WO2009001360A2 - Systeme optique servant a enregistrer/lire des donnees dans un support optique de donnees - Google Patents

Systeme optique servant a enregistrer/lire des donnees dans un support optique de donnees Download PDF

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Publication number
WO2009001360A2
WO2009001360A2 PCT/IL2008/000877 IL2008000877W WO2009001360A2 WO 2009001360 A2 WO2009001360 A2 WO 2009001360A2 IL 2008000877 W IL2008000877 W IL 2008000877W WO 2009001360 A2 WO2009001360 A2 WO 2009001360A2
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WO
WIPO (PCT)
Prior art keywords
data
optical
signal
carrier
recording
Prior art date
Application number
PCT/IL2008/000877
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English (en)
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WO2009001360A3 (fr
Inventor
Ori Eitan
Ilya Rubinovich
Yehuda Rosenblatt
Yair Salomon
Original Assignee
Mempile Inc.
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Application filed by Mempile Inc. filed Critical Mempile Inc.
Publication of WO2009001360A2 publication Critical patent/WO2009001360A2/fr
Publication of WO2009001360A3 publication Critical patent/WO2009001360A3/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
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/125—Optical beam sources therefor, e.g. laser control circuitry specially adapted for optical storage devices; Modulators, e.g. means for controlling the size or intensity of optical spots or optical traces
    • G11B7/127—Lasers; Multiple laser arrays
    • 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
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/1381—Non-lens elements for altering the properties of the beam, e.g. knife edges, slits, filters or stops
    • 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
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/13—Optical detectors therefor

Definitions

  • This invention is generally in the field of recording/reading data in an optical data carrier, and is particularly useful for recording/reading data in three-dimensional data carriers.
  • optical storage media such as optical disks in general and DVDs in particular
  • data is stored along tracks formed in the bulk of the optical disk and is read by focusing a laser beam produced by light sources (typically semiconductor diodes) on to the tracks, while spinning the disk on its axis.
  • the tracks generally comprise spiral tracks on which data is written and from which the data is read.
  • the conventional CDs and DVDs utilize reflective recording media, and therefore are limited to a single data layer configuration.
  • An alternative to a reflective-type medium is a medium based on one- or multi- photon absorption (e.g. fluorescence phenomena).
  • the data is presented as local variations of non-linear response to interaction to one- or multi-photon light beam.
  • the substance is illuminated with radiation at excitation wavelength(s) during data recording and reading processes, and the non-linear response signal emitted in response to the reading radiation is registered at a different wavelength.
  • a simple spectral filter can separate such non-linear response signal at a receiver from the noise of the excitation radiation.
  • An example of utilizing these principles in the optical storage is the implementation of a 3-D storage enabling creation of a three-dimensional data pattern in the form of spaced-apart recording regions arranged in multiple layers (e.g.
  • This approach utilizes a non-linear (e.g. fluorescent) medium containing photochromic molecules capable of existing in two forms.
  • the first form A has absorption bands for UV radiation, and is capable of being transferred into the second isomeric form B upon the simultaneous absorption of two long wavelength photons.
  • the second form B is capable of exhibiting fluorescence response different from fluorescence response of form A upon simultaneous two-photon absorption of a reading light in the infrared range.
  • U.S. Pat. No. 5,268,862 describes an active medium including a dedicated photochromic material, i.e., spirobenzo-piran, maintained in a 3-D polymer matrix.
  • an optical system for use in at least one of data reading and recording processes in an optical data carrier, the system comprising: a light source system configured and operable for generating at least one of recording and reading light beams to illuminate the carrier from a first side so as to record data within said carrier and/or read the recorded data; one or more light directing arrangements for directing said recording and/or reading light beams towards said optical data carrier; a detection system comprising a first detector unit configured and operable for tracking a trajectory of the recording or reading light beam while scanning the carrier by detecting a light component coming from said first side of the optical data carrier while being recorded or read, and generating data indicative thereof; and a second detector unit having a high bandwidth collection and configured and operable for receiving a light response signal coming from the opposite second side of said carrier, and generating data indicative thereof.
  • the optical data carrier has a recording medium in which data is recorded and read as a result of one- or multi-photon interaction.
  • the light component detected by the first detector unit may include a light signal interaction with the recording medium while being read, in response to a reading beam; and/or may include light reflected from a reference layer in the data carrier during a recording or reading process therein. Accordingly, the first detector unit may include a detector for detecting the response light and/or a detector for detecting the reference beam reflection.
  • the system comprises a collector for receiving a light response signal coming from said optical data carrier while being read, within a large incident angle.
  • the collector is configured and operable to filter the light response signal coming from the opposite second side of said carrier thereby enabling the transmission of only a predetermined wavelength range.
  • the inner surface of said collector comprises a filter, enabling the filtration of said light response signal.
  • only fluorescent signal is transmitted through said collector.
  • the second detector unit is in contact with or in proximity to said collector.
  • the collector has a large collection portion at its proximal end enabling a high numerical aperture and a small aperture emission opening at its distal end through which the signal is emitted.
  • the second detector unit being in contact with or in proximity to said emission opening has a diameter approximately identical to said emission opening.
  • the collector has a numerical aperture higher than 0.7 and a conical-like portion.
  • the optical system also includes a first light directing arrangement configured for directing recording and reading beams, and possibly also a reference beam, onto the data carrier from a first side, and for collecting light coming from the data carrier through said first side to direct at least a part of this light to the first detector unit.
  • a first light directing arrangement configured for directing recording and reading beams, and possibly also a reference beam, onto the data carrier from a first side, and for collecting light coming from the data carrier through said first side to direct at least a part of this light to the first detector unit.
  • the system also comprises a second light directing arrangement for collecting the light response signal coming from the first side of the optical data carrier and directing at least a part thereof back towards the optical data carrier to pass therethrough.
  • a second light response signal is formed to add with a first light response signal emerging from the opposite second side of the optical carrier; such that the second detector unit detects the summation of the first light response signal and the second signal.
  • the first and second detection units are configured for optimizing the detection efficiency of the recording or reading light beams coming from both sides of the optical carrier, said optimizing comprising selecting the aperture size of the first and second detection units and distances between the optical carrier's opposite sides and said first and second detector units respectively.
  • the system comprises a control unit configured and operable for receiving and analyzing data indicative of outputs of the first and second detectors, for eliminating fluctuations of a background signal in said data.
  • the control unit is configured and operable for extracting a track indicating signal from the total signal received by each detector, indicative of the outputs by modulating the recording or reading light beam.
  • control unit is configured and operable for extracting a track indicating signal from the total signal received by each detector, by operating a data recording process for embedding in a recording media at least one identifiable tone.
  • the system comprises a first detector unit configured and operable to detect a first type of an optical response of the medium to an optical beam during at least one of the data reading and recording processes, and a second detector unit configured and operable to detect a second type of an optical response of the medium to an optical beam during at least one of the data reading and recording processes and/or to detect a modulation of the reading beam arriving at said second detector.
  • the system comprises a housing for housing an optical disk, the housing having a sliding shutter arrangement which protects and covers the disk.
  • an optical system for use in at least one of data reading and recording processes in an optical data carrier.
  • the system comprises a light source system configured and operable for generating at least one of recording and reading light beams to illuminate the carrier from a first side so as to record data within said carrier and/or read the recorded data; one or more light directing arrangements for directing said recording and/or reading light beams towards said optical data carrier; a detection system comprising a position sensitive detector configured and operable for tracking a trajectory of the recording or reading light beam while scanning the carrier, by detecting a light component coming from the optical data carrier while being recorded or read and generating data indicative thereof; and a control unit configured and operable for receiving and analyzing data indicative of output of said position sensitive detector, for extracting at least one of the following: a track error signal and a focus error signal by separating said track indicative signal from the background signal.
  • the detection system may comprise a position sensitive detector for detecting the light response signal coming from a first side of the carrier, and comprises a second detector unit having a high bandwidth collection and configured and operable for receiving a light response signal coming from the opposite second side of said carrier and generating data indicative thereof.
  • an optical system for use in at least data reading process in an optical data carrier.
  • the system comprises a light source system for producing a reading light beam for scanning the data carrier with the focused reading light beam with a first effective numerical aperture, and a detection system configured for detecting a light response of a recording media to interaction with the reading beam and generating data indicative thereof, the light response induced at a focal position of the reading beam having a potential directionality of propagation while inside the recording media and while emerging therefrom, said detection system being configured to collect the light response from the focal position of the reading beam with an effective numerical aperture of collection not exceeding the first effective numerical aperture of the scanning.
  • an optical collector for use in data signal transmission having a large conical collection portion at its proximal end enabling a high numerical aperture and a small aperture emission opening at its distal end through which the incoming signal is emitted; said optical collector is configured and operable to transmit said incoming signal by internal reflection and to filter said incoming signal thereby enabling the transmission of only a predetermined wavelength range.
  • the inner surface of the optical collector may be coated, enabling the filtration of the incoming signal, such that the optical collector transmits only a predetermined wavelength range.
  • the optical collector may have a conical-like portion.
  • the small aperture emission opening has a diameter of about 5 mm.
  • the collector has a length of about 12 mm and a collection portion having a diameter of about 10 mm.
  • the incoming signal is collected from an optical data carrier.
  • a multi-layer multi-photon data carrier comprising a disk-like recording medium and a cartridge housing in which said disk is housed, the housing having a shutter arrangement which is shiftable between its closed position in which it protects and covers the disk and its open position in which it exposes both sides of the disk simultaneously for recording/reading radiation.
  • the present invention also provides a multi-layer multi-photon data carrier comprising data tracks with at least one identifiable embedded tone.
  • Fig. IA is a simplified schematic view of an optical system according to an embodiment of the present invention
  • Fig. IB is a simplified schematic view of an optical system according to another embodiment of the present invention
  • Fig. 1C is a simplified schematic view of an optical system according to yet another embodiment of the present invention.
  • Fig. 2 represents the collection efficiency as a function of NA for a disc having 40% weight content of the chromophore.
  • Fig. 3 is a perspective view of a light collector according to one embodiment of the present invention.
  • Fig. 4 is an exploded perspective view of a light collector according to another embodiment of the present invention
  • Fig. 5 A schematically illustrates the effects of tracking error and objective de- centering on the image of the data and background signals reaching a first section of a bi- sectioned detector
  • Fig. 5B schematically illustrates the Track Indicating Signal (TIS) extraction for one detector section
  • Fig. 5C illustrates the orientation of a quad detector relative to the track direction
  • Fig. 5D schematically illustrates direct background signal elimination for one detector section;
  • Fig. 6A represents the power spectral density of the original max entropic sequence
  • Fig. 6B represents the power spectral density of the polarity encoded sequence, assuming 50Mbps the tone frequency is about 27 KHz
  • Fig. 7 is a perspective view of a cartridge in a closed shutter's position
  • Fig. 8 is a perspective view of the cartridge of Fig. 7 in an open shutter's position.
  • Fig. IA exemplifying an optical system, generally designated 10OA, including a light source system 10, a detection system including detection units 20 and 40, and a control unit 45 connected to the light source and detection systems (via wires or wireless signal transmission).
  • the light source system 10 is configured and operable for generating recording and reading light beams 90 (which may be of the same or different wavelengths) to, respectively, illuminate an optical data carrier 50 from a first side 52 so as to create recorded units (marks/regions) within the carrier 50, and read the recorded data (i.e. pattern of spaced-apart recorded marks).
  • the optical data carrier 50 (optical disk) has a recording medium in which data is recorded and read as a result of one- or multi-photon interaction and is in the form of a three- dimensional pattern of spaced-apart recording regions arranged in multiple planes (grids).
  • the recording medium may include one or more recording layers (or plates), each for recording therein a data pattern distributed in multiple recording planes (grids).
  • An optical data carrier may include one or more reference layers, in which case the light source system may also be configured and operable for generating a reference beam of a wavelength different from that/those of the recording and reading beams. This configuration will be described further below with reference to Fig. IB.
  • the first detector unit 20 is configured and operable for tracking a trajectory of the recording or reading light beam 90 while scanning the carrier during the recording or reading process.
  • the detector 20 may be configured as an imaging or non-imaging detector.
  • the first detector 20 is oriented for detecting a light response signal (a reading signal, which is a non-linear response in case of such a non-linear recording medium) 92 coming from said first side 52 of the optical data carrier 50 while read, and generating data indicative thereof.
  • the reading signal 92 coming from the data carrier first side 52 may be focused via a focusing assembly (objective lens assembly) forming an image onto the first detector 20. This detector is used for tracking the reading beam scan of the desired recording plane (grid) in the recording layer.
  • the second detector 40 is oriented for detecting light from the opposite second side 54 of the data carrier 50, and is used for detecting the reading signal F 1 coming from the data carrier side 54.
  • the second detector 40 may be configured as an imaging or non- imaging detector:
  • the reading signal F 1 coming from the data carrier side 54 may be focused via a focusing assembly (objective lens assembly) forming an image onto the detector 40.
  • the focusing assembly may be an integral part of the respective detector.
  • light from both sides of the data carrier may be detected by the detectors 20 and 40 using non-imaging optics.
  • the first detector 20 may be of lower sensitivity/lower bandwidth/lower noise, as compared to the second detector 40, as for a tracking procedure operation with a relatively low BW (under 100 KHz) is sufficient, e.g. the tracking detector 20 includes one or more PIN diodes.
  • the second detector unit 40 is used for data reading and accordingly is to be of high sensitivity, as compared to the "tracking" detector 20.
  • the detector 40 has a relatively high bandwidth collection (higher than 3 MHz) and low noise, e.g. an APD.
  • This detector 40 is configured and operable for receiving the light response signal F 1 coming from the opposite second side 54 of said carrier 50, and generating data indicative thereof.
  • the detector 40 is associated with an optical displacement actuator. This is aimed at calibrating the detector by inputting a signal to the actuator to cause the actuator to move the detector 40 (or its associated lens, as the case may be) from a first location to a second location.
  • the system IOOA also includes a light directing arrangement 60 including a wavelength-selective beam splitter/combiner 60a and a lens unit 60b for directing the beams 90 and 92 towards the optical data carrier 50 and from the data carrier towards said first detector unit 20, respectively.
  • a light directing arrangement 60 including a wavelength-selective beam splitter/combiner 60a and a lens unit 60b for directing the beams 90 and 92 towards the optical data carrier 50 and from the data carrier towards said first detector unit 20, respectively.
  • the control unit 45 is a computer system configured for receiving and analyzing data indicative of outputs of the detectors 20 and 40 and recording/retrieving data thereof.
  • the output of the detector 20 is analyzed to identify an error in the focusing position of the reading/recording beam with respect to the addressed recording plane/grid (i.e. currently recorded/read plane) and adjust the recording/reading beam propagation accordingly.
  • the reading signal is provided by the medium in response to one- or multi-photon interaction with the reading beam, typically a fluorescent signal.
  • the light source unit 10 is operable to generate a reading and/or recording beam of radiation of a suitable wavelength range (e.g. around 660 nm) to effect a light response signal of the medium to the incident radiation.
  • the reading radiation may be focused via a focusing assembly (objective lens assembly) onto a data track (e.g. spiral-like track) of a data layer/grid of a multilayer fluorescent disk.
  • the fluorescence is collected by the first detector unit 20 and by the second detector unit 40.
  • the detector 40 generates output signals, which are correlated with the fluorescence signal (non-linear response) and with the amount of fluorescent material in the medium, to retrieve the recorded data. Focusing and tracking error signals are generated when the respective data track is out of focus of the optical system 10OA. This may be identified by the tracking detector 20, which may be a position sensitive detector (PSD) e.g. a multi-segmented detector.
  • PSD position sensitive detector
  • the change of position of the reading beam with respect to the data track being read provides changes in the distribution and amplitude of fluorescent light at the detector 20 enabling to control the reading beam propagation and correct its focusing.
  • the data reading detector 40 may be an APD (Avalanche Photo Diode) having low noise and high bandwidth.
  • APD Anagonal Photo Diode
  • the first tracking detector 20 it may be of a lower bandwidth, including for example any known suitable position sensitive PIN diode detector.
  • the optical data carrier has a recording medium in which data is recorded and read as a result of one- or multi-photon interaction.
  • the reading signal may be a result of more than one type of reading beam interaction during the reading process.
  • the detector 20 may be configured to detect a first type of response, e.g. a fluorescence response, and the detector 40 may be configured to detect other types of responses (generally, a second type of optical response), e.g. two-photon absorption response and/or other modulation of the read beam arriving at the detector 40.
  • a first type of response e.g. a fluorescence response
  • the detector 40 may be configured to detect other types of responses (generally, a second type of optical response), e.g. two-photon absorption response and/or other modulation of the read beam arriving at the detector 40.
  • a second type of optical response e.g. two-photon absorption response and/or other modulation of the read beam arriving at the detector 40.
  • an optical data carrier may include one or more reference layers.
  • the reference layer is configured to define a reflecting interface with a recording layer.
  • One reference layer may be associated with more than one recording plate and with more than one plane/grid in each respective plate.
  • all the layers in the data carrier are at least partially transparent for the recording and reading wavelength range(s) and for the wavelength range of the reading signal (response, e.g. fluorescence), and having small refractive index changes for the reading beam wavelength between marks and spaces.
  • the recording layers are at least partially transparent for the reference beam
  • the reference layer one or more interfaces is at least partially reflective for the reference and recording/reading beams' wavelengths.
  • optical data carrier configuration with a reference layer structure examples are disclosed in WO06111972, WO06111973, WO07069243, all assigned to the assignee of the present application and incorporated herein by reference.
  • detection of reflection of the reference beam from the reference layer may, alternatively or additionally to the detection of the reading signal by a tracking detector, be used for controlling a scan of the recording/reading beam in the recording layer.
  • the reference layer is appropriately patterned, e.g. by an array of spaced-apart pits or grooves, or a spiral like groove.
  • Fig. IB exemplifies an optical system, generally designated 10OB, configured for recording/reading data in an optical data carrier 50 having one or more recording layers - two recording layers (plates) 51a and 51b being shown in the present example, and one or more reference layers - a single reference layer 53 being shown in the present example located between the recording layers (plates).
  • the same reference numerals are used for identifying components that are common in all the examples of the invention.
  • the system IOOB includes a light source system 10, a detection system, and a control unit 45.
  • the light source system 10 is configured and operable for generating recording, reading and reference beams, where the reference beam is of a wavelength range different from that/those of the recording and reading beams.
  • This may be implemented using a first emitter 10a for the recording and reading beams and a second emitter 10b for the reference beam, or using a single broadband emitter or using three emitters for each of these three beams, respectively (not shown).
  • the detection system includes a tracking detector unit 20 and data detector unit 40 located at opposite sides 52 and 54 of the data carrier 50, respectively (generally appropriately accommodated and/or associated with light deflectors, for detecting light emerging from the carrier at opposite sides thereof).
  • the detector unit 20 includes a reference detector 20a configured for detecting reflection of the reference beam from the data carrier (e.g. a four-part split detector), and optionally also includes a tracking detector 20b for detecting the reading signal (e.g. fluorescence) coming from the data carrier.
  • the reading detector 40 is configured for detecting the reading signal.
  • a light directing arrangement includes a wavelength selective beam splitter/combiner (e.g. dichroic mirror) 60a, a lens unit (objective) 60b, and beam splitter/combiners 60c and 6Od.
  • the beam splitter/combiner 6Od is accommodated in optical paths of a recording/reading beam 90, coming from the light source 10a, and a reference beam 91, coming from the light source 10b, and respectively transmits the beam 90 and reflects the beam 91.
  • either one or both of the beam splitter/combiners 60c and 6Od might be a wavelength/selective filter (e.g.
  • the beam splitter 6Od is accommodated in optical paths of a response signal 92, coming from the first side 52 of the carrier 50 and reflection 91' of the reference beam 91, and directs these beams towards detectors 20b and 20a, respectively.
  • the optical system 100 A, IOOB also preferably includes a collector 30 associated with the data reading detector 40.
  • the collector 30 collects light including a light response signal Fi coming from said optical data carrier while being read and directs the light response signal F 1 to the detector 40.
  • the collector 30 is configured and operable to filter the collected light, so as to enable the detection of only a predetermined wavelength range (that of the response signal) by the detector 40.
  • the collector 30 operates as a filter element optimized to maximize the transmission of fluorescent light emanating from the medium and to reject other wavelengths. Therefore, the detection of optical response from the data carrier can be performed without any mutual interference between the excited and the exciting light signals, as well as any other signals (e.g. ambient light). It should be noted that with regard to excited light (light response), the collector 30 receives a portion of the light coming from the second side 54 of the optical carrier 52 and forms a read signal which is a result of the reading beam interaction during the reading process.
  • the collection efficiency of the reading signal in this direction might be increased (up to 10%) by appropriately selecting the aperture diameter of a light collecting element and the distance between such light collecting element and the optical data carrier.
  • the light collecting element is constituted by the detector itself (detector 40 or 20) and by the collector 30 in case it is used in front of the detector.
  • the present invention provides a method for optimizing the collection of the radiation (energy signal) result of interaction (e.g. excitation) at a specific location (focal spot of reading beam) and exiting from the optical carrier in specific direction(s).
  • the radiation signal F 1 induced by the focused reading light beam 90 and collected by the collector 30 corresponds to a part of the radiation signal and the larger the aperture size (e.g. diameter) of the collector 30, the larger the part of the excited radiation collected on the data reading detector 40.
  • the collector 30 is appropriately shaped in accordance with the detector with which it is associated and in accordance with the required collection angle. More specifically, the collector has a large collection portion at its proximal end by which it faces the data carrier enabling a high numerical aperture, and has a small aperture emission opening at its distal end through which the signal emerges towards the detector, thereby enabling the use of high bandwidth detector. It should be noted that such configuration has been calculated to enhance the collection of the data signal by more than 70% in comparison with untapered light collector.
  • FIG. 1C representing yet another configuration of the optical system of the present invention.
  • An optical system, generally designated 200 is shown, which in distinction to the above-described systems IOOA and 10OB, includes a second light directing arrangement 6Od ⁇ i.e. a beam splitter or a dichroic mirror) for collecting a light response signal F 2 coming from the first side of said optical data carrier 50 and directing at least a part thereof back towards the optical data carrier 50 to pass therethrough.
  • a second light response signal is formed, in addition to a first light response signal F 1 directly emerging from the opposite second side 54 of the optical carrier.
  • the summation of said first light response signal F 1 and said second signal F 2 is detected by detector 40, thereby increasing the signal to noise ratio of the data reading.
  • the data carrier may or may not be symmetric and/or two sided and may or may not include reference layer(s), and accordingly the light source system and the detection system may or may not include a reference light source and a reference detector, respectively.
  • a tracking process may be based on detection of a response signal and/or detection of reflection of a reference beam from the data carrier.
  • the data carrier 50 is of a kind having a reference layer structure 53 between two recording layers 51a and 51b.
  • the optical system is configured for producing a reference beam 91 (e.g. using a separate light source 10b) and for detecting reflection 91' of this beam from the data carrier by a reference detector 20a.
  • the aspect of the invention associated with optimized collection efficiency of the non-linear optical response (e.g. from fluorescent point-like source or that induced by chi(3) process such as CARS or Raman scattering) from the information carrier is based on the understanding that although such fluorescence or the like non-linear response source emits in multiple directions, the response signal propagation from the carrier has potential directionality.
  • this directionality may be associated with effects of absorption of fluorescence, generated by a point-like fluorescent source, during its propagation through the recording medium in the data carrier, in particular the effects of dependence of the absorption on the path length of fluorescent response signal.
  • the directionality might be that of inherent light-matter interaction, such as in CARS processes.
  • the directionality has surface transmittance angle dependency.
  • the optical system is preferably configured such that the same objective lens unit is used for focusing the interrogating beam and collecting the optical response signal, i.e. the so-called epi-collection, namely collection in reverse direction to the direction of the interrogating beam propagation.
  • the effective numerical aperture of light collection will be equal or lower than that of the interrogating beam propagation towards a ⁇ fluorescent source.
  • utilization of the objective numerical aperture is achieved by appropriate expanding of the interrogating beam propagating towards the objective.
  • the interrogating beam has a profile with the maximal energy portion covering the entire aperture of the objective, resulting in the substantially uniform beam incidence onto the objective, however in many cases even if the beam incidence profile is not uniform the effective NA is close to the objective NA.
  • the effective NA is close to the objective NA.
  • the fluorescent signal emanating out of the disk its profile is practically such that maximal beam intensity will subsist only at the central part of the objective resulting in a lower effective numerical aperture of collection.
  • the effective (fluorescence) epi-collection NA will be lower or approximately equal to the possible NA of beams directed through the same objective into the media.
  • the spectrum of the fluorescence and the absorption spectrum of the medium should preferably be taken into account e.g. for non-linear media disclosed in WO 2006/075327 and WO 2007/060674, assigned to the same assignee, i.e. media that is predominantly in a first isometric state ⁇ trans state).
  • the optical path lengths of the fluorescent signal propagation in the data carrier and the absorption coefficients, as measured by the molar absorption coefficient, obtained from the absorption spectra recorded at different concentrations of the trans state chromophore, have to be taken into account.
  • the total collection efficiency can thus be estimated by the following formula:
  • Equation (1) ⁇ ⁇ ) ⁇ n ⁇ )dM ⁇ d ⁇ (1) where the integration is done over the wavelengths range of the spectrum and over the solid angle of collection.
  • Parameters in (1) are the following: F(X) - fluorescence spectrum, P - integral of the fluorescence spectrum, for normalization, T( ⁇ )- transmittance of disc-air interface (average of s- and p- polarization), T s and T p are given by Fresnel equations. T is used for unpolarized light.
  • Fig. 2 representing the collection efficiency dependence on the numerical aperture (NA) of the collector, for the disk with 40% weight content of chromophore and for the different depths of source in the range 0.1 - 1.1mm. It is seen from the graphs that absorption brings to decrease of collection efficiency with the increase of depth of source. For example, for an objective with optimal NA of 0.9 (e.g. uniform interrogating beam at the objective), collection efficiency decreases from 0.084 to 0.078 (a 7% decrease) when the depth is growing from 0. lmm to 1.lmm.
  • NA numerical aperture
  • additional collection assembly leveraging the directionality of the signals emanating out of the disk could be used.
  • additional collection assembly may be implemented by addition of a detector across the disk in forward collection.
  • the aperture size (diameter) of the detector 20 and 40 and the distance between the tracking detector 20 and the optical data carrier 50 may be appropriately adjusted according to the collection efficiency considerations as detailed above.
  • the collection efficiency is increased due to the appropriate geometrical configuration of two detectors collecting radiation from the two sides of the optical data carrier.
  • the optical collector 30 has a conical collection portion enabling a high numerical aperture collection at its proximal end 32, at the data carrier side, and a small aperture emission opening 34 at its distal end through which the incoming signal is output to the detector 40.
  • the shape of the inner reflecting surface of the collector and the size of the opening 34 are selected to direct incoming read signal (response) to a small area in accordance with that of the sensing surface of the detector 40.
  • the collector 30 has the appropriate conical shape.
  • the optical collector 30 is made up of three pieces, i.e. two aluminum reflectors (42, 44) and a funnel-like collector (filter) 30 made of BG39 color filter glass.
  • the thickness of the BG39 color filter glass is empirically determined based on the system requirements.
  • the maximum loss for the detection of fluorescence should not be greater than 50 %.
  • the filter has front and back coatings optimized for wavelengths between 400nm and 600nm, enabling that the transmission loss is only 27 %.
  • the size of the emission opening 34 of the collector 30 can fit onto the front window of the second detector unit 40 (i.e. a 5mm APD (avalanche photo detector)).
  • the size of the collector 30 may 12 mm long by 10.25 mm diameter.
  • the collector is used for high data signal collection of low power signal with high sensitivity and low noise.
  • the first detector unit (20 in Fig. IA and 20b in Fig. IB) is configured and operable for tracking a trajectory of the recording or reading light beam 90 while scanning the data carrier, by detecting a light response signal 92 coming from said first side 52 of the optical data carrier 50 while being read, and generating data indicative thereof.
  • Suitable method of tracking is disclosed in the following patent publications US 20030174594 and WO 03/077240, both assigned to the assignee of the present application. These techniques are aimed at correcting tracking errors while reading/recording in an optical storage medium formed of multiple tracks arranged in different layers. A light spot that is nominally focused on to a track is directed into the optical storage medium.
  • the spot is continually moved in axial and radial directions.
  • a signal having amplitude, which varies according to respective offsets from the track in radial and/or axial directions is received, and used to determine a direction of a respective offset from the track in radial and axial directions, and adjust a location of the reading spot accordingly.
  • a format formed by inscription of marks onto a 3D translucent optical medium is provided e.g. by use of a formatter for inscription of marks to enable recording and retrieval of information from the medium.
  • the first detector unit (20 in Fig. IA and 20b in Fig. IB) may have a low bandwidth and the signal used for tracking can be imaged on a PSD to extract relative position signal and error signal from the image on the PSD.
  • the optical beam should be correctly focused on a desired recording plane, and then its scan within said plane and scan along a data track should also be controlled.
  • a PSD e.g. four-quadrant detector
  • a reference layer and reference beam based technique e.g. by another property embedded in the recording plane.
  • the background signal i.e. the signal emanating from space surrounding recorded marks along a recorded track as well as spaces between the recorded regions on the track
  • the background signal fluctuations and track run-outs signal are both coupled to disk rotation and to other effects occurring in the same spatial frequency range.
  • the offset of the objective relative to the nominal center of the detector optical path ⁇ objective de-centering) and other factors such as disk tilt, may also cause a bias of the distribution of the background signal on the detector ⁇ image offset). This should be separated from the bias of the signal due to being off-track.
  • the background signal is much stronger than the track error signal, in some cases 10-20 times stronger and a track average signal may have a low modulation depth of about 5-10%, which in turn affects the track signal detectability. If un-separated, spatial fluctuations of the background signal (fluctuations of the image position and amplitude of the background signal), e.g. due to objective de-centering may result in strong noise in the tracking error signal.
  • a Track Indicating Signal is extracted from the total signal by selecting an identifiable signal property that is substantially different of the track signal and the background signal, e.g. is absent in one of them.
  • This property may be an inherent track property or embedded in the recording media in advance, e.g., during the data recording process.
  • this property may be a tone pattern embedded in the data pattern, such that the tones related signals are of spatial frequencies different from that of the data signals.
  • a tone may be embedded during the track recording using analog methods e.g. by modulation of the recording power or periodic wobble of the recorded track position. Alternatively, the tone can be embedded by digital methods as will be elaborated in an example below.
  • the data track is represented by a pattern of mark regions (recorded regions) and space (non-recorded regions) between the mark regions.
  • the depth or level of modulation may be defined as the contrast ratio of intensity of a read signal (response of the recording media) from the recorded marks and a non-recorded space (background) and typically is in the range 5-50%.
  • the track information and (tone) modulation signals are thus coupled to the background signal fluctuations, however this coupling is partial and properties of the recorded track such as the proportion between spaces and marks along the track (typically 50%) may be used to separate between the background signal and the track signal.
  • a four-quadrant detector may be used as a PSD for tracking and focusing on a data track.
  • TES track error signal
  • the selected track signal on each of the detector sections is sensitive to the optical beam position relative to the track. This sensitivity can be approximated as a position dependent multiplicative factor.
  • the track (marks) signal may vary by a spot-track offset factor whose magnitude is proportional (linearly or non-linearly) to the offset magnitude.
  • Fig. 5A schematically represents an approximated linearized model of the effects of tracking error and objective de-centering on the image of the data and background signals reaching a first section of a bi-sectioned detector (e.g. a detector composed of A1+A2 in reference to Fig 5C below).
  • a bi-sectioned detector e.g. a detector composed of A1+A2 in reference to Fig 5C below.
  • DOM denotes the (average) modulation depth
  • BG denotes the background signal, which may be normalized to one.
  • this model takes into account a data modulation scheme that is subtractive of the background signal (SlO), i.e. the signal from the marks is lower than the signal from the spaces, and as a result of offset from the total signal increases.
  • the effect of the objective de-centering denoted by OD on the background signal is predominant (horizontal arrow onto SlO) and induces a positional fluctuation of the background signal relative to the bi-sectioned detector central line (e.g. the line between A1+A2 and B1+B2 in Fig 5C).
  • the data temporal profile is denoted by Data. This is multiplied by the
  • the track signal is proportional to the background (space) signal by a modulation depth factor. If the background fluctuates, so does the track signal. This is indicated by a multiplicative factor S20 representing the (fluctuating) amplitude of the modulation of the data signal, which is also affected by the objective de-centering displacement.
  • the Data temporal profile is comprised of 50% of marks and 50% of space positions i.e. the same lengths statistical distribution. The average DOM would be then 50% of mark DOM.
  • the data-encoding scheme may require controlled statistical frequency of occurrence of the marks and or spaces of certain sizes, e.g. DC free encoding. Therefore, if the data signal has a constant DC component, the fluctuations of the received signal around this DC component are caused by the fluctuations of the background signal around the data track position and not by the encoded user information. Without loss of generality the average Data effect (as a multiplicative factor to the DOM) will be -0.5.
  • An additional system encoding in the low frequency regime may be performed.
  • H 4 BG(DOM ⁇ Data" (l - TE A - OD)).
  • the fluctuations of the background signal on each section of the detector due to objective de-centering are not fluctuations of the total signal but fluctuations of the image between the different sections.
  • the direction (of amplitude change) of the background signal is of complementing sign and a relation similar to the first relation can be derived;
  • S B BG(l + OD + DOM - Data(l - TE B + OD)), where TE B is defined as TE A respective to the second section of the detector. Note the complementary sign preceding OD.
  • a demodulation scheme may be used to extract the TIS using a technique similar to AM demodulation techniques, separately for each section of the PSD.
  • Fig. 5B-5D illustrating the use of a 4Q detector for TES extraction.
  • the sum of two detector sections e.g. Al and A2 referred to as section A
  • section A the sum of two detector sections
  • Signal from the (first) detector section is separated into low and high frequency components L A and H A .
  • the envelope E A of the high-frequency component H ⁇ can be detected by separating the fluctuations, denoted by the factor 1 - OD - TE A from the data signal. Envelope detection is sometimes referred to as separation of a 'signal' (in this case the fluctuations), from a 'signal carrier' (in this case the data):
  • E A BG(DOM(I - TE A - OD)) .
  • Envelope detection may be performed by various methods such as rectification methods.
  • L A + 0.5E A - BG((I ⁇ OD)) which is a signal that is proportional to the background signal fluctuation and is practically free of tracking error fluctuations. From this signal the DC can be separated and the result is a dynamic estimation of the background fluctuations which for clarity is denoted OD .
  • the noise in the estimation of OD can be further reduced by taking into account the coupling between the different sections of the detector, e.g. by dynamically averaging the estimates of the different sections.
  • Fig 5B illustrates the scheme for TIS extraction which comprises; (i) separating the incoming signal into high and low frequency components (ii) performing fluctuations (envelope) detection of the high frequency component and estimate OD, (iii) extraction the TIS (TE 4 )
  • the estimator OD can now be used to extract the TIS (which is proportional to TE A ) from the envelope detected signal E A .
  • TES may be derived by comparison of the different sides of the detector.
  • Fig. 5C illustrates the orientation of a quad detector relative to the track direction.
  • the tracking error signal can be calculated by TE A - TE B .
  • envelope detection which may be performed by rectification methods; however, these may require a detector system with a high bandwidth, introducing complexity and noise.
  • An alternative approach enabling the use of low pass detectors, such as sectioned PIN detectors may be disclosed.
  • the embedded tone may be used for separating the TIS (TE A ) from other fluctuations.
  • the steps described above can be performed, mutatis mutandis for the tone instead of the data as a whole; the tone signal and its fluctuations (due to tracking error and background fluctuations which generally correspond to mechanical fluctuations) may be separated from recorded user data and envelope detection may be performed in a combined step that is similar to AM detection.
  • the fluctuations are the ' signal' and the tone is the 'signal carrier'.
  • the detected signal may be multiplied (synchronously or asynchronously) by a signal having the same frequency as the embedded tone.
  • the multiplied signal is filtered via a Low-Pass Filter (LPF) eliminating the high frequencies and enabling to extract TIS (i.e. relative position of the spot to the track). It is preferable in this case that the power of the tone will be significantly higher than the spectral content of the recorded track in nearby frequencies.
  • LPF Low-Pass Filter
  • tone For efficient channel use, it is preferred that such tone will be encoded in the low frequency regime (relative to data frequencies) where typical DC free encoding already influences, typically below 1/50, or 1/100 of the channel bit rate.
  • tone encoding any encoding or modulation of the data track, from which the fluctuation signal is separable can be used.
  • Standard methods for extracting Focus Error Signal typically use a position sensitive detector e.g. in combination with cylindrical lenses that deforms the image of the targeted imaged position when it is not in the beam focus.
  • This kind of signal as the TES discussed above may suffer from distortion by fluctuations of the background signal and there is a need to separate its component from the background signal.
  • a different combination of the signals can provide FES.
  • the optical path part of a collection and tracking system that provides for extracting TES and FES (the part from the dichroic mirror separating the fluorescence signal to the position sensitive detector) may be similar to the conventional path used in reflective media (from the element separating the reflected signal from the incoming beam to the PSD).
  • the methods and systems for extracting the TES and FES are different as they rely on special separation of track indicative signal from the background signal having identifiable feature to this type of data carrier.
  • the TIS may be extracted from the total signal by embedding, in advance during recording, an identifiable tone (i.e. tone signal of a different spatial frequency range than the spatial frequency range of the data signal) embedded in the data that is unique to the track signal.
  • an identifiable tone i.e. tone signal of a different spatial frequency range than the spatial frequency range of the data signal
  • These signals are of the same wavelength (e.g. fluorescent response) but vary during a scan with different spatial frequencies and can thus be detected and distinguished by using an appropriate band filter.
  • Encoding (embedding) of tones in an optical data carrier may be performed by digitally combining a tone with a data stream, whose active bandwidth is selected to avoid the frequency region in which tones are recorded.
  • Digital embedding has the advantage that it does not deteriorate the signal to noise ratio though it does somewhat reduce channel coding efficiency (with respect to user data) as additional bits are required to modify the data to include the tone(s).
  • Addition of a polarity bit is a simple example of a multi-mode code.
  • a polarity bit may be appended to each word and the polarity bit and the word (comprising bits ⁇ , e ⁇ -l,+l ⁇ ) are switched to minimize Running n Digital Sum (RDS), RDS - ⁇ a, where 0 is the beginning of the sequence and n in the end
  • Every word has 'multi' i.e. two optional encoding modes.
  • Decoding is performed by first taking off the appended polarity bit and then performing conventional decoding the word.
  • DC can be controlled by forcing the RDS towards a certain value; for a DC free sequence RDS may forces towards zero.
  • a sequence with high DC content can be created by forcing the RDS towards a positive or negative direction.
  • Frequency content of a sequence can be controlled by controlling a modified RDS n function; ⁇ a 1 exp[- y 2;zf ⁇ /] where / is the targeted frequency.
  • a different RDS n function ⁇ a 1 exp[- y 2;zf ⁇ /] where / is the targeted frequency.
  • RLL Limited
  • Spectral constraints encoding DC content limiting and tone embedding
  • a max-entropic sequence sequence having the widest words distribution under a set of constraints
  • Efficient codes have a Power Spectral Density that is close to Power Spectral Density of a max-entropic sequence and thus this approximation is valid.
  • Fig.6A shows the power density spectrum of an RLL (2.7) max-entropic sequence
  • Fig 6B shows the spectrum shape as a result of the additional DC free and tone embedding encoding.
  • the code is characterized by -22db attenuation at normalized frequency of le-4 (compare to -30db in EFM plus, the code used in DVD) and tone at slightly over 5e-4 of the normalized frequency with amplitude of around 35 db above neighboring frequency range.
  • the tone is a narrow tone - indicative of tone stability.
  • the background signal may be eliminated directly by modulating the reading beam thereby inducing the modulation of the read signal.
  • the modulation is in a frequency and bandwidth having minor interference with data reading and therefore practically absent in the track.
  • Fig. 5D illustrates this TIS extraction, for example the read laser power is modulated by 2 percent (peak to peak) at 20 KHz then the data will comprise noise energy in this frequency (which could be taken into account) compared however to the bandwidth of the data, this noise will be negligible.
  • envelope detection e.g.
  • the background signal fluctuations can be separated or alternatively balanced out using corrected detector signal
  • the media of the optical data carrier is at least partially transparent for the wavelengths used for recording/reading/tracking and for the signal emanating from the disk and that the surface of the data carrier should be kept transparent for access and retrieval of data from both sides.
  • the optical data carrier is preferably housed in an appropriately configured cartridge. The latter is generally similar to that used for the conventional double-sided disk cartridge, differing therefrom in the configuration and operation of shutters.
  • Such a disk cartridge 300 is schematically illustrated in Figs. 7 and 8 showing the cartridge in, respectively, the closed and open shutters' positions.
  • the cartridge 300 includes a housing or case body 302 accommodating an optical data carrier (disk) 50.
  • the case body 302 has a substantially rectangular shape formed of an upper half 302a and a lower half 302b.
  • An opening 304 (shown in Fig.8) is provided in the upper and lower surfaces of the case body 302. This opening serves for accommodating an optical pickup or for propagating therethrough incident and returned light towards and from the data carrier during recording and reading processes.
  • the cartridge 300 has a sliding shutter arrangement 306 provided on the case body 302 and serving for protecting and covering the disk when in the cartridge and not in use and uncovering the disk when in use.
  • the shutter arrangement may be configured as a U-shaped plate defining two shutter elements at opposite sides of the cartridge (i.e. of the disk) which are thus sliding together to cover and uncover vertically aligned disk regions.
  • the cartridge shutter opening may be extended to cover the central hole of the data carrier.
  • the shutter arrangement 306 may be formed of two separately operative sliding shutter units at opposite sides of the disk.
  • the shutter arrangement when in its open position may expose both sides of the disk simultaneously for recording/reading radiation.
  • the cartridge has a further advantage of mechanical protection of the disk.
  • the opening of the shutter of the cartridge is configured to enable close approach of the collector 40 to the surface of a data carrier so as to maximize signal for selected collector size.

Abstract

L'invention concerne un système optique destiné à être utilisé au moins dans des processus de lecture ou des processus d'enregistrement de données dans un support optique de données. Ce système comprend : un système de source de lumière; au moins un agencement d'orientation de lumière; et un système de détection. Le système de source de lumière est conçu pour générer au moins un faisceau lumineux de lecture ou d'enregistrement pour éclairer la support provenant d'un premier côté, de manière à enregistrer des données dans ledit support et/ou lire les données enregistrées. Le(s) agencement(s) d'orientation de lumière est/sont conçu(s) pour orienter les faisceaux lumineux d'enregistrement et/ou de lecture vers le support optique de données. Le système de détection comprend un premier détecteur servant à suivre la trajectoire du faisceau lumineux d'enregistrement ou de lecture tout en balayant le support, par détection d'une composante de lumière provenant du premier côté du support optique de données pendant l'enregistrement ou la lecture, et par génération de données indicatives associées; et un deuxième détecteur à collecte de largeur de bande élevée conçu pourr recevoir un signal de réponse lumineux provenant du deuxième côté opposé du support, et pour générer des données indicatives associées.
PCT/IL2008/000877 2007-06-28 2008-06-26 Systeme optique servant a enregistrer/lire des donnees dans un support optique de donnees WO2009001360A2 (fr)

Applications Claiming Priority (2)

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US94674907P 2007-06-28 2007-06-28
US60/946,749 2007-06-28

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WO2009001360A3 WO2009001360A3 (fr) 2009-04-02

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1471507A2 (fr) * 2003-04-23 2004-10-27 TDK Corporation Procédé d'enregistrement et de lecture holographique des données et appareil pour sa mise en oeuvre
WO2007069243A2 (fr) * 2005-12-12 2007-06-21 Mempile Inc. Support optique de donnees et procede de lecture/d'enregistrement des donnees sur celui-ci
WO2007083308A1 (fr) * 2006-01-18 2007-07-26 Mempile Inc. Support de données optique et procédé de lecture et enregistrement de données sur ledit support

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1471507A2 (fr) * 2003-04-23 2004-10-27 TDK Corporation Procédé d'enregistrement et de lecture holographique des données et appareil pour sa mise en oeuvre
WO2007069243A2 (fr) * 2005-12-12 2007-06-21 Mempile Inc. Support optique de donnees et procede de lecture/d'enregistrement des donnees sur celui-ci
WO2007083308A1 (fr) * 2006-01-18 2007-07-26 Mempile Inc. Support de données optique et procédé de lecture et enregistrement de données sur ledit support

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