JPH08287552A - Tracking controller - Google Patents

Abstract

PURPOSE: To provide variable-speed reproduction tracking without using any control signal and to accelerate access by providing a tracking control means for performing the tracking control of a rotary magnetic head. CONSTITUTION: A tracking control means 19 is composed of a track number error detecting means 20, tracking error detecting means 21, switching means 22 and phase control means 23. Concerning this device, the speed of a magnetic tape 3 is accelerated to a prescribed value by a high-speed running control means 9 in the case of a variable-rate reproducing operation at any arbitrary speed higher than ordinary reproducing rate and afterwards, the pull-in setting of rotary magnetic heads 2a and 2b to a desired scanning track phase is controlled based on the error signal of the track number error detecting means 20. After the scanning phase reaches inside the prescribed range of the desired phase, while controlling the switching means 22, the tracking of the magnetic heads 2a and 2b is performed based on the error signal of the tracking error detecting means 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital V which records and reproduces a digital video signal using a rotary magnetic head.
The present invention relates to TR, and more particularly to a tracking control method during variable speed reproduction in which reproduction is performed at an arbitrary speed higher than the normal reproduction speed.

[0002]

2. Description of the Related Art Recent advances in digital technology are remarkable,
In the fields of broadcasting and communication, digitization of video signals is progressing, and digital broadcasting is about to be put to practical use in the United States and the like.

Under such circumstances, digital VTRs are being developed in various places. For example, there has been attempted a method of recording and reproducing digital moving image data by using a so-called analog VHS (registered trademark) VTR which is widely used as a home VTR.

When digitizing a moving image, an image compression technique is used because the amount of information is huge.

A well-known MPEG (Moving picture Experts Group) system is a typical image compression technique. However, many image compression techniques such as the MPEG system provide a high compression rate without degrading the image quality. To achieve
A method of coding and compressing only the difference between frames (motion compensation predictive compression) using frame correlation is used.
The amount of data is being reduced.

However, even with the digital image data compressed as described above, the data can be compared with the conventional analog recording.
The amount of data is very large, and when recording on a tape by helical scanning, even one frame of image data spans several tracks. For this reason, in high-speed reproduction (variable speed reproduction), reproduction data does not become a continuous frame, and a frame in which motion compensation predictive compression is performed from preceding and succeeding images cannot be reproduced (restored). Therefore, there is a drawback that variable speed reproduction cannot be performed simply by increasing the tape speed as in the conventional analog recording.

In view of the above-mentioned drawbacks, as a method of utilizing the image compression by the MPEG method and enabling variable speed reproduction, for example, "FIRST SCAN TECHNOLOGY FOR DIGITAL VI
DEOTAPE RECORDERS (IEEE Transaction on Consumer El
ectronics Vol.39, No.3, AU-GUST 1993) ”has been proposed. This method allows variable speed reproduction to be performed in advance so that image data can be restored even in variable speed reproduction. The dedicated image data processed for variable speed reproduction is dispersedly recorded at a specific position on the tape corresponding to the scanning locus of the reproducing head according to the recording pattern. FIG. 8 shows an example of the playback direction (3 × speed and 9 × speed variable speed reproduction in the forward direction).

In FIG. 8, 3 is a magnetic tape, 60 and 61.
Is a scanning locus of a magnetic head having a positive azimuth angle and a negative azimuth angle at the time of normal reproduction, 62 and 63 are respectively a scanning locus of a positive azimuth angle and a negative azimuth angle head at the time of reproduction, and 64 and 65 are respectively 9 times speed. Scanning loci of the positive and negative azimuth angle heads during reproduction, the blank portion of 66 is an area where image data for normal reproduction is recorded, the shaded portion of 67 is triple speed reproduction, and hatching of 68 The portion marked with is an area in which image data for 9 × speed reproduction is recorded, and the data of 67 and 68 are recorded independently corresponding to both the positive azimuth angle head and the negative azimuth angle head. Is shown. Also, 69 is a conventional analog V
Similar to the HS / VTR, this is a control track in which a control signal is recorded as a signal for tracking control. Since the VTR is a helical scan system, the actual track is recorded obliquely on the tape 3 as is well known, but in FIG. 8, the tape is recorded in order to make it easy to see the recording pattern. It is expressed linearly in the width direction.

As is clear from FIG. 8, according to the present recording method, the heads having the positive azimuth angle and the negative azimuth angle are caused to scan the loci of 62 and 63, or 64 and 65, respectively, so that the positive and negative azimuth tracks are formed. Image data
67 groups and 68 groups can be reproduced, and high speed reproduction of 3 × speed and 9 × speed can be performed, respectively.

[0010]

However, in order to realize the variable speed reproduction operation by the recording method as described above,
There are the following issues.

First, since the image data for variable speed reproduction is recorded only on a specific track that matches the head scanning locus, when the normal reproduction state is changed to the variable speed reproduction, or the variable speed reproduction is performed. When the speed is changed during playback, the rotary magnetic head will naturally
That is, the phase control (tracking control) must be performed so as to accurately scan a predetermined track on which the data is recorded.

As is well known, in the conventional tracking control in the variable speed reproduction of the analog VHS / VTR, the reproduction control signal is simply divided according to the speed ratio of the variable speed reproduction, and the divided signal and the phase reference are used. It suffices to perform control by performing a phase comparison with a reference signal, which is used as the control signal.However, since the recording track of the image data is specified in this recording method, the control signal is simply divided and the phase comparison signal is It is not possible to apply a conventional technique such as In other words, a tracking control method that does not use the control signal is indispensable for the variable speed reproduction operation. Moreover, the method is
It is necessary to consider compatible playback of the tape.

The second problem is high-speed access in consideration of operability. When considering access to a variable speed reproduction track as shown in FIG. 8, it is the track phase pull-in control that affects the access time. Assuming that the variable speed reproduction speed is n, the phase pull-in of maximum ± n tracks is required, and naturally, the larger the variable speed reproduction speed n is set, the longer the time required for the phase pull-in. Image data for variable speed reproduction is not reproduced until the scanning phase of the rotary magnetic head scans a desired track, and during this period, the reproduced image is interrupted,
Considering the operability and the quality of the reproduced image, it is desired that this time be shortened as much as possible.

However, any solution to these problems has not been considered or disclosed in the prior art.

An object of the present invention is to solve the above-mentioned problems, and the scanning phase of the rotary magnetic head can be pulled into the variable speed reproduction track without using the control signal, and the variable speed reproduction track can be accurately tracked. It is an object of the present invention to provide a tracking control device that is capable of achieving high-speed pull-in to a variable-speed reproduction track.

[0016]

In order to achieve the above object, according to the present invention, high speed running control means for running a magnetic tape at a speed higher than a normal playing speed, and image information from a signal reproduced by a rotary magnetic head. And a digital image reproduction signal processing means for restoring the sub information signal, and the tape by the high speed traveling control means, at the time of high speed traveling, the rotary magnetic head based on the sub information signal reproduced by the digital image reproduction signal processing means. Tracking control means for detecting the deviation from the desired scanning track phase to perform track pull-in control, and for detecting the tracking error with respect to the desired scanning track center based on the sub-information signal to perform tracking control of the rotary magnetic head. And a control means for controlling the high-speed traveling control means and the tracking control means. After the speed of the magnetic tape is raised to a predetermined value by the high speed traveling control means, the tracking control means is brought into an operating state, and the desired scanning track of the rotary magnetic head is set based on the reproduced sub information signal. The phase pull-in control and tracking control are performed.

Further, in the present invention, in order to speed up the access, there is provided damping coefficient control means which is controlled by the control means and controls the damping coefficient at the time of tape traveling speed control by the high speed traveling control means. .

[0018]

In the variable speed reproduction operation, the high speed traveling control means drives the tape so that the traveling speed of the magnetic tape becomes a predetermined speed in response to a command from the control means.
Controls the rotation speed of the motor.

The tracking control means detects the sub information signal of the track number and the block number of the head scanning track which is restored by the digital image reproduction signal processing means and outputted, and the reference track number and block corresponding to the desired scanning phase. It performs a comparison with the number, generates an error signal according to the comparison error, and performs tracking control based on this. That is, by using only the sub-information signal reproduced by the digital image reproduction signal processing means, the deviation of the rotary magnetic head from the desired scanning track phase is detected, and the polarity corresponding to the deviation direction and the error corresponding to the track number deviation amount are detected. A signal is generated to control the pulling of the track scanning phase, and after the head scanning phase reaches within a predetermined range of the desired phase, the deviation of the rotary magnetic head from the center of the desired scanning track is detected and the deviation direction is detected. Tracking control is performed so that the head scans the center of the desired scanning track phase by generating an error signal having a different polarity and corresponding to the amount of deviation.

With such a configuration, in the variable speed reproduction operation, the high speed running control means raises the speed of the magnetic tape to a predetermined value, and then the tracking control means is brought into an operating state and is reproduced by head scanning. The phase lead-in control and tracking control to the desired scanning track of the rotary magnetic head are performed based on the sub information signal.

The damping coefficient control means sets the damping coefficient to the first predetermined value and the desired phase until the scanning phase of the rotary magnetic head reaches a predetermined range of the desired phase under the control of the tracking control means. After reaching the range, it works to switch to a second predetermined value larger than the first.

As a result, in the process of pulling in the error in the number of tracks, the damping effect of the speed control can be weakened, the maximum speed of the capstan motor is increased, and the phase pull-in, that is, the pull-in response to the variable speed reproduction track is accelerated. ,
Access can be speeded up.

[0023]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a tracking control device according to the present invention. In the figure, 1 is a rotary drum, 2a and 2b are a pair of rotary magnetic heads mounted on the rotary drum and having opposite azimuth angles, where 2a has a positive azimuth angle and 2b has a negative azimuth angle. And 3 is a magnetic tape, 4 is a control head for recording and reproducing control signals, 5 is a capstan for driving the tape, 6 is a pinch roller, and 7 is a capstan model for controlling the rotation of the capstan 5. -Ta,
Reference numeral 8 is an FG (tachogenerator) that generates a frequency signal synchronized with the rotation speed of the capstan motor 7, 9 is a high speed running control means for rotating the capstan motor 7 at a high speed and running the tape at a high speed, 10 is an adder, 11 Is a motor drive circuit, 1
Reference numeral 2 is an amplifier for amplifying the reproduction signal of the control head 4, 13 and 14 are amplifiers for amplifying the reproduction signal of the rotary magnetic heads 2a and 2b, respectively, and 15 is 13 and 1.
4, a changeover switch for changing over the reproduction signal, 16 for a changeover circuit, and 17 for performing tracking control during normal reproduction C
TL tracking control circuit, 18 is control means, 19 is track number error detection means 20, tracking error detection means 21, tracking control means composed of switching means 22 and phase control means 23, and 24 is main information such as image and sound. At the same time, digital image reproduction signal processing means 25 for reproducing the sub information signal such as the track number and the block number is an output terminal.

The basic principles of the drum rotation control and the tracking control during normal reproduction in the embodiment of FIG. 1 are no different from those of the conventional analog VHS / VTR. That is, the rotation of the drum is controlled to 1800 rpm (30 Hz) by the speed and phase control using the FG signal and the tack pulse (neither is shown), and the rotation phase is also relative to the reference signal (30 Hz). It is controlled so as to have a predetermined phase. This control is the same when recording and reproducing a signal. During recording, the control head 4 records the reference signal used for drum rotation phase control as it is on the control track on the tape, and during reproduction, the CTL tracking control circuit 1
The playback timing of this control signal and 3
By performing phase comparison control with the 0 Hz reference signal,
The tracking operation is performed so that the head scans the recording track correctly. The control method and the like are conventionally known in analog VHS / VTR.

The recording pattern of the digital VTR tape which is the object of the present invention recorded in this manner is also shown in FIG.
Is the same as that shown in. The details of the recording method are omitted since they are not directly related to the gist of the present invention, but a compressed image signal for normal reproduction and a dedicated image signal compatible with variable speed reproduction are recorded on a track according to a predetermined format. .

The data recorded on each track is divided into a plurality of blocks, and each block includes a digital image data, a track number indicating the position of the track, a block number indicating the position of the block, and the like. Sub information signal data
Data, and a correction code for error correction is added.

The recording track is azimuth recording by two heads 2a and 2b opposed to each other by 180 °. The head 2a having a positive azimuth angle indicates a + azimuth track in FIG. 8 and the head 2b having a negative azimuth angle indicates −azimuth. The tracks are recorded sequentially.

In the case of variable speed reproduction (forward) of 9x speed and 3x speed, the data for 9x speed reproduction is + azimuth track on the scanning locus 64 of the head 2a as shown in FIG. Also, like the 68 group on the azimuth track on the scanning locus 65 of the head 2b, the data group 67 for triple speed reproduction is also on the scanning locus 62 of the head 2a and the scanning locus 63 of the head 2b. Are recorded in each.

The track number is added, for example, according to the number of scanning tracks per one rotation of the drum in variable speed reproduction, and in FIG. 8, it corresponds to the maximum speed of 9 times speed. It is assumed that the scan start track (referenced to the scan start of the head 2a) is number 0 and the repetition numbers 0 to 17 are given. Also, at 3x speed playback, 9
Since the tape speed is 1/3 as compared with the double speed reproduction, the scanning start track is not only 0 but 6 and 12 correspond to this.

The operation of each part of FIG. 1 will be described below.

When the control means 18 receives the variable reproduction speed command input S selected and designated by the user, the control signal C for controlling the high speed traveling control means 9 and the switching circuit 16 is received.
In addition to outputting 1, the specified speed information value n for variable speed reproduction is output to the tracking control means 19. Also, the tape traveling speed of the variable speed reproduction is monitored, and when the speed reaches a predetermined value, for example, the control error signal Ve of the high speed traveling control means 9 is detected.
This is detected, the control signal C2 for controlling the switching circuit 16 again is output, and when the scanning phase of the head reaches a predetermined range of the desired phase by the control of the tracking control means 19, for example, the track number error detection means. It is configured to detect this from the control error signal Tn of 20 and output the control signal Vt which inverts from "L" to "H" for controlling the switching means 22.

The high speed traveling control means 9 controls the rotation speed of the capstan motor 7 so that the tape 3 is caused to travel at a predetermined speed in response to the control command signal C1 from the control means 18. For example, the speed servo means for normal reproduction is also used, and the speed servo is performed by using the capstan FG whose frequency is divided according to the speed ratio during variable speed reproduction.

The switching circuit 16 switches the tracking control signal at the time of normal reproduction and at the time of variable speed reproduction, and at the time of variable speed reproduction, the control signal C1 from the control means 18 is used.
The contact point is b in the figure, and the contact point c is the control signal C2.
Work to close.

When the control signal Vt from the control means 18 is "L", the switching means 22 has its contact point at w1 in the figure.
At the time of switching to "H", that is, at the point where the scanning phase of the head has reached within a predetermined range of the desired phase under the control of the tracking control means 19, it works to close to the w2 side in the figure.

The track number error detecting means 20 detects the deviation of the rotary magnetic head from the desired scanning track phase based on the sub information signals of the track number and the block number restored by the digital image reproduction signal processing means 24. An error signal having a polarity according to the direction of deviation and a level according to the amount of deviation is output.

FIG. 2 shows a block diagram of a specific configuration example of the track number error detecting means 20. In the figure, 31 is a track number detecting circuit, 32 is a block number detecting circuit, 3
Reference numeral 3 is a scanning track number error calculation circuit, and 34 is an error signal generation circuit.

The sub information signal Ds reproduced from the digital image reproduction signal processing means 24 is the track number detecting circuit 3
1 and the block number detection circuit 32. The track number detection circuit 31 detects the track number added to each block from the Ds signal and supplies it to the scanning track number error calculation circuit 33. Further, the block number detection circuit 32 detects the block number added to each block of the Ds signal and supplies it to the scanning track number error calculation circuit 33. The scanning track number error calculation circuit 33 calculates the error of the number of scanning tracks with respect to the original desired scanning phase based on the track number and block number of the reproduced Ds signal and the reproduction speed information value n input from the control means 18. To do.

This operation will be described below by taking the variable speed reproduction of 9 × speed (forward) shown in FIG. 3 as an example. In FIG. 3, the same reference numerals as those in FIG. 8 indicate the same things.

During 9 × speed reproduction, the rotary magnetic head 2a reproduces data across 9 tracks in one scan. For example, if one track is composed of 96 blocks from 0 to 95, data will be reproduced over 8 tracks, with about 12 blocks per track. Therefore, when you specify the track number,
By detecting the block number reproduced on this track and comparing it with a reference value, the error in the number of scanning tracks for a desired scanning phase can be obtained.

The scanning track number error calculation circuit 33 sets the reference value of the reproduction block number at a specific track number to N.
Then, the operation of (M−N) / 12 is performed using the actual reproduction block number M at this specific track number.

For example, let us consider a case where the rotary magnetic head 2a is scanning with a shift to the left as shown by A in the figure with respect to the original desired scanning phase 64. Now, when the track number is specified as 2, the head of the reference block number N to be reproduced on this track by the head 2a is 18, as shown in the figure. On the other hand, track number 2 reproduced by scanning A
The block number at the beginning is 48, that is, M is 48.

Based on this, the scanning track number error calculating circuit 33 calculates (48-18) / 12 to obtain +2.5, which is taken as the scanning track number error for the desired scanning phase 64, and the error signal generating circuit 34. Output to. Here, the fact that the error in the number of scanning tracks is positive means that the scanning phase of the rotary magnetic head 2a leads the desired scanning phase 64 as shown in A of FIG. Further, as the scanning phase of the head 2a shifts in the direction A in the figure, the value of M becomes larger, so that the error in the number of scanning tracks naturally increases.

On the other hand, the scanning phase of the rotary magnetic head 2a is
The case is not limited to the case of A in FIG. 3, but there is also a case like the locus of B, which shifts to the right side in the drawing with respect to the desired scanning phase 64. With respect to the track scanning deviation in the B direction, the scanning track number error calculation circuit 33 is configured to specify the track number 6 and perform the calculation.

For example, if the scanning of the rotary magnetic head 2a is as shown in B in the figure, when the track number is specified as 6, the head 2a reads the reference block number 66 to be reproduced on this track. Since the head of the block number reproduced by the scan of B is 36, the scanning track number error calculation circuit 33 calculates (36-66) / 12 based on this and obtains -2.5. Here, the fact that the scanning track number error is negative means that the scanning phase of the rotary magnetic head 2a is delayed with respect to the desired scanning phase 64 as shown in B of FIG. Further, the more the scanning phase of the head 2a shifts in the B direction in the figure, the smaller the value of M becomes, so that the error in the number of scanning tracks naturally increases.

The error signal generating circuit 34 generates an error signal Tn having the characteristic shown in FIG. 4 according to the scanning track number error calculation result from the scanning track number error calculating circuit 33. That is, when the scanning phase of the head 2a is deviated in the A direction with respect to the desired scanning phase 64 as shown in FIG. 3, the error signal having the positive polarity and the level corresponding to the track number deviation amount is reversed. If the shift is in the B direction, an error signal having a negative polarity and a level corresponding to the track number shift amount is output as an error signal for track pull-in control.

The tracking error signal detecting means 21 detects the deviation of the rotary magnetic head from the desired scanning track center based on the sub information signals of the track number and block number reproduced by the digital image reproduction signal processing means 24.
An error signal for tracking control having a polarity according to the deviation direction and a level according to the deviation amount is generated.

FIG. 5 shows a block diagram of a specific structural example of the tracking error detecting means 21. In the figure, 35 is a block number detecting circuit, 36 is a specific track number detecting circuit, 37 is a block error calculating circuit, and 38 is an error signal generating circuit.

The sub information signal Ds reproduced from the digital image reproduction signal processing means 24 is the block number detecting circuit 3
5 and the specific track number detection circuit 36. The block number detection circuit 35 detects the block number added to each block from the Ds signal and supplies it to the block error calculation circuit 37. Further, the specific track number detection circuit 36 detects a specific track number from the track numbers added to each block of the Ds signal and supplies it to the block error calculation circuit 37. Block error calculation circuit 37
Is based on the track number and block number of the reproduced Ds signal and the reproduction speed information value n inputted from the control means 18, from the reproduction block number in the specific track number scanned by the rotary magnetic head to the center of the desired scanning track. The amount of deviation is detected.

This operation will be described below by taking variable speed reproduction at 9 × speed as an example.

FIG. 6 shows the relationship between the desired scan of the head 2a and the block address in the track number 2 shown in FIG.

As described above, the variable speed reproduction data of 9 × speed is recorded in the block positions of the block numbers 18 to 29 in the track of the track number 2, and in order to reproduce this, the scanning of the head 2a is performed. The phase must be 64 as shown by a thick solid line (here, it is assumed that data reproduction is possible if the head 2a scans 1/2 of the track width).

On the other hand, if the tracking of the head 2a shifts in the direction A or B in the figure, the reproduced block number shifts vertically. That is, the block numbers reproduced in the tracking in the A direction, for example, in the tracking as shown by the thin solid line in the figure, are 20 to 31. On the contrary, when it shifts in the B direction and the tracking state as shown by the broken line in the figure is reached, the reproduction block number shifts from 16 to the lower side of 27.

For example, when the track number is specified to be 2 by the specific track number detection circuit 36, the block error calculation circuit 37 determines the track number with respect to the reference value based on the maximum and minimum values of the block numbers reproduced in this track. Calculate the deviation of the average block number. That is, the average block number 23.5 (center value of 18 and 29) as the reference is 25.5 (2 as the average block number in the scan of A).
The central value of 0 and 31) is calculated, and +2 is output as an error with respect to the reference value. On the contrary, in the scan of B, the average block number is calculated as 21.5 (center value of 16 and 27), and -2 is calculated and output as the error with respect to the reference value.

Further, the error signal generation circuit 38, in accordance with the block error calculation result from the block error calculation circuit 37,
The error signal Te having the same characteristic as shown in FIG. 4 is generated. That is, when the scanning phase of the head 2a is deviated in the A direction with respect to the desired scanning phase 64 as shown in FIG. 6, an error signal having a positive polarity and a level corresponding to the block deviation amount is reversed to B In the case of deviation in the direction, an error signal having a negative polarity and a level corresponding to the amount of block deviation is output as a tracking control signal. This control signal is a very fine signal in block units. That is, in 9 × speed reproduction, since signals for 96 blocks are reproduced over 8 tracks, detection in units of 1 block corresponds to a resolution of about 0.1 (8/96) in terms of track width. In other words,
This is equivalent to detecting a tracking error with an accuracy of 1/10 or less of the track width.

The phase control means 23 controls the pull-in control of the head 2a to a desired scanning phase and the center of the desired scanning phase based on the control signals Tn and Te from the track number error detecting means 20 and the tracking error detecting means 21, respectively. Performs tracking control. That is, when the control signals Tn and Te are positive error signals as shown in FIG. 4, the tape speed is accelerated to relatively delay the scanning phase of the head, and conversely, the negative error signals are used. In some cases, phase control is performed so as to reduce the tape speed and relatively advance the scanning phase of the head.

The configuration and operation of each part of the embodiment shown in FIG. 1 have been described above.

The overall operation of the above configuration will be described below.

A user operates a command key (not shown) for variable speed reproduction, for example, 9 times speed reproduction (forward).
When the control signal C1 is selected, the control means 18 recognizes this and sends the control signal C1 to the switching circuit 16 and the high speed traveling control means 9.
At the same time, the tracking control means 19 is supplied with n = 9 as a speed command value.

The switching circuit 1 is controlled by the control signal C1.
The contact point 6 is closed on the side b in the figure, and the rotation speed control of the capstan motor 7 by the high speed traveling control means 9 is started in the state where the phase control system for tracking is not operated, and the speed of the tape 3 is started. Is started up to the designated 9 × speed playback speed.

Next, when the tape speed reaches a predetermined speed of 9 times, the control means 18 detects this from the convergence state of the control error voltage Ve of the speed control system included in the high speed traveling control means 9 and switches it. The control signal C2 is issued again so that the contact of the circuit 16 is switched from b to c in the figure, that is, the output of the tracking control means 19 is supplied to the adder 10. As a result, when the tape speed reaches 9 times speed, the phase control system by the tracking control means 19 is closed and the phase control is brought into the operating state. At this time, the contact of the switching means 22 is closed on the w1 side in the figure.

At the moment when the phase control system is closed, the head 2a
The scanning locus (as is the case with the head 2b) does not always scan the recording track of the 9 × speed reproduction data. For example, a desired scanning locus such as the locus of A or B of FIG. There is a deviation.

After the phase control system is closed, when the scanning of the head 2a is in phase with respect to the locus of FIG. 3A, that is, the desired variable speed reproduction track, the track number error detecting means is used. An error signal Tn for positive track pull-in shown in FIG. 4 is output from 20 and is supplied to the motor drive circuit 11 via the switching means 22, the phase control means 23, the switching circuit 16 and the adder 10. Therefore, the motor is accelerated, that is, the tape speed is accelerated, and the error of the head scanning track number is pulled in.

Conversely, when the scanning of the head 2a is deviated in the direction of B in FIG. 3 after the phase control system is closed, that is, when the phase is delayed with respect to the desired variable speed reproduction track. The track number error detecting means 20 outputs a negative error signal. As a result, the tape speed is decelerated and the head scanning phase is similarly pulled in to the variable speed reproduction track.

Next, when the scanning phase of the head 2a reaches within a predetermined range of the desired scanning phase, for example, within one track by the phase pull-in control by the track number error detecting means 20, the control means 18 controls the track number error detecting means 20. This is detected from the convergence state of the control signal Tn, and the control signal Vt for inverting the contact point of the switching means 22 from "L" to "H" for switching from w1 to w2 in the drawing is output. As a result, thereafter, the fine tracking control of block unit detection using the control signal Te by the tracking error detecting means 21 works, and the scanning of the head 2a accurately tracks the track center where the variable speed reproduction data is recorded. It will be done.

The embodiment of FIG. 1 has been described above.

In the above embodiment, the 9 × speed reproduction in the forward direction is taken as an example, but the present invention is not limited to this, and the variable speed reproduction in the reverse direction can be similarly developed. With respect to, it is possible to operate at an arbitrary speed as necessary.

Further, in FIG. 1, the track number error detecting means 20 is provided.
Also, an example in which the error detection operation by the tracking error detection means 21 is performed on one specific track has been shown, but the present invention is not limited to this. Tracking error detection may be performed.

Further, in FIG. 1, the structure in which the track number error detecting means 20 and the tracking error detecting means 21 are provided independently of each other is shown, but this is not particularly limited, and it is also possible to adopt a common structure. Is. That is, the tracking error detecting means 21 is independently provided, while the track number error detecting means 20 is capable of relatively rough detection, whereas the center of the desired scanning track is not affected by variations in head width. This is for performing extremely fine tracking error detection, and it is of course possible to share the function of the tracking error detection means 21 with the track number error detection means 20 within the range where this constraint is allowed. Is.

FIG. 7 is a block diagram showing an embodiment of another tracking control device according to the present invention. In the figure,
Reference numeral 26 is a damping coefficient control means, and the other parts denoted by the same reference numerals as those in FIG. 1 indicate the same parts, and their operations are also the same.

In the embodiment shown in FIG. 7, the tracking control means 1 is used.
Only in the track number error pull-in control process by 9
The damping coefficient control means 26 weakens the damping of the speed control to increase the maximum speed of the capstan motor, speed up the phase pull-in response, and speeds up access to the variable speed reproduction track.

In a control system that uses both speed control and phase control, the response of the phase pull-in becomes slower as the damping coefficient of the speed control, that is, the sensitivity ratio of the speed control system to the phase control system becomes larger, and conversely the sensitivity ratio becomes smaller. That is, the smaller the damping coefficient, the faster the response. Therefore,
Although it is sufficient to set the damping coefficient small in order to accelerate the phase pull-in, considering the stability of the control system during normal phase control (tracking control), the damping coefficient cannot be uniquely reduced.

In consideration of the stability of the control system, the damping coefficient is generally set to a value of about 1 to 2, so that the response of the phase pull-in is naturally restricted.

However, the stability of the control system is not particularly required in the process of introducing the error in the number of tracks, and the damping coefficient can be reduced only in this process.

In view of this point, the embodiment of FIG. 7 does not require stability of the control system in the track number error pull-in process, and therefore damping is weakened to speed up access.

Although not described in detail, the damping coefficient control means 26 sets the damping coefficient of the speed control system to a second predetermined value during normal reproduction (including variable speed reproduction) and a second predetermined value smaller than the second predetermined value. For example, the gain switching circuit is configured to switch to a predetermined value of 1, and the gain is switched by the control signals C2 and Vt from the control means 18.

With this structure, as described in the embodiment of FIG. 1, when the tape speed reaches a predetermined variable speed reproduction speed by the control of the high speed traveling control means 9, the control means 1
The identification control signal C2 is output from 8 and input to the damping coefficient control means 26.

Upon receiving C2, the damping coefficient control means 26 sets the gain to the first value smaller than the second value during the normal reproduction.
Works to switch to the value of. As a result, the control sensitivity of the speed control system is weakened during the pull-in control operation to the desired scanning track phase by the track number error detection means 20 of the tracking error detection means 19. That is, the control sensitivity of the phase control system becomes relatively strong, which causes the capstan mode
The maximum speed of the data is increased and the phase response is accelerated.

Next, when the scanning phase of the head 2a reaches within a predetermined range of the desired scanning phase, that is, within one track described in the embodiment of FIG. 1, by the phase pull-in control by the track number error detecting means 20, the control means. The identification control signal Vt is output from 18, and the damping coefficient control means 26 is output.
When this signal is received, acts again to switch the gain from the first small value to the second value during normal reproduction. As a result, when the tracking control operation by the tracking error detection means 21 of the tracking control means 19 shifts, the damping coefficient of the speed control system corresponds to that at the time of normal reproduction.
Is held at a regular value, and thereafter, the tracking operation is performed in a state where the stability of the control system is ensured.

The embodiment of FIG. 7 has been described above.

FIG. 7 shows a configuration in which the damping coefficient control means 26 is arranged in the speed control path, but this is not particularly limited, and it is arranged in, for example, the phase control system path and the track number pull-in control process. Sometimes, the control sensitivity of the phase control system may be relatively high. Further, since the switching of the damping coefficient may be performed before the transition to the tracking control, it is not particularly limited to the time when it converges within one track as described above, and the switching is also limited to once. It is also possible to carry out stepwise a plurality of times without depending on the pull-in convergence of the number of tracks, and it is easy to make various modifications without departing from the spirit of the present invention.

[0082]

As described above, according to the present invention,
The control signal is used for the tracking control signal,
In the variable speed reproduction tracking control of the magnetic tape in which the digital image data dedicated to the variable speed reproduction of the arbitrary speed faster than the normal reproduction is dispersed and independently recorded at each track position according to the scanning locus of the rotary magnetic head. , The tracking error is detected based on the sub-information signal of the track number and the block number, and the phase pull-in control to the desired scanning phase is performed, and the tracking error is detected based on the sub-information signal of the track number and the block number. Since the tracking control of the head is performed by using the head, stable and highly accurate variable speed reproduction tracking can be realized without using the control signal.

Since no control signal is used,
It is possible to provide a stable and simple tracking control device without the need for the tracking correction means that was indispensable for the compatibility reproduction due to the variation in the mounting position of the control head as in the prior art.

Further, according to the present invention, in the process of pulling in the phase to the variable speed reproduction track, the damping coefficient of the speed control is controlled to be switched to a small value, so that the access speed can be increased and the operability and the reproduced image A tracking control device capable of improving quality can be realized.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a tracking control device according to the present invention.

FIG. 2 is a block diagram showing a specific configuration example of a track number error detection means 20 in the tracking control means 19.

FIG. 3 is a diagram for explaining the operation of the track number error detection means 20 of FIG.

FIG. 4 is a diagram showing characteristics of an output signal of the track number error detection means 20 of FIG.

FIG. 5 is a block diagram showing a specific configuration example of a tracking error detection means 21 in the tracking control means 19.

FIG. 6 is a diagram for explaining the operation of the tracking error detection means 21 in FIG.

FIG. 7 is a block diagram showing an embodiment of another tracking control device according to the present invention.

FIG. 8 is a diagram showing a recording pattern of a magnetic tape according to the present invention.

[Explanation of symbols]

1 ... Rotating drum, 2a, 2b ... Rotating magnetic head, 3 ... Magnetic tape, 5 ... Capstan, 7 ... Capstan mode
, 9 ... High-speed traveling control means, 18 ... Control means, 19 ... Tracking control means, 20 ... Track number error detection means,
21 ... Tracking error detection means, 22 ... Switching means, 23 ... Phase control means, 24 ... Digital image reproduction signal processing means, 26 ... Damping coefficient control means

Claims (3)

[Claims] 1. A helical scan system having a rotary magnetic head, wherein a control signal is used for tracking control, each track on a tape is divided into a plurality of data blocks, and each block is divided into a plurality of blocks. The digitized image information signal for normal reproduction and sub-signals for identification information such as track number and block number are recorded, and digital image information for variable speed reproduction at an arbitrary speed faster than normal reproduction is recorded in the rotary magnetic head. A tracking control device for reproducing magnetic tape recorded in a distributed manner at each track position according to a scanning locus, the high-speed traveling control means for traveling the magnetic tape at a speed higher than a normal reproduction speed. A digital image reproduction signal processing means for restoring the image information and the sub information signal from the signal reproduced by the rotary magnetic head; When the tape is run at a high speed by the high speed running control means, the deviation of the rotary magnetic head from the desired scanning track phase is detected on the basis of the sub information signal reproduced by the digital image reproduction signal processing means to control the track pull-in. Tracking control means for performing tracking control of the rotary magnetic head by detecting a tracking error with respect to the center of the desired scanning track based on the sub-information signal, control means for controlling the high speed traveling control means, and the tracking control means. In a variable speed reproduction operation at an arbitrary speed higher than the normal reproduction speed, the tracking control means is brought into an operating state after the speed of the magnetic tape is raised to a predetermined value by the high speed traveling control means, Based on the reproduced sub-information signal, the phase pull-in control for the desired scanning track of the rotary magnetic head is performed. And tracking control apparatus being characterized in that to perform the Torakingu control. 2. The tracking control means detects a deviation of the rotary magnetic head from a desired scanning track phase on the basis of the sub information signal reproduced by the digital image reproduction signal processing means, and determines the deviation direction according to the deviation direction. The deviation of the rotary magnetic head from the desired scanning track center is determined based on the track number error detection means for outputting an error signal having a polarity and in accordance with the deviation amount, and the sub information signal reproduced by the digital image reproduction signal processing means. Tracking error detection means for detecting and outputting an error signal having a polarity according to the direction of deviation and an error signal according to the deviation amount, and the output of the track number error detection means and the tracking error detection means controlled by the control means. Switching means for switching and outputting, and a position for controlling the scanning phase of the rotary magnetic head based on the output of the switching means. Phase control means, in the variable speed reproduction operation, after the speed of the magnetic tape is raised to a predetermined value by the high speed running control means, the above-mentioned error signal from the track number error detection means The pulling control of the rotary magnetic head to the desired scanning track phase is performed, and after the scanning phase reaches within the predetermined range of the desired phase, the switching means is controlled to perform tracking based on the error signal of the tracking error detecting means. A tracking control device characterized by being performed. 3. The variable speed reproduction operation according to claim 1, further comprising damping coefficient control means which is controlled by the control means and controls a speed damping coefficient when the tape traveling speed is controlled by the high speed traveling control means. , The damping coefficient reaches a first predetermined value until the scanning phase of the rotary magnetic head by the tracking control means reaches a predetermined range of the desired phase, and thereafter, the damping coefficient reaches a first predetermined value. Is controlled to be switched to a second predetermined value larger than the first value.