A Computerized Research Microdensitometer for Spectrographic Data Analysis

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Abstract
A research grade microdensitometer has been modified and updated with a linear optical encoder to monitor and control accurately photographic plate position and digitized read out of density data. This measurement system is fully interfaced to a Data General time-shared computer network. Plate position is controlled to within ±0.0001 in. (0.0025 mm) via a closed-loop computer, stepper motor, and incremental linear optical encoder system. Plate movement and density sampling are under computer control with resulting data stored on disc memory for later analysis. Program techniques, including error analysis, have been developed to determine unknown wavelengths to within ±0.006 Å from spectral dispersion data fit to third-order polynomials. Analytical implications, especially relating to sequential multi-element analysis, are discussed. The completed instrument may be applied to a variety of spectroscopic and nonspectroscopic problems.