Patent Publication Number: US-10313663-B2

Title: 3D viewing with better performance in both lumen per watt and brightness

Description:
BACKGROUND 
     The present invention generally relates to three-dimensional (3D) displays, and more particularly relates to a method of providing a 3D display to a viewer. 
     Presentation of a 3D image to a viewer is achieved using a technique known as “stereoscopy,” in which two offset images are separately displayed to the right and left eye of a viewer. When the viewer&#39;s brain combines those images, the user perceives the otherwise two-dimensional (2D) images as being 3D. With the recent rise in popularity of 3D films and video games, technological advances have been made in stereoscopy. 
     With recent 3D televisions, “active shutter” glasses have been used to achieve a 3D effect. Active shutter glasses include two lenses, each having a liquid crystal layer that can be controlled to be dark (and prevent image viewing) or be transparent (and facilitate image viewing). The glasses are synchronized with an electronic display (e.g. a television) to rapidly alternate which of the lenses if darkened at any given time, which achieves the desired effect of each eye seeing only the image intended for it. 
     “Autostereoscopy” refers to the display of stereoscopic images without the use of special headgear or glasses on the part of the viewer. A popular form of autostereoscopic display utilizes a parallax barrier that includes a plurality of spaced apart columns arranged to block a given eye from seeing an image portion meant for the opposite eye. This carefully arranged blocking enables two separate images to be displayed to the right and left eyes simultaneously. 
     However, only a portion of a video frame or image is typically displayed in 3D at any given time, with the remaining portion being presented in 2D. Thus, for the non-3D image areas, essentially the same image is being separately shown to a viewer&#39;s right and left eyes simultaneously. 
     SUMMARY 
     Embodiments of the present invention provide a parallax barrier for controlling what is seen by a viewer&#39;s right and left eyes from a 3D display. A color difference is determined between corresponding right and left eye images areas, and if the difference is beneath a predefined threshold, indicating that there is little or no difference between the corresponding image areas, then the parallax barrier may display both of those areas to the viewer simultaneously. 
     According to one embodiment, a method of providing a three-dimensional display to a viewer is disclosed. If a color difference between pixels of a right eye image area and corresponding pixels of a left eye image area is greater than or equal to a predefined difference threshold, a parallax barrier is controlled to block either the right or the left eye image area from the viewer. Otherwise, if the color difference is less than the predefined threshold, the parallax barrier is controlled to display both the right and left eye image areas to the viewer. The method may be performed by an autostereoscopic display, or a pair of active shutter glasses, for example. 
     An exemplary autostereoscopic electronic display operable to perform the method includes a display layer upon which an image is projected, with the image including a plurality of adjacent sets of right and left eye image areas. A parallax barrier is situated between the display layer and a viewer. The parallax barrier includes a plurality of separate parallax barrier areas each corresponding to one of the adjacent sets of right and left image areas. A controller is configured to control each parallax barrier area. The controller controls each parallax barrier area to block either its corresponding right or left eye image area from the viewer responsive to a color difference between pixels of the right eye image area and corresponding pixels of the left eye image area being greater than or equal to a predefined difference threshold. The controller controls each parallax barrier to display both of its corresponding right and left eye image areas to the viewer responsive to the color difference being less than the predefined threshold. 
     Exemplary active shutter glasses operable to perform the method are synchronized with an electronic display to provide a three-dimensional view of the electronic display to a viewer. The active shutter glasses include a right lens and a left lens through which an image projected from the electronic display may be viewed. The active shutter glasses also include a right lens parallax barrier and a left lens parallax barrier corresponding to the right lens and the left lens, respectively. A controller is configured to control the parallax barriers. The controller controls the parallax barriers to block viewing of either a right lens image area or a left lens image area if a color difference between corresponding pixels of the right and left lens image areas is greater than or equal to a predefined difference threshold. The controller controls the parallax barriers to permit viewing of the projected image through the right lens image area and the left lens image area simultaneously if the color difference between the corresponding pixels is less than the predefined threshold. 
     Of course, the present invention is not limited to the above features and advantages. Indeed, those skilled in the art will recognize additional features and advantages upon reading the following detailed description, and upon viewing the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an example autostereoscopic display. 
         FIG. 2  illustrates another view of the example autostereoscopic display. 
         FIGS. 3A-B  illustrates views of exemplary active shutter glasses. 
         FIGS. 4A-4B  illustrate example right lens image areas and left lens image areas of the active shutter glasses. 
         FIG. 5  illustrates an exemplary blocking feature of the active shutter glasses. 
         FIG. 6  schematically illustrates an example method of providing a three-dimensional display to a viewer. 
     
    
    
     DETAILED DESCRIPTION 
     Methods and apparatus are disclosed for controlling portions of a parallax barrier in a 3D display system based on the relative color differences between corresponding right eye and left eye image areas of a stereoscopic image. Although autostereoscopic display and active shutter glasses embodiments are disclosed below, these are embodiments are exemplary, and should not be construed as limiting. 
     Referring now to the drawings,  FIG. 1  schematically illustrates an example autostereoscopic display  10  including a display layer  12  and a parallax barrier  14 . The display  10  may correspond to a television, or portable gaming device, for example. An interleaved image is projected on the display layer  12 , with the image comprising a plurality of adjacent sets  16 A-E of right eye image areas  18  and left eye image areas  20 . The right eye image areas  18  and left eye image areas  20  are interleaved through their arrangement into set  16 . The parallax barrier  14  is situated between the display layer  12  and a viewer  22 . The parallax barrier  14  includes a plurality of separate parallax barrier areas  24 A-F each corresponding to one of the adjacent sets  16  of right and left image areas  18 ,  20 . Although five sets  16  of image areas are shown in  FIG. 1 , it is understood that this is only a non-limiting example, and that other quantities of sets of image areas could be used. 
     A controller  26  is configured to control each of the parallax barrier areas  24 . The controller  26  may include hardware, software, or any combination thereof. In one example, the controller  26  includes one or more microprocessors. If a color difference between pixels of a right eye image  18  area and corresponding pixels of a left eye image  20  area are greater than or equal to a predefined difference threshold, the controller  26  controls a corresponding each parallax barrier area  24  to block either its corresponding right or left eye image area from the viewer  22 . Otherwise, if the color difference is less than the predefined threshold, the controller  26  controls the parallax barrier area  14  to display both of its corresponding right and left eye image areas to the viewer. 
     Take set  16 A of image areas  18 A,  20 A as an example. A color difference is determined between pixels of image area  18 A and corresponding pixels of image area  20 A. If the color difference is greater than or equal to the predefined difference threshold, then corresponding parallax barrier area  24 A is turned ON to block the viewer&#39;s right eye from viewing image area  20 A, such that within set  16 A, the right eye only sees image area  18 A, and the left eye only sees image area  20 A. However, if the color difference is less than the predefined threshold (i.e., indicating that there is little or no difference between the image areas  18 A,  20 A), then the parallax barrier area  24 A is turned partially or completely OFF so that image area  20 A is visible to both the right and left eyes of the viewer  22 . 
     As another example, refer to set  16 B of image areas. When turned ON, the parallax barrier area  24 B associated with this set  16 B performs the following functions: (1) blocking the viewer&#39;s right eye from viewing image area  20 B, and (2) blocking the viewer&#39;s left eye from viewing image area  18 A (of set  16 A). If a color difference between image areas  18 B,  20 B of set  16 B is below the difference threshold, then parallax barrier area  24 B will be turned OFF so that blocking (1) above is not performed. However, as an unintended consequence blocking (2) also will not be performed, causing the viewer&#39;s left eye to see neighboring image areas  18 A,  20 A. If image areas  18 A,  20 A are determined to have 3D information (i.e. their color difference exceeds the difference threshold), it may be unpleasant for the viewer to areas  18 A,  20 A with the left eye. To address this problem, the color difference of neighboring sets  16  of image areas  18 ,  20  may be analyzed, so that parallax barrier  24 B is only turned OFF if it parallax barrier  24 A is also able to be turned OFF (i.e. the color difference between image areas  18 A,  20 A is beneath the difference threshold). 
     The controller  26  is also configured to compare color scale values of corresponding pixels of the sets of right and left image areas to determine a color difference between the corresponding pixels, and may store the color differences in a difference map in memory  27 . Thus, to determine if the difference color between right and left eye image areas  18 A,  20 A is greater than or equal to the threshold, a difference map for the set  16  of image areas  18 A,  20 A may be reviewed. In one example, the difference map is predetermined, and the controller  26  only needs to retrieve the predetermined difference map from memory  27 . 
     The difference map may be based, for example, on a 0-255 color scale. A stored color difference within the map represents corresponding (i.e. similarly located) displayed areas within each larger image area  18 ,  20 . Depending on the granularity of the difference map, the displayed area represented by the color difference may represent a single pixel, or a group of pixels. In one example, different red, green, and blue (RGB) values of a pixel or group of pixels are separately compared, and a largest difference between the respective red, green and blue color values in the displayed area is stored in the difference map. In one example, the predefined threshold is “9” on the 0-255 color scale. Of course, this is only an example threshold, and it is understood that other thresholds could be used. 
     A brightness of a set of right and left image areas may be reduced responsive to the color difference between corresponding pixels of the right and left image areas being less than the predefined threshold. Thus, to use the example of set  16 A from above, with parallax barrier area  14  turned partially or completely OFF, in order to prevent image area  20 A from appearing too bright, the brightness of one or both of the image areas  18 A,  20 A may be adjusted to achieve a desired brightness. This may include operating each of the image areas  18 A,  20 A at 50% brightness, for example. Of course other adjustments would be possible, such as increasing the brightness of other image areas  18 ,  20  whose corresponding parallax barrier area  24  is turned ON (e.g., neighboring image areas that have a corresponding color difference that is greater than or equal to the predefined threshold). Thus, using this technique, brightness of a 3D display may be reduced, which can result in better performance in both lumens per watt and also brightness. 
     In one example, the parallax barrier  14  comprises a liquid crystal display (LCD), which optionally may be a monochrome LCD. In this example, controlling the parallax barrier includes adjusting a voltage applied to an appropriate one of the parallax barrier areas  24 A-F to permit a desired amount of light to pass through the parallax barrier area  24 A-F. 
       FIG. 2  schematically illustrates another view of the example autostereoscopic display  10 . As shown in  FIG. 2 , the image areas  18 ,  20  and their corresponding parallax barrier areas  24  may extend vertically as columns within the display  10 . Each parallax barrier area  24  may be controlled as a single unit, such that if there is any color difference meeting or exceeding the difference threshold within a set  16  of image areas  18 ,  20 , the entire parallax barrier area  24  corresponding to the set  16  is turned ON. Alternatively, each parallax barrier area  24  may include separately controllable areas  30 , so that portions of a given parallax barrier area  24  may be differently controlled. This would enable a portion of an image area  18 ,  20  to be viewable only by a right or left eye, but other portions of the image area could be viewed by both eyes. Of course, although the image areas  18 ,  20  and parallax barrier areas  24  are shown as vertical bars, it is understood that this is only an example, and that diagonal or horizontal bars could instead be used, depending on a viewer&#39;s orientation with respect to the electronic display  10 . 
       FIGS. 3A-3B  illustrate active shutter glasses  40  that may be used to achieve a similar effect as the autostereoscopic display  10  described above. The active shutter glasses  40  are synchronized with an electronic display  42  (e.g., a viewing area of a television) to provide a three-dimensional view of the electronic display  42  to a viewer. A controller  52  communicates with the display  42  to provide the synchronization (e.g., over a wireless connection). The controller  52  may include hardware, software, or any combination thereof. In one example, the controller  52  includes one or more microprocessors. 
     The glasses include a right lens  44  and a left lens  46  through which an image projected from the electronic display  42  may be viewed. The glasses  40  also include a right lens parallax barrier  48  corresponding to the right lens  44 , and a left lens parallax barrier  50  corresponding to the left lens  46 . The parallax barriers  48 ,  50  may be located in front of, behind or within their corresponding lens  44 ,  46 . 
     The controller  52  is configured to control the parallax barriers  48 ,  50  to block viewing of either a right lens image area or a left lens image area (i.e. a portion of either a right lens image or a left lens image) if a color difference between corresponding pixels of the right and left lens image areas is greater than or equal to a predefined difference threshold. The controller  52  is also configured to control the parallax barriers to permit viewing of the projected image through the right lens image area and the left lens image area simultaneously if the color difference between the corresponding pixels is less than the predefined threshold. 
     Referring to  FIGS. 4A-B , a plurality of right lens image areas  54 A-F and corresponding left lens image areas  56 A-F are illustrated. Each image area  54 ,  56  has a corresponding parallax barrier portion  48 ,  50  that is controlled to permit or restrict viewing through its associated image area. Thus, if a color difference between lens image areas  54 A and  56 A is greater than or equal to the threshold, then the parallax barrier portions  48 A,  50 A operate as usual, so that only one of the lens image areas  54 A,  56 A is visible at any given time. 
     However, if the color difference between the lens image areas  54 A,  56 A is less than the difference threshold (i.e., indicating that there is little or no difference between the image areas  54 A,  56 A), then the corresponding parallax barrier portions  48 A,  50 A may be operated to display both of the areas  54 A,  56 A simultaneously. In one example, each area is shown but only with partial transparency (e.g. 50% transparency for each area  54 A,  56 A). In another example, the areas  54 A,  56 A are shown at or near full brightness, but the controller  52  communicates with the display  42  to reduce the brightness of other image areas to conserve power. 
     The glasses  40  include a right camera lens  58  operative to record the projected image of the display  42  from the perspective of the right lens  44 , and a left camera lens  60  operative to record the projected image of the display  42  from the perspective of the left lens  46  (see  FIG. 3B ). In one example, the controller  52  is configured to determine if a color difference between corresponding pixels of the right and left lens image areas  54 ,  56  is greater than or equal to a predefined difference threshold by comparing images recorded by the right and left camera lenses  58 ,  60 . 
     The controller  52  may the determined color differences in a difference map in memory  53 . The recorded right and left images may also be stored, even if temporarily, in the memory  53 . The controller  52  may create the difference map in the same fashion as the controller  26 . Thus, the difference map may be based on a 0-255 color scale, may store values for pixels or groups of pixels, may separately analyze RGB pixel values, etc. 
     The controller  52  may optionally be further configured to control the right and left lens parallax barriers  48 ,  50  to at least partially block right and left lens image areas that are not used to view the image projected from the electronic display  42  based on a timer, a user preference, or both. Referring to  FIG. 5 , an image  62  corresponding to the display  42  and also an image  64  corresponding to an area outside of the display  42  (see cross-hatched area) may be viewable through the right and left lenses. Based on a stored user preference, or a timer indicating passing of a predefined time period, the parallax barriers  48 ,  50  may be controlled to partially or fully block the area  64  from viewing in either lens. Such blocking may be used to provide a more immersive 3D viewing experience. Use of the timer, however, may be beneficial, as a user may want to see outside of the display  42  when they are setting up a video viewing event (e.g., a user may want to see and/or view a keyboard or remote control). 
     The controller  52  may also be configured to wirelessly transmit a notification to the electronic display  42  indicating which right lens image areas  54  and corresponding left lens image areas  56  a viewer is being permitted to view through the right lens  44  and the left lens  46  simultaneously. A wireless transceiver for performing such transmissions may be located within the controller  52 , for example. 
       FIG. 4  schematically illustrates an example method  100  of providing a three-dimensional display to a viewer. A color difference is determined between pixels of a right eye image area and corresponding pixels of a left eye image area (step  102 ), and the determined difference is compared to a predefined difference threshold (step  104 ). If a color difference between pixels of the right eye image area and corresponding pixels of the left eye image area is greater than or equal to a predefined difference threshold, a parallax barrier is controlled to block either the right or the left eye image area from the viewer (step  106 ). Otherwise, if the color difference is less than the predefined threshold, the parallax barrier is controlled to display both the right and left eye image areas to the viewer (step  108 ). 
     The foregoing description and the accompanying drawings represent non-limiting examples of the methods and apparatus taught herein. As such, the present invention is not limited by the foregoing description and accompanying drawings. Instead, the present invention is limited only by the following claims and their legal equivalents.