Patent Publication Number: US-10317678-B2

Title: Catadioptric on-axis virtual/augmented reality glasses system and method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 62/292,805, filed Feb. 8, 2016, the entire contents of which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to display technology, and more particularly to virtual/augmented reality glasses systems. 
     BACKGROUND 
     Virtual reality (e.g., Oculus® Rift, etc.) and/or augmented reality (e.g., Google® Glass, etc.) head mounted displays (HMDs) are gaining popularity in the consumer marketplace. This technology has also been adapted in many professional applications, such as being implemented in training simulators or targeting systems. The primary goal of these devices is to provide visual information to a user wearing a headset, where the visual information appears as natural as possible. Such headsets aim to preserve good optical qualities such as image sharpness, expansive Field-of-View (FOV), accurate color reproduction, high refresh rates, and low latency. Current techniques for implementing such devices include: (1) utilizing a beam-splitter to present off-axis visual information as being received from an on-axis orientation; (2) utilizing freeform optics that leverage complex, aspheric surfaces implemented inside a prism to unify the functions of separate relay, magnification, and combining of a virtual image; and (3) utilizing a direct-view, near-eye display such as a display implemented as a contact lens that includes polarization-selective filters and a microlens array. 
     However, these current techniques have some deficiencies. The first major challenge is relaying an off-axis optical path to be received at the eye from an on-axis orientation. The various solutions to this challenge introduce distortions (e.g., geometric distortions, chromatic aberrations, replicated images due to diffraction, large spatial variation of optical performance, etc.), are limited to a small FOV that is different from the FOV of a human eye, do not support color information, lead to complex light engines for supporting accommodation cues, lead to eye aperture, size-dependent complex image formation techniques, and are restricted to a small eye box that enables a user to perceive the display. A more robust design is desired to correct or mitigate one or more of these deficiencies. 
     SUMMARY 
     A method and system for operating a catadioptric glasses system is presented. The method includes the steps of generating an image via a light engine included in a glasses system and projecting the image onto a display that includes a diffusion layer positioned between a curved mirror and a user&#39;s retina. Light emitted from a surface of the diffusion layer is reflected off the curved mirror to the user&#39;s retina through the diffusion layer, and the diffusion layer is located between a focal point of the curved mirror and a surface of the curved mirror. The diffusion layer may be mechanically moved relative to the user&#39;s eye to enable light to pass through transparent regions in the diffusion layer in a time multiplexed fashion. The glasses system may also include a mirror stack to enable different virtual images to be formed at different depths. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a head mounted display, in accordance with one embodiment; 
         FIG. 2  illustrates the operation the head mounted display, in accordance with one embodiment; 
         FIGS. 3A through 3C  illustrate the operation of a rotating diffuser, in accordance with one embodiment; 
         FIG. 4  illustrates the operation of the head mounted display, in accordance with another embodiment; 
         FIG. 5  illustrates the operation of the head mounted display, in accordance with yet another embodiment; 
         FIG. 6  illustrates a light engine of the glasses system, in accordance with one embodiment; 
         FIG. 7  illustrates a flowchart of a method for operating the glasses system, in accordance with one embodiment; and 
         FIG. 8  illustrates an exemplary system in which the various architecture and/or functionality of the various previous embodiments may be implemented. 
     
    
    
     DETAILED DESCRIPTION 
     A catadioptric system utilizes both refraction and reflection to focus light in an optical system. A catadioptric head mounted display (HMD) utilizes one or more lenses to focus a beam of light from an off-axis projector onto a diffusion layer and one or more curved mirrors to reflect light from the diffusion layer onto a user&#39;s retina from an on-axis orientation. Various embodiments of the diffusion layer enable light reflected off the curved mirror to pass through the diffusion layer and reach the user&#39;s retina. The curved mirror may also be translucent or transparent in a range of wavelengths or polarizations that enable the user to see through, at least partially, both the diffusion layer and the curved mirror such that the HMD can be utilized in an augmented reality application. 
       FIG. 1  illustrates a head mounted display  100 , in accordance with one embodiment. The HMD  100  includes a light engine  110  and a display  120 . The light engine  110  is configured to multiplex and modulate light to project visual information to the display  120 . The display  120  includes a diffuser that is at least partially see-through. The display  120  also includes a curved mirror that reflects light from the diffuser to relay the light back to a user&#39;s retina. 
     In one embodiment, the light engine  110  projects light onto the diffuser from an off-axis orientation. As shown in  FIG. 1 , the light engine  110  may be placed on the side of the user&#39;s head by fixing the light engine  110  to a frame of the HMD  100 . The light engine  100  includes a projector and one or more lenses capable of projecting an image onto a surface of the diffuser. The light engine  110  is configured to modulate at least one of a polarization of light, a wavelength (color) of light, and a focus of light projected onto a surface of the diffuser. 
     In one embodiment, the light engine  110  includes a processor and a memory. Images, in the form of a sequence of image frames to be projected onto the diffuser, may be received by the light engine  110  and stored in the memory. The images may be processed by the processor to generate control signals for operating the projector. The light engine  110  may also include a communications interface, either wired or wireless, for receiving the images. For example, the images may be received via a Bluetooth or WiFi interface, or the images may be received via a USB interface and stored in the memory. 
     In one embodiment, the HMD  100  is a monocular display in that a light engine  110  and display  120  project visual information into a single eye of the user. In another embodiment, the HMD  100  is a binocular display in that the HMD  100  includes a pair of light engines  110  and corresponding displays  120  for each of the user&#39;s eyes. 
       FIG. 2  illustrates the operation the HMD  100 , in accordance with one embodiment. As shown in  FIG. 2 , the HMD  100  includes a projector  210  (included in the light engine  110 ) that projects light  212  forming an image on a surface of a diffuser  220 . The light is diffused through the diffuser  220  such that the front surface (i.e., the side furthest from a user&#39;s eye  200 ) of the diffuser  220  is illuminated with the image projected by the projector  210 . The image is reflected off a curved mirror  230  back through the diffuser  220  to be directed at the user&#39;s eye  200 . The light reflected by the curved mirror  230  passes through the lens  202  of the eye and strikes the user&#39;s retina  204 . Light paths  240  and  250  illustrate how the curved mirror  230  reflects light from particular points on the surface of the diffuser  220  back to corresponding locations on the retina  204 . 
     In one embodiment, the curved mirror  230  is at least partially transparent to enable the HMD  100  to be utilized in an augmented reality environment. The curved mirror  230  may be designed to only reflect a portion of light from the diffuser  220  back to the user and allow a portion of light from beyond the curved mirror  230  to pass through the curved mirror  230  to reach the user&#39;s eye. Consequently, the curved mirror  230  enables a user to combine visual information from the front surface of the diffuser  220  with visual information from the environment beyond the curved mirror  230 . As used herein, the front surface of the diffuser  220  refers to the surface proximate the curved mirror  230  and the rear surface of the diffuser  220  refers to the surface proximate the user&#39;s eye  200 . In some embodiments, the curved mirror  230  may be replaced with any equivalent optical structure that enables some light to pass through the structure from the environment beyond the optical structure and reflects at least some light from the diffuser  220  back towards the user&#39;s eye  200 . 
     It will be appreciated that the curvature of the curved mirror  230  may be adapted to change the perceived depth of the virtual image reflected back to the user&#39;s eye  200 . The image is a virtual image when the front surface of the diffuser  220  is located between the focal point of the curved mirror  230  and the surface of the curved mirror  230 . The location of the diffuser  220  relative to the focal point and the radius of curvature of the curved mirror  230  may also be adjusted to change a magnification of the virtual image compared to the image formed on the front surface of the diffuser  220  as well as to change a perceived depth of the virtual image. Some prior art displays have been adapted with diffusers and microlens mirror arrays to project an image to a viewer. However, the focal point of each lens in the microlens array is located closer to the lens than the diffuser, such that the image seen by the viewer does not appear to be a virtual image further from the viewer than the display. Consequently, this type of technology is not suitable for near eye displays such as the HMD  100  because the image formed would be outside of the accommodation range of the user&#39;s eye. In contrast, a single curved mirror  230  rather than a microlens array enables the diffuser  220  to be placed at a location at which formation of a virtual image at a position beyond the front surface of the curved mirror  230  is optimal for near eye displays. 
     The diffuser  220  is partially transparent to allow light reflected off the curved mirror  230  to pass through the diffuser  220  on the way to the eye  200 . In one embodiment, the diffuser  220  is manufactured as a transparent sheet overlaid on a light diffuser film, where portions of the light diffuser film have been removed to form a grid of alternating translucent and transparent regions. The transparent sheet may be rigid, such as a polycarbonate resin or other polymer with see-through properties. In another embodiment, the diffuser  220  may include a liquid crystal material. The diffuser  220  allows light to pass through the transparent regions while light from the projector  210  that strikes the front side of the diffuser  220  is diffused throughout the translucent regions. Consequently, the translucent regions can act as point light sources for a blurred portion of the image projected onto the front side of the diffuser  220  by the projector  210 . 
       FIGS. 3A through 3C  illustrate the operation of a rotating diffuser  220 , in accordance with one embodiment. As shown in  FIG. 3A , the diffuser  220  may be positioned perpendicular to a line of sight from a user&#39;s eye. A top view  310  of the diffuser  220  shows the orientation of the diffuser  220  to the line of sight. A magnified front view  320  of the diffuser  220 , illustrates the grid of alternating translucent and transparent regions of the diffuser  220 . A wireframe drawing of a sphere can be seen through the transparent regions of the diffuser  220 , while the translucent regions at least partially obscure the wireframe drawing of the sphere. 
     The resolution of the grid is small enough such that a user may not be able to resolve individual cells of the grid when the diffuser  220  is positioned close to the eye  200 . This is especially true when the user&#39;s focus is directed to a point far beyond the surface of the curved mirror  230 . In effect, the user simultaneously perceives a low-resolution view of the translucent regions of the diffuser  220  (possibly out of focus) along with a low-resolution view of the environment beyond the diffuser  220 . The result is that a user will combine the visual information from the translucent environment on the front surface of the diffuser  220 , albeit potentially out of focus, visual information from the back surface of the diffuser  220 , reflected off the curved mirror  230 , and the visual information from the environment beyond the curved mirror  230 . As used herein, “the environment beyond the curved mirror  230 ” refers to the environment located in space a distance further away from the user&#39;s eye  200  than the reflective surface of the curved mirror  230 . 
     In one embodiment, the diffuser  220  may be located outside the accommodation range of a user&#39;s eye. In other words, the diffuser  220  may be located at a position close enough to the eye  200  that the user cannot bring the front surface of the diffuser  220  into focus. This is desired because, ideally, the goal is to augment a virtual image of the front surface of the diffuser  220 , as reflected off the curved mirror  230 , located at a perceived depth that is proximate to the point of focus of the user in the environment beyond the curved mirror  230 . In other words, the goal is to allow the user&#39;s eye to focus at a particular depth that keeps both the virtual image from the display and objects in the environment beyond the curved mirror  230  in focus at the same time. This prevents fatigue as the user&#39;s eye  200  is not straining to resolve objects at two different depths. 
     Still, if the location of the diffuser  220  is static, any visual information from the external environment obscured by the translucent regions of the diffuser  220  will not reach the user&#39;s eye (or will at least be blurred as the visual information is diffused throughout the translucent region). As an example, the view of the sphere in the front view  320  of  FIG. 3A  shows the translucent regions of the diffuser  220  as obscuring approximately half of the sphere. Since the HMD  100  is a wearable device, the natural motion of the user&#39;s head is likely to change the view of the sphere that passes through the transparent regions of the diffuser  220 . However, additional steps can be implemented to reduce the amount of visual information that is obscured by the translucent regions of the diffuser  220 . 
     In one embodiment, the diffuser  220  may be dynamically moved relative to the user&#39;s eye  200  in order to change the visual information that reaches the eye  200  through the transparent regions of the diffuser  220 . As shown in the top view  310  of  FIG. 3B , the diffuser  220  may be rotated around an axis offset from the line of sight such that the horizontal projection of the each of the cells of the grid in the diffuser  220  is not perpendicular to the line of sight. The diffuser  220  is rotated relative to a plane perpendicular to the line of sight by an angle α 1 . As shown in the front view  320  of  FIG. 3B , the location and projection of the grid has changed relative to the user&#39;s eye  200 , enabling different visual information from the external environment to reach the user&#39;s eye  200  through the transparent regions of the diffuser  220 . As shown in the top view  310  of  FIG. 3C , the diffuser  220  may continue rotating around the axis such that the angle between the diffuser  220  and the plane perpendicular to the line of sight is increased to an angle α 2 . Again, as shown in the front view  320  of  FIG. 3C , the location and projection of the grid has once again changed relative to the user&#39;s eye  200 . 
     In operation, the orientation of the diffuser  220  relative to the line of sight may be cycled between a range of angles such that the relative location of the transparent regions of the diffuser are continuously moving. The cycling rate of the orientation throughout the range of angles may be fast enough that the user perceives a full picture of the visual information from the external environment as the visual information is accumulated on the retina. The cycling rate may be fast enough that the user cannot perceive the small change in orientation of the diffuser  220  and the diffuser simply appears transparent to the user. 
     In another embodiment, the diffuser  220  may be rotated around a horizontal axis such that the grid shifts and the projection changes in a vertical direction. In yet another embodiment, the diffuser  220  may be shifted in a horizontal direction or vertical direction along the plane perpendicular to the line of sight such that the projection of the grid on the retina is not compressed in any one direction, but the relative location of the grid is moved relative to the retina. For example, the diffuser  220  may be shifted to the left by an amount equal to the width of one cell of the grid, and then shifted back to the right by an equal amount. The shifting can be accomplished by a piezo-electric device that operates at a high frequency. 
     In one embodiment, the projector  210  is synchronized with the motion of the diffuser  220 . For example, the projector may be configured to project an image onto the diffuser  220  when the diffuser is approximately perpendicular to the line of sight. However, as the diffuser  220  is moved such that the angle between a normal of the surface of the diffuser  220  and the line of sight increases above a threshold angle, the projector  210  will block the light  212  from being projected onto the surface of the diffuser  220 . In one embodiment, the projector may include a liquid crystal element and a polarizer filter that enables the projector to attenuate the light through the liquid crystal element. The liquid crystal element can then be synchronized with the angle of the diffuser to only allow light  212  to be projected onto the surface of the diffuser  220  when the angle is within a certain range. 
     It will be appreciated that the layout of the grid is only one exemplary layout, and that, in other embodiments, the layout of the grid may be different than an alternating 2D pattern shown in  FIGS. 3A through 3C . In one embodiment, the grid remains the same, but the ratio of translucent regions to transparent regions is different such that there are many more transparent regions that fully surround translucent regions. In another embodiment, the shape of translucent regions may be circular and arranged in a 2D grid over a transparent field. In yet another embodiment, the grid may be an a periodic structure that, when combined with the motion of the diffuser  220 , scans across a plane to form a full translucent region in a time multiplexed fashion. 
       FIG. 4  illustrates the operation of the HMD  100 , in accordance with another embodiment. As shown in  FIG. 4 , the HMD  100  includes a projector  410  (included in the light engine  110 ) that projects polarized light  412  on a polarization-selective scatterer  420 , thereby forming an image on a front surface of the scatterer  420 . The scatterer  420  is a form of diffuser that only diffuses light polarized at a specific orientation, or within a small band of orientations (e.g., +/−5 degrees of vertical polarization). Light polarized at other orientations passes through the scatterer  420  as if the scatterer  420  was transparent. In one embodiment, the scatterer  420  comprises liquid crystal elements stretched along one axis to diffuse light along the long axis that has a polarization. 
     The scatterer  420  is illuminated with the light  412  projected by the projector  410 , the projector  410  is configured to polarize the light  412  such that the light is diffused by the scatterer  420 , thereby forming an image on the front surface of the scatterer  420  that is proximate the reflective surface of a curved mirror  430 . The image is then reflected off the curved mirror  430  and reflected back through the scatterer  420  to be directed at the user&#39;s eye  200 . The curved mirror  430  may include a surface treatment that changes the polarization of the light reflected off the curved mirror  430  such that the light, passing back through the scatterer  420  is not diffused and passes directly back towards the eye  200 . The light reflected by the curved mirror  430  passes through a polarizer  440 . The polarizer  440  is located between the scatterer  420  and the eye  200  such that light reflected or emitted from the front surface of the scatterer  420  does not reach the eye  200  directly (i.e., only the light of different polarization after being reflected off the curved mirror  430  will pass through the polarizer  440  to reach the user&#39;s eye  200 ). Again, the scatterer  420  may be located at a distance from the surface of the curved mirror that is between the focal point of the curved mirror  430  and a surface of the curved mirror  430 . Consequently, the only visual information that reaches the eye  200  should be visual information reflected off the curved mirror  430  and visual information from the external environment that passes through the curved mirror  430 . 
     In one embodiment, the surface treatment on the curved mirror  430  comprises a wave retarder film affixed to the surface of the curved mirror  430 . In another embodiment, the surface treatment may be omitted in lieu of a Quarter-Wave Plate placed between the scatterer  420  and the curved mirror  430 . In this case, the Quarter-Wave Plate changes the polarization of light as the light passes through the Quarter-Wave Plate from linear polarized light to circular polarized light, which is then reflected off the surface of the curved mirror  430  and passes back through the Quarter-Wave Plate to change the circular polarized light back to linear polarized light having an orientation 90 degrees relative to the orientation of the light emitted from the diffuser  420 . 
     The polarization selective scatterer  420  does not need to be rotated like the diffuser  220  in  FIG. 2  because the surface of the scatterer  420  is uniform and there is no difference between different regions of the scatterer  420 . Again, light polarized off axis relative to the polarization of the scatterer  420  will pass through the scatterer  420  towards the eye without being diffused, whereas light  412  from the projector  410 , polarized at a particular polarization to match a characteristic of the scatterer  420 , will be diffused, forming an image on the front surface of the scatterer  420  that is reflected back to the eye  200  at a different polarization. It will be appreciated that the polarization-selective scatterer  420  is not an ideal component. In other words, the scatterer  420  will diffuse some horizontally polarized light as well as vertically polarized light, although the diffusion of the horizontally polarized light may be much less than the diffusion of the vertically polarized light. 
       FIG. 5  illustrates the operation of the HMD  100 , in accordance with yet another embodiment. As shown in  FIG. 5 , the HMD  100  includes a projector  510  (included in the light engine  110 ) that projects polarized light  512  towards a diffuser  520 , forming an image on a front surface of the diffuser  520 , similar to the technique described above corresponding to the diffuser  220  of  FIGS. 2 and 3A through 3C . However, instead of a single curved mirror  230 , the HMD  100  includes a stack  530  of a plurality of curved mirrors. Each curved mirror in the stack  530  has a different radius of curvature, such that the magnification and perceived depth of the virtual image is different for each mirror. Each mirror, such as mirror  532 , mirror  534 , and mirror  536 , selectively reflects light of a specific wavelength or polarization, or within a small band of wavelengths or polarizations. Again, the diffuser  520  may be located at a distance from the surface of each curved mirror in the stack  530  that is between the focal point of the curved mirror and a surface of the curved mirror. 
     For example, mirror  532  may reflect light of wavelengths corresponding to a first color band, mirror  534  may reflect light of wavelengths corresponding to a second color band, and mirror  536  may reflect light of wavelengths corresponding to a third color band. The projector  510  may then project light  512  to form an image with light in each of the three color bands. The portion of the image corresponding to light in the first color band will be reflected by mirror  532  in a virtual image at a first perceived depth, the portion of the image corresponding to light in the second color band will be reflected by mirror  534  in a virtual image at a second perceived depth, and the portion of the image corresponding to light in the third color band will be reflected by mirror  536  in a virtual image at a third perceived depth. The light engine  110  may then process images to generate light  512  of a certain wavelength to create a virtual image that is perceived by a user at a particular depth. In addition, the image processing may combine images of different wavelengths into a single, multi-color image projected onto the diffuser  520  to produce virtual images perceived by a user at different depths. 
     In a different embodiment, the diffuser  520  may be replaced by sets of polarization scatterers  420  and corresponding polarizers  440  corresponding to the different mirrors in the stack  530  of curved mirrors. In such an embodiment, the mirrors may selectively reflect light of different polarizations. Consequently, the light engine  110  may be configured to generate images of particular polarization to create virtual images perceived by a user at different depths. The projector  510  may be configured to display the images at different polarizations in a time division multiplexed manner, such that light  512  of a first polarization is projected to form a first image on a corresponding scatterer  420  during a first time period, light  512  of a second polarization is projected to form a second image on a different scatterer  420  during a second time period, and so forth. The time periods may be of short duration such that a number of different images are projected at a frequency where the images are perceived as combined to a user (e.g., cycling the images such that a full cycle of a plurality of images of different polarizations are projected at a frame rate of 30 Hz or greater). 
     In one embodiment, the HMD  100  may be a varifocal display. By moving the diffuser  220  and the curved mirror  230  closer to or further from the eye  200 , the focal plane of the virtual image will move relative to the eye  200 . Consequently, the diffuser  220  and curved mirror  230  can be actuated to move along the line of sight to accommodate various focal planes in a dynamic fashion. Varifocal displays are particularly useful in augmented reality displays because the object of a user&#39;s focus may be at various distances from the user, and varying the focal plane of the virtual image to be at a proximate distance of a particular object makes using augmented reality displays more comfortable as the user is not trying to focus at two vastly different distances. It will be appreciated that the scatterer  420  and curved mirror  430  as well as the diffuser  520  and stack  530  may be moved in a similar fashion to the diffuser  220  and curved mirror  230 . 
       FIG. 6  illustrates a light engine  110  of the glasses system  100 , in accordance with one embodiment. Again, the light engine  110  includes electronics for generating images to project onto the display  120 , and a projector to modulate a light source (included in the projector) to project those images onto a diffusion layer of the display  120 . In one embodiment, the light engine  110  includes a projector  610 , a processor  620 , a memory  630 , an interface  650 , a power management integrated circuit (PMIC)  680 , and a battery  685 . The projector  610  may be projector  210 , projector  410 , or projector  510  of  FIGS. 2, 4, and 5 . The processor  620  and memory  630  may be implemented in a single package configuration (e.g., package-on-package (POP)) and affixed via solder to a printed circuit board (PCB) that includes the interface  650  and PMIC  680  affixed thereto. The battery  685  may be a lithium ion battery, which may be recharged using the PMIC  680  when the glasses system  100  is connected to an external power source. Alternatively, the battery  685  may be a disposable coin-type battery that can be replaced when the battery  685  is drained of charge. 
     In one embodiment, the interface  650  comprises a controller that implements a wireless communications standard such as IEEE 802.15 (i.e., Bluetooth) or IEEE 802.11 (i.e., Wi-Fi). The controller may include one or more transceivers and an antenna array consisting of one or more antennas for transmitting or receiving data via wireless channels. The controller may also include an on-chip memory for storing data received from the processor  620  for transmission over the wireless channels or data to be transmitted to the processor  620  received over the wireless channels. In another embodiment, the interface  650  comprises a controller that implements a wired communications standard such as a USB interface. The interface  650  may include a physical interface for plugging a cable into the glasses system  100  as well as a controller for managing communications over the communications channel(s). 
     In one embodiment, the processor  620  receives image data to be displayed on the glasses system  100  via the channels connected to the interface  650 . The image data may be stored in the memory  630 . The processor  620  may also implement algorithms for modifying the image data in the memory  630 . For example, the processor  620  may warp the image data based on parameters stored in the memory  630  that map the image data to a user&#39;s retina based on characteristics of the display and/or a user&#39;s eye. For example, the parameters may enable image data to be warped to correct for aberrations in the optical components of the display  120 . Alternatively, the parameters may enable image data to be warped to accommodate a corrective lens prescription for a user so that the display can be seen without corrective lenses. In another embodiment, the processor  620  receives instructions and/or data and is configured to generate image data for display. For example, the processor  620  may receive 3D geometric primitive data to be rendered based on the instructions to generate the image data in the memory  630 . 
     The image data may then be transmitted to the projector  610 , which modulates a light source to project light to the display  120 . In one embodiment, the projector may include a white light source positioned behind one or more lenses, light modulating elements (e.g., liquid crystal panels, micro-electromechanical scanners (MEMS), or digital micromirror devices (DMD)), color filter arrays, and polarizing filters. The projector  610  is configured to modulate at least one of a polarization of light, a wavelength of light, and/or a focus of light projected onto a surface of the diffusion layer by controlling the various elements enumerated above. The light is projected to form an image on a surface of the diffusion layer of the display  120 . 
     It will be appreciated that the light engine  110  described and shown in  FIG. 6  is only one such example of the light engine  110 . Other embodiments of the light engine  110  are contemplated as being within the scope of the present disclosure, including but not limited to different light modulating technology such as laser projection; an application specific integrated circuit (ASIC) that includes the processor  620 , memory  630 , PMIC  680 , and/or interface  650  on a single die; and a more complex system with multiple processors (e.g., CPU and GPU) as well as other components in addition to or in lieu of the components shown in  FIG. 7 . 
       FIG. 7  illustrates a flowchart of a method  700  for operating the glasses system  100 , in accordance with one embodiment. It will be appreciated that at least some steps of the method  700  are described within the scope of software executed by a processor; however, in some embodiments, portions of the method  700  may be implemented in hardware or some combination of hardware and software. 
     The method  700  begins at step  702 , where a light engine  110  included in the glasses system  100  generates an image. In one embodiment, the light engine  110  receives image data from a communications channel and stores the image data in a memory. A processor in the light engine  110  may be configured to process the image data prior to display, such as by warping the image data to form image data for a corresponding warped image. In another embodiment, the light engine  110  implements a program (i.e., a set of instructions) that renders the image data from source data, such as a stream of geometric primitives associated with a 3D model. 
     At step  704 , the image is projected onto a display that includes a diffusion layer positioned between a curved mirror and a user&#39;s retina. In one embodiment, a projector  210  projects light onto a rear surface (i.e., the surface proximate the user&#39;s eye) of the diffuser  220 , which forms an image on the front surface of the diffuser  220 . The image on the front surface of the diffuser  220  is reflected off the surface of the curved mirror and directed back towards the user&#39;s retina  204  through the transparent regions of the diffuser  220 . The diffuser  220  is dynamically moved relative to a line of sight of the eye  200  such that the image reflected back through the different transparent regions of the diffuser  220  reaches as much of the user&#39;s retina  204  as possible, thereby preventing the user from perceiving the occluded portion of the reflected image striking the translucent regions of the diffuser  220 . In another embodiment, a projector  410  projects polarized light onto a rear surface of a scatterer  420 , which forms an image on the front surface of the scatterer  420 . The image on the front surface of the scatterer  420  is reflected off the surface of the curved mirror, passing through a wave retarder film on the surface of the curved mirror, and directed back towards the user&#39;s retina  204  through the scatterer  420 , which transmits the reflected image of different polarization through a polarizing filter  440  and to the user&#39;s eye  200 . In yet another embodiment, a projector  510  projects light of one or more wavelengths and/or polarizations onto a diffuser  520 , which forms an image on the front surface of the diffuser  520 . The image on the front surface of the diffuser  520  is reflected off the surface of one of a plurality of curved mirrors having selective-reflective characteristics based on polarization and/or wavelength and directed back towards the user&#39;s retina  204 . 
       FIG. 8  illustrates an exemplary system  800  in which the various architecture and/or functionality of the various previous embodiments may be implemented. As shown, a system  800  is provided including at least one central processor  801  that is connected to a communication bus  802 . The communication bus  802  may be implemented using any suitable protocol, such as PCI (Peripheral Component Interconnect), PCI-Express, AGP (Accelerated Graphics Port), HyperTransport, or any other bus or point-to-point communication protocol(s). The system  800  also includes a main memory  804 . Control logic (software) and data are stored in the main memory  804  which may take the form of random access memory (RAM). 
     The system  800  also includes input devices  812 , a graphics processor  806 , and a display  808 , i.e. a conventional CRT (cathode ray tube), LCD (liquid crystal display), LED (light emitting diode), plasma display, HMD, or the like. User input may be received from the input devices  812 , e.g., keyboard, mouse, touchpad, microphone, and the like. In one embodiment, the graphics processor  806  may include a plurality of shader modules, a rasterization module, etc. Each of the foregoing modules may even be situated on a single semiconductor platform to form a graphics processing unit (GPU). 
     In the present description, a single semiconductor platform may refer to a sole unitary semiconductor-based integrated circuit or chip. It should be noted that the term single semiconductor platform may also refer to multi-chip modules with increased connectivity which simulate on-chip operation, and make substantial improvements over utilizing a conventional central processing unit (CPU) and bus implementation. Of course, the various modules may also be situated separately or in various combinations of semiconductor platforms per the desires of the user. 
     The system  800  may also include a secondary storage  810 . The secondary storage  810  includes, for example, a hard disk drive and/or a removable storage drive, representing a floppy disk drive, a magnetic tape drive, a compact disk drive, digital versatile disk (DVD) drive, recording device, universal serial bus (USB) flash memory. The removable storage drive reads from and/or writes to a removable storage unit in a well-known manner. 
     Computer programs, or computer control logic algorithms, may be stored in the main memory  804  and/or the secondary storage  810 . Such computer programs, when executed, enable the system  800  to perform various functions. The memory  804 , the storage  810 , and/or any other storage are possible examples of computer-readable media. 
     In one embodiment, the architecture and/or functionality of the various previous figures may be implemented in the context of the central processor  801 , the graphics processor  806 , an integrated circuit (not shown) that is capable of at least a portion of the capabilities of both the central processor  801  and the graphics processor  806 , a chipset (i.e., a group of integrated circuits designed to work and sold as a unit for performing related functions, etc.), and/or any other integrated circuit for that matter. 
     Still yet, the architecture and/or functionality of the various previous figures may be implemented in the context of a general computer system, a circuit board system, a game console system dedicated for entertainment purposes, an application-specific system, and/or any other desired system. For example, the system  800  may take the form of a desktop computer, laptop computer, server, workstation, game consoles, embedded system, and/or any other type of logic. Still yet, the system  800  may take the form of various other devices including, but not limited to a personal digital assistant (PDA) device, a mobile phone device, a television, etc. 
     Further, while not shown, the system  800  may be coupled to a network (e.g., a telecommunications network, local area network (LAN), wireless network, wide area network (WAN) such as the Internet, peer-to-peer network, cable network, or the like) for communication purposes. 
     While various embodiments have been described above, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of a preferred embodiment should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.