Patent Publication Number: US-2009231440-A1

Title: Brightness automatically adjusting system and method for adjusting brightness thereof

Description:
FIELD OF THE DISCLOSURE 
     The present disclosure relates to a brightness adjustment system and a brightness adjustment method of a liquid crystal display. 
     GENERAL BACKGROUND 
     Liquid crystal display devices are capable of displaying clear and sharp images via thousands or even millions of pixels that make up the complete image. 
     Liquid crystals in the liquid crystal display do not themselves emit light, and require a light source to display data. Backlight modules applied with the liquid crystal display often provide the required light. Power consumption of the backlight module, however, makes up a large part of the overall power consumption of the unit. Automatic adjustment of brightness of the liquid crystal display can decrease electric power consumption. 
     However, a typical automatic backlight adjustment method requires a light sensor to detect environmental brightness and a related control circuit to calculate the environmental brightness, a costly solution. 
     It is desirable to provide a brightness adjustment system and method which can overcome the described limitations. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of a brightness adjustment system for a liquid crystal display according to the present disclosure, including a web camera, a computer, and a signal processor. 
         FIG. 2  is an environmental image captured by the web camera of  FIG. 1 . 
         FIG. 3  is a flowchart of a method of a computer providing a brightness adjustment parameter for a liquid crystal display. 
         FIG. 4  is a flowchart of a method of a signal processor processing the brightness adjustment parameter of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSURE 
     Reference will now be made to the drawings to describe various inventive embodiments of the present disclosure in detail, wherein like numerals refer to like elements throughout. 
       FIG. 1  is a block diagram of a brightness adjustment system for a liquid crystal display according to the present disclosure, including a web camera  100 , a computer  101 , and a liquid crystal display  10 . The liquid crystal display  10  includes a signal processor  102 , a backlight control circuit  103 , and a backlight unit  104 . The web camera  100  is electrically connected to the computer  101  via a universal serial bus (USB) interface and captures environmental images in real time. The computer  101  receives and analyzes the environmental image from the web camera  100  for generating a brightness adjustment command and a brightness adjustment parameter, and sends the brightness adjustment command and the brightness adjustment parameter to the signal processor  102 . The signal processor  102  adjusts the brightness of the backlight unit  104  according to the brightness adjustment command and the brightness adjustment parameter via the backlight control circuit  103 , thereby controlling the brightness of the liquid crystal display  10 . The backlight unit  104 , can, for example, be a cold cathode decoration lamp (CCFL) or a light emitting diode (LED). 
     Referring to  FIG. 2 , an environmental image  11  captured by the web camera  100  of  FIG. 1  is shown. Because the computer  101  requires considerable memory resources to analyze the environmental image  11 , execution of the following steps can acquire an accurate environmental brightness measurement utilizing minimum memory resources, and generate calculation results without undue influence by calculation processing. 
     In Step  1 , the environmental image  11  is divided into a 3×3 rectangular matrix, resulting in nine rectangles, each having the same area. 
     In Step  2 , a number of circles a, b . . . , h are defined within eight rectangles leaving the center rectangle unoccupied. A center of each rectangle is defined as a corresponding center of each circle, and half length of a short side of each rectangle is defined as a corresponding radius of each circle. The three circles in the first row of the rectangle matrix are respectively denoted as a, b, and c. The two opposite circles in the second row of the rectangle matrix are respectively denoted as d and e. The three circles in the third row of the rectangle matrix are respectively denoted as f, g, and h. Because the central part of the environmental image  11  is often a focus of the image, generating little environmental brightness, the central part of the environmental image  11  represented by the rectangle in the center of the environmental image  11  is ignored. Circles a, b . . . , h are tasked with analyzing the environmental brightness to eliminate the influence liquid crystal display  10  rotation. 
     In Step  3 , a low pass filter (not shown) is employed to filter off high frequency parts of the environmental image  11  within the eight circles a, b . . . , h, in other words, to filter off detailed parts of the environmental image  11  within the eight circles a, b . . . , h. Because the detailed parts of the environmental image  11  have insufficient information regarding environmental brightness, the detailed parts of the environmental image  11  are filtered off to reduce influence on later processing. 
     A histogram and brightness Hi (i=a, b, c . . . h) in each circle a, b . . . , h is calculated according to: 
         Hi =(pixel value×a histogram value of pixel)/pixel number in circle, wherein the pixel value is in a range of 0-255. 
     An average brightness of all the eight circles a, b . . . , h is defined as the environmental brightness. 
     Referring to  FIG. 3 , a flowchart of a method for the computer  101  providing a brightness adjustment parameter to the liquid crystal display is shown. The method includes the following steps. 
     In Step S 10 , the method is implemented. 
     In Step S 11 , the computer  101  connects and initializes the web camera  100 . 
     In Step S 12 , the web camera  100  captures the environmental image  11  and sends the environmental image  11  to the computer  101 . 
     In Step S 13 , the computer  101  calculates an average brightness in the eight circles a, b . . . , h to obtain the environmental brightness. 
     In Step S 14 , the computer  101  determines whether the environmental brightness exceeds or equals a brightness of the liquid crystal display  10 . If so, Step S 141  is executed. If not, step S 142  is executed. 
     In Step S 141 , the computer  101  calculates an increment of the brightness. 
     In Step S 142 , the computer  101  calculates a decrement of the brightness. 
     In Step S 15 , the computer  101  sends an adjustment parameter to the signal processor  102 . 
     In Step S 16 , it is determined whether operations are complete. If so, Step S 17  is executed. If not, Step S 12  is executed. 
     In Step S 17 , the operation is terminated. 
     Referring to  FIG. 4 , a flowchart of a method of the signal processor  102  processing the brightness adjustment parameters is shown. The method includes the following steps. 
     In Step S 20 , the method is implemented. 
     In Step S 21 , the signal processor  102  is initialized and firmware thereof initialized. 
     In Step S 221 , the signal processor  102  is interrupted to receive a command from the computer  101 . 
     In Step S 23 , the command is interpreted by the signal processor  102 . 
     In Step S 24 , the signal processor  102  ascertains whether the command is an adjustment command. If so, Step S 25  is executed. If not, Step S 26  is executed, in which a look up table in the firmware storing a number of adjustment commands is consulted. The signal processor  102  determines whether the received command matches any of the stored adjustment commands. If so, Step S 25  is executed. If not, Step S 26  is executed. 
     In Step S 25 , backlight control circuit  103  adjusts the brightness of the backlight unit  104 . 
     In Step S 26 , the operation is terminated. 
     The brightness adjustment system of liquid crystal display  10  of the disclosure employs web camera  100  to capture an environmental image  11  in real time. The computer  101  analyzes the received environmental image  11  to obtain the environmental brightness, which it then compares with a brightness of the liquid crystal display  10 , utilizing the result to determine whether signal processor  102  needs adjust brightness of the liquid crystal display  10 . When the environmental brightness is less than the brightness of the liquid crystal display  10 , the brightness of the liquid crystal display  10  is decreased to equal the environmental brightness. When the environmental brightness exceeds the brightness of the liquid crystal display, the brightness of the liquid crystal display is increased to equal the environmental brightness. 
     The web camera  100  is low in cost and requires no complicated control circuitry to obtain the environmental image, thus the cost of the brightness adjustment system is reduced. Furthermore, the environmental brightness is calculated according to the environmental image  11  captured by the web camera  100 , avoiding information errors when environmental brightness is detected by a light sensor. 
     The high frequency parts of the environmental image  11  are filtered off to calculate the environmental brightness, such that computer  101  requires only minimal memory resources when the environmental image  11  is analyzed. 
     Because an average brightness in eight circles a, b . . . , h of the environmental image  11  is defined as the environmental brightness, and the signal processor  102  can direct the backlight control circuit  103  to adjust the brightness of the backlight unit  104  according to an adjustment parameter obtained by comparing the environmental brightness and the brightness of the liquid crystal display  10 , brightness adjustment is accomplished in real time. 
     Alternatively, the web camera  100  can be replaced by other types of image capturing device such as a digital camera. The web camera  100  can also be positioned inside the liquid crystal display  10 . 
     It is to be understood, however, that even though numerous characteristics and advantages of certain inventive embodiments have been set out in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only; and that changes may be made in detail, especially in matters of arrangement of parts within the principles of present invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.