1. Multispectral imaging apparatus comprising a wavelength-independent focus reflective optical system for receiving visible and infrared radiation from a scene and for focusing the visible and infrared radiation at a common focal plane; detector means responsive to both the visible and the infrared radiation focused at the common focal plane, the detector means providing first and second signals representative, respectively, of the visible and the infrared radiation received by the detector means; and means responsive to the first and second signals for displaying a composite image of the scene, the composite image comprising a black and white visual image of the scene with portions of the image highlighted in color in accordance with the infrared radiation received from corresponding portions of the scene.