| 摘要 |
An optical pick-up device for use in an information recording/reproducing apparatus for recording and/or reproducing information on an optical record medium. The device comprises a semiconductor laser, an information record medium having plural record layers laminated thereon, an outward route system for irradiating laser light from the semiconductor laser onto the information record medium through a beam splitter and objective lens, and an inward route system having a light detector for receiving the light reflected from the information record medium and transmitted through the objective lens, the beam splitter and pin-hole. The pin-hole has a radius, which is decided in such a manner that an expression Vp=2pir/(lambd/NA) satisfies following condition 3<=Vp>=6, wherein r is radius of the pin-hole, NA is lens aperture of the detection system, lambd is wave length of the laser light, and Vp is radius of Airy disc.
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