Headwall Photonics Blog

Spectral Imaging Solves Mystery of Stolen Books by Suicidal Librarian

Posted by Christopher Van Veen on Tue, Jul 21, 2015

Multi-Million Dollar Theft Of National Heritage, Followed By International Intrigue, Suicide, And An Explosion Injuring Dozens...

Not Hollywood But … Headwall’s Hyperspectral Imaging Sensors Provide Forensic Analysis Help Solve the Mystery & Repatriate a Stolen Rare Book!

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David Walter Corson is curator of the History of Science collection at the Cornell University Library. Through years of study and procurement, the Cornell collection...35,000 volumes in all...has some esteemed and cherished works written by Sir Isaac Newton, and others, and represents the world’s most extensive university collection on the evolution of scientific thought and research over the few centuries.

One of the books in this vast collection at Cornell was simply known as the ‘Oculus,' written by Christopher Scheiner in 1619. Scheiner was a brilliant geometer, physicist and astronomer, who developed theories of optics which later formed the basis for the development of lenses. Schiener’s book showed that the retina is the seat of vision, and it was a recognized treasure that Cornell was very pleased to have acquired in 1999 from Jonathan Hill, the preeminent New York-based bookseller of rare books and manuscripts. However, it was five years later that the Scheiner Book was reported to have been stolen from the National Library of Sweden, along with around 55 other notable works worth millions.

Unbeknownst to Jonathan Hill or to David Corson, the Library of Sweden theft was a daring one carried out by an employee of the National Library by the name of Anders Burius.  Burius sold the works he stole between the years 1995 and 2004 to German auction house Ketterer Kunst. Burius was subsequently arrested and confessed in 2004. However, while free on bail in Sweden, Mr. Burius attempted suicide by slitting his wrists and then cutting the gas line in his apartment. The explosion finished the deed, flattening the building and injuring scores of neighbors.

The story is widely known throughout Sweden and is recounted in The History Blog, http://www.thehistoryblog.com/archives/17824.

And, yes, it is also the subject of television mini-series.

Where do Headwall’s hyperspectral imaging sensors fit in?

Initially, Headwall’s spectral imaging analysis was focused on the examination of spectral enhancement techniques on Cornell’s extensive collection of Lincoln documents such as the Gettysburg Address, the Emancipation Proclamation, the 13th Amendment to the US Constitution, Lincoln Executive Mansion Letters, and others.

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Studying historically significant treasures like Cornell’s Lincoln Collection must be done with great care. The Hippocratic oath for physicians (and, by extension, to curators and conservators) somewhat loosely states, 'First Do No Harm.' Indeed, any sort of spectral imaging must not involve harsh lighting, heat or be otherwise 'invasive.' Assured that it was a safe form of scientific analysis, Cornell teamed with Headwall to carefully image some artifacts, art work, and rare books that can be truly described as priceless treasures of cultural heritage.

Now back to Scheiner’s Oculus book … As Sweden worked with Interpol to track down these stolen treasures, David Corson of Cornell became aware of the book theft and began working with the FBI to determine if the Cornell version of Scheiner’s Oculus was in fact stolen from the National Library of Sweden.

To make a forensic determination, some scientific analysis was necessary which led to Headwall's expertise in hyperspectral imaging and the use of Headwall’s Hyperspec VNIR and SWIR sensors to analyze the book. Headwall’s non-invasive hyperspectral imaging technique yielded a highly resolved spectral and spatial datacube that allowed application engineers to analyze component and constituent material differences in the book such as color change, deterioration, and alterations, as well as the ability to identify disguised text and “under drawings” not visible to the naked eye.

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"Your analytic techniques were exactly what we needed," explained Corson. "The totality of the circumstantial evidence that emerged from Headwall's study of The Scheiner Book is, indeed, what ultimately convinced us to 'repatriate' the volume." Through the use of data collected by Headwall’s VNIR and SWIR hyperspectral sensors, Janette Wilson of Headwall’s technical sales team undertook a rigorous PCA approach (Principal Component Analysis) that was able to yield definitive proof that faint, non-visible markings on the book were correlated to the National Library of Sweden’s catalogue system.

"We had independently asked the National Library of Sweden whether there were any unique bookplates or similar identification devices that the library might have used in the past that we should look for," recalled Corson. But there was no apparent evidence of previous bookplates in Cornell's acquired copy, aside from the one Cornell added themselves. But spectral imaging revealed remnants in the corner sections of the front pastedown (a reasonable location for a bookplate) of a previous label. Corson thus had his first bit of evidence: "This finding showed measured dimensions almost identical to those of a bookplate the National Library had told us was once used in their books!"

The challenge before Corson was compounded by the fact that the National Library could not accurately corroborate any of these findings after it was determined that all of its records had been destroyed. "The effect was as if the Library had never even had the titles in its holdings," recalled Corson. In any case, The National Library did send Corson two possible shelf marks for the Scheiner volume, based on their best recollection.  Hyperspectral imaging thus revealed that the sequence of 'marks’ were the same as those provided by the National Library.

In the end, hyperspectral imaging did indeed prove instrumental in uncovering findings previously unknown. “What is significant is that Headwall’s technique and approach can reveal definitive evidence in situations like these,” noted Corson. The technology readily adapts itself for use with paintings, maps, manuscripts, even non-flat artifacts.

Tags: forensics, Cornell University, artifacts, antiquities, Artwork

Hyperspectral Takes Old Maps Into New Territory

Posted by Christopher Van Veen on Thu, Mar 26, 2015

Late in 2014, Headwall sponsored a successful event at London’s Natural History Museum. The purpose of the gathering was to introduce curators and preservationists to the advantages and capabilities of hyperspectral imaging. Professionals in this field understand that the treasures under their control...paintings, documents, and artifacts...need to be preserved using the most advanced techniques available. Preservation largely means having an excellent understanding of the chemical composition of the underlying materials used to create the treasures. And what the eye cannot see, hyperspectral imaging can.

The Bodleian Library (Oxford, UK) has been an acknowledged pioneer with respect to the use of spectral imaging technology. While newer than other imaging techniques, hyperspectral is relatively affordable and provides a wealth of image data that experts can pore through. With this data, the overall body of knowledge is exponentially increased on treasures having enormous historical prestige and significance. The identification of specific materials, inks, pigments, and substrates can help determine when (and perhaps even where) a document or artifact was created. Everything a hyperspectral sensor sees can be categorized with respect to its chemical signature, or ‘fingerprint.’ The color ‘Yellow’ resonates a certain way to the eye, but spectral imaging can discern the chemical composition of a particular ‘Yellow’ and match it to known spectral libraries. The results are clearly beneficial to the Bodleian, which is why the Library has taken great measure to partner with Headwall Photonics to implement systems geared specifically to what they'd like to see and learn.

BodleianTwo prized maps at The Bodleian...the 17th-Century Selden Map of China, and the medieval Gough Map of Britain...recently underwent precise analysis using Headwall’s hyperspectral sensor. The Gough Map in particular represents a mystery to Bodleian experts: when was it created, by whom, and why. By illuminating the map with non-invasive, non-destructive ‘cold’ lighting, the near infrared and shortwave infrared sensors collect a digital map of inks and materials. It even highlights features that were deliberately masked and others that simply faded or flaked away over time.

The Bodleian’s David Howell, an early advocate of spectral/chemical imaging and who helped spearhead Headwall’s Natural History Museum event, has been extremely pleased at the results seen thus far. In an interview with the BBC, Howell said that he was “blown away by the data that’s already coming out.” He noted that the technology first and foremost does not put the treasures at risk. The imaging illumination is non-destructive and the treasures themselves do not need to be removed from their climate-controlled premises.

Howell concluded with a plug for the promise of hyperspectral imaging technology: “Our biggest problem now is there’s just so much data to sort through to fully explore what we’ve uncovered!”

To read the BBC article on this exciting venture, click here.

Tags: hyperspectral imaging, artifacts, antiquities, Artwork, artwork preservation

Spectral Imaging Within the Collection-Care Industry

Posted by Christopher Van Veen on Mon, Dec 29, 2014

Hyperspectral imaging is finding a home in so many interesting places, among them the fascinating field of cultural preservation. Conservation care professionals across academia and the museum world are tasked with learning as much as they can about the treasures under their care.  These treasures range from artifacts such as vases, to paintings, documents, and maps.

spectral imaging in collection careIn all cases the objective is to non-invasively increase the body of knowledge. Are there features that are invisible by any other means of analysis? Are there chemical pigmentation signatures on paintings that spectroscopy can ‘see?’ Are there any hidden writings that can be uncovered? Hyperspectral imaging can help conservation-care experts determine origins, dates, materials, and other characteristics useful to their work. Indeed, spectroscopy can also help improve the preservation of these treasures by uncovering evidence of similar efforts done years or decades previously. Hyperspectral imagers offer scholars, curators and conservators unique advantages:

  • Enhance faded or hidden features-text/signatures
  • Detect restorations and repairs via chemical signa­ture
  • Monitor and track changes of the object, or repairs and restorations
  • Identify local material components for proper re­pair
  • Assess original coloring and pigmentation

On December 9 at The Natural History Museum in London, Headwall organized and sponsored a workshop and seminar on hyperspectral imaging in the collection-care industry. Noted experts from worldwide universities, museums, and libraries came to hear about how hyperspectral imaging can help unlock hidden secrets while advancing the overall body of knowledge of the treasures under their care.

Mr. David Howell of The Bodleian Libraries spoke about building a suite of non-destructive imaging techniques. Mr. Chris Collins of The Natural History Museum spoke about assessing fading in natural history specimens. And Christina Duffy of The British Library discussed their use of multispectral imaging on the treasures under their care (including the Magna Carta!).

Setting the stage for the day was Mr. Kwok Wong, who serves as Headwall’s Senior Systems Applications Engineer. Kwok has done considerable work with The Museum of Fine Arts (MFA) in Boston, imaging a Mayan Vase and other artifacts. Kwok explained the basics behind multispectral and hyperspectral imaging and the kinds of valuable information that can be collected in a non-destructive, non-invasive manner.

Dr. Greg Bearman, a noted expert in the field of spectral/chemical imaging within the collection-care industry, discussed his impressive work to date and how the techniques can best be applied. Dr. Bearman’s examples included paintings, documents, and artifacts...with each requiring a slightly different approach depending on the spectral ranges that need to be covered.

Guests were encouraged to bring samples of their treasures for Headwall to image during the day. A few of the attendees did so, and Headwall had its VNIR (Visible/Near-Infrared) Starter Kit operational in the room. Attendees could see first-hand how the science of spectroscopy can be used to further their preservation and analytical efforts.

Most often, the collection-care industry cares most about imaging in the VNIR (380-1000nm) and SWIR (950-2500; short-wave infra-red) ranges.  Imaging in the VNIR and SWIR has a number of impor­tant and interesting applications for Cultural Heritage because this type of imaging technology provides a more complete representation of the entire field of view. This is a critical distinction because true con­text is provided on what are typically heterogeneous objects; by comparison, point sensors can only sam­ple discrete locations. Imaging in the VNIR has been used since the mid 1990s for texts and paintings. For texts, the application is typically content; for example, reading palimpsests and faded or damaged texts and maps. For art, the application is typically color and pig­ment mapping. SWIR imaging offers the possibility of chemical imaging, allowing the conservator to monitor and track chemistry changes over time.

Since little or no preparation of the document or ar­tifact is necessary, this non-destructive spectral tech­nique is invaluable for a wide range of conservation research relating to changes in color, chemical and substrates. Within the field of view of the Hyperspec® sensor, hy­perspectral imaging provides quantitative spectral information for all wavelengths across the complete spectral range of the sensor.

The key to spectral data is calibration; well-calibrated datasets can be compared and analyzed over time and between mul­tiple users. There is an existing and significant body of spectral analysis, classification and mapping algo­rithms and software available to work with spectral data. Most of this software has been developed over the last 20 years for satellite remote sensing and is easily available.

The job of the hyperspectral sensor is to collect image data and then assemble this valuable information into a ‘datacube,’ which represents a data set that includes all of the spatial and spectral information within the field of view.

 

Tags: Natural History Museum, artifacts, antiquities, Artwork, chemical imaging, artwork preservation, Museum of Fine Arts