Testing requirements and advantages of LED lights applied in the automotive market

LED automotive light adopts LED (light emitting diode) as a light source. Since the LED possesses advantages of high brightness, variety of colors, low power consumption and long life, and it has enhanced that daytime running lights must be applied for motor vehicle in European before 2011, LED is more widely used in automotive interior and exterior, especially the application of interior automotive color LED lighting has been very mature. For example, applied in instrument lights, backlight switch, auto reading light and head-up display system etc. For exterior, it mainly adopts combined LED taillights, such as combines brake lights, turn signals, stop lamps etc.

Advantages:
1) Energy saving: LED automotive light is cold light source with low power consumption not more than -W, which can save more than 70% energy compared to traditional light source.

2) Eco-friendly: Typical green led light source. No ultraviolet or infrared spectrum, without heat or radiation, small glare, and waste recyclable, no pollution, no mercury elements, safe touch.

3) Long life: No loose parts in light fixture, without defect of filament is easy to burn when lighting, heat deposition, lumen attenuation etc. The service of life can be up to 60,000~100,000 hours under right current and voltage, more than 10 times longer than traditional light sources.

4) High-brightness, high temperature resistant.

5) Occupies small size, designers are free to change the lamp mode, so diversified automotive styling.

6) High stability and strong seismic performance: resin package, difficult to break, easy to store and transport.

7) High purity, colorful, without shade filter. Spectrum wavelength error is less than 10 nm.

8) High reaction speed without hot start time, can light on in microseconds, which can prevent rear-end collision. However, the traditional glass lamp bulb may be 0.3-second delayed.

According to IEC, EN, ECE, SAE, FMVSS108 federal regulations and relevant test standards, automotive LED lights is required to test optical characteristics, including the spatial distribution and total flux of luminous intensity (cd), spectral characteristics, chromaticity coordinates, dominant wavelength, luminance (cd / m2), color temperature etc parameters. Currently, most of the lights testing standards and requirements are based on the light intensity and illuminance values, almost all of the design and testing personnel will test lamp light distribution design and testing based on these data.

To obtain these data, we mainly use goniophotometer to test. According to CIE and FMVSS108 standards, LISUN recommend LSG-1950/LSG-1950S CIE A-α Goniophotometer. It mainly for measuring transportation industry lighting, such as traffic lights, buses, trains, ships and aerospace equipment lamps. The photometer head keeps static and face to the test sample while the test sample rotates around both horizontal axis and vertical axis, so the luminous intensity and illuminance of the tested lamp or luminaires can be tested.

Measurements:
Luminous Intensity Distribution Curve, Luminous Intensity Distribution Curve on any cross-section, Equal Illuminance Distribution Curve, Luminance Limitation Curves, Zonal Luminous Flux, Luminaires Efficiency, Glare rating, Maximum Ratio of Distance to Height, Equal Illuminance Diagrams, Curves of Luminaires VS Lighting Area, Isocandela Diagrams, Efficient Luminescence Angle, EEI, UGR and so on.

Traditional photometric measurement method is to fix the automotive lights on goniophotometer, or project the light distribution directly on the test wall to test the spatial light intensity and illuminance distribution. But this approach cannot intuitively obtain the light distribution in the road, it has to be obtained by the conversion of illumination and light intensity. However, since the reflection characteristics of the road surface is not completely Langbo scattering, leading to the inconsistencies of the actual brightness seen by the driver and the light distribution data measured by the above method. To solve this problem, there are several commonly used methods:
1)  Use goniophotometer to measure luminaires intensity distribution, then to deduce the illuminance distribution.

2) Converting the illuminance distribution data on the wall, to generate Aerial view of illumination data in the road.

3) According to the illuminance data of several sampling points in the road, to obtain the illuminance distribution effects.

Meanwhile, goniophotometer can also measure the total flux of automotive LED lights with very high precision (under the corrected conditions of detector spectral response curve). This is the absolute measurement method of LED total flux. In industrial applications, it also commonly used integrating sphere (relative method) to measure. Lisun LPCE-2(LMS-9000)Integrating Sphere Spectroradiometer LED Testing System for identifying the performance of single LEDs and LED lamps. According to CIE127-1997, IES LM-79-08 and IES LM-80-08, it recommends to using an array spectroradiometer with integrating sphere to test SSL products. The LPCE-2(LMS-9000A) also can do the LED optical maintenance test such as Flux VS time, CCT VS time, CRI VS time, Power VS time and so on which is meet LM-80. It can test LED lamps for CCT, CRI, Spectrum, Lumen, lumen efficient, power, power factor, current and voltage and so on which is meet LM-79.

In addition, LED lights are also being required to do conduction, radiation, surges, electrostatic, power frequency magnetic field interference and immunity tests, which can improve the photometric, colorimetric and temperature sensitivity of LED light source.