A highly linear and accurate touch data extraction algorithm based on polar coordinates for large-sized capacitive touch screen panels

Abstract

In this paper, a polar coordinate-based touch data extraction (PCTDE) algorithm is proposed to enhance the linearity and accuracy of touch coordinates for large-sized capacitive touch screen panels (TSPs) with a wide electrode pitch. The proposed PCTDE algorithm accurately extracts the touch coordinates by calculating the distance and directional angle between the touch point and the intersection of the transmitter and receiver electrodes. In addition, the interference between two touch points in multi-touch is reduced by decreasing the differential rate of touch data so that the exact touch coordinates can be determined. We evaluated the proposed algorithm using a 46-inch TSP with an 8.5 mm electrode pitch. To verify the linearity and accuracy of touch coordinates, the standard deviation of the slope of the touch coordinates and the average distance error are calculated, respectively. In single-touch, the linearity and accuracy of touch coordinates are improved by 56.7 % and 57.8 %, respectively, compared with those using the best previously-reported touch-sensing algorithm. In multi-touch, the linearity and accuracy of touch coordinates are improved by 56.7 % and 64.2 %, respectively.