1. An optical touch panel system, for positioning an object in a touch control area, the system comprising: at least two reflective elements respectively disposed on a first side and a second side of the touch control area, wherein the first side and the second side are adjacent to each other, and wherein the sum of lengths of the first side and the second side is larger than the sum of lengths of the two reflective elements; two lighting elements respectively disposed on a third side and a fourth side of the touch control area, wherein the third side and the fourth side are adjacent to each other; an image sensor capturing an image of the object to form a projected object image and at least one mirror image of the object formed by the two reflective elements to form at least one projected mirror image; and a processor calculating coordinates of the object according to geometric information of at least two of the projected object image and the at least one projected mirror image; wherein the reflective element disposed on the second side occupies a middle portion of the second side and does not extend to two ends of the second side.