Metrology system and coherence adjusters

A coherence adjuster comprising:

• a waveguide device comprising:
• an input configured to receive spatially coherent radiation;
• and
• an output;
• a multimode waveguide device comprising:
• an input configured to receive radiation from the waveguide device;
• and
• an output configured to output a coherence adjusted beam of radiation;
• and
• an actuator coupled to the waveguide device and configured to actuate the waveguide device to change a position of a focus spot of radiation at the input of the multimode waveguide device in a deterministic, non-random manner to increase a homogeneity or an apparent coherence of the coherence adjusted beam.

A coherence adjuster comprising:

• a multimode waveguide device comprising:
• an input configured to receive spatially coherent radiation;
• and
• an output configured to output a coherence adjusted beam of radiation;
• and
• an adjusting device coupled to a portion of the coherence adjuster and configured to change a position of a focus spot of radiation, and thereby an impingement characteristic, at the input of the multimode waveguide device in a deterministic, non-random manner to increase a homogeneity or an apparent coherence of the coherence adjusted beam, wherein
• an interference pattern of the coherence adjusted beam is adjusted based on the change of the impingement characteristic,
• the impingement characteristic comprises a distribution of incidence angles, and
• the coherence adjuster is configured to adjust a beam diameter of the coherence adjusted beam based on a change of the distribution of incidence angles.