IR Technology Fundamentals

doi:10.1117/3.2588946.ch3

Book: Testing and Evaluation of Infrared Imaging Systems, Third Edition

Author(s): Gerald C. Holst

Published: 2008

https://doi.org/10.1117/3.2588946.ch3

Author Affiliations +

Abstract

Radiometry describes the energy or power transfer from a source to a detector. When the source size is much larger than the projected area of the detector, the source is said to be resolved or the system is viewing an extended source. Equivalently, the detector is flood-illuminated. The system’s responsivity or signal transfer function (SiTF) applies to a system viewing an extended source. As the source size becomes smaller, the responsivity must be modified by the aperiodic transfer function (ATF). The ratio of the actual response to the ideal response is the target transfer function (TTF). As the source size approaches a point, the target transfer function approaches the point visibility factor (PVF) or ensquared power value.