Patent ID: 8913245

Claim:
An apparatus suitable for interferometric autofocusing, comprising: a camera disposed along a primary optical axis, wherein the camera is configured to collect a portion of light reflected from a surface of one or more specimens disposed on a specimen stage; a two beam interference optical system including a shutter-less reference path, wherein the two beam interference optical system includes: an illumination source; a reference mirror configured to reflect substantially less light from a center region than from a peripheral region; and a first beam splitter configured to direct a first portion of light from the illumination source along an object path to the surface of one or more specimens disposed on the specimen stage and a second portion of light from the illumination source along the shutter-less reference path to the surface of the reference mirror, wherein the first beam splitter is configured to direct a portion of light reflected from the peripheral regions of the surface of the reference mirror along a primary optical axis, wherein the camera and reference mirror are arranged such that light reflected from peripheral regions of the reference mirror does not impinge on a field of view (FOV) of the camera; an autofocusing system disposed along a secondary optical axis, wherein the autofocusing system is configured to analyze one or more interference fringes created by a superposition of light reflected from the surface of the specimen and light reflected from the peripheral region of the surface of the reference mirror simultaneously with an imaging of the surface of the one or more specimens by the camera.