An intensity regulation system for a monochromator

In the investigation of phenomena involving both optical intensity and wavelength, an instrument is often desired which allows one of the quantities to be held constant while the other is varied. A relatively inexpensive system is described which utilizes a commercial grating monochromator and external feedback electronics to regulate the output intensity as the wavelength is varied. In this system, a sample of the output intensity is taken by a photosensor with known spectral response. The output of the photosensor is then compared electronically with that of a pre-programmed function generator which cancels nonlinearities in the photo-sensor. The resulting signal is used to regulate the monochromator light source. System output intensity has been observed to be constant to within five per cent from 475 millimicrons to 800 millimicrons --Abstract, page ii