Patent ID: 6344639
Filing Date: 2002-02-05
Classification: G01C,G02B

Abstract:
A beam splitting optical system for an automatic focusing apparatus comprising:an optical system having an objective optical system and a viewing optical system; a beam splitter provided between the objective optical system and the viewing optical system, said beam splitter being provided with a splitter surface to split object-carrying light transmitted through the objective optical system, said splitter surface comprising a multi-layered dielectric film; a focus detection optical system having a pair of light receiving elements which respectively receive an object-carrying light beam split by and transmitted through the splitter surface of the beam splitter, said focus detection optical system being arranged so that said object-carrying light beam to be respectively received by each of said pair of light receiving elements is incident upon the splitter surface at different angles; and an optical element that is provided between said splitter surface and said pair of light receiving elements, wherein one of said object-carrying light beams received by a light receiving element having a larger quantity of light is reduced, by said optical element, in the quantity of light to be transmitted, to thereby reduce the difference in quantity of light between each said object-carrying light beam received by each of said pair of light receiving elements.