| 摘要 |
PROBLEM TO BE SOLVED: To make an optical head thin by arranging a thin prism in a space below an objective lens and to make an optical disk device small in size. SOLUTION: A laser beam is made incident on an objective lens 20 at a right angle by a prism 13 making a laser beam being incident on the objective lens 20 incident into the inside through a first transmission plane 12, totally the beam reflect to the inside by a first reflection plane 14, again totally the beam reflect by a second reflection plane 15 and thereafter, the beam reflect by a third reflection plane 16 inclining at a third prescribed angle to the first reflection plane 14. Or the laser beam 3 is made as a parallel luminous flux 3A, by a collimating lens made incident on a prism from a first transmission plane 26 inclining at a first prescribed angle, made totally to reflect on a first reflection plane 27 and thereafter, the parallel light beam is made incident on the objective lens 20 at right angle by means of a prism 25 provided with a second reflection plane 28 inclining at a second prescribed angle θ6 to a disk 1. By either of the constitution, the prism is made thin. |
