 Optical pickup used with both DVD and CD |
| The present invention has been made to solve above-mentioned problems and it is an object of the ... |
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| Objective lens for optical pick-up head of optical disk drive |
| It is therefore the principle object of the present invention to provide an objective lens for ... |
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| Optical head |
| For solving the problem of the prior art, an optical head of the present invention comprises, light ... |
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| Compound objective lens having two focal points |
| A first object of the present invention is to provide, with due consideration to the drawbacks of ... |
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| Polarizing plate and liquid-crystal display containing the same |
| What is claimed is: 1. A polarizing plate comprising: a protective film, 5 to 150 μm thick, ... |
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| Polarization independent wavelength tunable filter based on birefringence compensation |
| It is an object of the present invention to provide a tunable, polarization independent wavelength ... |
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| Wavelength division multiplexer and demultiplexer |
| This invention is based on the observation that many filters have the characteristic property that ... |
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Optical recording/reproducing apparatus for optical disks with various disk substrate thicknesses
| Details |
Inventors: Miyagawa, Naoyasu; Gotoh, Yasuhiro;
Assignee: Matsushita Electric Industrial Co., Ltd. (Osaka, JP)
Primary Examiner: Psitos; Aristotelis
Assistant Examiner: Hindi; Nabil
Attorney, Agent or Firm: Stevens, Davis, Miller & Mosher
An optical disc apparatus for recording, reproducing or erasing an information signal by converging a light flux onto a recording layer through a transparent substrate. The apparatus includes one or a plurality of optical heads having a plurality of objective lenses whose aberrations have respectively been corrected for a plurality of disc substrates of different thicknesses, a cartridge for enclosing the optical disc, a discrimination hole which is formed on the cartridge, and a sensor for detecting the opening/closing state of the discrimination hole and for generating a discrimination signal. In accordance with the result of the discrimination as to the thickness of the loaded optical disc, the objective lens, in which the occurrence of the aberration is smallest, is used, so that the information signal can preferably be recorded, reproduced or erased onto/from the optical discs having different substrate thicknesses. Instead of an optical head having objective lenses, an optical head having a waveguide and a plurality of converging grating couplers whose aberrations have respectively been corrected for a plurality of disc substrates of different thicknesses is provided to achieve the same object. |
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DETAILED DESCRIPTION In consideration of the above drawbacks, it is an object of the invention to provide an optical disc apparatus which can record, reproduce, or erase information signals onto/from a plurality of optical discs in which thicknesses of disc substrates are different.
To accomplish the above object, according to the invention, there is provided an optical disc apparatus for recording, reproducing, or erasing information signals onto/from an optical disc by converging light fluxes onto a recording layer through a transparent disc substrate, comprising: N converging means whose aberrations have been corrected for N (N.
gtoreq.
2) disc substrates having different thicknesses, respectively; disc discriminating means for discriminating the thickness of the disc substrate of the optical disc which has been loaded and for generating a discrimination signal according to the result of the discrimination; and control means for selecting one of the converging means in which the occurrence of the aberration due to the disc substrate is smallest in accordance with the discrimination signal.
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Optical Systems 
