KR900000015B1 - Control circuit for the automatic track detection - Google Patents

Abstract

The controller comprises an error signal detector (10) for comparing the pilot signal in the RF signal passing through a low pass filter (1) and the signal with reference frequency from a balanced modulator and for transmitting the frequency difference data to peak value detectors (5,6) through bandpass filters (3,4), a timing signal generator (20) controlled by a PBH and HP signals for controlling a sample and hold unit (8) and for selecting the reference signal, and a track detector (25) for generating the tracking signal applied to the timing signal generator and for generating the capstern motor driving signal.

Description

Rapid Stabilization Control Circuit for Automatic Track Detection

1 is a circuit diagram of the present invention.

2 is a circuit diagram of each part of the present invention.

3 is a state diagram when the phase of the comparison frequency and the reference frequency recorded on the tape is the same.

4 is a waveform diagram of each part of the circuit diagram of the present invention.

* Explanation of symbols for main parts of the drawings

10: error signal detection unit 25: tape trajectory determination unit

20: timing generator 14: reference frequency generator

1: low pass filter 2: balance modulator

3, 4: band pass filter 5, 6: peak-to-peak detection unit

8, 9: sample and hold section 11, 12: buffer

15, 16, 17: Monostable multivibrator 18: Divider

EXOR: Exclusive transceiver 21, 22: Delay

According to the present invention, in the capstan motor control method employing the Automatic Track-Finding (ATF) system, an error output during automatic track detection is judged to obtain a tape track plate output and the output is fed back. The present invention relates to a control circuit for auto-track detection of a rapid stabilization method to shorten the stabilization time.

In order to ensure that the video head tracks the recorded tape on the player, the pilot signal is combined with the pilot signal to be modulated, recorded on the video tape, and detected during playback to control the capstan motor. However, in the case of temporarily tracking several fields laterally in one field period (at double speed, which is a variable speed mode), it generates a reference frequency corresponding to the mode and generates a pilot signal applied from the video head. It was necessary to stabilize the time compared correctly.

It is an object of the present invention to control the speed of the capstan motor according to each mode transformation by varying the reference frequency that can be compared with each mode transformation, so that the head can accurately track the track recorded on the videotape. In order to provide a control circuit for automatic track detection, a reference frequency signal, which is compared with a pilot signal recorded on a tape, is converted to various modes by being delayed and applied as a head switching pulse applied when the output of the tape trace determining unit is fed back. This is to improve the performance of the VTR by making it stable quickly.

This will be described in detail with reference to the accompanying drawings.

FIG. 1 is a circuit diagram of the present invention. The output of the error signal detector 10 is configured to be applied to the tape trace determining unit 25 so that the output of the reference frequency generator 14 is fed back under the control of the timing generator 20. The error signal detection unit 10 is configured such that the reference frequency can be converted, so that the pilot signal (low frequency signal) is transmitted from the balance modulator 2 through the low pass filter 1 among the high frequency signals RF applied from the video head. The difference frequency is configured to be compared with the output of the generator 14 and then applied to the peak detection section 5, 6 via the band pass filter 3, 4.

The tape trajectory determination unit 15 is configured such that the output of the OP amplifier 7 is output from the sample and hold units 8 and 9 to the buffers 11 and 12, and the constant speed signal (PBH) and the head switching signal. The divider 18 and the monostable multi-vibrator 15, 16, 17 are controlled to drive the sample and hold section 8, 9 with the HP and then the The output of is configured such that the reference frequency of the reference frequency generator 14 is output through the retarder 21, 22. The monostable multivibrator 15, 17 has an inverter I ₁ on the input side as shown in FIG. The multi-level signal connected to the resistor (R ₃ ) and the capacitor (C ₃ ) is configured by outputting the state signal applied through the resistor R ₁ (R ₂ ) and the diode (D ₁ ) (D ₂ ) as a constant level signal. It is configured to drive the vibrator (M ₁ ).

Here, C ₁ and C ₂ are used for noise removal, and the resistor R ₃ and the capacitor C ₃ can select the triggering period as a time constant. FIG. 2B is an implementation circuit diagram of the monostable multivibrator 16. The monostable multivibrator M _{2 in} which a signal applied through the capacitor C _{6 is} connected to the resistor R ₅ and the capacitor C ₅ . After the drive is configured to drive the output of the inverter I ₂ to be inverted, the delayers 21 and 22 are the constant speed signal PBH at the terminal (-) of the comparator CP ₁ as shown in FIG. ) Is distributed to and applied to resistors (R ₈ ) (R ₉ ), and the output of the Excavator Orchestrator (EXOR) consists of a resistor (R ₆ ) (R ₇ ) and a capacitor (C ₆ ) It is configured to be input through the diode D ₅ , and the resistor R ₁₀ is intended to give hysteretic characteristics, and a delay time can be selected as a time constant of the resistors R ₆ -R ₉ and the capacitor C ₆ .

The frequency divider 18 is configured to connect the flip-flop FF to the output side of the transceiver ocator EXOR ₁ so as to divide in half as shown in FIG. as 2 degrees f help cycle each minute the oscillator _{(OSC) (P 1 -P 4} ) was connected to the frequency divider which is driven according to the output of the oscillator (OSC) with doengeot connects configure multiplexer (MF) (P ₁ -P ₄₎ selection of an output multiplexer (MF) from the input terminal (PR ₁₎ (PR _2), each divider (P ₁ -P ₄₎ by the output which is applied is selected in the so configured to output a reference frequency will be. In the videotape recorded in the present invention configured as described above, one signal of _four pilot frequencies f _{1 to} f ₄ is recorded for each field of each image, and a high frequency signal (RF) obtained from the head at the time of reproduction is recorded. From these four pilot signals are applied sequentially. That is, it is selected according to the input signal of the reference signal PR ₁ (PR ₂ ) applied to the reference frequency generator 14 (2 ² ) f _4- f _3- f _2- f _1- f ₄ . Are output from the reference frequency generator 14 to the balance modulator 2 in this order. Therefore, when the pilot signal of the reference pilot signal of the reference frequency generator 14 and the pilot signal of the high frequency signal RF applied from the head are applied through the low pass filter 1 in the balance modulator 2, the 47KHZ component is balanced. Frequency signal and 16KHZ frequency signal are outputted, and the output signal is applied to the peak value detection section (5) (6) through the band pass filter (3) (4) and then the peak values of the two components are applied to the OP amplifier (7). ).

Looking at this phase control system in more detail, the pilot signal to which both signals are compared is the frequency of f ₁ , f ₂ , f ₃ , f ₄ , respectively, and the frequency difference between each frequency is | f ₁ -f ₂ | = | f ₃ -f ₄ | = 16KHZ | f ₁ -f ₄ | = | f ₂ -f ₃ | = 47KHZ is set so that each field corresponds to f ₁ -f ₂ -f ₃ -f ₄ -f ₁ . It is sequentially recorded as follows, and is balanced and modulated with the reference frequency signal from the balance modulator 2, and the frequency of the reference pilot signal is f ₁ -f ₄ -f ₂ -f ₂ -f ₁ -f ₄ . The output will be in the reverse order of the order of recording.

If the reference frequency signal and the pilot signal recorded on the tape have the same order as shown in FIG. 3, the frequency components obtained for the late phase and the fast are generated differently.

That is, at the time point A of FIG. 3, when the phase of the reference frequency is fast, the reference frequency (f ₃ ) -comparative frequency (f ₄ ) = | f ₃ -f ₄ | = 16KHZ frequency difference occurs, but the phase of the reference frequency is When it is late, the comparison frequency f ₂ compared with the reference frequency f ₃ = f ₂ -f ₃ | 47 KHZ is generated. However, when the phase of the reference frequency is fast at the point of position B, the reference frequency (f ₁ ) -comparative frequency (f ₄ ) = | f ₁ -f ₄ | = 47 KHZ is generated, and when the phase is late, the comparison frequency (f ₃₎ )-Reference frequency (f ₄ ) = | f _3- f ₄ | It is difficult to use it for control because it is alternately these two. Therefore, it is necessary to make sure that a constant frequency is detected each time when the phase is fast or late. Therefore, in order to appropriately change the order of the applied reference frequency, the order of the recording frequency is applied in the reverse order to the order of application when recording, so that the output of the balance modulator 2 always outputs a frequency component of 16 KHZ when the phase is fast. When it is late, the frequency component of 47KHZ is output. However, if the reference frequency appears in the order f ₃ -f ₂ -f ₁ on the time axis at which the signal obtained from the video head is applied as the frequency signal f ₁ -f ₂ -f ₃ , the video head corresponding to the actual channel CH ₁ channel (CH ₁₎ should make it through the track is recorded, and the channel head, which corresponds to the (CH ₂₎ a channel (CH ₂₎ a reference frequency when the faster is the case, the phase to be to pass the track where the recording (f ₃₎ If the phase is late, | f ₂ -f ₃ | = 47KHZ, and the phase is late, | f ₄ -f ₃ | = 16KHZ is output. On the contrary, the phase difference is outputted more so that the rotation of the capstan motor becomes uneven temporarily.

In order to prevent this phenomenon, the present invention outputs a reference frequency applied by delaying a predetermined time (2 to 4 ms) and outputting the reference frequency f _{4 which} is delayed for a certain time when the recorded comparison frequency f ₁ is applied. The difference frequency is 47KHZ, and this signal component is applied to the non-inverting terminal (+) of the OP amplifier (7) to obtain a high potential output (H output), and the monostable multivibrator in the timing of 2-4ms Samples are held by the low potential output (L output) of Fig. 16 and held to hold the track determination signal (H level) of the tape for one field.

That is, the output of the peak detection unit 5, 6 is applied with a difference frequency of 16 KHZ to the inverting terminal (-) of the OP amplifier 7 and a difference of 47 KHZ is applied to the non-inverting terminal (+). In each field, the sample and hold section 9 controls the speed of the capstan motor through the buffer 12.

In the constant speed reproduction, the reference frequency as described above is obtained by delaying the head switching pulse HP for 2-4 ms. If the output of the OP amplifier 7 is sampled and held within this time, the pilot obtained from the video head is obtained. An output that determines the order of frequency components and reference frequency components can be obtained. When the head switching pulse HP is applied as shown in the waveform diagram of FIG. 3, the divider 18 extracts the output divided by 1/2. It is applied to one side of the shiver oar gate (EXOR) and receives the output of the buffer 11 on the other side, when the output of the other buffer is a low potential signal, it generates an output pulse like a solid line, and the output of the other buffer 11 is in a high potential state. In the case of a signal, an output pulse such as a dotted line is generated, so that the delay unit 21 to which the output of the transceiver ogate is applied and the constant speed to be applied at the constant speed mode are applied. The delay pulse PBH is delayed by a predetermined time (2-4 ms) in the delay unit 22 and applied to the reference frequency generator 14.

The monostable multivibrator 15 is triggered by the head switching pulse HP to hold the sample and hold section 9 when the high potential state signal is output and to hold the buffer 12 when the low potential state signal is output. By controlling the speed of the capstan motor through the output of the monostable multi-vibrator 17, the sample and hold section 8 is controlled when the output of the mono-stable multi-vibrator 16, which is negatively triggered by the output of the monostable multi-vibrator (17) After sampling and holding the output, the output of the path determination of the tape is output through the buffer 11 when the low potential signal is applied. The output of the reference frequency generator 14 as shown in FIG. 4 is delayed (21) (22). Four frequencies are selected (2 ² ) by the output signal (PR ₁ ) (PR ₂ ) of) and at this point, the track of the tape is judged when the output of the monostable multivibrator (16) As per signal It is possible to compare the difference signals accurately by the output fed back from the output side when it is controlled, and as a result, the output order of the reference frequency generator 14 can be changed as follows.

Pilot signal obtained from video head: f ₁ -f ₂ -f ₃ -f ₄

Original reference signal: f ₃ -f ₂ -f ₁ -f ₄

Tape trace signal output: L → H

Changed reference signal: f ₃ -f ₁ -f ₄ -f ₃ -f ₂

In this way, the reference signal whose reference frequency is changed from f ₃ to f ₁ is supplied at the timing of changing from the low potential state signal (L level) to the high potential state signal (H level). There is a number.

As described above, the present invention compares a pilot signal recorded on a tape with a reference frequency signal, and when detecting an error signal, the timing generator controls the output of the tape trace determining unit so that the reference frequency of the reference frequency generator can be output. The timing signal is controlled by the status signal (PBH) and the head switch (HP) signal during constant speed mode so that the feedback output of the buffer is delayed in the delayer so that the output of the reference frequency is changed. It is effective to shorten the time to stabilize.

Claims (2)

The reference frequency applied to the balance modulator 2 and the comparison frequency through the low pass filter 1 are configured to be balanced modulated so that the error is output from the band pass filter 3 and the output to the peak detector 5 and 6. By configuring the signal detection unit 10, the tape trajectory determination unit 25 is configured so that the output of the OP amplifier 7 is output from the sample and hold probes 8 and 9 to the buffers 11 and 12. The feedback output of the sample and hold probe 8 is controlled to be controlled by the output of the timing generator 20 controlled by the PBH and the head switching pulse HP, and then through the delayers 21 and 22. A control circuit for detecting automatic tracks of a rapid stabilization method, wherein the output of the reference frequency generator 14 is selected. The timing and generation unit 20 driven by the constant speed mode signal PBH and the head switching pulse HP is connected to the sample and hold unit by the monostable multivibrators 15, 16, and 17. 8) the output of the divider 18 and the output of the divider 18 and the output of the buffer 11 are connected to the reference frequency generators in the delay circuits 21 and 22 through the EXCEROR OORGATE. A control circuit for automatic track detection of rapid stabilization type configured to be applied to 14).

Images