| 摘要 |
PURPOSE:To perform a correct tracking control by mounting an objective lens, two polarized beam splitters, two lambda/4 plates and a lambda/2 plate by combining them on a moving optical system. CONSTITUTION:A laser beam is horizontally projected on a mobile optical system 13 in an S polarized state from the semiconductor laser inside a stationary optical system 11. This S polarized laser beam is reflected by being polarized 90 deg. to an objective lens 14 side by the polarization reflecting face 15a of a 1st polarized beam splitter 15. It is then made a circularly polarized light by passing a 1st lambda/4 plate 16, condensed on the optical disk 10 surface by the objective lens 14 and the reflecting light from the disk 10 is attained to a P polarized light via the objective lens 14 and lambda/4 plate 16, attained to an S polarized light by being made incident on a lambda/2 plate 17 by passing a polarized reflection face 15a via the splitter 15, made incident on a 2nd polarized beam splitter 18 and reflected to a stationary mirror 12 side by a polarized reflection face 18a. At this time the laser beam is faced to the stationary mirror 12 in the state of a circularly polarized light by passing a 2nd lambda/4 plate 19, attained to a P polarized light by passing the lambda/4 plate 19 again, passing the reflection face 18a with its reincidence on the splitter 18 and projected toward the stationary optical system 11 by passing the reflection face 18a.
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