JPH04351189A - Signal processing circuit for liquid crystal projection type video display device - Google Patents

Abstract

PURPOSE:To obtain excellent picture quality even when an optical component of a display device is similar to that of a conventional system by adopting the configuration for output processing including shading correction, voltage shift correction and sequential scanning conversion processing. CONSTITUTION:The processing circuit is provided with a 1st storage means 8 storing shading correction data by one frame, a multiplier means 10 using video information as a multiplicand and using a shading correction data stored in the 1st storage means 8 as a multiplier for the multiplication, a 2nd storage means 14 storing a voltage shift correction quantity by one frame, an adder means 16 adding the video information and the voltage shift correction quantity stored in the 2nd storage means 14 and an output processing means 20 for displaying visually the video information obtained through cascade connection of the multiplier means 10 and the adder means 16.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal processing circuit applicable to a signal processing circuit including a circuit for driving a liquid crystal panel of a liquid crystal projection type image display device.

0002

[Prior Art] Compared to cathode ray tube projection display devices, liquid crystal projection video display devices are being developed due to their advantages such as smaller volume and shorter device depth, and some prototype devices have been developed. It has been published. However, the signal processing circuit used here is an application of a circuit for driving a liquid crystal panel for a pocket-type direct-view liquid crystal television. Some devices are also equipped with a circuit that corrects the applied voltage and the transmittance of the liquid crystal.

0003

SUMMARY OF THE INVENTION However, the following problems are apparent in conventional liquid crystal projection type image display devices.

(2) Optical unevenness (shading) occurs due to characteristics of lens aberrations, optical system mechanisms, light valve configurations, screens, etc.

[0005] Since the liquid crystal drive circuit performs analog signal processing, there are voltage fluctuations (temperature within the drive circuit, drift over time, and variations between drive circuits).

[0006] Cathode ray tube projection display devices use interlaced display except in special cases, but when display devices using liquid crystal display interlaced, every other scanning line becomes black, and the absolute brightness decreases. It becomes half. Further, depending on the display mode, the screen becomes white, but in this case, the entire screen becomes whitish, and the sharpness is relatively deteriorated.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a signal processing circuit for a liquid crystal projection type image display device that can solve the above-mentioned problems and provide a display image of good quality.

[0008]

[Means for Solving the Problems] A signal processing circuit for a liquid crystal projection type image display device according to the present invention includes a first storage means for storing shading correction data for one frame, video information as a multiplicand, a multiplier that performs multiplication using the shading correction data stored in the first storage means as a multiplier; a second storage means that stores a voltage shift correction amount for one frame; and video information and the second storage means. and an output processing means for visually displaying the image information obtained by cascading the multiplication means and the addition means.

[0009]

According to the present invention, a high-quality display image can be obtained by performing output processing including shading correction, voltage shift correction, progressive scan conversion processing, and the like.

That is, the present invention has two circuits that hold information for one frame, and one of these circuits uses shading correction data as multiplier data to perform shading correction by multiplying the video information that is the multiplicand. In the other system, the voltage shift correction data is added to the video information as the summend to perform voltage shift correction, and in the final stage, it is converted to sequential scanning and displayed. It is.

[0011]

EXAMPLES Examples of the present invention will be described in detail below.

FIG. 1 is a block diagram showing a signal processing circuit of a liquid crystal projection type image display device according to an embodiment of the present invention. Note that although this figure shows the configuration of only the green channel due to space limitations, the remaining blue and red channels are also subjected to the same processing as the green channel.

In FIG. 1, 2 is a matrix circuit which converts a luminance/color difference signal system into three primary color signals of green, blue, and red. That is, when the three primary color signals of green, blue, and red are not used as the video input signal, for example, the input of the luminance/color difference signal system is converted by the matrix circuit 2.

4 is an A/D converter that digitizes each of the three primary color signals (R, G, B).

6 is an inverse gamma processing circuit. In other words,
When video signals commonly used today are displayed on a cathode ray tube display, the input device (for example, a camera) must perform a correction that matches the gamma characteristics of the cathode ray tube display in advance so that the applied voltage and brightness are directly proportional. However, this theory does not apply to liquid crystals. Therefore, the function of converting the gamma correction signal into a linear signal is called "inverse gamma processing."

A first correction memory 8 stores shading correction data for one frame.

10 is a multiplier, and a first correction memory 8
By performing multiplication processing using the shading correction data read out from the shading correction data as a multiplier and using the output of the inverse gamma processing circuit 6 as a multiplier, shading-corrected video information is output.

That is, in this embodiment, as means for correcting shading, a voltage corresponding to the amount of light that causes uneven brightness due to shading is added (or subtracted) to the video signal in advance. This converts the amount of shading actually measured over the entire screen into voltage, writes it into the first correction memory 8 for one frame as a multiplication coefficient, reads it out in synchronization with the video information, and simultaneously multiplies the video information. Realize it.

At this time, it does not matter whether the process of measuring the shading amount and writing it into the first correction memory 8 is performed automatically or by manual means, as this is not the gist of the present invention. In this embodiment, a personal computer (PC
) 22.

12 is a VT correction circuit. That is,
"V-T correction" corresponds to gamma correction of liquid crystal, and converts a video signal based on the relationship between applied voltage and transmittance of liquid crystal.

Reference numeral 14 denotes a second correction memory that stores data (for one frame) for voltage variation correction of the drive circuit.

16 is an adder, and the second correction memory 1
The voltage change is corrected by adding the voltage change correction data read from 4 and the output of the VT correction circuit 12.

That is, in this embodiment, as means for correcting the voltage variation of the drive circuit, an amount corresponding to the voltage generated by the voltage variation is added (or subtracted) to the video signal in advance. This converts the amount equivalent to the voltage change actually measured as brightness over the entire screen into voltage, and writes it into the second correction memory 14 for one frame as addition/subtraction information.
This is achieved by reading out in synchronization with video information and adding it to the video information at the same time.

[0024] At this time, the amount of voltage change is measured and
It does not matter whether the process of writing into the correction memory 14 is performed automatically or by manual means, as this is not the gist of the present invention. In this embodiment, the configuration is such that the data is loaded from a personal computer (PC).

Reference numeral 18 denotes a D/A converter, which outputs an analog video signal in order to monitor the signal processing process on an analog display device. Therefore, there may be cases where this D/A converter is not required.

20 is an output processing circuit, and as shown in FIG. 2, it includes a non-interlace conversion circuit 20A and a time axis (
It consists of a CRT→light valve) conversion circuit 20B, a line/field inversion circuit 20C, and a multilayer expansion circuit 20D.

Here, since the circuit 20A for converting to non-interlaced display corresponds to, for example, clear vision conversion in the current television system, a detailed explanation will be omitted. Further, due to the operating speed of the integrated circuit for driving the liquid crystal panel, the signals are developed in multiple layers in the final stage, but in this embodiment, the signals are developed in 12 layers.

Reference numeral 22 denotes a personal computer, which writes/reads relevant information into/from the correction memories 8 and 14. These correction memories 8
, 14 is written in a separately provided optical measurement system (
(not shown), this measurement system can be automated by using the personal computer.

Further, 24 is a synchronous processing circuit, and 26 is a PLL.
(phase locked loop) circuit, 28 is a clock distribution circuit. The processing of this synchronization signal system is handled separately from the video system processing, but for example, when inputting a video signal in which synchronization information is superimposed on the three primary color signals of green, blue, and red, a synchronization separation circuit, which is not described because it is publicly known, is used. , shall be separated into horizontal synchronization information and vertical synchronization information.

[0030]

[Effects of the Invention] As explained above, according to the present invention, since the structure is configured to perform shading correction, voltage shift correction, and output processing, good image quality can be achieved even though the optical part of the display device is the same as before. It becomes possible to provide

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a detailed block diagram of an output processing circuit 20. FIG.

[Explanation of symbols]

2 Matrix circuit 4 A/D converter 6 Inverse gamma processing circuit 8 First correction memory 10 Multiplier 12 VT correction circuit 14 Second correction memory 16 Adder 18 D/A converter 20 Output processing circuit 20A Non Interlace conversion circuit 20B Time axis conversion circuit 20C Line/field inversion circuit 20D Multilayer expansion circuit 22 Personal computer 24 Synchronization processing circuit 26 PLL circuit 28 Clock distribution circuit

Claims (3)

[Claims] 1. A first storage means for storing one frame's worth of shading correction data; and a multiplication device for performing multiplication using video information as a multiplicand and the shading correction data stored in the first storage means as a multiplier. means, second storage means for storing a voltage change correction amount for one frame, addition means for adding video information and the voltage change correction amount stored in the second storage means, said multiplication means, and said multiplication means. 1. A signal processing circuit for a liquid crystal projection type image display device, comprising: output processing means for visually displaying image information obtained by cascading adding means. 2. The signal processing circuit for a liquid crystal projection type video display device according to claim 1, wherein signal processing is performed independently on each of the three primary color video signals of green, blue, and red to obtain a video display signal for each color. 3. The signal processing circuit for a liquid crystal projection type video display device according to claim 2, wherein the synchronizing signal is obtained in a system separate from the video signal processing system.