JPH01161986A - Color signal processing circuit - Google Patents

Abstract

PURPOSE:To obtain a color signal with less missing of color even if the feedback rate of a recursive filter component is increased or the improving effect of the S/N is increased by selecting optimizingly the character of a limiter in use. CONSTITUTION:A chroma signal is fed from an input terminal IN and added to an original chroma signal by an adder 3 via a delay device 2. In the selection of a delay of the delay device 2 is selected, e.g., as one horizontal scanning period(1H), a signal retarded by 1H at a color non-correlation section is fed to a limiter 4, and in the selection of the characteristic of the limiter 4, the limiter passes a signal below the limiter level and a signal over the limiter level is selected to a cause 0 or gradual 0, then as the output signal from the limiter 4, the signal with large amplitude with remarkable color missing is made nearly zero. Thus, the output is fed to a subtractor 1 via a coefficient device 5 with a feedback coefficient K2, then the output of the limiter 4 is almost zero in a large amplitude having a color whose missing is eminent in color missing. Thus, the color signal without color missing is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a color signal processing circuit used in a magnetic recording/reproducing circuit such as a video tape recorder.

(Prior Art) In recent years, in the field of televisions and video tape recorders, there has been an increasing demand for higher quality recorded color images.

FIG. 2 shows a chroma recursive circuit for processing a single color signal as an example of the above-mentioned high image quality technology.

1 is a first subtracter, 2 is a delay device, 3 is an adder, and 4 is a limiter, the characteristics of which are shown in FIG. Also, 5 is a feedback coefficient of 2, and 6 is a feedback coefficient (mix ratio) K□
, and 7 is the second subtractor. The chroma recursive circuit configured in this manner operates as follows.

First, when a chroma signal is applied from the input terminal IN, it is delayed by a delay device 2, added to the original chroma signal by an adder 3, and then set to a limiter level by a limiter 4 having general limiter characteristics as shown in FIG. The following components are extracted and multiplied by 2 through the feedback coefficient 2 coefficient multiplier 5, and the difference from the original chroma signal is taken by the subtracter 1 to create a vertical comb characteristic, and the limiter 4 outputs is passed through a coefficient unit 6 of 8 as a feedback coefficient, and subtracted from the original chroma signal using a subtracter 7 to output the result.

With this configuration, when the feedback coefficient of the coefficient unit 5 is increased to a value of 2 to increase the feedback rate, the comb characteristic of the chroma signal becomes steeper, and the S/N ratio of the flat part of the chroma signal is improved. can do.

(Problem to be Solved by the Invention) However, in the above configuration, if the recursive comb characteristic is made steeper to improve the S/N ratio of the chroma signal and the feedback characteristic is improved, the color uncorrelation Since the section uses a general limiter consisting of a diode with the characteristics shown in Figure 2, the delay due to the color delay @2 of the non-correlation section is output as a constant, and it is used as the feedback coefficient by the coefficient multiplier of 2. 5
Since the color is fed back to the input side via the filter, there has been a problem that color fading becomes even greater.

An object of the present invention is to eliminate the above-mentioned problems and provide a color signal processing circuit that improves color fading by optimizing limiter characteristics.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a color signal processing circuit with a characteristic in which signals below the limiter level are passed through, and signals above the limit are set to 0 or gradually become 0. Solved by using a limiter.

(Function) With the above configuration, the present invention improves the S/N ratio of the chroma signal by increasing the feedback rate of the recursive filter composed of a delay device, so that even if the comb characteristic is made steep, one color can be processed. A color signal processing circuit with less dropout is formed.

(Embodiment) Hereinafter, the color signal processing circuit of the present invention will be explained by way of an embodiment using FIG. 2 mentioned above.

In the color signal processing circuit shown in FIG. 2, first, a chroma signal is applied from an input terminal IN, passes through a delay device 2, and is added to the original chroma signal by an adder 3. Here, if the delay amount of the delay device 2 is, for example, one horizontal scanning period (hereinafter abbreviated as IH), a signal delayed by 1H is applied to the limiter 4 in the uncorrelated part of one color. If the characteristics of 4 are set as shown in Figure 1, in which signals below the limiter level are passed through and signals above it are 0 or gradually become 0, IH-delayed signals that occur in uncorrelated areas of colors can also be eliminated. , only passes signals below the limiter level.

Since a signal with a level higher than that will not be outputted, the output signal of the limiter 4 is almost O for a large amplitude signal of a color with noticeable color fading. Therefore, if the output is applied to the subtracter 1 through the coefficient unit 5 of 2 as a feedback coefficient, 1
For large amplitude signals with noticeable color fading, use limiter 4.
The output is almost O, and discolored parts are no longer fed back as in the conventional case. That is, since the color fading is improved, the output of the limiter 4 is multiplied by K by the coefficient multiplier 6, and subtracted from the original person's color signal by the subtracter 7, thereby obtaining a color signal with less color fading.

(Effects of the Invention) As is clear from the above explanation, the present invention improves the feedback rate of the recursive filter component by optimally selecting the characteristics of the limiter used in the color signal processing circuit constituted by the recursive circuit. Even if the S/N ratio is improved, a color signal with less color loss can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of the characteristics of a limiter used in the present invention, FIG. 2 is a block diagram showing an embodiment of the circuit of the present invention, and FIG. 3 is a diagram showing the characteristics of a general limiter. 1.7...Subtractor, 2...Delay unit, 3...Adder, 4...Limiter, 5,6...Coefficient unit. Patent applicant: Matsushita Electric Industrial Co., Ltd. Figure 1 Figure 2 Figure 3... 77II + Bookkeeping 4 Somitta 5.6.
ll! F, *x Figure 3

Claims (1)

[Claims] A delay device that delays the input signal, an adder that takes the sum of the output of this delay device and the input signal, and a signal that is below the limiter level is passed through the output of the adder, and a signal that is input above the limiter level is set to 0. or a limiter that gradually sets the output to 0, a first coefficient multiplier that multiplies the output of the limiter by K_2, a first subtractor that takes the difference between the output of the coefficient multiplier and the input signal, and 1. A color signal processing circuit comprising a second coefficient multiplier that multiplies by K_1 and a second subtracter that takes the difference between its output and an input signal.