Halogen vs. LED vs. HID vs. Laser: A Complete Guide to Car Headlights
Headlights have always been essential for safe vehicle operation, enabling drivers to navigate safely at night and in poor weather by illuminating the road ahead. Over time, technological innovations have transformed automotive lighting, progressing from basic 6-volt incandescent bulbs to advanced systems such as halogen, LED, and laser headlights. For example, the introduction of LED headlights improved energy efficiency and brightness, while adaptive systems now automatically adjust beam direction to avoid blinding oncoming drivers. As technology advanced, headlights gained the ability to adapt to changing road conditions and traffic, providing optimal illumination without compromising safety for other vehicles. These advancements continue to enhance driving safety and comfort, making modern headlight systems a vital part of vehicle design.
Types of Headlight Technology
Halogen Headlights
The most common type of headlight until a few years ago was the halogen headlight. This type of headlight utilizes a tungsten filament in an enclosed envelope filled with iodine or bromine gas (Kovalenko & Zhuravlyova, 2020). This transitioned from a large, sealed beam headlight that required the entire assembly to be changed to a smaller, more modular bulb. These types of bulbs utilized a reflector type of technology which used the light generated by the filament to reflect from the rear of the sealed beam or housing to shine forward of the vehicle (Nkrumah, Cai, Jafaripournimchahi, & Wang, 2024). This design is a very economical way of generating light and provides a fairly robust design to operate within the volatile automotive environment. As the power was transmitted through the tungsten electrode, it begins to evaporate tungsten atoms. Because the environment is immersed in a gas, it reacts with the gas to create the tungsten halide compound. As the gas is hot, it starts to travel back to the tungsten electrode and redeposits back into the filament.
With this continuous atom transfer, some of the disadvantages to this design include increased heat generation of higher amperage filament. With tungsten filament, the amount of power needed to generate light is higher than other conventional bulbs, and the cycle needed to generate that light is a lot of energy conversion events. This increased heat generation decreases the life span of the bulb and limits the lumen output of the entire system. The reason they were utilized so long in the automotive systems was the fact they did not require any different types of electrical system or technology to operate. To increase the use of halogen headlights and later light emitting diode (LED) headlights was the projector type of headlight. Unlike the reflector type of headlight assembly, the projector type provides a shutter to adapt the reflector surface to high beam request creating an environment that projects the light out further based on the driver’s input. These types of headlight assemblies provide the crossover between conventional halogen/LED bulb style headlight systems to the higher output high intensity discharge (HID) lights.
Xenon (HID) Headlights
Xenon headlights, also known as High-Intensity Discharge (HID) headlights, operate differently than conventional light bulbs do. Instead of a filament, they utilize an electric arc between two electrodes within a bulb filled with xenon gas and metal salts. This arc generates a bright, white light that closely mimics natural daylight. This increased brightness and lack of a filament to fail provides for a longer lasting headlight. To allow this light emission to occur, the electricity must jump the gap between the two electrodes and maintain that arc to an extended period of time. For this to occur, the power needed to maintain this arc for an extended period of time to keep the light projecting. This increased power needed to operate these lights requires a transformer. The transformer is supplied with 12 volts DC, and it is increased to over 25,000 volts to start the arc after the arc is generated it drops to 80-90 volts (Nkrumah, Cai, Jafaripournimchahi, & Wang, 2024). This increased light projection can cause a glare for those oncoming vehicles which must be managed to reduce the power output when a vehicle is coming towards it. The ability to illuminate the road in a way that was not seen before has helped to keep the driver seeing any potential obstacles in the roadway before a collision might occur.
LED Headlights
Light-Emitting Diode (LED) headlights represent one of the most advanced technologies utilized to project light forward of the vehicle. Unlike halogen or xenon headlights, there are no elements or electricity-produced-arches required to achieve illumination. Since LED’s are solid state electronics, their ability to produce light is inherent in their physical structure. Utilizing a semiconductor material as power (V) is passed through the material, the electrons recombine with the holes in the molecular structure of the material (Kim et al., 2020). When this recombination occurs, the emission is light which is then projected outward from the material. With the ability to put these in smaller packages and the fact that there are no moving components in this light structure, the longevity of this technology far exceeds most other lighting designs. No moving or thermally active components results in lower operating temperatures, which increases the lifespan of the component. Because of the flexibility of the material, the designers of the headlight systems can now adapt these to various shapes to work better with the contour of the vehicles' lines. Without this heat generation, one of the disadvantages is the lack of ice melting on the headlights in sub-freezing weather. Where the halogen and xenon lights generate some heat which would thaw out the ice attached to the lens of the light. Another disadvantage is the management of solid-state materials utilized in light. Just because it doesn’t put off a lot of heat, the material does heat up to the point that a thermal management system has to be put into place to dissipate that heat buildup. Because it is a solid-state electronic component, that heat threshold is such that it must be controlled of the supporting electronics may fail with a runaway thermal event.
Laser Headlights
Laser headlights are the latest innovation in automotive lighting technology. These systems use laser diodes to generate a highly focused and intense beam of light. The laser beams are directed onto a phosphor plate, which then emits a bright white light. The brightness of this style of head lamp surpasses most other forms of road illumination. The combination of solid-state electronics (similar to LED headlights) and a set of mirrors that project the light forward of the lens. The ability of the projector mirrors can provide some measure of control of where the light is directed. As the light is generated through reflection of a small output, the energy use of this style of light is lower than a conventional headlight which increases its use case for the roadway. The range of this light beam also exceeds most other forms of lighting which provides the driver with an illuminated roadway. Because of the level of brightness that these lights produce, the ability to use on the roadways of the United States was prohibited until recently (NHTSA, 2022). As work has progressed in Europe, the need for these highly expensive lighting systems has waned. Because of the complexity of light generation and the move toward adaptive lighting systems, the need for this technology is no longer on the top of the OEM’s development list.
Adaptive Headlight Systems
Adaptive headlight systems, also known as adaptive front-lighting systems (AFS), are an advanced feature found in many modern vehicles. These systems automatically adjust the direction and range of headlights based on various factors such as vehicle speed, steering angle, and road conditions. Making the headlights adjustable to the situation provides the vehicle and the operator with the adjustments necessary to keep their attention on driving the vehicle. Along with taking over the task of changing the brightness of the lights while driving, integrating the lights with the steering and other ADAS systems allow the vehicles ECMs to control what type of lighting that is needed for the situation. When a vehicle approaches the vehicle, the ECM can dim the lights, adjust the projection of the lights, or keep the brights on depending on the situation. One of the disadvantages of this system is that with increased control, the complexity of the system also increases the possibility of failure. As the systems become more complicated, the need for electrical diagnosis increases and understanding of how the system is supposed to operate is vital to diagnosing any part of the system that is failing. With Adaptive Driving Beam (ADB) headlights, the lights can adjust the beam coming out of the light to remove the area where the oncoming vehicle is moving. These types of vehicles incorporate a version of Artificial Intelligence (AI) to adjust the output of the headlight to provide the highest possible illumination without blinding the driver in the other vehicle (Nkrumah, Cai, Jafaripournimchahi, Wang, et al., 2024).
Matrix Headlights
Matrix headlights, also known as matrix LED, use multiple individual light sources to create a highly adaptable and precise beam pattern. As the vehicle is operated with these types of headlights, they can individually dim or turn off specific diodes to prevent glare for the vehicle driving towards them. This can keep the light as bright as possible for the driver while not hindering the person in the other vehicle. This precision control only covers a portion of the beam as the rest of the beam of light will continue the outward projection. This increased control does bring with it an increased complexity which requires an ECM and data line to communicate with other components to help control the lumens output. As with any system that increases its complexity, the cost will increase to meet those requirements. From more computing power to increased components, tomorrow's technology is paid for in today's dollars. As these systems proliferate throughout the automotive industry, the increased cost will be passed to the owner of the vehicle.
Conclusion
The evolution of automotive headlight systems demonstrates remarkable advancements in technology and engineering over the years. From the simplicity of halogen headlights to the sophistication of laser and matrix systems, each type of headlight offers distinct advantages and drawbacks. Understanding these different headlight systems allows consumers to make informed decisions when selecting a vehicle or upgrading their existing lighting systems, ultimately enhancing safety and driving experience. The purpose of the headlight was to illuminate the roadway for the driver to have an unobstructed view of the road, no matter the lighting conditions. When overcompensating for the lack of light with super bright light, the vehicle can overwhelm those driving towards it which then causes another problem. Mitigating all of the potential pitfalls for increasing the lighting capability of the vehicle must be considered when adopting a particular type of technology. After that decision is made and that technology is adopted, then the repair and replacement portion of the discussion must commence.
Technicians that understand how the system functions and where the failure points are located are vital to supporting this technology into the future. From halogen bulbs to adaptive lighting systems the vehicle is ever changing and we as an industry must adapt to those changes. Integration with other ADAS components, electrical and occupant systems will further enhance the ability of the vehicle to meet the changing needs of society. Keeping up to date with mobility changes, such as this, will help you keep the wheels rolling throughout the world.
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About the Author
Nicholas Goodnight, PhD is an Advanced Level Certified ASE Master Automotive and Truck Technician and a Professor at Ivy Tech Community College. With over 25 years of industry experience, he brings his passion and expertise to teaching college students the workplace skills they need on the job. For the last several years, Dr. Goodnight has taught in his local community of Fort Wayne and enjoys helping others succeed in their desire to become automotive technicians. He is also the author of many CDX Learning Systems textbooks, including Light Duty Hybrid and Electric Vehicles (2023), Automotive Engine Performance (2020), Automotive Braking Systems (2019), and Automotive Engine Repair (2018).
References
Kim, H.-Y., Kim, M.-S., Lee, K.-H., Kang, K.-M., Oh, J.-T., Jeong, H.-H., & Seong, T.-Y. (2020). Optimization of InGaN-based LED Package Structure for Automotive Adaptive Driving Beam Headlamp. ECS Journal of Solid State Science and Technology, 9(5), 055017. https://doi.org/10.1149/2162-8777/ab9dc6
Kovalenko, O. Y., & Zhuravlyova, Y. A. (2020). Analysis of characteristics of halogen and led automobile lamps. Light and Engineering, 28(4), 57–62. https://doi.org/10.33383/2019-067
NHTSA. (2022, February 15). NHTSA to Allow Adaptive Driving Beam Headlights on New Vehicles, Improving Safety for Drivers, Pedestrians, and Cyclists. https://www.nhtsa.gov/press-releases/nhtsa-allow-adaptive-driving-beam-headlights-new-vehicles-improving-safety-drivers
Nkrumah, J. K., Cai, Y., Jafaripournimchahi, A., & Wang, H. (2024). An evaluation of Halogen, HID, and LED illumination intensities in projector and reflector headlights for safe nighttime driving environment. Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, 239, 5088–5102. https://doi.org/10.1177/09544070241272799
Nkrumah, J. K., Cai, Y., Jafaripournimchahi, A., Wang, H., & Atindana, V. A. (2024). Highway Safety with an Intelligent Headlight System for Improved Nighttime Driving. Sensors, 24(22). https://doi.org/10.3390/s24227283