P2I-2 Characteristics of SAW Grating Reflectors with Arbitrary Angles of Incidence in Ultrasonic Touch Sensors

Rayleigh-wave (SAW) touch panels are widely used in a number of applications such as information kiosks, interactive museum exhibits, and amusement arcade games. Such products involve 90deg scattering of Rayleigh waves by grating reflector arrays for which each reflector grating element is at an angle of 45deg with respect to the incident wave. Development of innovative ultrasonic touch sensors motivates generalization to arbitrary angles of incidence. Results are expressed in terms of monopole, dipole, and quadrupole scattering amplitudes from point-like perturbations. Via superposition, such results generalize to arbitrary geometry including that of grating arrays. The angular dependence of the reflection amplitude depends strongly on the mechanical properties of the reflector materials. This conclusion is supported by experiment, 3D ultrasonic simulation and analytic expressions derived from theory. Efficient as well as problematic combinations of reflector angles and materials may be determined from presented quantitative results