JPS60253042A - Recording time mode discriminating circuit of magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To discriminate a recording time mode by a pilot signal in four frequency tracking system by discriminating the recording time mode by a period in which an instantaneous level of a tracking error signal formed by the pilot signal obtained from an adjacent track becomes equal to a prescribed level. CONSTITUTION:The previous track by two from a track in which a pilot signal of the same frequency as a frequency of an output of a four frequency signal generating circuit 8 is recorded is scanned at intervals of one field corresponding period, a direction in which a tracking error signal is varied is reversed at intervals of one field corresponding period, and a triangular wave signal component of about 30Hz is generated in the tracking error signal. As a result, a triangular wave signal of 30Hz as shown in a figure (A) is supplied to a zero crossing detecting circuit 24. When an MMV26 is triggered by a rise edge of a pulse, and a time constant is selected so that an inversion time becomes longer enough than a period corresponding to 30Hz, a positive level signal is outputted continuously as a Q output of the MMV26, and it is discriminated that the recording time mode is an LP mode. In case of an SP mode, the MMV26 is not triggered, the Q output remains a low level, and it is discriminated that the recording time mode is the SP mode.

Description

TECHNICAL FIELD The present invention relates to a recording time mode determining circuit for a magnetic recording/reproducing apparatus, and more particularly to a recording time mode determining circuit for a magnetic recording/reproducing apparatus that performs tracking control using a four-frequency tracking method.

BACKGROUND ART In a conventional magnetic recording/reproducing device (hereinafter referred to as VTR), a pulse signal (hereinafter referred to as a CTL signal) corresponding to drum rotation is sent to a control track provided along the edge of a magnetic tape during recording. Tracking control is performed by recording the CTL signal and controlling the tape speed so that the phase of this CTL signal coincides with the drum phase during reproduction.

Such conventional VTRs are capable of recording at tape speeds corresponding to two or three recording time modes with different recording times on a magnetic tape of a predetermined length, and are capable of recording at tape speeds corresponding to two or three different recording time modes on a magnetic tape of a predetermined length.
Normally, the recording time mode, such as the generation cycle of the L signal, is automatically determined, and reproduction is automatically performed at the same tape speed as when recording.

On the other hand, a so-called 8 mm VTR of edge force/l scanning type that has been proposed recently employs a four-frequency tracking method. In this four-frequency tracking method, four pilot signals having different frequencies and a predetermined relationship are sequentially superimposed and recorded on an information signal, and during playback, the pilot signals are read as crosses from adjacent tracks. Since it is a racking control method, C
The recording time mode cannot be determined based on the TL signal.

SUMMARY OF THE INVENTION An object of the present invention is to provide a recording time mode determination circuit for a magnetic recording/reproducing apparatus that can determine the recording time mode based on a pilot signal in a four-frequency tracking system.

The recording time mode discriminating circuit of the magnetic recording/reproducing apparatus according to the present invention detects two bi'not signals simultaneously obtained from two recording tracks adjacent to one of the plurality of recording tracks being scanned by the rotary head during reproduction. The recording time mode is determined based on the period in which the instantaneous level of the tracking error signal, which has an instantaneous level corresponding to the difference in the signal level of , becomes equal to a predetermined level.

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In FIG. 1, a speed detection signal having a frequency corresponding to the rotational speed of a capstan motor 1 serving as a transfer means is supplied to a speed detector 2 and a phase difference detector 3. This speed detection signal is output from, for example, a pickup (not shown) that detects the magnetic flux of a macnet (not shown) fixed to the rotating shaft of the cab tan Tanabata 1. The speed detector 2 receives a command specifying a recording time mode from an operation unit (not shown), for example, and generates a voltage according to the frequency of the speed detection signal using a conversion coefficient according to the designated recording time mode. It consists of 4 F/V + (frequency/voltage) converters, and the output of this F/V converter is used as a speed error signal. The output of this speed detector 2 becomes the single power of the adder 4.

The added output of the adder 4 becomes a rotation control signal for the capstan motor 1 via the driver 5. The phase difference detector 3 is supplied with a head switching signal SWP obtained from a reference signal generating circuit 6 which receives as input the output of a phase generator (not shown) fixed to the rotating drum motor. The phase difference detector 3 is configured to output a phase error signal according to the phase difference between the head switching signal SWP and the speed detection signal. A switch S is turned on when the output of this phase difference detector 3 is recorded.
1 to the adder 4. Head switching signal S
WP is also supplied to the four-frequency signal generation circuit 8. 4
The frequency signal generating circuit 8 generates 65 fH, 7, 5 fH, and 1 fH, respectively, each time the state of the head switching signal S W )) changes.
It is configured to sequentially output four signals f, ~f4 of 0.5 fH and 9.5 fH (width is horizontal periodic frequency). The output of this 4-frequency signal generation circuit 8 is added as a pilot signal to an information signal such as an FM signal including video information and audio information by an adder 9, and then synthesized.
, H, and is recorded on the magnetic tape "I" as a recording medium. Note that the pilot signals are f,, f2. f
3. What should be recorded in the order of f4? For example, if f is recorded just before moving to the recording pause state, what happens next when moving from the recording pause state to the recording state? The four-frequency signal generating circuit 8 is formed so that the signals are recorded in the above order starting from if2, and the continuity of the pilot signal for tracking control is maintained.

The switch S3f, which is turned on when the signal is generated, serves as another input to the adder 4 via the switch S3f.

During playback, the 4F error detector 11 is supplied with R and F signals read from the magnetic tape T by the rotary heads A and H via the changeover switch S2. 4F error detector 1
1, the RF signal is amplified by a pre-amplifier 12, and then high-frequency components are removed by a low-pass filter 13 to extract four pilot signals f1 to f4. These reproduced pilot signals f1 to f4 are supplied to a mixer 15 after passing through an amplifier 14 and mixed with the output of a four-frequency signal generating circuit 8. The fH and 3fH components are extracted from the output of the mixer 15 by bandpass filters 16 and 17, respectively, and then supplied to detectors 18 and 19. The detectors 18 and 19 output voltages corresponding to the signal levels of the fH and 3fH components, and are applied to the positive and negative input terminals of the differential amplifier 20, respectively. The output of the differential amplifier 20 is directly applied to one input terminal of the signal switching circuit 21 and simultaneously applied to the other input terminal of the signal switching circuit 21 via the inverting amplifier 22 . A head switching signal SWP is applied to a control input terminal of the signal switching circuit 21. The output of the differential amplifier 20 and the output of the inverting amplifier 22 are alternatively derived from the signal switching circuit 21 and the 4F error detector 11
The output is a tracking error signal.

This tracking error signal is supplied to a recording time mode discrimination circuit 23 according to the present invention. In the recording time mode detection circuit 23, the tracking error signal is supplied to a zero cross 41j circuit 24 as a level detection means via a DC cut capacitor C. The cello cross detection circuit 24 is formed of, for example, a comparator having a hysteresis, and is configured so that the reference voltage with which human power can be compared is either +VI- or Vr depending on the state of the output. The output of this zero cross detection circuit 24 is a retrigger pull mono multivibrator (hereinafter referred to as R
25 trigger input terminals (referred to as MMV) are fully supplied. For example, the Q output of the RMMV 25 is supplied to a trigger input terminal of a mono multivibrator (hereinafter referred to as MMV) 26. These RMΔ425 and MMV26 form a cycle detection means, and the Q output of MMv26, for example, is supplied to the operation section (not shown) as an output of the recording time mode detection circuit 23.

As shown in FIG. 2, the rotary heads A and B are fixedly attached to the drum H at 180 degrees apart with respect to the rotation axis so as to rotate together. Drum 4 receives the vertical synchronization signal of the input video signal or the internal reference signal (for example, 3.58M) (
It is designed to be rotationally driven in synchronization with a signal obtained by dividing the frequency of Z subcarrier).

The magnetic tape T is transported along rotation nodes A and B by a capstan motor 1 at a speed corresponding to the number of rotations of the rotary heads A and B, and as shown in FIG. It is formed. At the same time, one field's worth of video information is recorded on each recording track, and the pilot signal is frequency-multiplexed, f,, f.
2. f3. f, and are switched for each recording track and recorded sequentially.

Track A in FIG. 3 corresponds to rotary head A, and track B corresponds to rotary head B. In FIG.

The frequencies of the four pilot signals f, ~f4 frequency-multiplexed and recorded together with video information, etc. on these recording tracks are 6.5 fH, ? , 5 fH, 10, 5fH,
9,5fH (f) is the horizontal synchronization frequency, so the following relationship holds true.

1'I-f21 = l's'41 = fH(
1) 1 '2 '31 = l fl '41 = 3f
H. (2) The frequencies of these four pilot signals are
]00, and there is almost no loss due to azimuth, so not only the pilot signal recorded on the recording track being scanned by rotary head A or B, but also the two tracks adjacent to this recording track. The two pilot signals respectively recorded in are also reproduced as crosstalk.

The level of this crosstalk is approximately proportional to the width of the rotating head that is in contact with the adjacent track. Therefore, the relative position in the vertical direction of the recording track of the rotary head to the recording track can be detected based on the difference in signal level between the two pilot signals that can be reproduced as crosstalk.

Now, each recording track has a pilot signal of fl.

f2. f3. Since they are recorded sequentially in the order of f4,
If the pilot signal recorded on the recording track that rotary head A or B is in contact with is fl, the pilot signals recorded on the two adjacent tracks are f
4 and f2. Then, fH in the output of mixer 15
The acid component and the 3fH component correspond to f2 and f4, respectively. Therefore, when the output of the differential amplifier 20 is at a high level, the signal level of the f2 configuration is positive, that is, the rotary head is shifted in the direction opposite to the tape running direction with respect to the recording track. Further, when the output of the differential amplifier 20 is at a negative level, the signal level of the f4 configuration is deviated from the recording track in the tape running direction.

Next, if the pilot signal recorded on the recording track that the rotating head is in contact with is f2, the pilot signals recorded on the two adjacent tracks are fl
and f3, and fH and 3fH in the output of mixer 15
The components correspond to fl and f, respectively.

Therefore, in this case, when the output of the differential amplifier 20 is at a positive level, the signal level of the f1 configuration is positive, that is, contrary to the above case, the rotation gutter is shifted in the tape running direction with respect to the recording track. become. Further, when the output of the differential amplifier 20 is at a negative level, the signal level of the f3 configuration is positive, that is, the rotary head is shifted in the direction opposite to the tape running direction with respect to the recording track.

Therefore, from the signal switching circuit 21 -\sodo switching signal SWP
If the output of the differential amplifier 20 and the output of the inverting amplifier 22 are outputted alternately, a continuous error signal is obtained and a quick puffer control is performed.

Here, there are two types of recording time modes: LP mode and SP mode, and in the LP mode, the tape speed is slow and the recording time is twice that of the SP mode. At this time, if the switch S3 is kept open for a predetermined period of time immediately after the start of the playback operation and the magnetic tape is transported at a tape speed corresponding to the SP mode, the recording time mode at the time of recording is set to LP.
mode, and during playback, the rotary head scans the recording trunk formed as shown by the solid line in FIG. 4 over at least two recording tracks within a period equivalent to one field, as shown by the broken line in the same figure. becomes. Then, the recording track that should be scanned, that is, the track two tracks ahead of the track where the pilot signal with the same frequency as the output frequency of the 4-frequency signal generation circuit 8 is recorded, is scanned every period equivalent to one field, resulting in a tracking error. The direction in which the signal changes is reversed every period equivalent to one field, and a triangular wave signal component of approximately 3011□ is generated in the tracking error signal. As a result, a triangular wave signal of 30H2 as shown in FIG.
can be supplied to. Then, the zero-cross detection circuit 24 outputs a pulse with a repetition frequency of 30H2, as shown in FIG. If the RMMV25 is triggered by the rising edge or falling edge of this pulse, and the values of the resistor and capacitor for time setting are set so that the inversion time is slightly longer than the period corresponding to 30H2, this RMMV25 The Q output becomes a pulse with a repetition frequency of 30H2. The rising edge of this pulse causes MM
If the time constant is selected so that when V26 is triggered and reversed, 1■] is sufficiently longer than the period corresponding to 30H2, MM■
A positive level signal is continuously output as the Q output of No. 26, and it is determined that the recording time mode is in the LP mode. If the operation section (not shown) is configured so that a command to specify the LP mote is issued when a positive level signal is output from the MhiV25, the tape speed during playback will automatically be the same as during recording. Becomes speed.

Next, when the recording time mode at the time of recording is the SI mode, a fluctuation component of 60H2 is generated in the tracking error signal due to track bending due to compatible playback of the tape or a discrepancy between the playback speed and the recording speed. When the fluctuation width of the tracking error signal due to this fluctuation component becomes 2.1 or more, Vr, -
The 60H2 component exceeding the Threnjord level, which is one of the values of Vr, is supplied to the zero cross detection circuit 24, and a pulse having a repetition frequency of 60H2 is output as shown in the figure. Then, the RMMV 25 continues to be in an inverted state, and the Q output remains at a low level. Therefore, in this case, MMV26 is not triggered and this MMV
The Q output of No. 26 becomes a low level it, and it is determined that the recording time mode is the SP mode. still,
When the fluctuation width of the tracking error signal is smaller than 2'4, no pulse is output from the zero-cross detection circuit 24, so the RMMV 25 is not triggered. Therefore, MMV2
6 is also not triggered, and it is determined that the recording time mode is the SP mode.

Effects As detailed above, the recording time mode determination circuit of the magnetic recording/reproducing apparatus according to the present invention determines the recording time mode according to the period in which the instantaneous level of the tracking error signal formed by the pilot signal obtained from the adjacent track is equal to a predetermined level. Since it is configured to discriminate, it automatically discriminates the recording time mode during recording of a magnetic recording and reproducing device that performs tracking control using the 4-frequency L/Ranoki/G method, and automatically records the tape speed during playback. This means that the tape speed can be set to the same speed as the current tape speed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a rotary head A in the apparatus shown in FIG. FIG. 3 shows a recording track formed on a recording medium by the apparatus of FIG. 1, and FIG. 4 shows the movement of a rotary head with respect to the recording track. 5 and 6 are waveform diagrams showing the operation of the apparatus of FIG. 1. Explanation of symbols of main parts 1...Cab's tongue motor 11...4F error detector 23...Recording time mode discrimination circuit 24...Zero cross detection circuit 25...RMMV 26...MMV Applicant: Pioneer Co., Ltd. Agent Patent attorney Shi Motohiko Fujimura 2nd figure [, Qn view 3rd figure 4 kl 33 rn 5ec (30Hz) - J@
凰6pu

Claims (1)

[Claims] at least two rotary heads that rotate together; and the recording medium is moved along the at least two rotary heads at a speed corresponding to a designated recording time mode such that the at least two rotary heads alternately scan the recording medium. forming a plurality of recording tracks on the recording medium so as to be parallel to each other during recording, and simultaneously transmitting a plurality of pilot signals having different frequencies and a predetermined relationship to each other to the plurality of recording tracks; of the plurality of pilot signals obtained simultaneously from two recording trunks that are sequentially recorded and adjacent to one of the plurality of recording tracks being scanned by one of the at least two rotary heads during playback; The relative position of the recording track in the vertical direction of the rotary head scanning the recording medium with respect to the recording track is controlled by a tracking error signal having an instantaneous level corresponding to a difference between two signal levels. A recording time mode determination circuit for a magnetic recording and reproducing device, the circuit comprising:
a level detection means for generating a level coincidence detection signal when the instantaneous level of the tracking error signal becomes equal to a predetermined level; and a level detection means for detecting a generation cycle of the level coincidence detection signal and detecting a signal corresponding to the generation cycle for the recording time. 1. A recording time mode discriminating circuit for a magnetic recording/reproducing device, comprising period detecting means for generating a signal indicating a mode.