Colour-light signal using LEDs

摘要

The device has at least one LED signal light for providing green light in a wavelength range between 494 and 509 nm, which is easily distinguished from a yellow light signal. A first number of diodes (LEDg) provide green light with a dominant wavelength range between 550 and 565 nm and a further number of diodes (LEDb) provide blue light with a dominant wavelength range between 460 and 490 nm. The number of diodes of each type are selected to obtain a ratio of between 8:1 and 10:1 between the green light output and the blue light output, with the required overall light intensity.