Library of Congress – Transmissive Imaging
Background and History
In June 2018, Avian Rochester began a fourth project with the Library of Congress (LC). This project continued the move towards implementing spectral imaging within the library and museum communities. Specifically, this work focused on two efforts: research of imaging prior art and best practice related to human visual perception and transmissive digitization; and creation of prototype spectral based transmissive calibration target, and an appropriate methodology to implement their use in a FADGI compliant digitization program.
Details from the Executive Summary
After reviewing the general requirements for imaging transmissive materials, the state of the art at the Library of Congress is presented. The current practice is limited to the use of the IT/8 family of film-based scanner characterization targets. This may be sufficient for certain cultural heritage scanning applications, but it not suitable for the general case. The literature offers some improved solutions, but again these are not likely suitable given the requirements of general transmissive imaging.
The fully general case for transmissive or reflective imaging is a spectral approach, where the sample spectral transmittance (or reflectance) is predicted for every pixel in a given image. Some potential technologies for spectral imaging are mentioned, followed by the advantaged of such an approach.
The final section describes the new physical transmissive target provided as a part of the current contract. The use of the target is also described. (download the full report).