CA2207664A1 - Apparatus and method for elimination of parallax distortion in images including palm images - Google Patents
Apparatus and method for elimination of parallax distortion in images including palm imagesInfo
- Publication number
- CA2207664A1 CA2207664A1 CA002207664A CA2207664A CA2207664A1 CA 2207664 A1 CA2207664 A1 CA 2207664A1 CA 002207664 A CA002207664 A CA 002207664A CA 2207664 A CA2207664 A CA 2207664A CA 2207664 A1 CA2207664 A1 CA 2207664A1
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- Prior art keywords
- palm
- image
- segments
- lens
- prism
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Classifications
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
- H04N1/387—Composing, repositioning or otherwise geometrically modifying originals
- H04N1/393—Enlarging or reducing
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/117—Identification of persons
- A61B5/1171—Identification of persons based on the shapes or appearances of their bodies or parts thereof
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
- G06V40/00—Recognition of biometric, human-related or animal-related patterns in image or video data
- G06V40/10—Human or animal bodies, e.g. vehicle occupants or pedestrians; Body parts, e.g. hands
- G06V40/12—Fingerprints or palmprints
- G06V40/13—Sensors therefor
- G06V40/1324—Sensors therefor by using geometrical optics, e.g. using prisms
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
- G06V40/00—Recognition of biometric, human-related or animal-related patterns in image or video data
- G06V40/10—Human or animal bodies, e.g. vehicle occupants or pedestrians; Body parts, e.g. hands
- G06V40/12—Fingerprints or palmprints
- G06V40/1335—Combining adjacent partial images (e.g. slices) to create a composite input or reference pattern; Tracking a sweeping finger movement
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- Engineering & Computer Science (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Physics & Mathematics (AREA)
- Multimedia (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Heart & Thoracic Surgery (AREA)
- Medical Informatics (AREA)
- Molecular Biology (AREA)
- Surgery (AREA)
- Animal Behavior & Ethology (AREA)
- Pathology (AREA)
- Public Health (AREA)
- Veterinary Medicine (AREA)
- Human Computer Interaction (AREA)
- Biomedical Technology (AREA)
- Biophysics (AREA)
- Theoretical Computer Science (AREA)
- Optics & Photonics (AREA)
- Signal Processing (AREA)
- Image Input (AREA)
- Stereoscopic And Panoramic Photography (AREA)
- Collating Specific Patterns (AREA)
- Developing Agents For Electrophotography (AREA)
- Manufacturing Of Printed Wiring (AREA)
- Printing Plates And Materials Therefor (AREA)
Abstract
The present invention provides an optical system operable in eliminating parallax distortion in a captured image. Specifically, the apparatus eliminates parallax distortion in a palm print image. The apparatus includes a prism having a receiving surface and an object surface. A palm is placed on the receiving surface and a light illuminates the receiving surface so that an image representative of the palm is propagated from the object surface. The propagated image includes a plurality of segments. A lens selectively magnifies each of the segments by a different amount, as to create a plurality of magnified segments of equal length. A image recording medium then captures the magnified segments. The invention also provides a cylindrical device operable in capturing the image of the palm, where the palm may be rolled across a transparent cylinder and reflected light is captured by a recording medium representative of the palm print.
Description
CA 02207664 1997-0~-29 W O96/17480 PCT~US95/14226 PALM PRI~rrER
Field of the Invention The present invention relates to a method and apparatus for optically eliminating parallax distortion in an image including a method and apparatus for processing skin pattern images representative of a palm print.
Backqround of the Invention Parallax in optics describes the situation when the apparent relative orientation of ob~ects changes when the position from which the objects are viewed changes. Parallax causes a condition generally known as keystone distortion, which describes the situation in which different portions of an image appear disproportionate. Parallax distortion must be addressed when capturing an image with a prism. Apparatus which capture images with a prism include finger print capturing apparatus.
In recent years, many law enforcement agencies have turned to devices which optically process and digitize fingerprint images as opposed to using ink and rolling the fingerprint. Two apparatus and methods which are commonly used by law enforcement agencies are disclosed in commonly assigned U.S. Patent Nos.
4,933,976 and 5,230,025.
United States Patent No. 4,933,976 discloses a method for generating data characteristic of a rolled 30 finger print in real time. The method includes the steps of storing arrays of digital data characteristic of a fingerprint and generating a composite array of digital data characteristic of a rolled fingerprint image. The device of United States Patent No. 4,933,976 ~ 35 includes a prism, which utilizes the principle of total internal reflection to capture the image of a fingerprint, a video camera, a frame digitizer and a processor.
CA 02207664 1997-0~-29 W O 96/17480 PCTrUS95/14226 United States Patent No. 5,230,025 also discloses a method for generating data characteristic o~
a rolled fingerprint. The device of United States Patent No. 5,230,025 also includes a prism, which utilizes the principle o~ total internal reflection to capture the image of a fingerprint, a video camera, a frame digitizer and a processor. However, the method of United States Patent No. 5,230,025 includes the steps of continuously recording images as a finger rolls across the prism and converting those images into digital signals.
Both United States Patent Nos. 4,933,976 and 5,230,025 utilize CCD arrays to capture a pattern of light reflected through the prism when the finger is placed upon a surface of the prism. The CCD array of both United States Patent Nos. 4,933,976 and 5,230,025 are two dimensional CCD arrays, for example, 768 x 960 array. Through the use o~ a lens and mirrors, the image of the fingerprint is ~ocused onto the CCD array so that the image of the fingerprint may be captured.
Many foreign countries, including Japan, as well as many private organizations (such as, corporations desiring high security) desire devices which optically capture the image of a palm print, in addition to the image of a finger print. A palm print is desirable because, for example, it includes approximately 17 times the data contained on a fingerprint. Also, palm prints are often left at crime scenes.
Some countries, including Saudi Arabia, regularly take a palm print when processing an individual who has been arrested. The methods currently employed in Saudi Arabia and other ~oreign countries, include the use of ink and are dif~icult to administer.
The greater volume of data associated with the palm is beneficial in categorizing individuals and comparing di~ferent palm print images to determine whether there CA 02207664 1997-0~-29 W O 96/17480 PCTrUS95114226 is a match. In fact, it is estimated that up to one-third of all criminal identifications are made in ~ part on the basis of a palm print.
The CCD arrays and lens of both United States Patent Nos. 4,933,976 and 5,230,025 have an associated resolution sufficient to provide detailed images of the patterns of the fingerprint. The CCD arrays associated with the devices of the prior art are capable only of providing the desired resolution for a fixed surface area of the prism. This fixed surface area is approximately four times the size of an ordinary fingerprint. Significant problems are presented in merely increasing the size of the prisms and the other equipment disclosed in United States Patent Nos.
4,933,976 or 5,230,025 in order to capture the image of a palm print. These problems are related to parallax distortion, resolution, and lighting.
A problem associated with any optical system which, for example, captures an image, such as a fingerprint or palm print through the utilization of a prism, is parallax distortion, and in particular keystone distortion. Specifically, keystone distortion describes the condition when the top of a image is disproportionately narrower or wider than the bottom portion of an image. Keystone distortion is directly related to parallax.
Parallax distortion is created because the object, in this case one surface of the prism, is slanted relative to the other sur~aces. Because of the slant, the image focused through the lens will also be slanted. The slanted image can be focused onto a vertical CCD array (i.e., one that is not slanted) if the depth of field associated with the lens the image is being focused through is great enough. Depth of field describes the distance toward and away from the focal point of the lens in which clear focus is available. It is well known that depth of field is a function of the CA 02207664 1997-0~-29 W O96/17480 PCT~US95/14226 f-stop, or the size of the aperture of the lens. As the f-stop increases, that is as the aperture becomes smaller, the depth of field becomes greater. Similarly, as the f-stop decreases the depth of field becomes less.
Additionally, as the f-stop increases so does the amount of light necessary to properly expose the CCD.
Elimlnation of parallax distortion and providing adequate resolution are critical for optical systems which capture fingerprints. For example, if the fingerprint image is keystoned, it is skewed with respect to fingerprints it is being compared against.
The skew makes it almost impossible to compare the two images. Additionally, if the resolution is too low, the image will be smudged, which is also virtually useless in comparing fingerprints.
Parallax distortion can be solved either optically, or by computer enhancement. It is understood that most law enforcement agencies throughout the world require that the parallax distortion be corrected optically. In some finger printing devices of the prior art, parallax distortion is minimized through the use of a slanted CCD array in combination with a lens having a high f-stop and an anamorphic prism. Specifically, the CCD array is slanted to the objective distribution plane of the prism. The objective distribution plane is positioned at an angle equal in magnitude but opposite in phase from the plane in which the clearest focus is possible. The image achieved in the objective distribution plane does not include significant parallax distortion. ~owever, a drawback in positioning the CCD
array in the objective distribution plane is that a greater depth of field is necessary to achieve acceptable resolution. Therefore, a greater f-stop is required to achieve a greater depth of field which in turn requires more illumination. The anamorphic prism is used to properly orient the image for reception by the CCD array.
CA 02207664 1997-0~-29 The devices disclosed in United States Patent Nos. 4,933,976 and 5,230,025 could be utilized to -capture the image of a palm print at great financial expense. Because the palm is of much greater surface ~5 area than a finger, a CCD array including a much larger configuration would be necessary to capture the palm print image. These larger CCD arrays are substantially more expensive than those utilized by United States Patent Nos. 5,230,025 and 4,933,976. For example, MEGAPLUS array manufactured by KODAK, having a 2,000 x 2,000 array, would have adequate capacity to produce the required resolution needed for a palm print. However, such CCD arrays cost almost as much as entire commercial systems for capturing fingerprints.
Further, to eliminate parallax distortion and gain the required resolution in a system of the prior art, if it was large enough to capture the image of a palm, the f-stop would need to be substantially increased with a corresponding increase in illumination.
However, if f-stop is increased too far, the entire image will fall out of focus. Assuming an acceptable focus was possible, the level illumination required to capture the image of a palm with a very high f-stop would require considerable energy and probably would cause thermal problems.
Despite increased costs associated with capturing a palm print through utilization of the methods and apparatus disclosed in United States Patent Nos. 4,933,976 and 5,230,025, a need exists to provide a method and apparatus for digitizing the image of a palm.
The prior art has provided limited devices and methods to scan palm prints. One such device is disclosed in United States Patent No. 4,032,889 to Nassimbene and assigned to International Business Machines Corporation. United States Patent No.
4,032,889 utilizes photocells to capture the image of a palm. The photocells used in U.S. Patent No. 4,032,889, -~~ CA 02207664 1997-0~-29 as well as the method taught by U.S. Patent No.
4,032,889, are basic methods which may be useful in comparing two dif~erent palm prints, but lack other desirable characteristics. For example, the device disclosed in United States Patent No. 4,032,889 does not provide the necessary resolution to print an image of a palm print, a task often required by law enforcement agencles.
European Patent Application 326,497 shows an electronic video dental camera which uses an image device such as a CCD. The camera may have three different types of lenses: wide angle, telephoto and relay lenses. However, EP-A 326,497 does not discuss the problem o~ parallax distortion. Nor does it provide a solution for this problem.
Canadian Patent 1,286,032 describes an opticaI
scanning and recording apparatus for fingerprints.
Improved image capture and contrast is achieved by addltional lighting shown at the inter~ace o~ the truncated apex and the surrounding air. However, C 1,286,023 does not address the problem of parallax distortion. Nor does it provide a solution for this problem.
Therefore, a need has arisen to provide a device and method for digitizing the image o~ a palm which solves these and other problems of the prior art.
Summary of the Invention The present invention relates to an apparatus for eliminating keystone distortion in an image. The image is dividable into a plurality of linear segments where each of the segments has an associated length.
The apparatus includes a lens operative in selectively magnifying each of the segments of the image by a different amount as to create a plurality of magnified lines of equal length. A medium operable in being selectively exposed by one of the magnified segments is AME~ ,CET
CA 02207664 1997-0~-29 6a also included. In the first preferred embodiment, the medium is a fixed horizontal distance from the lens.
The first pre~erred embodiment of the present invention is an apparatus for generating digital data characteristic of a palm. The apparatus includes a prism including a receiving surface and an object surface. The receiving surface receives the palm. The palm is dividable into a plurality of linear segments.
A source o~ light illuminates the receiving surface so that an image representative of the palm is propagated from the object surface. The propagated image includes a plurality of linear segments corresponding to the linear segments of the palm. Each of the segments of the propagated image includes an associated length. A
~ 15 medium for capturing the image of the palm is movable .. ..
CA 02207664 1997-0~-29 W O96/17480 PCT~US95/14226 between a plurality of locations relative to the ob~ect surface of the prism as to capture each of the segments ~ of the propagated images at a different location.
The first preferred embodiment may also include a lens operable in magnifying the segments of the propagated image so that they are all of equal length.
Brief DescriPtion of the Drawinqs Figure 1 is a block diagram representation of a system which can be used to generate rolled palm print images in accordance with the present invention.
Figure 2 is a diagrammatic side view of the palm print device of the first preferred embodiment of the present invention.
Figure 3 is a diagrammatic view of an image recorder of the first preferred embodiment.
Figure 4 is a side view of a hollow prism.
Figure 5 is a diagram of a palm including a plurality of segments.
Figure 6 is a side view of a fingerprint device included with the palm print device of Figure 2.
Figure 7 is a side view of the palm print device of the second preferred embodiment.
Figure 8 is a cut-away of Figure 7 taken along the line 8-8.
Figure 9 is a side vie~w of the device of Figure 7 with a palm being rolled.
Figure 10 is a cut away of a cylinder in the second preferred embodiment showing a light and an image recorder within the cylinder.
Figure 11 is a side view of a palm being rolled across the device of Figure 7.
CA 02207664 1997-0~-29 W O96/17480 PCTrUS95/14226 Petailed PescxiPtion of the Preferred Embodiments In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings which form a part hereof, and which is shown by way of illustration, specific embodiments in which the invention may be practiced. It is to be understood that the other embodiments of the invention may be utilized and structural changes may be made without departing from the scope of the present invention.
To understand the concept behind the invention, one can divide the palm image into a plurality of linear segments so that the parallax distortion may be characterized by segments having different lengths and widths. The segments are spaced between a far segment at one end and a near segment at the other end. The far segment is the furthest from the lens while the near segment is the closest to the lens.
Parallax distortion is created because the dif~erent segments of the image are subject to different magnifications within the prism, thereby creating segments having different dimensions, i.e. length and width. The different dimensions are eliminated by selectively adjusting the magnification of the lens relative to each segment of the image so that each segment includes the same dimensions.
The prism of the present invention includes a palm receiving surface and a object surface. The palm is placed upon the palm receiving surface. The object surface is the surface of the prism from which the image of the palm is projected. The object surface is slanted with respect to the palm receiving surfac~e. Because the object surface is slanted with respect to the palm receiving surface, light reflected from different portions of the palm, i.e. the far segment relative to the near segment, must travel different distances within the prism before being projected. The different CA 02207664 1997-0~-29 W O 96/17480 PCTrUS95/14226 distances the light must travel creates parallax.
While not being bound to any particular ~ theory, the present invention focuses on the length of the linear segments rather than their width. It may be assumed that the different lengths associated with different segments of the palm creates the parallax distortion. Parallax distortion may be eliminated by magnifying each linear segment of the palm by a different amount and making them the same length. For example, the near segment may be magnified so that its length is the same as the far segment. A11 of the segments may then be added to create an image of a palm print. The added segments may then be processed, according to the methods of either U.S. Patent Nos.
4,933,976 or 5,230,025, both of which are incorporated by re~erence.
In the first preferred embodiment of the present invention a linear CCD array travels along a predetermined angled vector relative to a prism. The vector includes vertical and horizontal components.
Specifically, a lens moves horizontally relative to the prism while maintaining a constant horizontal distance from a CCD. A CCD moves vertically relative to the lens. The linear CCD array is capable of only capturing one segment of the palm image at a time. For each segment of the palm image being captured, the lens and linear CCD array are repositioned relative to the prism.
By repositioning the lens and the CCD array, different segments of the palm image may be magnified by different amounts. By magnifying the segments o~ the palm image different amounts, segments of otherwise unequal length can be made equal.
The invention also provides a movable light source which illuminates only that portion of the prism corresponding to the portion of the palm, the image of which is being captured. The movable light source preferably includes a light bar and a mirror positioned CA 02207664 1997-0~-29 W O96/17480 PCTrUS95/14226 on a movable arm. The mirror reflects light into the prism at different locations dependent upon the position of the arm. In the preferred embodiment, the palm printer also includes, in combination, a fingerprint capture device.
According to the first preferred embodiment of the invention, the lens and linear CCD array will be closer to the prism when the near segment is captured, thereby providing increased magnification for that segment, and the lens and CCD array will be farther away when the far segment is captured, thereby providing less magnification. A standard length for a segment of the image may be chosen, and each segment of the image may then be scanned individually and magnified by a different amount so that each segment has the same length when projected onto the CCD.
The second preferred embodiment of the present invention optically eliminates parallax distortion by providing a clear cylinder over which a palm may be rolled. The second preferred embodiment utilizes a linear CCD array in a fixed position relative to the cylinder. Parallax distortion is not an issue in the second preferred embodiment because the portion of the palm in contact with the clear cylinder, as it is rolled across the cylinder, is a constant distance away from the lens and CCD array.
A palm print system 10 which can be used to optically produce palm print images in accordance with the present invention is illustrated generally in Figure 1. Palm print system 10 is a microprocessor-based system which includes processor 12 and associated random access memory (RAM) 14 and read only memory (ROM) 16.
Image recorder 22, digitizer 24, video monitor 26, alarm 30, printer 28, and terminal 18 are interfaced into processor 12. The palm print images are captured by utilizing a prism 250. Prism 250 includes a receiving surface 256 and an ob~ect surface 258.
CA 02207664 1997-0~-29 W O 96117480 PCT~US95/14226 A palm is placed in contact with receiving surface 256 which is illuminated, and an image is propagated from object surface 258 which is imaged by recorder 22 and digitized by digitizer 24.
Specifically, a light source 200 is directed through prism 250 and reflects off of receiving surface 256.
Through the principle of total internal reflection those portions of a palm in contact with receiving surface absorb light and those portions of the palm not in contact with receiving surface reflect light. For example, a valley or crease in the palm will reflect light, while a ridge of the palm will absorb light. The reflected light is propagated from object surface 258 and is characteristic of the image of a palm. The image of the palm is projected towards image recorder 22. An array of digital data representative of the palm print image is provided to processor 12.
Image recorder 22 generally includes a lens, a shutter mechanism, and a recorder medium for controlled recording of palm print images. Terminal 18 includes a keyboard (not separately shown) which is used by an operator to interface with palm print system 10. Palm print images generated by system 10 can be displayed on video monitor 26 or printed onto a standard palm print card by printer 28. Alarm 30 is activated when a palm print is not properly captured, providing the operator with an indication that the capture procedure must be repeated. Systems operative in optically digitizing a fingerprint are disclosed in commonly assigned Fishbein et al. U.S. Patent No. 4,933,976, and Fishbein et al.
5,230,025, the specification and drawings of which are hereby incorporated by reference.
The first preferred embodiment of the present invention is diagrammatically shown in Figures 2 and 3.
Figure 2 includes a prism 250 positioned to receive a palm. Prism 250 is large enough to receive the entire palm surface. In the first preferred embodiment, CA 02207664 1997-0~-29 WO96/17480 PCT~S95/14226 receiving surface is at least 144 square centimeters although larger receiving surfaces are also contemplated.
With reference to Figure 4, and in an alternative embodiment, prism 250 may be hollow with sidewalls constructed from plexiglass. The prism may be filled with a clear fluid having a refractive index ranging from approximately 1.1 to 4.0, although an index above 1.5 is preferred.
Referring to Figure 5 there is generally shown a palm which has been divided into a plurality of segments, 1 through N. Segment 1 represents the segment closest to the lens, while segment N represents the segment farthest from the lens. Absent the present invention, when imaged through a prism segment N will be disproportionately longer than segment 1.
The mechanism of the present invention positions image recorder 22 such that each segment, 1 through N, is the same length when recorded. With reference back to Figures 2 and 3, image recorder 22 includes a lens 110 and a high-latency linear CCD array device 120 adapted to receive images over the desired period of time. Lens 110 is preferably a 60mm lens, available from a variety of manufacturers, for example Thompson Composants Militaires et Spatiaux of France or Dalsa of Waterloo, Ontario. In the preferred embodiment CCD array device 120 is purchased from Dalsa as a Dalsa CCD array model CL-C73456. Referring speci~ically to Figure 3, lens 110 is rigidly held into place by an image recorder frame or carriage 121. Carriage 121 is slidably positioned on gear bar 102 which is positioned proximate prism 20. Gear bar 102 is engaged to a linear stepper motor 140 operable in moving carriage 121 horizontally toward and away from prism 250, along gear bar 102, as best illustrated in Figure 2. The segments of the image are magnified by moving the lens toward and away ~rom the prism.
CA 02207664 1997-0~-29 W O96/17480 PCT~US95/14226 Stepper motor 140 is configured to receive digital input ~rom a processor (not separately shown) so that it may be precisely controlled. Such motors are commercially available from THK, as model 306K. Lens 110 is rigidly fixed to carriage 121 and operates to magnify each segment of the palm a different amount as it moves toward and away from prism 250. The rate at which carriage 121 moves is dependent upon the sensitivity of linear CCD 120. Typical scan rates in the present invention may be 220 ~ per line.
As best shown in Figure 3, linear CCD 120 is positioned a fixed horizontal distance from lens 110.
In the ~irst pre~erred embodiment, CCD 120 is slidably positioned on a vertical rail 122 of carriage 121.
Specifically, CCD array 120 is connected to a rolling guide 124 on vertical rail 122 so that CCD 120 may move up and down vertical rail 122. The top of guide 124 is hinged to a slanted rail 126. Slanted rail 126 is in a fixed position relative to gear bar 102. As carriage 20 121 moves toward and away from prism 250 along gear bar 102, rolling guide 124 and CCD array 120 move up and down vertical rail 122. In this fashion, CCD array 120 is at a different vertical position for each different horizontal position of carriage 121.
Moving CCD array 120 up and down as carriage 121 moves horizontally toward and away from prism 20 defines an angled vector at an angle e . Angle 0 is determined by the configuration o~ prism 250.
Specifically, angle 6 is determined by the refractive index of the prism material and in the first preferred embodiment is 47~.
The present invention provides significant advantages. Utilization of a linear CCD array 120 is significantly cheaper than the two dimensional CCD
arrays of the prior art. This is especially true because o~ size limitations placed on two dimensional CCD arrays large enough to capture the image of a palm.
CA 02207664 l997-0~-29 W 096/17480 PCT~US95/14226 Further, by moving the CCD array up and down the CCD can be positioned at the focal point of the lens for any given segment of the palm which is being captured. By continuously positioning the CCD array at the focal point of the lens, the f-stop of the lens does not need to be very high to obtain the proper resolution.
Additionally, the illumination requirements are minimized which in turn decrease power requirements of the device.
It is to be understood that the image segments may be magnified using a variety of other techniques.
For example, instead of moving the lens toward and away from the prism as described above, the lens may be of the telephoto variety magnifying the image segments by 15 rotating the telephoto mechanism. Also, the medium, or CCD could be moved toward or away from a lens where the lens is a fixed distance from the prism.
In the first preferred embodiment a movable light source 200 is provided. With reference to Figure 20 2, movable light source 200 illuminates approximately a single segment of the palm on receiving surface 256.
Specifically, light source 200 illuminates a different portion of receiving surface for each different position of carriage 121. In the first preferred embodiment, 25 light source 200 is a quartz rod 202. As best seen in Figure 2, quartz rod 202 projects light toward a mirror 206 positioned on an arm 204. Arm 204 is mounted to a guide 208 which in turn is received on a rail 210 so that arm 204 and guide 208 are movable thereon. As arm 30 204 moves on rail 210, arm 204 rotates through approximately 7~. Arm 204 rotates so that light is reflected toward receiving surface 256. Specifically, arm 204 is driven along rail 210 by a second stepper motor 214. Mirror 206 has a length sufficient to 35 project light across the width (corresponding to the length of the segment of the palm) of prism 250. As shown by phantom line 275 in Figure 2, light reflects CA 02207664 1997-0~-29 W O 96/17480 PCT~US95114226 off of mirror 206 and into prism 250. In an alternative embodiment, arm 204 may be replaced with a cam (not shown) rotatable about 7 degrees and movable along rail 210. Quartz light 202 may be replaced with a fiber optic light source.
In the first preferred embodiment, the data captured by CCD array 120 is delivered to digitizer 24 and processor 12 each time the lens mo~es. The rate at which carriage 121 reciprocates horizontally toward and away from prism 250 is a function of the sensitivity of CCD array 120 and the strength o:~light source 20o. The preferred embodiment includes scan rates of approximately 220 ~ per line. A scan is defined by the time it takes CCD array 110 to gather the in~ormation from a segment of the image of the palm print propagated ~rom object surface 258. As the information is gathered by CCD array 120, it is integrated together to process an image of the palm print. The integration can occur "piece meal" as the information is gathered and then the integrated pieces can be integrated together, or, the integration may be over the entire time required to gather the information representative of the palm print. However, operation under both methods require that CCD array 110 be cleared prior to each segment of the palm being captured. The methods for capturing a palm print through the above-described methods are described in commonly assigned U.S. Patent Nos.
4,933,976 and 5,230,025, respectively, which have been previously incorporated by reference.
In operation, a palm is placed on receiving sur~ace 34 o~ prism 20, and quartz light 202 projects light which is reflected off mirror 206. Mirror 206 reflects light onto a limited portion of the receiving surface 256 such that a single portion of the palm is illuminated. Through the principle of total internal reflection, light images representative of that portion of the palm print will pass through lens 110 and will be CA 02207664 1997-0~-29 W O96/17480 PCT~US95114226 focused onto CCD array 120. By selectively positioning carriage 121, including lens 110, each segment of the palm will be magnified by a different amount such that their lengths will be a constant value. CCD array 120 is oriented such that it is at the focal point of lens 110 relative to any given segment of the palm which is being captured. Arm 204 repositions mirror 206 so that each time carriage 121 is repositioned, mirror 206 is repositioned to illuminate a different portion of receiving surface. For example, if segment 1 of palm, as shown in Figure 5, was captured initially, carriage 121 and thereby lens 110 would move forward towards prism 250 and CCD array 120 would move upward relative to lens 110. Correspondingly, arm 204 and mirror 206 would be also repositioned. By positioning lens 110 closer to prism 250 when segment 2 is captured, segment 2 is magnified a greater amount than the segment 1. The difference in magnification is such that the segments are the same length. CCD array 120 is moved vertically upward because the focal point of lens moves upward when capturing the second segment. This process continues until the entire palm print is captured.
The digital information gathered by CCD array 120 will then be integrated according to the methods disclosed in U.S. Patent Nos. 4,933,976 or 5,230,025, both of which have been previously incorporated herein by reference. Once the image of the palm print has been processed, it can be transmitted to monitor 26 for visual inspection or to printer 28. If the image is not satisfactory, alarm 30 will sound and the palm print can be taken again.
With reference to Figure 6, the preferred embodiment of the present invention may also include, in combination, a device for optically capturing the image of a fingerprint.
The fingerprint device includes two lenses 100 and 101 positioned adjacent one another operating to CA 02207664 1997-0~-29 W O96117480 PCTrUS95/14226 focus the image o~ a finger onto two separate, two dimensional CCD arrays, 110 and 111. CCD arrays 110 and 111 gather light and convert it into a dlgital data representative o~ the fingerprint. Data gathered by CCD
arrays 110 and 111 is then integrated separately or integrated in its entirety according to the methods disclosed above, which are ln accordance with commonly assigned U.S. Patent Nos. 4,933,976 and 5,230,025, which have been previously incorporated by re~erence.
Each lens 100 and 101 needs to be adjusted so that there is a slight overlap of data gathered by each CCD array 110 and 111. The overlap is then compensated for by techni~ues known in the art, and the images are integrated together.
The second pre~erred embodiment of the invention is disclosed in Figures 7-10. With initial reference to Figures 7 and 8, the second preferred embodiment utilizes a clear cylindrical tube 400. As shown in Figure 9, a palm can be rolled across clear cylinder 400 in order to capture the image o~ the palm.
Cylinder 400 includes a cylindrical surface 402. As best shown in Figures 7 and 8, the palm capturing device of the second preferred embodiment also includes an encoder 410, an image recorder 422 and a light 440.
Image recorder includes a lens and a CCD.
The palm printer of the second pre~erred embodiment also utilizes the principle of total internal reflection. As best shown in Figure 8, light reflects through cylindrical surface 202 at an angle ~. Places where the palm is in contact with cylinder surface 402 of cylinder 400 absorb light, while those portions of the palm which are not in contact with skin reflect light. In operation, the palm is rolled over cylinder 400 either in a frontways or a sideways configuration as best shown in Figures 9 and 11.
Clear cylinder 400 is rotatable about an axis 404. Clear cylinder 400 may include two open ends CA 02207664 1997-0~-29 W O96/17480 PCTrUS95/14226 having a lumen therebetween, or may be of solid construction. Clear cylinder 400 may be rotated by a motor 406. If cylinder 400 is rotated by motor 406, cylinder 400 will pull the palm across it. If no motor is utilized, clear cylinder 400 will rotate in response to the palm being drawn across it.
As the hand is rolled across cylinder 4Q0, light propagated from light source 440 will reflect or be absorbed relative to that portion of the palm in contact with cylinder surface 202 of clear cylinder 200.
The reflected light is captured by recorder 422 which is fixed in position relative to cylinder 400. CCD array 430 then communicates the data to a digitizer and a processor in a similar manner or described above.
The processor then correlates the amount of rotation determined by encoder 410 against the data collected from CCD array 230 and integrates that data in accordance with the method of either U.S. Patent Nos.
4,933,976 or 5,230,025. The image may then be used in the same fashion as disclosed above_ Image recorder 422 may be positioned within the clear cylinder, as shown in Figure 10, or external to cylinder 400, as shown in Figure 8. If image recorder 422 is positioned within the cylinder, mirrors 450 are required to increase the distance which the reflected light travels so that the proper resolution is achieved.
In the second embodiment, the curved surface which receives the palm provides easy operation as the palm can be rolled across the cylinder. The edge of a palm may also be captured by taking a second roll of the edge of the palm and integrating it with the first.
Each system also includes the advantages of both the 4,933,976 and 5,230,025 patents insofar as those patents describe the general nature of the method used to process the fingerprint.
W O 96/17480 PCTrUS95/14226 While the foregoing detailed description of the present invention describes the invention of the preferred embodiments, it will be appreciated that it is the intent of the invention to include all modifications and equivalent designs. Accordingly, the scope o~ the present invention is intended to be limited only by the claims which are appended hereto
Field of the Invention The present invention relates to a method and apparatus for optically eliminating parallax distortion in an image including a method and apparatus for processing skin pattern images representative of a palm print.
Backqround of the Invention Parallax in optics describes the situation when the apparent relative orientation of ob~ects changes when the position from which the objects are viewed changes. Parallax causes a condition generally known as keystone distortion, which describes the situation in which different portions of an image appear disproportionate. Parallax distortion must be addressed when capturing an image with a prism. Apparatus which capture images with a prism include finger print capturing apparatus.
In recent years, many law enforcement agencies have turned to devices which optically process and digitize fingerprint images as opposed to using ink and rolling the fingerprint. Two apparatus and methods which are commonly used by law enforcement agencies are disclosed in commonly assigned U.S. Patent Nos.
4,933,976 and 5,230,025.
United States Patent No. 4,933,976 discloses a method for generating data characteristic of a rolled 30 finger print in real time. The method includes the steps of storing arrays of digital data characteristic of a fingerprint and generating a composite array of digital data characteristic of a rolled fingerprint image. The device of United States Patent No. 4,933,976 ~ 35 includes a prism, which utilizes the principle of total internal reflection to capture the image of a fingerprint, a video camera, a frame digitizer and a processor.
CA 02207664 1997-0~-29 W O 96/17480 PCTrUS95/14226 United States Patent No. 5,230,025 also discloses a method for generating data characteristic o~
a rolled fingerprint. The device of United States Patent No. 5,230,025 also includes a prism, which utilizes the principle o~ total internal reflection to capture the image of a fingerprint, a video camera, a frame digitizer and a processor. However, the method of United States Patent No. 5,230,025 includes the steps of continuously recording images as a finger rolls across the prism and converting those images into digital signals.
Both United States Patent Nos. 4,933,976 and 5,230,025 utilize CCD arrays to capture a pattern of light reflected through the prism when the finger is placed upon a surface of the prism. The CCD array of both United States Patent Nos. 4,933,976 and 5,230,025 are two dimensional CCD arrays, for example, 768 x 960 array. Through the use o~ a lens and mirrors, the image of the fingerprint is ~ocused onto the CCD array so that the image of the fingerprint may be captured.
Many foreign countries, including Japan, as well as many private organizations (such as, corporations desiring high security) desire devices which optically capture the image of a palm print, in addition to the image of a finger print. A palm print is desirable because, for example, it includes approximately 17 times the data contained on a fingerprint. Also, palm prints are often left at crime scenes.
Some countries, including Saudi Arabia, regularly take a palm print when processing an individual who has been arrested. The methods currently employed in Saudi Arabia and other ~oreign countries, include the use of ink and are dif~icult to administer.
The greater volume of data associated with the palm is beneficial in categorizing individuals and comparing di~ferent palm print images to determine whether there CA 02207664 1997-0~-29 W O 96/17480 PCTrUS95114226 is a match. In fact, it is estimated that up to one-third of all criminal identifications are made in ~ part on the basis of a palm print.
The CCD arrays and lens of both United States Patent Nos. 4,933,976 and 5,230,025 have an associated resolution sufficient to provide detailed images of the patterns of the fingerprint. The CCD arrays associated with the devices of the prior art are capable only of providing the desired resolution for a fixed surface area of the prism. This fixed surface area is approximately four times the size of an ordinary fingerprint. Significant problems are presented in merely increasing the size of the prisms and the other equipment disclosed in United States Patent Nos.
4,933,976 or 5,230,025 in order to capture the image of a palm print. These problems are related to parallax distortion, resolution, and lighting.
A problem associated with any optical system which, for example, captures an image, such as a fingerprint or palm print through the utilization of a prism, is parallax distortion, and in particular keystone distortion. Specifically, keystone distortion describes the condition when the top of a image is disproportionately narrower or wider than the bottom portion of an image. Keystone distortion is directly related to parallax.
Parallax distortion is created because the object, in this case one surface of the prism, is slanted relative to the other sur~aces. Because of the slant, the image focused through the lens will also be slanted. The slanted image can be focused onto a vertical CCD array (i.e., one that is not slanted) if the depth of field associated with the lens the image is being focused through is great enough. Depth of field describes the distance toward and away from the focal point of the lens in which clear focus is available. It is well known that depth of field is a function of the CA 02207664 1997-0~-29 W O96/17480 PCT~US95/14226 f-stop, or the size of the aperture of the lens. As the f-stop increases, that is as the aperture becomes smaller, the depth of field becomes greater. Similarly, as the f-stop decreases the depth of field becomes less.
Additionally, as the f-stop increases so does the amount of light necessary to properly expose the CCD.
Elimlnation of parallax distortion and providing adequate resolution are critical for optical systems which capture fingerprints. For example, if the fingerprint image is keystoned, it is skewed with respect to fingerprints it is being compared against.
The skew makes it almost impossible to compare the two images. Additionally, if the resolution is too low, the image will be smudged, which is also virtually useless in comparing fingerprints.
Parallax distortion can be solved either optically, or by computer enhancement. It is understood that most law enforcement agencies throughout the world require that the parallax distortion be corrected optically. In some finger printing devices of the prior art, parallax distortion is minimized through the use of a slanted CCD array in combination with a lens having a high f-stop and an anamorphic prism. Specifically, the CCD array is slanted to the objective distribution plane of the prism. The objective distribution plane is positioned at an angle equal in magnitude but opposite in phase from the plane in which the clearest focus is possible. The image achieved in the objective distribution plane does not include significant parallax distortion. ~owever, a drawback in positioning the CCD
array in the objective distribution plane is that a greater depth of field is necessary to achieve acceptable resolution. Therefore, a greater f-stop is required to achieve a greater depth of field which in turn requires more illumination. The anamorphic prism is used to properly orient the image for reception by the CCD array.
CA 02207664 1997-0~-29 The devices disclosed in United States Patent Nos. 4,933,976 and 5,230,025 could be utilized to -capture the image of a palm print at great financial expense. Because the palm is of much greater surface ~5 area than a finger, a CCD array including a much larger configuration would be necessary to capture the palm print image. These larger CCD arrays are substantially more expensive than those utilized by United States Patent Nos. 5,230,025 and 4,933,976. For example, MEGAPLUS array manufactured by KODAK, having a 2,000 x 2,000 array, would have adequate capacity to produce the required resolution needed for a palm print. However, such CCD arrays cost almost as much as entire commercial systems for capturing fingerprints.
Further, to eliminate parallax distortion and gain the required resolution in a system of the prior art, if it was large enough to capture the image of a palm, the f-stop would need to be substantially increased with a corresponding increase in illumination.
However, if f-stop is increased too far, the entire image will fall out of focus. Assuming an acceptable focus was possible, the level illumination required to capture the image of a palm with a very high f-stop would require considerable energy and probably would cause thermal problems.
Despite increased costs associated with capturing a palm print through utilization of the methods and apparatus disclosed in United States Patent Nos. 4,933,976 and 5,230,025, a need exists to provide a method and apparatus for digitizing the image of a palm.
The prior art has provided limited devices and methods to scan palm prints. One such device is disclosed in United States Patent No. 4,032,889 to Nassimbene and assigned to International Business Machines Corporation. United States Patent No.
4,032,889 utilizes photocells to capture the image of a palm. The photocells used in U.S. Patent No. 4,032,889, -~~ CA 02207664 1997-0~-29 as well as the method taught by U.S. Patent No.
4,032,889, are basic methods which may be useful in comparing two dif~erent palm prints, but lack other desirable characteristics. For example, the device disclosed in United States Patent No. 4,032,889 does not provide the necessary resolution to print an image of a palm print, a task often required by law enforcement agencles.
European Patent Application 326,497 shows an electronic video dental camera which uses an image device such as a CCD. The camera may have three different types of lenses: wide angle, telephoto and relay lenses. However, EP-A 326,497 does not discuss the problem o~ parallax distortion. Nor does it provide a solution for this problem.
Canadian Patent 1,286,032 describes an opticaI
scanning and recording apparatus for fingerprints.
Improved image capture and contrast is achieved by addltional lighting shown at the inter~ace o~ the truncated apex and the surrounding air. However, C 1,286,023 does not address the problem of parallax distortion. Nor does it provide a solution for this problem.
Therefore, a need has arisen to provide a device and method for digitizing the image o~ a palm which solves these and other problems of the prior art.
Summary of the Invention The present invention relates to an apparatus for eliminating keystone distortion in an image. The image is dividable into a plurality of linear segments where each of the segments has an associated length.
The apparatus includes a lens operative in selectively magnifying each of the segments of the image by a different amount as to create a plurality of magnified lines of equal length. A medium operable in being selectively exposed by one of the magnified segments is AME~ ,CET
CA 02207664 1997-0~-29 6a also included. In the first preferred embodiment, the medium is a fixed horizontal distance from the lens.
The first pre~erred embodiment of the present invention is an apparatus for generating digital data characteristic of a palm. The apparatus includes a prism including a receiving surface and an object surface. The receiving surface receives the palm. The palm is dividable into a plurality of linear segments.
A source o~ light illuminates the receiving surface so that an image representative of the palm is propagated from the object surface. The propagated image includes a plurality of linear segments corresponding to the linear segments of the palm. Each of the segments of the propagated image includes an associated length. A
~ 15 medium for capturing the image of the palm is movable .. ..
CA 02207664 1997-0~-29 W O96/17480 PCT~US95/14226 between a plurality of locations relative to the ob~ect surface of the prism as to capture each of the segments ~ of the propagated images at a different location.
The first preferred embodiment may also include a lens operable in magnifying the segments of the propagated image so that they are all of equal length.
Brief DescriPtion of the Drawinqs Figure 1 is a block diagram representation of a system which can be used to generate rolled palm print images in accordance with the present invention.
Figure 2 is a diagrammatic side view of the palm print device of the first preferred embodiment of the present invention.
Figure 3 is a diagrammatic view of an image recorder of the first preferred embodiment.
Figure 4 is a side view of a hollow prism.
Figure 5 is a diagram of a palm including a plurality of segments.
Figure 6 is a side view of a fingerprint device included with the palm print device of Figure 2.
Figure 7 is a side view of the palm print device of the second preferred embodiment.
Figure 8 is a cut-away of Figure 7 taken along the line 8-8.
Figure 9 is a side vie~w of the device of Figure 7 with a palm being rolled.
Figure 10 is a cut away of a cylinder in the second preferred embodiment showing a light and an image recorder within the cylinder.
Figure 11 is a side view of a palm being rolled across the device of Figure 7.
CA 02207664 1997-0~-29 W O96/17480 PCTrUS95/14226 Petailed PescxiPtion of the Preferred Embodiments In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings which form a part hereof, and which is shown by way of illustration, specific embodiments in which the invention may be practiced. It is to be understood that the other embodiments of the invention may be utilized and structural changes may be made without departing from the scope of the present invention.
To understand the concept behind the invention, one can divide the palm image into a plurality of linear segments so that the parallax distortion may be characterized by segments having different lengths and widths. The segments are spaced between a far segment at one end and a near segment at the other end. The far segment is the furthest from the lens while the near segment is the closest to the lens.
Parallax distortion is created because the dif~erent segments of the image are subject to different magnifications within the prism, thereby creating segments having different dimensions, i.e. length and width. The different dimensions are eliminated by selectively adjusting the magnification of the lens relative to each segment of the image so that each segment includes the same dimensions.
The prism of the present invention includes a palm receiving surface and a object surface. The palm is placed upon the palm receiving surface. The object surface is the surface of the prism from which the image of the palm is projected. The object surface is slanted with respect to the palm receiving surfac~e. Because the object surface is slanted with respect to the palm receiving surface, light reflected from different portions of the palm, i.e. the far segment relative to the near segment, must travel different distances within the prism before being projected. The different CA 02207664 1997-0~-29 W O 96/17480 PCTrUS95/14226 distances the light must travel creates parallax.
While not being bound to any particular ~ theory, the present invention focuses on the length of the linear segments rather than their width. It may be assumed that the different lengths associated with different segments of the palm creates the parallax distortion. Parallax distortion may be eliminated by magnifying each linear segment of the palm by a different amount and making them the same length. For example, the near segment may be magnified so that its length is the same as the far segment. A11 of the segments may then be added to create an image of a palm print. The added segments may then be processed, according to the methods of either U.S. Patent Nos.
4,933,976 or 5,230,025, both of which are incorporated by re~erence.
In the first preferred embodiment of the present invention a linear CCD array travels along a predetermined angled vector relative to a prism. The vector includes vertical and horizontal components.
Specifically, a lens moves horizontally relative to the prism while maintaining a constant horizontal distance from a CCD. A CCD moves vertically relative to the lens. The linear CCD array is capable of only capturing one segment of the palm image at a time. For each segment of the palm image being captured, the lens and linear CCD array are repositioned relative to the prism.
By repositioning the lens and the CCD array, different segments of the palm image may be magnified by different amounts. By magnifying the segments o~ the palm image different amounts, segments of otherwise unequal length can be made equal.
The invention also provides a movable light source which illuminates only that portion of the prism corresponding to the portion of the palm, the image of which is being captured. The movable light source preferably includes a light bar and a mirror positioned CA 02207664 1997-0~-29 W O96/17480 PCTrUS95/14226 on a movable arm. The mirror reflects light into the prism at different locations dependent upon the position of the arm. In the preferred embodiment, the palm printer also includes, in combination, a fingerprint capture device.
According to the first preferred embodiment of the invention, the lens and linear CCD array will be closer to the prism when the near segment is captured, thereby providing increased magnification for that segment, and the lens and CCD array will be farther away when the far segment is captured, thereby providing less magnification. A standard length for a segment of the image may be chosen, and each segment of the image may then be scanned individually and magnified by a different amount so that each segment has the same length when projected onto the CCD.
The second preferred embodiment of the present invention optically eliminates parallax distortion by providing a clear cylinder over which a palm may be rolled. The second preferred embodiment utilizes a linear CCD array in a fixed position relative to the cylinder. Parallax distortion is not an issue in the second preferred embodiment because the portion of the palm in contact with the clear cylinder, as it is rolled across the cylinder, is a constant distance away from the lens and CCD array.
A palm print system 10 which can be used to optically produce palm print images in accordance with the present invention is illustrated generally in Figure 1. Palm print system 10 is a microprocessor-based system which includes processor 12 and associated random access memory (RAM) 14 and read only memory (ROM) 16.
Image recorder 22, digitizer 24, video monitor 26, alarm 30, printer 28, and terminal 18 are interfaced into processor 12. The palm print images are captured by utilizing a prism 250. Prism 250 includes a receiving surface 256 and an ob~ect surface 258.
CA 02207664 1997-0~-29 W O 96117480 PCT~US95/14226 A palm is placed in contact with receiving surface 256 which is illuminated, and an image is propagated from object surface 258 which is imaged by recorder 22 and digitized by digitizer 24.
Specifically, a light source 200 is directed through prism 250 and reflects off of receiving surface 256.
Through the principle of total internal reflection those portions of a palm in contact with receiving surface absorb light and those portions of the palm not in contact with receiving surface reflect light. For example, a valley or crease in the palm will reflect light, while a ridge of the palm will absorb light. The reflected light is propagated from object surface 258 and is characteristic of the image of a palm. The image of the palm is projected towards image recorder 22. An array of digital data representative of the palm print image is provided to processor 12.
Image recorder 22 generally includes a lens, a shutter mechanism, and a recorder medium for controlled recording of palm print images. Terminal 18 includes a keyboard (not separately shown) which is used by an operator to interface with palm print system 10. Palm print images generated by system 10 can be displayed on video monitor 26 or printed onto a standard palm print card by printer 28. Alarm 30 is activated when a palm print is not properly captured, providing the operator with an indication that the capture procedure must be repeated. Systems operative in optically digitizing a fingerprint are disclosed in commonly assigned Fishbein et al. U.S. Patent No. 4,933,976, and Fishbein et al.
5,230,025, the specification and drawings of which are hereby incorporated by reference.
The first preferred embodiment of the present invention is diagrammatically shown in Figures 2 and 3.
Figure 2 includes a prism 250 positioned to receive a palm. Prism 250 is large enough to receive the entire palm surface. In the first preferred embodiment, CA 02207664 1997-0~-29 WO96/17480 PCT~S95/14226 receiving surface is at least 144 square centimeters although larger receiving surfaces are also contemplated.
With reference to Figure 4, and in an alternative embodiment, prism 250 may be hollow with sidewalls constructed from plexiglass. The prism may be filled with a clear fluid having a refractive index ranging from approximately 1.1 to 4.0, although an index above 1.5 is preferred.
Referring to Figure 5 there is generally shown a palm which has been divided into a plurality of segments, 1 through N. Segment 1 represents the segment closest to the lens, while segment N represents the segment farthest from the lens. Absent the present invention, when imaged through a prism segment N will be disproportionately longer than segment 1.
The mechanism of the present invention positions image recorder 22 such that each segment, 1 through N, is the same length when recorded. With reference back to Figures 2 and 3, image recorder 22 includes a lens 110 and a high-latency linear CCD array device 120 adapted to receive images over the desired period of time. Lens 110 is preferably a 60mm lens, available from a variety of manufacturers, for example Thompson Composants Militaires et Spatiaux of France or Dalsa of Waterloo, Ontario. In the preferred embodiment CCD array device 120 is purchased from Dalsa as a Dalsa CCD array model CL-C73456. Referring speci~ically to Figure 3, lens 110 is rigidly held into place by an image recorder frame or carriage 121. Carriage 121 is slidably positioned on gear bar 102 which is positioned proximate prism 20. Gear bar 102 is engaged to a linear stepper motor 140 operable in moving carriage 121 horizontally toward and away from prism 250, along gear bar 102, as best illustrated in Figure 2. The segments of the image are magnified by moving the lens toward and away ~rom the prism.
CA 02207664 1997-0~-29 W O96/17480 PCT~US95/14226 Stepper motor 140 is configured to receive digital input ~rom a processor (not separately shown) so that it may be precisely controlled. Such motors are commercially available from THK, as model 306K. Lens 110 is rigidly fixed to carriage 121 and operates to magnify each segment of the palm a different amount as it moves toward and away from prism 250. The rate at which carriage 121 moves is dependent upon the sensitivity of linear CCD 120. Typical scan rates in the present invention may be 220 ~ per line.
As best shown in Figure 3, linear CCD 120 is positioned a fixed horizontal distance from lens 110.
In the ~irst pre~erred embodiment, CCD 120 is slidably positioned on a vertical rail 122 of carriage 121.
Specifically, CCD array 120 is connected to a rolling guide 124 on vertical rail 122 so that CCD 120 may move up and down vertical rail 122. The top of guide 124 is hinged to a slanted rail 126. Slanted rail 126 is in a fixed position relative to gear bar 102. As carriage 20 121 moves toward and away from prism 250 along gear bar 102, rolling guide 124 and CCD array 120 move up and down vertical rail 122. In this fashion, CCD array 120 is at a different vertical position for each different horizontal position of carriage 121.
Moving CCD array 120 up and down as carriage 121 moves horizontally toward and away from prism 20 defines an angled vector at an angle e . Angle 0 is determined by the configuration o~ prism 250.
Specifically, angle 6 is determined by the refractive index of the prism material and in the first preferred embodiment is 47~.
The present invention provides significant advantages. Utilization of a linear CCD array 120 is significantly cheaper than the two dimensional CCD
arrays of the prior art. This is especially true because o~ size limitations placed on two dimensional CCD arrays large enough to capture the image of a palm.
CA 02207664 l997-0~-29 W 096/17480 PCT~US95/14226 Further, by moving the CCD array up and down the CCD can be positioned at the focal point of the lens for any given segment of the palm which is being captured. By continuously positioning the CCD array at the focal point of the lens, the f-stop of the lens does not need to be very high to obtain the proper resolution.
Additionally, the illumination requirements are minimized which in turn decrease power requirements of the device.
It is to be understood that the image segments may be magnified using a variety of other techniques.
For example, instead of moving the lens toward and away from the prism as described above, the lens may be of the telephoto variety magnifying the image segments by 15 rotating the telephoto mechanism. Also, the medium, or CCD could be moved toward or away from a lens where the lens is a fixed distance from the prism.
In the first preferred embodiment a movable light source 200 is provided. With reference to Figure 20 2, movable light source 200 illuminates approximately a single segment of the palm on receiving surface 256.
Specifically, light source 200 illuminates a different portion of receiving surface for each different position of carriage 121. In the first preferred embodiment, 25 light source 200 is a quartz rod 202. As best seen in Figure 2, quartz rod 202 projects light toward a mirror 206 positioned on an arm 204. Arm 204 is mounted to a guide 208 which in turn is received on a rail 210 so that arm 204 and guide 208 are movable thereon. As arm 30 204 moves on rail 210, arm 204 rotates through approximately 7~. Arm 204 rotates so that light is reflected toward receiving surface 256. Specifically, arm 204 is driven along rail 210 by a second stepper motor 214. Mirror 206 has a length sufficient to 35 project light across the width (corresponding to the length of the segment of the palm) of prism 250. As shown by phantom line 275 in Figure 2, light reflects CA 02207664 1997-0~-29 W O 96/17480 PCT~US95114226 off of mirror 206 and into prism 250. In an alternative embodiment, arm 204 may be replaced with a cam (not shown) rotatable about 7 degrees and movable along rail 210. Quartz light 202 may be replaced with a fiber optic light source.
In the first preferred embodiment, the data captured by CCD array 120 is delivered to digitizer 24 and processor 12 each time the lens mo~es. The rate at which carriage 121 reciprocates horizontally toward and away from prism 250 is a function of the sensitivity of CCD array 120 and the strength o:~light source 20o. The preferred embodiment includes scan rates of approximately 220 ~ per line. A scan is defined by the time it takes CCD array 110 to gather the in~ormation from a segment of the image of the palm print propagated ~rom object surface 258. As the information is gathered by CCD array 120, it is integrated together to process an image of the palm print. The integration can occur "piece meal" as the information is gathered and then the integrated pieces can be integrated together, or, the integration may be over the entire time required to gather the information representative of the palm print. However, operation under both methods require that CCD array 110 be cleared prior to each segment of the palm being captured. The methods for capturing a palm print through the above-described methods are described in commonly assigned U.S. Patent Nos.
4,933,976 and 5,230,025, respectively, which have been previously incorporated by reference.
In operation, a palm is placed on receiving sur~ace 34 o~ prism 20, and quartz light 202 projects light which is reflected off mirror 206. Mirror 206 reflects light onto a limited portion of the receiving surface 256 such that a single portion of the palm is illuminated. Through the principle of total internal reflection, light images representative of that portion of the palm print will pass through lens 110 and will be CA 02207664 1997-0~-29 W O96/17480 PCT~US95114226 focused onto CCD array 120. By selectively positioning carriage 121, including lens 110, each segment of the palm will be magnified by a different amount such that their lengths will be a constant value. CCD array 120 is oriented such that it is at the focal point of lens 110 relative to any given segment of the palm which is being captured. Arm 204 repositions mirror 206 so that each time carriage 121 is repositioned, mirror 206 is repositioned to illuminate a different portion of receiving surface. For example, if segment 1 of palm, as shown in Figure 5, was captured initially, carriage 121 and thereby lens 110 would move forward towards prism 250 and CCD array 120 would move upward relative to lens 110. Correspondingly, arm 204 and mirror 206 would be also repositioned. By positioning lens 110 closer to prism 250 when segment 2 is captured, segment 2 is magnified a greater amount than the segment 1. The difference in magnification is such that the segments are the same length. CCD array 120 is moved vertically upward because the focal point of lens moves upward when capturing the second segment. This process continues until the entire palm print is captured.
The digital information gathered by CCD array 120 will then be integrated according to the methods disclosed in U.S. Patent Nos. 4,933,976 or 5,230,025, both of which have been previously incorporated herein by reference. Once the image of the palm print has been processed, it can be transmitted to monitor 26 for visual inspection or to printer 28. If the image is not satisfactory, alarm 30 will sound and the palm print can be taken again.
With reference to Figure 6, the preferred embodiment of the present invention may also include, in combination, a device for optically capturing the image of a fingerprint.
The fingerprint device includes two lenses 100 and 101 positioned adjacent one another operating to CA 02207664 1997-0~-29 W O96117480 PCTrUS95/14226 focus the image o~ a finger onto two separate, two dimensional CCD arrays, 110 and 111. CCD arrays 110 and 111 gather light and convert it into a dlgital data representative o~ the fingerprint. Data gathered by CCD
arrays 110 and 111 is then integrated separately or integrated in its entirety according to the methods disclosed above, which are ln accordance with commonly assigned U.S. Patent Nos. 4,933,976 and 5,230,025, which have been previously incorporated by re~erence.
Each lens 100 and 101 needs to be adjusted so that there is a slight overlap of data gathered by each CCD array 110 and 111. The overlap is then compensated for by techni~ues known in the art, and the images are integrated together.
The second pre~erred embodiment of the invention is disclosed in Figures 7-10. With initial reference to Figures 7 and 8, the second preferred embodiment utilizes a clear cylindrical tube 400. As shown in Figure 9, a palm can be rolled across clear cylinder 400 in order to capture the image o~ the palm.
Cylinder 400 includes a cylindrical surface 402. As best shown in Figures 7 and 8, the palm capturing device of the second preferred embodiment also includes an encoder 410, an image recorder 422 and a light 440.
Image recorder includes a lens and a CCD.
The palm printer of the second pre~erred embodiment also utilizes the principle of total internal reflection. As best shown in Figure 8, light reflects through cylindrical surface 202 at an angle ~. Places where the palm is in contact with cylinder surface 402 of cylinder 400 absorb light, while those portions of the palm which are not in contact with skin reflect light. In operation, the palm is rolled over cylinder 400 either in a frontways or a sideways configuration as best shown in Figures 9 and 11.
Clear cylinder 400 is rotatable about an axis 404. Clear cylinder 400 may include two open ends CA 02207664 1997-0~-29 W O96/17480 PCTrUS95/14226 having a lumen therebetween, or may be of solid construction. Clear cylinder 400 may be rotated by a motor 406. If cylinder 400 is rotated by motor 406, cylinder 400 will pull the palm across it. If no motor is utilized, clear cylinder 400 will rotate in response to the palm being drawn across it.
As the hand is rolled across cylinder 4Q0, light propagated from light source 440 will reflect or be absorbed relative to that portion of the palm in contact with cylinder surface 202 of clear cylinder 200.
The reflected light is captured by recorder 422 which is fixed in position relative to cylinder 400. CCD array 430 then communicates the data to a digitizer and a processor in a similar manner or described above.
The processor then correlates the amount of rotation determined by encoder 410 against the data collected from CCD array 230 and integrates that data in accordance with the method of either U.S. Patent Nos.
4,933,976 or 5,230,025. The image may then be used in the same fashion as disclosed above_ Image recorder 422 may be positioned within the clear cylinder, as shown in Figure 10, or external to cylinder 400, as shown in Figure 8. If image recorder 422 is positioned within the cylinder, mirrors 450 are required to increase the distance which the reflected light travels so that the proper resolution is achieved.
In the second embodiment, the curved surface which receives the palm provides easy operation as the palm can be rolled across the cylinder. The edge of a palm may also be captured by taking a second roll of the edge of the palm and integrating it with the first.
Each system also includes the advantages of both the 4,933,976 and 5,230,025 patents insofar as those patents describe the general nature of the method used to process the fingerprint.
W O 96/17480 PCTrUS95/14226 While the foregoing detailed description of the present invention describes the invention of the preferred embodiments, it will be appreciated that it is the intent of the invention to include all modifications and equivalent designs. Accordingly, the scope o~ the present invention is intended to be limited only by the claims which are appended hereto
Claims (18)
1. An apparatus for capturing a keystoned image, said image dividable into a plurality of segments, each of said segments having an associated length, said apparatus comprising:
a lens magnifying said segments of said image, the lens being adjustable so that the magnification of each segment is adjustable, resulting in magnified segments of equal length; and an image capturing medium comprising a CCD
array, constructed to be selectively exposed to each of said magnified segments.
a lens magnifying said segments of said image, the lens being adjustable so that the magnification of each segment is adjustable, resulting in magnified segments of equal length; and an image capturing medium comprising a CCD
array, constructed to be selectively exposed to each of said magnified segments.
2. An apparatus as in claim 1 wherein said medium is positioned at fixed horizontal distance from said lens.
3. An apparatus as in claim 1 wherein said CCD is a single dimension CCD operable in moving through a plurality of positions as to capture each of said magnified segments.
4. An apparatus as in claim 1 wherein said apparatus is sized to capture an image of a palm.
5. An apparatus as in claim 4 further comprising:
a prism having a palm receiving surface and an object surface, said receiving surface constructed and arranged to receive said palm;
a light source operative in illuminating said palm receiving surface of said prism so that an image representative of said palm is propagated from said object surface.
a prism having a palm receiving surface and an object surface, said receiving surface constructed and arranged to receive said palm;
a light source operative in illuminating said palm receiving surface of said prism so that an image representative of said palm is propagated from said object surface.
6. An apparatus as in claim 5 wherein said light source is constructed and arranged as to selectively illuminate said palm receiving surface of said prism so that only a portion of said image of said palm is projected from said imaging surface, said portion of said image including at least one segment of said image and said lens positioned to magnify said segment and said medium being exposed by said magnified segment.
7. An apparatus as in claim 6 wherein said light source further comprises linear illumination means, which directs light at a mirror selectively positionable to illuminate discrete portions of said palm receiving surface.
8. An apparatus as in claim 1 wherein said lens comprises a telephoto lens selectively positionable between a plurality of different magnification levels.
9. An apparatus for generating digital data characteristic of an image as in claim 1, further comprising moving means for moving the lens toward and away from said prism while maintaining a constant distance between the lens and the medium.
10. An apparatus for generating digital data characteristic of a palm comprising:
a prism including a receiving surface and an object surface, said receiving surface constructed as to receive said palm, said palm including a plurality of segments;
a source of light operable in illuminating the receiving surface so that an image representative of said palm is propagated from the object surface, said propagated image including a plurality of segments corresponding to said segments of said palm, said segments of said propagated image including an associated length; and, an image recorder movable between a plurality of positions relative to the object surface of the prism as to capture each of said segments of said propagated image at a different location.
a prism including a receiving surface and an object surface, said receiving surface constructed as to receive said palm, said palm including a plurality of segments;
a source of light operable in illuminating the receiving surface so that an image representative of said palm is propagated from the object surface, said propagated image including a plurality of segments corresponding to said segments of said palm, said segments of said propagated image including an associated length; and, an image recorder movable between a plurality of positions relative to the object surface of the prism as to capture each of said segments of said propagated image at a different location.
11. An apparatus as in claim 13 wherein said image recorder comprising a lens and a medium, said lens and said medium spaced away from said object surface such that said lens is positioned between said object surface and said medium, said lens operable in selectively magnifying said segments of said propagated image by different amounts such that said segments are of equal length.
12. An apparatus as in claim 11 wherein said prism includes a lumen filled with an liquid having a refractive index above 1.1.
13. An apparatus as in claim 11 further comprising a second prism operable in receiving the surface of a finger, and a second digitizer operable in digitizing an image of a fingerprint.
14. An apparatus as in claim 11 further comprising an encoder for measuring the amount the transparent cylinder has rotated, the encoder operably connected to the digitizer.
15. A method of generating data characteristic of a palm print image, wherein the method comprises the steps of:
providing a cylindrical palm receiving surface which reflects light as a function of a ridge and valley pattern of a palm brought into contact with a palm receiving surface;
providing an image recording medium positioned to receive the propagated light;
rolling a palm across the palm-receiving surface wherein said image of said palm is propagated to said image recording medium;
converting the palm image into digital signals; and generating an array of digital data characteristic of a complete rolled palm print image from the digital signals.
providing a cylindrical palm receiving surface which reflects light as a function of a ridge and valley pattern of a palm brought into contact with a palm receiving surface;
providing an image recording medium positioned to receive the propagated light;
rolling a palm across the palm-receiving surface wherein said image of said palm is propagated to said image recording medium;
converting the palm image into digital signals; and generating an array of digital data characteristic of a complete rolled palm print image from the digital signals.
16. The method according to claim 15 wherein the step of generating the array includes generating the array in real time as the palm is being rolled.
17. The method according to claim 15 wherein the step of converting the palmprint image includes determining a threshold value for the digital data to determine presence or absence of contact of the palm with the palm-receiving surface.
18. The method according to claim 15 wherein the step of converting the palmprint image comprises:
storing arrays of digital data characteristic of adjacent and overlapping palm print images of portions of the palm as the palm is rolled across the palm receiving surface; and generating a composite array of digital data characteristic of a rolled palm print image as a mathematical function of overlapping image data from a plurality of arrays and characteristic of the overlapping portions of the fingerprint images.
storing arrays of digital data characteristic of adjacent and overlapping palm print images of portions of the palm as the palm is rolled across the palm receiving surface; and generating a composite array of digital data characteristic of a rolled palm print image as a mathematical function of overlapping image data from a plurality of arrays and characteristic of the overlapping portions of the fingerprint images.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US34663994A | 1994-11-30 | 1994-11-30 | |
| US08/346,639 | 1994-11-30 |
Publications (1)
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| CA2207664A1 true CA2207664A1 (en) | 1996-06-06 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002207664A Abandoned CA2207664A1 (en) | 1994-11-30 | 1995-11-03 | Apparatus and method for elimination of parallax distortion in images including palm images |
Country Status (9)
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| EP (1) | EP0795248A2 (en) |
| JP (1) | JPH10510075A (en) |
| CN (1) | CN1167556A (en) |
| AU (1) | AU4142596A (en) |
| BR (1) | BR9509933A (en) |
| CA (1) | CA2207664A1 (en) |
| MX (1) | MX9703856A (en) |
| NO (1) | NO972448L (en) |
| WO (1) | WO1996017480A2 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6111977A (en) * | 1997-04-17 | 2000-08-29 | Cross Match Technologies, Inc. | Hand-held fingerprint recognition and transmission device |
| US6263090B1 (en) | 1997-05-19 | 2001-07-17 | Cross Match Technologies, Inc. | Code reader fingerprint scanner |
| US6038332A (en) * | 1997-09-05 | 2000-03-14 | Digital Biometrics, Inc. | Method and apparatus for capturing the image of a palm |
| US6178255B1 (en) | 1998-04-28 | 2001-01-23 | Cross Match Technologies, Inc. | Individualized fingerprint scanner |
| JP3079310B2 (en) * | 1998-09-16 | 2000-08-21 | 日本エルエスアイカード株式会社 | Fingerprint imaging device |
| US6175407B1 (en) * | 1998-12-17 | 2001-01-16 | Identix Incorporated | Apparatus and method for optically imaging features on the surface of a hand |
| US6272562B1 (en) | 1999-05-28 | 2001-08-07 | Cross Match Technologies, Inc. | Access control unit interface |
| US8036431B1 (en) * | 1999-10-29 | 2011-10-11 | Identix Incorporated | Portable apparatus for identification verification |
| WO2001067390A1 (en) * | 2000-03-08 | 2001-09-13 | Seiko Instruments Inc. | Image reader |
| DE60323208D1 (en) | 2002-01-17 | 2008-10-09 | Cross Match Technologies Inc | FINGERPRINT WORKSTATION AND METHOD |
| US7227978B2 (en) | 2002-06-20 | 2007-06-05 | Casio Computer Co., Ltd. | Image input device |
| US20040114785A1 (en) | 2002-12-06 | 2004-06-17 | Cross Match Technologies, Inc. | Methods for obtaining print and other hand characteristic information using a non-planar prism |
| JP2004206412A (en) | 2002-12-25 | 2004-07-22 | Casio Comput Co Ltd | Card type device and authentication system |
| US7081951B2 (en) | 2003-10-09 | 2006-07-25 | Cross Match Technologies, Inc. | Palm print scanner and methods |
| WO2024063798A1 (en) * | 2022-09-20 | 2024-03-28 | Hid Global Corp. | Biometric identification system using movable image plane |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4485406A (en) * | 1982-09-29 | 1984-11-27 | Eastman Kodak Company | Film video player with zoom and scan |
| JPS62154853A (en) * | 1985-12-26 | 1987-07-09 | Canon Inc | Image reader |
| US5016098A (en) * | 1987-03-05 | 1991-05-14 | Fuji Optical Systems, Incorporated | Electronic video dental camera |
| JPH0813088B2 (en) * | 1990-09-18 | 1996-02-07 | 富士ゼロックス株式会社 | Image reader |
| US5142557A (en) * | 1990-12-21 | 1992-08-25 | Photometrics Ltd. | CCD and phosphor screen digital radiology apparatus and method for high resolution mammography |
| US5206503A (en) * | 1991-08-07 | 1993-04-27 | Northrop Corporation | X-Y translational imaging device with housing supporting means for a camera body including image sensing means |
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1995
- 1995-11-03 JP JP8518789A patent/JPH10510075A/en active Pending
- 1995-11-03 MX MX9703856A patent/MX9703856A/en unknown
- 1995-11-03 CA CA002207664A patent/CA2207664A1/en not_active Abandoned
- 1995-11-03 BR BR9509933-6A patent/BR9509933A/en not_active Application Discontinuation
- 1995-11-03 CN CN95196530A patent/CN1167556A/en active Pending
- 1995-11-03 WO PCT/US1995/014226 patent/WO1996017480A2/en not_active Application Discontinuation
- 1995-11-03 EP EP95939714A patent/EP0795248A2/en not_active Ceased
- 1995-11-03 AU AU41425/96A patent/AU4142596A/en not_active Abandoned
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1997
- 1997-05-29 NO NO972448A patent/NO972448L/en unknown
Also Published As
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|---|---|
| WO1996017480A3 (en) | 1996-09-06 |
| BR9509933A (en) | 1999-11-30 |
| NO972448D0 (en) | 1997-05-29 |
| JPH10510075A (en) | 1998-09-29 |
| AU4142596A (en) | 1996-06-19 |
| MX9703856A (en) | 1998-02-28 |
| EP0795248A2 (en) | 1997-09-17 |
| WO1996017480A2 (en) | 1996-06-06 |
| CN1167556A (en) | 1997-12-10 |
| NO972448L (en) | 1997-07-25 |
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| Date | Code | Title | Description |
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