Image Density Correction for Cyclic Variations in Long Sheet Printing
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Solution Overview
Problem
Conventional electrophotographic image forming apparatuses face challenges in maintaining constant image quality when forming images continuously on long sheets due to cyclic density variations caused by rotational runout of photoconductors and developer bearing members, leading to uneven image density.
Innovation Solution
An image forming apparatus and method that includes a sheet conveyance section, an image forming section with a photoconductor and developer bearing member, a density unevenness cycle acquiring section, a cycle control section, and a density correction section, which acquires and adjusts the image length to match the density profile cycle, forms a patch image for correction, and creates correction data based on detected density to offset density variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If images are continuously formed on long sheets without periodic density profile acquisition, then productivity is improved, but manufacturing precision deteriorates due to density profile changes over time
Solution Approach 1:
The patent implements periodic density profile acquisition by forming patch images at regular intervals during continuous production. The control section periodically creates correction data by detecting density variations in patch images, ensuring that density correction remains accurate even during continuous long-sheet printing operations without stopping production.
2Device complexity
If correction data is created based on initial density profile only, then device complexity is reduced, but manufacturing precision deteriorates when density profile changes with time
Solution Approach 1:
The patent establishes a feedback mechanism where density variations detected from patch images formed during continuous printing are fed back to the control section. The control section creates updated correction data based on this feedback, ensuring that density correction remains accurate throughout continuous production by adapting to actual density profile changes.
3Productivity
If patch image size is smaller than density profile cycle, then productivity is improved, but measurement precision deteriorates in detecting density variations
Solution Approach 1:
The patent forms patch images with dimensions specifically designed to cover at least one complete cycle of the density profile in the sub-scanning direction. This ensures that each patch image captures sufficient density variation information for accurate correction data creation, while the patch images are positioned strategically to minimize impact on overall printing productivity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution efficiently corrects cyclic density variations in the sub scanning direction, ensuring consistent image quality across continuous images on long sheets by synchronizing image length with the density profile cycle and using correction data for precise density adjustment.
Implementation Method 1
irradiate (expose) a uniformly-charged photoconductor (for example, a photoconductor drum) with (to) light based on image data to form an electrostatic latent image on the surface of the photoconductor
Implementation Method 2
The electrostatic latent image is then visualized by supplying toner from a developing device to the photoconductor on which the electrostatic latent image is formed
Implementation Method 3
the toner image is directly or indirectly transferred to a sheet through an intermediate transfer belt, followed by heating and pressurization for fixing at a fixing section
Data Source
AI summary
An image forming apparatus includes: an image forming section including a rotational member and configured to form an image on the long sheet; a density unevenness cycle acquiring section configured to acquire a cycle of a density profile that represents density variation in a sub scanning direction; a cycle control section configured to operate such that, in a case where a same image is continuously formed on the long sheet, a length of the image in the sub scanning direction is an integer multiple of a cycle length that corresponds to one cycle of the density profile; and a density correction section configured to form a patch image for correction that has a size greater than the cycle length of the density profile on the image bearing member, and perform density correction using correction data created based on a detection result regarding the patch image for correction.