Improved high resolution image processing of bright field electron micrographs: I. Theory

Abstract

Two new improved methods of computer image reconstruction are presented. The well known MAP method of image reconstruction is generalized to include reconstruction of a single (higher resolution) image from multiple observations of the object with different imaging conditions. The resolution of the input images is assumed to be determined by the aberrations of the optical system. The first method involves an approximate form of partial coherence that allows the use of fast Fourier transforms (FFT's) to reduce the required computer time. The second method uses the more rigorous transmission cross-coefficient description of partial coherence. Although both methods have applications in both electron and light optical imaging, the discussion presented here is directed towards the reconstruction of the phase and amplitude of the specimen transmission function from a defocus series of high resolution bright field conventional transmission electron micrographs of radiation-damage-resistant specimens. This is the first of a two-part report. The theory is presented in this part and the experimental results of applying these methods to actual 500 keV micrographs will be presented in the second part of this report.