GB732004A - Polarization interferometer - Google Patents

Abstract

732,004. Optical apparatus. CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE. May 13, 1953 [May 14, 1952], No. 13448/53. Class 97 (1). A polarization interferometer for observing an object in white or monochromatic light comprises a polarizer, a birefringent prism, the inlet face of which is parallel to the plane wave issuing for the polarizer and whichsplits the beams into two relatively inclined beams, an observation system the focus of which is at the outlet of the prism, means for maintaining the object in the light beam and means for measuring the resulting interference effects. As shown in Fig. 3, light from a suitable source is plane polarized by a polarizer P<SP>1</SP> with axis at 45 degrees to the plane of the drawing and passes to the birefringent prism ql which divides it into two diverging oppositely polarized beams, a glass prism q2 being provided to maintain the general direction of the two beams. The beams pass to a condenser C, the object X to be examined and an objective O in the rear focal plane of which is a second birefringent prism Q<SP>2</SP> arranged with the axis perpendicular to that of the prism ql. Any phase differences introduced into the two beams by the object give rise to interference effects localized at the image plane X<SP>1</SP> and are viewed through an eye-piece and a polarizer P<SP>2</SP>, a Babinet compensator K being provided to facilitate measurement of the interference effects. For wider angles of field the prisms q<SP>1</SP>, q<SP>2</SP>, Q<SP>1</SP>, Q<SP>2</SP> may be replaced by Wollaston prisms. In a modification the object is illuminated by collimated unpolarized light and the objective is followed by a plane polarizer and a double prism formed by connecting the prisms q<SP>1</SP> and Q<SP>1</SP> together, giving unlocalized interference fringes observable in a suitable viewing system. For examination by reflected light the system shown in Fig. 5 may be employed. This comprises a polarizer P<SP>1</SP> from which light passes via a condenser and a reflector G to a Wollaston prism ql, q<SP>2</SP> an image of which is formed on itself by the objective O by light reflected by the surface X under examination. The resulting interference effects are viewed through a polarizer p<SP>2</SP>, a Babinet compensator K being provided' to facilitate measurement. For the examination of an irregular reflecting surface X, Fig. 8, a plane surface V having a reflecting portion M is placed upon W and the resulting interference effects observed.