摘要 |
PCT No. PCT/GB79/00006 Sec. 371 Date Sep. 13, 1979 Sec. 102(e) Date Aug. 9, 1979 PCT Filed Jan. 11, 1979 PCT Pub. No. WO79/00506 PCT Pub. Date Aug. 9, 1979.In a Michelson interferometer system arranged to give four output interferograms, two at each orthogonal direction of polarization, the reflection and transmission coefficients of the interferometer beam splitter (10) at the two polarization directions are chosen so that the ratios of the a.c. component to the d.c. component are equal in three of the interferograms. Difference signals derived from the three interferograms are suitable for use with an automatic, reversible, fringe counting system. |