Design Study for a New Generation Microdensitometer.
Abstract
Tradeoff studies and tests on the various subsystems of a microdensitometer have resulted in a recommended design configuration for a New Generation Microdensitometer. The photometric subsystem includes laser sources suitable for color operation, an illumination system capable of producing a 1 micrometer spot on the film, a wide angle collection system (NA = 1.0), a photodiode detector, and digital density conversion. Performance of the photometric system was verified by breadboard tests. The results include an MTF (square wave response) of 99% at 200 lp/mm and 90% at 500 lp/mm, and linearity (object independence) to greater than 400 lp/mm. The photometric precision is + or - 0.01 D from 0 D to 2 D and + or - 0.02 D from 2 D to 4 D. These specifications are attained at scanning speeds up to 8000 samples per second. A two beam optical system and automatic focus control ensure photometric repeatability. The two axis stage is driven by phase-locked loop servos incorporating interferometric position sensors. The servos permit scanning at skew angles obviating stage rotation. The stage subsystem is precise to within + or - 0.5 micrometer over 5 inches of travel. Stage speed is variable from 4 mm/sec to 400 mm/sec. Human factors features include rapid target acquisition by virtue of a viewing system with magnification variable from 12X to 250X and simplified operator control through a CRT graphic terminal. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 1973
- Accession Number
- AD0910009