Abstract: A thermal imaging system generating high resolution images at commercial T.V. rates while scanning relatively large apertures comprising a facet mirror mounted for rotation about a rotational axis, a framing mirror mounted on axis for oscillation about an oscillatory axis, and an off axis, magnifying relay lens system for reimaging the pupil at the facet mirror onto the framing mirror so that there is a real pupil at the framing mirror with no image artifacts. The relay lens system is located in the optical path between the facet mirror and the framing mirror. The relay lens system defines an image plane and at least one point blackbody is located substantially at the image plane for purposes of providing a video reference and calibration. A detector receives the focused beam of radiation reflected by the facet mirror for subsequent display on commercial T.V. monitors. The detector shares vacuum with the high-speed scanner.