who wants to "see" how lenses (plural) work? i can explain almost all of it now...

Flashlight Modding and DIY Parts
1

Okay… the math of the single lens zoomie? its not terribly hard to “grok” it, once i realized that a “numerical aperture” was REALLY just my precious Fnumber, with a fake ID card, hiding under an assumed name.

I am realizing, that while the equations in the edmunds scientific engineering paper are “complete”? the 2 short equations and explanation “covering” the 2 lens precollimated zoomie?? are just an “intro”, it is not complete. it IS the “main topic”, but… it falls short.

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I dont have benefit of a professor lecturing me, and i cant raise my hand when i miss something… and get it explained a different way. I’m doing this “cold” by myself. What i NEED, is to “grok” what exactly is going on. For those who mightnot know? “grok” simply means “fully understand in every way possible”, roughly translated. (“Stranger in a strange land”, for those who care where the quote comes from, lol)

OK… here goes.

Most of all of this? Goes on in the “camera world” and the microscope world… its unfortunate thats the “point of view” all the math papers take on optics. Its the opposite of projecting light… but… i am beginning to “grok” this…

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MAIN IDEA, is to understand “entrance pupil” and “exit pupil”… then to RELATE that to lens diameter and focal length. I cant just do some equations, I have to understand the “how” and the “why”. I just had an epiphany, and the light bulb above my head started to glow a little… share it with me….

first off? in optics examples that always seem to use a camera looking at a TREE. I dont know why, its just a convention. QUIT thinking like “you” are the camera or the lens… imagine YOU are the TREE. THATS how to grok this!

so… first case? there is no lens, just a camera… with a gaping hole, and you can see the film thru the hole. that hole? thats the APERTURE. Remember? you are the tree… if you are close? you can see the hole and the film inside the camera. As you get farther away? you can not “see” the film, and farther back you cant even see the hole. You seed the hole to get BIGGER to know the hole is there, and to see the film.

second case… single lens.

Ignore the whole idea of “focal length” as anything except longer focal length? Equals “more magnification”. Lens diameter? is just lens diameter… easy. remember this is a single lens.

YOU are the tree. Up close? with a little (small diameter) lens, up close… you can SEE the film. If the lens is LOW magnification, you can see the film in the middle, and all around it too. As the magnification of the lens goes UP, still the same small diameter? You see the film get bigger and bigger, but, you see less and less of around the film.

if the magnification gets TOO much? you start to only see more and more of the middle of the film. If you want to see more of the film? all of it? keeping that high magnification, you at this point have no choice but to have the lens diameter get bigger. THEN you can see all of the film again.

the diameter of the single lens? is the APERTURE… its what YOU as the TREE can “see”. In a single lens? there is no “entrance pupil” and “exit pupil”, there is only “pupil” or “entrance pupil” only.

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dual lens…

you as the tree? you dont “know” there is a second lens back there, all you “see” is the main focusing lens out front. ALL you know as the tree? Is whether you can “see” the film or not… and if you can see all around the film? or just the film… or just the center of the film. thats all you know as the tree…

lets “assemble” this any of two ways… first? we will START with the little lens in the back… it works just like the single lens did… BUT, the second focusing lens out front? its going to MAGNIFY the image of the film behind it! If the COLLIMATING lens is by itself just over-magnifying the film? and you could only “See” the middle of the film? EITHER that lens is too small diameter, or, its too high of magnification.

then, the main focusing lens we add? its going to magnify THAT image MORE… clearly? that first lens can no longer just let the tree see just the film, no no no… it has to show the film and LOTS around the film. BECAUSE then when the front lens gets put in front? THEN we as the tree will see just the FILM.

or, start with the 2 lenses set right? and “take out” the collimating lens… suddenly we see the film as “tiny”. the front lens was chosen and placed assuming that lens was there… now? we see the entire camera insides around the tiny film.

if we were to take out the front lens? we are left with just too tiny of a lens, with too low of magnification to see anything at our distance away.

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what WE SEE being the tree? the APERTURE is still the diameter of the front lens… the OVERALL magnification of the lenses? determines if we see all the film or not. The “entrance pupil” is the diameter of the front lens… the “exit pupil” is the apparent size of the what we can see of the image of the film… its how big or how small it looks to us, and we are the tree.

in either the single lens, OR the dual lens setup? either way… the fnumber, the numerical aperture, the “angle”??? is nothing more and certainly nothing less? than HOW MUCH OF THE FILM WE CAN SEE.

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my mom taught me when i was wee little? i had trouble putting together a MODEL as a 1st grader… she said to go watch cartoons, and when i had done that? putting the model would be easy again. i argued with her? but weatched cartoons anyways… muttering how stupid of an idea that was… sure enough? when i went BACK? having took a break and cleared my mind?

dang thing put itself together. i was amazed mom was right, she just smiled and said not to forget it. I never did…

i was sitting here, getting nowhere, thinking and imagining this all? gave up again, and just listened to music on you tube. smoked cigs and drank coffee, and made scrambled eggs with boiled potatoes and the potato water left, for sandwiches.

out of NOWHERE, i laughed once again at “the stupid tree” analogy that drives me up a wall?

and i SUDDENLY imagined BEING THE TREE, and what i could “see” looking into the lens… BOOM, all the terms started to make sense… one lens was EASY that way to “visualize it”…. and the dual lens made sense looking at it that way, and i was now able to in my mind? see what each of the 2 lenses were “doing” and how they worked together.

i am “pretty sure” though not definite? The rear lens, the collimation lens? will be at its focal length… and the front focusing lens, will be at ITS focal length FROM THE IMAGE PLANE OF THE REAR LENS.

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tekwyzrd?? playing around making the “airgap” be the special case of FL1 plus FL2 ?

was right and didnt even know it, and neiher did i… i told him “no, its not a telescope…”

i think it IS a telescope, basically.

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this explains why in the “dual lens” equations at the end of the edmunds scientific paper? the RATIO of the two lenses was so important, and the ratio of the focal lengths replaced the focal length of the ONE lens that was so important in the single lens equations.

it always did trouble me? that the “ratio” looked a LOT like the simple telescope magnification rule….

focal length? is magnification… our OVERALL magnification (effective focal length of two lenses) is purely derived form the ratio of both focal lengths.

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i am not “done” by any stretch? BUt… i can now “see” it all working in my brain when i close my eyes and imagine it. I sort of know what role each lens is playing. I see what they are doing.

we are not ready to eat yet? but… i am so close to dinner time? i can TASTE it…

i am very, very CLOSE to busting this wide open…

but at least i am understanding all the terms. I grasp what is happening. I know i can “solve” for the correct focal length of the collimator, when “given” the front lens… conversely, i can “solve” for the NEW front lens, to provide the “proper” focal length we used with a single lens zoomie, to keep the emitter image the same size…

magnification? is focal length… focal length? IS magnification… the RATIO of the two? yields the magnification of a simple telescope… which is simply the effective overall focal langth.

maybe now? i am far enough “along” that i can provide MISTER ENDERMAN, with a better idea(s) for ray traces… because i am pretty sure, that i can say “where” to locate the lenses in object space. (the last math paper i put the link up to in another thread? used “object space” to explain dual lenses imaging a tree, lol…

object space let me “see” the distances of the lenses…

you see, mr enderman has this one cool lens… and its pretty close, but, no cigar to getting the “one million moon bats” they want so desperately to see. they are close though… something like almost 800,000 moon bats… and 4wheeler has the same lens… BUT, that lens has too high of a focal langth, its a little over “1”… we want to put a collimating lens under it, such that the fnumber is lower, BUT such that the emitter stays the same size (small)…

very, very close to that… very very close… might even be there, and dont realize it…

2

hm.

i have a certain diameter front focusing lens, the existing lens in a single lens zoomie. that lens is a focal length that paints a small, bright emitter image. Why when we get a collimating lens working, is the emitter bigger and brighter?

simple… we kept the diameter of the front lens… which gives us our “entrance pupil” and aperture size. we LOWERED the focal length of the overall system, which had the net effect of lowering the Fnumber… which allowed more light to pass. the emitter is a little bigger, but if its only a LITTLE bigger, that means that sometimes the emitter is “brighter” than the original lens was.

HERE, when playing with the number? is exactly WHERE the “illuminance equations” will be of value. Using them by themselves? isnt of any help doing the pre collimator.

we MIGHT now have enough tools in our tool box, to do this job… we just dont know which tool to use when, thats all.

everyone keeps asking me “well? what lens do i use for the precollimator huh???” and i dont know yet… but… i can answer a lot of questions, at every step along the way. i might have filled in enough blanks and just dont fully realize it yet.

hm. using the original lens? there is NO WAY to lower its f-number, AND keep the same focal length… its a fools quest. since the RATIO of the focal lengths sets the new focal length? the only way to have the new focal langth equal the original focal length? would be to have the collimator lens have a focal length of “1 mm”, which was why the final equations spit out a “1” when i “fed it” the single lens dquations “best possible lens”.

and furthermore? since the same lens has the same front diameter? the f-number is the same… it gains nothing.

hmmmm. a different way to look at this? you guys are in love with your throw equation. it tells you how much OF the light is being spread out over how much area. you like to see “how many moon bats PER SQUARE INCH is being painted”, clearly. in other terms? you only have a gallon of paint at best… the f number specifies how much of that gallon of paint gets thru the lens… then the throw equation tells you how thick the paint gets on each square foot.

we cant work miracles? but… we CAN calculate how thick the paint is.

okay… where are we? if we go looking for a collimating lens to stick under the existing lens? we have no choice but to lower the overall focal length, and we are keeping the same diameter front lens… and we can calculate how thick the paint is being applied to se how we are doing.

as we start wanting a wider diameter front lens? that comes at the cost of higher and higher focal lengths, we are chasing our own tail.

BUT… what we CAN DO, is pick the RATIO of the 2 lenses??? to guarantee and predict the f-number of what we create with them !!

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lets list what we have, what we know… and what we CAN DO…

1) we know that the f-number needs to be as low as possible, to let more light thru the lens, or the LENSES… thats paramount. We can calculate the f-number of a single lens… because we already know the ratio of the diameter to the focal length.

2) we know that the size of the projected emitter? is controlled by only the focal length of the single lens we start with. whatever focal length that is? thats what we want to “hit”. we use a larger diameter front lens, with an increased focal length… which would SEEM to be counter productive… except we can pick the ratio of front lens to back lens to “hit” the focal length we WANT.

3) we get the diameter of the front lens UP… but by selection of the collimation lens? we bring the focal length back DOWN to original FL… we KEEP the increased diameter of the front lens, which lowers the precious f number.

here? i will tip my hat… to the notion that “only increased diameter increases throw”, but, only in a certain WAY. we want a lower f-number, but keeping the focal length we like.

we USE a larger diameter lens, B-U-T this only brings us to the normal tail-chasing, because it raises the focal langth too… the perfect lens is “unobtainium” WITH A SINGLE LENS… when we increase the diameter of the front lens? AND we choose the rear collimation lens such that it brings the focal length back to what we want? then we “gain”…

note that we were BOTH right… i am right about f-number being the only measure of how much light goes thru the lens… the idea that “only diameter throw” is “correct”, but… only when you use the collimation lens to relower the increased focal length of the wider diameter lens.

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ANY time we look at ANY combination of lenses? i *think” we can see how it stacks up now… using the EFFECTIVE focal length of both together? and the diameter of the front lens? we can get a f-number that we always want to lower…

if someone wants to know “what a collimation lens” they are looking at will “do” under a given front existing single lens? we can figure that out, i think. we will be able to run your precious “throw equation” thru it, looking to see how many moonbats PER SQUARE MILLIMETER are being painted.

i THINK where we will end up? is looking at a “same diameter front lens” with a MUCH hjigher focal length than we would ORDINARILY even think of… which will be lowered by the RATIO of the back lens to it…

we MIGHT have all the ingredients we need now, to cook this dish… the only missing thing i might need? is that i only know the “magnification” (ratio) of the dual lens… and i want to nail the same focal langth of the new 2 lens setup, so as to paint the same size emitter.

since magnification is just focal langth under an assumed name and a fake ID? i need to relate “magnification” to “focal langth”. that way? what the telescope is “3x”… i can know “how many x” the original single lens had…

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and we can measure how many layers of moon-bat paint any time we want then…

we might have this, boys !!! or we are SO close, its just around the corner…

3

NOW…

at ANY time?? we cant work miracles. we cant disobey the laws of physics… namely? the COLLIMATION lens??? its the first thing the emitter goes thru… it HAS TO have a low, ridiculously low, fnumber… why? simple…

the first lens, if it has too high of a fnumber? will not allow enough moon bats thru it… think about it? the first lens does not CARE theres a second lens out there… the first lens is doing what its doing, regardless of you have a second lens or not… ergo, that first lens HAS to have the super low fnumber…

hmmm… mr barkuti HAS SUCH A LENS… its got a fnumber of something like .35 !!!

the only thing he DOESNT like about it? is that is paints such a HUGE emitter?? its useless as a thrower… but, THAT will make the PERFECT precollimation lens !!!

lets call it 10mm focal length, just to throw a number out there…

step 2?

we take mr. barkuti’s FOCAL LENGTH,and find a front focusing lens… such that the ratio of focal langths yields us the focal langth we WANT, which is a big one… why? because mr enderman and 4wheeler LOVE long focal lengths… they paint a tiny emitter (they already know that a 125mm FL in a 100mm diameter lens? is “pretty cool”)

we normally wouldnt LOOK at, say, a 1250mm FL lens? thats 100mm in diameter? because we know the f-number sucks… but? the RATIO of mr. barkuti’s 10mm when combined with the 1250mm front lens? will YIELD, i believe, a 125mm focal langth!!!

why? because i already know by my compound lens imaging i di with night vision? that focal length “is” magnification.

50mm FL, for instance? give me “about” 4x… when i “drop down” a 250mm FL lens, with another lens? calculated with the compound lens formula? i GET the exact “power” i am looking for, when i hit the resultant FL…

so? lets recap…

mr barkuti HAS a f-number .35 lens… mr enderman and 4 wheeler? have a 125mm FL lens THEY like…. but, its 100mm diameter, which has a f-number over 1.0

we simply need? a BIG focal length new front lens, that will divide out to the focal langth we WANT… which in this case? is the 125mm FL that those 2 guys like.

and, if we cant find the exact FL we “need”? thats easy… we just grab 2 much bigger FL lenses, and airgap them to “hit” what we need. easy.

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we can calculate the new f-number of the system? because we know the front lens diameter… and we can already calculate the “throw” we get out of the system

i think we might have all the ingredients to make this dish…

4

on a hunch? i dont think the FL divide out in ratio like i think they do… but on the other hunch, i think that once i relate “magnification” to FL… i might be home free.

that might be easier…

this would seem to make sense, i know the only “way” any 2 lenses arranged with the bigger FL in front of the short FL? they can be “airgapped” to make the range of FLs, from touching they are “just above the little FL” and raise up a considerable amount “towards” becoming the longer FL.thats one way…

and the other way? is the “telescope arrangement” of them…

and when you “play” with focusing them up? you see this… to “see” the telescope arrangement first? you set the air gap “huge” and come IN… the “first” emitter that focuses up? THATS the telescope emitter… then you pass az blurry area, THEN you see the emitter smoothly change sizes, going thru the “compound FL” values smoothly…

we would want the “first one”, so to speak… THATS the hand tuning we would use.

okay… on that logic? I just need to know the “magnification” of mr. enderman and mr. 4wheeler’s 125FL “cool lens”… because we know the resulting FL will be

approx 125/11 = 11.3x magnification = which equals “some FL”… and if i can figure out how to relate FL to “magnification” then i might be able to predict this… hmmmm…. runs in my mind, i saw this equation somewhere… just gotta find it…

okay…magnification of a thin single lens lens, is… more complicated than that… angular sizes and all that.

it says the best way to visualize the magnification of a given lens, is to use it at a newspaper, and compare the ratio of sizs of the print…

well, I think if we use Mr Barkutis 11mm f=.35 lens as a collimator… and mr endermans 125mm big lens, with an airgap of 136mm ? we might see what we are looking for on the “ray trace’ of it…

then? its a matter of selecting the “right” front lens in front of mr barkutis collimator, that produces a projected emitter “close to” the size of mr endermans big lens used alone…

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and anecdotally? this is why using 2 lenses as the focusing lens, and varying the airgap, and constantly retuning up? gave me the success it did… i was incrementally adjusting the FL of the “focusing lens” against the FL of the rear 2 lens “collimator”… adjusting airgaps slowly and refocusing slowly…

allowed me to hit the magnification ratio, that corresponded to a FL slightly below the original “big single lens”. which was where i saw my “somewhat bigger, but way brighter” emitter image.

I think i am very close… i am pretty sure i am wrong about the ratio of focal lengths calculating the new FL? but, i think using the MAG as a relative indicaor of FL? is the easiest way to model it… and using 2 lenses out front and introducing airgap and constantly refocusing? lets you “catch” the situation you are looking for…

I was using the IR camera and relative brightness/size of the emitter so i knew when i caught it… you guys would use your METER as your guide, performing roughly the same function.

when i “peaked” my brightness of my slightly bigger emitter? i got more distance… when you guys “peak” your meter readings? you should get what you want…

the reason i couldnt demonstrate my IR precollimator that worked, by simply switching to a visible emitter?? was because i would have had to retune the whole thing ground up start to finish because all the focal lengths are noticable different than visible, which with a single lens isnt much of an issue? but, with 3/4 lenses and the critical airgaps? there was no way to hit the groove.

knowing whats going on, if this is more correct than i was before? should cut off most of the long hand tuning process, i would think… i would know what i was doing…

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So much info. I will read eventually. Hoping you find some readily available, budget lenses that hit the goal. Or at least a easy to follow guideline/recipe for us aspheric muggles to follow.

Power on friend. Listening and will read the details if I ever get a good chance.

7

Did some Googling …

Could it be that the IR collimated better because it was more monochromatic than other LEDs ?
Maybe chromatic dispersion is more of a problem with testing ‘white’ LEDs …

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thanks sedstar……. check out “two against nature” steely dan

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404: no picture was found in this theard
I’m scare of wall of text. If only there are pictures

10

QUOTE
404: no picture was found in this theard
I’m scare of wall of text. If only there are pictures
ENDQUOTE

i know, its okay…
thats why i am going through this mainly alone. If i wait for help? i’ll die without accomplishing this.

its somehow “helpful” that i can see my “work” as i work through this, hence the sort of “blog” of my work… probably more helpful to me than anyone else, i suppose.

i’m pretty sure, i am close… almost “there”…

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at jacktheclipper —-

i definitely “get away with a lot” in night vision, dealing with monochromatic light, mainly in imaging… i dont have to worry nearly as much about different wavelengths focusing differently, as a camera guy would worry about. Plus? the achromatic objectives help too.

but… chromatic dispersion doesnt seem to stop “vinz” from doing it in visible… it didnt stop the “violin teacher” from making his… it doesnt stop RCE engineering from making them…

no, “what one man can do? another man can do…”

11

at this juncture? its starting to look like… well really, a “beam expander”… which is another way of looking at a simple 2 lens galilean telescope, just in “reverse”…

i’m just missing something… gotta figure out what i am missing…