Patent ID: 8300235

Claim:
An image scanner configured to detect a size of an original, comprising: a carriage configured to emit light to an original, which is placed on a platen, along a main scanning direction, the carriage being movable in an auxiliary scanning direction; a driving mechanism configured to drive the carriage to move; and an image processing unit configured to process image signal which is obtained based on light reflected from the original; the image processing unit including: a candidate determining unit configured to determine at least one candidate size of the original based on a pre-scan image of the original scanned at a position in the vicinity of one end, in the auxiliary scanning direction; a candidate length determining unit configured to determine candidate lengths for the original if there are multiple candidate sizes; a scan/non-scan section determining unit configured to determine a non-scan section and a scan section in the auxiliary scanning direction based on the candidate lengths; and a sheet size detecting unit configured to detect the size of the original based on the pre-scan image of the original scanned at the scan section; wherein the driving mechanism moves the carriage at a first speed in the scan section and at a second speed in the non-scan section, the second speed being faster than the first speed.