Distortion Metrology Test for Large Field Lens

Project Goal: Research and develop a prototype metrology test for distortion and field curvature that will enable ASML to accurately test a specific large field-of-view lens used in their lithography systems.

It is important to minimize aberrations when designing and assembling an optical system. Finding the main source of each aberration in an assembled system requires physically measuring the aberrations contributed by each optical element within the system.

This prototype metrology test uses moiré fringes to accurately measure the distortion and field curvature of a wide field-of-view test lens. The lens images an object’s space grating under test and projects it onto an image space grating, which creates a moiré fringe pattern. A camera then captures the distorted pattern, which is analyzed by custom-developed MATLAB code. The result is the amount of distortion and field curvature produced by the lens.