Needle Shape Sensing With Fabry-Perot Interferometers

Anovel approach for fiber optics shape sensing, applicable to mini-invasive bio-medical devices, is presented. A kinematic model based on rotation vector is established and used to predict the trajectory. The movement of the flexible needle caused by two control inputs (the straight forward and the bevel orientation velocity) is described as the circular motion around the equivalent axis and the rotation of the needle axis. The model is simple, precise and efficient, and has an acceptable reconstruction effect on complex spatial curves. With the characteristics of compact structure (less than 100 mu m), high strain sensitivity, low temperature sensitivity and ultra-low cost, Fabry-Perot interferometer (FPI) is used for curvature sensing. Calibration experiments show that FPI has higher (more than three times) curvature sensitivity and lower curvature-temperature cross sensitivity than fiber Bragg grating. The three dimensional shape sensing is obtained by converting the measured bending curvature and shape deformation using the proposed kinematic model.