Oblique illumination at high NA

Here you can discuss different microscopic techniques and illumination methods, such as Brightfield, Darkfield, Phase Contrast, DIC, Oblique illumination, etc.
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microscopeboi
Posts: 41
Joined: Wed Apr 15, 2020 11:26 pm

Oblique illumination at high NA

#1 Post by microscopeboi » Wed Jan 26, 2022 8:11 pm

Hey,

so im looking to get oblique illumination to work as well as it does at low na <.6 at high na >.6. Whenever i try using simple oblique techniques like setting the condenser off or using a patch the effect ruins resolution on my objectives with an NA higher than .6. i am wondering if there is a simple solution to this or possible other lighting techniques (other than DIC) that can achieve the 3D effect like basic oblique illumination while maintaining high resolution at higher NA's. I remember reading about an alternative oblique method that works but I forget what it was called. Any information is appreciated. Thanks!

richbart
Posts: 71
Joined: Thu Jan 28, 2021 2:07 pm
Location: Iowa, USA

Re: Oblique illumination at high NA

#2 Post by richbart » Sat Feb 05, 2022 12:56 am

I use frosted tape placed on a coverslip. Then place the cover slip on the condenser under the specimen slide withe tape side down. Then add a DF patch and close the field diaphragm until you get a bluish color. You have to toy with the diaphragm opening and field diaphragm until you get the effect you like. Under pictures and videos , I have a picture of the rotifer platyias quadricornis I took. See what you think.

Greg Howald
Posts: 1185
Joined: Tue Oct 20, 2020 6:44 am

Re: Oblique illumination at high NA

#3 Post by Greg Howald » Sat Feb 05, 2022 3:24 am

I read your post and couldn't resist trying it. Very good results. Greg

Greg Howald
Posts: 1185
Joined: Tue Oct 20, 2020 6:44 am

Re: Oblique illumination at high NA

#4 Post by Greg Howald » Sat Feb 05, 2022 7:32 pm

Here's a suggestion.

I made a filter but punching out a 1 1/4 inch spot and cut out a 3/4 hole in it that is off center. I placed a 1" spot over top of that leaving a very slender crescent 🌙.
In use I got outstanding oblique lighting from 4x to 60x when linear polarized at about thirty degrees.

It works very well. :P
Greg

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