JPH07109456B2 - Brightness adjustment device for color display - Google Patents

Description

The present invention relates to a brightness adjusting device for a color display, and more particularly to a brightness adjusting device for a color display suitable for adjusting the brightness of a liquid crystal color display.

“Prior Art” Conventionally, as shown in FIG. 6, a liquid crystal color display device includes a liquid crystal color display 10, a white light source 11, and a reflecting mirror.
A structure having 12 and having the light from the white light source 11 reflected by the reflecting mirror 12 and incident on the liquid crystal color display 10 has been adopted. As shown in FIG. 7, an output signal Y of the brightness adjuster 13 is supplied to the white light source 11, and the brightness of the liquid crystal color display 10 is adjusted according to the output level of the brightness adjuster 13. It can be adjusted.

However, regarding the human spectral luminosity characteristics, the characteristic diagram proposed by Gibson and Tyndall in the bright place and the characteristic diagram proposed by Crawford in the dark place are authorized. The characteristics are shown.

According to this characteristic diagram, the relative luminous efficiency of red significantly decreases in a dark place. On the other hand, the relative luminous efficiency of blue increases although it is relative.

Further, this characteristic does not suddenly switch to the scotopic characteristic when shifting from a bright place to a dark place, but may have an intermediate characteristic. For this reason, it is necessary to dim the screen when viewing the screen darkly, for example, when watching TV so as not to bother other people in the same room after turning it off at a hospital, etc. Then, from the characteristics shown in FIG. 8, the red sensation deteriorates and the blue sensation improves. Therefore, the color balance as a dark screen is required for a good screen when the screen is darkened.

[Problems to be Solved by the Invention] However, in the conventional device, as shown in FIG. 7, the brightness signal Y ′ is adjusted by the brightness adjuster 13 so that the red, green, and blue colors are energetic. Since the configuration that evenly dims the light was adopted, there was a problem that when the screen was darkened, the red color appeared dark and the blue color appeared bright.

An object of the present invention is to provide a brightness adjusting device for a color display, which can correct the collapse of the color balance at low brightness.

“Means for Solving Problems” In order to achieve the above-mentioned object, the present invention provides a light emitting element group that emits light of red, green, and blue colors toward a display with a light emission intensity according to a current value, and A first brightness adjusting means for commonly adjusting the brightness of the light emitting elements by the light emitting elements;
As the brightness level is adjusted toward the lower level by the first brightness adjusting means, the brightness level of the green light emitting element group is set to an intermediate value and the brightness level of the red light emitting element group is increased to blue. And a second brightness adjusting means for reducing the brightness level of the light emitting element group for use in a color display brightness adjusting device.

[Operation] When the brightness level of each light emitting element is adjusted to a low level by the first brightness adjuster, the brightness level of the green light emitting element group is set as an intermediate value by the second brightness adjuster, and the red level is adjusted. The brightness level of the light emitting element group increases and the level of the blue light emitting element group decreases.

That is, the red extinction rate becomes smaller and the blue extinction rate becomes larger with reference to the green extinction rate. This allows
It is possible to correct the collapse of the color balance at low brightness.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, the programmable constant voltage circuit 20 is configured to receive electric power from a battery and output a voltage V according to the level of the potentiometer 21.

The constant-voltage circuit 20 and the potentiometer 21 constitute a first brightness adjuster, and the current due to the output voltage V of the constant-voltage circuit 20 passes through the variable resistors 22, 23, 24 and emits blue light.
25, the light emitting element group 26 for red and the light emitting element group 27 for green are supplied, and the brightness due to the light emission of each light emitting element is adjusted in common.
As shown in FIG. 2, each light emitting element group has a backlight 28.
It is arranged for each color on the top, and emits light with a light emission intensity according to the current value.

The light emitted by each light emitting element group enters the liquid crystal color display 30 through the diffusion plate 29.

The variable resistors 22, 23, 24 are configured to adjust the current of each light emitting element group when the output level of the potentiometer 21 is high, that is, when the brightness is high.

Further, current is supplied to each light emitting element group from the constant current circuits 31, 32, and 33, and even when the level of the output voltage V of the constant voltage circuit 20 becomes 0 volt by the adjustment of the potentiometer 21, each light emission is performed. A constant current is supplied to the element group. This current is the current of each light emitting element group at low luminance, the luminance level of the green light emitting element group 27 is an intermediate value, the luminance level of the red light emitting element group 26 is large, and the luminance level of the blue light emitting element group 25 is It is set to be smaller. That is, the constant current circuits 31, 32 and 33 are configured as a second brightness adjuster.

Therefore, as shown in FIG. 3, when the screen is darkened,
That is, when the luminance is low, the red extinction ratio becomes small and the blue extinction ratio becomes large with reference to the green extinction ratio.
As a result, even if the screen is darkened, it is possible to correct reddish black and blue too bright.

Further, as shown in FIG. 4, instead of using the constant current circuits 31, 32, 33, a variable resistor that works in conjunction with the potentiometer 21.
34 is inserted into the circuit of the blue light emitting element group 25 and the red light emitting element group 26, the light emitting element group 25, depending on the resistance value of the variable resistor 34,
By adjusting the current value of 26, the same effect as that of the above embodiment can be obtained.

That is, when the voltage level of the potentiometer 21 is adjusted to a low level, the variable resistor 34 is moved to the red light emitting element group 26 side to increase the current value of the red light emitting element group 26 and the blue light emitting element group 25. By reducing the current, the emission intensity of the red light emitting element group 26 can be made higher than that of the blue light emitting element group 25. In this case, it is necessary to adjust the light emission intensity of the green light emitting element group 27 to an intermediate light emission intensity between blue and red by the variable resistor 24. Further, as a light emitting element group, as shown in FIG. Instead, by using the red discharge tube 35, the green discharge tube 36, and the blue discharge tube 37, it is possible to obtain the same effect as the above embodiment.

[Advantages of the Invention] As described above, according to the present invention, the luminance level of the red light emitting element group is increased and the blue light emitting element group is increased with the luminance level of the green light emitting element group at the low luminance as an intermediate value. Since the luminance level is adjusted to be small, it is possible to correct the collapse of the color balance when the luminance is low, and the luminance characteristic is greatly improved.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a simplified perspective view of a color display according to the present invention, FIG. 3 is a diagram showing a relationship between output voltage and light emission intensity, and FIG. FIG. 5 is a circuit diagram showing another embodiment of the present invention, FIG. 5 is a perspective view showing another embodiment of the light emitting element group, FIG. 6 is a simplified perspective view of a color display shown as a conventional example, and FIG. Example schematic,
FIG. 8 is a relative luminous efficiency characteristic diagram. 20 …… Programmable constant voltage circuit 21 …… Potentiometer 22,23,24,34 …… Variable resistance 25 …… Blue light emitting element group 26 …… Red light emitting element group 27 …… Green light emitting element group 31,32, 33 ... Constant current circuit

Claims (1)

[Claims] 1. A light emitting element group for emitting red, green, and blue colors toward a display with a light emission intensity according to a current value, and adjusting the luminance by the light emission of each light emitting element in common to each light emitting element. As the brightness level is adjusted toward the lower level by the first brightness adjusting means and the first brightness adjusting means, the brightness level of the green light emitting element group is set to an intermediate value, and the red light emitting element group A brightness adjusting device for a color display, comprising: a second brightness adjusting means for increasing the brightness level and decreasing the brightness level of the blue light emitting element group.