Camera phones focus liquid lenses on expanding market

"The delivery of the Arctic 320 liquid lens is a watershed event that will usher in the mass production of camera-phones using liquid lenses," said John Barber, vice president of business development at Varioptic."Because of their advantages, we expect that liquid lenses will rapidly become the leading system for auto-focus or zooming capabilities in the camera-phone market."

The Arctic 320 liquid lens changes shape automatically, under the influence of a variable voltage but, significantly, without any mechanical manipulation. Acting like the human eye, the lens focus changes with the adjustment of the border between two drops of liquid that form the lens. Varioptic's patented "electrowetting" technology also offers several advantages over traditional lenses, in terms of size, cost, speed, durability and quality.

Since introducing its first patented liquid lenses in 2005, the Lyon-based company has been working closely with Samsung Electro-Mechanics (Semco) to develop auto-focus lenses for camera phones. Varioptic has refined its liquid lenses, expanding the storage temperature range to -40 to 85°C and the operating range to -20 to 60°C, which had been the last hurdles to the acceptance of this technology by the phone handset manufacturer.

Other enhancements in durability, low power consumption and miniaturization enable the Arctic 320 lens to fit within the existing "x-y" camera module footprints, required by the mobile phone market.

"We are expecting to see a camera handset in production later in 2006," Varioptic product marketing manager Philippe Ruffin told optics.org. "Most of the competitive lens technologies are based on mechanical systems so it makes a big difference to have a system with no moving parts."

Varioptic is confident that, in the short term, 50% of the emerging 2M pixel phone camera models will have auto-focus functionality; the other 50% being fixed-focus. But when considering the next-generation 3M pixel camera marketplace, Varioptic expects 100% of that market will comprise auto-focus cameras. Eventually auto-focus could well be standard on all cameras fitted with 2M pixel and higher resolution sensors. And this may not be far off: "At least a couple of 3.2M pixel phone cameras were demonstrated at 3GSM Barcelona 2006," Ruffin said.

"The market trend we are seeing is that the adoption of 2M pixel cameras for phones is ramping up very quickly. Up to now, the handset manufacturers have been considering 1/3inch chip cameras but now the market demand seems to heading towards 1/4inch models - Varioptic's form factor - which really presents us with a good opportunity."

Varioptic lens deformation

The liquid lens, which measures 10.5mm (diameter) by 2.5mm (thickness), is mounted on the top of the camera module's fixed focus lens. To control it requires a relatively high voltage driver (0-60V), which Varioptic has also developed. The driver can be integrated into the printed circuit board. The lens control power need is less than 1mW while the combined lens and driver requires 12-15mW but Ruffin expects this total to be further reduced. Competing mechanical technologies to do the same typically require 200mW, he says.

The composition of the liquids involved is one of Varioptic's trade secrets. Essentially, there is a mixture of two immiscible liquids of the same density; the majority is the aqueous solution with just "a drop" of an oil. The interaction of these allows the desired properties: a focus at infinity at 0V and down to 4-5cm at 60V (with a tiny current).

The volume of the liquid lens is less than 0.05cm³ contained in a simple enclosure between two glass windows, above and below, in a cap of stainless steel. Electrodes dipping into the liquid mix create the voltage to cause the deformation. Varioptic's engineers overcame early problems of unwanted deformation caused by gravity and movement.

The company was established in 2002 but the background research for this technology goes back 10 to 12 years. It was originally developed in publicly-funded research in Grenoble by Bruno Berge, who eventually founded the company with the assistance of some VC investors. The associated key technology behind Varioptic's capabilities is called electro-wetting. Berge's core invention was to apply electro-wetting to lenses and optical surfaces leading to the variable focus behaviour.

Liquid lenses certainly will not be limited to the camera phone sector. Varioptic expects the market for its lenses to be "really big". Ruffin again: "Beyond phone cameras, we see liquid lens technology going into other markets such as webcams, barcode readers, automotive and medical devices, such as endoscopes because of the small form-factor. This technology could also have applications at other wavelengths and we are keen to speak with other parties in the laser industry."

"We are still improving both the electro-wetting and the liquid lens technology. We expect to further expand our product portfolio over 2006-7, to match the current trend for ever thinner handsets. We are working on a zoom version and we also have an R&D team working to improve the liquids to enable both larger and smaller liquid lenses."