Patent ID: 8199104

Claim:
A character input device for a mobile device or a wearable terminal, comprising: a bio radar unit configured to transmit a signal toward a fingertip of a finger of a user and to measure the strength of a signal reflected from the fingertip; a tilt sensor configured to sense a tilt of hands of the user; a microprocessor configured to calculate final input information of the user by processing signals received from the bio radar unit and the tilt sensor; and a wireless communication module configured to transmit the final input information to the mobile device or the wearable terminal of the user, wherein, the microprocessor is configured to calculate a direction of the finger, based on a ratio between a total scan period of the bio radar unit and a period of time taken to perceive the fingertip, and to calculate a distance to the fingertip, based on the strength of the reflected signal, the microprocessor is configured to detect the input of a special key according to the tilt measured by the tilt sensor, the microprocessor, when three or more of the fingers are detected as input, is configured to process this case as a character input error and not determine the input character, the microprocessor, when two of the finders are detected as input, is configured to detect fingertip thickness information of each of the fingers, and to obtain final input information by comparing the detected fingertip thickness information to the fingertip thickness information of the reference information, when α a ≥ β b , a finger corresponding to ‘a’ is detected as input information and when α a < β b , a finger corresponding to ‘b’ is detected as input information, where a and b represent reference fingertip thickness information for the two fingers, and α and β represent detected fingertip thickness information.