Patent ID: 6128129
Filing Date: 2000-10-03
Classification: G02B

Abstract:
An automatic focusing apparatus for a microscope, comprising:mounting means on which an object to be observed is placed;an objective caused to face the object on said mounting means;driving means for driving at least one of said mounting means and said objective;an image forming optical system for forming an image of said object via said objective;an optical path difference optical system for giving an optical path difference to a front focused position and a back position that are conjugate with respect to the image forming point of said image forming optical system;image sensing means for sensing the image of said object via said optical path difference optical system; andcontrol means for determining the degree of focusing of said object on the basis of image information from said image sensing means and-causing said driving means to operate to direct said object on said mounting means to a focused position, whereinsaid control means has four automatic focusing control modes:an object search mode in which an object to be observed is searched for,a rough focus mode in which said object is brought to a roughly focused position with a lower accuracy of focusing,a front and back defocus sensing mode in which the degrees of front and back focusing of said object in at least a front and a back place with respect to the roughly focused position in said rough focus mode are determined, anda fine focus mode in which the degree of focusing of said object with a higher accuracy of focusing is approximated linearly on the basis of the degrees of front and back focusing determined in said front and back defocus sensing mode and said object is brought to said focused position.