Interesting optics thread

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thijsco19
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Those are used for these type of setups:

Agro
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That’s what I thought…but then I couldn’t find anything but COBs under acrich name.
Thank you thijsco19!

kikkoman
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Could be either a clear or matte dome… or a fresnel + reflector setup, that’s where I’d bet my money.
With the central dome being hollow, it can’t be (single-surface) refraction towards the reflector.

Agro
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Doing some searches I stumbled upon interesting quote:
http://www.ltioptics.com/en/optical-design.html#experience

"ltioptics" wrote:
Reflector and lens optics have been designed for LED headlamps and lanterns for the leading outdoor equipment manufacturer Black Diamond. All headlamps use compact Fresnel/TIR collimator style lenses allowing low profile packaging designs

Any pictures of BD headlamp lenses? Smile

kikkoman
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Facepalm

LouieAtienza
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kikkoman wrote:
Facepalm

!{width:75%}https://i.imgur.com/C8zCM0O.png!

Aaaah now that makes sense! Facepalm Facepalm

kikkoman
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Look what else I found… SORAA has been at this for a while (this is from 2015 or even earlier):
https://www.nextgenerationled.be/assets/downloads/Product-Guide.pdf

I see the MR16 or GU10 spots (50mm) go for 40€ apiece on Amazon, but on ebay a few pop up for 10-15GBP (+shipping Crying )

Agro
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Is that Yajiamei lens RXI as well?
https://www.aliexpress.com/store/product/COB-LED-lens-diameter-69MM-12-degrees-CREE-CXA-Condenser-lens-Plastic-plating-reflection-lens/209770_32639660451.html

It doesn’t look like RXI but it’s flat and narrow.
Note: there are variants from 50 to 75 mm.

LouieAtienza
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Agro wrote:
Is that Yajiamei lens RXI as well?
https://www.aliexpress.com/store/product/COB-LED-lens-diameter-69MM-12-degrees-CREE-CXA-Condenser-lens-Plastic-plating-reflection-lens/209770_32639660451.html

It doesn’t look like RXI but it’s flat and narrow.
Note: there are variants from 50 to 75 mm.

Description says optical grade PC…..

Agro
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RXI is just fine with PC. It’s all about folding optical path. Light goes up and is reflected (by TIR or metalization) down towards the bottom and towards the sides. Then the main reflector directs it forwards.
Refraction as the light enters and leaves the lens is usually used as well.

LouieAtienza
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A while back I remember a camera “lens” that was relatively flat ike Carclo’s catadioptric but used multiple folds…

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BTW every time I see that flat 50 mm optics I can’t help by wonder:
BLF Q8 has 4 domed XP-L.
XHP70 has 4 XP-L dies under a single dome.

How would the beam of Q8 compare to XHP70 under a flat optics?
Similar LED config.
Similar size, most XHP70 lights tend to have long heads but this one wouldn’t. Actually it would be shorter.

The flowery spill wouldn’t be there.
Those flat lenses don’t tend to be as narrow as possible. Would they have a donut hole?
Assuming a lens is wide enough to eliminate the donut – what would throw better? Q8 loses some frontal area due to being a quad. Lens needs to compensate for the donut.

Thoughts?

Agro
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Guangdong Hengzheng hexagon seems nice.
https://gdhengzheng.en.alibaba.com/product/60785241872-806113421/hexagon...

Very low height due to fresnelized TIR. And packaging efficiency is very good. A 7-up would have about 40 mm diameter. 19-up would be about 66 mm.
Too bad there are no throwier versions. It significantly reduces the benefit of packing them tight.

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Agro wrote:
Guangdong Hengzheng hexagon seems nice.
https://gdhengzheng.en.alibaba.com/product/60785241872-806113421/hexagon...

Very low height due to fresnelized TIR. And packaging efficiency is very good. A 7-up would have about 40 mm diameter. 19-up would be about 66 mm.
Too bad there are no throwier versions. It significantly reduces the benefit of packing them tight.

The lenses from Polymer Optics are hexagonal also, allowing for tight packing. They also come in narrow spot (LED dependent).

kikkoman
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Weird, just weird.

12-30° from <9mm COBs?
I’d like to see one of these in action… TIR RLT collar ?

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That doesn’t look like a collar but rather a pre-collimator.

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Agro wrote:
That doesn’t look like a collar but rather a pre-collimator.

Ah, I see what you mean. I was distracted by the aperture stem between the two elements.
Still scratching my head a bit…

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Thinking more about that lens. It’s interesting. Smile

  • cheap way of doing pre-collimation
  • the centre of the front lens must have different focal length the the rest – because light goes there through the channel, w/out 2 intermediate reflections
    • light that goes right next to the channel gets refracted
      • some (not much) will hit the channel side and TIR from it, then enter the second lens at off ang
      • some will enter the lens and join the light that passed the channel – but it was refracted and travels at different angle
      • you’re going to get a few artifacts with it
        • typically frosted aspheric lenses have frosting on the first surface. This has at the last so it can remove those artifacts
  • would like to see it tried

Agro
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I wouldn’t expect too much innovation from a brand like Trustfire, but it looks to me that they introduced RXI-style lens to AAA sized lights.

https://www.aliexpress.com/item/4000080687843.html

I’m impressed!

ADDED: it actually may be the same lens as the one they use f.e. in MINI3:

SKV89
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Interesting light. I might get one to put in an E21A with 10mm virence board

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There’s something going on with Trustfire MC1 as well.


Fresnelized TIR? Or maybe regular Fresnel?

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Firelight2 wrote:
I’m not sure a 15mm fresnel lens with 3mm focal length would be that useful though.
(…)
  • Flood mode would probably be relatively narrow. The problem is the focal length is just too short. For practical purposes you need to leave at least a 1mm gap between the back of the lens and the top of the emitter dome… that’s already 1/3 of the focal length used up. Then there is the height of the dome itself. Even for an XPL HI or Black Flat with a flat dome that’s probably another 1 mm.
    (…)

I didn’t fully believe that and decided to check it out.
I took https://lightmachinery.com/optical-design-center/lens-design-cloud/ and drew a strong aspheric lens. Diameter 15, thickness 8, radius -4, conic constant -0.9, PMMA. I’m not sure what was the FL but definitely more than 3 mm. Placed it 0.1 mm in front of the LED. Result?
The beam was indeed very narrow unless I made the LES huge. 8 mm LES produced a 2m diameter beam at 1m. With 3mm FL it would be worse than that.
Agro
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Agro wrote:
Firelight2 wrote:
I’m not sure a 15mm fresnel lens with 3mm focal length would be that useful though.
(…)
  • Flood mode would probably be relatively narrow. The problem is the focal length is just too short. For practical purposes you need to leave at least a 1mm gap between the back of the lens and the top of the emitter dome… that’s already 1/3 of the focal length used up. Then there is the height of the dome itself. Even for an XPL HI or Black Flat with a flat dome that’s probably another 1 mm.
    (…)

I didn’t fully believe that and decided to check it out.
I took https://lightmachinery.com/optical-design-center/lens-design-cloud/ and drew a strong aspheric lens. Diameter 15, thickness 8, radius -4, conic constant -0.9, PMMA. I’m not sure what was the FL but definitely more than 3 mm. Placed it 0.1 mm in front of the LED. Result?
The beam was indeed very narrow unless I made the LES huge. 8 mm LES produced a 2m diameter beam at 1m. With 3mm FL it would be worse than that.

Though now that I think about it there’s an easy solution to having too narrow beam.
Add more emitters. Evil
You’ll have higher output as well and probably higher efficiency as well than with a weaker lens and fewer emitters.

Actually I see 2 uses for these lenses.
Take a powerful mule like one of the Vinh’s superlights and replace the glass lens with a negative Fresnel (or positive Fresnel + glass).
You get similar high output, nice smooth beam but narrower with sharp cutoff. Higher brightness than pure mule over a smaller area. Myself I love this kind of beam.

The other use would be a zoomie, with this style LED setup.
In flood mode it would be superb, just like any zoomie.
In throw….it would be special, in a way that’s neither good nor bad.
Astrolux FT-02 is available with 2 emitters (third on the way but this is irrelevant).
Compared to the initial SST-40, XHP50.2 offers roughly:

  • twice lumens
  • half intensity
  • double power consumption

For some users XHP50.2 makes a significantly worse thrower but for others this kind of tradeoff works very well.
Here if we compare a regular aspheric to a super-strong fresnel we get:

  • 1.5-3 times the lumens
  • much lower intensity (I won’t try to guesstimate)
  • same power consumption

Clearly not for everyone but it doen’t look like intristically bad tradoff.
Would put more lumens down the range than any regular reflector light with the same LED, competing with recoil setups.

And super short focal length offers new packaging possibilities.
Typically zoomies are quite bulky for whatever battery they support. They can have very short length but if they do – the diameter is significantly larger than that of a comparable reflector light. To make a narrow zoomie, the entire zooming mechanism has to be placed in front of the battery. With regular focal lengths that makes the light very long. With this kind of lens that’s not the case…
Here’s a pic that shows the concept (I think it’s slightly too compact at some places but it’s meant to show the idea rather than a design)

As narrow as a tube light and length-wise it can compete with a reflector light as well.

So…a zoomie is usually a Jack of all trades and a master of none. This kind of setup could offer different tradeoffs than regular aspherics. In some ways much worse. In some much better.

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I’ve got my Trustfire MINI3.
Yes, I think it uses RXI-style optics, though so far I’m failing to disassemble it so I only got view from the front.

The beam is unlike anything I’ve seen before. There’s a square hotspot like in almost focused aspheric lens, but also very wide secondary beam, almost like a mule.

I tried to make a comparison to Astrolux A01 219B at the same distance from a yellow wall:

Astrolux runs high powered 10440 while TF does its only mode while powered by AAA; any other combo would lead to the latter being way way brigher and spoil the comparison.
This picture does not really match what my eyes see but it’s as good as I could make with my phone.
The differences:

  • TF secondary beam looks like it’s prograssively dimming down and disappears. Really the dimming is not very visible but a sharp cutoff (way in the dark on this pic) – is. That is – it is visible when looking for it, normally it lights up everything down to the limits of eyesight. It is also blinding others.
  • TF looks green, my eyes don’t see that. Not rosy but if there’s green – I’m not disturbed by it.
  • TF has visible discolouration at the edge of the narrow beam which can’t be seen here

Agro
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Ilenstech now also makes metalized plastic lenses which resemble RXI. Though I fail to see how this can work. Sad


http://www.ilenstech.com/product/62070713504-804691643/12_degree_narrw_b...

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Ah, interesting topic.

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