Fig. 1.

Schematic drawing that shows how points within an object are imaged with a constantly changing value of defocus as the object is rotated. It is assumed that the center of the object is the only exception, i.e. the central point is always imaged with the same amount of defocus. An asterisk indicates the position of one such voxel, located a distance R from the center of the object. Faint, dotted lines indicate the Z-height locations of the voxel in question and the center of the object, for a given radial position of the voxel and a given rotation of the object.