Abstract: A variable focus lens apparatus for use in spectacles or the like is formed from a fluid envelope comprising two sheets, at least one of which is flexible. The flexible sheet is retained in place between two rings, which are directly secured together. This may be by means of adhesive, ultrasonic welding, or any similar process. If the other sheet is rigid, then it may be directly secured to one of the rings.

Abstract: A variable focus lens apparatus for use in spectacles or the like is formed from a fluid envelope comprising two sheets, at least one of which is flexible. The flexible sheet is retained in place between two rings, which are directly secured together. This may be by means of adhesive, ultrasonic welding, or any similar process. If the other sheet is rigid, then it may be directly secured to one of the rings.

Abstract: A variable focus lens comprises first and second transparent, flexible membranes (2) which are tensioned and which define a cavity (30) in which a transparent, silicone oil (4) is sealed. Adjustment of the pressure or volume of the oil in the cavity changes the focal length of the lens. To fabricate the lens, the periphery of each membrane (2) is engaged between two rings (8, 10; 10, 12) of a set of three interengaging rings (8, 10, 12). The interengaged rings are crimped together to tension the membranes (2) and seal the cavity (30).

Abstract: An apparatus for detecting the presence of a target material such as a multicomponent gas is disclosed. The apparatus includes a source of electromagnetic radiation and a device for dispersing the radiation into different frequency bands for targeting the material at different wavelengths corresponding to absorption bands in the material. Spaced apart optoelectric transducers detect the different frequency bands. A processor detects the changes in the output of the transducers occasioned by partial absorption of the electromagnetic radiation from the source by the target material. Processing means also compensates for temperature variations in the source.

Abstract: An adjustable liquid lens or mirror has a chamber delimited by a flexible membrane surface, which flexible membrane is supported in tension between a pair of resilient rings. A first fluid medium fills the chamber which, in the case of a lens, has a different refractive index from that of a second fluid medium contacting the other side of the flexible membrane. An annular support member for the flexible membrane comprises relatively movable first and second component parts, the first and second component parts of the support member being adjustably linked in a fluid-tight manner whereby the volume of the chamber is adjustable by moving one component part of the support member relative to the other in such wise as to vary the pressure in the first fluid medium and thereby to alter the shape of the said membrane surface.