Patent ID: 6404353
Filing Date: 2002-06-11
Classification: G06F,H03K

Abstract:
Process for optimizing the detection of the point of touching of a rectangular capacitive tactile surface according to which the conducting layer is supplied with high-frequency energy successively at each of its corners via a reference capacitance, the opposite corner to the corner supplied with power being earthed and the other two corners being â€œidleâ€ , characterized in that it includes a first step which consists in determining along each of the diagonals of the tactile surface, for a number of points corresponding to the sought-after resolution, the values of a parameter which is dependent on the two output voltages obtained by successively supplying each of the corners at which the relevant diagonal terminates, and also dependent on the position of the point of touching on the relevant diagonal, the said parameter being independent of the value of the capacitance added by the user at the point of touching, then in determining, for points distributed over the whole surface of the slab, the values of the said parameter relating to one of the diagonal then the values of the said parameter relating to the other diagonal, in storing the pairs of parameters as a function of the coordinates of each of the corresponding points, and a second step of determining the position of the point of touching which consists, on the basis of a measured pair of output voltages after successive supplying of the four corners of the tactile surface in determining the said two parameters respectively associated with the two diagonals and, in retrieving from memory the corresponding and unique coordinates of the point of touching on the basis of these two parameters.