Abnormal Pixel Detection in Image Scanners
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Solution Overview
Problem
Existing image reading apparatuses face challenges in accurately detecting and correcting abnormal pixels caused by contaminants like dirt, stains, or flaws on the moving document reading glass, often leading to erroneous corrections and noticeable image distortions, especially when the contaminant's density is close to the original or base surface density.
Innovation Solution
The apparatus employs a dual abnormal pixel detection process using line sensors for respective colors, where a first detection process reads a reference member before the original passes through, and a second process reads the original's leading end portion, with threshold values adjusted to differentiate between dirt on the glass and the original, allowing for precise identification and correction of abnormal pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If abnormal pixel detection is performed using only the reading result of the original guide before the original is conveyed, then dirt adhered to the moving document reading glass can be detected, but normal pixels are sometimes erroneously detected as abnormal pixels when the density of dirt on the original guide is close to the density of the base surface or image of the original end portions
Solution Approach 1:
The patent performs a first abnormal pixel detection process using the original guide reading result before the original is conveyed, to preliminarily identify the position of abnormal pixels caused by dirt on the moving document reading glass. This preliminary detection establishes a baseline for comparison with the actual original reading results.
Solution Approach 2:
The patent performs a second abnormal pixel detection process using the reading result of the leading end portion of the original, and compares this feedback with the first detection results. By comparing the two detection results, the system can distinguish between actual dirt contamination and normal variations in the original document, thereby reducing false positives while maintaining detection accuracy.
2Manufacturing precision
If abnormal pixels are corrected by replacing with adjacent pixels, then the abnormal pixels caused by dirt can be corrected, but the corrected portion becomes visually noticeable in screen images
Solution Approach 1:
The patent performs abnormal pixel detection and identification before the final image processing step. By detecting and flagging abnormal pixels in advance through two separate detection processes, the system can apply targeted corrections only where necessary, avoiding unnecessary correction of normal pixels that would create visual distortion in screen images.
Solution Approach 2:
The patent applies correction only to specifically identified abnormal pixels at precise locations where dirt contamination is detected, rather than applying uniform correction across the entire image. This localized approach maintains the natural quality of the image while correcting only the problematic areas caused by dirt on the reading glass.
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 method enables high-accuracy detection and correction of abnormal pixels, minimizing unnecessary corrections and maintaining image quality by distinguishing between dirt on the glass and the original, thus reducing visually noticeable distortions.
Implementation Method 1
a reading unit having line sensors for respective colors... to read through the moving document reading glass the original passing through the moving document reading position
Data Source
AI summary
An image reading apparatus capable of accurately detecting abnormal pixels caused by a contaminant such as dirt, stain, or flaw on a moving document reading glass being read. An image processing unit of the image reading apparatus performs a first abnormal pixel detection process to detect pixel signals representing abnormal pixels and output from image sensors for respective colors when a reading unit reads a guide plate in a main scanning direction in a state before an original passes through a moving document reading position, performs a second abnormal pixel detection process to detect pixel signals representing abnormal pixels and output from the image sensors when an original being conveyed is read by the reading unit in the main scanning direction, and detects a main scanning direction of abnormal pixels based on results of these detection processes.