Patent ID: 7256942

Claim:
A single lens element used for converting a divergent pencil of rays, radiated from a light source, into a predetermined convergent state, wherein the single lens element is made from a resin and has a positive optical power due to a refraction effect and a positive optical power due to a diffraction effect, the diffraction effect is based on a diffraction structure formed on at least one of an incident side surface and an exit side surface of the single lens element, and following expressions are satisfied: 0.1<NA<0.3 0.4<T/f<0.75 2.2<fr/f<3 wherein, f is a focal length of the entire single lens element, fr is a focal length due to the refraction effect of the single lens element, T is a thickness of the single lens element on an optical axis, and NA is a numerical aperture of a single lens element at an incident side.