Variable focusing power optical devices and an augmented reality headset or helmet incorporating such a device

Abstract

A membrane assembly () for a variable focusing power optical assembly () comprising a distensible membrane () that is held under tension around its periphery by at least one bendable support ring () and one or more curvature controllers () that are mounted to respective discrete sections of the support ring () for actively controlling the curvature of those sections of the ring in a plane (Btz) that is parallel to a z-axis normal to an (x,y) plane which is defined by the un-deformed support ring and tangential (t) to the periphery (boundary B) of the membrane. Also disclosed is a variable focusing power optical assembly () comprising such a membrane assembly, which has a compressible fluid-filled envelope having a first wall formed by the distensible membrane (), an inflexible second wall () opposite the first wall, the support ring () being held at a fixed distance from the second wall at hinge points that are spaced apart around the support ring () and being bendable towards or away from the second wall intermediate the hinge points on the z-axis which is substantially aligned or coincident with an optical axis of the optical assembly (), and a side wall () between the first and second walls that is collapsible to accommodate such bending; wherein the membrane () is arranged to distend in a direction towards or away from the second wall upon bending of the support ring () between the hinge points. In some embodiments, the second wall () may be formed by or supported on a surface () of a rigid body (), and the support ringmay be mounted on the rigid body () by support pins () at the hinge points. Also disclosed is an augmented reality headset or helmet () comprising an augmented reality display module () comprising two such variable focusing power optical assemblies () arrange one in front of the other in optical alignment with a waveguide display () interposed therebetween.