Balplan condenser for phase contrast

Here you can discuss different microscopic techniques and illumination methods, such as Brightfield, Darkfield, Phase Contrast, DIC, Oblique illumination, etc.
Post Reply
Message
Author
microb
Posts: 729
Joined: Wed Mar 27, 2019 6:39 am

Balplan condenser for phase contrast

#1 Post by microb » Fri May 21, 2021 6:15 am

What is the height of the side here marked in blue of this Balplan condenser for phase contrast?
I’m asking because I don’t see how a second lens fits above the PH disk and below the 1.25NA condenser lens aimed at the sample. Is the second lens thin or something?
Attachments
Inkedb_fig_12-2_LI.jpg
Inkedb_fig_12-2_LI.jpg (35.15 KiB) Viewed 1948 times

apochronaut
Posts: 6272
Joined: Fri May 15, 2015 12:15 am

Re: Balplan condenser for phase contrast

#2 Post by apochronaut » Fri May 21, 2021 10:53 am

The Balplan condenser is thin. There isn't a lot of room under the stage. While I don't have that particular condenser body, I do have the rotary one and the distance from the diaphragm to the top lens surface is only about 33mm.

I have been working on a 1.4 N.A. condenser to go along with my Balplan 125X 1.4 N.A. Flat Field Apochromat by building one into the housing of the standard 1.25 abbe aspheric and it is not an easy task because they are so shallow.

It appears that B & L had a fairly limited range of condensers by the time the Balplan program was discontinued in favour of the Microstar IV by either Cambridge or Leica.
A 1.25 abbe, a 1.25 abbe aspheric, a 1.25 abbe (aspheric?) phase condenser , a low N.A. (.65?) L.W.D. condenser, cardioid DF condenser and a paraboloid D.F. condenser. The earlier 1.4 N.A. widefield condenser and the 1.4 N.A. achromat/aplanat had been dropped.
There is quite a lot of difference between the 1.25 abbe aspheric BF condenser and the 1.25 abbe phase condenser. Both focal lengths are different between them and the phase condenser also has a supplementary lens built in that focuses the field diaphragm at the object plane. Presumably the slightly longer front focal distance of the phase condenser throws the position of the field diaphragm off, so that is a compensating lens. There is a similar lens in the AO series 10 phase condenser.
Perhaps the condenser from a Dyna series microscope is closer? The 1.3 from those more resembles the 1.25 Balplan phase and might make a better possible substitute than a Balplan BF condenser. I think they used the same condenser for phase and BF on that model. Bram might know.

I have found a patent of George Aklin's for a multi-lens condenser of high N.A., comprising 9 optical elements or something like that, I can't remember exactly., maybe even more. I would assume it to be as a mate to the higher magnification Balplan Flat Field Apochromats he had also patented. Probably only prototypes exist but that would be a feat to get that under a Balplan stage.

microb
Posts: 729
Joined: Wed Mar 27, 2019 6:39 am

Re: Balplan condenser for phase contrast

#3 Post by microb » Tue May 25, 2021 5:51 pm

31-55-13 condenser rough form factor model:
Attachments
condenser34view.JPG
condenser34view.JPG (129.06 KiB) Viewed 1895 times

apochronaut
Posts: 6272
Joined: Fri May 15, 2015 12:15 am

Re: Balplan condenser for phase contrast

#4 Post by apochronaut » Wed May 26, 2021 3:56 pm

That is a pretty nice rendering. I'm trying to get on the same page here. Are you intending to print a phase condenser body based on the 31-55-13 as a model?

microb
Posts: 729
Joined: Wed Mar 27, 2019 6:39 am

Re: Balplan condenser for phase contrast

#5 Post by microb » Thu May 27, 2021 5:15 pm

apochronaut wrote:
Wed May 26, 2021 3:56 pm
That is a pretty nice rendering. I'm trying to get on the same page here. Are you intending to print a phase condenser body based on the 31-55-13 as a model?
I need to get the snap in base correct to build a phase contrast condenser. I'm thinking of using a cheap new condenser for the ball lens assembly. So I might not be able to use the same size B&L phase rings. Don't know.

Side note: I opened up the 31-55-13 condenser and there are three lenses inside, not counting the fourth swing out one at the bottom. Second side note: the iris is held together with a wave ring spring.

Yep. It's going to take some time to put that puppy back together.

apochronaut
Posts: 6272
Joined: Fri May 15, 2015 12:15 am

Re: Balplan condenser for phase contrast

#6 Post by apochronaut » Fri May 28, 2021 11:43 am

microb wrote:
Thu May 27, 2021 5:15 pm
apochronaut wrote:
Wed May 26, 2021 3:56 pm
That is a pretty nice rendering. I'm trying to get on the same page here. Are you intending to print a phase condenser body based on the 31-55-13 as a model?
I need to get the snap in base correct to build a phase contrast condenser. I'm thinking of using a cheap new condenser for the ball lens assembly. So I might not be able to use the same size B&L phase rings. Don't know.

Side note: I opened up the 31-55-13 condenser and there are three lenses inside, not counting the fourth swing out one at the bottom. Second side note: the iris is held together with a wave ring spring.

Yep. It's going to take some time to put that puppy back together.
The phase condenser is quite different than the 31-55-13. They use a common dovetail section that is removable as you know so buying that section makes sense, and making the condenser section makes sense.
The phase condenser is marked as an abbe 1.25 as well but is unlike any abbe I have pulled apart. Unlike the 31-55-13 , which carries the 3rd aspheric lens, the phase condenser has a very thick assymetrical bi-convex second lens, which is about 15mm thick, built into the top plate of the rotary body. Also both lenses are in contact or within a hair's breadth when the top lens carrier is tightened down. The phase lenses are considerably wider than those on the 31-15-13. The top lens is around 15mm across and the lower surface of the bottom lens is about 27-28 mm across. It has a shorter focal length.
There is a further concave convex lens below the iris.
This is similar to the construction of the AO 1240 condenser body, which was used on the 10. When used on the 20, the aux. lens is removed. It allows the 10 to focus on the considerably closer location of it's field diaphragm when compared to that of the 20.
With the B & L Balplan, that lens likely does the same thing but I cannot see any difference in the field diaphragm location between the 20 watt Balplan and the 100 watt, although the filament location and collimating lens arrray are quite different. This aux. lens is quite important in obtaining the correct conjugation of planes in the phase system.

Both condensers, further require an aux. swing in lens to accomodate the illumination field requirements of the 4X objective if such is included in a 5 hole nosepiece.

Post Reply