Abstract: Images of two fields of view of one or two scenes in a radiation sensor are generated by use of a single detector and common signal process circuitry. The two imaged fields of view, typically a narrow view and a wide view, are provided by two independent telescopes (18, 20), and are combined by use of a field-of-view switch (32) comprising a chopper wheel (34) or an optical switch in synchronized operation with a mirror scanner (22). The same field-of-view switch is employed in performing detector non-uniformity correction functions, such as automatic responsivity control and direct current restoration. Folding optics couples scanned radiation from the scanner to the switch. An additional field of view may be introduced by displacing a folding mirror of the folding optics. Also, a portion of a reflecting surface of the switch may be tilted to admit a reference beam of radiation useful in performing the functions of responsivity control and D.C. restoration.