| 摘要 |
PROBLEM TO BE SOLVED: To provide an objective lens unit constituted so as to cut unnecessary light by a simple structure. SOLUTION: A lens holder having an objective lens OL is engaged into a shaft on an act base, the lens holder is formed so as to be slidable in the focal directions (a), (b) along the shaft and swingable in the tracking directions c, d around the shaft by excitation actions of a focal coil and a tracking coil provided in the lens holder, an act cover 8 which covers the lens holder and in which an aperture 9 is formed at a position opposite to the objective lens is attached to the act base, the act cover 8 is arranged at a position slightly higher than the highest position of the objective lens OL, horizontal width t1 in the tracking directions c, d of the aperture 9 of the act cover 8 is set to be larger than outer diameter n1 of incident light passing through the aperture 9 when the objective lens OL is swung maximally in the tracking directions c, d and smaller than outer diameter m of a parallel light flux C passing through a collimator lens. COPYRIGHT: (C)2007,JPO&INPIT
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