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Tham khảo tài liệu 'optical fibre, new developments part 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Optical fibres in aeronautics robotics and civil engineering 29 Applied force Scattering Fig. 13. Sketch of the single sensing element taxel . Recently we proposed a solution based on the scattering of the light illuminating the surface of urethane foam De Maria et al. 2008 . The configuration makes use of a couple of emitter receiver fibres placed at the edge of a micromachined well covered by the foam. The distance between the two fibres can be chosen in order to ensure a desired sensitivity of the sensing element. As a demonstration of the effectiveness of the proposed configuration we present the results of two sensors in which the relative distance between the two fibres was properly selected in order to fit the range of pressures to be detected. Top and lateral schematic views of a single taxel are shown in Fig. 13. The sensor works as follows the light emitted by the illuminating fibre is scattered by the internal surface of the urethane foam and a fraction of its power is collected by the receiving fibre depending on the applied pressure. In particular when one applies a pressure on the external surface of the urethane foam the distance between the tip of the collecting fibre and the internal surface of the foam is reduced and this will result in an increased fraction of power collected by the receiving fibre. The use of a scattering surface such as that of the urethane foam employed for the realization of the prototypes is justified by the fact the multiple scattering permits to smooth average-out local variation of light intensity within the cavity and thus reduce the sensitivity of the collected power on micro-displacements of the illuminating and or receiving fibre. As the power collected by the receiving fibre is a function of the pressure applied on the foam surface it can be used as a measure of the applied force. Obviously the collected light is also a function of the relative distance between the illuminating and the receiving fibres. In our .
