JP2591859Y2 - Optical fiber type processing head for laser - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION This invention is suitable for a laser beam output from the laser oscillator to transmit the laser processing head, easily enters the laser beam of high output and high focusing especially on the diameter of the optical fiber And an optical fiber type processing head for laser.

[0002]

2. Description of the Related Art In general, a fiber-guided laser processing apparatus focuses a laser beam emitted from a laser oscillator on an optical fiber incident end face by a condensing lens, impinges the optical beam on the optical fiber, and transmits the laser beam through the optical fiber. In addition, a condensing lens is used to condense and irradiate a workpiece onto a workpiece to perform processing such as cutting and welding of the workpiece. In such a laser processing apparatus, in order to enhance the processing performance, it is important to enhance the condensing property of the laser beam at the processing point, and for that purpose, the laser beam is incident on an optical fiber as small as possible and transmitted. Is important. This is because the spot diameter at the processing point depends on the core diameter of the optical fiber, and the energy density increases as the light collecting property increases.

[0003] Normally, laser light used in a laser processing apparatus has a high output, so that various devices have been conventionally devised for incidence and transmission on a small-diameter fiber.

Conventional example 1: A large number of combination lenses are arranged on the front surface of an optical fiber in order to cause a high-power laser such as a YAG laser to be incident on a small-diameter optical fiber, and the beam is focused on the end face of the optical fiber and incident. In general, a method of doing so is adopted. In this case, an antireflection film is often attached to the end face of the fiber in order to prevent reflection loss at the end face.

Conventional example 2: Japanese Patent Application Laid-Open No. Sho 62-151286 discloses a method for irradiating a workpiece with high-energy laser light 15 as shown in FIG. Output mirror 17 of laser resonator L
Is appropriately selected, the beam waist of the laser beam 15 is formed outside the laser resonator L, and the beam is incident on the incident lens 12 with a minimum spread angle, and then focused on the optical fiber end face 13a and incident. Is what you do. In the figure, reference numeral 14 denotes a condenser lens, and reference numeral 16 denotes a processing point. Conventional Example 3: In Japanese Patent Publication No. 3-9834, a transmission optical fiber and a processing optical fiber are selectively used. That is, a transmission optical fiber having a large core diameter which is easy to enter is used, and a processing optical fiber having a small diameter is used to reduce the spot diameter. In this case, the transmission optical fiber and the processing optical fiber are connected via a relay converter.

[0006]

When an anti-reflection film is provided to reduce the reflection loss at the end face of an optical fiber as in Conventional Example 1, when the energy density of the incident beam is high, the light resistance of the film is limited. The film may be broken. Therefore, in the case of this conventional example, it is difficult to make a high-power laser beam incident on a small-diameter fiber because the light resistance of the antireflection film is low.

In order to solve this problem, a method of reducing the convergence of the beam or a method of directly entering the end face of the optical fiber without an antireflection film as in the conventional example 2 shown in FIG. 4 is adopted. However, when the beam convergence is reduced, the beam is transmitted through an optical fiber having a large diameter, and there is a problem that the light-collecting property at the processing point is reduced and the processing performance is deteriorated. When a high-focus beam is directly incident on a small-diameter fiber, the energy density at the fiber end face may increase, possibly exceeding the light resistance of the fiber end face.In this case, the end face becomes very sensitive to dirt and becomes dirty. May be heated by absorbing the laser beam, causing heat loss to the end face of the optical fiber. In addition, there is a disadvantage that reflection loss (Fresnel reflection) at the interface between the lens surface and the fiber surface and the air is large.

In the case of Conventional Example 3, a relay converter (consisting of a concave / convex lens for a collimator) is indispensable for transmission from a large-diameter to a small-diameter optical fiber, resulting in a large energy loss and a complicated apparatus. In addition, there are inconveniences such as the necessity of two types of optical fibers having different diameters, which is not practical.

As described above, at present, a simple technique for facilitating the incidence of a high-power laser on a small-diameter fiber, which is used in a laser processing apparatus or the like, has not been established.

A main object of the present invention is to provide an optical fiber type processing head for a laser, which can efficiently input a laser beam emitted from a laser oscillator to a small-diameter optical fiber while protecting the end face thereof. is there.

[0011]

In order to achieve the above object, an optical fiber type processing head for a laser according to the present invention is arranged such that an incident end of an optical fiber for transmitting a laser beam emitted from a laser oscillator is connected to the optical fiber. Fiber numerical aperture NA
The optical fiber conical output end is formed on an end face having a large area by expanding in a conical shape with the above spread angle, and the optical fiber output end is also conically expanded with a spread angle of not less than the numerical aperture NA. An optical element such as a total reflection type solid condensing mirror of the same material as the core is integrally rotatable around the optical axis of the optical fiber so that the direction of laser reflection from the optical element is It is characterized in that it can be at a predetermined angle with respect to the optical axis.

[0012]

Since the end of the optical fiber on the beam incident side is expanded beyond its numerical aperture NA, the beam diameter can be increased at the incident end face, and the energy density at the incident end face can be reduced accordingly. Become. This makes it easy to make high-power laser light incident on the small-diameter fiber with high efficiency. At the same time, since the laser beam can be made incident at a low energy density, there is almost no influence from dust or dirt attached to the end face of the optical fiber, and there is no possibility that the end face is damaged by heat. In addition, since the emission end of the optical fiber is expanded in a conical shape, the energy density of the laser light transmitted through the optical fiber and the return light from the processing point can be reduced at the conical portion, and the emission of the optical fiber can be reduced. There is no risk of heat loss at the end face.

Further, since an optical element having the same quality as the core of the optical fiber is provided integrally with the output end of the optical fiber, the reflection loss of the laser is reduced, and the spread of the laser is reduced because the refractive index does not change. As a result, the processing head is reduced in size. Furthermore, if the optical element is made rotatable, for example, welding and cutting of pipes that cannot be accessed from the outside,
This is made possible by inserting the processing head into the pipe.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG . 1 shows the premise of the working head of the present invention.
(A) is a laser including an optical fiber
FIG. 2B is a schematic view of a processing optical system, and FIG. 2B is an enlarged sectional view of an optical fiber incident end.

As shown in FIG. 1A, a condenser lens 2 on the incident side, an optical fiber 3 for transmission, and a condenser lens 4 on the emission side are arranged on the optical axis 1 and a laser oscillator ( A laser beam 5 output from a not-shown condenser lens 2 on the incident side.
Then, the light is condensed and transmitted into an optical fiber 3 to be described later, and is converged to a processing point 6 by a condenser lens 4 on the emission side to process a workpiece.

The optical fiber 3 is formed such that at least an incident end, and preferably both ends of the input and output, as shown in the figure, are conically enlarged. That is, the optical fiber 3 is composed of the small-diameter fiber portion 3a and the conical fiber portions 3b and 3c. The conical fiber portion 3b is connected to the incident-side end of the small-diameter fiber portion 3a, and the output side of the small-diameter fiber portion 3a. The conical fiber portion 3c is also connected to the end. The small-diameter fiber portion 3a and the conical fiber portions 3b and 3c may be formed integrally, or may be made of the same material by fusion welding to form an integral structure. Is held.

As shown in FIG. 1 (b), the conical fiber portions 3b and 3c have at least a numerical aperture NA of the optical fiber.
And has a large area at the end face. Here, the numerical aperture NA is an index indicating the magnitude of the amount of light that can be incident on the optical system, and is also used for evaluating the incident condition of the optical fiber. As shown in FIG. Is defined as For example, when the core is quartz, the numerical aperture NA is 0.2, and 2
θ is about 23 °. Normally, laser light incident on an optical fiber propagates through the optical fiber while repeating total reflection at the interface between the core and the cladding. It is known that large ones cannot be totally reflected at the boundary surface and escape from the clad, which may damage the clad or cause energy loss. Therefore, by enlarging the end of the small-diameter optical fiber into a conical shape having a divergence angle equal to or larger than the numerical aperture NA as in the present invention, the above-described disadvantages are provided as long as the laser beam is incident within this divergence angle. Is avoided, and at the same time, the beam diameter at the conical end face (optical fiber incident end face) 3d is made large and the energy density can be reduced here, so that the dirt or the like adheres to the optical fiber incident end face. Therefore, a highly reliable optical system without heat loss can be obtained.

As described above, the laser beam 5 converged by the condenser lens 2 on the incident side is incident from the conical end face of the enlarged large area, and the core end face 3f of the small diameter fiber portion 3a.
Therefore, even a high-power laser beam can be incident on a small-diameter optical fiber without leaking laser light from the core while protecting the incident end face. Being able to enter the small diameter optical fiber means that the convergence at the processing point 6 is increased (spot diameter is reduced) and the energy density is increased here. Improvement can be achieved.

It is to be noted that the reason why the end portion on the optical fiber outgoing side is expanded conically in the same manner as the incident side is that the energy density at the end face of the laser light transmitted through the optical fiber and the return light from the processing point 6 are increased. This is to prevent heat loss also at the optical fiber emission end face 3e by reducing.

FIGS. 2 (a) and 2 (b) show the premise of the working head of the present invention.
In the optical system described above, in the above-described optical system, the condenser lens on the input side and the output side is independently disposed at a position away from the optical fiber. An interface with air exists on the end face of the optical fiber, and reflection loss (Fresnel reflection) occurs at this interface. Therefore, the optical system shown in FIG.
In the system, condensing lenses 2a and 4a are integrally formed at the conical ends having a divergence angle equal to or larger than the numerical aperture NA of the optical fiber, and the interface is reduced as much as possible to reduce the reflection loss. The same components as those of the above-described optical system are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 3 shows a processing head of the present invention, in which a laser beam 5 transmitted through the optical fiber 3 is processed at a processing point by a conical optical fiber emitting end 3e having a divergence angle 2θ of at least the numerical aperture NA. An optical element 7 such as a total reflection type solid mirror, prism, lens or the like for converging light onto the light source 6 is integrally provided to reduce the number of reflection surfaces to improve the efficiency.
Moreover, the condensing optical element 7 is configured to be rotatable around the optical axis 1 of the optical fiber 3 (in the direction of the arrow in the figure) with the optical fiber exit end face 3e as a boundary. The conical portion A and the mirror solid portion B of the conical fiber portion 3c are made of the same material (for example, quartz) as the core portion of the optical fiber 3, and have the same refractive index as the laser beam 5 emitted from the optical fiber 3. The size of the processing head is reduced by suppressing the spread of the processing head. When the processing head is miniaturized, connection and disconnection of a small-diameter pipe that cannot be accessed from the outside becomes possible by inserting the processing head into the pipe.

[0023]

[Effect of the invention] According to the processing head of the invention, the following effects can be obtained.
It has the following advantageous effects while retaining the fruit .

Since the end of the optical fiber on the laser beam incident side is enlarged in a conical shape having a numerical aperture of NA or more, the light can be incident with a reduced energy density so as not to exceed the light resistance at the end face, and a high output power can be obtained. It becomes easy to make the laser light incident on a small-diameter optical fiber. At the same time, the optical fiber end face does not suffer from heat loss due to dust or dirt. Since the exit end of the optical fiber is also expanded in a conical shape, the energy density of the laser beam transmitted through the optical fiber and the return light from the processing point can be reduced at the conical portion, and the exit end face of the optical fiber can be reduced. Thus, it is possible to prevent heat loss.

[0025] When the light converging optical element of the core part and the material of the optical fiber is provided integrally with the optical fiber emission ends, it is advantageous in that high efficiency less reflecting surface, the spreading of the laser is reduced There is an advantage that the processing head can be reduced in size. When the optical element is rotatably provided, it is possible to weld and cut a pipe that cannot be accessed from outside.

[Brief description of the drawings]

FIG. 1 (a) and (b) are used presupposedly for the machining head of the present invention .
Schematic view of an optical system including a laser optical fiber for there is an enlarged sectional view of the entrance end.

FIGS. 2 (a) and 2 (b) are used for the processing head of the present invention .
FIG. 4 is a schematic view of an optical system including another laser optical fiber, and an enlarged sectional view of an incident end.

FIG. 3 shows an optical system of an optical fiber emitting end according to the present invention .
FIG. 3 is a schematic diagram of a processing head including:

FIG. 4 is a schematic diagram of an optical system of a conventional laser processing apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Optical axis 2 ... (incident side) Condensing lens 3 ... Optical fiber 3a ... Small diameter fiber part 3b, 3c ... Conical fiber part 3d ... Incident end face 3e ... Outgoing end face 4 ... (Emitting side) Condensing lens 5 ... Laser beam (laser beam) 6 ... Processing point 7 ... Solid mirror for focusing 2θ ... Spread angle of numerical aperture NA

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-54-5747 (JP, A) JP-A-61-188509 (JP, A) JP-A-63-303309 (JP, A) JP-A-49-49 68733 (JP, A) JP-A-55-96133 (JP, A) JP-A-60-162205 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G02B 6/42

Claims (1)

(57) [Scope of request for utility model registration] 1. An optical fiber for transmitting a laser beam emitted from a laser oscillator, the incident side end of which is conically expanded at a divergence angle equal to or larger than the numerical aperture NA of the optical fiber to form an end surface having a large area. At the same time, the exit end of the optical fiber is also expanded in a conical shape with a divergence angle of a numerical aperture NA or more. An optical element such as a solid mirror is configured to be rotatable around the optical axis of the optical fiber so that a laser reflection direction from the optical element can take a predetermined angle with respect to the optical axis. Optical fiber type processing head for laser.