Laser processing apparatus and laser processing method

Abstract

To improve adjustment speed of a focal position of laser beam.SOLUTION: A focal position of laser beam emitted from a laser machining head 3 is changed by measuring a distance between the laser machining head 3 and a machining target 30 and changing a wavelength of the laser beam on the basis of the measurement result.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a laser processing apparatus and a laser processing method.

Background Art

[0002] In Patent Document 1, in order to increase the processing depth for a thick workpiece, the beam is focused on different focal points on the optical axis, and the laser light is repeatedly turned on in the order of shorter wavelengths, so that the center of processing is moved from the surface of the workpiece in the order of shallowness. A configured is disclosed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, when performing laser processing, for example, it is necessary to adjust the focal position to an appropriate height with respect to the processing target using an articulated robot.

[0005] However, when the gain of the motor is increased to increase the response speed of laser processing, there is a problem that the laser processing head vibrates due to inertia, and it is difficult to adjust the focal position of the laser beam.

[0006] The present invention has been made in view of such points, and an object thereof is to improve the adjustment speed of the focal position of the laser beam.

Means for Solving the Problems

[0007] The present invention relates to a laser processing apparatus comprising a laser oscillator that outputs multiple laser beams of different wavelengths by wavelength synthesis, and a laser processing head that emits the laser beams output from the laser oscillator onto a workpiece, and provides the following solutions.

[0008] In other words, the first invention includes a distance measuring unit for measuring the distance between the laser processing head and the workpiece, The system includes a control unit that changes the wavelength of the laser light based on the measurement results of the distance measuring unit, thereby changing the focal position of the laser light emitted from the laser processing head.

[0009] In the first invention, the distance between the laser processing head and the workpiece is measured, and the wavelength of the laser light is changed based on the measurement result, thereby changing the focal position of the laser light emitted from the laser processing head.

[0010] In this way, by changing the wavelength of the laser beam, the focal position of the laser beam can be adjusted to the appropriate height relative to the workpiece. This suppresses vibration of the laser processing head due to inertia and improves the speed of adjustment of the laser beam's focal position.

[0011] The second invention is, in the first invention, The control unit lengthens the wavelength of the laser light when the focal position of the wavelength-combined laser light is shorter than the distance to the workpiece, and shortens the wavelength of the laser light when the focal position is longer than the distance to the workpiece.

[0012] In the second invention, the wavelength of the laser light is lengthened when the distance between the focal point of the wavelength-combined laser light and the workpiece is short. Conversely, the wavelength of the laser light is shortened when the distance between the focal point of the laser light and the workpiece is long.

[0013] In this way, by changing the wavelength of the laser beam, the focal position of the laser beam can be adjusted to the appropriate height relative to the workpiece.

[0014] The third invention is, in the first or second invention, The laser oscillator comprises a plurality of laser diodes that emit a plurality of laser beams, and a diffraction grating that causes the laser beams to resonate externally. The plurality of laser diodes include a long-wavelength laser diode that emits laser light with a wavelength longer than the central wavelength of the wavelength-combined laser light, and a short-wavelength laser diode that emits laser light with a wavelength shorter than the central wavelength. The control unit selectively operates the long-wavelength laser diode or the short-wavelength laser diode to change the wavelength of the laser light by changing the angle of incidence of the laser light onto the diffraction grating.

[0015] In the third invention, a long-wavelength laser diode or a short-wavelength laser diode is selectively operated based on the distance between the focal position of the wavelength-combined laser beam and the workpiece.

[0016] In this way, by changing the wavelength of the laser beam, the focal position of the laser beam can be adjusted to the appropriate height relative to the workpiece.

[0017] The fourth invention relates to the first or second invention, The laser oscillator comprises a plurality of laser diodes that emit a plurality of laser beams, a diffraction grating that causes the laser beams to resonate externally, and an angle adjustment mechanism that adjusts the tilt angle of the diffraction grating relative to the laser diodes. The control unit operates the angle adjustment mechanism to change the angle of incidence of the laser light onto the diffraction grating, thereby changing the wavelength of the laser light.

[0018] In the fourth invention, the wavelength of the laser light is changed by adjusting the tilt angle of the diffraction grating relative to the laser diode and thereby changing the angle at which the laser light is incident on the diffraction grating.

[0019] Specifically, increasing the incident angle of the laser beam to the diffraction grating can increase the wavelength of the laser beam. On the other hand, decreasing the incident angle of the laser beam to the diffraction grating can shorten the wavelength of the laser beam.

[0020] Thus, by changing the wavelength of the laser beam, the focal position of the laser beam can be adjusted to an appropriate height with respect to the object to be processed.

[0021] The fifth invention is directed to a laser processing method in which a plurality of laser beams having different wavelengths are wavelength - synthesized, and the wavelength - synthesized laser beam is emitted from a laser processing head to an object to be processed. And a first step of measuring the distance between the laser processing head and the object to be processed, and a second step of changing the wavelength of the laser beam based on the measurement result in the first step to change the focal position of the laser beam emitted from the laser processing head.

[0022] In the fifth invention, the distance between the laser processing head and the object to be processed is measured, and by changing the wavelength of the laser beam based on the measurement result, the focal position of the laser beam emitted from the laser processing head is changed.

[0023] Thus, by changing the wavelength of the laser beam, the focal position of the laser beam can be adjusted to an appropriate height with respect to the object to be processed. Thereby, it is possible to suppress the vibration of the laser processing head due to inertia and improve the adjustment speed of the focal position of the laser beam.

[0024] The sixth invention is an improvement on the fifth invention, wherein in the second step, when the focal position of the wavelength - synthesized laser beam is shorter than the distance to the object to be processed, the wavelength of the laser beam is increased, while when it is longer than the distance to the object to be processed, the wavelength of the laser beam is decreased.

[0025] In the sixth invention, the wavelength of the laser light is lengthened when the distance between the focal point of the wavelength-combined laser light and the workpiece is short. Conversely, the wavelength of the laser light is shortened when the distance between the focal point of the laser light and the workpiece is long.

[0026] In this way, by changing the wavelength of the laser beam, the focal position of the laser beam can be adjusted to the appropriate height relative to the workpiece. [Effects of the Invention]

[0027] According to the present invention, the speed of adjusting the focal position of the laser beam can be improved. [Brief explanation of the drawing]

[0028] [Figure 1] This is a schematic diagram showing the configuration of the laser processing apparatus according to this embodiment 1. [Figure 2] This is a schematic diagram showing the configuration of a laser oscillator. [Figure 3] This is a diagram to explain the principle of wavelength synthesis. [Figure 4] This graph shows the relationship between the measurement location and the power density ratio. [Figure 5] This is a schematic diagram showing the configuration of a laser oscillator when a long-wavelength laser diode is in operation. [Figure 6] This graph shows the relationship between the wavelength and light intensity of a laser light with a longer wavelength. [Figure 7] This is a schematic diagram showing the configuration of a laser oscillator when a short-wavelength laser diode is in operation. [Figure 8] This graph shows the relationship between the wavelength and light intensity of a shortened laser light. [Figure 9] This figure shows the state in which the focal position of the laser beam is changed according to the distance to the workpiece. [Figure 10] This figure shows the state in which the focal position of the laser beam is changed according to the distance to the workpiece. [Figure 11] This figure shows the state in which the focal position of the laser beam is changed according to the distance to the workpiece. [Figure 12] This figure shows the controllable amount of the focal position and the power density. [Figure 13] This graph shows the relationship between the laser light emission time and output power. [Figure 14] This graph shows the relationship between the processing speed of the laser beam and the amount of travel required to reach the rise time. [Figure 15] This is a schematic diagram showing the configuration of the laser oscillator according to this second embodiment. [Figure 16] This diagram illustrates the principle by which laser light becomes longer in wavelength based on the tilt angle of the diffraction grating. [Figure 17] This graph shows the relationship between the wavelength and light intensity of a laser light with a longer wavelength. [Figure 18] This is a schematic diagram showing the configuration of a laser oscillator with the diffraction grating tilted inward. [Figure 19] This diagram illustrates the principle by which laser light is shortened in wavelength based on the tilt angle of the diffraction grating. [Figure 20] This graph shows the relationship between the wavelength and light intensity of a shortened laser light. [Figure 21] This is a schematic diagram showing the configuration of the laser oscillator according to this third embodiment. [Figure 22] This diagram illustrates the principle by which laser light becomes longer in wavelength based on the tilt angle of the diffraction grating. [Figure 23] This is a schematic diagram showing the configuration of a laser oscillator with the diffraction grating tilted inward. [Figure 24] This diagram illustrates the principle by which laser light is shortened in wavelength based on the tilt angle of the diffraction grating. [Figure 25] This is a schematic diagram showing the configuration of the laser oscillator according to this fourth embodiment. [Figure 26] This is a schematic diagram showing the configuration of a laser oscillator with the diffraction grating tilted inward. [Modes for carrying out the invention]

[0029] Embodiments of the present invention will be described below with reference to the drawings. The following description of preferred embodiments is essentially illustrative and is not intended to limit the present invention, its applications, or its uses.

[0030] Embodiment 1 As shown in Figure 1, the laser processing apparatus 1 comprises a laser oscillator 10, an optical fiber 2, a laser processing head 3, an assist gas supply device 4, a manipulator 5, and a control unit 6.

[0031] The laser oscillator 10 outputs laser light having multiple wavelength components (hereinafter referred to as multi-wavelength laser light) and directs it into the optical fiber 2.

[0032] The optical fiber 2 transmits the multi-wavelength laser light output by the laser oscillator 10 to the laser processing head 3.

[0033] The laser processing head 3 emits multi-wavelength laser light transmitted through the optical fiber 2 onto the workpiece 30. The workpiece 30 can be made of materials such as mild steel, stainless steel, or aluminum alloy. The laser processing head 3 is equipped with a distance measuring unit 15.

[0034] The distance measuring unit 15 is composed of, for example, a capacitive sensor. The distance measuring unit 15 measures the distance between the laser processing head 3 and the workpiece 30. The measured value obtained by the distance measuring unit 15 is transmitted to the control unit 6.

[0035] The assist gas supply device 4 is connected to the laser processing head 3. The assist gas supply device 4 supplies assist gas to the laser processing head 3.

[0036] The manipulator 5 changes the position and angle of the laser processing head 3 with a high degree of freedom. This allows the multi-wavelength laser light emitted from the laser processing head 3 to be directed to the processing position of the workpiece 30.

[0037] The control unit 6 is connected to the laser oscillator 10, the assist gas supply device 4, and the manipulator 5. The control unit 6 controls the output of multi-wavelength laser light from the laser oscillator 10, the amount of assist gas supplied from the assist gas supply device 4, and the operation of the manipulator 5.

[0038] The control unit 6 moves the laser processing head 3 along the surface of the workpiece 30 and performs tracking control to adjust the focal position of the laser beam to an appropriate height relative to the workpiece 30 based on the measurement results of the distance measuring unit 15.

[0039] <About laser oscillators> As shown in Figure 2, the laser oscillator 10 includes a semiconductor laser device 11, a focusing lens 12, a transmissive diffraction grating 13, and an output coupler 14. The operation of the semiconductor laser device 11 is controlled by the control unit 6.

[0040] The semiconductor laser device 11 has a plurality of laser diodes 20. The laser diodes 20 are composed of a microlens array. The laser diodes 20 have a plurality of emitters (for example, 40). The laser diodes 20 emit wavelength-synthesized laser light by wavelength-synthesizing the outputs of the plurality of emitters.

[0041] Multiple laser diodes 20 emit laser light with different wavelengths from each other. In the example shown in Figure 2, a first laser diode 21, a second laser diode 22, and a third laser diode 23 are arranged, but for example, ten laser diodes 20 may be arranged.

[0042] The first laser diode 21 is a long-wavelength laser diode that emits laser light with a wavelength longer than the central wavelength of the wavelength-synthesized multi-wavelength laser light (for example, 1000 nm).

[0043] The second laser diode 22 emits laser light with a wavelength that is approximately the same as the central wavelength of the multi-wavelength laser light.

[0044] The third laser diode 23 is a short-wavelength laser diode that emits laser light with a wavelength shorter than the central wavelength of the multi-wavelength laser light (for example, 950 nm).

[0045] The end of the semiconductor laser device 11 on the diffraction grating 13 side is the laser emission end. The end of the semiconductor laser device 11 opposite to the laser emission end is the total reflection end, which totally reflects the laser light.

[0046] The laser light emitted from the laser output end of the semiconductor laser device 11 is focused by the focusing lens 12, then passes through the diffraction grating 13, and a portion of it is reflected by the output coupler 14.

[0047] The laser light reflected by the output coupler 14 passes through the diffraction grating 13 and the focusing lens 12 and returns to the emitted semiconductor laser device 11. The laser light that returns to the semiconductor laser device 11 is reflected at the total reflection edge of the semiconductor laser device 11.

[0048] In this way, resonance occurs between the output coupler 14 and the total reflection edge of the semiconductor laser device 11, causing laser light to oscillate from the semiconductor laser device 11. As a result, multi-wavelength laser light is incident on the optical fiber 2.

[0049] As described above, a laser oscillator 10 is formed between the total reflection edge of the semiconductor laser device 11 and the output coupler 14 via a diffraction grating 13. This configuration is called an external resonator because the laser light is emitted including the region outside the semiconductor laser device 11.

[0050] Here, the laser beams emitted from the first laser diode 21, the second laser diode 22, and the third laser diode 23 are incident on the diffraction grating 13 from different directions relative to the diffraction grating 13. The diffraction grating 13 has the characteristic of emitting multiple laser beams with different incident angles at a common exit angle.

[0051] As shown in Figure 3, if the aperture spacing d of the diffraction grating 13 is α, the angle of incidence α of the laser beam onto the diffraction grating 13 is β, the scattering angle is β, the diffraction order is m (m = 0, ±1, ...), and the wavelength of the laser beam is λ, then the optical path difference is d × (sinα - sinβ). Therefore, the following equation (1) holds.

[0052] d×(sinα-sinβ)=m×λ ···(1) From equation (1), it can be seen that the wavelength λ of the laser light becomes longer as the incident angle α increases, and the wavelength λ of the laser light becomes shorter as the incident angle α decreases.

[0053] Here, by arranging multiple laser diodes 20 in different directions relative to the diffraction grating 13, the emission directions of multiple laser beams emitted from multiple laser diodes 20 can be made identical. Furthermore, the outputs of the laser beams emitted from multiple laser diodes 20 with different wavelengths can be added together.

[0054] In other words, by having the semiconductor laser device 11 and the output coupler 14 form an external resonator via the diffraction grating 13, a higher output laser beam can be obtained by summing the outputs of both without degrading the beam quality of each laser beam.

[0055] Furthermore, by arranging multiple laser diodes 20 in different directions relative to the diffraction grating 13, the multiple laser diodes 20 can emit laser light with different wavelengths from each other.

[0056] In this way, by focusing multi-wavelength laser light containing multiple wavelengths with the laser processing head 3, multiple focal points with slightly shifted focal lengths can be formed. This allows the workpiece 30 to be heated uniformly by multiple focal points, enabling processing under optimal conditions tailored to the workpiece 30.

[0057] By the way, when laser processing the workpiece 30, it is necessary to move the laser processing head 3 along the surface of the workpiece 30 and adjust the focal position of the laser beam to an appropriate height relative to the workpiece 30 in order to suppress the decrease in the power density of the laser beam.

[0058] Specifically, in the example shown in Figure 4, the focal position of the wavelength-combined laser beam is used as the reference position, and the power density ratio of the laser beam at the reference position is set to 100%. As shown in Figure 4, it can be seen that the power density ratio of the laser beam decreases when the measurement position moves away from the reference position in the positive or negative direction without adjusting the focal position of the laser beam. For example, when the measurement position is ±0.5 mm away from the reference position, the power density ratio decreases by an average of 8%.

[0059] However, if the laser processing head 3 is moved at high speed to increase the response speed of laser processing, the laser processing head 3 will vibrate due to inertia, making it difficult to adjust the focal position of the laser beam.

[0060] Therefore, in this embodiment, the laser diode 20 is selectively operated based on the distance between the focal position of the wavelength-synthesized laser light and the workpiece 30.

[0061] Specifically, as shown in Figure 5, by selectively operating the first laser diode 21, which has a longer wavelength, among the multiple laser diodes 20, and increasing the incidence angle of the laser beam onto the diffraction grating 13, the wavelength of the laser beam output from the laser processing head 3 can be made longer than the central wavelength of the multi-wavelength laser beam (see Figure 6).

[0062] On the other hand, as shown in Figure 7, by selectively operating the third laser diode 23, which has a shorter wavelength, among the multiple laser diodes 20, and reducing the incident angle of the laser beam onto the diffraction grating 13, the wavelength of the laser beam output from the laser processing head 3 can be made shorter than the central wavelength of the multi-wavelength laser beam (see Figure 8).

[0063] In the example shown in Figure 9, a stepped recess 31 is provided on the surface of the workpiece 30. The laser processing head 3 moves along the surface of the workpiece 30 from left to right in Figure 9.

[0064] At this time, the distance measuring unit 15 measures the distance between the laser processing head 3 and the workpiece 30 and transmits the measured value to the control unit 6. The control unit 6 compares the measured value from the distance measuring unit 15 with a predetermined target value and calculates the amount of movement of the laser processing head 3 by the manipulator 5. Then, the control unit 6 uses the manipulator 5 to move the laser processing head 3 and performs tracking control to adjust the focal position of the laser beam to an appropriate height relative to the workpiece 30.

[0065] Then, while the laser processing head 3 is moving in a tracking motion, the control unit 6 fine-tunes the focal position of the laser beam by changing the wavelength of the laser beam when the difference between the measurement value of the distance measuring unit 15 and the target value becomes larger than a predetermined threshold.

[0066] Specifically, in the example shown in Figure 9, when the laser processing head 3 descends toward the recess 31 of the workpiece 30, the focal position of the multi-wavelength laser beam becomes shorter than the distance to the workpiece 30.

[0067] Therefore, the control unit 6 selectively operates the first laser diode 21 to lengthen the wavelength of the laser light.

[0068] This allows for correction of insufficient and shallow focal point of the laser beam without moving the laser processing head 3 up and down.

[0069] Next, we will describe the case where the workpiece 30 is formed of a micro-corrugated sheet. In the example shown in Figure 10, the surface of the workpiece 30 is provided with a recess 31 and a protrusion 32. The laser processing head 3 moves linearly along the surface of the workpiece 30, from left to right in Figure 10.

[0070] Here, as the laser processing head 3 passes through the recess 31 of the workpiece 30, the focal position of the multi-wavelength laser beam is shorter than the distance to the workpiece 30. At this time, the control unit 6 selectively operates the first laser diode 21 to lengthen the wavelength of the laser beam.

[0071] This allows for correction of insufficient and shallow focal point of the laser beam without moving the laser processing head 3 up and down.

[0072] On the other hand, when the laser processing head 3 passes over the protrusion 32 of the workpiece 30, the focal position of the multi-wavelength laser beam is longer than the distance to the workpiece 30. At this time, the control unit 6 selectively operates the third laser diode 23 to shorten the wavelength of the laser beam.

[0073] This allows for correction of the excessive depth of the laser beam's focal point without having to move the laser processing head 3 up and down.

[0074] In the example described above, the control unit 6 adjusts the distance between the laser processing head 3 and the workpiece 30, and then changes the wavelength of the laser beam if the focal position of the laser beam is misaligned with the surface of the workpiece 30. However, the system is not limited to this configuration.

[0075] Specifically, in the example shown in Figure 11, a recess 31 and a protrusion 32 are provided on the surface of the workpiece 30. The laser processing head 3 moves along the surface of the workpiece 30 from left to right in Figure 11.

[0076] At this time, the distance measuring unit 15 measures the distance between the laser processing head 3 and the workpiece 30 and transmits the measured value to the control unit 6. The control unit 6 compares the measured value from the distance measuring unit 15 with a predetermined target value and calculates the amount of movement of the laser processing head 3 by the manipulator 5 and the amount of focal length adjustment by changing the wavelength of the laser light.

[0077] The control unit 6 then controls the manipulator 5 to adjust the distance between the laser processing head 3 and the workpiece 30, and to adjust the wavelength of the laser light by selectively operating the laser diode 20.

[0078] In this way, by adjusting the distance between the laser processing head 3 and the workpiece 30 and changing the wavelength of the laser beam, the focal position of the laser beam can be finely adjusted, allowing the laser processing head 3 to operate smoothly.

[0079] In other words, the focal length adjusted by adjusting the wavelength of the laser beam eliminates the need to move the laser processing head 3, resulting in smoother movement of the laser processing head 3 and reduced vibration.

[0080] Furthermore, the adjustment of the focal position by changing the wavelength of the laser beam can be performed at a higher speed than the movement of the laser processing head 3 by the manipulator 5. Therefore, it is preferable to actively adjust the focal position of the laser beam within the range of the laser beam wavelength adjustment.

[0081] Furthermore, the position adjustment of the laser processing head 3 by the manipulator 5 should be controlled so that the focal position, achieved by adjusting the wavelength of the laser light, is at the neutral position (the midpoint of the wavelength).

[0082] As shown in Figure 4, the power density ratio of the laser beam decreases by an average of 8% when the laser beam is moved ±0.5 mm away from the focal point, which significantly impacts the quality of laser processing. Therefore, it is preferable to ensure a controllable range of approximately 0.5 mm for the laser beam power density (see Figure 12).

[0083] In this embodiment, the focal position of the laser beam is changed by changing the wavelength of the laser beam. Therefore, it is possible that the heat input will be affected by the delay in the rise time from the emission of the laser beam until the maximum output is obtained. This point will be examined below.

[0084] As shown in Figure 13, when the laser diode 20 is selectively operated to change the wavelength of the laser light, 50 μs of emission time elapses until the laser light output reaches 100%.

[0085] As shown in Figure 14, when the laser processing head 3 is moved at a constant processing speed, the amount of movement until the rise time within the operating speed range of the laser beam is less than 3% of the beam diameter of the laser beam.

[0086] Thus, even when the focal position of the laser beam is changed by adjusting the wavelength of the laser beam, the impact on the heat input due to the delay in the rise time of the laser beam is small.

[0087] As described above, according to the laser processing apparatus 1 of this embodiment, the focal position of the laser beam can be adjusted to an appropriate height relative to the workpiece 30 by changing the wavelength of the laser beam. This suppresses vibration of the laser processing head 3 due to inertia and improves the speed of adjustment of the focal position of the laser beam.

[0088] Embodiment 2 Figure 15 is a schematic diagram showing the configuration of the laser oscillator according to this second embodiment. Hereafter, the same parts as in the first embodiment will be denoted by the same reference numerals, and only the differences will be described.

[0089] As shown in Figure 15, the laser oscillator 10 includes a semiconductor laser device 11, a focusing lens 12, a transmissive diffraction grating 13, an output coupler 14, and an angle adjustment mechanism 40. The operation of the semiconductor laser device 11 and the angle adjustment mechanism 40 is controlled by the control unit 6.

[0090] The diffraction grating 13 is supported so as to be rotatable about a predetermined central axis 13a.

[0091] The angle adjustment mechanism 40 adjusts the tilt angle of the diffraction grating 13 relative to the laser diode 20. The angle adjustment mechanism 40 includes a biasing spring 41 and a linear motion unit 45.

[0092] The biasing spring 41 biases the diffraction grating 13 to a predetermined inclination angle. One end of the biasing spring 41 is attached to the upper end of the diffraction grating 13, above the central axis 13a in Figure 15. The other end of the biasing spring 41 is attached to the spring fixing part 42. The spring fixing part 42 is located to the left of the diffraction grating 13 in Figure 15. The biasing spring 41 is made of a compression spring. The biasing spring 41 presses the upper end of the diffraction grating 13 to the right in Figure 15, thereby biasing the diffraction grating 13 to rotate clockwise.

[0093] The linear motion unit 45 adjusts the tilt angle of the diffraction grating 13 by moving back and forth relative to the diffraction grating 13, against the biasing force of the biasing spring 41. The linear motion unit 45 has an extendable / retractable section 46 and a voltage application section 47. The tip of the extendable / retractable section 46 is attached to the upper end of the diffraction grating 13, above the central axis 13a. The extendable / retractable section 46 is made of, for example, a piezoelectric element.

[0094] The voltage application unit 47 applies a voltage to the expandable / contractible section 46, which is made of a piezoelectric element, causing the expandable / contractible section 46 to expand and contract. As a result, the expandable / contractible section 46 moves forward and backward relative to the diffraction grating 13.

[0095] As shown in Figure 15, by retracting the telescopic section 46, the upper end of the diffraction grating 13 is pulled by the telescopic section 46. As a result, the diffraction grating 13 rotates clockwise in Figure 15 due to the biasing force of the biasing spring 41.

[0096] As shown in Figure 16, when the diffraction grating 13 is rotated clockwise and tilted away from the laser diode 20, the incident angle α of the laser light becomes larger compared to before the diffraction grating 13 was tilted.

[0097] Here, from equation (1) above, the wavelength λ of the laser light becomes longer as the incident angle α increases, so the wavelength of the laser light output from the laser processing head 3 can be made longer (see Figure 17).

[0098] On the other hand, as shown in Figure 18, extending the telescopic portion 46 pushes the upper end of the diffraction grating 13 against the telescopic portion 46. As a result, the diffraction grating 13 rotates counterclockwise in Figure 18 against the biasing force of the biasing spring 41.

[0099] As shown in Figure 19, when the diffraction grating 13 is rotated counterclockwise and tilted toward the laser diode 20, the incident angle α of the laser light becomes smaller compared to before the diffraction grating 13 was tilted.

[0100] Here, from equation (1) above, the wavelength of the laser light becomes shorter as the incident angle α decreases, so the wavelength of the laser light output from the laser processing head 3 can be shortened (see Figure 20).

[0101] The following describes the case in which the laser processing head 3 is moved linearly from left to right along the surface of the workpiece 30 (see Figure 10) which is provided with a recess 31 and a protrusion 32.

[0102] When the laser processing head 3 passes through the recess 31 of the workpiece 30, the focal position of the multi-wavelength laser beam is shorter than the distance to the workpiece 30. At this time, the control unit 6 operates the angle adjustment mechanism 40 to tilt the diffraction grating 13 away from the laser diode 20, thereby increasing the incident angle and lengthening the wavelength of the laser beam.

[0103] This allows for correction of insufficient and shallow focal point of the laser beam without moving the laser processing head 3 up and down.

[0104] On the other hand, when the laser processing head 3 passes over the protrusion 32 of the workpiece 30, the focal position of the multi-wavelength laser beam is longer than the distance to the workpiece 30. At this time, the control unit 6 operates the angle adjustment mechanism 40 to tilt the diffraction grating 13 in a direction closer to the laser diode 20, thereby reducing the incident angle and shortening the wavelength of the laser beam.

[0105] This allows for correction of the excessive depth of the laser beam's focal point without having to move the laser processing head 3 up and down.

[0106] As described above, according to the laser processing apparatus 1 of this embodiment, the focal position of the laser beam can be adjusted to an appropriate height relative to the workpiece 30 by changing the wavelength of the laser beam. This suppresses vibration of the laser processing head 3 due to inertia and improves the speed of adjustment of the focal position of the laser beam.

[0107] Embodiment 3 As shown in Figure 21, the laser oscillator 10 includes a semiconductor laser device 11, a focusing lens 12, a reflective diffraction grating 13, an output coupler 14, and an angle adjustment mechanism 40.

[0108] The angle adjustment mechanism 40 comprises a biasing spring 41 and a linear motion unit 45. The linear motion unit 45 has an extendable / retractable section 46 and a voltage application section 47.

[0109] By retracting the telescopic section 46, the upper end of the diffraction grating 13 is pulled by the telescopic section 46. As a result, the diffraction grating 13 rotates clockwise in Figure 21 due to the biasing force of the biasing spring 41.

[0110] As shown in Figure 22, when the diffraction grating 13 is rotated clockwise and tilted away from the laser diode 20, the incident angle α of the laser light becomes larger compared to before the diffraction grating 13 was tilted.

[0111] Here, if we consider the aperture spacing d of the diffraction grating 13, the angle of incidence α of the laser beam onto the diffraction grating 13, the scattering angle β, the diffraction order m (m = 0, ±1, ...), and the wavelength λ of the laser beam, then the optical path difference is d × (sinα + sinβ). Therefore, the following equation (2) holds.

[0112] d×(sinα+sinβ)=m×λ (2) Here, from equation (2), as the incident angle α increases, the wavelength λ of the laser light becomes longer, so the wavelength of the laser light output from the laser processing head 3 can be made longer.

[0113] On the other hand, as shown in Figure 23, extending the telescopic portion 46 pushes the upper end of the diffraction grating 13 against the telescopic portion 46. As a result, the diffraction grating 13 rotates counterclockwise in Figure 23 against the biasing force of the biasing spring 41.

[0114] As shown in Figure 24, when the diffraction grating 13 is rotated counterclockwise and tilted toward the laser diode 20, the incident angle α of the laser light becomes smaller compared to before the diffraction grating 13 was tilted.

[0115] Here, from equation (2), as the incident angle α decreases, the wavelength λ of the laser light becomes shorter, so the wavelength of the laser light output from the laser processing head 3 can be shortened.

[0116] Embodiment 4 As shown in Figure 25, the laser oscillator 10 includes a semiconductor laser device 11, a focusing lens 12, a reflective diffraction grating 13, an output coupler 14, and an angle adjustment mechanism 50.

[0117] The angle adjustment mechanism 50 includes a biasing spring 41, a cam 51, and a motor 52. The biasing spring 41 is made of a compression spring. The biasing spring 41 presses the upper end of the diffraction grating 13 to the right in Figure 25, thereby biasing the diffraction grating 13 to rotate in a clockwise direction.

[0118] The cam 51 is formed in a roughly triangular shape. The cam surface of the cam 51 is in contact with the upper end of the diffraction grating 13. The motor 52 rotates the cam 51 to adjust the tilt angle of the diffraction grating 13 against the biasing force of the biasing spring 41.

[0119] As shown in Figure 25, when the side of the triangular cam 51 is positioned opposite the upper end of the diffraction grating 13, the diffraction grating 13 rotates clockwise due to the biasing force of the biasing spring 41 and comes into contact with the cam 51.

[0120] In this way, by rotating the diffraction grating 13 clockwise and tilting it away from the laser diode 20, the incident angle α of the laser light becomes larger compared to before tilting the diffraction grating 13. This makes it possible to lengthen the wavelength of the laser light output from the laser processing head 3.

[0121] On the other hand, as shown in Figure 26, when the cam 51 is rotated and the vertex of the triangular cam 51 comes into contact with the upper end of the diffraction grating 13, the diffraction grating 13 rotates counterclockwise against the biasing force of the biasing spring 41.

[0122] In this way, by rotating the diffraction grating 13 counterclockwise and tilting it toward the laser diode 20, the incident angle α of the laser light becomes smaller compared to before tilting the diffraction grating 13. This makes it possible to shorten the wavelength of the laser light output from the laser processing head 3.

[0123] Other embodiments The above embodiment may also have the following configuration.

[0124] In this embodiment, the semiconductor laser device 11 may be composed of a semiconductor laser bar having multiple emitters, or a semiconductor stack formed by stacking multiple semiconductor laser bars. [Industrial applicability]

[0125] As described above, the present invention is extremely useful and has high industrial applicability because it provides the highly practical effect of improving the speed of adjusting the focal position of the laser beam. [Explanation of Symbols]

[0126] 1. Laser processing device 3. Laser processing head 6 Control Unit 10. Laser Oscillator 13 Diffraction grating 15 Distance measuring unit 20 Laser Diodes 21. First laser diode (long-wavelength laser diode) 23. Third laser diode (short-wavelength laser diode) 30. Object to be processed 40 Angle adjustment mechanism 50 Angle adjustment mechanism

Claims

1. A laser processing apparatus comprising a laser oscillator that outputs multiple laser beams of different wavelengths by wavelength synthesis, and a laser processing head that emits the laser beams output from the laser oscillator onto a workpiece, A manipulator for changing the position of the laser processing head relative to the workpiece, A distance measuring unit for measuring the distance between the laser processing head and the workpiece, A laser processing apparatus comprising a control unit that, based on the measurement results of the distance measuring unit, calculates the amount of movement of the laser processing head by the manipulator and the amount of focal length adjustment by changing the wavelength of the laser light, and changes the wavelength of the laser light while adjusting the distance between the laser processing head and the workpiece based on the amount of movement and the amount of focal length adjustment, thereby changing the focal position of the laser light emitted from the laser processing head.

2. In claim 1, The control unit lengthens the wavelength of the laser beam when the focal position of the wavelength-combined laser beam is shorter than the distance to the workpiece, and shortens the wavelength of the laser beam when it is longer than the distance to the workpiece.

3. In claim 1 or 2, The laser oscillator comprises a plurality of laser diodes that emit a plurality of laser beams, and a diffraction grating that causes the laser beams to resonate externally. The plurality of laser diodes include a long-wavelength laser diode that emits laser light with a wavelength longer than the central wavelength of the wavelength-combined laser light, and a short-wavelength laser diode that emits laser light with a wavelength shorter than the central wavelength. The control unit selectively operates the long-wavelength laser diode or the short-wavelength laser diode to change the incident angle of the laser light on the diffraction grating, thereby changing the wavelength of the laser light.

4. In claim 1 or 2, The laser oscillator comprises a plurality of laser diodes that emit a plurality of laser beams, a diffraction grating that causes the laser beams to resonate externally, and an angle adjustment mechanism that adjusts the tilt angle of the diffraction grating relative to the laser diodes. The control unit operates the angle adjustment mechanism to change the incident angle of the laser light on the diffraction grating, thereby changing the wavelength of the laser light.

5. A laser processing method comprising combining multiple laser beams of different wavelengths and emitting the combined laser beam from a laser processing head toward a workpiece, A first step is to measure the distance between the laser processing head and the workpiece, A laser processing method comprising: a second step of calculating the amount of movement of the laser processing head and the amount of focal length adjustment by changing the wavelength of the laser light based on the measurement results in the first step, and changing the focal position of the laser light emitted from the laser processing head by changing the wavelength of the laser light while adjusting the distance between the laser processing head and the workpiece based on the amount of movement and the amount of focal length adjustment.

6. In claim 5, In the second step, a laser processing method is provided in which, when the focal position of the wavelength-combined laser light is shorter than the distance to the workpiece, the wavelength of the laser light is increased, and when it is longer than the distance to the workpiece, the wavelength of the laser light is decreased.

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