LED Color Control Using Sensor Calibration Matrices
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Solution Overview
Problem
LED lighting systems face challenges in maintaining consistent color output due to aging-related spectral shifts and variations in operation conditions, which affect color rendering and require complex and costly measurement methods like spectrometers for accurate color control.
Innovation Solution
A method for operating LED lighting systems with multiple emitters using a color sensor and calibration matrices to adjust drive settings, ensuring consistent color output by comparing measured color coordinates to target coordinates and iteratively adjusting settings until a predetermined matching condition is met.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a spectrometer is used to measure the color of LED emitters, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent uses a color sensor that measures color in a different color space (sensor color space) and transforms these measurements through calibration matrices to obtain accurate color information without requiring a spectrometer. This creates a simplified copy or representation of the spectral information that is sufficient for color control applications.
Solution Approach 2:
The patent replaces expensive spectrometers with inexpensive color sensors that have limited spectral resolution but can still provide accurate color measurements when used with properly designed calibration matrices. This substitution dramatically reduces cost while maintaining adequate measurement precision for LED color control.
2Measurement precision
If filters are selected to match CIE colorimetric functions, then measurement precision is improved, but ease of manufacture deteriorates
Solution Approach 1:
The patent transforms the measurement parameters by using calibration matrices that convert readings from sensors with simple filters (or no filters) into accurate color space coordinates. This parameter transformation approach eliminates the need to manufacture difficult-to-produce filters while maintaining measurement precision through mathematical correction.
Solution Approach 2:
The patent replaces the physical filter system (which would require precise optical filtering to match CIE functions) with a mathematical transformation system using calibration matrices. This substitution of mechanical/optical filtering with computational processing simplifies manufacturing while preserving measurement accuracy.
3Adaptability or versatility
If LED emitters are operated at different drive settings, then adaptability is improved, but color stability deteriorates
Solution Approach 1:
The patent implements a feedback control system where color sensors continuously monitor the actual color output of LED emitters at various drive settings, and this information is used to adjust control parameters. This feedback loop compensates for color shifts that occur when operating conditions change, maintaining color stability across different operational states.
Solution Approach 2:
The patent performs preliminary characterization of LED emitters by measuring their color output at multiple drive settings and storing this data in lookup tables or calibration matrices. This preliminary action enables the system to predict and compensate for color shifts before they occur during actual operation, maintaining color stability across varying drive conditions.
4Measurement precision
If multiple LED emitters with different primary colors are used, then color rendering is improved, but device complexity increases
Solution Approach 1:
The patent uses calibration matrices that establish mathematical relationships between the drive settings of multiple LED emitters and the resulting color output. By transforming the control problem into a parameter optimization problem, the system can manage the complexity of controlling multiple emitters through systematic mathematical methods rather than trial-and-error approaches.
Solution Approach 2:
The patent implements dynamic control of multiple LED emitters where the drive settings are continuously adjusted based on feedback from color sensors and target color specifications. This dynamic optimization allows the system to maintain excellent color rendering by actively balancing the contribution of each emitter based on real-time conditions and calibration data.
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
This approach allows for precise control of LED lighting systems to maintain target colors across varying temperatures and currents, improving color rendering and reducing the need for expensive measurement equipment.
Implementation Method 1
A color sensor or colorimeter is used to measure the color of the LED light output. Such sensors are typically composed of three filtered detectors
Implementation Method 2
Light-emitting diodes (LED) lighting systems, emitting either white light or colored light
Implementation Method 3
Light-emitting diodes (LED) lighting systems
Data Source
AI summary
A method for operating a LED lighting system at a target output color is provided. The LED system includes a color sensor and three or more LED emitters each operable at a controllable emitter drive setting. The method provides at least one calibration matrix defining a relationship between measurements obtained from the color sensor, represented by sensor color point coordinates, and absolute color point coordinates in an absolute color space. In some embodiments, a calibration matrix defining a non-linear relationship between the two color spaces is provided. In other embodiments, individual calibration matrices are provided for each LED emitter.