Why terahertz imaging?
Today, the need for high-performance tools in numerous fields of application provides an ideal opportunity for terahertz imaging technologies, a wavelength being located in between microvawes and infrareds. With in the emerging market i2S has integrated an innovative sensor from the CEA-LETI into a camera, the TZCAM to address the markets of Non destructive testing and medical applications.
The TZCAM camera integrates a 320×240 Microbolometric Detector designed by the CEA-LETI. The technology embedded into this sensor is proprietary to the CEA-LETI and sets a new worldwide reference in terms of performances. i2S has developed a dedicate imaging electronic for this sensor with dedicated signal processing
The CEA/i2S solution is the best camera on the market in terms of sensitivity and acquisition performance. Compared to its competitors, it is a a piece of electronic equipment with a very low signal to noise ratio, the better to obtain the most precise dynamics.
Aujourd’hui, la nécessité d’outils de haute performance dans de nombreux champs applicatifs est une occasion idéale pour les technologies de l’imagerie Térahertz, une gamme spectrale située entre les ondes radio et le rayonnement infrarouge. Ainsi, i2S a intégré le capteur du CEA-Leti dans une caméra Térahertz TZ_CAM pour adresser le marché de l’imagerie du contrôle non destructif et du médical.
La caméra TZ_CAM intègre le capteur matriciel de 320×240 pixels bolométriques du CEA-Leti, une technologie innovante propriétaire du CEA-Leti reconnue comme étant à l’état de l’art international. i2S a développé son électronique avec une optimisation forte du rapport signal sur bruit afin d’obtenir les dynamiques les plus fines, permettant d’assurer une sensibilité et des performances d’acquisition au meilleur niveau par rapport à la concurrence.
The story of terahertz imaging at i2S
It all began in 2007, with a joke at the end of a dinner of business leaders and researchers, organized by CEA CESTA, a major actor in research & development and innovation in France. A researcher asked the guests a question, « If you had a dream, how would you put it into words? » Jean-Louis Blouin, CEO of i2S, was at the table, and he produced his famous notebook, open to a page where he had written a premonition, « If someone is capable of digitizing a book without opening it, I’m interested! ».
After laughter from the guests, Laurent Sarger, a researcher at CEA came to see us and offered a solution based on non-visible radiation, the famous terahertz. The topic was highly confidential at the time. Laurent briefed i2S’ R&D teams on the basic operating principles of this new technology that lies between microwaves and infrared, and has have the distinctive quality of being non-ionizing and not harmful to the human body. Out of his desire and the presentation of the potential of terahertz imaging, i2S created a collaborative research & development project with the laboratory at the University of Bordeaux, the CPMOH (Centre de Physique Moléculaire Optique and Hertzienne), and especially with Patrick Mounaix, director of research at LOMA (Laboratoire ondes et matière d’Aquitaine) and LaBRI. The team began to experiment with how to read the pages in the middle of a book without opening it. At this time, the technology was more than developing, it was developed to the point where everything depended on the sensor. Sensors capable of capturing terahertz images are produced by micro-bolometers, infrared sensors spread out over the spectrum.
Christophe Lacroix, who is head of optronics at i2S, explained to us the beginnings of this new human and experimental adventure that, « With two or three sheets of paper, we know how to count the pages of the book, penetrate the material . . . there were, moreover, disparities in the lead content of the ink used, etc. We also validated supra-resolution principles to increase the resolution since the distinctive feature of this wavelength is that it isn’t very definied. A whole bunch of incredible experiences have brought us to the end of this program. »
This program ended with very low TRL (Technology Readiness Levels), level 1 or 2, which at this stage does not allow it to respond to industrial problems such as digitizing books without opening them, or for example non-destructive tests on composite materials in the automobile and aeronautics sectors, with which we work regularly. The potential exists but at this stage i2S cannot, on its own, support the resulting investment risks of designing a « disruptive » innovation in this market.
Therefore, interest in this technology strongly exists at i2S, and CEA Tech, contacted us again in 2010 to ask us to help them with an engineering program that was part of a project using terahertz imaging. i2S’ mission is to implement a sensor developed by CEA LETI. As a result, i2S developed an engineering service for integrating this sensor, but in a particular context and under strong technological constraints. Indeed, the powerful lasers used to provide the sources of light are quantum cascade lasers, which cost, at the time, several hundreds of thousands of Euros. Another technological barrier that needs to be broken is the cooling of the lasers with liquid nitrogen devices, combined with the constraints of vacuum packaging since any kind of humidity is a barrier to the diffusion of the radiation. Christophe summarizes the end of the step as, by « manipulating a 3m cube that provides results as a technology demonstrator. »
At this stage, the means of implementation strongly limit the economic potential for useful application in the fields of surveillance and defense. There is a proof of concept leading to technological success, but no window for practical application.
In 2015, once again initiated by the CEA, a new opportunity in arose as part of a demonstration of the CEA Tech platform at Photon City (Cité de la Photonique), where terahertz was one of the main priorities. With a desire to get results from everyone involved, i2S launched into prototyping a terahertz camera which today not only exists but has successfully passed the electronic and optical validation steps; all that remains is integrating the the final sensor, whose in-factory vacuum packaging is the responsibility of CEA, and i2S can assure the final integration.
A platform for demonstrating terahertz imaging
During the first trimester of the year 2016, we will be providing a sample terahertz camera on the CEA Tech platform. Its goal is to be used to validate applications such as non destructive testing and testing water resource stress in vegetation in the agri-foodstuffs field, especially in viticulture, where a certain number of pilot projects will be initiated in 2017. At i2s, we haven’t forgotten the scope of the non-destructive tests inherent in the market for aeronautics with thorough inspection of all carbonaceous structures especially at one of the flagship stores in greater Aquitaine. All that remains is to nourish it more and more in order to gain even more from terahertz in 2017.
In 2015 Vincent, an electronic engineer at i2S, worked on the prototype of the terahertz camera. The experience allowed him to acquire new skills. His mission consisted of, « guiding the sensors according to their specifications, recovering an image and transferring it electronically via USB 3 to a conventional PC. » He appreciated working on this kind of collaborative R&D project that allowed his business to be more competitive and to acquire new professional skills. He added that the work done on the 70MP camera, the e-HIRIS, allowed him to advance more quickly: « We were inspired by the camera to use a USB 3 transmission card to which we added the CEA’s sensor, but we have to get rid of the noise or at lease minimize it as much as possible at the request of the CEA. »
Eight years after the first seeds of terahertz imaging were planted at at i2S, it’s finally time to harvest the rewards of the collective work of i2S’ collaborators and to put our partner, CEA Tech, in a business perspective vis-à-vis terahertz. We would like to thank them for the confidence they have had in us since 2007. Everything is possible and nothing is impossible at i2S and Bruno Hiberty, an optical engineer, concludes, « It’s a great process that illustrates the whole journey that you can go on between the most basic research, done in a laboratory, and the association with a business such as ours which, ultimately, provides the concrete means to create prototypes. » We’re looking for the « killer application » which will make terahertz indispensible.
Anticipating the changes linked to the use of the images that we are asked to capture or enrich is our mission. Our mission is to make our partners’ images even more intelligent, and make visual information even more accessible. It is these kinds of accomplishments and results, created through collective intelligence, that give birth to other ideas for use and to more results. That way our our vision will become reality: becoming the undisputed worldwide actor in imaging.
« Knowledge progresses by incorporating uncertainty and not by banishing it. » (Edgar Morin/The Method). We have shared so much progress on terahertz with CEA Tech since 2007.