Patent Publication Number: US-2013229397-A1

Title: Display Apparatus for Capturing Images and Operation Method Thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to Taiwan Application Serial Number 101106770, filed Mar. 1, 2012, which is herein incorporated by reference. 
     BACKGROUND 
     1. Field of Invention 
     The present invention relates to a webcam apparatus, and more particularly to a webcam apparatus integrated into a TFT array of a photodetector display. 
     2. Description of Related Art 
     A webcam digitalizes the signals from image sensing devices and transfers the resulting digital signals to a computer. A user watches the images captured by the webcam through the display. These images can be also transferred to another computer through the Internet. 
     Typically, a webcam is installed in the edge of a display. That is, a position for assembling the webcam is pre-defined in the frame of the display. Such a structure runs counter to efforts to reduce the size of displays. 
     SUMMARY 
     The present invention provides a display apparatus for capturing images. The display apparatus at least includes a first substrate, a pixel array disposed on the first substrate, a thin film transistor array disposed in the pixel array and a photodetector array disposed in the pixel array. The pixel array includes a plurality of sub-pixels. The thin film transistor array controls image data transferred to the pixel array. When a light illuminates a sub-pixel of the pixel array, a photodetector corresponding to the sub-pixel of the photodetector array generates a leakage current in response to a gray-level of the light. 
     In an embodiment, the display apparatus further comprises a plurality of data lines disposed in the first substrate and arranged in a column direction and a plurality of scan lines disposed in the first substrate and arranged in a row direction, wherein the data lines cross the scan lines to define the pixel array. 
     In an embodiment, the display apparatus further comprises a second substrate facing the first substrate. A color layer and a black matrix are formed in the second substrate. The color layer further includes a plurality of color-units, wherein the color units include red color-units, blue color-units and green color-units arranged on the second substrate in a repeated pattern to pass red color light, blue color light and green color light respectively. The color units correspond to sub-pixels respectively. The black matrix is disposed among the color-units. 
     In an embodiment, each sub-pixel of the pixel array comprises a thin film transistor of the thin film transistor array and a photodetector of the photodetector array, and the black matrix is disposed in the second substrate and in locations over the thin film transistors and in locations surrounding the photodetectors. 
     In an embodiment, the photodetector is a thin film transistor. 
     In an embodiment, the thin film transistor array and the photodetector array are made by the same process. 
     The present invention also provides a display apparatus for capturing images. The display apparatus includes a first substrate, a second substrate and a liquid crystal layer located between the first substrate and the second substrate. The first substrate comprises a pixel array, a thin film transistor array disposed in the pixel array and a photodetector array disposed in the pixel array. 
     The pixel array includes a plurality of sub-pixels. The thin film transistor array controls image data transferred to the pixel array. When a light illuminates a sub-pixel of the pixel array, a photodetector corresponding to the sub-pixel of the photodetector array generates a leakage current in response to a gray-level of the light. The second substrate faces the first substrate. A color layer and a black matrix are formed in the second substrate. The color layer includes a plurality of color-units. The color units include red color-units, blue color-units and green color-units arranged on the second substrate in a repeated pattern to pass red color light, blue color light and green color light respectively, wherein color units corresponds to sub-pixels respectively, and the black matrix is disposed among the color-units. 
     The present invention also provides a method for capturing an image. First, the photodetector array is used to detect color lights illuminating the pixel array to generate leakage currents corresponding to the sub-pixels respectively. Next, the leakage currents are transformed to gray-levels. The gray-levels are then mixed to generate a color image of a pixel. Finally, all color images of pixels are grouped to obtain an image. 
     In an embodiment, the color lights include a red color light, a blue color light and a green color light. Mixing the gray-levels to generate a color image of a pixel involves mixing the gray-levels of adjacent three sub-pixels corresponding to the red color-unit, the blue color-unit and the green color-unit respectively. 
     Accordingly, in the present invention, an additional photodetector array is formed in a thin film transistor array. The photodetector array may capture images to make the display apparatus with capturing image function. Therefore, it is not necessary to assemble a webcam to the display apparatus, and as a result, the size of the display apparatus is significantly reduced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to make the foregoing as well as other aspects, features, advantages, and embodiments of the present invention more apparent, the accompanying drawings are described as follows: 
         FIG. 1  illustrates a schematic diagram of a display apparatus according to an embodiment of the present invention. 
         FIG. 2  illustrates a cross-sectional view taken along line A-A′ of  FIG. 1 . 
         FIG. 3  illustrates an arrangement of color-units according to an embodiment of the present invention. 
         FIG. 4  illustrates a flow chart of a method for using the display apparatus of  FIG. 1  to capture an image. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the present embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts. 
     Typically, a webcam is assembled in the edge of a display. That is, a position for assembling the webcam is pre-defined in the frame of the display. Such a structure runs counter to efforts to reduce the size of displays. In the present invention, the pixel array of a display apparatus includes a thin film transistor array and a photodetector array. The photodetector array may capture images to make the display apparatus with capturing image function. Therefore, it is not necessary to assemble a webcam to the display apparatus, and as a result, the size of the display apparatus is significantly reduced. Moreover, the photodetector is a thin film transistor. As a consequence, the thin film transistor array and the photodetector array are made by the same process, and therefore, no additional process is needed to form the photodetector array. The following is an example to describe the claimed invention. 
       FIG. 1  illustrates a schematic diagram of a display apparatus according to an embodiment of the present invention.  FIG. 2  illustrates a cross-sectional view taken along line A-A′ of  FIG. 1 . In this embodiment, each sub pixel in the pixel array substrate includes a first thin film transistor to serve as a switch and a second thin film transistor to serve as a photodetector for capturing an image. As illustrated in  FIGS. 1 and 2 , the display apparatus  100  includes a pixel array substrate  110 , a filter substrate  120  and a liquid crystal molecule layer  130  located between the pixel array substrate  110  and the filter substrate  120 . 
     The pixel array substrate  110  includes a first substrate  101  and a thin film transistor array and a photodetector array. The thin film transistor array and the photodetector array are formed on the first substrate  101 . The thin film transistor array includes a plurality of first thin film transistors  105 . Each first thin film transistor  105  acts as a switch. The photodetector array includes a plurality of second thin film transistors  106 . Each second thin film transistor  106  acts as a photodetector to capture an image. 
     In the explanation to follow, one of the first thin film transistors  105  and one of the second thin film transistors  106  will be given by way of example. However, it is to be understood that the thin film transistor array and the photodetector array respectively include a plurality of first thin film transistors  105  and a plurality of second thin film transistors  106 , as described above. 
     The first thin film transistor  105  and the second thin film transistor  106  are formed on the first substrate  101  at the same time and using the same process. Moreover, the first thin film transistor  105  and the second thin film transistor  106  have the same structure. For example, a gate electrode  1051  of the first thin film transistor  105  and a gate electrode  1061  of the second thin film transistor  106  are disposed on the first substrate  101 . In this embodiment, the first substrate  101  is a glass substrate. A dielectric layer  102  is disposed on the gate electrode  1051  and the gate electrode  1061 . A channel  1052  of the first thin film transistor  105  and a channel  1062  of the second thin film transistor  106  are disposed on the dielectric layer  102  and over the gate electrode  1051  and the gate electrode  1061 . The channel  1052  and the channel  1062  are manufactured using amorphous silicon. Subsequently, a source electrode  1053  and a drain electrode  1054  of the first thin film transistor  105  are disposed on the channel  1052  and the dielectric layer  102 , and a source electrode  1063  and a drain electrode  1064  of the second thin film transistor  106  are disposed on the channel  1062  and the dielectric layer  102 . Next, a protection layer  103  is disposed on the source electrodes  1053  and  1063  and the drain electrodes  1054  and  1064 . A contact hole  1055  is formed in the protection layer  103  to partially expose the drain electrode  1054  of the first thin film transistor  105 . A pixel electrode  1056  is connected to the drain electrode  1054  through the contact hole  1055 . In this embodiment, indium tin oxide (ITO) is used for forming the pixel electrode  1056 . 
     The filter substrate  120  includes a second substrate  121 , a black matrix  123 , a color layer  124  and an ITO layer  125 . The black matrix  123 , the color layer  124  and the ITO layer  125  are disposed on the second substrate  121 . The color layer  124  includes a plurality of each of three color-units, namely, a plurality of red color-units  124   a , a plurality of blue color-units  124   b  and a plurality of green color-units  124   c . The three color-units  124   a ,  124   b  and  124   c  are disposed on the second substrate  121  in a repeated pattern to allow corresponding color light to pass therethrough. Each color-unit  124   a ,  124   b  or  124   c  corresponds to a sub-pixel. A pixel is composed of three adjacent sub-pixels corresponding to one red color-unit  124   a , one blue color-unit  124   b  and one green color-unit  124   c  respectively. The black matrix  123  is disposed between the red color-units  124   a  and the blue color-units  124   b , and between the blue color-units  124   b  and the green color-units  124   c  to prevent light pass therethrough. The ITO layer  125  and the pixel array substrate  110  control the rotation angle of the liquid crystal molecules  130 . The different rotation angles of the liquid crystal molecules  130  control the quantity of light passing through the color layer  124  to display different gray-levels of red color, blue color and green color. By mixing these colors with different gray-levels, a color image is displayed. 
     Moreover, in this embodiment, the black matrix  123  is also disposed in a color-unit that is over the second thin film transistor  106 , and the black matrix  123  is arranged surrounding the second thin film transistor  106 . As illustrated in  FIG. 2 , the second thin film transistor  106  is disposed in a sub-pixel corresponding to the green color-unit  124   c . Accordingly, the black matrix  123  is disposed in the green color-unit  124   c  and is arranged surrounding the second thin film transistor  106 . Therefore, only light that enters from directly above the second thin film transistor  106  (i.e., straight light) can pass through the green color-unit  124   c  to illuminate the second thin film transistor  106 , and as a result, different color light cannot be sensed by the second thin film transistor  106 . Such a structure ensures that the second thin film transistor  106  captures images that face the display. 
     In the above embodiment, one of the second thin film transistors  106  is disposed in each sub-pixel. However, in another embodiment, six adjacent color units are grouped together, one of the second thin film transistors  106  is alternately disposed in sub-pixels. That is, one of the second thin film transistors  106  is disposed in one of two adjacent sub-pixels corresponding to color-units with the same color.  FIG. 3  illustrates an arrangement of color-units according to an embodiment of the present invention. In this embodiment, six color units located in the region  301  are grouped together. For sensing the strength of the light that illuminates the red color-units  301   a  and  301   b , one of the second thin film transistors  106  is disposed in one of the two sub-pixels corresponding to the red color-units  301   a  and  301   b . In another embodiment, the second thin film transistor  106  can be disposed at a position adjacent to the two sub-pixels corresponding to the red color-units  301   a  and  301   b . That is, it is not necessary for the second thin film transistor  106  to be located in a sub-pixel. Moreover, the present invention can be applied in other types of arrangements of the color-units to dispose the second thin film transistor  106  to capture images. 
     As best illustrated in  FIG. 1 , the pixel array substrate  110  includes a plurality of data lines  107  arranged in a column direction, and a plurality of scan lines  108  arranged in a row direction. The data lines  107  cross the scan lines  108  to define a pixel matrix with a plurality of pixels. In this embodiment, each pixel is composed of three sub-pixels corresponding to a red color-unit  124   a , a blue color-unit  124   b  and green color-unit  124   c  respectively. Each sub-pixel includes at least two thin film transistors, that is, a first thin film transistor  105  and a second thin film transistor  106 . The first thin film transistor  105  acts as a switch, and the second thin film transistor  106  acts as a photodetector to capture an image. The first thin film transistor  105  is disposed at a location where one of the data lines  107  crosses one of the scan lines  108 . The second thin film transistor  106  is disposed at a location separated from the first thin film transistor  105 . 
     The first thin film transistor  105  includes a gate electrode  1051 , a source electrode  1053  and a drain electrode  1054 . The gate electrode  105  is formed on the substrate  101  and connected to the scan line  108 . The source electrode  1053  is connected to the data line  107 . The drain electrode  1054  is connected to a pixel electrode  1056  through a contact hole  1055 . The pixel electrode  1056  is disposed in the sub-pixel  104 . 
     The second thin film transistor  106  includes a gate electrode  1061 , a source electrode  1063  and a drain electrode  1064 . The first thin film transistor  105  acts as a switch, as described above. When the scan line  108  is selected to turn on the first thin film transistor  105 , the data transferred in the data line  107  is transferred to the pixel electrode  1056  through the source electrode  1053  and the drain electrode  1054  to drive the liquid crystal molecule to rotate to a specific angle to pass light. The second thin film transistor  106  acts as a photodetector, as described above. Therefore, when a color light illuminates the second thin film transistor  106 , a leakage current is generated. By detecting the leakage current, a gray-level of this color light is determined. In an embodiment, a conductive line is connected to the source electrode  1062  of the second thin film transistor  106  to transfer the leakage current to a detector. Moreover, the gate line  108  overlaps a storage electrode  109  to define a storage capacitor. The storage electrode  109  is connected to the pixel electrode  1056  through the contact hole  109   a.    
     Accordingly, the red color-units  124   a , the blue color-units  124   b  and the green color-units  124   c  are formed in the filter substrate  120  and in the locations corresponding to the sub-pixels  104  respectively. A black matrix  123  is also disposed in the filter substrate  120 . The black matrix  123  is disposed over the first thin film transistor  105  and around second the thin film transistor  106 . The red color-units  124   a , the blue color-units  124   b  and the green color-units  124   c  are made using resin. 
       FIG. 4  illustrates a flow chart of a method for using the display apparatus  100  to capture an image.  FIGS. 1-4  are referred. Each sub-pixel has a second thin film transistor  106  acting as a photodetector. When the display apparatus captures an image, in step  401 , the leakage currents generated by the second thin film transistors  106  in response to color lights, a red color light, a green color light and a blue color light, are detected. In an embodiment, a red color light passes the red color-units  124   a  to induce the corresponding second thin film transistors  106  to generate first leakage currents. A blue color light passes the blue color-units  124   a  to induce the corresponding second thin film transistors  106  to generate second leakage currents. A green color light passes the green color-units  124   a  to induce the corresponding second thin film transistors  106  to generate third leakage currents. 
     Next, in step  402 , each leakage current is transformed to a corresponding gray-level of a color light. In an embodiment, a conductive line is connected to the source electrode  1062  of each of the second thin film transistors  106  to transfer the corresponding leakage current to a detector. The detector detects the leakage currents and transforms the leakage currents to gray-levels. For example, the first leakage currents are transformed to corresponding gray-levels of red color light. The second leakage currents are transformed to corresponding gray-levels of blue color light. The third leakage currents are transformed to corresponding gray-levels of green color light. 
     In step  403 , the gray-levels of red color light, the gray-levels of blue color light and the gray-levels of green color light are mixed to generate a color image of pixels. In an embodiment, the gray-levels of red color light, the gray-levels of blue color light and the gray-levels of green color light corresponding to three adjacent sub-pixels are mixed to generate a color image of a pixel. Then, in step  404 , an image front of the display apparatus is obtained by grouping all the images generated by the pixels. 
     Accordingly, the pixel array of a display apparatus includes a first thin film transistor array and a second thin film transistor array. The first thin film transistor array includes a plurality of first thin film transistors which act as switches. The second thin film transistor array includes a plurality of second thin film transistor which act as photodetectors to capture images. Therefore, it is not necessary to assemble a webcam to the display apparatus. Hence, the size of the display apparatus is significantly reduced. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims.