The Specification of Imaging Properties by Response to a Sine Wave Input

The imaging properties of an optical system can be in many cases completely specified by a function of a single variable. A convenient function is the response to a sine wave test pattern as a function of “frequency,” i.e., lines/mm. The difficulty of experimentally providing such a test pattern can be avoided by measuring the response to a square wave (bar pattern) and calculating by a simple formula the corresponding sine wave response factor. The convenience of the sine wave response factor in calculating system performance is illustrated by application to a fluoroscopic imaging system.