Fingerprint image reconstruction based on motion estimate across a narrow fringerprint sensor

A system for assembling a fingerprint image acquired from a fingerprint sensor, the system comprising:

• a swipe fingerprint sensor for acquiring a sequence of images, wherein each image comprises a portion of said fingerprint image;
• memory for storing at least two consecutive images of said sequence of images acquired by said swipe fingerprint sensor;
• a reconstructed image buffer;
• and
• a processor, coupled to said memory and said reconstructed image buffer, adapted to access said at least two consecutive images in said memory and to compute:
• a first correlation function between a prior frame, Fk, and a next frame, Fk+1, wherein rows from said prior frame have previously been added to said reconstructed image buffer, and wherein rows from said next frame will subsequently be added to said reconstructed image buffer;
• and
• a second correlation function between an extracted frame, {circumflex over (F)}k, and said next frame, Fk+1, wherein said extracted frame is extracted from most recently added rows to said reconstructed image buffer,
• wherein said first and second correlations are computed to compensate for variations due to movement error, wherein each frame includes first and second directions, said first direction being generally perpendicular to a finger movement direction, said second direction being generally parallel to said finger movement direction, and wherein a correlation is derived from an averaged delay from two or more functions computed in said second direction, said processor being further adapted to:
• locate peak correlation locations and calculate a delay factor, τ, based on said peak correlation locations;
• and
• in response to said calculated delay factor having a value greater than zero, to transfer a portion of at least one of said images to said reconstructed image buffer.

An apparatus, comprising:

• one or more processors;
• and
• a non-transitory computer-readable storage medium having instructions encoded thereon for execution by the one or more processors, and when executed being operable to:
• generate a plurality of frames representing image data for a finger, wherein each frame includes first and second directions, said first direction being generally perpendicular to a finger movement direction, said second direction being generally parallel to said finger movement direction;
• transfer a first of said plurality of frames to a reconstructed image buffer;
• determine new lines that have moved into each frame compared to lines in said reconstructed image buffer for each of a remaining plurality of frames, wherein said determination comprises compensating for variations due to movement error by computing:
• a first correlation between a prior frame and a next frame, wherein rows from said prior frame have previously been added to said reconstructed image buffer, and wherein rows from said next frame will subsequently be added to said reconstructed image buffer;
• and
• a second correlation between said next frame and an extracted frame, wherein said extracted frame is extracted from most recently added rows to said reconstructed image buffer, and wherein at least one of said first and second correlations is derived from an averaged delay from two or more functions computed in said second direction;
• and
• update said reconstructed image buffer by appending only said new lines from each of said remaining plurality of frames.