Random printmasks in a multilevel inkjet printer

Abstract

One form of the printer inks multiple tonal levels, as for continuous-tone images. A generally randomized printmask controls the printer. What is randomized is, for each pixel respectively, an indicator of whether to print or not. Each indicator is, preferably, a discriminator number for comparison with desired-image data--specifically with a desired tonal level, at each pixel, for the desired color image--to make each printing decision. Preferably the printer is thereby deciding whether to deposit a certain number of drops per pixel; it compares the discriminator with a particular number of desired drops, for the desired image. The discriminator at each pixel is in general different for multiple passes and these discriminators for the passes form a sequence. The sequence, for each pixel., is preferably selected at random from a multiplicity of sequences. Preferably the sequence for each pixel is preselected at random; and the selected sequences for all pixels are prestored in nonvolatile memory. To do this, preferably each sequence is numbered and the sequence for each pixel is selected by randomly selecting a sequence number. Another preferred form of the printer is not necessarily multilevel but the sequences are selected as just described. A method is included for initial construction, and storage on a tangible medium, of the sequences--and later recall and use.