Car headlights, also referred to as car headlights, are lighting fixtures that illuminate the road and identify obstacles ahead when the car is driving at night or in heavy fog, rain and snow.
- The function of the headlamp:
(1) It can illuminate the road ahead, making it easier for drivers to identify roadblocks, pedestrians, and traffic signs, making it safer and more convenient to travel at night;
(2) It has the function of information transmission, which can convey the driving state of the vehicle itself through the change of light, effectively avoid conflicts with other vehicles, play the role of warning and reminding, and even can change the abnormal light to other drivers in emergency situations. staff for help.
- The development history of headlamps:
In October 1885, the German Karl Benz (Karl.Benz) developed the world's first real car, although the main components of the vehicle were fully equipped, but no headlights were installed.
In 1887, a driver lost his car in the dark and was lucky enough to come across a farmer with a lantern to get home safely, and the household lantern became the first car headlamp.
First generation, acetylene headlamps
The development from the earliest acetylene headlamps to today's reflective headlamps with lenses has spanned about 120 years of development. During this period, automotive headlamps have roughly gone through five generations of development.
In 1909, acetylene gas was first used as a light source for automobile headlights and continued until 1925. Acetylene is a kind of flammable gas, which is produced by the chemical reaction of calcium carbide and water in the headlights.
Second generation, incandescent headlamps
In 1913, helical tungsten filament was used as the filament of incandescent light bulbs. The American Cadillac car used this kind of light bulb to make headlights, which opened the era of automotive electrical lighting. Incandescent lamp is the first "electric lamp" used for automotive lighting in the true sense. It emits light by heating the filament to an incandescent state. Its birth opened the prelude to the era of electric lighting for automotive lamps. However, at that time, the on-board electrical equipment was still very backward, and the popularization and application of incandescent headlamps was very slow.
3rd generation, halogen headlamps
In 1964, the French "Spey" company produced the first halogen tungsten bulb headlamps, which have longer life and higher brightness than traditional headlights, and successfully replaced ordinary incandescent lamps.
Halogen lamps are an advanced version developed on the basis of ordinary incandescent lamps, and their appearance greatly extends the life of tungsten filament lamps.
The halogen lamp injects halogen gas into the bulb. After the tungsten filament is energized, the evaporated tungsten filament reacts with the halogen gas to form tungsten halide, so that the evaporated tungsten can be re-condensed on the tungsten filament, thus avoiding the premature failure of the tungsten filament. break, thereby extending the life of the bulb. The early halogen lamps still had various problems such as insufficient stability. Since then, with the continuous technical improvement of halogen lamps, they have been used until now. At present, most of the headlights on low-end cars still basically use halogen lamps as headlights.
Fourth generation, HID xenon lamps
HID（High Intensity Discharge Lamp）Namely high pressure gas discharge lamp. Xenon lamps can replace halogen headlamps mainly in the following aspects:
(1) The light color is pure, the color system is wide, and the color temperature is high. The light color is close to the color of noon sunlight, which is more suitable for the visual experience of the human eye. Such lights are used in the night lighting of vehicles to help ease the driver's safety. Tension and fatigue while driving.
(2) The power of normal work is small, only about 35w, but the luminous flux is large, and the service life is 10 times longer than that of ordinary halogen lamps;
(3) The xenon lamp will not go out suddenly, so in the event of equipment failure, the xenon lamp can still provide illumination until it gradually dims, which can give the driver corresponding response time for emergency treatment and increase driving safety;
Compared to halogen headlamps, the technological advancement of xenon headlamps is overwhelming. But the only "trouble" of xenon lamps is that they need special equipment to convert the vehicle power supply voltage into a stable high voltage. This equipment is called an electronic ballast, also known as a ballast.
Compared with halogen lamps, xenon lamps have various performance advantages, making them more and more widely used in automobile headlights, but the high technical requirements of ballasts have pushed up product costs, so currently only medium and high-end cars are usually equipped with Xenon lights.
Fifth generation, LED headlamps
LED, or Light Emitting Diode (LED), is the most promising new solid-state light source at present. As the light source of automobile headlight, LED has many advantages such as small size, fast response, low energy consumption, flexible design, reliability and durability.
The LED light source is an innovative lighting source, which is unique in that the LED headlamp does not have a filament, but uses a semiconductor to emit light. Compared with the halogen lamps and xenon lamps that are widely used at present, LED headlamps have obvious advantages in energy consumption, life, efficiency, structure, etc. The luminous efficiency of LED light sources can reach 20 times that of incandescent lamps. Automotive lighting also has the following characteristics:
(1) Safety: The LED light source is low-voltage power supply, and the voltage of the automotive power supply system is typically 12v or 24v, suitable for LED light sources. And the response time is extremely short, and the nanosecond response time is not only suitable for high-frequency operation, but also provides more reaction time for the driver.
(2) Stability: LED is a solid-state light source, which has physical characteristics such as shock absorption, impact resistance, and stability, and is fully adapted to the working environment of automotive lighting.
(3) Long lifespan: Theoretically, the lifespan can reach 100,000 hours, which reduces the number of repairs for car lights.
(4) Convenient design: small in size, light in weight, the area of a single chip is only 3~5mm2, and the chips can be arranged more flexibly according to the body structure and assembled into various shapes. The characteristics of easy control and management can better meet the needs of adaptive front lighting system design.
(5) Rich colors: LED light sources with different wavelengths can be made by changing semiconductor materials, which can be used inside and outside the car, and can be customized according to the needs of car owners.
(6) Energy saving and environmental protection: LED production materials do not contain heavy metals such as mercury, waste can be recycled, and have high luminous efficiency and low energy consumption, which can effectively reduce environmental pollution and help improve the greenhouse effect. Under the background, LED is applied to automobile headlamps as the fourth-generation lighting source, which effectively improves the life and efficiency of headlamps.
LED (Light Emitting Diode) light source, as the most promising new solid light source, has the advantages of long life, small size, low energy consumption, anti-vibration and impact, fast lighting speed, flexible design and flexible control. LED light sources have been widely used in interior lighting devices and exterior signaling devices. With the development of LED light source technology, its height and stability have been greatly improved, and it has become an inevitable trend to replace traditional bulb light sources in automotive headlights.
The sixth generation, laser headlights
In addition, the development of automotive headlamps has not stopped, and manufacturers are still trying new technologies and developing new products. At the CES show held in 2015, BMW launched an innovative laser headlight product, which can achieve a lighting range of up to 600 meters, which is equipped with a concept version of the hybrid sports car.
