An optical apparatus having a movable member movable with a stepping motor as a drive source, and movement controller for moving the movable member to a set position. The movement controller step-drives the stepping motor in one direction by a first frequency so that the movable member may bear against...http://www.google.ca/patents/US5572270?utm_source=gb-gplus-sharePatent US5572270 - Optical apparatus having a motor control device
