Image Density Correction in Printer Controllers
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Solution Overview
Problem
Conventional image forming apparatuses experience density and color tone differences between images on the left and right sides of a double-page spread or between multiple images on the same sheet, due to inadequate timing of shading correction, especially when using CCFL illumination units in low-temperature environments.
Innovation Solution
An image forming apparatus with a controller that calculates a correction coefficient based on reference image data and corrects image density variations caused by light source orientation and pixel sensitivity, determining the interval for detection operations according to the light source characteristics and image arrangement manner, ensuring uniform image density across the output sheet.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If shading correction is executed only once before document reading starts, then the operation is simple and fast, but image density varies from document to document due to light source warm-up time
Solution Approach 1:
The patent implements periodic shading correction by executing the detection operation at predetermined intervals during document reading. The controller is configured to periodically perform shading correction based on the characteristic of the light source (warm-up time), ensuring that correction is applied at appropriate moments without stopping the ADF continuously. This periodic approach maintains both productivity and image density uniformity.
2Manufacturing precision
If shading correction is executed at fixed intervals during document reading, then image density uniformity is improved, but the correction timing may not align with image arrangement boundaries causing density differences between adjacent images
Solution Approach 1:
The patent uses feedback by having the controller determine the detection operation interval based on the characteristic of the light source and the arrangement manner of images. The system receives feedback about the light source warm-up characteristics and adjusts the shading correction timing accordingly, ensuring corrections occur at optimal moments that align with image reading sequences and arrangement boundaries.
Solution Approach 2:
The patent implements dynamic adjustment of shading correction timing by adapting the detection operation interval to match both the light source characteristics and the specific image arrangement manner (e.g., N-in-1, double-page spread). This dynamic approach allows the system to optimize correction moments for each different printing scenario, preventing density differences between adjacent images while maintaining overall uniformity.
3Manufacturing precision
If the detection operation interval is determined based on light source characteristic and image arrangement manner, then image density uniformity across arranged images is achieved, but the control complexity increases
Solution Approach 1:
The patent manages complexity by changing parameters in a structured way - the controller determines the detection operation interval based on predetermined light source characteristics (warm-up time) and predefined image arrangement manners. By establishing clear relationships between these parameters and the correction timing, the system achieves uniform image density without excessive complexity. The controller stores and references characteristic data about the light source and applies appropriate correction intervals based on the selected arrangement manner.
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 ensures no density or color tone differences between images on the same sheet, improving print quality by dynamically adjusting shading correction intervals based on light source characteristics and image arrangement, thereby enhancing user satisfaction.
Implementation Method 1
Reflected light from the document is subjected to photoelectric conversion, whereby image data is detected
Data Source
AI summary
An image forming apparatus comprises a image reader unit and a controller. The controller is configured to i) execute a detection operation of calculating a correction coefficient based on reference image data obtained by applying the light from a light source to a reference unit and receiving, by a photoelectric conversion unit, the reflected light from the reference unit to perform photoelectric conversion of the received light to the reference image data, ii) correct image density variations of the image data caused by orientation variations of the light source and pixel sensitivity of the photoelectric conversion unit based on the correction coefficient, iii) form an output image to be printed on output paper in accordance with an arrangement manner, based on the corrected image data, and iv) determine an interval at which the detection operation is executed, in accordance with a characteristic of the light source and the arrangement manner.