How do I choose/source microscope optics?
October 19, 2022 8:16 AM   Subscribe

I am building a PUMA microscope, but instructions leave the optics to the builder. How do I choose an eyepiece and objective, and how do I know if a specific used one is in acceptable condition, say on EBay? I can't find much in terms of microscope optics reviews online. Build notes refer to "Olympus SPlan objective and Olympus WK 10x/20L-H eyepiece" as the opposite of "plastic toy from Ali Express", so failing any other information that is what I will purchase!

"Although not a limitation of the scope itself, this seems like an appropriate place to emphasize that the optical image quality can only be as good as the quality of the optics used. If you use an Olympus SPlan objective and Olympus WK 10x/20L-H eyepiece (which you can use with PUMA) then you can get the optical image quality of a professional Olympus BH-2 microscope. However, if you use a cheap plastic toy RMS objective costing £5 from AliExpress and a cheap plastic toy eyepiece then you will get the optical viewing experience of a cheap plastic toy microscope."

Specifications:
Eyepiece (Ocular Lens)
I don’t specify specific eyepeices because there are so many types and you can buy good ones second hand, etc. However you need to get one that has a 20 mm field number and ideally this should also be of wide field type and with high eye reliefe (sutable for spectacle wearers). The barrel of the eyepeice must fit a standard 23.2 mm (sometimes just specified as 23 mm) tube.

Objective Lens
For similar reasons I do not specify particular objectives. However the type of objective required should have the following characteristics.
It must have an RMS thread to connect it to the scope. It must have a conjugate focal distance of 195 mm and a parfocal length of 45 mm. It must be made to work with a finite mechanical tube length of 160 mm (infinity objectives will not work with the configuration of PUMA you are building here).
As for magnification, x4 or x10 is recommended for this Foundation scope because it does not have an Abbe condenser. If you want to use higher magnification objectives then you will need to upgrade your scope with the PUMA Abbe condenser module.
For best image quality use a ‘Plan’ objective as opposed to a simple achromat. Plan objectives will give an image that is in focus all the way across the field of view from the centre to the periphery while ‘semi-plan’ or simple achromats will show either the centre or the periphery in focus at any one time but not both. Of course, ‘Plan’ objective are more expensive due to the extra corrective optics they employ
posted by lemonade to Science & Nature (2 answers total) 3 users marked this as a favorite
 
Best answer: Any 4x or 10x Plan objective from the major microscope manufacturers will do the job: that is Nikon, Olympus, Leica, or Zeiss. The objective is more important than the eyepiece. A 10x Plan objective is not a particularly high-end component, and there will really be no significant difference from manufacturer to manufacturer. Olympus probably gives you the best bang for your buck.

As for condition, you can tell a lot by simple visual inspection, ideally with a magnifying glass or jeweler’s loupe. You’re looking for scratches on the front lens or places where this lens is separating from the body of the objective. This is harder for something on eBay of course.
posted by mr_roboto at 8:57 AM on October 19, 2022 [2 favorites]


Response by poster: This is very helpful, thanks!
posted by lemonade at 5:11 PM on October 20, 2022


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