GB712092A - Spectrophotometers - Google Patents

Abstract

712,092. Spectrophotometers. NATIONAL RESEARCH DEVELOPMENT CORPORATION. April 20, 1951 [April 20, 1950], No. 9703/50. Class 97(1) In a spectrophotometer a light beam is modified in its spectral composition and developed into a spectrogram and has superposed on it an interferring beam, the optical path differences of the two beams is varied along the length of the colour lines of the spectrogram to set up a dark fringe or fringes transverse to the colour lines, and one beam is also subjected to an intensity variation along the length of the colour lines. As shown, light from a source 1 is focused by condenser 2 on a slit 4 and is collimated by a lens 5 which also focuses a slit 3 on mirrors 11, 12. The light beam from the slit is split at 6 and, on its way to and from the mirrors 11, 12, passes through an object 7 and a non- absorbing optical wedge 9, and a non-absorbing object 8 and optical wedge 10. Mirror 12 is inclined at a small angle to the optical axis, and the light reflected by the mirrors is collimated at 13 before passing through the dispersing prism 14 and being focused at 15 on a photographic plate 16. This plate, when processed, has the appearance shown in Fig. 3, the string of black dots constituting the absorption or wavelength curve for object 7. In another form, the beam-splitter 6 is wedgeshaped and a compensating plate similar thereto is introduced in the light path to mirror 11, a Fery prism as described in Specification 10330/10, [Class 97(1)], with aplanatic spherical surfaces is used to disperse the light, and the slit 3 is focused on the mirrors 11, 12 by a concave mirror. To produce a large number of straight, parallel fringes 'one mirror may have a further profile formed as described in Specification 712,105.