A directionally-oriented reflective device is optically coupled to a prism
surface in a skin ridge pattern imaging system to reflect illumination
light at relatively small angles, along an optical path to an imaging
device, so that minimal light is lost from the optical system. Examples
of such directionally-oriented reflective devices include, but are not
limited to, echelon reflectors, faceted reflective surfaces,
retroreflectors, aluminum paint, nacreous pigment, and slightly rough
mirror surfaces.