Making a negative meniscus lense ?

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Matador
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Joined: Sun Apr 25, 2021 4:55 pm

Making a negative meniscus lense ?

#1 Post by Matador » Mon Apr 26, 2021 2:52 am

Looking for a Zeiss part that seems unobtainable after many hours of searching the web (will continue to look, but I'm pretty sure I will never find it (it seems to me like this part was rarely even sold during the time the Axioskop was sold new).

I'm looking for an "Auxiliary lens" (zeiss part 44 52 65) that is supposed to be mounted in the rotating turret of my phase/DIC condenser for my Zeiss Axioskop 50.
I posted a "Want to buy post" in the apropriate section of this forum.

The reason this part is usefull is that it's the only way to have a wide enough illumination light cone to be able to use my Plan-NEOFLUAR 1,25x objective (otherwise, I only have about 50-60% of the field illuminated in my field of view, but the periphery remains dark. I have no problem with my other objectives (2.5x, 5x, 10x, 20x, 40x and 100x).

The part in question I post about here (with diaphragm and pictures, and the patent info) : https://www.microbehunter.com/microscop ... 16&t=12713

Wondering if I can just make the lens myself or find someone who can custom make it ?

Anybody has experience with this kind of work ?
Anybody has experience with calculations required for this kind of work ?

Matador
Last edited by Matador on Sun May 09, 2021 3:31 pm, edited 2 times in total.

PeteM
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Re: Making a negative meniscus lense ?

#2 Post by PeteM » Mon Apr 26, 2021 5:44 am

You could try removing the condenser, dropping it way down with the top lens off or a wider angle top lens substituted, or replacing it entirely as needed with a wide angle condenser modified from another brand.

Maybe add a diffuser to the field lens if the field is still uneven while trying the above. Not perfect, but you should be able to illuminate the entire field of view.

Leica was another maker with a DIC-condenser-resident supplemental lens to fit a turret and cover a wider field. Possible wide enough and able to be adapted to your condenser. I've seen these show up from time to time and have one myself.

Someone else here will better know the Zeiss range.

MichaelG.
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Re: Making a negative meniscus lense ?

#3 Post by MichaelG. » Mon Apr 26, 2021 6:30 am

Matador wrote:
Mon Apr 26, 2021 2:52 am


I'm looking for an "Adapter lens" (zeiss part 44 52 65) that is supposed to be mounted in the rotating turret of my phase/DIC condenser for my Zeiss Axioskop 50.

.

The part in question I post about here (with diaphragm and pictures, and the patent info) : https://www.microbehunter.com/microscop ... 16&t=12713

Wondering if I can just make the lens myself or find someone who can custom make it ?

.
.

I have just looked through your referenced thread:

Your highlight on the patent drawing indicates a simple meniscus lens element ... but the photo from ebay has evident signs of delamination on the 44 52 74... So perhaps 44 52 65 may be more complex than you have assumed.
[ admittedly there is only one area of cross-hatching on the patent, but are you sure it’s not a two element lens ? ]

MichaelG.
.
Edit: I have now read the patent :oops: ... I should have done that before posting !
You are correct: It simply states
The other switching position accommodates an auxiliary lens in the form of a concave-convex negative member 10.
Too many 'projects'

apochronaut
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Re: Making a negative meniscus lense ?

#4 Post by apochronaut » Mon Apr 26, 2021 10:47 am

On other microscopes I have looked at the lens profile of the aux. lens, found out it's diameter and purchased a similar lens from one of the surplus dealers for around 10.00. Worked well but in these cases, I had an original mount and no lens.

Still, you have the lens dimensions and probably the glass type from the patent, I would presume. It isn't impossible to find a close match since there are so many lenses in surplus and probably worth the 10 or 15.00 to try it out.

Matador
Posts: 35
Joined: Sun Apr 25, 2021 4:55 pm

Re: Making a negative meniscus lense ?

#5 Post by Matador » Mon Apr 26, 2021 8:49 pm

MichaelG. wrote:
Mon Apr 26, 2021 6:30 am
I have just looked through your referenced thread:
Your highlight on the patent drawing indicates a simple meniscus lens element ... but the photo from ebay has evident signs of delamination on the 44 52 74... So perhaps 44 52 65 may be more complex than you have assumed.
[ admittedly there is only one area of cross-hatching on the patent, but are you sure it’s not a two element lens ? ]

MichaelG.
.
Edit: I have now read the patent :oops: ... I should have done that before posting !
You are correct: It simply states
The other switching position accommodates an auxiliary lens in the form of a concave-convex negative member 10.
The 44 52 74 is actually a DIC prism that mounts in the phase condenser's rotating turret.
The 44 52 65 is the 1.25 auxiliary lens that also mounts in the phase condenser's rotating turret.

They are different, but I suppose they should be about the same diameter size. I also wondered if the lens mount is similar between 44 52 74 and 44 52 65.
Honestly, I'm note sure if the auxiliary lens is a single or a lens doublet.
I have not being able to find a single picture of this 44 52 65 auxiliary lens on the web, so I'm kind of looking for a part without knowing how it looks. I don't even know if it has the 44 52 65 number written on if it was just weitten on the package it was in when it was avaible for sell by Zeiss.

Matador

Matador
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Re: Making a negative meniscus lense ?

#6 Post by Matador » Mon Apr 26, 2021 8:51 pm

apochronaut wrote:
Mon Apr 26, 2021 10:47 am
On other microscopes I have looked at the lens profile of the aux. lens, found out it's diameter and purchased a similar lens from one of the surplus dealers for around 10.00. Worked well but in these cases, I had an original mount and no lens.

Still, you have the lens dimensions and probably the glass type from the patent, I would presume. It isn't impossible to find a close match since there are so many lenses in surplus and probably worth the 10 or 15.00 to try it out.
Thanks for the reply, I will search for that. I might need to remove the phase condenser cover to take measurments with a caliper. But for lens curvature values, I guess it will be trial and error.

Matador

MichaelG.
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Re: Making a negative meniscus lense ?

#7 Post by MichaelG. » Mon Apr 26, 2021 9:02 pm

Reading the patent :

Yes, I am pretty confident that it is a simple meniscus lens design ... BUT
No, I cannot find any reference to the glass or the curvatures

Just for the sport of it ... If you can give me a useful dimension for any item clearly visible on the patent drawing: I will try to ‘reverse engineer’ the lens.

My estimates will probably be way-off ... but better than nothing !

MichaelG.
Too many 'projects'

Matador
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Re: Making a negative meniscus lense ?

#8 Post by Matador » Mon Apr 26, 2021 9:56 pm

MichaelG. wrote:
Mon Apr 26, 2021 9:02 pm
Reading the patent :

Yes, I am pretty confident that it is a simple meniscus lens design ... BUT
No, I cannot find any reference to the glass or the curvatures

Just for the sport of it ... If you can give me a useful dimension for any item clearly visible on the patent drawing: I will try to ‘reverse engineer’ the lens.

My estimates will probably be way-off ... but better than nothing !

MichaelG.
So I took out the DIC Prism I have mounted in my phase condenser to measure dimensions. The phase condenser has 4 positions, two position (1 and 2) for phase rings (these positions have centering apertures to put in centering screws) and two other position (DIC and H/DIC). Both DIC and H/DIC position have a place to mount a DIC lens in addition to each having their own independant iris diaphragm...

I measured the DIC prism lens dimension thinking that would correspond to the auxiliary lense width dimensions but I'm not so sure anymore. The axioskop manual seems to say that the auxiliary lens would be mounted either in the 1 or 2 position rather than the H/DIC or DIC position (meaning the auxiliary lens could be centerable, but would not have an iris diaphragm above it).

Anyway, might as well still post the dimensions of that phase prism (bit delaminated) for future reference. Diameter might be the same, but I suspect thickness would be more for the auxiliary lense as there is no iris diaphragm above it.

Lens face toward the light source:
445274_pic 001.jpg
445274_pic 001.jpg (123.35 KiB) Viewed 471 times
445274_pic 003.jpg
445274_pic 003.jpg (116.44 KiB) Viewed 471 times
Lens face toward the nosepiece:
445274_pic 002.jpg
445274_pic 002.jpg (124.91 KiB) Viewed 471 times



Side view:
445274_pic 004.jpg
445274_pic 004.jpg (64.06 KiB) Viewed 471 times


Dimensions measured with caliper:
445274_pic 005.jpg
445274_pic 005.jpg (84.75 KiB) Viewed 471 times
The threaded ring (spanner wrench needed) is screwed on the face of the lens facing the light source and holds the lense in place.

I think I'll need to take apart the condenser once more to see if measurements are similar in the 1 and 2 positions as it is on the DIC and H/DIC positions

Matador.

Matador
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Re: Making a negative meniscus lense ?

#9 Post by Matador » Mon Apr 26, 2021 9:58 pm

Condenser towards nose piece (eBay image):
1.jpg
1.jpg (118.36 KiB) Viewed 471 times
Condenser towards light source (eBay image):
2.jpg
2.jpg (74.26 KiB) Viewed 471 times

MichaelG.
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Re: Making a negative meniscus lense ?

#10 Post by MichaelG. » Mon Apr 26, 2021 10:34 pm

Here’s a direct quote from column 3 of the patent text:
For illuminating still larger objective fields, that is for the work with objectives having an imaging magnification of 1.25X, the auxiliary lens 10 is additionally switched into the beam path beneath the composite lens 7 in the immediate vicinity of the aperture diaphragm 9 which is then pivoted out.
.

MichaelG.
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MichaelG.
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Re: Making a negative meniscus lense ?

#11 Post by MichaelG. » Tue Apr 27, 2021 8:18 am

.

Work in progress :
.
One small step for Man ...
One small step for Man ...
BEF81C90-799A-442F-A281-A0175748818C.jpeg (84.51 KiB) Viewed 429 times
.

Now we need to scale it ... Then choose a glass

MichaelG.
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MichaelG.
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Re: Making a negative meniscus lense ?

#12 Post by MichaelG. » Sat May 01, 2021 2:47 pm

UPDATE

Assuming the glass diameter to be 24mm ... here’s my best effort at dimensioned sketch of the lens element :
.
adapted from the drawing in US patent 4,807,980
adapted from the drawing in US patent 4,807,980
59269735-1BDA-4798-967E-246F9D9B8126.jpeg (84.88 KiB) Viewed 325 times
[ if anyone knows the actual diameter, I can re-scale it ]

MichaelG.
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MichaelG.
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Re: Making a negative meniscus lense ?

#13 Post by MichaelG. » Sat May 01, 2021 3:11 pm

Based on that ^^^ ... here’s a model :
.
E02584D4-EAF9-4191-8D10-4D85A65A2A46.jpeg
E02584D4-EAF9-4191-8D10-4D85A65A2A46.jpeg (169.71 KiB) Viewed 320 times
.

So ... allowing for many approximations, and the likelihood that Zeiss would use a higher Refractive Index glass : I think we have a nominally 20 Diopter negative lens [which could probably be produced by your local optical lab at a reasonable price]

MichaelG.
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MichaelG.
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Re: Making a negative meniscus lense ?

#14 Post by MichaelG. » Wed May 05, 2021 9:00 am

Just bumping this, because it’s already fallen off page_1

I was hoping to prompt some wider discussion
... Does anyone actually have an example of the lens, that they could check ?

MichaelG.
Too many 'projects'

Matador
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Re: Making a negative meniscus lense ?

#15 Post by Matador » Thu May 06, 2021 4:56 am

MichaelG, thanks for taking the time to explain all this. I have not forgotten you.
I actually contacted Ziess to inquire about obtaining this part from them (I was hoping they might have "new old stock", but no luck). They said they do not have part 445265-0000-000 (discontinued).

Kind of too busy with work right now *(up until mid may), but I definitly plan to take very accurate measurements with a caliper (with vernier) once I can find a bit of time to take my phase condenser appart.
No jokes, I've been gradually upgrading my skop for 2 years now, and I'm not ready to stop (and I really want to profit being able to use my 1,25x Plan-NEOFLUAR I just bought used for almost a grand).
I need to get the lens diameter right so we can at least get some reference measurment to extrapolate all other measurements from the patent diagram (extrapolate R1, R2 an lens thickness).
Might be off by a bit, but i think it should work. Heck I've even considered braking and polishing a small tall beer glass because the bottom of the glass has a concave surface.
THORLAB also makes lenses negative mesiscus lense, but I was only able to find one with -100mm focal lenght on their website and a bit too wide a diameter (25mm).

One we get the measurements, who do you think could custom make such a lense ?

I'm also wondering, MichelG do you also own a Zeiss Axioskop ? In any case, thank you for all the precious insights and drawings.

I'll get back to you in 2 weeks (or before if I can... with this crazy busy work surge I got right now) with some new measurements and pictures.
I really hope we can solve this and come up with a lense.
I told Zeiss there is absolutely no way I can give up on such a beautifull instrument, I love my axioskop too much, and love the Zeiss Plan-APOCHROMATS !

Matador

MichaelG.
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Re: Making a negative meniscus lense ?

#16 Post by MichaelG. » Thu May 06, 2021 7:46 am

Thanks for the response, Matador

No, I regret that I do not have an Axioskop myself ... so this is just an interesting academic exercise for me.

Frankly; it is outrageous to even try scaling a lens from a mere sketch in a patent; but I would love to see how close we can get. ... Given that this is just an ‘expander’ I think we might have a fighting chance of success.

Having confirmed, to my satisfaction, that the two surfaces are not aspherical:
When we know the curves, it looks like you could get this reproduced at your friendly local ‘Optical Lab’
20 Dioptres [my current ‘best guess’] is just within the range of regular prescription spectacles; so the guys that supply the dispensing Opticians should be able to do it.

I’m in no rush ... but I would get great satisfaction from a success !!

MichaelG.
.

Not sure where you are, but this is the sort of firm that I would approach:
https://www.manchesteroptical.com/presc ... unglasses/
... if they couldn’t make the lens themselves; they would know a man who can !
Too many 'projects'

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