Yi Wan and Wah Chiu, International Conference on Communications, Circuits and Systems, 2004. ICCCAS 2004. 2: 960.964
Over the past years electron cryo-microscopy (cryo-EM) has established itself as an important tool in studying the three dimensional structure of biological molecules up to the resolution of 6-9 Å. However, as we pursue even higher resolution (i.e., 3-4 Å), the depth-of-field problem inherent in the contrast transfer function emerges as a limiting factor. This problem has been previously addressed in the research community (Jensen, G.J., 2000; DeRosier, D.J., 2000; Zhou, Z.H. and Chiu, W., 2003; Cohen, H.A. et al., 1984). We develop a full theoretical solution to this problem. We show that the projected image from the electron microscope corresponds to neither a slice, nor an Ewald sphere, in the Fourier space, but a pair of quadratic surfaces in that space. The general solutions to this problem for both single and double defocus exposures are developed. Simulations show the correctness of the theory.
CTF, full contrast transfer function correction