Image Forming Apparatus Density Unevenness Correction
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Solution Overview
Problem
Existing image forming apparatuses face challenges in accurately correcting density unevenness in the main scanning direction of output images due to variations in temperature, humidity, and other environmental factors, as well as performance degradation and sensitivity issues, leading to suboptimal correction results.
Innovation Solution
An image forming apparatus that includes a photosensitive member, charging, exposure, and developing units, along with an image processing unit and a controller, which forms and reads pattern images to generate conversion conditions for each position in the main scanning direction, allowing for precise correction of density unevenness by deriving appropriate conversion coefficients based on measured density distributions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single density pattern is used for correction, then the correction process is simple, but the correction accuracy is insufficient
Solution Approach 1:
The patent divides the correction process into multiple segments by using three different density patterns (first, second, and third pattern images) instead of a single pattern. Each pattern provides different measurement information, and their combined results achieve high-precision correction while maintaining a systematic and manageable correction process.
Solution Approach 2:
The patent changes the parameters of the density patterns by using three different patterns with varying characteristics. This allows measurement of density unevenness under different conditions, enabling more accurate derivation of correction values that account for various factors affecting image density.
2Measurement precision
If multiple density patterns are used to improve correction accuracy, then measurement precision improves, but the device complexity increases
Solution Approach 1:
The patent makes the image forming unit universal by enabling it to perform both normal image formation and pattern image formation functions. The same charging unit, exposure unit, and developing unit are used for both purposes, eliminating the need for separate dedicated measurement equipment and reducing overall system complexity.
Solution Approach 2:
The image forming apparatus performs self-measurement and self-correction by using its own image forming capabilities to create density patterns, measure the resulting density unevenness, and derive correction values. This self-service approach eliminates the need for external measurement devices and simplifies the overall system architecture.
3Measurement precision
If correction values are derived from single pattern measurement, then processing is fast, but correction precision is insufficient
Solution Approach 1:
The patent performs preliminary measurements using three different density patterns before final correction value derivation. This preliminary action gathers comprehensive data about density unevenness characteristics, enabling more accurate correction while the systematic approach ensures efficient processing through predefined measurement and calculation procedures.
Solution Approach 2:
The patent implements a feedback mechanism where the reading unit measures the actual density of formed patterns, and the controller uses these measurements to derive correction values that are then applied to subsequent image formation. This closed-loop feedback ensures high correction accuracy while maintaining efficiency through automated iterative adjustment.
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 approach enables high-precision suppression of density unevenness in the main scanning direction, ensuring accurate image formation by adjusting the conversion coefficients according to the tone characteristic of the printer and the type of sheet used, thereby improving correction accuracy and consistency.
Implementation Method 1
a charging unit configured to charge the photosensitive member
Implementation Method 2
an exposure unit configured to expose the photosensitive member charged by the charging unit to form an electrostatic latent image on the photosensitive member
Implementation Method 3
a developing unit configured to develop the electrostatic latent image on the photosensitive member
Data Source
AI summary
In an image forming apparatus, an image processing unit converts image data based on a plurality of conversion conditions corresponding to a plurality of positions in a predetermined direction. A controller controls an image forming unit to form an image based on the image data converted by the image processing unit, and controls the image forming unit to form a plurality of pattern images including first, second and third pattern images. The controller controls a reading unit to read the plurality of pattern images on the sheet, generates correction conditions corresponding to the plurality of positions in the predetermined direction based on a reading result of the reading unit, and generates the plurality of conversion conditions based on the reading result and the correction conditions corresponding to the plurality of positions in the predetermined direction.