Diffractive lens.

摘要

A diffractive lens has a plurality of diffractive zones at least one of which has an optical step having an optical height equal to j lambda and at least one of which has an optical step having an optical height equal to k lambda where lambda is a design wavelength of the lens and j and k are unequal nonzero integers. Alternatively stated at least one of the optical steps induces a relative phase shift of 2j pi at the back conjugate point between two light rays emerging from a point source at the front conjugate point and striking the lens immediately on opposite sides of the step and at least one of the steps induces a relative phase shift of 2k pi at the back conjugate point between two light rays emerging from a point source at the front conjugate point and striking the lens immediately on opposite sides of that step.