Abstract: A rotating polygonal mirror which scans a target both vertically and horizontally in a raster scan electromagnetic illumination or detection system is disclosed. The rotating mirror includes a plurality of individual planar facets disposed around the periphery of the mirror. The facets are arranged so that each of them intersects the principal axis of rotation of the mirror at a predetermined angle characteristic of the particular facet. A perpendicular to each facet drawn from the substantial center of the facet in its horizontal dimension passes through the axis of rotation. By this geometry, a target is scanned by horizontal scan lines in a manner which is equivalent to prior art mirrors having a plurality of facets all of which are parallel to the axis of rotation, and the vertical stepping of the raster scan is accomplished by stepping between adjacent facets of the mirror having distinct angles of intersection with the axis of rotation.

Abstract: Apparatus for storing and retrieving large volumes of microfiche data, and a related method for its operation. The apparatus includes a number of conventional microfiche storage carousels, all mounted on a rotatable turntable to provide the increased storage capacity. Upon selection of a particular fiche for display, the turntable is rotated, if necessary, in an optimum direction and at an optimum speed, until the selected carousel reaches an operative position with respect to a retrieval station, which is then moved to an operative position with respect to the carousel for withdrawal of the selected fiche within the carousel.