Dynamic information storage or retrieval – Storage or retrieval by simultaneous application of diverse...
Reexamination Certificate
1998-03-20
2001-01-30
Hindi, Nabil (Department: 2753)
Dynamic information storage or retrieval
Storage or retrieval by simultaneous application of diverse...
Reexamination Certificate
active
06181650
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an optical disk drive and a super-resolution reproduction method for an optical disk.
Optical disk memories, which accomplish information reproduction alone or information recording and reproduction by irradiation of a light beam, have been put to practical use, as high-capacity, fast-access and portable storage media, in various files, such as audio data, image data and computer data. It is expected that development of those memories will continue. There may be several schemes available to increase the density of optical disks, such as shortening the wavelength of a gas laser for cutting a master, shortening the wavelength of a semiconductor laser as an operational light source, increasing the numerical aperture of an objective lens and making optical disks thinner. With regard to recordable optical disks, various other approaches are possible: mark length recording, and land/grove recording.
As a scheme having a great effect on improvement on the density of optical disks, a super-resolution reproduction technique which uses a medium film has been proposed. The super-resolution reproduction was originally proposed as a scheme specific to magneto-optical disks. In the super-resolution reproduction for magneto-optical disks, a magnetic film (super-resolution film) is provided on the reproduction-beam incident side with respect to the recording layer so as to cause exchange coupling or magnetostatic coupling between them. Then, a reproduction beam is irradiated to raise the temperature of the super-resolution film to change the exchange force or magnetostatic force, thereby forming an optical aperture or optical mask in the super-resolution film to realize super-resolution reproduction.
Later, for ROM disks in addition to MO disk, was reported an attempt to provide a super-resolution film whose light transmittance varies with the irradiation of a reproduction beam, on the reproduction-beam incident side with respect to the recording layer for the purpose of super-resolution reproduction. It has become obvious that super-resolution reproduction can be adapted to all optical disks like a magneto-optical disk, CD-ROM, CD-R, WORM and a phase change optical disk.
Implementation of super-resolution reproduction of optical disks requires that the transmittance of the super-resolution film should change by a significant amount with practical reproduction power, an optical aperture should be formed fast in as a short period as the pass time of the reproduction beam spot, and repeated reproduction should be accomplished stably. Prior arts cannot however meet all of those requirements.
BRIEF SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to ensure super-resolution reproduction of an optical disk under practical conditions and achieve high density of an optical disk.
An optical disk drive according to this invention is designed to reproduce an optical disk having a recording layer and a super-resolution film provided on a reproduction-beam incident side with respect to the recording layer, the super-resolution film being formed of such a material that an optical aperture formed by irradiation of a reproduction beam remains after the reproduction beam passes, and comprises a reproduction light source for generating the reproduction beam; a reproduction optical system for detecting a reproduction beam having been incident to the recording layer via the optical aperture formed in the super-resolution film, and reflected from the recording layer; and an initialization light source, provided at a back of the reproduction light source in a track direction of the optical disk, for generating an initialization beam for closing the optical aperture remaining on the super-resolution film.
A super-resolution reproduction method using this optical disk drive comprises a step of irradiating a reproduction beam to form an optical aperture in the super-resolution film, a step of detecting a reproduction beam having been incident to the recording layer via the optical aperture, and reflected from the recording layer, and a step of irradiating an initialization beam to close the optical aperture remaining on the super-resolution film prior to irradiation of the next reproduction beam.
A super-resolution reproduction method according to this invention reproduces an optical disk having a recording layer and a super-resolution film provided on a reproduction-beam incident side with respect to the recording layer, the super-resolution film being comprised of a field control film which is demagnetized by irradiation of a reproduction beam and a magnetization change film whose magnetization direction changes due to an influence of a magnetic field of the field control film, and comprises the steps of irradiating a polarized reproduction beam to change magnetizations of the field control film and the magnetization change film, thereby rotating a polarization plane of the polarized reproduction beam; and detecting the polarized reproduction beam having been incident to the recording layer via the field control film and the magnetization change film, and reflected from the recording layer.
Another optical disk drive according to this invention reproduces an optical disk having a recording layer and a super-resolution film provided on a reproduction-beam incident side with respect to the recording layer, the super-resolution film being comprised of a photoconductive film which becomes conductive with irradiation of a reproduction beam, a switching film for producing an optical aperture when applied with an electric field equal to or greater than threshold strength, and a pair of conductive films for applying an electric field to a stack of the photoconductive film and the switching film, and comprises a power supply for applying the electric field to the stack of the photoconductive film and the switching film through the pair of conductive films; a reproduction light source for generating the reproduction beam; and a reproduction optical system for detecting a reproduction beam having been incident to the recording layer via the optical aperture formed in the switching film, and reflected from the recording layer.
A super-resolution reproduction method using this optical disk drive comprises a step of irradiating a reproduction beam to form an optical aperture in the switching film while applying an electric field to the stack of the photoconductive film and the switching film via the pair of conductive films, and a step of detecting a reproduction beam having been incident to the recording layer via the optical aperture and reflected from the recording layer.
Additional object and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The object and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
REFERENCES:
patent: 4853912 (1989-08-01), Akasaka et al.
patent: 4888750 (1989-12-01), Kryder et al.
patent: 5093822 (1992-03-01), Kugiya et al.
patent: 5717662 (1998-02-01), Nishimura
patent: 5740133 (1998-04-01), Tamanoi et al.
patent: 5830589 (1998-11-01), Nishimura
patent: 5966350 (1999-10-01), Tanaka et al.
patent: 5995472 (1999-11-01), Fujii et al.
patent: 6018511 (2000-01-01), Nishikiori et al.
Proc. Joint ISOM/OPS Conference '93 Th 3.2 “Premastered Optical Disk by Superresolution” K. Yasuda et al.
Proc. ISOM '95, We-C1 ' Super Resolution Using Variable Transmittance Detection, M. Kuroda; 1995.
Hindi Nabil
Kabushiki Kaisha Toshiba
Pillsbury Madison & Sutro LLP
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