with the local intensity (brightness) of the surface area. Image intensity is roughly correlated with the height of texture protrusions. A data glove originating at Sandia (Sandia, 1995) uses rod-like plungers to tap the fingertips lightly to simulate tactile sensations, and a magnetic tracker and strain gauges to follow the movements of the user's hand and fingers. Howe (1996) notes that vibrations are particularly helpful in certain kinds of sensing tasks, such as assessing surface roughness, or detecting system events (for example, contact and slip in manipulation control). Researchers at the Fraunhofer Institute for Computer Graphics in Darmstadt have developed a glove-like haptic device they call the ThermoPad, a haptic temperature display based on Peltier elements and simple heat transfer models; they are able to simulate not only the "environmental" temperature but also the sensation of heat or cold one experiences when grasping or colliding with a virtual object. At the University of Tsukuba, Japan, Iwana, Yano, and Hashimoto (1997) are using the HapticMaster, a 6 DOF device with a ball grip that can be replaced by various real tools for surgical simulations and other specialized applications. A novel type of haptic display is the Haptic Screen (Iwana, Yano, and Hashimoto, 1997), a device with a rubberized elastic surface with actuators, each with force sensors, underneath. The surface of the Haptic Screen can be deformed with the naked hand. An electromagnetic interface couples the ISU Force Reflecting Exoskeleton, developed at Iowa State University, to the operator's two fingers, eliminating the burdensome heaviness usually associated with exoskeletal devices. Finally, there is considerable interest in 2D haptic devices. For example, Pai and Reissell at the University of British Columbia have used the Pantograph 2D haptic interface , a two-DF force-feedback planar device with a handle the user moves like a mouse, to feel the e...
