System and method for iris data acquisition for biometric identification
A system and related method for acquiring high quality images of the iris of an unconstrained subject comprising a camera; a controllable focusing component; a focus controller component that controls the lens to focus at successively different points within a focus range, such focus control performed without any input from measurement of whether the image is in focus or out of focus, be it based from measurements of the image or other distance metrics to the subject; and a sharpness detection component that rejects the most out-of-focus images based on measurement of focus on the image is disclosed.
1. A system for acquiring a series of images of an unconstrained subject, the system comprising:
a sensor configured to acquire one or more images of an unconstrained subject;
a controller configured to:
detect an eye that is open or partially open in the acquired image;
monitor quality criteria comprising an estimated extent of an iris of the unconstrained subject that is exposed according to the openness of the eye and acquired in the one or more images;
determine, according to the monitored quality criteria comprising the estimated extent of the iris that is exposed and acquired, a time period during which there is a high probability that iris biometric data valid for biometric matching can be acquired from the unconstrained subject;
increase, responsive to the determination, a rate of acquisition of images of the unconstrained subject within the determined time period, without input from measurement of whether a corresponding image to be acquired is in focus; and
replace a first image stored in a storage device with a second image acquired within the determined time period, when a quality score of the second image is higher than that of the first image.
2. The system of claim 1 , wherein the controller is further configured to determine the quality score of the second image according to an extent of the iris that is acquired in the second image and available for biometric matching.
3. The system of claim 2 , wherein the controller is further configured to determine the quality score of the second image according to sharpness or contrast of features determined in the second image.
4. The system of claim 1 , wherein the controller is further configured to measure an extent of a physical area of the iris that is exposed for biometric acquisition and available for biometric matching.
5. The system of claim 1 , wherein the controller is further configured to detect a feature of the subject's face or eye on the acquired one or more images.
6. The system of claim 1 , wherein the controller is configured to further determine the time period according to at least one of: a result of biometric matching using the acquired image, and detection of a physical feature or motion of the unconstrained subject from the one or more images.
7. The system of claim 1 , wherein the controller is configured to determine at least one of: a duration for the time period, an image acquisition rate, or a number of images, for the acquisition of the images within the determined time period.
8. The system of claim 1 , wherein the controller is configured to determine, based on an estimated degree of motion of the subject, at least one of: a duration for the time period, a rate for acquisition and a number of images, for the acquisition of the images within the determined time period.
9. The system of claim 1 , wherein the sensor is configured to acquire the images within the determined time period, at focus values according to one of a monotonic pattern, a sawtooth pattern, and a random scan pattern.
10. The system of claim 1 , wherein the controller rejects at least one of the images acquired within the determined time period, based on one or more of: a result of biometric matching, measurement of image sharpness, measurement of image contrast, and detection of a feature of the subject's eye.
11. A method for acquiring images of an unconstrained subject, the method comprising:
acquiring, by a sensor, one or more images of an unconstrained subject;
detecting an eye that is open or partially open in the acquired image;
monitoring, by a controller executing on one or more processors, quality criteria comprising an estimated extent of an iris of the unconstrained subject that is exposed according to the openness of the eye and acquired in the one or more images;
determining, by the controller according to the monitored quality criteria comprising the estimated extent of the iris that is exposed and acquired, a time period during which there is a high probability that iris biometric data valid for biometric matching can be acquired from the unconstrained subject;
increasing, by the controller responsive to the determination, a rate of acquisition of images of the unconstrained subject within the determined time period, without input from measurement of whether a corresponding image to be acquired is in focus; and
replacing, by the controller, a first image stored in a storage device with a second image acquired within the determined time period, when a quality score of the second image is higher than that of the first image.
12. The method of claim 11 , further comprising determining, by the controller, the quality score of the second image according to an extent of the iris that is acquired in the second image and available for biometric matching.
13. The method of claim 12 , further comprising determining, by the controller, the quality score of the second image according to sharpness or contrast of features determined in the second image.
14. The method of claim 11 , further comprising measuring, by the controller, an extent of a physical area of the iris that is exposed for biometric acquisition and available for biometric matching.
15. The method of claim 11 , further comprising detecting, by the controller, a feature of the subject's face or eye on the acquired one or more images.
16. The method of claim 11 , wherein determining the time period further comprises determining the time period according to at least one of: a result of biometric matching using the acquired image, and detection of a physical feature or motion of the unconstrained subject from the one or more images.
17. The method of claim 11 , further comprising determining, by the controller, at least one of: a duration for the time period, an image acquisition rate, or a number of images, for the acquisition of the images within the determined time period.
18. The method of claim 11 , further comprising determining, by the controller, based on an estimated degree of motion of the subject, at least one of: a duration for the time period, a rate for acquisition and a number of images, for the acquisition of the images within the determined time period.
19. The method of claim 11 , further comprising acquiring, by the sensor, the images within the determined time period, at focus values according to one of a monotonic pattern, a sawtooth pattern, and a random scan pattern.
20. The method of claim 11 , further comprising rejecting, by the controller, at least one of the images acquired within the determined time period, based on one or more of: a result of biometric matching, measurement of image sharpness, measurement of image contrast, and detection of a feature of the subject's eye.