Integrated Digital Imaging Systems - Hyperspectral Imaging
Background: When we look at a document, what we normally see is not necessarily all that is there. The
unaided eye can not always identify important characteristics such as colorants, or detect features
such as inks that are erased, hidden by overwriting or varnish, or faded because of environmental
factors. Such features on photographs, manuscripts, maps, and other materials are ofen important for
scholars, authentication, “fingerprinting” and the care of collections. Looking at
documents at various magnification levels and in various types of light (raking, transmitted and
different wavelengths) can capture these elusive features. The application of hyperspectral
imaging to the preservation analysis and study of paper, parchment and other materials is a powerful,
non-invasive, non-destructive technique to assess treatments, colorants and environmental factors.
Imaging with LED lighting, in 13 spectral bands and raking light for preservation studies, provides
a system with safe conservation lighting that is integrated with the camera to minimize light on the
object. Hyperspectral images have been used to analyze the Waldseemüller 1507 world map,
the L’Enfant plan of Washington D.C., daguerreotypes and other LC collection items.
Contributing Study: http://www.archimedespalimpsest.net/
Project Description: High resolution hyperspectral imaging (HSI) measures the spectrum from ultraviolet, through visible to infrared and can detect variance at any wavelength or combination of wavelengths. The images in this image cube can be digitally combined with or subtracted from each other to form images for precise analysis. This allows components to be characterized based upon their specific spectral response, discriminating between similar compounds, identifying and possibly quantifying materials present in the image. HSI allows the establishment of baseline data where deterioration assessment techniques can be linked to micro-analysis. The accurate determination of parameters associated with inks, pigments, colorants and base materials over time from a baseline response without sampling is critical to the assessment and preservation of many international items of cultural heritage. This provides essential information and data for object investigation and authentication in analyzing the ink composition, and layers of information retained on the document or object.
Outcomes/Findings:
Imaging has allowed for a range of analyses to be undertaken:
- Identifying the response of specific characteristics of the maps, including printers inks, pigments, iron gall, effects of treatments, and other aspects
- Using raking-incidence illumination to enhance the visibility of any “topographic” features, e.g. relating to the wood block printing of the Waldseemüller map and any other mechanical contact
- Using advanced processing techniques to create pseudocolor images to map specific components, and regions of interest
- Development of new protocols for imaging of watermarks, substrate features and other areas of interest
- Establishment of standards for the integration of data for digital access, with defined metadata and robust processes for validating and refining data into a central repository and archive to the production of digital data for preservation and analyses
Acknowledgements: The team from R.B. Toth Associates; Michael B. Toth, Dr. Roger Easton (RIT). Dr. William Christens-Barry (Equipoise Imaging), Dr. Keith Knox (Boeing), Douglas Emery (Emery IT), Kenneth Boydston (MegaVision)
Update and Images:
March 2008: Fenella France and Roger Easton presented a TOPS talk at LC.
January 2009: A session on hyperspectral imaging at LC was presented at the Winter Technology Showcase of the mid-winter ALA meeting in Denver CO.
January 2009: A paper on the new integrated camera technology was presented at SPIE in San Jose, CA.
June 2009: A paper on the “digital cultural object” was presented at Digital Humanities in College Park, MD
July 2009: A paper on the development of scientific reference sample collection developments for spectral imaging was presented at Archiving 2009 in Crystal City, VA