Abstract:
A scanning device for electronically capturing a fingerprint image, employing a finger guide unit and a platen. The finger guide unit positions a finger for scanning by means of a gap into which the finger is placed. The guide maintains the finger within the print scanning range when used in conjunction with a movable platen. The guide unit is rotatable allowing the guide to be moved to expose the whole movable platen. The finger guide unit has two guide plates disposed adjacent one another creating a gap. The gap width is adjustable by means of an adjustment device, allowing fingers of any size to be properly positioned and guided within the scanner reading range. The guide plates each have an edge lined with low-friction material which contacts the finger when in use. The guide plates each have an extension which serves as a handle for raising the guide unit and as a hanger for suspending the guide unit above the platen for use. The guide plates also have an alignment rod disposed between them to ensure stabilization and alignment.

Description:
This is a continuation-in-part of U.S. application Ser. No. 09/422,937, filed Oct. 22, 1999, abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the field of fingerprinting. 
     2. Related Art 
     Fingerprinting is a common method of distinguishing an individual. No two people have identical fingerprints on all ten fingers. Fingerprinting is used for identification in many commercial and legal settings. Law enforcement officials have often used fingerprinting for identification purposes. Conventional techniques for obtaining fingerprint images include application of ink to a person&#39;s fingertips and rolling or pressing the tips onto a recording card. This method has severe limitations. For instance, the ink can be extremely messy, and easily smear or blur, often requiring many attempts before a usable print is obtained. Further, it is difficult to adapt ink prints for computerized storage and retrieval, thus making it difficult for various governmental agencies to reliably transfer and share data. 
     To address this problem, fingerprint scanners have been developed to capture fingerprint images in digital data form, allowing an image to be saved in a database and allowing the saved image to be easily accessed and retrieved. Fingerprint Examiners and/or Automated Fingerprint Identification Systems can then use the digital images for identification of individuals. However, use of a scanner to capture the print still holds drawbacks. Current scanners require trained personnel to guide the fingers over the optical reading area while maintaining an accurate position and rate of rotation. If the fingers are not rotated at a proper rate, or their position is inaccurate, then data is lost, requiring the procedure to be conducted again. The problem is compounded when the person being fingerprinted is uncooperative, as is sometimes the case in law enforcement. Such methods require training and practice and can be both time consuming and tedious. 
     SUMMARY OF THE INVENTION 
     Movable platens allow the finger axis to be fairly stationary, while the finger rotates. This reduces the difficulty of rotating a finger at a specific, correct speed, but still requires proper positioning of the finger. The finger must be held in-line with the stationary scanning optics, as current scanners input only a narrow slice of data at a time. Therefore, there is a need for a finger guide, to provide a positioning framework for a finger. The finger guide of the present invention fills this need by providing a positioning reference, preferably used in conjunction with a movable platen. The guide assists when taking roll fingerprints, and may be moved out of the way when taking impressions or flat prints. 
     The present invention is a scanning device for electronically capturing a fingerprint image, employing a finger guide unit and a platen. The guide unit positions a finger for scanning. A finger is placed in a gap in the guide. The guide maintains the finger within a print scanning range when used in conjunction with a movable platen. This increases the likelihood of capturing a clear, well-defined print in the scanning process. This, in turn, increases efficiency. 
     The guide unit is rotatable allowing the whole unit to be moved to expose the movable platen. This allows the operator to access the whole platen when desirable, such as when an officer would need to capture a four-finger plain impression or to clean the platen. The guide rotates about a pivot shaft 180 degrees to a resting position. When desired, the guide may be rotated back into position above the platen to aid in further roll fingerprinting. 
     The finger guide unit of the preferred embodiment has two guide plates disposed adjacent one another creating a gap in which a finger can be placed for scanning. The gap width is adjustable by means of an adjustment device, allowing fingers of any size to be properly positioned and guided within the scanner reading range. The adjustment device changes the gap width by means of an adjustment wheel and threaded screws disposed in threaded apertures in the guide plates. When the adjustment wheel is turned, the screws rotate and move both guide plates equally and simultaneously in opposite directions, allowing the gap centerline to remain undisturbed. The adjustment wheel is held between the guide plates by means of an adjustment mount. The pivot shaft and threaded screws likewise pass through this adjustment mount. The guide plates each have an edge lined with low-friction material which contacts the finger when in use. This allows the finger to be smoothly rotated within the guide, allowing for easy and simple print capturing. 
     The finger guide plates each have an extension which serves as a handle for raising the guide unit and as a hanger for suspending the guide unit above the platen for use. The guide plates also have an alignment rod disposed between them to ensure stabilization and alignment. 
     Further embodiments, features and advantages of the present invention, as well as the structure and operation of the various embodiments of the present invention, are described in detail with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE FIGURES 
     FIG. 1A is a view of a tenprint scanner with the finger guide unit in a “slap” position rotated off of the platen. 
     FIG. 1B is a view of a tenprint scanner with the finger guide unit in a “finger roll” position. 
     FIG. 2 is a top view of the finger guide unit. 
     FIG. 3 is a front view of the finger guide unit. 
     FIG. 4 is an isolated view of the adjustment device. 
     FIG. 5 is a view of the optical assembly without the housing shown in FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention relates to the field of fingerprinting for security control, and in particular., to assist in simplifying the acquisition of fingerprint images using a digital communication interface. The present invention specifically serves to increase efficiency, repeatability, and readability of fingerprint images. 
     The preferred embodiment of the present invention is now described with reference to the figures where like reference numbers indicate identical or functionally similar elements. While the invention is described in terms of a specific embodiment, it should be understood that this is done for illustrative purposes only. A person skilled in the relevant art will recognize that various modifications, rearrangements and substitutions can be made without departing from the spirit of the invention. 
     To more clearly delineate the present invention, an effort is made throughout the specification to adhere to the following term definitions consistently. 
     The term “finger” refers to any digit on a hand including, but not limited to, a thumb, an index finger, middle finger, ring finger, or a pinky finger. 
     The term “fingerprint scanner” is any type of scanner which can obtain an image of all or part of one or more fingers in a live scan including, but not limited to, a tenprint scanner. A “tenprint scanner” is a scanner that can capture images representative of ten fingers of a person. The captured images can be combined in any format including, but not limited to, an FBI tenprint format. 
     The term “platen” refers to a component that include an imaging surface upon which at least one finger is placed during a live scan. A platen can include, but is not limited to, an optical prism, set of prisms, or set of micro-prisms. 
     FIG. 1A shows the finger guide unit  100  of the present invention in conjunction with a tenprint scanner  110 . Finger guide unit  100  is in the “slap” position, rotated to expose a platen  102 . Tenprint scanner  110  includes a housing  106  enclosing scanning optics which capture a fingerprint image through platen  102 . Platen  102  is slidably movable in the direction of the major axis of the tenprint scanner  110 . Platen  102  slidably moves, yet the detector is maintained in a stationary position within scanner housing  106 . In one example, platen  102  is preferably one face of a prism. This prism is located in an optical path to reflect light from a fingerprint resting on the face to the scanning detector. See, for example, commonly owned co-pending application 09/067,792, Individualized Fingerprint Scanner (1823.0020000), now U.S. Pat. No. 6,178,255 (which is incorporated herein in its entirety by reference). In another example, platen  102  can also include a plurality of parallel prisms. See, e.g., U.S. Pat. No. 5,920,384 issued to Borza (incorporated herein by reference in its entirety). 
     FIG. 1B shows the tenprint scanner of FIG. 1A with finger guide unit  100  in a “finger roll” position. A portion of platen  102  is exposed through a gap  104 . When scanning a fingerprint, platen  102  slidably moves below finger guide unit  100 , which is held fixed and stable. Finger guide  100  serves to keep the finger being scanned properly aligned with the scanning optics. For a proper roll print, a finger is placed in gap  104  onto platen  102 . The finger is rotated from fingernail to fingernail so that the whole print has contacted platen  102  during the roll. The scanning optics capture only a portion of the finger&#39;s image at a time, so it is important that the finger stay within the scanning area as the finger rotates. The finger rotates around its axis, with the axis remaining substantially stationary, with the finger properly positioned by finger guide  100 . 
     FIG. 5 shows the preferred embodiment of the housing interior  500  of the tenprint scanner of FIGS. 1A and 1B. Top housing  106  is removed revealing the optical assembly  510  fixedly attached to the housing bottom  502 . Optical assembly  510  is comprised of a linear camera  512 , a camera focus mount  514 , an imaging optics housing  516 , an imaging lens  518 , a mirror  520 , an illumination fold assembly  522 , and an LED illuminator assembly  524 . A floating image of movable platen  102  is also shown as an element of optical assembly  510 . To capture a fingerprint image, a finger is placed in the scanning area on platen  102 . LED illuminator assembly  524  serves as a light source and is comprised of cylinder lenses and an array of computer controlled LEDs. The beam of light from illuminator assembly  524  is reflected through an additional cylinder lens and mirror, which comprise illumination fold assembly  522 . From illumination fold assembly  522  light refracts through a wedge face on platen  102 , reflects off the finger on the top surface of platen  102  to be again refracted to mirror  520 . The light image is reflected into imaging lens  518  fixedly secured in image optics housing  516 . The light image passes through camera focus mount  514  to be captured by linear camera  512 . 
     As shown, finger guide unit  100  is rotatably removable, exposing the whole platen. Proper finger-printing requires not only rolled prints be taken, but also that plain impression or “slaps” be taken to verify finger sequence. This is a print of all four fingers of each hand and the two thumbs. In order to properly take an impression print, the fingers are placed on the platen, and the movable platen is slid, along with the fingers, so that all fingers pass through the stationary scanning area. The image of the four fingers of each hand are captured in sequence and matched against the rolled prints. To accomplish this, finger guide unit  100  is rotated to the slap position as shown in FIG.  1 A. The means of rotatable attachment is described in reference to FIG. 2 below. 
     FIG. 2 shows a top view of finger guide unit  100 . Finger guide unit  100  is rotatably attached to pivot shaft  214 . Pivot shaft  214  passes out each side of an adjustment mount  216 , through a smooth bore in guide plates  210 , and into scanner housing. The bore has a slightly larger diameter than pivot shaft  214 , allowing guide plates  210  to move smoothly along pivot shaft  214  both slidably and rotatably. To expose the platen, guide unit  100  may be rotated 180 degrees from a finger roll position to a slap position. Pivot shaft  214  may be in any number of convenient pieces, whose ends may pass through adjustment mount  216  or alternatively, may be enclosed or embedded in adjustment mount  216 . In the preferred embodiment, adjustment mount  216  is fixedly located on pivot shaft  214 , forcing guide unit  100  to maintain its position on pivot shaft  214  and keeping the unit aligned with the scanner optics. Further, adjustment mount  216  may be made of one or more pieces. In the preferred emobodiment, adjustment mount  216  is comprised of two half pieces. This is done for ease of assembly. 
     The preferred embodiment of finger guide unit  100  is comprised of two guide plates  210 , each having a contact edge  202  which serves to position a finger in the proper location for print scanning. Guide plates  210  are mirrored pieces, having a right plate and a left plate disposed adjacent one another and spread apart to create gap  104 . In the finger roll position, finger guide unit  100  remains in a stable position, with the centerline of gap  104  aligned with the scanning device optics. 
     Finger guide unit  100  assists in properly placing the finger for simple, easier scanning. A finger placed in gap  104  may be rotated, yet, because of the stationary finger guide, will not axially change position. The finger will be in contact with the moveable platen, which will glide with the equivalent rotational velocity of the finger. This allows the print scanner to capture all sides of the print though the finger maintains its axial position. 
     The width of gap  104  is adjustable by means of an adjustment device  400  (shown in FIG. 4) comprised of an adjustment wheel  206 , adjustment mount  216 , and threaded screws  208  threaded into apertures in guide plates  210 . Adjustment wheel  206  is a knurled cylinder fixedly coupled with threaded screws  208 . In the preferred embodiment, adjustment wheel  206  and threaded screws  208  are simultaneously manufactured from the same piece of material, resulting in a single component comprised of adjustment wheel  206  and threaded screws  208  each threaded in opposite directions. Threaded screws  208  are rotatably inserted into threaded bores in guide plates  210 . Because threaded screws  208  are threaded in opposite directions, turning adjustment wheel  206  moves the guide plates in opposite directions to lessen or increase the width of gap  104 . By turning adjustment wheel  206 , the guide plates are moved linearly toward or away from the center of gap  104  (in other words, the gap centerline). Because the detector inside the housing images the gap centerline area, it is important that the gap centerline remain constant to keep the finger aligned. However, as previously explained, the moveable platen  102  allows a print to be scanned as the finger is rotated in conjunction with the moveable platen. Adjustment wheel  206  allows simple versatile use of the guide by accommodating fingers having different diameters. Adjustment mount  216  snugly holds adjustment wheel  206  in relation to pivot shaft  214 . When adjustment mount  216  is properly secured to pivot shaft  214 , guide unit  100  cannot slide along threaded screws or along pivot shaft  214 . In the preferred embodiment, adjustment mount  216  is fixedly secured to pivot shaft  214  by means of set screws, tightened in adjustment mount  216  against pivot shaft  214 . This ensures that the centerline of gap  104  and the scanning area of the optics within housing  102  are properly aligned for clear fingerprint capturing. 
     Because the unit is a guide, and not a clamp, it is desirable to have a unit that allows the finger to be easily and smoothly rotated. Therefore, finger contact edge  202  is located low on the inner edge of each guide plate  210 . Contact edges  202  keep the finger in location during rotation. Contact edges  202  are manufactured of, or coated with a low friction material, such as polytetrafluoroethylene or daflon, to assist in keeping the finger centered in gap  104 . A guide without a low friction material could be problematic in that as the finger is rotating, the finger would bind with contact edge  202 , causing the resulting print to be skewed or stretched. Further, such binding may cause the finger to move away from guide unit centerline, requiring the print to be scanned again. The low friction material creates a slick surface for the finger to contact with low friction during rotation. It further eliminates excessive skin contact with the metal edge of guide plate  210  keeping the edge clean. 
     Contact edge  202  of the preferred embodiment may be removed from the guide plate, and has a replaceable low friction coating. This allows for easy replacement of the low friction coating should it become worn or dirty. Further, contact edge  202  of the preferred embodiment is a rod of stainless steel disposed along the edge of gap  104 , bending around guide plate corner, and running substantially the length of the front edge of each guide plate  210 . The low friction coating may cover the length of contact edge  202  or only the portion of contact edge  202  corresponding to gap  104 . 
     In one example, a removable sleeve is placed on the rod along the length at gap  104 . The sleeve is made of a low frictional material, such as, polytetrafluoroethylene or deflon. Contact edge  202  is secured to guide plate  210  by means of a single set screw, tightened in place. This screw can be removed to allow the rod to be freed at one end to allow the sleeve to be removed. In this way, sleeves can be replaced at appropriate times to maintain a level of cleanliness and hygiene. 
     Guide unit  100  is further provided with an alignment rod  212  which is disposed between guide plates  210  and is substantially parallel to pivot shaft  214 . Alignment rod  212  is a smooth rod inserted into a smooth bore in each of left and right guide plates  210 . This enables guide plates  210  to be adjusted by means of adjustment wheel  206  without introducing bending stress on pivot shaft  214 , thus eliminating the chance of binding. 
     Guide unit  100  is also provided with an extension  320  to support guide plates  210  when in its usable position, rotated down onto the platen. Extension  320  rests on the scanner body, holding guide unit  100  about 0.030 to 0.040 inch above platen  102 , permitting platen  102  to freely slide without additional frictional force. Extension  320  holds finger contact edge  202  at an optimal height above platen to provide guidance when taking a print. The guide however, could function substantially similar without the extension, relying on the low friction surfaces of the finger contact edge to rest directly on the platen. The extension further serves as a handle to ease the rotation of guide unit  100  to its slap or finger roll position.