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Liquid crystal lenses to make phones more efficient

The secret of the EvoSens lens is they have used a novel electrode structure which consumes less power, making it perfect for smartphones.
The secret of the EvoSens lens is they have used a novel electrode structure which consumes less power, making it perfect for smartphones.

A new type of lens could make the batteries in your smartphone and tablet last longer, and it’s based on liquid crystal.

‘Our lenses don’t need a lot of power to work, especially in comparison to classical lenses used in mobile phone cameras,’ explained Dr Nicolas Fraval, research and development engineer at EvoSens, a French optical engineering company.

‘The technology they (currently) use is well controlled, but its main inconvenience is its electrical power consumption.’

Battery life is a big issue in consumer technology at the moment, with gadgets such as smartphones and tablet computers having to be charged often. While manufacturers are trying to improve batteries, another approach is to reduce the power consumption of components like lenses.

Most lenses used in current optical technologies are made of glass or plastic, and to adjust the focal length and focus them, the position of the optical elements in the lens relative to each other is changed.

However, lenses found in nature focus in a completely different way. For example, your own eye focuses by changing the shape of the cornea and its refractive index. Deformable lenses based on the principles seen in nature are now being developed. These lenses are much easier to shrink than mechanical lenses, making them useful for many applications.

Electrode structure

Liquid crystal lenses contain a layer of liquid crystals that change orientation when a voltage is applied to them, which changes the refractive index of the lens. By adjusting the voltage, the lens can be focused or ‘tuned’.

‘Our lenses don’t need a lot of power to work, especially in comparison to classical lenses used in mobile phone cameras.’

Nicolas Fraval, research and development engineer, EvoSens

They were first developed in the 1970s, but early versions required high voltages to control their focal length. The secret of the EvoSens lens is they have used a novel electrode structure which uses less power.

EvoSens’ micro-lens has many other potential applications outside of consumer electronics. ‘It could be used in all applications that need a small lens, like endoscopy and beam shaping for lasers – you can change the shape of the laser beam by tuning the lens,’ Dr Fraval said.

‘Another example is fibre optic communications. When you want to put light in an optical fibre, you need to focus the light on the end of the fibre, so it can be useful to have a small tunable lens that you can use to redirect the light.’

One of the big problems that the company faced was finding a way to mass-produce their new lens. ‘I started to develop this technology in a local laboratory and we made some prototypes but when we wanted to develop an industry process we didn’t have the facilities,’ Dr Fraval said.

‘For the next step, to make a commercial product we needed some help and facilities that we don’t have. In order to go to mass production we needed a process that was more repetitively accurate and access to more expensive equipment.’

That’s where the EU-funded ACTMOST project came in. It brought together universities from across Europe to give small companies such as EvoSens access to advanced optics technology. ‘ACTMOST gave us the facilities and helped to develop a production prototype,’ Dr Fraval said.

The pilot ended last year, but it will now be followed up with a bigger project called ACTPHAST.

‘ACTPHAST expands the number of technology platforms and now also embraces speciality fibre technology and photonic integrated circuits in different materials,’ explained Prof. Hugo Thienpont, coordinator of ACTMOST and now ACTPHAST, from the Vrije Universiteit Brussel (VUB) in Belgium.

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