JPH0677290B2 - 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. Is.

2. Description of the Related Art In a recording / reproducing crisis, for example, in a magnetic recording / reproducing device (hereinafter simply referred to as a VTR) such as a video tape recorder, when reproducing an information signal recorded on a recording track, a reproducing head is arranged on the recording track. Tracking control for on-track and reproduction scanning is required.

As a method of obtaining a tracking error signal over the recording track and the entire area, a pilot signal for tracking control is recorded on the recording track, and at the time of reproduction, reproduction of each pilot signal reproduced from both adjoining tracks of the main track for reproduction scanning by the head. There is a method of comparing the levels to obtain a tracking error signal. According to this method, since a tracking error signal can be obtained over the entire area of the recording track, the reproducing head is mounted on an electro-mechanical conversion element including a piezoelectric element and the mechanical position of the head is determined by using the tracking error signal. If changed, it is possible to construct a control system capable of following the track bend. However, in this method, since it is necessary to superimpose and record the pilot signal on the information signal, the band of the information signal is deleted by the band of the pilot signal.
There is a drawback that S / N deteriorates.

In order to solve these drawbacks, there has been proposed a method of obtaining a tracking error signal over the entire recording track without using a pilot signal. This method is disclosed in
It is shown in the public relations No. 55-150129, and uses the relationship between the track deviation in azimuth recording and the reproduction time difference of the reproduction signal. Since the present invention relates to this method, the basic idea of this method will be described below.

FIG. 15 shows the magnetization loci recorded by two heads having different azimuth angles. In the figure, reference numeral 1501 denotes a magnetic tape, which is transported in the direction of arrow 1502. Reference numerals 1503 and 1540 are heads having mutually different azimuth angles, and simultaneously scan in the arrow 1505 direction. Such a head, that is, a head that simultaneously scans and has different azimuth angles,
Hereafter, it will be called a pair head. Reference numerals 1506 and 1507 indicate head gaps in each head. A ₁ , A ₂ ......
Is the magnetization locus recorded by the head having the same azimuth angle as the A head shown by 1503, and B ₁ , B ₂ ... was recorded by the head having the same azimuth angle as the B head shown by 1504. It is a magnetization locus. The track pair of A ₁ , B _{1 and} the track pair of A ₂ , B ₂ may be recorded by the same pair head, and
It may be recorded by other pair heads. 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. Signals recorded on each magnetization locus, for example, a magnetization pattern such as a horizontal synchronization signal is 1508 and 1509.
As indicated by, the recording is performed with an angle inclined with respect to the longitudinal direction of the track, that is, an azimuth angle.

The method of recording / reproducing the information signal using the pair head is effective when the information signal to be handled and the frequency band are 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, if the pair head is used, the information signal and the frequency band can be divided and distributed to each head, so that the recording wavelength can be set substantially longer.

FIG. 13 shows three types of positional relationships between the recording magnetization locus and the reproducing scanning head. In the figure, 1301, 130 indicated by broken lines
2, 1303 are pair heads, each of which is composed of A and B heads. Each pair head scans in the direction of arrow 1304. A ₁ , B
₁ is the magnetization locus recorded by the pair head, from 1305 to 1
The signal indicated by 310 indicates the horizontal synchronizing signal and the recording position. The position of the pair head with respect to the recording magnetization locus is shifted to the left on the paper surface in FIG. 13a, and on-track in FIG. 13b.
13c is shifted to the right. 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, in FIG. 13a, the horizontal sync signal 1305
Is reproduced by the head A later than the time when the horizontal synchronizing signal 1306 is reproduced by the head B. In FIG. 13b, the reproduction times of both horizontal synchronizing signals are equal, and in FIG. 13c, the time when the horizontal synchronizing signal 1309 is reproduced by the head A is longer than the time when the horizontal synchronizing signal 1301 is reproduced by the head B. Will be faster. 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. 14 is a diagram showing the relationship between the track deviation and the reproduction time difference of each horizontal synchronization 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 synchronizing signals reproduced by the A and B heads, and the on-track position is when the time difference is zero. Further, when the time of the horizontal synchronizing 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 reproduction signals is 1401. As is clear from FIG. 14, if the tracking control circuit is configured such 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 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. 11 is a diagram showing a relationship between a recording magnetization locus and a reproducing head when a pair of heads having a different mounting position is used to reproduce a magnetization locus recorded on the magnetization locus. Reference numerals 1101 and 1102 denote A and B heads, and 1103 and 1104 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 1105.
And 1106 corresponds to the difference in distance. That is, there is a time difference between the reproduced signals even during on-track.

FIG. 12 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, 1401 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 1201 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 1202.

The mounting accuracy of the A and B heads is determined by the mechanical accuracy when assembling the heads, 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 1105 shown in FIG.
Since the distance relationship with 1106 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 JP-A-62-77751. This method is a method of detecting the maximum value of the reproduction signal when the head 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 also effective when the reproducing head width is the same as the recording track width, but has a problem when the reproducing head width is wider than the recording track. This problem will be described next.

FIG. 7 is a diagram showing the relative positional relationship between the recording track and the wide head. In the figure, A ₁ and B ₁ indicate recording tracks, and 701 and 702 indicate specific signals and recording positions. 70
3,704 is a wide reproducing head. Such a head arrangement can be realized by the configuration shown in FIG. In FIG. 8, 703 and 704 are wide heads. The head 703 is fixed to the rotating member 802 via the mounting member 801,
704 is directly fixed to the rotating member 802. Rotating member 802
Rotates in the direction of arrow 803. The distance 804 in the height direction of each head is set broadly to the width of one track shown in FIG. 7, and the distance 705 in the longitudinal direction between the heads shown in FIG.
Corresponds to the distance indicated by the same number in FIG. If the distance 705 between the heads is set equal to the distance 706 between the recording positions of the specific signal, the reproduction time difference of the specific signal becomes zero when the head on-tracks and scans the recording track. However, when using such a wide head, the problem of mounting error similarly occurs.

FIG. 9 shows a scanning locus when each head having a different head width crosses a recording track of the same width, and FIG. 10 shows a level change of a reproduction output signal obtained from each head at this time. In FIG. 9, reference numeral 901 denotes a recording track, and 9
A scanning locus of a head having a head width of 03 is indicated by 902, and a scanning locus of a head having a head width of 905 is indicated by 904. The reproduction signal obtained when such head scanning is performed is
A signal corresponding to the hatched area shown in the figure is obtained, and the reproduction level of the signal is obtained according to the length of the hatching line. That is, in FIG. 9A, the maximum output level can be obtained at 906. FIG. 9b
Then, the maximum output signal can be obtained from 907 to 908.

FIG. 10 is a diagram showing the level change of the reproduction signal obtained at the time of each head scan, in which the horizontal axis represents time and the vertical axis represents the level of the reproduction output signal. The scan shown in FIG.
Corresponding to Figure a, the scan shown in Figure 9b corresponds to Figure 10b. In FIG. 10a, the maximum value of the reproduction output signal is only one point indicated by 1001, but in FIG. 10b, the maximum value of the output signal is always indicated in the time region indicated by 1002. Therefore, there is a problem that the conventional method that uses the reproduction time difference of the specific signal at the time when the maximum value of the reproduction signal is detected as the reference value cannot accurately detect the on-track position when the wide head is used. .

The present invention provides a tracking error signal generation circuit that can accurately detect the head and on-track positions even when a wide head is used, and can obtain a tracking error signal without the influence of a head mounting error. With the goal.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a means for obtaining a specific and signal reproduction time difference contained in each reproduction signal, which is reproduced by at least two heads having different azimuth angles, and reproduction. Comparing means for comparing the output voltage of the signal with the reference voltage, first and second storing means for storing the reproduction time difference at the rising and falling timings of the output signal of the comparing means, and each of these storing means. A reference value creating means for calculating an average value of the stored values, and means for using a value of a difference between an output value of the reference value creating means and a reproduction time difference as a tracking error signal. There is.

Operation According to the present invention, since the reference value of the on-track state is set to the optimum state by the reference value creating means even when the wide head is used, the recording position of the specific signal on the recording track is adjusted. Even if there is a deviation or variation in the mounting position of the reproducing head, the reproducing head can always perform on-track on the recording track for reproduction scanning.

Embodiment FIG. 1 is a block diagram showing an embodiment of the present invention. The time difference detection circuit 109 and the reference value generation circuit 11 shown in FIG.
2, and details of the latch pulse generation circuit 114 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
Output from 106. Also, from the reproduction signal processing circuit 105,
A specific signal reproduced from each head, that is, each horizontal synchronizing signal 107 and 108 is output. The circuit 109 is a time difference detection circuit that detects a reproduction time difference between these horizontal synchronization signals. The signal 110 corresponding to this time difference is supplied to the track deviation calculation circuit 111 and the reference value creation circuit 112. The time difference detection circuit 109 outputs a time difference signal and also outputs a polarity determination signal 113 for determining which horizontal synchronization signal is reproduced earlier among the respective horizontal synchronization signals reproduced from the A and B heads. To do. The circuit 114 is a latch pulse generation circuit, and as will be described later, a pulse signal having a rising edge and a falling edge at the time when the head causes a track deviation symmetrically from the position where the head is on-track and scans the recording track. Outputs 115. Reference value creation circuit 112
Is a circuit that calculates the average value of the time difference signal at the timing of the rising edge of the signal 115 and the time difference signal at the timing of the falling edge and timing, and outputs the reference value when creating the tracking error signal. The track deviation calculation circuit 111 calculates a difference and a signal between the time difference signal 110 supplied from the time difference detection circuit 109 and the reference value supplied from the reference value generation circuit 112, and outputs a tracking error signal.
Outputs 116. The tracking error signal 116 is supplied to the capstan motor control loan 117, and the addition circuit 1
It is supplied to the piezoelectric element drive circuit 119 via 18. In the capstan motor control circuit 117, the tracking error signal 1
Use 16 to control the tape feed phase. The piezoelectric element drive circuit 119 is used to detect the head 10 by using the tracking error signal 116.
1 and 102 are displaced to perform track curve follow-up control.
The circuit 120 is a system control circuit and outputs various mode command signals according to the key input signal 121. The system control circuit 120 is supplied with not only a key input signal but also a PG signal indicating the rotational position of the rotary head from the terminal 122. The gate signal 123 output from the system control circuit 120 is a signal which becomes a high level only in one scanning period during which one head reproduces and scans one recording track in the reproduction mode. Only during the high level period of the gate signal 123, the latch pulse generation circuit 114 operates and the switch 124 is closed. The circuit 125 is a preset waveform creating circuit. This preset waveform creation circuit
Reference numeral 125 is a circuit for creating a sawtooth wave signal for driving the piezoelectric element so that the reproducing 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. The circuit 203 is a delay circuit, which is triggered by the rising edge of the signal (3-a) and outputs a high-level pulse signal (3-b) only during the period 301 shown in FIG. The circuit 204 is a reset-set flip-flop (RS-FF) circuit, and the signal (3
-C) is set at the rising edge, and the signal (3-
It is reset at the falling edge of b). R / S-FF
The output signal (3-d) of the circuit 204 and the output signal (3-b) of the delay circuit 203 are input to the exclusive OR (EX-OR) circuit 205 to obtain the signal (3-e). Since the high level period 302 of the signal (3-e) indicates the time between the horizontal synchronizing signals, if the mounting state of the A and B heads is normal, this time indicates a track shift. It will be. circuit
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. The circuit 208 is a latch circuit, and latches the count value of the counter circuit 206 at the signal (3-e) and the falling edge. 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
A value corresponding to the time indicated by 03 is stored.

The signal (3-a) is delayed by the delay circuit 209, and (3
-Obtain the output signal shown in i). The circuit 211 is a D flip-flop (D-FF) circuit and latches the input level of the signal (3-e) at the rising edge of the signal (3-i). Therefore, the horizontal sync signal (3-
If the horizontal synchronizing signal reproduced by the B head is delayed with respect to a) as shown in (3-c), the D-FF circuit 211
The output signal of 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 2 of the D-FF circuit 211 is
13 is B for the horizontal synchronizing signal reproduced from the A head.
Is the horizontal sync signal reproduced from the head delayed?
It is a signal indicating whether or not it is advancing, that is, a signal indicating the polarity of the tracking error signal (whether it is deviated to the right or left from the on-track position).

FIG. 4 is a detailed block diagram of the latch pulse generation circuit 114 shown in FIG. 1, and FIG. 5 shows waveforms at various parts in FIG. In both figures, the same symbols indicate the same things.

In FIG. 4, a reproduction signal (5-b) is input from the terminal 401. The reproduced signal (5-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. For 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 501 in the normal reproduction mode. Alternatively, if the tape is in a stopped state, the head performs reproduction scanning for a period indicated by 501. Playback signal (5-
The signal b) is detected and rectified by the detection and rectification circuit 402 and becomes a signal indicated by a solid line 502 in FIG. The circuit 403 is a voltage comparison circuit, which compares the voltage level of the signal (5-c) with the voltage level of the reference voltage generator 404, and outputs (5-
The latch pulse signal 504 shown in d) is output. 5 in FIG.
The level indicated by 03 is the reference potential.

When the head is on-track on the recording track, that is, the time when the center line in the width direction of the head and the center line in the width direction of the recording track coincide with each other is half the position where the maximum output level is obtained. It is the time indicated by t ₀ . If the head shifts from the on-track position, the reproduction output signal decreases. This degree of decrease is symmetrical with respect to the left and right track shifts. Therefore, the track deviation amounts at the time points t ₁ and t _{2 at} the intersection of the level of the reproduction output signal 502 and the reference voltage 503 are equal and the directions are different. Therefore, if the average value of the track deviation amount at the time t ₁ (the rising edge of the latch pulse 504) and the track deviation amount at the time t ₂ (the falling edge of the latch pulse 504) is calculated, this value is the track deviation at the time t ₀ . Amount. For example, the amount of track deviation at t ₀ , t ₁ , t ₂ is 0 μm, −5
When μm and +5 μm, the track deviation amount at t ₁ and t ₂ and the average value, that is, 0 μm is the track deviation amount at t ₀ . Now, due to variations in mounting accuracy of the head, the tracking deviation amount at t ₀ is -3 μm.
, The track deviation amount at t ₁ and t ₂ is
It means -8 μm and +2 μm. At this time, t ₁ and
-3 μm from the arithmetic mean value of the track deviations at t ₂ and
It can be known that is the amount of track deviation at t ₀ . From the above, if the arithmetic mean value of each tracking error signal at the rising and falling edges of the latch pulse 504 is calculated, the value of the tracking error signal at the time when the head is on-track on the recording track, that is, the mounting of the head You can know the variation in accuracy.

In FIG. 4, a circuit 405 is a switch circuit, and a terminal 409
The switch is switched according to the level of the gate signal supplied from. Terminal 40 when the gate signal is high level
When the switch is connected to the 6 side and it is at low level, terminal 4
A switch is connected to the 07 side. Therefore, the latch pulse (5-d) is output to the terminal 408.

FIG. 6 is a detailed block diagram of the reference value generating circuit 112 shown in FIG. In the figure, the tracking error signal 110 corresponding to the reproduction time difference of the specific signal is input from the terminal 601. Reference numerals 602 and 603 denote latch circuits, which latch the value of the error signal 110 by the rising and falling pulses of the latch pulse (5-d) input from the terminal 605. Each latched value is supplied to the arithmetic circuit 608. Arithmetic circuit 6
08 is the timing of the falling pulse of the gate signal (5-a) input from the terminal 607, and calculates the arithmetic mean value of the values supplied from the latch circuits 602 and 603, and calculates the terminal 609.
Is output to. When calculating the arithmetic mean value,
The sign of the value is determined in consideration of the polarity signal supplied from the terminal 606. The signal output to the terminal 609 is a reference value in consideration of variations in head mounting accuracy, and this reference value is supplied to the track deviation calculation circuit 111 shown in FIG.

EFFECTS OF THE INVENTION As is apparent from the above description, according to the present invention, even when a head having a width wider than the width of a recording track is used, a specific signal at a position where the head is on-track on the recording track is used. Since it is possible to know the difference in playback time, the difference in playback time of the specific signal that is played back at that time can be used to calculate the reference value for calculating the tracking error signal, and tracking deviation due to mounting error of the pair head can be prevented. Has the effect that can.

[Brief description of drawings]

FIG. 1 is a block diagram showing a tracking error signal generating circuit according to an embodiment of the present invention, and FIG. 2 is a detailed block diagram of a time difference detecting circuit and a reference value generating circuit according to the present invention.
FIG. 4 is a waveform diagram showing the waveform of each part of FIG. 2, FIG. 4 is a detailed block diagram of a latch pulse generating circuit according to the present invention, and FIG.
FIG. 6 is a waveform diagram showing waveforms of respective portions in FIG. 4, FIG. 6 is a detailed block diagram of a reference value generating circuit according to the present invention, and FIG. 7 is a relative positional relationship between a width ratio furnace head and recording tracks. FIG. 8 is a plan view showing the mounting state of the width-ratio furnace head, FIG. 9 is a schematic view showing the relative positional relationship between the scanning track and the recording track of heads having different head widths,
FIG. 10 is a characteristic diagram showing a change in reproduction output signal obtained when the head scanning shown in FIG. 9 is performed, and FIG. 11 is a magnetization locus recorded by using a head in an irregularly mounted state and other irregularities. Diagram of relative positional relationship with head in various mounted states, No. 12
The figure shows the change in tracking error signal when the head is mounted in an irregular state, Fig. 13 is the relative position relationship between the recording magnetization locus and the reproducing head, and Fig. 14 is the tracking error in the regular mounting state. FIG. 15 is a signal change diagram, and FIG. 15 is a diagram showing the relationship between the magnetization locus and the pair head. 101,102 …… Recording / playback head, 103,104 …… Playback amplifier,
204 ... Reset-set flip-flop circuit, 211 ...
... D flip-flop circuit, 503 ... reference voltage, 703,704
...... Head, 801,802 …… Mounting member, 1103,1104 ……
Recording position of specific signal, 1401 …… Regular tracking error signal, 1201 …… Unusual tracking error signal, 15
03 …… 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 heads having different azimuth angles, and means for crossing the reproduction head in a width direction of a recording track. Comparing means for comparing the output voltage of the reproduced signal obtained at a time with the reference voltage, and first and second storing means for storing the reproduction time difference at the rising and falling timings of the output signal of the comparing means,
A reference value creating means for calculating an average value of the respective values stored in the respective storage means, and a value of a difference between the output value of the reference value creating means and the reproduction time difference is used as a tracking error signal. A circuit for creating a tracking error signal, characterized by: