A fingerpress is formed by pressing a finger against the back surface of a transparent glass plate and holding it in a predetermined position thereon. This fingerpress is interrogated by a light beam directed through the front surface of the glass plate. The interrogating beam is partially reflected at the back surface to provide a signal beam carrying fingerpress information. The signal beam is created by virtue of the optical discontinuity between the glass plate and the fingerpress. There is one discontinuity between the glass plate and the air underlying the valleys of the fingerpress and another discontinuity between the glass plate and the finger oil at the crests of the fingerpress. The two discontinuities cause differing amounts of light to be reflected and the signal beam is thus created. The signal beam is correlated against a hologram of the same fingerpress to provide identification. The hologram is created either from a film image of the fingerpress or from the fingerpress in real time. The finger is held in predetermined registration position both in making the hologram, or film on which the hologram is made, and when being interrogated for identification so that correlation can be properly made. The front surface of the glass plate is coated with an anti-reflectant coating and the back surface is coated with a coating to enhance the difference in reflectivity of the valleys and crests of the fingerpress.
A finger guide (2) comprises first and second orthogonally-oriented portions (4,12) each comprising a pair of opposed converging surfaces (6,8;14,16) into which the end and the shank, respectively, of a finger for examination fit. Because of the relative orientation of the surfaces, movement of the finger relative to an examination surface (22) is reproducibly constrained.
A method for optically detecting error in shape wherein a laser irradiates with a large angle of incidence the surface of an object to be inspected for its shape and the light wavefront of its positive reflected light from the surface is converted by using a special optical element into a light wavefront that is easily converged, the converted light wavefront is converged and the state of the convergence is detected by a photoelectric detector array, and output signals from the photoelectric detector array are processed to detect and measure the shape error of the surface of the object.
An optical apparatus for a fingerprint identification system having a multi-LED for emitting a light, a prism having a slant surface to which a fingerprint being identified is contacted and in which the incident light is absorbed at each ridge but reflected at each valley of the fingerprint, a cover glass functioning as a partial reflecting glass adapted to partially relfect the beam representing a fingerprint image reflected from the prism, a target adapted for focusing a virtual image of the fingerprint thereon, a magnifying glass for magnifying the fingerprint image partially reflected by the cover glass, thereby allowing the user to easily see the fingerprint image, a producing lens for producing the fingerprint image transmitted through the cover glass, and a CCD camera module for converting the fingerprint image produced by the producing lens into an electric signal. The optical fingerprint identification system enables a user to easily adjust the identifying position of the fingerprint improving the accuracy of the fingerprint identification.
A fingerprint sensor for transforming the topological pattern of a finger into an electric output signal. The sensor includes an array of cells arranged beneath a contact surface for sensing the pressure and/or temperature variations existing at the surface as a result of a fingerprint pressed against it. Each cell includes a transistor set to operate at a point within its amplification range. This operating point is varied in dependence upon the pressure and/or temperature at the adjacent contact surface. A circuit is provided to measure the amount of current passing through the transistor in each cell and to derive an electrical output signal therefrom.
A method of detecting fingerprints by sensing scanning with ultrasonic waves. For comparison, an acoustic hologram of the characteristics of the respective finger is disposed in an identification card. The hologram is compared in a recognition device with an ultrasonic interference pattern which is obtained by reflection of ultrasonic waves at an interface formed between the surface of the finger and a planar application or support surface.
