Variable focus lens

Abstract

The invention relates to a variable focus lens (10), comprising a rigid ring (22), a flexible membrane (20) attached to the front surface of the ring, a rigid transparent front cover (40), attached to the flexible membrane (50), and a rigid rear cover (20) on the rear surface of the ring (22). A cavity (60) is formed between the flexible membrane (50) and the rear cover (20), and the cavity is filled with a liquid. The amount of liquid in the cavity can be varied to vary the curvature of the flexible membrane and so vary the optical characteristics of the lens. The rear cover can be integral with the ring, or formed separately. Further, a second flexible membrane can be positioned between the rear cover and the ring. The various parts of the lens can be held together by adhesive.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application is a continuation of U.S. application Ser. No. 12 / 091,934, filed on Oct. 27, 2006, now allowed, which claims priority to Great Britain Patent Application Nos. 0522030.6, filed Oct. 28, 2005 and 0613688.1 filed Jul. 10, 2006, the contents of all of which are incorporated herein by reference in their entirety.BACKGROUND[0002]1. Field[0003]The present invention relates to a variable focus lens, and more particularly to a variable focus lens of simple construction suitable for mass-production. Variable focus lenses are well known. They normally consist of a liquid-filled chamber, at least one face of which is formed by a transparent flexible membrane. As liquid is introduced into or removed from the chamber, the flexible membrane is deformed, and its curvature accordingly changes. This change in curvature leads to a change in the optical characteristics and power of the lens. The power of the lens can thus be varied simply by ...

AI Technical Summary

Benefits of technology

[0007]In the lens of the invention, the flexible membrane is held between the ring and the front cover, which may be formed with flat faces. This places less stringent requirements regarding tolerances on the parts of the lens, and so simplifies manufacture. Further, there is a wider choice of materials from which the lens can be formed.

[0008]In a preferred form, the rear cover and the ring are formed integrally, for example by moulding as a single piece. This reduces the number of steps required to assemble the lens. However, this is not a necessary feature, and in an alternative form, the rear cover is formed separately from the ring, and is attached to the rear surface of the ring.

[0010]Further, it will be appreciated that in all of these lenses, the flexible membranes are protected from damage, as they are behind rigid covers. The durability and toughness of the lenses is thus improved.

[0013]In a further preferred form, two or more septa are provided. This makes it easier to fill the cavity, as a needle pushed through one septum can be used to introduce liquid, and a needle pushed through the other septum can be used to withdraw air.

[0015]It is also preferred for the refractive index of the liquid in the first cavity to be approximately equal to the refractive index of the material from which the rear cover is formed. This reduces the visibility of any flaws, scratches and the like on the inside of the rear cover.

Problems solved by technology

However, this design places certain requirements (such as ductility) on the materials used to form the rings, and also requires strict tolerances in the manufacturing of the rings.

Further, each lens is formed from a large number of separate parts, which complicates manufacture.

This reduces the visibility of any flaws, scratches and the like on the inside of the rear cover.

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