JP2000261738A - Picture display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To automatically correct fluctuation in brightness due to a temperature change or a changeover aging. SOLUTION: The display device consists of a video amplifier circuit 1, an additional pulse generating circuit 2, a switch circuit 3 that superimposes the pulse signal on a blanking period of an input video signal, an A/D converter 4, a level detection circuit 5 that accumulates the digitally converted video signal, a microcomputer 6, a dot clock generator 7 that provides a control clock, and a D/A converter 8. The display device detects a mean luminance of the pulse added for a blanking period of the video signal and brightness and contrast setting value to the video amplifier circuit 1 are controlled depending on the detected value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for automatically correcting a change in brightness due to a temperature change or aging of a video amplifier circuit in an image display device such as a computer display monitor.

[0002]

2. Description of the Related Art In an image display device such as a computer display monitor, a temperature change or an aging change causes
The preset brightness and contrast may fluctuate. As means for automatically adjusting this change, for example, as disclosed in Japanese Patent Application Laid-Open No. 9-146487, a cathode current of a cathode ray tube is detected for a certain period, current-to-voltage conversion is performed, and according to a comparison error with a reference voltage. There is a method of performing an automatic adjustment loop by raising and lowering the black level of a video signal so that the reference luminance level is always constant.

[0003]

In recent years, as image display devices such as computer display monitors, those using liquid crystal panels instead of cathode ray tubes as display elements have been commercialized by various companies.

For example, in the case of a liquid crystal display monitor, the cathode current does not exist, the data to be passed to the panel is a digital signal, and digital control is performed from the latter stage of the video amplifier.

[0005]

In order to solve this problem, the present invention detects an average luminance of a pulse signal superimposed in a blanking period of a video signal, and calculates an average luminance of the pulse signal according to a difference between the detection result and a reference value. An image display device characterized by controlling set values of brightness and contrast. According to the present invention, it is possible to automatically correct a change in brightness due to a temperature change, a secular change, or the like of a video amplifier circuit.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS According to a first aspect of the present invention, an average luminance of a pulse signal superimposed during a blanking period of a video signal is detected, and the brightness is determined according to a difference between the detection result and a reference value. And an image display device characterized by controlling a set value of contrast and contrast. With this configuration, it is possible to automatically correct a change in brightness due to a temperature change or an aging change of a video amplifier circuit. It has the effect of becoming.

Next, the invention according to claim 2 of the present invention is:
A video amplifier circuit for amplifying an input video signal and adjusting brightness and contrast, an additional pulse generation circuit, a switch circuit for superimposing a pulse signal in a blanking period of the input video signal, and an A for converting the video signal from analog to digital /
A D converter, a level detection circuit for accumulating and adding the digitally converted video signal in a predetermined area for each dot clock, a microcomputer, a dot clock generator for providing a control clock to the A / D converter and the level detection circuit And digital control signals from the microcomputer
2. The image display device according to claim 1, further comprising: a D / A converter for performing analog conversion, wherein the total sum of the luminance of a pulse portion added during a blanking period of the video signal is detected, and the total number of pixels in a detection area is detected. By calculating the average brightness of the detection area by dividing by the above, the brightness and contrast set values to the video amplifier circuit are controlled from the microcomputer via the D / A converter according to the change of the average brightness detection value. In addition, there is an effect that it is possible to automatically correct a change in brightness due to a temperature change, a secular change, or the like of the video amplifier circuit. In addition, since digital data is detected for each dot clock, a large amount of data is detected and averaged, which has an effect of controlling noise with high stability.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image display device according to an embodiment of the present invention will be described below with reference to FIGS.

(Embodiment 1) FIG. 1 is a block diagram showing an image display apparatus according to a second embodiment of the present invention.
In FIG. 1, reference numeral 1 denotes a video amplifier circuit, which can control the amplitude and black level of an input video signal (RGB analog video signal). Reference numeral 2 denotes an additional pulse generation circuit.
The generated pulse signal is generated by a switch circuit indicated by reference numeral 3,
It is superimposed on the blanking period of the input video signal. Code 4
Denotes an A / D converter, which performs analog-to-digital conversion on the output of the video amplifier circuit. Reference numeral 5 denotes a level detection circuit, which can obtain the total sum of the luminance of the detection area by accumulatively adding the signal level of the designated area for each dot clock.

In the case of the present invention, the level of the pulse signal added during the blanking period is cumulatively added for each dot clock. By dividing this by the total number of pixels in the detection area, the average luminance of the detection area can be obtained. Code 6
Denotes a microcomputer, which controls the brightness and contrast set values of the video amplifier according to the detection result of the average luminance. Reference numeral 7 denotes a dot clock generator, which supplies a control clock to the A / D converter and the level detection circuit. Reference numeral 8 denotes a D / A converter, which performs digital-to-analog conversion of a control signal from the microcomputer.

FIG. 2 shows a diagram of an additional pulse for level detection and a diagram of a detection area. The signal generated by the additional pulse generation circuit is superimposed during the blanking period of the input video signal. This pulse signal is a signal that outputs the same level for a certain period of time, and the output level is changed in conjunction with the user adjusting the contrast by OSD or the like. FIG.
The block diagram of the level detection circuit is shown in FIG. FIG. 4 shows a relationship diagram between the dynamic range of the A / D converter and the additional pulse.
As an example, assume that the input dynamic range of the A / D converter to be used is 1 to 3 V and the output is 8 bits.

According to the present invention, by maintaining the average luminance value of the signal area added during the blanking period at a constant value which is the input section of the A / D converter, the brightness of the video amplifier circuit changes due to temperature change and aging. The purpose of the present invention is to automatically correct the fluctuation of.

FIG. 5 shows an adjustment procedure diagram. As an example, a case where the average luminance value of the additional pulse area is kept at 80H will be described. For the pulse signal added during the blanking period,
First, a luminance detection region is set in the region of the lowest gradation, and the sub-brightness is adjusted so that the luminance detection result becomes 0H for RGB. Next, a luminance detection region is set in the region of the highest gradation, and the sub-contrast is adjusted so that the luminance detection result for RGB becomes 80H.

According to this configuration, in the image display device, it is possible to automatically correct a change in brightness due to a temperature change, an aging change, or the like of the video amplifier circuit.
Further, by detecting and averaging a large amount of digital data, it is possible to perform control with high stability against noise and high stability.

[0015]

As described above, according to the present invention, in an image display device, the average luminance of a pulse signal region superimposed on a blanking period of a video signal is detected, and the average luminance is determined according to the difference between the detection result and a reference value. By controlling the settings of brightness and contrast, fluctuations in brightness due to changes in the temperature or aging of the video amplifier circuit can be automatically corrected by noise-resistant and highly stable control. Will be possible.

[Brief description of the drawings]

FIG. 1 is a block diagram of an image display device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an additional pulse for level detection and a detection area.

FIG. 3 is a block diagram of a level detection circuit;

FIG. 4 is a diagram showing a relationship between a dynamic range of an A / D converter and an additional pulse.

FIG. 5 is a diagram of an adjustment procedure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Video amplifier circuit 2 Additional pulse generator 3 Switching conversion circuit 4 A / D converter 5 Level detection circuit 6 Microcomputer 7 Dot clock generator 8 D / A converter 9 Absolute value circuit 10 Cumulative addition circuit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5C026 CA01 CA02 5C058 AA06 BA05 BB04 BB11 BB25 5C080 AA01 AA09 AA10 BB05 DD03 EE29 FF09 GG02 GG08 GG10 GG11 JJ02 JJ04

Claims (2)

[Claims] The temperature of a video amplifier circuit is detected by detecting the level of a pulse signal superimposed during a blanking period of a video signal and controlling set values of brightness and contrast according to a difference between the detected result and a reference value. An image display device which automatically corrects a change in brightness due to a change or aging. 2. A video amplifier circuit for amplifying an input video signal and adjusting brightness and contrast, an additional pulse generating circuit, a switch circuit for superimposing a pulse signal on a blanking period of the input video signal, and An A / D converter for analog-to-digital conversion, a level detection circuit for accumulating and adding digitally converted video signals, a microcomputer, a dot clock generator for providing a control clock to the A / D converter and the level detection circuit, , Which converts a control signal from a microcomputer into a digital-to-analog signal
An A-converter detects the average luminance of the pulse portion added during the blanking period of the video signal, and, from the microcomputer via the D / A converter according to a change in the detected value.
An image display device characterized in that by controlling brightness and contrast set values for a video amplifier circuit, it is possible to automatically correct fluctuations in brightness due to a temperature change, an aging change, and the like of the video amplifier circuit.