Patent ID: 6246859
Filing Date: 2001-06-12
Classification: B65H,G03G,H04N

Abstract:
An original sensing device for sensing the presence/absence of an original placed on an original tray of a document feeder by using an output signal from a photodetector which receives a light beam emitted by a light projector and reflected by said original tray, comprising:a projecting/photodetecting unit including said light projector and said photodetector, said light projector and said photodetector being arranged to oppose said original tray such that a projecting optical axis and a photodetecting optical axis are substantially parallel to each other; andan optical member interposed between said projecting/photodetecting unit and said original tray,wherein boundary surfaces of said optical member are constructed such that a portion of a light beam on the projecting optical axis emerges toward a direction of said original tray via at least two boundary surfaces, a reflected light beam from said original tray is guided to said photodetector via at least two boundary surfaces, and other part of the light beam on the projecting optical axis does not emerge toward the direction of said original tray but is reflected by a boundary surface facing said original tray and is totally reflected by a boundary surface facing said photodetector.