GB703530A - Improvements in spectrometers - Google Patents

Abstract

703,530. Spectroscopes. PERKIN - ELMER CORPORATION. June 9, 1952 [June 22, 1951], No. 14483/52. Class 97(1) [Also in Group XL(b)] Apparatus for simultaneously comparing the intensity of light at two wave-lengths from one source comprises means for refracting part of a beam which is chopped by a rotating disc to allow the different wave-lengths to fall alternately on to a photocell or other detector, and means for comparing the intensities of the two wave-lengths in a phase-sensitive amplifier fed with a reference voltage. An optical system comprising a light source 10, entrance and exit slits 11, 17, lenses 14, 16 and a prism 15 is arranged so that only part of the beam passes through a refracting element 12. Both parts of the beam are focused on the exit slit 17 at different places, and pass through it to energize a photocell 18 after being chopped by a rotating disc 19 mounted on a shaft 20, also carrying a generator 21, and driven by a motor 22, the shape of the disc 19 being such that refracted and unrefracted light alternately reach the photocell 18. A chamber 13 containing a sample to be analyzed is placed in the path of the beam, and the angular positions of the prism 15 and refracting element 12 are adjusted so that the refracted and unrefracted light passing through the exit slit 17 are respectively two wave-lengths whose intensities are to be compared in a phase-sensitive amplifier fed with a reference voltage from the generator 21. The output of the light source may range from ultraviolet to infra-red. In the examination of a gaseous mixture the complete apparatus may be enclosed in the cell containing the gas. By suitable positioning of the light source and detector the entrance and/ or exit slit may be dispensed with.