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Found the flattest ever eyepieces - price to match!

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#1 patta

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Posted 02 December 2020 - 09:04 AM

Hello, this post is about eyepieces and microscopes...

but NOT about using microscope eyepieces for astronomy!   

And it's not serious. lol.gif   Well, flatter, it is true.

 

I've realized that eyepieces and microscope objectives have almost the same design! 

In fact, they do a very similar job; only aperture and image get swapped: the exit pupil of the eyepiece is the observation area of the microscope objective.

The "eye relief" is the working distance, and the angle of view corresponds to the objective NA.

I tried a couple of microscope objectives, and it works. Sharp? I don't know, needs more testing. Wide? not much, the widest I manage to look through had 50 degrees. There are wider, but with very short working distance (eye relief).

 

For those with unlimited money and craving for the ultimate eyepiece, that may be a new good drain flowerred.gif :  there is plenty of those "long working distance" objectives, rigorously Apo and flat to less than one micron.  Prices starting at 2000$.

Below the scheme of an eyepiece and a microscope objective, so to convince you.

eyepiece microscope objective.jpg

Images copied from: Eyepiece    Microscope objective


Edited by patta, 02 December 2020 - 09:16 AM.

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#2 25585

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Posted 02 December 2020 - 09:29 AM

Is that the 12.5mm APM 84°? 



#3 patta

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Posted 02 December 2020 - 09:31 AM

Is that the 12.5mm APM 84°? 

you're right! as reverse- engineered by Vladimir Sacek

but I picked this model randomly, just as example, to show the similarity with the microscope objective.  I don't actually have it.


Edited by patta, 02 December 2020 - 10:01 AM.

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#4 Jon Isaacs

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Posted 02 December 2020 - 09:36 AM

How does it work at F/4?

 

A flat field is not normally the issue with telescope eyepieces, off-axis astigmatism is normally the largest aberration.

 

Microscopes do not have the the steep light cone angles of a telescope, the steep light cone is what causes the astigmastim.  

 

Jon


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#5 25585

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Posted 02 December 2020 - 09:38 AM

Thanks. The APM Ultra Flat Field is a smaller AFOV range, whike their 84° is so far a one-off (an 18mm was promised at one time), as the late lamented Docter was.

 

But its interesting to compare similarities between the 84° eyepiece and UFF designs. 

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Edited by 25585, 02 December 2020 - 09:40 AM.


#6 patta

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Posted 02 December 2020 - 09:48 AM

How does it work at F/4?

 

A flat field is not normally the issue with telescope eyepieces, off-axis astigmatism is normally the largest aberration.

 

Microscopes do not have the the steep light cone angles of a telescope, the steep light cone is what causes the astigmastim.  

 

Jon

Well, all truth said, on my f/10 scope the (only actually usable) microscope objective I tried, a 50x NA 0,45, translated as 4mm, 50° FOV eyepiece, was already well foggy at the borders. Don't expect wonder improvements at f/4.

I was expecting better, since in fact, the microscope objectives with high NA do have a steep light cone; look at the image, the light cone (coming from left) is very wide for both. NA 0,45 is about 50 deg FOV.  High-power objectives have NA up to 0.95, meaning 170 deg FOV!  But are unusable, literally 0,2 mm eye relief.

 

I tried microscope objectives the other way around, as wide-angle photographic lenses and - as you said - Astigmatism! tons of it.


Edited by patta, 02 December 2020 - 02:43 PM.


#7 TOMDEY

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Posted 02 December 2020 - 10:34 AM

Your similarity observation is really cool!

 

Microscope objectives are (of course) optimized for diffraction-limited resolution, over the entire (small, flat) field. That field is in the neighborhood of 10mm/mag. e.g. a 10x microscope objective has a field size about 1mm across. And it's that little object-space field where your analogy places the exit pupil of the ~similarity eyepiece~. So, trying/using a microscope objective as an eyepiece... it will have a perfectly-corrected exit pupil there. The quality or the imagery (seen through that perfect pupil / using it as an eyepiece) will probably be hit/miss because the optimizations are so profoundly different.

 

I worked at B&L back in the good old days (1967-80). At their peak, B&L employed an entire department of optical designers, some spending their entire careers designing only microscope objectives!

 

It was common for the scientists and engineers to occasionally grab a microscope objective and use it as a loupe. I used one like that, in that way, as a loupe/eyepiece, to examine/focus the image of a star coming in from my F/1.65 Super Schmidt Camera. It was spectacular for that unusual use, otherwise I couldn't get in close enough, and the cone was too fast. I always kept that lens right with the camera, as the dedicated eyepiece!    Tom

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#8 patta

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Posted 02 December 2020 - 02:37 PM

Thanks for the appreciation!

Nice, I didn't think about the pupil size... we may solve this issue with a slower OTA? F/20 should match the pupil size...tongue2.gif

Yes, imagery quality, the eyepiece will be optimized to have its rays (at the exit pupil) parallel, while the microscope, the rays must converge precisely at the subject - but they don't need to be exactly parallel. That kills my dreams of uber-eyepiece.

 

The objective/eyepiece I've used, 50x 0.45, the only one I have with enough eye relief - it is one of the last made by B&L!  Actually branded Leica-Made in USA, for the B&L Microzoom. Used as it should, on a microscope, it works great. I've disassembled it for cleaning, and it was made with exceedingly high precision and tight fittings; never seen such quality in eyepieces (well, I never wrecked a good eyepiece actually, only cheap ones smirk.gif ).

 

I never thought to use a microscope objective as loupe- I'll try. I have tried to use eyepieces as loupe, screwing out the barrel. But it is difficult to keep them at the right distance.


Edited by patta, 02 December 2020 - 02:54 PM.


#9 MitchAlsup

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Posted 02 December 2020 - 04:30 PM

How does it work at F/4?

Probably pretty well--the lens arrangement is operating faster than F/1.0 as a microscope objective !!


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#10 TOMDEY

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Posted 02 December 2020 - 06:36 PM

Thanks for the appreciation!

Nice, I didn't think about the pupil size... we may solve this issue with a slower OTA? F/20 should match the pupil size...tongue2.gif

Yes, imagery quality, the eyepiece will be optimized to have its rays (at the exit pupil) parallel, while the microscope, the rays must converge precisely at the subject - but they don't need to be exactly parallel. That kills my dreams of uber-eyepiece.

 

The objective/eyepiece I've used, 50x 0.45, the only one I have with enough eye relief - it is one of the last made by B&L!  Actually branded Leica-Made in USA, for the B&L Microzoom. Used as it should, on a microscope, it works great. I've disassembled it for cleaning, and it was made with exceedingly high precision and tight fittings; never seen such quality in eyepieces (well, I never wrecked a good eyepiece actually, only cheap ones smirk.gif ).

 

I never thought to use a microscope objective as loupe- I'll try. I have tried to use eyepieces as loupe, screwing out the barrel. But it is difficult to keep them at the right distance.

Hi, patta!

 

And probably no coincidence that microscope objectives provide a relatively uniform ~F/18-ish feed to the microscope eyepiece!

 

I'm still excited over what you noticed and presented in your topic here. For any imaging system, object and image conjugates cascade through, from physical object to final image, which is then examined with a sensor array or an eyepiece/eye combo. And that same system simultaneously cascades pupil conjugates, from entrance pupil to exit pupil. All of that happening simultaneously, of course, "percolating in the background". An extreme example is complex periscopes, where all the functions are relayed, often several times, to thread the whole package into a skinny tube (e.g. a submarine periscope).

 

That duality, comprising all optical imaging systems... object/image/pupils/stops. And that's an "advanced topic" covered only later, in detail, in the geometrical optics books and courses. Even among my professional associates... some guys seem to have never fully internalized the duality.

 

It can be as arcane and philosophically challenging as the "wave-particle duality" of field/particle physics. And the gestalt is the realization that both are operative... together... simultaneously... happily opposite conjugate sets.

 

Also no coincidence that those object/pupil anti-conjugate pairs cascade through the imaging system, obeying all the way... the Lagrange Invariant, solid angle area product. Which is the étendue, driven by QM and Emmy Noether's Theorem.

 

So, it all expresses the same insight from the physics of light, not only how light behaves... but how it must behave. Which was/is Emmy's insight. Gestalt!

 

It all ties together, neatly... as it must.    Tom

 

Etendue or étendue is a property of light in an optical system, which characterizes how "spread out" the light is in area and angle. It corresponds to the beam parameter product in Gaussian beam optics.

 

ge·stalt
/ɡəˈSHtält/
noun PSYCHOLOGY
an organized whole that is perceived as more than the sum of its parts.

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  • 137 etendue.jpg

Edited by TOMDEY, 03 December 2020 - 04:32 AM.

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#11 patta

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Posted 03 December 2020 - 03:24 AM

Probably pretty well--the lens arrangement is operating faster than F/1.0 as a microscope objective !!

Well, unfortunately no, since we have traded aperture for a wide view.. as Tomdey wrote, microscope objectives would match a meagre f/18 scope; and consensus says that we don't need much complex eyepieces at such aperture!

The F/1.0 would hold if we use the microscope objective in the other orientation, like, flip the eyepiece and look from the back - but there we'll have a very narrow FOV (and the exit pupil is hidden inside).

This flipping may work with simple, symmetric eyepieces (Plossl) and with their conjugates, the 10x 0.25 microscope objectives.

 

About conjugates, another happening of this principle is.. digital

the Jpeg files are built as the Fourier transform of the image.. that is basically what also the aperture is, in terms of wave optics.

So when we share images as Jpeg, they travel through copper cables in the form of aperture.

More bandwidth, more aperture!

 

By the way, our brain itself work with waves - so may be the case that we perceive images as their Fourier transform? 

("we imagine in Jpeg")


Edited by patta, 03 December 2020 - 03:39 AM.

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#12 Adam Long

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Posted 03 December 2020 - 06:22 AM

Interesting! You had me all ready to oil my eyeball to my Zeiss Neofluar high NA objective for a moment there. Funnily enough when my posterior vitreous detachment started earlier in the year the doctor used an optical gel to oil a circular mirror to pupil so he could examine the edges of my retina. It wasn't uncomfortable to start with...


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#13 j.gardavsky

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Posted 03 December 2020 - 12:36 PM

Well, unfortunately no, since we have traded aperture for a wide view.. as Tomdey wrote, microscope objectives would match a meagre f/18 scope; and consensus says that we don't need much complex eyepieces at such aperture!

The F/1.0 would hold if we use the microscope objective in the other orientation, like, flip the eyepiece and look from the back - but there we'll have a very narrow FOV (and the exit pupil is hidden inside).

This flipping may work with simple, symmetric eyepieces (Plossl) and with their conjugates, the 10x 0.25 microscope objectives.

 

About conjugates, another happening of this principle is.. digital

the Jpeg files are built as the Fourier transform of the image.. that is basically what also the aperture is, in terms of wave optics.

So when we share images as Jpeg, they travel through copper cables in the form of aperture.

More bandwidth, more aperture!

 

By the way, our brain itself work with waves - so may be the case that we perceive images as their Fourier transform? 

("we imagine in Jpeg")

Very good ideas, Patta!

 

There are a few spatial frequency filters in the human visual perception, with the job to increase the visibilty of the finest details. And these filters employ the Fourier transformations, like the spectral power density on the visual signals.

 

Best,

JG
 


Edited by j.gardavsky, 03 December 2020 - 12:38 PM.

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#14 Thomas_M44

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Posted 03 December 2020 - 04:25 PM

Personally,  I'm not presently interested in purchasing any more wide-field eyepieces until and unless some reputable optical manufacturing concern makes arrangement to start commercially producing Donald Dilworth's remarkable 8-element 90-degree AFOV design which has apparently sat unused since it's 1988 inception.

 

The man is an optical wizard:  http://www.dilworthoptics.com/

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Edited by Thomas_M44, 03 December 2020 - 04:32 PM.

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#15 j.gardavsky

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Posted 04 December 2020 - 07:32 AM

Hello all,

 

here are some Leitz microscope planar (Pl) objectives with the Leitz proprietary fluoride glass materials (Fl),

 

Leitz Fl and APO microscope objectives.jpg

 

They work as the magnifying loupes pretty well, actually better than the Zeiss aplanatic loupes.,

And they might be repurposed as high precission apochromatic eyepieces for the flat field telescopes.

The drawback would the very small field, competeing with the small AFOV of the monocentric eyepieces.

 

Best,

JG


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#16 RichA

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Posted 04 December 2020 - 08:52 PM

Your similarity observation is really cool!

 

Microscope objectives are (of course) optimized for diffraction-limited resolution, over the entire (small, flat) field. That field is in the neighborhood of 10mm/mag. e.g. a 10x microscope objective has a field size about 1mm across. And it's that little object-space field where your analogy places the exit pupil of the ~similarity eyepiece~. So, trying/using a microscope objective as an eyepiece... it will have a perfectly-corrected exit pupil there. The quality or the imagery (seen through that perfect pupil / using it as an eyepiece) will probably be hit/miss because the optimizations are so profoundly different.

 

I worked at B&L back in the good old days (1967-80). At their peak, B&L employed an entire department of optical designers, some spending their entire careers designing only microscope objectives!

 

It was common for the scientists and engineers to occasionally grab a microscope objective and use it as a loupe. I used one like that, in that way, as a loupe/eyepiece, to examine/focus the image of a star coming in from my F/1.65 Super Schmidt Camera. It was spectacular for that unusual use, otherwise I couldn't get in close enough, and the cone was too fast. I always kept that lens right with the camera, as the dedicated eyepiece!    Tom

Microscopes are also a nightmare to image though using any kind of large sensor, from m4/3rds to FF.  People used to suggest using them for planetary photograph in telescopes though.


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#17 RichA

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Posted 04 December 2020 - 08:53 PM

Hello all,

 

here are some Leitz microscope planar (Pl) objectives with the Leitz proprietary fluoride glass materials (Fl),

 

attachicon.gifLeitz Fl and APO microscope objectives.jpg

 

They work as the magnifying loupes pretty well, actually better than the Zeiss aplanatic loupes.,

And they might be repurposed as high precission apochromatic eyepieces for the flat field telescopes.

The drawback would the very small field, competeing with the small AFOV of the monocentric eyepieces.

 

Best,

JG

In microscopy, aren't they a step below Plan-apos?



#18 TOMDEY

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Posted 04 December 2020 - 09:45 PM

Microscopes are also a nightmare to image though using any kind of large sensor, from m4/3rds to FF.  People used to suggest using them for planetary photograph in telescopes though.

Yeah, the intended direct image diameter of nearly all traditional microscope objectives, used in the ~usual~ way... is 18mm max diameter. That's one reason the eyepiece tubes are OK being so skinny. I sometimes wonder if that may also relate to why nearly all Night Vision Photocathode Arrays are 18mm across. That's actually generous, by old CCD standards... only recently supplanted by the larger arrays that some of us use today. "Full Frame" sensors are a throw-back to 35mm wide perforated tractor film used in old film SLR cameras... which have an designed image 24mm wide by 36mm long. The history of film imagery is imbedded in most all standards, often in non-obvious ways.

 

There are even standards on railroad tracks, roads, and automobiles that hearken back to horse-powered vehicles... literally horse-driven.   Tom

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#19 TOMDEY

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Posted 04 December 2020 - 09:46 PM

nother pic >>>    Tom

 

~click on~ >>>

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#20 patta

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Posted 05 December 2020 - 03:47 AM

Yeah, the intended direct image diameter of nearly all traditional microscope objectives, used in the ~usual~ way... is 18mm max diameter. That's one reason the eyepiece tubes are OK being so skinny. I sometimes wonder if that may also relate to why nearly all Night Vision Photocathode Arrays are 18mm across. That's actually generous, by old CCD standards... only recently supplanted by the larger arrays that some of us use today. "Full Frame" sensors are a throw-back to 35mm wide perforated tractor film used in old film SLR cameras... which have an designed image 24mm wide by 36mm long. The history of film imagery is imbedded in most all standards, often in non-obvious ways.

 

There are even standards on railroad tracks, roads, and automobiles that hearken back to horse-powered vehicles... literally horse-driven.   Tom

Yes, the railroad track width is defined as two horse-asses.

What about telescope mirrors that are built in standard sizes or 8 or 12 INCHES?


Edited by patta, 05 December 2020 - 03:47 AM.


#21 TOMDEY

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Posted 05 December 2020 - 08:24 AM

Yes, the railroad track width is defined as two horse-asses.

What about telescope mirrors that are built in standard sizes or 8 or 12 INCHES?

Hi, patta!

 

Corning was the 1st to invent and market their wonderful separately-cast and fine-annealed "full-thickness" Pyrex Telescope Mirror Blanks. My recollection  is that their ~standard sizes~ were 3, 4.25, 6, 8, 10, 12.5, and 16 inches. They could, would and did make custom bigger sizes... up to 200-inches, which cost a wee bit more. I personally had all of the smaller sizes, including the 16", turning all into telescopes... cept the 16". But the Syracuse Club had a Cave 16" and my friend Rick built a 16" from the ground up, pushing the glass by hand and using a singlet null lens for Foucault testing. I tested that mirror in my (24") test-tower and it was wonderful! Those were the days when most hobbyists actually made their telescopes entirely from scratch.    Tom

 

I always wondered where the 12.5-inch size came from. That "extra" half inch seemed like some kinda bonus. And then Coulter Optics peculiar signature sizes 13.1. 17.5 and 29 inches. Now, where did those sizes come from!  I know Jim cut them from Corning Pyrex sheet glass slabs, which started out as something like 36x36 inches and were very coarse. I later got Bob Salsman at Glass Fab Inc. in Rochester, NY --- to generate some 14 and 26-inch blanks for me. He suggested those sizes because he could get the most out of the slabs that way.

 

Here's (one of my) old defunct company logos... My trademark alludes to two eyeballs, because I made things for binoculars. I never cleared a profit in small business, but it was fun. Working contracts for the Big Guys was lucrative, so I did a lot of that.    Tom

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#22 j.gardavsky

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Posted 05 December 2020 - 09:54 AM

In microscopy, aren't they a step below Plan-apos?

The Leitz PL APO 6.3/0.20 is Plan APO, planar apochromatic.

 

The quality grades are defined in relation to the depth of focus DoF = λ/(NA)2:

Plan:

Focus position at the field edge deviates from the axial focus position within 2.5×DoF .

APO:

Longitudinal chromatic aberration is corrected within 1xDoF. In microscopy, this CA is corrected from 430nm up to 644nm, this means in a wider spectral range than the 486nm up to 656nm.

 

(This definition does not address the spherochromatism)

 

A similar concept based on the DoF has been used by Zeiss for the astronomy telescopes.

 

Best,

JG


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