Shape sensor and tubular insertion system

1. A shape sensor comprising:

a light source;

a shape sensor main body which comprises at least one optical fiber and an optical characteristic material, wherein

the optical fiber comprises a core extending within the optical fiber and a cladding around the core, the optical fiber configured to receive, at one end of the shape sensor main body, detection light emitted from the light source and to propagate the detection light by the core and the cladding,

the optical characteristic material disposed in an opening at a portion of an outer periphery of the optical fiber, the opening extending up to the core, the optical characteristic material being configured to one of absorb or wavelength-convert the detection light, and

the shape sensor main body is configured to allow for measurement of a shape of the optical fiber based on a change in characteristics of the detection light, the characteristics of the detection light being changed by the optical characteristic material in accordance with a change in curvature of the optical fiber;

an optical sensor disposed at the one end of the shape sensor main body and configured to receive, from the optical fiber, the detection light having passed through the optical characteristic material, and to photoelectrically convert the received detection light into an electric signal indicative of a light quantity; and

a curving direction regulator comprising an elastic core member comprising a rectangular cross section and fixed onto the outer periphery of the optical fiber by a bonding member along a light propagating direction of the optical fiber, the curving direction regulator configured to regulate, by an elastic force of the core member, the optical fiber from curving in a direction of a short side of the rectangular cross section of the core member.

2. The shape sensor according to claim 1 , wherein the core member of the curving direction regulator comprises four rectangular cross sections as ribs that together form two planes orthogonal to each other at 90° to form an X-shaped profile, wherein a bending rigidity of the core member in planar directions of the respective two planes is stronger than a bending rigidity of the core member in a direction dividing, into two equal portions, an angle between the two planes.

3. The shape sensor according to claim 1 ,

wherein the core member comprises core materials aligned therein, and

a bending rigidity of the core member is weak in a direction along which the core materials are aligned is weaker than a bending rigidity of the core member in a direction orthogonal to the direction along which the core materials are aligned.

4. The shape sensor according to claim 3 ,

wherein the shape sensor main body comprises annular fiber holders each comprising one or more openings to hold the at least one optical fiber, respectively, the fiber holders arranged along the light propagating direction with intervals, and

the bending rigidity of the core member is regulated by an arrangement of the core materials varying in bending rigidities in the fiber holders.

5. The shape sensor according to claim 4 , wherein the curving direction regulator is arranged near a center of each of the fiber holders, and the optical fiber is arranged on an outer peripheral side of the curving direction regulator.

6. The shape sensor according to claim 4 , wherein the curving direction regulator is arranged on or near an outer periphery of each of the fiber holders, and the optical fiber is arranged inside a maximum circumscribed circle defined by an outermost peripheral portion of the curving direction regulator.

7. The shape sensor according to claim 4 , wherein a curvable direction of the shape sensor and a direction for detecting curving of the optical fiber are coincide with each other at least in a range where the curving is regulated, and the optical fiber and each of the fiber holders are bonded.

8. A tubular insertion system comprising:

an insertion tube that is inserted into a tube space and has a curving section that curves; and

the shape sensor according to claim 1 that detects a curved shape of at least a part of the insertion tube,

wherein the shape sensor is mounted or incorporated in the insertion tube such that the curving direction regulator of the shape sensor regulates the optical fiber from curving in a direction different from a direction in which the curving section of the insertion tube curves.

9. A tubular insertion system comprising:

an insertion tube that is inserted into a tube space and has a curving section that curves; and

the shape sensor according to claim 1 that detects a curved shape of at least a part of the insertion tube,

wherein the shape sensor is mounted or incorporated in the insertion tube such that a strength required to curve the insertion tube is larger than a strength required to curve the shape sensor in a direction in which the curving section of the insertion tube curves.

10. A shape sensor comprising:

a light source;

a shape sensor main body which comprises a plurality of optical fibers and a plurality of optical characteristic materials corresponding to the respective optical fibers, wherein

the optical fibers are different in bending rigidities and each comprise a core extending within the optical fiber and a cladding around the core, the optical fibers each configured to receive, at one end of the shape sensor main body, detection light emitted from the light source and to propagate the detection light by the core and the cladding,

the optical characteristic materials are each disposed in an opening at a portion of an outer periphery of the corresponding optical fiber, the opening extending up to the core, the optical characteristic materials each configured to absorb or wavelength-convert the detection light, and

the shape sensor main body is configured to allow for measurement of a shape of the optical fibers based on a change in characteristics of the detection light, the characteristics of the detecting light being changed by the optical characteristic materials in accordance with a change in curvature of the optical fibers;

an optical sensor disposed at the one end of the shape sensor main body and configured to receive, from the optical fibers, the detection light having passed through the respective optical characteristic materials, and to photoelectrically convert the received detection light into an electric signal indicative of a light quantity; and

a pair of core members disposed between the optical fibers of different bending rigidities, the pair of core members configured to regulate the optical fibers from curving in a direction where the bending rigidities of the optical fibers are small.

11. The shape sensor according to claim 10 , wherein the optical fibers of different bending rigidities differ in materials of one of the cores or the coating.