LED auto lightings use LED technologies for both exterior and interior lighting. They offer long service life (up to 50,000 hours), strong vibration resistance, and stable brightness over time. To ensure quality and compliance, various detection technologies are used to evaluate optical, electrical, and thermal performance.
Optical Performance Testing
Luminous Intensity
Luminous intensity measures the light emitted in a specific direction. Due to the directional nature of LEDs, the CIE127 standard is used with conditions A (far-field) and B (near-field, commonly used). A detector with a 1 cm² area captures light intensity data.
Luminous Flux and Light Efficiency
Luminous flux quantifies the total light output. Two main methods are used:
- Integrating Sphere Method: Measures and compares output from a reference lamp and the test lamp. It’s simple but sensitive to color temperature differences.
- Spectral Method: Calculates flux based on spectral power distribution across wavelengths (380–780 nm) using a monochromator.
Luminous efficiency is the ratio of luminous flux to power consumption. Constant current supply ensures accurate measurement.
Spectral Characteristics
Key parameters include spectral power distribution, color coordinates, color temperature, and color rendering index (CRI). These are measured with a spectrophotometer to ensure consistent light color and quality.
Light Intensity Distribution
This test maps how light intensity varies with angle, forming a distribution curve. It helps determine beam pattern and uniformity, commonly measured using automated goniophotometers.
Temperature Effects
Temperature can shift the LED’s emission spectrum and color. Controlled thermal testing ensures optical consistency under various conditions.
Surface Brightness
Measured using a surface or sighting brightness meter, this test evaluates how bright the LED appears from a given angle.
Electrical Performance Testing
Electrical parameters determine basic LED functionality:
- Forward Voltage: Measured by applying a constant current and recording the voltage drop.
- Reverse Current: Measured by applying reverse voltage and monitoring leakage current.
Accurate testing requires proper meter placement due to the LED’s directional conductivity.
3. Thermal Performance Testing
Heat affects both optical and electrical performance. Key parameters include:
- Junction Temperature: The PN junction temperature, measured via electrical parameter methods using the linear relationship between voltage drop and temperature.
- Thermal Resistance: The resistance from the junction to the LED surface, indicating heat dissipation efficiency.
Common methods include infrared imaging, electrical characteristic analysis, and micro thermocouples.
Conclusion
Comprehensive testing of LED car lights—covering optical, electrical, and thermal parameters—is essential for performance validation, safety, and compliance. These detection technologies ensure that automotive LEDs deliver reliable, long-lasting illumination in all driving conditions.