Headlamps in automobile

Headlamps in automobile have come of age with a whole lot innovations and technology being introduce all to make night driving safer when traveling through the darkness. Headlamps have what are called beams and they are divided into two different types which are Low beam and High beam.
LOW BEAM
Low beam is also know as dipped beam headlamp provides a distribution of light which is designed to give an adequate forward and lateral illumination with limits on light that is directed towards the eyes of other road users, to control glare. The low beam is meant to be use when other vehicles are present ahead.
HIGH BEAM
High beam also know has full beam or driving beam headlamps provides a bright, centre-weighted distribution of light with no particular control of light directed towards other road users' eyes. As such, they are only suitable for use when alone on the road, as the glare they produce will dazzle other drivers.
DAYTIME RUNNING LAMP (DRL)
As the name implies it’s a lamp that keeps running in vehicles during daytime it is intended to increase the conspicuity of vehicles in motion during the daytime. It is standard in some countries that all vehicles made in or brought into their country must have DRL while in some countries any one goes like Nigeria you can either have a daytime running light or not.
TYPES OF HEADLAMPS
From 1880s to date they have been different introduction of headlamps into the automobile industries like the Acetylene lamps, Bilux bulb etc. This lamps and the technology behind them was what gave birth to the modern headlamps we have in the market today and they are
1. Tungsten
2. Tungsten - Halogen
3. HID (xenon)
4. LED
TUNGSTEN
This is the first electric headlamp and it is not as effective as the newer light source technology that we have today because it gives out small amounts of light relative to the power they consume.
When lamps are turned on blackening occur. This is because tungsten boils off the surface of the filament and condenses on the bulb glass reducing the light output of the filament and blocking some of the light that would pass through an un-blackened bulb glass.
Plain tungsten filaments are all but obsolete in automotive headlamp service.
TUNGSTEN – HALOGEN
This is halogen technology also know as quartz – halogen. It provides drivers with more light by making the tungsten filaments a more effective producer of light than what was available from non-halogen filaments at the same power consumption.
Theoretical it is said to slightly increase fuel economy and reduced vehicle construction cost through reduced wire and switch ratings.
HID (XENON)
HID stands for high-intensity discharge, a term referring to the electric arc that produces the light. The automotive HID lamps are commonly called xenon headlamps.
These lamps are formally known as gas-discharge burners, and produce more light for a given level of power consumption than ordinary tungsten and tungsten-halogen bulbs. Because of the increased amounts of light available from HID burners relative to halogen bulbs, HID headlamps producing a given beam pattern can be made smaller than halogen headlamps producing a comparable beam pattern. Alternatively, the larger size can be retained, in which case the xenon headlamp can produce a more robust beam pattern.
Advantages
1. Increased safety
2. Efficacy and output (produce more light from less power)
3. Longevity (Last longer than halogen)
Disadvantages
1. Glare: It causes high levels of glare to other road users for this reason they to be equipped with headlamp lens cleaning systems and automatic beam leveling control to reduce the tendency of high-output headlamps. It does not apply everywhere like in North America lens cleaners and beam levelers are permitted, they are not required.
2. Mercury content: HID headlamp bulb types D1R, D1S, D2R, D2S and 9500 contain the toxic heavy metal mercury. The newer HID bulb designs D3R, D3S, D4R, and D4S which are in production since 2004 contain no mercury but are not electrically or physically compatible with headlamps designed for previous bulb types.
3. Cost: HID headlamps are significantly more costly to produce, install, purchase, and repair.

LED
LED stands for light-emitting diodes, present designs, such as those available as optional equipment on the 2010 Toyota Prius, give performance between halogen and HID headlamps, with system power consumption slightly lower than other headlamps, longer lifespan and more flexible design possibilities. As LED technology continues to evolve, the performance of LED headlamps is predicted to improve to approach, meet, and perhaps one day surpass that of HID headlamps.