Abstract
The orientation of images taken with a telecentric lens (TL) camera is discussed. For reverse engineering of small parts a TL camera have many advantages. It is characterized by orthonormal projection instead of central projection and by small lens distortions, which enables 3D measurement by photometric stereo, though distortion calibration is necessary for high precision measurement.
This paper shows a process of orientation of multiple view images and discusses the resulting precision of object points coordinates and magnitude of distortions. Since the orthonormal projection holds, so-called factorization method can be applied to obtain initial values of unknowns for ensuing bundle adjustment. The estimated precision of image coordinates by bundle adjustment with no additional parameters is 0.44 pixels (3.3 μm) which corresponds to 11.4 μm in the object space. Self-calibrating bundle adjustment with inner orientation parameters, however, is shown not available, since high convergence exposures are not possible because of shallow depth of object field.
