Sensing alignment of multiple layers

摘要

Using an imaging system in relation to a plurality of material layers in an initial alignment state is provided, a first of the plurality of material layers at least partially obscuring a second of the plurality of material layers in the initial alignment state. The first material layer is moved from a first position corresponding to the initial alignment state to a second position out of a field of view of the imaging system, and a first image of the second material layer is stored. The first material layer is moved back the first position to restore the initial alignment state. A second image of the first material layer is acquired. The second image and the stored first image are processed to determine the initial alignment state.