Geometric and radiometric performance evaluation of the Leica/Helava DSW200 photogrammetric film scanner

In this paper geometric and radiometric investigations performed with two Leica/Helava DSW200 scanners will be presented. Good quality test patterns and accurate processing methods for their performance evaluation have been employed. The geometric tests include global and local geometric errors, misregistration between colour channels, geometric repeatability, and determination of the geometric resolution. Efforts were made to separate the contribution of various error sources (especially mechanical positioning, electronic errors and lens distortion) on the total error. The radiometric tests include investigations on noise, linearity, dynamic range, spatial, temporal and spectral variation of noise, and artifacts. After a brief description of the scanner, details on the above investigations, used analysis methods and achieved results will be presented. The most important errors, especially for organisations employing the scanner in production, are nonrepeatable geometric errors that are due to mechanical positioning inaccuracies and vibrations. This causes whole CCD image tiles (4 million pixels) to be systematically shifted with respect to their neighbouring tiles, with obvious negative influence on any subsequent measuring task.