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microdensitometer(mÿ-kroh-den-să-tom -ĕ-ter) An optical instrument that measures and records small changes in the transmission density on a photographic plate, such as the faint features in a spectrum. The plate, mounted on a carriage, is moved through a light beam. A photomultiplier measures the amount of light transmitted by the plate and the output is fed to a chart recorder or computer.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006
A high-sensitivity densitometer used in spectroscopy to detect spectrum lines too faint on a negative to be seen by the human eye.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.