Help needed with new DIC setup

[aidanmoore]

Hi,

I’m hoping for some insight and suggestions on how to test and improve my new Nikon 50i DIC setup.

I’ve put together a DIC system piece-wise, and I’ve made some component substitutions based on ideas in this forum, but I’m not yet seeing the “3D” DIC effect that I’ve observed in other photos here.

Working off of an idea from Rogelio to modify a microscope to accommodate a DIC turret, I used an angle grinder to cutaway some metal to allow a DIC sextuple turret to be mounted on an older Nikon 50i microscope. The results are very good mechanically, and I see no reason to suspect any optical issues, as the image quality is excellent.

I then upgraded the light source to a 3000 Lumen LED source, and rewired the 50i to retrofit the LED dimmable power supply. I made sure the optical plane of the LED emitter was at the same point as the original halogen light, and, again the results are good.

I have the CU turret with the DIC prisms, and a single DIC PF10 DIC prism in the turret. The objective is a 10X Plan Apo.

I have not been able to locate the correct polarizer/analyser combination for DIC, but from what I understand, a simple polarizer/analyser should work as long as the polarizer can be rotated. So I am using a simple polarizer setup, and just rotating the polarizer on the field illuminator assembly.

I’m stuck as to why my images do not have a 3D effect. Could it just be the subject material? I’m looking at algae and pond critters, but they look pretty flat to me no matter what angle the polarizer is turned.

Could it be I do not have a quarter wave plate on the polarizer? I thought this component was optional, but I’m not an expert in DIC at all.

I’ve attached a few pics for comment. I’m really enjoying this process as a learning experience, and I really do appreciate the feedback from this forum.

Thanks,

Aidan

[steveminchington]

Hi Aidan,
I'm a relative novice with DIC but I have had reasonable success with a Nikon Optiphot materials microscope with a DIC set up. So whilst others may know a lot more than me about DIC, I can share what I have learned so far.

Firstly the polarising filters need to crossed at 90 degrees to achieve total extinction. If you put them together and hold them up to the light then rotate one on the other until they block the light, then this is how they want to be in your scope. Mark a little dot on each one for correct alignment.

The objectives should be "strain free" DIC, like P objectives, otherwise any stress in the glass could be seen under polarised light. I'm not sure about using an APO objective as it has more lens elements than a plan achromat. Others may have more knowledge about this.

I am using reflected light so only have one Normaski prism under the objective. This is an adjustable quartz wedge which when moved will change the interference pattern and colours under the polarised light. I understand with transmitted light you need two DIC prisms, one under the objective and one under the condenser. Also the DIC prism has to match the NA of the objective you are using. It looks like your condenser prisms are fixed, so the one in the turret should slide.

I have found that the best effect of DIC works with reflective or slightly transparent things. Non reflective objects look ordinary and dull. Some things look amazing! I hope to posting some images soon.

I hope that helps... others may be able to shed a little more light on the subject.

Regards, Steve

[Ichthyophthirius]

Hi Aidan,

You need to find the set-up instructions for a de Sénarmont DIC system from Nikon, either on the web or by contacting them directly.

Usually, you start by setting up the crossed polarisers. http://microscopyu.com/tutorials/java/d ... igure1.jpg

Then swing in the condenser prism alone and check the orientation of the interference fringes by looking down the tube without an eyepiece (or with the aid of a phase telescope). http://microscopyu.com/tutorials/java/d ... igure1.jpg

Then swing out the condenser prism and swing in the objective prism alone and check the orientation of the interference fringes. The fringes need to be in the same orientation.

Then combine both prisms and you should see a strong darkfield DIC effect in the object. To modulate the contrast, the waveplate and the correct setup with the waveplate are necessary.
http://www.microscopyu.com/articles/dic ... onfig.html
http://microscopyu.com/tutorials/java/d ... index.html


The Planfluor (PF) and Planapo 10x objectives may have different exit pupils, so the PF prism might be completely incompatible with the Planpo objective.

There may also be a defect in the Planapo 10x; check that it is free of excessive strain by putting it between cross polarisers. There should be a nice, symmetric pol cross when looking down the tube without an eyepiece.

Regards, Ichty

[Pau]

Your sample image doesn't look DIC but pol with the polarizers partially crossed or with a 1/4 plate in the path.

The first thing to test is the polarizer and analyzer orientation:
The polarizer must be oriented E-W (right to left of the observer, yours is marked) and the analyzer N-S. Test if the background is really black without DIC prisms nor wave plate, if not fine tune them.
Follow Ichty's directions. The orientation of the DIC prisms seems that can be rotated in the condenser, so it's possible that they are mounted in a wrong orientation.

Even if the prims don't match well with the objectives some DIC effect is to be expected, maybe with a not uniform background.

Does your condenser top lens have 0.9 written on? Condenser prisms for 1.4 condenser are likely different

Your pond water subject is fully adequate for DIC

The original Polarizer is very expensive. Because you have a nice Nikon polarizer and it seems that you're DIY prone you can buy a 1/4 wave plate (Edmund Optics sells good ones) and a make rotatable adapter to mount it over the polarizer to have the De Sénarmont system

[aidanmoore]

Hi,

Thanks for all the suggestions.

I'm experimenting with different polarizer/prism/analyzer settings and I will post the results once I see an improvement.

Thanks again

Aidan