Spread functions and modulation transfer functions of fibre-optic bundles

This paper discusses the modulation transfer functions and line spread functions of fibre-optic bundles. In particular, attention is drawn to a description of the discrete or sampled nature of the imaging process, which is used to derive an explicit relationship between image and object, valid for a limited set of circumstances where the `long-slit' approximation is inapplicable. This relationship is further used to explore the combination of bundles in tandem and is able (unlike a theory based on the usual concept of MTF) to account for the physically obvious fact that a second bundle in exact registration with the first has ideally no effect on the image. The status of the spatially averaged or `long-slit' LSF is discussed, and examples are calculated for square and circular fibres.