Patent ID: 11892283
Assignee: CARL ZEISS SMT GMBH
Field: Measurement (Instruments)
Classification: CPC G | IPC G

Claim 0:
1. A measurement apparatus for interferometrically determining a shape of a surface of a test object, comprising:
a radiation source providing an input wave,
a multiply-encoded diffractive optical element, which is configured to produce by diffraction from the input wave a test wave, which is directed at the test object and has a wavefront formed as a free-form surface, as well as at least one calibration wave,
wherein the calibration wave has a wavefront with a non-rotationally symmetric shape, wherein cross sections through the wavefront of the calibration wave along cross-sectional surfaces aligned transversely to one another each have a respective curved shape and wherein the respective curved shapes in the cross-sectional surfaces differ in terms of an opening parameter, and

a capture device for capturing a calibration interferogram formed by superimposing a reference wave with the calibration wave after interaction with a calibration object.