JPS623576A - Tracking control device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Hereinafter, the present invention will be explained in the following order.

A. Industrial field of application B9 Summary of the invention C8 Prior art 0 Problems to be solved by the invention E0 Means for solving the problems F3 Effects G. Examples G-1 Configuration G-2 Operation H. Effects of the Invention A, Industrial Application Field The present invention sequentially records a pilot signal whose frequency changes i-cyclically for each track, and when reproducing it, reproduces it from a track adjacent to the track to be tracked. A tracking control device that detects a signal component having a frequency that is the difference between the frequency of a reproduced pyro/soto signal and the frequency of a reference pilot signal, and obtains a tracking error signal of the head based on this signal component, For example, recording video signals using a rotating magnetic head device.
This is commonly used to perform tracking control in a so-called still playback operation mode such as frame advance playback, slow playback, or still playback in a so-called helical scan video tape recorder that performs playback.

B6 Summary of the Invention The present invention sequentially records a pilot signal whose frequency changes cyclically for each track, and when reproducing, the frequency and standard of the reproduced pilot signal reproduced from a track adjacent to the track that the head/nod is trying to track. In a tracking control device that detects a signal component having a frequency different from the frequency of a pilot signal and obtains a tracking error signal of the head based on this signal component, the tape speed error signal of the tape running control system and the above-mentioned tracking error signal are detected. By making it possible to control the mixing ratio with the tracking error signal,
When setting the still playback operation mode, tracking control is performed with the gain of the tracking error signal raised above, and then a certain amount of brake is applied at a certain timing to stop the tape running, resulting in extremely low noise. This allows a variable speed slow playback screen to be obtained.

C1 Prior Art In a so-called helical scan video tape recorder that uses a rotating magnetic head device to record and reproduce video signals, recordings are arranged on a magnetic tape at a predetermined angle of inclination with respect to the tape running direction. A video signal is sequentially recorded, for example, one field at a time, on a track, and a reproduced video signal is obtained by tracing the recorded track with a rotating magnetic head during reproduction. In addition to the normal playback operation in which video tape recorders perform playback at the regular tape running speed,
There has been provided a device having a function of variable speed playback operation in which the tape is run at a high or low speed different from the normal tape running speed and the playback operation is performed.

In the helical scan type video tape recorder as described above, a method for controlling the tracking of the rotating magnetic head with respect to the recording track on the magnetic tape is to provide a control track on the magnetic tape, and to set a control track on the magnetic tape at the position of the recording track of the video signal. The so-called CTL method is used to record the corresponding control signal and use the control signal to control the drive amount and timing of a capstan for driving tape running, the brake amount and its timing, and the control signal for each track of a video signal. A so-called A system in which a viroft signal whose frequency changes cyclically is superimposed on a video signal and recorded, and tracking control is performed using the pilot signal.
TF Houni et al. have been known for some time. The above-mentioned ATF type tracking control device is, for example, disclosed in Japanese Patent Application Laid-Open No. 59-659.
It is disclosed in Publication No. 62.

D8 Problems to be solved by the invention - C: Helical scan type video - y - 7" L/
With D-da, it is not possible to obtain a reproduced image of good quality due to tracking deviation during playback operation, and especially in the case of variable speed playback operation in which the tape is run at a speed other than the normal tape running speed, the rotating magnetic head Since tracing is performed over a plurality of recording tracks, the state of occurrence of noise on the playback screen changes depending on the state of tracking.

Therefore, in order to obtain a reproduction screen with less noise and good image quality in both normal reproduction operation and variable speed reproduction operation, it is necessary to perform tracking control according to each operating state.

By the way, the CTL type tracking control device described above is
In general, there are many adjustment points and the circuit scale is enormous, so if tracking control is performed according to each operating state as described above, a great deal of effort and time is required for manufacturing and adjustment.

In addition, in the above ATF type tracking control device, the C/N ratio of the reproduction output obtained from the rotating magnetic head affects the control characteristics, especially when the error output is digitized and used for control. There were problems such as when the required C/N ratio was not obtained, the desired A/D conversion output could not be obtained and control became uncontrollable, and the A/D conversion output was swayed by noise, causing hunting. .

Means for Solving the E0 Problem In order to solve the above-mentioned problem, the tracking control device according to the present invention sequentially records a pilot signal whose frequency changes cyclically for each track, and causes the head to track during playback. A signal component having a frequency that is the difference between the frequency of a reproduced pilot signal reproduced from a track adjacent to the target track and the frequency of a reference pilot signal is detected, and based on this signal component, the tracker/7king engineer of the head is The tracking control device configured to obtain the signal includes a control means for varying the mixing ratio of the tape speed error signal of the tape running control system and the above-mentioned tracking error signal, and a control means for controlling the mixing ratio of the tape speed error signal of the tape running control system and applying a fixed amount of brake at a certain timing to the above-mentioned tape running control system. 1. An l-racking control device comprising: a brake signal generating means for applying a brake signal.

F9 action In the tracking control device according to the present invention, the control means for varying the mixing ratio of the tape speed error signal of the tape running control system and the tracking error signal adjusts the mixing ratio of the tracking error signal when setting the still reciprocating operation mode. ° Increase the gain to speed up the tracking control response of the tape running control system. The brake signal generating means applies a predetermined amount of brake at a predetermined timing to stop tape running while the tape is trunked to a target track by the control means.

G. Embodiment Hereinafter, an embodiment of the tracking control device according to the present invention will be described in detail with reference to the drawings.

In the embodiments shown in FIGS. 1 to 6, the present invention is applied to a video tape recorder for so-called 8 mm video.

G-1 Configuration In the block diagram of FIG. 1 showing the configuration of the playback system of the video tape recorder of this embodiment, a magnetic tape I is wound in an Ω shape around the outer periphery of a rotating magnetic head device 2. It is held between a pinch roller 3 and a capstan shaft 4 disposed on the downstream side of the device 2, and the capstan shaft 4 is rotationally driven by a cabstan morph 5, so that it comes into sliding contact with the outer periphery of the rotating magnetic head device 2. A predetermined tape path is coded by a loading means (not shown) so that the tape can be run while moving. The running speed of the magnetic tape 1 is detected by a frequency generator 6 which outputs a frequency signal corresponding to the number of rotations of the capstan shaft 4.

In this embodiment, the rotating magnetic head device 2 includes three magnetic heads 8A on a head drum 7 rotated at a constant speed by a head drive motor (not shown).

8B and 8A' are arranged, and each of the above magnetic heads 8A
, 8B, 8A', the reproduction R obtained by sequentially tracing the recording track TR on the magnetic tape 1.
The F output is outputted via the rotary transformer 9.

Here, as schematically shown in FIG. 2, the magnetic tape 1 has four types of frequencies [l,
f2. f3. A pilot signal for controlling f- in a circular manner is recorded superimposed on the video signal. The frequencies f+, fz, f, +, f4 of the above pilot signals are l f, -fz l=l f3-f, l=Δfalf
z fy 1=lf+ fl −Δf
It is set to satisfy the first two relationships of b.

Of the 203 magnetic heads 8A, 8B, 8A' of the rotating magnetic head device, the first and second magnetic healds 8A, 8B arranged symmetrically have different azimuths of their respective magnetic gaps. Odd-numbered recording tracks TR+ and TR3 on the magnetic tape 1 are traced by the first magnetic head 8A, and even-numbered recording tracks TR2 and TR4 are traced by the second magnetic head 8B. It is used to perform normal recording and playback operations. Further, a second magnetic head 8A' disposed on one side of the second magnetic head 8B is connected to the first magnetic head 8A'.
It has a magnetic gap of the same azimuth as the magnetic head 8A, and traces odd-numbered recording tracks TR2, -1 on the magnetic tape 1 alternately with the first magnetic head 8A. , used to perform variable speed playback operations.

The reproduced RF output signal obtained by the rotary magnetic head device 2 is taken out from the rotary transformer 9 via the RF switch circuit 10, and is sent to the reproduced video signal processing circuit 12 and the error signal forming circuit via the preamplifier 11. 14.

Here, the RF switch circuit 10 includes a first switch IOA that switches between the second magnetic head 8B and the third magnetic head 8A', and the second or third switch selected by the first switch IOA. magnetic head 8B,
8A' and a second switch IOB that alternately selects the first magnetic head 8A. The first switch IOA is controlled by an operation mode designation signal that designates the operation mode of the video tape recorder of this embodiment, and selects the second magnetic head 8B during normal playback operation, and selects the second magnetic head 8B during still playback operation mode. Third
The second switch 10B is configured to select the P magnetic head 8A'' whose level is inverted every 1/2 rotation in synchronization with the rotation of the rotary magnetic head device 2.
The switching operation is performed according to the G pulse.

The reproduced video signal processing circuit 12 includes the switch circuit 1
The reproduced RF output signal supplied through the output terminal 13 is subjected to predetermined signal processing to form a reproduced video signal, and this reproduced video signal is output from the reproduced output terminal 13.

Further, the error signal forming circuit 14 is supplied with a reference pilot signal from the reference pilot signal generation circuit 15, and generates a tracking error signal based on the reference pilot signal and the regenerated pilot signal included in the regenerated RF output signal. This error signal is supplied to the signal mixing circuit 17 via the gain switching circuit 16. The reference pilot signal generation circuit 15 is controlled by a pilot signal switching circuit 18 to which the operation mode designation signal and PG pulse are supplied, and generates reference pilot signals of the four predetermined frequencies f+, fz, fl+r4. The signals are sequentially supplied to the error signal forming circuit 14.

Here, the error signal forming circuit 14 used has a configuration as shown in FIG. 3, for example.

In FIG. 3, a first signal input terminal 101 is supplied with a regenerated RF output signal from the above-mentioned preamplifier 16, and a second signal output terminal 102 is supplied with a reference pilot signal from the reference pilot signal generator 19. A signal is provided. The regenerated RF output signal is sent from the first signal input terminal 101 to the multiplication circuit 10 via a low-pass filter 103 from which the regenerated pilot signal component contained in the signal is extracted.
4. °This multiplication circuit 104 includes the second
The reference pilot signal is supplied from the signal input terminal 102 of. The output of the multiplication circuit 104 is the first and second difference frequency Δfa, Δrb detection circuit 105,
106.

The first difference frequency Δfa detection circuit 105 detects the difference frequency Δfa included in the output of the multiplication circuit 104.
A first DC conversion circuit 1 extracts the frequency component fa.
Supply on 07. Further, the second difference frequency Δfb detection circuit 105 extracts the frequency component Δrb shown in the above-mentioned No. 2, which is included in the output of the multiplication circuit 104, and supplies it to the second DC conversion circuit 108. . Then, the DC level signals of the components of the first and second difference frequencies Δfa and Δfb obtained in each of the DC conversion circuits 107 and 108 are supplied to the subtraction circuit 109.

The output of this subtracting circuit 109 is supplied directly and via an inversion circuit 110 to a signal selection switch 111, and from the signal selection switch 111 is given to a signal output terminal 113 via a buffer amplifier 112. The signal selection switch 111 performs a selection operation in response to the above-mentioned RF pulse.

Further, the gain switching circuit 16 switches the gain of the tracking error signal obtained by the error signal forming circuit 14 and supplies it to the signal mixing circuit 17. For example, as shown in FIG.
01 and two resistors 202 and 203 having different resistance values, and between the signal input terminal 200 and the signal output terminal 204,
It is configured to be connected via the two resistors 202 and 203 selected by the switch 201. The changeover switch 201 is controlled by the operation mode designation signal described above, and selects the first resistor 202 having a large resistance value in the normal operation mode.
In still operation mode, a second resistor 20 with a small resistance value is used.
3 is to be selected. By the selection operation of the changeover switch 201, in the still operation mode, a tracking error signal having a larger gain than in the normal operation mode is supplied from the signal output terminal 204 to the signal mixing circuit 17.

Furthermore, the signal mixing circuit 17 includes a
A frequency/voltage converter 19 converts the output of a frequency generator 6, which generates a frequency signal corresponding to the number of rotations of a capstan motor 5 that drives a capstan shaft 4 that drives a capstan shaft 4, that is, the tape speed, into a voltage signal by a frequency/voltage converter 19. The resulting speed error signal is provided and is mixed with the tracking error signal. The output of this signal mixing circuit 17 is supplied to a capstan motor drive circuit 21 via a buffer amplifier 20.

Furthermore, each bias circuit 2 is connected to the capstan motor drive circuit 21 via a first mode switching circuit 22.
A DC drive bias voltage is supplied from 3.24, and a drive control signal specifying the drive and rotation direction of the capstan motor 21 is supplied from the timing control circuit 26 via the second mode switching circuit 25. There is. In this embodiment, a starting circuit 27 whose operation is controlled by the output of the frequency generator 6 is connected to the capstan motor drive circuit 21.

In the playback system of the video tape recorder of this embodiment, an operation mode designation signal for designating the playback system operation to the still playback operation mode is sent from the first control 1 input terminal 31 to the R input terminal 31.
The signal is supplied to the F switch circuit 10, the gain switching circuit 16, the pilot signal switching circuit 18, the first and second mode switching circuits 22 and 25, and the timing control circuit 26. Further, a PG pulse whose level is inverted every 1/2 rotation in synchronization with the rotation of the rotary magnetic head device 3 is supplied from the second control output terminal 32 to the RF Suinosen circuit 1.
0, the error signal forming circuit 14, the pilot signal switching circuit 18 and the timing control circuit 26.

G-2 Operation In the video tape recorder of the embodiment configured as described above, in normal normal playback operation, the tracking error signal obtained by the tracking error signal forming circuit 14 is lowered in gain by the gain switching circuit 16, and the gain is lowered by the gain switching circuit 16. The signal is supplied to the signal mixing circuit 17. The signal mixing circuit 17 feeds back the speed error signal supplied from the one frequency/voltage generator to the capstan motor drive circuit 21 as a main error signal.

The capstan motor 5 driven by the capstan motor drive circuit 21 is subjected to speed servo by the speed error signal supplied as the main error signal, and tracking servo is performed by the tracking error signal with the gain lowered. The magnetic tape 1 is run so that the recording track TR on the magnetic tape 1 is correctly traced by each of the magnetic heads 8A and 8B.

In the video tape recorder of this embodiment, in a still playback operation mode in which frame-by-frame playback, slow playback, still playback, etc. The first switch IOA of the circuit 10 selects the third magnetic head 8A', and the gain switching circuit 16 also selects the third magnetic head 8A'.
is controlled so as to increase the gain of the tracking error signal obtained by the tracking error forming circuit 14 and supply it to the signal mixing circuit 17. Then, the signal mixing circuit 17 feeds back the tracking error signal to the capstan motor drive circuit 21 as a main error signal. Further, the tracking error signal with the increased gain is supplied to the capstan motor drive circuit 21 as a main error signal, and then the tracking error signal with the increased gain is supplied as the main error signal.
A brake signal is supplied from the timing control circuit 26 at a constant timing via the mode switching circuit 25. The capstan motor 5 driven by the capstan motor drive circuit 21 is subjected to a tracking servo with a quick response by the trunking error signal with an increased gain, so that the capstan motor 5 can track the target recording track TR on the magnetic tape 1. The magnetic tape 1 is run to a target position where it is correctly traced by each of the magnetic heads 8A, 8A', and is stopped at the target position by the brake signal. Tracking control in this example is
Predetermined frequencies f, , f2 . f.

, f4 cyclically repeating the pilot signal,
Each magnetic head 8A is controlled by a closed rope based on a relative error signal level formed from the signal level of the frequency component of the difference between the reproduced pilot signal and the reference pilot signal.

It is not affected by the absolute value of the 8B output. Moreover,
By tracking control using the tracking error signal with increased gain, each of the magnetic heads 8A and 8B can be accurately tracked on the target recording track TR, and can be reliably stopped by a brake signal at a constant timing. .

Here, the operation when switching from the normal reproduction operation mode to the still reproduction operation mode is performed will be explained in detail using the timing chart of FIG. 5.

In the timing chart of FIG. 5, during the normal reproduction operation mode, while the magnetic tape 1 is running at a normal tape speed, each magnetic head 8A, 8B of the rotating magnetic head device 2 is used to record the magnetic tape 1 on the magnetic tape 1. By sequentially tracing each recording track TR, the above-mentioned predetermined frequencies f1, f2 . f3. A reproduced RF output of the video signal on which the f4 biloft signal is superimposed is obtained, and the above-described tracking control is performed based on the reproduced pilot signal included in the reproduced RF output and the reference pilot signal.

For example, if the switching operation to the still playback operation mode is performed at timing ts in FIG. 5 above,
After this timing ts, first the first magnetic head 8A
After one frame period has elapsed from the timing to when a reproduced high lot signal with a frequency of f is obtained, one frame advance is performed, and a still reproduction operation is performed at a timing t1 when a reproduced biloft signal with a frequency of next fl is obtained. An operation mode designation signal designating a mode is supplied from a system controller (not shown) to the first control input terminal 31, and the control operation of the still playback operation mode described above is performed. That is, at the timing t, the first switch 10 of the RF switch circuit 10 selects the third magnetic head 10A'' by the operation mode designation signal supplied to the first control input terminal 32; The gain switching circuit 16 is controlled to increase the gain of the tracking error signal obtained by the tracking error forming circuit 14 and supply it to the signal mixing circuit 17. A constant brake signal is supplied from the timing control circuit 26.

A constant brake signal is supplied from the timing control circuit 26 to the capstan motor drive circuit 21, and the recording track TR, from which a reproduced pilot signal of frequency fl is obtained, is connected to the first and third magnetic heads. 8A
, 8A', the capstan motor 5 is stopped as shown in the still trace.

In this embodiment, in consideration of positional deviation caused by stopping the magnetic tape 1 from the normal tape speed, the recording track T R+ is
After stopping the capstan motor 5 so as to perform still tracing with the magnetic heads 8A and 8A'', the frame feed operation is performed once. In this frame feed operation, the starting voltage is set by the starting circuit 27 to The magnetic tape 1 is supplied to the stun motor drive circuit 21 to quickly increase the rotational speed of the capstan motor 5, perform tracking control using the tracking error signal with the increased gain, and send the magnetic tape 1 by one frame, that is, two tracks. The recording track TR3 from which a reproduced pyro-node signal of frequency f3 is obtained is transferred to the first and third magnetic heads 8A, 8A'.
The capstan motor 5 is stopped as shown in the still trace at . Then, field still reproduction is performed by still tracing the recording track TR3 with the first and third magnetic heads 8A, 8A'' as indicated by the solid line arrow in FIG. I do.

H2 Effects of the Invention As is clear from the description of the embodiments described above, the tracking control device according to the present invention adjusts the mixing ratio of the tape speed error signal and tracking error signal of the tape travel control system when setting the still playback operation mode. A variable control means increases the gain of the tracking/knocking error signal to speed up the response of the tracking control of the tape running control system,
While this control means is tracking the target track, the brake signal generating means stops the tape running by applying a certain amount of brake at a certain timing to the tape running control system, so that the tape running can be stopped at a variable speed with very little noise. A playback screen can be obtained, and the intended purpose can be fully achieved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a video tape recorder to which a tracking control device according to the present invention is applied, FIG. 2 is a schematic diagram showing a recording format of a magnetic tape in the above embodiment, and FIG. The figure is a block diagram showing the structure of the error signal forming circuit in the above embodiment, FIG. 4 is a circuit diagram showing the structure of the gain switching circuit, and FIG. 5 is a block diagram showing the structure of the gain switching circuit in the above embodiment. This is a timing chart, and FIG. 6 is also a schematic diagram showing trace loci of each magnetic head. 1... Magnetic tape 2... Rotating magnetic head device 4... Capstan shaft 5... Capstan motor 6... Frequency generators 8A, 8B, 8A'... Magnetic head 10... R
F switch circuit 14...Error signal forming circuit 15...Reference viroft signal generation circuit 16...Gain switching circuit 17...Signal mixing circuit 21...Capstan motor drive circuit 26...Timing control circuit

Claims (1)

[Claims] A pilot signal whose frequency changes cyclically for each track is sequentially recorded, and during playback, the frequency of the reproduced pilot signal and the frequency of the reference pilot signal are reproduced from a track adjacent to the track that the head attempts to track. In a tracking control device that detects a signal component having a frequency different from that of the above-mentioned tracking error signal and obtains a tracking error signal of the head based on this signal component, the tape speed error signal of the tape running control system and the tracking error signal are and a brake signal generating means that applies a certain amount of brake to the tape running control system at a certain timing. Tracking control characterized by controlling the mixing ratio of the error signal and the tracking error signal to increase the gain of the tracking error signal, and then applying a certain amount of brake at a certain timing to stop tape running. Device.