JPH01179913A - Back light and color balance adjusting device for liquid crystal color display device - Google Patents

Abstract

PURPOSE:To easily adjust the white balance by preliminarily determining the white balance of a liquid crystal color display device in accordance with the tone of a back light. CONSTITUTION:The output voltage of a programmable constant voltage circuit 20 is impressed to a potentiometer 21, variable resistances 22 and 23, a resistance 24, an LED group 25 for green, an LED group 26 for blue, and an LED group 27 for red and the output level is changed by the adjustment of the potentiometer 21. LED groups 25, 26, and 27 are constituted as the back light arranged on a back light substrate 28, and currents of LED groups 25 and 26 are adjusted by variable resistances 22 and 23, and light from respective LED groups is projected to a liquid crystal color display device 30 through a diffusing plate 29. Thus, the color balance of the liquid crystal color display device is adjusted to an optimum state.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a backlight for a liquid crystal color display and a color balance adjustment device using this backlight.

[Prior Art] As shown in FIG. 5, a conventional liquid crystal color display device has a white light source 11 disposed as a backlight on the back side of a liquid crystal color display 10, and lights from the white light source 11 is directed to the liquid crystal color display 10. The configuration is such that an image is displayed on the liquid crystal color display 10 by direct irradiation of the light onto the mirror 12 as well as irradiation of reflected light from the mirror 12 .

As shown in FIG. 6, the liquid crystal color display 10 has
R (red), G (green), and B (display color images in dots)
A filter is provided in which a large number of blue) pixels are arranged in a mosaic pattern, and each 'i1! Poles are installed separately for each of RlG and B. Then, at the intersection of each matrix, F
A switching element such as ET is provided, and the R, G, and B filters are configured to transmit light from the white light source 11 by the operation of this switching element.

``Problem to be Solved by the Invention'' In the case of a conventional liquid crystal color display, due to the characteristics of the liquid crystal plate and semiconductors such as FET, as shown in FIG.
The characteristic of the transmittance T becomes a non-linear characteristic. Therefore, if you adjust the brightness of RlG and H by setting the brightness signal to maximum in order to maintain white balance, the color balance will be disrupted when the brightness signal level is low, resulting in poor color balance on dark screens. There was a problem.

That is, in the liquid crystal color display 10, R, G, and H pixels arranged in a mosaic pattern are opened in the form of dots and images are obtained by viewing the light from a backlight.
, B dots are fully opened, the transmittance of the R, G, and H filters does not have ideal characteristics. Therefore, when the white light source 11 is used as a backlight, the light transmitted through the liquid crystal color display 10 is mixed. The color cannot be recognized as white.

Therefore, in order to maintain white balance, RlG, B
The maximum levels of the luminance signals YR, YG, and YB are converted into voltages VR, VG, and VB as shown in FIG. 7, and are applied to the liquid crystal color display 10 to obtain white balance.

However, if the transmittance of the liquid crystal color display 10 at the maximum level of the luminance signals YR, YG, and YB is set to 100%, a dark screen appears as shown in FIG.
Where the level of the luminance signal is low, the white balance is disrupted and accurate colors cannot be reproduced.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a backlight for a liquid crystal color display that can determine the white balance in the liquid crystal color display based on the color tone of the backlight, and a color balance adjustment device using this backlight.

[Means for Solving the Problems] In order to achieve the above objects, the present invention includes a red light source, a green light source, and a blue light source, and is provided with a backlight that illuminates a liquid crystal color display with light of each color. The configuration is such that the luminance of the light source is determined in advance and the white balance of the liquid crystal color display is maintained.

The present invention also provides a backlight light source that emits light in at least two colors out of the three colors of red, green, and blue, and that illuminates a liquid crystal color display with light of each color, and that adjusts the emission intensity of each light source for each light source. This is a color balance adjusting device for a liquid crystal color display, which includes a brightness adjuster and a brightness adjuster.

"Function" In the invention of claim (1), the white balance of the liquid crystal display is maintained appropriately by the light of each color from the backlight.

In the invention of claim (2), each light source emits at least two colors out of the three colors red, green, and blue, and each color is irradiated onto the liquid crystal color display. Since the emission intensity of each light source can be adjusted for each light source using the brightness adjuster, color balance is improved. For example, even when displaying an image at a low brightness signal level, the color balance on the LCD color display is optimized. It can be adjusted to the desired condition.

``Example'' An example of the present invention will be described below with reference to the drawings.

In FIG. 1, the power supply voltage is supplied to the programmable constant voltage circuit 2°, and the output voltage of the constant voltage circuit 2° is applied to the potentiometer 21, the variable resistor 22, 23, and the resistor 24.
, green LED group 25, blue LED group 26, red L
It is applied to the ED group 27.

This constant voltage circuit 20 is configured so that its output level can be changed by adjusting a potentiometer 21.

That is, by adjusting the potentiometer 21, the output level of the constant voltage circuit 20 can be adjusted as desired.

As shown in FIG. 2, the LED groups 25, 26, and 27 are configured as a backlight disposed on a backlight board 28, and each of the LED groups 25, 26, and 27 is connected to a variable resistor 22.
In other words, the variable resistor 22 is configured as a brightness regulator that adjusts the current of the LED group 25 to adjust the emission intensity of the green light source, and the variable resistor 23 is configured to adjust the current of the LED group 25. 26 current in yA! 1, it is configured as a brightness adjuster that adjusts the emission intensity of the blue light source. Note that when the output level of the constant voltage circuit 20 is set by the potentiometer 21, the light emission intensity of the LED group 27 as a red light source is adjusted by the current determined by the resistor 24. Then, the light from each LED group passes through a diffusion plate 29 to a liquid crystal color display 30.
is irradiated.

This liquid crystal color display 30 is similar to the conventional example, and has a display screen in which a large number of dot-shaped color display elements are arranged in a matrix, and is arranged vertically.

Each color display element is caused to emit light in response to a horizontal synchronization signal to display an image.

In this way, in this embodiment, since the emission intensity of each light source of the backlight can be adjusted for each light source, the light from each LED group is irradiated onto the liquid crystal color display 30, and the light emitted from the liquid crystal color display 30 is Assuming that a white color is obtained with the applied voltages VG, VR, and VB as shown in FIG. 7, the transmittance of R, G, and B of the liquid crystal color display 30 at this time is 100% for G; R is r%.

B is b%. Therefore, when using the applied voltage VG=VR=VB based on the transmittance of R and H, in order to obtain the same balance as the above-mentioned conditions.

The R and B components are each r% and b as the color tone of the backlight.
For example, by opening all the RlG and B dots of the liquid crystal color display 30 to 100%, and turning off the switch 31 inserted in the blue light source circuit, the G and R dots can be reduced to 100%. LED group 25
．． 27 is turned on and the variable resistor 22 is adjusted so that the light transmitted through the liquid crystal color display 30 becomes yellow. After this, turn on the switch 31 and turn on the LED
White color can be obtained by causing the group 26 to emit light and adjusting the variable resistor 23.

After adjusting the white balance as described above, the resistance values of the variable resistors 22 and 23 are fixed so that they cannot be changed. Also, when mass producing LCD color displays, the resistance value of the variable resistor 22.23 is measured when the white balance is adjusted, and a fixed resistor with this resistance value is installed in place of the variable resistor 22.23. It can also be configured. Note that the brightness of the entire screen can also be adjusted using the potentiometer 21.

Furthermore, if the current of the LED groups 25 and 26 is adjusted through variable resistors 32 as shown in FIG.
By adjusting the variable resistor 32, the color balance can be adjusted for each programmable source or according to individual preference. That is, normally, the variable resistor 32 is set to a neutral position, and the G and H light emission intensities are adjusted by adjusting the variable resistors 22 and 23. Then, when the variable resistor 32 is operated to the G side, the resistance value in the circuit of the LED group 25 is lowered, and the L
The light emission intensity of the ED group 25 becomes stronger, and the light emission intensity of the LED group 26 becomes weaker.

Further, as the backlight source, as shown in FIG. 4, it is also possible to use a red cathode tube 33, a green cathode tube 34, and a blue cathode tube 35. Note that 36 is a reflecting mirror.

Further, in the above embodiment, a backlight light source using three colors of R, G, and H has been described, but the same effect can be obtained by using a two-color light source depending on the purpose of the liquid crystal display.

Furthermore, according to the above embodiment, since it is not necessary to provide a brightness adjustment circuit, a white balance circuit, and a color balance circuit in the brightness signal/color signal circuit, the circuit can be simplified and the signal components can be reduced. Since this is not necessary, it is possible to obtain high-quality images, and furthermore, it is easier to reproduce intermediate color tones, and the electrical characteristics of R, G, and B can be aligned with respect to the transmittance, so dark images can be obtained. You can also get images with good color balance on the screen.

"Effects of the Invention" As explained above, according to the present invention, the white balance of a liquid crystal color display is predetermined by the color tone of the backlight. You can get color balance.

Further, according to the present invention, by adjusting the brightness of the backlight for each light source, it is possible to obtain a display image with a color balance that suits an individual's preference.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a white balance adjustment device showing an embodiment of the present invention, and FIG. 2 is a simplified exploded perspective view of a light source as a backlight according to the present invention. FIG. 3 is a circuit diagram showing another embodiment of the above adjustment device;
The figure is a perspective view showing an example of another light source as a backlight, FIG. 5 is a simplified perspective view of a liquid crystal color display shown as a conventional example, and FIG. 6 is a configuration diagram of a filter of a conventional example.
Figure 7 is a characteristic diagram showing the relationship between luminance signal and transmittance.
The figure is a characteristic diagram showing the relationship between luminance signal and transmittance when all dots of a liquid crystal color display are opened. 20...Programmable constant voltage circuit 21...Potentiometer 22.23.32...Variable resistor 24...Resistor 25...Green LED group 26...Blue LED group 27...Red LED group 30...Liquid crystal color display Patent applicant: Stanley Electric Co., Ltd. No. 1821 jlI8vIJ G B

Claims (2)

[Claims] (1) A liquid crystal display that is equipped with a red light source, a green light source, and a blue light source, and is equipped with a backlight that illuminates the liquid crystal color display with light of each color, and that the luminance of each of the above light sources is predetermined and the white balance of the liquid crystal color display is moderate. Color display backlight. (2) A backlight light source that emits light in at least two of the three colors red, green, and blue, and illuminates the LCD color display with light of each color, and a brightness that adjusts the emission intensity of each light source for each light source group. A color balance adjustment device for a liquid crystal color display characterized by comprising a regulator.