US Patent 7535604 Book scanner with a uniform light source

A book scanner comprises a transparent platen, a carriage and a housing. The carriage is disposed in the housing, and the transparent platen with an angular structure is disposed on the housing for an original placed to be scanned. The carriage has a strip-shaped light tube disposed corresponding to the transparent platen. The part of the light source that has the highest luminance is disposed in the position farthest away from the transparent platen, while the part of the light source that has the lower luminance is disposed in the position closer to the transparent platen to assure a uniform and stable luminous intensity of light on each scan line when the light source illuminates the original.