Patent ID: 8035603

Claim:
An illumination system, comprising: a plurality of light sources each emitting a different color light; lighting period varying means for varying the lighting period of each light source; light emission intensity varying means for varying the light emission intensity of each light source; control means for controlling the lighting period varying means and the light emission intensity varying means to control the light emission amount of each light source to obtain a specific color light by mixing the different color lights, wherein the control means controls a driving period T[s] of the light source such that the relation (1/T)≧20 kHz is satisfied and thereby a drive frequency (1/T) is not an audible frequency; and detection means for detecting the light emission amount of each light source, the detection means including: a plurality of first light receiving elements each extracting and receiving each color component from a mixed color light produced by mixing color lights from the light sources, and first detection means for concurrently performing, during a predetermined gate period τ, sampling on a light receiving signal from each of the first light receiving elements, wherein the control means controls the gate period τduring which the sampling on the light receiving signal from the first light receiving elements is performed and a driving period T of the light source such that a ratio of the two periods satisfies the relation (τ/T)<0.5.