Overlap Control for Line Head Streaking
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Solution Overview
Problem
Conventional image forming apparatuses with long line heads face high manufacturing costs, low production yields, and reliability issues, and the overlap region between short heads can cause image quality degradation due to misalignment and defective ejection of recording material, leading to noticeable streaky irregularities.
Innovation Solution
An image forming apparatus with a line head formed by multiple short heads having an overlap region, where the ejection share rates of recording elements are gradually adjusted to minimize misalignment and defective ejection, using a controller to identify and compensate for defective nozzles and optimize ejection rates across the overlap area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple short heads are disposed in the main scanning direction to form a long head, then manufacturing cost is reduced and reliability is improved, but misalignment between short heads causes deviation of landing point and impairs image quality in the overlap region
Solution Approach 1:
The patent changes the ejection rate parameter of recording elements in the overlap region to compensate for misalignment. By gradually changing the ejection rate from one short head while correspondingly changing the ejection rate of the other short head, the landing point deviation is compensated, resolving the contradiction between using multiple short heads for reliability and maintaining manufacturing precision.
2Manufacturing precision
If ejection rate is gradually changed in the overlap region to reduce landing point deviation, then image quality is improved, but ejection defective recording elements cannot eject recording material properly, impairing image quality in the corresponding area
Solution Approach 1:
The patent extracts or identifies defective recording elements from the overlap region and excludes them from the gradual ejection rate change process. By detecting defective elements and preventing them from being subjected to ejection rate modulation, the patent avoids exacerbating their ejection problems while still applying the compensation strategy to functional elements, thus resolving the contradiction between improving alignment precision and maintaining ejection reliability.
3Manufacturing precision
If ejection share rates are gradually changed to compensate for misalignment, then landing point deviation is reduced, but the region with gradually changing rates may be small, causing steep rate changes and noticeable streaky irregularities
Solution Approach 1:
The patent performs preliminary detection of defective recording elements before applying the gradual ejection rate change strategy. By pre-identifying defective elements and adjusting the overlap region boundaries accordingly, the patent ensures that the gradual change region is optimally sized and positioned, preventing both excessive steepness and noticeable streaky irregularities while maintaining effective compensation for functional elements.
Data Source
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AI summary
Provided is an image-forming apparatus that limits reductions in image quality such as streaking even when print element discharge failure occurs in the overlap region (ab) of short heads (150A, 150B) that configure a long head. In the overlap region (ab), among multiple overlap areas (R1, R2, R3) configured from rows of consecutive print elements that do not comprise print elements that have been specified as discharge failure print elements (N1, N2), the overlap area (R2) with the largest number of overlapping print elements is specified. When the number of print elements in said overlap area (R2) is greater than a fixed number (Z), an overlap control for gradually changing the discharge apportionment for the fixed number (Z) of print elements in each short head (150A, 150B) is performed. Since the discharge failure of the print element (N1) is present in an area in which the short head (150A) print apportionment is 100%, the discharge failure is supplemented by, for example, increasing the discharge amounts of the adjacent print elements (a07, a09). But because the discharge failure of the print element (N2) is present in an area in which the short head (150B) print apportionment is 0%, supplementation is not performed.