Indexing mechanism

摘要

An indexing mechanism comprises a disc (2) rotatable about a central axis, suitable for holding objects such as lenses. Detents (8) are provided on the disc which interact with a pawl (14) on a fixed surface adjacent the disc (2). When the disc rotates in a first direction the pawl (14) is deflected by each passing detent (8), returning to its rest position when the detent (8) is passed. When the disc is rotated in an opposite direction, the pawl (14) abuts a detent (8) to define an index position. The disc is driven or biased in this direction to retain this position. A stop (10) may be provided on the disc (2) adjacent each detent (8) which defines the position of the pawl (14) relative to the disc (2). The disc (2) may be driven by a motor (12) and drive means. An alternative system may be used in which lever (40) interacts with a plurality of protrusions (46) on the disc to rotate the disc in a first direction or bias the disc in a second direction so that the pawl (14) abuts a detent (8).