Abstract: Wide field of view correction for wide spectral band imaging systems is achieved in reflective versions of the Schmidt and Schmidt-Cassegrain systems by the use of a fold mirror which also serves as a corrector plate. A method for fabricating the corrector plate is described.

Abstract: A scanning system comprising input optics including an afocal telescope, output optics including an imaging lens and a linear spaced array of detectors, a scanner including a hollow inwardly reflecting polygonal prism rotated about its longitudinal axis, which is subtantially parallel to the axis of the input optics, and two folding mirrors which are contained within the outline of the prism, and with respect to which the prism rotates.

Abstract: An improved, compact optical system comprising a concave primary mirror and a convex secondary mirror. The primary mirror converges radiation to the secondary mirror. The secondary mirror comprises a lens having a first and a second surface. The second surface is coated with reflective material. The radiation received by the lens is refracted at the first surface, reflected back from the second surface, and then refracted once again by the first surface. The first and second surfaces have a shape for providing control of field curvature.

Abstract: An optical system having a dual field of view. The system includes a wide-angle objective comprising a lens, a concave primary mirror, and a movable convex secondary mirror having a first position and a second position. When in the first position, the secondary mirror permits the wide-angle objective to focus radiation. When in the second position, the secondary mirror prevents radiation from being focused by the wide-angle objective. The combination of the secondary mirror when in the second position and the primary mirror comprise a narrow-angle objective with the primary mirror converging radiation to the secondary mirror and the secondary mirror focusing radiation. Thus, the optical system has a wide-angle field of view whenever the secondary mirror is in the first position and a narrow-angle field of view whenever the secondary mirror is in the second position.