| 摘要 |
PCT No. PCT/JP95/02770 Sec. 371 Date Aug. 23, 1996 Sec. 102(e) Date Aug. 23, 1996 PCT Filed Dec. 28, 1995 PCT Pub. No. WO96/20473 PCT Pub. Date Jul. 4, 1996An optical pick-up device invention is adapted according to the present invention to reproduce an information signal recorded on a multi-layer optical disc having a plurality of information signal storage layers on which information signals are stored. The optical pick-up device includes a light source for emitting a light beam, an optical means for dividing the light beam emitted from the light source into three separate beams composed of a main beam and first and second side beams and radiating these beams onto the multi-layer optical disc, a main beam-receiving member for receiving the main beam reflected from the multi-layer optical disc, first and second side beam-receiving members for receiving the first and second side beams reflected from the multi-layer optical disc, respectively, and a means for outputting a detection signal indicative of a quantity of light in response to the light quantity received by the main beam-receiving member, the first side beam-receiving member and the second side beam-receiving member. The first side beam-receiving member and the second side beam-receiving member are spaced a given distance apart from the main beam-receiving member so that no interference with the main beam reflected from an unfocused information signal storage layer of the multi-layer optical disc is caused, so that the light beam reflected from the unfocused information signal storage layer of the multi-layer optical disc does not have any influence on function of the device.
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