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
  • G11B7/08547—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
  • G11B7/002—Recording, reproducing or erasing systems characterised by the shape or form of the carrier
  • G11B7/003—Recording, reproducing or erasing systems characterised by the shape or form of the carrier with webs, filaments or wires, e.g. belts, spooled tapes or films of quasi-infinite extent
• • 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
• • 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

Definitions

• Quarter wave plate 11 converts the linearly polarized beam into a righthand circularly polarized beam, which is provided to a focussing lens 12 for focussing onto an acousto-optical deflector 13.
• Beam deflector 13 is preferably capable of scanning at least small angles at frequencies of up to 20 Khz, and is used to provide the desired tracking correction for the invention.
• the circularly polarized beam expands and is passed through a dichroic beam splitter 14 and is collimated by a lens 15 which, together with focussing lens 12, functions as a telescope to expand the beam to a diameter of approximately 30 mm, which permits focussing of the beam to a 2 m spot on the optical tape.
• the scanned beam, reflected by galvanometer 16, is focussed on the optical medium, flexible tape 18 through an optical window 19, which may be provided in a tape cartridge.
• the objective lens 17 is preferably provided with. a relatively large depth of focus, so that even if the optical tape to objective lens distance were to vary the spot size would remain fairly constant.
• the present invention includes autofocus control optics and circuitry, so that the spot size is maintained constant' and in sharp focus on the tape 18.
• the tape cartridge or other tape conveying mechanism used in conjunction with the invention includes tape curving means for providing curvature to the optical tape in conformity with the curvature of field introduced by objective lens 17, thus further assuring constancy of focus and accuracy of the optical system.
• the tape may be shaped by rollers, by a capstan, or by vacuum hold-down devices in order to minimize the va ' riations in the focussed spot on the medium surface.
• the tape may be differently mounted, without using a cartridge.
• the beam output by laser 7 may itself be used for reading the data, as well as to provide tracking and/or focus control, as described below. Additionally, it may be the same laser beam which is used to read the data and to provid optical control for a linear or rectangular array ⁇ f photodiodes.
• the galvo mirror may be designed to be at least partially transmissive, so that the image of the data tracks may be projected therethrough onto a linear CCD photodetector array as illustrated in Figure 3, for example. Such an array provides a parallel readout of the data tracks on the tape.
• the beam splitter 10 reflects the returning S- polarized beam to the tracking and focussing control optics.
• a narrow band filter is provided at the reflecting output of polarizing beam splitter 10 / in order to block any stray light or unrelated reflection from the beam provided to the control optics.
• an essentially pure data beam is provided to beam splitters 20 and 23 for the tracking and focussing optics, respectively.
• Beam splitter 20 utilizes a portion of the reflected beam to control tracking by reflecting that portion to a focussing lens 21, which in turn focusses the portion of the beam on a split photodiode detector
• pregrooved data tracks are imaged on the split photodetector 22 which straddles the image thereof.
• the difference voltage between outputs C and D of photodetectors 26 and 28 is proportional to the focussing error.
• the outputs of photodetectors 26 and 28 are amplified by amplifiers 52 and 54, respectively, and are used to drive a focussing servo 56 as shown in Figure 2.
• a focus motor 58 may be mounted either on the objective lens 17 or on the focussing lens 12, for example.
• a separate focus control may not be necessary.
• the preferred embodiment further provides for writing of optical data on the optical tape 18.
• Data to be written on the tape is provided from a data buffer 62 to a driver 64 for the laser diode 7.
• the data may be provided to the buffer 62 by a computer 66.
• data may be keyboard entered to computer 66, or may be received from other devices.
• the data is then provided to buffer 62 for controlling driver 64.
• a fast pulse generator 68 may be used to trigger the laser diode driver 64.
• a further difference between the embodiments of Figures 1 and 3 relates to the tracking control mechanism.
• the present embodiment incorporates a linear motor 84 built into lens 17, the linear motor responding to the outputs of split photodetector 22 and the tracking servo 44 to cause the lens to oscillate as necessary to maintain proper tracking.
• the scanning beam is controlled by galvo 16 to scan in a right-left orientation in the plane of the drawing figure.
• the control system utilized in focussing servo 56 is illustrated in greater detail. More particularly, as shown therein the output signals of amplifiers 52 and 54 are provided to a difference amplifier 96 for generating a focussing error output signal.
• the focussing error output signal is provided to a focussing motor 97 associated with the collimating lens 8, or to a focussing motor 98 associated with the objective lens 17.
• a focussing motor 97 associated with the collimating lens 8 or to a focussing motor 98 associated with the objective lens 17.
• the linear motor 84 associated with lens 17 provides movement perpendicular to the plane of the drawing in Figure 3 while the focussing motor associated with the same lens assembly provides vertical movement in the drawing Figure 3.

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• Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Optical Recording Or Reproduction (AREA)
• Optical Head (AREA)

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Family Cites Families (10)

• 1986
  • 1986-10-09 EP EP19860906579 patent/EP0241537A1/de active Pending
  • 1986-10-09 WO PCT/US1986/002129 patent/WO1987002499A1/en unknown

Non-Patent Citations (1)

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