Abstract: A hybrid injection-compression variable focal power optical element comprising a fluid-filled envelope having a rigid first wall (310) and a second wall opposite the first wall which comprises a distensible membrane (320) held by a peripheral support ring (330), 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 (365); at least one spacing control device (380) for controlling the spacing between the peripheral support ring and the first wall; and an electronically operable injector (390) for introducing more or withdrawing some of the fluid from the envelope via a port (340); 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.

Abstract: A deformable membrane assembly comprises a deformable membrane (70) in contact with a body of fluid (90) and a selectively operable adjuster for adjusting the pressure of the fluid (90) for causing distension of the membrane (70) in accordance with a predefined form. The membrane is held peripherally by a bendable supporting member (50) that is coupled to a fixed support by at least three engaging members (82) at spaced locations round the supporting member (50). An engaging member (82) is provided at or proximate at least one point round the supporting member (50) where the profile of the supporting member (50) corresponding to the predefined form of the membrane (70) exhibits locally maximum or minimum curvature in the direction of distension of the membrane (70).

Abstract: A deformable membrane assembly comprises a deformable membrane (70) in contact with a body of fluid (90) and a selectively operable adjuster for adjusting the pressure of the fluid (90) for causing distension of the membrane (70) in accordance with a predefined form. The membrane is held peripherally by a bendable supporting member (50) that is coupled to a fixed support by at least three engaging members (82) at spaced locations round the supporting member (50).