Hitachi Maxell, Limited

Hitachi, Ltd.

Hitachi Maxwell, Ltd.

Koichiro Wakabayashi

Yasuyuki Sugi

Mitsuhiro Miyauchi

Takeshi Maeda

Shigeru Nakamura

Yutaka Makino

Keiko Hirao

Yoshikazu Mitsui

Nobuyuki Inaba

Teruaki Takeuchi

Yoshiaki Minakawa

A pickup lens with a phase compensator is composed of a condenser lens and a phase compensator. At least one surface of the condenser lens has a step-like annular zone structure to compensate wavefront aberration generated when recording and reproducing data on an information recording medium having a substrate thickness of twith a laser beam having a wavelength &#x3bb;and wavefront aberration generated when recording and reproducing data on an information recording medium having a substrate thickness of twith a laser beam having a wavelength &#x3bb;. The phase compensator compensates wavefront aberration generated when recording and reproducing data on an information recording medium having a substrate thickness of twith a laser beam having a wavelength &#x3bb;

Pickup lens with phase compensator and optical pickup apparatus using the same

An optical pickup lens focuses laser beams having different wavelengths &#x3bb;and &#x3bb;on at least three kinds of optical discs. At least one side of the optical pickup lens has a concentric loop zonal structure for compensating wavefront aberration occurring when recording or reproducing an optical disc having a substrate thickness tby the laser beam having the wavelength &#x3bb;and wavefront aberration occurring when recording or reproducing an optical disc having a substrate thickness tby the laser beam having the wavelength &#x3bb;. When recording or reproducing an optical disc having a substrate thickness tby the laser beam having the wavelength &#x3bb;, a phase difference given to the laser beam having the wavelength &#x3bb;due to the concentric loop zonal structure is about 0.15&#x3bb; or smaller.

Optical pickup lens and optical pickup apparatus

An optical pickup system for reading information of three kinds of optical recording media. The optical pickup system has a wavelength selective filter that includes an outer area for shielding one light beam of light beams having three kinds of wavelengths and an inner area for allowing all the light beams to pass through. The optical pickup system also has an objective lens that focuses each light beam having passed through the wavelength selective filter on each light recording medium. An optical head and an optical disk apparatus have the optical pickup system.

Optical pickup system, optical head, optical disk apparatus, and objective lens

An information recording medium, an information recording/reproduction head, and an information storage device are provided for performing a track servo operation at a smaller track pitch than that conventionally used without reducing the widths of servo burst patterns. The widths of servo burst patterns () are increased over a track pitch (TP) and the end of the servo burst pattern is disposed so as not to coincide with a center line () of an information track. In addition, a servo magnetic head () and a reproduction magnetic head () are implemented in one magnetoresistance element ().

Information recording medium, information recording/reproducing head, and information storage device

An optical information reproducing method for reproducing information recorded at at least one mark on an optical information medium. The method includes irradiating a laser to the optical information medium, detecting a reflected beam reflected from the optical information medium, and reproducing information recorded on the optical information medium from an output signal of a detector which detects the reflected beam. The step of reproducing information is changed in dependence upon a length of the mark of the optical information medium.

Optical information reproducing method for reproducing information by generating a signal representing a center of a mark

Optical information reproducing method in which either a first edge signal or a second edge signal is selected depending on a length of a mark on an optical information medium

Information recorded on an optical disk in accordance with a mark edge recording scheme is detected by a center detection circuit which includes a bisected beam detector to obtain a mark center position signal. In succession, the mark center position signal is converted to a mark edge position signal by an edge signal generating circuit. An information reproducing device is implemented which is capable of performing reproducing operation on an information medium conforming to a high-density mark edge recording scheme and which is stable against changes of recording paper, recording sensitivity and reflectivity.

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Ibaraki, Japan

Koichiro Wakabayashi