JPH033111A - Rotating head type reproducing device - Google Patents

Abstract

PURPOSE:To make the best use of the respective advantages of a synchronous detecting system and a synchronizing signal timing system and to prevent a reproduced image from fluctuating by executing tracking control with the aid of using a synchronous detection servo in the first transition term from stop to reproduction and with the aid of a synchronizing signal servo after the first transition term. CONSTITUTION:An ablique track formed on a tape 4 is scanned by rotating heads 1a and 1b and a video signal is outputted and reproduced through a reproducing amplifier 7. By synchronously detecting the envelope signal Se of the reproduced RF signal with the aid of a signal for wobbling Sw, a phase error signal Ss for controlling tracking is formed. By using the synchronous detection servo 10 in the first transition term from the stop of the action mode of a VTR to the reproduction thereof and using the synchronizing signal servo circuit 19 in a regular term thereafter, the time difference between the prescribed positions of the rotating heads 1a and 1b and a prescribed signal gated by a window pulse which is formed on the basis of a reproduced vertical synchronizing signal is detected. Then, the dislocation of the tracking is corrected according to the time difference.

Description

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

[Summary of the Invention] The present invention provides a rotary head type reproducing device in which a rotary head scans diagonal tracks formed on a tape to reproduce a video signal. The envelope signal of the reproduced RF signal which is wobbled by the signal and reproduced by the rotating head is synchronously detected by the wobbling signal, and the first
A tracking control signal is generated, and a second tracking control signal is generated in response to a time difference from a predetermined position of the rotary head to a predetermined signal gated with a window pulse formed based on the reproduced vertical synchronization signal. In the rising period after the transition, tracking control is performed using the first tracking control signal, and in the steady period after the rising period, tracking control is performed using the second tracking control signal. Tracking deviation can be well corrected without using it.

[Prior Art] A rotary head type VTR requires tracking control so that the head can correctly scan the diagonal tracks formed during recording during reproduction. As one method of tracking control, a control signal of 307 frequencies formed from a vertical synchronization signal separated from the recorded video signal is recorded in the longitudinal direction of the tape during recording, and during playback, a control signal of 307 frequencies is recorded in the longitudinal direction of the tape. It is known to control the tape running speed so that the rotational phase of the head 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 fl, f2, etc. as shown below. f3. The pilot signal of f4 is 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 rh (horizontal frequency) and 3fh.

f1-6.5fh! :1102.5kHzf2=
7.5fh! =il19.0kHzf3=10.5
fh'=165.2kHzf4=9.5fh'1
During reproduction at 148.7 kHz, a tracking error is detected by comparing the levels of the frequency difference components (fh, 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-mentioned problems, a tracking control method that does not require special signals for control such as control signals or pilot signals has been proposed. The synchronous detection method is one of these tracking control methods. In this synchronous detection method, the envelope of the reproduced RF signal wobbles by wobbling the capstan with a low-frequency sine wave signal, and this reproduced RF signal becomes the same as the above sine wave signal. Tracking error information can be obtained by synchronous detection.

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 pilot 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.

[Problems to be solved by the invention] The synchronous detection method is not easily 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 with the reference time difference, and if this reference time difference cannot be detected correctly, good tracking control cannot be achieved. There are some drawbacks that make it difficult.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a rotary head type reproducing apparatus that takes advantage of the respective advantages of the above-mentioned synchronous detection method and synchronous signal timing method.

[Means to solve the problem]

In the present invention, in a rotary head type reproducing apparatus in which the rotary heads la and lb scan diagonal tracks formed on the tape 4 to reproduce video signals, the speed of the capstan motor 5 is adjusted to a predetermined frequency. Signal Sw
A first tracking control circuit 1 that generates a tracking control signal by wobbling and synchronously detecting an envelope signal Se of a reproduced RF signal reproduced by the rotary heads 1a and 1b using a wobbling signal Sw.
0 and a predetermined position of the rotary heads la, lb to a predetermined signal gated with a window pulse formed based on the reproduced vertical synchronization signal, and corrects the tracking deviation according to the time difference. In the rising period after the mode transition, the first tracking control circuit 10 performs tracking control, and in the steady period after the rising period, the second tracking control circuit 19 performs tracking control. Circuit 1 to switch to
2 is provided.

[Effect]

In the rising period after the VTR operation mode changes from stop to playback, synchronous detection servo is used, and in the steady period, synchronous signal timing servo is used. Therefore, the reference time difference necessary for the synchronization signal timing servo can be detected by the synchronization detection servo, and the problem of the reproduced image being shaken due to wobbling does not occur.

〔Example〕

The present invention will be explained below with reference to the drawings. This description will be given in the following order.

a. Overall configuration of one embodiment, synchronous detection servo system C0 Synchronous signal servo system d. Modification a. Overall configuration of one embodiment In FIG. 1, 1a and 1b are frame frequencies (3
The rotating heads are shown mounted at opposing spacing of 180° on a drum rotating at 0 Hz). Rotating head 1a and lb
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 PC corresponding to the rotational phase of the drum motor 2. Further, 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 40 magnetic tapes is
If necessary, it may be increased to 210' so that the PCM audio signal is recorded during the overramp period. Reference numeral 5 indicates a capstan motor for feeding the magnetic tape 4, and a rotation detector 6 is provided for generating a detection signal FC corresponding to the rotation frequency and rotation phase of the capstan motor 50.

The reproduction signals from the rotary heads 1a and 1b are converted into one-channel reproduction RF signals by a reproduction switching circuit (not shown), and are supplied to a cFM demodulation circuit 8 and an envelope detection circuit 9 via a reproduction amplifier 7.Envelope An envelope signal Se of the reproduced RF signal is obtained from the detection circuit 9, and this envelope signal Se is supplied to the synchronous detection servo circuit 10.The synchronous detection servo circuit 10 receives a sine wave signal for wobbling from the signal generation circuit 11. As will be described later, the synchronous detection servo circuit 10 performs synchronous detection of the envelope signal Se with the wobbling sine wave signal Sw, thereby detecting scratchiness corresponding to the direction of the tracking deviation and tracking deviation. A phase error signal Ss for tracking control of the same level is formed.The phase error signal Ss from the synchronous detection servo circuit 10 is supplied to one input terminal 13a of the switch circuit 12.

A reproduced video signal from the FM demodulation circuit 8 is taken out to a terminal 14, and is supplied to a reproduced signal processing circuit (not shown) and also to a composite synchronization signal separation circuit 15. Composite synchronization signal C8Y from composite synchronization signal separation circuit 15 is supplied to vertical synchronization signal separation circuit 16 and AND gate 17.

The vertical synchronization signal VSY is separated by the vertical synchronization signal separation circuit 16. This vertical synchronizing signal VSY is supplied to the pulse generating circuit 18, and a window pulse WN is formed for extracting a predetermined horizontal synchronizing signal after the timing of the vertical synchronizing signal SY. This window pulse WN is A
The signal is supplied to an ND gate 17, and a predetermined horizontal synchronizing signal ph is output from the AND gate 17.

The horizontal synchronization signal Ph extracted by the AND gate 17 is supplied to the synchronization signal servo circuit 19 and the reference detection circuit 20. The output signal of the rotation detector 3 associated with the drum motor 2 is supplied to the amplifier 21, and the amplifier 21 generates a detection signal PC having a phase corresponding to the rotation phase of the drum (rotary heads la, lb). This detection signal PC is supplied to a synchronization signal servo circuit 19 and a reference detection circuit 20. The synchronization signal servo circuit 19 uses a synchronization signal timing detection method, and the time difference Td between the detection signal PC and the horizontal synchronization signal Ph from the AND gate 17 is compared with the reference value Tr detected by the reference detection circuit 20. Thus, a tracking control signal St is formed. In the synchronous signal servo method,
The tracking state may be detected not only from the horizontal synchronization signal but also from a pilot signal for tracking control added to a predetermined position in the video signal. Synchronous signal servo circuit 19
A tracking control signal St is supplied to the input terminal 13b of the switch circuit 12.

The tracking control signal selected by the switch circuit 12 is supplied to the adder circuit 22 and added to the speed error signal. The switch circuit 12 is controlled by a control signal generated by a timing generation circuit 23. Timing generation circuit 23
is supplied with the detection signal PC and the operation mode signal from the terminal 24.

When the operation mode of the VTR changes from stop to play, this control signal is at a low level during a predetermined rising period immediately after the mode transition, and is at a high level during a subsequent steady period. During the rising period when the control signal is at a low level, the input terminal 13a of the switch circuit 12 is selected, and during the steady period when the control signal is at a high level, the input terminal 13b is selected.

An output signal from a rotation detector 6 that detects the rotation speed of the capstan motor 5 is supplied to an amplifier 25.

The detection signal FC from the amplifier 25 is sent to the speed error detection circuit 2.
6. Since this detection signal FC has a frequency proportional to the rotation speed of the capstan motor 5, the speed error detection circuit 26 uses the speed of the capstan motor 5 detected from the cycle of the detection signal FG and the speed reference. are compared to form a speed servo signal. This speed servo signal is supplied to the adding circuit 22. An adder circuit 22 adds the tracking control signal from the switch circuit 12 and the speed servo signal.

The output signal of the adder circuit 22 is supplied to an adder circuit 29 via a phase compensation circuit 27 and a servo amplifier. The phase compensation circuit 27 is provided to control the phase characteristics of the servo loop, and the servo amplifier 28 is provided to control the gain characteristics of the servo loop. The adding circuit 22 is supplied with the wobbling sine wave signal Sw from the signal generating circuit 11 via the switch circuit 30. The switch circuit 30 is turned on during a rising period when the output of the timing generation circuit 23 is at a low level, and turned off during a steady period when its output is at a high level. The output signal of the adder circuit 29 is supplied to the capstan motor 5 via the drive amplifier 31. The capstan motor 5 runs the magnetic tape 4 at a constant speed using a tracking control signal and a speed servo signal so as not to cause a tracking error. During the rising period, the switch circuit 30 is turned on and the sine wave signal Sw is used to drive the capstan motor 5, so the rotational speed of the capstan motor 5 is modulated by the sine wave signal Sw. The sine wave signal Sw is a low frequency signal that can be followed by the capstan motor 5.

During the rising period when the control signal from the timing signal generation circuit 23 is at a low level, the reproduced video signal is muted and the reproduced image is not displayed.

The rotation of the capstan motor 5 becomes stable and the reference time difference T
After the detection of r is completed, during a steady period during which tracking control can be performed by the synchronization signal servo circuit 19, the output signal of the timing signal generation circuit 23 changes to a high level. Based on this control signal, tracking control is performed by the synchronous detection servo circuit 10 during the rising period, and tracking control is performed by the synchronous signal servo circuit 19 during the steady period.

In the above-described embodiment of the present invention, the portion surrounded by the broken line in FIG. 1 can be constructed digitally using a microcomputer. In the case of microcomputer control, the operation is controlled as shown in the flowchart shown in FIG.

At the time of mode transition (startup of capstan motor 5) when the VTR operation changes from stop to playback, the synchronous detection servo is started by the phase error signal Ss (step 4).
1).

When tracking control is performed by the synchronous detection servo, a time difference Td between a detection signal PC indicating a predetermined rotational position of the rotating drum and a gated horizontal drum signal ph is detected,
By integrating this time difference Td, the reference time difference Tr
is detected (step 42). When the synchronous detection servo is operating, the detected time difference Td is also affected by wobbling, so the value averaged by integration is taken as the reference value Tr. The detected reference time difference Tr is stored in the storage means (step 43).

Next, the envelope level ENV is detected (step 44). After the detection of the reference time difference Tr is completed, the servo system is switched from synchronous detection servo to synchronous signal servo (step 45).

In the subsequent steady period, tracking is controlled by synchronizing signal servo (step 46).

b. Synchronous detection servo system FIG. 3 shows an example of a synchronous detection servo circuit 10. 51
An envelope signal Se is supplied from an envelope detection circuit 9 to an input terminal indicated by . A synchronous detection circuit 53 is connected to the input terminal 51 via a bypass filter 52. A sine wave signal SW for wobbling from an input terminal 54 is supplied to the synchronous detection circuit 53 via a phase correction circuit 55. The phase correction circuit 55 is provided to correct a delay until the speed of the capstan motor 5 is modulated by the sine wave signal Sw. The output signal of the synchronous detection circuit 53 is supplied to a low-pass filter 56, and a phase error signal Ss for tracking control is taken out at an output terminal 57.

Since the capstan motor 5 is vibrated by the sine wave sin ωt, the envelope signal Se contains tracking information θ(1), and converts sin(ω to 1,000(t)
)It can be expressed as. From the synchronous detection circuit 53, sin ωtXsin (ω is 10(t)) − A (co
s (-θ(t))-CO3(2(1) t, 10θ(t
)) A phase error signal Ss is obtained. By passing this phase error signal Ss through the low-pass filter 56, twice the frequency component is removed.

Therefore, from the low-pass filter 56, 'ACO3(-
A phase error signal SS represented by 〇(t)) is obtained.

Detection of a tracking error by the synchronous detection servo circuit 10 will be described with reference to FIGS. 4 and 5. Fourth
In FIG. A and FIG. 5A, T indicates a part of the track formed on the magnetic tape 4, and )1 indicates the scanning locus of the rotary head 1a or 1b.

During the rising period of the capstan motor 5, the sine wave signal Sw is supplied to the addition circuit 29 via the switch circuit 30, so the rotational speed (tape speed) of the capstan motor 5 is modulated according 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. From the envelope detection circuit 9, FIG.
An envelope signal Se shown in is generated, and the envelope signal Se is passed through the bypass filter 52 to the synchronous detection circuit 5
3. Further, a sine wave Sw for wobbling is supplied to the synchronous detection circuit 53. This sine wave Sw is converted into the pulse signal shown in Figure 4 in the synchronous detection circuit 53 and multiplied by the envelope signal Se, so the synchronous detection circuit 53 generates the output signal shown in Figure 4. do. This output signal is supplied to a low-pass filter 56,
A phase error signal Ss shown in FIG. 4F is generated from the low-pass filter 56. When there is no tracking error,
The phase error signal Ss is O.

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 locus H do not coincide), the RF signal shown in FIG. 5B is generated, 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, from the low-pass filter 56, a phase error signal Ss with a loss level corresponding to the direction of the track deviation and a level corresponding to the track deviation is obtained. Phase error signal Ss formed by the synchronous detection servo circuit 10
is 0 when there is no tracking error, increases as the tracking error occurs, and reaches its maximum level when the tracking error is equal to the track pitch Wp.

C9 synchronization signal servo system The synchronization signal servo circuit 19 compares the timing of the synchronization signal with a predetermined rotational phase of the rotary head and detects a tracking error based on the time difference between the detection signal PG and the horizontal synchronization signal Ph from the AND gate 17. Performs tracking control. Formation of a tracking control signal using the synchronous signal servo method will be explained with reference to FIG. Figure 6A is
A composite synchronizing signal C3YNC separated from the reproduced video signal by the composite synchronizing signal separating circuit 15 is shown, and FIG. 6B shows a vertical synchronizing signal VSYNC separated from the reproduced video signal by the vertical synchronizing signal separating circuit 16. The window pulse WN shown in FIG. 6C is generated by the pulse generating circuit 18 from the vertical synchronizing signal VSYNC.

This window pulse WN has a pulse width of ±y2H with respect to the horizontal synchronization signal Ph used for detecting a time difference. The predetermined horizontal synchronization signal ph shown in the sixth diagram gated by the window pulse WN and the detection signal PC of the phase corresponding to the predetermined rotational phase of the drum (Fig. 6E)
) is supplied to the synchronization signal servo circuit 19 and reference detection circuit 20, and the time difference shown by Td in FIG. 6 is detected. When the tracking deviation is corrected by the synchronous detection servo, the time difference Td becomes the reference value, so the integrated value of the time difference Td is detected as the reference value Tr.

Tracking control using the synchronization signal servo method described above will be explained with reference to FIGS. 7 and 8.

FIG. 7 shows a recording pattern formed on the magnetic tape 4, where Ta indicates the track formed by the rotating head la (+azimuth), and Tb indicates the track formed by the rotating head 1b (-azimuth).
It shows the track formed by In this example, there is no guard band, the distance between the starting ends of two adjacent tracks Ta and Tb corresponds to a time difference of %H, and the recording position of the horizontal synchronization signal is in the direction perpendicular to the tracks. are lined up. In FIG. 7, Lr is a line for indicating the predetermined rotational phase of the rotary heads la and lb, that is, the phase of the detection signal PC.

The head 1a rotates on the center track Ta in FIG.
A case will be explained in which control is performed so that the image scans correctly. When there is no track deviation, that is, when a scanning trajectory SO is drawn in which the center of the track Ta and the center of the rotary head 1a coincide, the time difference between the detection signal PC and the horizontal synchronization signal Ph recorded on the track Ta is the reference value. Matches the value Tr (
(See Figure 8), with respect to a state where there is no track deviation, a track deviation in which the scanning locus at the center of the rotary head 1a deviates to the upstream side of the tape is considered positive; The track deviation in the state of deviation to the downstream side is considered negative.

As shown by the scanning trajectories S1 and S2, ±y2Wp(WP
When there is a track deviation of ±Wp, the time difference is (Tr±”h H).As shown in the scanning trajectories S3 and S4, when there is a track deviation of ±Wp, the time difference is (Tr±ηH). ). Therefore, the relationship between the track deviation and the detected time difference is as shown in FIG. 8. Tracking control is performed by controlling the rotational speed of the capstan motor 5 according to the detected time difference. It can be carried out.

Note that the time difference between the horizontal synchronization signal and the detection signal PC is
The detection is not limited to once on one track, but may be performed multiple times to further improve tracking accuracy.

Note that the present invention can also be applied to patterns other than the recording pattern shown in FIG. 7, such as patterns in which the starting ends of adjacent tracks are offset by IH. In a pattern where there is no guard band and adjacent tracks have a deviation of IH, the width of the window pulse WN is set to ±IH.

d. Modified example Furthermore, it is not limited to mode transition from stop to playback, but also when switching between short-time recording mode (SP mode) and long-time recording mode (LP mode) in the middle of a tape. The present invention can be similarly applied to cases where a transition occurs at a switching point, a transition occurs at a splicing point of a spliced tape, or the like.

〔Effect of the invention〕

In this invention, during the start-up period after a mode transition such as when the operation mode of the VTR changes from a stop state to a playback state,
Tracking control is performed by synchronous detection servo, and after the rising period, tracking control is performed by synchronous signal servo. Therefore, the reference value Tr for the synchronization signal servo can be detected by the synchronization detection servo, and the synchronization signal servo operates using this reference value Tr during the steady period, so that highly accurate control can be performed. Also, in the steady period,
Since a synchronization signal servo is used, it is possible to prevent the problem of the reproduced image shaking due to wobbling.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of this invention, and FIG. 2 is a flowchart used to explain the operation of an embodiment of this invention.
Figure 3 is a block diagram of an example of a synchronous detection servo circuit, Figure 4
Figures 5 and 5 are route maps used to explain tracking error detection using synchronous detection servo, Figure 6 is a timing chart used to explain synchronous signal servo, and Figures 7 and 8 are tracking control using synchronous signal servo. It is a route map used for explanation. 19: Synchronous signal servo circuit, 12.30: Switch circuit.

Claims (1)

[Claims] In a rotary head type playback device in which a rotary head scans diagonal tracks formed on a tape to reproduce video signals, the speed of a capstan motor is wobbled by a signal of a predetermined frequency. a first tracking control means for generating a tracking control signal by synchronously detecting an envelope signal of a reproduced RF signal reproduced by the rotary head with the wobbling signal; a second tracking control means that detects a time difference to a predetermined signal gated with a window pulse formed based on a vertical synchronization signal and corrects a tracking deviation according to the time difference; , switching means for performing tracking control with the first tracking control means and performing tracking control with the second tracking control means during the steady period after the rising period; Head type playback device.