KR100510682B1 - apparatus for black-level extended of video signal - Google Patents

Abstract

The present invention is to provide a digital image display device that controls gradation so that a black level is represented in detail even when the gradation ratio is increased in a digital image system. The present invention provides a digital image display that detects and expands a black level of a digital image signal. A level expansion device, comprising: a gray scale control signal generator for generating a magnitude factor, which is a gray scale control signal, and controlling a contrast ratio of a digital image signal input through a multiplier; A luminance control signal generator for controlling the brightness of the video signal output from the control signal generator, and multiplying the size factor output from the gray scale control signal generator according to the black level of the digital video signal and the output signal Or a black level gradation selection circuit for controlling the input signal to bypass. The.

Description

Apparatus for black-level extended of video signal}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the contrast of digital video signals, and more particularly, to an apparatus for expressing fine images in moving images by extending a black level in a digital video signal.

Conventionally, if a background of an image displayed on a cathode ray tube is dark while displaying an image of a broadcast signal transmitted from a broadcasting station or an external input signal input from the outside, the image of an object displayed together with the background is clearly displayed. I could not distinguish the background from the object.

In order to solve this problem, a reference intermediate level value and a signal input to a signal input below a middle level value (black level) among the gray level and luminance signals of an image signal received from a broadcasting station or an externally input gray level and luminance signal By correcting the black level of the signal using the difference value of the intermediate level of, the background and the object of the image displayed on the cathode ray tube are distinguished more clearly.

1 is a block diagram of a black level control apparatus in the conventional digital image processing.

Referring to FIG. 1, the contrast of the input digital image signal V is controlled by the multiplier 10, and the brightness is controlled by the adder 20.

That is, the gradation of the digital image signal V is adjusted according to an arbitrary adjustment value a generated by the gradation control signal generator 100 in the multiplier 10, and the brightness is an offset value of the magnitude factor b of the addition. Controlled by

In this case, the gradation is emphasized in proportion to amplifying the amount of change in the digital image signal, and the luminance is emphasized by increasing the value added to the digital image signal, thereby representing the image signal at the black level.

However, the conventional black level expansion device of the video signal has a low gray level ratio in the black level in a digital system such as a DMD projection, and when the gray level ratio, that is, the slope is increased through the multiplier 10, the gray level according to the prior art. As shown in FIG. 3, which shows a transfer characteristic adjusted by the graph, only the gray scale ratio is increased in a limited state (0 to 255) of the digital video signal, resulting in a problem that the video signal is saturated.

Accordingly, an object of the present invention is to provide a digital image display device that controls gray levels so that black levels are expressed in detail even when the gray level is increased in a digital image system.

Another object of the present invention is to provide an apparatus for quickly displaying an image by reducing a black level calculation amount of an input image signal.

In order to achieve the above object, a characteristic of the black level expansion apparatus of a video signal according to the present invention is a black level expansion apparatus of a video signal that detects and expands a black level of a digital video signal, and a size factor that is a gray scale control signal. A brightness control signal generator for controlling the contrast ratio of the digital video signal generated by the multiplier, and a brightness signal of the video signal output from the gray control signal generator through an adder by generating a brightness control signal. ) And a black level gradation control for controlling to multiply the input signal by the magnitude factor output from the gradation control signal generator according to the presence or absence of the black level of the digital video signal or to bypass the input signal. It is configured to include a circuit.

In this case, the size factor is preferably 1 or more and 10 or less.

The black level of the digital video signal is preferably within 10% of the maximum luminance of the digital video signal.

Other objects, features and advantages of the present invention will become apparent from the following detailed description of embodiments taken in conjunction with the accompanying drawings.

Referring to the accompanying drawings, a preferred embodiment of the black level expansion device for a video signal according to the present invention will be described.

2 is a block diagram showing an apparatus for extending a black level of a digital video signal according to the present invention.

In the black level expansion device of the video signal for detecting and extending the black level of the digital video signal,

Referring to FIG. 2, a gray scale control signal generator 100 for generating a gray scale control signal and controlling a contrast ratio of the digital image signal V input through the multiplier 10 and a luminance control signal is generated. The brightness control signal generator 200 for controlling the brightness of the image signal output from the grayscale control signal generator 100 through the adder 20 and the black level grayscale for controlling the grayscale of the black level. In this case, the black level gradation selection circuit 300 includes a comparator for comparing whether the luminance of the input digital video signal is 20 or less, and if the luminance of the digital image signal is 20 or less, the front end is performed. In the gray scale control signal generator, multiply the magnitude factor by the input signal and bypass the output signal. If the luminance is 20 or more, the gray scale control signal generator multiplies the magnitude factor a by the input signal. It comprises a divider dividing the signal which is output again to the size factor to the comparator and the divider (divider).

When configured as described above, the gray level of the input digital video signal is adjusted by combining the input digital video signal V through the multiplier 10 with the magnitude factor a generated by the gray scale control signal generator 100.

In this case, the multiplier 10 outputs the digital video signal aV amplified in proportion to the magnitude factor a corresponding to the contrast control signal. And the size factor a must be a> 1 in order to express the image in detail at the black level.

The black level gray scale selection circuit 300 outputs a value obtained by multiplying the magnitude factor and the input signal by the gray scale control signal generator 100 according to the black level of the digital image signal, or does not multiply the magnitude factor. That is, if the luminance of the digital video signal is 20 or less, the gray scale control signal generator 100 at the front end multiplies the output signal by multiplying the magnitude factor a by the input signal, and if the luminance is 20 or more, The gray scale control signal generation unit multiplies the magnitude factor a by the input signal and divides the output signal back into a, thereby outputting a digital image signal not multiplied by the magnitude factor.

In an embodiment, when the input signal is assumed to be 8 bits, the digital video signal that can be represented by the 8-bit input signal is 0 to 255.

In this case, when the luminance value of the digital image signal is 20 or less, the black level gradation selection circuit 300 multiplies the size factor a output from the gradation control signal generator 100 by the input signal V and outputs the digital image signal. If the luminance value is between 20 and 255, the input signal is selected to be bypassed and controlled to be output.

Herein, the luminance value of 20 or less as the digital image signal means a black level of 10% of the maximum value 255 of the digital image signal.

Accordingly, as shown in FIG. 4, which shows a transmission characteristic in which grayscales are adjusted according to the present invention, the grayscale ratio is emphasized (increased inclination) at 20 or less corresponding to the black level of the input digital video signal, and thus the detail is reduced in the dark portion. Image representation becomes possible.

As described above, the apparatus for extending a black level of an image signal according to the present invention can express a fine image on a dark screen of a video by expanding black level saturation due to bit limitation or black level of a digital image signal in a DMD projection. It has an effect.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the embodiments, but should be defined by the claims.

1 is a block diagram showing a black level expansion device of a video signal according to the prior art

2 is a block diagram showing an apparatus for extending a black level of an image signal according to the present invention;

FIG. 3 is a graph showing a transfer characteristic in which grayscales are adjusted in FIG. 1. FIG.

FIG. 4 is a graph showing a transfer characteristic in which grayscales are adjusted in FIG.

* Explanation of symbols for main parts of the drawings

10: multiplier 20: adder

100: gradation control signal generator 200: luminance control signal generator

300: black level gradation selection circuit

Claims (4)

In the black level expansion device of the video signal for detecting and extending the black level of the digital video signal, A gray scale control signal generator for generating a magnitude factor which is a gray scale control signal and controlling a contrast ratio of the digital image signal input through the multiplier; A luminance control signal generator for generating a luminance control signal and controlling a brightness of an image signal output from the gray scale control signal generator through an adder; And a black level gray level selection circuit for controlling the gray level control signal generator to output a value multiplied by an input signal as it is or to output an input signal not multiplied by the magnitude factor according to the presence or absence of a black level of a digital image signal. And a black level expansion device for a video signal. The method of claim 1, And the size factor is 1 or more and 10 or less. The method of claim 1, And the black level of the digital video signal is within 10% of the maximum luminance of the digital video signal. The method of claim 1, wherein the black level gradation selection circuit A comparator for comparing whether the luminance of the input digital video signal is 20 or less; As a result of the comparison, when the luminance of the digital image signal is 20 or less, the previous gray scale control signal generator multiplies the output signal by multiplying the magnitude factor by the input signal, and when the luminance is 20 or more, the gray scale control signal using a divider. And a divider for multiplying the magnitude factor a by the input signal and dividing the output signal into the magnitude factor in the generation unit.