JPS61269272A - Rotary recording body reproducing device - Google Patents

Abstract

PURPOSE:To execute exactly tracking at a high speed and by moving, at first, linearly and quickly a reproducing head to the vicinity of its recording track when executing the tracking, and subsequently, stopping the reproducing head by feeding back and error signal corresponding to an actual position. CONSTITUTION:In case of an access mode, a reproducing head is transferred in the direction as indicated with an error Fi or Fo by feeding it at a prescribed speed first, and switched to a servo-feed immediately after it has passed through a track position center part Rn of a desired track or a recording track center position (rn). Subsequently, in case of the servo-feed, an error voltage (vn) related to its track is read out of a memory 80 and a tracking control signal SE is set to VBS-vn, and it is applied to head position signals Ea, Eb from a position detecting device 300. Accordingly, the reproducing head 12 is vibrated in the directions as indicated with the arrows Fi, Fo as a servo-feed control voltage Vd is converged and converged to the recording track center position (rn) and stopped at that position.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a playback device that performs tracking when playing back video signals, information signals, etc. recorded on a rotating recording medium such as a magnetic disk, and particularly relates to a playback device that performs tracking when playing back video signals, information signals, etc. recorded on a rotating recording medium such as a magnetic disk. The present invention relates to a playback device that can perform high-precision tracking.

(Prior Art) Recently, a still image of a subject formed through a lens is converted into a video signal by a solid-state image sensor, this is recorded on a magnetic disk, and the image is played back using a separate television system. Electronic still camera systems have been developed that allow users to print or print hard copies using printers.

This camera system uses a small magnetic disk 10 with a diameter of about 5 cm, and as shown in FIG. 16, concentric track positions Rn with a track width of 60 μm and a guard band width of 40 μm are formed on the disk recording surface 10a. A plurality of heads, for example, 6 o's, are set, and while the disk 10 is rotationally driven at a constant speed, for example, 3.60 rpm, the recording or reproducing head 12 shown by a dotted line is opposed to each track position Rn, and the head is rotated around the track position Rn. Record or play back one field's worth of signals.

However, if the disk is mounted eccentrically in the recording device or if the recording head is not positioned accurately, the trace where the signal was actually recorded, that is, the recording track rn, will deviate from the track position, and the disk 10 will be misaligned in the playback device. Again, when tracing the track position R with the reproducing head 12 while rotating at a constant speed of 3.80 rpm, the signal of the recording track rn may not be read well, or the adjacent recording track may be scanned, causing crosstalk. Sometimes.

Such tracking deviation during reproduction may be caused by the disc 10 being deformed after recording due to thermal expansion or the like, or by the disc 1o being mounted eccentrically in the reproducing apparatus.

Therefore, the playback 851 of this type of camera system includes:
A tracking servo is required for the reproducing head 12 to accurately scan the recording track rn.

Although various tracking servo systems have been proposed so far, so-called hill-climbing control is most commonly used. This is to detect the envelope of the signal read from each recording track rn during reproduction and control the position of the reproduction head 12 so that the envelope reaches its peak value.

Tracking by mountain climbing control will be explained with reference to FIG. In this figure, en conceptually represents the envelope of the signal read out when the reproduction head 12 moves in the direction across one recording track rn, that is, in the direction of arrows Fl and Fo in FIG. 15, and its peak value e
np is obtained at the center position (r'n) of recording track rn.

Now move the playback head 12 from position X1 to an appropriate distance d in the direction of arrow Fl! The envelope level E2 after the shift is compared with the envelope level El before the shift.

Then, El < E2, and it is determined that the peak value Ep is located further away in the direction of arrow F1.

Therefore, the reproducing head 12 is further moved by an appropriate distance d2 in the direction of the arrow F1. When the envelope level E3 after the movement is compared with the previous envelope level E2, E2 < E3, and it is determined that the peak value Ep is further away in the direction of the arrow FI. Therefore, the reproduction head 12 is further moved in the direction of the arrow F1 by an appropriate distance d3, and the envelope level E4 after the movement is compared with the previous envelope level E3. Then, this time E3>E4, it is determined that the peak value Ep has gone too far in the direction of the arrow Fl, and then the playback head 1
2 by an appropriate distance d4 in the direction of arrow Fo.

Envelope preview before and after movement iLt E 4
+E5, E4<E5, and it is determined that the peak value Ep is further away in the direction of arrow Fl, and the reproducing head 12 is moved by an appropriate distance d5 in the direction of arrow Fo. In this way, playback Rad1
2 is the recording track center position where the peak value enp is obtained (
When the envelope levels En-1 and En before and after the movement become En-1=En, the playback head 12 is near the recording track center position (rn), that is, at the on-track position. It is determined that there is
Then, the movement of the RAD 12 is stopped for regeneration.

A microcomputer is used as a control unit for performing such hill-climbing control, and a step motor is used as the head moving means. The control unit monitors the envelope level of the signal read by the playback head 12 one by one via an analog-to-digital (A/D) converter, and performs the required head movement based on the comparison judgment of the envelope level as described above. A number of command pulses corresponding to the amount are sequentially given to the step motor. The step motor rotates by one unit of rotation angle, for example, 1.5° per one command pulse,
As a result, the reproducing head 12 is moved in the direction of the arrow Fl or Fo by one unit of transport distance, for example 4.2 μm.

(Problems to be Solved by the Invention) As described above, in the conventional tracking servo using mountain climbing control, the playback head is moved in steps, the envelope level is detected each time, and the envelope level is compared with the envelope level before the movement. Based on the comparison result, the read head is gradually moved closer to the center position of the recording track by repeating an operation cycle in which the read head is moved in steps by an appropriate distance toward the center position of the recording track where the peak value is obtained. At this time, the reproducing head position is converged to the recording track center position while gradually decreasing the head movement amount.

However, if the reproducing head is moved stepwise many times in this way, high-speed access or tracking cannot be achieved. Even if the detection and comparison of envelope levels and the pulse rate of command pulses can be increased in the control section, the response speed of the entire tracking servo will not increase because there is a limit to the followability of the step motor.

Furthermore, the amount of movement of the reproducing head is determined by the number of command pulses given to the step motor by the control unit.
transmission elements from the step motor to the playback head support;
For example, if there is play or misalignment in gears or the like, backlash will occur and the actual head position will not reach the desired head position indicated by the command pulse, making it impossible to move the head accurately.

Further, the program required for the above-mentioned mountain climbing control is complex and enormous, and not only is programming itself troublesome, but it also imposes significant restrictions on the system control of the playback device.

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, an object of the present invention is to provide a rotating recording medium reproducing apparatus that can quickly access or track a desired recording track during reproduction.

Another object of the present invention is to provide a rotary recording medium reproducing apparatus that can perform accurate tracking using a relatively simple tracking servo mechanism.

(Means for Solving the Problems) The configuration of the present invention that achieves the above object is based on a reproducing head that reads signals from recording tracks respectively formed at a plurality of annular track positions provided at a predetermined pitch on a rotating recording body. and head transport means for transporting the playback head in a direction across the track position; coupled to a portion of the head transport means that supports the playback head, the head transport means is coupled to a portion of the head transport means that supports the playback head, and is coupled to a portion of the head transport means that moves the playback head across the track position to prevent an error with respect to the pitch when the playback head moves across the track position. head position detection means for generating a head position signal whose level changes so as to generate a signal and reaches a predetermined reference level when the reproducing head faces the center of the track position;
a head movement control means for controlling the head movement means to move the playback head within a predetermined vicinity range of a desired track position; and a head movement control means for controlling the head movement means to move the playback head within a predetermined vicinity range of a desired track position; head positioning means for moving the playback head according to the level of the head position signal and positioning the playback head so that the level of the head position signal converges to a predetermined value; and an envelope for detecting the envelope of the signal read by the playback head from the recording track. Detecting means; means for storing the level of an error signal when the envelope reaches a peak value for each recording track as an error level for the recording track; when tracking a desired recording track, reads the error level from the storage means and adds this to the level of the head position signal given from the head position detection means to the head positioning means, whereby the level of the head position signal converges to a point deviating from the reference level by the error level. and tracking control means for positioning the reproducing head so as to

In the present invention, the rotary recording medium refers to a disk- or drum-shaped rotatable recording medium on which video signals, information signals, etc. are recorded as physical patterns using a magnetic, optical, or capacitive recording method.

Furthermore, the reproducing head refers to an element that faces the rotating recording medium and reads out a physical recording pattern by such a recording method as an electrical or optical signal.

Furthermore, the plural annular track positions refer to the track positions where each recording track is to be formed on a locus such that the relative positions of the recording start and end coincide with each other. For example, in a magnetic disk, the rotation axis It means a track position where recording tracks are to be formed concentrically around the center, and also a track position where a large number of recording tracks are to be formed in parallel in the circumferential direction on a magnetic drum. Further, the recording track means a track where a signal is actually recorded along the track position, that is, a track where the above-mentioned physical recording pattern extends.

Furthermore, "within a predetermined neighborhood range" means a head movement range of a limited distance that includes the position when the playback head faces the center of the track position, and preferably overlaps with the neighborhood range of an adjacent track position. It is set so that it does not occur.

(Operation) Prior to tracking a desired recording track, or at a preliminary stage thereof, the error level regarding the recording track is detected. To do this, the playback head is moved across the track, which changes the level of the head position signal and at the same time changes the envelope of the signal read by the playback head from the recording track.When the envelope reaches its peak value, an error signal is detected. .

The level of is taken as the error level. The level of the head position signal, and therefore the level of the error signal, represents the relative position of the playback head with respect to the track pitch, and the reference level is reached where the playback head faces the center of the track position, so the error signal is at the corresponding track position. represents the deviation of the center position of the recording track from the center of the track.

In tracking or access, the head movement control means first operates to move the reproduction head to the vicinity of a desired recording track, and then the head positioning means operates to position the reproduction head according to the head position signal or error signal. When the tracking control means reads out the error level from the storage means and adds it to the level of the head position signal, the head positioning control means determines a position shifted from the reference position, that is, the center of the track position, by an amount corresponding to the error level. That is, the reproducing head is positioned at the center of the recording track. At this time, the playback head is transported back in the opposite direction after passing the center position of the desired recording track, and when it passes the center position in the opposite direction, it changes direction and is transported back toward the center position. . In this way, the reproducing head vibrates around the center position of the recording track, converges thereon, and then stops.

(Embodiment) An embodiment in which the present invention is applied to a playback device for an electronic still camera system will be described with reference to FIGS. 1 to 14.

All m- FIG. 1 shows the overall configuration of this embodiment.

The magnetic disk 10 has a recording surface 10a having the format shown in FIG. 15, and is detachably mounted on a spindle 16 that is rotationally driven by a DC motor 14. The DC motor 14 includes a frequency generator 18 for generating an AC frequency signal, and is controlled by a servo circuit 20 to a constant speed, e.g.
The drive is controlled to rotate at rpm. Servo circuit 2
0 controls rotational driving and stopping of the disk 10 in response to a control signal SWI from the control device 22.

A phase generator 24 disposed at a predetermined position near the recording surface 10a of the disk 10 picks up leakage magnetic flux coming from a small yoke (not shown) provided at a corresponding predetermined position of the disk core 10b, and generates the leakage flux of the disk 10. A PG pulse φ representing the rotational phase is generated.

This PG pulse φ is passed through the amplifier 26 to the servo circuit 20.
The signal is supplied to the control gfj device 22, and is used in the servo circuit 20 as a comparison signal for the phase servo system, and in the control device 22 as a timing signal for controlling a video signal processing section 62, which will be described later.

Furthermore, the control device 22 and the servo circuit 20 are supplied with a reference clock from a reference clock generator 28 . In this embodiment, a high-speed clock, for example, 3.58 MHz, is supplied to the control device 22, and a 60H2 clock, which is equal to the field frequency, is supplied to the servo circuit 20.

A magnetic transducer for reproducing, that is, a reproducing radar 12 is disposed facing the recording surface 10a, and is supported by a head transfer device II200, which will be described in detail later. This head transfer mechanism 200 is driven by a direct current (DC) motor 30 as conceptually shown by dotted lines, and is driven by arrows Fl,
As shown by Fo (corresponding to the arrows Fl and Fo in FIG. 15), the recording head 12 is configured to be transported in both radial directions along the recording tloa.

The DC motor 30 is operated with characteristics as shown in FIG. 3 by a bidirectional drive circuit 100 with a speed servo, which will be described in detail later. In other words, the DC motor 30 stops when the unipolar (positive in this example) speed control voltage Va input to the drive circuit 100 is at the predetermined value VHS, and when the speed control voltage Va becomes higher than that, the difference occurs. The DC motor 30 rotates in the forward direction (for example, clockwise) at a proportional speed, and conversely, when the speed control voltage Va becomes lower than the motor stop voltage VBS, the DC motor 30 rotates in the opposite direction (counterclockwise) at a speed proportional to the difference. It is designed to rotate (around).

The speed control voltage Va input to the drive circuit 100 is converted into a switching control signal SW2. SW3 causes the servo feed voltage Vd from the operational amplifier 38 and the constant speed feed control voltage V1. from the constant voltage source 34.38. Selected from V2.

That is, SW2. When SW3 is Co, 0), the switch 32 is connected to terminal a to select the servo feed voltage Vd, and SW2. When SW3 is (0, 1), the switch 32 is connected to the terminal S, and the forward constant speed feed control voltage Vt is selected, and SW2. When SW3 is (1, 0), switch 32 is connected to terminal C and opposite direction constant speed feed control voltage v2 is selected.

A head position detection device 300 is coupled to the head transport mechanism 200, and this detects the recording head 12 as will be described in detail later.
When the heads move in the directions of arrows Fl and Fo, voltage signals (head position signals) Ea and Eb having opposite phases are generated whose levels change in a substantially sinusoidal manner at a cycle of the track pitch pt. These voltage signals E a and E b are connected to the resistor 40
．． 42 to the inverting input terminal and non-inverting input terminal of the operational amplifier 38, respectively. On the other hand, a digital tracking control signal SE is applied from the control device 22 to a digital-to-analog (D/A) converter 46, and an analog voltage signal Ec is obtained from its output terminal. and is supplied to the non-inverting input terminal of the operational amplifier 38. The operational amplifier 38 has input resistors 40,4
2.48 and the feedback resistor 44 constitute a differential amplifier, and its output voltage Vd is determined by the resistance values R40 and R42 of the resistor 40.42 being selected to be the same, and the resistance values R44 and R48 of the resistor 44.48 being being selected to be the same. Therefore, it can be expressed as follows.

Vd: EC+AI'' (Eb - Ea) However, AI = R44/R40 = R48/R42 The output voltage Vd of this operational amplifier 38 is determined by the changeover switch 3 described above.
2 as a servo feed voltage, and is also supplied to the respective input terminals of a Schmitt trigger circuit 50 and an analog-to-digital (A/D) converter 52.

The Schmitt O trigger circuit 50 provides the control device 22 with a pulse ST indicating the timing when the voltage Vd becomes equal to the set value VH5. The A/D converter 52 is
The control device 2 converts the voltage Vd into a digital value SV.
Give to 2.

The reproducing head 12 has a magnetic disk 10 of 360 Orpm.
When rotating, one desired recording track rn formed in the recording chamber 10a is scanned and one field's worth of FM video signal FS is read therefrom. This FM video signal FS is passed through an amplifier 80 to a video signal processing circuit 62.
and is supplied to the envelope detection circuit 66.

The video signal processing circuit 62 includes an FM demodulation circuit, a de-emphasis circuit, a video amplification circuit, etc., and generates a reproduced video signal FSo of baseband, for example, NTSC system, and sends it to the device output terminal 64.

The video signal processing circuit 62 is supplied with a control signal SM such as a field/frame conversion control signal or a mute control signal from the control unit rI 122, while a control signal SM, such as a field/frame conversion control signal or a mute control signal, is supplied from the video signal processing circuit 62 to the control device 22 from the reproduced video signal FSo. The envelope detection circuit 66 to which the synchronization signal YS is applied detects the envelope of the FM video signal FS and outputs a voltage signal Ev representing its level. This voltage signal Ev is amplified by an envelope amplifier 68 and then converted into analog or digital (A
/D) M transformer 701? It is converted into a digital value and given to the control section 22.

The control device 22 is composed of a microprocessor (CPU), and writes various programs and data into a rewritable memory 80 as needed, and reads them out as necessary. In particular, in this embodiment, as will be described later, the output voltage Vd of the differential amplifier 38 when the envelope of the FM video signal FSo reaches its peak value for each recording track rn is the error voltage V
It is stored in the memory 80 as HS+Vn, and the corresponding error voltage vn is read out when tracking is performed for that recording track.

The control device 22 is provided with a reproduction half-rPLJ 90. which instructs the control device 22 to start and stop the reproduction device. Forward key rFWJ9 for moving the head 12 in the forward direction of the track number (F1 direction)
2. And reverse disclosure to move the head 12 in the opposite direction (Fo force direction) - "RVJ 94 is also connected. The track number specified by key 92. θ4 is the monitor TV etc. connected to the control device 22 A switch 224 connected to the control device 22 is connected to the head transfer mechanism 20 as will be described later.
0, which is closed when the playback head 12 reaches the home position HP and provides a detection signal to the control device 22.

Further, various mechanical sections 9 and circuit sections not shown in FIG. 1 are connected to the control device 22 for system control, but since they are not directly related to this embodiment, their explanations will be omitted.

The overall configuration of this embodiment has been explained above with reference to FIG. 1, and FIGS. 2 to 10 show the bidirectional drive circuit 100 with speed servo. The configurations of head transfer mechanism 200 and head position detection device 300 will be described in more detail.

Servo Nu Oa In FIG. 2, the input terminal 102 is supplied with the speed control voltage Va from the changeover switch 32 described above. This speed control voltage Va is supplied to a non-inverting input terminal of an operational amplifier 120 that constitutes a speed servo system comparison circuit.

The output terminal of operational amplifier 120 is connected to the inverting input terminal of operational amplifier 108A via resistor 108A, and is directly connected to the non-inverting input terminal of operational amplifier 106B. A preset motor stop voltage VBS is supplied from the DC voltage source 104 to the non-inverting input terminal of the operational amplifier 106A, and this motor stop voltage VBS is supplied to the non-inverting input terminal of the operational amplifier 106A.
It is also supplied to the inverting input terminal of operational amplifier 106B via 8B. Both operational amplifiers 108A and 108B have the same amplification characteristics, and the resistance values of both resistors 108A and 108B are selected to be the same (R108).

The output terminal of the operational amplifier 106A is a drive transistor 114A forming a complementary circuit.

Connected to the base of 116A. On the other hand, operational amplification i! 1
The output terminal of 08B is connected to the paces of drive transistors 114B and 118B forming a complementary circuit. These drive transistors 114A to 116B are bridge-connected, and the DC motor 30 is connected between them.

Further, the feedback resistors 110A and 110B of the operational amplifiers 108A and 108B are connected to their inverting input terminals and the output terminals 118A of the drive transistors 114A to 116B.

118B, respectively. The resistance values of feedback resistors 110A and 1.10B are the same (RIIO)
The capacitances of the phase compensation capacitors 112A and 112B connected in parallel with these capacitors are also selected to be the same. Note that a capacitor 119 connected in parallel with the DC motor 30 is for a noise killer, and a resistor 138 connected in series with the DC motor 30 is part of a speed servo system to be described later.

The above configuration is a bidirectional drive system excluding the speed servo system, and its operation will be explained next. In order to facilitate understanding, the operational amplifier 120 and resistor 138 of the speed servo system will be omitted from the description.

The speed control voltage Va applied to the input terminal 102 is supplied to the inverting input terminal of the operational amplifier 106A through the resistor 108A, and is also directly supplied to the non-inverting input terminal of the operational amplifier 106B.

When this speed control voltage Va is vBS+ΔV, the terminal 11
8A, 1188: the resulting voltages V (A), V (B
) is expressed as follows.

V(A) = VH5-A2-AV V(B) = VBS+A2 I AV However, A2 = R108/RIIO Here, VBS is the motor stop voltage as mentioned above, and R108 and RIIO are the resistors as mentioned above. 10
8A (108B), and the resistance value of the resistor 110A (110B). Therefore, the DC motor 30 has a threshold voltage V
(A) and V (B), that is, a voltage of 2A2·AV is applied, and the DC motor 30 rotates in the forward direction (clockwise) at a speed N (VH5 + ΔV) that is approximately proportional to the applied voltage (Fig. 3). reference). In this case, the drive transistor 11
4B and 118A are turned on, and the drive transistor 114
A and 116B are turned OFF.

When the speed control voltage Va is VBS-AV, the motor terminal voltages V (A) and V (B) are as follows, and V
(A)=VH5+A2・AV V(B)=VBS−A2・AV Therefore, the voltage applied between both terminals of the DC motor 30 is -2A2・AV, and the DC motor 30 moves in the opposite direction (counterclockwise). The speed N(
VBS-AV) (see Figure 3). in this case,
Drive transistor 114A.

116B is turned on, and the drive transistors 114B, 1
18A is turned OFF.

Also, when the speed control voltage Va is VBS, if AV is set to zero in the above equation, the motor terminal voltage V (A).

V (B) is applied, and in this case both are VBS, so the DC motor 30 is in a stopped state with no voltage applied.

In this way, when the positive speed control voltage Va applied to the input terminal 102 (more precisely, one input terminal of the operational amplifiers 108A and 108B) is equal to the motor stop voltage VBS, the DC motor 30 comes to a stop state. , when the speed control voltage Va is higher than the motor stop voltage VH5, the DC motor 30 rotates in the positive direction (clockwise) at a speed approximately proportional to the difference, and the speed control voltage Va is higher than the motor stop voltage VB.
When it is lower than S, the DC motor 30 rotates in the opposite direction (counterclockwise) at a speed substantially proportional to the difference.

Next, the configuration and operation of the speed servo system added to the above-mentioned bidirectional drive system will be explained. Generally speaking, high-performance constant-speed control is a prerequisite for performing high-precision position control using a motor, but DC motors have the characteristics shown in Figure 4, and are subject to fluctuations in load and applied voltage. Since the rotational speed tends to fluctuate, a speed servo is required to cancel out such disturbances. In this embodiment, an electronic governor type speed servo system is provided as described below.

In FIG. 2, the speed servo system of this embodiment is denoted by reference numeral 1.
It consists of elements numbered 20 to 142.

The operational amplifier 120 constitutes a speed servo system comparison circuit,
The speed control voltage Va is compared with a feedback signal vf from an operational amplifier 122, which will be described later, to create an error signal, which is further amplified by an amplification factor A4 to output an error control voltage V a t. This error control voltage Va' is applied to the operational amplifier 106 as a voltage signal that directly controls the rotational speed of the DC motor 30.
A through a resistor 108A and directly to the non-inverting input terminal of an operational amplifier 108B.

On the other hand, around the DC motor 30 are resistors 132 to 138.
are bridge-connected including a DC source 30 as shown, and terminals 140 and 142 are connected to an inverting input terminal and a non-inverting input terminal of an operational amplifier 122 via resistors 124 and 126, respectively.

When the DC motor 30 is rotating in the forward direction, V(A)
<V(B)-? ' Yes, the induced electromotive force KN of the DC motor 30 (K is a constant, N is the rotational speed of the DC motor 30) is in the direction shown in the figure. The resistance value of the internal resistance of the DC motor 30 is Rat, and the resistance value of the resistors 132 to 138 is R132 to R1.
38, the voltage V obtained at terminals 140, 142
(C) and V (D) are expressed as follows.

V (C) = (V (B) V (A) −KN) Ra
/ (Ra+R138)V (D)” (V(B) −
V(A)) Ro/ (Ro+R13G) However, Ro
= RI32+ R134 The resistor 134 is a variable resistor (volume), and by adjusting it, R13G / Ro =
When R138/Ra = H (constant), the voltage V
(C) and V (D) are as follows.

V(C)=(V(B)-V(A)-KN)/(
1+H)V(D)=(V(B)-v(A))/
(1+H) Therefore, the potential difference between the terminals 140 and 142 is V(D)-V(C)=KN/(1+H), which is proportional to the rotational speed N of the DC motor 30.

Furthermore, when the DC motor 30 is rotating in the opposite direction, the induced electromotive force KN is in the opposite direction to that shown in the diagram, so V(D)-V(C)=-KN/(1+H) and the polarity is Invert. As described above, the absolute value of the potential difference between the terminals 140° and 142 is proportional to the rotational speed N of the DC motor 30, and the polarity thereof corresponds to the rotational direction of the DC motor 30.

Voltages V(C) and V(D) are supplied to the inverting input terminal and non-inverting input terminal of the operational amplifier 122 through resistors 124 and 128, respectively, and the non-inverting input terminal is connected to the resistor 130.
A motor stop voltage VBS from a constant voltage source 104 is also supplied through the motor. Operational amplifier 122 has these input resistors 124
, 128, 130 and the feedback resistor 128 constitute a differential amplifier, and its output voltage Vf is
Since the resistance values R124 and R12G of resistors 24 and 126 are selected to be the same, and the resistance values R128 and R130 of the resistors 128 and 130 are selected to be the same, it is expressed as follows.

Vr = VBs + A3 e (v(D) - V(c)) where A3 = R128/R+24 = RI30/RI
2G, ', Vf: VBS±A3・KN/ (1+H),
', Vf=VBS±KoN However, KO:=A3 ・/(1+H) In other words, the output voltage Vf of the operational amplifier 122 is the stop voltage VH
5 plus a level fluctuation (±Ko N) proportional to the rotational speed N of the DC motor 30. This output voltage Vf is supplied as a negative feedback signal to an inverting input terminal of an operational amplifier 120 constituting a comparator.

Since the operational amplifier 120 compares both input voltages Va and Vf and amplifies the error with the amplification degree A4, the output error control voltage Va' is expressed as follows.

Va'=A4 e (Va - vr),', Va'=
A4 m (Va - (VBS±KON)) However, A
4=Rh/Ra When the speed control voltage Va is equal to the motor control voltage VHS, the DC motor 30 is stopped and the servo loop is in an equilibrium state. In this state, Vf=VH5. Therefore, the output error control voltage Va' is the speed control voltage V
a (V R5), terminals 118A, 11
8B + 71% - 9 terminal voltage V (A), V (Both Bl are balanced at approximately VBS, and the voltage applied to the DC motor 30 is approximately
It is zero.

When the speed control voltage Va changes to VBS+ΔV from such a state, the error control voltage Va'' increases and the terminal 118
A, motor terminal voltage V (A) of 118B.

V(B) Ni big! ';C difference (V(A) <V(B)
) The DC motor 30 begins to rotate in the forward direction.

Then, the feedback voltage Vf (VBS+Ko N) also increases and approaches the speed control voltage Va, thereby controlling the error! The pressure Va' converges to VH5+AV, and the DC motor 3
The rotational speed of ° converges to N(VH5+ΔV) and reaches an equilibrium state. Similarly, the speed control voltage Va changes from VBS to VBS.
-ΔV, the DC motor 3° starts rotating in the opposite direction, the error control voltage VaI converges to VBS-ΔV, and the rotational speed of the DC motor 30 becomes N(VBS-ΔV
) and reach an equilibrium state.

By the way, in a stable state, for example, when the speed control voltage Va is VBS+ΔV, the rotational speed of the DC motor 3o is N(VBS
+ΔV), when a disturbance such as load fluctuation occurs and the torque Q decreases by ΔQ, the speed servo operates as follows. That is, due to the characteristics shown in FIG. 4, the rotational speed of the DC motor 30 tends to increase by ΔN, but since the feedback voltage Vf increases by that amount, the error control voltage Va' becomes lower than VBS+ΔV by δV, and the DC Motor 3017) rotation speed is N (VBS+AV
) k: Work to maintain. Conversely, when torque Q increases by ΔQ, feedback voltage Vf decreases by that amount, and error control voltage Va' becomes higher than VBS+ΔV by δV, resulting in D
It works to maintain the rotational speed of the C motor 30 at N (VBs+ΔV). In response to other disturbances, such as fluctuations in the power supply voltage Vcc, the same speed servo as described above works to reduce the
Stable rotation of the C motor 30 is maintained.

As described above, in the bidirectional drive circuit 100 with speed servo, the unipolar (positive in this example) speed control voltage Va
It is possible to switch the rotation of the DC motor 30 in both directions using the motor, and to control the rotational speed linearly, thereby enabling highly accurate speed control. It should be noted that when the speed control voltage Va of negative polarity is selected, the same effect as described above is achieved, only that the rotational direction of the DC motor 30 is opposite to that in the case of positive polarity with respect to its absolute value.

Hera 9.

FIG. 5 shows the configuration of the head transfer mechanism 200.

In this figure, 202 is a speed reduction mechanism linked to the DC motor 30, and its output stage engages with the sector gear 204. A pulley 20B that rotates integrally with the sector gear 204 is attached to the sector gear 204, and one point of the wire 210 is fixed thereto by a tightening means 208. wire 210
Both ends of the head carriage 216 are fixed to a side surface 216a of the head carriage 216 by fastening means 212 and 214.

The head carriage 216 supports the playback head 12, and the head carriage 216 slides on the guide rod 218 in accordance with the rotational drive of the DC motor 30, thereby moving the playback head 12 in the directions of arrows Fl and FO (first direction). Figure 1 and 1st
(corresponding to the direction of arrow F I + F o in Fig. 6). That is, when the DC motor 30 rotates in the forward direction (clockwise), the head carriage 218 slides on the guide rod 218 in the F1 direction, and the reproducing head 12
is transferred in the same direction, and when the DC motor 30 rotates in the opposite direction (counterclockwise), the head carriage 216 slides on the guide rod 218 in the direction of the arrow Fo, and the reproducing head 1
2 in the same direction.

When the inner packet of this playback device is opened because the magnetic disk 10 housed in the package 230 is loaded into the housing 220, or when the power is turned on with the magnetic disk 10 loaded, the playback head 12 is transported in the direction of arrow Fo. The outer end of the transfer stroke is the home position HP, which is detected by a limit switch 224 located on a member 222 fixed to the housing 220. That is, the sector gear 204
An arm 204b is protruded from a part of the circular portion 204a, and when the recording head 12 comes to the home position HP,
The switch 224 is closed by the arm 204b coming into contact with the movable member of the switch 224. A detection signal is then sent from the switch 224 to the control device 22, and in response, the control device 22 starts a search mode as described below.

In FIG. 5, the tip 21 of the head carriage 216
6b is the movable slit plate 3 of the head position detection device 300.
Both ends 302a of 02 are fixed, so that the movable slit plate 302 moves integrally with the helad carriage 218 in the direction of arrow F.
It is designed to move in the directions of l and Fo. On the other hand, a position detection device fixing part 304 configured to allow the movable slit plate 302 to pass through is attached to the housing 220.

FIG. 6 shows the configuration of the head position detection device 300. Above the movable slit plate 302 are two light emitting elements having the same configuration and the same characteristics, for example, light emitting diodes 308A and 308A.
08B are arranged in parallel, and below the movable slit plate 302, two light receiving elements having the same configuration and the same characteristics, for example, photodiodes 310A and 3
10B are juxtaposed.

FIGS. 7(a) and 7(b) show the movable slit plate 302 and the fixed slit plate 308 in detail. Movable slit plate 30
2, the slit width W is 50 μm and the slit pitch PS is 100 μm in the length direction, and they are 1/2 of each other.
PS (2 rows of sleeves offset by 50 μm)) 30
2A and 302B are formed. On the other hand, the fixed slit plate 308 has a slit width Wo of slits 302A and 3
One slit 308C is formed, which is the same as the slit width W of 02B (50 μm) and whose slit length LO is somewhat larger than the distance between both ends of the slits 301A and 301B.

However, it will be appreciated that the slit length LO may be the same or smaller than the spacing.

In FIG. 6, a light emitting element 308A, a movable slit plate 3
The slit 302A of 02, the slit 308C of the fixed slit plate 308, and the light receiving element 310A are lined up and down, while the light emitting element 308B, the slit 302B of the movable slit plate 302, and the slit 30 of the fixed slit plate 308
8G, the light receiving elements 310B are arranged in a vertical line. When the movable slit plate 302 moves together with the helad carriage 21θ in a direction perpendicular to the plane of the paper (corresponding to the direction of arrow FOIF1 in FIG. The intensity, and therefore the photocurrent Ia flowing through the light receiving elements 310A and 310B
, Ib change periodically according to the movement of the movable slits 302A, 302B, and are converted into voltage signals Ea, Eb by current-voltage converters 312A, 312B having the same configuration and the same characteristics. These voltage signals Ea, E
b is a head position signal whose level changes at the cycle of the track pitch pt according to the position of the playback head 12, as described later, and is input to the inverting input terminal of the operational amplifier 38 via resistors 40 and 42 (FIG. 1). , are supplied to the non-inverting input terminals, respectively.

Next, as shown in FIGS. 8 and 9, the head position detection device 3
The operation of 00 will be explained in more detail. Figure 8(a)-(
In e), when the movable slit plate 302 moves at a constant speed U in the direction of the arrow Fi, the light emitting elements 308A and 308B
A downward view is shown at regular time intervals from a side position. While the movable slit plate 302 is moving, the light receiving element 310
A, 310B have movable slits 302A, 302B
Light with an intensity approximately proportional to the areas SA and SB where the fixed slit 308 and the fixed slit 308 overlap is incident, and the level of the voltage signal Ea+Eb changes in proportion to the intensity of the light.

In FIG. 8(a) (time tl in FIG. 9), the overlapping area SA of the movable slit 302A and the fixed slit 308 is maximum, the voltage signal Ea is also at the maximum level VM, and the -force light receiving element 310B is connected to the movable slit plate 308. (SB
=O) The voltage signal Eb is at the minimum level Vm (&vO). Thereafter, as the movable slit plate 302 moves in the direction of the arrow Fl, the overlapping area SA of the movable slit 302A and the fixed slit 308 decreases, and at the same time, the overlapping area SB of the movable slit 302B and the fixed slit 308 decreases.
increases, and at time t2 when 1/4T (T=period) has passed from time t1, as shown in FIG. Both E a +Eb become the center level Vo. Then, after 174T has passed since time t2,
As shown in FIG. 8(C), the light receiving element 310A is shielded by the movable slit plate 302 (SA = 0), and the voltage signal Ea becomes the minimum level V, while the movable slit plate 302
The area SB where the fixed slit 2B and the fixed slit 308 overlap becomes maximum, and the voltage signal Eb reaches the maximum level VM. After that, as the movable slit plate 302 moves in the direction of the arrow Fl, the overlapping area SA of the movable slit 302A and the fixed slit 308 increases, and at the same time, the movable slit 30
The overlapping area SR of 2B and the fixed slit 308 decreases,
At time t4 (Fig. 8 d), the voltage signals E asE b both reach the center level Vo, and at time t5 (Fig. 8 e)
Then, the voltage signal Ea becomes the maximum level VM and the voltage signal Eb becomes the minimum level Vm.

In this way, when the movable slit plate 302 moves in the direction of the arrow Fl, the levels of the voltage signals El and E2 are in opposite phase to each other in the time period T (Ps/u) determined by the moving speed U and the slit pitch Ps. That is, they change in a substantially sinusoidal manner with a 180° phase difference. This is the movable slit plate 30
The same applies when 2 moves in the direction of arrow Fo.

Regarding the movement of the movable slit plate 302, the levels of the voltage signals E a and E b are the same as those of the fixed slit 3.
The period of the slit pitch Ps (100 μm) according to the relative position between 08C and the movable slits 302A and 302B
It changes almost sinusoidally. By the way, the movable slit plate 3
02 is the head carriage 216 like the reproduction head 12
The slit pitch PS is the same as the track pitch pt (10
0ttm). Therefore, playback head 1
2 moves in the direction of arrows Fi and Fo, the voltage signal E
a.

The level of Eb changes in a substantially sinusoidal manner with a period of track pitch Pt. In this embodiment, the reproduction head 12
When the fixed slit 308C and the movable slit 302A, 3 face the center part (R1)t (R2) of each track position R1, R2...
02B is set to be in the relative position shown in FIG. 8(d). As a result, the levels of the voltage signals Ea and Eb become as shown in FIG.
2... Central part (R1,), (R2)
Both are at the center level V when facing .
It becomes o.

As described above, in the head position detection device 300, when the playback head 12 moves in the directions of the arrows Fi and Fo, the levels change at the cycle of the track pitch pt, and the playback head 12 moves to each track position R1, R2, etc. The voltage signals Ea and Eb, which are opposite in phase to each other and have the same level vO at the center part (R1)t (R2) of .., are used as head position signals. occurs.

These head position signals Ea and Eb are supplied to both input terminals of the operational amplifier 38 via the resistors 40 and 42, respectively, as described above.

Gong 1 Sad Rainbow 1 Next, the overall operation of this embodiment will be explained with reference to FIG. 1 again.

(A) Initialization mode As mentioned above, when the inner packet is opened because the magnetic disk 10 is loaded into the housing 220 (FIG. 5) of this playback device, or when the power is turned on, the playback head 12 is moved to the home position HP. During the transfer of the reproducing head 12, the switching control signal 1 S W2 . given from the control device 22. S W3 is (1, 0), so that the switch 32 is connected to the terminal C, and the opposite direction constant speed feed control voltage V2 from the constant voltage source 36 is inputted to the drive circuit 100 as the speed control voltage Va. This causes the DC motor 30 to rotate in the opposite direction (counterclockwise) and slide the head carriage 216 in the direction of arrow FO.

In this initialization mode, the power is turned on with the disc 10 loaded in advance, and then the playback key 90 is pressed.
Also occurs when is pressed.

(B) Search Mode When the playback head 12 reaches the home position HP, the control device 22 starts the search mode in response to a detection signal from the switch 224.

To this end, the control device 22 first outputs a switching control signal SW2.
．． Switch SW3 to (0,1). As a result, the switch 32 is connected to the terminal S, and the forward constant speed feed control voltage V1 from the constant voltage source 34 is selected as the speed control voltage Va input to the drive circuit 100. The forward constant speed feed control voltage v1 is a constant voltage higher than the motor stop voltage VH5 by a predetermined value, as shown in FIG. This control voltage V
1, the DC motor 30 rotates in the forward direction (clockwise) at a rotation speed N (Vl) to drive the head carriage 216 and transport the reproducing head 2 in the direction of the arrow Fl. Along with this, the movable slit plate 302 also moves in the direction of the arrow F1, and the level changes from the head position detection device 300 as shown in FIG. 9 in terms of time and as shown in FIG. 10 regarding the movement of the reproducing head 12. head position signal E alE
b are supplied to the non-inverting input terminal 1 and the inverting input terminal of the operational amplifier 38, respectively.

On the other hand, at this time, a digital positioning control signal SE corresponding to Va5 is given from the control device 22 to the D/A converter 46, and an analog voltage signal Ec obtained at its output terminal
(Va5) is supplied to the non-inverting input terminal of the operational amplifier 38 via the resistor 48.

Therefore, the output voltage Vd of the operational amplifier 38 is expressed as follows: Va = VH5 + A1 e (Eb - Ea) The level changes as shown in FIG. That is, the head 12
moves in the direction of arrow Fl, the level of voltage Vd changes approximately sinusoidally with a period of track pitch pt, and the head 12 moves to the center (R1) of track positions R1, R2, etc. , (R2)..., Vd=BBS. Although this voltage Vd is not supplied to the drive circuit 100 as the speed control voltage Va,
The signal is monitored by the control device 22 via the /D converter 52.

The control device 22 also sends a control signal SWI to the servo circuit 20.
is given, which causes the DC motor 14 to operate,
Disc 10 is 3. Rotationally driven by E300.

The playback head 12 moves from the home position HP to the arrow F1.
When moving in the direction of each recording track rLr2...
. . . and read the FM video signal FS recorded there. The envelope en (FIG. 12) of each FM video signal FS is detected by the envelope detection circuit 66, and its digital value is given to the control device 22 by the A/D converter 70. The control device 22 monitors the envelope eLe2 for each recording track rl, r2, etc., and determines the peak values epl, ep2, etc. ( The value of voltage Vd when the voltage Vd becomes VBS+ v 1. VBS+v2・
...... (Fig. 11) is taken in and Vl, V2.
. . . are sequentially written to predetermined locations in the memory 80 as error voltages.

The peak value 6pn of each envelope en is the playback head 1
2 is obtained when it faces the center position (rn) of the recording track rn. Therefore, when the recording track rn exactly overlaps the track position Rn, the error voltage vn is zero because the center position (rn) of the recording track rn coincides with the center part (Rn) of the track position Rn. be. However, as shown in FIG. 12, when the recording track rl deviates from the track position R1 in the direction of the arrow F1, vl<0 as shown in FIG. When the deviation is more in the direction of arrow FO, V2>0. In addition, the first
When the error voltage VllV2 as shown in FIG. 1 is obtained, the head position signal E from the position detection device 300
a and Eb are levels (val, Vbl) t (va2.
vb2) “”.

In this way, when the reproducing head 12 crosses the last recording track r50 and the error voltage v50 for that recording track r5G is written into the memory 80, the control device 22 transmits the switching control signal SW2. Switch SW3 to (1,0). As a result, the switch 32 is connected to the terminal C, and the opposite direction constant speed feed control voltage V from the constant voltage source 36 is connected.
2 is again manually applied to the drive circuit 100 as the speed control voltage Va. As a result, the DC motor 30 rotates in the opposite direction (counterclockwise) at a rotational speed N (V2) to drive the head carriage 216 and transport the reproducing head 12 in the direction of the arrow Fo. Then, when the playback RAD 12 reaches the home position HP, a detection signal is sent from the switch 224 to the control device 22, and in response, the control device 22
The DC motor 30 is stopped and the reproducing head 12 is placed on standby at the home position HP.

Note that after the search mode ends, the reproducing head 12 may be left on standby at a position inside the disk 10 (for example, at recording track r50) without returning to the home position HP. However, in this embodiment, the following access mode will be explained for the case where the playback head 12 is placed on standby at the home position HP as described above.

(C) Access mode After that, the first track is set to t using the forward key 92.
If so, the switching control signal S from the control device 22
W2. SW3 changes to (0,1) and switch 32
is connected to the terminal S, and as a result, the forward constant speed feed control voltage Vl is selected as the speed control voltage Va, and the DC motor 30 rotates in the forward direction (clockwise) at the rotational speed N (Vl) to rotate the head carriage 218. and drive the playback head 12.
Then, the movable slit plate 302 is moved in the direction of arrow Fl.

On the other hand, a digital tracking control signal SE also corresponding to Vl5 is given from the control device 22 to the D/A converter 46, and an analog voltage signal Ec equal to Vl5 obtained at its output terminal is sent to the operational amplifier 38 via a resistor 48. is supplied to the non-inverting input terminal of Therefore, the output voltage Vd of the operational amplifier 38 is expressed as follows: Vd = VH5 + A1 · (Eb - Ea) The level changes as shown in FIG. That is, playback head 1
2 is the center part of track positions R1, R2... (R1>
, (R2)... Vd:VB
S, and the reproducing head 12 moves to the recording tracks rI, r2.
... Center position of the song (rl)t (r2)...
Where it faces teVd =VBS+vl
, VBS+v2...

While the reproducing head 12 is moving from the home position HP in the direction of the arrow Fl, a timing pulse ST is applied from the Schmitt trigger circuit 50 to the control device 22 each time the voltage Vd becomes equal to Vl5. The control device 22 accumulates these pulses ST, and calculates a predetermined pulse ST.
is given, that is, when a pulse ST indicating the timing at which the reproducing head 12 passes through the center of the track position (R1) of the first track is given, the switching control signal S is given.
W2. Switch SW3 to (0,0). As a result, the switch 32 is connected to the terminal a, and the output voltage (servo feed control voltage) Vd of the operational amplifier 38 is selected as the speed control voltage Va input to the drive circuit 100.

At the same time, the control device 22 reads the error voltage vl for the recording track rl from the memory 80, and reads Vl5-
A tracking control signal SE corresponding to vl is applied to the D/A converter 46, whereby an analog voltage signal Ec equal to VHS −v 1 is applied to the operational amplifier 38 via a resistor 48.
is supplied to the non-inverting input terminal Vd of. Therefore, the output voltage Vd of the operational amplifier 38 is expressed as follows, Vd = VBS - vl + Ale (Eb -
Ea) The level changes as shown in FIG. 13 (enlarged view). That is, the waveform is the same as in FIG. 11, but the center level is changed to VHS-vl. In the above equation, the second term on the right side indicates that the playback head 2 is at the center position of the recording track rl (rl
) becomes Vl. Therefore, the fourteenth
In the figure, the reproducing head 12 is moving to the recording track r! Vd = VBS - vl + vl = VBS at a place facing the center position (rl) of .

When the speed control voltage Va is switched to the servo feed control voltage Vd as described above 1, the reproducing head 12 has come to a position Xt slightly beyond the center position (rl) of the recording track rt, and as shown in FIG. As shown in Vd<VH
It is S. As a result, the DC motor 30 is rotated in the reverse direction (counterclockwise), and the reproducing head 12 is moved in the direction of the arrow Fo.

Then, the playback head 2 moves to the recording track center position (rl
) in the direction of the arrow Fo, Vd>VBS and the DC motor 30 switches to normal rotation (clockwise).
The head 12 is again transported in the direction of arrow Fl.

Then, when the head 12 passes the recording track center position (rl) in the direction of the arrow Fj, Vd<VHS again, the DC motor 30 rotates in reverse, and the head 12 again moves toward the arrow Fo.
change direction in the direction of However, the direction change position
is the recording track center position (
rl). In this way, the head 12
The recording track center position (rl
) and stop there. In this stopped state,
Vd=VH5, and the head position signals Ea and Eb from the position detection device 300 are at levels (val, vbl) that are deviated from the reference level Vo (see FIG. 1O).

As a result, the reproducing head 12 faces the first recording track rl rotating at 3800 rpm,
The video signal processing circuit 62 repeatedly reads the M video signal FS, and in response to it, the video signal processing circuit 62 converts the NTSC system reproduced video signal FSo.
is generated and supplied from the device output terminal 64 to an external device, such as a television receiver, and the still image (photograph) recorded in the first recording track rl is displayed on the screen of the television receiver.

Next, when the forward key 92 is pressed again to indicate the second track, the control device 22 outputs the switching control signal SW2.
SW3 is switched to (0, 1), and the forward constant speed feed control voltage Vl from the constant voltage source 34 is inputted to the drive circuit 100 as the speed control voltage Va.

As a result, the DC motor 30 starts rotating in the forward direction, and the reproducing head 12 is moved in the direction of the arrow Fl. At the same time, the control device 22 reads out the error voltage V2 for the second recording track r2 from the memory 80. Switch the tracking control signal SE to VBS-v2. Therefore, the output voltage Vd of the operational amplifier 38 is expressed as follows, Vd = VBS - v2 + Ai e (E
b-Ea) The level changes as shown in Figure 14 (enlarged view). That is, compared to the one in FIG. 13, the center level changes from VBS-vl to VEIS-v2. In the above equation, the second term on the right side becomes v2 where the reproducing head 12 faces the center position (r2) of the recording track r2, so in FIG. ), Vd = VBS - v2 + v2 = VBS.

As a result, when the reproducing head 12 passes the center position (r2) of the recording track r2, a pulse ST indicating the timing is generated from the Schmitt trigger circuit 50,
In response, the control device 22 outputs a switching control signal SW2.
Switch SW3 to (0,0).

As a result, the changeover switch 32 is connected to the terminal a, the servo feed control voltage Vd is input to the drive circuit 100, and the reproducing head is placed at the position where Vd=VH5, that is, at the center position (r2) of the recording track r2, as described above. Servo feeding is performed so that the 12 positions converge. Thus, the playback head 12 repeatedly reads one field of FM video signal FS from the recording track r2 rotating at 3.80 rpm, and the still image recorded on the recording track r2 is displayed on the screen of the television receiver. It will be done.

Next, when the third track is designated by the forward key 92, tracking is performed in the same manner as described above. Fourth
The same goes for the following tracks.

Also, when the reverse direction key 94 is pressed, tracking is performed in substantially the same manner as described above, but in that case, the switching control signal SW2. S
W3 is switched to (1,0) and the reproducing head 12 is moved in the direction of arrow Fo.

Then, the playback head 12 is directed to the designated recording track rn.
In response to the negative direction pulse ST' generated by the Schmitt trigger circuit 50 when passing the center position (rn) of the switching control signal SW2. SW3 is switched to (0,0), thereby performing servo feeding so that the position of the reproduction track 12 converges on the recording track center position <rn>.

Furthermore, random access is also possible in which the playback head 12 is accessed from an arbitrary position to a desired track; in that case, the playback head 12 is first moved at a constant speed.
2 is transported in the direction of the arrow Fl or FO, and immediately after it passes the track position center (Rn) of the desired track or the recording track center position (rn), it is switched to servo feeding.

As described above, in the above embodiment, when the envelope en of the FM video signal FS read from each recording track rn in the search mode reaches the peak value epn (that is, when the reproduction head 12 The output voltage Vd of the operational amplifier 38 (when facing the center position (rn)) is stored in the memory 80 as the error voltage vn, and in the access mode, the playback head 12 is first moved at a constant speed to the arrow Fl or F.

The track position center (Rn) of the desired track or the recording track center position (rn
) can be switched to servo feed immediately after passing. In servo feed, the error voltage vn for that track
is read out from the memory 80 and the tracking control signal S
E is set to VBS-vn, which is the position detection device 30.
By adding the head position signals E a and E b from 0 to 0, the servo feed control voltage Vd converges to VBS, that is, the head position signals E a and E b are
The reproducing head 12 vibrates in the directions of arrows Fl and FO so as to converge to the recording track center position (rn), and stops there.

This type of tracking is significantly improved in speed and accuracy compared to tracking using conventional hill-climbing control.

In other words, in the conventional system, the playback head is moved stepwise many times, the envelope level of the playback signal is detected and compared each time, and based on the comparison results, a command is issued to move the playback head closer to the center position of the recording track. Since the tracking servo applies pulses to the step motor, it takes a long time for the reproducing head to converge near the center position of the recording track. Furthermore, if the amount of head movement per step is increased in order to shorten the tracking time, the tracking accuracy will decrease. Furthermore, since the head position is controlled by command pulses given to the step motor from the control section, errors in the actual head position are likely to occur due to backlash or the like in the head transfer means.

However, in the servo feed according to the present embodiment, the actual position of the reproducing head 12 is expressed as the level of the head position signal E a +Eb and fed back, and the levels of these head position signals E a and E b correspond to the recording track center position (
100% on-track position).
The servo is applied so that the actual position of the reproducing head 12 converges to the center position of the recording track (1
Since an equilibrium state is reached at the point where the track position is 00% on, the convergence speed (tracking speed) and convergence precision (tracking precision) are high, and even if backlash or the like occurs, no error occurs in the actual head position.

Furthermore, in the constant speed feed according to this embodiment, the playback head 12
Since it is monitored through the levels of the head position signals Ea and Eb whether the head has come close to the desired track while being moved in one direction, the head 12 can be quickly and reliably moved to the recording track center position (100% ON O track position). ) can be approached.

In addition, one of the head position signals E a and E b, for example, E
It is also possible to use only a, so that the level of the voltage signal Ec indicated by the tracking control transfer signal SE from the control device 22 need only be higher by A1*Vo in each case of the above embodiments, thereby In servo feed, the head position 'signal Ec level is va
When n, servo feed 11) Control a □ Voltage Vd is V
It becomes equal to BS, that is, it becomes an equilibrium condition, and the same effect as the above embodiment is achieved.

However, in that case, errors are likely to occur when the level of the head position signal Ea fluctuates due to the temperature characteristics of the position detection device 300, offset voltage, etc. The difference between the two head position signals Ea and Eb (Eb - Ea) is a predetermined value vn/A
Since an equilibrium condition is obtained when reaching I, even if level fluctuations occur in both head position signals Ea and Eb, they are compensated for by the difference, and are not affected by such temperature characteristics or offset voltage. You don't have to.

Further, in the above embodiment, the timing pulse ST generated from the Schmitts)-) rigging circuit 50 is monitored, and the reproducing head 12 is moved to the center of the track position (Rn) of the desired track.
) or immediately after passing the recording track center position (rn), the direction of the reproducing head 12 is changed by switching to servo feeding. Normally, the direction change position
It is sufficient if the distance is within the range of /4 Pt. Therefore, instead of the timing pulse ST from the Schmitt trigger circuit 50, the FM signal is generated at the timing of the peak value of the servo feed voltage Vd monitored through the A/D converter 52 or through the envelope detection means (6668, 70). Pulse feeding may be switched to servo feeding at the timing of the peak value epn of the envelope en of the video signal FS.

Furthermore, in the above embodiment, each recording track r
The error voltage vn regarding n is stored in the memory 80, but
It is also possible to execute the direct access mode without using such a search mode. That is, in constant speed feed in the access mode, the forward direction constant speed feed control voltage Vl from the constant voltage source 34 or the opposite direction constant speed feed control voltage from the constant voltage source 36 is used as the speed control voltage Va input to the drive circuit 100. V2 is selected and playback head 12
is transported in the direction of the arrow Fl or Fo, which is the same head movement as in the search mode.

Therefore, when the control device 22 monitors the envelope en of the FM video signal FS during constant speed feeding in the access mode and reaches the peak value epn (that is, when the reproduction head 12 is at the center position of the recording track rn) rn)) is taken in as an error voltage vn via the A/D converter 52,
At the same time as switching to servo feed, the error voltage vn may be added to the head position signals ga and Eb as in the above embodiment. In that case, the error voltage vn may not be particularly stored in the memory 80, but may be temporarily stored in a buffer within the control device 22.

(Effects of the Invention) In the present invention, when accessing or tracking a desired recording trunk, the playback head is first moved linearly and quickly to the vicinity of the recording track, and then the actual (current) position of the playback head is A head position signal whose level changes is fed back to represent the error signal and generate an error signal according to the deviation, and the playback head is stopped after converging on the center position of the recording track, thereby eliminating the effects of backlash, etc. Fast and accurate tracking can be performed without any interference.

Furthermore, in the present invention, since the position of the playback head is controlled according to such a head position signal, there is less burden on the microcomputer that controls the operation of the entire playback device, and therefore, compared to conventional mountain climbing control. A microcomputer with a small capacity can be used, or a microcomputer with the same capacity can be provided with more functions.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the overall configuration of an embodiment in which the present invention is applied to a playback device for an electronic still camera system, and FIG. 2 shows the configuration of a bidirectional drive circuit 100 with speed servo in the above embodiment. The circuit diagram shown in FIG.
FIG. 4 is a diagram showing the characteristics of the C motor 30, FIG. 4 is a diagram for explaining the operation of the speed servo system of the bidirectional drive circuit 100 with speed servo, and FIG. 5 is a diagram showing the characteristics of the head transfer mechanism 200 in the above embodiment. FIG. 6 is a schematic side view showing the configuration of the position detecting device 300 in the above embodiment; FIG. 7 is a plan view showing the structure of the position detecting device 300; FIG. 8 is a schematic plan view for explaining the operation of the head position detection device 300; FIG. 9 is a timing diagram for explaining the operation of the head position detection device 300; FIG. FIG. 10 is a diagram showing changes in the levels of the head position signals Ea and Eb when the reproduction head 12 moves in the above embodiment, and FIG. 11 shows the change in the level of the head position signals Ea and Eb when the reproduction head 12 moves in the search mode in the above embodiment. The output voltage V of the operational amplifier 38 when
FIG. 12 is a diagram showing the envelope of the FM video signal FS when the RAD 12 moves to the playback mode in the search mode in the above embodiment, and FIG. 13 is a diagram showing the change in the level of d. FIG. 14 is a diagram for explaining the operation when the reproduction head 12 converges on the first recording track rl in the access mode of the above embodiment. 15 is a diagram illustrating a typical recording format of the magnetic disk 10 by an electronic still camera system, and FIG. 16 is a diagram illustrating tracking using conventional mountain climbing control. This is a diagram for 10... Magnetic disk, 12... Playback head,
22...control device, 30...direct current (DC) motor, 32...changeover switch, 34.36...constant voltage source, 38 operational amplifier, 40-44.48...・・・
Resistor, 46...Digital-to-analog (D/A) converter, 50...Schmitt trigger circuit, 52
...analog-digital (A/D) converter,
100... Bidirectional drive circuit with speed servo, 200...
...Head transport mechanism, 300...Head position detection circuit, 8B-...Envelope detection circuit Fig. 3 Fig. 6 Fig. 7 Fig. 8 Fig. U Fig. 12 "o Fi Fig. 13 Figure 14

Claims (1)

[Scope of Claims] A reproducing head that reads signals from recording tracks formed at a plurality of annular track positions provided at a predetermined pitch on a rotating recording body, and transporting the reproducing head in a direction across the track positions. a head transport means, coupled to a portion of the head transport means supporting the playback head, the level varying to generate an error signal relative to the pitch as the playback head moves across the track position; head position detecting means for generating a head position signal that reaches a reference level when the reproducing head faces the center of the track position; and a head position detecting means for controlling a head moving means to move the reproducing head to a desired track position. a head movement control means for moving the playback head within a nearby range; when the playback head enters the vicinity range, the head movement control means is controlled to move the playback head according to the level of the head position signal; head positioning means for positioning the playback head so that the level of the head position signal converges to a predetermined value; envelope detection means for detecting an envelope of a signal read by the playback head from the recording track; means for storing the level of the error signal when the envelope reaches a peak value for a track as an error level for the recording track; and when tracking is performed for a desired recording track, the error level for the recording track is stored. A point where the level of the head position signal is read from the storage means and added to the level of the head position signal given from the head position detection means to the head positioning means, and the level of the head position signal deviates from the reference level by the error level. A rotating recording medium reproducing apparatus, comprising: tracking control means for positioning the reproducing head so as to converge on the reproducing head.