JPS6166214A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To attain easily accurate tracking control by controlling the tracking shift amount while looking at a tracking meter so that the phase difference between a vertical synchronizing signal of a reproduction signal and a reproduction control pulse at a value close to zero. CONSTITUTION:A reproduction video signal (a) supplied to a terminal 1 is turned into the pulse of a signal (d) through a vertical synchronizing separator circuit 4, a gate circuit 5 and a monostable multivibrator 6. The signal (d) and a reproduction control signal (e) of a terminal 3a are supplied to a phase comparator 8 for comparison with each other. When the signal (d) is advanced more than the signal (e), a terminal at one side delivers an output. While a terminal at the other side delivers an output if the signal (d) is slower than the signal (e). These both outputs are mixed together by a mixing circuit 9 to obtain an output (f). This output (f) is integrated by an LPF10 to obtain a DC output (g). The output (g) is amplified 11 and supplied to a tracking meter 12. Then the output (g) is maximum when the complete coincidence of phase is obtained between the signals (d) and (e). The maximum position of the pointer of the meter 12 is identical with the optimum tracking position.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a helical scan type magnetic recording/reproducing device.

Conventional configuration and problems Helical scan video tape recorder (hereinafter referred to as VT)
In the normal playback mode, in the normal playback mode, you can determine whether the rotary head is properly positioned above the recording track by visually checking the approximate position on the screen, as is often the case with home VTRs. In addition, for commercial and broadcasting VTRs, the tracking meter should be adjusted so that the deflection of the tracking meter pointer is maximized.
Normally, the correct position is determined by adjusting the adjustment knob attached to the front of the VTR. The conventional traffking meter drive method is
As shown in Figure 1, the playback F from the rotating head "21°22"
The M-hood output is amplified by the head amplifier 23, and its output (commonly known as envelope output) is sent to the envelope detection circuit 24.
The DC output is amplified by the DC amplifier 26 to drive the tracking meter 2ef. In other words, the position where the head output is approximately maximum is found by adjusting the trafking shifter barrel. 2
7 is a tape.

However, with this conventional tracking/knocking meter drive system, there are changes due to temperature and aging even in self-recording and playback, and there are also problems with compatibility between decks, as shown in Figure 2.
The difference in the linearity of rotation and leader running as shown in Figure 2, and the CH1 head 21 and CH as shown in Figure 2.
2. Due to mechanical running differences such as differences in height when installing the head of Sodo 22, (II) and (IT) in Figure 2 are required.
(In ideal conditions, the envelope waveform is as shown in (1).) As you adjust the tracking volume, the envelope waveform changes depending on the amount of tracking deviation. It may change from II) to (7), or from (Shu to ('')), and when the detection output is at its maximum (the meter pointer is at its maximum), the rotating 1. C is accurately positioned on the recording track. In addition, when there is a step in the envelope as shown in Fig. 2 (2), it is not particularly accurate. In addition, 2 in Fig. 2 is the output of 7 and 21 to CHl, Figure 2 E is CH2 Hefd 2
This is the output of 2. In cases where particularly accurate tracking is required, such as with an editing machine, this type of meter cannot meet the requirements.

OBJECTS OF THE INVENTION The present invention solves the above-mentioned conventional drawbacks, and an object thereof is to provide a magnetic recording/reproducing device that allows precise and easy fine tuning of trunking/lid.

Structure of the Invention In order to achieve the above objects, the magnetic recording and reproducing apparatus of the present invention detects a synchronizing signal of a reproduced signal obtained by scanning a recording track of a magnetic tape by rotation, decoding, and generating a vertical synchronizing pulse. A synchronization signal output circuit is generated, a phase difference detection circuit detects the phase difference by comparing the reproduction control signal obtained by the fixed control head and the vertical synchronization pulse, and detects the detection output of this phase difference detection circuit. The meter drive circuit is provided with a meter drive circuit that is controlled by a phase difference detection output from the detection means, and a meter that is driven.

DESCRIPTION OF THE EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.The control signal is normally in phase with the vertical synchronization signal of the signal to be recorded on the time axis. Therefore,
During reproduction, the state in which the vertical synchronization signal of the reproduction signal and the reference edge (usually the rising pulse edge) of the control signal are at exactly the same position in time is the state in which the tracking is most accurately controlled. In this embodiment, an example of a circuit configured to detect the above-mentioned state in a meter will be described.

First, the principle of operation will be explained using the time chart shown in FIG.

a is a playback video signal, b is a vertical synchronization signal generated from the playback video signal a, and C is a head switching signal (DG pulse), and this head switching signal C is set to always come before the vertical synchronization signal. Therefore, using the vertical synchronization signal and the switching signal C,
By gating one with the other, a 30Hz vertical synchronization signal that is in phase with the 5oHz playback control signal is created. The signal d is obtained by passing it through a monomultiply and giving it a certain width. e is a signal obtained by amplifying the reproduction control signal. (Only the two reference signals) The signal e is a solid line when the control signal comes T1 hours before the vertical synchronization signal, and the difference obtained by the line when it comes 12 hours later is the signal f. The mix circuit of FIG. 4, which will be described later, uses this signal f.
A DC converted signal q is obtained through a low-pass filter, amplified, and the output is supplied to a transducer and a ranking meter.

This signal q becomes a DC output corresponding to the phase difference between the reproduction vertical synchronization signal and the reproduction control signal, and therefore the pointer of the tracking meter moves according to the phase difference between the two signals. Therefore, if you operate the tiger and 7 king volume while watching the meter so that the pointer is at maximum deflection,
The position of the tracking shifter amount is the position where the phase difference between the control signal and the reproduction synchronization signal is zero, and the reproduction video head reproduces the most accurate position of the recording track.

Next, the block diagram shown in FIG. 4 that implements the above operation will be explained.

A playback video signal is input to terminal 1, and a playback control signal is input to quadruple 3. Signals a to q in FIG. 4 correspond to signals ♂ to q in FIG. 3. The reproduced video signal input to terminal 1 is transmitted through vertical synchronization separation circuit 4, gate circuit 5 (switching gate shown in Fig. 3), and monomulti 6
and becomes a pulse signal d. 8 is a phase comparator;
Reference numeral 9 denotes a mix circuit, and FIG. 6 shows an embodiment of the mix circuit, and FIG. 6 shows its timing diagram. If d and e are input to the phase comparator 8, and the comparison output is that e is ahead of d, the sixth
A pulse having a width shown in FIG. 6 is output from the A terminal shown in the figure, and from the B terminal if e is delayed from d, respectively.

These A and B are mixed by a mix circuit 9 to obtain an output f shown in FIG.

Returning to FIG. 4, the output signal f thus obtained is integrated by a low-pass filter 1o to obtain a DC output q. q is amplified by the next amplifier 11 and its output is supplied to the tracking meter 12.

In FIG. 3, the vertical synchronizing signal d and the reproduction control pulse e (if the ice phases are completely coincident, q, is vrnax
The optimum tracking position is j4 at the maximum position of the meter pointer.

Note that the present invention is not limited to the above-described practical example, but can be realized by detecting the phase difference between the control signal and the vertical synchronization signal of the reproduced video signal, converting it to direct current, and supplying it to the tracking meter. Any configuration is sufficient as long as it can detect the phase difference and find the optimum tracking point.

As described in detail, according to the present invention, the vertical synchronization signal of the reproduced signal and the reproduction control signal N are phase-compared, and tracking is performed while watching a tracking meter so that the phase difference is close to zero. Since the amount of lid is adjusted, accurate tracking can be easily obtained. Therefore, accurate tracking adjustment can be obtained even when the magnetic tape is deformed or when compatible reproduction is performed between VTRs of the same format.

[Brief explanation of the drawing]

Figure 1 is a block diagram of the detection and drive circuit of a trunking meter of a conventional magnetic recording/reproducing device, Figure 2 is a waveform diagram of the force/velope output, and Figure 3 is a partial phase comparison of Figure 4. A circuit diagram of one embodiment of the device FIG. 6 is a signal waveform diagram of the circuit shown in FIG. 4... Synchronous separation circuit, 5... Gate circuit, 6... Mono multi, 8... Phase comparator, 9... Mix 110...Low pass filter, 12...Tracking meter. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
Figure -2, 2 Figure 3'' Ki2L σV

Claims (1)

[Claims] A synchronization signal output circuit detects a synchronization signal in a reproduction signal obtained by scanning a recording track of a magnetic tape with a rotating magnetic head and generates a vertical synchronization pulse, and a reproduction control signal obtained by a fixed control head and the vertical synchronization. a phase difference detection circuit that detects the phase difference by comparing the pulses, a detection means that detects the detection output of the phase difference detection circuit, and a meter drive circuit that is controlled by the phase difference detection output from the detection means; A magnetic recording and reproducing device equipped with a driven meter.