Refractive-diffractive hybrid optical element for true beam smoothing

A refractive-diffractive hybrid optical element for true beam smoothing is designed with the precise design method. The intensity of any point on the focal plane is fully filled with the required demand, besides the sampling points used in the optimization. An aspheric refractive surface gives a good initial intensity distribution on the focal plane and can decrease the phase depth of the diffractive surface. After the optimization, the phase depth of the diffractive surface is smaller than 1.1 pi, which is correspondingly easy to fabricate. (C) 2003 Society of Photo-Optical Instrumentation Engineers.