Petrographic OFM

Hi there,
I’m working on a low cost microscope for petrography, based on OFM V6.1.5 with C270 cam. I put a polarizer inside the optical tube and made an accessory to put the other polarizer in the condenser.

Finally, I designed a rotary stage based on the sample riser:

I would be glad to reading your feedback!


That is very nice. The rotation is remarkably smooth about its axis. What magnification objective are you using?

This is really cool Pablo!
The convex part of the condenser is pointing to the sample on purpose?
Maybe this can be added as an optional part into the V6 documentation? Don’t know how to do that but would be nice to see this integrated somehow

Thank you William, Nano,
I’m using a 10x objective, which is typical in petrography, according to the people I’m working with.
The rotation is really smooth! I put an o-ring in the patter grove which helps smoothing out any printing imperfections, the z seam mostly. Plus, the bearings keep the platter perfectly centered

Nano, I didn’t realized the condenser was upsidedown, thank you.

It would be great to include this mod in the ofm repo. I would need some help.


Really cool!

We need to work out where best to store mods to older versions. We could do it in a v6 branch. Or if people want to share full STLs we can think of another place to host them.

It would be interesting to think about how we could combine something like this into V7. The decision to integrate the riser has been helpful from the perspective of not having threads that strip on the main body. But has made it harder to have these sort of stage mods.

One think that @WilliamW suggested is we may want to have a second mounting point on the optics module, or a different optics module entirely that mounts higher allowing risers for v7.

1 Like

Hi Pablo,
I am actually building an openflexure v7 for the same purpose!
Would you share the stl with me?
Also, where do you source the polarizer?

Hi Julian,
I think we could store this mod in branch V6. I still have to clean the code a little bit a document it. Anyway, before any further step I want to have a feedback from people working on petrography at my university to see if this fits their needs. One of the limitation of this rotary stage is the diameter, which allows only short slides.

1 Like

Hi Nicolas,
It would be really cool to see a rotary stage mod for v7. I have some ideas to automate the rotation, so as to avoid shaking the stage with your hands.
This is the repo were I store the design files:
Regarding the polarizer, a friend of mine gave me a couple of them. You can get them on aliexpress

1 Like

I forgot there was a v6 mod branch. And as it’s all on OpenSCAD that makes it pretty simple to get merged in.

Do you have any issues with the plastic lens affecting the lens polarisation?It might be possible to make something that sits on the illumination dovetail under the condenser above the sample to hold the polariser?

I still have to make some validation with people working on petrology here. I don’t think lens affects polarization. Anyway, I’m aware of this development which would solved the issue. However, one important requirement is that the user should know the relative position of polarizers. This is not something that you can easily infer from the image, as the C270 has automatic low light compensation. That’s why I decided to create a polarizer holder that has 2 fixed positions.

1 Like

Hi everyone,
A little update on the project.

I changed the screws used to hold the bearings in place for others that have shorter head, so as to be able to lower the platter a couple of millimeters. However, the platter was still a bit high, making it impossible to get the sample on focus. I ended up cutting out the camera mount a little bit, so I can place it a little bit higher.

I think it would be better to modify the C270 mount and leave the OFM body as it is.

I also designed sample clips that fits in the holes of the platter I made to be able to assemble the rotary stage.

I’m still waiting for geologist to tell me if this design fits their needs. The code still needs some cleaning and some magic numbers need to be clarify, but otherwise I would say this mode is ready to be shared.

1 Like

The optics module for an infinity corrected objective comes out slightly longer than the standard one for objectives with 160mm tube length. Might that be enough to make the difference for you?

I need 3mm, maybe less. I could try the optic module for infinity corrected. Thanks.

1 Like