<title>Comparison Of Laser Imaging And Thermal Imaging OTFs In The Longwave IR Region</title>

Abstract

The optical transfer function (OTF) of an IR imaging system using coherent (laser) illumination was compared to its performance when imaging with incoherent (thermal) radiation. The imaging system under consideration is a basically passive framing infrared system in which the IR detector is scanned throughout an 8°x10° field of view (FOV) to develop an IR image. The system can be operated in the laser imaging (active) mode by synchronously scanning a CO2 laser beam with the detector. The linespread function method was used to derive the respective OTFs. From the measured lineshape response, the OTF was computed using Fast Fourier Transform (FFT) techniques. These measurements and analyses have shown that (1) the OTF is a valid and reproducible measure of the system's frequency response, even when coherent illumination is used, and (2) the active mode tended to give a reproducibly higher MTF than the passive mode for all wire targets used.