A surface plasmon resonance (SPR)-based optical touch sensor structure is proposed that provides high switch sensitivity and requires a weak activating force. Our proposed SPR-based optical touch sensor is arranged in a compact Kretschmann–Raether configuration in which the prism acting as our sensor head is coated with a metal nanofilm. Our optical-based noise rejection scheme relies on wavelength filtering, spatial filtering, and high reflectivity of the metal nanofilm, whereas our electrical-based noise reduction is obtained by means of an electrical signal filtering process. In our experimental proof of concept, a visible laser diode at a centered wavelength and a prism made from BK7 with a thick gold layer on the touching surface are used, showing a optical contrast ratio for the first touch. An estimated weak mechanical force of is also observed that sufficiently activates the desired electrical load. It is tested for operations without sensor malfunction under typical and very high illumination of , respectively. In this case, a measured average optical contrast of is obtained with a fluctuation, implying that the refractive index change in a small of the overall active area is enough for our SPR-based optical touch sensor to function properly. Increasing optical contrast in our SPR-based optical touch sensor can be accomplished by using a higher polarization-extinction ratio and a narrower-bandwidth optical beam. A controlled environment and gold-coated surface using the thin-film sputtering technique can help improve the reliability and the durability of our SPR-based optical touch sensor. Other key features include ease of implementation, prevention of a light beam becoming incident on the user, and the ability to accept both strong and weak activating forces.
© 2006 Optical Society of AmericaFull Article | PDF Article