NZ794500A - Spatially variable liquid crystal diffraction gratings - Google Patents

Abstract

diffraction grating, comprising: a plurality of different diffracting zones arranged in a continuous layer in a lateral direction substantially parallel to a major surface of a substrate, the different diffracting zones having a same thickness vertically defined by upper and lower surfaces of the continuous layer and having a same lateral dimension corresponding to a grating period adapted for light diffraction, wherein each of the different diffracting zones is laterally divided into a first region and a second region each comprising liquid crystals, wherein the liquid crystals of the first region are aligned along a first alignment direction which forms a first alignment angle with respect to a reference direction, and wherein the liquid crystals of the second region are aligned along an alignment direction different from the first alignment direction which forms a different alignment angle relative to the first alignment angle, wherein substantially all of the liquid crystals of the first region between the upper and lower surfaces are permanently aligned in the first alignment direction and substantially all of the liquid crystals of the second region between the upper and lower surfaces are permanently aligned in the second alignment direction, and wherein the different diffracting zones are arranged differently from each other with respect to arrangements of liquid crystals in corresponding portions of different second regions. continuous layer and having a same lateral dimension corresponding to a grating period adapted for light diffraction, wherein each of the different diffracting zones is laterally divided into a first region and a second region each comprising liquid crystals, wherein the liquid crystals of the first region are aligned along a first alignment direction which forms a first alignment angle with respect to a reference direction, and wherein the liquid crystals of the second region are aligned along an alignment direction different from the first alignment direction which forms a different alignment angle relative to the first alignment angle, wherein substantially all of the liquid crystals of the first region between the upper and lower surfaces are permanently aligned in the first alignment direction and substantially all of the liquid crystals of the second region between the upper and lower surfaces are permanently aligned in the second alignment direction, and wherein the different diffracting zones are arranged differently from each other with respect to arrangements of liquid crystals in corresponding portions of different second regions.

Description

A diffraction grating, comprising: a plurality of different diffracting zones arranged in a continuous layer in a lateral direction substantially parallel to a major surface of a substrate, the different diffracting zones having a same thickness vertically defined by upper and lower surfaces of the continuous layer and having a same lateral ion corresponding to a grating period adapted for light diffraction, wherein each of the different diffracting zones is laterally divided into a first region and a second region each sing liquid crystals, wherein the liquid crystals of the first region are aligned along a first alignment direction which forms a first ent angle with respect to a nce direction, and wherein the liquid crystals of the second region are aligned along an alignment direction different from the first alignment ion which forms a different alignment angle relative to the first ent angle, wherein substantially all of the liquid crystals of the first region between the upper and lower surfaces are permanently aligned in the first alignment direction and substantially all of the liquid ls of the second region between the upper and lower surfaces are permanently aligned in the second alignment direction, and n the different diffracting zones are arranged differently from each other with respect to arrangements of liquid crystals in corresponding portions of different second regions. 794500 A1 LLY VARIABLE LIQUID CRYSTAL DIFFRACTION GRATINGS CROSS-REFERENCE TO RELATED APPLICATIONS This ation claims the benefit of priority to U.S. ional Patent Application Number 62/424,310, filed November 18, 2016, entitled “SPATIALLY VARIABLE LIQUID CRYSTAL DIFFRACTION GRATINGS,” the content of which is hereby incorporated by reference herein in its entirety. [0001A] This application is a divisional of New Zealand Patent Application No. 753432, the entire content of which is incorporated herein by reference.

BACKGROUND Field The present disclosure relates to display systems and, more particularly, to ted reality display systems.

Description of the Related Art Modern computing and display technologies have facilitated the development of systems for so called “virtual y” or nted reality” experiences, wherein digitally reproduced images or portions thereof are ted to a user in a manner wherein they seem to be, or may be perceived as, real. A virtual reality, or “VR”, scenario lly involves tation of digital or virtual image information without transparency to other actual real-world visual input; an augmented reality, or “AR”, scenario typically involves presentation of digital or virtual image information as an augmentation to visualization of the actual world around the user. A mixed reality, or “MR”, scenario is a type of AR scenario and typically involves virtual objects that are integrated into, and responsive to, the natural world. For example, in an MR scenario, AR image content may be blocked by or otherwise be perceived as interacting with s in the real world.

Referring to Figure 1, an augmented reality scene 1 is depicted wherein a user of an AR technology sees a real-world park-like setting 1100 ing people, trees, buildings in the background, and a concrete platform 1120. In addition to these items, the user of the AR technology also perceives that he “sees” “virtual content” such as a robot statue 1110 standing upon the real-world platform 1120, and a cartoon-like avatar character 1130 flying by which seems to be a personification of a bumble bee, even though these elements 1130, 1110 do not exist in the real world. Because the human visual perception system is complex, it is challenging to produce an AR technology that facilitates a comfortable, natural-feeling, rich presentation of virtual image elements t other virtual or real-world imagery ts.

Systems and methods disclosed herein address s challenges d to AR and VR technology.

SUMMARY Accordingly, numerous devices, s, ures and s are disclosed . For instance, an example diffraction grating is disclosed that includes a plurality of different diffracting zones having a ically repeating lateral dimension corresponding to a grating period adapted for light diffraction. The diffraction grating additionally includes a plurality of different liquid crystal layers corresponding to the different diffracting zones. The different liquid crystal layers have liquid crystal molecules that are aligned differently, such that the different diffracting zones have ent optical properties associated with light diffraction.

An example method of fabricating a diffraction grating is disclosed that includes providing a substrate and providing a plurality of different diffracting zones on the substrate having a periodically repeating lateral dimension corresponding to a grating period d for light diffraction. The method further includes g a plurality of different liquid l layers comprising liquid crystal molecules over the ate, the different liquid crystal layers corresponding to the different diffracting zones, wherein forming the different liquid crystal layers comprises aligning the liquid crystal molecules differently, thereby providing different optical properties associated with light diffraction to the ent diffracting zones.

Another example diffraction grating is disclosed that includes a plurality of contiguous liquid crystal layers extending in a lateral direction and arranged to have a periodically repeating lateral dimension, a thickness and indices of refraction such that the liquid crystal layers are configured to diffract light. Liquid crystal molecules of the liquid crystal layers are arranged differently in different liquid crystal layers along the lateral direction such that the contiguous liquid l layers are configured to ct light with a gradient in ction efficiency.

An example head-mounted display device that is configured to project light to an eye of a user to display augmented reality image content is also disclosed. The head-mounted display device includes a frame configured to be supported on a head of the user. The head-mounted y device additionally includes a display disposed on the frame, at least a portion of said y comprising one or more waveguides, said one or more waveguides being transparent and disposed at a location in front of the user’s eye when the user wears said head-mounted display device such that said transparent portion transmits light from a portion of an environment in front of the user to the user’s eye to provide a view of said portion of the nment in front of the user, said display further comprising one or more light sources and at least one diffraction grating configured to couple light from the light sources into said one or more waveguides or to couple light out of said one or more waveguides. The diffraction grating includes a plurality of different diffracting zones having a periodically repeating lateral dimension corresponding to a grating period d for light diffraction. The diffraction grating additionally includes a plurality of different liquid crystal layers corresponding to the different diffracting zones, wherein the different liquid crystal layers have liquid crystal les that are aligned differently, such that the different diffracting zones have different optical properties associated with light diffraction.

] In one broad form, the present invention seeks to provide a ction grating, comprising: a plurality of different diffracting zones arranged in a continuous layer in a lateral direction substantially parallel to a major surface of a substrate, the different diffracting zones having a same thickness vertically d by upper and lower es of the continuous layer and having a same l dimension corresponding to a grating period adapted for light diffraction, wherein each of the different diffracting zones is laterally divided into a first region and a second region each comprising liquid crystals, wherein the liquid crystals of the first region are aligned along a first alignment direction which forms a first alignment angle with respect to a nce direction, and wherein the liquid crystals of the second region are aligned along an alignment direction different from the first alignment direction which forms a different alignment angle relative to the first alignment angle, wherein substantially all of the liquid crystals of the first region between the upper and lower surfaces are permanently aligned in the first ent direction and substantially all of the liquid crystals of the second region between the upper and lower surfaces are permanently aligned in the second alignment direction, and wherein the different diffracting zones are arranged differently from each other with respect to arrangements of liquid crystals in corresponding portions of different second regions. [0009B] In one embodiment, the liquid crystals of the different first regions of the different diffracting zones have substantially the same first alignment angle. [0009C] In one embodiment, the liquid crystals of different second regions of the different cting zones have substantially the same second alignment angle. [0009D] In one embodiment, the liquid crystals of different second regions of the different diffracting zones have alignment angles that are different from each other. [0009E] In one embodiment, a ratio of lateral widths between the first region and the second region is substantially the same for different diffracting zones. [0009F] In one embodiment, a ratio of lateral widths between the first region and the second region is substantially different for different diffracting zones. [0009G] In one ment, the alignment angles are azimuthal angles that are measured in a plane parallel to the major surface of the ate and between respective alignment directions and a reference direction that is parallel to the major surface.

] In one embodiment, the alignment angles are pre-tilt angles that are measured in a plane perpendicular to the major surface of the substrate and between respective ent ions and a reference direction that is normal to the major surface. [0009I] In one embodiment, liquid crystals of the first region are aligned along a plurality of first alignment directions which form a ity of first ent angles with respect to the reference direction, and wherein liquid crystals of the second region are aligned along a plurality of second ent directions which form a ity of second ent angles with t to the reference direction. [0009J] In a further broad form, the present invention seeks to provide a diffraction g, comprising: a plurality of different diffracting zones arranged in a continuous layer in a lateral direction substantially parallel to a major surface of a substrate, the different diffracting zones having a same thickness vertically defined by upper and lower surfaces of the continuous layer and having a same lateral dimension corresponding to a grating period adapted for light diffraction, wherein each of the different diffracting zones is laterally divided into a first region and a second region each comprising liquid crystals, a combined width of the first and second regions being the same lateral dimension, wherein the liquid crystals of the first region are aligned along a first alignment direction which forms a first alignment angle with respect to a reference direction, and wherein the liquid crystals of the second region are aligned along an alignment direction different from the first alignment direction which forms a different alignment angle relative to the first alignment angle, wherein substantially all of the liquid crystals of the first region between the upper and lower surfaces are permanently aligned in the first alignment ion and substantially all of the liquid crystals of the second region between the upper and lower surfaces are permanently aligned in the second alignment direction, and wherein the different diffracting zones are arranged differently from each other with respect to ratios of lateral widths between tive first and second regions. [0009K] In one embodiment, the liquid crystals of the different first regions of the different diffracting zones have substantially the same first alignment angle. [0009L] In one embodiment, the liquid crystals of different second regions of the ent diffracting zones have substantially the same second alignment angle. [0009M] In one ment, the liquid crystals of different second regions of the different diffracting zones have alignment angles that are different from each other. [0009N] In one embodiment, a ratio of lateral widths between the first region and the second region increases along the l direction across three or more ent diffracting zones. [0009O] In one embodiment, the alignment angles are azimuthal angles that are measured in a plane parallel to a major surface of the substrate and between respective alignment directions and the nce direction that is el to the major surface. [0009P] In one embodiment, the alignment angles are lt angles that are measured in a plane perpendicular to a major surface of a substrate and between respective alignment directions and the reference direction that is normal to the major surface. [0009Q] In one embodiment, the first s and the second regions of the different cting zones alternate with each other in the lateral direction such that immediately nt ones of the first and second regions contact each other without having intervening liquid crystals therebetween. [0009R] In one embodiment, the first regions and the second s of the different cting zones alternate with each other in the lateral direction such that immediately adjacent ones of the first and second regions contact each other without having intervening liquid crystals therebetween.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 illustrates a user’s view of augmented reality (AR) through an AR device.

Figure 2 illustrates an example of wearable display system.

Figure 3 illustrates a conventional display system for simulating threedimensional imagery for a user.

Figure 4 illustrates aspects of an approach for simulating threedimensional imagery using multiple depth planes.

Figures 5A-5C illustrate onships between radius of ure and focal radius.

Figure 6 illustrates an example of a waveguide stack for ting image information to a user.

Figure 7 illustrates an example of exit beams outputted by a waveguide.

Figure 8 illustrates an example of a stacked waveguide assembly in which each depth plane includes images formed using multiple different component colors.

Figure 9A illustrates a cross-sectional side view of an example of a set of d waveguides that each includes an incoupling optical t.

Figure 9B illustrates a perspective view of an example of the plurality of stacked waveguides of Figure 9A.

Figure 9C illustrates a top-down plan view of an example of the ity of stacked waveguides of Figures 9A and 9B.

Figures 10A-10C rate sectional side views of diffraction gratings having zones in which liquid crystal molecules have different pre-tilt angles, according to embodiments.

Figures 11A-11B are cross-sectional side views of an intermediate structure and a diffraction grating illustrating a method of fabricating the diffraction gratings illustrated in Figures 10A-10C, according to embodiments.

Figures C are cross-sectional side views of intermediate structures and a diffraction grating illustrating a method of fabricating the diffraction gratings illustrated in Figures 10A-10C, according to embodiments.

Figures 13A-13B illustrate cross-sectional side views of ction gs having zones in which liquid crystal molecules have different pre-tilt angles, according to ments.

Figures 14A-14B are cross-sectional side views of an intermediate structure and a diffraction grating illustrating a method of fabricating the diffraction gratings illustrated in Figures 13A-13B, according to embodiments.

Figures 15A-15C illustrate top down plan views of diffraction gratings having zones in which liquid l molecules have different azimuthal angles, according to embodiments.

Figure 16A illustrates a top down plan view of a diffraction grating having zones in which liquid crystal molecules have different azimuthal , according to embodiments.

Figure 16B is a schematic graph illustrating variations in hal angles in a lateral direction across different zones of the diffraction g illustrated in Figure 16A.

Figures 17A-17D illustrate cross-sectional side views of intermediate structures and a diffraction gs rating a method of fabricating the diffraction gratings illustrated in Figures 15A-15C, ing to embodiments.

Figure 17E illustrates a top down plan view of the diffraction grating illustrated in Figure 17D, according to embodiments.

Figures 18A-18C illustrate cross-sectional side views of intermediate structures and a diffraction gratings illustrating a method of fabricating the diffraction gratings illustrated in Figures 16A, according to embodiments.

Figure 18D illustrates a top down plan view of the diffraction grating rated in Figure 18C, according to embodiments.

Figures 19A-19B illustrate top down and cross-sectional side views of a diffraction grating having zones in which liquid crystal molecules have different ity, according to embodiments.

Figure 20 is a cross-sectional side view of a diffraction grating having zones in which liquid crystal molecules have different chirality, according to embodiments.

Figures 21 is a cross-sectional side view of a diffraction grating having zones in which liquid crystal layers are formed of different liquid crystal materials, according to embodiments.

DETAILED DESCRIPTION AR systems may y virtual content to a user, or viewer, while still allowing the user to see the world around them. Preferably, this content is displayed on a ounted display, e.g., as part of eyewear, that projects image information to the user’s eyes. In addition, the display may also transmit light from the surrounding nment to the user’s eyes, to allow a view of that surrounding nment. As used herein, it will be appreciated that a “head-mounted” display is a display that may be d on the head of a viewer.

Reference will now be made to the drawings, in which like reference numerals refer to like parts throughout.

Figure 2 illustrates an example of wearable display system 80. The display system 80 includes a display 62, and various mechanical and electronic modules and systems to support the functioning of that display 62. The display 62 may be coupled to a frame 64, which is wearable by a display system user or viewer 60 and which is configured to position the display 62 in front of the eyes of the user 60. The display 62 may be considered eyewear in some embodiments. In some ments, a r 66 is coupled to the frame 64 and positioned adjacent the ear canal of the user 60 (in some embodiments, another speaker, not shown, is positioned adjacent the other ear canal of the user to e for stereo/shapeable sound control). In some embodiments, the display system may also include one or more microphones 67 or other devices to detect sound. In some embodiments, the hone is ured to allow the user to provide inputs or commands to the system 80 (e.g., the selection of voice menu commands, natural language questions, etc.), and/or may allow audio communication with other persons (e.g., with other users of similar display systems The microphone may further be configured as a peripheral sensor to continuously collect audio data (e.g., to passively collect from the user and/or environment). Such audio data may include user sounds such as heavy breathing, or environmental sounds, such as a loud bang indicative of a nearby event. The display system may also include a peripheral sensor 30a, which may be separate from the frame 64 and attached to the body of the user 60 (e.g., on the head, torso, an extremity, etc. of the user 60). The peripheral sensor 30a may be configured to acquire data characterizing the physiological state of the user 60 in some embodiments, as bed r herein. For example, the sensor 30a may be an electrode.

With continued reference to Figure 2, the display 62 is operatively coupled by communications link 68, such as by a wired lead or wireless connectivity, to a local data processing module 70 which may be mounted in a variety of configurations, such as y attached to the frame 64, fixedly attached to a helmet or hat worn by the user, embedded in headphones, or otherwise removably attached to the user 60 (e.g., in a backpack-style configuration, in a belt-coupling style uration). Similarly, the sensor 30a may be operatively coupled by communications link 30b, e.g., a wired lead or wireless connectivity, to the local processor and data module 70. The local processing and data module 70 may se a hardware processor, as well as digital memory, such as non-volatile memory (e.g., flash memory or hard disk drives), both of which may be utilized to assist in the processing, caching, and storage of data. The data include data a) captured from sensors (which may be, e.g., operatively coupled to the frame 64 or otherwise attached to the user 60), such as image e devices (such as cameras), microphones, inertial measurement units, accelerometers, compasses, GPS units, radio s, gyros, and/or other sensors disclosed herein; and/or b) acquired and/or processed using remote processing module 72 and/or remote data repository 74 (including data relating to virtual content), possibly for e to the display 62 after such processing or retrieval. The local processing and data module 70 may be operatively coupled by communication links 76, 78, such as via a wired or wireless communication links, to the remote processing module 72 and remote data tory 74 such that these remote modules 72, 74 are operatively coupled to each other and ble as resources to the local processing and data module 70. In some embodiments, the local processing and data module 70 may include one or more of the image capture devices, microphones, inertial measurement units, accelerometers, compasses, GPS units, radio devices, and/or gyros. In some other embodiments, one or more of these sensors may be attached to the frame 64, or may be standalone structures that icate with the local processing and data module 70 by wired or wireless communication pathways.

With continued reference to Figure 2, in some embodiments, the remote processing module 72 may comprise one or more processors configured to e and process data and/or image information. In some embodiments, the remote data repository 74 may comprise a digital data storage facility, which may be available through the internet or other networking configuration in a “cloud” resource configuration. In some embodiments, the remote data repository 74 may include one or more remote servers, which provide ation, e.g., information for generating ted y content, to the local processing and data module 70 and/or the remote processing module 72. In some embodiments, all data is stored and all computations are performed in the local processing and data module, allowing fully autonomous use from a remote module.

The perception of an image as being “three-dimensional” or “3-D” may be achieved by ing ly different presentations of the image to each eye of the viewer.

Figure 3 illustrates a conventional y system for ting three-dimensional imagery for a user. Two distinct images 5, 7—one for each eye 4, 6—are outputted to the user. The images 5, 7 are spaced from the eyes 4, 6 by a distance 10 along an optical or z-axis parallel to the line of sight of the viewer. The images 5, 7 are flat and the eyes 4, 6 may focus on the images by assuming a single accommodated state. Such systems rely on the human visual system to combine the images 5, 7 to provide a perception of depth and/or scale for the combined image.

It will be iated, however, that the human visual system is more complicated and providing a realistic perception of depth is more challenging. For example, many viewers of conventional “3-D” display systems find such systems to be uncomfortable or may not perceive a sense of depth at all. Without being limited by theory, it is believed that viewers of an object may perceive the object as being “three-dimensional” due to a ation of vergence and accommodation. Vergence movements (i.e., rotation of the eyes so that the pupils move toward or away from each other to converge the lines of sight of the eyes to fixate upon an object) of the two eyes ve to each other are closely associated with focusing (or “accommodation”) of the lenses and pupils of the eyes. Under normal conditions, changing the focus of the lenses of the eyes, or accommodating the eyes, to change focus from one object to another object at a different distance will automatically cause a matching change in vergence to the same distance, under a relationship known as the “accommodation-vergence ,” as well as pupil dilation or constriction. Likewise, a change in vergence will trigger a matching change in accommodation of lens shape and pupil size, under normal conditions. As noted herein, many stereoscopic or “3-D” display systems display a scene using slightly different presentations (and, so, slightly different images) to each eye such that a three-dimensional perspective is perceived by the human visual system.

Such systems are uncomfortable for many viewers, however, since they, among other things, simply provide a different presentation of a scene, but with the eyes viewing all the image information at a single accommodated state, and work against the “accommodation-vergence reflex.” Display systems that provide a better match between accommodation and vergence may form more realistic and comfortable tions of three-dimensional imagery contributing to sed duration of wear and in turn compliance to diagnostic and therapy protocols.

Figure 4 illustrates aspects of an approach for simulating threedimensional imagery using multiple depth planes. With reference to Figure 4, objects at various distances from eyes 4, 6 on the z-axis are accommodated by the eyes 4, 6 so that those objects are in focus. The eyes (4 and 6) assume particular odated states to bring into focus objects at different distances along the z-axis. uently, a particular accommodated state may be said to be associated with a particular one of depth planes 14, with has an associated focal ce, such that objects or parts of objects in a particular depth plane are in focus when the eye is in the accommodated state for that depth plane. In some ments, three-dimensional imagery may be simulated by providing ent presentations of an image for each of the eyes 4, 6, and also by providing different presentations of the image ponding to each of the depth planes. While shown as being separate for clarity of illustration, it will be appreciated that the fields of view of the eyes 4, 6 may overlap, for e, as ce along the z-axis increases. In addition, while shown as flat for ease of illustration, it will be appreciated that the contours of a depth plane may be curved in al space, such that all features in a depth plane are in focus with the eye in a particular accommodated state.

The ce between an object and the eye 4 or 6 may also change the amount of divergence of light from that , as viewed by that eye. Figures 5A-5C illustrates relationships between distance and the divergence of light rays. The distance between the object and the eye 4 is represented by, in order of decreasing distance, R1, R2, and R3. As shown in Figures 5A-5C, the light rays become more divergent as distance to the object decreases. As distance increases, the light rays become more collimated. Stated another way, it may be said that the light field produced by a point (the object or a part of the object) has a spherical wavefront curvature, which is a function of how far away the point is from the eye of the user. The curvature increases with decreasing distance between the object and the eye 4. Consequently, at different depth planes, the degree of ence of light rays is also different, with the degree of divergence increasing with decreasing distance between depth planes and the ’s eye 4. While only a single eye 4 is illustrated for clarity of illustration in Figures 5A-5C and other figures herein, it will be appreciated that the discussions regarding eye 4 may be applied to both eyes 4 and 6 of a viewer.

Without being limited by theory, it is believed that the human eye typically can ret a finite number of depth planes to provide depth perception.

Consequently, a highly believable simulation of perceived depth may be ed by providing, to the eye, different presentations of an image corresponding to each of these limited number of depth planes. The different presentations may be tely focused by the viewer’s eyes, thereby helping to provide the user with depth cues based on the accommodation of the eye required to bring into focus different image features for the scene located on ent depth plane and/or based on observing different image features on different depth planes being out of focus.

Figure 6 illustrates an example of a waveguide stack for outputting image information to a user. A display system 1000 includes a stack of ides, or stacked waveguide assembly, 1178 that may be ed to provide three-dimensional perception to the eye/brain using a plurality of waveguides 1182, 1184, 1186, 1188, 1190. In some embodiments, the display system 1000 is the system 80 of Figure 2, with Figure 6 tically showing some parts of that system 80 in greater detail. For example, the waveguide assembly 1178 may be part of the display 62 of Figure 2. It will be appreciated that the display system 1000 may be ered a light field display in some embodiments.

With continued reference to Figure 6, the waveguide assembly 1178 may also include a plurality of features 1198, 1196, 1194, 1192 between the waveguides. In some ments, the features 1198, 1196, 1194, 1192 may be one or more lenses. The waveguides 1182, 1184, 1186, 1188, 1190 and/or the plurality of lenses 1198, 1196, 1194, 1192 may be configured to send image information to the eye with various levels of wavefront curvature or light ray divergence. Each waveguide level may be ated with a particular depth plane and may be configured to output image information corresponding to that depth plane. Image injection devices 1200, 1202, 1204, 1206, 1208 may function as a source of light for the waveguides and may be utilized to inject image information into the waveguides 1182, 1184, 1186, 1188, 1190, each of which may be configured, as described herein, to distribute incoming light across each respective waveguide, for output toward the eye 4. Light exits an output surface 1300, 1302, 1304, 1306, 1308 of the image ion devices 1200, 1202, 1204, 1206, 1208 and is injected into a ponding input surface 1382, 1384, 1386, 1388, 1390 of the waveguides 1182, 1184, 1186, 1188, 1190. In some embodiments, the each of the input surfaces 1382, 1384, 1386, 1388, 1390 may be an edge of a corresponding waveguide, or may be part of a major surface of the corresponding waveguide (that is, one of the waveguide surfaces directly facing the world 1144 or the viewer’s eye 4). In some embodiments, a single beam of light (e.g. a ated beam) may be injected into each waveguide to output an entire field of cloned collimated beams that are directed toward the eye 4 at particular angles (and amounts of divergence) corresponding to the depth plane associated with a particular waveguide. In some embodiments, a single one of the image injection devices 1200, 1202, 1204, 1206, 1208 may be associated with and inject light into a ity (e.g., three) of the waveguides 1182, 1184, 1186, 1188, 1190.

In some embodiments, the image injection devices 1200, 1202, 1204, 1206, 1208 are discrete ys that each produce image ation for injection into a corresponding waveguide 1182, 1184, 1186, 1188, 1190, respectively. In some other embodiments, the image injection devices 1200, 1202, 1204, 1206, 1208 are the output ends of a single multiplexed display which may, e.g., pipe image information via one or more optical conduits (such as fiber optic cables) to each of the image injection devices 1200, 1202, 1204, 1206, 1208. It will be appreciated that the image information provided by the image injection devices 1200, 1202, 1204, 1206, 1208 may include light of different wavelengths, or colors (e.g., different component colors, as discussed herein).

In some embodiments, the light injected into the ides 1182, 1184, 1186, 1188, 1190 is provided by a light projector system 2000, which comprises a light module 2040, which may include a light emitter, such as a light emitting diode (LED). The light from the light module 2040 may be directed to and modified by a light modulator 2030, e.g., a spatial light modulator, via a beam splitter 2050. The light modulator 2030 may be configured to change the ved intensity of the light injected into the waveguides 1182, 1184, 1186, 1188, 1190. Examples of spatial light tors include liquid crystal ys (LCD) including a liquid crystal on silicon (LCOS) displays.

In some embodiments, the display system 1000 may be a scanning fiber display comprising one or more scanning fibers configured to project light in various patterns (e.g., raster scan, spiral scan, Lissajous patterns, etc.) into one or more waveguides 1182, 1184, 1186, 1188, 1190 and ultimately to the eye 4 of the viewer. In some embodiments, the illustrated image injection s 1200, 1202, 1204, 1206, 1208 may schematically represent a single scanning fiber or a bundles of scanning fibers configured to inject light into one or a plurality of the waveguides 1182, 1184, 1186, 1188, 1190. In some other embodiments, the illustrated image injection devices 1200, 1202, 1204, 1206, 1208 may tically represent a plurality of scanning fibers or a ity of bundles of scanning, fibers each of which are configured to inject light into an associated one of the waveguides 1182, 1184, 1186, 1188, 1190. It will be appreciated that the one or more optical fibers may be configured to transmit light from the light module 2040 to the one or more waveguides 1182, 1184, 1186, 1188, 1190. It will be appreciated that one or more intervening optical structures may be provided between the scanning fiber, or fibers, and the one or more waveguides 1182, 1184, 1186, 1188, 1190 to, e.g., redirect light exiting the scanning fiber into the one or more waveguides 1182, 1184, 1186, 1188, 1190.

A ller 1210 controls the operation of one or more of the stacked ide assembly 1178, including ion of the image ion devices 1200, 1202, 1204, 1206, 1208, the light source 2040, and the light modulator 2030. In some embodiments, the controller 1210 is part of the local data processing module 70. The ller 1210 includes programming (e.g., instructions in a non-transitory medium) that regulates the timing and ion of image information to the waveguides 1182, 1184, 1186, 1188, 1190 according to, e.g., any of the various schemes sed herein. In some embodiments, the controller may be a single integral device, or a distributed system connected by wired or wireless communication channels. The controller 1210 may be part of the processing modules 70 or 72 (Figure 1) in some embodiments.

With continued reference to Figure 6, the waveguides 1182, 1184, 1186, 1188, 1190 may be configured to propagate light within each respective waveguide by total internal reflection (TIR). The waveguides 1182, 1184, 1186, 1188, 1190 may each be planar or have another shape (e.g., curved), with major top and bottom surfaces and edges extending between those major top and bottom surfaces. In the illustrated configuration, the waveguides 1182, 1184, 1186, 1188, 1190 may each include outcoupling optical elements 1282, 1284, 1286, 1288, 1290 that are configured to extract light out of a ide by cting the light, propagating within each respective waveguide, out of the waveguide to output image ation to the eye 4. Extracted light may also be referred to as outcoupled light and the outcoupling l ts light may also be referred to light extracting optical elements. An ted beam of light is outputted by the waveguide at locations at which the light propagating in the waveguide strikes a light extracting l element. The outcoupling optical elements 1282, 1284, 1286, 1288, 1290 may, for example, be gratings, including diffractive optical features, as discussed further herein. While illustrated disposed at the bottom major es of the waveguides 1182, 1184, 1186, 1188, 1190 for ease of description and drawing clarity, in some embodiments, the outcoupling optical elements 1282, 1284, 1286, 1288, 1290 may be disposed at the top and/or bottom major surfaces, and/or may be disposed directly in the volume of the waveguides 1182, 1184, 1186, 1188, 1190, as sed further herein. In some embodiments, the outcoupling optical elements 1282, 1284, 1286, 1288, 1290 may be formed in a layer of material that is attached to a transparent substrate to form the waveguides 1182, 1184, 1186, 1188, 1190. In some other embodiments, the ides 1182, 1184, 1186, 1188, 1190 may be a monolithic piece of material and the outcoupling optical elements 1282, 1284, 1286, 1288, 1290 may be formed on a surface and/or in the interior of that piece of material.

With continued reference to Figure 6, as discussed herein, each waveguide 1182, 1184, 1186, 1188, 1190 is configured to output light to form an image corresponding to a ular depth plane. For example, the waveguide 1182 nearest the eye may be configured to deliver ated light, as injected into such waveguide 1182, to the eye 4.

The collimated light may be representative of the optical infinity focal plane. The next waveguide up 1184 may be configured to send out collimated light which passes h the first lens 1192 (e.g., a negative lens) before it can reach the eye 4; such first lens 1192 may be configured to create a slight convex wavefront curvature so that the eye/brain interprets light coming from that next waveguide up 1184 as coming from a first focal plane closer inward toward the eye 4 from optical infinity. Similarly, the third up waveguide 1186 passes its output light through both the first 1192 and second 1194 lenses before ng the eye 4; the combined optical power of the first 1192 and second 1194 lenses may be configured to create another incremental amount of wavefront curvature so that the eye/brain interprets light coming from the third waveguide 1186 as coming from a second focal plane that is even closer inward toward the person from optical infinity than was light from the next ide up 1184.

The other waveguide layers 1188, 1190 and lenses 1196, 1198 are similarly configured, with the highest waveguide 1190 in the stack sending its output through all of the lenses between it and the eye for an aggregate focal power representative of the closest focal plane to the person. To compensate for the stack of lenses 1198, 1196, 1194, 1192 when viewing/interpreting light coming from the world 1144 on the other side of the stacked waveguide assembly 1178, a compensating lens layer 1180 may be ed at the top of the stack to compensate for the aggregate power of the lens stack 1198, 1196, 1194, 1192 below. Such a uration provides as many perceived focal planes as there are available waveguide/lens pairings. Both the outcoupling optical elements of the waveguides and the focusing s of the lenses may be static (i.e., not c or electro-active). In some alternative embodiments, either or both may be dynamic using electro-active features.

In some ments, two or more of the waveguides 1182, 1184, 1186, 1188, 1190 may have the same associated depth plane. For example, multiple waveguides 1182, 1184, 1186, 1188, 1190 may be configured to output images set to the same depth plane, or multiple subsets of the waveguides 1182, 1184, 1186, 1188, 1190 may be configured to output images set to the same plurality of depth planes, with one set for each depth plane. This can provide advantages for forming a tiled image to provide an expanded field of view at those depth planes.

With continued reference to Figure 6, the outcoupling optical elements 1282, 1284, 1286, 1288, 1290 may be configured to both redirect light out of their respective waveguides and to output this light with the appropriate amount of divergence or collimation for a particular depth plane associated with the waveguide. As a result, waveguides having ent associated depth planes may have different configurations of outcoupling l ts 1282, 1284, 1286, 1288, 1290, which output light with a different amount of divergence depending on the associated depth plane. In some embodiments, the light extracting optical elements 1282, 1284, 1286, 1288, 1290 may be volumetric or surface features, which may be configured to output light at specific angles. For example, the light extracting l elements 1282, 1284, 1286, 1288, 1290 may be volume holograms, surface holograms, and/or diffraction gratings. In some embodiments, the features 1198, 1196, 1194, 1192 may not be lenses; rather, they may simply be spacers (e.g., cladding layers and/or structures for forming air gaps).

In some embodiments, the pling optical elements 1282, 1284, 1286, 1288, 1290 are diffractive features that form a diffraction pattern, or active optical t” (also referred to herein as a “DOE”). Preferably, the DOE’s have a sufficiently low diffraction efficiency so that only a portion of the light of the beam is deflected away toward the eye 4 with each intersection of the DOE, while the rest ues to move h a waveguide via total internal reflection. The light carrying the image ation is thus divided into a number of related exit beams that exit the waveguide at a multiplicity of locations and the result is a fairly uniform pattern of exit emission toward the eye 4 for this particular ated beam bouncing around within a waveguide.

In some embodiments, one or more DOEs may be switchable between “on” states in which they actively diffract, and “off” states in which they do not significantly diffract. For instance, a switchable DOE may comprise a layer of polymer dispersed liquid crystal, in which microdroplets comprise a diffraction pattern in a host medium, and the refractive index of the microdroplets may be switched to substantially match the refractive index of the host material (in which case the pattern does not appreciably diffract incident light) or the microdroplet may be switched to an index that does not match that of the host medium (in which case the pattern ly diffracts incident light).

In some ments, a camera assembly 500 (e.g., a digital camera, including visible light and infrared light cameras) may be provided to capture images of the eye 4 and/or tissue around the eye 4 to, e.g., detect user inputs and/or to monitor the physiological state of the user. As used herein, a camera may be any image capture .

In some embodiments, the camera assembly 500 may include an image capture device and a light source to t light (e.g., infrared light) to the eye, which may then be reflected by the eye and detected by the image capture device. In some embodiments, the camera assembly 500 may be attached to the frame 64 e 2) and may be in electrical ication with the processing modules 70 and/or 72, which may process image information from the camera assembly 500 to make various determinations regarding, e.g., the physiological state of the user, as sed herein. It will be appreciated that information regarding the physiological state of user may be used to ine the behavioral or emotional state of the user. Examples of such information include movements of the user and/or facial expressions of the user. The behavioral or emotional state of the user may then be triangulated with collected environmental and/or virtual content data so as to determine relationships between the behavioral or emotional state, physiological state, and environmental or virtual content data. In some embodiments, one camera assembly 500 may be utilized for each eye, to separately monitor each eye.

With reference now to Figure 7, an example of exit beams outputted by a waveguide is shown. One waveguide is illustrated, but it will be appreciated that other waveguides in the waveguide assembly 1178 (Figure 6) may function similarly, where the waveguide assembly 1178 includes multiple ides. Light 400 is injected into the waveguide 1182 at the input surface 1382 of the waveguide 1182 and propagates within the waveguide 1182 by TIR. At points where the light 400 impinges on the DOE 1282, a portion of the light exits the waveguide as exit beams 402. The exit beams 402 are illustrated as substantially parallel but, as discussed , they may also be redirected to propagate to the eye 4 at an angle (e.g., forming divergent exit beams), depending on the depth plane ated with the waveguide 1182. It will be appreciated that substantially parallel exit beams may be indicative of a waveguide with outcoupling optical elements that outcouple light to form images that appear to be set on a depth plane at a large distance (e.g., optical infinity) from the eye 4. Other waveguides or other sets of outcoupling optical elements may output an exit beam pattern that is more divergent, which would require the eye 4 to accommodate to a closer distance to bring it into focus on the retina and would be interpreted by the brain as light from a distance closer to the eye 4 than optical infinity.

In some embodiments, a full color image may be formed at each depth plane by overlaying images in each of the component , e.g., three or more component colors. Figure 8 illustrates an example of a stacked waveguide assembly in which each depth plane includes images formed using multiple different component colors. The illustrated embodiment shows depth planes 14a – 14f, although more or fewer depths are also contemplated. Each depth plane may have three component color images associated with it: a first image of a first color, G; a second image of a second color, R; and a third image of a third color, B. Different depth planes are ted in the figure by different s for diopters (dpt) following the letters G, R, and B. Just as examples, the s following each of these letters indicate diopters (1/m), or inverse distance of the depth plane from a viewer, and each box in the figures represents an individual component color image. In some embodiments, to t for differences in the eye’s focusing of light of ent wavelengths, the exact placement of the depth planes for different component colors may vary. For example, different component color images for a given depth plane may be placed on depth planes corresponding to different distances from the user. Such an arrangement may increase visual acuity and user comfort and/or may decrease chromatic aberrations.

In some embodiments, light of each component color may be outputted by a single dedicated ide and, consequently, each depth plane may have multiple waveguides associated with it. In such embodiments, each box in the figures including the letters G, R, or B may be understood to represent an individual waveguide, and three ides may be ed per depth plane where three component color images are provided per depth plane. While the waveguides associated with each depth plane are shown adjacent to one r in this drawing for ease of description, it will be appreciated that, in a physical device, the waveguides may all be arranged in a stack with one waveguide per level.

In some other embodiments, multiple component colors may be outputted by the same waveguide, such that, e.g., only a single waveguide may be provided per depth plane.

With continued reference to Figure 8, in some embodiments, G is the color green, R is the color red, and B is the color blue. In some other ments, other colors associated with other wavelengths of light, including magenta and cyan, may be used in addition to or may replace one or more of red, green, or blue. In some embodiments, features 198, 196, 194, and 192 may be active or passive optical filters configured to block or selectively light from the ambient environment to the viewer’s eyes.

It will be appreciated that references to a given color of light hout this disclosure will be understood to ass light of one or more wavelengths within a range of wavelengths of light that are perceived by a viewer as being of that given color. For example, red light may include light of one or more wavelengths in the range of about 620– 780 nm, green light may include light of one or more wavelengths in the range of about 492– 577 nm, and blue light may include light of one or more wavelengths in the range of about 435–493 nm.

In some embodiments, the light source 2040 (Figure 6) may be configured to emit light of one or more wavelengths outside the visual perception range of the , for example, infrared and/or ultraviolet wavelengths. In addition, the incoupling, outcoupling, and other light redirecting structures of the waveguides of the display 1000 may be configured to direct and emit this light out of the display towards the user’s eye 4, e.g., for imaging and/or user stimulation applications.

With reference now to Figure 9A, in some embodiments, light impinging on a waveguide may need to be redirected to incouple that light into the waveguide. An incoupling optical element may be used to redirect and incouple the light into its corresponding waveguide. Figure 9A illustrates a cross-sectional side view of an example of a plurality or set 1200 of stacked waveguides that each includes an incoupling optical t. The waveguides may each be configured to output light of one or more different wavelengths, or one or more different ranges of wavelengths. It will be appreciated that the stack 1200 may correspond to the stack 1178 (Figure 6) and the illustrated ides of the stack 1200 may correspond to part of the plurality of waveguides 1182, 1184, 1186, 1188, 1190, except that light from one or more of the image injection s 1200, 1202, 1204, 1206, 1208 is injected into the ides from a position that requires light to be redirected for incoupling.

The illustrated set 1200 of stacked waveguides includes waveguides 1210, 1220, and 1230. Each waveguide includes an associated incoupling optical element (which may also be referred to as a light input area on the waveguide), with, e.g., incoupling optical element 1212 disposed on a major surface (e.g., an upper major surface) of waveguide 1210, incoupling optical t 1224 disposed on a major surface (e.g., an upper major surface) of waveguide 1220, and incoupling optical element 1232 disposed on a major e (e.g., an upper major surface) of waveguide 1230. In some embodiments, one or more of the incoupling optical elements 1212, 1222, 1232 may be disposed on the bottom major surface of the respective waveguide 1210, 1220, 1230 (particularly where the one or more incoupling optical elements are reflective, deflecting optical elements). As illustrated, the incoupling optical elements 1212, 1222, 1232 may be disposed on the upper major surface of their respective waveguide 1210, 1220, 1230 (or the top of the next lower waveguide), particularly where those incoupling optical elements are transmissive, deflecting l ts. In some embodiments, the ling optical elements 1212, 1222, 1232 may be ed in the body of the respective waveguide 1210, 1220, 1230. In some embodiments, as discussed herein, the incoupling optical elements 1212, 1222, 1232 are wavelength selective, such that they selectively redirect one or more wavelengths of light, while transmitting other wavelengths of light. While illustrated on one side or corner of their respective waveguide 1210, 1220, 1230, it will be appreciated that the incoupling optical elements 1212, 1222, 1232 may be disposed in other areas of their respective waveguide 1210, 1220, 1230 in some embodiments.

As illustrated, the incoupling optical elements 1212, 1222, 1232 may be lly offset from one another. In some ments, each incoupling optical element may be offset such that it receives light without that light passing through r ling optical element. For example, each incoupling optical element 1212, 1222, 1232 may be configured to receive light from a different image injection device 1200, 1202, 1204, 1206, and 1208 as shown in Figure 6, and may be separated (e.g., laterally spaced apart) from other incoupling optical ts 1212, 1222, 1232 such that it substantially does not receive light from the other ones of the incoupling optical elements 1212, 1222, 1232.

Each waveguide also es associated light distributing elements, with, e.g., light buting elements 1214 ed on a major surface (e.g., a top major surface) of waveguide 1210, light distributing elements 1224 disposed on a major surface (e.g., a top major surface) of waveguide 1220, and light distributing elements 1234 disposed on a major e (e.g., a top major surface) of waveguide 1230. In some other embodiments, the light distributing elements 1214, 1224, 1234, may be disposed on a bottom major surface of associated waveguides 1210, 1220, 1230, respectively. In some other embodiments, the light distributing elements 1214, 1224, 1234, may be disposed on both top and bottom major surface of associated ides 1210, 1220, 1230, respectively; or the light buting elements 1214, 1224, 1234, may be disposed on different ones of the top and bottom major surfaces in different associated waveguides 1210, 1220, 1230, respectively.

The waveguides 1210, 1220, 1230 may be spaced apart and separated by, e.g., gas, liquid, and/or solid layers of material. For e, as illustrated, layer 1218a may separate waveguides 1210 and 1220; and layer 1218b may separate waveguides 1220 and 1230. In some embodiments, the layers 1218a and 1218b are formed of low refractive index als (that is, materials having a lower refractive index than the material forming the immediately adjacent one of waveguides 1210, 1220, 1230). ably, the tive index of the material forming the layers 1218a, 1218b is 0.05 or more, or 0.10 or more less than the refractive index of the material g the waveguides 1210, 1220, 1230. Advantageously, the lower refractive index layers 1218a, 1218b may function as cladding layers that facilitate total internal reflection (TIR) of light through the waveguides 1210, 1220, 1230 (e.g., TIR between the top and bottom major surfaces of each waveguide). In some embodiments, the layers 1218a, 1218b are formed of air. While not rated, it will be appreciated that the top and bottom of the illustrated set 1200 of waveguides may include immediately neighboring cladding layers.

Preferably, for ease of manufacturing and other considerations, the material forming the waveguides 1210, 1220, 1230 are similar or the same, and the material forming the layers 1218a, 1218b are similar or the same. In some embodiments, the material forming the waveguides 1210, 1220, 1230 may be different between one or more waveguides, and/or the material forming the layers 1218a, 1218b may be ent, while still holding to the various refractive index relationships noted above.

With ued reference to Figure 9A, light rays 1240, 1242, 1244 are incident on the set 1200 of waveguides. It will be appreciated that the light rays 1240, 1242, 1244 may be injected into the waveguides 1210, 1220, 1230 by one or more image injection s 1200, 1202, 1204, 1206, 1208 (Figure 6).

In some embodiments, the light rays 1240, 1242, 1244 have different properties, e.g., different wavelengths or different ranges of wavelengths, which may correspond to different colors. The incoupling optical elements 1212, 122, 1232 each deflect the incident light such that the light propagates through a respective one of the waveguides 1210, 1220, 1230 by TIR.

For example, incoupling l t 1212 may be configured to deflect ray 1240, which has a first wavelength or range of wavelengths. Similarly, the transmitted ray 1242 impinges on and is deflected by the ling optical element 1222, which is configured to deflect light of a second wavelength or range of ngths.

Likewise, the ray 1244 is ted by the incoupling optical element 1232, which is configured to selectively deflect light of third wavelength or range of wavelengths.

With continued reference to Figure 9A, the deflected light rays 1240, 1242, 1244 are ted so that they propagate through a corresponding waveguide 1210, 1220, 1230; that is, the incoupling l elements 1212, 1222, 1232 of each waveguide deflects light into that corresponding waveguide 1210, 1220, 1230 to incouple light into that corresponding waveguide. The light rays 1240, 1242, 1244 are deflected at angles that cause the light to propagate through the respective waveguide 1210, 1220, 1230 by TIR. The light rays 1240, 1242, 1244 propagate through the respective waveguide 1210, 1220, 1230 by TIR until impinging on the waveguide’s corresponding light distributing elements 1214, 1224, 1234.

With reference now to Figure 9B, a perspective view of an example of the ity of stacked waveguides of Figure 9A is illustrated. As noted above, the led light rays 1240, 1242, 1244, are deflected by the incoupling optical elements 1212, 1222, 1232, respectively, and then propagate by TIR within the waveguides 1210, 1220, 1230, respectively. The light rays 1240, 1242, 1244 then impinge on the light distributing elements 1214, 1224, 1234, tively. The light distributing elements 1214, 1224, 1234 deflect the light rays 1240, 1242, 1244 so that they propagate towards the outcoupling optical elements 1250, 1252, 1254, respectively.

In some embodiments, the light distributing ts 1214, 1224, 1234 are orthogonal pupil expanders (OPE’s). In some embodiments, the OPE’s both deflect or distribute light to the outcoupling optical elements 1250, 1252, 1254 and also increase the beam or spot size of this light as it propagates to the pling optical elements. In some embodiments, e.g., where the beam size is already of a desired size, the light distributing elements 1214, 1224, 1234 may be omitted and the ling optical elements 1212, 1222, 1232 may be configured to deflect light ly to the outcoupling optical elements 1250, 1252, 1254. For example, with reference to Figure 9A, the light distributing elements 1214, 1224, 1234 may be replaced with outcoupling optical elements 1250, 1252, 1254, tively. In some embodiments, the outcoupling l elements 1250, 1252, 1254 are exit pupils (EP’s) or exit pupil ers (EPE’s) that direct light in a viewer’s eye 4 (Figure Accordingly, with reference to Figures 9A and 9B, in some embodiments, the set 1200 of waveguides includes waveguides 1210, 1220, 1230; incoupling optical elements 1212, 1222, 1232; light distributing elements (e.g., OPE’s) 1214, 1224, 1234; and outcoupling optical elements (e.g., EP’s) 1250, 1252, 1254 for each component color. The waveguides 1210, 1220, 1230 may be stacked with an air gap/cladding layer between each one. The incoupling optical elements 1212, 1222, 1232 redirect or deflect incident light (with different incoupling l elements receiving light of different ngths) into its waveguide. The light then propagates at an angle which will result in TIR within the respective waveguide 1210, 1220, 1230. In the example shown, light ray 1240 (e.g., blue light) is deflected by the first incoupling optical t 1212, and then continues to bounce down the waveguide, interacting with the light distributing element (e.g., OPE’s) 1214 and then the outcoupling optical element (e.g., EPs) 1250, in a manner described earlier. The light rays 1242 and 1244 (e.g., green and red light, respectively) will pass through the waveguide 1210, with light ray 1242 impinging on and being deflected by incoupling optical t 1222. The light ray 1242 then bounces down the waveguide 1220 via TIR, proceeding on to its light distributing t (e.g., OPEs) 1224 and then the outcoupling optical element (e.g., EP’s) 1252. Finally, light ray 1244 (e.g., red light) passes through the waveguide 1220 to impinge on the light incoupling optical elements 1232 of the waveguide 1230. The light incoupling optical elements 1232 deflect the light ray 1244 such that the light ray propagates to light distributing element (e.g., OPEs) 1234 by TIR, and then to the outcoupling optical element (e.g., EPs) 1254 by TIR. The outcoupling optical element 1254 then finally outcouples the light ray 1244 to the viewer, who also receives the outcoupled light from the other waveguides 1210, 1220.

Figure 9C illustrates a top-down plan view of an example of the ity of stacked waveguides of Figures 9A and 9B. As illustrated, the waveguides 1210, 1220, 1230, along with each waveguide’s associated light distributing element 1214, 1224, 1234 and associated pling optical element 1250, 1252, 1254, may be vertically aligned. r, as discussed herein, the incoupling optical elements 1212, 1222, 1232 are not vertically aligned; rather, the incoupling optical elements are preferably non-overlapping (e.g., laterally spaced apart as seen in the wn view). As discussed further , this rlapping spatial arrangement facilitates the injection of light from different ces into different waveguides on a one-to-one basis, thereby ng a specific light source to be uniquely coupled to a ic ide. In some embodiments, arrangements ing nonoverlapping spatially-separated incoupling optical elements may be referred to as a shifted pupil system, and the in coupling optical elements within these arrangements may correspond to sub pupils.

Spatially Variable Liquid Crystal Diffraction Gratings As described above in reference to Figures 6 and 7, display systems according to various embodiments described herein may include outcoupling optical elements (e.g., optical elements 1282, 1284, 1286, 1288, 1290 in Figure 6), which may include diffraction gratings. As described above in reference to Figure 7, light 400 that is injected into the waveguide 1182 at the input surface 1382 of the waveguide 1182 propagates within the waveguide 1182 by total internal reflection (TIR). Referring back to Figure 7, at points where the light 400 impinges on the outcoupling optical element 1282, a portion of the light exits the waveguide as exit beams 402. In some implementations, it may be desirable to have the optical element 1282 be configured as a ction grating having spatially varying optical properties, ing diffraction properties. Such configuration may be desirable, for example, when the intensity of the light substantially ates as it propagates within the waveguide 1182. Under such circumstances, it may be desirable have certain diffraction characteristics of the grating 1282, e.g., ction efficiency (a ratio of diffracted beam intensity to the incident beam intensity) or refractive index, vary along the light propagation direction, such that uniformity of the intensity of the exiting beams 402 are ed. Such configurations may also be desirable, for example, to intentionally skew the light intensity across the grating 1282 to adapt to spatial and/or r variation of g efficiencies associated with the human eye to maximize the user experience. Thus, there is a need for pling optical elements, e.g., diffraction gratings, having spatially varying optical characteristics.

For some applications, graded diffraction properties can be achieved by urally varying periodic structures of the grating, e.g., by using semiconductor processing technology. For example, semiconductor etching technology can be used to holographically pattern gs into rigid substrate materials such as fused silica. By spatially g the etch profiles, for instance, correspondingly spatially varying duty cycle or grating depth can be produced. However, such ches often involve relatively complex and expensive processes, e.g., multiple etch processes. Thus, diffraction gratings with spatially varying optical properties, which can be fabricated with relatively simple processing technologies, could be beneficial. To this end, according to s embodiments disclosed herein, liquid crystal materials are used to spatially vary diffraction characteristics across the area of a diffraction gratings, e.g., by spatially varying ent characteristics or other material properties of the liquid crystal molecules. In s embodiments, photopolymerizable liquid crystal materials, or reactive ns, are used to spatially vary the diffraction characteristics of diffraction gratings. For example, by coating different areas of a grating with a liquid crystal material and spatially varying its ties, e.g., alignment properties, spatially varying diffraction properties can be generated.

In the following, various embodiments of liquid crystal (LC) gratings having varying optical properties, e.g., gradient optical properties, such as varying diffraction properties ing diffraction efficiency. lly, diffraction gratings have a periodic structure, which splits and diffracts light into several beams travelling in different directions.

The directions of these beams depend, among other things, on the period of the periodic structure and the wavelength of the light. To achieve certain l properties that lly vary across the area of the grating, e.g., spatially varying diffraction efficiencies, for certain applications such as outcoupling l element 282 having uniform intensity of the exiting light beams 402, material ties of liquid crystals can be spatially varied.

Generally, liquid crystals possess physical properties that may be intermediate between conventional fluids and solids. While liquid crystals are fluid-like in some aspects, unlike most fluids, the ement of molecules within them exhibits some structural order. Different types of liquid crystals include thermotropic, lyotropic, and polymeric liquid crystals. Thermotropic liquid crystals disclosed herein can be implemented in various physical states, e.g., phases, including a nematic state/phase, a smectic state/phase, a chiral c state/phase or a chiral smectic state/phase.

As described herein, liquid crystals in a nematic state or phase can have calamitic (rod-shaped) or ic (disc-shaped) c molecules that have relatively little positional order, while having a long-range ional order with their long axes being roughly parallel. Thus, the organic molecules may be free to flow with their center of mass positions being randomly distributed as in a liquid, while still maintaining their long-range directional order. In some implementations, liquid ls in a nematic phase can be uniaxial; i.e., the liquid crystals have one axis that is longer and preferred, with the other two being roughly equivalent. In other implementations, liquid crystals can be biaxial; i.e., in addition to ing their long axis, the liquid crystals may also orient along a secondary axis.

As described herein, liquid crystals in a c state or phase can have the organic molecules that form relatively well-defined layers that can slide over one another.

In some entations, liquid crystals in a smectic phase can be positionally ordered along one direction. In some implementations, the long axes of the molecules can be oriented along a direction substantially normal to the plane of the liquid l layer, while in other implementations, the long axes of the molecules may be tilted with respect to the direction normal to the plane of the layer.

As bed herein, nematic liquid crystals are composed of rod-like molecules with the long axes of neighboring molecules approximately aligned to one another. To describe this anisotropic structure, a dimensionless unit vector n called the director, may be used to be the direction of preferred orientation of the liquid crystal molecules.

As describe herein, liquid crystals in a c state or a smectic state can also exhibit ity. In a chiral phase, the liquid crystals can exhibit a twisting of the molecules perpendicular to the director, with the molecular axis parallel to the director. The finite twist angle between adjacent molecules is due to their asymmetric packing, which results in -range chiral order.

As described herein, liquid crystals in a chiral smectic state or phase can be configured such that the molecules have positional ng in a layered ure, with the molecules tilted by a finite angle with respect to the layer normal. In on, chirality can induce successive azimuthal twists from one layer to the next, producing a spiral twisting of the molecular axis along the layer normal.

As described herein, liquid crystals displaying chirality can be described as having a chiral pitch, p, which can refer to the distance over which the liquid crystal molecules undergo a full 360° twist. The pitch, p, can change when the ature is altered or when other les are added to the liquid crystal host (an achiral liquid host material can form a chiral phase if doped with a chiral al), allowing the pitch of a given material to be tuned accordingly. In some liquid crystal systems, the pitch is of the same order as the wavelength of visible light. As described herein, liquid crystals displaying chirality can also be bed as having a twist angle, which can refer, for example, to the relative azimuthal angular on between an uppermost liquid crystal molecule and a lowermost liquid crystal molecule across a thickness of the liquid crystal material.

According to various ments described herein, liquid crystals having various states or phases as described above can be configured to offer various desirable al properties for diffraction gratings, including, e.g., birefringence, optical anisotropy, and manufacturability using thin-film processes. For example, by changing surface conditions of liquid crystal layers and/or mixing different liquid crystal materials, grating structures that exhibit spatially varying diffraction properties, e.g., gradient ction efficiencies, can be fabricated.

As described herein, “polymerizable liquid crystals” may refer to liquid crystal materials that can be polymerized, e.g., in-situ photopolymerized, and may also be described herein as reactive mesogens (RM).

It will be appreciated that the liquid crystal molecules may be polymerizable in some embodiments and, once polymerized, may form a large network with other liquid crystal molecules. For example, the liquid crystal molecules may be linked by chemical bonds or linking chemical species to other liquid l molecules. Once joined er, the liquid crystal molecules may form liquid crystal domains having substantially the same orientations and locations as before being linked together. For ease of description, the term “liquid crystal molecule” is used herein to refer to both the liquid l molecules before polymerization and to the liquid crystal domains formed by these molecules after polymerization.

According to ular ments described herein, photopolymerizable liquid crystal als can be configured to form a diffraction grating, whose material properties, including birefringence, chirality, and ease for le-coating, can be ed to create gratings with graded diffraction efficiencies, as changes in these material properties (e.g., birefringence, chirality, and thickness) result in ions in diffraction efficiencies accordingly.

It will be appreciated that, as described herein, a “transmissive” or “transparent” ure, e.g., a transparent substrate, may allow at least some, e.g., at least 20, or 50%, of an incident light, to pass therethrough. Accordingly, a transparent substrate may be a glass, sapphire or a polymeric substrate in some embodiments. In st, a “reflective” structure, e.g., a reflective substrate, may t at least some, e.g., at least 20, , 50, 70, 90% or more of the incident light, to reflect therefrom.

Optical properties of a grating are determined by the physical structures of the grating (e.g., the periodicity, the depth, and the duty cycle), as well as material properties of the grating (e.g., refractive index, absorption, and birefringence). When liquid crystals are used, l properties of the grating can be controlled by controlling, e.g., molecular orientation or distribution of the liquid crystal materials. For example, by varying molecular orientation or distribution of the liquid crystal material across the grating area, the grating may exhibit graded ction efficiencies. Such approaches are described in the following, in reference to the figures.

In various embodiments, a diffraction grating comprises a substrate and a plurality of different diffracting zones having a ically repeating lateral dimension ponding to a grating period adapted for light diffraction. The diffraction grating further comprises a ity of different liquid l layers corresponding the different diffracting zones, wherein the different liquid crystal layers have liquid crystal molecules that are aligned differently, such that the different diffracting zones have different optical properties associated with light ction.

Photo-aligned Spatially Variable Liquid Crystal Diffraction Gratings Referring to Figures 10A-10C, cross-sectional side views (viewed along the x-z plane) of diffraction gratings 100A-100C ing to some embodiments are illustrated. Each of the diffraction gratings 100A-100C comprises a substrate 104 and a plurality of diffracting zones, i.e., diffracting zones , 108A-2,…and 108A-n as rated in Figure 10A, diffracting zones 108B-1, 108B-2,…and 108B-n as illustrated in Figure 10B, and diffracting zones 108C-1, 108C-2,…and 108C-n as illustrated in Figure The cting zones of each of the diffraction gratings 100A-100C have a periodically repeating lateral ion or a grating period  and include corresponding liquid crystal layers formed of liquid l molecules 112. In the illustrated embodiment and throughout this disclosure, the liquid crystal molecules 112 can be in a nematic state or a smectic state, or a mixture thereof, among other possible states of liquid crystal les.

In the illustrated embodiment and throughout, various embodiments can have the grating period  that is between about 100 nm and about 10,000 nm, between about 200 nm and about 2000 nm or between about 300 nm and about 1000 nm, such that the plurality of diffracting zones are configured to diffract visible light.

The cting zones 108A-1, 108A-2,…108A-n of the diffraction grating 100A have corresponding liquid crystal layers 116A-1, 116A-2,… 116A-n, respectively; diffracting zones 108B-1, 108B-2,…108B-n of the diffraction grating 100B have corresponding liquid crystal layers 116B-1, 116B-2,…116B-n, respectively; and diffracting zones 108C-1, 108C-2,…108C-n of the diffraction grating 100C have corresponding liquid crystal layers 116C-1, 116C-2 and 116C-n, respectively.

It will be understood herein and throughout the specification that “n” can be a suitable integer for representing the number of ent zones. For example, diffracting zones 108B-1, 108B-2,…108B-n indicates that there can be n number of diffracting zones, where n is an integer. The number (n) of diffracting zones that is omitted from the Figures can be, for example, between 1 and about 500, between about 1 and about 200 or between about 1 and about 100. In some implementations, optical properties of a diffraction grating can vary continuously across the surface. In one implementation, , for example, there can be one grating period per diffracting zone for at least some of the diffracting zones. When each diffracting zone has one g period , the number (n) of diffracting zones can represent the number of grating periods  It will be understood herein and throughout the specification that, “…,” when ted in a , can ent the presence of onal diffracting zones between the illustrated zones, which can be contiguously connected and similar or the same as any other adjacently illustrated zone. In addition, “…” can also represent an arrangement of diffracting zones that periodically repeat any suitable number of times.

Each of the liquid crystal layers 116A-1, 116A-2 and 116A-n of the diffraction grating 100A in turn has differently arranged first and second diffracting regions 116A-1L and 116A-1R, 116A-2L and 116A-2R,…and 116A-nL and 116A-nR, respectively.

Similarly, each of the liquid crystal layers 116B-1, 116B-2 and 116B-n of the ction grating 100B in turn has differently arranged first and second diffracting regions L and 116B-1R, 116B-2L and 116B-2R,…and 116B-nL and 116B-nR, respectively. Similarly, each of the liquid crystal layers 116C-1, 116C-2 and 116C-n of the diffraction grating 100C in turn has differently arranged first and second diffracting regions 116C-1L and 116C-1R, 116C-2L and 116C-2R,…and 116C-nL and 116C-nR, respectively. The s are sometimes referred to as domains of liquid crystal molecules Still referring to FIGS. 10A-10C, each of the different diffracting zones further comprises an alignment layer 120 interposed n the ate 104 and the corresponding liquid crystal layer, wherein the alignment layer is configured to induce the alignment of the liquid crystal molecules in different regions of each zone. Interposed between the substrate 104 and the first/second diffracting regions 116A-1L/116A-1R, 116A- 2L/116A-2R,…and 116A-nL/116A-nR of the diffraction grating 100A of Figure 10A are first and second alignment layers L/120A-1R, L/120A-2R,…and 120A- nL/120A-nR, respectively. rly interposed between the substrate 104 and the first/second diffracting regions 116B-1L/116B-1R, 116B-2R/116B-2R,…and 116B- nL/116B-nR of the diffraction grating 100C of Figure 10B are first/second alignment layers 120B-1L/120B-1R, 120B-2L/120B-2R,…and 120B-nL/120B-nR, respectively. Similarly, interposed between the ate 104 and ently arranged first/second diffracting regions 116C-1L/116C-1R, 116C-2L/116C-2R,…and 116C-nL/116C-nR of the diffraction grating 100C of Figure 10C are first/second alignment layers 120C-1L/120C-1R, L/120C- 2R,…and 120C-nL/ 120C-nR, respectively.

Herein and throughout the disclosure, an alignment ion of ted liquid crystal molecules can refer to the direction of elongation of the liquid crystal molecules, or the direction of the director vector n.

Herein and throughout the disclosure, a tilt angle or a pre-tilt angle Φ can refer to an angle measured in a plane perpendicular to a major surface (in an x-y plane) of the liquid crystal layers or of the substrate, e.g., the x-z plane, and measured between an alignment direction and the major surface or a direction parallel to the major surface, e.g., the x-direction.

Herein and throughout the disclosure, an azimuthal angle or a rotation angle φ is used to describe an angle of rotation about an axis normal to a major surface (in an x-y plane), which is measured in a plane parallel to a major surface of the liquid crystal layers or of the substrate, e.g., the x-y plane, and measured between an alignment direction and a direction el to the major surface, e.g., the y-direction.

Herein and throughout the disclosure, when an alignment angle such as a pre-tilt angle Φ or a on angle φ are referred to as being substantially the same n different regions, it will be understood that an average alignment angles can, for example, be within about 1%, about 5% or about 10% of each other although the average alignment can be larger in some cases.

Herein and throughout the specification, a duty cycle can, for example, refers to a ratio between a first lateral ion of a first region having liquid crystal molecules aligned in a first alignment direction, and the g period of the zone having the first . Where applicable, the first region corresponds to the region in which the alignment of the liquid crystals does not vary between different zones.

Still referring to Figures 10A-10C, each zone of the diffraction gratings 100A, 100B and 100C include first and second regions that alternate in the x-direction. Each of the first regions 116A-1L, L,… and 116A-nL of the ction grating 100A, each of the first regions 116B-1L, L,… and 116B-nL of the diffraction grating 100B and each of the first regions 116C-1L, 116C-2L,… and 116A-nL of the diffraction grating 100C have liquid crystal molecules 112 that are aligned substantially along the same first alignment direction and have a first lt angle Φ that is substantially the same. Each of the second regions 116A-1R, 116A-2R,… and 116A-nR of the diffraction grating 100A, each of the second regions 116B-1R, 116B-2R,… and 116B-nL of the ction grating 100B and each of the second regions 116C-1R, 116C-2R,… and 116C-nR of the diffraction grating 100C have liquid crystal molecules 112 that are aligned substantially along a second alignment direction different from the first alignment direction and have second pre-tilt angles Φ that are different, e.g., greater, than the first pre-tilt angle Φ of the tive first regions.

In each of the diffraction gratings 100A-100C of Figures 10A-10C, respectively, at least some of the diffracting zones have liquid crystal layers formed of liquid crystal molecules that are lly arranged ently, e.g., have different pre-tilt angles from each other (Figures 10A and 10C), or have laterally varying duty cycles (Figures 10B and 10C), such that the diffracting zones have different optical properties, e.g., different refractive indices and different diffraction efficiencies, according to embodiments.

In particular, ing to ction grating 100A of Figure 10A, in addition to having alignment directions and lt angles Φ that are different from the first pre-tilt angle Φ of the first regions 116A-1L, 116A-2L,…and 116A-nL, the liquid crystal molecules of different second regions 116A-1R, 116A-2R,…and R are aligned along second alignment directions that are different from each other. For example, in the illustrated embodiment, the zones , 108A-2 and 108A-n are arranged such that the first s and second regions alternate in the x-direction, where each of the first regions 116A-1L, 116A-2L,…and 116A-nL has substantially the same pre-tilt angle Φ, while the second regions 116A-1R, 116A-2R,…and 116A-nR have pre-tilt angles Φ that are different from each other. By way of example, the first regions 116A-1L, 116A-2L,...and 116A-nL have a pre-tilt angle Φ that is between about ±15 degrees or between about ±10 s or between about ±5, e.g., 0 s. The second regions 116A-1R, 116A-2R,…and 116A-nR can have pre-tilt angles Φ that are different from each other and are each between about 60 degrees and about 90 degrees or between about 65 degrees and about 85 degrees, for instance about 75 degree; between about 35 s and about 65 degrees or n about 40 degrees and about 60 degrees, for ce about 50 degrees; between about 10 degrees and about 40 degrees or between about 15 degrees and about 35 degrees, for instance about 25 degrees.

Still referring to Figure 10A, in some embodiments, as illustrated, the second regions 116A-1R, 116A-2R,…and 116A-nR can have tilt angles Φ that vary, e.g., increase or decrease in one ion in a lateral direction, such that a gradient in diffraction properties is created. In other ments, the second regions 116A-1R, 116A-2R,…and 116A-nR can have tilt angles Φ that do not vary in one ion in the lateral direction.

Still referring to Figure 10A, the duty cycle, defined above, can be between about 10% and about 30%, between about 30% and about 50%, between about 40% and 60% (e.g., about 50%), between about 50% and about 70% or between about 70% and about 90%.

Referring now to Figure 10B, the diffraction grating 100B share some common features as the diffraction grating 100A of Figure 10A. However, unlike the diffracting grating 100B of Figure 10A, while the liquid crystal molecules of different second regions 116B-1R, 116B-2R,…and 116B-nR have pre-tilt angles Φ that are different from the first pre-tilt angle Φ of the first regions 116B-1L, L,…and 116B-nL, they are not aligned differently from each other. For e, in the illustrated embodiment, the zones 108B-1, 108B-2 and 108B-n are arranged such that the first regions and second regions alternate in the x-direction, where each of the first regions 116B-1L, 116B-2L,… and 116B- nL has substantially the same first pre-tilt angle Φ, and each of the second s 116B-1R, 116B-2R,…and 116B-nR has substantially the same second pre-tilt angles Φ. The first and second pre-tilt angles of the first and second regions can have any of the values discussed above with t to the diffraction grating 100A of Figure 10A.

Still referring to Figure 10B, unlike the grating 100A of Figure 10A, the zones 116B-1, 116B-2 and 116B-3 have substantially the same pre-tilt angle, e.g., between about 0 to 90 degrees, while having a duty cycle between about 40% and about 60%, for instance about 50%; between about 30% and about 50%, for instance about 40% and a duty cycle between about 20% and about 40%, for instance about 30%, respectively, such that the diffraction grating 100B has spatially varying optical properties.

Still referring to Figure 10B, in some embodiments, as illustrated, the zones can have duty cycles that vary, e.g., increase or decrease in one direction in a lateral direction, such that a gradient in optical properties is created. In other embodiments, the duty cycles do not vary in one direction in the lateral ion.

Referring now to Figure 10C, the illustrated diffraction grating 100C es features similar to those described above with respect to the diffraction gratings 100A and 100B of Figures 10A and 10B. In particular, the liquid crystal molecules of different second regions 116C-1R, 116C-2R,…and 116C-nR can have pre-tilt angles Φ that are different from the first pre-tilt angle Φ of the first regions 116C-1L, L,… and 116C-nL, and d differently from each other. In addition, the duty cycle varies between adjacent zones across a lateral direction, e.g., x-direction. The first and second pre-tilt angles of the first and second regions can have any of the values discussed above with respect to the diffraction grating 100A of Figure 10A. In addition, the duty cycle variation between adjacent zones across a l ion, e.g., x-direction, can also have values discussed above with respect to the diffraction grating 100B of Figure 10B.

In the diffraction gratings 100A-100C illustrated in Figures 10A-10C and hout the disclosure, it will be appreciated that, in addition to the grating period and duty cycle discussed above, the ction properties can be further defined by, among other , the thickness and the refractive index of the liquid crystal layer 116. According to various embodiments disclosed herein, the thickness of the liquid crystal layers sed herein can have a thickness between about 1 m and about 100 m, between about 0.5 m and about 20 m or between about 0.1 m and about 10 m. An e refractive index of the liquid crystal layers disclosed herein can be between about 1.8 and about 2.0, between about 1.6 and about 1.8 or between about between about 1.4 and about 1.2. The resulting average diffraction efficiency of various diffraction gratings sed herein can be between about 1% and about 80%, between about 1% and about 50% or between about between about % and about 30%.

As a result of implementing various embodiments disclosed herein and throughout the disclosure, different zones can have indices of refraction that vary between about -30% and about +30%, between about -20% and about +20% or between about -10% and about +10% across the surface area of the diffraction grating, with respect to the e refractive index. As a further result, different zones can have diffraction efficiencies that vary between about 1% and about 80%, between about 1% and about 50% or between about 1% and about 30% across the surface area of the diffraction grating, with respect to the average diffraction efficiency.

Figures 11A and 11B illustrate a method for fabricating diffraction gs having liquid crystal molecules with non-uniform pre-tilt angles across the surface such as, e.g., diffraction gs 100A-100C of Figures 10A-10C described above, using photo-alignment techniques, according to embodiments.

Referring to an intermediate ure 100a of Figure 11A, a ate 104 is provided, on which a alignment layer 120 is formed. The substrate 104 can be an optically transparent substrate that is transparent in the e spectrum, such as, e.g., silicabased glass, quartz, sapphire, indium tin oxide (ITO) or polymeric substrates, to name a few examples.

As described herein, a alignment layer can refer to a layer on which, when a liquid crystal molecules are deposited, the liquid l molecules become oriented, for example, due to anchoring energy exerted on the liquid crystal molecule by the photoalignment layer. Examples of photo-alignment layers include ide, linear-polarization photopolymerizable polymer (LPP), azo-containing polymers, courmarine-containing polymers and cinnamate-containing polymers, to name a few.

The photo-alignment layer 120 can be formed by dissolving precursors, e.g., monomers, in a suitable solvent and coating, spin-coating, the surface of the substrate 104 with the solution. The solvent can thereafter be removed from the coated solution.

After coating and drying the photo-alignment layer 120, a photomask 130 can be used to expose different regions of the underlying photo-alignment layer 120 to different doses of light and/or different polarizations of light. For e, the regions of the photo-alignment layer 120 that are to be exposed ently can correspond to first (e.g., left) and second (e.g., right) regions of each of zones 108A-1 and 108A-2 described above with respect to the diffraction grating 100A of Figure 10A.

In some embodiments, the photo-alignment layer 120 can be ured such that the resulting liquid l molecules are oriented substantially parallel to the polarization direction of the exposure light (e.g., the azimuthal angle φ and the linear polarization angle of the exposure light are substantially the same). In other ments, the photo-alignment layer 120 can be configured such that the liquid crystal molecules are oriented substantially orthogonal to the zation direction of the exposure light (e.g., the azimuthal angle φ and the linear polarization angle of the exposure light are substantially offset by about +/-90 degrees).

In one example, the photomask 130 can be a gray-scale mask having a plurality of mask regions 130a-130d that are at least partially transparent and possibly have one or more opaque regions. Different ones of the plurality of mask regions 130a-130d may be configured to transmit ent s of the incident light 140, such that transmitted light 140a-140d transmitted through different ones of the plurality of mask regions 130a- 130d has varying intensities that are proportional to the relative transparency of the different mask regions 130a-130d to the incident light 140. However, embodiments are not so limited and other mask types can be used. For example, the photomask 130 can be a binary mask having the plurality of mask regions 130a-130d each being fully or nearly fully transparent or fully or nearly fully opaque, such that transmitted light 140a-140d transmitted through the plurality of mask regions 30d has binary ities.

The photomask 130 can be formed of a suitable material which at least partially s UV light. In some embodiments, the varying intensities of itted light across different mask regions 130a-130d can be achieved by using different materials (e.g., having different absorption coefficients) in the different regions, materials doped possibly different amounts in ent regions or by using different thicknesses in the different regions. Other types of masks can be used. In some embodiments, the photomask 130 can contact the ying photo-alignment layer 120, while in other embodiments, the photomask 130 does not contact the underlying photo-alignment layer 120.

The incident light can be UV light, e.g., from a high re Hg-lamp, e.g., for their spectral lines at 436 nm ("g-line"), 405 nm ("h-line") and 365 nm ("i-line").

However, embodiments are not so limited, and the incident light can be any suitable light to which the alignment layer 120 is responsive, including visible light. When polarized, the incident UV-light can be polarized using a suitable polarizer. Accordingly, in various cases, the mask is transmissive to UV-light. Other ways of patterning besides utilizing a photo-mask can be employed.

In some embodiments, the incident light 140 can be generated for a duration by using a single uniform incident light source. However, embodiments are not so limited, and in other embodiments, the incident light 140 can vary in intensity across different mask s 30d. Furthermore, in yet other ments, the incident light 140 can be ively generated for different durations across different mask s 130a- 130d.

Furthermore, in the illustrated ment, the incident light 140 can be polarized, e.g., linearly polarized, as schematically depicted by polarization vectors 134a- 134d. However, the incident light 140 according to other embodiments can be circularly or elliptically polarized. In some embodiments, the polarization vectors 134a-134d can ent different polarization angles, while in some other embodiments, the incident light 140 can have a single polarization angle.

Without being bound to any theory, the combination of the photoalignment material and the different doses and polarization(s) of the transmitted light 140a- 140d causes various regions of the ing photo-alignment layer 120 to exert different amounts of anchoring energy on the overlying liquid l molecules, thereby causing the different orientations of the liquid crystal les, as described herein. Other methods that may or may not employ masks may be used as well.

Referring to Figure 11B, after exposing the photo alignment layer 120 to varying doses of transmitted light 140a-140d using s techniques described above, a liquid crystal layer 116 can be formed on the photo alignment layer 120.

The liquid crystal layer 116 can be formed by dissolving liquid crystal precursors, e.g., monomers, in a suitable solvent and coating, e.g., oating, the surface of the alignment layer 120 with the solution having the liquid crystal precursors dissolved therein. The solvent can thereafter be removed from the coated solution In various embodiments, the reactive mesogen als used for forming the liquid crystal layer 116 include liquid crystalline mono- or di-acrylate, for example.

Because of the different doses and or polarization angle of light received by different regions of the photo ent layer 120 as described above, the liquid crystal layer, e.g., as-deposited, forms the liquid crystal layers 116A-1 and 116A-2 in zones 108A-1 and 108A-2, respectively. The liquid crystal layers 116A-1 and 116A-2, in turn, have first and second diffracting regions 116A-1L and 116A-1R, and L and 116A-2R, respectively. As described above with respect to Figure 10A, the first regions and second regions ate in the x-direction, where each of the first regions 116A-1L and 116A-2L has substantially the same first pre-tilt angle Φ, while the second regions 116A-1R and R have pre-tilt angles Φ that are different from each other and from the first pre-tilt angle of the first regions. Without being bound to any theory, in some types of lignment materials, exposure of the underlying photo-alignment layer 120 to light is ed to increase the anchoring energy that causes the in-plane alignment of the liquid crystal molecules. As a result, in these photo–alignment materials, increasing the exposure leads to a corresponding reduction in the pre-tile angle Φ of the liquid crystal layers formed n, according to embodiments. However, in other types of photo-alignment als, exposure of the underlying photo-alignment layer 120 to light is believed to decrease the anchoring energy that causes the in-plane alignment of the liquid crystal molecules. As a result, in these alignment materials, increasing the re leads to a corresponding increase in the pre-tilt angle Φ of the liquid crystal layers formed n, according to embodiments.

Thus, according to embodiments, the degree of tilt, as measured by the pre-tilt angle Φ, is inversely proportional to the dose of transmitted light received by the underlying photo-alignment layer 120. For example, in the illustrated embodiment, the photo-alignment layers 120A-1L and 120A-2L receive the highest amount of incident light, followed by the alignment layer 120A-1R, followed by the alignment layer 120-2R. As a , the resulting pre-tilt angles are highest for the second region 116A-2R of the zone 108A-2, followed by the second region 116A-1R of the zone , followed by the first regions 116A-1L and 116A-2L of the zones 108A-1 and 108A-2, respectively.

Figures C illustrate another method for fabricating diffraction gratings having non-uniform pre-tilt angles, e.g., diffraction gratings 100A-100C of Figures 10A-10C described above, using photo-alignment techniques, according to embodiments. In particular, in the illustrated embodiment, the method uses multiple exposures of the alignment layers prior to formation of the liquid crystals.

In the illustrated method of Figures C, similar to the method illustrated with respect to Figures B, a substrate 104 is provided on which a photoalignment layer 120 is formed. However, unlike the method illustrated with respect to Figures 11A-11B, prior to using a photomask 130 to expose different regions of the underlying photo-alignment layer 120 to different doses of light and/or different polarizations of light, the photo-alignment layer 120 is d to a primary (e.g., blanket) pattern of light using a first incident light 140A. The primary pattern of light may be ed using, e.g., t exposing using, e.g., a blanket semitransparent gray scale mask (not shown). In the illustrated ment, a mask may be omitted for the blanket exposure to the primary pattern of light.

The first incident light 140A can be polarized, e.g., linearly polarized at a first polarization angle, as schematically depicted by polarization vectors 134a-134d. The first incident light 140A that is linearly polarized can create a uniform alignment of the liquid crystal molecules. Subsequent to exposing to the primary (e.g., t) pattern of light, the alignment layer 120 may be further exposed to a ary pattern of light using a second incident light 140B and a photomask 130, which is configured to expose different regions of the underlying photo-alignment layer 120 to different doses of light and/or different polarizations of light, in a manner ntially similar to the method bed above with respect to Figures 11A-11B. For example, different regions of the photo-alignment layer 120 corresponding to first (e.g., left) and second (e.g., right) regions of each of zones 108A-1 and 108A-2 as described above with respect to the diffraction g 100A can be exposed to different doses and/or ent polarization of light. Unlike the first incident light 140A, the second incident light 140B can be unpolarized or circularly polarized. The second incident light 140B that is unpolarized or circularly polarized can redistribute alignment directions of the liquid l molecules. The resulting diffraction grating 100A is similar to that described above with respect to Figure 11B, where first regions and second regions alternate in the x-direction, and where each of the first regions 116A-1L and 116A-2L has substantially the same first pre-tilt angle Φ, while the second regions R and 116A-2R have lt angles Φ that are different from each other and from the first pre-tilt angle of the first regions.

The second incident light 140B can be polarized, e.g., ly polarized at a second polarization angle different from, e.g., onal to, the second polarization angle of the first incident light 140A, as schematically depicted by polarization vectors 134e-134h.

In some other embodiments, the first and second polarization angles are the same. In yet some other embodiments, the first and second polarization angles are different while not orthogonal. Furthermore, the second incident light 140B according to other embodiments can be circularly or elliptically polarized, having similar or different polarization orientation ve to the first incident light 140A.

In the embodiments described above in reference to Figures 11A-11B and Figures 12A-12C, methods of controlling pre-tilt angles of liquid crystals using photoalignment technique have been described. However, it will be appreciated that other embodiments are possible, including a process ed to as micro-rubbing, in which the ent layers are rubbed with a metallic object, e.g., a metallic sphere under a load. For example, a metallic sphere is in direct contact with the alignment layer may be moved across the alignment layer to creating micrometer-sized rubbed lines, which induce the pre-tilting of the subsequently deposited liquid crystals. In yet other embodiments, alignment materials pre- configured to induce different pre-tilt angles can be deposited, d of post-treating them to induce the pre-tilting of the liquid crystal molecules.

Referring now to Figures 13A and 13B, cross-sectional (x-z plane) views of ction gs 103A and 103B according to some other embodiments are illustrated.

The diffraction gratings 103A and 103B can be zation gratings (PGs), which are configured to locally modify the polarization state of transmitted light, which can be achieved by spatially varying birefringence and/or ism. While not shown for clarity, each of the diffraction gratings 103A and 103B comprises a substrate and an alignment layer formed thereon, and a plurality of differently arranged diffracting zones 154A-1 and 154A-2 in Figure 13A and diffracting zones 154B-1 and 154B-2 in Figure 13B. The diffracting zones 154A-1 and 154A-2 of the ction grating 103A have corresponding liquid crystal layers 144A-1 and 144A-2, respectively and diffracting zones 154A-1 and 154A-2 of the diffraction g 103B have corresponding liquid crystal layers 154B-1 and 154B-2, respectively.

Each of the liquid crystal layers 144A-1 and 144A-2 of the diffraction grating 103A in turn has a plurality of differently arranged diffracting regions a through g and 144A-2a through 144A-2g, respectively. Similarly, each of the liquid crystal layers 144B-1 and 144B-2 of the diffraction grating 103B in turn has a ity of differently arranged diffracting regions 144B-1a through 144B-1g and 144B-2a h 144A-2g, respectively.

Referring to the diffraction grating 103A of Figure 13A, each of the plurality of regions 144A-1a to 144A-1g of the zone 154A-1 and each of the plurality of regions 144A-2a to 144A-2g of the zone 154A-2 has liquid l molecules 112 that are d substantially along the same alignment direction within the same region. The liquid crystal molecules 112 of all regions of the zone 154A-1 have a first pre-tilt angle Φ that is substantially the same. In contrast, the liquid crystal molecules 112 of ent regions of the zone 154A-2 have different pre-tilt angles Φ. While in the illustrated embodiment, the pre-tilt angle Φ of a central region (144A-2d) of the zone 154A-2 has a pre-tilt angle Φ that is the smallest with increasing pre-tilt angles Φ for increasingly outer regions of the zone 154A- 2, embodiments are not so limited. In addition, while the central region (144A-2d) in the illustrated embodiment has a pre-tilt angle Φ that is similar to the first pre-tilt angle Φ of the zone 154A-1, ments are not so limited. The pre-tilt angles of different regions of the diffraction grating 103A can have any of the magnitudes described supra with t to Figures 10A-10C.

Still referring to Figure 13A, in the rated embodiment, the liquid crystal molecules 112 of different regions of the zone 154A-1 have different azimuthal angles φ. However, embodiments are not so limited and in other embodiments, the liquid crystal molecules 112 of different regions of the zone 154A-1 can have the same azimuthal angles φ. The azimuthal angles of different regions of the diffraction grating 103A can have any of the magnitudes described infra with respect to Figures 15A-15C.

Referring to the diffraction grating 103B of Figure 13B, similar to the diffraction grating 103A of Figure 13A, each of the plurality of regions 144B-1a to 144B-1g of the zone 154B-1 has liquid l molecules 112 that are aligned substantially along the same alignment direction within the same region. Similar to the zone 154A-2 of the diffraction grating 103A of Figure 13A, the liquid crystal molecules 112 of different regions of the zone 154B-1 have substantially different lt angles Φ and substantially different azimuthal angles φ. In contrast, each of the plurality of regions 144B-2a to g of the zone 154B-2 has liquid crystal molecules 112 that are aligned substantially ently within the same region. That is, the individual liquid crystal molecules 112 of each region of the zone 154B-2 have substantially different pre-tilt angles Φ and substantially different azimuthal angles φ. For example, the liquid crystal les 112 of each region of the zone 154B-2 can have chirality, as described more in detail with respect to Figures 19A and 19B, infra.

Still referring to Figures 13A and 13B, while specific combinations of zones and regions within different zones have been presented as examples, it will be appreciated that the zone and regions within the zones can be mixed and matched. For example, a combination of the zone 154A-1 of Figure 13A and the zone 154B-2 of Figure 13B in a diffraction grating is possible.

Figures 14A-14B illustrate another method for fabricating ction gratings having non-uniform pre-tilt angles, e.g., diffraction gs 103A and 103B of s 13A and 13B, respectively, using photo-alignment techniques, ing to embodiments. In particular, in the illustrated embodiment, the method comprises polarization interference holographic re using a gray-scale mask, according to embodiments.

Polarization interference holographic exposure is a technique to create an interference pattern using multiple beams of nt light. While most conventional holography uses an intensity modulation, polarization holography es a modulation of the polarization state to create an interference pattern.

Referring to Figure 14A, in the illustrated method, processes leading up to exposing the photo-alignment layer 120 to UV light is similar to the method described above with respect to Figures B. In particular, the photo-alignment layer 120 is formed on a substrate 104 and a gray scale mask 130 is disposed partially over the photo-alignment layer 120. Thereafter, a plurality of coherent light beams 142a, 142b having ent polarizations are directed to the plurality of differently arranged diffracting zones 154A-1 and 154A-2. In the illustrated embodiment, the light beams 142a and 142b include orthogonal ar polarized light beams. r, the light beams 142a and 142b can include non-orthogonal circular polarized light beams, for example. In the illustrated embodiment, the zone 154A-1 is exposed while the zone 154A-2 is masked with the gray scale mask 130. The plurality of light beams 142a and 142b are positioned and polarized such that the resulting interference effect results in the liquid crystal layers 144A-1 and 144A-2 of the diffraction grating 103A having a plurality of differently arranged diffracting regions 144A-1a through 144A-1g and 144A-2a through g, respectively, as described above with respect to Figure 13A.

Similarly, using similar concepts, referring back to Figure 13B, the liquid crystal layers 144B-1 and 144B-2 of the diffraction grating 103B having a ity of differently ed diffracting regions 144B-1a through 144B-1g and 144B-2a through 144B-2g, respectively, can be fabricated.

Referring to s 15A-15C, top-down views (viewed along the x-y plane) of diffraction gratings 150A-150C ing to various embodiments are illustrated.

Because Figures 15A-15C are top down views, only the liquid crystal layers (as opposed to the alignment layer or substrate) are illustrated, while underlying features are not shown.

However, it will be tood that the liquid crystal layer of each of the diffraction gratings 150A-150C is formed over a substrate and comprises a plurality of diffracting zones, i.e., diffracting zones 148A-1, 148A-2,…and 148A-n in Figure 15A, diffracting zones 148B-1, 148B-2,…and 148B-n in Figure 15B, and diffracting zones , 148C-2,…and 148C-n in Figure 15C.

The diffracting zones of each of the diffraction gratings 150A-150C have a periodically ing lateral ion or a grating period  and include corresponding liquid crystal layers formed of liquid crystal molecules 112. The lateral ion or the grating  can be similar to those described above with respect to s 10A-10C.

Analogous to Figures 10A-10C, the diffracting zones 148A-1, 148A- 2,…148A-n of the diffraction grating 150A have corresponding liquid crystal layers 156A-1, 156A-2,… 156A-n, respectively; diffracting zones 148B-1, 148B-2,…148B-n of the diffraction grating 150B have corresponding liquid crystal layers 156B-1, 156B-2,…156B-n, respectively; and diffracting zones 148C-1, 148C-2,…148C-n of the diffraction grating 150C have corresponding liquid crystal layers 156C-1, 156C-2 and 156C-n, respectively. The number of each type of diffracting zones can be similar to those described above with respect to Figures 10A-10C. In addition, the diffracting zones as arranged can periodically repeat any suitable number of times.

Each of the liquid crystal layers 156A-1, 156A-2 and 156A-n of the diffraction grating 150A in turn has differently arranged first and second diffracting regions 156A-1L and 156A-1R, 156A-2L and 156A-2R,…and 156A-nL and 156A-nR, respectively.

Similarly, each of the liquid crystal layers 156B-1, 156B-2 and 156B-n of the diffraction grating 150B in turn has differently arranged first and second diffracting regions 156B-1L and 156B-1R, L and 156B-2R,…and 156B-nL and 156B-nR, respectively. Similarly, each of the liquid crystal layers 156C-1, 156C-2 and 156C-n of the diffraction grating 150C in turn has differently arranged first and second diffracting regions 156C-1L and 156C-1R, 156C-2L and 156C-2R,…and 156C-nL and 156C-nR, respectively.

Analogous to the diffraction gratings 100A-100C described above with t to FIGS. 10A-10C, each of the different diffracting zones further comprises an ent layer (not shown) interposed between the ate and the corresponding liquid l layer. That is, while not shown for clarity, interposed between the substrate 104 and differently arranged first/second diffracting regions L/156A-1R, 156A-2L/156A- 2R,…and 156A-nL/156A-nR of the ction grating 150A of Figure 15A are first and second alignment layers 160A-1L/160A-1R, L/160A-2R,…and 160A-nL/160A-nR, respectively. Similarly interposed between the substrate 104 and differently arranged first/second diffracting regions 156B-1L/156B-1R, 156B-2L/156B-2R,…and 156B-nL/ 156B-nR of the diffraction grating 150C of Figure 15B are first/second ent layers 160B-1L/160B-1R, 160B-2L/160B-2R,…and L/160B-nR, respectively. Similarly, interposed between the substrate 104 and differently arranged first/second diffracting regions 156C-1L/156C-1R, 156C-2L/156C-2R,…and L/156C-nR of the diffraction grating 150C of Figure 15C are second alignment layers 160C-1L/160C-1R, 160C-2L/ 160C- 2R,…and 160C-nL and 160C-nR, respectively.

Still referring to Figures 15A-15C, each zone of the ction gratings 150A, 150B and 150C include first and second regions that alternate in the x-direction. Each of the first regions 156A-1L, 156A-2L,… and 156A-nL of the diffraction grating 150A, each of the first regions 156B-1L, L,… and 156B-nL of the diffraction grating 150B and each of the first regions L, 156C-2L,… and L of the diffraction grating 150C have liquid crystal molecules 112 that are d substantially along the same first alignment ion and have an azimuthal angle φ that is substantially the same. In contrast, each of the second regions 156A-1R, 156A-2R,… and 156A-nR of the diffraction grating 150A, each of the second regions 156B-1R, R,… and 156B-nL of the diffraction grating 150B and each of the second regions 156C-1R, 156C-2R,… and R of the diffraction grating 150C have liquid crystal molecules 112 that are aligned substantially along a second alignment direction different from the first alignment direction and have a second azimuthal angle φ that is different, e.g., smaller, than the first azimuthal angle φ of the respective first s.

In each of the diffraction gratings 150A-150C of Figures 15A-15C, respectively, at least some of the diffracting zones have liquid crystal layers formed of liquid crystal molecules that are spatially arranged differently, e.g., have azimuthal angles that are different from each other (Figures 15A and 15C), or have different duty cycles that are different from each other es 15B and 15C), such that the diffracting zones have different optical properties, e.g., different refractive indices and/or different diffraction efficiencies, according to embodiments.

In particular, referring to diffraction grating 150A of Figure 15A, in addition to having alignment directions and azimuthal angles φ that are different from the first azimuthal angle φ of the first regions 156A-1L, 156A-2L,… and L, the liquid crystal les of the second regions 156A-1R, R,…and 156A-nR are aligned along second alignment directions that are different from each other. For example, in the illustrated embodiment, the zones 148A-1, 148A-2 and 148A-n are ed such that the first regions and second regions alternate in the x-direction, where each of the first regions 156A-1L, 156A-2L,… and 156A-nL has substantially the same azimuthal angle φ, while the second regions 156A-1R, 156A-2R,…and 156A-nR have azimuthal angles φ that are different from each other. By way of example, the first regions 156A-1L, 156A-2L,…and 156A-nL have a an azimuthal angles φ that is between about 0 and about 15 s or between about 0 and 10 degrees, for instance 0 degrees. The second regions 156A-1R, 156A-2R,…and 156A-nR can have azimuthal angles φ that are different from each other, where each can be n about 75 degrees and about 90 degrees, for instance about 90 degrees; between about 60 degrees and about 90 degrees or n about 65 degrees and about 85 degrees, for instance about 75 ; n about 30 degrees and about 60 degrees or between about 35 degrees and about 55 degrees, for instance about 45 s; between about 10 degrees and about 40 degrees or between about 15 degrees and about 35 degrees, for instance about 25 degrees.

Still ing to Figure 15A, in some embodiments, as illustrated, the second regions 156A-1R, 156A-2R,…and 156A-nR can have azimuthal angles φ that vary, e.g., increase or decrease in one direction in a lateral direction, such that a gradient in diffraction properties is created. In other embodiments, the second regions 156A-1R, 156A- 2R,…and 156A-nR can have azimuthal angles φ that do not vary in one direction in the lateral direction.

Still referring to Figure 15A, the duty cycle can be between about 10% and about 30%, between about 30% and about 50%, between about 50% and about 70% or between about 70% and about 90%, which in the illustrated embodiment is substantially constant in the x-direction.

Referring now to Figure 15B, as discussed above, the diffraction grating 150B share some common features as the diffraction grating 150A of Figure 15A. However, unlike the diffracting g 150B of Figure 15A, while the liquid crystal molecules of different second regions 156B-1R, 156B-2R,…and 156B-nR have azimuthal angles φ that are different from the first azimuthal angle φ of the first regions 156B-1L, 156B-2L,… and 156B-nL, they are not d differently from each other. For example, in the illustrated embodiment, the zones 148B-1, 148B-2 and 148B-n are arranged such that the first regions and second regions alternate in the x-direction, where each of the first regions 156B-1L, L,… and 156B-nL has substantially the same first azimuthal angle φ, and each of the second s 156B-1R, 156B-2R,…and 156B-nR has substantially the same second azimuthal angle φ. The first and second azimuthal angles of the first and second regions can have any of the values discussed above with respect to the diffraction grating 150A of Figure r, unlike the grating 150A of Figure 15A, the zones 148B-1, 148B-2 and 148B-3 have substantially the same azimuthal angle, e.g., between about 0 to 50 degrees, while having substantially different duty cycles, e.g., between about 40% and about 60%, for instance about 50%; between about 30% and about 50%, for instance about 40% and a duty cycle between about 20% and about 40%, for instance about 30%, respectively, such that the diffraction grating 150B has spatially varying optical properties.

Still referring to Figure 15B, in some embodiments, as illustrated, the zones can have duty cycles that vary, e.g., increase or decrease in one direction in a lateral direction, such that a gradient in optical properties is created. In other embodiments, the duty cycles do not vary in one direction in the l direction.

Referring now to Figure 15C, the illustrated diffraction grating 150C es features similar to those described above with respect to the diffraction gs 150A and 150B of Figures 15A and 15B. In particular, the liquid crystal molecules of different second regions 156C-1R, 156C-2R,…and 156C-nR can have azimuthal angles φ that are different from the first azimuthal angles φ of the first regions 116C-1L, 116C-2L,… and 116C-nL, and ent from each other. In addition, the duty cycle varies between adjacent zones across a lateral direction, e.g., x-direction. The first and second azimuthal angles of the first and second regions can have any of the values discussed above with respect to the diffraction g 150A of Figure 15A. In addition, the duty cycle variation n adjacent zones across a lateral direction, e.g., x-direction, can also have values discussed above with t to the diffraction grating 150B of Figure 15B.

Referring now to Figures 16A, a top-down view (x-y plane) of a diffraction g 160 according to some other embodiments are illustrated, in which azimuthal angles of liquid crystal molecules rotate across a lateral length of a zone. The diffraction grating having such arrangement is sometimes ed a polarization grating.

While not shown for clarity, the diffraction grating 160 comprises a substrate and an alignment layer formed thereon, and a plurality of differently arranged diffracting zones 164- 1 and 164-2. The diffracting zones 164-1 and 164-2 have corresponding liquid l layers 168-1 and 168-2, respectively. Each of the liquid crystal layers liquid l layers 168-1 and 168-2 of the diffraction grating 160 in turn has a plurality of differently arranged diffracting regions 168-1a to 168-1i and 168-2a to 168-2i, respectively. Each of the plurality of regions 168-1a to 168-1i of the zone 164-1 and each of the plurality of regions 168-2a to 168-2i of the zone 164-2 has liquid crystal molecules 112 that are aligned substantially along the same alignment direction within the same region. Thus, it will be understood that, each of the zones include a stack of liquid l molecules d in the z-direction.

The liquid crystal molecules 112 of each of the diffracting regions 168- 1a to 168-1i of the zone 164-1 and regions 168-2a to 168-2i of the zone 164-2 have substantially the same azimuthal angle φ within the same region. However, the liquid crystal molecules 112 of different diffracting regions have substantially different azimuthal angles.

In addition, the liquid crystal molecules 112 of different diffracting regions can have substantially the same or different pre-tilt angle Φ, similar to as described above with respect to Figures 13A and 13B.

In the illustrate ment, the liquid crystal molecules 112 of each of the diffracting regions 168-1a to 168-1i of the zone 164-1 and the corresponding regions 168- 2a to 168-2i of the zone 164-2 have substantially the same azimuthal angle φ within the same region. However, distances between adjacent regions are substantially different between the zone 164-1 and the zone 164-2, such that spatially g diffraction properties are ted, as illustrated in reference to Figure 16B. Referring to Figure 16B, a graph 162 schematically showing the azimuthal angle φ as a function of a lateral position x for the diffraction grating 160 in Figure 16A is illustrated. The x-axis represents a lateral distance in the x-direction and the y-axis represents the azimuthal angle φ. The curves 162-1 and 162-1 represent the azimuthal angle φ as a function of the lateral position x for the zone 164-1 and the zone 164-2, respectively.

Referring back to Figure 16A, the liquid crystal molecules 112 of the diffracting region 164-1 are arranged such that the rate of change in azimuthal angle φ per a unit of l length, i.e., φ/x in the ction, is relatively nt, as illustrated by the curve 162-1 of Figure 16B. In contrast, the liquid l les 112 of the diffracting region 164-2 are arranged such that the φ/x in the x-direction varies ntially across x, as illustrated by the curve 162-2 of Figure 16B. As a result, the curve 162-2 is characterized by a central region of the zone 164-2 in which the φ/x varies relatively slowly and end regions of the zone 164-2 in which the φ/x varies relatively rapidly. As a result, the diffraction properties (including efficiencies and refractive indices) differ from those of the g with a uniform variation of its azimuthal angle of liquid crystals.

Figures 17A-17E illustrate a method for fabricating diffraction gratings having non-uniform azimuthal angles, e.g., diffraction gratings 150A-150C of Figures 15A- 15C described above, using photo-alignment techniques, according to embodiments. In ular, in the illustrated embodiment, the method uses multiple exposures of the alignment layers prior to deposition of the liquid crystals. In the illustrated method of Figures 17A-17E, similar to the method illustrated with respect to Figures 11A-11B, a substrate 104 is provided on which a photo-alignment layer 120 is formed.

Referring to an intermediate structure 150A illustrated in Figure 17A, after forming the photo-alignment layer 120 on the ate 104, a first photomask 174A is used to expose different regions of the underlying photo-alignment layer 120 to different doses of light and/or different polarizations of light. For e, different regions of the photoalignment layer 120 corresponds to first (e.g., left) and second (e.g., right) s of each of the zones 148A-1 and 148A-2 as described above with respect to the diffraction grating 150A in Figure 15A.

In some embodiments, the first photomask 174A can be a gray-scale mask having a plurality of mask regions 174Ato 174A-4 that are at least partially transparent and possibly have one or more opaque s. ent one of the ity of mask regions 174Ato 174A-4 may be configured to it different doses of a first incident light 172A, such that transmitted light 172A transmitted through different ones of the plurality of mask regions have g intensities that are proportional to the relative transparency of the different mask regions. In other embodiments, the photomask 174A can be a binary mask having the plurality of mask regions 174Ato 174A-4 each being fully or nearly fully transparent or fully or nearly fully opaque, such that transmitted light 172A has binary intensities. In the illustrated example, the first nt light 172A can be polarized, e.g., linearly polarized at a first angle, e.g., 0 degrees, as schematically depicted by polarization vectors 178A, and substantially transmits h the mask regions 174A-1 and 174A-3 corresponding to first (e.g., left) regions of each of the zones 148A-1 and 148A-2 of the diffraction grating 150A as illustrated in Figure 15A, while substantially being blocked in other regions. ing to an ediate structure 150B illustrated in Figure 17B, after exposing different regions of the photo-alignment layer 120 to the first incident light 172A, a second photomask 174B is used to expose different regions of the underlying photoalignment layer 120 to different doses of light and/or different polarizations of light using a second incident light 172B.

In some ments, the second photomask 174B can be a gray-scale mask different from the first photomask 174A and having a plurality of mask regions 174B- 1-to 174B-4 that are at least partially transparent and possibly have one or more opaque regions. Different ones of the plurality of mask regions 174Bto 174B-4 may be configured to transmit different doses of the second incident light 172B. In other embodiments, the photomask 174B can be a binary mask having the plurality of mask regions 174Bto 174B-4 each being fully or nearly fully arent or fully or nearly fully opaque, such that itted light 172B has binary intensities. The second incident light 172B can be zed, e.g., linearly polarized at a second angle different, e.g., orthogonal, from the first zation angle of the first incident light 178A. For example, the second incident light 172B can be orthogonally linearly polarized relative to the first incident light 172A, e.g., at 90 degrees, as schematically depicted by polarization vectors 178B and substantially transmits through the mask region 174B-2 corresponding to a second (e.g., right) region of the zone 148A-1 of the diffraction grating 150A illustrated in Figure 15A, while substantially being blocked in other regions.

Referring to an intermediate structure in Figure 17C, after ng different regions of the photo-alignment layer 120 to the second incident light 172B, a third photomask 174C is used to expose different regions of the underlying photo-alignment layer 120 to different doses of light and/or different zations of light using a third incident light 172C.

In some embodiments, the third photomask 174C can be a cale mask different from the first and second photomasks 174A, 174B and having a plurality of mask regions 174Cto 174C-4 that are at least partially transparent and ly have one or more opaque regions. Different ones of the plurality of mask regions 174Cto 174C-4 may be configured to transmit ent doses of the third incident light 172C. In other embodiments, the photomask 174C can be a binary mask having the ity of mask regions 174Cto 174C-4 each being fully or nearly fully transparent or fully or nearly fully opaque, such that transmitted light 172C has binary intensities. The third incident light 178C can be zed, e.g., linearly polarized at a third angle different from the first and second polarization angles of the first and second incident lights 178A and 178B. In the illustrated embodiment, the third incident light 172C is linearly polarized at 45 degrees, as schematically ed by polarization vectors 178C and substantially transmits through the mask region 174A-4 corresponding to a second (e.g., right) region of the zone 148A-2 of the ction grating 150A illustrated in Figure 15A, while substantially being blocked in other regions.

Referring to s 17D (cross-sectional view) and 17E (top-down view), after ng ent regions of the photo alignment layer 120 through the multi-exposure process described above with respect to Figures 17A-17C, a liquid crystal layer can be deposited on the photo alignment layer 120. As a result of the different doses and/or polarizations of light received by different regions of the photo alignment layer 120, differently configured liquid crystal layers 156A-1 and 156A-2 are formed in respective zones 148A-1 and 148A-2, respectively. The liquid crystal layers 156A-1 and 156A-2 have first and second diffracting regions 156A-1L and 156A-1R and 156A-2L and 156A-2R, respectively. As described above with respect to Figure 15A, the first regions and second regions ate in the x-direction, where each of the first regions 156A-1L and 156A-2L has substantially the same first azimuthal angle φ, while the second regions 156A-1R and 156A-2R have azimuthal angles φ that are different from each other and from the first hal angle of the first regions. Without being bound to any theory, in some cases, exposure of the underlying photo-alignment layer 120 to light having different polarization angles leads to different azimuthal angles of the liquid l molecules.

Still referring to FIGS. 17D and 17E, the azimuthal angle φ of the liquid crystal molecules can be determined by the linear polarization angle of the exposure light and the type of photo-alignment layer 120. In the illustrated embodiment, the photo-alignment layer 120 is configured such that the degree of rotation of the liquid crystal molecules, as measured by an absolute value the azimuthal angle φ up to +/- 90 degrees, is ined by the linear polarization orientation angle of transmitted light received by the underlying alignment layer up to +/- 90 degrees. In some ments, such as the illustrated embodiment, the alignment layer 120 can be configured such that the liquid crystal molecules are oriented substantially parallel to the polarization direction of the exposure light (e.g., the azimuthal angle φ and the linear polarization angle of the exposure light are ntially the same). Embodiments are not so limited, however, and in other embodiments, the photo-alignment layer 120 can be configured such that the liquid crystal molecules are oriented substantially orthogonal to the polarization direction of the exposure light (e.g., the azimuthal angle φ and the linear polarization angle of the exposure light are substantially offset by about +/-90 degrees). For example, in the illustrated embodiment, the photo-alignment layers L and 160A-2L receive light with the same linear polarization orientation and the photo ent layer 160A-1R receives light with the larger ence in linear polarization orientation angle with respect to the linear polarization orientation of the photo-alignment layers 160A-1L and 160A-2L, followed by the photo alignment layer 160A-2R. As a result, the resulting azimuthal angles are the same for the first regions 156A-1L and 156A-2L and the difference in the ing azimuthal angles with respect to the first regions 156A-1L and 156A-2L is larger for the second region 156A-1R than that for the second region 156A-2R In s embodiments described herein, photomasks can comprise linear polarizers such as wire-grid polarizers having a regular array of parallel metallic wires placed in a plane perpendicular to the direction of propagation of the nt light. In some embodiments described herein, the photomasks may be configured to e illumination having uniform polarization angle across the photo-alignment layer. When comprising wiregrid polarizers, these embodiments may be realized by configuring the array of metallic wires to be uniform across the photomasks, e.g., m in the thickness and/or the density of the metallic wires. In other embodiments, the photomasks may be configured to e illumination having non uniform or having multiple polarization angles across different regions of the photo-alignment layer. When comprising wire-grid polarizers, these embodiments may be realized by configuring the array of metallic wires to be nonuniform and varying across the photomasks, e.g., nonuniform and varying in the thickness and/or the density of the metallic wires. Thus, varying the thickness and density of metallic wires, both the polarization angle and the ittance of the light can be controlled, according to various embodiments.

Figures 18A-18D illustrate another method for ating a diffraction grating 160 according to some other ments, in which azimuthal angles of liquid crystal molecules rotate across a lateral length of a zone, e.g., polarization grating. In ular, in the illustrated embodiment, the method uses polarization interference holographic re using a gray-scale mask, according to embodiments.

Referring to Figure 18A showing an intermediate structure 160A, in the illustrated method, processes leading up to forming the photo-alignment layer 120 to UV light is similar to the method described above with t to Figures 17A-17E. Thereafter, a plurality of coherent light beams 182A, 182B having ent polarizations are directed to the plurality of ently arranged diffracting zones 164A-1 and 164A-2. In the illustrated embodiment, the light beams 182A and 182B include orthogonal circular zed light beams. However, the light beams 182A and 182B can include elliptical polarized light beams, for example. In the illustrated embodiment, both zones 164-1 and 164-2 are unmasked.

Thereafter, referring to Figure 18B showing an ediate structure 160B, a photomask 184 is used to expose different zones of the underlying photo-alignment layer 120 to ent doses of light and/or different polarizations of light using a linearly polarized incident light 188 having any polarization angle discussed above with respect to Figures 17A-17E. For example, different zones of the photo-alignment layer 120 may correspond to the zones 164-1 and 164-2 as described above with respect to the diffraction grating 160 in Figure 16B. As a result of the secondary exposure to linearly polarized light 188, a fraction of the photo-alignment layer 120 can be realigned. t being bound to any theory, when the photo-alignment layer 120 is exposed twice with different linear polarization orientations, the orientations of the liquid crystal molecules can be determined by the relative linear polarization orientations and the re doses of two exposures. ing now to Figures 18C and 18D, a cross-sectional view (x-z plane) and a top-down view (x-y plane) of the diffraction grating 160 corresponding to that in Figure 16B is illustrated. At least in part as a result of the first and second exposures as described above with respect to Figure 18A and 18B, liquid crystal layers 168-1 and 168-2 having a plurality of differently arranged diffracting regions 168-1a to 168-1i and 168-2a to 168-2i are generated, respectively. Each of the plurality of regions 168-1a to 168-1i of the zone 164-1 and each of the ity of regions 168-2a to 168-2i of the zone 164-2 has liquid crystal molecules 112 that are aligned ntially along the same alignment direction within the same region. Thus, it will be understood that, each of the zones include a stack of liquid crystal molecules stacked in the z-direction.

Spatially Variable Liquid l Diffraction Gratings Based on Spatially Varying Liquid Crystal als In various embodiments discussed supra, the liquid crystal molecules are fabricated using photo-alignment techniques. However, other embodiments are possible, which can be fabricated with or without photo-alignment.

Referring to Figures 19A and 19B, top-down (viewed along the x-y plane) and side (viewed along the x-z plane) views of a diffraction grating 190, which can be fabricated with or without photo-alignment, according to some ments are illustrated.

The diffraction grating 190 comprises a plurality of diffracting zones, i.e., diffracting zones 198-1, 198-2,…and 198-n that have a periodically repeating lateral dimension or a g period  and include corresponding liquid crystal layers formed of liquid crystal les 112. The lateral dimension or the grating period  can be similar to those described above with respect to Figures 10A-10C.

The diffracting zones 198-1, 198-2,…198-n of the diffraction grating 190 have corresponding liquid l layers 186-1, 186-2,… 186-n, respectively. The number of each type of diffracting zones can be similar to those described above with respect to Figures 10A-10C. In addition, the diffracting zones as arranged can periodically repeat any le number of times. Each of the liquid crystal layers 186-1, 186-2 and 186-n of the diffraction grating 190 in turn has differently arranged first and second diffracting regions 186-1L and 186-1R, 186-2L and 186-2R,…and 186-nL and 186-nR, respectively.

The different liquid crystal layers 186-1, 186-2 and 186-n have liquid crystal les 112 that are arranged to have different degrees of chirality. As described above, chirality can be described by a chiral pitch, p, which can refer to the distance over which the liquid crystal molecules undergo a full 360° twist. The ity can also be characterized by a twist deformation angle, which is an angle of twist the liquid l molecules undergo within a thickness of the liquid crystal layer. For example, in the rated embodiment, the first liquid crystal layer 186-1 has the first and second cting regions 186-1L and 186-1R that have liquid crystal les 112 having different azimuthal angles with little or no chirality (very large or infinite chiral pitch p). The second and third liquid crystal layers 186-2 and 186-n have respective first/second diffracting regions 186- 2L/186-2R and 186-nL/186-nR, respectively, that have liquid crystal molecules 112 having substantial and substantially different degrees of chirality. Similarly, in various embodiments, the azimuthal angles of or the difference in azimuthal angles n the uppermost liquid crystal molecules in the first and second diffracting regions 186-2L/186-2R and 186-nL/186-nR of the second and nth liquid crystal layers 186-2 and 186-n, respectively, can be any value described above with respect to the diffraction gs 150A-150C in Figures 15A-15C In some embodiments, each pair of first/second diffracting s within a zone, e.g., the pair of regions 186-2L/186-2R of the zone 198-2 (see Figure 19A) and the pair of s 186-nL/186-nR of the zone 198-n have uppermost liquid crystal les that have different azimuthal angles φ but have the same chiral pitch p. In some other embodiments, the pairs of regions within zones have uppermost liquid crystal molecules that have the same azimuthal angles φ but have different chiral s p. In various ments, a chiral twist (e.g., twist angle or twist deformation angle) of the liquid crystal molecules in a given region of the pair of regions 186-2L/186-2R of the zone 198-2 and the pair of regions 186-nL/186-nR of the zone 198-n can be, e.g., about +/-45o, about +/-90o, about +/-135o, or about +/-180o. The corresponding chiral period p can be 8D, 4D, or 3D, where 2D is the thickness of the liquid crystal .

For example, in the illustrated embodiment, the uppermost liquid crystal molecules of the first and second regions 186-2L and 186-2R have first and second azimuthal angles φ of, e.g., 135o and 45o, respectively, while having a first chiral pitch, e.g., of about 8D, where D is the thickness of the liquid crystal layers. As a result, in each of the first and second regions 186-2L and 186-2R, the uppermost liquid crystal molecule and the lowermost liquid crystal molecule are twisted relative to each other by about -45 degrees. In addition, in the illustrated embodiment, the uppermost liquid crystal molecules of the first and second regions 186-nL, 186-nR have third and fourth hal angles φ of, e.g., 90o and 0o, tively, while having a second chiral pitch of about 4D, where D is the thickness of the liquid l layers. As a result, in each of the first and second regions 186-nL and 186-nR, the ost liquid crystal molecule and the lowermost liquid crystal molecule are twisted ve to each other by about -90 degrees. r, the hal angles φ of uppermost liquid crystal molecules of the second diffracting regions /186-2R and 186- nL/186-nR can have any value such as described above with respect to Figure 15A-15C.

Still referring to Figures 19A and 19B, in some embodiments, the liquid crystal les 112 in each region have the same pre-tilt angle Φ, which can be zero or higher.

Still referring to Figures 19A and 19B, the duty cycle of different liquid crystal layers 186-1, 186-2 and 186-n, can be different, and each can be n about 10% and about 30%, between about 30% and about 50%, between about 50% and about 70% or between about 70% and about 90%.

Referring now to Figure 20, cross-sectional side (x-z plane) view of a diffraction grating 200 according to some other embodiments are illustrated. While not shown for clarity, the diffraction grating 200 comprises a substrate and a plurality of differently arranged diffracting zones 208-1 and 208-2 having corresponding liquid l layers 196-1 and 196-2, respectively. Each of the liquid crystal layers liquid crystal layers 196-1 and 196-2 of the diffraction grating 200 in turn has a plurality of differently arranged diffracting regions 196-1a through 196-1g and 196-2a through 196-2g, respectively.

Similar to liquid crystal molecules 112 of the liquid crystal layer 186-1 of Figures 19A/19B, the liquid crystal molecules 112 of the diffracting regions 196-1a through 196-1g of the liquid crystal layer 196-1 illustrated in Figure 20 has different azimuthal angles but little or no chirality (very large or infinite chiral pitch p) from layer to layer. The azimuthal angles and other arrangements of adjacent diffracting regions 196-1a through 196- 1g are similar to those described with respect to the first and second diffracting regions 186- 1L and 186-1R with respect to Figures 19A/19B.

Similar to liquid crystal molecules 112 of the liquid crystal layers 186-2 and 186-n of Figures 19A/19B, the liquid crystal les 112 of the diffracting regions 196-2a through 196-2g of the liquid crystal layer 196-2 illustrated in Figure 20 have substantial and ntially ent s of chirality along the length of the zone (along the x direction), and have uppermost liquid molecules that have different azimuthal angles.

The azimuthal angles, the chirality and other arrangements of adjacent diffracting regions 196-2a through 196-2g are similar to those described with respect to the first and second diffracting regions 186-2L/186-2R and 186-nL/186-nR of the second and nth liquid crystal layers 186-2 and 186-n.

It will be iated that, when a twist is induced to liquid crystal molecules as illustrated above with respect to Figures 19A/19B and 20, the resulting diffraction grating ts spatially varying diffraction properties, ing refractive index and diffraction efficiencies. Some liquid crystal molecules can be made chiral by substituting one or more of the carbon atoms asymmetrically by four different ligands. Other liquid crystal molecules can be made chiral by adding mesogenic or sogenic chiral dopants at varying concentration to one of liquid crystal phases described above. According to embodiments, by adding small concentrations, including, for e, but not limited to below 5%–10% by weight, chirality related effects can be increased with the concentration of the dopant. Some examples of chiral liquid crystal les include cholesteryl-benzoate, a ferroelectric liquid crystal N(p-n-Decyloxybenzylidene) p-amino 2-methylbutyl cinnamate (DOBAMBC), and achiral MBBA (4-butyl-N-[4-methoxy-benzylidene]-aniline), which is a room temperature nematic, doped with chiral R1011. Other chiral liquid crystal molecules may be used.

Referring to Figure 21, a side view (viewed along the x-z plane) of a diffraction grating 210, which can be fabricated with or without photo-alignment, according to some embodiments are illustrated. The diffraction g 210 comprises a plurality of diffracting zones, i.e., diffracting zones 218-1, 218-2,…and 218-n that have a periodically repeating lateral dimension or a grating period  in a similar manner to those described above with respect to Figures 10A-10C. The diffracting zones 218-1, …and 218-n of the diffraction grating 210 have ponding liquid l layers 206-1, … and 206- n, respectively. The number of each type of diffracting zones can be similar to those described above with respect to Figures 10A-10C. In addition, the diffracting zones as arranged can periodically repeat any suitable number of times.

In the diffraction grating 210, different liquid crystal layers 206-1, 206-2 and 206-n comprise different liquid crystal als. In ular, first and second diffracting s 206-1L and 206-1R, 206-2L and 206-2R,…and 206-nL and 206-nR have liquid crystal molecules 212-1L and 212-1R, 212-2L and 212-2R,…and 212-nL and 212-nR, respectively which can be the same or different liquid crystal molecules. For example, in some implementations, regions within a first zone can have a first liquid crystal material, regions within a second zone can have a first liquid crystal material and regions within a third zone can have a third liquid crystal material. In other implementations, any given zone can have a first region having a first liquid crystal material and a second region having a second liquid crystal material. Accordingly, the optical properties can be changed along the length of the diffraction grating by changing the composition of the material, for example, using the same host material with different level of the same dopant (or with different dopants with same or different levels), and not ary changing the orientation of the liquid crystal molecules.

In some embodiments, different zones have different liquid crystal molecules while other s of the liquid crystal orientation, e.g., the tilt angle, the azimuthal angle, and ity as described above are similar or the same n different zones. In some other embodiments, different zones have different liquid crystal molecules while having other aspects of the liquid crystal orientation, e.g., the tilt angle, the azimuthal angle, and chirality that are also different, as discussed supra in the context of s embodiments.

By depositing different liquid crystal materials during deposition or by modifying the liquid crystal material after deposition, local birefringence can be lled to be different across different zones. In various embodiments, birefringence of individual zones can be between about 0.05 and about 0.15, for instance about 0.10, between about 0.15 and about 0.25, for instance about 0.2, and between about 0.25 and about 0.35, for instance about 0.3.

Additional Examples In a 1st e, a diffraction grating includes a plurality of different diffracting zones having a periodically repeating lateral dimension corresponding to a g period adapted for light diffraction. The diffraction grating onally includes a plurality of ent liquid crystal layers corresponding to the different diffracting zones. The ent liquid crystal layers have liquid crystal molecules that are d differently, such that the different diffracting zones have different optical properties associated with light diffraction.

In a 2nd example, in the diffraction grating of the 1st example, the optical properties include one or more of tive index, absorption coefficient, diffraction efficiency and birefringence.

In a 3rd example, in the diffraction grating of any of the 1st to 2nd examples, each of the ent liquid crystal layers has a plurality of differently ed s, wherein the differently arranged regions have liquid crystal molecules that are aligned differently with respect to each other.

In a 4th example, in the diffraction grating of any of the 1st to 3rd examples, each of the different diffracting zones further comprises an alignment layer interposed between a ate and the corresponding liquid crystal layer, wherein different alignment layers between the different cting zones and the substrate are formed of the same material composition, said different alignment layers causing the liquid crystal molecules to be aligned differently in the different diffracting zones.

In a 5th example, in the diffraction grating of any of the 1st to 4th examples, the liquid crystal molecules se calamitic liquid crystal molecules that are elongated and aligned along an elongation direction.

In a 6th example, in the ction grating of any of the1st to 5th examples, the different liquid crystal layers include a first region and a second region, wherein liquid crystal les of the first region are aligned along a first ent direction which forms a first alignment angle with respect to a reference direction, and n liquid crystal molecules of the second region are aligned along a second alignment direction which forms a second alignment angle with respect to the reference direction, the second alignment angle different from the first alignment angle.

In a 7th example, in the ction grating of the 6th example, liquid crystal molecules of a first region of a first liquid crystal layer and liquid crystal molecules of a corresponding first region of a second liquid crystal layer have substantially the same alignment angle.

In an 8th example, in the diffracting g of the 7th example, liquid crystal molecules of a second region of the first liquid crystal layer and liquid crystal molecules of a corresponding second region of the second liquid crystal layer have different alignment angles.

In a 9th example, in the diffraction grating of the 6th e, liquid l molecules of a first region of a first liquid crystal layer and the liquid crystal molecules of a ponding first region of a second liquid crystal layer have substantially different alignment angles, and n liquid crystal les of a second region of the first liquid crystal layer and liquid crystal molecules of a corresponding second region of the second liquid crystal layer have different alignment angles.

In a 10th example, in the ction grating of the 6th example, a ratio of lateral widths between first regions and second regions is substantially the same between different zones.

In an 11th example, in the diffraction grating of the 6th example, liquid crystal molecules of a second region of a first liquid crystal layer and liquid l molecules of a second region of a second liquid crystal layer have substantially same alignment angles, and wherein a ratio of lateral widths between the first regions and the second regions is substantially different n different zones.

In a 12th example, in the ction grating of the 6th example, liquid crystal molecules of a second region of a first liquid l layer and liquid crystal molecules of a second region of a second liquid crystal layer have different alignment angles, and wherein a ratio of lateral widths between the first regions and the second regions is substantially different between different zones.

In a 13th example, in the diffracting g of the 6th example, the first and second alignment angles are pre-tilt angles that are measured in a plane perpendicular to a major surface of a substrate and between respective alignment directions and the major surface.

In a 14th example, in the diffraction grating of the 6th example, the first and second alignment angles are azimuthal angles that are measured in a plane parallel to a major e of the substrate and between respective alignment directions and a reference direction parallel to the major surface.

In a 15th example, in the diffraction grating of the 3rd example, the different liquid crystal layers include a first region and a second region, wherein liquid crystal molecules of the first region are aligned along a plurality of first alignment directions which forms a plurality of first alignment angles with respect to a reference direction, and wherein liquid crystal molecules of the second region are aligned along a plurality of second alignment ions which forms a plurality of second alignment angles with respect to the reference direction.

In a 16th e, in the diffraction grating of any of the 1st to 15th examples, the diffraction grating is a transmissive ction grating having a arent substrate.

In a 17th example, in the diffraction grating of any of the 1st to 16th es, different diffracting zones comprise different material compositions such that the different diffracting zones have different optical ties associated with light diffraction.

In an 18th example, a method of ating a diffraction grating includes providing a substrate. The method additionally es providing a plurality of different diffracting zones having a periodically repeating lateral dimension corresponding to a grating period adapted for light diffraction. The method r includes forming a plurality of ent liquid crystal layers comprising liquid crystal molecules over the substrate, the different liquid crystal layers corresponding to the different diffracting zones, wherein forming the different liquid crystal layers comprises aligning the liquid crystal les differently, thereby providing different optical properties associated with light diffraction to the different diffracting zones.

In a 19th example, in the method of the 18th example, the method further includes forming a photo-alignment layer on the substrate prior to forming the liquid crystal layers and illuminating the photo-alignment layer y causing the liquid l molecules formed on the alignment layer to be aligned differently in the different diffracting zone.

In a 20th example, in the method of the 19th example, forming the photoalignment layer includes depositing a material selected from the group consisting of polyimide, linear-polarization photopolymerizable polymer, azo-containing polymers, courmarine-containing polymers, cinnamate-containing polymers and combinations thereof.

In a 21st example, in the method of any of the 19th and 20th examples, the method further includes, after forming the photo-alignment layer and prior to forming the liquid crystal layers, exposing the different diffracting zones to different doses of light using a gray scale mask.

In a 22nd example, in the method of any of 19th to 21st examples, forming the different liquid l layers includes forming a plurality of differently arranged regions in the different liquid crystal layers, wherein the differently arranged regions have liquid crystal les that are aligned differently with t to each other.

In a 23rd example, in the method of the 22nd example, forming the different liquid crystal layers comprises forming a first region and a second region, wherein forming the first region comprises aligning liquid crystal molecules of the first region along a first alignment ion which forms a first alignment angle with respect to a reference ion, and wherein forming the second region comprises aligning liquid crystal molecules of the second region along a second alignment direction which forms a second alignment angle with respect to the reference direction, wherein the second alignment angle different from the first alignment angle.

In a 24th example, in the method of the 23rd example, aligning the liquid molecules of the first and second s includes forming the respective first and second alignment angles that are inversely proportional to the different doses of light.

In a 25th example, in the methods of any of the 18th to 24th examples, forming the plurality of different liquid crystal layers comprises inducing ity in at least some of the liquid l molecules by adding a chiral dopant to the liquid crystal layers.

In a 26th example, in the method of the 18th example, forming the different liquid crystal layers includes forming a first region and a second region in the liquid l layers, wherein liquid crystal molecules of the first region are aligned along a plurality of first alignment directions which forms a plurality of first alignment angles with respect to a reference ion, and wherein liquid crystal les of the second region are aligned along a plurality of second alignment directions which forms a plurality of second alignment angles with respect to the reference direction.

In a 27th example, a diffraction grating includes a plurality of contiguous liquid l layers extending in a lateral direction and arranged to have a periodically repeating lateral dimension, a thickness and indices of refraction such that the liquid crystal layers are configured to diffract light. Liquid crystal les of the liquid crystal layers are arranged differently in different liquid crystal layers along the lateral direction such that the contiguous liquid crystal layers are configured to diffract light with a nt in diffraction efficiency.

In a 28th example, in the diffraction grating of the 27th example, the liquid crystal layers have a first region and a second region, and wherein the contiguous liquid crystal layers are arranged such that a plurality of first regions and a plurality of second regions alternate in the lateral direction.

In a 29th example, in the diffraction grating of the 28th example, the liquid crystal molecules in the first regions have substantially the same ent orientation, whereas the liquid crystal molecules in the second regions are have substantially different alignment directions.

In a 30th example, a head-mounted display device is configured to project light to an eye of a user to display augmented reality image t. The head-mounted display device includes a frame configured to be supported on a head of the user. The headmounted display device additionally includes a display disposed on the frame, at least a portion of said display comprising one or more ides, said one or more waveguides being transparent and disposed at a location in front of the user’s eye when the user wears said head-mounted display device such that said transparent portion transmits light from a portion of an environment in front of the user to the user’s eye to provide a view of said portion of the environment in front of the user, said display further comprising one or more light sources and at least one diffraction grating configured to couple light from the light s into said one or more ides or to couple light out of said one or more waveguides. The diffraction grating includes a plurality of ent cting zones having a periodically repeating lateral dimension corresponding to a grating period adapted for light diffraction. The diffraction g additionally includes a plurality of different liquid crystal layers ponding to the different diffracting zones, wherein the different liquid crystal layers have liquid crystal molecules that are aligned ently, such that the different cting zones have different l properties associated with light diffraction.

In a 31st example, in the device of the 30th example, the one or more light sources include a fiber scanning projector.

In a 32nd example, in the device of any of the 30th to 31st examples, the display is ured to project light into the user’s eye so as to present image content to the user on a plurality of depth planes.

In a 33rd example, in the diffraction grating of any of the 30th to 32nd examples, the optical properties include one or more of refractive index, absorption coefficient, diffraction efficiency and birefringence.

In the embodiments bed above, augmented reality display systems and, more particularly, spatially varying diffraction gratings are described in connection with particular embodiments. It will be tood, however, that the principles and advantages of the embodiments can be used for any other s, apparatus, or methods with a need for the spatially varying diffraction grating. In the foregoing, it will be appreciated that any feature of any one of the embodiments can be combined and/or tuted with any other feature of any other one of the ments.

Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise,” “comprising,” “include,” “including” and the like are to be construed in an inclusive sense, as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to.” The word “coupled”, as generally used herein, refers to two or more elements that may be either directly connected, or connected by way of one or more intermediate elements. Likewise, the word “connected”, as generally used herein, refers to two or more elements that may be either directly ted, or connected by way of one or more intermediate elements. onally, the words “herein,” “above,” ,” “infra,” “supra,” and words of similar import, when used in this ation, shall refer to this application as a whole and not to any particular portions of this application. Where the context permits, words in the above Detailed Description using the singular or plural number may also include the plural or singular number, respectively. The word “or” in reference to a list of two or more items, that word covers all of the ing interpretations of the word: any of the items in the list, all of the items in the list, and any combination of the items in the list. er, conditional language used herein, such as, among others, “can,” “could,” “might,” “may,” “e.g.,” “for example,” “such as” and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is lly intended to convey that certain embodiments e, while other embodiments do not include, certain features, elements and/or states. Thus, such ional language is not generally intended to imply that features, ts and/or states are in any way required for one or more embodiments or whether these features, elements and/or states are included or are to be performed in any particular embodiment.

While certain embodiments have been described, these embodiments have been ted by way of example only, and are not intended to limit the scope of the disclosure. Indeed, the novel tus, methods, and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems bed herein may be made without departing from the spirit of the disclosure. For example, while blocks are presented in a given arrangement, alternative embodiments may m similar functionalities with different components and/or circuit topologies, and some blocks may be deleted, moved, added, subdivided, combined, and/or modified. Each of these blocks may be implemented in a variety of different ways. Any suitable combination of the elements and acts of the s embodiments described above can be combined to provide further embodiments. The various features and processes described above may be implemented independently of one another, or may be combined in various ways. All suitable combinations and subcombinations of es of this disclosure are intended to fall within the scope of this disclosure.

The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that the prior ation (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

Claims (18)

WHAT IS CLAIMED IS:

1. A diffraction grating, comprising: a plurality of different diffracting zones arranged in a continuous layer in a lateral direction substantially parallel to a major surface of a substrate, the different diffracting zones having a same ess vertically defined by upper and lower surfaces of the continuous layer and having a same lateral dimension corresponding to a grating period adapted for light diffraction, wherein each of the different diffracting zones is laterally divided into a first region and a second region each comprising liquid crystals, n the liquid crystals of the first region are aligned along a first alignment direction which forms a first alignment angle with respect to a reference direction, and wherein the liquid crystals of the second region are aligned along an alignment direction different from the first ent direction which forms a different alignment angle relative to the first ent angle, wherein substantially all of the liquid crystals of the first region n the upper and lower surfaces are permanently aligned in the first alignment direction and substantially all of the liquid crystals of the second region n the upper and lower es are permanently aligned in the second alignment direction, and wherein the different diffracting zones are arranged differently from each other with respect to arrangements of liquid crystals in corresponding portions of different second regions.

2. The diffraction grating of Claim 1, n the liquid crystals of the different first regions of the different diffracting zones have substantially the same first alignment angle.

3. The ction grating of Claim 2, wherein the liquid crystals of different second regions of the different diffracting zones have substantially the same second alignment angle.

4. The diffraction grating of Claim 2, n the liquid crystals of different second regions of the different diffracting zones have ent angles that are different from each other.

5. The diffraction grating of any one of the Claims 1 to 4, wherein a ratio of lateral widths between the first region and the second region is substantially the same for different diffracting zones.

6. The diffraction g of any one of the Claims 1 to 4, n a ratio of lateral widths between the first region and the second region is substantially different for different diffracting zones.

7. The diffraction grating of any one of the Claims 1 to 6, wherein the alignment angles are azimuthal angles that are measured in a plane parallel to the major surface of the substrate and between respective alignment directions and a nce direction that is parallel to the major surface.

8. The diffraction grating of any one of the Claims 1 to 6, wherein the alignment angles are pre-tilt angles that are measured in a plane perpendicular to the major surface of the substrate and n tive alignment directions and a reference direction that is normal to the major surface.

9. The diffraction grating of Claim 1, wherein liquid crystals of the first region are aligned along a plurality of first alignment directions which form a plurality of first alignment angles with respect to the reference direction, and n liquid crystals of the second region are aligned along a plurality of second alignment directions which form a plurality of second alignment angles with t to the reference direction.

10. The diffraction grating of Claim 1, n the first regions and the second regions of the ent diffracting zones alternate with each other in the lateral direction such that ately adjacent ones of the first and second regions contact each other without having intervening liquid crystals therebetween.

11. A diffraction grating, comprising: a plurality of different diffracting zones arranged in a continuous layer in a lateral direction substantially parallel to a major surface of a substrate, the different diffracting zones having a same thickness vertically defined by upper and lower surfaces of the continuous layer and having a same lateral dimension corresponding to a grating period adapted for light diffraction, wherein each of the different diffracting zones is laterally divided into a first region and a second region each comprising liquid crystals, a combined width of the first and second regions being the same lateral dimension, n the liquid crystals of the first region are aligned along a first alignment direction which forms a first alignment angle with respect to a reference direction, and wherein the liquid crystals of the second region are aligned along an alignment direction different from the first alignment ion which forms a different alignment angle relative to the first alignment angle, wherein substantially all of the liquid ls of the first region between the upper and lower surfaces are permanently aligned in the first alignment direction and substantially all of the liquid crystals of the second region between the upper and lower surfaces are permanently aligned in the second ent direction, and wherein the different diffracting zones are arranged differently from each other with respect to ratios of lateral widths between respective first and second regions.

12. The diffraction grating of Claim 11, wherein the liquid crystals of the different first regions of the different diffracting zones have substantially the same first ent angle.

13. The diffraction grating of Claim 12, wherein the liquid crystals of ent second regions of the different diffracting zones have substantially the same second ent angle.

14. The diffraction grating of Claim 12, wherein the liquid crystals of different second regions of the different diffracting zones have alignment angles that are different from each other.

15. The diffraction grating of Claim 11, wherein a ratio of lateral widths between the first region and the second region increases along the lateral direction across three or more different diffracting zones.

16. The diffraction grating of any one of the Claims 11 to 15, wherein the alignment angles are azimuthal angles that are measured in a plane parallel to a major surface of the ate and between respective alignment directions and the reference ion that is parallel to the major surface.

17. The ction grating of any one of the Claims 11 to 15, wherein the alignment angles are pre-tilt angles that are measured in a plane perpendicular to a major surface of a substrate and between respective ent directions and the reference direction that is normal to the major surface.

18. The ction grating of Claim 11, wherein the first regions and the second regions of the different diffracting zones alternate with each other in the lateral direction such that immediately adjacent ones of the first and second regions contact each other without having intervening liquid crystals therebetween. WO 94079 a r80 30b _[____ |local Processing: & 211020322 76\_Z \(78 |__ _—| |__Remote_