The present invention provides a method and system for generating electronic purchase orders and purchase order responses. Each of the individual offset fields is smoothly varying, and so is represented using a low-dimensional spline. An inner seal material is deposed on one of the substrates and an outer seal material is deposited in the trench. The system is configured to prevent the spoke when transiting the optical path between the light source and the light output window to simultaneously transit a first optical path between the first light-emitting unit and the light output window and a second optical path between the second light-emitting unit and the light output window.