Asymmetric Digital Filter for Halftone Dot Gain

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Solution Overview

Problem

Current digital printing workflows face challenges in accurately adjusting dot-gain for halftone binary bitmaps, leading to inconsistencies between proofing and press runs, resulting in production losses and compromised print quality due to differences in RIPs, inkjet resolution limitations, and the need for time-consuming re-ripping processes.

Innovation Solution

The use of an asymmetric digital filter to adjust dot-gain by inputting a halftone binary bitmap file, filtering the pixels to generate a weighted sum, and comparing it to a preset level to produce a multi-level pixel output, thereby increasing the number of discrete dot sizes and reducing quantization errors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a symmetric digital filter is used for dot-gain adjustment, then the filtering process is simple and fast, but the number of output states is limited resulting in quantization artifacts

Engineering Contradiction:

Improvedot-gain adjustment accuracyVSAvoidfilter complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent applies asymmetry by using an asymmetric digital filter kernel where the weights are not symmetric around the center pixel. This asymmetric weighting scheme maximizes the number of unique output states from the filtering operation, thereby increasing the number of discrete dot sizes available and reducing quantization artifacts in the halftone image.

Inventive Principle:

Principle #4Asymmetry

2Adaptability or versatility

If multiple RIPs are used for proofing and plate making, then flexibility in workflow is improved, but inconsistencies in dot-gain correction occur leading to mismatch between proof and press run

Engineering Contradiction:

Improveworkflow flexibilityVSAvoiddot-gain correction consistency

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent changes the parameter of the filter kernel from symmetric to asymmetric, which fundamentally alters the filtering characteristics and maximizes output states. This parameter change enables more precise dot-gain adjustment that can be consistently applied across different RIPs, improving reliability while maintaining workflow flexibility.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If inkjet printer is used for digital proofing, then cost and accessibility are improved, but resolution limitations cause inability to accurately reproduce halftone dot structure

Engineering Contradiction:

Improveproofing accessibilityVSAvoidhalftone dot structure accuracy

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent segments the dot-gain adjustment process into multiple discrete levels by maximizing the number of output states from the asymmetric filter. This segmentation creates distinct dot size levels that can be more accurately reproduced by inkjet printers, improving the fidelity of halftone dot structure despite resolution limitations.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS7826097B2Asymmetrical digital filters for dot gain adjustments

Publication Date: 2010.11.02 EASTMAN KODAK CO

AI summary

A method for adjusting dot-gain for a halftone binary bitmap file comprises inputting a halftone binary bitmap file consisting of binary pixels (400) to an asymmetric digital filter (500). The binary pixels are filtered with the asymmetric digital filter and generates multi-level pixels (506). The multi-level pixel are compared to a preset level (408) and generates a binary pixel output (410). The binary pixel output is collected and forms an adjusted halftone binary bitmap file (270).