IMAGE PICKUP LENS, PHASE DIFFRACTION GRATING HAVING OPTICAL LOW PASS EFFECT, AND IMAGE PICKUP OPTICAL SYSTEM

摘要

PROBLEM TO BE SOLVED: To provide an inexpensive and compact photographing optical system suitable for a camera for conference using a personal computer by forming a phase diffraction grating having a low pass effect at least on one lens surface in a single focused photographing lens. ;SOLUTION: The phase diffraction grating having a low pass effect is integrally formed on the refractive surface of a single photographing lens. A phase diffraction grating in the shape of a one-dimensional sine-wave grating having a low pass effect is formed on a second surface. The shape of grating is a rotationally symmetric aspheric surface superposed on a onedimensional sine- wave grating and oriented so as to generate the low pass effect in the longitudinal direction of a rectangular photographic screen. A lens forming a phase diffraction grating is manufactured by mold forming. When injection molding using thermoplastic resin is performed, it is particularly manufactured to be inexpensive and when a glass material is used, a lens having excellent environmental characteristic is obtained. In the phase diffraction grating, the pitch of grating is changed so as to become larger in the peripheral part than the pitch near the optical axis.;COPYRIGHT: (C)1999,JPO