SPECTRAL IMAGING FOR CULTURAL HERITAGE

S P E C T R A L I M A G I N GF O R C U L T U R A L H E R I T A G E

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The science of spectral imaging in the infra-red ranges is extremely valuable to the field of artwork analysis and conservation.

Using this non-invasive technique, users can ‘see the invisible.’ Pigments and parchment that may be spectrally similar in the visible range look quite different in NIR/SWIR region. Faded, damaged, altered (restored) artifacts usually exhibit spectral differences.

In addition, contrast tends to increase at various wavelength ranges, especially outside the visible range. Colors that look similar to the eye can have markedly different spectral characteristics.

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Detecting TextHeadwall has successfully scanned portions of historical documents using Principle Components Analysis (PCA) in the Visible-Near-Infrared (VNIR) range from 400-1000nm. The results are strikingly significant.

Visible (400-710nm) 900nm image

Fresh Ink and Parchment Dead Sea Scroll Ink and Parchment

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. Bearman, G.; Christens-Barry, W. A. Palarch’s J. Arch. of Egypt/Egyptology 2009, 6(7) 1-20.

Dead Sea Scrolls‘Strappado’ Etching (1633)

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Identify Rightful Owner of Rare BookHyperspectral imaging played a vital role in the successful repatriation of a rare book. Cornell University has a vast collection of historically valuable books. One of these was simply known as the ‘Oculus,’ written by Christopher Scheiner in 1619.

Before arriving at Cornell, however, the book was thought to have been stolen in a daring robbery at the National Library of Sweden many years before. To verify whether the Cornell book did indeed belong to Sweden, Principal Component Analysis (PCA) in the VNIR spectral range was used. The forensic work provided a clear view of previous catalog markings, which corresponded with catalog numbering used by the National Library of Sweden.

The book was successfully repatriated back to Sweden thanks to the use of Headwall’s VNIR Hyperspec® sensor.

RGB IMAGE 488nm VNIR

old writing

Pigment and Binder MappingChemical imaging in the Shortwave-Infrared (SWIR) range between 900-2500nm can assist in understanding paint-ing technology for a given time period. This includes how inks were made and the evolution of an artist’s techniques. In addition, chem-ical imaging allows conservat ion-care experts to identify repairs and resto-rations, detect paint changes over time, analyze parchment, and detect forgeries.

Dooley et al, Analyst 138, 4838-4848 (2013)

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About Headwall PhotonicsHeadwall is a global leader in spectral imaging solutions, with products and software for both OEMs and end users.

Imaging sensors include hyperspectral and Raman, based on Headwall’s own holographic diffraction gratings that deliver high spectral and spatial resolution, high signal-to-noise, and low stray light.

For cultural heritage Headwall provides everything needed: spectral imaging sensors for both VNIR and SWIR spectral ranges as well as scanning kits and pan-and-tilt systems specifically designed for this type of work.

Headwall Photonics, Inc.580 Main Street • Bolton, MA USA 01740+978-353-4100information@headwallphotonics.comwww.headwallphotonics.com

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Headwall BVBAPegasus Park • De Kleetlaan 5 / 9 1831 Diegem • [email protected]

Headwall’s headquarters in Bolton, Massachusetts

Scanning kits for inspection and scanning of historical works.

Pigment Spectra in SWIRDefined as ‘chemical imaging,’ hyperspectral SWIR from 900-2500nm allows cultural care professionals to understand the constituents used for pigments and to detect paint changes over time due to oxidization, reduction, and other chemistries. Perhaps more topically significant is the ability of hyperspectral imaging in the SWIR region to successfully identify fakes and forgeries based on very detailed spectral features the technology is able to detect.