Electron microscope and method for controlling focus position thereof
US6984823B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Jun 10, 2002 |
| Grant date | Jan 10, 2006 |
| Priority date | — |
| Expiry date | Jul 30, 2022 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01J2237/216
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
There are provided an electron microscope capable of carrying out focusing and astigmatism correction without depending on characteristics of a sample, and a method for controlling its focus position.The electron microscope according to the present invention comprises: an electron optical system (2); a focus control part (3); an image detecting part (4); a first operating part (11) for mutually dividing first and second transformed images (9) and (10), which are obtained by carrying out the fast Fourier transform of first and second images (7) and (8) detected at two focus positions of a first focus position (f1) and a second focus position (f2) shifted from the first focus position by a known focus shifted quantity Δf, to obtain a measured divided quantity Rexp; divided quantity data (12) previously prepared and stored as a function of focus positions and spatial frequencies as a set of theoretical divided quantities, the theoretical divided quantities being obtained by substituting the two focus positions shifted by the focus shifted quantity Δf for an image transfer function (r,f) to obtain first and second transfer function values K(r;f) and (r;f+Δf) to mutually divide the firs…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.