JPH0143381B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a reproducing device for reproducing signals sequentially recorded as concentric recording tracks on a rotatably driven disc-shaped recording medium using a reproducing pickup means. The relative position of the re-correcting pickup means and the recording medium is automatically regulated at a position where an optimal reproduction signal can be obtained from the recorded track to be reproduced.

Structure of a conventional example and its problems FIG. 1 shows a partial structure of a reproducing apparatus using a magnetic sheet (hereinafter referred to as "sheet") as a recording medium.

First, second, third, . . . recording tracks 3, 4, 5 are provided concentrically on a sheet 2 which is rotated by a sheet motor 1 in a CW (clockwise) direction. Reference numeral 6 denotes a playback head for reading out information (for example, a video signal) recorded on this recording track.

When the reproducing head 6 is moved in the radial direction, the head output becomes maximum when the head 6 is located at the center of each track 3, 4, 5 as shown in FIG.

Therefore, when reproducing the first track 3, for example, the head 6 is moved radially in the vicinity as shown by the arrow.
The best reproduction can be achieved by vibrating the head 6 and fixing the head 6 at a position where its output is maximum. Conventionally, the best detection and control method at this time is to set the head so that the value of the output of the head 6 at a certain rotation angle of the sheet 2, or the integral value of the output of the head 6 during one rotation period, is maximized. Generally, a method is used in which the position is finely adjusted and then fixed.

For example, if the magnetic particles on the sheet are arranged in parallel (hereinafter referred to as orientation) as shown in FIG. , at the center position and slightly toward the outer periphery,
At that time, the head outputs are as shown in FIG. 4a, b, and c, respectively. Therefore, in this case, the above-mentioned head output is best detected by both the former method (assuming that the output is detected at a minute time ΔT after the time T of one rotation period shown in the figure) and the latter method. Fourth
The output waveform shown in Fig. b was determined to be the best, and this b was considered to be the best.

In addition, if the recording pattern of the first track 3 is eccentric as shown in FIG.
When the head is positioned slightly towards the inner circumference, approximately at the center position, and slightly towards the outer circumference with respect to the track 3, the head output at that time is as shown in Fig. 6a, respectively.
It will look like b and c. Therefore, in this case, to determine whether the above-mentioned head output is the best, the waveform a is detected as the best in the former case, and the waveform a or c is detected as the best in the latter case. However, in general, the head output is the minimum envelope amplitude B relative to the maximum envelope amplitude A, as shown in b, that is, B/A.
It is said that the closer the value of is to 1 and the larger the head output, the better. Therefore, in this case, the waveform of b must be detected as the best. Therefore, neither the former nor the latter detection can be said to be correct.

Purpose of the invention In the present invention, the value of B/A is closer to 1 than the above-mentioned value,
Another object of the present invention is to provide a reproducing apparatus configured to determine that the head output is best at a position where the head output is closer to the maximum, and to set the head position at that position.

Structure of the Invention In the present invention, the minimum envelope amplitude B of the head output is detected every one rotation of the sheet while the head position is slightly moved in the width direction of the track, and the reproduction head position where the value is maximum is determined. The configuration is such that the head position is set based on this to obtain the best playback conditions.

DESCRIPTION OF EMBODIMENTS FIG. 7 shows a configuration diagram of an image reproducing apparatus according to an embodiment of the present invention.

In the figure, a sheet 2 rotated by a sheet motor in the CW direction (clockwise direction, counterclockwise direction is CCW) has first, second, third... recording tracks (hereinafter referred to as tracks) 3. , 4, 5... are provided concentrically. Reference numeral 6 denotes a reproducing head for reading out the image signal recorded on this track, which converts the rotational movement of the stepping motor 7 into linear movement by means of first and second gears 8 and 9, and converts the rotational movement of the stepping motor 7 into linear movement. It moves in a straight line with respect to the circumferential direction. 10 is a stepping motor drive circuit;
Microprocessor 1 that controls the entire device, etc.
In response to the CW direction rotation command pulse (hereinafter referred to as CW pulse) 12 and CCW pulse 13 from 1, the stepping motor 7 is rotated in the CW and CCW directions, and the reproducing head 6 is rotated in the outer circumferential direction and the direction relative to the sheet 2. Move it toward the inner circumference. 14 is a seat motor drive circuit for rotating the seat 2 at a constant speed.

A reproduced signal 16 from the reproduction head 6 obtained by amplification by the first amplifier circuit 15 is converted into a video signal by a demodulation circuit 17 and a second amplifier circuit 18, and is output to an output terminal 19. An envelope signal 21 obtained by envelope detection of the reproduced signal 16 by a detection circuit 20 is input to a minimum value hold circuit 23 after passing through a first voltage buffer circuit 22 . The first hold output 2 of this minimum value hold circuit 23
4 picks up the leakage magnetic flux of the rotational position detection magnet 25 that rotates together with the seat 2 with a magnetic field detection element 26, and transmits the output to a rotational position detection signal amplification circuit 27, a shaping circuit 28, and a first monostable multivibrator (hereinafter referred to as MM) 29 converts it into a first rotational pulse signal 30 with a duty of approximately 50:50, and a second M.M31 that operates on the rising edge of this first rotational pulse signal 30 generates a second signal. The third M.M3 operates on the falling edge of the rotation pulse signal 32.
In response to the third rotation pulse signal 34 of 3, the reset circuit 35 sets a positive potential (Vcc) with respect to the GND potential.
will be reset to Therefore, the first rotation pulse signal 34 just before the rising edge of the third rotation pulse signal 34 occurs.
The hold output 24 holds the minimum value of the envelope signal 21 of the reproduced signal 16 from the falling edge of the third rotation pulse signal 34 generated approximately one revolution before the sheet. Here, since the pulse widths of the second and third rotation pulse signals 32 and 34 are set to be sufficiently short for one rotation period of the sheet 2, the minimum value hold circuit 23 can hold approximately one rotation period of the sheet 2. Rotating envelope signal 21
This means that the minimum value of is detected every rotation.

This first hold output 24 passes through a second voltage buffer 36 and is input to first and second sample and hold circuits (hereinafter referred to as S&H) 37 and 38. The first and second S&Hs 37 and 38 each receive a second rotation pulse signal 32 as a latch command pulse from the microprocessor 11 that is output for one cycle in synchronization with the rising edge of the first rotation pulse signal 30. The first latch output 41 latched by the first latch circuit 40, which uses the falling edge of the first rotation pulse signal 30 as the clock input, is used as the clock input, and the third rotation pulse signal 34 is output. is latched by a second latch circuit 42 which has a reset input, and its second latch output 4
3 as a gate control signal.
The rotation pulse signal 32 of the second latch output 43 is gated, and the gate output 45 is controlled by the switching circuit 47 according to the output logic level of a bistable multivibrator (hereinafter referred to as FF) 46 which operates at the falling edge of the second latch output 43. The output of the second voltage buffer 36 is held in accordance with the switched first and second sample pulses 48 and 49. The second of this first S&H37
The hold output 50 of is input to the + input terminal of the comparator 51, the third hold output 52 of the second S&H 38 is input to the - input terminal, and the comparator output 53 and the output of F.F46 are input to the exclusive OR circuit. 54, its output is latched by a third latch circuit 55 that operates on the falling edge of the first rotation pulse signal 30, and its third latch output 56
is input to the microprocessor. Therefore, this third latch output 56 is the latch command pulse 39
If the output value of the second voltage buffer 36 at the output timing of the second rotation pulse signal 32 is increasing every time the second rotation pulse signal 32 is output, the "H" level is set.
In the opposite case, it continues to maintain the "L" level. Although not shown, the F.F 46 is initially set to such a logic level.

FIG. 8 shows a time chart of various signals when determining the optimum positional relationship between the reproduction head 6 and the track (first track 3 in FIG. 7) in order to obtain the best reproduction signal 16. Here at time t ₀
It is assumed that the output of F.F46 is set to "H". It is also assumed that the third hold output 52 has a sufficiently larger value than the second hold output 50 and that the playback head 6 is located near the first track 3.

In order to obtain the above relationship, a latch command pulse 39 is output for a period from time t ₁ to t ₃ , and the gate circuit 44 is closed for a period from time t ₂ to t ₄ by the second latch output 43 obtained from this. Since the output of the F.F 46 at this time is "H", the switching circuit 47 has been switched to the a side, so that the first sample pulse is generated for a period from time _t3 to time _t4 . Therefore, the reproduced signal 16 during the period from time t ₁ to t ₃ (corresponding to one rotation period of the sheet 2)
The level of the lowest part of the envelope signal 21 (hereinafter referred to as the minimum value) is held in the first S&H 37. Next, when the CCW pulse 13 is output in synchronization with the fall of the first rotation pulse signal 30,
The position of the reproducing head 6 is slightly moved toward the inner circumference. Here, when the latch command pulse 39 is output at time t ₆ , the gate circuit 44 is closed for a period from time t ₇ to t ₉ , and the output of F.F 46 at this time is "L" and the switching circuit 47 is switched to the b side. Since the second sample pulse 49 is generated from time _t8 to time _t9 .
Therefore, from time t ₆ after the position of head 6 has moved,
The minimum value of the envelope signal 21 during the period _t8 is the second
It is held in S&H38.

With the above operation, the minimum values of the envelope signal 21 before and after moving the position of the head 6 are held in the first and second S&Hs 31 and 38, respectively, so that the third latch latched at time _t10 Since the output 56 becomes "H", it is found that the position of the reproducing head 6 is near the center of the first track 3 and has moved from the outer circumferential side toward the center. If the third latch output 56 is "L" at this time, it means that the position of the reproducing head 6 has moved from the center of the first track 3 to the inner circumference.
The position of the playback head 6 is moved in the outer circumferential direction, and the position of the playback head 6 where the minimum value of the envelope signal 21 is the largest is determined in the same way as in the method described later.

As mentioned above, it has been found that the position of the reproducing head 6 has moved from the outer circumferential side of the first track 3 toward the center thereof, so the CCW pulse 13 is outputted at each of times t ₁₀ and t ₁₃ to further move the reproducing head 6. 6 in the inner circumferential direction, and the envelope signal 21 is
Comparing the minimum values of , it can be seen that the minimum value is always increasing since the third latch output 56 always maintains "H". However, when the CCW pulse 13 is output at time _t16 , the third latch output 56 changes to "L" at time _t19 , so it becomes clear that the minimum value of the envelope signal 21 has changed in the direction of decrease rather than the direction of increase. .

Although it is not necessary to carry out the same procedure, if the CCW pulse 13 is output even after time _t19 , the third latch output 56 continues to maintain "L".

Therefore, the reproduced signal from time t ₁₄ to t ₁₅ is
It was found that the performance was better than that from t ₁₁ to t ₁₂ or from time t ₁₇ to t ₁₈ , so one pulse was applied from the playback head 6 position at time t ₁₇ , and two pulses from time t ₂₀ . By outputting the CW pulse 13 to return the position of the playback head 6 to the state at time _t14 , the positional relationship between the playback head 6 and the first track 3 can be optimally set, so that the best playback signal 16 can be obtained.
is obtained.

In this first embodiment, a stepping motor 7 is used to move the position of the playback head 6 in steps to detect the optimum position, but a general motor is used to control the number of rotations. At the same time, the playback head 6 may be moved to find the optimum position.

Effects of the Invention As described above, in the image reproducing apparatus according to the present invention, the minimum value of the envelope of the reproduced signal during one rotation period of the recording medium is compared in magnitude while the pickup means for obtaining the reproduced signal is moved in the width direction of the track.
Since the configuration is such that both are set in the positional relationship between the playback pickup and the track where the value is the largest, a playback signal whose output is close to the maximum and whose minimum/maximum envelope values are close to 1 can be obtained. Good quality playback output can be obtained.

[Brief explanation of drawings]

Figure 1 is a plan view showing an overview of a reproducing device using a magnetic sheet, Figure 2 is a view showing changes in head output with respect to head position, and Figure 3 is a plan view schematically showing the orientation of the magnetic sheet. , FIG. 4 is a diagram showing the head output with respect to the head position when it is affected by orientation, FIG. 5 is a plan view when the recording track is eccentric, and FIG.
This figure shows the relationship between the head position and the head output in the case of FIG. 5, FIG. 7 is a block diagram of an image reproducing apparatus according to an embodiment of the present invention, and FIG. 8 is a signal waveform diagram of each part thereof. DESCRIPTION OF SYMBOLS 1... Seat motor, 2... Seat, 3... First track, 6... Reproduction head, 7... Stepping motor, 8... First gear, 9... Second gear, 10... ...Stepping motor drive circuit, 1
1... Microprocessor, 12... CW pulse, 13... CCW pulse, 14... Seat motor drive circuit, 15... First amplifier circuit, 16...
Reproduction signal, 17... Demodulation circuit, 18... Second amplifier circuit, 20... Detection circuit, 21... Envelope signal, 22... First voltage buffer, 23...
Minimum value hold circuit, 24... first hold output, 25... rotational position detection magnet, 26... magnetic field detection element, 27... rotational position detection signal amplification circuit,
28... Shaping circuit, 29... First MM, 30
...First rotation pulse signal, 31...Second M.
M, 32... second rotation pulse signal, 33... third MM, 34... third rotation pulse signal, 3
5...Reset circuit, 36...Second voltage buffer, 37...First S&H, 38...Second S&H
H, 39... Latch command pulse, 40... First latch circuit, 41... First latch output, 42...
...Second latch circuit, 43...Second latch output, 44...Gate circuit, 45...Gate output,
46...FF, 47...switching circuit, 48...first
sample pulse, 49... second sample pulse, 50... first hold output, 51... comparator, 52... second hold output, 53...
...Comparator output, 54...Exclusive OR circuit,
55...Third latch circuit, 56...Third latch output.

Claims (1)

[Claims] 1. When reproducing a concentric recording track recorded on a rotationally driven disc-shaped recording medium by a pickup means, the reproducing means is moved relatively in the width direction of the recording track to be reproduced. It is characterized by detecting a minimum value of an envelope for each rotation period of a reproduction signal from a recording track to be picked up, and stopping the relative movement of the pickup means at a position where the minimum value for each rotation period becomes maximum. playback device.