JPS5851474B2 - Color television signal recording method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a recording method for color television signals.

Traditionally, helical scan type magnetic recording and playback devices (
A well-known method for recording and reproducing color television signals with VTRs is the color signal low frequency conversion method.

FIG. 1 is a conceptual diagram showing this low frequency conversion method.

That is, a color television signal as shown in FIG.

The color signal C is frequency modulated by f.

This is a method in which the frequency is converted from f5 to f5 and recorded while being superimposed on the frequency-modulated low frequency band of Y (FIG. 1b).

In this method, since the color signal is converted to a low frequency signal and recorded, a high-quality reproduced image can be obtained with less time axis fluctuation during recording and reproduction.

Also, the maximum Y band is shown in Figure 1 (/.

−f, ) can be taken up to C/, = 2/
s).

On the other hand, helical scan type VTRs are 18
The tape is wound slightly more than 180° around a drum with two rotating heads AtB placed opposite each other at 0°, and each head alternately records video signals for one field at a time, creating a recording trajectory as shown in Figure 2. Obtain A and B.

During playback, the head A rotates accurately on the trajectory shown in Figure 2.
, B. Tracking servo is applied to play back tracks, but if one head plays across two adjacent tracks, the signals from the adjacent tracks will be received as interference, so in order to prevent this, an appropriate A space Ts is provided, and the track width TW.

The sum of the spaces Ts is the track pitch Tp.

However, recently there has been a growing trend towards high-density recording, and methods have been taken to eliminate the space Ts.

One method for this is to use azimuth loss to make the gap directions of the two rotating heads AtB different from each other so that even if one head plays across two tracks, adjacent signals will not be picked up (the third figure).

However, although the azimuth loss is large at high frequencies, it becomes almost insignificant at low frequencies, so in the case of the above-mentioned low frequency conversion method, almost no effect can be expected on color signals.

Therefore, a complicated configuration is required to remove color signal interference mixed in from adjacent tracks.

The present invention takes these points into consideration and provides a recording method that is simple and can obtain high-quality reproduction signals without interference from adjacent color signals.

FIG. 4 shows a conceptual diagram of the present invention and will be explained.

The luminance signal Y in the color television signal is the central carrier f.

Angle modulation (frequency modulation) is performed with 18', the upper sideband is removed, and a color signal modulated with the center carrier 18' is superimposed and recorded on that part.

If you perform azimuth recording as shown in Figure 3 using this recording method, the color signal will be in the high range, so it will be different from the adjacent signal.
There is sufficient azimuth loss and there is no interference.

In addition, the lower sideband of the high-frequency component of the angle-modulated luminance signal comes in the low-frequency part, but the energy in this part is very small compared to the energy contained near the carrier, and due to the nature of angle modulation, there is no mutual interaction. There is little impact.

The time axis fluctuations that the color signal undergoes are larger than in the case of low frequency conversion (Figure 1b), but in the case of NTSC or PAL
For color signals that have been quadrature two-phase modulated as in
If this signal is angularly modulated with fs' and recorded, then if it is reproduced and angularly demodulated, the time axis fluctuation experienced by this color signal will be the same as the time axis fluctuation experienced by the f8 signal,
It is possible to obtain the same image quality as in the case of low-frequency conversion.

FIG. 5 shows a conceptual diagram of the present invention in the case of the NTSC system or the PAL system, and FIG. 6 shows an example of a block diagram of a recording/reproducing circuit.

In Fig. 6, 1 is a color television signal input terminal, 2 is a low-pass filter for separating the luminance signal, 3 is a frequency modulator for frequency modulating the luminance signal, and 4 is the upper side of the frequency-modulated luminance signal. 5 is a bandpass filter for separating the modulated color signal; 6 is a frequency converter; 1 is a local oscillator; 8 is for frequency modulating the color signal converted to the low band. 9 is a high-pass filter for removing the low frequency portion of the frequency-modulated color signal, 10 is a mixer, 11 is a recording amplifier, 12 is a head, 13 is a reproduction amplifier, 14 is a low-pass filter for extracting a frequency-modulated luminance signal from the reproduced signal, 15 is a frequency demodulator for the luminance signal, and 16 is a high-pass filter for extracting a frequency-modulated color signal from the reproduced signal. , 11 is a color signal frequency demodulator, 18 is a frequency converter, and 19 is a reproduced demodulated color signal for removing time axis fluctuations from the low frequency converted color signal and converting it to the original frequency. 20 is a mixer, and 21 is a reproduced color television signal output terminal.

As is well known, the continuous signal generator 19 is constituted by, for example, an APC circuit that generates a continuous signal phase-synchronized with the burst signal in the reproduced signal.

In the embodiment shown in FIG. 6, the modulated color signal that has been low-pass converted from fc to f8 by the frequency converter 6 is frequency-modulated by the frequency modulator 8 at fs' shown in FIG. The modulated luminance signal from which the upper sideband has been removed is mixed in a mixer 10 so as to have the relationship shown in FIG. 5, and is recorded as shown in FIG.

As described above, according to the present invention, since the color signal is located in the high range, there is no negative influence of the color signal from adjacent tracks in a recording method using azimuth loss, and it is also possible to lower one set of color signals. Since the signal is frequency-converted to the high-frequency range and then angularly modulated to the high-frequency side, the time axis fluctuation component of the reproduced color signal obtained by demodulation during reproduction is small.

[Brief explanation of the drawing]

Figure 1 is a conceptual diagram showing the low frequency conversion recording method for color television signals, Figure 2 is a diagram showing the recording trajectory of a helical scan VTR, and Figure 3 is a diagram showing the recording trajectory of a helical scan VTR that uses azimuth loss. 4 is a conceptual diagram of the present invention, FIG. 5 is a conceptual diagram of the present invention in an NTSC or PAL color television signal, and FIG. 6 is a block diagram showing an embodiment of the present invention. 1... Input terminal, 2, 4, 14... Low pass filter, 3.8... Frequency modulator, 5...
... Bandpass filter, 6゜18 ... Frequency converter, γ ... Local oscillator, 9゜16 ... High-pass filter, 10,20 ... ...Mixer, IL13・
...... Magnifier, 12... Magnetic head, 15
．． 1γ...Demodulator, 19...Continuous signal generator, 21...Output terminal.

Claims (1)

[Claims] 1. A head of a magnetic head that separates a color television signal to be recorded into a luminance signal and a chrominance signal, angularly modulates the luminance signal, and then superimposes the chrominance signal on the upper sideband to record and reproduce adjacent tracks. When recording on a magnetic recording medium using a group of magnetic heads with different gap directions,
The color television signal to be recorded is an NTSC or PAL color television signal, and the color signal superimposed on the upper sideband of the angle-modulated luminance signal is in the color television signal to be recorded. A color television signal recording method characterized in that a carrier color signal is converted to a low frequency band, and the carrier color signal converted to the low frequency band is angularly modulated.