Inline Print Inspection Using CIS for Cross-Process Defect Detection
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Solution Overview
Problem
Existing printing inspection systems, particularly those using inline contact image sensors (CIS), are limited in their ability to detect cross-process defects due to their cost-effective hardware, which cannot support comprehensive print reproduction defect detection.
Innovation Solution
An optimized inline inspection system that identifies and analyzes horizontal and vertical portions of printed sheets with colorant values above a threshold, using existing CIS sensors to detect defects without requiring expensive vision system hardware, enabling both process and cross-process defect detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If expensive vision system hardware is used, then comprehensive print reproduction defect detection capability is improved, but device cost increases
Solution Approach 1:
The inspection system divides the printed sheet into multiple scan lines and processes them sequentially. The CIS sensor captures images line by line as the sheet passes through, breaking down the comprehensive inspection task into smaller, manageable segments that can be handled by lower-cost hardware.
Solution Approach 2:
The system uses periodic scanning where the CIS sensor captures images at regular intervals as the sheet moves through the printer. This periodic capture method allows comprehensive inspection over time without requiring all pixels to be captured simultaneously, enabling defect detection across the entire sheet using sequential imaging.
2Device complexity
If inline CIS sensors are used, then device cost is reduced, but cross-process defect detection capability deteriorates
Solution Approach 1:
The system compensates for the limited field of view of the CIS sensor by utilizing the time dimension. As the sheet moves through the printer, the sensor captures multiple scan lines at different positions, effectively adding a temporal dimension to the inspection process. This allows coverage of the entire sheet area including cross-process regions that would be invisible in a single static image.
Solution Approach 2:
The system performs preliminary scanning of the sheet as it passes through the printer before final processing. By capturing images of all scan lines during the printing process, the system prepares comprehensive data that can be analyzed later for cross-process defects, enabling detection capability without requiring expensive dedicated hardware.
3Measurement precision
If entire document pages are captured for inspection, then comprehensive defect detection is improved, but processing time increases
Solution Approach 1:
The system segments the inspection process into individual scan line processing units. Instead of capturing and analyzing one large full-page image, the CIS sensor captures and processes multiple small scan line images sequentially. This segmentation reduces the data processing burden for each frame while maintaining comprehensive coverage over time.
Solution Approach 2:
The system extracts only the necessary scan lines from the printed sheet for inspection, rather than processing the entire document page. By selectively capturing and analyzing only the scan lines that contain printed content, the system reduces processing time and computational requirements while still achieving comprehensive defect detection coverage.
Data Source
AI summary
A printing device includes an inline inspection system using one or more sensors to determine defects on a printed sheet. The control unit, or other component connected to the printing device, determines a plurality of horizontal and vertical portions within one or more images on the sheet that are above a colorant value, or CMYK, threshold. A set of the plurality of horizontal and vertical portions are identified from the images on the sheet. The set of horizontal portions may differ from the set of vertical portions. The printed images of these portions are captured by the inline sensor. The captured data is analyzed to determine a defect within the printed sheet.