JP2536496B2 - Information signal reproduction device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in the following order.

A Industrial Field B Outline of Invention C Conventional Technology D Problems to be Solved by the Invention E Means for Solving Problems F Action G Example G ₁ First Example G ₂ Second Implementation Example G ₃ Third embodiment H Effect of the invention A Industrial field of application The present invention is suitable for application to a VTR or the like in which tracking servo is performed based on a pilot signal recorded on an oblique track during reproduction. Information signal reproducing apparatus.

B. Summary of the Invention The present invention provides a reference pilot in an information signal reproducing apparatus for performing tracking servo based on a pilot signal when reproducing a magnetic tape on which an information signal is recorded by overwriting on a diagonal track together with a pilot signal. Switching means for switching the center value of the tracking servo by switching the signal generation timing, when the magnetic tape has the first erasing rate in overwriting with respect to the pilot signal, and when the magnetic tape is worse than the first erasing rate. When the magnetic tape has the second erasing rate, tracking of the overwriting portion by the unerased pilot signal is performed. Switching the center value of the tracking servo to improve the deviation By the the like, regardless of the magnetic characteristics of the magnetic tape, in which good tracking servo is to be performed.

C Conventional Technology Conventionally, a VTR has been proposed in which a pilot signal is recorded together with a video signal on an oblique recording track, and tracking servo is applied based on the pilot signal during reproduction.

In FIG. 6, (1) is a rotary drum, and the rotary drum (1) has different azimuth angles from each other.
_A pair of magnetic heads H _A and H _B are mounted with an angular interval of °. Further, (2) is a magnetic tape, which is slid around the peripheral surface of the rotary drum (1) in an angular range of about 180 ° and is run. The magnetic heads H _A and H _B rotate once in one frame, the magnetic head H _A scans the magnetic tape (2) in the odd field, and the magnetic head H _B scans the magnetic tape (2) in the even field. 2) It is designed to scan above.

On the magnetic tape (2), the recording time of the magnetic head H _A, the recording track T _A, which is inclined by H _B, is T _B are successively formed.
The frequency is f ₁ , f ₂ , f ₃ , f ₄ , f ₁ , ... for each recording track T _A , T _B.
.. and four cyclically changing pilot signals for tracking servo are frequency-multiplexed with the video signal (combined signal of the low-frequency conversion color signal C _L and the FM modulation luminance signal Y _FM ) and recorded.

The frequencies f _{1 to} f ₄ of the pilot signal are low frequency conversion color signals C _L
Selected for the lower band side, for example 102.544kHz, 118.95, respectively.
1kHz, 165.210kHz, 148.689kHz, and the frequencies of the pilot signal of a certain recording track and the pilot signal of the adjacent recording track are Δf _A = f _H , Δf _B = 3f _H (f _H is the horizontal frequency) Is being done.

In this case, the width of the magnetic heads H _A and H _B is, for example, 15 μm. Therefore, in the standard mode in which the running speed of the magnetic tape (2) is fast (hereinafter referred to as "SP mode"), the inclined recording tracks T _A and T _B are formed as shown in FIG. That is, the track pitch is, for example, 20 μm, the track width is 15 μm, and a guard band is provided. On the other hand, in the long time mode in which the running speed of the magnetic tape (2) is slow (hereinafter referred to as "LP mode"), inclined recording tracks T _A and T _B are formed as shown in FIG. That is,
The track pitch is, for example, 10 μm, and the track width is regulated to 10 μm by overwriting, and no guard band is provided.

During reproduction, reproduction signals obtained from the magnetic heads H _A and H _B are supplied to the A-side and B-side terminals of the head changeover switch (4) via the reproduction amplifiers (3A) and (3B). The magnetic head H _A in the head change-over switch (4), synchronized with the rotational phase of H _B, so-called RF switching pulse SWP is supplied as a switching control signal, the head change-over switch (4), the magnetic head H _A is The 1-field period for scanning the magnetic tape (2) is connected to the A side, and the 1-field period for the magnetic head H _B to scan the magnetic tape (2) is connected to the B side.

The continuous reproduction signal output from the head changeover switch (4) is supplied to the high pass filter (21) and the band pass filter (22). FM modulated luminance signal Y _FM from the high pass filter (21).
z, the white peak is 5.4 MHz, and the frequency deviation is 1.2 MHz), and the FM modulated luminance signal Y _FM is supplied to the FM demodulator (23). Then, the luminance signal Y obtained from the FM demodulator (23) is supplied to the synthesizer (24). Further, a low-pass conversion color signal (for example, a color subcarrier frequency is 743 kHz) C _L is obtained from the bandpass filter (22), and the low-pass conversion color signal C _L is
It is supplied to the frequency converter (26) via the ACC circuit (25). The carrier color signal C having a color subcarrier frequency of 3.58 MHz obtained from the frequency converter (26) is supplied to the synthesizer (24), and the terminal (27) derived from the synthesizer (24).
A video signal SV is obtained at.

The continuous reproduction signal output from the head changeover switch (4) is supplied to a pilot signal detection circuit (5) having a low-pass filter configuration. The pilot signal detected by the detection circuit (5) is supplied to the multiplication circuit (6). Further, (7) is a frequency signal generation circuit, and signals of frequencies f ₁ , f ₂ , f ₃ , f ₄ are generated from this generation circuit (7) and supplied to the switch circuit (8) respectively. . An RF switching pulse SWP (shown in FIG. 9A) is supplied to the switch circuit (8) as a switching control signal. From the switch circuit (8), the frequency of the pilot signal of the recording tracks T _A and T _B to be scanned by the magnetic heads H _A and H _B in each field period (shown by f _{1 to} f ₄ in FIG. 9A). A signal having a frequency equal to is output (illustrated in FIG. 9B).

The output signal of the switch circuit (8) is supplied to the multiplication circuit (6) as a reference pilot signal. In the multiplication circuit (6), the pilot signal from the detection circuit (5) and the reference pilot signal from the switch circuit (8) are multiplied.

The output signal of the multiplication circuit (6) is supplied to the detection circuit (9A) of the difference frequency Δf _A composed of a bandpass filter, and the output signal of this detection circuit (9A) is a peak detection circuit (10A).
The output signal of the peak detection circuit (10A) is supplied to the terminals on the A side and B side of the changeover switches (11) and (12), respectively. Further, the output signal of the multiplication circuit (6) is supplied to the detection circuit (9B) of the difference frequency Δf _B composed of a bandpass filter, and the output signal of this detection circuit (9B) is supplied to the peak detection circuit (10B). The output signal of the peak detection circuit (10B) is supplied to the B side and A side terminals of the changeover switches (11) and (12), respectively.

The RF switching pulse SWP is supplied to the changeover switches (11) and (12) as a changeover control signal, and the changeover switches (11) and (12) are changed when the head changeover switch (4) is changed over to the A side and the B side. , Are switched to the A side and the B side, respectively. Then, the changeover switches (11) and (12)
The output signals S1 and S2 of are respectively supplied to the comparator (13).

The comparator (13) outputs, for example, zero when S1 = S2, a positive signal whose level depends on the difference when S1> S2, and a negative signal whose level corresponds to the difference when S1 <S2. To be done.

Here, when the magnetic head H _A scans the recording track T _A , the frequencies Δf _A and Δf _B output from the multiplication circuit (6)
The level of the difference frequency signal of is the same level when the scanning position is at the center, and the level of the difference frequency signal of frequency Δf _B becomes larger as the scanning position shifts to the front recording track side, and the scanning position moves backward. The level of the difference frequency signal of the frequency Δf _A becomes larger as it is closer to the recording track side. Therefore, the levels of the output signals of the peak detection circuits (10A) and (10B) are the same when the scanning position is at the center, and the level of the output signal of the peak detection circuit (10A) becomes closer to the recording track side later. And the level of the output signal of the peak detection circuit (10B) becomes larger as the scanning position shifts to the side of the previous recording track.

On the other hand, when the magnetic head H _B scans the recording track T _B , the level relationship of the difference frequency signal between the frequencies Δf _A and Δf _B is different from that when the magnetic head H _A scans the recording track T _A as described above. The opposite is true. Therefore, the level relationship of the output signals of the peak detection circuits (10A) and (10B) is also the relationship opposite to that when the magnetic head H _A scans the recording track T _A.

However, the change-over switch (11) and (12), one field period in which the magnetic head H _A scans the recording track T _A is A
Side, on the other hand, the magnetic head H _B scans the recording track T _B 1
The magnetic head is connected to the B side during the field period.
When H _A and H _B scan the recording tracks T _A and T _B , the levels of the output signals S1 and S2 of the changeover switches (11) and (12) become the same level when the scanning position is at the center, and the scanning position is The output signal S1 becomes larger as it shifts to the rear recording track side, and the signal S2 becomes larger as the scanning position shifts to the front recording track side. Therefore, when the magnetic heads H _A and H _B scan the recording tracks T _A and T _B , the comparator (13) indicates zero when the scanning position is at the center, and when the recording heads are deviated to the recording track side later, the deviation is made. When a positive signal having a level proportional to the magnitude is offset to the previous recording track side, a negative signal having a level proportional to the magnitude of the offset is output.

Further, (14) is a capstan motor, (15) is a motor drive circuit that controls the rotation thereof, and (16) is a frequency generator that generates a frequency signal corresponding to the rotation speed of the capstan motor (14). The frequency signal from the frequency generator (16) is supplied to the speed servo circuit (17), and the speed error signal from this speed servo circuit (17) is added to the adder (18).
Is supplied to the motor drive circuit (15) via. Thereby, the rotation speed of the capstan motor (14) is controlled to be constant.

The output signal of the comparator (13) described above is the adder (1
8) is supplied to the motor drive circuit (15) as an ATF error signal (phase error signal) E _ATF . As a result, the rotational phase of the capstan motor (14) is controlled so that the magnetic heads H _A and H _B correctly scan the center positions of the recording tracks T _A and T _B. So-called tracking servo is performed.

D Problems to be Solved by the Invention Thus, according to the example of FIG. 6, theoretically correct tracking servo is performed. However, in the case of the LP mode, when the magnetic tape (2) is a metal powder tape (hereinafter referred to as "MP tape"), there is a problem that the tracking servo cannot be performed correctly. The reason will be described below.

FIG. 10 shows a track pattern in the LP mode. In the LP mode, the track width is restricted by overwriting as described above. Magnetic tape (2) is MP
When the tape is used, the erasure rate is -6 because the magnetic layer is thick.
Bad with ~ -8dB. Therefore, as for the pilot signal, the previously recorded pilot signal is not completely erased but remains in the overwritten portion shown by hatching in FIG. For _{example, f 1, f 2, f} 3, f 4 of the recording tracks T _A pilot signal of the frequency is recorded, the track side of the front of the T _B are each _{f 4, f 1, f 2} , f 3 The frequency pilot signal remains.

Now, consider a case where the magnetic tape (2) is reproduced by the magnetic head H having a head width wider than the track width T _P.
Here, attention is paid when scanning the recording track T _A on which the pilot signal of the frequency f ₁ is recorded.

At this time, in relation to the deviation of the magnetic head H, the frequency f ₄ and f ₂ magnetic head H is picked up from the recording track T _B before and after
The levels of the pilot signals are shown by solid lines a and b in FIG. 11, respectively.
As shown in FIG. 5, the amount of deviation of the magnetic head H is zero, and they are at the same level during just tracking. However, in relation to the amount of deviation of the magnetic head H, the level of the pilot signal of the frequency f ₄ picked up by the magnetic head H from the recording track T _A is
As shown by the broken line c in FIG. 11, the level of the pilot signal of the frequency f ₄ picked up by the magnetic head H is as shown by the alternate long and short dash line d in FIG. 11, and as a result, the amount of displacement of the magnetic head is zero. Even during the just track, the level of the pilot signal of frequency f ₄ is higher than the level of the pilot signal of frequency f ₂ .

Therefore, in relation to the deviation amount of the magnetic head H, the ATF
The error signal E _ATF becomes as shown by the broken line b in FIG. 12, it does not become zero during the just track, and the magnetic head H has a predetermined amount l.
However, it will shift to the track side after the just track state (see the broken line in Fig. 10). Note that FIG. 12 the solid line a in a case where the recording tracks T _A no remaining pilot signal of the frequency f _4, a frequency from the recording track T _A magnetic head H
ATF error signal E when the pilot signal of f ₄ is not picked up
_It shows _ATF, and it is zero at the just track.

Thus, in the LP mode, the magnetic tape (2)
When the tape is an MP tape, the magnetic head H is displaced from the just track state. As a result, the magnetic head H
Will pick up the signal from the same adjacent track of azimuth, and there is a problem that the playback screen is disturbed.

In the above description, the case where the magnetic tape (2) is reproduced by the magnetic head H having a head width wider than the track width is shown. However, when the magnetic tape (2) is reproduced by a magnetic head having a head width equal to or narrower than the track width. In the same manner, the magnetic head is displaced, and in this case, there is a problem that the reproduction signal is reduced and the reproduction screen is disturbed.

By the way, when the magnetic tape (2) is a metal vapor deposition tape (hereinafter referred to as "ME tape"), the erasing rate is good at -15 to -17 dB because the magnetic layer is thin. Therefore, in the overwritten portion, the previously recorded pilot signal is almost completely erased. Therefore, the ATF error signal E _ATF becomes as shown by the solid line a in FIG. 12 in relation to the deviation amount of the magnetic head H, becomes zero at the time of just track, and the magnetic head H does not shift from the just track state, Tracking servo is performed.

The present invention has been made in view of the above circumstances and is configured to perform good tracking servo regardless of the magnetic characteristics of the magnetic tape.

E Means for Solving Problems The present invention provides a pilot signal when reproducing a magnetic tape (2) in which an information signal, for example, a video signal is recorded together with a pilot signal on oblique tracks T _A and T _B by overwriting. It is premised on an information signal reproducing device which performs tracking servo based on the above. Further, according to the present invention, the switching means (switch circuit (8) / connection switch (32) / level adjusting circuit (41)) for switching the center value of the tracking servo by switching the generation timing of the reference pilot signal, and the magnetic tape ( 2) has a first erasing rate in overwriting with respect to the pilot signal, and when the magnetic tape (2) has a second erasing rate that is worse than the first erasing rate. The magnetic tape (2) is provided with a control means (Sc ₁ / Sc ₂ / Sc ₃ ) for controlling the switching means (switch circuit (8) / connection switch (32) / level adjusting circuit (41)). When the erase ratio is provided, the center value of the tracking servo is switched so that the tracking deviation due to the unerased pilot signal in the overwritten portion is improved.

For example, when the magnetic tape (2) is an MP tape, the generation timing of the reference pilot signal is delayed by a predetermined time.

F 2 action Depending on the magnetic characteristics of the magnetic tape (2), the previous pilot signal remains in the overwritten portion without being completely erased. Therefore, the ATF error signal E _ATF cannot be obtained correctly. However, by switching the center value of the tracking servo as described above, the ATF error signal E _ATF is corrected and good tracking servo is performed regardless of the magnetic characteristics of the magnetic tape (2).

For example, when the magnetic tape (2) is an MP tape, the ATF error signal E _ATF decreases, for example, and has a negative value at the time of just tracking. However, by delaying the generation timing of the reference pilot signal by a predetermined time, the ATF error The signal E _ATF is corrected so as to become zero at the just track.

G Example G ₁ First Example First, a first example of the present invention will be described with reference to FIG. In FIG. 1, parts corresponding to those in FIG. 6 are designated by the same reference numerals, and detailed description thereof will be omitted.

In this example, a control signal S _C1 is supplied to the switch circuit (8) from the system controller (not shown), and the generation timing of the reference pilot signal supplied to the multiplication circuit (6) from the switch circuit (8) is controlled. It LP for example
In mode, when the magnetic tape (2) is ME tape,
The generation timing is the same as in the example of FIG. That is, in each field period, a signal having a frequency equal to the frequency of the pilot signal of the recording tracks T _A , T _B to be scanned by the magnetic heads H _A , H _B is output (shown in FIG. 2B). on the other hand,
In the LP mode, when the magnetic tape (2) is an MP tape, the generation timing of the reference pilot signal is delayed. That is, a signal having a frequency equal to the frequency of the pilot signal of the recording tracks T _B , T _A before the recording tracks T _A , T _B to be scanned by the magnetic heads H _A , H _B is output in the period α of each field period. Then, during the remaining period β, a signal having a frequency equal to the frequency of the pilot signal of the recording tracks T _A and T _B to be scanned by the magnetic heads H _A and H _B is output (shown in FIG. 2C). In addition, FIG. 2A shows the RF switching pulse SWP.
And is the same as FIG. 9A.

 Others are the same as those in the example of FIG.

In the above configuration, the magnetic tape (2) is in LP mode.
In the case of the ME tape, the generation timing of the reference pilot signal supplied from the switch circuit (8) to the multiplication circuit (6) is the same as that in the example of FIG. 6, so that the tracking servo is similarly performed correctly.

When the magnetic tape (2) is an MP tape in the LP mode, the generation timing of the reference pilot signal supplied from the switch circuit (8) to the multiplication circuit (6) is delayed. In this case, a frequency equal to the frequency of the pilot signal of the recording tracks T _B , T _A before the recording tracks T _A , T _B to be scanned by the magnetic heads H _A , H _B generated in the period α of each field period. when only the signal, the magnetic head H _a, in relation to the shift amount of H _B, ATF error signal E _ATF third FIG dashed line a
On the other hand, when the magnetic heads H _A and H _B generated in the period β of each field period have only signals having a frequency equal to the pilot signal frequency of the recording tracks T _A and T _B to be scanned, , ATF in relation to the amount of deviation between the magnetic heads H _A and H _B
The error signal E _ATF is as shown by the broken line b in FIG. Therefore, the combined ATF error signal E _ATF becomes as shown by the solid line c in FIG. 3, and does not become zero at the just track,
The magnetic heads H _A and H _B are controlled so as to be shifted to the previous track side by a predetermined amount 1 '. This predetermined amount l'is
Although it can be changed arbitrarily by changing the ratio of α and β, in the case of this example, the magnetic heads H _A and H _B are just adjusted due to the previous pilot signal remaining in the overwritten portion of the MP tape. It is determined so as to cancel the deviation of a predetermined amount 1 toward the track side after the track state (see FIG. 12). That is, the ATF error signal E
_{The ATF} is determined to be zero.

Therefore, in this example, even when the magnetic tape (2) is the MP tape in the LP mode, the ATF error signal E _ATF becomes zero at the time of just tracking, so that the tracking servo is correctly performed.

As described above, according to this example, there is an advantage that the tracking servo is correctly performed regardless of whether the magnetic tape (2) is the ME tape or the MP tape.

G ₂ Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIG. In FIG. 4, parts corresponding to those in FIG. 6 are designated by the same reference numerals, and detailed description thereof will be omitted.

In this example, the ATF which is the output signal of the comparator (13)
The error signal E _ATF is supplied to the adder (31). Further, the predetermined voltage E _MP is added to the adder (31) via the connection switch (32).
Is supplied to. Then, the output signal of the adder (31) is supplied to the motor drive circuit (15) via the adder (18).

The voltage E _MP is a positive voltage of the same magnitude as the negative ATF error signal E _ATF (see broken line b in FIG. 12) that occurs during just tracking due to the previous pilot signal remaining in the overwritten portion of the MP tape. It is said that

Further, although not shown, the system controller supplies a control signal S _C2 to the connection switch (32) to control the connection. For example, it is turned off when the magnetic tape (2) is an ME tape in the LP mode, and is turned on when the magnetic tape (2) is an MP tape in the LP mode.

 Others are the same as those in the example of FIG.

In the above configuration, the magnetic tape (2) is in LP mode.
When the tape is an ME tape, the connection switch (32) is turned off, and since it is the same as in the example of FIG. 6, the same operation is performed and the tracking servo is correctly performed.

When the magnetic tape (2) is an MP tape in the LP mode, the connection switch (32) is turned on and the adder (31) adds the voltage E _MP to the ATF error signal E _ATF . Therefore, the negative AFT that occurs during just tracking due to the previous pilot signal remaining in the overwritten portion
The error signal E _AFT cancels out and becomes zero. Therefore, the tracking servo is correctly performed.

As described above, also in this example, there is an advantage that the tracking servo is correctly performed regardless of whether the magnetic tape (2) is the ME tape or the MP tape.

G ₃ Third Embodiment Next, a third embodiment of the present invention will be described with reference to FIG. In FIG. 5, those parts corresponding to those in FIG. 6 are designated by the same reference numerals, and a detailed description thereof will be omitted.

In this example, the output signal S2 of the changeover switch (12) is supplied to the comparator (13) via the level adjusting circuit (41).

Further, although not shown, the system controller supplies the control signal S _C3 to the level adjusting circuit (41) to control the level of the signal S2. For example, magnetic tape (2) in LP mode
Is a ME tape, the level remains as it is, LP
In mode, when the magnetic tape (2) is an MP tape, it is attenuated by a predetermined level. This amount of attenuation is set to a value such that the signal S2 becomes equal to the signal S1 during just tracking.

 Others are the same as those in the example of FIG.

In the above configuration, the magnetic tape (2) is in LP mode.
In the case of ME tape, the output signal S2 of the changeover switch (12) is supplied to the comparator (13) at the same level, so that the same operation as in the example of FIG. 6 is carried out and the correct tracking servo is performed.

Further, when the magnetic tape (2) is an MP tape in the LP mode, it is supplied to the comparator (13) after being attenuated by the level adjusting circuit (41) so that the signal S2 becomes equal to the signal S1 during just tracking. Therefore, the ATF error signal E _ATF does not become negative during the just track due to the previous pilot signal remaining in the overwritten portion of the MP tape (see broken line b in FIG. 12). Therefore, the tracking servo is correctly performed.

As described above, also in this example, there is an advantage that the tracking servo is correctly performed regardless of whether the magnetic tape (2) is the ME tape or the MP tape.

In the above embodiment, the ATF error signal E when the MP tape is used.
_This is an example in which the _ATF is corrected, but conversely, it is possible to configure the circuit so that the tracking servo is correctly performed for the MP tape and to correct the ATF error signal E _ATF for the ME tape.

Further, in the above-mentioned embodiment, although the case of the ME tape and the MP tape is described, the center value of the tracking servo is similarly switched according to the magnetic characteristics for other magnetic tapes, and the ATF error signal E _ATF is changed. Good correction servo is performed by the correction.

Further, according to the above-mentioned embodiment, it is an example in which the present invention is applied to a VTR, but the present invention is the other information in which an information signal such as a voice signal is similarly recorded on an oblique track and tracking servo is performed by a pilot signal. The same can be applied to the signal reproducing device.

H Effect of the Invention As is apparent from the above-described embodiments, according to the present invention, the center value of the tracking servo is switched according to the magnetic characteristics of the magnetic tape. There is the benefit of having good tracking servo.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention, FIGS. 2 and 3 are diagrams for explaining the same, FIGS. 4 and 5 are configuration diagrams showing another embodiment of the present invention, FIG. 6 is a block diagram of a conventional example,
FIG. 7 to FIG. 12 are diagrams for explaining this. (1) is a rotary drum, (2) is a magnetic tape, (4) is a head changeover switch, (5) is a pilot signal detection circuit,
(6) is a multiplication circuit, (7) is a frequency signal generation circuit,
(8) is a switch circuit, (9A) and (9B) are differential frequency detection circuits, (10A) and (10B) are peak detection circuits, and (1
1) and (12) are changeover switches, (13) is a comparator, (1
4) is a capstan motor, (15) is a motor drive circuit, (18) and (31) are adders, (32) is a connection switch, and (41) is a level adjustment circuit.

Claims (1)

(57) [Claims] 1. When reproducing a magnetic tape recorded with an information signal together with a pilot signal on a track oblique to the longitudinal direction of the magnetic tape such that the pitch of the track is smaller than the recording head width, the pilot is used. In an information signal reproducing apparatus adapted to perform tracking servo based on a signal, switching means for switching the center value of the tracking servo by switching the generation timing of the reference pilot signal, and the magnetic tape for overwriting the pilot signal. Control means for controlling the switching means for the center value of the tracking servo depending on when the magnetic tape has a second erasing rate which is worse than the first erasing rate. When the magnetic tape has a second erasing rate, the overwriting Minute information signal reproducing apparatus characterized by switching the center value of the tracking servo as displacement tracking is improved by unerased pilot signal.