Electronic devices with compound planetary gearboxes

Abstract

Electronic devices such as head-mounted electronic devices may include displays for presenting images to users. To accommodate variations in the interpupillary distances associated with different users, a head-mounted device may have left-eye and right-eye optical modules that move with respect to each other with actuators. The actuators may include motors, compound planetary gearboxes, and lead screws that move the optical modules. In particular, the compound planetary gearboxes may have high reduction ratios to reduce the size of the actuators while providing sufficient torque to move the optical modules. The compound planetary gearboxes may include first and second planet gears coupled to common shafts, and carriers that carry the planet gears and that drive the lead screws. The second planet gears may have smaller diameters than the first planet gears, and the second planet gears may mesh with teeth on a ring gear, to provide the high reduction ratio.