| 摘要 |
In a Michelson interferometer system arranged to give four output interferograms (1 to 4), two at each orthogonal direction of polarisation, the reflection and transmission coefficients of the interferometer beam splitter (10) at the two polarisation directions are chosen so that the ratios of the a.c. component to the d.c. component are equal in three of the interferograms. Thus d.c. components, can be removed by photoelectrically deriving difference signals from the three interferograms. The difference signals are suitable for use with an automatic, reversible, fringe counting system, e.g. for making distance or velocity measurements. <IMAGE> |
