Method and apparatus for distinguishing a human finger from a reproduction of a fingerprint
First Claim
1. An apparatus for scanning a fingerprint comprising:
- a first light positioned to generate a first image showing illumination in areas where skin is in contact with a platen and showing less illumination in areas where no skin is in contact with the platen;
a second light source positioned to generate a second image showing illumination in areas where no skin is in contact with the platen and showing less illumination in areas where skin is in contact with the platen;
an imaging device positioned to capture an image of the fingerprint illuminated by light from either the first light source or the second light source; and
a comparison logic for determining if the fingerprint is from a human finger if a mathematical comparison between the first image and the second image meets or exceeds a predetermined criteria.
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Accused Products
Abstract
A method and apparatus for distinguishing a human finger from a reproduction of a fingerprint. A finger is placed on a transparent platen having a prism or microprism array attached. A first light source directs light to the platen, the first light positioned to show illumination in the areas where the skin is in contact with the platen. A first image of the fingerprint is captured by an imaging device when the finger is illuminated by the first light source. A second light source directs light at the platen, the second light positioned to show illumination in the areas where there is no skin contact. A second image of the fingerprint is captured by the imaging device when the finger is illuminated by the second light source. A determination that the fingerprint is from a human finger is made if a mathematical comparison of the two images meets some predetermined criteria.
245 Citations
26 Claims
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1. An apparatus for scanning a fingerprint comprising:
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a first light positioned to generate a first image showing illumination in areas where skin is in contact with a platen and showing less illumination in areas where no skin is in contact with the platen;
a second light source positioned to generate a second image showing illumination in areas where no skin is in contact with the platen and showing less illumination in areas where skin is in contact with the platen;
an imaging device positioned to capture an image of the fingerprint illuminated by light from either the first light source or the second light source; and
a comparison logic for determining if the fingerprint is from a human finger if a mathematical comparison between the first image and the second image meets or exceeds a predetermined criteria. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method for determining if a fingerprint is from a human finger, the method comprising:
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capturing with an imaging device a first image of the fingerprint illuminated by a first light source;
capturing with the imaging device a second image of the fingerprint illuminated by a second light source;
determining that the fingerprint is from a human finger if a mathematical comparison between the first image and the second image meets or exceeds a predetermined criteria. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22)
the first light is positioned to generate a first image showing illumination in areas where skin is in contact with the platen and showing less illumination in areas where no skin is in contact with the platen; - and
the second light source is positioned to generate a second image showing illumination in areas where no skin is in contact with the platen and showing less illumination in areas where skin is in contact with the platen.
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16. The method of claim 15, wherein the first light is positioned to illuminate both the ridges and valleys of the fingerprint, the scattered light from the first light yielding a low- or zero-contrast image of skin, and a higher contrast image of a reproduction fingerprint.
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17. The method of claim 16, wherein the platen is a roller.
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18. The method of claim 16, wherein capturing the fingerprint image further comprises using a hologram to reflect the light.
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19. The method of claim 14, wherein
the first light source directs light substantially orthogonal to the platen; - and
the second light source directs light at an acute angle to the platen.
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20. The method of claim 14, wherein the first image is captured at a first instant and the second image is captured at a second instant.
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21. The method of claim 20, wherein determining comprises:
determining that the fingerprint is from a human finger if the difference between the width of a ridge on the first image and the width of the ridge on the second image is greater than a flattening threshold value.
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22. The method of claim 20, wherein determining comprises:
determining that the fingerprint is from a human finger if the difference between the area of contact of the first image and the area of contact of the second image is greater than a contact area threshold value.
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23. A method for determining if a fingerprint is from a human finger placed on a platen, the method comprising:
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illuminating the finger with a first light source positioned to direct light substantially orthogonal to the platen;
illuminating the finger with a second light source positioned to direct light at an acute angle to the platen;
capturing with an imaging device an image of the fingerprint illuminated by the first light source and the second light source; and
determining that the fingerprint is from a human finger if the difference between a light intensity of a ridge of the fingerprint and a light intensity of a valley of a fingerprint is less than a contrast threshold value.
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24. A method for determining if a fingerprint is from a human finger placed on a platen, the method comprising:
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illuminating the finger with a first light source positioned to direct light substantially orthogonal to the platen;
capturing with an imaging device a first image of the fingerprint illuminated by the first light source;
illuminating the finger with a second light source positioned to direct light at an acute angle to the platen;
capturing with the imaging device a second image of the fingerprint illuminated by the second light source;
comparing the first image to the second image; and
determining that the fingerprint is from a human finger if lighter areas of the first image generally correspond to darker areas of the second image, and vice versa.
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25. A method for determining if a fingerprint is from a human finger placed on a platen, the method comprising:
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illuminating the finger with light from a light source;
capturing with an imaging device a first image of the fingerprint at a first time instant;
capturing with the imaging device a second image of the fingerprint at a second time instant;
comparing the first image to the second image; and
determining that the fingerprint is from a human finger if the difference between the width of a ridge on the first image and the width of the ridge on the second image is greater than a widening threshold value.
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26. A method for determining if a fingerprint is from a human finger placed on a platen, the method comprising:
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illuminating the finger with light from a light source;
capturing with an imaging device a first image of the fingerprint at a first time instant;
capturing with the imaging device a second image of the fingerprint at a second time instant;
comparing the first image to the second image; and
determining that the fingerprint is from a human finger if the difference between the area of contact of the first image and the area of contact of the second image is greater than a threshold value.
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Specification