The propagation environment around airborne platforms may significantly degrade the performance of Electro-Optical
(EO) self-protection systems installed onboard. To ensure the sufficient level of protection, it is necessary to understand
that are the best sensors/effectors installation positions to guarantee that the aeromechanical turbulence, generated by the
engine exhausts and the rotor downwash, does not interfere with the imaging systems normal operations.
Since the radiation-propagation-in-turbulence is a hardly predictable process, it was proposed a high-level approach in
which, instead of studying the medium under turbulence, the turbulence effects on the imaging systems processing are
assessed by means of an equivalent statistical model representation, allowing a definition of a Turbulence index to classify
different level of turbulence intensities.
Hence, a general measurement methodology for the degradation of the imaging systems performance in turbulence
conditions was developed. The analysis of the performance degradation started by evaluating the effects of turbulences
with a given index on the image processing chain (i.e., thresholding, blob analysis). The processing in turbulence (PIT)
index is then derived by combining the effects of the given turbulence on the different image processing primitive
functions.
By evaluating the corresponding PIT index for a sufficient number of testing directions, it is possible to map the
performance degradation around the aircraft installation for a generic imaging system, and to identify the best installation
position for sensors/effectors composing the EO self-protection suite.
We studied the infrared properties randomly oriented silver nanowires films deposited onto different substrates. The investigated nanowires have cross-sectional diameters included between few to hundreds nanometers, while their lengths span from some microns to some tenths microns. Several films of silver nanowires were realized and the infrared emission of the obtained films was characterized in the long infrared range, i.e. 8-12 microns, by observing their temperature evolution under heating regime (maximum applied temperature ~90°) with a focal plane array (FPA) infrared camera. Under heating conditions, the apparent temperature of the silver nanowires films qualitatively follows the trend of the corresponding heating source temperature, while the absolute value keeps always somewhat lower. The experimental results show that the choice of metal filling factor may affect the resulting infrared emission and suggest that these coatings are suitable for infrared signature reduction applications.
The thermal analysis (TA) of the wave propagation in the long-wave (LWIR) infrared bands, performed on
metamaterials and nano-materials, is suitable for manufacturing a new type of infrared (IR) thermal vision camouflage,
useful for defence, military and security application and to evaluate the capability of new kind of materials to block night
vision (NV) thermal sighting capabilities as new countermeasure technology. This is mainly generated by the very
detailed signature characterization database, available in most automatic vision systems that are able to detect targets by
the IR spectral signature provided by the IR sensor. These metamaterials, called photonics band gap devices (PBG) or
more in general photonic crystal (PhC), works on IR photons providing absorbing, transmission and reflecting bands. All
the optical properties are function of the specific nano design tuned in the thermal wavelength.
The thermal analysis (TA) of the wave propagation in the mid-wave (MWIR) and long-wave (LWIR) infrared bands
performed by the direct solutions of the Maxwell electromagnetic (EM) problem with numerical methods is used to
propose the design of metamaterials suitable for a new type of thermal vision camouflage, that can be prepared using a
nano particle lattice in the IR bands. This lattice, called photonics band gap devices (PBG) or more in general photonic
crystal (PhC) works on IR photons providing absorbing, transmission and reflecting bands. All the optical properties are
function of the specific nano design tuned in the IR wavelength.
We utilize the Finite Element Model (FEM) and Finite Difference Time Domain (FDTD) numerical solution of the
Electromagnetic wave propagation in the Short Wave Infrared (SWIR) and Long Wave Infrared (LWIR) bands in order
to calculate the target radiance propagation and environment attenuation due to transmission, absorption and reflections
in atmosphere and obstacles. We leave to traditional minimum resolvable temperature (MRTD) the model of the camera
radiance collection (actual thermal sensitivity of the camera). The main advantage of the numerical propagation is that
there is the possibility to model exactly the specific target shape and the specific environment (depending of the
computational power) and calculate the residual temperature.
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