Method of making white light LEDs and continuously color tunable LEDs

Abstract

A light emitting diode comprising of a fluorescent microsphere coating is proposed. The coating consists of fluorescent microspheres which fluoresce at green and red wavelengths, excited by a shorter wavelength LED. Due to the micron-scale dimension of the spheres, they are non-resolvable to the human eye and the overall optical output appears as color mixed. By varying the proportions of green and red fluorescent microspheres and the wavelength of the excitation source, the color of the optical output can be tuned. If the optical output has of blue, green and red components in the correct proportions, white color emission can be achieved. The light emitting diode can be sectioned into multiple individually-addressable regions. Each section can emit at a different wavelength according to the type of fluorescent microspheres coated.; By varying the intensity of the blue, green and red regions by changing the bias voltage, the output wavelength (color) can be continuously tuned (varied).