Mantis Microscope Repair/Teardown

[nikonoid]

Success at last:

Last weekend I finally had some time to open the microscope a bit more. I removed the black bottom plate with glass aperture.



At this point I could see every bit of the optical system. This proved conclusively that nothing is broken or moved.

At this point it was clear the only part of the optical system that could be giving me trouble with double image in the middle is the right angle mirrors:



Mirrors looked to be approximately at the right angle. How can we make sure? Lasers of course!

If mirror are at the right angle they will return the beam that is parallel to the source. More over if you point laser exactly at the point where mirrors meet, they will return a single dot if they are aligned and dual dots if they are not. The distance between two dots is representative of the angle error. If the mirrors are perpendicular to each other and laser beam if perpendicular to line where they intersect, the mirrors will return the beam back to the source.

In a pinch I used good quality well aligned laser from a distance meter and several 1-2-3 blocks.




Simple experiment with a target 4 feet away from the mirror revealed about 1.5" error! Then I raised the contraption by 1" to measure different section of the mirror, the error was almost the same. Set screws were user to correct the error as much as I could. Once seemingly perfect, then I repeated the same experiment at 15 feet and adjusted again and well and I could. This time the error was about 1/8".

I was not sure what is good enough here. So I assembled the microscope back to check and ... IT WORKED!!! The double vision is gone. The picture is spectacular.

The design of the Mantis is ingenious. It is almost too simple - four plastic parts, bunch of mirror held by double tape and single large lens. Yet I still do not completely understand how and why it works. There is no separate image path for every eye. All the optics on inside is "wide enough" to cover both eyes.

Taking pictures of bunch of mirrors is almost pointless. It is like Alice in Wonderland: all you see is countless reflections and not the reality.
Here is a crude diagram of what I found inside, with some basic explanations:

[Samogon]

Congratulations!!!
And thank you for sharing this journey to unknown.

[Zucca]

So so cool... thank you so much. 

You should have done a Youtube video on this, i guess 100K views in less than a month.,,

[nikonoid]

Thank you guys, it was a cool project and I enjoyed working on it.

I am waiting for 4x lens and since lens protection caps for these cost quite a lot, I am making my own from 52mm clear UV filter.


I have never done videos before. Maybe one day.

[Koray]

Thanks for the light path diagram! Amazing!

K.

[Pinkus]

Cool repair documentation. Thank you for sharing it.
One hint:
As being said: the 8x lens usually does not provide enough space for soldering, and even with the 6x lens, this often is difficult. The 4x lens on the other hand often does not offer enough magnification.
However, the famous 6x SLWD ("super long working distance" I guess) offers you even more working space as the 4x lens. Thus I use it all the time. It is a massive chunk of glass and unfortunately pretty expensive ($1500 new, at least $500 used) but worth it.

Edit: here: https://www.thingiverse.com/thing:1330221 somebody is showing a DIY version of a SLWD lens. Before purchasing the genuine one, I tried this DIY lens myself, but the picture quality was very poor.

[nixxon]

Copy of PM:

In the original Manis, the concave (light focusing) mirror in the back of the unit could be tilted up/down to elevate/lower the right output images. The top concave mirror could be routinely adjusted with a knob in the horizontal direction, to move the left output image to match the distance between the user's eyes.

I actually disassembled a Compact as well to clean the optics. It was sold shortly after that. I don't think I ever adjusted the image up/down on the Compact, so I'm afraid I can't help you with the Compact. If the working principles are similar between the models, the flat mirror assembly in the middle of the head should be fixed and oriented in precise relation to each other (reflecting light 90 degrees every time). The concave mirrors seated in the outer shell should be adjustable, to adjust right/left output images either sideways or up/down.

[ruairi]

Fantastic thread, thank you.

I bought an original Mantis used a little while back but haven't had time to mount it on a bench and test it.  It came with a pair of x 10 lenses so I need to track down a x 4 or swap with someone. 

Cheers,
Ruairi

[toybuilder]

The "semitransparent mirror" is a beam splitter.  Half of the light passes through half of it reflects.  This creates two sets of beams -- the left eye beam is affected by the aim of left eye mirror, the right eye beam is affected by the right eye mirror.  Here's a simplified diagram (as I understand it):


The left and right eye focusing mirror (at least the concave mirrors on my original Mantis), as diagrammed, are aimed to overlap the exit beams -- but if the mirrors are tilted they will shift the beams paths creating the offsets needed for stereo viewing.