Patent ID: 7710580

Claim:
A method comprising: providing scanning interferometry data for a test object using phase shifting interferometry, the data comprising intensity values for each of multiple scan positions for each of different spatial locations of the test object, the intensity values for each spatial location defining an interference signal for the spatial location, the intensity values for a common scan position defining a data set for that scan position; temporally transforming at least some of the interference signals into a first frequency domain signal; determining an estimate of a phase profile of the test object based on the first frequency domain signal; determining a carrier pattern based on a data set for a particular scan position, the carrier pattern representing a relation between the intensity of data points in the data set and the estimated phase associated with the data points; determining phase shifts at the multiple scan positions based on the estimated phase profile; and determining a more accurate phase profile of the test object based on the estimated phase profile and the phase shifts experienced at the multiple scan positions.