Measurement system and method of use

A measurement system, comprising:

• an illumination system arranged to illuminate a measurement patterning device with radiation, wherein the measurement patterning device is disposed in a pupil plane of the illumination system and comprises a plurality of first patterned regions arranged to receive the radiation and to form a plurality of diffraction beams, the plurality of diffraction beams being separated in a shearing direction;
• a radiation detector;
• and
• a grating arranged to receive the plurality of diffraction beams, wherein the grating comprises a plurality of second patterned regions arranged such that at least some of the plurality of diffraction beams form interference patterns on the radiation detector;
• wherein the first patterned regions of the measurement patterning device comprise a plurality of first sets of paired patterned regions and a plurality of second sets of paired patterned regions arranged in an alternate manner between directly adjacent ones of the plurality of first sets of paired patterned regions across an entire major axis of the measurement patterning device, and
• wherein pitches of the plurality of first and second sets of paired patterned regions are different.