A sweeping glance creates images that appear and disappear in the blink of an eye.
A strip of 64 computer-controlled LEDs flashes on and off extremely rapidly. When you look in the mirror and quickly move it from side to side—or sweep your eyes sideways—the changing pattern of light leaves a visual imprint on the light sensitive cells at the back of your eye. Your visual system “remembers” light for up to a tenth of a second, long enough for you to see the complete image. This phenomenon, called persistence of vision, is also at work in videos and movie projections, which also flash on and off rapidly.