JPH0734280B2 - Tracking error signal generation circuit - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention particularly relates to a tracking error signal generation circuit for obtaining a tracking error signal by utilizing a reproduction time difference between signals reproduced by at least two heads having different azimuth angles. It is about.

2. Description of the Related Art Recording / reproducing equipment, such as magnetic recording / reproducing apparatus (hereinafter simply referred to as VT
(Referred to as “R”) and the like, when reproducing an information signal recorded on a recording track, tracking control is required for the reproducing head to perform on-track reproduction scanning on the recording track.

In azimuth recording, as a method of obtaining a tracking error signal over the entire area of a recording track, a method of utilizing a relationship between a track deviation and a reproduction time difference of a specific signal is known. This method is disclosed in JP-A-55-150129, and since the present invention relates to this method, the basic concept of this method will be described below.

FIG. 16 shows the magnetization loci recorded by two heads having different azimuth angles. In the figure, 1601 is a magnetic tape, which is transported in the direction of arrow 1602. Reference numerals 1603 and 1604 are heads having mutually different azimuth angles, and simultaneously scan in the arrow 1605 direction. Such heads, that is, heads that simultaneously scan and have different azimuth angles are hereinafter referred to as pair heads. Reference numerals 1606 and 1607 indicate respective head gaps. A ₁ , A ₂ , ... Are magnetization loci recorded by a head having the same azimuth angle as the A head shown by 1603, and B ₁ , B ₂ , ... Are the B head shown by 1604. It is a magnetization locus recorded by a head having the same azimuth angle. The track pair of A ₁ and B _{1 and} the track pair of A ₂ and B ₂ may be recorded by the same pair head, or may be recorded by another pair head. This relationship is determined by the number of rotations of the rotary cylinder that incorporates the rotary head and the number of paired heads that are incorporated, and can be freely determined when designing the device. A signal recorded on each magnetization locus, for example, a magnetization pattern such as a horizontal synchronizing signal is recorded with an angle inclined with respect to the longitudinal direction of the track, that is, an azimuth angle, as indicated by 1608 and 1609.

The method of recording and reproducing the information signal using the pair head is effective when the frequency band of the information signal to be handled is large. This is because, when an information signal is recorded at a constant head scanning speed, the higher the recording frequency of the information signal, the shorter the recording wavelength to be recorded on the magnetic tape, and the shorter the recording wavelength, the more difficult practical recording and reproduction becomes. This is because the frequency band of the information signal can be divided and distributed to each head by using the paired heads, so that the recording wavelength can be set substantially longer.

FIG. 14 shows three types of positional relationship between the recording magnetization locus and the reproducing scanning head. In the figure, 1401, 140 indicated by broken lines
2 and 1403 are pair heads, which are composed of A and B heads, respectively. Each pair head scans in the direction of arrow 1404.
A ₁ and B ₁ are the magnetization loci recorded by the pair head,
Signals 1410 to 1410 indicate the recording position of the horizontal synchronizing signal.
The position of the pair head with respect to the recording magnetization locus is shifted to the left on the paper surface in FIG. 14 (a), on-track in FIG. 14 (b), and to the right in FIG. 14 (c). . When a head having such a relative positional relationship is used to perform reproduction scanning on a recording track, the reproduction time differs even for signals recorded at the same time. For example, the 14th
In FIG. 7A, the time for which the horizontal synchronizing signal 1405 is reproduced by the head A is delayed as compared with the time for which the horizontal synchronizing signal 1406 is reproduced by the head B. In FIG. 14 (b), the reproduction times of both horizontal synchronizing signals are equal, and in FIG. 14 (c), the horizontal synchronizing signal 1409 is reproduced by the head A while the horizontal synchronizing signal 1409 is reproduced by the head B. It will be faster than the time it is played. Therefore, the track deviation can be known by examining the time difference between the horizontal sync signals reproduced by the A and B heads. Note that the signal for checking the time difference is not limited to the horizontal synchronization signal and may be another specific signal, but in the following description, the horizontal synchronization signal will be described as a specific signal.

FIG. 15 is a diagram showing the relationship between the track deviation and the reproduction time difference of each horizontal synchronizing signal reproduced by each of the A and B heads. The horizontal axis indicates the track shift, and the position indicated by zero is the on-track position. The shifts shown on the right and left correspond to the shift direction on the paper surface of the head with respect to the recording track shown in FIG. The vertical axis represents the reproduction time difference of the horizontal sync signals reproduced by the A and B heads, and the time when the time difference is zero is the on-track position. When the time of the horizontal sync signal reproduced by the A head is later than that of the B head,
The direction is. At this time, the relationship between the track shift and the time difference between the reproduced signals is as indicated by 1501. As is clear from FIG. 15, if the tracking control circuit is configured so that the time difference shown on the vertical axis becomes zero, the reproducing head always performs on-track reproduction scanning on the recording track.

As described above, the method of performing tracking control by detecting the time difference between the signals reproduced by the pair of heads is effective when the center positions of the head gaps of the A and B heads are exactly the same, but they are the same. If it is not there, a track shift will occur. This will be described next.

FIG. 12 is a diagram showing the relationship between the recording magnetization locus and the reproducing head when the magnetization locus recorded by the pair head in which the mounting position of the head is deviated is reproduced by another pair head deviated. Reference numerals 1201 and 1202 denote A and B heads, and 1203 and 1204 denote recording positions of horizontal synchronizing signals. This figure shows a state in which the pair heads perform on-track scanning on the recording track, and at this time, the time difference between the reproduction times of the horizontal synchronizing signals reproduced by the A and B heads is 12
The time is equivalent to the difference between the distances indicated by 05 and 1206. That is, there is a time difference between the reproduced signals even during on-track.

FIG. 13 shows the relationship between the track deviation and the time difference of the reproduced signal, and the vertical axis and the horizontal axis have the same meaning as in FIG. In the figure, 1501 has the same characteristics as those shown in FIG. That is, the on-track position is when the time difference is zero. On the other hand, the characteristic indicated by 1301 is the characteristic when the relationship between the head and the recording magnetization locus has the relationship shown in FIG. That is, the time difference does not become zero at the on-track position. At this time, if control is performed so that the time difference becomes zero, the control system becomes stable at the track position indicated by 1302.

The mounting accuracy of the A and B heads is determined by the mechanical accuracy during head assembly, and variations always occur. Therefore, it can be said that the relationship between the signal recording position and the reproducing pair head is generally that shown in FIG. Moreover, with 1205 shown in FIG.
Since the distance relationship with 1206 is different for each deck, the method shown in JP-A-55-150129 cannot be practically used unless this problem is solved.

A method for solving this problem is described in Japanese Patent Application No. 62-77751. This method is a method of detecting the maximum value of the reproduction signal when one of the pair heads crosses the recording track and using the time difference of the reproduction signal at the time of detection as a reference value.

However, the above method is effective when the mounting position of the pair heads is accurately mounted in the track width direction, but when the head mounting position varies in the track width direction, , Not the best way. This problem will be described next.

FIG. 11 is a diagram showing a practical mounting structure of a pair head, and FIG. 10 is a diagram showing a relative positional relationship between a scanning position of a head installed in such a structure and a recording track. In both figures, the same symbols indicate the same things.

In FIG. 10, A ₁ and B ₁ indicate recording tracks, and 1001 and 1002 indicate recording positions of specific signals. 1003 and 1004 are reproducing heads. Such a head arrangement can be realized by the configuration shown in FIG.

In FIG. 11, 1003 and 1004 are A heads and B heads having different azimuth angles. Head 1003 is a mounting member 11
It is fixed to the rotating member 1102 through 01, and the head 1004
Are directly fixed to the rotating member 1102. The rotating member 1102 rotates in the direction of arrow 1103. Distance in the height direction of each head
1104 is set equal to the width of one track shown in FIG. 10, and the longitudinal distance 1005 between the heads shown in FIG. 11 is
It corresponds to the distance indicated by the same number in FIG. If the distance 1005 between the heads is set equal to the distance 1006 between the recording positions of the specific signal, the reproduction time difference of the specific signal becomes zero when the head is on-track and scans the recording track. However, even when using such a head, the problem of head mounting error occurs. Then, this mounting error occurs not only in the direction of the distance 1005 in the time axis direction but also in the direction of the distance 1104 in the track width direction.

With such a pair head having a mounting error in the width direction, the maximum value of the reproduction signal when any one of the pair heads shown in Japanese Patent Application No. 62-77751 crosses the recording track is detected. However, if a method that uses the time difference of the reproduction signal at the time of detection as a reference value is used, a large amount of reproduction output can be obtained from one head, but the reproduction signal decreases from the other head by an amount according to the head mounting error. I have a problem to do. This state is shown in FIGS. 8 and 8. In both figures, A ₁ and B ₁ are recording tracks,
Is an A head and 802 is a B head. Both heads have a mounting error by an amount indicated by 803. FIG. 8 is a diagram showing a stable state of tracking when the reference value is formed when the output reproduced by the A head is the maximum value, and FIG.
It is a figure showing a stable state of tracking when a standard value is constituted when an output reproduced by a head is a maximum value. As is apparent from Japanese Patent Application No. 62-77751, the tracking control is controlled so as to approach the state when the reference value is calibrated, and therefore is stable in the states shown in both figures.

When recording / reproducing an analog signal, the phenomenon in which the S / N deteriorates as much as the reproduction output of one head decreases, but the content of the reproduced image was never lost. However, when recording or reproducing a digital signal, if the signal deteriorates beyond a certain value, error correction cannot be applied, and mosaic noise unrelated to the content of the recorded signal occurs, resulting in a very hard-to-see image. Becomes Therefore, it is necessary to avoid the problem that the reproduction output signal of only one head decreases in recording and reproducing a digital signal as much as possible.

According to the present invention, even when a pair head having an attachment error in the width direction is used, there is no problem that the reproduction output signal of only one head is significantly deteriorated, and a tracking error signal generation circuit capable of calibrating a reference value. The purpose is to provide.

Means for Solving the Problems In order to solve the above problems, the present invention provides a means for obtaining a reproduction time difference of a specific signal included in each reproduction signal reproduced by at least two magnetic heads having different azimuth angles, and tracking. Reference value creating means for creating a control reference value, computing means for computing the difference between the playback time difference and the reference value, or the sum value, displacement means for changing the mechanical height position of the magnetic head, and playback The reference value creating means comprises a means for detecting the maximum value of the signal, and the reference value creating means, the reproduction time difference at the time when the maximum value of the reproduction signal reproduced from one magnetic head is detected, and the reproduction reproduced from the other magnetic head. The average value with the reproduction time difference at the time when the maximum value of the signal is detected is calculated and output as the reference value of the tracking error signal.

Effect The present invention, of course, eliminates the influence of the mounting error of the pair head in the time axis direction by the above configuration,
Even in a pair head that has a mounting error in the width direction,
Since the deterioration of the reproduction output signal due to the mounting error can be evenly distributed to each head, there is an advantage that the influence of the image quality deterioration due to the decrease of the S / N can be made uniform.
In addition, in recording / reproducing of a digital signal, there is an effect that it is possible to obtain a large allowable value of the track deviation until the image quality suddenly deteriorates with respect to the track deviation due to other factors such as track bending.

Embodiments Before describing the embodiments of the present invention, the basic idea of the present invention will be described first.

FIG. 7 is a diagram showing a stable state of tracking when a reference value is calibrated using the present invention described later. In the figure, A ₁ and B ₁ indicate recording tracks, and 701 and 702 are pair heads. Reference numeral 703 indicates a mounting error in the width direction of both heads. As shown in the figure, in the tracking stable state, the mounting error 703 is evenly distributed to the track deviation amounts 704 and 705 of each head. In order to make the tracking stable state as shown in FIG. 7, the value obtained by averaging the reproduction time differences of the specific signals obtained when each head is in the on-track state may be used as the reference value.
That is, the reproduction time difference of the specific signal in the state shown in FIG. 8 and the reproduction time difference of the specific signal in the state shown in FIG. 9 may be arithmetically averaged and used as a reference value.

When self-recording / reproducing is performed by the head having the structure shown in FIG. 7, the relative positional relationship between the recording track and the reproducing head does not become as shown in FIG. This is because the head 702 records on the track recorded by the head 701 in an overlapping manner, so that the width of the track A ₁ becomes narrower and the width of the track B ₁ becomes wider. However, in reality, the relative positional relationship between the recording track and the head as shown in FIG. 7 is general. This is because, in a recording / reproducing apparatus that uses a method of obtaining a tracking error signal over the entire area of a recording track, a reproducing head is mounted on an electromechanical conversion element composed of a piezoelectric element, etc., and track bending follow-up control is performed using the tracking error signal. I do.
However, since the absolute mechanical height position of the electromechanical transducer changes with time, the head mounted on this transducer cannot be used as a recording head.
It is common to use a dedicated recording head. That is, it is general to use different heads for recording and for reproducing, and at this time, the relative positional relationship between the head and the recording track is as shown in FIG. Also, when playing commercially available soft tapes,
The relationship between the head and the track is as shown in FIG. Therefore, in the following description of the present invention, description will be made on the premise of the relative positional relationship shown in FIG.

An embodiment of the present invention will be described below.

FIG. 1 is a block diagram showing an embodiment of the present invention, and details of the time difference detection circuit 109 and the reference value creation circuit 113 shown in FIG. 1 will be described later.

In FIG. 1, 101 and 102 are an A head and a B for reproduction.
The head. 103 and 104 are regenerative amplifiers. Reference numeral 105 denotes a reproduction signal processing circuit, which converts the signal reproduced from each head into the same form as the original signal to form a reproduced video signal, and a terminal
The reproduced video signal is output from 106. Further, the reproduction signal processing circuit 105 outputs a specific signal reproduced from each head, that is, each horizontal synchronization signal 107 and 108. The time difference detection circuit 109 is a circuit that detects a reproduction time difference of each of these horizontal synchronization signals. The signal 110 corresponding to this time difference is supplied to the track shift calculation circuit 112 and the reference value creation circuit 113. The time difference detection circuit 109 outputs a time difference signal and also outputs a polarity determination signal 111 for determining which of the horizontal synchronization signals reproduced from the A and B heads is reproduced earlier. .

The reference value generation circuit 113 calculates the arithmetic mean value of the time difference signals 110 at each maximum value of the output signals reproduced from each head, and outputs the reference value signal 114. The track deviation calculation circuit 112 calculates a signal of the difference between the time difference signal 110 supplied from the circuit 109 and the reference value supplied from the reference value creation circuit 113, and outputs a tracking error signal 115. The tracking error signal 115 is the capstan motor control circuit 1
It is supplied to the piezoelectric element driving circuit 118 through the adding circuit 117 as well as being supplied to the piezoelectric element driving circuit 118. Capstan motor control circuit 1
At 16, the tracking error signal 115 is used to control the tape feed phase. The piezoelectric element drive circuit 118 displaces the heads 101 and 102 using the tracking error signal 115 to perform track bending follow-up control.

119 is a system control circuit, which is a key input signal 1
Various mode command signals are output according to 20. The system control circuit 119 is supplied with not only a key input signal but also a head switching signal (H.SW signal) indicating the rotation phase of the rotary head from the terminal 121. The gate signal 122 output from the system control circuit 119 is a signal which becomes a high level only during one scanning period in which one head performs reproduction scanning of one recording track in the reproduction mode. Only while the gate signal 122 is at the high level, the reference value generating circuit 113 operates and the switch 124 is closed.

The circuit 123 is a preset waveform creating circuit. The preset waveform creating circuit 123 is a circuit for creating a sawtooth wave signal for driving the piezoelectric element so that the read head crosses the recording track.

FIG. 2 is a diagram showing a detailed block diagram of the time difference detection circuit 109 shown in FIG. 1, and FIG. 3 shows signals of respective parts of FIG. The same symbols in FIGS. 2 and 3 indicate the same things.

In FIG. 2, a horizontal sync signal (3-a) included in a signal reproduced by the A head is input from a terminal 201, and a horizontal sync signal (3) included in a signal reproduced by the B head is input from a terminal 202. -C) is input. 203 is a delay circuit, which is triggered by the rising edge of the signal (3-a),
The high-level pulse signal (3-b) is output only during the period 301 shown in FIG. Reference numeral 204 denotes a reset-set flip-flop (hereinafter referred to as R-S-FF) circuit, which is set at the rising edge of the signal (3-c) and reset at the falling edge of the signal (3-b). R
The output signal (3-d) of the S-FF circuit 204 and the output signal (3-b) of the delay circuit 203 are input to the exclusive OR (hereinafter referred to as EX-OR) circuit 206, and the signal (3-e) is input. To get Since the high level period 302 of the signal (3-e) indicates the time between the horizontal synchronizing signals, this time indicates a track deviation if the mounting state of the A and B heads is normal. It will be.

A counter circuit 206 starts counting at the rising edge of the signal (3-e) and resets the count value at the falling edge of the signal (3-b). A clock for counting is input from the terminal 207. Reference numeral 208 denotes a latch circuit, which latches the count value of the counter circuit 206 at the falling edge of the signal (3-e). Therefore, the latch circuit 208 latches the value corresponding to the time difference between the horizontal synchronizing signals.

A signal (3-f) shown in FIG. 3 is a diagram showing a state in which the signal (3-c) is ahead of the signal (3-a) in time, and R at this time is shown. The output (3-d) of the S-FF circuit 204 has the waveform shown in (3-g). Also,
The output of the EX-OR circuit 205 at this time has a waveform shown in (3-h). Also at this time, the latch circuit 208 has 3
The value corresponding to the time indicated by 03 is recorded.

The signal (3-a) is delayed by the delay circuit 209, and (3
-Obtain the output signal shown in i). Reference numeral 211 is a D flip-flop (D-FF) circuit, which latches the input level of the signal (3-e) at the rising edge of the signal (3-i). Therefore, the horizontal sync signal reproduced by the B head is (3-a), while the horizontal sync signal reproduced by the B head is (3-a).
If it is delayed as shown in c), the output signal of the D-FF circuit 216 becomes high level. On the contrary, if the signal (3-f) has proceeded, the output signal of the D-FF circuit 211 becomes low level. Therefore, the output signal 111 of the D-FF circuit 211 is
A signal indicating whether the horizontal sync signal reproduced from the B head is delayed or advanced with respect to the horizontal sync signal reproduced from the A head, that is, the polarity of the tracking error signal (shifted from the on-track position to the right). Signal or whether it is shifted to the left).

Next, a specific example of the reference value creation circuit 113 shown in FIG. 1 will be described.

FIG. 4 is a detailed block diagram of the reference value generating circuit 113, FIG. 5 is a detailed block diagram of the maximum value detection circuit 406 shown in FIG. 4, and FIG. 6 is a waveform of each part of FIG. Indicates. In the drawings, the same symbols indicate the same things.

In FIG. 4, the output signals of the regenerative amplifiers 103 and 104 shown in FIG. 1 are input from terminals 402 and 403. 406
Reference numerals 407 and 407 denote maximum value detection circuits having the same circuit configuration. FIG. 5 shows a detailed block diagram of the maximum value detection circuit.

In FIG. 5, a reproduction signal (6-b) is input from the terminal 501. The reproduction signal (6-b) shown in FIG.
In the period shown by (1), the head scans across the recording magnetization locus in the width direction, and in the other periods, the reproduced signal obtained when the head performs on-track reproduction scanning on the recording track is shown. In such head scanning, the head may be moved by an electro-mechanical conversion element such as a piezoelectric element only during a period indicated by 601 in the normal reproduction mode. The reproduced signal (6-b) is detected and rectified by the detection and rectification circuit 503 and becomes a signal indicated by a broken line 602 in FIG. 6 (c). 504 is a peak hold circuit that holds the maximum value of the signal 602, and the output signal thereof is the signal indicated by 603. The gate signal (6-a) is input from the terminal 502. This gate signal is the output signal 122 of the system control circuit 119 shown in FIG. 1, and at any time in the reproduction mode,
This signal is high level only during the period when the head scans one track. The peak hold circuit 504 operates while the level of the gate signal is high, and the output signal also becomes low level while the level of the gate signal is low.

Reference numeral 505 is a level comparison circuit, which detects the level of the output signal 602 of the detection rectification circuit 503 and the output signal 60 of the peak hold circuit 504.
Compare with 3 levels. The output signal of the comparison circuit 505 is the sixth
As shown in FIG. 7D, when the level of the output signal of the peak hold circuit 504 is higher than the output signal level of the detection rectification circuit 503, a high level signal is output. The switch circuit 506 takes out the signal (6-d) when the gate signal (6-a) is at the high level, and is connected to the ground side during the low level period. A timing signal (6-d) for creating a reference value described later is taken out to the terminal 507.

In FIG. 4, the time difference signal 110 is input from the terminal 404. 408 and 409 are latch circuits. Time difference signal 110
Are latched at timings of the timing signals output from the maximum value detection circuits 406 and 407 and the rising edges of 412 and 413. Timing signals 412 and 413 are signals (6-d) shown in FIG. 410 is an arithmetic circuit,
Calculation is performed only when the gate signal (6-a) is high,
The calculation result is held during the low period. Regarding the content of the calculation, the addition average value of the output signal values of the latch circuits 408 and 409 is calculated in consideration of the polarity of the polarity signal 111 supplied from the terminal 405, and the reference value signal 114 is output. The track deviation calculating circuit 112 shown in FIG. 1 calculates the sum or difference value of the reference value 114 and the time difference signal 110 at each time, and outputs it as a tracking error signal.

EFFECTS OF THE INVENTION As is clear from the above description, according to the present invention, since the average value of each time difference signal when each head outputs the maximum value is used as the reference value, the pair heads in the time axis direction In addition to eliminating the effect of mounting error, even in a pair head that has a mounting error in the width direction, it is possible to distribute the degradation of the reproduction output signal due to the mounting error evenly to each head, which results in a decrease in S / N. There is an advantage that the influence of image quality deterioration can be made uniform. Further, in recording / reproducing a digital signal, there is an effect that a large allowable value of the track deviation until the image quality suddenly deteriorates can be taken with respect to the track deviation due to other factors such as track bending.

[Brief description of drawings]

FIG. 1 is a block diagram showing a tracking error signal generation circuit in an embodiment of the present invention, FIG. 2 is a detailed block diagram of the time difference detection circuit, and FIG. 3 is a waveform diagram showing waveforms of respective parts of FIG. 4, FIG. 4 is a detailed block diagram of the reference value generation circuit, FIG. 5 is a detailed block diagram of the maximum value detection circuit shown in FIG. 4, FIG. 6 is a waveform diagram of each part of FIG. 5, and FIG. FIG. 8 is a pattern diagram showing a relative positional relationship between a reproducing head and a recording track when the present invention is applied, and FIGS. 8 and 9 show a reproducing head and a recording track when a reference value by a conventional method is used. Pattern diagram showing the relative positional relationship of
Fig. 10 is a pattern diagram showing the relative positional relationship between the head and recording track that are mounted for practical use, Fig. 11 is a schematic diagram showing a practical head mounting state, and Fig. 12 is an irregular FIG. 13 is a pattern diagram showing the relative positional relationship between the mounted head and the recording track. FIG. 13 is a characteristic diagram showing changes in the tracking error signal when the head in an abnormal mounted state is used. FIG. 15 is a pattern diagram showing the relative positional relationship between the head and the recording track, FIG. 15 is a characteristic diagram showing changes in the tracking error signal in the normal mounting state, and FIG. 16 is a pattern diagram showing the relationship between the magnetization locus and the pair head. Is. 101, 102 ... Recording / playback head, 103, 104 ... Playback amplifier, 204 ... Reset / set flip-flop circuit, 2
11 ... D flip-flop circuit, 701, 702 ... Playback head having mounting error in track width direction, 1101, 11
02 …… Mounting member, 1001, 1002 …… Recording position of specific signal, 1501 …… Regular tracking error signal, 1301 ……
Illegal tracking error signal, 1603, 1604 ... Pair head

Claims (1)

[Claims] 1. A means for obtaining a reproduction time difference of a specific signal included in each reproduction signal reproduced by at least two magnetic heads having different azimuth angles, and a reference value generating means for generating a reference value for tracking control. From the calculation means for calculating the difference between the reproduction time difference and the reference value or the sum value, the displacement means for changing the mechanical height position of the magnetic head, and the means for detecting the maximum value of the reproduction signal. The reference value creating means has the reproduction time difference at the time when the maximum value of the reproduction signal reproduced from one magnetic head is detected and the time at which the maximum value of the reproduction signal reproduced from the other magnetic head is detected. A tracking error signal generating circuit for calculating an average value with the reproduction time difference and outputting the average value as a reference value of the tracking error signal.