JPS628352A - Magnetic tape and magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To realize stably the state shifting a tracking to an information track by a prescribed quantity by recording an information signal to the 2nd track nearly in parallel with the 1st track formed with a tilt in the running direction and displaced by a prescribed quantity. CONSTITUTION:Rotary heads A, B for recording/reproducing an information signal are parted by 180 deg. mutually, rotary heads C, D for recording a pilot signal are parted by 180 deg. mutually, and the rotary heads A, B and the rotary heads C, D are parted by 90 deg. mutually. The rotary heads C, D are fitted to a rotary drum at a position higher by 1 track pitch to the rotary heads A, B, the rotary heads A, B have mutually different azimuth angle and the rotary heads C, D have the identical azimuth angle. The width of the magnetic gap of the rotary heads C, D is set nearly the same as that of the track pitch but the width of the magnetic gap of the rotary heads A, B is equal to or slightly wider than the track pitch.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording/reproducing device typified by a video tape recorder.

[Summary of the invention]

The present invention provides a magnetic tape in which a pilot signal for tracking control is recorded on a first track formed at an angle with respect to the running direction, and a pilot signal for tracking control is recorded on a first track formed at an angle with respect to the running direction. The information signal is recorded on a second track that is approximately parallel to the magnetic tape and displaced by a predetermined amount. A first rotary head for recording signals and a second rotary head for recording information signals on tracks inclined with respect to the running direction of the magnetic tape are provided, and the first rotary head for recording pilot signals is used for recording information signals. The second rotary head for recording is mounted on the drum for one rotation so that the track on which the pilot signal is recorded is substantially parallel to the track on which the information signal is recorded and is displaced by a predetermined amount. In a magnetic recording/reproducing device that performs pilot tracking control, it is possible to stably achieve a state in which tracking is shifted by a certain amount, and a magnetic tape for testing thereof can be obtained with a simple configuration. This is what I did.

[Conventional technology]

Conventionally, tracking control methods for magnetic recording and reproducing devices include a CTL method and a pilot method. C.T.L.
This method utilizes one of the rising and falling edges of a CTL signal recorded on a track parallel to the running direction of the magnetic tape for tracking control. In this method, it is not always possible to perform accurate tracking control, so a tracking adjustment knob is provided at a position that can be operated relatively easily by general users, and by adjusting this knob, tracking can be adjusted. Generally, it is possible to shift (shift) a predetermined amount.

On the other hand, in the pilot method, pilot signals f1 to f4 for tracking control are sequentially recorded on an inclined track formed by a rotating head at an angle with respect to the running direction of the magnetic tape, superimposed on an information signal. . As such pilot signals f2 to f4, for example, 6.
5f,,7゜5f++, 10.5f11, 9.5
f (f, I is the frequency of the horizontal synchronization signal, NTSC
In the case of this method, signals with a frequency of 15°734 Hz) are used. Pilot signal components simultaneously obtained from tracks adjacent to the front and rear of the target track are detected, and a tracking error signal is generated from the level difference between them to perform tracking control.

Incidentally, magnetic tape travel adjustment during manufacturing, rotating head replacement, and other repairs is generally performed while observing the shape of the envelope of the reproduced RF signal using a waveform observation device. That is, for example, as shown in FIG. 5(a).

If the width of the rotating head for playback is wider (e.g. 26 μm) than the width of the track on which the information signal is recorded (e.g. 20 μm)
), when normal tracking control is performed, even if the scanning locus of the one-rotation head is curved as shown by the broken line in the figure, the shape of the RF multiplied signal envelope obtained at that time will be as shown in Figure 5 (b). The curve of the scanning trajectory of the rotary head cannot be determined from the shape of the RF signal envelope. However, for example, the sixth
As shown in Figure 6(a), when the tracking state is shifted by a predetermined amount, the shape of the RF multiplied signal envelope obtained at that time approximately corresponds to the degree of curvature of the scanning trajectory (approximately) as shown in Figure 6(b). Therefore, the degree of curvature of the scanning locus of the rotary head can be determined from the shape of the RF multiplied signal envelope.

Furthermore, as shown in Fig. 7(a), when the width of the rotating head for reproduction is narrower (for example, 16 μm) than the width of the track on which the information signal is recorded (for example, 20 μm), if normal tracking control is performed, it will rotate 5 times. Even if the scanning trajectory of the head is curved as shown by the broken line in the figure, the shape of the RF multiplied signal envelope obtained at that time does not correspond to the degree of curvature of the scanning trajectory, as shown in FIG. 7(b), and the RF It is not possible to determine the degree of curvature of the scanning locus of the rotary head from the shape of the double signal envelope. However, even in this case, if the tracking state is shifted by a predetermined amount, the degree of curvature of the scanning locus of the rotary head can be determined from the shape of the RF multiplied signal envelope.

[Problem that the invention seeks to solve]

Even in devices that perform tracking control using conventional pilot signals, it is possible to reduce noise during still image or slow playback, and to share a rotating head even when magnetic tape speeds are different (and therefore track widths are different). The width of the rotary head often does not match the width of the track for the purpose of providing a margin for tracking during compatible playback between devices. However, in conventional devices that perform tracking control using pilot signals, the servo is extremely stable and tracking deviations hardly occur, so there is no knob for tracking adjustment. There was a drawback that it was difficult to adjust the running of the magnetic tape. Therefore, for example, it is conceivable to give a predetermined amount of offset to the tracking error signal. However, the eighth
As shown in the figure, the level of the tracking error signal (vertical axis) varies sinusoidally with respect to changes in the number of tracks (horizontal axis) as the amount of error. Further, when the operating point of the servo is shifted in the positive or negative direction, the level of the tracking error signal changes due to the level change of the reproduced pilot signal. Further, when reproducing magnetic tapes recorded by different devices, the widths of the tracks and the rotary head differ, and the waveform of the sinusoidal tracking error signal also changes. Therefore, it is difficult to stably obtain a constant shift amount by applying a predetermined amount of offset to the tracking error signal.

[Means for solving problems]

FIG. 1 shows a block diagram of a magnetic recording/reproducing apparatus according to the present invention. In the figure, a servo circuit 1 controls the rotation of a rotary head, a capstan, etc., and outputs head switching pulses to a delay circuit 2 and a video circuit 3. The delay circuit 2 delays the head switching pulse by a predetermined time (a time corresponding to the phase difference between the rotary heads A and B for recording and reproducing information signals and the rotary heads C and D for recording pilot signals) and supplies the pulse to the pilot signal generation circuit 4. It is outputting. 5 is a control circuit such as a microcomputer;
It controls various circuits and means in addition to the delay circuit 2 and the pilot signal generation circuit 4. The video circuit 3 detects a vertical synchronization signal from the input video signal, outputs the detection signal to the servo circuit 1, and outputs the frequency-modulated video signal to the adder circuit 6, which is added to the frequency-modulated audio signal. It is supposed to be done. The output of the adder circuit 6 is sent to the recording/reproducing rotary heads A and H via the recording amplifier 7.
is supplied to the computer and recorded on magnetic tape. 8 is a recording amplifier, and a pilot signal generation circuit 4
The pilot signal outputted from the magnetic tape is amplified and supplied to rotary heads C and D for recording the pilot signal to be recorded on the magnetic tape.

As shown in FIG. 2, rotary heads A and B for recording and reproducing information signals are separated by 180 degrees from each other, and rotary heads C and D for recording pilot signals are also separated by 180 degrees from each other. Rotary heads A and B for recording and reproducing information signals and rotary heads C and D for recording pilot signals are spaced apart from each other by 90 degrees.

Furthermore, as shown in FIG. 3, the rotary heads C and D for recording pilot signals are different from the rotary head A for recording and reproducing information signals.
, B is attached to the rotating drum at a position one track pitch (20.5 .mu.m) higher than B. Rotary heads A and B for recording and reproducing information signals have mutually different azimuths (for example, ±10 degrees), while rotary heads C and D for recording pilot signals have the same azimuth (of course, ). Further, since the rotary heads C and D for recording pilot signals record only relatively low frequency signals, the length of their magnetic gap may be longer than that of the rotary heads A and B for recording and reproducing information signals. Furthermore, the width of the magnetic gap portions of rotary heads C and D may be set to be approximately equal to the track pitch, but it is better to set the width of the magnetic gap portions of rotary heads A and H to be equal to or slightly wider than the track pitch. .

[Effect]

The effect will now be explained. The servo circuit 1 rotates the rotary drum in synchronization with a vertical synchronization signal of the video signal, and outputs a head switching pulse synchronized with the rotation to the delay circuit 2 and the video circuit 3. The delay circuit 2 generates a head switching pulse delayed by a time corresponding to the phase difference (90 degrees in this embodiment) between the rotary heads A and B for recording and reproducing information signals and the rotary heads C and D for recording pilot signals. It is output to the pilot signal generation circuit 4. Therefore, the pilot signal generation circuit 4 is configured to operate the rotary head A,
Pilot signals of frequencies fl to f4 are sequentially switched and generated at a timing 90 degrees earlier (or later) than the timing when B is switched. This pilot signal is alternately supplied to the rotary heads C and D via the recording amplifier 8, and is recorded on the magnetic tape to form an inclined track. Therefore, on the magnetic tape, for example, as shown by the solid line in FIG. 4, pilot signals of frequencies fl to f4 are sequentially recorded on each track. FIG. 4 shows the timing when recording by the rotary head C ends and recording by the rotary head D starts.

The two-dot chain line in the figure represents the rotation plane of the lower edges of the rotation heads C and D.

On the other hand, the video signal input to the video circuit 3 is frequency modulated, output to the adder circuit 6, and added to the frequency modulated audio signal. This added information signal is supplied to the rotary heads A and B via the recording amplifier 7, and is recorded on the inclined track on the magnetic tape. A head switching pulse that is not delayed by the delay circuit 2 is input to the video circuit 3, and the rotating heads A and B are switched by this head switching pulse. Therefore, the timing of switching between rotating heads A and B is as follows: rotating heads C and D.
The switching timing is 90 degrees later (or earlier) than the switching timing. That is, as shown in FIG.
At the timing when recording by the rotary head D ends and recording by the rotary head D starts, the rotary head A rotates once to the rotary head C.
and D, and the rotary head B is in a position where it is not in contact with the magnetic tape. Moreover, as shown by the broken line in FIG. 4, the inclined tracks formed by the rotary heads A and B are parallel to the inclined tracks formed by the rotary heads C and D, and are shifted by 1/2 track pitch. Become.

Since the pilot signals supplied to the rotating heads C and D have relatively long wavelengths (the running speed of the magnetic tape is set to 3.75
m/s, the frequency of the pilot signal is 100kHz
z to 165 kHz, the wavelength is 2.27 μm to 3.75 μm), and is recorded in a magnetized state deep into the magnetic layer of the magnetic tape. On the other hand, since the carrier waves of the information signals supplied to the rotating heads A and B have relatively short wavelengths (assuming the frequency of the carrier waves is 5 MHz,
(wavelength is 0.75 μm), only the surface of the magnetic layer is recorded in a magnetized state, and the deep magnetization state caused by the pilot signal remains as it is. That is, the Pikotsu 1 signal is recorded deep.

In the I18 RTTN video tape recorder standard, the recording level of the pilot signal is defined as -14 dB±2 dB from the optimal color signal level. The optimum level of the color signal for the carrier wave of the video signal is -12d.
If it is about B, a pilot signal of about -26 dB from the video carrier wave should remain on the magnetic tape. To do this, for example, the residual amount of the pilot signal that has been attenuated by the current of the video carrier wave that will be recorded later is set to 126 dB, or the pilot signal is subjected to an appropriate high-frequency bias instead of unbiased saturation recording. Bias recording can be performed in which a pilot signal is superimposed. Rotating head A.

If there is a gap in the track formed by B, the track where the pilot signal in that part is recorded will remain without receiving the necessary attenuation, and the level of the pilot signal will partially rise in that part. become. Therefore, it is preferable that the gap width between the rotary heads A and B be equal to or slightly wider than the track pitch.

The pilot signal for tracking control is applied to the first track formed at an angle with respect to the running direction, and is substantially parallel to the first track formed at an angle to the running direction. , and a magnetic tape on which information signals are recorded on the second track that has been displaced by a predetermined amount is played back by a device that performs tracking control using a normal pilot method in order to test the running state of the magnetic tape, for example, and the 5-turn head A is played back. , B trace the pilot signal track shown by the solid line in FIG. In other words, control is performed such that the boundary between the two tracks on which the information signals shown by broken lines in the figure are recorded is located at the center of the rotary heads A and B. That is, the tracking servo circuit is completely on-track with the pilot signal track, but the tracking is shifted with respect to the information track. Since the rotary heads A and B have azimuths and reproduced signals can be obtained only from tracks with the same azimuth, the RF multiplied signal level at this time is approximately 1/2 of that when tracking a normal magnetic tape. By observing the shape of the RF multiplied signal envelope using a waveform observation device, it is possible to know the degree of curvature of the scanning trajectory of the heads A and B for one revolution. Therefore, it becomes possible to make necessary adjustments.

If the sequence in FIG. 4 is such that the pilot signal f4 is recorded on the track C where the pilot signal f is recorded, it is possible to shift in the direction of 1/2 track delay during reproduction.

Further, the phase difference between the rotary heads A and B for recording and reproducing information signals and the rotary heads C and D for recording pilot signals does not necessarily have to be 90 degrees. The direction and amount of shift can be arbitrarily set by the phase difference, mounting height, and pilot signal sequence. For example, two or more sets of rotary heads for pilot signal recording may be provided, and the direction and amount of shift may be switched at predetermined time intervals to record on one magnetic tape. Furthermore, it is convenient to record the direction, amount, etc. of the tracking shift at that time in the corresponding video signal, so that the magnetic tape can be adjusted while viewing it during playback. Further, the information signal does not necessarily have to be a carrier wave modulated by a video or audio signal, but may be an unmodulated wave of an appropriate frequency.

〔effect〕

As described above, the present invention records a pilot signal for tracking control on a first track formed at an angle with respect to the running direction in a magnetic tape, and also records a pilot signal for tracking control on a first track formed at an angle with respect to the running direction. Information signals are recorded on a second track that is approximately parallel to the first track and displaced by a predetermined amount, and in a magnetic recording/reproducing device, tracking is performed on a track that is inclined with respect to the running direction of the magnetic tape. A first rotating head for recording pilot signals for control and a second rotating head for recording information signals on tracks inclined with respect to the running direction of the magnetic tape are provided. The rotating drum is moved so that the drag on which the pilot signal is recorded is approximately parallel to the track on which the information signal is recorded and is displaced by a predetermined amount with respect to the second rotating head for recording the information signal. This makes it possible to stably achieve a state in which the tracking of the information track is shifted by a certain amount in a normal magnetic recording/reproducing device that performs pilot-type tracking control. This can be obtained with a simple configuration. Therefore, the work of adjusting the running of the magnetic tape becomes easier.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the magnetic recording/reproducing apparatus of the present invention, and FIG.
The figure is a schematic plan view of the rotating drum, FIG. 3 is a schematic developed side view, FIG. 4 is a schematic plan view of tracks on the magnetic tape, and FIGS. 5 to 7 are conventional magnetic recording systems. FIG. 8 is a schematic plan view of the tracks of the reproducing device and the helad trajectory, a schematic waveform diagram of the RF multiplied signal envelope, and a schematic waveform diagram of the tracking error signal. 1... Servo circuit 2... Delay circuit 3... Video circuit 4... Pilot signal generation circuit 5... Control circuit 6... Addition circuit 7.8... Recording amplifier or higher

Claims (2)

[Claims] (1) A pilot signal for tracking control is recorded on the first track formed at an angle with respect to the running direction, and a pilot signal for tracking control is recorded on the first track formed at an angle with respect to the running direction. A magnetic tape characterized in that an information signal is recorded on a second track that is substantially parallel to the other tracks and displaced by a predetermined amount. (2) A first track that records a pilot signal for tracking control on a track that is inclined with respect to the running direction of the magnetic tape.
and a second rotary head for recording information signals on tracks inclined with respect to the running direction of the magnetic tape, the first rotary head for recording the pilot signal being for recording the information signal. The rotary drum is configured such that the track on which the pilot signal is recorded is substantially parallel to the track on which the information signal is recorded and is displaced by a predetermined amount with respect to the second rotating head. A magnetic recording and reproducing device characterized in that it is attached.