Abstract: A system for tuning an imaging sensor adapted for use with an electromagnetic imaging sensor having a focal plane array of detectors. The inventive system includes a target slide for providing a simulated far field target. A translation stage adjusts the position of the target slide relative to the imaging sensor. The sensor has a focal plane and a lens disposed between the array and the target slide. A computer connected to the imaging sensor measures an output of the focal plane array at each of a plurality of positions of the target slide. The computer provides a signal representative of an optimal distance between the lens and the array in response to the output of the focal plane array of the sensor. In the illustrative embodiment, an electromagnetic energy source, a collimator, and a slit target slide provide a first strip of collimated electromagnetic energy.