Halftone Dot Matrix With Rotated Dot Centers

Solution Overview

Problem

Existing halftone dot image generation techniques suffer from moire and graininess issues, particularly in AM and FM screening methods, where random or stochastic distribution of dot centers leads to uneven dot joining and concentration, resulting in undesirable printed matter quality.

Innovation Solution

A method involving the alternate arrangement of highlight-side and shadow-side dot centers at regular intervals, with rotation around reference points to adjust dot areas based on gray level variations, improving uniformity and reducing moire and graininess by determining threshold values that change halftone dot areas accordingly.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If dot centers are arranged randomly to reduce moire, then moire is suppressed, but graininess arises due to great variation in distance between adjacent dot centers causing uneven dot joining

Engineering Contradiction:

ImprovemoireVSAvoidgraininess

Core Design Contradiction:

Object-affected harmful factorsVSObject-generated harmful factors

Solution Approach 1:

The patent applies local quality by differentiating the arrangement of highlight-side dot centers and shadow-side dot centers. Highlight-side dot centers are arranged to minimize distance variation for uniform joining, while shadow-side dot centers are stochastically distributed to suppress moire. This localized differentiation of arrangement strategies resolves the contradiction between preventing moire and avoiding graininess.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent employs asymmetry by treating highlight-side and shadow-side dot centers differently in terms of their arrangement patterns. Instead of using a uniform random arrangement for both types, the invention uses asymmetric arrangement strategies: regular intervals for highlight-side and stochastic distribution for shadow-side, thereby optimizing each region's contribution to image quality.

Inventive Principle:

Principle #4Asymmetry

2Manufacturing precision

If shadow-side dot centers are arranged regularly around highlight-side dot centers, then dot joining is uniform, but moire arises due to periodic structure

Engineering Contradiction:

Improvedot joining uniformityVSAvoidmoire

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The patent applies local quality by differentiating the arrangement of highlight-side dot centers and shadow-side dot centers. Highlight-side dot centers are arranged to minimize distance variation for uniform joining, while shadow-side dot centers are stochastically distributed to suppress moire. This localized differentiation of arrangement strategies resolves the contradiction between preventing moire and avoiding graininess.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent uses the highlight-side dot centers as intermediary elements that structure the overall pattern, while shadow-side dot centers fill the spaces between them in a stochastic manner. This intermediary arrangement allows the highlight-side dots to provide structural regularity for uniform joining, while the shadow-side stochastic distribution breaks periodicity to suppress moire.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS7471421B2Method of generating threshold matrix and recording medium storing data of threshold matrix

Publication Date: 2008.12.30 SCREEN HOLDINGS CO LTD

AI summary

In a matrix area (720), a plurality of highlight-side dot centers (731) and a plurality of shadow-side dot centers (741) are regularly arranged and a plurality of reference points (751) are set while being distributed almost uniformly. Each of the dot centers (731, 741) is rotated about a nearest reference point (751). Threshold values of the matrix area (720) are determined so that halftone dot areas should be changed around a plurality of highlight-side dot centers (731) after being rotated in accordance with the variation in gray level on the highlight side and a halftone dot area (i.e., joined dot areas) should be changed around a plurality of shadow-side dot centers after being rotated in accordance with the variation in gray level on the shadow side. In a halftone dot image generated by using the matrix area which is thus generated, it is possible to suppress moire and graininess.