A finger-shaped tactile sensor using an optical waveguide

Three versions of a novel tactile sensor have been developed for the fingertip of a robotic hand. Using optical phenomena, the developed tactile sensor, which has a hemispherical surface, can detect the point where an object contacts the sensor surface and the normal to the surface of the contacted object. The primary element of the tactile sensor is a hemispherical optical waveguide made of a glass shell. Light is injected at the edge of the waveguide to illuminate the interior. The injected light maintains total internal reflection at the inner surface of the waveguide and is enclosed within it. Therefore light scatters when an object contacts the surface of the waveguide, because of the changing reflection conditions. A prototype finger-shaped tactile sensor was developed to confirm the feasibility of this principle. Next, a miniaturized version was developed, and its tactile-sensing capability was experimentally evaluated. Through further miniaturization and integration, a fingertip diameter of 20 mm has been achieved in the latest fingertip-size version of the tactile sensor.<<ETX>>