UNEVEN SURFACE IMAGE TRANSFER APPARATUS

摘要

Enhanced performance of an uneven surface image transfer apparatus is provided by using a well-defined convergent field of illumination that is nominally focussed at the stop of an imaging lens. The transfer apparatus includes an aspheric illuminating lens (128) that directs radiant energy onto a presentation platen (130) from which fingerprint or bar code images are transferred to an external image sensing device (168), such as a charged coupled device chip. An evanescent wave image is totally internally reflected (TIR) off of the platen along an optical path including a plurality of TIR surfaces (134, 136, 138, 140) to achieve a predetermined optical path length. Two of the plurality of TIR surfaces (138, 140) are located either side of the focal point of the aspheric illuminating lens. An aspheric imaging lens (142) having a split-axis aperture stop transfers the image rays to the image sensing device.