Planning an aspheric scratch build

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sedstar
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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.

With enough black coffee and cigarettes? all things are possible…

I am currently still shipping… REAL GENUINE CREE xp-g emitters, the classic… brace yourself? as low as 20 cents apiece!! Check out the SALES THREAD, everyone is happy… then PM me

SALES THREAD:
http://budgetlightforum.com/node/52528

if you are into reloading? this is my site… I inherited the remains of what was once arguably the best reloading site on the internet… its the “BLF” of reloading sites…

http://reloadbench.freeforums.net/

if you think night vision would be cool? It IS… this site i am a member of, and its basically the “BLF” of home made scratch-built digital night vision. They are at the leading forefront of advanced DIY for digital night vision, and thats gun mounted or handheld… builds rival and exceed commercial offerings…

http://nightvisionforumuk.com/

luminarium iaculator
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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 3×42(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.

Modding is making something how you want it to be, not how it comes stock...

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Enderman
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sedstar wrote:

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?

luminarium iaculator
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Enderman wrote:
sedstar wrote:

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. You can’t even put enough effort in to use punctuation or make full sentences.

This is rude man… Why rudeness?

Modding is making something how you want it to be, not how it comes stock...

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luminarium iaculator wrote:

This is rude man… Why rudeness?


Edited
He was being condescending.
luminarium iaculator
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Enderman wrote:
sedstar wrote:
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?

Now that’s the spirit… Thumbs Up

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: http://budgetlightforum.com/node/34516

Modding is making something how you want it to be, not how it comes stock...

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luminarium iaculator
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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?

Modding is making something how you want it to be, not how it comes stock...

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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 

luminarium iaculator
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Barkuti wrote:

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

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.

Modding is making something how you want it to be, not how it comes stock...

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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”. Wink

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

Cheers 

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Barkuti wrote:

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 


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.

EasyB
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Enderman wrote:

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.

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?

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Quote:
if the 2 lenses are touching? ( 1 / F ) = ( 1 / F1 ) + ( 1 / F2 )

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

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EasyB wrote:

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?

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.

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Enderman wrote:

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

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.

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Thumbs Up

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.

sedstar
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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...

=============================

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…

With enough black coffee and cigarettes? all things are possible…

I am currently still shipping… REAL GENUINE CREE xp-g emitters, the classic… brace yourself? as low as 20 cents apiece!! Check out the SALES THREAD, everyone is happy… then PM me

SALES THREAD:
http://budgetlightforum.com/node/52528

if you are into reloading? this is my site… I inherited the remains of what was once arguably the best reloading site on the internet… its the “BLF” of reloading sites…

http://reloadbench.freeforums.net/

if you think night vision would be cool? It IS… this site i am a member of, and its basically the “BLF” of home made scratch-built digital night vision. They are at the leading forefront of advanced DIY for digital night vision, and thats gun mounted or handheld… builds rival and exceed commercial offerings…

http://nightvisionforumuk.com/

sedstar
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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)

With enough black coffee and cigarettes? all things are possible…

I am currently still shipping… REAL GENUINE CREE xp-g emitters, the classic… brace yourself? as low as 20 cents apiece!! Check out the SALES THREAD, everyone is happy… then PM me

SALES THREAD:
http://budgetlightforum.com/node/52528

if you are into reloading? this is my site… I inherited the remains of what was once arguably the best reloading site on the internet… its the “BLF” of reloading sites…

http://reloadbench.freeforums.net/

if you think night vision would be cool? It IS… this site i am a member of, and its basically the “BLF” of home made scratch-built digital night vision. They are at the leading forefront of advanced DIY for digital night vision, and thats gun mounted or handheld… builds rival and exceed commercial offerings…

http://nightvisionforumuk.com/

Enderman
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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?

sedstar
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well, right before i take a STAB at that? Now that i at least have your attention, let me use that attention to “plop” the rest of the answer out.

you will notice that the “simple” equation to calculate the new effective focal length of the new compound lens to replace the original single lens? its all stated as mainly “reciprocals” which are a pain in the tookus to work with. you CAN “play” with different values of lenses to see what results come out of the playtime, but, its tedious. Also you have to plug in the BackFocalLength each and every time.

heres the same equation? stated the way you WANT to see it, and its much easier to plug in values and use them. I simply re-solved the equation again and again, until i didnt make any stupid algebra errors. The solution with all variables? It QUICKLY grows more and more complex, getting nuts… until right at the end? All the huge craziness starts to “cancel out” and it simplifies down…

new focal length = (F1 * F2) / (F1 + F2 – Airgap)

all units have to be identical (i suggest millimeters, for obvious reasons)

F1 = focal length of lens 1
F2 = focal length of lens 2
Airgap = distance of air between both lenses

you “plug in” to the BFL equation with each solution to see the new back focal length.

it should be obvious, that if the lenses are touching? the airgap is zero millimeters… and you are left with just the “products” divided by the “sums”. If you start using two DIFFERENT focal lengths? and start varying them each time you play? is when it really starts to get interesting…

==========================

Now that we are all c-a-l-m ? And you are at least willing to entertain my idea? I can now state… that i am sorry i had to act a little rude, and a little arrogant, to get your attention. I heartily apologize. But, you are the FIRST person, on three different sites, and of all the hundreds of people? That at least seemed to know what he is doing with math! I NEEDED you… where have you BEEN the last 3 years, tall dark and handsome? eh?

in addition to “playing” with the CORRECTLY STATED “re-solved” equation i made? to see what 2 lenses will MAKE when used as a compound lens?

How about… you start putting THIS idea into your (very powerful) ray tracing software, and seeing what you can get out of it? Up until NOW, you have been stuck with the notion of finding “just the right collimation lens” to stick behind “the cool single lens”.

I think but do not know… that when you talk about putting the “small asphere collimation lens” next to the LED emitter? i think what you are doing, is putting it at its focal length? Stop doing that… start LOOKING at the problem the proper way. Namely, that you are going to find two lenses focal length values, that combine to produce “one compound lens”.

the BFL ? will tell you for each play, how far away from the LED it is “set”. The “airgap” tells you the distance to the front lens…

I am not “smarter” than anyone else here, in fact? you are smarter and better educated than “me” at this, sunshine. You have a VERY POWERFUL TOOL, your ray tracing software? I just want you to start USING your (i admit it) superior math skills? and your superior tools at your disposal? To crack this.

Heres what will happen, if you just “pick” two lenses out of a hat? you WILL GET some advantage, but, at first blush, it wone be enough of an advantage, to overcome the slight loss of using a second lens. But, once you get “somewhere”, you can go back and “replace” one of those 2 lenses? with two other lenses.

your new THREE lens solution? will be the same focal length as the ORIGINAL single lens ! and each lens will shape a little of the beam down along the way… THAT overcomes the slight losses of using more lenses…

you ray tracing model will not be perfect in real life? but… “hand tuning” with a yardstick and “helping hands” holding lenses… will guide you with practical real world results to guide you quicker. cigarette smoke blown in to allow you to SEE whats going on, and moving a piece of white paper back and forth to measure the diameters of the cones of light? will tell you where you are “losing” at each small step thru the lenses.

YOU know “who” the brains on this site are? Who dont poop their pants when faced with a little algebra? you guys just need to start LOOKING at the problem from THIS point of view… its the keys to the kingdom, and its not as hard as it looks, once you start playing and hand tuning the solution…

for the record? i went to a small state university, that wasn’t very “highly rated” when i got out into my own professional field when young. Smug men were always showing off their “much better school” degrees and making fun of me. You know what? I programmed them “under a table” and fried them…

You guys are all standing around ina group, looking up a TREE, wondering how to get up to the upper branches? I come along, and i am looking at the tree from the other side? I have a COMPLETELY different VIEW of the “problem”…

“hey guys! we can climb up right over here! come look!”

you guys can build better than me, there are MANY guys way better than me at the math. Your just not looking at the problem fromthe correct point of view. THIS is the correct view.

With enough black coffee and cigarettes? all things are possible…

I am currently still shipping… REAL GENUINE CREE xp-g emitters, the classic… brace yourself? as low as 20 cents apiece!! Check out the SALES THREAD, everyone is happy… then PM me

SALES THREAD:
http://budgetlightforum.com/node/52528

if you are into reloading? this is my site… I inherited the remains of what was once arguably the best reloading site on the internet… its the “BLF” of reloading sites…

http://reloadbench.freeforums.net/

if you think night vision would be cool? It IS… this site i am a member of, and its basically the “BLF” of home made scratch-built digital night vision. They are at the leading forefront of advanced DIY for digital night vision, and thats gun mounted or handheld… builds rival and exceed commercial offerings…

http://nightvisionforumuk.com/

Enderman
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Well, that didn’t really answer the question, but if you want you can download the ray tracer for yourself and try it out, it’s free and pretty cool.
Takes a while to figure out though.
https://arachnoid.com/OpticalRayTracer/

tekwyzrd
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Quote:
new focal length = (F1 * F2) / (F1 + F2 – Airgap)

Using 100mm as the focal length for two lenses and 133.34mm as the airgap the combined focal length would be 150.0150015mm

(100 * 100) / (100 +100 -133.34) = 10000/66.66

Quote:
BFL = ( F2 * ( D – F1 ) ) / ( D – ( F1 + F2 ) )

Using the same 100mm focal lengths and 133.34mm airgap the back focal length would be -50.0150015

(100 * (133.34 – 100)) / (133.34 – (100 + 100)) = 3334 / -66.66

boundless.com page on compound lenses

boundless page linked above wrote:
If the separation distance is equal to the sum of the focal lengths (d = f1+f2), the combined focal length is infinite. This corresponds to a pair of lenses that transform a collimated beam into another collimated beam. This type of system is called an afocal system (a simple optical telescope).
sedstar
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if you play with 2 lenses of equal FL ? (here, both 100mm FL)

start with 0mm airgap (touching) and do it a few times in steps of increasing gap? and stop just shy of 100mmm airgap.

a negative BFL? indicates you tried to do something impossible… here? with two 100mm FL lenses? you cant hit 100mm airgap nor go over it… with two 100mm FL lenses? stay below 100mm airgap….

each lens is doing SOME of the work, neither lens is doing ALL of the work.

With enough black coffee and cigarettes? all things are possible…

I am currently still shipping… REAL GENUINE CREE xp-g emitters, the classic… brace yourself? as low as 20 cents apiece!! Check out the SALES THREAD, everyone is happy… then PM me

SALES THREAD:
http://budgetlightforum.com/node/52528

if you are into reloading? this is my site… I inherited the remains of what was once arguably the best reloading site on the internet… its the “BLF” of reloading sites…

http://reloadbench.freeforums.net/

if you think night vision would be cool? It IS… this site i am a member of, and its basically the “BLF” of home made scratch-built digital night vision. They are at the leading forefront of advanced DIY for digital night vision, and thats gun mounted or handheld… builds rival and exceed commercial offerings…

http://nightvisionforumuk.com/

sedstar
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you’ll see a RANGE of values from 50mm to close to 100mm as you do it in steps…

With enough black coffee and cigarettes? all things are possible…

I am currently still shipping… REAL GENUINE CREE xp-g emitters, the classic… brace yourself? as low as 20 cents apiece!! Check out the SALES THREAD, everyone is happy… then PM me

SALES THREAD:
http://budgetlightforum.com/node/52528

if you are into reloading? this is my site… I inherited the remains of what was once arguably the best reloading site on the internet… its the “BLF” of reloading sites…

http://reloadbench.freeforums.net/

if you think night vision would be cool? It IS… this site i am a member of, and its basically the “BLF” of home made scratch-built digital night vision. They are at the leading forefront of advanced DIY for digital night vision, and thats gun mounted or handheld… builds rival and exceed commercial offerings…

http://nightvisionforumuk.com/

sedstar
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tekwyzrd? you are NOT making a “beam expander”, nor are you making anything even remotely resembling a “galilean telescope” setup… all you are doing? is combining 2 independent lenses, into one compound lens…

if the focal lengths are the same 100mm (easiest to start with) you have to keep the airgap under 100mm…

after a while you get bored trying different matching FL’s… i would suggest trying to play with one “littler one” and one “bigger one”… the littler one is always the collimating lens, and the bigger one is always the main objective. i think the convention is #1 is always the collimating and the #2 is always the main objective? but dont quote me…

and anytime you get a negative BFL ? you tried to do something impossible… this will not allow you to violate the laws of physics…

With enough black coffee and cigarettes? all things are possible…

I am currently still shipping… REAL GENUINE CREE xp-g emitters, the classic… brace yourself? as low as 20 cents apiece!! Check out the SALES THREAD, everyone is happy… then PM me

SALES THREAD:
http://budgetlightforum.com/node/52528

if you are into reloading? this is my site… I inherited the remains of what was once arguably the best reloading site on the internet… its the “BLF” of reloading sites…

http://reloadbench.freeforums.net/

if you think night vision would be cool? It IS… this site i am a member of, and its basically the “BLF” of home made scratch-built digital night vision. They are at the leading forefront of advanced DIY for digital night vision, and thats gun mounted or handheld… builds rival and exceed commercial offerings…

http://nightvisionforumuk.com/

sedstar
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it IS going to mess with your head, at first? having two lenses, neither one at its own “focal length”, because each lens is doing PART of the job formerly done by the ONE lens…

i think this is whats irking Mr. Enderman… i think his “small asphere collimating lens” is set at its focal length in his ray trace of it, i believe anyways, i could be wrong.

think of it? as… with the traditional ONE LENS zoomie? you are getting further away from the paint can… this allows you to put half the paint can at the start and half the paint can a ways towards the final lens.

or? witha single lens zoomie? you are looking for this ONE HUGE GUY to carry a giant LOG down the trail? you run out of guys big enough and wide enough, they dont exist… so what do you do? you get 4 regular guys to line up and carry the log… each of 2 or more lenses is doing PART of the work, none of them is doing ALL the work.

hence, none of them are sitting at their focal length.

With enough black coffee and cigarettes? all things are possible…

I am currently still shipping… REAL GENUINE CREE xp-g emitters, the classic… brace yourself? as low as 20 cents apiece!! Check out the SALES THREAD, everyone is happy… then PM me

SALES THREAD:
http://budgetlightforum.com/node/52528

if you are into reloading? this is my site… I inherited the remains of what was once arguably the best reloading site on the internet… its the “BLF” of reloading sites…

http://reloadbench.freeforums.net/

if you think night vision would be cool? It IS… this site i am a member of, and its basically the “BLF” of home made scratch-built digital night vision. They are at the leading forefront of advanced DIY for digital night vision, and thats gun mounted or handheld… builds rival and exceed commercial offerings…

http://nightvisionforumuk.com/

tekwyzrd
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sedstar wrote:
if you play with 2 lenses of equal FL ? (here, both 100mm FL)

start with 0mm airgap (touching) and do it a few times in steps of increasing gap? and stop just shy of 100mmm airgap.

a negative BFL? indicates you tried to do something impossible… here? with two 100mm FL lenses? you cant hit 100mm airgap nor go over it… with two 100mm FL lenses? stay below 100mm airgap….

each lens is doing SOME of the work, neither lens is doing ALL of the work.

I know it wasn’t possible. Just trying to provoke a ‘Huh? What?’ reaction. Ughh

2× 100mm fl lenses = < 100mm
80mm and 100mm = < 80

sedstar
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if anmyone first start to “see it” and have the “eureka moment”?? my money is on tekwyzrd… i can clearly see his enthusiasm, and i can see his “sideways thinking” he is capable of…

how? he’s seeing what i saw, the weird way the equation sort of resembles the way we figure out parallel resistances and series capacitors in electronics. i dont know why it looks similar to that…

but, working with reciprocals is maddening… working with the resolved equation is much nicer…

I suppose one could re-solve the equation to isolate either the collimating lens or the main objective lens… i never had much use for it for my purposes…

but, now you know “how” this light was put together by the designer…
http://www.candlepowerforums.com/vb/showthread.php?364098-Modded-MTE-H8-...

and its not HALF as mysterious to you as it was before… you start with “2 lenses” replacing one lens? then the forward lens gets broken into 2 lenses… etc etc

when you use only 2 identical big fl lenses? you still get the “free lunch”, but… its just usually a twig of parsel;y on the side, unless you get a collimating lens working perfect. But when you get 3 or even 4 lenses working, each a little bit apart?? you start to get a “free double order of fires” with your burger, it becomes worth it, but, only once its “tuned” by hand in the build.

I’m honestly and truly? Trying to “give back” to the site the best and biggest gift i can bestow. Anyone else but me? would probably keep this a secret, and want to charge big money for THEIR builds they sold. I’m feeling guilty, that i am only “here” to learn to fabricate and then to get used to machining, and now foundry work? practicing on flashlights, so i can do my “real work” on another site?? I’m TRYING to give you the keys that allow you to start and drive a racecar instead of a regular commuter car or a big truck.

once you have played enough? you start to see the “practical rules of thumnb” using two lenses to create a new single compound lens… it becomes almost second nature…

With enough black coffee and cigarettes? all things are possible…

I am currently still shipping… REAL GENUINE CREE xp-g emitters, the classic… brace yourself? as low as 20 cents apiece!! Check out the SALES THREAD, everyone is happy… then PM me

SALES THREAD:
http://budgetlightforum.com/node/52528

if you are into reloading? this is my site… I inherited the remains of what was once arguably the best reloading site on the internet… its the “BLF” of reloading sites…

http://reloadbench.freeforums.net/

if you think night vision would be cool? It IS… this site i am a member of, and its basically the “BLF” of home made scratch-built digital night vision. They are at the leading forefront of advanced DIY for digital night vision, and thats gun mounted or handheld… builds rival and exceed commercial offerings…

http://nightvisionforumuk.com/

tekwyzrd
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It helps to have a calculator that can re-use calculations and touch where you want to change values. A good android calc is MathsApp

sedstar
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Hmm. I guess thats similar to the small vis-basic app i once made, to run and re-run the calculations at the click of a moue i used for myself till i got used to this. (then a crackhead ran off with that laptop, also lost my reloading software i wrote for everyone on yet another site, ha ha)

same crackhead(s) got my adult air rifle, i had my working best prototype night vision gun mounted unit working on, to demonstrate it for people… so, if you ever see some crackhead with a “gun scope” with a fold-out screen on the side with analog imaging wires coming out of it, and an 8xAA NiMH battery pack wired up in the gun stock? GET them alone, and put a heavy glass asphere into a strong SOCK, and use it to beat them down senseless with it, ha ha… and rummage around in their house for my laptop, LMAO

maybe i’ll have to see about re-writing the visual basic program, i guess… it makes this fast and easy to see it…

PS – i tried the ray tracing program? it wants me top upgrade to WIN8, and t-h-a-t aint going to happen anytime soon, i know that. Maybe my other laptop (7) will run it, i dont know, next time i get it out and running, i’ll give it a try.

i just thought if someone used to ray tracing software could model this, it would cut the learning curve down a good bit less. You know, if anyone owns a well-working “pre-collimator” zoomie thrower?? this lets you enter the FL for both lens, and the air gap distance, and see how it works… if you built it you might already know the variables to enter….

…and you could see the “result FL” for the overall system get spit out.

With enough black coffee and cigarettes? all things are possible…

I am currently still shipping… REAL GENUINE CREE xp-g emitters, the classic… brace yourself? as low as 20 cents apiece!! Check out the SALES THREAD, everyone is happy… then PM me

SALES THREAD:
http://budgetlightforum.com/node/52528

if you are into reloading? this is my site… I inherited the remains of what was once arguably the best reloading site on the internet… its the “BLF” of reloading sites…

http://reloadbench.freeforums.net/

if you think night vision would be cool? It IS… this site i am a member of, and its basically the “BLF” of home made scratch-built digital night vision. They are at the leading forefront of advanced DIY for digital night vision, and thats gun mounted or handheld… builds rival and exceed commercial offerings…

http://nightvisionforumuk.com/

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