Micro Touch Board Specially Designed for SliT that Is the Japanese Character Input Method for Smartwatches

摘要

We developed a touch board to solve the problem of smartwatches that screen is hidden by the finger during character input. It is used attached to the watchband under the screen. The board is optimized for the character input method named SliT (Slide-in and Tap method). Advantage of SliT is that the input speed of the novice is fast and the screen occupancy rate is low. Specifically, the speed is 28.7 [CPM (Characters Per Minute)] and the rate is 26.4%. In SliT, Japanese hiragana characters are input by combining 12 kinds of strokes and 8 tapping points. The board is designed to detect only those strokes and the taps. Eight touch sensors are arranged so as to surround the circular area placed at the center of the touch board. Between the sensors, numbers from 1 to 8 are allocated clockwise. Only when two adjacent sensors are touched at the same time, the number assigned to their boundary is entered. In stroke input, a fingertip is slid until passing through three boundaries, and three continuous numbers are entered. However, in rare cases, the last number may be lost. So, the stroke is judged from the first two numbers. The stroke recognition rate by this method is 98.7%. In tap input, users touch only one boundary. However, in a very few cases, an unnecessary number is added. In this case, the tap is judged from the first number. The tap recognition rate by this method is 99.4%.