Abstract: Apparatus for both rotating and translating a scanning mirror is provided. The mirror is carried by a hollow shaft which is rotated by air under pressure. Such air is fed into the hollow cavity in the shaft and escapes through a turbine which is a part of the shaft. The turbine rotates the shaft. The shaft is supported by air bearings from a surrounding housing. That housing is supported by a slide which is pneumatically supported from a stationary rail. The slide is translated parallel to the axis of the shaft by a lead screw driven by a stepping motor. The lead screw cooperates with a lead screw nut which is affixed to said slide. The aforesaid arrangement provides great accuracy and minimum instability during the scanning operation.

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.