GB571912A - Improvements in or relating to liquid lenses - Google Patents

Abstract

571,912. Lenses. DESSAUER, F. May 18, 1942, No. 6727. Convention date, May 25, 1941. [Class 97 (i)] A liquid-filled lens comprises one or more flexible membranes, of high-polymer transparent materials such as vinylic or acrylic resins or cellulose esters, forming one or more chambers filled with liquid of suitable refractivity, the focus being adjusted by applying suitable pressure to the liquid by means of a pump, together with means to maintain the amount of contained liquid constant after adjustment so that the membranes retain their adjusted shape and do not undergo the further deformation which occurs when a constant pressure is maintained on the contained liquid, owing to their imperfect elasticity. The lens shown comprises a single membrane 4. forming, together with a glass plate 1, a chamber 5 containing liquid to which pressure is applied by a pump by way of a tube having in it a cock 8 which is closed when the desired focus is attained in order to maintain the volume of the enclosed liquid constant. The cock 8 may be replaced by a non-return valve which prevents outflow of the liquid, a separate cock being provided to allow this to occur. The lens may comprise a number of membranes forming chambers containing liquids of different refractivities. Concave lenses may be produced by applying suction to a chamber formed between membranes or pressure from without. By employing liquids of different refractivity inside and outside the membrane-bounded chamber, unsymmetrical distortion of the membranes due to weight of liquid on one side when the axis of the lens is horizontal may be avoided. The curvature assumed by the membrane may be controlled by using one having an initial curvature of a thickness varying radially, or by suitable curvature of the contact surfaces of the packing ring 6. The liquid or membranes may be coloured to form light filters, and the liquid may be a solution, the optical properties of which may be varied by altering the concentration.