Chromaticity Correction for Optical Brightening Agents
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Solution Overview
Problem
Color management systems fail to accurately correlate colorimetric values measured under fixed measurement illumination conditions with the perceived appearance, especially when optical brightening agents (OBAs) are present, leading to measurement errors and inaccuracies in color verification and profile generation.
Innovation Solution
An image processing system that includes an image forming apparatus and an image processing apparatus, where the image forming apparatus acquires chromaticity values using a sensor with a fixed light source and transmits them to the image processing apparatus, which converts these values based on the specified measurement condition and the amount of optical brightening agent in the sheet, ensuring accurate color management regardless of the OBA's influence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a color measurement device with a fixed light source characteristic is used, then the device structure is simple and easy to operate, but the measured chromaticity value cannot conform to the desired measurement condition when optical brightening agents are present
Solution Approach 1:
The system changes the parameter of chromaticity value conversion by introducing OBA amount information as a new parameter. The conversion unit uses both the measured chromaticity value and the OBA amount to calculate a corrected chromaticity value that conforms to the desired measurement condition, thereby resolving the contradiction between simple device operation and accurate measurement.
Solution Approach 2:
The system introduces an intermediary conversion process between the measured chromaticity value and the final used chromaticity value. The chromaticity value conversion unit acts as an intermediary that adjusts the measured value based on OBA information, bridging the gap between the fixed light source limitation and the requirement for condition-conformant measurements.
2Illumination intensity
If optical brightening agents are used in sheets, then the brightness and appearance of printed products are improved, but measurement errors occur because the fluorescent radiation light adds to reflected light
Solution Approach 1:
The system converts the harmful fluorescent radiation from OBAs into a beneficial correction factor. By measuring the OBA amount and using it to correct the chromaticity value, the system turns the OBA's fluorescent effect from a measurement error source into a controllable parameter that can be compensated for, achieving accurate measurements despite OBA presence.
Solution Approach 2:
The system implements feedback by using the measured OBA amount to correct the measured chromaticity value. The conversion unit feeds back the OBA information into the measurement process, adjusting the final chromaticity value to compensate for the fluorescent radiation effect, thereby maintaining measurement precision despite the presence of OBAs.
3Device complexity
If chromaticity values are measured under fixed measurement illumination conditions, then the measurement process is simple, but the colorimetric values cannot be accurately correlated with perceived appearance when OBAs are present
Solution Approach 1:
The system performs preliminary action by measuring the OBA amount in advance and storing it as correction information. This preliminary measurement of OBA content allows the conversion unit to prepare appropriate correction factors before the actual color measurement, enabling accurate chromaticity value conversion without increasing the complexity of the measurement device itself.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system enables the acquisition of chromaticity values that conform to the intended measurement condition, reducing measurement errors and ensuring stable color management by considering the optical brightening agent's effect, even when using color measurement devices with fixed light sources.
Implementation Method 1
The OBA works based on the fluorescent principle, and therefore absorbs ultraviolet (UV) radiation at a wavelength of 400 nanometers (nm) or shorter and emits light mainly in a blue visible spectrum at 400 to 450 nm
Data Source
AI summary
An image processing system includes an image forming apparatus, and an image processing apparatus connected to the image forming apparatus. The image forming apparatus forms an image, acquires a chromaticity value that is a result of measurement of a sheet on which the image is formed with use of a sensor in which a characteristic of a light source is fixed, and transmits the acquired chromaticity value to the image processing apparatus. The image processing apparatus receives the transmitted chromaticity value, specifies a condition when the result of the measurement using the sensor is acquired, and converts the received chromaticity value with use of the specified condition and information regarding an amount of an optical brightening agent contained in the sheet on which the image is formed.