JPH08171371A - Non-linear characteristic correction circuit - Google Patents

Abstract

PURPOSE: To realize a high definition liquid crystal projector capable of precisely. correcting a voltage-transmissivity characteristic over the whole screen. CONSTITUTION: One representative point is set at every area of a liquid crystal panel divided to plural parts, and the correction data correcting the voltage- transmissivity characteristic in the representative point in linear are stored in look-up table RAMs 1-4. The correction data in four representative points close to the input data are read out from the look-up table RAMs 1-4. The correction data from the look-up table RAMs 1-4 are linearly interpolated in the horizontal and vertical directions by an interpolation circuit 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-linear characteristic correction circuit for correcting a non-linear voltage-transmittance characteristic in a liquid crystal panel used in a liquid crystal projector or the like into a linear characteristic.

[0002]

2. Description of the Related Art A liquid crystal panel used in a liquid crystal projector or the like usually has a non-linear voltage-transmittance characteristic as shown in FIG. 5A. Therefore, conventionally, a characteristic correction circuit having an input / output characteristic as shown in FIG. 9B is provided, and a voltage after passing through the characteristic correction circuit is applied to the liquid crystal panel to show the voltage-transmittance characteristic as shown in FIG. Was corrected. This voltage-transmittance characteristic is corrected by, for example, the voltage-transmittance characteristic measured as described in 1992 Television Society Annual Conference Proceedings P345-P346 "Signal processing device for rear projection type liquid crystal display for high vision". This is done by using the RAM table in which the reverse characteristic of is written as the correction data.

By the way, strictly speaking, the liquid crystal panel has different voltage-transmittance characteristics for each pixel due to manufacturing variations. For this reason, when used in a high-definition liquid crystal projector for high-definition television or the like, if the method of correcting with one correction data for one liquid crystal panel as in the conventional case, accurate voltage-transmittance over the entire screen is obtained. The characteristics could not be corrected, which caused color unevenness.

[0004]

SUMMARY OF THE INVENTION The present invention provides a non-linear characteristic correction circuit capable of accurately correcting the voltage-transmittance characteristic over the entire screen and realizing a higher definition liquid crystal projector.

[0005]

According to the present invention, one representative point is set for each area of a liquid crystal panel divided into a plurality of areas, and correction data for linearly correcting the voltage-transmittance characteristic at the representative point is set. A non-linear circuit including a memory for storing the data It is a characteristic correction circuit.

Further, according to the present invention, one representative point is set for each area of the liquid crystal panel divided into a plurality of areas, and the correction data and the reference correction data for linearly correcting the voltage-transmittance characteristic at the representative point are set. A first memory that stores difference correction data that is a difference between the first and second memory, a second memory that stores the reference correction data, and a memory control circuit that reads the difference data at a predetermined address of the first memory with respect to input data. A nonlinear characteristic correction circuit including an interpolation circuit that interpolates the input data with difference correction data at a plurality of the representative points, and an adder circuit that adds the first memory output and the interpolation circuit output.

[0007]

In the present invention, the liquid crystal panel is divided into a plurality of areas, and a representative point is set for each area. Correction data for linearly correcting the voltage-transmittance characteristic at each representative point is stored in the memory. After the correction data at a plurality of representative points is read from the memory for the input data, the interpolation circuit linearly interpolates the interpolation data for the input data in the horizontal and vertical directions based on the correction data and outputs the interpolation data.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings.

First, the principle of the present invention will be described. As shown in FIG. 1, the liquid crystal panel is divided into sub blocks SB formed of a plurality of pixels, and one representative point b is set in each sub block SB. Then, the voltage-transmittance characteristic is measured for each of the representative points, and the correction data having the opposite characteristic is written in the look-up table RAM described later. The sub blocks form one block in units of four, and each block has horizontal addresses 0 to n and vertical addresses 0 to.
m is attached.

Next, FIG. 2 is a block diagram showing a first embodiment of the present invention. Reference numerals 1 to 4 show correction data for correcting input data in order to linearly correct the voltage-transmittance characteristic of a liquid crystal panel. It is a stored look-up table RAM, and each RAM stores the correction data at the representative point. Reference numeral 5 is a block address creating circuit for creating and outputting a horizontal block address and a vertical block address for the RAM based on the horizontal pixel address and the vertical pixel address.

Reference numeral 6 is an interpolation circuit for interpolating the corrected data for the input data based on the output of each RAM, and is composed of multipliers 61 to 66 and adders 67 to 69. Reference numeral 7 is a coefficient creating circuit for creating the interpolation coefficient of the interpolation circuit 6 based on the horizontal pixel address and the vertical pixel address.

Next, the operation of this embodiment will be described.

First, the input data is input to the RAMs 1 to 4. The block address creating circuit 5 calculates the block address according to the pixel address of the input data. That is,
When the input data as shown in FIG. 3 is for the pixel at the position a1, interpolation is performed using four adjacent representative points b1 to b4, so the correction data for each representative point is stored. The block address of each RAM is designated. That is, in this case, the block addresses of RAM1 to RAM4 are N in the horizontal direction and M in the vertical direction.

When the input data is a2, b3 to b6 are selected as the representative points, so the block addresses of RAM3 and RAM4 are the same as in the above case, but RAM1
And the block address of RAM2 is N horizontally,
Vertical is M + 1.

Next, the outputs of the RAMs 1 to 4 designated by the block addresses are supplied to the multipliers 61 to 64 of the interpolation circuit 6, and first, the linear interpolation in the horizontal direction is performed. That is, on the line connecting the representative points b1 and b2, the correction data at the point where the input pixel data a1 is projected is interpolated by the correction data of the representative points b1 and b2, and similarly, on the line connecting the representative points b3 and b4. The correction data at the point where the input pixel data a1 is projected is represented by the representative points b3 and b4.
Interpolation is performed using the correction data of. Then, the correction data of the input pixel data a1 is interpolated by performing the linear interpolation in the vertical direction with the correction data of the both projection points.

Specifically, the multipliers 61 and 63 are supplied with the interpolation coefficient 1-KH created by the interpolation coefficient creating circuit 7, and the multipliers 62 and 64 are supplied with the interpolation coefficient KH. The outputs of the multiplier 61 and 62 are added by the adder 67.
And the outputs of the multipliers 63 and 64 are added by the adder 6
8 is added to perform linear interpolation in the horizontal direction. Further, the outputs of the adders 67 and 68 are supplied to multipliers 65 and 66, respectively. The multiplier 65 is supplied with the interpolation coefficient 1-KV, and the multiplier 66 is supplied with the interpolation coefficient KV.
Is supplied. Then, the outputs of the multipliers 65 and 66 are added by an adder 69 to be linearly interpolated in the vertical direction.

By doing so, even if the voltage-transmittance characteristic differs for each pixel of the liquid crystal panel, the voltage-transmittance characteristic can be approximately corrected for each pixel. Next, another embodiment of the present invention will be described with reference to FIG.

In this embodiment, the lookup table RA is used.
A look-up table RAM 7 is provided in addition to M1 to 4,
Average correction data obtained by averaging the correction data of each representative point is stored in this RAM, and difference correction data obtained by taking the difference between the correction data of each representative point and the average correction data is stored in RAM1-4. Keep it. The interpolation circuit 6 interpolates the difference correction data, and the output is added to the output of the RAM 7 by the adder 8,
An output similar to that of the first embodiment can be obtained. Incidentally, R
The data stored in the AM 7 may be correction data at any one representative point other than the average correction data, and the point is that the correction data is a reference.

According to this embodiment, instead of providing an extra RAM for storing average correction data, the correction data for each representative point stored in RAMs 1 to 4 need only be difference correction data with a small amount of data, so that the entire RAM is stored. The capacity can be significantly reduced.

[0020]

As described above, according to the present invention, since the voltage-transmittance characteristic can be accurately corrected over the entire screen, a higher definition liquid crystal projector can be realized.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is a circuit diagram of a nonlinear characteristic correction circuit according to an embodiment of the present invention.

FIG. 3 is a diagram illustrating the operation of FIG.

FIG. 4 is a circuit diagram of a non-linear characteristic correction circuit according to another embodiment of the present invention.

FIG. 5 is an explanatory diagram illustrating correction of voltage-transmittance characteristics.

[Explanation of symbols]

 1-4, 8 Look-up table RAM 5 Block address creation circuit 6 Interpolation circuit 7 Coefficient creation circuit

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Haruhiko Murata 2-5-5 Keihan Hondori, Moriguchi City, Osaka Sanyo Electric Co., Ltd. 5-5 Sanyo Electric Co., Ltd. (72) Inventor Toshiya Iinuma 2-5-5 Keihan Hondori, Moriguchi City, Osaka Prefecture Sanyo Electric Co., Ltd. (72) Inventor Toshiyuki Okino Keihan Hondori, Moriguchi City, Osaka Prefecture 2-5-5 Sanyo Electric Co., Ltd.

Claims (2)

[Claims] 1. A memory for storing correction data for setting one representative point for each area of a liquid crystal panel divided into a plurality of areas, and linearly correcting the voltage-transmittance characteristic at the representative point, and input data. A non-linear characteristic correction circuit including a memory control circuit that reads out the correction data at a predetermined address of the memory and an interpolation circuit that interpolates the input data with the correction data at the plurality of representative points. 2. One representative point is set for each area of the liquid crystal panel divided into a plurality of areas, and the difference between the correction data for linearly correcting the voltage-transmittance characteristic at this representative point and the reference correction data is set. A first memory for storing certain difference correction data; a second memory for storing the reference correction data; a memory control circuit for reading the difference data at a predetermined address of the first memory with respect to input data; On the other hand, a non-linear characteristic correction circuit including an interpolation circuit that interpolates with difference correction data at a plurality of the representative points, and an addition circuit that adds the first memory output and the interpolation circuit output.