LED automotive lighting applications require unique SAE standards

The development of AlInGaP materials technology in the early 1990s led to higher efficiency and better reliability in yellow-to-red light-emitting diodes (LEDs). Around the same time, led street light wholesale for various illumination applications was on the rise. Automotive exterior lighting was one of the first such applications starting with center high-mounted stop lamps (CHMSLs). In the late 1980s, the SAE (Society of Automotive Engineers) International Lighting Committee started to develop LED automotive lighting standards and their work continues today. Most automotive exterior lighting lamps are considered safety devices, and as such, these lamps are regulated at a federal or state level. Due to the nature of safety requirements, the introduction of LEDs brought together several different perspectives that became the central focus of LED lighting standard development with the SAE Lighting Committee.
SAE LED lighting standards have two categories:. Component or packaged LED-level (LED package) standards and system-level standards including the entire lamp, ie, a signaling lamp or headlamp (Note that in the auto industry the system-level lighting product is referred to as a lamp as opposed to a luminaire). The system-level standards only address lamp testing and performance when LED sources are used. Other source requirements are not included.
Auto signaling applications
The first established LED automotive lighting standard was SAE J1889, a standard for LED signal devices including all signaling and marking lamps such as stop lamps, tail lamps, turn signals, and daytime running lamps (DRLs). This standard has been updated several times over the years.
A key item in SAE J1889 addresses how procedures should differ when testing a signaling lamp using LEDs versus a signaling lamp using incandescent sources, as LED lamps include electronic components while incandescent lamps do not. Since LEDs are a temperature-dependent light source and the light output reduces as the junction temperature increases, the testing requirements must capture this characteristic to ensure the lamp installed on a vehicle fulfills the photometric performance requirements. A photometry test is conducted when the lamp is thermally stabilized.
Furthermore, most automotive lamps have both minimum and maximum photometric level requirements (light intensity values ​​at angular test points). There is an intensity ratio requirement for combined function lamps as well. For example, the intensity ratio between a stop function versus a tail function must have levels distinguishable by the human eye. These functional intensity ratio requirements are captured in the various SAE lamp documents. Also, SAE J1889 addresses the areas of initial light intensity output, stabilized light intensity output, device performance of minimum and maximum values, as well as light intensity ratio requirements.
Forward lighting standards
In the early 2000s, after breakthroughs in white LED technology made LED headlamps possible, the SAE Lighting Committee developed and established an additional LED lighting standard, SAE J2650, which addresses the need for LED forward illumination devices such as headlamps and fog lamps.
The tests to determine maximum and minimum photometry level ratios and thermal stability are similar to those of SAE J1889;. However, two additional performance requirements have been added for LED forward lighting devices The first addition is the red color content test because it is important to effectively render the color red in the roadway environment including obstacles, pedestrians, and signage - most notably the red stop sign.
The light spectrum emitting from headlamps must contain sufficient red color content to render these signs effectively for drivers to properly recognize the signs. Therefore, SAE J2650 includes a requirement for red color content as a percentage of the full visible-light spectral power distribution.
The second addition is the requirement of lumen maintenance over lifetime. Typically, SAE lighting standards do not address product lifetime requirements, but in this case the consideration was based on the fact that LEDs are longer-life light sources. As an led street light fixture Manufacturer output declines over lifetime, the guideline was designed to ensure that LED headlamps maintain a recommended minimum photometric output of 80% of initial light output over the rated lifetime.

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