METROLOGY AND CONTROL SYSTEM

A metrology and control system (100, 400, 500) for a laser beam in an EUV radiation source is disclosed. The system comprises an optical pickup (405, 540, 550) configured to measure a forward beam (410, 510, 520, 530) directed towards a target location (420, 535) and a return beam (415) reflected from the target location. The system also comprises actuatable optical devices (425, 430, 435, 465, 475, 555, 560, 565) configurable to direct and focus the forward beam onto the target location and align a measurement plane of the optical pickup with the target location. The actuatable optical devices are disposed before and after the optical pickup in a path of the forward beam, and the actuatable optical devices are controlled in response to a measurement of the forward beam and the return beam by the optical pickup.