Patent ID: 11940264
Assignee: ASML NETHERLANDS B.V.
Field: Measurement (Instruments)
Classification: CPC G | IPC G

Claim 12:
13. The method according to claim 1, wherein the interferometer system includes a third interferometer, wherein the third interferometer is arranged to provide a third position signal representative of the position of the object in the X-direction by directing a third measurement beam on the first mirror, wherein the combination of the first and third interferometers allows measurement of a rotation of the object about an axis extending parallel to the Z-direction, and further comprising et generating a third data set comprising the first position signal and the third position signal for each of a plurality of positions of the object in the Y-direction while the object is maintained in a constant rotational orientation about the axis parallel to the Z-direction using a sensor other than the first, second and third interferometers, and wherein in step d. the third data set is used to determine the shape of the first mirror in Y-direction.