OPTICAL SYSTEM HAVING LUMINOUS FLUX DIVIDING ELEMENT

摘要

PURPOSE:To constitute an image-forming optical system having low aberration with a simple constitution by using a non-spherical rotational two-dimensional curved-face mirror as a luminous flux dividing element. CONSTITUTION:The photographing optical system consisting of elements 1-1, 1-3 has an image-forming picture 1-4 and luminous flux on an axis at a focusing time is a focal between the lens groups 1-1 and 1-3. A luminous flux dividing element 1-2 for dividing a part of the luminous flux passing the photographing optical system has a shape corresponding to a part of a rotary parabolic surface and is arranged on a position separated from the optical axis. The optical system consisting of elements 1-1, 1-2 has an image forming picture 1-5 which is a conjugate surface with the image forming picture 1-4 and a parabolic surface forming the mirror 1-2 has a vertex 1-6. Thus, the economical focus detecting optical system can be obtained with the simple constitution.