US Patent 7388696 Diffuser, wavefront source, wavefront sensor and projection exposure apparatus

A wavefront source having a wavefront formation structure (4a) and a diffuser with a scattering structure (2b) in the beam path in front of or at the level of the wavefront formation structure; also a diffuser configured to be used therefor, and a wavefront sensor equipped therewith, as well as a corresponding projection exposure apparatus. The diffuser has a diffractive computer-generated hologram (CGH) scattering structure with a predetermined angular scattering profile. The wavefront source includes such a diffuser and/or a focusing element with a reflecting diffractive focusing structure (3a) in the beam path at the level of the scattering structure or between the scattering structure (2b) and the wavefront formation structure (4a). The disclosed structures are used, e.g., in the wavefront measurement of projection objectives in microlithography projection exposure apparatuses in the EUV wavelength range.