At first, LEDs were used as indicator light sources for instruments and meters. Later, LEDs of various light colors were widely used in traffic lights and large-area display screens, resulting in good economic and social benefits. Take the 12-inch red traffic signal as an example. In the United States, a 140-watt incandescent lamp with long life and low light viewing efficiency was used as the light source. It produces 2000 lumens of white light. After passing through the red filter, the light loss is 90%, leaving only 200 lumens of red light. In the newly designed lamp, Lumileds uses 18 red LED light sources, including circuit losses, and consumes a total of 14 watts to produce the same light effect. Automobile signal light is also an important field of LED light source application.