DIC Question

Here you can discuss different microscopic techniques and illumination methods, such as Brightfield, Darkfield, Phase Contrast, DIC, Oblique illumination, etc.
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LouiseScot
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Re: DIC Question

#241 Post by LouiseScot » Tue Aug 24, 2021 3:51 pm

jmp wrote:
Tue Aug 24, 2021 2:48 pm
Yes, it be good to know if that's the case. I've postponed work on this project for several reasons, one being that I need to re-design the prism sliders. My current 3D printed sliders did work for some tests, but they deform even when a small bending force is applied to the prism... and then don't 'slide' into the microscope. I might need to try a different filament (perhaps one of the carbon reinforced ones) or be creative with the use metal to craft a frame, without a milling machine (which shouldn't be as hard as it might sound). Of course, it would be good to know if I should re-design each slider to hold one or two prisms before going any further.
Hi again

Are you trying to do it with like normal prism sliders? I think that would be difficult - which is why Rathi used the open frame design. They created the smaller condenser prism to fit inside their actual Olympus condenser. I've tried using a smaller frame for the condenser prism but the fringes in the much smaller prism didn't seem right. I'll have another look when I can. Also, putting in a proper condenser, though sensible, seems to mess everything up. So I'll have to have another look at that also. Using an extra piece of polycarbonate before the condenser prism does seem to work ok :). Similarly with the objective prism. I was trying to figure out whether it made a difference as to whether the extra polycarbonate went before or after the objective prism. At the moment, I've supposed it should be the same as the condenser prism and go before.

Here is a crop of some diatoms with the prisms and extra polycarbonate arranged as above:
Both_15mmCond_Crop_Adj2_016.jpg
Both_15mmCond_Crop_Adj2_016.jpg (114.76 KiB) Viewed 159668 times
There is some background hue - probably left over from the fringing. Illumination is from a white LED. The fringes from each of the prisms seem to largely cancel each other out. I'll try again to get the proper condenser working.

Louise
A Nikon CF plan 20x; A Swift 380T; A DIY infinity corrected focus rail system with a 40x/0.65 Olympus Plan, a 10x/0.30 Amscope Plan Fluor, and a 20x/0.75 Nikon Plan Apo

jmp
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Re: DIC Question

#242 Post by jmp » Wed Aug 25, 2021 2:59 pm

LouiseScot wrote:
Tue Aug 24, 2021 3:51 pm
Are you trying to do it with like normal prism sliders? I think that would be difficult - which is why Rathi used the open frame design.
The sliders for this microscope are relatively large. The smallest one is l=80mm by w=30mm, with the constraint being on the width. Two stacked polycarbonate prisms, covering the entire exit pupil of the objective, will fit there and it should be possible to adjust the bending force if the frame is made of metal (aluminum should be enough, though perhaps brass would be better).
LouiseScot wrote:
Tue Aug 24, 2021 3:51 pm
The fringes from each of the prisms seem to largely cancel each other out.
I noticed this when I did some tests with single prism sliders. When I inserted only one slider the (asymmetric) interference pattern was visible at the back focal plane of the objective. Once I got both sliders in, with the prisms aligned on the same axis, I didn't see any interference pattern, but if the sliders (and prisms) were at 45deg the interference pattern looked like a crosshatch!

LouiseScot
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Re: DIC Question

#243 Post by LouiseScot » Wed Aug 25, 2021 3:44 pm

jmp wrote:
Wed Aug 25, 2021 2:59 pm
LouiseScot wrote:
Tue Aug 24, 2021 3:51 pm
Are you trying to do it with like normal prism sliders? I think that would be difficult - which is why Rathi used the open frame design.
The sliders for this microscope are relatively large. The smallest one is l=80mm by w=30mm, with the constraint being on the width. Two stacked polycarbonate prisms, covering the entire exit pupil of the objective, will fit there and it should be possible to adjust the bending force if the frame is made of metal (aluminum should be enough, though perhaps brass would be better).
LouiseScot wrote:
Tue Aug 24, 2021 3:51 pm
The fringes from each of the prisms seem to largely cancel each other out.
I noticed this when I did some tests with single prism sliders. When I inserted only one slider the (asymmetric) interference pattern was visible at the back focal plane of the objective. Once I got both sliders in, with the prisms aligned on the same axis, I didn't see any interference pattern, but if the sliders (and prisms) were at 45deg the interference pattern looked like a crosshatch!
But aren't objective prism sliders usually designed for Nomarski prisms? The Sanderson prisms are more like Wollaston prisms which I think need special objectives? Unless maybe a low magnification objective is used and which has its back focal plane outside of the objective casing. The condenser prisms, however, can be Wollaston type. I think if I had a scope with spaces for prism sliders I might just buy Nomarski objective prisms. You might still get away with a Sanderson Prism in the condenser if you can get one to fit :)
I've been trying to get things to work with an actual condenser but it seems to mess things up when using the prisms. Rathi's diagram shows a 15mm spacing between the condenser lens and the condenser prism but I can't do that with a standard condenser. I'll have to try and disassemble the condenser to take the lenses out and then 3D print a new holder. Even then it could be very tight. I'd really like to see exactly how a DIC condenser is put together...

Louise
A Nikon CF plan 20x; A Swift 380T; A DIY infinity corrected focus rail system with a 40x/0.65 Olympus Plan, a 10x/0.30 Amscope Plan Fluor, and a 20x/0.75 Nikon Plan Apo

Scarodactyl
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Re: DIC Question

#244 Post by Scarodactyl » Wed Aug 25, 2021 3:51 pm

I wonder if a sanderson prism in condenser + an epi DIC top would make for a good combination.

LouiseScot
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Re: DIC Question

#245 Post by LouiseScot » Wed Aug 25, 2021 3:55 pm

Scarodactyl wrote:
Wed Aug 25, 2021 3:51 pm
I wonder if a sanderson prism in condenser + an epi DIC top would make for a good combination.
I've no idea - but if you have a DIC condenser you could give it a go!

Louise
A Nikon CF plan 20x; A Swift 380T; A DIY infinity corrected focus rail system with a 40x/0.65 Olympus Plan, a 10x/0.30 Amscope Plan Fluor, and a 20x/0.75 Nikon Plan Apo

LouiseScot
Posts: 1167
Joined: Tue Jul 07, 2020 1:51 pm
Location: Scotland

Re: DIC Question

#246 Post by LouiseScot » Wed Sep 15, 2021 3:54 pm

Just a quick update. Well not much to say actually as I've been busy with other things... So no further DIC progress. I ordered some lenses from Surplus Shed a few weeks ago. They are a bit slow with shipping and I'll have to wait for them to make their way through UK customs and post. I might get a bill for customs charges. Still, it shouldn't be too long before I'm back on it - again! :)

Louise
A Nikon CF plan 20x; A Swift 380T; A DIY infinity corrected focus rail system with a 40x/0.65 Olympus Plan, a 10x/0.30 Amscope Plan Fluor, and a 20x/0.75 Nikon Plan Apo

dolmadis
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Re: DIC Question

#247 Post by dolmadis » Thu Nov 11, 2021 5:09 pm

Hi

Been reading this and the other threads on evolving Sanderson Prisms.

Looking at figure 2b on the Rathi paper has anyone delved into or speculated upon the description which cites that the bending moment is modulated by two set screws (the condenser prism) ?

Where were the two set screws placed relative to the smaller polycarbonate beam which is mounted within the circular frame?

Where should they be placed if that has not been disclosed or deduced to achieve the effect that contributors here have re-produced in the open frame?

Thanks, John

LouiseScot
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Re: DIC Question

#248 Post by LouiseScot » Thu Nov 11, 2021 8:33 pm

dolmadis wrote:
Thu Nov 11, 2021 5:09 pm
Hi

Been reading this and the other threads on evolving Sanderson Prisms.

Looking at figure 2b on the Rathi paper has anyone delved into or speculated upon the description which cites that the bending moment is modulated by two set screws (the condenser prism) ?

Where were the two set screws placed relative to the smaller polycarbonate beam which is mounted within the circular frame?

Where should they be placed if that has not been disclosed or deduced to achieve the effect that contributors here have re-produced in the open frame?

Thanks, John
Hiya

My current condenser prism has been fabricated roughly in proportion to Rathi's open frame design. Fortunately, I'm not constrained to using an existing condenser. The exact spacing between set screws / supports isn't critical - just has to be symmetrical. I'm just finalising my condenser/ prism version but I'm using a Nikon DIC objective nosepiece with the small Sanderson prism for the condenser. I hope to post an update before too long :)

Louise
A Nikon CF plan 20x; A Swift 380T; A DIY infinity corrected focus rail system with a 40x/0.65 Olympus Plan, a 10x/0.30 Amscope Plan Fluor, and a 20x/0.75 Nikon Plan Apo

dolmadis
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Re: DIC Question

#249 Post by dolmadis » Thu Nov 11, 2021 8:42 pm

Hi Louise

Thanks for sharing your understanding which you have amassed so far.

I assume that the Rathi condenser prism is a rectangular prism?

It would be useful if a condenser prism could be fashioned from a disc of polycarbonate but I would imagine that it has to be in the form of a beam?

Best, John

LouiseScot
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Re: DIC Question

#250 Post by LouiseScot » Thu Nov 11, 2021 9:28 pm

dolmadis wrote:
Thu Nov 11, 2021 8:42 pm
Hi Louise

Thanks for sharing your understanding which you have amassed so far.

I assume that the Rathi condenser prism is a rectangular prism?

It would be useful if a condenser prism could be fashioned from a disc of polycarbonate but I would imagine that it has to be in the form of a beam?

Best, John
Hi
Yeah, it needs to be rectangular. I cut my current one from a small piece (A5, think) of 2mm clear polycarbonate. It's cheap and the small pieces are easy to get via Ebay. I sawed a section that's 39mm x 14mm for the condenser prism. You need to cut a second piece which sits to one side of (in front or behind) the stressed prism. The second piece has to be cut from the A5 sheet at right angles to the original piece, and it functions as a waveplate.
Here's a quick pic:
DIC_prism_small.jpg
DIC_prism_small.jpg (18.43 KiB) Viewed 159242 times
The 'extra' piece is just being held in place by some tape. I've used M4 grub screws for the 'set screws'.

Louise
A Nikon CF plan 20x; A Swift 380T; A DIY infinity corrected focus rail system with a 40x/0.65 Olympus Plan, a 10x/0.30 Amscope Plan Fluor, and a 20x/0.75 Nikon Plan Apo

dolmadis
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Joined: Mon Jan 08, 2018 6:06 pm

Re: DIC Question

#251 Post by dolmadis » Thu Nov 11, 2021 9:55 pm

Many thanks for the demonstration in response to the naive question I posed. Very helpful.

Looking forward to seeing the results of your experimentation with the DIC nosepiece.


Best, John

amphicyon
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Re: DIC Question

#252 Post by amphicyon » Fri Dec 03, 2021 10:02 am

Hello
I am writing here for the first time, although I have been reading for a long time.
I am also a amateur microscopist, from Ukraine (so forgive me for my english).
You don't need a fully symmetric DIC system, one prism is enough. In condenser you need to insert a SLIT diaphragm in aperture plate. In the cut of which you need to place a strip of prism the same color. And you get a real DIC.
I use this method on my Carl Zeiss Jenaval scope with one dic prism from metallurgical scope.

viktor j nilsson
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Re: DIC Question

#253 Post by viktor j nilsson » Fri Dec 03, 2021 10:44 am

I'd love to see some pictures. That is the principle of Zeiss's recent plasDIC system, and PZO also provided a slit condenser for the same purpose. I haven't played around with it myself, but was under the impression that it is limited in color range and resolution (as you are not filling the objective aperture).

amphicyon
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Re: DIC Question

#254 Post by amphicyon » Fri Dec 03, 2021 10:57 am

Yes, slit method does not full fill a aperture of objective and resolution is decrease. But not so hard. And color is fine.
I have a PZO DIC system also, but its condenser not compatible with Zeiss. I made slider in condenser from common microscope slide and blades of old safe razor.

Video from Zeiss with "slit condenser".
https://youtu.be/4FOW0dZOKLw

viktor j nilsson
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Re: DIC Question

#255 Post by viktor j nilsson » Fri Dec 03, 2021 2:07 pm

More colorful than I had expected, but the low resolution of the video really makes it hard to judge.

But I'm curious to test it myself, it's definitely an interesting technique that should get more attention as it's so easy to diy.

amphicyon
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Re: DIC Question

#256 Post by amphicyon » Fri Dec 03, 2021 3:57 pm

Video really not sharp. Maybe this photo shows the quality better.
ImageDIC Nikon 20x0.75 by Konstantin M, on Flickr

The field not solid because this i used Nikon Planapo 20x0.75 objective, wich not good work with my DIC prism.

tpruuden
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Re: DIC Question

#257 Post by tpruuden » Wed Dec 15, 2021 3:43 pm

dolmadis wrote:
Thu Nov 11, 2021 8:42 pm
I assume that the Rathi condenser prism is a rectangular prism?
It would be useful if a condenser prism could be fashioned from a disc of polycarbonate but I would imagine that it has to be in the form of a beam?
The prism can be any arbitrary shape, as long one can create suitable stress gradient in the material (may not be easy). Additionally, there is some DIC even if the gradients are not fully overlapping for both prisms. The example image is of frameless, nearly square prism, I also experimented with D and other multifaceted shapes.
Attachments
photo1639840464.jpeg
photo1639840464.jpeg (64.15 KiB) Viewed 158798 times

tpruuden
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Re: DIC Question

#258 Post by tpruuden » Sat Jan 01, 2022 6:49 pm

It may be interesting to use other types of shear gradients:
Attachments
Circular gradient.jpg
Circular gradient.jpg (27.73 KiB) Viewed 158687 times

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