Abstract:
A parallax barrier includes a first electrode comprising a first sub-electrode and a second sub-electrode. A second electrode is opposed to the first electrode. A plurality of liquid crystal molecules are disposed between the first electrode and the second electrode. A parallax barrier driver provides a voltage difference between the first electrode and the second electrode to form a light-shielding region overlapping with both the first sub-electrode and the second sub-electrode, and forms a transverse electric field between the first sub-electrode and the second sub-electrode. It is noteworthy that the transverse electric field adjusts the rotation angles of the liquid crystal molecules to adjust the width of the light-shielding region, and the parallax barrier&#39;s transmittance can thereby be changed.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a parallax barrier, a three-dimensional display, and a method of adjusting parallax barrier&#39;s transmittance. The present invention especially relate to a parallax barrier having an adjustable transmittance. 
         [0003]    2. Description of the Prior Art 
         [0004]    Recently, 3D display has developed several different displaying ways for form 3D vision. 3D vision is formed by providing different images to left and right eyes, and the brain will create a convincing 3D effect. Currently, 3D vision has divided into stereoscopic system needs wearing glasses and auto-stereoscopic system. However, it is not convenient and comfortable by wearing the glasses, so the stereoscopic system is gradually replaced by the auto-stereoscopic system. 
         [0005]    The auto-stereoscopic system is operated by installing a beam controlling element in front of a display panel. The beam controlling element is generally called “a parallax barrier”, and it controls beams such that different images are seen according to an angle change even at the same position on the beam control element. For example, a 2D/3D liquid crystal display device is equipped by another LCD as a parallax barrier on the display panel. 
         [0006]    The parallax barrier is usually disposed between the back light module and the display panel. The on/off of the parallax barrier can be controlled. When the parallax barrier is turned off, the parallax barrier is turned off as well and the parallax barrier becomes transparent so the beam from the back light module can pass through the parallax barrier entirely. When the 3D mode is turned on, the parallax barrier is also turned on and provides different images for right/left eyes and forms 3D vision. 
         [0007]    Based on different requirements, the parallax barrier covers different area ratios of the display panel. If the parallax barrier covers too small an area, the transmittance will increase; however, this results in crosstalk. If the parallax barrier covers too large an area, the transmittance will decrease. Generally, in the process of making the parallax barrier, deviations may occur. Therefore, the parallax barrier transmittance is hard to control. 
       SUMMARY OF THE INVENTION 
       [0008]    In light of the above, the present invention provides a parallax barrier, a three dimensional display thereof, and a method of adjusting parallax barrier&#39;s transmittance. The parallax barrier has an adjustable transmittance. 
         [0009]    According to a preferred embodiment of the present invention, a parallax barrier comprises: a first electrode comprising a first sub-electrode and a second sub-electrode, a second electrode disposed opposing the first electrode, a plurality of liquid crystal molecules disposed between the first electrode and the second electrode and a parallax barrier driver for providing a voltage difference between the first electrode and the second electrode to form a light-shielding region overlapping with both the first sub-electrode and the second sub-electrode, and to form a transverse electric field between the first sub-electrode and the second sub-electrode, wherein the transverse electric field adjusts the rotation angles of the liquid crystal molecules so as to adjust the width of the light-shielding region. 
         [0010]    According to another preferred embodiment of the present invention, a three dimensional display comprises a display unit comprising a light source, where the display unit provides a first image and a second image; a parallax barrier comprising a first electrode comprising a first sub-electrode and a second sub-electrode, a second electrode opposing the first electrode; and a plurality of liquid crystal molecules disposed between the first electrode and the second electrode; and a parallax barrier driver for providing a voltage difference between the first electrode and the second electrode to form a light-shielding region overlapping with both the first sub-electrode and the second sub-electrode, and to form a transverse electric field between the first sub-electrode and the second sub-electrode, wherein the transverse electric field adjusts the rotation angle of the liquid crystal molecules so as to adjust the width of the light-shielding region. 
         [0011]    According to another preferred embodiment of the present invention, a method of adjusting parallax barrier&#39;s transmittance, comprises: first, a parallax barrier is provided. The parallax barrier comprises: a first electrode comprising a first sub-electrode and a second sub-electrode, a second electrode disposed opposing to the first electrode and a plurality of liquid crystal molecules disposed between the first electrode and the second electrode, wherein when a full dark voltage difference is applied between the first electrode and the second electrode, a first light-shielding region is formed and overlaps with the first sub-electrode and the second sub-electrode, and the parallax barrier has a first transmittance. Then, a voltage difference is provided to the first electrode and the second electrode to form a second light-shielding region overlapping with the first sub-electrode and the second sub-electrode, and to form a transverse electric field between the first sub-electrode and the second sub-electrode, wherein the transverse electric field adjusts the rotation angle of each of the liquid crystal molecules so as to adjust the width of the second light-shielding region and make the parallax barrier have a second transmittance different from the first transmittance. 
         [0012]    The transverse electric field between the first sub-electrode and the second sub-electrode adjusts the rotation angle of the liquid crystal molecules, so that the transmittance of the parallax barrier can be increased or decreased without changing the structure of the parallax barrier. 
         [0013]    These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  depicts a three dimensional display of the present invention schematically. 
           [0015]      FIG. 2  depicts a three dimensional diagram of a parallax barrier of the present invention schematically. 
           [0016]      FIG. 3  depicts a cross sectional view of the parallax barrier taken along line AA′ in  FIG. 2 . 
           [0017]      FIG. 4  depicts a first electrode, a second electrode and panel schematically. 
           [0018]      FIG. 5  depicts the parallax barrier applying an operational voltage difference. 
           [0019]      FIG. 6  is a flow chart depicting a test of the parallax barrier&#39;s transmittance. 
           [0020]      FIG. 7  depicts the voltage ratio vs. transmittance. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    Certain terms are used throughout the description and following claims to refer to particular components. As one skilled in the art will understand, electronic equipment manufacturers may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not function. In the following description and in the claims, the terms “include” and “comprise” are used in an open-ended fashion, and thus should be interpreted to mean “include, but not limited to . . . .” 
         [0022]      FIG. 1  depicts a three dimensional display of the present invention schematically. As shown in  FIG. 1 , a three dimensional (3D) display  10  includes a panel  12  and a parallax barrier  14 . A back light module  16  is used as a light source of the 3D display  10 . When displaying a 3D image, the parallax barrier  14  is turned on, and at least two two-dimensional (2D) images are provided on the panel  12 . The 2D images provide light  34 . The parallax barrier  14  forms bright and dark stripes, where the stripes can direct light  34  formed by the two 2D images to the right eye and the left eye, respectively, of an observer. 
         [0023]      FIG. 2  depicts a three dimensional diagram of a parallax barrier of the present invention schematically.  FIG. 3  depicts a cross sectional view of the parallax barrier taken along line AA′, wherein like numbered numerals designate similar or the same parts, regions or elements. As shown in  FIGS. 1 to 3 , a parallax barrier  14  includes a first electrode  18 , a second electrode  20  and numerous liquid crystal molecules  22  disposed between the first electrode  18  and the second electrode  20 . The second electrode  20  has a top surface  21  contacting with the liquid crystal molecules  22 . Each liquid crystal molecule  22  has a long axis L. In addition, a first polarizing film  23  and a second polarizing film  24  sandwich the first electrode  18  and the second electrode  20 . The polarizing directions of the first polarizing film  23  and the second polarizing film  24  are usually perpendicular to each other. Furthermore, the first electrode  18  and the second electrode  20  are made of transparent material. The first electrode  18  includes a lot of striped sub-electrodes. For example, the first electrode  18  includes a first sub-electrode  26  and a second sub-electrode  27  disposed alternatively. A frame  28  connects to two ends of the first sub-electrode  26 , and two ends of the second sub-electrode  27 . A space  30  is disposed between the first sub-electrode  26  and the second sub-electrode  27 . The light  34  provided by the back light module  16  will pass the second polarizing film  24  then enter the parallax barrier  14 . 
         [0024]    Generally, the widths of the first sub-electrode  26  and the second sub-electrode  27  are the same. However, based on different view points, the widths of the first sub-electrode  26  and the second sub-electrode  27  can be adjusted to become wider or narrower, simultaneously or individually.  FIG. 4  depicts a first electrode, a second electrode and panel schematically, wherein like numbered numerals designate similar or the same parts, regions or elements. As shown in  FIG. 4 , the frame  28  surrounds the display region  31  of the panel  12 . The second electrode  20  overlaps with the display region  31  entirely. 
         [0025]    Please refer to  FIG. 3  and  FIG. 1 . In order to provide a 3D image with 2 viewpoints or 4 viewpoints, under an ideal circumstance, a full dark voltage difference V 1  is applied between the first electrode  18  and the second electrode  20  to turn on the parallax barrier  14 . At this point, a vertical electric field will form between the first sub-electrode  26  and the second electrode  20 , and the second sub-electrode  27  and the second electrode  20  so as to make the liquid crystal molecules  22  rotate. Therefore, the direction of the light  34  will be changed by the liquid crystal molecules  22 . By the help with the first polarizing film  23  and the second polarizing film  24 , a light-shielding region  36  is formed. At this point, it&#39;s called a full dark mode of the parallel barrier  14 . The light-shielding region  36  is on the first polarizing film  23  at a region where the first sub-electrodes  26 ,  27  overlaps with the second electrode  20 . In other words, the full dark voltage difference V 1  is applied to the first electrode  18  and the second electrode  20 . The long axis L of each liquid crystal molecule  22  between the first sub-electrode  26  and the second electrode  20  is perpendicular to the top surface  21  of the second electrode  20 . At the same time, the long axis L of each liquid crystal molecule  22  between the second sub-electrode  27  and the second electrode  20  is perpendicular to the top surface  21  of the second electrode  20 . A light-penetrating region  38  is formed on the first polarizing film  23 , and at a region where the space  30  overlaps with the second electrode  20 . The light-penetrating region  38  and the light-shielding region  36  are disposed alternatively so as to form bright stripes and dark stripes. The aforesaid full dark voltage difference V 1  is related to the type of liquid crystal molecules  22 . Generally, the full dark voltage difference V 1  is 5V. According to a preferred embodiment of the present invention, when the full dark voltage difference V 1  is applied to the first electrode  18  and the second electrode  20 , the long axis L of each liquid crystal molecule  22  between the first sub-electrode  26  and the second electrode  20 , and the second sub-electrode  27  and the second electrode  20  is perpendicular to the surface  21  of first sub-electrode  26  and the second sub-electrode  27 . After the light  34  shielded by the second polarizing film  24  and the first polarizing film  23 , a region where the first polarizing film  23  overlaps with the first sub-electrode  26  and the first polarizing film  23  overlaps with the second sub-electrode  27  forms the full dark mode. The light-shielding region  36  will be overlapping with the first sub-electrode  26 , and the second sub-electrode  27 . Therefore, part of the light  34  will be blocked by the light-shielding region  36 . 
         [0026]    Taking a 4 view point 3D display as example, to provide high transmittance and low cross talk, the ideal design of the parallax barrier  14  is that when applying the full dark voltage difference V 1 , 25% of the light  34  provided by the back light module  16  can pass through the parallax barrier  14 . The remaining 75% of the light  34  will be blocked by the light-shielding region  36 . In other words, the parallax barrier  14  transmittance is 25%. Taking the 2 view point 3D display as an example, when applying the full dark voltage difference V 1 , 50% of the light  34  provided by the back light module can pass through the parallax barrier  14 . The remaining 50% of the light  34  will be blocked by the light-shielding region  36 . In other words, the parallax barrier  14  transmittance is 50%. 
         [0027]    However, because of the process deviation or other unexpected factors, the parallax barrier&#39;s transmittance may be higher than the ideal value when applying the full dark voltage difference V 1 . In other words, the width of the light-shielding region  36  is too small. Therefore, crosstalk may happen to the 3D display  10 . Sometimes, the width of the light-shielding region  36  is too large, resulting in the brightness of the display not being enough. Taking the 4 view point 3D display as an example, the parallax barrier&#39;s transmittance is only 18% when applying the full dark voltage difference V 1 , although the ideal value should be 25%. Therefore, the insufficient 7% needs to be compensated by the method provided in the present invention. 
         [0028]      FIG. 5  depicts the parallax barrier applying an operational voltage difference, wherein like numbered numerals designate similar or the same parts, regions or elements. The structure of the parallax barrier in  FIG. 5  is the same as that in  FIG. 3 . As shown in  FIG. 5 , a parallax barrier  14  includes a first electrode  18 , a second electrode  20  and numerous liquid crystal molecules  22  disposed between the first electrode  18  and the second electrode  20 . Please refer to  FIGS. 3 to 5 . The first electrode  18  includes a plurality of striped first sub-electrodes  26  and the second sub-electrode  27 . A frame  28  connects two ends of the first sub-electrodes  26  and the second sub-electrode  27 . A space  30  is disposed between the first sub-electrodes  26  and the second sub-electrode  27 . In addition, a first polarizing film  23  and a second polarizing film  24  sandwiches the first electrode  18  and the second electrode  20 . 
         [0029]    When the parallax barrier  14  is turned on, a parallax barrier driver  32  provides an operational voltage difference V 2  between the first electrode  18  and the second electrode  20 . It is note worthy that an operational voltage difference V 2  is different from the full dark voltage difference V 1 , and the operational voltage difference V 2  is smaller than the full dark voltage difference V 1 . At this point, a transverse electric field is formed between the first sub-electrode  26  and the second sub-electrode  27  so the liquid crystal molecules  22  near the space  30  are influenced by the transverse electric field so as to change the direction of the long axis L of the liquid crystal molecules  22 . Therefore, the long axis L of the liquid crystal molecules  22  near the space  30  will not be perpendicular to the surface of the first sub-electrode  26  or the second sub-electrode  27 . Also, the long axis L of the liquid crystal molecules  22  near the space  30  will not be perpendicular to the top surface  21  of the second electrode  20 . Therefore, the direction of the light  34  near the edge of the first sub-electrode  26  and the edge of the second sub-electrode  27  is changed. As a result, part of the light  34  near the edge of the first sub-electrode  26  and the edge of the second sub-electrode  27  can pass through the first polarizing film  23  to form a gray scale. The gray scale will be determined as a bright state by a viewer&#39;s eyes. At this point, the width of the light-shielding region  36  is smaller than the width of the first sub-electrode  26  and the second sub-electrode  27 . The width of the light-penetrating region  38  is increased. 
         [0030]    As shown in  FIG. 3 , by applying the full dark voltage difference V 1  to the parallax barrier  14 , the parallax barrier&#39;s transmittance is 18%. As described in  FIG. 5 , by applying the operational voltage difference V 2  to the parallax barrier  14 , the parallax barrier&#39;s transmittance can be raised to approximately 25% because the transverse electric field changes the direction of the liquid crystal molecules  22  and the width of the light-shielding region  36  becomes smaller than the width of the first sub-electrode  26  and the second sub-electrode  27 . Furthermore, when the operational voltage difference V 2  is turned off, the parallax barrier  14  is also turned off. When the operational voltage difference V 2  is turned off, there will be no electric field between the first electrode  18  and the second electrode  20 , so the long axis L of each the liquid crystal molecule  22  will be parallel to the top surface  21  of the second electrode  20 . At this point, all the light  34  can pass through the liquid crystal molecules  22  without being blocked. 
         [0031]    According to a different embodiment, the operational voltage difference V 2  can be higher than the full dark voltage difference V 1  to make the light  34  near the edge of the first sub-electrode  26  and the second sub-electrode  27  unable to pass the first polarizing film  23 . Therefore, the width of the light-shielding region  26  will be larger than the width of the first sub-electrode  26  and the width of the second sub-electrode  27 . Then, the parallax barrier&#39;s transmittance is decreased. 
         [0032]      FIG. 6  is a flow chart depicting a test of the parallax barrier&#39;s transmittance, wherein like numbered numerals designate similar or the same parts, regions or elements. Please refer to  FIGS. 1 ,  3 ,  5 , and  6 . First, in the step  100 , a 3D display  10  is provided. Then, in the step  102 , a full dark voltage difference V 1  is provided to the parallax barrier  14 . In the step  104 , the parallax barrier&#39;s transmittance is tested to see whether the parallax barrier&#39;s transmittance meets the requirements. If the parallax barrier&#39;s transmittance meets the requirements, the flow proceeds to the step  108  to finish the test. If the parallax barrier&#39;s transmittance does not meet the requirements, then the flow proceeds to the step  106 . In the step  106 , the operational voltage difference V 2  is applied to the parallax barrier  14 . The operational voltage difference V 2  is different from the full dark voltage difference V 1 . Then, the step  104  is run again to test whether the parallax barrier&#39;s transmittance meets the requirements. If the parallax barrier&#39;s transmittance meets the requirements, then the step  108  is run to finish the test. If not, then step  106  and step  104  are repeated until the parallax barrier&#39;s transmittance meets the requirements.  FIG. 7  depicts the voltage ratio vs. transmittance. The experimental data is the test of a 4-view parallax barrier. The x-axis represents the voltage ratio, and the Y-axis represents the transmittance. The voltage ratio equals the operational voltage difference V 2  divided by the full dark voltage difference V 1  and multiplied by 100%. For example, if the liquid crystal molecules in the parallax barrier have 5V as their full dark voltage difference, when the operational voltage difference V 2  equals 5V, the voltage ratio equals 100%. Then, when the voltage ratio equals is 100%, the transmittance is 18%. But, if the operational voltage difference V 2  equals 3.335V, the voltage ratio equals 66.9%. The transmittance can be raised to 19.5%. 
         [0033]    To sum up, the parallax barrier provided in the present invention can finely modulate its transmittance. By changing the operational voltage difference between the first electrode and the second electrode, the transmittance of the parallax can be increased or decreased. 
         [0034]    Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention.