Measurement of the MTF and MRTD for focal plane arrays

The use of focal plane arrays (FPAs) in infrared imaging systems is becoming increasingly important. There are problems, however, in measuring their modulation transfer function (MTF) and their minimum resolvable temperature difference (MRTD) since these performance measures vary with the exposition of the image on the FPA. This limitation has been overcome through the introduction of a discrete MTF for these imaging systems using discrete Fourier transform techniques. This discrete MTF is a unique function of spatial frequency and has been measured using a microscanned discrete line spread function. It has also formed the basis of an objective MRTD, the results of which have been compared with subjective measurements.