Polarization-based multiplexing of diffractive elements for illumination optics

Abstract

The systems and methods provide improved illumination optics for various applications. The illumination optics may include an optical beam-expanding structure that provides a large divergence angle for an incident collimated beam or provides finer detail or resolution compared to conventional diffractive optical elements. The optical beam-expanding structure may include a first spatially varying polarizer and a second spatially varying polarizer optically aligned with each other. The first spatially varying polarizer and the second spatially varying polarizer may be formed of a liquid crystal material, such as a multi-twist retarder (MTR). The first spatially varying polarizer and the second spatially varying polarizer may diffract light of orthogonal polarization states, thereby allowing different diffraction patterns to be used in a single optical structure. The two patterns may together provide a combined field of view larger than either the first field of view or the second field of view, or may provide finer detail or resolution than either the first field of view or the second field of view alone.

Description

[Technical field]

[0001] The present disclosure relates generally to illumination optics. [Background technology]

[0002] Various applications utilize illumination optics that provide an illumination pattern using a collimated beam (e.g., laser beam) and optics that expand the collimated beam (e.g., negative lens, beam splitter). Such applications may include head-up displays, head-mounted display (HMD) systems, time-of-flight sensors, stereo depth sensors, and the like. For example, effective stereo camera sensing may use a projected pattern of infrared (IR) in conjunction with one or more cameras capable of detecting IR. For certain applications, it may be desirable to provide sensors and illumination optics that operate at a larger field of view and greater distances with higher resolution.

[0003] To generate such patterns, IR lasers in conjunction with one or more diffractive optical elements (DOEs) have been used as illumination sources or projectors due to their reduced size, weight, and their capabilities. However, the field of view or "spread angle" of a DOE is essentially limited to its pitch or the distance between the gratings, which requires a tradeoff between spread angle and detail or resolution. Thus, there is a need to provide illumination optics for various applications that provide a larger field of view and / or provide finer detail or resolution than currently available.

[0004] As described above, exemplary applications for such illumination optics include virtual reality (VR) experiences generated using a head-mounted display (HMD), which may be tethered to a stationary computer (such as a personal computer (PC), laptop, or game console), combined and / or integrated with a smartphone and / or its associated display, or may be self-contained. HMDs are generally display devices that are worn on the user's head and have a small display device in front of one eye (monocular HMD) or each eye (binocular HMD). These display units are typically miniaturized and may include, for example, CRT, LCD, liquid crystal on silicon (LCos) or OLED technologies. Binocular HMDs have the potential to display different images to each eye. This capability is used to display stereoscopic images.

[0005] With the development of smartphones, high definition televisions, and other electronic devices, the demand for high performance displays is increasing. Such demand is further increased by the popularity of virtual reality and augmented reality systems, especially those using HMDs. Virtual reality systems typically completely envelop the wearer's eyes and replace the actual or physical view (or actual reality) in front of the wearer with a "virtual" reality, while augmented reality systems typically provide a semi-transparent or transparent overlay of one or more screens in front of the wearer's eyes so that the actual view is augmented with additional information, and mediated reality systems may similarly present information to the viewer that combines real-world elements with virtual elements. In many virtual reality and augmented reality systems, the movement of the wearer of such a head-mounted display may be tracked in various ways, such as, for example, via sensors internal and / or external to the head-mounted display, to enable images to be shown that reflect the user's movements.

[0006] Positional tracking allows an HMD to estimate its position relative to the surrounding environment using a combination of hardware and software to detect absolute position. Positional tracking is a key feature in virtual reality. It allows for tracking of movements with six degrees of freedom (6DOF). Positional tracking facilitates various benefits to the virtual reality experience. For example, positional tracking may change the user's viewpoint to reflect different movements such as crouching, leaning forward, or jumping, and may allow for the representation of the user's hands or other objects in the virtual environment. Positional tracking also improves the 3D perception of the virtual environment due to parallax (i.e., the way objects closer to the eye move faster than objects that are farther away).

[0007] There are different methods of positional tracking including acoustic tracking, inertial tracking, magnetic tracking, optical tracking, etc., and / or combinations thereof. Inside-out tracking is one type of positional tracking and may be used to track the position of the HMD and / or associated subject (e.g., controller). Inside-out tracking differs from outside-in tracking due to the location of the camera or other sensor used to determine the position of the HMD. In inside-out tracking, the camera or sensor is located on the HMD or on the subject being tracked, whereas in outside-out tracking, the camera or sensor is located at a fixed location in the environment.

[0008] HMDs that use inside-out tracking use one or more cameras to "keep watch" and determine how their position is changing relative to the environment. If the HMD moves, the sensors readjust their location in the room and the virtual environment responds in real time. This type of position tracking can be achieved with or without markers placed in the environment.

[0009] A camera placed on the HMD observes features of the surrounding environment. When markers are used, they are designed and placed in specific areas to be easily detected by the tracking system. In "markerless" inside-out tracking, the HMD system uses distinctive characteristics (e.g., natural features) that are inherently present in the environment to determine position and orientation. The HMD system's algorithms identify specific images or shapes and use them to calculate the device's position in space. Data from the accelerometer and gyroscope can also be used to improve the accuracy of position tracking. Summary of the Invention

[0010] The optical beam expanding structure may be summarized as including a first spatially varying polarizer configured to receive an incident light beam from a light source, the first spatially varying polarizer operable to diffract light of a first polarization state over a first field of view and to pass incident light having a second polarization state orthogonal to the first polarization state without being diffracted by the first spatially varying polarizer, and a second spatially varying polarizer optically aligned with the first spatially varying polarizer and positioned to receive light from the first spatially varying polarizer, the second spatially varying polarizer operable to diffract light of the second polarization state over a second field of view and to pass incident light having the first polarization state without being diffracted by the second spatially varying polarizer. Each of the first spatially varying polarizer and the second spatially varying polarizer may include a multi-twist retarder. Each of the first and second spatially varying polarizers may include a liquid crystal material. The first and second fields of view may together form a combined field of view that is larger than each of the first and second fields of view. The optical beam expanding structure may be a component in a head mounted display, a head up display, a time of flight sensor, or a stereo depth sensor. The first spatially varying polarizer may diffract light of the first polarization state into a first diffraction order, and the second spatially varying polarizer may diffract light of the second polarization state into a second diffraction order different from the first diffraction order. One of the first and second diffraction orders may include the +1 diffraction order, and the other of the first and second diffraction orders may include the -1 diffraction order.

[0011] The optical beam expanding structure may further include a laser light source operable to generate the incident light beam. The incident light beam may be polarized at an angle that is 45 degrees relative to the first and second polarization states. The first and second fields of view may at least partially overlap each other. The second field of view may be different from the first field of view. One of the first and second polarization states may include p-polarized light, and the other of the first and second polarization states may include s-polarized light. The first spatially varying polarizer may implement a negative lens with a tilt in a first direction, and the second spatially varying polarizer may implement a negative lens with a tilt in a second direction that is different from the first direction. The first spatially varying polarizer may implement a negative lens with a tilt in a first direction, and the second spatially varying polarizer may implement a negative lens with a tilt in a second direction that is opposite to the first direction.

[0012] The illumination source may be summarized as including a laser light source and an optical beam spreading structure having a first spatially varying polarizer configured to accept an incident light beam from the laser light source, the first spatially varying polarizer operable to diffract light of a first polarization state over a first field of view and to allow incident light having a second polarization state orthogonal to the first polarization state to pass without being diffracted by the first spatially varying polarizer, and a second spatially varying polarizer optically aligned with the first spatially varying polarizer and positioned to accept light from the first spatially varying polarizer, the second spatially varying polarizer operable to diffract light of the second polarization state over a second field of view different from the first field of view and to allow incident light having the first polarization state to pass without being diffracted by the second spatially varying polarizer. Each of the first and second spatially varying polarizers may include a multi-twist retarder. The first and second fields of view may together form a combined field of view that is larger than each of the first and second fields of view. The illumination source may be a component in a head mounted display, a head up display, a time of flight sensor, or a stereo depth sensor. The first spatially varying polarizer may diffract light of the first polarization state into a first diffraction order, and the second spatially varying polarizer may diffract light of the second polarization state into a second diffraction order different from the first diffraction order. One of the first and second diffraction orders may include the +1 diffraction order, and the other of the first and second diffraction orders may include the -1 diffraction order. The incident light beam may be polarized at an angle that is 45 degrees relative to the first and second polarization states. The first spatially varying polarizer may implement a negative lens having a tilt in a first direction, and the second spatially varying polarizer may implement a negative lens having a tilt in a second direction different from the first direction.

[0013] The depth camera system may be summarized as including at least one camera; an illumination source including a laser light source; and an optical beam spreading structure having a first spatially varying polarizer configured to accept an incident light beam from the laser light source, the first spatially varying polarizer operable to diffract light of a first polarization state over a first field of view and to allow incident light having a second polarization state orthogonal to the first polarization state to pass without being diffracted by the first spatially varying polarizer; and a second spatially varying polarizer optically aligned with the first spatially varying polarizer and positioned to accept light from the first spatially varying polarizer, the second spatially varying polarizer operable to diffract light of the second polarization state over a second field of view and to allow incident light having the first polarization state to pass without being diffracted by the second spatially varying polarizer. [Brief description of the drawings]

[0014] In the drawings, identical reference numbers identify similar elements or acts. The sizes and relative positions of elements in the drawings are not necessarily drawn to scale. For example, the shapes and angles of various elements are not necessarily drawn to scale, and some of these elements may be arbitrarily enlarged and positioned to improve the legibility of the drawings. Furthermore, the particular drawn shapes of these elements are not necessarily intended to convey any information regarding the actual shape of those particular elements, but may only be selected for ease of recognition in the drawings.

[0015] [Figure 1] 1 shows a top view of a head mounted display system including a binocular display in a particular embodiment according to the described techniques of this disclosure.

[0016] [Diagram 2]FIG. 2 is a front view pictorial diagram of a head mounted display system including a binocular display subsystem and a forward facing camera and projector that are components of a stereo depth camera in a particular format in a particular embodiment according to the described techniques of this disclosure.

[0017] [Figure 3A] FIG. 13 is a side cross-sectional view of a first spatially varying polarizer of an optical beam expanding structure illustrating functionality according to one non-limiting illustrated implementation.

[0018] [Figure 3B] FIG. 13 is a side cross-sectional view of a second spatially varying polarizer of an optical beam expanding structure illustrating functionality according to one non-limiting illustrated implementation.

[0019] [Figure 4A] FIG. 2 is a plan view of a first spatially varying polarizer showing its exemplary phase profile according to one non-limiting illustrated implementation.

[0020] [Figure 4B] FIG. 1 is a plan view of a second spatially varying polarizer showing its exemplary phase profile according to one non-limiting illustrated implementation.

[0021] [Diagram 5] FIG. 2 is a cross-sectional side view of an illumination source including an optical beam expanding structure including a first spatially varying polarizer and a second spatially varying polarizer according to one non-limiting illustrated implementation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] In the following description, certain specific details are set forth to provide a thorough understanding of various disclosed implementations. However, those skilled in the art will recognize that implementations may be practiced without one or more of these specific details, or with other methods, components, materials, etc. In other instances, well-known structures associated with computer systems, server computers, and / or communication networks have not been shown or described in detail to avoid unnecessarily obscuring the description of implementations.

[0023] Unless the context requires otherwise, throughout this specification and the claims which follow, the word "comprising" is synonymous with "including" and is inclusive or open-ended (i.e., does not exclude additional, unrecited elements or method actions).

[0024] Throughout this specification, a reference to "one implementation" or an "implementation" means that a particular feature, structure, or characteristic described in connection with that implementation is included in at least one implementation. Thus, the appearances of the phrase "in one implementation" or "in an implementation" in various places throughout this specification are not necessarily all referring to the same implementation. Furthermore, particular features, structures, or characteristics may be combined in any suitable manner in one or more implementations.

[0025] As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. It should also be noted that the term "or" is generally utilized in its sense including "and / or" unless the context clearly dictates otherwise.

[0026] The headings and abstracts provided herein are for convenience only and do not interpret the scope or meaning of the implementations.

[0027] The systems and methods of the present disclosure relate to providing improved illumination optics for various applications such as head-up displays, head-mounted display (HMD) systems, time-of-flight sensors, stereo depth sensors, etc. According to one non-limiting illustrated implementation, an optical beam spreading structure is provided that can provide a relatively large spread angle for an incident collimated beam and / or provide finer detail or resolution compared to conventional diffractive optical elements that are limited by the pitch or distance between diffraction gratings.

[0028] As described further below, the optical beam expanding structure may include a first spatially varying polarizer and a second spatially varying polarizer that are optically aligned with each other. The first spatially varying polarizer and the second spatially varying polarizer may be formed of a liquid crystal material, such as a multi-twist retarder (MTR). The first spatially varying polarizer may be configured to receive an incident light beam from a light source, such as a laser source. In at least some implementations, the incident light beam may be polarized at a particular angle. The first spatially varying polarizer may be operable to diffract light of a first polarization state on a first field of view and to allow incident light having a second polarization state orthogonal to the first polarization state to pass through the first spatially varying polarizer without being diffracted. For example, the first spatially varying polarizer may implement a negative lens having a tilt pattern in a first direction for light in the first polarization state. The second spatially varying polarizer may be positioned to receive light from the first spatially varying polarizer and may be operable to diffract light of the second polarization state onto the second field of view and to allow incident light having the first polarization state to pass through the second spatially varying polarizer without being diffracted by the second spatially varying polarizer. For example, the second spatially varying polarizer may implement a negative lens having a tilt pattern in a second direction (e.g., opposite to the first direction) for light in the second polarization state. Thus, the first and second fields of view together provide a combined field of view that is larger than either the first and second fields of view and / or provide finer detail than either the first or second fields of view alone provide.

[0029] First, a non-limiting exemplary HMD system application for the illumination optics of the present disclosure will be described with reference to Figures 1 and 2. As described above, the features of the present disclosure may be used in numerous applications where it is desirable to use optics that provide relatively large spread angles and / or finer detail relative to conventional DOEs. Next, one embodiment of an illumination source including the optical beam spreading structure of the present disclosure will be described with reference to Figures 3-5. (Example Application: Stereo Depth Camera for HMD)

[0030] 1 is a simplified top view of an HMD system 100 including a pair of near-to-eye display systems 102 and 104. The near-to-eye display systems 102 and 104 include displays 106 and 108 (e.g., OLED microdisplays), respectively, and include respective optical lens systems 110 and 112, each having one or more optical lenses. The display systems 102 and 104 may be attached to a support structure or frame 114 or other mounting structure including a front portion 116, a left temple 118, and a right temple 120. The two display systems 102 and 104 may be secured to the frame 114 in an eyeglass arrangement that may be worn on a head 122 of a user 124. The left temple 118 and the right temple 120 may rest on the user's ears 126 and 128, respectively, while a nose assembly (not shown) may rest on the user's nose 130. Frame 114 may be shaped and sized to position each of the two optical systems 110 and 112 in front of one of the user's eyes 132 and 134, respectively. Although frame 114 is shown in a simplified manner similar to glasses for purposes of explanation, it should be understood that in practice more sophisticated structures (e.g., goggles, integrated headbands, helmets, straps, etc.) may be used to support and position display systems 102 and 104 on head 122 of user 124.

[0031] The HMD system 100 of FIG. 1 can present a virtual reality display to the user 124, such as through a corresponding video presented at a display rate such as 30 frames (or images) per second or 90 frames per second, while other embodiments of similar systems can present an augmented reality display to the user 124. Each of the displays 106 and 108 may generate light that is transmitted through respective optical systems 110 and 112 and focused to the eyes 132 and 134, respectively, of the user 124. Although not shown here, each of the eyes includes a pupil opening, through which light passes into the eye. Typical pupil sizes range from 2 mm (millimeters) in diameter in very bright conditions to up to 8 mm in dark conditions, while the larger iris, in which the pupil is included, may have a size of approximately 12 mm. The pupil (and the iris surrounding it) may typically move several millimeters horizontally and / or vertically within the visible portion of the eye with the eyelids open. This also moves the pupil to different depths from the optical lens or other physical elements of the display for different horizontal and vertical positions as the eyeball rotates about its center (and thus results in a three-dimensional volume in which the pupil may move). The light that enters the user's pupil is seen as an image and / or video by the user 124. In some implementations, the distance between each of the optical systems 110 and 112 and the user's eyes 132 and 134 may be relatively short (e.g., less than 30 mm, less than 20 mm). This may result in the HMD system 100 advantageously appearing lighter to the user, as the weight of the optical and display systems is relatively close to the user's face, and may also provide the user with a larger field of view.

[0032] The HMD system 100 may also include forward cameras 136a and 136b, which may be cameras of a stereo depth camera 136. The stereo depth camera 136 may be operable to capture image data that may be selectively presented to the user 124, for example, in an augmented reality application or in conjunction with a virtual reality application. Additionally or alternatively, the stereo depth camera 136 may be used by a position tracking system of the HMD system 100 to track the position of the HMD system 100 during use, as described elsewhere herein. By way of example, each of the cameras 136a and 136b may comprise a video camera and an associated lens system having a relatively wide angle (e.g., 60°, 90°, 120°, 150°) and capturing images within the field of view of the forward camera at a frame rate (e.g., 30 Hz, 60 Hz, 90 Hz). The camera 136 may generally be any device capable of capturing an image of at least a portion of a target area. The image may be a color image or a grayscale image. As an example, the camera 136 may include a number of lenses that modify, redirect, and / or focus the light that enters the camera through an aperture. A light sensor (e.g., a CCD) may accept the light that passes through the lenses and output data that represents a number of pixels of the image. For example, the data may provide an intensity value for each pixel.

[0033] The HMD system 100 may also include an illumination source or projector 138 that projects a light pattern (e.g., a structured light pattern) toward a target area or environment. The target area or environment may be at any number of different ranges of distance from the HMD system 100, including ranges of orders of meters, centimeters, millimeters, etc., depending on the particular application. As non-limiting examples, the projector 138 may generate a structured light pattern that may include a number of dots, lines, grids, coded or non-coded patterns, or other patterns detectable by the camera 136.

[0034] As described further below with reference to Figures 3-5, projector 138 may include one or more light sources and optical beam expanding structures operable to expand a collimated beam. Projector 138 may also include control circuitry (e.g., controller 334 of Figure 5) to control the operation of the one or more light sources or optical beam expanding structures. The one or more light sources may include one or more lasers (e.g., IR lasers), light emitting diodes (LEDs), lamps, other light sources, or some combination thereof.

[0035] The optical beam spreading structure transforms or otherwise modifies the light emitted by the light source into a desired light pattern. In some implementations, the optical beam spreading structure is stationary. For example, the optical beam spreading structure may focus or defocus the emitted light to a single depth focus. As another example, the optical beam spreading structure may have a specific diffractive pattern that results in diffraction of the emitted light to form a desired structured light pattern, as further described below.

[0036] In other implementations, the optical beam expanding structure allows for dynamic focus modulation (i.e., different diffractive patterns may be selectively applied to impart a variety of different focal points to the output light). As one example, the optical beam expanding structure may include a liquid crystal material such as a multi-twist retarder that allows for high frequency switchable diffractive patterns.

[0037] Although not shown in FIG. 1, some embodiments of such an HMD system 100 may include various additional internal and / or external sensors, such as for performing pupil tracking separately for each eye 132 and 134, for tracking head position and orientation (e.g., as part of head tracking), for tracking various other types of body movements and positions of the user, other cameras for recording external images (e.g., of the environment), etc.

[0038] Further, the described techniques may be used in some embodiments having a display system similar to that shown in FIG. 1, while other embodiments may use other types of display systems, including those having a single optical lens and display device or those having multiple such optical lenses and display devices. Non-exclusive examples of other such devices include cameras, telescopes, microscopes, binoculars, spotting scopes, surveying scopes, and the like. In addition, the described techniques may be used with a variety of display panels or other display devices that emit light to form an image that one or more users view through one or more optical lenses. In other embodiments, a user may view one or more images through one or more optical lenses that are generated in a manner other than through a display panel, such as on a surface that reflects some or all of the light from another light source.

[0039] The HMD system 100 may include a processor and memory that may be physically local or remote from the HMD system. The processor may be one processor or multiple processors operatively coupled together. The processor may be any processing device such as a microprocessor, a microcontroller, an integrated circuit, a circuit implementing computer logic, or some combination thereof. The memory may include any non-transitory information storage device including, but not limited to, RAM, ROM, a hard drive, a flash drive, an optical medium, other memory devices, or some combination thereof. The memory may store information that is accessible by the processor including instructions that may be executed by the processor. The instructions may be any set of instructions that, when executed by the processor, cause the processor to provide a desired function. The memory may also store data.

[0040] The HMD system 100 may include a depth determiner module or circuitry operable to determine multiple depth values ​​for one or more images captured by the camera 136. In some implementations, the depth determiner includes processor-executable instructions stored in or loaded into memory and executed by a processor. In other implementations, the depth determiner includes one or more circuits (e.g., integrated circuits), logic components, or other items of computer hardware arranged to implement computer logic or perform other functions. In other implementations, the depth determiner may be implemented using some combination of processor-executable instructions or data and circuitry.

[0041] The HMD system 100 may be coupled to a network, which may be any type of communications network, such as a local area network (e.g., an intranet), a wide area network (e.g., the Internet), an internal device bus, or some combination thereof, and may include any number of wired or wireless links. In general, communications between components of the HMD system 100 over the network may be conveyed via any type of wired and / or wireless connections using a variety of communications protocols (e.g., TCP / IP, HTTP, SMTP, FTP), encodings or formats (e.g., HTML, XML), and / or protection schemes (e.g., VPN, Secure HTTP, SSL).

[0042] Although the example provided is an HMD system for purposes of illustration, the functionality provided may be utilized for a variety of other devices or applications. For example, the functionality may be provided in a depth camera system embedded in a vehicle, a test equipment, an artificial intelligence device, an automation system, or any other system or device in which determining depth values ​​is beneficial. In other implementations, the features of the present disclosure may be provided in a desktop computer, a laptop computer, a tablet computer, a smartphone, a gaming console, one or more server computing devices, or some combination thereof, and may be used to provide other functions.

[0043] 2 illustrates a front view of an exemplary HMD system 200 as worn on the head of a user 202. The HMD system 200 includes a support structure 204 that supports forward-facing or forward stereo depth cameras 206a and 206b and a projector 208. The camera 206a may be referred to herein as the left camera 206a, and the camera 206b may be referred to herein as the right camera 206b. The stereo depth cameras 206a and 206b may be similar or identical to the cameras 136a and 136b described above with reference to FIG. 1. Similarly, the projector 208 may be similar or identical to the projector 138 of FIG. 1.

[0044] The above description is provided to present example applications of the illumination optics of the present disclosure. As noted above, the features of the present disclosure may be utilized in numerous other applications, including head-up displays, time-of-flight sensors, other devices utilizing illumination optics, and the like. (Example Illumination Sources)

[0045] 3-5 show an exemplary illumination source 300 (FIG. 5) that may be used in various applications, such as the stereo depth camera application described above or other applications. As will be further described below, in the illustrated example, the illumination source 300 includes an optical beam spreading structure 301 (FIG. 5) including a first spatially varying polarizer 302 and a second spatially varying polarizer 318. FIG. 3A is a side cross-sectional view of the first spatially varying polarizer 302 showing the function, and FIG. 3B is a side cross-sectional view of the second spatially varying polarizer 318 showing the function. FIGS. 4A and 4B are plan views of the first spatially varying polarizer 302 and 318, respectively, showing exemplary phase profiles. FIG. 5 is a side cross-sectional view of the illumination source 300 including the optical beam spreading structure 301 including the first spatially varying polarizer 302 and the second spatially varying polarizer 318 according to one non-limiting illustrated implementation.

[0046] One or both of the first and second spatially varying polarizers 302 and 318 of the optical beam expanding structure 301 may include a wavelength retarder formed of a birefringent material. Birefringence is a property of a material having a refractive index that depends on the polarization and propagation direction of the light. A wavelength retarder changes the polarization state or phase of light traveling through the wavelength retarder. A wavelength retarder may have a slow axis (or extraordinary axis) and a fast axis (or ordinary axis). As polarized light travels through the wavelength retarder, light travels more quickly along the fast axis than along the slow axis.

[0047] In at least some implementations, the spatially varying polarizers 302 and 318 may be formed of multi-twist retarders (MTRs), which are waveplate-like retardation films that provide precise, customized levels of broadband, narrowband, or multi-band retardation in a single thin film. More specifically, MTRs comprise two or more twisted liquid crystal (LC) layers on a single substrate and with a single alignment layer. The next LC layer is directly aligned with the previous layer, allowing for simplified manufacturing, providing automatic inter-layer alignment, and resulting in a monolithic film with a continuously varying optical axis.

[0048] FIG. 3A shows a diagram 303 of the operation of the first space-changing polarizer 302, shown separately from the second space-changing polarizer 318 shown in FIG. 3B for illustrative purposes. A light source 304 generates a collimated beam 306 that is linearly polarized at an angle (e.g., 45 degrees). Although not shown, optical structures (e.g., polarizers) may be provided to shape the beam 306 into a suitable pattern and polarization state. The first space-changing polarizer 302 includes a diffraction pattern 322 (FIG. 4A) that is operable to diffract light 310 of a first polarization state at a divergence angle 313 on a first field of view 312, and is designed to allow incident light 314 having a second polarization state orthogonal to the first polarization state to pass through the first space-changing polarizer 302 without being diffracted by the first space-changing polarizer 302. In the illustrated example, the light source 304 provides a collimated light beam 306 polarized at a 45 degree angle for both a first polarization state (e.g., p-polarized) and a second polarization state (e.g., s-polarized). The first spatially varying polarizer 302 is configured to diffract the first polarization state light 310 with an upward tilt (as shown) onto a field of view 312 having a divergence angle 313. By way of example, the diffraction pattern 322 of the first spatially varying polarizer 302 may be designed to implement a combination of a negative lens and a tilt pattern designed for a particular diffraction order (e.g., +1, -1, etc.).

[0049] As shown in FIG. 3B, the second spatially varying polarizer 318 includes a diffraction pattern 324 (FIG. 4B) designed to diffract the second polarization state light 314 with a divergence angle 321 on the second field of view 320 and to allow incident light 310 having a first polarization state orthogonal to the second polarization state to pass through the second spatially varying polarizer 318 without being diffracted by the second spatially varying polarizer 318. In the example shown, the second spatially varying polarizer 318 is configured to diffract the second polarization state light 314 with a downward tilt (as shown) on the second field of view 320 with a divergence angle 321. By way of example, the diffraction pattern 324 of the second spatially varying polarizer 318 may be designed to implement a combination of a negative lens and a tilt pattern designed for a particular diffraction order (e.g., +1, -1, etc.). In at least some implementations, the tilt pattern of the second spatially varying polarizer 318 may be in a different direction (e.g., the opposite direction) than the tilt pattern of the first spatially varying polarizer 302. For example, the first spatially varying polarizer 302 may be designed toward the +1 diffraction order, and the second spatially varying polarizer 318 may be designed toward the −1 diffraction order.

[0050] 5 illustrates an illumination source 300 including an optical beam spreading structure 301 when a first spatially varying polarizer and a second spatially varying polarizer 302 and 318 are optically aligned with one another. As shown, the first spatially varying polarizer 302 diffracts light 310 of a first polarization state with a spread angle 313 on a field of view 312 with an upward tilt (as shown), and the second spatially varying polarizer 318 diffracts light 314 of a second polarization state with a spread angle 321 on a second field of view 320 with a downward tilt. Thus, the first and second fields of view 312 and 320 together provide a combined field of view having a spread angle 332 that is larger than the first and second fields of view. As a non-limiting example, if a first field of view and a second field of view each have a spread angle of 30 degrees and overlap each other by 10 degrees, the combined field of view may have a spread angle of 50 degrees (i.e., 30° + 30° - 10° = 50°).

[0051] In at least some implementations, the first spatially varying polarizer 302 diffracts light of the first polarization state into a first diffraction order, and the second spatially varying polarizer 318 diffracts light of the second polarization state into a second diffraction order different from the first diffraction order. As a non-limiting example, one of the first and second diffraction orders may include the +1 diffraction order, and the other of the first and second diffraction orders may include the -1 diffraction order.

[0052] 5, in at least some implementations, the first field of view 312 and the second field of view 320 may at least partially overlap one another, although such a feature is not required. In at least some implementations, the second field of view 320 is different from the first field of view 312. In other implementations, the first and second fields of view 312 and 320 are substantially the same, but together provide greater resolution than could be provided using a single diffractive optical element. As can be appreciated, if the overlap between the two fields of view is minimal, the combined field of view may be nearly twice the size of the individual fields of view without loss of resolution.

[0053] In at least some implementations, the optical beam spreading structure 301 may be operatively coupled to a controller 334 to selectively vary the spatially dependent phase difference of the first spatially varying polarizer or the second spatially varying polarizer 302 and 318 to any desired configuration, thereby providing a variable combined field of view. In such implementations, one or more electrode layers (e.g., thin film transistor (TFT) layers) that enable the spatially dependent phase difference of the first spatially varying polarizer and the second spatially varying polarizer 302 and 318 may be provided to be selectively controlled by the controller 334. The controller 334 may control the phase difference at any desired rate, such as once only, periodically, or at a rate on the order of milliseconds or microseconds. As another example, each of the spatially varying polarizers 302 and 318 may include a stack of two or more layers that may each be selectively switched between enabled and disabled states by the controller 334 to provide the desired polarization characteristics.

[0054] It will be understood that the illustrated systems and devices are merely exemplary and are not intended to limit the scope of the present disclosure. Such computing systems or devices may comprise any combination of hardware that may interact and perform the types of functions described, such as when programmed or otherwise configured with appropriate software, including, but not limited to, desktop computers, laptop computers, slate computers, tablet computers or other computers, smartphone computing devices and other mobile phones, Internet appliances, PDAs and other electronic organizers, database servers, network storage devices and other network devices, wireless phones, pagers, television-based systems (e.g., using set-top boxes, and / or personal / digital video recorders, and / or game consoles, and / or media servers), and various other consumer goods that include appropriate intercommunication capabilities. For example, the illustrated systems may include executable software instructions and / or data structures in at least some embodiments that, when loaded onto and / or executed by particular computing systems or devices, may be used to program or otherwise configure these systems or devices, such as to configure the processors of these systems or devices. Alternatively, in other embodiments, some or all of the software system may execute in memory on another device and communicate with the illustrated computing system / device via computer-to-computer communications. Additionally, while various items are shown as being stored in memory or storage at various times (e.g., while in use), these items or portions thereof may be transferred between memory and storage and / or between storage devices (e.g., in different locations) for purposes of memory management and / or data integrity.

[0055] Thus, in at least some embodiments, the illustrated system is a software-based system that includes software instructions that, when executed by a processor and / or other processor means, program the processor to automatically perform the described operations for the system. Furthermore, in some embodiments, some or all of the system may be implemented or provided, at least in part, in firmware and / or hardware means, including but not limited to, one or more application specific integrated circuits (ASICs), standard integrated circuits, controllers (e.g., by executing appropriate instructions and including microcontrollers and / or embedded controllers), field programmable gate arrays (FPGAs), complex programmable logic devices (CPLDs), etc. Some or all of the system or data structures may also be stored (e.g., as software instruction content or structured data content) in a non-transitory computer-readable storage medium, such as a hard disk or flash drive or other non-volatile storage device, volatile or non-volatile memory (e.g., RAM), network storage device, or portable media product (e.g., DVD disk, CD disk, optical disk, flash memory device, etc.) that is loaded by an appropriate drive or via an appropriate connection. The systems, modules, and data structures may also be transmitted in some embodiments as a generated data signal (e.g., as part of a carrier wave or other analog or digital propagated signal) over a variety of computer-readable transmission media, including wireless-based media and wired / cable-based media, and may take a variety of forms (e.g., as part of a single or multiplexed analog signal, or as multiple individual digital packets or frames). Such computer program products may take other forms in other embodiments. Thus, the present disclosure may be implemented with other computer system configurations.

[0056] Those skilled in the art will recognize that many of the methods or algorithms described herein may utilize additional operations, omit certain operations, and / or perform operations in a different order than specified.

[0057] The various implementations described above can be combined to provide further implementations. In light of the above detailed description, these and other changes can be made to the implementations. In general, in the following claims, the terms used should not be interpreted to limit the claims to the specific implementations disclosed in the specification and claims, but should be interpreted to include all possible implementations along with the full scope of equivalents covered by such claims. Thus, the claims are not limited by this disclosure.

Claims

1. a first spatially varying polarizer configured to receive an incident light beam from a light source, the first spatially varying polarizer operable to diffract light of a first polarization state over a first field of view and to allow incident light having a second polarization state orthogonal to the first polarization state to pass through the first spatially varying polarizer without being diffracted by the first spatially varying polarizer; a second spatially varying polarizer in optical alignment with the first spatially varying polarizer and positioned to receive light from the first spatially varying polarizer, the second spatially varying polarizer operable to diffract light of the second polarization state over a second field of view and operable to pass incident light having the first polarization state without being diffracted by the second spatially varying polarizer; Equipped with the first spatially varying polarizer implements a negative lens having a tilt in a first direction, and the second spatially varying polarizer implements a negative lens having a tilt in a second direction different from the first direction; Optical beam expanding structure.

2. The optical beam expanding structure of claim 1 , wherein the first spatially varying polarizer and the second spatially varying polarizer each have a multi-twist retarder.

3. The optical beam expanding structure of claim 1 or 2, wherein the first spatially varying polarizer and the second spatially varying polarizer each comprise a liquid crystal material.

4. 4. The optical beam expanding structure of claim 1, wherein the first field of view and the second field of view together form a combined field of view that is larger than each of the first field of view and the second field of view.

5. The optical beam expanding structure of claim 1 , wherein the optical beam expanding structure is a component in a head mounted display, a head up display, a time of flight sensor, or a stereo depth sensor.

6. 6. The optical beam expanding structure of claim 1, wherein the first spatially varying polarizer diffracts light of the first polarization state into a first diffraction order, and the second spatially varying polarizer diffracts light of the second polarization state into a second diffraction order different from the first diffraction order.

7. 7. The optical beam expanding structure of claim 6, wherein one of the first diffraction order and the second diffraction order comprises a +1 diffraction order, and the other of the first diffraction order and the second diffraction order comprises a -1 diffraction order.

8. a laser light source operable to generate said incident light beam The optical beam expanding structure of claim 1 , further comprising:

9. 9. The optical beam expanding structure of claim 1, wherein the incident light beam is polarized at an angle that is 45 degrees relative to the first polarization state and the second polarization state.

10. The optical beam expanding structure of claim 1 , wherein the first field of view and the second field of view at least partially overlap each other.

11. The optical beam expanding structure of claim 1 , wherein the second field of view is different from the first field of view.

12. 12. The optical beam expanding structure of claim 1, wherein one of the first and second polarization states comprises p-polarized light and the other of the first and second polarization states comprises s-polarized light.

13. 13. The optical beam expanding structure of claim 1, wherein the first spatially varying polarizer implements a negative lens with a tilt in a first direction and the second spatially varying polarizer implements a negative lens with a tilt in a second direction that is opposite to the first direction.

14. A laser light source; 1. An optical beam expanding structure, comprising: a first spatially varying polarizer configured to receive an incident light beam from the laser light source, the first spatially varying polarizer operable to diffract light of a first polarization state over a first field of view and to allow incident light having a second polarization state orthogonal to the first polarization state to pass through the first spatially varying polarizer without being diffracted by the first spatially varying polarizer; a second spatially varying polarizer in optical alignment with the first spatially varying polarizer and positioned to receive light from the first spatially varying polarizer, the second spatially varying polarizer operable to diffract light of the second polarization state over a second field of view different from the first field of view and operable to pass incident light having the first polarization state without being diffracted by the second spatially varying polarizer; an optical beam expanding structure having Equipped with the first spatially varying polarizer implements a negative lens having a tilt in a first direction, and the second spatially varying polarizer implements a negative lens having a tilt in a second direction different from the first direction; Widen the lighting source.

15. 15. The illumination source of claim 14, wherein the first spatially varying polarizer and the second spatially varying polarizer each have a multi-twist retarder.

16. 16. An illumination source according to claim 14 or 15, wherein the first field of view and the second field of view together form a combined field of view that is larger than each of the first field of view and the second field of view.

17. 17. The illumination source of claim 14, wherein the illumination source is a component in a head mounted display, a head up display, a time of flight sensor, or a stereo depth sensor.

18. 18. The illumination source of claim 14, wherein the first spatially varying polarizer diffracts light of the first polarization state into a first diffraction order and the second spatially varying polarizer diffracts light of the second polarization state into a second diffraction order different from the first diffraction order.

19. 20. The illumination source of claim 18, wherein one of the first and second diffraction orders comprises a +1 diffraction order, and the other of the first and second diffraction orders comprises a -1 diffraction order.

20. 20. An illumination source according to any one of claims 14 to 19, wherein the incident light beam is polarized at an angle that is 45 degrees relative to the first and second polarization states.

21. At least one camera; 1. An illumination source comprising: A laser light source; 1. An optical beam expanding structure, comprising: a first spatially varying polarizer configured to receive an incident light beam from the laser light source, the first spatially varying polarizer operable to diffract light of a first polarization state over a first field of view and to allow incident light having a second polarization state orthogonal to the first polarization state to pass through the first spatially varying polarizer without being diffracted by the first spatially varying polarizer; a second spatially varying polarizer in optical alignment with the first spatially varying polarizer and positioned to receive light from the first spatially varying polarizer, the second spatially varying polarizer operable to diffract light of the second polarization state over a second field of view and operable to pass incident light having the first polarization state without being diffracted by the second spatially varying polarizer; an optical beam expanding structure having an illumination source having Equipped with the first spatially varying polarizer implements a negative lens having a tilt in a first direction, and the second spatially varying polarizer implements a negative lens having a tilt in a second direction different from the first direction; Depth camera system.

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