GB774277A - Interference polarizing device for study of phase objects - Google Patents

Abstract

774,277. Optical apparatus. CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE. May 13, 1953 [May 14, 1952], No. 13449/53. Class 97(1) A microscope system comprising a light source, a diaphragm, a condenser, a support for a phase object and an objective is combined with an interference polarizing device comprising two plane polarizers with their planes of polarization relatively inclined and between them at least a main birefringent wedge of non-uniform thickness located at or adjacent the plane in which the microscope system produces an image of the diaphragm, the interference fringes being localized at said image, whereby the object is made visible. The main wedge may be circular with its greatest thickness at the centre and the diaphragm may be omitted. As shown in Fig. 1 the image of a slot 5 is formed in the rear focal plane of objective O, by condenser C and objective O at the binefringent wedge Q before which is a polarzer P<SP>1</SP>. A compensator K formed of two relatively movable wedges is provided to compensate the birefringence at the centre of the plate Q and a polarizer P<SP>2</SP> crossed with respect to polarizer P<SP>1</SP> is provided before the eyepiece. In a modification the slot 5 is circular and the plate Q has one face spherical. In the modification shown in Fig. 3 the diaphragm is replaced by two quartz plates q<SP>1</SP>, q<SP>1</SP> with curved surfaces relatively movable to the equivalent to a prismatic plate of variable dihedral angle. The plote Q is formed of two plates Q<SP>1</SP>, Q<SP>2</SP> with perpendicular optic axes to provide compensation of the birefringence at the centre. Where the slit image is found within the objective O the plate Q<SP>2</SP> may have its optic axis inclined to that of the plate Q<SP>1</SP> to displace the fringe system to the said slit image. The arrangement shown in Fig. 7 may be used to test the accuracy of a spherical mirror M the birefringent wedge Q being placed at the centre of curvature of the mirror and an image of the source S being formed thereat by a condenser C the resulting image of the mirror being viewed directly or photographed by an objective O. If the mirror M has no errors the space between the mirror M and wedge Q may be used for studying the strictions of gaseous or liquid bodies. Alternatively the mirror M may be replaced by a plane mirror or by an object to be examined in reflected light. The system may be applied to a microscope employing a reflecting objective.