Invisibility
Figure 2: Repeated Reflection. 4 The technology functions in the same way as an anechoic chamber. The pyramidal shape maximizes the number of reflections radar waves experience. With each reflection, attenuation occurs, resulting in decreased signal strength. Thus, a reduced signal strength is received by the radar, which in turn reduces the RCS of an object.
Figure 3: Carbonyl Iron Powder – it contains a unique microstructure which allows it to effectively absorb microwave frequencies. 5 This relies on ‘electron energy -level transitions, relative vibration of atoms in optical waves, and changes in the atomic rotation energy level and atomic magnetic energy level. ’ 6 Radar waves have long wavelengths, so they have low energy (by E=hc/ λ). It can be deduced that Carbonyl Iron Powder has sm all
energy differences between energy levels, which means photons in radar waves are more likely to be absorbed by the powder coating. The radar waves lose energy, thus reducing its signal and the object’s RCS. The absorbed energy is later released in the form of heat energy.
One pioneering technique is optical camouflage, which seeks to cloak an object by covering it in a projection of a scene behind it. 7 Essentially, optical camouflage requires a setup that encompasses retro-reflective materials (Fig.4), 8 video cameras, computer, projector, and combiner. 9 The retro- reflective material ensures the observer always receives a bright reflection to ensure maximum image clarity. Meanwhile, a video camera mounted behind the screen capture the image, which is then processed by the computer to ensure the projected image is of an appropriate perspective to simulate
Figure 4: Retro-Reflecting Material. Retroreflective materials ensure minimum light scattering and that light is reflected to the observer at a wide range of angles. There are currently two techniques which are utilized: spherical beads and microprisms. Spherical beads are typically used in soft, flexible material whilst microprisms are typically used on hard surfaces . Microprisms, however, are much more effective than glass beads.
reality. 10 The modified image is projected via an iris diaphragm (Fig.5). Meanwhile, a combiner uses a special mirror, called a beam
4 James Carron, 01:05. 5 BASF The Chemical Company (n.d.) Carbonyl Iron Powder , p4-7, https://www.dispersions- pigments.basf.com/portal/load/fid827906/CIP_General_PO_e.pdf (Accessed: 14 July 2020).
6 Duan, Y.P., Li, G.F., Liu L.D., and Liu, S.H. (2010), ‘Electromagnetic properties of carbonyl iron and their microwave absorbing characterization as filler in silicone rubber’, Bulletin of Material Science, 33(5), p634. 7 Bhardawaj, A., Samyal, P., Yadav, P. and Ratra, L. (20 14), ‘A review of retro reflective technology for optical camouflage applications’, International Journal of Information & Computation Technology, 4(11), p1057-1058. 8 Schultz, R., (2014), PROVIZ 100%Retroreflective Jacket Review , available at: https://biketestreviews.com/proviz- 100-retroreflective-jacket/ (Accessed: 13 July 2020). 9 Bhardawaj, A. et al, p1058. 10 Ibid.
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