A fingerprint reader for acquiring a fingerprint image has a platen with a micro prism sheet on its underside. An arrangement of fold mirrors is used to receive light from the platen and fold the optical path twice before reaching the imagers. The reader has multiple imagers, each imager having at least an imaging lens and an image sensor. Each imager is configured so that the image plane of the image sensor is tilted relative to the optical axis of the imaging lens, such that keystone distortion in the fingerprint image is corrected.
Joseph N. Mitchell; Michael J. McFadden