JPH10333648A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make simply executable γ-correction in response to an optional operation mode, by selecting and switching the reference voltage corresponding to the level of the input video signal from reference voltages, and carrying out a specified γ-correction to the input image signal for display. SOLUTION: Digitized image signals aligned temporally in series for picture elements are taken by registers of a register group A 23 as signals for picture elements and shifted to a register group B 24 via the control of a shift register 22. The output signals of the registers of the register group B 24 are converted into analog signals of sizes corresponding to the luminance of individual picture elements. The D/A-converted analog signals are replaced with the corresponding γ-corrected reference voltages by a selector group 26, and the reference voltages are source-applied to the liquid crystal elements of the picture elements of the display screen of an LCD panel 1. When the gate voltage of the liquid crystal elements is applied from a gate driver 3, the liquid crystal elements are displayed at the brightness corresponding to the voltages applied via the selector group 26.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device capable of selecting and displaying a desired one from a plurality of types of gradation display characteristics.

[0002]

2. Description of the Related Art FIG. 7 shows a configuration of a conventional liquid crystal display device. In the figure, reference numeral 100 denotes an LCD panel having a source line 210 forming a data line and a gate line 310 forming a scanning line.
To the source line 210 and the scanning signal from the gate driver 300 to the gate line 310 for display. Reference numeral 400 denotes a display control interface that separates a video signal supplied from the outside via the input signal line 410 into a digitized video signal 420, a source driver control signal 430, and a gate driver control signal 440 necessary for display on the LCD panel 100. Reference numeral 500 denotes a reference voltage source for multi-tone display.

Next, the operation will be described. The digitized video signal 420 is controlled by the shift register 220
The signal is taken into the register A230 separately for each pixel,
The signal is converted into an analog signal by the D / A converter 250 via the register B240. The analog signal voltage is converted into a voltage (reference voltage) having a voltage value after gamma correction corresponding to the analog signal voltage by controlling an analog switch of the selector 260. The voltage after this gamma correction is applied to the source of the liquid crystal element of the display pixel of the LCD panel 1. The conversion into the voltage having the voltage value after the gamma correction is performed as follows. A reference voltage power supply 500 is provided which generates a plurality of voltages (reference voltages) having a voltage value obtained by multiplying the voltage value by a gamma correction coefficient in accordance with a voltage value in a possible range of the analog signal voltage. Have been. Then, by controlling the analog signal voltage, the analog signal voltage is switched to a reference voltage from a reference voltage source having the gamma correction value having a magnitude corresponding to the voltage value of the analog signal.

The reference voltage power supply 500 is a stabilized power supply 5
The voltage from 10 is divided by resistors (R1 to R10),
It comprises a voltage dividing circuit 520 for outputting via an emitter follower (EF1 to EF0), and a reference voltage is sent to a reference power supply line 510. Note that each resistance value of the voltage dividing circuit corresponds to a specific gamma correction coefficient,
It is set and incorporated in advance.

[0005]

Since the conventional device has the above-described configuration, in order to change the gamma correction coefficient, it is necessary to change the combination of each resistor of the voltage dividing circuit. The request for changing the gamma correction coefficient could not be met. However, as the image quality of the display device improves and the number of opportunities to handle color-type screens increases, there has been a strong demand to be able to set gamma correction for each type each time. The fixed type can no longer be used.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide a liquid crystal display device which can easily switch to a plurality of types of gamma correction coefficients. I have.

[0007]

According to the present invention, there is provided a liquid crystal display device comprising: a memory unit for accumulating reference voltage data for gamma correction for each operation mode corresponding to each level of a video signal; A D / A converter for converting the output reference voltage data in the designated mode to a corresponding reference voltage, a reference voltage generator for generating each reference voltage for gamma correction, and each level of the video signal A selector unit that selects and switches a reference voltage corresponding to the level of an input video signal from among the reference voltages prepared for each, and supplies a selector to the display unit in place of the input video signal. The display is performed with gamma correction.

The data relating to the gamma correction stored in the memory unit includes a graphic mode, a natural image mode, and a TV mode.
Data corresponding to one or more of the data relating to the gamma correction in the image mode is included, and the data relating to the gamma correction in each of these modes can be used by selection.

Further, the gamma correction data stored in the memory section is temporarily read out to a rewritable memory, and is read out from the rewritable memory and supplied to a reference voltage generating section during operation in the same mode.

Further, the data relating to the first gamma correction and the data relating to the second gamma correction stored in the memory section are once read into rewritable memories, respectively, and the data obtained by averaging both data is used as new data. A reference voltage for gamma correction is generated as a gamma correction coefficient.

Further, instead of the data relating to the gamma correction stored in the memory unit, any data relating to the gamma correction is written into a rewritable memory, and this data is generated as a data relating to a gamma correction coefficient to generate a reference voltage. It was done.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. FIG. 1 shows a configuration diagram of a liquid crystal display device according to Embodiment 1 of the present invention. In FIG. 1, 1 is
On the LCD panel, the source line 21 and the gate line 31
The display is performed by applying a data signal from the source driver 2 to the source line 21 and a scanning signal from the gate driver 3 to the gate line. Reference numeral 4 denotes a display control interface for dividing an external video signal into signals required for display on the LCD panel 1. Reference numeral 5 denotes a reference voltage power supply for multi-tone display.

Next, the operation will be described. The video signals digitized and temporally arranged in series for each pixel are taken in as signals for each pixel by the registers of the register group A23 under the control of the shift register 22, and then transferred to the register group B24. The output signal of each register of the register group B24 is converted by the D / A converter group 25 into an analog signal having a size corresponding to the luminance of each pixel. In the selector group 26, the analog signal after the D / A conversion is replaced by the corresponding reference voltage after the gamma correction in the selector group 26, and the source is applied to the liquid crystal element of each pixel on the display screen of the LCD panel 1. When a gate voltage of the liquid crystal element is applied from the gate driver 3, the liquid crystal element is switched to the selector group 26.
The display of the brightness according to the voltage applied through is performed.

The relationship between the analog voltage of the D / A converter and the corresponding reference voltage is determined according to a gamma correction coefficient.
It is out of line. Specifically, depending on the display contents, FIG. 3 in the graphic mode, FIG.
In the image mode, the relationship shown in Fig. 5 (the relationship shown numerically in Fig. 6)
Is set to In these figures, the horizontal axis is the input data, and the vertical axis is the corresponding output voltage. This voltage is equal to the reference voltage (V1,.
・) Is supported. With the above configuration, in order to perform display by changing gamma correction corresponding to each mode each time display is performed, the reference voltage power supply 5 needs to correspond to each voltage value in the range that the analog signal can take. The reference voltage required for each mode must be able to be generated by a simple operation. In the liquid crystal display device according to the present invention, the reference voltage power supply 5 for generating a reference voltage capable of meeting such a demand is configured as follows.

FIG. 2 is a diagram for explaining the details of the reference voltage power supply 5. In FIG. 2, reference numeral 51 denotes a mode selection terminal;
Is an address conversion circuit for each mode, 53 is an address designating section,
Reference numeral 54 denotes voltage data of a reference voltage for each mode (for example, voltage data of mode a: V1a, V2a,..., V10a,
.. memory (RO) for storing voltage data
M) and 55 are rewritable memory groups (RAM) provided corresponding to each reference voltage, 56 is a D / A converter group provided corresponding to each reference voltage, and 57 is a reference A reference voltage line led to the selector group 26, 58 is a RAM rewriting circuit, and 59 is a rewriting control terminal.

Next, the operation will be described. Mode designation terminal 51
When a mode designating signal is applied to the memory, the mode designating signal is converted into an address signal by the mode-specific address converting unit 52, and is guided to the memory 54 via the address designating unit 53.
The address of the voltage data of the reference voltage for gamma correction in the designated mode stored in the memory 54 is designated and read out. The read voltage data of the reference voltage is temporarily stored in a readable memory group 55. This voltage data is a data set corresponding to each reference voltage stored in the form of digital data. This set of digital data corresponds to the reference voltages V1, V2,..., V10... Of the designated mode, and the D / A converter group 56 prepared respectively.
Are converted into analog voltages by the respective D / A converters, and supplied to the selector group 26 via the reference voltage line 57. When the voltage data corresponding to the reference voltage for each mode is stored in the memory 54 as described above, the voltage data can be designated and called, and the corresponding reference voltage can be generated. Screen display with gamma correction coefficient applied can be performed.

In the above, a case has been described in which data relating to one set of gamma correction coefficients is read and gamma correction is performed. However, data relating to two sets of gamma correction coefficients is read at a time, and the average value of the two data is calculated. Alternatively, it is also possible to calculate a weighted average value and use this to perform gamma correction. This makes it possible to meet the demand for performing an intermediate correction between the two modes. In addition, since data stored in the writable memory 55 can be read from the rewriting instruction terminal 59 through the RAM rewriting circuit 58, data temporarily read into the memory 54 can be used in addition to data prepared in the memory 54 in advance. Also, gamma correction corresponding to the new mode can be performed.

[0018]

According to the liquid crystal display device of the present invention, the reference voltage data relating to the gamma correction is stored in a memory, which is called up, converted into a voltage, and used as a reference voltage. By preparing as reference voltage data corresponding to a mode, there is an effect that gamma correction can be easily performed in any operation mode.

Also, since a rewritable memory is provided together with the memory to generate a reference voltage using information stored in the memory, any data can be stored in the memory without being limited to the data stored in the memory. Can perform gamma correction.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram according to a first embodiment.

FIG. 2 is a detailed configuration diagram of a reference voltage power supply unit according to the first embodiment.

FIG. 3 is an explanatory diagram relating to gamma correction in a graphic mode.

FIG. 4 is an explanatory diagram relating to gamma correction in a natural image mode.

FIG. 5 is an explanatory diagram relating to gamma correction in a TV image mode.

FIG. 6 is data showing input / output voltage relationships in various modes, relating to a gamma correction coefficient.

FIG. 7 is a configuration diagram of a conventional liquid crystal device.

[Explanation of symbols]

Reference Signs List 1 LCD panel, 2 source drivers, 21 source line group, 22 shift register, 23 register group A, 24 register group B, 25 D / A converter group, 26 selector group, 3 gate driver, 31
Gate line group, 4 display control interface, 41
Input signal line, 42 video signal line, 43 source driver control line, 44 gate driver control line, 5 reference voltage source, 51 mode selection terminal, 52 mode-specific address conversion unit, 53 address designation unit, 54 memory, 55 rewritable Memory group, 56 D / A converter group, 57 reference voltage line, 58
RAM rewriting circuit, 59 rewriting control terminal.

Claims (5)

[Claims] 1. A memory unit for accumulating reference voltage data relating to gamma correction for each operation mode corresponding to each level of a video signal, and the reference voltage data in a designated mode read from the memory unit. D / A to convert to reference voltage
A reference voltage generator for generating each reference voltage for gamma correction, corresponding to the level of the input video signal from among the reference voltages prepared for each level of the video signal A liquid crystal display device comprising a selector unit for selecting and switching a reference voltage and supplying the selected image signal to a display unit in place of the input image signal, and performing display by applying a specified gamma correction to the input image signal. 2. The gamma correction data stored in the memory unit includes data corresponding to one or more of gamma correction data of a graphic mode, a natural image mode, and a TV image mode. 2. The liquid crystal display device according to claim 1, wherein data relating to gamma correction in each of these modes can be used. 3. The data relating to gamma correction stored in the memory unit is temporarily read out to a rewritable memory, and when operating in the same mode, the data is read out from the rewritable memory and supplied to a reference voltage generator to generate a predetermined reference voltage. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is configured to perform the following. 4. A gamma correction data obtained by reading first gamma correction data and second gamma correction data stored in a memory unit into a rewritable memory and averaging both data. 3. The liquid crystal display device according to claim 1, wherein a reference voltage is generated as data relating to new gamma correction. 5. A method according to claim 1, wherein arbitrary data relating to gamma correction is written in a rewritable memory in place of data relating to gamma correction stored in a memory unit, and a reference voltage is generated based on the data. The liquid crystal display device according to claim 1 or 3, wherein: