1. An image scanner for scanning an image by using an image sensor with a plurality of imaging devices disposed in a single row, comprising: an imager unit having a plurality of sensor chips disposed in a single connected row, each sensor chip having a plurality of imaging devices; an A/D converter unit for converting an image signal output from the imager unit to digital pixel data; a compensator unit for correcting for variations in characteristics of the imaging devices of the sensor chips; and an interpolator unit for interpolating missing pixel data occurring at points where the sensor chips are mutually connected; wherein the interpolator unit performs missing pixel interpolation after the compensator unit corrects for the variations in the characteristics of the imaging devices.