KR960012999B1 - Helical head tracking apparatus of vcr - Google Patents

Abstract

The apparatus is designed to make video head of a video recorder/player to trace along the track correctly. The apparatus consists of: a pilot signal recording means for counting system clock in accordance with head switching pulse and generating pilot signal when coefficient value and reference value to record pilot signal at specified position of helical track; a tracking error detecting means for counting system clock in accordance with played control signal and detecting the tracking error by comparing coefficient value when pilot signal is inputted with reference value at recording.

Description

VEAL's Helical Head Tracking Device

1 is a configuration diagram of a helical recording format of a tape.

2 is a block diagram of a conventional ATF device.

3 is a block diagram of a pilot signal recording circuit of the present invention.

4 is a block diagram of a tracking error detection circuit of the present invention.

5 is a pilot signal recording state diagram according to the present invention.

6 is a waveform diagram of input and output parts of FIG.

7 is an input / output waveform diagram of each part of FIG.

* Explanation of symbols for main parts of the drawings

10,50: counter 20,60: comparator

30: pilot signal generator 40: head amplifier

70: adder

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an automatic tracking device in which a video head is accurately traced along a track in a helical scan image recording and reproducing apparatus. In particular, a pilot signal is recorded at a predetermined position of the helical track and then reproduced. And a helical head tracking device of V-Cal which detects and changes the running speed of the tape according to the error to correct head skew.

Generally, a video recording and reproducing apparatus is classified into a drum system composed of a head for recording or reproducing a signal on a tape, a drum and a drum motor on which the head is mounted, and a capstan system for running the tape at a constant speed.

In order to stabilize the rotation speed of the tape and drum, a frequency generator (FG) and a pulse generator (PG) are installed in the drum motor and the capstan motor to compare the current rotation speed with the reference value. The motor speed is adjusted accordingly to speed control and phase control.

In the multi-head helical scanning method, as in the tape recording format of FIG. 1, the track on which a signal is recorded is inclined in the tape length direction, starting at the lower end of the tape, and the head is alternately recorded and reproduced by tracing one track. .

Therefore, the control signal is recorded in the control track located in the longitudinal direction at the bottom of the tape, and the signal is detected during playback to control the phase of the capstan motor, and the starting position at which the head traces the track by the head switching pulse using the control pulse, That is, the timing of the head switching is adjusted, and the track is synchronized with the capstan motor.

When the head mounted on the drum plays back what is recorded on the helical track of the tape, it records a specific pilot signal to the track so that the head accurately traces the track, and supplies the pilot signal to the automatic tracking following device of FIG. An error signal was created to correct.

As shown in FIG. 2, a conventional ATF apparatus includes an equalizer 1 for amplifying a signal reproduced through a head to compensate for reproduction characteristics, a limiter 2 for limiting the output signal level of the equalizer 1, A synchronization detector 3 for detecting a synchronization signal among the output signals of the limiter 2, a pulse generator 4 for generating pulses ATS1 and ATS2 having a phase difference using the detected synchronization signal, and a reproduced signal. A low pass filter (5) for filtering the low pass component of the envelope, and an envelope detector (6) for detecting an envelope of the signal passing through the low pass filter (5) and detecting the signal recorded by FM modulation as an original signal And a sample-hold circuit 7 which receives the output signal of the envelope detector 6 and outputs an envelope value at each time the pulse ATS1 of the pulse generator 4 is applied, and a sample-hold circuit. Comparatively amplify the signal sampled at (7) and the output signal of the envelope detector (6). A sample-hold circuit 9 which receives the differential amplifier 8 and the output signal of the differential amplifier 8 and outputs a signal value when the pulse ATS2 of the pulse generator 4 is applied as a tracking error signal; It consisted of.

The ATF device configured as described above detects the magnitude of the signal read by the head in the neighboring track and the current track, detects the degree of the track's bias in the head, and controls the capstan motor according to the degree of the bias to increase the speed of the tape. Will change.

However, in the conventional method using the ATF servo device, a head 1.5 times larger than the recording track must be used to obtain the signal detection amount of the adjacent track, and the pilot signal having a certain pattern and the sync signal are separated between the adjacent tracks to distinguish the tracks. There was a problem that should be recorded on the tape.

SUMMARY OF THE INVENTION The present invention has been made to solve the conventional problems as described above, and an object of the present invention is to provide a helical head tracking device of V-CAL which enables the use of a miniaturized head of the same size as the recording track width.

Another object of the present invention is to establish a helical head tracking device of V-CAL which simplifies the automatic tracking operation by recording the same pilot signal at a predetermined position for each track without the need to record the pilot signal and the synchronization signal to distinguish between adjacent tracks. To provide.

In order to achieve the above object, the present invention records a pilot signal at a position that has passed a predetermined time since the head switching point of the track, and the position of the track currently being traced using the pilot signal and the control signal detected at the time of recording is compared with the position at the time of recording. The match is compared and the speed of the tape is adjusted according to the error.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to FIGS. 3 through 7.

3 is a pilot signal recording circuit diagram of the helical head tracking apparatus of the present invention, and as shown therein, a counter 10 for operating a head switching signal to count a system clock signal, and an output signal level of the counter 10; A comparator 20 for comparing the comparison reference value, a pilot signal generator 30 for generating a pilot signal when the count value is equal to the comparison reference value according to the output signal of the comparator 20, and data for recording the pilot signal in the track. Amplified together with a head amplifier 40 for outputting to the head.

4 is a tracking error detection circuit diagram using a pilot signal in the helical head tracking apparatus of the present invention, as shown therein, which operates by a control signal to count a system clock signal and outputs a count value when inputted to the pilot signal A comparator 60 for detecting a tracking error by comparing the output value of the counter 50 with a comparison reference value, and combining the output signal of the comparator 60 with the speed and phase gain of the capstan motor to obtain a capstan motor driving circuit. It consists of an adder 70 outputting.

The operation at the time of recording and reproduction of the present invention configured as described above will be described based on the waveform diagrams of FIG. 6 and FIG.

First, when the pilot signal is to be recorded at an appropriate position of the helical track, a system clock signal as shown in FIG. 6A and a head switching signal like FIG. 6B generated by the system controller at the time of recording are It is input to the counter 10 of FIG.

The counter 10 starts counting at the rising edge of the input head switching signal and counts the system clock, and outputs the counted value to the comparator 20 as shown in FIG.

The comparator 20 compares the count value with the comparison reference value, and the pilot signal generator 30 uses the output signal of the comparator 20 when the count value and the comparison reference value are the same as in FIG. 6A. The pilot signal is output to the head amplifier 40, which outputs the pilot signal along with other data to be recorded to the head and records the track on the tape.

If a pilot signal is generated after a certain time has elapsed from the head switching time point, the pilot signal is recorded at a predetermined position of the helical track as in the tape recording configuration of FIG.

At the time of reproduction, a system clock signal as shown in FIG. 7A and a control pulse as shown in FIG. 7B as detected in the control track of the tape are input to the counter 50 in FIG.

The counter 50 starts counting by the input control pulse, counts the system clock as shown in FIG. 7C, and detects the pilot signal as shown in FIG. 7D recorded on the helical track of the tape. When the counter 50 is input, the count is stopped and the count value at that time is output to the comparator 60.

The comparator 60 compares the count value with the comparison reference value used in recording to detect a tracking error, that is, the degree of the tape track biased from the head, and applies the tracking error to the capstan motor control loop through the adder 70. By controlling the speed of the capstan motor, the speed of the tape is adjusted so that the head accurately traces the helical track.

As described above, the present invention has an effect that the head finds and traces the correct track position by having the position of the helical track having the position and velocity in the tape length direction and the quantitative physical quantity.

In addition, a miniaturized head of the same size as the recording track width can be used, and the same pilot signal is recorded and reproduced at a predetermined position for each track without the need for complicated recording of the pilot signal to distinguish between adjacent tracks. There is an effect to simplify the correction operation.

Claims (3)

A pilot signal recording means for counting the system clock according to the head switching pulse and generating a pilot signal when the count value and the reference value coincide to record the pilot signal at a predetermined position of the helical track; and the system clock according to the reproduced control signal. And a tracking error detecting means for detecting a tracking error by comparing the count value when the pilot signal is input with the reference value at the time of recording and detecting the tracking error. 2. The apparatus of claim 1, wherein the pilot signal recording means comprises: a counter (10) operating by a head switching signal to count a system clock signal, a comparator (20) for comparing an output signal level of the counter (10) with a comparison reference value; And a pilot signal generator 30 for generating a pilot signal when the count value is equal to the comparison reference value according to the output signal of the comparator 20, and a head amplifier for amplifying the pilot signal together with the data to be recorded in the track and outputting it to the head. A helical head tracking device of V-C, comprising (40). 2. The counter according to claim 1, wherein the tracking error detecting means operates by a control signal to count a system clock signal and output a count value when a pilot signal is input, and compares an output value of the counter 50. Comparator 60 for detecting the tracking error compared to the reference value, and the adder 70 for combining the output signal of the comparator 60 with the speed and phase gain of the capstan motor and outputs it to the capstan motor driving circuit VEAL's helical head tracking device.