Hoffman Modulation Contrast

[Radazz]

Olympus IX70
20x objective
Hoffman Modulation Contrast




A bit heavy handed, but I’m learning.
Enjoy,
Radazz

[MicroBob]

Hi Radazz,
looks a bit like "Parkinson Contrast". There seems to be an effect like camera shake in the images.
Maybe diatoms with their clear grid structure are not the right objects for this contrast system? Do you know what it was intended for? I think it was for something in the medical field.
The colours are nice and the resolution is good for a 20x objective.

Bob

[Radazz]

Operator error, I have no doubt.
This one came from a genetics lab. It has a heated stage, but I didn’t get a power supply for it.

[MichaelG.]

Do you know what it was intended for? I think it was for something in the medical field.

I investigated [well, browsed really] this a while ago, but didn't find much by way of explanation:
https://en.m.wikipedia.org/wiki/Hoffman ... microscopy
https://en.m.wikipedia.org/wiki/Differe ... microscopy
If one of our experts could compare DIC / Nomarski / Hoffman I would be grateful.

MichaelG.

[Radazz]

Me too. Still can’t afford DIC, but this will make some interesting images.

[mnmyco]

Hoffman avoids the costly prisms of DIC, that is the main bonus. The book, Light and Video Microscopy by Randy Wayne has a great chapter on it. It only uses a polarizing filter, retardation film, and slits in filters to to convert phase differences in the specimen into visible differences. A slit filter is placed in the condenser and the objective and between the light source and condenser you need a polarizing filter. That is it. In DIC, polarized light is split into two separate light beams via a very costly prism. To make it simple, the two go through the specimen and then are combined by another costly prism. Hoffman produces great images, without the glow around the specimen like phase contrast and avoids costly prisms.

mnmyco

[MichaelG.]

Hoffman avoids the costly prisms of DIC, that is the main bonus. The book, Light and Video Microscopy by Randy Wayne has a great chapter on it. ...

Thank You

MichaelG.

[ImperatorRex]

Hi,
I tried the Hoffman Modulation Contrast (HMC) some time ago - results are something between Phase Contrast and oblique illumination. Made test photos with Paramecium Caudatium ... need to find those

It is usually applicable to lower up to middle magnifications only and my impression was, that HMC somehow reduces the numerical aperture and therefore resolution is not at its max level (compared to DIC). However contrast is very strong! I got some feedback from a HMC user (where I sold my HMC stuff) that HMC shows better results compared to DIC on his vertical microscope where he uses petri dishes (objective 10x).

Manufacturer is Modulation Optics, on their website there is also an operating manual avaialble, if I remember correctly.

There are also two articles available in the MIKROKOSMOS journal describing how to make a DIY solution for HMC condensor and objectives. (Mikrokosmos, Band 71(11), S. 346 (1982) & Mikrokosmos, Band 72(2), S. 58 (1983)) - however it is a journal in german language.
Technical details are also described in the US patent no 4,200,353 and US 4,200,354 (Apr. 29, 1980)

Post Scriptum:

Further interesting link: http://micro.magnet.fsu.edu/primer/tech ... index.html

Some photos are also posted here: https://www.mikroskopie-forum.de/index. ... #msg165396

[wporter]

Hoffman is especially best for use with plastic petri dishes; since crossed polarizers (i.e., a polarizer and an analyzer) are not used, as they are in DIC, there is no colored strain-patterning in the field, as there would be if DIC was used with plastic dishes. The resolution is not as good as DIC's, but can be maximized in the Hoffman systems by the use of an offset slitplate, rather than one that has the slit centered. In many of the Hoffman (or the similar systems from Leica, Olympus, etc.), the slitplate in the condenser is made from polarizing film, so an underneath rotating polarizer can be used to vary the intensity of the transparent edge of the slit, thus changing the apparent gradation intensity of the specimen in the field of view.

[MicroBob]

There are also two articles available in the MIKROKOSMOS journal describing how to make a DIY solution for HMC condensor and objectives. (Mikrokosmos, Band 71(11), S. 346 (1982) & Mikrokosmos, Band 72(2), S. 58 (1983))

One funny thing about Hoffman contrast is that there are in fact two Hoffman(n)s!

The first Mikrokosmos article is about Hoffman, Robert, USA
The second Mikrokosmos article is about Hoffmann, Peter, Germany

They do similar things, but it looks as if Robert was first.

Bob

[ImperatorRex]

The second Mikrokosmos article is about Hoffmann, Peter, Germany

Yes, in fact a funny coincidence. I was able to contact the Mikrokosmos author Peter Hoffmann two years ago by email. He was somehow surprised to get some questions about the selfmade HMC

[MicroBob]

He was somehow surprised

The Mikrokosmos never forgets!

What did he say? Is he still active in microscopy and how does he evaluate his system today?
Overall it is probably the most elaborate DIY contrast system.

[ImperatorRex]

Hello Bob,
indeed the great MIKROKOSMOS journal...now it is history.
Ups, it was 2012 when I contacted him. He told me that he is hardly active in microscopy ... other interest and tasks. He ist busy for the Naturschutzbund NABU and has a nice website http://www.parsprofoto.de/index.html and http://www.nabu-soest.de/

[mnmyco]

Hoffman is especially best for use with plastic petri dishes; since crossed polarizers (i.e., a polarizer and an analyzer) are not used, as they are in DIC, there is no colored strain-patterning in the field, as there would be if DIC was used with plastic dishes. The resolution is not as good as DIC's, but can be maximized in the Hoffman systems by the use of an offset slitplate, rather than one that has the slit centered. In many of the Hoffman (or the similar systems from Leica, Olympus, etc.), the slitplate in the condenser is made from polarizing film, so an underneath rotating polarizer can be used to vary the intensity of the transparent edge of the slit, thus changing the apparent gradation intensity of the specimen in the field of view.

In the all descriptions I have seen, the slit plate, has retardation film, polarizing film, and a filmless portion. I see it heavily used in mammalian cell culture images.

mnmyco

[Radazz]

Looking through the Bertrand lens, I see the slits are off-center. These are the type with most of the plate being clear.
I’ve added an analyzer that I can insert into the nose-piece slot, in order to get straight pol or a combination.

Oh! I think I’ve found the problem with the above images.
Must place the slides on the stage upside down.