The AM halftoning is the most commonly used digital halftoning method in current color image printing. In its application, the most key issue is to select the appropriate screen angle to avoid producing Moiré fringe. As we all know, the strength of the Moiré fringe varies with the change of overlap angle of two halftone image. Its rules follow the Tollennaar formula. However, in our research, we find that the Tollennar Moiré formula is correct only when screening line n1 equals to screening line n2. When the difference between n1 and n2 is much, the Moiré curve based on the observation data does not accord with the Tollenaar Moiré formula, many new phenomena and rules are found out. Such as, when the overlap angle is near to 0°, the strength value of Moiré fringe is not divergent but convergent. We also find out that when the value of n1 is bigger than n2 to 15 and the overlap screen angles from 20° to 30°, the Moiré fringe becomes the weakest. By researching the above phenomena and rules, many special issues in halftone image duplication can be solved.
Chen Guang-xue, Chen Qi-feng, "Study on the Phenomena of Moiré Fringe in Digital Halftoning" in Proc. IS&T Int'l Conf. on Digital Printing Technologies and Digital Fabrication (NIP25), 2009, pp 334 - 336, https://doi.org/10.2352/ISSN.2169-4451.2009.25.1.art00093_1