Quantitative Phase Measurement in Hard X-ray Microscopy

DoctorQuantitative phase imaging is an emerging field to study weakly scattering and absorbing specimens. Since its invention in 1930, Zernike phase contrast method has played significant role in visible light imaging and x-ray imaging. By inserting a specially designed phase plate at the focal plane of the objective lens, only the phase of the reference wave is shifted by the phase ring, whereas the phase of the object wave is not changed by the phase ring. The phase difference between the two waves enhances the image contrast. Zernike phase contrast is especially important in hard x-ray imaging because of its high transmittance and low absorption contrast. However, Zernike phase contrast image is only an intensity distribution, in which the phase information is coupled nonlinearly and cannot be retrieved quantitatively. We combined Zernike phase contrast method and phase shifting interferometry mechanism in order to perform quantitative phase measurement of microscopic objects