in FIG. 8 ) are optically coupled to a second dichroic combiner cube 812, which combines the outputs of the three laser diodes 804, 804, and the second blue laser diode into a single beam. In addition, a third red laser diode 806, a third green laser diode 807, and a third blue laser diode 808 are optically coupled to a third dichroic combiner cube 813, which combines the outputs of the third set of laser diodes 806, 807, and 808 into a single beam. Additionally, a fourth red laser diode (not visible in FIG. 8 ), a fourth green laser diode 809, and a fourth blue laser diode 810 are optically coupled to a fourth dichroic combiner cube 814. The above-described dichroic combiner cubes 811, 812, 813, 814 each include a buried red-reflective (short wavelength pass) filter 815 along one diagonal and a buried blue-reflective (long wavelength pass) filter 816 along a second diagonal, such that the red-reflective filter 815 and the blue-reflective filter intersect at 90°.

[0044] Laser collimating lenses 817 (only a portion of which is visible in FIG. 8) are positioned between the input faces 818 of the dichroic combiner cubes (only a limited number of which are labeled to avoid cluttering the figure) and the laser diodes 801-810. A first set of laser diodes 801, 802, 803, whose outputs are combined by a first dichroic combiner 811, can have a polarization (S or P) that is perpendicular to the polarization (P or S) of a third set of laser diodes 806, 807, 808, whose outputs are combined by a third dichroic combiner 813. The first dichroic combiner 811 and the third dichroic combiner 813 are optically coupled to a first polarizing beam splitter (PBS) 819 (acting as a combiner) so that the PBS 819 receives the combined outputs of the first set of laser diodes 801, 802, 803 at a first input face 820, receives the combined outputs of the third set of laser diodes 806, 807, 808 at a second input face 821, and outputs a combined collinear collimated beam comprising the combined outputs of the first and third sets of laser diodes 801, 802, 803, 806, 807, 808 at an output face 822.

[0045] Similarly, second dichroic beam combiner 812 and fourth dichroic beam combiner 814 are optically coupled to second PBS combiner 823. Similar to the case described above, the second set of laser diodes 804, 805 (and a second blue laser diode not visible in FIG. 8 ), whose outputs are combined by second dichroic combiner 812, can have a polarization (S or P) that is perpendicular to the polarization (P or S) of the fourth set of laser diodes 809, 810 (and a fourth red laser diode not visible in FIG. 8 ), whose outputs are combined with third dichroic combiner 813. The second PBS 823 receives the combined output of the second red laser diode 804, the second green laser diode 805, and the second blue laser diode (not visible in FIG. 8) from the second dichroic beam combiner 812, and the combined output of the fourth red laser diode (not visible in FIG. 8), the fourth green laser diode 809, and the fourth blue laser diode 810 from the fourth dichroic beam combiner, and generates therefrom a six-component beam including the outputs of a second set of laser diodes 804, 805, and the second blue laser diode (not visible in FIG. 8) and the outputs of a fourth set of laser diodes 809, 810 including the fourth red laser diode (not visible in FIG. 8). Corresponding color laser diodes (e.g., first red laser diode 801 and third red laser diode 806) optically coupled to the first PBS 819 preferably have nominally identical emission wavelengths (accepting manufacturing variations), and corresponding color laser diodes (e.g., second green laser diode 805 and fourth green laser diode 809) optically coupled to the second PBS 823 preferably have nominally identical emission wavelengths; however, in one embodiment, there is an intentional difference in the emission wavelengths of corresponding color laser diodes coupled to the first PBS 819 and second PBS 823.For example, the first green laser diode 802 and the third green laser diode 807 may have an emission wavelength of 520 nanometers, while the second green laser diode 804 and the fourth green laser diode may have an emission wavelength of 535 nanometers.

[0046] The six-component output of the first PBS 819 is optically coupled to a three-spectral component reflector 825 through a beam-folding mirror 824. Note that the beam-folding mirror 824 and the three-spectral component reflector 825, like the dichroic beam combiners 811, 812, 813, and 814, and the PBSs 819 and 823, are embedded in a transparent cube. The six-component output of the second PBS 823 is also optically coupled to the three-spectral component reflector 825. The three-spectral component reflector 825 reflects the output of the second PBS 823 and transmits the output of the first PBS 819 due to the difference in wavelength of the light coupled through the first PBS 819 and the second PBS 823, which results from the difference in the emission wavelengths of the laser diodes 801-810 discussed above. Note that the three spectral components reflected by the reflector 825 each contain two different polarization components originating from two different laser diodes. The three-spectral-component reflector 825 therefore outputs a twelve-component beam 845, including four components per color channel (i.e., four red, four green, and four blue components). For each color channel, the four color components are distinguished by linear polarization orientation and wavelength, with two possible polarization orientations and two possible wavelengths per color channel. The twelve-component output of the three-spectral reflector 825 is coupled to the scanning mirror 830 through a quarter-wave plate (QWP) 826. The QWP 826 converts one linear polarization state to a right-handed circular polarization (RHCP) state and a second linear polarization state, perpendicular to the first, to a left-handed circular polarization (LHCP) state.

[0047] The scanning mirror 830 has a multilayer diffraction grating 832 on its beam-facing surface 833. The multilayer diffraction grating 832 can include twelve spectrally polarization-state selective layers, each with a predetermined grating period and orientation designed based on a predetermined operating wavelength to diffract one component of the twelve-component beam 845 in a specific direction for each orientation of the scanning mirror 830. The scanning mirror 830 has two degrees of freedom so that it can generate a 2D image. The multilayer diffraction grating 832 can include, for example, multiple cholesteric liquid crystal grating (CLCG) layers. The CLCG diffraction grating has a handedness that represents the relative rotation between the molecular layers. The CLCG diffraction grating reflectively diffracts circularly polarized light that matches the handedness of the CLCG and transmits circularly polarized light of the opposite handedness without diffraction. In some embodiments, the 12-component beam may include two red light components with wavelengths of 625 nm, two red light components with wavelengths of 650 nm, two first green light components with wavelengths of 520 nm, two second green light components G2 with wavelengths of 535 nm, two blue B1 light components with wavelengths of 450 nm, and two blue light components with wavelengths of 465 nm. Components with common wavelengths are distinguished by the handedness of their circular polarization. Multilayer diffraction grating 832 reflectively diffracts the components of 12-component beam 845.

[0048] Upon diffraction by the multilayer diffraction grating 832, the 12 components of beam 845 can be separated into four quadrant beams 841, 842, 843, and 844, each having a red, green, and blue component that are modulated using image information from a quadrant of the full field of view. As the scanning mirror deflects, the four quadrant beams 841, 842, 843, and 844 are angularly scanned, creating a wider field of view due to the diverse beams and their angular separation. In an embodiment of the present invention, portions of the video data for the full field of view are used to separately modulate the multiple scanned beams. Furthermore, the intensity modulation applied to quadrant beams 841, 842, 843, and 844 can be adjusted to produce identical chromaticity coordinates across the chromaticity coordinate area corresponding to the overlapping color gamut associated with the wavelengths in each of the four quadrant beams 841, 842, 843, and 844.

[0049] The four quadrant beams 841, 842, 843, and 844 are combined through an input coupling grating (ICG) 850 in a waveguide / eyepiece 851. The waveguide / eyepiece 851 is a component of the augmented reality glasses (not shown in FIG. 8 ). The waveguide / eyepiece 851 also includes an orthogonal pupil expander (OPE) 852 and an exit pupil expander (EPE) 853. The OPE 852 serves to distribute light vertically (in the orientation of FIG. 8 ) across the EPE 853, which serves to outcouple the light into a user's eye (not shown) that looks through the EPE 853. The EPE continuously outputs portions of the beams that propagate beyond it, thereby forming a wider output beam that is a composite of the multiple outcoupled portions. The beam output from the EPE 853 originates from the beam input through the input coupling grating 850. Note that EPE 853 may be displaced perpendicular to the plane of the drawing relative to OPE 852 rather than being in an overlapping relationship.

[0050] FIG. 9 is a simplified schematic diagram illustrating another image display system according to some embodiments of the present invention. As shown in FIG. 9, the image display system 900 includes a light source (not shown) for providing a collimated incident light beam 920, which includes multiple incident light beams, which may have different wavelengths or different polarizations. The image display system 900 also includes a scanning mirror 930 with a diffractive surface 932 for receiving the collimated incident light beam and providing multiple reflectively diffracted light beams with different diffraction angles. The diffractive surface may have the structure of the multilayer diffraction grating 832 discussed above with reference to FIG. 8. Each of the multiple reflectively diffracted light beams is configured to provide an image within a separate field of view (FOV). The waveguide 950 includes an input coupling optical element 952 for coupling the multiple reflected light beams into the waveguide and an output coupling optical element 954 for projecting multiple output light beams 946 from the waveguide to form a projected image with a composite field of view (FOV) 966.

[0051] In the embodiment of FIG. 9 , the scanning mirror 930 is positioned on the opposite side of the waveguide 950 from the light source providing the incident light beam 920. The waveguide input coupling optical element 952 is configured to allow the collimated incident light beam 920 to pass through the input coupling element 952 and the waveguide 950 and is configured to couple the multiple reflectively diffracted light beams 940 into the waveguide 950 by diffracting the multiple reflectively diffracted beams at an angle above the critical angle of the waveguide. In some embodiments, the input coupling optical element 952 is a polarization-sensitive input coupling grating (ICG). One type of polarization-sensitive ICG that can be used is discussed below with reference to FIG. 19 . Each of the multiple incident light beams comprises a composite RGB light beam to form a scanned image. In an embodiment, the multiple incident light beams include a first composite RGB light beam with R1 G1 B1 having wavelengths of 625 nm, 520 nm, and 450 nm, respectively, and a second composite RGB light beam with R2 G2 B2 having wavelengths of 650 nm, 535 nm, and 465 nm, respectively.

[0052] Figure 10 is a side view of a waveguide display system 1000 according to an alternative embodiment. An image modulation light source 1002 outputs a composite beam 1004 including at least two sets of red (R), green (G), and blue (B) spectral components (e.g., R1, G1, B1; R2, G2, B2), each of which is modulated based on video data. The sets of RGB spectral components can be distinguished by linear polarization state, by circular polarization handedness (e.g., LH vs. RH), or by slight differences in wavelength. The composite beam 1004 passes through an eyepiece waveguide 1006 and impinges on a two-degree-of-freedom scanning mirror 1008. A diffraction grating 1009 is formed on or supported on a surface 1007 of the scanning mirror 1008 upon which the composite beam 1004 is incident. Diffraction grating 1009 is designed to angularly separate the at least two sets of RGB components such that one of the at least two sets of RGB components illuminates a first portion of the field of view of waveguide display system 1000 and a second of the at least two sets of RGB components illuminates a second portion of the field of view of waveguide display system 1000. As shown, diffraction grating 1009 separates composite beam 1004 into first RGB set beam 1111 and second RGB set beam 1115. Although not shown, the individual RGB components may also be angularly separated and, in such case, modulated with video information with R, G, B channel delays set according to the angular separation of the RGB components. The diffraction grating 1009 may take the form of, for example, a stack of six cholesteric liquid crystal gratings (CLCGs), each with a helical pitch tuned to a particular spectral component (one of the R1, G1, and B1 components; R2, G2, and B2 components) and a grating (lateral) pitch set according to a designed diffraction angle. Thus, a first set of RGB components can be diffracted at a first angle, and a second set of RGB components can be diffracted at a second angle. Note that such angular dispersion differs from that produced by a typical diffraction grating, in which the diffraction angle is a monotonic function of wavelength. CLCGs are discussed further below with reference to Figures 19 and 20.If a CLCG is used, the image modulated light source 1002 can be configured to output circularly polarized light, for example, by including a wideband quarter wave plate (QWP).

[0053] The scanning mirror 1008 deflects the first RGB set beam 1111 and the second RGB set beam 1115 into a first surface 1010 of an input coupling prism 1012. The scanning mirror 1008 is driven in coordination with modulation of the RGB components of the beams 1111, 1115. The input coupling prism 1012 has a second surface 1014 that is coupled to a first surface 1016 of the eyepiece waveguide 1006 using an index-matching adhesive 1015. The beams 1111, 1115 propagate through the input coupling prism 1112 into the eyepiece waveguide 1006 at angles above the critical angle for total internal reflection and undergo multiple reflections at the first surface 1116 and the opposite second surface 1018 of the eyepiece waveguide 1006 while propagating along the eyepiece waveguide 1006. Eventually, the beams 1011, 1115 reach an orthogonal pupil expander 1016, which takes the form of a diffraction grating with grooves extending in a plane perpendicular to the plane of the paper and at 45 degrees to the plane of the paper. The orthogonal pupil expander 1016 incrementally reflects portions of the beams 1011, 1115 perpendicular to the plane of the paper towards an exit pupil expander (not shown) which takes the form of a diffractive optical element (e.g., a grating) that redirects the light out of the eyepiece waveguide 1006 towards the user's eye.

[0054] FIG. 11 is a simplified schematic diagram illustrating another image display system according to some embodiments of the present invention. The image display system 1100 of FIG. 11 is similar to the image display system 1000 of FIG. 10. Unlike the image display system 1000 of FIG. 10, which relies on an input-coupling prism 1112 to couple a light beam into a waveguide, in the image display system 1100, an input-coupling element 1052 is used to couple a light beam into the waveguide 1050, and the input-coupling element 1052 need not be polarization-sensitive. To simplify illustration, the same reference numbers are used in both FIGS. 10 and 11 to designate common components. As shown in FIG. 11, the image display system 1100 includes a scanning mirror 1030, e.g., a MEMS scanning mirror, for receiving an incident light beam 1020 and providing a scanned reflected light beam 1040. The image display system 1000 also includes a waveguide 1050 for receiving the scanned reflected light beam. The incident light beam 1020 is multiplexed to contain wavelengths in the vicinity of red, green, and blue, e.g., R1 R2..., G1 G2..., B1 B2..., as described above. Furthermore, the incident light beam 1020 is directed to enter the waveguide 1050 at an angle less than the total internal reflection (TIR) critical angle and therefore is not coupled into the waveguide 1050. The scanning mirror 1030 can include a diffractive element that directs components of the incident light beam in different directions depending on their wavelength, resulting in separate light beams. The diffraction grating 832 discussed above in connection with FIG. 8 can be used for the diffractive element included in the scanning mirror 1030. The angles of incidence of these light beams into the waveguide are varied using the MEMS scanning mirror rotation angle. In the simplified diagram of FIG. 11, two light cones 1041 and 1042 are shown as a result of scanning the two light beams reflected from the scanning mirror 1030. In some embodiments, light beams 1041 and 1042 are coupled into waveguide 1050 by an input coupling element 1052, such as an ICG. In this embodiment, input coupling element 1052 need not be polarization sensitive.

[0055] 11 , scanned light beam 1041 undergoes total internal reflection (TIR) within waveguide 1050 and is projected from the waveguide through output coupling optical element 1054 to form a first image within second field of view (FOV1) 1066. Similarly, scanned light beam 1042 undergoes total internal reflection (TIR) within waveguide 1050 and is projected from the waveguide through output coupling optical element 1054 to form a second image within second field of view (FOV2) 1068. In embodiments of the present invention, image data is encoded into the multiple scanned beams as needed. Image display system 1100 is configured to form an image within a composite FOV 1060, including first FOV 1066 and second FOV 1068.

[0056] 11 , in some embodiments, a light source providing incident light beam 1020 is positioned on the opposite side of waveguide 950 from scanning mirror 1030. The light source is configured to provide incident light beam 1020 at an angle relative to waveguide 1050 that is less than the TIR critical angle. Thus, incident light beam 1020 passes through waveguide 1050 to reach scanning mirror 1030 without being coupled into the waveguide. Furthermore, reflected light beam 1040 enters waveguide 1050 through input coupling optical element 1052 that is offset from incident light beam 1020. In some embodiments, the reflective surface of the scanning mirror can be made approximately parallel to the substrate (to save volume) by using a diffractive off-axis mirror, where the angle of incidence is not the same as the angle of reflection, which may lead to a more compact configuration of the imaging device.

[0057] FIG. 12 is a simplified flowchart illustrating a method for displaying an image. As shown in FIG. 12, method 1200 includes providing two or more input light beams to a scanning mirror (1210). The method also includes scanning the two or more input light beams to provide multiple reflected light beams (1220). Each of the multiple reflected light beams is configured to provide an image within a respective field of view (FOV). The method further includes receiving the multiple reflected light beams in a waveguide (1230). In addition, the method includes projecting the multiple output light beams from the waveguide (1240) to form a projected image within the combined field of view (FOV). Examples of image display systems that implement method 1200 are described above in connection with FIGS. 1-10. In some embodiments of the method, the combined field of view is wider than the FOV provided by each of the two or more input light beams. The image within the combined FOV can be a tiled image including an image from each of the input light beams.

[0058] FIG. 13 is a schematic diagram of a light engine 1300, according to an embodiment. The light engine 1300 can be used as any of the light sources 110, 310, 510, or 710 of the display systems described hereinabove. Referring to FIG. 13, the light engine 1300 includes a red light source 1302, a green light source 1304, and a blue light source 1306. The light sources 1302, 1304, 1306 may take the form of, for example, laser diodes (LDs) or light-emitting diodes (LEDs). A red channel collimating lens 1308, a green channel collimating lens 1310, and a blue channel collimating lens 1312 are arranged at the outputs of the red light source 1302, the green light source 1304, and the blue light source 1306, respectively. Blue light source 1306 is optically coupled through blue channel collimating lens 1312, via blue channel optical path folding mirror 1314, via green band-reflecting dichroic mirror 1318, via red band-reflecting dichroic mirror 1320, to beam deflecting prism 1322. Green light source 1304 is optically coupled through green channel collimating lens 1310 and via green band-reflecting dichroic mirror 1318 to beam deflecting prism 1322. Red light source 1302 is optically coupled through red channel collimating lens 1308 and via red band-reflecting dichroic mirror 1320 to beam deflecting prism 1322. Light from light sources 1302, 1304, and 1306 arrive at beam deflecting prism 1322 as a multi-spectral component collimated beam 1324. The multi-spectral component collimated beam 1324 enters the input surface 1326 of the beam deflecting prism 1322 and exits through an angled surface 1328 of the beam deflecting prism 1322, which serves to refract and thereby deflect the multi-spectral component collimated beam 1324. Optionally, a diffraction grating (not shown) can be placed on the input surface to contribute to the deflection of the beam 1324 and compensate for chromatic dispersion associated with refraction at the angled surface 1328. The beam deflecting prism 1322 is rotated by an angle alpha about an axis 1330 that is parallel to the incident multi-spectral component collimated beam 1324.Rotating the beam-deflecting prism 1322 by angle alpha serves to impart a beam direction cosine perpendicular to the plane of the drawing. Multiple light engines of the configuration shown in FIG. 13 , e.g., two, four, or more, can be arranged in an assembly (not shown) with their individual beam-deflecting prisms 1322 oriented so that the multispectral component beams 1324 from the four multiple light engines 1300 converge at the surface of one of the beam-scanning mirrors used in the embodiments described hereinabove. Although not shown in FIG. 13 , more light sources, each with a different spectral output, can be added in a manner similar to the arrangement shown in FIG. 13 . For example, a pair of narrowband light sources with different peak wavelengths and substantially non-overlapping spectral outputs can be provided for each of red, blue, and green. Providing such additional light sources would result in an increased color gamut for the display systems described hereinabove.

[0059] FIG. 14 is a schematic diagram of a light engine 1400 according to another embodiment, and FIG. 15 is a front (output end) view of the light engine 1400 shown in FIG. 14. The light engine 1400 can be used as any of the light sources 110, 310, 510, or 710 of the display systems described hereinabove. With reference to FIGS. 14-15, the light engine 1400 includes a first beam source 1402, a second beam source 1404, a third beam source 1502, and a fourth beam source 1504. The third beam source 1502 and the fourth beam source 1504 will have identical structures, with the notable exception of the positioning of the beam-forming lenses, as discussed further below. With particular reference to FIG. 14, internal details of the first beam source 1402 and the second beam source 1404 are shown. The first beam source 1402 includes a first output lens 1414 a, and the second beam source 1404 includes a second output lens 1414 b. Each beam source 1402, 1404 includes a red laser diode 1406, a green laser diode 1408, and a blue laser diode 1410 that are coupled through a dichroic beam combiner 1412 to associated collimating and beam deflecting lenses 1414 a, 1414 b. (Alternatively, laser diodes 1406, 1408, 1410 may be replaced with other types of light sources, such as, for example, light-emitting diodes.) Each dichroic beam combiner 1412 includes an input surface 1416, a lower beam-fold mirror surface 1418 tilted at +45 degrees from the indicated Z-axis, an upper beam-fold mirror surface 1420 tilted at −45 degrees from the indicated Z-axis (assuming that the left edge of each individual surface is considered the axis of rotation in each case), and an output surface 1422. Beam-fold mirror surfaces 1418, 1420 may be, for example, total internal reflection (TIR) surfaces or metalized surfaces. A blue band-reflecting dichroic mirror 1424 tilted at +45 degrees and a red band-reflecting dichroic mirror 1426 tilted at −45 degrees are embedded in dichroic beam combiner 1412. Dichroic beam combiner 1412 may be made from multiple pieces of optical glass coated with a dichroic coating and joined with an optical adhesive.Light from the blue laser diode 1410 is coupled to the output lenses 1414a, 1414b via the lower beam folding mirror surface 1418, the blue band-reflecting dichroic mirror 1424, and the output surface 1422. Similarly, light from the red laser diode 1406 is coupled to the output lenses 1414a, 1414b via the upper beam folding mirror surface 1420, the red band-reflecting dichroic mirror 1426, and the output surface 1422. Light from the green laser diode 1408 passes through the input surface 1416, the blue band-reflecting dichroic mirror 1424, the red band-reflecting dichroic mirror 1426, and the output surface 1422 to the output lenses 1414a, 1414b.

[0060] Referring also to FIG. 15, the third beam source 1502 includes a third output lens 1514a, and the fourth beam source 1504 includes a fourth output lens 1514b. In FIG. 15, crosshairs indicate the centers of the output lenses 1414a, 1414b, 1514a, 1514b. The output lenses 1414a, 1414b, 1514a, 1514b serve to collect, modify the divergence angle (e.g., collimate), and deflect the light emitted by the laser diodes 1406, 1408, 1410. The optical path length of the light from the red laser diode 1406 and the blue laser diode within the dichroic beam combiner 1412 is longer than the optical path length of the light from the green laser diode 1408 as shown in FIG. 4. Additionally, the output lenses 1414a, 1414b, 1514a, 1514b are simple refractive lenses made from homogeneous optical material and may exhibit some chromatic aberration, meaning that the output lenses 1414a, 1414b, 1514a, 1514b have different focal lengths for the light from the red, green, and blue laser diodes 1406, 1408, 1410. To compensate for the chromatic aberration and different path lengths within the dichroic beam combiner, each laser diode 1406, 1408, 1410 is set at a different distance from the input surface 1416 of the dichroic beam combiner 1412. As an example, when output lenses 1414a, 1414b, 1514a, 1514b are used to collimate light, each particular laser diode 1406, 1408, 1410 can be separated from its associated output lens 1414a, 1414b, 1514a, 1514b by an optical path distance equal to the back focal length characteristic of the peak wavelength of the emission of the particular laser diode 1406, 1408, 1410.

[0061] Output lenses 1414a, 1414b, 1514a, 1514b are displaced off-axis (by an amount identified in terms of incremental ΔX and ΔY) relative to a composite optical axis 1415 of light from laser diodes 1406, 1408, 1410. At the input to lenses 1414a, 1414b, 1514a, 1514b, composite optical axis 1415 is parallel to the Z axis shown in FIG. 14. Offsetting lenses 1414a, 1414b in the X and Y directions serves to induce beam propagation directions with non-zero X and Y direction cosines. Note that for first beam source 1402, the beam X and Y lens offset is (ΔX, ΔY), while for second beam source 1404, the X and Y lens offset is (-ΔX, ΔY). The antisymmetry of the X-coordinate offset serves to steer the light beams formed by the two beam sources 1402, 1404 to an intersection point 1428 that coincides with the surface of the beam scanning mirror used in the embodiments described hereinabove. While the lenses 1414a, 1414b in the pair of beam sources 1402, 1404 shown in FIG. 14 have a positive Y-axis offset with respect to the combined optical axis reaching the lenses 1414a, 1414b, the second pair of beam sources 1502, 1504 has a negative Y-axis offset (-ΔY). Such antisymmetry of the Y-axis offset serves to cause the beams from the two pairs of beam sources 1402, 1404, 1502, 1504 to intersect at the aforementioned intersection point 1428. Thus, divergence-controlled (e.g., collimated) beams of four multispectral components can be directed at a single beam scanning mirror. The output lenses 1414a, 1414b, 15141, 1514b may be glass or plastic, may be cemented achromatic compound lenses, and may include diffractive optical surfaces, by way of non-limiting examples.

[0062] FIG. 16 is a top view of a four-channel light engine 1600, according to one embodiment, and FIG. 17 is a cross-sectional view of a portion of the light engine 1600 shown in FIG. 16. The light engine includes a substrate 1602 in which a recess 1604 is formed. The substrate 1602 can be silicon or ceramic, by way of non-limiting example. The substrate 1602 is etched to form mounting protrusions and positioning features (not shown) for components described below. If a hermetic seal is not required, the substrate 1602 can be a fiberglass printed circuit board. Various optical components, as described herein below, are mounted in the recess 1604, and an optical window 1606 is sealed onto the substrate 1602, overlapping and sealing the recess 1604. Four multispectral (RGB) component beam sources 1608, 1610, 1612, and 1614 are located within the recess 1604. Similar to the embodiment described above with reference to Figures 14-15 and as will be described below, the internal details of the beam sources 1608, 1610, 1612, 1614 are identical, except for the offset of the output lenses 1616a, 1616b, 1616c, 1616d. With reference to the first beam source 1608 shown in Figure 16, a blue laser diode 1618, a green laser diode 1620, and a red laser diode 1622 are optically coupled to a first lens 1624 via one of the dichroic beam combiners 1412. Reference is made to the description herein above in connection with Figures 14-15 for a description of the internal details of the dichroic beam combiner 1412.

[0063] 17, which is a cross section through a portion of the second multispectral component beam source 1610 (as shown in FIG. 16), the first lens 1624 is a first plano-convex lens having a flat surface 1626 that is bonded to an input surface 1630 of a beam-folding prism 1632 with optical adhesive 1628. A reflective surface 1634 of the beam-folding prism 1632 deflects the beam exiting the dichroic beam combiner 1412 upward by 90 degrees toward the optical window 1606. The beam-folding prism 1632 includes an exit surface 1636 that is bonded to a lower surface 1640 of the optical window 1606 with optical adhesive 1638. The planar surface 1642 of the plano-convex output lens 1616b is cemented using optical adhesive 1644 to the top surface 1646 of the optical window 1606, which overlaps the exit surface 1636 of the beam-folding prism 1632. Alternatively, the first lens 1624 achieves the desired beam divergence change (e.g., collimation), and the plano-convex output lenses 1616a, 1616b, 1616c, 1616d are replaced with beam-deflecting components such as prisms and / or diffractive optical elements. Alternatively, a divergence-modifying (e.g., collimating) lens 1648 is positioned on the input surface 1416 of the dichroic beam combiner 1412, as shown for the first multispectral component beam source 1608. Alternatively, diffractive, reflective optics, catadioptric, or other refractive components or subsystems may be used in place of or in addition to the first lens 1624, the lens 1648, and / or the output lenses 1616a, 1616b, 1616c, 1616d. Each of the beam sources 1608, 1610, 1612, 1614 includes one of the output lenses 1616a, 1616b, 1616c, 1616d, which are laterally offset by an amount shown in terms of distance increments ΔX and ΔY relative to the combined optical axis (lateral beam centroid) 1415 of that beam source 1608, 1610, 1612, 1614.In this manner, the beams output from the four beam sources 1608, 1610, 1612, 1614 intersect at common intersection points 1648, 1650, which may be located on the surface of one of the beam scanning mirrors in the embodiments described hereinabove. Thus, four multispectral component beams, each with independently modulated red, green, and blue spectral components, can be impinged on a single scanning mirror and scanned by the scanning mirror across the input optical element (e.g., an input coupling grating) of the display waveguide. The scanning mirror can be driven to scan each multicomponent beam over a sufficient angular range that is at least half the angular separation between the multicomponent beams incident on the scanning mirror. In this way, each beam can be scanned over a subrange that joins together to (at least) contiguously fill a wider solid angle range. (Overlapping subranges are also possible.) Such a wider solid angle range corresponds to a wider field of view for a user looking through the waveguide display eyepiece into which the beams are input. Each laser diode in each beam source can be separately modulated with image data to form color image modulated light.

[0064] FIG. 18 is a partial view of a waveguide display system 1800, according to one embodiment. As shown in FIG. 18, the waveguide display system includes a red laser diode 1802, a green laser diode 1804, and a blue laser diode 1806, each having an emission direction facing a biconvex aspherical collimating lens 1808. Alternatively, another type of collimating optic or optical system may be used, such as, by way of non-limiting example, a compound lens, a diffractive, reflective optic, and / or a catadioptric component. Light collimated by lens 1808 is incident on a quarter-wave plate (QWP) 1810. To the extent that the light emitted by the laser diodes 1802, 1804, and 1806 is substantially linearly polarized, the QWP 1810 serves to convert the polarization state to either right-hand (RH) or left-hand (LH) circular polarization. Light exiting the QWP 1810 passes through a first blue anti-reflection (AR) coating 1830, a blue input coupling grating (ICG) 1814, a blue light guide 1809, a second blue AR coating 1831, a first green AR coating 1832, a green ICG 1816, a green light guide 1811, a second green AR coating 1833, a first red AR coating 1834, a red ICG 1818, a red light guide 1812, and a second red AR coating 1836. The ICGs 1814, 1816, and 1818 are preferably reflective cholesteric liquid crystal gratings (CLCGs). The structure of the input coupling CLCGs 1814, 1816, and 1818 is discussed in further detail below. Blue ICG 1814 is supported on a front side 1824 of blue optical waveguide 1809, green ICG 1816 is supported on a front side 1826 of green optical waveguide 1811, and red ICG 1816 is supported on a front side 1828 of red waveguide 1812. The front sides 1824, 1826, 1828 of waveguides 1809, 1811, 1812 face toward laser diodes 1802, 1804, 1806. A first blue AR coating 1830, a first green AR coating 1832, and a first red AR coating 1834 are disposed on a laser-facing surface 1838 of blue ICG 1814, a laser-facing surface 1840 of green ICG 1816, and a laser-facing surface 1842 of red ICG 1818, respectively.

[0065] Only portions of the waveguides 1809, 1811, and 1812 are visible in FIG. 18 . The remaining portions of the waveguides 1809, 1811, and 1812 include or have additional optical components formed thereon to control the coupling of light into the user's eye. Such additional components may include, for example, an orthogonal pupil expansion grating (OPE) and an exit pupil expansion grating (EPE). The waveguides 1809, 1811, and 1812 are transparent to allow the user to simultaneously view the virtual content and the real environment. After passing through the waveguides 1809, 1811, and 1812 and the ICGs 1814, 1816, and 1818, the light emitted by the laser diodes 1802, 1804, and 1806 is reflected at the front surface 1820 of the scanning mirror 1822. When the light first passes through the QWP 1810, the light is converted from linearly polarized light to a specific initial handedness of circularly polarized light, which can be LH or RH. The ICGs 1814, 1816, 1818 have handedness opposite to the initial handedness of the light, so that the light initially passes through the ICGs substantially without deflection. The front surface 1820 of the scanning mirror 1822 may be specular or may include a reflective diffraction grating (e.g., a blazed surface relaxation grating, or, e.g., a volume holographic grating) that redirects the light into a non-zero diffraction order. Upon reflection from the front surface 1820, the handedness of the circularly polarized light is reversed to match the handedness of the CLCG ICGs 1814, 1816, 1818; therefore, light reflected from the front surface 1820 of the scanning mirror 1822 is reflectively diffracted to a first diffraction angle above the critical angle for TIR in the waveguides 1809, 1811, 1812.

[0066] FIG. 19 is a cross-sectional view through a portion of the waveguide display system 1800 shown in FIG. 18. FIG. 19 includes a cross-sectional elevation view through blue AR coatings 1830, 1831, blue ICG 1814, and blue waveguide 1809, including internal details of blue ICG 1814. Green ICG 1816 and red ICG 1818 have structures similar to that of blue ICG 1814, albeit with different axial and lateral pitches, which will be discussed further below. Blue ICG 1814 includes a cholesteric liquid crystal material 1902 located within a first cell 1908 formed by a first substrate 1910, a second substrate 1912, and a first edge seal 1914. First cell 1908 includes an alignment layer 1928 formed on first substrate 1910. The cholesteric liquid crystal includes a stack of multiple layers of liquid crystal material. Assuming that the stacking direction corresponds to the Z direction of the Cartesian triad shown, as in Figure 19, the orientation of the molecules in each successive layer in the stack is rotated by small angular increments about the Z axis. The rotation about the Z axis is characterized by pitch, which is the Z distance corresponding to one full rotation of the molecule. Chiral dopant molecules can be added to control the direction of twist, which can be either left-handed or right-handed. Reflectivity is maximized for light with circular polarization that matches the twist handedness of the cholesteric liquid crystal and with a wavelength that matches the Z-direction pitch. The pitch that characterizes the rotation of the molecules about the Z axis for the blue CLCG is equal to half the pitch in Figure 19, labeled dimension 0.5. * It is indicated by Pitch_Z.

[0067] A grating can be created by establishing periodic lateral (e.g., X direction in Figure 9) variations in the orientation of molecules within each layer. Alignment layer 1928 is used to establish lateral variations in the orientation of the cholesteric liquid crystal. Alignment layer 1928 may be a photo-alignment layer, in which a pattern for establishing local alignment of the liquid crystal molecules is established by exposure to a pattern of polarized light. Examples of photo-alignment layers include polyimide, linearly polarized photopolymerizable polymer (LPP), azo-containing polymers, coumarin-containing polymers, and cinnamate-containing polymers. The lateral pitch of liquid crystal material 1902 is labeled Pitch_X in Figure 19. Liquid crystal material 1902 forms a reflective polarization handedness-selective grating that preferentially diffracts light into the first diffraction order. The vertical pitch of liquid crystal material 1902 is set according to the wavelength of light it is intended to reflect (e.g., the wavelength of light emitted by blue laser diode 1806). The lateral pitch, Pitch_X, is set according to a grating equation to establish the diffraction angle of the first-order diffracted light. In the context of waveguide display system 1800, the lateral pitch of liquid crystal material 1902 is selected so that the diffraction angle from liquid crystal material 1902 for all orientations of scan mirror 1822 exceeds the critical angle for total internal reflection with respect to waveguide 1812. It should be understood that the references to "vertical" and "lateral" with respect to pitches Pitch_X and Pitch_Z are applicable to the orientation of system 1800 shown in FIG. 19 , and that in practice system 1800 can be used in any orientation. Similar to that shown in FIG. 19 , green input coupling grating 1816 and red input coupling grating 1818 have a vertical pitch Pitch_Z corresponding to the wavelength of light at which they operate (e.g., the wavelengths emitted by red laser diode 1802 and green laser diode 1806), and a lateral pitch Pitch_X based on the wavelength at which they operate, which light will be diffracted at angles that exceed the critical angle for TIR within the respective waveguides 1811 and 1812, in accordance with this specification.

[0068] FIG. 20 is a schematic plan view of a first alignment layer 1928 according to an embodiment. As shown in FIG. 20, the alignment layer 1928 includes a series of strip-shaped areas 2002-2034. It should be understood that the diagram shown in FIG. 20 shows only more than two periods (represented as Pitch_X), and in practice, the first alignment layer 1928 would include a larger number of pitch periods. Within each pitch period (Pitch_X), each successive strip area (e.g., 2002-2016) has an alignment direction that is incremental relative to the preceding strip area. As shown in FIG. 20, there are eight strip-shaped areas per pitch period, each with a different alignment direction. Alternatives, such as four or sixteen strip-shaped areas, each with a different alignment direction, may be provided per pitch period. Alternatively, the alignment direction may vary continuously. Continuous variation can be obtained, for example, by exposing a photo-alignment material, such as the photo-alignment materials cited above, to an interference pattern generated by the interference of two beams with oppositely handed circular polarizations, the amplitude sum of which is linearly polarized and whose orientation varies as a function of the phase difference and therefore varies across the photo-alignment layer.

[0069] 21 is a top view of a photonic chip-based two-RGB color channel combiner 2100 and a first lens 2102 and a second lens 2104, according to one embodiment. The combiner 2100 includes a polished glass plate 2106 in which a first branch waveguide 2108 and a second branch waveguide 2110 are defined. The branch waveguides 2108, 2110 can be defined by a patterned modification of the refractive index of the polished glass plate. The refractive index modification can be accomplished, for example, by implanting or injecting exogenous atomic species through a mask pattern.

[0070] The first branch waveguide 2108 has a first red receive branch 2112 and a first blue receive branch 2116 that are coupled to the trunk 2118. A first red laser diode 2122 is optically coupled to an input end 2124 of the first red receive branch 2112, a first green laser diode 2126 is optically coupled to an input end 2128 of the trunk 2118, and a first blue laser diode 2130 is optically coupled to an input end 2132 of the first blue receive branch 2116. An output end 2134 of the first red receive branch 2112 is coupled to the trunk 2118 at a first Y-junction 2136. Similarly, an output end 2138 of the first blue receive branch 2116 is coupled to the trunk 2118 at a second Y-junction 2140.

[0071] The second branch waveguide 2110 has the same structure as the first branch waveguide 2108 as described above and serves to couple light from the second red laser diode 2142, the second green laser diode 2144, and the second blue laser diode 2146 to the output end 2148 of the backbone 2114 of the second branch waveguide 2110.

[0072] The first lens 2102 is positioned in front of and optically coupled to the output end 2120 of the trunk 2118 (and thus of the first branch waveguide 2108), and the second lens 2104 is positioned in front of and optically coupled to the output end 2148 of the second branch waveguide 2110. A first lens optical axis (e.g., axis of rotational symmetry) 2150 of the first lens 2102 and a second optical axis 2152 of the second lens 2104 are shown in FIG. 21. The first lens optical axis 2150 is offset downward (from the perspective of FIG. 2) and in a direction perpendicular to the plane of the drawing relative to the trunk 2118 of the first branch waveguide 2108. Similarly, the second lens optical axis 2152 is offset upward and in a direction perpendicular to the plane of the drawing relative to the trunk 2114 of the second branch waveguide 2110. The aforementioned offset of the lens optical axes 2150, 2152 serves to direct light emerging from the output ends 2120, 2148 of the trunks 2118, 2114 to a common intersection 2154 that is aligned coincident with the surface of one of the beam scanning mirrors (e.g., 330, 730) used in the embodiments described herein above.

[0073] 22 is a top view of a photonic chip-based two RGB color channel combiner 2200 according to another embodiment. Combiner 2200 has many elements in common with combiner 2100, as indicated by common reference numbers. Combiner 2200 differs from combiner 2100 in that output end 2134 of red receive branch 2112 and output end 2116 of blue receive branch 2116 are coupled to backbone 2118 by evanescent coupling instead of at Y-junctions 2136 and 2140.

[0074] 21-22 , according to one embodiment. The top-positioned combiners 2100, 2200 and the bottom-positioned combiners 2100, 2200 are positioned on opposite sides of a spacer block 2300. As shown, the lenses 2102, 2104 are offset relative to their associated trunk output ends 2120, 2148 so that light emerging from the output ends 2120, 2148 of the trunks 2118, 2114 is focused at a common intersection 2154 that would be located coincident with the surface of one of the beam scanning mirrors (e.g., 330, 730) when the light engine 2300 is used in the embodiments described hereinabove.

[0075] FIG. 24 is a top view of a 4RGB channel light engine 2400 according to another embodiment, and FIG. 25 is a partial cross-sectional elevation view of a portion of the 4RGB channel light engine 2400 shown in FIG. 24. The light engine 2400 includes a glass plate 2402 having a first branch waveguide 2404, a second branch waveguide 2406, a third branch waveguide 2408, and a fourth branch waveguide 2410 defined therein. The branch waveguides 2404, 2406, 2408, 2410 may be established in the manner discussed above with reference to the embodiment shown in FIG. 21. As shown, the plate 2402 is square and includes a first side 2412, a second side 2414, a third side 2416, and a fourth side 2418. Alternatively, a shaped glass plate 2402 may also be used. A first set 2420 of red, green, and blue (RGB) laser diodes are arranged along a first side 2412, a second set 2422 of RGB laser diodes are arranged along a second side 2414, a third set 2424 of RGB laser diodes are arranged along a third side 2416, and a fourth set 2426 of RGB laser diodes are arranged along a fourth side 2418.

[0076] The first set 2420 of RGB laser diodes includes a red laser diode 2428, a green laser diode 2430, and a blue laser diode 2432. The first branch waveguide 2404 is positioned adjacent the first side 2412 and serves to couple light from the first set of laser diodes 2420 to a first output coupling facet 2434. The first branch waveguide 2404 includes a red receive branch 2436 optically coupled to the red laser diode 2428, a green receive branch 2438 optically coupled to the green laser diode 2430, and a blue receive branch 2440 optically coupled to the blue laser diode 2432. The red, green, and blue receive branches 2436, 2438, 2440 connect to (or alternatively are transiently coupled to) a backbone 2442 of the first branch waveguide 2404. The backbone 2442 extends to a first out-coupling facet 2434. The out-coupling facet 2434 is a total internal reflection (TIR) surface tilted at 45 degrees relative to the orientation of the backbone 2442. The first out-coupling facet 2434 reflectively deflects light out of the plane of the glass sheet 2402.

[0077] The second, third, and fourth branch waveguides 2406, 2408, 2410 have the same structure as that of the first branch waveguide 2404 as described, but are rotated relative to the first branch waveguide so that they are aligned with their adjacently positioned respective sides 2414, 2416, 2418. The second, third, and fourth branch waveguides 2406, 2408, 2410 are coupled to the second output coupling facet 2444, the third output coupling facet 2446, and the fourth output coupling facet 2448, respectively. The first lens 2450, the second lens 2452, the third lens 2454, and the fourth lens 2456 are positioned across the first output coupling facet 2434, the second output coupling facet 2444, the third output coupling facet 2446, and the fourth output coupling facet 2448, respectively. Each of lenses 2450, 2452, 2454, 2456 is offset relative to the output coupling facets where it overlaps toward a midpoint between output coupling facets 2434, 2444, 2446, 2448. Lenses 2450, 2452, 2454, 2456 thus serve to direct light emerging from output coupling facets 2434, 2444, 2446, 2448 to a common intersection point 2458 that coincides with the surface of one of the beam scanning mirrors (e.g., 330, 730) used in the embodiments described hereinabove. Intersection point 2458 is spaced above the glass plate, although this is not apparent from the plan view of FIG. 24. Alternatively, laser diodes emitting at other wavelengths and associated receiving branches are added to light engine 2400 such that light engine 2400 provides more than three (RGB) wavelength channels. For example, the additional channel could be infrared light, which is useful for providing illumination for an eye-tracking system.

[0078] 26 is a top view of a four RGB channel light engine 2600 according to another embodiment. A red laser bar 2602, a green laser bar 2604, and a blue laser bar 2606 are arranged adjacent to a red input side 2608, a green input side 2610, and a blue input side 2612, respectively, of a glass plate 2614 on which a waveguide network 2616 is formed. The red laser bar 2602 includes four independently controllable red laser diodes 2602A, 2602B, 2602C, and 2602D; similarly, the green laser bar 2604 includes four independently controllable green laser diodes 2604A, 2604B, 2604C, and 2602D; similarly, the blue laser bar 2606 includes four independently controllable blue laser diodes 2606A, 2606B, 2606C, and 2606D. Four output facets 2608A, 2608B, 2608C, and 2608D are defined in a glass plate 2614. The output facets 2608A, 2608B, 2608C, and 2608D may have the same design as that of output facet 2434 shown in FIG. 25, or alternatively, a different design. One of the separately controllable laser diodes from each of the laser bars 2602, 2604, 2606 is coupled to each of the output facets 2608A, 2608B, 2608C, and 2608D through a waveguide network 2616. Lenses 2450, 2452, 2454, 2456 are positioned over the output facets 2608A, 2608B, 2608C, and 2608D and function as described above in connection with FIG. 24. According to an alternative embodiment, another laser bar, which may operate at a different wavelength (e.g., infrared), may be positioned along a fourth side of the glass plate 2614 and optically coupled to the output facets 2608A, 2608B, 2608C, and 2608D via a waveguide network 2616, which may be extended for such purpose.

[0079] Figure 27 is a schematic diagram of a waveguide display system 2700 that can be used in augmented reality glasses, according to one embodiment of the present invention. Referring to Figure 27, the system includes a polarizing beam splitter (PBS) 2702, in this case used as a polarization beam combiner. The PBS 2702 includes a polarization selective reflector 2704 embedded along the diagonal of the PBS 2702. The polarization selective reflector 2704 can be, for example, a wire grid array or a MacNeille type.

[0080] A first dichroic X-cube combiner 2706 is arranged adjacent to a first face 2708 of the PBS 2702, and a second dichroic X-cube combiner 2710 is arranged adjacent to a second face 2712 of the PBS 2702. The first dichroic X-cube combiner 2706 includes a first embedded red-reflecting dichroic mirror 2714 along a first diagonal and a first embedded blue-reflecting dichroic mirror 2716 along a second diagonal that intersects the first diagonal at 90 degrees. The second dichroic X-cube combiner 2710 similarly has a second embedded red-reflecting dichroic mirror 2718 along one diagonal and a second embedded blue-reflecting dichroic mirror 2720 along the second diagonal. Alternatively, other optical subsystems for combining light from multiple laser diodes may be used in place of the X-cube combiners 2706, 2710. For example, components such as the RGB color channel combiners shown in Figures 21 and 22 above may be used.

[0081] Referring to the first dichroic X-cube combiner 2706, a first red light collimating lens 2722 is arranged adjacent to a first red light input surface 2724 of the first dichroic X-cube combiner 2706, a first green light collimating lens 2726 is arranged adjacent to a first green light input surface 2728, and a first blue light collimating lens 2730 is arranged adjacent to a first blue light input surface 2732. Referring to the second dichroic X-cube combiner 2710, a second red light collimating lens 2734 is arranged adjacent to a second red light input surface 2736 of the second X-cube combiner 2710, a second green light collimating lens 2738 is arranged adjacent to a second green light input surface 2740, and a second blue light collimating lens 2742 is arranged adjacent to a second blue light input surface 2744.

[0082] In the following discussion, s-polarized and p-polarized light orientations are defined in terms of light incident on polarization-selective reflector 2704. Referring again to Figure 27, s-polarized red laser diode 2746 is arranged facing first red-light-collimating lens 2722 and first red input face 2724 of first dichroic x-cube combiner 2706, s-polarized green laser diode 2748 is arranged facing first green-light-collimating lens 2726 and first green input face 2728, and s-polarized blue laser diode 2750 is arranged facing first blue-light-collimating lens 2730 and first blue light input face 2732. Similarly, a p-polarized red laser diode 2752 is arranged facing the second red light collimating lens 2734 and second red light input face 2736 of the second dichroic x-cube combiner 2710, a p-polarized green laser diode 2754 is arranged facing the second green light collimating lens 2738 and second green light input face 2740, and a p-polarized blue laser diode 2756 is arranged facing the second blue light collimating lens 2742 and second blue light input face 2744. The polarizations of these laser diodes can be determined simply by determining the orientation in which they are mounted. The laser diodes are modulated based on pixel color intensity values for a series of pixels. As will be further described below, s-polarized laser diodes 2746, 2748, 2750 illuminate a first portion of the field of view produced by waveguide display system 2700, and p-polarized laser diodes 2752, 2754, 2756 illuminate a second portion of the field of view produced by waveguide display system 2700. Collimating lenses 2722, 2726, 2732, 2734, 2738, 2742 are depicted as plano-convex, but may alternatively be bi-convex or have another shape.

[0083] The first dichroic x-cube combiner 2706, by the effect of the first embedded red dichroic reflective mirror 2714 and the first embedded blue dichroic reflective mirror 2716, combines the light from the s-polarized laser diodes 2746, 2748, 2750 into a collimated s-polarized red-blue-green (RGB) beam that passes from the first dichroic x-cube combiner 2706 into the first face 2708 of the PBS 2702. Similarly, the second dichroic x-cube combiner 2710, by the effect of the second embedded red dichroic reflecting mirror 2718 and the second embedded blue dichroic reflecting mirror 2720, combines the light from the p-polarized laser diodes 2752, 2754, 2756 into a collimated p-polarized RGB beam that passes from the second dichroic x-cube combiner 2710 into the first second face 2712 of the PBS 2702.

[0084] Polarization-selective reflector 2704 is oriented to reflect the collimated s-polarized RGB beam arriving from first surface 2708 and transmit the collimated p-polarized RGB beam arriving from second surface 2712, thereby forming a composite s-polarized RGB and p-polarized RGB beam that is output via third surface 2758 of PBS 2702. Stray light absorber 2760 is positioned proximate fourth surface 2762 of PBS 2702 and serves to absorb any p-polarized light reflected by polarization-selective reflector 2704 and any s-polarized light transmitted by polarization-selective reflector 2704 due to non-ideal performance of polarization-selective reflector 2704.

[0085] After passing through the third surface 2758 of the PBS 2702, the light passes through a quarter-wave plate (QWP) 2764. The PBS converts one of the polarization components (S or P) to right-handed circularly polarized light (RHCP) and the remaining polarization component (P or S) to left-handed circularly polarized light (LHCP). Which linearly polarized component is converted to which circularly polarized component can be altered by rotating the QWP 2764. The output of the QWP includes an RHCP RGB beam and an LHCP RGB beam derived from the s-polarized RGB beam and the p-polarized RGB beam. For purposes of discussion, assuming that s-polarized light is converted to RHCP light and p-polarized light is converted to LHCP light, the RHCP light will illuminate the above-described first portion of the FOV, and the LHCP light will illuminate the above-described second portion of the FOV generated by the system 2700.

[0086] System 2700 further includes a waveguide 2766, an input coupling grating (ICG) 2770, an orthogonal pupil expansion grating (OPE) 2772, and an exit pupil expansion grating (EPE) 2774, which are used to transport the image-modulated light to a user's eye position 2768. Substantially collimated light is input through the ICG and deflected by the ICG 2770 toward the OPE grating 2772. The OPE grating 2772 incrementally deflects a portion of the light toward the EPE grating 2774, and in doing so, increases the lateral width (x-direction in FIG. 27 ) of the collimated beam. An XYZ coordinate triplet structure is shown in FIG. 27 for reference. The EPE grating 2774 incrementally diffracts the light outward toward the user's eye position 2768, and in doing so, increases the y-direction extent of the collimated beam. The beam expanding effect of the OPE and EPE gratings 2772, 2774 creates a relatively large exit pupil (eyebox), which helps ensure that light will be coupled into the user's pupil, which can move around as the user looks in different directions.

[0087] Along the optical path between the QWP2764 and the ICG2770 is a two-axis scanning mirror 2780. The scanning mirror 2780 can be, for example, a microelectromechanical system (MEMS) mirror. A single scanning mirror movement may be resonant in one degree of freedom and quasi-statically controlled in a second degree of freedom. For example, the resonant axis may correspond to a movement similar to a movement along a line of the display, and the quasi-statically controlled second degree of freedom may correspond to a movement similar to a vertical movement between the lines of the display. For relatively high-resolution images, for example, it is desirable to have the equivalent of 1,000 or 2,000 scan lines and a frame refresh rate of 30 to 60 frames per second. Such parameters require a line rate of 30 KHz to 120 KHz. For miniature MEMS scanners small enough to be included in augmented reality wearables, there is generally a trade-off between the angular range of the resonant axis (relative to the field of view (FOV)) and the resonant frequency (equivalent to the line rate). It would be desirable to avoid this trade-off and obtain both a wide field of view and a high line rate.

[0088] In system 2700, the FOV is increased through the provision of the portions of system 2700 described above in combination with two different types of polarization selective gratings. In system 2700, a set 2776 of left-handed (LH) reflective liquid crystal gratings and a set 2778 of right-handed (RH) reflective liquid crystal gratings are disposed on a two-axis scanning mirror 2780. The sets of reflective liquid crystal gratings 2776 and 2778 will be described further below.

[0089] Attention is now directed to FIG. 28, which includes a three-space Cartesian (XYZ) coordinate system along with a representation of the scan mirror 2780 and ICG 2770 of the system 2700 shown in FIG. 27. The Cartesian coordinate system shown in FIG. 28 corresponds to the coordinate triplet structure shown in FIG. 27. In the case illustrated in FIG. 28, which is merely illustrative of a range of possible configurations, the incident beam (e.g., a beam arriving from the QWP 2764) is propagating in the −X direction. The scan mirror 2780 includes an inner gimbal pivot point 2802 that allows the scan mirror 2780 to rotate relative to the frame 2804 by an angle shown as β. The frame 2804 is supported by an outer gimbal pivot point 2806, which allows the entire frame 2804 to rotate. The axis of rotation about the inner gimbal pivot point 2802 is orthogonal to the axis of rotation about the outer gimbal pivot point 2806. Rotation about the outer gimbal pivot point 2806 is represented by the angle α+α, where α corresponds to the midline rest position of the frame 2804 and α corresponds to the deviation from α. Rotation about the inner gimbal pivot point 2802, represented by β, may be referred to as "roll," and rotation about the outer gimbal pivot point 2806, represented by α+α, may be referred to as "pitch." The gratings 2776, 2778 are illustrated diagrammatically on the surface of the scanning mirror 2780 as a series of horizontal lines, although the actual structure, as described above and further below, is more complex.

[0090] Figure 29 is a schematic diagram of a six-layer polarization-responsive liquid crystal grating stack 2900 that may be used on a scanning mirror in the system shown in Figure 27, in accordance with an embodiment of the present invention. Stack 2900 includes an LH reflective liquid crystal grating 2776 and an RH reflective liquid crystal grating 2778. LH reflective liquid crystal grating 2776 includes an LH red reflective layer 2902, an LH green reflective layer 2904, and an LH blue reflective layer 2906. Similarly, RH reflective liquid crystal grating 2778 includes an RH red reflective layer 2908, an RH green reflective layer 2910, and an RH blue reflective layer 2912. LH reflective liquid crystal grating 2776 will interact with the LH-polarized RGB light beam component received from QWP 2764, and RH reflective liquid crystal grating 2778 will interact with the RH-polarized RGB light beam component received from the QWP.

[0091] Each of the layers 2902, 2904, 2906, 2908, 2910, 2912 preferably has a structure like the blue ICG 1814 shown in Figures 19-20, but with a Z-axis pitch (referring to the coordinate system of Figure 19) selected to match the wavelength of light it is intended to work with and a lateral pitch selected to diffract light into either the first or second FOV portion. As will be explained further below, different grating pitches are selected for the layers 2902, 2904, 2906, 2908, 2910, 2912 such that the LH reflective liquid crystal grating 2776 will illuminate a first portion of the FOV of the system 2700 and the RH reflective liquid crystal grating 2778 will illuminate a second portion of the FOV of the system 2700 adjacent to the first portion of the FOV. The deflection of light rays by the reflective gratings can be expressed by Equation 1 below: [ka] where I is the incident ray vector, N is a unit length vector that is normal to the surface of the lattice, D is the diffracted ray vector, G is a unit length vector in the plane of the grating parallel to the grating lines, Λ is the lattice parameter and is given by Equation 2 below. [ka] where m is the diffraction order (e.g., 1); λ is the free-space wavelength of the light, d g is the grating line pitch.

[0092] The dependence of the diffracted ray vector D on the wavelength λ0 is the same ratio λ0 / d in each of the LH-reflection LC grating set 2776 and the RH-reflection grating set 2778. g is used for the RGB layer, but the ratio λ0 / d g Different values of are used in the two sets 2776, 2778, so that d g This can be addressed by choosing values of .times. ...

[0093] Equation 1 can be decomposed into three (X, Y, and Z) component equations, and a supplemental normalization equation that sets the Euclidean length of the diffracted ray vector D to a unity scale can be used in combination with two of the previous component equations to solve for the X, Y, and Z vector components of the diffracted ray vector D (labeled Dx, Dy, Dz) in terms of the normal vector N defined by the pitch angle α0 + α1 and the roll angle β. (Based on the values of α0 + α1 and β, the normal vector N and the grating vector G can be transformed to the UVW coordinate system and, in turn, to the XYZ coordinate system.) Referring to the XYZ coordinate system of Figures 27 and 28, a selected value of Dx, for example, Dx = 0.0, can be selected as the boundary between the two portions of the FOV illuminated by the two grating sets 2776, 2778, respectively. The normal vector N can be set based on the minimum and maximum extreme values of α1 and the selected value of β (e.g., zero or an extreme value), and in each case (minimum and maximum values of α1), Equation 1 becomes λ0 / d g λ0 / d gcan be solved for λ0 / d g One value of λ0 / d is used for LH reflection LC reflection grating set 2776. g Other values of d will be used for the RH reflection grating set 2778. Within each of the grating sets 2776, 2778, g The value of will be changed for each layer 2902-2912 according to the value of λ for each layer 2902-2912 (i.e., based on its design for one of the R, G, or B color components).

[0094] According to an alternative embodiment, one of the grating sets 2776, 2778 is replaced with a liquid crystal reflector (which may be referred to as a zero-order reflector in the context of grating terminology). Such an alternative liquid crystal reflector would have a vertical pitch (Pitch_Z in FIG. 19) but no lateral periodicity (Pitch_Y in FIG. 19). Such an alternative would be to replace λ / d where one extremum of α+α is equal to 45°. g This is consistent with the method described above for determining

[0095] FIG. 30 is a graph 3000 including scan angles in two portions of the full field of view, each resulting from different polarization states, generated by the system 2700 shown in FIG. 27 using the multilayer selective liquid crystal grating 2900 shown in FIG. 29 , according to one embodiment of the present invention. The horizontal axis of the graph indicates the value of the X-component (denoted as Dx) of the light diffracted by the six-layer stack 2900, and the vertical axis indicates the Y-component (denoted as Dy) of the light diffracted by the six-layer stack 2900. A first portion 3002 of the FOV of the system 2700 is generally to the right of the vertical axis of FIG. 30, and a second portion 3004 of the FOV of the system 2700 is generally to the left of the vertical axis of FIG. 30, although there is some slight curvature at the boundary between the two portions 3002, 3004. The diffracted light in the first portion 3002 is represented by a round plot symbol, and the diffracted light in the second portion 3004 is represented by a square plot symbol. Each section 3002, 3004 individually corresponds to the full range of variable pitch angle α and roll angle β of the scanning mirror. The left section 3002, for example, is a LH reflective LC grating 2776 (λ / d g ) while the right portion 3004 may be generated by, for example, an RH reflective LC grating 2778 (which will have a value of λ / d g may be generated by (which may have different values of λ0 / d g The value of λ0 / d may be determined as explained above. Alternatively, the handedness and λ0 / d g The relevance of the values of may be swapped.

[0096] Thus, by providing an LH reflective liquid crystal grating 2776 and an RH reflective liquid crystal grating 2778 to achieve separate regions of the FOV, it is not necessary to increase the mechanical scan range of the scan mirror 2776, which would typically be done at the expense of the achievable line frequency and vertical resolution or frame rate. Thus, a relatively high FOV, frame rate, and vertical resolution can be obtained in one system.

[0097] FIG. 31 is a schematic diagram of a waveguide display system 3100 that can be used in augmented reality glasses, according to one embodiment of the present invention. Referring to FIG. 31 , system 3100 includes a red light engine 3102, a green light engine 3104, and a blue light engine 3106. To the extent that the three light engines 3102, 3104, 3106 have identical structure except for the substitution of the appropriate color laser diodes therein, only the structure of red light engine 3102 will be described in detail. Reference numbers for component parts of the red light engine will include the letter "R" suffix, and equivalent components in green light engine 3104 and blue light engine 3106 will have the letter "G" suffix and the letter "B" suffix, respectively.

[0098] The red light engine 3102 includes a polarizing beam splitter 3108R (used in this case as a polarization beam combiner) having a structure similar to the PBS 2702 shown in Figure 27, including polarization-selective reflectors that are not distinguishable from the perspective of Figure 31. A p-polarized collimating lens 3110R is positioned proximate to the p-polarized input face 3112R of the PBS 3108R, and an s-polarized collimating lens 3114R is positioned proximate to the s-polarized input face 3116R of the PBS 3108R. A p-polarized red laser diode 3118R is positioned facing the p-polarized collimating lens 3110R and the p-polarized input face 3112R; similarly, an s-polarized red laser diode 3120R is positioned facing the s-polarized collimating lens 3114R and the s-polarized input face 3116R. The PBS 3108R serves to combine the s-polarized and p-polarized light emitted by the p-polarized red laser diode 3118R and p-polarized red laser diode 3120R into a single beam emitted at the output face 3122R of the PBS 3108R. After passing through the output face 3122R, the light from the laser diodes 3118R, 3120R passes through a quarter-wave plate (QWP) 3124R, which converts the p-polarized and s-polarized light into two different circular polarization states, RHCP light and LHCP light, forming a composite RHCP and LHCP red light beam 3126R. Any assignment between linear and circular polarization states can be used, and the option is implemented by rotating the QWP 3124R. The red laser diodes 3118R, 3120 will be separately modulated based on red channel information from separate but adjacent portions of the total field of view of the system 3100. Thus, the RHCP light and LHCP light will be image modulated based on pixel information from separate but adjacent portions of the FOV of the system 3100.

[0099] Red RHCP and LHCP light beam 3126R, green RHCP and LHCP light beam 3126G, and blue RHCP and LHCP light beam 3126B are incident on surface 3128 of 2-D scanning mirror 3130. Overlapping LH reflective liquid crystal grating 3132 and RH reflective liquid crystal grating 3134 are disposed on surface 3128 of 2-D scanning mirror 3130. LH reflective liquid crystal grating 3132 will deflect the LHCP light into a first solid angle range corresponding to a first portion of the FOV of system 3100, while RH reflective liquid crystal grating 3134 will deflect the RHCP light into a second solid angle range corresponding to a second portion of the FOV of system 3100 that does not substantially overlap the first portion of the FOV. Light reflected by the liquid crystal gratings 3132, 3134 will enter the ICG 2770 and propagate to the user's eye position 2768, as described above in connection with FIG. 27. In contrast to the embodiment shown in FIG. 27, in the embodiment shown in FIG. 31, the LH and RH reflective liquid crystal gratings 3132, 3134 include one layer that addresses all three R, G, and B color components. A higher birefringence liquid crystal material can be used to achieve a wider reflectance band. However, the grating pitch d g To compensate for the fact that the radii cannot be set individually for each color, the three light engines 3102, 3104, 3106 are oriented so that the three RHCP and LHCP composite beams are angularly separated. The purpose is to compensate for the wavelength dependence of the diffraction angles in order to more closely align the fields of view of the three (RGB) color channels than if all three color components arrived at the scanning mirror 3130 in parallel beams.

[0100] According to an alternative embodiment, rather than using polarizing beam splitters 3108R, 3108G, 3108B, p-polarized and s-polarized laser diodes 3118R, 3118G, 3118B, 3120R, 3120G, 3120B are positioned side by side facing the 2-D scanning mirror 3130 through one or more collimating lenses.

[0101] In some embodiments, the method includes providing two or more RGB (red-green-blue) combiners positioned on opposite sides of the waveguide from the scanning mirror and configured to provide two or more light beams having different angles of incidence, and further including configuring an input coupling optical element in the waveguide to allow an input light beam to pass through the waveguide and reach the scanning mirror, configured to couple a reflected light beam into the waveguide.

[0102] In some embodiments, the method also includes positioning two or more RGB combiners at different angles relative to the scanning mirror to provide two or more incident light beams having different angles of incidence.

[0103] In some embodiments, the method also includes positioning two or more RGB combiners at the same angle relative to the scanning mirror, and providing a reflective optical element to direct two or more light beams toward the scanning mirror at different angles of incidence.

[0104] In some embodiments, the method also includes providing two or more RGB combiners positioned on the same side of the waveguide as the scanning mirror. The two or more RGB combiners provide two or more light beams having different angles of incidence. A quarter-wave plate is positioned adjacent to the scanning mirror, and a polarization-sensitive beam splitter is positioned between the quarter-wave plate and the waveguide. The polarization-sensitive beam splitter is configured to direct the two or more light beams from the RGB combiner mirror through the quarter-wave plate toward the scanning mirror. The light beam reflected from the scanning mirror is configured to propagate through the quarter-wave plate and the polarization-sensitive beam splitter and be coupled into the waveguide by an input-coupling diffractive optical element.

[0105] In some embodiments, a method for providing a compound field of view (FOV) includes providing a collimated incident light beam comprising multiple incident light beams; and providing a scanning mirror with a diffractive surface to receive the collimated incident light beam and to provide multiple reflected light beams having different angles of incidence. Each of the multiple reflected light beams is configured to provide an image within a respective field of view (FOV). The method also includes receiving the multiple reflected light beams in a waveguide; and projecting multiple output light beams from the waveguide to form a projected image within the compound field of view (FOV). In some embodiments, the multiple incident light beams comprise light beams having different wavelengths. In some embodiments, the multiple incident light beams comprise light beams having different polarizations.

[0106] In some embodiments, a method for providing a composite field of view (FOV) includes providing a collimated incident light beam comprising multiple incident light beams. The method also includes providing a scanning mirror with a diffractive surface for receiving the collimated incident light beam and for providing multiple reflected light beams in different directions, each of the multiple reflected light beams configured to provide an image within a respective field of view (FOV). The method also includes configuring a waveguide for input coupling the multiple reflected light beams with different angles of incidence above a total internal reflection (TIR) critical angle. The multiple reflected light beams undergo total internal reflection within the waveguide and are projected from the waveguide through an output coupling optical element to form a corresponding multiple field of view. The method also includes forming a composite FOV comprising the multiple fields of view.

[0107] In some embodiments, a method for providing a composite field of view (FOV) includes providing a collimated incident light beam comprising multiple incident light beams. The method includes providing a scanning mirror with a diffractive surface for receiving the collimated incident light beam and for providing multiple reflected light beams. Each of the multiple reflected light beams has a different reflection angle and is configured to provide an image within a respective field of view (FOV). The method also includes configuring a waveguide for input coupling the multiple reflected light beams with different incidence angles at an input coupling optical element. The multiple reflected light beams undergo total internal reflection within the waveguide and are projected from the waveguide through an output coupling optical element to form a corresponding multiple field of view. The method further includes forming a composite FOV comprising the multiple fields of view.

[0108] While preferred embodiments of the present invention have been shown and described, it will be clear that the present invention is not limited to these embodiments alone. Numerous modifications, changes, variations, substitutions, and equivalents will be apparent to those skilled in the art without departing from the spirit and scope of the present invention as set forth in the claims.

Claims

1. 1. A method for providing a compound field of view, the method comprising: providing two or more input light beams to a scanning mirror; using the scanning mirror to scan the two or more input light beams to provide a plurality of reflected light beams at different angles, each of the plurality of reflected light beams configured to provide an image within a separate field of view; diffracting the plurality of reflected light beams into a waveguide including an input coupling optical element, the input coupling optical element being positioned on an opposite side of the waveguide from the scanning mirror; and forming a projected image within the composite field of view by projecting a plurality of output light beams from the waveguide, the composite field of view being wider than the individual fields of view provided by each of the two or more input light beams; A method comprising:

2. providing two or more RGB (red, blue, green) combiners positioned on opposite sides of the waveguide from the scanning mirror, the two or more RGB combiners configured to provide different angles of incidence for the two or more input light beams; configuring the input coupling optical element within the waveguide to allow the input light beam to pass through the waveguide to reach the scanning mirror and to couple the reflected light beam into the waveguide; The method of claim 1 further comprising:

3. The method of claim 2 , further comprising providing the two or more input light beams by positioning the two or more RGB combiners at different angles relative to the scanning mirror.

4. positioning the two or more RGB combiners at the same angle relative to the scanning mirror; providing a reflective optical element to direct the two or more input light beams toward the scanning mirror at different angles of incidence; The method of claim 2 further comprising:

5. A method for providing a compound field of view using a waveguide and a scanning mirror, said method comprising: providing two or more RGB combiners located on the same side of the waveguide as the scanning mirror, each of the two or more RGB combiners providing one of two or more input light beams at a different angle of incidence; providing a quarter wave plate positioned adjacent to the scanning mirror; providing a polarization sensitive beam splitter disposed between the quarter wave plate and the waveguide; directing the two or more input light beams from the RGB combiner through the quarter wave plate toward the scanning mirror; using the scanning mirror to scan the two or more input light beams to provide a plurality of reflected light beams at different angles, each of the plurality of reflected light beams configured to provide an image within a separate field of view; propagating the light beam reflected from the scanning mirror through the quarter wave plate and the polarization sensitive beam splitter; diffracting the light beam into the waveguide using an input coupling optical element located on the same side of the waveguide as the scanning mirror; forming a projected image within the composite field of view by projecting a plurality of output light beams from the waveguide, the composite field of view being wider than the individual fields of view provided by each of the two or more input light beams; A method comprising: the two or more input light beams are linearly polarized light beams; method.

6. The method described in claim 1, wherein the input coupling optical element is configured to reflectively diffract the multiple reflected light beams into the waveguide.

7. The method of claim 6 , wherein the input coupling optical element comprises a polarization selective device.

8. The method of claim 6 , wherein the input coupling optical element comprises a diffraction grating including a cholesteric liquid crystal.

9. The method of claim 8 , wherein the input coupling optical element further comprises an alignment layer that establishes a periodic lateral variation in an alignment direction of the cholesteric liquid crystal.

10. An image display system, the image display system comprising: a light source operable to provide a collimated incident light beam comprising a plurality of incident light beams; a scanning mirror with a diffractive surface operable to receive the collimated incident light beam and to provide a plurality of reflected light beams, each of the plurality of reflected light beams operable to provide an image within a respective field of view; a waveguide operable to diffract the reflected light beams at different angles of incidence into the waveguide at a diffractive input coupling optical element, the diffractive input coupling optical element being positioned on an opposite side of the waveguide from the scanning mirror, the reflected light beams undergo total internal reflection (TIR) within the waveguide and are projected from the waveguide through an output coupling optical element to form a corresponding plurality of fields of view; Equipped with The image display system is configured to form a composite field of view that includes the corresponding plurality of fields of view.

11. 11. The image display system of claim 10, wherein the light source is positioned on an opposite side of the waveguide from the scanning mirror, and the light source is configured to provide the collimated incident light beam at an incident angle to the waveguide that is less than a TIR critical angle, such that the collimated incident light beam passes through the waveguide and reaches the scanning mirror.

12. The image display system of claim 10 , wherein the plurality of incident light beams include light beams having different wavelengths.

13. The image display system of claim 10 , wherein the plurality of incident light beams comprises light beams having different polarization states.

14. The image display system of claim 10 , wherein the scanning mirror comprises a diffractive off-axis scanning mirror.

15. the scanning mirror is positioned on an opposite side of the waveguide from the light source; 11. The image display system of claim 10, wherein the diffractive input coupling optical element of the waveguide is configured to allow the collimated incident light beam to pass through the waveguide, and the diffractive input coupling optical element is configured to couple the multiple reflected light beams into the waveguide.

16. the plurality of reflected light beams are configured to propagate within the waveguide by total internal reflection (TIR); 11. The image display system of claim 10, wherein the composite field of view includes images from the multiple reflected light beams to form a tiled image within an expanded field of view.

17. 11. The image display system of claim 10, wherein each of the plurality of incident light beams comprises a composite RGB light beam for forming a scanned image.

Images