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
  • G11B7/085—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
  • G11B7/08505—Methods for track change, selection or preliminary positioning by moving the head
• • 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
• • 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
  • G11B7/004—Recording, reproducing or erasing methods; Read, write or erase circuits therefor
  • G11B7/005—Reproducing
  • G11B7/0053—Reproducing non-user data, e.g. wobbled address, prepits, BCA

Definitions

• the present invention is related to methods and apparatuses for detecting the movement of transducer heads in optical storage systems.
• Servo systems in optical data recording devices such as optical tape drives utilize tracking error signals, detected from the optical media via an optical pickup unit (OPU) device, to accurately record and then retrieve data on the optical media.
• OPU optical pickup unit
• Figures 1 and 2 illustrate a portion of a typical optical recording medium.
• FigurelA is a top view while Figure IB is a side view.
• Optical recording media 10 includes a nanostructure surface relief pattern embossed on the surface of the optical medium.
• the nanostructure includes lands 12 and grooves 14 embossed in the Z direction (i.e., perpendicular to the face of optical recording medium 10) thereon in a preformatting process.
• These surface relief patterns are used to generate the tracking signals used by a servo system to track the position of an optical head reading or writing to the medium.
• An optical drive OPU with the aid electronic signal processing generates a tracking error signal (TES) from the detected patterns.
• TES tracking error signal
• edges of these embossed lands 12 and grooves 14 relief patterns are structurally modulated in the horizontal direction parallel to the face of optical recording medium 10 (e.g., Y axes to track X axes) with sinusoidal patterns 16 (i.e., wobbles ) which contain individual track address codes.
• Figure 1A also depicts recording marks 18 encoded thereon.
• FIG. 1 A technique referred to as “Radial Push Pull” Tracking signal generation (also referred to as “Main Push Pull” (MPP), has been conventionally used to generate the Tracking Error Signal (TES) for the rewritable optical recording media preformatted with "land” and “groove” track geometries as set forth above.
• This scheme generates a reference tracking signal based on the geometries of land and grooved tracks on the media and detectable by a main quad photodetector (QPD) of the OPU.
• Figure 3 provides a schematic illustration of a typical signal processing scheme for the TES signal generated by the QPD.
• Signal processing system 20 includes recording/reading head 21.
• Recording/reading head 21 includes quad photodetector 22 which includes individual photodetectors 24, 26, 28, and 30. Signals 32, 34, 36, 38 from photodetectors 24, 26, 28, 30 are amplified by amplifiers 42, 44, 46, 48 to provide signals 52, 54, 56, 58. Signals 52, 54 are provided to adder 60 which outputs summed signal 62. Signals 56, 58 are provided to adder 64 which outputs summed signal 66. Summed signal 62 and summed signal 66 are inputted into subtractor circuit 70 with outputs difference signal 72 which is further processed to provide TES signal 78 and wobble signal 80.
• low pass filter 82 receives difference signal 72 as an input and outputs TES signal 78
• band pass filter 84 receives difference signal 72 and outputs wobble signal 80.
• the high frequency wobble signal includes, among other information, the key data track ID and Address codes.
• TES signal 78 and wobble signal 80 are used by recording/reading head servo system 86 to provide positioning information regarding the position of head 21.
• digital servo systems control the dynamic operation of the OPUs by using wobble signal information to place the OPU on the correct desired data track.
• the Radial Push Pull method of TES derivation generates a quantized sinusoidal signal as the OPU 22 moves across multiple data track on the media 10 along direction di while the medium is moving along direction dtap e .
• directional information is not provided by this method because of the quantized sinusoidal nature of the signal as depicted in Figure 5.
• Figure 5 demonstrates that movement first along direction di and then along direction d 2 produces the same TES signal as movement only along direction di . This lack of direction information has a severe impact on the robust control of the tracking servo system especially during cross track OPU motion. It is significant that the TES signals from both Figure 4 and 5 do not show any difference as OPU motion changes direction.
• the present invention solves one or more problems of the prior art, by providing a method for providing tracking error signals in an optical data storage system.
• the method generates signals that provide directional information on the motion of Optical Pickup Units across data tracks in optical recording media
• the optical data storage system includes a head having a wobble detection system.
• the method includes a step of receiving a wobble signal having a first frequency from the wobble detection system.
• the wobble detection system includes an optical pick up unit that detects positions of the head relative to lands and grooves.
• the wobble signal for the optical pick up unit centered on a land is 180 degrees out of phase with the wobble signal for the optical pick up unit centered on a groove.
• the wobble signal is amplitude modulated for positions intermediate between the land and the groove.
• the method further includes a step of receiving a primary tracking error signal from the wobble detection system.
• the wobble signal is multiplied with a synchronous signal to about a product signal.
• the product signal is positive for a first direction of motion and negative for a second direction of motion that is opposite that of the first direction.
• the product signal is integrated to obtain a quadrature track error signal.
• the quadrature track error signal is 90 degrees out of phase with the primary track error signal.
• the quadrature track error signal and the primary track error signal in combination and individually provide direction information about movement of the tape head across the width of the tape.
• an apparatus for implementing the method set forth above in which tracking error signals are provided in an optical storage system.
• the apparatus includes a transducer head having a wobble detection system.
• the wobble detection system includes an optical pick up unit that detects positions of the transducer head relative to lands and grooves and provides a wobble signal having a first frequency.
• the wobble signal for a land is amplitude modulated for positions intermediate between the land and the groove.
• a synchronous multiplier multiplies the wobble signal with a square wave signal having the first frequency to provide a product signal.
• the product signal is positive for a first direction of motion and negative for a second direction of motion that is opposite that of the first direction.
• An integrator integrates the product signal to obtain a quadrature track error signal.
• the quadrature track error signal being 90 degrees out of phase with the track error signal, the quadrature track error signal and the track error signal in combination provide direction information about movement of the transducer head across data tracks.
• FIGURE 1 provides a top view of optical recording media showing the embossed lands and grooves
• FIGURE 2 provides a side view of optical recording media showing the embossed lands and grooves
• FIGURE 3 provides a schematic illustration of a system for detecting a tracking error signal and a wobble signal from an optical storage medium having wobble patterns embossed thereon;
• FIGURE 4 provides a schematic of an OPU crossing multiple tracks with the related
• FIGURE 5 provides a schematic of an OPU crossing multiple tracks along two opposite transverse directions with the related TES signal
• FIGURE 6 A provides an example of a wobble signal for an optical pickup unit centered on a groove
• FIGURE 6B provides an example of a wobble signal for an optical pickup unit centered on a land
• FIGURE 7 provides a schematic showing the evolution of a wobble signal as the
• FIGURE 8 provides a schematic illustration of a system for detecting a tracking error signal and a quadrature track error signal from an optical medium with wobble patterns embossed thereon;
• FIGURE 9 provides a schematic illustration of a system for detecting a tracking error signal and a quadrature track error signal from an optical medium with wobble patterns embossed thereon;
• FIGURE 10 provides a schematic of an OPU crossing multiple tracks along two opposite transverse directions with the related TES signal and quadrature track error signal;
• FIGURE 11 provides a schematic flow chart of the method implemented by the system of Figure 8 for detecting the quadrature track error signal.
• Embodiments and variations of the invention advantageously utilize wobble signal information from a digital data storage media to generate a novel complimentary Quadrature Track Error Signal (QTES) that provides the directions of OPU motion information.
• QTES Quadrature Track Error Signal
• a system such as that described by Figure 3 is utilized to provide a wobble signal.
• Methods for detecting wobble signals and/or Tracking Error Signals are set forth in U.S. Pat. Nos. 5,383,169; 6,009059; and 6,937,542; the entire disclosures of which are hereby incorporated by reference.
• the QTES signal allows robust control of OPU motion by allowing in combination detection of the movement of the recording head.
• Figure 6A provides an example of a wobble signal obtained when the OPU is centered on a groove while Figure 6B provides an example of a wobble signal when the OPU is centered on a land.
• the wobble signals are the result of the wobbled edge structure of the grooved tracks at very high spatial frequency with narrow high frequency band passing filtering of MPP.
• FIG. 7 provides a schematic showing the evolution of a wobble signal as OPU 22 moves across the data tracks of optical storage medium 10. Due to the properties of the diffraction pattern generated by the land and groove media surface structure, the polarity of the wobble signals changes as OPU 22 moves along direction di and medium 10 moves along direction dtap e . When OPU is placed over groove 14 at track n, the wobble signal is described by item number 90.
• Optical data storage system 100 includes transducer head 102 in communication with a wobble detection system 104.
• Wobble detection system 104 includes optical pick up unit 22 that detects positions of the transducer head relative to lands and grooves as set forth above with respect to the descriptions of Figures 1-3. Optical pick up unit 22 is positioned in transducer head 102. In a refinement, the wobble detection system of Figure 2 is used in this embodiment. Wobble detection system 104 provides direct track error signal 78 and wobble signal 80. As used herein, the term direct track error signal 78 refers to the normal prior art track error signal that is detected by the "Main Push Pull" (MPP) method or the differential push pull method. Wobble signal 80 is characterized by having a first frequency (i.e., a wobble signal frequency).
• MPP Mainn Push Pull
• Wobble signal 80 is characterized by having a first frequency (i.e., a wobble signal frequency).
• the wobble signal frequency is from 0.5 megahertz to 10 megahertz. Typical wobble signal frequencies are about 1 megahertz.
• wobble signal 80 for a land is 180 degrees out of phase with the wobble signal for a groove with wobble signal 80 being amplitude modulated for positions intermediate between the land and the groove. More particularly, in this context, being 180 out of phase means that wobble signal peaks maxima for lands correspond to wobble signal minima for grooves and wobble signal peaks minima for lands correspond to wobble signal maxima for grooves.
• Synchronous multiplier 106 multiplies wobble signal 80 with square wave 108 signal derived from synchronous clock 1 10 having the first frequency to provide a product signal 112.
• square wave 108 has a voltage amplitude varying from 0 volts to a peak value (e.g. 1 volt).
• Product signal 112 is positive for a first direction of motion of transducer head 102 and negative for a second direction of motion of transducer head 102 that is opposite that of the first direction. These directions of motion are recognized as directions di and d 2 from Figure 5.
• Integrator 114 integrates the product signal 112 to obtain quadrature track error signal 120. Characteristically, quadrature track error signal 120 is 90 degrees out of phase with the track error signal.
• Quadrature track error signal (QTES) and the track error signal 78 in combination provide direction information about movement of the transducer head across data tracks as set forth below.
• Optical storage system 100 also includes phase lock loop 122 which allows square wave 108 to lock onto wobble signal 80.
• Phase lock loop 122 receives the appropriate locking frequency from wobble signal 80.
• Phase lock loop 122 is phase adjustable to maximize product signal 112.
• Figure 9 provides aligned plots of direct track error signal 78, wobble signal 80, square wave signal 108, product signal 112, and quadrature track error signal 120.
• Figure 10 provides a schematic of an OPU crossing multiple tracks along two opposite transverse directions with the related TES signal and quadrature track error signal.
• Direct track error signal 78 and quadrature track error signal 120 both independently include an oscillating pattern as the transducer head moves across tracks.
• the quadrature track error signal and the direct track error signal may each independently be approximated by a sinusoidal function as head moves across data tracks in an optical data storage medium.
• the sinusoidal functions are within 5 percent of the actual values for the quadrature track error signal and the track error signal.
• the direct track error signal leads the quadrature track error signal for the first direction of motion d .
• the quadrature track error signal leads the direct track error signal for the second direction of motion d 2 .
• quadrature track error signal 120 changes such that the product signal 112 is positive for first direction of motion di and negative for second direction of motion d 2 that is opposite that of the first direction.
• direct track error signal 80 includes a first set of regions that are approximated by linear functions li and quadrature track error signal 12 includes a second set of regions that are approximated by linear functions 1 2 .
• the first set of regions that are approximated by linear functions and the second set of regions that are approximated by linear functions include non-overlapping portions with respect to displacement of the transducer head from a land or groove. Moreover, the first set of regions that are approximated by linear functions and the second set of regions that are approximated by linear functions provide complete linearization of the motion of the transducer head across the data tracks.
• step a) wobble signal 80 having a first frequency is received from a wobble detection system 104 such as the system depicted in Figure 2.
• the wobble detection system includes an optical pick up unit that detects positions of a transducer head relative to lands and grooves.
• Wobble signal 80 for the optical pick up unit centered on a land is 180 degrees out of phase with the wobble signal for the optical pick up unit centered on a groove.
• the wobble signal is amplitude modulated for positions intermediate between the land and the groove.
• step b) a direct tracking error signal 78 from the wobble detection system is received.
• step c) wobble signal 80 is multiplied with a synchronous signal to about product signal 112.
• Product signal 112 is positive for a first direction of motion and negative for a second direction of motion that is opposite that of the first direction.
• step d) product signal 112 is integrated to obtain quadrature track error signal 120.
• the quadrature track error signal is 90 degrees out of phase with the primary track error signal.
• the quadrature track error signal and the primary track error signal in combination and individually provide direction information about movement of the tape head across the width of the tape as set forth above.
• TES signal 78 and wobble signal 80 are used by recording/reading head servo system 86 to provide positioning information regarding the position of the transducer head.
• digital servo systems controls the dynamic operation of the OPUs by using wobble signal information to place the OPU on the correct desired data track.

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• 2013
  • 2013-11-26 US US14/090,240 patent/US9734859B2/en active Active
• 2014
  • 2014-09-26 WO PCT/US2014/057594 patent/WO2015080794A1/en not_active Ceased
  • 2014-09-26 AU AU2014355132A patent/AU2014355132B2/en active Active
  • 2014-09-26 EP EP14784166.2A patent/EP3074976B1/en active Active
  • 2014-09-26 NZ NZ718003A patent/NZ718003A/en unknown
  • 2014-09-26 JP JP2016524081A patent/JP6321157B2/ja active Active
  • 2014-09-26 CN CN201480055502.2A patent/CN105612579B/zh active Active
• 2017
  • 2017-05-19 US US15/600,624 patent/US10079037B2/en active Active

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