# Why is there not a standardized, optimized optics solution?

#### Mullet

##### Newly Enlightened
Hey CPF, I've been lurking for quite some time after I recently sold my BMW M3, bought a Jeep JK (horrible stock lighting) and moved to Bend, Oregon (where it happens to be really, really dark at night - few streetlights, small ambient light footprint from the small town of 80k people and desolate roads outside of town).

As I've read through the different auxiliary lighting threads, and hearing about the different light spread patterns, hot spots, artifacts, and trade offs, my question is this:

What is the engineering challenge behind optimizing the optics for a truly pleasing, even spread of light in either spot, driving, or nearfield solutions? Although I'm not an engineer, I studied to be one in college, and it would seem to be a relatively simple physics problem, to bend the light in the correct way either with reflectors or lenses, to create the optimal light pattern desired But it must be more difficult than I imagine, because the lights vary so much and we read of these hot spots, and dark spots, and other artifacts. Is it because the light being produced by the filament or other source is not consistent? It must also be because the light coming from the source is not one-directional (all beams coming in a straight line from the source).

I realize that the different manufacturers have different goals for each light, but there would seem to be a mathematically optimized solution that says a driving light should have X pattern, a nearfield (fog lights) should have Y pattern, and then based on the bulb build the optics to produce exactly the desired pattern, in an event, optimally dispersed way.

Another way to state the question is "Against what constraints are the engineers who are designing the lights working against?"

Hopefully this post makes sense.

Incidentally, I've purchased JW Speaker Evolution 8700 J lights for my Jeep, and am considering adding Hella 4000 auxiliary lights (probably LEDs) once I've lived with the JW Speaker units for a period of time. And although I miss my M3, I have to say owning a Jeep JK Unlimited has been some of the most fun I've had with a vehicle. The Jeep far exceeds my expectations.

#### Alaric Darconville

##### Flashlight Enthusiast
Welcome to the CandlePowerForums! Glad you've moved from "lurker" to "poster".
Hey CPF, I've been lurking for quite some time after I recently sold my BMW M3, bought a Jeep JK (horrible stock lighting) and moved to Bend, Oregon (where it happens to be really, really dark at night - few streetlights, small ambient light footprint from the small town of 80k people and desolate roads outside of town).
It's amazing how many places get dark at night... it's almost as if the planet's rotation has turned part of the Earth away from direct sunlight.

Although I'm not an engineer, I studied to be one in college, and it would seem to be a relatively simple physics problem, to bend the light in the correct way either with reflectors or lenses
Light can be bent (temporarily) with lenses, but then exits the lens in a straight line and is uncurved (gravity notwithstanding, but with the speed of light and the strengh of our gravity, it's immaterial).

Reflectors do not bend light at all (one could say there is a small amount of refraction in the protective coating of the primary surface reflectors in headlamps, but that coating is so thin it's negligable).

But it must be more difficult than I imagine, because the lights vary so much and we read of these hot spots, and dark spots, and other artifacts. Is it because the light being produced by the filament or other source is not consistent? It must also be because the light coming from the source is not one-directional (all beams coming in a straight line from the source).
The light source is pretty consistent, emanating from a near point source, which emits light in very nearly 4pi steradians (spherically). However, there is some amount of optical noise (shadowing and nth​ order reflections from filament supports and filament shields (depending on bulb type)).

I realize that the different manufacturers have different goals for each light, but there would seem to be a mathematically optimized solution that says a driving light should have X pattern, a nearfield (fog lights) should have Y pattern, and then based on the bulb build the optics to produce exactly the desired pattern, in an event, optimally dispersed way.
They have the goal of providing a beam that complies with the law from a lamp that is stylish, that doesn't cost a whole lot to make.
Another way to state the question is "Against what constraints are the engineers who are designing the lights working against?"
Redundant question is redundant.

[Incidentally, I've purchased JW Speaker Evolution 8700 J lights for my Jeep, and am considering adding Hella 4000 auxiliary lights (probably LEDs) once I've lived with the JW Speaker units for a period of time. And although I miss my M3, I have to say owning a Jeep JK Unlimited has been some of the most fun I've had with a vehicle. The Jeep far exceeds my expectations.
Nice lamps. The OEM lamps were compliant and objectively good, but they just weren't pleasant to drive behind for some reason.

#### -Virgil-

##### Flashaholic
Hey CPF, I've been lurking for quite some time after I recently sold my BMW M3, bought a Jeep JK (horrible stock lighting) and moved to Bend, Oregon (where it happens to be really, really dark at night

Many, many years ago I regularly drove through Bend in the course of long-distance drives. I tried to time things so I'd hit Bend after dark, pull off the highway, and lie on the hood of the car just taking in the amazingly starry sky. I hope (against probable reality) the light pollution there isn't too much worse now.

What is the engineering challenge behind optimizing the optics for a truly pleasing, even spread of light

Then there are organizations like Consumer Reports with their own headlamp tests (which are questionable in terms of their validity, but nevertheless are regarded as very important by automakers who want good ratings for their cars from CR). Then let's bring in the constraints imposed by whatever technologies we're using in terms of light source and optics. Then let's bring in the packaging constraints, the cost constraints, and the design/appearance goals.

it would seem to be a relatively simple physics problem, to bend the light in the correct way

That's contingent on there being one definition of "correct". There isn't. In the past, headlamps on American roads were very much more homogenous than they are now. All cars had sealed-beam headlamps and they all produced very similar beam patterns. We don't do it that way any more, for better and/or worse.

the lights vary so much and we read of these hot spots, and dark spots, and other artifacts. Is it because the light being produced by the filament or other source is not consistent?

No, headlamp light sources are quite standardized; that's not it. It's because the regulations do not control aesthetic/comfort aspects of headlamp output, they only control safety aspects: seeing light and glare light. This is done by specifying minimum and/or maximum allowable intensities at a range of points and zones within the beam. Therefore, a large range of overall beam characteristics are allowed.

It must also be because the light coming from the source is not one-directional (all beams coming in a straight line from the source

I don't follow your line of thinking here.

there would seem to be a mathematically optimized solution that says a driving light should have X pattern, a nearfield (fog lights) should have Y pattern, and then based on the bulb build the optics to produce exactly the desired pattern, in an event, optimally dispersed way.

Each different type of beam (low beam, high beam, fog beam, auxiliary high "driving" beam, etc...and even stop lights, turn signals, reversing lamps, and other signals we don't typically think of in terms of having a "beam") has its own specification as described above, with minimum and/or maximum intensities at various points and zones within the beam. It would not be practical (or a good idea) to tighten down the screws and say "A fog lamp shall have exactly 8,000 candela at this point, no more and no less. It shall have exactly 3,000 candela at these points, no more and no less. It shall have a cutoff with gradient 0.2, no more and no less", etc.

I've purchased JW Speaker Evolution 8700 J lights for my Jeep

Good lamps.

am considering adding Hella 4000 auxiliary lights

Also good lamps.

Aim is very crucial, make sure it's done right -- preferably with an optical aiming machine.

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#### TEEJ

##### Flashaholic
In a nut shell, I think the single largest challenge is simply the inverse square law.

If you want an even spread of light (A stated objective in post), the intensity of the illumination dropping with the distance via that law means that the farther away from the source, the dimmer the illumination (lux).

Unfortunately, this is the opposite of what we are typically going for in road lighting, as, typically, the problem is more along the lines of too much foreground light, and not enough distal light (lux).

Ideally, we could have less up close where we need less, and more off in the distance, where we need more. (We need a higher lux level, further away, to see the same detail that we can see with a lower lux level up close)

To get light to illuminate enough to work off in the distance, the beam's hot spot needs to be aimed so as to hit the ground, with high lux, but not oncoming driver's eyes.

As beams tend to fatten with distance from their source, shaping a beam to still be below an oncoming driver's eyes, yet put high lux on the road, becomes increasingly challenging...akin to a sharp shooter shooting the gun from the bad guy's hand, with a shotgun.

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