By Tony Henning
Rhevision Technology, Inc., a San Diego developer of miniature tunable optical systems, announced the completion of its first venture financing, led by EDF Ventures and joined by In-Q-Tel, the independent investment fund that identifies innovative technologies to support the mission of the Central Intelligence Community (CIA) and the larger Intelligence Community. The funding announcement brought the company to our attention and put them squarely on our radar screen.
“Soon, camera-phones will have image sensors comparable to the quality of digital still cameras. What’s lacking is the optical zoom and auto-focus functions due to size, weight and cost limitations,” says Rhevision’s CEO, Tim Rueth. “Our optical zoom lenses will meet these market demands and offer auto-focus and 3x optical zoom while fitting in the small form factors of new cell phone designs. Our unique and proprietary approach will prove superior to competing approaches.”
Although the company is still essentially in stealth mode, we were able to ferret out a bit of information about Rhevision’s tunable lens systems “that will revolutionize the world of mobile imaging.” (You know that phrase caught our attention.) Developed by Professor Yuhwa Lo’s group at the University of California at San Diego and then spun out into a separate company, the Rhevision approach tunes the focal length of each lens in its system by simply adjusting the fluidic pressure. The body of the lens consists of two back-to-back fluidic adaptive lens chambers that sit either side of a glass substrate. To control the pressure, the researchers use a battery-powered miniature pump coupled to fluid inlet and outlet valves integrated within the chamber. In the design, where the lens can be changed between convex and concave in shape, the team has demonstrated the integration of a telephoto system and a wide-angle system using the same set of liquid lenses.
Changing lens shape enables optical zoom by adjusting focal point ratios for magnification. This approach doesn’t require mechanical motion and is implemented as a very compact module. Key innovations include a piezoelectric microfluidic device to pump fluid through micro channels into a spherical membrane. Resulting pressure deforms the membrane to change lens shape and focal point. Specialized membrane and fluid materials are incorporated within a simple design to ensure long product life and excellent lens characteristics. The miniature camera lens is capable of up to 5x optical zoom (without changing lens distance), focal distance tuning (f#: 0.7 to >100), wide range field-of-view tuning (7 – 65 degrees), and auto-focusing.
Rhevision says its approach produces images that are crisper and consistently better than those of competing technologies such as Varioptic’s electrowetting because of its superior aperture size and ability to admit sufficient light when photos are taken. Cost is far lower than competitors (under $3), the firm says, with good manufacturability and durability. When comparing Varioptic’s and Rhevision’s systems, however, Varioptic’s research director Bruno Berge believes that Varioptic’s main advantage is the electrowetting method that is used to focus and zoom. “Rhevision’s lens is easier to manufacture than ours,” he said. “It only has one liquid chamber, but it needs a pump to function. This can be large and slow and can take a lot of battery power. Our lens is harder to manufacture, but it only needs a small voltage to function.”
And so the race is on to see which of these approaches can get the market traction necessary to shut the window of opportunity for the other. At this point, Varioptic has a considerable head start. Join us at the Mobile Imaging Summit in Monterey, October 24 to see the latest advances in optics and opto-mechanics for Mobile Imaging, and judge for yourself who has the best solution.