Interference apparatus for measuring absolute and differential motions of same or different testing surface

摘要

An interference apparatus is disclosed wherein the high-visibility quadrature interference signals are obtained by making a pair of polarization beamsplitter, a 45-degree oriented quarter-waveplate and four light-beam detected photodiodes. A three-dimensional interference optical configuration is made. The test-surface light beam and reference light beams are traveled on this optical configuration. The test-surface light beam and reference light beams have orthogonally linearly polarization state with each other. After they pass through the quarter-waveplate, one right circularly polarized light beam and one left circularly polarized light beam are produced. The vector sum of these two circularly polarized light beams is again a linearly polarized light beam which is then divided into two light beams by a non-polarization beamsplitter. A pair of polarization beamsplitters, whose axes are 45 degrees apart, are utilized to create the 90 degrees phase difference of the light beam intensity signal measured at the photodiodes.