JPH0463089A - Y/c separating circuit - Google Patents

Abstract

PURPOSE:To suppress the degradation of picture quality due to interference between a luminance signal and a color signal by providing first and second band-pass filters and a comb line filter which outputs the color signal and using optimum band-pass filters for the luminance signal and the color signal respectively. CONSTITUTION:Band-pass filters 1 and 5 having a color subcarrier signal fSC as the center frequency and a comb line filter 3 which outputs the color signal and uses signals of plural scanning lines are provided. A color video signal subjected to frequency interleaving as the input signal successively pass the band-pass filter 1 and the comb line filter 3 and is subtracted from the input signal delayed in a delay circuit 2 by an adder 4 to output a luminance signal Y. The input signal passes the band-pass filter 1, the comb line filter 3, and the band-pass filter 5 in series to output a color signal. Thus, the luminance Y has a comb characteristic in a wide band, and the color signal has a narrow band.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a Y/C separation circuit for color video signals subjected to frequency interleaving.

Conventional technology As the demand for high image quality increases in recent years, the Y/
A sophisticated C separation method is also required, and comb filters that utilize signals from a plurality of scanning lines are often used.

FIG. 3 shows the configuration of a Y/C separation circuit using a conventional comb filter.

In the figure, 11 is a color subcarrier signal (f, c
), 12 is a delay circuit for delay time adjustment, 13 is a comb filter that uses signals from a plurality of scanning lines to output color signals, and 14 is an adder circuit.

A color video signal as an input signal passes through a bandpass filter 11 and a comb filter 13 in sequence to obtain a color signal C.
is output as On the other hand, the input signal is delayed for a predetermined time by the delay circuit 12, and then the above color signal is subtracted by the adder circuit 14 to obtain the luminance signal Y. Figure 4 shows an outline of the frequency spectrum at each node of the circuit in Figure 3.
). a.

a′ has the same spectrum as the input signal. Since the signal b passes through the bandpass filter 11, the band is limited around the frequency f1. C has a comb characteristic with a horizontal synchronization frequency (r+) period due to the comb filter 13, and the luminance signal Y has a spectrum obtained by subtracting the color signal C from the input signal a.

Problems to be Solved by the Invention However, in the conventional configuration described above, since the band of the color signal is limited by the bandpass filter 11, the following problems arise.

First, when the passband of the bandpass filter 11 is narrowed, a signal that is not near f Ie among the color signals C is regarded as a luminance signal Y due to band limitation. For this reason, when the sideband of the color signal C widens at a sudden change in color, the leakage from the color to the luminance increases, causing dot interference.

A diagonal component of the luminance signal Y that is not near f Ie is not considered a color signal, and cross color is unlikely to occur.

On the other hand, when the passband of the bandpass filter 11 is widened, the diagonal component of the luminance signal Y is regarded as the color signal C in a wide frequency band, resulting in cross color.

Since the color signal C is not band-limited much, dot interference is unlikely to occur even at a sudden change in color.

As described above, in the conventional configuration, regardless of whether the passband of the bandpass filter is narrowed or widened, the image quality deteriorates due to interference between the luminance signal Y and the color signal C. An object of the present invention is to provide a Y/C separation circuit that minimizes such image quality deterioration.

Means for Solving the Problems In order to achieve this object, the Y/C separation circuit of the present invention provides the first. A second band-pass filter and a comb-shaped filter are used to output a color signal using the signals of a plurality of scanning lines. , the obtained signal is subtracted from the input signal to obtain a luminance signal, and a signal obtained by sequentially passing the input signal through a second bandpass filter and a comb filter is used as a chrominance signal.

Effect This configuration prevents leakage from the color signal to the luminance signal.
Leakage from the luminance signal to the color signal is suppressed, and a screen with less interference can be obtained.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of this embodiment. In Figure 1, 1.5 is the color subcarrier signal (f sc)
2.6 is a delay circuit for delay time adjustment; 3 is a comb filter that uses signals from a plurality of scanning lines to output color signals; and 4 is an adder.

In this circuit, a color video signal subjected to frequency interleaving as an input signal is sequentially passed through a bandpass filter 1 and a C-shaped filter 3, and then input to an adder 4 where it is delayed by a delay circuit 2. This is subtracted from the signal and output as a luminance signal Y, and the input signal is passed through a bandpass filter 1, a <C-shaped filter 3 . The signal passed through the it column through the bandpass filter 5 is output as a color signal C.

An outline of the frequency spectrum at each node of the circuit of FIG. 1 is shown in FIG. 2 (al to tel).The luminance signal Y has a comb characteristic in a wide band, and the band of the color signal C has a narrow band.

Effects of the Invention According to the Y/C separation circuit of the present invention, a luminance signal, a color signal,
Since an optimal bandpass filter is used for each, Y/C separation can be achieved that minimizes image quality deterioration due to interference between luminance and color signals.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the Y/C separation circuit of the present invention, FIG. 2 is a diagram showing a schematic diagram of the frequency spectrum at each node in FIG. 1, and FIG. FIG. 4, a block diagram of the separation circuit, is a diagram showing an outline of the frequency spectrum at each node in FIG. 3. 1.5...Band pass filter, 2.6...
...Delay circuit, 3...Comb filter, 4.
...Adder. Name of agent: Patent attorney Shigetaka Awano Haka 1 person X Okezuka

Claims (1)

[Claims] It has first and second band-pass filters, and a comb-shaped filter that outputs a color signal using signals of a plurality of scanning lines, and the input signal is transmitted to the first band-pass filter and the comb-shaped filter. A signal obtained by subtracting a signal obtained by sequentially passing through the input signal from the input signal is output as a luminance signal, and a signal obtained by sequentially passing the input signal through the second bandpass filter and the comb filter. A Y/C separation circuit characterized in that a color signal is a Y/C separation circuit.