Semiconductor Laser Abnormality Detection via Pulse Control
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Solution Overview
Problem
Current light emitting devices with semiconductor laser elements and wavelength conversion members lack reliable safety measures to detect defects in the wavelength conversion member, which can lead to direct emission of laser beams posing risks to human eyes.
Innovation Solution
A method and device configuration that involves pulse-driving the semiconductor laser element to emit excitation light, measuring the optical intensity of both excitation and fluorescent light, and determining if it falls within a prescribed range to detect abnormalities in the wavelength conversion member, such as cracks or detachment, using a light receiving element positioned to detect excitation light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the wavelength conversion member is defective or comes loose, then the blue laser light is emitted directly to the outside, but safety measures to stop the laser diode are not reliably activated
Solution Approach 1:
The patent performs preliminary detection of the wavelength conversion member's integrity before allowing normal operation. By measuring the optical intensity of excitation light during a pre-check phase (when the light guide is in the detection position), the system identifies potential defects beforehand and prevents unsafe operation, thereby resolving the contradiction between reliability of safety measures and prevention of laser beam risk
Solution Approach 2:
The patent implements a feedback mechanism where the light receiving element continuously monitors the optical intensity of excitation light. When the measured intensity exceeds a predetermined threshold, the control unit receives feedback indicating a defective wavelength conversion member and automatically stops the laser diode operation, ensuring reliable safety activation based on real-time detection
2Measurement precision
If the light receiving element is positioned to detect excitation light through the wavelength conversion member, then detection accuracy improves, but the device complexity increases
Solution Approach 1:
The patent makes the light guide serve multiple functions: it acts as both the optical waveguide for transmitting laser light during normal operation and as the detection path for measuring excitation light intensity during safety checks. By positioning the light receiving element to detect excitation light through the same light guide structure, the system achieves accurate defect detection without adding separate detection pathways, thereby resolving the contradiction between measurement precision and device complexity
Solution Approach 2:
The patent uses the existing optical components (laser diode, wavelength conversion member, and light guide) to perform self-detection. The system utilizes the excitation light that already passes through these components during normal operation to detect their integrity, eliminating the need for separate external detection systems and reducing overall device complexity while maintaining high detection accuracy
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 more accurate and reliable detection of defects in the wavelength conversion member, enabling timely safety measures like stopping the semiconductor laser element's drive to prevent direct laser emission, thus enhancing safety.
Implementation Method 1
a semiconductor laser element configured and arranged to be pulse-driven by pulse-control to emit excitation light
Implementation Method 2
a wavelength conversion member including a phosphor and configured and arranged to emit fluorescent light by being irradiated with the excitation light
Data Source
AI summary
A method for detecting abnormality in a light emitting device including a semiconductor laser element that is pulse-driven by pulse-control to emit excitation light, a wavelength conversion member including a phosphor and that emits fluorescent light by being irradiated with the excitation light, and a light receiving element disposed on a light extraction side of the wavelength conversion member and that detects the excitation light, the method includes: pulse-controlling an applied voltage with a pulse width shorter than a time from a start of voltage application until an optical intensity of light extracted from the wavelength conversion member reaches a maximum intensity, thereby pulse-driving the semiconductor laser element to achieve laser oscillation; measuring an optical intensity of the excitation light, or optical intensities of both the excitation light and the fluorescent light; and determining whether or not the optical intensity or the optical intensities falls within a prescribed range.