| 摘要 |
This invention relates to a motorised focusing system with an electromagnetically actuated lens drive, for example for use in a photographic camera having an automatic rangefinder. The lens (16) is adjusted axially by the rotation of the lens holder (14) on a fixed support (40). The lens holder is rotated by an epicyclic motor having a stator (46) concentric with the optical axis of the lens with poles (48) which are energised sequentially to cause a hollow armature (36) within the stator to roll eccentrically around a fixed armature support (54). Armature teeth (70) engage teeth (72) on the fixed armature support and armature teeth (78) engage teeth (80) on the lens holder (14), resulting in a speed reduction in the drive to the lens holder. The lens moves incrementally in response to pulses applied to the stator windings, a given number of pulses representing a known amount of axial movement of the lens. |
