It is well known that sense of touch is inevitable for understanding the real world. The use of force feedback to enhance computer-human interaction has often been discussed. A haptic interface is a feedback device that generates sensation to the skin and muscles, including a sense of touch, weight and rigidity. Compared to ordinary visual and auditory sensations, haptics is difficult to synthesise. Visual and auditory sensations are gathered by specialised organs, the eyes and ears. On the other hand, a sensation of force can occur at any part of the human body, and is therefore inseparable from actual physical contact. These characteristics lead to many difficulties when developing a haptic interface. Visual and auditory media are widely used in everyday life, although little application of haptic interface is used for information media.
Haptic interface presents synthetic stimulation to proprioception and skin sensation. Proprioception is complemented by mechanoreceptors of skeletal articulations and muscles. There are three types of joint position receptors: free nerve ending as well as Ruffini and Pacinian corpuscles. Ruffini corpuscle detects static force. On the other hand, Pacinian corpuscle has a function to measure acceleration of the joint angle. Position and motion of the human body is perceived by these receptors. Force sensation is derived from mechanoreceptors of muscles; muscle spindles and Goldi tendons. These receptors detect contact forces applied by an obstacle in the environment.
Skin sensation is derived from mechanoreceptors and thermorecepters of skin. Sense of touch 29 History of haptic interface is evoked by those receptors. Mechanoreceptors of skin are classified into four types: Merkel disks, Ruffini capsules, Meissner corpuscles, and Pacinian corpuscles. These receptors detect edge of object, skin stretch, velocity, and vibration respectively.
The tactile display that stimulates skin sensation is a well-known technology. It has been applied to communication aids for blind person as well as master system of teleoperators. A sense of vibration is relatively easy to produce, and a good deal of work has been done using vibration displays [1, 2]. The micro-pin array is also used for tactile displays. Such a device has enabled the provision of a teltaction and communication aid for blind persons [3, 4]. It has the ability to convey texture or 2-D geometry .