JP2837020B2 - Video signal processing device - Google Patents

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 apparatus, and more particularly, to a visual axis mounted on a liquid crystal display image observation surface opposite to a backlight irradiation surface with respect to a liquid crystal panel of a backlight type liquid crystal display device. The present invention relates to a video signal processing device that removes brightness unevenness, brightness unevenness, and contrast change observed in a conversion finder.

[0002]

2. Description of the Related Art Conventionally, a display screen of a liquid crystal display device illuminates a liquid crystal panel by a backlight method, and a screen displayed when a video signal is applied to each pixel in the liquid crystal panel is sufficiently separated from a liquid crystal panel surface. Since the observation is made 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 due to the difference in viewing angle for observing the liquid crystal panel. Therefore, it is not necessary to change the operating point and operating level of the video signal depending on the difference in the image display position of the liquid crystal display panel, and it is only necessary to clamp the pedestal level to a fixed operating point for operation.

[0003]

However, when the visual axis conversion finder is attached to the display image observation side of the liquid crystal panel in the display device, the luminance level of the display screen observed in the visual axis conversion finder is as shown in FIG. As shown, it changes with the viewing angle. For example, as shown in FIG.
When the liquid crystal display screen is observed from above and below the display surface (when the liquid crystal panel 8 is arranged in a vertical direction) from a direction inclined at a certain angle (optical paths B and C), uneven brightness, uneven brightness and contrast are observed. There was a bad point that change appeared. As shown in FIG. 3, this depends on the viewing angle (shown on the horizontal axis) and the brightness level D for black display and the brightness level E for white display, and (white display brightness / (black display brightness) = contrast (shown in FIG. 3). Therefore, the present invention relates to such a luminance unevenness and contrast change observed in a visual axis conversion finder attached to a liquid crystal display image observation surface of a liquid crystal panel of a liquid crystal display device. It is an object of the present invention to provide a video signal processing device capable of preventing the occurrence of the video signal.

[0004]

In order to achieve the above object, according to the first aspect of the present invention, in a liquid crystal display device having a visual axis conversion finder mounted on a display image observation side of a liquid crystal panel, the visual axis conversion finder is mounted. The clamp level of the video processing signal to be sent to each pixel in the liquid crystal panel only at the time of mounting the visual axis conversion finder is changed at the start and end of the vertical scanning period by the mounting detection signal generated at the same time. In a liquid crystal display device having a visual axis conversion finder attached to a display image observation side of a liquid crystal panel, a mounting detection signal generated when the visual axis conversion finder is attached is used only when the visual axis conversion finder is attached. 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]

In order to achieve the above object, the invention of claim 1 is directed to a display image observation side of a liquid crystal panel.
Of a liquid crystal display with a visual axis conversion finder
An image signal processing device, and a liquid crystal display device has a visual axis conversion file.
The device detection signal generated when the
When installing the visual axis conversion finder,
Vertical scanning of the clamp level of the video processing signal sent to each pixel
Control signals that change at the beginning and end of the period
Control means for sending to the clamp circuit in the display device is provided.
LCD panel display viewed through the visual axis conversion finder
An image characterized by correcting visual distortion at the top and bottom of the screen
It is a signal processing device. The invention of claim 2 is a liquid crystal panel.
A viewing axis conversion finder is installed on the viewing side of the panel display screen
Video signal processing device for a liquid crystal display device,
Occurs when a visual axis conversion finder is attached to the device
When the visual axis conversion finder is attached by the device detection signal
To clamp the video processing signal sent to each pixel in the LCD panel
Level and video processing signal level
Control signals that change at the start and end of the scanning period
Send to clamp circuit and amplifier circuit in liquid crystal display
Equipped with control means, through visual axis conversion finder
Correct the viewing angle distortion on the upper and lower parts of the LCD screen display screen
A video signal processing apparatus characterized in that:

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

[0007]

An embodiment of the present invention will be described below with reference to the drawings. The video signal processing device of the present embodiment has the circuit configuration shown in FIG. That is, the composite video signal input to the input terminal 1 is separated by the Y / C separation circuit 10 into a luminance signal Y and a chroma signal C. The separated luminance signal Y is input to a matrix circuit 14 described later via the image quality adjustment circuit 11. Further, the chroma signal C is supplied to the R-control circuit 13 by a voltage-controlled oscillation circuit (VCO) 13 and a demodulation circuit 12.
After being demodulated into a Y color difference signal and a BY color difference signal, the signal is 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 R demodulated signal waveform is illustrated in FIG. 2A), and each of the R, G, B The demodulated signals are respectively R, G, B clamp circuits 16-1, 16-2, 16
-3 and γ correction circuits 17-1, 17-2, and 17-3, and are adjusted to an applied signal level and an operating point that match the voltage-transmittance characteristic (VT characteristic) of the liquid crystal pixel. At this time, it is required that no DC voltage is applied to the liquid crystal to prevent the liquid crystal from being degraded by the DC 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.

The driver circuit for the TFT liquid crystal panel 23 includes a source driver circuit 21 for receiving R, G, and B signals and outputting a signal for each horizontal scanning line of the liquid crystal panel in a line-sequential manner, and a vertical driver for the liquid crystal panel. There is a gate driver circuit 22 for scanning each gate of the scanning line. The control circuit 20 separates the composite video signal input to the terminal 1 from the sync separation (s / se).
p) The synchronizing signal is separated through the circuit 19, and clock pulses synchronized with the synchronizing signal are generated based on the synchronizing signal to generate gate and source driver signals. 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 this embodiment, a visual axis conversion finder 9 is attached to the liquid crystal panel 23 on the liquid crystal display screen observation side opposite to the backlight irradiation side, as shown in FIG. The display image on the liquid crystal panel 23 is viewed through the finder 9. In this specification, the "view axis conversion finder" refers to an optical system for observing a liquid crystal display image from a direction perpendicular to a normal line of a liquid crystal display surface of a liquid crystal panel as described above. For example, as shown in FIG. A prism 3, mirrors 4 and 5, and lenses 6 and 7 arranged so as to be observed from the vertical direction (illustrated as a light ray A) at the center of the screen. As described above, when the right-angle prism 3, mirror 4, and mirror 5 are provided so that they can be observed from the right angle direction (light ray A) at the center of the liquid crystal display screen, the upper direction of the screen (light ray B direction) and the lower direction (light ray A direction). C direction) is viewed at a certain angle, and in the upper and lower portions of the screen, the black level luminance tends to be high, the white level luminance tends to decrease, and the contrast decreases. That is, uneven brightness appears on the upper and lower portions of the liquid crystal display screen viewed by the visual axis conversion finder 9. Therefore, if the operating point of the applied signal is changed only for the upper and lower portions of the liquid crystal display surface (claim 1), or the applied signal level is changed together with the operating point (claim 2), the above-mentioned viewing angle distortion can be eliminated.

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 liquid crystal of the normally white mode. The transmittance of the liquid crystal changes according to the R, G, and B signals that change within the illustrated video signal application range. The image is displayed as a color image. These operating points and operating ranges are designated by 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, and 15-
3 is determined. Now, when clamping the pedestal level as a 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 at the vertical scanning period shown in FIG. The addition to the clamp circuit 16-1, the G clamp circuit 16-2, and the B clamp circuit 16-3 suppresses an increase in black level luminance and improves viewing angle distortion (FIG. 2E).

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

According to the signal processing device of the present embodiment, a mounting detection signal is generated in conjunction with the mounting of the visual axis conversion finder mounted on the display image observation surface of the liquid crystal panel 23, and mounted on the control circuit 20 from the terminal 2. A detection signal is sent. From the control circuit 20 to the bright controller 2
5, a luminance control signal for changing the clamp level at the start and end of the vertical scan (the waveform is shown in FIG. 2C) is output from the R / clamp circuit 16-1, the G clamp circuit 16-2, Sent to the B clamp circuit 16-3,
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. It is possible to suppress an increase in the luminance of the level and eliminate the viewing angle distortion.

Further, if the signal amplitude level is simultaneously changed in addition to the above-described correction using the clamp level, the decrease in the brightness of the white level due to the correction of the clamp level can be improved, and the contrast can be corrected. Can be corrected. FIG. 2D shows the corrected video signal waveform at this time, and FIG. 2F shows the output signal waveform of the clamp circuit at this time. According to the video signal processing device of the present embodiment, if the visual axis conversion finder is removed from the liquid crystal display device, no device detection signal is generated, and the visual signal processing 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 apparatus of the present invention, the visual signal distortion applied to the upper and lower portions of the liquid crystal display screen accompanying the mounting 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, the correction can be easily made and the image can be viewed with the same display quality as in the case of direct viewing.

[Brief description of the 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.

FIGS. 2 (a), (b), (c), (d), (e) and (f) are the time width of one vertical scanning period, demodulation R
FIG. 5 is a diagram illustrating a signal waveform, a brightness 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 versus a luminance level of a liquid crystal.

FIG. 4 is a characteristic diagram showing a relationship between an applied voltage and a transmittance of the 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]

REFERENCE SIGNS LIST 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

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-148126 (JP, U) JP-A-3-8320 (JP, U) (58) Fields surveyed (Int.Cl. ⁶ , DB name) G02F 1/133 G02F 1/13 G09G 3/36

Claims (2)

(57) [Claims] 1. A video signal processing method for a liquid crystal display device having a visual axis conversion finder attached to a display image observation side of a liquid crystal panel.
An apparatus, by the device detection signal generated with the mounting of the visual axis conversion finder liquid crystal display device, taken in the visual axis conversion finder
At the time of attachment , 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
Controller that sends control signals to the clamp circuit in the LCD
B - with Le means, the display screen of the liquid crystal panel as seen through the viewing axis conversion finder
A video signal processing device for correcting upper and lower viewing angle distortions . 2. A video signal processing device of a liquid crystal display device having a visual axis conversion finder attached to a display screen observation side of a liquid crystal panel.
A clamp level and a video processing signal level of a video processing signal to be sent to each pixel in the liquid crystal panel when the visual axis conversion finder is mounted, according to a device detection signal generated when the visual axis conversion finder is mounted on the liquid crystal display device. Control signal to change the start and end of the vertical scanning period of the video processing signal.
To send to the clamp circuit and amplifier circuit in the crystal display device.
Ntoro - comprising a Le means, the display screen of the liquid crystal panel as seen through the viewing axis conversion finder
Video signal characterized by correcting upper and lower viewing angle distortions
Processing equipment .