A quantitative computer simulation of microscopic imaging

SUMMARY A versatile program is described for a BBC‐ or IBM‐compatible microcomputer, which uses a fast Fourier transform in calculating diffraction‐limited microscopic images. The defined ‘object’ can be a diffraction grating or a discrete specimen seen in cross‐section, of arbitrary interval (or width), transmittance and retardation. Many microscopical techniques can be simulated including bright‐field, phase contrast, central and peripheral dark‐field, schlieren, apodization, fluorescence, differential interference contrast and confocal scanning. Instrumental settings which can be varied include the aperture, focus and primary spherical aberration of the objective, the coherence and obliquity of the illumination, and in phase contrast the width, transmittance and retardation of the phase plate. The Fourier transform and various other algorithms used in the program are explained.