JP2940729B2 - 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 tracking control device for a video tape recorder (VTR) or the like.

[0002]

2. Description of the Related Art A so-called 8 mm VTR employs a configuration in which a pilot signal for tracking is recorded at the time of recording, the pilot signal is reproduced at the time of reproduction, and a predetermined process is performed to perform a tracking process. Have been.

Japanese Patent Application Laid-Open No. 63-261568 discloses a configuration for automatically realizing the best tracking state by using the envelope of a reproduced signal.

[0004]

Since the tracking control using the pilot signal utilizes the leakage of the pilot signal from the adjacent track, the tracking control can be effectively performed on the tape pattern provided with the guard band. May not be done. This is for the following reasons. Consider a system in which the level of a tracking error signal is proportional to the magnitude of the tracking deviation. In such a system, when a tape provided with a guard band is reproduced, as shown in FIG. 3, when the tracking deviation is small, the characteristics of the tracking error signal do not change (the dead zone exists). Do). That is, tracking cannot be controlled in an optimal state.

[0005]

SUMMARY OF THE INVENTION Therefore, the present invention solves the above-mentioned drawbacks by using both tracking control using a pilot signal and tracking control using an envelope of a reproduced signal. That is, normally, tracking control based on a pilot signal is performed, and means for detecting the influence of a guard band is provided. Based on an output from the detecting means, tracking control using an envelope of a reproduced signal is performed. Use means together.

[0006]

In other words, tracking control using a pilot signal is normally performed. However, when it is detected that the signal is affected by a guard band, tracking control using the envelope of a reproduced signal is also used. Optimal tracking control can be realized regardless of the presence or absence of a band.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the embodiment, and FIG. 2 is an explanatory diagram showing the relationship between tapes and tracks.

In FIG. 1, a signal recorded on a magnetic tape 1 on which a video signal or the like is recorded is reproduced by a magnetic head 2. Of the reproduced signals, the pilot signal is 4
Low-pass filter (L
PF) 3 and supplied to the servo circuit 4. The servo circuit outputs a tracking error signal based on the obtained pilot signal. As described above, the tracking error signal is configured so that the level of the tracking error signal increases as the deviation from the tracking center increases. The tracking control using the four-frequency pilot signal is well known and will not be described in detail.

On the other hand, the servo circuit 4 includes a guard band detecting means, and outputs a dead zone detection signal from the servo circuit. The dead zone detection signal controls on / off of the switch 8 and a control signal generation circuit 9 described later.

The dead zone is, as shown in FIG.
This is a range in which the level of the tracking error signal is at the center of the variation width despite being shifted from the center of the tracking center. The detection of this range utilizes the detection of a state where the level of the tracking error signal is within a predetermined level range. Further, the formation of the guard band is known in advance from the relationship between the head width and the tape speed (for example, 8 mm V in the PAL system).
TR SP (standard) mode. At this time, a guard band is formed because the track width determined by the tape running is 34 μ, whereas the head width is only 27 μm.
On the other hand, in the LP (long time) mode, since the overwriting is performed, no guard band is formed. ), The servo circuit also uses a signal indicating the recording mode. That is, in the SP mode, the tracking error signal is within a predetermined range (for example, a range of 2.5 ± 0.5 V when the center is 2.5 V).
Should be detected.

The reproduced signal from the magnetic head is also selected by a bandpass filter (BPF) 5 for selecting an audio signal, and an audio FM signal is supplied to an AGC circuit 6 for the audio signal. The audio AGC circuit is a circuit for making the reproduction level of the audio FM signal constant. The AGC detection voltage of the AGC circuit is supplied to the switch 8. This AGC detection voltage is a signal proportional to the level of the reproduced FM audio signal.

The AGC detection voltage is supplied to a tracking control signal generation circuit 9. The tracking control signal generation circuit 9 generates and outputs a control signal for performing tracking control by hill-climbing control using the AGC detection voltage. A dead zone detection signal is supplied to the creation circuit 9, and the operation is controlled by this signal. That is, the creation circuit 9 operates only when the dead zone detection signal is being output.

The hill-climbing control using the output level is well known and will be described briefly. The control here is
The created error signal is changed by a predetermined level,
This is to find an error signal that maximizes the reproduction signal output level. Therefore, data on the previous error signal and the reproduction output level are stored, and the error signal is changed in the same direction as long as the current output level is higher than the previous one. If the current output level is lower than the previous one, it is determined that the error signal at the previous time is the signal having the maximum reproduction level, and the operation of changing the error signal is stopped.

When the switch 8 is on, the AGC detection voltage and the tracking error signal from the servo circuit are added by the adder 7 and supplied to the motor as a tracking control signal. When the dead zone is detected (when it is determined that there is a guard band), the tracking error signal from the servo circuit 4 is almost fixed at a predetermined value, and therefore the AGC detection voltage is used. The tracking control signal thus obtained is used for tracking control.

That is, when the recording mode is a specific mode and the level of the ATF error signal falls within a predetermined range, the dead zone detection signal becomes active. Then, the creation circuit 9 creates a control signal with the predetermined value in the predetermined range as an initial value, and starts the hill-climbing control.
Accordingly, tracking control is performed based on the reproduction level. As the initial value, for example, an upper limit value or a lower limit value of the predetermined range is used.

In the above embodiment, the configuration using the envelope of the FM audio signal has been described. However, the configuration is not limited to this, and a configuration using the envelope of the FM luminance signal, the low-band color signal, or the pilot signal is also conceivable. .

[0017]

As described above, according to the present invention, in a tracking control device using a pilot signal, it is possible to prevent a state in which optimal control cannot be performed due to the presence of a guard band. is there.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a state of a track on a tape.

FIG. 3 is an explanatory diagram showing a tracking error signal.

[Explanation of symbols]

 Reference Signs List 1 tape 2 magnetic head 4 servo circuit 6 audio FM signal AGC circuit 7 adder 8 switch 9 tracking signal generation circuit

Claims (1)

(57) [Claims] 1. A tracking control device for reproducing a tape on which a pilot signal for tracking is recorded and performing tracking control based on a level difference from a pilot signal from an adjacent track detects an influence of a guard band. A tracking control device comprising: a detection unit; and a unit that controls, based on an output of the detection unit, information on an envelope of a reproduction signal to be used for tracking.