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The Application of a Kalman Filter to Improve the Optical Monitoring System of a Vacuum Deposition Process

M Nixon

PhD Thesis - The University of Reading, Department of Cybernetics (1983)


The optical reflectance excursions during vacuum deposition of infrared coatings and multilayer thin-film filters are highly nonlinear and corrupted by noise. A Kalman filter has been applied, using a modern microprocessor-based computer, to interpret these excursions and thus to produce on-line estimates of deposition rate and thickness. The estimation proved sufficiently reliable to "navigate" regular manufacture as controlled by a skilled operator, and subsequently to control the deposition of filters without human interpretation or intervention whilst maintaining exemplary product quality. Optical control by means of this Kalman filter application is therefore considered suitable as a basis for the automated manufacture of infrared coatings and multilayer thin-film filters.