Color Conversion System Using Device-Specific Tables
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Solution Overview
Problem
Current color management systems, such as ICC profiles and CMMs, face challenges in accurately converting RGB images to device-independent L*a*b* color space, especially when dealing with different paper media and color materials under varying illumination conditions, leading to significant color errors due to differences in spectral characteristics of input illumination and light sensors.
Innovation Solution
A color conversion system that utilizes a specific color chart for each medium and color material, converting colorimetric values from various input devices to L*a*b* values using a dedicated colorimetric device, and then to a standard colorimetric device, employing a color conversion engine to match colorimetric values across different devices and illumination conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ICC profile and CMM are used for color conversion from RGB input devices to L*a*b* color space, then color management is enabled, but significant color errors occur when dealing with different paper media and color materials under varying illumination conditions
Solution Approach 1:
The patent segments the color management system into device-specific colorimetric value tables for different input devices (scanners, cameras) and medium-specific tables for different paper types and color materials. Each table contains colorimetric values measured under specific illumination conditions, allowing precise conversion by selecting the appropriate table combination rather than using a single universal ICC profile.
Solution Approach 2:
The system dynamically selects and switches between different colorimetric value tables based on the actual input device, paper medium, and illumination conditions detected during operation. This dynamic adaptation allows the color conversion process to adjust to varying conditions rather than relying on static ICC profiles that cannot accommodate different media and lighting scenarios.
2Ease of manufacture
If device-specific ICC profiles are created for scanners and cameras, then color conversion to L*a*b* is achieved, but color errors increase when the paper medium or color material differs from the chart used for profile creation
Solution Approach 1:
The patent creates a universal colorimetric value database that serves multiple functions: it stores colorimetric values for various input devices, different paper media, color materials, and illumination conditions. This universal database can be queried with different parameter combinations to handle diverse color conversion scenarios, eliminating the need for separate ICC profiles for each device-medium-condition combination while maintaining high accuracy.
Solution Approach 2:
The patent introduces an intermediary colorimetric value table that acts as a bridge between device-specific RGB values and medium-specific color characteristics. Instead of directly converting from device RGB to print colors, the system uses the intermediary table containing L*a*b* values measured under controlled conditions to mediate the conversion process, accounting for differences in paper white, color material, and illumination.
3Stability of the object's composition
If standard colorimetry methods are used with fixed illumination sources, then measurement consistency is maintained, but color reproduction accuracy deteriorates under different illumination conditions
Solution Approach 1:
The patent systematically varies and records colorimetric values under different illumination parameters (color temperature, spectral distribution, illumination angle) when creating the colorimetric value tables. By measuring and storing values under multiple illumination conditions, the system can select or interpolate the most appropriate table for the actual viewing conditions, maintaining accuracy despite changes in lighting environment.
Data Source
AI summary
A color conversion system includes a first colorimetric input machine having a first color gamut and performing colorimetry of an object to output a first colorimetric value; an input portion to which the first colorimetric value is input; a converting portion converting the first colorimetric value to a second colorimetric value; and an output portion outputting the second colorimetric value. The converting portion stores a first colorimetric value table having color information about each measurement light source used when performing colorimetry by the first colorimetric input machine, and a second colorimetric value table having color information about each measurement light source used when performing colorimetry by a second colorimetric device having a second color gamut, and converts the first colorimetric value to the second colorimetric value by causing colorimetric values of the first colorimetric value table to correspond to colorimetric values of the second colorimetric value table.