JPH01263966A - Tracking controller - Google Patents

Abstract

PURPOSE:To simplify the circuit configuration and reduce the cost of the title controller by alternately recording two kinds of pilot signals with fluctuating levels and different frequencies on a recording track together with recording signals at the time of recording and scanning the recording track in accordance with the reproduced pilot signals at the time of reproduction. CONSTITUTION:At the time of recording, pilot signals which have levels proportional or inversely proportional to the distance (x) from the starting end P of each recording track to the position Q of a magnetic head in the directions L1-L6 and frequencies f1 and f2 are alternately recorded together with recording signals on recording tracks T1-T6 on a tape 1. At the time of reproduction, on the other hand, after detecting and differentiating the signals having a frequency difference DELTAfa between two frequencies obtained when the pilot signals of frequency f1 or f2 recorded on the right side or left side adjacent track of the recording track being scanned and signals of the frequency f2 or f1 are multiplied by each other, a magnetic head is controlled so as to scan the recording track based on the differentiated signals. Therefore, the circuit configuration of this tracking controller can be simplified and the cost of the controller can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a tracking control device used in video tape recorders (hereinafter referred to as VTRs) and the like.

[Prior Technology J] Tracking for still playback of a conventional example in which four types of pilot signals with different frequencies are recorded on the recording track of a videotape together with a video signal, and tracking control is performed by detecting the pilot signals during playback. A control device is proposed, for example, in Japanese Patent Laid-Open No. 60-201560.

In this device, as shown in FIG. 6, four pilot signals P1 to P4 having different frequencies rt to f4 are sequentially recorded together with a video signal in corresponding recording tracks TI to 4, and are adjacent to each other during playback. Tracking control is performed so that a magnetic head provided on a rotating drum of a VTR scans a predetermined recording track by detecting a frequency difference between pilot signals reproduced from a recording track. The frequency difference between the pilot signals can be obtained from the reproduced pilot signal reproduced from the recording track and the reference pilot signal output from the oscillator in the VTR. Each recording track TI
They are output from the oscillator in the same order as the regenerated pilot signals and have the frequencies 11 to f4 corresponding to the pilot signals regenerated from T4 to T4, respectively. The frequency of each pilot signal above is “1-1
02kHzS f2= 1 1 6kHz, f3=
1 60kHz.

f4 = set to 146kHz.

Therefore, if the reproduction track deviates to the right on the videotape in FIG. 6 from the recording track where normal tracking should be performed, for example, the relationship between the reproduction pilot signal S2 to be reproduced and the reference pilot signal S3 will change to B in FIG. and C. In addition, the pulse RF-3W of A in FIG. 7 is
As is well known, a pair of magnetic fields are placed opposite the rotating drum of a VTR at an angle of 180 degrees and at different azimuth angles.
.

This is a head switching pulse for switching the reproduction signal output from the head.

Here, the absolute value of the frequency difference between frequencies r1 and f2 and the absolute value of frequencies f3 and f4 are set as Δra, and the frequencies f2 and f3
The absolute value of the frequency difference and the absolute value of frequencies f4 and fl are Δ
When rb is the frequency difference Δfa and Δ′b, each frequency difference Δfa and Δ”b are expressed by the following equations.

Δfa=Nl-f21=lra-r41=14kHzΔ
rb=B2 ral=lr4-rt I=44kHz At D in FIG. 7, the frequency differences Δra and Δrb at each timing when the reproduction track is shifted to the right from the recording track to be scanned as described above are shown. on the other hand,
When the playback track is shifted to the left from the recording track to be scanned, another frequency difference Δfa different from the above case where the playback track is shifted to the right at each timing.
, Δrb. Therefore, by detecting the frequency difference Δ'a, Δrb, it is possible to determine in which direction the reproduction track is shifted on the videotape compared to the recording track to be scanned, so the frequency difference Δ
By performing tracking control based on fa and Δrb, it is possible to control the magnetic head that performs reproduction to accurately scan the recording track to be scanned.

[Problem to be solved by the invention] However, the above-mentioned automatic track following method (hereinafter referred to as A
This is called the TF method. ) tracking control device using
Because it is controlled using four-frequency pilot signals,
There is a problem in that the circuit configuration becomes complicated and the control device is therefore expensive.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide a tracking control device that has a simpler circuit configuration and is less expensive than conventional examples.

[Means for solving the problem] A magnetic recording device for a tracking control device of the first invention includes:
In a magnetic recording device for a tracking control device that records a pilot signal for tracking control along with a recording signal on a plurality of recording tracks on a magnetic tape, a generating means for generating first and second pilot signals having different frequencies; , a switching means for alternately switching and outputting the first and second pilot signals generated by the generating means based on a manually inputted switching signal at a period of 1/2 of the switching signal; and based on the switching signal the level of the first or second pilot signal outputted from the switching means from the first level to a second level higher than the first level in proportion to time with a period of 1/2 of the switching signal. or from the second level to the first level continuously or stepwise in proportion to time, and from the first level to the second level. level changing means for outputting the first or second pilot signal by repeating the change from the second level to the first level twice each; The apparatus is characterized by comprising a recording means for recording the first or second pilot signal outputted from the changing means on the recording track on the magnetic tape using a magnetic head.

The magnetic reproducing device for a tracking control device according to the second invention includes:
A magnetic head is used to reproduce first and second pilot signals having different frequencies that are alternately recorded on a plurality of recording tracks on a magnetic tape, and the magnetic head is activated based on the reproduced pilot signals. In a magnetic reproducing device for a tracking control device that controls scanning of the recording track to be scanned, a pilot signal recorded on the recording track on the magnetic tape is transmitted using a magnetic head based on an input switching signal. a reproduction means for reproducing, a generation means for generating a pilot signal having the same frequency as the frequency recorded on the recording track to be scanned, a pilot signal reproduced by the reproduction means and a pilot generated by the generation means; a multiplication means for multiplying a signal by a signal; an extraction means for extracting a signal having a difference in two frequencies between the first and second pilot signals from the multiplied signal output from the multiplication means; a detection means for detecting a signal having a difference between the two extracted frequencies; a differentiation means for differentiating the signal detected by the detection means with respect to time; and a differentiation means for differentiating the signal detected by the detection means with respect to time. and control means for controlling the recording track to be scanned.

A magnetic reproducing device for a tracking control device according to a third invention includes:
A magnetic head is used to reproduce first and second pilot signals having different frequencies that are alternately recorded on a plurality of recording tracks on a magnetic tape, and the magnetic head is activated based on the reproduced pilot signals. In a magnetic reproducing device for a tracking control device that controls scanning of the recording track to be scanned, a pilot signal recorded on the recording track on the magnetic tape is transmitted using a magnetic head based on an input switching signal. a reproducing means for reproducing, an extracting means for respectively extracting a first and a second pilot signal from among the pilot signals regenerated by the reproducing means, and a first and a second pilot signal extracted by the extracting means based on the switching signal. switching means for outputting a pilot signal having a frequency different from that of the pilot signal recorded on the recording track to be scanned among the two pilot signals; a detection means for detecting the pilot signal outputted by the switching means; A differentiating means for differentiating the pilot signal detected by the detecting means with respect to time, and a control means for controlling the magnetic head to scan the recording track to be scanned based on the signal differentiated by the differentiating means. It is characterized by:

A tracking control device according to a fourth aspect of the invention includes the magnetic recording device for a tracking control device according to the first aspect, and the second aspect of item -h.
A magnetic reproducing device for a tracking control device according to the invention is provided.

A tracking control device according to a fifth invention is characterized by comprising the magnetic recording device for a tracking control device according to the first invention and the magnetic reproducing device for a tracking control device according to the third invention.

By configuring as in the first invention, after the generating means generates the first and second pilot signals having different frequencies, the switching means generates the first and second pilot signals based on the input switching signal. The first and second pyro and /to signals generated by the generating means are alternately switched at a period of 1/2 of the switching signal and output. Next, the level converting means changes the level of the first or second pilot signal outputted from the switching means based on the switching signal to a first level at a period of 1/2 of the switching signal.
from the level to a second level higher than the first level continuously or stepwise in proportion to time, or from the second level to the first level continuously in proportion to time. or change stepwise, and repeat the change from the first level to the second level and the change from the second level to the first level twice, respectively, to achieve the first or second level. Outputs a pilot signal. moreover,
The recording means records the first or second pilot signal output from the level changing means based on the switching signal on the recording track on the magnetic tape using a magnetic head. Therefore, the first
Alternatively, a second pilot signal is recorded on each recording track on the magnetic tape.

Further, by configuring as in the second aspect of the invention, the reproducing means reproduces pilot signals recorded in recording tracks on the magnetic tape based on input switching signals using magnetic heads, respectively; Meanwhile, the generating means generates a pilot signal having the same frequency as the frequency recorded on the recording track to be scanned. Next, the multiplication means multiplies the pilot signal reproduced by the reproduction means and the pilot signal generated by the generation means, and the extraction means extracts the first and second signals from the multiplied signal output from the multiplication means. After extracting a signal having a difference between the two frequencies of the second pilot signal, the detection means detects a signal having a difference between the two frequencies extracted by the extraction means. moreover,
After the differentiation means differentiates the signal detected by the detection means with respect to time, the control means controls the magnetic head to scan the recording track to be scanned based on the signal differentiated by the differentiation means. do. Therefore, by reproducing the first or second pilot signal recorded on each recording track on the magnetic tape, the reproduced first pilot signal is
Alternatively, the magnetic head is controlled to scan the recording track to be scanned based on the second pilot signal.

By configuring as in the third invention, the reproducing means reproduces the pilot signals recorded in the recording tracks on the magnetic tape based on the input switching signals using respective magnetic heads. After that, the extracting means extracts the first and second pilot signals from among the pilot signals reproduced by the reproducing means. Next, the switching means outputs a pilot signal having a frequency different from that of the pilot signal recorded on the recording track to be scanned among the first and second pilot signals extracted by the extraction means based on the switching signal. After that, the detection means detects the pilot signal outputted by the switching means. Further, the differentiating means differentiates the pilot signal detected by the detecting means with respect to time, and then the control means scans the recording track to be scanned by the magnetic head based on the signal differentiated by the differentiating means. Control as follows. Therefore, the first or second pilot signal recorded on each recording track on the magnetic tape is reproduced, and the record to be scanned by the magnetic head is determined based on the reproduced first or second pilot signal. Controlled to scan the track.

By configuring as in the fourth or fifth invention,
A first or second pilot signal for tracking control is recorded on each recording track on the magnetic tape, and the first or second pilot signal recorded on each recording track on the magnetic tape is reproduced. Based on the reproduced first or second pilot signal, the magnetic head is controlled to scan a recording track to be scanned.

[Embodiment] First Embodiment FIG. 1 is a block diagram of a tracking control device for a VTR, which is a first embodiment of the present invention.

During recording, the tracking control device of the first embodiment is arranged so that, as shown in FIG.
The frequencies f! each have a level that is proportional or inversely proportional to the distance lx from the starting end P of each track to the position of the magnetic head in the direction of 6. a pilot signal of frequency t2 and a pilot signal of frequency t2 are alternately recorded together with the recorded television signal,
On the other hand, during reproduction, the frequency fl or the second pilot has a level that changes as the magnetic head scans as described above, and is recorded in recording tracks adjacent to the right and left sides of the recording track being scanned. The magnetic head accurately scans the recording track based on the differentiated signal after detecting a signal having a frequency Δfa that is the difference between the two frequencies obtained by multiplying the signal by a signal with a frequency f2 or fl, respectively. It is characterized by being controlled as follows. Here, the frequency fl and the second frequency are, for example, the same as the frequency in the conventional example.

In FIG. 1, a pair of magnetic heads Ha for recording and reproduction,
Hb is provided on the rotating drum 2 of the VTR at an angle of 180 degrees to each other and at different angles, and connects one recording track on the video tape 1 wound around the rotating drum 2 to a pair of magnetic nodes. One of the magnetic heads scans.

The reproduction signals reproduced by the magnetic heads t(a, Hb) are respectively input to the a side and b side of the switch SWI. or at the falling edge, they are alternately switched to side a or side b, respectively.The playback signal output from the common terminal of switch SW1 is a low-pass signal that passes pilot signals of frequencies f+ and f2 and removes the recorded television signal. The first of multiplier 4 passes through filter (hereinafter referred to as LPF) 3.
is input to the input terminal of

On the other hand, the pyrograph signal generation circuit 10 outputs two pyrograph and throat signals having frequencies fl and f2 to the switch circuit 11. The switch circuit 11 receives a switching signal RF-3W output from the system control circuit 20.
At the rising edge or the falling edge of
On the other hand, a pilot signal of frequency f1 or f2 to be recorded on the recording track scanned during recording is outputted to the recording processing circuit 24 via the variable attenuator 23. In response to this, the recording processing circuit 24 mixes the manually input pilot signal and the recorded television signal, performs a predetermined process, and then transfers the mixed signal to the magnetic head Ha.
Output to Hb and record.

The multiplier 4 multiplies the pilot signal of frequencies fl and r2 input to the first input terminal by the pilot signal of frequency f2 or fl input to the second input terminal to obtain the frequency fl+f2. The signal containing frequency fl-122 frequency fl and frequency 12 is passed through a band pass filter (hereinafter referred to as BPF).
That's what it means. )5. BPF5 is the difference frequency Δf
After extracting only the beat signal component having a=f1-f2, it is output to the detection circuit 6. The detection circuit 6 is made of, for example, a semiconductor diode, performs envelope detection on the input beat signal to extract a DC component, and extracts the DC component of the beat signal via a differentiation circuit 7 that differentiates the input signal with respect to time. , as DC voltage Vc.

output to the a side of switch SW2, and outputs IN/<-IN
It is output to the b side of switch SW2 via V.

The switch SW2 selects the a side or the b side at the falling edge and rising edge of the switching signal RF-3Wa, which has a frequency that is 1/2 of the frequency of the head switching signal RF-3W output from the frequency divider 21. The signal outputted from the differentiating circuit 7 or the signal outputted from the differentiating circuit 7 via the inverter INV is output as a tracking error signal to the capstan drive circuit 9 via the amplifier 8. The capstan drive circuit 9 drives the magnetic heads Ha and H based on the level and polarity of the input tracking error signal, as will be described in detail later.
The rotation of a capstan (not shown) is controlled so that the capstan (not shown) accurately scans a predetermined recording track.

On the other hand, the variable attenuator 23 is formed of, for example, a pin diode, and increases the amount of attenuation of the input pilot signal in proportion to time or inversely proportional to time in accordance with the bias control voltage output from the voltage control circuit 22, which will be described later. The attenuated pilot signal is output to the recording processing circuit 24. In response to this, the recording processing circuit 24 mixes the input pilot signal and the recorded television signal to be recorded on the video tape l, and then sends the mixed signal to the magnetic head Ha.

Hb is used to record a predetermined recording track T as shown in FIG.
1 to T6.

The voltage control circuit 22 is composed of, for example, a microcomputer equipped with a central processing circuit and a timer counter, and receives the head switching signal RF-3W outputted from the system control circuit 20 and the switching signal RF-3Wa outputted from the frequency divider 21. Based on this, as shown in FIG.
Every 2 cycles, level a is the positive AC effective voltage. level a, which is a positive AC effective voltage higher than level a0 from
1 continuously in proportion to time, or from the level a1 to the level a. Then, the bias control voltage is outputted to the variable attenuator 23 so as to continuously change in inverse proportion to time. That is, from time t1 to time t2, from time t4 to time [5, and from time t5 to time t6 in FIG.
As described above, the head switching signal RF-3
When W is at H level and switching signal RF-SWa is at L level, or head switching signal RF-3
When W is at the L level and the switching signal RF-3Wa is at the H level, that is, the head switching signal RF-3Wa is at the H level.
When the level of 3W and the level of the switching signal RF-SWa are different, the level of the pilot signal output from the variable attenuator 23 is proportional to the elapsed time.1. It is controlled to be high.

On the other hand, as shown in FIG. 5 from time t2 to time t3, from time t3 to time t4, from time t6 to time t7, etc., the head switching signal RF-SWh (at H level and the switching signal RF-3Wa When the head switching signal RF-3W is at the H level, or when the head switching signal RF-3W is at the L level and the switching signal RF-SWa is at the L level, that is, the level of the head switching signal RF-5W and the level of the switching signal RF-8Wa are When they are the same, the level of the pilot signal output from the variable attenuator 23 is controlled to decrease in inverse proportion to the elapsed time.

In addition, in FIG. 3, the frequencies fl and f2 of the pilot signals recorded on each of the recording tracks TI to T6 are
and level changes. Here, the level changes are indicated by arrows L1 to L6, indicating that the voltage level of the pilot signal increases in the direction of the arrow from the starting end P or ending end Q of each recording track, which indicates the pilot signal in FIG. The voltage level change of the signal corresponds to the voltage level change in FIG.

The tracking operation during playback of the VTR tracking control device configured as above will be described below.

As shown in FIG. 3, let P be the starting end of each recording track, Q be the ending end of each recording track, and let X be the distance from the starting end P of each recording track to the scanning position of the magnetic healds Ha and Hb.
For example, recording tracks TI, T4. The voltage levels vl and v2 of each pilot signal of frequencies f1 and f2 reproduced by scanning T5 can be expressed by the following equations.

V 1=-V2=k (ao+ (at ao)X
/11...(1) Here, k is a proportionality constant determined by the reproduction system circuit, and C is the length of each recording track in the scanning direction.

Also, recording track T2 in FIG. T3. The voltage levels v1° and V2′ of the respective pilot signals of frequencies fl and f2 reproduced by scanning T6 can be expressed by the following equations.

vl'=v2゜=k (a, -(a, -a,)x/Q 1...(2
) Now, for example, when the magnetic head is scanning the recording track T2 as shown in FIG. 4, the magnetic head is located at a point where the distance X from the starting end P of the recording track is Xo,
The area where the magnetic head reproduces the recording track TI adjacent to the left side of the recording track T2 is 81, and the area where the magnetic head reproduces the recording track T3 adjacent to the right side of the recording track T2 is 83. In FIG. 4, for convenience of explanation, the areas sl and s3 are shown much larger than they actually are; When scanning a track, the width is set to be slightly wider than the width of the recording track to be scanned, so that almost no recorded television signal recorded on an adjacent recording track is reproduced.

When the magnetic head is scanning the recording track T2, if the magnetic head deviates to the left as shown by Hl in FIG. 4, if it deviates to the right as shown by H2, or if it deviates to the right as shown by H3, Accurately record track T without deviation
In either case of scanning 2, the magnetic head moves in a direction perpendicular to the longitudinal direction of the recording track, so the following equation holds true.

In other words, the phase of the area Sl and the area S3 is constant.

On the other hand, two recording tracks adjacent to recording track T2, T1. The voltage level W1 of the frequency "pyro y of l" signal reproduced from T3 can be expressed by the following equation.

Wl"S l'L (ao+ (at ao)xo/
σ) 10S 3- + Ia +- (a +-ao) x
o/(l l...(3) Here, kl is a constant determined by the reproduction system circuit.

Next, both sides of the above equation (3) are set to X. By partial differentiation with respect to , we obtain the following equation.

1□・(Sl-33) (4) In the following, the value on the right side of equation (4) is assumed to be the ratio U.

Therefore, from equation (4), when the magnetic head moves and the distance The ratio U is proportional to the difference between the area s1 and the area S3.

As shown in FIG. 1, in the multiplier 4, the pilot signal of the frequency \if1 inputted to the first input terminal is converted into a pyro signal of frequency f2 having a constant voltage level inputted to the second input terminal. , the voltage level Vc of the beat signal obtained by differentiating the beat signal with the difference Δfa between the two frequencies obtained by multiplying the two frequencies by the differentiating circuit 7 with respect to time is the distance X. increases in proportion to time, so it can be easily seen from the result of equation (4) that it is proportional to the difference between the area S1 and the area S3.

Therefore, when the magnetic head is located at H3 in FIG. 4 and is accurately scanning the recording track T2, the area Sl is equal to the area S3, and the voltage level Vc of the beat signal proportional to the ratio U is O. be.

Further, when the magnetic head is located at 82 in FIG. 4 and is shifted to the right from the recording track T2, that is, when Sl<33, the voltage level Vc of the beat signal proportional to the ratio U is 5t-33. (<0). moreover,
When the magnetic head is located at 81 in FIG. 4 and is shifted to the left from the recording track T2, that is, when Sl>33, the voltage level V of the beat signal is proportional to the ratio U.
c is s1. -s 3 (>O).

Therefore, the voltage level Vc of the beat signal is output as is through the a side of the switch SW2, and the signal voltage obtained by amplifying the voltage Vc of the beat signal by the amplifier 8 is output as a tracking error signal to the capstan drive circuit 9. In response to this, the capstan drive circuit 9 controls the rotation of the capstan based on the tracking error signal so as to move the magnetic head in a direction perpendicular to the longitudinal direction of the recording track T2 to be scanned. That is, the capstan drive circuit 9 moves the magnetic head in a direction perpendicular to the longitudinal direction of the recording track T2 and in the direction of the adjacent recording track TI in FIG. 4 in response to a positive tracking error signal. On the other hand, in response to the negative tracking error signal, the capstan drive circuit 9 moves the magnetic head to the adjacent recording track T3 in a direction perpendicular to the longitudinal direction of the recording track T2 in FIG.
control to move in the direction.

Further, for example, when the magnetic head is scanning the recording track T4 as shown in FIG. 4, the distance X of the magnetic head from the starting end P of the recording track is X.

, and the magnetic head is located at a recording track T4.
The area for reproducing the recording track T3 adjacent to the left side of
3°, and the area where the magnetic head reproduces the recording track T5 adjacent to the right side of the recording trunk T4 is S5°.
shall be. At this time, when the magnetic head is scanning the recording track T4, if the magnetic head deviates to the right as indicated by H4 in FIG. 4, or to the left as indicated by H2 in FIG.
In addition, even when the recording track T4 is accurately scanned without deviation as shown by H3, the magnetic head moves in a direction perpendicular to the longitudinal direction of the recording track, so the following equation holds true as in the above case. do.

Furthermore, two recording tracks T3.S3', which are adjacent to the recording track T4. When the voltage level W2 of the pilot signal of frequency fl reproduced from T5 is partially differentiated with respect to the above X0, the following equation is obtained similarly to equation (4).

(5) Therefore, from equation (5), when the magnetic head moves and the distance X increases slightly, the pilot signal of frequency fl reproduced from the adjacent recording tracks T3 and T5 as described above. The rate of slight increase in the voltage level U° is proportional to the difference between the area S5° and the area S3°, and the voltage Vc of the beat signal output from the differentiating circuit 7 is
is also proportional to the difference between the area S5° and the area S3′. Therefore, when scanning the recording track T4, the polarity of the voltage Vc proportional to the ratio U° differs when the recording track is shifted to the right and to the left, compared to when scanning the recording track T2. In each case, both are reversed.

Therefore, when the switching signal RF-8Wa is at H level, such as when scanning the recording track T4, the switch SW2 is switched to the a side, and the voltage VC of the beat signal output from the differentiating circuit 7 is inverted. It is output to the capstan drive circuit 9 as a tracking error signal. Note that the operation of the cab stan drive circuit 9 is similar to the case of scanning the recording track T2 described above.

As explained above, during recording, each of the recording tracks TI to T6 on the video tape 1 as shown in FIG.
A pilot signal having a frequency f1 and a frequency f2 having a level proportional to or inversely proportional to the distance X from the starting end P of each track to the position of the magnetic head in the direction of arrows Ll to L6, respectively, for each of the two recording tracks. recording the pilot signal alternately with the recorded television signal,
On the other hand, during reproduction, the frequencies fl and f2 have levels that change as the magnetic head scans as described above.
The frequency Δf of the difference between the above two frequencies obtained by multiplying the pilot signal by the signal of frequency f2 or fl, respectively.
Based on the differentiated signal after detecting the signal with a,
The magnetic head can be controlled to accurately scan the recording track to be scanned. Therefore, the tracking control device of this first embodiment scans the recording track to be scanned by the magnetic head using pilot signals of two frequencies fl, f;) recorded alternately on each of the recording tracks. Since the tracking is controlled in this manner, as described above, the circuit configuration of the device is simpler than that of the conventional example, and there is an advantage that an inexpensive device can be realized.

Figure 2 is a block diagram of a tracking control device for a VTR which is a second embodiment of the present invention.
Components that are the same as those in the figures are given the same reference numerals.

The difference between the device of the second embodiment and the device of the first embodiment described above is that pilot signals of frequencies f1 and f2 are extracted from the signal output from the common terminal of the switch SWl by a BPF 31 and a BPF 32, respectively. Then, one of the extracted pilot signals of frequencies fl and f2 is used as the head switching signal RF-3W.
The switch SW3 selectively switches the output signal based on the output signal to the detection circuit 6. below,
The above differences will be explained below.

BPF31. The BPF 32 extracts pilot signals of frequencies fl and f2 output from the switch SW1, respectively, and outputs them to the a side and the b side of the switch SW3. The switch SW3 selects the frequencies f1 . The other frequency f2. which is different from f2. side a or b so as to output the fl pilot signal to the detection circuit 6.
can be switched to the side. That is, the head switching signal R
When F-3W is at H level, switch SW3 is switched to the b side, while head switching signal RF-3W
When is at L level, switch SW3 is switched to the a side.

In the tracking control device for a VTR configured as described above, the voltage of the pilot signal output from the switch SW3 is determined as shown in the equations (4) and (5) above, as in the first embodiment. It is proportional to the proportion U, U'. Therefore, during recording, the operation is the same as in the first embodiment, while during reproduction, the pilot signal recorded on the recording track to be scanned has a level that changes as the magnetic head scans as described above. Extract a pilot signal of another frequency fl or f2 different from the frequency of
1. Based on the level of the differentiated signal after detecting the pilot signal extracted above, 1. The recording track can be controlled to accurately scan the recording track to be scanned.

Therefore, the device of this second embodiment operates in the same manner as the first embodiment and has similar effects.

In the first and second embodiments described above, the voltage control circuit 22
The voltage level of the control signal output from the variable attenuator 23 is 1/1 of the cycle of the head switching signal RF-3W.
Every 2 cycles, level a is the positive AC effective voltage. From level a. level a, which is a positive AC effective voltage higher than
1, continuously varying in proportion to time, or from the level a to the level a. In this case, the control voltage is outputted to the variable attenuator 23 so as to change continuously in inverse proportion to time, but the present invention is not limited to this, and the level of the pilot signal outputted from the variable attenuator 23 changes over time. The bias control voltage may be outputted to the variable attenuator 23 so that the level of the pilot signal has discrete voltage values as time passes.

[Effects of the Invention] As detailed above, according to the present invention, during recording,
First or second pilot signals having varying levels and different frequencies as described above are alternately recorded together with recording signals on recording tracks on a magnetic tape, and during playback, the first or second pilot signals recorded on the recording tracks are The first or second pilot signal is reproduced, and the magnetic head is controlled to scan the recording track to be scanned based on the reproduced pilot signal. Therefore, compared to a conventional control device that performs tracking control using pilot signals of four frequencies, there is an advantage that the circuit configuration is simpler and an inexpensive device can be realized.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a VTR tracking control device according to a first embodiment of the present invention, FIG. 2 is a block diagram of a VTR tracking control device according to a second embodiment of the present invention, and FIG. 3 is a block diagram of a VTR tracking control device according to a second embodiment of the present invention. Figure 4 shows the frequency and level of the pyro and soto signals recorded on each recording track on the video tape in the apparatus shown in Figures 1 and 2. Figure 5 shows the operation of the apparatus shown in Figures 1 and 2. 6 is a diagram showing the frequency of the pilot signal recorded on each recording track when a conventional VTR tracking control device is used. FIG. 7 is a diagram showing the operation of a conventional VTR tracking control device. FIG. l... Video tape, 2... Rotating drum, 3... Low pass filter (LPF), 4... Multiplier, 5... Band pass filter (BPF), 6... Detection circuit , 7... Differential circuit, 8... Amplifier, 9... Cab stan drive circuit, 10... Pilot signal generation circuit, 1'l... Switch circuit, 20... System control circuit, 21 ... Frequency divider, 22... Voltage control circuit, 23... Variable attenuation circuit, 24... Recording processing circuit, 31.32... Band pass filter, Ha, Hb... Magnetic head, swl, sw2. swa...switch, INV...-
inverter.

Claims (5)

[Claims] (1) In a magnetic recording device for a tracking control device that records pilot signals for tracking control along with recording signals on multiple recording tracks on a magnetic tape, first and second pilot signals having different frequencies are generated. a generating means; a switching means for alternately switching and outputting first and second pilot signals generated by the generating means based on an input switching signal at a period of 1/2 of the switching signal; The level of the first or second pilot signal output from the switching means based on the signal is changed from the first level to the first level at a period of 1/2 of the switching signal.
or from the second level to the first level continuously or stepwise in proportion to the time. , and repeating the change from the first level to the second level and the change from the second level to the first level twice each to output the first or second pilot signal. Level changing means; Recording means for recording a first or second pilot signal outputted from the level changing means on the recording track on the magnetic tape using a magnetic head based on the switching signal. A magnetic recording device for a tracking control device, characterized in that: (2) A magnetic head is used to reproduce first and second pilot signals having different frequencies that are alternately recorded on a plurality of recording tracks on a magnetic tape, and the In a magnetic reproducing device for a tracking control device that controls the magnetic head to scan the recording track to be scanned, a pilot signal recorded on the recording track on the magnetic tape is transmitted to each magnetic head based on an input switching signal. a generating means for generating a pilot signal having the same frequency as the frequency recorded on the recording track to be scanned, and a pilot signal reproduced by the reproducing means and generated by the generating means. a multiplication means for multiplying the first and second pilot signals by a multiplied signal, an extraction means for extracting a signal having a difference in two frequencies between the first and second pilot signals from the multiplied signal output from the multiplication means; a detection means for detecting a signal having a difference between the two frequencies extracted by the extraction means; a differentiation means for differentiating the signal detected by the detection means with respect to time; and a signal differentiated by the differentiation means. A magnetic reproducing device for a tracking control device, comprising: a control means for controlling the magnetic head to scan the recording track to be scanned. (3) A magnetic head is used to reproduce first and second pilot signals having different frequencies that are alternately recorded on a plurality of recording tracks on a magnetic tape, and the above-mentioned signals are generated based on the reproduced pilot signals. In a magnetic reproducing device for a tracking control device that controls the magnetic head to scan the recording track to be scanned, a pilot signal recorded on the recording track on the magnetic tape is transmitted to each magnetic head based on an input switching signal. a reproducing means for reproducing a first pilot signal and a second pilot signal from among the pilot signals regenerated by the reproducing means; and a first pilot signal extracted by the extracting means based on the switching signal. switching means for outputting a pilot signal having a frequency different from that of the pilot signal recorded on the recording track to be scanned among the first and second pilot signals; and a detection means for detecting the pilot signal outputted by the switching means. and a differentiation means for differentiating the pilot signal detected by the detection means with respect to time, and a control means for controlling the magnetic head to scan the recording track to be scanned based on the signal differentiated by the differentiation means. A magnetic reproducing device for a tracking control device, comprising: (4) A tracking control device comprising the magnetic recording device for a tracking control device according to claim 1 and the magnetic reproducing device for tracking control device according to claim 2. (5) A tracking control device comprising the magnetic recording device for a tracking control device according to claim 1 and the magnetic reproducing device for tracking control device according to claim 3.