Color Space Calibration Matrix for LED Temperature Compensation
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Solution Overview
Problem
Color-tunable LED-based light sources face challenges in maintaining color accuracy and consistency across varying ambient temperatures and intensities, requiring improved color space transformation methods to ensure accurate color perception and control.
Innovation Solution
A method for calibrating color space transformation involving the generation of a conversion matrix from RGB to XYZ color space, accounting for different temperatures and correlated color temperatures, using a calibration mode to create a 3×3 conversion matrix through measurements and optimization techniques, and a productive mode to adjust light source parameters for accurate color control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a standard RGB to XYZ color space conversion matrix is used, then the transformation is simple and fast, but color accuracy deteriorates under varying temperatures and intensities
Solution Approach 1:
The patent applies preliminary action by performing a calibration mode before productive operation. During calibration, the light source is driven at a reference temperature and intensity to establish an initial conversion matrix. This preliminary calibration data is then used to correct measurements taken under varying temperature and intensity conditions, improving color accuracy without requiring complex real-time adjustments during operation.
Solution Approach 2:
The patent applies parameter changes by adjusting the conversion matrix based on temperature and intensity variations. Instead of using a fixed conversion matrix, the system modifies the matrix parameters according to the actual operating conditions (temperature and intensity), thereby maintaining color accuracy across different environmental conditions while keeping the transformation approach relatively simple.
2Ease of operation
If color measurements are performed in RGB color space, then measurement is technically favorable and simple, but color perception accuracy for human observers deteriorates
Solution Approach 1:
The patent applies the intermediary principle by introducing a conversion matrix as a mediator between the RGB measurement space and the XYZ perception space. The system performs measurements in the technically favorable RGB color space, then uses the conversion matrix to transform these measurements into the XYZ color space, which better represents human color perception. This intermediary transformation maintains measurement simplicity while improving perception accuracy.
3Adaptability or versatility
If the light source operates at varying temperatures and intensities, then adaptability to different conditions is improved, but color consistency deteriorates
Solution Approach 1:
The patent applies feedback by using the measured temperature and intensity values to correct the color space transformation. The system continuously monitors the operating conditions (temperature and intensity) and uses this feedback information to adjust the conversion matrix or apply correction factors, thereby maintaining color consistency despite variations in operating conditions while preserving adaptability.
Data Source
AI summary
A method for calibrating a color space transformation according comprises driving of a light source at a first ambient temperature T1. The light source it is tuned to emit light with a number N of combinations of at least two correlated color temperatures and at least two intensities. Furthermore, the method includes receiving first red coordinates, first green coordinates and first blue coordinates measurements in the RGB color space. First x-coordinates, first y-coordinates and first z-coordinates are received from measurements in the XYZ color space. 3×N matrices RGB_1 and XYZ_1 are constructed based on the received coordinates. A 3×3 conversion matrix C is generated to fulfil the relation XYZ_1=C*RGB_1.