GB732058A - Improvements in multiple slit spectrograph for direct reading spectrographic analysis - Google Patents

Abstract

732,058. Spectrometers. LEEDS& NORTHRUP CO. July 28, 1952 (Aug. 10, 1951], No. 19021/52. Class 97 (1). [Also in Group XL (b)] In a photo-electric spectrometer for determining the peak intensities of predetermined spectral lines in which radiant energy passes between a collimating and dispersing element the radiant energy falls on one of said elements through an aperture defining structure and passes to a second such structure from the other element, means co-operating with one of the structures to select a spectral line and further means with the other to scan the selected line to determine its peak intensity. As shown, (Fig. 6), light produced by a spark passing between electrodes 13 of the material to be analysed passes through a slit 14 to a concave collimating mirror 15 from which it is reflected through a slit 14 to a concave collimating mirror 15 from which it is reflected on a concave diffraction grating 16, the spectrum produced being reflected by plane mirror 34 on to a disc 35 provided with a number of slots such as 35b. The spectral line to be scanned is selected by rotating the disc so that the appropriate slot. is positioned in front of a light integrating housing which directs the light on to a photoelectric cell 36. The cell housing may'be provided with a number of uniformity spaced slits spanning the entire useful spectrum, the disc being arranged to pass light sequentially through the selected slits. To avoid the necessity of accurately positioning each exit slit the entrance slit 14 is made movable, being carried on a pivoted lever 38, the angular position of which is adjusted by prepared studs in the edge of a cam 40. The length of each stud is so adjusted that the slit image is positioned in the slit. The slit may also be turned through a small angle to ensure measurement of the peak intensity of a band by means of an eccentric 21 engaging the edge of a further lever 20 carrying the slot 14. The output of the photo-cell is compared with that of a reference cell 23 in a ratio-recorder 27. In the arrangement of Fig. 1 (not shown), the light sensitive cell is mounted in a hemispherical housing, the flat face of which has a number of slits each with its own shutter and so that any selected one may be opened. In that of Fig. 2 (not shown), the light source is situated in such a housing the cell being situated in another housing with a single slit. This latter housing may be oscillated slightly. The arrangement of Fig. 3 (not shown), differs from Fig. 2 only in that the light travels to the grating before the collimating mirror while Fig. 4 (not shown), differs from Fig. 1 in the same respect. In the arrangement of Fig. 5 (not shown), shutters are provided both in the source housing which can be oscillated slightly and in the photo-cell housing. The various combinations of shutters simplify the separation of two lines which are very close together. An arrangement is described with reference to Fig. 7 (not shown), in which a prism is used instead of a diffraction grating. Specification 731,943 is referred to.