JPH04632Y2 - - Google Patents

Description

[Detailed description of the invention] Industrial field of application This invention relates to a luminance signal separation circuit suitable for application to the recording and reproducing system of television receivers and VTRs, and in particular to a luminance signal separation circuit that can remove residual chroma signals. .

BACKGROUND TECHNOLOGY AND PROBLEMS The recording and reproducing system of a VTR is equipped with a separation circuit to separate a luminance signal from a composite color video signal. This separation circuit generally uses a comb filter, and FIG. 3 shows an example of a conventional separation circuit 10.

In FIG. 3, a color video signal consisting of a luminance signal Y and a chroma signal (carrying chroma signal) C supplied to a terminal 1 is transmitted to a delay line 2 and an adder 3, which are selected for a delay time of one horizontal period (1H). The luminance signal Y is separated from the color video signal by being supplied to a comb-shaped filter 4 consisting of the following.

When this comb filter 4 is used, only the luminance signal Y is separated from the color video signal, and it is conceivable that no unnecessary signals are output to the output end. However, in reality, the delay line 3 has temperature characteristics, and the delay time of the delay line 2 is not necessarily 1H due to changes in the comb filter 4 over time. Usually, the delay time varies on the order of several microseconds.

Therefore, if the current color video signal and the color video signal delayed by 1H are simply added, the chroma signals contained in each cannot be completely canceled out, and a small amount of chroma signal C is output. That is, as shown in FIG. 3, the comb filter 4 outputs not only the luminance signal Y but also the residual chroma signal ΔC.

Therefore, conventionally, after the comb filter 4,
A low-pass filter or, as shown in the figure, a trap circuit 5 whose trap frequency is the subcarrier frequency is provided to prevent the residual chroma signal ΔC from being output to the output terminal 6.

However, when the trap circuit 5 is inserted in this way, although the residual chroma signal ΔC can be removed, the frequency characteristics on the high frequency side of the obtained luminance signal Y naturally deteriorate.

Purpose of the invention Therefore, this invention proposes a luminance signal separation circuit that can avoid the deterioration of the frequency characteristics of the luminance signal due to the removal of the residual chroma signal.

Summary of the invention Therefore, in this invention, a chroma extraction circuit is provided after the comb filter, and a mixed signal of the luminance signal and residual chroma signal output from the comb filter is supplied to the chroma extraction circuit to extract only the residual chroma signal. The residual chroma signal is extracted and added to the mixed signal to remove the residual chroma signal.

According to this, the residual chroma signal can be removed without deteriorating the frequency characteristics of the luminance signal.
Extraction of the residual chroma signal is performed using the horizontal correlation of the residual chroma signal.

Embodiment Next, a luminance signal separation circuit according to the invention will be described in detail with reference to FIGS. 1 and 2.

In this invention as well, as shown in FIG. 1, the above-described comb filter 4 is used, and the mixed signal S _M of the luminance signal Y and the residual chroma signal ΔC output from the comb filter 4 is sent to the delay circuit 11. and the chroma extraction circuit 20, and the residual chroma signal ΔC output from the chroma extraction circuit 20 is supplied to the adder 12 and added to the mixed signal S _M with the polarity shown.

Through this addition process, the residual chroma signal ΔC is canceled out, and a luminance signal Y whose frequency characteristics extend to the high range is obtained at the output terminal 6.

The delay circuit 11 is for matching the phases of the residual chroma signal ΔC outputted from the chroma extraction circuit 20 and the residual chroma signal ΔC included in the mixed signal S _M.

The chroma extraction circuit 20 is configured as follows.

The mixed signal S _M is supplied to a high-pass filter 21 to extract a signal having a frequency band higher than that of the residual chroma signal ΔC, and a high-frequency luminance signal Y _H obtained from this is extracted.
The residual chroma signal ΔC is supplied to the horizontal correlator 23 after the amplitude of the high-frequency luminance signal Y _H that is greater than the amplitude of the residual chroma signal ΔC is limited by the limiter 22 .

The horizontal correlator 23 includes a pair of cascade-connected delay elements 24 and 25, an inverter 26, and a delay element 2.
The horizontal correlation means 27 is supplied with the input signal S ₁ of No. 4 and the output signals S ₂ and S ₃ of the delay elements 24 and 25, respectively. Now, if an input signal S ₁ containing a subcarrier 1/2 wavelength (λ/2) high-frequency luminance signal Y _H and a residual chroma signal ΔC is supplied as the input signal S ₁ , as shown in Figure 2 A. , the horizontal correlation means 27
In addition to this input signal S ₁ , the output signals S ₂ and S ₃ shown in FIGS. 2B and 2C are supplied.

The horizontal correlation means 27 is configured as an AND circuit, and when there is horizontal correlation, the correlation signal is outputted, and when there is no horizontal correlation, it is not outputted. Since the high-range luminance signal _YH is a horizontal uncorrelated signal and the residual chroma signal is a horizontally correlated signal, the horizontal correlation means 27 outputs only the residual chroma signal ΔC with horizontal correlation as shown in FIG. 2D. be done.

The residual chroma signal ΔC is added to the mixed signal S _M in the adder 12, resulting in a residual chroma signal ΔC
are canceled out, and only the luminance signal Y is output to the output terminal 6. Here, since no signal processing is performed on the luminance signal Y included in the mixed signal S _M , its frequency characteristics are not degraded and are output with their broadband characteristics intact.

Effects of the invention As explained above, according to this invention, only the residual chroma signal contained in the mixed signal is extracted using horizontal correlation, and the extracted residual chroma signal is used to generate the chroma signal remaining in the luminance signal. Since the residual chroma signals are canceled out, the residual chroma signal can be reliably removed, and since the luminance signal is not involved at all in this residual component removal process, the frequency characteristics of the luminance signal will not deteriorate.

Therefore, since the luminance signal can be separated while maintaining its broadband characteristics, this invention is extremely suitable for application to luminance signal separation circuits used in VTRs and television receivers.

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing an example of a luminance signal separation circuit according to this invention, Fig. 2 is a waveform diagram for explaining its operation, and Fig. 3 is a system diagram showing a conventional example of a luminance signal separation circuit. . 4 is a comb filter, 20 is a chroma signal extraction circuit, 23 is a horizontal correlator, 21 is a high-pass filter, 22 is a limiter, 24 and 25 are delay elements, 2
7 is a horizontal correlation means.

Claims (1)

[Scope of utility model registration request] The color video signal is fed to a comb filter with a delay line of one horizontal period to separate a mixed signal comprising a luminance signal and a chroma signal remaining in the luminance signal, and this mixed signal is divided into 1/2 subcarriers.
The residual chroma signal is extracted by being supplied to a chroma extraction circuit composed of a pair of delay elements with a delay time of two wavelengths and a horizontal correlation means, and this extracted residual chroma signal is added to the above mixed signal to determine the luminance. A luminance signal separation circuit designed to extract only the signal.