custom baseplate optimisation

48 views

Skip to first unread message

Ed Hayter

unread,

Dec 5, 2024, 10:18:51 AMDec 5

to Miniscope

Hello miniscope gang!

First off, massive thanks to the creators and community for all the effort you’ve put in. It’s a great project and I can’t wait to see where it goes.

We’ve been trying to get some images through the inscopix 0.6mm lenses and Shylos’ custom baseplates, and it’s going well but there are definitely improvements to be made. Initially to get the lens into the baseplate I was standing it upright on a test slide and lowering the baseplate until in focus at ewl=0 as suggested by another poster. This seems to be ok, but gives quite a lot of distortion and I found it difficult to get cells in focus. I then tried the same thing, but with a couple of cover slips between the test slide and the bottom of the grin lens when attaching the lens to the baseplate (based on the assumption that there’s an optimal distance between lens & imaging plane which is not 0) and noticed a few things as you increase distance between slide & lens: Less zoomed in image, less distortion, changes in vignetting, but rather than having a bright spot in the middle there’s more of a bright halo round the outside. Here are some images of a slide to show what I mean (no lens, lens attached to baseplate with 0 coverslips, 3 coverslips (~300um, but could vary a lot), and no sample. All focused at EWL=0).

So, my questions are:

Is this approach worth considering, and if so is there an optimum distance between lens and imaging plane? I couldn’t find any documentation on the lenses.

Or, is adjusting the focal distance between sample + lens functionally the same as changing the distance from top of lens to objective (or changing the electronic focus), so getting the lens into the baseplate is just a case of ‘close enough’?

What is causing this light halo / bright spot in the middle, and is there a way to get rid of it? In my initial tests it’s messing with the analysis quite a lot, despite seeing cells quite clearly (I’ve tried CaImAn, Min1Pipe & Minian). I realise this may be mitigated with brighter cells – currently using transgenic gcamp6 which seems to be too dim really.

Bonus question – in the above image there’s a bright area in the top left of the lens, any ideas what could be causing this? I suspect it’s a chipped lens or glue, but there does often appear to be a sort of glare in that area even using other lenses.

I hope this makes sense. I’m trying to wrap my head around the optics of these lenses and how to optimise image quality. Any advice appreciated.