Nikon Interference Phase Contrast (IPC)

[dolmadis]

Thanks Peter. I’ll look forward to that.

In the meantime Google is having a struggle helping me find out what a Schlieren Stop is and some idea of how to fabricate one assuming that is the way forward.

Sorry to ask, but help !!

Many further thanks to get me started.

John

[TiggerScope]

No problem, John, ask away.

Try this for starters and take it from there. Remember we have a conjugate back focal plane which is freely accessible (unlike standard microscopes) and we can put there anything we want; similarly we can change the shape of the illuminating aperture in the condenser (so you might want a spare condenser for playing about with).

https://www.sciencedirect.com/topics/en ... /schlieren

[zzffnn]

These Schlieren implementations may be easier to follow:

https://www.google.com/search?q=schlier ... DkigiqST6M

www.microscopy.cz/html/2514.html

https://www.researchgate.net/figure/Rel ... _326693064

I haven’t extensively compared oblique (relief contrast) to Schlieren, but with my limited tries with Schlieren on live protists on live slides, I actually don’t like its overly busy / dark shadow effect.

Sometimes too much contrast (shadow details) is not visually pleasing (I much prefer how background melts / blurs away in high magnification DIC).

I would be interested to hear others’ hands-on experience.

[dolmadis]

Thank you to you both for the interesting reading list which leads me to think about how to exploit access to the objective focal plane using an IPC.

Obviously as prompted by Peter, Hoffman filters are on the list but I think that I would struggle to create these by diy.

During other threads on DIC I have seen members suggest using a slit condenser with a Wollaston prism at the objective focal plane together with crossed polarisers.

So I have alighted here to ask if that arrangement could be arranged by 3D printing in place of the usual silver slider on an IPC.

Posting to learn so it might be a daft idea.

Anyone diy a Hoffman?

Thanks, John

[dolmadis]

Hi all

Having delved some more I found this up to date link explaining Hoffman Modulation Contrast.

The suggested design of filters does seem to be within diy!

https://www.olympus-lifescience.com/en/ ... -contrast/

Hope this is of interest to others. It is for me.

Would I be correct in seeking to place the Slit at the bottom of the Abbé condenser and the modulator in the IPC path in between the polarisers?

Thanks for any input of advice.

Best, John

[zzffnn]

Interesting. I don’t have IPC and haven’t studied or used Hoffman Modulation Contrast.

That article doesn’t seem to provide all the details of implementation.

In addition to JOhn’s question, I also wonder:

1, condenser slit plate seems to contain only G (gray) and B (bright) in slit area, so rest of the slit plate is all D (dark)?

That configuration may not use full aperture of a high NA objective (for example, article does not mention using Hoffman Modulation with 100x objectives).

2, what difference do they make in images, if one compares set 2A vs set 2B in Figure 2?

[photomicro]

Thank you to you both for the interesting reading list which leads me to think about how to exploit access to the objective focal plane using an IPC.

Obviously as prompted by Peter, Hoffman filters are on the list but I think that I would struggle to create these by diy.

During other threads on DIC I have seen members suggest using a slit condenser with a Wollaston prism at the objective focal plane together with crossed polarisers.

So I have alighted here to ask if that arrangement could be arranged by 3D printing in place of the usual silver slider on an IPC.

Posting to learn so it might be a daft idea.

Anyone diy a Hoffman?

Thanks, John

Yes John, I have had some success with it in the past, and am actually being sent a Hoffman part today, by complete coincidence.

A DIY suggestion was also given by my friend Chris Hammond in;

Hammond, C. A modified modulation contrast technique for transmitted and reflected light microscopy Microscopy,
The Journal of the Quekett Microscopical Club, Volume 40, Part 6 (Ed. - Dr. B. Bracegirdle) Quekett Microscopical Club [Winter 2007], p.495

Then there are also a few bits and pieces written by Robert Hoffman himself, which I have photocopies of somewhere, and the odd bit of operating instructions written for use with altered objectives and condensers for Nikon and Olympus systems, but also I think Leitz.

Plus there is VAC; Variable Amplitude Contrast, which was written about quite extensively in 'Strange's Variable Amplitude Contrast' by Brian Wilkinson in an issue of 'Balsam Post' (PMS) in April 2011, and then once or twice in subsequent follow-up articles.

Both are often referred to as a 'poor Man's DIC' which is somewhat true, but also a little unfair in some ways.

VAC is fairly easy to do on even modest equipment, and costs very little.

Mike

[TiggerScope]

I was given some Nikon-HMC objectives but no condenser. But I think the genuine Hoffman condenser is a poor design. The only fuction of the polariser is to vary the intensity of illumination in Zone 2.

This makes any pol work impossible, and I assume it's simply a cheaper way of implementing the adjustment, which could also be made mechanically. So I re-purposed a Zeiss phase contrast condenser by making some masks with a clear slot, which would line up with Zone 2.

I was also a bit disappointed that all the available objectives were just plan achros. So I found a 4x planapo and a 10x fluor which had the BFP accessible above the glass, and made Hoffman plates with round coverslips, smoked over a candle using a razor blade as a straightedge.


Here's an old example of Hoffman Pol, Nikon 10x/0.5, vitamin C I believe

UNIDXtalHMC10f (Custom).jpg (195.82 KiB) Viewed 1625 times