Apparatus and measuring method for modifying an interferometer into a quantitative dual-channel phase quadrature interferometer, and the Michelson interferometer thus modified

摘要

The invention relates to an apparatus and associated measuring method for the modification of an optical interferometer for quantitative definition by repetition of the instantaneous wavefront distortion caused by an unsteady phenomenon in the test beam of the interferometer. The modified interferometer system generates phase quadrature interference patterns along two optical channels and is connected via an interface to a computer system. This interface comprises, separately for each optical channel, a detector and a digitization apparatus, the reciprocal synchronization of which guarantees simultaneous digitization of pairs of phase quadrature interference patterns from the unsteady phenomenon. The interface also performs the translation of a mirror in the interferometer over fractions of wavelength of the laser light used in order to calibrate the two optical channels prior to a measurement. Finally, with specific computer software, the wavefront distortion in the test beam is defined in an unambiguous manner from each digitized pair of phase quadrature interference patterns using the calibration data for the two optical channels. The invention offers a "multi-channel" interferometer system of minimum scope in terms of the number of optical channels in the interferometer, the number of detectors, the number of digitization channels and, for storage of the digitized interference patterns in a computer, also imposes minimal requirements in terms of the speed and size of the computer memory. Furthermore, through the use of a polarizing subcube (corner cube) as a "spatial phase-shifting" mechanism, the invention offers a spatial division between the two orthogonal optical channels over a relatively small distance, thereby permitting the use of a separate detector for each channel. Furthermore, the image distortion in the two optical channels is identical, as a result of which a perfect reciprocal alignment of the interference patterns is achieved.