Patent ID: 11879721
Assignee: CARL ZEISS SMT GMBH
Field: Measurement (Instruments)
Classification: CPC G | IPC G

Claim 0:
1. Measurement method for interferometrically measuring a shape of an optical surface of a test object, comprising:
providing a first input wave having a first wavelength λ1 and a second input wave having a second wavelengthλ2, which differs from the first wavelength λ1;
producing a first test wave, which is directed at the test object and has a wavefront that is adapted at least partially to a desired shape of the optical surface, and a first reference wave, which is directed at a first reflective optical element and has a propagation direction that deviates from a propagation direction of the first test wave, from the first input wave by diffraction at a diffractive optical element,
producing a second test wave, which is directed at the test object and has a wavefront that is adapted at least partially to the desired shape of the optical surface, and a second reference wave, which is directed at a second reflective optical element and has a propagation direction that deviates from a propagation direction of the second test wave, from the second input wave by diffraction at the diffractive optical element,
superimposing the first test wave, after interaction with the test object, with the first reference wave after back-reflection at the first reflective optical element and superimposing the second test wave, after interaction with the test object, with the second reference wave after back-reflection at the second reflective optical element, wherein the first and the second test waves and the first and the second reference waves are diffracted again in each case at the diffractive optical element for superposition;
capturing a first interferogram produced by the superposition of the first test wave and the first reference wave in a first capture plane and a second interferogram, produced by the superposition of the second test wave and the second reference wave in a second capture plane; and
jointly evaluating the first and the second interferograms taking into account a difference between the first wavelength and the second wavelength.