| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical scanner using a reflection mirror, having high absolute reflectance and little wavelength dependence and little angular dependence in an optical scanner, using a short wavelength light source whose wavelength is <=500 nm. SOLUTION: After divergent light from a semiconductor laser 1 is changed into a nearly parallel light beams by a collimator lens 2, a luminous flux diameter is restricted to a desired spot diameter by a diaphragm 3, and the reflected light from a polygon mirror 5 is formed to a very small light spot over the entire scanning area by scanning image-formation lenses 6 and 7. The laser 1 is a semiconductor laser is gallium nitride, and its oscillation wavelength is 408 nm. A reflecting mirror, satisfying k(λ)>√(-n(λ)<2> +18n(λ)-1) when the complex index of refraction N of a metal film contributing to the reflection characteristic of the reflection mirror, is defined as N(λ)=n(λ)-ik(λ), is used as a polygon mirror 5 (reflecting mirror). |
