Direct linear calibration
Advantages:
•Very simple to formulate and
solve
•Once you know the projection
matrix, can compute intrinsics and extrinsics using matrix
factorizations
Disadvantages?
•Doesn’t
model radial distortion
•Hard
to impose constraints (e.g., known focal length)
•Doesn’t
minimize the right error function
For these
reasons, nonlinear methods are preferred
•Define
error function E between projected 3D points and image positions
–E is
nonlinear function of intrinsics, extrinsics, radial distortion
•Minimize
E using nonlinear optimization techniques
–e.g.,
variants of Newton’s method (e.g., Levenberg Marquart)