JP2001091924A - LCD display contrast adjustment device - Google Patents

Abstract

(57) Abstract: In adjusting the contrast of an LCD display using a conventional temperature table, a complicated initial setting manual operation manually performed using a variable resistor is not required, and the LCD is adjusted.
Regarding the contrast of the display, regardless of the temperature, the transmittance of light, which is an essential characteristic of the LCD, is measured.
Provided is an automatic contrast adjusting device that can adjust the contrast of a CD display and always maintain a constant good contrast. An LCD using a backlight of an LCD is provided.
A transmittance measurement system for measuring the transmittance by detecting the transmitted light of the display unit with an optical sensor;
And the display voltage of the setting suitable for the transmittance is input to the CPU 2.
The LCD automatic contrast adjusting device includes at least means for adjusting the display voltage 4 of the LCD driver and adjusting the contrast 5 of the LCD display according to the result.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic contrast adjusting device for an LCD (Liquid Crystal Display) display.

[0002]

2. Description of the Related Art FIG. 4 shows an example of a conventional system for adjusting contrast (contrast / contrast) such as brightness and color and color of characters and figures displayed on an LCD. FIG. 4 is a block diagram showing a procedure for temperature compensation of the contrast of the LCD display. In the figure, reference numeral 20 denotes a temperature measurement system, 21 denotes a CPU (Central Processing Unit ... a central processing unit including both control and calculation devices and a main storage device), and 22 denotes a D (digital) / A (analog) converter (D / A). converter),
23 is a variable resistor, 24 is an adjustment of the display voltage of the LCD driver, 25 is an adjustment of the LCD display contrast, and 26 is a temperature table memory. As shown in FIG.
LCD with temperature measurement system 20 (liquid crystal display)
Is measured and input to the CPU 2. The CPU 2 compares the temperature with the temperature table memory 26 indicating the appropriate voltage of the LCD display contrast which has been input in advance,
The display voltage suitable for the measured temperature is output to the A converter 22, the display voltage of the LCD driver is adjusted 24 by the variable resistor 23, and the contrast of the LCD display is adjusted 25. Since the LCD and the LCD driver have temperature characteristics, the contrast of the LCD display changes depending on the temperature. Therefore, L in FIG.
As shown in the temperature compensation circuit for CD display contrast,
The temperature of the LCD 33 or the LCD driver 34 is actually measured, and the temperature table memory 32 shown in Table 1 and the actually measured temperature data, which are input in advance to the memory (storage device) of the CPU 29, are stored in the memory. In comparison, by outputting a voltage suitable for the temperature data to the D / A converter 30 and adjusting the liquid crystal display voltage of the LCD driver 34 by the variable resistor 31, the contrast of the LCD display is adjusted. .

[0003]

[Table 1]

The temperature table shown in Table 1 shows, for example, a voltage Vc at which the contrast of an LCD display is appropriate at three temperatures of 45 ° C., 25 ° C. and -10 ° C.
(V). Thus, the conventional LCD
The initial setting of the display contrast is manually performed using a variable resistor, and when a temperature table is created, the LCD is maintained at an arbitrary temperature (for example, a temperature of -10 to 45 ° C). It is necessary to set the liquid crystal display voltage Vc while maintaining the LCD at a constant temperature by using a constant temperature chamber or the like for this purpose, which is extremely troublesome and requires many inspection man-hours. Was. Further, depending on how the temperature table is divided, the contrast of the LCD display varies, and when characters and figures are drawn on the screen, the black and white and color are not sharpened, and the image is blurred or the image becomes dark. And blurring.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the need for a complicated initial setting operation manually performed using a variable resistor in adjusting the contrast of an LCD display using a conventional temperature table. To measure the light transmittance, which is an essential characteristic of the LCD, regardless of the temperature, and adjust the contrast of the LCD display based on this, regardless of the temperature, and always maintain a constant good contrast. It is an object of the present invention to provide a device for automatically adjusting the contrast of an LCD display.

[0006]

Means for Solving the Problems In order to achieve the above object of the present invention, the present invention is configured as described in the claims. That is, according to the present invention, as described in claim 1, means for measuring the transmittance of the LCD display unit, inputting the transmittance to the CPU, and setting a display voltage suitable for the transmittance by the CPU. The present invention provides an automatic LCD display contrast adjusting device including at least means for adjusting the display voltage of the LCD driver in accordance with the result of calculation and adjusting the LCD display contrast.

[0007] Further, the present invention provides,
In claim 1, the means for measuring the transmittance of the LCD display unit includes means for measuring the transmittance by detecting the transmitted light of the LCD display unit with an optical sensor using a backlight of the LCD. This is an automatic contrast adjusting device for LCD display.

[0008] Further, the present invention provides,
The means for measuring transmittance according to claim 1 or 2 is performed using an optical sensor, and has means for performing temperature compensation using a thermistor so as not to be affected by the temperature characteristics of the optical sensor. This is an automatic contrast adjusting device for LCD display.

According to the LCD automatic contrast adjusting device of the present invention as set forth in claims 1 to 3, a complicated initial setting of the contrast of the LCD display is performed by operating a conventional variable resistor. Is unnecessary, and the contrast of the LCD display can be changed regardless of the temperature.
The light transmittance, which is an essential characteristic of D, is measured, and the contrast of the LCD display is adjusted based on the measured light transmittance. Therefore, there is no variation in contrast, and the contrast of the LCD display can be constantly maintained at a good level. There is an effect that the device can be realized.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing a method for automatically adjusting the contrast of an LCD display exemplified in an embodiment of the present invention. In the figure, 1 is a transmittance measurement system, 2 is a CPU (central processing unit "central processing unit of a computer"), 3 is a D / A (digital / analog) converter, 4 is adjustment of display voltage of an LCD driver, 5 is 5 7 illustrates adjustment of the contrast of an LCD display. According to the present invention, as shown in FIG. 1, the transmittance of a display unit of an LCD is measured, the transmittance is input to a CPU 2, and a display voltage of a setting suitable for the transmittance is calculated by the CPU 2, and as a result, To D
This device performs automatic adjustment 5 of the contrast of the LCD display by outputting to the / A converter 3 and adjusting 4 the display voltage of the LCD driver. That is, by replacing the conventional temperature measurement method with the transmittance measurement method of the present invention in which the contrast of the LCD display is automatically adjusted based on the transmittance which is an essential characteristic of the LCD, the conventional variable measurement method can be used. The troublesome work of initial setting of the contrast of the LCD display, which was manually performed by using a resistor, can be omitted, and the contrast of the LCD display varies depending on the conventional method of dividing the temperature table. Can be eliminated.

FIG. 2 shows an example of an automatic contrast adjusting circuit for LCD display using the transmittance measuring system of the present invention. FIG. 3 shows an example of the transmittance measurement system of the LCD display unit. The transmittance is measured by using a backlight 16 mounted on the LCD, passing through the display unit 15 of the LCD 6, and reflecting a reflector (mirror) 13 provided on the protective glass 14.
The intensity of the light reflected by is detected by the optical sensor 12 and LC
The transmittance of the D display unit is measured. That is, FIG.
2 shows a circuit for automatically adjusting the contrast of an LCD display using the transmittance measuring system shown in FIG. 1. The transmittance measured by the transmittance measuring system 1 is read by the CPU 2 and the display voltage of a setting suitable for the transmittance is determined. The calculation is performed by the CPU 2, and the result is output to the D / A converter 3 and connected to the liquid crystal display power supply terminal 10 and the boost output power supply terminal 11 of the LCD driver 7 via the resistor 9, and the display contrast of the LCD 6 is automatically adjusted. Adjusted. The measurement of transmittance is
By providing a means for temperature compensation using, for example, a thermistor so as not to be affected by the temperature characteristics of the optical sensor 12, the accuracy of the measured transmittance can be improved and the variation in the contrast of the LCD display can be almost eliminated. Was.

The automatic contrast adjustment of the LCD display according to the present invention is a method of automatically adjusting the contrast of the LCD display based on the transmittance, which is an essential characteristic of the LCD, regardless of the temperature. As in the case of the temperature measurement method, the initial setting of the contrast of the LCD display is manually performed by using a variable resistor. Since there is no need to set the liquid crystal display voltage Vc while maintaining the temperature, the contrast of the LCD display can be easily and reliably adjusted, and the constant good contrast can be always adjusted. Was. Furthermore, in the conventional temperature measurement method, the contrast of the LCD display varies depending on the way of dividing the temperature table, and when drawing characters and figures on the screen, the black and white and the color are not sharp, and are blurred. Although problems such as blackening or blurring of the image occurred, good contrast of the LCD display was obtained by using the automatic contrast adjustment method of the LCD display based on the transmittance of the present invention.

[0013]

According to the automatic adjustment of the contrast of the LCD display of the present invention, the display voltage is adjusted on the basis of the transmittance which is an essential characteristic of the LCD, so that it is extremely easy regardless of the temperature of the LCD. In addition, the initial setting of the contrast of the LCD display can be automatically adjusted, so that a constant good contrast can always be obtained. Therefore, the method for automatically adjusting the contrast of the LCD display according to the present invention based on the light transmittance has an effect that the operating temperature range of the LCD device can be expanded as compared with the case where the conventional temperature is used as a reference.

[Brief description of the drawings]

FIG. 1 is an exemplary block diagram showing a procedure for automatically adjusting the contrast of an LCD display exemplified in an embodiment of the present invention.

FIG. 2 is a diagram showing an automatic contrast adjustment circuit for LCD display using the transmittance measurement system exemplified in the embodiment of the present invention.

FIG. 3 is a schematic diagram showing a configuration of a transmittance measurement system exemplified in the embodiment of the present invention.

FIG. 4 is a block diagram showing a procedure for contrast temperature compensation of a conventional LCD display.

FIG. 5 is a diagram showing a conventional contrast temperature compensation circuit for an LCD display using a thermistor.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Transmissivity measurement system 2 ... CPU (Central processing unit) 3 ... D / A converter 4 ... Adjustment of display voltage of LCD driver 5 ... Adjustment of contrast of LCD display 6 ... LCD (liquid crystal display) 7 ... LCD driver 9 ... Resistance (R) 10: LCD driver power supply terminal of LCD driver 11: Booster output power supply terminal of LCD driver 12: Optical sensor 13: Reflector (mirror) 14: Protective glass 15: LCD display 16: Backlight 20: Temperature Measurement system 21 CPU (Central Processing Unit) 22 D / A converter 23 Variable resistor (VR) 24 Adjustment of LCD driver display voltage 25 Adjustment of LCD display contrast 26 Temperature table memory 27 Thermistor 28 ... A / D converter 29 ... CPU (central processing unit) 30 ... D / A converter 31 ... Variable resistor 32 ... temperature table memory 33 ... LCD (liquid crystal display) 34 ... boost output power supply terminal 37 ... resistance of the liquid-crystal display power terminal 36 ... LCD driver LCD driver 35 ... LCD driver (R) 38 ... power supply voltage (V _DD )

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Claims (3)

[Claims] 1. A means for measuring the transmittance of an LCD display unit;
The transmittance is input to a CPU, and a display voltage of a setting suitable for the transmittance is calculated by the CPU.
An automatic LCD display contrast adjusting device comprising at least means for adjusting the display voltage of a D driver to adjust the contrast of an LCD display. 2. The method according to claim 1, wherein the means for measuring the transmittance of the LCD display unit uses a backlight of the LCD.
A device for automatically adjusting the contrast of an LCD display, comprising means for measuring the transmittance by detecting light transmitted through a display unit of the LCD with an optical sensor. 3. The means for measuring transmittance according to claim 1 or 2, wherein the means for measuring transmittance is performed using an optical sensor, and the temperature is measured using a thermistor so as not to be affected by the temperature characteristics of the optical sensor. L having means for compensating
Automatic contrast adjustment device for CD display.