Inkjet Print Density Correction via Localized Dot Adjustment

Solution Overview

Problem

Existing image processing techniques struggle to reduce unevenness in spatial frequency due to variance in ejection characteristics between nozzles in a print head, particularly when the print head lacks nozzles capable of ejecting small-size dots and low-density ink.

Innovation Solution

An image processing apparatus and method that generates correction target values based on print density to adjust the number of ink dots, updating these values for both the affected region and adjacent regions to minimize dot pattern differences and achieve uniformity, regardless of the print head configuration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the number of dots is greatly changed to correct density unevenness in regions with large ejection amount variance, then density uniformity is improved, but spatial frequency unevenness increases and dot pattern differences become visually recognizable

Engineering Contradiction:

Improvedensity uniformityVSAvoidspatial frequency unevenness

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The patent applies local quality by making the correction amount variable depending on the region's ejection characteristic variance. Regions with large variance receive different correction amounts compared to regions with small variance, optimizing both density uniformity and spatial frequency characteristics for each local area

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the correction parameter (number of dots) based on the measured ejection characteristic variance. By dynamically adjusting the correction amount according to the variance magnitude, the system achieves optimal correction that prevents both density unevenness and spatial frequency unevenness

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If small-size dots and low density ink are used to reduce spatial frequency unevenness, then spatial frequency uniformity is improved, but the print head configuration requirements increase

Engineering Contradiction:

Improvespatial frequency unevennessVSAvoidprint head configuration compatibility

Core Design Contradiction:

Object-affected harmful factorsVSAdaptability or versatility

Solution Approach 1:

The patent changes the correction parameter (number of dots) based on the measured ejection characteristic variance. By dynamically adjusting the correction amount according to the variance magnitude, the system achieves optimal correction that prevents both density unevenness and spatial frequency unevenness

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses feedback from measured print density to determine correction amounts. By measuring actual print characteristics and using this information to adjust correction strategies, the system adapts to different print head configurations without requiring specific hardware modifications

Inventive Principle:

Principle #23Feedback

3Ease of operation

If correction values are generated based on predetermined target density values, then processing simplicity is maintained, but density uniformity and color uniformity deteriorate due to ejection characteristic variance

Engineering Contradiction:

Improveprocessing simplicityVSAvoiddensity uniformity

Core Design Contradiction:

Ease of operationVSManufacturing precision

Solution Approach 1:

The patent uses feedback from measured print density to determine correction amounts. By measuring actual print characteristics and using this information to adjust correction strategies, the system adapts to different print head configurations without requiring specific hardware modifications

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent performs preliminary measurement of print density and ejection characteristics before generating correction values. This preliminary action allows the system to calculate appropriate correction amounts for each region, improving both density uniformity and color uniformity while maintaining processing efficiency

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS11836554B2Image processing apparatus, image processing method, and storage medium with generation of correction target value based on print density

Publication Date: 2023.12.05 CANON KK

AI summary

A first set correction target value set for a correction target value generation region including a unit region corresponding to one or more nozzles is updated based on a difference between the first set correction target value and a print density in the unit region corresponding to the correction target value generation region. Also, a second set correction target value set for a correction target value generation region being adjacent to an updated region which is a correction target value generation region updated in the correction target value and having yet to be updated in the correction target value is updated based on a difference between the second set correction target value and the correction target value of the updated region.