Shortest 400x microscope/magnifier?

[Beatsy]

What's the shortest 400x "microscope" you could construct from off-the-shelf optical parts without using mirrors to fold the light path (i.e. just one straight tube - as narrow as is possible and practical)? For transmitted (brightfield) illumination at N.A. 0.65 or better. Sub-millimetre working distance fine.

Thanks.

[Chris S.]

Steve, does 400x refer to viewing through an eyepiece, or projection on sensor? If the latter, what size sensor?

--Chris S.

[Beatsy]

Eyepiece. For visual use only, but a "comfortable" field of view as per a normal scope.

[Chris S.]

Thanks for the additional detail.

One more question: No cover glass?

--Chris S.

[Beatsy]

With cover glass. For quick but detailed survey of wet mounts in the field, but with emphasis on very small size and weight. Likely using a "proper" objective (perhaps).

Edit: actually, it just occurred to me that a collapsible tube (like the old fashioned telescopes) using a normal objective and eyepiece could fit the bill.

But a fixed piece of tube would be more robust, so still interested if "shortened optics" are possible.

[Beatsy]

Further to my previous comments, someone on a FB micro group posted links to vintage "minor field microscopes" on Ebay. While I don't think these have the magnification I want, they are certainly the right size and form. So there may be a solution there - more searching required.

https://www.ebay.com/itm/vintage-Leitz-Wetslar-1920s-minor-field-folding-microscope-w-leather-case/312049286241

https://www.ebay.com/itm/Antique-Hensoldt-Wetzlar-Model-DRP-A-Pocket-Field-Expedition-Microscope-Good/253380268577

[ChrisR]

I assume you know of these:
http://www.brunelmicroscopes.co.uk/handheld.html
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Chris R

[Beatsy]

[zzffnn]

Regular optics, NA 0.65 (which demands a condenser) and no folding light path:

the smallest / lightest you can easily buy is Tiyoda MKH.
It is about 3lbs without case.

If you allow folding light path and mini objectives, then the Chinese army TWX-1 is supposed to be the best. It can get to real NA 1.25. There are also Nikon H, McArthur, Swift and clones. Some have no condenser and won't get to NA 0.65. They usually don't operate that comfortably, compared to the Tiyoda though.

You cannot shrink the size or weight that much, when you demand NA 0.65. That in turns demands decent fine focus gear and condenser, which add significant bulk and weight.

Edit: there are scopes lighter and slightly smaller than your Swfit, but they don't go much over NA 0.25 and use mini objectives and folded light path.

Edit 2: Beatsy, if you manage to make /find something else, please let me know. I thought of making a DIY Frankenstein scope, but it would end up at around 4lbs fully loaded and no smaller than the Tiyoda.

[ChrisR]

What's the longest lens you carry? Screw an infinite on and use expanded LV!
Perhaps you could make a slide holder which clips onto an objective.
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Chris R

[Ichthyophthirius]

[zzffnn]

[Ichthyophthirius]

[Beatsy]

Yes - I have (inadvertently) over egged the required N.A. I could definitely compromise on that.

Also, I should add that I have a Swift FM-31 which is great, I'm very pleased with the image quality and will happily take it out if I want to do any extended viewing "in the field". I was just looking for a smaller option for the times I'm hiking or cycling with a primarily photographic intent (non micro), but might get opportunity for some sample-taking too.

Thanks to feedback here and elsewhere, it appears I got a little too deep into the "make something" mode before looking at all available options. Something like a Hensoldt Protami or similar might just do the job - if I am patient enough to wait for one to turn up.

I'm finding the thread very interesting all the same. Thanks for the responses everyone.

[Pau]

Do you carry small binoculars when hiking?
Inspired in a device made by Zeiss that converts binoculars in a stereomicroscope I quickly tested the idea hand holding a 10X infinite corrected objective just on the front lens of one of the binoculars light paths. It seems to work pretty well at the center, the image borders are not good but could be useful for your application making some custom designed adapters and a focusing device.

Likely it would not work well at 40X but could be at 20X.

To avoid condensers I have two ideas: A LED illuminating a diffuser placed just under the slide (again a Zeiss invention, the Lucigen "condenser") or a LED illuminating the slide laterally to get darkfield

Just quick suggestions needing to be proven
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Pau