JPS63275285A - Compensation system for gamma correction on image-sending side of television signal - Google Patents

Abstract

PURPOSE:To prevent the deterioration of details with respect to the pictures of primary color and pictures in which three primary color signals are mixed by adding signals in which amplitude change is large in the signals of specified first and second high frequency components to signals of low frequency components. CONSTITUTION:In an image-sending side, an oscillation change in the high frequency component VH in a luminance signal consisting of the red, green and blue (R, G and B) signals to which gamma-correction is executed, and the high frequency component YgammaCH in a signal in which the luminance signal consisting of linear R, G and B signals to which gamma-correction is not executed is gamma-corrected are compared and the signal having a large change quantity is added to the low frequency component YL in the luminance signal consisting of gamma-corrected R, G and B signals as the interpolation signal. Thus, interpolation of gamma correction without the deterioration of the details can be realized with respect to the picture with the optional mixing ratio of the three primary color signals and the picture quality of a television can be made improved and detailed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a compensation system for gamma correction on the transmission side of television signals, and particularly to a compensation system for gamma correction suitable for reproducing details in high-chroma images.

[Prior Art] In current television signals, red, green, and blue (hereinafter referred to as R and G) are gamma-corrected on the image sending side in order to correct the gamma characteristics of the receiver.

B) A luminance signal and two color difference signals are generated from the signal.

However, the color difference signal is limited to 1.5M H due to band limitation.
Since the value is kept within z, there is a problem of deterioration of detail in high chroma images. As a compensation method to solve this problem, a compensation method as described in Japanese Patent Application Laid-Open No. 57-99089 is known.

[Problems to be Solved by the Invention] The above-mentioned conventional technique is an extremely effective method in the case of a primary color image, for example, only an R signal. However, for images in which three primary color signals are mixed, the high-frequency components of the luminance signal may become smaller due to compensation in some cases.
As a result, there was a problem in that details deteriorated.

SUMMARY OF THE INVENTION An object of the present invention is to provide a compensation system for gamma correction on the image sending side that does not cause a decrease in detail for either a primary color image or an image in which three primary color signals are mixed.

[Means for solving problems] The above purpose is the current gamma corrected R,G.

A high-frequency component yYM of a luminance signal created from the B signal, and a high-frequency component Y of a signal obtained by gamma-correcting the luminance signal created from linear R, G, and B signals without tolerance correction. H
Compare the amplitude changes of both γ and add the signal with the larger amount of change as a compensation signal to the low-frequency component YL of the luminance signal created from the gamma-corrected R, G, and B signals. This is achieved by

[Example] Hereinafter, an example of the present invention will be described with reference to FIG. This embodiment shows a case where the input signals are three primary color signals Ry, G 7 and B7 subjected to tolerance correction.

Matrix operation 1 uses the three primary color signals to generate the luminance signal Y1.
Two color difference signals I and Q are generated by the matrix calculation shown below.

Yi=0.3R+0.59G +0.11B'I
=0.6R-0,28G-0,32ByQ =0
．． 21Ry-0, 52Gy+0.318y The luminance signal Y1 obtained by the matrix circuit 1 generates a luminance low-frequency component YL and a high-frequency component Y□ by an LPF circuit 5 and a bypass filter (HPF) circuit 6, respectively.

On the other hand, the inverse gamma circuit 2 generates a linear three primary color signal RL.
, GL, BL, and Y matrix circuit 3 converts 0, 3
RL + 〇, 59 GL + 0, 11 B
A linear luminance signal Y is produced by the Δ calculation of L, and a gamma-corrected luminance signal Y is produced. Then, the HPF circuit 6 converts the high frequency components to Y. Extract as □.

One of the two high frequency components YM+YCg is selected by the switch 9. This selection control is performed by selecting the IYHII Yy cu u
A magnitude comparator circuit 8 compares the magnitude of the l signal and selects the signal corresponding to the larger numerical value. That is, for the high-frequency component of the luminance signal, the signal component with a larger amplitude change is selected.

This selected signal is added to the YL signal in an adder circuit 10 to generate a luminance signal Y that has undergone gamma correction.

Note that the low-pass filter (LPF) circuit 5 and HPF circuit 6 are one-dimensional only in the horizontal direction, or two-dimensional in the horizontal and vertical directions.
Any three-dimensional characteristics such as horizontal, vertical, and temporal characteristics can be applied.

Next, another embodiment of the present invention will be described with reference to FIG. In this embodiment, the input signals are linear primary color signals RL and G.
This is the case for L and BL. Since the operation and the like are the same as in FIG. 1, the explanation will be omitted since it can be easily understood from the drawing.

Next, another embodiment of the present invention will be described with reference to FIG. This example is the same except that the Y CM acid component production is different γ , so the explanation up to Y CM production γ will be given. A matrix circuit 1 generates linear luminance signals and color difference signals from linear primary color signals. These filters limit the signal to a predetermined band using the filters LPFI to LPF3, and the inverse matrix circuit 14
The signal is converted into linear R, G, and B signals again. A gamma circuit performs gamma correction on these signals, and a matrix circuit 1 generates gamma-corrected color difference signals I, Q,
and a brightness signal, and this high frequency component is sent to the HPF circuit 6.
Extract with Y. Generate M signal.

γ Then, by selecting the one with the larger amplitude change γ of yH and 'y CH multiplied signals and adding the YL multiplied signals, a luminance signal Y compensated for gamma correction is constructed.

Note that the gamma circuit 4, the inverse gamma circuit 2, etc. can be easily realized using a ROM or the like.

[Effects of the Invention] According to the present invention, it is possible to perform gamma correction without deteriorating details even for images with arbitrary mixing ratios of three primary color signals, so that it is possible to achieve high-quality images and high-definition televisions. It has a great effect on

It is clear that the embodiments of the present invention can be applied to analog signal formats, digital signal formats, or a mixed format of both.

Further, the passband of the HPF circuit 6 is preferably equal to or higher than the passband of the color signal, but it does not need to be particularly limited, and may be within the passband of the color and signal depending on the case.

In this embodiment, the case where I and Q signals are used as the color difference signals has been described, but it is obvious that the present invention can also be applied to RY, BY signals, etc.

[Brief explanation of the drawing]

1 to 3 are configuration diagrams of embodiments according to the present invention. 1... Matrix circuit, 2... Inverse gamma circuit, 3...
・Y matrix circuit, 4... Gamma circuit, 5...
LPF circuit, 6... HPF circuit, 7... Absolute value circuit, 8... Size comparison judgment circuit, 9... Switch circuit,
11...LPFI for luminance signal, 12...L for I signal
PF2.13... LPF for Q signal 3.14... Inverse matrix circuit, 10... Adder circuit.

Claims (1)

[Claims] The low-frequency component and the first high-frequency component of the luminance signal composed of gamma-corrected red, green, and blue signals, and the first component of the luminance signal composed of linear red, green, and blue signals subjected to gamma correction. comprising means for generating two high-frequency components, and composes a corrected luminance signal by adding a signal with a large amplitude change of the first and second high-frequency component signals to the low-frequency component signal. A compensation method for gamma correction on the transmission side of a television signal, characterized in that: