Oblique Illumination for Sheet Surface Flaw Detection
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Solution Overview
Problem
Existing image reading technologies fail to effectively detect flaws such as rips and creases on sheets after image forming and color erasing processes, making it difficult to determine the reusability of sheets.
Innovation Solution
An image reading apparatus with obliquely arranged illumination sections and a reading section that can switch between two-side and single-side illumination modes to enhance the detection of surface flaws by forming shadows that indicate damage, allowing for accurate determination of sheet reusability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the sheet is read simply in the planewise manner, then the reading process is simple, but the flaws in appearance such as rips and creases cannot be recognized
Solution Approach 1:
The patent transitions from planewise (2D top-down) illumination to oblique illumination (introducing a 3D angle dimension). By illuminating the sheet surface at an angle, the system creates shadow effects that reveal surface topology variations such as rips and creases, which are invisible under planewise lighting.
Solution Approach 2:
The patent utilizes optical property changes caused by oblique illumination. The interaction between oblique light and surface flaws creates variations in reflected light intensity and shadow patterns, effectively making the flaws visible through optical contrast changes rather than actual color changes in the sheet material.
2Measurement precision
If oblique illumination is used to detect surface flaws, then flaw detection capability is improved, but the device complexity increases
Solution Approach 1:
The patent employs asymmetric oblique illumination geometry where the light source is positioned at a specific angle relative to the sheet surface. This asymmetric arrangement creates directional shadows that highlight surface flaws, achieving enhanced detection capability through geometric asymmetry rather than complex multi-directional illumination systems.
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 apparatus effectively identifies rips and creases through image data analysis, enabling proper sorting of reusable and non-reusable sheets, ensuring practical reuse based on the presence of detectable noise relative to the background.
Implementation Method 1
obliquely illuminate a surface of a sheet in an image reading area... obliquely illuminate the surface of the sheet in the image reading area
Data Source
AI summary
An image reading apparatus includes a first illumination section configured to obliquely illuminate a surface of a sheet in an image reading area, a second illumination section arranged upstream of the first image reading area and configured to obliquely illuminate the surface of the sheet in the image reading area, and a reading section configured to read the surface of the sheet illuminated in the image reading area. The apparatus can switch between a two-side illumination mode in which the image reading area is illuminated by both illumination sections, and a single-side illumination mode in which the image reading area is illuminated by only one illumination section. The apparatus further includes a determination section configured to determine the state of the surface of the sheet (e.g., rip or creases) based on image data corresponding to the surface read in the single-side illumination mode.