A scope cylinder rotation tracking method for oblique-viewing endoscopes without attached sensing device

Since the view direction of an oblique-viewing endoscope can be changed by rotating the scope cylinder to obtain a larger field of view, the rotation angle of the scope cylinder is one of the parameters in its camera model. In order to perform the augmented reality visualization in the surgery using the oblique-viewing endoscope, tracking of the rotation angle is required to determine the view direction. The optical tracking markers or the rotary-encoder have been used for the rotation tacking in the previous studies. However, the additional components attached to the endoscope can be obstructive during the surgery. We propose the rotation tracking method without any additional components based on detection of the wedge mark in the endoscopie image, which indicates the cylinder angle. In the experiment, the difference of the proposed method from the rotary encoder used as the gold standard was less than 1.5 degrees.