JPH02168435A - Optical spot positioning method and optical disk storage device - Google Patents

Abstract

PURPOSE:To attain high speed seek by selecting a band of a control system of a micro moving mechanism moving an optical spot to be 10kHz or over at track locking. CONSTITUTION:A light radiated from a laser diode 101 is collimated by a collimate lens 102, shaped into a circular beam by a beam shaping prism 103 and enters an optical polarizer 104 acting like a micro moving mechanism. The light beam whose radiation angle is varied by the optical polarizer 104 enters a polarizing prism 105. The light radiated from the polarizing prism 105 is converted into a circularly polarized light by a lambda/4 plate 106 and light spot is focused onto an optical disk 10 through a rise mirror 107 and an aperture lens 108. High speed seek is implemented for the optical polarizer 104 by using a moving mechanism having a prescribed amplitude characteristic whose frequency is 10kHz or over. Then after the track locking is finished, the band of the control system is switched to 5kHz or below.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an optical information recording and reproducing method and an optical disc storage device that record and/or reproduce information by irradiating a light spot onto an optical recording medium using a laser beam. More specifically, the present invention relates to a light spot positioning method for rapidly positioning a light spot on a desired track using a macro movement mechanism and a micro movement mechanism, and an optical disk storage device using the same.

[Background Art] An optical disk storage device has been developed as an information storage device configured to record and reproduce information on a high-density rotating recording medium, or to erase information as necessary. An optical disk, which is a rotating recording medium, has a large number of concentric or spiral tracks arranged at a constant pitch, and each track has a large number of sectors for indicating data divisions. In order to record external information at any location, or to reproduce or erase information at any location, first find one track from among the many tracks on the disk surface.
An access operation (seek operation) is required to find one sector on this track. In other words, macro seek control that moves the light spot near the target track at high speed, track following control that maintains the light spot on the center of the track, and micro seek control that corrects the deviation from the target track is required. . Access operations in such optical disk storage devices are described in Japanese Patent Application Laid-Open No. 58-91.
No. 536 and JP-A-58-169370. [Problems to be Solved by the Invention] Conventional optical disk storage devices use a macro movement mechanism such as a linear motor to move the optical head, and a voice coil or the like to drive the galvanometer mirror or objective lens mounted on the optical head. The positioning of the light spot is controlled by a micro-movement mechanism. That is, when seeking, first, the optical head for recording and reproduction is approximately positioned with respect to the track on the optical disk by a macro movement mechanism such as a linear motor (macro seek control). After the macro seek operation is settled, a track following operation is performed (track following control) by the cooperative operation of the macro movement mechanism and the micro movement mechanism. Then, the track address at that location is read and the deviation from the target track is determined. In order to correct the deviation from the target track, a micro-movement mechanism such as a galvanometer mirror repeatedly performs track jumps to move the light spot to the target track (micro-seek control). When the light spot reaches the target track, tracking control is performed again and the seek operation is completed. In order to shorten the macro seek time, it is necessary to drive the optical head at high acceleration. In an optical disk device, the optical head is equipped with a lens actuator for narrowing down the light spot, the aforementioned micro-movement mechanism, optical components, etc., and therefore, the rigidity of the head is generally lower than that of a magnetic disk device. Therefore, due to the influence of mechanical sub-resonance, the bandwidth of the speed control system during macro seek cannot be increased much. If the head is driven at high acceleration without increasing the band of the speed control system, the speed deviation, which is the deviation from the target speed, will increase. The macro seek target speed curve is set such that the speed is decelerated at the maximum acceleration to shorten the seek time, and the relative speed between the light spot and the track on the target track is decelerated to a speed that allows the track to be pulled in. This track pull-in speed is limited by the size of the detection range of the track deviation signal and the band of the light spot control loop, and is approximately 3 am/sec in an optical disk device. On the other hand, the speed deviation is approximately 5 if the deceleration acceleration and speed control system band is 25G and 700Hz, which is comparable to a magnetic disk device.
It becomes 5mm/see. In other words, the optical disc device cannot pull in tracks. In the case of optical disk drives, the band of the speed control system is even lower and the speed deviation becomes larger, so it has not been possible to drive the disks at the same high acceleration as a magnetic disk drive. Furthermore, in addition to speed deviation, when an optical head is driven at high acceleration, there is a problem of residual vibration due to the low rigidity of the head, as described above. Even after the macro seek movement was completed, it took time for the head to stabilize until the vibrations subsided, and the seek time could not be reduced much. Optical disk devices generally perform seek operations in two stages: macro seek and micro seek, so even if the macro seek speed is comparable to that of a magnetic disk device,
Micro-seek takes an extra amount of time. The reason why micro-seek is necessary is that the track pitch of an optical disc is as fine as about 1.6 μm. In other words, it is difficult to reach the target track by macro seek alone due to problems with the positioning accuracy of the macro movement mechanism, the accuracy of the head position detection device, and the large eccentricity of the optical disk. Therefore, it is difficult to reach the target track by macro seek alone. This is corrected by micro-seek. On the other hand, in a magnetic disk storage device, the track pitch of the magnetic disk is as large as about 20 μm, and the eccentricity of the disk is also smaller than that of an optical disk, so it is possible to reach the target track only by macro seek. In this way, it is difficult for optical disk drives to drive at the same high acceleration as magnetic disk drives.
Moreover, even when driven at high acceleration, the seek time could not be reduced much. On the other hand, as a theta method that does not perform micro-seek, there is a method called cross-track seek. This cross-track seek method is based on the above-mentioned JP-A-58-
As disclosed in Japanese Patent No. 91536, the number of track passing pulses output every time the track is crossed is counted, and the optical head is positioned on the target track by only macro seek using a macro movement mechanism. However, when performing a cross-track seek at high speed, the header and data signals written on the disk are mixed into the track misalignment signal.
Since the band overlaps with the band of the track passing pulse, an erroneous count of the number of tracks passing through one occurs. Therefore, it is not possible to correctly position the target track, and it is necessary to perform correction by micro-seek, and even with the cross-track seek method, it is difficult to shorten the seek time. Due to the above-mentioned problems, optical disk devices have a problem in that the seek time is longer than that of conventional storage devices, especially magnetic disk devices. 141 The average seek time of a magnetic disk storage device is 15 m.
5ec, whereas a 12' optical disk storage device has a very slow speed of about 200m5ec. SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and to provide an optical spot positioning method that can achieve high-speed seek comparable to that of a magnetic disk device, and an optical disk storage device using the method. 1. Means for Solving the Problems In order to achieve the above object, the present invention uses the following means. ■ Set the control system band of the optical spot micro-movement mechanism to 10 KHz or more during track pull-in movement. By setting the control band of the micro-transfer mechanism to 10KHz or more,
Track pull-in can be performed while the relative speed between the track and the light spot is high. Although the bandwidth of the control system is limited by the characteristics of the micro-moving mechanism, micro-moving mechanisms that can operate at higher speeds than conventional galvanometer mirrors or two-dimensional actuators, non-mechanical optical devices such as A10 deflection elements and SAW elements, etc. By using a deflector, it is possible to increase this band to 10 KHz or more. Then, during the track following operation after the track pull-in is completed, the control system of the micro movement mechanism is switched to a lower frequency band of 5KHz.
The following shall apply. This is because if the control system band of the micro-transfer mechanism is kept high, the tracking performance is good up to high frequencies, but the light spot will be deflected more than necessary due to track defects, minute dust, noise, etc. It is. As described above, the present invention is characterized in that the band of the control system of the micro-moving mechanism is changed between the track pull-in operation and the track follow-up operation. ■ As a linear scale for detecting the amount and speed of movement of the optical head, there is a scale with grooves with a pitch similar to the track pitch of the optical disk, and an optical system fixed to the base to detect the grooves. A fine-pitch laser scale consisting of ■ The track error detection and output means for detecting a track error signal from the reflected light of the optical spot is a means for correcting the offset caused by the reflected light being shifted from the optical center axis due to the movement of the optical spot by the micro-movement mechanism. has. Then, based on the offset-corrected track error signal output from the track error detection means, the macro movement mechanism and the micro movement mechanism are driven during the track pull-in operation and the track follow-up operation to activate the two-stage tracking servo system. Configure.

[Function] By raising the control system band of the optical spot micro-movement mechanism to 10 KHz or more during track pull-in operation,
Even if a macro seek is performed by driving the optical head at high acceleration, the optical spot can be drawn onto the track while the relative speed between the track and the optical spot is high. For example, if you increase the band to about 12KHz, 55mm/
sec. If the frequency is increased to about 22 KHz, it becomes possible to pull in tracks at a speed of 15 Gms/see, which is comparable to a magnetic disk device. Therefore, macro seek can be performed at high acceleration, and the time required for macro seek can be shortened. In addition, when the head is driven at high acceleration, the mechanical residual vibration of the head increases after the macro seek is completed, but this residual vibration can be suppressed by increasing the bandwidth of the control system of the micro movement mechanism. . Therefore, there is no need to wait for this residual vibration to decay. Moreover, the time required for track pull-in itself is also shortened. For example, when the band is set to about 12 KHz, the time required for acquisition is 15 Gμsec, and when the band is set to 20 KHz, it is 60 μsec. Furthermore, by increasing the control band of the micro-movement mechanism, the operation of the micro-movement mechanism becomes faster than in the past, and the time required for micro-seek can be shortened. By using micropitch laser scale signals,
An operation almost equivalent to cross-track seek can be performed. That is, the number of pulses from the fine pitch laser scale is counted, and the optical head is positioned on the target track using a macro movement mechanism. Even in the case of high-speed seek, there is no crosstalk other than the position signal, so no erroneous counting occurs, and it is possible to almost accurately position the target track just by macro seek. Even if it is not possible to position the target track, the deviation is quite small, and less correction by micro-seek is required. By using a micro-pitch laser scale, more accurate speed information than before can be obtained, and speed control during macro seek can be performed accurately, stably, and at high speed. The mechanical residual vibration of the head can also be reduced, and the settling time can also be shortened. Since the tracking error detection means includes the offset correction means, even if the reflected light deviates from the optical center axis and moves on the detection surface of the detector due to the movement of the light spot by the micro-movement mechanism, accurate tracking errors can be detected. The signal can be detected, the optical spot can be accurately and stably positioned on the target track, and tracking control can be performed. With the above-described effects, the time required for macro-seek or micro-seek can be shortened, and an optical disk device capable of high-speed seek comparable to that of a magnetic disk device can be realized.

【Example】

An embodiment of the light and head used in the present invention is shown in FIG. The light emitted from the laser diode 101 is turned into parallel light by the collimating lens 102, and the beam shaping prism 103
After being shaped into a circular beam by , it enters an optical deflector 104 that operates as a micro-transfer mechanism. The optical deflector 104 is
It is composed of a non-mechanical optical deflection element such as an A10 deflection element or a SAW element, and a beam shaper. Optical deflector 104
The light beam whose output angle is changed by polarizing prism 1
Enter 05. If the polarization of the light beam at this time is set to be P-polarized light with respect to the polarizing prism 105, most of the light beam will travel straight through the polarizing prism 105. The light beam exiting the polarizing prism 105 passes through the λ/4 plate 106 and becomes circularly polarized light.
8 and is irradiated onto the optical disc 10.
This light spot can be moved in the tracking direction by the aforementioned optical deflector 104. The light reflected by the optical disc 10 is again passed through the aperture lens 108, the raising mirror 107 . After passing through the λ/4 plate 106, the light beam is turned back into linearly polarized light by the λ/4 plate 106. What is the polarization at this time? Since the light is S-polarized with respect to the polarizing prism 105,
The light is reflected without passing through the polarizing prism 105 and guided to the detection optical system. That is, the reflected light beam enters the half prism 109 and is split into two directions. On the one hand, a detector 1 for detecting a track deviation signal is formed by a convex lens 111.
15, and the other is narrowed down by a convex lens 110 and focused by a half prism 112 onto detectors 113 and 114 for front-back differential focus shift detection and data signal detection. Namely. One detector 113 is provided behind the condensing point, and the other detector 114 is provided in front of the condensing point. When the focus of the light spot irradiated onto the optical disk 10 coincides with the information recording surface, both detectors 113 and 114 are arranged so as to receive light of the same intensity. The optical head 15G can be moved in the disk radial direction by a coarse actuator such as a near motor 20 (see FIG. 16), which operates as a macro movement mechanism. A laser scale 200 is used to detect the amount and speed of movement of the optical head 15G. That is, a scale 200b with a minute pitch is attached to the optical head 15G, and this scale is irradiated with a laser beam from an optical system 200a attached to the base 15. By looking at the reflected light, the moving amount, moving speed, etc. of the optical head 15G are detected. FIG. 2(a) shows an example in which an A10 deflection element is used in the optical deflector 104 that operates as a micro-movement mechanism. It would be preferable if the light beam could be deflected as a circular beam, but the normal A10
Since the aperture of the deflection element 118 is rectangular, it is necessary to convert the beam into an ellipse to increase efficiency. The incident laser beam is focused into an elliptical beam by a beam conversion prism 117, enters an A10 deflection element 118, and the output beam is returned to a circular beam by a beam conversion prism 119. The operation of the A10 deflection element 118 will be explained using FIG. 2(b). The A10 deflection element 118 includes a medium 118a that is transparent to laser light, a piezoelectric transducer 118b that propagates ultrasonic waves in the medium, and a high frequency source 120 that drives the piezoelectric transducer.
When the ultrasonic waves generated by the piezoelectric transducer 118b are propagated inside the medium 118a, the compression waves of the ultrasonic waves cause periodic changes in the refractive index due to the photoelastic effect of the medium 118a. It acts as a phase grating for the light incident on it, and the light is diffracted. When the frequency of the ultrasonic wave is f, the propagation speed of the ultrasonic wave is V, and the wavelength of the incident light is λ, the diffraction angle θ is expressed by the following equation. (2) Normally, the propagation velocity V of the ultrasonic wave and the wavelength λ of the incident light are constant, so the frequency f and the diffraction angle θ are proportional. Therefore, by changing the frequency f, the diffraction angle θ can be changed, that is, the deflection angle of light can be changed. In conventional optical disk devices, a mechanical rotating mirror such as a galvanometer mirror is used as a micro-movement mechanism to deflect light. Figure 3 shows an example of the characteristics of a mechanical actuator using a galvanometer mirror.The gain decreases beyond the main resonance point fr+a, and has a gain peak at the sub-resonance point frs. Bandwidth 4~
It could only extend up to 5KHz. Figure 4 shows the A10 used as a micro-transfer mechanism in the present invention.
An example of the characteristics of a deflection element is shown. As mentioned above, the A10 deflection element can change the deflection angle θ by changing the frequency f, and the frequency f can be changed electrically by a high frequency source, so it can operate at high speed.
The gain is constant at OdB up to high frequencies. It also does not have sub-resonance like mechanical actuators. In this way, unlike mechanical actuators such as galvanometer mirrors used in conventional optical disc devices, the A10 deflection element is capable of high-speed operation and can move the optical spot at high speed. Furthermore, since the deflection angle of the light beam is determined by the frequency applied to the A10 deflection element, the amount of movement of the light spot can be determined accurately. In this example, an example in which an A10 deflection element is used as the micro-movement mechanism has been described, but the SA
W element Element horizontal 1 Mechanical deflection element It doesn't matter, 1
Any moving mechanism may be used as long as it has constant amplitude characteristics in which the gain does not change up to a high frequency of 0 KHz or higher. In this embodiment, a front-rear differential method is used to detect the focus error signal. This is a known technique in which detectors 113 and 114 are placed before and after the focal point of a convex lens 110, respectively, as shown in FIG. 1, and the difference in their output signals is taken. FIG. 5 shows a focus error signal detection system. In the configuration shown in FIG. 1, when the light beam is deflected by the light deflector 104, the light spots on the detectors 113 and 114 also move. , 114 must be set as shown in FIG. 5(a) to prevent interference with the focus error signal. That is, each of the detectors 113 and 114 is configured with a two-part detector that detects only the peripheral part of the light spot irradiated onto its detection surface, and the divided band is set in the direction of the deflection of the light by the optical deflector 104 (arrow (indicated by ). In this way, the optical deflector 104 allows the detector 1 to
Even if the light spot on 13, 114 moves in the direction of the arrow, the amount of light received by the detection parts a, b or c, d provided on both sides of the dividing band does not change, and the light by the optical deflector 104 does not change. The influence of spot movement can be removed. Furthermore, data reproduction signals can also be obtained using the signals from these detectors 113 and 114. The configuration of the signal system is shown in FIG. 5(b). That is, the two-part detector 11
An adder 501 adds the two outputs of No. 3, and an adder 502 adds the two outputs of the two-divided detector 114. Then, the outputs of the adders 501 and 502 are added together by an adder 503 to obtain a data reproduction signal, and the difference between the outputs of both adders 501 and 502 is obtained by a differential amplifier 504 and used as a focus error signal. The data reproduction signal is input to a demodulator and demodulated. In addition, the focus error signal is transmitted to the aperture lens 10.
The distance between the diaphragm lens 108 and the optical disc is adjusted so that the focal point of the light spot irradiated from the diaphragm lens 108 coincides with the information recording surface of the optical disc 10. A diffracted light tracking method (push-pull method) is used to detect the track error signal. This technique is also known. The shape of the detector 115 is shown in FIG. 6(a), and the signal system is shown in FIG. 6(b). In FIG. 6(a), the solid line arrow indicates the direction of light deflection by the optical deflector 104, and the dotted line arrow indicates the direction of light deflection by the optical deflector 104. This is the direction of the track projected onto the detector 115, and the detector 115 has two detection units arranged symmetrically with respect to the track direction and arranged in the interference region of the O-th order diffracted light and the ±1st-order diffracted light caused by the track. It has e and f. The tracking error signal Tr is obtained by differentially outputting the two outputs of the detector 115 using a differential amplifier 609. Same as for detection of focus error signal. When the optical beam is deflected by the optical deflector 104, as shown in FIG.
As shown in a), the light spot on the detector 115 also moves. As a result, depending on the deflection angle of the light beam,
An offset is added to the track error signal. A method for correcting the offset of the track error signal will be described below. The first is a method in which the relationship between the deflection angle of the light beam by the optical deflector 104 and the offset amount is calculated or measured in advance and stored, and the tracking error signal is corrected according to the deflection angle of the light beam. be. The method is shown in FIG. Using the control signal R of the optical deflector 104, the simulator 505 simulates the offset, and the track error signal detection circuit 507 (FIG. 6(b)
) and the differential amplifier 509, and correct the track error signal detected by the track error signal detection circuit to generate a corrected track error signal T.
Get r'. Note that the optical deflector 104, for example, the A10 deflection element 118. It is driven by an optical deflection element drive circuit 65 to which a control signal R is input. In this method, if an offset occurs due to a factor other than the deflection of the light beam by the optical deflector 104, it may not be possible to correct it completely. A second method for correcting the offset of the track error signal is to intermittently provide blank areas with no data on the tracks of the optical disc 10 as shown in FIG. The amount of track error is determined by wobbling the track error signal Tr, and the track error signal Tr detected by the track error signal detection circuit (differential amplifier 609) is corrected based on the amount of track error, thereby obtaining a corrected track error signal Tr' having no offset. The wobble method is disclosed in Japanese Patent Application Laid-open No. 49-94304 and Japanese Patent Application Laid-open No. 50-68413, so a description thereof will be omitted. The offset correction of the track error signal Tr in this embodiment is performed using an A10 deflector as a micro-movement device. This becomes possible for the first time by using a non-mechanical optical deflector such as a SAW element. Conventional mechanical actuators do not allow high-speed wobbling, and there is a problem in that the light beam is deflected even in the data area (recording area). The configuration of the offset correction circuit is shown in FIG. 8(b). The track error signal Tr caused by normal diffracted light tracking is corrected by the track error signal Tro caused by wobbling. The timing circuit 601 generates a signal that wobbles the light spot when the light spot is located in the blank area;
Drives the optical deflector drive circuit 65. The amount by which the light spot is wobbled is preferably 174, which is the track pitch. For example, when the track pitch is 1.6 μm, the amount of wobbling around the track is preferably about 0.4 μm;
In reality, taking into account vignetting caused by the aperture lens 108, the distance is usually about 0.15 μm. The difference between the outputs e and f of the detector 115 is determined by a differential amplifier 609. Then, the sum of the outputs e and f of the detector 115 is added to the adder 61.
1 and input it to sample/hold circuits 603 and 605. Timing circuit 601 also outputs control signals for sample/hold circuits 603 and 605. A pair of sample/hold circuits 603 and 605 store the amount of reflected light when the light spot is swung to both sides of the track, and a differential amplifier 607 calculates the difference between them to obtain a wobbling track error signal Tro. This is input to the adder 613 via the gain adjuster 2. Adder 6
13 other inputs. The output Tr of the differential amplifier 609, which is a track error signal Tr due to diffracted light tracking, is connected to the gain adjuster via 1. Gain Kl. By changing the value of K2, it is possible to change the ratio between the error signal Tr due to diffraction light tracking and the error signal Tro due to wobbling. When K1=0, the tracking operation is equivalent to sample servo. The offset-corrected tracking error signal Tr' is given to the tracking control circuit 45 as described later, and is subjected to one-phase compensation to generate a micro tracking control signal (optical deflection element control signal) R and a macro tracking control signal (coarse actuator control signal 7). )G, and the micro tracking control signal (light deflection element control signal) R is the micro movement mechanism (light deflection element) drive circuit 65.
The micro-movement mechanism (light deflection element) 104 is driven via. A third method for correcting the offset of the track error signal will be explained. As shown in FIG. 9, this is to cause the light spot to wobble (vibrate) discretely, thereby canceling the offset component from the track error signal. Let the position of the light spot in the disk radial direction be X, and the track pitch be p. Track error signal with offset
It is assumed that Tr is expressed by the following formula. Tr = a sin (27CX/P) + b
Here, a is the amplitude of the track error signal, and b is the offset. The amount of movement of the light spot due to wobble is ±W,
Letting the track error signals Tr at that time be E'' and E-, the sum of E'' and E'''' is expressed by the following equation. E"+E-=:2(asin(2πx/p) C08(
2πw/p)+b) Therefore, by performing the following calculation, it is possible to obtain the track error signal Tr' with the offset canceled. Tr' = Tr-(E"+E-)/2 = a(1-cos (2w/p)) sin (2πx
/p) Usually, w=p/ so that the amplitude of Tr' is maximum.
2 is selected. The configuration of the offset correction circuit is shown in FIG. 10(a), and the control signal of the correction circuit is shown in FIG. 10(b). The difference between the outputs e and f of the two-split detector 115 is determined by a differential amplifier 609, and an error signal Tr is obtained by diffraction light tracking (push-pull). The timing circuit 601 outputs a wobble control signal Cw and control signals Tl, T2 and T for sample and hold.
Generates 3. The light spot is wobbled by a wobble control signal Cw. That is, the wobble control signal Cw is added to the optical spot control signal R from the servo system in an adder 621, and drives the optical deflector (micro moving mechanism) 104 through the optical deflector (micro moving mechanism) driving circuit 65. With conventional mechanical actuators, it was necessary to detect the amount of movement and apply feedback in order to wobble the optical spot by a certain amount, but with non-mechanical optical deflectors such as A10 deflection elements and SAW elements, driving Since the change in frequency f is proportional to the change in deflection angle θ, wobbling can be performed without applying feedback. The track error signal E+E- when wobbled is sampled and held by sample and hold circuits 603 and 605 controlled by control signals Tl and T2, respectively. Since it takes time for the ultrasonic waves to propagate through the medium of the optical deflector, Tl lags behind the change in the wobbling control signal Cw. A sample signal of T2 is output. The sum of the outputs of the sample and hold circuits 603 and 605 is determined by an adder 625 and inputted to the differential amplifier 23 via a gain adjuster K. The output Tr of the differential amplifier 609 is connected to the other input of the differential amplifier 623, and the offset component is corrected from the error signal Tr caused by this diffraction light tracking to generate the offset-corrected track error signal Tr'. obtain. The sample hold circuit 627 is controlled by the control signal T3, and holds the previously offset-corrected track error signal Tr' during wobbling Tw to prevent the servo system from being shaken. The gain adjuster has K
= 1/2. It is desirable to make Tw as short as possible. Since the optical deflection element operates at high speed, Tw can usually be set to 10 μs or less. The wobbling interval Ti is T
It can be changed within the range of i>Tw, but as Ti increases, the phase delay of the track error signal also increases, so in consideration of the stability of the control system, it should be changed within the range of Tw<Ti<1/(3・fcf). Set to . However, fcf is the band of the micro control system. As will be described later, it is necessary to increase the band of the micro control system during track pull-in, so Ti is made as short as possible within the range of Tw<Ti. During track following, it is not necessary to increase the band of the micro control system so much, so Tw can be made long. In particular, when reading/writing data, if the optical spot is wobbled, reading/writing cannot be performed. Therefore, as shown in FIG. 8(,), blank areas with no data are provided here and there on the tracks of the optical disc, and the light spot is wobbled around the tracks. In that case, the timing circuit 601 in FIG. 10(a) detects this blank area while looking at the data signal, and generates the wobble control signal Cw, sample and hold control signals Tl, T2, T3, and the like. Let Ti be the interval at which the blank area appears, and if it is made as long as possible within the range satisfying Ti<1/(3·fcf), the reduction in recording area due to providing the blank area can be reduced. For example, the band of the micro control system when pulling in the track is set to 1.
If it is 0KHz, the wobble interval Ti is Tw
<Ti<33 μs, and it should be made as short as possible. Assuming that the band of the micro control system during track following is 3 KHz, the wobble interval Ti is T i < 110 μs.
Make it as long as possible. Although the above embodiment uses diffracted light tracking to detect the track error signal Tr, it is also possible to detect the track error signal from the total amount of reflected light from the optical disc by wobbling the optical spot. An example is shown below. The manner in which the light spot is wobbled is similar to that shown in FIG. In this embodiment, a detector having a detection section j as shown in FIG. 11(a) is used as the track error signal detection detector 115. In order to detect the total amount of reflected light, the detection unit j is larger than the light spot of the reflected light and is longer in the direction in which the light is deflected by the light deflector 104.The light spot moves as shown by the dotted line by the light deflector 104. Even if it is, it can be covered. The output of the detector 115 is amplified by an amplifier 631 to provide a total light amount signal F. A method of detecting a track error signal Tr without offset from a total light amount signal F of reflected light will be described. In the ninth time, the position of the light spot in the disk radial direction is assumed to be X, and the track pitch is assumed to be p. It is assumed that the total light amount signal F of reflected light is expressed by the following equation. F=ccos(2πx/p)+d where C is the amplitude component of the total light amount signal, and d is the DC component. Assuming that the shift at of the light spot due to wobble is ±W, and the total light amount signal at that time is F'' F-. If we take the difference between F+ and F-, we get the track error signal Tr'.
can be obtained. Tr'=F"-F- =-2csin (27CW/P) sin (27C
X/P) Normally, w=p so that the amplitude of Tr' is maximum
/4 was selected. The configuration of the track error signal detection circuit is shown in FIG. 11(b).
The state of the control signal is shown in FIG. 11(c). The timing circuit 601 outputs a wobble control signal Cw and control signals T4, T5 and T5 for sample and hold.
Generates 6. The method by which the light spot is wobbled by the control signal Cw is similar to that described in the explanation of FIG. The total light amount signal F" F- when wobbled is a sample hold 603 controlled by control signals T4 and T5.
And sample and hold is carried out by sample hold 605. Since it takes time for the ultrasonic waves to propagate in the medium of the optical deflector 104, T4. A sample signal of T5 is output. The sample hold 619 is controlled by the control signal T6 and holds the track error signal during wobbling Tw to prevent the servo system from being shaken. The settings for Tw and wobbling interval Ti are as follows:
This is the same as the offset correction in the diffracted light tracking described above, so a description thereof will be omitted. As shown in FIG. 12(a), the laser scale is a fine pitch scale 200b attached to the optical head 15G.
and a fixed optical system 200a attached to the base 15. The fine pitch scale 200b has grooves cut at a pitch comparable to the track pitch of the optical disk 10, and the laser beam from the fixed optical system 200a is focused on this, and the reflected light is detected. laser diode 20
The laser beam emitted from the diffraction grating 202 and the half mirror 2
03 and becomes parallel light at the collimating lens 204. After being reflected by the rising mirror 205, the light is focused by the lens 206 and connects three light spots on the fine pitch scale 200b. The reflected light is separated by a half mirror 203, becomes parallel light by a concave lens 207, and is sent to a detector 20.
Enter 8. In order to detect the moving amount, moving speed, and moving direction of the head, it is sufficient to obtain two signals whose phases are shifted by about π/2 as shown in FIG. 12(b). The three light spots mentioned above are arranged on a fine pitch scale of 200
It is arranged as shown in FIG. 12(c) with respect to the groove b. That is, two sub-light spots 210a and 210b are arranged with the main light spot 209 in between, so that the phase of the amount of reflected light is shifted by about ±π/2 with respect to the amount of reflected light of the main light spot 209. The reflected light amount signals of these three light spots are
If corrected by the circuit shown in the block diagram of FIG. 12(d),
Two signals having a phase difference of approximately π/2 are obtained as shown in FIG. 12(b). Note that 3. in FIG. 12(d). 4 shows the reflected light amount of the main light spot 209 and the sub light spot 2.
This is to compensate for the difference in the amount of reflected light from 10a and 210b. Although a method using three light spots has been described here, a signal as shown in FIG. 12(b) can be obtained even if the amount of reflected light and diffracted light are used in one spot. Next, a method for realizing high-speed seek using the optical head having the configuration shown in FIG. 1 will be described. Regarding the two-stage theta method in optical disk devices,
JP-A-58-91536 and JP-A-58-16937
It is stated in No. 0. When looking at the two-stage theta method from the viewpoint of seek time, it is as shown in FIG. 13(a). In other words, the total seek time is the sum of ■time required for macro seek, ■time required for track pull-in operations for settling and activating the track following servo, ■time required for confirming the track address, and ■time required for micro-seek. . On the other hand, in the case of magnetic disk devices,
Because the track pitch is coarse, two
There is no need to perform a step-by-step seek. In other words, since positioning can be performed only by the linear motor, which is the macro movement mechanism of the optical disk device,
There is no need to perform micro-seeks. When trying to achieve high-speed seek comparable to that of a magnetic disk with an optical disk device having a conventional configuration, the following problems arise. ■To reduce the time required for macro seek,
When the optical head is driven at high acceleration, the residual vibration after the macro seek movement is completed becomes large. Therefore, it is necessary to wait until the residual vibration subsides, which increases the settling time (2). In addition, in order for the track following servo (2) to start, the relative speed between the track on the disk and the optical spot must be small enough to enable track pull-in. However, since the track pitch of optical discs is fine,
You have to wait until the relative speed becomes even smaller than that of a magnetic disk. In this way, due to the problem of residual vibration or speed deviation, which will be described later, in the optical disk device, it is necessary to gradually reduce the deceleration acceleration as shown in (2) in FIG. 13(a), and the macro seek takes time accordingly. In addition, if the disk rotation speed is high and the disk eccentricity is large, the relative speed between the track on the optical disk and the optical spot may become large, and the track following servo is activated to read the track address after the macro seek has settled. Even if the track tracking operation is performed, the track deviation occurs, and the time (2) until the track following operation actually starts becomes longer. Regarding the positioning accuracy of the optical head, the resolution of the linear scale is poor compared to the track pitch, which not only causes rounding errors, but also deviations due to the target position itself moving during macro movement due to eccentricity during disk rotation. Therefore, the position of the light spot after macro movement deviates from the correct target. For this reason, the distance to be corrected by the micro-seek in the next step becomes long, and combined with the fact that a mechanical actuator is used in the micro-movement mechanism, the time required for the micro-seek (2) is long. Because of the above problems, the seek time of optical disk devices is slower than that of magnetic disk devices. for example,
141 magnetic disk drive, if you seek 1/2 of all tracks, it takes approximately 14 m5 for the macro seek of ■.
The seek is completed in a total of 15 m5 ec, including 1 m5 ec for setting ec, , , and starting the track following servo. On the other hand, in a 12' optical disk device, it takes approximately 15G m5ec for the macro seek (2), approximately 50 m5ec for setting and starting the track following servo (2), and approximately 50 m5ec for the micro seek (2), for a total of 200 m.
The seek time is 5ec. The seek time of the optical spot positioning method according to the present invention is shown in FIG. 14(a), and the movement of the optical head and the optical spot is shown in FIG.
As shown in the figure. The optical spot is controlled at high speed by using a non-mechanical optical deflector 104 such as an A/○ deflection element or a SAW element mounted on the optical head or base as a micro-movement mechanism. A high-thrust actuator 20 is used in the macro movement mechanism that drives the optical head 15G, and provides an acceleration equal to or greater than that of a magnetic disk device. As a result, the 14th
As shown in Figure (a), the time required for the macro seek in (2) can be reduced. The reason why it has become possible to provide an acceleration equal to or higher than that of a magnetic disk device is as follows. At the end of the macro seek, the macro movement mechanism must be decelerated to a speed that allows the optical deflector, which is the micro movement mechanism, to pull in the track. When the band of the macro seek speed control system is fv and the deceleration acceleration is α, the following relationship exists between the deviation Ve from the speed target. α 2πfv When fv=700Hz and a=25G, V e
4 55mm/sec. Therefore, even if the speed at the macro seek target track is O
Even if you decide the speed target curve so that. In reality, it still has a velocity of Ve. In conventional optical disc devices, the track cannot be pulled in until the relative speed between the optical disc track and the light spot reaches approximately 3 mm/sec. FIG. 13(b) shows the relative velocity between the track and the light spot during macro seek deceleration in a conventional optical disc device. The dotted line is the target speed curve, and the solid line is the actual speed. The difference between the dotted line and the solid line is the speed deviation V.
Since it is not possible to pull the vehicle into the track as it remains large, the deceleration and acceleration are reduced as it approaches the target track, as shown by ■ in Fig. 13 (b), and the speed deviation Vs is 3 m.
m/sec. The truck was pulled in after it became small enough. As the deceleration acceleration is reduced, extra time is required for the macro seek in (■). Also, this extra time
The larger the initial deceleration acceleration, the larger the proportion of the macro seek time. However, as in the present invention, by increasing the band of the control system of the micro-moving mechanism to 10 KHz or more, for example, 12 KHz or more during the track pull-in operation, the speed deviation Ve can be reduced to 5.
The track can now be pulled in even at 5mm/sec. FIG. 14(a) shows the overall seek time in the present invention, and FIG. 14(b) shows the relative speed between the track and the light spot during macro seek deceleration. Figure 14 (
In b), the dotted line is the target speed curve and the solid line is the actual speed. The difference between the dotted line and the solid line is the speed deviation Ve. Since the track can be pulled in even if the speed deviation Ve remains large, when a deceleration deflector is used as shown in Fig. 13(b), there is no need to reduce the relative acceleration to change the applied frequency, which saves extra time. Since it does not take time, the time required for the macro seek in (2) can be shortened. In the present invention, by driving the optical head at high acceleration, mechanical residual vibration increases at the end of macro seek, but by increasing the band of the control system of the optical spot micro movement mechanism, this residual vibration can be reduced. Since it can be suppressed, the settling time of (■) is also shortened. Regarding the track pull-in operation for settling and starting the track following servo in (2), in the case of a magnetic disk device, the pull-in operation is performed using a linear motor, which is the macro-movement mechanism of the optical disk, so the band of the control system cannot be increased. Since the band of the control system of the mechanism can be increased to 10 KHz or more during the track pull-in operation, the operation can be completed in a shorter time than a magnetic disk device. The micro-seek in (2) can also be performed faster than before by increasing the bandwidth of the micro-transfer mechanism. In addition, the micro movement mechanism is A10. In particular, the pitch of the scale can be seen on optical discs. Therefore, the micro seek movement operation ends at - degrees. Furthermore, it takes several microseconds, L/l, for the light spot to actually complete movement after changing the applied frequency. Therefore, the time required for micro-seek movement can be almost ignored in terms of the overall seek time. Conventionally, a light emitting diode and a slit with a pitch of about 15 Gμm have been used as a linear scale for detecting the amount and speed of movement of an optical head, so even if frequency division is performed, a resolution of only about 10 μm can be obtained at most. Since the moving target of the macro seek was based on this linear scale, the error with the target track inevitably became large, and the number of tracks moved by the micro seek increased. In the present invention, highly accurate position information can be obtained by using the signal from the aforementioned micropitch laser scale, and the position of the Rin no Buddha spot at the end of the macro seek is quite close to the target track. It matches the track and almost eliminates the need for micro-seeks. Furthermore, since highly accurate position information can be obtained, the influence of eccentricity can be eliminated by moving the macro seek movement target in accordance with the eccentricity of the optical disc. Furthermore, when performing speed control using macro seek, by using a fine pitch laser scale, highly accurate speed information can be obtained even at low speeds. Velocity information is obtained one by one each time the light spot passes through a groove in the scale. For example, if the cutoff frequency of the speed control loop is 700Hz and the allowable phase delay is 45'', then approximately 91IIm/s
Speed information with sufficient accuracy can be obtained up to ec. As described above, according to the present invention, the seek time can be reduced to
The time required for the macro seek, the time required for the settling of ■ and the start-up track pull-in operation of the track following servo,
This is the sum of the time required to confirm the address in (2). for example,
Stroke is 70ma+, acceleration of macro movement mechanism is 2
If it is 5G, approximately 18 m5ec is required for the macro seek of ■.
, Approximately 1m5ec for setting (■), starting the track following servo, and confirming the address (■), totaling approximately 19m5ec.
, the seek ends. In the second embodiment described later, by dividing the optical head into a movable head and a fixed optical system, the weight of the movable part can be reduced, and even with the same thrust force of the macro movement mechanism, a larger acceleration can be generated. can. Furthermore, if the disk surface is sought using a large number of light spots, the stroke for the seek can be shortened. For example, if you want to seek 172 of all tracks, and the stroke is 35a+m and the acceleration of the macro movement mechanism is 50G, the macro seek of ■ will take about 9m.
5ec, approximately 1m5ec for setting in ■, starting the track following servo, and micro seek in ■, totaling approximately 10m5.
ec. The seek ends at , making it possible to achieve faster seeks than with magnetic disk drives. The overall system for performing a seek operation will be explained. FIG. 16 shows a first embodiment of the present invention, and is a block diagram showing the overall configuration of a seek control circuit. A linear motor 20 that moves the entire optical head 15G is used as a macro movement mechanism over the entire disk radius, and a micro movement mechanism for highly responsive minute positioning that follows a minute range is shown in Figure 1 or Figure 2. An optical deflector using a non-mechanical optical deflection element such as the A10 deflection element shown in FIG. 4 or a SAW element is used. The optical disc 1o is rotated by a spindle motor 7 around the rotation axis.
It is rotated by 5. Optical head lOO is base 1
5 in the radial direction of the optical disc 10 according to the rotation of the rollers 116. The optical head 15G has a linear motor 20
driven by. Signals from each detector in the optical head 15G are sent to the optical spot control signal detection and information reproducing circuit 35, where a track error signal (tracking signal) Tr' and a data signal are detected by the method described above. The data signal is used for reproducing data information, is sent to the servo control circuit 30, and the data information (including header information) recorded on the optical disc 10 is demodulated. Note that the optical head 15G is provided with a defocus detection optical system as described above, and a focus error signal is also detected, but this is omitted because it is not directly involved in the seek operation. The tracking error signal Tr' is the tracking control circuit 4
5, and a micro follow-up control signal R and a macro follow-up control signal G are output. At this time, the servo control circuit 30
The micro-moving mechanism driving mode switch circuit 55 and the macro-moving mechanism driving mode switching circuit 60 are set to the track following mode, and from this, the micro-following control signal R is sent to the optical deflector 1 in the optical head 15G via the micro-moving mechanism driving circuit 65.
ill 04! The irradiation position of the light spot is controlled so that the light spot follows the center of the track. On the other hand, the macro follow-up control signal G drives the linear motor 20 via the macro movement mechanism drive circuit 70 to drive the optical head 1.
5G is moved in the radial direction of the optical disc 10, and the optical deflector 104, which is a micro movement mechanism, and the linear motor 20, which is a macro movement mechanism, cooperate to perform a track following operation. This is called a two-stage tracking servo system.
It is disclosed in Japanese Patent Application Laid-Open No. 58-91536. The macro tracking control signal G can be obtained by electrically simulating the micro tracking control signal R as disclosed in Japanese Patent Application Laid-Open No. 58-91536. When using A/○ deflection element,
The micro follow-up control signal R may be used as is. In such a follow-up control state, address information OA to be accessed is sent from a higher-level control device (not shown) to the servo control circuit 30, and an access operation (seek operation) is activated. Then, the servo control circuit 30
The servo control circuit 30 reads the currently located track address from the reflected light amount signal, calculates the macro seek movement amount N, and sends it to the macro seek control circuit 50.
The micro moving mechanism drive mode switch 55 is set to lock mode, and the control signal R to the micro moving mechanism drive circuit 65 is set to a hold state. When an optical deflection element is used in the micro movement mechanism, the micro movement mechanism drive circuit 65 is configured with vCo, and by holding the control signal R, the drive frequency f of the optical deflection element 104 is held, and the optical deflection The deflection angle of light by element 104 is fixed. On the other hand, the macro movement mechanism drive mode switch circuit 60 is set to the macro seek mode, and the output H of the macro seek control circuit 50 drives the near motor 20 via the macro movement mechanism drive mode switch circuit 60 and the macro movement mechanism drive circuit 70. death,
The optical head 15G is moved at high speed in the radial direction of the optical disk 10. The movement position signal of the optical head 15G is detected by the fine pitch laser scale 200 and fed back to the macro seek control circuit 50, and a suitable control signal depending on the position of the optical head 15G is given to the macro movement mechanism drive circuit 70. . This preferred control signal is the first
This is the target speed shown in FIG. 4(b). By this control signal, when the light spot comes on the moving target track, the relative speed between the light spot and the track is changed so that the light spot that can pull the track by the micro movement mechanism comes on the target track and the macro seek is completed. The seek control circuit 50 sends a signal A indicating that the macro seek has ended to the servo control circuit 30. Servo control circuit 3
0 means that the micro-moving mechanism drive mode switch circuit 55 is set to 0.
Analyzing from the tracking mode, the macro moving mechanism parking mode switch circuit 60 is set to the track following mode, the track is pulled in, and the two-step tracking control described above is performed again. The servo control circuit 30 reads the current track address from the information signal from the optical disc 10, calculates the micro seek movement amount J that is the error from the target address information,
It is sent to the micro seek control circuit 40. Further, the servo # control circuit 30 includes a macro movement mechanism drive mode switch circuit 6.
0 is the track following mode, and the macro following control signal G is connected to the macro moving mechanism immediate action circuit 70. The micro seek control circuit 40 switches the micro moving mechanism drive mode switch circuit 55 between the track following mode and the micro seek mode. When the micro displacement mechanism drive mode switch circuit 55 is in the micro seek mode, the micro seek control circuit 40 outputs a track jump signal and drives the optical deflector 104 via the micro displacement mechanism drive circuit 65.
Position the light spot to the target track. If the error between the pulled-in track and the target track at the end of the macro seek is within the range that can be covered by the micro movement mechanism, the track jump operation will be completed in one go, but if the target track cannot be reached in one track jump, the micro movement mechanism will The motion mode switch g55 is repeatedly switched between the track following mode and the micro seek mode, and the track jump and track following operations are repeated several times. The operation of the macro seek control circuit 50 shown in FIG. 16 will be explained in detail using the block diagram shown in FIG. 17. A value N obtained by converting the number of moving tracks by the scale pitch of the fine pitch laser scale 200 is written into the macro seek movement amount counter 51. In particular, when the track pitch and scale pitch are the same, the macro seek movement amount N is the same as the number of moving tracks. For example, when the number of moving tracks M=15G01, the track pitch p=1.6 μm, and the scale pitch L=2.0 μm, L 2.0 is converted to an integer and N=8001 is set in the macro seek movement amount counter 51. Write. The rounding error E at this time is 0.2. Even in the worst case, the amount of error due to rounding is never greater than the scale pitch. The macro seek movement counter 51 receives up and down pulse signals Kups K that are output according to the movement direction for each scale pitch of the fine pitch laser scale 200.
Count up by down. is counted down. In accordance with the macro seek deviation, which is the value of the macro seek movement amount counter 51, the macro seek/settling controller 52 controls the macro moving mechanism drive circuit 70, which is the driver of the linear motor 20, via the macro moving mechanism drive mode switch circuit 60. to drive. At this time, the output of the macro moving mechanism rotation mode switch 60 is connected to the macro moving side H by the macro seek/track following switching signal A'. In addition, the macro seek/settling controller 5
2 is a speed detection circuit, a target speed control curve generation circuit, and D
It consists of a /A converter and a differential amplifier. That is, the macro seek deviation from the macro seek movement amount counter 51 is input to the target speed curve generation circuit, and an optimal target speed signal is outputted according to the deviation amount. This target speed curve is as shown by the dotted line in FIG. 14(b), and is proportional to the square root of the macro seek deviation during deceleration. Here, since the output of the macro seek movement amount counter 51 is given digitally, the RO
A square root table is stored in M in advance, and a target speed signal is digitally output in accordance with the macro seek deviation to the target position. This target speed signal is input to a D/A converter, converted into an analog quantity, and input to one input of a differential amplifier. The speed signal from the speed detection circuit is input to the other input.
The difference is taken away. The output of this difference is the difference between the target speed and the actual speed. This is the output H of the macro seek control circuit 50.
becomes. Further, at the start of macro seek, the control signal A' causes the micro movement mechanism drive mode switch 55 to be placed in the lock mode, and the sample/hold circuit 56 to be placed in the hold state. The micro movement mechanism drive circuit 65 is composed of a vCO, and by holding the control signal, the drive frequency of the optical deflection element is held, and the deflection angle of light by the optical deflection element is fixed. When using a mechanical actuator such as a galvano mirror for the micro movement mechanism as in the past, if the actuator is not locked during macro seek movement, it will vibrate due to the acceleration during movement, and it will take time to settle. . In order to lock, it was necessary to provide a position detector for the micro-movement mechanism, such as a deflection angle sensor, and to use the signal to create a feedback loop. However, if a non-mechanical optical deflection element is used in the micro-transfer mechanism as in the present invention,
Since locking can be achieved simply by holding the drive frequency, there is no need to provide a position detector or feedback loop. Furthermore, when using an optical deflection element, there is no need to lock it in terms of vibration of the micro-movement mechanism. However, since the macro seek movement amount counter 51 is based on the position of the micro movement mechanism immediately before the seek, if this moves, it will result in a macro seek error. Therefore, the micro movement mechanism is locked in the state immediately before the macro seek movement. Further, as shown in FIG. 15, the light spot can be advanced in the theta direction from the head by a micro movement mechanism during macro seek. This is effective when the coverage area of the micro-transfer mechanism is small. In that case, it is necessary to correct the macro seek movement amount counter 51 by the amount by which the micro movement mechanism is advanced. When the light spot reaches the target track, the value of the macro seek movement amount counter 51 becomes zero, and the settling operation ends.
The macro seek/track following switching signal A', which is the output of the macro seek end determination circuit 54, switches the macro moving mechanism drive mode switch circuit 60, and also switches the sample/hold circuit 56 in the micro moving mechanism beating mode switch circuit 55. becomes the sample state. As a result, the macro tracking control signal G and the micro tracking control signal R from the tracking control circuit 45 are applied to the macro movement mechanism drive circuit 70 and the micro movement mechanism drive circuit 65, respectively, and a track pull-in operation is started. When the track is pulled in and a track following operation is started, the track address is read by the information reading circuit in the servo control circuit 30, and the amount of deviation J from the target track is calculated. Pulled truck QJt day #! l)%
Main meal at Rariku 7h Se1 operation (seek operation) is all completed. When the target track is not the target track, a track jump signal is generated to move the light spot by the deviation amount J by the optical deflector 104. In addition, the sample/hold circuit 5
6 is placed in a hold state, the switch 57 is turned on, and the micro-moving mechanism drive circuit 65 is driven. The optical deflector is faster than conventional mechanical micro-movement mechanisms, and the track jump ends instantly. After the track jump, the sample/hold circuit 56 is put into the sample state by the track jump switching signal JT, and the switch 57 is turned off to start track following control. Check the address and if it is the target track, exit, otherwise repeat the track jump. Move to the target track. In particular, since a micropitch laser scale with a pitch almost the same as the track pitch of the optical disk is used to detect the amount of movement of the optical head, there is almost no error between the track pulled in after macro-seek movement and the target track, and the light spot due to micro-seek The amount of movement is small. In this embodiment, the track jump switching signal J
Both the sample/hold circuit 56 and the switch 57 are controlled by T, but if the track jump signal is turned off at the same time as the sample/hold circuit 56 switches to the sample state, the micro movement mechanism will be at high speed and will not be able to follow the track. The light spot may return before the control system starts operating. In such a case, the trap switching signal JT is divided into a switching signal for the sample/hold circuit 56 and a switching signal for the switch 57, and each is controlled separately. That is, the sample/hold 56 is set to the hold state by the track jump switching signal JT, and at the same time, the switch 57 is turned on by the track jump switching signal JT2 to start the track jump, and after the track jump, the sample/hold 56 is set to the hold state by the track jump switching signal JT. to the sample state and start track following. Thereafter, the track jump signal is returned to zero again, but the speed at which it is returned to zero is such that the macro movement mechanism can follow it. When the track jump signal returns to zero again, the switch 57 is turned off by the track jump switching signal JT2. Further, in this embodiment, the macro seek movement amount counter 51
In order to perform eccentricity correction by adding the eccentricity of the optical disk to The amount counter 51 is corrected. 1) As shown in the figure, the optical disc 1 is driven by the spindle motor 75.
0 rotates slightly eccentrically, and the rotation angle detector 80
outputs rotation angle information θ of the optical disc 10 and one reference angle index signal ID per rotation. The eccentricity counter 53 receives the reference angle index signal I.
It is designed to be reset every rotation by D. The disk eccentricity ε, which is the output of the eccentricity counter 53, and θ' from the rotation angle detector 80 are measured over multiple rotations of the optical disk at the first start of the optical disk, and the average relationship between the eccentricity and the rotation angle, That is, ε=f(θ') is stored. Note that the description of the disk eccentricity ε includes the up and down pulse signals Kuρ, Kdo from the fine pitch laser scale 60 when the micro movement mechanism (optical deflector) is in the lock mode and track following operation is performed.
wn is used. The macro seek movement amount counter 51 is an eccentric amount counter 54
At the end of the macro seek, the macro seek end determination circuit 54 determines the end of settling by looking at the macro seek deviation which is the output of the macro seek movement counter 51. Next, the tracking control system shown in FIGS. 16 and 17 will be described in detail. The tracking control system is basically based on Japanese Patent Application Laid-Open No. 58-91.
The two-stage tracking servo disclosed in No. 536 is used. That is, the optical disc iJJf uses a two-stage tracking servo configured as shown in FIG. 18(a). Gd is the characteristic of the track error signal detection system, Of is the characteristic of the micro movement mechanism including the drive circuit, G
c represents the characteristics of the macro movement mechanism including the drive circuit. Xc
is the position of the macro movement mechanism, Xf is the displacement of the light spot by the micro movement mechanism, and the sum Xs of Xc and Xf is the position of the light spot. The difference between the position ffX5 of the light spot and the position Xt of the target track to be followed is detected by the track error signal detection system described in FIG. 7, FIG. 8, FIG. 10, or FIG. 11. The micro movement mechanism follows this track error signal. The track pitch of an optical disc is at most a few μm,
The linear range of the track error signal is less than half of that. However, the position resolution of the macro movement mechanism is much worse than that, and the tracking error signal cannot follow the target. Therefore, the movement of the micro-movement mechanism is taken as the target to be followed by the macro-movement mechanism. Gs is a simulator that simulates the characteristics of a micro-movement mechanism in order to provide an operation target for the macro-movement mechanism. In this example, an A10 deflection element is used as the micro-movement mechanism.
An optical deflector such as a SAW element is used. These optical deflectors operate at high speed because they do not have mechanically moving parts as described above. That is, when looking at its characteristics, as shown in FIG. 4, the gain is constant up to a high frequency sum, and there is no position delay. Figure 18 (
b) is a redrawn version of Fig. 18(a). In the figure, the part surrounded by a dotted line is a loop ■, and the outer loop is a loop ■. Loop ■ is the feedback system of the micro-transfer mechanism,
Loop ■ is a feedback system of the macro movement mechanism. The open-loop characteristics of loop (2) and loop (2) are shown in FIG. 19. In the figure, fcf and fcc are the cutoff frequencies of the loop ■ and the entire loop, respectively. The values of fcf and fcc will be described later. An example of the configuration of the other side of the two-stage tracking servo used in the present invention is shown in No. 20, and A1 is used as a micro-movement mechanism.
When using optical deflection elements such as zero deflection elements and SAW elements, these optical deflectors do not have mechanically moving parts and change the deflection angle electrically, so the gain is constant up to high frequencies and there is no sub-resonance. However, the phase may be delayed at high frequencies because it takes a certain amount of time for the ultrasonic waves to propagate through the device and there is also the effect of wobbling as described above. If a feedback loop is configured as is, the phase may rotate and the servo system may become unstable. Therefore, as shown in FIG. 20, a low-pass filter GQ is inserted to reduce the gain at high frequencies. In the figure, Gd is the characteristic of the track error signal detection system, Of is the characteristic of the micro movement mechanism including the drive circuit, and G
c represents the characteristics of the macro movement circuit including the drive circuit, and the first
This is similar to Figure 8. API is a phase lead circuit for stabilizing the micro movement mechanism, and Gp2 is a phase lead circuit for stabilizing the macro movement mechanism. Xc is the position of the macro movement mechanism, Xf is the displacement of the light spot due to the micro movement mechanism, and the sum of Xc and Xf is
s is the position of the light spot. light spot position fiXs
The difference between the position Xt of the target track and the position Xt of the target track
What is detected by the l-track error signal detection system explained in FIG. 10 or 11 is the same as that in FIG. Furthermore, the movement of the micro-movement mechanism is taken as the target to be followed by the macro-movement mechanism, but if an optical deflection element is used for the micro-movement mechanism, the movement of the micro-movement mechanism is
The input will be faithfully reflected. Therefore, the input of Of can be used as the operation target of the macro movement mechanism, the simulator Gs for simulating the characteristics of the micro movement mechanism can be omitted, and the configuration of the servo system can be simplified. FIG. 20(b) is a redrawn version of FIG. 20(a). The characteristic G of the entire tracking control system of this embodiment can be expressed as follows. G=Gd-Gpl・GQ・(Gf+Gp2・Gc) The Bode diagram is shown in FIG. 21, and the micro-transfer mechanism control loop Gd-Gpl・GQ・Of of loop I and the loop
Macro movement mechanism control loop Gd-GPl・GΩ・Gp
If the frequency at which 2·Gc intersects is fcc, then the two operate in cooperation so that at frequencies lower than fCc, the macro movement mechanism mainly acts, and at frequencies higher than fcc, the micro movement mechanism mainly acts. Gpl is for stabilizing the micro-transfer mechanism, so the gain of the micro-transfer mechanism control loop is OdB.
The phase is advanced around the zero cross frequency fcf. Gp2 advances the phase around the cross frequency fee in order to stabilize the macro dye transfer mechanism. Conventionally, the characteristics of the micro-transfer mechanism control loop I are mainly determined by the characteristics of the mechanical actuator. Although the characteristics of a second-order spring-one-mass system have been shown, in this embodiment, the characteristics can be freely determined using the low-pass filter GΩ. When the low-pass filter GQ is of second order, it can have characteristics similar to those of a conventional mechanical actuator. However, as shown in Fig. 3, there is no sub-resonance, which is a problem with mechanical actuators, so the zero cross frequency fc
f, that is, the bandwidth of the micro-transfer mechanism control loop, can be increased. Further, when the low-pass filter GQ is first-order, the phase delay near the zero-crossing frequency fcf is only about 90°, so the phase lead circuit Gpl for stabilizing the micro-moving mechanism is not necessary. Next, the band fcf of the micro movement mechanism control loop and the band fee of the control loop of the macro movement mechanism will be described. Generally, the transient response characteristics of a feedback control system are
It can be approximated as the following system. Therefore, consider the system shown in Figure 22. The object with initial velocity Vo at position Xo is
shall be stationary around. As shown in FIG. 23(a), it oscillates around Xo, but the damping ζ of the system takes effect and the amplitude gradually decreases. Letting the maximum value of the amplitude from Xo be Xmax and the band of the control system be fn, the following relationship exists. ) (aax・2ycfn≧f(ζ)・v. However, π ζ f (ζ)= An example of this is shown in FIG. 23(b). When pulling in a track in a two-stage tracking servo system Consider. If the track pitch is p = 1.6 μm, the detection range of the tracking signal will be ±0.4 μm. When pulling in the track, Xmax = 0.4 p
m%V o = 55*a+/sec. (Relative velocity Ve between the light spot and the track at the end of macro seek), and ζ=0.4. f (ζ)=0.55
Then, the band fcf of the micro-transfer mechanism control loop (2) is. 12 KHz In other words, the control loop of the optical deflection element needs to have a band of approximately 12 KHz or more. Such a high bandwidth can only be achieved by using an optical deflection element that does not have mechanically movable parts. Furthermore, even if the 0.4 μm pull-in range is expanded using a cross-track count signal, there is a problem in that it takes a long time to complete the pull-in, and the band of the micro-transfer mechanism control loop is expanded. I have no choice but to. For example, V o == 15Gmm/sec, ,
Set ζ=0.5, and the deviation from the target track is 0.0.
Assuming that the pull-in is completed when it becomes 3 μm or less, the band of the micro-transfer mechanism control loop is approximately 20 KHz, 15 G μsec with the time required for the pull-in being 6 Q psec.
, a frequency of about 12 KHz or more is required. It would be fine if the optical deflection element could cover all the tracks, but for example, the angle of light that can be deflected by an A10 deflection element is actually about ±3 mrad, and if a focusing lens with a focal length of 51 m1 is used, the light spot on the optical disc will be The amount of movement is ±15 μm. Therefore, the macro movement mechanism only needs to be able to pull the optical head into a width of 30 pm. Xmax = 15 pm, Vo = 55mm
/see. ζ=0.4. When f (ζ)=0.55, the band fee of the macro movement mechanism control loop is: In other words, it is sufficient that the band fee is approximately 320 Hz or more. As described above, in order to perform track pull-in while maintaining a high relative speed between the track and the light spot, it is necessary to increase the bandwidth of the micro-moving mechanism control loop. Although it depends on the relative speed between the track and the light spot, that is, the magnitude of the speed deviation at the end of the macro seek, the band of the micro movement mechanism control loop is set to 10 KHz or more during the track pull-in operation. Furthermore, if the center frequency of the phase lead of the path Gpl is also changed, it may be inconvenient to keep the band of this micro-transfer mechanism control loop high. That is, since the tracking ability is good up to high frequencies, it may also track signals caused by defects in the tracks on the disk, minute dust, noise, etc., and the light spot may be deflected more than necessary. In that case, during track following, the band of the micro-moving mechanism control loop is switched to a lower value. To switch the band of the microtransfer mechanism control loop,
For example, in FIG. 18(b), this can be done by changing the gain of the track error signal detection system Gd. The band of the micro-movement mechanism control loop during track following is normally desirably 5 kHz or less. Furthermore, in the servo control system as shown in FIG. 20, when the low-pass filter GQ is of second order, Gd. Switch the Gpl or GQ gain. In that case,
Although the cross frequency fcc, which is the band of the macro movement mechanism control loop in FIG. 21, does not change, the zero cross circumference frequency fcf, which is the band of the micro movement mechanism control loop, changes. Therefore, it is determined that the pull-in is completed when one phase advance time continues. Then there's the point. When the gain of Gf is changed, the zero cross frequency fcf and the cross frequency fe
Since e also changes, it is also necessary to change the center frequency of the phase lead of the phase lead circuit Gp2. Therefore, Gd. It is preferable to switch the gain of either Gpl or Gfl. - When it sees the end signal A, it knows that the track pull-in operation has started, and uses the band switching signal B to increase the gain of the low-pass filter GQ to raise the band to 10 KHz or more. At that time,
Since the zero cross frequency fcf changes, the center frequency of the phase lead of the phase lead circuit Gpl is also changed at the same time by the band switching signal B. The track pull-in operation ends when the positioning accuracy of the optical spot becomes less than a certain tolerance value, for example, 0.03 μm or less. Therefore, the track pull-in completion determination circuit 90:
The track error signal becomes less than 0.03μm equivalent,
Once again, the band switching signal B switches the gain of the low-pass filter GQ and the center frequency of the phase lead of the phase lead circuit Gpl, lowering the band to 5 KHz or less. Although the case where the gain of the low-pass filter GQ is switched is shown here, the gain of -Gd or Gpl may also be switched. When the low-pass filter GQ is first-order, the phase advance G
pl becomes unnecessary. Therefore, in order to switch the band, it is sufficient to switch the gain of Gd or GQ. Another embodiment of the optical head used in the present invention is shown in FIG. In the above embodiment, all the optical systems are composed of the movable optical head 15G.
However, in this embodiment, the optical head is composed of a fixed optical system 400 fixed to the base 15 and a movable optical system 300 driven by a macro movement mechanism. The laser diode 401 is a laser diode that oscillates laser beams of two different wavelengths. The light emitted from the laser diode 401 is turned into parallel light by the collimating lens 402, and the beam shaping prism 403
After being shaped into a circular beam, it enters an optical deflector 404 used as a micro-moving mechanism. As described above, the optical deflector 404 is composed of a non-mechanical optical deflection element such as an A10 deflection element or a SAW element, and a beam shaper. The light beam whose emission angle has been changed by the optical deflector 404 is separated into two light beams by the wavelength separation filter 405. The light beam reflected by the wavelength separation filter 405 is
The optical path is changed by the reflecting mirror 406 and made almost parallel to the light beam that passed through the wavelength separation filter 405, so that the two beams become almost parallel. The two beams then enter polarizing prisms 407 and 408. If the polarization of the light beam at this time is set to P polarization with respect to the polarizing prisms 407 and 408, most of the light beam will be polarized by the polarizing prism 407 and 408.
Go straight on 7,408. The two light beams exiting the polarizing prisms 407 and 408 pass through a λ/4 plate 409 and 410, become circularly polarized light, and are emitted from the fixed optical system 400. The light emitted from the fixed optical system 400 enters the movable optical system 300 driven by a macro movement mechanism. Within the movable optical system 300, the two light beams reflected by the rising lenses 302 and 303 are focused by the focusing lenses 304 and 305, respectively, and form a light spot on the optical disc 10. These light spots can be moved in the tracking direction (direction across the track) by the aforementioned optical deflector 404. The light reflected by the optical disk 10 passes through the aperture lens 304, 409, and 410 again and returns to linearly polarized light. The polarized light at this time is the polarizing prism 407, 408
Since the light is S-polarized, it is reflected without passing through the polarizing prism. The reflected light beam is focused onto its detector 415, 417 or 416° 418. To detect the amount and speed of movement of the optical head 300 (movable optical system), the fine pitch laser scale 2 attached to the base 15 and the movable optical system 300 is used, as in the previous embodiment.
Use 00. Detector 415, 417 or 41 in FIG.
The shape of 6,418 is shown in FIG. 26(a). This has a structure in which the detectors for detecting focus error and tracking error signals (see FIGS. 5 and 6) in the previously described embodiments are provided on the same substrate. In the front-rear differential scanning method, when a focus shift occurs, the size of the light spot image on the detector changes, but in order to prevent this focus shift from interfering with the tracking error signal, the configuration of the signal system is shown in Figure 26 (b). Do as shown. Regarding correction of the offset of the track error signal, see Figures 7 and 8.
This embodiment is similar to the embodiment described in FIG. 10 or 11. In the present invention, as explained in FIG. 14(a), most of the seek time is occupied by macro seek. Therefore, in order to achieve high-speed seek, it is necessary to shorten the time required for macro seek. for that purpose,
There are two methods: shorten the seek stroke and increase the acceleration applied to the head. If the entire disk surface is sought using multiple spots, the number of tracks to be covered by one spot will be reduced. Therefore, the stroke of the optical head becomes shorter, and the time required for macro seek can be further reduced. For example, when two spots are used and the distance between the two spots is set to 172 of the radius of the disk to be sought, the average amount of head movement becomes 1/2. The time required for macro seek in this way is 1/V2. In this embodiment, by dividing the optical head into a fixed optical system 400 and a movable optical system 300, the number of components of the movable head 300 is reduced. As a result, the movable head 300 can be made smaller and lighter, the burden on the macro movement mechanism is reduced, and the movable head can be driven with greater acceleration. Also. As the movable head 300 is made smaller and lighter, it is possible to increase the rigidity of the movable head 300, and it is possible to reduce sub-resonance of the head that adversely affects the servo system. In addition, the optical deflection element 404 and the aperture lens 304.30
5, track offset is likely to occur due to the distance shown in FIG. 8 mentioned above. Offset cancellation by wobbling or detection of a tracking error signal from the total amount of reflected light as explained in FIG. 10 or 11 is also effective in this embodiment. The seek method in this embodiment is shown in FIG. 16. Since it is the same as the above-mentioned embodiment explained using FIG. 17, the explanation will be omitted. Effects of the Invention 1 As described above, according to the present invention, the seek time in an optical disk device can be shortened to the same level as a magnetic disk device or even shorter.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of an optical head used in the present invention, FIG. 2 is a diagram showing an example of an optical deflector using an A10 deflection element used as a micro-movement mechanism, and its operating principle, and FIG. 4 is a diagram showing an example of the characteristics of a mechanical actuator, and FIG. 4 is a diagram showing an example of the characteristics of a mechanical actuator.
10 is a diagram showing an example of the characteristics of the deflection element. FIG. 5 is a diagram showing a detector that detects a focus error signal and a data signal and its signal detection system. FIG. 6 is a diagram showing a detector that detects a track error signal and its signal. 7 is a diagram showing the detection system, FIG. 7 is a diagram showing the first method of correcting the offset of the track error signal, FIG. 8 is a diagram showing the second method of track offset correction, and FIGS. 9 and 10 are diagrams showing the detection system.
The figure shows the third step that corrects the offset of the track error signal.
Fig. 11 is a diagram showing a detector for detecting the total amount of reflected light, and a circuit configuration and timing for detecting a track error signal from the amount of reflected light.
Figure 2 shows the configuration of the micropitch laser scale, its output,
A diagram showing the light spot arrangement on the scale and a signal detection system, FIG. 13 is a diagram for explaining the conventional two-stage seek, and FIG. 14 is a diagram for explaining the seek time of the two-stage seek according to the present invention. FIG. 15 is a diagram showing the movement of the optical head and the optical spot in the two-step seek of the present invention. FIG. 16 is a diagram showing an example of the configuration of a seek control circuit according to the present invention, FIG. 17 is a diagram explaining details and operation of the control circuit, and FIG. 18 is a diagram showing an example of the configuration of a tracking servo control system. 19 is a diagram showing the characteristics of the control loop, FIG. 20 is a diagram showing another configuration example of the tracking servo control system, and FIG. 21 is a diagram showing the characteristics of the control loop.
FIG. 22 is a diagram showing a linear position control system, FIG. 23 is a diagram for explaining FIG. 22, FIG. 24 is a diagram showing an example of a configuration for changing the band of the control system, and FIG. The figure shows another embodiment of the optical head used in the present invention, and FIG.
26 is a diagram showing a detector and its signal detection system in the embodiment of FIG. 25. FIG. Explanation of symbols 10... Optical Tisph, 15... Base, 2o...
Macro movement mechanism, 30... Servo control circuit, 35...
・Optical spot control signal detection and information reproducing circuit, 40・
...Micro seek control circuit, 45...Tracking control circuit. 50...Macro seek control circuit, 55...Micro movement mechanism perversion mode switch circuit, 6
0... Macro movement mechanism drive mode switch circuit, 65
...Micro movement mechanism drive circuit, 70...Macro movement mechanism drive circuit, 75...Spindle motor, 80...Rotation angle detector, 90...Track pull-in end determination circuit, 15G.
...Optical head, 101...Semiconductor laser, 104...
- Optical deflector, 113, 114...Detector for detecting focus error signal, 115...Detector for detecting track error signal, 1
18... A10 deflection element, 200a... Fine pitch laser scale optical system, 200b... Fine pitch scale, 300... Movable head, 400... Fixed optical system, 401... Semiconductor laser, 404 ... Optical deflector, 405 ... Wavelength separation filter, 4151\416.
417,418...detector. Figure 113 Figure 5 Figure 6 Figure 茅? Figure early q Figure rod IO diagram Figure 11 (αn ascending diagram Figure 13 CCL) (Cn (CL) No. 12 Figure <b) Figure 14 (Mountain) Figure 15 Figure 14 (b Roof 1 Roof π (a,) tθ Figure 21 Figure 23 Time Figure 2C

Claims (1)

[Claims] 1. A seek operation for positioning a recording/reproducing light spot on a target track on a recording medium is performed by a macro movement mechanism of an optical head and a micro movement mechanism mounted on the optical head or the base of the device. . A method for positioning a light spot, characterized in that the band of the control system of the micro-movement mechanism is set to 10 KHz or more during track pull-in operation. 2. A seek operation for positioning a recording/reproduction light spot on a target track on a recording medium is performed by a macro movement mechanism of the optical head and a micro movement mechanism mounted on the optical head or the base of the device, and the movement of the micro movement mechanism A light spot positioning method characterized in that the band of a control system is changed between a track pull-in operation and a track following operation. 3. The optical spot positioning method according to claim 2, wherein the band of the control system of the micro-movement mechanism is set to 10 KHz or more during the track pull-in operation. 4. The optical spot positioning method according to any one of claims 1 to 3, characterized in that the band of the control system of the micro-movement mechanism is set to 5 KHz or less during track following operation. 5. The optical spot positioning method according to claim 1, wherein a non-mechanical optical deflector is used for the micro-movement mechanism. 6. The optical spot positioning method according to any one of claims 1 to 5, characterized in that during the macro seek of the seek operation, deceleration is performed at a constant acceleration to the target track during deceleration. 7. The optical spot positioning method according to claim 1, wherein when changing the band of the micro movement mechanism, the band of the macro movement mechanism remains constant. 8. The optical spot positioning method according to claim 1, wherein a mechanism having constant amplitude characteristics within a band of its control system is used as the micro-movement mechanism. 9. The optical spot positioning method according to claim 8, wherein a non-mechanical optical deflection element is used as the micro-movement mechanism. 10. The optical spot positioning method according to claim 8 or 9, characterized in that the control system of the micro-movement mechanism is provided with a low-pass filter to lower the high-frequency gain. 11. The optical spot positioning method according to claim 10, wherein the low-pass filter is a first-order low-pass filter. 12. The optical spot positioning method according to claim 10, wherein the low-pass filter is a second-order low-pass filter. 13. The optical spot positioning method according to claim 11, characterized in that the band of the control system of the micro-movement mechanism is changed by changing the gain of the control system of the micro-movement mechanism. 14. Claim 12, characterized in that the band of the control system of the micro-moving mechanism is changed by changing the gain of the control system of the micro-moving mechanism and changing the center frequency of the phase lead circuit of the micro-moving mechanism. The optical spot positioning method described. 15. The optical spot positioning method according to claim 8 or 9, wherein the tracking target of the macro movement mechanism is the same as the control input of the micro movement mechanism during the track following operation. 16. During the macro seek of the above seek operation,
7. The optical spot positioning method according to claim 6, wherein the target to be followed by the macro movement mechanism is determined to be decelerated at an acceleration of 15 G or more during deceleration. 17. An optical spot positioning method characterized in that a linear scale having a resolution comparable to the track pitch of an optical disk is used as an external linear scale for detecting the position of the optical head. 18. The optical spot positioning method according to claim 17, wherein the resolution of the linear scale is made the same as the track pitch of the optical disc. 19. The optical spot positioning method according to claim 16 or 19, wherein the seek operation for positioning the recording/reproducing optical spot on the target track of the optical disc is performed by counting signals from the linear scale. 20. A seek operation for positioning a recording/reproduction light spot on a target track on the recording medium is performed by the macro movement mechanism of the optical head and the micro movement mechanism mounted on the optical head or the base of the device, and the optical spot is irradiated from the optical head. A method for positioning a light spot, the method comprising: wobbling a light spot from its original position in both directions of the track, and detecting a track error signal from the difference in the amount of reflected light at that time. 21. A seek operation for positioning a recording/reproducing light spot on a target track on a recording medium is performed by a macro movement mechanism of the optical head and a micro movement mechanism mounted on the optical head or on the base of the device, and the optical head The offset of the track error signal is corrected by wobbling the light spot irradiated from the original position in both directions of the track, calculating the sum of the track error signals at that time, and subtracting 1/2 of the sum from the original signal. A method for positioning a light spot, characterized by: 22. Claim 20 or 21, characterized in that the optical spot is wobbled using the micro-movement mechanism.
The optical spot positioning method described. 23. The optical spot positioning method according to claim 20, wherein when wobbling the optical spot, the optical spot is wobbled by 1/2 of a track pitch in both directions of the track radius from the original position. 24. The optical spot positioning method according to claim 22, wherein a non-mechanical optical deflection element is used in the micro-movement mechanism. 25. The time Tw required for wobbling the above light spot is 1
0 μs. The optical spot positioning method according to any one of claims 20 to 24, characterized in that: 26. The light spot according to any one of claims 20 to 25, wherein the wobble interval Ti of the light spot is set to Ti<i/(3·fcf) with respect to the band fcf of the control system. Positioning method. 27. The optical spot positioning method according to any one of claims 20 to 26, characterized in that the wobble interval Ti of the optical spot is made variable. 28. The optical spot positioning method according to claim 27, wherein the wobble interval Ti of the optical spot is made longer during the track following operation than during the track retracting operation. 29. The wobble interval Ti of the light spot is defined as the time T required for the light spot to wobble during the track pull-in operation.
Claims 20 to 28 characterized in that they are the same as w.
The optical spot positioning method described in any one of . 30. An optical disk, an optical head that irradiates a recording/reproducing light spot onto a track on the optical disk, a macro movement mechanism that moves the optical head, and a macro movement mechanism that is mounted on the optical head or the base of the device and that is mounted on the optical head or the base of the device to move the track during a track pull-in operation. An optical disk storage device comprising a micro-movement mechanism that moves the optical spot and has a different control band during a follow-up operation. 31. The optical disk storage device according to claim 30, wherein the micro-movement mechanism has a control band of 10 KHz or more during track pull-in operation. 32. An optical disk, an optical head that illuminates a track on the optical disk with a recording/reproducing light spot, a macro movement mechanism that moves the optical head, and a macro movement mechanism that is mounted on the optical head or the base of the device and that is capable of moving 10K during track pull-in operation.
An optical disk storage device comprising a micro-movement mechanism that has a control band of Hz or more and moves the optical spot. 33. The above-mentioned micro-movement mechanism has a speed of 5K during track following operation.
Claim 3 characterized by having a control band of Hz or less.
The optical disc storage device according to any one of 0 to 33. 34. The optical disc storage device according to any one of claims 30 to 33, wherein the micro-movement mechanism comprises a non-mechanical optical deflector. 35. The optical disk storage according to any one of claims 30 to 34, characterized in that it has a linear scale having a resolution comparable to the track pitch of the optical disk, and the position of the optical head is detected by the linear scale. Device. 36. Claim 3, wherein the resolution of the linear scale is the same as the track pitch of the optical disc.
5. The optical disc storage device according to 5. 37. The above-mentioned linear scale is characterized by comprising a diffraction grating attached to a movable part of the optical head, and an optical system attached to a base, which narrows and irradiates laser light to the diffraction element and detects the reflected light. Claim 35 or 3
6. The optical disc storage device according to 6. 38. Track error detection means for detecting a track error signal from the reflected light of the recording/reproducing light spot, comprising means for correcting an offset caused by the reflected light being deviated from the optical center axis. 38. The optical disc storage device according to claim 30, further comprising a detection means. 39. Based on the output of the track error detection means,
39. The optical disk storage device according to claim 38, wherein the macro movement mechanism and the micro movement mechanism are driven during the track pull-in operation and during the track follow-up operation. 40. The optical disk storage according to claim 38 or 39, wherein the offset correction means includes means for obtaining a difference in the amount of reflected light when the recording/reproducing light spot is wobbled in the radial direction of the optical disk. Device. 41. The optical disc storage according to claim 38 or 39, wherein the offset correction means includes means for obtaining the sum of the track error signals when the recording/reproducing light spot is wobbled in the radial direction of the optical disc. Device. 42. Claim 42, wherein the track error detection means comprises means for detecting the track error signal from a difference in the amount of reflected light when the recording/reproducing light spot is wobbled in the radial direction of the optical disk. 39. The optical disc storage device according to 38 or 39. 43. The time Tw required for wobbling the above light spot is 1
0 μs. The optical disc storage device according to any one of claims 40 to 42, characterized in that: 44. The optical disk storage device according to any one of claims 40 to 43, wherein the wobble interval Ti of the optical spot is set to Ti<1/(3·fcf) with respect to the band fcf of the control system. . 45. The optical disk storage device according to claim 40, wherein the wobble interval Ti of the optical spot is made longer during the track following operation than during the track pull-in operation. 46. The wobble interval Ti of the light spot is defined as the time T required for the light spot to wobble during the track pull-in operation.
Claims 40 to 45 characterized in that they are the same as w.
The optical disc storage device according to any one of.