Sunglasses Block the Brightest of Light

LCD lenses and sensor eliminate glare

4 November 2011

tech_glasses Photo: University of Buffalo

A bright, sunny day poses a threat to motorists if they’re blinded by glare. But a new kind of sunglasses can do a lot to reduce that glare, thanks in part to Albert Titus, IEEE senior member [right] and co-chair of the biomedical engineering department at the University of Buffalo, in New York. He has helped develop sunglasses with a twist: glare-blocking spots on the lenses that move with the wearer as his or her relation to the sun changes.


Chris Mullin, founder and chief executive officer of Dynamic Eye, in Pittsburgh, brought Titus in on his research team to develop battery-operated sunglasses equipped with components that detect glare and darken specific parts of the lens to block bright light.


Although the high-tech shades are not ready for the market, they were named one of Popular Science magazine’s top 10 inventions of the year.


SMART SHADES

To create the sunglasses, the team used transparent LCD screens for the lenses. A small sensor was attached to the bridge of the glasses to monitor the user’s line of vision. In addition, Titus helped design a glare-sensing chip, similar to a light meter in a handheld digital camera.


“The low-power sensor chip is designed to detect glare and determine what direction it’s coming from,” he says. 


When brightness has exceeded a certain threshold, the sensor triggers an adjacent microcontroller to darken specific pixels on the lens. A 4-by-6-millimeter rectangle is created that moves around each lens to block blinding light as the wearer moves his or her head. The entire process—from image analysis to darkening the pixels—takes about 50 milliseconds.


The rectangle is not completely opaque. “It is dark enough to eliminate glare, but it does not obscure the wearer’s vision,” Titus says.


SHIELD YOUR EYES

Mullin came up with the idea for glare-blocking sunglasses in 2002 after he found it difficult to drive home in late afternoon because of the sun’s low position on the horizon. He designed glasses that would not darken uniformly, like transition lenses, but would get dark only in the areas of the lens that need it. The following year he founded Dynamic Eye to build a prototype.


That prototype included a large circuit board attached to the bridge of the glasses and was tethered to a laptop. Titus began working with Mullin in 2004 on a low-power sensor that would require a smaller battery than the original sensor. The team worked to shrink the components, and four years later, the battery, sensor, and microcontroller were small enough to fit within standard sunglasses frames.


In 2008 it was time to take the glasses out of the laboratory and into the sunlight. The team brought its fifth prototype to a public park and asked people at random to put them on.


“They told us they were surprised at how well the sunglasses worked to block out glare,” Titus says.


He notes that the glasses could benefit glaucoma patients who are sensitive to light. The U.S. Air Force is interested in the technology; it is funding the team’s research on protective eyewear for fighter pilots.


Car manufacturers might come calling, too. According to Titus, vehicles’ rearview mirrors could be made to darken specific pixels, rather than the entire mirror.


The smart shades are at least 18 months away from commercial availability, Titus says. “The initial retail price will be about US $400 to $500,” he says, “but the price should drop over time.”


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