Light Scanning Device Dot Displacement Correction
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Solution Overview
Problem
Conventional electrophotographic image forming apparatuses face challenges in maintaining image density uniformity due to dot displacement in the main scanning direction, caused by vibrations and other factors, which affect the quality and resolution of the output.
Innovation Solution
The apparatus incorporates a light scanning device with a plurality of light-emitting portions arranged at a predetermined angle, a polygon mirror for scanning light beams, and a control portion that adjusts the timing of light emission based on evaluation charts to correct dot displacement, using first and second evaluation patterns with specific dot row arrangements to detect and correct density differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a multi-beam laser is used to increase image output speed and resolution, then productivity and manufacturing precision are improved, but dot displacement occurs due to vibrations and conveying system irregularities, degrading image quality
Solution Approach 1:
The patent applies preliminary action by forming evaluation charts before actual image formation to detect dot displacement characteristics. The control portion uses these pre-detected characteristics to adjust light emission timing in advance, ensuring accurate dot positioning during subsequent image formation operations.
Solution Approach 2:
The patent implements feedback by detecting actual dot positions through evaluation charts and using this information to adjust the light emission timing. The control portion compares detected dot positions with expected positions and modifies the emission timing accordingly, creating a closed-loop control system that continuously corrects dot displacement.
2Manufacturing precision
If dot displacement detection and correction mechanisms are added, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The patent applies universality by using the same light scanning device and control portion for both evaluation chart formation and actual image formation. The control portion performs multiple functions: it controls light emission timing, detects dot displacement through evaluation charts, and adjusts timing based on detection results, thereby reducing the need for separate dedicated components.
Solution Approach 2:
The system applies self-service by using the evaluation chart formation process itself to detect dot displacement characteristics. The control portion utilizes the existing light scanning and developing mechanisms to create evaluation charts that automatically reveal positioning errors, eliminating the need for separate detection equipment.
3Measurement precision
If evaluation charts with specific dot row arrangements are used, then measurement precision of dot displacement is improved, but the complexity of chart formation and data processing increases
Solution Approach 1:
The patent applies segmentation by dividing the evaluation chart into multiple evaluation patches, each containing first and second dot rows with specific spatial relationships. This segmented structure allows the control portion to analyze dot displacement locally within each patch, making the detection process more manageable and the characteristics easier to identify and process.
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 effectively corrects dot displacement, ensuring higher image density uniformity and accuracy in image formation, allowing for improved resolution and quality by adjusting light emission timing based on detected density differences.
Implementation Method 1
a polygon mirror which deflects and scans light beams emitted from the light-emitting portions
Implementation Method 2
uses the light beams to form an electrostatic latent image on an image carrying member
Implementation Method 3
The developing portion forms a toner image by visualizing the electrostatic latent image
Data Source
AI summary
An image forming apparatus includes a light scanning device, a developing portion, a control portion and a storage portion. An evaluation chart includes a first evaluation pattern and a second evaluation pattern. The first evaluation pattern includes a first patch row. The first patch row is formed by arranging a plurality of first evaluation patches. The first evaluation patch includes a first dot row and a second dot row. The second evaluation pattern includes a second patch row. The second patch row is formed by arranging a plurality of second evaluation patches.