Halogen headlight
Advantages: strong penetrating power, uniform light, easy installation and low cost
Disadvantages: low brightness and short life
Period of use: 1925 to the present
As the most common source of halogen light, it was the incandescent lamp invented by Edison, but the fatal flaw of incandescent lamp is that the tungsten wire is bright when it is energized, but the brightness is limited by the melting point of the tungsten wire, and the tungsten wire will volatilize at high temperature. Condensed on the outer casing, causing the bulb to ignite, affecting the life. Obviously, this incandescent lamp can not be directly used in the car, so people fill the incandescent lamp with halogen element gas, which can effectively increase the melting point and life of the tungsten wire. At power, the brightness of halogens can reach 1.5 times that of incandescent lamps, and its lifetime is 2 to 3 times. Reliable technology and low maintenance costs have been used until today.
Xenon lights
Advantages: high color temperature and strong brightness
Disadvantages: poor penetration, long delay time, short life and high cost
Period of use: 1992 to the present
In the 1990s, the increase in car penetration rate also made consumers expect higher values ​​for cars. The brightness of the original halogen lamps could not meet the demand, and driving safety also attracted people's attention. So in 1992, Hella and Bosch released their first Xenon technology headlights, and the BMW 7 Series (chassis code E32) released in 1992 was the world's first car with Xenon headlights.
At present, Xenon headlights are widely used in mid-to-high-end models. Xenon headlights are more popular because they have higher brightness and generally have better visual effects after being equipped with lenses. Because the color temperature is higher, the xenon lamp can be discerned by the human eye. At present, the color temperature of the mainstream xenon lamp is 4200K-6000K, and the light color is closer to the white light of the midday sun. The closer the theoretical color is to the color of the sun, the easier it is for the human eye to adapt. In addition to the higher brightness than halogen lamps, the tungsten-free formula also makes the life longer than the halogen lamp; then the power saving is better, the xenon lamp is only 35W, and the 55W halogen lamp is 3.5 times or more. The light greatly reduces the load on the automotive power system, and the power loss is saved by more than 40%. However, xenon lamps also have disadvantages. The most obvious is that in the extreme weather, its penetration is weaker than that of halogen lamps, and the cost and maintenance cost are much higher than the original halogen lamps. Therefore, halogen lamps and xenon lamps coexist for a long time. Each autumn is divided.
LED light
Advantages: good durability, high safety, long life, small LED size
Disadvantages: high cost, poor heat dissipation, discontinuous light, short life
Period of use: 2008 to present
LED headlights have a very common name: LEDs, a solid-state semiconductor device that converts electrical energy into visible light, which converts electricity directly into light, as early as 1962 by General Electric of the United States (GE). Holo nyak Jr developed a visible light LED. Now widely used in the market, it often appears as a light box, a signboard and a variety of electrical indicators and backlights, and is often used as an important component of car taillights, high-position brake lights, and daytime running lights. The real appearance in the car was that in 2008, the Lexus LS model used the LED light group as the headlight of the vehicle for the first time, and opened the LED as the source of the headlight light source.
In the early period, the LED components were sensitive to temperature changes. If the junction temperature (the PN junction temperature of the LED, the PN junction, or the LED illumination source) is high, the LED's illumination performance will be reduced, so the LED headlights require heat dissipation. Higher, requires a good thermal design to ensure the temperature stability of the LED components. It is precisely because of this that we will see behind the LED headlights, the rear of those LED components are equipped with heat sinks and even fans, which is not currently available in ordinary halogen headlights and xenon lamps. However, with today's LED headlights breaking through the layer-by-layer technology bottleneck, it has been quite perfect: small size, high stability, low energy consumption, and no problems such as thermal deposition and light degradation, so LED headlights are widely used in each On the model.
Laser headlight
Advantages: high brightness, energy saving, small size, long life
Disadvantages: high cost and poor security
Period of use: 2014 to present
The theoretical basis of the laser is proposed by Einstein in 1917 (stimulated emission), and the principle of laser can be traced back to the particle level. The light-emitting component of the laser headlight is a laser diode , which is actually thousands of LEDs. Their connections have many similar advantages, such as fast response, energy saving, small size, long life and low brightness attenuation. It has a greater advantage than LED in terms of energy consumption and volume.
Taking the BMW i8 as an example, the laser headlights will be used as an option. In terms of the illumination distance, the laser headlights can reach the range of 600 meters ahead. The model with LED high beam can only reach 300 meters. This setting also allows car owners to achieve better safety in sparsely populated areas. Like LEDs, laser diodes can only emit monochromatic lasers, which need to be synthesized by multiple monochromatic laser sources, or by passing the laser through a transparent medium such as quartz, resulting in broadening of the spectrum to form white light. BMW used the method commonly used by white LEDs - blue monochromatic light + fluorescent filters to make white light. According to BMW, the brightness and color temperature of laser headlights have been studied, and the illumination effect is in line with the visual habits of the human eye. Although the headlights have a high brightness and the light source is a laser, the laser headlights are fully compliant with the requirements of everyday use, and the lights do not cause harm to the human eye. However, because the laser has great energy, it will cause harm to humans, animals and plants, so it has high requirements on technology and has not been popularized so far.
summary
Regardless of the type of lighting, there is still a sense of existence. Halogen is also a good choice for the price-friendly models because of its low cost and low maintenance. If you are looking for higher quality Xenon and LED light sources, the price must be high. It is also relatively high, not cost-effective from the consumer's point of view; and laser headlights are not popular because of high cost, safety, etc., but with the advancement of technology, I believe that the functionality of future lights is also Will get better and better.
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