Sanyo Electric Co., Ltd.

Sanyo Optec Design Co., Ltd.

Hiroyuki Ichikawa

Ryoichi Kawasaki

Tohru Hotta

Yuki Koshimizu

An optical pickup apparatus includes: first and second laser diodes to emit first and second laser beams having first and second wavelengths for reading signals recorded in first and second optical discs, respectively; a first objective lens configured to condense the first laser beam onto the signal recording layer of the first optical disc; a second objective lens arranged, along with the first objective lens, in a radial direction of the first and the second optical discs, the second objective lens configured to condense the second laser beam onto the signal recording layer of the second optical disc; a first optical system configured to guide the first laser beam from the first laser diode to the first objective lens; and a second optical system configured to guide the second laser beam from the second laser diode to the second objective lens independently of the first optical system.

Optical pickup apparatus

An optical-pickup apparatus includes: a laser diode; an objective lens; a diffraction grating; a photodetector including main-beam-, first-sub-beam-, and second-sub-beam-light-receiving portions; a quarter-wave plate having either a second area allowing a reflected-laser beam to pass therethrough without polarization or a third area allowing the reflected beam to pass therethrough at a polarization angle different from that of the first area; and a polarizing member having a separate-light-amount ratio set therefor with respect to the reflected beams passing through the second or third area and an area excluding the second or third area from the first area, such that proportions of the reflected beams passing therethrough toward the photodetector are different, thereby decreasing an irradiation level when the first- and second-sub-beam-light-receiving portions are irradiated, as stray light, with the reflected beam reflected from either one, not subjected to a signal-reading operation, of the first- and second-signal-recording layers of an optical disc.

A method of manufacturing a synthetic resin lens, comprising: adjusting a degree of change in transmittance of a lens member made of synthetic resin for a blue violet laser beam with accumulated application of the blue violet laser beam, by applying to the lens member an electromagnetic wave shorter in wavelength than the blue violet laser beam.

Method of manufacturing synthetic resin lens, method of manufacturing reformed synthetic resin material and optical pickup apparatus

An objective lens formed of a synthetic resin material having characteristics of substantially not reducing transmittance of the objective lens when a first laser beam having a first wavelength passes through the objective lens, and reducing the transmittance according to an elapsed time to apply a second laser beam when the second laser beam having a second wavelength shorter than the first wavelength and longer than a wavelength of ultraviolet light passes through the objective lens, the objective lens being irradiated with the ultraviolet light in advance for a predetermined time such that a change in the transmittance for the second laser beam is set within a predetermined range.

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Hanno, Japan

Hiroyuki Ichikawa