| 摘要 |
PURPOSE: To provide a prism for optical head which can be made inexpensive by decreasing constitution components and saving labor for adjustment among elements as much as possible. CONSTITUTION: When an elliptical beam is made incident on an incident plane 4a as a light beam, for example, this elliptical beam is refracted on this incident plane 4a and shaped so as to be close to a circular beam and the incident/ refracted light from this incident plane 4a is reflected on a first reflection plane 4b. The reflected light from this first reflection plane 4b is reflected on a second reflection plane 4c and turned toward a medium 6 by raising its optical path, for example, the total of phase difference between P and S waves on these first and second reflection planes 4b and 4c is made into (2n+1).λ/4 [(n) is a natural number including 0] and the functions of beam shaping prism, λ/4 board and rising mirror can be provided only with such a prism 4 for optical head. |
