In addition, in SAR imaging processing, the maximum phase error for range that will not result in defocus of the image is π/4 rad[19].
Also, astigmatism and defocus of the image was estimated using the CTFFIND3 software (Mindell and Grigorieff 2003) that is implemented in 2dx.
Correctly estimated defocus in the image enabled precise positioning of minimal CTF in the Fourier transform, and the simulated CTF indicates oscillating positive and negative CTF as a function of resolution as well as resolution-dependent attenuation of phase amplitude.
We defocused the images by using SDFPs corresponding to ΔVa = 5 m/s, 10 m/s, and 20 m/s.
Their DfD uses two differently defocused images and the filters accurately model the relative defocus in the images and provide a fast calculation of distance.
In Fig. 4 b, c, the conventional image with defocused target and the image produced by sparsity-driven imaging without any motion compensation are displayed respectively.
In Fig. 5 b, c, the conventional image with defocused target and the image produced by sparsity-driven imaging are displayed.
For a given microscope setup, the voltage and spherical aberration are constant, but the defocus varies from image to image because of variations in lens settings, sample height, and thickness.
The experiment data point is sampled after focusing, and the focus position and Brenner evaluation function curve are shown in Figure 13.Figure 13 shows that the Brenner function value is small when the defocusing amount of the image is bigger.
Estimation of defocus indicated that that the image was slightly astigmatic, where defocus of the image was estimated to be 13,917 and 13,447 Å in the longest and shortest dimensions that are perpendicular.
