| 摘要 |
PURPOSE:To prevent return of the reflected light of a laser beam to a semiconductor laser light source by using a polarizing plate and 1/4 wavelength plate. CONSTITUTION:A laser beam outputted by a semiconductor laser 1 and having the plane of polarization parallel to a P-N junction face passes through a polarizing plate 6, and is polarized to circularly polarized light by a 1/4 wavelength plate 7 disposed so as to increase a 45 deg. angle to the P-N junction face. A drum 5 is optically scanned by this circularly polarized light via a scanning part 3 and an imaging lens 4. When the reflected light from the drum 5 passes through the plate 7 via a reverse optical path, a 90 deg. change in phase is generated therein and this light is polarized to the linearly polarized light in the direction perpendicular to the P-N junction; therefore, it is shut off by the plate 6. Thereby, the return of the reflected light to the laser 1 is obviated and the fluctuation in the light source output is eliminated. Hence, the stable laser beam scanning is accomplished. |
