GB766909A - Improvements in spectrographs and monochromators - Google Patents

Abstract

766,909. Spectroscopic apparatus. HILGER & WATTS, Ltd. June 29, 1955 [July 2, 1954], No. 19502/54. Class 97(1) In a spectrograph or monochromator in which the dispersive element, when used with the slit alone, produces superimposed spectra of different orders; a second dispersive means is placed behind the slit so that the spectra are presented separately and individually. Preferably, the dispersive element and the dispersive means disperse the light in directions which are substantially at right-angles so that the spectra 9, 10, 11 of successive orders appear side by side. In the spectrograph or monochromator shown in Fig. 2, the slit 2 is placed at the focus of a concave mirror 3 and a plane reflection grating 4 having rulings parallel to the direction of the slit may be placed nearer to the mirror 3 than the focal distance. A thin prism 6 separates the spectra 9, 10, 11 which may be formed on a photographic plate (not shown). Alternatively, a larger form of prism 6 may be interposed between the mirror 3 and the photographic plate. In the monochromator shown in Fig. 3, the first order spectrum is given by light which has only passed once into the prism 14 and the second order by light which has passed twice. A prism 20 may be interposed in the light beam in either of the positions shown to separate the spectra.