Novel Geometric Calibration Method for Pan-Tilt Camera With Single Control Point

Abstract

Pan-tilt (PT) camera is an indispensable part of the video surveillance systems due to its rotatable property and low cost. As the primitive output of the PT camera limits its practical applications, an accurate calibration method is required. Previous single point calibration method (SPCM) was presented to estimate angles Pan and Tilt via single control point. For the more intuitive geometric interpretation and more robust performance, we propose a novel single point calibration method (novel SPCM). In this scheme, a nonlinear PT camera function (PT function) is established via a normalization approach. With PT function, calibration problem is converted as the intersection situation of two circles formed by Pan and Tilt. Solutions can be regarded as the intersection points of two circles in 3D space. Theoretical analysis shows that novel SPCM is stable to measurement noise, for it still finds the least-square solutions even if two circles have no intersection. In the simulation experiments, reprojection error of novel SPCM is 32.4% smaller than SPCM for the large noise situation. It is 25.1% faster than SPCM. With the angle smooth strategy, novel SPCM achieves accurate and stable performance in the real data experiment.

Keywords

• Calibration
• pan-tilt camera
• control point
• video surveillance