Measuring apparatus for interferometrically determining a surface shape

Abstract

A measurement apparatus (10) for interferometrically determining a surface shape of a test object (14). A radiation source provides an input wave (42), a multiply-encoded diffractive optical element (60), which is configured to produce by diffraction from the input wave a test wave (66) that is directed at the test object and has a wavefront in the form of a free-form surface and at least one calibration wave (70), and a capture device (46). The calibration wave has a wavefront with a non-rotationally symmetric shape (68f), wherein cross sections through the wavefront of the calibration wave along cross-sectional surfaces each aligned transversely to one another have a curved shape. The curved shapes in the different cross-sectional surfaces differ in terms of an opening parameter. The capture device (46) captures a calibration interferogram formed by superimposing a reference wave (40) with the calibration wave after interaction with a calibration object (74).

Dependencies are inferred from the claim text.