In UV excimer laser coordinated motion imaging, both the mask and part are mounted to computer-controlled X,Y stages. During processing, the mask and part perform interpolated moves in opposing directions, the magnitude of mask movement being larger by a scale factor equal to the image system demagnification. This opposing motion causes the laser image to precisely track the position of the moving part, remaining at the same position relative to the part as different areas of the mask are exposed. The lens system employed can be simple since the lens is always used in the paraxial, on-axis condition. By carefully programming moves, you can make the beam expose only the open areas of the mask, resulting in high beam utilization efficiency.