At-Wavelength Interferometry of High-NA Diffraction-Limited EUV Optics

We propose a design method of phase-analysis algorithms based on two-dimensional grating phase shifting for Talbot interferometry, Talbot-Lau imaging, or the Ronchi test. These algorithms are designed to separate the two orthogonal shearing wavefronts and eliminate error effects of unwanted diffraction orders, simultaneously. Taking the effect of multidiffraction into account, moving the two-dimensional grating along a certain pass leads to a series of phase-shifted interfrograms, from which two orthogonal shearing wavefronts are derived, for the tested wavefront to be retrieved. The designing process is demonstrated, and the residual errors are analyzed via simulation works and experimental comparison.

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Common-path and compact wavefront diagnosis system based on cross grating lateral shearing interferometer

Ling

Yang

Yue

et al. 2014

Appl. Opt.

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A common-path and compact wavefront diagnosis system for both continuous and transient wavefronts measurement is proposed based on cross grating lateral shearing interferometer (CGLSI). Derived from the basic CGLSI configuration, this system employs an aplanatic lens to convert the wavefront under test into a convergent beam, which makes it possible for CGLSI to test the wavefront of collimated beams. A geometrical optics model for grating pitch determination and a Fresnel diffraction model for order selection mask design are presented. Then a detailed analysis about the influence of the grating pitch, the distance from the cross grating to the order selection mask and the numerical aperture of the aplanatic lens on the system error is made, and a calibration method is proposed to eliminate the system error. In addition, the differential Zernike polynomials fitting method is introduced for wavefront retrieval. Before our experiment, we have designed several grating pitches and their corresponding order selection mask parameters. In the final comparative experiment with ZYGO interferometer, the wavefront diagnosis system exhibits both high precision and repeatability.

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At-Wavelength Interferometry of High-NA Diffraction-Limited EUV Optics

Cited by 3 publications

References 14 publications

Mathematical modeling analysis on a small and compact two-dimensional CGLSI interference system

Mathematical modeling analysis on a small and compact two-dimensional CGLSI interference system

Method for designing phase-calculation algorithms for two-dimensional grating phase-shifting interferometry

Common-path and compact wavefront diagnosis system based on cross grating lateral shearing interferometer

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