Abstract: A scanning system using at least one mirror for scanning material to read (or alternatively to be written upon) with a laser beam is provided. Air under pressure is fed into a hollow shaft and escapes through a turbine on the shaft to rotate the shaft. The shaft is supported by air bearings. The shaft rotates the mirror during scanning. Air pressure escaping from the air bearings is vented to the ambient atmosphere. Two special thrust bearings are provided to improve the stability of the shaft. Each thrust bearing applies a force on the shaft in a direction parallel to the axis of the shaft and opposite to the force applied by the other thrust bearing. Each thrust bearing comprises a cavity in the housing, a flat plate attached to the shaft, and a porous bronze plate between the cavity and the flat plate. The air pressures in the two cavities are separately adjustable to enable the operator to select pressures that provide the system with maximum stability.

Abstract: The transport, that carries the material to be scanned to and from scanning position, is held against its support by suction. After the transport has been moved into scanning position the suction is applied progressively starting at one end of the transport and continuing to the other end. A squeegee roller presses the transport against its support. This roller passes over the portion of the transport to which suction has just been applied, but prior to the time that suction is applied to the next section of the transport.