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

Area of Science:

• Optoelectronics
• Nanotechnology
• Sensor Technology

Background:

• Traditional touch sensors face limitations in sensitivity and activation force requirements.
• Optical touch sensing offers potential for enhanced performance and novel applications.

Purpose of the Study:

• To propose and demonstrate a surface plasmon resonance (SPR)-based optical touch sensor.
• To achieve high switch sensitivity with a weak activating force.

Main Methods:

• Utilized a compact Kretschmann-Raether configuration with a metal-nanofilm-coated prism.
• Implemented optical noise rejection via wavelength/spatial filtering and high reflectivity.
• Employed electrical signal filtering for noise reduction.
• Experimental setup included a 655 nm laser diode and a gold-coated BK7 prism.

Main Results:

• Achieved a 7.85 dB optical contrast ratio for the initial touch.
• Demonstrated activation with a mechanical force <0.1 N.
• Successfully operated for 51 cycles without malfunction under varying illumination (342-3000 lx).
• Measured an average optical contrast of 0.80 dB with +/-0.47 dB fluctuation.
• Indicated that a 3.2% refractive index change in the active area is sufficient for functionality.

Conclusions:

• The proposed SPR-based optical touch sensor is effective and reliable.
• Further improvements in optical contrast can be achieved through polarization and beam bandwidth optimization.
• Controlled environments and sputtering techniques enhance sensor durability and reliability.