New ringlights

GaryB · Post by **GaryB** » Wed Apr 18, 2018 8:27 pm

Hi all.

I just bought a new 40mm ringlight cob to try out for COL, Darkfield and Phase contrast and it works great. The older generation had problems in that they had quite a bit of spacing between the LEDs which caused problems with out of focus objects looking very messy. The newer types have more LEDs that are closer together and have a coating of silicon(?) which blurs the individual LEDs even more.

The effect of all this mean a much smoother light without nasty artifacts on out of focus objects. It gives incredible COL, good darkfield on lower (20x) objectives and excellent phase as the new rings are thinner than the previous generation. The cost is a little more at about $5 but the difference in light quality is well worth it.

Video using phase contrast to show the clean lighting:
https://youtu.be/SpnbubHAvHY

I bought mine from this ebay seller as they're in the US so delivery was faster but they're almost out now.

https://www.ebay.com/itm/40mm-COB-LED-C ... 2749.l2649

There are numerous sellers from China selling the same thing.

Old type

New type

I have to say, I'm impressed.

Pau · Post by **Pau** » Thu Apr 19, 2018 12:14 am

Nice find!
Could you post your whole illumination setup? (with or without condenser, position at the microscope...)

ray_parkhurst · Post by **ray_parkhurst** » Thu Apr 19, 2018 6:27 am

I've been using these for a while for my coin photography. I mask-off parts of the ring to give the lighting proper directionality.

I'm very fond of the new COB technology. Instead of putting the phosphor directly onto the packaged LEDs, the LEDs are sold bare, and the PCB mfrs dispense the phosphor after SMT attach. This gives great flexibility in board design and also allows any stray light from the LEDs to be better captured by emitting phosphor, improving efficiency.

elf · Post by **elf** » Thu Apr 19, 2018 12:57 pm

Is 40mm the ID or the OD? If the OD, what is the distance between the OD and ID?

ray_parkhurst · Post by **ray_parkhurst** » Thu Apr 19, 2018 2:01 pm

elf wrote:Is 40mm the ID or the OD? If the OD, what is the distance between the OD and ID?

The ID is ~41mm, OD ~50mm

elf · Post by **elf** » Thu Apr 19, 2018 2:25 pm

Thanks

Lou Jost · Post by **Lou Jost** » Thu Apr 19, 2018 2:35 pm

There's an interesting alternative design which can be the basis of a customizable well-diffused ringlight. The design uses LEDs around the edge of a thick translucent sheet of plastic, sandwiched between a special thin diffuser on one side, and a white reflector on the other. Diffusion is essentially perfect. I've partially disassembled one for this picture:

I bought a bunch of these, in different sizes, both round and square, so I can drill out a hole in the middle for a lens. I hope to use cake decorating tubes to connect them to my objectives via glued-on step-up ring. I will remove the metal frame.

GaryB · Post by **GaryB** » Thu Apr 19, 2018 6:31 pm

My LED and Ray's are different. Mine is 40 outside and 31 inside which is a more convenient size for standard microscopy. I currently have it perched on top of the lamp housing until I come up with a better solution. The light is passing through the condenser and the apparent ring size is adjusted By moving the condenser up and down. Down gives phase, up gives COL and DF.

It's handy like this as you don't need to remove the condenser or mess with settings each time. It's also nicely reachable for placing Pol or Rheinberg filters over it and the inner ID is just the right size for the lamp to be unobstructed.

ray_parkhurst · Post by **ray_parkhurst** » Thu Apr 19, 2018 7:34 pm

Aha, I measured a "50mm" rather than "40mm" Angel Eyes COB ringlight...indeed I found some 40OD/31ID in my stock box as well. I am hoping to find some even smaller ones someday but so far the "40mm" are smallest Angel Eyes I can find.

I do have a few even smaller ones that I have yet to find a use for. They have 8mm ID and 16mm OD on the COB deposit itself, though the substrate goes beyond in both directions. The inside hole is 4mm but I think it can be expanded to ~8mm. The outside extent is 19mm, and likely can't be reduced since you either must make wire connections on the inside or outside of the COB ring.

GaryB · Post by **GaryB** » Thu Apr 19, 2018 7:42 pm

I'd love it if I could find smaller ones. 25 OD would be good for me. If made the same way as the 40 it would be extremely useful. Apparently the makers only see these as useful for cars, so smaller sizes are unlikely to come around anytime soon.

mjkzz · Post by **mjkzz** » Fri Apr 20, 2018 2:39 am

do these LEDs have high CRI? Or does it matter in this application?

GaryB · Post by **GaryB** » Fri Apr 20, 2018 3:11 am

Nope, no high CRI, but for these purposes it really doesn't matter much. Phase, COL and darkfield all alter the look of things to a high degree anyway.

Beatsy · Post by **Beatsy** » Fri Apr 20, 2018 5:17 am

Interesting. I can see those fitting nicely to a ping-pong ball "light tent" too. A few questions..

Will any old 12v supply do (of correct current capacity of course)?
Do they need a heatsink or cooling?
Is the light constant or are they duty cycled (thinking of banding in photographs taken at certain shutter speeds)?
Can one buy an "off the shelf" power supply with a dimmer function for LED units like this?

Thanks in advance for answers.

mjkzz · Post by **mjkzz** » Fri Apr 20, 2018 5:53 am

actually, I wrote a blog about it, you can use battery to power it.

https://pylin.com/2017/02/25/making-a-f ... acro-lens/

Beatsy · Post by **Beatsy** » Fri Apr 20, 2018 6:26 am

mjkzz wrote:actually, I wrote a blog about it, you can use battery to power it.

https://pylin.com/2017/02/25/making-a-f ... acro-lens/

Brilliant. Looks a very promising solution. I sometimes have trouble getting enough light on the front of my larger diffuser dome when using certain high power objectives. This looks like it could provide extra fill there - as well as playing nicely with the ping pong ball diffusers.

Ordering some from China now. A selection of different sizes and a couple of different colours for grins. Thanks.