Photogrammetric calibration of a consumer grade flatbed scanner

摘要

The photogrammetric utility of an Agfa Studio Scan II si flatbed colour scanner was examined. The scanner has a 400 ppi horizontal and 800 ppi vertical optical resolution with a pixel size of 64 μm by 32 μm. Systematic linear and non-linear distortions in the scanned images were observed, indicating the need for calibration. The calibration was done with the assistance of a distortion model, which produced a scanner distortion atlas. Distortions in the image coordinates were found by directly scanning a glass calibration grid-plate. In the absence of corrective adjustments, the measured distortions produced deviations of 0.6% or less from the object coordinates. For this particular scanner the tilt of the scanner head appears to be about 6.0 arcminutes, with a scaling distortion in the x-direction of 0.9941 and 0.9992 in the y-direction. The periodic distortion appears to have an amplitude of 1.6 pixels, and a wavelength of 4.9 cm. There appears to be no aliasing in the periodic distortion measurements.