1. An input device for scanning a biometric image, comprising: a housing; a scan head movably mounted to the housing wherein the scan head is comprised of at least a light source; a platen moveably mounted to the housing and the scan head for movement relative to the housing and the scan head between a first position and a second position; an encoder target having a grid pattern representing a plurality of binary numbers, wherein the boxed pattern and the platen are associated to allow the scan head to capture a plurality of scan lines such that each member of the plurality of scan lines includes at least a portion of the grid pattern representing a binary number and at least a portion of the platen, and wherein the captured plurality of scan line are assembled based on a binary number value associated with the captured portion of the grid pattern; a biasing device configured to bias the platen toward the first position; a start of scan switch located such that the start of scan switch is activated when the platen moves in a downward translation from the first position; and an end of scan switch located such that the end of scan switch is activated when the platen is at the second position.