GB540876A - Improvements in or relating to polariscopes - Google Patents

Abstract

540,876. Polariscopes &c. PARNUM, D. H., and AITKEN, I. M. E. June 9, 1939, Nos. 16900 and 20988. [Class 97 (i)] In a polariscope, polarimeter &c. the light beam is divided into two parts passing separately through polarizers having a wide angle, for example 90 degrees, between their planes of polarization, and alternate impulses from the two beams are applied to a photo-electric cell or other light sensitive device for end point determination ; an amplifier may be interposed between the light sensitive device receiving the outputs and the indicating &c. instruments. Fig. 1 shows a construction using a lamp S fed with direct current, and having a rotating slotted disc D at any position between the lamp and analyzer A, but preferably before the polarizer P. The polarizer P may comprise two elements arranged to divide the beam into parts and polarizing them in perpendicular planes, and the disc D may have two rings of slots passing the parts alternately. The analyzer A may be rotatable in association with a divided circle C for measurement, or quartz wedges, respectively fixed and slidable across the beam, may be used ; the output may be received by a photo-electric cell PC, the current from which is amplified by an amplifier 13 and applied to an indicating instrument I. The positions in the beam of the polarizer P and analyzer A, with their associated parts, may be interchanged. Fig. 5 shows a construction wherein polarization of the parts of the beam is effected by two separated nicols N 1 , N 2 , the beam being divided and re-directed to the tube T by mirrors M 1 ...M 4 , and the parts being alternately passed by a rotating slotted disc D. The circuits of the amplifier 13 may be tuned for the frequency of light variation, and may, by known methods, produce greater sensitivity of indication as the zero or minimum reading is approached. The indicator I may be replaced by a recorder, or by a signalling or control device. Specification 456,286 is referred to