GB1335185A - Polarizing interferometers - Google Patents

Abstract

1335185 Polarizing inter-ferometers D H MARTIN and E F PUPLETT 27 Oct 1970 [8 April 1970] 16743/70 Heading G2J A polarizing inter-ferometer, using infrared radiation, comprises a plane polarizer P 1 , a partially transmitting means D which transmits radiation 1 polarized in one plane and reflects radiation 2 polarized or thoyonally, reflectors R 1 , R 2 to reflect the beams 1, 2 to a recombing means, e.g. D, one of the reflectors R 1 , R 2 being moveable to give a defined path difference, and comparison means including an analyser P 2 for plane polarizing the recombined beam 3. Preferably the analyser P 2 splits the recombined beam 3 into two components to enable comparison to be made between the intensity of beam 3 after polarization at P 2 in one plane inclined at an angle relative to the plane of polarization of beam 3 before the analyser P 2 and the intensity of beam 3 after polarization at P 2 in a different plane. The comparison is made for zero path difference. The polarizer and analyser are in the form of wire grids and the reflectors R 1 , R 2 are metal plates preferably in the form of cube-corner prisms. The recombined beam 3 is elliptically polarized with an ellipticity varying periodically with the path difference between the components. The outputs from analyser P 2 may be fed to detectors d 1 , d 2 . These may produce interferograms which enable the intensities of the two beams to be compared. The detectors d 1 , d 2 may be connected in opposition to yield a single averaged interferogram. To obtain spectral information about a sample, the sample may be located either in the beam path before polarizer P 1 or in either of the paths 1, 2 after the partial transmitter D, or in either of the paths after analyser P 2 . In an alternative embodiment the polarizer P, may be a rotatable disc consisting of segments which alternately polarize the incident beam in the two orthogonal directions. Consequently only a single detector d 1 or d 2 is required; however if both detectors are used and a sample is located in one of the beams after analyser P 2 spectral information about the sample is obtained. In a further embodiment the beam components from the partial-transmitter D are reflected back along their paths from plane metal reflectors, without rotation of their planes of polarization. Consequently the recombined beam travels back towards the source. In this embodiment the polarizer also acts as the analyser. In another embodiment similar to that of Fig.1 the polarized beam is split at D d but recombined at D e . Also the corner reflectors R 5 , R 6 do not rotate the planes of polarization of their respective beams. Polarizer P 1 may be stationary or rotate as in Fig.1.