The Institute for Human Science and Biomedical Engineering (IHSBE) of the National Institute of Advanced Industrial Science and Technology (AIST), one of independent administrative institutions, developed has come up with a concept of a contact locating system based on force and torque caused by a touch of user’s finger, and developed a prototype model of tactile display for persons handicapped with severely impaired vision, to implement not only graphic display (output) but also basic function of input operation through intensity and direction of touch, in collaboration with the University of Electro-Communications (UEC) and the KGS Corporation (KGS).
In the information-intensive society, most of IT equipments are operated through visual info such as graphics and figures, which hardly accessible for visually handicapped people. Tactile displays, to convert graphic info into tactile pattern and display it on a touch panel, have been developed as a promising means for communications with the visually handicapped. But as their functions are limited mainly to the info display, and those for communications such as creating, utilizing and delivering info were less than adequate. The tactile display equipped with output and input capability will provide a powerful means for communications with visually handicapped people.
The prototype tactile display panel (Photo. 1) consists of 1536 pins in total which move up and down independently from one another for displaying various patterns. When any point on the panel is pressed, its location is exactly identified and the nearest pin rises up. Therefore, when a finger moves over a tactile display panel, corresponding pins rise up on the panel to trace the finger move in real time. Based on this principle, it has become possible to draw and erase a picture freely without resorting to vision through sensing the finger move and by substituting the “mouse” actions such as selecting, displacing and scrolling with the move of finger and palm.
The prototype tactile display represents a new development from a touch-based info display (output) to a touch-based communication I/O terminal, and its contribution is expected to upgrade the tactile interface for the visually handicapped.
The present R&D work is carried out under the Project “Development of High Density Tactile Graphic Device to Support Communications with the Visually Handicapped” (FS2003) under the “R&D Program for Supporting Small and Medium Enterprises” of the Ministry of Economy, Trade and Industry (METI).
The collaborative research group, consisting of IHSBE-AIST, UEC and KGS, is going to carry out the R&D works for consolidating basic functions of tactile display and implementing communication interface based on them.
A rigid panel attached with a sensor for force and torque is fixed at a point. When a point on the panel is pressed, force and torque detected may vary depending upon the magnitude and direction of pressing force and the location of pressing point. Under the ideal conditions, the location can be determined through the inverse calculation, regardless of pressing mode. In the prototype display system, a tactile display unit is mounted on a panel, and on the basis of this principle, the contact position on the tactile display surface is identified through the inverse calculation of sensor output and the correction of deviation caused by mounting error and structural distortion.
The prototype tactile display has 1536 pins arranged at 2.4-mm spacing, 32 (lengthwise) X 48 (crosswise), which indicate various patterns through vertical shifts of individual pins, and at the same time, allows detecting the position of finger. As the finger itself deforms when making contact, it is rather difficult to evaluate the locating accuracy with actual finger, but when a pin position is pressed with a pen tip, the position is exactly identified (Photo. 3). When a finger moves over the tactile display surface, pins rise up to trace the finger locus in real time (Photo. 4). In this way, it is demonstrated that the proposed contact position locating method and the tactile display meets the basic requirements for entering info.
With the proposed contact position locating method and the prototype tactile display, it has become possible not only to make a display of various patterns, but also to draw and erase a picture freely on a tactile display panel without using vision, and to implement mouse functions such as selecting, moving and scrolling displayed pattern.
Owing to the simple structure with a single sensor attached to the bottom of display panel, complicated wirings are not needed, and the tactile display panel can be modified independently.
Previous works using ultrasonic position sensor, or locating contact position by following a mark placed on a finger with a TV camera, can detect the position info only. The proposed contact position locating method can provide interface functions much more variable that that based on position info only, as contact data such as intensity and direction of pressing force on the panel. This system will serve as a platform for the visually handicapped to design and propose an easy-to-use interface by themselves.