A photoelectric attachment for conventional types of visual precision polarimeters, utilizing the “method of symmetrical angles,” has been developed, and its performance characteristics have been analyzed. A comparison of the precision of the photoelectric and visual observations indicates that they are of the same order when the mercury 546.1 mμ and sodium 589.25 mμ lines are used, provided that large apertures and high light transmission of samples can be maintained, and provided that the visual observations are made in a darkroom with a dark-adapted eye. In the case of micro and semimicro observations and samples of low light transmission, the photoelectric method yields a precision up to one order higher than that of visual measurements, with the additional benefits of reducing operator eye fatigue and eliminating the necessity of a darkroom.
Methods of compensating for photometer drift, polarization effects in photomultiplier tubes, and high light absorption of samples are explained and an analysis of the problem of the optimum symmetrical angle is made.
Errors in quartz control plate measurements indicate that more rigid specifications for color filters to be used with the sodium and mercury lamps must be developed to assure readings which agree with quartz control plate calibration values.
© 1955 Optical Society of AmericaFull Article | PDF Article
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