Patent Number: 
Section: claims

1. A testing device for an extreme ultraviolet (EUV) optical system, comprising:a generating unit configured to generate wavelength-variable radiation providing test spectra to the EUV optical system,wherein the generating unit comprises a filter unit comprising two mirrors arranged opposing each other, wherein the filter unit has at least one entrance opening for entrance radiation of the wavelength-variable radiation, wherein the filter unit is configured to reflect beams of the entrance radiation multiple times between the mirrors, and wherein the filter unit has at least one exit opening through which exit radiation of the reflected beams emerges, anda sensor unit configured to detect the test spectra following interaction with the EUV optical system,wherein a target spectrum (Z) of the wavelength-variable radiation generated by the generating unit has at least two generated different, superimposed base spectra (B1, B2). 2. The testing device as claimed in claim 1, wherein the generating unit comprises a plasma source, and wherein the plasma source comprises at least one gas which emits in an operative wavelength range of the EUV optical system. 3. The testing device as claimed in claim 2, wherein the at least one gas comprises a gas selected from the group consisting of argon, krypton, xenon, nitrogen, neon and oxygen. 4. The testing device as claimed in claim 2, wherein the plasma source comprises at least two gases and is configured to vary a mixture ratio of the gases. 5. The testing device as claimed in claim 4, wherein the target spectrum (Z) is defined by a mathematical function having three parameters, wherein the parameters comprise a maximum value, a width and a central wavelength of the target spectrum (Z). 6. The testing device as claimed in claim 1, wherein the target spectrum (Z) is determined through sequential application of the base spectra (B1, B2) to the EUV optical system. 7. The testing device as claimed in claim 1, wherein the generating unit is configured to set a test spectrum through: variation of a distance between the entrance opening and the exit opening and/or through variation of a plate distance between the mirrors. 8. The testing device as claimed in claim 1, wherein the generating unit is configured to set a parallelism between the two mirrors. 9. The testing device as claimed in claim 1, wherein the filter unit has plural entrance openings on a first side and has plural exit openings on a second side, and wherein the entrance openings and the exit openings are each arranged in respective grids, and wherein distances between the entrance openings and the exit openings are respectively set in accordance with a coordinate alignment. 10. The testing device as claimed in claim 1, wherein at least one of a position or an orientation of the filter unit is configured to adjust within the generating unit. 11. The testing device as claimed in claim 1, wherein the filter unit is arranged upstream and/or downstream of the EUV optical system. 12. A method for testing an extreme ultraviolet (EUV) optical system, comprising:generating a wavelength-variable test radiation by reflecting beams of radiation multiple times between two mirrors and providing an exit opening for a portion of the reflected beams, to produce test spectra,applying the wavelength-variable test radiation to the EUV optical system;detecting the test radiation downstream of the EUV optical system with a sensor unit; andevaluating the detected test radiation with an evaluation unit. 13. A computer program product comprising a non-transitory computer-readable medium comprising program code configured to perform the method as claimed in claim 12 when executed on an electronic control unit. 14. A computer program product stored on a non-transitory computer-readable data carrier and comprising program code configured to perform the method as claimed in claim 12 when executed on an electronic control unit. 15. A testing device for an extreme ultraviolet (EUV) optical system, comprising:a generating unit configured to generate wavelength-variable radiation to provide test spectra to the EUV optical system, anda sensor unit configured to detect the test spectra generated by the EUV optical system,wherein a target spectrum (Z) generated by the generating unit has at least two generated different, superimposed base spectra (B1, B2), andwherein the target spectrum (Z) is determined through sequential application of the base spectra (B1, B2) to the EUV optical system.