Inkjet Head Gradation Control for Density Banding
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Solution Overview
Problem
Ink jet recording apparatuses experience density irregularities and gloss banding due to the staggered arrangement of recording heads, leading to uneven ink distribution and image quality issues, particularly in bi-directional printing and overlapping regions.
Innovation Solution
A liquid discharging apparatus with a head unit arranged in the main scanning direction, featuring a moving unit for alternating scanning operations and a gradation setting unit that adjusts the printing ratio to increase the center printing ratio and decrease the end printing ratio, using a pattern that sets gradation for each head array to minimize banding and density irregularities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If recording heads are arranged in a staggered configuration to cover the entire recording medium width, then the printing coverage is improved, but density irregularities and gloss banding occur in overlapping regions
Solution Approach 1:
The patent applies local quality by setting different printing ratios for different regions of the head array. Specifically, the central region of each head array has a higher printing ratio (100%) while the end regions have lower printing ratios (0% or reduced), creating a gradient distribution that prevents overlapping density issues while maintaining full coverage.
Solution Approach 2:
The patent changes the printing ratio parameter across different regions of the head array. By varying the printing ratio from 100% in the center to 0% at the ends, and adjusting these ratios based on the number of heads and their overlap patterns, the system achieves uniform image density while preventing gloss banding in bi-directional printing.
2Ease of operation
If the printing ratio is uniformly set across all heads, then the control simplicity is maintained, but gloss banding occurs due to overlapping in bi-directional printing
Solution Approach 1:
The patent introduces local quality variations in the printing ratio across different head arrays and regions. The gradation setting unit assigns different printing ratios to central and end regions of head arrays, and adjusts these ratios based on the head array index, thereby preventing gloss banding while maintaining systematic control.
Solution Approach 2:
The patent makes the printing ratio dynamic by adjusting it based on the head array index and the total number of head arrays. The printing ratio for end regions is calculated as a function of the head array position, creating an adaptive control system that prevents gloss banding in bi-directional printing while maintaining simplicity in unidirectional printing.
3Manufacturing precision
If the end printing ratio is reduced to eliminate density irregularities, then the density uniformity is improved, but the overall productivity decreases due to reduced printing coverage
Solution Approach 1:
The patent applies local quality by reducing the printing ratio only at the end regions of head arrays while maintaining 100% printing ratio in the central regions. This localized adjustment eliminates density irregularities in overlapping areas without significantly reducing the overall printing coverage and productivity.
Solution Approach 2:
The patent uses partial action by applying the reduced printing ratio only to the end regions of head arrays rather than uniformly across all regions. This partial reduction is sufficient to prevent density irregularities and gloss banding while minimizing the impact on overall printing efficiency.
Data Source
AI summary
A liquid discharging apparatus includes a head unit arranged in a main scanning direction includes head arrays each having nozzles discharging liquid are arranged in a sub scanning direction, a moving unit that alternately performs a main scanning operation while discharging the liquid and a sub scanning operation causing the head unit or the recording medium to move in the sub scanning direction without discharging the liquid, and a gradation setting unit that sets a first pattern setting a gradation to increase a center printing ratio at a center and decrease an end printing ratio at both ends for a whole area of the head array in the sub scanning direction and a second pattern in which a gradation is set so as to increase the printing ratio setting a gradation to increase the center printing ratio and decrease the end printing ratio for an arbitrary number of the heads.