Can 365nm UV EpiFluorescence damage PlanApo Objectives?

aidanmoore · Post by **aidanmoore** » Fri Apr 07, 2017 5:42 pm

Hi,

I have been following the UV autofluorescence discussions in this forum, and I see some great information on using UV LEDs for macro photography where the light is bounced directly off the subject and the emitted light then UV filtered.

However, I'm not clear on whether the UV energy affects the optics in a microscope objective when a UV light is transmitted through a microscope objective.

Is it possible to damage non UV objectives when, say, a 10W LED 365nm UV light is transmitted through the optics? I am particularly worried about PlanApo objectives used in epifluorescence, as they are quite expensive.

It seems to me that all major microscope makers have epifluorescent attachments that use the objective as the light condenser, but it is not clear if the objectives need to be of special construction for use with epi UV fluorescence.

Many thanks,

Aidan

Ichthyophthirius · Post by **Ichthyophthirius** » Sat Apr 08, 2017 3:21 am

Hi Aidan,

The old (160 mm) Planapos pre 1980s often had low transmission and high autofluorescence in near UV so they were unusable anyway.

The modern Planapos are designed with fluorescence in mind and some of the newest have special colour correction for near-UV excitation and blue emission.

However, there are SO MANY designs ... since you're talking about modern Planapos, just call or mail their technical service. They can give you advice on individual models.

Regards, Ichty

P.S.: 10W UV? Is that really necessary? Living biological samples would be severely damaged by such high-intensity illumination.

Lou Jost · Post by **Lou Jost** » Sat Apr 08, 2017 6:12 am

I think it is extremely unlikely that optical glass would be damaged by UV light.

Pau · Post by **Pau** » Sat Apr 08, 2017 6:47 am

Maybe not the glass itself but the cement between elements could be if it absorbs enough energy. That said I don't think (just a guess) it will happen with a 365 LED, it could be more an issue with powerful HBO lamps that also emit shorter wavelengths.

Lou Jost · Post by **Lou Jost** » Sat Apr 08, 2017 7:25 am

Pau, I would guess that the effect on glue depends only on the energy, not the wavelength (within the range of wavelengths we are talking about). X watts of UV light shouldn't be much different than X watts of visible light, unless there happens to be a strong absorption band in the UV...

Pau · Post by **Pau** » Sat Apr 08, 2017 7:43 am

Lou Jost wrote:...I would guess that the effect on glue depends only on the energy, not the wavelength (within the range of wavelengths we are talking about). X watts of UV light shouldn't be much different than X watts of visible light, unless there happens to be a strong absorption band in the UV...

Yes (if we are speaking only about of a fixed quantity of thermal energy and not about photochemical effects) , but absorption spectrum does and so the amount of absorbed energy as you suggest.

mjkzz · Post by **mjkzz** » Sat Apr 08, 2017 5:34 pm

there are objectives specially designed for UV, besides the obvious spectrum consideration, maybe there are some other considerations regarding UV, such as coating on glasses, glue used (as Pau pointed out) etc.

mawyatt · Post by **mawyatt** » Sun Apr 09, 2017 6:19 am

Itchy,

I have a Mitutoyo M Plan NUV 50X 0.42 that is/was used on our semiconductor wafter probe stations. These optics are used with lasers to trim chips where metal lines are opened. Over 25 years ago I developed a technique to actively trim chips while they were operating to adjust various parameters, this required the development of special chip probes (Cascade Membrane Probes) to allow this on a Bell Labs process we were working with at the time. We taught Maxim this technique and they utilized this to tune their chip VCOs (Voltage Controlled Oscillators), others soon followed.

So this is an example of an optic specifically designed to support high intensity UV transmission. It has a distinctive blue barrel rather than the usual Mitutoyo silver. I don't know if special glass and/or adhesives and plastic are used though.

Best,

Mike

aidanmoore · Post by **aidanmoore** » Tue Apr 11, 2017 4:04 am

Hello and thanks for all the information.

I am actually using a 3W UV LED, the LED ENGIN LZ4-04UV00 UV LED, which has about 10W at 16V, and 3W radiant flux from the datasheet.

I modified an old Nikon HBO enclosure as many have done here, and the results are quite impressive, although I am now struggling with getting good stacks with such little actual light.

Attached a few pictures of the setup, and a very rough stack of 5 images.