1. Biometric device for capturing fingerprint information and for extracting significant data from a partial fingerprint area, comprising, a line sensor for consecutively capturing fractional fingerprint images from fractional areas of a finger through a relative sliding movement between the finger and the line sensor, a first memory configured to consecutively store the fingerprint information from the fractional fingerprint images, a decision-making processor configured to decide when the information stored in the first memory constitutes a partial fingerprint area which is large enough for the extraction of the significant data, an extraction processor configured to extract significant data from the partial fingerprint area stored in the first memory, a second memory configured to store the extracted significant data, and a storage-determining processor configured to control the storage of the captured fractional fingerprint images in the first memory by comparing the several consecutive fractional fingerprint images with the previously captured fractional fingerprint images, combining the fractional fingerprint images together to form a partial fingerprint area which is large enough for the extraction of the significant data, and discarding the oldest stored fractional fingerprint image from the first memory when a new fractional fingerprint image is stored in the first memory, wherein the partial fingerprint area comprises at least 32 lines of information, and wherein the extraction processor is configured to extract the significant data from the partial fingerprint area stored in the first memory according to an extraction interval of between one-half and one-quarter of the partial fingerprint area.