A simple calibration device


The last two points above can be used to design a simple calibration device as follows. The image of three squares on three different planes (not necessarily orthogonal) are sufficient to give calibration. Consider the following steps:

  1. For each square compute the homography $ {\bf H}$ that maps its corner points, $ (0,0)^T,(0,1)^T,(1,0)^T,(1,1)^T$ to their imaged points.
  2. Compute the imaged circular points for the plane of that square as $ {\bf H}(1,\pm i,0)^T$ .
  3. Fit a conic $ {\bf\omega}$ through the six imaged points. Note that five points are sufficient to define a conic.
  4. Compute $ {\bf C}$ from $ {\bf\omega} = ({\bf C}{\bf C}^T)^{-1}$ using Cholesky decomposition.

Subhashis Banerjee 2008-01-20