Microstar IV - DIY polarizing filters

[dtsh]

I've had some curiosity involving polarized microscopes for some time, I just hadn't gotten around to learing the basics of what's needed until a recent discussion with another member.
I was working on a proper insert to fit under the head with a wheel for rotating the polarizer, etc but decided to go with something very simple instead; I may revisit the other design in the future if I find it might add some extra utility for the effort.

It needs two 32mm diameter polarizers and one 30mm 1/4 wave lambda plate. There really isn't much to it, one of the polarizers drops in under the head, the second sits on top of the field lens, and the lambda plate holder slides in under the condenser and is retained by a clip. Unfortunately, the lambda holder requires a Cat.1201 condenser or other compatible with the filter slot, so if you have a Cat.1970 or other, it might need some redesigning (it does work with the 1205 phase turret). Converting it back to basic BF involves pulling the clip and removing the lambda holder and taking the polarizer off the field lens, which should take little effort and no significant disassembly. The field polarizer and the lambda plate rotate, allowing the adjustment of the polarization. The only difficult part is connecting the lambda plate holder to the condenser body as the retaining tabs are short so controlled use of force will be required.

Here's a view from FreeCAD so you can see what the parts are.

CAD_exploded.jpg (56.71 KiB) Viewed 1413 times

Here's an image of all the printed parts with the filters and lambda ready to be installed into the microscope.

410_pol_all_parts.jpg (124.77 KiB) Viewed 1413 times

Working our way from the top down, drop the polarizer in the head. There's a square block on one side to allow easier retreival with a pair of forceps.

410_pol_head.jpg (93.79 KiB) Viewed 1413 times

Here's a shot showing the condenser parts ready to be inserted.

410_pol_condenser_parts.jpg (101.4 KiB) Viewed 1413 times

And assembled

410_pol_condenser_assembled.jpg (78.97 KiB) Viewed 1413 times

[dtsh]

And lastly, the field lens polarizer/analyzer just sits on top of the field lens. I added knurling to the this part and the lambda holder to make it easier to grip them when rotating.

410_pol_field_filter.jpg (88.2 KiB) Viewed 1412 times

Now onto the results....
A sample of Orange G stain in brightfield.

orange_g_bf.jpg (54.73 KiB) Viewed 1412 times

Orange G in polarized light.

orange_g_pol.jpg (152.83 KiB) Viewed 1412 times

A copepod I mounted, in brightfield.

copepod_bf.jpg (70.66 KiB) Viewed 1412 times

And polarized light.

copepod_pol.jpg (48.25 KiB) Viewed 1412 times

The necessary files are on Thingiverse for those that want them.
https://www.thingiverse.com/thing:5167470

I appreciate your suggestions on improvements, criticisms, and comments!

[dtsh]

Combining polarization and phase contrast appear to be too much for the 410's illumination, otherwise I'd have included some samples of that too.