Patent ID: 7619746

Claim:
An interferometry method, comprising: directing test light to a first calibration surface over a range of illumination angles and combining the test light emerging back from the first calibration surface with reference light to form an interference pattern, wherein the test light from the first calibration surface and the reference light are derived from a common source; directing at least a portion of the combined light from the first calibration surface to a multi-element detector so that different elements of the detector correspond to different illumination angles of the first calibration surface by test light; directing test light to a second calibration surface different from the first calibration surface over a range of illumination angles and combining the test light emerging back from the second calibration surface with reference light to form an interference pattern, wherein the test light from the second calibration surface and the reference light are derived from the common source; directing at least a portion of the combined light from the second calibration surface to the multi-element detector so that different elements of the detector correspond to different illumination angles of the second calibration surface by the test light; and determining information about an interferometry system based on interference signals measured by the different elements of the detector for the test light emerging from the first and second calibration surfaces and other information about the first and second calibration surfaces, wherein: the information about the interferometry system comprises information corresponding to at least one of a spectral distribution of the common source, a relative attenuation of a polarization state perpendicular to the plane of incidence compared to a polarization state parallel to the plane of incidence, a variation of the spectral distribution of the illumination across a pupil plane of the interferometry system, a variation of the mean intensity of the illumination across a pupil plane of the interferometry system, a variation of the phase of the illumination across a pupil plane of the interferometry system, and a variation of the spectral intensity of the illumination across a pupil plane of the interferometry system.