1. A method for constructing a unified image of biometric data, comprising: receiving a sequence of images of biometric data that is captured over a given period of time by a biometric recognition sensor; as the images in the sequence are received, repeatedly selecting a sliding window of images of biometric data from the sequence of images of biometric data, wherein each sliding window includes a given number of images in the sequence of images and at least one image that is not included in an immediately preceding sliding window; selecting one or more images of biometric data to be included in the unified image of biometric data from at least one of the sliding windows; and constructing the unified image of biometric data using the selected one or more images of biometric data.