Conditions for solvability
•Optimal (u, v) satisfies Lucas-Kanade equation
When is This Solvable?
•ATA should be invertible
•ATA should not be too small due to noise
–eigenvalues l1 and l2 of ATA should not be too small
•ATA should be well-conditioned
–  l1/ l2 should not be too large (l1 = larger eigenvalue)
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