Reference Illuminant Spectrum for High-Fidelity Color Reproduction
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Solution Overview
Problem
Automatic white balancing in digital images often fails to produce high-fidelity colors when no known reflectance spectrum is present in the scene, leading to inconsistent and visibly incorrect color representations.
Innovation Solution
Introduction of a reference illuminant spectrum created by a multi-channel light source with known spectral properties, which allows for high-fidelity color reproduction without the need for portable references like gray cards or color checkers, by capturing images with different illuminant spectrums and computing a calibration matrix to adjust pixel values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If automatic white balancing is used without known reflectance spectra, then the process is simple and fast, but color accuracy deteriorates
Solution Approach 1:
The system performs preliminary action by capturing multiple images under different illuminant spectrums (e.g., different LED color temperatures) before final white balance processing. This allows the computational module to analyze spectral variations and determine accurate reflectance spectra in advance, resolving the contradiction between processing speed and color accuracy by preparing data structures that enable fast subsequent processing.
Solution Approach 2:
The invention introduces an intermediary computational module that acts as a mediator between image capture and final white balance output. This module uses known illuminant spectra as reference intermediaries to calculate unknown reflectance spectra of scene objects, enabling accurate color representation without requiring direct measurement of object reflectance, thus maintaining both speed and accuracy.
2Measurement precision
If multiple illuminant spectrums are used for calibration, then color accuracy improves, but device complexity increases
Solution Approach 1:
The light source is designed with multi-functionality by incorporating multiple LED channels (e.g., blue, green, red LEDs) that can produce different illuminant spectrums. This universal light source can serve multiple calibration purposes under different lighting conditions, eliminating the need for separate calibration devices for each spectrum type and reducing overall system complexity while maintaining high color accuracy.
Solution Approach 2:
The system changes parameters by varying the operational state of LED channels to produce different illuminant spectrums. By adjusting which LED channels are active and their intensity levels, the system generates multiple known spectra without hardware changes, simplifying the device while enabling accurate multi-spectrum calibration through computational parameter variation.
3Measurement precision
If portable references like gray cards are used, then color accuracy improves, but ease of operation deteriorates
Solution Approach 1:
The system implements self-service by using the scene objects themselves as calibration references. Instead of requiring external portable references like gray cards, the computational module analyzes images captured under multiple known illuminant spectrums to automatically determine the reflectance spectra of scene objects. This eliminates the need for manual placement of reference materials, maintaining color calibration accuracy while dramatically improving ease of operation.
Solution Approach 2:
The invention uses computational algorithms as intermediaries to replace physical reference materials. The computational module acts as a digital intermediary that processes images under multiple illuminant spectrums to infer reflectance characteristics, eliminating the need for physical gray cards or color checkers and thereby improving operational convenience while maintaining calibration accuracy.
4Reliability
If mixed lighting conditions are present, then scene realism is maintained, but white balance accuracy deteriorates
Solution Approach 1:
The system applies segmentation by separating the contribution of different illuminant spectrums in mixed lighting conditions. The computational module analyzes images captured under multiple known illuminant types and decomposes the mixed lighting effects, allowing accurate determination of object reflectance spectra by isolating and processing each illuminant's contribution separately, thus maintaining both scene realism and white balance accuracy.
Solution Approach 2:
The invention implements feedback by using the known illuminant spectra as reference feedback to correct white balance in mixed lighting. The computational module continuously compares captured images against the database of known illuminant spectra and adjusts the white balance calculation accordingly, providing accurate color representation even when multiple lighting sources with different color temperatures are present in the scene.
Data Source
AI summary
Introduced here are computer programs and associated computer-implemented techniques for achieving high-fidelity color reproduction in the absence of any known reflectance spectrums. That is, high-fidelity color reproduction can be achieved without portable references, such as gray cards and color checkers. To accomplish this, a new reference spectrum—the “reference illuminant spectrum”—is introduced into scenes to be imaged by image sensors. The reference illuminant spectrum is created by a multi-channel light source whose spectral properties are known.