Apparatus for reproducing information data from magneto-optical recording medium using linear polarized beam

• US 7,251,200 B2
• Filed: 02/06/2003
• Issued: 07/31/2007
• Est. Priority Date: 12/19/1996
• Status: Expired due to Fees

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Murakami, Motoyoshi, Miyatake, Norio
• Primary Examiner(s): DINH, TAN X
• Application Number:
  US10/360,363
• Publication Number:
  US 20030137913A1
• Time in Patent Office: 1,636 Days
• Field of Search: 369/13.31, 369/13.3, 369/13.29, 369/13.05, 369/110.01, 369/110.02, 369/110.03, 369/110.04, 369/275.2, 430/270.13
• US Class Current: 369/13.31
• CPC Class Codes: G06T 1/0021 Image watermarking
• CPC Class Codes: G06T 2201/0064 for copy protection or copy management, e.g. CGMS, copy only once, one-time copy
• CPC Class Codes: G11B 11/10506 by modulating only the light beam of the transducer
• CPC Class Codes: G11B 11/10515 Reproducing compensating pit shift G11B11/1053
• CPC Class Codes: G11B 11/10584 characterised by the form, e.g. comprising mechanical protection elements
• CPC Class Codes: G11B 11/10595 Control of operating function
• CPC Class Codes: G11B 20/00086 Circuits for prevention of unauthorised reproduction or copying, e.g. piracy indicating unauthorised use of record carriers in general G11B23/28; scrambling for television signal recording H04N5/913; network architectures or network protocols for network security H04L63/00; cryptographic mechanisms or cryptographic arrangements for secret or secure communication H04L9/00
• CPC Class Codes: G11B 20/00123 the record carrier being identified by recognising some of its unique characteristics, e.g. a unique defect pattern serving as a physical signature of the record carrier
• CPC Class Codes: G11B 20/00166 involving measures which result in a restriction to authorised contents recorded on or reproduced from a record carrier, e.g. music or software
• CPC Class Codes: G11B 20/00181 using a content identifier, e.g. an international standard recording code [ISRC] or a digital object identifier [DOI]
• CPC Class Codes: G11B 20/0021 involving encryption or decryption of contents recorded on or reproduced from a record carrier
• CPC Class Codes: G11B 20/00231 wherein the key is obtained from a local external medium, e.g. a card
• CPC Class Codes: G11B 20/0026 the key being stored as a barcode
• CPC Class Codes: G11B 20/00268 said barcode being recorded in a burst cutting area [BCA]
• CPC Class Codes: G11B 20/00347 wherein the medium identifier is used as a key
• CPC Class Codes: G11B 20/00876 wherein physical copy protection means are attached to the medium, e.g. holograms, sensors, or additional semiconductor circuitry
• CPC Class Codes: G11B 20/00884 involving a watermark, i.e. a barely perceptible transformation of the original data which can nevertheless be recognised by an algorithm
• CPC Class Codes: G11B 20/10 Digital recording or reproducing
• CPC Class Codes: G11B 20/1217 on discs
• CPC Class Codes: G11B 20/1258 where blocks are arranged within multiple radial zones, e.g. Zone Bit Recording or Constant Density Recording discs, MCAV discs, MCLV discs
• CPC Class Codes: G11B 2020/122 : Burst cutting area [BCA]
• CPC Class Codes: G11B 2020/1244 : CAV zone, in which a constant angular velocity is used
• CPC Class Codes: G11B 2020/1245 : CLV zone, in which a constant linear velocity is used
• CPC Class Codes: G11B 23/281 : by changing the physical properties of the record carrier
• CPC Class Codes: G11B 23/288 : Protecting disks from being written or overwritten
• CPC Class Codes: G11B 23/40 : Identifying or analogous means applied to or incorporated in the record carrier and not intended for visual display simultaneously with the playing-back of the record carrier, e.g. label, leader, photograph
• CPC Class Codes: G11B 7/0037 : with discs
• CPC Class Codes: G11B 7/0045 : Recording G11B7/006, G11B7/0065 take precedence
• CPC Class Codes: G11B 7/00736 : Auxiliary data, e.g. lead-in, lead-out, Power Calibration Area [PCA], Burst Cutting Area [BCA], control information sector headers or adresses in prepits G11B7/00745; address data in track wobble G11B7/24082
• CPC Class Codes: G11B 7/24 : Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the arrangement of information on the carrier G11B7/007

Abstract

An apparatus is provided for reproducing optical disks. An optical head irradiates linearly polarized light onto an optical disk. A change of a polarization orientation of light that is transmitted or reflected from the optical disk is detected in accordance with a recording signal on the optical disk. The apparatus moves the optical head into a pre-determined portion of the optical disk where write-once information is stored, and reproduces the write-once information after detecting a change of a polarization orientation of light that is transmitted or reflected from the pre-determined portion.

Claims

1. An apparatus for reproducing optical disks, wherein an optical head irradiates linearly polarized light onto an optical disk, and a change of a polarization orientation of light that is transmitted or reflected from the optical disk is detected in accordance with a recording signal on the optical disk;

and the apparatus comprises;

means for moving, when necessary, the optical head into a pre-determined portion of the optical disk where write-once information is stored, and

means for reproducing the write-once information after detecting a change of a polarization orientation of light that is transmitted or reflected train the pre-determined portion, the write-once information being recorded by lowering the magnetic anisotropy in a direction perpendicular to a surface of the recording film to create a low level magnetic anisotropy in a direction perpendicular to the surface of the recording film.

2. The apparatus according to claim 1, further comprising means for detecting an identifier indicating whether write-once information within control data of the optical disk is present, the indication being based on a detection signal of detection light that is received with at least one photo-detector of the optical head or on an all-sum signal of detection signals of detection light that is received with a plurality of photo-detectors of the optical head,

wherein to detect the identifier and to verify whether write-once information is resent, the optical head is moved to the pre-determined portion of the optical disk where write-once information is stored, when necessary.

3. The apparatus according to claim 1, further comprising decoding means for phase-encoding decoding during reproduction of the write-once information.