PATENT DOCUMENT

Publication Number: US-12111467-B2
Application Number: US-201916409681-A
Country: US
Kind Code: B2

Title: Electronic device with multi-element display illumination system

Abstract:
An electronic device may have a spatial light modulator. Control circuitry in the electronic device may use the spatial light modulator to generate images. A light source may be used to produce illumination for the spatial light modulator. An optical system may direct the illumination onto the spatial light modulator and may direct corresponding reflected image light towards eye boxes for viewing by a user. Head-mounted support structures may be used to support the spatial light modulator, light source, and optical system. The light source may include light-emitting elements such as light-emitting diodes or lasers. Multiple light-emitting elements may be provided in the light source in a one-dimensional or two-dimensional array. During operation, the control circuitry can individually adjust the light-emitting elements.

Claims:
What is claimed is: 
     
       1. An electronic device comprising:
 light sources configured to produce illumination; 
 a spatial light modulator configured to produce light by reflecting the illumination; and 
 optics configured to redirect the light, wherein
 the optics impart the light with an off-axis roll off in intensity across a field of view of the light, 
 the light sources are configured to compensate for the off-axis roll off in intensity produced by the optics, and 
 the optics comprise a hologram or an optical combiner. 
 
 
     
     
       2. The electronic device of  claim 1 , wherein the optics comprise at least one lens. 
     
     
       3. The electronic device of  claim 1 , wherein the optics comprise a waveguide. 
     
     
       4. The electronic device of  claim 1 , wherein the spatial light modulator comprises a digital micromirror device. 
     
     
       5. The electronic device of  claim 1 , wherein the spatial light modulator comprises a liquid-crystal-on-silicon device. 
     
     
       6. The electronic device of  claim 1 , wherein the light sources are arranged in an array. 
     
     
       7. The electronic device of  claim 6 , wherein the light sources comprise a first light source at a central axis of the array and a second light source off the central axis of the array, the first light source has a first intensity, and the second light source has a second intensity less than the first intensity. 
     
     
       8. The electronic device of  claim 1 , wherein the light sources are configured to compensate for the off-axis roll off in intensity by producing the illumination with an intensity profile that varies across the field of view. 
     
     
       9. An electronic device comprising:
 light sources configured to produce illumination; 
 a spatial light modulator configured to produce light by reflecting the illumination; and 
 optics configured to redirect the light, wherein the optics impart the light with an off-axis roll off in intensity across a field of view of the light, the light sources are configured to compensate for the off-axis roll off in intensity produced by the optics, the light sources are configured to compensate for the off-axis roll off in intensity by producing the illumination with an intensity profile that varies across the field of view, and the intensity profile decreases away from a central axis of the field of view. 
 
     
     
       10. An electronic device comprising:
 light sources configured to produce illumination; 
 a spatial light modulator configured to produce light by reflecting the illumination; 
 optics configured to redirect the light, wherein
 the optics impart the light with an off-axis roll off in intensity across a field of view of the light, and 
 the light sources are configured to compensate for the off-axis roll off in intensity produced by the optics; and 
 one or more processors configured to provide image data to the spatial light modulator, the one or more processors being configured to further compensate for the off- axis roll off in intensity by pre-distorting the image data. 
 
 
     
     
       11. An electronic device comprising:
 an array of light sources configured to emit illumination; 
 a spatial light modulator configured to generate reflected light based on the illumination; and 
 optics configured to direct the reflected light, the array of light sources being configured to exhibit an intensity profile that has a variation across a field of view of the reflected light, wherein
 the optics impart the reflected light with an off-axis distortion across the field of view that at least partially reverses the variation in the intensity profile exhibited by the one or more light sources, and 
 the one or more processors are configured to control the array of light sources to exhibit the intensity profile by performing an operation selected from the group consisting of: 
 adjusting pulse width modulation of the light sources across the array, and 
 adjusting current provided to the light sources across the array. 
 
 
     
     
       12. The electronic device of  claim 11 , wherein the spatial light modulator comprises a digital micromirror device. 
     
     
       13. The electronic device of  claim 11 , wherein the spatial light modulator comprises a liquid-crystal-on-silicon device. 
     
     
       14. The electronic device of  claim 11 , the one or more processors being configured to provide image data to the spatial light modulator and being configured to further compensate for the off-axis roll off in intensity by pre-distorting the image data.

Description:
This application claims the benefit of provisional patent application No. 62/691,513, filed Jun. 28, 2018, which is hereby incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     This relates generally to electronic devices and, more particularly, to electronic devices with displays. 
     Electronic devices often include displays. For example, a head-mounted device such as a pair of virtual reality or mixed reality glasses may have a display for displaying images for a user. The display may include a spatial light modulator with pixels that produce images for a user. An optical system provides illumination for the spatial light modulator so that the user can view the images. 
     It can be challenging to form display illumination systems for devices such as head-mounted devices. If care is not taken, an illumination system will not be sufficiently compact to wear on the head of a user or may not exhibit satisfactory optical performance. 
     SUMMARY 
     An electronic device may have a spatial light modulator. Control circuitry in the electronic device may use the spatial light modulator to generate images. A light source may be used to produce illumination for the spatial light modulator. An optical system may direct the illumination onto the spatial light modulator and may direct corresponding reflected image light towards eye boxes for viewing by a user. 
     Head-mounted support structures may be used to support the spatial light modulator, light source, and optical system. The light source may include light-emitting elements such as light-emitting diodes or lasers. Multiple light-emitting elements may be provided in the light source in a one-dimensional or two-dimensional array. During operation, the control circuitry can individually adjust the light-emitting elements. 
     The light-emitting elements may be arranged in an array so that different light-emitting elements produce light that illuminates different regions of the spatial light modulator. The light-emitting elements may include white light emitting elements or colored light-emitting elements such as red, green, and blue light-emitting elements. 
     The optical system may use lenses, optical combiners based on dichroic wedges, holograms, tunable gratings, metastructures, or other optical combiner structures, may include polarizing beam splitters, may include prisms, beam steering devices, and/or other optical components. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a diagram of an illustrative electronic device having a display in accordance with an embodiment. 
         FIGS.  2  and  3    are diagrams of illustrative optical system components for providing illumination to a spatial light modulator and directing image light to an eye box for viewing by a user in accordance with embodiments. 
         FIG.  4    is a diagram of an illustrative display system in accordance with an embodiment. 
         FIG.  5    is a graph in which illumination intensity has been plotted as a function of distance across the spatial light modulator of  FIG.  4    in accordance with an embodiment. 
         FIGS.  6 ,  7 , and  8    are diagrams of illustrative multielement light sources for display illumination systems in accordance with embodiments. 
         FIG.  9    is a cross-sectional side view of a portion of a tapered light tunnel array and associated light source element in accordance with an embodiment. 
         FIG.  10    is a diagram of an illustrative illumination system that includes a combiner that combines light of different wavelengths to provide multiwavelength illumination in accordance with an embodiment. 
         FIGS.  11  and  12    are diagrams of illustrative patterns of light-emitting elements that may be used in forming a multielement light source for the illustrative system of  FIG.  10    in accordance with an embodiment. 
         FIG.  13    is a diagram of an illustrative display system having an optical system with components for combining light of multiple wavelengths to provide multiwavelength illumination to a spatial light modulator in accordance with an embodiment. 
         FIGS.  14  and  15    are diagrams of an illustrative display system with a fly&#39;s eye array and a multielement light sources in accordance with an embodiment. 
         FIG.  16    is a diagram of an illustrative display system with an optical combiner that includes wedge-shaped substrates in accordance with an embodiment. 
         FIG.  17    is a diagram of an illustrative display system with an optical combiner without wedge-shaped substrates in accordance with an embodiment. 
         FIG.  18    is a diagram of an illustrative display system with microlenses over light-emitting elements for minimizing gaps between the light-emitting elements in accordance with an embodiment. 
         FIG.  19    is a diagram showing how light-emitting elements may be independently controlled as a function of pixel position to compensate for off-axis intensity variations in illumination provided to a spatial light modulator in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Head-mounted devices and other electronic devices may be used for virtual reality and mixed reality (augmented reality) systems. These devices may include portable consumer electronics (e.g., portable electronic devices such as cellular telephones, tablet computers, glasses, other wearable equipment), head-up displays in cockpits, vehicles, etc., display-based equipment (projectors, televisions, etc.). Devices such as these may include displays and other optical components. Device configurations in which virtual reality and/or mixed reality content is provided to a user (viewer) with a head-mounted display device are described herein as an example. This is, however, merely illustrative. Any suitable equipment may be used in providing a user with visual content such as virtual reality and/or mixed reality content. 
     A head-mounted device such as a pair of augmented reality glasses that is worn on the head of a user may be used to provide a user with computer-generated content that is overlaid on top of real-world content. The real-world content may be viewed directly by a user through a transparent portion of an optical system. The optical system may be used to route images from one or more pixel arrays in a display system to the eyes of a user. A waveguide such as a thin planar waveguide formed from a sheet of transparent material such as glass or plastic or other light guide may be included in the optical system to convey image light from the pixel arrays to the user. The display system may include reflective displays such as liquid-crystal-on-silicon displays, microelectromechanical systems (MEMs) displays (sometimes referred to as digital micromirror devices), or other displays. 
     A schematic diagram of an illustrative electronic device such as a head-mounted device is shown in  FIG.  1   . As shown in  FIG.  1   , head-mounted device  10  may have a head-mountable support structure such as support structure  20 . The components of head-mounted display  10  may be supported by support structure  20 . Support structure  20 , which may sometimes be referred to as a housing, may be configured to form a frame of a pair of glasses (e.g., left and right temples and other frame members), may be configured to form a helmet, may be configured to form a pair of goggles, or may have other head-mountable configurations. 
     The operation of device  10  may be controlled using control circuitry  16 . Control circuitry  16  may include storage and processing circuitry for controlling the operation of head-mounted display  10 . Circuitry  16  may include storage such as hard disk drive storage, nonvolatile memory (e.g., electrically-programmable-read-only memory configured to form a solid state drive), volatile memory (e.g., static or dynamic random-access-memory), etc. Processing circuitry in control circuitry  16  may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processors, power management units, audio chips, graphics processing units, application specific integrated circuits, and other integrated circuits. Software code may be stored on storage in circuitry  16  and run on processing circuitry in circuitry  16  to implement operations for head-mounted display  10  (e.g., data gathering operations, operations involving the adjustment of components using control signals, image rendering operations to produce image content to be displayed for a user, etc.). 
     Head-mounted device  10  may include input-output circuitry such as input-output devices  12 . Input-output devices  12  may be used to allow data to be received by head-mounted display  10  from external equipment (e.g., a tethered computer, a portable device such as a handheld device or laptop computer, or other electrical equipment) and to allow a user to provide head-mounted device  10  with user input. Input-output devices  12  may also be used to gather information on the environment in which head-mounted device  10  is operating. Output components in devices  12  may allow head-mounted device  10  to provide a user with output and may be used to communicate with external electrical equipment. Input-output devices  12  may include sensors and other components  18  (e.g., image sensors for gathering images of real-world object that are digitally merged with virtual objects on a display in device  10 , accelerometers, depth sensors, light sensors, haptic output devices, speakers, batteries, wireless communications circuits for communicating between device  10  and external electronic equipment, etc.). 
     As shown in  FIG.  1   , input-output devices  12  may include one or more displays in a display system such as display system  14 . Display system  14 , which may sometimes be referred to as a display, may be used to display images for a user of head-mounted device  10 . Display system  14  include a light source such as light source  14 A that produces illumination  22 . Illumination  22  may pass through optical system  14 B and reflect off of spatial light modulator  14 C. Spatial light modulator  14 C may be a liquid-crystal-on-silicon device, a microelectromechanical systems (MEMs) device (e.g., a device with an array of micromirrors, sometimes referred to as a digital micromirror device), or other spatial light modulator. 
     Spatial light modulator  14 C has an array of individually adjustable pixels P. During operation, control circuitry  16  can use spatial light modulator  14 C to produce an image that is illuminated by illumination  22 . Corresponding image light  22 R (e.g., illumination  22  that has reflected from pixels P in spatial light modulator  14 C and that therefore corresponds to a computer-generated (virtual) image formed by spatial light modulator) may be directed to eye boxes such as eye box  24  for viewing by the eyes of a user. 
     Optical system  14 B may use prisms, mirrors, beamsplitters, holograms, gratings (e.g., electrically tunable gratings), lenses, waveguides, polarizers, and/or other optical components. Optical system  14 B may use components such as these to form an optical combiner to pass image light  22  to spatial light modulator  14 C while directing reflected image light  22 R to eye box  24 . System  14 B may include lens structures (one or more discrete lenses and/or optical structures with an associated lens power) so that a viewable image is formed for the user in eye box  24 . If desired, system  14 B may contain components (e.g., an optical combiner, etc.) to allow real-world image light  26  (e.g., real-world images or real-world objects such as real-world object  28 ) to be combined optically with virtual (computer-generated) images such as virtual images in image light  22 . In this type of system, which is sometimes referred to as an augmented reality system, a user of device  10  may view both real-world content and computer-generated content that is overlaid on top of the real-world content. Camera-based augmented reality systems may also be used in device  10  (e.g., in an arrangement which a camera captures real-world images of object  28  and this content is digitally merged with virtual content on spatial light modulator  14 C). Display system  14  may be used in a virtual reality system (e.g., a system without merged real-world content) and/or any suitable type of system. 
     Illustrative configurations for portions of optical system  14 B that may be used to pass illumination to spatial light modulator  14 C while directing reflected image light from spatial light modulator  14 C to eye boxes such as eye box  24  are shown in  FIGS.  2  and  3   . In the example of  FIG.  2   , optical system  14 B includes polarizing beamsplitter  30  and quarter wave plate  32 . Light  22  from light source  14 A passes through polarizing beamsplitter  30 . Light  22  may initially have a given polarization state (e.g., light  22  may be s-polarized at the output of beamsplitter  30  as shown in  FIG.  2   ). After passing through quarter wave plate  32  and reflecting from the surface of spatial light modulator  14 C, light  22 R may have a different polarization state (e.g., an orthogonal linear polarization state such as the p-polarized state in the example of  FIG.  2   ). This causes reflected light  22 R to be directed towards eye box  24  by polarizing beamsplitter  30 . In the example of  FIG.  3   , illumination  22  is directed towards spatial light modulator  14 C through prism  34  and reflected image light  22 R from spatial light modulator  14 C is reflected by prism  34  toward eye box  24 . Other configurations for optical system  14 B that pass illumination to spatial light modulator  14 C while directing reflected image light to eye boxes may be used, if desired (e.g., systems using waveguides, coupling elements formed from holograms, etc.). Optical system  14 B may also include optical components that help gather and direct illumination to spatial light modulator  14 C from light-emitting diodes or other light-emitting devices. 
     Display system  14  may use a multielement light source configuration. Light source  14 A may be based on light-emitting diodes or lasers (e.g., vertical cavity surface emitting lasers or other diode lasers). As an example, light source  14 A may have an array of three red light-emitting diodes, three green light-emitting diodes, and three blue light-emitting diodes. Each array of colored light-emitting diodes in this example may have multiple individually controllable light-emitting elements (e.g., diodes). Arrangements in which individually controllable light-emitting elements are based on lasers may also be used. 
     During operation, control circuitry  16  can control each of the light-emitting elements in light source  14 A separately. In this way, illumination uniformity can be enhanced, local dimming operations can be performed on the image being displayed for the user, and/or display output can be selectively turned off in unused portions of a user&#39;s field of view to conserve power. 
     An illustrative multielement display system is shown in  FIG.  4   . As shown in  FIG.  4   , multielement light source  14 A may have multiple individually controlled light-emitting elements  44 . Collimating lenses  36 , optional diffuser  38 , and condenser lens  40  may be used to produce illumination  22  for spatial light modulator  14 C. Optical system components (see, e.g., the illustrative optical components of  FIG.  2    or  FIG.  3   ) may be interposed in the optical path between light source  14 A and spatial light modulator  14 C at a location such as location  42  (e.g., to pass illumination  22  to spatial light modulator  14 C while directing corresponding reflected image light from spatial light modulator  14 C to eye boxes such as eye box  24 ). Such optical system components are omitted from optical system  14 B of  FIG.  4    and subsequent FIGS. to avoid over-complicating the drawings. 
     There are three light-emitting elements  44  in the example of  FIG.  4   , but other numbers of light-emitting elements  44  may be included in light source  14 A, if desired (e.g., at least 3, at least 10, at least 50, at least 100, fewer than 150, fewer than 75, fewer than 40, fewer than 30, fewer than 20, fewer than 12, fewer than 5, etc. Elements  44  may produce light  22  of any suitable colors (e.g., white, red, green, blue, yellow, etc.). In some arrangements, sets of light-emitting elements  44  (e.g., one or more groups of three red light-emitting diodes, one or more groups of three green light-emitting diodes, etc.) may be incorporated into light source  14 A. 
     As shown in  FIG.  4   , the optical components of system  14  may be configured so that light from first light-emitting element  44 - 1  is directed onto a first region  46 - 3  of spatial light modulator  14 C, light from second light-emitting element  44 - 2  is directed onto a second region  46 - 2  of spatial light modulator  14 C, and light from a third light-emitting element  44 - 3  is directed onto a third region  46 - 1 . Each light source may produce light with a Lambertian intensity distribution or other suitable intensity profile and the emitted light from each source may overlap slightly. The resulting overall light distribution for light source  14 A on spatial light modulator  14 C is shown by curve  48  of  FIG.  5   , which is a graph in which illuminance I of the illumination from light source  14 A that is illuminating spatial light modulator  14 C has been plotted as a function of lateral distance X across spatial light modulator  14 C. The three peaks of curve  48  correspond to the three elements  44  of light source  14 A in the example of  FIG.  4    and may be individually adjusted (e.g., to turn off illumination for unused portions of display system  14  to conserve power, to adjust relative light intensity to help create a uniform light distribution, etc.). Variations of light intensity within each illuminated region can be compensated by adjusting the pixels of spatial light modulator  14 C accordingly. No light homogenizers (e.g., fly&#39;s eye lens arrays) other than diffuser  38  (e.g., a thin frosted glass, a layer of polymer with light-scattering particles, etc.) need be included in system  14 B, which helps reduce the volume occupied by system  14 B and display system  14 . If desired, diffuser  38  may be omitted from system  14 B. 
     Light-emitting elements  44 - 1 ,  44 - 2 , and  44 - 3  of  FIG.  4    may, if desired, be white light sources W, as shown in  FIG.  6   . Light source  14 A of  FIG.  4    has a one-dimensional array with three elements. In general, there may be N×M elements  44  in light source  14 A, where N and/or M may be at least 1, at least 2, at least 3, at least 4, at least 5, at least 10, at least 20, at least 50, fewer than 100, fewer than 25, fewer than 11, fewer than 6, or other suitable values. 
       FIG.  7    shows how elements  44  may be arranged in a two-dimensional array of red R, green G, and blue B light-emitting elements  44 . There may be more green elements than red and blue elements (e.g., to accommodate the enhanced sensitivity of human eyes to green light) and/or other numbers of red, green, and blue elements may be included in light source  14 A. 
       FIG.  8    shows another illustrative arrangement. In the example of  FIG.  8   , each set of R, G, and B light-emitting elements  44  is located at a different array location in a 3×3 array (e.g., each of the locations of the 3×3 array may include a packaged light-emitting device containing three light-emitting elements  44 ). In general, any suitable packaging scheme may be used for elements  44  (e.g., schemes in which commonly colored light-emitting elements are formed in common packages, schemes in which light-emitting elements of different colors are placed in common packages, arrangements in which all of elements  44  in light source  14 A are formed on a common substrate, etc.). 
     In some arrangements for light source  14 A, light-emitting diodes with relatively small dimensions (e.g., micro-light-emitting diodes or vertical cavity surface emitting lasers with lateral dimensions of less than 10 microns), may be used in forming elements  44 . Configurations in which the lateral dimensions of light-emitting elements (light-emitting diodes or lasers) are more than 10 microns, 10-200 microns, at least 40 microns, less than 500 microns, or other suitable sizes may also be used. If desired, light-emitting elements  44  may be provided with optional tapered tunnels such as tapered tunnel  50  of  FIG.  9   . Each tunnel, which may be, for example, part of a two-dimensional tunnel array that mates with a corresponding two-dimensional array of light-emitting devices  44 , may be formed form clear polymer or other transparent material and may expand the size of the emitted light area of each light-emitting element  44  (e.g., from smaller area  52  of  FIG.  9    at the input of tapered tunnel  50  to enlarged area  54  at the output surface of tapered tunnel  50 ). 
     If desired, a wavelength selective optical combiner may be used to merge illumination  22  of different wavelengths. Consider, as an example, illustrative multiwavelength light source  14 A of  FIG.  10   . As shown in  FIG.  10   , light source  14 A may include a first set of light-emitting elements  44 ′ (e.g., green light-emitting elements  44 ) and a second set of light-emitting elements  44 ″ (e.g., sets of red and blue light-emitting elements  44 ). Combiner  56  may combine the green light from source  44 ′ and the red and blue light from source  44 ″ to produce red, green, and blue illumination  22 . Combiner  56  may be based on a wedge dichroic combiner (e.g., a wedge-shaped substrate that includes a red-light-reflecting-and-green-light-passing dichroic coating on a first surface of the substrate facing source  44 ″ and that includes a blue-light-reflecting-and-green-light passing dichroic coating on a second opposing surface of the substrate). The wedge dichroic combiner will reflect red and blue light towards spatial light modulator  14 C and will allow green light to pass towards spatial light modulator  14 C. This arrangement or other wavelength multiplexing arrangements (e.g., wavelength multiplexers based on holograms, nanostructures, tunable optical components such as tunable gratings, etc.) may combine the light output from sources  44 ′ and  44 ″ so that illumination  22  includes individually adjustable red, green, and blue light components. Different regions of spatial light modulator  14 C may be illuminated by light from different elements  44 . During operation, individual elements  44  may be independently adjusted to adjust the spatial distribution of illumination  22  on spatial light modulator  14 C. With one illustrative configuration, light source  44 ″ includes a 3×3 array of red light-emitting elements  44  and a 3×3 array of blue light-emitting elements  44 , as shown in  FIG.  11   , and light source  44 ′ includes a 3×3 array of green light-emitting elements  44 , as shown in  FIG.  12    and each light-emitting element  44  may be individually adjusted. Other numbers of elements  44  may be included in light source  14 A if desired. 
     In the illustrative configuration of light source  14 A that is shown in  FIG.  13   , collimator and beam steering elements  60  are used to selectively route light from light-emitting elements  44  such as blue element B, green elements G, and red elements R to spectral and angular combiner elements  62 . Spectral and angular combiner elements combine red, green, and blue light from corresponding red, green, and blue elements  44  into a portion of illumination  22 . Elements  60  and/or  62  may be formed from multiplexed volume holograms, switchable Bragg gratings (e.g., electrically adjustable liquid crystal gratings), and metamaterial elements (e.g., nanostructure elements each formed from an array of nanopillars of transparent material on a transparent substrate that have heights and other attributes that are configured to allow each element to serve as a wavelength multiplexer for light passing through the substrate of that element). As shown in  FIG.  13   , a first set  44 A of elements  44  may be configured to provide illumination  22  in first area  46 - 3  of spatial light modulator  14 C, a second set  44 B of elements  44  may be configured to provide illumination  22  in second area  46 - 2  of spatial light modulator  14 C, and a third set  44 C of elements  44  may be configured to provide illumination  22  in third light area  46 - 1  of spatial light modulator  14 C. Elements  44  may be arranged in a one-dimensional array (e.g., elements  44  may all lie in the page of  FIG.  13   ) or may be formed in a two-dimensional array. 
     Another illustrative arrangement for display system  14  is shown in  FIGS.  14  and  15   . In this illustrative configuration, light-emitting element set  44 R includes nine elements  44  that produce red light (e.g., in a 3×3 array), light-emitting element set  44 G includes nine elements  44  that produce green light (e.g., in a 3×3 array), and light-emitting set  44 B includes three blue light-emitting elements  44  (e.g., in a 3×3 array). There may be, as an example, nine sets of elements  44  in a 3×3 array of sets (only one column of sets being shown in  FIG.  14   ). Optical system  14 B may include a fly&#39;s eye lens array  66  and relay lens  68  (e.g., a relay lens formed from two or more lens elements or other suitable relay lens). 
     As shown in  FIG.  15   , lens array  66  may include microlenses such as lenses  66 E that each receive and homogenize light emitted from a respective light-emitting element  44  and that provide that light to relay lens  68 . Elements  44  may be organized in a one-dimensional array or a two-dimensional array. Optical system  14 B may be configured so that elements  44  provide light to a different areas of spatial light modulator  14 C. For example, each of the three red elements R of set  14 R of  FIG.  15    may be individually adjusted to individually control light  22  in three respective regions  70  on spatial light modulator  14 C. 
       FIG.  16    is a diagram of another illustrative optical combiner that may be used to merge illumination  22  of different wavelengths. As shown in  FIG.  16   , light source  14 A may include a green light source  100 , a red light source  102 , and a blue light source  104 . Green light source  100  may be an M-by-N or N-by-N array of green light-emitting elements  44 . Red light source  102  may be an M-by-N or N-by-N array of red light-emitting elements  44 . Blue light source  104  may be an M-by-N or N-by-N array of blue light-emitting elements  44 . Light sources  100 ,  102 , and  104  may be 7-by-7 arrays, 1-by-1 arrays, or 3-by-3 arrays of light-emitting elements  44 , as just a few examples. 
     Light source  14 A may include optical combiner  106  (e.g., an optical combiner such as optical combiner  56  of  FIG.  10   ). Optical combiner  106  may include red-light-reflecting-and-green-light-passing dichroic coating  116  and blue-light-reflecting-and-green-light-passing dichroic coating  118 . Coatings  116  and  118  may be formed on the surfaces of wedge-shaped substrates  114 . Optical combiner  106  will reflect red light  110  from red light source  102 , will reflect blue light  112  from blue light source  104 , and will allow green  108  light from green light source  100  to pass as illumination  22  towards a spatial light modulator (e.g., spatial light modulator  14 C of  FIGS.  1 - 4  and  13 - 15   ). When configured in this way, light  110 ,  108 , and  112  may be coaxially aligned when provided to the spatial light modulator. 
     In the example of  FIG.  16   , optical combiner  106  includes four wedge-shaped substrates  114 . This is merely illustrative and, in general, optical combiner  106  may include any desired number of wedge-shaped substrates  114  or may include substrates of other shapes. Light sources  100 ,  102 , and  104  may emit light of any desired wavelengths (e.g., coating  116  may pass light from light source  100  while reflecting light from light source  102  whereas coating  118  may pass light from light source  100  while reflecting light from light source  104 ). Optional collimating optics such as lenses may be interposed between light sources  100 ,  102 , and  104  and optical combiner  106  if desired. In another suitable arrangement, optical combiner  106  may be formed without wedge-shaped substrates, as shown in the example of  FIG.  17   . As shown in  FIG.  17   , optical combiner  106  may include red-light-reflecting-and-green-light-passing plate  122  and blue-light-reflecting-and-green-light-passing dichroic plate  120 . Plates  120  and  122  may, for example, include glass substrates or other substantially planar substrates provided with dichroic coatings. 
     The example of  FIG.  15    in which microlenses  66 E are provided in lens array  66  is merely illustrative. In another suitable arrangement, each light-emitting element  44  may be provided with a respective microlens, as shown in  FIG.  18   . As shown in  FIG.  18   , light-emitting elements  44  in light source  14 A may be relatively small, such that elements  44  are separated by gaps  130 . A respective microlens  132  may be provided over each element  44 . Each microlens  132  may have width  134  that is much wider than the underlying element  44 , such that adjacent microlenses  132  bridge the gaps  130  between elements  44 . This may allow light from each element  44  to appear as if it was being emitted over a greater area (e.g., the area provided by microlenses  132 ) than would otherwise be provided in the absence of microlenses  132 . 
     If desired, the intensity of the light-emitting elements  44  in light source  14 A may be independently controlled to compensate for inherent off-axis roll off in intensity and/or distortion on light from the peripheral pixels associated with optics (e.g., optics in optical system  14 B) that provide variable magnification as a function of pixel position.  FIG.  19    is a diagram showing how the intensity of light-emitting elements  44  may be independently controlled to mitigate these effects. 
     As shown in  FIG.  19   , the horizontal axis illustrates pixel position along a lateral axis of light source  14 A (e.g., horizontal or vertical pixel position across an array of M-by-N or N-by-N light-emitting elements  44 , as described above in connection with  FIGS.  4 - 18   ). Curve  156  of  FIG.  19    illustrates the intensity of illumination  22  produced by light source  14 A. Curve  150  illustrates the maximum intensity producible by light source  14 A. As shown by curve  156 , illumination  22  may exhibit a roll off from a peak intensity at central axis C to a minimum intensity at pixel positions off of central axis C (e.g., for pixels at the periphery of the array). This variation in intensity may, for example, be produced by inherent off-axis roll off in intensity associated with light source  14 A and/or optical system  14 B and/or off-axis distortion on light from peripheral pixels produced by the lens elements in optical system  14 B (e.g., lens elements that provide variable magnification as a function of pixel position). 
     In order to mitigate this variation, light-emitting elements  44  located off of central axis C (e.g., at the periphery of the array) may be independently controlled to emit light with an increased intensity, as shown by arrows  154 . This boost in peripheral pixel intensity may provide illumination  22  with a uniform intensity for each pixel position by the time the light has passed through optical system  14 B. In another suitable arrangement, light-emitting elements  44  located at central axis C may be independently controlled to emit light with decreased intensity (e.g., with an intensity that matches that of the lowest-intensity pixels), as shown by arrow  158 . This reduction in central pixel intensity may provide illumination  22  with a uniform intensity for each pixel position by the time the light has passed through optical system  14 B. These adjustments in intensity may be provided by adjusting the current provided to each light-emitting element  44 , by adjusting the pulse width modulation used to control each light-emitting element  44 , etc. By independently controlling the intensity of each light-emitting element  44  in the array as a function of pixel position, light of uniform intensity may be provided despite distortions introduced by optical system  14 B. In another suitable arrangement, pre-distortion techniques may be used instead of or in addition to these pixel-by-pixel intensity adjustments to provide illumination  22  with uniform intensity. The example of  FIG.  19    is merely illustrative. Curves  150 ,  156 , and  152  may have other shapes. 
     The foregoing is merely illustrative and various modifications can be made to the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20190510
Publication Date: 20241008
Grant Date: 20241008
Priority Date: 20180628
Inventors: BHAKTA, Vikrant
CHOI, Hyungryul
PENG, GUOLIN
DELAPP, SCOTT M.
Assignee: APPLE INC
CPC Classifications: [{"code": "G02B2027/013", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B2027/0114", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B27/30", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B27/126", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B27/1026", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B3/0037", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B2027/013", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B2027/0114", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B2027/0118", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B3/0037", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B26/0833", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B19/0066", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B19/0057", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B27/30", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B27/126", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B27/1033", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B26/0833", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B27/1033", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B19/0066", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B19/0057", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B2027/0118", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B27/0172", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B27/0172", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B27/0172", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B27/0172", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B2027/013", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B2027/0114", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B27/30", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B27/126", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B27/1026", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B3/0037", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B27/0172", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 67003762