Interesting optics thread

This is one of the biggest TIRs, 75mm
It’s only been tested with COBs up to 23mm but the LED opening seems much bigger than that.

Only problem is that when using a TIR with a large LES LED then the angle of incidence varies a lot, which may cause light leakage since total internal reflection only works at large incidence angles.

Auer makes a 110mm hybrid reflector but only takes max 9mm dia. COB.

I found a manufacturer on Alibaba that makes 100mm TIRs for COBs up to 30mm in 10, 15, and 30 deg. FWHM.

Khatod Cosmo is another family of lenses that employs Fresnel TIRs.

There’s one zoomie construction that I haven’t seen on a flashlight yet but found 3 lens makers that do it:
Moving lenslet array based.

Near the LED there’s a fixed TIR. The TIR has a lenslet array at the front face.
In front of the TIR there’s another lens. Its back is the exact negative of the TIR’s lenslet array; the front may be flat or refract the light in other ways.

When both lenses are very close (pretty much touching each other) - the lenslet array doesn’t do much, it’s almost like a regular TIR.
When they move out - the beam gets wider.

Pros:

  • fair efficiency, TIR capctures all the LED light
  • no need to put LED on a pole
  • easy to do fair waterproofing: seal at the TIR. Beam will be bad under water but submersion won’t cause damage.
  • short zooming movement

Cons:

  • current implementations don’t have AR coating which hurts efficiency
  • lenses need to be well aligned
  • can throw OK but never as well as a single TIR

Makers:

Polymer Optics makes zoomable TIRs even a 7-up version….

Indeed. I was interested in it a lot some time ago but stopped caring because beam shape when zoomed out.

They have a really cool color mixing TIR with a spot beam…

As well as 7-up XHP50.2 lenses. Hint! Hint! :wink:

I said I didn’t expect good beam shape from multi-led Fresnel lenses.
Now I see that Khatod makes PL1172, a 90 mm 9-up:
http://www.khatod.com/EN/product-1010/Fresnel-Lenses-for-Power-LEDs—Autofocus-Lenses.html
Beam actually looks OK except that flood is not spotless it’s more like a reflector than like aspheric.

Here I see a reference to PL1175 - a 50 mm triple Fresnel but I fail to find anything more about it.

I can’t figure out how does this reflector work:

Where do I put the COB?

The description states PC with aluminum coating… I can only postulate that the center is not coated; helping to effect the large beam angle. And it’s a HUGE angle…

That said, out of curiosity I requested a sample…

:slight_smile:

Those are used for these type of setups:

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

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.

Doing some searches I stumbled upon interesting quote:

Any pictures of BD headlamp lenses? :slight_smile:

:person_facepalming:

Aaaah now that makes sense! :person_facepalming: :person_facepalming:

Look what else I found… SORAA has been at this for a while (this is from 2015 or even earlier):

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 :cry: )

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.