JPH06217243A - Image display device - Google Patents

Abstract

PURPOSE:To provide the image display device which prevents color unevenness due to a secular change and suppresses picture quality deterioration. CONSTITUTION:This device is equipped with a lamp 21 for image display, an illumination time integrating circuit 28 which integrates the illumination time of the lamp 21, a driving circuit 1 which is previously stored with correction data regarding correction of color unevenness corresponding to the illumination time of the lamp 21 and reads the correction data out according to the illumination integrated time and corrects a video signal according to the read correction data, and liquid crystal panels 24a, 24b, and 24c which modulate the light emitted by the lamp 21 according to the corrected video signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display device for displaying an image using a video signal such as a television or a computer.

[0002]

2. Description of the Related Art In recent years, as a new image display device replacing a CRT, an image display device using a small liquid crystal panel has been attracting attention and research and development has been actively conducted. An optical image is formed on this liquid crystal panel by changing the transmittance according to the video signal, and this optical image is irradiated with light emitted from a lamp, and the optical image generated by passing through the liquid crystal panel is projected by a projection lens. A method of enlarging and projecting on a screen is well known (for example, see SID87 digest page 75).

As described above, in the image display device using the liquid crystal as the display element, a large screen image can be easily obtained, and C
It has features such as smaller size and lighter weight than the RT system, and already has 300,000 pixels on one liquid crystal panel, NTSC, EDTV compatible projection TV, and more than 1 million pixels. An HDTV-compatible projection television has been announced and commercialized.

An example of a conventional NTSC-compatible image display device using liquid crystal as a display element will be described below with reference to the drawings.

FIG. 5 is a block diagram of a conventional liquid crystal projection type television using three liquid crystal panels. In FIG. 5, 21
Is a lamp as a light source for projection, 22 is a condensing lens that makes the light emitted from the lamp 21 a parallel light beam, and 23a is a dichroic that reflects only red (hereinafter R) light and transmits light of other colors. Mirror (hereinafter referred to as RDM), 23
b is a dichroic mirror (hereinafter referred to as GDM) that reflects only green (hereinafter referred to as G) light and transmits light of other colors, and 23c reflects only blue (hereinafter referred to as B) light and other Dichroic mirror that transmits color light (hereinafter, B
DM), 24a is an R image display liquid crystal panel (hereinafter referred to as an R liquid crystal panel), 24b is a G image display liquid crystal panel (hereinafter referred to as a G liquid crystal panel), and 24c is a B image display liquid crystal panel (hereinafter referred to as a G image liquid crystal panel). Hereinafter referred to as B liquid crystal panel), 25
a is an R image projection lens, 25b is a G image projection lens, 2
5c is a B image projection lens, 26 is a screen on which an image is projected, 2 is a video signal input terminal, 3 is a color demodulation circuit, and 5 is a liquid crystal application circuit. 27 is a lighting circuit for the lamp 21.

The operation of the conventional liquid crystal projection type television configured as described above will be described.

In FIG. 5, the NTSC composite signal input from the video signal input terminal 2 is demodulated by the color demodulation circuit 3 into an R signal, a G signal, and a B signal, and the liquid crystal application circuit 5
Entered in. The liquid crystal application circuit 5 adjusts each input signal to a predetermined voltage level and a predetermined amplitude, and then applies each to the R liquid crystal panel 24a, the G liquid crystal panel 24b, and the B liquid crystal panel 24c to form an optical image corresponding to each color signal. To do.

On the other hand, the lamp 21 is lit by the lighting circuit 27 to emit white light, and the condenser lens 22 converts the emitted light into parallel light. Converted white parallel light is RD
After being separated into R light, G light, and B light by the M 23a, GDM 23b, and BDM 23c, respectively, the R liquid crystal panel 24a, the G liquid crystal panel 24b, and the B liquid crystal panel 24c.
To form an optical image. R liquid crystal panel 2
The optical images of the 4a, G liquid crystal panel 24b, and B liquid crystal panel 24c are combined into one image by the R image projection lens 25a, the G image projection lens 25b, and the B image projection lens 25c on which the optical images of three colors are superimposed. Is enlarged and projected.

By the above operation, the screen 26
An image corresponding to the input image signal will be displayed on.

[0010]

However, the lamp used as the lamp 21 cannot always radiate the radiant light whose white balance is secured to the entire screen uniformly. Due to the change over time, the color unevenness on the screen changes.

An example of color unevenness at each place on the screen will be described below. The input video signal is a white raster signal for simplicity of description.

Here, regarding the lamp, a metal halide lamp used as a backlight will be described for reasons of high efficiency and the like. (Hereinafter, simply referred to as a lamp.)
Although the RGB spectral spectrum is determined by the substance to be enclosed in the lamp, the light-emitting body of the lamp has color unevenness even in the initial state. Therefore, the color unevenness of the light-emitting body is enlarged and projected on the screen 26 as it is, so that the color unevenness occurs at each place. The initial shape correction of the luminous body can be carried out by measuring the color nonuniformity state and modulating the video signal with a modulation signal corresponding thereto, but the color nonuniformity state has a change with time.

Explaining one example thereof, the lamp is devitrified, that is, the inside of the arc tube becomes cloudy and the temperature inside the tube changes depending on the period of use. Since the emission spectra of R, G, and B also change with changes in temperature conditions, the uneven color state has a change over time, and, for example, coloration occurs in the peripheral portion of the image due to long-term use. Therefore, there is a problem in that the image quality is deteriorated due to the color unevenness at each place on the screen, which changes with time.

SUMMARY OF THE INVENTION The present invention has been made in view of such problems of the conventional image display device, and an object thereof is to provide an image display device capable of preventing color unevenness due to aging and suppressing deterioration of image quality. Is.

[0015]

SUMMARY OF THE INVENTION The present invention is directed to a light source for image display, an operation amount calculating means for calculating a past substantial operation amount of the light source, and correction of image display light corresponding to the operation amount of the light source. Storage means for storing the correction information regarding the correction information, a correction information reading means for reading the stored correction information according to the operation amount, and a video for displaying an image based on the read correction information. The image display device includes a video signal correction unit that corrects a signal, and a video modulation unit that modulates light emitted from a light source according to the corrected video signal.

[0016]

According to the present invention, the operating amount calculating means calculates the past actual operating amount of the light source, and the correction information reading means reads the correction information stored in the storing means in accordance with the operating amount.
The video signal correction means corrects the video signal for displaying an image based on the read correction information, and the video modulation means modulates the light emitted from the light source according to the corrected video signal. Then, the image is displayed by the light.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings showing its embodiments.

FIG. 1 is a block diagram of a liquid crystal projection television according to an embodiment of the present invention. That is, the liquid crystal projection television is provided with a video signal input terminal 2 for inputting a video signal, and the video signal input terminal 2 has a driving circuit 1 for driving the liquid crystal by the video signal (see FIG. 2 for details). R) liquid crystal panel 24a for displaying an R light optical image, G liquid crystal panel 24b for displaying a G light optical image, and B light for displaying an B light optical image. The liquid crystal panel 24c is connected. Further, a lamp 21 as a light source for emitting white light for image display is provided, and a lighting circuit 27 for turning on / off is connected to the lamp 21, and the lighting circuit 27 has a working amount calculating means. Is connected to a lighting time integration circuit 28 for integrating the lighting time of the lamp 21, and the output thereof is connected to the drive circuit 1.

On the other hand, the lamp 21 and each liquid crystal panel 24a,
A condenser lens 22 for converting the light emitted from the lamp 21 into parallel light, and RDMs 23a, GDM2 for separating the parallel light into R light, G light, and B light are provided between 24b and 24c.
3b and BDM 23c are arranged, and each liquid crystal panel 24
An R image projection lens 25a, a G image projection lens 25b, and a B image projection lens 25c are arranged on the front surfaces of a, 24b, and 24c, respectively, and further, at the positions for projecting images,
A screen 26 is provided.

FIG. 2 is a block diagram of the drive circuit 1 of the liquid crystal projection television of the above embodiment. In FIG. 2, a color signal demodulation circuit 3 for demodulating an NTSC composite signal into an R signal, a G signal, and a B signal is connected to a video signal input terminal 2, and each signal output of the color demodulation circuit 3 has a video signal correction As means, R amplitude modulation circuit 4a, G amplitude modulation circuit 4
The b and B amplitude modulation circuits 4c are connected. Each of the amplitude modulation circuits 4a, 4b, 4c is connected to a liquid crystal application circuit 5 for driving liquid crystal, and the liquid crystal application circuit 5 is connected to each of the liquid crystal panels 24a, 24b, 24c.
The liquid crystal application circuit 5 and the liquid crystal panels 24a, 24
b and 24c constitute the image modulating means.

On the other hand, the output of the lighting time integration circuit 28 of FIG. 1 is provided with a control circuit 6 which is a correction information reading means, and the control circuit 6 has a storage means for storing a correction amount of a change with time for each color. R-ROM 7a stored in advance,
G-ROM 7b and B-ROM 7c are connected and R
The OMs 7a, 7b, 7c are connected to the amplitude modulation circuits 4a, 4b, 4c via the D / A converter 8, respectively.

Here, the lighting time integration circuit 28 starts counting the time from the initial value 0 at the moment when the lighting circuit 27 lights the lamp 21, and the value of the time T at the moment when the lighting circuit 27 turns off the lamp 21. It is assumed to have a function of stopping the counting while holding the lamp and restarting the counting from the time T which was held last time at the moment when the lighting circuit 27 lights the lamp 21 again.

Further, the input video signal is a white raster signal. Further, for the sake of simplicity of description, regarding the color unevenness on the screen 26, only R is considered, and when the lighting time of the lamp 21 is initial, the white balance of the right side portion of the screen 26 shifts in the R direction, and the lighting time of the lamp 21. The area where the white balance shifts increases with the passage of. It is assumed that the state of the change is known because it is determined by the lamp. In addition, it is assumed that the RGB luminance distributions (hereinafter, referred to as ideal distributions) for realizing a uniform image having no color unevenness are preset, and the R-ROM 7a and the G-ROM 7 are provided.
b, it is assumed that the B-ROM 7c stores correction data for making the uneven color state that changes depending on the cumulative lighting time into an ideal distribution (the change in the uneven color state with the aging of the lamp has a certain tendency. It can be grasped by holding and measuring). Further, the correction data for the temporal variation of the color unevenness of the lamp 21 is such that the lighting time T is 0 ≦ T.
It is assumed that the data is stored in correspondence with three types of time of <T1, T1 ≦ T <T2, T2 ≦ T.

Next, the operation of the liquid crystal projection type television of the above embodiment will be described.

First, when the lamp lighting integrated time T is in the range of 0 ≦ T <T1, the lighting time integration circuit 28 outputs the integrated time T to the control circuit 6. The control circuit 6 outputs the correction data corresponding to the integration time T and the horizontal and vertical positions of the image to the R
-Read from ROM 7a. The read correction data is converted into an analog signal by the D / A converter 8,
It is input as a correction signal to the R amplitude modulation circuit 4a. The R amplitude modulation circuit 4 a modulates the input R video signal with the correction signal and outputs the modulated R video signal to the liquid crystal application circuit 5. The liquid crystal application circuit 5 includes an R liquid crystal panel 24a, a G liquid crystal panel 24b, and a B liquid crystal panel 24b.
A signal is applied to the liquid crystal panel 24c, and each liquid crystal panel 24c
An image is formed on a, 24b, and 24c.

Next, when the cumulative lamp lighting time T is in the range of T1≤T <T2, the color unevenness on the screen 26 changes due to the temporal change of the lamp 21.

FIG. 3 (a) is a diagram showing the brightness distribution of R before correction when the lamp lighting integrated time T is 0 ≦ T <T1.

FIG. 3 (b) is a diagram showing the luminance distribution of R before correction when the lamp lighting integrated time T is T1≤T <T2.

Here, AA 'in FIG. 3 is the screen 2
6 shows one horizontal portion and the luminance distribution shown by a dotted line is an ideal characteristic. From FIG. 3, it can be seen that the color unevenness area on the right side of the screen 26 changes (increases) according to the cumulative lighting time T of the lamp. This is because the area of the light emitting portion of the lamp 21 changes with time. However, if the correction data for making an ideal distribution for the state of this temporal change is stored in the R-ROM 7a and the lamp lighting integrated time T is T1 ≦ T <T2, the lighting time integrating circuit 28 is a control circuit 6
The integrated time T is output to. The control circuit 6 uses the correction time R-
It is read from the ROM 7a. The correction data read out is D
Is converted into an analog signal by the A / A converter 8 and R
It is input to the amplitude modulation circuit 4a as a correction signal. The R-amplitude modulation circuit 4 a modulates the input video signal with a correction signal and outputs it to the liquid crystal application circuit 5. The liquid crystal application circuit 5 includes an R liquid crystal panel 24a, a G liquid crystal panel 24b, and a B liquid crystal panel 2.
A signal is applied to 4c, and each liquid crystal panel 24a, 24b, 2
An image is formed on 4c. The correction signal at this time is shown in FIG.
FIG. 4B shows the luminance distribution of R after correction as shown in FIG.

Next, the cumulative lighting time T of the lamp is T2 ≦ T Therefore, even after T2, the video signal is modulated by using the correction data corresponding to the cumulative lighting time T of the lamp as a correction signal, and then applied to the liquid crystal panel. It is possible to provide an image in which the white balance in the projection plane is always maintained.

In the above embodiment, the correction of only the R light has been described, but it goes without saying that the G light and the B light are similarly corrected.

In the above embodiment, the cumulative lighting time of the lamp 21 is used as the actual operating amount in the past, but the present invention is not limited to this, and if the amount corresponds to the temporal variation of the color unevenness, for example, to the lamp. You may use the integrated electric energy etc. which are input.

In the above embodiment, the total lighting time is set to 3
Although the correction data is prepared separately for each range, the correction data is not limited to this, and for example, the correction data for every fixed time may be used. Alternatively, the correction data may be set for each change in the characteristics that actually needs correction.

Further, in the above-mentioned embodiment, the ROM is used as the storage means for the correction data, but it is not limited to this and, for example, R
Of course, other memory such as AM may be used.

In the above embodiment, the video signal is described as an analog signal, but the invention is not limited to this, and a digital signal may be used.

Further, in the above embodiment, the liquid crystal projection type television is used, but the present invention is not limited to this and is also effective when applied to a liquid crystal direct view type television, for example.

Further, in the above embodiment, the video signal is converted to NTS.
Although C is used, it is needless to say that the present invention is not limited to this and is also effective for high-definition signals and computer signals.

Further, in the above embodiment, the control circuit 6 and the lighting time integration circuit 28 are constituted by dedicated hardware, but instead of this, the same function may be realized by software using a computer. .

[0039]

As is apparent from the above description, the present invention provides the operation amount calculating means for calculating the past actual operation amount of the light source, and the correction information for reading the stored correction information according to the operation amount. Since the reading means and the video signal correcting means for correcting the video signal for displaying the image based on the read correction information are provided, color unevenness due to aging is prevented, and image deterioration is suppressed. It has the advantage of being able to

[Brief description of drawings]

FIG. 1 is a configuration diagram of a liquid crystal projection television according to an embodiment of the present invention.

FIG. 2 is a block diagram of a drive circuit of the liquid crystal projection television of the embodiment.

FIG. 3 (a) shows that the lamp lighting accumulated time T is 0 ≦.
The figure which shows the brightness distribution of R before correction in T <T1, and the figure (b) is a figure which shows the brightness distribution of R before correction in T1 <= T <T2.

FIG. 4 (a) is a diagram showing a correction signal, and FIG. 4 (b).
[Fig. 4] is a diagram showing a corrected R luminance distribution.

FIG. 5 is a configuration diagram of a conventional liquid crystal projection television.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 drive circuit 4a R amplitude modulation circuit 4b G amplitude modulation circuit 4c B amplitude modulation circuit 6 control circuit 7a R-ROM 7b G-ROM 7c B-ROM 21 lamp 27 lighting circuit 28 lighting time integration circuit

Claims (9)

[Claims] 1. A light source for displaying an image, an operating amount calculating means for calculating a past actual operating amount of the light source, and correction information regarding correction of image display light corresponding to the operating amount of the light source are stored in advance. Depending on the stored means and the operating amount,
A correction information reading unit that reads the stored correction information, a video signal correction unit that corrects a video signal for displaying an image based on the read correction information, and a correction unit that responds to the corrected video signal. And an image modulating means for modulating the light emitted from the light source. 2. The image display device according to claim 1, wherein the operating amount calculation means integrates the lighting time of the light source. 3. The image display device according to claim 1, wherein the video signal correction means includes a video signal amplitude modulation circuit that amplitude-modulates the video signal voltage. 4. The correction information is at least one of a red video signal voltage, a green video signal voltage, and a blue video signal voltage.
The image display device according to claim 1, which is for correcting one video signal voltage. 5. The image display device according to claim 1, wherein the correction information is stored in correspondence with a horizontal position and a vertical position of a displayed image. 6. The image display device according to claim 1, wherein the correction information is data according to a luminance attenuation characteristic of the light source. 7. The data includes a chromaticity distribution characteristic serving as a reference,
The image display device according to claim 6, wherein the image display device is calculated from chromaticity distribution characteristics of a display image for each lighting time. 8. The data is a reference luminance distribution characteristic,
7. The image display device according to claim 6, wherein the image display device is calculated from a brightness difference or a brightness ratio with respect to a brightness distribution characteristic of a display image for each lighting time. 9. The image display device according to claim 6, wherein the data is calculated from a luminance distribution characteristic of a raster image of a predetermined level displayed every lighting time.