Patent ID: 7712955
Filing Date: 2010-05-11
Classification: G01N

Abstract:
1. A method of determining a case depth of a hardened sample comprising a material, said method comprising the steps of: a) providing a modulated reference signal; b) modulating an intensity of an optical beam according to said modulated reference signal using a modulation means; c) measuring an unhardened reference sample comprising said material by scanning a frequency of said modulated reference signal over selected frequencies within a frequency interval, while performing the following steps at each said selected frequency: d) measuring said hardened sample by scanning a frequency of said modulated reference signal over said selected frequencies within said frequency interval, while performing the following steps at each said selected frequency: e) calculating a normalized phase difference for each said frequency by subtracting said reference sample phase difference from said hardened sample phase difference; f) determining a phase-minimum frequency corresponding to a frequency at which said normalized phase difference is minimized; and g) relating said phase-minimum frequency to said case depth using a pre-determined calibration curve.