Fingerprint authentication with parallel processing

1. A method of authenticating a user by means of a fingerprint authentication system comprising a fingerprint sensing arrangement and authentication circuitry, said method comprising the steps of:

acquiring, by said fingerprint sensing arrangement, a first candidate fingerprint image of a finger of said user during a finger placement event when said finger is not moving across a surface of said fingerprint sensing arrangement;

acquiring, by said fingerprint sensing arrangement, a second candidate fingerprint image during said finger placement event; adjusting at least one setting of said fingerprint sensing arrangement after the step of acquiring said first candidate fingerprint image and before the step of acquiring said second candidate fingerprint image;

processing, while acquiring said second candidate fingerprint image, said first candidate fingerprint image by said authentication circuitry, said processing resulting in a processed representation of the first candidate fingerprint image;

evaluating said processed representation of the first candidate fingerprint image in respect of at least a first evaluation criterion; and

when said processed representation of the first candidate fingerprint image fails to fulfill said at least one evaluation criterion:

authenticating said user based on said second candidate fingerprint image.

2. The method according to claim 1 , wherein said authentication is additionally based on said first candidate fingerprint image.

3. The method according to claim 1 , wherein said step of authenticating comprises the steps of:

retrieving a stored enrolment representation for said user;

processing, by said authentication circuitry, said second candidate fingerprint image to determine an authentication representation based on said second candidate fingerprint image;

determining if a match between said authentication representation and said stored enrolment representation fulfills an authentication requirement; and

providing, when said match fulfills said authentication requirement, a signal indicating a successful authentication.

4. The method according to claim 3 , wherein said authentication representation is additionally based on said first candidate fingerprint image.

5. The method according to claim 1 , wherein said method further comprises the steps of:

when said processed representation of the first candidate fingerprint image fulfills said at least first evaluation criterion:

authenticating said user based on said first candidate fingerprint image.

6. The method according to claim 1 , wherein:

the step of processing said first candidate fingerprint image comprises the step of:

determining an authentication representation based on said first candidate fingerprint image; and

the step of evaluating said processed representation of the first candidate fingerprint image comprises the steps of:

retrieving a stored enrolment representation for said user; and

determining if a match between said authentication representation based on said first candidate fingerprint image and said stored enrolment representation fulfills an authentication requirement.

7. The method according to claim 1 , wherein said first evaluation criterion is based on said second candidate fingerprint image.

8. A fingerprint authentication system for authenticating a user, comprising:

a fingerprint sensing arrangement for receiving a finger of said user on a surface thereof;

a memory; and

processing circuitry connected to said fingerprint sensor, and to said memory, said processing circuitry comprising:

image acquisition circuitry for:

controlling said fingerprint sensing arrangement to acquire a first candidate fingerprint image of a candidate fingerprint to be authenticated during a finger placement event when said finger is not moving across the surface of said fingerprint sensing arrangement; adjusting at least one setting of said fingerprint sensing arrangement after the step of acquiring said first candidate fingerprint image and before the step of acquiring said second candidate fingerprint image; adjusting at least one setting of said fingerprint sensing arrangement after the step of acquiring said first candidate fingerprint image and before the step of acquiring said second candidate fingerprint image; and

controlling said fingerprint sensing arrangement to acquire a second candidate fingerprint image of said candidate fingerprint to be authenticated during said finger placement event; and

authentication circuitry for:

processing, while said fingerprint sensing circuitry acquires said second candidate fingerprint image, said first candidate fingerprint image, said processing resulting in a processed representation of the first candidate fingerprint image;

evaluating said processed representation of the first candidate fingerprint image in respect of at least a first evaluation criterion; and

when said processed representation of the first candidate fingerprint image fails to fulfill said at least one evaluation criterion:

authenticating said user based on said second candidate fingerprint image.

9. The fingerprint authentication system according to claim 8 , wherein said authentication is additionally based on said first candidate fingerprint image.

10. The fingerprint authentication system according to claim 8 , wherein said authenticating circuitry is configured to authenticate said user by:

retrieving a stored enrolment representation for said user from said memory;

processing said second candidate fingerprint image to determine an authentication representation based on said second candidate fingerprint image;

determining if a match between said authentication representation and said stored enrolment representation fulfills an authentication requirement; and

providing, when said match fulfills said authentication requirement, a signal indicating a successful authentication.

11. An electronic device comprising;

a fingerprint authentication system according to claim 8 ; and

a processing unit 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.