Abstract:
A noisy signal analysis in which a threshold value is set to evaluate the presentation of the display device. The analysis can produce the range of noise level of the image for measuring the distortion block of image caused by the display devices. Furthermore, the apparatus includes a step function generator for producing step functions, a transforming unit for changing threshold value in step functions, and a display for showing the image corresponding to both the high value and low value.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a method and an apparatus of noisy signal analysis, and more especially, to a method and an apparatus of noisy signal analysis applied to the liquid crystal display (LCD). 
     2. Background of the Related Art 
     Currently, since the liquid crystal display (LCD) is booming in IT industry, the monitors of PC have shifted from CRT to the LCD, moreover, the price of LCD is declining very quickly than expected. Although the LCD has a big screen advantage in flat shape, some disadvantages still exist, for example, color temperature, visible angle, contrast, response time and so on. 
     The LCD manufacturing processes include: array, cell, and assembly, all these processes encounter many component and assemblies. At end products, the test and adjustment are needed due to low stability of processes, the test includes gray test, brightness test, then the electrical adjustment for characteristic, sometimes, the screen displays have noisy signal unseen from human eyes, such as flicker. 
     SUMMARY OF THE RELATED ART 
     In order to solve the problems mentioned above, the present invention provides a method of noisy signal analysis applied to a liquid crystal display. The method adjusts a threshold in a step function and obtains a noisy signal range, which may provide the information to tune the gray value and brightness for the LCD. 
     In order to solve the problems mentioned above, the present invention provides an apparatus of noisy signal analysis applied to a liquid crystal display. The apparatus adjusts the gray value and brightness for the LCD to observe the noisy range, and provides test person to measure the LCD quality. 
     Accordingly, one embodiment of the present invention provides a method of noisy signal analysis, including: setting a predetermined step function, which changes each signal in a signal group to a first identical value; changing a threshold value of the predetermined step function to a first threshold value which induces a first step function, wherein the first step function changes a signal in the signal group from becoming the first identical value to becoming a second identical value; and continuing changing the first threshold value of the first step function to a second threshold value which induces a second step function, wherein the second step function changes all signals in the signal group from becoming the first identical value to becoming the second identical value. 
     Additionally, another embodiment of the present invention provides a method of noisy signal analysis, including: setting a first step function having a first threshold value, and the first step function changes each signal in a signal group to a first identical value, wherein the first threshold value changes a specified quantity causing the first signal in the signal group from becoming the first identical value to becoming the second identical; and setting a second step function having a second threshold value, and the second step function changes each signal in a signal group to a second identical value, wherein the second threshold value changes the specified quantity causing the second signal in the signal group from becoming the second identical value to becoming the first identical value; wherein the signal group has noisy distribution between the first threshold value and the second threshold value. 
     Furthermore, another embodiment of the present invention provides an apparatus of noisy signal analysis, including: a step function generator generating a plural step functions, which comprises a first step function having a first threshold value and a second step function having a second threshold value; a transforming unit changing each signal in a signal group to a first identical value according to the first step function and changing every signal of the signal group to the second identical value according to the second step function, wherein the first threshold value changes a specified quantity causing the first signal in the signal group from becoming the first identical value to becoming the second identical, and the second threshold value changes the specified quantity causing the second signal in the signal group from becoming the second identical value to becoming the first identical value; and a display device outputting a range of noisy distribution according to the first threshold value and the second threshold value. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a functional diagram of the apparatus of noisy signal analysis in accordance with an embodiment of the present invention. 
         FIG. 2  is a flow chart of the method of noisy signal analysis in accordance with an embodiment of the present invention. 
         FIG. 3  is another flow chart of the method of noisy signal analysis in accordance with an embodiment of the present invention. 
         FIG. 4  illustrates the original image curve displayed on the LCD. 
         FIG. 5  illustrates the gamma curve of  FIG. 4  in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A method and an apparatus of noisy signal analysis are disclosed. The invention uses a threshold value in a predetermined step function to test signal appearance in an image displayed on a screen of Flat Panel Display (FPD), whereupon, a noisy distribution will be obtained for noisy signal analysis for that FPD. 
       FIG. 1  is a functional diagram of the apparatus of noisy signal analysis in accordance with an embodiment of the present invention. The apparatus of noisy signal analysis includes: a step function generator  12 , a transforming unit  14 , and a display device  16 . The step function generator  12  is for generating a step function with a threshold, a first step level and a second step level according to a gamma correction function. The threshold is variable, and the first step level and the second step level are respectively set to be a first identity value and a second identity value. The transforming unit  14  transforms each signal in a signal group with the step function received from the step function generator  12  and controls the step function generator  12  to change the threshold of the step function iteratively. until a first threshold value and a second threshold value have been obtained. The first threshold value is characterized such that if changed by a predetermined amount, a first signal in the signal group is caused to be transformed to the second identity value, and the second threshold value is characterized such that if changed by the predetermined amount, a second signal in the signal group is caused to be transformed to the first identity value. The display device  16  outputs the range of the signal group according to the first threshold value and the second threshold value. 
     According to an embodiment, the first identity value is greater than the second identity value, and the first threshold value is smaller than the second threshold value. The first threshold value is characterized to cause the first signal in the signal group to be transformed to the second identity value if increased by the predetermined amount, and the second threshold value is characterized to cause the second signal in the signal group to be transformed to the first identity value if decreased by the predetermined amount. 
     According to another embodiment, the first identity value is smaller than the second identity value, and the first threshold value is greater than the second threshold value. The first threshold value is characterized to cause the first signal in the signal group to be transformed to the second identity value if decreased by the predetermined amount, and the second threshold value is characterized to cause the second signal in the signal group to be transformed to the first identity value if increased by the predetermined amount. 
     Additionally, the display device  16  may be a flat panel display (FPD) or a liquid crystal display (LCD). 
       FIG. 2  is a flow chart of the method of noisy signal analysis in accordance with an embodiment of the present invention. The method of noisy signal analysis includes the following steps: setting a step function with a threshold (step S 10 ); changing the threshold of the step function to form a first step function with a first threshold value (step S 11 ); changing the first threshold value of the first step function to form a second step function with a second threshold value (step S 12 ); and obtaining a noisy signal range between the first threshold value and the second threshold value (step S 13 ). In step S 10 , when setting the step function, two step levels are respectively set to be two identity values, a high value (HVAL) and a low value (LVAL) of gray level on an image signal of the display device, and the threshold is set to he a predetermined threshold value, so that the step function transforms each signal in the group of image signals to HVAL. In step S 11 , the threshold of the step function is increased starting from the predetermined threshold value and each signal in the signal group with the step function is transformed iteratively, until the threshold reaches the first threshold value so that the step function transforms a signal in the signal group to LVAL. The first threshold value is the lower bound of the image signal. In step S 12 , the threshold in step Sll is continually increased starting from the first threshold value and each signal in the signal group with the step function is transformed iteratively, until the threshold reaches the second threshold value so that the step function transforms all signals in the signal group to LVAL. The second threshold value is the upper bound of the image block and is greater than the first threshold value. In step S 13 , a noisy signal range, a range between the upper bound and the lower bound of the group of image signals on display device, is obtained. According to an embodiment, the noisy signal analysis method is carried out by a processor. 
     Furthermore, changing the threshold value causing the signal in the image signal to be transformed to HVAL using the flowchart of  FIG. 2  is another method of noisy signal analysis in accordance with an embodiment of the present invention. The method of noisy signal analysis includes the following steps: setting a threshold of a step function to be a first threshold value (step S 10 ); changing the threshold of the step function to form a first step function with a first threshold value (step S 11 ); changing the first threshold value of the first step function to form a second step function with a second threshold value (step S 12 ); and obtaining a noisy signal range between the first threshold value and the second threshold value (step S 13 ). In step S 10 , when setting the step function, two step levels are respectively set to be two identity values, a low value (LVAL) and a high value (HVAL) of gray level on a an image signal of the display device, and the threshold is set to be a predetermined threshold value, so that the step function transforms each signal in the group of image signals to LVAL. In step S 11 , the threshold of the step function is decreased starting from the threshold value and each signal in the signal group with the step function is transformed iteratively, until the threshold reaches the first threshold value so that the step function transforms a signal in the signal group to HVAL. The first threshold value is the upper bound of the image signal. In step S 12 , the threshold in step S 11  is continually decreased starting from the first threshold value and each signal in the signal group with the step function is transformed iteratively, until the threshold reaches the second threshold value so that the step function transforms all signals in the signal group to HVAL. The second threshold value is the lower bound of the image block and is smaller than first threshold value. In step S 13 , a noisy signal range, a range between the upper bound and the lower bound, is obtained for noisy signal correction of the image on display device. According to an embodiment, the noisy signal analysis method is carried out by a processor. 
     Additionally, the display device may be a flat panel display (FPD) or a liquid crystal display (LCD). 
       FIG. 3  is a flow chart of the method of noisy signal analysis in accordance with another embodiment of the present invention. The method of noisy signal analysis includes the following steps: a step, S 20 , of setting a threshold of a function to be a first threshold value, wherein a first step level and a second step level of the step function is preset to be a first identity value and a second identity value, and the first threshold value is set by iteratively changing the threshold of the step function and transforming each signal in a signal group with the step function until the threshold reaches the first threshold value so that the step function transforms each signal in the signal group to the first identity value, and if the first threshold value is changed by a predetermined amount, a first signal in the signal group is caused to be transformed to the second identical; and a step, S 21 , of setting the threshold of the step function to be a second threshold value, wherein the second threshold value is set by iteratively changing the threshold of the step function and transformings each signal in the signal group with the step function until the threshold reaches the second threshold value so that the step function transforms each signal in the signal group to the second identity value, and if the second threshold value is changed by the predetermined amount, a second signal in the signal group is caused to be transformed to the first identical value; wherein the signal group is bounded between the first threshold value and the second threshold value. According to an embodiment, the noisy signal analysis method is carried out by a processor. 
     Accordingly, the first identity value is greater than the second identity value, and the first threshold value is smaller than the second threshold value. The first threshold value is characterized to cause the first signal in the signal group to be transformed to the second identity value if increased by the predetermined amount, and the second threshold value is characterized to cause the second signal in the signal group to be transformed to the first identity value if decreased by the predetermined amount. In another embodiment, the first identical value is smaller than the second identical value, and the first threshold value is greater than the second threshold value. The first threshold value is characterized to cause the first signal in the signal group to be transformed to the second identity value if decreased by the predetermined amount, and the second threshold value is characterized to cause the second signal in the signal group to be transformed to the first identity value if increased by the predetermined amount. 
     Accordingly, the gamma correction function may be used as the step function in the invention.  FIG. 4  illustrates the original image curve  30  displayed on the LCD. In applying the invention, the  FIG. 5  illustrates the gamma curve of  FIG. 4  in accordance with an embodiment of the present invention. Firstly, setting HVAL  41  and LVAL  42 ; secondly, setting a threshold value and increasing threshold valve until lower bound (LB)  43  value displayed in the image block; next, continually increasing the threshold value until all image block display upper bound (UB)  44  value; finally, the range between lower bound value and upper bound value is used for gray noisy signal in display device. 
     Furthermore, the invention is not limited to the gamma correction function, further the Look Up Table (LUT), polynomial function, and piecewise interpolation may be used and make the present invention displays noisy signal effectively for checking the defects of the display device. 
     Although the present invention has been explained in relation to its preferred embodiment, it is to be understood that other modifications and variation can be made without departing the spirit and scope of the invention as hereafter claimed.