Condenser Confusion

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GerryR
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Condenser Confusion

#1 Post by GerryR » Thu May 26, 2022 11:15 am

I've been looking at various microscopes with condensers and have studied how to set up the microscope with condensers. This is where the confusion starts.
First, many scopes that have condensers do not contain a "field" diaphragm, so how do you adjust lighting to get the edges of the non-existent field diaphragm "sharp?" Is there a different procedure for these microscopes?
Second, some of the condensers do not have height adjustment. I must assume that these scopes have been set up at some compromised point that make lighting reasonably good for all objective settings.
Third, on many condensers that I have looked at, there is a filter carrier at the base of the condenser. However, on some of these units, there is a lens in the carrier that can be swung out of the way. Why the lens?
Fourth, I have a condenser on one of my field scopes that has a filter carrier. Above the carrier is a frosted glass filter glued to the condenser. On one setup procedure that I read, it said to "remove any frosted glass filters" before trying adjustment and also to swing the lens out of the way if it had one in the carrier, which mine does not.

Needless to say I am slightly confused about the lighting setups presented. I do realize that on the more expensive scopes, with all the bells and whistles, this isn't a problem, but what about lighting setup for the student/amateur scopes for optimum viewing. Any comments will be appreciated. Thanks in advance, and also, if this is a totally dumb group of questions, feel free to say so; I'm not thin-skinned!

apochronaut
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Re: Condenser Confusion

#2 Post by apochronaut » Thu May 26, 2022 1:13 pm

Microscopes that do not have a field diaphragm are using an illumination system that does not rely on one. Usually such systems have preset devices such as the condenser. If the condenser is focusable, then the instructions for the microscope should include a method for focusing the condenser, if necessary. Led systems do not really need to be Köhler or focus on a diaphragm, because Köhler was invented as a technique with which to blur a small chromatic source of light. Using the location of the field diaphragm was because that's where the illumination was the most even, plus the condenser back and front focus points were ideal. If in doubt ,try to find a user's manual.

The swing out lens on some condensers is an aux. field lens, designed to increase the field coverage of the condenser. Objectives under 10X , sometimes have fields of view which exceeds that of the condenser image circle or the circle the condenser illuminates when properly focused. The aux. lens reduces the N.A. and magnification of the condenser, broadening the area that it illuminates. It is usually swung in for objectives under 10X and out for obectives over 10X . It can be left in usually for the 10X but there is a noticeable drop in quality once a 20X is dialled up.

When adjusting the condenser height relative to an illumination system, a frosted glass inhibits the view of any elements that one needs to focus on, so it has to be removed as would an aux. lens and anything else inhibiting view. Usually , a frosted glass is used a an alternate tool with which to even out the illumination, rather than something like Köhler and when an original part, sometimes doing the bulk of that job. If adjustment is necessary or likely and the frosted filter glued to the condenser base, that seems odd. Is it possible that the filter has been glued on by a former user?

GerryR
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Re: Condenser Confusion

#3 Post by GerryR » Thu May 26, 2022 2:25 pm

Thank you for all the information! The frosted filter is actually glued onto the base of the condenser above the filter holder and just below the iris diaphragm. It looks as though that is intentional as there is a counterbore in the base into which it fits. However, I did get the scope used so who knows and being a Swift scope, there is no really good documentation or support. The users manual, which doesn't address the issue, is all I have to go by. The scope is a field M2 and only goes to 400x, so perhaps not an issue. Thanks again for your input.

apochronaut
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Re: Condenser Confusion

#4 Post by apochronaut » Thu May 26, 2022 2:50 pm

Swift has gone through several incarnations. Originally , an English microscope maker, James Swift, the Swift trademark ended up on Japanese microscopes from maybe the 70's on. I think Lorez knows the complete history. It is now a Chinese brand, probably made by Motic.The Swift field microscope most commonly referenced is the FM 31, kind of a standard inverted handheld type.
The M42. Was that an older black horseshoe microscope?

GerryR
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Re: Condenser Confusion

#5 Post by GerryR » Thu May 26, 2022 3:41 pm

The one I have is an M2, picture attached. The Micro lens is 16X and two macros at 0.8x and 1.6x and 10x eyepiece. The "Magnachanger" provides 5x-400x. Objectives are infinity corrected.
Attachments
Swift M2_9A.jpg
Swift M2_9A.jpg (117.29 KiB) Viewed 1508 times
Swift M2_8.jpg
Swift M2_8.jpg (95.5 KiB) Viewed 1508 times

BramHuntingNematodes
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Re: Condenser Confusion

#6 Post by BramHuntingNematodes » Thu May 26, 2022 4:04 pm

Well that's nifty
1942 Bausch and Lomb Series T Dynoptic, Custom Illumination

apochronaut
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Re: Condenser Confusion

#7 Post by apochronaut » Thu May 26, 2022 4:11 pm

Oh, that one. Sorry. The new one made by Motic. Interesting design and looks decently practical. Incident and transmitted illumination. Purpose built objectives.

Might be possible the ground glass filter is cemented in but then removing it? Maybe a call to the Motic/Swift didtributor in your area would be in order.

GerryR
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Re: Condenser Confusion

#8 Post by GerryR » Thu May 26, 2022 6:48 pm

Motic still sells the M3 version of this, but they modified it with three micro objectives (if I recall, 4x, 10x, 40x) and a 1x macro. Not nearly as "nifty" IMO as the M2 with the "Magnachanger."

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