Patent Publication Number: US-2003227435-A1

Title: Method for adjusting and detecting brightness of liquid crystal displays

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001] This Application claims priority to Taiwan Patent Application No. 091112193 entitled “METHOD FOR ADJUSTING AND DETECTING BRIGHTNESS OF LIQUID CRYSTAL DISPLAYS”, filed Jun. 6, 2002.  
       FIELD OF INVENTION  
       [0002] This present invention relates to a liquid crystal display, and more particularly, to a liquid crystal display allowing detection and adjustment of brightness.  
       BACKGROUND OF THE INVENTION  
       [0003] In general, the liquid crystal display includes a backlight module behind the display panel for generating backlight illuminating the display panel from behind. The light passes through the pixels of display panel selectively to produce the visible images on the display panel. The liquid crystal display of this type has high CONTRAST allowing the users to perceive the displayed images even in the dark environment.  
       [0004] Typically, the sources generating backlight, e.g. cold cathode fluorescent tube (CCFL), LED, EL, have features of high BRIGHTNESS and use-perseverance. With respect to the locations of backlight modules, the backlight module may be classified into straight-below and side-edge types.  
       [0005] In earlier ages, the liquid crystal displays were applied in digital products, e.g. calculators and watches. In recent years, the sizes of the liquid crystal display grows bigger allowing their applications in areas of desk-top monitors and notebook computers.  
       [0006] It is found that bulbs for generating the backlight age and the brightness of bulb deteriorates as times go by. Since the deterioration of brightness might not be noticed by the users, the visual capabilities of the users may have been damaged for a period of time before the damage comes above the surface. Therefore, it is desirable to have a method for notifying the users as the brightness of backlight lowers and for making suitable adjustment.  
       SUMMARY OF THE INVENTION  
       [0007] One aspect of the present invention provides a method for adjusting brightness of backlight of the liquid crystal display.  
       [0008] Another aspect of the present invention provides a method for detecting brightness of backlight of the liquid crystal display.  
       [0009] In the present invention, the liquid crystal display includes the backlight, the luminance sensor, the A/D converter, the microprocessor and the memory. The adjustment method includes setting a target brightness value; detecting brightness of the backlight via the luminance sensor and denoting as X; the A/D converter converting signal of X into signal of Y; the microprocessor comparing signal of Y with the target brightness value and generating a corresponding result; if signal of Y is not equal to the target brightness value, the microprocessor determining an adjustment value; and adjusting brightness of the backlight based on the adjustment value.  
       [0010] The detection method includes adjusting the backlight to a maximum brightness; detecting maximum brightness of the backlight and denoting as analog signal of X; converting the analog signal of X into a digital signal of Y; comparing digital signal of Y with the predetermined value and outputting a corresponding signal.  
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0011]FIG. 1 is a functional block of the preferred embodiment;  
     [0012]FIG. 2 is a flow chart of the first embodiment; and  
     [0013]FIG. 3 is a flow chart of the second embodiment. 
    
    
     DETAILED DESCRIPTION  
     [0014] As shown in FIG. 1, according to the present invention, the liquid crystal display  10  includes a backlight  12 , a luminance sensor  14 , an A/D converter  16 , a microprocessor  18  and a memory  20 . The luminance sensor  14  is configured to detect the brightness of backlight  12 . The A/D converter  16  is configured to transform the analog signal into digital signal. The microprocessor  18  is configured to compare the result of detection and a target brightness value and send commands to control the brightness of backlight  12 . The memory  20  is configured to store predetermined values that include the target brightness value.  
     [0015] As shown in FIG. 2, the first embodiment may be employed to adjust the brightness of liquid crystal display. In step  501 , the embodiment first sets a target brightness value and stores this value into the memory  20 . In succession, in step  503 , the embodiment turns on the backlight  12 , uses the luminance sensor  14  to determine the brightness of backlight  12 , and denotes the brightness as X which is an analog signal. In step  505 , the signal X is transformed into digital signal Y by the A/D converter  16 .  
     [0016] In step  507 , the microprocessor  18  compares Y with the target brightness value and generates a corresponding result. In step  509 , the microprocessor  18  determines if Y is not equal to the target brightness value. If Y is not equal to the target brightness value, in step  511 , the microprocessor  18  determines an adjustment value. In step  513 , the microprocessor  18  adjusts brightness of the backlight  12  based on the adjustment value. Afterwards, repeat step  503 ,  505 ,  507  and  509 .  
     [0017] In step  509 , if Y is substantially equal to the target brightness value, then in step  515 , wrap up the adjustment procedure and output the result. The result outputted may be in form of image type that includes graphics or text on a monitor. Or, alternatively, the result is presented in the form of an audio type or, alternatively, in the form of an audio and/or image type.  
     [0018] After the users use the liquid crystal display for a period of time, the embodiment as shown in FIG. 3 can be used to determine whether the replacement of backlight  12  is needed.  
     [0019] As shown in FIG. 3, responsive to user&#39;s instruction, in step  601 , the microprocessor  18  sends a signal to adjust the backlight  12  to a maximum brightness. Afterwards, in step  603 , the luminance sensor  14  detects the maximum brightness of the backlight and denotes it as analog signal of X. In step  605 , by the A/D converter  16 , the signal X is transformed into digital signal of Y. In step  607 , the microprocessor  18  compares the digital signal of Y with the predetermined value and outputting a corresponding signal.  
     [0020] In step  611 , the corresponding signal from the microprocessor  18  denotes that no replacement of the backlight  12  is required if Y is larger than or substantially equal to the predetermined value stored in memory  20  and wrap up the procedure. On the contrary, in step  613 , the corresponding signal from the microprocessor  18  denotes that replacement of the backlight is required if Y is smaller than the predetermined value and wrap up the procedure.  
     [0021] And the corresponding signal may be in form of image type that includes graphics or text on a monitor. Or, alternatively, the result is presented in the form of an audio type or, alternatively, in the form of an audio and/or image type.