Patent ID: 6052223
Filing Date: 2000-04-18
Classification: G02B

Abstract:
A focus detection device for a microscope having an image sensor, the focus detection device comprising:a first image-forming optical system for producing an optical specimen image of a specimen onto said image sensor;a focus detection unit for calculating a value indicating an extent of defocusing with respect to an output of said image sensor, and for detecting a focus condition of said first image-forming optical system with respect to said specimen based on the calculated value indicating the extent of defocusing;a peripheral system having a second image-forming optical system different from said first image-forming optical system, said second image-forming optical system producing another optical specimen image of said specimen in the peripheral system;a cube corner lens unit inserted in an optical path from said specimen, said cube corner lens unit having a plurality of selectable cube corner lenses and being optically associated with said first and second image-forming optical systems; andcorrection means for determining a correction amount of an optical path length of said first image-forming optical system based on a selected one of the plurality of cube corner lenses of the cube corner lens unit, and for correcting the optical path length in accordance with the correction amount so as to prevent an out-of-focus condition in said second image-forming optical system.