WO2008142676A2 - Support de données optiques tridimensionnel et procédé de correction d'erreurs de piste - Google Patents

Support de données optiques tridimensionnel et procédé de correction d'erreurs de piste Download PDF

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Publication number
WO2008142676A2
WO2008142676A2 PCT/IL2008/000676 IL2008000676W WO2008142676A2 WO 2008142676 A2 WO2008142676 A2 WO 2008142676A2 IL 2008000676 W IL2008000676 W IL 2008000676W WO 2008142676 A2 WO2008142676 A2 WO 2008142676A2
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WO
WIPO (PCT)
Prior art keywords
data
recording
reading
layer
optical
Prior art date
Application number
PCT/IL2008/000676
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English (en)
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WO2008142676A3 (fr
Inventor
Rene Hamer
Yehuda Rosenblatt
Ori Eitan
Kozo Nakao
Yair Salomon
Ortal Alpert
Per-Olof Gutman
Ronen Hagai
Original Assignee
Mempile Inc.
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Application filed by Mempile Inc. filed Critical Mempile Inc.
Publication of WO2008142676A2 publication Critical patent/WO2008142676A2/fr
Publication of WO2008142676A3 publication Critical patent/WO2008142676A3/fr

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Classifications

    • 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
    • G11B7/095—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 discs, e.g. for compensation of eccentricity or wobble
    • G11B7/0956—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 discs, e.g. for compensation of eccentricity or wobble to compensate for tilt, skew, warp or inclination of the disc, i.e. maintain the optical axis at right angles to the disc
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y10/00—Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
    • 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
    • G11B7/085—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam into, or out of, its operative position or across tracks, otherwise than during the transducing operation, e.g. for adjustment or preliminary positioning or track change or selection
    • G11B7/08547—Arrangements for positioning the light beam only without moving the head, e.g. using static electro-optical elements
    • G11B7/08564—Arrangements for positioning the light beam only without moving the head, e.g. using static electro-optical elements using galvanomirrors
    • 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
    • G11B7/0901—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 for track following only
    • 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
    • G11B7/0938—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 servo format, e.g. guide tracks, pilot signals
    • 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
    • G11B2007/0003—Recording, reproducing or erasing systems characterised by the structure or type of the carrier
    • G11B2007/0009—Recording, reproducing or erasing systems characterised by the structure or type of the carrier for carriers having data stored in three dimensions, e.g. volume storage
    • 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
    • G11B7/0908—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 for focusing only
    • 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
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/2403—Layers; Shape, structure or physical properties thereof
    • G11B7/24035—Recording layers
    • G11B7/24038—Multiple laminated recording layers

Definitions

  • the present invention is generally in the field of optical data storage and relates to a three-dimensional optical data carrier and a method of correction of tracking errors in an optical storage system.
  • Some optical disks have, in addition to information marks written on them, so-called servo or formatting marks.
  • Servo marks are embossed or optically recorded marks or symbols having a certain pattern that indicates the coordinates of the optical pick-up head relative to a nominal track. Knowledge of the coordinates allows synchronized or guided information recording, reading and erasing.
  • Conventional optical storage carriers typically comprise one or a few partially reflective data layers in which data and servo marks are recorded in a certain order. Diffraction limited spots track the data layer directly and record or retrieve data therefrom. Tracking methods include imaging the spot or a split beam on a position sensitive detector (PSD) and 2D sampled servo.
  • PSD position sensitive detector
  • recording media include recording in multiple virtual recording layers.
  • Such carriers represent an optically monolithic disk-like plate of a photochromic material (active plate), or a number of plates adhered to each other, in the depth of which the data in the form of a three-dimensional pattern of spaced-apart data marks is recorded.
  • the marks are organized to form nominally, almost planar, patterns.
  • Data is recorded in the form of marks on circular or spiral tracks, the radial distance between which is about 0.8 microns and the spacing between the virtual layers may be 2 to 10 microns.
  • such carriers include at least one servo or reference layer that indicates the location of the reading/recording beam.
  • Data recording in such a multi-layer optical recording medium requires precise control of size and location of the recording/reading spot in the thickness direction of the medium, or in the axial optical pick-up unit (OPU) direction (i.e. in the direction of the optical axis of the OPU).
  • OPU optical pick-up unit
  • optical storage media such as optical disks in general and three- dimensional disks in particular, data is stored in form of a pattern of marks (voxels in three-dimensional disks) and spaces along tracks formed in the bulk of the optical disk.
  • the tracks generally comprise spiral tracks located on and in the vicinity of a nominal position on which the data is to be written and from which the data is to be read.
  • a focused laser beam illuminates these voxels, while the disk is rotated around its axis.
  • Interaction of laser light with disk material results in material change or recording.
  • Interaction of laser light with already recorded disk material produces a luminescent response or a non-linear response that may be detected and the data may be interpreted.
  • a monolithic photochromic material disk-like plate may be between 300 and 1200 microns, far exceeding the depth of field of the existing OPUs, therefore the distance between the reference layer and the data layer may be 300 to 1200 microns.
  • US patent No. 6,738,322 to Amble et al discloses an optical data storage system that comprises an optical medium including a servo plane (i.e. servo layer) and at least one data plane.
  • a first laser is positioned to generate a servo laser beam and address the servo plane with a first servo focal spot.
  • a second laser is positioned to generate a read-write laser beam and address the data plane with a second read-write focal spot.
  • a first servo system is associated with the first laser and is configured to provide focus and tracking error correction according to servo information associated with the servo plane.
  • a second servo system is associated with the second laser and is configured to provide focus and tracking error correction according to servo information associated with the data plane.
  • a certain servo pattern is embedded into the data layers. This reduces the capacity of the carrier and increases recording complexity. Three-dimensional carriers contain multiple recording layers, the number of which may be few hundred of layers. Recording of servo marks in each of these layers would place a burden on either factory pre- formatting or on formatting in the drive speed.
  • disks in addition to reading and recording beams have a reference or servo layer, which, when scanned by a focused laser beam, allows the focused beam spot to coordinate determination.
  • the location of the reference spot is typically coordinated with the location of the recording or reading beam.
  • Knowledge of the coordinates of the reference beam allows determination of the coordinates of the data-reading beam.
  • Three-dimensional disks are relatively thick disks (0.3 mm to 6.0 mm thick) and data is recorded about the nominal position of a data track, which means that voxels may be below, above, to the right or left of the track.
  • mechanical errors such as axial and radial disk run-out, and mechanical vibrations complicate the coordination of the reference and data reading beams locations.
  • a three-dimensional optical carrier refers to a medium configured for recording and reading data in the form of a three-dimensional pattern of spaced-apart recorded regions located in multiple planes.
  • a method for use in at least reading data in a three-dimensional optical data carrier having at least one reference layer and at least one data layer comprises: a) focusing a recording/reading beam and a reference beam onto said optical carrier through a common optical element creating two focal spots in different optical planes; and, b) controlling the movement of at least said optical element such that the focal spot of said reading/recording beam tracks a data track in an addressed data layer, said controlling comprising identifying a change in an error signal from the reference layer during the reference beam tracking the reference layer, thereby adjusting a tracking target for control of the movement of the reference beam.
  • the error signal from the reference layer has a spatial frequency bandwidth larger than that of an error signal from the data layer. This enables identification of the change in the error signal from the reference layer.
  • the method of the invention also provides for at least partially correcting for an error of the reference beam focal position.
  • the controlling of the movement of at least said optical element comprises keeping axes of the common optical element and the recording/reading and the reference beams to be coaxial.
  • the recording/reading focal spot and the reference focal spot are coordinated in a predetermined relation.
  • the controlling of the movement of at least said optical element comprises utilizing location of the reference focal spot in the reference layer to locate the recording/reading beam focal spot in a target location in the optical data carrier.
  • the controlling of the movement of said optical element can be achieved by at least one of the followings: (a) axes of the reading/recording beam and the reference beam can be kept parallel to the optical axis of the optical element; and (b) the reference beam can be deflected or offset in a radial or tangential direction.
  • a method for use in at least reading data in a three-dimensional optical data carrier having at least one reference layer and at least one data layer comprises: a) focusing a recording/reading beam and a reference beam onto said optical data carrier through a common optical element creating a recording/reading focal spot and a reference focal spot in different optical planes; and; b) controlling position of said reference focal spot and reading/recording focal spot by manipulation of an optical path common to both recording/reading and reference beams and by at least one additional manipulation of optical path of one of said beams.
  • the manipulation of the optical path common to both beams may be carried out by actuating an objective lens system to locate the reference focal spot, tracking a reference track in the tangential direction.
  • the additional manipulation of one of the optical paths may be carried out by actuating a mirror in said one of the optical paths to locate said reference focal spot on the reference track in the radial direction.
  • the movement of said reference beam and reading/recording beam can be controlled by coupling said objective lens system to a mirror and actuating said objective lens system and said mirror together.
  • the movement of at least one common optical element can be controlled by estimating an anticipated required movement of said common optical element.
  • the invention in its yet another aspect provides a method for use in at least reading data in a three-dimensional optical data carrier comprising at least one reference layer associated with one or more data layers and having a reference pattern arranged along reference tracks, the method comprising tracking said reference pattern by a reference beam having a focal spot size exceeding a pitch between two adjacent tracks in the reference layer.
  • the invention also provides a three-dimensional optical data carrier comprising a recording volume associated with at least one reference layer having reference patterns indicative of reference information pieces arranged along reference tracks, wherein said reference patterns are separated from servo patterns located on adjacent tracks in a radial direction, said servo patterns having at least one of the following arrangement: (i) with no angular overlap between the servo patterns located on adjacent tracks; (ii) said separation between the servo patterns of adjacent tracks includes separation in a frequency domain; and (iii) said separation between the servo patterns of adjacent tracks includes separation in a signal domain.
  • the reference patterns may contain tracking information, and/or clock for data recording and retrieving, and/or carrier format information such as layer, track sectors numbers.
  • the reference patterns may be embedded as tones or Baker coded or Complementary Code Keying coded.
  • the recorded volume may comprise one or more data layers including servo patterns embedded as tones in the data layer.
  • the reference patterns are preferably configured to provide a smooth substantially continuous transition between tracks in the reference layer.
  • a three dimensional optical data carrier comprising a recording volume with a plurality of data layers recorded therein, each data layer comprising data pattern arranged along data tracks, a radius of the most external track decreasing from the upper surface of the recording volume towards the lower surface thereof in a direction of propagation of incident light.
  • Such data carrier may comprise at least one reference layer configured as described above, namely comprising a reference pattern arranged along reference tracks.
  • a distance between the most external reference tracks of the reference layer and an external surface of said volume determines numerical aperture of a reading/recording beam to be used for recording/reading data in/from a data layer coupled to said reference layer and the maximal recording radius in said data layer.
  • a three dimensional optical data carrier comprising at least one reference layer and at least one data layer, wherein the radii of said layers decrease stepwise with the distance from an upper surface of the carrier with respect to a direction of incident light propagation during recording/reading processes.
  • a data carrier may have a double-sided configuration.
  • the data layers may be arranged in groups, and may be interspaced by group separation intervals.
  • the groups may be defined by virtual base layers.
  • an optical system for recording and/or reading in a three-dimensional optical data carrier having at least one reference layer and at least one data layer comprising: a) a light source system generating a reference beam and a recording/reading beam; b) a beam combiner combining said beams such that said beams being coaxial and having at least a common optical path section; c) a common optical element (e.g.
  • an objective lens unit located on the common optical path section; and d) a control unit configured and operable for controlling movement of said common optical element such that a focal spot of said reading/recording beam tracks a data track in an addressed data layer, said controlling comprising identifying a change in an error signal from the reference layer during the reference beam tracking the reference layer, thereby adjusting a tracking target for control of the movement of the reference beam.
  • the common objective lens unit is operable to locate the reference focal spot, and tracking the reference track, in the radial direction and in the tangential direction.
  • the invention provides an optical system for recording and/or reading in a three-dimensional optical data carrier having at least one reference layer and at least one data layer; said system comprising: a) a light source system for generating a reference beam and a reading/recording beam; b) a beam combiner combining said beams such that said beams are coaxial and have at least a common optical path section; c) a common optical element located on the common optical path section, wherein movement of said optical element being used for controlling the position of both beams; d) at least one additional optical element located in one of the separate optical paths of said beams, movement of said additional optical element being used for controlling position of one of said beams.
  • the objective lens system being the common optical element may be actuated to locate the reference beam, and to track the reference track in the tangential direction.
  • the additional optical element may be a mirror actuated to locate the reference beam on the reference track in the radial direction.
  • the system preferably comprises a detector providing a feedback signal indicative of the position of at least one of the beams, and a control unit configured for receiving the feedback signal and generating a correction signal.
  • the latter is used for affecting the movement of the common optical element, and/or the additional optical element and/or an optical pickup unit.
  • Fig. IA and Fig. IB are schematic illustrations of a typical multilayer optical data carrier structure
  • Fig. 2A-2C are schematic illustrations of some relative reference and recording/reading spot locations in a data carrier
  • Fig. 3 is a schematic illustration of a typical S-curve
  • Fig. 4A is a schematic illustration of the present reference surface layout
  • Fig. 4B illustrates a simplified block of marks that comprise servo and to some extent additional data information encoded with Barker codes
  • Fig. 5 is a schematic illustration of the present reference layer format and tracking method
  • Fig. 6 is a schematic illustration of the proportional range generated by different servo tracking methods
  • Fig. 7 is a schematic illustration of the overlapping proportional ranges of the present reference surface format
  • Fig. 8 is a schematic illustration of a deviation of a data track projected on the reference layer tracks, showing the need for overlapping proportional ranges of the reference layer format
  • Fig. 9 is a schematic illustration of a tracking error servo system loop operating according to the present layer principles
  • Fig. 10 is a schematic illustration of a focal/axial servo system loop operating according to the principles disclosed
  • Fig. 11 is a schematic illustration of an embodiment of an optical system for recording and reading a multilayer three-dimensional optical data carrier
  • Fig. 12 is a schematic illustration of a typical multilayer three-dimensional optical data carrier and of some relative reference and recording/reading spot locations in a data carrier;
  • Figs. 13A-13C are schematic illustrations of an embodiment of the principle of determined relation between the reference and recording/reading focal spots in the optical layout of Fig. 11;
  • Fig. 14 is a schematic illustration of another embodiment of an optical system for recording and reading a multilayer three-dimensional optical data carrier
  • Fig. 15 is a schematic illustration of an optical system layout, details of which are shown in Table 1.
  • Fig. 16 is a schematic illustration of a three-dimensional non-linear optical carrier
  • Fig. 17 is a schematic illustration of a problem associated with the use of a high numerical aperture optical system
  • Fig. 18 is a schematic illustration of one of the embodiments of the three- dimensional information carrier
  • Fig. 19 is a schematic illustration of another embodiment of the three dimensional information carrier.
  • Fig. 20 is a schematic illustration of an embodiment of a double sided three- dimensional information carrier
  • Fig. 21 is a schematic illustration of a further embodiment of the three dimensional information carrier; and; Figs. 22A-22B are schematic illustrations of another embodiment of the three dimensional information carrier.
  • the optical data carrier 100 includes a recording volume 104, having a disk-like shape, located on top of and in direct contact with a flat surface 108 supporting the entire stack.
  • the recording volume 104 may be made of a transparent or translucent polymer material, such as Polymethylmethacrylate (PMMA) and compositions including acrylate and methacrylate monomers.
  • PMMA Polymethylmethacrylate
  • the recording volume 104 may also be made of a non-linear photochromic material in which, upon photochemical excitation of the chromophores, a change of the chromophore's state (e.g.
  • the recording volume 104 is a bulk monolithic material, e.g. as discussed in WO 06/075327, or may be an assembly of disk like plates made of the same material.
  • a reference layer 112 is located on the top of flat surface 108. In the example of Fig. IA, this reference layer is associated with all the recording planes, while in the example of Fig. IB, an additional reference layer is provided between two groups of recording planes.
  • the flat surface/support layer 108 can be associated with (e.g. composed of) a second recording volume, or a second recording volume with a reference layer followed by a third recording volume, and so on.
  • Reference or servo layers may be recorded similarly to data layers, for example, by recording method and systems such as disclosed in International publications WO2005/015552 and/or WO 2006/1 1 1972.
  • the recording volume 104 is configured and operable to record data therein and read the recorded data therefrom, where the data is in the form of a three- dimensional pattern of spaced-apart recorded marks arranged in multiple recording layers.
  • the data may be optically recorded in the carrier 100 in practically any location, although it is convenient to record it on a plurality of "virtual" layers 120 as a series of three dimensional (3D) regular or oblong and tilted data marks.
  • the nominal spacing between adjacent data layers may be 3 to 15 microns.
  • the recording volume is configured for recording/reading data arranged in multiple planes, and includes one or more reference layers.
  • the reference layer is a structure defining a reflective interface for a reference beam of a certain wavelength range.
  • the reference layer is at least partially reflective for the reference beam and in case it is located in between recording layers it is substantially transparent for recording and reading beams.
  • the reference layer is interposed between a data layer and a non-recording layer.
  • the data layer and non-recording layers have different optical properties with respect to one- or multi-photon interaction used for recording/reading data in the data carrier.
  • the reference layer preferably has a pattern in the form of spaced-apart pits arranged along a spiral track or multiple concentric rings. The pits may be arranged in a spaced-apart relationship along a groove or grooves.
  • a reference beam focus or spot 105 is located on reference layer 112.
  • the intersection of the spot 105 with detectable pits on the reference layer 112 modulates the intensity of the reflected signal.
  • the pits may modulate the signal by several methods such as the formation of refractive interference, or if the reference layer is a recordable photochromic layer, the modulation of the amount of fluorescence (between pits/marks and spaces) at the nominal interface (between the reference layer 112 and the recording volume (plate) 104) position.
  • the reference beam or spot 105 is coupled to the recording/reading beam/spot 134 such that the reference surface in reference layer 112 can be used to locate a recording/reading light beam on a desired position in the recording volume 104, above and/or below the reference layer 112.
  • the reference layer enables to keep the focal position of the recording/reading beam on the addressed plane, by detecting light response of the reference layer (e.g. reflection of the reference beam); and in case the reference layer is patterned it enables to control the recording/reading beam position while scanning the addressed plane.
  • beams 105 and 134 may be directed from another direction on the carrier 100.
  • the recording volume 104 may be composed of a non-linear photochromic medium having a fluorescent property variable on occurrence of one or multi-photon (e.g. two-photon) absorption.
  • the recording volume may be composed of any medium supporting volumetric recording, such as a recording medium disclosed in US Patent No. 7,01 1,925 and in International publication WO 2006/075327, all assigned to the assignee of the present application.
  • the surface support layer 108 may serve as a base layer for the reflective reference surface (layer) 112 on which servo patterns (arrangement of spaced-apart pits) for tracking are embossed or optically recorded.
  • the surface 108 is made of at least one transparent material such as polycarbonate, methacrylic resin, or polyolefin.
  • the surface 108 may also comprise a photochromic medium having similar or different properties as the recording volume 104.
  • Methods and appropriate media for extracting the basic signal from the reference layer, methods of calibration of layers location, and methods of tracking the recorded data, and an optical system adapted for this purpose are disclosed in the International Publications WO2007/069243 and WO2007/083308 all assigned to the assignee of the present application and incorporated herein by reference.
  • the reference layer 112 is characterized by a certain pattern in the form of a plurality of pits/marks arranged in a spaced apart relationship either in nominally concentric circular arrays or nominally along zoned spiral tracks.
  • the surface of the reference layer is a reflecting surface, which may be formed by well-known methods on the pitted/protruded surface 108.
  • the reference pattern may be formed on the surface of recording volume 104 (e.g. by direct embossing or printing).
  • the reference layer 112 generates a signal indicative of the positional information of the data such that the data can be recorded/read with the aid of the tracking direction position signal in the record/read layers.
  • the carrier 100 may contain more than one reference layer 112.
  • Reference layer 112 may be a printed layer or a conventional embossed CD-like stamped layer.
  • the servo or reference spot 105 follows a reference track and is located slightly above (or below in the plane of the drawing) the reference spot; a read/record spot scans a data layer.
  • the distance along the vertical axis between the recording/reading focal beam/spot 134 and the reference beam foci can range from complete overlap (zero distance) up to 300 - 1500 microns.
  • a calibration procedure that determines the relative location of recording/reading focal spot with respect to the reference beam focal spot within recording volume 104 is carried out, for further controlling the recording/reading spot axial moving distance.
  • the calibration procedure utilizes determination of the reflection of the reference beam from the interface surfaces (e.g. the reflective surface of the reference layer 112 or the outer surface of the disk) and change of read signal (e.g. fluorescence) caused by the reading spot interaction with the same interface surfaces.
  • the recording spot moves upward (in the plane of the drawing) within the carrier 100 in a predetermined motion mode to define and record a recording layer.
  • the reading layer location may be established by moving the reading spot upward (in the plane of the drawing) from the reference layer 112 into the recording volume 104 of the carrier 100.
  • the spot scans the recorded layers and the interaction between the spot and the recorded marks causes a varying response (e.g. fluorescence) to be emitted.
  • the response identifies the location and the distance of the recorded layer from the reference surface of the reference layer 112.
  • the tracking of a reading spot moving along a recorded track may be performed by making simultaneous spot movements in two directions orthogonal to the track (wobbling).
  • the reference layer is subject to mechanical assembly errors, which may cause tilt of the reference layer relative to the optical axis of the beam propagation through the carrier, as well distortions due to thermal and mechanical load, and other errors.
  • Figs 2A-2C illustrating different disk distortion examples, where for the sake of comparison Fig. 2A illustrates the ideal case in which the carrier surface 200, the reference layer 204 and the data layer 216 are ideally perpendicular to the optical axis 226 and parallel to the disk surface.
  • the spatial (radial and tangential) location of the reference beam 220 focus or spot 224 and the recording/reading beam 232 and focus or spot 236 are correlated and coaxial.
  • Fig. 2B illustrates the same configuration on a tilted carrier
  • Fig. 2C illustrates the same configuration for a tilted and distorted carrier.
  • the reference beam 220 and recording/reading beam 232 may remain coaxial, but their relative spatial position along the optical axis is liable to change between the recording process and the data retrieving process due to the mechanical error of the assembly, tilt of the reference layer 204 relative to the disk surface 200 and internal mechanical changes in the disk.
  • the offset 244 shows the difference between the actual position of the reference spot 240 and the recording/reading spot 236.
  • the beams' refraction by the disk material and the loss of common optical axis (centering) of the reference beam 220 and the recording/reading beam 232 may further contribute to the absence of correlation.
  • the relative location of the data layer 216 with respect to the reference layer 204 is due to the drive-to-drive compatibility or the mechanical and optical tolerances of each drive. Because of such differences, the motion of the recording spot with respect to the servo (reference) spot might not be substantially coaxial. This may result in different, drive dependent data marks locations and adversely affect the disk interchangeability.
  • the amplitude of the described offset for a disk with tilt tolerance of 2-10 milliradian and thickness of 0.6-2.4 mm may be in the order of microns in either one of axial (focal or tangential) or radial directions.
  • the offset between the reference beam and the data recording/reading beam increases, the coupling between the reference beam and the data recording/reading beam becomes less accurate, and reading the data track requires compensation for the induced errors.
  • the tilt and the de-center of the rotating carrier, and the carrier shape distortions caused by carrier aging or improper mechanical and thermal load application, might lead to so-called low frequency deformations (in the range of KHz) or errors of the data tracks relative to the reference layer.
  • the errors which are not relative to the reference layer and to the mechanical vibrations of the system cause disturbances that may comprise high frequency disturbances (in the range of MHz).
  • the high frequency disturbances might exceed the bandwidth of the direct position error signals from the recorded data track.
  • the present invention in one of its aspects, enables the correction of both high frequency disturbances and low frequency errors caused by any disturbances such as disk distortion.
  • This correction is based on combining high frequency error signal from the reference layer (for correction of high frequency disturbances) with low frequency error signal from the data layer (for correction of low frequency distortions and disturbances).
  • the error signals that could be detected in the optical axis (axial or tangential) direction are termed Focus Error Signals (FESs) and those in the radial direction are termed Tracking Error Signals (TESs).
  • FESs Focus Error Signals
  • TESs Tracking Error Signals
  • a common objective lens unit is used for focusing the reference and recording/reading beams into the recording volume.
  • the present invention thus also enables the use of the respective error signals (FESs or TESs) associated with the data and reference layers and being thus of different spatial frequencies (high and low frequencies, respectively) to identify a distance between the reference layer and the addressed recording layer and to keep the reference and the recording/reading data beams coaxial.
  • FESs or TESs error signals
  • the above-mentioned distortions are predominately generators of a low frequency error signal as also is the disk eccentricity. Therefore, high frequency error signals are predominately the result of disturbances, and the tracking errors, as induced by mechanical vibrations and disk eccentricity, are common for both the data layer tracking and the reference layer tracking.
  • the reference beam reflection (reference signal) from the reference layer generated error signal which is in general a high quality signal with good signal-to-noise ratio. It allows for correction of the errors on both data and reference track.
  • the difference in the relative location (orientation and position) of the data track with respect to the reference (the relative error) track must be properly detected.
  • the low frequency character of the relative error allows for narrower bandwidth and lower signal-to-noise ratio's detection methods. Furthermore, this error has a dominant periodic component (it repeats every revolution of the disk with the same error pattern.)
  • the error can be detected and learned by a "feed forward" method incorporated to the control of a correcting actuator (as will be described below with reference to Fig. 1 1). This could eliminate errors caused by disk distortion and disk eccentricity and prevent beam de-centering errors by prevention of large objective offsets. This method further reduces the requirements for reliable detection signal-to-noise ratio of the signal and reduces the loss in data signal quality.
  • optical systems for data recording/reading are aberration corrected optical systems that keep the optical path of the recording/reading beam with minimal losses.
  • the reference (reflected) signal is typically a stronger signal as compared to the response signal caused by the interaction of the recording/reading spot with the bulk (optically) monolithic material of the carrier.
  • proper design considerations require utilization of a common objective lens unit for both the reference beam and the recording/reading beam. Since proper spherical aberration correction is more simply applied to only one of the spots, it has to be applied to the read/write spot.
  • the reference beam quality is less critical and it may form a relatively large, lower effective NA, aberration tolerant reference pattern scanning spot. Since the same objective lens unit projects both the reference and the reading/recording spots, unavoidable losses and aberrations could be placed in the reference beam path allowing for a diffraction limited recording/reading spot. Moreover, a longer wavelength may be used for the reference beam (the reference pattern scanning spot).
  • an S-curve may be calculated using the output of a position sensor (See "Optical Recording" by A. Marchant, pages 168 - 172, Addison- Wesley 1990, ISBN 0-201-76247-1). Reference is made to Fig.
  • the range of the linear section of the S-curve 350, indicated by the horizontal bar 310 determines the more appropriate working range derivable from the servo signal.
  • the accuracy and reliability of the servo signal are conveniently characterized by the slope and noise margins of the S-curve.
  • Standard radial tracking error signal (TES) generation methods are characterized by a relatively small proportional range S-curve and may have a TES range that is much smaller than 1 micron. These methods should be modified for use in combined tracking error correction using signals from the reference layer tracking and from the layer tracking data.
  • the size of the spot should be such as to enable reliable error signal S-curve generation. It should be noted that using sampled servo, the size of spot may vary over a relatively wide range (compared to other servo methods such as push-pull tracking), and yet sampled servo tracking error signal (TES) may still be characterized by a reliable and accurate S-curve enabling the determination of the location of the spot. Thus, the exact size of the spot and the strict maintenance of the spot size become less important, allowing a relative freedom in the design of the system and reliable operation.
  • Fig. 4A representing a reference pattern 500 and its associated signal generated by the spot 516 moving along the nominal center of a track.
  • the servo or reference marks (pits or spaces between them) 504 are optically recorded or embossed on tracks A, B, and C.
  • the error signal generated by the difference between the intensities reflected by the marks 504 read by the large spot 516, equal to (A-B) or (B-C), would not provide a decisive indication on the spot location.
  • the spot 516 may have dimensions larger than the pitch (i.e. the distance 520 between two adjacent tracks).
  • the diagram 528 illustrates the signal generated by the spot movements.
  • the carrier may rotate and the spot may be static.
  • the spot 516 moves along the track B in the direction indicated by arrow 524.
  • the center of the spot 516 follows track B.
  • the content reflected signal 532 originating in track A or C is minimal
  • the location of the spot between the tracks may be determined and used to track the spot in arbitrary positions within the servo response range.
  • the error signal could be expressed as the difference between the signals generated by tracks A and C.
  • the marks 504 of the adjacent tracks in the reference layer are used as sampled servo marks. Despite its size, the reference spot can follow a track, with a high resolution.
  • mark 504 may be constituted by a single pit/space or by a group of the spaced-apart pits, where a distance between the pit/space within the group 504 is smaller than that between the groups (i.e. between the last pit- space in one group and the first pit/space in the adjacent group.
  • the block 504 of marks may be a single-mark or multiple-marks block.
  • the blocks of marks 504 are relatively sparse on each of the tracks such that no block of marks angularly overlaps another mark block located on an adjacent track, i.e. there is no overlap between the blocks in a radial direction. Therefore, the relatively large spot 516 will not cover simultaneously marks on the adjacent tracks. Such marks location allows for removing ambiguity or interference that could exist if a relatively large spot, like spot 516, would overlap marks on all of two (or three) tracks A, B (and C). Further to this, the spot may vary in a relatively large range from two to three track pitches allowing for significant defocusing to be absorbed without affecting the signal.
  • Reference layer formats having tracks densely populated by reference or servo marks may have, especially for a low quality (low resolution) spot, relatively significant interference between the tracks signals.
  • This effect may be overcome, for example, by interleaving servo mark and other information (e.g. synchronization bits, sector identification, disk standard, manufacturer's identification, etc.) and by having the servo marks angularly separated from the other information patterns.
  • servo signaling marks provide high update frequency (preferably greater than 500 indications per disk rotation, more preferably greater than 1500 indications per disk rotation, and most preferably more than 4500 indications per disk rotation) so that noise may be averaged out.
  • blocks of marks may spatially overlap each other, if their respective signals are separable in the signal domain such as tone embedding or signal spreading approaches in which generally signals are encoded to practically orthogonal in a certain decoding scheme.
  • the signal domain signifies that different servo marks have different signal contents; and the frequency domain signifies that different servo marks have different frequency contents.
  • Fig. 4B illustrates a simplified block of marks that comprise servo marks and to some extent additional information encoded with Barker codes (i.e. sequence of N values of + 1 and -1).
  • Each ellipse 540 denotes one clock interval or a minimal mark (which may encode more than one clock event).
  • First reference track 544 is encoded by using 1 1 digits (+1 +1 +1 -1 -1 -1 +1 -1 +1 -1 +1 -1 ) for section 548 and 5 digits (+1 +1 +1 -1 +1) Barker codes for section 552.
  • Second track 556 is encoded using 13 digits (+1 +1 +1 +1 +1 +1 -1 -1 +1 +1 -1 +1 -1 +1) in section 560 and 4 digits (+1 -1 +1 +1) Barker codes in section 564. This structure requires less coordination (in the radial direction) of the marks' positions with respect to the adjacent track.
  • any known suitable method for separating signals can be used either using one beam for tracking or using splitting optics for data tracking.
  • the signal domain i.e. different servo marks having different signal content
  • the frequency domain i.e. different servo marks having different frequency content
  • the time-space domain can also be used as well as other domains such as wavelet domains.
  • Servo or data patterns in adjacent tracks are characterized by being substantially orthogonal and/or multiplexed in the space-time, frequency and/or another signal domain.
  • the signals can be considered to be well separated, if the inter-signal interference (interference/signal) is less than -10 dB, preferably less than -15 dB and more preferably less than -20 dB.
  • Fig. 5 representing a schematic illustration of a reference layer format according to an example of the present invention.
  • the marks 504 within the reference layer are represented as well as their location on tracks, and the distance (pitch) between the tracks.
  • Blocks 600 of marks 504 could be pre-formatted and recorded/embossed in a way that they would enable an accurate spot location determination.
  • Servo marks or patterns may further comprise additional information such as track position as is indicated schematically by the detailed structure of 610.
  • each mark block 600 contains information on the track address, sector index and possibly additional information.
  • These reference layer structural features may also allow tracking with other methods such as split beam imaging on a position sensitive detector, which in principle can be used instead of the sampled servo method.
  • each segment contains tracking information, clock for data recording and retrieving, format information on layer, track sectors numbers and specific disk info information.
  • the segments may be formatted in correlation to provide the same synchronization by adjacent tracks.
  • a signal 704 produced by a push-pull servo serves as a reference for comparison with the other options.
  • Horizontal bar 708 indicates the proportional tracking range.
  • the tracking range 708 produced by a push-pull servo is limited.
  • the tracking range 712 of the sampled servo examples below is larger than the one produced by the push-pull servo. It is produced by a sampled servo based on signals (A-B) and (B-C).
  • the tracking range 716 produced by the present method (A-C) is substantially larger than the others.
  • Fig. 7 representing a schematic illustration of the overlapping proportional ranges of the reference surface format according to the example of the present invention and some possible tracking options (derivation of the tracking error signal).
  • Letters A-E designate tracks.
  • Lines 804, 808, and 812 indicate different possible tracking signals.
  • the overlap 820 between horizontal bars 816 indicates the proportional tracking range when the reference scanning spot moves from one track to another track, meaning that a tracking option in which the tracking signal is generated by Track n - Trackn +2 is feasible.
  • Fine servo capability is achieved by the large overlap denoted 820.
  • a large proportional ranges overlap 820 enables a smooth continuous transition between the tracking alternatives including the tracking between the recorded tracks.
  • Servo resolution depends on a number of additional parameters such as signal-to-noise ratio, sampled servo frequency, and others.
  • Fig. 8 representing a schematic illustration of a deviation of a data track projected on the reference layer tracks, showing the need for overlapping proportional ranges of the reference layer format. It illustrates a feedback obtained from a reference pattern or a track that has been forced by a low frequency relative disturbance to pass (jump) over more than one reference track.
  • Line 900 indicates a trajectory of the reference spot that must be followed to compensate for example for relative data position and OPU imperfect positioning.
  • the spot was in a location where the (high frequency) tracking signal was generated as a difference between the signals (A-C) obtained by detecting the intensity of the reflected beam.
  • the servo simply switches to the next tracking alternative, and a signal (B-D) generated by the next closest track is generated.
  • the servo gradually returns to the original (A-C) signal, stressing the cyclic partially repeatable nature of disk deformations as a function of angular position.
  • the structure of the present reference layer offers a number of spot position tracking options that rely on the ability to separate the mark segments (blocks) in the radial direction (e.g. sparseness of marks, if sampled servo is used) and dense mark location in the angular direction (e.g. high repetition frequency if sampled servo is used).
  • the ability to separate mark segments in the radial direction allows for the use of a wide range of spot sizes on the reference layer, ' while the dense location of marks in angular direction allows for the use of low signal quality e.g. caused by low contrast, defocusing or significant spot aberrations that can be improved by averaging.
  • the clock can be scaled to the actual data clock.
  • the presented method and system enable to follow spot position even when the spot is located between the tracks and is independent from the fixed tracking track pitch (i.e. the radial distance between scanned virtual/nominal tracks).
  • the method and system also provide a large effective servo offset range.
  • the tracking error signal detection using sampled servo does not require use of a quadrant detector for spot location determination.
  • ZCAV Zoned Constant Angular Velocity
  • Block 1000 indicates the servo section processing the reflected pattern signal from the reference pattern
  • block 1004 indicates the servo section processing the luminescent data signal generated by interaction of the recorded marks with the reading laser spot.
  • the TES signal generated by the reference layer has a wider bandwidth range (spatial frequency of the pattern features) allowing the "jump" from tracking one reference layer track to another.
  • the reference layer tracking aims at annihilating the high frequency disturbances and not at correcting distortions, therefore only the direction and the amplitude of the high frequency disturbance are required to be estimated for correction.
  • the use of sampled servo TES that has a large overlap as shown in Fig. 7 enables determining a TES at any point from at least one track and allows smooth shifting/transition from using high frequency TES derived from one "track" to another track.
  • Standard focal (axial) error signal (FES) generation methods are characterized by a relatively wide proportional range S-curve and may have a FES range of more than 20 microns. As the relative (reference layer - data layer) tracking errors are typically much smaller, the reference layer may be followed with sufficient offset still enabling to follow the data layer. These methods can also be used for combined axial error correction, using signals from the reference layer tracking and from the data layer tracking.
  • Fig. 10 representing a schematic illustration of a servo system correcting high frequency disturbances.
  • Block 400 indicates the servo section processing the reflected signal from the reference pattern
  • block 404 indicates the servo section processing the luminescent data signal generated by the interaction of the recorded marks with the reading laser spot.
  • the FES of the reference layer has a long range, but it is an indirect signal as compared to the direct data signal and thus cannot be used for the correction of the distortion of the data track with respect to the reference track.
  • the low frequency tracking of the data layer allows correction of the low frequency distortions and disturbances.
  • the low frequency portion of the reference layer FES allows for adjusting the relative distortions, and the high frequency range of the reference layer FES can be used to indicate the amplitude and the direction of the high frequency disturbances and therefore to correct the high frequency disturbances.
  • Fig. 11 is a schematic illustration of an embodiment of an optical system for recording and reading a multilayer three dimensional optical data carrier.
  • the optical system has two branches: a branch 102 that provides first or reference beam and a branch 106 that provides a second or reading/recoding beam.
  • the branch 106 includes a beam expander device 110 composed of a positive lens 114 and a negative lens 118.
  • the negative lens 118 as shown by an arrow 122 has a freedom of movement along the system optical axis 126 forming a variable magnification beam expander system providing a variable divergence reading or recoding beam.
  • the beam expander 110 may have a different structure and may, for example, comprise two positive lenses.
  • a beam combiner 1134 collects the second or recording/reading beam 130 and changes the direction of beam 130 such that it propagates along the optical axis 138 of an objective lens unit 142.
  • the objective lens 142 focuses the recording/reading beam 130 within the bulk of an optical data carrier 146, such as for example that described in the present disclosure. Changes in the convergence or divergence of the second or recording/reading beam 130 would move the beam focal spot 150 along the optical axis 138 within the bulk of the data carrier 146. This allows focusing the beam 130 on any one of hundreds of different data layers 154 populated for example with data voxels 156 recorded within data carrier 146.
  • the read/write branch 106 of the optical system in combination with the objective lens 142 (when in the fixed position thereof) corrects the spherical aberrations of the variable divergence of reading/recording beam 130 at different focal spot locations in the depth of carrier 146.
  • the branch 102 of the system includes a beam expander device (not shown) that collimates the first or reference beam 158 or otherwise finitely conjugates the beam source with a targeted spot depth in the disk.
  • a mirror 162 folds the beam optical path such that the optical axis 164 of the beam after passing the beam combiner 1134 coincides with the folded optical axis 126 of the recording/reading beam optical axis and with the optical axis 138 of objective lens 142.
  • the beam combiner 1134 combines beams 130 and 158 such that they form a section of a common optical path where the optical axis 138 of the objective lens 142 becomes a common optical axis of both beams.
  • Beam 158 may be of wavelength different from the wavelength of beam 130. It should be noted that the reference beam 158 should not interfere with the reading/recording processes, or the signal detection, and that the separation may be achieved, for example, by use of different wavelengths and/or polarizations.
  • the first reference beam 158 may be of wavelength of about 780 nm and the recording/reading beam 130 may be of about 650 nm wavelength (the recording and reading beams may in turn be of the same or different wavelengths).
  • the objective lens 142 focuses the beam 158 into a spot 166 located in the plane of reference or servo layer 170 of the optical data carrier 146.
  • both the beam 130 and the beam 158 are focused by the same objective lens 142, although in different optical planes, the beams are optically coupled. Any movement of the objective lens 142 in the plane perpendicular to the drawing, as shown by arrows 168 affects location of both focal points 150 and 166 simultaneously. The degree at which each of the beams is affected is different, because they have different wavelength and divergence.
  • the mirror 162 that folds the first beam 158 has certain freedom of movement for adjustment purposes around axis 164, as shown by arrows 171 and in direction perpendicular to axis 164.
  • Located in the optical path of the reference beam 158 are a beam combiner 174 and a quarter- wave plate 178.
  • the beam combiner 174 folds the light reflected by the reference layer beam 182 and directs it through a focusing lens 186 onto a Position Sensitive Detector 190 (PSD).
  • PSD Position Sensitive Detector 190
  • the focusing lens 186 may be capable of lateral movement in the plane perpendicular to «the plane of the drawing.
  • the movement of the focusing lens 186 changes the location of an image 198 of a particular track of a reference layer 170 and a focal spot 166 formed by the lens 186 on the detector 190.
  • the quarter wave plate 178 rotates the polarization plane of the reflected beam 182 directed towards detector 190 to avoid undesired interference with the original reference beam 158.
  • the detector 202 may be located on any of the sides of the optical carrier 146.
  • Fig. 11 shows a transmission like configuration.
  • the detector 202 may be a Position Sensitive Detector (PSD), or non-PSD, and may be used to measure the signal and compare its value produced by different sections of the detector.
  • PSD Position Sensitive Detector
  • the fluorescent signal generated by the interaction of the focal point 150 of the reading beam 130 with the recorded data marks pattern 156 and distributed in the depth of the optical carrier 146 is a relatively weak signal and a signal collection system 206 comprising mirrors 210 having curvature of second or higher order and a filter 214 allows a better collection and signal-to-noise reduction of the fluorescent signal.
  • both reading and recording of a three- dimensional optical carrier is performed with at least two beams: a reference beam and a recording/reading beam or first and second beam.
  • the beams are optically coupled and coordinated in a determined relation, such that the location of reference spot 166 in a reference layer 172 could be used to locate a recording/reading beam spot 150 in a desired position in the recording volume of the optical carrier 146.
  • the coupling and the coordination between the beams are achieved by maintaining the objective lens 142 focusing the reference beam 158 and the reading/recording beam 130, into the focal spots 166 and 150, in a fixed position with respect to the reference layer 172. Changes in divergence of the reading/recording beam 130 moves spot 150 from one data layer to another data layer.
  • Fig. 13A illustrates in detail the effect of offset between the incident axes of a reference beam 163 and a recording/retrieving beam 126 relative to the axis 138 of the objective or an OPU.
  • the offset may be linear or angular or a combination of both of them.
  • Fig. 13A an ideal positioning is presented in which the focal spots 150 and 166 of the reading beam and of the reference beam respectively overlap and are located along the optical axis 138. Therefore, there is no offset between the axis 138 of the objective 142 and the reference beam axis 163, and the recording beam axis 126, and the beams are coaxial.
  • the spatial (radial and tangential) location of the reference beam focal spot 166 and the recording/reading beam focal spot 150 are correlated and coaxial.
  • the focal spots 150 and 166 of the reading beam and reference beam are not along the optical axis 138 and an offset exists between their respective locations, with regard to the axis 138.
  • the lateral movement of the objective lens 142 indicated by the arrow 219 creates an offset between the incident reference beam axis 163 and the recording/reading beam axis 126, and the focal spots 150 and 166 focused by the objective lens 142.
  • the image is laterally shifted by the objective 142 relatively to the optical axes of beams 130 and 158 inducing a shift in the location of the focal points 166 and 150 of the reference 158 and recording 130 beams respectively.
  • the shift of the focal points 166 and 150 is not identical, i.e. an offset difference (because of a change in location of a common optical element) is formed.
  • the numeral 234 marks the optical carrier surface.
  • This offset may vary, being dependent on the relative spatial position (angular and linear) of the reference beam 158 and the recording beam 130 versus the objective 142.
  • the beams may have different divergence, an angle may exist between their optical axes, and the beams may not be coaxial with the optical axis 138 of the objective lens.
  • the offset between the foci positions (spots) is dependent on additional factors such as the effective NA and the angle of divergence of the incoming beams.
  • the reference and read/record beam axes and the objective axis should be kept at determined relation.
  • the process, by which the actuators control the spots influences the amount of the de-centering of the beams relative to the objective axis and consequently the relative offsets and the quality of data recording and data retrieving processes.
  • the spots offsets can be controlled by limiting the movement of the objective lens actuator and controlling directly the position of the objective (for example, by limiting the voltage on the coil holding the objective), and distributing the required movement to other elements than to the objective lens actuators.
  • the control of the relative position of the two focal points can also be achieved, for example, by use of a galvanometer mirror (or a piezo actuated mirror) deflecting or offsetting the beam in the radial or tangential directions and by altering the beam through the objective pass in a predetermined amount.
  • the relative position of the reference beam focal point and of the focal point of the recording/reading beam should be in a determined relation.
  • the axes of the reading/recording beam and the reference beam may be parallel to the optical axis of the objective lens.
  • the beams are not necessarily coaxial. Even if the objective lens and the incident beam are not in a substantially optimal position (coaxial and parallel to the objective optical axis), the two focal points may be in a controlled relative position.
  • the relative position of the spots can be monitored by feedback from the optical system, e.g. by monitoring the voltages at the objective actuators and other actuators, thereby allowing full control on the relative positions of the two focal points.
  • the objective lens movement should vary the location of the recording/reading beam focus, such that the target location of the focal point may be in a determined relation with respect to the focal position of the reference or servo beam.
  • the determined relation should include the difference between the depth of the servo layer and the focused point of the recording/reading beam.
  • the tilt or offset of the beams can be controlled e.g. by a PZT actuated mirror.
  • the vertical distance between the focus at the reference layers and the focus of the recording beam in the medium is 500 microns
  • a lateral movement of the objective lens of 100 microns gives an offset difference of 8 microns.
  • the effect of the change in the location of a common optical element (e.g. objective lens 142) on the location of the focal spot positions can generally be described by a change dfl of a first focal spot and df2 of a second focal spot and by a function of a change in the location dx or displacement of a common optical element.
  • the change may be well approximated by a proportion factor k being a function of the vertical distance (in the direction of the optical axis) between the focal positions.
  • the offset difference may be attributed to the different beams divergence
  • the focal position of the beam focused closer to the objective will move to a smaller extent.
  • This difference in the lateral offset of the focal spots may, but not necessarily, be approximated as a bilinear function of the extent of the lateral movement of a first focal position and of the distance along the optical axis between the two focal positions.
  • the lateral offsets 218 and 222 as shown in Figs. 13B and 13C are dynamic offsets that vary, being dependent on the relative spatial position (angular and linear) of the reference and recording beams versus the dynamic position of the objective 142 and/or of additional common optical elements.
  • the lateral offsets 218 and 222 may also be a function of the optical carrier position relative to the elements of the optical system.
  • the servo or control system dynamically controls the positioning of all the relevant optical elements (as shown by arrows), such that it keeps the reference beam on the reference layer to provide first tracking information and keeps the reading/recording beam on a track in an addressed plane to record a data track or to retrieve data thereof, optionally providing second tracking information.
  • Dynamic offsets may be formed when tracking in the lateral direction is performed, using optical elements located in the common optical path for example, such as the objective lens 142. These dynamic offsets may have the following effects (attributed to dynamic offset difference): (/) in course of recording, the offsets may cause one record track to cross over and/or overlap a neighbor track; (// ' ) during the reading, they may force the reading beam off-track.
  • the focal spot 166 of the reference beam 158 scans the tracks of the reference layer 170.
  • the reference layer 170 partially reflects the reference beam 158.
  • the imaging lens 186 collects the reflected beam 182 and forms an image of a section of the reference layer 170 track scanned, on the detector 190.
  • the reference spot 166 gets off-track, its image on the detector 190, which may be a Position Sensitive Detector, gets off the center of detector, and an error feedback signal marking this de-centering may be generated and communicated to the servo controller 250.
  • the controller 250 generates a correction signal that moves the objective 142 such as to correct the error feedback signal for both reference and reading beams.
  • a split beam derives the tracking information from the reference layer.
  • the earlier disclosed tracking principles are mutatis mutandis applicable to the use of a split beam for focusing on the reference layer and tracking the reference layer.
  • wobble or sampled servo structures on the reference layer are used to derive the tracking information and the tracking error signal without using position sensitive imaging of the reflected beam.
  • the servo controller 250 may get a tracking signal from either the reference 170 or the data layers 154.
  • the tracking signal from the data track may de derived for example by methods described in WO2005/015552 assigned to the assignee of the present application. These methods may be used for extracting the error signal directly from the data track while recording or reading.
  • the constraints on tracking by the data track and that by the reference layer track are essentially different.
  • Tracking of the reference layer is basically required for providing an error signal to correct the data in the recording/reading beam position; it does not necessarily require locking onto a specific track, as long as the focal positions are at a determined relation.
  • the second constraint is far less stringent and some of the embodiments of the invention directly leverage this difference.
  • the radial tracking error signals are processed by the servo controller 250 that generates position correction signals directed to affect the optical elements that influence the beam focal positions.
  • the position correction signals are directed to the actuator of the common objective 142 and to the actuator of the complete optical pickup unit (OPU) relative to the disk (not shown).
  • OPU complete optical pickup unit
  • the movement of each element and the consequent movement of the recording/reading spot position dfl and the movement of the reference beam focal spot df2 are proportional to the correction signal.
  • ⁇ (df2 - dfl)
  • the reference layer tracking target should also change dynamically. Therefore, changing dynamically the reference layer tracking target is a kind of forward feedback control.
  • the system anticipates future errors (due to dynamic offset) and by modifying the command (the tracking target on the reference layer), corrects them in advance.
  • the tracking target may be changed practically continuously, providing targeting resolution significantly smaller than the track pitch.
  • a one micron offset of the objective lens 142 would offset the tracking target for the reference layer by approximately 0.08 microns.
  • the tracking system should now being centered at a position that is offset with respect to the embossed track center by 0.08 microns.
  • An additional, complementing method to reduce the magnitude of the offset is to smooth out the required objective movements by forward feedback, i.e. to anticipate the required objective movement and to prevent it by an alternative actuation of the optical system in a way that would keep the first and second beams at more appropriate positions relatively to the objective and to other common optical elements.
  • a smooth actuation of the complete OPU can be performed in anticipation of the following of the spiral track shape.
  • the weights of the sampling servo may be changed appropriately to a predetermined function or by subtracting an offset from the error signal appropriately according to a known (predetermined) error signal curve (behavior).
  • the optical system may be configured as a direct correction system in which the correction affects both beams' focal positions in a determined relation in response to an error signal to be used by the beams coupling optical element to move the both beams' focal positions.
  • the determined relation between the focal positions may be changed by variation of the location of an optical element located on the reading/recording optical branch.
  • the offset of the center of the recording beam relative to the axis of the common optical path changes the relation between the focal positions of the reference beam and the reading/recording beam in a determined relation.
  • the determined relation between the focal positions may be changed by altering the location of an optical element located on the reference optical branch.
  • the offset of the axis of the reference beam 158 relative to the axis of common optical path 138 (the optical axis of the common optical element) changes the relation between the focal positions of the reference beam 166 and the reading/recording beam 150 in a determined relation.
  • the optical system may be configured as an indirect correction system in which the correction affects a first beam (coupled to the second beam) in response to a first error signal by means of an intermediate creation of a tracking error in the tracking by the second beam such as to create a second error signal to be used by the beams coupling optical element to move the first beam focal position.
  • the position of the reflected beam 182 relative to the PSD 190 may be shifted, by change of the location of an optical element located along the separate reference beam optical path, e.g. by movement of a beam splitter 174 and associated with it the reflecting surface 176, or by the movement of the PSD 190, as shown by arrow 230.
  • the offset of the center of the reflected reference beam spot 198 relative to the PSD 190 results in a corresponding signal communicated to servo 250. According to the signal, servo
  • the offsets of the optical system comprise the dynamic foci offset (due to objective offsets) and deformation like offsets.
  • the present invention also provides a tracking system and method for eliminating deformation like offsets, by, for example, separating between the disturbance/deformation by use of different frequency regimes.
  • the control system 250 comprises two actuator utilities (not shown), each configured for handling a separate beam combination e.g. each moving one optical element in one of the separate optical branches, or having one of the actuator utilities configured for moving an optical element in the common optical path and the other actuator for moving one optical element in one of the separate optical branches.
  • a read beam actuator performs small (in the order of 10 microns) movements to correct (low frequency) offsets that are result of the objective offsets (as detailed above) and a second actuator performs the main tracking of the reference layer.
  • two actuators handle the combined tracking.
  • a drive mechanism (not shown) of the movable mirror 162 responds to the tracking signal generated by a respective actuator utility of the controller 250 in accordance with the data tracking detected by detector 202 (in response to the tracking error indication of the data).
  • a drive mechanism of the objective 142 responds to the tracking signal generated by a respective actuator utility of the controller 250 in accordance with the reference layer tracking detected by detector 230, to move the objective 142 accordingly.
  • the reference beam in response to a tracking error signal from the data track (lower bandwidth signal), indicating an offset to a first direction, the reference beam is offset by the actuation of e.g. the mirror 162 according to the amount indicated by the tracking error signal, thereby creating an offset of the first reference beam in the same direction as the offset of the data reading beam (relative to the data track).
  • both the reference beam and the data read beam are actuated to move to the second direction to correct the first (read beam) offset.
  • the coupling of the movement of both beams achieved by the actuation of the mirror 162 creates a process which transfers the majority of the movement of the read spot relative to the data track to the movement of the objective (inducing a movement of both beams).
  • This process of transferring the error to the actuation of common elements (and possibly, to the whole OPU relative to the disk) ensures that the mirror would have to correct basically only the non-common tracking errors.
  • the mirror is required to actuate the beam in a limited range, which is similar to the possible range of the dynamic offset between the beams.
  • Fig. 14 representing a schematic illustration of another embodiment of an optical system for recording and reading a multilayer three- dimensional optical data carrier.
  • the optical layout of this embodiment is somehow similar to the one of Fig. 11; however the recoding/reading beam in this case has a constant divergence.
  • the same reference numbers are used for identifying components that are common in the examples of Fig. 11 and Fig. 14.
  • a variable magnification beam expanding device 261 similar to beam expander 110 is included in the optical branch 102 of the first or reference beam 158.
  • the beam expander device 261 is composed of a positive lens 264 and a negative lens 268.
  • Negative lens 268, as shown by arrow 272 has a freedom of movement along the optical axis 164 forming a variable magnification beam expander system providing a variable divergence reference beam. Changes in the convergence or divergence of the first or reference beam 158 would move the beam focal spot 166 along the optical axis 138 within the bulk of the optical carrier 146. This allows focusing beam 130 in different depth within optical carrier 146.
  • the read/write branch 106 has a fixed beam expansion ratio and the objective 142 focuses it at the same constant plane with respect to the objective 142.
  • the reference and the reading/recording beams are optically coupled and coordinated in a determined relation, it is possible to focus the recording/reading beam 130 on a data layer and by a change of the divergence of the reference beam 158 to bring its focal spot 166 to the reference layer 172.
  • any data layer may be selected for the determination of the distance to the reference layer 172.
  • the selection of a data layer closer or even next to the reference layer 172 could simplify the task.
  • the beam expander 261 is activated to change the divergence of the reference beam 158 such as to locate the reference spot 166 in the reference layer 172.
  • the objective lens 142 moves axially, as indicated by arrow 280, to relocate the recording/reading focal spot 150 to the next layer in the volume of the optical carrier 146 by a mechanism of indirect correction.
  • the axial movement of the objective lens 142 introduces spherical aberration at least into the reference beam focused spot 166.
  • a compensation plate 290 is introduced in the optical path of both beams.
  • Fig. 15 representing a non-limiting example of the parameters of the lenses controlling the shape and the focusing of the beam reading/recording beam 130 after the collimation.
  • the numerals in the drawings correspond to the description of the optical surfaces geometry in Table 1 and Table 2 below.
  • the objective lens of this example has a numerical aperture of 0.7.
  • the drawings take into account optical apertures only.
  • Table 1 Main parameters for surfaces 4. 5, 6, 7, 13 and 14 as designated in
  • the optical requirements are not extremely stringent, and the reference beam is not required to be fully focused to diffraction limit.
  • the reference beam may reach thus the objective 142 with divergence controlled by conventional optical elements.
  • the objective 142 may be rigidly coupled with the folding mirror 162 and actuated together. In this configuration, the folded optical axis of the recording/reading beam and the optical axis of the objective lens are collimated or have a very small divergence angle. Therefore, the offsets caused by the movement of the folding mirror 162 and the objective 142 coupled to the folding mirror 162, will be substantially reduced or eliminated.
  • the whole system responds to the TES by the movement of the sled or as described in the US patent application No.
  • US2007288947 assigned to the present assignee by a rotating swing arm.
  • the movement of the actuators for the low frequency distortions and disturbances can be smoothed and planned (e.g. by forward Kalman filtering) so as to minimize the lag between the low frequency error and the response and to control and limit the required movement of the actuators directly controlling the objective, and the offsets between the beams and the objective. This may be facilitated by providing servo marks and track addresses at sufficient frequency.
  • the sampled servo frequency would preferably be greater than 500, more preferably greater than 1500, and most preferably more than 4500 indications per disk rotation (track revolution).
  • the high quality signal would enable high quality feedback, forward feedback, smooth movement of the optical system and minimize the movement of the objective lens, preventing uncontrolled movement of one of the focal points with respect to the other focal point.
  • the method and system described enable high-resolution data reading and recording using relatively large low-resolution reference scanning spot.
  • the data is recorded on tracks with a pitch of about 0.8 microns and recorded with a diffraction limited spot.
  • the servo signal may be embedded as tones in the data layers/tracks to assist the positioning of recording/reading focus in the recording volume.
  • Such marks may be also used as data clocks.
  • a combination of the reference pattern presented with servo data embedded in the data layers/tracks as tones provides a highly redundant reading/recording spot location tracking system. Very accurate clock can be derived from the difference between the frequencies of tones in adjacent tracks.
  • FIG. 16 representing an optical carrier 100 having a peripheral annular section 136 (i.e. the rim of the carrier) and an inner annular section 140.
  • the inner annular section 140 is the section that is in contact with the rotational support or spindle.
  • the spindle dimensions although standardized, limit its utilization.
  • Non-linear three-dimensional storage carriers require high power; high brightness recording/reading spot usually achieved by a high numerical aperture (NA) optical system.
  • Fig. 17 is a schematic illustration of an optical carrier 100 with recorded layers 144 extended into the peripheral 136 and inner annular section 140. High numerical aperture of the recording beam 151 causes at the peripheral and inner annular sections of the carrier recording/reading beam truncation.
  • Data layers 170 begin at the annular peripheral section 136 (i.e. the most external tracks of said data layers) and have their largest size at the sections of the carrier 180 located close to flat surface 108 facing the source of light or OPU.
  • Data layers 172 located at a distance from surface 108 or OPU have smaller size.
  • the numerical aperture of the recording optical system will define the difference in the dimensions of the layers, and the incremental change of the size of two adjacent layers should be proportional to the numerical aperture.
  • the reference layer 132 serves for determination of the coordinates of the recording beam 151 in one or more data layers.
  • the size of the embossed or optically recorded reference layer 132 should be at least equal to the size of the largest data layer or even larger.
  • the numerical aperture of reference beam 160 (Fig. 17) is smaller than the numerical aperture of the recording beam 151. As it may be a limiting factor of the size of the reference layer, it is another advantage of the less stringent requirements of the reference beam focus.
  • Fig 19 is a schematic illustration of another embodiment of the three dimensional information carrier 191.
  • Carrier 191 has data layers 170 of variable size interspaced by a number of reference layers 175 having different size.
  • Each of reference layers 175 serves as a source of coordinates for a group of data layers 170. If the carrier is an assembly of plates having for example, embossed reference layers, the size or radii of the reference layers may be equal.
  • each of reference layers 175 may have the size matching the size of the largest data layer 170 of the group of the data layers associated with the particular reference layer. The size of data layers decreases stepwise away from the recording beam light source.
  • the reference layers are optically recorded (virtual reference layers). Some of these layers may be partially recorded in a formatting process as disclosed in WO2005/015552 or WO2006/1 1 1972 assigned to the same assignee and in general, in cases where embossed, printed layers or virtual layers are used for recording.
  • the radii of the layers may be substantially continuous and decrease in a stepwise mode away from the source of the recording light or OPU.
  • Fig. 20 illustrates a double-sided three-dimensional information carrier 211.
  • Fig. 21 illustrates a three-dimensional information carrier 213 having a symmetrical reference layer structure 215 in which, in addition to improved utilization of the active plate volume (i.e. increase of the storage capacity of the carrier), the reference layers are covered by support plates 218 which may be of material different from the active layer material and which may provide mechanical strength.
  • the support plates may be polycarbonate cover plates enabling an accurate reference layer embossing on the polycarbonate plates.
  • films of about 100 micrometer thickness may be used instead of polycarbonate substrates to provide low variation of the reference layer distance from the surface of the disk, mechanical strength, and an efficient active plate recording and volume usage.
  • Figs. 22A-22B are schematic illustrations of another embodiment of a three dimensional information carrier.
  • the carrier 281 has a structure of a pre-formatted grid 291 (Fig. 22A) of variable size interspaced by group separation intervals of different size.
  • Each of group 294 has an embedded grid with position indication marks that serves as a source of coordinates for a group of data layers 291.
  • the groups may be defined by virtual base layers 295 (Fig. 22B) which are used for stepwise recording of grid and/or data layers 299.
  • the indication marks may be for example sampled servo marks or tone marks as disclosed in WO2005/015552 and WO 2006/111973 assigned to the same assignee.
  • the present carrier and the recording and reading method allow better utilization of the volume of the carrier available for data storage.
  • the method enables a larger carrier capacity and does not complicate production or exploitation of the carrier.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Nanotechnology (AREA)
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  • Mathematical Physics (AREA)
  • Theoretical Computer Science (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Optical Recording Or Reproduction (AREA)

Abstract

L'invention concerne un procédé et un système utilisable pour au moins la lecture de données dans un support de données optiques tridimensionnelles ayant au moins une couche de référence et au moins une couche de données. Un faisceau d'enregistrement/lecture et un faisceau de référence sont concentrés sur le support optique à travers un élément optique commun, créant ainsi deux points focaux dans différents plans optiques. Un déplacement au moins dudit élément optique est contrôlé de telle sorte que le point focal dudit faisceau de lecture/enregistrement suit une piste de données dans une couche de données adressée, cette opération de contrôle comportant l'identification d'un changement dans un signal d'erreur à partir de la couche de référence pendant que le faisceau de référence suit la couche de référence, ajustant ainsi une cible d'alignement pour le contrôle du déplacement du faisceau de référence.
PCT/IL2008/000676 2007-05-17 2008-05-18 Support de données optiques tridimensionnel et procédé de correction d'erreurs de piste WO2008142676A2 (fr)

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
US93851007P 2007-05-17 2007-05-17
US60/938,510 2007-05-17
US94222707P 2007-06-06 2007-06-06
US60/942,227 2007-06-06
US98162207P 2007-10-22 2007-10-22
US60/981,622 2007-10-22

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WO2008142676A2 true WO2008142676A2 (fr) 2008-11-27
WO2008142676A3 WO2008142676A3 (fr) 2009-03-26

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1014347A2 (fr) * 1998-12-21 2000-06-28 Deutsche Thomson-Brandt Gmbh Appareil de reproduction ou d'enregistrement d'un support d'enregistrement optique avec plusieurs couches d'enregistrement d'informations
EP1262963A2 (fr) * 2001-05-30 2002-12-04 Fujitsu Limited Procédé de suivi de piste et appareil de stockage
US6574174B1 (en) * 2000-04-15 2003-06-03 Siros Technologies, Inc. Optical data storage system with multiple layer media
US20040047271A1 (en) * 2002-07-08 2004-03-11 Sony Corporation Optical-recording-medium playback apparatus and optical recording medium
WO2007007248A2 (fr) * 2005-07-07 2007-01-18 Koninklijke Philips Electronics N.V. Balayage de supports supports d'enregistrement optiques multicouches

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1014347A2 (fr) * 1998-12-21 2000-06-28 Deutsche Thomson-Brandt Gmbh Appareil de reproduction ou d'enregistrement d'un support d'enregistrement optique avec plusieurs couches d'enregistrement d'informations
US6574174B1 (en) * 2000-04-15 2003-06-03 Siros Technologies, Inc. Optical data storage system with multiple layer media
EP1262963A2 (fr) * 2001-05-30 2002-12-04 Fujitsu Limited Procédé de suivi de piste et appareil de stockage
US20040047271A1 (en) * 2002-07-08 2004-03-11 Sony Corporation Optical-recording-medium playback apparatus and optical recording medium
WO2007007248A2 (fr) * 2005-07-07 2007-01-18 Koninklijke Philips Electronics N.V. Balayage de supports supports d'enregistrement optiques multicouches

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