JPS5921589Y2 - magnetic recording and reproducing device - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a magnetic recording and reproducing device that has a single rotating magnetic head and is configured to perform recording and reproducing so as to form magnetic tracks obliquely with respect to the longitudinal direction of a magnetic tape. In particular, it is an object of the present invention to provide an apparatus that can prevent disturbances in the reproduced image due to deletion of synchronizing signals near the vertical retrace interval in the reproduced video signal and obtain a high-quality reproduced image.

The magnetic recording/reproducing device according to the present invention has a single rotating magnetic head, forms a magnetic track diagonally with respect to the longitudinal direction of the magnetic tape, and has a single rotating magnetic head within the vertical retrace interval of the video signal. In a magnetic recording and reproducing device that performs recording and reproducing so that the switching interval of the magnetic head occurs, a signal indicating the position of a single rotating magnetic head is generated in synchronization with the rotation of the single rotating magnetic head. a pulse generator; a circuit for forming a first signal indicating a switching interval based on a position signal and a second signal equivalent to a vertical synchronization signal; an external synchronization type oscillator having a self-oscillation frequency close to the horizontal frequency; a circuit for supplying a horizontal synchronization signal in the reproduced video signal to the external synchronization type oscillator at least in an interval other than the switching interval by the signal No. 1, and generating an oscillation output in which the frequency of the horizontal synchronization signal is doubled; and an oscillation output to form a composite synchronization signal including equalized pulses, and the composite synchronization signal from the synchronization signal formation circuit is inserted into a switching section of the reproduced video signal. This is how you should be warned.

A magnetic recording medium that has one rotating magnetic head and records so as to form a magnetic track for one frame or one field of a video signal diagonally with respect to the longitudinal direction of the magnetic tape, and then plays back the magnetic track. In recording and reproducing mounting, the magnetic tape is guided around a tape guide drum having a rotating magnetic head by winding it approximately 360° in α or Ω windings so as to wrap it at an angle. In this magnetic recording and reproducing device, it is not possible to record all of the video signals to be recorded on the magnetic tape, and only a portion of the video signal is transferred from one magnetic track to an adjacent magnetic track.
It is unavoidable that some portions may be deleted and recorded by several H to several 10 H (where H is the horizontal period).

Therefore, in such a magnetic recording/reproducing device, the utilization rate of magnetic tape is low.

Accordingly, in one embodiment of the present invention, in a magnetic recording/reproducing apparatus having one rotating magnetic head, the area near the vertical blanking interval that does not change depending on the video information in the video signal, for example, the vertical synchronizing signal interval or the A video signal is recorded on a magnetic tape so that, for example, one frame or one field of the video signal forms one magnetic track so that the section extending from the front to the rear becomes a deleted section, and then the video signal is reproduced. At times, a synchronizing signal near a newly created vertical retrace interval is reinserted into the reproduced video signal so as to fill at least the deleted interval in the reproduced video signal.

FIG. 1 shows the main parts of a magnetic recording and reproducing apparatus according to an embodiment of the present invention, and shows its reproducing system.

Reference numeral 1 denotes a rotating magnetic head for recording and reproducing, which is arranged so as to rotate facing the outside within the gap between the upper and lower drums of the tape guide drum, although it is not shown. Winding close to 360° is such that the winding is guided at an angle.

Approximately one frame or one field of the video signal is placed on this magnetic tape 2 at a diagonal angle with respect to its longitudinal direction.
The F of the video signal forms magnetic tracks one by one.
An M modulation signal is recorded.

Figure 2A shows the waveform of an NTSC television signal, which is an example of a video signal recorded and reproduced by this magnetic recording and reproducing device, where Fe and Fo are the odd and even field video signal sections, respectively, and Tvb is the vertical blanking line. section, Pv is the vertical synchronization pulse, Pe is the equalization pulse, Ph is the horizontal synchronization pulse, tl-42 is the front equalization pulse section, t2-43 is the vertical synchronization signal section, t3-t4 is the rear equalization pulse section, t4
-45 indicates horizontal synchronization pulse sections, respectively.

In this embodiment, the missing section of the video signal recorded on the magnetic tape 2 is, for example, the vertical synchronizing pulse section t2-1.
3 or including the front or rear equalization pulse interval t1-t2
．． Recording is performed so as to cover a part of the interval t3-14, and the synchronization signal of the interval t1-t4 of the vertical retrace interval Tvb of the television signal is reproduced in the reproduced video signal. inserted.

The reproduced signal from the rotating magnetic head 1 is supplied to the amplifying circuit 3 and the FM demodulating circuit 5 for FM demodulation, and the demodulated reproduced video signal is supplied to the amplifying circuit 6 through the changeover switch SW1. is being done.

The changeover switch SW1 is a changeover switch' (actually an electronic switch using a transistor, etc.) for reinserting a new synchronization signal into the output of the FM demodulation circuit 5, and has a movable contact a, a fixed contact S, and a switch C. , and the movable contact a is the amplifying circuit 6
The fixed contact C is connected to the input side of the FM demodulation circuit 5, and the fixed contact C is connected to the input side of a synchronization signal generation circuit 7 that generates a synchronization signal to be reinserted, which will be described later. is the output end of

A switching signal for controlling the changeover switch SW1 is generated based on a position signal indicating the rotational position of the rotary magnetic head 1.

That is, pulse generating means for generating pulses of 3Q Hz or 60 Hz in accordance with the rotation of the rotary magnetic head 1 is provided.

This pulse generating means is composed of a magnet attached to the rotating shaft of the rotary magnetic head 1 and a pulse detecting magnetic head opposed to this magnet.
is the magnetic head for pulse detection.

The position of the position signal detected by the magnetic head 10 is arranged to be a time γ1 before the time t1 at which the vertical retrace interval Tvb of the television signal begins, for example, as shown in FIG. 2B. shall be.

Therefore, the detection output of the magnetic head 10 is supplied to the monostable multivibrator 12 of time width γ1 through the amplification circuit 11, and the output of this monostable multivibrator 12 is supplied to the monostable multivibrator 13 of another time width. be done.

The time width of this monostable multivibrator 13 is
It is selected to be equal to the time width of the interval t1-t4 of the television signal in Figure A.

Therefore, from this monostable multivibrator 12, the second
As shown in FIG. B, a rectangular wave signal that rises and falls at time t1 is obtained at a time point γ1 before time t1.

Further, from the monostable multi-bi break 13, as shown in FIG. 2C, a rectangular wave signal is obtained which rises at time tl and falls at time t4.

The output of the monostable multivibrator 13 controls switching of the changeover switch SW1.

That is, the movable contact a of the changeover switch SW1 is normally switched to the fixed contact side, and the movable contact a is switched to the fixed contact C side from time t1 to time t4.

The movable contact a of the changeover switch SW1 is switched to the fixed contact C side for one vertical period when one magnetic track is formed by one field of the television signal in Fig. 2A. If one frame (= 2 fields) is formed on one magnetic track, 2
Once per vertical period.

In this embodiment, the synchronization signal generation circuit 7 generates a synchronization signal for the period t1-44 of the television signal in FIG.
This is the minute synchronization signal.

In this synchronization signal generation circuit 7, the output of the monostable multivibrator 12 has a time width γ( = 3 H), and the output of this monostable multivibrator 15 is supplied to the monostable multivibrator 16 (its output waveform is shown in the second figure) with a time width of % (= 3 H). the output waveform is shown in Figure 2E),
From the monostable multivibrator 16, the time width γ4 (=3H) rises at time t2 and falls at time t3
) is obtained, which is supplied to the synchronization signal generation circuit 7.

Reference numeral 18 denotes an externally synchronized oscillation circuit having a self-oscillation frequency close to the horizontal frequency, which is a flywheel oscillation circuit in this embodiment, and is designed to be able to vary its self-oscillation frequency.

This flywheel oscillation circuit 18 is an oscillation circuit whose oscillation frequency approaches its own oscillation frequency with a predetermined time constant from the moment that external synchronization is no longer applied, and finally reaches that frequency.

The output of the amplification circuit 6 is an on-off switch S, which will be described later.
The horizontal synchronizing signal is supplied to the synchronizing signal separation circuit 19 via W2, whereby the horizontal synchronizing signal is separated, and this is supplied to the oscillation circuit 18 as an external synchronizing signal.

Note that this on/off switch SW2 is a changeover switch SW.
1 and controlled by the output of the monostable multivibrator 13, it is always on and off from time t1 to time t4.

The output of the oscillation circuit 18 is then supplied to the frequency doubling circuit 20, where the frequency is doubled, and the horizontal frequency (15, 7
5KHz) is supplied to the clock signal generation circuit 21, and a pulse signal with a frequency of 31.5KH2 and a pulse width of 2.5 μs is obtained from the clock signal generation circuit 21. The signal is supplied to the synchronization signal generation circuit through.

Then, by the clock signal from this clock signal generation circuit 21, the front and rear equalization pulses Pe,
A split pulse of Pe and vertical synchronization signal Pv is formed.

Note that the gate circuit 22 is a monostable multivibrator 22.
from time t1 to time t4.
It will only be open until then.

According to the magnetic recording/reproducing apparatus shown in FIG. 2, the synchronization signal of the interval t1-t4 from the synchronization signal generation circuit 7 is reinserted into the FM demodulated reproduced video signal output from the FM demodulation circuit 5.

Therefore, at the output end 8, a reproduced video signal is obtained in which the synchronization signal near the vertical retrace section is not deleted or distorted, eliminating disturbances in the reproduction screen and improving the utilization rate of the magnetic tape. do.

Furthermore, when the synchronization signal is reinserted, if the external synchronization of the externally synchronized oscillation circuit 18 is removed, the oscillation frequency gradually changes to the self-oscillation frequency (set to an appropriate value) with a predetermined time constant. When external synchronization is applied, the oscillation frequency gradually approaches the external synchronization frequency with a predetermined time constant. Occurrence of jumping in the moving part is prevented.

Further, skew control can be performed by varying (for example, manually adjusting) the self-oscillation frequency of the oscillation circuit 18.

According to the present invention described above, in a magnetic recording and reproducing apparatus that has a single rotating magnetic head and is configured to perform recording and reproducing so as to form magnetic tracks diagonally with respect to the longitudinal direction of a magnetic tape, a reproduced image can be It is possible to obtain a high-quality reproduced image by preventing disturbances in the reproduced image due to deletion of the synchronizing signal near the vertical retrace interval in the signal.

The magnetic recording and reproducing apparatus according to the present invention can handle either black-and-white video signals or color video signals, as well as television signals of the NTSC system and other systems.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing an embodiment of the present invention, and FIG. 2 is a waveform diagram for explaining the same. 1 is a rotating magnetic head, 2 is a magnetic tape, 7 is a synchronous signal generation circuit, 18 is an external synchronous oscillation circuit, SW1 is a changeover switch, and SW2 is an on/off switch.

Claims (1)

[Scope of utility model registration request] It has a single rotating magnetic head, forms a magnetic track diagonally with respect to the longitudinal direction of the magnetic tape, and records and plays so that the switching section of the single rotating magnetic head is within the vertical retrace section of the video signal. The magnetic recording and reproducing apparatus is configured to include a pulse generator that generates a signal indicating the position of the single rotating magnetic head in synchronization with the rotation of the single rotating magnetic head, and a pulse generator that generates a signal indicating the position of the single rotating magnetic head, and a circuit for forming a first signal indicating the switching interval and a second signal equivalent to the vertical synchronization signal based on the switching interval; an external synchronization type oscillator having a self-oscillation frequency close to the horizontal frequency; a circuit that generates an oscillation output in which the horizontal synchronization signal in the reproduced video signal is supplied to the externally synchronized oscillator in an interval other than the switching interval, and the frequency of the horizontal synchronization signal is doubled; a synchronization signal forming circuit that is supplied with the oscillation output and forms a composite synchronization signal including an equalized pulse; A magnetic recording and reproducing device that can be used as if it were inserted.