JPH03116544A - Track access control circuit for optical disk device - Google Patents

Abstract

PURPOSE:To compatibly provide both of stability and the follow-up characteristic to the track deviation at the time of fine control by lowering a servo band during the prescribed setting time upon switching to an operation state at the arrival at a target track. CONSTITUTION:The beam of an optical head 12 is made to follow up the target track by the double servo of putting the 1st and 2nd track servo means 18, 10 into a non-operation state and a speed control means 22 into an operation state to move the beam to the target track position by a 2nd track actuator 16 at the time of seeking, then of putting the speed control means 22 into the non-operation state and simultaneously putting the 1st and 2nd track servo means 18, 10 into the operation state at the time of arrival at the target track position. A servo band switching means 26 to lower the servo band during the prescribed setting time upon switching to the operation state at the arrival at the target track and to return the servo band to the original high servo band thereafter is provided in the 2nd track servo means 20 in this case. The stability at the time of the jumping of the fine control and the follow-up characteristic of the track deviation during the fine control are improved in this way.

Description

[Detailed Description of the Invention] [Summary Track servo control and VC of actuator with built-in co-head
M) Regarding the track access control circuit of an optical disk device that performs fine control using double servo and rack servo control, we investigated the stability when jumping from speed control to fine control using double servo using a seek operation, and the track access control circuit during fine control. In order to achieve both tracking performance against eccentricity, during the settling time until the unstable tracking error signal TBS stabilizes when switching from speed control to fine control, the servo band of the rack servo system (VCM) is adjusted. lower the servo band, and then return it to the original high servo band.

[Industrial Field of Application] The present invention relates to a track access control circuit for an optical disk device that performs fine control by dual servo control of a head built-in actuator and a rack servo control (VCM).

Optical disk devices have a large storage capacity because the track spacing can be set on the order of several microns, and have recently attracted attention as large-capacity storage devices for computer systems and the like.

Optical disks used as rotating media have rotational eccentricity due to various factors such as manufacturing, usage environment, loading conditions, etc., and tracking control to accurately follow a light beam on a track is essential.

This tracking control is normally performed by servo control of a track actuator mounted on the optical head.

However, in a track actuator such as a galvanometer mirror, the track range that can be tracked may be smaller than the range of track fluctuations due to eccentricity. In such a case, since tracking cannot be performed using only the actuator built into the head, a voice coil motor (hereinafter referred to as rVCMJ), which moves the optical head in the disk radial direction, is used.
That is, double servo control is performed to drive the positioner so as to follow the eccentricity of the track.

However, when double servo control is adopted, when the seek is completed and the VCM speed control is switched to fine control using double servo, the tracking error signal TES used for servo control of the actuator built in the head is
is unstable, and furthermore, the time during which the tracking error signal TBS is unstable becomes longer due to overshoot of the servo control of the positioner by the VCM. In order to solve this problem, if the positioner servo band is set low, the ability to follow track eccentricity during fine control decreases, and a device that can achieve both stability and followability is desired.

[Prior Art] Conventionally, in an optical disk device that performs a seek operation in which a beam is moved to a target track position by speed control of a VCM, a seek operation is performed at time 11, as shown in the beam movement speed diagram of FIG. 10, for example. When this starts, the fine control (on-track control) using double servo is switched to VCM speed control (positioner speed control).

This vCM speed control calculates the beam movement speed from the zero-crossing interval of the tracking error signal TES obtained from the medium reflected beam of the optical head, and generates the target speed according to the number of remaining tracks with respect to the target track, and generates a speed error between the two. The VCM is servo-controlled to minimize.

When the number of remaining tracks becomes zero and the target track position is reached at time t2 due to such VCM speed control, the beam is switched to fine control using double servo to make the beam on-track on the target track.

Here, the double servo control during fine control is the first servo control that controls the head built-in actuator to minimize the tracking error signal TBS, and the direction position detection signal L that indicates the position and direction of the head built-in actuator.
It is composed of a second servo control that controls the VCM so that PO3 is at a minimum (neutral position).

[Problems to be Solved by the Invention] However, in such a conventional device that performs fine control using double servo, when jumping from VCM speed control to fine control using double servo due to seek operation, If an attempt is made to increase the stability of the track eccentricity, the track eccentricity cannot be followed, and conversely, if the track eccentricity is improved, an unstable state occurs when fine control jumps in.

FIG. 11 shows the response when the servo band of the VCM servo circuit is increased. When the target track is reached and fine control is entered, beam hunting occurs and an unstable state 5 exists near the target track.

Figure 12 shows the response when the servo band of the VCM servo circuit is lowered. Although there is no unstable state near the target track, it is insufficient to follow track eccentricity, which is the purpose of double servo. This is the frequency response characteristic.

Furthermore, immediately after jumping into fine control at the end of access, the tracking error signal TES generated from the return light from the disk is also in an unstable state as shown in FIG. This period in which the tracking error signal TES is unstable occurs at the same time as the period in which the tracking error signal TES is unstable when the servo band of the VCM servo circuit shown in FIG. 11 is increased. Therefore, the unstable state of the vMC servo circuit cannot be compensated for by the servo circuit for the actuator built in the head.

Therefore, increasing the servo band of the VCM servo circuit improves responsiveness, but causes instability when jumping from VCM speed control to fine control, while lowering the servo band of the VCM servo circuit results in stability when jumping into fine control. Sexuality improves. However, the servo tracking range is ±50
It is about μm, but the read/write range is ±20 μm.
Since it is about m, the residual error of track eccentricity becomes large and read/write cannot be performed, and it is difficult to achieve both by simply setting the servo band.

The present invention has been made in view of these conventional problems, and provides an optical disc that can achieve both stability when switching from vCM speed control to fine control using double servo and responsiveness during fine control. The present invention is characterized by providing a track access control circuit for the device.

[Means to solve the problem] FIG. 1 is a diagram explaining the principle of the present invention.

In FIG. 1, an optical head 12 is provided for recording and reproducing information on tracks of a medium 10 that is rotated at a constant speed, and the optical head 12 includes a first track actuator that moves a light beam in a direction across the medium tracks. 14, drive means for, for example, a galvano mirror is provided.

Furthermore, the optical head 12 is connected to the second track actuator 1.
The medium 10 is moved in the radial direction by the VCM 6 .

A first track actuator 14 mounted on the optical head 12 receives a tracking error signal TBS obtained from the medium reflected beam by a first track servo means 18.
is controlled so that it is minimized.

Also, the VCM as the second track actuator 16
is controlled by the second track servo means 20 so that the direction position signal LPO8 indicating the direction and deviation from the neutral position of the first track actuator 14 is minimized.

Furthermore, VC as the second track actuator 16
A speed control means 22 is provided to control the speed of M and move the beam to the target track position.

The control means 24 then deactivates the first and second track servo means 18, 20 (servo-off) and activates the speed control means 22 (servo-on) at the time of seek, and the second track actuator 16 causes the optical The beam of the head 12 is moved to the target track position, and when the target track position is reached, the speed control means 22 is deactivated and at the same time the first and second track servo means 18, 20 are activated, so that the double servo to make the beam follow the target track.

In the present invention, for such an optical disk device, when the second track servo means 20 is switched to the operating state upon reaching the target track, the servo band is lowered for a predetermined settling time, and then the servo band is lowered to the original level. A servo band switching means 26 for returning to a higher servo band is provided.

Here, the servo band switching means 26 is configured to switch the leading phase start frequency of the phase compensation circuit provided in the second track servo means 20.

Also, the settling time when switching to the lower servo band is VCM
It is set based on the time it takes for the tracking error signal to stabilize after switching from speed control to fine control.

Note that the speed control means 22 outputs a racking error signal TBS.
The speed of the second track actuator 16, ie, VCM, is controlled so as to minimize the speed error between the beam movement speed based on the zero-crossing period of 1 and the target speed generated based on the number of remaining tracks relative to the target track.

[Function] According to the track access control circuit of the optical disk device according to the present invention having such a configuration, immediately after jumping from speed control to fine control using double servo, vCM
Since the servo band of the track servo circuit is switched to a lower servo band for a predetermined settling time, the VCM) rack servo will remain unstable until the tracking error signal TES, which is unstable due to jumping into fine control, is stabilized. After stable operation and the tracking error signal stabilizes, the servo band of the rack servo (VCM) is returned to the original high servo band to improve responsiveness, allowing the beam to accurately track the track eccentricity during fine control. This makes it possible to both improve anxiety during fine control diving and improve followability of track eccentricity during fine control.

[Embodiment] FIG. 2 is a block diagram showing an embodiment of the present invention.

In FIG. 2, reference numeral 10 denotes an optical disk as a medium, which is driven at a constant speed by a spindle motor 28, e.g.
It is rotating at 0 rpm. An optical head 12 is provided on the optical disc 10 so as to be movable in the radial direction. This optical head 12 has a configuration shown in FIG. 3, for example.

In FIG. 3, a semiconductor laser 32 is provided in an optical head 12 mounted on a positioner 30 that is movable in the radial direction, and the laser light from the semiconductor laser 32 is converted into a flat beam by a collimator lens 34. The beam passes through the beam splitter 36 and the λ/4 plate 38, is further reflected by the galvanometer mirror 40, is focused into a minute beam spot by the objective lens 42, and is irradiated onto the optical disk 10. Further, the return light reflected by the optical disk 10 is transmitted to the objective lens 4.
2. The light passes through the galvanometer mirror 40 and the λ/4 plate 38, and enters the polarizing beam splitter 36, where it is split into orthogonal directions. A portion of this returned light is reflected by the half mirror 44, enters the light receiving section 48 by the condensing lens 46, and is RF
Obtain the reproduced signal RFS. Furthermore, the beam transmitted through the half mirror 44 is reflected by a critical angle prism 50 and enters a four-split photodetector 52, and a tracking error signal TBS and a focus error signal FES are generated based on the received light output of the four-split photodetector.

The objective lens 42 is driven vertically by a focus actuator 54 to form an optimal beam spot on the optical disc 10 .

Further, the galvano mirror 40 is connected to the track actuator 5.
6, and can move a light beam in a direction across the tracks on the optical disk 10 via the objective lens 42. Here, the track actuator 56
The track range of the beam that can be driven by the galvanometer mirror 40 is, for example, within 30 microns. On the other hand, the range of track variation due to eccentricity in a normal optical disk 10 is around 50 microns at most, and the beam cannot follow the track eccentricity only by driving the galvanomirror 40 by the track actuator 56.
Dual servo control is performed in which the second track servo is applied by driving the positioner by vCM, which will be explained later.

Furthermore, a position sensor 58 is provided for the galvanometer mirror 40. The position sensor 58 has a neutral position where the drive current of the track actuator 56 is zero as a reference position, and is used to detect a direction position signal LPO8 corresponding to the direction and amount of movement of the galvanomirror 40 with respect to the neutral position. The position sensor 58 may be a sensor that optically detects the movement of the galvano mirror 40, or a potentiometer that mechanically detects the movement of the galvano mirror 40.

Referring again to FIG. 2, the optical head 12 is provided with a VCM 16 as a second track actuator. In contrast, the track actuator 56 of the galvano mirror 40 shown in FIG. 3 is positioned as the first track actuator.

A first track servo circuit 18 is composed of a tracking error detection circuit 60 and a phase compensation circuit 62.

The tracking error detection circuit 60 detects a tracking error signal TBS based on the light reception output of the four-split light receiver 52 provided in the optical head 12.

FIG. 4 is a block diagram showing one embodiment of the tracking error detection circuit 60.

In FIG. 4, a 4-split light receiver 52 provided on the optical head 12 has four light receiving sections A, B, C, and D, and the θ-order diffracted light of the return light from the optical disk 10 and the 1st-order light are reflected on the light receiving surface. The light reception pattern created by combining the folded lights is imaged,
Light receiving part A in on-track condition.

When the amounts of light received by D, B, and C become equal, and the beam deviates from the track, one increases and the other decreases. The light-receiving outputs of the light-receiving parts A and D of the four-division light receiver 52 are added together via resistors R1 and R2, and the sum is applied to the non-inverting input terminal of the differential amplifier 64.

Furthermore, the light receiving parts B and C are added together via resistors R3 and R4,
It is connected to the inverting input terminal of the differential amplifier 64 to which the input resistor R6 is connected. The differential amplifier 64 has a feedback resistor R5 at its output and non-inverting input terminal, and the gain is determined by the feedback resistor R5 and the input resistor R6. The differential amplifier 64 outputs a difference signal between the combined light reception signal of the light receiving sections A and D and the combined light reception signal of the light receiving sections B and C as a tracking error signal TES.

Therefore, if the beam crosses the track during seek, the fifth
A tracking error signal TBS that changes as shown in Figure (a) is obtained.

Referring again to FIG. 2, a phase compensation circuit 62 provided subsequent to the tracking error detection circuit 60 performs phase lead compensation in the high frequency portion of the servo band in order to improve the stability of servo control. Since this phase lead compensation simultaneously raises the gain, the steady response characteristics can also be improved as a result. The output of the phase compensation circuit 62 is given to the power amplifier 68 via the switch S1 of the control switch circuit 66, and the power amplifier 68 outputs the tracking error signal T.
The galvanometer mirror 40 is controlled by driving a track actuator 56 built into the optical head 12 based on the BS.

A second track servo circuit 20 is composed of a direction position signal detection circuit 70 and a phase compensation circuit 72.

The direction position signal detection circuit 70 includes a position sensor 5 that detects the position of the galvanometer mirror 40 provided on the optical head 12.
8 is input, and a direction position signal LPO8 indicating the amount and direction of deviation of the galvanometer mirror 40 from the neutral position is output.

FIG. 6 is an embodiment configuration diagram showing one embodiment of the direction position detection circuit 70, in which two light receiving parts A are used as the position sensor 58.
, D is used. Specifically, a slit plate is fixed on the side of the galvanometer mirror 40, and light from a light emitting diode is irradiated onto the slit side of the slit plate and received by a two-split light receiver serving as a position sensor 58. When the galvano mirror 40 is at the neutral position, the amount of light received by the two light receiving sections A and D is equal, but when the galvano mirror 40 is rotated from the neutral position, the amount of light received by one increases and the amount of light received by the other decreases. I come to do it.

Light receiving parts A and D of a two-split light receiver as a position sensor 58
The received light output is input to the differential amplifier 74 via resistors R7 and R8, respectively. The differential amplifier 74 has an input resistance R
9 and a feedback resistor RIO.

For example, as shown in the characteristic diagram of FIG. 7, the differential amplifier 74 increases in the positive direction when the beam is driven toward the outer side by the galvanomirror 40, changes in the negative direction when the beam is driven toward the inner side, and increases at the neutral position. A direction position detection signal LPO3 of 0 volts is output.

Referring again to FIG. 2, a phase compensation circuit 72 is provided following the direction and position signal detection circuit 70. Basically, this phase compensation circuit 72, similar to the phase compensation circuit 62 on the first servo control circuit 18 side, performs phase lead compensation on the high frequency portion of the servo band in the track servo, thereby improving stability and responsiveness. The points are basically the same.

However, in the present invention, the phase compensation circuit 72 provided in the second track servo circuit 20 controls the servo control when jumping from VCM speed control (positioner speed control) to fine control using double servo during a seek operation. A servo band switching means is provided for switching the band to a low servo band for a predetermined established time and then returning to the original high servo band.

FIG. 8 is an embodiment configuration diagram showing an embodiment of the phase compensation circuit 72 provided in the second track servo circuit 20, and is a servo band switching circuit that switches the servo band into two, a high band and a low band. It is equipped with 26.

In FIG. 8, 76 is a differential amplifier, and resistor R16
A direction position detection signal LPO8 is inputted to the non-inverting input terminal via. A servo band switching circuit 26 is provided at the inverting input terminal of the differential amplifier 76, and is connected to a high band setting circuit 80 via a changeover switch 78.
A low band setting circuit 84 is connected via 2.

The high band setting circuit 80 is composed of a series circuit of a capacitor C1 and a resistor R14, and a resistor R12 connected in parallel.

Similarly, the low band setting circuit 84 is constructed by connecting a resistor R1 in parallel to a series circuit of a capacitor C2 and a resistor R15.

The changeover signal C1 is directly applied to the changeover switch 78, and the changeover signal C1 is inverted by an inverter 86 and applied to the changeover switch 82.

Therefore, when the changeover switch 78 is on, the changeover switch 8
2 is off, when the changeover switch 78 is off, the changeover switch 8
2 is turned on.

High band setting circuit 80 and low band setting circuit 84 shown in FIG.
The compensation characteristics of the phase compensation circuit 72 are as shown in the following table.

As is clear from this table, the gain is determined by the feedback resistor R11 and the resistor R12 or R13 of each setting circuit 80,84. Also, the phase lead start frequency is R for high bands.
The circuit constants are determined by the time constants of R14XC1 and R15XC2 for the low band, and each circuit constant is naturally determined so that the time constant of the high band is larger than the time constant of the low band. Furthermore, the degree of advance of the phase degree is determined by the resistors R14 and R1 of each setting circuit 80.84.
Determined by the value of 5.

Therefore, in the present invention, the servo band is set to a high band so that each characteristic of the high servo band can sufficiently follow track eccentricity during fine control using double servo. On the other hand, for low servo band, vCM
The servo band is set to be low enough to have a large gain margin and phase margin that will not cause beam instability when switching from speed control to fine control using double servo.

Referring again to FIG. 2, the output of the phase compensation circuit 72 is applied to the power amplifier 90 via the switch S2 provided in the control switch circuit 66 and the adder 88, which outputs the output from the phase compensation circuit 72 based on the direction position detection signal LPO8. Tracking control of the optical head 12 is performed by driving the VCM 16 with the output of the optical head 90.

Next, when seeking, the speed of the VCM 16 is controlled and the optical head 12
In this embodiment, the speed control means for moving the beam to the target track position is realized by program control by the MPU 100. A zero cross comparator 92, a DA converter 94, and an adder 88 are provided for VCM speed control by the MPU 100.

The zero cross comparator 92 receives the tracking error signal TES output from the tracking error detection circuit 60.
Outputs a signal that is inverted at the zero crossing of That is, during VCM speed control by seek operation, the tracking error signal TES shown in FIG. 5(a) is obtained, and by inputting this to the zero cross comparator 92, a comparison output shown in FIG. Enter. MPUl
00, for example, the falling cycle T of the comparison output shown in FIG. The beam moving speed V is calculated by dividing by the zero crossing time T. Further, the output of the zero cross comparator 92 shown in FIG. 5(b) indicates the passage of one track at the falling timing of the comparison output, and therefore a track cross swing pulse can be obtained from the output of the zero cross comparator 92. MPU1
00, the current number of remaining tracks can be calculated by subtracting the sequentially obtained tracking cross pulses from the number of remaining tracks from the initial position to the target track position. The calculation result of the number of remaining tracks for this target track is used to generate a target speed in VCM speed control. That is, a target track table having a target speed corresponding to the number of remaining tracks with respect to the target track is prepared in advance in MPUIQQ, and the corresponding target speed vT is calculated from the number of remaining tracks detected at that time by the track crossing swing pulse. .

Then, the velocity error V is obtained by subtracting the beam velocity V calculated at that time from the target velocity VA, and this velocity error data vE is set in the DA converter 94 and converted into an analog signal, thereby driving the drive by the power amplifier 90. The speed of the VCM 16 is controlled so that the speed error vE is minimized, that is, the target speed Va is achieved.

Next, the seek operation according to the present invention will be explained with reference to the operation flow diagram of FIG.

In FIG. 9, first, when a seek command is given to the MPU 100, in step SL (hereinafter, steps are omitted), tracking is performed by the galvano track servo, that is, the galvano mirror mounted on the optical head 12 by the first track servo circuit 18. Turn off control. Specifically, the MPU 100 turns off the switch S1 provided in the control switch circuit 66.

Next, in S2, the 70M track servo is turned off.

That is, 70M16 by the second track servo circuit 20
Turn off tracking control. Specifically, MPU10
0 turns off the switch S2 provided in the control switch circuit 66.

Next, the process advances to S3 and VCM speed control is turned on.

Turning on the VCM speed control means that the VCM speed control function provided in the MPU 100 under program control is activated.

When VCM speed control is turned on in S3, MPU
Reference numeral 100 sets an accelerating voltage in the DA converter 94, and drives the VCM 16 with the maximum current by the power amplifier 90 to increase the moving speed of the optical head 12 toward the target speed.

In S5, it is checked whether the beam speed after setting the acceleration voltage reaches the target speed. When the beam speed reaches the target speed, the process proceeds to 86, where the acceleration voltage for the DA converter 94 is returned to 0, and so-called open loop control is performed. The system then shifts to closed-loop control based on speed error.

That is, in S7, the beam velocity V at that time is detected from the zero-crossing interval of the tracking error signal TES obtained by the zero-crossing comparator 92, and then in S8, the number of remaining tracks relative to the target track is obtained based on the track-crossing swing pulse. , a target speed v7 corresponding to the number of remaining tracks is read (Va may be constant), and a speed error Vt given by the speed difference from the speed V detected in S7 is detected. Next, DA converter 9 on S9
4, the speed error V is set, the data is converted to an analog voltage, and the data is applied to the power amplifier 90 via the adder 88 to obtain the speed difference V. Based on this, the speed of the VCM 16 is controlled to maintain the target speed Va at that time.

Next, in S10, it is monitored whether the remaining tracks are zero or not.
The processes from 87 to S9 are repeated until the number of remaining tracks becomes zero.

When the beam reaches the target track and the number of remaining tracks becomes zero, the process proceeds from S10 to Sll, where the VCM speed control is ended and the galvanometer mirror built into the optical head 12 is activated by the galvano track servo, that is, the first track servo circuit 18. Turn on tracking control. Specifically, M
The PU 100 turns on the switch S1 of the control switch circuit 66.

Subsequently, the MPU 100 outputs a switching signal C1 for setting the servo band to the low band LO to the phase compensation circuit 72 provided in the second track servo circuit 20. This switching signal C1 is, for example, an L level signal, so that the changeover switch 82 in the phase compensation circuit 72 shown in FIG. can get.

Next, the process proceeds to S13, where the 70M track servo, that is, the second
The track control of the VCM 16 by the track servo circuit 20 is turned on. Specifically, the MPU 100 turns on the switch S2 of the control switch circuit 66. Therefore, VCMI
6 is a response of the rack servo (VCM) in which tracking control is performed to minimize the direction position detection signal LPO8 that has undergone phase compensation due to the low servo band set in the phase compensation circuit 72, and the servo band is low. The beam can be moved to the target track without causing instability.

After turning on the rack servo (VCM) in S13, the next 81
4, wait for a predetermined establishment time and maintain the state of switching to the lower servo band. This establishment time is the tracking error signal T when jumping from VCM speed control to fine control.
This is predetermined based on the time it takes for the ES to stabilize, and is, for example, about 2 to 3 ms.

When the establishment time has elapsed in S14, the process proceeds to the next step 815, where it is determined that the unstable state caused by jumping into fine control has been overcome, and the 76M track servo band is set to a high band. Specifically, by setting the switching signal C1 for the phase compensation circuit 72 to H level, the changeover switch 82 shown in FIG. 8 is turned off, and by turning on the changeover switch 78, the high band setting circuit 80 is enabled and the high servo Switch to band. For this reason, after the unstable state immediately after switching from speed control to fine control, phase compensation is applied that extends to a high servo band that can sufficiently follow the amount of track eccentricity, and the galvano track servo is switched between the galvano track servo and the rack servo (VCM). The heavy servo allows the beam to accurately follow the track without being affected by the amount of track eccentricity.

Although the above embodiment uses a galvano mirror as a track actuator built into an optical head, the present invention is not limited to a galvano mirror, and the present invention is not limited to a galvano mirror, but can also be applied to track movement of a beam using an actuator built into the head. The present invention can be applied as is to optical disk devices whose range is smaller than the track movement range due to eccentricity.

[Effects of the Invention] As explained above, according to the present invention, by switching the servo band of vCM servo control, beam stability can be compensated for when switching to speed control by seek operation or fine control by double servo, and at the same time. , it is possible to improve the beam tracking performance for track eccentricity during fine control, and it is possible to realize track access using double servo that achieves both stable access operation and good eccentricity tracking performance.

[Brief explanation of drawings]

Fig. 1 is a diagram explaining the principle of the present invention; Fig. 2 is a block diagram of an embodiment of the present invention; Fig. 3 is a block diagram of an embodiment of the optical head of the present invention; Fig. 4 is a block diagram of a tracking error detection circuit of the present invention. ; Fig. 5 is an explanatory diagram of tracking error signal and speed detection; Fig. 6 is a configuration diagram of the direction position signal detection circuit of the present invention; Fig. 7
The figure is a characteristic diagram of the direction position detection circuit; Figure 8 is a configuration diagram of an embodiment of servo band switching of the present invention; Figure 9
The figure is an operation flow diagram of the present invention; Figure 10 is a beam movement speed diagram during seek; Figure 11 is an explanatory diagram of the response when the servo band is high; Figure 12 is an explanatory diagram of the response when the servo band is low; FIG. 13 is an explanatory diagram of a tracking error signal when a seek is completed. In the figure, 10: Medium (optical disk) 12: Optical head 14: First track actuator 16: Second track actuator (voice coil motor VCM) 18: First track servo means (circuit) 20: Second track Servo means (circuit) 22: Speed control means 24: Control means 26: Servo band switching means (circuit) 28 Spindle motor 30: Positioner 32: Semiconductor laser 40: Galvano mirror 42: Objective lens 52: 4-split light receiver 56: Actuator 58: Position sensor (2-split photoreceiver) 60 Ni tracker detection circuit 62.72: Phase compensation circuit 64.74, 76: Differential amplifier 68.90: Power amplifier 70 Two-way position signal detection circuit 78.82: Switch circuit 80: High band setting circuit 84: Low band setting circuit 86: Inverter 88: Adder 92: Zero cross comparator 94: DA converter 100: MPU

Claims (3)

[Claims] (1) An optical head (12) for optically recording and reproducing information on the tracks of a medium (10) rotating at a constant speed; mounted on the optical head (12) and directing a light beam to the tracks of the rotating medium. a first track actuator (14) for moving the optical head (12) in a radial direction of the rotating medium (10); and a second track actuator (16) for moving the optical head (12) in a radial direction of the rotating medium (10).
and; first track servo means (18) for controlling the first track actuator so that a tracking error signal (TES) obtained from the medium reflected beam of the optical head is minimized; ) a second track servo that controls the second track actuator (16) so that a direction position detection signal (LPOS) indicating the deviation from the neutral position and direction of the first track actuator (LPOS) provided in the first track actuator (16) is minimized; means (20); speed control means (22) for controlling the speed of the second track actuator to move it to a target track position;
8, 20) are inactivated and the speed control means (22) is activated to move the beam of the optical head (12) to the target track position by the second track actuator (16). when the speed control means (22) is inactivated, the first and second track servo means (18, 20)
and a control means (24) for causing the beam to follow the target track by means of a double servo; 1. A track access control device for an optical disk device, characterized in that a servo band switching means (26) is provided for lowering the servo band for a predetermined settling time when the servo band changes, and then returning it to the original high servo band. (2) The servo band switching means (26) switches an advanced phase start frequency of a phase compensation circuit provided in the second track servo means (20).
A track access control circuit for the optical disc device described above. (3) During the settling time when the servo band switching means (26) switches to a lower servo band, the unstable tracking error signal (TES) is stabilized by switching from speed control to fine control using double servo. 2. The track access control circuit for an optical disc device according to claim 1, wherein the track access control circuit is set based on the time until the start of the track access control circuit.