Hoffman Modulation Contrast

[Craig Gerard]

If I understand this correctly, Hoffman Contrast Modulation is way of achieving DIC type results with inverted scopes for the practical and technical reasons previously outlined in this thread. I understand there more advantages and disadvantages.

Hoffman Contrast Modulation can also be used with upright microscopes with appropriate modified objectives and condensor (are there more bits required?).

What advantages would Hoffman Contrast Modulation have over Differential Interference Contrast or Nomarski when using an upright microscope?

Are DIC components more readily available? What are the components required for DIC on an Olympus BH-2?

There is more info for DIC on Wikipedia than HMC.
DIC:
http://en.wikipedia.org/wiki/Differenti ... microscopy

HMC:
http://en.wikipedia.org/wiki/Hoffman_Mo ... n_Contrast


Craig

[Choronzon]

Craig, my comments in red

If I understand this correctly, Hoffman Contrast Modulation is way of achieving DIC type results with inverted scopes for the practical and technical reasons previously outlined in this thread. I understand there more advantages and disadvantages.

Hoffman Contrast Modulation can also be used with upright microscopes with appropriate modified objectives and condensor (are there more bits required?).
really, just a different condenser and polarizer (shorter working distance)

What advantages would Hoffman Contrast Modulation have over Differential Interference Contrast or Nomarski when using an upright microscope?
Initial cost, and the ability to work through plastic, unlike DIC, however, with the first order plate, DIC gives you pretty colors!, a never ending source of amazement for young and old.

Are DIC components more readily available? What are the components required for DIC on an Olympus BH-2?
Probably, but way more expensive when available because of the bigger demand, and more complex components. Less is known about the Hoffman contrast, so it's much less of a known entity. You will need the condenser with appropriate prisms for objectives used, the the prisms for each objective above each objective position, and the polarizer and analyzer. Plus the first order plate if you want color contrasting. Some systems use a single, moveable prism (a wedge really) above all the objectives. In reality, there are several type systems developed over the years, and you must have all the matching components for the version you intend on using. This could actually be the subject of a lengthy post on DIC types, as there are many confusing components developed over the years. For the Olympus, Charles, here most certainly knows more than I.
There is more info for DIC on Wikipedia than HMC.
DIC:
http://en.wikipedia.org/wiki/Differenti ... microscopy

HMC:
http://en.wikipedia.org/wiki/Hoffman_Mo ... n_Contrast


Craig

[Charles Krebs]

This could actually be the subject of a lengthy post on DIC types, as there are many confusing components developed over the years.

I'll say! And these parts all need to work "together" for proper implementation so it's always best to get a full working system. Trying to locate a missing "piece" for a non-current system can be extraordinarily difficult and frustrating.

What are the components required for DIC on an Olympus BH-2?

This is the only system I have any real familiarity with so here goes:

You need a BH2-NA Nomarski DIC intermediate tube. This is positioned between the stand and the viewing/trinocular head. It has a slot for the movable "wedge" slider prism Choronzon mentioned (offhand I don't remember the Olympus designation for the DIC slider). With this Olympus system there are no individual prisms above each objective. (Incidentally, this tube adds a 1.25X magnification to everything). That takes care of the "top".

Below the stage you need a DIC condenser. This condenser has a rotating turret that holds individual Nomarski prisms for each objective, as well as a polarizer at the bottom. Olympus made two. The first was a NA 1.4 Acromatic Aplanatic. It held "fixed" prisms designed to be used with the S Plan Achromat objectives. There was also a "brightfield" position in the turrret, and (I think!... this is not the condenser I have) some phase contrast positions. The second DIC condenser (which is what I have) is the BH2-UCD Universal Condenser. It is a NA 0.90 AA condenser with a "flip" top for lower power objectives. This has a five-position turret, but the inserts (Nomarski prisms or phase annuli) are user interchangeable. There is a good description of insert possibilities on page 13 of the Olympus BHS/BHT brochure on my site here:
www.krebsmicro.com/BHS-BHT_Microscopes.pdf
Initially I was interested in the first model since it was a NA 1.4 and had more turret positions. But now I'm glad I came across a BH2-UCD first. This is because I could get Nomarski prisms meant to be used with the Olympus D Plan Apo objectives (and I found out that they work quite well with my S Plan Apo's... an initial concern, but a pleasant "surprise"). These have larger prisms so you can take advantage of the higher NA's of the Apo objectives. (Many Apo's of that era were not "recommended" for illumination methods that utilized polarization). I wish it had a couple more positions in the turret like the earlier model, because while not difficult to change inserts, it's not something you want to do on a regular basis. (Mine is set up with Nomarski prisms for 20X, 40X and 60X objectives, a brightfield position, and a position with a homemade darkfield stop. So if I want 10X DIC or phase I need to change something. (BTW... I like the DIC this system gives from 20X and up. With the 10X objectives the DIC effect is very strong, but it's hard to get a "background" of even color and intensity.... I should probably play around with that some more, but I hate to give up the darkfield position). If you locate a BH2-UCD you should be sure it has the prisms you want/need. It can take years to locate these. (After 5 years or so I'm still looking for the UNP100 for the 100X objectives, although the 100X works pretty nicely with the prism for the 60/1.4 S Plan Apo)

I have "heard" of people removing the "fixed" prisms in the first condenser and putting in the D-Apo prisms from the newer BH2-UCD condenser, but frankly I would never screw around with a system that is so expensive and requires such precise integration of components.

[RogelioMoreno]

Wow, the kit is now listed on eBay!

http://cgi.ebay.com/Hoffman-Modulation- ... 4aa387d298

Rogelio

[Craig Gerard]

Nice set!

Watch the shipping costs. Obviously the seller wants to send it via the most appropriate means.

Here's a guess....In approximately 3 hrs (at time of writing) this item will be headed for Poland.....

Craig

[Doc.Al]

Hi All,

Thanks for the comments

I am slightly sad that it has to go, but I don't think that I am likely to find a cheap enough IX microscope any time soon for me to use it with. Even the cheaper infinity corrected inverted scopes are a bit out of my price range at the moment.

Watch the shipping costs.

I am never sure what to do about this. The item weighs 3kg (6-7lb) and obviously I want to send it by an insured carrier (I tend to use Royal Mail or Parcel Force here in the UK). Any recommendations as to a cheaper option would be happily received.

Alex

[Craig Gerard]

Alex,

I did not realise this was your HMC set. I sold my set recently.

Well presented listing. Hope it goes well for you; but I still believe they are worth more than the listed price.

Looks like I was wrong about Poland...

Craig

[Doc.Al]

Hi Craig,

The listed price is a starting price and not a "buy it now" price.

I have had a few items go really cheaply recently and don't want that to happen to this set.

Lets see what happens!

Did you get a good price for your set?

Alex

[Craig Gerard]

Alex,

Yes, I was happy with the price I received. I had 3 people view the auction before it sold (it sold in a matter of hours); but my set was no where near the calibre of yours.

I am watching your auction out of curiosity.

Can I make a suggestion; see if you can fit the word 'objective' or 'objectives' in the sub-title.

Craig

[Doc.Al]

Hi,

I probably should have posted the ebay item itself, but wasn't sure if it was allowed.

Here it is anyway

http://cgi.ebay.co.uk/Hoffman-Modulatio ... 4aa387d298

Alex