White Reference Plate Read Start Position Detection for Shading Correction
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Solution Overview
Problem
Image forming apparatuses face challenges in accurately correcting high-frequency and low-frequency distortions in image signals due to variations in photoelectric conversion sensor sensitivity and optical system inefficiencies, leading to issues like white streaks in scanned documents when foreign matter is present on the white reference plate.
Innovation Solution
The apparatus includes a photoelectric conversion unit, a white reference plate, a white reference signal generation unit, and a shading correction unit that detects and corrects image signals by calculating the read start position on the white reference plate where brightness is within a given range, ensuring accurate shading correction even with dust or contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a white reference member is used to generate white reference signal for shading correction, then shading correction can be performed to correct high-frequency and low-frequency distortion, but foreign matter such as flaw or contamination on the white reference member causes white streak-like images to appear on read images
Solution Approach 1:
The patent applies preliminary action by reading multiple candidate regions of the white reference member before generating the final white reference signal. The system pre-reads a first candidate region, detects foreign matter, and if foreign matter is detected, reads a second candidate region as a backup. This preliminary detection and backup preparation prevents foreign matter from affecting the final shading correction accuracy.
2Quantity of substance
If the entire white reference member is read to generate white reference signal, then sufficient reference data is obtained for correction, but any foreign matter on the white reference member is included in the reference signal causing distortion
Solution Approach 1:
The patent applies the taking out principle by extracting and excluding regions containing foreign matter from the white reference signal generation process. The system reads the white reference member, detects foreign matter in the first candidate region, and excludes this contaminated region from the final reference signal by using a clean second candidate region instead. This extraction of harmful elements maintains reference signal accuracy.
Solution Approach 2:
The patent applies local quality by treating different regions of the white reference member differently based on their cleanliness. Instead of uniformly using the entire white reference member, the system identifies clean regions (second candidate region without foreign matter) and uses only those regions for generating the white reference signal, while excluding contaminated regions (first candidate region with foreign matter). This localized selection ensures high reference signal quality.
3Measurement precision
If manual inspection and adjustment of white reference plate is performed to avoid foreign matter, then accurate shading correction can be achieved, but operational steps and time are increased
Solution Approach 1:
The patent applies self-service by enabling the image reading device to automatically detect foreign matter on the white reference member and autonomously select appropriate candidate regions for generating the white reference signal. The system performs automatic foreign matter detection, automatically reads candidate regions, and automatically generates the white reference signal without requiring manual inspection or adjustment. This automation maintains shading correction accuracy while eliminating time-consuming manual operations.
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 enables precise correction of image signals, preventing white streaks and maintaining image quality by determining the optimal read start position on the white reference plate, even when dust or contamination is present, thus reducing manual adjustments and operational steps.
Implementation Method 1
a photoelectric conversion unit configured to sequentially convert an image of the original document scanned in a sub-scanning direction into image signals
Data Source
AI summary
An image forming apparatus to generate image data from an original document and to form an image includes a photoelectric conversion unit to sequentially convert an image of the original document scanned in a sub-scanning direction into image signals made of a plurality of pixels constituting one line in a main scanning direction, a white reference plate which is white reference for the image signals, a white reference signal generation unit to generate a white reference signal from image signals obtained by photoelectric converting an image for a given number of lines from a given read start position of the white reference plate in the sub-scanning direction by the photoelectric conversion unit, a shading correction unit to correct the image signals of the original document image photoelectric converted by the photoelectric conversion unit based on the white reference signal, and a read start position acquisition unit to calculate and acquire the read start position on the white reference plate, and the read start position acquisition unit includes a start position calculation unit to detect a portion of the white reference plate where brightness is within a given range and to calculate the read start position.