About car light technology
On and in cars lanterns or lights are used to light up the surroundings for better view, to light up the interior, for signalling purposes and for indicators. There are several light pulb technologies currently used, and all of them are used for any of the purposes.
SIMPLE LIGHT BULBS: Originally simple light bulbs where the light comes from heating of a reistance wire due to electric current was the basic technology variant used fomerly, and is still in use, but by now mostly for signal light and internal light. The reistance element is commonly made of tungsten (also called wolfram), often alloyed with the metal osmium. Both osmium and tungsten have a very high melting temperature and are therefore suited for making reistance elements. The bulb is either vacuumized or filled with a inert gas.
HALOGEN LIGHT: Halogen lights is partly based on the same technology with a metal conductor. But the bulb is also filled with a blending of halogen gasses. These gasses emit light by their own when heated to a high temperature. What happens is that the electrons in the gas molecules are kicked into higher orbits and the molecules emit light when the electrones fall back again to lower orbits.
GAS DISCHARGE LIGHTS (xenon lights) For high duty light bulbs like the long and short distance driving light, gas discharge light bulbs are by now often used. These light bulbs have a negative electrode or katode, a positive electrode or anode and in the bulb there is a blending of noble gasses like neon, argon, krypyon and especially xenon. The katode is constructed as a resistance elements and it is both held negatively charged and is kept hot by a current through the element. The electric potential between the katode and anode is held at a high voltage by a transformer.
What happens in a gas discharge bulb is rather complex. Electrones in the resitance element are kicked out of the elements by the heat to be free and are pulled towards the anode by the electric field. Such an electron then will collide with a gas atom and kick a new electron out of its orbit in that atom, and now there are two free electrons. One of these electrons will be pulled further to collide by another gas atom. The other will fall back in an orbit again in the first atom and then the potential energy is released as light. This process repeats itself all the way towards the anode. The blending of gasses in the bulb will determine the frequency blend of the light emitted.
LIGHT EMITTING DIODES: This technology has for long been used in indicators at the dashboard. More recently it has come into use for signal lights and by now it is steadily more used for higher duty purposes like fog light and near vision light. The diode consists of two semiconductor elements joined togeather which are doped differently but also based on different substrate meterials. Electrones in the element at the negative side has a much higher potential than those at the other elements, and when they pass the gap between the elements the potetial energy is released as light. Since such diodes are small and many such diodes can be joined together in more complex structures, the technology opens for a high degree of creativity and artistery in the design of lights. They are also higly efficient in that much of the consumed energy goes into light production and not production of heat.
LIGHT OPTICS: A car light, whatever purpose, contains not only a bulb and associated components, but also optics to distribute the light in the right directions. One purpose of the optics is to focus light. The focusing aspect is partly done by a mirroring holster with a concave shape where the bulb is situated. It is also partly done by a convexe glass at the front of the light device. Andother purpose is however to spread and diffuse some of the light also. This is done by smaller convexe and concave patterns in the glass or in the mirroring inside of the holster.
When using light diode as the light source, it is also posible to use optical fibers or tubes with mirroring insides to lead lights in the desired directions.
