Optical probe microscope having a fiber optic tip that receives both a dither motion and a scanning motion, for nondestructive metrology of large sample surfaces

摘要

An optical probe microscope includes an optical fiber oriented in a vertical direction. The fiber has a tip that emits light onto a horizontal surface of a sample to be measured. This surface can have both desired and undesired departures from planarity. An electromechanical device for imparting dither motion to the fiber tip is superposed on another electromechanical device for imparting two-dimensional horizontal scanning motion to the fiber tip. The dither motion has a much higher frequency than that of the scanning motion. Between successive scannings, another device moves the sample itself from one horizontal position to another. A microscope receives the optical radiation either transmitted or reflected by the sample surface. The microscope forms a (magnified) image of this received optical radiation on the surface of an optical image position detector. The surface of this detector has a relatively large area compared with that of the (magnified) image. The resulting electrical signal developed by the detector provides desired information concerning the scanning position of the fiber tip. Also, this electrical signal is processed and fed back to a vertical pusher that maintains desirably constant the distance of the fiber tip from the sample surface.