JPH05249439A - Video signal processor - Google Patents

Abstract

PURPOSE:To prevent the unevenness of brightness and the change of contrast by changing the clamping level of a video processing signal at a starting time and an ending time of a vertical scanning interval at the time of attaching a visual axis conversion finder. CONSTITUTION:A load detective signal is generated interlocked with the attaching of the visual axis conversion finder on the display image observation surface of a liquid crystal pannel 23 and sent to a control circuit 20 from a terminal 2. Then a brightness control signal changing the clamping level at a starting time and an ending time of the vertical scanning interval is sent to an R clamping circuit 16-1, a G clamping circuit 16-2 and a B clamping circuit 16-3 from the control circuit 20 through a brightness controller 25. Then the signals of output waveforms generating a high output signal at a starting time and an ending time of scanning are outputted from the R, G, B clamping circuits 16-1 to 16-3. Thus, the ascending of the brightness of a black level is suppressed and the distortion of a visual angle is eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal processing device, and more particularly to a visual axis mounted on a liquid crystal display image observation surface opposite to a backlight irradiation surface of a liquid crystal panel of a backlight type liquid crystal display device. The present invention relates to a video signal processing device that removes unevenness in brightness, unevenness in brightness, and changes in contrast observed in a conversion finder.

[0002]

2. Description of the Related Art Conventionally, a display screen of a liquid crystal display device is sufficiently illuminated from the liquid crystal panel surface by illuminating the liquid crystal panel by a backlight system and applying a video signal to each pixel in the liquid crystal panel. Since the observation is performed from the position, the liquid crystal display surface can be observed at substantially the same angle. Therefore, there was no difference in brightness and luminance depending on the viewing angle for observing the liquid crystal panel. Therefore, it is not necessary to change the operating point and the operating level of the video signal depending on the difference in the image display position of the liquid crystal display panel, and it is sufficient to clamp the pedestal level at a certain operating point and operate.

[0003]

However, when the visual axis conversion finder is attached to the display image observing side of the liquid crystal panel in the display device, the brightness level of the display screen observed in the visual axis conversion finder is shown in FIG. As shown, it changes depending on the viewing angle. For example, as shown in FIG. 5, the liquid crystal panel 8
When the liquid crystal display screen is observed (optical paths B, C) above and below the display surface (however, when the liquid crystal panel 8 is arranged in the vertical direction) from a direction tilted by a certain angle, uneven brightness, uneven brightness, and contrast. There was a bad point that changes appeared. This is because, as shown in FIG. 3, the brightness level D for black display and the brightness level E for white display, and (white display brightness / (black display brightness) = contrast (not shown in the figure), depending on the viewing angle (shown on the horizontal axis). Therefore, the present invention is directed to such uneven brightness and contrast change observed in the visual axis conversion finder mounted on the liquid crystal display image observation surface of the liquid crystal panel of the liquid crystal display device. An object of the present invention is to provide a video signal processing device capable of preventing the occurrence of the above.

[0004]

In order to achieve the above object, according to the invention of claim 1, in a liquid crystal display device in which a visual axis conversion finder is attached to a display image observation side of a liquid crystal panel, a visual axis conversion finder is attached. With the mounting detection signal generated together with this, the clamp level of the image processing signal sent to each pixel in the liquid crystal panel is changed at the start and end of the vertical scanning period only when the visual axis conversion finder is mounted. Further, according to claim 2, in the liquid crystal display device in which the visual axis conversion finder is attached to the display image observation side of the liquid crystal panel, only when the visual axis conversion finder is attached by the attachment detection signal generated together with the attachment of the visual axis conversion finder. The clamp level and the video processing signal level of the video processing signal sent to each pixel in the liquid crystal panel are changed at the start and end of the vertical scanning period of the video processing signal.

[0005]

According to the video signal processing apparatus of the first aspect of the present invention, the clamp level of the video processing signal sent to each pixel in the liquid crystal panel is changed at the start and end of the vertical scanning period. The light transmittance of is changed, and the uneven brightness due to the viewing angle dependency is eliminated. According to the video signal processing device of claim 2, the clamp level and the signal processing level of the video processing signal sent to each pixel in the liquid crystal panel are changed at the start and end of the vertical scanning period. Changes the light transmittance of
The unevenness in brightness, the unevenness in brightness, and the change in contrast due to the viewing angle dependence are eliminated.

This is due to the property that the light transmittance of the liquid crystal changes depending on the applied voltage, as shown in the voltage-light transmittance characteristic diagram of FIG.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. The video signal processing apparatus of this embodiment has the circuit configuration shown in FIG. That is, the composite video signal input to the input terminal 1 is separated into the luminance signal Y and the chroma signal C by the Y / C separation circuit 10. The separated luminance signal Y is input to the matrix circuit 14 described later via the image quality adjustment circuit 11. Further, the chroma signal C is converted into R- by the voltage controlled oscillation circuit (VCO) 13 and the demodulation circuit 12.
After being demodulated into the Y color difference signal and the BY color difference signal, they are sent to the matrix circuit 14 and added to the luminance signal Y to obtain R, G, B demodulated signals.

The R, G, B demodulated signals have waveforms as shown in FIG. 2B (only the waveform of the R demodulated signal is illustrated in FIG. 2A), and the respective R, G, B are shown. The demodulated signals are R, G, B clamp circuits 16-1, 16-2, 16 respectively.
-3 and .gamma. Correction circuits 17-1, 17-2, 17-3, and the applied signal level and operating point are adjusted to match the voltage-transmittance characteristic (VT characteristic) of the liquid crystal pixel. At this time, the voltage applied to the liquid crystal is required not to be applied with a direct current voltage in order to prevent the liquid crystal from being deteriorated due to the direct current separation action, and the polarity inversion / switching circuits 18-1, 18-2,
The polarity is inverted for each horizontal scanning line of the TFT liquid crystal panel 23 via 18-3 and is input to the source driver circuit 21 of the liquid crystal panel.

As a driver circuit of the TFT liquid crystal panel 23, a source driver circuit 21 for receiving R, G, B signals and line-sequentially outputting a signal for each line of horizontal scanning of the liquid crystal panel, and a vertical direction of the liquid crystal panel. There is a gate driver circuit 22 for each gate scan of the scan line. In the control circuit 20, the composite video signal input to the terminal 1 is synchronously separated (s / se).
p) A synchronizing signal is separated via the circuit 19, clock pulses synchronized with each other are generated based on the synchronizing signal, gate and source driver signals are generated, and an internal horizontal synchronizing scanning signal, an internal vertical scanning signal, The polarity inversion signal is supplied to the source driver circuit 21, the gate driver circuit 22, and the polarity inversion / switching circuit 18-1, respectively.
Input to 18-2 and 18-3.

In the present embodiment, a visual axis conversion finder 9 is attached to the liquid crystal display screen observation side, which is opposite to the backlight irradiation side of the liquid crystal panel 23, as shown in FIG. The display image on the liquid crystal panel 23 is viewed through the finder 9. In this specification, the “visual axis conversion finder” refers to an optical system for observing a liquid crystal display image from a direction perpendicular to the normal line of the liquid crystal display surface of the liquid crystal panel, as shown in FIG. 5, for example. , A prism 3, mirrors 4 and 5, and lenses 6 and 7 which are arranged so as to be observed in the vertical direction (illustrated as a light ray A) in the central portion of the screen. Thus, when the right-angle prism 3, the mirror 4, and the mirror 5 are provided so that the liquid crystal display screen can be observed from the right angle direction (light ray A direction), the screen upper direction (light ray B direction) and the lower direction (light ray B direction). In the upper and lower parts of the screen, the black level luminance tends to be high and the white level luminance tends to be low, so that the contrast is low. That is, uneven brightness appears on the upper and lower parts of the liquid crystal display screen visible to the visual axis conversion finder 9. Therefore, the above-mentioned viewing angle distortion can be eliminated by changing the operating point of the applied signal only on the upper and lower portions of the liquid crystal display surface (claim 1) or by changing the applied signal level together with the operating point (claim 2).

The video signal processing method will be described below. FIG. 4 is a characteristic diagram showing the relationship between the applied voltage and the transmittance of the normally white liquid crystal, and the transmittance of the liquid crystal changes according to the R, G, and B signals that change within the illustrated image signal application range. However, it is displayed as a color image. This operating point and operating range are R, G, and R in the block diagram of FIG.
B clamp circuits 16-1, 16-2, 16-3 and R, G, B amplifier circuits 15-1, 15-2, 15-
Determined in 3. Now, when clamping the pedestal level as the clamp point, the clamp level C shown in FIG.
The LP point becomes constant, and the operating range is determined by the amplitude of the signal from the clamp level CLP. Therefore, the brightness control signal for changing the clamp-up level at the scanning start point and the scanning end point is changed to R in the vertical scanning cycle shown in FIG. By adding to the clamp circuit 16-1, the G clamp circuit 16-2, and the B clamp circuit 16-3, it is possible to suppress the increase in black level luminance and improve the viewing angle distortion (FIG. 2 (e)).

The brightness control signal is generated based on the visual axis conversion finder mounting detection signal from the terminal 2, and when there is no visual axis conversion finder mounting detection signal, the luminance control signal is clamped to a constant level as in the conventional case. Furthermore, in addition to the above-mentioned correction by the clamp level, if the signal amplitude level is also changed at the same time, in particular, the decrease in the brightness of the white level accompanying the clamp level correction can be improved, and the contrast can also be corrected.
Higher-performance correction can be performed. A waveform diagram of the video signal after contrast correction at this time is shown in FIG. 2D, and a waveform diagram of the clamp circuit is shown in FIG. 2F.

According to the signal processing apparatus of this embodiment, a mounting detection signal is generated in association with the mounting of the visual axis conversion finder mounted on the display image observing surface of the liquid crystal panel 23, and the terminal 2 mounts it on the control circuit 20. A detection signal is sent. From the control circuit 20 to the bright controller 2
A luminance control signal (whose waveform is shown in (c) of FIG. 2) for changing the clamp level at the start and end of the vertical scanning via the R.C. It is sent to the B clamp circuit 16-3, and R,
As shown in FIG. 2F, the G and B clamp circuits 16-1, 16-2, and 16-3 output a signal having an output waveform that generates a high output signal at the start and end of scanning, so that the black signal is output. It is possible to suppress the increase in the brightness of the level and remove the viewing angle distortion.

Further, in addition to the above-mentioned correction by the clamp level, if the signal amplitude level is also changed at the same time, it is possible to improve the brightness reduction of the white level accompanying the clamp level correction, and it is also possible to correct the contrast. Can be corrected. The corrected video signal waveform at this time is as shown in FIG. 2D, and the output signal waveform of the clamp circuit at this time is as shown in FIG. 2F. According to the video signal processing device of this embodiment, if the visual axis conversion finder is removed from the liquid crystal display device, no device detection signal is generated and the device functions as a video signal processing device of the conventional liquid crystal display device. By attaching and detaching the conversion finder, it can be used as both video signal processing devices.

[0015]

As is apparent from the above description, according to the video signal processing device of the present invention, the visual angle distortion of the upper and lower portions of the liquid crystal display screen accompanying the attachment of the visual axis conversion finder is applied to the liquid crystal panel. By simply changing the clamp level or the clamp level and the signal amplitude level, it is possible to easily correct and see with the same display quality as when looking directly.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit configuration of a video signal processing device according to an embodiment of the present invention.

2 (a), (b), (c), (d), (e) and (f) are the time width of one vertical scanning period and demodulation R, respectively.
FIG. 5 is a diagram showing a signal waveform, a luminance control signal waveform (when the contrast is constant), an R amplifier output signal waveform, an R clamp circuit output signal waveform (when the contrast is constant), and an output signal waveform from the R clamp circuit (when the contrast is variable).

FIG. 3 is a characteristic diagram showing a change in a viewing angle of a liquid crystal against a brightness level.

FIG. 4 is a characteristic diagram showing a relationship between applied voltage and transmittance of a liquid crystal panel.

FIG. 5 is a side view showing a state in which a visual axis conversion finder is attached to a display screen observation surface of a liquid crystal panel.

[Explanation of symbols]

1 input terminal 2 visual axis conversion finder mounting signal input terminal 9 visual axis conversion finder 10 Y / C separation circuit 11 image quality adjustment circuit 12 demodulation circuit 13 voltage controlled oscillator 14 matrix circuit 15-1, 15-2, 15-3 R, G, B amplifier circuit 16-1, 16-2, 16-3 R, G, B clamp circuit 17-1, 17-2, 17-3 γ correction circuit 18-1, 18-2, 18-3 Polarity inversion / Switching circuit 20 Control circuit 21 Source driver 22 Gate driver 23 TFT liquid crystal panel

Claims (2)

[Claims] 1. A liquid crystal display device in which a visual axis conversion finder is attached to a display image observing side of the liquid crystal panel, and a liquid crystal panel is attached only when the visual axis conversion finder is attached by an attachment detection signal generated when the visual axis conversion finder is attached. A video signal processing device, characterized in that a means for changing a clamp level of a video processing signal to be sent to each of the pixels at the start and end of a vertical scanning period is provided. 2. In a liquid crystal display device in which a visual axis conversion finder is attached to a display screen observation side of a liquid crystal panel, a mounting detection signal generated together with the mounting of the visual axis conversion finder causes only a visual axis conversion finder to be attached.
Video signal processing for a liquid crystal display device, comprising means for changing the clamp level and the video processing signal level of the video processing signal sent to each pixel in the liquid crystal panel at the start and end of the vertical scanning period of the video processing signal. method.