US Patent 7880880 Alignment systems and methods for lithographic systems

An alignment system for a lithographic apparatus has a source of alignment radiation; a detection system that has a first detector channel and a second detector channel; and a position determining unit in communication with the detection system. The position determining unit is constructed to process information from said first and second detector channels in a combination to determine a position of an alignment mark on a work piece, the combination taking into account a manufacturing process of the work piece. A lithographic apparatus has the above mentioned alignment system. Methods of alignment and manufacturing devices with a lithographic apparatus use the above alignment system and lithographic apparatus, respectively.