Abstract: In an optical fingerprinting system a truncated prism is used. The prism has an imaging surface against which a finger is applied, an illumination surface substantially parallel to the imaging surface and an inclined viewing surface between the imaging and illumination surfaces. Opposite the included viewing surface is another inclined surface that is coated with light absorbent material. The remaining two end surfaces of the prism may also be similarly coated. When a light source is positioned beside the illumination surface light enters the prism and causes an image of the fingerprint to be invisible on the viewing surface. As a finger is rolled on the imaging surface a linear charge coupled device (CCD) may be moved in synchronism to record the whole image.