Abstract: A head-mounted device may include optical assemblies for presenting images to a user. Motors may be used to adjust the spacing between the optical assemblies to accommodate different interpupillary distances. The force with which the motors move the optical assemblies towards a central nose bride portion of the device may be limited. The force may be limited using a clutch such as a magnetic clutch or a physical clutch based on structures that decouple from each other to limit the force. The force may also be limited by monitoring the force and halting the motors in response to detection of a given amount of force. Sensor measurements and electrical motor load measurement may be used in measuring the force. If desired, motor operation may be controlled by a user-operated button.

Abstract: A head-mounted device may have a display with pixel arrays that display content for a user. A head-mounted support structure in the device supports the pixel arrays on the head of the user. A left positioner may be used to position a left lens assembly that includes a left lens and a first pixel array. A right positioner may be used to position a right lens assembly that includes a right lens and a second pixel array. Control circuitry may adjust the positions of the left and right lens assemblies using interpupillary distance information. Sensing circuitry such as force sensing circuitry may be used to ensure that the lens assemblies do not apply excessive force on a nose. Force sensors may be included between the lens assemblies and the nose, such as in, on, or adjacent to a nasal flap, or may be coupled to the lens assemblies.