Chromaticity Conversion for Optical Brightening Agent Compensation
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Solution Overview
Problem
The use of optical brightening agents (OBA) in printing sheets causes a discrepancy between colorimetric values and actual appearance, especially when measured under different illuminant conditions, leading to inaccurate color management and profile creation due to the fixed light source characteristics of inline sensors, which do not account for ultraviolet light effects.
Innovation Solution
An image processing apparatus that includes a sensor with a fixed light source to acquire chromaticity values, a unit to designate measurement conditions, and a conversion unit to adjust for the optical brightening agent amount, allowing for accurate color management by converting chromaticity values based on the determined OBA content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a sensor with a fixed light source is used for color measurement, then the device complexity is reduced and ease of operation is improved, but measurement precision deteriorates due to inability to account for ultraviolet light effects on optical brightening agents
Solution Approach 1:
The patent introduces an intermediary conversion process that translates measurement data between different illuminant conditions. The chromaticity value conversion unit acts as a mediator, converting chromaticity values measured under the fixed light source (D50) to the desired measurement condition (D65 or other illuminants), thereby enabling accurate color management without requiring the sensor to physically change its light source characteristics.
Solution Approach 2:
The patent changes the parameter of illuminant condition through software processing rather than hardware modification. By detecting the optical brightening agent amount and applying appropriate conversion based on the designated measurement condition, the system adapts the chromaticity values to different illuminant parameters (D50, D65, A, etc.), effectively resolving the contradiction between fixed hardware and variable measurement requirements.
2Device complexity
If chromaticity values are measured without considering optical brightening agent content, then the measurement process is simplified, but color management accuracy deteriorates due to discrepancy between colorimetric values and actual appearance
Solution Approach 1:
The patent performs preliminary detection of the optical brightening agent amount before final color conversion. The determination unit detects OBA content in advance, and this information is stored and used during the chromaticity conversion process. This preliminary action enables the system to prepare appropriate conversion parameters based on the detected OBA amount, ensuring accurate color management without adding complex hardware.
Solution Approach 2:
The patent implements a feedback mechanism where the detected optical brightening agent amount informs the conversion process. The chromaticity value conversion unit uses the OBA detection results as feedback to select appropriate conversion methods and parameters, creating a closed-loop system that continuously adapts to the specific characteristics of the printing material being measured.
3Measurement precision
If multiple measurement conditions are supported with variable light sources, then measurement precision under different illuminants is improved, but device complexity increases due to need for multiple light sources
Solution Approach 1:
The patent makes the fixed light source sensor universally applicable to multiple illuminant conditions through software-based conversion. Instead of requiring separate hardware for each illuminant (D50, D65, A, etc.), the system uses a single sensor that can measure under its fixed light source and then convert the results to any desired illuminant condition, thereby achieving multi-functionality without increasing hardware complexity.
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
Enables stable and accurate color management by considering the OBA content, even with inline sensors having fixed light sources, thereby reducing measurement errors and ensuring compatibility with varying OBA amounts in printing materials.
Implementation Method 1
The OBA acts in accordance with a principle of fluorescence, and thus absorbs radiation of ultraviolet ray (UV) whose wavelength is 400 nanometers (nm) or less and emits light mainly with a region of a blue visible spectrum of 400 to 450 nm
Data Source
AI summary
A chromaticity value, which is a measurement result for a sheet to be measured, is acquired by using a sensor in which a light source has fixed characteristics, a condition under which the measurement result is acquired by the sensor is designated, an optical brightening agent amount contained in the sheet is determined by using a spectral reflectance obtained by performing measurement on the sheet with use of the sensor, and the acquired chromaticity value is converted by using the designated condition and information about the determined optical brightening agent amount.