Method and device for characterizing the surface shape of an optical element

US11927500B2 · kind B2 · utility

Assignee

• Carl Zeiss SMT GmbH · DE

Inventors

• Steffen SIEGLER · Aalen, DE
• Johannes Ruoff · Aalen, DE
• Alexander Wolf · Oberkochen, DE
• Michael Carl · San Marcos, US
• Toralf Gruner · Hennef (Sieg), DE
• Thomas Schicketanz · Aalen, DE

Key dates

• Filing date: Apr 14, 2022
• Grant date: Mar 12, 2024
• Expiry date: Apr 14, 2042

Classification

• Technology area (CPC G): Physics
• CPC primary: G01B11/2441
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

Methods for characterizing the surface shapes of optical elements include the following steps: carrying out, in an interferometric test arrangement, at least a first interferogram measurement on the optical element by superimposing a test wave, which has been generated by diffraction of electromagnetic radiation on a diffractive element and has been reflected at the optical element, carrying out at least one additional interferogram measurement on in each case one calibrating mirror for determining calibration corrections, and determining the deviation from the target shape of the optical element based on the first interferogram measurement carried out on the optical element and the determined calibration corrections. At least two interferogram measurements are carried out for the at least one calibrating mirror, which differ from one another with regard to the polarization state of the electromagnetic radiation.