Composite image generating method, and a fingerprint detection apparatus
First Claim
1. A method of generating a composite image (14) from a sequence of partial image frames (13a-x), which represent different but at least partially overlapping areas of a body-specific pattern, wherein displacements between successive image frames are determined so as to combine the image frames correctly when generating the composite image, characterized in that the following steps are performed for said sequence of image frames:
- selecting a predetermined number of subareas (22a-f) of a first image frame (13j), for each subarea, determining a correlation (25) with a second image frame (13), which succeeds the first image frame, calculating a linear combination (29) of the correlations (25a, 25b) for all subareas, and determining, from the calculated linear combination, the displacement between the first and second image frames.
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Abstract
A fingerprint detection apparatus has a fingerprint sensor (10), which produces a sequence of at least partially overlapping fingerprint frames (13), when a finger (11) is moved in relation to the fingerprint sensor. The apparatus also has a processing device, which is coupled to the fingerprint sensor and produces a complete fingerprint image (14) by computing a relative displacement between respective fingerprint frames and combining the fingerprint frames accordingly. The processing device determines the relative displacement between a first fingerprint frame and a second fingerprint frame by selecting a plurality of subareas in the first fingerprint frame. For each subarea, a respective correlation with the second fingerprint frame is determined. Then a linear combination of the respective correlations is computed, and finally, from the computed linear combination, the relative displacement is determined.
71 Citations
13 Claims
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1. A method of generating a composite image (14) from a sequence of partial image frames (13a-x), which represent different but at least partially overlapping areas of a body-specific pattern, wherein displacements between successive image frames are determined so as to combine the image frames correctly when generating the composite image, characterized in that the following steps are performed for said sequence of image frames:
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selecting a predetermined number of subareas (22a-f) of a first image frame (13j), for each subarea, determining a correlation (25) with a second image frame (13), which succeeds the first image frame, calculating a linear combination (29) of the correlations (25a, 25b) for all subareas, and determining, from the calculated linear combination, the displacement between the first and second image frames. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A fingerprint detection apparatus, comprising a fingerprint sensor (10) adapted to produce a sequence of at least partially overlapping fingerprint frames (13), when a finger (11) is moved in relation to the fingerprint sensor, and a processing device (15), which is coupled to the fingerprint sensor and is adapted to produce a complete fingerprint image (14) by computing the relative displacement between respective fingerprint frames and combining the fingerprint frames accordingly, characterized in that the processing device (15) is adapted to determine the relative displacement between a first fingerprint frame (13j) and a second fingerprint frame (13) by:
- selecting a plurality of subareas (22a-f) in the first fingerprint frame;
for each subarea, determining a respective correlation (25) with the second fingerprint frame;
computing a linear combination (2a) of the respective correlations (25a, 25b), and determining, from the computed linear combination, the relative displacement. - View Dependent Claims (11, 12, 13)
- selecting a plurality of subareas (22a-f) in the first fingerprint frame;
Specification