Diffractive optical system of telepoto type

摘要

PURPOSE: A diffractive optical system in telephoto type is provided to correct chromatic aberration through a hybrid lens adopting a diffractive optical element(DOE) on one lens surface. CONSTITUTION: An iris(11) controls an intensity of a light beam incident on the first lens group. The first lens group(12) is constituted with a hybrid lens(15) by attaching a refractive optical element(13) and a diffractive optical element(DOE)(14) of the lens group so that the light beam incident by the iris to be refracted and diffracted to the second lens group(16), and has positive(+) power. The second lens group is located in front of the first lens group, and emits the light beam emitted through the first lens group to an optical low pass filter(OLPF)(17), and has negative(-) power. The optical low pass filter performs low pass filtering as to the light beam from the second lens group, and prevents imaging characteristics from being degraded on a CCD(Charge Coupled Device)(18). And the CCD converts the light beam of low frequency into an electrical signal.