ONERA has developed the EMIR technology, which makes it possible to obtain instant images revealing the intensity of electromagnetic waves. These waves, which are invisible to our eyes, transmit data from one point to another at the speed of light, for example for mobile phones, radio or television antennas, radars, etc. The EMIR images make it possible to know the amount of electromagnetic energy carried by waves and their direction of emission.
Viewing and quantification of radiation near a mobile phone (distances are in millimeters and the electric field intensities are not representative of the normal operation of a telephone)
The process is simple in its principle and implementation. Photothermal film exposed to radiation becomes heated. An infrared camera picks up the variations in temperature of the film and computer processing allows the radiation causing the phenomenon to be traced, as well as mapping to be done. Displacement of the film in space will allow CT scans to be performed and the scene to be characterized in 3D from the electromagnetic point of view.
View of the electromagnetic field using infrared thermography
The EMIR method (which stands for ElectroMagnetic InfraRed) was originally developed to make sure that there are no radiation leaks where radiation must remain confined, for example, in the cockpit of a fighter plane, or to ensure that it does not penetrate where it is undesirable, for example, the hold of an aircraft or a kerosene tank.
Recent work on EMIR has consisted in improving the measurement resolution, both in time and space and, of course, the radiation values. This is a technology that has matured slowly, at the rate of successive scientific breakthroughs, and whose field of application extends beyond the scope of aeronautics: characterization of innovating antennas, diagnosis of existing equipment, prevention against electromagnetic aggressions, etc.
The success of the method relies on the convergence of several fields mastered by ONERA: electromagnetism of course, but also materials science and, of course, infrared optics. The core of the measurement is the film, which is a multilayer metal and polymer material capable of absorbing a portion of the wave to convert it into heat. The very sensitive thermal camera with infrared optics makes it possible to measure temperature increases with high accuracy and very good definition. Finally, perfect knowledge of the physical process of energy conversion by the film provides an excellent quantification of the radiation levels and an edifying view. The image is obtained almost instantly.
Of course, there are other ways to have access to these images called radiation patterns. radio by wave specialists. For example, by moving small antennas, which receive the waves and transform them into light signals. However, the images obtained by this method take a long time to obtain and are generally of poor quality.
EMIR illustrates ONERA’s ability to develop innovative solutions that address technological issues, such as electromagnetic radiation. The field of aerospace research is particularly fertile for these leading edge developments that require time - and patience - and the ability to combine scientific fields at the highest level.
