Hyperspectral document image processing : Applications, challenges and future prospects

Automatic image analysis is a crucial component of many intelligent systems designed for high-level understanding of documents. Most document image understanding systems are usually based on applying pattern recognition techniques to conventional three channel RGB images. Airborne and satellite based macro scale Hyperspectral Imaging (HSI) systems are well established for geosciences. Recently, owing to advancements in imaging speed and reduced camera costs, micro scale HSI systems are also gaining importance in ground based applications such as hyperspectral document image analysis. HSI is non destructive and offers new opportunities via measuring richer information along spectral dimension by imaging the document in contiguous bands across the electromagnetic spectrum. Hyperspectral document imaging has shown potential for solving many challenging problems of document image analysis including signature extraction, ink or document aging, information retrieval from historical document images, paintings and forensic analysis of documents. In this paper, we explore the potential of HSI for document image analysis and present a comprehensive review of the literature and future prospects. We highlight and discuss the challenges involved in the acquisition and processing of hyperspectral document images. A review of commercial HSI systems for document image analysis is also presented.