JP2638115B2 - Automatic tracking control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an automatic tracking control circuit (AT) that records a pilot signal together with, for example, a video signal on an adjacent track and performs tracking using the pilot signal.
More specifically, F) relates to a track shift technique necessary for adjusting a tape path or taking a splice.

[Summary of the Invention] The present invention relates to an automatic tracking control circuit for recording a pilot signal on a track arranged adjacently and performing tracking with a reproduced pilot signal picked up by a head. Error data indicating the amount of shift of the head is calculated by using a reference pilot signal having the same frequency as the pilot signal of the pilot signal, and using the reproduced pilot signal and a reference pilot signal having the same frequency as the pilot signal recorded on a track adjacent to the reproduction track. Lock data indicating the non-shift amount of the head is calculated, and data obtained by multiplying the error data by a first variable coefficient and data obtained by multiplying the lock data by a second variable coefficient are added to obtain a phase error value. Calculate, and in front of the Shaft track The first variable coefficient is set to 1 and the second variable coefficient is set to 0. In the case of a track shift, the first variable coefficient and the second variable coefficient are changed corresponding to the shift amount, and the phase error is set. By performing the desired track shift based on the value, the desired track shift can be performed only by sampling at least two locations per track, and the data processing becomes very simple.

2. Description of the Related Art A VTR (Video Tape Recorder) employs automatic tracking control in which a pilot signal superimposed on a video signal is recorded on a track and tracking is performed. In this control, as shown in FIG. 3, tracks TR ₁ , TR ₂ ,... Are formed guardless and narrower than the width of the head H ₁ , and a plurality of pilot signals are provided on the tracks TR ₁ , TR ₂ ,. f ₁ , f ₂ , f ₃ ,
f ₄ is recorded repeatedly in a certain order. The plurality of pilot signals f ₁ , f ₂ , f ₃ , f ₄ have a low frequency of 100 KHz to 150 KHz and a frequency difference of | f ₁ −f ₂ | = | f ₃ −f ₄ | = 16 KHz, | f ₂ − f
₃ | = | f ₁ −f ₄ | = 46 KHz. Therefore, the frequency difference between the pilot signals f ₁ , f ₂ , f ₃ , f ₄ recorded on the left and right adjacent tracks for each track TR ₁ , TR ₂ ,.

A conventional automatic tracking control circuit is shown in FIG. The In Figure 4, the reproduction pilot signal two heads H _1, H ₂ is picked up is sent to the balanced modulation circuit 1 via the switch (SW), f ₁ from a reference oscillator 2 to the balanced modulation circuit 1 , f ₂ , f ₃ and f ₄ are input. The balanced modulation circuit 1 balance-modulates the reproduced pilot signal and the reference pilot signal, and outputs the outputs to a 16 KHz bandpass filter 3 and a 46 KHz bandpass filter 4, respectively. The outputs of the band-pass filters 3 and 4 are input to the operational amplifier circuit 5, and the output of the operational amplifier circuit 5 is supplied to the capstan motor control circuit as a capstan servo error voltage.

Therefore, when just tracking, the head
Track H _1, H ₂ is playing, for example, the head H ₁ as shown in FIG. 3 is a reference pilot signal f ₁ of the same frequency recorded on the track TR ₂ when the scanning the track TR ₂ The reference oscillator 2 outputs to the balanced modulation circuit 1. Then, the balanced reproduced pilot signal head H ₁ is picked up to the modulation circuit 1, i.e., the signal and the left and right adjacent tracks TR ₁ of f ₁ picked up from the track TR _2,
The signals of f ₄ and f ₂ picked up from TR ₃ are input, and the reproduced pilot signal and the reference pilot signal are balanced-modulated to output (f ₄ ± f ₁ ) and (f ₂ ± f ₁ ) signals. You. This signal is both 16KHz bandpass filter 3 and 46K
Hz band-pass filter 4 and an operational amplifier circuit 5
Receives a frequency difference signal of (f ₂ −f ₁ ) and (f ₄ −f ₁ ). The value of (f ₂ -f ₁₎ and (f ₄ -f ₁₎ is proportional to the lateral shift amount of the head H _1, when the shift amount of the head H ₁ is zero (just track) (f ₂ - f ₁ ) and (f ₄ −f ₁ ) become the same, and the operational amplifier circuit 5 receives the reference voltage (for example, 2.5 V).
Outputs, when the head H ₁ is shifted (f ₂ -
The values of f ₁ ) and (f ₄ −f ₁ ) are different, and the operational amplifier circuit 5 outputs a voltage proportional to the shift amount centering on the reference voltage as an error error signal, and controls the capstan motor so that the shift amount becomes zero. Control the circuit.

In addition, when shifting from the just track position by a predetermined amount (track shifting), as shown in FIG. 5, the reference pilot signal of f _{2 is included in} the reference pilot signal of f ₁ output from the reference oscillator 2. Insert Then, since the controlled so as to just track the track TR _2, is controlled so as to just track the track TR ₃ when that transmits a reference pilot signal f ₂ when they are sent to the reference pilot signal f _1, head H ₁ to the total basis is f ₁
It will be shifted in proportion to the time allocation of the reference pilot signal of the reference pilot signal and f ₂ of. Therefore, the heads H ₁ and H ₂ have been controlled to arbitrary shift positions by controlling the time distribution of the reference pilot signal.

[Problems to be Solved by the Invention] However, when the above tracking control is used in a digitized servo system, there is no problem when just-tracking, but the following problems occur when performing track shift. That is, the shift amount of the heads H ₁ and H ₂ is determined by the time distribution of the reference pilot signal mixed during one track scan, so that a very large number of samplings are required and data processing becomes complicated. Further, even if sampling is performed within the maximum possible range, the shift amount can be determined only stepwise with a rough value.

Accordingly, it is an object of the present invention to provide an automatic tracking control circuit that can perform a desired track shift with very little sampling.

[Means for Solving the Problems] To achieve the above object, an automatic tracking control circuit according to the present invention is provided in which an adjacent track is provided with a frequency difference between each track and a pilot signal recorded on right and left adjacent tracks. In the automatic tracking control circuit that records a pilot signal in which the left and right values are constant at different values and detects the frequency mixing ratio of the reproduced pilot signal picked up by the head and performs tracking, the same frequency as the pilot signal recorded in each track is used. A frequency oscillator for outputting a reference pilot signal, a read pilot signal picked up by the head and a reference pilot signal having the same frequency as a pilot signal recorded on a track scanned by the head are used to indicate a shift amount of the head. Calculate the error data and Data calculation for calculating lock data indicating a non-shift amount of the head using a reproduced pilot signal picked up by the head and a reference pilot signal having the same frequency as a pilot signal recorded on a track adjacent to the track scanned by the head. Means for calculating a phase error value by adding data obtained by multiplying the error data by a first variable coefficient and data obtained by multiplying the lock data by a second variable coefficient. A first variable coefficient is set to 1; the second variable coefficient is set to 0; and a track shift is performed by an arithmetic unit that changes the first variable coefficient and the second variable coefficient in accordance with a shift amount. A desired track shift based on the phase error value.

[Operation] When the head scans a track, the frequency oscillator outputs a reference pilot signal having the same frequency as the pilot signal of the track, and the data calculation means uses the reference pilot signal and the reproduced pilot signal of the head to generate error data. Is calculated. Further, the frequency oscillator outputs a reference pilot signal having the same frequency as the pilot signal of the adjacent track, and the data calculation means calculates lock data using the reference pilot signal and the reproduced pilot signal of the head. An arithmetic unit calculates a phase error value by adding data obtained by multiplying the error data by a first variable coefficient and data obtained by multiplying the lock data by a second variable coefficient. The first variable coefficient is set to 1, the second variable coefficient is set to 0, and when the track is shifted, the first variable coefficient and the second variable coefficient are changed according to the shift amount, and the phase is changed. Apply servo based on error value. Therefore, desired tracking can be performed by sampling at least two points for obtaining error data and lock data for one track.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

 An embodiment of the present invention is shown in FIGS.

Third track TR _1, TR _2, ... head H ₁ above is shown, the head H _1, H ₂ and the track TR _1, TR _2, ... of the relationship and the track TR _1, TR _2, recorded ... in Pilot signals f ₁ , f ₂ , f ₃ , f
The description of ₄ has been described in the section of the conventional example, and will not be described.

FIG. 1 shows a block diagram of the automatic tracking control circuit. In FIG. 1, two heads H ₁ and H ₂ are arranged at positions 180 ° opposite to a rotating drum, and two heads H ₁ and H ₂ alternately and sequentially follow a track TR ₁ by rotation of the rotating drum. , TR ₂ ,... The reproduced pilot signals picked up by the _two heads H ₁ and H ₂ are sent to the balanced modulation circuit 1 via the changeover switch SW. The changeover switch SW is the switching control by the microcomputer 7, always tracks TR _1, TR _2, ... is switched to the head H _1, H ₂ side being scanned.

The frequency oscillator 2 is configured to selectively oscillate the reference pilot signals of f ₁ , f ₂ , f ₃ , and f ₄ , and the oscillation frequency is controlled by the microcomputer 7. The output of the frequency oscillator 2 is supplied to the balanced modulation circuit 1.

The data calculation means A includes a balanced modulation circuit 1, two band-pass filters 3 and 4, and an operational amplifier circuit 5. The balanced modulation circuit 1 balance-modulates the reproduced pilot signal and the reference pilot signal and outputs a sum signal and a difference signal of the two signals.
Each is sent to the band pass filter 4. Both bandpass filters 3 and 4 have respective pass frequencies, that is, 16K.
The Hz bandpass filter 3 outputs the difference signal of | f ₂ −f ₁ |, | f ₄ −f ₃ |, and the 46 KHz band pass filter 4 outputs the difference signal of | f ₃ −f ₂ |, | f ₄ −f ₁ | The difference signal between the two is supplied to the operational amplifier circuit 5. This operational amplifier circuit 5 outputs a reference voltage (for example, 2.5 V) if the two difference signals have the same value, and outputs a voltage proportional to the difference centering on the reference voltage if there is a difference between the two difference signal values. Then, this output voltage is supplied to the A / D converter 6 as error data or lock data.

The A / D converter 6 digitizes the output of the operational amplifier circuit 5 based on a sampling clock from the microcomputer 7, and the digital signal is sent to the microcomputer 7.

The microcomputer 7 controls the changeover switch SW, the frequency oscillator 2, the A / D converter 6, and the like. That is, the changeover switch SW
, A control signal is output to switch to the heads H ₁ and H ₂ scanning the tracks TR ₁ , TR ₂ ,. Frequency oscillator 2
In the case of the just track, the scanning tracks TR ₁ , TR ₂ ,.
A reference pilot signal having the same frequency as the pilot signal recorded in the
Scanning tracks TR _1, TR _2, as shown in FIG., The scanning tracks TR ₁ interposed reference pilot signal of the recorded pilot signal and the same frequency ... and this reference pilot signal, TR _2, it is recorded on ... adjacent tracks And a reference pilot signal having the same frequency. The sampling clock is sent to the A / D converter 6 at a plurality of points in one feed,
At the time of track shift, at least one time (second time) when a reference pilot signal having the same frequency as the pilot signal recorded on the track adjacent to the scanning tracks TR ₁ , TR ₂ ,.
(Point B in the figure) A sampling clock is output. Further, the microcomputer 7 has a built-in calculation unit 8, which calculates the phase error value by executing the following equation.

Here, if S is changed, the track shift amount (shift amount from the just track position) is changed.

This phase error value is converted into an analog value by the D / A converter 9 and sent to the capstan motor control circuit.

 Hereinafter, the operation of the above configuration will be described.

When the rotary drum rotates, the two heads H ₁ and H ₂ alternately scan the tracks TR ₁ , TR ₂ ,... Of the tape, and the changeover switch SW is switched to the heads H ₁ and H ₂ during the track scanning. The reproduced pilot signal f ₁ , picked up by the heads H ₁ , H ₂
f ₂ , f ₃ and f ₄ are sent to the balanced modulation circuit 1. Where the head
When the H ₁ is scanning the track TR _2, as shown in FIG. 3 is adjacent the f ₁ to the main as shown in FIG. 2 track TR
₁ , the reproduced pilot signals of f ₄ and f ₂ picked up from TR ₃ are sent to the balanced modulation circuit 1. Reference oscillator 2 supplies a first reference pilot signal f ₁ as shown in FIG. 2 to a balanced modulation circuit 1. From the balanced modulation circuit 1, (f ₄ ±
A sum signal and a difference signal of (f ₁ ) and (f ₂ ± f ₁ ) are output, and a 16 KHz band-pass filter 3 is selected from the sum signal and the difference signal.
Then, the difference signal of (f ₂ −f ₁ ) which is 16 KHz is extracted by the 46 KHz band-pass filter 4 and the difference signal of (f ₄ −f ₁ ) which is 46 KHz is extracted. The difference signal and the difference signal (f ₄ -f ₁₎ of (f ₂ -f ₁₎ is supplied to the operational amplifier circuit 5, an error that indicates the operational amplifier circuit 5 is the head H ₁ is shifted much from the just-track position The data is output to the A / D converter 6. Since the microcomputer 7 outputs to the A / D converter 6 to the sampling clock as shown in FIG. 2, sampling the error data at a point in the second view of A _1, the error data is sent to the microcomputer 7.

In addition, the reference oscillator 2 operates after f ₁ as shown in FIG.
The reference pilot signal of f ₂ is supplied to the balanced modulation circuit 1. From the balanced modulation circuit 1, (f ₂ ± f ₁ ) and (f ₄ ± f ₂ )
Is output from the sum signal and the difference signal, and a 16 kHz (f ₂ −
The difference signal of f ₁ ) is extracted. However, since the difference signal of (f ₄ −f ₂ ) is not 46 KHz, no signal is extracted from the 46 KHz bandpass filter 4. Therefore, the operational amplifier circuit 5 is supplied with a difference signal and a zero signal (f ₂ -f _1), the amount the operational amplifier circuit 5 which head H ₁ is positioned on the track TR _2, i.e., non-shifting amount of the head H ₁ Lock data indicating
Output to the A / D converter 6. The A / D converter 6 samples the lock data at a point B in FIG. 2, and the lock data is sent to the microcomputer 7. Thereafter, the reference oscillator 2 to supply the reference pilot signal f ₁ to a balanced modulation circuit 1 again, the error data in A _2, A ₃ points of FIG. 2 in the same manner as described above is sampled.

When data is sent from the A / D converter 6, the microcomputer 7 performs the operation of the above equation and outputs a phase error value as a result of the operation. Here, when performing the just track, the calculation is performed with the S value set to zero. Then, the expression amount of shift head H ₁ becomes phase error value = error data is outputted as a phase error value. When the track is shifted as in the tape path adjustment, an S value corresponding to the shift amount is set, and a phase error value calculated based on the S value is output.

The calculation at the sampling point of the error data uses the lock data of the previous track, and the calculation at the sampling point of the lock data uses the average value of the error data of the previous track and the same track. Use of the average value can prevent adverse effects such as signal noise.

The D / A converter 9 obtains the phase error value thus obtained.
Is converted to an analog value, and the capstan motor control circuit is controlled by the phase error value.

In this embodiment, four data points are taken for one track, but theoretically, two data points of error data and lock data may be taken for one track.

[Effects of the Invention] As described above, according to the present invention, in the automatic tracking control circuit for recording a pilot signal on an adjacent track and performing tracking with a reproduced pilot signal picked up by a head, Error data indicating the shift amount of the head is calculated from a pilot signal and a reference pilot signal having the same frequency as the pilot signal recorded on the reproduction track, and the same frequency is used as the reproduction pilot signal and the pilot signal recorded on a track adjacent to the reproduction track. The lock data indicating the non-shift amount of the head is calculated from the reference pilot signal of the above, and the data obtained by multiplying the error data by a first variable coefficient and the data obtained by multiplying the lock data by a second variable coefficient are calculated. Addition to calculate the phase error value, In the case of track, the first variable coefficient is set to 1,
The second variable coefficient is set to 0, and in the case of a track shift, the first variable coefficient and the second variable coefficient are varied according to the shift amount, and a desired track shift is performed based on the phase error value. With this configuration, a desired track shift can be performed with only a very small number of samplings (sampling at a minimum of two locations per track), and an effect that a digitized servo system can be realized.

[Brief description of the drawings]

1 to 3 show an embodiment of the present invention, FIG. 1 is a block diagram of an automatic tracking control circuit, FIG. 2 is an output waveform diagram of each part, and FIG. 3 is a diagram showing a head position on a track. 4 and 5 show a conventional example, FIG. 4 is a block diagram of an automatic tracking control circuit, and FIG. 5 is a diagram showing correspondence between a head scanning track and a reference pilot signal. TR ₁ to Tr ₄ ...... track, A ...... data calculation means, 2 ......
Frequency oscillator, 8 ... Calculation unit.

Claims (1)

(57) [Claims] 1. A reproduced pilot picked up by a head, in which a pilot signal in which a frequency difference between a pilot signal recorded in right and left adjacent tracks and a pilot signal recorded in right and left adjacent tracks is constant at different values in left and right is recorded on adjacent tracks. An automatic tracking control circuit that performs tracking by detecting a frequency mixing ratio of a signal; a frequency oscillator that outputs a reference pilot signal having the same frequency as a pilot signal recorded on each track; a reproduced pilot signal picked up by the head; Using a reference pilot signal of the same frequency as the pilot signal recorded on the track being scanned by the head, calculate error data indicating the shift amount of the head,
Data for calculating lock data indicating a non-shift amount of the head using a reproduced pilot signal picked up by the head and a reference pilot signal having the same frequency as a pilot signal recorded on a track adjacent to a track scanned by the head. Calculating means; data obtained by multiplying the error data by a first variable coefficient;
A phase error value is calculated by adding data obtained by multiplying the lock data by a second variable coefficient, and when the track is just track, the first variable coefficient is set to 1;
And a computing unit that varies the first variable coefficient and the second variable coefficient in accordance with a shift amount when a track shift is performed, and a desired track shift is performed based on the phase error value. An automatic tracking control circuit characterized in that the automatic tracking control circuit is configured to perform the following.