Terahertz spectroscopy: the new tool to help detect art fraud

http://theconversation.com/terahertz-spectroscopy-the-new-tool-to-help-detect-art-fraud-77173

When we look at a painting, how do we know it’s a genuine piece of art?

Everything we see with the unaided eye in a painting – from the Australian outback images of Albert Namatjira or Russell Drysdale, to the vibrant works of Pro Hart – is thanks to the mix of colours that form part of the visible spectrum.

But if we look at the painting in a different way, at a part of the spectrum that is invisible to our eyes, then we can see something very different.

As our recently published research shows, it could even help us detect art fraud.

A matter of frequency

The electromagnetic spectrum ranges from very high-frequency gamma rays down to the extremely low-frequency radiation of just a few hertz. Hertz is the unit of measurement for frequency.

The frequency of colours in the visible spectrum range from blue, at about 800 terahertz (THz), through to red at about 400THz (1 THz = 10¹² or 1,000,000,000,000 hertz).

If we drop to frequencies below the visible spectrum we find the near-infrared at about 300THz and then the mid-infrared at about 30THz.

Then comes the far-infrared and at last we meet the frequencies around 1THz.

The terahertz (10¹²) region of the electromagnetic spectrum. The Conversation, CC BY-ND

Continuing even further brings us to microwaves and radio waves where frequencies range from the gigahertz down to kilohertz. Thus the terahertz part of the electromagnetic spectrum lies between the radio and the visible parts – in other words, between electronics and photonics.

Things can look very different when viewed with “eyes” that can see in the terahertz range. Some things that are transparent to visible light, such as water, are opaque to terahertz light.

Conversely, some things that visible light won’t penetrate, such as black plastic, readily transmit terahertz radiation.

Intriguingly, two objects that have the same colour when viewed by the unassisted eye may transmit terahertz radiation differently. So their terahertz signal can be used to tell them apart.

Pigments and colour

This points to the potential use of terahertz radiation in differentiating paints and pigments. Terahertz spectroscopy can distinguish different pigments with similar colours.

We recently used terahertz spectroscopy to distinguish between three related pigments. All come from a family of chemical compounds called quinacridones. These are used widely in producing stable, reproducible pigments that range in colour from red to violet.

Measurements at the University of Wollongong provided the experimental data in the range of 1THz to 10THz. Numerical modelling at Syracuse University (New York) reproduced the experimental data, and gave physical insight into the origin of the features observed.

The combined experimental and theoretical work, published last month in the Journal of Physical Chemistry, unequivocally demonstrates that terahertz spectroscopy is able to distinguish three different quinacridones.

This brings us to the subject of art authentication – or more importantly, detecting cases of art fraud.

Art fraud

Museums, galleries and collectors are typically very protective of their art collections, but terahertz spectroscopy is well suited to examining their works.

While terahertz spectrometers are often located in laboratories, there are also portable models.

Unlike an analysis that requires removing and consuming some material (by reacting it with chemicals, or burning it), there is no contact made with the material, and thus no harm done to the artwork.

The terahertz radiation simply shines on the painting, and the transmitted radiation is measured. The low energy and low density of terahertz radiation means that the painting is not damaged in any way.

This all makes it suitable for examining art in a way that does not damage it and can be performed where it is located – in a gallery, or home, or almost anywhere.

From theory to practice

So how can terahertz spectroscopy assist in detecting art fraud in practice?

Here’s an example. Let’s say terahertz spectroscopy picks up a quinacridone pigment in a painting. Quinacridone is an artificial material that was first synthesised in 1935, so the painting must date from 1935 or later.

Any claim that the painting is a work by Leonardo da Vinci (who died in 1519), Vincent van Gogh (died 1890) or Claude Monet (died 1926) could therefore be dismissed. Any claim the the work was by an artist who worked after 1935 could not be so easily disproved on this basis.

Of course, other physical methods than terahertz spectroscopy may be applied to analyse paintings. One direct way to analyse art work is by sophisticated, quantitative measurements of the visible spectrum.

Artworks may also be interrogated by other species of light that lie above the blue end visible spectrum. Here the ultraviolet (uv) photons are higher in energy than visible photons. That means they can put energy into a material that is re-radiated as visible photons.

This is the phenomenon of fluorescence, and uv-fluorescence is an established tool in art conservation.

Moving further above the ultraviolet, X-rays may be used to examine works of art. For example, X-ray fluorescence at the Australian Synchrotron has been used to find hidden layers in works by Degas and Streeton.

A genuine fake?

There are many aspects to authenticating an artwork, the physical examination being but one of them.

Nonetheless, technical analysis of the materials used – the paints, the canvas, the frames – plays a fundamental role, and that is where terahertz spectroscopy contributes.

But other approaches also play a role. For example, documentation such as records of sales may provide key evidence, as may the more subtle appraisal of style by art historians.

The perceptions of people who assess and buy art is itself an important factor. The word of the artist might be thought to be definitive, but even this has been overruled by expert opinion, as in the case of Lucian Freud.

Finally, the legal dimension is critical, as has been reported recently in the quashing of the art fraud convictions of Peter Gant and Mohamed Siddique. These related to the paintings Blue Lavender Bay, Orange Lavender Bay, and Through the Window. At issue was whether the paintings were the work of Brett Whiteley.

Other uses

Of course, art fraud is just one application of terahertz spectroscopy. There are many more.

Able to penetrate paper and cardboard, terahertz radiation can be used to look inside envelopes for contraband, or inside packaged food for contamination.

Terahertz methods have been used to assess burns and to monitor the hydration of plants.

As better terahertz sources, detectors and components are developed, the range of applications will further expand.

TeTechS blog-The High-Fashion Side of Terahertz

http://tetechs.com

It happens to the best of us.
We see that shiny new purse or stylish pair of running shoes and we think “I have GOT to have that!”

Your eyes go to the label – its your favourite designer! You slowly turn the price-tag over…*cringe*

BUT its worth it.
After all, you’re paying for a high-quality designer brand that you’ve pretty much decided is the next best thing since chocolate cake or coffee on a Monday.

Right??

In reality however, 10% of all fashion related products sold are counterfeits and approximately 1 in 5 shoppers who are in search of a bargain are falling victim to fraud.

According to a recent study by the European Union, counterfeit designer goods cost the industry approximately $28.5 BILLION USD each year which then results in a loss of jobs upwards of 500 000 annually.

Designers have been combatting counterfeits by stepping up their design-game to deliver products of even higher quality, but what is the solution for protecting consumers from this type of fraud?

According to the United Kingdom’s National Physics Laboratory, terahertz is the answer to this billion-dollar problem!

Terahertz technology – specifically terahertz time-domain spectroscopy – is capable of identifying natural and artificial textiles. This means, that this technology could be used to help detect and prevent fraudulent goods from entering or leaving a country at customs clearance.

How?
Each fabric has a distinct transmission pattern, which affects both the amplitude and the phase of the terahertz radiation. Essentially, the material of your favourite designer scarf would possess a specific “signature” to differentiate it from imposters – and terahertz technology would be able to detect this.

SpectroscopyNOW- Geometric resonator: Tuning the infrared

• Author: David Bradley
• http://www.spectroscopynow.com/ir/details/ezine/15216bf9014/Geometric-resonator-Tuning-the-infrared.html

Meta resonator

Meta material resonators that allow emission in the infrared to be tuned through changes in the geometry of the resonator have been demonstrated by scientists in France.

Researchers at MINAO, a joint lab between The French Aerospace Lab in Palaiseau and the Laboratoire de Photonique et de Nanostructures in Marcoussis, have used a sub-wavelength scale metal-insulator-metal, or MIM, resonator to spatially and spectrally control emitted light up to the diffraction limit. This, the team says, allows them to create arrays of resonators that can be used to form an image in the infrared region of the spectrum analogously to the way in which the pixels of a television screen form a visible light image. The new technology has potential in biochemical sensing, optical storage, anti-counterfeit devices and in infrared imaging.

“MIM metasurfaces are great candidates for infrared emitters thanks to their ability to completely control thermal emission, which is groundbreaking compared to the usual thermal sources, such as a blackbody,” explains Patrick Bouchon, of The French Aerospace Lab, also known as ONERA. “Moreover, this study shows the possibility to create infrared images with the equivalent of visible colours.”

Funnel

Writing in the journal Applied Physics Letters, Bouchon and his colleagues explain how they had previously demonstrated the ability to manipulate light through tailoring its absorption or converting its polarization, and investigated the “funnelling effect,” in which incoming light energy is coupled to a nanoantenna. Now, they have made a MIM nanoantenna consisting of a rectangular metallic patch on top of an insulating material, on top of an additional metal layer. The majority of metasurfaces, the aggregate of many nanoantennae on a substrate, contain a periodic repetition of a given pattern, and exhibit no spatial modulation. For their MIMs, Bouchon and his colleagues deposited 50 nanometre-thick rectangular patches of gold on top of a 220 nanometre silicon oxide layer, on top of an opaque 200 nanometre gold layer. The idea of modifying the emissivity with nanostructures is relatively recent, with this same team showing that it is possible to combine several antennae in the same subwavelength period as recently as 2012.

“We had to theoretically predict the response of 100 million antennae, and to subsequently fabricate it,” explains team member Mathilde Makhsiyan from The French Aerospace Lab. To do this, the researchers developed their own software, as well as specific software to generate the electron-beam files for the fabrication of spatially modulated emissivity metasurfaces.

IR pixels

They explain that once constructed, each nanoantenna acts as an independent deep subwavelength emitter for a given polarization and wavelength of infrared. This allows them to control emission properties such as wavelength, polarization, and intensity through the device's specific geometry and orientation. When juxtaposed on a large scale, these MIMs cause the emissivity to be defined at the sub-wavelength scale, allowing the researchers to encode several images on the same metasurface.

Importantly, the emission information is encoded within a unit cell that is smaller than the infrared wavelength. As such, two neighbouring cells can have different encoded information and encode the information spatially. This is what allows a static infrared image to be generated on a display. The next step will be to develop a way to contr

Better detection of counterfeit banknotes through new terahertz wave light source technology

http://www.tohoku.ac.jp/en/news/research/news20151017.html

Researchers at Tohoku University's School of Engineering have developed a new terahertz wave light source - featuring both light and radio-wave characteristics - that can lead to faster and more efficient detection of counterfeit and damaged banknotes.

Terahertz waves are radio waves with frequencies tens to thousands of times higher than those used by cell phones. They were previously known as "unattainable wavebands" because they were extremely difficult to generate and detect. (Fig 1)

(Figure 1)

Ultrathin resin tape is attached to the banknotes of many currencies for the purpose of detecting forgeries and damage. The tape is approximately half to a quarter width of a human hair, and the most common method currently available for detecting this tape is with stylus profiling. Because physical contact is required with stylus profiling, the speed with which the tape can be detected is limited. And the physical contact also comes with the risk of damage.

To get around those limitations, the research team, led by Professor Yutaka Oyama, created a database of terahertz permeability characteristics for banknotes and resin tapes, and then successfully attained visibility of the extremely thin tape without physical contact. (Fig 2)

(Figure 2)

Unlike irradiation methods using X-rays and gamma rays which are conventionally used for transmission inspections, this new terahertz wave method is also believed to be safe even when exposed to the human body.

The research team expects this new method to improve inspection speeds and prevent paper damage, thus drastically improving the efficiency of banknote inspections carried out every day throughout the world.

The research was a joint project between Tohoku University and Laurel Bank Machines Co. Ltd. Part of the results were announced at the CLEO (Conference on Lasers and Electro-Optics) Pacific Rim Conference held in Busan, South Korea, in August 2015.

Contact:

Yutaka Oyama
Department of Materials Science
Tohoku University, Graduate School of Engineering
Tel: +81-22-795-7327
Email: oyamamaterial.tohoku.ac.jp

Cooperation on anti-counterfeiting technology

http://www.protemics.com/index.php/news/56-cooperation-on-anti-counterfeiting-technology

Aachen/Pleasanton - Rolith, Inc. has developed a new type of security labels which are invisible to the human eye and standard equipment but can be read-out by Terahertz microprobe sensors from Protemics. Both companies are now cooperating on the development of custom-specific end-user solutions.

Figure: (Background) Photograph of the glass wafer carrying the hidden transparent label. (Bottom left) Image of the label showing the Rolith logo as measured using the Terahertz microprobe from Protemics (shown at the bottom right). The label image is formed by mapping electrical conductivity over the area revealing resistivity differences inside and outside the Logo letters.

Background

Counterfeiting presents a global economical and security problem. Fake pharmaceuticals, foods and beverages pose direct treat to the public health. Fake ID cards and passports are serious problems for governments. The drain on the global economy due to counterfeited goods and piracy will exceed $US1 trillion dollars by 2015. There is an urgent need for truly covert coding of individual items, to allow for reliable and robust authentication and tracing. This is the area where new technologies should be utilized more to assist brand owners and protect consumers.

State of the art anti-counterfeiting solutions include RFID chips, tags and labels, holograms, tamper-evident closures, special inks and nanomaterials. At present counterfeiters are able to copy most anti‐counterfeiting technologies within 18 months. A new technology which are covert and require complicated manufacturing capabilities on a nanoscale would make counterfeiting much more difficult, time consuming and expensive.

It is desirable to find ways to an secure anti-counterfeiting feature so it does not impact the overall branding and design of the product or packaging. Ideally such a solution would be a security technique that does not rely upon any feature or taggant that has to be added to an item or product. And, preferably, a non-contact technique could be used.

Hidden label on transparent material

Rolith has developed a new anti-counterfeiting technology, which is not based on optical interrogation (visual or laser-based) or tags. This new principle is based on a minute structural difference in metallic nanostructures fabricated on material surface, which are affecting electrical characteristics.

The ID/labels are invisible even on transparent materials like glass or polymer films rendering this technology very attractive for the direct integration into many products as for example smartphones, displays or watches. With this approach the first problem a potential counterfeiter has to face is to discern whether there is a security label or not because the labels cannot be visually seen or otherwise revealed using broadly available equipment. Furthermore, the technological hurdles to circumvent the security protections of this new label technology are hence extremely high. It requires special nanotechnology tools (RML® lithography) as developed by Rolith.

The contrast mechanism which is utilized for the efficient read-out of the security labels in Rolith technology is based on small sheet resistance variations. For anti-counterfeiting purposes Rolith’s trademarked NanoWeb® transparent metal mesh conductor is designed to integrate a specific Logo, code or any other useful identification and protection information into otherwise uniform conductive mesh.

The reason why it is so difficult to see the labels even with commonly used inspection tools is given by the extremely small size of structural variations on the nanometer scale which are spread over a large (mm-scale) area. Due to sub-micron features of NanoWeb structures such ID is absolutely invisible for the eye and even in inspection using regular optical microscope. To capture a full area of a label in order to extract its information using nano-analytic equipment like raster scanning electron microscopes would be extremely time consuming and difficult.

Unlocking of label information using the “Terahertz key”

Protemics has developed a new measurement technology based on advanced microprobes operating in the Terahertz frequency range which is offering world-leading performance for sheet resistance imaging in regard of measurement speed and spatial resolution. Equipped with these key features the technology qualifies as the currently most efficient solution for the read-out of the invisible labels.

Rolith and Protemics are now cooperating on the development of custom-specific end-user solutions. For example, one of the most attractive anti-counterfeiting solutions for mobile electronics would be to utilize an invisible Logo integrated into a touch screen display sensor.

REFERENCES:

Press release: http://www.prweb.com/releases/2014/09/prweb12168666.htm

Rolith, Inc.: http://www.rolith.com 

MEDIA CONTACTS

Protemics GmbH
Dr. Michael Nagel
CEO
info@protemics.com
+49 241 8867 140

Rolith, Inc.
Boris Kobrin, Ph.D.
Founder and CEO
info@rolith.com
+1 925 548 6064