JPH0716259B2 - Video tape recorder - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a video tape recorder for recording a one-field video signal composed of a frequency-modulated luminance signal and a low-frequency converted color signal on each of a plurality of video tracks of a video tape, The frequency of the video signal recorded on the odd-numbered track or the even-numbered track is moved by, for example, half the frequency of the horizontal synchronizing signal for each horizontal period to simplify the adjustment work and simplify the circuit configuration to reduce the crosstalk component. It tries to suppress the influence.

Conventional 1-hour mode of β-type video tape recorder, 3
In the case of the time mode, and in the case of the 2 hours mode and 6 hours mode of the VHS type video tape recorder, the recording positions of the horizontal sync signals of the respective video tracks of the video tape are the same as those of the horizontal sync signals of the adjacent video tracks. A so-called H-arrangement is continuously performed at the recording positions, but in the case of the 2-hour mode of the β-type video tape recorder and the 4-hour mode of the VHS-type video tape recorder, it is shown in FIG. 1 (a). Thus, for example, each recording position (Pa) of each horizontal synchronizing signal of the video track (Ta) is changed from each recording position (Pb) of each horizontal synchronizing signal of the video track (Tb) adjacent to the video track (Ta). 0.25H based on the distance corresponding to 1/4 of the frequency of the horizontal sync signal, that is, one cycle H of the horizontal sync signal
It becomes impossible to perform the H arrangement because the distance is shifted by the distance indicated by.

When the H-arrangement cannot be performed, at the time of reproduction, due to the crosstalk component of the horizontal synchronizing signals of the adjacent video tracks, as shown in FIG. 1 (b), the left side of the reproduction screen (1),
Beat disturbances occur at the right ends (1a) and (1b).

By the way, a recorded video signal recorded on each video track is formed of a frequency-modulated luminance signal, that is, a modulated luminance signal and a low-frequency converted color signal, that is, a converted color signal, and is reproduced from a video tape. When the above-mentioned crosstalk component is mixed in the signal, the influence on the demodulation video signal by the crosstalk component of the frequency close to the frequency of the reproduced carrier signal, that is, the demodulation of the reproduced modulated luminance signal and the reproduced converted color signal. The effect on the demodulated video signal formed by the processing is reduced,
On the contrary, the influence on the demodulated video signal by the crosstalk component of the frequency apart from the frequency of the reproduced carrier signal increases.

Note that when H-arrangement is performed, since the field correlation on the video tape is strong, the difference between the frequency of the crosstalk component from the adjacent track and the frequency of the carrier signal of the video track to be reproduced becomes small.

Therefore, β-type and VHS-type video tape recorders employ a method in which the frequency of the carrier signal recorded on adjacent video tracks is moved by half the frequency of the horizontal sync signal to visually suppress the effect of crosstalk components. As shown in FIG. 2, the luminance signal of the input terminal (Ia), that is, the luminance signal of the input video signal is changed by the frequency modulation unit (FMa) including the variable frequency oscillation circuit according to the amplitude of the luminance signal. Frequency modulation is performed, and a modulated luminance signal is output to the output terminal (Oa). At this time, the fundamental oscillation frequency of the frequency modulation unit (FMa) is the same as that of the capacitor (Ca) connected to the frequency modulation unit (FMa) and the resistance (Ra). ), (Rb), (Rc) in parallel with the series circuit to set to about 3.6MHz. The resistor (Rb) is formed of a variable resistor for adjusting the fundamental oscillation frequency.

On the other hand, to the input terminal (Ib), for example, a 30 Hz signal from a drive servo circuit, that is, a high frequency switching pulse signal having a frequency half the frequency of the vertical synchronizing signal is input,
The signal causes the NPN transistor (Qa), whose base is connected to the input terminal (Ib) via the resistor (Rd), to switch each time a video track is recorded.

By the way, the emitter of the transistor (Qa) is grounded, and the collector of the transistor (Qa) is connected to the sliding piece of the resistor (Re) which is a variable resistor for frequency shift control. One end is grounded, and the other end of the resistor (Re) is connected to a power supply terminal (+ V) through a series circuit of resistors (Rf) and (Rg). A resistor (Rh) is provided in parallel with the resistor (Re).

And the sliding piece of resistance (Rb) is resistance (Rf), (Rg)
Each time the transistor (Qa) is switched, the fundamental oscillation frequency of the frequency modulation unit (FMa) moves by half the frequency of the horizontal synchronization signal, and the carrier signal recorded in the adjacent video track is connected. The frequency shifts by half the frequency of the horizontal sync signal, and the phase of the crosstalk component during reproduction is inverted every horizontal period, and the effect of the crosstalk component is suppressed by the visual integration effect.

However, the fundamental oscillation frequency of the frequency modulator (FMa) is 3.6MH
z is very high for the horizontal sync signal frequency of 15.734 kHz, and the ratio of half the horizontal sync signal frequency to the fundamental oscillation frequency is 0.26 as shown in the following formula.
It is only 2%, and it becomes very difficult to adjust the resistance (Re). Note that fh indicates the frequency of the horizontal synchronizing signal, and fo indicates the fundamental oscillation frequency.

0.5fh / fo = 0.5 × 15.7 34 × 10 ³ /3.6×10 ⁶ ≈0.262 (%) And actually, adjust the resistance (Re) so that the influence of the crosstalk component is most suppressed while watching the reproduced image. .

Further, the adjustment is likely to be lost due to the temperature change, and it is difficult to perform the adjustment completely.

The present invention has been made with the above points in mind,
In addition to frequency-modulating the luminance signal of the input video signal,
In a video tape recorder for converting a color signal of the input video signal into a low frequency band and recording a recording video signal composed of a modulated luminance signal and a converted color signal on each of a plurality of odd tracks and even tracks of a video tape, A frequency modulation unit that frequency-modulates and outputs the modulated luminance signal, and a frequency and a phase of a predetermined constant frequency part of the recording video signal at the time of recording on one of the odd-numbered track and the even-numbered track as a positive phase reference. The frequency and the phase of the signal are controlled, and the frequency and the phase of the constant frequency portion are reversed for each horizontal period during recording of the other track by inverting the frequency and the phase of the normal phase reference signal and the phase of the normal phase reference signal. A phase control unit that alternately controls the frequency and phase of the phase reference signal, and the phase control unit A reference signal circuit that outputs the positive-phase reference signal when recording the second track, and alternately outputs the positive-phase reference signal and the negative-phase reference signal every horizontal period when recording the other track; A phase detection circuit that compares the phase of the constant frequency part of the video signal with the phases of the positive phase reference signal and the negative phase reference signal and outputs a phase comparison signal according to the phase difference, and at least the phase comparison signal. An integrating circuit which has a first integrating element that integrates only when recording one of the video tracks, and which outputs a control signal to the frequency modulator is provided, and a carrier wave of the recording video signal when recording the other track. In the video tape recorder, the frequency of the signal is moved every horizontal period.

Therefore, a so-called PLL is constituted by the frequency modulation unit and the phase control unit, and the carrier signal frequency of the recording video signal is moved every horizontal period during recording of the other track according to the control of the PLL. The frequency of the carrier signal is moved accurately every horizontal period with a simple circuit configuration without performing any adjustment work, and the frequency of the carrier signal is shifted for each adjacent video track. A first for suppressing the influence and at least integrating the phase comparison signal only when recording the one video track;
Since the phase control section is provided with an integration circuit which has the integration element and outputs the control signal to the frequency modulation section, it is possible to prevent the deviation of the oscillation frequency that occurs at the switching time point for each video track.

Next, one embodiment of the video tape recorder of the present invention will be described with reference to the drawings starting from FIG.

In FIG. 3, (FMb) is a frequency modulator for frequency-modulating the luminance signal input from the input terminal (Ic), that is, the luminance signal of the input video signal through the pre-emphasis circuit and the non-linear emphasis circuit. The oscillation circuit changes the oscillation frequency according to the amplitude change of the input luminance signal and outputs the modulated luminance signal to the output terminal (Ob).

(Pc) is a phase control unit having a reference signal circuit (VS), a phase detection circuit (PD), and an integration circuit (LF). The reference signal generation circuit (VS) includes a color subcarrier of 3.579545 MHz of a color oscillator. An input terminal (Id) to which a signal is input and a color subcarrier signal of the input terminal (Id) are input, and a color subcarrier signal is output from the output terminal (Oc) and an output terminal (Od)
Is controlled by a reference signal generator (Vs) that outputs an inverted carrier signal in which the phase of the color subcarrier signal is inverted from, and a signal that is half the frequency of the horizontal synchronization signal that is input to the input terminal (Ie). A switch (Sa) that alternately outputs the color subcarrier signal of the output terminal (Oc) and the inverted carrier signal of the output terminal (Od) every horizontal period, and a high-frequency switch of 30 Hz input to the input terminal (If) Switching control is performed by the pulse signal, and the color subcarrier signal of the input terminal (Id) is output when recording one of the odd track and the even track of the video track, and the switch (when recording the other track of the video track There is provided a switch (Sb) for alternately outputting the color subcarrier signal and the inverted carrier signal via Sa) every horizontal period.

In addition, the phase detection circuit (PD) has a frequency modulator (FMb).
The modulated luminance signal of, and the color subcarrier signal and the inverted carrier signal output from the switch (Sb) are transmitted, and the gate signal from the input terminal (Ig), that is, as shown in FIG. 4 (a). In addition, as shown in FIG. 4 (b), it becomes a logical 1 (hereinafter referred to as "1") only during a period in which the sync signal front end (A) of the input video signal which is always held at a constant level is modulated. A gate signal is input, and by the gate signal of "1", only the sync signal tip of the modulated luminance signal, that is, the sync signal tip of the recorded video signal is taken into the phase detection circuit (PD), and the phase detection circuit (PD) The phase of the tip of the recorded video signal is compared with the phases of the color subcarrier signal and the inverted carrier signal of the switch (Sb), and a phase difference signal according to the phase difference is output from the phase detection circuit (PD). Note that "0" indicates a logical 0.

Further, the integration circuit (LF) includes a capacitor (Cb) for removing a high frequency component of the phase difference signal of the phase detection circuit (PD) and two integrating elements or capacitors for integrating the phase difference signal with the high frequency component removed. (Cc), (Cd) and input terminal (I
It is switched by the high frequency switching pulse signal of h), and the phase difference signal through the resistor (Ri) is changed to the capacitor (C
Switch (Sc) to alternately integrate by c) and (Cd)
And a resistor (Rj) for outputting a DC control signal formed by the integration of both capacitors (Cc) and (Cd) to the input side of the frequency modulator (FMa).

A so-called PLL is formed by the frequency modulation unit (FMb) and the phase control unit (PC), and at this time, the capacitor (C
The double integrator circuit of b) and the capacitor (Cc) and the double integrator circuit of the capacitor (Cb) and the capacitor (Cd) are switched and used for each video track.

Therefore, the frequency of the sync signal tip portion of the recording video signal recorded on one of the odd track and the even track is controlled to 3.579545 MHz by the above-mentioned PLL,
The frequency of the leading edge of the sync signal recorded on the other track is alternately controlled to 3.579545MHz and a frequency that is deviated from 3.579545MHz by half the frequency of the horizontal sync signal for each horizontal period. The frequency distribution of the burst signal recorded on the track is as shown in FIG.
When controlled to 3.579545MHz, it is distributed at the frequency of the horizontal sync signal centered on 3.579545MHz, and when controlled to a frequency that is shifted from 3.579545MHz by half the frequency of the horizontal sync signal, ), As shown in 3.579545MH
It is distributed at the frequency of the horizontal sync signal with a shift of half the frequency of the horizontal sync signal from z. During playback, the phase of the crosstalk component is inverted every horizontal period, and the visual integration effect is the same as before. This suppresses the influence of the crosstalk component.

In the above-mentioned case, the double integrator circuit of the capacitor (Cb) and the capacitor (Cc) and the double integrator circuit of the capacitor (Cb) and the capacitor (Cd) are switched and used for each video track. It is possible to prevent the deviation of the oscillation frequency of the frequency modulator, which occurs when the control is performed by providing only one multiple integration circuit, that is, the deviation of the oscillation frequency at the time of switching for each video track.

Also, the reference signal generator (Vs) output terminals (Oc), (Od)
The color subcarrier signal and the inverted carrier signal are output from each of them, and the switch (Sa) is controlled to be switched so that the color subcarrier signal and the inverted carrier signal of the reference signal generator (Vs) are alternately detected. ), The configuration can be simplified as compared with the case where the color subcarrier signal and the inverted carrier signal are alternately output to the phase detection circuit (PD) without providing the switch (Sa), for example. it can.

A reference signal generator that outputs a color subcarrier signal is provided instead of the reference signal generation circuit (VS), and an integration circuit that has only one double integration circuit is provided instead of the integration circuit (LF). , Furthermore, when controlling the frequency of the sync signal recorded on the track, the integrator circuit integrates the phase difference signal according to the difference between the phase of the modulated luminance signal and the phase of the chrominance subcarrier signal. While outputting one control signal to the frequency modulation unit (FMb) and controlling the frequency of the sync signal tip recorded on the other track, the integration circuit outputs a horizontal sync signal to the one control signal. The auxiliary signal that shifts the frequency of the synchronization signal by half the frequency is superimposed to form the other control signal, and the other control signal is output to the frequency modulator (FMb) to speed up the PLL response speed. Of course, it is possible.

It is also possible to incorporate and control a constant frequency part below the sync signal tip part of the modulated luminance signal in the phase detection circuit (PD).

[Brief description of drawings]

FIGS. 1 (a) and 1 (b) are explanatory views of the positional deviation of the horizontal synchronizing signal recorded on the video tape and beat interference due to the positional deviation, and FIG. 2 is a connection diagram of a part of a conventional video tape recorder, FIG. 3 and the following drawings show one embodiment of the video tape recorder of the present invention. FIG. 3 is a block connection diagram of essential parts, and FIGS. 4 (a) and 4 (b) show input video signals and gate signals, respectively. Waveform diagram, FIG. 5 (a),
(B) is a frequency distribution chart of the burst signal. (FMa) ... Frequency modulator, (PC) ... Phase controller, (LF)
… Integrator circuit, (PD)… Phase detection circuit, (VS)… Reference signal generation circuit, (Cc), (Cd)… Capacitor.

Claims (4)

[Claims] 1. A luminance signal of an input video signal is frequency-modulated, and a chrominance signal of the input video signal is converted into a low frequency band, and a modulated luminance signal and a converted chrominance signal are respectively applied to a plurality of odd tracks and even tracks of a video tape. A video tape recorder for recording a video signal, comprising: a frequency modulation unit that frequency-modulates the luminance signal and outputs the modulated luminance signal; and the video at the time of recording either one of the odd track and the even track. The frequency and phase of the predetermined constant frequency part of the signal are controlled to the frequency and phase of the positive phase reference signal, and the frequency and phase of the constant frequency part are set to the frequency and phase of the normal phase reference signal when recording the other track. The position to alternately control the frequency and phase of the reversed-phase reference signal, which is the inverted phase of the positive-phase reference signal. A control unit, which outputs the positive phase reference signal to the phase control unit when recording the one track and outputs the normal phase reference signal and the negative phase reference signal to one horizontal line when recording the other track. A reference signal circuit alternately outputting for each period, a phase comparison signal according to a phase difference by comparing the phase of the constant frequency portion of the recording video signal with the phase of each of the positive phase reference signal and the negative phase reference signal And a phase detection circuit that outputs at least the phase comparison signal and a first integration element that integrates the phase comparison signal only during recording of the one video track, and an integration circuit that outputs a control signal to the frequency modulation unit. The video tape recorder, wherein the frequency of the carrier signal of the recording video signal is moved every horizontal period when the other track is recorded. 2. A positive phase reference signal is formed by a color subcarrier signal, and a constant frequency portion of the recording video signal is formed by a leading edge portion of the synchronizing signal of the recording video signal. The video tape recorder described in the item. 3. The integrating circuit has a second integrating element that integrates the phase comparison signal only when recording the other video track, and is formed by integrating each of the first and second integrating elements. The video tape recorder according to claim 1, wherein the video tape recorder outputs a control signal to the frequency modulator. 4. The integrator circuit outputs the output of the first integrator circuit and a signal obtained by superimposing a predetermined auxiliary signal on the output of the first integrator circuit to the frequency modulator when recording the other track. The video tape recorder according to claim 1, wherein the video tape recorder outputs the video tape recorder as a control signal.