Interferometer with two phase-conjugate mirrors

摘要

In an interferometer apparatus used for monitoring an object surface, the apparatus having a source of coherent light, a beam splitter for dividing the coherent light into a reference beam and an object beam, another beam splitter for dividing the object beam into two separate portions, and a light detector for detecting light interference, comprising an externally-pumped phase-conjugate mirror working in conjunction with a self-pumped phase-conjugate mirror. The externally- pumped phase-conjugate mirror receives the reference beam, receives one portion of the object beam, and reflects the received portion of the object beam to the detector as a first phase-conjugate beam. The self- pumped phase-conjugate mirror receives a second portion of the object beam and reflects the received portion of the object beam to the detector as a second phase-conjugate beam. The first and second phase-conjugate beams interfere at the detector, and the interference produced thereby is representative of changes in longitudinal distance between the object surface irrespective of roughness and the phase-conjugate mirrors.