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Applied Optics

Applied Optics

APPLICATIONS-CENTERED RESEARCH IN OPTICS

  • Vol. 45, Iss. 1 — Jan. 1, 2006
  • pp: 172–177

Surface plasmon resonance-based highly sensitive optical touch sensor with a hybrid noise rejection scheme

Sarun Sumriddetchkajorn and Kosom Chaitavon  »View Author Affiliations


Applied Optics, Vol. 45, Issue 1, pp. 172-177 (2006)
http://dx.doi.org/10.1364/AO.45.000172


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Abstract

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 655   nm centered wavelength and a prism made from BK7 with a 50  nm thick gold layer on the touching surface are used, showing a 7.85   dB optical contrast ratio for the first touch. An estimated weak mechanical force of < 0.1   N is also observed that sufficiently activates the desired electrical load. It is tested for 51 operations without sensor malfunction under typical and very high illumination of 342   and   3000   lx , respectively. In this case, a measured average optical contrast of 0.80   dB is obtained with a ± 0.47   dB fluctuation, implying that the refractive index change in a small 3.2 % 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 America

OCIS Codes
(120.3890) Instrumentation, measurement, and metrology : Medical optics instrumentation
(120.5700) Instrumentation, measurement, and metrology : Reflection
(240.6680) Optics at surfaces : Surface plasmons
(350.4600) Other areas of optics : Optical engineering

ToC Category:
Optics at Surfaces

Virtual Issues
Vol. 1, Iss. 2 Virtual Journal for Biomedical Optics

Citation
Sarun Sumriddetchkajorn and Kosom Chaitavon, "Surface plasmon resonance-based highly sensitive optical touch sensor with a hybrid noise rejection scheme," Appl. Opt. 45, 172-177 (2006)
http://www.opticsinfobase.org/ao/abstract.cfm?URI=ao-45-1-172

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