Olympus BH-2 (BHS) LED Conversion

[phil_H]

I was considering upgrading my Olympus BHS microscope to led. I found this unit on eBay, but was interested if anybody had done this and what are the advantages and disadvantages.
Are there any other units on the market?
Thanks
Phil

[PeteM]

Phil, Retrodiode makes a decent LED conversion - and it would make good sense if, for example, your BHS power supply had failed. However, the 100 watt tungsten halogen lamp you have will be brighter and have a more even spectrum than a 10 watt LED with a decent but not spectacular CRI. It might make more sense to upgrade the 20 watt system in something like a BHTU or BHT. There it would provide a bit more light.

If you really need a bright lamp, you might stick with what you have for a while. LED dies are improving in price and performance, but not yet to the point I'd suggest swapping out a perfectly good BHS lamp assembly.

[mneium]

Retrodiode and similar consumer-market replacements for microscope lamps are bad IMO for two reasons:

1) The CRI and tint is horrific. I saw a "high-end" one using an XHP70, which is a green tinted mess of an LED.
2) Some of them use fans (moving, vibrational parts attached to your microscope...)

I thus have been experimenting with some of my own, using various high-CRI emitters.



I'll make a thread about this in a couple weeks when I get all the parts in to complete my testing, but so far, using some Bridgelux and Sunlike COBs, even 0.01 amps of power is nearly as bright (in the microscope viewfield, anyway) as the original 100w halogen I replaced. Turning the current up to the LEDs' maximum specification produces an eye-damaging view, not unlike looking into the sun.

Experimenting with this has produced one funny new technique for me which I lovingly refer to as "brute force transillumination." When you're dumping 2500+ lumens directly into the collection lens of a BH2, it turns out you can transilluminate extremely thick specimens. No need for metallurgical lighting, ha ha. Oh, and if the specimen is dark in color it can catch on fire...

[Pau]

Time ago I bought one of those retrodiode lamps for my Zeiss microscopes, an older model, the one you link seems clearly improved.

Anyway those are my impressions of the one I bought:

- powerful enough for most microscope techniques
- very good regulation and no flickering if you use the 21KHz PWM (now it seems that all they are selling are good 20KHz but the former ones were flickering)
- No long LED duration but good replacement service
- Not well designed for my microscope: a 9 point COB LED without lens was unable to deliver good Kölher illumination (the one you link has a lens but the characteristic of the lens and LED are not disclosed)

Now I don't use it anymore, I found a much better and cheaper alternative placing a single die Cree LED 5000K LED at the right position in a Zeiss lamp housing. And I think that this is the best option as it uses the microscope illumination train as designed

Forum member Saul also sells on Ebay LED/Flash adapters that seem very good (no direct experience nor affiliation with him)
https://www.ebay.com/itm/Olympus-BH2-BH ... Sw99ReSbGU

[phil_H]

Thank you all for the advice it has been very informative and look forward to mneium thread on LEDs. At the point in time I well being keeping the original setup as I have only had the microscope for about a month. Yesterday I stripped down the light unit and cleaned all the lenses and screens and it has made a big difference.

Thanks
Phil

[micro_pix]

I have the 10w from Retrodiode and for me it seems around the same brightness as the 100w halogen on the BHS. I bought it to use on a BHT and CK2 that I use occasionally and it’s excellent for those, especially for light hungry polarising or phase contrast. I like the colour and prefer it to halogen.

Where I do need more light on the BH2 BHS is for photography when using DIC. I’m looking forward to mneium’s thread on high cri emitters.

Dave

Edit: I’ve posted a comparison of LED and Halogen for the Olympus BH2 BHS here https://www.photomacrography.net/forum/ ... 25&t=43188