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Electrical Stimulation |
| Electrocutaneous stimulation has quite a long history. However, application has been limited to clinical use, mainly due to two problems. The first problem was the difficulty in confining the generated sensation to a small area. Even for electrodes with sufficient density, the generated sensation could not be localized under the electrodes. This problem was first solved by Kaczmarek[5][6]. Although most of the previous methods for electrical stimulation utilized cathodic (negative) electrical current to stimulate nerve fibers, Kaczmarek used anodic (positive) current pulse and showed that the sensation becomes quite localized and could be used as a Braille symbol display. After his success, we showed mathematically why the anodic current elicited a concentrated sensation[4] . The second problem was the unstable relationship between the amount of current and generated sensation. A sudden (~1[s]) change of sensation gives an "invasive" impression. It even causes fear. This is a typical reason why electrical stimulation was not widely accepted to consumer use. Our solution is as follows: by setting a force sensor under the electrodes, we measure the finger pressure. The applied pulse height or width is set as a monotonically increasing function of this pressure． We can therefore control the amount of sensation by regulating finger pressure[4]. After this improvement, all participants could feel a stable tactile (vibratory) sensation with confidence. |
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Selective Stimulation |
| The idea of selective receptor stimulation for tactile display was first proposed by Asamura[7]. We extended the idea to electrical stimulation and showed that selective stimulation is possible through electro-tactile display[3]. The basic idea is to utilize the different placement of sensory nerves, and to control the electric field by changing the current source distribution of the skin surface. |
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Augmented Reality of Haptics |
| In our group, we have been working on the field of haptic display system. In Siggraph 2001, we presented the first realization of Augmented Reality of Haptics, the "SmartTool"[1]. SmartTool captures information with a sensor attached at the tip of the tool, and conveys it to the operator through a haptic force display integrated into a hand tool such as a scalpel or pen. One of their proposed applications was in surgical operation. When a "smart" scalpel contacts a vital region such as an artery, the sensor detects surface information, and the display produces a repulsive force to protect the region. Another development in Augmented Haptics is SmartFinger, which was demonstrated in Siggraph 2002[2]. In SmartFinger, a vibrating tactile display and a sensor are both mounted on the fingernail. The vibrator drives the finger vertically, which induces force between the finger and the contacting object. Thus, skin sensation is generated indirectly, while natural tactile sensation is unhindered by the display. Our SmartTouch is a natural extension of these developments in Haptics AR. While SmartTool and SmartFinger both employed only one sensor and one actuator to display the information of single point, SmartTouch has a matrix of stimulation and sensing points. The wearer can therefore feel two-dimensional surface information at all times. |
 SmartTool |
 SmartFinger |
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Visual-to-Tactile conversion system |
| There has been extensive research efforts on visual-to-tactile conversion systems. Bliss[8] has developed the first converter system, and the representative commercial product "Optacon" was developed in 1980s using a video camera and a matrix of vibrating pins [9]. However, their aim was for a visually impaired person to read printed material, but not to "augment" the real world. Specifically in their system, the participant must have a video camera in one hand and tactile information is displayed onto another hand. On the contrary, in our system, the optical sensor and the tactile display are located at practically the same place, and work in combination as a new skin "receptor". |
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References |
| [1] T. Nojima, D. Sekiguchi, M. Inami and S. Tachi, "The SmartTool: A system for augmented reality of haptics," in Proc. of the IEEE-VR Conference 2002, pp.67-72, Orlando, Mar 2002. [2] H. Ando, T. Miki, M. Inami and T. Maeda, "The nail-mounted tactile display for the behavior modeling," ACM SIGGRAPH 2002 Conference Abstracts and Applications, page264, 2002. [3] H. Kajimoto, N. Kawakami, T. Maeda, S. Tachi, "Tactile feeling display using functional electrical stimulation, " in The Ninth International Conference on Artificial reality and Telexistence (ICAT'99), 1999. http://www.ic-at.org [4] H. Kajimoto, N. Kawakami, T. Maeda, S. Tachi, "Electro-tactile display with force feedback," in Proc. of World Multiconference on Systemics, Cybernetics and Informatics(SCI2001), Orlando Vol.X1, pp.95-99, July 2001. [5] K. A. Kaczmarek, M. E. Tyler, and P. B. y Rita, "Electrotactile haptic display on the ?ngertips: Preliminary results," in Proc. 16th Int. Conf. IEEE Eng. Med. Biol. Soc., pp. 940-941, 1994. [6] K. A. Kaczmarek and M. E. Tyler, "Effect of electrode geometry and intensity control method on comfort of electrotactile stimulation on the tongue," in Proc. of the ASME Dynamic Systems and Control Division, Vol.2, pp.1239-1243, 2000. [7] N. Asamura, N. Yokoyama, and H. Shinoda. A method of selective stimulation to epidermal skin receptors for realistic touch feedback. In Proc. IEEE VR'99, pp. 274-281, 1999 [8] Bliss, Katcher, Rogers, and Shepard "Optical-to-Tactile Image Conversion for the Blind," IEEE Trans. Man-Machine Systems, vol.MMS-11, no.1 Mar. pp.58-65, 1970. [9] Stein," The Optacon: Past, Present, and Future", in the National Federation of the Blind (NFB) website, http://www.nfb.org/bm/bm98/bm980506.htm |
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