JPH0683287A - Display control device for liquid crystal display - Google Patents

Abstract

PURPOSE:To improve visibility of liquid crystal under bright environment by controlling automatically both or either of brightness and contrast of a liquid crystal display screen based on operation of a brightness detecting sensor or manual switching. CONSTITUTION:Brightness adjusting range can be set more wide than a conventional device and contrast adjusting, and a gamma characteristic can be controlled externally by providing an input terminal 4 for a contrast control signal and an input terminal 20 of a gamma control signal, in this display control device for liquid crystal display. That is, it is fundamentally considered seriously that a display screen is brightly set, and visibility is improved rather than accurate reproducibility of display, then, amplitude of a video signal is made large and contrast is made large, and a screen is made bright by setting a brightness setting point to a more bright point than conventional brightness. Further, concerning compensation of a gamma characteristic relating to linearity of display brightness, a characteristic in which display contrast of an intermediate level is improved is attained even if fidelity of gradation in a white and a black levels are damaged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display control device for a liquid crystal display, and more particularly to a display control device for a liquid crystal display in which the visibility is improved by automatically or manually switching the brightness in a bright environment.

[0002]

2. Description of the Related Art A conventional display control device for this type of liquid crystal display is constructed as shown in FIG.

In FIG. 4, 1 is a video input terminal for inputting a color video signal, 2 is an input terminal for a tint control signal,
Reference numeral 3 is an input terminal for a color density control signal by adjusting the chroma signal level, 5 is an input terminal for a brightness control signal, 6 is a demodulation inversion switching circuit, 7 is an RGB amplifier circuit, 8 is a clamp circuit,
9 is a sync separation circuit, 10 is a clock generation circuit, 11 is X
A driver circuit, 12 is a Y driver circuit, and 13 is a liquid crystal panel which is a liquid crystal display.

First, the color video signal input to the video input terminal 1 is R (red), G in the demodulation inversion switching circuit 6.
It is demodulated into (green) and B (blue) signals and each polarity inversion signal bar R, bar G, bar B is created, and further 1H
Switching signals R, R, G, G, B, and B are output for each (horizontal scanning period). This is because the signal applied to the liquid crystal panel 13 is required not to be applied with a DC voltage in order to ensure long-term reliability of the liquid crystal.

As an adjustment from the outside of the display,
Generally, an input terminal 2 for a tint control signal by VCO (voltage control oscillator) phase adjustment and an input terminal 3 for a color density control signal by chroma signal level adjustment are provided in the demodulation inversion switching circuit. Makes it possible to set optimally according to the usage environment.

The contrast of the display screen of the liquid crystal panel 13 is determined by the amplitude level of the signal applied to the liquid crystal panel 13, that is, Vin in the liquid crystal applied voltage vs. transmittance characteristic diagram of FIG. The optimum point is set to ensure faithful gradation display.

Then, in the RGB amplifier circuit 7 of the next stage,
At the same time as the amplification of the demodulation signal level, the white balance is adjusted by finely adjusting the level difference variation for each RGB.

In the clamp circuit 8 in the next stage, the pedestal portion of the RGB signal is fixed (clamped) to a constant voltage, and the operating point of the display black level (Vin of the liquid crystal applied voltage in FIG.
(B) Level) is constant. By adjusting the clamp level, the set point of the brightness (brightness) of the display screen is determined, and the brightness can be adjusted from the outside so that the user can easily see the brightness according to the usage environment conditions.

This will be further described with reference to the liquid crystal applied voltage to the liquid crystal panel shown in FIG. 2 and the transmittance characteristic (VT characteristic).
In the normal brightness state, the liquid crystal applied voltage range is Vin
With respect to the applied voltage of (N), it operates in the range in which the transmittance changes in the range of T (N) and the V-T characteristic changes almost linearly, and each gradation is displayed faithfully. Also, when the brightness is dark,
The liquid crystal applied voltage range becomes Vin (MIN), and the transmittance change range becomes T (MIN) accordingly.

That is, the screen is darkened because it is used in the range of low transmittance. Similarly, in the bright state of the brightness adjustment, the applied voltage of Vin (MAX) becomes T (MAX) and the screen becomes bright.

Next, an outline of horizontal and vertical transfer clock processing in connection with image display on the liquid crystal panel 13 will be described.

First, the color video signal input to the video input terminal 1, that is, the input video signal is separated by a sync separation circuit 9 into horizontal and vertical sync signals, and horizontal and vertical transfer clocks synchronized with these are generated. It is generated by the circuit 10 and input to each of the X driver circuit 11 and the Y driver circuit 12, and the input video signal is displayed on the liquid crystal panel 13.

With the above structure, the user can freely set the optimum display screen according to the usage environment or the like under the environment of normal brightness such as indoors.

[0014]

If the conventional liquid crystal display display control device configured as described above is used,
There is no practical problem in an environment where the ambient brightness is limited such as indoors, but in a very bright environment such as outdoors on a sunny day, for example, in an environment where the illuminance is about 10,000 lux or more,
There is a drawback that sufficient visibility cannot be obtained due to reflection on the display surface and dark screen.

The display control device for a liquid crystal display according to the present invention focuses on the fact that visibility can be improved by setting bright, for example, even in a bright environment, and a brightness detection sensor for detecting that it is in a bright environment for use. Alternatively, it is intended to improve the visibility of the liquid crystal in a bright environment by controlling both the brightness and the contrast of the liquid crystal display screen or one of them based on the manual switching operation.

[0016]

The display control device for a liquid crystal display according to the present invention eliminates the above-mentioned drawbacks. A sensor for detecting the ambient brightness of the liquid crystal display or a control signal by a manual operation is used. Depending on the brightness of the operating environment of the liquid crystal display, the input means and the amplitude and / or operation reference level of the video signal applied to the liquid crystal display based on the control signal from the input means are automatically controlled. Control means for controlling the brightness and contrast of the liquid crystal display screen to improve the visibility in a bright environment.

[0017]

The liquid crystal display display control device of the present invention configured as described above uses the brightness detection signal or the switching signal to brighten the bright setting of the display video signal processing to the liquid crystal display and increase the contrast setting. The halftone in the setting of γ characteristic is extended and
By increasing the brightness of the display screen, the visibility under that environment is improved.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a display control device for a liquid crystal display according to the present invention will be described below with reference to FIG.

The display control device for a liquid crystal display of the present invention is basically the same as the display control device for a conventional liquid crystal display shown in FIG. It is possible to set a large value, and it is possible to externally control the contrast adjustment and the γ (gamma) characteristic. Further, these circuits are composed of an IC and can be controlled by a DC voltage, and therefore can be realized by switching the DC voltage setting of the IC terminal.

The outline of the circuit operation of the display control device of the liquid crystal display of the present invention is the same as the conventional one, and the explanation thereof is omitted, but the adjustment set point will be explained.

The display control device of the liquid crystal display of the present invention is basically to set the display screen bright,
With a focus on improving visibility rather than faithful reproduction of the display, the video signal amplitude is made large and the contrast is made large, and the bright set point is set to a particularly bright set point to make it brighter. .

First, setting of brightness (brightness) and contrast will be described with reference to FIG.
That is, the amplitude level Vin of the video signal and the bright set point Vin
In contrast to (B), the amplitude level is increased to V'in and V'in (B), respectively, and the bright setting is also made brighter.

The video signal in the bright portion at this time operates in the non-linear portion of the VT characteristic and is impaired in terms of faithful gradation display. For example, a liquid crystal is used for a monitor of a video camera. When using a display, etc., it is often used in a bright outdoor environment, and if there is no problem as a basic function if the angle of view of the subject can be confirmed, then visibility is more important and significant. is there.

Next, the correction of the γ characteristic related to the linearity of the display brightness will be described. Normally, the characteristic changing with γ1 and γ2 shown by the polygonal line A in FIG. 3 is approximated, and V-T in FIG.
The characteristics of the portion having a low transmittance and the portion having a small change in the transmittance with respect to the applied voltage to the liquid crystal are corrected by increasing the applied signal level in advance.

Here, regarding the correction in the γ correction circuit, since the display contrast of the intermediate level is increased by emphasizing the improvement of the visibility of the normal video signal, the polygonal line of FIG. 3 is applied only to the signal levels of γ1 and γ2. As shown in B, it has a characteristic in which the amplification degree of the correction circuit is increased.

By this correction, the contrast at the halftone level is increased, and the gradation at the black and white levels deteriorates the fidelity. However, when the merit of improving the visibility in the above environment is greater, It is valid.

Next, regarding the switching of the characteristics of each part for improving the above-mentioned visibility, in the case of the method by the manual switching,
By switching the control DC voltage of the brightness control signal input terminal 5 (brightness), the contrast control signal input terminal 4 (contrast), or the γ control signal input terminal 20 (γ characteristic) to each desired characteristic. Easy to implement.

Further, in the case of automatic control by the brightness sensor, for example, when a photo sensor is used as the brightness sensor, this control DC voltage can be changed according to the brightness, and a manual step is required. It is more effective than manual switching.

[0029]

Since the display control device of the liquid crystal display of the present invention has the above-mentioned structure, as a measure for improving the visibility in a bright environment such as outdoors, a brightness detection sensor or manual switching is performed. Thus, the visibility can be improved by switching the brightness (brightness) and the contrast of the display screen and further the γ correction characteristics to increase the brightness of the halftone level display.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit configuration of an embodiment of a display control device for a liquid crystal display of the present invention.

FIG. 2 is an explanatory diagram of a liquid crystal applied voltage-transmittance characteristic to a liquid crystal panel.

FIG. 3 is an explanatory diagram of a γ correction characteristic related to linearity of display brightness.

FIG. 4 is a block diagram showing a circuit configuration of a display control device for a conventional liquid crystal display.

[Explanation of symbols]

 1 Video input terminal 2 Color tone control signal input terminal 3 Color density control signal input terminal 4 Contrast control signal input terminal 5 Brightness control signal input terminal 6 Demodulation inversion switching circuit 7 RGB amplifier circuit 8 Clamp circuit 9 Synchronization Separation circuit 10 Clock generation circuit 11 X driver circuit 12 Y driver circuit 13 Liquid crystal panel

Claims (3)

[Claims] 1. A sensor for detecting ambient brightness of a liquid crystal display, or means for inputting a control signal by manual operation,
By automatically controlling the amplitude and / or the operation reference level of the video signal applied to the liquid crystal display based on the control signal from the input means, the liquid crystal display screen A display control device for a liquid crystal display, comprising: a control unit that controls brightness and contrast to improve visibility in a bright environment. 2. A display control device for a liquid crystal display, wherein the control means according to claim 1 is provided with means for controlling a gamma characteristic. 3. The control means according to claim 1, further comprising means for preferentially improving an amplification degree at a halftone level in the liquid crystal display display capability of the liquid crystal display when the illuminance of ambient light is high. A display control device for a liquid crystal display.