Figure 3-5 A black-and-white picture (A) reconstructed from 12 projections with Convolution (B), ART (C) and Density Modulation (D). The original picture was a 120x120 matrix, and in order to perform a complete reconstruction it would have been necessary to work with 120 projections in a full 180° angular range.

MRM: the family of the memory algorithms

One of the interesting features of Density Modulation is that the reconstructions of “black and white” pictures (Figure 3-5) contain less errors than those obtained with “gray” (or chiaroscuro) pictures, i.e. with pictures which have intermediate degrees of density (Figure 3-6). This is understandable, because in black and white images all points are either minima or maxima, and the number of vortices is potentially very high.