'Tactical'flashlights - torches for shining into people's eyes - are already popular in the US amongst certain special interest groups and now a Californian firm has taken the concept one stage further.

With $1m from the Department of Homeland Security, Intelligent Optical Systems of Los Angeles has created the LED Incapacitator.

"The device doesn't injure you which is in stark contrast to the tasers used in similar situations today that can cause serious harm. This is a defense technology, not a weapon," said CEO John Farina - although what would stop it being used as a weapon was not made clear.

It works by flashing brilliant coloured LEDs in a random pattern and according to a CBS news report, is effective.