Method and apparatus for rolled fingerprint image capture with variable blending
First Claim
1. A method for capture of a fingerprint image as a finger is rolled across a platen surface, comprising the steps of:
- (a) capturing a plurality of fingerprint image frames, each captured frame including pixel data representative of a print on the platen surface at a time of capture as the finger is rolled across the platen surface; and
(b) combining said plurality of captured fingerprint image frames into a composite fingerprint image;
wherein said combining step includes at least partially blending pixel data in successive frames as a function of roll speed of the finger across the platen surface.
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Accused Products
Abstract
A composite image of a finger rolling relative to an imaging device is generated by stitching together image data from a plurality of image frames. The areas of each image that contain useful fingerprint information are identified and the speed of movement of the finger relative to the imaging path is determined. The frames are stitched together in sequence and data for pixels near the boundary between adjacent images is blended, so that values for those pixels are determined based on redundant data from both adjacent images. The extent of blending is based at least in part on movement speed of the finger, so that as speed increases blending is applied to an increasing number of the pixels in the boundary area. Blending may be accomplished using a weighting function where data from a primary frame is given primary weight while data from a secondary or redundant frame is given relatively less weight, and weight given to pixels from the secondary frame declines as distance increases between those pixels and the boundary between frames.
117 Citations
26 Claims
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1. A method for capture of a fingerprint image as a finger is rolled across a platen surface, comprising the steps of:
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(a) capturing a plurality of fingerprint image frames, each captured frame including pixel data representative of a print on the platen surface at a time of capture as the finger is rolled across the platen surface; and
(b) combining said plurality of captured fingerprint image frames into a composite fingerprint image;
wherein said combining step includes at least partially blending pixel data in successive frames as a function of roll speed of the finger across the platen surface. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method for generating a composite fingerprint image in a rolled fingerprint capture system, comprising the steps of:
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(a) capturing a first fingerprint image frame and a second fingerprint image frame as a finger is rolled across an imaging surface;
(b) identifying at least one boundary pixel representing corresponding fingerprint image data appearing in both the first and second image frames; and
(c) assigning a blended value to said boundary pixel where said blended value is a function of the values of corresponding pixels in said first and second fingerprint image frames and roll speed of the finger across the imaging surface during said capturing step; and
(d) combining said first and second fingerprint image frames into a composite fingerprint image incorporating said blended value for said boundary pixel. - View Dependent Claims (9, 10, 11, 12)
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13. A method for generating a composite image of a finger moving across an imaging area, comprising the steps of:
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(a) capturing a first image frame and a second image frame as the finger moves across the imaging area;
(b) determining a relative change in position of the finger between said first image frame and said second image frame;
(c) identifying a region containing pixels for which there is corresponding fingerprint image data in the first and second image frames; and
(d) for pixels in said region, assigning a blended value to said pixels where said blended value is a function of the values of corresponding pixels in said first and second image frames and said relative change in position of the finger between frames; and
(e) combining said first and second image frames into a composite fingerprint image incorporating said blended value for said pixels.
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14. A system for capturing a fingerprint image as a finger is rolled across a platen surface, comprising:
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image capture means for capturing a plurality of fingerprint image frames, each captured frame including pixel data representative of a print on the platen surface at a time of capture as the finger is rolled across the platen surface;
blending means for combining said plurality of captured fingerprint image frames into a composite fingerprint image, wherein said blending means operates to blend pixel data from successive frames as a function of roll speed of the finger across the platen surface. - View Dependent Claims (15, 16, 17, 18, 19, 20)
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21. A system for generating a composite fingerprint image in a rolled fingerprint capture system, comprising:
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capture means for capturing a first fingerprint image frame and a second fingerprint image frame as a finger is rolled across an imaging surface;
blending means for identifying at least one boundary pixel representing corresponding fingerprint image data appearing in both the first and second image frames and assigning a blended value to said boundary pixel where said blended value is a function of the values of corresponding pixels in said first and second fingerprint image frames and roll speed of the finger across the imaging surface during said capturing step; and
image processing means for combining said first and second fingerprint image frames into a composite fingerprint image incorporating said blended value for said boundary pixel. - View Dependent Claims (22, 23, 24, 25)
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26. A system for generating a composite image of a finger moving relative to an imaging area, comprising:
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capture means for capturing a first image frame and a second image frame as the finger moves relative to the imaging area;
calculating means for determining a relative change in position of the finger between said first image frame and said second image frame;
processing means for identifying a region containing pixels for which there is corresponding fingerprint image data in the first and second image frames and assigning a blended value to said pixels where said blended value is a function of the values of corresponding pixels in said first and second image frames and said relative change in position of the finger between frames and combining said first and second image frames into a composite fingerprint image incorporating said blended value for said pixels.
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Specification