Abstract:
This invention applies a luminance detection device to determine the brightness of the place where the display device is located and adjusts the power of the light source accordingly. The photo sensor can also be place in front of the light source to detect the color deviation and to compensate the deviation by adding or subtracting the value of the corresponding color component which has color deviation. The image to be displayed is examined to determine the level of luminance and adjusts the power of the light source accordingly.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of Invention  
         [0002]     The present invention relates to display device, and more particularly relates to the method and apparatus to reduce the power required for a display device and to compensate the color deviation of the light source.  
         [0003]     2. Description of Related Art  
         [0004]     In the past decades, the breakthrough of the optoelectronic technology, have driven the display system popular with top image quality. The display technology includes the LCD, Liquid Crystal Display, OLED. Organic Light Emitter Display, PDP, Plasma Display Panel, LCD Projectors. The prevailing advantage of enhanced image quality makes the derivative products popular in mass applications including LCD monitor, LCD/PDP TV, screen of note book computer, display screen of mobile phone (OLED or LCD), PDA, GPS, e-dictionary, . . . etc. The digital image and motion video have been adopted in an increasing number of applications, which include digital camera, scanner/printer/fax machine, video telephony, videoconferencing, surveillance system, VCD (Video CD), DVD, digital TV . . . etc. The success of development of the digital image and video compression standards fuels wider applications in digital display devices.  
         [0005]     Taking the TFT, Thin Film Transistor LCD as an example, it uses liquid crystal to control the passage of light. The TFT-LCD panel may be thought of as two glass substrates sandwiching a layer of liquid crystal. The front glass substrate has a “coat” of a color filter, while the back glass has transistors fabricated on its surface. When voltage is applied to a transistor, the liquid crystal is crystallized and bent, allowing light to penetrate through to form a pixel. A light source locating at the back of the panel is called a “Back Light”. The front glass substrate is fitted with a color filter, which gives each pixel its own color. These pixels with each comprising in principle Red, Green and Blue color components form the image on the panel.  
         [0006]     Some display devices like the projector uses a light source with high power to project the image out to a flat object to display the image through color filter in between the light source and the lens.  
         [0007]     The light source is a device within the display system which consumes most power. The power consumption of a display device is dependent on the size of the display size. The larger the display the higher power is required. And, any light source will have more or less the color deviation. The longer a display is showing image, the higher degree of color deviation can be. Taking an LCD TV as an example, after turning on for several hours, the white light starts turning a little yellow which mixed with “Blue” can make pixels turn to “Green” this kind of color deviation degrades the image quality of display.  
         [0008]     This invention of integrating a luminance detection to measure the brightness of the place where the display device is positioned and to adjust the power of the light source accordingly and to compensate the color deviation helps significantly reducing the power consumption of the display system and providing better image quality.  
       SUMMARY OF THE INVENTION  
       [0009]     The present invention is related to a method and apparatus of the image display device, which plays an important role in power reduction, specifically in the light source of the display device. The present invention significantly reduces the power consumption of the display system. 
        The present invention examines the luminance of an image to be displayed, if the picture has high degree of brightness, then, less power will be applied to the light source, if less brightness, the light source will be turned to brighter.     The present invention detects the degree of luminance of the place where the display device is positioned and adjusts the power of the light source of the display device.     According to an embodiment of the present invention, several photo sensor cells are used to detect color, said Red, Green and Blue of the projecting back/front light source, should deviation happens, then, information of the photo detector will be used to the display driver circuit to adjust the corresponding value to compensate the color deviation.     According to an embodiment of the present invention, for speeding up the performance, one Green component of every predetermined amount of pixels is selected to be examined to decide the brightness of an image to be displayed.     According to an embodiment of the present invention, should color deviation happens and color compensation is applied to adjust the color, the degree of deviation of each color component is added/subtracted to the value of the corresponding R,G and B color component in the display driver.        
 
         [0015]     It is to be understood that both the foregoing general description and the following detailed description are by examples, and are intended to provide further explanation of the invention as claimed. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]      FIG. 1  illustrates a prior art of block diagram of the display device.  
         [0017]      FIG. 2  illustrates this invention of a display panel with automatic light source brightness adjustment.  
         [0018]      FIG. 3  depicts the cross section of the light source and the basic display system.  
         [0019]      FIG. 4  depicts the cross section of the principle of the image in a display system.  
         [0020]      FIG. 5  depicts the block diagram of a cell of the display driver.  
         [0021]      FIG. 6  illustrates the present invention of applying a luminance detector to adjust the brightness of the light source of the display system.  
         [0022]      FIG. 7  illustrates the present invention of applying a luminance detector to detect the color deviation of the light source of the display system and to compensate in the display driver.  
         [0023]      FIG. 8  illustrates the display system with the circuit of compensation in a display driver.  
         [0024]      FIG. 9  depicts the means of brightness analysis of an image to be display in a display system. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0025]     The quality of the display device has improved in the past decade coupled with the cost reduction has made the display device like the LCD, OLED and PDP display devices more popular.  FIG. 1  illustrates the display devices which include an image source  11 , a controller  12  and a display driver  13 , a display panel  14  and in some devices, a user adjustable brightness controller  18 . In some applications, the image to be displayed is temporarily stored in the frame buffer  16  for scaling or deinterlacing and the last image to be displayed is stored in a frame buffer  17  embedded in the display driver.  
         [0026]     This invention as shown in  FIG. 2  can significantly reduce the power consumption of a display device by implementing a luminance detector unit  21  which measures the brightness of the place where the display device is located. The level of brightness is sent to the electronic light source adjustment unit  22 . When the brightness is higher, higher power of the light source will be applied to turn the light source brighter, while, When the brightness is lower, lower power of the light source will be applied to turn the light source less brighter. This mechanism reduces the power consumption when inside a building or in evening time. The light will penetrate through the display panel  23  to reach the observer.  
         [0027]      FIG. 3  depicts the principle of a display device which comprises a light source  31  and a display panel which includes a display driver  32  sticking to the panel and two transparent material with a layer of electrically On-Off material  37 , for example the liquid crystal. A layer of color filter  36  with 3 color components Red, Green and Blue films  39  is placed between the light source and the display panel to let filtered colors with predetermined level of color to penetrate  33 ,  34  in the selected location which equivalent to 3 color components (R, G and B) and reach the observer  38 .  
         [0028]      FIG. 4  depicts details of how the color filters coupled with the display driver work. An image source  41  to be displayed  42  is temporarily stored in an RAM  42  and driven out to be displayed controlled by a timing controller  48 . The gate driver  45  functions as the row selector to determined which row (line) of image to be driven out The source driver  43 ,  44  drive out the color components with R, G and B colors each pixel of corresponding column by turning on the cells of the color filters of the corresponding locations. The color filters  46 ,  49  are coated on the display panel (ex. a layer of glass) by a thin film with 3 color components each pixel.  FIG. 5  shows details of the color filter  53  and the driving circuitry which comprises of a selecting and driving transistor  54  (ex. TFT transistor), a transparent thin film with color  53 , a selecting signal named “Gate Line”  51  and a signal source (or so named “Source Line”  52 ). The gate line turns on the transistor, and the source line provides corresponding strength of color of signal which is converted from the image data from the image buffer RAM.  
         [0029]      FIG. 6  illustrates details of this invention of deploying a luminance detection unit, for instance, a photo detector diode  62  with a voltage meter to measure the degree  63  of the charge trapped in the photo diode. The luminance detector is to measure the brightness of the place where the display device is located. The measured information of the luminance is used to determine the power of the light source  61 . The stronger the luminance, the strong the light power would be needed to show good image quality, the weaker the luminance, the less light power would be needed. Therefore, the luminance detector information is used to adjust  62  the power of the light source. A layer of color filter  66  with 3 color components, Red, Green and Blue films  69  is placed between the light source and the display panel to let filtered colors with predetermined level of color (done by a driver  65 ) to penetrate in the selected location which equivalent to 3 color components (R, G and B) and reach the observer  68 .  
         [0030]     To achieve higher image quality in displaying, another mechanism of this invention is shown in  FIG. 7 . A color detection device comprising of 3 photo diodes with Red, Green and Blue color filter on top of them is deployed to detect the 3 color components  71  of the light source. The detected color deviation information of any of the 3 color components are measured and analyzed  73  and connected to the display driver for color compensation  75  for the corresponding color component which has color deviation. A redundant photo diode is deployed for replacing the defect photo diode of the 3 diodes with no color filter on top. Should one of the 3 photo diodes is bad, a corresponding color filter will be put on top of the redundant photo diode to form a new replacement. This color compensation circuitry can detect the color deviation and compensate it and hence provides better image quality in display.  
         [0031]      FIG. 8  depicts how the color deviation detection and compensation circuitry works with the display driver. An image frame to be displayed is stored in a frame buffer  81  and shifted line by line  82  to a register before the digitized color information is converted into analog signals. The color deviation detection  88  circuitry provides the analyzed color information of Red, Green and Blue to the driver circuitry to be added (or subtracted) to/from the digitized pixel data and converted into analog voltage through the DAC, Digital-2-Analog Converter  83 ,  84  before driving out to the so called source line  866  which is conducted through a selecting transistor to turn the color filter  85  which is a thin film coated on to the display panel. When no color deviation happens, the deviation information can be set to all “0” and the driver provides normal voltage from the DAC. Should the color is deviated, the value of compensation wil be added or subtracted to be combined with the image data.  
         [0032]     For further enhancing the image quality in displaying and reducing power consumption, an image luminance examination mechanism is applied to check the brightness of an image to be displayed  91 . Should the image has most pixels with less brightness, the power of the light source can be turned higher to let the observer see low brightness. Should the image has most pixels with high brightness, the power of the light source can be turned lower. For speeding up the process of examining the image brightness, only one of every predetermined amount of Green components within an image is accumulated to the sum of Green color components since Green dominates most degree of the brightness of an image.  
         [0033]     It will be apparent to those skills in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or the spirit of the invention. In the 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 and their equivalents.