Collimating lens with temperature compensation and an optical scanning apparatus using the same

摘要

A temperature-compensated collimating lens provided of a single piece of lens, which does not have variation in its focal distance due to temperature changes, and an optical scanning apparatus using the same. The collimating lens to transform a ray of light from a light source into approximate parallel rays. The collimating lens is provided a single lens of plastic, and the single lens has a refraction surface provided on one side and a diffraction surface provided on the other side. The refraction surface and the diffraction surface have predetermined powers to prevent power of the collimating lens from changing due to change in temperature. The refraction surface and the diffraction surface have a power to satisfy the condition of, $-3<=\frac{K_d}{K_r}<=-2.$