Whenever the subject being reproduced has a regular pattern, the conventional type of halftone screen, because of its regular structure, may produce an objectionable beat pattern, called moiré. In multicolor printing, the regular patterns of the several structured images produce complex beat patterns whose effects are minimized, but not eliminated, through proper choice of screen angles. This paper describes a procedure in which a continuous-tone image is scanned; and the resulting photo-tube signal is used to actuate a light valve in such a manner as to produce a structured image containing dots that are, in effect, distributed at random. It is shown that this procedure avoids both the distortions in tone reproduction and the moiré patterns associated with the conventional use of halftone screens.
ARTHUR C. HARDY and F. L. WURZBURG, JR., "A Photoelectric Method for Preparing Printing Plates1," J. Opt. Soc. Am. 38, 295-295 (1948)