Collimator lens and optical scanning device which uses it

摘要

A collimator lens having only two lens elements, wherein the surface of the collimator lens nearest the collimated light side is concave, and at least one of the two lens elements includes an aspherical surface having diffraction optical element zones thereon which provide dispersion of opposite sign to the dispersion provided by refraction of light by the lens element on which said zones are formed. Preferably, a specified condition is satisfied in order to facilitate manufacture of diffraction zones of the diffraction optical element (DOE) surface(s).