This application claims priority from Taiwan application Ser. No. 092132464, entitled “Method for Eliminating Flickers of Liquid Crystal Display”, filed on Nov. 19, 2003 by Tean-Sen Jen, Ming-Tien Lin, Deuk-Su Lee and Ta-Wei Tseng, which application is incorporated herein in the entirety by this reference thereto.
1. Field of the Invention
The present invention relates to a method for eliminating flickers of a liquid crystal display (LCD), and more particularly to a method for the elimination of flickers by adjusting the areas of storage capacitors.
2. Description of the Related Art
Three-level capacitive coupling driving is a driving method often applied to a liquid crystal display for the time being. According to the driving method, there are three different levels for the scanning signals 17 working on the scanning lines 11, namely Vgh, Vgl and Vgc, as shown in
In order to measure the flicker levels of the liquid crystal display 20, positions of a plurality of pixels P1-P49 arranged in a grid-point matrix are shown on the panel, as shown in
In general, one may adjust the level Vgc for a liquid crystal display by turning the knob of a variable resistor, and solve the flicker problem of the screen by varying the level Vgc. Unfortunately, it is impossible to solve the flicker problem of the screen by means of one single level Vgc, as verified with a test conducted on the three curves 41, 42 and 43 shown in
In short, conventional technology fails to address the flicker problem of the screen of a liquid crystal display using one single adjustable level Vgc, thus there is great demand for a method intended to solve the flicker problem of a liquid crystal display.
An objective of the present invention is to provide a method for eliminating flickers that may otherwise appear on the screen of a liquid crystal display, wherein the method involves adjusting the compensation area or the capacitance of a storage capacitor so as to eliminate flickers that may otherwise appear on the screen because of an RC delay.
The second objective of the present invention is to provide a method for fuzzing the difference between the hue gradation of different portions, wherein a transition portion is interposed between the respective portions having storage capacitors whose compensation areas differ, so as to gradually blur the displayed hue discontinuation caused by a sudden variation in the storage capacitor area.
The present invention discloses a method for eliminating flickers of a liquid crystal display (LCD). First, the screen is divided into a compensation portion, a compensation transition portion and a non-compensation portion in a sequence arranged along the scanning line. Then storage capacitor areas of the pixels in the non-compensation portion are made equal, whereas the difference between the storage capacitor area of the pixel in the compensation portion and that in the non-compensation portion is set to one constant basic compensation area. Afterward, the average of the storage capacitor areas of the pixels on each data line in the compensation transition portion progressively varies along the scanning line, where the average is greater than or equal to any of the storage capacitor areas of the pixels in the non-compensation portion. The direction of the scanning line is designated as either the direction in which scanning signals are transmitted or the direction opposite thereto.
The invention will be described according to the appended drawings in which:
In order to address the drawback of conventional technology, that is, as it is impossible to eliminate flickers from a screen using one single adjustable level Vgc, the present invention is designed in such a way that an adjustment is made in the storage capacitor areas of the pixels on the left portion in the hope of equalizing the transverse axis reading to which the minimum readings on the lengthwise axes for the curves 41, 42 and 43 in
where Vgl denotes the low level at which a thin film transistor is switched off using three-level driving signals, and Vgc(left) denotes the transverse axis reading to which the minimum reading on the lengthwise axis for the curve 41 in
Vgc(center)−Vgc(left)≈0.2V
where Cst denotes the storage capacitance of a conventional liquid crystal display, and the storage capacitance of the pixel of an conventional liquid crystal display is set to a constant value. The storage capacitance is obtained from the following equation:
wherein A is the area of the storage capacitor, ε is a permittivity, and d is the distance between the two terminals of the storage capacitor.
Because ε and d are constants for a general liquid crystal display, Cst is in direct proportion to A. Hereinafter, the storage capacitance Cst is directly represented by the storage capacitor area A rather than ε and d. But, the scope of the present invention is not limited by the simplified relation.
Given Cst=2045 μm2, the aforesaid Formula 1 yields the equation ΔCst=100 μm2 by substitution. However, it is feasible to set the basic compensation area ΔCst to 105 μm2 for the sake of an uncomplicated circuit layout. Hence, the storage capacitor area of the pixels on the left portion is Cst+ΔCst=2150 μm2.
Although the flicker problem of a screen is solved by one single adjustable level Vgc after adding a basic compensation area of 105 μm2 to the storage capacitor area of the pixel on the left portion, a chromatic aberration boundary obviously visible to the naked eye appears between the left and the center portions because of the difference between the respective storage capacitor areas of the pixels that adjoin the boundary between the left and the center portion, where the display has the same hue configuration.
It is also feasible to have the compensation area disposed on the right portion, increase the storage capacitor area of the pixel therein by a basic compensation area of 105 μm , and have the non-compensation area disposed on the left portion, depending on the manufacturing process or design of the liquid crystal display circuit. An alternative arrangement is that the compensation area is still disposed on the left portion, but the storage capacitor area of the pixel therein is added by a basic compensation area carrying a negative sign. Similarly, chromatic aberration is also found in the boundary between a portion where the storage capacitor areas are compensated for and another portion where the storage capacitor areas are not compensated for.
In order to solve the aforesaid problem of the chromatic aberration boundary, a method for fuzzing the discontinuous hue gradation across a boundary between two different portions is put forth in accordance with the present invention. The method for fuzzing the hue gradation involves further dividing the left portion of the liquid crystal display 50 into a compensation portion I and a compensation transition portion II, as shown in
Cst1≧Cst2(n)≧Cst3;
Cst1=Cst3+ΔCst; and
Cst2(n+1)≦Cst2(n)
In short, the steps taken to implement the present invention are summarized as follows: the screen of the liquid crystal display is divided into a compensation portion, a compensation transition portion and a non-compensation portion in a sequence arranged along the scanning line, as shown in the step 61 of
There are at least two embodiments for the method for fuzzing hue gradation in accordance with the present invention, namely processing the compensation transition portion using linear gradation and processing the compensation transition portion using random gradation. Detailed descriptions of the two embodiments are as follows:
Linear Gradation
As shown in
If the basic compensation area ΔCst for the storage capacitors in the compensation area I is set to 105 μm2 and the fundamental area for the storage capacitors in the non-compensation portion III is set to 2,045 μm2, the storage capacitor area of the pixel on the 385th data line in the compensation transition area II is as follows:
Cst2(385)=2,045 μm2+105 μm2
As shown by the present embodiment, the storage capacitor area varies with an equal difference, 0.5 μm2, along the scanning line. Related expressions are as follows:
Cst2(386)=2,045 μm2+104.5 μm2;
Cst 2(387)=2,045 μm2+104 μm2;
. . . ; and
Cst2(594)=2,045 μm2
Since the difference between the storage capacitor areas of the respective pixels of two contiguous data lines 52 is always 0.5 μm2, no chromatic aberration boundary visible to the naked eye appears. However, the storage capacitors Cst2(n) on every data line 52 in the compensation transition portion are all equal in the entire compensation area, and thus conspicuous variations in hue appearing along the scanning line 53 is likely to occur. For this reason, the alternative method, that is, random gradation, is intended to address the drawback of the aforesaid method.
Random Gradation
As shown in
Cst1=2,045 μm2+105 μm2;
Cst2(n,m)=2,045 μm2+ΔCst2(n,m|105;52)μm2;
Cst3(i,m)=2,045 μm2+ΔCst3(i,m|52;0)μm2;
Cst4=2045 μm2;
where n=385-504; i=505-624; m denotes the numbers given to the scanning lines 73.
ΔCst2(n,m|105;52) denotes the compensation area for the pixel disposed at the intersection of the nth data line 72 and the mth scanning line 73. The compensation area for the pixels is randomly set to either 105 μm2 or 52 μm2 to satisfy the following expression:
In other words, the average compensation area for the storage capacitors of the pixels on every data line in the first compensation transition portion II is progressively decreased along the scanning line (that is, the direction in which scanning signals working on the scanning lines are transmitted). The equal difference between the average storage capacitor areas of the pixels on two contiguous data lines 72 remains as 0.5 μm2 approximately.
Similarly, ΔCst3(i,m|52;0) denotes the compensation area for the storage capacitors of the pixels disposed at the intersection of the ith data line 72 and the mth scanning line 73. The compensation area for the storage capacitors of the pixels is randomly set to either 52 μm2 or 0 μm2 to satisfy the following expression:
In other words, the average compensation area for the storage capacitors of the pixels on every data line in the second compensation transition portion III is progressively decreased along the scanning line. The equal difference between the average storage capacitor areas of the pixels on two contiguous data lines 72 remains 0.5 μm2 approximately.
As regards another embodiment, the equal difference between the average storage capacitor areas of the pixels on two contiguous data lines 72 remains as 0.5 μm2 approximately, but the storage capacitor areas of the pixels on each data line 72 remains to be in pseudo-random uniform distribution.
In the first compensation transition portion, there is a white dot indicating that the storage capacitors of the pixels have a compensation area of 105 μm2 and a black dot indicating a compensation area of 52 μm2. In the second compensation transition portion, there is a white dot indicating that the storage capacitors of the pixels have a compensation area of 52 μm2 and a black dot indicating a compensation area of 0 μm2.
As mentioned earlier, the present invention can also meet the demand for liquid crystal displays based on various design principles. For instance, a screen is divided into a compensation portion IV, a first compensation transition portion III, a second compensation transition portion II and a non-compensation portion I, in a sequence arranged along the scanning line 93 and heading toward the left, as shown in
C′st4=2,045 μm2+105 μm2;
C′st3(i, m)=2,045 μm2+ΔCst2(i,m|105;52)μm2;
C′st2(n, m)=2,045 μm2+ΔCst3(n,m|52;0)μm2;
C′st1=2,0451 μm2;
where n and i respectively denote the numbers given to the data lines 92; m denotes the numbers given to the scanning lines 93.
Furthermore, ΔCst3(i,m|105;52) denotes the compensation area for the pixels disposed at the intersection of the ith data line 72 and the mth scanning line 73. The compensation area for the pixels is randomly set to either 105 μm2 or 52 μm2 to satisfy the following expression:
In other words, the average compensation area for the storage capacitors of the pixels on every data line in the first compensation transition portion III is progressively decreased along the scanning line (that is, in the direction opposite to the direction in which scanning signals working on the scanning lines are transmitted). The equal difference between the average storage capacitor areas of the pixels on two contiguous data lines 92 remains as 0.51 μm2 approximately.
Similarly, ΔCst2(n,m|52;0) denotes the compensation area for the storage capacitor of the pixel disposed at the intersection of the nth data line 92 and the mth scanning line 93. The compensation area for the storage capacitors of the pixels is randomly set to either 52 μm2 or 0 μm2 to satisfy the following expression:
In other words, the average compensation area for the storage capacitors of the pixels on every data line in the second compensation transition portion II is progressively decreased along the scanning line. The equal difference between the average storage capacitor areas of the pixels on two contiguous data lines 92 remains as 0.5 μm2 approximately.
As shown by the present embodiment, the equal difference between the average storage capacitor areas of the pixels on two contiguous data lines 92 remains as 0.5 μm2 approximately, but the storage capacitor areas of the pixels on each data line 92 remains to be in pseudo-random uniform distribution.
In the first compensation transition portion, there is a white dot indicating that the storage capacitors of the pixels have a compensation area of 105 μm2 and a black dot indicating a compensation area of 52 μm2. In the second compensation transition portion, there is a white dot indicating that the storage capacitors of the pixels have a compensation area of 52 μm2 and a black dot indicating a compensation area of 0 μm2.
The above-described embodiments of the present invention are intended to be illustrative only. Numerous alternative embodiments may be is devised by persons skilled in the art without departing from the scope of the following claims.
Number | Date | Country | Kind |
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92132464 A | Nov 2003 | TW | national |
Number | Name | Date | Kind |
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6028650 | Kuroha et al. | Feb 2000 | A |
6738106 | Tanahara et al. | May 2004 | B1 |
6982775 | Lee et al. | Jan 2006 | B2 |
Number | Date | Country | |
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20050264517 A1 | Dec 2005 | US |