Facsimile Reproduction On Matrix Impact Printers
Original Publication Date: 1979-Oct-01
Included in the Prior Art Database: 2005-Feb-20
Digital halftoning is a process where variable levels of grey are generated by varying the number of dots printed in a given area of paper. It has been found that the most acceptable results are achieved by clustering the dots into an approximation to the diagonally spaced pattern of variable sized black/white dots used in conventional grey scale image printing. For practical matrix impact printers this technique leads to an unhappy compromise between the number of grey levels that can be represented and the coarseness of the perceived pattern of clusters. For instance, if 16 levels of grey are to be represented, then a cluster must be formed of from zero to 16 dots which leads to a spacing of four dot pitches between cluster centers in both directions. This corresponds to a horizontal cluster pitch of .