Patent ID: 7626701

Claim:
A lithographic apparatus, comprising: a first alignment arrangement comprising a first detector configured to detect by a first alignment measurement a first alignment mark on an object and to produce a first alignment signal, wherein the first alignment arrangement comprises a first light source configured to produce a first light beam; a second alignment arrangement using a second alignment measurement different than the first alignment arrangement and comprising a second detector arranged to detect the first mark and to produce a second alignment signal, wherein the second alignment arrangement comprises a second light source configured to produce a second light beam; and a processor connected to the first detector and to the second detector, and configured to: receive the first alignment signal from the first detector; calculate a position of the first mark based on the first alignment signal; receive the second alignment signal from the second detector; calculate a further first position of the first mark based on the second alignment signal; and combine the position of the first mark and the further position of the first mark to calculate a calculated position of the first mark.