JPH033110A - Rotating head type recording and reproducing device - Google Patents

Abstract

PURPOSE:To prevent a delay time at a consecutive recording time from being prolonged by syncronously detecting the envelope signal of a reproduced RF signal with the aid of a signal for wobbling and controlling tracking. CONSTITUTION:This is a rotating head type recording and reproducing device where a video signal is recorded on a tape 4 as an oblique track by rotating heads 1a and 1b and which reproduces a video signal by making the rotating heads 1a and 1b scan the track. When consecutive recording is executed by a video camera, the reproduced RF signal of a reproducing amplifier 10 is supplied to an envelope detection circuit 11 and the envelope signal Se is supplied to a synchronous detection circuit 14 from the envelope detection circuit 11. The signal for wobbling is supplied to the synchronous detection circuit 14 through a switching circuit 15 and synchronously detected. Then, a tracking control signal Ss is generated. Thus, when the consecutive recording is executed, the delay from the time when a recording pause is released to the time when the recording is started is prevented from being prolonged.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a rotary head type recording/reproducing device, and particularly to tracking control using a synchronous detection method.

[Summary of the invention]

In this invention, in a rotary head type recording and reproducing apparatus in which a video signal is recorded as a diagonal track on a tape by a rotary head, and the rotary head scans the track to reproduce the video signal, the scanning locus of the rotary head and The relative position of the track is wobbled with a signal of a predetermined frequency, and a tracking control signal is generated by synchronously detecting the envelope signal of the reproduced RF signal reproduced by the rotating head with the wobbling signal. By performing tracking using this synchronous detection method during the playback operation, it is possible to perform track alignment during continuous shooting in a short time.

[Conventional technology]

A rotary head type VTR requires tracking control so that the head can correctly scan the diagonal tracks formed during recording during reproduction. One method of tracking control is to record a control signal with a frequency of 30 Hz formed from a vertical synchronization signal separated from the recorded video signal in the longitudinal direction of the tape during recording, and during playback, the reproduced control signal and the head It is known to control the tape running speed so that the rotational phase has the same relationship as during recording.

This method of using control signals for tracking requires a head for recording and reproducing the control signals, and also requires a track extending in the longitudinal direction for the control signals, which increases cost and increases the recording density. There was a problem that hindered improvement.

In addition, the 8mm VTR has four types of frequencies [1, f2... The pilot signals [3 and [4] are sequentially recorded together with the video signal, so that the pilot signals of both adjacent tracks and the pilot signal of the track of interest have a frequency difference of fh (horizontal frequency) and 3fh.

fl=6. 5fh #102. 5kHzf2=
7.5fh #119.0kHzf3=10.5f
h! #165. 2-kHzf4=9. 5fh
t148. During 7 kHz reproduction, a tracking error is detected by comparing the levels of the frequency difference components (rh, 3fh) between the crosstalk components from both adjacent tracks and the local pilot signal in the reverse order from the recording time.

As described above, the process of switching the frequency of the pilot signal for each track and comparing the levels of frequency difference components has the problem of complicating the circuit configuration.

In order to solve the above problems, several tracking control methods have been proposed that do not require special signals for control such as control signals or pilot signals. The synchronous detection method is one of these tracking control methods. In this synchronous detection method, the capstan wobbles with a low-frequency sine wave signal.
(meaning of vibration), the envelope of the reproduced RF signal wobbles, and tracking error information is obtained by synchronously detecting this reproduced RF signal with the above-mentioned sine wave signal.

A synchronization signal timing detection method has been proposed as another tracking control method that does not require a special signal for tracking control. In the synchronization signal timing detection method, a specific horizontal synchronization signal (
Alternatively, the synchronization signal added to the recorded video signal for tracking is extracted, and the time difference between the reference time when the rotating head passes a predetermined position and the time when a specific horizontal synchronization signal is reproduced is detected, and from this time difference, The direction and amount of track deviation are determined.

Furthermore, as another tracking control method, an envelope method has been proposed in which the envelope level of the reproduced RF signal is detected and tracking control is performed so that the envelope level becomes the maximum value.

The synchronous detection method is less affected by deviations in tape speed;
In addition, it has the advantage that the control operation starts quickly, and on the other hand,
The wobbled tape causes uneven rotational speed of the drum, which increases jitter in the reproduced video signal and causes the reproduced image to shake.

The synchronization signal timing detection method is less susceptible to deviations in tape speed and does not require a detection circuit or the like, so it has the advantage of a simple circuit configuration.

However, with the synchronization signal timing method, it is necessary to compare the time difference between the reference time and the gated horizontal synchronization signal for each tape used with the reference time difference, and if this reference time difference cannot be detected correctly, The disadvantage is that tracking control is difficult. The envelope method has the advantage that it is not easily affected by fluctuations in the time axis of the recorded video signal. However, it is easily affected by speed deviation, and it is necessary to find the maximum value of the envelope level.Furthermore, when the head width is larger than the track width, the control signal level The tracking error cannot be reduced to zero because a dead zone occurs in which the tracking error does not change.

[Problem B to be Solved by the Invention] In a VTR that records output signals from a video camera, noise is prevented from occurring by maintaining track continuity during continuous shooting. Figure 6 shows this continuous shooting operation. When the recording operation is finished and the recording pause switch button is pressed at tape position A, the tape position is returned from A to B, and then from B to The tape position advances to C, enters a pause state, and the tape stops. When the switch button is pressed again, the recording pause is canceled, the playback operation is performed from C to D, and the recording operation is switched from a tape position slightly before the A position.

By the playback operation performed between C and D, tracking control is performed so that the rotary head correctly scans the recorded track, and continuity between the previous track and the track formed by the next recording is maintained. be done. Therefore, the time from C to D during continuous shooting is the delay time from when the recording pause is released until when recording is started. It is desirable that this delay time be short.

The above-mentioned tracking control methods (synchronous detection method, synchronous signal timing method, envelope method) can be applied to the tracking control performed in the playback operation when connection is lost. However, in the synchronization signal timing method, there is a delay time for detecting the reference time difference, and even in the envelope method, there is a delay time until the maximum value of the envelope level is detected. Therefore, in these tracking control methods, a problem arises in that the delay time from when the recording pause is released to when recording is started becomes long.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a rotary head type recording and reproducing apparatus that can prevent delay time from increasing during continuous shooting by performing tracking control using a synchronous detection method.

[Means to solve the problem]

In the present invention, a rotary head type recording/reproducing system is used, in which a video signal is recorded as diagonal tracks on a tape 4 by rotary heads la and lb, and the rotary heads 1 a s 1 b scan the tracks to reproduce the video signal. In the device, the scanning trajectories of the rotating rads la and lb and the relative positions of the tracks are wobbled with a signal of a predetermined frequency, and the reproduction RF
A tracking control circuit 14, 16, and 19 generates a tracking control signal Ss by synchronously detecting the envelope signal of the signal with a wobbling signal. Circuits 21 and 22 are provided for controlling the tracking control circuits 14, 16, and 19 to perform tracking control during a playback operation during continuous shooting in which a playback operation is performed.

Further, in order to enable lower edge tracking when the transition is close, a circuit 18 is provided to control the phase of the signal for synchronous detection.

[Effect]

When splicing is done by a video camera, the tape is returned and the tape is moved back before the next recording is made to maintain continuity between the tracks formed by the previous recording and the tracks formed by the new recording. A playback operation is performed. In this reproduction operation, tracking control is performed using a synchronous detection servo method. Therefore, it is possible to prevent a long delay from when the recording pause is released until the next recording is made.Also, by shifting the phase of the wobbling signal supplied to the synchronous detection circuit, continuous recording can be performed. Time tracking control is
A predetermined amount of shift occurs compared to normal playback operation.

Therefore, tracking control is possible in which the lower edges of the rotary heads 1a, 1b match the edges of the tracks.

[Example] The present invention will be described below with reference to the drawings. This description will follow the order of the items below.

a. Overall configuration and operation of one embodiment. Synchronous detection servo system a. Overall configuration and operation of one embodiment In FIG. 1, la and 1b are frame frequencies (3
01(z) shows rotating heads mounted on a rotating drum at opposing intervals of 180".Rotary heads 1a and 1
In b, the extending directions of the differential gaps are shifted by a predetermined angle, and so-called inclined azimuth recording is performed. Reference numeral 2 indicates a drum motor, and reference numeral 3 indicates a rotation detector that generates a detection signal corresponding to the rotational phase of the drum motor 2. Also,
The magnetic tape 4 is fed at a predetermined speed while being wound around the circumferential surface of the drum at a winding angle slightly larger than 180'. The winding angle of the magnetic tape 14 may be widened, such as 210', if necessary, so that a PCM audio signal is recorded during the overlap period. 5 is a cap for sending the magnetic tape 4. A rotation detector 6 is provided which generates a detection signal corresponding to the rotational frequency and rotational phase of the capstan motor 5, which represents a stun motor.

A recording signal from a recording amplifier 8 is supplied to the rotary heads 1a, 1b through a recording side terminal r of a recording/reproduction changeover switch 7. This recording signal is supplied to the recording amplifier 8 from the input terminal 9. Further, the signals reproduced by the rotary drives la and lb are supplied to the reproduction amplifier 10 through the reproduction side terminal p of the recording/reproduction changeover switch 7. The output signal of the reproduction amplifier 10 is converted into a one-channel reproduction RF signal by a reproduction switching circuit (not shown).

In this embodiment, as shown in FIG.
The head width wh of each of a and 1b is larger than the track width Wt. - As an example, (Wh=25
am, , Wt = 20.65 am). FIG. 3 shows the tracking state of the rotary head la (same as the rotary head 1b) during recording and reproduction when the magnetic tape 4 is fed in the direction of the arrow. Due to the above-mentioned relationship between the head width Wh and the track width Wt, during recording, the rotating head forms the next track partially overlapping the previously formed track. Therefore, the rotating head la
, lb lower edge EHI and track winding edge E
i matches. On the other hand, during normal reproduction, tracking control is performed so that the centers of the rotary heads 1a, 1b coincide with the center of the track.

As shown in FIG. 1, the reproduced RF signal is supplied to an envelope detection circuit 11 and taken out to an output terminal 12. Although not shown, a circuit for performing reproduction processing such as FM demodulation is connected to the output terminal 12. An envelope signal Se of the reproduced RF signal is obtained from the envelope detection circuit 11, and this envelope signal Se is supplied to the synchronous detection circuit 14 via the bypass filter 13.The synchronous detection circuit 14 includes a switch circuit 15. A sine wave signal for wobbling is supplied via the signal generating circuit 16.
As a result, a low-frequency sine wave signal Sw that can be followed by the capstan motor 5 is formed. This sine wave signal Sw is supplied to the input terminal a of the switch circuit 15 via the phase correction circuit 17. The phase correction circuit 17 receives a sine wave signal Sw.
This is provided to compensate for the delay until the speed of the magnetic tape 4 actually wobbles.

The output signal of the phase correction circuit 17 is supplied to the delay circuit 18, and the output signal of the delay circuit 18 is supplied to the input terminal of the switch circuit 15. The delay circuit 1 day is provided for lower edge tracking during continuous shooting.

As mentioned above, during normal playback, the rotating heads la, 1
Tracking is controlled so that the center of b coincides with the center of the track. However, when splicing, a reproduction operation is performed to maintain the continuity of the tracks formed on the tape, so it is necessary to control the tracking in the same relationship as during recording. In other words,
The lower edges EHI of the rotating wheels la and lb are controlled so as to coincide with the winding edge ELL of the track. Therefore, when the connection is full, the scanning position is shifted to the supply side compared to normal reproduction operation. For this shift,
The delay circuit 18 shifts the phase of the sine wave signal by a predetermined amount.

The output signal of the synchronous detection circuit 14 is supplied to a low-pass filter 19, and from the low-pass filter 19, as described later,
A phase error signal Ss for tracking control having a polarity corresponding to the direction of the tracking deviation and a level corresponding to the tracking deviation is obtained.

A phase error signal Ss from the low-pass filter 19 is supplied to an adder circuit 20. The sine wave signal Sw from the signal generation circuit 16 is also supplied to the addition circuit 20 . Addition circuit 2
The output signal of 0 is sent to the adder circuit 25 via the switch circuit 21.
supplied to

Recording/reproduction changeover switch 7, switch circuits 15 and 2
1 is switched by a control signal generated by the control signal generation circuit 22. The control signal generation circuit 22 is supplied with a mode signal from a terminal 23 indicating the operating mode of V i'R. Further, the output signal of the rotation detector 3 associated with the drum motor 2 is supplied to the amplifier 24.
A detection signal PG having a phase corresponding to the rotational phase of the drum (rotary heads 1a, lb) is generated. This detection signal PC is supplied to the control signal generation circuit 22.

An adding circuit 25 adds a speed error signal to the sum of the phase error signal SS and the wobbling sine wave signal Sw passed through the switch circuit 21. An output signal from a rotation detector 6 that detects the rotation speed of the capstan motor 5 is supplied to an amplifier 26 . A detection signal FG from the amplifier 26 is supplied to a speed error detection circuit 27. Since this detection signal FC has a frequency proportional to the rotational speed of the capstan motor 5, the speed error detection circuit 27 compares the detected speed of the capstan motor 5 with the speed reference from the period of the detection signal FG. are compared to form a speed servo signal. This speed servo signal is added to the adder circuit 2.
5.

The output signal of the adder circuit 25 is supplied to the capstan motor 5 via the drive amplifier 28. capstan motor 5
is based on the tracking control signal and the speed servo signal so as not to cause a tracking error at a constant speed.
The magnetic tape 4 is made to run.

The switch circuit 15 is controlled so as to select input terminal a during normal playback operation, and select input terminal A during playback operation during continuous shooting. The switch circuit 21 is controlled to be turned on when tracking control is required, that is, during normal playback operation and playback operation during continuous shooting.

b. Synchronous detection servo method The synchronous detection servo method will be explained below.

17 to O-7” envelope signal S from the detection circuit 11
e is the capstan motor 5 with a sine wave signal sin ωt.
Since it is vibrated, it includes tracking information θ(1), and can be expressed as 5in(ωt+θ(t)). During normal playback operation when the terminal d of the switch circuit 15 is selected, the synchronous detection circuit 14 outputs sin (1) t
t))='A (cos (-〇(t))-Cos(2
An output signal expressed as (&) t±θ(t)) is obtained. By passing this output signal through the low-pass filter 19, twice the frequency components are removed. Therefore, from the low-pass filter 19, '/2cos (-〇(t))
A phase error signal Ss expressed as is obtained.

During continuous shooting, one terminal of the switch circuit 15 is selected, and the delay circuit 18 outputs a phase-shifted sine wave signal (
sinωt+00) (002 phase shift amount) is supplied to the synchronous detection circuit 14. Therefore, from the synchronous detection circuit 14, 5in (ωt+θQ)Xsin (ωt+θ(L))
=A (cos (θ0−θ(t)) −cos (
An output signal expressed as 2(1)L00(1)+00)) is obtained. Low pass filter 19
, a phase error signal Ss expressed as %cos (θO−θ(t)) is obtained. In other words, when shooting continuously,
An offset corresponding to θO is constantly added to the phase error signal Ss. Therefore, the polarity of this offset is selected in the direction in which the scanning position shifts toward the supply side, and
Lower edge tracking is achieved by selecting the amount as a percentage of the difference between the head width wh and the track width Wt.

Detection of tracking errors will be described with reference to FIGS. 4 and 5. In FIG. 4A and FIG. 5A,
T indicates a part of the track formed on the magnetic tape 4,
H indicates the scanning locus of the rotary head 1a or 1b. Since the sine wave signal Sw is supplied to the addition circuit 20, the rotation speed (tape speed) of the capstan motor 5 is equal to the sine wave signal Sw.
A wobbling scanning trajectory H is formed.

FIG. 4 shows the operation when there is no tracking error. In the diagonally shaded area where the track T and the scanning locus H overlap, a reproduced RF signal is obtained from the track, as shown in FIG. 4B. The envelope detection circuit 11 generates an envelope signal Se shown in FIG. 4C, and the envelope signal Se is supplied to the synchronous detection circuit 14 via the bypass filter 13. Also, sine wave Sw for wobbling
is supplied to the synchronous detection circuit 14. This sine wave SW is
In the synchronous detection circuit 14, the pulse signal is converted into the pulse signal shown in FIG. 4 and multiplied by the envelope signal Se, so that the output signal shown in FIG. 4E is generated from the synchronous detection circuit 14. This output signal is supplied to the low-pass filter 19, which generates a phase error signal Ss shown in FIG. 4F. When there is no tracking error, the phase error signal SS is 0.

On the other hand, as shown in FIG. 5A, when there is a tracking error (that is, when the center of the track T and the center of the scanning trajectory H do not match during normal playback), as shown in FIG. A reproduced RF signal is generated, and an envelope signal Se shown in FIG. 5C is obtained.

Since this envelope signal Se is multiplied by the pulse signal shown in Figure 5, the synchronous detection output shown in Figure 5 is generated. Therefore, as shown in FIG. 5F, a phase error signal Ss is obtained from the low-pass filter 19, with a polarity corresponding to the direction of the track deviation and a level corresponding to the track deviation.

The phase error signal Ss becomes O when there is no tracking error, and becomes thick (becomes) corresponding to the tracking error.
The tracking error reaches its maximum level when it is equal to the track pitch Wp.

C0 variant In one embodiment of the invention described above, the phase error signal S
The synchronous detection for forming s, the formation of a control signal for controlling the switch circuit, etc. can be implemented digitally using a microcomputer.

Furthermore, instead of causing the capstan motor to wobble, the rotary head may be supported by a piezoelectric element, and the rotary head may be caused to wobble by driving this piezoelectric element with a sine wave signal.

Furthermore, the present invention can also be applied to cases where the tracking phase of the synchronous detection servo is controlled other than during continuous shooting.
The delay circuit 18 may be configured with a variable delay circuit.

〔Effect of the invention〕

In this invention, tracking control is performed using a synchronous detection servo method when reproducing a previously recorded track for connection, so there is a long delay from when the recording pause is released until recording starts. This can be prevented. Further, lower edge tracking, which is necessary when the head width is wider than the track width, can be easily performed.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2 is a route diagram showing the relationship between head width and track width in an embodiment of the invention, and Fig. 3 is a diagram for explaining lower edge tracking. Route map, Figures 4 and 5 are route maps used to explain tracking error detection by synchronous detection servo,
FIG. 6 is a route map used to explain the connecting motion. Explanation of main symbols in the drawings la, lb: rotating head, 4: magnetic tape, 5: capstan motor, 11: envelope detection circuit, 14: synchronous detection circuit, 15.212 switch circuit. Tora, Sokinfiniraka? Nothing, 1B4 tiger, when there is a no-kink work.

Claims (2)

[Claims] (1) In a rotary head type recording and reproducing apparatus, a video signal is recorded as a diagonal track on a tape by a rotary head, and the rotary head scans the track to reproduce the video signal. a tracking control means for wobbling the relative position of the scanning locus and the track with a signal of a predetermined frequency and generating a tracking control signal by synchronously detecting an envelope signal of the reproduced RF signal with the wobbling signal; and a recording operation. means for controlling the tracking control means to perform tracking control during the playback operation during splicing, in which the tape position is returned from the end of the recording operation and the playback operation is performed before the next recording operation. A rotating head type recording and reproducing device. (2) In a rotary head type recording and reproducing apparatus, a video signal is recorded as a diagonal track on a tape by a rotary head, and the rotary head scans the track to reproduce the video signal. a tracking control means for wobbling the relative position of the scanning locus and the track with a signal of a predetermined frequency and generating a tracking control signal by synchronously detecting an envelope signal of the reproduced RF signal with the wobbling signal; A rotary head type recording/reproducing apparatus comprising means for controlling the phase of the wobbling signal in order to control the tracking state between the head and the track.