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Design of an Objective Lens with Minimum Chromatic Aberration Coefficient
Published online by Cambridge University Press: 02 July 2020
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The Schelzer resolution is defined as the highest spatial frequency which is transferred into the image with the same phase as all lower frequencies. The resolution of the information limit is, however, determined by the information from the specimen which is equal to the degree of noise. The Schelzer resolution is determined by the wave length and the spherical aberration coefficient Cs of the objective lens. It reached 0.1 nm at 1250 kV. The limit of the resolution has been calculated numerically and it is written as d = 4.65(BsVr)−1/4 (nm), where Bs (in T) is the saturation magnetic flux density of the pole-piece material and Vr the relativistically corrected accelerating voltage. The resolution of the information limit is determined by the axial chromatic aberration coefficient Cc and incoherent effects such as the finite size of the source, beam divergence, energy spread, instabilities of the high voltage and lens current. The limit of the resolution is not clear. Most of the objective lenses of commercial microscopes are designed to optimize Cs rather than Cc. In this investigation, however, we describe the limit of Cc for 200 kV microscopes.
- Type
- Advances in Instrumentation for Microanalysis and Imaging
- Information
- Microscopy and Microanalysis , Volume 3 , Issue S2: Proceedings: Microscopy & Microanalysis '97, Microscopy Society of America 55th Annual Meeting, Microbeam Analysis Society 31st Annual Meeting, Histochemical Society 48th Annual Meeting, Cleveland, Ohio, August 10-14, 1997 , August 1997 , pp. 1083 - 1084
- Copyright
- Copyright © Microscopy Society of America 1997
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