For a transparent well with a known volume capacity, changes in fluid level result in predictable changes in magnification of an overhead light source. For a given well size and fluid, the relationship between volume and magnification can be calculated if the fluid's index of refraction is known or in a naive fashion with a calibration procedure. Light source magnification can be measured through a camera and processed using computer vision contour analysis with OpenCV. This principle was applied in the design of a 3D printable sensing device using a raspberry pi zero and a camera
@article{arxiv.2303.14233,
title = {A computer vision based optical method for measuring fluid level in cell culture plates},
author = {Pierre V. Baudin and Mircea Teodorescu},
journal= {arXiv preprint arXiv:2303.14233},
year = {2023}
}