JPS59180861A - Tracking control circuit - Google Patents

Abstract

PURPOSE:To eliminate the inversion of polarity of a tracking control signal for each track by changing the generating timing of two signals which are not adjacent to each other for the pilot signal to be mixed to the writing order of four different types of pilot signals. CONSTITUTION:An extracted pilot signal is mixed at the 2nd mixing circuit 11 with pilot signals f1-f4 supplied from a pilot signal generating circuit 9. Thus a beat component of a mixed double frequency containing two types of frequency differences fT1 and fT2 of a fixed frequency and ¦f3-f1¦ or ¦f4-f2¦ is pro duced. Therefore the levels of output signals of wave detecting circuits 20 and 21 are decided in accordance with the amplitudes of the differences fT1 and fT2. These output signals are supplied to a comparator 22, and a tracking control signal which varies on the basis of the reference value is delivered. The change of this tracking control signal shows a shift amount of tracking. A motor control circuit 4 controls the revolving speed of a capstan motor 3 in response to said control signal. Thus the tracking shift is corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a tracking control circuit for a video disc or a video tape recorder (hereinafter simply referred to as VTll'L), and in particular a tracking control circuit using four predetermined types of no-chillot signals. This invention relates to a tracking control circuit using a so-called pilot method.

BACKGROUND TECHNOLOGY In a video disc or VTR, the tracks recorded on a recording medium such as a disc or tape are:
The value deviates from the design center value due to manufacturing and processing precision of the recording device, etc. Especially in VTRs, due to the processing accuracy of the cylinder and uneven tension around the cylinder,
The tracks on the recording medium are curved in an S-shape.

Therefore, when playing back a recording medium in this type of device,
It would be ideal if tracking could be performed automatically while moving the pickup or magnetic head that traces the track in the width direction of the entire track.

For this reason, several tracking control methods have been proposed for this type of device. Among them, recently there have been four types of J? A method called the Nogirotto method using pilot signals has been proposed and is receiving attention.

This No. ξ pilot method uses four kinds of No. ξ pilot signals f1 + f2 consisting of predetermined mutually different frequencies.
The frequency differences of +f3 +f4 are determined to have the relationship shown in FIG. r4 is sequentially switched as . . . fl + f 2 + f 3 + f 4 for each track, and is superimposed on the recorded signal and written on the recording medium. Therefore, when reproducing a track in which, for example, the number ξ pilot signal f1 is written, the number ξ pilot signal f2+f4 recorded in the adjacent tracks on both sides will also be reproduced due to crosstalk. In this case, The extracted no.xilot signal fp in is f1+f2*f4
becomes. Therefore, when the extracted pilot signal fp is mixed with the pilot signal f1 recorded on the playback track, the output is f2±h'1if4±flllfl.
10ftl appears, and if we extract only the difference component, we get 1fz-ftl = f'r1e from the relationship shown in Figure 1 (B).
If4-ftl=f'r, 1fl-fll=0 is obtained. As a result, when a track shift occurs during reproduction, the amplitude of either fTl or fT2 increases depending on the direction of the shift.

For example, as shown in Fig. 2, a pickup or magnetic spatula PH traces a track (A) in the direction of arrow A, and this trace corresponds to each track (A) to (A) on the recording medium.
Assuming that (c) is sequentially moved in the direction of arrow B,
Each track (a) ~ ni) has four types of oirot signals f.
l +f2 af3 +'4 sequentially...fl, fl
It is written in the order of +f3 sf4... Therefore,
If the pickup or magnetic head H shifts as shown by
Tl becomes smaller than fT+.

Therefore, if the pickup or magnetic head H is moved in a direction perpendicular to the track or the recording medium is moved so that the amplitudes of s fTl r fTz become equal, the pickup or magnetic head Hid@2 is shown as Z in Fig. As a result, a normal tracking state can be maintained. For example, since a magnetic tape is used as a recording medium in a VTR, the running speed of this magnetic tape, that is, the capstan motor that runs the magnetic tape, is corrected to have the value of the above-mentioned amplitude difference between fTl and fT2. The speed is controlled by a signal, or if the above-mentioned movement control of the magnetic head is performed, tracking is automatically performed. Further, in the case of video discs, since the disc is used as a recording medium, tracking control cannot be performed in this case even if the motor that rotates the disc is controlled. For this purpose, in the case of a video disc, tracking adjustment is performed by moving the pickup in the radial direction of the disc.

By the way, in a tracking control circuit using such a digital pilot method, in order to obtain the frequency differences fT1 and fT2 shown in FIG. The pilot signal is the pilot signal f11 in the truck (A) shown in Figure 2).
In the rack (b), it is necessary to switch the pilot signal f2 for each track so as to correspond to a predetermined writing order. Therefore, the frequency difference fT1 m in the direction of deviation of the pickup or magnetic head H
The amplitude relationship of fTil is reversed for each track.

As a result, the polarity of the correction signal having the above-mentioned amplitude difference value must be reversed for each track and then supplied to the speed control circuit of the motor or the like. For this purpose, after determining the frequency difference fT1 a fT2, an inverting circuit consisting of an analog switch and an inverting amplifier is required to invert the polarity of the signal for each track by inputting the amplitude level difference between the two to the input or output side of the comparator. Met.

To solve this problem, the magnetic head H The applicant of the present application has proposed a method in which the magnitude relationship of the amplitude of the frequency difference fT1 # fTz with respect to the shift direction is always the same.

This means that the four types of pilot signals written during recording are
When repeated in the order of +f2, fl *f4,
fTt # Mix for production of fT2. The generation timing is controlled so that the o pilot signals are handled in the order fl #f2 efl #f4 . . . or in the order fl tf4 #hff2 . In this way, four types of log signals ft * fz are written during recording.
*For the sequentially repeated writing order of fs p fa, the pilot signal to be mixed for the generation of %fTl#fT+ is mixed with two signals that are not adjacent to each other in the writing order of the no ξ pilot signal at the time of writing. By changing the generation timing, even if the magnetic head H sequentially moves to the next track, the deviation direction and frequency difference fTt
# The magnitude relationship of fT2 is always corrected to correspond. Therefore, as described above, an inverting circuit including an analog switch, an inverting amplifier, etc. for correcting the polarity of the correction signal whose polarity is sequentially inverted as the magnetic head H moves along the track becomes unnecessary.

Here, in the tracking control circuit having the above configuration, during recording, the o-lot signal fp is transmitted to one of the magnetic heads H.
A Kfl and fl are supplied, and the other magnetic spatula FHB
f2+f4 are respectively given to the magnetic head HA#.
It is only possible to distinguish HB, but it is not possible to distinguish between fl and fl or fz and f4 of the pilot signal fp recorded in the track currently being traced. For this reason, at the start of playback, etc., the frequency difference fT1 s fT2
When the combination timing of the pilot signal mixed with the extracted pilot signal fp for extracting the signal is shifted by two tracks, the polarity of the tracking control signal is reversed, and tracking is controlled in the direction out of alignment. As a result, the control in the direction of tracking deviation is executed for two tracks before returning to normal tracking control, resulting in a problem of longer tracking alignment time or distortion of the reproduced image. .

For this reason, in the tracking control circuit having the above configuration, if the timing of the combination of the extracted pilot signal fp and the mixed pilot signal is shifted by two tracks, the If3-fll signal extracted at the time of mixing is When these components rise above a predetermined level, it is assumed that a timing shift of two tracks has occurred, and the polarity of the tracking control signal is inverted.

As a result, in the tracking control circuit described above, although polarity inversion for each track is no longer necessary, an inversion circuit is again required in order to shorten the tracking settling time when there is a deviation of two tracks. I have a problem with this.

DISCLOSURE OF THE INVENTION It is an object of the present invention to
Reliable tracking control and tracking stabilization while completely eliminating the need for polarity reversal for the tracking control signal when the combination timing of the mixed pilot signal with respect to the polarity reversal of each track and the extracted pilot signal is shifted by two tracks. It is an object of the present invention to provide a tracking control circuit that can reduce time.

In order to achieve such an object, the tracking control circuit according to the present invention adjusts the pilot signals to be mixed to generate an extracted pilot signal according to the writing order of the four types of pilot signals during recording. By interchanging the generation timings of two non-adjacent signals in the writing order of s fTt l fT!, it becomes unnecessary to invert the polarity of the tracking control signal for each track, and s fTt l fT! Assuming that a two-track timing shift occurs when the level of If3-fll or l f<-h1 generated when generating the signal exceeds a predetermined level, the timing difference of two tracks occurs when the extraction R pilot signal is generated. To restore the two signals that are generated by switching the generation timings above,
Furthermore, by interchanging the generation timings of two signals other than these two signals, it is no longer necessary to invert the polarity of the tracking control signal in response to a timing shift between the two tracks.

Therefore, in the tracking control circuit configured in this way, an analog switch and an inverting amplifier for inverting the polarity of the tracking control signal are not required, which simplifies the circuit and greatly reduces costs. Contribute.

Furthermore, in the present invention, even if the timing of the mixed pilot signal with respect to the extracted pilot signal deviates by two tracks, the polarity of the generated tracking control signal is always in the direction of the track deviation. Since they match, it has various excellent effects such as extremely short settling time for tracking.

BEST MODE FOR CARRYING OUT THE INVENTION FIG. 3 is a block diagram showing one embodiment of a tracking control circuit according to the present invention. In the figure, reference numeral 1 indicates a magnetic tape as a recording medium, and the present invention will be explained below based on an example in which the present invention is applied to a VTR using a helical scanning system. Reference numeral 2 denotes a capstan shaft that is rotationally driven by a capstan motor 3 to run the magnetic tape 1 in the direction of the arrow, and the rotational speed of the capstan motor 3 is controlled by a motor control circuit 4. . Further, the magnetic tape 1 includes a pair of magnetic heads 5a.

The recorded signal is written in by 5bK. In this case, the pair of magnetic heads 5a and 5b are mounted at positions 180 degrees apart from each other on the circumference of a rotating cylinder (not shown). Since this rotating cylinder is rotated diagonally across the longitudinal direction of the magnetic tape 1 at high speed, a pair of magnetic spatulas)'5a and 5b are attached to the magnetic tape 1.
You will be tracing diagonally across the top. Here, the relationship between the rotating cylinder (not shown) and the running speed of the magnetic tape 1 is as follows:
It is determined that each of the pair of magnetic heads 5a, 5b completes one trace on the magnetic tape 1 in one rotation of the rotating cylinder. Therefore, a pair of magnetic heads 5a.

5b is switched in accordance with the rotation of the rotary cylinder to alternately write recorded signals onto the magnetic tape 1.

As a result, two recording tracks are formed on the magnetic tape 1 by one rotation of the rotating cylinder.

Here, 6 is a switch for switching the recorded signal supplied to the magnetic heads 5a and 5b in accordance with the rotation of the above-mentioned rotary cylinder.

The above is an outline of the two-height rvTa using the generally known helical scanning method, and since its details have already been made public, the details will be omitted here.

In the VTR constructed in this way, numeral 7 is a mode command circuit which instructs switching between the recording mode P and the reproduction mode P, and the output switch 8 is switched by the generated command signal. Further, the command signal generated from the mode command circuit 7 is also supplied to the Nonoirot signal generation circuit 9 to inform it of which mode it is in. The pilot signal generating circuit 9 generates and outputs the aforementioned four types of pilot signals fl sf2 +f3 *f4 in a predetermined order for each track written on the magnetic tape 1. This predetermined order is the recording mode R.
The generated pilot signals fl *f2 *f3 *f4 are set to be different in advance for the playback mode PP and the playback mode PP.
is supplied to the first mixing circuit 10 and the second mixing circuit 11.

The first mixing circuit 10 superimposes the Nonolot signal '1 +f2 ef3 +f4 on the video signal RF supplied from the outside, and supplies it to the recording amplifier 12 as a recorded signal. Therefore, the recorded signal output from the recording amplifier 12 is supplied to the R side terminal of the above-mentioned changeover switch 8. When the command signal supplied from the mode command circuit 7 is in the recording mode PFL, the selector switch 8 switches either one of the magnetic spatulas (5a and 5b) selected by the switch 6 to the R side terminal. Connected. Further, when the command signal indicates the reproduction mode PP, one of the magnetic heads 5a and 5b selected by the switch 6 is connected to the P side terminal. Therefore, recording mode PR
In this case, the recorded signal generated from the recording amplifier 12 is passed through a changeover switch 8 to a pair of magnetic spatulas F''5a,
It is supplied to either one of 5b and 5b according to the switching operation of the switch 6. In the reproduction mode rP, reproduction signals alternately reproduced by the pair of magnetic heads 5a and 5b are supplied to the reproduction amplifier 13 via the switch 6 and the changeover switch 8. The reproduction signal output from the reproduction amplifier 13 is supplied as a video signal RF to a well-known video signal processing system, and is also supplied to a low-nos filter 15 via an automatic gain control circuit 14.

Here, the relationship between the video signal RF constituting the reproduced signal and the pilot signal fl A2 + f3 + f4 is the video signal B
, F are generally several MH2, whereas the ξ pilot signal is set to about several hundred KHz so as not to affect the video signal KF. Therefore, from the low-noise filter 15, the pilot signals '1,
Only f2 m '3 s f4 will be extracted as an extracted pilot signal. And this extraction ξ
The pilot signal is a pilot signal '1 *f2 sf3, f4 supplied from the pilot signal generation circuit 9.
(and mixed in the second mixing circuit 11), the two frequency differences fT1 s fT2 and Ifa-ftl or l f4 of the constant frequency shown in FIG.
- A mixed two-frequency beat component containing hl is generated.

This beet ingredient is.

A first pantone pass filter 16 that passes only the frequency difference fTs, a second pantone pass filter 17 that passes only the frequency difference fT2, and a third pantone pass filter 18 and l that passes only the 1fa-fll component.
The signal is supplied to the 47th node ξ filter 19 which passes only the f4-f21 components. The frequency difference fT that has passed through the 17th second pass filter 16 is detected in the first detection circuit 20, and the frequency difference fT that has passed through the 229th second pass filter 17 is detected in the second detection circuit 20.
1 is detected.

Therefore, this first. Each output signal of the second detection circuit 20.21 has a frequency difference (Tl, , JT□
The level will be determined according to the amplitude of. The eleventh second detection circuit 20.21 generated in this way
The output signal of the comparator 2 composed of a differential amplifier
2, and outputs a tracking control signal that changes around a constant reference value in accordance with the level difference between the human power signals. That is, when the traces of the magnetic spatulas F''5a, 5b are shifted in the track width direction, the amplitude of the frequency difference f+11#fTz varies in magnitude depending on the direction of the shift, as described above.

As a result, the comparator 22 generates a tracking control signal that increases or decreases from a constant reference value depending on the direction of displacement. In this case, since the amount of change in the tracking control signal changes according to the difference in the power levels of both people in the comparator 22, this amount of change ultimately depends on the difference in amplitude between the frequency differences fT1 and fT2. This indicates the amount of tracking deviation. Furthermore, when no track deviation occurs, the level difference between the surface input signals of the comparator 20 is zero, so the generated tracking control signal is supplied to the motor control circuit 4 as a signal having a constant reference value. be done. Therefore, the motor control circuit 4 often corrects the shift in track by controlling the rotational speed of the capstan motor 3 in accordance with the tracking control signal generated in this way.

In this way, each part operates according to the recording mode and the playback mode P, and the pilot signal generation circuit 9 also operates in both modes.
The generation order of the pilot signals fl#f24f3tf4 is changed depending on the state of the track deviation.

That is, the Nonoirot signal generating circuit 9 includes, for example, an oscillation circuit 911, a frequency dividing circuit 92, a switch circuit 93, and so on, as shown in FIG. It is composed of a waveform converter 94 and a switch control circuit 95. The oscillation circuit 91 receives the video signal E
, F, and generates a reference clock signal of a predetermined frequency in synchronization with the horizontal synchronization signal HD included in the signals HD. The oscillation circuit 91 that performs such an operation is, for example, a voltage controlled oscillator 9.
11, a phase difference detection circuit 912, a frequency dividing circuit 913, and a low-pass filter 914. The reference clock pulse generated from this reference oscillation circuit 91 is frequency-divided in a frequency dividing circuit 92, and is then divided by the four types of pilot signals f1 m'2 * mentioned above.
f3 *F4 is individually output as a rectangular wave from the output terminals O1 to 04 and input to the switch circuit 93)
pl-p are respectively supplied to the A larel. The switch circuit 93 receives input from the switch control circuit 95) Fi
Selection control signals supplied to P14, respectively. ,~8
4 types of pilot signals fx ef21f3
+f4 is selected and output. The selected type of pilot signal is supplied to the waveform converter 94, where it is integrally integrated to convert it into a triangular wave, and then converted into a sine waveform by a well-known polygonal function generator or the like and output.

On the other hand, four types of ξ pilot signals h # f2 + f34f are sent to the switch control circuit 95 and the switch circuit 93.
Selection control signal J-64 to select one type from 4.
occurs. When the selection control signals e1 to e4 are generated, the four types of pilot signals are selected in one order in recording mode R and two in playback mode P, for a total of three selection orders.
It is necessary to perform control so that the pilot signals are repeatedly generated in different predetermined orders, and to control the switching timing so that they are the same in both modes. This switch control circuit 95 includes exclusive OR circuits 951 and 952 and a flip-flop circuit 9.
53 and a binary-decimal decoder (hereinafter referred to as a decoder) 954. The exclusive OR circuit 951 receives as input signals command signals E, /P generated from the mode command circuit 7 and a head switch signal SH whose polarity is inverted every trace period of one track, and outputs the command signals E and /P generated from the mode command circuit 7. The flip-flop circuit 953 is triggered at the falling edge of the signal. In addition, the exclusive OR circuit 9
Reference numeral 52 inputs the set output Q of the flip-flop circuit 953 and a two-track deviation detection signal supplied from a two-track deviation detection circuit to be described later. Further, the decoder 954 inputs the head switch signal SH to the input terminal A which is responsible for the LSB of the input terminals A and B having a 2-bit configuration, and inputs the head switch signal SH to the input terminal B which is responsible for the MSB. The output signal of 952 is input.

In the switch control circuit 95 configured in this manner, in the recording mode PfL state, the command signal R/P becomes R and becomes logic 1L'. Therefore, head switch signal S
When H is supplied in the state shown in FIG. 5(a), exclusive OR circuit 951 generates an output signal matching this Heller switch signal SR and supplies it to T-type flip-flop circuit 953. As a result, the flip-flop circuit 9
53 is not triggered in synchronization with the falling edge of the head switch signal SH, and its set output Q is at logic 'L' since the two-track deviation detection signal K is at logic 'L'.
The signal G is supplied to the input terminal B of the decoder 954 via the exclusive OR circuit 952 as shown in FIG. 5(b). As a result, the input terminal A of the deco-da 954.

Signals SH and G supplied to B and output signal e
1 to e4, the output signal el +
62 +63 +e4 will be output in sequence. When the output signal ~e4 generated in this way is supplied to the input port pH~PI4 of the switch circuit 93 as a selection control signal "1 r e2 se3 j e4, the switch circuit 93 inputs the input port pH ~ PI4 to the input port pH~P4, respectively. The supplied ξ pilot signals f1mf2+f, , f4 are sequentially and repeatedly selected and output.

Next, the command signal R when the two-track deviation detection signal K is 'L'
/P is set to 'H'. As a result, the output signal of the exclusive OR circuit 951 is in a state in which the polarity of the head switch signal SH shown in FIG.
It will be triggered at a point in time. The output of this flip-flop circuit 9530 is transmitted to the decoder 9 as an output signal G shown in FIG. 7(b).
54 is supplied to the input end B of 54. Therefore, in this case, the relationship between the input/output signal of the decoder 954 and the selected output signal of the switch circuit 93 is as shown in FIG. 8, and the pilot signal is repeatedly selected in the order of '3e'2eflsf4. Output.

However, as shown in FIG. 6, the timings of generation of two types of non-adjacent non-adjacent non-initial signals f1 and f3 generated during recording are switched.

Next, when the two-track deviation detection signal K is inverted to logic 1H' representing a two-track deviation, the set output of the flip-flop circuit 953 is the output signal G with the polarity inverted.
is generated as shown in FIG. 9(b) and sent to the decoder 954.
is supplied to the input end B of. As a result, the relationship between the human output signal of the decoder 954 and the selected output of the switch circuit 93 is as shown in FIG.
2, the generation timings of the two types of non-adjacent ξ pilot signals f2sf4 are switched, which is different from the case of FIG. 8.

Next, in FIG. 3, 23 is a third detection circuit that detects the output of the third non-node detection filter 18, and its output signal is supplied as a control signal to the automatic gain control circuit 14, and the second The output level of the mixing circuit 11 is kept constant. 2
Reference numeral 4 denotes a fourth detection circuit which receives the output signal of the fourth node ξ filter 19, and detects the output of the fourth band o-sphere filter 19. Reference numeral 25 denotes a two-track deviation detection circuit, which determines that a two-track deviation has occurred when the output signal of the fourth detection circuit 24 is output for a predetermined period, and outputs the two-track deviation detection signal K as described above. The o pilot signals are supplied to the pilot signal generation circuit 9, and the generation order of the o pilot signals, which are generated in the order shown in FIG. 8 or 10, is reversed to the generation order shown in FIG. 10 or 8.

In the circuit configured as described above, if the pair of magnetic heads 52 and 5b that trace the recording track in the reproduction mode Pp deviate in the width direction of the track, the track deviation can be corrected as follows. Corrections will be made. - Well, either one of the pair of magnetic heads 5 a m 5 b is @
As shown in Figure 2, the pilot signal '1 +f2 *f3
*One track recorded in f4 order (a)
When b is traced, the low-pass filter 15 outputs fl and f4 and f2 due to crosstalk from the adjacent track as extracted pilot signals and supplies them to the second mixing circuit 11. In this case, the pilot signal generation circuit 9 detects the %L in which the 2-track deviation detection signal K generated from the 2-track deviation detection circuit 25 indicates the non-detection state.
7 state, the output signal G of the exclusive OR circuit 952 of the pilot signal generation circuit 9 detailed in FIG. 4 becomes the same as the set output Q of the flip-flop circuit 953. The generation order of the /quilot signal is '3 s12 mfl sf4' repeatedly as described in FIG.

As a result, as mentioned above. When tracing the track (A) on which the e-pilot signal f1 is recorded, the pilot signal f3 is generated from the pilot signal generation circuit 9, and is supplied to the second mixing circuit 11 and mixed with the extracted pilot signal. . Therefore, the output of the second mixing circuit 11 is Ifs±
'tl*lf3±f41°Ir3±hl. As explained earlier using FIG. 1 (5) and (B), this output signal is a frequency difference fTt s of a predetermined constant frequency.
It is a mixed two-frequency beat component including fl2 and 1f3-hl, and the first and 27th P pass filters 16 in the next stage
．． 17, the above fT1 = l fa - f41
When fl2 = l fa - ft 1, if the pair of magnetic heads 5 a s 5 b are not misaligned in the track width direction, % fT1 + f, r? The size of is f, 1. l = fl2, and as mentioned above, the comparator 22 generates a signal having a constant reference value and supplies it to the motor control circuit 4, thereby controlling the motor 3.
Leave the rotation as it is. Further, the 37th second pass filter 18 controls the I
r3-r, I is extracted, rectified and smoothed in the detection circuit 23, and then supplied to the automatic gain control circuit 4, thereby preventing the output level of the second mixing circuit 11 from fluctuating. There is.

In this case, since the output signal of the second mixing circuit 11 does not include the component 1b-hl, there is no output from the fourth node ξ filter 19, and this
The output signal of the non-pass filter 19 is transmitted to the fourth detection circuit 3.
The two-track deviation detection circuit 25, which receives the input via 4, continues to be in an inoperable state.

Next, the magnetic spatula P5a or 5b moves to the next adjacent track (
b) side, the above-mentioned crosstalk will be fi(
h, so the above frequency difference fT1 e f
l2 becomes fTl<fl2. Therefore, the comparator 22 has a value that is either larger or smaller than the above-mentioned constant reference value.

Furthermore, if the magnetic head 5a or 5b shifts to the previous adjacent track (unmarked) side, the losstalk as described above will occur at f4.
) ft, so the above frequency difference fT, and fT
z satisfies fTl>fl2. Therefore, the comparator 22 generates a correction signal having a value that is opposite to the above-mentioned deviation to correct the track deviation.

Next, if the magnetic head 5a or 5b traces the next track (b) and marks it as b, then the low-nos filter 1
5 is an extracted pilot signal, and fl and fa are output as crosstalk between ft and the adjacent track, and are supplied to the second mixing circuit 11. At this time, the pilot signal generation circuit 9 generates the pilot signal f2 and supplies it to the second mixing circuit 11, as is clear from the relationship between FIGS. 6 and 8.

Therefore, the output of the second mixing circuit 11 becomes lfZ±f21°lh±fll, lf2±f31. As a result, the first
And the 20th Nogsufu f Shita 16, 17 is 1h-
fl I=fTl, I ft-'fs'1=fTs
Take out each +, and take out the 1st. Second detection circuit 20.2
1 to the comparator 22. At this time, if there is no deviation of the magnetic head 5a or 5b, a signal containing the same reference value as in the above case is generated from the comparator 22, and this is supplied to the motor controller circuit 4 as a tracking control signal. .

Furthermore, if the magnetic head 5a or 5b shifts to the next adjacent track (c), the above-mentioned crosstalk fls
Since f3 is ft<fs, the above-mentioned frequency difference f
T11 fl2 becomes fTl<fl2. Therefore, the output of comparator 2 in this direction of deviation becomes a tracking control signal that matches the direction of deviation when tracing the track (a) described above. Then, the crosstalk when shifting to the previous adjacent track (A) side is ft>
Since fa, the frequency difference fT1>fTz,
In this case as well, the comparator 22 outputs a tracking control signal that matches the shift direction when tracing the track (a) described above.

In this way, even if the magnetic head 5a or 5b sequentially moves to the next track (c, ni), (e), (to), etc., the deviation direction and frequency difference The magnitude relationship between fT1 and fT2 remains unchanged.

Next, a case will be described in which the magnetic head 5a or 5b traces a track that is two tracks away from the predetermined relationship at the time of starting or canceling the pause operation. For example, when the pilot signal generating circuit 9 generates the pilot signal f2, the pilot signal generating circuit 9 generates a signal (for example, to the track shown in FIG. 2).
When traced by the magnetic head 5a or 5b, f3sfl is generated from the low-pass filter 15 due to crosstalk from the reproduced pilot signal f4 and its adjacent tracks (c) and (e). Therefore, the output of the second mixing circuit 11 is 1fa-f+I.

I fs-h l e l fl-f, I will be included.

In this case, Ifl is output from the first pantone filter 16.
-f, I=fT, is taken out, l fa -hl = fez is taken out from the second bandpass filter 17, and its output signal is the first. The magnetic spatula P is supplied to the comparator 22 via the second detection circuits 20 and 21 respectively.
If 5a or 5b shifts to the track (E) side, s
When f·rt>fTz, tracking control in the opposite direction is added as described above, resulting in the inconvenience that it takes a long time to settle the tracking.

Here, if a two-track deviation occurs as described above, the output of the second mixing circuit 11 will have lfa -fz as described above.
Since a component 'l is included, the p1 4th/dnogus filter 19 extracts this If, -f21 and extracts the 4th
The signal is supplied to the detection circuit 24. The fourth detection circuit 24 detects the output signal of the fourth filter 19 and supplies the output signal to the two-track deviation detection circuit 25. In this case, the magnetic head 5a or 5b tracks (b), (e)...
・If you play by moving sequentially, the second
If4-f21 is generated from the mixing circuit 11, and accordingly, the output signal of the fourth detection circuit 24 is also output every other track.

On the other hand, the two-track deviation detection circuit 25 is connected to the fourth detection circuit 24.
The determination is made using the output signals of every other track output from the fourth detection circuit 24 as input, and when a predetermined number of outputs are generated from the fourth detection circuit 24 within a predetermined time, a two-track deviation occurs. The two-track deviation detection signal K ('H#) is generated and held.

When the two-track deviation detection signal K is generated in this manner, the output signal G of the exclusive logic circuit 952 shown at 952 in FIG.
will be reversed. 21 - When the rack misalignment detection signal K is generated, the input terminal A of the decoder 954,
The upper bit signal of the 2-bit input signal supplied to H is forcibly inverted, and as a result, the pilot signal generation order of the pilot signal generation circuit 9 is changed to that shown in FIG. 'l j'4 s'3 m' as shown
2 efl... is changed to repeat in the order. Therefore, the pilot signal 'l +f2*f3+f
Tracks ′ (a), (
B).

(C), (for a signal reproduced with a two-track deviation with respect to the gradient...) ξIlot signal'
I If4 If3 If2 . . . are sequentially mixed to output mixed components of 21 frequencies. In this case, since the deviation between the two tracks in the combination of the mixed pilot signal and the mixed pilot signal recorded on the playback track is corrected, the tracking control signal is Normal tracking control can be obtained without performing polarity reversal.

When a deviation between the two tracks is detected in this way and the order in which the pilot signals are generated is corrected, the polarity of the tracking control signal is instantly reversed, so the tracking settling time is extremely short. Along with this, the unstable period of the reproduced image becomes almost negligible.

Note that once the 2-track deviation detection circuit 25 detects a 2-track deviation, it continues to generate the 2-track deviation detection signal K, and the 2-track deviation detection circuit 25 continues to generate the 2-track deviation detection signal K. Then, when a two-track deviation is detected again, the two-track deviation detection signal K is set to 'L', and the order in which the non-pilot signals are generated is returned to its original state. Summary 9.2 Each time a track deviation is detected, the generation order of pilot signals is alternately reversed to the states shown in Figs. 8 and 10, and the polarity (tracking control direction) of the tracking control signal is corrected. become.

FIG. 11 is a circuit diagram showing a specific example of the two-track deviation detection circuit shown in FIG. 3, particularly when constructed using an analog system. In the figure, reference numeral 26 denotes a low-pass filter that removes noise contained in the signal supplied every other track from the fourth detection circuit 24 and outputs the signal.

The output signal of this low-pass filter 26 is compared with a reference value set by a variable resistor 28 in a comparator 27, so that the output signal is as shown in FIG. 12(a).
formatted and output.

The thus shaped output signal of the comparator 27 is integrated in an integrating circuit 29, and an integrated signal shown in FIG. 12(b) is output. In this case, the charging and discharging routes of the integrating circuit 29 are changed to give different time constants. During charging, current flows through the route of resistor R1 - diode D - capacitor Of, and during discharging, current flows through the route of capacitor 01 - resistor R2. Then, by setting the value of the resistor R1*R2 as Rt < R2, the charging time constant τ1 becomes τ1""R1"0
1, and the discharge time constant τ2 is τ2−R
2601, which is set to a relatively large value.

Note that the transistor T1 and the resistor R3 constitute a circuit for forced discharge. The output signal of the integrating circuit 29 is compared with a reference value Vrl set by a variable resistor 31 in a comparator 30.

The comparator 30 is provided with hysteresis characteristics by having the output signal plugged into the input side by the resistor 32, and when the input signal exceeds the reference value Vrl, the output changes as shown in FIG. As shown in c), it becomes 'H〃. Here, since the output signal of the comparator 30 is supplied to the base of the transistor T via the resistor 33,
At the same time as the output of the comparator 30 is generated, the transistor T1 is turned on and the capacitor C1 is forcibly discharged, so that the output of the integrator circuit 29 decreases as shown at time t2 in FIG. Then, the integral output is the reference value (lower limit value Vr2.
), the output signal of comparator 30 becomes
As shown at time t3 in Figure (c), the signal is reversed to "L#".

Here, when the output signal of the comparator 30 becomes 'H' at time t2 in FIG. 12(c), the T-type flip-flop circuit 34 is triggered and its output is as shown in FIG. 12(d).
As shown in FIG. 2, the signal becomes H, and this 'H1 output is supplied to the ξ pilot signal generation circuit 9 as a two-track deviation detection signal. This flip-flop circuit 34 is
When the 1H'' signal is supplied again from the comparator 30, it is inverted and the output signal K is held in the % L l state.
As shown in FIG. 12(a) between time points j4+t5, when a single signal is generated from the comparator 27, the integration circuit 2
The output signal of 9 is sent to the comparator 30 as shown in FIG. 12(b).
The reference value Vrl on the upper limit side cannot be exceeded, thereby preventing an erroneous two-track deviation detection signal K from being generated.

FIG. 13 shows a two-track deviation detection circuit 25 constructed using a digital system, and the same parts as in FIG. 11 are shown using the same symbols. In this case, the output signal of the comparator 26 triggers the mono multi-novel ibrator 35, so that the capacitor C
2 and the value of resistor R4. Since the output signal of this mono-multi-novel circuit 35 is supplied as a clear signal to the counter 36, the counter 36 calculates the number of output signals of the comparator 26 in the period until the next clear signal is supplied. Count. When this count value exceeds a predetermined value, an output signal is generated to trigger the flip-flop circuit 34, thereby generating a two-track deviation detection signal.

In the above explanation, If3-flI is used for automatic gain control, and l'f4-f21 is used to detect a two-track deviation, but it is also possible to reverse the input polarity of the comparator 22 or By performing processing such as reversing the directionality of the control of the motor control circuit 4, If3-rll can be used for detecting a two-track deviation, and 1f4-f21 can be used for automatic gain control. It is possible.

As explained above, according to the tracking control circuit according to the present invention, there is no need for a circuit for inverting the polarity of the tracking control signal, and the generation timing of the mixed signal ξ plot relative to the extracted sample ξ plot is set to the start time. Even if a prisoner deviates by two tracks when releasing the pose, etc., the tracking settling time is extremely short in order to detect this two-track deviation and correct the timing of mixed pilot generation.

[Brief explanation of drawings]

Figure 1 is a spectrum diagram showing an example of the frequency array of the 4-frequency ξlot method, Figure 1 (B) is a diagram showing the relationship between the 4 frequencies and the beat component of their difference, and Figure 2 is a spectrum diagram showing an example of the frequency arrangement of the 4-frequency ξlot method. The recording track and the magnetic spatula P are schematic diagrams showing the misalignment of the pickup. FIG. 3 is a circuit diagram showing an embodiment of the tracking control circuit according to the present invention. FIG. Circuit diagram showing an example of a signal generation circuit, No. 5
Figures (a), (b), Figure 7 (a), (b)
, FIG. 9(a) I(b) is a waveform diagram showing the operation of the tracking control circuit shown in FIG. 4, FIG. 6, FIG. 8, and FIG.
Figure 0 is a diagram showing the generation order of the Nonolot signal in each mode of the tracking control circuit shown in Figure 4, and Figures 11 and 13 are specific examples of the two-track deviation detection circuit in Figure 3. 12(a) to 12(d) are operation waveform diagrams of each part of the two-track deviation detection circuit shown in FIG. 11. DESCRIPTION OF SYMBOLS 1... Magnetic tape (recording medium), 2... Cap stand, 3... Motor, 4... Motor control circuit, 5a, 5b... Magnetic spatula r, 6... Switch, 7... ...Mode command circuit, 8...Selector switch, 9
... Nogilot signal generation circuit, 10.11 ... 1st and 2nd mixing circuit, 12 ... Recording amplifier, 13 ...
Reproduction amplifier, 14... automatic gain control circuit, 15...
Ronogus filter, 16-19...1st to '4th Nodono Q filter, 20, 21. , 23 , 24
. . . 1st to 4th detection circuits, 25 . . . 2 track deviation detection circuit. Applicant: ShinNippon Electric Co., Ltd.

Claims (1)

[Claims] (υ Four types of pilot signals having different predetermined frequencies from the recorded signal) f1ef2++f3+
One type of f4 is written for each track, and each of the e-lot signals fl#f2*f3+f4
The writing order of f! is sequentially written for each track. By sequentially tracing each track on a recording medium in which data is repeatedly written in the order from f1 to f4, the recorded signal of that track and each pilot signal f1 * f2 m'3 + f4 are determined. Any one type of extracted pilot signal is reproduced, and the frequency difference between the pilot signal of the adjacent track and the extracted pilot signal obtained by shifting the position of the trace toward one of the adjacent tracks is detected. , this frequency difference is predetermined in advance to have two types of constant frequencies, one for when the trace level is shifted to the one track side and the other for the case where the trace level is shifted to the other track side, and this constant frequency is In a tracking control circuit that detects a deviation in the trace position and corrects the tracking deviation by detecting the type and amount, the extraction node R is also used as a trace example for each track.
When the pilot signal is repeatedly reproduced in the order from f1 to f4, '3af2+f1+f4 or
By sequentially mixing signals generated in the order of 1 tf4 *f3 + f2 at timings corresponding to the order of the extracted pilot signals, the polarity of the deviation amount detection signal in the direction of deviation of the trace position for each track can be determined. At the same time, when the mixed output of the extracted pilot signal and the generated pilot signal contains a component of If3±fll or If4±fil, the generation order of the generated pilot signal is flwf4#flllf2 or '3af2+fa. By switching to the order of
A dragging control characterized in that polarity reversal of the deviation amount detection signal is prevented when the combination of the extracted pilot signal and the generated ξ pilot signal deviates from the predetermined timing by two trunks. circuit.