JPH10134380A - Tracking control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance tracking control pull-in performance without always widening a tracking control band by raising a gain of a D signal component generating system of a PID control system during the time from immediately after operating a tracking control means to control of a tracking control system. SOLUTION: At the time of operating the tracking control, a terminal (a) of a microcomputer 201 is made to be H level to operate switches 133 and 139 to connect with their respective terminals (b) and (a). Consequently, a digital filter 204 is released from its clear state, and a focusing lens 103 is driven in accordance with a TE signal. The level change of the terminal (a) from L level to H level is detected by a timer 209 to make its terminal (b) H level during a prescribed period of time from the point of this changing time. After a lapse of the prescribed time, the gain of the D signal component generating system becomes a normal gain. Consequently, the normal tracking control is carried out. In other words, the control band is widened during the prescribed period of time, thus enhancing the tracking control pull-in performance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tracking control device for positioning a head when recording or reproducing information on a disk having a large number of information tracks by using a semiconductor laser or the like.

[0002]

2. Description of the Related Art A conventional tracking control device will be described with reference to FIG.

FIG. 18 is a block diagram of a conventional tracking control device. The disk 100 is mounted on a rotating shaft 102 of a motor 101 and rotates at a predetermined rotation speed.

A transfer table 115 has a laser 109, a coupling lens 108, a polarizing beam splitter 110,
/ 4 wavelength plate 107, total reflection mirror 105, photodetector 113,
Actuator 104 is attached and transfer table 1
Reference numeral 15 is configured to move in the radial direction of the disk 100 by a transfer motor 103 such as a DC motor.

[0005] The laser 10 attached to the transfer table 115
The light beam generated from 9 is coupled to the coupling lens 108.
After being collimated by the polarization beam splitter 110,
The light passes through the 波長 wavelength plate 107, is reflected by the total reflection mirror 105, is focused on the information surface of the disk 100 by the focusing lens 103, and is irradiated.

The light reflected by the information surface of the disc 100 passes through a converging lens 103 and passes through a total reflection mirror 105.
The light passes through a quarter-wave plate 107, a polarizing beam splitter 110, a detection lens 111, and a cylindrical lens 112 to irradiate a four-divided photodetector 113. The focusing lens 103 is attached to a movable portion of the actuator 104. The actuator 104 comprises a focusing coil, a tracking coil, a focusing permanent magnet, and a tracking permanent magnet. Therefore, when a voltage is applied to the focusing coil (not shown) of the actuator 104 by using the power amplifier 127, a current flows through the coil, and the coil is magnetized from a permanent magnet (not shown) for focusing. Receive strength. Therefore, the focusing lens 103 moves in a direction perpendicular to the surface of the disk 100 (vertical direction in the figure). The focusing lens 103 always keeps the focus of the light beam on the disc 10 based on a focus error signal indicating a deviation between the focus of the light beam and the information surface of the disc.
0 is controlled to be located on the information surface.

When a voltage is applied to the tracking coil (not shown) using the power amplifier 128, a current flows through the coil and receives a magnetic force from a tracking permanent magnet (not shown). Therefore, the focusing lens 103
Is the radial direction of the disk 100, that is, the disk 100
Move across the upper track (left and right in the figure).

The reflected light from the disk irradiated onto the photodetector 113 is converted into a current by the photodetector 113 divided into four parts, and is converted into I / V converters 116 and 117.
118 and 119 are input. I / V converter 116, 1
17, 118 and 119 convert an input current into a voltage according to the current level. Adders 120, 121,
123 and 124 add the input signals. Differential amplifier 12
2 calculates the difference between the input voltages and outputs the calculated value. The optical system shown in FIG. 18 constitutes a focus error detection method generally called an astigmatism method. Therefore, the output of the differential amplifier 122 is different from the focus of the light beam 106 and the disk 1
It becomes a focus error signal (hereinafter, referred to as an FE signal) indicating a deviation from the information surface of No. 00. The FE signal is sent to the power amplifier 127 via the phase compensation circuit 126. A current flows through the focusing coil of the actuator 104 by the power amplifier 127. The phase compensation circuit 126 stabilizes the focus control system. Since the focusing lens 103 is driven according to the FE signal, the focal point of the light beam is always located on the information surface.

The differential amplifier 125 calculates the difference between the input voltages and outputs the calculated value. The optical system shown in FIG. 18 constitutes a tracking error detection method generally called a push-pull method. Accordingly, the output of the differential amplifier 125 becomes a tracking error signal (hereinafter, referred to as a TE signal) indicating a deviation between the focus of the light beam 106 and the track of the disk 100. The TE signal is supplied to the phase compensation circuit 180,
The signal is sent to the power amplifier 128 via the switch 133. A current flows through the tracking coil of the actuator 104 by the power amplifier 128. Phase compensation circuit 18
0 stabilizes the tracking control system. Since the focusing lens 103 is driven according to the TE signal, the focal point of the light beam is always located on the track. The TE signal is supplied to the power amplifier 12 through the low-pass filter 140 and the switch 139.
9 Therefore, the transfer motor 114 is controlled according to the low frequency component of the TE signal. That is, in the tracking control system, the actuator 104 follows a disturbance of a high frequency, and the transfer motor 114 such as a DC motor follows a disturbance of a low frequency component.

Since a large number of tracks are formed on the disk 100, a search for moving the focal point of the beam 106 to a target track is performed. The search will be described. The search is performed according to the following procedure. First, the switches 133, 1
The tracking control is disabled by connecting the terminal a and the terminal c at 39. Next, a predetermined value is set in the D / A converter 202 and the transfer motor 114 is driven to send the transfer table 115 to a target track. When the target track is reached, the tracking control is operated again. By the way, when the transfer motor 114 arrives at the target track,
Even if the driving voltage is switched to the low frequency component of the TE signal, the transfer table 115 does not completely stop due to inertia.

The operation at the time when a target track is reached will be described with reference to FIG. (A) shows the state of the actuator 104 when the transfer table 115 reaches the target track. The horizontal direction in the figure corresponds to the radial direction of the disk. It is assumed that the transfer table 115 has moved from the left side to the right side during the search. When the transfer table 115 reaches a target track, the focusing lens 103 is at the center position.
That is, the lengths of the springs 1 and 2 are equal. In this state, the tracking control starts operating. However, as described above, since the transfer table 115 cannot be stopped suddenly, it moves to the right. The movement of the transfer table 115 becomes a disturbance for the tracking control system. Therefore, the focusing lens 103 follows the target track, and the spring 1 is shortened and the spring 2 is extended. Further, the control error E increases according to the amount of disturbance.

[0012]

When the drive voltage of the transfer motor 114 is switched to the low frequency component of the TE signal when the target track is reached, the transfer table 115 does not stop completely due to inertia. Therefore, when the tracking performance of the tracking control system is low, the control error E increases, and the light beam cannot follow the target track. In order to reduce the control error, it is conceivable to widen the control band of the tracking control. However, noise included in the TE signal is amplified, and an excessive current always flows through the tracking coil, causing a problem such as burning of the coil. Therefore, the control band of the tracking control cannot always be expanded.

Further, there is a case where the state shown in FIG. In this state, when the tracking control system is deactivated and the current flowing through the tracking coil is reduced to zero, the focusing lens 103 moves toward the center position by a spring. The center position is the state shown in FIG. Ordinary actuators have characteristics that easily vibrate at a natural frequency. Therefore, the focusing lens 103 starts oscillating in the radial direction of the disk at the natural frequency when the current becomes zero. If the displacement of the focusing lens 103 immediately before the search is large, the vibration continues even when the target track is reached. Since this vibration causes disturbance in the tracking control system, the pull-in of the tracking control becomes unstable.

In view of the above problems, an object of the present invention is to provide a tracking control device capable of stably pulling in tracking control without completely stopping the transfer table 115 due to inertia.

It is another object of the present invention to provide a tracking control device capable of reducing the vibration at the time of reaching a target track and stably pulling in tracking control even when the displacement of the focusing lens 103 immediately before the search is large.

[0016]

In order to achieve the above object, a tracking control device according to a first aspect of the present invention comprises a track deviation detecting means for detecting a positional deviation between a light beam irradiated on an information surface of a disk and a track. Moving means for moving the light beam across the track, tracking control means for performing PID control of the moving means so that the light beam is on the track based on the output of the track shift detecting means, Search means for moving the light beam to another track by disabling the tracking control means, and the search means completes the operation,
Immediately after operating the tracking control means until the tracking control system settles, the DID of the PID control
The gain of the signal component generation system is increased.

According to a second aspect of the present invention, in the tracking control apparatus according to the first aspect, it is determined that the tracking control system has settled when a predetermined time has elapsed.

According to a third aspect of the present invention, there is provided a tracking control device, comprising: a track shift detecting means for detecting a shift between a light beam irradiated on an information surface of a disk and a track;
A first moving means for moving the light beam across the track, a second moving means for moving the first moving means across the track, and Tracking control means for driving the first moving means to control the light beam to be positioned on the track; and disabling the tracking control means to drive the second moving means to drive another track. And a driving value M of the first moving unit immediately before the searching unit starts operating.
And the initial value is set to M when the search means starts operating.
And driving means for driving the first moving means with a gradually decreasing drive value.

According to a fourth aspect of the present invention, there is provided a tracking control device, comprising: a track shift detecting means for detecting a position shift between a light beam irradiated on an information surface of a disk and a track;
A first moving means for moving the light beam across the track, a second moving means for moving the first moving means across the track, and Tracking control means for driving the first moving means so that the light beam is positioned on the track; and relative control for detecting the relative speed of the light beam with respect to the track based on the output signal of the track deviation detecting means. A search for moving the light beam to another track by driving the first and second moving means based on an output signal of the relative speed detecting means with the speed detecting means and the tracking control means in an inactive state; Means for storing the driving value N of the first moving means immediately before the search means completes the operation, and the tracking control means starts the operation. The drive value gradually decreases the initial value of N is obtained so as to sum the drive value of the tracking control means.

According to a fifth aspect of the present invention, there is provided a tracking control device, comprising: a track shift detecting means for detecting a position shift between a light beam irradiated on an information surface of a disk and a track;
A first moving means for moving the light beam across the track, a second moving means for moving the first moving means across the track, and Tracking control means for driving the first moving means to perform PID control so that the light beam is positioned on the track; and detecting a relative speed of the light beam with respect to the track based on an output signal of the track deviation detecting means. Making the relative speed detecting means and the tracking control means inoperative, driving the first and second moving means based on the output signal of the relative speed detecting means to move the light beam to another track; Search means for storing a drive value N of the first moving means immediately before the search means completes the operation, and the tracking control means to start the operation. Then in which the initial value of the integrator of the I signal producing system of the PID control and to set to a value corresponding to N.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The tracking control device of the present invention can stably pull in tracking control even if the transfer table 115 does not stop completely due to inertia. Further, even when the displacement of the focusing lens 103 immediately before the search is large, the vibration at the time of reaching the target track can be reduced.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. (Embodiment 1) Hereinafter, a tracking control device according to Embodiment 1 of the present invention will be described with reference to FIG. The same blocks as those in the conventional example shown in FIG. 18 are denoted by the same reference numerals, and description thereof will be omitted. The TE signal is converted into a digital signal by the analog / digital converter 203. Hereinafter, it is described as an A / D converter. A / D
The output value of converter 203 is sent to digital filter 204. The digital filter 204 is a phase compensation circuit and stabilizes the tracking control system. The phase compensation circuit implements a PID operation for performing a proportional operation, an integral operation, and a differential operation. P corresponds to a proportional operation, I corresponds to an integral operation, and D corresponds to a differential operation. The digital filter 204 is in a clear state when the terminal c is at a low level. When the terminal d goes high, the gain of the I signal component generation system in the PID operation increases. The output of the digital filter 204 is sent to the power amplifier 128 via the digital / analog converter 205 and the switch 133. Power amplifier 128
As a result, a current flows through the tracking coil of the actuator 104. Hereinafter, the digital / analog converter is referred to as D
/ A converter. The binarization circuit 206 converts the TE signal to a high level or a low level based on the zero level. The counter 207 counts the rising edge of the signal input to the terminal a. The count value is output from terminal b. When the terminal c is at the high level, the count value is cleared. The comparator 208 sets the terminal c to a high level when the data input to the terminal a is equal to the data input to the terminal b. When the terminal a changes from the low level to the high level, the timer 209 sets the terminal b to the high level for a period of time Tup from that point. Therefore, the gain of the I signal component generation system of the digital filter 204 described above increases.

Next, the digital filter 204 will be described. FIG. 2 shows a block diagram of the digital filter 204 shown in FIG. 2, an input terminal 300 is connected to the A / D converter 203 of FIG.
1, terminal 316 is connected to the D / A converter 205, and terminal 321 is connected to the terminal b of the timer 209. In the switches 303 and 314, the terminal a and the terminal b are connected when the terminal d is at a high level, and the terminals a and c are connected when the terminal d is at a low level. The switch 303 switches the input signal of the filter to a digitally converted TE signal or zero. The switch 314 switches and outputs an input signal or an output signal of the multiplier 313. Adder 3
04, 315 and 317 add and output the input signals. The subtractor 312 subtracts the input signal and outputs the result. Multipliers 311, 313, and 319 multiply input signals by coefficients and output the result. The digital filter 204 operates in synchronization with the rising edge of the reference clock CLK having a period T, and the delay circuits 310 and 318 delay the input signal by the period T and output the delayed signal. The delay circuits 310 and 318 convert the digital data input to the terminal a into the reference clock CL.
A random access memory (RAM) is stored in synchronization with the rising edge of K and output from a terminal b. Hereinafter, the RAM of the delay unit 318 is referred to as RAM1,
The RAM of the delay unit 310 is called RAM2. A block A indicated by a dotted line of the digital filter 204 is a phase delay compensation filter for increasing the low-frequency gain of the tracking control system. Block A is an I signal generation system and is an integrator. Block B is a phase lead compensation filter for securing a phase margin near the gain intersection. Block B is D
It is a signal generation system. That is, the digital filter 204 is a phase compensation filter for realizing a PID control system. The values stored in the delay circuits 310 and 318 are cleared when the terminal c becomes low level. That is, the operation of the delay is stopped.

FIG. 3 shows gain and phase characteristics of the digital filter 204. It is a characteristic diagram generally called a Bode diagram. The solid line indicates the characteristic when the terminal 321 is at a low level, and the dotted line indicates the characteristic when the terminal 321 is at a high level. The characteristic (a) is the characteristic of the block A, and the characteristic (b) is the block B
The characteristics (c) are the characteristics of block A, block B and P
The overall characteristics obtained by adding the signals are shown. Note that the vertical axis indicates gain and phase, and the horizontal axis indicates frequency. The characteristic (a) of block A indicates integration and the slope of gain is -2.
0 dB / dec. The characteristic (b) of block B
Is approximately 20 dB / dec.
Becomes The frequency fg1 shown in the characteristic (c) is the gain intersection point of the tracking control system, and the phase lead is maximized at that frequency to secure a phase margin. The effect of the phase delay compensation filter of the block A appears below the frequency fl, and the phase is delayed accordingly. Generally, fg1 is set to several hundred Hz to several kHz. When the terminal 321 is at the high level, the gain of the block B, which is the D signal component generation system, increases. The gain difference corresponds to the coefficient value of multiplier 313. For example, when the coefficient value of the multiplier 313 is 2, the gain is increased by 6 dB. In the following, description will be made assuming that the coefficient is 2.

Next, the characteristics of the actuator 104 will be described. FIG. 4 shows frequency characteristics of the actuator 104. It is a diagram generally called a Bode diagram. The horizontal axis indicates frequency. The vertical axis of the characteristic diagram (a) indicates the gain. The vertical axis of the characteristic diagram (b) indicates the phase. The focusing lens 103 of the actuator 104 is attached to the transfer table 115 via a spring. In addition, a viscous substance such as rubber is attached to the spring. The current flowing through the coil by the power amplifier 128 is defined as i, and the position of the focusing lens 103 is defined as x.
Then, the relationship between x and i can be expressed by the differential equation of (Equation 1).

[0026]

(Equation 1)

W is generally called a natural angular frequency, and a is called an attenuation rate. When (Equation 1) is represented by a Bode diagram, the Bode diagram of FIG. 4 described above is obtained. Therefore, if the frequency is 50Hz
, The gain becomes higher and the phase becomes -90 degrees. Also, 5
At frequencies lower than 0 Hz, the sensitivity is constant regardless of the frequency, and there is no phase delay. At frequencies higher than 50 Hz, the slope is -40 dB / dec. In the present embodiment, the natural frequency is set to 50 Hz as an example.

The tracking control will be described. When operating the tracking control, the microcomputer 201 sets the terminal a to the high level and connects the terminals b and a of the switches 133 and 139. Therefore, digital filter 2
04 clears the clear state and the focusing lens 103
It is driven according to the E signal. Timer 209 is connected to terminal a
Is changed from the low level to the high level, and the terminal b is set to the high level during the time Tup from that point. After the elapse of the time Tup, the D signal component generation system has a normal gain. Therefore, normal tracking control is performed. The open loop characteristic of the tracking control system will be described with reference to FIG. The solid line indicates the characteristic when the terminal 321 is at a low level, and the dotted line indicates the characteristic when the terminal 321 is at a high level.
The characteristic diagram (a) shows the gain characteristic. The characteristic diagram (b) shows the phase characteristic. The horizontal axis indicates frequency. The vertical axis of the characteristic diagram (a) indicates the gain. The vertical axis of the characteristic diagram (b) indicates the phase. The open loop characteristic of the tracking control system is a characteristic obtained by multiplying the transfer function of the digital filter 204 by the transfer function of the actuator 104. Therefore, the gain increases at frequencies below fl and the phase advances at frequencies near fg1. When the terminal 321 indicated by the dotted line is at a high level, the level of the D signal component is high, so that the gain near the gain intersection is high. Therefore, the gain intersection changes from fg1 to fg2. That is, the control band is widened. Since the phase advances, a sufficient phase margin can be secured and the control system does not become unstable. That is, the control band is widened during the time Tup, and the pull-in performance of the tracking control is improved.

Next, the search will be described. FIG. 6B shows the TE signal when the light beam crosses the track. The schematic diagram (a) shows a truck. The TE signal is
Zero between track center and track. The waveform (c) shows the output signal of the binarization circuit 206. The rising edge indicates the track center. The period from the rising edge to the next rising edge is a period in which the light beam traverses one track. Therefore, if the track pitch is Tph, and the time of the edge from the rising edge to the next rising is Tw, the relative speed of the light beam to the track is Tph
ph / Tw. Here, a search from track 1 to track 2 will be described. The number of traversing tracks is three. The microcomputer 201 sets the terminal a to low level and sets D /
A value is set in the A converter 202. Therefore, the light beam starts moving toward track 2. In addition, microcomputer 2
01 sets 3 to the terminal b of the comparator 208. The counter 207 counts the rising edge of the signal input to the terminal a. Therefore, the output of the counter 207 becomes 3 when the light beam reaches the track 2. When the output of the counter 207 becomes 3, the values of the terminals a and b of the comparator 208 become equal.
8 goes high. When the output signal of the comparator 208 becomes high level, the microcomputer 201 sets the terminal a to high level and operates the tracking control. When the terminal a changes from the low level to the high level, the timer 209 sets the terminal b to the high level during the time Tup. Therefore, as described above, the level of the D signal component of the digital filter 204 is increased, and the pull-in performance of the tracking control is improved. The time Tup is a time from when the tracking actuator 104 settles to when the light beam settles to substantially the center of the track. The time Tup is usually set to several ms. Therefore, the control band of the tracking control can be expanded without an excessive current always flowing through the tracking coil.

(Embodiment 2) Hereinafter, a tracking control apparatus according to Embodiment 2 of the present invention will be described with reference to FIG. The same blocks as those in the conventional example shown in FIG. 18 are denoted by the same reference numerals, and description thereof will be omitted. The phase compensation circuit 200 is a filter for stabilizing the tracking control system. When the terminal c is at a low level, it is in a clear state and the output becomes zero. When the terminal c changes from the high level to the low level, the signal generation circuit 280 takes in the level M of the terminal a immediately before the terminal c changes. Then, a signal that gradually decreases as the initial value is M is output from the terminal b. When the terminal c becomes high level, the level of the terminal b is forcibly set to zero.

The tracking control will be described. When operating the tracking control, the microcomputer 281 sets the terminal a to a high level and connects the terminals b and a of the switches 133 and 139. Accordingly, the clear state of the phase compensation circuit 200 is released, and the focusing lens 103 is driven according to the TE signal. FIG. 8 shows an output signal of the terminal b of the phase compensation circuit 200 in the tracking control state. Since the disk 100 has an eccentricity, a voltage for following the eccentricity is output. Time Tt is the time during which the disc makes one revolution. It is assumed that the frequency of rotation of the disk is lower than 50 Hz which is the natural frequency of the actuator. Therefore, the output signal of the terminal b of the phase compensation circuit 200 substantially corresponds to the displacement of the focusing lens 103. FIG. 9 shows the position of the focusing lens 103 with respect to the eccentricity. The schematic diagram (a) shows a case without eccentricity, and the schematic diagram (b) shows a case with eccentricity.
When there is no eccentricity, since the transfer table 115 almost follows the track, the focusing lens 103 is located at the center position, and the spring 1
And the length of the spring 2 are equal. If there is eccentricity, the transfer motor 114 cannot follow the disturbance due to the eccentricity, so the focusing lens 103 follows the eccentricity. Therefore, the focusing lens 1
03 is located at a position shifted from the center position. The lengths of the springs 1 and 2 are different. By the way, when the current of the tracking coil is reduced to zero in this state, the focusing lens 103 starts moving toward the center by the springs 1 and 2. Therefore, the focusing lens 103 vibrates at a natural frequency of 50 Hz.

The search will be described. The microcomputer 281 sets the terminal a to low level and connects the terminals a and c of the switches 133 and 139. Therefore, the tracking control becomes inoperative. Next, a predetermined value is set in the D / A converter 202, and the transfer motor 114 is driven to move the transfer table 115 in the direction of the target track. Further, since the terminal c changes from the high level to the low level, the signal generation circuit 280 takes in the level M of the output signal of the phase compensation circuit 200 immediately before the terminal c. Then, a signal that gradually decreases as the initial value is M is output from the terminal b. Since the current flowing through the tracking coil does not become zero immediately after starting the search, the focusing lens 103 does not vibrate.

The signal generation circuit 280 will be described with reference to the block diagram of FIG. The terminal 350 is connected to the terminal b of the phase compensation circuit 200, the terminal 353 is connected to the terminal a of the microcomputer 281, and the terminal 351 is connected to the terminal c of the switch 133.
The multiplier 356 multiplies the input signal by a coefficient and outputs the result. Note that the coefficient is a value less than 1. This signal generation circuit 280 operates in synchronization with the rising edge of the reference clock CLK having a period T. The delay circuit 355 is composed of a random access memory (RAM) that stores digital data input to the terminal a in synchronization with the rising edge of the reference clock CLK and outputs the digital data from the terminal b.
The delay circuit 355 has a function of writing predetermined data from outside. Terminal d is a terminal for inputting data, and terminal e is a terminal for inputting a write pulse. When a write pulse is input to the terminal e, the data set at the terminal d at that time is stored in the RAM. The falling edge detection circuit 354 detects a falling edge of the input signal and outputs a pulse. Therefore, when the level of the terminal 353 changes from the high level to the low level, the delay circuit 3
A write pulse is input to the terminal e of 55. That is, the signal level M at the terminal b of the phase compensation circuit 200 immediately before starting the search is stored in the RAM of the delay circuit 355. Since the coefficient of the multiplier 356 is less than 1, the reference clock CLK
The level of the terminal a of the delay circuit 355 gradually decreases at every rising edge of the signal.

The operation of the signal generation circuit 280 will be described with reference to FIG. The waveform (a) corresponds to the terminal b of the phase compensation circuit 200.
Are shown. Waveform (b) shows the signal at terminal a of microcomputer 281, waveform (c) shows the signal at terminal b of signal generation circuit 280, waveform (d) shows the signal at terminal a of switch 133,
The solid line of the waveform (e) indicates the amount of displacement of the focusing lens 103.
At time t0, the tracking control becomes inactive. The signal generation circuit 280 operates at the time t at the terminal b of the phase compensation circuit 200.
A value M of 0 is taken. Then, a signal that gradually decreases as the initial value is M is output from the terminal b. Therefore, the signal at the terminal a of the switch 133 becomes a signal that gradually decreases after time t0. Since the current flowing through the tracking coil also becomes a signal corresponding to the waveform (d), the movement of the focusing lens 103 gradually approaches zero as shown in the waveform (e). Time t1
Then, the tracking control is activated. Focusing lens 10
Since the displacement of No. 3 is zero, the pull-in of the tracking control becomes stable. On the other hand, the dotted line of the waveform (e) shows the movement of the focusing lens 103 when the current of the tracking coil is set to zero immediately after the start of the search. Since the current suddenly becomes zero, the focusing lens 103 vibrates at the natural frequency as described above. The vibration does not decrease even at time t1. Therefore, since the focusing lens 103 is displaced and vibrates, the pull-in of the tracking control becomes unstable.

(Embodiment 3) A tracking control device according to Embodiment 3 of the present invention will be described below with reference to the block diagram of FIG. The same blocks as those in the conventional example shown in FIG. 18 are denoted by the same reference numerals, and description thereof will be omitted. The binarization circuit 206 calculates T based on the zero level.
The E signal is converted to a high level or a low level. The counter 207 counts the rising edge of the signal input to the terminal a. The count value is output from terminal b. When the terminal c is at the high level, the count value is cleared. The comparator 208 receives the data input to the terminal a and the terminal b
When the data inputted to the terminal c are equal, the terminal c is set to the high level. Note that the binarization circuit 206, the counter 207, and the comparator 208 are the same as the blocks used in the first embodiment. Therefore, the count value of the counter 207 indicates the number of tracks traversed by the light beam. When the output of the comparator 208 becomes high level, it is the timing when the target track is reached.

The phase compensation circuit 200 is a filter for stabilizing the tracking control system. When the terminal c is at a low level, it is in a clear state and the output becomes zero. When the terminal c changes from the high level to the low level, the signal generation circuit 280 takes in the level N of the terminal a at that time. Then, a signal that gradually decreases with the initial value set to N is output from the terminal b. When the terminal c becomes high level, the level of the terminal b is forcibly set to zero. Note that the phase compensation circuit 200 and the signal generation circuit 280 are the same as the circuits used in the second embodiment. Adder 406 adds the input signals and outputs the result. The subtractor 403 subtracts the input signal and outputs the result. The speed detection circuit 404 measures the period of the input signal, calculates the moving speed of the light beam based on the measured value, and outputs the calculated speed. Inverter 407 inverts the input signal and outputs the inverted signal. The reference speed generating circuit 405 outputs a target moving speed at the time of searching the transfer table 115 according to the count value of the counter 207. LPF 400 is a low-pass filter.

The tracking control will be described. When operating the tracking control, the microcomputer 401 sets the terminal a to the high level and connects the terminals b and a of the switches 133 and 139. Accordingly, the clear state of the phase compensation circuit 200 is released, and the focusing lens 103 is driven according to the TE signal. Note that the level of the output signal of the signal generation circuit 280 is zero. The output signal of the terminal b of the phase compensation circuit 200 in the tracking control state is the same as the waveform of FIG. 8 used in the second embodiment. Since the disk 100 has an eccentricity, a voltage for following the eccentricity is output. Time Tt is the time during which the disc makes one revolution.
The search is started from this state.

The search will be described. The description will be made as a search that crosses 100 tracks. Microcomputer 40
1 sets 100 to the reference speed generation circuit 405 and the comparator 208 via the terminal b. The reference speed generation circuit 405 generates a reference speed according to the count value of the counter 207. The transfer table 115 is controlled according to the reference speed. FIG. 13 shows the relationship between the reference speed and the count value. V1 <V
2 <V3. The count value accelerates up to 40 and decelerates after 60. From 80, the speed becomes constant. The count value indicates the number of tracks traversed by the light beam as described above. The subtractor 403 outputs the difference between the moving speed of the light beam and the reference speed. Hereinafter, this difference is referred to as a speed error signal. The speed error signal is sent to the tracking coil via the power amplifier 128. Further, it is sent to the transfer motor 114 via the LPF 400. Therefore, the transfer table 115 is controlled to be at the reference speed. Since the transfer motor 114 is driven by a low-frequency signal component of the speed error signal,
Except for the timing at which the reference speed changes, the transfer motor 11
The drive value of 4 is a signal corresponding to the reference speed. The current flowing through the tracking coil is a current corresponding to the eccentricity of the disk.

This will be described with reference to the waveforms shown in FIG. The waveform (a) shows the output signal of the phase compensation circuit 200 and the waveform (b)
Represents the output signal of the terminal a of the microcomputer 401, the waveform (c) represents the output signal of the LPF 400, and the waveform (d) represents the subtractor 403.
The waveform (e) shows the output signal of the signal generation circuit 280, and the waveform (f) shows the output signal of the adder 406. The waveform (a) shows a signal when the disk 100 is eccentric. At time t10, the terminal a of the microcomputer 401 becomes low level, and the search is started. LPF4
The output signal of 00 has a waveform corresponding to the output waveform of the reference speed generation circuit 405. That is, the transfer motor 114 is driven so as to be substantially equal to the reference speed. Therefore, the focusing lens 103 is driven to follow only the eccentric component of the disk. The drive current has a waveform corresponding to the eccentricity of the disk as shown in waveform (d). At time t11, the count value of the counter 207 becomes 100, and the output of the comparator 208 goes high. The microcomputer 401 sets the terminal a to the high level, and the terminals a and b of the switches 133 and 139.
Connect. Therefore, the tracking control system starts operating.

Next, the operation of signal generation circuit 280 will be described. The output value of the subtractor 403 immediately before the time t11 when the output of the terminal a of the microcomputer 401 becomes high level is N.
The signal at the terminal a of the microcomputer 401 is input to the terminal c of the signal generation circuit 280 via the inverter 407. Therefore, the signal generation circuit 280 operates as the subtractor 403 at time t11.
And outputs a signal that gradually decreases with the initial value being N. The operation of signal generation circuit 280 is similar to the operation of the second embodiment. Level N is a drive voltage of the actuator for following the eccentricity of the disk. Therefore, even if the tracking control system starts operating at time t11, the focusing lens 103 does not return to the center position once. Assuming that the output of the signal generation circuit 280 is always zero, the output of the phase compensation circuit 200 is set at time t1.
Since it is zero at 1, the output level once drops as shown by the dotted line in the waveform (f). That is, the focusing lens 103 tries to return to the center position once. If the eccentricity is large, the tracking control cannot be stably drawn into the target track.

(Embodiment 4) A tracking control apparatus according to Embodiment 4 of the present invention will be described below with reference to the block diagram of FIG. Blocks similar to those of the third embodiment shown in FIG. 12 are denoted by the same reference numerals, and description thereof is omitted. The difference from the third embodiment is that the signal generation circuit 280, the inverter 407, and the adder 406 are omitted.
The digital filter 204 is the digital filter 500
Is replaced by Also, the A / D converter 50
1. A D / A converter 502 is added. The digital filter 500 will be described with reference to FIG. FIG. 16 shows a block diagram of the digital filter 500.
Terminal 700 is connected to A / D converter 501. The terminal 762 is connected to the D / A converter 502, the terminal 761 is connected to the terminal a of the microcomputer 401, and the terminal 763 is connected to the output terminal of the subtractor 403. The digital filter 500 according to the fourth embodiment differs from the digital filter 204 according to the first embodiment in that the D signal component generation system has no gain switching function. It is also a function of the RAM 1. The RAM 1 is provided with a function of writing predetermined data from outside. The terminal d of the RAM 1 is a terminal for inputting data, and the terminal e is a terminal for inputting a write pulse. When a write pulse is input to the terminal e, the data set at the terminal d at that time is stored in the value of the RAM1. When the terminal 761 changes from a high level to a low level, the write pulse detects a falling edge and outputs a write pulse. Accordingly, the value N of the subtractor 403 immediately before the search operation is completed and the tracking control is operated again is written into the RAM 1 by the A / D converter 764. Therefore, the I signal component generation system starts operation with the initial value N. Note that the coefficient of the multiplier 319 is 1. If the coefficient of the multiplier 319 is not 1, the result of the multiplication is N
Is written into RAM1.

This will be described with reference to the waveforms shown in FIG. The waveform (a) is the output signal of the digital filter 500, the waveform (b) is the output signal of the terminal a of the microcomputer 401, the waveform (c) is the output signal of the LPF 400, and the waveform (d) is the output signal of the subtractor 403. And the waveform (e) shows the output signal of the switch 133. Waveform (a) shows disk 100
3 shows a signal when there is eccentricity. At time t20, the terminal a of the microcomputer 401 becomes low level, and the search is started. The output signal of LPF 400 has a waveform corresponding to the output waveform of reference speed generation circuit 405. That is, the transfer motor 114 is driven so as to be substantially equal to the reference speed. Therefore, the focusing lens 103 is driven to follow only the eccentric component of the disk. The drive current has the waveform (d)
As shown in FIG. 7, the waveform is in accordance with the eccentricity of the disk. At time t21, the count value of the counter 207 becomes 100, and the output of the comparator 208 goes high. Microcomputer 4
01 sets the terminal a to a high level and switches 133 and 13
9 is connected to terminal a and terminal b. Therefore, the tracking control system starts operating. The subtractor 403 immediately before the time t21 when the output of the terminal a of the microcomputer 401 becomes high level.
Is an output value of N. Since the value N is set in the RAM 1 of the I signal component generation system of the digital filter 500, the initial output value of the digital filter 500 is N. The value N is the drive voltage of the actuator for following the eccentricity of the disk. Therefore, even if the tracking control system starts operating at time t21, the focusing lens 103 does not return to the center position once. If the initial value of the digital filter 500 is zero, the output level temporarily drops at time t31 as shown by the dotted line in the waveform (e). That is, the focusing lens 103 tries to return to the center position once. If the eccentricity is large, the tracking control cannot be stably drawn into the target track.

[0043]

As described above, according to the tracking control apparatus of the first aspect, the track deviation detecting means for detecting the positional deviation between the light beam irradiated on the information surface of the disc and the track, and the light beam Moving means for moving the beam across the track, tracking control means for performing PID control of the moving means so that the light beam is on the track based on the output of the track deviation detecting means, and tracking control means. A search means for moving the light beam to another track in a non-operation state, wherein the search means completes an operation, and the tracking control system is settled immediately after operating the tracking control means, Since the gain of the D signal component generation system of the PID control is increased, the control band of the tracking control is always widened. And without tracking control of the pull-in performance can be improved.

According to the tracking control device of the second aspect, since the tracking control device of the first aspect determines that the tracking control means has settled when a predetermined time has elapsed, a simple configuration is provided. Can detect that the tracking control means has settled.

According to a third aspect of the present invention, there is provided a tracking control device, comprising: a track deviation detecting means for detecting a positional deviation between a light beam irradiated on an information surface of a disk and a track; A first moving unit that moves, a second moving unit that moves so that the first moving unit traverses a track, and driving the first moving unit in response to a signal from the track shift detecting unit. Tracking control means for controlling the light beam to be positioned on a track; and search means for disabling the tracking control means and driving the second moving means to move the light beam to another track. And the drive value M of the first moving means immediately before the search means starts operation, and when the search means starts operation, the initial value is gradually set to M. Since a driving means for driving the first moving means at the driving value to small, the during the search 1
The moving means does not vibrate, and the pull-in of the tracking control is stabilized.

According to a fourth aspect of the present invention, there is provided a tracking control device, comprising: a track deviation detecting means for detecting a positional deviation between a light beam irradiated on an information surface of a disk and a track; A first moving unit that moves, a second moving unit that moves so that the first moving unit traverses a track, and driving the first moving unit in response to a signal from the track shift detecting unit. Tracking control means for controlling the light beam to be positioned on the track; relative speed detection means for detecting a relative speed of the light beam with respect to the track based on an output signal of the track deviation detection means; and the tracking control means In a non-operating state, and drives the first and second moving means on the basis of an output signal of the relative speed detecting means to drive the other track. And a search means for moving the climate beam, the first just before the searching means completes the operation
Since the drive value N of the moving means is stored, and when the tracking control means starts operating, the drive value gradually decreasing from the initial value N is added to the drive value of the tracking control means. Immediately after the operation, the first moving means does not try to return to the center position, and the pull-in of the tracking control is stabilized.

According to a fifth aspect of the present invention, there is provided a tracking control device, comprising: a track deviation detecting means for detecting a positional deviation between a light beam irradiated on an information surface of a disk and a track; A first moving unit that moves, a second moving unit that moves so that the first moving unit traverses a track, and driving the first moving unit in response to a signal from the track shift detecting unit. Tracking control means for performing PID control so that the light beam is positioned on a track; relative speed detection means for detecting a relative speed of the light beam with respect to a track based on an output signal of the track deviation detection means; The first and second moving means are driven based on the output signal of the relative speed detecting means by disabling the means, and other trucks are driven. Search means for moving the light beam to a light source, storing a drive value N of the first moving means immediately before the search means completes the operation, and controlling the PID control when the tracking control means starts operating. Since the initial value of the integrator of the I signal generation system is set to a value corresponding to N, the first value is set immediately after the tracking control is operated.
The moving means does not try to return to the center position, and the pull-in of the tracking control is stabilized.

[Brief description of the drawings]

FIG. 1 is a block diagram of a tracking control device according to a first embodiment of the present invention.

FIG. 2 is a block diagram of a digital filter 204 according to the first embodiment.

FIG. 3 is a Bode diagram showing characteristics of digital filter 204 according to the first embodiment.

FIG. 4 is an actuator 10 according to the first embodiment.
Block diagram of 4

FIG. 5 is a Bode diagram showing open-loop characteristics of the tracking control system according to the first embodiment.

FIG. 6 is a schematic diagram showing a track and a waveform diagram showing a TE signal and an output signal of a binarization circuit 206 according to the first embodiment.

FIG. 7 is a block diagram of a tracking control device according to a second embodiment of the present invention;

FIG. 8 shows a phase compensation circuit 200 according to the second embodiment.
Waveform diagram showing output signal of

FIG. 9 is a schematic diagram showing a positional relationship between a track and a focusing lens 103 according to the second embodiment.

FIG. 10 shows a signal generation circuit 28 according to the second embodiment.
Block diagram of 0

FIG. 11 shows a phase compensation circuit 20 according to the second embodiment.
Waveform diagram showing output signal of 0, signal of terminal a of microcomputer 281, output signal of signal generation circuit 280, signal of terminal a of switch 133, and displacement of focusing lens 103.

FIG. 12 is a block diagram of a tracking control device according to a third embodiment of the present invention.

FIG. 13 is a waveform chart showing an output signal of reference speed generation circuit 405 in the third embodiment.

FIG. 14 shows a phase compensation circuit 20 according to the third embodiment.
0, the output signal of the terminal a of the microcomputer 401, L
Waveform diagram showing an output signal of PF400, an output signal of subtractor 403, an output signal of signal generation circuit 280, and an output signal of adder 406.

FIG. 15 is a block diagram of a tracking control device according to a fourth embodiment of the present invention.

FIG. 16 is a block diagram of a digital filter 500 according to the fourth embodiment.

FIG. 17 is a waveform chart showing an output signal of the digital fill 500, an output signal of the terminal a of the microcomputer 401, an output signal of the LPF 400, an output signal of the subtractor 403, and an output signal of the adder 406 in the fourth embodiment.

FIG. 18 is a block diagram of a conventional tracking control device.

FIG. 19 shows a track and a focusing lens 1 in the conventional example.
Schematic diagram showing the positional relationship of 03

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 disk 101 motor 103 focusing lens 104 actuator 105 total reflection mirror 106 light beam 107 波長 wavelength plate 108 coupling lens 109 laser 110 polarization beam splitter 111 detection lens 112 cylindrical lens 113 photodetector 114 transfer motor 115 transfer table 116, 117, 118, 119 I / V converter 120, 121 Adder 122 Differential amplifier 123 Adder 124 Adder 125 Differential amplifier 126 Phase compensation circuit 127, 128, 129 Power amplifier 133 Switch 139 Switch 140 LPF 201 Microcomputer 202 D / A converter 203 A / D converter 204 Digital filter 205 D / A converter 206 Binarization circuit 207 Counter 208 Comparator 209 Timer

Claims (5)

[Claims] 1. A track deviation detecting means for detecting a positional deviation between a light beam irradiated on an information surface of a disk and a track, a moving means for moving the light beam across a track, and the track deviation detecting Tracking control means for performing PID control of the moving means so that the light beam is on a track based on the output of the means; and search means for disabling the tracking control means and moving the light beam to another track The search means has completed the operation, until immediately after the tracking control system is settled immediately after operating the tracking control means,
A tracking control device, wherein the gain of a D signal component generation system of the PID control is increased. 2. The tracking control device according to claim 1, wherein the settling of the tracking control system is determined by elapse of a predetermined time. 3. A track shift detecting means for detecting a positional shift between a light beam irradiated on an information surface of a disk and a track; a first moving means for moving the light beam across the track; A second moving means for moving the first moving means across the track, and driving the first moving means in response to a signal from the track deviation detecting means so that the light beam is positioned on the track. Tracking control means for controlling the tracking control means to a non-operational state, a search means for driving the second moving means to move the light beam to another track, and the search means starts operation. The drive value M of the first moving means immediately before is stored, and when the search means starts operating, the drive value for driving the first moving means with a gradually decreasing drive value with the initial value being M. Tracking control apparatus characterized by comprising a means. 4. A track shift detecting means for detecting a positional shift between a light beam irradiated on an information surface of a disk and a track; a first moving means for moving the light beam across the track; A second moving means for moving the first moving means across the track, and driving the first moving means in response to a signal from the track deviation detecting means so that the light beam is positioned on the track. Tracking control means, a relative speed detection means for detecting a relative speed of the light beam with respect to a track based on an output signal of the track deviation detection means, and a detection of the relative speed by disabling the tracking control means. Searching means for driving the first and second moving means based on an output signal of the means to move the light beam to another track, A driving value N of the first moving means immediately before the search means completes its operation is stored, and when the tracking control means starts operating, the driving value of the tracking control means is gradually reduced with an initial value being N. A tracking control device characterized by adding to a value. 5. A track deviation detecting means for detecting a positional deviation between a light beam irradiated on an information surface of a disk and a track; a first moving means for moving the light beam across the track; A second moving means for moving the first moving means across the track, and driving the first moving means in response to a signal from the track deviation detecting means so that the light beam is positioned on the track. PID
Tracking control means for controlling; relative speed detection means for detecting a relative speed of the light beam with respect to a track based on an output signal of the track deviation detection means; and the relative speed detection means for disabling the tracking control means. Searching means for driving the first and second moving means on the basis of the output signal to move the light beam to another track, wherein the first movement immediately before the searching means completes its operation. The driving value N of the PID control is stored when the tracking control means starts operating.
A tracking control device, wherein an initial value of an integrator of a signal generation system is set to a value corresponding to N.