Finger-Shaped Tactile Sensor

Principle & φ32 mm tactile sensor (video WMV 560 kB)

The developed tactile sensor uses an optical phenomena. The optical waveguide is a hemispherical shell of glass and the light induced from the light source is injected into the waveguide at its edge. Most of the injected light is totally reflected internally at the surface of the waveguide and is enclosed inside it. The waveguide is covered with an elastic cover with an appropriate clearance from the waveguide.

When an object contacts the cover, the cover is depressed and part of it makes contact with the waveguide. At this time, the light enclosed in the waveguide scatters at the contact location due to the change of the reflection condition. The scattered light is observed by an optical detector and the contact location is determined using the geometries of the waveguide and the detector.

• Miniaturization and integration of waveguide, light source, optical device, optical detector and electric circuit.
• Eight infrared LEDs directly built in at the edge of the waveguide.
• FOP for compact optical transmission.
• PSD for an optical detector.
• Amplifiers integrated in the sensor.
• Diameter of φ32 mm, a length of 60 mm.

FOP Fiber Optic Plate

A squeezed bundle of fine optical fibers capable of transmitting an image from one end to the other without distortion. In developed sensor, one end of the FOP is hemispherically shaped to fit the inner surface of the waveguide and the other end is plane shaped to fit the detector.

PSD Position Sensitive Detector

An optical detector which can convert the location of the centroid of the light intensity on its surface to four electric signals. Precise and fast detection (spatial resolution: 6 µm, detection area: 12 mm×12 mm, response time: 0.5 µs) is feasible.

• Furthermore miniaturization and integration.
• For size and cost reduction, FOP is replaced by lenses and aperture that were designed using optical CAD.
• Diameter of φ20 mm, a length of 44 mm that is compact enough for installing at the fingertip of robot hand.
• Detection time of 0.2 ms.