JP5090539B2 - Optical fiber, light source device for illumination, and image display device - Google Patents

Description

  The present invention relates to an optical fiber used as an optical transmission means in an illumination light source device, an image display device, or the like.

  In a light source device in which a light source and an output end of light emitted from the light source are arranged at different positions, an optical fiber that can give a high degree of freedom to the configuration of the optical transmission path is often used. In particular, when a laser capable of emitting light with high directivity from a light emitting point having a small size is used as a light source, high light utilization efficiency can be obtained when laser light is incident on the optical fiber. Is effective as an optical transmission means of a light source device employing a laser light source.

  The optical fiber core wire includes a core that guides light, a cladding layer that is a covering member, and a covering layer. The clad layer and the cover layer are generally made of a material having a high light absorptance such as a resin-based material, and when light enters these layers, the temperature rises due to light absorption. In particular, at the incident end face of the optical fiber or in the vicinity of the incident end, when light leaks from the coupling portion of the optical fiber and light enters the cladding layer or coating layer that is the coating member, the cladding layer or coating layer on the outer periphery of the core The amount of heat generated in the optical fiber increases, which may cause problems such as deterioration in performance due to changes in physical properties of the optical fiber and thermal damage, and deterioration in safety due to combustion.

  When a low-power laser light source is adopted as a light source, such as an optical communication device, the amount of heat generated due to the light absorption is small, and no heat dissipation structure is particularly required. On the other hand, when a high-power laser light source is used as the light source, such as a laser processing apparatus, the amount of light absorption at the optical fiber incident end increases, and thus a heat dissipation structure for suppressing temperature rise is required.

  For example, Japanese Utility Model Laid-Open No. 59-38403 (Patent Document 1) includes an apparatus for cooling an optical fiber by providing a cooling fluid passage around the outer periphery of the optical fiber and flowing a cooling fluid such as water into the passage. It is disclosed. Japanese Patent Application Laid-Open No. 61-221704 (Patent Document 2) discloses a method of cooling an optical fiber by a Peltier effect provided with a semiconductor element at the end of the optical fiber.

Japanese Utility Model Publication No.59-38403 JP 61-221704 A

  Laser light sources used in illumination light source devices, image display devices, etc. are not as high in output as laser light sources used in laser processing devices, etc., but those with a relatively high output are adopted. Even at the incident end of the optical fiber to which the light is coupled, a heat dissipation structure for suppressing the temperature rise is required. However, the method including the water cooling device and the Peltier device has a problem that the device becomes complicated, and the light source device for illumination and the image display that require a simple configuration for downsizing and cost reduction of the device. It is not optimal as a heat dissipation structure for equipment.

  The present invention has been made in view of the above, and an object of the present invention is to efficiently dissipate heat at the incident end of an optical fiber with a simple configuration and enable transmission of laser light having a relatively high output. It is another object of the present invention to provide a fiber, and an illumination light source device and an image display device using the optical fiber.

An optical fiber according to the present invention includes a heat conducting member that covers a mounting start portion of the covering member of an optical fiber core wire that includes a core that confines and transmits light and a covering member that covers an outer periphery of the core, and that directly contacts the covering member. It is characterized by that.
Furthermore, in the optical fiber, the core from the mounting start portion of the cover member protrudes, mounting start portion of the incident side of light of the covering member, light spatial intensity distribution of a light beam propagated through the core is made uniform, the covering The energy density of the light beam leaking into the member is reduced, and the temperature increase of the covering member is arranged at a position within the range of the heat dissipation capability of the heat conducting member, and the heat conducting member in the length direction of the optical fiber core wire The length X of the core is longer than the length covering the first peak of the amount of light leaking from the core to the covering member, the diameter of the core of the optical fiber core wire is d, and the critical surface at the boundary surface between the core and the covering member The angle θc, the length from the incident side end surface to the mounting start portion L, and the light beam with the optical fiber allowable light receiving angle of the portion where the coating member is mounted is the first boundary between the core and the coating member On the surface When the total number of reflections in the core at the time of reflection is α, the length X of the heat conducting member is expressed by the following formula (4), and the total number of reflections α in the core is It is expressed by the following formula (5) .

  According to the present invention, an optical fiber that can transmit a light beam having a relatively high output by suppressing a temperature rise at the optical fiber incident end with a simple configuration, and an illumination light source device using the optical fiber, and An image display device can be provided.

1 is a cross-sectional view illustrating a configuration of an optical fiber illustrating a first embodiment. It is a characteristic view which shows the spatial light intensity distribution of the light which leaks to a clad. FIG. 6 is a cross-sectional view showing the configuration of an optical fiber showing a second embodiment. FIG. 6 is a cross-sectional view showing the configuration of an optical fiber showing a third embodiment. FIG. 6 is an exploded perspective view showing a configuration of an optical fiber showing a fourth embodiment. FIG. 10 is a cross-sectional view showing a configuration of an optical fiber showing a fifth embodiment. FIG. 10 is a cross-sectional view illustrating propagation of light rays in an optical fiber core according to a sixth embodiment. FIG. 10 is a cross-sectional view illustrating propagation of light rays in an optical fiber core according to a sixth embodiment.

  Hereinafter, the optical fiber according to the present invention will be described in detail. The invention is not limited to these embodiments.

Embodiment 1 FIG.
FIG. 1 is a cross-sectional view showing a configuration of an optical fiber according to Embodiment 1, and FIG. The optical fiber 14 according to the first embodiment includes an optical fiber core wire 15 and a heat conducting member 23. The optical fiber core 15 includes a core 16 made of quartz glass having a low light absorption rate, a cladding layer 17 made of fluorine-containing resin having a refractive index lower than that of quartz glass, and a coating layer 18 made of UV curable resin.

  The covering member 100 composed of the cladding layer 17 and the covering layer 18 is approximately 15 mm in the direction from the light incident end 19 of the optical fiber 14 to the light emitting end (not shown) of the optical fiber 14 which is the right direction in FIG. Removed to position. That is, the core 16 protrudes approximately 15 mm from the mounting start portion 22 of the covering member 100, and the outer periphery of the core 16 is in contact with the air layer at the core protrusion 20. In the vicinity of the mounting start portion 22 of the covering member 100, brass having high thermal conductivity and heat resistance is used as a base material, and a diameter slightly larger than the outer periphery of the optical fiber core wire 15, that is, the outer shape of the covering layer 17, is inserted at the center. A cylindrical heat conducting member 23 through which the hole passes is attached.

  The optical fiber core wire 15 is passed through the insertion hole of the heat conducting member 23, and the end 24 on the light incident side of the heat conducting member 23 is approximately 0.1 mm from the mounting start portion 22 of the covering member 100 in FIG. It is attached so as to be located on the light incident end 19 side which is the left direction. The heat conducting member 23 is in direct contact with the coating layer 18 by being deformed by external pressure. The optical fiber core wire 15 is fixed to a ferrule (not shown) at a position on the light emitting end side of the optical fiber 14 that is in the right direction in FIG. 1 from the position where the heat conducting member 23 is provided.

  As described above, the optical fiber core wire 15 of the optical fiber 14 includes the core 16 made of quartz glass, the clad layer 17 made of fluorine-containing resin, and the coating layer 18 made of UV curable resin. The optical fiber 14 is determined by the difference in refractive index between the core 16 and the cladding layer 17 by using a glass material having a high refractive index for the core 16 and a resin material having a low refractive index for the cladding layer 17. This is because the allowable light receiving angle can be increased. Moreover, in the coating layer 18 which covers the outer periphery of the cladding layer 17 and protects the surface of the cladding layer 17, UV curable resin or thermosetting resin is employed because of high manufacturability.

  In general, the clad layer 17 or the coating layer 18 that is the optical fiber coating member 100 is made of a resin material in the same manner as in the first embodiment because of the wide acceptance angle of the optical fiber and high manufacturability. Is widely used. These resin-based materials generally have a high light absorptance, and the light absorptance increases remarkably particularly for short-wavelength light. Light source devices for illumination, video display devices, and the like often use light in the visible light region from 380 nm to 780 nm, and in particular, light of 500 nm or less used for displaying blue light has a light absorptance in resin-based materials. Is expensive. In addition, these resin-based materials are poor in thermal conductivity and heat resistance, and since heat generated by light absorption is not released, the temperature becomes locally high, causing problems such as performance deterioration and damage.

  In the first embodiment, the resin member material is used for the covering member 100, but the heat generated in the covering member 100 is efficiently radiated, so that the allowable light receiving angle of the optical fiber 14 is widened and high. While realizing manufacturability, it is possible to suppress a decrease in safety due to performance deterioration or damage. Specifically, the heat conducting member 23 is provided so as to cover the mounting start portion 22 of the covering member 100 that becomes high temperature due to light leakage, and, for example, pressure is applied to the heat conducting member 23 from the outside in the direction of the white arrow in FIG. By deforming the heat conducting member 23, the covering layer 18 and the heat conducting member 23 are directly brought into close contact with each other, thereby reducing the thermal resistance between the covering member 100 serving as a heat source and the heat conducting member 23 serving as a heat radiating member.

  In addition, by attaching the heat conducting member 23, it is possible to cool by natural cooling by natural convection around the optical fiber without using a cooling fan or the like, but when the cooling effect is insufficient, positively incorporate cooling air. When the thermal conductive member 23 is sprayed and cooled, a high heat dissipation effect can be obtained efficiently.

  In the optical fiber 14 according to the first embodiment, the core 16 protrudes approximately 15 mm from the mounting start portion 22 of the covering member 100, and the outer periphery of the core 16 is in contact with the air layer at the core protruding portion 20. Even when optical coupling leakage occurs on the incident end face 19 of the optical fiber 14 due to the misalignment of the optical fiber coupling optical system, fluctuation of the laser light source, or the like due to the core protruding portion 20, the optical absorptance at the optical fiber incident end 19. Since the high coating layer 18 does not exist, the optical fiber core wire 15 can avoid damage and performance deterioration at the optical fiber incident end 19.

  However, when light exceeding the allowable light receiving angle of the optical fiber 14 is present, for example, light exceeding the allowable light receiving angle of the optical fiber 14 is incident on the optical fiber 14 or the light incident on the optical fiber 14 is scattered. Therefore, the temperature rise of the covering member 100 due to leakage of propagating light from the core 16 to the covering member 100 cannot be avoided only by removing the covering member 100 at the light incident end 19 as described above. This is because air is a substance having the lowest refractive index, and when the periphery of the core 16 made of a glass material is an air layer, the optical fiber receiving angle is 90 degrees, and light having any incident angle is used. Even if it exists, it can propagate in the core 16.

  On the other hand, in the part provided with the covering member 100 around the core 16, the optical fiber allowable light receiving angle determined by the difference in refractive index between the core 16 and the covering member 100 is an optical fiber determined by the difference in refractive index between the core 16 and the air layer. It becomes smaller than the permissible acceptance angle. Accordingly, light exceeding the allowable light receiving angle of the optical fiber 14 due to scattering or the like propagates without being attenuated in the core projecting portion 20 and leaks out of the core 16 when reaching the mounting start portion 22 of the covering member 100. Therefore, the temperature rise at the mounting start portion 22 of the covering member 100 is significantly generated.

  FIG. 2 shows the result of simulating the intensity distribution of light leaking into the cladding layer 17 outside the core 11 when light having an incident angle larger than the optical fiber allowable acceptance angle is incident on the optical fiber. Here, FIG. 2A shows a two-dimensional spatial light intensity distribution of light leaking into the clad layer 17, the horizontal axis is the distance from the clad layer mounting start portion 13, and its scale is 0.2 mm. is there. FIG. 2B shows a one-dimensional light intensity distribution, where the horizontal axis is the distance from the cladding layer mounting start portion 13 and the scale is 0.2 mm. The vertical axis represents the light intensity, but the purpose of this simulation is to confirm only the tendency of the light intensity distribution, so the unit is arbitrary.

  In this simulation, light 10 having an outermost shell light incident angle of 30 degrees is made incident on an optical fiber 9 having a numerical aperture of 0.45 (allowable light receiving angle half angle of 26.7 degrees). The light source 10 was a uniform light source having a uniform spatial light intensity distribution and angular light intensity distribution. A core having a refractive index of 1.50 is surrounded by an air layer having a refractive index of 1.00 up to a position of 15 mm from the optical fiber incident end, and a clad having a refractive index of 1.43 is provided on the outer periphery of the core 11 after 15 mm. Layer 12 is attached.

  As is apparent from FIG. 2, every time the light having an optical fiber allowable acceptance angle or more is reflected at the interface between the core 11 and the cladding layer 12, a part of the light leaks into the cladding layer 12, and in particular, the cladding layer. In the vicinity of the twelve attachment start portions 13, the amount of leaked light is significantly large. In FIG. 2, the optical fiber 9 corresponds to the optical fiber core wire 15 described in FIG.

  From FIG. 2 (b), it can be seen that the intensity of light leaking most in the range from 0.5 mm to 1.4 mm from the mounting start portion 13 of the cladding layer 12 is high. From this, when the temperature rise of the cladding layer 12 is estimated, the position and the edge of the coating layer adjacent to the position are peaked at a portion where the light intensity in the range from 0.5 mm to 1.4 mm is high from the cladding layer mounting start portion 13. It is considered that heat is transmitted to the portion 13 and the temperature is sufficiently high. In the simulation conditions of FIG. 2, there is no light incident on the coated end 13, but there may be light incident at a position closer to the coated end 13, for example, when the incident angle of light is larger. Then, heat will be generated at that part.

  Also from this, by covering the covering end portion 13 with the heat conducting member 23, it is possible to suppress thermal damage and performance deterioration due to a temperature rise in the mounting start portion of the covering member 100 including the covering end portion 13. In FIG. 1, the heat conducting member 23 has a certain length in the axial direction of the optical fiber 9, which is the left-right direction in FIG. 1, but the length is at least the first light intensity in FIG. It is formed so as to cover the peak range.

  Based on the above reason, the optical fiber 14 according to the first embodiment covers the mounting start portion of the covering member 100 including the mounting start portion 22 of the covering member 100 with the heat conducting member 23, and the covering member 100 in which the temperature rise is remarkably generated. The mounting start portion and the heat conducting member 23 are in direct contact with each other. The heat generated at the mounting start portion of the covering member 100 is transmitted to the heat conducting member 23, and the heat conducting member 23 cools the covering member 100 by natural cooling by heat exchange with the air around the heat conducting member 23. According to this configuration, since the mounting start portion of the covering member 100 including the mounting start portion 22 of the covering member 100 serving as a heat source and the heat conducting member 23 are in direct contact with each other, the thermal resistance therebetween is reduced, and an efficient heat dissipation action is achieved. can get.

  In addition, since the heat conducting member 23 is deformed by applying pressure from the outside, the covering member 100 serving as a heat source and the heat conducting member 23 are in contact with each other without any gap, so that the thermal resistance between them is reduced and a high heat radiation effect is obtained. Can do.

  As a method of deforming the heat conducting member 23, for example, a method of making a cylindrical heat conducting member 23 with a notch parallel to the axis from one end and bending the other end without the notch as a cantilever is used. Conceivable. In this case, the outer diameter of the cylindrical shape is a shape having an inclination that gradually decreases from an end surface without cut to an end surface with cut. On the other hand, a cylindrical sleeve member having an inclined inner diameter corresponding to the inclination is inserted outside the heat conducting member 23 from the axial direction of the end portion where the heat conducting member 23 is cut. As a result, the end portion of the heat conducting member 23 with the incision is bent toward the inner diameter side by the inner wall having the slope of the sleeve member, and comes into close contact with the coating layer 18 of the optical fiber core wire 15.

  The optical fiber 14 according to the first embodiment is configured such that the light incident side end 24 of the heat conducting member 23 is attached to the light incident side 0.1 mm from the mounting start portion 22 of the covering member 100. It is not limited to this. In order to enhance the heat dissipation effect at the mounting start portion of the covering member 100 including the mounting start portion 22 of the covering member 100 where the temperature rise is most remarkable, the mounting start portion of the covering member 100 including the mounting start portion 22 of the covering member 100 and heat Any configuration that reduces the thermal resistance between the conductive member 23 and the end surface 19 of the light incident side of the heat conductive member 23 is always on the same plane as the end surface of the mounting start portion 22 of the covering member 100. Alternatively, it may be positioned closer to the light incident end 19 side of the optical fiber 14 than the mounting start portion 22. However, in consideration of simplification of the manufacturing process, it is desirable that the light incident side end portion 24 of the heat conducting member 23 is disposed on the light incident side from about 0.1 mm to 1 mm from the mounting start portion 22 of the covering member 100. .

  In the optical fiber 14 according to the first embodiment, the core 16 protrudes approximately 15 mm from the mounting start portion 22 of the covering member 100, and the outer periphery of the core 16 is in contact with the air layer at the core protruding portion 20. It is not limited to this. It is important to obtain a high heat conduction effect and heat dissipation effect by always bringing the heat conducting member 23 into contact with the mounting start portion of the covering member 100 including the mounting start portion 22 of the covering member 100 where the temperature rise is most noticeable.

  If this configuration is achieved, a great effect can be obtained regardless of the length of the core projecting portion 20, but the mounting start portion 22 of the covering member 100 is shifted rearward on the right side in FIG. 1 to lengthen the core projecting portion 20. As a result, the light leaks from the mounting start portion 22 of the covering member 100 to the covering member 100 after the spatial intensity distribution of the light propagated in the optical fiber 14 is made uniform, so that the energy density of the leaked light is reduced. It becomes possible to prevent the temperature from becoming high locally.

  Therefore, it is desirable to place the mounting start portion 22 of the cladding layer 17 and the coating layer 18 as the coating member 100 as far from the optical fiber incident end 19 as possible. In this way, by providing the core projecting portion 20 and providing the heat conducting member 23 at the mounting start portion 22 of the covering member 100, the temperature rise of the optical fiber 14 can be further suppressed. In this case, the fixing of the optical fiber formed at the portion where the covering member 100 is attached is also performed at a position away from the optical fiber incident end 19, so that the configuration is It is also necessary to consider the influence on position accuracy and strength.

  The position of the light incident side end portion 24 for determining the length of the heat conducting member 23 is determined from the position of the covering member mounting start portion 22. On the other hand, the position of the light emitting end side end 2A is such that at least light incident on the optical fiber 14 at an angle equal to or larger than the allowable light receiving angle of the optical fiber 14 is behind the mounting start portion 22 of the covering member 100, that is, in FIG. It is necessary to be behind the first reflecting position in the light emitting end side direction of the right optical fiber 14. Accordingly, the amount of light leaking out of the core 16 is remarkably large, and the portion of the covering member 100 that generates a large amount of heat thereby is always in contact with the heat conducting member 23, so that the heat radiation action is efficiently performed.

  As described above, the optical fiber 14 according to the first embodiment removes the vicinity of the light incident end 19 of the cladding layer 17 or the coating layer 18 that is the coating member 100 of the optical fiber core wire 15 and attaches the coating member 100. By covering the start portion 22 with a heat conducting member 23 and applying a pressure to the heat conducting member 23 from outside to deform the heat conducting member 23, the heat conducting member 23 and the covering member 100 are brought into direct contact with each other. A high heat dissipation effect can be obtained and the temperature rise at the optical fiber incident end can be suppressed. As a result, an illumination light source device and an image display device using an optical fiber can be provided.

Embodiment 2. FIG.
The optical fiber 25 according to the second embodiment includes a heat conducting member 33, an optical fiber core wire 26, a core 27 made of quartz glass having a low light absorption rate, and a clad layer 28 made of a fluorine-containing resin having a refractive index lower than that of the quartz glass. Has been. FIG. 3 is a cross-sectional view showing a configuration of the optical fiber 25 in the second embodiment.

  The cladding layer 28 as a covering member is removed from the light incident end 29 of the optical fiber 25 to a position 10 mm behind, and the core 27 protrudes, and the outer periphery of the core 27 is in contact with the air layer at the core protrusion 30. In the vicinity of the mounting start portion 32 of the clad layer 28, a cylindrical heat conductive member 33 that uses brass having high thermal conductivity as a base material and covers the outer periphery of the optical fiber core 26 is provided on the light incident side of the heat conductive member 33. The end portion 34 is provided so as to be positioned on the light incident end 29 side on the left side in FIG. 3 by about 0.1 mm to 1 mm from the mounting start portion 32 of the cladding layer 28. The heat conducting member 33 is pressed against the clad layer 28 by applying pressure from the outside and deformed so that the heat conducting member 33 and the clad layer 28 are brought into close contact with each other. The optical fiber core 26 is fixed to a ferrule (not shown) at the rear, which is the right side in FIG. 3 from the position where the heat conducting member 33 is provided.

  As described above, the optical fiber 25 of the second embodiment can obtain the same heat dissipation effect as that of the first embodiment. In the second embodiment, since the thermal resistance between the clad layer 28 and the heat conducting member 33 is very small because it is in direct contact with the clad layer 28 serving as a heat source, a high heat conduction effect is exerted on the clad layer 28. In addition, a heat dissipation effect can be obtained. Thereby, it is possible to obtain a high heat dissipation effect with a simple configuration and suppress an increase in temperature of the optical fiber incident end, and to provide an illumination light source device and an image display device using the optical fiber.

Embodiment 3
In the third embodiment, a case where a triangular protrusion 440 is provided on the inner surface portion of the heat conducting member 44 is shown. FIG. 4 is a cross-sectional view showing the configuration of the optical fiber 35 in the third embodiment.

  The optical fiber 35 according to the third embodiment includes a core 37 made of quartz glass whose optical fiber core wire 36 has a low light absorption rate, a clad layer 38 made of fluorine-containing resin having a refractive index lower than that of quartz glass, and a coating made of UV curable resin. The layer 39 is composed. The cladding layer 38 and the coating layer 39 which are the coating members 300 are removed from the light incident end 40 of the optical fiber 35 to a rear position on the right side in FIG. The core 37 protrudes from the covering member 300, and the outer periphery of the core 37 is in contact with the air layer at the core protrusion 41.

  In the vicinity of the mounting start portion 43 of the clad layer 38 and the covering layer 39, a heat conductive member 44 is used which covers the outer peripheral surface of the optical fiber core wire 36 and is made of brass having a high thermal conductivity as a base material. . The heat conducting member 44 has a triangular protrusion 440 on the inner surface. The light incident side end 45 of the heat conducting member 44 is located on the light incident side which is about 0.1 mm to 1 mm from the mounting start portion 43 of the covering member 300 on the left side in FIG. The heat conducting member 44 is pressed against the covering layer 39 by applying pressure from the outside and deformed to bring the heat conducting member 44 and the covering layer 39 into close contact. The optical fiber core 36 is fixed to a ferrule (not shown) behind the position where the heat conducting member 44 is provided.

  According to the optical fiber 35 of the third embodiment, as described in the first embodiment, the light leaks from the core 37 in the vicinity of the mounting start portion 43 of the covering member 300 having a high light absorption rate. At 300, a temperature rise due to light absorption occurs. However, the heat conduction member 44 is provided so as to cover the attachment start portion of the covering member 300 including the attachment start portion 43 of the covering member 300, and the heat conduction member 44 is deformed by applying pressure from the outside to deform the heat conduction member 44. The member 44 is directly adhered.

  Thereby, the thermal resistance between the covering member 300 as a heat source and the heat conducting member 44 as a heat radiating member is reduced, and the heat conducting member 44 cools the covering member 300 by natural cooling by heat exchange with the surrounding air. The configuration. The heat conducting member 44 can suppress an increase in the temperature of the covering member 300 due to an efficient and high heat dissipation effect, avoid performance deterioration of the optical fiber, and improve reliability. In particular, since the heat conducting member 44 of the third embodiment has the protrusions 440 on the surface in contact with the coating layer 39, the surface area in contact with the coating layer 39 is increased, a higher heat dissipation effect is obtained, and further temperature rise suppression capability Have

  As described above, it is possible to obtain a high heat dissipation effect with a simple configuration and suppress an increase in the temperature of the optical fiber incident end, and to provide an illumination light source device and an image display device using the optical fiber.

  In addition, although the heat conductive member 44 of this Embodiment 3 has comprised the triangular protrusion shape extended in the circumferential direction of a cylindrical shape, this invention is not limited to this. The protrusion shape may be, for example, a triangular protrusion shape extending in the axial direction that is the length direction of the cylindrical shape, or a shape that increases the surface area in contact with the coating layer 39, such as a wave shape or a rectangular shape, instead of a triangle. Any shape is acceptable.

Embodiment 4
In the fourth embodiment, the case where the two heat conducting members 52a and 52b sandwich the coating layer 50 of the optical fiber core wire 47 is shown. FIG. 5 is a perspective exploded view showing the configuration of the optical fiber 46 in the fourth embodiment.

  The optical fiber 46 according to the fourth embodiment is composed of heat conducting members 52 a and 52 b and an optical fiber core wire 47 including a core 48 and a coating layer 50. The core 48 is made of quartz glass having a low light absorption rate, the cladding layer 49 is made of a fluorine-containing resin having a refractive index lower than that of the quartz glass, and the coating layer 50 is made of a UV curable resin having a refractive index lower than that of the quartz glass.

  In the vicinity of the mounting start portion 51 of the covering member 400 composed of the cladding layer 49 and the covering layer 50, there are provided heat conducting members 52a and 52b whose base material is brass having high thermal conductivity. The light incident side end portions 53a and 53b of the heat conducting members 52a and 52b are provided so as to be positioned on the light incident side which is about 0.1 mm to 1 mm from the mounting start portion 51 of the covering member 400 on the left side in FIG. The heat conducting members 52 a and 52 b have groove portions 520 a and 520 b having a diameter slightly smaller than the outer diameter of the optical fiber core wire 47. The optical fiber core 47 is fixed to a ferrule (not shown) at the rear on the right side in FIG. 5 from the position where the heat conducting members 52a and 52b are provided.

  The heat conductive members 52a and 52b, which are plate-shaped members, are linearly shaped in a one-dimensional direction with a semicircular cross section having a diameter slightly smaller than the outer diameter of the optical fiber core wire 47 on the surface facing the optical fiber core wire 47. Groove portions 520a and 520b extending in the vertical direction. The optical fiber core 47 has semi-circular groove portions 520a and 520b of the heat conducting members 52a and 52b, and the mounting start portion 51 of the covering member 400 is more than the light incident side end portions 53a and 53b of the heat conducting members 52a and 52b. About 0.1 mm to 1 mm are arranged so as to be positioned on the optical fiber emitting end side (not shown) on the right side in FIG. The heat conducting members 52a and 52b are connected and fixed by screws. As a result, the groove portions 520a and 520b of the heat conducting members 52a and 52b compress the coating layer 50 of the optical fiber core wire 47 and are in direct contact with the optical fiber coating layer 50.

  On the light incident end side on the left side in FIG. 5 of the optical fiber 46 according to the fourth embodiment, light is emitted from the core 48 at the mounting start portion of the covering member 400 including the mounting start portion 51 of the covering member 400 having a high light absorption rate. Leaks out. Although light is absorbed and heat is generated in the covering member 400, since the covering layer 47 is in close contact with the heat conducting members 52a and 52b having high thermal conductivity, temperature rise in the cladding layer 49 and the covering layer 50 is suppressed. As a result, performance degradation of the optical fiber can be avoided and reliability can be improved.

  As described above, it is possible to obtain a high heat dissipation effect with a simple configuration and suppress an increase in the temperature of the optical fiber incident end, and to provide an illumination light source device and an image display device using the optical fiber.

Embodiment 5 FIG.
In the fifth embodiment, the case where the heat conducting member is integral with the ferrule is shown. FIG. 6 is a cross-sectional view showing the configuration of the optical fiber 55 in the fifth embodiment.

  The optical fiber 55 according to the fifth embodiment includes a ferrule having a function of a heat conducting member and an optical fiber core wire 56 including a core 57 and a clad layer 58. The core 57 is made of quartz glass having a low light absorption rate, and the covering member 500 is composed of a cladding layer 58 made of a fluorine-containing resin having a refractive index lower than that of quartz glass and a covering layer 59 made of a UV curable resin.

  The covering member 500 composed of the cladding layer 58 and the covering layer 59 of the optical fiber core wire 56 is removed from the light incident end 60 by about 10 mm to the rear position on the right side in FIG. 6, and the core 57 protrudes from the covering member 500. . The inner diameter of the ferrule 63 is larger than the diameter of the core 57, and the outer periphery of the core 57 is in contact with the air layer at the core protrusion 61.

  The optical fiber core 56 is passed through a brass ferrule 63 having a through hole having an inner diameter larger than the diameter of the optical fiber core 56. The ferrule 63 and the coating layer 59 are brought into close contact with each other by compressing the portion 65 of the ferrule 63 corresponding to the mounting start portion of the covering member 500 including the cladding layer 58 and the mounting start portion 64 of the coating layer 59 from the outside. At this time, the light incident side position 66 of the ferrule compression part 65 is located on the light incident side which is about 0.1 mm to 1 mm from the attachment start part 64 of the cladding layer 58 and the coating layer 59 on the left side in FIG.

  In the optical fiber 55 of the fifth embodiment, in addition to the function of fixing the optical fiber core wire 56 to the ferrule 63, the ferrule 63, which is a member having high thermal conductivity, is light-absorbed as in the first to fourth embodiments. It adheres to the covering member 500 with a high rate. The ferrule 63 cools the covering member 500 by natural cooling by heat exchange with the surrounding air. As a result, a temperature rise suppressing function due to a high heat dissipation effect can be added to the ferrule 63, and with a small number of components, it is possible to avoid performance degradation of the optical fiber and improve reliability.

  As described above, it is possible to obtain a high heat dissipation effect with a simple configuration and suppress an increase in the temperature of the optical fiber incident end, and to provide an illumination light source device and an image display device using the optical fiber.

  In the first to fifth embodiments, quartz glass is used for the core, fluorine-containing resin is used for the cladding, and UV curable resin is used for the coating. However, the present invention is not limited to this. If a material having a low light absorption rate is used as the core material and a material having a refractive index that realizes the required optical fiber allowable acceptance angle is used as the cladding material, any material can be used as long as there is no problem in manufacturing. It may be adopted. At this time, when using, for example, doped glass having a low light absorptivity and a refractive index lower than that of the core material as a cladding material, a member having high thermal conductivity is in close contact with the mounting start portion of the coating having a high light absorptance. By adopting such a configuration, it is possible to avoid deterioration of the performance of the optical fiber due to temperature rise and improve reliability.

  In the first to fifth embodiments, the light incident side end of the heat conducting member is arranged on the light incident side by about 0.1 mm to 1 mm from the cladding layer or the coating layer start portion of the coating layer. However, the present invention is not limited to this. In order to enhance the heat dissipation effect at the mounting start portion of the covering member where the temperature rise is most remarkable, it is important to reduce the thermal resistance between the mounting start portion of the covering member and the heat conducting member. The incident side end portion may be on the same plane as the covering member mounting start portion, or may be positioned closer to the light incident end side of the optical fiber than the covering member mounting start portion. However, in consideration of simplification of the manufacturing process with respect to assembly variations, it is desirable that the light incident side end portion of the heat conducting member be disposed about 0.1 mm to 1 mm from the mounting start portion of the covering member on the light incident side.

  In the first to fifth embodiments, the heat conductive member and the ferrule base material are brass, but the present invention is not limited to this. You may employ | adopt the other member with high heat conductivity which consists of iron, aluminum, stainless steel, etc. In order to improve heat dissipation, it is effective to provide heat dissipation fins.

  In the first to fifth embodiments, the mounting start portion of the clad layer or the coating layer is set to a position about 10 mm or 15 mm behind the optical fiber incident end, but the present invention is not limited to this. As described above, it is important that the temperature rise occurs most markedly in the cladding layer or the covering layer at the mounting start portion thereof, so that the portion is always covered and closely adhered to the heat conducting member. If this configuration is achieved, a great effect can be obtained regardless of the position of the mounting start portion of the covering member.

  However, damage to the optical fiber incident end surface can be avoided by shifting the mounting start portion of the covering member rearward to increase the length of the core protruding portion. In addition, since the light propagated in the optical fiber reaches the mounting position of the covering member after the spatial intensity distribution is made uniform, the light energy density at the mounting start portion of the covering member becomes small, and light leaks out of the core. By taking out, it becomes possible to prevent the coating member from being locally heated. Therefore, it is desirable to place the cladding layer, which is a coating member, or the mounting start portion of the coating layer as far as possible from the optical fiber incident end. In this case, the fixing of the optical fiber formed at the portion where the cladding layer or the coating layer as the coating member is attached is also performed at a position away from the optical fiber incident end. It is also necessary to consider the influence on the positional accuracy and strength of the optical fiber tip.

Embodiment 6 FIG.
In the sixth embodiment, the length necessary for the heat conducting member 23 will be described. 7 and 8 are cross-sectional views of the optical fiber core wire 15 and show the propagation of the light beam 10 a in the core 11. In addition, in order to make it easy to understand the propagation of the light beam 10 a in the core 11, a parallel oblique line is not drawn on the cut surface of the core 11. The covering member is a clad layer 12 in direct contact with the core 11.

  The light beam 10a is refracted at the optical fiber incident end 19 according to Snell's law. Thereafter, the light is totally reflected on the wall surface of the core 11 and proceeds. However, when the covering member enters the portion that covers the core 11, the difference in refractive index between the core 11 and the covering member becomes smaller than the difference in refractive index between the core 11 and air, so that the light beam 10a has a reflection angle smaller than the total reflection angle. Advances toward the covering member, and the light beam 10a leaks out of the core 11.

  Here, the allowable light receiving angle of the optical fiber core wire 15 is θmax, the critical angle at the interface between the core 11 and the cladding layer 12 is θc, the diameter of the core 11 of the optical fiber core wire 15 is d, and the refractive index of the cladding layer 12 is nc. , The refractive index of the core 11 is ng, the length of the core protruding portion 20 from which the cladding layer 12 is removed is L, and the light beam 10a having the optical fiber allowable light receiving angle θmax from the optical fiber incident end 19 is the first time between the core 11 and the cladding layer 12. The length from the coating member mounting start portion 22 to the position where the light beam 10a having the optical fiber allowable light receiving angle θmax is incident on the boundary surface between the core 11 and the cladding layer 12 for the first time is represented by X. In the portion where the cladding layer 12 is mounted, the core 11 when the light beam 10a having the optical fiber allowable light receiving angle θmax is reflected at the boundary surface between the core 11 and the cladding layer 12 for the first time. If the total number of reflections is α, the critical angle θc at the interface between the core 11 and the cladding layer 12 is expressed by the following equation (1). The allowable acceptance angle of the optical fiber refers to the maximum angle that can propagate in the optical fiber among the angles formed by the normal line of the incident end surface and the light beam at the optical coupling portion to the incident end surface of the optical fiber. It is uniquely determined by the ratio of the refractive index to the cladding layer. The angular intensity distribution of the laser light generally has a shape with a high center intensity and an exponential intensity decreasing as the angle becomes wide, but has a slight intensity even at a wide angle. When such laser light is incident on an optical fiber, it is practically difficult to put all the light beams of the angular intensity distribution of the laser light within the optical fiber allowable light receiving angle θmax. The light enters the optical fiber as light exceeding the allowable light receiving angle θmax of the optical fiber. Since these lights exceed the critical angle θc, they leak into the cladding layer 12. Taking these into consideration, it can be seen that it is practical and effective to cover the optical fiber allowable light receiving angle θmax to the position where it is first reflected by the cladding layer 12 with the heat conducting member 23.

  The optical fiber allowable light receiving angle θmax is expressed by the following equation (2).

  The length a from the optical fiber incident end 19 to the position at which the light beam 10a having the allowable acceptance angle θmax of the optical fiber is incident on the boundary surface between the core 11 and the clad layer 12 for the first time is expressed by the following equation (3).

  The length X from the covering member mounting start portion 22 to the position at which the light beam 10a having the optical fiber allowable light receiving angle θmax first enters the boundary surface between the core 11 and the cladding layer 12 is the difference between the length a and the length L. Therefore, the length X is expressed by the following formula (4).

  However, the total number of reflections α in the core 11 when the light beam 10a having the optical fiber allowable light receiving angle θmax of the portion where the coating layer 18 is mounted is reflected at the boundary surface between the core 11 and the cladding layer 12 for the first time is It is an integer satisfying the formula (5).

  From the above, it can be seen that the position where the light beam 10a first leaks to the cladding layer 12 is from the covering member mounting start portion 22 to the position of the length X represented by the formula (4). On the other hand, the amount of the light beam 10a leaking into the cladding layer 12 is the case where the light beam 10a first enters the boundary surface between the core 11 and the cladding layer 12, so the length of the heat conducting member 23 is the total number of reflections. It is necessary that α is larger than the length X obtained by Equation (4) in the case of Equation (5).

  Next, a case where a light beam is incident at an angle exceeding the angular intensity distribution of the laser beam described above due to scattering or the like will be considered. That is, an equation for always covering the position where the light that greatly exceeds the permissible light receiving angle θmax may first enter the coating layer with the heat conducting member 23 is examined.

  As described above, the angular intensity distribution of laser light generally has a shape in which the central intensity is high and the intensity decreases exponentially as the angle is widened. ing. In the coupling optical system, light existing in this wide angle range exists as light exceeding the allowable light receiving angle θmax of the fiber.

  The length X is obtained as shown in FIG. After the light is reflected at a position immediately before the covering member mounting start portion 22, an incident angle at which the light exceeds the critical angle θc is defined as an incident angle θs. That is, the range of the incident angle θs is 0 ° ≦ θs <θc. When the incident angle θs is incident on the interface between the core 11 and the cladding layer 12, the light having the incident angle θs is the rearmost position where the incident light can enter the cladding layer 12. The rear indicates the right side in FIG.

  Therefore, in order to always cover the entire range in which light can first enter the clad layer 12 with the heat conducting member 23, the position of the rear end face of the heat conducting member 23 is the allowable light receiving angle θmax of the optical fiber core wire 15. After the light is reflected at a position immediately before the covering member mounting start portion 22, it is necessary to be behind the position where the light enters the cladding layer 12. That is, the length X of the clad layer 12 that is a covering member covered with the heat conducting member 23 is expressed by the following formula (6).

  It should be noted that, in the case of the expressions (3) to (5), it is a condition that can suppress heat generation due to absorption of light slightly overflowing in the angular intensity distribution of the laser light by the coating, In designing a product, it is close to the case where light is incident on the optical fiber in a range slightly narrower than the allowable acceptance angle θmax of the optical fiber. Further, depending on the combination of the allowable light receiving angle θmax of the optical fiber core wire 15 and the covering member mounting start position 22, there is an advantage that the portion where the heat conducting member 23 is brought into close contact with the optical fiber core wire 15 can be reduced.

  On the other hand, in the case of the formula (6), the required length X of the heat conducting member 23 is longer than the case shown in the formulas (3) to (5). However, since there is a possibility that light exceeding the allowable light receiving angle θmax may exist due to light scattering or the like, it is possible to cool the coating layer more reliably by providing the heat conducting member 23 based on the equation (6). .

  As a result, the optical fiber can efficiently dissipate the incident end of the optical fiber without using a complicated cooling structure, and can transmit a laser beam having a relatively high output with a simple configuration. An illumination light source device and an image display device using a fiber can be provided.

  By coupling light radiated from a light source such as a laser light source to the optical fiber shown in the first to fifth embodiments and confining it in the transmission, it is possible to provide a relatively high output with a simple configuration. A light source device. Further, by providing the light source device with an illumination optical system, a projection optical system, and a screen, it is possible to provide an illumination light source device or an image display device that has a simple configuration and excellent reliability. Even when a high output is required as a light source of a large-screen video display device, it is possible to provide a large-screen video display device with high brightness and compactness by mounting a plurality of light source devices of the present invention.

The optical fiber of the present invention is effective for devices that require relatively high output laser light, in addition to the illumination light source device and the video display device. For example, it can be used as a light source device such as a laser microscope, a laser measuring device, a laser processing machine, photolithography, or solid laser excitation.

  As described above, the optical fiber according to the present invention covers the mounting start portion of the covering member having a high light absorption rate that can serve as a heat source with a member having high heat conductivity, and the covering member serving as the heat source and the heat conducting member serving as the heat radiating member. With a simple configuration in which the optical fiber is directly adhered, it is possible to solve the problems of optical fiber performance degradation and safety degradation caused by temperature rise caused by light absorption.

  10 luminous flux, 10a light beam, 11, 16, 27, 37, 48, 57 core, 12, 17, 28, 38, 49, 58 cladding layer, 13, 32 cladding layer mounting start portion, 9, 14, 25, 35, 46,55 Optical fiber, 15, 26, 36, 47, 56 Optical fiber core wire, 18, 21, 39, 50, 59 Cover layer, 19, 29, 40, 60 Optical fiber incident end, 20, 30, 41, 61 Core protrusion, 22, 43, 51, 64 covering member mounting start part, 23, 33, 44, 52a, 52b heat conducting member, 24, 34, 45, 53a, 53b light incident side end of heat conducting member, 2A Light emitting end side end, 100, 300, 400, 500 Cover member, 520a, 520b Groove portion of heat conducting member, 5A screw, 63 ferrule, 65 ferrule Le compression unit, 66 light incident side position of the ferrule compression unit.

Claims (7)

An optical fiber core wire having a core for confining and transmitting a light beam and a covering member covering the outer periphery of the core;
A heat conducting member that covers the mounting start portion of the light incident side of the covering member and is in direct contact with the covering member;
The core protrudes from the mounting start portion of the covering member,
The mounting start part on the light incident side of the covering member is:
The light space intensity distribution of the light beam propagated in the core is made uniform, the energy density of the light beam leaking to the covering member is reduced, and the temperature rise of the covering member is within the range of the heat dissipation capability of the heat conducting member. Placed in the position,
The length X of the heat conducting member in the length direction of the optical fiber core wire is longer than the length covering the first peak of the amount of light leaking from the core to the covering member,
The diameter of the core of the optical fiber core wire is d, the critical angle at the interface between the core and the covering member is θc, the length from the incident-side end surface to the mounting start portion is L, and the covering member is attached When the total number of reflections in the core when the light beam having the permissible acceptance angle of the optical fiber is reflected on the boundary surface between the core and the covering member for the first time is α, the length of the heat conducting member X is

Represented by the formula
The total number of reflections α in the core is

An optical fiber represented by the formula   The optical fiber according to claim 1, wherein the covering member is a clad layer or a clad layer and a cover layer.   3. The optical fiber according to claim 1, wherein the heat conducting member is in direct contact with the covering member by being deformed by an external pressure. 4. 4. The optical fiber according to claim 1, further comprising a protrusion on a surface of the heat conducting member that contacts the covering member. 5.   The optical fiber according to any one of claims 1 to 4, wherein the heat conducting member has a function of fixing the optical fiber core wire.   An illumination light source device comprising the optical fiber according to any one of claims 1 to 5.   An image display device comprising the illumination light source device according to claim 6.

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