I watched a presentation today and I was sold to build an openflexure microscope.The printing and fasteners and Pi seem clear. But I have no idea about the optics.
The most important seems to be the objective and in the help I see ‘or obtained very cheaply on AliExpress’ (I pasted at the end the full quote for completeness).
The issue is finding such an product on aliExpress when you don’t really know anything about optics.
Does anybody has a decent link or a BOM with a link to an AliExpress item?
I’m afraid I’ll buy a part that will not work at all.
The microscope should accept most RMS-threaded objective lenses, and depending on whether you use the sample riser it will use either 35mm or 45mm parfocal distance. These objectives can typically be scavenged from old equipment, or obtained very cheaply on AliExpress. We recommend going for Plan or Semi-Plan corrected lenses at 40x, and definitely Plan corrected or better at 100x.
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You can find affordable and decent enough objective lenses from North American suppliers. Here’s an example:
Since you’re not totally sure what to look for, I can’t recommend either Aliexpress or eBay. You can get good deals on eBay but you really have to know what you’re doing.
Thank you for your comment.
Just a clarification. I’m looking or a general molecular bio microscope with cell culture monitoring capabilities (prokaryotes and eukaryotes).
Thank you for your reply. The article about resolution was very interesting.
I’m into molecular bio with little interest in other areas.
So probably a general molecular bio microscope with cell culture monitoring capabilities (prokaryotes and eukaryotes).
I have no idea about the magnification but I suspect 40x or maybe even 100x would be OK.
I found these choices on aliexpress: https://www.aliexpress.com/item/1005001892135517.html?spm=a2g0s.8937460.0.0.4f552e0eOYJuQV
or
I’m not sure what the OIL stuff is all about
It seems to be slightly cheaper than the Amazon
If you add the cost of a modern PI and the rest it will get into 400-500$ range so not exactly cheap
Oil refers to index-matching oil that’s used between the objective and the sample. It’s necessary for most high-magnification objectives. For cell culture, depending on what you’re doing exactly, you might do what WilliamW suggested and start with the lens from the Pi camera itself rather than getting an objective. If that doesn’t work for you, then you can upgrade easily enough.
It’s definitely not anywhere near $400 all in, though. A RPi 4 2GB is $35, a Pi v2 camera is $30, the official USB-C supply is $8, a good quality 64GB SD card is around $12. So, that’s $85. If you add a passive heatsink and expensive shipping that’s maybe $100 for the RPi hardware.
The printed parts are $20 in filament if you have your own printer or a friend with a printer, o-rings and hex nuts and all the miscellaneous fasteners can be had for another $20 - that’s also more or less the price for the illumination and hardware kit from the website. Then if you add the motors and use the provided driver boards instead of having a sangaboard made, that’s another $10. So in the neighborhood of $150.
With the high quality optics, you need the tube lens and an objective. The tube lens I got from Edmund Optics for $32.50 plus $8 shipping. If you opt for one of the garbage objectives from Aliexpress, you can easily come in under $250.
Thank you for your comments. Can you please add some links that show these prices? The cheapest RPi 4 2GB I can find is around 80$ after shipping with no sink etc. The 40x Plan objectives from Edmund Optics seem to start at 500$. I was in a presentation ofered by Openflexure and they stated they get objectives from AliExpress quite often as also stated in the documentation…
Objective lenses have a range of prices and performance. It is hard to make a lens where all colours are focused at the same position and where everything is in sharp focus across a wide and flat area and also where there is no darkening towards the edges of the field of view and no colour tint. The most expensive lenses are designed to get all of these things as good as possible with sharpness only limited by diffraction, lower cost lenses will not be as good in some areas. The cost also goes up rapidly if you want a long working distance between the sample and the lens. The Openflexure microscope has an automatic calibration function that compensates for dark corners and colour tint. It is also motorised with automatic slide scanning, so you can tile images together to get a wider field of view and compensate if the edges of individual images are not in focus. These functions mean that you don’t really need the more expensive microscope objectives.
Hi William, and thank you for the pointer. Indeed a long thread and sometimes it’s hard to make up if those people really used those parts or just ordering.
It would be cool to have some kind of comparison database using images. You would think a project as old as OpenFlexure would have that.
Cheers
Hi Thomas,
Thank you for the pointers, great list. I have not used that company before and the prices seem quite good for the specific articles. It comes around 185 CAD$ including shipping and taxes and including the memory. You also mentioned Edmund Optics for the lens. Do you still happen to have the link to that?
Many thanks,
Adrian
You might want to just start with what WilliamW suggested, use the lens that comes with the Pi v2 camera and then if that doesn’t do what you need, then you can order more optics. The tube lens I posted about before is out of stock, but the achromat tube lens can be found in many places, as well as microscope objectives.
