Single Optical Block Interferometer Means

1,184,080. Interferometers. OPTOMECHANISMS Inc. Sept.19, 1967, No.42590/67. Heading G2J. An interferometer comprises a glass prism having a first face 1 at which an inclined incident beam A is refracted towards a semi-silvered surface 2 giving rise to a reflected beam B, and a transmitted beam C, beam B being reflected back along its path to surface 2 by silvered surface 4, while beam C is also returned to surface 2 after reflection at axially movable corner reflector 5 and externally silvered face 3 of the prism, the resulting interference between beams B and C being measured by photo-detectors at 10. Surface 6 is diffusing to prevent multiple internal reflections. In another form, a single movable mirror returns beam C directly to semi-silvered face 2, face 3 in this case being diffusing. The direction of motion of reflector 5 is shown by introducing a quarter-wavelength retardation over half the wavefront.