| 摘要 |
PROBLEM TO BE SOLVED: To form a driving means of an expander lens excellent in terms for various conditions. SOLUTION: A light beam emitted from a light emitting element 10 is turned to a parallel light beam by a collimator lens 11, etc., and made incident on a beam splitter 13. The light beam transmitted through the beam splitter 13 is made incident on the expander lens 16 constituted of a concave lens 16a and a convex lens 16b and a recoding medium (not illustrated) is irradiated with the light beam passed through the expander lens 16 via a mirror 17, a wavelength plate 18 and an objective lens 19. For example, a stepping motor 22 is further provided as a rotation motor for driving the expander lens 16, a lead screw mechanism 23 is connected with its rotational axis and a rotational motion is converted into sliding motion. And the sliding motion is transmitted, for example, to a lens holding member 25a of the concave lens 16a of the expander lens 16 via a rack 24 for driving.
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