Patent ID: 7274467

Claim:
A phase shifting interferometric method of measuring an object, the method comprising: superimposing reference light with measuring light having interacted with the object; generating at least four different phase settings of the reference light relative to the measuring light superimposed therewith; detecting an image of an intensity distribution of the superimposed reference light and measuring light at each of the different phase settings; determining, for each of the different phase settings, a distribution of values corresponding to relative phases between the reference light and the measuring light superimposed therewith, based on the detected images and based on a model for approximating the distribution of the values corresponding to the relative phases, wherein the model has a plurality of adaptable parameters, and wherein the plurality of adaptable parameters comprises at least three phase parameters related to actual values of phase differences between the different phase settings; and determining a distribution of a physical property of the object across an area thereof, based on the determined distribution of the values corresponding to the relative phases.