WO2005124750A1 - 光学ヘッドおよび光ディスク装置 - Google Patents
光学ヘッドおよび光ディスク装置 Download PDFInfo
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- WO2005124750A1 WO2005124750A1 PCT/JP2005/010950 JP2005010950W WO2005124750A1 WO 2005124750 A1 WO2005124750 A1 WO 2005124750A1 JP 2005010950 W JP2005010950 W JP 2005010950W WO 2005124750 A1 WO2005124750 A1 WO 2005124750A1
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- spherical aberration
- optical
- optical head
- information recording
- aberration correction
- Prior art date
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Classifications
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
- G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
- G11B7/1365—Separate or integrated refractive elements, e.g. wave plates
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
- G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
- G11B7/1365—Separate or integrated refractive elements, e.g. wave plates
- G11B7/1369—Active plates, e.g. liquid crystal panels or electrostrictive elements
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
- G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
- G11B7/1372—Lenses
- G11B7/1376—Collimator lenses
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
- G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
- G11B7/1372—Lenses
- G11B7/1378—Separate aberration correction lenses; Cylindrical lenses to generate astigmatism; Beam expanders
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
- G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
- G11B7/1392—Means for controlling the beam wavefront, e.g. for correction of aberration
- G11B7/13925—Means for controlling the beam wavefront, e.g. for correction of aberration active, e.g. controlled by electrical or mechanical means
- G11B7/13927—Means for controlling the beam wavefront, e.g. for correction of aberration active, e.g. controlled by electrical or mechanical means during transducing, e.g. to correct for variation of the spherical aberration due to disc tilt or irregularities in the cover layer thickness
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
- G11B7/09—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
- G11B7/0948—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following specially adapted for detection and avoidance or compensation of imperfections on the carrier, e.g. dust, scratches, dropouts
Definitions
- the present invention relates to an optical disk device that reproduces and records audio, images, and various data for a computer, and also relates to an optical head of the optical disk device.
- a second method is a method using a liquid crystal element.
- This method is disclosed in Patent Document 2, for example.
- the principle and specific configuration of the spherical aberration correction by the liquid crystal element are described in detail in Patent Document 2! Therefore, although the details are omitted here, a liquid crystal element whose refractive index changes by applying a voltage is arranged in an optical path directed to the light source and the objective lens.
- the liquid crystal element is divided into a plurality of areas, and the voltage applied to each area is controlled to change the refractive index of each divided area to give a phase difference to the transmitted light, so that it is condensed and generated by the objective lens.
- the spherical aberration of the light spot to be corrected is corrected.
- a third method is to use an optical element having a predetermined thickness.
- This method is disclosed in Patent Document 3, for example.
- an optical element having a predetermined thickness is inserted into a divergent light beam emitted from a light source to an objective lens, a predetermined spherical aberration determined by the refractive index and the thickness of the optical element is generated, and the light is collected by the objective lens.
- This is a method of relatively canceling out the spherical aberration of the light spot.
- Patent Document 1 Japanese Patent Application Laid-Open No. 11-195229
- Patent Document 2 JP-A-09-128785
- Patent Document 3 Japanese Patent Application Laid-Open No. 09-138957
- the liquid crystal element itself is transparent.
- the phase difference that can be given to overlight is inherently small, and high-order aberrations are likely to occur, which is not suitable for large spherical aberration correction.
- the amount of correction is determined by the thickness of the optical element and the refractive index thereof, so that the amount of spherical aberration to be corrected is uniquely determined. Go.
- spherical aberration generated due to a thickness error of the cover layer or the like is generally oscillatory (AC-like), it cannot be practically used for correcting such spherical aberration.
- a mechanism for inserting and removing the optical element itself in the optical path is required, which is an obstacle to miniaturization of the optical head. In particular, when a large amount of correction is required, it may become a bottleneck for downsizing the optical head.
- An object of the present invention is to provide an optical head having a large spherical aberration correction capability and an optical disk device using the same, which solves the above problem.
- the present invention is an optical head including a light source and an objective lens that collects light from the light source and forms a light spot in a mountable optical information recording medium, A first spherical aberration corrector for correcting the first spherical aberration and a second spherical aberration corrector for correcting the second spherical aberration, between the light source and the objective lens on the optical axis of the light; (1)
- the spherical aberration correction unit performs the first spherical aberration correction on the mounted optical information recording medium with the first spherical aberration correction amount, and the second spherical aberration correction unit performs the first spherical aberration correction smaller than the first spherical aberration correction amount.
- This optical head performs the second spherical aberration correction with the second spherical aberration correction amount.
- the first spherical aberration correction amount is preferably a predetermined constant value.
- the second spherical aberration correction amount is a predetermined constant value.
- the second spherical aberration correction amount can be changed during one rotation of the mounted optical information recording medium.
- the first spherical aberration correction amount is determined according to a standard value of a distance between a surface of the information recording layer included in the mounted optical information recording medium and the information recording layer. Is preferable.
- the second spherical aberration correction amount is set according to a standard value of a distance between a surface of the information recording layer included in the mounted optical information recording medium and the information recording layer. Is preferable.
- the second spherical aberration correction amount is a deviation of a standard value force from the distance between the information recording layer included in the mounted optical information recording medium and the surface of the medium optical head. Preferably, it fluctuates in response to the fluctuation.
- the fluctuation of the second spherical aberration correction amount indicates a periodic fluctuation synchronized with the rotation of the mounted optical information recording medium.
- the first spherical aberration correction unit is a collimating lens that is displaceable in the optical axis direction of light.
- the first spherical aberration correction unit is an optical element having a predetermined thickness and a predetermined refractive index, which is arranged to be insertable into and removable from an optical path of light.
- the optical element is preferably a cover glass.
- the first spherical aberration correction unit is an optical path length changing liquid crystal element whose refractive index can be controlled by applying a voltage.
- the second spherical aberration corrector is a liquid crystal element capable of changing a refractive index for each of a plurality of regions concentric with the optical axis by applying a voltage. Is preferred.
- the second spherical aberration correction unit is a collimating lens that is displaceable in the optical axis direction of light.
- a first spherical aberration corrector and a second spherical aberration corrector is a single collimating lens that can be displaced in the optical axis direction of the power light.
- the first spherical aberration corrector and the second spherical aberration corrector are a single optical path length changing liquid crystal element whose refractive index can be controlled by applying a voltage. Is preferred.
- an optical head including a light source and an objective lens configured to collect light having a light source power and form a light spot in a mountable optical information recording medium.
- a third spherical aberration corrector for correcting aberration wherein the first spherical aberration corrector performs the first spherical aberration correction on the mounted optical information recording medium with the first spherical aberration correction amount.
- the second spherical aberration correction unit performs the second spherical aberration correction with the second spherical aberration correction amount smaller than the first spherical aberration correction amount
- the third spherical aberration correction unit includes at least the first spherical aberration correction unit and the second spherical aberration correction unit.
- N-th (n is an integer greater than 3) spherical surface caused by deviation of the correction performed by the aberration corrector
- the third spherical aberration corrector includes a higher order spherical aberration corrector capable of changing a refractive index for each of a plurality of regions concentric with the optical axis by applying a voltage. It is preferably a liquid crystal element.
- n is preferably 5.
- the present invention is an optical disc device used for at least one of recording and reproducing information on an optical information recording medium, wherein the optical head according to any one of the aspects of the present invention includes: It is an optical disk device having.
- the optical head of the present invention has a plurality of spherical aberration correction units, and each of the spherical aberration correction units is configured to perform spherical aberration correction for different purposes and different correction amounts. Therefore, it is possible to correct spherical aberration over a large range with only a single optical head, and it is possible to enhance the performance of an optical head and an optical disk apparatus using the same, and to reduce the size.
- FIG. 1 is a configuration conceptual diagram of an optical head according to a first embodiment of the present invention.
- FIG. 2A is a graph showing a relationship between a change in a correction amount of first and second spherical aberration corrections and rotation of a disk.
- FIG. 2B is a graph showing a relationship between a change in the correction amount of the first and second spherical aberration corrections and the rotation of the disk.
- FIG. 3 is a flowchart of an operation for recording information and playing back Z.
- FIG. 4 is a plan view of a liquid crystal spherical aberration corrector 3 and a graph of expected spherical aberration and corrected spherical aberration.
- FIG. 5 is a conceptual diagram of a configuration of an optical head according to a second embodiment of the present invention.
- FIG. 6 is a conceptual diagram illustrating a configuration of a modification of the optical head according to the second embodiment.
- FIG. 7 is a conceptual diagram illustrating a configuration of an optical head according to a third embodiment of the present invention.
- FIG. 8 is a conceptual diagram illustrating a configuration of a modification of the optical head according to the third embodiment.
- FIG. 9 is a configuration conceptual diagram of an optical head according to a fourth embodiment of the present invention.
- FIG. 10 is a plan view of a liquid crystal element 12 for correcting higher order spherical aberration, and a graph of expected higher order spherical aberration and corrected higher order spherical aberration.
- FIG. 11 is a configuration conceptual diagram of a modification of the optical head according to the fourth embodiment.
- FIG. 12 is a block diagram of an optical disk device according to the present invention.
- FIG. 1 is a conceptual diagram showing a configuration of an optical head 101 of an optical disc device which is an optical information recording / reproducing device according to a first embodiment of the present invention.
- the optical head 101 has a light source (semiconductor laser) 1, and divergent light emitted from the light source 1 is converted into substantially parallel light by a collimating lens 2 constituting a first spherical aberration correction unit in the present embodiment.
- the light passes through the liquid crystal spherical aberration corrector 3 constituting the second spherical aberration corrector in the embodiment, and enters the objective lens 4.
- the incident light is condensed by the objective lens 4 and is incident on an optical disk 5 which is an optical information recording medium to form a light spot in the optical disk 5.
- the light spot is reflected by two information recording layers located at two predetermined depths in the optical disc 5.
- the two information recording layers are the first recording layer 5b as the first information recording layer or the zeroth recording layer 5d as the second information recording layer.
- the reflected light passes through the objective lens 4 and the liquid crystal spherical aberration correction element 3, is reflected by the mirror 7, and enters the detector 8.
- the detector 8 sends information about the reflected light to a circuit unit (not shown) in real time.
- the optical disc 5 of the present embodiment is a two-layer disc having two information recording layers.
- the optical disk 5 has, from the optical head side, a cover layer 5a having a thickness of 75 ⁇ ⁇ (0.075 mm) and a first recording layer 5b located at a depth of 75 m from the optical disk surface on the optical head side. twenty five It has a 0th recording layer 5d located at a depth of 100 m (0.1 mm) from the optical head side surface with an intermediate layer 5c having a thickness of ⁇ (0.025 mm) interposed therebetween.
- the optical disc to which the present invention can be applied is not limited to a two-layer disc having two information recording layers like the optical disc 5.
- the optical head according to the present invention is applicable to a single-layer disc having only one information recording layer and a multi-layer disc having three or more information recording layers.
- the optical information recording medium is a Blu-ray Disc having two information recording layers.
- CDs compact 'disks'
- DVDs digital 'versatile' disks
- information recording (writing) and information reproduction on existing optical information recording media such as CDs (including CD-R, etc.), DVDs (including DVD players R, etc.), Blu-my discs, etc. It is also possible to perform (reading) with one optical head of the present invention.
- the collimating lens 2 is supported by a collimating lens driving device 6 including a solenoid element 6a and a holder 6b.
- the driving device 6 is controlled by a signal from the optical head driving Z control unit 51.
- the optical head control Z drive unit 51 includes a control unit 51a, a first drive unit 51b, and a second drive unit 51c.
- the optical head control Z drive unit 51 is included in the circuit unit 23 (see FIG. 12), and the control unit 51a outputs a first drive control signal based on information input from other parts also included in the circuit unit 23. It is sent to the section 51b and the second drive section 51c.
- the first and second drive units 51b and 51c output first and second drive signals, respectively.
- the drive device 6 of the present embodiment receives the first drive signal output from the first drive section 51b, and drives the solenoid element 6a based on the input first drive signal.
- the solenoid element 6a is driven, the collimating lens is driven in the optical axis direction via a holder 6b connected to the element 6a.
- the collimating lens 2 is displaced back and forth in the direction of the optical axis, substantially parallel light traveling from the collimating lens 2 to the objective lens 4 slightly becomes divergent light or convergent light, and the spherical aberration of the objective lens 4 is corrected. (1 spherical aberration correction).
- the liquid crystal spherical aberration correction element 3 is an optical element whose refractive index can be changed by applying a voltage, as described later.
- the element 3 is divided into a plurality of regions, and each region changes a refractive index according to an applied voltage to give a phase difference to transmitted light. This phase difference is condensed by the objective lens 4 and the spherical spot of the light spot formed on the information recording layer is collected. Correct the difference (second spherical aberration correction).
- the above-described first spherical aberration correction is performed for the purpose of forming an aberration-free light spot on the information recording layer located at one of a plurality of preset depths.
- a plurality of information recording layers are present in the disc, it has a function of switching the information recording layer for recording and reproducing information.
- the second spherical aberration correction corrects an error from a specified value of the depth from the optical head side disk surface of the information recording layer of the existing optical disk that actually performs information recording and Z reproduction. Specifically, spherical aberration caused by an error between the actual thickness of the cover layer 5a and the intermediate layer 5c, or the actual thickness of the cover layer 5a or the intermediate layer 5c, and each layer is corrected. This is performed for the purpose of forming a light spot without aberration on the information recording layer.
- the first spherical aberration correction performs a relatively large-scale spherical aberration correction caused by an optical distance larger than an optical distance between a plurality of information recording layers included in one disc.
- the first recording layer and the zeroth recording layer have a distance of 25 m in the thickness direction of the disc.
- the first spherical aberration correction corrects the aberration caused by the optical distance corresponding to 25 m.
- the second spherical aberration correction performs spherical aberration correction on a smaller scale than the first spherical aberration correction. Therefore, the range of the amount of aberration that can be corrected by the second spherical aberration correction may be relatively small.
- the thickness of the cover layer 5a and the like of the optical disk 5 irregularly has an error of ⁇ 2 m at every point in the plane of the disk. Therefore, the thickness error of the cover layer 5a and the like changes synchronously with the rotation cycle due to the rotation of the optical disk 5.
- the second spherical aberration correction corrects the aberration due to the periodic, small-scale fluctuation of the thickness of the cover layer 5a and the like.
- FIGS. 2A and 2B are graphs showing the relationship between the correction performed by the first and second spherical aberration correctors and the rotation cycle of the optical disk 5.
- the line including the pulsed undulations plotted at the top is the rotation synchronization signal 41 emitted each time the optical disk 5 makes one rotation.
- a pulse-like undulation appears in the signal 41.
- the vertical axis of the lower graph is the first and second spherical aberration correctors. This is the amount of spherical aberration correction by each.
- the spherical aberration correction amount is represented by a change amount of a position (depth) where a light spot having no aberration is formed in a direction perpendicular to the main surface of the disk 5.
- the correction amount is X [m]
- the first correction amount 43 by the first spherical aberration correction is 25 [m].
- This first correction amount 43 is constant regardless of the rotation of the disk 5.
- the second correction amount 45 by the second spherical aberration correction varies in a range of ⁇ 2 m.
- This fluctuation fluctuates within the time width of one rotation of the disk 5, and fluctuates in synchronization with the rotation of the disk 5. This is because the thickness unevenness of the cover layer 5a and the intermediate layer 5c fluctuates in the circumferential direction of the disk 5, and the second spherical aberration correction unit performs aberration correction according to the detected thickness unevenness, To show that
- the first spherical aberration corrector corrects aberrations generated when the information recording layer is switched, and the second spherical aberration corrector is included in one information recording layer and has a periodicity due to rotation of the disk. It is desirable to correct aberrations that change dynamically.
- At least the second spherical aberration correction unit can variably control the correction amount during at least one rotation of the disk.
- the width of change in the depth of the information recording layer that can be corrected by the first spherical aberration corrector is about 1000 m (lOmm).
- the fluctuation of the depth of the information recording layer that can be corrected by the second spherical aberration corrector is about the number of persons / zm, but can cope with the fluctuation that changes at a high speed.
- the first correction amount 43 is 25 [m] as in FIG. 2A, but the second correction amount 45 is different from the case in FIG. m]. Therefore, the total correction amount of the first correction amount and the second correction amount is a fixed amount of 27 [m].
- the optical head of the present embodiment is also capable of correcting spherical aberration in such a setting. This can be used when forming a light spot on each recording layer in a multilayer disc having three or more layers.
- FIG. 3 is a flowchart of an optical head control Z drive program stored in a memory device (not shown) included in the circuit unit 23 (see FIG. 12) of the optical disk device and executed by the CPU (not shown).
- An operator mounts the optical disk 5 having the two information recording layers in the optical disk device.
- the apparatus reads the information by referring to the data recorded on the first recording layer 5b or the 0th recording layer 5d of the optical disc 5.
- the information recording layer is determined to be the first recording layer 5b or the 0th recording layer 5d.
- the information recording layer to be read first may be set and stored in advance by the device.
- recording information first, check whether there is room for information to be recorded on the 0th recording layer 5d, and if so, first record the information on the 0th recording layer 5d. , ( Figure 3, S102).
- the following describes the case where the information recording layer from which information is read in step S102 is determined to be the 0th recording layer 5d.
- the first control signal is sent from the control unit 51a to the first drive unit 51b (S102 in FIG. 3), and based on the first control signal, the first drive unit 51b outputs light having no aberration to the 0th recording layer 5d.
- the first spherical aberration correction is performed by driving the collimating lens 2 so as to form a spot (FIG. 3, S103).
- a light spot having no aberration is formed at a position at a depth of 100 m from the surface of the optical disk 5 on the optical head side.
- the thickness of the cover layer 5a and the intermediate layer 5c of the optical disk 5 slightly includes an error, and the amount of error is expected to be different at each point on the optical disk 5 surface.
- the amount of this error is assumed to be about 2 / zm. In other words, it is expected that the thickness of the disk up to the 0th recording layer 5d varies from 98 ⁇ m to 102 ⁇ m at each point in the plane of the disk 5.
- the thickness variation of the disc surface periodically changes during information recording / reproducing. Therefore, if only the aberration of the light spot generated by the optical head 101 is corrected by the first spherical aberration corrector 2, it may not be possible to properly record and reproduce information Z on a certain portion of the optical disk 5. Therefore, in the present embodiment, the periodically fluctuating aberration caused by the thickness error is corrected by using the liquid crystal spherical aberration correction element 3, which is the second spherical aberration corrector.
- the information recording layer from which information is to be reproduced at present is the 0th recording layer 5d, and that the information recorded in the inner peripheral portion thereof is to be reproduced.
- the device irradiates a light spot formed at a depth of 100 m without aberration by the first spherical aberration correction onto the track on the inner peripheral portion of the optical disk 5, and the reflected light is detected by the detector 8 and detected. From the reflected light, the distribution state of the thickness error particularly at the inner peripheral portion of the disk 5 is recognized (FIG. 3, S105).
- the control unit 51a analyzes the distribution of the detected thickness error, and sends a second drive unit 51c to the second drive unit 51c so as to appropriately correct the aberration amount that periodically fluctuates with the rotation of the optical disc 5. 2 Send a control signal (Fig. 3, S106).
- the second drive unit 51c applies a predetermined voltage to the liquid crystal spherical aberration correction element 3, which is the second spherical aberration correction unit (Fig. 3, S107).
- This applied voltage can be changed at a high speed in synchronization with the rotation cycle of the disk 5.
- Figure 4 shows a plan view of the liquid crystal spherical aberration correction element 3 ( Figure 4 (a)), the third-order spherical aberration ( Figure 4 (b)) expected to be included in the light spot, and the liquid crystal spherical aberration correction.
- the third-order spherical aberration (FIG. 4 (c)) after correction by the element 3 is shown.
- the liquid crystal spherical aberration correction element 3 is divided into three regions concentrically with the optical axis, and the electrode 31 is a terminal for externally supplying a voltage applied to each region.
- a predetermined voltage is applied to the shaded region in FIG.
- the refractive index of the region changes by a predetermined amount, and a phase difference is generated between the light transmitted through this region and the light transmitted through other regions.
- FIG. A corrected, aberration-free light spot is formed on the 0th recording layer 5d.
- a light spot having no aberration is formed on a track on the inner peripheral portion of the 0th recording layer 5d.
- the information is reproduced (or recorded) (Fig. 3, S108).
- the portion of the disk 5 to be irradiated with the light spot changes due to the above-mentioned predetermined time or reproduction (recording) of a predetermined amount of information.
- the irradiation of the light spot starting from the inner periphery shifts to the middle portion of the disk with time, and further to the outer periphery of the disk.
- the thickness error detected in step S105 is a thickness error in the inner peripheral portion of the disc, and the thickness error in the intermediate portion and the outer peripheral portion may be different from the thickness error. If the part that reproduces (or records) information changes by a specified amount (elapse of a specified time or the specified amount of information is changed by the reproduction (recording) of the specified amount of information), the thickness error is detected again.
- step S109 it is determined whether or not it is necessary to switch the information recording layer for reproducing (or recording) information. If it is determined that the switching is not required (NO in S109 in FIG. 3), the reproduction (recording) of the information is continued, and if it is determined that the switching is necessary (YES in S109 in FIG. 3), the process proceeds to step S102.
- the information recording layer on which information is reproduced (or recorded) is determined.
- the collimating lens driving device 6 is operated by the layer switching signal from the control circuit 51, displacing the collimating lens 2 in the direction of the optical axis in the direction of the objective lens 4 force, and slightly diverging the light.
- spherical aberration equivalent to the thickness of the layer 5c is corrected and focused on the 0th recording layer 5d to form a light spot.
- the control circuit 51 The first recording is performed by operating the collimating lens driving device 6 in response to the layer switching signal to displace the collimating lens 2 in the direction of the optical axis toward the objective lens 4 and to make the light enter the objective lens 4 with slightly converging light. The light is focused on the layer 5b to form a light spot.
- the spherical aberration generated by the unevenness is determined by a signal from the detector 8 as a detecting means in a plurality of areas of the liquid crystal spherical aberration correction element 3.
- a signal from the detector 8 as a detecting means in a plurality of areas of the liquid crystal spherical aberration correction element 3.
- the collimating lens 2 is moved in the optical axis direction
- the liquid crystal spherical aberration correcting element 3 includes the first and second spherical aberration correcting units, and the layer switching is performed by the collimating lens 2.
- the liquid crystal spherical aberration correcting element 3 In the case where movement is performed in the optical axis direction and spherical aberration caused by thickness unevenness of the cover layer 5a and the intermediate layer 5c is shared by the liquid crystal spherical aberration correction element 3 so that both corrections are performed by moving the collimating lens 2.
- the movement amount and frequency of the collimating lens 2 are smaller than those of the collimating lens 2, and the light capturing efficiency of the objective lens 4 is poor, and the information recording / reproducing performance is deteriorated due to a change in the shape of the light spot itself focused on the optical disk. Can be reduced. Also, the size of the collimating lens driving device can be reduced.
- the liquid crystal spherical aberration correction element 3 is used in a range where the phase difference generated by correcting only the spherical aberration corresponding to the thickness unevenness of the cover layer 5a and the intermediate layer 5c is not so large and the generation of high-order aberration is small. be able to.
- FIG. 5 is also a conceptual diagram of the configuration of the optical head 102 as an example of the present invention. Note that the same members as those in FIG. 1 are denoted by the same reference numerals, and a description of a range that is obvious from the description of the first embodiment is omitted.
- the difference between the configuration in FIG. 5 and the configuration shown in FIG. 1 is that the collimating lens 2 is fixedly disposed, and the first spherical surface in the present embodiment in the divergent light flux of the light source 1 and the collimating lens 2.
- a cover glass 9 constituting the aberration correction unit is provided, and a cover glass driving device 10 including a solenoid element 10a and a holder 10b capable of inserting and removing the cover glass 9 in a light beam is provided.
- the liquid crystal spherical aberration correction element 3 also has the second spherical surface in this embodiment.
- An aberration correction unit is configured.
- the cover glass 7 is in a state where information is recorded or reproduced (recording / reproducing) on the first recording layer 5b via the cover layer 5a of the optical disc 5, and when information is recorded on the 0th recording layer 5d.
- the thickness and refractive index are set so that the spherical aberration to be corrected when switching between the recording and playback modes can be corrected.
- the cover glass 9 is removed from the light beam by the cover glass driving device 10.
- the first driving unit 51b drives the solenoid element 10a based on the first control signal from the control unit 51a. Then, the cover glass 9 is displaced via the holder 10b and inserted into the light beam.
- FIG. 6 is a diagram showing an optical head 103 which is a modification of the present embodiment.
- the difference between the optical head 102 and the optical head 103 is that the optical head 103 forms a first spherical aberration corrector in place of the cover glass 9 that forms a first spherical aberration corrector in the optical head 102.
- a second liquid crystal spherical aberration correction element 11 The other points are the same as those of the optical head 102.
- the second liquid crystal spherical aberration corrector 11 constituting the first spherical aberration corrector is different from the liquid crystal spherical aberration corrector 3 in that the refractive index is changed by changing the voltage applied to the element 11, By changing the optical distance corresponding to the thickness of 11, the optical path length from the light source 1 to the collimating lens 2 is changed. The degree to which light is converged by the collimating lens 2 changes, A light spot having no aberration is formed on the recording layer 5b or the 0th recording layer 5d. Compared to the optical head 102, the optical head 103 can be further reduced in size without the drive unit 10.
- FIG. 7 is a conceptual diagram of the configuration of the optical head 104 as an example of the present invention.
- the optical head 104 of the present embodiment eliminates the liquid crystal spherical aberration correction element 3 constituting the second spherical aberration correction unit in the previous embodiment, and performs spherical aberration correction for layer switching, that is, first spherical aberration correction.
- the cover glass 7 constituting the first spherical aberration correction unit is inserted and removed, and the thickness unevenness correction of the cover layer 5a and the intermediate layer 5c, that is, the second spherical aberration correction is performed in the present embodiment. This is performed by moving the collimating lens 2 that forms the second spherical aberration correction unit.
- the movement amount of the collimating lens 2 can be further reduced, and the information due to the deterioration of the light capturing efficiency of the objective lens 4 and the shape change of the light spot itself focused on the optical disk 5 Therefore, it is possible to further suppress the deterioration of the recording / reproducing performance, and the size of the collimating lens driving device 6 can be further reduced. Further, since the liquid crystal spherical aberration compensating element 3 is unnecessary, it is possible to further reduce the size and cost of the optical head.
- FIG. 8 is a view showing an optical head 105 which is a modification of the present embodiment.
- the difference between the optical head 104 and the optical head 105 is that the optical head 105 forms a first spherical aberration corrector in place of the cover glass 9 that forms the first spherical aberration corrector in the optical head 104.
- a second liquid crystal spherical aberration correction element 11 The other points are the same as those of the optical head 104.
- the second liquid crystal spherical aberration correction element 11 constituting the first spherical aberration correction section changes the refractive index by changing the voltage applied to the element 11, and By changing the optical distance corresponding to the thickness of 11, the optical path length from the light source 1 to the collimating lens 2 is changed. The degree to which the light is converged by the collimating lens 2 changes, and a light spot having no aberration is formed on the first recording layer 5b or the zeroth recording layer 5d.
- the optical head 103 can be further miniaturized in that it does not include the drive unit 10.
- FIG. 9 is a conceptual diagram of the configuration of an optical head 106 as an example of the present invention.
- the liquid crystal which has almost the same configuration as the optical head 101, but constitutes the second spherical aberration corrector of the optical head 101.
- the spherical aberration corrector 3 is eliminated, and the higher order spherical aberration corrector liquid crystal constitutes the third spherical aberration corrector.
- Element 12 is provided.
- the liquid crystal spherical aberration correction element 3 is responsible for correcting the thickness variation of the cover layer 5a and the intermediate layer 5c by moving the collimating lens 2 for the layer switching.
- both the first and second spherical aberration corrections are performed by moving the collimating lens 2, and the higher-order spherical aberration generated when the collimating lens 2 is moved is corrected by the higher-order spherical aberration. This is performed by the aberration correction liquid crystal element 12.
- the collimating lens 2 forms the first and second spherical aberration correcting units of the present embodiment, and the higher order spherical aberration correcting liquid crystal element 12 forms the third spherical aberration correcting unit of the present embodiment.
- FIG. 10 is a plan view of the higher-order spherical aberration correcting liquid crystal element 12 (FIG. 10 (a)) and a graph showing fifth-order spherical aberration as an example of higher-order spherical aberration (FIG. b)) and a graph showing the spherical aberration corrected by the element 12 (FIG. 10 (c)).
- the high-order spherical aberration correcting liquid crystal element 12 is divided into five regions concentrically with the optical axis as shown in FIG. 10 (a), and the electrode 121 supplies a voltage applied to each region from outside. Terminal. When it is considered that the light spot generates a fifth-order spherical aberration as shown in FIG.
- a predetermined voltage is applied to the shaded region in FIG.
- the refractive index of the region changes by a predetermined amount, and a phase difference is generated between the light transmitted through this region and the light transmitted through other regions.
- This correction amount that is, the magnitude of the applied voltage and the region to which the voltage is applied are set in accordance with the expected higher-order spherical aberration, thereby correcting the higher-order spherical aberration.
- This correction amount that is, the magnitude of the applied voltage and the region to which the voltage is applied are set in accordance with the expected higher-order spherical aberration, thereby correcting the higher-order spherical aberration.
- FIG. 11 is a view showing an optical head 107 which is a modification of the present embodiment.
- the difference between the optical head 106 and the optical head 107 is that, instead of the collimating lens 2 forming the first and second spherical aberration correction units in the optical head 106, the optical head 107 has first and second spherical aberrations. This is the point that the liquid crystal spherical aberration correction element 11 constituting the correction unit is provided. The other points are the same as those of the optical head 106.
- the second liquid crystal spherical aberration corrector 11 constituting the first and second spherical aberration correctors changes the refractive index by changing the voltage applied to the element 11, and corresponds to the thickness of the element 11. Change the optical distance to change the optical path length from the light source 1 to the collimating lens 2. The degree to which the light is converged by the collimating lens 2 changes, and a light spot having no aberration is formed on the first recording layer 5b or the 0th recording layer 5d. Further, it is possible to change the refractive index at a high speed so as to cope with the aberration caused by the thickness unevenness of the cover layer 5a and the intermediate layer 5c. This higher-speed change in the refractive index is performed by a signal sent from the second driver 51c. Compared to the optical head 106, the optical head 107 can be further reduced in size in that the drive unit 6 is not provided.
- FIG. 12 is a conceptual block diagram of a configuration of an optical disc device 201 as an example of the present invention.
- the device 201 has an optical disk device housing 21, and includes an optical disk drive unit 22, an optical head 101, and a circuit unit 23, which are optical information recording medium drive units, inside the housing 21.
- the optical disk drive unit 22 has a function of loading the optical disk 5 from the outside to the inside of the housing 21 and a function of driving the optical disk 5 to rotate.
- the optical head mounted on the present apparatus is the optical head 101 according to the first embodiment.
- the circuit section 23 has a function of driving and controlling the optical disc drive section 22 and the optical head 12 (optical disc detection Z drive section 53 and optical head drive Z control section 51), and a signal of an information signal received by the optical head 12. It has a function of performing processing (information signal detection Z processing section 52) and a function of interfacing an information signal with the outside and inside of the casing 10 (interface section 55).
- the circuit unit 23 further includes a system control unit 54 that controls these functions in a comprehensive manner. Since the optical head 101 to 107 according to any one of Embodiments 1 to 4 is mounted as an optical head, an improvement in information recording / reproducing performance is expected as an optical disk device. Further, it is possible to reduce the size and cost of the apparatus.
- a single optical head can be used to record information on various optical discs as well as multi-layer discs.
- optical head and the optical disk device of the present invention are useful when recording and reproducing information recording media having a plurality of information recording layers.
- the present invention can be applied to a compatible optical head which can be used by one optical head for different types of information recording media having different cover layer thicknesses.
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JP2004177853A JP2007272931A (ja) | 2004-06-16 | 2004-06-16 | 光学ヘッドおよび光ディスク装置 |
JP2004-177853 | 2004-06-16 |
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PCT/JP2005/010950 WO2005124750A1 (ja) | 2004-06-16 | 2005-06-15 | 光学ヘッドおよび光ディスク装置 |
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WO2007081079A1 (en) * | 2006-01-10 | 2007-07-19 | Lg Electronics Inc. | An apparatus for reproducing and/or recording and recording medium |
Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH0917023A (ja) * | 1995-04-28 | 1997-01-17 | Konica Corp | 情報ピックアップ装置及び光ディスク装置 |
JPH09128785A (ja) * | 1995-08-31 | 1997-05-16 | Pioneer Electron Corp | 光ピックアップ |
JPH10255318A (ja) * | 1997-03-13 | 1998-09-25 | Olympus Optical Co Ltd | 集積型光学ユニット |
JP2000076665A (ja) * | 1998-08-27 | 2000-03-14 | Pioneer Electronic Corp | 光ピックアップ装置 |
JP2002170257A (ja) * | 2000-12-05 | 2002-06-14 | Sharp Corp | 光ピックアップ装置 |
-
2004
- 2004-06-16 JP JP2004177853A patent/JP2007272931A/ja active Pending
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2005
- 2005-06-15 WO PCT/JP2005/010950 patent/WO2005124750A1/ja active Application Filing
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH0917023A (ja) * | 1995-04-28 | 1997-01-17 | Konica Corp | 情報ピックアップ装置及び光ディスク装置 |
JPH09128785A (ja) * | 1995-08-31 | 1997-05-16 | Pioneer Electron Corp | 光ピックアップ |
JPH10255318A (ja) * | 1997-03-13 | 1998-09-25 | Olympus Optical Co Ltd | 集積型光学ユニット |
JP2000076665A (ja) * | 1998-08-27 | 2000-03-14 | Pioneer Electronic Corp | 光ピックアップ装置 |
JP2002170257A (ja) * | 2000-12-05 | 2002-06-14 | Sharp Corp | 光ピックアップ装置 |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2007081079A1 (en) * | 2006-01-10 | 2007-07-19 | Lg Electronics Inc. | An apparatus for reproducing and/or recording and recording medium |
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