Image forming apparatus with toner detection

摘要

An electrophotographic image forming apparatus which comprises a photoreceptor medium including a substrate and a photosensitive layer formed on the substrate, and a photo-electric toner sensor assembly for measuring the amount of rays of light undergoing a diffuse reflection from the photoreceptor medium. The substrate has a regularly developed pattern of grooves formed thereon. The photoelectric toner sensor assembly comprises a light emitting element for projecting the rays of light onto the photoreceptor medium so as to reflect therefrom and a light receiving element for detecting the rays of light undergoing the diffuse reflection. The light emitting and receiving elements are so positioned that a common plane containing respective optical axes of those light emitting and receiving elements can lie substantially parallel to any one of the grooves on the substrate.