JPH1069653A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform exact recording/reproduction by driving a first actuator to decrease the movement of a second actuator required for following up a track with a light beam while being linked with the detected movement. SOLUTION: This device uses a first actuator 312 (position control means) having a wide movable range and a second actuator 230 (position control means) having a narrow movable range but high responsiveness and the positioning accuracy unattainable by only one actuator is realized by linking two actuators with each other. At this time, a problem of linkage of two actuators arises, but, in this device, the movement of a light spot is detected by the second actuator 320 for highly accurate positioning and the first actuator 312 is driven linked with the movement.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information storage device for recording and reproducing information by using a light beam, and more specifically, to position a light beam on a desired track with submicron accuracy. For an information storage device.

[0002]

2. Description of the Related Art At present, an information recording film (for example, a metal film) is deposited on a substrate, and a rotating disk is irradiated with a laser beam to narrow it down to a spot of about 1 μm, and the irradiation power is modulated to modulate the irradiation power. Information is recorded in a form in which a hole is thermally formed in the film. At the time of reproduction, a weak laser beam is condensed and irradiated on the metal film, and the information is reflected by a change in the amount of light reflected from the information hole (called a pit). An information storage device called a digital optical disk for reading has been proposed. Proposals of this type include Electronics, Nov.
23, 1987, p. 75, "Ten Billion
Bits Fit on to Two Sides
of 12-inch disc ".

For example, FIG. 1 shows a typical configuration of this type of system. That is, a digital optical disc 3 having a sandwich structure with a diameter of 30 cm is rotated in the direction of an arrow by a rotation motor 5 about a rotation shaft 4. An optical head 2 including a laser light source and an optical system is mounted on a swing arm actuator 1 used for a magnetic disk or the like, and is driven in a radial direction of the disk 3.

A method of recording and reproducing information in such a configuration will be described with reference to FIG. FIG. 2 is a partially enlarged view of the disk 3. That is, a glass or plastic substrate 11
Referred to as a guide groove 13 by a UV resin 14 or the like,
A track having a concave cross section having a certain width and depth is formed, and a metal film 10 is deposited thereon. When recording,
The pits 12 are formed by guiding the focused spot from the optical head 2 along the guide track 13 and melting the metal film 10 by modulating the irradiation power of the spot. At the time of reproduction, a light spot is similarly illuminated along the guide track 13 and the amount of reflected light is read. Further, a signal for controlling the light spot is also detected from the amount of reflected light.

A signal for controlling the light spot includes a focus shift detection signal for detecting a focus shift due to a vertical shake of the disk, and a track shift detection signal for detecting a shift between the center of the light spot and the center of the guide track. The main signal is a displacement detection signal itself, or a control signal that can be used for track following control formed from this signal is referred to as a “tracking signal”. These signals all use the amount of reflected light.

This optical disc has a track pitch of 1.
If it is 6 μm, about 5
Data stored in each track is about 4,000 bytes. Each of these tracks is provided with a plurality of sectors for indicating a data delimiter in the rotation direction for each track.

In order to record and reproduce information from the outside at an arbitrary position, it is necessary to perform an access operation of searching for one track and then finding one sector on the periphery of the track. That is, a so-called seek control for moving the light spot to a selected desired track on which desired information is recorded or to be recorded, and a method of reading or recording information, and moving the light spot on the center of the track with a minimum displacement error. So-called tracking (follow-up control) for maintaining the light spot is required.

[0008]

Conventionally, there is a magnetic disk as an apparatus which requires this kind of access operation. The magnetic disk has a track pitch of about 150 μm to about 30 μm, which is one digit in pitch as compared with an optical disk. Therefore, the access method used for the magnetic disk cannot be used as it is for the optical disk. That is, when the magnetic head is positioned at a desired track by an actuator (for example, a linear motor), a steady deviation (deviation from a target position) of about 5 to 10 μm is generated depending on the configuration and performance of the actuator. This is due to friction, etc.
In the transient state of the position control, an overshoot may occur with respect to the target position, and this value is also about 5 μm. Therefore, in the access method used for the magnetic disk, since the stop accuracy is extremely low, about 10 μm, the same positioning method cannot be adopted for a high-density optical disk having a track pitch of about 1.6 μm. There is a point.

A conventional magnetic disk access method will be described with reference to FIG. FIG. 3 is a block diagram of a seek control circuit, and FIG. 4 is a block diagram of a tracking control circuit. The difference value 20 to the target track is set in the difference counter 21.
A track pulse 22 to be described later is input to the difference counter 21, and the count is sequentially decreased from the set number of tracks each time a track pulse is input.

The count-down output 23 is input to an optimum speed generation circuit 24, which outputs a target speed curve for controlling speed, and is input to a speed comparator 25. The other input of the speed comparator 25 receives an actual speed signal 26 described later, and outputs a value of a difference between the target speed and the actual speed. This output is input to a logic circuit 27 for switching between seek control and follow-up control, and enters a current amplifier 28 to drive a positioner 29. For example, in the case of a voice coil type linear motor as an example of a positioner, a current 30 flowing through a coil is input to an integrator 31 and integrated, which indicates an actual operating speed at which the positioner is actually moving. A dynamic speed signal 26 is detected. on the other hand,
The position signal 33 read from the servo head 32 mounted on the positioner is input to a track pulse generating circuit 34 for generating the track pulse 22, and outputs one track pulse for each passing one track. With the above seek control circuit, speed control is performed according to the optimum speed curve up to the target track.

FIG. 4 shows a tracking control circuit. When the target track is reached, tracking control operated by the tracking control circuit shown in FIG. 4 is performed. That is, the difference between the track deflection XT and the head displacement XH is detected by the position signal generation circuit 35, and the position signal 33 is generated. This is a phase lead circuit 3
6. The signal is input to the power amplifier 28 described with reference to FIG. At this time, the logic circuit 27 described with reference to FIG. 3 is switched from seek control to follow-up control, and the positioner 29 is controlled by the position signal.

FIG. 5 shows the position signal. The position signal has a triangular waveform as shown in the figure as the head moves by the displacement x on the disk radius. A black dot indicates an odd-numbered track, and a white circle indicates an even-numbered track. The track pulse generation circuit 34 generates a track pulse at black points and white points which are zero points.

The half period Δ of the triangle in FIG. 5 is approximately equal to the track width. In a recent high-density magnetic disk, it is about 35 μm. When the positioner is controlled by the above-mentioned position signal, it varies depending on the configuration and performance of the positioner, but 5 μm.
Steady deviation of about 10 to 10 μm (deviation from target point)
Occurs. This cause is caused by friction or the like. Further, in the transient state of the position control, an overshoot may occur with respect to the target point, and this amount is also about 5 μm.

As described above, the track interval of the optical disk is
At present, the minimum is about 1.6 μm, so that it is difficult to perform positioning by the control described above. Another difficulty arises because the track pitch is as narrow as 1.6 μm. Seek control,
For tracking control, a signal for detecting the position at which the optical head passes through the disk must be detected.
Such a signal is a tracking signal when a light spot passes through a track. When the seek control and the follow-up control are performed using this signal, the following problem occurs.
At the beginning and end of the seek control, the moving speed of the optical head becomes very low. If this speed is lower than the maximum eccentric speed caused by the track eccentricity, if the number of tracks is counted each time the vehicle passes through the track, a counting error occurs, and an accurate position cannot be detected.

In FIG. 6, the trajectory 40 of the light spot is the maximum eccentric velocity and passes through a group of eccentric tracks, and each solid line represents a temporal change with respect to the disk radial position of the track. I have. In this case, the number of tracks passed and the number of tracks passed are the same. However, the trajectory 41 of the light spot is a case where the track has passed through the track group at a speed smaller than the maximum speed of the eccentricity. In this case, the number of tracks passed does not match the number of tracks actually passed, and the track is counted a lot. There's a problem.

An object of the present invention is to solve the above-mentioned problems and to provide an information storage device which performs high-precision positioning suitable for an optical disk.

[0017]

According to the present invention, there is provided an information storage device for irradiating a recording medium having a track with a light beam and positioning the light beam on the track in order to record and reproduce information along the track. Then, the tracking signal is detected for the light beam to follow the track, the second actuator having high response is driven by the tracking signal, the movement of the light beam by the second actuator is detected, and the movement is interlocked with the detected movement. Then, the first actuator is driven such that the movement of the second actuator required for the light beam to follow the track is reduced.

[0018]

The concept of the present invention will be described below in detail.

The present invention uses a first actuator (position control means) having a wide movable range and a second actuator (position control means) having a narrow movable range and high responsiveness. By interlocking, positioning accuracy that cannot be achieved with only one actuator is realized. At this time, a method of linking the two actuators is a problem. In the present invention, the movement of the optical spot by the second actuator for high-precision positioning is detected, and the first actuator is driven in conjunction with the movement. .

FIG. 7 is an explanatory diagram of a method for creating a signal indicating the direction of passing through a track and the signal indicating that the track has passed in order to accurately detect the position of the optical head from the disk. In FIG. 7A, a light beam emitted from the light source of the optical head is an objective lens (not shown).
Then, a spot 50 is formed on the metal film 10 through the substrate 11 on the disk and the UV resin 14 constituting the guide track 13. At this time, the N.V.
Assuming that A is 0.50 and the wavelength of the light source is 830 nm, the spot size (diameter at which the intensity is 1 / e2) is about 1.6 μm. Assuming that the pitch of the guide tracks created on the disk is 1.6 μm, as this spot moves in the radial direction of the disk in the direction of the arrow, a tracking signal 52 representing the deviation between the track center and the center of the spot.
Changes as shown in FIG. The method of generating the tracking signal includes a method using two spots disclosed in JP-A-49-50954 and a method using the two spots disclosed in JP-A-49-50954.
No. 94304, a track wobble method disclosed in JP-A-50-68413, a method using diffracted light disclosed in JP-A-49-60702, etc. There is.

When the spot moves in the direction of the arrow, the total amount of reflected light from the disk changes as shown in FIG. The total amount of reflected light is smallest at the center of the track and is largest at the center between the tracks. The signal 51 in which the total reflected light amount is detected by the photodetector and converted into an electric signal has a relationship in which the period is equal to that of the tracking signal 52 and the phase is shifted by 90 °. The tracking signal 52 is zero at the center of the track, and has different polarities depending on whether the light spot is on the right or left side of the track (corresponding to the outer or inner circumference of the disk). By utilizing this feature, it is possible to know the passing direction of the truck.

The total amount of reflected light described herein indicates the total amount of light reflected from the disk by a lens having a specific numerical aperture and passing through the opening of the lens. This kind of light amount is used for detecting an information signal recorded on the disk. This information signal focuses the light beam passing through the lens aperture on the light receiving surface of one photodetector and converts it into a photocurrent, or irradiates the light beam to a photodetector group having a plurality of divided light receiving surfaces. , The sum of the photocurrents from the respective photodetectors, or by converting the photocurrents into voltages and adding them. This signal can be used as the signal 51 of the total reflected light amount described above.

A method for performing accurate position detection using the tracking signal 52 and the total reflected light amount signal 51 will be described below.

FIG. 8A shows the AC component of the signal of the total amount of reflected light. FIG. 3B shows a tracking signal.

In the example of FIG. 8, if the spot is inside the disc, plus (+) and outside the disc is minus (-), the light spot moves from the outside to the inside of the disc. Shows changes of the above two signals with respect to the time axis when stopped in the middle and moved in the opposite direction. FIG. 8C shows a track signal 90 indicating the location of a track. This is a comparison between the signal of the total reflected light amount and a certain voltage E1 by utilizing the fact that the total reflected light amount decreases where the track exists. Is performed to correspond to the state of “0” at the logical level when the level is small. Then, when observing the change of the signal 90 on the time axis, the falling edge of the waveform substantially corresponds to the edge of the track where the spot starts to cross the track. Therefore, a pulse 92 with a narrow time width is created from this fall. Further, in order to know the direction of the edge through which the spot passes, a signal (referred to as a track polarity signal) 91 is created by comparing the tracking signal 52 with a zero level. By comparing the track polarity signal 91 with the timing of the track passing edge signal 92, the direction of the track passing can be known.

Therefore, if one wants to know the number of passing tracks when the light spot moves from the outside to the inside,
It is sufficient to count the number of pulses of the track passing edge signal 53 (FIG. 8 (g)) when the track polarity signal 91 becomes low level. The same applies to the movement in the reverse direction.

FIG. 9 shows a specific circuit example for realizing the operation described above. The signal 51 of the total reflected light amount is input to the (+) terminal of the comparator 93, and the voltage E is applied to the (-) terminal.
1 is input and the total reflected light amount signal 51 is compared with the voltage E1. If the level of the signal 51 is higher than E1, the logical level becomes "1", and in other cases, it becomes "0". The output signal 90 is input to the monostable multivibrator 94, and a pulse having a constant width is created from the falling edge of the signal 90. This output signal 92 is input to respective terminals of AND circuits 95 and 96 which take a logical product. AND circuit 9
5 and 96 are provided with a polarity signal 9 obtained by inputting the tracking signal 52 to the comparator 97.
1 and a signal obtained by inverting the polarity signal 91 by an inverting circuit 98, and a positive edge signal 54 that generates a pulse each time the light spot passes from the inside to the outside of the track; It outputs a negative direction edge signal 53 that generates a pulse each time it passes from the outside to the inside. Therefore, by using these signals, it is possible to know the number of remaining tracks up to the target track during access, which is necessary for controlling the speed control.

For example, in the circuit of FIG. 9, the access polarity signal 56 indicating the direction of access is made to correspond to the logical level "0" when accessing from the outside to the inside. Then, the positive edge signal 54 is selected and input to the up terminal (U) of the counter 104 and the negative edge signal 53 is selected to the down terminal (D) of the counter 104 by the logic circuit including the logic elements 98 to 103. Is entered. The counter 104 stores the absolute value of the difference to the inner target track at the start of access, ie, 5
5 is loaded. When the light spot starts moving from the outside to the inside, a negative edge signal 53 is generated each time the light spot crosses the track from the outside to the inside.
, A pulse is generated, and the content of the counter 104 is reduced. When the light spot returns halfway for some reason and crosses the track from inside to outside, a pulse is generated in the positive edge signal 54 and the counter 104
And outputs the accurate absolute value 57 of the remaining track being accessed. When the content of the counter 104 becomes zero, the counter 10 is input from the BR terminal of the counter 104.
A pulse A is generated indicating that the content of 4 has become zero.
By recognizing the pulse A, it is possible to know that the light spot has reached the edge of the target track.

The plus and minus direction edge signals 5
By using 4, 53, it is possible to know the absolute value of the speed during access, which is necessary for controlling the speed control. For example, in the circuit diagram of FIG.
The negative direction edge signal 53 is supplied to the frequency-voltage converter 10.
5 and the positive edge signal 54 is input to the frequency-voltage converter 106. Assuming that the track pitch p and the absolute value of the speed at which the track passes are v, the frequency f of the pulse train generated at the edge of the track every time the track passes,
Is given by the following equation.

F = v / p By knowing this frequency, the absolute value of the speed at which the light spot passes through the track can be known, and the direction in which the light spot passes can be known by the signs of the edge signals 53 and 54.

The circuit shown in FIG. 10 is an example for realizing this concretely. The outputs of the frequency-voltage converters (hereinafter referred to as F / V converters) 105 and 106 are obtained by converting the speed of track passage into an analog value of voltage for each polarity of track passage. It is a convenient form for speed comparison. The outputs of the F / V converters 105 and 106 are differentiated by the differential amplifier 107, and the outputs are respectively input to the input of the inverting circuit 108 and the switching circuit 1
Enter 09. The output of the inverting circuit 108 is input to the switching circuit 110 and is controlled by an inverted signal of the signal 56 for controlling the switching circuit 109. The outputs of the switching circuits 109 and 110 are combined to form a signal 111 representing the absolute value of the speed. That is, since the access polarity signal 56 now corresponds to the logical level "1" when going from the inside to the outside, when accessing from the inside to the outside, the F / V conversion output of the positive edge signal 54 is output. Becomes positive polarity even in the differential output, and the switching circuit 109 is turned on because the access polarity signal is “1”, and appears as the absolute value signal 111 of the speed. Conversely, when accessing from the outside to the inside, the access polarity signal 56 is "0" at a logical level, so that the switching circuit 110 switches ON by the output of the inverter 112 which inverts the access polarity signal 56.
And the F / V conversion output of the negative edge signal 53 becomes negative in the differential amplifier 107, but the inversion circuit 108
, And becomes the absolute value signal 111 of the speed.

A procedure for creating a timing signal for switching from speed control to position control will be described with reference to FIG. Assuming that the position control servo system performs linear operation,
It is usually designed. This comes from the ease of analysis and the simplicity of the circuit configuration. Incidentally, the tracking signal 52 changes sinusoidally as a function of the track position as shown in FIG. 7B, and has a non-linear characteristic as a control input. In such a system, the timing of starting the operation of the servo system is an important factor for the stable operation of the system.

As shown in FIG. 11A, when the spot crosses from the inside to the outside of the disk and approaches the Nth target track, the tracking signal 52 changes as shown in the figure. When the tracking signal is expressed as a sine wave with the target point 115 (zero point of the tracking signal) as the origin, the timing at which the operation is stably performed (the start of the position control)
Is, according to the experiment, between the peak points of + polarity and -polarity closest to the target point (between ± π / 2 in terms of the sine wave phase).
Preferably, a linear region having the origin as a symmetric point is good. In addition, it is necessary to operate at the edge portion before passing through the zero point of the target track. Considering the above, when approaching the target track from the inside to the outside of the disc, the position servo system should be turned on after passing through the zero point of the track immediately before the target track and passing through the next positive peak point. Good. Conversely, when approaching the target track from the outside to the inside of the disk, the position servo system is turned on after passing through the zero point of the track immediately before the target track and passing through the next negative peak point.

FIGS. 12 and 13 show circuits for realizing the above. 11A, 11B, 11C, and 11G show a tracking signal 52 when approaching from the inside to the outside of the disk, a signal 113 indicating a linear area, and a position servo system O.
Signal B indicating N, signal 1 indicating that the target track has been reached
14. In FIG. 12, the tracking signal 52 is input to the + terminal of the comparator 117, and the voltage E2 is input to the-terminal. The level of the voltage E2 is shown in FIG.
As shown in (a), the target point 1 of the tracking signal 52
15 is set to a positive level having substantially linearity.
The output of the comparator 117 is input to one of the AND circuits 120, and the access polarity signal 56 is input to the other. The tracking signal 52 is output from the comparator 118
, And the voltage E3 is input to the + terminal. The level of the voltage E3 is as shown in FIG.
The target signal 115 of the tracking signal 52 is set to a negative level having substantially linearity.

The output of the comparator 118 is the AND circuit 1
A signal obtained by inverting the access polarity signal 56 by the inverter 119 is input to one input of the input terminal 21 and the other input. The output of the AND circuits 121 and 120 is the OR circuit 12
2 and the logical sum is obtained. By doing so, the output 113 of the OR circuit 122 becomes a signal as shown in FIG. 11B when the access polarity signal 56 is “1”, and as shown in FIG. 11E when the access polarity signal 56 is “0”. Become like In each case, the falling edge of the pulse signal represents the end of the linear region centered on the target point. In order to perform position control on the target point 115 of the target track, it is necessary to know the linear area of the target track. Therefore, the BR output A (a signal output when the counter content 57 becomes zero) A described with reference to FIG. 9 is used.

The pulses 54 and 53 passing through the track are shown in FIG.
As described in (f) and (g), a pulse is generated at an edge portion of the passing track that appears earlier in time. Therefore, the rising portion of this pulse substantially corresponds to the peak point of the tracking signal. Assuming that the signal A is a pulse signal that rises when the content of the counter 104 becomes zero,
This is input to a flip-flop 128 to generate a signal 114 rising at the rising of the signal A. Signal 1
14 to one of the AND circuits 123 and the signal 113
To the other and the linear region of the target track to signal 1
14 to select. The output of the AND circuit 123 is input to a trailing edge reaction type (master-slave type) flip-flop 124 to generate a position control start signal B rising at the trailing edge. This signal B is also shown in FIG.
The circuit shown in the figure can also be created. The tracking signal 52 is input to a switching circuit 125 while being input to an inverting amplifier 116, inverted, and
to go into. Switching circuit 125 has access polarity signal 5
6, the switching circuit 126 controls the access polarity signal 56 with a signal inverted by the inverter 119. Switching circuits 125, 12
6 are combined and input to the + terminal of the comparator 127.

The negative terminal of the comparator 127 has the voltage E2
Is generated, and a signal 113 is generated in which the falling of the comparator output represents the end of the linear region centered on the target point. Subsequent processing is the same as the operation in FIG. in this case,
The positive peak level and the negative peak level of the tracking signal 52 must be substantially equal. FIG. 13 shows FIG.
Is the case where the first half of is processed in an analog manner.

A signal processing circuit block for performing an access operation will be described with reference to FIG. In the example of FIG. 14, as the positioning moving mechanism, the optical head is integrally moved to largely move in the disk radial direction, and
The seek control and the follow-up control are performed by one actuator by using the swing arm 1 capable of positioning accuracy of a degree. The reflected light amount detected by the optical head 2 is subjected to photoelectric conversion by a photodetector (not shown), and the tracking signal generation circuit 201 and the total reflected light amount signal generation circuit 200
Is input to Here, the method of creating the tracking signal will not be described in detail. Tracking signal generation circuit 201
, A tracking signal 52 is obtained, and a total reflected light amount signal generation circuit 200 obtains a total reflected light amount signal 51.
The tracking signal 52 and the total reflected light amount signal 51 are input to an edge signal generation circuit 202 which generates a positive direction edge signal 54 and a negative direction edge signal 53, and are subjected to arithmetic processing.

FIG. 9 shows this calculation processing in detail. plus,
The negative edge signals 54 and 53 are input to a differential counter 203 for calculating the difference to the target track and a speed detection circuit 204, respectively, and an absolute value signal 57 of the difference to the target track and an absolute value signal 111 of the speed are output. You. For these, the operation of the differential counter 203 has been described in detail with reference to FIG. 9, and the operation of the speed detection circuit 204 has been described in detail with reference to FIG. The absolute value signal 57 of the difference to the target track is input to the target speed curve generation circuit 205. The target speed curve generation circuit 205 outputs an optimum speed in accordance with the difference to the target track. Generally, it is considered that the optimum speed is preferably proportional to the square root of the difference to the target track. Here, since the output of the counter 104 is given digitally, a table of the square root is stored in advance in the ROM, and the target speed signal 206 is digitally converted according to the absolute value signal 57 of the difference to the target track. Output.

The target speed signal 206 is supplied to the D / A converter 2
07 and converted to an analog quantity,
Into one of the inputs. The other input receives the absolute value signal 111 of the speed from the speed detection circuit 204 and calculates the difference. The output of the difference is input to the polarity inversion circuit 209. Since the output of the speed difference is an absolute value, the polarity inversion circuit 209 performs an operation of giving a sign to the speed difference in accordance with the logic level of the access polarity signal 56. Therefore, this output is the difference between the target speed having a sign and the actual speed. This is the seek control / position control switching circuit 21
0, and is controlled by a timing signal B for starting position control. That is, when the timing signal B is LOW, the seek control is performed, and the signal of the speed difference is switched to the switching circuit 21.
0, which corresponds to the swing arm drive circuit 2
The swing arm 1 is driven via 11. When the seek control is completed and the light spot reaches the target track, the timing signal B becomes high and the control is switched to the position control. The generation circuit 214 of the timing signal B has been described in detail with reference to FIGS. When the tracking signal 52 is input to the switch circuit 211 and is high under the control of the timing signal B, the signal flow of the position control is connected to the position compensation circuit 212. This output is input to an adding circuit 213 together with a jump signal D to be described later, added, and enters the switching circuit 210. In this way, the position control is started by the timing signal B, and the target track can be stably pulled.

The tracking signal 52 is input to the timing circuit 214 for generating the timing signal B together with the access polarity signal 56 and the signal A. The operation of the circuit 214 has been described in detail with reference to FIGS.

The target track is accessed by the above procedure,
The address information stored in the track is read. This reading means is omitted in the above description. The read information is transferred to a controller (not shown) to determine whether the track is a target track.

The controller referred to here is a control device used for a magnetic disk or the like, and is usually a drive device having a minimum required drive mechanism and a drive circuit for reading and writing data (this is a drive device according to the present invention). ). In order to read and write data, control is performed by giving a command to a drive device. As this kind of function, at the time of access, it receives the desired track number from the computer connected to the controller, compares it with the currently read track, and calculates the absolute value and sign of the difference between the number of tracks to the desired track. The result is sent to the driving device. When the drive device performs seek control and position control by itself, and starts reading data from the target track and tracks near the target, the controller decodes the data and knows the number of the track currently being read, The subsequent access procedure is determined. For example, if the track is a target track, the jump number signal 58 indicates a signal indicating one number, and if the track on the disk is recorded spirally from inside to outside, a jump indicating the direction of jumping from outside to inside. The controller sends a polarity signal. The jump number signal 58 is input to the jump start circuit 215. The jump start circuit 215 sends a jump polarity signal to the jump waveform generation circuit 216 and generates pulses for jump start by the number of jumps at a specific time interval. Jump waveform generating circuit 216 receives this pulse and generates drive signal D for performing a jump according to the jump polarity signal. For details of the jump operation, see Philips Technica.
l Review Vol. 33, p. 178 is omitted here.

Therefore, in order to reach the target track and read it out steadily, the jump number signal 58 includes a signal indicating the number of jumps for each rotation of the disk and a jump polarity indicating the direction of the jump from the outside to the inside. It is sent from the controller including the signal. If the location inside the address of the track whose position is controlled when the access is completed is different from the target track, the difference between the currently read track and the target track is set to a certain number (for example, 64 or 128). If it is small, the light spot is moved to the target track by repeating the jump. At this time, the controller sends a jump number signal 58 including the number of tracks to the target track and its direction. If the difference from the target track is larger than a certain set value, an access including speed control is started. This is a repetition of the access procedure described so far.

As described above, in the example of FIG. 14, the light spot moves from the outside to the inside of the track based on the total reflected light amount signal and the tracking signal generated when the light spot passes through the guide track recorded on the optical disk. Knowing whether to pass through or from the inside to the outside eliminates errors due to eccentricity, mechanical vibration, and the like. In the speed detection as well, the relative speed between the light spot and the track is accurately detected by using the signal of the light spot passing through the track. In the example of FIG. 14, a swing arm capable of performing coarse positioning over the entire surface of the disk radius to fine positioning of about 0.1 μm is used as the actuator.

In the example of FIG. 14, one actuator is used.
It performs both coarse and fine positioning over the entire radius of the disk. However, this type of actuator has a problem in the frequency characteristic of displacement with respect to the drive current,
Cutoff frequency cannot be increased when a servo system for position control is configured. Therefore, apart from the first actuator for coarse positioning, only a small range can be moved, but the second actuator, which has a good frequency response performance and can increase the cutoff frequency even when a servo system is configured, is separately provided. It is desirable to provide. In this case, how the two actuators work together while following the track becomes a problem.

An example using two actuators will be described with reference to FIG. Here, as a first actuator for coarse positioning, a linear motor used for a magnetic disk will be described as an example. The gist does not change with other actuators. On the other hand, a galvano mirror or a pivot mirror is used as a second actuator having high response which follows a minute range. The disk 3 rotates in a fixed direction about the rotation axis 4, and the optical head 314
The movable table 315 moves on the base 309 according to the rotation of the roller 310. Mobile table 3
Reference numeral 15 is connected to the coil 311 via the support mechanism 313, and is driven by the electromagnetic force of the magnet 312 and the current flowing through the coil 311. An objective lens 306 for forming a light spot on the disc in the optical head 314;
A galvanomirror 308 as deflection means for moving the light spot on the disk surface, a photodetector 307 for receiving light reflected from the disk surface, a light source, and an optical system for guiding a light beam from the light source to an objective lens. There is an optical system for guiding the reflected light to the photodetector, but the light source and the optical system are omitted because they are unnecessary for describing the present invention.

A process of creating a total reflected light amount signal 51 and a tracking signal 52 from the output of the photodetector 307, creating signals 53 and 54 indicating the direction of track passage, and performing speed control using these signals. Are detailed in the example of FIG. 14, so that only the same block is presented and the description is omitted. The block 214 for generating the timing signal B for the position control from the tracking signal 52 and the part for performing the jump function are also the same, so that they are omitted. Only the procedure of the position control will be described. The switching circuit 211 is closed by the timing signal B for position control, and the tracking signal 52 is guided to the phase compensation circuit 212 to perform phase compensation for improving the stability and the tracking performance of the control system, and is added to the jump signal D and the addition circuit 213. After that, the signal becomes the mirror drive signal E. The mirror drive signal E drives the galvanomirror 308 via the galvanomirror drive circuit 305 to cause the light spot to follow the track. In this state, since there is no target signal for the position for positioning the first actuator, it is necessary to generate a positioning signal.

Here, the positioning signal will be described. When the light spot is fixed to the center of the field of view of the objective lens described later, and the linear motor moves in the radial direction on the disk surface, the tracking signal 52 shows the amount of movement shown in FIG.
It changes like 0. It is conceivable to use the tracking signal 52 as a signal for positioning the linear motor. However, since the linear range Δ of this signal is only as large as the track width, it is impossible to perform control unless the tracking accuracy δ is within this range. Become. Following accuracy is 2-3μ with a normal linear motor
When it is larger than m, it reaches about 10 μm. However, the track pitch p is about 1.6 μm for performing high-density information recording on a digital optical disk, and the track width Δ is about 0.8 to 0.6 μm. Therefore, using the tracking signal 52, the track center 4
It is impossible to control the positioning of the linear motor with a target of 05. Therefore, the linear region is wider than the tracking signal, and a signal representing the deviation between the track for tracking the target and the linear motor is created, and using this signal,
It is necessary to position the linear motor. As such a signal, there is a trajectory of a light spot followed by a galvanomirror.

That is, the circular area shown by the dotted line in FIG. 21 is the field of view 402 of the objective lens, and the trajectory 403 is the time t of the track tracked by the galvanomirror.
It is a locus with respect to. The track following in the lens visual field 402 changes sinusoidally with eccentricity as shown in FIG. Since the objective lens is fixed to the moving base of the linear motor at the center 404 of the lens field 402, the lens field center 404 also moves integrally with the linear motor. Neutral point of galvanometer mirror (determined when the mirror is mechanically set on the linear motor carriage)
Is a spring support mechanism, is uniquely determined when the drive signal E is zero, and is usually adjusted so that the light spot is located at the center 404 of the objective lens field 402 when the galvanomirror is at the neutral point. Have been. The reason for this adjustment is that the center within the lens field has the least residual aberration of the lens. There is a certain linear relationship between the movement amount of the light spot in the lens field and the rotation angle of the galvanomirror determined by the optical arrangement and the focal length of the objective lens. Accordingly, the deviation from the center of the lens field of view to the track tracked by the light spot can be known from the rotation angle of the galvanomirror.

The rotation angle of the galvanometer mirror can be known from the drive signal E. The rotation angle of the galvanomirror has different characteristics depending on the frequency component of the drive signal E (ie,
Frequency characteristic), which is already known. In FIG. 20, even if the center of the lens field of view is aligned with the track center 405 and the linear motor is stopped, the galvanometer mirror is driven to move the light spot from one end of the objective lens field to the other. Similarly, the tracking signal 52 is detected, and the galvanomirror driving signal E at this time becomes zero at the target track center 405,
It has a negative polarity at one end of the lens field and a positive polarity at the other end, and has a linear relationship with the light spot in the lens field, and the linear region covers the entire field of the objective lens.

In FIG. 15, a drive signal E is input to a circuit 300 for simulating the frequency characteristics of a galvanomirror, a shift signal F of the light spot from the center of the lens field is created, and the shift signal F is closed by a timing signal B for position control. By driving the linear motor through the phase compensation circuit 301 via the switching circuit 316, the linear motor is driven in conjunction with the movement of the light spot by the galvanomirror. In this way, the position of the linear motor is controlled such that the light spot is centered in the lens field of view, reducing the movement required for the light spot to follow the track. At this time, the deviation signal F of the light spot from the center of the lens visual field has a wide linear region and is at least 100 μm.
m, so that the tracking accuracy of the linear motor is 2-3 μm.
There is no problem even if there is m.

In FIG. 21, the solid circular area 406 is the field of view of the objective lens after performing the above-described operation.

That is, in conjunction with the light spot following the track 403 by the galvanomirror,
The displacement between the light spot and the lens field center 407, that is, the movement of the light spot by the galvanomirror is detected, and the linear motor is positioned. As a result, the center of the lens field of view (indicated by a white circle) 407 integrated with the linear motor follows the movement of the light spot by the galvanomirror. Off by minutes. Thus, the movement of the linear motor works to keep the light spot close to the center of the lens field of view, despite large fluctuations due to track eccentricity, and the light spot is required to follow the track correctly. The movement of the light spot by the galvanomirror is only the error δ, and is greatly reduced. Although this positioning error δ differs depending on the characteristics of the positioning servo system of the linear motor, FIG. 21 shows a case where the servo band has a servo band that can follow a large eccentricity. In the present invention, improving the band of the linear motor positioning servo system has another effect. This is controlled so that the light spot always comes near the center of the field of view of the objective lens, so that an area with little residual aberration can be used. as a result,
Spot size of light spot (light intensity distribution is the maximum value of 1
/ E2) becomes the smallest, the amplitude of the reproduced signal from the recorded hole becomes large at the time of reproduction, and the light emission power of the light source required to make a hole of a constant diameter at the time of recording is small. . Conversely, when the spot size required for a digital optical disc is determined to be a fixed value, aberrations are reduced only at the center of the field of view, compared to a method in which the spot is moved within the field of view of the objective lens using a galvanometer mirror. Since the size of the objective lens may be reduced, the number of constituent lenses of the objective lens is reduced, and the objective lens is reduced in weight, size and cost.

FIG. 16 shows an example of a circuit 300 for generating a displacement signal F of the light spot from the center of the lens field of view from the drive signal E of the galvanomirror in order to detect the movement of the light spot by the galvanomirror. The drive signal E enters the buffer amplifier 302 and is sent to an electric circuit that resembles the frequency characteristics of a galvanomirror. Since the characteristic of the drive voltage (or current) of the normal galvanomirror versus the deflection angle shows the characteristic of the secondary reduction filter, in this embodiment, the secondary is composed of the capacitors C1 and C2, the resistors R1 and R2, and the buffer amplifier 304. A low-pass active filter is used. This output will therefore represent the deflection of the galvanomirror. Since the deflection of the galvanomirror and the movement of the spot on the lens field are usually in a linear relationship, the linear amplifier 303
By correcting the sensitivity (between the deflection angle and the spot movement amount), a shift signal F of the light spot from the lens field is obtained.

As a method of detecting a deviation signal of the light spot indicating the movement of the light spot from the lens field of view by the galvanometer mirror, a method of directly detecting the deflection angle of the mirror other than electrically simulating the mirror drive signal E described above. There is.

FIG. 17 shows a specific example. A light beam 328 emitted from a light source (not shown) is moved along an optical axis 329 to a mirror 3
The light enters the optical system 20 and is reflected in the direction of 45 °, and the optical path is bent in the direction of the objective lens (not shown). A permanent magnet 321 is attached to the back surface of the mirror 320, and an electromagnetic force is generated by a current flowing through a coil 322 surrounding the permanent magnet 321.
Rotate around 31. The bearing 331 is fixed to a part 332 of the optical head by a support rod 330. Bearing 33
1 is formed of an elastic rubber material. This structure is a kind of pivot mirror. In order to detect the deflection angle of the mirror, the light beam from the light emitting diode 326 is
7, the light is condensed on the reflection surface of the mirror 320, and the reflected light beam is received by the two photodetectors 323 and 324. After alignment is performed so that the optical axis 329 of the light beam reflected by the mirror 320 coincides with the optical axis of the objective lens in a state where the driving voltage is zero, the light beam from the light emitting diode is equally received by the photodetectors 323 and 324. Adjust so that Then, the outputs of the photodetectors 323 and 324 are output to the differential amplifier 325.
When the difference between the two is calculated, the output F 'becomes a signal indicating the deflection angle of the mirror, and the movement of the light spot by the mirror can be detected. In the method of directly detecting the deflection angle of the mirror as described above, the movement of the mirror due to mechanical vibration can be known. This is effective when the mirror mounted on the motor may vibrate.

That is, the movement of the mirror is detected, the mirror is positioned at the first set point, and the fluctuation of the optical axis of the objective lens can be prevented. Therefore, the signal F 'is used for the above operation when the coarse positioning is performed by the speed control of the linear motor, and the mirror 3
When the light spot is minutely positioned by deflecting the light 20, it can be used as a shift signal from the center of the lens field of view. FIG. 18 shows an embodiment using the signal F 'obtained by directly detecting the mirror deflection angle described above. The speed control using the linear motor is the same as the embodiment described so far,
Since the parts represented by the same block numbers are common, the description is omitted. The switching circuit 333 allows the mirror deflection signal F ′ to pass only during this period because the position control timing signal B is LOW in the speed control,
Is controlled to stop mechanical vibration and stop at a set point. When the timing signal B for the position control becomes high, the tracking signal 52 is passed, and the light spot is tracked by the mirror. On the other hand, the mirror deflection signal F 'is input to the switching circuit 316 via the amplifier 334 for sensitivity correction, passes only when the position control timing signal B is high, drives the linear motor, and moves the mirror to the center of the lens field of view. Is controlled so that the track being tracked is located.

[0059]

FIG. 19 shows a two-dimensional actuator as a second actuator which follows only a minute range with high responsiveness. This is a mechanism that moves the objective lens 340 in parallel with the optical axis 342 for focusing, and at the same time, moves it vertically to the optical axis for tracking. FIG.
(A) is a plan view seen from above, and (b) is a side view seen from the side. The optical axis 342 is bent by the mirror 343 and coincides with the optical axis of the objective lens 340. The objective lens 340 is a ring spring 3 having a metallic spiral shape.
Frame 3 supported by 41 and holding the outer periphery of the spring
Reference numeral 61 is connected to a support portion 347 for driving in the track direction. A coil 344 is wound below the frame 362 connected to the inner periphery of the spring, and is parallel to the optical axis by a current flowing electromagnetically through the coil 344 by a magnetic circuit including a permanent magnet 345, a center pole 346, and a yoke. The objective lens 340 is driven. Mirror 343 is coupled above center pole 346. On the other hand, as shown in FIG. 19A, a coil 348 is wound around the tip of the support portion 347, and is driven in the track radial direction by a magnetic circuit including a permanent magnet 349, a center pole 350 and a yoke. A sliding bearing 351 is connected to the frame body 361 that holds the ring spring 341, and a shaft 352 is in contact with the sliding bearing 351. The shaft 352 is attached to a base 353 that supports the shaft, and is fixed to a base. Accordingly, in the track radial direction, the mechanism for driving the objective lens parallel to the optical axis and the mirror 342 are integrally driven. In the above configuration, when the track is positioned by the linear motor, the center of the lens field of view coincides with the movement of the two-dimensional actuator in the track direction. Therefore, the position shift of the mechanism that integrally supports the objective lens 340 and the mirror 342 is performed. I just want to know.

Therefore, the permanent magnet 354 is attached to the sliding bearing 351.
When the Hall elements 355 and 356 are mounted on a base on which the shaft support 353 is fixed, and the difference between the outputs of the Hall elements 355 and 356 is input to the differential amplifier 357, the output of the differential amplifier becomes
The displacement between the geometric center of the two Hall elements 355 and 356 and the permanent magnet 354 is shown. When the permanent magnet 354 is disposed on an extension of a perpendicular line from the optical axis of the objective lens 340 to the slide axis 352, when the two-dimensional actuator tracks the track, the optical axis of the objective lens and the position of the track have a one-to-one correspondence. As a result, the output of the differential amplifier 357 represents the deviation between the track and the geometric center of the Hall elements 355 and 356 set in the linear motor.
Therefore, the output of the differential amplifier 357 is used as a signal F 'for position control of the linear motor.

As described above, a combination of an actuator which can perform coarse positioning but has a poor accuracy in the past and an actuator which has only a small movable range but has a high response and a high tracking accuracy is combined as a whole to provide a high response and a high tracking accuracy. This embodiment makes it possible to realize high-level access.

In the above description, a detailed description of a method of detecting an information signal and a method of detecting a tracking signal has been omitted, and these methods will now be described with reference to FIGS.
3, and will be described in detail with reference to FIG. FIG. 22 is a principle diagram of a tracking signal detection method using diffracted light,
(A) shows a simple configuration of the optical system. First, the light source 504
A light beam (for example, a semiconductor laser or the like) is converted into parallel light by a coupling lens 503, passes through a polarizing beam splitter 502, passes through a quarter-wave plate 501, and is rotated around a rotation axis 4 by an objective lens 500. It converges on the rotating optical disk 3. This reflected light is reflected by the objective lens 50.
0 again, the plane of polarization is rotated by 90 ° with respect to the incident light by the quarter-wave plate, and the polarization beam splitter 50
2, the optical path is bent in the direction of the converging lens 505,
The light is converged toward the convergence point 506 by the converging lens 505. The light detector 5 is located between the converging lens 505 and the convergence point 506.
07 is arranged. (B) illustrates the structure of the photodetector 507 and the means for detecting the tracking signal 52 and the information signal 512. The photodetector 507 is composed of photodetectors 508 and 509 divided into two parts,
2 is obtained by taking the output from these photodetectors by the difference amplifier 510, and the information signal 512 is obtained by taking the sum of the outputs of the photodetectors 508 and 509 by the adder 511.

FIG. 23 is a principle diagram of the tracking signal detection method using two spots. FIG. 23A is different from FIG. 22A in that the diffraction grating 514 is provided after the coupling lens 503. And parallel light flux of 3
The point is that it is separated into two. In this way, three spots are formed on the disk surface, one of the spots is arranged in the middle of the track, and the other two spots are symmetrically shifted by a slight amount from the center of the track. To place. The light detector 513 is set to the converging point 50 of the converging lens.
6 above, as shown in FIG.
Three spots surrounded by oblique lines are formed. Photodetector 5
Reference numeral 13 includes three independent photodetectors corresponding to the three spots. The output from the middle photodetector passes through a buffer amplifier 515 to become an information signal 512, and the outputs from the remaining two photodetectors enter a differential amplifier 510 to generate a tracking signal 52.

FIG. 24 is a principle diagram of a wobbling and pre-wobbling tracking signal detection system. In FIG.
5, and has the same configuration as the optical system of FIG. (B) In the figure, the photodetector 516 is a photodetector having a single light receiving portion, and has one light spot (a region surrounded by oblique lines) formed on the photodetector surface. When the output of the photodetector 516 is amplified by the buffer amplifier 517, it becomes an information signal 512, which is converted into an envelope signal 519.
To remove the effect of the data signal recorded through the filter, extract the wobbled or pre-wobbled component through a band filter 520 having the center frequency of the wobbled or pre-wobbled frequency. Put in. Synchronous detection circuit 521
Has a signal 522 of a wobbling frequency having a reference phase.
Is input, synchronous detection is performed, and the tracking signal 52
Get. The signal 522 having the reference phase is formed from the information signal 512 in the case of pre-wobbling (for details, refer to Japanese Patent Application No. 53-68793). In the case of wobbling, the optical head or the deflector is tracked. Made from signals driving in the direction.

Next, means for detecting the total reflected light amount signal 51 from the information signal 512 will be described. When there is no information pit 12 in the guide groove 13, the information signal 512 is equal to the total reflected light amount signal 51. However, when the information pits 12 are present, the information signal 512 is transmitted as shown in FIG.
It changes according to (c). The portion surrounded by the solid line and the dotted line represents the modulation of the amount of reflected light by the information pit. This signal 512 is input to an envelope detection circuit 524 via a buffer amplifier 523 as shown in FIG.
When output via the buffer amplifier 525, the total reflected light amount signal 51 is obtained. At this time, the envelope detection circuit 5
The values of the capacitor C and the resistance R which determine the time constant of 24 are sufficiently smaller than the lowest repetition frequency of the information pit in the information signal 512 and the highest repetition frequency of the total reflected light amount signal 51 when passing through the track. Choose to be high enough. In order to eliminate the influence of the information bit on the tracking signal 52, the same means as described above can be considered. This is described in Japanese Patent Application No. 56-138583 entitled "Light Spot Control System" filed on Sep. 4, 1981. Details are omitted here.

[0066]

As described above, according to the present invention, an inexpensive and lightweight lens can be used to control the light beam to always pass near the center of the lens of the optical head during the tracking operation. A spot having a size close to the diffraction limit with high accuracy can be formed, and accurate recording and reproduction can be performed.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of a digital optical disk.

FIG. 2 is a partially enlarged perspective view of a disk.

FIG. 3 is a circuit block diagram for explaining an access method of a magnetic disk.

FIG. 4 is a block diagram of a tracking control circuit of the magnetic disk.

FIG. 5 is a waveform chart showing a tracking signal in the magnetic disk.

FIG. 6 is a waveform diagram illustrating a relationship between a light spot locus and eccentricity.

FIG. 7 is a perspective view illustrating a method of detecting a signal when passing through a track.

FIG. 8 is a waveform chart for explaining a position detection method.

FIG. 9 is a circuit block diagram for explaining position detection.

FIG. 10 is a circuit block diagram for explaining speed detection.

FIG. 11 is a waveform chart for explaining the timing of position control.

FIG. 12 is a circuit block diagram for explaining position control.

FIG. 13 is a circuit block diagram for explaining position control.

FIG. 14 is a block diagram illustrating a signal processing circuit that performs an access operation.

FIG. 15 is a block diagram illustrating an example of an information storage device.

FIG. 16 is a block diagram of a simulation circuit of the actuator.

FIG. 17 is a block diagram for explaining a mirror deflection detection method.

FIG. 18 is a block diagram showing an embodiment of the information storage device of the present invention.

FIG. 19 is a plan view and a cross-sectional view illustrating a configuration of a two-dimensional actuator used in the present invention.

FIG. 20 is a plan view for explaining the present invention.

FIG. 21 is a waveform chart for explaining the present invention.

FIG. 22 is a configuration diagram for explaining a tracking signal and a total reflection light amount signal detection method used in the present invention.

FIG. 23 is a configuration diagram for explaining a method of detecting a tracking signal and a total reflected light amount signal used in the present invention.

FIG. 24 is a configuration diagram for explaining a method of detecting a tracking signal and a total reflected light amount signal used in the present invention.

FIG. 25 is a configuration diagram for explaining a method of detecting an information signal and a total reflected light amount signal used in the present invention.

[Explanation of symbols]

3, recording medium, 314, irradiation means, 307, photodetector,
52: tracking signal, 320: second position control means, 312: first position control means.

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[Procedure amendment]

[Submission date] August 7, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Name of invention

[Correction method] Change

[Correction contents]

[Title of the Invention] Optical disk drive

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0001

[Correction method] Change

[Correction contents]

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an optical disk apparatus, speaking more specifically, it relates to an optical disk device for positioning in a submicron precision light beam to a desired track.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masahiro Takasago 2880 Kozu, Kofu, Odawara City, Kanagawa Prefecture Inside Odawara Plant, Hitachi, Ltd. 72) Inventor Tokuya Kaneda 2880 Kozu, Odawara City, Kanagawa Prefecture Inside the Odawara Plant of Hitachi, Ltd.

Claims (1)

[Claims] 1. An information storage device for optically recording or reproducing predetermined information along a track of an optical disk, comprising: an optical head for irradiating a laser beam as a spot on the optical disk through an objective lens; Light receiving means for receiving a reflected light of the light and outputting a signal;
Tracking signal forming means for forming a tracking signal indicating a deviation of the spot from the track based on the output of the light receiving means; first driving means for moving the optical head on the optical disk; A second driving means for moving a lens in parallel with the optical disk surface to move the spot on the optical disk so as to follow a desired track; and a second driving means for moving at least the second driving means. Detecting means for detecting the movement of the driving means, and outputting a signal indicating the movement of the driving means, wherein the first driving means performs the second driving while the second driving means follows the desired track. Moving the optical head on the optical disc in accordance with the output of the detecting means so that the magnitude of the displacement of the spot moved by the driving means is reduced; Spot information storage device to follow the track by moving in accordance with movement of the first and second drive means.