Image scanner apparatus with scanning magnification correcting function

摘要

A scanner unit optically scans an original in a first direction to obtain an optical image. A mark is provided with a predetermined distance within a range in a second direction perpendicular to the first direction. The range is a range which can be scanned by the scanner unit. A line sensor is arranged in the second direction to read the optical image line by line in cooperation with the scanner unit. A converter converts a read output from the line sensor into digital data. An instruction section instructs to read the mark to the scanner unit and the line sensor prior to reading of the original. A distance calculating section calculates distance data corresponding to the predetermined distance of the mark in accordance with the digital data from the converter when the scanner unit and the line sensor cooperate to read the mark in accordance with an instruction from the instruction switch. A correction data calculating section calculates correction data corresponding to a difference between reference data and the distance data calculated by the distance calculating section. The correction data represents the number of bits of data extraction or addition corresponding to the difference. A read magnification correcting section executes bit extraction from or addition to the digital data from the converter in accordance with the number of bits represented by the correction data output from the correction data calculating section. A read magnification defined by the scanner unit and the line sensor is corrected to a defined read magnification corresponding to the reference data.