Patent ID: 6331918
Filing Date: 2001-12-18
Classification: G01C,G02B

Abstract:
A light interception structure for an automatic focus detection surveying instrument comprising:a telescopic optical system having an objective optical system and an ocular optical system;a beam splitting optical element which splits objective light transmitted through the objective optical system of the telescopic optical system, said beam splitting optical element including a splitting surface; anda focus detection device having a light receiving device for receiving light split by the beam splitting optical element;wherein one surface of the beam splitting optical element is provided with an anti-reflection treatment, said one surface comprising a surface upon which external light entering the telescopic optical system through the ocular optical system is first incident after passing through or being reflected by the beam splitting surface of the beam splitting optical element,said beam splitting optical element comprising a Porro prism with a prism attached to a reflection surface of said Porro prism, a boundary between said Porro prism and said prism comprising said splitting surface.