Light from an illumination source is injected into a prism of a print scanner through an illumination injection surface that is not directly imaged by an optical system and an image sensor of the print scanner. This light travels across the prism and hits a highly reflective surface of the prism. When this light hits the highly reflective surface, it is scattered and becomes diffused. Some of this diffused light remains in total internal reflection (TIR) within the prism and is reflected off the inside of the platen surface of the prism. The diffused light reflected off the inside of the platen surface is imaged by the optical system and the image sensor.