JPH05300448A - Video display device - Google Patents

Abstract

PURPOSE:To perform the video control of pictures with different aspect ratios with high accuracy by detecting whether the picture of input video signal is laterally long or not and switching the detecting area of a peak value or the like based on the detected result. CONSTITUTION:When it is detected that the picture of input video signal is laterally long, a laterally long picture detection circuit 20 supplies the detected output signal together with horizontal and vertical synchronizing signals H- SYNC and V-SYNC given from a video signal processing circuit 3 to a picture area setting circuit 4. The circuit 4 sets the detecting area of video signal within the display area of the laterally long picture corresponding to a control signal from the circuit 20. In the detecting area of the laterally long picture set by the circuit 4, a peak detection circuit 5, mean value detection circuit 6 and black level detection circuit 7 detect the peak value, mean value and black level of a luminance signal Y. Thus, the effect of a non-signal part or the like generated at the upper and lower parts of the laterally long picture can be removed, and optimum video control is enabled at all times.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video display device for displaying a video signal using a liquid crystal panel or a cathode ray tube.

[0002]

2. Description of the Related Art Conventionally, in various image display devices,
In order to display an image in an optimum state, a method of correcting the characteristic peculiar to each image display device according to the level of an input signal is used. In particular, since a video display device using a transmissive or projection type liquid crystal panel can obtain a bright display, it has been used as a display device instead of a cathode ray tube in a direct view type liquid crystal television receiver or a projection type liquid crystal projection device. There is.

However, since the liquid crystal panel has a narrower range of input voltage capable of expressing gradation as compared with a cathode ray tube, there is a tendency for blackout and whiteout to occur. FIG. 2 shows the transmittance of the liquid crystal panel with respect to the applied voltage (V), and the portion corresponding to ΔV of the electro-optical characteristics of the liquid crystal is the input voltage range. In order to cope with such a problem that the width of the applied voltage that can be applied as the input voltage is narrow, in the liquid crystal display device, the AGC is applied to the input video signal according to the input video level to control the contrast or to adjust the gradation. Some of them are performing image control such as brightness and gamma correction for improvement.

[0004]

In the above conventional video display device, the screen area for extracting the video level detection signal which is the basis for controlling the video is set to the area of the normal screen (aspect ratio 4: 3). Therefore, black areas are generated in the upper and lower parts of a horizontally long screen image (16: 9 aspect ratio), which affects the detected video level when such a video signal is input as a video level detection signal. There was a problem that video control was not performed.

[0005]

In order to solve the above problems, the present invention detects the peak value, the average value, the black peak value and the pedestal level value of the luminance signal of the input video signal at every predetermined period and detects this. In a video display device adapted to control a video contrast value, a brightness value, a gamma value, etc. based on data, a screen detection area designating means for designating a detection area of a screen for detecting each of the detection data, and an input video image. Screen detection means for detecting whether the screen aspect ratio of the signal is a normal screen (aspect ratio 4: 3) or a landscape screen (aspect ratio 16: 9), and the above-mentioned screen based on the screen information detected by the screen detection means. A control means for controlling the detection area setting means to switch the area on the screen for detecting the level of the video signal according to the normal screen or the horizontally long screen is provided.

[0006]

According to the above construction, when the input video signal is supplied, the screen detection means detects the screen information indicating whether the input video signal is the normal screen or the landscape screen from the luminance signal of the input video signal. Based on this screen information, the screen detection area setting means sets a detection area for detecting each optimum detection data on the screen. Therefore, even if the input video signal is switched between the normal screen and the landscape screen, the optimum detection area is always set on the screen of the input video signal, and from this detection area, the peak value and average value of the luminance signal of the input video signal are set. , Black peak value and pedestal level value are detected. Then, based on the respective detection data, the input video signal is corrected according to the characteristics of the video display device and the like.

[0007]

FIG. 1 is a block diagram of an embodiment of the present invention. In FIG. 1, an input video signal supplied from an input terminal T is sampled, quantized and converted into an 8-bit digital signal by an analog / digital (hereinafter referred to as A / D) conversion circuit 1, and then Y / The C separation circuit 2 separates the luminance signal Y and the chroma signal C, and further, the video signal processing circuit 3 performs various kinds of video signal processing such as sync separation and demodulation, and the R, G, B signals and the horizontal sync signal H-. The SYNC and the vertical synchronization signal V-SYNC are derived. The R, G, B signals are corrected by the R, G, B control circuit 14 by a control signal described later and supplied to the liquid crystal panel 15 to display an image.

Reference numeral 4 in the drawing denotes a screen area setting circuit used for detecting the luminance signal Y. The detection area of the video signal is detected by a control signal from a horizontally long screen detecting circuit 20 which will be described later.
The area is set in the shaded area in (b). That is, when the horizontally long screen detection circuit 20 determines that the input video signal is for the horizontally long screen, the screen area setting circuit 4 detects the detection area within the horizontally long screen display area indicated by the diagonal lines in FIG. 3B. If it is determined that the input video signal is not for a horizontally long screen, it means that this is for a normal screen. Therefore, the screen area setting circuit 4 detects the detection area as shown in FIG. As indicated by the slanted lines in, the display area is expanded beyond the display area of the horizontally long screen to the display area of the normal screen.

In the detection areas which are set by the screen area setting circuit 4 and are different between the horizontally long screen and the normal screen, the peak value, the average value and the black level of the luminance signal Y are the peak detection circuit 5 and the average value detection circuit 6, respectively. And a pedestal level is detected by the pedestal detection circuit 8.

The peak value, the average value and the black level of the luminance signal Y detected by the peak detection circuit 5, the average value detection circuit 6 and the black level detection circuit 7 are corrected by the pedestal level detection circuit 8 in the correction calculation circuit 9. According to the derived pedestal level, correction calculation is performed to the true video signal level excluding the sync signal level, and the calculation results are stored in the peak data register 10, the average value register 11 and the black level data register 12, respectively.

The peak value, the average value and the black level of the luminance signal Y derived from the peak data register 10, the average value register 11 and the black level data register 12 are supplied to the video control arithmetic circuit 13, and this video control arithmetic circuit is supplied. At 13, a control signal such as a contrast control signal, a brightness control signal or a gamma correction control signal for correcting the R, G, B signals according to the characteristics of the liquid crystal panel 15 is calculated, and the control signals are calculated as R, G, B. It is supplied to the control circuit 14 to correct the R, G, B signals.

On the other hand, the horizontally long screen detection circuit 20 surrounded by the one-dot chain line detects that the input video signal has a horizontally long screen with an aspect ratio of 16: 9, and its detection output signal is the video signal processing circuit 3. Is supplied to the screen area setting circuit 4 together with a horizontal synchronizing signal H-SYNC and a vertical synchronizing signal V-SYNC which are derived from a synchronizing signal separating circuit (not shown) in The setting is performed in an area suitable for a vertically long screen as indicated by the diagonal lines in FIG. 3B, and when the screen is not the vertically long screen, that is, in the case of a normal screen, the normal as shown by the diagonal lines in FIG. Set it so that it is performed in an area suitable for the screen.

Next, the horizontal screen detection circuit 20 will be described. Luminance signal Y separated by the Y / C separation circuit 2
Is guided to the screen area setting circuit 34 for setting the detection area of the luminance signal Y, and the detection area indicated by the diagonal lines in FIG.
Is set. That is, the above-mentioned detection areas are formed in the upper part and the lower part of the display screen, and their positions are provided outside the horizontally long screen display area shown between the dotted lines in the central part of the display screen.

The peak value, the black level and the average value of the luminance signal Y are respectively detected in the detection areas shown in FIG.
24 and average value detection circuits 25 and 26, and the detected outputs are corrected and calculated by the correction arithmetic circuit 27 by the pedestal level detected by the pedestal level detection circuit 37 in the same manner as in the correction arithmetic circuit 9 described above. The outputs are peak data registers 28 and 29, black level data registers 30 and 31, and average value data register 32,
Write in 33.

The peak data and the black level data from the peak data registers 28 and 29 and the black level data registers 30 and 31 are supplied to the coincidence detection circuit 38, and the coincidence detection circuit 38 detects the white peaks for each of the detection areas. It is detected that the level coincides with the black peak level, and the average value data in the detection area from the average value data registers 32, 32 is led to the average image level determination circuit 35, and the average image level determination circuit At 35, it is detected that the average level data is, for example, 5% or less.

The detection outputs of the coincidence detection circuit 34 and the average video level determination circuit 35 are the horizontal screen discrimination circuit 3 respectively.
If the white peak level coincides with the black peak level in both the detection areas and the average value level data satisfies the above condition, the horizontal screen determination circuit 36 determines that the horizontal screen is displayed, When the condition is not satisfied, it is determined that the screen is not the landscape screen but the normal screen.

Then, the judgment output of the horizontal screen discrimination circuit 36 is guided to the screen area setting circuit 4 as a control signal, and when the screen setting circuit 4 judges that the screen is horizontal, the luminance signal detection area is shown. 3 (b) is set in the shaded area, and when it is determined that the screen is not horizontally long, that is, when it is the normal screen, it is set in the shaded area in FIG. 3 (a).

[0018]

Since the present invention has the above-described structure, the peak value, average value, and black level detection areas of the input video signal detected for correcting the input video signal are switched between the horizontally long screen and the normal screen. Since it can be optimized, it is possible to eliminate the influence of a part different from the main video signal, such as a no-signal part at the top and bottom of the screen when displaying a horizontal screen video signal, and always perform optimal video control. You can

[Brief description of drawings]

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

FIG. 2 is an electro-optical characteristic diagram of a liquid crystal panel.

FIG. 3 is an explanatory diagram of a signal detection area of the present invention.

FIG. 4 is an explanatory diagram of a detection area used for screen detection of the present invention.

[Explanation of symbols]

 4, 34 Screen area setting circuit 5 Peak detection circuit 6 Average value detection circuit 7 Black level detection circuit 13 Video control arithmetic circuit 14 R, G, B control circuit 20 Horizontal screen detection circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location G09G 5/10 Z 8121-5G H04N 7/00 A 9070-5C 7/01 J 9070-5C

Claims (1)

[Claims] 1. A peak value, an average value, a black peak value and a pedestal level value of a luminance signal of an input video signal are detected every predetermined period, and based on the detected data, a contrast value, a brightness value, a gamma value or the like of an image. In a video display device for controlling the above, a screen detection area setting means for designating a detection area of the screen for detecting each of the detection data, and a screen aspect ratio of the input video signal is a normal screen (aspect ratio 4: 3). ) Or a horizontally long screen (aspect ratio 16: 9), and the screen detection area setting means to detect the level of the video signal based on the screen information detected by the screen detection means. An image display device, comprising: a control means for switching the area on the screen depending on whether the screen is a normal screen or a landscape screen.