JP2010098631A - Liquid crystal display and whiteness degree adjustment method of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display and whiteness degree adjustment method thereof which can adjust a whiteness degree by electrically correcting an input image signal. <P>SOLUTION: The liquid crystal display includes: a determination circuit 120 for determining whether R, G, B signals of an image signal are coincident when the image signal containing the R, G, B signals is input; a correction processing section 130 for correcting at least one of the R, G, B signals to adjust the whiteness degree when the determination circuit 120 determines that all of the R, G, B signals are coincident; and a drive circuit 40 for driving a liquid crystal display 50 based on the image signal output from the correction processing section 130. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for adjusting whiteness in a liquid crystal display device.

  Liquid crystals are used as color displays for televisions and personal computers. A liquid crystal display device is usually configured to include a backlight, a liquid crystal panel, a color filter, and the like. However, variations in chromaticity of LEDs used for the backlight, and R (red), G (green), The displayed whiteness varies depending on the transmission characteristics of B (blue). Such whiteness adjustment is known as white balance adjustment or white point adjustment.

  Patent Document 1 discloses a white point adjusting device in which the color temperature of the white point with the highest gradation or the highest luminance can be set in the RGB color system, and the color temperature at each gradation is substantially constant. In this Patent Document 1, a first table for determining an offset amount from the highest gradation in one color signal for each color temperature and setting a white point, and an intermediate gradation for each color temperature set by the first table. A second table for setting an offset amount for converging the white point in the white point, and a white point adjustment unit for adding an offset amount set by the first table and the second table to the input video signal.

JP 2001-119717 A

  When the luminances of the R, G, and B signals are equal or when the gradation levels are the same, white is displayed, but this whiteness is different for each liquid crystal display device, while the whiteness is specified by the customer. There are many. For example, Company A requests blue-based white (chromaticity x: 0.300, y: 0.300), and Company B requests yellow-based white (chromaticity x: 0.330, y: 0.330). As the background of such demand, with the increase in the number of liquid crystal display devices installed per automobile in recent years, the difference in white (whiteness) between the liquid crystal display devices becomes a major design problem. For this reason, there is a strong demand from customers for the same chromaticity.

  For adjusting the whiteness of a conventional liquid crystal display device, there is a method of changing the chromaticity or transmission characteristics of a color filter. However, since this method has to change the color filter for each liquid crystal display device, it is not practical for reasons such as loss of setup due to switching of the color filter in the manufacturing process and increase in material cost of the color filter. If this method is used, there will be significant cost increases and quantity compensation problems.

  Another method is to change the chromaticity of the LED used in the backlight. The LEDs are usually ranked according to chromaticity, and if the manufactured LEDs of all chromaticities are not used, the price of the LED increases. For this reason, a method of changing the chromaticity of the LED for each liquid crystal display device is also not realistic.

  Further, there is a method of adjusting whiteness by correcting RGB γ curves in a driving circuit for driving liquid crystal. When this method is used, the slope of the γ curve is distorted, so even if the whiteness can be adjusted desirably, non-white colors and RGB single colors are distorted, the color reproduction range is shifted, and natural color reproduction is achieved. It has the problem that it cannot be done.

  The present invention solves such a conventional problem, and provides a liquid crystal display device for adjusting whiteness by electrically correcting an input image signal and a whiteness adjustment method thereof. Objective.

  The liquid crystal display device according to the present invention includes a determination unit that determines whether or not the R, G, and B signals of the image signal match when an image signal including R, G, and B signals is input; Correcting means for adjusting at least one of the R, G, and B signals to adjust the whiteness when the R, G, and B signals are all determined to match, and the image signal corrected by the correcting means And a driving means for driving the liquid crystal display.

  Preferably, the correction means corrects at least one of the R, G, and B signals according to a predetermined coefficient. The correction unit may correct at least one of the R, G, and B signals according to the gradation of the R, G, and B signals. The correction unit may include a table that defines a change in coefficient according to the gradation, and may correct at least one of the R, G, and B signals with reference to the table. When the R, G, and B signals do not match, the correcting means outputs the input image signal without correcting it. The liquid crystal display includes a liquid crystal and R, G, and B color filters that transmit light from the liquid crystal, and the liquid crystal is driven by an image signal from the driving unit. Preferably, the liquid crystal display is disposed in a vehicle interior, and the correction unit adjusts the whiteness of the image signal so as to match a color tone in the vehicle interior.

  The whiteness adjustment method according to the present invention is performed in a liquid crystal display device that includes liquid crystal and R, G, and B color filters that transmit light from the liquid crystal, and that drives the liquid crystal based on an image signal, The step of inputting an image signal including R, G, and B signals, the step of determining whether or not the R, G, and B signals of the input image signals match, and the R, G, and B signals all match When determined, the method includes a step of correcting at least one of the R, G, and B signals to adjust the whiteness, and a step of driving the liquid crystal based on the corrected image signal.

  According to the present invention, when the R, G, and B signals coincide with each other, at least one of the R, G, and B signals is corrected. Therefore, the whiteness can be adjusted by electrical correction. There is no need to change optical members such as a color filter of a liquid crystal display and a light source of a backlight as in the prior art. For this reason, since it becomes possible to provide a standard liquid crystal display, the whiteness can be adjusted at low cost, and the demand from each customer can be met. Furthermore, in the case of an in-vehicle liquid crystal display, it is possible to perform a white color scheme that matches the color tone of the passenger compartment.

  The best mode for carrying out the present invention will be described in detail with reference to the drawings. FIG. 1A is a diagram for explaining a whiteness adjustment method for a liquid crystal display device according to the present invention. In the whiteness adjustment method according to the present invention, when an image signal including R, G, and B signals is input, and R = G = B, a white color image signal, At least one is corrected, and an image signal having an arbitrary RGB gradation color and adjusted in whiteness is output to a liquid crystal display (LCD) in real time. If the image signal is R ≠ G or G ≠ B, the R, G, and B signals are not corrected at all, and the image signal is output as it is. On the other hand, as shown in FIG. 1B, the whiteness adjustment method by γ correction corrects an image signal when the input image signal is white or non-white. For this reason, distortion occurs in colors other than white-based colors and RGB single colors, but such distortion is not generated in the present invention.

FIG. 2 is a block diagram showing the configuration of the liquid crystal display device according to the embodiment of the present invention.
The liquid crystal display device according to this embodiment includes an image signal input unit 20 that inputs an image signal from a computer device, a television, and the like, a signal processing unit 30 that adjusts the whiteness of the input image signal, and the signal processing unit 30. Drive circuit 40 for driving the liquid crystal display based on an output signal from the liquid crystal display, and a liquid crystal display 50 in which liquid crystals are arranged in a two-dimensional matrix.

  FIG. 3 shows the internal configuration of the signal processing unit. The signal processing unit 30 includes an analog / digital conversion unit 100, a digital RGB conversion unit 110, a determination circuit 120 that determines whether the image signal is a white color, and a correction that performs correction processing of the RGB signal according to the determination result. And a processing unit 130.

  When the input image signal is an analog signal, the analog / digital conversion unit 100 converts the image signal into a digital signal and outputs the digital signal to the digital RGB conversion unit 110. When the input image signal is a digital signal, the image signal is directly input to the digital RGB conversion unit 110.

  The digital RGB converter 110 converts the input digital image signal into R, G, and B signals. The image signal is composed of the number of bits corresponding to the gradation level that can be displayed on the liquid crystal display 50. For example, when 256-color display is performed, the image signal is composed of 24-bit data, and the R, G, and B signals are each composed of 8-bit data.

  The determination circuit 120 receives R, G, and B signals from the RGB conversion unit 120. When each of R, G, and B matches (R = G = B), it determines that the image signal is a white color, and matches If not (R ≠ G ≠ B), it is determined that the image signal is other than a white color. When each of the R, G, and B signals is composed of 8-bit data, the highest gradation or the highest luminance is represented by “11111111”, and the lowest gradation or the lowest luminance is represented by “00000000”. On the contrary, the highest gradation may be represented by “00000000” and the lowest gradation may be represented by “11111111”. As shown in FIG. 5, the combinations in which the 8-bit data of the R, G, and B signals are equal are the number of gradations, and there are 256 combinations in total. When the determination circuit 120 determines that the R, G, and B signals match, the determination circuit 120 supplies the determination result to the correction processing unit 130.

  When it is determined that the image signal is a white color, the correction processing unit 130 performs at least one correction of the R, G, and B signals so that the whiteness of the image signal is adjusted. When it is determined that the image signal is other than white, the digital RGB signal is output as it is without correcting the image signal.

  FIG. 4 is a diagram illustrating an internal configuration of the drive circuit. The drive circuit 40 includes a timing controller 140, a column driver 150, and a row driver 160. The timing controller 140 receives the digital RGB signal output from the signal processing unit 30 and outputs a timing signal corresponding to the digital RGB signal to the column driver 150 and the row driver 160. The column driver 150 and the row driver 160 drive the liquid crystal display so that the liquid crystal display is scanned line by line according to the timing signal.

  As shown in FIG. 7, the liquid crystal display 50 includes, on a backlight 52, an opposing transparent electrode 54, a liquid crystal 56 sandwiched between the opposing transparent electrodes 54, and R, G, and B color filters 58. The liquid crystal 54 is selected by the column driver 150 and the row driver 160, and an electric field corresponding to an image signal is applied to the selected liquid crystal 54, and the liquid crystal 54 is modulated. The light from the liquid crystal 54 in which the amount of light transmitted from the backlight is varied according to the degree of modulation of the liquid crystal further passes through the corresponding R, G, and B filters. The resolution of the liquid crystal display 50 is appropriately selected from VGA (640 × 480), SVGA (800 × 600), XGA (1,024 × 768), SXGA (1,280 × 1,024), and the like.

  Next, details of the correction processing unit shown in FIG. 3 will be described. When the gradation levels or luminances of the R, G, and B signals match, the display by the image signal becomes a white color. When the image signal is a white color, the correction processing unit 130 changes at least one gradation level of the R, G, and B signals to an arbitrary gradation level so as to conform to the required whiteness.

In the first correction method of this embodiment, correction is performed such that the gradation levels of the R, G, and B signals decrease or increase at a constant rate. Preferably, coefficients K _R , K _G and K _B for changing the gradation level are set, and the gradation levels of the R, G and B signals are multiplied by the coefficient. When the corrected image signal is Ra, Ga, and Ba, correction is performed such that Ra = K _R · R, Ga = K _G · G, and Ba = K _B · B. That is, when the gradation level is decreased, the coefficient is set smaller than “1”, and when the gradation level is increased, the coefficient is set larger than “1”. When the gradation levels of the R, G, and B signals are not changed, the coefficient is set to “1”. Here, in order to make the explanation easy to understand, the coefficients are multiplied in an analog manner. However, the correction processing unit 130 converts the bit data of the R, G, and B signals so as to be equal to the multiplication of the coefficients. change. For example, G signal "11111111" is changed to Ga signal "11111101", this change is equal to the multiplication of the coefficient K _G.

Further, the correction processing unit 130 does not necessarily need to set all the coefficients K _R , K _G , and K _B. When any of the R, G, and B signals is not changed, it is not necessary to set a coefficient for the signal. Further, the correction processing unit 130 can set the coefficient in advance, but it is also possible to change the coefficient or set it later by using a programmable memory, for example. Thereby, it is possible to easily adjust the whiteness of each liquid crystal display device.

  Next, the second correction method of this embodiment will be described. In the first correction method, the gradation level is uniformly reduced or increased regardless of the gradation levels of the R, G, and B signals. In the second correction method, the coefficient is varied according to the gradation level. . If the gradation levels of the R, G, and B signals are different, the white gradation display is also different, and it may be desirable to adjust the whiteness accordingly. For example, when the R, G, and B gradation levels are the lowest, the display is black. In such a case, even if the gradation levels of the R, G, and B signals are corrected, the display is affected. There is no need to make corrections. Similarly, when the gradation levels of the R, G, and B signals are smaller than a certain value, the change ratio of the gradation levels of the R, G, and B signals is decreased, and when the gradation level is larger than the certain value, the change is made. You may make it enlarge a ratio.

In the second correction method, as shown in FIG. 6A, the coefficients K _R , K _G , and K _B can be varied linearly according to the gradation level. In addition, as shown in FIG. 6B, the R, G, and B signals may be corrected when the gradation level becomes a certain value or more. In this case, the coefficients K _R , K _G , and K _B can be set to “1” up to a certain value, and the coefficient can be changed at a gradation level that is a certain value or more. Furthermore, as shown in FIG. 6C, the coefficients K _R , K _G , and K _B may change stepwise in addition to the linear change. In the case where such changes in the coefficients K _R , K _G , and K _B can be expressed by mathematical formulas, the correction processing unit 130 holds such formulas, and changes the gradation levels of the R, G, and B signals. Then, the coefficient is determined from the detected gradation level. In addition to the mathematical expression, the correction processing unit 130 stores a table defining the relationship between the gradation level and the coefficient in the memory, and the coefficient corresponding to the detected gradation level of the R, G, and B signals. May be selected from the table.

  FIG. 7 is a diagram for explaining the operation of the liquid crystal display device. As described above, the liquid crystal display 50 includes the backlight 52, the transparent electrode 54, the liquid crystal 56, R, G, and B color filters 58. As shown in FIG. 7A, when the R, G, and B signals have the highest gradation, the transmission amount of R, G, and B light that passes through the R, G, and B filters is 100%. Accordingly, the pixels of the liquid crystal display display white with the highest luminance.

  When the whiteness adjustment is performed using the correction method according to this embodiment, the transmission state shown in FIG. 7A is corrected to the transmission state shown in FIG. In the example of FIG. 7B, the gradation level of the R signal is reduced to 98%, the gradation level of the G signal is changed to 100%, and the gradation level of the B signal is changed to 93%. Yes. As a result, the amount of R light transmitted from the R filter is 98%, the amount of G light transmitted from the G filter is 100%, and the amount of B light transmitted from the B filter is 93%. Thus, the pixels of the liquid crystal display are adjusted to display yellowish white. Thus, in this embodiment, the whiteness can be adjusted by correcting the R, G, and B signals to the enemy without adjusting the color filter and the backlight.

  FIG. 8A is a chromaticity diagram when the γ correction method is used, P indicates a color reproduction region before correction, and Q indicates a color reproduction region after γ correction. N indicates a color reproduction region by a CRT display as a reference example. In the γ correction method, the white display is shifted from W to W1 by changing the color reproduction region. On the other hand, FIG. 8B is a chromaticity diagram when the whiteness adjustment of the present embodiment is performed. P indicates a color reproduction region before correction, and Q indicates a color reproduction region after correction. As is apparent from the figure, in this embodiment, the color reproduction region is not changed before and after the correction, and the white display can be shifted from W to W1. Therefore, in this embodiment, unlike the γ correction method, the distortion of RGB single colors other than the white color is not caused.

  Next, another configuration example of the signal processing unit of the present embodiment is shown in FIG. The signal processing unit 30A includes an R register 130, a G register 132, and a B register 134 that temporarily store the R, G, and B signals output from the digital RGB conversion unit 110, and the R, G, and B signals stored in these registers. A determination circuit 120 that determines whether or not they match, a correction processing unit 130 that corrects at least one of the R, G, and B signals when determined to match, and multiplexers (MUX) 140, 142, and 144, Have

  The determination circuit 120 outputs a determination signal S of logic H when it is determined that the R, G, and B signals match, and a logic L determination signal S when it is determined that they do not match, to the correction processing unit 130 and the multiplexers 140, 142, and 144, respectively. The multiplexer 140 has an input unit that inputs the R signal of the R register 130 and the Ra signal output from the correction processing unit 130, and an output unit that outputs an input selected based on the determination signal S. Similarly, the multiplexer 142 receives the G signal and the Ga signal from the G register 132 and outputs a signal selected based on the determination signal S, and the multiplexer 144 receives the B signal and the Ba signal from the B register 134. A signal selected based on the determination signal S is output.

  In response to the determination signal S from the determination circuit 120, the correction processing unit 130 corrects the R, G, and B signals according to the correction method when the image signal is a white color, and the multiplexers 140, 142, and 144 are The corrected signals Ra, Ga, Ba are output to the drive circuit 40. On the other hand, when the image signal is other than a white color, the correction processing unit 130 does not perform correction processing of the R, G, and B signals. The multiplexers 140, 142, 144 output the R, G, B signals from the R register 130, the G register 132, and the B register 134 to the drive circuit 40 according to the determination signal S.

  The preferred embodiment of the present invention has been described in detail above, but the present invention is not limited to the specific embodiment, and various modifications can be made within the scope of the present invention described in the claims. Deformation / change is possible.

FIG. 1A is a diagram for explaining a whiteness adjustment method of the present invention, and FIG. 1B is a diagram for explaining a whiteness adjustment method by γ correction. It is a block diagram which shows the structure of the liquid crystal display device based on the Example of this invention. It is a figure which shows the structure of the correction | amendment process part shown in FIG. FIG. 3 is a diagram illustrating a configuration of a drive circuit illustrated in FIG. 2. It is a figure which shows the example in which R, G, and B signal correspond. It is a figure explaining the example of a setting of the coefficient of a correction process part. It is a figure explaining operation | movement of the liquid crystal display device by a present Example. FIG. 8A is a chromaticity diagram obtained by the γ correction method, and FIG. 8B is a chromaticity diagram obtained when whiteness adjustment is performed according to this embodiment. It is a figure which shows the other structural example of the signal processing part of a present Example.

Explanation of symbols

10: liquid crystal display device 20: image signal input unit 30: signal processing unit 40: drive circuit 50: liquid crystal display 100: analog / digital conversion unit 110: digital RGB conversion unit 120: determination circuit 130: correction processing unit

Claims (12)

A determination unit that determines whether or not the R, G, and B signals of the image signal match when an image signal that includes the R, G, and B signals is input;
Correction means for correcting at least one of the R, G, and B signals to adjust whiteness when the determination means determines that the R, G, and B signals all match;
Driving means for driving the liquid crystal display based on the image signal corrected by the correcting means;
A liquid crystal display device. The liquid crystal display device according to claim 1, wherein the correction unit corrects at least one of the R, G, and B signals according to a predetermined coefficient. 3. The liquid crystal display device according to claim 1, wherein the correction unit corrects at least one of the R, G, and B signals according to the gradation of the R, G, and B signals. 4. The liquid crystal display according to claim 2, wherein the correction unit includes a table that defines a change in coefficient according to a gradation, and corrects at least one of the R, G, and B signals with reference to the table. apparatus. 2. The liquid crystal display device according to claim 1, wherein when it is determined that the R, G, and B signals do not match, the correction unit outputs the input image signal without correction. The liquid crystal display according to claim 1, wherein the liquid crystal display includes a liquid crystal and R, G, and B color filters that transmit light from the liquid crystal, and the liquid crystal is driven by an image signal from the driving unit. apparatus. The liquid crystal display device according to claim 1, wherein the liquid crystal display is disposed in a vehicle interior, and the correction unit adjusts the whiteness of the image signal so as to match a color tone in the vehicle interior. A method for adjusting the whiteness of a liquid crystal display device including a liquid crystal and R, G, B color filters that transmit light from the liquid crystal and driving the liquid crystal based on an image signal,
Inputting an image signal including R, G, B signals;
Determining whether the R, G, B signals of the input image signal match;
Correcting at least one of the R, G, and B signals to adjust the whiteness when it is determined that the R, G, and B signals all match;
Driving the liquid crystal based on the corrected image signal;
A method for adjusting whiteness. 9. The whiteness adjustment method according to claim 8, wherein the correcting step corrects at least one of R, G, and B signals according to a predetermined coefficient. The whiteness adjustment method according to claim 8 or 9, wherein the correcting step corrects at least one of the R, G, and B signals according to the gradation of the R, G, and B signals. 11. The white color according to claim 9, wherein the correcting step includes a table that defines a change in a coefficient according to a gradation, and corrects at least one of the R, G, and B signals with reference to the table. Degree adjustment method. The whiteness adjustment method according to claim 8, further comprising a step of outputting the input image signal as it is without correction when it is determined that the R, G, and B signals do not coincide with each other.

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