Parameter Estimation for Perspective Projection Based on Camera Calibration in Skull-Face Overlay

Craniofacial superimposition is a forensic process that aims to identify a missing person from a photograph and an unknown dead's skull. One of the crucial steps is skull-face overlay in consistent with photographic space according to the face photo. Thus parameter estimation of perspective projection becomes key problem. In this paper, we employ a method of camera calibration based on vanishing point(VPBC) to estimate relevant parameters including perspective angle, orientation of camera and photographic object distance. Firstly, according to two vanishing points in image calculate the perspective angle and focal length using photo-geography theory, then evaluate camera direction and photographic object distance based on equal focal length, finally, map the 3D skull according to above known parameters, and implement skull-face overlay process. Result shows that this approach is effective, efficient and accurate for follow-up research work.