GB1210556A - Spectrometric grating devices - Google Patents

Abstract

1,210,556. 556. Spectrometers. OFFICE NATIONAL D'ETUDES ET DE RECHERCHES AEROSPATIALES. Feb. 27, 1968 [Feb. 28, 1967; Sept. 21, 1967], No.9525/68. Heading G2J. [Also in Division G1] In a spectrometer in which the input and output slits are replaced by grid-like members having alter - nate zones of different optical properties, e.g. transparent and opaque, the zones are formed by concentric rings divided into equal sectors e.g. divided into two, by a diameter as shown in Fig. 2. In passing radiation 29, into a spectrometer, Fig. 3, having such grid-like members 28, 21, the opaque zones of member 21 being reflective, collimating mirrors 31, 23 and dispersive prism or diffraction grating 25, the image of member 28 is only superimposed on member 21 for the wavelength corresponding to the setting of the dispersive system 25 and so by rotating one of the members 28, 21, at a constant speed and passing the output current from detector 33 through an amplifier 40 tuned to the frequency corresponding to the rate of rotation, the output signal is indicative of the quantity of radiation conveyed at the wavelength to which the dispersive system 25 is adjusted. In a modification in which the member 28 works by reflection instead of by transmission, mirror 30 is omitted and the beam passes along the dotted path. The member 28 or 21 which is rotated is produced by photographing a large-scale drawing so that the boundary lines of the rings are perfectly circular and then the other member 21 or 28 which is fixed is obtained by photographing the first member through the spectrometer. In a further form Fig. 10 (not shown) a double beam spectro-photometer is provided with the grid-like members (107, 116).