JPS62103864A - Tracking control device - Google Patents

Abstract

PURPOSE:To detect a tracking error signal with a good S/N by forming a reference pilot signal from a master clock frequency-corrected corresponding to a frequency dislocation against the frequency of a reproducing signal in a recording time. CONSTITUTION:A master clock MCK is supplied from the first - the fourth frequency dividing circuits 481-484 to a switch circuit 24, and a signal of some frequency out of signals at the circuit 24 is taken out selectively with switching signals SL1 and SL2 from a switch control circuit 20 and is supplied to a multiplier circuit 22 and is multiplied by a reproducing pilot signal from a band-pass filter 21. The reference pilot signal includes a share of dislocation in a normal reproducing time when the frequency dislocation of a recording pilot signal within a tolerance occurs, or when the relative speed of a rotary head is varied by the change of a tape speed in a variable speed reproducing time. Therefore, a dislocation between frequency differences DELTAfA and DELTAfB is reduced, and a good tracking error can be obtained through band-pass filters 25 and 26 in the variable speed reproducing time.

Description

[Detailed description of the invention] The invention will be explained in the following order.

A. Field of industrial application B. Outline of the invention C. Prior art D. Problems to be solved by the invention E. Means for solving the problems F. Effects G. Example clBi Scope of Required Item 2 Implementation of the invention Example explanation (
1 to 3) G2 Description of an embodiment of the invention set forth in claim 3 (FIGS. 4 to 9) Description of another example of the G3 master clock generation means (1st O
(Fig. 11) Effect A of the Invention Field of Industrial Use This invention relates to a ruffing control device for a rotary head during reproduction of a recording and reproducing apparatus that records and reproduces video signals and audio signals using a rotary head.

B. Summary of the Invention The present invention is a device that performs tracking control during playback using a pilot signal that is cyclically recorded with a rotating head with an information signal and a frequency changed for each track. When obtaining a tracking error signal using a beat signal with a beat signal, the reference pilot signal is formed from a master clock whose frequency is synchronized with the playback signal, so that the tracking error signal can be obtained not only during normal playback but also during variable speed playback. It is designed to be detectable.

C Conventional technology In popular home VTRs, when performing tracking control in which the rotary head correctly scans the recording track during playback, conventionally a control signal is formed in the longitudinal direction of the tape using a fixed magnetic head. This is done using the playback control signal from the track. However, the method of using such a fixed magnetic head is disadvantageous because the width of the tape becomes wider and when it is desired to downsize the recording/reproducing apparatus, the fixed head cannot be installed due to the location.

Therefore, a method of tracking control without using such a fixed head has been proposed. This method, for example,
As described in Japanese Patent Application Laid-open No. 3416120 and Japanese Patent Application Laid-open No. 59-65962, a low-frequency tracking pilot signal is recorded on the track where the video signal is recorded, superimposed on it, using a rotary head, and is used during playback. , the tracking servo is performed by detecting the amount of stalking of this pyrono signal from the adjacent track. For this reason,
The pilot signal is frequency-multiplexed and recorded so that it can be easily separated during playback, as a signal on the low-frequency side of the frequency spectrum where no recorded video signal exists, and is selected to have a frequency with a small azimuth loss.

First, an overview of this tracking control method will be explained.

In this example, pilot signals of four different frequencies are cyclically and sequentially frequency-multiplexed recorded on diagonal tracks.

For example, 21[1i!] with different so-called azimuth angles! When recording is performed by a rotary head device in which rotary heads HA and HB are arranged 180° apart, as shown in FIG. Four different frequencies f1.
f2. f3. As shown in FIG. 12, the four pilot signals of f are sequentially changed for each track and recorded cyclically.

That is, one rotary head HA rotates every other track T1. as shown in FIG. T3 is formed and an FM modulated video signal is recorded, and a pilot signal with a frequency of "1" is recorded on track T1.
3, a pilot signal of frequency f3 is superimposed and recorded.

In addition, every other track T2.T4 is sequentially formed by the other rotary heel t"HB, and an FM-modulated video signal is recorded on the track T2. A pilot signal with a frequency f2 is recorded on the track T2.

A pilot signal having a frequency f4 is superimposed and recorded on each of the signals. And this track T1~T
4 is repeatedly recorded, pi[]soto signals of four different frequencies are also sequentially and cyclically recorded on these tracks T1 to T4.

In this case, during playback, the head HA is on tracks T□ and T3.
When the head HB correctly scans the tracks T2 and T→, it is in a just ranking state, and when the head HB correctly scans the tracks T2 and T→, it is in a just tracking state. Therefore, assuming that the gap width of the belly button F' HA and HB matches the track width, the head HA, HB
When sequentially scanning tracks T1 to T4, in synchronization with this, signals P1 to P4 of frequency ", ~f4 are supplied as a reference pilot signal to a multiplication circuit, and the frequency difference with the reproduced pilot signal is detected. No frequency difference can be obtained in the just tracking state.

On the other hand, if the tracking position is shifted as shown in (1) and (2) of the head position (this is the case of head HA) in FIG. Since the signal is obtained as crosstalk, a frequency difference occurs between the signal and the crosstalk signal, and its level is proportional to the amount of deviation.

Therefore, the frequency C
By selecting 1 to f4, tracking servo can be easily performed. That is, Δ'8=Irt-f21=l f3 F41AfB
=1r2-f] 1=1f4 fl l. In this way, the existence of the frequency difference ΔrA means a rightward deviation for the head HA and a leftward deviation for the head HB, and the existence of the frequency difference ΔF means a leftward deviation for the head)IA. For the head HB, this means a rightward shift, and the levels of the differences Δ'A and ΔfB are proportional to the amount of shift.

Therefore, in principle, these frequency differences Δ'A.

ΔfB indicates the amount of tracking error, and if this is controlled to become zero, just 7 kings can be achieved.

However, in the example shown in Fig. 12, it is a case of so-called overwriting, so as shown by the solid line (:3) in the figure, the track that is originally to be scanned is scanned across tracks on both sides of it by slightly the same amount. is the state of just tracking. That is, when the frequency differences ΔfA and ΔrB are equal in one novel, just tracking is achieved, and tracking control is performed by controlling so that the level difference between the differences Δr8 and ΔfB becomes zero.

FIG. 13 is a block diagram of an example of the tracking control device.

This example is an example of the case of 8 millimeters, and the bi-J throat signal is a signal that is even lower than the band of the low-frequency conversion carrier color signal.

In FIG. 13, the playback outputs of heads HA and HB are provided by rotary transformers (114) and (11B), respectively.
The switch circuit (13) is supplied to the switch circuit (13) through the head amplifiers (128) and (12B), respectively, and the head switching signal RFSW (FIG. 14A) is sent through the terminal (14). ) (Synchronized with the rotation of the amplifier (B), the head HA or HB scans the tape and is alternately switched to one and the other terminal for a period of 180° angular interval. Therefore, the amplifier (1
5) is a signal 14 in which the reproduction outputs of the heads HA and HB are continuously connected, and this is sent to the terminal (
16) to the reproduction signal processing system.

The output of the amplifier (15) is also passed through a bandpass filter (
21) and the pilot signal is extracted from the reproduced signal. The reproduced pilot signal from this bandpass filter (21) is supplied to a multiplication circuit (22).

On the other hand, a pilot signal generation circuit (23) is provided, from which the frequency f1. f2. f3. f+ reference pilot signal P1. P2. P3. P4 are obtained and these are supplied to the switch circuit (24).

This switch circuit (24) includes a switch control circuit (20
) are supplied with select signals SL1 and SL2, and these select signals SL1. One of the pilot signals of four frequencies is connected to this switch circuit (2) by SL2.
4). Switch control circuit (2
0) is the head switching signal RFS from the terminal (14).
- is supplied, the select signals SL1 and SL2 change at the rising and falling points of this signal RFS-, and the reference pilot signal obtained from the switch circuit (24) is changed. For example, during a 180° period when the head HA scans the track T1, the switch control circuit (24) outputs a signal P with a frequency f1 as a reference pilot signal, and during a 180° period when the head HB scans the tracks 1 and 2. During the period, the signal P2 of frequency r2 is...
The four frequency signals P1 to P4 are sequentially switched and obtained as shown in Fig. 14B.
).

A reference pilot signal from this switch circuit (24) is supplied to a multiplication circuit (22). Therefore, this (
Signals with frequencies ΔfA and ΔrB, which are the difference between the reference pilot signal and the regenerated pilot signal, are obtained from the calculation circuit (22), and these are extracted by bandpass filters (25) and (26), respectively, and sent to the detection circuit ( 2
7) and (28) to produce DC level outputs SA and SB.

Here, the gains of the bandpass filters (25) and (26) are made equal to each other.

Detection outputs SA and SB of detection circuits (27) and (28)
is a level proportional to the amount of the frequency difference Δ[A and Δre components, that is, the magnitude of the pilot signal included as a cocoon stalk in the reproduced pilot signal, and
This corresponds to the tracking amount of the right and left adjacent tracks.

These detection outputs SA and SB are supplied to a subtraction circuit (29), from which a subtraction output SD of both is obtained. This subtraction output SD is a signal indicating which side is more shifted, left or right, but as mentioned above, the frequency difference ΔfA
and Δf8, the directions of deviation are opposite when the head HA scans and when the head HB scans.

Therefore, the output SD of the subtraction circuit (29) is supplied as is to one input terminal of the switch circuit (30), and its polarity is inverted via the polarity inversion circuit (31).
30).

This switch circuit (30) sends a head switching signal RFSW&therefore, when the head HA scans and when the head HB
A tracking error voltage SE corresponding to the direction of shift is obtained from the amplifier (-32) by being alternately switched during scanning. Therefore, if this is supplied to the capstan motor, tracking control will be performed.

For example, when the head HA is in a scanning state shifted to the right as shown in position (2) in FIG. 12, the reproduced pilot signal from the low-pass filter (21) is
As shown in FIG. 12, the pilot signal of the adjacent truck on the right in FIG. 12 is also included. Then, the multiplication circuit (22
), frequency differences ΔfA and Δf8 showing a right shift for the heads HA and HB are obtained alternately for each scanning period, as shown in Figure 14. Therefore, the detection circuit (
The output SA of the detector circuit (27) is as shown in E of the same figure.
The output SB of 8) is as shown in F in the same figure, and the subtracted output SD is as shown in G in the same figure. Then, the tracking error signal SE enters a state indicating a right-shift error, as shown in H in the figure.

D Problems to be Solved by the Invention By the way, it is extremely difficult to strictly control the frequency when reproducing the recorded pilot signal, so it is difficult to strictly control the frequency, so the frequency must be controlled with a tolerance of 0.1% (approximately ±100Hz). Discrepancies are acknowledged. However, it is difficult to vary the passing center frequency of the bandpass filters (25) and (26) of the tracking error detection system in accordance with this shift.
It was undeniable that the S/N was slightly worse.

Further, in the case of 8 mm video, variable speed playback is often performed by setting the tape speed to a speed different from that during normal playback. In this case, unless correction is made by changing the rotational speed of the rotary head, the relative speed of rotation to and from the tape will deviate from the speed at the time of recording, the reproduction pilot frequency will also deviate by that amount, and the beat frequency ΔfA+Δre will also deviate.

Therefore, when the deviation in the relative speed of the rotating head is large, the attenuation in the bandpass filters (25) and (26) becomes thick, and as a result, the tracking error detection system based on this reproduced pilot signal S/N deteriorates,
There was also the drawback that it ultimately became impossible to detect.

By the way, in the case of the above-mentioned 8mm video, the pilot signal frequency f1 + I2 + f3 + f4 is selected to interleave with the horizontal frequency fH of the video signal so that it will not affect the video signal. Each signal is obtained by frequency-dividing the master clock from the oscillator. For example, in the 8 mm video standard (NTSC), the master clock frequency rM is fM=378rHte, and the frequencies r1 to f4 and ΔA and ΔfB are selected as follows.

r t = f M / 58 = 6.517r H#
102.542kllzf 2= f M / 50=
7.560f H”; 11B, 949kHzr v
= f M / 36 = 10.500f H# 1
65.207kHzr 4 = f M / 40 =
9.450f H#t48.686ktlzΔfA=
f2f 1= 1.043fH# 16.407
kllzΔfA=f3 f4= 1.050fH
#16.521kHzΔfa = f4fx = 2.9
33fH# 4B, 144kHzΔfs = f3-f
y = 2.94OfH# 46.258kllzLooking at these frequencies, we see that the pilot signal frequency is not exactly interleaved with the horizontal frequency 'H' and that the pilot signal frequency is Δfa is also slightly different.

Originally, it is preferable in terms of accuracy that the passbands of the bandpass filters (25) and (26) of the tracking error detection system be as narrow as possible. If the center frequencies of the bandpass filters (25) and (26) in the tracking error signal detection system can be slightly shifted, even narrowband bandpass filters can cope with the above-mentioned difference in beat frequency. Since it is difficult to shift the center frequency like this, it is generally set as a fixed center frequency, and its value is selected to be approximately the average value of each beat frequency, and the passband width also differs depending on the beat frequency. It has become relatively wide to cover.

E. Means for Solving the Problems The invention of this application corrects the frequency in response to the frequency deviation of the reproduced signal with respect to the recording frequency when tracking control is performed using, for example, a four-frequency pilot signal as described above. master clock generating means for obtaining a master clock obtained by the master clock, and signal forming means for obtaining signals of respective frequencies of the plurality of pilot signals from the master clock. The signal or a reference pilot signal formed based on the signal from the signal forming means is multiplied to obtain a signal corresponding to the amount of track deviation as a frequency component of the difference between the two signals.

In addition, as a reference pilot signal, a fixed frequency signal is frequency-added to the signal from the signal forming means, the frequency-added signal is used, and this is multiplied by a regenerated pilot signal, and among the multiplied output, the above-mentioned fixed frequency A tracking error signal is obtained by extracting only the component of .

F Effect The signal to be multiplied by the reproduced pilot signal is a signal obtained from the master clock whose frequency has been corrected in accordance with the frequency deviation with respect to the frequency at the time of recording of the reproduced signal, or a frequency addition signal of this signal and a constant frequency. Contains frequency shift components during playback. Therefore, if this is multiplied by a reproduced pilot signal having the same frequency shift to obtain an output of the frequency difference between the two, the frequency shift will be canceled, and the frequency difference will always be the same as during normal reproduction or not much different. In other words, during variable-speed playback, even if the playback frequency of the pilot signal deviates, the difference beat frequency does not change much, so the bandpass filter with a fixed center frequency produces a beat signal with a level corresponding to the tracking deviation during variable-speed playback. Good S/N can also be obtained.

In addition, when the signal to be multiplied by the regenerated pilot signal is a frequency sum signal of a signal obtained from the master clock and a signal with a constant frequency rs, the output of the multiplication means has the constant frequency fs and a leading phase. Alternatively, a signal with a level proportional to the amount of tracking deviation in a slow phase relationship can be obtained, and this can be obtained from a bandpass filter. Therefore, in this case, a narrow band filter with a center frequency fs can be used as a filter for extracting components in the amount of deviation and the direction of deviation, and the tracking error signal based on the reproduced pilot signal can be detected with a good S/N ratio. It is something.

G Example G1 Explanation of an embodiment described in claim 2. FIG. 1 shows an embodiment of the invention of - of this application, and parts corresponding to the example in FIG. 12 are given the same reference numerals. show.

In this example, a tracking error signal can be obtained even during variable speed playback by obtaining a reference pilot signal with a frequency that follows the change in the relative speed of the rotating head to the tape during playback as follows. Do it like this.

That is, the reproduction signal from the amplifier (15) is supplied to the bypass filter (41), and a signal multiplied by it of the color video signal is obtained therefrom. This luminance signal is sent to the demodulation circuit (42)
The demodulated output is sent to a low-pass filter (43) and a de-emphasis circuit (44).
The signal is supplied to a synchronization separation circuit (45) through which a synchronization signal is obtained. This synchronization signal is supplied to a half-H killer circuit (46) and is converted into a horizontal synchronization pulse from which the equalization pulse within the vertical blanking section has been removed, and this is used as a horizontal synchronization pulse from which the PLL
The signal is supplied to a circuit (47), from which a master clock MCK having a frequency fM=378fH, for example, which is phase-locked to this horizontal synchronizing pulse is obtained. Since this master clock MCK is phase-locked to the reproduced horizontal synchronizing pulse, its frequency corresponds to the relative speed deviation of the rotary head.

This master clock MCK is applied to the first to fourth frequency dividing circuits (
48x) to (484).

Then, the master clock MCK is input to the frequency dividing circuit (481
), the frequency is divided into 1158, and from this the frequency f□
The frequency dividing circuit (482) divides the frequency by 1150 to obtain a signal of frequency f2, and the frequency dividing circuit (483) divides the frequency by 1/36 to obtain a signal of frequency f2. A signal of frequency r3 is obtained, and the frequency dividing circuit (48
In 4), the frequency is divided by 1/40 and the frequency is
A signal of , is obtained.

The signals from these frequency divider circuits (481) to (484) are supplied to the switch circuit (24), and the signal of one of the frequencies is changed to the above by switching signals SL1 and SL2 from the switch control circuit (20). Similarly, it is selectively extracted from this signal and supplied to the multiplication circuit (22), where it is multiplied by the reproduced pilot signal from the bandpass filter (21).

Hereinafter, the switch circuit (3
0), a tracking error signal is obtained, which is added to the speed error signal from the speed servo circuit from the terminal (33), and is supplied to the capstan motor (34) through the drive amplifier (32) to drive the rotating head H.
The phase shift amount of the tape is controlled so that the tracking phases of A and HB are correct.

In the above example, the reference pilot signal is the PLL circuit (
47) is obtained by dividing the frequency of the horizontal synchronizing signal in the reproduced signal using frequency dividing circuits (481) to (484), so during normal reproduction, it is within the tolerance of the recorded pilot signal. When there is a frequency shift, or when there is a change in the relative speed of the rotary head due to a change in tape speed during variable speed playback, the reference pilot signal also includes that shift.

Therefore, the frequency difference Δ obtained from the multiplication circuit (22)
The deviation between fA and ΔfB becomes small, and tracking errors can be obtained satisfactorily even during variable speed reproduction through the bandpass filters (25) and (26). However, in this case, the bandpass filter (25
) and (26) are made slightly wider than in the case where they are supported only during normal playback.

For example, when performing quadruple speed playback, when the rotary heads HA and HB scan as shown with diagonal lines in FIG. 2H, the second As shown in FIG. C, the pilot signals recorded in the tracks traversed by the heads HA and HB are reproduced for each period corresponding to the length of the traversal of the tracks T1 to T4.

Therefore, when the switch circuit (24) is switched based on the signal RFS- and the reference signal is supplied to the multiplication circuit (22) as shown in FIG. 2B, the component of ΔfA passes through the bandpass filter (25). The signal is supplied to the detection circuit (27) and detected, from which a detection output SA as shown in the figure is obtained, and the component of Δ'B is supplied to the detection circuit (28) through the bandpass filter (26). The wave is detected, and a detected output SB as shown in the upper part of the figure is obtained.

Therefore, the output SD of the subtraction circuit (29) becomes as shown in FIG. F, and the tracking error signal SE from the switch circuit (30) becomes as shown in FIG. Since this signal SE is a signal having a period corresponding to the repetition period of the fl-f4 pilot signal, it has a period corresponding to the tape speed and becomes tape speed information.

Further, the zero-crossing point of this signal SE is the point in time when the head HA scans the center of the track T3 (or track Ti) during the scanning period of the head HA, and the zero-crossing point of this signal SE is the point in time when the head HA scans the center of the track T3 (or track Ti) during the scanning period of the head HB. This is the point in time when the center of the track T2) is scanned, and becomes phase information.

Therefore, using this phase information, the video signal is
information for phase alignment of burst signals when the signal is a signal, and information for each track during variable-speed playback where another set of heads with the same azimuth angle as heads HA and HB is provided and playback is performed across multiple tracks. By always obtaining a reproduction output from a rotary head corresponding to the azimuth, it can be used as a switching timing control signal when variable speed reproduction is performed without noise.

In the above, switching of the switch circuits (24) and (30) was performed using the signal RFSH, but by appropriately switching the switching cycle in accordance with the switching cycle of the reproducing pilot signal as follows, it is possible to perform a cue/review function. Noise bars generated on the screen when the rotary head traverses tracks having different azimuth angles during variable-speed playback can be fixed at fixed positions on the screen to make the playback images easier to see.

In other words, for example, when performing quadruple speed playback, the rotary head scans across four track areas;
For example, if the rotating heads HA and HB are always at the same tracking phase with respect to the recording track pattern that scans only four tracks, as shown with diagonal lines in FIG. 2, the noise bar will appear on the screen. Fixed.

In order to obtain such a tracking phase, the reference pilot signal in the above-mentioned example of FIG. The center of the magnetic gap is at each scanning track T2, T3.

The switch circuit (24) may be used to switch the time for each time it takes to cross Ts and T1. That is, head HA,
Assuming that the time length of one scanning period of HB is 3t, during t/2 when crossing track T2, the track T with frequency 12 is
], the frequency is [3], and the frequency r4 is the frequency [3], and the frequency r4 is the frequency t/2 when the track T1 is crossed.
Between 0 and 0, a regenerated pilot signal of frequency f1 is obtained as shown in FIG. If, each t/2゜mm,
L, during period t/2, the rotating head is at T2. T3゜T4. T
Tracking servo is applied to always scan on i, and the tracking servo is always scanned with the tracking phase as shown in FIG.

G2 Detailed Description of the Invention Recited in Claim 3 In the case of the example shown in FIG. Although it is necessary to use a wide one,
The embodiment described below is an example in which the frequency to be extracted and the passing center frequency match as a bandpass filter of the tracking error detection system, and a filter having a narrow bandwidth can be used.

That is, FIG. 4 is a system diagram of this embodiment, and parts corresponding to those in FIG. 1 are designated by the same reference numerals and their explanation will be omitted.

In this example, the frequency "
The signal of frequency 1 and the signal of frequency 2 from the frequency dividing circuit (482) are switched by the switch circuit (50I), and the signal of frequency 3 from the frequency dividing circuit (4Eb: A signal with a frequency r4 from a frequency dividing circuit (484) is switched by a switch circuit (50B).The head switching signal RFSW (Fig. 5A) from a terminal (14) is used for switch control. circuit(
51), and the same signal as the signal RFSW is obtained from this switch control circuit (51). As a result, as shown in FIG. A signal with a frequency f2 is extracted from the switch circuit (50A), and a signal with a frequency f4 is extracted from the switch circuit (50B).
), a signal with frequency f1 is sent to the switch circuit (50B)
The signal of frequency f3 is switched so that it is extracted from each of them. During normal reproduction, as a reproduction pilot signal from the bandpass filter (21), pi[1 soto signals of frequencies f1 and T3 are alternately obtained during the scanning period of the head HA as shown in FIG. 5B. During the scanning period of the head HB, a state in which pilot signals of frequencies f2 and T4 are obtained alternately is a just tracking state. Therefore, the switch circuit (50A)
From (50B), it is assumed that the pilot frequency of the crosstalk between the adjacent tracks on both sides can be obtained for the scanning track of each head HA and HB during normal playback.

The frequency signals from these switch circuits (508) and (50B) are supplied to multiplication circuits (52A) and (52B), and are multiplied by a signal of frequency fs, for example, 110 kllz, from a fixed oscillator circuit 53), respectively.

The output signals of the ift calculating circuits (52A) and (52B) are supplied to bandpass filters (54A) and (54B), which receive the frequency signals from the switch circuits (50A) and (50B) and the frequency fs signal. A signal with a frequency of the sum of is obtained.

And these band pass filters (54A) and (
The output signal of 54B) is sent to the multiplication circuit (55^) and (55
B).

On the other hand, the reproduced pilot signal from the bandpass filter (21) is transmitted to these multiplication circuits (55A) (55B).
supplied to

For example, if the tracking phase advances (shifts to the right) during normal playback, the reproduced pilot signal will shift from the track pattern on the right in FIG. 5B, as is clear from the track pattern in FIG. Includes pilot signals at frequencies indicated in parentheses. Now, for example, the head HA is moving over the track Tl to the track T2 on the right.
When the band-pass filter (21) is in a state where the signal is reproduced across the
A pilot signal with a frequency of f1±Δ and Δ above 2 is obtained.On the other hand, at this time, the bandpass filter (54A)
As shown in FIG. 6B, a signal with a frequency of rs+f2±Δ is obtained. Therefore, from the multiplication circuit (55A), as shown in FIG. )=rs f
f2−f□ ■(fs+r2±Δ)+ ([2±Δ)=fs+2
(f2±Δ) ■(fs+f2±Δ) (f2±Δ)=4' of fs
Two frequency components are obtained. These multiplication circuits (55A
) is supplied to a narrowband bandpass filter (56^) with a passing center frequency fs, and only the component of the frequency fs (2) is extracted therefrom.

This frequency fs component is the frequency f of the regenerated pilot signal.
j/) and has a level corresponding to the level of the reproduced pilot signal of frequency f2.

That is, the component of frequency rs obtained by this bandpass filter (56A) is nothing but a signal corresponding to the tracking deviation. This frequency fs component is detected by the detection circuit (57
A), the level is detected and the detection output S
AA (Figure 5G) is increased by one thickness.

On the other hand, when this head HA scans the track Ts, a signal of Δ above the frequency rs+r4 is obtained from the bandpass filter (54B), and since there is no frequency f2 component, the output of the multiplication circuit (55B) has a frequency fs component does not exist. Therefore, in this period, the passing center frequency r
The output level of the narrowband bandpass filter (56B) of s is zero, and the output level of the detection circuit (57B) is
(H in Figure 5) also becomes zero.

Next, in the period when the head HB scans the track T2, if the tracking phase shifts to the right, the fifth
As shown in Figure B, the frequency f from the right adjacent track T3
] is included in the regenerated pilot signal.

On the other hand, at this time, the output of the bandpass filter (54B) is ft+f3±Δ (Fig. 5F), so the frequency f has a level corresponding to the pilot signal component of this frequency r3.
A signal of s is obtained from the multiplication circuit (55B), which is obtained through the bandpass filter (56B), and detected by the detection circuit (57B), and its output SBB (Fig. 5H
), a signal with a level corresponding to the amount of deviation is obtained.

Similarly, during the scanning period of the next head HA, a signal with a frequency rs of a level corresponding to the pilot signal component of f4 on the right is filtered through the bandpass filter (56
B), and during the scanning period of the track T4 of the next head HB, a signal with a frequency M number fs of a level corresponding to the pilot signal component of the frequency r1 on the right side is obtained from the band pass filter (56A), and the following is obtained. , in exactly the same way, the rotary head HA is obtained from the multiplication circuits (55A) and (55B), respectively.

A signal with a frequency fS of a level corresponding to the magnitude of the pilot signal component from the left and right tracks adjacent to the track that the HB should originally scan is obtained, and this is passed through the band pass filter (to 56) and the detection circuit (57A'), respectively. ) and band pass filter (56B), detection circuit (57B)
＞ Detected at .

The outputs SAA and SBB of the negative wave circuits (57A) and (57B) are then supplied to the subtraction circuit (58), where the output SBB is subtracted from the output SAA, and from this the subtraction output SDD (Fig. 5 ■) is obtained. can get.

This subtracted output SDD is a signal representing a tracking error, and when the head HA scans the track T1 and when the head HA scans the track T3, one system detects the tracking error, and one system connects the multiplier circuit (55A) to the detection circuit (
57A) and the other is a multiplication circuit (55B) to a detection circuit (
57B) and is replaced.

The same holds true when head HB scans tracks T2 and T4. Therefore, since the direction of deviation during one scanning period is reversed, it is necessary to correct this. Therefore, in this case, the output S of the subtraction circuit (58)
DD is supplied as it is to one input terminal of the switch circuit (60), and after its polarity is inverted by a polarity inversion circuit (59), it is supplied to the other input terminal of this switch circuit (60).

Then, from the switch control circuit (51), the signal RFSW
The state is reversed at the rising point of the head)T
The period in which A scans the track child and the period in which the head HB scans the track T4 is "1", and the period in which the head HA scans the track T3 and the period in which the head HB scans the track T2 is "0". The signal INV (Fig. 5 J) (
Signal 1? This signal INV is supplied to the switch circuit (60), and the switch circuit (60) is switched to the polarity inversion circuit (59) during the rlJ period. .

In this way, the tracking error signal SEE (FIG. 5K) is obtained from the switch circuit (60).

Then, in the multiplication circuits (55^) and (55B), the reproduced pilot signal and the bandpass filter (548) and (
54B), and a component of frequency Is is obtained as a frequency difference, so the tolerance Δ is canceled out, and the frequency extracted is always fs, which does not include the tolerance.

For the same reason, even if the tape speed changes, the relative speed of the rotating head changes, and the frequency of the reproduced signal changes, if the change is seen as Δ, the multiplication circuit (5
5A ) (55B ) cancels out the change,
Tracking error detection is performed using narrow band bandpass filters (56A) and (56B) of frequency Is, and a detection circuit (
57A) (57B).

In this case as well, the tape speed information and track phase information at the time of double speed reproduction can be obtained as the tracking error signal SEE, just as in the example shown in FIG.

That is, FIG. 7 shows a timing chart during quadruple speed playback, and the switch circuits (50^) and (50B) are switched in the same way as during normal playback based on the head switching signal RFSW (FIG. 7A). fl, r2. in the sequence shown in Figures C and D. Frequency signals of r3°f4 are obtained, respectively. At this time, if the heads HA and HB scan as shown in FIG. 2H, the reproduced pilot signal will be as shown in FIG. 2B, as described above.

Therefore, the output SAA of the detection circuit (57A) is E in the same figure.
The output SBB of the detection circuit (57B) becomes as shown in F in the same figure, and the output of the subtraction circuit (58) becomes as shown in G in the same figure. Therefore, when the switch circuit (60) is switched by the switching signal INV as shown in FIG. A signal with exactly the same period and phase as at double speed is obtained.

In this example, by utilizing the fact that the tracking error signal SEE is obtained with a good S/N ratio at all tape speeds, the tape speed during recording can be determined by detecting the period of this signal SEE.

In other words, for 8mm video, there is an SP mode with a tape speed that allows one hour of recording and playback on standard tape, and an LP mode with a tape speed that allows double the recording and playback of two hours. can be done at times.

Of course, the same can be done in the case of the example shown in FIG.

The basic principle of this mode discrimination is based on the switching frequency (f1 to f
, one period). This is nothing but determining the recording pattern from the tape speed information and the current tape running mode. Since the tape speed information can be obtained by detecting the cycle of the signal SEE, it is sufficient to determine whether or not to switch modes based on the detection cycle of the signal SEE.

That is, (70) is a mode discrimination circuit, and the signal SEE is supplied to the Schmitt circuit (71) for waveform shaping. The frequency of the output signal SS of this Schmitt circuit (71) is 1511z during double speed playback in the forward direction, 30Hz during triple speed playback, 45Hz during quadruple speed playback, and 15x(n-1)( during nx speed playback). nil, hereinafter the same). Furthermore, when playing at n times the speed in the rewind direction, the frequency becomes 15X (n+1) Hz.

When changing from the SP mode recording portion on the tape to the LP mode recording portion, the respective signals SS
The frequency of the signal S is doubled, and when the recording part of the LP mode changes to the recording part of the SP mode, the signal S
The frequency of S becomes 1/2.

This signal SS is supplied to a programmable counter (72) and is frequency-divided according to the precent data from a terminal (73). In this case, when the speed is n times in the forward direction, the signal SS is frequency-divided by 1/(n-1), and when the speed is n times in the reverse direction, the signal SS is frequency-divided by 1/(n+1). Ru. Therefore, if the mode is appropriate, the output signal of this programmable counter (72) will be a 15Hz signal no matter what the tape speed is (except normal speed), and the tape portion recorded in SP mode will be converted to LP mode. When played back in , the frequency becomes 7.5Hz, and when a tape portion recorded in LP mode is played back in SP mode, it becomes 30Hz. Therefore, the mode can be determined by detecting the period of the output signal of this programmable counter (72). In other words, the output SF of the counter (72) is detected by the rise detection circuit (74).
is supplied to the pulse output PJ at the rising edge of the signal.
is obtained. This pulse PJ is supplied to the clear terminal of the counter (76) through a delay circuit (75) with a minute delay time.

This counter (76) is supplied with a clock having a constant frequency higher than the frequency of the signal SS from a clock generation circuit (77). Also, this counter (7
The count value output of 6) is latched by the latch circuit (78) by the pulse PJ. Therefore, the latch circuit (7
8), the count value output immediately before the counter (76) is cleared by the pulse PJ is launched. This latched count value output is a count value corresponding to the period of the pulse PJ, and is nothing but a detection signal of the period of the signal SS.

Then, the count value output CO of this launch circuit (78)
is supplied to comparison circuits (79) and (80).

In the comparator circuit (79), when the signal SS is, for example, 1 OHZ, the value latched by the launch circuit (78) is 1 and the output CO.
An output C□ which becomes "1" when the value of the output CO becomes larger than 1 is obtained.

Further, in the comparator circuit (80), the signal SS is, for example, 20Hz.
At this time, the value latched in the launch circuit (78) is compared with 2 and the output CO, and when the value of the output CO becomes smaller than 2, an output C2 that rises to rlJ is obtained.

And the output C of these comparison circuits (79) (80)
1 and C2 are supplied to the trigger terminal of a mode signal forming flip-flop circuit (82) through an OR gate (81).

Therefore, when the signal S S7><15Hz and the recording and playback modes match, the comparator circuit (
The outputs C1 and C2 of (79) and (80) are both rOJ
The output FQ of the flip-flop circuit (82) maintains its current state. At this time, the output FQ of the flip-flop circuit (82) is rlJ in SP mode, for example.
, is "0" in LP mode.

Next, when the part recorded in SP mode is played back in LP mode, the signal SS becomes 7.5Hz, so the comparison circuit (
The output of 79) rises to "1", thereby inverting the state of the flip-flop circuit (82), and its output FQ changes from "0" to "1", thereby determining that it is in the SP mode.

Also, when a portion recorded in LP mode is played back in SP mode, the signal SS becomes 30Hz, so the comparator circuit (80Hz)
) rises to "1", which inverts the state of the flip-flop circuit (82) and outputs FQ.
changes from "1" to rOJ, and it is determined that the mode is LP mode.

The key to the above mode discrimination is to be able to detect when the period of the signal SS is not 15Hz but 7.51 (z) and when it is 30Hz, and a counter can be used as in the example above. Alternatively, for example, it may be performed by combining a plurality of Ridrigger type monostable multi-bibreaks, or a microcomputer may be used.

Figure 8 shows an example of mode discrimination using a microcomputer, in which the output SS of the programmable counter (72)
is sampled two or more times in one field and inputted into an 8-bit shift register (83), and the 8
Microprocessor bit data (4 fields)
At Step 7 (84), the data is latched in parallel and the data pattern is recognized to make the determination.

In other words, the shift register (
Since the 8-pin data pattern of 83) changes, the mode can be determined by recognizing this pattern.

Note that during normal playback, the error signal SEE becomes a DC signal if the mode matches, and when a part with a different mode is played back, it becomes a signal with a predetermined frequency. Mode discrimination is possible by determining that a recorded portion of a different mode is being scanned when a zero cross point is detected.

Note that, if only for the purpose of mode discrimination, a voltage obtained by discriminating the reproduced pilot signal by a frequency discriminator may be used as the tape speed information supplied to the Shemint circuit (71).

In other words, the level of this voltage changes depending on the frequency,
Moreover, the frequency of the level change changes depending on the tape speed.

Also in the example of FIG. 4, the switch circuit (504) (
50B) and (60) are not switched at the timing of the head switching signal RFSW and its 1/2 frequency divided signal, but by appropriately selecting them according to the switching cycle of the reproduction pilot signal, the noise bar is fixed at double speed in the forward and reverse directions. Reproduction is possible.

FIG. 9 is a timing chart for five-times-speed playback in the forward direction, and the noise bar is fixed when the rotary heads HA and HB scan the tape in the trunking phase as shown in FIG.

At this time, if the head switching signal 1'1FsW is as shown in A of the same figure, the reproduced pilot signal is obtained by sequentially switching the signals 11 to r4 as shown in the same figure.

Accordingly, the switch circuit (50A) is switched as shown in FIG. C, and the switch circuit (50B) is switched as shown in FIG. The SW7000 circuit (60) is switched to the inverter (59) side when the frequency of the reproduced pilot signal is f and [□. In this way, the output SEE of the switch circuit (60) will be as shown in G in the same figure, and this will be connected to the drive amplifier (3).
2) to the motor (34), the error signal sEE becomes 0 level due to the integral effect, and the tape is transported with the tracking phase shown in FIG. 9F.

Note that the zero cross point P of the signal SEE shown in FIG.
may be sampled and held, and its bold output may be supplied to the motor as a tracking error signal.

Explanation of other examples of G3 master clock generation means The above examples are all cases in which the frequency of the master clock is corrected by the reproduced horizontal synchronization signal in the reproduced video signal, and when this video signal is not recorded, the frequency Cannot be corrected. The example below is an improved version of this.

The example in FIG. 10 is an example of using an FM audio signal recorded on a video track, in which the reproduced FM audio signal and the variable frequency oscillator (
The phase comparison circuit (93) compares the phase of the oscillation output of the oscillator (91) with a signal whose frequency is divided by the frequency divider (92), and the comparison output is sent to the variable frequency oscillator (9) via the low-pass filter (94).
1) to control its oscillation frequency. In this way, the variable frequency oscillator (91) generates a frequency of 378
At rH, a signal synchronized with the carrier frequency of the reproduced FM audio signal is obtained.

The example in FIG. 11 is an example in which the regenerated pilot signal itself is used.

That is, (101) is a variable frequency oscillator with a free running frequency of 11, the oscillation signal of this oscillator (101) and the regenerated pilot signal are compared in a phase comparison circuit (102), and the comparison output is passed through a low-pass filter (103). is supplied to the oscillator (101) via the oscillator (101) to synchronize the oscillation frequency of this oscillator (101) with the regenerated pilot signal of frequency f1.

The oscillation signal is then supplied to a detection circuit (105) via a 90° phase shift circuit (104) to detect a reproduced pilot signal. Then, when a reproduced pilot signal of frequency f is obtained, an output that becomes larger than this is obtained, which is supplied to the level comparison circuit (106) and from this, fl
An output equal to rlJ is obtained only at the time of the regenerated pilot. The output of this comparison circuit (106) is the switch circuit (
107), and this switch circuit (107) is turned on during the "1" period.

(10B) is a variable frequency oscillator with a free-running center frequency of 378fH, and the output of this oscillator (108) is the frequency dividing circuit (10B).
9), a signal of frequency f1 is obtained by dividing the frequency by 1158, and this signal and the regenerated pilot signal are phase-compared in the comparator circuit (110). Only the comparison output is supplied to the oscillator (10B) via the low-pass filter (111) and the switch circuit (107) to control its oscillation output. Although the switch circuit (107) is turned off during the period of the pilot signal having a frequency other than the frequency f1, the comparison error signal is held in the capacitor (112), and the output of the oscillator (108) is controlled by the held output.

As a result of the above, the output of the oscillator (108) becomes synchronized with the regenerated pilot signal of frequency f1, and becomes a master clock whose frequency is corrected by the regenerated signal.

Note that a programmable counter may be used instead of the frequency dividing circuits (4Eh) to (484) for obtaining signals of frequencies f1 to f4 from the master clock.

H Effects of the Invention According to this invention, the reference pilot signal for multiplying the reproduced pilot signal to obtain the tracking error signal is formed from the master clock whose frequency is corrected by the reproduced signal. Even if the relative speed changes and the frequency of the reproduction pyro 7) signal deviates from the frequency at the time of recording, the frequency of the reference pilot signal also deviates correspondingly, so tracking errors can be avoided even during variable speed playback such as double speed playback. Obtainable.

Since the obtained tracking error signal has information corresponding to the tape speed and track phase information, this tracking error signal can be used to perform various controls during variable speed reproduction.

Also, as in the example shown in Fig. 4, if the signal obtained by adding a fixed frequency signal to the reference pilot signal formed from the master clock is used as the reference pilot signal to be multiplied by the reproduced pilot signal, tracking can be achieved. The passing center frequency of the band-pass filter for obtaining the error is the above-mentioned fixed frequency, and a very narrow band filter can be used to obtain a tracking error with a good S/N ratio.

[Brief explanation of drawings]

Fig. 1 is a system diagram of an embodiment of the invention of this application;
3 and 3 are timing charts for explaining the same,
FIG. 4 is a system diagram of an embodiment of another invention of this application, and FIG.
Figure 6 is a timing chart for normal playback, Figure 6 is a diagram for explaining the operation of the main parts, Figure 7 is a timing chart for quadruple speed playback, and Figure 8 is another example of the mode discrimination circuit. Block diagram: Figure 9 is a timing chart for 5x speed playback with a fixed noise bar; Figures 10 and 11 are block diagrams of other examples of the main parts of the present invention; Figure 12 is a tracking control using only a rotating head. FIG. 13 is a block diagram showing an example of a conventional device for tracking control, and FIG. 14 is a timing chart for explaining the tracking control. HA and HB are rotating heads, (21) is a low-pass filter for extracting the reproduced pilot signal, (47) is a PLL circuit,
(481) to (484) are frequency dividing circuits for forming a reference pilot signal, (25) and (56A) are band pass filters that extract components in one direction of deviation, (26) and (
56B) is a bandpass filter that extracts the component in the other direction of deviation.

Claims (1)

[Claims] 1. An information signal is recorded as a diagonal track by a rotating head, and a plurality of pilot signals having different frequencies are recorded on one track by the rotating head in a state where the frequency can be separated from the information signal. 1 hit
When reproducing from a recording medium to which pilot signals of two frequencies are allocated and recorded cyclically, the reproduced pilot signal separated from the output of the rotary head for reproduction is multiplied by the reference pilot signal, and the multiplied output is The tracking error signal of the reproducing rotary head is obtained based on the reference pilot signal, wherein the reference pilot signal is formed from a master clock whose frequency is corrected in accordance with a frequency deviation with respect to the frequency at the time of recording of the reproducing signal. A tracking control device made like this. 2. Information signals are recorded as diagonal tracks by the rotating head, and a plurality of pilot signals with different frequencies are recorded on the tracks by the rotating head, one per track, in a state that can be separated in frequency from the information signal.
When reproducing from a recording medium to which pilot signals of two frequencies are allocated and recorded cyclically, obtaining the frequency component of the difference between the reproduced pilot signal separated from the output of the reproducing rotary head and the reference pilot signal, Of the frequency components of this difference, the component in the direction of deviation, either leading or lagging relative to tape transport, is extracted from the first filter, and the component in the direction of the other deviation is extracted from the second filter. The tracking error signal of the reproducing rotary head is obtained by the level difference of the output of the second filter, and the master clock is frequency-corrected in accordance with the frequency deviation with respect to the recording frequency of the reproducing signal. and a signal forming means for obtaining signals of respective frequencies of the plurality of pilot signals from the master clock, and the tracking control device is configured to obtain the reference pilot signal from the signal forming means. . 3. Information signals are recorded as diagonal tracks by the rotary head, and a plurality of pilot signals with different frequencies are recorded on the tracks by the rotary head, one per track, in a state where the frequency can be separated from the information signal.
A device that performs tracking control of a rotary head for reproduction using the pilot signal during reproduction from a recording medium to which pilot signals of two frequencies are allocated and recorded cyclically, the apparatus comprising: a master clock generating means for obtaining a master clock whose frequency has been corrected in accordance with the frequency deviation; a signal forming means for obtaining signals of respective frequencies of the plurality of pilot signals from the master clock; and a frequency signal from the signal forming means. means for frequency-adding a signal of a constant frequency; a multiplication means for multiplying the added frequency signal by a reproduced pilot signal; and a direction of advance and delay deviation of the output of the multiplication means with respect to tape transport. comprises first and second band-pass filters having the above-mentioned constant frequency as a center frequency for extracting the component, and subtraction means for taking the difference between the outputs of the first and second band-pass filters, A tracking control device that obtains a tracking error signal from means.