Not everyone is happy about the proliferation of digital cameras and camcorders. In fact there are plenty of places where they are most unwelcome: cinemas, celebrity weddings and lavatories spring to mind, which is why researchers at the Georgia Institute of Technology have been looking into ways to block their use. A prototype unit has been developed, which uses a pair of cameras to scan the protected area, looking for the image sensors in digital cameras. These have a very specific ‘retroreflective’ characteristic, which basically means that like a cat’s eye it bounces light back to its source. When one is detected a beam of visible light is shone directly at the camera sensor, effectively ruining the recording. Later versions will probably use an invisible infrared laser, which has the same effect.