Eye-safe laser lighting with phosphor conversion and feedback control
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Solution Overview
Problem
Laser-based light sources for illumination face challenges in ensuring eye-safety due to their high brightness and coherence, which can lead to unsafe conditions, especially when tampered with or when components degrade.
Innovation Solution
A laser-based light source system that includes a laser device, a light-conversion device, laser-output sensors, and a controller to monitor and adjust operations based on safe-to-operate parameters derived from laser and converted light signals, ensuring compliance with safety thresholds and reducing coherence through scattering devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If laser light is used for illumination, then brightness is improved, but eye-safety deteriorates
Solution Approach 1:
A light conversion device (phosphor) is introduced as an intermediary between the laser light source and the illumination output. The phosphor converts a portion of the coherent laser light into incoherent broadband light, reducing the coherence and brightness concentration that cause eye safety issues while maintaining overall illumination intensity
Solution Approach 2:
The spectral parameters of the light are changed by using multiple phosphors with different emission characteristics. This creates a broader spectrum output that reduces the intensity at any single wavelength, thereby improving eye safety while maintaining total luminous output
2Object-affected harmful factors
If laser light is converted to broadband light via phosphor, then eye-safety is improved, but brightness is reduced
Solution Approach 1:
Multiple phosphor materials with different emission spectra and efficiencies are combined in a composite light conversion layer. This composite structure optimizes the balance between converting laser light to broadband light (improving eye safety) and maintaining overall luminous output (preserving brightness)
3Reliability
If monitoring sensors and control systems are added, then eye-safety reliability is improved, but device complexity increases
Solution Approach 1:
Optical sensors continuously monitor the light output from the laser and phosphor conversion system, providing feedback to a control unit. This enables real-time detection of unsafe conditions (such as phosphor degradation or laser drift) and automatic adjustment of operating parameters to maintain eye safety within acceptable thresholds
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
The system provides reliable eye-safety monitoring and automatic adjustment of the light source operation, preventing unsafe conditions by detecting tampering, component misalignment, or degradation, thereby ensuring continuous safe operation.
Implementation Method 1
a laser device adapted for generating laser light of a predetermined laser wavelength and emitting this laser light as a laser beam
Implementation Method 2
a light-conversion device for converting at least part of the laser light into converted light
Implementation Method 3
Especially the use of a scattering device is advantageous, since this allows reducing the coherence of the beam and, thus, reduces speckle
Data Source
AI summary
A laser-based light source includes a laser device configured to generate laser light of a predetermined laser wavelength and emit this laser light as a laser beam. A light-conversion device is configured to convert at least part of the laser light into converted light and a laser-output sensor is configured to determine a laser-output signal proportional to the output of laser light emitted by the laser device. Further, a converted-light sensor is configured to determine a converted-light signal proportional to the output of converted light emitted by the light-conversion device. A controller is configured to receive the laser-output signal and the converted-light signal, to determine a safe-to-operate parameter, based on the laser-output signal and the converted-light signal, and to control the operation of the laser-based light source based on a comparison of the safe-to-operate parameter with a at least one predefined threshold.