A Fast Optical Method for the Determination of Liquid Levels in Microplates

Table 1

Procedure and parameters in the algorithms designed.

Name	TemplateBased()	ReflexionPattern()	HoughCircles()
Computational steps	(i) Difference between image and template; (ii) Thresholding (1); (iii) Morphological opening (2,3); (iv) Sum over pixel values equals blob size	(i) Blurring; (ii) Edge detection with Sobel filter (1); (iii) Calculation of statistical moments; (iv) Calculation of moment differences between image and template	(i) Laplacian-of-Gaussian filter (1); (ii) Hough-transformation (2,3); (iii) Calculation of the distance; between well tangent; and object tangent
Parameters to adjust for labware and device	(1) Threshold; (2) Size of the structuring element; (3) Iterations	(1) Filter order in 𝑥- and 𝑦-direction	(1) Filter threshold; (2) Accumulator threshold; (3) Min/max Radius
Result	Blob size	Differences in variance, skewness, excess	Radius, distance between well; and object tangents