JPH09247593A - Distortion correction device for liquid crystal projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To dissolve the notches of a screen projection screen generated by the keystone distortion correction of a liquid crystal projector. SOLUTION: Pixel data are successively read from a memory 4 storing video data after the keystone distortion correction in an address generation part 3. At the time, for correction object pixel data, in a data computing part, peripheral eight pixel data adjacent to the pixel data are also read and the data of the nine picture elements are averaged and written in the memory 5 as correction pixel data. When the read data of the memory 5 are displayed on a liquid crystal panel and projected on a screen, the notches are eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distortion correction device for a liquid crystal projector, and more particularly to a trapezoidal image signal to be displayed on a liquid crystal panel when the image obtained through the liquid crystal panel is projected and displayed on a screen. The present invention relates to a distortion correction device in a liquid crystal projector that projects a distortion correction process on a screen.

[0002]

2. Description of the Related Art In a projection type liquid crystal projector, image light obtained through a liquid crystal panel is formed and projected on a screen. In this case, when a liquid crystal panel screen as shown in FIG.
As shown in (B), the screen projection screen has an inverted trapezoidal shape and causes keystone distortion. In addition, in FIG. 5B, a black portion indicates a blank portion.

In order to correct this keystone distortion, as shown in FIG. 6A, the video signal displayed on the liquid crystal panel is preliminarily distorted into a trapezoidal shape and corrected, and the liquid crystal corresponding to this video signal is corrected. When projecting the panel screen onto the screen,
As shown in FIG. 6B, a normal projection screen can be obtained.

A technique for electrically correcting a video signal in this way is disclosed in Japanese Patent Laid-Open No. 4-323979. That is, the ratio of the number of clocks is sequentially changed within the effective display period of the video signal and outside the effective display period (blank part) according to the vertical position of the liquid crystal panel screen, and the blank data is changed to the black part of FIG. 6 (A). By displaying such as, the keystone distortion is electrically corrected.

[0005]

In the conventional liquid crystal projector keystone distortion correction device of this type, by processing the image signal data input to the liquid crystal panel, the screen on the liquid crystal panel becomes an inverted trapezoid. Since it is distorted, the screen on the screen has a drawback that the boundary between the blank portion and the display portion is jagged as shown in FIG. 7B.

Incidentally, FIG. 7A shows a liquid crystal panel display screen, and FIG. 7C is a partially enlarged view thereof.

It is an object of the present invention to provide a distortion correction device for a projector capable of eliminating the jaggedness on the projection screen caused by the keystone distortion correction of the liquid crystal projector.

[0008]

According to the present invention, when an image obtained through a liquid crystal panel is projected and displayed on a screen, a trapezoidal distortion correction process is performed on an image signal to be displayed on the liquid crystal panel. A distortion correction device in a liquid crystal projector for projecting on a screen after performing the image correction, wherein an image portion corresponding to at least a boundary position between a blanking portion and an image portion of the image signal after the trapezoidal distortion correction processing is performed. There is provided a distortion correction device for a liquid crystal projector, characterized in that it includes a correction means for performing a correction process on each pixel in consideration of surrounding pixels adjacent to the pixel.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The operation of the present invention will be described. Regarding the video signal data obtained by correcting the keystone distortion of the video signal data displayed on the liquid crystal panel, the data of the correction target pixel is converted by referring to the data of the pixels in the vicinity of the correction target pixel. As a result, the image data is interpolated and the jaggedness of the screen in the keystone distortion correction is eliminated.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention. In FIG. 1, the memory 4 stores the video signal data after the keystone correction processing which is the video signal data of the liquid crystal panel screen shown in FIG. 7 (A).

The correction improving apparatus 1 according to the present invention corrects the read data from the memory 4 and stores it in the memory 5. The correction improving apparatus 1 has an address generation unit 3 that generates a read address of the memory 4 and a write address to the memory 5, and a data calculation unit 2 that corrects the read data (pixel unit) from the memory 4. ing.

FIG. 2 is a flow chart showing the operation of the correction improving apparatus 1 of FIG. The operation of the embodiment of the present invention will be described with reference to FIG. As described above, it is assumed that the video signal data after the keystone correction shown in FIG. 7A is stored in the memory 4 for one frame in advance.

In order to read the video signal data from the memory 4 pixel by pixel in order from the upper left to the right (horizontal direction) of the screen and from the upper side to the lower side (vertical direction) in a scanning manner, in this order. A read address of the memory 4 is generated (step 21). Corresponding pixel data is sequentially read from the memory 4 according to this address (step 22).

It is determined whether the read pixel data is a pixel to be corrected (step 23). As this determination method, pixels belonging to a pixel group that is continuously located from a boundary between a blank portion (black portion) and a screen portion (white portion) in FIG. 7A to a certain number of screen portions (white portion). It is performed by determining whether or not. If it belongs to a pixel group located in the screen portion for a certain number of consecutive times, it is a pixel to be corrected, and if not, it is not a pixel to be corrected.

It should be noted that the determination as to whether the pixel belongs to this pixel group can be made based on the read address of the memory 4.

If it is a pixel to be corrected, the addresses of all adjacent pixels surrounding the pixel to be corrected are generated and read from the memory 4 (steps 24, 25, 26).

In FIG. 3, when the pixel to be corrected is D0,
The positional relationship of all the pixels D1 to D8 around it is shown.
The correction calculation is performed by using a method such as a moving average method for obtaining an average value of data of all the pixels of D0 and D1 to D8 (step 27). This correction calculation result is written in the corresponding portion of the memory 5 (steps 28 and 2).
9).

If the pixel is not the pixel to be corrected in step 23, the correction calculation is not performed and the data is directly written in the corresponding portion of the memory 5 (steps 28 and 2).
9).

In this manner, the correction target pixel is corrected by referring to all the surrounding pixels and taking an average value,
Since the pixels after this correction will be averaged,
In the display on the screen, the jagged edges are virtually eliminated.

As an example of the determination of the pixel to be corrected, a fixed pixel group including the boundary position pixel between the blank portion and the pixel portion is set in advance, and when the address of the memory 4 corresponding to this pixel group is determined. The pixel to be corrected may be used.

[0022]

As described above, according to the present invention, it is possible to prevent jaggedness on the screen projection screen by further correcting the image signal data after the keystone correction of the liquid crystal projector. effective.

[Brief description of drawings]

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

FIG. 2 is a flowchart showing the operation of the embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between a correction pixel D0 and surrounding pixels D1 to D8.

FIG. 4 is a diagram showing a state where jaggedness is eliminated by a correction process.

FIG. 5 is a diagram illustrating keystone distortion.

FIG. 6 is a diagram illustrating a keystone distortion correction process.

FIG. 7 is a diagram showing an example of occurrence of jaggedness caused by keystone distortion correction processing.

[Explanation of symbols]

 1 correction improvement device 2 data calculation unit 3 address generation unit 4, 5 memory

Claims (3)

[Claims] 1. When a video image obtained through a liquid crystal panel is projected and displayed on a screen, the video signal to be displayed on the liquid crystal panel is subjected to trapezoidal distortion correction processing and then projected on the screen. Distortion correction device in a liquid crystal projector, wherein a pixel of a video part corresponding to at least a boundary position between a blanking part and a video part of the video signal after the trapezoidal distortion correction process is adjacent to the pixel A distortion correction device for a liquid crystal projector, comprising: a correction unit that performs correction processing in consideration of surrounding pixels. 2. The correction means has a calculation means for calculating an average value of a pixel corresponding to the boundary position which is a correction target pixel and all peripheral pixels adjacent to this pixel, The distortion correction device for a liquid crystal projector according to claim 1, wherein the distortion correction device replaces the pixel to be corrected. 3. The correction means is characterized in that the correction target pixel is a fixed number of continuous pixels from the boundary position, and a correction process is performed on each of these correction target pixels. Distortion correction device for liquid crystal projector described.