JP2693425B2 - 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 H Effect of the Invention A Industrial field of application The present invention relates to an information signal reproducing apparatus suitable for application to, for example, a rotary two-head type VTR. B Outline of the Invention The present invention is directed to a rotary reproducing head (HA) according to a frequency component of a difference between a reproduction pilot signal and a reference pilot signal.
(HB) tracking control is performed, an offset is generated in the tracking control, and the rotary reproduction head (HA),
When the reproduction signal level from (HB) decreases, the tracking state of the rotary reproduction heads (HA) and (HB) is controlled according to the output signals from the detection means (31) and (32). is there. 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. FIG. 5 shows the structure of the reproducing system. In the figure, (1) is a rotary drum, and a pair of magnetic heads H _A and H _B having different azimuth angles and 180 ° angular intervals are attached to the rotary drum (1). . 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. Magnetic heads H _A and H _B are 1 per frame
Made to rotate, magnetic head in odd field
The H _A scans the magnetic tape (2), and the magnetic head H _B scans the magnetic tape (2) in the even field. 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"), the 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. 8A) is supplied to the switch circuit (8) as a switching control signal. From the switch circuit (8), the frequencies of the pilot signals 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. 8A). A signal having a frequency equal to is output (shown in FIG. 8B). 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 magnetic tracks T _A and T _B , the comparator (13) indicates zero when the scanning position is at the center, and when the magnetic heads H _A and H _B deviate 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 As described above, according to the side of FIG. 5, theoretically correct tracking servo is performed. However, in the LP mode, when the magnetic tape (2) is a metal powder tape (hereinafter referred to as "MP tape"), the tracking servo cannot be performed correctly. In this case, when the head width of the magnetic heads H _A and H _B during reproduction is substantially equal to the track width (for example, 13 μm) as in the case of the LP mode only,
This is a problem because it causes a drop in the reproduction signal. The reason will be described below. FIG. 9 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 slightly 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 in solid lines a and b in FIG. 10, 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. 10, the level of the pilot signal of the frequency f ₄ picked up by the magnetic head H eventually becomes as shown by the alternate long and short dash line d in FIG. 10, and as a result, the deviation amount 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. 11, does not become zero at the time of just tracking, and the magnetic head H has a predetermined amount l.
However, it is displaced to the track side after the just track state (see the broken line in FIG. 9). Note that FIG. 11 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. As described above, in the LP mode, when the magnetic tape (2) is the MP tape, the magnetic heads H _A and H _B deviate from the just track state, and the correct tracking servo cannot be performed. As a result, for example, there is a problem that the reproduction signal is lowered and the reproduction screen is disturbed. By the way, when the magnetic tape (2) is a metal vapor deposition tape (hereinafter referred to as "MB 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. 11 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. In view of such a point, the present invention is to always make the tracking state correct. E Means for Solving the Problems In the present invention, an information signal is recorded as at least a plurality of diagonal tracks on a magnetic tape recording medium having a thick magnetic layer by a rotary recording head having a predetermined recording track width, and the frequency difference is also recorded. A plurality of pilot signals selected at a frequency on the low frequency side of the information signal are cyclically recorded on the track, and each track is recorded from the recording medium in which a part of the track width direction is overlapped and recorded. An information signal for obtaining the frequency of the difference between the reproduction pilot signal from the recording track and the reference pilot signal during reproduction of the information signal and performing tracking control of the rotary reproduction heads (HA), (HB) according to the frequency component of the difference. A reproducing apparatus, wherein the rotary reproducing heads (HA), (HB) for the recording track on which the information signal is recorded by the rotary recording head. Change the tracking state of the reference pilot signal by controlling the generation timing of the reference pilot signal with respect to the switching timing of the RF switching pulse by a predetermined amount, and when the reproduction output exceeds the maximum position, the shift amount is changed. The rotary reproduction head is provided with detection control means (31), (32) for returning to the immediately preceding state and performing detection control so as to maximize the output, according to the frequency component of the difference between the reproduction pilot signal and the reference pilot signal. (HA), (HB) tracking control is performed, and when the tracking control is offset and the reproduction signal level from the rotary reproduction heads (HA), (HB) decreases, the detection control means (31) , (32) for controlling the tracking state of the rotary reproducing head in accordance with the output signal from (32). In the configuration above F action, the tracking state is controlled so that the reproduction output of the head becomes maximum, so that the tracking state is always correct. As a result, as described above, it is also possible to prevent the position of the magnetic head from being displaced due to the pilot signal remaining in the overwritten portion of the MP tape, and the correct tracking state from being lost. G Example G ₁ First Example First, a first example of the present invention will be described with reference to FIG. In FIG. 1, portions corresponding to those in FIG. 5 are denoted by the same reference numerals, and detailed description thereof will be omitted. In this example, the continuous reproduction signal output from the head changeover switch (4) is supplied to the envelope detection circuit (31), and the output signal of the detection circuit (31) is a microcomputer (hereinafter, referred to as "microcomputer") that constitutes a system controller. ")) (32). The switch circuit (8) is controlled by the microcomputer (32), and when the mode is changed from another mode such as recording to the reproduction mode, the generation timing of the reference pilot signal is controlled as described later. By controlling the generation timing of the reference pilot signal in this way, the tracking state of the magnetic heads H _A and H _B can be changed. For example, the recording track T to be scanned by the magnetic heads H _A and H _B in the period α of each field period.
_A signal having a frequency equal to the pilot signal frequency of the recording tracks T _B , T _A before _A , T _B is output, and the recording tracks T _A , H _B to be scanned by the magnetic heads H _A , H _B in the remaining β period. T _B
It is assumed that a signal having a frequency equal to the frequency of the pilot signal is output (illustrated in FIG. 2B). 2A shows the RF switching pulse SWP, which is the same as FIG. 8A. 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. In the case of only the signal of, the ATF error signal E _ATF becomes as shown by the one-dot chain line a in FIG. 3 in relation to the shift amount of the magnetic heads H _A and H _B , while it occurs in the period β of each field period. Recording tracks T _A , which are to be scanned by the magnetic heads H _A , H _B
When only a signal having a frequency equal to the frequency of the pilot signal of T _{B is used} , the ATF error signal E _ATF becomes as shown by the broken line b in FIG. 3 in relation to the amount of deviation between the magnetic heads H _A and H _B. Therefore, the synthesized ATF error signal E _ATF becomes as shown by the solid line c in FIG. 3, it does not become zero at the just track, and the magnetic heads H _A and H _B are shifted to the previous track side by a predetermined amount l ′. Will be controlled by. Actually, the rotation phase of the capstan motor (14) is controlled by the ATF error signal E _ATF , and the track is shift-controlled. This predetermined amount l'can be arbitrarily changed by changing the ratio of α and β. Contrary to the above description, the magnetic heads H _A and H _B are deviated to the subsequent track side by a predetermined amount by controlling the generation timing of the reference pilot signal to be advanced as shown in FIG. 2C. Will be controlled by. Thus, by generation timing of the reference pilot signal is controlled, the track is shifted control, magnetic head H _A, the tracking of the state of the H _B is changed. In the above configuration, when the mode is changed from another mode such as recording to the reproduction mode, the microcomputer (32) operates according to the flowchart shown in FIG. When the mode is changed to the reproduction mode, the track deviation information ΔT is set to 0 in step. Further, the output signal of the detection circuit (31) is sampled in step and the value is set to D ₀ . Further, N = 0 is set in the step. Next, in step N = N + 1. Further, the track deviation information ΔT = ΔT + 1 is set in step, the generation timing of the reference pilot signal from the switch circuit (8) is controlled based on the track deviation information ΔT, and the track is delayed by ΔT × W (W is Therefore, the magnetic heads H _A and H _B are controlled so as to be shifted by a predetermined unit amount), and are shifted to the previous track side by ΔT × W. Then, in step, the output signal of the detection circuit (31) is sampled and its value is set to D ₁ . Next, in step, it is judged whether D ₁ is larger than D ₀ . When it is larger, D ₁ is set to D ₀ in the step and is returned to the step. When it is not larger, the track deviation information ΔT = ΔT−1 is set in step. Next, in step, it is determined whether N is 2 or more.
When N is 2 or more, it means that the output of the detection circuit (31) is maximum in the tracking state corresponding to the track deviation information ΔT. Therefore, when N is 2 or more, the generation timing of the reference pilot signal from the switch circuit (8) is controlled based on the track deviation information ΔT in step, so that the track is shifted to the delay side by ΔT × W. The magnetic heads H _A and H _B are controlled so as to be displaced by ΔT × W toward the previous track side. On the other hand, when N is not 2 or more, that is, when N is 1, track deviation information ΔT = ΔT−1 is set in step, and the reference pilot signal is generated from the switch circuit (8) based on the track deviation information ΔT in step. The timing is controlled so that the track is shifted to the advance side by ΔT × W, and accordingly, the magnetic heads H _A and H _B are controlled to be shifted to the track side after ΔT × W. Then, in step, the output signal of the detection circuit (31) is sampled and its value is set as D ₂ . Next, in step, it is determined whether D ₂ is larger than D ₀ . When it is larger, D ₂ is set to D ₀ in the step and is returned to the step. When it is not larger, the track deviation information ΔT = ΔT + 1 is set in step. At this time, it means that the output of the detection circuit (31) is maximum in the tracking state corresponding to the track deviation information ΔT. Therefore, in step, the generation timing of the reference pilot signal from the switch circuit (8) is controlled based on the track deviation information ΔT, and the track is shifted toward the advance side by ΔT × W. Therefore, the magnetic heads H _A , H _B Is ΔT × W
However, it is controlled so as to be shifted to the subsequent track side. As described above, in this example, when the mode is changed to the reproduction mode, the tracking state is automatically controlled so that the reproduction signals from the magnetic heads H _A and H _B become maximum.
Therefore, according to this example, the tracking state is always correct. Thereby, for example, the magnetic heads H _A and H _B are generated due to the pilot signal remaining in the overwritten portion of the MP tape.
It is also avoided that the position of is shifted and the correct tracking state is not achieved. H Effect of the Invention According to the present invention described above, it is possible to prevent the effect of the offset of the automatic tracking due to the pilot signal, which occurs when the pilot signal in the overwritten portion remains without being completely erased. Play.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention, and FIGS.
FIG. 5 is a diagram for explaining it, FIG. 5 is a configuration diagram of a conventional example, and FIGS. 6 to 11 are diagrams for explaining it. (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, (31) is an envelope detection circuit, and (32) is a microcomputer.

Claims (1)

(57) [Claims] An information signal is recorded on a magnetic tape recording medium having a thick magnetic layer as at least a plurality of oblique tracks by a rotary recording head having a predetermined recording track width, and is selected as a low frequency side of the information signal having different frequencies. A plurality of pilot signals are cyclically recorded on the tracks, and each track is recorded on the recording medium in which a part of the track width direction overlaps. When reproducing the information signal, a reproduction pilot from the recording track is reproduced. An information signal reproducing apparatus for obtaining a frequency of a difference between a signal and a reference pilot signal and performing tracking control of a rotary reproducing head according to a frequency component of the difference, which is for a recording track on which the information signal is recorded by the rotary recording head. The tracking status of the rotary read head is set to the RF timing of the reference pilot signal generation timing. When the reproduction output exceeds the position where the reproduction output becomes maximum by changing the timing of switching the switching pulse by a predetermined amount, detection control is performed so that the above shift amount is returned to the state immediately before and the output becomes maximum. Detection control means for performing the tracking control of the rotary reproducing head according to the frequency component of the difference between the reproduction pilot signal and the reference pilot signal, and producing an offset in the tracking control. When the level decreases, the information signal reproducing apparatus is characterized in that the tracking state of the rotary reproducing head is controlled according to the output signal from the detection control means.