JPH0259537B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a magnetic recording and reproducing device, a so-called video tape recorder, for recording and reproducing information on a magnetic tape.

BACKGROUND ART FIG. 1 shows magnetization patterns recorded on a magnetic tape T by two rotating magnetic heads H having different azimuth angles. Magnetic tape T is arrow a
The rotary magnetic head H moves in the direction shown by arrow b.
Rotate in the direction of. Track A on magnetic tape T
For 1 to A4, frequency 1 = 6.5H, 2 = 7.5H,
Each pilot signal of 3=10.5H and 4=9.5H is P.
1, P2, P3, and P4 are recorded. However, H
is the horizontal frequency. During playback, rotating magnetic head H
When reproducing the magnetic pattern on the magnetic tape T, the tracking state can be detected by reproducing the pilot signals of the reproducing track and the adjacent track at the same time and extracting the beat signals of both. For example, when playing back track A1 on which pilot signal P1 is recorded,
Pilot signal P1 and adjacent pilot signal P2
The frequency of the beat signal with is the horizontal frequency H.
Further, the frequency of the beat signal between the pilot signal P1 and the adjacent pilot signal P4 is 3H.

FIG. 2 shows the relationship between each of the frequencies 1 to 4 of the pilot signals P1 to P4 and each level. When the tracking state of the rotating magnetic head H changes, the levels of the pilot signals P1 to P4 change, and the level of the beat signal changes accordingly.

FIG. 3 is a block diagram of a circuit included in a conventional magnetic recording/reproducing device. Information on the magnetic tape 1 is converted into an electrical signal by rotating magnetic heads 2 and 3, and the electrical signal is amplified by an amplifier circuit 4. The reproduced signal from the head amplifier circuit 4 is passed through a low-pass filter circuit 5.
Among the reproduced signals, the pilot signals P1 to P4 explained in FIG. 1 are taken out from the low-pass filter circuit 5.

On the other hand, the pilot signal generating circuit 7 generates pilot signals P1 to P4 having the same frequency as the pilot signal during recording. The selection circuit 8 arranges the received pilot signals P1 to P4 in the same order as when recording, that is, the pilot signals P1, P2, P3, P4.
4 to the mixing circuit 6 in this order. The mixing circuit 6 receives the pilot signal P1 from the low-pass filter circuit 5.
~P4 and the pilot signals P1 to P4 sequentially sent from the selection circuit 8,
and 3H beat signals B1 and B3 are generated. The beat signals B1 and B3 are efficiently output. This beat signal B1 is taken out from the bandpass filter circuit 9, and the beat signal B3 is taken out from the bandpass filter circuit 10.

Since the lead and lag in phase of these beat signals B1 and B3 is reversed every field when one track of the magnetic tape 1 is scanned, the changeover switch circuit 11 uses a head switching pulse to switch the rotating magnetic heads 2 and 3. Switch each field to match the phase. Rectifier circuit 12
is the beat signal B from the changeover switch circuit 11
1, and the rectifier circuit 13 is the changeover switch 1.
The beat signal B3 from 1 is rectified. Comparison circuit 1
4 performs level discrimination between a signal corresponding to the level of the beat signal B1 from the rectifier circuit 12 and a signal corresponding to the level of the beat signal B3 from the rectifier circuit 13. The tracking state is detected by the output of the comparison circuit 14. By applying the output of the comparison circuit 14 to the speed control circuit of the capstan servo, optimal tracking can be performed.

When the magnetic tape 1 changes from a stopped state to a running state, the order of the pilot signals P1 to P4 recorded on the magnetic tape 1 while the magnetic tape 1 is running is out of order with respect to the pilot signals P1 to P4 from the selection circuit 8. In this case, the frequencies 1 to 4 of the pilot signals P1 to P4 reproduced from the rotating magnetic heads 2 and 3
The frequencies of the pilot signals P1 to P4 from the selection circuit 8 are different, and the beat levels of the beat signals B1 and B3 become large. As a result, a tracking error signal is sent from the comparison circuit 14, and the tracking error signal causes the servo circuit to select the pilot signals P1 to P4 on the magnetic tape 1 at the frequency of the pilot signals P1 to P4 from the selection circuit 8.
4 to match.

In the circuit shown in FIG.
The time it takes for the servo circuit to reach a stable state after the frequency of the reproduced pilot signal from the servo circuit 8 and the pilot signal from the selection circuit 8 are different varies greatly and lacks stability.

Purpose The purpose of the present invention is to solve the above-mentioned technical problem,
It is an object of the present invention to provide a magnetic recording and reproducing device that reduces tracking errors and stabilizes its operation.

Embodiment FIG. 4 is a block diagram showing the electrical configuration of an embodiment of the present invention. The operation will be described below with reference to the waveform diagram shown in FIG. Information previously recorded on the magnetic tape 1 is converted into electrical signals by the magnetic heads 2 and 3, and amplified by the head amplifier circuit 4. The reproduced signal from the head amplifier circuit 4 is applied to a low-pass filter circuit 5, and the low-pass filter circuit extracts only the pilot signal contained in the reproduced signal.

FIG. 5 shows a recording pattern on the magnetic tape 1 when the rotating magnetic heads 2 and 3 rotate in the direction shown by the arrow b and the magnetic tape 1 runs in the direction shown by the arrow a. Tracks A1 to A4 on magnetic tape 1
Pilot signals P1 to P4 are respectively recorded in advance. Tracks A1 to A4 are respectively provided with areas a1 to a4 in which pilot signals P1 to P4 are not recorded, and the areas a1 to a4 are provided at different positions on tracks A1 to A4, respectively. From the low-pass filter circuit 5, FIG.
A pilot signal reproduction signal as shown in FIG. This pilot signal is applied to a detection circuit 15 and a mixing circuit 6. The detection circuit 15 detects the point where the signal level from the low-pass filter circuit 5 becomes low, that is, the position of the areas a1 to a4 where the pilot signals P1 to P4 are not recorded.
That is, the detection circuit 15 sends detection signals e1 to e4 shown in FIG. 6 to the positions of areas a1 to a4.

The pilot signal discrimination circuit 16 includes a detection circuit 15
Detection signal e1 indicating the position of areas a1 to a4 from
~e4 and the phase of the head switching pulse as shown in FIG. 6, which switches the switching state of the two rotating magnetic heads 2 and 3, and the pilot of the reproducing track is determined as shown in FIG. Determine the frequency of a signal. That is, the pilot signal discrimination circuit 16 discriminates the frequency of the pilot signal on the magnetic tape 1 currently running. The pilot signal generating circuit 7 generates pilot signals P1 to P4 that are the same as those used during recording. The selector circuit 17 selects the pilot signals P1 to P4 from the pilot signal generation circuit 7 according to the discrimination signal from the pilot signal discrimination circuit 16, and selects the pilot signals recorded on the reproduction track in synchronization with the head switching pulse. P1~P
A pilot signal matching the frequency of 4 is applied to the mixing circuit 6.

The mixing circuit 6 mixes the pilot signals P1 to P4 from the low-pass filter circuit 5 and the pilot signals P1 to P4 from the selection circuit 17, and adjusts the frequency.
H and 3H beat signals B1 and B3 are sent out. The frequency H of the beat signal B1 is a horizontal frequency, and the frequency of the beat signal B3 is three times the horizontal frequency. Beat signal B1 is taken out from bandpass filter circuit 9, and beat signal B3 is taken out from bandpass filter circuit 10. The beat signals B1 and B3 are reversed in phase lead and lag every field when one track of the magnetic tape 1 is scanned, so that the changeover switch circuit 11
Now, the phases are adjusted by switching each field using a head switching pulse that switches the rotating magnetic heads 2 and 3. The rectifier circuit 12 rectifies the beat signal B1 from the changeover switch circuit 11, and the rectifier circuit 13 rectifies the beat signal B3 from the changeover switch circuit 11. Comparison circuit 14
performs level discrimination between a signal corresponding to the level of the beat signal B1 from the rectifier circuit 12 and a signal corresponding to the level of the beat signal B3 from the rectifier circuit 13. By applying the output of this comparison circuit 14 to the speed control circuit of the capstan servo, optimal tracking can be performed.

Effects As described above, according to the present invention, tracking errors are reduced and reliability is improved.

[Brief explanation of drawings]

Fig. 1 is a diagram of the magnetization pattern of a conventional magnetic tape, Fig. 2 is a diagram showing the relationship between the frequency and level of a pilot signal, Fig. 3 is a block diagram of a circuit included in a conventional magnetic recording/reproducing device, and Fig. 3 is a diagram showing the relationship between the frequency and level of a pilot signal. FIG. 4 is a block diagram of an embodiment of the present invention, FIG. 5 is a diagram of the magnetization pattern of the magnetic tape of the embodiment, and FIG. 6 is a waveform diagram for explaining the operation of the embodiment. DESCRIPTION OF SYMBOLS 1... Magnetic tape, 2, 3... Magnetic head, 4... Head amplifier circuit, 5... Low pass filter circuit, 6...
Mixing circuit, 7... Pilot signal generation circuit, 9, 1
0... Bandpass filter circuit, 11... Changeover switch circuit, 12, 13... Rectifier circuit, 14... Comparison circuit, 15... Detection circuit, 16... Pilot signal discrimination circuit, 17... Selection circuit.

Claims (1)

[Claims] 1. Each pilot signal is recorded on a track corresponding to one field on a magnetic tape scanned by rotating magnetic heads having different azimuth angles, and the frequency of the pilot signal is recorded on both adjacent tracks. In a helical scan type magnetic recording and reproducing apparatus, which has a pilot signal frequency and a predetermined interval, and tracks the magnetic tape based on the pilot signal when reproducing information on the magnetic tape, information is recorded on the magnetic tape. During recording, each track is provided with a portion where no pilot signal is recorded, and the position of the portion where no pilot signal is recorded is different from the position of the portion where no pilot signal is recorded on both adjacent tracks. The frequency of the pilot signal is determined by detecting the position of the part where the pilot signal is not recorded, and the pilot signal is forced from the pilot signal generating means that generates a pilot signal of the same frequency as the pilot signal at the time of recording. 1. A magnetic recording and reproducing device characterized in that the magnetic tape is made to match a pilot signal of a magnetic tape during reproduction.