Imaging spatial resolution and instantaneous FOV

For thermal imagers, the IFOV expresses spatial resolution for imaging purposes but not for measurement purposes. Measurement instantaneous field of view (IFOVmeas or MFOV) expresses spatial resolution for measurement purposes. The modulation transfer function (MTF) is a measure of imaging spatial resolution. Modulation is a measure of radiance contrast and is expressed  

Modulation transfer is the ratio of the modulation in the observed image to that in the actual object. For any system, MTF will vary with scan angle and background. A methodology was established by the military and accepted by manufacturers and users alike, to measure the MTF of an imager and, thereby, to verify the spatial resolution for imaging (night vision) purposes. A sample procedure is illustrated in Fig. 3.8 

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