Patent ID: 7046371
Filing Date: 2006-05-16
Classification: G01B

Abstract:
1. A method comprising: imaging test light reflected from a test surface to interfere with reference light on a camera and form an interference pattern, the test light and reference light being derived from a spatially extended, common source, having a mean wavelength λ, and comprising chief rays and marginal rays that propagate along different paths, wherein the test light and reference light propagate along different paths in a main cavity comprising the test surface and also propagate along different paths in at least one remote cavity, and wherein a single pass through the main cavity introduces a non-zero optical path difference δ adjusting the optical path difference δ wherein the imaging comprises coupling the test light and reference light between the main cavity and the at least one remote cavity to cause a total optical path difference between the marginal rays of the test and reference light at the camera to be smaller than λ when the total optical path difference between the chief rays of the test and reference light at the camera is zero.