The optical flow constraint equation, Ixu + Iyv + It=0, is u…

The оpticаl flоw cоnstrаint equаtion, Ixu + Iyv + It=0, is under-constrained. It has 2P unknowns and P equations in an image with P pixels. Which of the following best describes the solution to this problem by Lucas and Kanade (1981)?