JP2009116181A - Optical isolator for laser machining and laser machining device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical isolator for laser machining having compact and inexpensive constitution, and capable of efficiently and surely removing reflected returning light from an object to be laser-machined, while making a laser beam for machining pass without virtually attenuating it. <P>SOLUTION: In the optical isolator 100, a first branching and coupling part 102, a Faraday rotator 104, a 1/2 wavelength plate 106 and a second coupling and branching part 108 are arranged in a line in this order in a propagating direction of the laser beam for machining FB. The first branching and coupling part 102 includes a reflection transmitting film 110 with which the inside of a glass cube 112 is coated, and a folding mirror 114 which is arranged in predetermined inclined posture at a predetermined position near the reflection transmitting film 110. The second coupling and branching part 108 comprises a reflection transmitting film 116 with which the inside of a glass cube 118 is coated, and a folding mirror 120 which is arranged in predetermined inclined posture at a predetermined position near the reflection transmitting film 116. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a laser processing apparatus that performs desired laser processing by irradiating a workpiece with a laser beam, and more particularly to an optical isolator for laser processing for blocking or removing reflected return light from the workpiece.

  Recently, fiber laser processing apparatuses that perform desired laser processing by irradiating a workpiece with laser light generated by a fiber laser oscillator have been put into practical use.

A fiber laser oscillator used in a fiber laser processing apparatus typically has an optical fiber for oscillation in which a core is doped with a rare earth element, as described in Patent Document 1, for example, as a pair of optical resonator mirrors. The optical fiber core is optically excited, and an oscillation beam having a predetermined wavelength that is axially emitted from the end face of the core is reciprocated between the optical resonator mirrors many times to resonate and amplify it. The laser light is taken out from the optical resonator mirror (partial reflection mirror or output mirror) on one side. Usually, an optical lens is arranged between the fiber end face and the optical resonator mirror, and the oscillation light beam reflected by the optical resonator mirror is focused (converged) by the optical lens to the core end face of the oscillation optical fiber. I try to return it. In addition, in order to optically excite the core of the oscillation optical fiber, a laser diode (LD) is used as the excitation light source, and the LD light (excitation light) is collected on the core end face through the optical resonator mirror and the optical lens. An LD end face excitation method in which light is incident is adopted.
JP2007-190566

  In the fiber laser processing apparatus as described above, the reflected return light from the processing point of the workpiece propagates in the reverse direction through the laser emitting unit and the laser transmission system and enters the laser oscillating unit, thereby the end face of the oscillation optical fiber. Has become a problem. If the core end face of the oscillation optical fiber burns out, the oscillation output of the fiber laser decreases and the quality of the laser processing deteriorates.

  Further, not only in a fiber laser processing apparatus but also in a YAG laser processing apparatus or the like, when an LD end face excitation method is used for laser oscillation, reflected light from a workpiece passes through an oscillator and enters the excitation LD. LD may be damaged. Furthermore, when power feedback control is performed in order to make the laser output of the processing laser beam follow the desired reference value or reference waveform, the reflected return light enters the laser output monitor unit via the oscillator, and power feedback control is performed. There is also a problem that the accuracy or reliability of the system is lowered.

  Conventionally, by making the numerical aperture (NA) of the oscillation optical fiber smaller than the numerical aperture (NA) of the transmission optical fiber, the reflected return light is confined in the oscillation optical fiber to protect the fiber end face. However, this is not a fundamental solution because it does not only increase the cost of the oscillation optical fiber but also does not remove the reflected return light out of the laser optical path.

Therefore, in order to prevent the reflected return light from the workpiece from entering the laser oscillation unit or the power monitor unit, an optical device that blocks or removes the light beam in the reverse direction while passing the light beam in the forward direction with almost no attenuation. That is, it is conceivable to employ an optical isolator in a laser processing apparatus. However, conventionally known optical isolators handle linearly polarized light and cannot be used in laser processing apparatuses. In other words, a processing laser beam oscillated and output by a fiber laser, a YAG laser, or the like is generally randomly polarized light or natural light having no regularity in the vibration direction of the light wave, and is generally configured by combining a polarizer and an analyzer. This optical isolator cannot be used.
The present invention has been made in view of the above-described problems of the prior art, and allows a laser beam for processing to pass through a compact and low-cost configuration while hardly attenuating from a workpiece. An object of the present invention is to provide an optical isolator for laser processing that can efficiently and reliably remove reflected return light.

  It is another object of the present invention to provide a laser processing apparatus that improves the quality and reliability of laser processing by eliminating the influence of reflected return light from the workpiece side.

  In order to achieve the above object, an optical isolator for laser processing according to the present invention is provided in the middle of a laser transmission system that optically connects a laser oscillation part and a workpiece, and forwards from the laser oscillation part side. An optical isolator for laser processing that removes reflected return light that has propagated in the opposite direction from the workpiece side through the processing laser beam that has propagated through the workpiece, and has a first branch as viewed from the laser oscillation unit side. A coupling unit, a Faraday rotator, a half-wave plate, and a second branch coupling unit are arranged in this order, and the first branch coupling unit converts the processing laser beam from the laser oscillation unit into a polarization plane. Are divided into two, which are orthogonal to each other and propagate in parallel to each other, and the Faraday rotator is configured to transmit the first and second linearly polarized light components from the first branch coupling unit. The common The first and second linearly polarized light beams are symmetric with respect to the optical axis direction of the crystal by rotating each polarization plane by 45 degrees in a predetermined rotation direction through an Faraday element. The polarization plane of each component is rotated by a predetermined angle, and the second branching and coupling unit combines the first and second linearly polarized components from the half-wave plate on the same laser beam path, The processing laser beam is restored, and the second branching and coupling unit has the same polarization plane as the first and second linearly polarized light components for the reflected return light from the workpiece, The third and fourth linearly polarized light components are divided into two, which are propagated parallel to each other, into two parts, the half-wave plate being symmetrical about the optical axis direction of the crystal. Rotate the polarization planes of the A Faraday rotator passes the third and fourth linearly polarized light components from the half-wave plate through the common Faraday element to rotate each polarization plane by 45 degrees in the predetermined rotation direction; A first branching and coupling unit guides the third and fourth linearly polarized light components from the Faraday rotator to a deviating optical path deviating from the laser transmission system in a different direction and removes them from the laser transmission system.

  In the above-described configuration, the processing laser beam oscillated and output as random polarized light or natural light from the laser oscillation unit generally propagates in parallel with each other with the polarization planes orthogonal to each other by the first branch coupling unit in the first stage. Divided into 1 and second linearly polarized light components. Then, both linearly polarized light components pass through a common or single Faraday element in the next-stage Faraday rotator, where each deflection surface is rotated by 45 degrees by the Faraday effect. Next, the first and second linearly polarized light components are incident on the half-wave plate while maintaining an orthogonal relationship and a parallel state, where each deflection surface is set at a predetermined angle with respect to the axis of the crystal optical axis as a reference. Just rotate. Here, by setting the rotation angle of the half-wave plate to an appropriate value with respect to the rotation angle (45 degrees) of the Faraday rotator, the polarization planes of the first and second linearly polarized light components are changed to the Faraday rotator. You can return to the original direction before entering. Thus, in the second branch coupling unit at the last stage, the first and second linearly polarized light components are synthesized on the same laser beam path by the reflective transmission and folding action that is the target of the first branch coupling unit, The processing laser beam is restored.

  On the other hand, the reflected return light propagating from the workpiece in the laser transmission system in the reverse direction first enters the second branch coupling portion, where it has the same polarization plane as the first and second linearly polarized light components, respectively. And is divided into two parts, the third and fourth linearly polarized light components that propagate in parallel with each other. These linearly polarized light components are incident on the half-wave plate, where the respective deflection surfaces are rotated by a predetermined angle relative to the axis object with reference to the crystal optical axis direction. Here, in the half-wave plate, the direction in which the third and fourth linearly polarized components are incident is opposite to the direction in which the first and second linearly polarized components are incident. The rotation direction of the polarization plane of the linearly polarized light component is also opposite to the rotation direction of the polarization planes of the first and second linearly polarized light components. Next, the third and fourth linearly polarized light components enter the Faraday rotator while maintaining an orthogonal relationship and a parallel state, where the respective deflection surfaces rotate by 45 degrees. The rotation direction at this time is also opposite to the rotation direction of the first and second linearly polarized light components. As a result, the third linear polarization component has a polarization plane orthogonal to the polarization plane of the first linear polarization component, and the fourth linear polarization component is a polarization plane orthogonal to the polarization plane of the second linear polarization component. Lead to having. Then, the third and fourth linearly polarized light components enter the first branch coupling portion from the opposite direction to the first and second linearly polarized light components, respectively, where they are asymmetric with the first and second linearly polarized light components. The light is guided to a deviating optical path deviated from the laser transmission system in a different direction under the effect of reflection and transmission and folding, and is removed from the laser transmission system.

  As described above, in the optical isolator according to the present invention, the laser beam for processing that is oscillated and output as random polarized light or natural light is passed through without being attenuated, and the reflected return light from the workpiece is reliably transmitted from the laser transmission system. Can be removed. In addition, since only one Faraday rotator is used, it can be realized in a small size and at a low cost.

  In a preferred aspect of the present invention, the first branch coupling portion includes a first reflection / transmission film coated on a transparent support and a first folding mirror. Then, the processing laser beam from the laser oscillation unit enters the first reflection / transmission film at an incident angle of 45 degrees. Of the incident processing laser beam, the first linearly polarized light component is transmitted straight toward the Faraday rotator, and the second linearly polarized light component is reflected at right angles toward the first folding mirror. In the first reflective / transmissive film, the third linearly polarized light component from the Faraday rotator is incident from a direction opposite to the transmission direction of the first linearly polarized light component and is reflected at right angles on the deviating optical path. The fourth linearly polarized light component from one folding mirror is incident from the direction opposite to the reflection direction of the second linearly polarized light component and is transmitted straight through the deviating optical path. In the first folding mirror, the second linearly polarized light component from the first reflection / transmission film is incident at an incident angle of 45 degrees and reflected at right angles toward the Faraday rotator, and from the Faraday rotator. The fourth linearly polarized light component enters at an incident angle of 45 degrees and is reflected at right angles toward the first reflective / transmissive film. According to such a configuration, the first and second linearly polarized light components are extracted on the extended line of the laser light path through which the processing laser beam has propagated, and the third and fourth linearly polarized light components are obtained at the first branching and coupling unit. Is extracted in a direction perpendicular to the laser beam path.

  In another preferred embodiment, the first branch / coupling portion includes a first reflective / transmissive film coated on a transparent support and a first folding mirror, and the first reflective / transmissive film includes: A processing laser beam from the laser oscillation unit is incident at an incident angle of 45 degrees. Of the incident processing laser beam, the first linearly polarized component is transmitted straight toward the first folding mirror, and the second linearly polarized component is reflected at right angles toward the Faraday rotator. In the first reflective / transmissive film, the third linearly polarized light component from the first folding mirror is incident from a direction opposite to the transmission direction of the first linearly polarized light component and reflected at right angles on the deviating light path. The fourth linearly polarized light component from the Faraday rotator enters from a direction opposite to the reflection direction of the second linearly polarized light component and is transmitted straight through the deviating optical path. In the first folding mirror, the first linearly polarized light component from the first reflection / transmission film is incident at an incident angle of 45 degrees and reflected at right angles toward the Faraday rotator, and from the Faraday rotator. The third linearly polarized light component is incident at an incident angle of 45 degrees and is reflected at right angles toward the first reflective / transmissive film. According to this configuration, the first and second linearly polarized light components are extracted in the direction perpendicular to the laser beam path through which the processing laser beam has propagated, and the third and fourth linearly polarized light components are extracted. The component is taken out on the opposite side of the first and second linearly polarized components perpendicular to the laser beam path.

  In another preferred embodiment, the second branch coupling portion has a second reflective / transmissive film and a second folding mirror coated on a transparent support. In the second reflection / transmission film, the first linearly polarized light component from the half-wave plate is incident at an incident angle of 45 degrees and is transmitted straight through the laser light path, and the second reflection mirror transmits the first linearly polarized light component from the second folding mirror. Two linearly polarized light components are incident at an incident angle of 45 degrees and are reflected at right angles on the laser beam path. In addition, reflected return light from the workpiece is incident on the second reflective / transmissive film at an incident angle of 45 degrees from the direction opposite to the transmission direction of the first linearly polarized light component. Of the incident reflected return light, the third linearly polarized component is transmitted straight toward the half-wave plate, and the fourth linearly polarized component is reflected at right angles toward the second folding mirror. In the second folding mirror, the second linearly polarized light component from the half-wave plate is incident at an incident angle of 45 degrees and is reflected at right angles toward the second reflective / transmissive film, and the second The fourth linearly polarized light component from the reflection / transmission film is incident at an incident angle of 45 degrees and is reflected at right angles toward the half-wave plate. According to such a configuration, the restoration processing laser beam is extracted on the laser beam path in the same direction as the propagation direction of the first and second linearly polarized light components in the second branching and coupling unit, and the third and fourth straight lines are extracted. A polarized component is extracted in the opposite direction to the first and second linearly polarized components on the side opposite to the laser optical path.

  As another preferred embodiment, the second branch / coupling portion includes a second reflective / transmissive film and a second folding mirror coated on a transparent support, and the second reflective / transmissive film includes a second reflective / transmissive film. The first linearly polarized light component from the second folding mirror is incident at an incident angle of 45 degrees and is transmitted straight through the laser optical path, and the second linearly polarized light component from the half-wave plate is incident at an angle of 45 degrees. And is reflected at right angles on the laser beam path. In addition, reflected return light from the workpiece is incident on the second reflective / transmissive film at an incident angle of 45 degrees from the direction opposite to the transmission direction of the first linearly polarized light component. Of the reflected return light that has entered, the third linearly polarized light component is transmitted straight toward the second folding mirror, and the fourth linearly polarized light component is reflected at right angles toward the half-wave plate. In the second folding mirror, the first linearly polarized light component from the half-wave plate is incident at an incident angle of 45 degrees and is reflected at right angles toward the second reflective / transmissive film, and the second The third linearly polarized light component from the reflection / transmission film is incident at an incident angle of 45 degrees and is reflected at right angles toward the half-wave plate. According to such a configuration, in the second branching and coupling unit, the restoration processing laser beam is extracted on the laser optical path in the direction orthogonal to the propagation direction of the first and second linearly polarized light components, and the third and fourth The linearly polarized light component is extracted in the direction opposite to the first and second linearly polarized light components perpendicular to the laser light path.

  According to a preferred aspect of the present invention, the first and second linearly polarized light components are extracted in parallel at a distance of 3 to 5 mm from the first branch coupling portion, and the third branch coupling portion is third. The fourth linearly polarized light component is extracted in parallel at a distance of 3 to 5 mm. With this configuration, the first and second linearly polarized light components can be easily passed through the common (single) Faraday element, and the third and fourth linearly polarized light components can be easily passed.

  The laser processing apparatus of the present invention includes a laser oscillation unit that oscillates and outputs a processing laser beam, a laser emitting unit that focuses and irradiates the processing laser beam toward a processing point on a workpiece, and the laser oscillation A laser transmission system for transmitting the processing laser beam oscillated and output from the unit to the laser emitting unit, and an optical isolator of the present invention provided in the middle of the laser transmission system.

  In the above apparatus configuration, the optical isolator of the present invention passes the laser beam for processing, which is propagated as random polarized light or natural light from the laser oscillation unit, to the laser emission unit side with almost no attenuation, and from the workpiece. Since the reflected return light propagating in the opposite direction is reliably removed from the laser transmission system, the workpiece laser beam can be irradiated to the workpiece with the desired laser output, and the reflected return light can be applied to the laser oscillation unit. The impact can be fundamentally resolved.

  In a preferred embodiment of the laser processing apparatus of the present invention, the laser oscillation unit oscillates a processing laser beam having a certain wavelength by exciting the core with a predetermined excitation light using the core containing the light emitting element as an active medium. A fiber laser oscillator having an optical fiber structure for output is provided. In this case, in particular, it is possible to reliably prevent the reflected return light from entering the end face of the oscillation optical fiber and burning the end face of the fiber.

  In another preferred embodiment, the laser oscillation unit includes an active medium, an excitation unit for optically exciting the active medium with excitation light, and a laser output measurement unit for measuring the laser output of the processing laser beam. And a laser power supply unit that controls the output of the excitation light so that the laser output measurement value obtained from the laser output measurement unit follows a preset reference value or reference waveform. In this case, in particular, it is possible to reliably prevent the power feedback control mechanism from being deteriorated in accuracy or malfunctioning due to the influence of the reflected return light.

  According to the optical isolator for laser processing of the present invention, the above-described configuration and operation allow the laser beam for processing to pass through the compact and low-cost configuration with almost no attenuation while reflecting from the workpiece. Return light can be efficiently and reliably removed.

  Further, according to the laser processing apparatus of the present invention, the influence and the reflected return light from the workpiece side can be eliminated and the quality and reliability of the laser processing can be improved by the configuration and operation as described above.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 shows a configuration of a fiber laser processing apparatus as one configuration example to which the optical isolator of the present invention can be suitably applied. The fiber laser processing apparatus includes an optical isolator 100 in addition to a fiber laser oscillator 10, a laser power supply unit 12, a laser incident unit 14, a fiber transmission system 16, a laser emitting unit 18, and a processing table 20.

  The fiber laser oscillator 10 includes an oscillation optical fiber (hereinafter referred to as “oscillation fiber”) 22, an electro-optical excitation unit 24 that irradiates one end surface of the oscillation fiber 22 with pumping excitation light MB, and an oscillation fiber. 22 and a pair of optical resonator mirrors 26 and 28 that are optically opposed to each other via 22.

  The electro-optic excitation unit 24 includes a laser diode (LD) 30 and a condensing optical lens 32. The LD 30 is lighted and driven by the excitation current from the laser power supply unit 12 and oscillates and outputs the excitation laser beam MB. The optical lens 32 condenses and enters the excitation laser beam MB from the LD 30 onto one end surface of the oscillation fiber 22. The optical resonator mirror 26 disposed between the LD 30 and the optical lens 32 transmits the excitation laser beam MB incident from the LD 30 side and transmits the oscillation light beam incident from the oscillation fiber 22 side on the optical axis of the resonator. It is configured to totally reflect.

  Although not shown, the oscillation fiber 22 has a core doped with, for example, rare earth element ions as a light emitting element, and a clad surrounding the core coaxially. The core is used as an active medium, and the clad is used as the propagation of excitation light. The light path. The excitation laser beam MB incident on one end face of the oscillation fiber 22 as described above propagates in the oscillation fiber 22 in the axial direction while being confined by total reflection at the cladding outer peripheral interface. The rare earth element ions in the core are photoexcited by crossing the core. In this way, an oscillating light beam having a predetermined wavelength is emitted in the axial direction from both end faces of the core, and this oscillating light beam travels back and forth between the optical resonator mirrors 26 and 28 and is resonantly amplified. A fiber laser beam FB having the predetermined wavelength is extracted from the optical resonator mirror 28. The fiber laser beam FB is a non-polarized or natural laser beam with no regularity in the vibration direction of the vibration vector of the light wave.

  In the optical resonator, the optical lenses 32 and 34 collimate the oscillating light beam emitted from the end face of the oscillation fiber 22 into parallel light and pass the collimated light to the optical resonator mirrors 26 and 28. The oscillating light beam reflected and returned by is condensed on the end face of the oscillating fiber 22. The excitation laser beam MB that has passed through the oscillation fiber 22 passes through the optical lens 34 and the optical resonator mirror 28 and is then folded back toward the side laser absorber 38 by the folding mirror 36. The fiber laser light FB output from the optical resonator mirror 28 passes straight through the folding mirror 36 and then passes through the beam splitter 40 before entering the laser incident portion 14.

The beam splitter 40 reflects a part (for example, 1%) of the incident fiber laser beam FB to a predetermined direction, that is, a light receiving element for power monitoring, for example, a photodiode (PD) 42 side. A condenser lens 44 that condenses the reflected light from the beam splitter 40 or the monitor light R _FB may be disposed in front of the photodiode (PD) 42.

The photodiode (PD) 42 photoelectrically converts the monitor light R _FB from the beam splitter 40 and outputs an electric signal (laser output measurement signal) S _FB representing the laser output (peak power) of the fiber laser light FB. This signal S _FB is sent to the laser power source 12. The laser power supply unit 12 is configured to supply an excitation current to the LD 30 by real-time power feedback control, and the laser output measurement signal S _FB from the photodiode (PD) 42 is set in advance as a laser output reference value. Alternatively, the LD excitation current is controlled so that the comparison error becomes zero compared with the reference waveform.

  The fiber laser beam FB that has entered the laser incident portion 14 is first folded in a predetermined direction by the vent mirror 46, and then condensed by the condenser lens 50 in the incident unit 48 to be transmitted by an optical fiber for transmission in the fiber transmission system 16 ( (Hereinafter referred to as “transmission fiber”). The transmission optical fiber 52 is made of, for example, an SI (step index) fiber, and transmits the fiber laser light FB incident in the incident unit 48 to the emission unit 54 of the laser emission unit 18.

  The emission unit 54 includes a collimator lens 56 that collimates the fiber laser light FB emitted from the end surface of the transmission fiber 52 into parallel light, and a condensing lens 58 that condenses the parallel fiber laser light FB at a predetermined focal position. And the fiber laser beam FB is condensed and applied to the processing point W of the workpiece 60 placed on the processing table 20.

  For example, in the case of laser welding, an excitation current having a pulse waveform is supplied from the laser power supply unit 12 to the LD 30, whereby the excitation laser beam MB having a pulse waveform is supplied from the LD 30 to the oscillation fiber 22 in the fiber laser oscillator 10. The fiber laser oscillator 10 oscillates and outputs a fiber laser beam FB having a pulse waveform. The fiber laser beam FB having the pulse waveform is condensed and irradiated onto the processing point W of the workpiece 60 through the laser incident part 14, the fiber transmission system 16 and the laser emitting part 18. At the processing point W, the material to be processed is melted by the energy of the fiber laser beam FB having a pulse waveform, and solidifies after the pulse irradiation to form a nugget.

  In this fiber laser processing apparatus, reflected return light from the processing point W of the workpiece 60 passes through the laser emitting unit 18 and the fiber transmission system 16 in the direction opposite to the fiber laser light FB, and is on the fiber laser oscillator 10 side. May propagate to.

  In this embodiment, the optical isolator 100 disposed between the fiber laser oscillator 10 and the laser incident portion 14 passes the fiber laser light FB propagating forward from the fiber laser oscillator 10 almost without attenuation. The reflected return light propagating in the reverse direction from the workpiece 60 side through the laser emitting section 18, the fiber transmission system 16, and the laser incident section 14 is removed from the laser optical path. As a result, it is possible to efficiently and reliably prevent the end face of the oscillation fiber 22 from being burned and deteriorated by the reflected return light without any structural limitations or special measures in the fiber laser oscillator 10. The power feedback control mechanism (42, 44, 12, 30, etc.) for controlling the laser output of the laser beam FB is not affected by the reflected return light, and there is no possibility of causing a decrease in accuracy or malfunction. Conventionally, the reflected return light passes through the fiber laser oscillator 10 and damages the pumping LD 30. However, the optical isolator 100 completely eliminates this problem. Therefore, the quality and reliability of laser processing on the workpiece 60 can be improved.

  Hereinafter, the configuration and operation of the optical isolator 100 in this embodiment will be described in detail.

  2A and 2B show a configuration of an optical isolator 100 according to one embodiment. The optical isolator 100 includes a first branch coupling unit 102, a Faraday rotator 104, a half-wave plate 106, and a second branch coupling unit 108 arranged in this order as viewed from the fiber laser oscillator 10 (FIG. 1) side. Is arranged.

  The first branch coupling portion 102 includes a glass cube 112 of a cube-shaped assembly formed by coating a reflection / transmission film 110 on an inner laminated slope, and a predetermined inclination posture at a predetermined position adjacent to the glass cube 112. And a folding mirror 114 to be arranged.

More specifically, the reflection / transmission film 110 in the glass cube 112 has reflection / transmission characteristics opposite to two linear polarization components whose polarization planes are orthogonal to each other, for example, a linear polarization component having a longitudinal polarization plane. For (P), it is transmitted as it is, and for the linearly polarized light component (S) having a lateral polarization plane, it is totally reflected, and the fiber laser oscillator 10 (FIG. 1). Are arranged with an inclination of −45 degrees (downward in FIG. 2A) with respect to the propagation direction (horizontal direction) of the fiber laser beam FB from the optical fiber. Accordingly, the fiber laser oscillator 10 fiber laser beam FB having propagated horizontally from is incident on the reflection transmission film 110, as shown in FIG. 2A, the linearly polarized light component P _F in the longitudinal direction of the fiber laser beam FB transreflective straight horizontally through the film 110, the linearly polarized light component S _F in the lateral direction is reflected vertically downward at a right angle.

2A, the folding mirror 114, reflection and transmission film is disposed at the same with the inclination of the parallel -45 degrees below the 110, the lateral direction of the linear polarized light component S _F here Faraday rotator from the transreflective layer 110 Reflects at a right angle toward 104.

Thus, in the first branch coupling portion 102, to a fiber laser oscillator 10 linearly polarized light component (Fig. 1) the vertical direction of the linearly polarized light component fiber laser beam FB having propagated horizontally from P _F and the transverse direction S _F 2 It is divided and taken out in parallel (horizontal) separating their linear polarization component P _F, a close range of S _F from each other for example 3 to 5 mm.

The Faraday rotator 104 includes, for example, a cylindrical Faraday element and a ring-shaped magnet provided around the Faraday rotator 104, and the first branch coupling portion 102 is provided on one end face (left end face in the drawing) of the Faraday element. both linear polarization component P _F from, allowed incident S _F, the other end face both linearly polarized light components by the Faraday effect until it exits from the (right end face) P _F Faraday element, a predetermined polarization plane (vibration plane) of S _F And 45 degrees in the rotation direction (for example, clockwise or clockwise as viewed from the first branch coupling portion 102 side).

Both linearly polarized light components P _F and S _F extracted from the Faraday rotator 104 are incident on the half-wave plate 106 horizontally while maintaining the parallel state of each other. The half-wave plate 106 is set such that the optical axis direction N of the crystal is inclined 22.5 degrees clockwise (clockwise) with respect to the vertical axis when viewed from the Faraday rotator 104 side. the crystal optical axis direction N in the axial object as a reference, is rotated by 45 degrees the polarization plane of one linear polarization component P _F to the left (counterclockwise), the polarization plane of the other linearly polarized light component S _F left Rotate around 225 degrees (in other words, 135 degrees clockwise). Thus, the polarization planes of both linearly polarized components P _F and S _F are returned to the original vertical direction and horizontal direction by the half-wave plate 106, respectively.

  The second branch coupling portion 108 is a glass cube 118 of a cube-shaped assembly formed by coating a reflection / transmission film 116 on the inner laminated slope, and adjacent to the glass cube 118 in a predetermined inclination posture at a predetermined position. It consists of a folding mirror 120 to be arranged.

More specifically, the reflection / transmission film 116 in the glass cube 118 has reflection / transmission characteristics opposite to two linear polarization components whose polarization planes are orthogonal to each other, for example, a linear polarization component having a longitudinal polarization plane. For (P), it is transmitted straight as it is, and for the linearly polarized light component (S) having a lateral polarization plane, it is totally reflected, and the restored fiber laser beam FB to be sent out. 45 ° inclination with respect to the propagation direction of the 'only 1/2 linearly polarized light component P _F of the wavelength plate 106, S the other linear polarization component P _F deviates from the linear polarized light component S _F of one of the _F It is arranged at a height position where the light is incident. On the other hand, the folding mirror 120, the slope beneath the same parallel 45-degree reflection and transmission film 116, is disposed at a height position to be incident only linearly polarized light component S _F from 1/2-wavelength plate 106.

In this configuration, 1/2 linearly polarized light component P _F of the wavelength plate 106, among the S _F, linearly polarized light component P _F having a vertical polarization plane is directly incident on the reflection and transmission film 116 of the glass cube 118 The linearly polarized light component S _{F that} is transmitted straight and has a lateral polarization plane is first incident on the folding mirror 120 and then reflected vertically upward and then incident on the reflective transmission film 116, where it is reflected at a right angle in the horizontal direction. is synthesized joins the linear polarization component P _F Te.

In this way, the laser beam composed of the two linearly polarized light components P _F and S _F whose polarization planes are orthogonal to each other is sent from the second branch coupling unit 108 to the subsequent laser transmission system as the restored fiber laser beam FB ′. .

Restore the fiber laser beam FB is transmitted from the optical isolator 100 ', both linearly polarized component P _F, elliptically polarized light by the light intensity and the phase relationship between S _F, may take the form of a circularly polarized light or linearly polarized light, the optical isolator If the absorption (loss) of optical components in 100 is ignored, it has a laser output that is almost the same as that of the original fiber laser beam FB before entering the optical isolator 100, and is substantially as a laser beam for processing. Is equivalent to

  On the other hand, the optical isolator 100 takes in the reflected return light RB propagating in the opposite direction on the same laser beam path as the restoration fiber laser beam FB ′ from the workpiece 60.

In FIG. 2B, the reflected return light RB from the workpiece 60 is generally a randomly polarized laser beam and first enters the glass cube 118 of the second branch coupling portion 108 and enters the reflection / transmission film 116. Here, the reflected return light RB, the longitudinal direction of the linearly polarized light component P _R through straight and level the reflection and transmission film 116, the linearly polarized light component S _R in the lateral direction is reflected to a right angle vertically downward. Then, the linearly polarized light component S _R enters the folding mirror 120 directly below, where it is reflected at right angles toward the half-wave plate 106, and has a close distance (for example, 3 to 5 mm) with the longitudinal linearly polarized light component P _R. It becomes parallel (horizontal) apart.

The two linearly polarized light components P _R and S _R extracted by the second branching and coupling unit 108 are horizontally incident on the half-wave plate 106 from the opposite direction (the right side in the figure) while maintaining the mutual parallel state. Here, the crystal optical axis direction N of the half-wave plate 106 is inclined 22.5 degrees counterclockwise (counterclockwise) with respect to the vertical axis when viewed from the second branch coupling unit 108 side. The half-wave plate 106, the crystal optical axis direction N in the axial object as a reference, is rotated by 45 degrees the polarization plane of one linear polarization component P _R to the left (counterclockwise), the other linear The polarization plane of the polarization component S _R is rotated counterclockwise by 225 degrees (in other words, clockwise by 135 degrees). Thus, the polarization plane of the linearly polarized light component P _R becomes one inclined 135 degrees with respect to the horizontal axis, the plane of polarization of linearly polarized light component S _R is as inclined 45 degrees to the horizontal axis.

Both linearly polarized light components P _R and S _{R that} have passed through the half-wave plate 106 in the opposite direction are transmitted to the Faraday rotator 104 while maintaining the polarization planes orthogonal to each other and maintaining a constant distance from the parallel (horizontal) propagation. Enter from the opposite direction (right side of the figure). The Faraday rotator 104 changes the polarization planes (vibration planes) of the linearly polarized light components P _R and S _R to a predetermined rotational direction (1) by the Faraday effect while the linearly polarized light components P _R and S _R pass through the Faraday element. / Clockwise (counterclockwise or counterclockwise as viewed from the wavelength plate 106 side), respectively, by 45 degrees. Thus, the polarization plane of the linearly polarized light component P _R becomes parallel i.e. transversely to the horizontal axis, the polarization plane of the linearly polarized light component S _R becomes longitudinally inclined 90 degrees to the horizontal axis.

The two linearly polarized light components P _R and S _{R that} have passed through the Faraday rotator 104 in the reverse direction are reversely directed to the first branch coupling unit 102 while maintaining the polarization planes orthogonal to each other and maintaining a constant distance from the parallel state. Enter from (right side of the figure). The linearly polarized light component P _R having a horizontal polarization plane enters the glass cube 110 and enters the reflection / transmission film 110, where it is reflected perpendicularly upward. Further, the linearly polarized light component S _R having the longitudinal polarization plane is incident on the folding mirror 114, where it is reflected perpendicularly upward, and then passes straight through the reflective / transmissive film 110 in the glass cube 110. Merges with the linearly polarized light component P _R.

Thus, the linearly polarized light components P _R and S _R merge on the departure optical path 122 set above the first branching and coupling unit 102, and the reflected return light RB ′ is restored and removed out of the laser transmission system. Is done. In order to prevent the restored reflected return light RB ′ from diffusing out of the optical isolator 100, a light absorber (not shown) may be provided at the tip of the departure optical path 122.

  As described above, the optical isolator 100 according to this embodiment passes the randomly polarized or natural fiber laser light FB propagating in the forward direction from the fiber laser oscillator 10 with little attenuation, while from the workpiece 60 side. The randomly polarized fiber laser beam FB propagating in the reverse direction can be excluded from the laser transmission system. In addition, since this optical isolator 100 has only one Faraday rotator (104) having the largest size and the most (very) expensive optical components to be used, it is a compact and low-cost optical device. Can be configured as

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the technical idea.

  For example, in the optical isolator 100 (FIGS. 2A and 2B) according to the above-described embodiment, the positional relationship between the glass cube 118 and the folding mirror 120 of the second branch coupling unit 108 is reversed, as shown in FIGS. 3A and 3B. It is also possible to modify to such a configuration.

More specifically, the reflection / transmission film 116 in the glass cube 118 is inclined by 45 degrees with respect to the propagation direction of the restored fiber laser beam FB ′ to be transmitted, and the linearly polarized light component P _F from the half-wave plate 106. , is disposed at a height position which deviates from the linear polarization component P _F of one is incident only the other linear polarization component S _F of S _F. On the other hand, the folding mirror 120, the slope just above the same parallel 45-degree reflection and transmission film 116, is disposed at a height position to be incident only linearly polarized light component P _F from 1/2-wavelength plate 106.

In this configuration, 1/2 linearly polarized light component P _F of the wavelength plate 106, among the S _F, one linear polarization component P _F is reflected transmitted from the first incident on and turn-back mirror 120 where vertically downward It enters the film 116, where it is reflected at a right angle in the horizontal direction and exits on the laser beam path. The other linear polarization component S _F is straight transmitted directly incident on the reflection transmission film 116 of the glass cube 118 out the laser beam path are synthesized joins the linearly polarized light component P _F. Thus, the fiber laser beam FB ′ restored on the laser beam path is obtained.

In the second embodiment, the half-wave plate 106 has an optical axis direction N of the crystal of 22.5 counterclockwise (counterclockwise) with respect to the vertical axis when viewed from the Faraday rotator 104 side. is set each time a direction inclined, the crystal optical axis direction N in the axial object basis, the polarization plane of one linear polarization component P _F from Faraday rotator 104 to the left (counterclockwise) 67. by five degrees is rotated, 315 ° the polarization plane of the other linearly polarized light component S _F from the Faraday rotator 104 counterclockwise (other words 45 ° clockwise if) simply by rotating. Thus, when both linearly polarized light components P _F and S _F from the Faraday rotator 104 pass through the half-wave plate 106, they have horizontal and vertical polarization planes, respectively.

In FIG. 3B, the reflected return light RB from the workpiece 60 first enters the glass cube 118 of the second branch coupling unit 108 and enters the reflection / transmission film 116. Here, in the reflected return light RB, the linearly polarized light component P _{R in} the vertical direction passes through the reflective / transmissive film 116 straight and horizontally, and the linearly polarized light component S _{R in} the horizontal direction is reflected vertically and vertically upward. incident on the folding mirror 120, where it reflected at a right angle toward the half-wave plate 106, becomes parallel (horizontal) at a longitudinal direction of the linear polarized light component P _R and short distance (e.g., 3 to 5 mm).

Half-wave plate 106, the crystal optical axis direction N in the axial object as a reference, is rotated by 22.5 degrees the polarization plane of one of the other linear polarization component P _R counterclockwise, linear polarization component S The polarization plane of _R is rotated counterclockwise (counterclockwise) by 225 degrees. As a result, the plane of polarization of the linearly polarized light component P _R is inclined 45 degrees with respect to the horizontal axis, and the plane of polarization of the linearly polarized light component S _R is inclined 135 degrees with respect to the horizontal axis.

Both linearly polarized light components P _R and S _{R that} have passed through the half-wave plate 106 in the opposite direction are transmitted to the Faraday rotator 104 while maintaining the polarization planes orthogonal to each other and maintaining a constant distance from the parallel (horizontal) propagation. Enter from the opposite direction (right side of the figure). Faraday rotator 104, while the two linearly polarized components P _R, S _R is passed through the Faraday element, both linearly polarized light component P _F Faraday effect, S _F of the plane of polarization (vibration surface) the predetermined rotational direction (1 / Clockwise (counterclockwise or counterclockwise as viewed from the wavelength plate 106 side), respectively, by 45 degrees. Thus, the polarization plane of the linearly polarized light component P _R becomes longitudinally inclined 90 degrees to the horizontal axis, a tilt clogging transverse of the plane of polarization of linearly polarized light component S _R 180 degrees with respect to the horizontal axis.

The two linearly polarized light components P _R and S _{R that} have passed through the Faraday rotator 104 in the reverse direction are reversely directed to the first branch coupling unit 102 while maintaining the polarization planes orthogonal to each other and maintaining a constant distance from the parallel state. Enter from (right side of the figure). Then, the linearly polarized light component S _R having the lateral polarization plane enters the glass cube 110 and enters the reflection / transmission film 110, where it is reflected perpendicularly upward on the deviation light path 122. Further, the linearly polarized light component P _R having the longitudinal polarization plane is incident on the folding mirror 114 and is reflected at a right angle vertically upward there, and then passes straight through the reflective / transmissive film 110 in the glass cube 110. It merges with the linearly polarized light component P _R on the departure optical path 122.

  As another modification, the laser optical path of the laser transmission system can be arbitrarily bent in the optical isolator 100, and FIGS. 4A and 4B show a third embodiment.

In the third embodiment, the fiber laser beam FB from the fiber laser oscillator 10 (FIG. 1) propagates vertically upward in FIG. 4A. In the first branch coupling portion 102 of the first stage, when the fiber laser beam FB enters the reflection and transmission film 110 of the glass cube 112, the linearly polarized light component P _F in the longitudinal direction of the fiber laser beam FB of the reflection and transmission film 110 straight through upward, linearly polarized light component S _F in the lateral direction is reflected at a right angle towards the Faraday rotator 104. Then, the linearly polarized light component P _F that has passed through the reflection and transmission film 110 upward is incident on the fold mirror 114, where it reflected at right angles towards the Faraday rotator 104. Thus, like the first embodiment described above (FIG. 2), the fiber laser oscillator 10 linearly polarized light component of the fiber laser beam FB is vertical (Fig. 1) P _F and the transverse direction of the linear polarized light component S _F The linearly polarized light components P _F and S _F are taken out in parallel (horizontal in the figure) with an appropriate close distance.

In the second branch coupler 108, 1/2 linearly polarized light component coming from the wave plate 106 P _F, of S _F, linearly polarized light component P _F having a vertical polarization plane, first folding mirror The light then enters 120 and is reflected vertically downward, and then passes straight through the reflective / transmissive film 116. On the other hand, linearly polarized light component S _F having the polarization plane of the transverse direction are directly incident on the reflection transmission film 116 of the glass cube 118, where it is reflected at a right angle vertically downward to join a linearly polarized light component P _F. Thus, even in this second branch coupling portion 102, two linearly polarized light components P _F which polarization planes orthogonal to each other, S _F are combined with the same laser beam path, recovered fiber laser beam FB 'is obtained .

On the other hand, as shown in FIG. 4B, the reflected return light RB from the workpiece 60 propagating in the laser beam path of the laser transmission system in the reverse direction is first reflected by the glass cube 118 at the second branch coupling unit 108. The light enters the transmission film 116. Of the incident light reflected back RB, linearly polarized light component P _R having a longitudinal polarization plane is straight through the reflection and transmission film 116 vertically upward and then to where the half-wave plate 106 is incident on the folding mirror 120 Reflects at a right angle toward. The linearly polarized light component S _R having the horizontal polarization plane is reflected by the reflection / transmission film 116 at a right angle toward the half-wave plate 106 and becomes parallel (horizontal) with a short distance from the linearly polarized light component P _R. .

Further, in the first branch coupling unit 102, linearly polarized light component P _R from the Faraday rotator 104, of S _R, linearly polarized light component P _R having the polarization plane of the transverse direction are initially incident on the fold mirror 114 Therefore, the light is reflected downward in the vertical direction, and then enters the reflection / transmission film 110 and is reflected at a right angle in the horizontal direction. On the other hand, linearly polarized light component S _R having the polarization plane of the longitudinal direction is incident directly on the reflective transmission layer 116 of the glass cube 118, where the pass through straight horizontally, and merges with the linearly polarized light component P _R.

Thus, also in the third embodiment, both the linearly polarized light components P _R and S _R merge on the deviation optical path 122 set outside the first branch coupling unit 102 in the horizontal direction, and the reflected return light RB is restored. Removed from the laser transmission system.

  In the third embodiment, the Faraday rotator 104 and the half-wave plate 106 operate in the same manner as in the first embodiment (FIG. 2).

  Although the above-described embodiment relates to the fiber laser processing apparatus, the present invention can also be applied to other laser processing apparatuses.

  For example, as shown in FIG. 5, the optical isolator 100 of the above embodiment can be applied to a YAG laser processing apparatus as it is. In this YAG laser processing apparatus, a YAG rod 72 is disposed between optical resonator mirrors 26 and 28 in a YAG laser oscillator 70, and a fiber coupling LD 74 is used to optically pump the YAG rod 72. Yes. That is, the excitation laser beam MB generated by the excitation LD 30 is condensed and incident on one end surface of the optical fiber 78 by the condensing lens 76, propagates in the optical fiber 78, and is emitted from the other end surface. 80, the condenser lens 82, and the optical resonator mirror 26 are incident on one end surface of the YAG rod 72. The YAG laser beam YB oscillated and output from the YAG laser oscillator 70 is irradiated to the processing point W of the workpiece 60 through the optical isolator 100 and the laser emitting unit 18 as a processing laser beam.

  Also in this YAG laser processing apparatus, the optical isolator 100 can pass the YAG laser light YB from the YAG laser oscillator 70 with almost no attenuation, and remove the reflected return light RB from the workpiece 60 from the laser transmission system. it can. Thereby, the YAG laser oscillator 70, the power feedback control mechanism (42, 12, 32) and the fiber coupling LD 74 can be protected from the reflected return light RB.

  As another example, as shown in FIG. 6, a laser beam LB for processing is generated by a high-power LD 84, and the laser beam LB for processing is passed through an optical fiber 86 for transmission at a desired processing location. The optical isolator 100 of the present invention can also be applied to an LD laser processing apparatus that performs processing. In FIG. 6, the condensing lens 88 condenses and enters the laser beam LB oscillated and output from the LD 84 onto one end surface of the optical fiber 86. Further, the comometer lens 90 causes the laser beam LB emitted radially from the other end surface of the optical fiber 86 to enter the optical isolator 100 as parallel light.

  The fiber laser processing apparatus of the present invention is not limited to laser welding, but can also be applied to laser processing such as laser marking, drilling, and cutting.

It is a figure which shows the structure of the fiber laser processing apparatus by one Embodiment of this invention. It is a figure which shows the structure of the optical isolator by a 1st Example, and the effect | action of each part with respect to a fiber laser beam. It is a figure which shows the structure of the optical isolator by 1st Example, and the effect | action of each part with respect to reflected return light. It is a figure which shows the structure of the optical isolator by 2nd Example, and the effect | action of each part with respect to a fiber laser beam. It is a figure which shows the structure of the optical isolator by 2nd Example, and the effect | action of each part with respect to reflected return light. It is a figure which shows the structure of the optical isolator by 3rd Example, and the effect | action of each part with respect to a fiber laser beam. It is a figure which shows the structure of the optical isolator by 3rd Example, and the effect | action of each part with respect to reflected return light. It is a figure which shows the structure of the YAG laser processing apparatus to which the optical isolator of this invention is applied. It is a figure which shows the structure of LD laser processing apparatus to which the optical isolator of this invention is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fiber laser oscillator 16 Fiber transmission system 18 Laser emission part 70 YAG laser oscillator 84 High output type LD
100 optical isolator 102 first branch coupling portion
104 Faraday rotator 106 Half-wave plate 108 Second branch coupling part 110, 116 Reflecting and transmitting film 112, 118 Glass cube 114, 120 Folding mirror

Claims (9)

Provided in the middle of the laser transmission system that optically connects the laser oscillation part and the workpiece, and passes the machining laser beam propagating in the forward direction from the laser oscillation part side, in the reverse direction from the workpiece side. An optical isolator for laser processing that removes reflected return light that has propagated,
The first branch coupling unit, the Faraday rotator, the half-wave plate, and the second branch coupling unit are arranged in this order when viewed from the laser oscillation unit side,
The first branching and coupling unit divides the processing laser beam from the laser oscillation unit into two first and second linearly polarized light components whose polarization planes are orthogonal to each other and propagate parallel to each other,
The Faraday rotator passes the first and second linearly polarized light components from the first branch coupling unit through a common Faraday element, and rotates each polarization plane by 45 degrees in a predetermined rotation direction;
The half-wave plate rotates the planes of polarization of the first and second linearly polarized light components by a predetermined angle in axial symmetry with respect to the optical axis direction of the crystal;
The second branching and coupling unit combines the first and second linearly polarized light components from the half-wave plate on the same laser optical path to restore the processing laser beam;
The second branching and coupling unit has a third and a third propagating unit that propagates the reflected return light from the work piece in parallel with each other, having the same plane of polarization as the first and second linearly polarized light components. Divide into 4 linearly polarized light components,
The half-wave plate rotates the planes of polarization of the third and fourth linearly polarized light components by a predetermined angle in axial symmetry with respect to the optical axis direction of the crystal;
The Faraday rotator passes the third and fourth linearly polarized light components from the half-wave plate through the common Faraday element to rotate each polarization plane by 45 degrees in the predetermined rotation direction;
The first branching and coupling unit guides the third and fourth linearly polarized light components from the Faraday rotator to a deviating optical path deviating from the laser transmission system in a different direction and removes them from the laser transmission system. Optical isolator for processing. The first branch coupling portion includes a first reflective / transmissive film coated on a transparent support and a first folding mirror;
The processing laser beam from the laser oscillator enters the first reflective / transmissive film at an incident angle of 45 degrees, and the first linearly polarized light component of the incident processing laser beam is the Faraday rotation. The second linearly polarized component is reflected at right angles toward the first folding mirror while being transmitted straight toward the child,
In the first reflective / transmissive film, the third linearly polarized light component from the Faraday rotator is incident from a direction opposite to the transmission direction of the first linearly polarized light component and is reflected at right angles on the departure optical path. And the fourth linearly polarized light component from the first folding mirror is incident from a direction opposite to the reflection direction of the second linearly polarized light component and is transmitted straight on the departure optical path,
In the first folding mirror, the second linearly polarized light component from the first reflective / transmissive film is incident at an incident angle of 45 degrees and reflected at right angles toward the Faraday rotator, and the Faraday rotation 2. The optical isolator according to claim 1, wherein the fourth linearly polarized light component from a child is incident at an incident angle of 45 degrees and is reflected at right angles toward the first reflective / transmissive film. The first branch coupling portion includes a first reflective / transmissive film coated on a transparent support and a first folding mirror;
The processing laser beam from the laser oscillation unit is incident on the first reflection / transmission film at an incident angle of 45 degrees, and the first linearly polarized light component of the incident processing laser beam is the first reflection beam. And the second linearly polarized light component is reflected at a right angle toward the Faraday rotator.
In the first reflective / transmissive film, the third linearly polarized light component from the first folding mirror is incident from a direction opposite to the transmission direction of the first linearly polarized light component and is perpendicular to the departure optical path. The fourth linearly polarized light component from the Faraday rotator is incident from a direction opposite to the reflection direction of the second linearly polarized light component and is transmitted straight through the deviating optical path,
In the first folding mirror, the first linearly polarized light component from the first reflective / transmissive film is incident at an incident angle of 45 degrees and is reflected at right angles toward the Faraday rotator, and the Faraday rotation 2. The optical isolator according to claim 1, wherein the third linearly polarized light component from the child is incident at an incident angle of 45 degrees and is reflected at right angles toward the first reflective / transmissive film. The second branch coupling portion has a second reflective / transmissive film coated on a transparent support and a second folding mirror;
In the second reflective / transmissive film, the first linearly polarized light component from the half-wave plate is incident at an incident angle of 45 degrees and is transmitted straight through the laser light path, and the second folding mirror. The second linearly polarized component from is incident at an incident angle of 45 degrees and reflected perpendicularly onto the laser beam path;
The reflected return light from the workpiece enters the second reflective / transmissive film at an incident angle of 45 degrees from the direction opposite to the transmission direction of the first linearly polarized light component. And the third linearly polarized light component is transmitted straight toward the half-wave plate and the fourth linearly polarized light component is reflected at right angles toward the second folding mirror,
In the second folding mirror, the second linearly polarized light component from the half-wave plate is incident at an incident angle of 45 degrees and is reflected at right angles toward the second reflective / transmissive film, and The fourth linearly polarized light component from the second reflective / transmissive film is incident at an incident angle of 45 degrees and is reflected at right angles toward the half-wave plate. Optical isolator. The second branch coupling portion has a second reflective / transmissive film coated on a transparent support and a second folding mirror;
In the second reflective / transmissive film, the first linearly polarized light component from the second folding mirror is incident at an incident angle of 45 degrees and is transmitted straight through the laser light path, and the half-wave plate The second linearly polarized component from is incident at an incident angle of 45 degrees and reflected perpendicularly onto the laser beam path;
In the second reflective / transmissive film, the reflected return light from the workpiece is incident at an incident angle of 45 degrees from a direction opposite to the transmission direction of the first linearly polarized light component, and the reflected return light Among them, the third linearly polarized light component is transmitted straight toward the second folding mirror and the fourth linearly polarized light component is reflected at right angles toward the half-wave plate,
In the second folding mirror, the first linearly polarized light component from the half-wave plate is incident at an incident angle of 45 degrees and is reflected at right angles toward the second reflective / transmissive film, and The third linearly polarized light component from the second reflective / transmissive film is incident at an incident angle of 45 degrees and is reflected at right angles toward the half-wave plate. Optical isolator.   The first and second linearly polarized light components are extracted in parallel at a distance of 3 to 5 mm from the first branch coupling portion, and the third and fourth linearly polarized light components are extracted from the second branch coupling portion. The optical isolator according to any one of claims 1 to 5, wherein the optical isolators are taken out in parallel at a distance of 3 to 5 mm. A laser oscillation unit for oscillating and outputting a laser beam for processing;
A laser emitting portion for focusing and irradiating the processing laser beam toward a processing point on the workpiece;
A laser transmission system for transmitting the processing laser beam oscillated from the laser oscillating unit to the laser emitting unit;
The laser processing apparatus which has the optical isolator as described in any one of Claims 1-6 provided in the middle of the said laser transmission system.   The laser oscillation unit includes a fiber laser oscillator having an optical fiber structure in which a core including a light emitting element is used as an active medium, and the processing laser beam having a predetermined wavelength is oscillated and output by exciting the core with predetermined excitation light. The laser processing apparatus according to claim 7. The laser oscillation unit is
An active medium;
An excitation unit for optically exciting the active medium with excitation light;
A laser output measuring unit for measuring the laser output of the processing laser beam;
The laser processing apparatus according to claim 7, further comprising: a laser power supply unit that controls the output of the excitation light so that a laser output measurement value obtained from the laser output measurement unit follows a preset reference value or reference waveform.

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