Patent ID: 6072642
Filing Date: 2000-06-06
Classification: G01C

Abstract:
A focusing lens position detection apparatus provided in an auto-focus surveying instrument that includes a telescopic optical system having a focusing lens which moves along an optical axis, a beam splitting element which splits object light transmitted through said focusing lens to produce light split from said telescopic optical system, and a focus detection device for receiving said split light from said beam splitting element, said focusing lens position detection apparatus comprising:an indicia member provided on said focusing lens, which is located outside the light path of said telescopic optical system; anda light path changing member provided between said beam splitting element and said focus detection device;a moving device which moves said light path changing member between a first position in which the split beam from said beam splitting element can be received by said focus detection device, and a second position in which the light from said indicia member can be received by said focus detection device.