Development of a Finger-Shaped Tactile Sensor Using a Hemispherical Optical Waveguide

A finger-shaped tactile sensor that uses an optical waveguide to detect the contact location and the surface normal of the contacted object has been developed. The hemispherical optical waveguide is covered with an elastic cover, and LEDs are installed for the light source on the edge of the waveguide. A fiber optics plate (FOP), consisting of high-density bundled optical fibers and a position sensitive detector (PSD) is used for the image guide and the optical detector. The injected light from the LEDs into the waveguide maintains total internal reflection at the surface of the waveguide and is enclosed within it. When an object contacts the sensor, the cover depresses and touches the waveguide. At that moment, scattered light occurs at the contact location due to the change of the reflection condition. The scattered light reaches the PSD through the FOP and the position of the optical input is converted to an electric signal. Processing this signal detects the contact location and the surface normal of the contacted object.