Main Theme and Variations of Phase Contrast Electron Microscopy

Two kinds of phase contrast electron microscopy, Zernike phase contrast and Hilbert differential contrast, both using phase plates, are described together with the theory of the contrast generation. Micrographs obtained by the two schemes are compared with those obtained with the scheme of defocus phase contrast most prevalent in conventional TEM. Higher contrast of unstained biological samples, without image deterioration, has been clearly demonstrated for the two phase contrast methods. As a variation of the Zernike phase contrast, complex observation is also introduced, which combines the two schemes, the conventional and the Zernike, to recover complex waves as exited from objects. It is shown that images in the complex form is the most appropriate to be corrected in image flaws arising from the spherical aberration and the defocus.