Reflector design is a common description of Parabolic and Free Form.
EFFICIENCY).
Parabolic: 27%
Ellepsodials, 1st gen (found on early 90s BMW): 36%
Free form: 45%
Ellepsodials, 2nd gen (found on late 96+ Audi, BMW): 52%
There has been a trend that more and more wehicles go away from the traditional
parabolic headlamp. The thick glass that are needed makes it a looser in the game
of efficient lighting. It seems like the majority of auto manufacturer selects
ellepsodials. They werent up to par in the first generation. The lower 180 degrees
of the bulb output were practically not getting out of the housing. The second
generation is designed with another focal point to increase efficiency.
BEAM CUTOFF). Projectors create a much sharper cutoff than reflectors. Allthough some parabolic reflectors can create pretty good cutoffs a projector will always be better. This has the main advantage that projectors can be aimed higher than reflectors because no stray light (above the cutoff) will exist to cause glare to oncoming drivers. This is especially important with high intensity light sources like HID and the new HIR halogen bulbs.
UNIVERSALITY). Projectors can be designed to be easily switchable from left drive to right drive beam patterns without loss of light. This usually done by turning the reflector housing in reference to the shield and you get the full 'opposite' beam pattern. UK needs this ability to drive legally on the continental Europe. This is why some cars for the UK market have projectors where the rest of the world don't. With a parabolic reflector, the 'kick up' part of the lens has to be taped up (so you lose the kick up completely).
VERSATILITY). Projectors are normally not used in combined high/low beam setups. Clearly, it's possible to have a moveable shield and this is just what happens with "bi-xenon projector" setups, but this would be very costly in a econo car with halogen setup. A regular H4 or 9007 application is much more cost effective.
What is the beam difference between ECE, DOT, JDM, and harmonized headlights?
Very simple, Bi-Xenon means that both high and low beam is created by
the same HID bulb. A Bi-Xenon system can be based on reflector and projector design.
The latter one is the simplest. Hella has a Bi-Xenon system that has a moveable shield inside a projector unit. This is acomplished by using a spring loaded solenoid
(just like in power door locks) or servo motor with 2 positions. Bi-Xenon came on many cars in 2002.
The advantage compared to a traditional projector HID low beam/Halogen
high beam is that you get HID low AND high beam.
Bi-Xenon systems have additional flash-to-pass separate halogen lamps.
Bi-Xenons System are a step up from regular low beam Xenons,
since there will be better high beams. The high beams in a HID low beam HID/
halogen high beam combination has a tendancy to be degraded to a beam cutoff softener.
It is easy to get spoiled by the powerful low beam HID which makes high beams with 65W
halogen almost dim in comparison. They should have been 140W high beam. Bi-Xenons
gives a better long distance view when high beam is on.
Bi-Xenons are not perfect either. Ideally, they should have made foreground lighting weaker
when switching solenoids over to high beams. But that feature in non avail so far.
See OEM HID database for cars with this option.
The downside with
Bi-Xenon systems and traditional low beam Xenon systems is that illumination close to the
car is too bright at high speed driving. This is one of the reasons why the "Vario Xenon"
system is superior.
See regulations section for more details.
How does a OEM Bi-Xenon system work?
Do not confuse OEM Bi-Xenon system with an aftermarked "Bi-Xenon HID kit".
This is described under the "HID kit" section.
The intention is to move bulb away from headlamps into a common, very powerful source. Weight will be saved because fibre optic wires are lighter than copper. Amount of bulbs will be saved. Fibre cable is terminated into a fresnel type lense which shapes the beam output. There are a number of prototypes out there, but they're still experimental. For a full-blown AFS lighting system (see further down), they'd be great, since the aiming motors would only have to move the light pipes, without moving the heavy, bulky fixtures. This would make the headlight "stylists" (and marketing people) happy too, since there wouldn't be any ugly clearance gaps between the moving part of the headlight and the surrounds.
How does a Vario-Xenon (Hella trademark) system work?
This is a future headlight system that will adapt to all kinds of conditions.
It has varoius sensors that make headlights adapt light distrubution
according to ambient light, speed, steering wheel position, and possibly
GPS coordinates. A common powerful Xenon bulb is placed away from the headlights.
Light is transferred through thin fibre optic cables to headlights,
where they terminate in variable fresnel lenses. Rumors say that
Verio-Xenon will be available during 2002 from Hella for automobile
manufacturers. The future will tell if they are able to get production
cost down. Volvo has been testing this system in their SCC concept
car since 2001.
What is AFL?
The Adaptive Forward Lighting (AFL) concept was later introduced
by Hella after Vario-Xenon,
probably a better name and probably lower cost. It utilises a
BI-Xenon projector unit to adapt to road conditions only
according to speed and steering wheel
position. The projector unit rotates up to +/- 15 degrees
to each side.
A second bulb and reflector will direct light 90
degrees sideways, which will help you see those dark pedestrians when you
take a right turn on red. Mercury Sable, Cadillac and some other north american
car models has similar function: A 25W bulb illuminates 50 degrees to the
side when turn signal is on.
AFL might be seen on a future Opel Vectra and Signum models, pending
ECE recognition.
What are the general options to get HID ligthing on my car?
The options are many. When converting to HID in Halogen housings, the success rate is mostly
based on how much light is actually going above the cutoff line, and how
even the beam spread is, not if the glass is fluted or not.
This page
describes all HID upgrade options, not just the "HID bulb placed into a halogen socket" option.
A reason for just choosing the best halogen available could be that you dont have time,
lots of patience, planning skills and finacial priorities for going
the HID route. An HID install will set you back $300 - $1800,
all depending on how much tools and parts
you already have. You dont know how much before you start planning.
What differs left and right side headlamps?
Optically, there will be no difference. Left and right beam pattern are the same.
Esthetically, left and right headlamp are of course mirrored, to make the front
look pretty. Internal components (ballasts, projector units) is most often mirrored
as well. Contents of components are the same, but mounting tabs, connector placement
and so forth, can be mirrored.
What can I gain from having HID in low beams, compared to halogen?
Having HID bulbs in low beams is widely used. Having a slow turn on HID bulb in a
low beam application is no downside. It is solved by having the low beams come on
right after engine is started, and they cannot be turned off before you switch ignition
off. In general, there are only advantages, besides from higher price.
What can I gain from having HID in high beams in a traditional
open reflector based system, compared to halogen?
Advantages:
1) Can use smaller reflector to achieve same or higher brightness compared to halogen.
2) Lower energy consumption. Physically heavy and amps sucking halogen based light
clusters seen on rally cars has become a thing of the past.
Disadvanteges:
1. HID bulbs do not achieve full brightness until the metallic salts in the HID
capsule are completely vaporized, which could take up to a minute (or more) on some
setups. This means they would not be much good for "flash to pass" signaling or
extra light on demand.
2. Decreased bulb life if turning HIDs off and back on again. Continuous use
in traffic passing situations would mean many hot re-strikes of HID arc, which
shortens HID capsule life and requires MORE startup current than a cold capsule,
thereby putting added wear & tear on your wiring and switching components.
3. Higher price. HID based systems costs more.
None of the above is a problem with a OEM "bi-xenon" setup, since the
high/low is accomplished thru a mechanical moving shield and/or moving reflector,
and the actual HID capsule remains constantly on, with no warm-up or hot
re-strike required.
A bigger diameter reflector result in that bulb sits further back and will result in more light getting reflected forward.
Per March 2003, there are no production cars using LED headlamps. However, several car manufacturers is experimenting
on prototypes. The first production models is expected to
reach production around 2005.
A typical LED headlamp will consist of 15-50 single LEDs. Each beam will be aimed in its unique direction. With an 80 degree beam opening angle and
15 LEDs, each beam will cover 5.3 degrees.
LED supplier Lumileds
is probably leading the LED output race with 120
lumens from a single LED. There is no doubt that Lumileds will
be one of the big suppliers of white LEDs for headlamp use.
Lumileds is a joint venture of Agilent Technologies (HP spinoff company)
and Philips Lighting.
For now, the challenges are:
Mitsubishi showed their prototype with LED headlamps in 2001.
Fioravanti Yak concept vehicle with LED headlamps was presented
in Geneva in March 2002. See article and pictures on
lumiled's press release.
Audi presented their prototype car, Nuvolari quattro, with LED headlamps
in Geneva in March 2003. See audiworld.com for deatils.
Copyright 2001, 2002, 2003 Automotive Ligthing FAQ