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UltravioletPhotography

UV microscopy of a sunscreen product emulsion


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I've been exploring the world of microscopy more recently, and of course wanted to do some UV microscope images.

 

The image below is a sunscreen product - an oil in water emulsion, with the UV absorbing ingredient in the oil phase - on a microscope slide, lit with a Xe lamp and imaged with a UV converted Nikon d810 camera. Overall magnification about 400x, so the oil droplets start at under a micron in diameter.

 

post-148-0-28727700-1592052746.jpg

 

The oil droplets contain the sunscreen, hence look dark.

 

I've written up more about it here - https://jmcscientificconsulting.com/uv-microscopy-of-sunscreen-formulations/ - including a rather funky UV video of when the emulsion collapses and the oil droplets fuse together, filmed at ISO 10,000...

 

Logistically it was not easy to do - the microscope needed supporting on a lab jack, to get the light port up to the same height as the output from my lamp. Cue the health and safety violations.....

 

post-148-0-01086300-1592053054.jpg

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Hi Steve. As I understand it my BHB is a bit earlier than the BH/BH2, and a different design.

 

Above the objective, the next piece of glass is a window in the bottom of the trinocular head (there is no glass in the objective turret or the stand though). Then there is a beam splitter which directs part of the light to the eyepieces and part through to the camera port. This cannot be completely slid out of the way to let light straight through to the camera port. Then we have a photoeyepiece, in my case a 3.3x magnification Olympus NFK. Then about 120mm of extension tubes. Finally the camera, which has a UV filter built in (one of the ACS ones which they don't publish the transmission curve for, but seems to behave similarly to a Baader U).

 

Phew, a lot of glass, and glass which is not optimal for UV.

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I am gobsmacked that UV made it through all that glass. I was thinking I would have to use the photo tube head (a dovetail with just the photo tube, no optics or way to view with an eyepiece). The BHB is the second from the top of the BH series of microscopes. The top of the line is the BHA which is the same except it has an interchangeable nosepiece turret. The BH2 series is the follow on to the BH series. Most, but not all, accessories can be used by either series. (condensers cannot, chromatic correction of the eyepiece/objective differs)

 

One issue with photomicrography with the BH/BH2 series is that chromatic aberration correction is in the eyepiece, instead of the objective. This means you cannot use direct objective projection with Olympus BH/BH2 objectives without losing chromatic correction. In you case, the NFK eyepiece is applying correction for an Olympus BH2 objective. Perhaps this is not that important if imaging in a narrow band of UV.

 

An excellent reference for the Olympus BH/BH2 systems is Alan Woods' site. His manuals section has a huge collection of downloadable Olympus manuals plus quite a number of complete teardown and refurbishment guides that he wrote himself.

 

http://www.alanwood....icroscopes.html

 

The equipment section of the Photomacrography.net site you referred me to has been very helpful, thank you very much.

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Here is a link to the vertical phototube on eBay (2 available as of this writing). He accepted an offer of $30 each for two. With a mirrorless camera or a DSLR with direct view, it should get all the glass in the head out of your way.

 

https://www.ebay.com...be/184067291859

 

I also have one of these. It is shorter, without the silver eyepiece part. I intend to use it for direct objective projection with non Olympus objectives. In this case, the sensor should be placed at the same location as the field stop in an eyepiece, given the tube length the objective was designed for. At least some m42 extension tubes will fit down over the vertical tube and rest solidly on the base flange. I might have to cut off some of the vertical tube to get the sensor close enough without the tube impinging into the camera body, but it should be doable.

 

https://www.ebay.com...be/133377641368

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Hi Steve,

 

Yes, most of the long wavelength UV still gets through (in relation to the amount of visible light), but the short wavelengths really suffer.

 

Thanks for the link about the phototube for the Olympus. I didn't know they existed, so that is good news. However I saw his shipping price to the UK - 70USD. Add on customs, VAT and handling to a 30USD purchase and I'd be looking at over 100GBP for that being shipped to me in the UK. I shall have a look around here though and see if I can find one.

 

I've got a couple of approaches to try and improve things.

 

Firstly, very simple. Dovetail to M42 and then just extension tubes to the camera. No eyepiece, no additional lens, just the objective. I have a couple of M42 to 52mm adapters to allow me to put different 52mm filters inline with this. Not ideal for the microscope objectives as they wont cover the sensor, but useful for the 25mm Luminar lens.

 

Next I've got a few Lomo UV eyepieces coming from Russia to try. May or may not work, but given how much they were it was worth a gamble.

 

Also, I have a spare binocular head which is a bit beaten up. I'm going to modify that to give an option for 'straight through to the eyepiece without going through the beam splitter'. If this works it'll be ideal, as I can still use the eyepieces to set up the shot, and then take the photo just by moving the beam splitter out of the way. I'll either just remove the window in the bottom of the binocular head, or replace it with a quartz one.

 

Eventually, I'd like to get hold of a spare base for the BHB and set about replacing the lenses and mirrors with UV suitable ones, but that'll be a long term project.

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