What controls the miniscope magnification and frame rate?

[Abby Vigderman]

Hi there! I am working to adapt miniscopes to image fluorescent beads injected into the vasculature as a proxy for blood flow velocity. Our colleagues have made some suggested modifications to our miniscope imaging that would optimize tracking of beads with their methods. From that, I am wondering what controls the magnification of the miniscope (which looks to be about 6x-7x), and are there ways to modify this? We would actually want to decrease the magnification to about a third of what it is currently, decreasing resolution but increasing the field of view, which would help with tracking of faster beads

Thanks so much!

Abby

[Daniel Aharoni]

Hi Abby,

It sounds like you are using a V3 Miniscope which does have a magnification of around 6 to 7x. My suggestion would be to switch over to the V4 Miniscope. The default lens configuration results in a magnification of around 2 to 3x but you can also swap out one or both of the lenses in the objective of the Miniscope to decrease this further, resulting in lower resolution but a larger FOV. https://github.com/Aharoni-Lab/Miniscope-v4/wiki/Lens-Configurations

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Daniel B. Aharoni, PhD

Assistant Professor
Dept. of Neurology, UCLA

DBAh...@gmail.com
DAha...@mednet.ucla.edu

[Abby Vigderman]

Hi Daniel,

Thanks so much for the quick response. I'll look into the V4 miniscope, but I have a few of the V3 ones on hand and may attempt switching out the CMOS sensor to play with the frame rate, so I'd like to try modifications on the V3 as well if possible. I wanted to ask whether your suggestions for the V4 would carry over into the V3, i.e. if I switch out the objective GRIN lens for one with a longer focal length, do you expect that I would be able to decrease the magnification? My understanding of how the magnification works is limited so any background on that would be helpful. Would you expect that changing the achromatic lens within the scope would alter the magnification as well? Thank you!

Abby

[Daniel Aharoni]

For the V3 Miniscope, you can try swapping out the achromatic tube lens to decrease the resolution a bit but this likely won't get you down to the magnification you want. You can search this google forum for more details on that. You could also conceivably swap out the objective GRIN lens for one with a different pitch but this might be difficult as sourcing custom versions of these lenses is very difficult due to Inscopix being the sole distributor of them.