Developer material end of life sensing

摘要

An electrophotographic printing machine in which a developer roller transports a developer material comprising carrier granules and toner particles closely adjacent to an electrostatic latent image recorded on a photoconductive surface so as to develop the latent image with the toner particles. A member is positioned closely adjacent to the developer roller to attract the toner particles to at least one surface thereof. A beam of energy is transmitted through the member onto the surface on which the toner particles adhere. The internal angle of incidence of the beam of energy is greater than the critical angle of incidence of the member. The intensity of the beam of energy internally reflected through the member is detected. A signal indicative of the quantity of toner particles attracted to the surface of the member is generated. The signal is processed and a signal transmitted indicating the end of the useful life of the developer material.