Patent ID: 8058634

Claim:
A method for determining a position of a selected area of a sheet of material relative to a reference plane, comprising: launching a first incident light beam at the selected area of the sheet of material such that the first incident light beam strikes the selected area at a first position and a first angle, thereby producing a first reflected light beam; launching a second incident light beam at the selected area of the sheet of material such that the second incident light beam strikes the selected area at a second position and a second angle, thereby producing a second reflected light beam, the second position and second angle being different from the first position and first angle, respectively; intercepting the first reflected light beam and the second reflected light beam at the reference plane; receiving the first angle and a first information related to a position at which the first reflected light beam was intercepted; receiving the second angle and a second information related to a position at which the second reflected light beam was intercepted; and correlating the first angle, the second angle, the first information, and the second information to the position of the selected area relative to the reference plane, wherein the correlating comprises resolving P n =b(2Î¸ n +2Î¸ 0 ), where P n is the location at which the reflected light beams are intercepted on the reference plane, Î¸ n is the angle at which the incident light beams strike the selected area, b is the distance from the selected area to the reference plane, and Î¸ 0 is the orientation of the selected area relative to the reference plane.