Method and apparatus for optically checking by interferometry the thickness of an object being machined

Abstract

A method for optically checking by interferometry the thickness of an object () being machined comprises a phase of direct checking wherein the spectrum of the result of interference between primary reflected radiations (R) generated by reflection of incident radiations (I) on an external surface () and secondary reflected radiations (R) generated by reflection on an internal surface of discontinuity () of the object is analyzed, and a preliminary phase wherein information relative to the variation of a virtual thickness (D) delimited and defined by a reference surface () and the external surface of the object, indicative of thickness variations of the object being machined. In the preliminary phase, the processing is based on the analysis of the spectrum of the result of interference between primary reflected radiations and reference reflected radiations (Rref) generated by the reflection of the incident radiations on the reference surface, that defines the length of a reference optical path. An apparatus that implements such method for optically checking includes an optical probe () that receives and detects the primary, secondary and reference reflected radiations, and a spectrometer () that analyzes the spectrum of the result of interference.