Plywood Defect Inspection Using Shape-Corrected Depth Measurement
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Solution Overview
Problem
Existing defect inspection systems for plywood fail to accurately detect defects such as warpage or bending due to bouncing during conveyance, which affects image and measurement accuracy.
Innovation Solution
Capture images of the plywood's face and back surfaces to generate depth information, measure the plywood's shape at a location different from the conveyor gap using shape measurement devices, and correct the depth information based on the shape information to detect defects like warpage or bending.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If images are captured at the conveyor gap location, then productivity is improved by continuous inspection, but measurement precision deteriorates due to plywood bouncing
Solution Approach 1:
The patent introduces shape information as an intermediary element to mediate between the depth information (affected by bouncing) and the final defect detection. The shape information, obtained at a stable location, serves as a reference to correct the depth information, thereby eliminating the harmful effect of bouncing while maintaining continuous inspection capability
Solution Approach 2:
The patent segments the measurement process into two distinct parts: depth information acquisition (performed at the conveyor gap for productivity) and shape information acquisition (performed at a stable location for precision). This segmentation allows each part to optimize for its specific purpose while the correction process integrates them
2Measurement precision
If depth information is corrected using shape information from a stable location, then measurement precision is improved, but device complexity increases due to multiple measurement locations
Solution Approach 1:
The shape measurement device performs multiple functions: it captures the overall shape of the plywood at a stable location, provides reference data for correcting depth information, and enables defect detection. This multi-functionality reduces the need for separate dedicated devices for each measurement task
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
Accurately detect defects in plywood without flattening deformation errors, ensuring precise detection of warpage or bending by correcting depth information with shape information.
Implementation Method 1
images of a face surface and a back surface of a plywood that is conveyed on conveyors are captured by imaging devices to generate depth information
Data Source
AI summary
Images of a face surface and a back surface of a plywood 10 that is conveyed on belt conveyors 5U and 5D are captured by imaging devices of first illumination and imaging units 1F and 1B to generate depth information, a shape of the plywood 10 is measured by shape measurement units 3F and 3B, which are provided at locations different from a location of a gap 51 where the image capturing is performed, to generate shape information, and the depth information is corrected based on the shape information, and then a defect in the plywood 10 is detected based on the depth information. By detecting a defect in the plywood 10 based on the depth information corrected using the shape information that is measured without being affected by vibrations that occur when the plywood 10 is conveyed over the gap 51, a defect such as warpage or bending can be accurately detected without deformation occurring in the plywood 10 being flattened by the correction of the depth information.