Clear Headlamps

[Frame57]

In the last few years automobile headlamps have went from Fresnel type glass lenses to clear polycarbonate covers with carefully shaped reflectors. Why the change and why couldn't it have been done years ago?

 

[Zelandeth]

If I remember correctly, it was only in the mid 1990's, that it was legalised to have polycarbonate covers on headlights. (Believe the Peugeot 406 was the first production car in the UK with them - I wouldn't swear by that though).

Whether that's the main reason or not I haven't a clue, but it does seem likely.

 

[naromtap]

I think the change is probably due to do polycarbonate being cheaper, certainley lighter & safer to pedestrians in an accident.

 

[Chris M.]

A lot of developments in car headlamps has come from advances in computer design over the years. A special faceted reflector that could produce a beam pattern up to European/British spec is not an easy thing to make without some very careful precision design. Computers make that relatively easy, with the added bonus that it`s cheaper. They can use simple, durable and bump resistant plastic (or glass) in place of fragile molded fresnel glass for the outer covers, while still using the same style chromed metal reflectors inside, only with a fancy shape designed by computer but made in a similar way to regular curved reflectors.

It could also come from changes in trends over the years. Clear lenses are just cool right now. Most every new car I see on the road has clear lenses front and back, save for the legally required red reflectors/lenses at the rear. The amber turn signals (which have to be amber on the front and back here) all have clear covers and those hopeless amber lacquered bulbs inside that fade to almost-white in 6 months. It almost seems like amber coloured lenses are not allowed any more - though that is not true of course. It`s just the present popularity, which will change in the future. My little white van is like that - no orange lenses anywhere. At least my turn signal bulbs seem to be a decent quality and are actually still orange after a year or so.

I rather like the projection type headlamps actually. They look good (a simple round lens behind a clear glass cover), and glare much less than regular types to oncoming traffic which is always a good thing, but the downside is a disconcerting blue flicker at the edges of the beam that can sometimes look like an oncoming emergency vehicle out of the corner of your eye. Emergency vehicles in this country only have blue strobe warning lights (not red or white as well), and asides from the occasional ricers and also heavy goods vehicles who frequently have a pair of blue LEDs shining out of their front windows, blue light is not seen on anything other than police, etc. Makes you turn round and look for a second or two.

But I digress....

/ubbthreads/images/graemlins/grin.gif

 

[Bob Snow]

It's really not the polycarbonate in the front lens that allows this. It would certainly be possible to make a clear glass cover and compound reflector. Typically, the reflector of the older sealed beam lamps were silvered glass and the front lens on a these lights had molded optical features to correct beyond what the simple reflector could do. Some aero front lenses are still glass, but the reflectors are typically plastic, with what I assume is a mylar coating. It is probably the change in reflector material along with computer design that allows this. Some reflectors are faceted, much like the stealth fighter, while others use compound curves more like the stealth bomber. I wonder if it has to do with more capable computer models? The other big design change is the projector beam which adds lenses to the light path. The one complaint I have heard about projection headlamps has to do with visibility by other cars. Some have very small front lenses that can be hard to see when approaching at some angles.