Metrology sensor for position metrology

A metrology device configured to produce measurement illumination comprising:

• a plurality of illumination beams, each of the illumination beams being spatially incoherent or pseudo-spatially incoherent and comprising multiple pupil points in an illumination pupil of the metrology device,
• wherein each pupil point in each one of the plurality of illumination beams has a corresponding pupil point in at least one of the other illumination beams of the plurality of illumination beams thereby defining multiple sets of corresponding pupil points, and
• wherein the pupil points of each set of corresponding pupil points are spatially coherent with respect to each other.

The metrology device of claim 79, wherein the metrology device is operable as an alignment sensor that is configured to measure position of a periodic structure on a substrate with respect to a fixed reference from the position of the interference pattern.