Patent ID: 7800089
Filing Date: 2010-09-21
Classification: B41J

Abstract:
1. A printing system comprising: a platen including a normal; a photosensor including an integrated lens, wherein the photosensor is oriented at a non-zero first angle with respect to the normal; a first light source configured to provide light, the first light source including an integrated lens, wherein the first light source is oriented at an angle with respect to the normal, the angle being equal in magnitude to the first angle; and an aperture oriented at the first angle with respect to the normal and disposed to provide a field of view, the field of view being a portion of a plane parallel to the platen, wherein reflected light from the first light source is specularly reflected and passes through the aperture to the photosensor without passing through an external lens; and a second light source oriented at a second angle with rest to the normal of the plane parallel to the platen and wherein the second angle is substantially equal to zero; wherein the first light source is a first characteristic wavelength and the second light source is a second characteristic wavelength that is longer than the first characteristic wavelength.