Deformable Membrane Assemblies

Abstract

A deformable membrane assembly 1 comprising a fixed support; a fluid-filled envelope, one wall of which is formed by an elastic membrane 8 that is held under tension around its edge by a flexible membrane supporting member 2, 10 , the membrane supporting member being coupled to the fixed support at a plurality of discrete control points 120 round the supporting member by respective engaging members for controlling the position of the membrane edge relative to the fixed support at the control points, and the member being unconstrained between said control points; and a selectively operable pressure adjuster for adjusting the pressure of the fluid within the envelope, thereby to adjust the shape of the membrane; wherein at least three control points are provided which are situated round the membrane edge at spaced locations on the member that are selected to increase the energy of the lowest order out-of-plane bending modes of the supporting member in response to loading through tension in the membrane that do not have a node round the whole supporting member. The invention further provides an article of eyewear comprising a deformable membrane assembly of the types described.

1 . A deformable membrane assembly comprising:
 a fixed support;   a fluid-filled envelope, at least one wall of which is formed by an elastic membrane that is held under tension around its edge by a flexible membrane supporting member, the membrane supporting member being coupled to the fixed support at a plurality of discrete control points round the supporting member by respective engaging members for controlling the position of the membrane edge relative to the fixed support at the control points, and the member being unconstrained between said control points; and   a selectively operable pressure adjuster for adjusting the pressure of the fluid within the envelope, thereby to adjust the shape of the membrane;   wherein at least three control points are provided which are situated round the membrane edge at spaced locations on the member that are selected to increase the energy of the lowest order out-of-plane bending modes of the supporting member in response to loading through tension in the membrane that do not have a node round the whole supporting member.   
     
     
         2 . A deformable membrane assembly comprising:
 a fixed support;   a fluid-filled envelope, at least one wall of which is formed by an elastic membrane that is held under tension around its edge by a flexible membrane supporting member, the membrane supporting member being coupled to the fixed support at a plurality of discrete control points round the supporting member by respective engaging members for controlling the position of the membrane edge relative to the fixed support at the control points, and the member being unconstrained between said control points; and   a selectively operable pressure adjuster for adjusting the pressure of the fluid within the envelope, thereby to adjust the shape of the membrane;   wherein at least three control points are provided which are disposed at locations round the edge of the membrane selected to allow the membrane to deform upon adjusting the pressure of the fluid in accordance with one or more desired modes, but to inhibit displacement of the membrane edge in accordance with one or more other undesired modes.   
     
     
         3 . A deformable membrane assembly comprising:
 a fixed support;   a fluid-filled envelope, at least one wall of which is formed by an elastic membrane that is held under tension around its edge by a flexible membrane supporting member, the membrane supporting member being coupled to the fixed support at a plurality of discrete control points round the supporting member by respective engaging members for controlling the position of the membrane edge relative to the fixed support at the control points, and the member being unconstrained between said control points; and   a selectively operable pressure adjuster for adjusting the pressure of the fluid within the envelope, thereby to adjust the shape of the membrane;   wherein at least three control points are provided which are situated at locations round the edge of the membrane selected to so as to induce one or more desired membrane bending lower order modes, while suppressing one or more undesired higher order modes.   
     
     
         4 . The deformable membrane assembly as claimed in  claim 1 , wherein the control points are situated to suppress at least the lowest order undesired mode. 
     
     
         5 . The deformable membrane assembly as claimed in  claim 1 , wherein the control points are positioned so as to allow the membrane to deform in accordance with at least the second order desired bending mode and optionally one or more selected other modes. 
     
     
         6 . The deformable membrane assembly as claimed in  claim 1 , wherein the desired modes of deformation of the membrane may be described by one or more Zernike polynomials, preferably the Arizona Fringe coefficient form of Zernike polynomials. 
     
     
         7 . The deformable membrane assembly as claimed in  claim 1 , wherein the control points are positioned to allow at least spherical deformation and optionally spherical and selected second, third and/or fourth order Zernike polynomials to introduce one or more deviations from spherical selected from astigmatism, coma and trefoil. 
     
     
         8 . The deformable membrane assembly as claimed in  claim 1 , wherein the membrane is non-circular. 
     
     
         9 . The deformable membrane assembly as claimed in  claim 1 , wherein the bending stiffness of the supporting member varies round the supporting member. 
     
     
         10 . The deformable membrane assembly as claimed in  claim 1 , wherein each control point may be angularly spaced from its adjacent control points by an angle of 30-120° about the centre of the membrane. 
     
     
         11 . The deformable membrane assembly as claimed in  claim 1 , wherein the adjuster is selectively operable for injecting or removing fluid from the envelope for controlling the pressure of fluid in the envelope. 
     
     
         12 . The deformable membrane assembly as claimed in  claim 11 , wherein each of said control points comprises a hinge point at which the membrane supporting member is hinged by the respective engaging member to the fixed support. 
     
     
         13 . The deformable membrane assembly as claimed in  claim 1 , wherein said adjuster is selectively operable for adjusting the volume of the envelope thereby to control the pressure of the fluid in the envelope. 
     
     
         14 . The deformable membrane assembly as claimed in  claim 13 , wherein at least one of the control points comprises an actuation point, the adjuster being connected to the membrane supporting member at the or each actuation point by the respective engaging member for controlled displacement of the supporting member relative to the fixed support for adjusting the volume of the envelope. 
     
     
         15 . The deformable membrane assembly as claimed in  claim 14 , wherein the position of one or more actuation points is selected to control displacement of the support member in accordant with one or more desired bending modes, especially lower order modes. 
     
     
         16 . The deformable membrane assembly as claimed in  claim 14 , wherein at least one other of the control points may comprise a hinge point at which the membrane supporting member is hinged by the respective engaging member to the fixed support. 
     
     
         17 . The deformable membrane assembly as claimed in  claim 1 , wherein a control point is situated at or proximate each location round the supporting member where the intersection of the outline shape of the edge of the membrane with the one or more desired modes of deformation of the membrane exhibits a turning point in the direction of the force or reaction applied to the supporting member by the respective engaging member, between two adjacent points where the profile of the supporting member exhibits an inflection point, or a turning point in the opposite direction. 
     
     
         18 . The deformable membrane assembly as claimed in  claim 17 , wherein said control points further comprise at least one additional hinge point situated at a point on the supporting member where the supporting member remains substantially stationary as the pressure in the envelope is adjusted. 
     
     
         19 . The deformable membrane assembly as claimed in any preceding  claim 1 , wherein said membrane is generally elongate, being longer on one axis than on an orthogonal axis, which axes pass through the centre of the membrane, and having two opposite long sides that extend across said orthogonal axis, and wherein the control points comprise at least one actuation point on the supporting member proximate one end of the one axis, at least one hinge point proximate the other end of the one axis and at least one intermediate hinge point on one of the long sides of the supporting member intermediate the one end of the one axis and the centre. 
     
     
         20 . The deformable membrane assembly as claimed in  claim 19 , wherein one or more actuation points are provided proximate the one end of the one axis, and at least two intermediate hinge points are situated on the supporting member between said one or more actuation points at the one end of the one axis and the centre of the membrane, one on one of the long sides of the supporting member and the other on the other long side. 
     
     
         21 . The deformable membrane assembly as claimed in  claim 1 , wherein the membrane is pre-tensioned on the membrane supporting member. 
     
     
         22 . The deformable membrane assembly as claimed in  claim 1 , wherein one or more bending controllers are provided to control the bending or other deformation of the membrane supporting member in response to the surface tension in the membrane. 
     
     
         23 . An article of eyewear comprising a deformable membrane assembly as claimed in  claim 1 .