An auto-alignment vision system with three-axis motion control mechanism

In this study a specially designed three-axis motion control mechanism was applied to an auto-alignment vision system. During the automated production process, the fed-in position of the object usually involves a small, but non-negligible rotational (theta-directional) error in addition to x- and y-directional errors. An analytic algorithm is employed to calculate the relationship between the rotational center (original position) of the motion control mechanism and the relative coordinates obtained by two CCD cameras. With the Delta x, Delta y and Delta theta, determined, the automatic motion control mechanism can make rotational and translational movements along the three axes (X, Y1, and Y2) accordingly to compensate for the difference in position and orientation, thus achieving accurate alignment. Results from over hundreds of experimental runs are deemed reproducible within +/- 5 mu m, proving that this design is feasible. Moreover, with the proposed design, the height of the three-axis motion control platform can be reduced from 300-400 mm to less than 120 mm, making it more compact.