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.
you’ll see a RANGE of values from 50mm to close to 100mm as you do it in steps…
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…
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.
I know it wasn’t possible. Just trying to provoke a ‘Huh? What?’ reaction. :disappointed:
2x 100mm fl lenses = < 100mm
80mm and 100mm = < 80
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…
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…
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
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.
Tests all done with a 100mm diameter, 75mm curvature radius, 19.1mm thick, plano-convex parabolic lens (closest to aspherical that I can do with this program)
Ray origin offset by 0.5mm to simulate the maximum angle of light coming from a ~1mm size LED.
Number of rays in test: 128 with a spread of 120 degrees (60 above and 60 below x axis) like a typical LED.
.
.
Single lens: placed at location of least divergence
Distance from LED: 124mm
Minimum spot diameter at 1km: 27.6m
Number of rays collected: 30
.
.
Double lens configuration A: placed as close together as possible
A1 distance from LED: 46mm
A2 distance from LED: 71.5mm
Minimum diameter at 1km: 41.2m
Number of rays collected: 63
.
.
Double lens configuration B: B1 moved 10mm back, B2 used to focus
B1 distance from LED: 36mm
B2 distance from LED: 94mm
Minimum diameter at 1km: 43.2m
Number of rays collected: 54
.
.
Double lens configuration C: C1 moved another 10mm back, C2 used to focus
C1 distance from LED: 26mm
C2 distance from LED: 110.5mm
Minimum diameter at 1km: 48.2m
Number of rays collected: 47
.
.
Single lens configuration placed in between A1 and A2 to simulate “joining” those two lenses together
Lens diameter: still 100mm
Distance from LED: 60mm
Lens curvature radius: 52.1mm
Minimum diameter at 1km: 180m
Number of rays collected: 61
.
.
Conclusions:
-With two identical lenses, the ideal configuration is having them close together (A is better than B or C).
-Two thin lenses are way better than one thick one, even though they will both collect the same amount of light (A is MUCH better than the test right above).
-A single lens (first case) still has better collimation than two lenses, but only collects a fraction of the light.
Additional points:
-The number of rays collected only represents a 2d slice, not the whole 3d column of light.
-The first lens in multi-stage tests (A, B and C) can be replaced by a smaller lens, such as in the image below:
Ok guys,
We need to start… Lenses source for multiple lenses flashlight system? Commercial available aspherical lenses can’t be used in such systems and even the one we can get have around 20% of performance play.
Camera lenses are very delicate one and far superior than classic aspheric lenses and for start I think we should start with them until we find reliable source for creating our own multiple lenses flashlight systems. So even cheap China ones could serve well… Or even better disassembled old M48(or any other old) camera lenses.
I listen you guys but my redneck head hurts from plenty of theory and numbers(sorry Seeds and other scientist members here; I hate math from the bottom of my hearth 
) cause my redneck brain rejects complexity and insists on simplicity.
But throw me some interesting idea and I’m hooked. Like precoolimator lenses at the days Vinz start using them and almost no one managed to crack that?… HA Almost no one I spend around 1000$ until I found right one that does not loose on performance one tiny bit and yet they enlarge de domed emitter projection for around 100. I saw Vinz builds claiming that he has 5 loss. I don’t have any loss with mine. That happened cause I was very intrigued by Vinz precoolimator as I am currently intrigued with multiple lens system.
I am not showing off I just want to say to Enderman and like-minded that there’s nothing that can’t be done… And again multiple lenses system is proven thing and it works.
Real aspherical flashlight fan would at least give a try to such system.
So scratch aspherical flashlight build? Give multiple lenses system a try…
I’m trying to deal with focal length requirements and effects. For example, a 3 lens system with lens 1 is closest to the emitter and lens 3 the farthest. What effect would lens 2 having a longer focal length than lens 3 have? Would there be benefit in using an achromatic lens after a biconvex lens 1?
Here is a page where you just type in the necessary values.
Mr enderman?
thank you from the bottom of my heart, for at least trying to model it. And my apologies for “how” i got you to do it. I know i got you to begin to try the traces in a very “base” and “crass” manner? By baiting you? But… it worked. I did the exact wrong thing, but, for a good reason and purpose. “Thanks”.
Maybe as people get bored, and get curious about the few precollimated lights that “work” someone might end up entering values that represent, for instance, the vinz light that pulls the trick off. Some of them are demonstrated to “work”, this should show in some ray trace somewhere, right?
let me keep going back up and reading and re-reading YOUR traces pictures, because (thank you) this is my first exposure to this power-tool. Maybe i can use the “online tool” he mentioned. I had the idea to start putting 3 or 4 thin lenses into the thing, and start changing their diameters and focal lengths and locations, trying to solve by “inspection”.
Like you? I would imagine that 2d is fine, nothing happening in 2d that isnt happening in 3d, as we’re modeling round objects.
Mr Enderman wins round #1… still, “bumblebees fly” and at one time, math of flight didnt yet “allow” a bumblebee to fly. Vinz’s pre-collimator flies, i SAW it happening in real life slowly over 8 hours of hand tuning, the emitter projection growing slowly brighter and larger.
Still? Round #1? is Enderman’s.
and thanks… and i hope this online tool works for me…
This multi-lens concept got me thinking about the possibility of a zoomie type light where the central lens is moved to change the focus similar to a zoom lens. This could be done using magnets mounted in a sliding ring around the head tube and in a ring around the movable lens.
oh. cool online calculator,just does the values though. still… neat.
one less thing…
You’re thinking about this wrong.
The way to make a spot larger or smaller is by changing the divergence of the beam.
For example a zoomie which can change the divergence from a few degrees to 60 degrees.
In that linked image all that’s changing is the beam width, it’s collimated in all three cases.
That’s not really useful in a flashlight because why would you want to change between a 5cm spot or a 10cm spot? 5cm -> 5m is a lot more useful
.
Also, it is currently impossible to make a beam narrower like you see in the third image.
Unless the light source is an infinitely small point, the light rays can never be collimated.
When you make the beam narrower, it diverges even more, causing it to become more uncollimated and form a cone of light.
.
This is why “beam expanders” exist, by making the beam a larger diameter, you can get less divergence, and closer to collimated light.
well? first off, i would be a lot happier if Mr Enderman would be a slightly less of a “good winner”. Quite frankly? Based on the “way” I enticed him in, baiting him in? He really “should” be enjoying himself just a TAD more than he is. When the numbers are in your favor at the moment? Enjoy it, i say.
I could care less about my feelings.
The more i stare at the ray tracings up there, and there are several… the more i am looking for any “shred” of anything that says anything positive.
Mr Enderman? While you are still in “gracious winner” mode? Is there any small situation where we saved at least one single “ray” ?
The endmunds optics paper, after you get tired of using “one single aspheric” the way we all traditionally do? They immediately describe using TWO of them, and if memory serves, the first is in regular position, the additional one added to the outside is “flipped around”, IE, the “flat side” of the collimator is to the LED, and the next one is flat side towards the target.
some danged aspheres are so thick it gets ridiculous? using a second one might put the first one so close to the LED source it wasnt even funny?
eh? unless the engineers at edmunds optics are writing instructional papers just for fun to have something to print…
Like this?
Some weird stuff is going on, looks like the spherical aberration you get when using spherical lenses instead of aspheric.
pictures small, i get 45 or 46 rays?
what happens when the lenses get closer to touching at the lumps?
@Enderman The portion of the linked image I was interested in was the central lens and was considering the possibility that divergence might be controlled by changing the position of a lens or pair of lenses relative to two fixed lenses. The motivation for the thought process is a zoomie with no twisting or sliding segment, just a sliding ring or other magnetically linked mechanism controlling lens positions. I’m new to this and still building a mental model of how different lens types and characteristics interact.
did you look at the edmunds optics white paper? if only out of curiosity? On “page 1” (part 1) they go over, basically, our entire basic site strategy. Which is one lens. They describe the LED source in terms of theta half angles, and the lens in terms of “NA” which is numerical aperture.
in terms of a camera, “aperture” makes sense to me. the numerical aperture of the beam, in this site wide strategy,is basically the sine of the half angle of the LED emission. They use an example of the LED with a plus/minus 50 degrees emission of half intensity. sounds fairly representative to me.
you get NAbeam = sin(100/2) = sin (50) = .77
I mean, THATS not hard, the sine of the half angle of the LED emission? is the “numerical aperture”. Any fool (like me?) with a TI-30 or the budget equivalent, can play along at home. If what you wan to illuminate is close enough to that beam? you dont need a LENS, but, we want to go further than a few inches.
you get a lens, which should sound familiar to any zoomie enthusiast. First, you want the NA of the lens to be greater or equal to the NA of the LED emission. the theta angle stated in radians, is the diameter of the source divided by the focal length of the lens.
namely, Theta prime(radians) = Ds / FL.
sounds a lot more complicated than it really is, radians convert directly to regular angles directly. Now, if you have born this out THUS far, they state at that point:
“This identity shows that a small beam
divergence may be achieved by either
reducing the source size or by increasing
the focal length of the collimating lens.”
and REALLY all they have done up to now? is state mathematically things we all already talk about. We already KNOW we would like a small sized LED, and we want the emission angle to be as small as we like. The xpg series being a “thrower”? Is simply described mathematically. We still havent moved off of anything we all dont already know, and that we all already talk about. The math hasnt gotten bad. Anyone awake in high school angebra and trig is still alive.
we cant GET a better LED yet, so, we increase the focal length of the lens. Gradeschool BLf, this is what we explicitly “do”.
They immediately state:
“As
the beam divergence of the light source
is reduced, the collimated beam diameter
increases proportionately. The collimated
beam diameter (Dc) right after the collimat-
ing lens can be estimated as follows:”
Dc = 2 * NAbeam * Fcol
which instead of us standing around and saying “wow! cool pencil beam!” or “hey, nice even flood!” ?? they mathematically state the diameter of the light beam. the number two, times the numerical aperture of the led, times the focal length of the lens? yields the beam diameter.
I can multiply on a calculator, i dont feel left out in the cold yet.
okay, so heres the “money shot”… they state our entire problem, still on page one/part one? as thus:
“As the focal length
of the lens is
increased while the
lens diameter stays
constant, there is a
tradeoff between
maximizing light
throughput and
minimizing beam
divergence”
THERE, in the middle of “page 1, part 1” our entire site strategy? and indeed,the entire site strategy of my night vision site? (IR zoomies, same thing) is summed up with MATH. you want better results? Theres a tradeoff, and we all know it. Hey, i’m a “redneck”, I l-i-k-e a “bigger hammer” theory, lol.
I have no problem with putting more amps thru the LED and doing better heatsinking. Its a bigger hammer. I like using the xpg or the best led, its a better hammer. I understand that using a larger diameter lens is a bigger hammer, and the redneck in me “groks” this perfectly. But, the paradox here is stated mathematically.
NOW, at this point? my night vision site? had us “fanning out” and infiltrating the flashlight sites, lol. We were running into the same “wall” as you guys here. longer focal length, wider lens… and you run into whats practical, and you run into the paradox.
==
in summation? the math hasnt gotten crazy. nothing beyond a few key presses on a TI-30. No gigantic equations. Youre doing ray traces, i assume YOU are still with me, right? The only thing i LIKE here? couple of things…
the entire “problem” is stated mathematically. No hunches, no “its all about the throw, dude” talk. They DO STATE your “diameter = throw” argument? They state it in a way that means something concrete.
Now, i know what you will say. “big deal, same problem we have, stated a different way” which is true, but This is page one, part one. They dont get off of PAGE ONE of the engineering paper? without the next best strategy…
i swear to GOD himself, theres no worse math than what we encountered here. Real simple. They tell us, the very next step. Will you permit me this indulgence? its just the next paragraph or two, and its easy to follow intructions and an equation no harder than what we saw here. easy.