Finger and stylus discrimination scheme based on capacitive touch screen panel and support vector machine classifier

This paper demonstrates a support vector machine (SVM) based capacitive touch screen scheme that can discriminate stylus and finger at the same time. The tip of a stylus provides pulses at the higher frequency than the transmitting (Tx) pulse of a touch screen. Then the digital value acquired from an analog-to-digital converter is transferred to an SVM classifier to make the decision of which touch is applied among no-touch, finger-touch, and stylus-touch. Three types of touches are processed on the SVM algorithm. The proposed method is evaluated by means of an 8 inch capacitive touch panel, connector board, Tx/Rx driver board, and host processor board. While Tx pulses are applied at 5 V and 32 kHz that lead to the 200 Hz reporting rate, stylus pulses are produced at 3 V and 315 kHz. The resultant bit error rate is measured as less than 10^-6 for all types of touches.