Plankton are tiny organisms that drift around in the ocean. They aren’t just whale food — they are responsible for fixing up to 50% of the world’s carbon dioxide. That, along with their position as the base of many important food chains, makes them interesting to science. Unfortunately, they are tiny and the ocean is huge. Enter Planktoscope. Billed as “an affordable modular quantitative imaging platform for citizen oceanography,” the device is a software-controlled microscope with the ability to deal with samples flowing through.
The software is in Python and uses existing libraries for user interface, image processing, and other tasks. The computing hardware is in the form of a Raspberry Pi. There are actually two prototypes of PlanktoScope available.
To give you an idea about the capabilities of the device, one test used a 25mm and 16mm lens coupled with a 3280×2464 pixel image sensor. The field of view was 2,300 microns wide by 1,730 microns high. The flow cell pumps about 0.8 microliters of fluid, stops, and takes an image, handling about 48 microliters per minute. You can see a brief video of the device in action below.
Plankton can be powerful — literally. For some people, it is even an artistic muse.
A couple things:
* The project website is at https://www.planktoscope.org.
* Detailed assembly instructions are at https://planktoscope.github.io/PlanktoScope/
* In the paper, they compare this to a commercial equipment called a FlowCam, which (see Figure 3) apparently costs $57k to $97k. Wow.
a good way to make sure they dont steal the recipe for your crabby patties too.
There’s something German with this project but I just can’t put my “Arbeitsspeicher” on it. ;-)
I am inspired. Thanks for publishing on Hackaday. I am having trouble holding-back my desire to try and start to build one right this second.
Could not find a concise explanation of the optics. :(
Most raspberry pi based microscopy projects use something closer to macro photography, moving the stock lens away from the camera for very close focus. The v2 camera is quite small so you don’t need significantly larger image for viewing microbes. Contrast can be limited compared to traditional microscopes.
From what I can tell, it looks like they have a 16mm and a 25mm lens in the m12 thread facing one another (not positive which they use as the objective, but I assume it’s just a regular reversed-lens macro setup) and they move the objective to focus. That’s a shame, because you can get real infinity-corrected microscope objectives for surprisingly low prices, and then your setup can be very much like a real microscope.
A brief description of the optical configuration for the currently-available PlanktoScope hardware can be found in section 3.1.2 of https://www.frontiersin.org/articles/10.3389/fmars.2022.949428/full (a new hardware iteration is being developed with different optics, but it’s not yet generally available). In all iterations of the PlanktoScope hardware, the lenses are mechanically fixed with respect to the camera, while the sample “stage” (a flowcell) is moved by a pair of stepper motors in order to adjust the focus.
As you mention, the currently-available PlanktoScope uses a 16 mm M12 lens and a 25 mm M12 lens, and the two lenses face each other. The assembly documentation (https://planktoscope.readthedocs.io/en/latest/assembly_guide/#step-6-lenses-tapping-and-mounting) refers to the 25 mm lens as the objective lens, but I believe that is a mistake. https://www.frontiersin.org/articles/10.3389/fmars.2022.949428/full describes the 16 mm lens as the objective lens (which goes on a removable mount) and the 25 mm lens as the tube lens (which is mounted right in front of the camera).
Thanks for the correction; yeah it looks like it worked out well with the setup they chose; maybe because the sensor is small and pixel-dense so the necessary optical magnification isn’t extreme. https://www.frontiersin.org/articles/10.3389/fmars.2022.949428/full#supplementary-material says 1.7um was their best resolution result optically, which was at 3x magnification with a 25 and an 8mm lens.
I suppose part of the other advantage of microscope objectives is various optical corrections for field flatness or whatever, but for resolution alone it’s not bad at all.
PlanktoScope software maintainer (as of 2023) here – just a minor correction on the software, currently there is a Python backend which performs (most of the) hardware control and provides an internal MQTT API; and then there is a Node-RED dashboard which talks to the internal MQTT API and provides a web browser GUI.
Please feel free to ask me any questions about the software!