In certain aspects, interferometry methods are disclosed that include providing one or more interferometry signals for a test object, wherein the interferometry signals correspond to a sequence of optical path difference (OPD) values which are not all equally spaced from one another because of noise, providing information about the unequal spacing of the sequence of OPD values, decomposing each of the interferometry signals into a contribution from a plurality of basis functions each corresponding to a different frequency and sampled at the unequally spaced OPD values, and using information about the contribution from each of the multiple basis functions to each of the interferometry signals to determine information about the test object.