Improvements in and relating to Interferometers.

摘要

1,184,594. Interferometers. DEUTSCHE AKADEMIE DER WISSENSCHAFTEN ZU BERLIN. March 16, 1967, No.12424/67. Heading G2J. An arrangement for producing multiple beam interferences in white light with sub-division of the order spacing of the interference fringes into N equal parts, consists of two interferometers in series, the separation of their plates having the ratio 1/N, and the test surface being included as one of the plates in the thinner interferometer while the plate separation in the thicker interferometer is greater than #2 o K2/4#d k N where #d k is the maximum measuring error for the air distance between the test plates, and k is the number of sub-divided spacings between m# o and m# k, where the said sub-divided spacing is the spacing between m# k and m# k-1 . White light from source 1 is focused on to Fabry-Perot interferometer 4 of variable plate separation, light then passing via diaphragm 5 and objective 6 through the wedge interferometer 7 including the test surface. The resulting fringe system is viewed or photographed. An interference filter 9 before the interferometers produces fringes in the vicinity of the white light fringe intensity maxima at the spacingγ/2N. In another form, collimated white light is passed through a Fabry Perot interferometer having the test surface as one plate and then through a wedge interferometer of N times the Fabry-Perot spacing.