Milestone developments of liquid lenses

The development of liquid zoom lenses is reviewed, ranging from pressure force lenses to liquid-air interface lenses controlled purely electrically, to sealed solution-oil interface lenses controlled by the convenient method of electro-wetting, and finally to advanced lenses that are capable of self-adjustment of the optical axis. An advanced type of liquid lens will be described in detail, covering its construction, operation, automatic adjustment of its optical axis, and its other excellent performance characteristics.