JPH01136127A - Color liquid crystal display device - Google Patents

Abstract

PURPOSE:To reduce to a level in which no flicker is sensed in an image so that the image is made easily visible by providing a circuit for decreasing a flicker noise component contained in a transmission light of an LCD panel. CONSTITUTION:The title color liquid crystal display device is provided with an LCD panel 1, an LCD panel driving circuit 2, a backlight 4 for illuminating the LCD panel 1 and a backlight driving circuit 5. Also, said device is provided with a band pass filter 8 for selecting a frame signal of this LCD panel driving circuit 2, a photodetector 9 for detecting transmission light from the LCD panel 1, an amplifier 10 for amplifying its output, and a band pass filter 11 for selecting a flicker noise component from an optical signal. Moreover, said device is provided with a phase control circuit 7 for detecting and controlling a phase difference of a frame signal and the flicker noise component, and a circuit 6 for bringing the backlight driving circuit 5 to amplitude modulation by an output signal of this phase control circuit 7. In such a way, the flicker noise component (about 30Hz) is decreased so that no flicker is sensed in an image.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a color liquid crystal display device, and more particularly to a liquid crystal display device with reduced optical flicker noise.

[Conventional technology]

Conventionally, this type of color liquid crystal display device has a multi-structure as shown in FIG. has been and is.

Then, a video signal 3 is applied to the LCD drive circuit 2, and the light from the backlight 4 is irradiated onto the LCD panel 1 to view the transmitted image.

[Problem that the invention seeks to solve]

The conventional color liquid crystal display device described above is AC driven at the frame period of the video signal (approximately 59 Hz), so as shown in Figure 3+8), the transmitted light component has a period twice the frame period. Flicker noise component (approximately 35
Hz), the video has a flickering effect and is difficult to view.

[Means for solving problems]

The present invention includes an LCD panel, an LCD panel drive circuit,
In a color liquid crystal display device having a backlight that illuminates an LCD panel and a backlight drive circuit, a band pass filter that selects a frame signal of the LCD panel drive circuit and a photodetector that detects light transmitted through the LCD panel. , an amplifier that amplifies the output thereof, a bandpass filter that selects the flicker noise component from the optical signal, a phase control circuit that detects and controls the phase difference between the frame signal and the flicker noise component, and an output signal of the phase control circuit. The present invention is characterized in that it includes a circuit that amplitude modulates the backlight drive circuit, and removes flicker noise components.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram of a first embodiment of the present invention. L
The CD panel 1 is driven by an LCD panel drive circuit 2 and is irradiated with light from a backlight 4 to which a backlight drive circuit 5 is connected. A frame signal from the LCD drive circuit 2 is connected to a phase control circuit 7 through a bandpass filter 8. A portion of the transmitted light of the LCD panel 1 is detected by a photodetector 9 and sent to an amplifier 10. The seven power noise components are selectively detected through the bandpass filter 11 and connected to the phase control circuit 7 and the amplitude modulation circuit 6. The output of the phase control circuit 7 is connected to the backlight drive circuit 5 through the amplitude modulation circuit 6.

Next, the operation will be explained. When the video signal 3 is applied to the LCD panel drive circuit 2, the light from the backlight 4 is applied to the LCD panel drive circuit 2.
LCD panel 1 is transmitted through panel 1 according to video signal 3
You can see the image. On the other hand, a part of the light transmitted through the LCD panel 1 is detected by a photodetector 9, and is filtered out by an amplifier 10 and a bandpass filter 11 to generate a flicker noise component (approximately 3QHz).
) is selected. This output is applied to the phase control circuit 7 and the amplitude modulation subcircuit 6, and amplitude modulates the backlight drive circuit 5 with a phase opposite to that of the flicker noise component.

Since the backlight is amplitude-modulated in the opposite phase to the flicker noise component, the flicker of the ridge image is reduced as shown in Figure 3(b).
As shown in Figure 2, it is reduced and becomes easier to see.

FIG. 4 is a block diagram of a second embodiment of the invention. L
A photodetector element 12 and an optical amplification element 13 are provided inside the CD panel 1, and their outputs are input to a bandpass filter 11. The rest is the same as the first embodiment. In this embodiment, since the photodetector and amplifier are included in the LCD panel 1, there is an advantage that it can be made smaller and lighter.

〔Effect of the invention〕

As explained above, the present invention has the effect that by providing a circuit for reducing the flicker noise component (approximately 39 Hz) in the light transmitted through the LCD panel, the flicker noise can be reduced to a level where the flicker is not felt in the image, making the image easier to see. There is.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the first embodiment of the present invention, Fig. 2 is a block diagram of a conventional color liquid crystal display device, and Fig. 3 (a) and tb) show the noise spectrum of the light transmitted through the LCD panel. FIG. 4 is a block diagram of a second embodiment of the present invention. 1...LCD panel, 2...LCD panel drive circuit, 3...video signal, 4...
・Backlight, 5... Backlight drive circuit, 6... Amplitude modulation circuit, 7... Phase control circuit, 8.11... Bandpass filter ,9
...Photodetector, 10...Amplifier, 12
. . . Photodetection element, 13 . . . Optical amplification element. Agent Patent Attorney Oto Uchihara 5 1: LCE) If') Le '7:
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Claims (1)

[Claims] In a color liquid crystal display device having an LCD panel, an LCD panel drive circuit, a backlight for illuminating the LCD panel, and a backlight drive circuit, the L
A bandpass filter that selects the frame signal of the CD panel drive circuit, a photodetector that detects the transmitted light of the LCD panel, an amplifier that amplifies the optical signal of this photodetector, and selects flicker noise components from the optical signal. It is characterized by comprising a bandpass filter, a phase control circuit that detects and controls a phase difference between a frame signal and a flicker noise component, and an amplitude modulation circuit that amplitude modulates the backlight drive circuit using an output signal of the phase control circuit. A color liquid crystal display device.