Contents I. Introduction
Research into interactions between biological material and the energy generated by personal communications devices is currently topical. This paper investigates the field perturbation effects due to thin wire spectacles of various common shapes with simple slab lenses with a CW source positioned in front of the head. A rigorous finite-difference time-domain (FDTD) model is used. In previous works [1] [2] [3] it has been demonstrated that metallic spectacles can alter the specific absorption rate in the head and in particularly in the eyes. In recent years some work has been written up regarding mobile phones positioned near the ear [4]–[7]. The head has also been irradiated from in front of the eye using realistic mobile phone models [6]–[8]. This is topical as such hand held devices held to the front of and away from the head may soon become popular. Dimbylow and Hirata have illuminated the head with a plane wave from the front [9], [10] and have previously found resonance in the eyes within typical cellular spectra. Bernardi [11] considered the eyes to be particularly sensitive organs due to their proximity to the surface of the head and the relatively low levels of blood flow when compared to other regions of the body. Dimbylow [6] also stresses the vulnerability of the eyes as they have a tendency to accumulate damage and cellular debris. In the same area Cooper [12], modeled a geometric head, and Bernardi [13] investigated an anatomical head, irradiated by simple dipoles positioned near metallic walls. Both found that metallic walls could increase the power absorbed in the head. Similarly Cooper [14] considered metal implantations inside the head and found that they increased the specific absorption rate (SAR) in the surrounding region. These papers show that metal objects close to biological matter may increase SAR in that matter. Spectacles have received limited attention in the literature, however, Bernardi [11] did model a glass lens in two dimensions. Troulis [15] used the FDTD method to briefly examine thin metallic spectacles on a heterogeneous phantom with a resolution of 5 mm. The excitation used was a monopole on a metallic box positioned at the side of the head. The paper showed that metallic spectacles can re-distribute the energy, produced by the cell phone's antenna, causing the efficiency to drop and the peak SAR to increase. Griffin [1] performed measurements with a phantom and metallic spectacles and showed that spectacles can increase or decrease the level of radiation near the eyes by up to 20 dB due to shielding, enhancement and depolarization effects. Anderson also performed measurements with a phantom wearing metallic spectacles. With phones operating at 835 MHz held by the ear, the SAR in the eye closest to the phone was found to increase by up to 29%.
