JP2524521B2 - Magnetic recording / reproducing device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a magnetic recording / reproducing device having a system conversion circuit, and is also applied to a part of a television device.

(Prior Art) A conventional magnetic recording / reproducing apparatus is exclusively for the NTSC system or the PAL system, and can display a screen only on a TV set corresponding to each system. Even in the multi-method VTR, a TV set compatible with the selected method is required.
In other words, even if a tape recorded in the PAL system is applied with a servo corresponding to the field frequency and played back on a VTR having an NTSC system chrominance circuit, it is not possible to reproduce colors in a normal hue on an NTSC system TV set. It was

The conventional NTSC system VH described above with reference to the drawings.
An example of the SVTR chroma signal processing circuit reproduction system will be described.

When the tape recorded by the NTSC system VHSVTR is reproduced, the recorded signal is taken out by the magnetic head 101 shown in FIG. 7, amplified by the reproduction amplifier 102, and then converted by the low-pass filter 103 into the low-pass conversion carrier color. The signal is obtained. In the case of a color bar signal, the signal waveform of one horizontal synchronization period is
Shown in Figure a (T _{1 in the} figure represents one horizontal synchronization period, YL: yellow,
CY: cyan, G: green, MG: magenta, R: red, B: blue). This signal is automatically adjusted in level by an ACC circuit (automatic saturation adjustment circuit) 104, then converted into a signal of an original color subcarrier frequency by a balanced modulator 105, and sent to a burst down circuit 106. The burst down circuit 106 adjusts the burst level according to the recording time mode, and then the band filter 107 extracts the correct chrominance signal. After that, it passes through the killer amplifier 108, further passes through the comb filter 109, and is output from the chrominance signal output terminal 110. This is the main path of the signal, but since the regenerated signal has many fluctuations on the time axis, an APC loop is configured to eliminate this. The signal output from the bandpass filter 107 is added to the burst gate circuit 111. The extracted burst signal, which is the output thereof, is applied to the phase comparator 112 together with the output of the 3.58 MHz reference oscillator 121, and the output error voltage of the phase comparator 112 controls the voltage controlled oscillator 113 and the voltage controlled oscillator. By counting down the output of 113, a low-pass conversion color subcarrier having the same time-axis fluctuation as the reproduced low-pass conversion carrier color signal is produced, and is added to the balanced modulator 114 together with the output of the reference oscillator 121. The sum component is extracted by the bandpass filter 115, added to the balanced modulator 105, and the time-axis fluctuation component is removed. On the other hand, the reproduced low-frequency conversion carrier color signal advances the phase by 90 ° every horizontal synchronization period in CH1 (6 ° to the right of head azimuth) and 90 ° every horizontal synchronization period in CH2 (6 ° to the left of head azimuth). Since it was recorded with the phase delayed, it is necessary to restore the phase when reproducing. The input signal 116 is a signal as shown in FIG. 8b, which is a signal for identifying whether the head is CH1 or CH2 in one vertical synchronization period, and T ₂ in the figure indicates one vertical synchronization period, For example, if the high-level period in FIG. 8b corresponds to CH1, CH2 corresponds to the low-level period, and the phase shift circuit 117 advances the phase when the input signal 116 is at the high level, and when the input signal 116 is at the low level. Behaves like a lag. 118
Is a reproduced luminance signal as shown in FIG. 8C, the horizontal synchronizing signal is extracted by the horizontal synchronizing signal separation circuit 119, and is guided to the phase shift circuit 117. In the phase shift circuit 117, the low-frequency conversion color subcarrier output from the countdown circuit 120 is C
The phase is advanced by 90 ° for each horizontal sync period during the 1 vertical sync period during which the signal is being reproduced from H1, and is delayed by 90 ° during each horizontal sync period during the 1 vertical sync period during which the signal is being reproduced from CH2. Then, it is added to the balanced modulator 114, and finally, the phase is returned to the normal phase by the main balanced modulator 105. Further, generally, there is a color killer circuit that determines whether the signal is color or black and white, and the output of the reference oscillator 121 and the burst signal extracted by the burst gate circuit 111 are compared by the phase comparator 122, and the output The signal controls the killer amplifier 108. The waveform of the chrominance signal of the NTSC standard color bar signal processed in this way is shown in FIG. 8d and its vector waveform is e.

(Problems to be Solved by the Invention) However, in the above-mentioned configuration, the PAL system VHSVT is used.
Even if the tape recorded by R is played with servo at the field frequency, the chrominance signal processing circuit is an NTSC system, so it is possible to reproduce colors with a normal hue on the screen of an NTSC system TV set. I had a problem that I could not.

In view of the above problems, an object of the present invention is to use the conventional NTSC system VH.
By adding a system conversion circuit to the chrominance signal processing circuit of the SVTR, not only can NTSC system signals be recorded and reproduced, but also PAL system VHS tapes can be reproduced to reproduce colors in normal hue on NTSC system TVs. Another object of the present invention is to provide a magnetic recording / reproducing device.

(Means for Solving the Problem) A magnetic recording / reproducing apparatus of the present invention has a servo system capable of recording / reproducing signals of various kinds of field frequencies, adopts a VHS-NTSC system as a chrominance processing circuit, and simultaneously When playing a tape recorded on a VHS-PAL VTR, the phase of the low-frequency conversion color signal is constant for the CH1 head (6 ° to the right of head azimuth) during one horizontal synchronization period, and the CH2 head (head azimuth to the left is constant). In a magnetic recording / reproducing apparatus having a function of delaying 90 ° at every horizontal synchronization period (this is called PAL mode), a burst gate circuit for extracting a burst of a chrominance signal reproduced in PAL mode and a burst The burst signal extracted from the gate circuit and the reference oscillator used to obtain the chrominance signal (NTSC standard TV color subcarrier frequency And a gate signal generation circuit that generates a gate signal that repeats a high level and a low level for each horizontal synchronization period in accordance with the positive / negative of the error voltage of the output of the phase comparator. And a phase shifter for shifting the phase of the reference oscillator, a frequency multiplier for converting the output of the phase shifter into a doubled frequency, and a balanced modulator for balanced modulation of the frequency multiplier output and the regenerated chrominance signal. And a filter for taking out a difference component of the balanced modulator output, and a chrominance output of the filter output and the regenerated chrominance signal by the gate signal generated by the gate signal generating circuit for one horizontal synchronization of + 135 ° burst phase. During the period, the chrominance signal of the reproduction processing is passed, and during one horizontal synchronization period of -135 ° burst phase, the chrominance signal of the filter output. A gate circuit for passing the scan signal, is obtained with a burst only shifting Sosuru phase shift circuit of the gate circuit output signal, the arrangement comprising a.

(Operation) According to the present invention, the signal recorded with the VAL of the PAL system VHS is reproduced in the PAL mode by the above-mentioned configuration and the obtained 3.58M
A carrier chrominance signal having a color subcarrier frequency of Hz and a phase in which the V axis is inverted by 180 ° for each horizontal synchronization period is used as it is for a horizontal synchronization period of + 135 ° burst phase, and remains at -135 °. During one horizontal synchronization period of the burst phase, this carrier color signal is balanced-modulated by a carrier having a frequency twice that of the reference oscillator, and the difference component is taken out to obtain a carrier color signal having a phase with the V axis inverted. , V including burst
A color subcarrier whose axis does not invert every horizontal synchronization period is obtained. However, since only the burst has a phase of + 135 °, an NTSC system chrominance signal can be obtained by advancing the + 45 ° phase with a phase shifter (however, the field frequency is PAL-
50Hz except for M). Even if this signal is connected to an NTSC TV set, the color can be reproduced in a normal hue.

(Example) An example of the present invention will be described with reference to FIGS.

FIG. 1 is a block diagram showing a video signal reproducing system of a magnetic recording / reproducing apparatus according to the first embodiment of the present invention. In FIG. 1, 1 is a magnetic head, 2 is a reproduction amplifier, 3 is a luminance signal processing circuit, 4 is a circuit for mixing a luminance signal and a chrominance signal, 5 is a chrominance signal processing circuit, and 6 is a chrominance signal processing circuit 5. A phase shift circuit, which is a part, and a reference oscillator, which is a part of the chrominance signal processing circuit 5. The above is the video signal processing circuit of the conventional VHS-NTSC VTR. The following chrominance conversion circuit is added to this.
8 is a circuit for switching output signals between NTSC and PAL, 9 is a burst phase shift circuit, 10 is a burst gate circuit, 11 is a gate circuit, 12 is a phase comparator, 13 is a gate signal generation circuit, 14 is a phase shift circuit, 15 Is a frequency multiplier, 16 is a balanced modulator, 17 is a filter, and 18 is a PAL / NTSC switch.

The operation will be described below with reference to FIGS. 1, 2, 3, and 4. The tape recorded by PAL system VHSVTR is reproduced by applying the servo corresponding to the field frequency. At the same time, the PAL / NTSC switch 18 switches the low-frequency conversion color subcarrier phase shift circuit 6 to operate in the PAL mode. The reproduced signal 31 has a color subcarrier frequency of 3.58 MHz and its phase is a PAL signal whose V axis is inverted every horizontal synchronization period. If the playback signal is a color bar signal,
The waveform envelope of signal 31 is shown in FIG. 2A. In Figure 2, YL: yellow, CY: cyan, G: green, MG: magenta, R:
Red, B: Blue, Bu: Burst shows the signal of one horizontal sync period in which the V axis is not inverted. The letters in ▲ ▼ and small letters correspond to each color, but the V axis is inverted in one horizontal sync period. Indicates a signal. When the waveform of FIG. 2A is displayed as a vector, it becomes B of FIG.

On the other hand, this signal is applied to the balanced modulator 16, and at the same time, the output signal of the reference oscillator 7 is phase-shifted by the phase shift circuit 14 and then balanced-modulated with the signal converted to double the frequency by the frequency multiplier 15. . The output of the balanced modulator 16 is added to the filter 17, and only the difference component is taken out. FIG. 2C is a vector diagram of the signal 32. The signal 31 becomes a signal inverted with respect to the V axis. On the other hand, the burst of the signal 31 is extracted by the burst gate circuit 10. In FIG. 3A, the waveform of the signal 33, the burst and the output of the reference oscillator 7 are applied to the phase comparator 12 so that an error voltage 34 appears at the output of 12. Third
FIG. B shows the waveform of the error voltage 34. This positive / negative error voltage is + 135 ° phase burst (Bu in symbol), −1
Corresponds to 35 ° phase burst (▲ ▼ in signal). Due to the error voltage 34, the gate signal generating circuit 13 generates the gate signal 35 whose synchronization corresponding to the polarity of the burst phase as shown in FIG. signal
The gate circuit 11 is controlled by 35, and the signal 31 is selected during one horizontal synchronizing period of the positive polarity burst, and the signal 32 is selected during one horizontal synchronizing period of the negative polarity burst. As a result, at the output of the gate circuit 11, the signal 36 shown in the waveform of FIG. 4A and the vector diagram of B appears. The next phase of the signal 36 is advanced by 45 ° by a burst by the next burst phase shift circuit 9. As a result, the signal 37 is a signal shown by the vector in FIG. 4C, that is, a chrominance signal which has a color subcarrier frequency of 3.58 MHz and which does not invert the V axis every horizontal synchronization period. The signal 37 is selected by the PAL / NTSC switching circuit 8,
The luminance / chrominance mixer 4 produces a video signal. When connected to an NTSC TV set, colors can be reproduced on the TV screen in the normal hue.

As described above, according to the present embodiment, in the conventional VHS-NTSC VTR, the burst phase shift circuit 9, the burst gate circuit 10, the gate circuit 11, the phase comparator 12, the gate signal generation circuit 13, the phase shift circuit. 14, frequency multiplier 15, balanced modulator 16, filter 17, PAL /
NTSC selector switch 18, PAL / NTSC signal selector circuit 8
By providing, not only recording and reproduction of NTSC signals,
You can also play PAL tapes and reproduce colors on an NTSC TV screen with normal hue.

A second embodiment of the present invention will be described below with reference to the drawings.

FIG. 5 is a block diagram showing the reproducing system of the chrominance signal processing circuit of the magnetic recording / reproducing apparatus showing the second embodiment of the present invention. In FIG. 5, 101 to 122 are conventional NTSC systems
The chrominance circuit reproduction system of VHSVTR is shown. 131 to 139 are circuits added for conversion. 131 is a gate circuit, 132
Is a gate signal generation circuit, 133 is a phase shifter, 134 is a frequency multiplier, 135 is a balanced modulator, 136 is a filter, 137 is a burst phase shifter, 138 is a PAL / NTSC switching circuit, and 139 is a PAL / NTSC switching signal. The generator circuit differs from that of the first embodiment in that a phase comparator is not newly provided and the phase comparator 112 for APC is used, and the control signal of the signal generator circuit 139 causes the PAL mode At the moment, the operation of burst down is prohibited. Although the basic operation of the chrominance signal conversion circuit configured as described above is the same as that of the first embodiment, the same effect can be obtained by reducing the number of additional circuits.

The third embodiment of the present invention will be described below. FIG. 6 is a block diagram showing a reproducing system of the chrominance signal processing circuit of the magnetic recording / reproducing apparatus. In the figure, 101 to 139 are similar to the configuration of FIG. The difference from the configuration of FIG. 5 is that the PAL comb filter 140 is provided at the output of the killer amplifier 108 and the control signal of the PAL / NTSC switching signal generation circuit 139.
This is the point where the killer amplifier 108 is forcibly operated in the color mode during PAL tape playback. The basic operation of the chrominance signal conversion circuit configured as described above is the same as that of the second embodiment, but a 40 ° PAL comb filter 140 is used.
By providing the above, it is possible to remove the head crosstalk component at the time of reproducing the PAL recording tape, and it is possible to obtain a stable signal by using the forced color.

In the second embodiment, the gate circuit 131 is a mixer, and a gate circuit is provided at the output of the killer amplifier 108,
° For one horizontal sync period of burst, add signal to mixer,
The signal is balanced modulator 135 during one horizontal synchronization period of 135 ° burst.
In addition to the above, it may be added to the mixer after passing through the filter 136.

Also, in the second embodiment, the 1-horizontal synchronization period of the -135 ° burst is balanced-modulated by the doubled carrier including the burst. However, the chrominance signal from the + 135 ° burst to the next -135 ° burst, The former is sent to the burst phase shifter as it is, and the latter is sent to the balanced modulator 135 and the signal after passing through the filter 136 is sent to the burst phase shifter and the burst phase shifter 137. At + 135 ° burst is 45
The phase may be advanced by-° and the -135 ° burst may be delayed by 45 °.

(Effect of the invention) As described above, according to the present invention, not only the recording and reproducing of the NTSC system signal but also the PAL signal recording tape is reproduced, and the color is reproduced in the normal hue on the NTSC TV set. it can. It is possible to obtain a magnetic recording / reproducing device capable of recording / reproducing signals of various kinds of feed frequencies.

[Brief description of drawings]

FIG. 1 is a block diagram showing a video signal reproducing system of a magnetic recording / reproducing apparatus according to the first embodiment of the present invention, FIG. 2, FIG.
FIG. 4 is a partial signal waveform and vector diagram in FIG. 1, FIG. 5 is a block diagram showing a second embodiment, FIG. 6 is a block diagram showing a third embodiment, and FIG. Conventional VHS-NTSC method
FIG. 8 is a block diagram showing the reproduction system of the chrominance signal processing circuit of the VTR, and FIG. 8 is a signal waveform and vector diagram of a part of FIG. 1,101 ... Magnetic head, 2,102 ... Reproduction amplifier, 3 ... Luminance signal processing circuit, 4 ... Luminance / chrominance mixer, 5 ... Chrominance signal processing circuit, 6,14 ... Phase shift circuit, 7,121 ... Reference Oscillator, 8,138 ... Switching circuit, 9
...... Burst phase shift circuit, 10,111 …… Burst gate circuit, 11,131 …… Gate circuit, 12,112,122 …… Phase comparator, 13,132 …… Gate signal generation circuit, 15,134 …… Frequency multiplier, 16,105,114,135 …… Balance modulator, 17,136 ...... Filter, 18 …… Changeover switch, 31,32,33,35,36,37
…… Signal, 34 …… Error voltage, 103 …… Low pass filter, 104 …… ACC circuit, 106 …… Burst down circuit, 10
7,115 …… Band filter, 108 …… Killer amplifier, 109,14
0: Comb filter, 110: Chrominance signal output terminal, 113: Voltage controlled oscillator, 116: Input signal, 117
...... Phase shift circuit, 118 …… Reproduced luminance signal, 119…
… Horizontal sync signal separation circuit, 120 …… Countdown circuit, 133 …… Phase shifter, 137 …… Burst phase shifter, 139 ……
Signal generation circuit.

Claims (1)

(57) [Claims] 1. A servo system capable of recording and reproducing signals of various kinds of field frequencies and adopting a VHS-NTSC system as a chrominance processing circuit, and at the same time VHS-
When playing a tape recorded with a PAL VTR, the phase of the low-frequency conversion color signal is set to CH1 head (6 to the right of head azimuth).
°) is constant during one horizontal sync period, and CH2 head (6 ° to the left of head azimuth) is 90 for each horizontal sync period.
In a magnetic recording / reproducing apparatus having a function of delaying (referred to as PAL mode), a burst gate circuit for extracting a burst of a chrominance signal reproduced in PAL mode, a burst signal extracted from the burst gate circuit, and A phase comparator that compares the phase of the output of the reference oscillator (which oscillates at the color subcarrier frequency of the NTSC standard TV system) used to obtain the chrominance signal, and corresponds to the positive or negative of the error voltage of the output of the phase comparator. A gate signal generation circuit that repeats a high level and a low level for each horizontal synchronization period, and a phase shifter that shifts the phase of the reference oscillator,
A frequency multiplier for converting the phase shifter output into a doubled frequency, a balanced modulator for performing balanced modulation of the frequency multiplier output and the regenerated chrominance signal, and a difference component of the balanced modulator output. The chrominance signal of the filter output and the chrominance signal of the filter output and the regenerated chrominance signal are passed through the regenerated chrominance signal in one horizontal synchronization period of + 135 ° burst phase by the gate signal generated by the gate signal generation circuit. Let
A gate circuit for passing the chrominance signal of the filter output during one horizontal synchronization period of -135 ° burst phase;
And a phase shift circuit that shifts only the burst of the gate circuit output signal.