GB626629A - Improvements in auxiliary plates utilised for examination in polarised light - Google Patents

Abstract

626,629. Polarising-apparatus. CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE. Oct. 22, 1945, No. 27824. Convention date, Nov. 24, 1944. [Class 97 (i)] The surfaces of an auxiliary element for use in polarising apparatus, for example a quarter or half-wave plate of mica, quartz or material known under the Registered Trade Mark " Cellophane," are coated with a transparent coating reducing reflection therefrom by interference. The coating on one surface may be suitable for one of the refractive indices of the plate and that on the other surface for the other refractive index. Alternatively the plate may be mounted between two glass plates whose outer surfaces are so coated and the intervening space filled with suitable liquid. The plates may be used in the apparatus described in Specification 626,621. According to the Specification as open to inspection under Sect. 91, for study of birefringence two such half-wave plates may be connected so that the retardations produced thereby are " mutually counteracted " and are rotated together between polariser and analyser, the object to be examined being located between the plates. A polariser may comprise a prism of spar, whose cross-section is a right-angled triangle, the beams being separated by internal reflection at the hypotenuse face. This subject-matter does not appear in the Specification as accepted.