Figure 8.

Error analysis of the single-bend and double-bend insertion experiments. Needle tip positions captured by the camera image are used as ground truth. (a) The three reconstruction methods show no obvious difference in absolute errors. At the insertion depth around 70 mm, the errors appear to be larger than average, because this area is the deepest position with only two sensors activated inside the phantom. At 75 mm, errors are decreased because the third sensor is activated, introducing one more curvature information. The mean errors are all below 1 mm throughout the whole depth. (b) The fourth-order reconstruction method (method 3) provides the best fit among the three methods. Average errors are mostly below 0.5 mm and maximum error is below 1 mm, compared with maximum average error of 1 mm and maximum error of 1.8 mm for the other two methods.