White pcLED Dual-Function Lighting and Lidar Detection
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Solution Overview
Problem
White phosphor-converted LEDs (pcLEDs) used in lidar systems face challenges due to their long decay time and variable delay time, which affect the accuracy of distance measurements and color rendering, limiting their use in high-accuracy optical detection and ranging, especially when combined with conventional lighting systems.
Innovation Solution
A dual-function lighting system utilizing white pcLEDs that performs both lighting and lidar functions by filtering light signals over specific wavelength bands, using a pulse-width modulation scheme to emit short-duration pulses, allowing for accurate distance measurement and color-independent calibration, without significantly impacting the primary lighting function.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If white pcLEDs are used in lidar systems, then the lighting function is maintained, but the long decay time of phosphor emission reduces measurement precision
Solution Approach 1:
The patent segments the detection process into two distinct wavelength channels: a first wavelength band (centered on blue emission around 450nm) for close-range detection requiring fast response, and a second wavelength band (centered on yellow luminescent emission around 560nm) for long-range detection requiring high energy. This segmentation allows each channel to be optimized for its specific detection range without compromise.
Solution Approach 2:
The patent changes the detection parameter from a single broadband channel to two spectrally-resolved wavelength bands. By filtering the detected light into these two distinct bands and processing them differently, the system achieves both fast response (using blue emission) and high energy (using yellow emission) for accurate ranging across different distances.
2Measurement precision
If white pcLEDs are used for high-accuracy optical detection, then the lighting function is provided, but the variable delay time between drive current and optical output reduces measurement precision
Solution Approach 1:
The patent applies preliminary action by pre-biasing the pcLED with a reverse-bias signal before firing it. This pre-biasing circuit prepares the LED junction to respond more quickly and consistently to the drive current pulse, reducing the variable delay time between current application and optical output. The pre-biasing ensures the LED is in an optimal state for rapid response, improving distance measurement accuracy.
3Adaptability or versatility
If white pcLEDs are used in lidar systems, then the lighting function is maintained, but the poor color rendering index limits application versatility
Solution Approach 1:
The patent changes the detection parameter from a single broadband channel to two spectrally-resolved wavelength bands. By filtering the detected light into these two distinct bands and processing them differently, the system achieves both fast response (using blue emission) and high energy (using yellow emission) for accurate ranging across different distances.
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
Enhances the accuracy of optical ranging by utilizing the faster decay time of blue emission for close-range detection and the higher energy of luminescent emission for long-range detection, while maintaining the lighting function's integrity, thereby improving distance resolution and sensitivity.
Implementation Method 1
A pcLED typically consists of a LED made from a single chip of a III-V semiconductor material such as indium gallium nitride (InGaN), and emitting light in a narrow wavelength range from about 450 nanometers (nm) to 470 nm
Implementation Method 2
A part of the blue light emitted by the LED is absorbed by a special material such as cerium-doped yttrium-aluminum-garnet ((Y1-aGda)3(Al1-bGab)5012:Ce3+), abbreviated as YAG:Ce. This special material is usually known as a phosphor, and it is embedded in an encapsulant transparent resin that surrounds the blue-emitting LED. The phosphor causes down-conversion of the absorbed blue photons through a photoluminescence process to yield a light emission characterized by a broad spectrum that peaks around the 550-nm wavelength
Implementation Method 3
The use of a pulse-width modulation scheme in combination with an optical filter that transmits blue light and blocks yellow luminescent emission
Data Source
AI summary
A method for detecting an object using visible light comprises providing a visible-light source having a function of illuminating an environment. The visible-light source is driven to emit visible light in a predetermined mode, with visible light in the predetermined mode being emitted such that the light source maintains said function of illuminating an environment. A reflection/backscatter of the emitted visible light is received from an object. The reflection/backscatter is filtered over a selected wavelength range as a function of a desired range of detection from the light source to obtain a light input. The presence or position of the object is identified with the desired range of detection as a function of the light input and of the predetermined mode.