Enabling more marks in alignment sensor

A substrate alignment apparatus, comprising;

• an illumination system configured to receive a beam of source radiation from a radiation source and direct the beam of source radiation toward a pupil plane;
• an optical component positioned at the pupil plane and configured to direct separate beams of the beam of source radiation toward a plurality of alignment marks on a substrate;
• at least one objective module disposed between the optical component and the substrate and configured to focus the separate beams of the beam of source radiation on corresponding separate ones of the plurality of alignment marks;
• and
• an interferometer configured to receive beams of diffracted radiation that are diffracted from the plurality of alignment marks, collected by the at least one objective module, and directed to the interferometer by the optical component.