Design and evaluation of an optical encoder coupler for laparoscope rotation tracking in image-guided surgery

We present a compact rotation-tracking coupler for oblique laparoscopes that enables accurate pose estimation without modifying existing surgical hardware. The device fits between the camera head and telescope, using an optical encoder to measure rotation with high resolution (0.18°) and a pair of lenses to maintain image clarity. The design addresses limitations of previous solutions by avoiding bulky attachments or dual sensors, improving clinical usability. Validation with an optical tracking system confirmed accurate rotation measurement, and image tests showed minimal impact on image quality. This coupler supports real-time augmented reality applications in minimally invasive surgery by enabling a practical solution to laparoscope rotation tracking.