JPH09139904A - Focus degradation prevention device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent focus blurs or the like in turning on the power of the picture tube of a television receiver or the like. SOLUTION: A microcomputer 107 instructs a video amplifier circuit 102 to adjust a signal level lower than normal in turning on the power of the picture tube 106 or the like and inhibits high-level signals from being inputted to a cathode immediately after the power is turned on when the cathode of the picture tube 106 is cold and prevents the generation of the focus blurs, red color blotting or the like in turning on the power.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention prevents focus blurring and blurring of red display (hereinafter, referred to as red area) for a few seconds immediately after power-on of a picture tube such as a cathode ray tube of a TV or a CRT monitor. Regarding the device.

[0002]

2. Description of the Related Art As a conventional focus deterioration preventing apparatus, Japanese Patent Laid-Open No. 4-373366 has been proposed, which describes an example of an apparatus for adjusting the brightness according to the level of a video signal to prevent focus blur.

The structure and operation of the above-mentioned Japanese Patent Laid-Open No. 4-373366 will be described with reference to FIG. FIG. 4 shows a cathode ray tube 40.
A cathode 1 has a beam current stabilization circuit 403, an average value detection circuit 405 for detecting an average value of a video signal is provided, and an output of the average value detection circuit 405 is connected to a brightness adjustment unit 406 of the drive circuit 402. As a result, a stable image of black level and white level can always be obtained with the cathode ray tube 401, and defocusing at the white peak can be prevented.

[0004]

However, in the above-mentioned conventional configuration, the average value detection circuit 405 is always operated and the level of the video signal is monitored to prevent focus deterioration such as focus blur. Unlike the invention, it does not prevent focus deterioration due to cooling of the cathode immediately after the power is turned on. Also, when a power signal is turned on and a video signal of a not so high level comes, the brightness cannot be suppressed, and as a result, even if the cathode cools and sufficient current does not flow, it is input to the picture tube with normal brightness, There was a problem that the focus blur immediately after turning on could not be avoided.

[0005]

In order to solve the above problems, a focus deterioration preventing apparatus according to the present invention includes a video amplifier circuit for amplifying a video signal to a size required as an input of a picture tube, and the video amplifier circuit. It is equipped with a contrast adjustment circuit included in the inside, which controls the contrast, a video amplification circuit in the first half of the year, and a microcomputer for instructing the contrast adjustment circuit to adjust the video signal. Sometimes the contrast is adjusted to a low level, the anode current amount information from the ABL circuit is monitored, and a sufficient current flows, or after a sufficient time has elapsed, the contrast adjustment is gradually returned to the normal level, so that the power supply This makes it possible to prevent focus blurring and red color due to the cold cathode when it is turned on.

As a result, it is possible to prevent the focus from blurring and the red color to occur immediately after the power is turned on when the cathode is cold.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention instructs to adjust the signal level lower than usual when the power of the picture tube is turned on, and the cathode of the picture tube cools. The high-level signal is not input to the cathode immediately after the power is turned on, and it is configured to prevent the occurrence of focus blur and red contact when the power is turned on. A command to turn on is issued to the video amplification circuit and the picture tube, but at this time the signal level is adjusted to be several tens of percent lower than usual and the power of the video amplification circuit and the picture tube is turned on to suppress the signal level. As a result, even if the cathode of the picture tube is cold, the level of the input signal is not so large that focus blurring or red contact does not occur. Further, the microcomputer reads the anode current amount information from the ABL circuit and adjusts the signal level to gradually return to a normal level when the cathode is sufficiently warmed so that a sufficient current flows or when a sufficient time has passed. To do. As described above, by adjusting the signal level to be lower than usual when the power is on, there is an effect that it is possible to prevent focus blurring and red contact when the power is on.

According to a second aspect of the present invention, when the power of the picture tube or the like is turned on, it is instructed to adjust the contrast to be lower than usual, and the cathode of the picture tube is cold. It is configured to prevent signals from being input to the cathode and to prevent focus blurring and red contact when the power is turned on.The image amplification circuit sends a command to turn on the power from the user or an external trigger by the microcomputer. Then, the contrast of the picture tube is cooled by adjusting the contrast to be several tens of percent lower than usual and turning on the power supply of the image amplifying circuit and the picture tube to suppress the contrast. However, since the level of the input signal is not high, focus blur and red contact do not occur.

The microcomputer is ABL
The anode current amount information from the circuit is read, and the cathode is warmed sufficiently to allow sufficient current to flow, or the contrast is gradually returned to the normal level after a sufficient time has elapsed. As described above, by adjusting the contrast to be lower than usual when the power is turned on, there is an effect that it is possible to prevent focus blurring and red contact when the power is turned on.

According to the third aspect of the present invention, when the power of the picture tube or the like is turned on, it is instructed to adjust the brightness to be lower than usual, and the cathode of the picture tube is cold, and the level is high immediately after the power is turned on. So that no signal is input to the cathode,
It is configured to prevent out-of-focus and red areas when the power is turned on.The microcomputer issues a command to turn on the power from the user or an external trigger to the image amplification circuit and the picture tube. By adjusting the power of the picture amplifier circuit and the picture tube by turning on the picture tube by adjusting the value to be several tens of percent lower than usual, the level of the input signal is not high even if the cathode of the picture tube is cold. No out-of-focus or red hits occur. Further, the microcomputer reads the anode current amount information from the ABL circuit and adjusts so that the cathode is sufficiently warmed so that a sufficient current can flow, or if a sufficient time has passed, the brightness is gradually returned to the normal level. . As described above, when the power is turned on, the brightness is adjusted to be lower than usual, so that there is an effect that it is possible to prevent the focus blur and the red hit when the power is turned on.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. (Embodiment 1) FIG. 1 is a block diagram of a focus deterioration preventing apparatus according to an embodiment of the present invention.

In FIG. 1, reference numeral 101 is a luminance signal, 1
02 is a video amplifier circuit, 103 is an ABL circuit, and 104 is R
GB output circuit, 105 is a color difference signal, 106 is a picture tube, 1
Reference numeral 07 represents a microcomputer.

The operation of the focus deterioration preventing apparatus constructed as above will be described below.

In FIG. 1, the luminance signal 101 separated from the chrominance signal in the preceding image amplification circuit is the image amplification circuit 102.
Then, the microcomputer 107 performs various image quality adjustments, signal amplification, and the like. The video amplification circuit 102 is controlled by the ABL circuit 103 to the extent of amplification. The amplified and adjusted luminance signal enters the RGB output circuit 104, is mixed with the color difference signal 105, is amplified, and is applied to the cathode of the picture tube 106.

When the television receiver or the like is turned on, the circuit group and the picture tube 106 are also turned on. Then, the luminance signal 101 is amplified by the video amplifier circuit 102 and a signal having a large amplitude is suddenly input to the cathode of the picture tube 106. However, since the cathode of the picture tube 106 is not yet sufficiently warm, a large current does not suddenly flow.

Therefore, when a signal having a brightness of a certain level or more is suddenly input to the picture tube 106 when the power is turned on,
Phenomena such as out-of-focus and red areas tend to occur.

In order to avoid the above-described focus blur and red color, the level of the input signal is kept low for a proper time when the power is turned on so that a signal of a large level is not suddenly input to the picture tube 106 when the power is turned on. Adjust it to.

Therefore, the microcomputer 107
When the power supplies of the video amplifier circuit 102 and the picture tube 106 are turned on, the video amplifier circuit 102 is instructed to adjust the signal level lower than usual. If the level of the input signal applied to the picture tube 106 is low, the cathode of the picture tube 106 does not try to flow a large current even when it is cold.

After that, the microcomputer 107
Read the anode current amount information from the ABL circuit 103,
When the cathode becomes warm and a sufficient current flows, the image amplification circuit 102 is instructed to gradually return the signal level to the normal state.

Since the current is originally low in the case of a dark screen, the image amplification circuit 102 is instructed to gradually return the signal level to the normal state even if a certain time has elapsed since the power was turned on.

(Second Embodiment) FIG. 2 is a block diagram of a focus deterioration preventing apparatus according to an embodiment of the present invention.

In FIG. 2, reference numeral 201 indicates a luminance signal, 2
Reference numeral 02 is a video amplifier circuit, 203 is an image quality adjusting circuit, 204 is a contrast adjusting circuit, 205 is a pedestal clamp circuit, 206 is a brightness adjusting circuit, 207 is an ABL circuit, and 20 is.
Reference numeral 8 is an RGB output circuit, 209 is a color difference signal, 210 is a picture tube, and 211 is a microcomputer.

The operation of the focus deterioration preventing device constructed as described above will be described below.

In FIG. 2, the luminance signal 201 separated from the chrominance signal in the preceding image amplification circuit is the image amplification circuit 202.
to go into. The luminance signal 201 in the image amplification circuit 202
First, the image quality adjusting circuit 203 is entered. The degree of adjustment is controlled by the microcomputer 211.

Next, the brightness signal is applied to the contrast adjustment circuit 2
04, the contrast of the luminance signal 201 is also controlled by the signal from the microcomputer 211. The pedestal clamp circuit 20 outputs the signal whose contrast has been adjusted.
At 5, the DC component is regenerated. Pedestal clamp circuit 20
5, a brightness adjustment circuit 206 is added, and the brightness adjustment in this case is also controlled by a signal from the microcomputer 211.

The ABL circuit 207 controls the brightness adjusting circuit 206 so as to suppress the increase in brightness when the anode current of the picture tube 210 increases.

The amplified and adjusted luminance signal enters the RGB output circuit 208, is mixed with the color difference signal 209, is amplified, and is applied to the cathode of the picture tube 210.

When the television receiver or the like is turned on, the circuit group and the picture tube 210 are also turned on. Then, the luminance signal 201 is amplified by the video amplifier circuit 202 and a signal having a large amplitude is suddenly input to the cathode of the picture tube 210. However, since the cathode of the picture tube 210 is not yet sufficiently warm, a large current does not flow suddenly.

Therefore, when a signal having a brightness of a certain level or more is suddenly input to the picture tube 210 when the power is turned on,
Phenomena such as out-of-focus and red areas tend to occur.

In order to avoid the above-described focus blur and red color, the level of the input signal should be kept low for a proper time when the power is turned on so that a signal of a large level is not suddenly input to the picture tube 210 when the power is turned on. Adjust it to.

Therefore, the microcomputer 211 is
When the power of the image amplification circuit 202 and the picture tube 210 is turned on, the contrast adjustment circuit 204 is instructed to adjust the contrast to be lower than usual. Picture tube 2
Since the level of the input signal applied to 10 is low, the picture tube 21
Even if the cathode of 0 is cold, it does not try to carry a large current.

After that, the microcomputer 211
Read the anode current amount information from the ABL circuit 207,
When the cathode becomes warm and a sufficient current flows, the contrast adjustment circuit 204 is instructed to gradually return the contrast adjustment to the normal state.

Since the current is originally low in the case of a dark screen, the contrast adjusting circuit 204 is instructed to gradually return the contrast adjustment to the normal state even after a lapse of a certain time after the power is turned on.

(Third Embodiment) FIG. 3 is a block diagram of a focus deterioration preventing apparatus according to an embodiment of the present invention.

In FIG. 3, reference numeral 301 denotes a luminance signal, 3
Reference numeral 02 is a video amplifier circuit, 303 is an image quality adjusting circuit, 304 is a contrast adjusting circuit, 305 is a pedestal clamp circuit, 306 is a brightness adjusting circuit, 307 is an ABL circuit, and 30 is.
8 is an RGB output circuit, 309 is a color difference signal, 310 is a picture tube, and 311 is a microcomputer.

The operation of the focus deterioration preventing apparatus constructed as described above will be described below.

In FIG. 3, the luminance signal 301 separated from the chrominance signal in the preceding image amplification circuit is the image amplification circuit 302.
to go into. The luminance signal 301 in the image amplification circuit 302
First, the image quality adjusting circuit 303 is entered. The degree of adjustment is controlled by the microcomputer 311.

Next, the brightness signal is applied to the contrast adjustment circuit 3
04, the contrast of the brightness signal 301 is also controlled by the signal from the microcomputer 311. The pedestal clamp circuit 30 outputs the signal whose contrast has been adjusted.
At 5, the DC component is regenerated. Pedestal clamp circuit 30
5, a brightness adjusting circuit 306 is added, and the brightness adjustment in this case is also controlled by a signal from the microcomputer 311. The ABL circuit 307 is the picture tube 31.
When the anode current of 0 increases, the brightness adjustment circuit 306 is controlled to suppress the increase in brightness.

The amplified and adjusted luminance signal enters the RGB output circuit 308, is mixed with the color difference signal 309, is amplified, and is applied to the cathode of the picture tube 310.

When the television receiver or the like is turned on, the circuit group and the picture tube 310 are also turned on. Then, the luminance signal 301 is amplified by the video amplifier circuit 302, and a signal with a large amplitude is suddenly input to the cathode of the picture tube 310. However, since the cathode of the picture tube 310 is not yet sufficiently warm, a large current does not flow suddenly.

Therefore, when a signal having a brightness of a certain level or more is suddenly input to the picture tube 310 when the power is turned on,
Phenomena such as out-of-focus and red areas tend to occur.
In order to avoid the above-mentioned focus blur and red color, it is necessary to adjust the level of the input signal to be low for a proper time when the power is turned on so that a signal of a large level is not suddenly input to the picture tube 310 when the power is turned on. Good.

Therefore, the microcomputer 311
When the power supply of the image amplification circuit 302 and the picture tube 310 is turned on, the brightness adjustment circuit 304 is instructed to adjust the brightness lower than usual. Since the level of the input signal applied to the picture tube 310 is low, the cathode of the picture tube 310 does not try to flow a large current even when it is cold.

Thereafter, the microcomputer 311
Read the anode current amount information from the ABL circuit 307,
When the cathode becomes warm and a sufficient current flows, the brightness adjustment circuit 304 is instructed to gradually return the brightness adjustment to the normal state. Since the current is originally low in the case of a dark screen, the brightness adjustment circuit 304 is instructed to gradually return the brightness adjustment to the normal state even after a certain time has elapsed since the power was turned on.

[0044]

As described above, according to the focus deterioration preventing apparatus of the present invention, the contrast or the brightness is adjusted to be low when the power is turned on, so that the level of the signal applied to the picture tube is kept low and the cathode is not warmed. It is possible to avoid a phenomenon such as defocusing and red hitting immediately after turning on.

[Brief description of the drawings]

FIG. 1 is a block configuration diagram of a focus deterioration preventing apparatus according to an embodiment of the present invention.

FIG. 2 is a block configuration diagram of a focus deterioration preventing apparatus according to an embodiment of the present invention.

FIG. 3 is a block configuration diagram of a focus deterioration preventing apparatus according to an embodiment of the present invention.

FIG. 4 is a block configuration diagram of a conventional focus deterioration preventing device.

[Explanation of symbols]

 101 luminance signal 102 image amplification circuit 103 ABL circuit 104 RGB output circuit 105 color difference signal 106 picture tube 107 microcomputer 201 luminance signal 202 image amplification circuit 203 image quality adjustment circuit 204 contrast adjustment circuit 205 pedestal clamp circuit 206 luminance adjustment circuit 207 ABL circuit 208 RGB output circuit 209 Color difference signal 210 Picture tube 211 Microcomputer 301 Luminance signal 302 Video amplification circuit 303 Image quality adjustment circuit 304 Contrast adjustment circuit 305 Pedestal clamp circuit 306 Brightness adjustment circuit 307 ABL circuit 308 RGB output circuit 309 Color difference signal 310 Picture tube 311 micro Computer

Claims (3)

[Claims] 1. When turning on the power supply of a picture tube or the like, the signal level is adjusted to be lower than usual so that a high level signal is not input to the cathode immediately after the power is turned on when the cathode of the picture tube is cold. A focus deterioration prevention device characterized by preventing the occurrence of focus blurring or red contact when the power is turned on. 2. A video amplifier circuit for amplifying a video signal to a size required as an input of a picture tube, a contrast adjustment circuit included in the video amplifier circuit for adjusting contrast, a video amplifier circuit for the first half and a contrast adjustment circuit. 2. A microcomputer for instructing the adjustment of a video signal is provided, and focus blur is prevented by adjusting the contrast to be low when the cathode of the picture tube is cold, such as immediately after the power is turned on. The focus deterioration prevention device described. 3. A video amplifier circuit for amplifying a video signal to a size required as an input of a picture tube, a brightness adjusting circuit included in the video amplifier circuit for adjusting brightness, a video amplifier circuit and a brightness adjusting circuit for the first period. 2. A microcomputer for instructing adjustment of a video signal is provided, and focus blurring or the like is prevented by adjusting the brightness to be low when the cathode of the picture tube is cold, such as immediately after power-on. The focus deterioration prevention device described.