Apparatus and method for measuring a wavefront using a screen with apertures adjacent to a multi-lens array

Abstract

A wavefront sensor is provided to determine characteristics of an incoming distorted energy beam, such as a tilt angle and/or a degree of focus. The sensor includes a multi-lens array, a screen, and a beam detector. The multi-lens array focuses the energy beam to a multiple focal points. The screen, positioned adjacent to the multi-lens array, has at least one aperture to allow a portion of the energy beam to pass, while blocking the remainder of the energy beam from arriving at the multi-lens array. Each aperture is aligned with a lens of the multi-lens array. The beam detector detects the resulted focal point(s) of the energy beam passing through the corresponding aperture(s) and determines the characteristics of the passing energy beam. The screen may include a central aperture to measure a local tilt angle of a segment of incoming wavefront entering a lens of the lens array. The screen may also include a plurality sets of apertures configured to align in a plurality of directions, each set of apertures measuring a degree of focus of the incoming wavefront along the corresponding direction. The screen may further include a combination of central aperture and a plurality sets of apertures aligned in a plurality of directions to simultaneously measure the local tilt angle and degree of focus of the incoming wavefront.