Patent Publication Number: US-2013235002-A1

Title: Auto stereoscopic display apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority benefit of Taiwan application serial no. 101107885, filed on Mar. 8, 2012. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a stereoscopic display apparatus. More particularly, the invention relates to an auto-stereoscopic display apparatus. 
     2. Description of Related Art 
     Auto-stereoscopic display technologies that are widely developed at present are mainly categorized into two types: the spatial multiplexing stereoscopic display technology and the temporal multiplexing stereoscopic display technology. These two types of displays are operated on condition that the human brain can fuse different images respectively perceived by left and right eyes, so as to generate a stereoscopic image vision. 
     According to the conventional temporal multiplexing display technology, a stereoscopic image display projects an image at one viewing angle into the left eye of a viewer at a time point and projects an image at another viewing angle into the right eye of the viewer at the next time point. If the images at the two viewing angles are switched fast enough, the brain will be unaware of the image switch, so as to fuse the images at the two viewing angles and generate a stereoscopic image pair. By contrast, according to the spatial multiplexing display technology, in order to accomplish the stereoscopic image effect, a lenticular lens or a parallax barrier is often applied to form different viewing zones within the space, such that a user is allowed to receive different image information respectively with the left and right eyes. Nonetheless, the spatial multiplexing display technology leads to the reduction of resolution of the stereoscopic display image. 
     SUMMARY OF THE INVENTION 
     The invention is directed to an auto-stereoscopic display apparatus capable of displaying an image at full resolution. 
     In an embodiment of the invention, an auto-stereoscopic display apparatus is provided. The auto-stereoscopic display apparatus includes a liquid crystal lens array and a display panel. The display panel has a plurality of pixels arranged in array. These pixels are divided into a plurality of first pixels and a plurality of second pixels. When the first driving electrodes are enabled, and the second driving electrodes are disabled, the first pixels display a first left-eye sub-frame, and the second pixels display a first right-eye sub-frame. When the second driving electrodes are enabled, and the first driving electrodes are disabled, the first pixels display a second right-eye sub-frame, and the second pixels display a second left-eye sub-frame. The liquid crystal lens array includes a first substrate, a second substrate, and a liquid crystal layer. The first substrate has a plurality of first driving electrodes electrically connected to one another and a plurality of second driving electrodes electrically connected to one another. The first driving electrodes are electrically insulated from the second driving electrodes. The first driving electrodes and the second driving electrodes are alternately arranged. The second substrate is located opposite to the first substrate and has a common electrode. The liquid crystal layer is located between the first substrate and the common electrode of the second substrate. 
     According to an embodiment of the invention, within a first sub-frame period, the first pixels display the first left-eye sub-frame, and the second pixels display the first right-eye sub-frame. Within a second sub-frame period, the first pixels display the second right-eye sub-frame, and the second pixels display the second left-eye sub-frame. The first sub-frame period, the second sub-frame period, and a time interval between the first sub-frame period and the second sub-frame period in total are shorter than or equal to a visual persistence time frame of human eyes. 
     According to an embodiment of the invention, the first driving electrodes and the common electrode together form a first electric field distribution, and the second driving electrodes and the common electrode together form a second electric field distribution. The first electric field distribution and the second electric field distribution do not overlap. 
     According to an embodiment of the invention, the first substrate further includes an insulating layer located between the first driving electrodes and the second driving electrodes. 
     According to an embodiment of the invention, the second driving electrodes are located on the same plane where the insulating layer is located, and the second driving electrodes are also located between the insulating layer and the second substrate. Besides, the first substrate further has a first base. The first driving electrodes and the second driving electrodes are located on the first base. The first driving electrodes are located on the same plane of the first base, and the first driving electrodes are also located between the insulating layer and the first base. 
     According to an embodiment of the invention, the first driving electrodes and the second driving electrodes are located on a same plane. 
     According to an embodiment of the invention, an extension direction of the first driving electrodes is parallel to an extension direction of the second driving electrodes. The pixels are arranged in matrix along a column direction and a row direction, and the extension direction of the first driving electrodes and the extension direction of the second driving electrodes interlace with the column direction and the row direction. 
     According to an embodiment of the invention, the first pixels and the second pixels are alternately arranged in the column direction and the row direction. 
     According to an embodiment of the invention, an extension direction of the first driving electrodes is parallel to an extension direction of the second driving electrodes. The pixels are arranged in matrix along a column direction and a row direction. The extension direction of the first driving electrodes and the extension direction of the second driving electrodes are substantially parallel to the column direction. 
     According to an embodiment of the invention, the first pixels are arranged in a plurality of first columns along the column direction. The second pixels are arranged in a plurality of second columns along the column direction. The first columns and the second columns are alternately arranged along the row direction. 
     Based on the above, the auto-stereoscopic display apparatus described in the embodiments of the invention drives two alternately-arranged sets of driving electrodes within different sub-frame periods, such that the liquid crystal lens array may guide a plurality of sub-frames displayed by two sets of pixels to the left and right eyes of a user. The user is thus allowed to watch a stereoscopic image at full resolution on the display apparatus. 
     In order to make the aforementioned and other features and advantages of the invention more comprehensible, embodiments accompanying figures are described in detail below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide further understanding, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments and, together with the description, serve to explain the principles of the invention. 
         FIG. 1A  and  FIG. 1B  respectively illustrate a status of an auto-stereoscopic display apparatus within a first sub-frame period and a second sub-frame period according to an embodiment of the invention. 
         FIG. 1C  is a schematic view illustrating a liquid crystal lens array according to an embodiment of the invention. 
         FIG. 1D  illustrates a driving state of the liquid crystal lens array depicted in  FIG. 1A  and  FIG. 1B  within a certain time period and images perceived by left and right eyes of a user. 
         FIG. 2A  and  FIG. 2B  respectively illustrate a configuration of pixels of a display panel within a first sub-frame period and a second sub-frame period according to an embodiment of the invention. 
         FIG. 3A  illustrates a correlation between first driving electrodes and pixels of a display panel. 
         FIG. 3B  illustrates a correlation between second driving electrodes and pixels of a display panel. 
         FIG. 4A  illustrates another correlation between first driving electrodes and pixels of a display panel. 
         FIG. 4B  illustrates another correlation between second driving electrodes and pixels of a display panel. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
       FIG. 1A  and  FIG. 1B  respectively illustrate a status of an auto-stereoscopic display apparatus within a first sub-frame period and a second sub-frame period according to an embodiment of the invention. With reference to  FIG. 1A  and  FIG. 1B , an auto-stereoscopic display apparatus  10  includes a liquid crystal lens array  100  and a display panel  200 . In the present embodiment, the display panel  200  may be a liquid crystal panel, for instance. However, the invention is not limited thereto, and the display panel  200  described in other embodiments may be an organic light-emitting display panel, a plasma display panel, an electrophoretic display panel, an electro-wetting display panel, or any other appropriate display panel. 
     The display panel  200  described in the present embodiment has a plurality of pixels arranged in array. These pixels may be divided into a plurality of first pixels  11  and a plurality of second pixels  22 . Besides, the display surface  202  of the display panel  200  faces toward the liquid crystal lens  100 . Consequently, the liquid crystal lens array  100  may pose an impact on images displayed on the display panel  200 , so as to generate a stereoscopic display vision. 
     The liquid crystal lens array  100  described in the present embodiment includes a first substrate  102 , a second substrate  104 , and a liquid crystal layer  106 . The first substrate  102  has a plurality of first driving electrodes  102   a  electrically connected to one another and a plurality of second driving electrodes  102   b  electrically connected to one another. The first driving electrodes  102   a  are electrically insulated from the second driving electrodes  102   b.  Besides, the first driving electrodes  102   a  and the second driving electrodes  102   b  are alternately arranged. 
     According to the present embodiment, the first driving electrodes  102   a  and the second driving electrodes  102   b  may belong to different film layer. That is to say, the first driving electrodes  102   a  and the second driving electrodes  102   b  may be located on different planes. In particular, the first substrate  102  may further include an insulating layer  102   c  located between the first driving electrodes  102   a  and the second driving electrodes  102   b.  The second driving electrodes  102   b  are located on the same plane P 1  where the insulating layer  102   c  is located, and the second driving electrodes  102   b  are also located between the insulating layer  102   c  and the second substrate  104 . The first substrate  102  further having a first base  102   d.  The first driving electrodes  102   a  and the second driving electrodes  102   b  are located on the first base  102   d . Besides, the first driving electrodes  102   a  are located on the same plane P 2  where the first base  102   d  is located, and the first driving electrodes  102   a  are also located between the insulating layer  102   c  and the first base  102   d.    
     However, the configuration of the first substrate is not limited to the above. According to another embodiment of the invention, the first driving electrodes and the second driving electrodes of the first substrate may be properly designed to be located on the same plane. This will be explained below with reference to the drawings.  FIG. 1C  is a schematic cross-sectional view illustrating a liquid crystal lens array according to another embodiment of the invention. With reference to  FIG. 1C , in the present embodiment, the first driving electrodes  102   a  and the second driving electrodes  102   b  of the liquid crystal lens array  100 A may be located on the same plane. To be more specific, the first driving electrodes  102   a  and the second driving electrodes  102   b  are located on the same plane P 3  where the insulating layer  102   c  is located, and the first driving electrodes  102   a  and the second driving electrodes  102   b  are also located between the insulating layer  102   c  and the second substrate  104 . 
     As shown in  FIG. 1A , the second substrate  104  described in the present embodiment is located opposite to the first substrate  102  and has a common electrode  104   a.  The liquid crystal layer  106  is located between the first substrate  102  and the common electrode  104   a  of the second substrate  104 . In the present embodiment, the second substrate  104  may further has a second base  104   b.  The first and second bases  102   d  and  104   b  may be rigid bases and may be made of glass, for instance. However, the invention is not limited thereto, and the first and second bases  102   d  and  104   b  described in another embodiment of the invention may be flexible bases and may be made of plastic, for instance. 
     In the liquid crystal lens array  100  described in the present embodiment, the liquid crystal layer  106  as a whole may be in a homogenic state when the first driving electrodes  102   a,  the second driving electrodes  102   b,  and the common electrode  104   a  are not driven. When the first driving electrodes  102   a  and the common electrode  104   a  are driven, and the second driving electrodes  102   b  are not driven (i.e., there is a voltage difference between the first driving electrodes  102   a  and the common electrode  104   a , and there is no voltage difference between the second driving electrodes  102   b  and the common electrode  104   a ), the first driving electrodes  102   a  and the common electrode  104   a  together produce a first electric field distribution E 1 . When the second driving electrodes  102   b  and the common electrode  104   a  are driven, and the first driving electrodes  102   a  are not driven (i.e., there is a voltage difference between the second driving electrodes  102   b  and the common electrode  104   a,  and there is no voltage difference between the first driving electrodes  102   a  and the common electrode  104   a ), the second driving electrodes  102   b  and the common electrode  104   a  together produce a second electric field distribution E 2 . The first electric field distribution El and the second electric field distribution E 2  do not overlap. Here, the first electric field distribution El and the second electric field distribution E 2  may change the arrangement of liquid crystal molecules in the liquid crystal layer  106 , such that the liquid crystal layer  106  exhibits a certain refractive index distribution. At this time, the refractive index distribution of the liquid crystal layer  106  achieves effects similar to those accomplished by an optical lens array. Since the liquid crystal lens array  100  poses an impact on images composed of the first pixels  11  and the second pixels  22  of the display panel  200 , the images may be traveled toward different directions (i.e., different viewing zones are formed), so as to achieve a stereoscopic image vision. 
       FIG. 1D  illustrates a driving state of the liquid crystal lens array depicted in  FIG. 1A  and  FIG. 1B  within a certain time period and images perceived by left and right eyes of a user. With reference to  FIG. 1D , the time period required by the auto-stereoscopic display apparatus for displaying a complete stereoscopic image is a frame period F according to the present embodiment. Each frame period F includes a first sub-frame period F 1  and a second sub-frame period F 2 .  FIG. 1A  and  FIG. 1B  respectively illustrate the condition of the liquid crystal lens array within the first sub-frame period F 1  and the second sub-frame period F 2 . 
     As shown in  FIG. 1A ,  FIG. 1B , and  FIG. 1D , in the stereoscopic display mode, a method of driving the liquid crystal lens array  100  includes driving the first driving electrodes  102   a  and the second driving electrodes  102   b  respectively within the first sub-frame period F 1  and the second sub-frame period F 2 . With reference to  FIG. 1A  and  FIG. 1C , within the first sub-frame period F 1 , the first driving electrodes  102   a  are enabled, and the second driving electrodes  102   b  are disabled. At this time, the refractive index distribution of the liquid crystal layer  106  may be represented by a curve R 1  due to the impact of the first electric field distribution E 1 , such that a plurality of first lens units  106   a  are formed in the liquid crystal layer  106 . Here, the functions of the first lens units  106   a  are similar to those of an optical lens. The refractive index of each of the first lens units  106   a  gradually decreases from the central area (between two adjacent first driving electrodes  102   a ) to the two side areas, as represented by the curve R 1 . Here, the first lens units  106   a  are capable of gathering and focusing light beams. 
     With reference to  FIG. 1A  and  FIG. 1D , within the first sub-frame period F 1 , a first left-eye sub-frame L11 composed of the first pixels  11  is refracted by the first lens units  106   a  and traveled to leave the auto-stereoscopic display apparatus  10  toward the upper-right corner of  FIG. 1A , and the first left-eye sub-frame L11 is then transmitted to the left eye EL of a user. Besides, a first right-eye sub-frame R11 composed of the second pixels  22  is refracted by the first lens units  106   a  and traveled to leave the auto-stereoscopic display apparatus  10  toward the upper-left corner of FIG.  1 A, and the first right-eye sub-frame R11 is then transmitted to the right eye ER of the user. The user can simultaneously receive the first left-eye sub-frame L11 and the first right-eye sub-frame R11 within the first sub-frame period F 1 . The brain of the user is capable of fusing the first left-eye sub-frame L11 and the first right-eye sub-frame R11, so as to allow the user to watch the first stereoscopic frame. 
     Nonetheless, in the present embodiment, the liquid crystal lens array  100  serves to transmit the sub-frames composed of adjacent first and second pixels  11  and  22  toward different directions. In other words, within the first sub-frame period F 1 , the auto-stereoscopic display apparatus  10  displays the stereoscopic image in a spatial multiplexing manner. At this time, the image information captured or received by either the left eye or the right eye of the user is half the total number of the pixels of the display panel  200 . Namely, within the first sub-frame period F 1 , an resolution of an image displayed by the auto-stereoscopic display apparatus  10  is half of an resolution of an image displayed by the display panel  200 . 
     To allow the user to observe the stereoscopic frame at full resolution with the second sub-frame period F 2 , the auto-stereoscopic display apparatus  10  described in the present embodiment can display a second left-eye sub-frame L22 and a second right-eye sub-frame R22 respectively complementary to the first left-eye sub-frame L11 and the first right-eye sub-frame R11. 
     In particular, as shown in  FIG. 1B  and  FIG. 1C , within the subsequent second sub-frame period F 2 , the second driving electrodes  102   b  are enabled, and the first driving electrodes  102   a  are disabled. At this time, the refractive index distribution of the liquid crystal layer  106  may be represented by a curve R 2  due to the impact of the second electric field distribution E 2 , such that a plurality of second lens units  106   b  are formed in the liquid crystal layer  106 . Here, the functions of the second lens units  106   b  are similar to those of an optical lens. It can be learned from  FIG. 1A  and  FIG. 1B  that the spatial distribution of the first lens units  106   a  and the second lens units  106   b  does not overlap. Namely, there is a relative displacement between the first and second lens units  106   a  and  106   b.  As indicated in  FIG. 1B , within the second sub-frame period F 2 , the second right-eye sub-frame R22 composed of the first pixels  11  is refracted by the second lens units  106   b  and traveled to leave the auto-stereoscopic display apparatus  10  toward the upper-left corner of  FIG. 1B , and the second right-eye sub-frame R22 is then transmitted to the right eye ER of the user. Besides, the second left-eye sub-frame L22 composed of the second pixels  22  is refracted by the second lens units  106   b  and traveled to leave the auto-stereoscopic display apparatus  10  toward the upper-right corner of  FIG. 1B , and the second left-eye sub-frame L22 is then transmitted to the left eye EL of the user. The user can simultaneously receive the second left-eye sub-frame L22 and the second right-eye sub-frame R22 within the second sub-frame period F 2 . The brain of the user is capable of fusing the second left-eye sub-frame L22 and the second right-eye sub-frame R22, so as to allow the user to watch the second stereoscopic frame. 
     It should be mentioned that the first sub-frame period F 1 , the second sub-frame period F 2 , and a time interval (0 in  FIG. 1C ) between the first sub-frame period F 1  and the second sub-frame period F 2  in total are shorter than or equal to a visual persistence time frame (e.g., 62.5 ms to 200 ms) of human eyes. Thereby, the user&#39;s brain is able to combine the first stereoscopic image (constituted by the first left-eye sub-frame L11 and the first right-eye sub-frame R11) at half the resolution and the second stereoscopic image (constituted by the second left-eye sub-frame L22 and the second right-eye sub-frame R22) at the other half the resolution, so as to generate the stereoscopic image at full resolution, and the stereoscopic image is visible to the user. In other words, the auto-stereoscopic display apparatus  10  in a stereoscopic display mode allows the user to observe the stereoscopic image at full resolution through the combination of spatial and temporal multiplexing technologies. 
     The stereoscopic display mechanism of the auto-stereoscopic display apparatus  10  is further described in the present embodiment with reference to  FIG. 2A  and  FIG. 2B .  FIG. 2A  and  FIG. 2B  respectively illustrate a display state of pixels of a display panel within a first sub-frame period and a second sub-frame period. As shown in  FIG. 2A , within the first sub-frame period F 1 , the right eye of the user can receive one portion of the frame at the right-eye viewing angle, and the frame (i.e., the first right-eye sub-frame R11) is composed of the second pixels  22 . In  FIG. 2B , within the second sub-frame period F 2 , the right eye of the user can receive the other portion of the frame at the right-eye viewing angle, and the frame (i.e., the second right-eye sub-frame R22) is composed of the first pixels  11 . 
     Similarly, as shown in  FIG. 2A , within the first sub-frame period F 1 , the left eye of the user can receive a portion of the frame at the left-eye viewing angle, and the frame (i.e., the first left-eye sub-frame L11) is composed of the first pixels  11 . In  FIG. 2B , within the second sub-frame period F 2 , the left eye of the user can receive the other portion of the frame at the left-eye viewing angle, and the frame (i.e., the second left-eye sub-frame L22) is composed of the second pixels  22 . Thereby, as the complete frame period goes by, the frames displayed within the two sub-frame periods are combined to generate a complete frame at the right-eye and left-eye viewing angles. As such, the image resolution sensed by the user is equal to the numbers of all the pixels of the display panel  200 , and the user is thus allowed to observe the stereoscopic image at full resolution. 
       FIG. 3A  illustrates a correlation between first driving electrodes and pixels of a display panel.  FIG. 3B  illustrates a correlation between second driving electrodes and pixels of a display panel. Note that a pair of first driving electrodes is exemplarily shown in  FIG. 3A , and a pair of the second driving electrodes is exemplarily shown in  FIG. 3B . The number of the first and second driving electrodes is not limited in the invention and can be properly determined based on actual demands. With reference to  FIG. 3A  and  FIG. 3B , in the present embodiment, an extension direction D 1  of the first driving electrodes  102   a  is parallel to an extension direction D 2  of the second driving electrodes  102   b.  The pixels  11  and  22  of the display panel  200  are arranged in matrix along a column direction y and a row direction x. The extension direction D 1  of the first driving electrodes  102   a  and the extension direction D 2  of the second driving electrodes  102   b  interlace with the column direction y and the row direction x. That is to say, the extending directions of the first driving electrodes  102   a  and the second driving electrodes  102   b  may tilt respect to the column direction y ,and he first driving electrodes  102   a  and the second driving electrodes  102   b  may be alternately arranged along the row direction x. Besides, the first pixels  11  and the second pixels  22  of the display panel  200  may be alternately arranged in the column direction y and the row direction x. Namely, in the present embodiment, the first pixels  11  and the second pixels  22  may be arranged in a chessboard-like manner. 
     Note that the correlation of the first driving electrodes, the second driving electrodes, and the display panel is not limited to the above, and other correlations will be exemplified hereinafter.  FIG. 4A  illustrates another correlation between first driving electrodes and pixels of a display panel.  FIG. 4B  illustrates another correlation between second driving electrodes and pixels of a display panel. Note that a pair of first driving electrodes is exemplarily shown in  FIG. 4A , and a pair of the second driving electrodes is exemplarily shown in  FIG. 4B . With reference to  FIG. 4A  and  FIG. 4B , in the present embodiment, the extension direction D 1  of the first driving electrodes  102   a  and the extension direction D 2  of the second driving electrodes  102   b  may be parallel to the column direction y. That is to say, the first driving electrodes  102   a  and the second driving electrodes  102   b  may extend along the column direction y and may be alternately arranged along the row direction x. Besides, the first pixels  11  of the display panel  200  may be arranged in a plurality of first columns T 1  along the column direction y, and the second pixels  22  of the display panel  200  may be arranged in a plurality of second columns T 2  along the column direction y. The first columns Ti and the second columns T 2  may be alternately arranged along the row direction x. 
     In light of the foregoing, the auto-stereoscopic display apparatus described in an embodiment of the invention drives two alternately-arranged sets of driving electrodes within different sub-frame periods, such that the liquid crystal lens array may guide a plurality of sub-frames displayed by two sets of pixels to the left and right eyes of a user. The user is thus allowed to watch a stereoscopic image at full resolution on the display apparatus. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.