JPH1173162A - Simultaneous adjusting circuit for brightness and contrast of liquid crystal display monitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of white saturation even when brightness is increased by video black level control. SOLUTION: This simultaneous adjusting circuit is provided with a video amplifier 4, a maximum brightness voltage detecting circuit 6, which detects a maximum brightness voltage value of a video signal, a level comparator 1, which adopts a drive voltage value of white saturation point as a reference voltage and inputs it and an output of the maximum brightness voltage detector 6, a microcomputer 2 which controls a contrast set point from the output of the level comparator 1, a D/A converter, and an A/D converter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to adjustment of brightness and contrast of a liquid crystal display monitor.

[0002]

2. Description of the Related Art When an input video signal (RGB video signal) is displayed on a liquid crystal display monitor, the input signal is first input to a video amplifier, where the brightness and contrast are controlled and then A / D converted. Various digital signal processing is performed and sent to the liquid crystal panel side. However, the light transmittance (brightness) of the liquid crystal panel shows a non-linear characteristic with respect to the applied voltage as shown in FIG. Because of this,
In the vicinity of the white level and the black level, display abnormalities such as underexposure and underexposure occur. For LCD TVs, etc.
As described in JP-A-117481, the brightness of the image display unit is changed in relation to the brightness of the image to obtain an easy-to-view image.

[0003]

Generally, a liquid crystal display monitor is provided with a function of adjusting brightness, contrast, and the like so as to realize a user's favorite image display state. Therefore, depending on the user, the luminance setting may be set to be particularly brighter than the reference value, with an emphasis on sharpening the display screen near the black level. However, as described above, the light transmittance of the liquid crystal panel shows a non-linear characteristic with respect to the applied voltage. Further, in order to normally obtain a large contrast ratio, the contrast gain is set so that a full range is obtained in a linear region. For this reason, when the user increases the brightness by controlling the black level, the peak portion of the video signal is cut in the vicinity of the white level, and an overexposure of the bright white portion where the bright portion of the screen is not correctly reproduced occurs.
In order to prevent this, the user must increase the luminance and then, by adjusting the contrast, lower the white level to a level that does not cause underexposure. By doing so, the color reproducibility level is reduced, but by preventing whiteout, even if the brightness is set particularly brighter than the reference value, an image with less discomfort is obtained.

[0004]

In order to solve this problem, the present invention solves this problem by automatically adjusting the brightness by the user by controlling the video black level and automatically adjusting the video signal to the white saturation point voltage. A brightness / contrast simultaneous adjustment circuit for a liquid crystal display monitor, wherein contrast control is performed, and a white level is reduced in accordance with an amount exceeding a white saturation point voltage, thereby preventing the occurrence of underexposure.

According to the present invention, in a liquid crystal display monitor, when a user sets a luminance higher than a reference in order to obtain a desired luminance, it is possible to prevent the occurrence of overexposure.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first invention of the present invention is directed to a video amplifier, a circuit for detecting a change in black level, and a microcontroller for adjusting a contrast gain in accordance with the change in black level. 2. The liquid crystal display monitor according to claim 1, further comprising: a computer; and a D / A converter that D / A converts a control signal from the microcomputer and controls a contrast adjustment terminal of the video amplifier. This adjustment circuit allows the user to increase the brightness of the LCD monitor to obtain the desired brightness by lowering the contrast by increasing the black level. Has the effect of becoming

A second invention is a video amplifier, an A / D converter for A / D converting an output of the video amplifier,
A circuit for detecting a driving voltage of the maximum luminance of the video signal during a predetermined period, a comparator for inputting the driving voltage of the maximum luminance of the video signal and the driving voltage value of the white saturation point as a reference voltage,
A microcomputer which receives the output of the comparator as an input, and adjusts so that a drive voltage having a maximum luminance of the video signal exceeds a drive voltage of the white saturation point so as to lower a contrast gain in accordance with an amount; 2. A brightness / contrast simultaneous adjustment circuit for a liquid crystal display monitor according to claim 1, further comprising: a D / A converter for D / A converting the control signal of (b) and controlling a contrast adjustment terminal of said video amplifier. Therefore, in a liquid crystal display monitor, when the user increases the brightness in order to obtain the desired brightness, it is possible to prevent the occurrence of overexposure by lowering the contrast by an amount that the video signal exceeds the white level. Having.

Hereinafter, a brightness / contrast simultaneous adjustment circuit according to an embodiment of the present invention will be described with reference to FIGS.

(Embodiment 1) FIG. 2 shows a block diagram of a simultaneous brightness / contrast adjustment circuit according to a first embodiment of the present invention. FIG. 3 shows a principle diagram of FIG.

In FIG. 2, reference numeral 4 denotes a video amplifier. RGB video signals are input to the video amplifier 4,
Output after adjustment of contrast and brightness. Reference numeral 7 denotes a black level change amount detection circuit, and reference numeral 2 denotes a microcomputer. When the black level is set higher than the reference value, the setting is made so as to lower the contrast according to the change amount of the black level. The set value from the microcomputer 2 is applied to a brightness control terminal and a contrast control terminal of the video amplifier 4 via the D / A converter 3.

The manner in which the brightness and contrast change at this time will be described with reference to FIG. Normally, the brightness and contrast are set so that the dynamic range is maximized in a range in which blackouts and blackouts do not occur. If the user adjusts the brightness from this state and sets the brightness setting to be particularly brighter than the reference, white loss occurs in a portion exceeding the white level. In the embodiment of the present invention, the amount by which the black level is increased is detected, and the contrast is adjusted at the same time according to the increased amount, thereby preventing the occurrence of overexposure.

According to this configuration, the contrast is controlled so as to decrease as much as the user increases the luminance.
Even when the luminance is increased, it is possible to prevent the occurrence of underexposure.

(Embodiment 2) FIG. 4 shows a block diagram of a brightness / contrast simultaneous adjustment circuit according to a second embodiment of the present invention. FIG. 5 shows the principle diagram of FIG.

In FIG. 4, reference numeral 4 denotes a video amplifier. RGB video signals are input to the video amplifier 4,
Output after adjustment of contrast and brightness. Reference numeral 5 denotes an A / D converter, which performs A / D conversion on the output of the video amplifier 4 and passes it to various control blocks.

Reference numeral 5 denotes a maximum luminance voltage detection circuit.
The maximum luminance voltage detection circuit inputs the signal after the A / D conversion, and in the case of a display monitor, it often displays a still image. For example, the maximum luminance voltage detection circuit detects video signal data during a predetermined period such as one frame, Outputs the maximum luminance value.

Reference numeral 1 denotes a level comparator. The drive voltage value of the white saturation point and the output of the maximum luminance voltage detection circuit are input to the level comparator 1, and when the output of the maximum luminance voltage detection circuit exceeds the white saturation voltage, the level comparator 1 responds to the amount. Outputs the voltage value.

Reference numeral 2 denotes a microcomputer which receives the output of the level comparator as an input, and converts a new set value for lowering the contrast gain according to the amount by which the maximum luminance voltage exceeds the white saturation voltage value into a D / A converter. 3 so that the signal is supplied to the contrast control terminal of the video amplifier 4.

The manner in which the brightness and contrast change at this time will be described with reference to FIG. Normally, the brightness and contrast are set so that the dynamic range is maximized in a range in which blackouts and blackouts do not occur. If the user adjusts the brightness from this state and sets the brightness setting to be particularly brighter than the reference, white loss occurs in a portion exceeding the white level. In this method, the contrast is adjusted at the same time according to the amount exceeding the white level by increasing the luminance, thereby preventing the occurrence of overexposure.

In the first embodiment, regardless of the content of the video signal, the contrast is reduced by the increased luminance. Therefore, even if a low-luminance video signal is input and white saturation does not occur even if the luminance is increased, However, according to this configuration, since the maximum luminance voltage of the video signal is detected and compared with the white level voltage, the above-described adverse effects do not occur. .

[0020]

As described above, according to the brightness / contrast simultaneous adjustment circuit of the present invention, when the user adjusts the brightness by controlling the video black level, and the video signal reaches the white saturation point, it is automatically adjusted. Since the contrast level is controlled and the white level is reduced in accordance with the amount exceeding the white saturation point, it is possible to prevent the occurrence of overexposure even when the luminance is set higher than the standard value.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between drive voltage and brightness of a liquid crystal panel.

FIG. 2 is a block diagram of a brightness / contrast simultaneous adjustment circuit according to the first embodiment of the present invention;

FIG. 3 is a principle diagram of FIG. 2;

FIG. 4 is a block diagram of a brightness / contrast simultaneous adjustment circuit according to a second embodiment of the present invention;

FIG. 5 is a principle diagram of FIG. 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Level comparator 2 Microcomputer 3 D / A converter 4 Video amplifier 5 A / D converter 6 Maximum luminance detection circuit 7 Black level change amount detection circuit

Claims (3)

[Claims] When a video signal reaches a white saturation point by performing luminance adjustment by video black level control, contrast control is performed at the same time, and a white level is reduced according to an amount exceeding the white saturation point, and white loss is caused. A simultaneous brightness / contrast adjustment circuit for a liquid crystal display monitor, characterized by preventing occurrence. 2. A video amplifier, a circuit for detecting an amount of change in black level, a microcomputer for reducing a contrast gain in accordance with the amount of change in black level, and D / A conversion of a control signal from the microcomputer And a D / A converter for controlling a contrast adjustment terminal of the video amplifier, wherein the contrast is reduced by an amount corresponding to the increase in the black level. 3. A video amplifier, an A / D converter for A / D converting an output of the video amplifier, a circuit for detecting a driving voltage having a maximum luminance of the video signal during a predetermined period, and a maximum luminance of the video signal. And a comparator for inputting the drive voltage and the drive voltage value of the white saturation point as a reference voltage, and the output of the comparator as an input, and the drive voltage of the maximum luminance of the video signal exceeds the drive voltage of the white saturation point. A microcomputer for lowering the contrast gain in accordance with the amount; and a D / A converter for D / A converting a control signal from the microcomputer to control a contrast adjustment terminal of the video amplifier. Simultaneous brightness / contrast adjustment circuit for liquid crystal display monitors, characterized in that the contrast is reduced by an amount exceeding the level.