Axiomat Objectives

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microb
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Axiomat Objectives

#1 Post by microb » Sun May 22, 2022 7:11 pm

Will the Zeiss M27 44 ## ## objectives work with the Axiomat tube lens? I don't know what corrections are in the optical path of the Axiovert versus the Axiomat.

And what about the 42###-9### ones?

It looks like Axiomats are 46 ## ## model numbers.

Thanks,
Ted
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apochronaut
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Re: Axiomat Objectives

#2 Post by apochronaut » Tue May 24, 2022 2:44 am

Based on the performance of Axiomat objectives when adapted to an Axioscope, they require a telan lens closing in on a 250mm focal length, maybe a little less. I don't know what the reference length of an Axiovert is : the same as an Axioscope; 164.5mm?

microb
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Re: Axiomat Objectives

#3 Post by microb » Thu May 26, 2022 2:35 am

apochronaut wrote:
Tue May 24, 2022 2:44 am
Based on the performance of Axiomat objectives when adapted to an Axioscope, they require a telan lens closing in on a 250mm focal length, maybe a little less. I don't know what the reference length of an Axiovert is : the same as an Axioscope; 164.5mm?
So how do you find that out? I was worried about aberrations. But you are talking about tube length, which I thought wouldn't really matter with infinity.

Scarodactyl
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Re: Axiomat Objectives

#4 Post by Scarodactyl » Thu May 26, 2022 5:26 am

Tube length (independent of corrections) doesn't matter if the difference is small since most objectives can handle being pushed 10% out of spec on magnification at least tolerably. But a difference this big is almost certainly going to cause trouble. Very few objectives can be pushed down that much in magnification and give good results--I guess mitutoyos can but they're really anomalous. You're probably going to get vignetting or see some really bad aberrations around the periphery.

apochronaut
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Re: Axiomat Objectives

#5 Post by apochronaut » Thu May 26, 2022 8:59 am

microb wrote:
Thu May 26, 2022 2:35 am
apochronaut wrote:
Tue May 24, 2022 2:44 am
Based on the performance of Axiomat objectives when adapted to an Axioscope, they require a telan lens closing in on a 250mm focal length, maybe a little less. I don't know what the reference length of an Axiovert is : the same as an Axioscope; 164.5mm?
So how do you find that out? I was worried about aberrations. But you are talking about tube length, which I thought wouldn't really matter with infinity.
The infinity tube length between the objective shoulder and the telan lens is unimportant within reason. Reference length is the focal length between the telan lens and the top of the eyepiece tube, essentially an equivalent type of measurement to that made between the objective shoulder and the top of the eyepiece tube in a finite system. The way to look at it is as though the objective shoulder has been moved to the telan lens and from there on the system is finite.

The infinity tube length or infinity space doesn't matter within reason but the reference length does in terms of magnification for sure. This has been tried before ( not by me) and the difference is apparently about 30-35%. I never heard any reports about any overt aberrations so the different series of Zeiss infinity objectives are likely very close in terms of their level of corrections.
Often, the easiest way to determine what is going on between two telan lens/objective combinations is by comparing eyepieces from two systems, if that is possible.

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

Re: Axiomat Objectives

#6 Post by microb » Sat May 28, 2022 3:43 pm

What I'm trying to understand is that between two objectives that need to pair with telan lenses 164.5mm and 250mm respectively, there appears to be something in the signal between to the objective shoulder and the telan lens that makes this pairing necessary. So somehow in the angle or image diameter of the distributed rays being considered "collimated light" between the objective shoulder and the telan lens, something makes it pair with the focal length 164.5 or 250. If it were perfect collimation, a thin telan lens of any FL could be used. Only the image diameter coming out of the objective would need to be to consider, because the only remaining issue would be a cropping issue for the camera at the image plane. But it's not just cropping. It's a quality of image issue being discussed, even with corrections/aberrations issues being skipped.

Given rays tracing out some sampling of position and angles shooting through an objective (ignoring frequencies, so one color), what aspect makes the objective dependent on a certain telan FL lens for image quality? Is the FL length of the telan lens somehow loosely defined by the position of the backplane of the objective such that the distance from it to the telan lens can have a wide sliding range of tolerance because the image is very collimated at the Fourier plane, but once focused at the telan lens, the quality of the best positioned image sampling plane is very specific and possibly compromised by using the wrong telan FL?

Given how Axiomat's build has a much longer image path in its infinity track than most other microscopes, were the objectives optimized for a telan lens that can reach back further to the objective's fourier plane's position with a sweet spot ranging +/- 50mm let's say?

Then again, if the 250mm telan lens was placed close to the Axiomat objective (10mm let's say) eliminating the Axiomat's long infinity track distance, would the image quality be drastically lowered?

I've not found a satisfying referenced article or image showing the ray tracing to explain this. I was hoping I didn't have to ray trace it myself to figure out an intuitive reason for this.

Scarodactyl
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Re: Axiomat Objectives

#7 Post by Scarodactyl » Sat May 28, 2022 8:25 pm

microb wrote:
Sat May 28, 2022 3:43 pm
there appears to be something in the signal between to the objective shoulder and the telan lens that makes this pairing necessary.
You're overthinking it. Two paired lenses like this (the front lens producing infinity focused light, the back lens accepting infinity focused light) give a magnification that is the ratio of their focal lengths. The shorter the front focal length and the longer the back focal length the greater the magnification. So if you design a '4x' objective for a 250mm focal length tube lens, your objective will have a focal length of 62.5mm. With a 250mm focal length back it will project its well corrected field across a reasonable field number, say 22mm. But let's say you have a 164mm tube lens instead. Suddenly it is only magnifying 2.6x! That 22mm field is now scrunched down to only 14mm(!) And what's outside? Nothing the objective designers meant for you to see. Maybe they overshot in their design and the extra field is also well corrected(it can happen--mitutoyo objectives nominally correct to 30mm but can cover full frame corners well). But maybe they were very precise and image quality is terrible out there, sudden bad CA, distortion, or even plain old vignetting. This is a typical outcome--I have a Nikon 50x/0.95 planapo which is very well corrected within its 25mm fn, but which has noticeable lateral CA immediately outside it on aps-c corners.

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