Real-time parameter adjustment for archival image scanning

Abstract

Many older documents are of poor quality and are deteriorating with the passage of time. Furthermore, many of these documents are currently stored in the form of paper or photographic film, and therefore storage space, accessibility, and security are serious problems. Because of these problems, many older documents are being restored and converted to digital form for archival. Image scanners which perform these tasks must be fast and must produce digital images that are of high quality.

A Scan Optimizer was developed by Image Processing Technologies, Inc., to assist in the restoration and conversion processes. This device dramatically improves the throughput of image scanners by the use of high-speed complicated image processing. As originally designed, however, the IPT Scan Optimizer requires the manual adjustment of several parameters to obtain the best results for a given document. Because of this manual adjustment, human intervention was often required, and conversion speeds were drastically reduced. In order to remove the need for manual adjustments, an Automatic Parameter Setting (APS) algorithm was developed. This algorithm relies on histogram analysis over non overlapping image regions for the computation of scan parameters.

This thesis describes a hardware realization of the APS algorithm. To achieve a real-time implementation that is low in cost, several compromises were necessary in the design. This two-board set is compatible with the AT bus, and is composed of one SPARC RISC chip, four Xilinx Programmable Logic Cell Arrays, ten PALs and many RAMs and supporting logic. This system has been designed, built, and successfully tested with many documents.