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Homemade Stereo Microscope

 
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benjamind2014



Joined: 18 Oct 2014
Posts: 214

PostPosted: Sat Mar 03, 2018 2:54 pm    Post subject: Homemade Stereo Microscope Reply with quote

https://www.flickr.com/photos/26262745@N08/sets/72157631847374417/

Seems to have a very cool idea of attaching a flat closeup lens cap in front of the binocular objectives to give 8x (or higher depending on the binocular magnification, typically 8 to 25x).

This is supposed to function as a "stereo microscope" that one can use to view flowers, insects, stones, etc.

Does anyone else here have any knowledge of this? Might pick up a pair of halfway decent 10x binoculars and flat closeup lens cap and see how this works, but I wanted a second opinion on whether or not this is worth it. Seems like an easy job but I'm just not sure whether this would actually work, what sort of artefacts I'd expect to see and of course the overall image quality.
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Ichthyophthirius



Joined: 07 Mar 2013
Posts: 800

PostPosted: Sat Mar 03, 2018 3:47 pm    Post subject: Reply with quote

Hi,

No personal experience with this but this has been around as a concept at least since the 1930s.

Zeiss marketed closeup lenses for binoculars ("Fernrohrlupe") although they were for monocular use(?). http://forum.astronomie.de/phpapps/ubbthreads/ubbthreads.php/topics/1139433/Das_Fernglas_als_Lupe

Further down in the thread (section 5) there is a special Zeiss stand for binocular use.

Regards, Ichty
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rjlittlefield
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Joined: 01 Aug 2006
Posts: 19177
Location: Richland, Washington State, USA

PostPosted: Sat Mar 03, 2018 3:48 pm    Post subject: Reply with quote

Yes, this is worth a shot.

What he's describing is a DIY stereo microscope using what's called the Common Main Objective (CMO) design approach. See Figure 4 at https://www.microscopyu.com/techniques/stereomicroscopy/introduction-to-stereomicroscopy .

This will work more or less well depending on the quality of the closeup lens and whether the closeup lens is wide enough for both sides of the binocular to get a clear view through it at the same time.

I just now ran a couple of quick tests with Pentax Papilio binoculars (focused at infinity), using Sigma Life Size Adapter and Raynox DCR-150 as closeup lenses. Neither of those lenses is wide enough to give a full clear view to both sides of the binocular. The result was a form of vignetting that degraded the image quality everywhere and limited the stereo effect to the center of the field. Nonetheless the combo worked better than I expected, though certainly not with either the comfort or the image quality of my Bausch & Lomb stereo microscope.

Note especially that the binoculars he's using have a quite narrow spacing between the two front lenses. This approach is not viable with many compact binoculars that have wider and/or variable spacing between the front lenses.

--Rik
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rjlittlefield
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Joined: 01 Aug 2006
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Location: Richland, Washington State, USA

PostPosted: Sat Mar 03, 2018 3:53 pm    Post subject: Reply with quote

Ichthyophthirius wrote:
Zeiss marketed closeup lenses for binoculars ("Fernrohrlupe") although they were for monocular use(?). http://forum.astronomie.de/phpapps/ubbthreads/ubbthreads.php/topics/1139433/Das_Fernglas_als_Lupe

Yes, and with that design it's important that only one half of the binoculars gets used. If you buy two closeup lenses and put one on either half, then each eye ends up seeing a magnified view of a small field, but the left and right fields are several inches apart, each in front of its own half of the binocular.

The special Zeiss stand shown later in the thread will have mirrors or prisms to correct that problem, so that both sides see the same field.

In the case of the CMO design, both sides of the binocular see the same field because of the closeup lens. The single closeup lens allows the system to focus closer, but equally important, it realigns the light bundles so that the bundles on left and right sides are parallel as they enter the binoculars, even though at the subject they fan out from a single point.

--Rik
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Ichthyophthirius



Joined: 07 Mar 2013
Posts: 800

PostPosted: Sat Mar 03, 2018 4:23 pm    Post subject: Reply with quote

rjlittlefield wrote:
The special Zeiss stand shown later in the thread will have mirrors or prisms to correct that problem, so that both sides see the same field.


That's correct. I've found the correct name. It's called "Mikroskop-Basis Stereo" https://www.invaluable.com/auction-lot/zeiss-mikroskop-basis-stereo-condition-ba-666-c-e4uy5fng9x

CMO stereomicroscopes are supposedly very demanding on the design of the main objective (as there is an angle); I'm wondering if a single lens can actually produce a decent image?
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rjlittlefield
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Joined: 01 Aug 2006
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Location: Richland, Washington State, USA

PostPosted: Sat Mar 03, 2018 5:11 pm    Post subject: Reply with quote

Ichthyophthirius wrote:
I'm wondering if a single lens can actually produce a decent image?

I suppose it depends on the criteria for "decent". Comparing Greenough and CMO, it is simpler and cheaper to get the same image quality with Greenough because all the lenses are small and centered. CMO requires looking through only the edge regions of the main objective, giving up the center where high quality is easier to achieve.

I notice that the author at Flickr writes that
Quote:
This not only works, it works substantially better than a stereo microscope of conventional optical design. Its greatest advantage, in addition to low cost and portability, is an extremely long working distance.

Assuming that his "works substantially better" is an honest judgement, I gather that he values long working distance, low cost, and portability more highly than image quality. Either that, or he's used to quite low quality stereo microscopes "of conventional optical design".

But still, if you're looking for a low cost and highly portable scope with usable image quality, and you're either lucky or diligent about finding appropriate binoculars and closeup lens, then I think the CMO DIY approach would definitely be worth a shot.

--Rik
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