Or relating to variable focusing power optical devices

Abstract

An adjustable fluid-filled lens or minor assemblycomprising a fluid-filled envelope and a supporting structure therefor; the fluid-filled envelope being constituted by a first wall that is formed of a distensible elastic membranehaving an exterior optical surface of variable focusing power, a second wallthat is spaced from the first wall on a z-axis, and a collapsible peripheral side wallthat extends between the first and second walls, and being filled with a substantially incompressible fluid; a membrane holding structurethat is attached to a peripheral edge of membranefor holding the membrane under tension; and one or more selectively operable actuator assemblies r, r, rfor moving one or more corresponding regions of the peripheral edge of the membrane on the z-axis towards and away from the second wallfor controlling the profile of the peripheral edge of the membrane; wherein the or each actuator assembly comprises a connecting memberthat is attached to the membrane or membrane holding structure at a respective actuation point, a linear actuatorthat is mounted to the supporting structure and a linkagethat is connected between the connecting member and an actuation point a, a, aon the linear actuator; wherein the linear actuator is a linear SMA actuator comprising an array of SMA wiresthat are coupled together to work in parallel and which extend transversely of the z-axis, and the linkage is configured for converting linear motion of the actuation point of the SMA actuator in a direction transverse the z-axis to linear motion of the connecting member on the z-axis, thereby to move the corresponding region of the peripheral edge of the membranetowards or away from the second wall