Inductive Sensor Reflective Temperature Monitoring
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Solution Overview
Problem
Existing safety devices for motor vehicle headlights with laser light sources require high technical effort to implement and often interfere with lighting quality, as they need to detect malfunctions without causing delays or reducing the reflective area of the reflector.
Innovation Solution
A lighting device with an inductive sensor arranged outside the reflector to detect temperature changes on the reflection side, allowing for rapid and non-invasive detection of faults without compromising lighting quality, using an electrically conductive layer on the reflector and a coil to generate a changing magnetic field that induces eddy currents for precise temperature measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sensors are positioned on the back of the reflector to detect malfunctions, then safety monitoring is achieved, but openings and cutouts in the reflector surface are required which negatively affects light characteristics
Solution Approach 1:
The patent replaces mechanical/optical sensors that require physical openings in the reflector with an inductive sensor that detects temperature changes through electromagnetic induction. The inductive sensor measures temperature changes on the reflective side of the reflector without requiring any physical access to that surface, thus substituting a mechanical measurement system with an electromagnetic field-based system that does not compromise the reflector's optical integrity.
Solution Approach 2:
The patent uses temperature changes on the reflector surface as an intermediary indicator of laser light faults. Instead of directly detecting laser light or its absence (which would require openings), the system detects temperature changes caused by absorbed laser energy on the reflective side. This intermediary measurement approach allows indirect detection of safety conditions without compromising the reflector's optical surface.
2Reliability
If multiple sensors are used to detect safety-critical conditions, then detection reliability is improved, but device complexity and technical effort increase significantly
Solution Approach 1:
The patent extracts the temperature detection function from the complex array of multiple sensors and consolidates it into a single inductive sensor that measures temperature changes on the reflective side of the reflector. This eliminates the need for multiple separate sensors (position sensors, phosphor sensors, cover lens sensors) and their associated complex evaluation logic, while maintaining comprehensive safety monitoring capability.
Solution Approach 2:
The inductive sensor serves multiple safety detection functions simultaneously by measuring temperature changes on the reflective side of the reflector. A single temperature measurement point provides information about laser light absorption, phosphor conversion efficiency, and potential faults, replacing the need for multiple specialized sensors and achieving multi-functionality with a single device.
3Speed
If sensors are placed within the headlight to monitor lighting conditions, then real-time detection is achieved, but interference with lighting quality is unavoidable
Solution Approach 1:
The patent moves the sensor detection from the optical dimension (where sensors would interfere with light paths) to the thermal dimension. The inductive sensor detects temperature changes on the reflective side of the reflector through electromagnetic induction, operating in a different physical dimension that does not intersect with the optical path. This allows real-time monitoring without any interference with lighting quality, as the sensor operates thermally rather than optically.
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
Enables reliable, fast, and interference-free detection of temperature changes on the reflector, preventing laser light from escaping and ensuring the lighting device's safety without reducing its performance or requiring costly modifications to the reflector.
Implementation Method 1
a temperature change can be detected in an extremely reliable, fast, accurate, and non-disruptive manner... Temperature changes in the electrically conductive layer alter the current of the eddy currents and thus the magnetic field they generate
Implementation Method 2
inductive sensor, which is arranged externally with respect to the reflector... generate a time-varying, and in particular periodically, magnetic field by means of the coil
Implementation Method 3
The laser light from the laser light source, located behind the reflector, is coupled into the reflector through a through-hole and directed onto a phosphor, which in turn emits light that is partially reflected back onto the reflector
Data Source
Figure 1
AI summary
The invention relates to a lighting device (10) for a motor vehicle, comprising a laser light source (16) which is designed to emit light (16a); a reflector (14) with a reflective side (14a), which is designed to reflect light, and an electrically conductive layer; and an outer side (14b), which faces away from the reflective side (14a) and is arranged opposite the reflective side. The lighting device further has a safety device (12) for detecting fault states of the lighting device (10). The safety device (12) has at least one inductive sensor (12a) which is arranged on the exterior of the reflector (14) such that the outer side (14b) of the reflector (14) faces the inductive sensor (12a), and the reflective side (14a) of the reflector (14) faces away from the inductive sensor (12a). The safety device (12) is designed to detect a temperature change of at least one region of the reflective side (14a) of the reflector (14) by means of the inductive sensor (12a).