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Liquid lens optical system delivers accurate focus from short distance

Posted: 14 Jul 2006 ?? ?Print Version ?Bookmark and Share

Keywords:Rogers? Varioptic? Liquid Lens? DUREL LL3 driver? optical system?

Rogers Corp. and France-based liquid lens maker Varioptic have announced production availability of components needed for miniature high resolution auto-focus cameras for handsets. The two companies have collaborated to provide OEMs and module makers in the handheld and other market segments with a new liquid lens optical system, consisting of Varioptic's auto-focus Liquid Lens and Rogers' integrated DUREL LL3 driver.

The Varioptic liquid lens system eliminates moving parts, enabling users to obtain accurate focus from a short distance. Based on the electrowetting phenomenon, the liquid lens uses two isodensity liquids; one is an insulator and the other a conductor. The variation of voltage leads to a change of curvature of the liquid-liquid interface, which in turn leads to a change of the focal length of the lens. In comparison to conventional auto-focus actuators, an optical system using the Varioptic liquid lens features smaller size, lower costs and reduced power consumption, according to the companies.

To provide its liquid lens with the needed voltage, Varioptic selected the DUREL LL3 driver from Rogers Durel Division, a manufacturer of electroluminescent lamps and high voltage drivers. This output device can drive the liquid lens up to 60Vrms into a capacitive load of 500pF maximum.

The liquid lens optical system features low operation power (typically 40mW focusing at 5cm and 20mW focusing at ). It has low standby current of 1A. There are two LL3 driver reference designs: I2C 2-wire serial interface and PWM one-wire interface. The DUREL LL3, 4-by-4mm leadless driver is available in a 16-pin, quad flat package in embossed tape on 360mm diameter reel.

"Varioptic's ARCTIC range of small, reliable and low power auto-focus lenses is the result of 10 years of extensive research and experimentation. It costs less than mechanical solutions and because it has no moving parts, it can never wear out," said Philippe Ruffin, product marketing manager at Varioptic. "We are excited to collaborate with Rogers to provide Varioptic's licensees with a complete liquid lens and driver solution, and thus ease integration and shorten time to market."

The liquid lens optical system can be shut down to conserve battery power. It boosts the DC input voltage from a battery (2.8-5.5V) up to a high DC voltage. A comparator continuously monitors the high voltage generated in the tank capacitor through a resistor divider and the PWM or I2C control. The output of the comparator feeds the control logic, which excites the inductor to achieve the high DC level desired. This DC value is fed directly to the H Bridge, which generates an AC voltage on the liquid lens.

"Thin is in," said Sushil Vij, product manager at Rogers. "Rogers' DUREL LL3 driver combined with Varioptic's liquid lens allows OEMs to obtain the thin profile desired by their customers and conserve battery life at the same time. It also provides the auto-focus functionality needed to take clear pictures with higher resolution cameras. This is an innovative technology that delivers a real solution to the marketplace."

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