PATENT DOCUMENT

Publication Number: US-10902796-B1
Application Number: US-201715651820-A
Country: US
Kind Code: B1

Title: Multi-user display system

Abstract:
Electronic equipment in a system such as a vehicle or building may include one or more displays. The displays may display image frames for users with light-modulating glasses. The image frames may include interspersed image frames corresponding to unique content for each of the users. Dummy frames may be incorporated into the displayed frames on the display to help obscure displayed content from external observers. The light-modulating glasses may have light modulators such as liquid crystal light modulators. Control circuitry in the glasses may adjust the light modulators to exhibit transparent intervals that overlaps desired image frames and opaque intervals that are aligned with other image frames and the dummy frames. This allows each user to view unique content on a shared display while preventing external observers without glasses from observing the content that is being presented.

Claims:
What is claimed is: 
     
       1. A system, comprising:
 electronic equipment having at least one display and control circuitry that displays a series of image frames and non-viewable dummy frames on the display; and 
 light modulators that exhibit opaque intervals and transparent intervals, wherein the transparent intervals are synchronized with the image frames and the image frames are visible through the light modulators, wherein the opaque intervals are synchronized with the non-viewable dummy frames and prevent the non-viewable dummy frames from being visible through the light modulators. 
 
     
     
       2. The system defined in  claim 1  further comprising a vehicle body, wherein the display is mounted to the vehicle body, wherein the vehicle body surrounds a vehicle interior, and wherein the light modulators are in the vehicle interior. 
     
     
       3. The system defined in  claim 2  further comprising glasses in the interior, wherein the glasses include the light modulators and include control circuitry that is coupled to the light modulators. 
     
     
       4. The system defined in  claim 3  wherein the electronic equipment and the glasses each include wireless communications circuitry and wherein the control circuitry in the electronic equipment and the control circuitry in the glasses use the wireless communications circuitry to synchronize the transparent intervals of the light modulators to the image frames displayed by the display. 
     
     
       5. The system defined in  claim 4  further comprising speakers in the glasses that are configured to play wirelessly received audio associated with the image frames, wherein the display comprises one of a plurality of displays that surround the vehicle interior. 
     
     
       6. The system defined in  claim 5  wherein the light modulators comprise liquid crystal light modulators. 
     
     
       7. The system defined in  claim 2  further comprising a window in the vehicle body that includes the display. 
     
     
       8. The system defined in  claim 1  further comprising:
 glasses, wherein the glasses include the light modulators; 
 structures that surround an interior region, wherein the display and the glasses are located in the interior region; 
 windows in the structures that are interposed between the interior region and an exterior region; and 
 additional light modulators in the windows, wherein the additional light modulators have transparent intervals that overlap the non-viewable dummy frames and have opaque intervals that overlap the image frames. 
 
     
     
       9. The system defined in  claim 1  wherein the image frames and the non-viewable dummy frames are displayed for equal amounts of time. 
     
     
       10. A vehicle system, comprising:
 a vehicle body structure surrounding an interior; 
 a display mounted to the vehicle body structure in the interior; 
 control circuitry that displays first image frames, second image frames, and non-viewable dummy frames on the display; 
 a first pair of glasses in the interior with light modulators having transparent intervals that overlap the first image frames and opaque intervals that overlap the non-viewable dummy frames and that overlap the second image frames; and 
 a second pair of glasses in the interior with light modulators having transparent intervals that overlap the second image frames and having opaque intervals that overlap the first image frames and that overlap the non-viewable dummy frames. 
 
     
     
       11. The vehicle system defined in  claim 10  wherein the display comprises one of a plurality of displays in the interior each of which displays the first image frames, the second image frames, and the non-viewable dummy frames. 
     
     
       12. The vehicle system defined in  claim 11  wherein at least some of the non-viewable dummy frames are complementary images of the first image frames. 
     
     
       13. The vehicle system defined in  claim 12  wherein at least some of the non-viewable dummy frames are complementary images of the second image frames. 
     
     
       14. The vehicle system defined in  claim 10  further comprising:
 wireless circuitry coupled to the control circuitry that transmits a first audio track associated with the first image frames to the first pair of glasses and that transmits a second audio track associated with the second image frames to the second pair of glasses. 
 
     
     
       15. The vehicle system defined in  claim 14  wherein:
 the first pair of glasses includes first speakers; 
 the first pair of glasses includes circuitry that wirelessly receives the first audio track and plays the first audio track through the first speakers; 
 the second pair of glasses includes second speakers; and 
 the second pair of glasses includes circuitry that wirelessly receives the second audio track and plays the second audio track through the second speakers. 
 
     
     
       16. The vehicle system defined in  claim 10  wherein the control circuitry displays the first image frames in a first pattern of time intervals on the display and displays the second image frames in a second pattern of time intervals on the display that is different than the first pattern. 
     
     
       17. A system, comprising:
 electronic equipment with a display and control circuitry that is configured to display a series of interspersed first image frames, second image frames, and third image frames; and 
 first light modulators that are configured to exhibit transparent intervals that overlap the first image frames and opaque intervals that overlap the second and third image frames; 
 second light modulators that are configured to exhibit transparent intervals that overlap the second image frames and opaque intervals that overlap the first and third image frames; and 
 third light modulators that are configured to exhibit transparent intervals that overlap the third image frames and opaque intervals that overlap the first and second image frames, wherein the control circuitry is configured to display non-viewable dummy frames interspersed with the first, second, and third image frames. 
 
     
     
       18. The system defined in  claim 17  further comprising a window, wherein the display is a transparent display that overlaps the window. 
     
     
       19. The system defined in  claim 17  wherein the control circuitry is configured to display the first, second, and third image frames in respective non-overlapping first, second, and third time-interval patterns. 
     
     
       20. The system defined in  claim 17  further comprising first glasses that include the first light modulators, second glasses that include the second light modulators, and third glasses that include the third light modulators.

Description:
This application claims the benefit of provisional patent application No. 62/393,508, filed on Sep. 12, 2016, which is hereby incorporated by reference herein in its entirety. 
    
    
     FIELD 
     This relates generally to systems with displays, and, more particularly, to systems with displays shared by multiple users. 
     BACKGROUND 
     Vehicles and other systems may sometimes include displays. It can be desirable for multiple users to share a display. For example, it may be desirable for multiple vehicle occupants to be able to view individualized content on an in-vehicle display. 
     It can be challenging to incorporate display systems for multiple users into a vehicle, building, or other system. If care is not taken, viewers may not be able to view desired content and privacy concerns may not be addressed. 
     SUMMARY 
     Electronic equipment in a system such as a vehicle or building may include one or more displays. The displays may display image frames for users with light-modulating glasses. 
     The image frames that are displayed on a display may include interspersed image frames corresponding to unique content for each of multiple users. Dummy frames may be interspersed among the image frames to help obscure user content from external observers. 
     The light-modulating glasses may have light modulators such as liquid crystal light modulators. Wireless circuitry in the light-modulating glasses may be used to synchronize the light modulators to the image frames. Control circuitry in the glasses may adjust the light modulators to exhibit transparent intervals that overlaps desired image frames and opaque intervals that are aligned with other image frames and the dummy frames. This allows each user to view unique content on a shared display while preventing external observers without glasses from observing the content that is being presented. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of an illustrative system in accordance with an embodiment. 
         FIG. 2  is a diagram of a system such as a vehicle with displays in accordance with an embodiment. 
         FIG. 3  is a diagram of an illustrative pair of glasses for a viewer in a system of the type shown in  FIG. 2  in accordance with an embodiment. 
         FIGS. 4, 5, 6, and 7  are timing diagrams showing how multiple users may be provided with individualized content using interspersed image frames on a shared display in accordance with an embodiment. 
         FIGS. 8 and 9  are timing diagrams showing how dummy content may be interspersed with content for viewers with light-modulating glasses in accordance with an embodiment. 
         FIGS. 10, 11, 12, and 13  are diagrams showing illustrative image frames and complementary dummy frames that may be displayed on a display in accordance with an embodiment. 
         FIG. 14  is a diagram showing how spatial interleaving techniques may be used in presenting individualized content to users in accordance with an embodiment. 
         FIG. 15  is a timing diagram showing how frames of content may be displayed with predetermined timing (time-interval) patterns that help ensure viewing privacy in accordance with an embodiment. 
         FIG. 16  is a diagram of an illustrative system in which windows have been provided with light modulators in accordance with an embodiment. 
         FIG. 17  is a timing diagram showing how window light-modulators and glasses may be synchronized with frames of content on a display in a system in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a diagram of an illustrative system of the type that may be used to allow multiple viewers to view individualized content on one or more shared displays. System  10  of  FIG. 1  may be a vehicle system, a building system (e.g., a home or office), or other system. Configurations in which individualized display content is presented to viewers in vehicles, offices, and other environments with one or more displays and in which viewers have light-modulating glasses may sometimes be described herein as examples. In general, any suitable equipment may be used to present users with individualized content. 
     As shown in  FIG. 1 , system  10  may include electronic equipment with displays such as electronic equipment  12 . Equipment  12  may include control circuitry  14 . Control circuitry  14  may include storage and processing circuitry for supporting the operation of system  10 . The storage and processing circuitry 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. Control circuitry  14  may also include processing circuitry based on one or more microprocessors, microcontrollers, digital signal processors, baseband processors, power management units, audio chips, application specific integrated circuits, etc. 
     The processing circuitry in control circuitry  14  may be used to control the operation of equipment  12  and other components in system  10 . For example, control circuitry  14  may be used to control vehicle controls (steering, brakes, propulsion, etc.) and other components in a vehicle or may be used to control environmental systems (heating, air conditioning, lighting, etc.) in a building. The processing circuitry in control circuitry  14  may also be used to gather input from input-output devices  16 , may use wireless communications circuitry  20  to communicate with external devices over wireless paths such as path  22 , and may control the operation of displays  18  and other input-output devices to provide users of equipment  12  with output. Input-output devices  16  may include sensors, buttons, keyboards, and other input-output devices that allow users to control equipment  12 . 
     System  10  may include one or more pairs of glasses  24 . Glasses  24  may contain control circuitry  26  (e.g., control circuit hardware of the type included in control circuitry  14  and/or other control circuitry). Circuitry  26  may use wireless communications circuitry  30  to communicate with wireless equipment such as equipment  12  over wireless links (see, e.g., path  22 ). If desired, circuitry  14  and circuitry  26  may communicate using wired paths in addition to or instead of using wireless communications. Wireless communications circuitry  20  and  30  may support Bluetooth® communications, other short-range wireless communications (e.g., IEEE 802.11 wireless local area network communications), cellular telephone communications, near-field communications, etc. 
     Control circuitry  14  may present media to multiple users with light-modulating glasses  24 . Each pair of glasses  24  in system  10  may have a light modulator  28  that is synchronized to a different portion of the content being displayed by displays  18 . For example, control circuitry  14  may display content for a first user during odd image frames and for a second user during even image frames. Control circuitry  26  in glasses  24  for the first user may be transparent during the odd frames and opaque during the even frames, so that the first user views only the content of the odd frames, whereas control circuitry  26  in glasses  24  for the second user may be opaque during the odd frames and transparent during the even frames, so that the second user views only the content of the even frames. Configurations with other types of content multiplexing may also be used, if desired. 
     Each pair of glasses  24  may have a set of speakers  32  for presenting individualized audio content to the user of that pair of glasses. Audio content may be provided to each user&#39;s wireless communications circuitry  30  by wireless communications circuitry  20  in equipment  12  using a separate respective wireless channel (as an example). 
       FIG. 2  is a top view of structures of the type that may be associated with system  10  in an operating environment such as a vehicle or office. As shown in  FIG. 2 , users  36  may each have a pair of glasses  24 . One or more displays  18  may be mounted in locations in which the displays can be viewed by users  36  through their glasses  24 . In the example of  FIG. 2 , system  10  is a vehicle or building having structures  34 . In a vehicle, structures  34  may include portions of a vehicle body (e.g., door panels, a roof, etc.). In an office, structures  34  may include interior and exterior building walls. Structures  34  may divide interior and exterior spaces from each other. As shown in  FIG. 2 , for example, structures  34  may separate interior regions  38  (e.g., a vehicle interior or an interior room in a building) from each other and from exterior  40  (e.g., the outside of a vehicle, the outside of a building, etc.). 
     Displays  18  may be mounted on opaque portions of structures  34  (e.g., opaque body panels in a vehicle, opaque walls in a building) or other portions of system  10 . If desired, displays  18  may be transparent displays that are mounted over windows  18 ′ in system  10  (e.g., displays that are integrated into transparent vehicle windows or that overlap transparent interior and/or exterior building windows). Windows with displays  18  may be formed from one or more laminated layers of glass and/or plastic or other window substrate materials. Displays  18  may be touch screen displays or may be insensitive to touch. 
     Displays  18  may include pixel arrays formed from rows and columns of pixels that display images. The images may be displayed in a series of image frames. Display  18  may be liquid crystal displays, organic light-emitting diode displays, displays based on arrays of light-emitting diode dies, electrophoretic displays, projector displays, or other displays. If desired, displays  18  may cover some or all of interior  38  (e.g., displays  18  may surround interior  38  and may be placed on all four sides of users  36  to surround users  36  and provide users  36  with an immersive visual environment). The content (image frames) displayed on displays  18  may include moving images (video) and/or still images (e.g., static text). Content may be captured using image sensors, may be generated by a computer (e.g., video-game content), and/or may be generated by other suitable sources in equipment  12  (e.g., by control circuitry  14 ). 
     Each user (vehicle occupant, room occupant, etc.) in system  10  may have a respective pair of glasses  24 . For example, if there are three users in system  10 , each of the three users may be provided with a respective pair of glasses  24 . A top view of an illustrative pair of glasses  24  is shown in  FIG. 3 . As shown in  FIG. 3 , glasses  24  may have support structures such as frame  40 . Frame  40  may have right and left temples  40 - 3  that are coupled to chassis  40 - 1  by hinges  40 - 2 . Speakers  32  may be mounted on temples  40 - 3  in alignment with a user&#39;s left and right ears  36 L and  36 R, respectively. Light modulators  28  may be mounted on chassis  40 - 1 . Light modulators  28  may include a left-eye light modulator aligned with a left eye  36 E of user  36  and a right-eye light modulator aligned with a right eye  36 E of user  36 . During operation, light modulators  28  may be dynamically placed in a transparent state or an opaque state. In the transparent state, user  36  may view displays  18  and nearby objects through light modulators  28 . In an opaque state, light modulators  28  are opaque and prevent light from reaching user  36 . 
     Light modulators  28  may alternate between the transparent and opaque states so undesired content on displays  18  can be filtered out and so that desired content on displays  18  may be viewed by user  36 . Light modulators  28  may be based on components that are electrically adjustable between transparent and non-transparent (e.g., opaque or diffuse) states. Light modulators  28  may, for example, be liquid crystal light modulators (sometimes referred to as liquid crystal shutters) that can be switched between transparent and opaque states or may be polymer dispersed liquid crystal light modulators that can transition between transparent and translucent states. Liquid crystal shutters may be based on guest-host liquid crystal light modulators that can transition between transparent and light-blocking states or may be based on non-guest-host liquid crystal light modulators (e.g., liquid crystal light modulators with polarizers). Cholesteric liquid crystal light modulators may also be used. If desired, other light modulators may be used in addition to or instead of liquid crystal light modulators. 
     In addition to or instead of using time-division light modulation techniques to allow users to share a display, glasses  24  may be provided with optical modulators that filter out different colors and/or polarizations of light to allow users to share a display. If desired, glasses  24  may combine time-based multiplexing, wavelength-based multiplexing, and/or polarization-based multiplexing techniques (e.g., to alternately pass red or green light, to alternately pass horizontally polarized light or vertically polarized light, etc.). Optical modulators such as spatial light modulators can also be provided to block out different portions of a scene at different times. 
     In the example of  FIG. 3 , glasses  24  are configured to be worn on the head of a user so that light modulators  28  are aligned with eyes  36 E. If desired, light modulators  28  and speakers  32  may be aligned respectively with eyes  36 E and ears  36 L and  36 R using other arrangements. For example, light modulators  28  and speakers  32  may be mounted in a helmet or other equipment associated with a heads up display. Glasses  24 , which may sometimes be referred to as head-mounted glasses, a wearable light modulator device, or a head-mounted device, may have two light modulators  28  or may have a single light modulator that extends over left eye  36 L and right eye  36 R. 
       FIGS. 4, 5, 6, and 7  show how system  10  may be used to provide each of multiple users  36  in system  10  with individualized content. As shown in  FIG. 4 , a graphics processing unit or other video source in control circuitry  14  may output a series of image frames F 1 , F 2 , F 3 , F 4 , F 5 , etc. that are displayed sequentially on one or more of displays  18 . Each image frame may contain potentially unique information (e.g., the pattern of red, blue, and green pixels of each frame may be different). For example, in configurations in which image frames F correspond to frames in a movie, each frame may contain a different portion of the movie. Frames F may be presented at any suitable frame rate (e.g., 60 Hz, 120 Hz, 240 Hz, 100-600 Hz, more than 50 Hz, less than 1000 Hz, etc.). In some arrangements, portions of frames F may correspond to static or nearly static content. For example, displays  18  may be used to present still images or static or slowly moving text. 
     Equipment  12  and glasses  24  may be synchronized by using a common clock and/or by wirelessly exchanging synchronization information using wireless communications circuitry  20  and  30 . Once synchronized, the transmission T of the light modulators may be operated in synchronization with frames F of image data provided by equipment  12  on displays  18 . For example, a first pair of glasses  24  may have light modulators that are modulated to produce light transmission curve T 1  for a first user and a second pair of glasses  24  may have light modulators that are modulated to produce light transmission curve T 2  for a second user, as shown in  FIG. 5 . 
     The light modulation patterns associated with curves T 1  and T 2  each include transparent time intervals in which T is high (e.g., 100% or other elevated amount) and opaque time intervals in which T is low (e.g., 0% or other lowered amount). The light modulation patterns allow the first and second users to view different subsets of image frames F and therefore different content on displays(s)  18 . Because transmission curve T 1  has transparent intervals that overlap odd frames F 1 , F 3 , F 5 , . . . and has opaque intervals that overlap even frames F 2 , F 4 , . . . , even frame content will be blocked and the first user will view only odd frame content. Transmission curve T 2  has transparent intervals that are aligned with even frames and opaque intervals that are aligned with odd frames, so the second user will be presented only with even frame content. 
     The frame rate of the odd frames and the frame rate of the even frames may each be sufficiently high to provide smooth video playback. This allows equipment  12  to provide a first movie or other video content V 1  to the first user as shown in  FIG. 6 , while simultaneously providing a second movie or other video content V 2  to the second user as shown in  FIG. 7 . To ensure that the first and second users are provided with appropriate audio content in synchronization with their video content, equipment  12  may simultaneously provide an audio track for the first movie to the first user using speakers  32  in the first pair of glasses and an audio track for the second movie to the second user using speakers  32  in the second pair of glasses. The video content that is provided to each user may be computer-generated content such as virtual reality images, may be moving images from a camera, or may be frames of stored video (e.g., for a movie, television show, etc.). If desired, video content may contain static or nearly static text, graphics, etc. 
     To enhance privacy, one or more frames that do not contain content for the first and second users may be interspersed with the image frames for the first and second users. As shown in  FIG. 8 , for example, a first set of image frames V 1  may be used to convey a first video to a first user, a second set of interspersed image frames V 2  may be used to convey a second video to a second user, and dummy content D may be interspersed with the first and second image frames. Dummy content D may contain image frames with random patterns or other noise, images that are the inverse (complement) of other frames, video for a movie or other content that is not intended to be watched by any of the users in system  10  and that is not visible through any of glasses  24 , or other content that is not viewed by users  36 . 
     Due to the averaging characteristics of human eyes, rapidly changing image content will be smoothed out and will appear as continuous images to an observer. When videos V 1  and V 2  have uncorrelated content and both contain moving images, this content will be smeared out to an external observer of display  18 . The external observer may therefore have difficulty viewing either V 1  or V 2 . However, if one of these streams of video (e.g., video V 2 ) temporarily becomes blank (e.g., during a long dark scene), the other video (e.g., video V 1 ) may become momentarily visible. 
     The presence of dummy content D may therefore be used to help obscure both videos V 1  and V 2 , even in scenarios in which one of the videos contains long dark passages or other static content that does not significantly interfere with the other video. For example, the presence of dummy content may make it difficult or impossible for outside observers of displays  18  in system  10  (e.g., pedestrians and occupants of vehicles other than a vehicle including system  10 , occupants of rooms other than a room of a building in which system  10  is located, or other external observers) to view video content such as video V 1  and V 2  of  FIG. 6  and  FIG. 7 . 
     In the example of  FIG. 8 , video frames for video V 1 , video frames for video V 2 , and dummy content D are being repeatedly presented in sequential frames. This is merely illustrative. There may be three or more users in system  10 , each of which may have a unique set of glasses  24  that is used to view a respective independent video stream, there may be two or more sets of dummy content frames D, and the dummy frames and/or user image frames may have different time-varying patterns. For example, video frames V 1  and video frames V 2  may be separated by interposed dummy frames D 1  and D 2  as shown in  FIG. 9 . 
     If desired, dummy content may be based at least partly on the non-dummy content (user image frames) that is being presented to users  36 . This type of arrangement is illustrated in  FIGS. 10, 11, 12, and 13 . As shown in  FIG. 10 , video V 1  may contain an image of an object such as white object  60  set against a background such as black background  62 . To ensure that external observers cannot view video V 1  (even if simultaneous video V 2  is not present or is dark), dummy video D 1  of  FIG. 9  may be created. Each dummy frame D 1  may be a complementary version of a corresponding one of video frames V 1 , so that the combined light output viewed by an external observer without glasses will appear white or will have another predetermined private appearance. 
     In general, displays  18  may display color and/or monochrome content. In the example of  FIG. 10 , object  60  is a white circle and background  62  is black. To obscure video V 1  from external observers, complementary dummy content such as dummy video D 1  of  FIG. 11  may be displayed on display  18 . Dummy video D 1  may contain a black circle  66  that is the inverse of the white circle  60  of video V 1  and may contain a white background  64  that is the inverse of black background  62 . When an external observer (i.e., an observer without glasses  24 ) views alternating frames of video V 1  and dummy video D 1 , the external observer will perceive that display  18  is filled with static white content. The same technique may simultaneously be used for each unique video stream that is present. For example, if display  18  is displaying video V 2  for a second user at the same time that display  18  is displaying video V 1  for a first user, control circuitry  14  may direct display  18  to display dummy content D 2  of  FIG. 13  that is complementary to video content V 2  of  FIG. 12 . Dummy frames D 1  and D 2  may also be combined, if desired. 
     In color displays, dummy content may contain complementary colors. For example, if a pixel in video V 1  contains only red and no green or blue, the complementary pixel in dummy content D 1  may contain only green and blue and no red. In this way, external observers will observe white content on display  18 , even though users in system  10  with glasses  24  will be able to view video V 1 . 
     Each user in a multi-user system may independently communicate with control circuitry  14  and may independently select unique content for viewing. For example, users in system  10  may have remote controls, cellular telephones, or other equipment that communicates wirelessly with equipment  12  to make video selections, to change television channels, to adjust playback volume settings, etc. In some situations, users may request identical content (e.g., a first and second user may both wish to view a common television program). By incorporating dummy content D into the displayed image frames on display  18 , privacy may be ensured (e.g., external observers will not be able to view the television program). 
     In some situations, multiple users may simultaneously view different content on different respective portions of a common display. As shown in  FIG. 14 , for example, text for a first electronic book or other content may be displayed in a first set of horizontal strips (see, e.g., the odd-numbered horizontal strips of display  18  of  FIG. 14 , which are filled with first content V 1 ), whereas text for a second electronic book or other content may be displayed on a second sent of horizontal strips (see, e.g., the even-numbered horizontal strips of display  18  of  FIG. 14 , which are filled with second content V 2 ). In configurations of the type shown in  FIG. 14  in which content for different users is placed at different spatial locations on display  18 , glasses  24  may include spatial light modulators. The spatial light modulators in glasses  24  for a first user may be adjusted to pass content V 1  and block content V 2  and the spatial light modulators in glasses  24  for a second user may be adjusted to pass content V 2  while blocking content V 1 . If desired, spatial light modulator schemes (which may be based on liquid crystal spatial light modulators or other suitable spatial light modulators) may be used in conjunction with time division multiplexing schemes such as the schemes of  FIGS. 4-9  and/or other multiplexing schemes that allow multiple users to share one or more displays  18 . Spatially separated content such as content V 1  and V 2  may, for example, be directed to different users based on color filtering techniques (wavelength multiplexing), based on polarization multiplexing, or using other multiplexing arrangements. 
     In schemes of the type shown in  FIGS. 4-7 , two viewers can share a display by choosing to view either even frames or odd frames, as appropriate. In this type of arrangement, an external observer who has a pair of liquid crystal light modulator glasses or other light modulating glasses may potentially view the even frames or odd frames by adjusting the light modulators in the glasses to exhibit a 50% duty cycle and by synchronizing the glasses to the odd or even frames (e.g., by monitoring light emissions from display  18  to extract a frame rate signal from display  18 ). To ensure that external observers cannot view potentially personal user content in this way, the pattern in which light modulators  28  darken and lighten (e.g., the pattern of transparent and opaque intervals in transmission curve T) may follow a predetermined code sequence. 
     This type of arrangement is illustrated in  FIG. 15 . As shown in the upper trace of  FIG. 15 , control circuitry  14  may generate a series of image frames F 1 , F 2 , F 3 , F 4 , etc. corresponding to content to be viewed by a user. Among these frames of content, control circuitry  14  may intersperse dummy frames D to obscure the frames of content from external observers. The user may have a pair of glasses  24  with light modulators  28  that are configured to exhibit transparent intervals TI in a pattern that matches the patterned used for content frames F 1 , F 2 , F 3 , and F 4 , as shown by transmission curve T (the middle trace of  FIG. 15 ). The patterns of time intervals used for displaying the content frames and the transparent intervals may be, for example, pseudorandom patterns, patterns that change in known progressions (e.g., following a set of code sequences that are known in advance to both equipment  12  and glasses  24  and that periodically repeat), or using other known patterns that are more complex than the repeating on/off patterns of  FIGS. 4 and 5 . This allows content frames F 1 , F 2 , F 3 , F 4 , . . . to be passed to the user while dummy frames D are blocked, as illustrated by the lower trace of  FIG. 15 . To avoid flickering, the frame rate of the image frames may be relatively high (e.g., more than 100 Hz, more than 200 Hz, more than 300 Hz, more than 500 Hz, less than 1000 Hz, etc.). In the example of  FIG. 15 , only a single user was provided with glasses  24 . If desired, different patterns (e.g., non-overlapping patterns) may be used for the playback of image frames for different users (e.g., two or more users, three or more users, four or more users, etc.). 
     As shown in  FIG. 16 , system  10  may include light modulators  70  that are incorporated into structures such as windows  18 ′ (e.g., interior or exterior windows in a building or vehicle). Light modulators  70  may be liquid crystal light modulators with polarizers, guest-host liquid crystal light modulators, polymer dispersed liquid crystal light modulators, cholesteric liquid crystal light modulators, or other suitable light modulators. During operation, control circuitry  14  may display frames of video for one or more users  36  in system  10  while displaying dummy frames to help obscure the displayed content for external observers. The transmission of glasses  24  may be modulated to allow each user to view a desired portion of the image frames on display  18 . The transmission of light modulators  70  may be modulated to block the user video content for one or more of the users. For example, if there is one user  36  in interior  38 , light modulators  70  may have opaque intervals that overlap the image frames for that user  36 , thereby preventing video content for that user from being observed outside of system  10 . If there are two users  36 , the opaque intervals of light modulators  70  may overlap the image frames of both users  36 , to provide both users with privacy. 
     If desired, light modulators  70  may exhibit transparent intervals aligned with one of the sets of image frames being displayed on display  18 . For example, if a user desires to publically share the content for that user that is being displayed on display  18 , control circuitry  14  can direct light modulators  70  to produce transparent intervals that are aligned with the image frames of that user. This allows the user&#39;s image frames to pass through windows  18 ′ for observation by external observers. Privacy may be maintained for all users  36  by aligning the transparent intervals of light modulators  70  with dummy frames (e.g., frames of content corresponding to an innocuous video, predetermined patterns, etc. that serve as dummy content for external viewers) and aligning the opaque intervals of light modulators  70  with non-dummy image frames. This type of scheme is illustrated in  FIG. 17 . 
     As shown in the uppermost trace of  FIG. 17 , control circuitry  14  may use display  18  to display image frames V 1  for user  36  and interspersed dummy frames D. Glasses  24  may be modulated so that opaque intervals TB overlap dummy frames D while transparent intervals TI overlap image frames V 1 , as shown by the middle trace of  FIG. 17 . This allows the user with glasses  24  to view a movie or other content associated with image frames V 1 . Privacy is ensured by blocking image frames V 1  from view by external viewers and by allowing dummy content to be viewed through windows  18 ′ by external viewers. As shown in the lowermost trace of  FIG. 17 , for example, light modulators  70  may be directed to produce opaque intervals TB that overlap image frames V 1  and transparent intervals TI that overlap dummy frames D. With this arrangement, user  36  in interior  38  may view video V 1  and external observers will see dummy content D through windows  18 ′. This scheme may be used in environments with one user  36 , two users  36 , or more than two users  36 . The configuration of  FIG. 17  is merely illustrative. 
     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: 20170717
Publication Date: 20210126
Grant Date: 20210126
Priority Date: 20160912
Inventors: Kingman, David E.
MAZUIR, Clarisse
WILSON, JAMES R.
Assignee: APPLE INC
CPC Classifications: [{"code": "H04N2013/403", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R2499/13", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R2420/07", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R5/033", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2380/10", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2358/00", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/36", "inventive": true, "first": true, "tree": "[]"}, {"code": "G09G2354/00", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2310/08", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0646", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2354/00", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2358/00", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2310/08", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/1423", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G3/3406", "inventive": true, "first": true, "tree": "[]"}, {"code": "G09G3/36", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R1/028", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B27/0172", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B2027/0178", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R2499/13", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/2092", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R2420/07", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B27/0101", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2380/10", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2300/0413", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2354/00", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R1/028", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B27/0172", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/1423", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B27/0101", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2380/10", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2300/0413", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R2420/07", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2310/08", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B2027/0178", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/36", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G3/3406", "inventive": true, "first": true, "tree": "[]"}, {"code": "G09G2358/00", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R2499/13", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/2092", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2320/0646", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 74190999