GB813579A - Improvements in or relating to polarimeters - Google Patents

Abstract

813,579. Photo-electric polarimeters. BELLINGHAM & STANLEY Ltd. March 27, 1957 [March 27, 1956], No. 9496/56. Class 40 (3). A polarimeter comprises an analyser 7 and means 6 for rotatably oscillating the plane of polarization of the transmitted light. Monochromatic light from a source 1 passes through (1) a Nicol prism system 3, (2) a tube or trough 5 containing the sample to be tested, (3) a Faraday cell 6 or any other device such as Poynting plates, an oscillating quartz wedge or a quartz crystal for rotating the plane of polarization, and (4) another Nicol prism system 7 or any rotatable polarizing device acting as an analyser which may be rotated through an angle indicated on scale 8 and observable through optical magnifier 9 to fall finally on (5) photo-electric cell 10, the output of which is applied to a frequency amplifier 11 having a dial 12. Instead of the oscillating device 6, the polarizer 3 or analyser 7 may be oscillated. A Poynting plate oscillator comprising a pair of Poynting plates mounted opposite each other at 120 degrees in a rotatable tube is illustrated at Fig. 2 (not shown). The device is first calibrated without the sample with the planes of polarization of the polarizer 3 and analyser 7 at right angles so that the cell 10 receives equal pulses of light at twice the frequency of the oscillator. Rotation produced by the sample will displace the mean plane of polarization and the pulses received by the cell will vary in intensity so that the high gain amplifier 11 tuned to the fundamental frequency of the oscillator and employing a twin-T rejector circuit in a negative feedback loop detects the absence of amplifier input and output at the fundamental frequency.