Vehicular Lighting Device Abnormality Detection
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Solution Overview
Problem
The existing vehicle lighting devices using laser diodes and phosphors face issues with detecting abnormalities, such as phosphor cracks or dislocation, which can result in direct emission of coherent excitation light, posing safety hazards, and current detection methods suffer from noise-related precision degradation due to long wire connections between photosensors and lighting circuits.
Innovation Solution
A vehicle lighting device equipped with a dual photosensor system and current/voltage conversion circuits that differentiate between excitation and fluorescent light, allowing for abnormality detection through voltage ratio analysis, and includes noise-resistant design features like offset voltage adjustment and operational amplifiers to enhance detection precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single photosensor is used to detect light intensity for abnormality detection, then the detection system is simple, but noise-related precision degradation occurs due to long wire connections
Solution Approach 1:
The single photosensor is divided into two separate photosensors with different spectral sensitivity characteristics. The first photosensor detects excitation light intensity while the second detects fluorescent light intensity. This segmentation allows independent optimization of each sensor's function and eliminates the need for long wire connections, thereby reducing noise while maintaining system simplicity.
Solution Approach 2:
The patent introduces an intermediary detection mechanism using two photosensors with different spectral responses. By measuring both excitation light and fluorescent light intensities separately and comparing their ratio, the system creates an intermediate measurement approach that is more resistant to noise from long wire connections compared to direct single-sensor intensity measurement.
2Illumination intensity
If phosphor is used to convert laser diode light, then white light with broad spectrum is generated, but abnormality detection becomes difficult when phosphor cracks or dislocates
Solution Approach 1:
The system implements feedback by continuously monitoring the intensity ratio between excitation light (detected by first photosensor) and fluorescent light (detected by second photosensor). Under normal conditions, this ratio remains within a predetermined range. When phosphor abnormalities occur, the ratio deviates from this range, providing immediate feedback for abnormality detection and ensuring reliable operation.
Solution Approach 2:
The patent utilizes color (wavelength) differentiation by employing two photosensors with different spectral sensitivity characteristics. One sensor is sensitive to the blue/violet region (excitation light) while the other is sensitive to the yellow/green region (fluorescent light). This color-based detection method enables reliable abnormality detection by comparing the intensity relationship between different wavelength regions, maintaining reliability even when phosphor conditions change.
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 effectively detects abnormalities in the phosphor and itself, improving safety by preventing direct coherent light emission and reducing noise-related errors, ensuring reliable operation across varying light intensities and power supply conditions.
Implementation Method 1
The laser diode 12 generates blue excitation light 20 instead of ultraviolet light. The excitation light 20 is focused on the phosphor 14 by means of the optical system 16. Upon reception of the blue excitation light 20, the phosphor 14 generates fluorescent light 22 having a spectral distribution over a wavelength region including wavelengths (green to red) that are longer than the excitation light 20.
Implementation Method 2
a first photosensor structured to be sensitive to a first wavelength and to be substantially insensitive to a second wavelength, and to receive a part of the output light so as to generate a first current that corresponds to an amount of received light; a second photosensor structured to be sensitive to the second wavelength, to be substantially insensitive to the first wavelength, and to receive a part of the output light so as to generate a second current that corresponds to an amount of received light
Data Source
AI summary
A first photosensor is sensitive to the wavelength of excitation light, insensitive to the wavelength of fluorescent light, and receives a portion of the output light to generate a first current corresponding to the amount of light received. A second photosensor is sensitive to the fluorescent light wavelength, insensitive to excitation light wavelength, and receives a portion of the output light to generate a second current corresponding to the received light amount. A first current/voltage conversion circuit outputs a first detection voltage corresponding to the voltage drop across a first resistor. A second current/voltage conversion circuit outputs a second detection voltage corresponding to the voltage drop across a second resistor. If (i) a relation between the magnitudes of the first detection voltage and the second detection voltage has reversed, or (ii) if the first detection voltage deviates from a normal voltage range, a judgment unit asserts an abnormality detection signal.