JPH05167888A - Gradation correcting circuit for video signal - Google Patents

Abstract

PURPOSE:To make a low luminance level area easily visible by claculating an occupancy rate in a screen in its area, and selecting the corresponding grada tion correcting characteristic, when its occupancy rate is within a prescribed range, and also, there is a motion in its area. CONSTITUTION:When a luminance level of a video signal is within a prescribed low level range, a dark part detector 2 outputs a detecting signal as a dark part, applies it to a motion detector 3, and also, sump up the number of data of the dark part in one screen, calculates an occupancy rate from the total number of data, and outputs the corresponding detecting signal to a gradation correcting device 5, when this occupancy rate is within a prescribed range. Subsequently, the motion detector 3 detects a motion from a video signal of an input 1, and a video signal delayed by one frame by a frame memory 4, outputs a motion detecting signal from the dark part detecting signal, when there is a motion in the dark part concerned, and applies it to the gradation correcting device 5. Also, the gradation correcting device 5 controls a gradation correcting characteristic in accordance with the motion detecting signal and the occupancy rate detecting signal, performs its gradation to the video signal delayed by one frame by the frame memory 4 and outputs its signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is a video signal gradation correction circuit for controlling the gradation of a video signal.

[0002]

2. Description of the Related Art In recent years, the adjustment of the receiving screen of a television receiver has been
It is called preset or auto etc., and it keeps the adjusted state at the time of factory shipment so that general viewers do not have to adjust it.
Alternatively, the adjustment unit is hidden by a door or a click is provided on the adjustment volume so that the original state can be immediately restored even after adjustment. However, this adjustment state is adjusted to a good position on average, and does not necessarily satisfy all screens.

[0003] For example, in a sports broadcast when the outdoor brightness is high in television broadcasting, a shadow of a stand appears on a part of the ground, and this shadow portion is a low brightness level area (hereinafter referred to as a dark area) on the TV screen. Therefore, when the ball flies to this dark area, the movement of the player may not be clearly seen.

[0004]

As described above, if there is movement even in a dark part, the viewer's point of gaze shifts to this part. However, when the gradation of the dark part is narrow, or the black level of the video signal is below the zero level of the brightness on the image receiving screen, and the dark part cannot be seen well, the brightness and contrast are adjusted.
When changing to another image receiving screen, there is a problem that the brightness becomes too high. In view of such a point, the present invention, when the dark area occupancy ratio is within a predetermined range and there is movement in the dark area, expands the gradation of the dark area and does not raise the average brightness so much that the dark area is increased. An object of the present invention is to provide a gradation correction circuit for a video signal that makes it easy to see.

[0005]

In order to achieve the above object, the present invention provides a predetermined dark portion detection signal and a predetermined dark portion occupancy ratio in a screen image of a video signal. Occupancy rate detection means for outputting an occupancy rate detection signal when in range,
Motion detecting means for outputting a motion detecting signal of the dark portion, and gradation correcting means for controlling the gradation correcting characteristic of the video signal in correspondence with the occupation ratio detecting signal and the motion detecting signal of the dark portion. It is configured to include.

[0006]

In the gradation correction circuit for a video signal according to the present invention having such a structure, the ratio of a predetermined dark portion in a screen of the video signal is within a predetermined range, and the dark portion is When motion is detected, depending on the proportion of the dark area,
The gradation of the dark part is enlarged so that the average brightness of the screen is not affected so much so that the dark part can be easily seen.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the outline of a gradation correction circuit for video signals according to an embodiment of the present invention. The video signal applied to the input 1 is applied to the dark area detector 2, the motion detector 3 and the frame memory 4. The dark part detector 2 outputs a detection signal as a dark part when the brightness level of the video signal is within a predetermined low level range, and in addition to the motion detector 3, further accumulates the number of data of the dark part in one screen. The occupancy rate is calculated from the total number of data, and when the occupancy rate is within a predetermined range, a corresponding detection signal is output to the gradation corrector.

The motion detector 3 detects a motion from the video signal of the input 1 and the video signal delayed by one frame in the frame memory 4, and detects a motion detection signal when there is a motion in the dark part from the dark part detection signal. Is output and added to the gradation corrector 5. The gradation corrector 5 controls the gradation correction characteristic in response to the motion detection signal and the occupation ratio detection signal, and applies the gradation correction characteristic to the video signal delayed by one frame in the frame memory 4. The corrected video signal is output to the output 6.

For example, gradation correction characteristics A and B shown in FIG.
And C. A is the same as the case where gradation correction is not performed for input / output 1: 1. B enlarges the gradation of the dark part, and C further enlarges the gradation of the dark part. The occupancy rate is divided into three ranges, small, medium, and large, with and without dark part movement. An example of these combined operations is shown in the characteristic control table of FIG. Even when there is a dark area motion, if the occupancy rate is small, A is selected as the gradation characteristic, and the gradation characteristic does not change. When the occupancy rate is medium, B is selected as the gradation characteristic, and the gradation in the dark area is expanded. Further, when the occupation ratio is large, C is selected as the gradation correction characteristic, and the gradation in the dark area is further expanded. When the gradation of the dark part is expanded, the gradation of the high brightness level region is correspondingly compressed, and the influence on the average brightness of the entire screen is small.

When there is no dark area motion, when the dark area occupancy ratio is small or medium, the characteristic A is selected, and the gradation characteristic does not change.
When the occupancy rate is high, the characteristic B is selected, and the occupancy rate is high even if there is no movement in the dark part, so the gradation of the dark part is enlarged. The case where a video signal delayed by one frame from the frame memory 4 is input to the gradation corrector 5 has been described. However, since the video signal has a high correlation between frames, even if the video signal of the input 1 is input, it is practically used. There is no problem on the top. Further, although the motion detection is performed only on the dark part, it may be performed regardless of the dark part.

[0011]

As described above, according to the gradation correction circuit for a video signal of the present invention, the gradation correction is controlled based on the occupancy ratio of the dark portion of the video screen and the motion detection signal, so that even the dark portion can be obtained. It is possible to obtain a video screen in which gradation is expanded and attention is taken into consideration.

[Brief description of drawings]

FIG. 1 is a configuration block diagram showing an embodiment of a video signal gradation correction circuit of the present invention.

FIG. 2 is a diagram showing an example of gradation correction characteristics of the gradation corrector shown in FIG.

3 is an occupancy ratio detection range of the dark area detector shown in FIG.
3 is a characteristic control table showing the relationship with the gradation correction characteristic shown in FIG. 2 selected from the motion detection result of the motion detector.

[Explanation of symbols]

 1 Input 2 Dark Area Detector 3 Motion Detector 4 Frame Memory 5 Gradation Corrector 6 Output A, B, C Gradation Correction Characteristics

Claims (1)

[Claims] 1. The input video signal, during the video for one screen,
A predetermined low-brightness level area detection signal, an occupancy rate detecting means for outputting an occupancy rate detection signal when the occupancy rate of the low-brightness level area is within a predetermined range, and a motion detection signal for the low-brightness level area. A gradation of a video signal, comprising: a motion detecting means for outputting; and a gradation correcting means for controlling a gradation correcting characteristic of the video signal corresponding to the occupation ratio detecting signal and the motion detecting signal. Correction circuit.