Narrow band, anisotropic stochastic halftone patterns and methods of creating and using the same
Assignee3M Innovative Properties Company
InventorRichard L. Rylander
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Abstract
A stochastic halftone pattern has been invented which has a narrow band power spectrum due to the incorporation of a dot growth process. The narrow band power spectrum may be matched to the resolution characteristics of specific printers, resulting in smoother printed halftone textures. The spectrum of a halftone pattern may be made anisotropic (angularly dependent), helping to de-couple sets of patterns for color printing with reduced color noise or mottle.
Claims29
A halftone pattern having a power spectrum which has a low spectral energy level at low frequencies, a high spectral energy level at frequencies corresponding to mid-tone ranges, and a low to moderate level at high frequencies, and wherein the peak energy level of the spectrum corresponds to a mean dot-to-dot distance just above the minimum spot size of the imaging engine with which the halftone pattern is to be used.
A halftone pattern having a power spectrum which has a low spectral energy level at low frequencies, a high spectral energy level at frequencies corresponding to mid-tone ranges, and a low to moderate level at high frequencies, and wherein the halftone pattern is anisotropic.
A method of creating a halftone mask for use in generating halftone images for use with an imaging engine which represents images using a plurality of spots, the method comprising:
- a) define a threshold matrix comprising a plurality of elements;
- b) arbitrarily select a first one of the elements and assign it the lowest or highest ranked threshold value for the matrix;
- c) select a next one of the elements by identifying the element having the minimum accumulated bias relative to all other elements previously selected, where the minimum accumulated bias is determined according to a formula which limits the minimum mean dot-to-dot spacing before existing dots start to grow, and assign such next element the next lowest or highest ranked threshold value for the matrix;
- d) repeat step (c) until all elements have been assigned a threshold value, thereby generating a matrix of elements, each having an assigned value, which matrix can serve as a halftone mask screen pattern.
Dependencies are inferred from the claim text.