ASML Holding N.V.
Laser beam monitoring system

Abstract:

A laser beam monitoring system configured to monitor an attribute of an incident laser beam (24), the laser beam monitoring system comprising a beam separating element (30) and a plurality of sensors (34a-34d), wherein the beam separating element is configured to form a plurality of sub-beams (24a-24d) from the incident laser beam (24), a first sub-beam being directed towards a first sensor of the plurality of sensors and a second sub-beam being directed towards a second sensor of the plurality of sensors, wherein relative intensities of the first and second sub-beams are determined by a spatial position at which the incident laser beam is incident upon the beam separating element.