Riken Corporation

Pulstec Industrial Co., Ltd.

Masahiko Ujiie

Satoshi Kawata

Takuo Tanaka

Takayuki Hayashi

An optical pickup apparatus comprises an orbicular zone forming lens groupfor forming the section of the laser beam, which is irradiated to an optical disc DK having plural recording layers, into an annular shape, a condenser lensthat converges the reflected beam from the optical disc DK, and a pinhole platehaving formed thereto a pinholewith a size corresponding to a flux diameter of the reflected beam converged by the condenser lens. The orbicular zone forming lens grouprefracts the laser beam irradiated to the optical disc DK so as to form the section of the laser beam into an annular shape in order that the internal diameter of the annular converged flux formed on the pinhole plateby the reflected beam from the recording layers other than the recording layer having an optical spot formed thereon becomes greater than the diameter of the pinhole

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Iwata, Japan

Masahiko Ujiie