Panoramic Camera Calibration Using 3D Straight Lines

Linear array CCD based panoramic cameras are being used for measurement applications. The elegant image acquisition mode and the high information content of those images make them suitable candidates for quantitative image analysis. For accurate measurements a sophisticated camera calibration is an important prerequisite. In our previous investigations we designed a sensor model for linear array CCD based rotating panoramic cameras, which models substantial deviations from the pinhole model using additional parameters. The additional parameters are related to the camera itself, the configuration of camera, the turntable, and mechanical errors of the camera system during rotation (i.e. tumbling). We measured the tumbling of the SpheroCam by an inclinometer and also modeled tumbling in connection with the collinearity equations. We showed a subpixel level accuracy after tumbling modeling. Determining tumbling parameters with bundle adjustment needs many control points and this makes the use of this sensor a bit inconvenient. Using existing object space information, such as 3D straight lines can provide extra conditions for reducing the number of control points for calibration and orientation. So far straight line information has been mainly used for determining interior orientation and additional parameters with single frame cameras. Due to the eccentricity of the projection center from the rotation axis the acquired panoramic images do not have a single projection center. Therefore the formulations which have been used for single projection center cameras cannot be applied in this case. In this paper we give a new formulation for the processing of 3D straight lines in panoramic cameras. We show how 3D straight line information can be used in addition to tie points for calibration and orientation. We will present the results of our new investigations by using 3D straight lines as stochastic constraints in the bundle system for determining the tumbling parameters in addition to the other additional parameters. This allows us to do a full calibration and orientation without control points, which makes the use of the sensor more efficient.