Measuring 3-D plant growth using optical flow

A method is presented for measuring 3-D plant growth using the optical flow computed on an image sequence of a growing corn seedling. Each image in the sequence consists of two views of the same seedling; one view of the corn seedling is front-on while the second view is a orthogonal view (at 90°) of the seedling made by projecting the plant's orthogonal image onto a mirror oriented at 45° with respect to the camera. We compute 3-D velocity (motion) of the corn seedling's tip by using a simple extension of the 2-D motion constraint equation used in optical flow analysis. This method is an extension of the work presented by Barron and Liptay where optical flow was used to measure the 2-D growth (in the vertical plane) of a corn seedling.