WO2006044620A2 - Apparatus for reading skin topology - Google Patents

Apparatus for reading skin topology Download PDF

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Publication number
WO2006044620A2
WO2006044620A2 PCT/US2005/036967 US2005036967W WO2006044620A2 WO 2006044620 A2 WO2006044620 A2 WO 2006044620A2 US 2005036967 W US2005036967 W US 2005036967W WO 2006044620 A2 WO2006044620 A2 WO 2006044620A2
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WO
WIPO (PCT)
Prior art keywords
sled
skin
window
optics
light
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Application number
PCT/US2005/036967
Other languages
French (fr)
Other versions
WO2006044620A3 (en
Inventor
Daniel H. Raguin
Christopher J. Butler
John S. Berg
Bradford J. Pope
Original Assignee
Aprilis, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to US61919004P priority Critical
Priority to US60/619,190 priority
Application filed by Aprilis, Inc. filed Critical Aprilis, Inc.
Publication of WO2006044620A2 publication Critical patent/WO2006044620A2/en
Publication of WO2006044620A3 publication Critical patent/WO2006044620A3/en

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Classifications

    • GPHYSICS
    • G06COMPUTING; CALCULATING; COUNTING
    • G06KRECOGNITION OF DATA; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K9/00Methods or arrangements for reading or recognising printed or written characters or for recognising patterns, e.g. fingerprints
    • G06K9/00006Acquiring or recognising fingerprints or palmprints
    • G06K9/00013Image acquisition
    • G06K9/00046Image acquisition by using geometrical optics, e.g. using prisms

Abstract

An apparatus (113) for reading a two-dimensional image of skin topology having a window (109, 801) against which the skin is locatable, and a sled (101, 806), in which the sled and the window are movable with respect to each other along a first dimension. The sled (101, 806) has optics (207, 402, 600) for directing one-dimension illumination (203, 621) along a second dimension through the window (109, 801) to the skin (201), and an image capture device (103) for receiving returned light from the illuminated skin. The image capture device (103) is capable of imaging the returned light without imaging optics, whereby the image capture device with movement relative to skin along the first dimension provides a two-dimensional image along the first and second dimensions representative of the topology of the skin.

Description

APPARATUS FOR READING SKIN TOPOLOGY

Description

The present application claims priority to U.S. Provisional Application No. 60/619,910, filed October 14, 2004.

Field of the Invention

This invention relates to an apparatus (system and method) for reading skin topology, and relates particularly to an apparatus capable of reading large areas of skin topology, such as of fingers and/or palm. The invention is useful for obtaining images for analysis of finger and/or palm prints in which such images are at or greater than 1000 ppi (points per inch) resolution, thereby enabling detailed analysis of the ridges, valleys and pores of the skin.

Background of the Invention

Growing concerns regarding domestic security have created a critical need to positively identify individuals as legitimate holders of credit cards, driver's licenses, passports and other forms of identification. A well-established method for identification is to compare a fingerprint with a previously obtained authentic fingerprint of the individual. Fingerprints have traditionally been collected by rolling an inked finger on a white paper. More recently, automated devices have been developed for obtaining fingerprints. Typically, these devices have a solid-state imager, such as a capacitive or optical sensor, to capture the fingerprint image in a digital format. By using a solid-state imager as part of a fingerprint identification apparatus, a fingerprint can be collected conveniently and rapidly, for example, during a security check, and subsequently correlated, in near real-time, to previously trained digital fingerprints in an electronic database that resides either in a computer at the security check point, a secure but portable or removable storage device, or on a remotely networked server.

A typical fingerprint comprises a pattern of ridges separated by valleys, and a series of pores that are located along the ridges. Such ridges are usually 100 to 300 μm wide and can extend in a swirl-like pattern for several mm to one or more cm. These ridges are separated by valleys with a typical ridge-valley period of approximately 250-500 μm. Pores, roughly circular in cross section, range in diameter from about 50 μm to 250 μm and are aligned along the ridges and can be isolated or grouped into two or more abutting or near abutting features. Almost all present-day fingerprint identification procedures use only ridge/valley minutiae patterns. These are simplified and identified as a pattern of ridge/valley features, such as end points, deltoids, bifurcations, crossover points, and islands, all together referred to as minutiae. Typically, a relatively large area of the fingerprint is required in order to obtain enough unique minutiae features, for example, at least 0.50 x 0.50 inches. Most modern fingerprint imagers therefore use up to one (1) full inch square or even larger, in order to obtain enough features to perform a useful means of identification. Fingerprints are compared using primarily this simplified description of the minutiae patterns. However, for the purposes of reducing failure to accept rates (FAR) and failure to reject rates (FRR), there is a movement towards higher resolution to enable capture of AFIS (Automated Fingerprint Identification System) Level 3 detail (i.e., poroscopy and edgeology).

Aprilis Inc. of Maynard Massachusetts, U.S.A., manufactures the HS500 and HSlOOO fingerprint readers. These readers are capable of capturing high-resolution images of the skin topography from a single finger. Although this reader allows for positive identification of an individual by high resolution imaging of a relatively small portion of a fingerprint, it is sometimes necessary to acquire images of a large area of skin at high resolutions. This is especially the case during enrollment of fingerprint images. Enrollment of fingerprint images occurs when a new fingerprint is imaged and stored in a database for future use. For example, enrollment occurs when a criminal suspect is fingerprinted by a law enforcement agency for the first time, hi this case, it is almost always required that all ten fingerprints of the suspect be imaged and stored in a database. Moreover, it is often required that four fingerprints (excluding the thumb) from each hand are acquired simultaneously in order to establish the sequence and relative position of fingerprints on each hand. This type of four print simultaneous acquisition is referred to as "four-finger slap" enrollment. In addition to four-finger slap enrollment, it is often necessary to capture prints of other portions of the skin topography of the hand. For example, law enforcement usually requires the enrollment of fingerprints that include an image of the skin from the sides of the finger. This type of fingerprint enrollment, referred to as "roll-prints". Rolled fingerprints are usually acquired by placing one side of the finger of interest upon the imaging device, the finger is then "rolled" onto the opposite side of the finger, during which time a print capture device records a spatially continuous image of the finger print from one side of the finger to the opposite side of the same finger. In addition to rolled and four-finger slap enrollments, it is sometimes necessary to enroll prints of the palm of the hand, side of the palm, or other large portions of skin topography. In order to meet the aforementioned enrollment requirements, it is necessary to use a print capture device capable of acquiring large areas of skin. Moreover, if one is to use pore detail in matching prints, it is necessary to acquire images of large areas of skin at substantially high resolutions.

Fingerprint capture devices capable of imaging prints at resolutions required for minutiae matching are, for example, manufactured by Smith Heimann Biometrics GmbH of Jena, Germany, CrossMatch Technologies of Palm Beach Garden, Florida, U.S.A., and Identix, Inc. of Minnetonka, Minnesota, U.S.A. These devices image fingerprints at a maximum resolution of lOOOppi. Sartor, U.S. Patent No. 6,175,407 describes a full-hand scanner, and it is believed the Identix Touchprint™ 3800 scanner incorporates the technology of this patent. This scanner has a platen capable of scanning a full handprint. Sartor describes the use of a 1-D detector and requires the hand to move over a convex surface with the detector remaining stationary, and also describes an imaging system that is composed of a plurality of lens and prisms. The Identix Touchprint™ 3800 also contains a flat platen for the purposes of capturing a flat 4-finger sequence. It is believes that this flat capture device is described in Maase, U.S. Patent No. 5,650,842. hi Maase, the system is static, and a prism and imaging optics are required to collect the light and image the skin topology onto a detector.

Smiths Heimann Biometrics markets the L Scan IOOOP scanner capable of scanning four fingers at 1000 dpi. This scanner is believed described in Hillmann et al., U.S. Patent No. 6,658,140. Though Hillmann et al. describes the platen on which fingers are placed as a scanning surface, there are no moving parts in the scanner. Instead, the entire two- dimensional (2-D) area of skin to be imaged is simultaneously illuminated and imaged using a 2-D detector.

CrossMatch Technologies markets a four-finger slap device model IDlOOO that is believed to incorporate a scanning system as described in Scott et al., U.S. Patent No. 6,628,813. As described by Scott et al., large areas are scanned through the movement of a large prism with the skin, while leaving the detector and imaging optics stationary.

McClurg, U.S. Published Patent Application No. 2004/109,245 describes a fingerprint scanning device where a subject's hands are placed on a prism with a non-planar surface, preferential the surface of a cone, for the purposes of acquiring the print of a subject's full hand, hi the acquisition of the handprint, the subject's hands are stationary and an optical system and a detector scans and images the light reflected from the prism-skin interface.

A drawback of the above-described automated fingerprint scanning devices is that they require imaging optics in the form of lens and/or prisms in the path of light from the skin to their respective detectors or sensing devices. This not only increases the cost of such device, but also their size and weight, which is especially a concern in making such devices portable. Such portable fingerprint scanning devices may be useful in a variety of environments, including airport security stations, customs and border crossings, police vehicles, home and office computing and entrance control sites of secure buildings. Thus, it is desirable to have an automated fingerprint scanning device for high-speed acquisition of images of large areas of skin topography that does not require imaging optics, such as lens and/or prisms, and which is further able to scan large areas of skin at image resolutions at or greater than lOOOppi. Removal of imaging optics would allow optical elements in the detector path to be closer and thus in a more compact arrangement, thereby size and facilitating portability of the scanning device.

Summary of the Invention

Accordingly, it is one object of the present invention to provide an improved apparatus for reading a two-dimensional image of skin topology which does not require use of imaging optics in the path of returned light from the skin to a detector.

It is another object of the present invention to provide an improved apparatus for reading a two-dimensional image of skin topology which is capable of imaging large scan large areas of skin at image resolutions at or greater than lOOOppi.

It is still another object of the present invention to provide an improved apparatus for reading a two-dimensional image of skin topology which facilitate portability of the apparatus.

Briefly described, the present invention embodies an apparatus for reading a two- dimensional image of skin topology having a window against which the skin is locatable, and a sled, in which the sled and the window are movable with respect to each other along a first dimension. The sled has optics for directing one-dimension illumination along a second dimension through the window to the skin, and a detector for receiving returned light from the illuminated skin. The detector is capable of imaging the returned light without imaging optics, whereby the detector with movement relative to skin along the first dimension provides a two-dimensional image along the first and second dimensions representative of the topology of the skin.

The sled may further have a coherent light source for producing a beam, and optics for shaping the beam into a thin one-dimension (or linear) illumination in addition to the optics for directing the beam toward the window. The light source may be an LED, laser, or an array of light sources, such as LEDs. Optionally, the optics for directing the beam to the window may shape the beam from the light source into the one-dimensional illumination, thereby avoiding the need for separate beam shaping optics. For example, the optics for directing the beam to the window may be a waveguide illumination device having a volumetric grating, which is capable of outputting a one-dimensional illumination in response to an incident illumination from the light source. Optionally, the light source, and optics for shaping the beam may be external from the sled.

In one embodiment the window is part of a stationary platen and the sled is moved along the first dimension on a rail system below the platen to enable the detector and skin to move relative to each other. This embodiment enables single or multiple slap fingerprints to be imaged. In another embodiment the window is part of a platen and the platen and sled are each movable with respect to each other, in which either the sled or platen is locked stationary, and the other moved along a rail system along the first dimension to enable the detector and skin to move relative to each other. This embodiment enables single or multiple slap or rolled fingerprints to be imaged.

Although the apparatus is described without imaging optics, imaging optics may optionally be provided in the apparatus by a lens or lens array, where the detector receives returned light through the lens or lens array for imaging the returned light from the skin onto the detector.

The present invention also embodies a system having a platen with a window against which skin is locatable, a sled located below the platen, and a rail system upon which one of the sled or platen is motor driven with respect to each other. The sled has at least optics for providing one-dimensional illumination towards the window for illuminating the skin, and a detector detecting returned light from the illuminated skin, in which the detector is capable of imaging the returned light without imaging optics. The system may also have a controller for receiving output from the detector and controlling movement of the motor driving the sled in response to at least one sensor along the sled or platen for reading encoded position information. The system output, with movement of detector relative to the skin, provides a two-dimensional image representative of the topology of the skin.

The present invention also embodies a method having the steps of providing a platen having a window against which skin is locatable, providing a sled located below the platen, moving at least one of the sled or platen with respect to each other, providing from the sled one-dimensional illumination through the window for illuminating the skin, and detecting in the sled returned light from the illuminated skin in which such detecting is capable of being carried out without the aid of imaging optics.

Brief Description of the Drawings

The foregoing objects, features and advantages of the invention will become more apparent from a reading of the following description in connection with the accompanying drawings, in which:

FIG. IA is a diagram of the apparatus in accordance with the present invention shown coupled to a computer for receiving image data from the apparatus;

FIG. IB is a perspective view of the scanning assembly of the apparatus of FIG. IA in which the platen of the apparatus is removed;

FIG. 1C is the same perspective view of the scanning assembly of FIG. IB in which the platen is shown attached to the scanning assembly;

FIG. 2 is a block cross-sectional diagram of the apparatus of the present invention for capturing the skin topography;

FIG. 3A is a top down view of the sled of the apparatus of FIG. 1A-1C;

FIG. 3B is an isometric view of the sled of FIG. 3 A;

FIG. 4A is a block diagram similar to FIG. 2 showing an alternative embodiment for providing illumination from the sled using a linear illumination array;

FIG. 4B a block diagram similar to FIG. 2 showing another alternative embodiment in which one or more lenses image light from the skin;

FIG. 5 is an example of a fingerprint image captured by the apparatus of FIGS. IA- IC;

FIG. 6A is a block diagram showing alternative optics providing linear illumination in the sled using a waveguide illumination device;

FIG 6B is a block diagram of the apparatus similar to FIG. 2 incorporating the waveguide illumination device of FIG 6 A; FIG. 7 is a block diagram of the apparatus similar to FIG. 2 in which the illumination beam is produced external of the sled;

FIG. 8A illustrates an embodiment of the apparatus of the present invention in which either the sled or the platen in movable enabling the apparatus of acquiring both slap and rolled fingerprints; and

FIG. 8B is a cross-sectional view of the apparatus of FIG. 8 A.

Detailed Description of the Invention

Referring now to FIGS. 1A-1C, the fingerprint scanning apparatus 113 is shown having a platen 112 mounted on a scanning assembly 100. The platen 112, scanning assembly 100, control circuit board 115, and interface circuit board 114, and mounted within a housing 113a. The scanning assembly 100 comprises a moving sled 101 containing an illumination system 102 and an image capture device (or detector) 103. The sled 101 travels on a rail system provided by a pair of rails 104, and is driven by a motor 105 that is shaft- coupled to a motor hub 106a. The motor hub drives a belt 107 that is attached to sled 101. The rail system has two ends located in fixtures 108 in housing 113a, which are assembled to retain the ends of rails 104, to fix such rails parallel to each other, and to provide slots for rotatably mounting hubs 106a and 106b. Hubs may represent gears or pulleys with a continuous surface for supporting the ends of continuous belt 107. In addition to rails 104, a bracket 111 also extends across fixtures 108. The sled travels beneath a window 109 that is mounted to the window holder 110 of the platen assembly 112, where FIGS. IB and 1C show the scanning assembly 100 without and with platen assembly 112, respectively. Window 109 may be a transparent glass or plastic plate, which is for example, may be less than 2mm thick, but other thicknesses may be used.

As the sled moves, the illumination system 102 illuminates the window-skin interface formed by pressing a skin surface against the window 109. The image capture device 103 records the pattern of the skin as the sled 101 travels below the window 109 (as indicated by arrow 150). The image data representing the pattern of the skin is transmitted from the image capture device to a stationary interface circuit board 114. The interface circuit board 114 relays the image data through a data cable 117 to a high-speed interface port on a computer 118. The high-speed interface port on of the computer 118, may include for example: digital data capture cards, USB 2.0 ports, IEEE1394, or other computer interface ports that facilitate the transmission and storage of high speed streaming data. Additionally, the interface circuit board 114 may include one or more memory storage elements 123 (e.g., RAM memory) for the purpose of storing the image data, which may be transmitted concurrently or at a later time via the high-speed interface. The image data or prints acquired by computer 118 may be stored and processed, such as for analysis of ridges, valleys, and/or pores of the skin of the image, as typical of fingerprint analysis software operating on the computer.

The interface circuit board 114 of FIG. IA contains power-conditioning circuitry that serves to provide power to all aspects of the apparatus 113. Power is supplied to the interface circuit board 114 through a AC/DC converter 116. Optionally, a battery may be provided in housing 113a to supply power. The power conditioning circuitry 121 of the interface circuit board 114 converts the power supplied by the AC/DC converter 116 to several voltage levels that will be used by various parts of the print capture device. In addition to power conditioning circuitry, the interface circuit board 114 may contain motion control circuitry 122 to drive the motor 105 that in-turn drives the motion of the sled 101. Alternatively, motion control circuitry could be housed on a separate circuit board and connected to the interface circuit board 114 through electrical connectors.

The interface circuit board 114 is electrically connected to a controller circuit board 115 through a multi-conductor cable 120. The controller circuit board 115 serves to control all aspects of operation of the apparatus 113. The controller circuit board 115 receives user input from the computer 118 through a controller cable 119. Such user input is processed by the controller circuit board 115 to instruct the apparatus 113 to operate. The controller circuit board for example, may instruct the motion controller on the interface circuit board 1,14, to actuate motor 105 (FIG. IB) in order to begin scanning the sled 101. In addition, the controller circuit board may receive input from an encoder system (the encoder head 124 and scale 125 is depicted in FIGS. IB and 1C) that indicates the position of the sled 101 during scanning. The position infoπnation of the sled, supplied by the encoder system may be used by the controller circuit board to generate the signals to control the image capture device 103, as will be described below in more detail. The controller circuit board 115 may also process the image data acquired by the image capture device 103, and then send the processed data back to the interface circuit board 114. Such data processing may include image data compression or other image processing. The controller circuit board 115 may have a controller, for example, one or more of microcontrollers, microprocessors which operate in accordance with a program stored in its memory or other memory on circuit board 115, and/or field programmable gate arrays. In order to enhance portability, the controller on the controller circuit board 115 may provide the functionality of the computer 118 with additional memory for supporting such functionality, whereby an external host computer is no longer required. Also, the apparatus may include a memory storage unit (e.g., hard or optical disk drive, or FLASH) accessible to the controller for storing captured and/or processed image data, and an on-board user interface (e.g., LCD display, keyboards, mouse, or buttons) to allow the user to control the apparatus. The apparatus may export such captured and/or processed image data from the memory storage unit to other computer(s) via interface circuit board 114.

In operation, when motor 105 is enabled, the sled 101 traverses the length of the rails 104 in a scanning motion along a direction defined by the z-axis. The motor can be driven in either direction allowing the moving sled to be scanned in either direction. The apparatus 113 of FIG. IB may comprise a linear encoder system for the purpose of determining the position of a moving sled 101 as the sled traverses the length of the rails 104. Linear encoder system may use optical or magnetic readers/sensors 124a to determine the position of an encoder head 124 along an encoder scale 125 (e.g., a reflective periodic grating). One of the encoder head and the encoder scale is translated across the other to produce signals representing the position of the encoder head relative to the encoder scale. The exemplary optical encoder system produces a pulse train signal resulting from a periodic structure in the encoder scale. As the periodic structure of the encoder scale may be well characterized, the time between pulses can be measured to determine the velocity of the moving component of the encoder system. In addition, the pulses in the pulse train can be counted to determine the cumulative distance traveled by the moving component of the encoder scale. For example, the scanning assembly 100 may utilize an optical encoder head 124 and encoder scale 125 manufactured by MicroE Systems of Natick, Massachusetts, U.S.A. Preferably, the encoder 124a is attached to the underside of the sled 101 in an orientation so as to address the complementary encoder scale 125 mounted on the inside of the scale mounting bracket 111. The encoder 124a is capable of locating the position of the sled 101 along the rails 104 with sufficient accuracy (e.g., within 1 micron for 4000ppi, or 4 microns for lOOOppi) the purposes of performing a scan at a controlled velocity or positioning sled 101 at a desired location. The encoder 124a may also perform the function of triggering the exposure period of the image capture device as the image capture device 103 travels on the sled. The period of the pulse train that results from scanning an encoder head across the encoder scale may be used to determine the exposure rate of the image capture device 103. The encoder pulse train may also be counted in order to determine the effective resolution of the resulting image. Triggering of the image capture device 103 to take a picture every set number of encoder pulse(s) in the z-direction sets the resolution in that direction. Such as triggering every 7 microns of sled movement as measured from the encoder system results in image capture resolution in z of 3629ppi, where pixel to pixel separation of the image capture device 103 dictates the resolution of the image in x. Each image captured by the device 103 is sent to the interface circuit board to build a raster scan 2-D image in the z and x dimensions.

The apparatus 113 of FIGS. IB and 1C may also contain switches 126 located along the direction of travel of the sled 101. These switches maybe mechanical, optical, or electronic in nature, and may provide indication to the controller of the apparatus 113 that the sled 101 has reached a particular location of interest along the travel of the rails 104. Such locations of interest may include, but are not limited to, end of travel locations, begin and end of image capture area locations, or center of travel locations. The controller on the control circuit board 115 provides signals to the motor control circuitry 122 of the interface circuit board, which in turn provides signals to the motor to drive the sled bi-directionally, via belt 107, along rails 104. For example, prior to each scan the controller may drive the motor in the direction in z to find the home position via switches 126, i.e., whether the sled is located at which end of its travel path along the rail system, in that the sled after each scan is located at one of such ends, or if not, the motor is driven accordingly.

FIG. 1C illustrates the scanning assembly 100 of FIG. IB with the addition of the platen assembly 112 comprising a window 109 and a window holder 110. The scanning assembly 100 can be used to image the topology of skin that is pressed against the window 109 by scanning the sled 101 under the window 109. Preferably, the window 109 is located close to the image capture device 103. The size of window 109 is shown for purposes of illustration, other sizes of window may be used, so long as the length of the linear (one- dimensional) illumination incident the window and the length of the image capture device 103 is sized accordingly. For example, images produced by the scans may be 4 inches in the z-direction by 3 inches in the x-direction, in which the window is sized approximately at least as large as the size of the scan. Preferably for a 4-finger slap, the window 109 is at least 3 inches by 3.2 inches to capture skin of same size, per U.S. Federal security specifications (e.g. AFIS Appendix F).

Referring to FIG. 2, a cross-section of an apparatus for the illumination and imaging of skin topography according to the present invention is illustrated. The skin of the object to be imaged, in this example finger print skin 201, is pressed against a transparent window 109. The moving sled 101 travels in the z direction below the window along the rails 104. The illumination system 102 (outlined by the dashed lines) contains a light source 210, beam conditioning (or shaping) optics 202, and light deflector 207. An image capture device 103 is also shown. The light source 210 of the illumination system 102 may contain a light generation device, such as a laser diode or light emitting diode (LED). The beam conditioning optics 202 may include, but are not limited to one or more of the following: refractive lenses, diffractive optical elements, and mirrors. The light 203 that is emitted from the beam conditioning optics 202 is constructed so as to produce optimum illumination of the window-skin interface 204, as will be shown for example in FIGS. 3A-3B. The light 203 may be directed towards a light deflector 207, having preferentially a highly reflective surface 211, which redirects the light beam 203 towards the window-skin interface 204. hi alternative embodiments, the light 203 may be directed towards the window-skin interface 204 directly from the beam conditioning apparatus 202. The light 203 is incident upon the window-skin interface 204. At the window-skin interface, portions of the skin topography that make sufficient optical contact with the window 109, cause the light 205 to be coupled into the skin (due to an approximate match of the index of refraction of the skin to that of the platen). Other portions of the skin topography that do not make sufficient optical contact at the window-skin interface cause the incident light to be reflected from the window-skin interface (due to a glass-air interface). The reflected light 206 travels towards the image capture device 103, passing through detector window 208, facilitating the recording of the topography pattern of the illuminated skin by the image capture device. Preferably, the image capture device 103 comprises a linear detector array that may include, but is not limited to a linear charge coupled device (CCD) array, a complementary metal oxide semiconductor (CMOS) array, photodiode array, or any combination thereof.

Detector window 208 which may be part of, or separate from, the detector providing image capture device 103. Detector window 208 may be composed of glass, such as Schott D263T, and at a minimum is useful to seal the detector from contaminants and accidental contact during assembly. However, it is preferred that the detector glass incorporate filters, such as spectral and polarization filters, to improve the operation of the device 103. The spectral filters, by way of example, may be absorptive or dichroic, but preferentially designed such that they transmit light of the wavelength emitted by the light source 301 and reject all other electromagnetic radiation that image capture device 103 is sensitive to. Polarization filters are advantageous due to skin behaving as a volumetric scatter. By way of example, if the light beam 203 is polarized when it strikes the window-skin interface 204, then the portion of light that transmits into the skin, where the skin makes contacts with the window- skin interface will scatter within the skin. The scattering process depolarizes the incident beam and a portion of the light is scattered back towards image capture device 103. Therefore, to maximize image contrast, by way of example, between the ridges and valleys of a fingerprint, a polarizer oriented to pass radiation of the polarization typically reflected by window-skin interface 204 if depolarizing skin were not present, is preferred. Such detector window may thus incorporate non-imaging optics in that such optics effect characteristics of the light received by the detector, but do not provide focusing or other optics necessary for enabling imaging on the detector.

The beam conditioning optics 202 of the illumination system 102 serve to produce a beam of light 203 that is substantially shaped into a line of light such that the length of the line of light is at least equal to the length of the image capture device (length being defined in the x direction). The beam conditioning optics 202 also serve to minimize the width (as defined in they direction) of the beam of light 203 at the window-skin interface 204. The minimization of the width of the beam of light will result in maximum contrast images of the skin topography by minimizing the area of the skin that is illuminated. The illumination of the skin produces light scatter that is recorded by the image capture device 103. If extraneous areas of skin are illuminated by light from the illumination system 102 due to an overly broad line width, excess scattered light will be sent into the image capture device 103. The excess scatter light will appear as background light in the image of the skin topography detail, thus reducing contrast between ridges, valleys, and skin pores of the skin. Therefore optimum contrast in the skin topography image can be achieved by minimizing the line width of the beam of light 203 produced by the illumination system 102 at the point which the light 203 makes contact with window-skin interface 204. Less preferably, the image capture device 103 may comprise a two-dimensional area detector array that may include, but is not limited to a CCD array, a CMOS array, photodiode array, or any combination thereof.

FIGS. 3 A and 3B illustrate an example of a sled 101 that may be used for the illumination of the skin topography with a line of light and the subsequent capture of the skin topography by image capture device 103. In this example, the sled represents a platform 101a for the illumination system 102 and image capture device 103, and below the platform is a support plate 101b with two blocks with parallel openings 101c for rails 104, in which the openings 101c are sized to enable the sled to slide along such rails. The illumination system 102 and image capture device 103 may be mounted on separate circuit boards or platforms to platform 101a. Although openings 101c are used, other mechanisms may be used in the rail system for enabling the sled to ride on rails, such as bearings, grooves, or brackets along the bottom of the sled, hi this example, a laser diode 301 is used as a light source. The beam emitted from the laser diode 301 is beam-shaped by a lens element 302. Preferably, lens element 302 is a cylindrical lens so as to control the divergence of the beam in the y-axis only. In the exemplary sled of FIGS. 3A and 3B, the cylindrical lens 302 allows for the minimization of the width (defined in y) of the illumination beam at the window-skin interface. Mirrors 303, 306, and 307 are used to fold the beam path for the purpose of minimizing the overall size of the illumination system 102. Lens element 304 is used to collimate the light in the x-z-plane. Preferably, a cylindrical lens element is used for lens element 304 and the optimum focal length of the cylindrical lens is selected such that the length of the line of light (defined in the x direction at the window-skin interface) will be sufficient to encompass the overall y-dimension of the image capture device 103 with sufficient intensity uniformity, as may be required. An optional λ/2 wave plate 305 is illustrated that can be used to rotate the polarization plane of the laser beam such that the polarization incident on diffractive optical element (DOE) 308 is the preferred polarization orientation for maximum efficiency. The DOE serves to make illumination system 102 as compact as possible by providing for anamorphic expansion of beam. The beam 320 entering the DOE has a width of dm- , while the exiting beam 321 has a width of J0Ut- Through proper design of a high-frequency grating (which by way of example may surface-relief or volume), expansion ratios J0UtMn of greater than 7: 1 can be achieved. The DOE being uniform in the y direction does not affect the beam width in said direction and hence the term anamorphic. The light beam incident upon the diffractive optical element 308 will produce a thin (iny) but long (in x) line of illumination as the incident beam diffracts from the grating towards a light deflector 207. Preferably, the light deflector 207 is a thin mirror that redirects the line of light towards the window-skin interface at a predefined angle.

The following are exemplary components in reference to the sled 101 of FIG. 3A. Light source 301 may be a 655-nm laser diode Model LD 1535 from Power Technology (Alexander, Arizona, U.S.A.). The output polarization for this laser is vertical (y-direction) as mounted. Lens elements 302 can be an/= 12.7 mm cylindrical lens P/N 01 LCP 002 from Melles Griot (Rochester, New York, U.S.A.) and Lens elements 304 can be an/= 50 mm cylindrical lens P/N 01 LCP 133. Coupled with diffractive optical element 308, these lenses can produce a beam of rays 203 that represents a collimated beam in x of width doυi and a focusing beam iny. By way of example, the DOE chosen for anamorphic beam expansion can be a replicated sinusoidal surface-relief grating from Spectra Physics Richardson Grating Lab (Rochester, New York, U.S.A.), Cat# 53999FL02-136H. This grating has a frequency of 1714.3 lp/mm, and as such with λ = 655 nm light incident at an angle of 82° can produce a - 1st order diffracted beam with a cross-section in the x-direction of 7.2 times of the width of incident beam. Since the grating achieves maximum diffraction efficiency for TM-polarized light, a half-wave plate 305 is needed to rotate the polarized light 90°. Other DOE elements may also be used, such as a volume grating using holographic material such as available from Aprilis, Inc. One skilled in the art will realize that mirrors 303, 306, and 307 may be have power to their respectively reflective surface in order to remove the requirement of having lens elements 302 and 304. However, for this illuminating example, the mirrors have planar surfaces and are used solely to fold and direct the beam paths of the optical system. For an image capture device 103 that is high-speed, one may select, for example, the Kodak KLI-8811 1-D CCD array. This CCD array is a monochrome 1 x 8800 array of 7 μm x 7 μm pixels, and as such, given unity magnification of the illumination system, means that a section of skin 61.6 mm in x can be scanned. Using these elements, the beam generated by the illumination system has less than 10% power variation across a reference 1-D detector. The above elements are examples, other element may be used to provide the desired illumination and detection.

Due to the unity magnification and the 7 μm pixels, the apparatus 113 is capable of scanning skin topology at a resolution of 3629 points per inch (ppi) in x. With a high- resolution encoder, 3629ppi can be achieved along z as well. Preferably the z-scan is at least 3.2 inches long. For the example of a 61.6mm x 100mm scan at this resolution, this requires the apparatus 113 to be capable of collecting 126 MB of data where each byte of data corresponds to a 255 grayscale representation of an image pixel. For example, such 126 MB of data may be acquired in approximately 1.26 seconds, resulting in a high acquisition rate of 100 MB/second. Such image data may be stored in a memory buffer that resides on a high¬ speed digital acquisition card within a computer 118 (or within apparatus 113 if functionality of such computer is provided within the apparatus, as described earlier). The data is transmitted from the apparatus 113 through a high speed parallel 32bit interface to such memory buffer. Alternatively, this memory buffer may be provided within the apparatus 113 to serve as a temporary buffer while data is transmitted to the computer 118 through a conventional PC interface, which by way of example may include USB 2.0 or IEEE 1394 (Firewire).

Additionally, to improve the resolution of the image capture device when no imaging optics are utilized, it is preferable that the optical distance between the photosensitive surface of image capture device 103 and the window-skin interface 204 is minimized. By way of example, the optical distance, termed optical path length (OPL), may be 6.0 mm (where window 109 is 1.6 mm thick, and the photosensitive surface of image capture device 103 is 2.0 mm below the bottom surface of detector window 208). By reducing this distance and/or by reducing the incident wavelength (for example replacing the 655 ran diode laser for a 405 run diode laser as a light source), the imaging resolution of the system may be improved.

For example, apparatus 113 may be approximately 30cm, 10cm, by 30cm, in x, y, z, respectively (as illustrated in FIG. IA for example), and weighs roughly 6.5 kg (such weight being without additional hardware for incorporating computer 118 functionality within the apparatus, as described earlier). Optionally, the circuit boards 114 and 115 may be integrated to further reduces the length of the device. Such further integration of the electronics can yield a reduction of the circuit board area, thus reducing the x-dimension of the exemplary device to approximately 15cm. In this example, the dimensions and weight of the apparatus 113 facilitates the portability of the device.

Another embodiment of the illumination system 102 on sled 101 is shown in FIG. 4 A having a linear illumination array 401 as a light source, wherein the illumination array is an array of light sources running in the x direction. The linear illumination array 401 may include an array of light emitting diodes (e.g., LED), an array of laser diodes (e.g., vertical cavity surface-emitting laser or VCSEL), or other linear light generation devices. The use of a linear illumination array provides a more compact and potentially less costly overall system. As described previously, the light source produces a line of illumination in the x-direction, where the line of illumination preferentially fills the length in the x-direction of the image capture device 103. In the current embodiment, a cylinder lens 402 that covers the length in x of linear illumination array 401 is used to minimize the width of the line of light 403 produced by the linear illumination array. The skin of the object to be imaged, in this example finger print skin 201, is pressed against a transparent window 109. The moving sled 101 travels below the window along the rails 104. The light 403 that is emitted from the combination of the linear illumination array 401 and the cylinder lens 402 is constructed so as to produce illumination of the window-skin interface 204. The light 403 is directed towards the window-skin interface 204. The light 403 is incident upon the window-skin interface 204. At the window-skin interface, portions of the skin topography that make sufficient optical contact with the window 109, cause the light 205 to be coupled into the skin (due to the low index of refraction difference between the window material and the skin being pressed against the window). Other portions of the skin topography that do not make sufficient optical contact at the window-skin interface cause the incident light to be reflected from the window- skin interface (due to the Fresnel reflection coefficient of glass-to-air interface in the case of window 109 being composed of glass). The reflected light 206 travels towards the image capture device 103 facilitating the recording the topography pattern of the illuminated skin by the image capture device 103.

Referring to FIG. 4B, the sled 101 can incorporate imaging optics 404 for the purposes of relaying the reflective light 206 onto image capture device 103. Preferably, the imaging optics 404 comprise an array of gradient-index (GRIN) microlenses that extends along the length of the linear detector array (in the x direction). An example of a suitable GRIN lens array may be found in a commercially available NSG SELFOC® lens array that can be used to transfer the image of the window-skin interface 204 to the face of the image capture device 103. Other light sources than a linear illumination array may also be used for generating linear illumination. The addition of the imaging optical system 404 may facilitate the acquisition of higher optical resolution images of the window-skin interface 204, if needed.

As FIGS. IA through 4A show, no imaging optical system, such as lenses, is present to relay the topography of the window-skin interface to the image capture device. Referring now to FIG. 2, the light that reflects from the window-skin interface 204 propagates mostly through free space to the surface of the detector of the image capture device 103. The topography of the skin typically contains features of interest ranging in size from tens of micrometers to hundreds of micrometers. The ability to acquire an image of the window-skin interface 204 is a function of the extent of diffraction of the illumination from the topographic features of the skin. The extent of diffraction of the illumination from the skin topography is a function of the topography feature size, the wavelength of illumination, and the optical path length between the window-skin interface 204 and the image capture device 103. By minimizing the optical path distance 209, the effect of diffraction will be minimized, allowing sufficient imaging of the skin topography. FIG. 5 depicts a fingerprint image that was captured using the sled of FIGS. 3 A and 3B in the apparatus of FIG. IA. The optical path length 209 used to generate the image in FIG. 5 is approximately 6.0mm. It was found that a 6.0 mm optical path length with a 655 ran wavelength laser diode is sufficient for imaging the fine detail of the skin ridges and valleys along with the skin pores of an adult finger.

In another embodiment of illumination system 102 that achieves a compact design, waveguide technology is utilized as shown in FIGS. 6A and 6B. In FIG. 6A a waveguide illumination device 600 is depicted, and in FIG. 6B the waveguide illumination device is incorporated into the sled 101 that operates within the apparatus 113. A light source 601 with diverging light 602 is collimated with a collimating optical lens 603. The light source is preferentially a monochromatic source such as a semiconductor laser, but may also be a light emitting diode (LED). The collimated beam 604 is focused by focusing lens 605 such that the focused beam 606 is coupled into waveguide region 607. The waveguide region comprises a region of higher index of refraction than its surrounding cladding material 608, where the cladding material may be the same or different material top and bottom of the waveguide region provided the indices of refraction for the cladding material is lower than that of the waveguide region. Waveguide region 607 contains a slanted volumetric grating designed to couple light out of the waveguide region. Preferentially the volumetric grating is designed such that the light 609 emitted from the waveguide illumination device has uniform intensity along the x direction, which, by way of example, requires a grating of lower diffraction efficiency towards the direction of the end coupling and a grating of higher diffraction efficiency towards the opposite direction. Preferentially, the volumetric grating takes light from waveguide region and focuses it in the y-z plane as shown in FIG. 6B.

FIG. 6B represents a y-z cross section of a portion of the apparatus 113. Focusing light 621 is illustrated being emitted by the waveguide illumination device 600, wherein the focusing light focuses substantially at skin- window interface 204. The waveguide illumination device is drawn encased in substrate block 620. It is desirable that the material of substrate 620 is similar in index of refraction as cladding material 608 and preferentially is made of the same material. Substrate block 620 is spatially separated from window 109 using spacers 623. The spacers are ideally made of a low-friction material such as Teflon™. In this manner, the separation of substrate block 620 from window 109 can remain constant as the sled 101 travels along the z axis. The sled, by way of example, can be pressed up against the underside 624 of window 109 via springs 626 that apply a force in the y direction. The light 622 reflected from skin-window interface 204 is captured by a detector 103 without the use of optical elements of power (i.e., no imaging lenses).

Since a reasonably coherent light source, such as an LED or a laser, is needed for imaging without the use of imaging optics, it is desirable that surfaces are anti-reflection (AR) coated. By way of example, the surfaces so coated may be surfaces 624, 625, 627, 628, and

629. In other figures, optical surfaces in the path of illumination or detection (e.g., the bottom surface of window 109, and refractive lens elements in the illumination path of FIG. 3A) may also be AR coated. Filter 630 represents a filter that is desirable for the purposes of filtering stray light in the form of scatter from the skin topology being examined or stray light from light source external to the print capture device. The filter, by way of example, can be any combination of a linear polarizer and a color filter. A linear polarizer is desirable since skin is a volumetric scatterer and hence light scattered by skin will be depolarized. By having a polarized illumination source, one orients the linear polarizer to be aligned to the transmission axis of the light source to filter out scattered light. The color filter, by way of example, may be an absorptive filter or a dichroic filter, passing only light of wavelengths emitted by the illumination source and to cut out light of all other wavelengths. The filter

630, by way of example, may be incorporated into detector window 208. Although the filter is shown in FIG. 6B, it may also be used in the scanning mechanisms shown in other figures.

The apparatus shown in FIGS. IA- 4, and 6B incorporate an illumination system 102 that is entirely integrated on a moving sled 101 that also incorporates the image capture device 103. hi another embodiment of the invention, the illumination system 102 is constructed such that a portion of the illumination system is mounted to the moving sled, while a remaining portion of the illumination system is mounted to stationary mechanics of apparatus 113. Such a configuration is referred to as a "split-head" architecture. A split-head architecture of the illumination system may be advantageous for fingerprint scanning apparatuses that have several optical components that comprise the illumination system. Placing at least a portion of the optical components of the illumination system in a stationary location within the apparatus housing 113a may reduce the overall size and weight of the sled. A reduction in the size of the sled may allow for a more compact print capture device, while a reduction of the weight of the sled may allow the sled to move faster, enabling skin topography images to be captured in a minimized time period. FIG. 7 illustrates an example of a split-head architecture. In FIG. 7, the light source 210 and at least a portion of the beam conditioning optics 202 are mounted to stationary mechanics of the apparatus, such as to one of fixtures 108 (FIG. IB). The light beam 203 emanating from the stationary beam conditioning optics 202, impinges upon the light deflector 207. The light beam 203 is shaped into a line of light where the beam conditioning optics 202 serve to minimize the width of the beam (in the z direction), while the length (in the x direction) of the beam is conditioned to be at least the length (in the x-direction) of the image capture device 103. The light deflector 207 directs the line of light toward the window-skin interface 204. Since the optical path from the light source 210 to the window-skin interface 204 varies as a function of sled position for a split-head design, the optics in the system preferentially accommodate this distance change and thereby achieve a constant footprint of reflected light beam 403 on window-skin interface 204. In one example, beam 203 is collimated, reflective surface 211 is planar, and as such the footprint of light beam 403 on the window-skin interface is essentially constant, hi another example, light beam 203 is collimated, but the reflective surface 211 has optical power that focuses reflected light beam 403 on the window-skin interface. In another, less desirable example due to its complexity, beam shaping optics 202, through the use of feedback from the encoders that determine the location of sled 101, dynamically accommodates and creates a focusing beam 203 such that for all positions of the sled, a constant footprint of reflected light beam 403 can be achieved on window-skin interface 204. The foregoing embodiments of apparatus 113 rely on the motion of a sled 101, which provides a scanning head for the acquisition of an image of skin topography features. Alternatively, scanning may require the sled 101 to remain stationary as the platen assembly, and thereby the window, is scanned across the sled 101 as the skin is pressed against the moving window. This alternative method of scanning requires the skin to be in motion and may lead to changes in the quality of the optical contact at the window-skin interface during scanning. Changes in the quality of optical contact at the window-skin interface may lead to inconsistent image quality across the acquired image. In order to insure uniform quality images, it has been a feature of the invention to provide an apparatus for acquiring large areas of skin topography while maintaining constant and stationary optical contact at the window-skin interface. In the specific case of imaging the skin topography of fingerprints, this serves to produce high-resolution images of so called "slap" finger prints. Slap finger print images are acquired by pressing a finger or multiple fingers flat upon the window surface and scanning an sled 101 below the window. However, this does not facilitate the capture of so called "roll" fingerprints. Rolled fingerprints are acquired by placing the finger of interest upon the window such that a side of the finger is in optical contact with the window. The subject proceeds to roll the finger onto the opposite side of the finger, during which time an image capture device records a temporally and spatially continuous image of the finger print from one side of the finger to the opposite side of the same finger. The afore¬ mentioned description will be clarified through examination of FIGS. 8 A and 8B that describe an embodiment of the present invention providing an apparatus that will capture images of both slap and rolled fingerprints.

Referring to FIG. 8A, alternative scanning assembly 800 is shown capable of capturing rolled fingerprints comprises a window 801 that is attached to a window holder or platen 802. Such scanning assembly and platen may be incorporated in apparatus 113 of FIG. IA instead of scanning assembly 100 and platen 102. The window holder 802 is supported on four corners by height adjustable supports 803. Each height-adjustable support rides on a pair of bearings 804 that seat on rails 805. The bearings 804 allow the window holder 802 and thus the attached window 801 to travel along the rails. The scanning assembly of FIG. 8A also comprises a sled 806 containing the image capture device 103 and at least some portion of the illumination system 102. The sled 806 may be similar to sled 101 described earlier, but uses at least a pair of bearings 807 that seat on the rails 805. The bearings 807 attached to the sled 806 allow the sled to travel along the rails 805.

Apparatus 800 may be operated to acquire slap fingerprint images by applying a mechanical lock 809 to render platen 802 stationary and thus the window 801 stationary. Once the window is held stationary, the sled 806 containing the image capture device and at least some portion of the illumination apparatus may scan below the window, acquiring a slap fingerprint image. A motor 105, hubs 106a and 106b, and belt 107 described earlier for moving sled 101 may be attached to the frame or structure 810 to similarly move sled 806 for bi-directional motion of the sled to enable scanning.

Apparatus 800 may be operated to acquire roll finger print images by applying a mechanical motion lock 808 to render the sled 806 stationary. When the sled is held stationary, the platen 802 and thus the window 801 maybe scanned above the sled 806, facilitating the acquisition of a rolled fingerprint. The platen 802 is moved by the user's motion of the fingers and/or palm. Locking of the sled 806 may additionally, or instead, be provided by non-motion of motor 105 if present. Optionally, a linear gear track may be provided on the bottom surface of platen 802 along the direction of travel, and a stationary motor mounted on structure 810 has a shaft coupled for rotating a gear having teeth mating with teeth along the linear tract, such that motion to the motor driven gear moves the platen with respect to the stationary sled 806. Motion circuitry in the apparatus would control both the sled driving and platen driving motors. Thus, in alternative case of a fixed platen and movable sled, non-motion to such platen driving motor may be used to lock the platen instead of or in combination with lock 809.

Sled motion and platen motion locks 808 and 809, respectively, perform motion locking by attaching a stationary portion of the lock to a non-stationary mating portion of the lock that is attached to structure 810 of scanning assembly 800. The mechanism for attaching the two portions of the lock may include for example, mechanical actuation of a latch or magnetic attraction of the two portions of the lock. The lock/unlock position of locks 808 and 809 are each set by a mechanical or magnetic actuator (e.g., solenoid) responsive to signals from controller of the apparatus 113.

The preferred embodiment of the apparatus 800 comprises a specific arrangement of bearings 807 on the sled 806 and bearings 804 on the platen 802. Preferably, the sled bearings 807 make contact with the rails only on the cross-sectional inner 180 degrees of the rails, and the platen bearings 804 make contact with the rails only on the cross-sectional outer 180 degrees of the rails. This arrangement of the bearing sets 804 and bearing sets 807 allow both the window holder and the sled to travel on a single set of rails 805, without collision or interference between the sled 806 and the platen 802. This bearing configuration is illustrated in the cross-section of FIG. 8B. Preferably, apparatus 800 of FIGS. 8A and 8B also uses a single encoder for locating the position of both the sled 806 and the platen 802. A single encoder system can be used by attaching an encoder read head 811 (similar to encoder head 124 of FIG. IB) by mounting fixture 810 to the sled and the complementary encoder scale 812 (similar to scale 125) to the platen 802. Alternatively, two separate encoder heads are used to locate the sled and window holder relative to a single static complementary encoder scale.

In summary, FIGS. 1 A-3B show apparatus 113 having an optical illumination system 102 that illuminates the portion of the skin that is pressed against the window 109 of platen assembly 112. The light pattern reflected back through the window is recorded by image capture device 103. In the present invention, a subset of the total area of skin under examination is collected. By scanning a sled 101 comprising the illumination system 102 and image capture device 103 relative to the skin under examination, the entire region of interest of the skin is illuminated and recorded by the image capture device. The skin under examination is stationary upon a window 109 while the sled 101 is scanned across the opposite surface of the window. It is advantageous to keep the skin surface stationary while acquiring high resolution images (also called prints), as high resolution images may become blurred by small motions of the skin during acquisition. For the same reason, it is advantageous to acquire the high resolution image of skin in a substantially short period of time, so as to limit the blurring of images caused by small motions of the hand. Therefore preferably, apparatus 113 acquires substantially high resolution images of stationary skin topography in a substantially short period of time.

Preferably in apparatus 113 the illumination system 102 is integrated entirely on the sled 101 that also houses the image capture device 103. The illumination system 102 consists of a light source that, by way of example, includes a laser, LED, or a filament source. Additional optics may be included in the illumination system in order to shape the light emanating from the light source. For such architecture, the light emanating from the light source is shaped by the illumination system 102 into a beam that is substantially a line whose orientation is substantially parallel to the image capture device 103 (e.g., one-dimensional array sensor) contained within the sled 191. Preferably, the illumination system 102 minimizes the width of the illumination line, referred to as the "line-width". The minimization of the line width will result in maximum contrast images of the skin topography by minimizing the area of the skin that is illuminated. The illumination of the skin produces light scatter that is recorded by the image capture device 103. If extraneous areas of skin are illuminated by light from the illumination system with an overly broad line width, excess scattered light will be sent into the image capture device. The excess scatter light will appear as background light in the image of the skin topography detail, thus reducing contrast between ridges, valleys, and skin pores. Therefore optimum contrast in the skin topography image can be achieved by minimizing the illumination system beam-width. The light may be shaped by the additional optics of the illumination system and directed towards the window 109 of the platen assembly 112. Light is reflected from the interface formed by the window and the skin that is in contact with the window. The image capture device 103 is positioned to receive the reflected light. There are no optical elements, such as lenses, imaging the skin topography onto the image capture device. The optical architecture of the present invention is therefore referred to as "non-imaging". In the non-imaging case, the preference is that the image capture device is placed as close as possible to the window of the platen assembly such that diffraction from the skin topography does not degrade the acquired image. Other illumination system utilizing an array of light sources and beam shaping optics may also be used, as shown in FIG. 4A.

In the preferred architecture, the image capture device 103 is a one-dimensional array sensor, such as a CCD (charge coupled device) or CMOS (complimentary metal oxide semiconductor) sensor. Alternatively, the image capture device 103 comprises a linear detector array, where discrete detector elements are arranged substantially along a line. For example, the linear detector may be a one-dimensional array of discrete detector elements. Further, alternatively the image capture device 103 may be an area detector array where the discrete detector elements are arranged in a two dimensional pattern for example, a rectangular array of detector elements.

In FIGS. 6A-6B, the illumination system 102 is provides by a waveguide device containing a grating, such that when illuminated by end-coupled radiation, the grating diffracts light substantially normal to the propagation direction of the end-coupled light wherein the diffracted light propagates towards the platen and to the skin under test. The grating contained in the waveguide structure can be, by way of example, a volume hologram or a surface-relief hologram. Preferentially the diffraction efficiency of the grating structure is lowest at the end of the waveguide closest to the illumination source and highest at the end of the waveguide furthest from the source with such a spatial diffraction efficiency profile along the length of the waveguide such that the diffracted beam emerging from the waveguide is substantially uniform. A non-imaging geometry is illustrated in which the light diffracted by the waveguide and reflected at the finger-platen interface has no optics of imaging power between the finger-platen interface and the optical sensor. This scenario is an illustrative example only, as the waveguide illumination embodiment can also be incorporated into a reader system whose imaging optical system contains imaging optics, for example GRIN lens arrays, between the finger-platen interface and the optical sensor.

As shown in FIG. 7, the illumination system 102 may be partially housed on the moving sled 101 and partially housed in a stationary position within the apparatus 113. In this "split-head" architecture, the light source 210, such as a laser and part of the optics of the illumination system are mounted in a stationary position, and point the light towards the moving sled 101 which houses the remaining portion of the optics comprising the illumination system. This may be particularly advantageous when the illumination system contains many optical elements. As shown in FIGS. 8 A and 8B, a scanning assembly 808 maybe used instead of the scanning assembly shown in FIG. IA, and has a sled 806 capable of motion and a platen 802 assembly capable of motion. In one case, the window is stationary and the sled moves, such that the detection moves relative to the stationary skin against the stationary window 801. The illumination and subsequent capture of an image of the skin that is pressed against the window 801 occurs while the moving sled 806 is scanning relative to the stationary skin placed against a stationary window, as is the case when acquiring "slap" fingerprints. Thus, the detector 103 moves relative to the stationary skin against the window. In another case, the illumination and subsequent capture of an image of the skin that is pressed against the window 801 may occur while the platen assembly is scanning relative to a stationary sled 806, as when acquiring "rolled" fingerprints. Thus, the skin against window 801 moves relative to a stationary detector 103. In still another case, the illumination and subsequent capture of an image of the skin that is pressed against the window 801 may occur while the sled 806 is moving as a finger is rolled across the stationary window 801. The moving sled must follow the translation of the rolling finger across the stationary window 801.

From the foregoing description, it will be apparent that improved apparatus, system and method for reading skin topology has been provided. Variations and modifications of the herein described apparatus, system, and method will undoubtedly suggest themselves, to those skilled in the art. Accordingly the foregoing description should be taken as illustrative and not in a limiting sense.

Claims

Claims:
1. An apparatus for reading a two-dimensional image of skin topology comprising: a window against which said skin is beatable; a sled in which said sled and said window are movable with respect to each other along a first dimension, and said sled comprises optics for directing one-dimension illumination along a second dimension through said window, and a detector for receiving returned light from said illuminated skin; and said detector is capable of imaging said returned light without imaging optics, wherein said detector with movement relative to skin along said first dimension provides a two- dimensional image along said first and second dimensions representative of the topology of the skin.
2. The apparatus according to Claim 1 wherein said optics represents first optics, and said sled further comprises: a light source producing a beam, and second optics for shaping said beam into said one-dimension illumination in which said first optics then directs said illumination through said window.
3. The apparatus according to Claim 2 wherein light source is a coherent light source.
4. The apparatus according to Claim 2 wherein light source is a laser diode, and said second optics comprise: a lens for minimizing the width of the beam; a beam expander for expanding the length of the beam along said second dimension; and one or more mirrors for relaying light between one or more of said laser diode, lens, and beam expander,- to said first optics.
5. The apparatus according to Claim 2 wherein second optics has at least a diffractive optical element for anamorphic expansion of said beam from said light source along said second dimension.
6. The apparatus according to Claim 5 wherein second optics further has a half- wave plate to orient the polarization of the beam for said diffractive optical element.
7. The apparatus according to Claim 1 wherein said detector is located in proximity to said window.
8. The apparatus according to Claim 1 wherein window is stationary and said sled is moved along said first dimension to enable said detector and skin to move relative to each other along said first dimension.
9. The apparatus according to Claim 1 further comprising a platen having said window, in which when said sled is stationary said platen is moved along said first dimension to enable said detector and skin to move relative to each other along said first dimension.
10. The apparatus according to Claim 1 further comprising at least one of a polarizer or filter, and said detector receives said returned light through said filter.
11. The apparatus according to Claim 1 further comprising a lens array, and said detector receives said returned light through said lens array for imaging said returned light onto said detector.
12. The apparatus according to Claim 11 wherein said detector is a linear detector array, and said lens array represents an array of GRIN microlenses extending along the length of the detector.
13. The apparatus according to Claim 1 wherein said first optics is a mirror for deflecting received one-dimension light through said window.
14. The apparatus according to Claim 1 wherein said detector is a one- dimensional detector aligned with said second dimension.
15. The apparatus according to Claim 1 wherein said detector is a two- dimensional detector.
16. The apparatus according to Claim 1 wherein said sled further comprises: an array of light sources along said second dimension; and said optics represents a lens for minimizing the width of light sources to provide said one-dimensional illumination and directing said one-dimensional illumination to said window.
17. The apparatus according to Claim 1 further comprising: a rail system upon which said sled is movable; means for moving said sled along said rail system; and means for encoding the position of said sled along said rail system.
18. The apparatus according to Claim 1 wherein said optics represents a waveguide illumination device capable of outputting said one-dimensional illumination.
19. The apparatus according to Claim 18 wherein said waveguide illumination device comprises: an inner region extending the length of the device from one end thereof; an outer cladding material, in which said inner region is of material having a higher index of refraction than the cladding material; and said inner region having a volumetric grating which when illumination from said one end provides said one-dimensional illumination through said cladding material toward said window.
20. The apparatus according to Claim 1 further comprising an illumination beam external from said sled incident said optics.
21. The apparatus according to Claim 1 wherein said optics represent first optics and said apparatus further comprises: a rail system upon which said sled is movable, wherein said rail system is movable between two stationary ends; means for moving said sled along said rail system; means for encoding the position of said sled along said rail system; one of said stationary ends having an illumination source, and second optics for shaping said beam from said illumination source into said one-dimensional illumination and directing said beam to said first optics which deflects said shaped beam to said window.
22. The apparatus according to Claim 1 wherein said skin against said tissue is at least one finger of the human hand, and said two-dimensional image provides sufficient resolution for analysis of the topology of said finger.
23. The apparatus according to Claim 1 further comprising a housing having said sled and means for moving said sled with respect to said window, in which said housing is portable.
24. The apparatus according to Claim 1 further comprising means for moving one of said sled or window with respect to each other to enable one of said detector or skin to move with respect to the other.
25. A system for reading skin topology comprising: a platen having a window against which skin is beatable; a sled located below said platen; means for moving at least one of said sled or platen with respect to each other; means in said sled for providing one-dimensional illumination through said window for illuminating said skin; and means in said sled for detecting returned light from said illuminated skin, in which said detecting means is capable of imaging said returned light without imaging optics.
26. The system according to Claim 25 further comprising a controller for controlling said moving means, and receiving output from said detecting means, in said which said output with movement of said detecting means relative to said skin by said moving means provides a two-dimensional image representative of the topology of the skin.
27. The system according to Claim 25 wherein said means for moving at least one of said sled or platen with respect to each other further comprises: first means for moving said sled with respect to said platen; second means for moving said platen with respect to said sled; and means for selecting one of said first and second moving means and locking the non- selected one of said first and second moving means
28. The system according to Claim 27 wherein said first and second means are integrated with each other along a common rail system.
29. A method for reading skin topology comprising: providing a platen having a window against which skin is locatable; providing a sled located below said platen; moving at least one of said sled or platen with respect to each other; providing from said sled one-dimensional illumination through said window for illuminating said skin; and detecting in said sled returned light from said illuminated skin in which said detecting detect is capable of being carried out without the aid of imaging optics.
30. An apparatus for reading skin topology comprising: an illumination system and a detection system; a window upon which skin is located; a sled in which at least one of said sled and window are movable with respect to each other; and said sled comprising at least part of said illumination system for illuminating said tissue with a line of light, and said detection system receives light from said illuminated tissue and is capable of imaging said light without imaging optics, in which movement of one of said sled or window with respect to each other along a direction orthogonal with said direction of said line of light provides an area image of said skin.
PCT/US2005/036967 2004-10-14 2005-10-14 Apparatus for reading skin topology WO2006044620A2 (en)

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Citations (5)

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US3576538A (en) * 1969-04-14 1971-04-27 Identimation Corp Finger dimension comparison identification system
US5650842A (en) * 1995-10-27 1997-07-22 Identix Incorporated Device and method for obtaining a plain image of multiple fingerprints
US6178255B1 (en) * 1998-04-28 2001-01-23 Cross Match Technologies, Inc. Individualized fingerprint scanner
US6658140B1 (en) * 1998-02-03 2003-12-02 Heimann Biometric Systems Gmbh Method and arrangement for obtaining image information relating to surface structures
US6687391B1 (en) * 1999-10-22 2004-02-03 Cross Match Technologies, Inc. Adjustable, rotatable finger guide in a tenprint scanner with movable prism platen

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3576538A (en) * 1969-04-14 1971-04-27 Identimation Corp Finger dimension comparison identification system
US5650842A (en) * 1995-10-27 1997-07-22 Identix Incorporated Device and method for obtaining a plain image of multiple fingerprints
US6658140B1 (en) * 1998-02-03 2003-12-02 Heimann Biometric Systems Gmbh Method and arrangement for obtaining image information relating to surface structures
US6178255B1 (en) * 1998-04-28 2001-01-23 Cross Match Technologies, Inc. Individualized fingerprint scanner
US6687391B1 (en) * 1999-10-22 2004-02-03 Cross Match Technologies, Inc. Adjustable, rotatable finger guide in a tenprint scanner with movable prism platen

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