A new instrument for displaying spectrophotometric curves almost instantly on a cathode-ray tube is described. The curves are presented on a linear percent transmission scale and a linear wavelength scale. The instrument includes a conventional spectrometer, light source, and photomultiplier combined with an optical means of correcting for the emission characteristics of the source and the spectral sensitivity of the photocathode. A novel sweep circuit, not an oscillator, is utilized to cause the cathode-ray tube spot to move nonlinearly with respect to time so as to compensate for the nonlinear dispersion of the optical system and plot the spectra on a linear wavelength scale. Spectra are displayed at the rate of 60 per sec, with a scanning time of approximately 1/180 sec per spectrum. A synchronous mirror drive in an inverse feedback system incorporating the nonlinear sweep circuit of the indicator is used to produce these results. Spectrophotometric curves may be viewed directly or recorded photographically. Means are described for obtaining diffuse reflectance curves as well as emission spectra with the same instrument. Photographic records of spectra of various types taken with this instrument are shown, and the basic design considerations are briefly discussed.
© 1953 Optical Society of AmericaFull Article | PDF Article
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