Digital Image Processing Algorithm for Determination and Measurement of In-Focus Spherical Bubbles

A novel image processing algorithm has been designed in MATLAB to analyze digital images of spherical bubbles which are backlit. The algorithm possess a series of steps to determine which bubbles are in focus, remove out of focus bubbles and record measurements of bubble size and location. Specifically, the algorithm relies on self-adaptive user determined thresholds, gradient detection, correlation determination, and multiple confirmation strategies. The results are capable of handling variations in bubble appearance due to inconsistent background and overlapping. This paper describes the details of the algorithm and its use in recording bubble measurements from images of varying bubble size and bubble number density. Results from the algorithm as compared with bubble measurements from the same image sets determined via the manual line drawing method.