| 摘要 |
PURPOSE: To suppress stray light reflection in an over field polygon design by means of using an optical isolator. CONSTITUTION: The optical isolator 16 positioned in an optical path contains a polarizer 40 and a quarter wavelength board 42. Parallel light beams pass through the polarizer 40 and are linearly polarized. The board 42 is adjusted so that an angleθbetween the electric field vector P of the incident linear polarized beam and the main plane 42A of the board becomes 45 degrees. At the angleθ, a scanning beam 22 emitted from the board 42 is circularly polarized clockwise and a reflected beam (stray light) 28 from a facet 24B is circularly polarized anticlockwise. The reflected beam passes through the board 42 and the beam 28' is linearly polarized again. It becomes vertical to original polarization. Thus, the stray light beam 28' cannot pass through the polarizer 40 and it is annihilated. |
