The design and development of a scanning monochromator-based optical spectrum analyser for use in the near-ultraviolet to near-infrared spectral region

The design and development of an inexpensive and versa tile optical spectrum analysis system is described from conception through to commercial production. Based on a novel scanning monochromator, which uses a continuously rotating diffraction grating as the wavelength dispersing component, the system is capable of rapid spectral scanning in the near ultraviolet to near infrared spectral region. A range of optical detectors and gratings may be used to optimise the sensitivity within this wavelength region. The system is presently capable of achieving a 2nm wavelength resolution in the 200nm to 1100nm range and a 5nm resolution in the infrared up to 1800nm. Furthermore the spectral scanning-and-wavelength identification techniques employed make it possible to repeatedly scan a complete UV/visible or near infrared spectrum once every 60ms whilst achieving a wavelength measurement accuracy of 1nm. The spectral data generated by the scanning monochromator may be displayed in real-time on a standard laboratory oscilloscope, plotted on a chart recorder, or monitored at discrete wavelengths on an analogue meter. Alternatively a complete spectrum may be sampled, digitized, and then transferred to a desk top computer for data processing. The latter technique makes it possible for example to rapidly determine the true spectral power distribution of steady state or repetitively triggered flash lamp-sources, and the transmission arid absorbance spectra of samples illuminated at the input. Applications range from the use of the basic scanning monochromator module as an educational tool for illustrating spectral phenomena to science students, to the use of the computerised instrument as part of an industrial measurement, quality assurance, or process-control system. A copy of an article published in 1980 which describes the basic design features of the Mk I optical spectrum analyser system; a copy of a paper given in 1981 by G. Heeke, Univ. of Munster, Fed. Rep. of Germany, illustrating a research application of the basic scanning monochromator; and two data sheets which summarise the specifications of the Mk I and Mk II systems are enclosed in a pocket inside the back cover of this thesis.