Patent ID: 7948479

Claim:
A system for distinguishing multiple touch points, comprising: a panel, N touch points being indicated on the panel, N being a positive integer larger than one; a first image capturing unit, disposed on a first position at an outer edge of the panel, for capturing a first image related to the N touch points; a second image capturing unit, disposed on a second position, which is opposite to the first position, at the outer edge of the panel, for capturing a second image related to the N touch points; at least one third image capturing unit, disposed at the outer edge of the panel and between the first image capturing unit and the second image capturing unit, for capturing a third image related to the N touch points; a processing unit for calculating N sets of coordinates corresponding to the N touch points according to the first image and the second image and for determining one set of real coordinates corresponding to the N touch points from the N sets of coordinates according to the at least one third image; wherein the processing unit calculates N sets of first slopes from the N sets of coordinates with respect to the third image capturing unit and calculates N second slopes corresponding to the N touch points according to the third image and a focus of the third image capturing unit; wherein the processing unit selects a set of first slopes from the N sets of first slopes according to an algorithm and determines the set of real coordinates corresponding to the N touch points from the selected first slopes; and wherein the algorithm calculates reciprocals of the N sets of first slopes and the N second slopes, obtains N values by processing the reciprocals of the N sets of first slopes and the N second slopes through an absolute differences method or a least squares method, and then selects a smallest one among the N values.