A finger-shaped tactile sensor previously reported in a scaled-up version was miniaturized and its signal processing speed improved. The miniaturized tactile sensor consists of a hemispherical optical waveguide with an elastic cover, a fiber-optics plate (FOP), a position-sensitive detector (PSD), and infrared light-emitting diodes (LEDs) for the light source. When an object comes in contact with the sensor, the elastic cover is depressed and light from the LEDs, which normally maintains total internal reflection within the waveguide, is scattered at the contact location of the waveguide and the cover. The scattered light is transmitted to the PSD through the FOP. The contact location and the normal to the surface of the object are determined from the output of the PSD. The sensor's fundamental characteristics were evaluated through experiments using the miniaturized version. The sensor was installed at the tip of a robotic finger to create an active touch system. By combining tactile sensing and motion control of the finger, the profile of an unseen object was successfully delineated.>