Use cases for ELWD Condensers

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aidanmoore
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Use cases for ELWD Condensers

Post by aidanmoore »

After a quick search of these forums I was unable to find much information on the use of ELWD condensers in microscopy.

I'm wondering where and why ELWD condensers are used?

Specifically I'm wondering if you have to match an ELWD objective with a ELWD condenser for coverslip work? Some ELWD objectives have phase rings, and I wonder if you need to use a special ELWD condenser for this application?

I see these items on eBay from time to time, and I cannot figure out why you would need extra working distance UNDER a sample.

Thanks Aidan
Nikon Eclipse 90i Blackmagic 4K studio camera Nikon D5300

Pau
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Post by Pau »

AFAIK, ELWD and LWD condensers are to be used with inverted microscopes, allowing room for sample manipulations, thick samples, etc..

I don't know about any utility for an upright microscope like the 90i.
Phase annuli and DIC prisms could match or not the non inverted objectives, only maker info or direct experience could tell you.
Pau

pbraub
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Post by pbraub »

Hi,

Pau is right. The ELWD condensers are used on inverted microscopes. In the lab I work in we use a NA 0.3 elwd condenser with phase contrast on a small scope for checking cell cultures (Olympus CKX41) (this is commonly right next to the incubator in the lab for visual inspection - vitalitiy, contamination etc.) There is a camera for documentation, but the image quality is horrible mostly due to the limited condenser NA.

On a bigger (and older) research scope (Olympus IX70) we use a NA0.55 lwd condenser. This condenser can accept inserts for phase contrast or dic. Olympus has its own dedicated DIC elements for the IX series. I do not know if there is a cross compatibiltiy to the DIC elements from the normal upright condenser. If so, Olympus does not tell us - but there is a lot more compatible than they tell us and there are even combinations explicitly incompatible (according to the manual) that work very well. As Pau says: someone will have to try (and hopefully post in the forum).
Image
CKX41 with ELWD condenser

Image
pre-centered phase contrast slider in the ELWD condenser

Image
IX70 with LWD condenser


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zed
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Post by zed »

Hi Aidan,

In an ideal world, for best resolution with transmitted light techniques you want to match the NA of the objective with the NA of the condenser.

From a practical standpoint, the NA of the condenser has a minimal impact on overall image resolution with NAs below 1.0. The objective does most of the heavy lifting. ELWD condensers with NA’s of 0.3-0.55 will perform very similarly to condensers with NA of 0.9.

Think about the math - Lambda*1.22/(ObjNA+CondNA). A dry objective with 0.75NA can theoretically resolve to 367nm (at 550nm). If you use a 0.55 condenser your resolution (at 550nm) would be 516nm. Using a 0.9 condenser it is 407nm. For an objective with 367nm of maximal resolution and thus your error - you wouldn’t see the 109nm difference.

As Pau mentioned - inverted stands often require significant space above the stage to mount all kinds of sample holders, commonly cuvettes or even large media chambers containing live cells or tissue. For this you sacrifice condenser NA for working distance. But it isn’t much of a sacrifice when you consider the objective NA used on scopes like the CKX41 in pbraub’s example.

The ‘horrible image quality’ that pbraub mentions has really nothing to do with the condenser NA but the overall quality of the CKX41 - which is a tissue culture scope used with relatively low NA objectives for screening purposes. When compared to the IX70, which is a research grade microscope used with much higher NA objectives (typically) and thus equipped with better quality routing optics (tube lens, etc) it is apples and oranges.

Bottom line - the choice of whether or not you require such precision will depend on the structures (or samples) you are trying to resolve. Techniques like phase contrast are not typically used for high resolution imaging. With techniques like DIC you could reliably measure a resolution difference between condensers but mostly the improvements lie when you shift to oil immersion objectives/condensers. Are you going to notice the difference between a 0.55 and 0.9 condenser on a research grade stand? Probably not - but I would love to see an example! Your alignment of the condenser assembly will be more critical than its NA for many of the applications that folks here are into.

Hope this helps!

pbraub
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Post by pbraub »

Oh sorry i was in a bit of an hurry. The CKX is actually equipped with planfluorite objectives of the same grade as in the ix70. The "horrible" was me reminding my attempts of creating an oblique lighting setup with this condenser. this did not work out because i could not decenter the condenser enough to create this effect and the low NA of the condenser did not provide the opportunity to insert an appropriate stop in the condenser plane.

If you use normal BF or Phase the IQ is very reasonable.

aidanmoore
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Location: Toronto

Post by aidanmoore »

Thank you all for the detailed clarification. I had assumed that the ELWD condensers were used somehow for upright transmitted light setups. Much clearer now thanks!
Nikon Eclipse 90i Blackmagic 4K studio camera Nikon D5300

abednego1995
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Post by abednego1995 »

Technical questions are already answered above, but from a users perspective, LWD, ELWD condensers in a upright setup help when you have to use dipping objectives. Must have when you're doing electro-physiology experiments.

Cheers,
John

JohnyM
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Post by JohnyM »

I often see LWD condensers in upright metalurgical microscopes.
Some samples are quite high, and you might want to observe upper part of it. Thanks to LWD design you can focus your light properly. In case of thick opaque samples, you might want to do measurments with backlight, and properly focused condenser is important then. It would not be possible to do with classic 1-2 mm WD condenser.
Higher NA models are also corrected for slide which is 1.2
LWD models are very tollerant for different thichness due to moderate NA.
I.e.: When observing cultures on petri dish on my upright microscope, im switching universal 1.4 to LWD 0.65 condenser.

About matching condenser and objective apertures: they are made specifically for one type of condenser.
Ie: PH2 insert for 0.9 condener will work as PH2 only when in 0.9 condenser.
But not to worry, for "universal" condensers, you usually can find any kind of insert that's needed.
Once you have a condernser with Ph2 inser, no matter if LWD or ELWD, you can use it with any Ph2 objective from that manufacturer. ELWD or normal.

P.s.: They also differeniate between upright and inverted LWD versions. Main difference being way polarizers and compensators are mounted. Ie: you cant simply take inverted DIC set and mount it on upright as shear dirrections will be missmatched. You'll need to turn some prisms 180 degrees.

aidanmoore
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Joined: Thu Sep 24, 2015 8:09 am
Location: Toronto

Post by aidanmoore »

OK...Understood. So the LWD condenser shown below for example could be used in an upright configuration when imaging irregular or large specimins, or used as a backlight.

Image
Nikon Eclipse 90i Blackmagic 4K studio camera Nikon D5300

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