Leica Integrated Modulation Contrast (Variant of Hoffman)

Here you can discuss different microscopic techniques and illumination methods, such as Brightfield, Darkfield, Phase Contrast, DIC, Oblique illumination, etc.
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microb
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Leica Integrated Modulation Contrast (Variant of Hoffman)

#1 Post by microb » Sat May 02, 2020 2:11 am

How would you do this technique with a 160mm inverted microscope?

https://www.leica-microsystems.com/scie ... trast-imc/

The slides for a Leica DM IL (in this case infinity) look like this: https://www.ebay.com/itm/Leica-IMC-for- ... Swc6Rei1zn

But looking at the slides though, are these knife edges or is there actually some polarizers on the big slide, and ND filters on the modulator side with 15% transmission and 1% transmission as mentioned in the first link?

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wporter
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Re: Leica Integrated Modulation Contrast (Variant of Hoffman)

#2 Post by wporter » Sat May 02, 2020 6:55 pm

Unlike the Leica website, that misrepresents this particular IMC set in fig 5, this ebay set has at least two components, the small slider and the big slider. The big slider also has two openings, an open one for brightfield, and an IMC one that has a variable slit, with the slit adjuster labeled for 10, 20, and 40x objectives. There are no polarizing filters in the big slider, just the slit and the clear opening.

The smaller slider is the 'modulator', and has two holes, one for BF (labeled such), and another that has a fixed film or membrane that partially covers the hole; you can see it best in image #1 in the ebay listing. The open area of that opening is 100% transmission, the edge 2-3mm of the film is 15%, and the rest ofthe film is about 1%. It is indeed an ND film, not polaroid.

"Polarizer 1" and "polarizer 2" would be in the microscope separate from the sliders.

IMHO, the ebay listing is way overpriced for what you are getting. The price may be acceptable to a big university, but the essential components of the system could be fabricated by yourself, if there are places (slider slots) in your scope that could accomodate them.

microb
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Re: Leica Integrated Modulation Contrast (Variant of Hoffman)

#3 Post by microb » Sat May 02, 2020 11:46 pm

Apparently they do sell. This one just sold at $317. (https://www.ebay.com/itm/Leica-Microsco ... SwdsFenf4u) I'd like to try making a set.

Could I put the small slide here replacing this ND triangular filter located 160mm below the trinocular head?

I haven't figure out how the 2-3mm wide 15% ND transmission filter adjacent to a 1% transmission filter would be assembled, and how much in the same plane is important.
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wporter
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Re: Leica Integrated Modulation Contrast (Variant of Hoffman)

#4 Post by wporter » Sun May 03, 2020 1:31 am

Whoops, I had it wrong about the small ND filter part of the smaller slider; it is actually a glass disk that covers the entire hole. On it are plated the areas of 15% and 1%, the rest left clear.

I can't say about your microscope. What make and model is it? What is the triangular filter for?

edit:
OK, I saw your other post. The manual for your DMIL doesn't mention the filter? It would have to be conjugate with the specimen plane to be a pointer...

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Re: Leica Integrated Modulation Contrast (Variant of Hoffman)

#5 Post by photomicro » Sun May 03, 2020 9:58 am

wporter wrote:
Sun May 03, 2020 1:31 am
Whoops, I had it wrong about the small ND filter part of the smaller slider; it is actually a glass disk that covers the entire hole. On it are plated the areas of 15% and 1%, the rest left clear.

I can't say about your microscope. What make and model is it? What is the triangular filter for?

edit:
OK, I saw your other post. The manual for your DMIL doesn't mention the filter? It would have to be conjugate with the specimen plane to be a pointer...


This triangular filter, and the accompanying (larger) one shown with it below, is in a bag from Leica labelled 'Relief Contrast'.


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The smaller disc is 20mm diameter, the larger 30mm.

The handwritten comment is mine, as someone suggested to me that is what it was designed for. I am uncertain how true this is, as I don't use Leica.

microb
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Re: Leica Integrated Modulation Contrast (Variant of Hoffman)

#6 Post by microb » Sun May 03, 2020 8:36 pm

Thanks. Maybe that's the answer. I'm missing the other filter. The annulus that goes into the slide in the lamp is just fitted under 30mm (29.98mm) and has the same flex-points built in to be put into a slide. Maybe I'm reading into it.

This article says it covers Leica's relief contrast. Not much detail though:

"Relief phase contrast was developed on two Leica (Leitz) microscopes, a Dialux and an HMLux III."

https://www.microscopyu.com/pdfs/Piper_ ... 9-2007.pdf
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Re: Leica Integrated Modulation Contrast (Variant of Hoffman)

#7 Post by apochronaut » Mon May 04, 2020 11:10 am

This, Hoffman, the variable slit interference condenser of PZO, the Goerz condenser and the original Zernicke/Zeiss phase system all seem to be variations on a theme. That of passing the original light source through a slit, rather than than through a circular or concentric aperture. I suppose, one could add to those, standard oblique, where as far back as pre w.w. I, oblique irises were incorporated into research substages. Through a series of half moon shaped leaves, they could be closed down to a slit located eccentrically. The addition of polarizers and complementary retardation plates into the system at various locations or in various forms is like adding the right proportion of salt to already shredded cabbage and then packing it into a barrel.

There are other systems that have at least reached the research stage. One, I might now have trouble finding from 2010 or so, was a phase DF hybrid, where the annular phase diaphragm was reduced to a series of pin holes marking it's location but established in a DF stop. This created a phase condition in DF , sort of but created an interference condition that yielded relief. I remember the images being quite impressive.


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