Method of measuring a deviation of an optical surface from a target shape

Abstract

A method of aligning at least two wave shaping elements, a method of measuring a deviation of an optical surface from a target shape and a measuring apparatus for interferometrically measuring a deviation of an optical surface from a target shape. The method of aligning at least two wave shaping elements, each of which wave shaping elements has a diffractive measurement structure for adapting part of a wave front of incoming light to a respective portion of the target shape, includes: providing a first one of the wave shaping elements with a diffractive alignment structure, arranging the wave shaping elements relative to each other such that each of the diffractive measurement structures is traversed by a separate subset of rays of the incoming light during operation of the measuring apparatus, and aligning the first wave shaping element and a second one of the wave shaping elements relative to each other by evaluating alignment light having consecutively interacted with the diffractive alignment structure and with the second wave shaping element.

Dependencies are inferred from the claim text.