1. Field of the Invention
The present invention relates to a curvature sensor that determines a bend of a measurement object.
2. Description of the Related Art
U.S. Pat. No. 6,256,090 discloses a technique of measuring a shape of an elongated flexible body by using four or five fibers provided with fiber Bragg grating (FBG) sensors. The four or five fibers are arranged around the flexible body. Three fibers are used for measurement of the shape of the flexible body based on a difference in response of each FBG sensor with respect to a change in shape of the flexible body. One fiber is used for temperature change correction. One fiber is used for twist correction.
U.S. Pat. No. 7,781,724 discloses a technique of measuring a shape of a flexible body by using three (two or more) cores provided with FBG sensors. The three cores are, in an example, cores of multicore fibers, and in another example, cores of single core fibers of a fiber bundle. An optical signal from each of three FBG sensors in each group is separated by a frequency domain reflectometer. The shape of the fiber or fiber bundle is determined by obtaining a bend amount of each portion of the fiber or fiber bundle from strain of each of the three FBG sensors in each group to integrate the bend amount of each portion.