Printed Image Position-Shift Detection Using Averaged Read Images
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for inspecting print position shifts in printed images suffer from inaccuracies due to variations in sheet conveyance and scanning, leading to increased threshold settings and decreased accuracy in determining relative shifts between sheets, especially when the print product is stacked.
Innovation Solution
An image processing apparatus that calculates a reference value for print position shift from a reference image on the first page and offsets this value when inspecting subsequent pages, using geometric transformation matrices and feature point detection to determine the presence/absence of print position shifts with high accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the threshold for print position shift determination is increased to account for conveyance variations, then false failures are reduced, but measurement precision deteriorates
Solution Approach 1:
The patent creates a reference image by averaging multiple read images to eliminate random variations. This reference image serves as a stable baseline for comparison, allowing accurate detection of actual print position shifts without being affected by conveyance variations or scanner fluctuations.
Solution Approach 2:
The patent performs preliminary processing by calculating the average position of multiple read images before comparison with the original document data. This preliminary averaging step removes random noise and establishes a stable reference, enabling more accurate subsequent comparison and threshold setting.
2Measurement precision
If ideal coordinates are used for shift calculation, then theoretical accuracy is improved, but practical measurement precision deteriorates due to conveyance variations
Solution Approach 1:
Instead of relying solely on ideal coordinates from original document data, the patent creates a practical reference by averaging multiple actual read images. This reference image captures real-world variations and serves as a reliable baseline for comparison, bridging the gap between theoretical and practical measurements.
Solution Approach 2:
The patent changes the reference parameter from ideal coordinates (theoretical) to an average of actual read images (practical). This parameter transformation adapts the measurement system to real-world conditions, making it reliable for practical determination while maintaining measurement precision through statistical averaging.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An image processing apparatus includes a calculation unit configured to calculate a first position shift between a reference image serving as a reference for a print product and a first read image obtained by reading the print product, and a second position shift between the reference image and a second read image obtained by reading the print product, and a determination unit configured to determine the presence/absence of a position shift in the second read image based on the first position shift and the second position shift.