JPH08195967A - Method and device for correcting white balance for cathode-ray tube device - Google Patents

Abstract

PURPOSE: To prevent the decline of the white balance of synthetic color pictures by individually detecting the luminance of fluorescent screens by plural luminance sensors arranged at the front of the fluorescent screens of plural projection cathode-ray tubes. CONSTITUTION: The plural luminance sensors 6 by CCD photoelectric converters or the like arranged at the front of the fluorescent screens of respective single color cathode-ray tubes 4B, 4C, and 4R are provided. The outputs of the luminance sensors 6 are individually inputted to a microcomputer 9 through an A/D converter 7 and compared with a reference value for white balance correction stored in a memory 8, a decline amount to a reference level is calculated and a chrominance signal output circuit 3 is controlled through a D/A converter 10. Further, a signal band for luminance detection is projected on a part of the fluorescent screen along with the pictures projected on the screen, the maximum luminance at the time of the actual operation of the respective single color cathode-ray tubes is detected in synchronism with the signals and the chrominance signal output circuit 3 is controlled so as to be a fixed ratio to the maximum luminance of respective colors. Thus, the change of the white balance due to fluorescent screen degradation in the elapse of time at the time of the actual operation is minimized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a white balance correction device and a correction method for a cathode ray tube device, and more particularly to a cathode ray tube effective for a projection type cathode ray tube device having a plurality of high-intensity monochromatic cathode ray tubes such as a color projector. The present invention relates to a white balance correction device and a correction method.

[0002]

2. Description of the Related Art A three-tube type color projector generally known as a projection type cathode ray tube device supplies a blue image, a green image and a red image on a phosphor screen by supplying blue, green and red color signals, respectively. A structure in which three monochromatic cathode ray tubes for displaying are displayed, and an image thereof is projected on a screen through an optical lens system arranged in front of the fluorescent surface of each cathode ray tube and is combined on the screen to obtain a color image. Is formed in.

In such a projection type cathode ray tube device, it is necessary to display a high brightness image on the phosphor screen of each monochromatic cathode ray tube. Therefore, the energy of the electron beam scanning the fluorescent screen is set higher than that in the case of a normal direct-view cathode ray tube. However, when the energy of the electron beam that scans the fluorescent screen is increased, the fluorescent material deteriorates due to the temperature rise, and so-called fluorescent screen burning occurs in which the brightness decreases. Since the degree of the decrease in brightness due to the burning of the fluorescent surface varies depending on each color phosphor, the brightness of each monochromatic cathode ray tube varies, and the white balance of the color image obtained by combining on the screen changes.

In order to prevent the decrease in brightness due to the burning of the fluorescent screen, conventionally, as shown in Japanese Patent Publication No. 63-48377 and Japanese Patent Publication No. 1-39183, a face having a fluorescent screen is formed. A method of providing a liquid-tight space on the outer surface of the plate, filling this space with a transparent liquid cooling medium having high thermal conductivity, and reducing the temperature rise of the fluorescent screen through the face plate has been put into practical use.

[0005]

As described above, since the three-tube type color projector displays a high-intensity image on the fluorescent screens of the three monochromatic cathode ray tubes, the electron beam scanning the fluorescent screens is used. The energy is set higher than in the case of a normal direct-view cathode ray tube. However, when the energy of the electron beam for scanning the fluorescent screen is increased, the fluorescent substance is deteriorated due to the temperature rise, and so-called fluorescent screen burning occurs in which the brightness is reduced. Since the degree of the decrease in brightness due to the burning of the fluorescent surface varies depending on each color phosphor, the brightness of each monochromatic cathode ray tube varies, and the white balance of the color image obtained by combining on the screen changes. Conventionally, in order to prevent the decrease in brightness due to the burning of the fluorescent screen, a liquid-tight space is provided on the outer surface of the face plate on which the fluorescent screen is formed, and this space is filled with a transparent liquid cooling medium having high thermal conductivity. A method of reducing the temperature rise of the phosphor screen through the plate has been put into practical use.

However, such a method can suppress the decrease in brightness due to the burning of the fluorescent screen to some extent, but cannot completely prevent it. Further, since the deterioration of the three-color phosphor cannot be suppressed to the same degree, it is possible to prevent the white balance change of the color image on the screen obtained by synthesizing the images displayed on the phosphor screen of each monochromatic cathode ray tube. This is one of the reasons why the image quality is deteriorated and the life of the color projector is significantly shortened.

The present invention has been made in view of the above-mentioned problems, and even if a decrease in luminance due to the burning of the fluorescent surface occurs to some extent, a change in white balance of a color image obtained by combining is corrected to obtain a long-term correction. The purpose is to be able to maintain a constant image quality.

[0008]

In a white balance correction device for a cathode ray tube device having a plurality of cathode ray tubes, the white balance correction device is arranged in front of the fluorescent surface of each cathode ray tube, and the brightness of the fluorescent surface of each cathode ray tube is separately adjusted. A plurality of brightness sensors to detect, and a correction circuit that electrically corrects the brightness of the cathode ray tube by calculating the amount of decrease in the brightness of the cathode ray tube due to aging of the cathode ray tube and its peripheral devices based on the output of the brightness sensor. Prepared for the configuration.

In addition, a luminance detection signal band is projected together with an image on a part of the fluorescent surface of each cathode ray tube of a cathode ray tube device having a plurality of cathode ray tubes, and the luminance of this luminance detection signal band is reflected by the fluorescence of each cathode ray tube. A method of detecting with multiple brightness sensors separately arranged on the front of the screen, and a brightness level signal from the output of each brightness sensor, and a composite color image obtained by projecting the image on the fluorescent surface of each cathode ray tube. When the white balance of is at a constant level, the brightness of the signal band for detecting the brightness of each cathode ray tube is used as the reference brightness level, and the decrease amount of the brightness level signal with respect to this reference brightness level is calculated. By adjusting the brightness of the tube, the white balance of the composite color image is corrected.

[0010]

When the white balance correction device of the cathode ray tube device is constructed as described above and the white balance is corrected by the above method, the decrease in the luminance of the cathode ray tube due to the aging of the cathode ray tube and its peripheral equipment is electrically compensated. As a result, it is possible to prevent the white balance of the composite color image from changing due to the difference in the deterioration of the fluorescent screen of each cathode ray tube.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described based on embodiments with reference to the drawings.

FIG. 1 is a projection type in which a monochromatic image projected on each phosphor screen of a plurality of monochromatic cathode ray tubes, which is one embodiment thereof, is projected on a screen via an optical system to display a composite color image on the screen. 1 shows a white balance correction device for a cathode ray tube device.

In order to display an image on the phosphor screen of each cathode ray tube, the video signal supplied to the input terminal 1 is converted into the video amplifier 2.
And the amplified video signal is separated by the color signal output circuit 3 into color signals B, G and R of three colors of blue, green and red, and further amplified to obtain monochromatic cathode ray tubes 4B, 4G ,. This is done by supplying to the cathode of a 4R electron gun.

The white balance correction device comprises a brightness sensor 6 comprising photoelectric converters such as a plurality of CCD cameras arranged in front of the fluorescent screens of the above-mentioned monochromatic cathode ray tubes 4B, 4G and 4R, and a brightness sensor 6 from the brightness sensor 6. An analog / digital conversion circuit 7 (AD conversion circuit) for converting the photoelectrically converted output into a digital signal as a brightness level signal, and a white balance correction reference stored in the memory 8 for output of the analog / digital conversion circuit 7. A microcomputer 9 for calculating the difference (amount of decrease in the brightness level signal value with respect to the reference brightness level) in comparison with the brightness level, and an output of the microcomputer 9 is converted into an analog signal and amplified, and the projection type A digital / analog conversion circuit 10 (D) for sending to the color signal output circuit 3 of the cathode ray tube device.
A conversion circuit).

As shown in FIG. 2, each of the plurality of brightness sensors 6 has a single color cathode ray tube 4 (4B, 4G, 4R).
), The image 13 to be projected on the screen is displayed on the phosphor screen 12, and the brightness detection signal band 14 is projected on a part of the phosphor screen 12 along the image 13, and the brightness of the brightness detection signal band 14 is displayed. It is placed opposite to its front face to detect. The brightness detection signal band 14 has the maximum brightness determined by the color signal output circuit so that the brightness level has a time-dependent change equivalent to the deterioration of the brightness of the image due to the deterioration of the fluorescent screen during the actual operation of each monochromatic cathode ray tube 4. On the other hand, it is set so that the ratio is always constant.

The white balance correction in this cathode ray tube device is performed as follows.

First, each monochromatic cathode ray tube 4B of the cathode ray tube device,
At the time of initial adjustment in which the 4G, 4R phosphor screen 12 is not deteriorated, an image 13 for projecting on the screen is projected on the phosphor screen 12 of each monochromatic cathode ray tube 4B, 4G, 4R, and at the same time, along this image 13. The brightness detection signal band 14 is projected, and the white balance of the color image projected by the screen and synthesized is adjusted to a predetermined level. And each monochromatic cathode ray tube 4B, 4G, 4R at that time
The brightness of the brightness detection signal band 14 is detected by the brightness sensors 6 each of which is composed of a photoelectric converter arranged on the front surface thereof, and photoelectrically converted, and the photoelectrically converted output is converted into a digital signal by the analog / digital conversion circuit 7. And the converted signal is stored in the memory 8 via the microcomputer 9 as a reference brightness level for white balance correction.

Then, when the cathode ray tube device is in operation, as in the initial adjustment of the cathode ray tube device, each monochromatic cathode ray tube 4 is operated.
At the same time as displaying the image 13 for projecting on the screen 12 on the phosphor screens of B, 4G and 4R, the brightness detecting signal band 14 is projected along the image 13 and the brightness of the brightness detecting signal band 14 is changed. , A brightness sensor 6 composed of a photoelectric converter arranged on the front surface thereof. Then, the photoelectrically converted output is converted into a digital signal as a luminance level signal by the analog / digital conversion circuit 7, and the converted signal is sent to the microcomputer 9. In the microcomputer 9, the white balance correction reference brightness level stored in advance is called from the memory 8 and the reference brightness level and the brightness level signal sent from the analog-digital conversion circuit 7 in the actual operation are read. In comparison, the difference (the amount of decrease in the brightness level signal value with respect to the reference brightness level) is calculated as a correction amount, and the difference signal is calculated by the change over time of the monochromatic cathode ray tubes 4B, 4G, 4R and its peripheral devices. It is sent to the digital-analog conversion circuit 10 as a correction signal for correcting the amount of decrease in brightness of the tubes 4B, 4G, 4R. Then, the digital-analog converter circuit 10 converts the above-mentioned correction signal into a digital signal and amplifies it, and supplies the digital signal to the color signal output circuit 3 for each monochromatic cathode ray tube 4.
This is done by amplifying the required drive voltages of B, 4G, and 4R.

When the brightness of each of the monochromatic cathode ray tubes 4B, 4G, 4R is restored to a predetermined level by such a correction, no correction signal is output, so that the brightness of each of the monochromatic cathode ray tubes 4B, 4G, 4R is reduced. It will never go above a certain level.

Therefore, when the projection type cathode ray tube device is provided with the white balance correction device as described above, the brightness of the single color cathode ray tubes 4B, 4G, 4R due to the burning of the fluorescent screen and the deterioration of the peripheral devices due to the deterioration of the peripheral devices are caused. , 4G,
It is possible to electrically correct the decrease in the brightness of 4R and prevent the change of the white balance of the composite color image caused by the deterioration of the brightness depending on each of the monochrome cathode ray tubes 4B, 4G and 4R.

In the above embodiment, the luminance of each monochromatic cathode ray tube of the cathode ray tube device is corrected by amplifying the drive voltage by the correction signal digitized by the digital-analog conversion circuit. The control grid may be controlled by the correction signal to adjust the brightness of each monochromatic cathode ray tube.

In the above embodiment, the correction device is composed of an analog / digital conversion circuit for converting the output from the luminance sensor, a microcomputer, a memory, a digital / analog conversion circuit, etc. The output from the luminance sensor may be integrated by using an integrating circuit and sent to the color signal output circuit. Further, in the above embodiment, the white balance correction of the projection type cathode ray tube device provided with a plurality of monochromatic cathode ray tubes has been described, but the present invention is applied to a multi-vision projection type receiver using a combination of a plurality of receivers. It is also possible to apply the above, and it is possible to display a very uniform image on a large screen for a long period of time by minimizing the changes in the brightness and white balance of each screen.

[0023]

A white balance correction device for a cathode ray tube device having a plurality of cathode ray tubes is arranged in front of the fluorescent surface of each cathode ray tube, and a plurality of white balance correction devices for individually detecting the brightness of the fluorescent surface of each cathode ray tube are provided. A brightness sensor and a circuit that electrically corrects the brightness of the cathode ray tube by calculating the brightness decrease amount of the cathode ray tube due to the change over time of the cathode ray tube and its peripheral devices based on the output of each brightness sensor, and , The brightness detection signal band is projected together with the image on a part of the phosphor screen of each cathode ray tube, and the brightness of this brightness detection signal band is separately arranged on the front surface of the phosphor screen of each cathode ray tube by a plurality of brightness sensors. When the white balance of the composite color image obtained by detecting and obtaining the brightness level signal from the outputs of the multiple sensors is projected on the fluorescent screen of each cathode ray tube at a predetermined level. Using the luminance of the signal band for detecting the luminance of the cathode ray tube as the reference luminance level, the amount of decrease in the luminance level signal with respect to this reference luminance level is calculated, and the luminance of each cathode ray tube is adjusted based on this amount of reduction to obtain a composite color. By correcting the white balance of the image, it is possible to electrically compensate for the decrease in the brightness of the cathode ray tube due to the aging of the cathode ray tube and its peripheral equipment, and to improve the white balance of the composite color image due to the difference in the fluorescent screen deterioration of each cathode ray tube. It is possible to prevent the change and realize a long-life cathode ray tube device having a uniform image for a long period of time.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a white balance correction device of a cathode ray tube device which is an embodiment of the present invention.

FIG. 2 is a diagram for explaining a cathode ray tube brightness detection method of the cathode ray tube device.

[Explanation of symbols]

 4B, 4G, 4R ... Monochromatic cathode ray tube 6 ... Luminance sensor 12 ... Phosphor screen 13 ... Image 14 ... Luminance detection signal band

Claims (2)

[Claims] 1. A plurality of brightness sensors arranged on the front surface of the phosphor screen of each cathode ray tube of a projection-type cathode ray tube device having a plurality of cathode ray tubes, the brightness sensors individually detecting the brightness of the phosphor screen of each cathode ray tube. And a correction circuit for electrically correcting the brightness of the cathode ray tube by calculating the brightness decrease amount of the cathode ray tube due to the change with time of the cathode ray tube and its peripheral devices based on the output of each brightness sensor. A white balance correction device for a cathode ray tube device. 2. A brightness detection signal band is projected together with an image on a part of a phosphor screen of each cathode ray tube of a projection type cathode ray tube device having a plurality of cathode ray tubes, and the brightness of this brightness detection signal band is adjusted to each cathode ray tube. And a method of detecting by a plurality of brightness sensors separately arranged on the front surface of the phosphor screen, and a brightness level signal is obtained from the output of each brightness sensor, and an image is projected on the phosphor screen of each cathode ray tube. The luminance of the luminance detection signal band of each cathode ray tube when the white balance of the composite color image is at a predetermined level is set as a reference luminance level, and the reduction amount of the luminance level signal with respect to this reference luminance level is calculated. A method for adjusting the brightness of the cathode ray tube based on the above method for correcting the white balance of the composite color image. .