Abstract: A fingerprint enhancement system has a platen with a liquid contacting and finger-touching surface. Two collimated interrogating light beams lie below and are opposite sides of the finger-touching surface. The horizontal extensions of the light beams assume an angle of approximately forty-five degrees with the finger longitudinal axis. Side surfaces of the platen are oriented normal to the incident colliminated light beams prior to interrogation. The light beam modulated by the fingerprint passes to a reflecting mirror, imaging means and a scanner below the platen. A polarizing filter lies between the platen and reflecting mirror. A second polarizing filter lies above the platen. A contrast enhancement circuit increases the modulation of the scanned fingerprint signal and automatically adjusts the level of the modulated signal without saturation. Circuit filtering eliminates spurious input signals. Finger position sensing by a light emitting diode and photo transistor is also provided.

Abstract: As a live finger is rolled across a glass platen in an optical scan fingerprint apparatus, a series of lights turn on and off to demarcate the line along the platen at which the optical scan is being taken. In this fashion, the finger applied to the platen can be rotated across the platen at a rate that keeps sufficient track with the scan to provide a complete (nail-to-nail) full roll scan.

Abstract: The technique for optically scanning a finger to produce a fingerprint image involves positioning the finger surface to be optically scanned so that it is exposed and, in particular, is not pressed against a platen. A slit light beam along the length of the forward part of the finger is circumferentially rotated about an axis about the nominal center of the finger. A reflected slit light beam carries modulation information which is focused on a linear array of photo-electric transducers to provide the fingerprint image. The interrogating light is coherent, substantially collimated, light. The plane of the interrogating slit light beam and the plane of the reflected modulated slit light beam are coplanar thereby establishing an illumination plane. The illumination plane is parallel to the axis of the finger and is rotated about that axis during the interrogating scan.

Abstract: A curved cylindrical segment platen has a concave touching surface. An interrogating slit light beam is scanned around the platen to scan a finger held against the touching surface. An optical imaging system images the zone illuminated onto an array of photo-transducers to provide a signal representing the fingerprint. The optical system is rotated around the platen. The axis of the interrogating light beam is substantially normal to the touching surface. The axis of the imaging system is off normal by about 56 degrees, an amount which is greater than a critical angle equal to the maximum angle of refraction in the platen. This critical angle is approximately 41 degrees. The axis of the imaging system is also off normal to the non-touching surface by an angle that is less than this critical angle of 41 degrees and thus less than the angle of total internal reflection. As a consequence, the image at the photo-transducers provides a completely dark valley zone and a sharply contrasting light image ridge zone.

Abstract: An automatic fingerprint enrollment and identification technique is provided for automatically processing an input image represented by pixels having either a one or zero value. The automatic processing involves a series of steps in which the initial processing is a rough screening technique for eliminating a reasonable portion of the noise while passing through almost all of the minutia. As the steps proceed, the processing becomes more complex to provide a tighter screening out of noise while passing through as much of the minutia as possible. The later steps by operating on relatively fewer minutia or anomaly points that the earlier steps can be economical though more complex so as to be more discriminate than the earlier steps. The processing provides an optimum trade off between enrolling as large a proportion of the population as possible while minimizing the number of false identification errors.

Abstract: An optical and electronic scan produces an image composed of binary value pixels. An automatic picture compression routine reduces the number of pixels in the image. A first stage four to one reduction in the number of pixels is achieved by treating each mutually exclusive four pixel unit as a separate set. A binary value is assigned to each four pixel set. That binary value is assigned to a single pixel in a first output image. The same process is repeated a second time to provide a final output image that has one-sixteenth the number of pixels as has the original input image. The value assigned to each four pixel unit set is a weighted function of the binary value of each of the sixteen pixels in a four pixel by four pixel subfield in which the unit set is centered. The greatest weight is give to the center pixels, that is, to the four pixels of the unit set. Lesser weight is given to the peripheral pixels.

Abstract: A set of Search identification points derived from an optical scan of a finger are compared against File identification points for the same finger. A multiple comparator divides the finger image into multiple segments. The Search and File points from each segment are compared separately. A difference table (D.T.) provides a proximity value Q for each search point. The D.T. is purged of all entries representing multiple Search points. The purge keeps those entries having the highest Q value. The purged D.T. with recalculated Q values is the basis for correcting the position of each Search point on the image plane to compensate for shift in finger position and for the variable distortion and changes that come about in a finger over time and upon successive applications of the finger to input scan. The corrected Search points are compared against the File points to establish a new D.T. A proximity value Q for each entry on this D.T. is calculated and a proximity value Q for the entire table is calculated.

Abstract: A gray scale image of a fingerprint composed of a field of pixels is converted to a binary image composed of a field of pixels by a technique which takes into account the directivity of the ridge and valley structure. Three intermediate binary images are developed, one by the use of a vertical filter, one by the use of a horizontal filter and a reference image by the use of a filter which is not directionally biased. Corresponding subfields around each pixel in each of the three images are compared. If the subfield for the vertically derived image is closer to that of the reference image then is the subfield for the horizontally derived image, then the binary value for the pixel from the vertically derived image is used in the final image; and vice versa. In this fashion, a fourth a final binary image is derived from a combination of the vertically derived image and horizontally derived image which includes the best imagery from each of those two intermediate images.

Abstract: In a matcher mechanism for verifying a match of a set of subject points having positional parameters against a set of reference points having positional parameters, the improvement of employing a set of Group tables derived from the difference table. Each line entry on the difference table constitutes a lead entry of a separate Group table. The Group table are overlapping subsets of the entries on the difference table. The members of the Group table are limited to only one line entry representing each reference point. That line entry is the one which is closest to the lead entry on the difference plane. In addition, all line entries within a Group are limited to those that are within a predetermined window on the difference plane around the lead line entry for the group. A quality score is determined for each of the Group tables based on a weighted proximity value between each pair of line entries in the Group involved.

Abstract: An input fingerprint image consists of ones and zeros pixels representing light and dark pixels which in turn correspond to ridge and valley formations. This image is compared with a reference file fingerprint to verify the identity of the input fingerprint. The reference file has two relatively small segments which are subfields of the entire field of pixels that constituted the original fingerprint image for the individual involved. Two substantially larger domain subfields are extracted from the input fingerprint image. The center of each segment corresponds to the center of a respective one of the domains. Each segment is scanned over its corresponding domain to determine the position of maximum ones correlation and maximum zeros correlation between each segment and its corresponding domain.

Abstract: In an optical fingerprint image processing apparatus a light beam is scanned across a finger placed against a transparent platen in order to provide a reflected modulated light beam carrying fingerprint information. The modulated light beam is imaged and the image is intercepted by an array of photo receptors that detect the image and convert the optical signal into electrical signals. The improvement is in placing a diffuser element, which may be a ground glass wafer, in the interrogating light beam. The diffusion of the light beam acts as an effective filter to eliminate the higher spatial frequency components of the optical image and thus provide a fingerprint image having improved continuity.

Abstract: A fingerprint processing apparatus is capable of generating a roll fingerprint image on a flat plane without distorting the image of the fingerprint. The apparatus includes a source of an interrogating light beam, optical scanning equipment, an array of photoelectric transducers, lenses, and electrical scanning equipment. A cylindrical-segment platen is provided having an upper surface with an anti-reflective coating which receives, positions and supports a finger, and a lower surface which receives and transmits the interrogating light beam. A finger positioned on the upper platen surface modulates the interrogating light beam to provide a reflected light beam having fingerprint information. A motor rotates the light source, optical scanning equipment, array, lenses, and an element of the electrical scanning equipment. The axis of rotation of the optical scanning equipment is substantially the same as the axis of the upper surface of the platen.

Abstract: A finger pressed against a platen or a fingerprint card provides a fingerprint object which is scanned by an interrogating beam of collimated light that is linearly displaced across the platen thereby maintaining a constant angle between the interrogating light beam and the plane of the object being scanned. As the beam scans across the fingerprint object, the reflected light beam is modulated. The modulated beam is imaged onto a linear array of photo-responsive devices to provide a series of output signals indicative of modulation information. The outputs of the devices are serially interrogated at each of successive scan positions to provide a set of signals containing fingerprint information.

Abstract: A finger pressed against a platen provides a fingerprint object which is scanned by an interrogating beam of collimated light in the form of a slit and that is linearly displaced across the platen. As the slit-beam scans across the back surface of the platen, the reflected light beam is modulated. The modulated beam is imaged onto a linear array of photodiodes to provide a series of output signals indicative of modulation information. The outputs of the diodes are serially interrogated at each of successive scan positions to provide a set of signals containing fingerprint information. The platen has a transparent glass base. A layer of transparent, compressible, resilient epoxy is on the back of the glass base. The epoxy layer has a flat back surface. A thin silver reflecting layer on the back surface of the epoxy provides a flat mirrored surface to reflect the light beam. A further epoxy layer on top of the silver provides mechanical filtering. A lacquer layer at the back protects the platen from wear.

Abstract: A system including electronic, mechanical and optical mechanisms which enable the system to: "read" a human fingerprint directly from a human finger; convert the ridge-valley pattern of that fingerprint into an electronic representation; transmit the electronic representation to a centralized location where image processing computing equipment can locate and extract the distinctive characteristics or minutiae of the fingerprint; compare the minutiae with minutiae previously recorded from the fingerprints of persons whom the system is responsible for identifying; determine whether the identity of the person whose fingerprint is read is known, and, if known, whether or not the person is authorized to enter the portal equipped with this system, or to otherwise act; and, to transmit a signal to the terminal and/or portal regarding the system's decision.

Abstract: A process and apparatus for encoding the ridge endings and bifurcations of an inquiry fingerprint and for automatically searching through a file of similarly encoded fingerprints for the fingerprint(s) whose minutiae are most similar to those of the inquiry fingerprint. The process does not require registration of the minutiae prior to storage or searching and the storage and search of file fingerprint cards can be implemented on a digital computer system since the minutiae data from each print is in a form easily processed by computer.