Device Seeks to Jam Covert Digital Photographers

Paparazzi and other snooping shutterbugs take note: Soon there may be a high-tech way to thwart digital cameras and to ensure some places remain photo-free zones.

Shwetak Patel, a Georgia Institute of Technology computer science graduate student, says he and his fellow researchers have developed a device that can detect the presence of digital imaging devices -- including camcorders and cell phone cameras -- and then blur the image by using simple blasts of light.

"The basic idea is that camera phones are becoming more and more ubiquitous. In Japan, it's something like 95 percent of [mobile] phones sold are camera phones," says Patel.

Because people are taking pictures where they didn't used to be able to in Japan, "there are a lot of places putting up 'no photography' signs."

Many museums, public security zones, locker rooms and other camera-sensitive places now try to bar or even confiscate camera equipment. But Patel and many privacy experts say such efforts aren't effective or practical against camera phones.

"In a research lab, for example, you can prohibit visitors from bringing in a camera or taking pictures. But how do you prevent someone from bringing in a [camera] phone that they might need for an important call?" asks Patel. "We wanted to develop a system that would allow the phone in, but disallow pictures."

Spotting That Digital 'Glow'

To solve the problem, Patel and his fellow computer science researchers -- Khai Truong, Jay Summet and professor Gregory Abowd -- hooked on to a unique characteristic of digital cameras.

Practically every digital camera uses either a "CCD" or a "CMOS" sensor -- devices that convert light coming through the lens into electronic signals. Both sensors use a highly "retroreflective" film that bounces some of the light -- especially invisible infrared light -- back out through the lens.

So the researchers modified a digital video camera that uses a special set of infrared lights and filters on its lens. If there is another digital camera in the area, the prototype camera will recognize the infrared light reflected off that camera's sensor as a unique white "glow."

A computer connected to the camera then activates a beam of intense light directly at the other camera's lens, thereby blurring or overexposing any image it tries to capture. The projector can also quickly vary the light beam so it can foil even advanced digital cameras equipped with automatic exposure compensation.

Chinks in the Armor

Patel's invention is just one of several potential responses to growing concern about camera lenses showing up in unwelcome places.

Hewlett-Packard, for example, has patented a similar picture-blurring idea. But that system, Patel says, requires additional parts to be installed inside digital cameras sold to consumers.

And Patel says there are still quite a few issues to work out before their system winds up in no-photo zones like museums and locker rooms.

For one, the camera jamming system has a limited range and scope. The infrared detectors have a limited field of view -- roughly a "cone" of 45 degrees vertical and horizontal. A crafty clandestine cameraman could still snap a picture if he can find the detection system's "blind spot." Also, the other camera must be within 33 feet of the device.

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