Multi-touch detecting method for touch screens

A multi-touch detecting method for touch screens relates to a system comprising the touch screen, a capacitance induction circuit, a capacitance data processing module and a host, wherein the touch screen comprises M*N mutual capacitance arrays formed from M transversal electrodes and N longitudinal electrodes which are orthogonal;

• The method comprises the following steps:
• A. The capacitance induction circuit detects all capacitance of the touch screen to obtain M*N real-time two-dimensional values corresponding to capacitances, and a two-dimensional array formed from these values is used as the data source for detection of touch points;
• The capacitances of a touched areas is smaller than that of an untouched area;
• if the original value of the whole untouched area is regarded as a flat, a concave can appear in the area touched effectively, and please regard the concave as a “depression”;
• B. Judge whether effective touch occurs or not, namely, to find “depressions” in accordance with the two-dimensional array obtained in Step A, if not, return to Step A;
• or else, do Step C;
• C. Separate the “depression” touched effectively;
• E. Determine the equivalent “depression” of the “depression” touched effectively;
• F. Calculate and output the coordinate corresponding to the equivalent “depression” of the “depression” touched effectively, and return to Step A.