The Role of the Pinhole in Confocal Imaging System

Abstract

Confocal scanning microscopes are particularly attractive by virtue of their enhanced lateral resolution, purely coherent image formation (in reflection) and optical sectioning (Wilson and Sheppard, 1984). It is probably the latter property that is most useful, as it gives rise to the ability to image a thick specimen in three dimensions. This is possible because the optical system detects information only from a thin region in the neighborhood of the focal plane. This permits us to store many image slices in a computer to give a three-dimensional (3D) data set that describes the object. Many sophisticated computer software systems are now available to display these data in various ways. Obvious examples include the extended-focus technique (Wilson and Hamilton, 1982), in which we merely add up (integrate) the images from various depths to provide an image of greatly extended depth of field. We may also produce images in which object height is coded as brightness, or combine the whole data set to provide an isometric view of the object (Fig. 1). It is also possible to use false color to label features of interest or, by simple processing, to obtain stereoscopic pairs (van der Voort, et al., 1985).