Tradeoff studies were made and tests were performed on the optical scanning system of a linear microdensitometer. The final system includes a laser source, an illuminator system capable of producing a 1 m spot on the film, a wide anglecollection system (NA > 1.0), and a photodiode detector. Performance of the optical system was verified by breadboard tests. The test results showed a square wave response of 99 percent at 200 kp/mm and greater than 90 percent at 500 Qp/mm. Tests performed with the 1µm scanning spot and NA 1.0 collection indicate that the optical system was linear (as measured by nonresponse to a phase target) for object frequencies up to 500 Qp/mm. The photometric precision was +0.01 D from 0 D to 2 D and +0.02 from 2 D to 4 D. These precisions were obtained at scanning speeds up to 8000 samples/sec.
David J. Cronin,
George O. Reynolds,
"Optical Design Considerations and Test Results for a Linear Microdensitometer," Optical Engineering 12(6), 126201 (1 December 1973). https://doi.org/10.1117/12.7971662