Printed Image Inspection Using Density Difference Correction
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Solution Overview
Problem
Existing image inspection techniques for printed products are unable to accurately detect defects due to variations in density caused by factors like toner adhesion and light source intensity, leading to inaccurate quality assessment.
Innovation Solution
An image processing apparatus that calculates density differences by considering average pixel values of comparison areas in both reference and printed images, using Equation (1) to correct for uniform density variations and accurately inspect printed products.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If image inspection is performed by comparing reference image data with printed image data, then defect detection is enabled, but density variations cause false defects or missed defects
Solution Approach 1:
The patent changes the parameter of density comparison by introducing a density correction value that compensates for uniform density variations. Instead of directly comparing pixel values, the system calculates a correction value based on the difference in average density between reference and printed images, then applies this correction to adjust the printed image data before defect detection. This transforms the inspection process from direct pixel comparison to corrected pixel comparison, resolving the contradiction between enabling defect detection and avoiding false detections caused by density variations.
2Device complexity
If re-generation of reference image is performed only when clear change occurs in printing apparatus, then device complexity is reduced, but inspection accuracy deteriorates due to undetected density variations
Solution Approach 1:
The system performs self-correction by automatically calculating density correction values from the images themselves without requiring external calibration or manual intervention. The correction mechanism is built into the inspection process, allowing the system to self-adjust for density variations caused by toner adhesion differences or light source intensity changes, thereby maintaining high inspection accuracy without increasing device complexity.
Data Source
AI summary
An image processing apparatus includes first, second, and third acquisition units, a setting unit, a calculation unit, and a processing unit. The first acquisition unit acquires information regarding a setting for inspecting an image. The second acquisition unit acquires first data that is data of a reference image representing a target print result. The third acquisition unit acquires second data that is data of a printed image to be inspected. The setting unit sets a comparison area including a pixel of interest in each of the reference image and the printed image based on the information and the first data. The pixels of interest correspond to an identical pixel position. The calculation unit calculates a density difference between the comparison areas based on the first data and the second data. The processing unit inspects the printed image based on the first data, the second data, and the density difference.