Peripheral surface-emitting linear light guide and method for manufacturing the same

1 . A peripheral surface-emitting linear light guide, comprising:

an optical fiber including a core, an outer peripheral surface of which is exposed from a cladding at one end in a longitudinal direction; and

a light-scattering member that covers an entire periphery of the outer peripheral surface of the core in an exposed portion over a predetermined axial length range,

wherein light emitted from the outer peripheral surface of the core is scattered and radiated by the light-scattering member,

wherein the light-scattering member comprises a light transmissive base material having a higher refractive index than the core and light-scattering particles that scatter the light incident on the base material, and the light-scattering particles are dispersed and mixed in a certain proportion throughout the base material,

wherein at least a portion of the light-scattering member in the longitudinal direction is an incremental portion whose thickness increases gradually toward a tip side of the core, and

wherein the outer peripheral surface of the incremental portion is a tapered surface inclined to a central axis of the core without steps.

2 . A method for manufacturing the peripheral surface-emitting linear light guide according to claim 1 , comprising:

processing the optical fiber to expose the outer peripheral surface of the core from the cladding;

preparing a liquid to be used as the light-scattering member;

immersing the exposed core in the liquid;

pulling-up the core from the liquid by moving the core and the liquid relative to each other in a vertical direction; and

curing the liquid adhered to the core,

wherein, in the pulling-up step, when forming the incremental portion of the light-scattering member, a pulling-up speed is varied to gradually increase a thickness of the liquid adhering to the outer peripheral surface of the core.

3 . The peripheral surface-emitting linear light guide according to claim 1 , wherein the incremental portion has a taper angle θ with respect to the central axis of the core, and

wherein 0.0006°≤θ≤0.0014°.

4 . The peripheral surface-emitting linear light guide according to claim 1 , wherein the light-scattering member further comprises, on the tip side of the core relative to the incremental portion, an annular thin-walled portion that is thinner than a thickest portion of the incremental portion.

5 . The peripheral surface-emitting linear light guide according to claim 4 , wherein an outer peripheral surface of the annular thin-walled portion is parallel to the central axis of the core.

6 . The peripheral surface-emitting linear light guide according to claim 4 , wherein the light-scattering member further comprises a tip-covering portion that covers a distal end face of the core.

7 . The peripheral surface-emitting linear light guide according to claim 1 , wherein the light-scattering particles are selected from the group consisting of titanium oxide, aluminum oxide, silver, copper, iron, and alloys thereof.

8 . The peripheral surface-emitting linear light guide according to claim 1 , wherein the light-scattering particles comprise titanium oxide (TiO 2 ).

9 . The peripheral surface-emitting linear light guide according to claim 1 , wherein the light transmissive base material comprises a silicone resin.

10 . The peripheral surface-emitting linear light guide according to claim 1 , wherein a refractive index of the light transmissive base material is at least 1.50 and a refractive index of the core is 1.46.

11 . The peripheral surface-emitting linear light guide according to claim 1 , wherein the core is made of a quartz glass and the cladding is made of a polymer cladding.

12 . The peripheral surface-emitting linear light guide according to claim 1 , wherein the exposed portion of the core covered by the light-scattering member has an axial length of 3 cm to 7 cm.

13 . The peripheral surface-emitting linear light guide according to claim 1 , wherein a mixing ratio of the light-scattering particles to the base material in the light-scattering member is homogeneous throughout the entire longitudinal direction.

14 . A peripheral surface-emitting linear light guide, comprising:

an optical fiber including a core, an outer peripheral surface of which is exposed from a cladding at one end in a longitudinal direction; and

a light-scattering member that covers an entire periphery of the outer peripheral surface of the core in an exposed portion over a predetermined axial length range,

wherein light emitted from the outer peripheral surface of the core is scattered and radiated by the light-scattering member,

wherein the light-scattering member comprises a light transmissive base material having a higher refractive index than the core and light-scattering particles that scatter the light incident on the base material, and the light-scattering particles are dispersed and mixed in a certain proportion throughout the base material,

wherein at least a portion of the light-scattering member in the longitudinal direction is an incremental portion whose thickness increases gradually toward a tip side of the core, and

wherein the light-scattering member further comprises, on the tip side of the core from the incremental portion, an annular thin-walled portion which is thinner than a thickest portion of the incremental portion.

15 . A method for manufacturing the peripheral surface-emitting linear light guide according to claim 14 , comprising:

processing the optical fiber to expose the outer peripheral surface of the core from the cladding;

preparing a liquid to be used as the light-scattering member;

immersing the exposed core in the liquid;

pulling-up the core from the liquid by moving the core and the liquid relative to each other in a vertical direction; and

curing the liquid adhered to the core,

wherein, in the pulling-up step, when forming the incremental portion of the light-scattering member, a pulling-up speed is varied to gradually increase a thickness of the liquid adhering to the outer peripheral surface of the core.

16 . The peripheral surface-emitting linear light guide according to claim 14 , wherein the incremental portion has a taper angle θ with respect to the central axis of the core, and

wherein 0.0006°≤θ≤0.0014°.

17 . The peripheral surface-emitting linear light guide according to claim 14 , wherein the core is made of a quartz glass and the cladding is made of a polymer cladding.

18 . The peripheral surface-emitting linear light guide according to claim 14 , wherein the exposed portion of the core covered by the light-scattering member has an axial length of 3 cm to 7 cm.

19 . The peripheral surface-emitting linear light guide according to claim 14 , wherein a mixing ratio of the light-scattering particles to the base material in the light-scattering member is homogeneous throughout the entire longitudinal direction.