In ordinary pan-tilt cameras, the physical camera rotation causes the spatial translation of the projection center of the optical system, because the projection center is not aligned on the rotation axes. Consequently, appearances of 3D objects change depending on viewing pan-tilt angles even if they are static objects. This introduces various difficult problems in mosaicing images into one panoramic view and tracking moving objects by active cameras.
Our idea to solve this problem is to develop a pan-tilt-zoom camera
whose projection center is kept aligned just on the rotation axes (Fig.
11). We call such pan-tilt-zoom camera
Appearance Sphere Camera (APS camera
, in short) and devised a calibration method for the
accurate camera alignment[9]. Figs.
12 and
13 show the developed APS camera and a synthesized
omnidirectinal APS image respectively. [10] in this
proceedings describes technical details of the APS camera and
demonstrates its practical utilities for moving object detection and
tracking.
Figure 11: Appearance sphere. The projection center is kept fixed against
pan-tilt rotations.
Figure 12: Appearance sphere camera. Several finely adjustable camera stages
are used for the precise calibration.
Figure 13: Appearance sphere image. Only panning was used to capture images and
the sophisticated calibration realizes the almost perfect seamless mosaicing.
