Even DF illumination for 4x objective

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zzffnn
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Re: Even DF illumination for 4x objective

Post by zzffnn »

For 4x objective, you may also try putting a piece of opaque black paper under subject, then provide side lighting (lit the subject with a ring of side lights) from above the the stage.
Last edited by zzffnn on Wed Feb 10, 2021 11:45 pm, edited 2 times in total.

zzffnn
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Location: Houston, Texas, USA
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Re: Even DF illumination for 4x objective

Post by zzffnn »

If your condenser has 2 or more lenses and the top lens can be removed, removing the top (oil immersion lens) will provide even darkfield at low magnification.

You can use cotton swabs fiber on glass slide as a darkfield imaging subject. Then play with removing or keeping field condenser, light source diffusion and hight /position (if adjustable), DIY stop size and condenser height.

I can get even darkfield from objective 1.2x NA 0.03 (almost all iris sizes) , 2x NA 0.04, 3x NA 0.08 (almost all iris sizes), 4x NA 0.1, 9x NA 0.2, all the way to 40x NA 0.65, with DIY darkfield stops. Centration of darkfield stop by looking down the empty eye tube (without eyepiece, to see objective back focal plane) is very important.

dolmadis
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Re: Even DF illumination for 4x objective

Post by dolmadis »

mrlowndes wrote:
Fri Feb 05, 2021 11:34 am
Alan Wood wrote:
Fri Feb 05, 2021 3:09 am
The Olympus condenser dovetail is slightly bigger than the Nikon one. It is definitely possible to use Nikon condensers on Olympus microscopes; I used a Nikon dark-ground condenser on my BH-2 until I found a cheap Olympus one. It may not be possible to use Olympus condensers on Nikon microscopes, I have not tried.

Nikon condensers are usually cheaper than Olympus ones.

Olympus say that their dark-ground condensers are for 10-40× (BH2-DCD) and 10-100× (BH2-DCW).

Olympus condensers for the BH-2 and BX do NOT have a filter tray.

On the rare occasions that I want 4× dark-ground, I use my CK2 inverted microscope with the 40× phase annulus.

Alan Wood
I found a $30 adapter that might let me fit an Olympus condenser onto my optiphot. It's in the post so i'll let you know if it works (although I don't have an Olympus condenser yet, either). I have read that the Olympus Aplanat Achromat condenser can have the top lens unscrewed and patch stop placed for DF and there are Olympus Aplanats available for $300 on Ebay. Is it possible to unscrew the top element of a Nikon Aplanat? - also, the only Nikon Aplanat condenser listed on Ebay is $800!

Further, there are vintage Olympus Aplanat condensers that have very large top elements, so they may accommodate 4X DF without the need to remove top element.
"I found a $30 adapter that might let me fit an Olympus condenser onto my optiphot. It's in the post so i'll let you know if it works "

Did it? If so can you tell us who sold it to you please?

Thanks

John

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