This is the third variant of this article, which was written originally for the December 2013 issue of the Industrial Automation INSIDER Newsletter (www.iainsider.co.uk), an industrial publication which I edit: while not being a typical telescope story, it links in to the original pioneers of 17th Century telescopes.
So what is a liquid lens?
A liquid lens is a very small lens device now commonly used in iPads and mobile phones. The liquid droplet forming the lens has its shape changed electronically, using an electronic control system. This is able to change focal length (to focus) and change optical axis (for optical image stabilization, ie to reduce camera shake effects) – all within a few milliseconds.
The idea for this invention came from research on the phenomenon known as “Electro-wetting” by Professor Bruno Berge, in Lyon, France, with the original patents being issued in 2002. Prof Berge started working on liquid interfaces from 1991 at the Ecole Normale Supérieure in Lyon, in co-operation with the Université Joseph Fourier of Grenoble, where he had two years previously done his PhD. Berge became fascinated by Electro-wetting, a topic first investigated by Gabriel Lippmann around 1900: Lippmann went on to win the Nobel prize for colour photography in 1908.
Berge believed that manipulating the shape of a water drop would also change the way it refracted light, which – for all practical purposes – would turn it into a lens. A drop of water affected by electro-wetting can function as a variable magnifying glass: so two clear, non-miscible liquids of the same density, one being electronically controlled water, can serve as a lens, depending on the curvature of the interface between them. If the second liquid is insulating (an oil), and not affected by the field, this curvature changes when a voltage is applied, enabling an image to be captured and focused (using a standard type of electronic feedback control system). The two liquids are sealed and held in a metal casing that is typically smaller than 10mm in diameter.
Where to use this?
Berge first approached Canon cameras with the invention, but attracted no funding. So with French state funding, and investment fund backing, Berge founded the company VariOptic in 2002. In 2007 they established a production line in China, and in 2009 the first industrial barcode reader with a VariOptic lens appeared on the market. In 2011, VariOptic was acquired by Parrot SA, and will focus on industrial applications: a separate company, Optilux, was formed in the USA to bring the liquid lens technology to smartphones and tablets. In 2013, Berge was selected by the European Patent Office (EPO) as a finalist in their annual review of patented inventions.
Machine vision manufacturer Cognex was an early adopter of the technology. Cognex has equipped both handheld and fixed versions of its barcode ID readers with VariOptic liquid lenses. Lattice Semiconductor Corporation has also announced a new video camera development kit, equipped with VariOptic liquid lens technology.
The name Berge is surely familiar?
The last recent technology step in lens construction was made by Peter Dollond in around 1760, for which he was granted one of the first UK patents: his recorded idea was to produce an achromatic lens by using a doublet (twin lenses nestled together) made of crown and flint glass, to be used as the objective (big) end of a telescope. Things were simpler in those days. His sister, Sarah Dollond, married Jesse Ramsden, and these two men were the best telescope makers in the world, working in the Strand, the Haymarket and then Piccadilly in London between 1760-1800.
One apprentice, who then went on to work for Jesse Ramsden, was called Matthew Berge, and he took over from Ramsden in around 1800 and worked in the Piccadilly premises from 1802-1817. Many years ago he gave your editor, via Ebay, a lovely sample of the type of nautical telescope he constructed there.
Who knows, maybe Prof Bruno Berge comes from the same lineage? Matthew Berge constructed these telescopes for use by the ship’s officers on the wooden sailing ships used by Nelson’s fleet, fighting at Trafalgar against the French and Spanish: what would he think today about these French-developed lenses housed in an iPad?