A system for matching images in which characteristic points of an image to be tested for a match, such as a fingerprint, are compared with characteristic points of a master image by attempting to match the distances between pairs of master characteristic points with distances between pairs of live characteristic points, whereby the coordinate system of the test image is not required to be aligned with the coordinate system of the master image. The matching system can be implemented in an identification mode in which the live image is attempted to be matched with each of a number of master images, or a verification mode in which the live image is attempted to be matched with a master image that is purported to be the same as the live image.

Apparatus and method for matching image characteristics such as fingerprint minutiae

In one embodiment, a fingerprint sensing system includes a sheet prism having a sensing surface and a number of prismlets positioned opposite to the sensing surface. Each prismlet has an entrance surface and an exit surface, and is adjacent to another prismlet. The width of the sheet is more than ten times the maximum thickness of any one of the prismlets. When a finger is positioned on the sensing surface, a portion of the radiation entering a number of the entrance surfaces and incident at the sensing surface is reflected through total internal reflection. The reflected radiation emits from a number of the exit surfaces to create an image of the fingerprint. In another embodiment, the system further includes a second sheet prism stacked together with the previously described sheet prism. The second sheet prism has a flat surface and a number of prismlets positioned opposite to the flat surface, which faces the prismlets of the previously described sheet prism. The image formed with two sheet prisms can have lower distortion. In yet another embodiment, the fingerprint sensing system is incorporated into a flat-profile package using mirrors to fold radiation and to compress the height of the package.

Apparatus and method for electronically acquiring fingerprint image with low cost removable platen and separate imaging device

Signalling means for enhancing the performance of automatic fingerprint identification systems by reducing system response to non-fingerprint-like regions within an image field pattern of interest. A two dimensional generalized sequency analyzer, such as a fast Fourier transform machine, responsive to a binary coded image signal identifies discrete frequency terms occurring within a selected bandwidth corresponding to a spatial frequency region of interest, associated with a fingerprint image. Logic means, responsive to the sequency analyzer, further identifies the relative energy levels of the bandwidth-limited spectral content of the binary coded image signal to signal the identity of a non-fingerprint-like region within the scanned image.

Non-fingerprint region indicator

An apparatus and method for acquiring an image of a patterned object such as a fingerprint including a light refracting device, a focusing lens, and a light source. The light refracting device can, for example, be a prism and includes an imaging surface, a light receiving surface and a viewing surface. Incident light from the light source is projected through the light receiving surface and reflected off a surface other than the imaging surface. This reflected light is then projected onto the imaging surface to create an image of the patterned object from substantially all scattered light through the viewing surface. The lens is placed adjacent to the viewing surface to focus the light on an image sensor.

High contrast, low distortion optical acquisition system for image capturing

A hybrid optical-digital technique is provided for automatic fingerprint verification. A coherent optical beam modulated with the characteristics of a fingerprint image passes through the lens performing an optical Fourier transform. The intensity array that represents the Fourier power spectrum is recorded and processed. In enrolment, several arrays related to the same finger are captured and processed. A template which is unique for each fingerprint is generated and stored. Using the set of arrays captured in enrolment and a set of templates from a standard database, the processor calculates dependences of false rejection rate and false acceptance rate upon a metric of comparison. The metric is obtained by calculating a relative distance between two arrays in Hilbert space. An individual threshold of verification for a person to be enroled is set and stored together with the template. In verification, the metric of comparison between the processed array derived from a fingerprint to be verified and the pre-stored template is determined and compared with the pre-stored individual threshold.

Hybrid optical-digital method and apparatus for fingerprint verification

Fingerprint identification apparatus including a light source and suitable lenses for directing a light beam sequentially onto discrete segments of a fingerprint and forming a Fourier transform of the instant illuminated segment. A rotatable radially slitted filter or a circularly disposed array of sequentially sampled photodetectors functions to scan about the center of the Fourier transform to determine the angular displacement of the diffraction lobes of each illuminated segment relative to a reference position of the transform and means is provided for converting the angular data to equivalent electrical signals.

Fingerprint identification apparatus

An optical pulse expansion device includes first and second ultrasonic light modulators and a coded mask positioned so that a collimated light beam can be passed serially through these elements and focused on a photodetector. The first ultrasonic light modulator is sandwiched between crossed polarizers that block the passage of light under quiescent conditions. First acoustic pulses are propagated through the first ultrasonic light modulator in synchronism with second acoustical pulses that are propagated through the second ultrasonic light modulator. These pulses limit the light to the acoustically stressed regions of the second ultrasonic light modulator when scanning the coded mask.

Optical pulse expansion system

A lensless recognition system including a hologram having interference patterns therein corresponding to known characters. The interference patterns are formed by a character beam which passes through a transparent mask of the character to be recorded and intersects a reference beam on a photographic plate. In the recognition process quasi-monochromatic incoherent illumination from an unknown character transmits through the hologram which is obtained by developing and bleaching the photographic plate. Correlated output signals of varying intensity are formed in the output plane at the locations occupied during the recording process by the transparent masks which most closely correspond to the unknown character. Each of a plurality of pinholes positioned at the locations corresponding to each mask transparency transmits the central value of a correlated output signal. A photodetector aligned with each pinhole senses the transmitted central value and produces a current signal that is processed in a postprocessor to provide an output signal that is indicative of the corresponding known character.

William T Maloney

Papers

Fingerprint identification apparatus

Optical pulse expansion system

Lensless optical recognition system