1. An apparatus for capturing a rolled fingerprint image, comprising: a fingerprint input unit for acquiring a plurality of sequential elemental image frames from a fingerprint as a finger that touches and rolls on a fingerprint input window, wherein each of the elemental image frames is composed of a plurality of pixels; a preprocessor for of processing corresponding pixels in each sequential pair of elemental image frames to reduce noise, and for producing, for each sequential pair of elemental image frames a corresponding improved image frame, thereby generating a plurality of sequential improved image frame, each of the improved image frames being composed of a plurality of pixels; a main data acquirer for processing corresponding pixels in each sequential [air of improved image frames, and for synthesizing, for each sequential pair improved image frames, a corresponding main data image frame with reduced data overflow and differentiating black and white portions of sequential improved image frames, thereby producing a plurality of sequential main data image frames, each of the main data frames being composed of a plurality of pixels; and an image merger for merging the sequential main data image frames to produce the rolled fingerprint image.