Downing Kenneth H, Glaeser Robert M
Lawrence Berkeley National Laboratory, University of California, Berkeley CA 94720, USA.
Lawrence Berkeley National Laboratory, University of California, Berkeley CA 94720, USA.
Ultramicroscopy. 2018 Jan;184(Pt A):94-99. doi: 10.1016/j.ultramic.2017.08.007. Epub 2017 Aug 19.
The extent to which the resolution varies within a three-dimensional (3-D) reconstruction, when the diameter of an object is large, is investigated computationally. Numerical simulation is used to model ideal three-dimensional point-spread functions at different radial positions within an object. It is shown that reconstructed density maps are affected less than might have been expected when particles are larger than the depth of field. This favorable outcome is attributed mainly to the fact that a point which lies outside the depth of field relative to the center, for some orientations of the object, will also lie within the depth of field for other orientations. We find, as a result, that the diameter of a particle can be as much as four times the depth of field (as defined by a 90° phase-error criterion) before curvature of the Ewald sphere becomes a limiting factor in determining the resolution that can be achieved.
当物体直径较大时，通过计算研究了三维（3-D）重建中分辨率在多大程度上变化。数值模拟用于对物体内不同径向位置的理想三维点扩散函数进行建模。结果表明，当粒子大于景深时，重建的密度图受到的影响比预期的要小。这一有利结果主要归因于这样一个事实，即对于物体的某些取向，相对于中心位于景深表之外的点，对于其他取向也将位于景深表之内。因此，我们发现，在埃瓦尔德球的曲率成为确定可实现分辨率的限制因素之前，粒子的直径可以达到景深（由90°相位误差标准定义）的四倍之多。
