JPH0225489B

PURPOSE:To eliminate the dependency on wavelength with a laser beam scanner of a diffraction grating type using a semiconductor laser by providing a stationary diffraction grating G on the light source side of a rotary grating disc GS, and interposing a lens L between both gratings GS and G so that both gratings are in the position conjugate with each other relatively with the lens L. CONSTITUTION:The incident angle i0 of a stationary diffraction grating G does not change when an oscillation wavelength changes from lambda to lambda+DELTAlambda, and the exit angle changes from (i) to i+DELTAi. Said beam is made incident by a lens L to the incident point when the oscillation wavelength on the grid disc GS is lambda. More specifically, if it is assumed that the incident angle changes from theta0 to theta0+DELTAtheta0 but that the exit angle theta from the disc GS does not change, the distance between both gratings is min. when m=+ or -1 wherein the magnification of the lens L is designated as (m). In other words, the device itself is made compact by disposing the grating G and the grating GS in an unmagnification relation.