JPH0554355A - Automatic tracking system - Google Patents

Abstract

(57) [Abstract] [Purpose] An object of the present invention is to provide an on-track system that enables reproduction in a stable track state even when a tape is dropped out at a constant speed and a variable speed. [Structure] By constantly monitoring the dropout information by the dropout detection circuit 3, feedback control is performed to maximize the head output level from the dropout presence / absence detection circuit 4 in the central portion of one track scanning period, and the dropout information is dropped to that portion. An auto-tracking system having a switch circuit 11 for automatically switching whether or not to prohibit the feedback control depending on whether or not there is an out.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an auto-tracking system which enables stable reproduction in an on-track state even with a reproduction tape having a dropout.

[0002]

2. Description of the Related Art In recent years, an auto-tracking system has been used as an auto-tracking system in which a piezoelectric head is used to move a video head to perform optimum tracking in a constant speed / shift mode.

An example of a conventional auto-tracking system will be described below with reference to the drawings.

As shown in FIG. 3, the control information 1 is the control information of the capstan FG, the control pulse, and the head switching. The tape speed detection circuit and the tape position detection circuit 2 operate according to the control information 1. Subsequently, it is composed of an amplifier 5, a head output detection circuit 6, a switch circuit 7, memories 8, 9, a comparison circuit 10, a drive waveform generation circuit 12, an integration circuit 13, a high voltage drive circuit 14, a piezoelectric element 15, a video head 16, and the like. ing.

The operation of the conventional auto-tracking system configured as described above will be described below.

First, based on the control information 1 of the capstan FG, the control pulse, and the head switching, the tape speed detection circuit and the tape position detection circuit 2 theoretically drive according to the tape feed speed and the head tracing position. A waveform is generated by the drive waveform generation circuit 12. And
The output signal of the reproducing video head 16 is amplified by the amplifier 5, and the head output detection circuit 6 extracts the head output value (amplitude value) and inputs it to the switch circuit 7. The switch circuit 7 outputs the output to the memory 8 each time the head is scanned.
9 is alternately switched and input, and the latest value of the head output value in the central portion of the one track scanning period of the reproduction track and the value in the track scanning immediately before that are stored. Next, the comparison circuit 10 compares the contents of the memories 8 and 9 and adds the result to the above-mentioned theoretical drive waveform to increase or decrease the output of the integration circuit 13 to increase or decrease the output voltage of the high voltage drive circuit 1.
By exciting the piezoelectric element 15 through the piezoelectric element 4, the piezoelectric element 1
The output level from the video head 16 adhered to No. 5 is kept at the maximum. In other words, by constantly monitoring the head output, the voltage applied to the piezoelectric element is gradually increased or decreased so that the value in the central portion of the one-track scanning period is maximized.

[0007]

However, in the above-described conventional configuration, when a dropout occurs in the head output at the center of the one-track scanning period that is constantly monitored, the piezoelectric element is passed through the comparison circuit. Since the head output level does not change even if the voltage applied to the track is increased or decreased little by little, one track as a whole becomes in an unstable trace state and reproduction cannot be performed in the on-track state. Was there.

The present invention solves the above-mentioned problems of the prior art by constantly monitoring the dropout information in the central portion of one track scanning period, and whether the results of the comparison circuit are added or not depending on the presence or absence of dropout. The purpose is to provide an auto-tracking system that switches between.

[0009]

In order to achieve the above object, the auto-tracking method of the present invention has a dropout during reproduction in a magnetic recording / reproducing apparatus having a reproducing movable video head adhered to a piezoelectric element. Also in this case, by constantly monitoring the dropout information, the control for maximizing the head output in the central portion of the one-track scanning period is performed by using the voltage corresponding to the theoretical drive waveform determined from the tape feed speed and the tape position information. By providing a circuit for automatically switching between addition and non-addition to the circuit given to the element, it is possible to reproduce in the on-track state even if a dropout occurs in the central portion of one track scanning period.

[0010]

According to the present invention, with the above-described configuration, the dropout information is constantly monitored, so that even if a dropout occurs in the central portion of one track scanning period in which the head output level is detected, the control method can be set to the dropout information. Thus, by automatically switching, it is possible to reproduce in the on-track state even in the reproduction tape in which the dropout has occurred.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, except that a dropout detection circuit 3, a dropout presence / absence detection circuit 4 in the central portion of one track scanning period, and a switch circuit 11 are newly provided, the description is the same as in the conventional example. Omit it.

The operation of the auto-tracking system configured as described above will be described below with reference to FIGS. 1 and 2.

First, as shown in FIG. 1, when the signal output from the reproducing video head 16 has a dropout,
The dropout detection circuit 3 detects the dropout pulse, and the dropout pulse is used to detect the dropout presence / absence detection circuit 4 in the central portion of the one-track scanning period. Works to switch. FIG. 2 shows an embodiment of the dropout presence / absence detection circuit 4 in the central portion of the one-track scanning period. In FIG. 2A, a waveform 20 is a reproduction RF signal when a dropout occurs in the central portion of one track scanning period, a waveform 21 is a dropout pulse signal obtained from the dropout detection circuit 3, and a waveform 22 is With the head switching waveform, the dropout pulse signal 21 is input to the flip-flop 24 shown in FIG. 2B, and the head switch center pulse 23 is supplied to the clock CL.
By inputting to K, the output 25 of the flip-flop 24
If the dropout is present in the central portion of the track scanning period, the L signal is output, and if not, the H signal is output. This signal is used to switch the control system of the piezoelectric element.

As described above, according to this embodiment, in the magnetic recording / reproducing apparatus having the reproducing movable video head adhered to the piezoelectric element, the head output at the central portion of the one-track scanning period of the track recorded during reproduction. Whether or not the voltage is applied to the piezoelectric element according to the theoretical drive waveform determined from the tape feed speed and tape position information by controlling the dropout information at all times. By providing a circuit for automatically switching the above, it is possible to maintain the optimum on-track state even when a dropout occurs.

[0016]

As described above, the present invention can realize an excellent auto-tracking system in which the optimum on-track state can be maintained even if a dropout occurs in the central portion of one track scanning period.

[Brief description of drawings]

FIG. 1 is a block diagram of an auto-tracking system according to an embodiment of the present invention.

FIG. 2A is a signal waveform diagram of a dropout presence / absence detection circuit at a central portion of a track scanning period. FIG. 2B is a flip-flop circuit diagram used in the detection circuit.

FIG. 3 is a block diagram of a conventional auto-tracking method.

[Explanation of symbols]

2 tape speed detection circuit and tape position detection circuit 3 dropout detection circuit 4 1 track scanning period central part dropout presence / absence detection circuit 8, 9 memory 10 comparison circuit 11 switch circuit 12 drive waveform generation circuit 13 integration circuit 15 piezoelectric element 16 video head

Claims (1)

[Claims] 1. A magnetic recording and reproducing apparatus having a reproducing movable video head adhered to a piezoelectric element, a circuit for applying a voltage to the piezoelectric element according to a theoretical drive waveform determined from tape feed speed and tape position information, Control for maximizing the head output by constantly monitoring the dropout information in the method of adding to the circuit for controlling the head output in the central part of one track scanning period of the track recorded during reproduction to be maximized. An auto-tracking system that is equipped with a circuit that automatically switches between playing and not playing so that even tapes with dropouts can always be played in the on-track state.