Print Inspection Apparatus Position Matching Accuracy
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Solution Overview
Problem
Existing inspection systems for print products face challenges in maintaining position matching accuracy, particularly when defects with similar colors to the image are present, leading to incorrect positioning of control points and reduced inspection accuracy.
Innovation Solution
The inspection apparatus employs a method that calculates approximate lines based on control points in the same column and row to correct the positioning of control points, ensuring accurate alignment between the scanned image and the reference image, thereby preventing lowering of position matching accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If non-rigid body alignment (free-form deformation) is used to correct local positional misalignment, then position matching accuracy is improved, but control points may be incorrectly displaced when defects with similar colors are present, causing position matching accuracy to deteriorate
Solution Approach 1:
The patent applies local quality by differentiating the treatment of control points based on their local image characteristics. Control points are classified into two types: those in defect areas (where color similarity causes false matching) and those in normal areas. Different correction strategies are applied to each type, allowing the system to maintain high position matching accuracy while avoiding incorrect displacements in defect regions.
Solution Approach 2:
The patent inverts the conventional approach by not directly using color similarity for all control point corrections. Instead, it identifies defect areas where color-based matching fails and applies an alternative correction method for those specific regions, while maintaining the color-based method for normal regions. This inversion prevents the harmful effect of color similarity from deteriorating position matching accuracy.
2Manufacturing precision
If control points are updated to minimize differences between images, then alignment accuracy is improved, but defects with similar colors are processed as part of the picture, causing control points to be displaced to unexpected places
Solution Approach 1:
The patent extracts defect areas from the overall image processing by identifying regions where defects with similar colors are present. These defect areas are separated from the normal picture regions, and control points within defect areas are handled differently. This extraction prevents defect position information from being lost or incorrectly processed as part of the picture content.
Solution Approach 2:
The patent segments the image into defect areas and normal areas based on color similarity analysis. By dividing the image into these distinct segments, the system can apply different control point update strategies to each segment, ensuring that defect position information is preserved while maintaining alignment accuracy in normal regions.
3Device complexity
If rigid body transformation is used for position matching, then processing simplicity is maintained, but local positional misalignment caused by uneven conveyance and elongation of paper cannot be corrected
Solution Approach 1:
The patent introduces dynamics by transitioning from rigid body transformation (static, uniform transformation) to free-form deformation (dynamic, localizable transformation). The system dynamically adjusts the transformation applied to each control point based on its local position and image characteristics, allowing correction of local positional misalignment while maintaining manageable processing complexity through automated classification and correction.
Data Source
AI summary
An inspection apparatus capable of preventing lowering of position matching accuracy. Control points are positioned in a lattice form on a scanned image of a print product, for performing position matching between the scanned image and a reference image registered in advance. An approximate line of a column and an approximate line of a row intersecting the approximate line of the column are calculated based on two or more control points positioned in the same column and the same row as one control point. One control point determined to be corrected is corrected based on the respective approximate lines of the column and the row. The print product is inspected by comparing a position-matched scanned image generated based on the control points including position-corrected control points and position-updated control points, and the reference image.