Portable microscope for snow surface imaging

Hi all,

I am working on a research project related to ski tracks where I want to observe changes in the top layer snow grains. I have used a AmScope SM745T microscope with a 5MP MU500 previously and found that illuminating the track from beneath made a huge difference in the contrast and ability to see grains.
Is there any recommended hardware to improve the visibility of the top surface grains, lighting, new microscope, filters etc?

Im looking for signs of melting, re-freezing, new grains rolling in etc.
Edit: About magnification, a good viewport has been 1mmx1mm so far.

An important aspect is that it is easy to move from the track to allow skiers to pass, and then back to the exact same spot so some kind of sliding trolley etc would be helpful.

Thanks in advance!

Maybe Rheinberg illumination? https://www.olympus-lifescience.com/en/microscope-resource/primer/techniques/rheinberg/

You won’t even need a fancy filter set, but rather just some different colored collimated LEDs shining on the same spot on the snow from different angles.

An alternative to this that I’ve used to get the surface profile of archaeological artifacts, was to take a series of images with the light shining on the surface from different angles. Basically, rather than color coded Rheinberg, this makes temporally coded Rheinberg. This worked very well for our application.

Thank you for the suggestions! The Rheinberg method looks interesting for observing grains that I can remove, however in this case I need to observe the track untouched, I can dig from below but at least 10-20cm should be left as is.
Maybe the second method could work if I can mount some lights to a frame to set up a somewhat fast workflow. The time it takes to capture is not the most important aspect but appreciated for longer sessions outside.

Is there any nice software to help with the processing of the images (plugin to ImageJ)?

Hello. Depending on how much work you are willing to put into it I would suggest you have a look at the new open source 3D printed ‘PUMA microscope’ - it is highly portable (you will appreciate that) yet very powerful - particularly when it comes to the huge range illumination options. It is my first post here so I will not post any links but you can easily find it by doing a web search for ‘PUMA microscope’.

Hello! Thank you for the suggestion, I will read up on the illumination options, do you know any in particular that could work well for snow surface imaging?

I am a medical histopathologist by trade so I don’t claim to be expert in snowflake imaging but, assuming you can deal with keeping the sample at the appropriate cold temperatures, I suggest you try one or more of the following: Dark ground (= dark field) illumination, cross-polarisation microscopy (both epi-polarisation and trans-polarisation) and Schlieren phase contrast. The PUMA system can do all of these with standard objectives (no need to spend big on special phase objectives). You can see examples of some of this on my Twitter as well as links to the PUMA project: @Paul_Tadrous

The temperature will be cold since I can’t remove the snow from the ground :slight_smile: Air temperature will will be varying from -10 to +2°C. I will read up on those techniques, the PUMA system seems really nice. I guess a problem can be that I dont look at single grains of ice and illumination has to pass through many layers before it reaches the surface.

I attached some images of the current setup where a LED-construction light was buried beneath the snow. This was just to test on blocks of snow, the idea is to dig a hole under a ski-track if illumination from beneath is needed.

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That looks very good. I suppose regarding techniques, a lot depends on exactly what information you need to get and for what purpose. PUMA has an epi-illumination mode but the stage is small so you would have to scoop up some snow to view it. Alternatively you could use just plonk the PUMA down on the snow surface and push down till the surface layer is just at the level of the stage (I have never tried this so not sure how good it will work). However, your current microscope looks pretty good for what you are doing - you might see a bit better if you do epi-illumination with crossed polars (assuming they have the required attachments available for your scope) - but I have no experience with snow (the crystal I look at are usually urate, oxalate or pyrophosphate).

Thanks a lot for your comments, I will look if the attachments you mention are available. I just starting this project so still learning how the snow behaves, but tracking single grains and see how their surfaces change (melt/abrade etc) would be interesting.
How do you think epi-illumination with crossed polars will affect imaging of transparent ice grains? Or transparent granular in general?

I am not sure if it will help with your case but crystalline structures in general can give birefringence which can distinguish them from background debris - so I am working on the assumption that the crystalline ice will do the same. You might want to check the literature on this - especially before spending any money. I can see a way to do this DIY with your microscope: Simply purchase a polarising film sheet that is large enough to cover your circular illuminator (you can get them cheap from AliExpress) . Cut a central hole in the sheet so it only covers your illuminator but not the objective area. Then stick a polarising filter in the filter compartment of your eyepiece and rotate your eyepiece while viewing to see the changing birefringence. You can probably rig this up for less than $30. If you decide to try it and it works please give feedback and post some shots. All the best.

I will definetly try this and post results later, thank you!