Patent attributes
A focus sensing system adaptable for use in microscopes or other optical systems incorporates a selective beam block. An outgoing reference beam, incident upon a target to be inspected, is reflected to become an incoming reference beam. A beam block inserted within the optical system selectively rejects unwanted reflections from surfaces other than the target allowing the desired incoming reference beam to be photodetected without interference from reflections off of surfaces that are not of interest. The photodetector generates an electronic signal corresponding to the displacement of the target from the ideal focal point. The electrical signal may be used to drive a servomechanism to displace either the target or the microscope objective lens to bring the target into focus.
