JPS6234195B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a magnetic recording/reproducing apparatus in which adjacent tracks are alternately scanned by two magnetic heads having two different azimuth angles. The present invention relates to a magnetic recording and reproducing device that can reproduce images with less noise in the case of so-called slow reproduction, in which images are transferred and reproduced in a slow motion.

Now, the tape transport speed is set to one-fifth of the normal transport speed, and FIG. 1 shows how two magnetic heads scan one track using the conventional method. In Figure 1a, recorded track 1
With respect to A, the magnetic head 2A, which has an azimuth angle equal to the azimuth angle of this track 1A, starts scanning from the same position as the scan start position when the tape is transported at a normal speed. However, since the tape transport speed is slow, the magnetic head 2A gradually shifts to the left from track 1A, and at its scanning end position,
The magnetic head 2A finishes scanning at a position shifted from the track 1A by about four-fifths of the track width. Next, FIG. 1b shows that the magnetic head 2B has an azimuth angle different from that of the track 1A.
This shows the state when the image is scanned for the second time.
When the magnetic head 2B starts scanning, the magnetic head 2B starts scanning from a position shifted from the track 1A by about one-fifth of the track width, gradually shifts to the left on the track 1A, and then completely stops. It passes the position where it got on the track, shifts further to the left, and ends the scan at a position shifted from track 1A by about three-fifths of the track width. Figure 1c
is the third scan of the track 1A by the magnetic head 2A. The magnetic head 2A starts scanning at a position offset by about two-fifths of the track width from the starting point of the track 1A, and gradually shifts to the left.
It completely rides on the track 1A at approximately the midpoint of the longitudinal length of the track 1A, then shifts further to the left, and ends scanning at a position shifted from the track 1A by about two-fifths of the track width. Similarly, FIG. 1d shows the fourth scan by the magnetic head 2B, and FIG.
indicates the fifth scan by the magnetic head 2A,
The scanning of track 1A ends with this fifth scanning.

Next, FIG. 2 schematically shows the video output in the scanning states shown in FIG. 1 a to e.
correspond to scanning periods a to e in FIG. In state a, magnetic head 2A and track 1A
The azimuth angles of the magnetic heads 2A and 2A are equal, and the magnetic head 2A is completely on the track 1A at the scanning start position.As the scanning progresses, the magnetic head 2A shifts to the left, so that the output gradually decreases. In state b, since the azimuth angles are different between the magnetic head 2B and the track 1A, the magnetic head 2B at the scanning start position receives the signal of the track recorded at the same azimuth angle as the magnetic head 2B on the right side of the track 1A. However, as the magnetic head 2B gradually shifts to the left, the video output further decreases, and when the magnetic head 2B is completely on the track 1A, the output becomes almost 0. Furthermore, as the magnetic head 2B shifts to the left, the signal recorded on the left track of the track 1A is extracted, and as the portion of the magnetic head 2B gradually increases to be on this left track, the video output gradually decreases. begins to increase. In state c, the magnetic head 2A
The azimuth angles of the magnetic head 2A and the track 1A are the same, and as scanning progresses, the portion of the magnetic head 2A that rides on the track 1A gradually increases, so the output gradually increases, and the video output reaches its maximum when it completely rides the magnetic head 2A. Going further, the magnetic head 2A is on track 1.
As it shifts to the left from A, the output gradually begins to decrease. In state d, since the azimuth angles of magnetic head 2B and track 1A are different, magnetic head 2B extracts a signal from the track on the right side of track 1A, but as magnetic head 2B gradually shifts to the left, the output decreases. Then, magnetic head 2
When B completely rides on track 1A, the video output becomes almost 0. At e, the magnetic head 2A starts scanning from a state where it is slightly close to the track 1A, gradually increases the part on the track 1A, and completely rides on the track 1A at the scanning end point, so the output gradually increases and at the end of the scanning, the magnetic head 2A starts scanning. Maximum.

The above is the scanning state of the conventional device when the tape transport speed is set to one-fifth of the normal speed. When such scanning is performed, the azimuth angle of the scanning track changes as shown in periods b and d in Fig. 2. Since there is a period during which scanning is performed with a magnetic head having an azimuth angle different from the azimuth angle, the video output is low and there is a lot of noise during this period, and the noise is especially significant in the portion where the output is almost 0. In addition, since the tracks before and after the scanning track are also scanned, if a fast-moving object is recorded, the recording position will be different depending on each track, so the screen will appear double,
It had the disadvantage of appearing as a triple statue.

In order to eliminate the above-mentioned drawbacks, this invention provides a second
During the period shown in Figures b or d, that is, during the period when the azimuth angle of the scanning track and the azimuth angle of the magnetic head are different, the azimuth angle of this magnetic head is made equal to the azimuth angle of the other magnetic head. A magnetic recording and reproducing method in which two magnetic heads with equal azimuth angles scan a track recorded at an azimuth angle equal to the azimuth angle of these magnetic heads by displacing the magnetic heads with different azimuth angles. It is related to the device. The following will be explained using examples.

FIG. 3 shows a block diagram of an embodiment of the present invention. In this embodiment, a case will be explained in which the tape transport speed is set to one-fifth of the normal speed. Reference numeral 10 denotes a control head which takes out a control signal recorded on a control track of a magnetic tape. This control signal is amplified by an amplifier 11 and applied to a phase comparison circuit 12. On the other hand, a pulse synchronized with the head drum is input from the input terminal 13, and is applied to the amplifier 14 for amplification. The output of the amplifier 14 is further applied to a 1/5 frequency divider 15 to divide the frequency into 1/5. And this 1/5 frequency divider 1
The output of the amplifier 5 is input to the phase comparison circuit 12, and the phase is compared with the output of the amplifier 11. Here, control is performed to match the phase of the control signal and a frequency-divided pulse synchronized with the head drum to one-fifth. The output of the phase comparator circuit 12 is input to an amplifier 16 which is a motor drive means and amplified, and this amplified output is sent to the capstan motor 1.
7 plus drives the capstan motor.
By the above mechanism, the capstan motor 17 is servoed so that the head drum rotates five times and the magnetic tape is transported by one track width. The timing pulse generating means is composed of a delay circuit 18 and pulse width conversion circuits 19 and 22. The head azimuth switching means is composed of a head drive circuit 20 and an actuator 21, or a head drive circuit 23 and an actuator 24.

Next, timing for head azimuth switching will be explained using FIGS. 3 and 4.

FIG. 4A shows pulses synchronized to the head drum. This pulse is applied to the magnetic head 2A in FIG.
is in a rising state during scanning, and the magnetic head 2B
It is assumed that the signal is in a falling state while it is being scanned. As mentioned above, this pulse A is input to input terminal 1.
3, is amplified by an amplifier 14, is added to a 1/5 frequency divider 15, and is divided into 1/5. This frequency-divided waveform is shown in FIG. 4B. This pulse B is input to the phase comparison circuit 12 and compared in phase with the control signal, and the servo is applied to the capstan motor 17 so that these phases match. is in phase with. That is, track 1
This pulse is in a rising state while scanning a track recorded at an azimuth angle equal to the azimuth angle of A, and is in a falling state while scanning a track recorded at an azimuth angle different from this. . One of the output pulses B of the 1/5 frequency divider is input to the delay circuit 18 and delayed by half a period as shown in FIG. 4C. Furthermore, this pulse C is applied to a pulse width conversion circuit 19 consisting of a trigger circuit and a monostable multivibrator, and is converted into a pulse A.
The pulse width is reduced by half the period of , resulting in the pulse shown in FIG. 4D. This pulse D is input to the head drive circuit 20, and the head drive circuit 2
0 drives the actuator 21 only during the rise time of the input pulse D to change the azimuth angle of the magnetic head 2A to be equal to that of the other magnetic head 2B.

On the other hand, the output of the 1/5 frequency divider 15 is also applied to a pulse width conversion circuit 22 which performs the same operation as the pulse width conversion circuit 19, and the rise time of pulse B is shortened by half the period of pulse A. , resulting in a pulse as shown in FIG. 4E. This pulse E is input to a head drive circuit 23 which performs the same operation as the head drive circuit 20, and drives the actuator 24 only during the rise time of the pulse E to change the azimuth angle of the magnetic head 2B to that of the magnetic head 2A. Displace equally.

Now, the pulse synchronized with the head drum is shown in Figure 4A.
If the pulses are output as shown in FIG. 4, the pulses applied to the head drive circuit 20 of the magnetic head 2A will be as shown in FIG. E
become that way. That is, at the same time that the magnetic head 2A starts the first scan of the track 1A recorded at an azimuth angle equal to the azimuth angle of this head, the pulse E becomes a rising state, and the magnetic head 2A starts scanning the track 1A as shown by the dotted line. While performing the first scan of 1A, the head drive circuit 23 drives the actuator 24,
The magnetic head 2B is displaced so that the azimuth angle of the magnetic head 2B becomes equal to the azimuth angle of the magnetic head 2A. In the second scan of track 1A, the azimuth angle of magnetic head 2B is displaced equal to the azimuth angle of 2A (hereinafter referred to as 2A).
Let it be B′. ) is carried out by Next, the third scan is performed by 2A, and the fourth scan is performed by 2B'. And then 2A is the 5th
When the second scan starts, the pulse E is in a falling state, so while the magnetic head 2A is scanning, the magnetic head 2B returns to its original state and the azimuth angle is not changed. The state will be the same as before.

At this point, the scanning of the track 1A ends, and next the scanning of the track 1B recorded at a different azimuth angle from that of the track 1A begins. Track 1B 1st
The second scan is performed by the magnetic head 2B which has previously returned to its original state. Since the pulse D rises at the start of scanning 2B, the head drive circuit 20 drives the actuator 21 while the magnetic head 2B is scanning, and the magnetic head 2A
The magnetic head 2A is displaced so that the azimuth angle of the magnetic head 2A becomes equal to the azimuth angle of the magnetic head 2B. The azimuth angle of the magnetic head 2A is displaced as 2.
A′, the second and fourth scans are 2
This is done by A′. The third and fifth scans are performed by the magnetic head 2B, but the magnetic head 2A', which was displaced in azimuth while 2B was scanning the fifth time, is returned to its original state and the magnetic head 2A
becomes. Thereafter, the above-described operations are repeated to perform scanning.

FIG. 4F shows an outline of the video output waveform when the above operation is performed. Since the waveform of FIG. 4 has fewer low-level parts than the waveform of FIG. 2, a good image can be obtained even during slow playback.

FIG. 5 shows an embodiment of the actuator.
Reference numeral 30 denotes a head chip, which is attached to one end of the head mounting base 31, and on the opposite side, one end of a rotating shaft 32 is arranged so that its center of rotation is at the center of the gap of the magnetic head. has been done. A spring 33 is provided between one end of the lower surface of the head mount 31 and a head drum (not shown) to constantly pull the head mount 31 counterclockwise. A stopper 34 is provided at a position opposite to the spring 33 with respect to the center of rotation of the head mounting base 31.
The rotation angle of the head mounting base 31 is regulated. The rotating shaft 32 is rotatably supported by bearings 35 and 36 provided on a head drum (not shown). Furthermore, the rotating shaft 32
A magnetic body mounting portion 37 is provided on the opposite side of the head mounting base 31, and a magnetic material 38 is provided on the lower surface of this mounting portion. An electromagnet 39 is fixed to the head drum below the magnetic body 38 so as to face it, and when this electromagnet 39 is energized by the head drive circuit 20 or 23, the magnetic body 38 is attracted downward, and further By rotating the rotating shaft 32 and the head mounting base 31 and tilting the head tip 30, the inclination of the head gap with respect to the direction perpendicular to the head drum surface, that is, the azimuth angle, is changed.

As is clear from the above, according to this invention
The VTR is equipped with a head azimuth switching means consisting of head drive circuits 20 and 23 and actuators 21 and 24 for each of the two magnetic heads, so that the azimuth angle of the two magnetic heads can be adjusted to the azimuth angle of the track scanned during slow playback. In order to match the azimuth angle of the track being scanned, the azimuth angle of the magnetic head on the side having an azimuth angle different from the azimuth angle of the track being scanned is made equal to the azimuth angle of the track, thereby performing slow playback. Furthermore, in order to determine the timing of the operation of the head azimuth switching means,
A control head 10, an input terminal 13, a frequency divider 15, a phase comparison circuit 12, a motor drive means using an amplifier 16, a delay circuit 18,
A timing pulse generation means consisting of pulse width conversion circuits 19 and 22 is provided to generate a signal obtained by dividing the control signal taken out from the control head 10 and the pulse inputted to the input terminal 13 by a 1/5 frequency divider 15. is input into the phase comparator circuit 12, and the capstan motor 17 is controlled to transport the magnetic tape so that the phase of the frequency-divided signal matches the phase of the control signal, and the timing pulse generating means The timing of switching the azimuth angle of each magnetic head is determined by this. Therefore, according to the present invention, one track is scanned by two magnetic heads having an azimuth angle equal to the azimuth angle of that track, so there are fewer low-level parts and a good signal-to-noise ratio, and moreover, the front and rear tracks can be scanned. Therefore, good images without double images can be obtained.

In the description of the embodiment, the case where the frequency division ratio is 1/5 has been described, but it is also possible to reproduce at different speeds by changing the frequency division ratio of the frequency divider. Further, in the embodiment of the actuator, an electromagnet is used as a means for displacing the magnetic head, but it can also be implemented using a piezoelectric element or the like. Furthermore, the specific configurations of the head azimuth switching means, timing pulse generation means, etc. are not limited to those shown in the embodiments.

[Brief explanation of the drawing]

Figure 1 shows 1/5 of the conventional magnetic recording/reproducing device.
FIG. 2 is a schematic diagram showing the magnetic track scanning state of the magnetic head during slow playback, FIG. 2 is a schematic diagram of the video playback output obtained from the scanning state shown in FIG. 1, and FIG. 3 shows an embodiment of the present invention. A block diagram, FIG. 4 is a schematic diagram of waveforms explaining the operation of the above embodiment, and FIG.
The figure is a perspective view showing one embodiment of the actuator. 1A... Track, 2A, 2B... Magnetic head, 1
0...Control head, 11, 14, 16...Amplifier, 13...Input terminal, 12...Phase comparison circuit, 1
5...1/5 frequency divider, 17...capstan motor,
18... Delay circuit, 19, 22... Pulse width conversion circuit, 20, 23... Head drive circuit, 21, 2
4...Actuator.

Claims (1)

[Claims] 1. In a magnetic recording/reproducing device having two magnetic heads having mutually different azimuth angles, the magnetic heads alternately form adjacent tracks on a magnetic tape. A control head that detects a control signal, a frequency divider that synchronizes with the head drum and divides the pulse input from the input terminal to a predetermined frequency division ratio, and compares the phase of the output of the frequency divider and the control signal. a phase comparator circuit that generates an output according to the phase difference;
a motor drive means for driving a capstan motor by the output of the phase comparison circuit; and a timing pulse generation means for generating a pulse for timing the switching of the azimuth angle of each of the two magnetic heads by the output of the frequency divider. head azimuth switching means for switching the azimuth angles of the two magnetic heads by the output of the timing pulse generation means, and when the magnetic tape is transferred and reproduced at a speed lower than the normal speed, the phase comparator circuit changes the azimuth angle of the two magnetic heads. The capstan motor is controlled so that one of the magnetic heads having an azimuth angle equal to the azimuth angle of one recording track on the magnetic tape starts scanning from the starting point of the track, and the azimuth angle is adjusted by the timing pulse generating means. The switching timing is set to match the azimuth angle of the recording track or the track to be scanned next, and the azimuth angle of the two magnetic heads is switched by the head azimuth switching means in accordance with the output of the timing pulse generating means. A magnetic recording/reproducing device characterized by performing the following.