Planning an aspheric scratch build

Flashlight Modding and DIY Parts
61

and yeah? i do this same thing with imaging lenses too, for night vision.

i buy a lens with longer FL than i want? and drop the FL by adding a lens behind it… which lowers the F number to wjerever i want it to be.

since the F number controls how “powerful” the night vision unit will be? it should be obvious my units are, uhm… “better”. and i can do things the other night vision builders cant do. or that they think is impossible or priced like unobtainium.

dont you see? i am an ENGINEER, i used to make “mathematical models” for a living when i was younger. i have 2 university degrees in mathematics and computer science.

look at my tag line? “with enough black coffee and cigarettes? all things are possible.”

thats not just a phrase to me… thats what i “do”.

62

you keep telling me, that it is impossible??

then riddle me this. Where exactly do you think compound camera lenses COME FROM? they dont come from planet pluto, do they? no, they come from earth. humans make them. they exist.

why do you suppose those equations are called the “lens maker equations”, eh? Because compounds lenses CANT be MADE ?

if i want a compound lens, that has a variable focal length? i simply choose the proper two lenses, then slide them from touching, to further apart. Then i readjust the emitter distance to re-focus up. Easy.

Didnt you ever notice there are a LOT of camera lenses that are 2,3 or 4 lenses only? fairly simple construction? Where do you think they come from? They get made by people doing what i do.

the reason its not being done in the flashlight world or almost never? simple… all of the optics engineers work for the camera lens and binocular and telescope companies. Also, no doubt? The chinese flashlight factories? Are going to be like the IR illuminators back on my night vision site? They are just interested in basic fabrication, fast money out the door. They have no vested interest in making the design or build more complicated. I, on the pother hand? am not a “businessm,an” in a suit that has to answer to investors. Its in my best interests to design something “better” and make it. Particularly enjoying it, if it IS more complicated or advanced.

again, not trying to be RUDE, but… you keep telling me theres some “delta problem” which you allow to keep you from thinking you can do anything. Since i was not aware it wasnt possible? I just found a few equations, solved for what i needed and set about making what i wanted to make.

its amazing what you CAN do, when you are unaware of how you are not supposed to be able to do it. Which is of course news to me? since i have already done this stuff before already, in real life. I just needed to learn fabricating and machining to make my units i already have designed and working already.

engineers like me? we arent particularly or necessarily any “better” at math? than anyone else that took math classes. In fact, most of us really arent the best at it, to be perfectly honest. Its the WAY we were taught to USE it thats different. Also? “most” engineers? are unfortunately like “regular math people”, in that they need an equation to use.

the TRICK is? to go out anmd FIND something that has all the variables you are going to use. Then usually, you have to rearrange (solve and resolve multiple times) the equations INTO the form you NEED. If it was sitting somewhere, ready to use? Iy obviously wouldnt be a “problem”, now would it?

and, for me, a big dose of my frame of MIND going in. I concentrate on what i DO know, and go on from there. Or, I have other “tricks”. I orften start at the “solution”, and concentrate on creating the LAST STEP (missing) that obviouly led to the solution. Then i figure out what the step before that must have looked like. Eventually i end up at the “beginning” and i am done.

Or i start at the easy beginning… AND at the solution… and i “come in” from the beginning, and i come in from the end… and i “finish up” in the middle. In the end, i have all the steps. the fact i solve them out of order? doesnt matter when i am done.

==

in real life? MOST people seem to find me “intelligent… but eccentric”

and i can live with that. and so can my CAT.

63

Sedstar,

I know that a lot of guys on NV forum used your theory and practical experiments to build their own product(and since they probably have better machinery they really made great NV equipment) and now all those guys are making some serious cash $ and all that because you are unselfishly sharing your knowledge to the world even into tiny details how do you actually do something.

The main idea is important so lets say cool futon builds of some members were grown from your original idea and yet that guys does not seem to pay respect to inventor.

Enderman,
You are also one knowledgeable man and since I am not on degree like lets say Sedstar or Djozz(as examples) I really can’t comment or argue your theory.

I only know what I build and what I see and when I strictly concentrate on pure die projection of SR multilens system (I don’t look other reflections around) only conclusion I have is wow… This is clearest die projection I saw in my life. Seriously you see tiniest phosphor imperfections. If you don’t trust me invest around 90$ build your own and then you’ll see.

Sunnranger is modified UF-T20 flashlight on which into their stock threads only by pure accident and without additionally machining you can fit Yukon 3x42(or even bigger) night vision lenses.

And in my theory those NV AR coated lenses when U stick white led into SR are preventing or obscuring throw capabilities that usually don’t happens with osram IR emitters.

42mm multilens IR SR is very close to performance of 67mm single aspheric. So I don’t even doubt that with right choice of lenses like Sedstar mentioned something fantastic and in small and acceptable size can be made.

64

Are you ok?
I never said something wasn’t possible, I just explained why I don’t like multi-lens systems.

Also, from your wikipedia” equation, it is already obvious that you can’t create a longer focal length than simply using one lens at the max distance.
Adding more lenses closer to the LED will always shorten the focal length. And I already explained what a shorter focal length does, it makes the delta angle larger because an LED is not a point source of light.
You keep talking a lot without providing any proof of what you’re saying. If you want to test out your theories then download a ray tracer and test it out, see for yourself if you can make it work.

PS- stop bragging about how many degrees or potatoes you have, nobody cares. One thing I learnt from university is that a degree says absolutely nothing about a person’s intelligence or ability to actually build something.

Nobody is stopping you from building a multi-lens flashlight, so go ahead and do it and come back with more results and less talk :wink: Maybe we should decide on a diameter and I will make a single-optic flashlight and you can try to beat it with a multi-optic design?

65

This is rude man… Why rudeness?

66

Edited
He was being condescending.

67

Now that’s the spirit… :+1:

Lets build it! I bet that multiple lenses system will beat a single lens one.

P.S.

I almost forgot on Ervin Anastasi…? Check this out: The other million bet beam

68

Sedstar,

Could this lenses be good contender?

I mean they don’t have AR coating like Yukon lenses? And it is about 4 lenses inside that? Is that worth a try? I mean I should machine the tube and pill but it should be doable?

69

Wow fellows, what a buttload of useless talk up there!

I think sedstar is trying to point out that the problem can be solved, and indeed it can. To the point that the emitter's size, and wether it is domed or not, would have very little impact on the final result for as long as the last lens (main collimator) were to be large and powerful enough with very low focal distance for maximum convergence and sufficient size for minimal loss of light:

Zoom lens @ Wikipedia

Of course, this implies a good quality host with fine threads for the lens' assembly.

Cheers

70

I disagree… This talk was very useful to certain point.

Multiple lenses flashlight/illuminators are not commercial available but they exists and I am one of plenty diyers that have build such system so I know that it works with IR light and that with little luck(proper lens selection) it should work with visible led light.

So there is no point that someone who builds only single aspherical system claims that multi can’t be done to guy or guys who have already build such systems.

There’s nothing that can’t be done. And if you can have for example 500kcd flashlight in a 50mm head diameter than it is worth a try.

71

luminarium iaculator, I just implied there was “a buttload of useless talk up there”, which is different than presuming “all of the above up there is a buttload of useless talk”. ;-)

The collimator just above the emitter could be a extremely strong custom made fresnel lens, big and thick.

Cheers

72

Have you ever tried using a lens to focus a COB LED?
You would know that the size of the emitter ALWAYS matters, and as long as it is not a point source of light, all those wikipedia drawings cannot be applied to real life.

As mentioned earlier, having a large thickness lens close to the LED will collect a lot of light yes but also make a huge spot.
Buy yourself a short focal distance lens and test it out yourself, it sucks for throw.

73

This depends on how you define throw. As long as the lens diameter is the same, the luminous intensity (candela) of the beam will be the same for different focal length lenses. I personally think having a larger spot is usually better. Isn’t putting as many lumens as possible downrange what this is all about?

74

Like calculating parallel resistance. (1/Rt) = (1/R1) + (1/R2)

75

True, but at the same time the point of having a concentrated point of light with no spill will kinda be defeated.
I prefer near-collimated light, so that the divergence is as close to 0 as possible.
It is also more complicated to make thick aspheres with a close focal length than thin aspheres with a long focal length.
The longer the focal length is, the more similar an aspheric lens gets to a spherical one.

It’s basically a compromise / personal preference between larger spot, more divergence, more lumens, vs smaller spot, less divergence, less lumens.

Later this week I am going to try the same math we did in the BLF GT thread to make a few graphs, there may or may not be an optimal point of lumens and divergence, since we determined that 45 degrees is where the most lumens are coming out of an LED.

76

Fair enough.

I like to use a precollimator lens in my aspheric throwers. It can easily double or triple the light collection and beam area (relative to a typical single lens) while reducing the throw by less than 10. Light collection efficiency into the beam can be around 70 with a simple precollimator setup.

It is not clear to me the advantage of using more than 2 lenses. I don’t think it can increase the throw as this is determined by the area of the front lens. So is it just to increase the efficiency even more? I would think the losses from additional lenses would tend to counteract this.

77

:+1:

Maybe sedstar can enlighten us with some of this complex “math” he speaks of, because so far there is no existing proof that a multi-lens setup can get more throw than a single lens of the same max diameter.

78

okay… okay… okay! (I am skimming the posts that appeared while i had my 8 or so hour much-needed nap)

Now? I am happy. Now we are cooking with gas!. Now, we have several people attracted, involved and engaged… all of whom are used to looking at basic equations.

a couple basic points i would like to make back?

—- Mr enderman can say whatever he wants to me, it doesnt bother me in ANY way. No ones “feelings” matter the slightest bit as far as to whether i am right or not right.
—- i like the how many potatoes joke back. i’m irish, and i have a sense of humor. good show!
—- what i think is confidence, anyone else could easily take for rude or conceited or arrogant. “semantics”
—- i write clear and concise enough english that all my information is completely conveyed. You keep insisting that perfect punctuation and grammar are what wins mathematical arguments? Let me know how that goes for you.

aha, here we go. Here’s a little gem:

“Maybe sedstar can enlighten us with some of this complex “math” he speaks of, because so far there is no existing proof that a multi-lens setup can get more throw than a single lens of the same max diameter.”

The equation isnt a particularly hard one? Its 8th grade algebra to solve it. It implies and states, among other things? that ANY lens with positive focal length? can be replaced by TWO OTHER LENSES with an airgap, such that the OVERALL focal length is exactly the same.

Necessarily, the rear lens will be CLOSER to the LED… it HAS to collect more light that wasnt lost by the original one lens being so far away. (you keep getting hung up on the idea that the SAME ORIGINAL LENS will then have less focal length? Perfectly true statement. If your original lens was 100mm FL? wonderful… simply choose 2 lenses of 150mm FL, as an example.

placed touching (no airgap)? they form a single lens of 75mm FL (which would seem to support enderman’s “always less” statements) BUT when you introduce the airgap? the focal length begins to RISE UPWARDS and approaches 150mm if you go far enough.

if you STOP increasing the airgap when the system hits 100mm FL? What have you achieved?

===

Build number 1? a single positive lens of 100mm FL is used. We ALL know the problem, but i state it anyways. The problem is that at that 100mm distance? a lot of light gets lost and doesnt hit the lens. Since you can only increase diameter to a certain practical extent? Youy are stuck like chuck with a “dance” between higher focal length, and the trade-off loss of lost light from the distance.

Build number 2? TWO lenses of 150mm FL e-a-c-h replace the single lens. At a certain airgap? They “hit” 100mm FL, which was the value of your original lens. The REAR lens is much closer to the LED, its losing less light that was lost. The overall FL is STILL 100mm FL in sum total.

no where did i state that any particular difficult to source lens was needed. ANY of us goes and buys a single 100mm FL lens, dont we? ANY of us can buy instead two 150mm FL lenses to replace the one lens, and have the same FL as we wanted originally, except now with one lens farther back, collecting and not wasting light.

choose the 2 lenses carefully? run the numbers enough? you can put things where you want them, and its always an advantage.

==

you want to SEE the math? right out in the open for you? hiding right out in PLAIN SIGHT ?

https://en.wikipedia.org/wiki/Lens\_(optics)

go down the page, down the page… right underneath “chromatic aberrations”? right below that is the “compound lens”. There are the 4 equations. If you sit and play with paper/pencil/calculator long enough? using the example i just used of my 2 lens build replacing the other 1 lens build? you will see it too… you just have to run it with the right airgap to “hit” it…

no ray traces,any 8th grade algebra student can handle it… and those equations? are hundreds of years old i bet,they are LAWS. they do not LIE. Perhaps instructive to note that there is no delta problem here, and CAMERA lenses seem to work in spite of the fact that Mr. Enderman seems hung up on things on his “ray tracing program” which I am glad i dont know about, they would prevent me from using paper and pencil to illustrate what i say.

LOOK, if you are going to use a 60mm diameter, 100mm long TUBE anyways? To have a 60mm diameter lens of 100mm FL anyways? You COULD use two 60mm diameter lenses, each with 150mm FL… and simply put THOSE into the tube. (you have an empty space of 60mm diameter, whats wrong with a second lens back there?)

THEN what Mr enderman seems hung up on, his “always shorter FL” hang-up? works right how you WANT IT to help you, instead of hurt you.

get off the idea of using the SAME lens with some “other” collimating lens behind it… get ONTO the idea of choosing two OTHER lenses that combine with airgap to REPLACE your original single lens.

the math? does not LIE. and? i’m npot the only one saying this.

Dr. JONES kept repeating himself saying it, out of hundreds of people arguing about “throw and beamshape” (meaningless drivel) that arent doing anything constructive? i was the only person that read that thread, and went and found what he was talking about.

THIS is how simple compound camera lenses work, they dont suffer from Mr Endermans “ray tracing perplexing delta issue”, do they? NO, they take pictures just fine.

THIS is why the “sunnranger” lens kicks butt, and has 4 lenses. THIS is why it has a higher FL than suggested by its short length.

THIS is what Dr Jones on CPF showed a picture of in the long trainwreck thread on his bench.

THIS is what the violin teacher thread someone posted the build is made from.

THIS is what they describe as “step two” in EDMUND OPTICS math white paper on “prototyping illumination systems”. step 1, is a single lens… step 2? two lenses, and the advantages!

https://www.edmundoptics.com/globalassets/resources/articles/prototyping-illumination-systems-with-stock-optical-components-en.pdf

=

its not just ME? all the experts are saying it.

people build this way. The engineers at edmunds optics, curiously dont describe the ray tracing delta paradox… i say? throw your ray tracing program away, its tell you something you dont need…

79

Look. almost everyone is doing “step 1” in the edmunds optics paper. Everyone is doing the same things, and expecting different results. insanity!

they describe the “throw problem, mannnnn” they just state it as MATH instead of undefined meaningless “rules” that dont seem to exist to me.

yeah, theres a limiting problem… edmunds optics? the very next thing, “step 2” immediately describes what i am saying to do… use 2 lenses to replace your single lens.

this is why i ended up with 2 IR illuminators that “throw more, man” than everyone ELSES build, and with slightly less diameter. One is 3 lenses the other is 4 lenses.

the advantages? are intuitive, and obvious.

(punctuation and grammar? do not win math arguments)

80

Say I have a 100mm diameter, 150mm focal length lens. (150mm away form the LED)

What two lenses <=100mm would you use (what is their focal length) and at what distances from the LED would you put them?