Patent Publication Number: US-2012032872-A1

Title: Dual view display system

Description:
TECHNICAL FIELD OF INVENTION 
     The invention generally relates to displays for displaying images or information, and more particularly relates to a system that time-multiplexes a single display with different images, and uses one or more optical elements in cooperation with light valves or shutter devices to display different images in different directions from the same display. 
     BACKGROUND OF INVENTION 
     Dual view displays capable of showing different images to distinct persons viewing the display from different directions have been proposed. Such displays can, for example, display navigation information to a vehicle operator while displaying a movie to a passenger. Some of the known dual view displays use a parallax barrier or patterned barrier to allow selected pixels on a display to be viewed from one direction and blocked when viewed from another direction. A description of such displays can be found in United States Patent Application Publication Number 2008/0001849 published Jan. 3, 2008 by Jin et al. and  2008 / 0061305  published Mar. 13, 2008 by Kim et al. Other dual view displays use a segmented backlighting source that directs light or emits light in a particular direction toward selected pixels by emitting light through apertures. The apertures are aligned with the pixels such that when the selected pixels are viewed from that particular direction, the selected pixels are more apparent than when viewed from another direction. A description of such a display can be found in U.S. Pat. No. 7,671,935 issued on Mar. 2, 2010 to Mather et al. In general, prior art devices rely on parallax angles and interlacing of images to display distinct images in different directions, and so when two images are displayed the resolution of each image is half of the resolution of the display. Furthermore, the direction that each image is displayed depends on careful control of lateral alignment and separation distance between the pixels and the parallax barrier or segmented backlighting source. 
     SUMMARY OF THE INVENTION 
     Described herein is a dual view display system that uses an optical element overlaying the display to direct an image on the display in two distinct directions, and two shutter devices operated in coordination with multiplexing images on the display so distinct images can be displayed in the distinct directions. 
     In accordance with one embodiment of this invention, a dual view display system is provided. The system includes a display device, an optical element, a first shutter device, and a second shutter device. The display device is configured to display a first image on a display surface during a first time period and display a second image on the display surface during a second time period distinct from the first time period. The optical element overlays the display surface and is configured to direct images displayed on the display surface toward a first direction and a second direction distinct from the first direction. The first shutter device is configured to allow viewing of the display surface through the optical element from the first direction during the first time period, and block viewing of the display surface from the first direction during the second time period. The second shutter device is configured to allow viewing of the display surface through the optical element from the second direction during the second time period, and block viewing of the display surface from the second direction during the first time period. 
     Further features and advantages of the invention will appear more clearly on a reading of the following detailed description of the preferred embodiment of the invention, which is given by way of non-limiting example only and with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The present invention will now be described, by way of example with reference to the accompanying drawings, in which: 
         FIG. 1  is a perspective view of vehicle interior equipped with a dual view display system in accordance with one embodiment; 
         FIG. 2  is a top sectional view of a dual view display of  FIG. 1  in accordance with one embodiment; 
         FIG. 3  is a block diagram of the dual view display system of  FIG. 1  in accordance with one embodiment; 
         FIG. 4  is a timing diagram of an operation in the dual view display system of  FIG. 1  in accordance with one embodiment; 
         FIG. 5  is a top sectional view of a dual view display of  FIG. 1  in accordance with one embodiment; and 
         FIG. 6  is a perspective view of a dual view display of  FIG. 1  in accordance with one embodiment. 
     
    
    
     DETAILED DESCRIPTION OF INVENTION 
     In accordance with an embodiment of a dual view display system  10 ,  FIGS. 1-2  illustrate a non-limiting example of a vehicle interior  12  equipped with a dual view display  11  located on a dashboard  22 . The system  10  in this example is configured so as illustrated in  FIG. 2 , a driver  14  may view a first image  34  from a first direction  16 , and a passenger  18  may view a second image  36  different from the first image  34  from a second direction  20  that is different from the first direction  16 . Such a dual view display system  10  may, for example, display navigation information as the first image  34  to the driver  14  while also displaying a movie as the second image  36  to the passenger  18 . By this arrangement, the system  10  appears to display two distinct images in two different directions for viewing by different persons at the same time from the same location on the dashboard  22 , As such, the system  10  is distinguished from 3-D display systems that display two similar images for viewing by the same person from the same general direction.  FIG. 2  illustrates a top sectional view of an embodiment of the dual view display  11  that includes a display device  24 , an optical element  26 , a first shutter device  28 , and a second shutter device  30 . 
       FIG. 3  illustrates a block diagram as a non-limiting example of the dual view display system  10 . The system  10  may include a controller  40  that may include a processor such as a microprocessor or other control circuitry as should be evident to those skilled in the art. The controller  40  may include memory, including non-volatile memory, such as electrically erasable programmable read-only memory (EEPROM) for storing one or more routines and captured data. The one or more routines may be executed by the processor to perform steps for determining if signals are received by the controller  40  for displaying images as described herein. As suggested in the illustration, the controller  40  may receive an image signal from a navigation system  42  that, for example, shows the present geographical location of the system  10 . The controller  40  may also receive information regarding vehicle operating status from a vehicle information system  44 . The vehicle operating status may include, for example, engine coolant temperature or vehicle interior heating and air conditioning settings. The controller  40  may also receive entertainment information from an entertainment system  46 . Entertainment information may include a pre-recorded movie. For reasons of avoiding distracting the driver  14 , it may be desirable that the movie information only be displayed to the passenger  16 . It will be appreciated that the dual view display system  10  may be used for non-vehicle applications where the controller  40  would receive signals from sources other than the systems  42 ,  44 , and  46  suggested in  FIG. 3 . It will also be appreciated that the same image could be displayed to both the driver  14  and the passenger  18  so, for example, both persons could view navigational information. 
     Referring again to  FIG. 2 , the display device  24  may be an organic light emitting diode (OLED) type device, or a liquid crystal display (LCD) type device, or any type of display capable of displaying images and having an image refresh rate sufficient for time-multiplexing the first image  34  and the second image  36  so each image has a sufficient update rate for what is being displayed. For example, if a movie is being displayed to the passenger  18 , a refresh rate of 30 frames per second for the second image  36  may be desirable. If navigation information is being displayed to the driver  14 , a refresh rate of 10 frames per second may be adequate. As such, for this example, a display device  24  with a refresh rate of at least 40 frames per second may be adequate. OLED and LCD type devices are readily available with refresh rates of 60 frames per second are readily available and so would be suitable to use for the display device  24 . With a refresh rate of 60 frames per second, the first image  34  and the second image  36  may be displayed every other frame so the refresh rate for the movie is adequate. If the display device  24  was limited to 40 frames per second, the first image  34  showing navigation information could be displayed every fourth frame, while the second image  36  showing the movie would be displayed during the intervening three frames. In general, the brightness of each frame is adjusted in accordance with the frame refresh rate. For example, if the passenger  18  turns the second image  36  off, the frame rate on the driver side may be increased and so the brightness of each frame displaying the first image  34  may need to be reduced to maintain the same brightness level as perceived by the driver  14 .  FIG. 4  illustrates a timing diagram depicting a repeating sequence of alternating a first time period T 1  and a second time period T 2  separated by a delay time T 3  for displaying the first image  34  and the second image  36  every other frame. In general, the display device  24  is configured to display a first image  34  on a display surface  32  during the first time period T 1  and display a second image  36  on the display surface  32  during a second time period T 2  distinct from the first time period T 1 . The first time period T 1  and second time period T 2  are preferably short enough so that by alternating the displaying the first image  34  and the second image  36 , both images appear to the driver  14  and passenger  16  to be uninterrupted. In general, any delay time T 3  between the end of one time period and the start of a subsequent time period should be minimized so as to maximize the brightness of each image. By way of a non-limiting example, the first time period T 1  and the second time period T 2  may both be about 16 milliseconds (ms), and the third time period T 3  may be about 1 ms. However, it will be appreciated that the first time period T 1  and the second time period T 2  do not need to be the same value. 
       FIG. 2  further illustrates the optical element  26  as overlaying and contacting the display surface  32 . The optical element  26  may be formed of a clear material such as glass or polymer. It will be appreciated that the material selected may be selected based on providing a particular index of refraction. The top view of the optical element  26  is depicted as having three planar faces defining a shape comparable to an isosceles triangle. The optical element  26  has a vertical height that corresponds to the height of the display surface  32 , as depicted in  FIG. 1 . In this non-limiting example, the optical element  26  defines a first direction surface  26 A oriented substantially normal or perpendicular to the first direction  16 , a second direction surface  26 B oriented substantially normal or perpendicular to the second direction  20 , and a third direction surface  26 C oriented substantially parallel to the display surface  32 . It will be understood that if a viewing direction and display surface are not precisely normal there may be some degradation of the image. As used herein, substantially normal means that the corresponding viewing direction and direction surface are sufficiently normal so the image can be discerned by, for example, the driver  14 , or the passenger  18 . It will also be appreciated that an optical element having a non-isosceles triangle shape or non-planer surfaces may also be useful for viewing the display surface  32 . It should also be recognized that other polygons may be used to provide more than two viewing directions. For example, an optical element having a shape like a trapezoid may be used to display an image for viewing from a third direction such as from a position between the driver  14  and the passenger  18 . 
       FIG. 2  illustrates the optical element  26  being in contact with the display surface  32  which may be desirable to minimize optical degradation of the image. Alternately, a polarizer, collimator, other type of filter, or an air gap may be present between the display device  24  and the display surface  32 . It will be appreciated that the lateral alignment and distance between the optical device  26  and the display surface  32  is not particularly critical for the dual view display  11  described herein to operate as intended, as is the case for prior art dual view displays relying on parallax to determine the directions for optimal viewing of the prior art dual view displays. 
       FIG. 2  illustrates the first shutter device  28  as overlying the first direction surface  26 A and so is configured to allow viewing of the display surface  32  through first direction surface  26 A of the optical element  26  from the first direction  16  during the first time period T 1 , and block viewing of the display surface  32  from the first direction  16  during the second time period T 2 . Similarly, the second shutter device  30  is illustrated as overlying the second direction surface  26 B and is operated to allow viewing of the display surface  32  through the optical element from the second direction  20  during the second time period T 2 , and block viewing of the display surface from the second direction during the first time period. 
     The first shutter device  28  and the second shutter device  30  are generally operable to a transparent state and a blocking or opaque state. The shutter devices  28  and  30  may be formed using various technologies including, but not limited to, liquid crystal display (LCD), electrowetting, electrochromic glass, and electrically switchable transreflective minors (ESTM). The shutter devices  28  and  30  may have a single element sized to correspond to the surfaces  26 A and  26 B, or may have a plurality of elements so that portions of the display surface  32  can be independently viewed or blocked from being viewed. It will be appreciated that the shutter devices  28  and  30  do not need to be the same technology, and so it may be advantageous to have one shutter device be one technology, for example an ESTM, and the other shutter device be a different technology, for example an LCD.  FIG. 2  shows a gap between the optical element  26  and the shutter devices  28  and  30  for the purposes of illustration. It will be recognized that the shutter devices  28  and  30  may be integrally formed with the optical element  24  using known processes. 
       FIG. 5  illustrates another embodiment of a portion of the dual view display  11  wherein the display surface  32  is overlaid by an optical element  26  comprising of a plurality of prisms  52 , each prism  52  having a top-view shape corresponding to an isosceles triangle. Similar to as described above, each prism  52  may have a shape other than an isosceles triangle, and may have a shape with more than three sides. Having a plurality of prisms  52  forming the optical element  26  is advantageous over the optical element illustrated in  FIG. 2  because the overall depth of the display  11  is reduced, and so may not require recessing the display  11  into the dashboard  22  for aesthetic reasons as suggested in  FIG. 2 . As such, each prism  52  defines a first direction surface  52 A oriented substantially normal to the first direction  16 , a second direction surface  52 B oriented substantially normal to the second direction  20 , and a third direction surface  52 C oriented substantially parallel to the display surface  32 . 
       FIG. 6  illustrates an embodiment of a dual view display  11  where each prism  52  may be described as a vertically oriented prism having a height dimension  60  much larger than width dimensions  64 ,  66 , and  68  of the respectively corresponding surfaces  52 A,  52 B, and  52 C. The height dimension  60  of each prism  52  may correspond to the height of the display surface  32 .  FIGS. 5 and 6  suggest that each prism  52  is aligned with a single pixel or column of pixels, for example pixels R, G, and B corresponding to red, green, and blue pixels respectively. However, the prisms  52  may be larger so that each of the prisms  52  has a width  68  that corresponds to more than one pixel. For example a prism  52  may be sized to have a width  68  that corresponds to ten (10) pixels, and so reduce the number of vertically oriented prisms  52  by a factor of 10. Alternatively, each prism  52  may have a height of only one or a few pixels of the display device  24 , and so a plurality of rows may be necessary to cover the display surface  32 . Each row of prisms  52  may be offset from rows above and below so the display  11  does not have the appearance of vertical lines extending the height of the display  11 . For example, each prism  52  may be sized to overlay an area of the display device  24  corresponding to a width of 10 pixels and a height of 10 pixels. It will be recognized that as the width  68  of each prism  52  approaches the width of one pixel, the alignment of each prism  52  with the edge of a pixel becomes more critical if the clarity and brightness of the images displayed is to be maintained. 
     The arrangement of the prisms  52  shown in  FIGS. 5 and 6  gives rise to a plurality of first direction surfaces  52 A that are substantially parallel with each other, and a plurality of second direction surfaces  52 B that are also substantially parallel with each other. As such, to effectively block or allow viewing of an image from a direction, a first shutter device  54  may comprise a plurality of first shutter devices overlying each of the plurality of first direction surfaces  52 A and a second shutter device  56  may comprise a plurality of second shutter devices overlaying each of the plurality of second direction surfaces  52 B. 
     Accordingly, a dual view display system  10  for displaying different images in different directions is provided. By using an optical element and two shutter devices, a system  10  displaying two distinct images is provided for less cost than two separate displays. The arrangement of the display device  24 , optical element  26 , and two shutter devices  28  and  30  do not require precise physical alignment as is the case with other dual view displays, particularly those relying on parallax to control the direction that images are displayed. Furthermore, the full resolution of the display device is maintained for both images, unlike the parallax based dual view display devices that halve the resolution of each image relative to the resolution of the display to display two distinct images. 
     While this invention has been described in terms of the preferred embodiments thereof, it is not intended to be so limited, but rather only to the extent set forth in the claims that follow.