Automated Threshold Data Generation.
Final technical rept. 19 Jan-19 Dec 72,
TECHNICAL OPERATIONS INC BURLINGTON MA
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In this program an automated simple and repeatable technique was developed to determine a system noise threshold curve for use in optical system performance evaluation. The approach to this problem was to scan a uniformly exposed area of film with a microdensitometer using various sized scanning apertures. A statistical analysis of the measured film transmission fluctuations in the computer is used to generate the minimum visibility as a function of spatial frequency. Aerial image modulation curves for various films 2401, 8403, 3414, 2430, 1414, and SO-192 were obtained by using this technique, and the sensitivity of the threshold to various parameters such as mean density, film gamma, and processing film age, was determined. It was also determined that the PDS microdensitometer has more noise that the Joyce-Loebl microdensitometer and hence PDS AIM data required a lower signal-to-noise ratio. The PDS instrument was more accurate at high frequencies, however. The repeatability of AIM data was better for the Joyce-Loebl than for the PDS machine. This data reduction technique has the advantage of generating noise data indicative of a portion of the film format on a film of interest. It also allows one to use MV data and work in density image space rather than effective exposure or aerial image space. This avoids effective exposure and film modulation transfer function ambiguities.
- Cartography and Aerial Photography