Image Forming Apparatus Density Correction via Dual Sensor Feedback
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Solution Overview
Problem
Existing image forming apparatuses face challenges in achieving highly accurate density correction due to density fluctuations in both the main scanning and sub-scanning directions, which are difficult to correct with current techniques that have a narrow dynamic range.
Innovation Solution
The implementation of an image forming apparatus that uses a density sensor and a home position sensor to detect density fluctuations and generate correction signals for the light source, allowing for precise control of the light amount in both directions, thereby reducing density fluctuations through a wide dynamic range of density correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If light amount adjustment is performed based on optics transmitting characteristics, then density correction in main scanning direction is improved, but the dynamic range of density correction remains narrow
Solution Approach 1:
The patent extends density correction from one dimension (main scanning direction based on optics transmitting characteristics) to two dimensions by adding correction for sub-scanning direction based on photosensitive body sensitivity variations. This dimensional expansion increases the dynamic range of density correction while maintaining accuracy in both directions
Solution Approach 2:
The patent changes the correction parameters by introducing sensitivity variation data of the photosensitive body in addition to optics transmitting characteristics. This allows the system to adjust light amount based on multiple parameters (optics transmission and photosensitive body sensitivity) thereby expanding the dynamic range and improving overall density correction accuracy
2Measurement precision
If correction data are created according to photosensitive body sensitivity variations, then density correction in sub-scanning direction is improved, but phase offset between rotational period and correction data causes errors
Solution Approach 1:
The patent implements feedback by detecting the actual rotational period of the photosensitive body and using this detected period to generate correction data. The system continuously monitors the rotational period and adjusts the correction timing accordingly, ensuring that correction data are always synchronized with the actual rotational phase, thereby eliminating phase offset errors
Solution Approach 2:
The patent makes the correction system dynamic by adapting the correction data generation to the actual rotational period of the photosensitive body. Instead of using fixed correction timing, the system dynamically adjusts the correction phase based on detected rotational variations, allowing the correction mechanism to adapt to changing operational conditions and maintain accuracy
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 highly accurate density correction across a wide range, improving image quality by effectively addressing density fluctuations in both the main scanning and sub-scanning directions.
Implementation Method 1
a density sensor... to detect density fluctuations
Implementation Method 2
a home position sensor to detect density fluctuations and generate correction signals
Implementation Method 3
allowing for precise control of the light amount in both directions
Data Source
Figure 1A
Figure 1B~1C
Figure 2A
AI summary
An image forming apparatus is disclosed, including a light source; a drum; an optical scanning apparatus; and an endless belt. The image forming apparatus further includes a pattern forming unit which forms, on the endless belt along a conveying direction of the endless belt, a density fluctuation detecting pattern having a period; a density sensor which detects the density fluctuating detecting pattern and outputs a density signal including information on density fluctuations in the conveying direction of the endless belt; and a period detecting sensor which detects the period included in the density fluctuations.