Welcome to the forum!!!!

I've played around with machining parabolic reflectors and attempts to create shaped beams using modified commercial parabolics. None of them were worth trying to incorporate into a light.

Having someone around that knows what works or why something that one thinks might work won't, will be a great resource.

 

Welcome!!! Sounds like I'm going to enjoy your contributions here.
Mole

 

Outbound, nice to see you here.

I've question for you already. Here on the forum we had some discussions about efficiency of reflectors (+ some glass lense to cover the front) vs. TIR optics. It is hard to compare directly since reflectors can be OP or SMO and TIR lenses might have dispersion surface, but can you give us some basics which are better for some situations? Shurely at same size and same source of light (ie. leds we use here, XM-L, XP-L, XP-G,...etc)

 

Outbound, nice to see you here.

I've question for you already. Here on the forum we had some discussions about efficiency of reflectors (+ some glass lense to cover the front) vs. TIR optics. It is hard to compare directly since reflectors can be OP or SMO and TIR lenses might have dispersion surface, but can you give us some basics which are better for some situations? Shurely at same size and same source of light (ie. leds we use here, XM-L, XP-L, XP-G,...etc)

Great question, and can be a very complicated and variable answer. So the right answer is.... it depends. Like a lot of things in life, haha.

I will apologize in advance, I tend to kind of ramble and sometimes can go on a tangent. Always feel free to ask me to clarify something if there is any confusion.

Anyways. I'll start with the basics. Materials. So as you already know, there are transmission losses when passing through a material, some materials such as pure glass and optical grade silicones have much higher transmission than materials like PMMA, or worse, PC. However they are only account for between 4-8% of the energy loss. What's the major driver when it comes to TIR vs reflector discussions is the size of the TIR vs the design and sizing of the reflector.

TIR sizing plays a large part in this because the smaller a TIR is, the harder it is to actually collect the light from a larger source such as an XML, or really any CREE source that isn't the new FX chip. Therefore you tend to lose a lot more light through scattering. I ran a quick simulation of a 10mm tall, 22mm outer diameter TIR that's designed to be a pure spot, put an XML2 chip at 1200 lumens and simulated at 20 million rays. an see in the righthand side next to the Flux measurement, 915 lumens, so divide that by 1200 original lumens coming from the source, and we have optical efficiency around 76.5%. Now to demonstrate the sizing effect, I kept the same designed spot pattern, but made the TIR 8mm tall, and an OD of 18mm. The new flux measurement is 810 lumens, so the efficiency is now 67.5%. Efficiency dropped almost 10% by reducing the overall diameter of the TIR by 20%.

Now let's go the other way. Increase the TIR size by 20%. So now we have a TIR OD of 26mm and a depth of 15mm (outer diameter way more important). Now the simulation shows 1054 lumens, so that's an efficiency of almost 88%! It's fairly linear. Smaller = way worse, and bigger = way better.

So a savvy engineer can try and balance out the size he/she has to work with for the product, figure out the sources they are working with, and determine if two tiny TIR's with mid lumens are going to be better than one big TIR. There are fabrication challenges with a large TIR (talking over 30-40mm size) as well as very expensive tooling due to things such as shrinkage. Generally when you get into a TIR that big, you have to have it custom designed (as one should for every optic IMO) and can start to better shape the beam pattern to the desired effect. I am always a fan of a large optic over large lumen sources. Whenever I see lamps with tons of tiny TIR's and lots of LED's I cringe. It's such a waste of energy. Having to drive the sources harder, generate more heat, suck down more power, when could have gotten away with half the lumen output and still have the same beam pattern and intensity just by going with a larger well designed optic. However there is a point of dimmishing returns when it comes to TIR since at some point, the transmission losses account for the majority of the loss compared to optical efficiency. So a well designed light will start with the largest and most efficient optic, and work down from there.

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As for reflectors, there are two types as you know. The parabolic bowl types that you see on things like NiteRider and lots of generic lamps coming from China, then the downward firing reflector that you see on things like the Phillips SafeRide, and high end lights like the B&M IQ series. I assume you are questioning about the bowl type so I'll mention those for now. In terms of losses due to materials, there is now the protective lens, and the loss through the aluminized reflector itself. These combined add up to about the same as a TIR loss in terms of materials, 3-6% but will be a little less. So what should really be focused on is the actual reflector design, not materials. The type of lens is almost inconsequential. Glass vs PMMA vs PC amounts to a 0.5-1.5% difference when talking a 2mm thick lens.

The big difference is how much light is where you actually want it. So these simulations are going to show why I hateeeeee shallow bowl optics. Keep in mind that on the measurements of the lumen amounts on the TIR optics, it was measuring almost 45* left and right, and 45* up and down, which is MASSIVE and totally beyond the actual FOV that a person would really experience. The real FOV, and what I should really be measuring for true opticial efficiency is around +/-40* horizontal, and -35* to 10-15* vertical. But for the sake of clarity, I'll stick with an overall sense of when someone shines a light on a wall.

So let's start with a bowl similar in size and such as the original TIR we started with. 10mm tall, 22mm diameter. You'll see a surprising answer. It's actually more efficient in terms of "to the wall". 1017 lumens verses 915 lumens on that similar sized TIR.

However that's measuring up to 45 in the sky…. Think about the last time you rode your bike. Were you craning your neck up 45* to look at a tree or something? If you measure out beam angles you'll find that anything above 15* is semi-useless. Up close there is enough scatter from the light itself and light bounces on the environment that you'll still spot objects such as a tree branch or something with plenty of time. So with this in mind… let's revist that measurement and figure out how many lumens are actually "useful", such as between the FOV horizontally, and the 15* up, and -35* down (35 or more and you are basically lighting up your bike tire excessively, another discussion for another day). Now we can see the actual useful lumens is 813, or 68% efficiency.

So there are obviously some ways around this, can make the bowl oval like to try and make the beam pattern a bit elliptical, or can make the bowl deeper to try and collect a bit more, but then at that point you are starting to sacrifice beam width for the collection of excess lumens going where you don't want it too. Others use a hood or something, but that's just also kind of a waste unless the hood is designed to also reflect light onto the ground. Every hood I've seen is just flat black.

Going bigger doesn't necessarily result in better performance either! So this picture shows the similar TIR size that gained us 88% efficiency, (15mm tall, 26mm OD) and we are at 940 "useful" lumens vs the TIR had 1054. Or 78% vs 88%. Can see the overall width of the pattern tightened up a bit, but the actual useful "on target" lumens didn't.

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So how do we boost that optical efficiency? We determine the ideal beam pattern for the riding that someone wants. Cutoff vs Flood vs spot vs whatever. Mostly determining the beam angles. Then you can backtrack those beam angles to figure out how much light you want in certain areas and redirect some to those areas. This is where powerful optical modeling tools are needed, and even then it's not as simple as clicking a button like it was for me to generate these TIR and parabolic reflector models. It takes a lot of engineering, a lot of experience, and a LOT of time. I'm happy to dive into that topic a little later, share the math behind it, the perceived brightness vs actual, etc. Figure this is a good starting point.

 

If you take measurements in a consistent way (at 10 meters or 32.8' away) in a pitch dark environment, can help better figure out what's making good lighting. Obviously beam patterns play a MUCH larger part in peak lux readings, but can also help identify which lamps will let you see further than others. I've complied some comparisons of my own on niterider, Ion 700, and a whole gaggle of cheap chinese lights I've bought. Some surprising gems, some total **** lights, haha.

Love to see the data you have on your lights. Especially interested in Niterider data since it's a very popular brand yet few if any of the regular posting members own them. I personally use a 2 meter distance for my light meter tests only because that matched the method of MTBR's Bike light comparison which is my largest data base on current bike light performance information.
Mole

 

Love to see the data you have on your lights. Especially interested in Niterider data since it's a very popular brand yet few if any of the regular posting members own them. I personally use a 2 meter distance for my light meter tests only because that matched the method of MTBR's Bike light comparison which is my largest data base on current bike light performance information.
Mole

I'll compile some of the preliminary stuff I wrote down. But when I measure stuff without the integrating sphere (has it's place, but it's not the whole story) I focus on Lux at 10m (I strongly disagree with the method that MTBR does) and then measure beam pattern width at 1m or around 3' just because it's far easier to measure on the wall at that distance. Then I look for things like concentrated hotspots, what the lux readings are at the edge of it and can backtrack those numbers to get a rough idea of candella and intensity. I've successfully been able to then replicate that optic inside OPTIS with the sources they are using. It's fun for me.

Generally though off the top of my head. Ion 700R = 60 lux peak, tighter hotspot but nice wide spot optic. I like it personally. NiteRider 1400 had a peak lux of 65, wider hotspot though and about the same beam width as the Ion 700, in the 60* range for overall, and hotspot is around 10*.

 

Welcome. What kind of lights are you currently using?


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Welcome. What kind of lights are you currently using?

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Currently, when I go on a ride (both MTB and road) I use a lamp from Sate Light that I had gotten when I was evaluating a lot of lamps. Large TIR optic, 700 lumens. Produces a very nice rectangular beam pattern with about a 40* width, and 15* total height.

Though I've been designing my own bike light using my knowledge from the automotive side, so once I get those prototypes going I'll be riding MTB with my MTB focused optic, and then put my road-going version on my road bike. Road one will basically meet low beam requirements for automobiles, while the MTB is focused more on beam width and homogeneity.

 

Outbound, great answers, thank you for your detailed explanation. So we can conclude in general (over the thumb) the TIR produces more useful beam pattern for our needs, right?

It is great to have you here with all that knowledge and experience. Hopefuly the others would have interesting questions too. For me the next question would be SMO vs OP reflector surface. We all know the OP reflectors make beam looks nicer, less ringy, but again how much do we loose. Well it is just academic question since the lumens we have are big enough anyway.

 

.......So we can conclude in general (over the thumb) the TIR produces more useful beam pattern for our needs, right?

IMO, no. Most cases, I'll take a reflector beam over a TIR. The best reflectors for my beam preference are nearly as deep or deeper than their diameter. A shallow bowl type reflector throws too much like out to the sides. A deep reflector gives a sharper cut off between the lit and unlit areas. I don't care for lighting up the trail to the side of the bike. For me that just creates shadows that are eye-catching and a distraction. If the trail is tight and twisty, that's what the helmet light takes care of. Look at where you want the bike to go, not at the sidelines.

 

Glad to have you here and sharing your knowledge. I hope you're also sharing knowledge over at BudgetLightForum.com where users geek out much more than us here.

About the optic vs. reflector discussion - I know this isn't a "budget" forum, but I think many of us are somewhat budget minded, so the ideal optic/reflector designs are really out of reach for us I guess. We really want "bang for the buck" over "bang for the lumens" (again, many of us). I think us MTBR's are trapped in the situation where manufacturing costs are so high to build something for a market that is so small.

I'm using the same lux meter (after seeing horrible #'s from a cheap HS1010). I really should take lux throw measurements with my lights. (I started to back with the HS1010 and that's when I discovered it was way off, but never revisited it). Would it be a lot better/more reliable to do these lux readings outdoors vs. inside?

-Garry

 

Glad to have you here and sharing your knowledge. I hope you're also sharing knowledge over at BudgetLightForum.com where users geek out much more than us here.

About the optic vs. reflector discussion - I know this isn't a "budget" forum, but I think many of us are somewhat budget minded, so the ideal optic/reflector designs are really out of reach for us I guess. We really want "bang for the buck" over "bang for the lumens" (again, many of us). I think us MTBR's are trapped in the situation where manufacturing costs are so high to build something for a market that is so small.

I'm using the same lux meter (after seeing horrible #'s from a cheap HS1010). I really should take lux throw measurements with my lights. (I started to back with the HS1010 and that's when I discovered it was way off, but never revisited it). Would it be a lot better/more reliable to do these lux readings outdoors vs. inside?

-Garry

Well, I guess begs the question, what is considered "out of reach"? Generally what I've found in developing my own lighting is that the good battery pack, as in samsung/panasonic cells, hard case, silicone straps, etc. is what makes up half the cost of the high end stuff. It can cost almost $25-35 from the manufacture itself, add in the high cost of shipping heavy cargo when buying 1000 of them, not to mention the tooling for a custom hard case, and can understand why companies like Lupine, NR, and others have battery packs pushing $100-150. But can safely bet they are going to hit their runtime and battery output numbers.

I've tested out some "claimed" 5400 Ah battery packs that were under $7 from a manufacture, and they'd be half the claimed output, just like claimed lumens. I know some of you guys do some excellent work testing out battery packs just like I have my electrical guy do. With load testing and actual logged measurement, which is freaking awesome to see.

So I guess begs the question as well. What if there was a good, well designed lamp that you could get without the battery pack? That'd probably bring pricing down to something that's more "budget minded" for the lighting enthusiast who already has a bunch of good battery packs. I know Lupine, NR, and L&M use proprietary connectors, which I understand... from a business sense.... but hate it from the tinkering point, as I am sure you guys do too.

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Regarding the lux testing. If you have a large enough space like an open basement then testing down there can be pretty reliable. However if it's a small 10x10' white walled room, it's going to be pretty inaccurate and better off doing it outside.

However like I had mentioned before, the best thing is simply consistency. If you are outside and already have a 3-5 ambient lux reading from surrounding light like a streetlight or something then that's not a worry at all. It doesn't need to be pitch black. What you can do is just take your ambient reading at a few points you plan on measuring, and then subtract that from your actual reading to get a fairly consistent reading across the board. Some lux meters you can zero out, but I don't believe the one I linked can.

If doing it outside, I'd mark off a consistent distance that you can setup, shine it against a large wall or garage door. Doesn't have to be 10m, it can be 3m or 5m. The key is to accurately state what distance you measured at. That way it can be backtracked to candella, and someone else can compare their measurements to whatever distance they measured at, or whatever distance they want to potentially know the light intensity would be.

 

Right on about the battery packs, which is why we requested lighthead only on our custom build (which in turn makes it harder for the average person to deal with, even though they sell Panasonic packs which they could lump in as a complete kit offer). I totally agree on the quality battery pack, this is no place to cut corners.

-Garry

 

Outbound: thanks so much for sharing your expansive knowledge!

 

Specialized Flux Pro

Very interesting and unique public project!
But why create something which is already available by Specialized (Flux Pro & Expert)?

 

Very interesting and unique public project!
But why create something which is already available by Specialized (Flux Pro & Expert)?

Just because someone else has had the same concept doesn't mean I don't think it can be improved on. That was one of the few lights I saw that had the right idea, but I felt could be improved on with a deeper reflector and a wider spread.

It seems that the light wasn't the best in terms of reviews, and honestly, haven't heard of anyone actually using one except for a few european sites. Hence I set out to develop my own.

 

^ Absolutely true. There is almost always room for improvement, especially as new technologies come about and allow for pushing the envelope even more. Optical grade silicone materials, thermally conductive plastics, magnesium die casting for heat sinks, smaller and more powerful LED chips, more powerful battery cells. All of those things weren't really around 3-4 years ago when the Specialized was developed, or really when any "new" generation of lights was developed. That's why I'm looking to try and usher in a new generation.

 

Nice to see your simulation possibilities. That's unfortunately only for the very brave to purchase for private use. Looking at your post #7 please give some hints on the losses through a TIR lens - as used for many Cree's (still have some LM for the MC-E lying around). Looking at such lens when lit, you can see the light "inside". That's also shown in your ray traces (is that the right word) - not all rays are reflected internally, some leave the plastic (or glass). Would it be helpful to give such lenses a coating, maybe even a reflective one like chrome/aluminium/silver coating as on "show plastic" or plastic reflectors ? Just to get the efficiency up ?

You mentioned a new software you now have to hand ? Are there significant differences in performance that means the resulting optics design from professional softwares ? I assumed such is only relevant on consumers level...

 

The optical loss through a TIR depends a lot on surface finish of the outer surfaces and the material itself. Most TIR's are made of PMMA which has a good clarity, but the real power of a TIR comes from how well polished the outside faces are, and that's where the difference between a cheap TIR and an expensive TIR come into play. It can cost upwards of 5-6 times the cost of the tool to get the proper polish, especially on small lenses while maintaining the proper curvatures. Doing a coating on the outside won't really improve things at all.

There is a massive difference in professional software vs cheap or freeware type of stuff. We are using the same software packages that OEM automotive designers use. The resulting surfaces that are generated allow for some very cool systems.