Patent ID: 7027139

Claim:
A photosensor apparatus comprising: a light receiving element that receives reflection light of light which is illuminated onto a reference pattern image formed on a moving member; a first illuminating unit that is disposed at a first position so that regular reflection light of light from the first illuminating unit by the reference pattern image enters to the light receiving element; a second illuminating unit that is disposed at a second position so that diffuse reflection light of light from the second illuminating unit by the reference pattern image enters to the light receiving element; and a light receiving optical system that conducts the regular reflection light and the diffuse reflection light generated at the reference pattern image to the light receiving element, wherein the light receiving optical system includes a lens; constitutes an image forming optical system that focuses the reference pattern image on a light receiving plane of the light receiving element with respect to the diffuse reflection light; and enters only a part of regular reflection light to the light receiving plane of the light receiving element with respect to the regular reflection light, the part of regular reflection light being reflected from substantially the same region where the diffuse reflection light is received by the light receiving element within the reference pattern image on the moving member.