Image Forming Apparatus Color Tone Control via Segmented Correction
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Solution Overview
Problem
Existing image forming apparatuses face challenges in maintaining color stability, particularly in responding to slight changes in highlight or shadow areas during mass printing, as current calibration techniques are limited by the number of parameters and can result in color cast and increased computation load.
Innovation Solution
An improved image forming apparatus incorporating a gradation converting circuit with threshold value generating and correcting sections, a printer engine, and a color tone control circuit that builds a prediction model to adjust gradation control parameters based on measured and predicted color values, reducing tone levels and minimizing color cast while maintaining efficient computation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If calibration is executed with a reduced number of parameters for correcting tone reproduction curve, then computation load is reduced, but the ability to respond to slight changes in highlight or shadow area is limited
Solution Approach 1:
The patent segments the tone reproduction curve correction into two distinct parts: highlight clipping correction and shadow clipping correction. Each part is handled by separate correction units with dedicated parameters. This segmentation allows the system to use fewer overall parameters while maintaining the ability to respond to slight changes in both highlight and shadow areas independently, thus resolving the contradiction between reduced computation load and maintained precision.
2Stability of the object's composition
If conventional calibration techniques are used, then color stability is maintained to some extent, but slight changes in highlight or shadow area cannot be responded to, resulting in color cast
Solution Approach 1:
The patent applies local quality by creating separate correction mechanisms for different regions of the tone reproduction curve. The highlight clipping correction unit specifically targets highlight areas with dedicated parameters, while the shadow clipping correction unit targets shadow areas separately. This localized correction approach allows the system to maintain color stability in overall composition while achieving high precision in specific critical regions, preventing color cast in highlight and shadow areas.
3Manufacturing precision
If more parameters are used for correcting tone reproduction curve to respond to slight changes, then color accuracy is improved, but computation load and device complexity increase
Solution Approach 1:
The patent divides the correction system into segmented functional units: a highlight clipping correction unit with dedicated parameters and a shadow clipping correction unit with dedicated parameters. This segmentation strategy reduces the total number of parameters needed compared to a comprehensive correction system, while maintaining high color correction accuracy for both highlight and shadow regions. The segmented approach simplifies the device structure and reduces computational complexity.
Solution Approach 2:
The patent extracts and separates the correction functions for highlight and shadow areas from a unified correction system. By taking out the highlight clipping correction and shadow clipping correction as independent functional units with their own parameters, the system achieves accurate color correction for critical regions without requiring a large number of parameters across the entire tone reproduction curve, thus reducing device complexity while maintaining precision.
Data Source
AI summary
An image forming apparatus includes a gradation converting circuit, a printer engine, an image inspecting circuit, and a color tone control circuit. The gradation converting circuit includes a threshold value generating section that generates threshold values, a first gradation correcting section that converts gradation values of image data, a second gradation correcting section that converts output values from the first gradation correcting section based on a gradation control parameter, and a gradation processing section that reduces tone levels of the second gradation correcting section by comparing output values from the second gradation correcting section and the threshold values. The color tone control circuit builds a prediction model for predicting, in response to the output values from the first gradation correcting section, measurement values to be measured by the image inspecting circuit, and corrects the gradation control parameter based on the measurement values and values predicted by e prediction model.