Patent ID: 7804641

Claim:
A method of automatically focusing a microscope having a light source, an objective lens, a light path to direct incident light through the objective lens to be reflected by an object, an aperture to limit the spatial extent of the incident light and serve as an illumination pupil, a light path to direct at least some of the reflected light to an imaging system, and an imaging system to image the reflected light so directed, the method comprising: directing a beam of light from a light source through an objective of a microscope system to an object whereby light is reflected from the surface thereof; collecting at least some of the light reflected thereby and directing the same to an imaging system, wherein the incident beam of light is limited in spatial extent by imaging an aperture to form an illumination pupil, a centroid of illumination of the illumination pupil is aligned with an incident optical axis, and reflected light is projected to the imaging system in which the reflected light is split into at least two images from eccentric sections of an imaging pupil differentially displaced from the optical axis, and wherein the separation of the images thereby produced is determined to provide an indication of a focus condition.