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. Gaze trackers may be used to make interpupillary distance measurements and eye relief measurements. Adjustments to the positions of the optical assemblies may be made by the motors based on the interpupillary distance measurements and eye relief measurements.

Abstract: A head-mounted device may include optical assemblies for presenting images to a user. Actuators may be used to adjust the spacing between the optical assemblies to accommodate different interpupillary distances. Upon detection of a power-down event or drop event, the device may be placed into an impact-safe mode. During the safe mode, the optical assemblies may be moved to predetermined impact-safe positions, brakes such as optical guide rail brakes may be adjusted, cushioning springs may be deployed, clutches may be adjusted, and/or other safety mechanisms may be activated to help protect the optical assemblies or other sensitive components from damage.

Abstract: A system such as a head-mounted device may have left and right displays for displaying images. The images may be presented to left and right eye boxes through left and right fixed (non-removable) lenses and corresponding left and right removable vision correction lenses. The left and right fixed lenses may be supported by left and right fixed lens supports to which the left and right displays are mounted, respectively. To removably attach the vision correction lenses to the fixed lenses, the fixed lens supports and vision correction lenses may be provided with bayonet mounts. The bayonet mounts may have push-and-turn structures such as pins that mate with corresponding slots.

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.