TIR optics for diving / Led choice

Common

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Jul 17, 2021
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Hello all,

I have a few questions for the experts on this forum.

I'm trying to make a dive light from scratch as a fun challenge. Atm the design idea is based on the teclight from tecline. It uses a central single led to create a narrow beam (6°) and 7 extra leds at the front to give a very wide angled "video" light. (120°)
Both can be activated independently. The waters here can be quite full of floating particles from time to time so the wide beam is often not desirable yet might be fun to use in certain situations.

Question 1:
In multiple threads the Cree leds (example being the XM-L series) are mostly mentioned negatively for their "rainbow halo" formed around the spot. LH351D is often given as a better alternative. However I see most commercial dive lights use the Cree leds instead, presumably for the higher Lumen/watt.
For the DIY light I'm trying to reach around 1200 lumen (dimmable) for a beam of +- 10° in the spot mode. With a single emitter a Cree led setup would be only just managable, using the max current and with a CRI of 70. The LH351D will only reach that output with a multi emitter setup (3 leds). However a CRI of 90 would be possible in that case. Which setup would be more favourable? Is a difference in CRI noticable during diving?

Question 2:
Optics for such leds seem to be mostly 'TIR', especially for the multi emitters. Is using a TIR optic desirable for dive lights? The light I use now uses a simple reflector. It creates a nice hot spot and the non-concentrated light gives an even halo around the spot. (8° for spot, +-60° for halo)
I'm worried that if I use a TIR optic I would only get the bright spot and no spill. Spill being usefull to see more of the area and missing less fauna. Does anybody have experience with TIR optics for dive lights? Atm I found this lens for the triple LH351D setup. https://www.ledil.com/data/prod/Tuija/11192/11192-ds.pdf
Any way I could simulate the spot?

(The spill might be usefull for when the 120° "video" light would be too much due to scatter by the floating particles and needs to be off.)

Question 3:
To create a multi emitter setup, are there any standard PCB's or do I have to create my own to match the lens? In other words, is the position of the leds in such a setup always the same or do they differ from lens to lens?


Sorry for the long post. I combined all my questions in one big one.
Thank you in advance for the help. :grin2:

Common
 

DIWdiver

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Connecticut, USA
Hello Common, and welcome to the forum!

I've built dive lights with TIR, glass aspheric, and plastic Fresnel aspheric lenses. I do think the aspheric lenses produce a nicer beam. They are all spot, no spill. The TIR ones that I used gave a less uniform spot and a small amount of spill, but I wouldn't say that was a big disappointment. You can see the artifacts in the beam when shining it against a white wall, not when diving. The same probably goes for the 'rainbow halo'. I think the TIR are better at gathering light from the LED. How much light an aspheric gathers depends on it's focal length. You want very short, like not more than the diameter of the lens (less is better).

The XM-L is an outdated emitter. Higher efficacies, higher CRI, and higher power are readily available. I would look at the XP-L and XHP-50.

For the diving I do most, I wouldn't pay a dime or a lumen for high CRI. If I were dusk or night diving and looking at flora and fauna, I probably would want better than 70CRI, and either warm or neutral tint.

There are some off-the-shelf LED boards available, and they are made to fit certain TIR lenses. Triples are the most common, but there are others. In the US I would look at Mountain Electronics. In Australia, Cutter is pretty good. I would guess, though, that you are unlikely to find exactly what you described.

It looks like the teclight uses a large TIR optic for the spot beam. Note that the spill LEDs are mounted on a separate board. This is so they can be very near the front of the light, which is necessary for the wide spill pattern. The spot emitter is pushed farther back by the depth of the TIR. The same would happen with aspheric lenses.
 

Common

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Jul 17, 2021
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Hello Common, and welcome to the forum!

... They are all spot, no spill. The TIR ones that I used gave a less uniform spot and a small amount of spill, but I wouldn't say that was a big disappointment....

...The XM-L is an outdated emitter. Higher efficacies, higher CRI, and higher power are readily available. I would look at the XP-L and XHP-50....

... If I were dusk or night diving and looking at flora and fauna, I probably would want better than 70CRI, and either warm or neutral tint....

Thank you for the response DIWdiver.

The spill is what I worried about with a tir optic. I believe the full 120° of light the led ring would provide, might be too much for regular use and would be more for lighting up points of interest temporarily. (statues, sepia eggs, ...)
I'm a bit afraid of it being reflected all over the place when diving in more particle heavy waters and thus only giving me the option of using the spot. If the spot is only a tight beam with no spill then it wouldn't really help see anything. (I dive in belgian waters so visibility is often no further than 3m. :shrug:)
Am I correct on this or am I way off? Or could simply dimming the 120° light to appropriate levels eleviate this problem?

Concerning the CRI, I almost exclusively do night dives so I will take your advice and take a high CRI setup. For the CCT I find multiple versions of what "neutral" levels should be. I assume this would be between 5000 and 6000K?

For the emitters I do see what you mean. The XHP-50 would let me make a single led setup and the XP-L(2) would be perfect for a triple led setup. For both I just found some appropriate boards online so that's a plus.
( https://led-mounting-bases.com/en/l...-led-cree-xp-l-compatible-optiques-ledil.html
https://led-mounting-bases.com/en/l...0-6v-ledil-et-carclo-led-lens-compatible.html )

Which one would be more preferable, single or triple led? (As for the leds, I could at maximum get the XPH50.2, the XPH50.3 is not available here.)

Once again, thanks for the help! :D

Common
 

Common

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Jul 17, 2021
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To clarify, this is the light I'm basing the DIY version on. As shown in the picture is only using the central single led.

https://imgur.com/a/nwioIiW