1. A method of iris image acquisition, the method comprising: acquiring, by a sensor, a plurality of images of a subject, the plurality of images including a first image of an iris of the subject; determining, by at least one processor, a quality metric for the acquired first image, the quality metric determined using an estimated area of the iris visible in the acquired first image and a level of focus measured from the acquired first image; and responsive to the determined quality metric, acquiring, by the sensor, another image if the determined quality metric is lower than a predetermined threshold, and storing, in a memory, the acquired first image of the iris of the subject if the quality metric is higher than the predetermined threshold.