Determining angle of incidence with respect to workpiece

A system for determining an angle of incidence of a light beam illuminating a workpiece positioned on a stage, the system comprising:

• means for positioning a calibration target on the stage with multiple different tilts;
• means for first determining an angle of incident of the light beam with respect to the calibration target with each tilt using a detector;
• means for mapping a response of the detector to a determined angle of incidence;
• and
• means for second determining the angle of incidence with respect to the workpiece based on a result of the mapping.

A computer program product for determining an angle of incidence of a light beam illuminating a workpiece positioned on a stage, comprising computer usable program code which, when executed by a computer system, enables the computer system to:

• position a calibration target on the stage with multiple different tilts;
• first determine an angle of incident of the light beam with respect to the calibration target with each tilt using a detector;
• map a response of the detector to a determined angle of incidence;
• and
• second determine the angle of incidence with respect to the workpiece based on a result of the mapping.