JPH05319180A - On-vehicle liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide an on-vehicle liquid crystal display device which can dis play an excellent image by adjusting the viewing angle characteristic of a screen in simple manner through the switch selection, for a driver at a different position such as on a front seat or rear seat in a vehicle. CONSTITUTION:A liquid crystal display 13 is installed in the room of a vehicle, and a switch board 16 operated according to the position of an operator who recognizes the liquid crystal display 13 is installed. An image signal processing circuit 11 is equipped with a contrast control input terminal which receives an image signal and outputs the signal for image display on the liquid crystal display after the color decoding processing, etc., and adjusts the cotrast by controlling the amplitude of the signal and a brilliancy control input terminal which adjusts the brilliancy by controlling the pedstal level of the signal. A control circuit 15 selects and applies voltage to the contrast control input terminal and the brilliancy input terminal according to the operation of the switch board 16, and adjusts the viewing angle characteristic of the liquid crystal display.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an on-vehicle liquid crystal display device, and more particularly to a liquid crystal display device capable of changing its viewing angle characteristics.

[0002]

2. Description of the Related Art Generally, a liquid crystal display device can have a thin structure, but has a narrow allowable viewing angle range, and the image quality is significantly deteriorated when the screen is viewed from an angle outside the allowable viewing angle range. To do. Therefore, in the liquid crystal display device mounted in the interior of a vehicle, there is a problem that the image quality is significantly deteriorated depending on the posture and position of the occupant sitting in the vehicle.

Conventionally, when such a liquid crystal display device is mounted on the back surface of a reclining seat of an airplane or the like, the reclining seat is provided with a detector for detecting its inclination angle and outputting a detection signal. The directivity of the liquid crystal display device is controlled by controlling the applied voltage of the contrast control input and the brightness control input in the brightness / chroma processing circuit according to the detection signal and adjusting the brightness and contrast according to the tilt angle of the reclining seat. A technique for adjusting and preventing an extreme deterioration of an image due to a viewing angle has been proposed (see Japanese Laid-Open Patent Publication No. 2-220576).

[0004]

However, in this conventional liquid crystal display device, the tilt angle of the reclining sheet is detected by the variable resistor, and the voltage adjusted by the variable resistor is applied to the contrast control input and the brightness control input. But
Since the viewing angle characteristics of the display device do not change linearly according to the tilt angle of the reclining seat, it is difficult to accurately adjust the viewing angle characteristics according to the tilt angle of the reclining seat.

Further, in the case of a liquid crystal display device mounted in the interior of an automobile, it is necessary to display a good image not only for the front seat occupant but also for the rear seat occupant. The device that adjusts the directivity according to the inclination angle of the vehicle has a problem in that the directivity of the display device cannot be appropriately adjusted for the occupants at positions that are greatly different, such as the front seat and the rear seat.

The present invention has been made in view of the above points, and the occupant at different positions such as the front seat and the rear seat in the vehicle can easily adjust the viewing angle characteristic of the screen by switching the switch. An object of the present invention is to provide a vehicle-mounted liquid crystal display device capable of displaying a good image.

[0007]

In order to achieve the above object, an in-vehicle liquid crystal display device of the present invention is, as shown in FIG. 1, a liquid crystal display installed in the interior of an automobile and a person who views the liquid crystal display. The switch that operates according to the position of the image signal, the image signal is input, the signal for image demodulation is processed, the signal for image display is output to the liquid crystal display, and the amplitude of the signal is controlled to adjust the contrast. An image signal processing means having a control input terminal and a brightness control input terminal for controlling the pedestal level of the signal to adjust the brightness, and a voltage is switched to the contrast control input terminal and the brightness control input terminal according to the operation of the switch means. And a control means for adjusting the viewing angle characteristics of the liquid crystal display by applying the voltage.

[0008]

In the vehicle-mounted liquid crystal display device having the above-described configuration, for example, the display state, that is, the viewing angle characteristic of the twisted nematic type liquid crystal display that is oriented so as to be white when viewed from the upward viewing angle is The switch means is switched for the passenger in the rear seat in a state where the optimum image is displayed for a person, that is, in a state where the gradation characteristics are good without white crushing, black crushing, image inversion, etc. If so, the control means switches each voltage so that the voltage applied to the contrast control input terminal is lowered and the voltage applied to the brightness control input terminal is raised.

Due to the decrease in the applied voltage of the contrast control input, the image signal processing means controls so that the amplitude of the signal waveform for image display is reduced and the contrast of the liquid crystal display is lowered. Further, the image signal processing means controls so as to raise the pedestal level of the output signal for display by raising the applied voltage of the luminance control input, and raise the luminance of the liquid crystal display.

As a result, the screen display of the liquid crystal display is adjusted to lower the contrast and increase the brightness, the viewing angle characteristics of the screen are changed to those for the rear seat in the room, and the gradation is good for the passengers in the rear seat. An image with the characteristics is displayed.

On the other hand, when returning to the state in which the optimum image is displayed for the person in the front seat in the vehicle, the switch means is switched again for the front seat, and the voltage applied to the contrast control input terminal is increased to increase the brightness control input. The voltage applied to the terminals is lowered, thereby increasing the contrast of the screen and lowering its brightness, thereby displaying an optimal image for the person in the front seat.

Thus, by simply operating the switch means, the viewing angle characteristics of the screen can be easily adjusted and a good image can be displayed for passengers at different positions such as the front seat and the rear seat in the vehicle. be able to.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a block diagram of a vehicle-mounted liquid crystal display device. This display device basically has an image signal processing circuit 11 for inputting an image signal and performing processing such as color demodulation,
A signal output circuit 12 for inputting an RGB signal or the like from an image signal, performing polarity inversion, gamma correction, etc., and outputting a display signal to a liquid crystal display 13, and a display controller 10 for controlling each unit including the circuit. And so on.

The image signal processing circuit 11 has a circuit for separating horizontal and vertical synchronizing signals from the input image signal, a circuit for color demodulating the image signal to generate an RGB signal, and the like.
The B signal and the horizontal and vertical synchronizing signals are sent to the signal output circuit 12. In addition, the image signal processing circuit 11 includes RGB signals.
A contrast control input terminal T1 for adjusting the signal amplitude to control the screen contrast and a brightness control input terminal T2 for adjusting the pedestal level of the RGB signals to control the screen brightness are provided.

A control circuit 15 for controlling the contrast control voltage and the brightness control voltage according to a switch operation is connected to the contrast control input terminal T1 and the brightness control input terminal T2, and a voltage signal is input thereto.

The signal output circuit 12 is the image signal processing circuit 1.
A correction circuit for gamma-correcting the RGB signal from 1, RGB
It has a circuit for inverting the polarity of each signal for each horizontal synchronization signal, a circuit for generating a voltage signal for applying to the common counter electrode in the liquid crystal display, and the like.
The GB signal, the voltage signal for the common electrode, and the horizontal / vertical synchronization signals are sent to the liquid crystal display 13.

The liquid crystal display 13 is composed of, for example, an active matrix type color liquid crystal display, the electrode lines are arranged in a matrix in the liquid crystal panel, and thin film transistors (TFTs) function as switching elements at the intersections of the electrode lines. Drive I that is placed and drives each TFT
C is built in. On the back surface of the liquid crystal display 13, a backlight device 14 for back lighting is provided.

The control circuit 15 is a circuit for controlling the contrast and brightness of the screen, and applies a voltage obtained by dividing the stabilizing voltage Vcc by the variable resistor VR1 and the resistors R1 and R5 to the contrast control input terminal T1. In addition, the stabilization voltage V
A voltage obtained by dividing cc by the variable resistor VR2 and the resistors R2 and R3 is applied to the brightness control input terminal T2. Further, the switch circuit S1 that short-circuits the resistor R1 is connected, and the switch circuit S2 that short-circuits the resistor R2 is connected.

Therefore, the contrast is adjusted by controlling the contrast control voltage by operating the variable resistor VR1 and turning the switch circuit S1 on and off, and the variable resistor VR1 is adjusted.
The brightness is adjusted by controlling the brightness control voltage by operating 2 and turning on / off the switch circuit S2.

The display controller 10 is a one-chip CP.
U is a main part and sends a control signal to the image signal processing circuit 11, the signal output circuit 12, the liquid crystal display 13, the backlight device 14, and the control circuit 15 to control the operation thereof. Further, the switch board 16 is connected to the display controller 10, and the switch board 16 has a fine adjustment switch 16a for finely adjusting the brightness and a front seat switch for displaying an image suitable for a front seat passenger in the vehicle. 16b, a rear seat switch 16c is provided for setting an optimal image for a rear seat passenger in the vehicle. As the switch board 16, a touch switch, an optical switch, a remote control switch, or the like provided on the front seat or the rear seat in the vehicle is used, and it may be a voice recognition input device.

The output circuit of the display controller 10 is connected to the switch circuits S1 and S2 of the control circuit 15, and the switch circuit S is operated when the front and rear seat switches of the switch board 16 are operated.
1, a switching signal is sent to S2. Further, when the output circuit of the display controller 10 is connected to the brightness control input terminal T2 via the D / A converter 17 and the resistor R4, and the fine adjustment switch 16a of the switch board 16 is operated,
The voltage signal is applied to the brightness control input terminal T2 through the resistor R4.
Send to.

In the vehicle-mounted liquid crystal display device having such a configuration, control is performed in advance so that an optimal screen display is provided to a person in the front seat in the vehicle when the switch circuits S1 and S2 of the control circuit 15 are off. Adjust VR1 and VR2 of the circuit 15,
Contrast control input terminal T1 and brightness control input terminal T2
The applied voltage of is adjusted. The image signal processing circuit 11 also receives image signals such as map information and vehicle information of television broadcasts, video recorders, and navigation devices.

When the liquid crystal display device is activated and an image signal is input to the image signal processing circuit 11, the image signal processing circuit 1
Reference numeral 1 denotes a horizontal and vertical synchronization signal separated from an input image signal, color demodulation of the image signal to generate an RGB signal, and the RGB signal, horizontal and vertical synchronization signal are output to a signal output circuit 12
Send to. The signal output circuit 12 gamma-corrects the RGB signal from the image signal processing circuit 11, inverts the polarity for each horizontal synchronizing signal, and sends the inverted signal to the liquid crystal display 13, and further
The vertical synchronizing signal and the voltage signal for the common counter electrode are sent to the liquid crystal display 13. The liquid crystal display 13 receives these RGB signals, horizontal / vertical synchronization signals, and common electrode voltage signal, and displays the image on the screen.

Since the switch circuits S1 and S2 of the control circuit 15 are in the OFF state when the liquid crystal display device is activated, the contrast control input terminal T1 and the brightness control input terminal T2 are connected to the front seat passenger in the vehicle. A voltage is applied so that the optimum screen display is obtained.

In this state, when the rear seat switch 16c of the switch board 16 is turned on, the display controller 10 outputs an on signal to the switch circuits S1 and S2 of the control circuit 15 to turn them on.

When the switch circuit S1 is turned on, the resistor R1 of the control circuit 15 is short-circuited, the voltage at the contrast control input terminal T1 is lowered to a predetermined value, and when the switch circuit S2 is turned on, the resistor R2 is short-circuited. , The voltage of the brightness control input terminal T2 rises to a predetermined value. This allows
The image signal processing circuit 11 operates so as to reduce the amplitude of the RGB signal to reduce the contrast of the screen, and further increase the pedestal level of the RGB signal to increase the brightness of the screen.

By such an operation, the liquid crystal display 1
By decreasing the contrast and increasing the brightness of the screen of No. 3, the viewing angle characteristics of the liquid crystal display 13 are changed so that the directivity of the display is directed to the rear seat, and the optimum screen display is made for the passenger in the rear seat of the vehicle. It becomes a state.

Therefore, the occupant in the rear seat is the switch panel 1
It is possible to easily bring the screen of the liquid crystal display 13 into an optimum state simply by operating the rear seat switch 16c.

On the other hand, when the front seat switch 16b is turned on in this state, the display controller 10 switches the switch circuit S.
1 and S2 operate to return to the off state. Therefore, the applied voltages of the contrast control input terminal T1 and the brightness control input terminal T2 are returned to the original values, the contrast and brightness of the screen are switched for the front seat, and the optimum screen display for the passenger in the front seat in the vehicle is displayed. It is ready to be done.

On the other hand, the fine adjustment switch 1 of the switch board 16
When 6a is operated, the display controller 10 displays D / A
A voltage signal of a minute voltage is applied to the brightness control input terminal T2 through the resistor R4 via the converter 17, and the voltage of the brightness control input terminal T2 is finely adjusted. As a result, an occupant in the front seat or the rear seat in the vehicle can finely adjust the brightness of the display screen to obtain a more optimal screen display. In this case, if a resistor having a high resistance is used as the resistor R4, the luminance is minutely changed. Therefore, even if the contrast is not adjusted, the display state of the screen is not deteriorated visually.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a vehicle-mounted liquid crystal display device of the present invention.

FIG. 2 is a block diagram of a vehicle-mounted liquid crystal display device according to an embodiment.

[Explanation of symbols]

 11-image signal processing circuit, 12-signal output circuit, 13-liquid crystal display, 15-control circuit, 16-switch board.

Claims (1)

[Claims] 1. A liquid crystal display installed in the interior of an automobile, a switch means for operating the liquid crystal display according to the position of a viewer, an image signal is input, and processing such as color demodulation is performed to display the image. Image signal processing means for outputting the signal of FIG. 3 to the liquid crystal display, and having a contrast control input terminal for adjusting the contrast by controlling the amplitude of the signal and a brightness control input terminal for controlling the pedestal level of the signal to adjust the brightness. And a control means for adjusting the viewing angle characteristics of the liquid crystal display by switching and applying a voltage to the contrast control input terminal and the brightness control input terminal according to the operation of the switch means. Liquid crystal display device.