Fingerprint authentication system and method providing for reduced latency
A fingerprint image is acquired, and it is determined if the finger is still touching the sensing surface. When the finger no longer touches the sensing surface, the user is authenticated based on one or several fingerprint image(s) acquired so far. When the finger still touches the sensing surface, a quality measure is determined for the fingerprint image. When a quality of the fingerprint image fulfills a predefined quality criterion, the user is authenticated based on one or several fingerprint images acquired so far. When the quality of the fingerprint image fails to fulfill the predefined quality criterion, a subsequent fingerprint image is acquired. When the finger still touches the sensing surface, and the quality measure indicates that the quality of the subsequent fingerprint image fulfills the predefined quality criterion, the user is authenticated based on one or several fingerprint images acquired so far including the subsequent fingerprint image.
1. A fingerprint authentication system for authenticating a user, comprising:
a fingerprint sensor;
finger detecting circuitry; and
processing circuitry connected to said fingerprint sensor and to said finger detecting circuitry, said processing circuitry being configured to:
control said fingerprint sensor to acquire a first fingerprint image of a finger touching said sensing surface;
receive, from said finger detecting circuitry, a first finger detect signal indicating whether or not the finger is still touching said sensing surface;
authenticate, when said first finger detect signal indicates that the finger is no longer touching said sensing surface, said user based on said first fingerprint image;
determine, when said first finger detect signal indicates that the finger is still touching said sensing surface, a quality measure for said first fingerprint image;
authenticate, when the quality measure indicates that a quality of said first fingerprint image fulfills a predefined quality criterion, said user based on said first fingerprint image;
control, when the quality measure indicates that the quality of said first fingerprint image fails to fulfill said predefined quality criterion, said fingerprint sensor to acquire a second fingerprint image of the finger touching said sensing surface;
receive, from said finger detecting circuitry, a second finger detect signal indicating whether or not the finger is still touching said sensing surface;
authenticate, when said second finger detect signal indicates that the finger is no longer touching said sensing surface, said user based on at least one of said first fingerprint image and said second fingerprint image;
determine, when said second finger detect signal indicates that the finger is still touching said sensing surface, a quality measure of said second fingerprint image; and
authenticate, when the quality measure indicates that a quality of said second fingerprint image fulfills said predefined quality criterion, said user based on at least one of said first fingerprint image and said second fingerprint image.
2. An electronic device comprising;
a fingerprint authentication system according to claim 1 ; and
at least one processor configured to control said fingerprint authentication system to carry out a fingerprint authentication of a user, and to perform at least one action only upon successful authentication of said user.
3. The fingerprint authentication system according to claim 1 , wherein said quality measure is determined based on a number of unsaturated pixels.
4. The fingerprint authentication system according to claim 3 , wherein said quality measure is determined based on said number of unsaturated pixels in relation to a total number of pixels.
5. The fingerprint authentication system according to claim 3 , wherein said quality criterion is indicative of a minimum number of unsaturated pixels.
6. The fingerprint authentication system according to claim 1 , wherein said processing circuitry is configured to, when said second fingerprint image has been acquired:
evaluate said first fingerprint image and said second fingerprint image to select one of said first fingerprint image and said second fingerprint image as an authentication fingerprint image;
retrieve a stored enrolment representation of said finger;
process said authentication fingerprint image to determine an authentication representation based on said authentication fingerprint image;
determine if a match between said authentication representation and said stored enrolment representation fulfills an authentication requirement; and
provide, when said match fulfills said authentication requirement, a signal indicating a successful authentication.
7. The fingerprint authentication system according to claim 1 , wherein said processing circuitry is configured to, when said second fingerprint image has been acquired:
retrieve a stored enrolment representation of said finger;
process said first fingerprint image and said second fingerprint image to determine an authentication representation based on said first fingerprint image and said second fingerprint image;
determine if a match between said authentication representation and said stored enrolment representation fulfills an authentication requirement; and
provide, when said match fulfills said authentication requirement, a signal indicating a successful authentication.
8. The fingerprint authentication system according to claim 1 , wherein said processing circuitry is configured to:
adjust at least one setting of said fingerprint sensor acquiring said first fingerprint image and before acquiring said second fingerprint image.