A compact, optically fast catadioptric imager. In one embodiment, the catadioptric imager of this invention includes a first group of optical elements optically disposed to receive electromagnetic radiation from an object and having positive optical power, a second group of optical elements, optically disposed between the first group of optical elements and an image plane, having at least one optical surface and having positive optical power, a third group of optical elements, optically disposed between the object and the second group of optical elements, having at least one optical surface and having negative optical power, a fourth group of optical elements substantially centered along an optical axis of said second group of optical elements and having negative optical power, and a fifth group of optical elements having positive optical power.