Fast and Robust Endoscopic Motion Estimation in High-Speed Laryngoscopy

Seven methods for endoscopic motion compensation for laryngeal high-speed videoendoscopy (HSV) are compared. Two of them are based on tracking the maximum of the crosscorrelation function of two images; two are based, respectively, on the minimization of the L2–norm and the magnitude difference distance between two images; and the other three utilize properties of the FFT-based cross-power spectrum of two images. All seven methods were applied to compensate the motion, at the sub-pixel level, of the endoscopic lens relative to the vocal folds in HSV recordings. The motion compensation methods based on FFT crosspower spectrum demonstrated remarkable computational speed and satisfactory accuracy, while also offered wider motion-tracking range. The proposed two-step least square fitting of the FFT cross-spectrum phase plane was found to be the fastest among all seven approaches.