Print Quality Inspection for Motion Thread Security Printing
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Solution Overview
Problem
Conventional print quality inspection apparatuses inaccurately detect print quality issues in security printing products with motion threads due to pattern changes with small angle variations, leading to false abnormalities even when the print quality is normal.
Innovation Solution
A print quality inspection apparatus that captures RGB images and performs inspections based on image data of the same hue as the motion thread, or uses monochrome images when the illuminator emits light of the same hue, allowing for accurate quality assessment by setting allowable values for determining normal print quality, and utilizing pattern matching to locate the motion thread position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional print quality inspection apparatus is used to inspect print paper sheets with motion threads, then the inspection can be performed, but false detection of abnormalities occurs due to pattern changes with small angle variations
Solution Approach 1:
The patent applies local quality by differentiating inspection methods for different regions. For motion thread areas, the system uses specialized inspection parameters that account for pattern variations, while other areas receive standard inspection. This localized approach prevents false detections in motion thread regions while maintaining accurate inspection elsewhere.
Solution Approach 2:
The patent changes inspection parameters dynamically based on the detected region. When motion threads are identified, the system adjusts color space conversion parameters and inspection thresholds to accommodate pattern variations. This parameter adaptation eliminates false positives while maintaining detection sensitivity for actual defects.
2Quantity of substance
If RGB images are captured and all color data is used for inspection, then comprehensive quality assessment is achieved, but inspection reliability decreases due to motion thread pattern variations
Solution Approach 1:
The patent extracts and separates motion thread regions from the overall image data. By identifying and isolating these regions, the system can apply specialized inspection parameters only where needed, while using standard parameters for the rest of the image. This extraction prevents motion thread variations from compromising overall inspection reliability.
Solution Approach 2:
The patent segments the inspection process into distinct phases: motion thread region identification, color space conversion, and quality assessment. This segmentation allows each phase to be optimized independently, with motion thread areas receiving specialized handling that prevents false detections while maintaining comprehensive coverage.
3Measurement precision
If monochrome images are captured with illuminator emitting light of the same hue as motion thread, then accurate inspection of motion thread area is achieved, but the complexity of the inspection system increases
Solution Approach 1:
The patent implements dynamic configuration of the illumination and capture system. The system can switch between RGB image capture mode and monochrome image capture mode with colored illumination based on the specific inspection requirements and detected motion thread characteristics. This dynamic adaptation achieves accurate motion thread inspection when needed while maintaining system flexibility.
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 solution enables accurate print quality inspection on print paper sheets with motion threads, preventing false detection of abnormalities and ensuring reliable quality assessment.
Implementation Method 1
an illuminator that emits light onto a printing product provided with a motion thread
Implementation Method 2
an image capturing device that captures an image of the printing product
Data Source
AI summary
The present invention relates to a print quality inspection apparatus comprising: an illuminator (35 or 35A-35C) for irradiating light onto a printout (1) provided with a motion thread (1b); a camera (34 or 34A) for capturing an image of the printout; and a print quality inspection unit (10) for inspecting the print quality of the printout (1) on the basis of image data captured by the camera (34 or 34A). The camera (34) captures images of printouts (1) for each RGB color, and the print quality inspection unit (10) performs a print quality inspection having a scope that includes the motion thread (1b) on the basis of image data of a color of the same hue as the color of the motion thread (1b), or the illuminator (35A-35C) emits a color of the same hue as the color of the motion thread (1b), and the monochrome camera (34A) captures a monochrome image.