JP2004289503A - Liquid crystal projector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correct the distorsion of an image by a keystone distorsion correction circuit and to simultaneously correct deviation of increase and decrease of brightness in the case that the projection optical axis of a liquid crystal projector is inclined to a screen face. <P>SOLUTION: The liquid crystal projector drives a liquid crystal panel on the basis of a video signal corrected by the keystone distorsion correction circuit, irradiates the liquid crystal panel with light from a light source, and projects the image onto the liquid crystal panel through a light projection lens on the screen face. The liquid crystal projector is provided with a bright correction circuit, and increases and decreases the brightness as it goes to the end of the image in response to a correction amount of the keystone distorsion correction circuit. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a liquid crystal projector device having a keystone distortion correction circuit, which corrects a screen distortion when a projection optical axis is inclined with respect to a screen surface, and also corrects a simultaneously occurring luminance bias. The present invention relates to a liquid crystal projector device which enables the above.
[0002]
[Prior art]
In a conventional liquid crystal projector, when the projection optical axis is inclined with respect to the screen surface, the image becomes distorted so that the image becomes larger as the distance from the plane perpendicular to the optical axis at the optical axis position of the screen surface increases, and the brightness decreases. Get dark. In addition, the image is distorted so that the image becomes smaller as the distance from the plane perpendicular to the optical axis increases, and the brightness increases and the brightness increases. As a countermeasure against the above, a keystone distortion correction circuit is provided for image distortion to correct the image distortion (for example, see Patent Document 1).
[0003]
FIG. 5A shows the optical axis when the optical axis of the liquid crystal projector device is swung vertically with respect to the screen surface, and FIG. 5B shows the optical axis when the optical axis of the liquid crystal projector device is swung right and left. Shows the optical axis. FIG. 6 shows an image in each case of FIG. 5, in which a distorted image (shaded portion) before correction is shown on the left, and an image (shaded portion) obtained by correcting it by the keystone distortion correction circuit is shown on the right. In the distorted image on the left side, the image is distorted, and the smallly distorted portion increases in brightness and becomes brighter, and the greatly distorted portion decreases in brightness and becomes darker. The distortion of the size of the image is corrected to a normal size by the keystone distortion correction circuit as shown in the image on the right, but the deviation of the luminance is not corrected.
[0004]
[Patent Document 1]
JP-A-9-275538 (pages 2-9, FIGS. 7 and 8)
[0005]
[Problems to be solved by the invention]
In this way, the keystone distortion correction circuit can correct the image distortion in the plane due to the tilted optical axis, but the brightness depends on the position of the screen surface caused by the tilted optical axis. However, the conventional liquid crystal projector device cannot correct the problem of the increase or decrease, and the luminance of the image remains uncomfortable.
Accordingly, the present invention provides a liquid crystal projector capable of correcting a distortion of an image by a keystone distortion correction circuit when the projection optical axis is tilted with respect to a screen surface, and also correcting a bias of increase or decrease in luminance. The task was to propose a device.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, a liquid crystal projector device according to the present invention drives a liquid crystal panel based on a video signal corrected by a keystone distortion correction circuit, irradiates light from a light source to the liquid crystal panel, A projection device for projecting the above image on a screen surface via a light projection lens, further comprising a brightness correction circuit for increasing or decreasing brightness toward an end of the image according to the correction amount of the keystone distortion correction circuit.
[0007]
Here, when the optical axis of the projection light is inclined in the vertical direction with respect to the screen surface, the brightness correction circuit corrects the level of the video signal every vertical cycle.
When the optical axis of the projection light is inclined in the left-right direction with respect to the screen surface, the luminance correction circuit corrects the level of the video signal every horizontal cycle.
Further, when the optical axis of the projection light is inclined in an oblique direction with respect to the screen surface, the brightness correction circuit corrects the level of the video signal for each of the vertical cycle and the horizontal cycle.
The luminance correction circuit includes a sawtooth wave generation circuit having a vertical cycle and / or a horizontal cycle, generates a sawtooth wave signal having a slope corresponding to the correction amount of the keystone distortion correction circuit, and converts the sawtooth signal into a video signal. To correct the level of the video signal.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a portion for performing keystone distortion correction and luminance correction of the liquid crystal projector device according to the present invention. In the figure, a keystone distortion correction circuit 1 performs keystone distortion correction on an input video signal based on a keystone distortion correction command input via a microcomputer 6 and a serial control unit 8 to perform a color unevenness correction circuit 2. Send to The color unevenness correction circuit 2 corrects the color unevenness of the input video signal and sends it to the mixer 3. On the other hand, the keystone distortion correction command from the microcomputer 6 via the serial control unit 8 is also sent to the luminance correction circuit 7.
[0009]
The brightness correction circuit 7 creates a correction signal for each horizontal cycle and vertical cycle based on the input command and sends it to the mixer 3. The mixer 3 superimposes the input video signal and the correction signal and sends them to the S / H drive circuit 4. The S / H drive circuit 4 samples the corrected video signal at predetermined intervals and drives the liquid crystal panel 5. As a result, the image displayed on the liquid crystal panel 5 is subjected to the keystone distortion correction and the luminance correction according to the keystone distortion correction. Note that the configuration excluding the mixer 3 and the luminance correction circuit 7 surrounded by a broken line in FIG. 1 is a circuit for executing a keystone distortion correction process in a conventional liquid crystal projector device.
[0010]
FIG. 2 is a block diagram specifically showing the mixer 3 and the luminance correction circuit 7 surrounded by a broken line in FIG. In the figure, serial control data as a keystone distortion correction command from the microcomputer 6 is input to the DAC 71, then converted into DC, and input to the sawtooth wave generation circuit (horizontal) 72 and the sawtooth wave generation circuit (vertical) 73. You. The sawtooth wave generation circuit (horizontal) 72 operates when the optical axis is swung in the left and right direction to execute the keystone distortion correction, and the inclination specified in the control data at the timing of the horizontal synchronization signal (H-SYNC). Is generated and sent to the MIX circuit 31.
[0011]
The sawtooth wave generation circuit (vertical) 73 operates when the optical axis is swung up and down to execute keystone distortion correction, and the inclination specified in the control data at the timing of the vertical synchronization signal (V-SYNC). Is generated and sent to the MIX circuit 31. The MIX circuit 31 superimposes the input sawtooth signal on the video signal and sends it to the S / H driver.
[0012]
FIG. 3 is a waveform diagram showing luminance correction of a video signal when the optical axis of the liquid crystal projector device is swung right and left. The video signal shown at the beginning of the drawing is corrected every horizontal period (1H). That is, when the optical axis is swung to the left, a sawtooth wave descending to the right is superimposed every horizontal cycle as shown in the following waveform, and a video signal descending to the right is obtained. Next, when the optical axis is swung to the right, an ascending sawtooth wave is superimposed every horizontal cycle as shown in the following waveform, resulting in an ascending video signal.
[0013]
FIG. 4 is a waveform diagram showing correction of a video signal when the optical axis of the liquid crystal projector device is swung up and down. The video signal shown at the beginning of the drawing is corrected every vertical cycle (1V). That is, when the optical axis is swung upward, a sawtooth wave descending to the right is superimposed every vertical cycle as shown in the following waveform, and a video signal descending to the right is obtained. Next, when the optical axis is swung downward, a sawtooth wave that rises to the right is superimposed every vertical cycle as shown in the following waveform, resulting in a video signal that rises to the right.
[0014]
Note that, when the optical axis of the liquid crystal projector device is tilted in the oblique direction, it is possible to cope with this by performing the correction for each horizontal cycle and the correction for each vertical cycle as in the case of the keystone distortion correction.
As described above, in the embodiment of the present invention, a keystone distortion correction circuit that operates based on a correction command to the keystone distortion correction circuit is added to a conventional liquid crystal projector device that includes a keystone distortion correction circuit. It is possible to correct the deviation of the luminance that occurs simultaneously with the occurrence of the stone distortion at the same time as the correction of the keystone distortion.
[0015]
【The invention's effect】
As described above, according to the present invention, when the projection optical axis is inclined with respect to the screen surface, the image distortion is corrected by the keystone distortion correction circuit only by inputting the correction command for the keystone distortion. In addition, since the deviation in the increase and decrease of the luminance is also corrected at the same time, an image having a high quality without any unnaturalness in the luminance can be obtained.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of a liquid crystal projector device according to the present invention.
FIG. 2 is a block diagram specifically showing a main part of FIG.
FIG. 3 is a waveform diagram showing correction of a video signal when the optical axis is swung right and left.
FIG. 4 is a waveform diagram showing correction of a video signal when the optical axis is swung up and down.
FIG. 5 shows an optical axis when the liquid crystal projector device is inclined with respect to the screen surface.
FIG. 6 shows an image and a corrected image in each case of FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Keystone distortion correction circuit 2 Uneven color correction circuit 3 Mixer 4 S / H drive circuit 5 Liquid crystal panel 6 Microcomputer 7 Brightness correction circuit 8 Serial control unit 31 MIX circuit 71 DAC
72 Sawtooth wave generation circuit (horizontal)
73 Sawtooth Wave Generator (Vertical)

Claims (5)

A liquid crystal panel that drives a liquid crystal panel based on the video signal corrected by the keystone distortion correction circuit, irradiates the liquid crystal panel with light from a light source, and projects an image on the liquid crystal panel onto a screen surface through a light projection lens. In a projector device,
A liquid crystal projector device comprising: a brightness correction circuit for increasing or decreasing the brightness toward an end of an image according to the correction amount of the keystone distortion correction circuit. 2. The liquid crystal projector device according to claim 1, wherein the brightness correction circuit corrects the level of the video signal for each vertical cycle when the optical axis of the projection light is vertically inclined with respect to the screen surface. . 2. The liquid crystal projector device according to claim 1, wherein the brightness correction circuit corrects the level of the video signal every horizontal cycle when the optical axis of the projection light is inclined in the horizontal direction with respect to the screen surface. . 2. The brightness correction circuit according to claim 1, wherein the brightness correction circuit corrects the level of the video signal in each of a vertical cycle and a horizontal cycle when the optical axis of the projection light is inclined in an oblique direction with respect to the screen surface. Liquid crystal projector device. The brightness correction circuit includes a sawtooth wave generation circuit having a vertical cycle and / or a horizontal cycle, generates a sawtooth wave signal having an inclination corresponding to the correction amount of the keystone distortion correction circuit, and superimposes the sawtooth signal on a video signal. 2. The liquid crystal projector according to claim 1, wherein the level of the video signal is corrected by performing the correction.

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