Ultimate Recovery of Low-Frequencies in Thin-film ZPC-TEM by Inverse Projector

We have developed a method for Zernike phase-contrast (ZPC) transmission electron microscopy (TEM) to recover very low frequency components. The ZPC-TEM using a Zernike phase plate (ZPP) made with thin amorphous carbon-film realizes very high contrast images [1], because it can visualize low frequency components, except for very low frequency components. The lack of the very low frequency components is caused by the phase plate design with a finite-sized central hole. While phaseplates with smaller hole-size is required to recover lower frequency components, the carbon-film with a smaller hole is exposed by stronger electron beam around the central beam-spot, and its lifetime becomes shorter due to the problem of charging. To solve the problem, we develop a method for recovering the very low frequency components by computer calculation, even for larger holes