GB528701A - Improvements in or relating to photometers - Google Patents

Abstract

528,701. Photo-electric comparison of spectrograms. HILGER, Ltd., A., TWYMAN, F., LOTHIAN, G. F. D., and SPENCER, L. J. May 12, 1939, No. 14249. [Class 40 (iii)] For comparing two photographic spectrograms in one of which, for example a standard one, the density of the bands or lines varies in a predetermined manner along the length of the bands, a recording photometer comprises means for producing photoelectric responses to radiation passed through different points on the spectrograms, and comparing the responses from the two spectrograms and recording their match-points. In the form shown, light from a mercury vapour lamp A, Fig. 1, energized by A.C. mains is directed by two lens systems B1, B2 side by side to the two spectrograms M<SP>1</SP>, M2 and from these by lens systems Cl, C2 through apertures Dl, D2 to photocells X1, X2. These cells are differentially coupled to an amplifier connected to an electrometer provided with a mirror E, Fig. 5, which remains in its central position when the cells are in balance and throws light from a lamp F to a slit G and thence by lenses L onto a photographic record plate P, where an impression is made indicative of the match-point. When the cells are not in balance, the mirror oscillates and no impression is made on the plafe P. The spectrograms M<SP>1</SP>, M<SP>2</SP> may be on a single test plate T, Fig. 4, rigid with a record plate R the whole being moved in zig-zag fashion as indicated on the plate R to scan the whole of the spectrograms.