Interferometer with a virtual reference surface

摘要

An imaging interferometer includes optics defining an interferometric cavity, in which the optics include a first beam-splitting optic positioned to separate an input beam into a test beam and a reference beam, a second beam-splitting optic positioned to transmit the test beam to the test surface, receive the test beam back from the test surface, and thereafter recombine the test beam with the reference beam, and a third optic positioned to direct the reference beam from the first optic to the second optic. The interferometric cavity defines a virtual reference surface positioned along a path for the reference beam between the second and third optics. The interferometer also includes an imaging channel positioned to receive the recombined test and reference beams, where the imaging channel includes an imaging detector, and at least one imaging element configured to image the test surface and the virtual reference surface onto the detector.

主权项

1. An interferometer, comprising:
a first beam splitter positioned to derive test light and reference light from input light and to direct the test light along a first path to contact a test object and direct the reference light along a second path different from the first path; a second beam splitter positioned in the first and second paths and arranged to combine the reference light with test light after the test light contacts the test object; an optical element positioned in the second path and arranged to direct reference light from the first beam splitter toward the second beam splitter; a detector positioned to receive the combined test and reference light; and an objective arranged to image the test object and a virtual reference surface onto the detector, wherein the virtual reference surface corresponds to a virtual surface optically conjugate to the detector between the first and second beam splitters; wherein the first and second paths between the first and second beam splitters, in combination with the optical element positioned in the second path, define a geometry corresponding substantially to a triangle.