Beyond 50x NA 0.55 (Mitty). What next?
Moderators: rjlittlefield, ChrisR, Chris S., Pau
Beyond 50x NA 0.55 (Mitty). What next?
I really like the working distance and image quality my 50x Mitty delivers, but now I have most of the vibration issues ironed out, I find myself craving even more resolution (mainly for diatom-related imaging). The attached two images show the typical "best" resolution I'm getting these days (FF image at 50x and a closer crop to show the smallest details resolved - just). It's good, but not always good enough any more.
I'm actively looking for a solution now and want an objective that will take resolution (and probably, but not necessarily, magnification) to the next level - whatever that may usefully be. Working distance as small as (say) 15mm is bearable - but I realise I'll probably have to tolerate less - insofar as it's still practical and feasible to use in a macro context. I'd rather have infinity corrected so I don't have to change too much when swapping lenses. I use a 42 megapixel sensor with 4.5 micron pixels for image capture.
Ideas and recommendations would be greatly appreciated - with approx costs if possible. Thanks.
Note: I know I may need to change my rail, or even make a another microscope-based setup to accommodate shallower DoF with a smaller step size (currently just a smidge under 1 micron with WeMacro). I'll tackle that separately.
I'm actively looking for a solution now and want an objective that will take resolution (and probably, but not necessarily, magnification) to the next level - whatever that may usefully be. Working distance as small as (say) 15mm is bearable - but I realise I'll probably have to tolerate less - insofar as it's still practical and feasible to use in a macro context. I'd rather have infinity corrected so I don't have to change too much when swapping lenses. I use a 42 megapixel sensor with 4.5 micron pixels for image capture.
Ideas and recommendations would be greatly appreciated - with approx costs if possible. Thanks.
Note: I know I may need to change my rail, or even make a another microscope-based setup to accommodate shallower DoF with a smaller step size (currently just a smidge under 1 micron with WeMacro). I'll tackle that separately.
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6.0mm WD, NA0.7 (the obvious)
https://www.ebay.com/itm/Mitutoyo-M-Pla ... 2358143184
3.4mm WD, NA0.8 (the contender)
https://www.edmundoptics.com/p/olympus- ... ive/30481/
There are those annoying physical limits of high NA and the possibility for not-so-oblique lighting...
Best regards,
Michael
https://www.ebay.com/itm/Mitutoyo-M-Pla ... 2358143184
3.4mm WD, NA0.8 (the contender)
https://www.edmundoptics.com/p/olympus- ... ive/30481/
There are those annoying physical limits of high NA and the possibility for not-so-oblique lighting...
Best regards,
Michael
- enricosavazzi
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I prefer to take a different approach in my answer, than listing a few choices of objectives. I also don't know if you are already using compound microscopes. If you do, much of the following will be obvious.
At 50x, you are probably already working at the limits of what you can reasonably expect from industrial slides and micrometric screws. Assuming that the next step will be 100x, my suggestion would be to strongly consider switching to a compound microscope stand. However, using Mitutoyo M Plan Apos on a Zeiss, Leitz etc. ordinary cheap microscope stand is unfortunately impossible without serious modifications.
For use with Mitutoyo M Plan Apos you may instead look for an industrial microscope stand like the Mitutoyo FS60 and FS70 series. They are not very common on eBay and somewhat expensive, but they do pop up now and then, and require no modification unless you want to get transmitted illumination. See http://savazzi.net/photography/mitutoyo_fs-60.htm
A measuring microscope stand may also work, as long as it is equipped (or can be modified without too much fuss) with coarse + fine focus. Working at 100x requires a good alignment and tight tolerances, however, so DIY solutions that work well at lower magnifications may not be precise enough at 100x. My preference would go to a ready-to-use stand.
You will need fine focusing on the order of (preferably) 100 microns per turn of the fine focus knob, or (at a minimum) 200 microns per turn. There are good reasons why virtually all compound microscopes use these focusing racks.
Since you already have a 50x Mitutoyo, keep in mind that using it on a microscope stand will be much easier and more enjoyable than on a micrometric rail. If you have other Mitutoyo M Plan Apos, then a Mitutoyo scope will make working with them a real pleasure. It would also make a Mitutoyo M Plan Apo 100 your next logical choice.
PS - keep in mind that the Mitutoyo M Plan Apo SL series has higher working distance and lower NA than the "ordinary" M Plan Apo series. The impact of the NA difference becomes more significant at higher magnification. Also, if you mix SL and non-SL objectives on the same scope they might not be parfocal (I am not completely sure about this).
At 50x, you are probably already working at the limits of what you can reasonably expect from industrial slides and micrometric screws. Assuming that the next step will be 100x, my suggestion would be to strongly consider switching to a compound microscope stand. However, using Mitutoyo M Plan Apos on a Zeiss, Leitz etc. ordinary cheap microscope stand is unfortunately impossible without serious modifications.
For use with Mitutoyo M Plan Apos you may instead look for an industrial microscope stand like the Mitutoyo FS60 and FS70 series. They are not very common on eBay and somewhat expensive, but they do pop up now and then, and require no modification unless you want to get transmitted illumination. See http://savazzi.net/photography/mitutoyo_fs-60.htm
A measuring microscope stand may also work, as long as it is equipped (or can be modified without too much fuss) with coarse + fine focus. Working at 100x requires a good alignment and tight tolerances, however, so DIY solutions that work well at lower magnifications may not be precise enough at 100x. My preference would go to a ready-to-use stand.
You will need fine focusing on the order of (preferably) 100 microns per turn of the fine focus knob, or (at a minimum) 200 microns per turn. There are good reasons why virtually all compound microscopes use these focusing racks.
Since you already have a 50x Mitutoyo, keep in mind that using it on a microscope stand will be much easier and more enjoyable than on a micrometric rail. If you have other Mitutoyo M Plan Apos, then a Mitutoyo scope will make working with them a real pleasure. It would also make a Mitutoyo M Plan Apo 100 your next logical choice.
PS - keep in mind that the Mitutoyo M Plan Apo SL series has higher working distance and lower NA than the "ordinary" M Plan Apo series. The impact of the NA difference becomes more significant at higher magnification. Also, if you mix SL and non-SL objectives on the same scope they might not be parfocal (I am not completely sure about this).
--ES
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Thanks guys. As I noted at the end of my post, I suspected a dedicated microscope stand (dedicated only to the higher mag/NA objective) might be needed. But something that fit my existing rig would be more convenient - so I kept it in the mix. Looks like that's not a sensible goal after all.
I have a full set of Zeiss EPI objectives, but the working distances are sub-millimeter at the high end, and they only fit my ICM 405, which is inverted. That and the need for correcting eyepieces makes them unsuitable.
I do have an old, but good, Wild M20 that's doing nothing. Happy to remove the optics from that if necessary and use the stand, stage and focus mech (with stepper attached to the fine focus knob). My main concern is to be able to get incident lighting onto the specimen for "macro like" outcomes. And more resolution of course.
I have a full set of Zeiss EPI objectives, but the working distances are sub-millimeter at the high end, and they only fit my ICM 405, which is inverted. That and the need for correcting eyepieces makes them unsuitable.
I do have an old, but good, Wild M20 that's doing nothing. Happy to remove the optics from that if necessary and use the stand, stage and focus mech (with stepper attached to the fine focus knob). My main concern is to be able to get incident lighting onto the specimen for "macro like" outcomes. And more resolution of course.
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Concerning macro-lighting and high NAs, I often thought about custom modding of objective tips to achieve a better usable light angle. Having a very thin fixture around the lens, conically opening up would be the best thing. Theoretically, with only the lens defining the objective's tip width, a light angle of ~45° should still be possible with NA0.8. Let's dremel our mitties!
I really dig the applet here to visualize it directly:
https://www.microscopyu.com/microscopy- ... l-aperture
Best regards,
Michael
I really dig the applet here to visualize it directly:
https://www.microscopyu.com/microscopy- ... l-aperture
Best regards,
Michael
Because NA is about the angle of light, large NA with good WD means a big frontal lens...and it also limits the external illumination angle for the very same reason.
For small subjects like diatoms an adequate approach could be to use BD objectives with DF epi illumination, maybe masking partially the illuminating ring to have more control of light. BD objectives are designed for this kind of work.
I have a nice Nikon MPlan Apo 40/0.80 and the only use I have for it is epifluorescence with uncovered specimens just because its small WD.
For small subjects like diatoms an adequate approach could be to use BD objectives with DF epi illumination, maybe masking partially the illuminating ring to have more control of light. BD objectives are designed for this kind of work.
I have a nice Nikon MPlan Apo 40/0.80 and the only use I have for it is epifluorescence with uncovered specimens just because its small WD.
Pau
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This is a great writeup--I hadn't read it before, but had seen some of your previous mentions of the fs60/70 while looking for upright image microscope heads. I have been scope creeping them on eBay, and found a few being sold as fs50s, and was wondering if they are of a similar caliber. Googlin' didn't reveal much either.enricosavazzi wrote: For use with Mitutoyo M Plan Apos you may instead look for an industrial microscope stand like the Mitutoyo FS60 and FS70 series. They are not very common on eBay and somewhat expensive, but they do pop up now and then, and require no modification unless you want to get transmitted illumination. See http://savazzi.net/photography/mitutoyo_fs-60.htm
- enricosavazzi
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There is a thread about the FS50: http://www.photomacrography.net/forum/v ... p?p=158889Scarodactyl wrote:This is a great writeup--I hadn't read it before, but had seen some of your previous mentions of the fs60/70 while looking for upright image microscope heads. I have been scope creeping them on eBay, and found a few being sold as fs50s, and was wondering if they are of a similar caliber. Googlin' didn't reveal much either.enricosavazzi wrote: For use with Mitutoyo M Plan Apos you may instead look for an industrial microscope stand like the Mitutoyo FS60 and FS70 series. They are not very common on eBay and somewhat expensive, but they do pop up now and then, and require no modification unless you want to get transmitted illumination. See http://savazzi.net/photography/mitutoyo_fs-60.htm
Personally I have never touched one, but judging from this thread it is pretty much like an FS60 without coaxial illumination. The scope body does not contain much more than a tube lens and beam splitter, so it should not be significantly different. The FS70 usually has slots for inserting additional optics into the optical path.
--ES
Seems to be quite a few FS50s available in the USA. This one for instance https://www.ebay.com/itm/163176265327
If the included Mitties (5,10,20 and 50x) are in good working order, 2800 bucks seems pretty good to me (not too far off the new cost of the 50x alone).
Anyway - I don't need 'em (have a set already), and there's an obvious risk one or more aren't up to scratch - so an international buy would be far too risky.
If the included Mitties (5,10,20 and 50x) are in good working order, 2800 bucks seems pretty good to me (not too far off the new cost of the 50x alone).
Anyway - I don't need 'em (have a set already), and there's an obvious risk one or more aren't up to scratch - so an international buy would be far too risky.
Thanks Mike, I briefly considered the 100x Mitty, but an increase in resolution from 0.5 to 0.4 microns hardly seems worth the cost. But perhaps a 20% improvement is better in practice that it sounds. Dunno.sushidelic wrote:6.0mm WD, NA0.7 (the obvious)
https://www.ebay.com/itm/Mitutoyo-M-Pla ... 2358143184
3.4mm WD, NA0.8 (the contender)
https://www.edmundoptics.com/p/olympus- ... ive/30481/
The contender is closer at a bit under 0.35 microns (ish) - but $6300!! Ouch.
Michael, you mean like this ?sushidelic wrote:Concerning macro-lighting and high NAs, I often thought about custom modding of objective tips to achieve a better usable light angle. Having a very thin fixture around the lens, conically opening up would be the best thing. Theoretically, with only the lens defining the objective's tip width, a light angle of ~45° should still be possible with NA0.8. Let's dremel our mitties!...
http://www.photomacrography.net/forum/v ... 463#235463
Saul
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Yes, I looked at that one but discounted it initially because of the comparatively short WD (5.2mm). But having spent quite some time looking at other options, I have to accept it's an unavoidable limitation at this end of the scale. What I do like is that NA0.75 is a smidge better than the 100x Mitty at NA0.7 and will resolve 0.3 microns with half as much "empty magnification". That's good!abednego1995 wrote:The Mitty MPA 50x HR is amazing...
Makes it top of the candidate list (of one) at the moment. But I fear a 5mm gap to get light in will preclude achieving the "macro lighting" I also want. (NB: Is there a proper name for that? EPI illumination doesn't quite describe it). That's a 100% non-negotiable requirement and if it's completely infeasible then it's not for me. I'll give it up and make do with the microscope-based EPI options I already have. Any comments on that aspect?
- enricosavazzi
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There may be another possibility. The FS60 and FS70 are equipped with a beam splitter for axial illumination (through the objective, not a sleeve around the objective). I have the required halogen fiber source and the proper Mitutoyo fiberoptic light guide and tried them at low magnification, but did not use this illumination afterwards because it gives an extremely "flat", "rabbit-in-the-headlights" type of illumination.Beatsy wrote:[...] But I fear a 5mm gap to get light in will preclude achieving the "macro lighting" I also want. [...] That's a 100% non-negotiable requirement and if it's completely infeasible then it's not for me. I'll give it up and make do with the microscope-based EPI options I already have. Any comments on that aspect?
However, higher-NA objectives have a wider entrance cone of light, which means a wider angle of illumination striking the subject through the lens. What about masking part of the illumination field before it strikes the illumination beamsplitter and enters the rear of the objective, so that most of the light comes from one side instead of dead head-on? It would be like COL (Circular Oblique Lighting) but from the objective side.
Probably it will be necessary to experiment with different positions of the central diaphragm along the illumination path, as there may be an optimal distance from the objective. It may also be necessary to widen the illumination angle inside the microscope body with a diffusor or (de)collimator, so that the entire field of view of the objective is used for illumination(as opposed to its central part only).
Some experimenting could be done with a simple LED illuminator (e.g. a single 5 mm LED) at the rear of the objective projecting the light onto a white paper (or a 3D test subject) at the normal WD in front of the objective.
A limitation is that this illumination cannot be any more oblique than the cone of light entering the front element of the objective, but together with some conventional incident lighting from outside the objective it might be enough, because the cone of light is pretty wide with NA around 0.7. The illumination cone is not wide enough to work well with the lower-NA objectives like the 10x.
If it works well enough with high-NA objectives, this could mean we have a new use for many of the objectives with short working distance that today just sit unused in our drawers or are only used with transmitted light microscopes.
See http://www.microscopy-uk.org.uk/mag/ind ... pjcol.html for transmitted COL.
--ES