Original name record: ADLENS LIMITED

A hybrid injection-compression variable focal power optical element comprising a fluid-filled envelope having a rigid first wall () and a second wall opposite the first wall which comprises a distensible membrane () held by a peripheral support ring (), the first and second walls being coupled together to permit movement of the peripheral support ring towards or away from the first wall, the envelope being filled with an incompressible fluid (); at least one spacing control device () for controlling the spacing between the peripheral support ring and the first wall; and an electronically operable injector () for introducing more or withdrawing some of the fluid from the envelope via a port (); whereby the focal power of the optical element is continually adjustable in use by controlling the spacing between the support ring and first wall and/or the volume of the fluid in the envelope. Also disclosed are a variable focal power optical device () comprising such a hybrid injection-compression optical element and an electronic control system () and an augmented reality headset comprising at least one group of optical elements including at least one such hybrid injection-compression optical element, a waveguide interposed therebetween for displaying a virtual image and an electronic control system.