A device that could foil movie pirates who covertly record films in cinemas has been developed in the US.
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The prototype is able to locate the position of a digital camera, before overwhelming it with white light to render any recorded images useless.
The Georgia Institute of Technology team says the invention could also prevent clandestine photography.
However, the device is unable to block conventional film or the SLR cameras, preferred by the paparazzi.
"We're at a point right now where the prototype we have developed could lead to products for markets that have a small, critical area to protect," said Professor Gregory Abowd of the Georgia Tech College of Computing.
In particular, his team is looking at ways to prevent photography in government buildings or at trade shows, where industrial espionage could be a problem.
The team is also working with the motion picture industry to prevent illegal copying of films, which has become a particular problem in parts of Asia.
A study released by the Motion Picture Association (MPA) said that movie piracy in China cost the film industry $2.7bn (£1.5bn) in 2005.
The technology works by looking for the digital camera's image sensor known as a charge-coupled device (CCD).
These silicon sensors are retroreflective, which means that they reflect light directly back to its origin, rather than scattering it.
Some road-signs and vehicle licence plates are also retroreflective.
The prototype uses two cameras, linked to a computer, to look for this reflected light from a target camera's CCD.
As the reflected light is travelling in a straight line from the CCD, it allows the computer system to accurately pinpoint the location of the camera.
Once found, the system floods the CCD with white light from a projector to "blind" the camera.
"The biggest problem is making sure we don't get false positives from, say, a large shiny earring," said Jay Summet, a research assistant at Georgia Tech who helped build the device.
"We need to make our system work well enough so that it can find a dot, then test to see if it's reflective, then see if it's retroreflective, and then test to see if it's the right shape."
In the future, the researchers believe the system could use infra-red lasers and photo-detecting transistors, rather than cameras to search for CCDs.
They also believe that a real-world version would probably use a laser to "blind" the image sensor.
At the moment, the team is close to developing a commercial system that neutralises still cameras.
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Still cameras are easier to spot than camcorders because their CCD is closer to the lens and there is less interference with the reflected light.
However, the ultimate goal is to develop a system to combat film piracy.
The movie industry is particularly keen to clamp down on this because of the billions of dollars in lost revenue blamed on illegal copying.
At present, the industry mostly relies on the alertness of staff at cinemas to spot people filming.
However, Disney took this one stage further in 2003 when it issued security staff with night vision goggles and metal detectors, ahead of screenings of the animated movie Finding Nemo.