The process of digital halftoning replaces a visually
continuous-tone image with a binary image. This procedure must be accomplished in such a way as to give the illusion of multiple gray levels while introducing a minimum amount of artifacts or structure
not present in the original continuous-tone image. In this investigation, nonperiodic noise patterns that were uniformly distributed, so as to maintain good continuous-tone reproduction, were generated and used as random halftone screens. The noise patterns also had a prescribed two-dimensional spatial correlation, chosen in an attempt to reduce the undesirable artifacts normally introduced by the halftone process. Noise that has a correlation such that its spectrum is lacking low-frequency power is sometimes referred to as "blue noise." An iterative method of generating random correlated noise patterns is described, and some examples of the resulting halftoned images are presented.