A rotary stage is a component of a motion system used to restrict an object to a single axis of rotation.
In common usage, the term rotary stage may or may not also include the mechanism by which the angular position of the platform is controlled relative to the base.
A rotary stage built with this type of bearing is usually only used for coarse positioning and is adjusted manually simply by turning the platform.
Typically, a pair of bearings is used and they are preloaded to take up any slack which could result in the stage platform lifting relative to the base.
The platform may have index marks for setting different angular positions relative to the base.
A locking mechanism may be provided to fix the platform to the base at the desired position.
When precise angular positioning over only a small total angle is required, a linear actuator (either manual, or motorized) may be used.