JPH0567110B2 - - Google Patents

Description

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

A Industrial application field B Summary of the invention C Prior art D Problem to be solved by the invention E Means for solving the problem F Effect G Example G-1 Configuration G-2 Operation H Effect of the invention A Industrial Application Field The present invention sequentially records a pilot signal whose frequency changes cyclically for each track, and when reproducing, the frequency and reference pilot signal of the reproduced pilot signal reproduced from a track adjacent to the track that the head attempts to track are recorded. Regarding a tracking control device that detects a signal component having a frequency different from that of a signal, and obtains a tracking error signal of the head based on this signal component, for example,
Recording and recording of video signals using a rotating magnetic head device
This invention is applied to tracking control of so-called still playback operation modes such as frame-by-frame playback, slow playback, and still playback in a so-called helical scan video tape recorder that performs playback.

B. Summary of the Invention The present invention sequentially records a pilot signal whose frequency changes cyclically for each track, and when reproducing, the frequency of the reproduced pilot signal reproduced from a track adjacent to the track that the head attempts to track and the reference pilot signal. In a tracking control device that detects a signal component having a frequency that is different from the frequency of 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, and then a certain amount of braking is applied at a certain timing. By applying this to stop the tape running, it is possible to obtain a variable speed slow playback screen with extremely little noise.

C. Prior Art In a so-called helical scan video tape recorder that records and reproduces video signals using a rotating magnetic head device, recordings are arranged on a magnetic tape at a predetermined angle 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. Also,
Conventionally, in video tape recorders, in addition to the normal playback operation in which the playback operation is performed at the regular tape running speed, variable speed playback is performed in which the tape is run at a higher or lower speed than the regular tape running speed and the playback operation is performed. A device with operational functionality is provided.

In a helical scan type video tape recorder such as the one 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 place a control track on the magnetic tape at the position of the recording track of the video signal. The so-called CTL method, which records the corresponding control signal and uses the control signal to control the drive amount and timing of the capstan for driving the tape, the brake amount and its timing, and the control signal for each track of the video signal. The so-called ATF method, etc., records a pilot signal whose frequency changes cyclically and superimposes it on a video signal, and performs tracking control using the pilot signal.
Traditionally known. The above-mentioned ATF type tracking control device is disclosed in, for example, Japanese Patent Laid-Open No. 59-65962.

D Problems to be Solved by the Invention In general, in helical scan type video tape recorders, it is not possible to obtain reproduced images with good image quality due to tracking deviation during playback operation.
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 will trace over multiple recording tracks, so depending on the tracking state, the The noise generation situation changes.
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 generally has many adjustment points and a huge circuit scale, so if tracking control is performed according to each operating state as described above, it will be difficult to manufacture and adjust it. It requires a lot of effort and time.

In addition, in the ATF type tracking control device described above, 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. If the required C/N ratio is not obtained, the desired A/D conversion output may not be obtained and control may become uncontrollable.
There were problems such as hunting caused by fluctuations in the A/D conversion output due to noise.

E. Means for Solving the Problems In order to solve the above-mentioned problems, the tracking control device according to the present invention sequentially records a pilot signal whose frequency changes cyclically for each track,
During reproduction, a signal component having a frequency that is the difference between the frequency of the reproduced pilot signal reproduced from a track adjacent to the track that the head attempts to track and the frequency of the reference pilot signal is detected, and the head is tracked based on this signal component. A tracking control device configured to obtain a tracking error signal includes a control means for varying a mixing ratio of a tape speed error signal of a tape running control system and the above-mentioned tracking error signal, and a control means for varying a mixing ratio of a tape speed error signal of a tape running control system and the above-mentioned tracking error signal; A tracking control device comprising: a brake signal generating means for applying a certain amount of brake.

F Effect 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 increases the gain of the tracking error signal when setting the still playback operation mode. Speed up the tracking control response. The brake signal generating means applies a predetermined amount of brake at a predetermined timing to stop tape running while the tape is being tracked 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 1 is wrapped 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 capstan motor 5, so that it slides on the outer periphery of the rotating magnetic head device 2. The tape is loaded onto a predetermined path by a loading means (not shown) so that the tape is run in contact with the tape. 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, 8A, and 8A on a head drum 7 rotated at a constant speed by a head drive motor (not shown).
8B, 8A' are arranged, and the reproduced RF output obtained by sequentially tracing the recording track TR on the magnetic tape 1 with each of the magnetic heads 8A, 8B, 8A' is transmitted to a rotary transformer 9.
Output via.

Here, as schematically shown in FIG. 2, the magnetic tape 1 has four types of frequencies f ₁ and f ₂ on recording tracks TR that are sequentially formed with a predetermined inclination with respect to the tape running direction. , f ₃ , and f ₄ are recorded superimposed on the video signal. The frequencies of the pilot signals f ₁ , f ₂ ,
f ₃ and f ₄ satisfy the relationship of the first equation: |f ₁ −f ₂ |=|f ₃ −f ₄ |=Δfa |f ₂ −f ₃ |=|f ₁ −f ₄ |=Δfb is set to . Of the three magnetic heads 8A, 8B, 8A' of the rotating magnetic head device 2, the first and second magnetic heads 8A, 8B arranged symmetrically are as follows:
The azimuths of the respective magnetic gaps are different from each other, and the odd numbered recording tracks TR ₁ and TR ₃ on the magnetic tape 1 are traced by the first magnetic head 8A, and the even numbered recording tracks TR ₂ and TR _{4 are} traced by the first magnetic head 8A.
is used to perform normal recording and reproducing operations by tracing it with the second magnetic head 8B. Further, a second magnetic head 8A' disposed on one side of the second magnetic head 8B has a magnetic gap with the same azimuth as the first magnetic head 8A. This is used to perform a variable speed reproduction operation by tracing odd numbered recording tracks TR _2o-1 on the magnetic tape 1 alternately with TR 8A.

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

Here, the RF switch circuit 10 connects the second magnetic head 8B and the third magnetic head 8B.
a first switch 10A that switches A'; and a second switch 10A selected by the first switch 10A.
Alternatively, the second switch 10B alternately selects the third magnetic heads 8B, 8A' and the first magnetic head 8A. The first switch 10A 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. The third magnetic head 8A' is selected. Further, the second switch 10B performs a switching operation in response to a PG pulse whose level is inverted every 1/2 rotation in synchronization with the rotation of the rotating magnetic head device 2.

The reproduced video signal processing circuit 12 performs predetermined signal processing on the reproduced RF output signal supplied via the switch circuit 10 to form a reproduced video signal, and outputs this reproduced video signal from the reproduced output terminal 13. do.

Further, the error signal forming circuit 14 is supplied with a reference pilot signal from the reference pilot signal generating circuit 15, and detects a tracking error based on this reference pilot signal and the reproduced pilot signal included in the reproduced RF output signal. A signal is formed and this error signal is sent to the gain switching circuit 1.
6 to a signal mixing circuit 17. 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 selects the four predetermined frequencies f ₁ , f ₂ , f ₃ , f ₄ . The reference pilot signal of
4 in sequence.

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 reproduced RF output signal is sent from the first signal input terminal 101 to the multiplication circuit 10 via a low-pass filter 103 that extracts the reproduced pilot signal component contained in the signal.
4. The multiplication circuit 104 is supplied with the reference pilot signal from the second signal input terminal 102. The above multiplication circuit 104
The output of is the first and second difference frequency Δfa, Δfb
The signal is supplied to detection circuits 105 and 106. The first difference frequency Δfa detection circuit 105 extracts the frequency component Δfa shown in the first equation above, which is included in the output of the multiplication circuit 104, and supplies it to the first DC converting circuit 107. Further, the second difference frequency Δfb detection circuit 105 is connected to the multiplication circuit 104.
Δfb shown in the first equation above included in the output of
The frequency component is extracted and supplied to the second DC conversion circuit 108. And each of the above DC converting circuits 1
The DC level signal of the components of the first and second difference frequencies Δfa and Δfb obtained at 07 and 108 is as follows:
The signal is supplied to a subtraction circuit 109. This subtraction circuit 10
9 is supplied directly and via a polarity 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 is adapted to perform 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. 201 and two resistors 202 and 203 having different resistance values, and between the signal input terminal 200 and the signal output terminal 204, the two resistors 2 selected by the switch 201 are connected.
02 and 203. The changeover switch 201 is controlled by the operation mode designation signal described above, and selects the first resistor 202 with a large resistance value in the normal operation mode, and selects the second resistor 203 with a small resistance value in the still operation mode. It is becoming more and more of a choice. 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 converts the output of a frequency generator 6 that generates a frequency signal in accordance with the number of rotations, that is, the tape speed, of a capstan motor 5 that drives a capstan shaft 4 that runs the magnetic tape 1 into a frequency signal. - A speed error signal obtained by converting it into a voltage signal in the voltage converter 19 is supplied, and this speed error signal and the tracking error signal are mixed. The output of this signal mixing circuit 17 is supplied to a capstan motor drive circuit 21 via a buffer amplifier 20. Furthermore, the capstan motor drive circuit 2
1 is supplied with a DC drive bias voltage from each bias circuit 23 and 24 via a first mode switching circuit 22, and is supplied with a DC drive bias voltage via a second mode switching circuit 25 to drive the capstan motor 21. A drive control signal specifying the rotation direction and rotation direction is supplied from the timing control circuit 26. 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 input terminal 31 to the RF switch circuit 10, gain switching circuit 16, Pilot signal switching circuit 18, first and second mode switching circuit 2
2, 25 and a timing control circuit 26. Further, a PG pulse whose level is inverted every 1/2 rotation in synchronization with the rotation of the rotating magnetic head device 3 is sent from the second control output terminal 32 to the RF switch circuit 10, the error signal forming circuit 14, and the pilot signal switching circuit. 18 and a timing control circuit 26.

G-2 Operation In the video tape recorder of the embodiment configured as described above, during 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 is supplied to the signal mixing circuit 17. Then, the signal mixing circuit 1
7 feeds back the speed error signal supplied from the frequency/voltage generator 19 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 speed servoed by the speed error signal supplied as the main error signal, and by the tracking error signal with the gain lowered. A tracking servo is applied so that the recording track TR on the magnetic tape 1 is connected to each of the magnetic heads 8A, 8.
The magnetic tape 1 is run so that it is correctly traced at point B.

In addition, in the video tape recorder of this embodiment, in the still playback operation mode in which frame-by-frame playback, slow playback, still playback, etc.
The first switch 10A of the RF switch circuit 10 selects the third magnetic head 8A' by the operation mode designation signal supplied to the control input terminal 32 of the RF switch circuit 10, and the gain switching circuit 16 selects the tracking error. The tracking error signal obtained by the forming circuit 14 is controlled to have a high gain and is supplied 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. Also,
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 timing control circuit 26 outputs the tracking error signal at a certain timing via the second mode switching circuit 25. The brake signal is supplied at The capstan motor 5 driven by the capstan motor drive circuit 21
A tracking servo with a quick response is applied to the tracking error signal with the increased gain, and the desired recording track on the magnetic tape 1 is tracked.
The magnetic tape 1 is run to a target position where the TR is correctly traced by each of the magnetic heads 8A, 8A', and stopped at the target position by the brake signal. The tracking control in this embodiment includes tracking each recording track on the magnetic tape 1.
Predetermined frequencies f ₁ , f ₂ , f ₃ , f ₄ recorded in TR
Based on the pilot signal that repeats cyclically,
Each magnetic head 8A, 8B is controlled by 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.
is not affected by the absolute value of the output. Moreover, by tracking control using the tracking error signal with increased gain, each of the magnetic heads 8A and 8B is accurately tracked on the target recording track TR, and stopped reliably by a brake signal at a constant timing. be able to.

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

In the timing chart of FIG. 5, during the normal playback operation mode, each magnetic head 8A, 8B of the rotating magnetic head device 2 plays a disc on the magnetic tape 1 while running the magnetic tape 1 at a regular tape speed. By sequentially tracing each recording track TR, the above-mentioned predetermined frequency f1,
A reproduced RF output of the video signal on which the pilot signals of f2, f3, and f4 are superimposed is obtained, and tracking control as described above is performed based on the reproduced pilot signal included in the reproduced RF output and the reference pilot signal. It is being said.

For example, if the switching operation to the still playback operation mode is performed at timing ts in FIG. 5 above, then after this timing ts, the first
After one frame period has elapsed from the timing to when the reproduction pilot signal of frequency _f1 is obtained by the magnetic head 8A, one frame of frame advance is performed.
At timing _t1 when the next reproduction pilot signal of frequency _f1 is obtained, an operation mode designation signal for specifying the still reproduction operation mode is supplied from the system controller (not shown) to the first control input terminal 31, and the above-mentioned still A control operation for the playback operation mode is performed. That is, at the timing t ₁ , the operation mode designation signal supplied to the first control input terminal 32 causes the first
The switch 10 selects the third magnetic head 10A', and the gain switching circuit 16 increases the gain of the tracking error signal obtained by the tracking error forming circuit 14 and sends it to the signal mixing circuit 17. At the same time, a constant brake signal is supplied from the timing control circuit 26 via the second mode switching circuit 25.

A constant brake signal is supplied from the timing control circuit 26 to the capstan motor drive circuit 21, and a recording track _TR1 from which a reproduction pilot signal of a frequency _f1 is obtained is set to the first and third recording tracks TR1.
The capstan motor 5 is stopped so that the magnetic heads 8A and 8A' are still traced.

In this embodiment, in consideration of the positional deviation caused by stopping the magnetic tape 1 from the normal tape speed, the recording track TR ₁ is transferred to the first and third magnetic heads 8A and 8A'. After stopping the capstan motor 5 so as to perform still tracing, the frame feeding operation is further performed by 1.
Do it once. In this frame feeding operation, the starting voltage is applied to the capstan motor drive circuit 2 by the starting circuit 27.
1, the rotational speed of the capstan motor 5 is quickly raised, tracking control is performed using the tracking error signal with the increased gain, and the magnetic tape 1 is sent by one frame, that is, two tracks. The capstan motor 5 is stopped so that the first and third magnetic heads 8A, 8A' still trace the recording track _TR3 from which a reproduction pilot signal of a frequency of ₃ is obtained. Then, by still tracing the recording track _TR3 with the first and third magnetic heads 8A and 8A', as shown by the solid line arrow in FIG. Perform field still playback.

H. Effects of the Invention As is clear from the description of the embodiments described above, in the tracking control device according to the present invention, when setting the still playback operation mode, the mixing ratio of the tape speed error signal of the tape running control system and the tracking error signal is adjusted. A control means for varying the tracking error signal increases the gain of the tracking error signal to quicken the response of the tracking control of the tape running control system, and in a state where the control means is tracking the target track, the brake signal generating means increases the gain of the tracking error signal. Tape running is stopped by applying a certain amount of brake at a certain timing to the running control system, so a variable speed slow playback screen with extremely low noise 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 a schematic diagram showing the trace locus of each magnetic head. 1... Magnetic tape, 2... Rotating magnetic head device, 4... Capstan shaft, 5... Capstan motor, 6... Frequency generator, 8A, 8B, 8
A'...Magnetic head, 10...RF switch circuit,
14...Error signal forming circuit, 15...Reference pilot signal generation circuit, 16...Gain switching circuit, 17...Signal mixing circuit, 21...Capstan drive circuit, 26...Timing control circuit.

Claims (1)

[Claims] 1. A pilot signal whose frequency changes cyclically for each track is sequentially recorded, and during reproduction, the frequency of the reproduced pilot signal reproduced from a track adjacent to the track that the head attempts to track and the reference pilot signal are In a tracking control device that detects a signal component having a frequency different from that of a tape drive control system and obtains a tracking error signal of the head based on this signal component, the tape speed error signal of a tape running control system and the tracking A control means for varying a mixing ratio with an error signal, and a brake signal generating means for applying a certain amount of brake at a certain timing to the tape running control system are provided, and when the still playback operation mode is set, the tape running control system After controlling the mixing ratio of the tape speed error signal and the tracking error signal to increase the gain of the tracking error signal, a certain amount of brake is applied at a certain timing to stop tape running. Features a tracking control device.