JP2003157056A - Gamma correction method for liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify a setting method for gamma correction in a projection type video display device provided with a liquid crystal display part. SOLUTION: In measurement of applied voltage-transmissivity characteristics, by performing detailed measurement at a curve part of the characteristics and performing simple measurement at a straight line part, the time is shortened. Also, by preparing several kinds of gamma correction data in the setting method and selecting them on the basis of a measured result of the applied voltage-transmissivity characteristics, the loads on an arithmetic processing required for the setting are reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to gamma correction in a liquid crystal display device, and more particularly to automatic adjustment of the gamma correction.

[0002]

2. Description of the Related Art In a liquid crystal display device having a liquid crystal display unit, particularly a projection type display device using three liquid crystal panels for display, each of the three liquid crystal panels has individual input voltage-transmittance characteristics. It is known that color reproducibility can be improved by performing a combined gamma correction.

A conventional gamma correction setting method will be described with reference to FIG. FIG. 2 is a system configuration diagram showing an embodiment of gamma correction. The level of the input signal input to the liquid crystal display device 6 is appropriately changed, the image projected from the liquid crystal display device is projected on the screen 7, and the brightness of the image is measured using the image pickup device 9. With this method, the input voltage-transmittance characteristic of the liquid crystal panel in the liquid crystal display device can be measured. Then, the measured input voltage-transmittance characteristic data is input to the arithmetic processing unit 8 to create gamma correction data that can obtain a desired gradation characteristic. At this time, the arithmetic processing unit 8 can also be used as an input signal source for inputting to the liquid crystal display device 6. Conventionally, a method of transferring the gamma correction data created by the arithmetic processing device 8 to the liquid crystal display device 6 has been used.

A conventional gamma correction block diagram inside the liquid crystal display device 6 is shown in FIG. The gamma correction data created by the arithmetic processing unit 8 is transferred and stored in the memory 10 of FIG. 4 under the control of the microcomputer 11. Then, the gamma correction circuit 1 performs gamma correction based on the stored gamma correction data. The gamma-corrected video signal is subjected to signal processing necessary for input to the liquid crystal panel. That is, the D / A conversion circuit 2 performs digital-analog conversion, the liquid crystal drive circuit 3 performs signal processing necessary for liquid crystal drive, and then supplies a video signal to the liquid crystal panel.

[0005]

However, in the above-mentioned conventional gamma correction setting method, it takes time to measure the input voltage-transmittance characteristic.

Particularly, in the mass production process, the increase of the set time becomes a big problem. Further, since the correction data necessary for gamma correction is created from the measurement result by using the arithmetic device, a large load is applied to the arithmetic processing.

The present invention is intended to solve the above-mentioned conventional problems, and it is an object of the present invention to shorten the time required for setting gamma correction and to reduce the load of arithmetic processing required for setting.

[0008]

In order to achieve the above object, the present invention provides an accurate measurement of the input voltage-transmittance characteristic in the high-luminance portion and the low-luminance portion of the characteristic, and in the medium-luminance portion. In the above, the measurement time is shortened by performing a simpler measurement than the high brightness and low brightness parts.

In the gamma correction setting method, instead of creating the gamma correction data based on the measurement result of the input voltage-transmittance characteristic, several kinds of gamma correction data are prepared in advance, and the input voltage-transmittance characteristic is prepared. By selecting the correction data on the basis of the measurement result, the load of the arithmetic processing in the arithmetic device can be reduced.

This makes it possible to obtain a gamma correction method capable of shortening the measurement time of the input voltage-transmittance characteristic and reducing the load on the arithmetic processing unit for setting the gamma correction.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention stores a predetermined number of types of gamma correction data in a memory of a liquid crystal display device, and the input voltage-transmission of the liquid crystal panel of the liquid crystal display device. This is a gamma correction method for a liquid crystal display device in which the rate characteristic is measured, and from the measurement results, gamma correction is performed by selecting from the several types of gamma correction data described above. is there.

Further, in the invention according to claim 2, the input voltage-transmittance characteristic of the liquid crystal panel is precisely measured in the high luminance portion and the low luminance portion, and the middle luminance portion is measured in the high luminance portion and the low luminance portion. The gamma correction method for a liquid crystal display device according to claim 1, wherein the measurement is performed more easily than the portion, and has an effect of shortening the time required to measure the input voltage-transmittance characteristic of the liquid crystal panel.

(Embodiment) A gamma correction method for a liquid crystal display device according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a system configuration diagram showing an embodiment of gamma correction. FIG. 1 is a block diagram of gamma correction setting according to the embodiment of the present invention. FIG. 3 is a diagram showing the input voltage-transmittance characteristic of the liquid crystal panel and its variation.

The same constituent blocks as those of the conventional art will be designated by the same reference numerals, and the description thereof will be omitted. The difference from the conventional method is that several kinds of gamma correction data are stored in advance in the memory 4 inside the liquid crystal display device 1. Then, the arithmetic processing unit 8 determines which of the several types of gamma correction data stored in the memory 4 is optimum, based on the measured input voltage-transmittance characteristic of the liquid crystal panel. , The judgment result is transmitted to the microcomputer 5. Then, the microcomputer 5 selects which gamma correction data is used inside the memory 4.

The gamma correction data prepared in advance and the determination method by the arithmetic processing unit 8 will be described with reference to the diagram showing the variation of the input voltage-transmittance characteristic in the liquid crystal panel of FIG. The input voltage-transmittance characteristic of a liquid crystal panel can be roughly classified into a high-luminance portion, a medium-luminance portion, and a low-luminance portion. Among them, the high-brightness part and the low-brightness part have a non-linear characteristic, and the middle-brightness part has a substantially linear characteristic. Regarding the variation in the input voltage-transmittance characteristic of the liquid crystal panel, the inclination of the transmittance with respect to the input voltage in the high-luminance portion and the low-luminance portion varies as shown by the characteristics 1, 2, and 3.
That is, the transmittance of characteristic 1 starts to decrease in the high-luminance portion as compared with characteristics 2 and 3 when the input voltage applied to the liquid crystal panel is in a low voltage state. In addition, the characteristic 1 is in a state where the transmittance is low at a low voltage as compared with the characteristics 2 and 3 even in the low luminance part. On the contrary, the characteristic 3 maintains high transmittance even in the high voltage state of the input voltage applied to the panel in the high brightness portion, and in the low brightness portion,
The characteristic is that the transmittance is high even at a high voltage. The characteristic 2 is a characteristic intermediate between the characteristic 1 and the characteristic 3, that is, an average input voltage-transmittance characteristic of the liquid crystal panel. It is known that the characteristics 1, characteristics 2, and characteristics 3 are almost linear in the middle luminance portion and have the same slope of the transmittance with respect to the input voltage, and there is no variation. Further, the high brightness portion and the low brightness portion are dispersed in a manner that tends to have a certain tendency like the characteristic 1, the characteristic 2, and the characteristic 3, and the variation is not uniform over the entire variation range. . Therefore, the gamma correction data prepared in the memory 4 may be of several types according to the variation tendency.

Here, assuming that the number of variation tendencies is n and the number of data to be prepared is x, x = n + (n-1) +2. This means that the number of data of the center value of the variation tendency is n, the number of data of the average value n−1 between the variations and the data of one each are provided outside the maximum and the minimum of the variation tendency. There is. For example, as shown in FIG. 3, assuming that there are three types of variation tendency, the number of data to be prepared is seven.

By preparing approximately this amount of data, the same image quality as the conventional gamma correction method can be secured.

Next, the determination method by the arithmetic processing unit 8 will be described. Regarding the measurement data of the input voltage-transmittance characteristic, which data is selected from the gamma correction data prepared in advance is set in each of the high-luminance portion and the low-luminance portion in which variations occur. The determination is performed by providing a threshold level of transmittance for a constant input voltage. The number of threshold levels is set as x-1 for the number of prepared data x.

The reason why the threshold level is set for each of the high-luminance portion and the low-luminance portion is that the data closer to the actual measurement can be selected by making a determination based on the threshold level of each of the high-luminance portion and the low-luminance portion. In addition, a plurality of determination points for the input voltage of the high-luminance portion and the low-luminance portion are respectively provided, and the threshold level number of x-1 is set for each of them to improve the selection accuracy. In the actual judgment, 10 judgment points are set for the input voltage in both the high-luminance portion and the low-luminance portion, the judgment values at each judgment point are calculated for all the prepared data, and the best matching one is selected. I have to.

Further, as another data selection method, the same result can be obtained by providing the threshold level of the input voltage with respect to the transmittance instead of providing the threshold level of the transmittance with respect to the input voltage.

When measuring the input voltage-transmittance characteristic, the high-luminance portion and the low-luminance portion are non-linear characteristics and precise measurement is performed in order to select accurately for variations, and the medium-luminance portion is measured. Can reduce the measurement time because it requires a minimum of 3 points for checking the linear characteristics.

[0022]

As described above, according to the present invention, in the gamma correction method for a liquid crystal panel, several kinds of correction data are stored in advance, and the correction data according to the measurement result of the input voltage-transmittance characteristic is selected. As a result, the calculation processing of the inverse characteristic according to the input voltage-transmittance characteristic is unnecessary,
The effect of reducing the load of the setting software and shortening the measurement time when measuring the input voltage-transmittance characteristic is exhibited.

[Brief description of drawings]

FIG. 1 is a gamma correction block diagram according to an embodiment of the present invention.

FIG. 2 is a system configuration diagram showing an embodiment of gamma correction.

FIG. 3 is a diagram showing an input voltage-transmittance characteristic and its variation.

FIG. 4 is a conventional gamma correction block diagram.

[Explanation of symbols]

1 gamma correction circuit 2 D / A conversion circuit 3 liquid crystal drive circuit 4 memory 5 for holding a plurality of gamma data 5 microcomputer having a data selection function 6 liquid crystal display device 7 screen 8 arithmetic processing device 9 imaging device 10 conventional memory 11 Microcomputer for transferring the created gamma correction data

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Claims (2)

[Claims] 1. A predetermined number of types of gamma correction data are stored in a memory of a liquid crystal display device, and an input voltage-transmittance characteristic of a liquid crystal panel of the liquid crystal display device is measured. A gamma correction method for a liquid crystal display device that selects the optimum data from the gamma correction data and performs gamma correction. 2. The input voltage-transmittance characteristic of the liquid crystal panel is precisely measured in a high-luminance portion and a low-luminance portion, and the middle-luminance portion is more easily measured than the high-luminance portion and the low-luminance portion. The gamma correction method for a liquid crystal display device according to claim 1.