GB774476A - Improvements in or relating to spectrometers - Google Patents

Abstract

774,476. Spectrometers. TOUVET, G. April 22, 1953, No. 11010/53. Addition to 774,473. Class 97(1) [Also in Group XL(b)] In an emission spectrometer an electric discharge takes place between electrodes of or in the substance under examination this discharge being produced by radio frequency currents between the electrodes. Radio-frequency excitation enhances the production of light in certain parts of the spectrum as is explained in Specification 774,475. As shown the discharge tube 11 containing the electrodes under examination is energized by a radio frequency oscillator 10, the output from the source being focused by a lens 13 on to a slit 14 which lens is the focal plane of a collimating lens 15. The light proceeding from the lens is dispersed by a prism 16 and then further dispersed by a lens 17. A further slit 18 then isolates part of the spectrum which is concentrated by a lens 19 on to a photo-electric cell. This cell may be of the multiplier type. The output of the cell is fed to a radio-frequency amplifier 21 feeding the " Y " plates of a cathode ray tube 22. The spectrum is scanned across the slot by a motor 16 which rocks prism 16 and drives a potentiometer arm to give a gradually increasing voltage to the " X " plates of the tube. Thus the response of the photo-cell is plotted against wavelength on the screen of the cathode ray tube. The amplifier 21 may be tuned to a harmonic of the oscillator frequency. The radio-frequency oscillation may be applied in the form of discontinuous wave trains or may consist of recurring direct current pulses including transients as described in Specification 774,475 [Group XL(a)]. The light source may be arranged to produce a substantially point source by means of a distorting lens (Fig. 4, not shown). A pair of light sources may be compared by means of a rotating mirror driven intermittently by gearing from motor 28, this mirror being arranged to reflect light to the spectrometer from each source in turn. Alternatively the two sources may be mounted on a rotating platform so that each is presented in turn to the spectrometer. The two samples to be compared are connected in series during test. By utilizing electronic metal and a cathode ray tube screen of,high persistance the emission spectra of the two samples may appear side by side on the screen. Specification 774,741 [Group XL(b)] also is referred to.