JPH08114801A - Liquid crystal display - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a liquid crystal display device capable of always observing in an easy-to-see state in accordance with incident light to the liquid crystal display panel and ambient light in front of the liquid crystal display panel and effectively reducing power consumption. . [Structure] Liquid crystal display panel 16 and this liquid crystal display panel 16
Backlight 17 for illuminating the LCD panel, a drive circuit (20, 21, R, X) for controlling the drive of the backlight 17, and a liquid crystal display panel
Light detection means (19, 11, 12) for detecting incident light incident on the display surface side of 16 and ambient light on the front side of the display surface side, and based on the output of this light detection means, through the drive circuit. Control means 13 for controlling the backlight 17 so as to reduce the amount of light emitted when the incident light and ambient light are dark, turn off the light when bright, and increase the amount of light emitted between them.
Have and.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device having a backlight.

[0002]

2. Description of the Related Art As a conventional liquid crystal display device, for example, there is one shown in FIG. This liquid crystal display device is
U1 includes a liquid crystal display panel and a liquid crystal display 2 having a backlight for illuminating the liquid crystal display panel, a backlight power supply device 3 and an adjusting volume 4, and CPU 1 causes the liquid crystal display panel of the liquid crystal display 2 to display necessary information. The adjustment volume 4 allows the brightness of the backlight of the liquid crystal display 1 to be arbitrarily adjusted through the backlight power supply device 3. However, in this type of conventional liquid crystal display device, the brightness of the backlight has to be adjusted by manually operating the adjusting volume 4, so that there is a problem that the operation is troublesome and the adjusting volume 4 is provided. However, there is a problem that the device becomes large.

As a solution to such a problem, for example, in Japanese Unexamined Patent Publication No. 5-299179, as shown in FIG. 8, an optical sensor 5 is attached to the entire surface of the device provided with the liquid crystal display 2, and the optical sensor 5 is attached. The output of the sensor 5 is amplified by the amplifier 6 and supplied to the backlight power supply device 3 as a power supply voltage. When the surroundings are dark, the output voltage of the backlight power supply device 3 is increased to increase the brightness of the backlight. However, when the surroundings are bright, there has been proposed a device that automatically lowers the output voltage of the backlight power supply device 3 and automatically adjusts the light so as to reduce the brightness of the backlight.

[0004]

However, in the conventional liquid crystal display device shown in FIG. 8, the brightness of the backlight is increased linearly so as to increase when the surroundings are dark and decrease it when the surroundings are bright. Since it is controlled to, there is a problem that the liquid crystal display panel cannot always be observed in an easy-to-see state, and there is a problem that power consumption by driving the backlight increases. That is, when the brightness of the backlight is increased when the surroundings are dark, the liquid crystal display panel becomes much brighter than the surroundings, and the eyes are easily tired and difficult to see, and more power is consumed than necessary. In addition, the backlight is essentially an auxiliary one, and when the light incident on the liquid crystal display panel is bright, it can be observed well without turning on the backlight. Therefore, the backlight is driven also in this case. That is a waste of power consumption.

Further, in the conventional liquid crystal display device shown in FIG. 8, the photosensor 5 is attached to the entire surface of the device provided with the liquid crystal display 2 to detect the ambient light.
When the light from the back side of the liquid crystal display 2, that is, the backlight is strong, there is a problem that it becomes more difficult to see if the brightness of the backlight is reduced.

The first object of the present invention is to appropriately observe the incident light to the liquid crystal display panel and the ambient light in front of the liquid crystal display panel so that the user can always observe in an easy-to-see state and to effectively reduce the power consumption. The liquid crystal display device thus constructed is provided.

The second object of the present invention is to provide the above-mentioned first object.
In addition to the above-mentioned object, the present invention provides a liquid crystal display device appropriately configured so that it can be well observed even when the backlight is strong.

[0008]

In order to achieve the above first object, a first invention is a liquid crystal display panel, a backlight for illuminating the liquid crystal display panel, and a drive for controlling driving of the backlight. A circuit, light detection means for detecting incident light incident on the display surface side of the liquid crystal display panel and ambient light in front of the display surface side, and based on the output of the light detection means, through the drive circuit. The backlight,
When the incident light and the ambient light are dark, the light emission amount of the incident light and the ambient light are reduced, and when the incident light and the ambient light are bright, the light emission amount is turned off, and in the middle thereof, the light emission amount is increased.

In order to achieve the second object, the second invention is a liquid crystal display panel, a backlight for illuminating the liquid crystal display panel, a drive circuit for controlling the driving of the backlight, First light detecting means for detecting incident light incident on the display surface side of the liquid crystal display panel and ambient light in front of the display surface side, and back light on the opposite side of the display surface side of the liquid crystal display panel. The second light detecting means, a comparing means for comparing the output of the second light detecting means with a predetermined value, and the second light receiving means according to the comparison result by the comparing means.
When the output of the light detecting means is less than or equal to the predetermined value, the backlight is controlled via the drive circuit based on the output of the first light detecting means, and when the incident light and the ambient light are dark. The light emission amount is reduced, the light is turned off when it is bright, and the light emission amount is controlled to increase in the middle of them.
When the output of the second light detecting means exceeds the predetermined value, the back light is increased so as to increase the light emission amount corresponding to the excess in addition to the control based on the output of the first light detecting means. It has a control means for controlling the light emission amount of the light.

[0010]

According to the first aspect of the present invention, the backlight reduces the light emission amount when the incident light incident on the display surface side of the liquid crystal display panel and the ambient light in front of the display surface side are low, and when the ambient light is bright, Since the light is turned off and the amount of light emission is increased in the middle thereof, it is possible to always observe the liquid crystal display panel in an easily visible state, and it is possible to effectively reduce power consumption.

Further, in the second invention, when the output of the second light detecting means for detecting the backlight is less than a predetermined value, the backlight is based on the output of the first light detecting means and the liquid crystal display panel. The incident light incident on the display surface side and the ambient light on the front side of the display surface side are controlled so that the light emission amount is reduced when the light is dark, the light is turned off when the light is bright, and the light emission amount is increased in the middle thereof. When the output of the second light detection means exceeds a predetermined value, the light emission quantity of the backlight is increased so that the light emission quantity corresponding to the excess is increased in addition to the control based on the output of the first light detection means. Since it is controlled, the liquid crystal display panel can be satisfactorily observed even when the backlight is strong.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a first embodiment of the present invention. This liquid crystal display device includes an optical sensor 11 and an amplifier 1.
2, a CPU 13, a backlight power supply device 14, and a liquid crystal display 15. The liquid crystal display 15 is provided with a liquid crystal display panel 16 and a backlight 17, and the CPU 13 causes the liquid crystal display panel 16 to display necessary information, and the backlight 17 illuminates the liquid crystal display panel 16 from the rear side. To get it. In this embodiment, the backlight 17 is formed by connecting in parallel a plurality of light emitting diode groups each including a plurality of light emitting diodes D connected in series. The optical sensor 11 is shown in FIG.
As shown in, the display main body 18 having the liquid crystal display 15
The front side of the liquid crystal display panel is arranged so as to receive incident light incident on the display surface side of the liquid crystal display panel and ambient light on the front side of the display surface side through the wide-angle lens 19, and the output thereof is amplified by the amplifier 12. , To the CPU 13.

Further, the backlight power supply device 14 is provided with a power supply 20 and a power supply control circuit 21, the power supply 20 is connected to the backlight 17 via the power supply control circuit 21, and the power supply control circuit 21 will be described later. In addition, the CPU 13 is configured to control the on / off of the backlight 17 and the light emission amount by controlling based on the output of the optical sensor 11. In this embodiment, the power supply control circuit 21
Is formed by connecting a plurality of series circuits of a resistor R and a switch circuit X in parallel, and the switch circuit X of each series circuit is controlled to be turned on / off by the CPU 13, thereby turning on / off the backlight 17 and emitting light. Are configured to control.

The operation of this embodiment will be described below with reference to FIG. In this embodiment, the liquid crystal display panel 16 in the CPU 13 is based on the output from the optical sensor 11.
The brightness of the incident light incident on the display surface side and the ambient light in front of the display surface side are detected, and the CPU 1 detects the brightness according to the brightness.
3, the switch circuit X of the power supply control circuit 21 is controlled to be turned on / off to reduce the light emission amount of the backlight 17 when the incident light and the ambient light are dark as shown by the solid line in FIG. At this time, the light is turned off, and the light emission amount is controlled to increase in the middle thereof. The broken line shown in FIG.
9 shows changes in the amount of light emitted by the conventional control method shown in FIG.

As described above, in this embodiment, when the incident light and the ambient light are dark, the light emission amount of the backlight 17 is reduced, and when the light is bright, the backlight 17 is turned off. Can be suppressed,
At an intermediate brightness, the light emission amount of the backlight 17 is increased, so that the display is easier to see than in the conventional case.

FIG. 4 shows a second embodiment of the present invention. In this embodiment, as shown in FIG. 5, an optical sensor 25 is added to the back side of the display main body 18 having the liquid crystal display 15 as in the first embodiment.
The output is amplified by the amplifier 26 and supplied to the CPU 13 to output the backlight 17 based on the outputs of the photosensor 11 constituting the first photodetector and the photosensor 25 constituting the second photodetector. The on / off and the light emission amount are controlled.

That is, in this embodiment, the CPU 13 detects the brightness of the incident light incident on the display surface side of the liquid crystal display panel 16 and the ambient light in front of the display surface side on the basis of the output from the optical sensor 11. And the optical sensor 2
Based on the output from 5, the brightness of the backlight is detected and compared with a predetermined value, and when the backlight is less than or equal to the predetermined value, the backlight 17 is changed to the output of the optical sensor 11 as in the first embodiment. Based on the brightness of the incident light and ambient light based on the above, the switch of the power supply control circuit 21 is set so as to decrease the light emission amount when it is dark, turn off the light emission when it is bright, and increase the light emission amount in the middle thereof. The circuit X is turned on / off.

On the other hand, when the backlight exceeds a predetermined value, in addition to the control based on the output of the optical sensor 11,
The switch circuit X of the power supply control circuit 21 is on / off controlled so as to increase the light emission amount according to the excess amount.

According to this embodiment, when the back light exceeds a predetermined value, the light emission amount of the backlight is increased so that the light emission amount corresponding to the excess is increased in addition to the control based on the output of the optical sensor 11. Since it is controlled, in addition to the effect of the first embodiment, the liquid crystal display panel 16 can be satisfactorily observed even when the backlight is strong.

It should be noted that the present invention is not limited to the above-described embodiments, and many variations and modifications are possible. For example, in the first and second embodiments, the light sensor 11 receives the incident light incident on the display surface side of the liquid crystal display panel 16 and the ambient light in front of the display surface side via the wide-angle lens 19. However, the incident light and the ambient light may be separately received.
In this case, as the incident light, for example, as shown in FIG. 6A, the light passing through the liquid crystal display panel 16 may be received and detected by the optical sensor 31, and the ambient light may be
For example, as shown in FIG. 6B, a wide-angle lens 19 may be provided on the upper surface of the liquid crystal display body 18, and a wide range of light may be received and detected by an optical sensor (not shown) via the wide-angle lens 19.

[0021]

As described above, according to the first aspect of the invention, it is dark depending on the brightness of the incident light incident on the display surface side of the liquid crystal display panel and the ambient light in front of the display surface side. When it is bright, the backlight turns off, and when it is bright, the backlight turns off, and the amount of light emitted from the backlight increases, so that you can always observe the LCD panel in a state that is easy to see and consume. Power can be effectively reduced.

Further, according to the second aspect of the invention, when the backlight is less than a predetermined value, it depends on the brightness of the incident light incident on the display surface side of the liquid crystal display panel and the ambient light in front of the display surface side. , When it is dark, the light emission of the backlight decreases,
When the light is bright, the backlight is turned off, and the amount of light emitted from the backlight increases between them. When the backlight exceeds a predetermined value, in addition to the above control, the amount of light emitted corresponding to the excess is increased. As described above, since the light emission amount of the backlight is controlled, in addition to the effect of the first invention, the liquid crystal display panel can be satisfactorily observed even when the backlight is strong.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a partial detailed view of FIG.

FIG. 3 is a diagram for explaining the operation of the first embodiment.

FIG. 4 is a block diagram showing a second embodiment of the present invention.

5 is a partial detailed view of FIG. 4. FIG.

FIG. 6 is a diagram for explaining a modified example of the present invention.

FIG. 7 is a block diagram for explaining a conventional technique.

FIG. 8 is likewise a block diagram for explaining a conventional technique.

[Explanation of symbols]

 11, 25, 31 Optical sensor 12, 26 Amplifier 13 CPU 14 Backlight power supply device 15 Liquid crystal display 16 Liquid crystal display panel 17 Backlight 18 Display body 19 Wide-angle lens 20 Power supply 21 Power supply control circuit D Light emitting diode R Resistance X switch circuit

Claims (2)

[Claims] 1. A liquid crystal display panel, a backlight for illuminating the liquid crystal display panel, a drive circuit for controlling driving of the backlight, incident light incident on the display surface side of the liquid crystal display panel, and the display surface. Light detection means for detecting ambient light on the front side of the side, and based on the output of this light detection means, the backlight through the drive circuit, and when the incident light and ambient light are dark, the light emission amount thereof is changed. A liquid crystal display device, comprising: a control unit that controls to decrease the light amount, turn off the light when it is bright, and increase the light emission amount between them. 2. A liquid crystal display panel, a backlight for illuminating the liquid crystal display panel, a drive circuit for controlling driving of the backlight, incident light incident on the display surface side of the liquid crystal display panel, and the display surface. Side first front light detection means for detecting ambient light, second light detection means for detecting back light on the side opposite to the display surface side of the liquid crystal display panel, and second light detection means for the second light detection means. When the output of the second photodetector is less than or equal to the predetermined value according to the comparison means for comparing the output and the predetermined value, the output of the first photodetector is set to the output of the first photodetector. Based on the above, the backlight is controlled via the drive circuit to reduce the amount of light emitted when the incident light and ambient light are dark, turn off the light when bright, and increase the amount of light emitted between them. , The second
When the output of the light detection means exceeds the predetermined value, the light emission of the backlight is increased so as to increase the light emission amount corresponding to the excess in addition to the control based on the output of the first light detection means. A liquid crystal display device comprising: a control unit for controlling the amount.