Billie Jean LED stairs
Each stair had an infrared emitter on one side sending a “beam” of infrared light across the stair. At the other side, an infrared photo-detector detected the infrared beam. When the beam was broken by someone stepping anywhere on the step, a transistor connected to the detector switched on a set of high power white LEDs to illuminate the entire step. The video only pics up the LED source, however the entire step was light up even with ambient lighting.