DIC for reflected microscope

[urbanpiper3]

Hello,

I am new to interference contrast enhancement methods in microscopy, and in particular about DIC. I have the following setup in my lab and was interested to learn what exactly does Olympus mean by Shear amount. I could not find any online resources as to the specifications of the DIC optics that's used in the DIC slider, there are no numbers to put against "shear amount" parameter. This limits my understanding the relationship between optimal shear amount vs particular NA objective lens.

• Scope: BXFM

• DIC slider: U-DICR

• Polarizer/Analyzer: U-POP3/U-AN360-3

• Objectives: LMPLFLN10x 0.25NA, LMPLFLN20x 0.5NA

List of DIC sliders for reflected microscope from Olympus


Questions:

• The images grabbed at low NA lens 10x 0.25NA DIC images seems to be very blurry and also shows ghost image artifacts, i.e., two images of the sample features. The fringe period (width) is also smaller with the FOV produced by this lens.

• Images grabbed at 50x 0.5NA lens seems to be of superb quality with clarity

• What needs to be changed in the microscope setup to get good images with 10x 0.1NA objective lens? Does this mean the U-DICR is not optimized to work with 10x lens as opposed to 50x lens?

• Other microscope manufacturers - e.g., Mitutoyo provides DIC sliders based on the objectives, https://www.mitutoyo.com/webfoo/wp-cont ... E14020.pdf, i.e. a specific DIC slider for each objective. What specifically would be different in this sliders optics compared with the Olympus DIC optics

• What would be the best way to model DIC - to understand trade offs b/w contrast and resolution at various shear magnitudes and how that is tied in w/ the objective lenses

Thanks in advance... Looking forward to learn a great deal from this forum and contribute as well. (Teaching is the best way to learn )
Cheers!

[Scarodactyl]

I haven't tried the newer Olympus system in particular. Shear definitely seems to have some relationship to that doubling effect--intuitively more shear seems like it should result in more doubling in addition to more color/contrast, but I am not sure. The older Olympus BH2 system I had for a while had individual prisms for each objective, as did a couple older Nikon ones I tried. They worked well but the Olympus system had objectionable doubling, and the Nikons were maybe a bit better on that front. In contrast the newer Nikon system I use has a single slider (L-DIC) and seems to work really well with my 2x and with my 100x alike. I don't understand that part as well.
The mitutoyo system is fairly half-baked. They don't have dedicated space in the nosepieces to accept the prisms, and you can only have one in at a time despite needing multiples for different objectives. I imagine they might buy the prisms from another supplier rather than making them as many of the second-stringers do, though I am not certain of that of course. My nikon slider works quite well with my Mitutoyo 2x, 5x, 10x and 20x, though not with my 10x HR. I also get great DIC with my Olympus MplanFl 50x and 100x objectives for what that's worth.
It would be great if you would post some sample images!

[urbanpiper3]

Thanks for your input.

Please see these images taken at 10x and 50x Objectives with the same DIC prism (Part Number U-DICR from Olympus). Look at the quality of 10x image compared with the 50x, it looks like as shown https://postimg.cc/gallery/KypKPHs.
As you can see, the 10x gives out a double image effect whereas the 50x doesn't. In both cases, they use the same DIC prism. So it leads me to believe that the DIC prism shear amount was more in line optimized for 50x.

Cheers!

[wabutter]

Whether DIC is used in transmitted light or reflected light the main components remain the same. First it is a polarized light method. So the light must be first polarized, then a Wollaston prism is introduced in the condenser,(in reflected light this is the objective and the objective/condenser prism are one I the same) the prism splits the ordinary and extra ordinary polarized light rays as they are presented to the specimen. After differences in nD of objects in the specimen do their magic. A second Wollaston prism is inserted at the exit pupil of the objective. Essentially recombining the e and o rays as they are presented to the analyzer .
According to Nomarski this required a individual prism for the objective in both the condenser and the objective position. As it was explained to me many many yes ago, he also licensed the use of the Nomarski concept to only one company per country.
As follows:
USA. American Optical. As far as I recall, B&L never had a DIC solution
Germany: Zeiss. Leigh used DIC after Smith
Austria: Reichert (owned by American Optical)
Japan: Olympus. Nikon used DIC Senarmont Method

The key element related to the shear angle is the Wollaston prism. By increasing or decreasing the difference between the e and o rays, the contrast/resolution conflict can be impacted. I am not aware of any specifications related to shear angle, as all manufacturers optimized the prism shear to achieve the optimum resolution for the objective in use.

As a point of reference, it is possible to have prisms that offer more than one level on contrast/resolution for a specified objective. Leica did this by creating D a d D1 prisms as well as C and C1 prisms for specific objectives.

Ultimately, the right shear angle is dependent on the objective in use as well as, and most importantly what is the specimen.
I would say don’t worry about the specs, do you see what you need to see?

[Scarodactyl]

Bausch and Lomb did offer epi DIC for the balplan, though it isn't super common. It's not bad, with a single slider for all the objectives. Actually kind of similar to this case since iirc it has more doubling at lower magnification, though I haven't played with it enough yet (the head I have on my balplan is misaligned enough to give me a headache and I haven't gotten a new one yet).
I am hoping it will be better once I have it dialled in. The results I've seen from the AO epi system are exceptional, so it would make sense that B&L had trouble competing, except that I don't think the AO system sold many copies either.

As to the olympus system, it is odd, more extreme than I've seen that I can remember. It makes intuitive sense that it might work that way, being optimized for one end of the scale and doing worse at the other, but my Nikon slider seems to work well across the whole range. I know it's an iffy proposition with the big 4 but maybe it would be worth contacting Olympus about.