Application of ray-path geometry to the design of an optical cloaking structure

We show that the geometrical optics method can be applied to hide an object and obtain an efficient cloaking effect with reasonable values for the refractive index. Although our structure is affected by the vincula of being fully functional only for e.m. fields impinging parallel to the main structure axis, it still appears to be useful to mask some obstacles to a coherent radiation coming from a given direction, other than being a good example to show how can invisibility be designed and easily obtained by the proper use of modern numerical resources; besides we would remark that perfect invisibility is impossible due to the uniqueness of the inverse-scattering problem for waves , and it has been showed that it is unachievable except in a finite set of discrete directions where the object appears to be squashed to infinite thickness, or for items small compared with the wavelengths into play; so the unidirectionality mentioned above does not seem a great limitation. On the contrary if materials with low dispersion are used, cloaking should have a rather large frequency band .