JP3336809B2 - Tracking control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital video signal for recording and reproducing digital video signals using a rotating magnetic head.
The present invention relates to a TR, and more particularly to a tracking control method at the time of variable speed reproduction for reproducing at an arbitrary speed higher than a normal reproduction speed.

[0002]

2. Description of the Related Art Recent advances in digital technology have been remarkable.
Digitalization of video signals is also progressing in the field of broadcasting and communication, and digital broadcasting is being put to practical use in the United States and other countries.

[0003] Under such circumstances, development of digital VTRs has been carried out in various places. For example, a method of recording and reproducing digital moving image data using a so-called analog VHS (registered trademark) type VTR widely used as a home VTR has been attempted.

[0004] When digitizing a moving image, an image compression technique is used because the amount of information becomes enormous.

As a typical image compression technique, there is the well-known Moving Picture Experts Group (MPEG) method. However, many image compression techniques such as the MPEG method require a high compression ratio without deteriorating the image quality. To realize,
A method of encoding and compressing only the difference between frames using frame correlation (motion-compensated prediction compression) is used.
Data reduction.

[0006] However, even with the above-mentioned compressed digital image data, the data is smaller than in conventional analog recording.
The data amount is very large, and when recording on a tape by helical scanning, even one frame of image data extends over several tracks. For this reason, in high-speed reproduction (variable-speed reproduction), reproduction data does not become continuous frames, and frames in which motion compensation prediction compression is performed from the preceding and following images cannot be reproduced (restored). Therefore, there is a disadvantage that the variable speed reproduction cannot be performed simply by increasing the tape speed as in the conventional analog recording.

In view of the above drawbacks, as a method of utilizing image compression by the MPEG system 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). This method preliminarily sets the tape speed of variable speed playback so that image data can be restored even at variable speed playback. 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 an example (an example corresponding to 3 × speed and 9 × speed variable speed reproduction in the forward direction).

In FIG. 8, 3 is a magnetic tape, 60 and 61.
Are the scanning trajectories of a magnetic head having a positive azimuth angle and a negative azimuth angle during normal reproduction, 62 and 63 are the scanning trajectories of the positive azimuth angle and the negative azimuth angle head at 3 × speed reproduction, and 64 and 65 are 9 × speed, respectively. The scanning trajectories of the positive azimuth angle and the negative azimuth angle head during reproduction, the blank area of 66 is the area where the image data for normal reproduction is recorded, the shaded area of 67 is triple speed reproduction, and the shading of 68 Is a region where image data for 9 × speed reproduction is recorded, and data 67 and 68 are recorded independently for both the positive azimuth angle and the negative azimuth angle head. Is shown. 69 is a conventional analog V
Like the HS / VTR, this is a control track on which a control signal is recorded as a signal for tracking control. Since the VTR is of the helical scan type, the actual track is recorded diagonally on the tape 3 as is well known. However, in FIG. 8, the tape is recorded in order to make the recording pattern easy to see. Expressed linearly in the width direction.

As is apparent from FIG. 8, according to the recording method, the heads having the positive azimuth angle and the negative azimuth angle scan the trajectories 62 and 63, or 64 and 65, respectively, to obtain the positive and negative azimuth tracks. Image data of
The data can be reproduced from the groups 67 and 68, and high-speed reproduction at 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 matching the head scanning trajectory, a transition from the normal reproduction state to variable speed reproduction is performed, or When the speed is changed in the playback state, the rotating magnetic head naturally causes the image data to be read.
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 in accordance with the speed ratio of the variable speed reproduction, and the divided signal and the phase reference are compared. It was sufficient to perform control only by comparing the phase with the reference signal, but in this recording method, since the recording track of the image data was specified, the control signal was simply divided and the phase comparison signal was obtained. Such a conventional technique cannot be applied. In other words, in the variable speed reproduction operation, a tracking control method that does not use a control signal is indispensable. And the method is
It is necessary to consider the compatible playback of the tape.

The second problem is a high-speed access considering operability. Considering access to a variable-speed reproduction track as shown in FIG. 8, it is the track pull-in control that determines the access time. Assuming that the variable speed reproduction speed is n, phase pull-in of a maximum of ± n tracks is required. Naturally, the longer the variable speed reproduction speed n is set, the longer the time required for the phase pull-in becomes. Until the scanning phase of the rotary magnetic head scans a desired track, the image data for variable speed reproduction is not reproduced. During this time, the reproduced image is interrupted.
It is desired that this time be reduced as much as possible in consideration of the operability and the quality of the reproduced image.

However, no solution to these problems has been considered or disclosed in the prior art.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to enable the scanning phase of a rotary magnetic head to be drawn into a variable-speed reproduction track without using a control signal, and to accurately track the variable-speed reproduction track. It is another object of the present invention to provide a tracking control device capable of realizing high-speed pulling into a variable-speed reproduction track.

[0016]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a high speed running control means for running a magnetic tape at a speed higher than a normal reproducing speed, and image information from a signal reproduced by a rotating magnetic head. Digital image reproduction signal processing means for restoring the sub information signal, and the rotary magnetic head based on the sub information signal reproduced by the digital image reproduction signal processing means when the tape runs at high speed by the high speed traveling control means. desired scanning and tracking control means for detecting and pull-in control of the track deviation for the track phase, when the tape running speed control by the high-speed running control means
Damping coefficient control means for controlling speed damping coefficient
The high-speed traveling control means, the tracking control means, and
And control means for controlling the damping coefficient control means. In a variable speed reproduction operation at a speed higher than the normal reproduction speed, the phase of the rotary magnetic head to a desired scanning track is determined based on the reproduced sub-information signal. When retraction control is performed ,
In addition, the tracking control means controls the rotation of the rotating magnetic head.
To change the damping coefficient according to the scanning phase
I did .

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

[0018]

In the variable speed reproducing operation, the high speed running control means performs a tape drive so as to drive the magnetic tape to a predetermined speed in accordance with a command from the control means.
Control 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 restored and output by the digital image reproduction signal processing means, and determines the reference track number and the block corresponding to the desired scanning phase. A comparison with the number is performed, an error signal corresponding to the comparison error is generated, and the tracking control is performed based on the error signal. That is, using only the sub-information signal reproduced by the digital image reproduction signal processing means, a deviation from the desired scanning track phase of the rotary magnetic head is detected, and an error corresponding to the polarity according to the direction of the deviation and according to the number of track deviations. A signal is generated to perform the pull-in control of the track scanning phase, and after the head scanning phase reaches within a predetermined range of the desired phase, a deviation from the center of the desired scanning track of the rotating magnetic head is detected, and according to the direction of the deviation. 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 in accordance with the shift amount.

With such a configuration, in the variable speed reproducing operation, after the speed of the magnetic tape is raised to a predetermined value by the high speed running control means, the tracking control means is led to the operating state and reproduced by head scanning. Based on the sub information signal, phase pull-in control and tracking control of a rotating magnetic head to a desired scanning track are performed.

The damping coefficient control means controls the damping coefficient to a first predetermined value and the predetermined phase to a predetermined value 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 serves to switch to a second predetermined value that is greater than the first.

Thus, in the process of pulling in the track number error, the damping effect of the speed control can be weakened, and the maximum speed of the capstan motor is increased to pull in the phase, that is, to speed up the pull-in response to the variable speed reproduction track. ,
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 rotating drum, 2a and 2b are a pair of rotating magnetic heads mounted on the rotating drum and having opposite azimuth angles, where 2a has a positive azimuth angle and 2b has a negative azimuth angle. And Reference numeral 3 denotes a magnetic tape, 4 denotes a control head for recording and reproducing a control signal, 5 denotes a capstan for driving the tape, 6 denotes a pinch roller, and 7 denotes a capstan model for controlling the rotation of the capstan 5. -Ta,
8 is an FG (tachogenerator) for generating 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 high speed and running the tape at high speed, 10 is an adder, 11 Is a motor drive circuit, 1
Numeral 2 denotes an amplifier for amplifying the reproduced signal from the control head 4, 13 and 14 denote amplifiers for amplifying the reproduced signal from the rotary magnetic heads 2a and 2b, respectively, and 15 denotes 13 and 1 respectively.
4 is a changeover switch for switching the reproduction signal, 16 is a changeover circuit, and 17 is a C for performing tracking control during normal reproduction.
TL tracking control circuit, 18 is a control means, 19 is a track number error detection means 20, a tracking error detection means 21, a tracking control means composed of a switching means 22 and a phase control means 23, 24 is main information such as an image and a sound. A digital image reproduction signal processing means for reproducing sub information signals such as a track number and a block number, and 25 is an output terminal.

The basic principle of the drum rotation control and the tracking control during normal reproduction in the embodiment of FIG. 1 is not different from the conventional analog VHS / VTR. That is, the rotation speed of the drum is controlled to 1800 rpm (30 Hz) by speed and phase control using an FG signal and a tack pulse (both not shown), and the rotation phase is controlled with respect to the reference signal (30 Hz). It is controlled so as to have a predetermined phase. This control is the same for recording and reproducing signals. At the time of recording, the reference signal used for the drum rotation phase control is recorded as it is on the control track on the tape by the control head 4, and at the time of reproduction, the CTL tracking control circuit 1 is used.
7, the reproduction timing of this control signal and 3
By performing phase comparison control with a 0 Hz reference signal,
The tracking operation is performed so that the head scans the recording track correctly. This control method and the like are conventionally well-known in analog VHS / VTR.

The recording pattern of the digital VTR tape thus recorded according to the present invention is also shown in FIG.
Is the same as that shown in FIG. The details of the recording method are omitted because they are not directly related to the gist of the present invention, but a dedicated image signal corresponding to variable speed reproduction is recorded in a track in accordance with a predetermined format together with a compressed image signal for normal reproduction. .

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

The recording track is azimuth recording by two heads 2a and 2b facing each other by 180 °. The head 2a having a positive azimuth angle causes a + azimuth track in FIG. 8 to be recorded, and the head 2b having a negative azimuth angle results in a -azimuth recording. Tracks are sequentially recorded.

In the case of variable speed reproduction (forward) at 9 × speed and 3 × speed, as shown in FIG. 8, data for 9 × speed reproduction is a + azimuth track on the scanning locus 64 of the head 2a. Also, data groups 67 are recorded on the azimuth track 65 on the scanning trajectory of the head 2b on the azimuth track 65, and the data group 67 for triple speed reproduction is also on the scanning trajectory 62 of the head 2a and the scanning trajectory 63 of the head 2b. Respectively.

The track number is added in correspondence with, for example, the number of scanning tracks per one rotation of the drum in variable speed reproduction. In FIG. 8, the track number corresponds to the maximum speed of 9 times. The scanning start track (based on the start of scanning of the head 2a) is numbered 0, and the repetition numbers 0 to 17 are assigned. In triple-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 also 6 and 12.

The operation of each unit in FIG. 1 will be described below.

When the control means 18 receives the variable speed reproduction speed command input S selected and specified by the user, the control signal C for controlling the high speed traveling control means 9 and the switching circuit 16 is provided.
And outputs the designated speed information value n for variable speed reproduction to the tracking control means 19. Further, the tape running 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 running control means 9 is controlled.
And outputs a control signal C2 for controlling the switching circuit 16 again. When the scanning phase of the head reaches a predetermined range of the desired phase under the control of the tracking control means 19, for example, the track number error detecting means This is detected from the 20 control error signals Tn, and a control signal Vt for inverting the switching means 22 from “L” to “H” is output.

The high-speed running control means 9 controls the rotation speed of the capstan motor 7 so that the tape 3 runs at a predetermined speed in response to the control command signal C1 from the control means 18. Is constructed, for example, by also using a speed servo means for normal reproduction, and performing speed servo using a capstan FG divided according to the speed ratio during variable speed reproduction.

The switching circuit 16 switches between a tracking control signal at the time of normal reproduction and a tracking control signal at the time of variable speed reproduction.
, The contact becomes b in the figure, and the contact becomes c by the control signal C2.
Work to close.

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

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

FIG. 2 is a block diagram showing a specific configuration example of the track number error detecting means 20. In the figure, 31 is a track number detection circuit, 32 is a block number detection circuit, 3
Reference numeral 3 denotes a scanning track number error calculating circuit, and reference numeral 34 denotes an error signal generating circuit.

The sub information signal Ds reproduced from the digital image reproduction signal processing means 24 is supplied to the track number detection circuit 3
1 and are input to the block number detection circuit 32. The track number detection circuit 31 detects a track number added to each block from the Ds signal, and supplies the track number error calculation circuit 33 with the track number. Further, the block number detection circuit 32 detects a block number added to each block of the Ds signal, and supplies the block number to the scanning track number error calculation circuit 33. The scanning track number error calculation circuit 33 calculates an 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. I do.

Hereinafter, this operation will be described with reference to the example of the 9 × speed (forward) variable speed reproduction shown in FIG. In FIG. 3, the components denoted by the same reference numerals as those in FIG. 8 indicate the same components.

At the time of 9-times speed reproduction, the rotating magnetic head 2a reproduces data across nine tracks in one scan. For example, assuming that one track is composed of 96 blocks from No. 0 to No. 95, data is reproduced over eight tracks, about 12 blocks per track. Therefore, when the track number is specified,
By detecting the block number reproduced in this track and comparing it with a reference value, an error in the number of scanning tracks with respect to a desired scanning phase can be obtained.

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

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

The scanning track number error calculating circuit 33 calculates (48-18) / 12 based on the result to obtain +2.5, which is used as an error signal generating circuit 34 as a scanning track number error with respect to a desired scanning phase 64. Output to Here, the fact that the scanning track number error has a positive polarity means that the scanning phase of the rotary magnetic head 2a is ahead of the desired scanning phase 64 as shown in FIG. Further, as the scanning phase of the head 2a shifts in the direction A in the figure, the value of M increases, so that the scanning track number error naturally increases.

On the other hand, the scanning phase of the rotating magnetic head 2a is
There is a case where the desired scanning phase 64 is shifted to the right side in the figure, not necessarily as shown in FIG. For a track scanning deviation in the B direction, the scanning track number error calculating circuit 33 is configured to specify, for example, the track number 6 and perform the calculation.

For example, assuming that the scanning of the rotary magnetic head 2a is as shown in B in the figure, the reference block number 66 to be reproduced on this track by the head 2a when the track number is specified to 6 is: Since the head of the block number reproduced in the scanning of B is 36, the scanning track number error calculating circuit 33 calculates (36−66) / 12 based on this to obtain −2.5. Here, the fact that the scanning track number error has a negative polarity means that the scanning phase of the rotating magnetic head 2a is delayed from the desired scanning phase 64 as shown in FIG. Further, as the scanning phase of the head 2a shifts in the direction B in the drawing, the value of M becomes smaller, so that the scanning track number error naturally increases.

The error signal generating circuit 34 generates an error signal Tn having the characteristics shown in FIG. 4 according to the result of the scanning track number error calculation from the scanning track number error calculating circuit 33. That is, when the scanning phase of the head 2a is shifted in the direction A with respect to the desired scanning phase 64 as shown in FIG. 3, an error signal having a positive polarity and a level corresponding to the amount of track number shift is inverted. If there is a shift in the B direction, an error signal of 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 track number and block number sub-information signals reproduced by the digital image reproducing signal processing means 24.
An error signal for tracking control having a polarity according to the direction of the shift and a level according to the shift amount is generated.

FIG. 5 is a block diagram showing one specific configuration example of the tracking error detecting means 21. As shown in FIG. In the figure, 35 is a block number detection circuit, 36 is a specific track number detection circuit, 37 is a block error calculation circuit, and 38 is an error signal generation circuit.

The sub information signal Ds reproduced from the digital image reproduction signal processing means 24 is supplied to the block number detection 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 the block number to the block error calculation circuit 37. Further, the specific track number detection circuit 36 detects a specific track number from the track number added to each block of the Ds signal and supplies it to the block error calculation circuit 37. Block error calculation circuit 37
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, the reproduction block number at the specific track number scanned by the rotary magnetic head is determined with respect to the center of the desired scanning track. The shift amount is detected.

Hereinafter, this operation will be described with reference to 9-times variable speed reproduction.

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

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

On the other hand, if the tracking of the head 2a shifts in the direction of A or B in the figure, the reproduced block number shifts up and down. That is, the block number to be reproduced is shifted from 20 to 31 in tracking in the direction A, for example, as shown by a thin solid line in the figure. On the other hand, when the reproduction block number shifts in the direction B and the tracking state as shown by the broken line in the figure is reached, the reproduction block number is shifted downward from 16 to 27.

For example, if the track number is specified to be 2 by the specific track number detecting circuit 36, the block error calculating circuit 37 calculates the block number with respect to the reference value based on the maximum and minimum values of the block number reproduced in this track. Calculate the deviation of the average block number. That is, for the average block number 23.5 (the center value of 18 and 29) as a reference, the average block number 25.5 (2
(Center value of 0 and 31) and outputs +2 as an error with respect to the reference value. Conversely, in the scanning of B, 21.5 (the center value of 16 and 27) is calculated as the average block number, and -2 is calculated and output as the error with respect to the reference value.

The error signal generation circuit 38 responds to the block error calculation result from the block error calculation circuit 37,
An error signal Te having the same characteristic as that shown in FIG. 4 is generated. That is, when the scanning phase of the head 2a is shifted in the direction A from the desired scanning phase 64 as shown in FIG. 6, an error signal having a positive polarity and a level corresponding to the block shift amount is conversely output to B. If there is a shift in the direction, an error signal having a negative polarity and a level corresponding to the block shift amount is output as a tracking control signal. This control signal is a very detailed signal in block units. That is, in the 9 × speed reproduction, a signal of 96 blocks is reproduced over eight tracks, so that detection in units of one block corresponds to a resolution of about 0.1 (8/96) in terms of a 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 of the head 2a to the 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. Perform 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 head scanning phase, and conversely, the negative error signal is used. In some cases, phase control is performed so that the tape speed is reduced and the scanning phase of the head is relatively advanced.

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

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

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

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

Next, when the tape speed reaches a predetermined nine-times speed, 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 running control means 9 and switches the tape. The control signal C2 is issued again so that the contact point of the circuit 16 is switched from b to c in the drawing, that is, the output of the tracking control means 19 is supplied to the adder 10. As a result, when the tape speed reaches the ninth speed, the phase control system by the tracking control means 19 is closed, and the phase control is led to the operating state. At this time, the contact point of the switching means 22 is closed on the w1 side in the drawing.

At the moment when the phase control system is closed, the head 2a
The scanning trajectory (as well as the head 2b) does not always scan the recording track of the 9 × speed reproduction data, and for example, a desired scanning trajectory like the trajectory A or B in FIG. Is out of alignment.

After the phase control system is closed, when the scanning of the head 2a is advanced in the trajectory A of FIG. 3, that is, when the phase is advanced with respect to the desired variable speed reproduction track, the above-mentioned track number error detecting means is used. 4 outputs the error signal Tn for pulling in the positive track shown in FIG. 4 and supplies it to the motor drive circuit 11 via the switching means 22, the phase control means 23, the switching circuit 16 and the adder 10. As a result, the motor is accelerated, that is, the tape speed is accelerated, and the head scanning track number error is drawn.

Conversely, when the scanning of the head 2a is shifted 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 an error signal of negative polarity. As a result, the tape speed is controlled to be reduced, and similarly, the pull-in control of the head scanning phase to the variable-speed reproduction track is performed.

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 a control signal Vt for inverting the contact of the switching means 22 from w1 to w2 in the figure from “L” to “H” is output. As a result, very fine tracking control of block unit detection using the control signal Te by the tracking error detecting means 21 operates, and the scanning of the head 2a accurately tracks the center of the track on which the variable speed reproduction data is recorded. Will do.

The embodiment of FIG. 1 has been described above.

In the above-described embodiment, the 9-times speed reproduction in the forward direction is taken as an example. However, this is not particularly limited, and the same applies to variable speed reproduction in the reverse direction. Can also be operated at any speed as required.

In FIG. 1, the track number error detecting means 20 is used.
Also, an example in which the error detection operation by the tracking error detection unit 21 is performed in one specific track has been described, but this is not a limitation, and the track number error detection and the Tracking error detection may be performed.

Further, FIG. 1 shows a configuration in which the track number error detecting means 20 and the tracking error detecting means 21 are provided independently of each other. However, this is not particularly limited, and a common configuration is also possible. It is. That is, the tracking error detecting means 21 is provided independently because the track number error detecting means 20 can perform relatively rough detection, whereas the tracking error detecting means 21 can be located at a desired scanning track center without being affected by variations in the head width. This is for the purpose of detecting a very fine tracking error, and in the range where this restriction is allowed, for example, the function of the tracking error detecting means 21 may be provided to the track number error detecting means 20 and shared. It is.

FIG. 7 is a block diagram showing an embodiment of another tracking control device according to the present invention. In the figure,
Numeral 26 denotes damping coefficient control means, and the elements denoted by the same reference numerals as those in FIG. 1 indicate the same elements, and the operation is also the same.

The embodiment shown in FIG.
9 only in the track number error pull-in control process by
The damping coefficient control means 26 reduces the damping of the speed control to increase the maximum speed of the capstan motor, speeds up the phase pull-in response, and speeds up access to the variable speed reproduction track.

In a control system using both speed control and phase control, as the damping coefficient of the speed control, that is, the sensitivity ratio of the speed control system to the phase control system increases, the response of the phase pull-in becomes slower, and conversely, the sensitivity ratio decreases. That is, the smaller the damping coefficient, the faster the response. Therefore,
To speed up the phase pull-in, it is sufficient to set the damping coefficient small. However, considering the stability of the control system during the 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 or 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 pulling in the track number error, and the damping coefficient can be reduced only in this process.

In view of this point, the embodiment of FIG. 7 does not require the stability of the control system in the process of pulling in the track number error, and therefore speeds up the access by weakening the damping.

Although the details are omitted, 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. The gain is switched by a control signal C2 and Vt from the control means 18, for example, by a gain switching circuit or the like so as to switch to the predetermined value of 1.

When the tape speed reaches a predetermined variable-speed reproduction speed under the control of the high-speed running control means 9 as described in the embodiment of FIG.
8, an identification control signal C2 is output and input to the damping coefficient control means 26.

Upon receiving C2, the damping coefficient control means 26 sets the first gain smaller than the second value during normal reproduction.
Works to switch to the value of. As a result, the control sensitivity of the speed control system is reduced during the pull-in control operation to the desired scanning track phase by the track number error detecting means 20 of the tracking error detecting means 19. In other words, the control sensitivity of the phase control system becomes relatively strong, so that the capstan
The maximum speed of the data is increased and the phase response is faster.

Next, when the scanning phase of the head 2a reaches a predetermined range of the desired scanning phase, that is, within one track described in the embodiment of FIG. The identification control signal Vt is output from the damping coefficient control means 26.
Receiving this signal, the signal acts to switch the gain again from the first small value to the second value during normal reproduction. Thus, at the time of transition to the tracking control operation by the tracking error detecting means 21 of the tracking control means 19, the damping coefficient of the speed control system is set to the second value corresponding to the normal reproduction.
, 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 on the speed control path. However, this is not particularly limited. At times, the control sensitivity of the phase control system may be relatively increased. Further, since the switching of the damping coefficient only needs to be performed before shifting to the tracking control, it is not necessary to limit the switching to the point in time within one track as described above, and the switching is also limited to one time. It is also possible to carry out stepwise a plurality of times in accordance with the convergence of the pull-in of the number of tracks without any modification, and it is easy to make various modifications without changing the gist of the present invention.

[0082]

As described above, according to the present invention,
A control signal is used as a tracking control signal,
In variable speed reproduction tracking control of magnetic tape in which digital image data dedicated to variable speed reproduction at an arbitrary speed higher than normal reproduction is dispersedly recorded at each track position according to the scanning locus of the rotating magnetic head and independently recorded. Detecting an error in the number of scanning tracks based on the sub-information signal of the track number and the block number, performing phase pull-in control to a desired scanning phase, and detecting a tracking error based on the sub-information signal of the track number and the block number. Since the head tracking control is performed by using the control signal, stable and high-precision variable-speed reproduction tracking can be realized without using a 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 which is indispensable for compatible reproduction due to the variation in the mounting position of the control head as in the related art.

Further, according to the present invention, in the process of pulling the phase into 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 can be sped up, the operability and the reproduction image can be reproduced. A tracking control device capable of improving quality can be realized.

[Brief description of the 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 detecting means 20 in the tracking control means 19;

FIG. 3 is a diagram for explaining the operation of the track number error detecting means 20 of FIG. 2;

FIG. 4 is a diagram showing characteristics of an output signal of a track number error detecting means 20 of FIG. 2;

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

FIG. 6 is a diagram for explaining the operation of the tracking error detecting means 21 of 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]

DESCRIPTION OF SYMBOLS 1 ... Rotary drum, 2a, 2b ... Rotary magnetic head, 3 ... Magnetic tape, 5 ... Capstan, 7 ... Capstan model
9, 9: high-speed traveling control means, 18: control means, 19: tracking control means, 20: track number error detection means,
21 tracking error detecting means, 22 switching means, 23 phase control means, 24 digital image reproduction signal processing means, 26 damping coefficient control means

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G11B 15/467 H04N 5/92

Claims (2)

(57) [Claims] 1. A is a helical scan type having a rotary magnetic head, tape - each track a plurality of data of the flop - ordinary image information signal for reproduction digitized in each block is divided into data blocks and A sub information signal for identification information such as a track number and a block number is recorded,
A tracking control device for reproducing a magnetic tape in which digital image information for variable speed reproduction at a speed higher than normal reproduction is dispersedly recorded at respective track positions according to a scanning locus of a rotating magnetic head, High-speed running control means for running the magnetic tape at a speed higher than the normal reproducing speed; digital image reproduction signal processing means for restoring the image information and sub-information signals from signals reproduced by the rotating magnetic head; At the time of tape high-speed running by the high-speed running control means, a deviation from a desired scanning track phase of the rotary magnetic head is detected based on the sub-information signal reproduced by the digital image reproduction signal processing means, thereby controlling track retraction. Tracking control means for performing the tape running speed control by the high speed running control means.
Damping coefficient control means for controlling the degree damping coefficient
The high-speed traveling control means, the tracking control means, and the
Control means for controlling the damping coefficient control means , in a variable speed reproduction operation at a speed higher than the normal reproduction speed,
Co If based on the sub information signal reproduced performs phase pull-in control to a desired scanning tracks of the rotary magnetic head
The rotating magnetic head by the tracking control means is
A tracking control device for changing the damping coefficient according to a scanning phase of the scanning . 2. The tracking control device according to claim 1, wherein in the variable speed reproduction operation, the damping coefficient is set to a first value until the scanning phase of the rotating magnetic head by the tracking control means reaches a predetermined range. A damping coefficient is switched to a second predetermined value larger than the first value after reaching a predetermined value within a predetermined range.