Patent ID: 9664501
Date: 2017-05-30
CPC Classifications: G01B,G01M

Claim:
1. An interferometer comprising: a light source; a beam splitter optically coupled to the light source to produce a reference beam directed to a reference mirror and a test beam directed to a sample surface through an objective; a scanning mechanism adapted to scan the objective relative to the sample surface; a translating mechanism coupled to the reference mirror; a motor driving the translating mechanism so as to enable focusing of the reference mirror; a counter configured to monitor an occurrence of a predetermined event; an automated controller connected to the motor; and a processor configured to drive the controller; wherein the processor is programmed to drive the controller so as to a) measure a parameter of interest in a reference surface to develop an empirical relationship between positions of said reference mirror and values of a parameter of interest, wherein said relationship identifies an in-focus position of the reference mirror as a function of the parameter of interest; b) place the reference mirror in said in-focus position; c) perform measurements on a plurality of samples sequentially until the occurrence of said predetermined event; and d) repeat steps a) and b) to recalibrate said in-focus position after the occurrence of the predetermined event.