Corrugated Board Defect Detection via Oblique Illumination
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Solution Overview
Problem
Existing corrugated board sheet defect detecting devices struggle to accurately assess defects in corrugated fiberboards due to deformation of corrugated flutes, as significant deformation causes overlapping shadows, while slight deformation may not be detected as a defect due to unchanged striped shadow counts.
Innovation Solution
A corrugated board sheet defect detecting device that uses a guide member with a curved surface and a radiating device emitting parallel light at an inclined angle to capture images of the core paper, allowing for precise definition and assessment of light and dark portions based on their lengths, enabling accurate detection of defects such as crushing, height, and length defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If light is radiated perpendicular to the single-faced cardboard sheet to create striped shadows, then the detection method is simple, but slight flute deformation cannot be detected as the shadow count remains unchanged
Solution Approach 1:
The patent changes the symmetric perpendicular illumination to asymmetric oblique illumination. By radiating light at an oblique angle (30°-60°) relative to the normal direction of the cardboard sheet, the shadow patterns become asymmetric and sensitive to flute deformation, enabling detection of slight deformations that would be invisible under perpendicular illumination.
Solution Approach 2:
The patent transitions from counting shadows in one dimension (perpendicular view) to measuring shadow lengths in another dimension (oblique view). By radiating light obliquely and measuring the length of light and dark portions along the transport direction, the system detects flute deformation through changes in shadow projection length rather than shadow count.
2Measurement precision
If the radiation angle is increased to improve defect detection, then slight deformations become detectable, but the definition of light and dark portions becomes more complex
Solution Approach 1:
The patent optimizes the radiation angle parameter within a specific range (30°-60°) to balance detection accuracy and processing simplicity. This parameter optimization ensures that shadow lengths are sufficiently distinct for accurate measurement while maintaining reasonable image processing complexity. The assessing device compares measured shadow lengths against reference values within this optimized angular range.
Solution Approach 2:
The patent replaces complex mechanical defect detection mechanisms with an optical measurement system. By using light radiation and image capture to measure shadow lengths, the system substitutes mechanical inspection with optical-field measurement, simplifying the overall device structure while improving measurement precision for flute deformation detection.
3Measurement precision
If parallel light is used to clearly define shadow boundaries, then light and dark portions can be precisely measured, but the device complexity increases compared to diffuse light
Solution Approach 1:
The patent replaces mechanical or diffuse light sources with a parallel light source (such as a laser or collimated LED system). This substitution provides well-defined shadow boundaries necessary for precise light and dark portion measurement, while the parallel light technology itself remains relatively simple and compact, minimizing the increase in overall device complexity.
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 device effectively detects defects in corrugated fiberboards with high accuracy by clearly defining light and dark portions, reducing false detection and improving defect detection precision, even in cases of slight flute deformation.
Implementation Method 1
a radiating device that radiates light toward the core paper at a radiation angle which is inclined through a predetermined angle set in advance relative to the single-faced cardboard sheet
Data Source
AI summary
A corrugated board sheet defect detecting device detects a defect in a single-faced cardboard sheet guided by a guide member with corrugated core paper facing outwards. The device includes a radiating device, an image capturing device, an image processing device, and an assessing device. The radiating device is configured to radiate light toward the core paper at a radiation angle relative to the single-faced cardboard sheet. The image capturing device is configured to capture an image of a portion of the core paper irradiated with the light. The image processing device is configured to a light portion and a dark portion in a direction in which the single-faced cardboard sheet is transported based on the captured image. The assessing device is configured to assess a quality by comparing a length of the light portion and a length of the dark portion.