Laser Processing Equipment

Abstract

A laser processing apparatus comprises at least a laser oscillator, an optical fiber (30), and a laser head (40). The laser head (40) has at least first and second shield glasses (45), (47) and first and second light-receiving units (51), (52) inside a second casing (41). The first and second shield glasses (45), (47) are respectively provided with first and second coating films (46), (48) on light-receiving surfaces that receive laser beams (LB). The first light-receiving unit (51) receives the laser beam (LB) reflected by the first coating film (46) and outputs a first light reception signal, and the second light-receiving unit (52) receives the laser beam (LB) reflected by a circumferential edge portion (48b) of the second coating film (48) and outputs a second light reception signal.

Description

[Technical field]

[0001] The present disclosure relates to a laser processing apparatus. [Background technology]

[0002] Conventionally, there is known a laser processing device that uses an optical fiber to perform laser processing on a workpiece located at a distance. In such a laser processing device, an optical component, for example, a focusing lens, is used to appropriately direct a laser beam emitted from a laser oscillator into an optical fiber.

[0003] However, when the output of a laser beam reaches a high output of kW class, part of the laser beam is absorbed by the focusing lens, causing the temperature to rise. In this case, the focal length of the focusing lens may change due to the thermal lens effect.

[0004] Therefore, Patent Document 1 discloses a method for detecting a change in focal length corresponding to a change in refractive index distribution of the condenser lens or a change in the numerical aperture of the laser light by using a thermocouple to measure the in-plane temperature distribution of the condenser lens through which the laser light passes. By correcting the focal position of the laser light based on the detection result, the spot diameter of the laser light irradiated on the workpiece can be maintained at an appropriate value. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5558629 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when a laser oscillator is used for a long time, its state may change due to the influence of temperature rise, etc. For example, the optical axis of the laser light may shift from the initial state. Also, when the output of the laser light is changed significantly, the divergence angle of the laser light may change before and after the change in output.

[0007] In such a case, the numerical aperture of the laser light incident on the optical fiber varies, and the beam quality and spot diameter of the laser light irradiated on the workpiece may not be maintained at the desired values, which may result in a loss of machining accuracy of the workpiece.

[0008] However, in the conventional method disclosed in Patent Document 1, a thermocouple is used to indirectly determine the refractive index distribution of the focusing lens, making it difficult to detect such changes in numerical aperture in a short period of time and in real time.

[0009] The present disclosure has been made in consideration of the above points, and its purpose is to provide a laser processing apparatus that can detect the numerical aperture of laser light incident on an optical fiber in a short period of time and in real time. [Means for solving the problem]

[0010] In order to achieve the above object, a laser processing apparatus according to the present disclosure includes at least a laser oscillator that generates laser light, an optical fiber that transmits the laser light incident on an incident end, and a laser head that receives the laser light transmitted by the optical fiber and irradiates it toward a workpiece, the laser head having at least a housing, a first optical component and a second optical component arranged inside the housing, and a first light receiving unit and a second light receiving unit arranged inside the housing, the first optical component is arranged at a position closer to the output end of the optical fiber than the second optical component, the first optical component is provided with a first coating film having a predetermined reflectance on at least one of its light receiving surfaces for the laser light, the second optical component is provided with a second coating film on at least one of its light receiving surfaces for the laser light, the first light receiving unit receives the laser light reflected by the first coating film and outputs a first light receiving signal, and the second light receiving unit receives the laser light reflected by a peripheral portion of the second coating film and outputs a second light receiving signal. Effect of the Invention

[0011] According to the present disclosure, the numerical aperture of laser light incident on an optical fiber and its change can be detected in a short time and in real time. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic configuration diagram of a laser processing device according to the first embodiment. [Diagram 2] FIG. 2 is a schematic cross-sectional view of an optical fiber. [Diagram 3] FIG. 3 is a schematic diagram of the inside of the laser head. [Figure 4] FIG. 4 is a schematic diagram showing a beam profile of a laser beam. [Diagram 5] FIG. 5 is a diagram showing an example of changes over time of the first light receiving signal and the second light receiving signal. [Figure 6] FIG. 6 is a diagram showing the relative intensities of the first and second received light signals with respect to the output power and NA of the laser light. [Figure 7] FIG. 7 is a diagram showing the relationship between the incident position of the laser light on the incident end face of the optical fiber according to the second embodiment and the NA of the laser light emitted from the optical fiber. [Figure 8] FIG. 8 is a schematic diagram of a film forming apparatus for forming the second coating film according to the third embodiment. [Figure 9] FIG. 9 is a diagram showing the positional relationship between the optical components and the gate during film formation. [Figure 10] FIG. 10 is a diagram showing the film thickness distribution of the second coating film. [Figure 11] FIG. 11 is a diagram showing the relationship between the wavelength of laser light and the reflectance of the second coating film. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the following description of the preferred embodiments is merely illustrative in nature and is not intended to limit the present disclosure, its application, or its uses.

[0014] (Embodiment 1) [Configuration of laser processing equipment and optical fiber] Fig. 1 shows a schematic diagram of the laser processing device according to this embodiment, and Fig. 2 shows a schematic cross-sectional view of an optical fiber. In the following description, the direction perpendicular to the incident end surface 30a1 of the optical fiber 30 may be referred to as the X direction, the direction from the laser head 40 toward the workpiece W may be referred to as the Z direction, and the direction perpendicular to each of the X direction and the Z direction may be referred to as the Y direction. Fig. 2 is merely a schematic diagram and differs from the actual dimensions of each part of the optical fiber 30.

[0015] 1, the laser processing apparatus 100 has at least a laser oscillator 10, an optical coupler 20, an optical fiber 30, a laser head 40, and a control unit 60. The laser processing apparatus 100 also has a power supply for driving the laser oscillator 10, etc., but for the sake of convenience, these are not shown and will not be described.

[0016] The laser oscillator 10 emits a laser beam LB. In this embodiment, the wavelength of the laser beam LB is about 950 nm to 1000 nm. However, the wavelength is not particularly limited to this value and may be other values.

[0017] The laser oscillator 10 of this embodiment is a semiconductor laser light source (DDL: Direct Diode Laser) that directly uses light emitted from a semiconductor laser. As the DDL light source, a plurality of semiconductor laser arrays each having a plurality of laser light emitters are used.

[0018] The optical coupler 20 has at least a first housing 21, a reflecting mirror 22, and a first condensing lens 23, and the reflecting mirror 22 and the first condensing lens 23 are housed inside the first housing 21 while maintaining a predetermined positional relationship with each other. The first housing 21 also has a light entrance port (not shown) into which the laser light LB emitted from the laser oscillator 10 is incident, and a light exit port (not shown) to which the entrance end 30a of the optical fiber 30 is connected.

[0019] The reflection mirror 22 reflects the laser light LB incident on the inside of the first housing 21 toward the first focusing lens 23. The first focusing lens 23 focuses the laser light LB reflected by the reflection mirror 22 so that the laser light LB is incident on the incident end surface 30a1 of the optical fiber 30.

[0020] As shown in FIG. 1, in the optical path of the laser light LB from the first focusing lens 23 toward the incident end 30a of the optical fiber 30, the angle between the optical axis of the laser light LB and the outermost edge of the laser light LB is defined as a divergence angle θ.

[0021] At this time, the numerical aperture (NA) on the incident side of the laser light LB is defined by the following formula (1).

[0022] N A = sinθ (1) A first position adjustment unit 71 is connected to the reflecting mirror 22. By driving the first position adjustment unit 71, the angle of the surface of the reflecting mirror 22 with respect to the incident direction of the laser light LB is adjusted. A second position adjustment unit 72 is connected to the first condensing lens 23. By driving the second position adjustment unit 72, the first condensing lens 23 moves in at least one of the X, Y, and Z directions, and its position is adjusted to a desired position.

[0023] In this embodiment, the initial positional relationship between the reflecting mirror 22 and the first condenser lens 23 is set so that the laser light LB is incident on the first core 31 of the optical fiber 30 (see FIG. 2).

[0024] However, as described later, the laser light LB may be incident on the second core 33 (see FIG. 2) of the optical fiber 30. In that case, the first position adjustment unit 71 and / or the second position adjustment unit 72 are driven to change the incident position of the laser light LB on the incident end surface 30a1 of the optical fiber 30.

[0025] 1, both the first position adjustment unit 71 and the second position adjustment unit 72 are disposed outside the first housing 21, but in reality, a portion of each is provided inside the first housing 21. Both the first position adjustment unit 71 and the second position adjustment unit 72 may be disposed inside the first housing 21.

[0026] The optical fiber 30 receives the laser light LB focused by the first focusing lens 23 of the optical coupler 20 and transmits it toward the laser head 40 .

[0027] As shown in FIG. 2, the optical fiber 30 has at least a first core 31 and a second core 33, each of which is an optical waveguide, and a first clad 32 and a second clad 34, and the outer surface of the second clad 34 is covered with a light-shielding coating (not shown).

[0028] The first core 31 has a circular shape in a cross-sectional view, and is disposed at the axis of the optical fiber 30. The first cladding 32 is in contact with the outer peripheral surface of the first core 31, and is disposed coaxially with the first core 31, and is ring-shaped in a cross-sectional view. The second core 33 is in contact with the outer peripheral surface of the first cladding 32, and is disposed coaxially with the first core 31, and is ring-shaped in a cross-sectional view. The second cladding 34 is in contact with the outer peripheral surface of the second core 33, and is disposed coaxially with the first core 31, and is ring-shaped in a cross-sectional view.

[0029] The first core 31, the second core 33, the first cladding 32, and the second cladding 34 are all made of quartz. However, the refractive index of the first cladding 32 is set to be lower than the refractive indexes of the first core 31 and the second core 33. In addition, the refractive index of the second cladding 34 is set to be lower than the refractive index of the second core 33.

[0030] The laser head 40 is configured to receive the laser light LB transmitted by the optical fiber 30 and irradiate it toward the workpiece W, and has a second housing (housing) 41 and a plurality of optical components. As shown in Fig. 1, the plurality of optical components include a collimation lens 42, a second condenser lens 43, and a protective glass 44. The plurality of optical components also includes a first shield glass (first optical component) 45 and a second shield glass (second optical component) 47, which will be described later (see Fig. 3).

[0031] The second housing 41 has a connector portion 41a to which the emission end 30b of the optical fiber 30 is connected, and a light emission port (not shown) through which the laser light LB is emitted toward the workpiece W. In addition, the above-mentioned multiple optical components are accommodated inside the second housing 41 while maintaining a predetermined positional relationship with each other.

[0032] The laser light LB entering the inside of the second housing 41 from the output end 30b of the optical fiber 30 passes through the first shielding glass 45 and the second shielding glass 47, respectively, and is incident on the collimation lens 42 and the second focusing lens 43, which are the focusing optical system.

[0033] The collimation lens 42 converts the laser light LB into parallel light, and the second condenser lens 43 is configured to condense the laser light LB that has passed through the collimation lens 42 onto the surface of the workpiece W.

[0034] Further, a third position adjustment unit 73 is connected to both or at least one of the collimation lens 42 and the second condenser lens 43. By driving the third position adjustment unit 73, the collimation lens 42 and / or the second condenser lens 43 move in the optical axis direction of the laser light LB traveling inside the second housing 41, and the condensing position of the laser light LB is adjusted to a desired position.

[0035] 1, the third position adjustment unit 73 is disposed outside the second housing 41, but in reality, a part of it is provided inside the second housing 41. The third position adjustment unit 73 may be disposed inside the second housing 41.

[0036] The protective glass 44 is provided to prevent fumes and spatters generated when the workpiece W melts due to irradiation with the laser light LB from entering the inside of the second housing 41 and adhering to other optical components.

[0037] It goes without saying that the protective glass 44 and other optical components are made of a material that transmits the laser light LB. In this embodiment, each of the optical components is made of synthetic quartz. However, the material is not particularly limited to this, and other materials can be selected appropriately depending on the wavelength of the laser light LB.

[0038] The control unit 60 is connected to the first to third position adjustment units 71 to 73, respectively, and outputs control signals to the first to third position adjustment units 71 to 73 to control their operations. The control unit 60 also receives a first light receiving signal and a second light receiving signal, which are output signals from the first light receiving unit 51 and the second light receiving unit 52 (see FIG. 3) provided in the laser head 40, respectively. The above-mentioned control signals are generated based on the first light receiving signal and the second light receiving signal.

[0039] The laser processing apparatus 100 may be provided with a manipulator (not shown) for holding the laser head 40. The manipulator is, for example, an articulated robot, and is connected to the control unit 60, and moves the laser head 40 to a desired position at a desired speed based on an operation command from the control unit 60. In this way, the laser light LB emitted from the laser head 40 is irradiated to draw a desired trajectory on the surface of the workpiece W. A separate control unit (not shown) for controlling the operation of the manipulator may be provided.

[0040] [Laser head configuration] Fig. 3 is a schematic diagram showing the inside of the laser head. For ease of explanation, the lower half of the laser head 40, such as the second condenser lens 43 and the protective glass 44, is omitted in Fig. 3.

[0041] As shown in Fig. 3, the output end 30b of the optical fiber 30 is disposed inside the second housing 41 through the connector portion 41a. The laser light LB output from the output end 30b of the optical fiber 30 is transmitted through the first shield glass 45 and the second shield glass 47 while expanding such that the optical axis and the outermost side form the above-mentioned expansion angle θ, and is then incident on the collimation lens 42. That is, the numerical aperture shown in formula (1) is maintained even on the output side of the optical fiber 30. Therefore, the numerical apertures of the laser light LB on the input side and output side of the optical fiber 30 may hereinafter be collectively referred to simply as the NA of the laser light LB.

[0042] The first shield glass 45 and the second shield glass 47 are disposed inside the second housing 41 between the emission end 30b of the optical fiber 30 and the collimation lens 42. The first shield glass 45 and the second shield glass 47 are disposed at an interval from each other in the optical axis direction of the laser light LB. The first shield glass 45 is disposed at a position closer to the emission end 30b of the optical fiber 30 than the second shield glass 47.

[0043] The first shield glass 45 and the second shield glass 47 prevent fumes and the like that have entered the inside of the second housing 41 from adhering to the emission end 30 b of the optical fiber 30 .

[0044] The first shield glass 45 has a first coating film 46 on the surface of the laser light LB receiving surface that is closer to the emission end 30b of the optical fiber 30. The first coating film 46 is disposed in the optical path of the laser light LB incident on the first shield glass 45, and has a predetermined reflectance, for example, a reflectance of several tenths of percent, for the laser light LB.

[0045] Similarly, the second shield glass 47 has a second coating film 48 on the surface that is closer to the emission end 30b of the optical fiber 30, among the light receiving surfaces for receiving the laser light LB.

[0046] The second coating film 48 is disposed in the optical path of the laser light LB incident on the second shield glass 47. However, unlike the first coating film 46, the second coating film 48 is composed of a central portion 48a and a peripheral portion 48b having mutually different reflectances. The reflectance of the central portion 48a is equal to the reflectance of the first coating film 46. On the other hand, the peripheral portion 48b is formed so as to have a higher reflectance than the central portion 48a. For example, the second coating film 48 is formed so that the reflectance of the peripheral portion 48b is about 1 to 10% higher than the reflectance of the central portion 48a.

[0047] In this specification, "same" and "equal" mean the same or equal, including the manufacturing tolerances of each part in the laser processing apparatus 100 and the first coating film 46 and the second coating film 48, and the allowable tolerances of the positional relationship of each part, and do not mean that the two objects being compared are the same or equal in the strict sense.

[0048] The first coating film 46 and the second coating film 48 are thin films made of a metal oxide dielectric material containing a metal such as Ta (tantalum), and are formed so as to have a higher refractive index than synthetic quartz with respect to the laser light LB. However, the present invention is not particularly limited to this, and other configurations may be used as appropriate. For example, the first coating film 46 and the second coating film 48 may be a dielectric multilayer film obtained by alternately stacking dielectric films having different dielectric constants from synthetic quartz. In addition, the second coating film 48 may be a structure that transmits the laser light LB but has a different refractive index distribution between the central portion 48a and the peripheral portion 48b. In this case, it is sufficient that the magnitude relationship of the reflectance described above is satisfied.

[0049] Moreover, the first coating film 46 and the second coating film 48 are configured to transmit most of the laser light LB, for example, 90% or more, while reflecting the remainder. It is preferable that the reflectance of the first coating film 46 and the second coating film 48 is not too high, because this would increase the loss of the laser light LB irradiated to the workpiece W. Moreover, if the reflected light intensity inside the laser head 40 becomes too strong, it may damage the internal components.

[0050] That is, the thickness of the central portion 48a and the peripheral portion 48b of the first coating film 46 and the second coating film 48 is preferably set so as to transmit most of the laser light LB, for example 90% or more, and reflect the remainder.

[0051] A first light receiving section 51 and a second light receiving section 52 are disposed inside the second housing 41. The first light receiving section 51 is disposed at a position where it can receive the laser light LB reflected by the first coating film 46. The second light receiving section 52 is disposed at a predetermined distance from the first light receiving section 51 and at a position where it can receive the laser light LB reflected by the peripheral portion 48b of the second coating film 48.

[0052] Both the first light receiving section 51 and the second light receiving section 52 are configured with a light receiving element such as a known photodiode. Moreover, both the first light receiving section 51 and the second light receiving section 52 are configured to output electrical signals according to the amount of received light as output signals, that is, as a first light receiving signal and a second light receiving signal, respectively, to the control section 60. Based on the first light receiving signal and the second light receiving signal input to the control section 60, the NA of the laser light LB is derived by the control section 60. This will be described in detail later.

[0053] Both the first light receiving section 51 and the second light receiving section 52 have a predetermined directivity. That is, the first light receiving section 51 and the second light receiving section 52 are configured to be able to receive only light incident at a light receiving angle within a predetermined range.

[0054] [Real-time monitoring of laser light NA and NA correction procedure] Fig. 4 shows a schematic diagram of a beam profile of a laser beam, specifically, a one-dimensional distribution of the light intensity of the laser beam LB. Fig. 5 shows an example of a time change of the first light receiving signal and the second light receiving signal, and Fig. 6 shows the relative intensities of the first light receiving signal and the second light receiving signal with respect to the output power and NA of the laser beam. Note that the signal intensity in Fig. 6 is shown as a relative value with the signal intensity of the first light receiving signal being set to 1 when the output power of the laser beam LB is 500 W.

[0055] The area between the two inner dashed lines shown in Fig. 4 is an area that contains 86% of the beam power of the laser light LB. In the example shown in Fig. 4, this area is designated as range D1. The first light receiving unit 51 receives the laser light LB included in this range D1 that is reflected by the first coating film 46, and outputs a first light receiving signal.

[0056] On the other hand, the portion sandwiched between the two inner dashed lines shown in Fig. 4 is a region that contains 100% of the beam power of the laser light LB. In the example shown in Fig. 4, this is range D2. The second light receiving unit 52 receives the reflected light of the laser light LB contained in range D2 (see the hatched area in Fig. 4) excluding range D1 that is reflected by the peripheral portion 48b of the second coating film 48, and outputs a second light receiving signal.

[0057] As described above, the NA of the laser light LB changes depending on the state of the laser oscillator 10 and changes in the output of the laser light LB. For example, in the example shown in FIG. 5, consider a case where the output of the laser light LB is discontinuously increased. At this time, the signal strength of both the first and second received light signals increases, but to different degrees. In the example shown in FIG. 5, the rate at which the second received light signal increases is higher than the rate at which the first received light signal increases before and after a change in the output of the laser light LB. This is because the NA of the laser light LB increases due to an increase in the output of the laser light LB.

[0058] 6, when the NA of the initial laser light LB is set to a small value, for example, about 0.1, if the output of the laser light LB increases from 500 W to 4000 W (=4 kW), the signal strength of the first light-receiving signal doubles, while the signal strength of the second light-receiving signal becomes 1.5 times. On the other hand, when the NA of the initial laser light LB is set to a large value, for example, about 0.18, if the output of the laser light LB increases from 500 W to 4000 W (=4 kW), the signal strength of the first light-receiving signal triples, while the signal strength of the second light-receiving signal also triples.

[0059] In this way, the signal intensities of the first and second received light signals and the signal intensity ratio between them change according to the change in the output power and NA of the laser light LB.

[0060] Therefore, the relationship between the signal intensities of the first and second received signals and the signal intensity ratio between them and the NA of the laser light LB is experimentally determined in advance and stored as a data table in a memory unit (not shown) provided inside or outside the control unit 60.

[0061] The control unit 60 is configured to compare the first and second light receiving signals input from the first and second light receiving units 51 and 52, respectively, and their intensity ratio with the aforementioned data table to derive the NA of the laser light LB, and also to detect changes in the NA of the laser light LB.

[0062] In addition, while the laser processing apparatus 100 is operating, specifically while the laser light LB is being output, the NA of the laser light LB and its changes can be monitored in real time by operating the first light receiving unit 51, the second light receiving unit 52 and the control unit 60.

[0063] If the derived NA exceeds a predetermined range, the control unit 60 controls the position of the optical components in the optical coupler 20 so that the NA of the laser light LB falls within the predetermined range. Specifically, the control unit 60 drives and controls the first position adjustment unit 71 and / or the second position adjustment unit 72 to adjust the position of the reflection mirror 22 and / or the first focusing lens 23. For example, the first position adjustment unit 71 is driven to adjust the angle of the surface of the reflection mirror 22, thereby changing the NA of the laser light LB incident on the optical fiber 30. In addition, the second position adjustment unit 72 is driven to adjust the position of the first focusing lens 23, thereby changing the NA of the laser light LB incident on the optical fiber 30.

[0064] The above-mentioned predetermined range is appropriately changed depending on the output of the laser light LB, the processing accuracy required for the laser processing, and further the material and shape of the workpiece W to be irradiated with the laser light LB.

[0065] [Effects, etc.] As described above, the laser processing apparatus 100 of this embodiment includes at least a laser oscillator 10 that generates laser light LB, an optical fiber 30 that transmits the laser light LB incident on the incident end 30a, and a laser head 40 that receives the laser light LB transmitted by the optical fiber 30 and irradiates the laser light LB toward the workpiece W.

[0066] The laser head 40 has at least a second housing (housing) 41, a first shielding glass (first optical component) 45 and a second shielding glass (second optical component) 47 arranged inside the second housing 41, and a first light receiving unit 51 and a second light receiving unit 52 arranged inside the second housing 41.

[0067] The first shield glass 45 is disposed at a position closer to the output end 30 b of the optical fiber 30 than the second shield glass 47 is.

[0068] The first shield glass 45 is provided with a first coating film 46 having a predetermined reflectance on at least one of its light receiving surfaces for the laser light LB, and the second shield glass 47 is provided with a second coating film 48 on at least one of its light receiving surfaces for the laser light LB.

[0069] The first light receiving section 51 receives the laser light LB reflected by the first coating film 46 and outputs a first light receiving signal, and the second light receiving section 52 receives the laser light LB reflected by the peripheral portion 48b of the second coating film 48 and outputs a second light receiving signal.

[0070] The laser processing apparatus 100 further includes a control unit 60 to which the first light receiving signal and the second light receiving signal are input. The control unit 60 is configured to detect a change in NA of the laser light LB incident on the optical fiber 30 based on an intensity ratio between the first light receiving signal and the second light receiving signal.

[0071] By configuring the laser processing apparatus 100 in this manner, it is possible to detect reflected light corresponding to the central portion 48a and the peripheral portion 48b (see FIG. 4) of the beam profile of the laser light LB, respectively, and obtain a first light receiving signal and a second light receiving signal corresponding to the respective intensities. This makes it possible to monitor the NA of the laser light LB and its change in real time. Furthermore, when the laser light LB is incident, the first light receiving unit 51 and the second light receiving unit 52 immediately output the first light receiving signal and the second light receiving signal. This makes it possible to detect the NA of the laser light LB and its change in a short period of time.

[0072] In the conventional method disclosed in Patent Document 1, as described above, the refractive index distribution of the condenser lens is indirectly obtained using a thermocouple, so it takes a long time to detect the change in the focal length. Therefore, it takes a long time to correct the focal position, and there is a risk that the laser processing cannot be performed appropriately.

[0073] In particular, when the NA of the laser light LB changes in accordance with a change in the state of the laser oscillator 10 or a change in the output of the laser light LB, it is difficult to detect the change in a short period of time with the conventional method disclosed in Patent Document 1.

[0074] On the other hand, according to the present embodiment, the NA of the laser light LB and its change are detected in a short time based on the first light receiving signal and the second light receiving signal, which are electrical signals respectively generated by the first light receiving unit 51 and the second light receiving unit 52. This makes it possible to maintain the NA of the laser light and, in turn, the spot diameter of the laser light LB irradiated on the workpiece W at appropriate values ​​by adjusting the positions of the various components inside the laser processing apparatus 100, etc.

[0075] The reflectance of the peripheral portion 48b of the second coating film 48 is set to be higher than the reflectance of the first coating film 46.

[0076] In this way, it is possible to increase the amount of reflected light incident on the second light receiving section 52 and increase the intensity of the second light receiving signal, thereby making it possible to accurately detect the NA of the laser light LB and its change.

[0077] The laser processing apparatus 100 further includes an optical coupler 20 for making the laser light LB emitted from the laser oscillator 10 incident on an incident end 30a of the optical fiber 30.

[0078] By providing the optical coupler 20, the laser light LB can be reliably incident on the optical fiber 30 and transmitted toward the laser head 40.

[0079] When the NA of the laser light LB exceeds a predetermined range, the control unit 60 controls the optical coupler 20 so that the NA falls within the predetermined range. Specifically, the control unit 60 drives and controls a first position adjustment unit 71 connected to the reflection mirror 22 provided inside the optical coupler 20 and / or a second position adjustment unit 72 connected to the first focusing lens 23 to adjust the positions of the reflection mirror 22 and / or the first focusing lens 23. This changes the NA of the laser light LB incident on the optical fiber 30 so that it falls within a desired range.

[0080] By configuring the control unit 60 in this way, even if the NA of the laser light LB changes due to a change in the state of the laser oscillator 10 or a sudden change in the output of the laser light LB, the change can be detected immediately and kept within a desired range. This makes it possible to maintain the beam quality of the laser light LB irradiated onto the workpiece W, and therefore the machining accuracy of the workpiece W.

[0081] The control unit 60 controls the laser head 40 so that the laser light LB is focused at a desired focusing position. Specifically, the control unit 60 drives and controls a third position adjustment unit 73 connected to the collimation lens 42 and / or the second focusing lens 43 provided inside the laser head 40 to adjust the position of the collimation lens 42 and / or the second focusing lens 43. This allows the laser light LB to be focused at a desired focusing position.

[0082] By configuring the control unit 60 in this manner, the spot diameter of the laser light LB irradiated onto the workpiece W can be reliably maintained at an appropriate value, and the laser processing can be performed on the workpiece W with the desired processing accuracy.

[0083] The optical fiber 30 has a first core 31 at its axis, and a first clad 32 that is in contact with the outer circumferential surface of the first core 31 and is provided coaxially with the first core 31. The optical fiber 30 also has at least a second core 33 that is in contact with the outer circumferential surface of the first clad 32 and is provided coaxially with the first core 31.

[0084] The optical fiber 30 may be configured in this manner. As described later, by changing the spot diameter or irradiation position of the laser light LB on the incident end surface 30a1 of the optical fiber 30, it is possible to irradiate the workpiece W with the laser light LB having a desired beam profile.

[0085] The type of optical fiber 30 used in the laser processing apparatus 100 of the present disclosure is not particularly limited to the example shown in Fig. 2. For example, it may have a single-core structure having only the first core 31 and the first cladding 32.

[0086] 3, the first coating film 46 is provided on a part of the surface of the first shield glass 45, but is not particularly limited to this. For example, the first coating film 46 may be provided on the surface of the first shield glass 45 that is farther from the emission end 30b of the optical fiber 30, or the first coating film 46 may be provided on the entire surface of the first shield glass 45.

[0087] Similarly, the second coating film 48 may be provided on the surface of the second shield glass 47 that is farther from the emission end 30b of the optical fiber 30, or the second coating film 48 may be provided on the entire surface of the second shield glass 47. In this case, however, both the central portion 48a and the peripheral portion 48b need to be positioned in the optical path of the laser light LB.

[0088] Moreover, either one or both of the first shield glass 45 and the second shield glass 47 may be omitted. When one of them is omitted, for example, the second coating film 48 is provided on the surface of the collimation lens 42 that is closer to the output end 30b of the optical fiber 30. The second coating film 48 may be provided on the entire surface of the collimation lens 42.

[0089] Furthermore, when both the first shield glass 45 and the second shield glass 47 are omitted, the first coating film 46 may be provided on the surface of the collimation lens 42 that is closer to the emission end 30b of the optical fiber 30. In that case, the second coating film 48 may be provided on the surface of the second focusing lens 43 that is farther from the emission end 30b of the optical fiber 30. However, in either case, both the central portion 48a and the peripheral portion 48b need to be positioned in the optical path of the laser light LB.

[0090] In other words, the first optical component is not limited to the first shield glass 45 , and the second optical component is not limited to the first shield glass 45 .

[0091] In the laser processing apparatus 100 of the present disclosure, the first optical component has a first coating film 46 provided on at least one of its light receiving surfaces for receiving the laser light LB, and the second optical component has a second coating film 48 provided on at least one of its light receiving surfaces for receiving the laser light LB.

[0092] (Embodiment 2) Fig. 7 shows the relationship between the incident position of the laser light on the incident end face of the optical fiber according to this embodiment and the NA of the laser light emitted from the optical fiber. Fig. 7(a) is a schematic diagram of the cross-sectional structure of the optical fiber 30, and is a diagram similar to Fig. 2. Fig. 7(b) shows the NA of the laser light LB emitted from the optical fiber 30. The horizontal axis of Fig. 7(b) corresponds to the diameter direction of the optical fiber 30. In Fig. 7 and the subsequent drawings, the same reference numerals are used for the same parts as those in the first embodiment, and detailed explanations will be omitted.

[0093] In the incident end face 30a1 of the optical fiber 30 having the structure shown in Fig. 3, the divergence angle θ of the laser light LB emitted from the optical fiber 30, i.e., the NA of the laser light LB emitted from the optical fiber 30, changes depending on the position at which the laser light LB is incident. As shown in Fig. 7, when the laser light LB is incident only on the first core 31 or the second core 33, the NA of the laser light LB emitted from the optical fiber 30 becomes a small value. On the other hand, when the laser light LB is incident not only on the first core 31 or the second core 33 but also on the first cladding 32, the NA of the laser light LB emitted from the optical fiber 30 becomes large. In other words, the divergence angle of the laser light LB becomes large.

[0094] Depending on the material of the workpiece W and the processing form, it may be more appropriate to have the NA of the laser light LB larger and somewhat expanded than to have the NA of the laser light LB emitted from the optical fiber 30 smaller and finely focused. For example, this is the case when cutting a thin plate.

[0095] Furthermore, when the laser light LB is transmitted only to the first core 31, the output of the laser light LB irradiated to the workpiece W may not reach a desired value. In such a case, the spot diameter of the laser light LB on the incident end face 30a1 is expanded to cause the laser light LB to be incident also on the second core 33, thereby increasing the output of the laser light LB irradiated to the workpiece W. At that time, the laser light LB is also incident on the first cladding 32, and the NA of the laser light LB increases.

[0096] According to the laser processing apparatus 100 of the present disclosure, the NA of the laser beam LB and its change can be monitored in real time. Also, the positions of the reflection mirror 22 and the first focusing lens 23 inside the optical coupler 20 can be adjusted by driving the first position adjustment unit 71 and / or the second position adjustment unit 72.

[0097] As a result, for example, while monitoring the NA of the laser light LB, the position of the reflecting mirror 22 can be adjusted by the first position adjustment unit 71, and the angle of the optical axis of the laser light LB incident on the optical fiber 30 can be changed. This makes it possible to increase the NA of the laser light LB and irradiate the workpiece W with the laser light LB of a desired spot shape. Also, while monitoring the NA of the laser light LB, the position of the first focusing lens 23 can be adjusted by the second position adjustment unit 72, and the spot diameter of the laser light LB on the incident end surface 30a1 can be expanded. This makes it possible to increase the output of the laser light LB irradiated to the workpiece W.

[0098] In other words, the control unit 60 of this embodiment changes at least one of the incident position and spot diameter of the laser light LB on the incident end face 30a1 of the optical fiber 30, and drives and controls the optical coupler 20, specifically at least one of the first position adjustment unit 71 and the second position adjustment unit 72, so that the NA of the laser light LB becomes a desired value.

[0099] (Embodiment 3) Fig. 8 shows a schematic diagram of the deposition apparatus for the second coating film according to the present embodiment, and Fig. 9 shows the arrangement of the optical components and the yator during deposition. Fig. 10 shows the film thickness distribution of the second coating film, and Fig. 11 shows the relationship between the wavelength of the laser light and the reflectance of the second coating film.

[0100] The second coating film 48 is formed on the surface of the optical component 280, for example, by using a film forming apparatus 200 shown in Fig. 8. In this embodiment, the second coating film 48 will be described by taking tantalum oxide as an example.

[0101] The film forming apparatus 200 includes a vacuum chamber 210 , a heater 220 , an electron gun 230 , a crucible 240 , a shutter 260 , and a substrate dome 270 .

[0102] After the inside of the vacuum chamber 210 is evacuated by a vacuum pump (not shown), an electron beam is irradiated from the electron gun 230 onto the deposition source 250, in this case a ceramic molded body of tantalum oxide, placed in the crucible 240, to evaporate the deposition source 250.

[0103] A substrate dome 270 is disposed above the deposition source 250. The substrate dome 270 is attached to the inner surface of the vacuum chamber 210 and can be rotated by a motor (not shown). The substrate dome 270 is provided with a plurality of holders 300 shown in FIG. 9, and each of the holders 300 holds an optical component 280 such as a second shield glass 47. The holder 300 is a so-called substrate holder, and has an opening in the center and holds the optical component 280 at the periphery of the opening. The heater 220 disposed around the substrate dome 270 heats the substrate dome 270 and the optical component 280 held therein to a predetermined temperature.

[0104] The optical component 280 is placed on the yatai 300, and while the substrate dome 270 is rotating, the deposition source 250 is irradiated with an electron beam, and the constituent material of the deposition source 250 becomes an evaporation flow. At this point, the substrate dome 270 and the optical component 280 are heated. After the evaporation flow is stabilized, the shutter 260, which was closed until then, is opened, and the evaporation flow flows toward the substrate dome 270, and the evaporation flow adheres to the optical component 280 through the opening of the yatai 300, and the deposition of the second coating film 48 begins. By opening the shutter 260 for a predetermined time, the second coating film 48 of the desired thickness is deposited on the surface of the optical component 280. The thickness of the second coating film 48 is monitored by a quartz thickness gauge 290 attached near the substrate dome 270, and when the desired thickness is reached, the shutter 260 is closed and the deposition is completed.

[0105] Usually, the thickness of the second coating film 48 formed in this manner decreases rapidly at the periphery. On the other hand, in the film forming apparatus 200 shown in this embodiment, a mesh portion 310 is provided on the inner periphery of the opening of the yatai 300. The mesh portion 310 includes a plurality of openings (not shown) that penetrate the yatai 300 in the thickness direction, and the dimensions of the openings are set to become smaller from the inner periphery of the openings toward the outside.

[0106] When the optical component 280 is held on the support 300 having the mesh portion 310 and the second coating film 48 is formed, the film thickness distribution decreases gradually from the central portion 48a to the peripheral portion 48b as shown in FIG.

[0107] For example, when the wavelength of the laser light LB is set to about 950 nm to 1000 nm, by setting the film thickness of the second coating film 48 to a predetermined value, the reflectance can be made almost zero, as shown in Fig. 11. If the film thickness at this time is set as the target film thickness, the reflectance of the second coating film 48 can be made about 1% to 5% by reducing the film thickness by 5% to 15% from the target film thickness.

[0108] That is, by making the film thickness distribution of the second coating film 48 as shown in FIG. 10, it is possible to make the reflectance of the peripheral portion 48b higher than that of the central portion 48a.

[0109] It should be noted that this embodiment is merely one example, and depending on the structure and material of the second coating film 48, the reflectance may be increased by making the film thickness of the peripheral portion 48b thicker than the film thickness of the central portion 48a.

[0110] However, it is generally known that the wavelength dependency of the reflectance of light changes when the film thickness of any dielectric film, including single-layer films and laminated films, is changed. Therefore, by making the film thickness of the central portion 48a of the second coating film 48 different from that of the peripheral portion 48b, it is possible to make the reflectance of the peripheral portion 48b higher than that of the central portion 48a.

[0111] (Other embodiments) In the present specification, the laser oscillator 10 is described as a DDL light source, but is not limited thereto. For example, the laser oscillator 10 may be a solid-state laser light source, a gas laser light source, or a fiber laser light source. [Industrial Applicability]

[0112] The laser processing apparatus of the present disclosure can detect the numerical aperture of a laser beam and changes therein in a short time and in real time, and is useful for maintaining the processing accuracy of a workpiece. [Explanation of symbols]

[0113] 10 Laser Oscillator 20 Optical coupler 21 1st cabinet 22 Reflective mirror 23 First focusing lens 30 Optical Fiber 30a entrance end 30a1 Incidence end face 30b Output end 31 First Core 32 First Clad 33 Second Core 34 2nd Clad 40 Laser Head 41 Second cabinet (cabinet) 42 Collimation Lens 43 Second focusing lens 44 Protective Glass 45 First shield glass (first optical component) 46 First coating film 47 Second shield glass (second optical component) 48 Second Coating Film 48a central part 48b Periphery 51 1st light receiving section 52 2nd light receiving section 60 Control section 71~73 1st~3rd position adjustment section 100 Laser processing equipment 200 Film deposition equipment 210 Vacuum Chamber 270 Substrate Dome 300 Yatoi 310 Mesh section LB laser light W work

Claims

1. A laser oscillator that generates a laser beam; an optical fiber that transmits the laser light incident on an input end; A laser head that receives the laser light transmitted through the optical fiber and irradiates the laser light toward a workpiece, The laser head includes: A housing and a first optical component and a second optical component disposed inside the housing; The light receiving device includes at least a first light receiving unit and a second light receiving unit disposed inside the housing, the first optical component is disposed at a position closer to the output end of the optical fiber than the second optical component; the first optical component is provided with a first coating film having a predetermined reflectance on at least one of the laser light receiving surfaces, the second optical component is provided with a second coating film on at least one of the laser beam receiving surfaces, the first light receiving unit receives the laser light reflected by the first coating film and outputs a first light receiving signal; The laser processing device is characterized in that the second light receiving section receives the laser light reflected by a peripheral portion of the second coating film and outputs a second light receiving signal.

2. 2. The laser processing apparatus according to claim 1, A laser processing apparatus, characterized in that the reflectance of a peripheral portion of the second coating film is higher than the reflectance of the first coating film.

3. 3. The laser processing apparatus according to claim 1, The optical fiber is A first core is disposed at the axis; a first clad provided coaxially with the first core in contact with an outer peripheral surface of the first core; a second core provided coaxially with the first core and in contact with an outer peripheral surface of the first clad.

4. 4. The laser processing apparatus according to claim 1, a control unit to which the first light receiving signal and the second light receiving signal are input, The laser processing apparatus is characterized in that the control unit is configured to detect a change in the numerical aperture of the laser light incident on the optical fiber based on the intensity ratio between the first light receiving signal and the second light receiving signal.

5. 5. The laser processing apparatus according to claim 4, The laser processing apparatus further comprises an optical coupler for making the laser light emitted from the laser oscillator incident on an incident end of the optical fiber.

6. 6. The laser processing apparatus according to claim 5, The laser processing apparatus according to claim 1, wherein the control unit controls the optical coupler when the numerical aperture exceeds a predetermined range so that the numerical aperture falls within the predetermined range.

7. 7. The laser processing apparatus according to claim 5, The control unit controls the optical coupler by changing at least one of the incident position and spot diameter of the laser light on the incident end face of the optical fiber so that the numerical aperture becomes a desired value.

8. 8. The laser processing apparatus according to claim 4, The laser processing apparatus according to claim 1, wherein the control unit controls the laser head so that the laser light is focused at a desired focusing position.

9. 9. The laser processing apparatus according to claim 1, 2. A laser processing apparatus according to claim 1, wherein a thickness of the second coating film in a central portion is different from a thickness of the second coating film in a peripheral portion.

10. 10. The laser processing apparatus according to claim 9, A laser processing apparatus, characterized in that the film thickness of the central portion is greater than the film thickness of the peripheral portion.

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