Image Inspection Apparatus for Preprint Print Quality
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Solution Overview
Problem
Existing image inspection methods for preprint printing fail to accurately determine print quality due to fluctuations in magnification or print position, leading to incorrect detection of defects when trying to mask the preprint image layer or calculating changes in magnification and print position between preprint and variable image layers.
Innovation Solution
An inspection apparatus that generates both preprint and variable master images, superimposes them to set an offset difference threshold, and calculates shifts to detect overlap between printed portions, allowing for accurate inspection of print quality by comparing the printed image with the master images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a preprint image layer of an inspection image is masked to generate the inspection image having only a variable image, then the inspection apparatus can compare the inspection image with a master image to inspect defects, but accurate results are not obtained because the preprint image content is not included in the master image and is detected as difference
Solution Approach 1:
The inspection image is divided into two separate layers: a preprint image layer and a variable image layer. This segmentation allows each layer to be processed independently - the preprint layer is used for masking and removal, while the variable layer contains the actual inspection content, thereby preventing preprint information from interfering with defect detection accuracy.
Solution Approach 2:
The preprint image layer is extracted and separately processed to be removed from the inspection image. By taking out the preprint content before comparison with the master image, the system eliminates the source of false defect detections while preserving the variable image content for accurate inspection.
2Manufacturing precision
If change in magnification and change in print position are calculated for each of a preprint image layer and a variable image layer of an inspection image, then print position defects can be detected, but overlap between the preprint image and the variable image may occur depending on the degree of change, leading to false negative defect determination
Solution Approach 1:
The system performs preliminary actions by calculating the overlap shift between preprint and variable image layers before conducting the actual defect inspection. This advance calculation establishes a threshold that prevents false negative determinations during the inspection process, ensuring reliable defect detection even when magnification or position changes occur.
Solution Approach 2:
The system applies preliminary anti-action by establishing an overlap shift threshold that counteracts the potential harmful effect of image overlap. By pre-calculating the maximum acceptable shift and using it to exclude overlapping regions from defect detection, the system prevents false negative determinations while maintaining manufacturing precision.
3Adaptability or versatility
If a master image is generated for each specific document to inspect preprint-printed matter, then inspection can be performed, but the process becomes complex and time-consuming since the master image does not include information on content printed on the preprint sheet
Solution Approach 1:
The master image is segmented into a preprint master image and a variable master image. The preprint master image contains the template content and is reused across multiple documents, while the variable master image contains document-specific content. This segmentation reduces the complexity of generating master images for each document while maintaining adaptability to different specific documents.
Solution Approach 2:
The preprint master image serves as a universal template that can be applied to multiple different documents. By separating the preprint content into a reusable master image, the system maintains versatility for inspecting different specific documents without requiring a completely new master image for each one, thereby reducing overall complexity.
Data Source
AI summary
An image inspection apparatus obtains a threshold value indicating an allowable range of offset differences between an output target inspection image and a pre-provided inspection image, and determines whether to inspect a read image obtained by reading an output target image formed on a recording sheet having a pre-provided image, using the threshold value.