Aspheric + secondary optics

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Agro
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Aspheric + secondary optics

Using a secondary optics is a rare design decision. It can greatly improve optical performance by redirecting light that would otherwise hit flashlight head, but for some reason few makers do it.
I’d like to compile knowledge on available aspheric+precollimator setups. I’d like to also try to quantify the throw loss, but so far I lack data to do that. I welcome any help.

So…what secondary optics are there in the wild?

As you can see…this post is very incomplete. May I get help with extra information to put in here?

Also: any idea why so few makers do it? Adding a smaller lens as a precollimator doesn’t sound like an expensive change…
Any other thoughts?

Relevant read:
Automotive matrix systems with improved efficiency
http://www.candlepowerforums.com/vb/showthread.php?277082-pre-collimator
http://budgetlightforum.com/node/5882
http://www.candlepowerforums.com/vb/showthread.php?273932-Aspheric-lens-...
http://budgetlightforum.com/node/45585

Edited by: Agro on 11/11/2020 - 11:32
Agro
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Thanks Agro, that’s an interesting topic.
I found a cool paper that may be relevant to the discussion:
Automotive matrix systems with improved efficiency

maukka
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Agro wrote:
Thanks Agro, that’s an interesting topic.

What?

Good list Agro!

EasyB
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In my first thread on the forum I explored precollimator lenses a bit. With some beam size and intensity measurements

http://budgetlightforum.com/node/45585

With a high quality precollimator lens the beam intensity doesn’t decrease much (~5%), while the beam area can increase by more than 2x. Effectively doubling the OTF lumens of the flashlight.

scianiac
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Having tried all of these I would say they are mostly rare because they are more complicated and not always suitable for mass production. The reflector + lens for instance is real hard to do if you want to use the lens to capture all the light the reflector doesn’t use because you have to somehow mount the lens floating in the middle of the reflector. Mounting the lens to the front lens actually works pretty well and is pretty easy but you only capture a small portion of the light and produce beam artifacts in the process. This is what I did and I did end up with a C8 at just under 300kcd but not a ton of that is actually from the lens. And really what you are doing is just making a really hard to assemble TIR.

And that brings me to the use of TIRs, TIRs are great if you’re main goal is total efficiency of OTF lumens and you’re willing sacrifice in some areas to get it. TIRs are made to capture as much light as possible and do so from a domed LED which will already be more efficient in terms of lumens, not to mention this means you have a better range of LED options like the 70.2 which you can’t dedome (funny enough you also can’t slice it and drive it nearly as hard as with it’s dome, many good 70.2s were sacrificed to learn that). And this was what I was trying to accomplish in the Storm, to still have a some serious throw but do so with a ton of lumens in the beam, not wasted as wash or inside the head. Using a TIR with a small high intensity LED would be mostly a waste, you would lose throw from optical losses and your total lumen output would still be pretty low, but paired with a high output LED you can really pump out some serious lumens at very respectable throw where all those lumens are used in that throw, not lighting up your feet. If you back me into a corner I would say the “cons” are potentially a little more loss in intensity than the pre-collimator lens and beam artifacts (which aren’t that bad unless you’re white wall hunting) and you do get a nice round beam instead of a square.

Co-owner/Engineer at STO Flashlights.

Agro
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I found another stock implementation of what looks like TIR + aspheric:
http://www.ledengin.com/files/products/lenses/FXCM-7-H_FCX-53-01-0R.pdf

LouieAtienza
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I believe the STO Storm of Ra has a TIR/aspheric combimation…

edit: Guh, I somehow missed this was already mentioned up top

LouieAtienza
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The Chauvet Q-Spot 260 used a Luminus CBT-90 (or CST-90) and two lenses in an adjustable-focus design. I always wanted to get one of these and pop a CFT-90 in there as it’s capable of driving the LED at 27A max… Then swap the lenses out to make it a mega-thrower (if I remember correctly the original literature had a 1M candela rating!)

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Agro
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One thing that might have been obvious to some just appeared in my head.
There might be others who haven’t noticed as well so I’ll share it.

Zoomies tend to be hard to waterproof because they change volume while zooming. They can’t be air-tight so they are hard to make water-tight.
Separating the head into 2 compartments, one tight and the other not, would enable good waterproofing. Maybe not something that would result in great beam underwater but at least it would prevent damage.

This is quite natural to do with a dual-lens zoomie as long as the first lens doesn’t move. Like with Xiaomi FZ101.
Therefore a dual lens zoomie can fairly easily overcome one of the major drawbacks of zoomies.
Note that the first lens might be a regular projection lens or a TIR sealing it is just the same job.

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The solution would be to have the optics move inside a completely sealed body. Bonus points for filling the entire chamber with an inert gas like nitrogen Cash

Agro
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LouieAtienza wrote:
The solution would be to have the optics move inside a completely sealed body. Bonus points for filling the entire chamber with an inert gas like nitrogen Cash

It can be done, in 2 ways:
  • move the lens inside, keep the one outside fixed
    • I believe it was considered on BLF – and rejected for some reason. Bad beam I think
    • also – zooming itself is hard. Servo motors? Magnetism? Complexity.
  • build a chamber around the regular zoomie head
    • increases size
    • adds the same complexity to zooming

Therefore I believe that a sealed chamber inside is a better option for general-purpose lights.
High-end or diving might be different.

LouieAtienza
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Agro wrote:
LouieAtienza wrote:
The solution would be to have the optics move inside a completely sealed body. Bonus points for filling the entire chamber with an inert gas like nitrogen Cash

It can be done, in 2 ways:
  • move the lens inside, keep the one outside fixed
    • I believe it was considered on BLF – and rejected for some reason. Bad beam I think
    • also – zooming itself is hard. Servo motors? Magnetism? Complexity.
  • build a chamber around the regular zoomie head
    • increases size
    • adds the same complexity to zooming

Therefore I believe that a sealed chamber inside is a better option for general-purpose lights.
High-end or diving might be different.

Or, just put your flashlight in a ZipLok bag. A heluva lot cheaper. And you can find them in virtually any supermarket. But in terms of:

Quote:
** also – zooming itself is hard. Servo motors? Magnetism? Complexity.

That’s quite simple. A thumb screw is easily sealable, and that can be attached either to a screw, or pinion that engages with a gear rack.

Not sure what your application is. If you just need rain resistance, even a regular zoomie would be mostly fine If you’re trying to make a diving zoomie then I don’t think you have much of a choice but make the entire optics system contained and adjustable in the body, otherwise you’d reach a depth where the zoomie head would be inoperable or possibly catastrophically fail because of pressure.

kikkoman
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If the light is big enough, one might be able to fit a pressure equalization valve somewhere. (See Pelican cases – it’s a GoreTex membrane basically.)

Agro
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LouieAtienza wrote:
Agro wrote:
LouieAtienza wrote:
The solution would be to have the optics move inside a completely sealed body. Bonus points for filling the entire chamber with an inert gas like nitrogen Cash

It can be done, in 2 ways:
  • move the lens inside, keep the one outside fixed
    • I believe it was considered on BLF – and rejected for some reason. Bad beam I think
    • also – zooming itself is hard. Servo motors? Magnetism? Complexity.
  • build a chamber around the regular zoomie head
    • increases size
    • adds the same complexity to zooming

Therefore I believe that a sealed chamber inside is a better option for general-purpose lights.
High-end or diving might be different.


Or, just put your flashlight in a ZipLok bag. A heluva lot cheaper. And you can find them in virtually any supermarket.

LouieAtienza wrote:
Not sure what your application is. If you just need rain resistance, even a regular zoomie would be mostly fine If you’re trying to make a diving zoomie then I don’t think you have much of a choice but make the entire optics system contained and adjustable in the body, otherwise you’d reach a depth where the zoomie head would be inoperable or possibly catastrophically fail because of pressure.

There is also intermediate step – kayaking. Putting the light under water is a part of the sport but it doesn’t have to work there well. And extreme depths are not required.
Zip bag works there…and is used a for many things…but a waterproof light is just more convenient.
But more importantly – this matters to other users. Because it enables rating the light as IPX8 as opposed to IPX6. This difference means a lot to many of those who simply want “good” w/out having specific waterproofing needs.
LouieAtienza wrote:
Quote:
** also – zooming itself is hard. Servo motors? Magnetism? Complexity.

That’s quite simple. A thumb screw is easily sealable, and that can be attached either to a screw, or pinion that engages with a gear rack.


Interesting. I remeber seeing such discussion but w/out a successful solution. Maybe it’s just my memory or maybe you can immediately find solutions that are hard to BLFers. Thumbs Up
LouieAtienza
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Agro wrote:
LouieAtienza wrote:
That’s quite simple. A thumb screw is easily sealable, and that can be attached either to a screw, or pinion that engages with a gear rack.
Interesting. I remeber seeing such discussion but w/out a successful solution. Maybe it’s just my memory or maybe you can immediately find solutions that are hard to BLFers. Thumbs Up

Methinks it’s rather simple… Same principle as a gate valve you have in the water mains – a sealed post. From there, what ever means you desire to convert rotary motion to linear is possible. The ratings of the seals would determine how far you could submerge the light as the pressure would multiply as you go further down. I would guess you’d need heavier gage walls for the battery components. I am not versed enough in battery technology to know what effects that would have on batteries.

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kikkoman wrote:
If the light is big enough, one might be able to fit a pressure equalization valve somewhere. (See Pelican cases – it’s a GoreTex membrane basically.)

Initially when I read this post I thought that fitting a valve on a light would take a lot of space.
But later…I got a different vision.
To describe it, let me start with SK68. It is applicable to many different designs but it’s relatively easy to explain with such starting point.
So…SK68. It has a number of fins on the fixed part of the head. These are perpendicular to the light’s axis.
Let’s turn them, so they are longitual.
Then – the bottom of the fins is a solid tube. Let’s remove it. Now fins are able to support the head.
Instead of the solid tube that’s one piece with the rest of the head, take a separate one. And not solid – a mesh.
Wrap GoreTex or another fabric-attached membrane around the mesh and put below the fins.

So…it has quite large membrane are relatively to the head volume. Is that enough to enable easy zooming?
Also, I’m not happy about membrane exposition – it is quite easy to pierce it.
But maybe with some refinements it has a chance of working?

kikkoman
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I have no grasp of how permeable that stuff is, but it appears, VERY:

https://www.gore.com/system/files/2018-11/GORE-Pressure-Vents-Datasheet-...

Agro
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I added 3 builds with precollimator lens. Including 2 zoomies which appear to have a hole in the middle of the flood beam.
Disappointing. Sad
I think that it can be avoided – after all camera lenses don’t have ringing issues like that. But how?….

The_Driver
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Agro wrote:
I added 3 builds with precollimator lens. Including 2 zoomies which appear to have a hole in the middle of the flood beam. Disappointing. Sad I think that it can be avoided - after all camera lenses don't have ringing issues like that. But how?....

 

The flood beam is also much narrower when you use a pre-collimator. Pre-Collimators only make sense when the focussed hotspot and/or the efficiency is of primary importance to you.

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Thank you Argo for this post, I found some cool new designs I have never seen before!

When using a pre-collimators with a lens,
I have always wondered at what angle does the light just want to “bounce off” instead of go into the lens when the angle reaches high enough.

How much does AR coating help with this?
Is there a general guideline or table that can show the transmittance relative to the angle?

Agro
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Reflections of light hitting lens at angle can be calculated from Fresnel equations
Yes, AR coating helps. But each AR coating is designed for some angle of incidence and works best there. If you read that UCL is 99% transmissive – that’s just with light hitting it straight ahead, at other angles of incidence the reflections will be stronger.
But at other angles AR coating helps too…and is actually quite critical when the angle is high.

I believe that aside from professional lenses pretty much all AR coatings are designed for light that hits them perpendicularly (which is not optimal).

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https://ricktu288.github.io/ray-optics/simulator/ a free program to play with lens configurations, a unvaluable help to design a system with less invest in different samples. i am designing a searchlight with precollimator system and this program helpme a lot. The main features of optics was on my mind, but whit this program you can emulate fast the possible efects of the light without a continous ( and expensive) trial and error.

Any way i need to say later of saw several designs of precolimator proyects here, the first stage would be ever a half ball lens, not plano convex lens having a part only of the ratio curve. the better system to collimate is a complete sphere, but there exist the problem o poor light collection.

I feell a litlle half ball lens like collector and a medium size plano convex with AR coated should work like the combination.

My prototype have a medium size plano convex+ 1 fresnel of 100mm dia. and i am geting a nice 1.7 millions of candelas with only 10 watts in the new osram leds. And the spot size is very adecuate for a searchlight use. Now i am waiting the arrive of the half ball lens samples, to see if i can compact the design to have a size head more litlle. My concern is not loose more light in the edges of the primary collector, and a better beam angle to the secondary to not loose any light in the head walls.

A half ball lens should be the answer.

https://ibb.co/9wH3w2s
https://ibb.co/j8gPpB8
https://ibb.co/bgWhGpJ
https://ibb.co/D52tMy7
https://ibb.co/FVcY6sB

https://ibb.co/r06V40n

Agro
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Interesting, thanks for posting. Smile

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Yes, spherical lenses ("half ball") are suitable for use as pre-collimators.