Patent ID: 7838896
Filing Date: 2010-11-23
Classification: H01J,H01L

Abstract:
1. A light emitting apparatus with open loop control, comprising: a blue light emitting diode (LED); a first phosphor layer disposed above the blue LED, wherein the first phosphor layer has a first phosphor material that is excited by a blue beam from the blue LED to emit a first light beam; and a second phosphor layer disposed between the blue LED and the first phosphor layer, wherein the second phosphor layer has a second phosphor material that is excited by the blue beam from the blue LED to emit a second light beam, such that the blue beam, first light beam and second light beam are mixed white light; wherein when the blue beam of a shorter wavelength excites the first and second phosphor layers, the excitation efficiency of the first phosphor layer is greater than that of the second phosphor layer; when the blue beam of a longer wavelength excites the first and second phosphor layers, the excitation efficiency of the first phosphor layer is less than that of the second phosphor layer; the wavelength of the peak intensity of the first light beam from the first phosphor layer is shorter than the second light beam of the second phosphor layer, and the dividing value between the short wavelength and the long wavelength is within the range from a first wavelength to a second wavelength; the weight ratio of the first phosphor material to the second phosphor material is determined according to the emission intensities of the first and second phosphor materials.