Direct Binary Search (DBS) algorithm with constraints Kartheek Chandu † , Mikel Stanich † , Chai Wah Wu * and Barry Trager * † Ricoh Production Print Solutions, LLC, 6300 Diagonal Highway, Boulder, CO 80301, USA * IBM T. J. Watson Research Center, P. O. Box 218, Yorktown Heights, NY 10598, USA ABSTRACT In this paper, we describe adding constraints to the Direct Binary Search (DBS) algorithm. An example of a useful constraint, illustrated in this paper, is having only one dot per column and row. DBS with such constraints requires greater than two toggles during each trial operation. Implementations of the DBS algorithm traditionally limit operations to either one toggle or swap during each trial. The example case in this paper produces a wrap-around pattern with uniformly distributed ON pixels which will have a pleasing appearance with precisely one ON pixel per each column and row. The algorithm starts with an initial continuous tone image and an initial pattern having only one ON pixel per column and row. The auto correlation function of Human Visual System (HVS) model is determined along with an initial perceived error. Multiple operation pixel error processing during each iteration is used to enforce the one ON pixel per column and row constraint. The constraint of a single ON pixel per column and row is used as an example in this paper. Further modification of the DBS algorithm for other constraints is possible, based on the details given in the paper. A mathematical framework to extend the algorithm to the more general case of Direct Multi-bit Search (DMS) is presented. Keywords: Direct Binary Search, DBS, Halftone, Inkjet printing, flushing 1. INTRODUCTION In recent years, inkjet printing technology has enabled use of printing as a manufacturing fabrication technique to create displays, solar panels, electronic boards, human organs and 3-D lithographic printing. 1 Along with this evolution, inkjet printing also has brought new trends in business and commercial printing. This include wide format printers, ultra-high speed production printers, digital textile printers, and packaging related applications. Many present high speed production inkjet printers employ fixed-array printheads, capable of printing on paper webs greater than 20 inches wide. The fixed-array system is constructed from multiple printhead mod- ules which are stitched together edge-to-edge. The array remains stationary while the media moves past the printheads, creating a printing process capable of operating at thousands of feet per minute. Previously, each printhead module in the fixesd-array contained hundreds of nozzles and could print less than one-inch width. Printheads wider than one-inch are now being used, having thousands of nozzles. A significant problem with inkjet printheads is clogging of nozzles and the greater the number of nozzles in a printhead the larger the prob- lem becomes. Factors which influence clogging include drying of ink in the nozzle, accumulated paper dust at the nozzle plate, increase in ink viscosity, and intrusion of air bubbles. Any of these factors can stop a nozzle from functioning creating a “jet out”, which results in no data being printed by that nozzle. The artifact produced by a jet out is a white streak on the printed output. Clogged nozzles in some cases may be recovered by cleaning. If a clogged nozzle is left uncleaned for a prolonged period of time, there will be only a small probability of recovering that nozzle. In addition clogging may propagate, leading to clogging of its neighboring nozzles. A single clogged nozzle might require replacement of the entire fixed-array printhead, depending on configuration of the individual printhead modules. Over a wide range of print jobs, sheet content alone is not adequate to keep the nozzles from clogging. While variable data printing will have different content on every sheet, nozzles at the edges or between pages may be used infrequently or not at all. Monochrome printing, employing on the black channel, may similarly cause Further author information: K.C.: E-mail: kartheek.chandu@ieee.org, Telephone: 1 720 663 3621 C.W.W.: E-mail: chaiwahwu@ieee.org, Telephone: 1 914 945 1567 Color Imaging XVIII: Displaying, Processing, Hardcopy, and Applications, edited by Reiner Eschbach, Gabriel G. Marcu, Alessandro Rizzi, Proc. of SPIE Vol. 8652 86520K · © 2013 SPIE-IS&T · CCC code: 0277-786X/13/$18 · doi: 10.1117/12.2002554 SPIE-IS&T/ Vol. 8652 86520K-1