Present Research Status of X-Ray Near-Field Speckle Based Wavefront Metrology

The fourth generation synchrotron radiation light source provides X-rays with higher brightness and coherence, and better performance for many research fields. To access the full potential of these beams, accurate beamline alignment and high-quality X-ray optics are required. Wavefront metrology plays an important role in these aspects. X-ray near-field speckle based wavefront metrology, which has been developed rapidly in the past 10 years, has the advantages of simplicity and high measurement accuracy. Based on the property of not changing in shape and size of the speckle in the deep Fresnel region, the cross-correlation between the reference image and the sample image is calculated, and the wavefront information of the incident wave, the transmitted wave or the reflected wave of the optics to be measured is extracted. The present research status of X-ray near-field speckle based wavefront metrology is summarized. The principles, experimental procedures, advantages and applications of X-ray speckle tracking, X-ray speckle vector tracking, X-ray speckle scanning, self-correlation X-ray speckle scanning, unified modulated pattern analysis and Ptychographic X-ray speckle tracking are introduced.