
Segmental Ronchigram Autocorrelation Function
Matrix (SRAM) for Aberration Correction
 Practical Electron Microscopy and Database 
 An Online Book 

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Sawada et al. [1] had used segmental Ronchigram autocorrelation function matrix (SRAM) method to measure the aberration coefficients before and after aberration corrections. Figure 2743a shows the central parts of the Ronchigram patterns in a focal series. The Ronchigrams from the amorphous film were divided into 7 × 7 segments in order to calculate the aberration coefficients (up to fifthorder) and to perform autocorrelation functions. The absolute values of each aberration coefficient were calibrated by referring to the difference between the defocus values of the two Ronchigrams [2]. Furthermore, the residual aberration can also be obtained by comparing the experimental and calculated simulations of Ronchigrams.
Figure 2743a. The focal series of Ronchigrams: (a) Underfocus of 128 nm and (b) Overfocus of 128 nm. (c) and (d) Grided images of (a) and (b), respectively. (e) and (f) Autocorrelation functions from (a) and (b), respectively.
Adapted from [1]
[1] Sawada H, Sannomiya T, Hosokawa F, Nakamichi T, Kaneyama T,
Tomita T, Kondo Y, Tanaka T, Oshima Y, Tanishiro Y, and Takayanagi
K (2008) Measurement method of aberration from Ronchigram by
autocorrelation function. Ultramicroscopy 108: 1467–1475.
[2]
J. A. Lin, J.M. Cowley, Ultramicroscopy 19 (1986) 31.

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