An image forming apparatus includes a detector for detecting light intensities of light from a light source, and a discrimination unit for obtaining the relative ratio of chroma signals of light with two or more wavelengths at the light intensities of the light source detected by the detector, to thereby...http://www.google.com.au/patents/US4952972?utm_source=gb-gplus-sharePatent US4952972 - Life expiration detector for light source of image processing apparatus
