Color Shift Detection Using Scan Image Reference Comparison

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Solution Overview

Problem

Conventional image quality inspection of printed materials relies heavily on operator-dependent visual checks, leading to variations in inspection quality and increased processing time, particularly due to the need for color space conversion and correction, which affects processing speed and costs.

Innovation Solution

An inspection apparatus with a scanning unit, an accepting unit for inspection settings, and a determination unit that uses a reference image to compare scan image data, allowing for efficient image inspection without affecting processing speed and reducing costs by minimizing the load on inspection processing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If color space conversion and correction are performed on print image data to detect color shift, then inspection accuracy is improved, but processing speed decreases and costs increase

Engineering Contradiction:

Improvecolor shift detection accuracyVSAvoidinspection processing speed

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

Instead of converting the print image data to scan image color space (the conventional approach), the patent inverts the approach by converting the scan image data to print image color space. This allows direct comparison with the original print image data without requiring complex color space conversion of the print data, thereby maintaining inspection accuracy while reducing processing load and improving speed

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent extracts only the necessary color information from the scan image data after converting it to print image color space, rather than performing full color space conversion and correction on the entire print image data. This selective extraction approach maintains color shift detection accuracy while significantly reducing the computational burden

Inventive Principle:

Principle #2Taking out (Extraction)

2Measurement precision

If color space conversion and correction are performed on print image data to detect color shift, then inspection accuracy is improved, but inspection costs increase

Engineering Contradiction:

Improvecolor shift detection accuracyVSAvoidinspection processing cost

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent inverts the conventional color space conversion approach by converting scan image data to print image color space rather than converting print image data to scan image color space. This reduces the computational complexity and processing time, thereby lowering inspection costs while maintaining the ability to accurately detect color shifts

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent creates a converted copy of the scan image data in print image color space for comparison with the original print image data. This copying approach allows accurate color shift detection without requiring expensive and time-consuming color space conversion of the original print image data

Inventive Principle:

Principle #26Copying

3Adaptability or versatility

If operator visual check is used for image quality inspection, then flexibility is maintained, but inspection time increases and consistency decreases

Engineering Contradiction:

Improveinspection flexibilityVSAvoidinspection time

Core Design Contradiction:

Adaptability or versatilityVSLoss of time

Solution Approach 1:

The patent replaces the manual operator visual check system with an automated image processing system that converts scan image data to print image color space and performs automated comparison. This substitution eliminates the time-consuming and inconsistent nature of manual inspection while maintaining the flexibility to detect various quality issues including color shifts

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces an intermediary color space conversion process that transforms scan image data into print image color space, enabling automated computational comparison. This intermediary step allows the system to maintain the adaptability of comprehensive quality checking while dramatically reducing inspection time compared to manual visual checks

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS9007658B2Inspection apparatus, inspection method, and program

Publication Date: 2015.04.14 CANON KK

AI summary

Color shift detection requires additional processing as compared to detection of other items, and thus increases the load on the inspection processing. Conventional inspection apparatuses have a problem that the processing speed associated with inspection is affected and the costs of the inspection processing apparatus are raised. In a case where an inspection setting specified by a user includes color shift detection (YES in S406), scan image data of a printed material for a test print is determined to be a reference (S407). Then, comparison is made between scan image data obtained by scanning the printed material associated with a print job and the scan image data of the printed material for the test print.