LED Array Density Correction for Image Forming Apparatus
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Solution Overview
Problem
Electrophotographic image forming apparatuses face issues with uneven image density in the main scanning direction due to variations in the light source, leading to vertical stripes and degraded image quality.
Innovation Solution
An image forming apparatus with a plurality of lighting elements aligned in the main scanning direction, which forms test images to acquire density data, calculates correction data to adjust the light amount of each lighting element, and iteratively corrects the light amount based on density data from sub-areas to achieve uniform image density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single light source is used for exposure, then the device structure is simple, but image density becomes uneven in the main scanning direction causing vertical stripes
Solution Approach 1:
The exposure device is divided into multiple independent lighting elements (LEDs) arranged in the main scanning direction. Each lighting element can be independently controlled to emit light, allowing separate adjustment of light amount for each element. This segmentation enables correction of density unevenness by individually adjusting the light output of each LED based on measured density data, thereby eliminating vertical stripes while maintaining a relatively simple overall device structure.
2Manufacturing precision
If light amount of lighting elements is adjusted to correct density unevenness, then image density uniformity is improved, but the correction process becomes complex requiring multiple test images and iterative calculations
Solution Approach 1:
The system performs preliminary correction by forming a first test image, measuring its density distribution, and calculating correction data for each lighting element before normal operation. This preliminary action establishes baseline correction values that are stored and applied during subsequent imaging operations, avoiding the need for complex real-time adjustments while achieving density uniformity.
Solution Approach 2:
The system uses a feedback mechanism where density data from the first test image is fed back to calculate correction data, which is then applied to adjust the light amount of each lighting element. This closed-loop feedback process enables automatic correction of density unevenness without requiring complex manual intervention or multiple iterative test images during normal operation.
3Measurement precision
If multiple test images are formed for correction, then correction precision is improved, but productivity decreases due to additional imaging and processing time
Solution Approach 1:
The system performs density measurement and correction data calculation as a preliminary action during device setup or maintenance periods, not during normal image formation operations. The first test image is formed and analyzed in advance to establish correction values that are then stored for use during high-speed normal operation, thus achieving precise density measurement without compromising productivity during actual work.
Solution Approach 2:
The system performs a single comprehensive correction using the first test image rather than multiple incremental corrections. By forming one test image and calculating complete correction data for all lighting elements based on its density distribution, the system achieves sufficient correction precision without the time penalty of multiple test images and iterative adjustments.
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
The solution effectively corrects density unevenness in the main scanning direction, eliminating vertical stripes and ensuring consistent image quality by iteratively adjusting the light amount of the lighting elements based on calculated correction data.
Implementation Method 1
an exposure device including a plurality of lighting elements (LEDs) arranged in a main scanning direction
Implementation Method 2
An optical writer irradiates the surface of the photoconductor thus charged with a light beam to form an electrostatic latent image on the surface of the photoconductor according to the image data
Implementation Method 3
The reader is configured to read the first test image
Data Source
AI summary
An image forming apparatus includes circuitry, a reader, and an exposure device that drives lighting elements aligned in a main scanning direction to form a first test image. The circuitry acquires density of first sub-areas, into which the first test image is divided in the main scanning direction, and calculates first correction data based on density of each of the first sub-areas and average density of the first sub-areas, to correct light amounts of the lighting elements. The exposure device forms a second test image with the light amounts corrected. The circuitry acquires density of second sub-areas, into which the second test image is divided in the main scanning direction, and calculates second correction data based on density of a second sub-area adjacent to each of the second sub-areas, to further correct the light amounts. The second sub-areas are differently located from the first sub-areas in the main scanning direction.