Proceedings PaperModulation Transfer Function Measurement System (MTFMS): A New Development In Image Quality Measurement
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The Modulation Transfer Function Measurement System (MTFMS) is a microdensitometric system which incorporates solid-state scanning technology to produce data useful for image quality assessment of photographic images. The MTFMS consists of a two-channel microscope system mounted on a moveable-bridge light table. The background illumination is high enough to permit searching of the trans-illuminated specimen, and is augmented with a mechanical tracking light source which provides the illumination required for measurement. The microscope provides a binocular viewing port to the operator and simultaneously images the specimen onto a 100:1 aspect ratio self-scanned photodiode array. The instrument thus simulates a slit-scanning micro-densitometer, but does not incorporate a moving stage. The instrument is largely self-calibrating, keeping track of its own dark current and providing automatic calibration of each individual diode in gain and offset. A focus meter is provided and provision for parfocalization is incorporated. Integration times are selected automatically and data is corrected for these changes. The basic system includes a PDP-11/03 computer and associated equipment in a small rack which serves as a base for the operator terminal. This hard copy device can be used as an output printer as well as an input device and is useful for providing printer plots of output data. Software is provided for special purposes. Detailed testing of the instrument has been performed, demonstrating its densitometric performance and other elements of system quality. The results of these tests are reported.