On Interoperability of Security Document Reading Devices

For travel document inspection systems in automated border control an inherent topic of interest is harmonization across devices ensuring vendor-independence at retained high security levels. This requires the development of (1) standards at hardware level, (2) unified approaches with regards to best-practice normalization methods in order to facilitate the comparison of passport images acquired using different readers, and (3) selection of robust optical security features to be investigated. This paper presents several normalization techniques for travel documents involving shading correction and colour calibration and evaluates its impact in cross-sensor setup using 9 different document readers. Results indicate a much better representation in terms of both well-known image metrics PSNR and SSIM facilitating harmonization of optical document inspection.