  The common approach to radial distortion is by the means of polynomial
approximation, which introduces distortion-specific parameters into the camera
model and requires estimation of these distortion parameters. The task of
estimating radial distortion is to find a radial distortion model that allows
easy undistortion as well as satisfactory accuracy. This paper presents a new
piecewise radial distortion model with easy analytical undistortion formula.
The motivation for seeking a piecewise radial distortion model is that, when a
camera is resulted in a low quality during manufacturing, the nonlinear radial
distortion can be complex. Using low order polynomials to approximate the
radial distortion might not be precise enough. On the other hand, higher order
polynomials suffer from the inverse problem. With the new piecewise radial
distortion function, more flexibility is obtained and the radial undistortion
can be performed analytically. Experimental results are presented to show that
with this new piecewise radial distortion model, better performance is achieved
than that using the single function. Furthermore, a comparable performance with
the conventional polynomial model using 2 coefficients can also be
accomplished.
