JPH0658749B2 - Magnetic recording / playback device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic head type magnetic recording / reproducing apparatus, and more particularly to a phase control for rotationally driving a rotary head in phase synchronization with a vertical synchronizing signal of a video signal to be recorded. Characterized by the system.

2. Description of the Related Art A magnetic tape is wound around a rotary head cylinder, in which a plurality of magnetic heads are arranged at equal intervals, by spirally winding the magnetic tape at a predetermined angle, and the plurality of magnetic heads are sequentially switched and used. In a helical scan type magnetic recording / reproducing apparatus for sequentially recording / reproducing a video signal of one field as a recording locus inclined with respect to the longitudinal direction of the head, the structure shown in FIG. 6 is used to make the diameter of the head cylinder smaller. Is being considered.

That is, in FIG. 6, reference numerals 21, 22, 23, and 24 denote four magnetic heads A, B, A ′, and B ′, which are arranged in the head cylinder 20 at equal intervals of 90 °, respectively. And 23 and 22 and 24 have the same azimuth angle.

The magnetic tape 4 is wound around the head cylinder 20 over 270 ° or more.

In this state, the heads 21, 22, 23, 2 are synchronized with the rotation phase of the head cylinder every 3/4 rotation of the head cylinder.
By sequentially switching to Nos. 4 and 21, the recording loci of recording loci A, B, A ', B', and A are obtained on the tape as shown in FIG.

At this time, since it is necessary to record the video signal of one field on each recording locus A, B, A ', B', it is necessary to drive the head cylinder in synchronization with the vertical synchronizing signal of the video signal to be recorded. is there.

That is, it is necessary to rotate the head cylinder 3/4 rotation in one cycle of the vertical synchronizing signal in phase synchronization with the vertical synchronizing signal.

For this reason, conventionally, the rotational phase detector (hereinafter referred to as PG The output of 7 is 1 /
A 15 Hz signal is obtained by dividing 1/3 by the 3 divider 8 and a vertical synchronizing signal obtained from the television signal to be recorded is divided by 1/4 by the 1/4 divider 9 to obtain a 15 Hz signal. Is compared by a phase comparator 10 and the cylinder motor 11 is controlled and driven so that the phases of the two signals match.

Problems to be Solved by the Invention In the configuration described above, the head cylinder is phase-controlled by the detection signal of 15 Hz.

That is, the phase of the head cylinder is controlled by a signal for every three rotations, and it is not always possible to expect good phase control.

In order to solve the above-mentioned problems, the present invention, in the case of the above-mentioned four-head type VTR, performs vertical synchronization with a signal obtained by dividing the output of the rotary phase detector of the head cylinder by 2/3. This is to compare the phase of the signal output and the signal obtained by dividing the signal output by 1/2, and to control the head cylinder motor so that both signals are in phase synchronization by the output.

Operation According to the above configuration, the signal applied to the phase comparator is the signal indicating the rotational phase of the head cylinder, which is 2/3 of 45Hz, 30H.
The control accuracy is improved compared with the conventional 15 Hz, which is z.

Embodiment One embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 shows a block diagram of a magnetic head switching signal generation circuit and a controlled signal generation circuit for a rotary head cylinder phase control circuit in a 4-head type magnetic recording / reproducing apparatus according to an embodiment of the present invention, and FIG. Shows the waveform of.

In FIG. 1, magnetic heads 21 having the same azimuth angle,
23 and the magnetic heads 22 and 24 having the azimuth angles opposite to those of the magnetic heads 21 and 23 are provided on the rotary head cylinder 3 provided at a distance of 90 °.
Is wound about 270 ° in the direction of arrow 5 and run.
The magnetic tape 4 is formed by the magnetic heads 21, 22, 23 and 24.
The video signal is sequentially recorded or reproduced.

The signal S ₂₂ from the PG 7 for detecting the rotational phase of the rotary head cylinder 3 is divided by 1/3 by the 1/3 frequency divider circuit 28 to obtain a signal S ₂₃ . Further, a frequency generator (hereinafter referred to as FG) 6 to 3 · M · _v for detecting rotation information of the rotary head cylinder 3
(M is an integer, _v is a vertical synchronizing signal frequency) For example, 180
The Hz signal S ₂₁ is input to the clock terminal of the 1/3 frequency dividing circuit 29, and the output signal S ₂₃ of the 1/3 frequency dividing circuit 28 is input to the reset terminal of the 1/3 frequency dividing circuit 29. / 3 frequency divider 29
Output signal S ₂₄ of the delay circuit 3 is input to the delay circuit 30 and
A resistor R and a capacitor C that determine the delay circuit of 0 are connected in series from the power source + V _cc , one end of the capacitor C is grounded, and a signal S ₂₅ is generated by the charging time constant, and the first, second and third capacitors are connected. By setting the threshold voltage, the first, second, and third delay circuit output signals S ₂₆ , S ₂₇ , S ₂₈ are obtained. The second delay time output signal S ₂₇ of the delay circuit 30 is input to the clock terminal of the 1/2 frequency divider circuit 26, and the output signal S ₂₃ of the 1/3 frequency divider circuit 28 is input to the reset terminal of the signal S. ₂₉ is supplied to the rotary head cylinder phase control circuit from the output terminal 27, and is phase-compared with a signal obtained by dividing the vertical synchronizing signal of the video signal to be recorded by 1/2 at the time of recording, and at the time of reproduction, is compared with the reproduction reference signal. Rotating head cylinder 3
Control the rotation phase of.

On the other hand, the output signals S ₂₆ , S ₂₇ , S _{28 of} the delay circuit 30 are input to the 4-phase head switching signal generating circuit 31, and the signals S ₃₀ , S ₃₁ , S ₃₂ , S ₃₃ are obtained according to the recording and reproducing. .

FIG. 3 shows a circuit diagram of an embodiment of the four-phase head switching signal generating circuit 31, FIG. 4 shows waveforms at various portions during recording, and FIG. 5 shows waveforms at various portions during reproducing. In FIG. 3, output signals S ₂₆ , S ₂₇ , S ₂₈ of the delay circuit 30 are input to input terminals 41, 42, 43, and switches 44, 45 are input.
Therefore, the signal S ₂₆ and the signal S ₂₈ are used during recording, and only the signal S ₂₇ is used during reproduction. The D-type flip-flops 47, 48, 49 with the reset terminal and the NOR gate 46 constitute a first four-phase ring counter, and the signal S ₂₈ is used as a clock signal during recording and the signal S ₂₈ during reproduction.
₂₇ , and the reset signal is the output signal S ₂₃ of the 1/3 frequency divider 28 from the input terminal 58. Similarly, D type flip-flops 55, 56, 57 and N with reset terminals
The OR gate 54 constitutes a second four-phase ring counter, and the signal S ₂₆ is input as a clock signal during recording, the signal S ₂₇ is input during reproduction, and the signal S ₂₃ is input as a reset signal. When the reset signal S ₂₃ becomes high level, all D-type flip-flops 47, 48, 4 with reset terminals are provided.
Since the outputs Q of 9, 55, 56 and 57 are all at the low level, the outputs of the NOR gates 46 and 54 are at the high level. After that, the high level is shifted to the right according to the clock input signal, and the signals S ₄₁ , S ₄₂ , S ₄₃ , S ₄₄ and the signal S
₄₅ , S ₄₆ , S ₄₇ , S ₄₈ are created. OR gate 50, 5
By taking the OR gate of the in-phase timing component of each 4-phase ring counter by 1, 52 and 53, the overlap winding amount at the time of recording is secured, and the output signals S ₃₀ and S
₃₁ , S ₃₂ , S ₃₃ can be created.

Output signals S ₃₀ , S ₃₁ , of the four-phase head switching signal generation circuit 31
S ₃₂ and S ₃₃ are input to the recording / reproducing amplifier 25, and during recording, the recording current is switched to the magnetic heads 21, 22, 23, and 24, and the magnetic tape 4 wound around the rotary head cylinder 3 runs ( (270 ° + Δθ) overlap recording is performed, and during reproduction, the resistance R of the delay circuit 30 is adjusted so that the reproduction output from the magnetic tape 4 comes to the position of the magnetic heads 21, 22, 23, 24. The head position is adjusted so that the reproduction output of each head can be obtained every 270 °.

In the above embodiment, the case of 4 heads is shown, but 6 heads are used.
The above idea can be applied to the method of winding the magnetic tape around the head by 300 ° and the method of winding the magnetic tape around the 315 ° cylinder with 8 heads. When N magnetic heads are used (where N is 4 or more), the output of the head cylinder rotation phase detector It suffices to compare the phase of the frequency-divided signal and the signal obtained by frequency-dividing the vertical synchronizing signal by 1/2, and the frequency of the FG in the embodiment of FIG. 1 is set to M (N-1) _.v . It should be installed.

EFFECTS OF THE INVENTION As described above, according to the present invention, the controlled signal frequency supplied to the phase control circuit of the head cylinder can be set to 1/2 _v, and a better phase control characteristic can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of a magnetic head switching signal generation circuit and a controlled signal generation circuit for a rotary head cylinder phase control circuit in a 4-head type magnetic recording / reproducing apparatus according to an embodiment of the present invention, and FIG. 2 is FIG. Waveform diagram of each part in
FIG. 4 is a circuit diagram of an embodiment of a 4-phase head switching signal generating circuit in the magnetic head switching signal generating circuit, FIG. 4 is a waveform diagram of each portion during recording in FIG. 3, and FIG. 5 is during reproducing in FIG. FIG. 6 is a waveform diagram of each part of FIG. 6, and FIG. 4 ... Magnetic tape, 6 ... FG, 7 ... PG, 8 ... 1 /
3 divider, 9 …… 1/4 divider, 10 …… Phase comparator, 11
...... Cylinder motor, 21, 22, 23, 24 ...... Magnetic head, 25 ...... Recording / reproducing amplifier, 26 ...... 1/2 divider circuit, 27 ...... Output terminal, 28 ...... 1/3 divider circuit , 29
...... 1/3 frequency divider circuit, 30 ...... delay circuit, 31 ...... 4-phase head switching signal creation circuit.

Claims (2)

[Claims] 1. An even number N of magnetic heads of 4 or more having different azimuth angles alternately. The rotary head cylinders that are spaced apart from each other A magnetic tape on which the magnetic head of the rotary head cylinder is sequentially recorded and reproduced, and a rotary phase detector for detecting the rotary phase of a specific magnetic head among the N magnetic heads; The output signal of the phase detector A first frequency dividing means for dividing the frequency, a second frequency dividing means for dividing the vertical synchronizing signal of the recording video signal by 1/2, an output of the first frequency dividing means and an output of the second frequency dividing means. And a means for controlling the rotary phase of the rotary head cylinder so that the phases of the two signals have a predetermined phase relationship according to the phase comparison error signal of the phase comparator. 2. The first frequency dividing means outputs the output of the rotational phase detector. Divide A frequency dividing circuit, a rotation information detector for detecting rotation information of the rotary head cylinder as a frequency signal of M (N-1) · _v (where M is an integer, and _v is a vertical synchronizing signal frequency) signal for one rotation; Rotation information detector output Divide and Can be reset by frequency divider output Frequency divider circuit, Input the frequency divider circuit output, and The magnetic recording / reproducing apparatus according to claim 1, wherein the magnetic recording / reproducing apparatus comprises a 1/2 frequency dividing circuit that can be reset by the output of the frequency dividing circuit.