Hi all — new here, first post.
I run a mold remediation company and I’m exploring whether the OpenFlexure can work as the starting imaging platform for a project I’m working on. The short version: I want to build a system that uses AI to count and classify mold spores on microscope slides from indoor air quality sampling cassettes, rather than sending them to a traditional lab.
The slides come from Air-O-Cell spore trap cassettes — standard in the indoor air quality industry. After collection, you open the cassette, mount the glass coverslip (roughly 10×15mm sample trace) on a standard 1×3" slide with lacto-phenol cotton blue stain, and examine it under a microscope. The particles of interest range from about 2–3 microns (Aspergillus/Penicillium conidia) up to around 30–40 microns for larger genera like Alternaria and Stachybotrys.
I want to use dark field rather than brightfield. The main reason is contrast — the small spores are lightly stained and can wash out under brightfield. Dark field also happens to be a different imaging approach than what existing commercial AI analysis services use, which matters for reasons I won’t bore you with. The ASTM D7391-20 standard for spore trap analysis explicitly mentions dark field and phase contrast as acceptable supplementary methods for looking at difficult particles, so it’s not outside the accepted methodology.
Right now I’m trying to figure out whether the OpenFlexure is the right starting point before I spend money on something more expensive. I have access to a 3D printer and I’m reasonably comfortable building things. I do not have a microscopy background — I’d be working with a certified spore analyst consultant to review image quality and label training data.
A few specific questions:
1. Dark field setup. I’ve seen reference in the forum to dark stop inserts for the condenser and the LED array approach in the Delta Stage paper. For this application — fixed slides, 40x, particles 2–40 microns — which approach would you actually recommend? Has anyone successfully done dark field on environmental particle slides specifically (as opposed to biological tissue or blood)?
2. Camera. I’m planning to use the 12MP Raspberry Pi HQ camera (IMX477) rather than the standard v2 module. I’ve seen at least one thread confirming this works. Is there anything non-obvious about fitting or configuring it — software settings, optics module changes, anything that bit you when you did it?
3. Objective for small spores. The concern I have is whether the standard 40x/0.65 NA plan objective can actually resolve a 2–3 micron Aspergillus spore well enough to distinguish it from debris or other small particles. Or does that size range really need 60x or 100x oil? I’d strongly prefer one objective that covers the full spore size range if that’s realistic.
4. Autofocus on sparse slides. Everything I’ve read about autofocus validation is on tissue sections or blood smears — high-contrast, dense samples. Air cassette slides are much sparser — mostly transparent particles on an adhesive background. Is autofocus reliable on that kind of low-contrast, low-density sample, or will it need manual help consistently?
5. Slide fit. The Air-O-Cell prep results in a thin glass coverslip mounted on top of a standard glass slide with mounting medium. The total thickness is a bit variable depending on how much medium was used. Any known issues with stage clearance or focus range on slides thicker than a standard single glass?
Thanks in advance — happy to share what I learn once I get into it. Seems like a different application than what most people here are working on but the underlying problem (automated particle counting from microscopy images) feels pretty aligned with the malaria and pathology work I’ve seen documented.
