A flickerless light source comprising a transparent or semitransparent diffuser, a lightpipe with a patterned surface inside the diffuser, and an LED light source attached to each end of the lightpipe is disclosed. The patterned surface of the lightpipe diffuses or reflects light emitted by the LED light sources and through the lightpipe to provide a light with uniform brightness and intensity. The lightpipe is coated with a thin layer of visible-light transparent material which is doped with organic dye molecules. The organic dye has strong ultraviolet light absorption characteristics. By changing the doping concentration of the dye molecules the coating can become total opaque or semi-transparent to certain wavelengths and selective wavelength conversion is obtained. In this way light color, brightness, and intensity can be varied or controlled.