JP2007102058A - Light guide structure for laser beam - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To uniformly distribute intensity of a laser beam in an output end face of an optical fiber, to surely guide a laser beam while contriving reduction of an optical fiber diameter, and to reliably output a laser beam from the output end face of the optical fiber. <P>SOLUTION: In a laser beam guiding structure in which a laser beam output from a laser beam oscillation member is guided to required places with an optical fiber, the optical fiber is made a polygonal optical fiber for which at least a cross section orthogonal to the longitudinal direction of the core is made polygonal and for which the optical fiber is twisted with a required reed for the formation. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  In the present invention, laser light oscillated from a laser oscillating member such as a laser diode (hereinafter referred to as LD), a carbon dioxide laser oscillator, a YAG laser oscillator, or the like is guided to a desired location by an optical fiber and irradiated to the desired location. The present invention relates to a laser light guide structure.

  For example, in a laser processing machine that welds or quenches workpieces using laser light, laser light oscillated from a number of LDs is output to the workpiece by means of an optical fiber, such as a YAG laser. The light is guided to an oscillator or the like, and this is used as an excitation light source to output a high-power laser beam.

  However, when the light is guided while reflecting the laser beam to the inner peripheral surface of the optical fiber, there is a problem that the light intensity distribution of the laser light on the output end surface tends to be uneven at the output end of the optical fiber. . If laser light output in such a state where the light intensity distribution is non-uniform is used as an excitation light source for a high-power laser oscillator, there is a problem that laser light cannot be reliably output from the high-power laser oscillator. As a result, when the workpiece is welded or quenched by the processing machine, heating unevenness occurs, causing a processing defect.

  In order to solve the above-described conventional drawbacks, an optical fiber is spirally wound around the core material, or laser light from the optical fiber is guided in a hollow or hollow kaleidoscope as disclosed in Patent Document 1, for example. Thus, the light intensity distribution of the laser light on the output end face of the optical fiber can be made uniform.

However, the former has a problem that the diameter of the optical fiber is increased by requiring a core material. In the latter case, the laser beam guided in the kaleidoscope is totally reflected on the output end side of the optical fiber and returns to the incident side, so that the laser beam cannot be output to the workpiece with a desired light intensity. have.
JP-A-5-45606

The problem to be solved is that the light intensity of the laser light at the output end face of the optical fiber becomes non-uniform. This is in the point that the diameter of the optical fiber is increased. The laser light cannot be reliably output from the output end face of the optical fiber.

The present invention relates to a laser light guide structure that guides laser light output from a laser light oscillation member to a required location by an optical fiber. The optical fiber has a polygonal shape at least in a cross section in the longitudinal direction of a core portion and a required lead. It is characterized by being a polygonal optical fiber that is twisted and formed.

The present invention makes the light intensity of the laser light uniform at the output end face of the optical fiber. In addition, the laser light is reliably guided while reducing the diameter of the optical fiber. Furthermore, laser light is reliably output from the output end face of the optical fiber.

The best mode of the present invention is that the optical fiber is formed into a polygonal shape at least in the longitudinal cross section in the longitudinal direction of the core portion and twisted with a required lead.

The present invention will be described below with reference to the drawings showing embodiments.
First, the outline of the optical system of the laser beam will be described. As shown in FIG. 1, the LD 1 as the laser beam oscillation member is arranged so that the incident end face of the polygonal optical fiber 3 faces each other. The polygonal optical fiber 3 has a required diameter in a length from the LD 1 to a laser oscillator 7 such as a YAG laser oscillator, which is mounted on a processing machine (not shown) for welding or quenching a workpiece, for example. On the output end side, an optical lens 5 is arranged for narrowing the laser beam to a desired spot diameter. On the emission side of the optical lens 5, there is provided a laser oscillator 7 that uses the laser light from the LD 1 as an excitation light source and outputs a high-power laser light.

  As shown in FIG. 2, the polygonal optical fiber 3 is coated on the outer peripheral side of the core portion 3a and the core portion 3a for guiding the laser light as is conventionally known, and has a higher refractive index than the core portion 3a (see FIG. 2). Among them, at least the core portion 3a has a cross section in the longitudinal orthogonal direction of a regular polygonal shape such as a triangle, a quadrangle, a pentagon, or an irregular polygonal shape. In addition, the core part 3a of the polygonal optical fiber 3 may have a corner or a chamfered outer corner.

  The polygonal optical fiber 3 is twisted with a lead that rotates once in the clockwise direction or in the counterclockwise direction every predetermined length of the cross-sectional width in the longitudinal orthogonal direction of the core portion 3a. The twist lead of the polygonal optical fiber 3 is appropriately set according to the cross-sectional width (thickness) in the longitudinal direction of the core portion 3a, the material of the optical fiber, and the like. Further, as the twisting mode of the polygonal optical fiber 3, as shown in FIG. 3, the twisted portion 3b and the straight portion 3c are alternately formed (in this mode, the twisted portion 3b is twisted via the straight portion 3c). The direction may be either the same direction or the opposite direction.) As shown in FIG. 4, the twisted part 3b and the reverse twisted part 3d twisted in the opposite direction to the twisted part 3b are alternately formed. Thus, it may be formed in a twisted shape as a whole.

Next, the light guide action of laser light by the polygonal optical fiber 3 will be described.
The laser light oscillated from the LD 1 is guided to the output end side while being totally reflected by the inner surface of the core portion 3a of the incident polygonal optical fiber 3, and then converged to a required spot diameter by the optical lens 5. Irradiated on the workpiece. As a result, the workpiece is subjected to, for example, welding or quenching by the heat of the irradiated laser beam.

  When the laser light is guided by the polygonal optical fiber 3, the laser light is guided to the output end side while being reflected by each inner surface of the core portion 3a having a polygonal cross section. At this time, since each reflection surface of the core portion 3a is a twisted surface, the reflection angle of the laser beam is less than the critical angle so that the light intensity of the laser beam at the output end surface is almost uniformly distributed. The light is guided to the output end side with total reflection at random.

  As described above, laser light having a substantially uniform distribution of light intensity is output from the output end face of the polygonal optical fiber 3. The output laser light is irradiated onto the workpiece in a state of being converged to have a required spot diameter by the optical lens 5, thereby heating the workpiece almost uniformly and performing desired processing without heating unevenness. I do.

  In this embodiment, the cross section in the longitudinal direction of the polygonal optical fiber 3 is formed in a polygonal shape, and the laser light guided inside by twisting with a required lead with respect to the longitudinal direction, the light intensity at the output end face Total reflection can be performed so that the distribution is almost uniform. As a result, the workpiece can be heated almost uniformly and processed into a desired state.

  As shown in FIG. 5, the polygonal optical fiber 11 according to the second embodiment has a polygonal cross section in the longitudinal orthogonal direction and is twisted with a required lead, like the polygonal optical fiber 3 of the first embodiment. In addition, a tapered portion 11 a that gradually tapers toward the output end is formed at the output side end of the polygonal optical fiber 11.

  In the present embodiment, when the laser light is guided in the polygonal optical fiber 11 as in the first embodiment, the reflection surface of the core portion 3a is twisted, so that the laser light is randomly transmitted below the critical angle. The light is uniformly reflected and distributed in the core portion 3a. When the laser light is output from the output end face of the polygonal optical fiber 11, the taper portion 11a gradually narrows the laser light to a desired end face while totally reflecting the laser light on the twisted face as described above. Output.

As a result, the laser light density at the output end face is increased, so that the laser light can have a high light intensity. Now, in the case where the output end face width is set to ½ of other portions by the tapered portion 11a, the light intensity at the output end can be quadrupled compared to the straight optical fiber.

  In FIG. 6, the output surfaces of a large number of LDs 1 are arranged so that the incident ends of ordinary cylindrical optical fibers 21 face each other, and condensing optical fibers 23 are provided at the output ends of the respective cylindrical optical fibers 21. The polygonal optical fiber 3 of the first embodiment in which the cross section in the longitudinal orthogonal direction is polygonal and twisted with a required lead at the output end of the condensing optical fiber 23 or the longitudinal cross section in the longitudinal direction is twisted with the required lead and output. An optical fiber 11 having a tapered portion 11a whose end portion side gradually becomes tapered is attached.

6 shows an example in which the optical fiber 1 of the first embodiment is attached to the output end of the concentrating optical fiber 23, but the same applies to the case where the optical fiber 11 according to the second embodiment is attached. Further, the same members and devices as those of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the present embodiment, the laser light collected by the condensing optical fiber 23 is output to the optical lens 5 in order to condense the laser light from each LD 1 and output it as the excitation light source of the laser oscillator 7. By guiding the inside of the optical fiber 3 (11), the light intensity of the laser light is distributed almost uniformly at the output end.

  As a result, the laser oscillator 7 is reliably excited to output a high-power laser beam, thereby making it possible to eliminate heating unevenness and perform work processing with high quality.

  In the above description, the light guide structure of the optical fiber has been described with one polygonal optical fiber. However, in order to obtain high output laser light, the number of LDs corresponding to the desired output is used and the number corresponding to the number of LDs is used. It is only necessary to guide the laser beam using the polygonal optical fiber. In this case, a concentrating optical fiber may be provided at the tip of many polygonal optical fibers and output.

It is explanatory drawing which shows the outline of a laser beam light guide structure. It is explanatory drawing which shows the twisted state of an optical fiber. It is explanatory drawing which shows another twist aspect. It is explanatory drawing which shows another twist aspect. FIG. 6 is an explanatory diagram illustrating the shape of an optical fiber according to a second embodiment. FIG. 6 is an explanatory diagram illustrating an outline of a laser light guide structure according to a third embodiment.

Explanation of symbols

1 LD as a laser beam oscillation member
3.11 Polygonal optical fiber 3a Core part 11a Taper part

Claims (10)

In a laser light guide structure that guides laser light output from a laser light oscillation member to a required position by an optical fiber, the optical fiber is formed into a polygonal shape at least in the cross section in the longitudinal orthogonal direction of the core portion and twisted with a required lead Light guiding structure with polygonal optical fiber. In a laser light guide structure for guiding laser light output from a laser light oscillation member to a required location by an optical fiber, the optical fiber for guiding laser light from the laser light oscillation member is a cylindrical optical fiber, and the cylindrical optical fiber A light guide structure having a polygonal optical fiber in which at least the cross section in the longitudinal direction of the core portion is polygonalized and twisted with a required lead on the output end side. The polygonal optical fiber according to claim 1 or 2, wherein the cross section in the longitudinal direction is a regular polygonal shape or an irregular polygonal shape. The polygonal optical fiber according to claim 1 or 2, wherein the twisted portion and the straight portion are alternately provided in the longitudinal direction. The twisted portion according to claim 4 is a laser light guide structure in which twist directions are alternately changed. The twisted portion of claim 4 is a laser light guide structure in which twist directions are matched. The polygonal optical fiber according to claim 1 or 2, wherein a plurality of twisted portions having different twist directions are provided for each required length. 8. The laser light guide structure according to claim 1, wherein the polygonal optical fiber has a tapered shape in which the output end side is gradually tapered toward the output end. 9. The laser light guide structure according to claim 1, wherein the number of laser light oscillation members is set according to a required output, and the laser light from each laser light oscillation member is condensed and guided by a single polygonal optical fiber. . 10. The laser light guide structure according to claim 1, wherein the laser light output from the polygonal optical fiber is an excitation light source of the laser oscillation device.

Images