Laser beam machine, and method for correcting center position of optical element

Abstract

To prevent the processing quality from deteriorating even when a center position of an optical element changes in the middle of processing by correcting the center position of the optical element in realtime.SOLUTION: A control unit 11 of a laser beam machine 1 detects a maximal value and a minimal value of optical strength from an optical strength distribution of a ring beam detected by a detection unit 7, detects a direction in which the maximal value has been detected from the center of the optical strength distribution of the ring beam, as a change direction along which the center position of an optical element has changed, calculates a ratio of the detected maximal value and minimal value as an optical strength ratio of the ring beam, divides the optical strength distribution of a Gaussian beam stored in a storage unit 9 by a distance from the beam center of the Gaussian beam into two regions, calculates a distance at which a ratio of the two divided regions matches the optical strength ratio of the ring beam, as a change amount by which the center position of the optical element has changed, and makes corrections so that the center position of the optical element coincides with the beam center of the Gaussian beam on the basis of the change amount and the change direction.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a laser processing machine and a method for correcting the center position of an optical element.

Background Art

[0002] Patent Document 1 discloses a laser processing apparatus that inserts an optical element such as an axicon lens into the optical path of a laser beam to change the beam profile of the laser beam.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the above-described conventional laser processing apparatus, due to heat from the laser beam or temperature changes in the external environment, etc., the center position of the optical element may change by more than the allowable value from the beam center of the laser beam. If the center position of the optical element changes during processing, the characteristics of the laser beam irradiated on the material change, resulting in a problem that the processing quality deteriorates.

Means for Solving the Problems

[0005] A first aspect of one or more embodiments includes an optical element that converts a Gaussian beam into a ring beam, a detection unit that detects the light intensity distribution of the ring beam, a storage unit that stores the light intensity distribution of the Gaussian beam, and a control unit that executes control to correct the center position of the optical element. The control unit detects a maximum value and a minimum value of the light intensity from the light intensity distribution of the ring beam detected by the detection unit, detects the direction in which the maximum value is detected from the center of the light intensity distribution of the ring beam as the change direction in which the center position of the optical element has changed, calculates the ratio of the detected maximum value and the minimum value as the light intensity ratio of the ring beam, divides the light intensity distribution of the Gaussian beam stored in the storage unit into two regions by the distance from the beam center of the Gaussian beam, calculates the distance at which the ratio of the two divided regions matches the light intensity ratio of the ring beam as the amount of change in which the center position of the optical element has changed, and corrects the center position of the optical element based on the amount of change and the change direction so that it coincides with the beam center of the Gaussian beam. This is a laser processing machine.

[0006] A second aspect of one or more embodiments is a method for correcting the center position of an optical element. The Gaussian beam of a laser processing machine is converted into a ring beam by an optical element, the light intensity distribution of the ring beam is detected by a detection unit, a maximum value and a minimum value of the light intensity are detected from the light intensity distribution of the ring beam detected by the detection unit, the direction in which the maximum value is detected from the center of the light intensity distribution of the ring beam is detected as the change direction in which the center position of the optical element has changed, the ratio of the detected maximum value and the minimum value is calculated as the light intensity ratio of the ring beam, the light intensity distribution of the Gaussian beam stored in a storage unit is divided into two regions by the distance from the beam center of the Gaussian beam, the distance at which the ratio of the two divided regions matches the light intensity ratio of the ring beam is calculated as the amount of change in which the center position of the optical element has changed, and based on the amount of change and the change direction, the center position of the optical element is corrected so that it coincides with the beam center of the Gaussian beam.

Advantages of the Invention

[0007] According to the laser processing machine and the method for correcting the center position of the optical element according to one or more embodiments, since the center position of the optical element can be corrected in real time, even if the center position of the optical element changes during processing, a decrease in processing quality can be prevented.

Brief Description of the Drawings

[0008]

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Embodiments for Carrying Out the Invention

[0009] [Configuration of Laser Processing Machine] Hereinafter, with reference to the drawings, the laser processing machine and the method for correcting the central position of the optical element according to the present embodiment will be described. FIG. 1 is a cross-sectional view showing the configuration of a processing head included in the laser processing machine according to the present embodiment. As shown in FIG. 1, the laser processing machine 1 according to the present embodiment includes a processing head 3, a mode conversion device 5, a detection unit 7, a storage unit 9, and a control unit 11.

[0010] The laser processing machine 1 is connected to a laser oscillator (not shown) that oscillates a laser beam, such as a fiber laser oscillator or a YAG laser oscillator, via a transmission fiber 13, and irradiates the material W with the laser beam supplied from the laser oscillator. The laser beam emitted from the transmission fiber 13 is a Gaussian beam.

[0011] The processing head 3 is formed of an L-shaped housing and includes a collimating lens 15, a bending mirror 17, and a focusing lens 19. The processing head 3 converts the divergent laser beam emitted from the transmission fiber 13 into collimated light with the collimating lens 15, bends the collimated light downward by 90° with the bending mirror 17, and focuses it with the focusing lens 19 to irradiate the material W. Since the bending mirror 17 is coated with HR (Highly Reflective), most of the laser beam is reflected, but a part of the laser beam is transmitted.

[0012] The mode conversion device 5 includes an optical element that converts the Gaussian beam emitted from the transmission fiber 13 into a ring beam, and switches between a mode of irradiating the Gaussian beam and a mode of irradiating the ring beam by inserting or retracting the optical element into or from the optical path of the Gaussian beam. The detailed structure of the mode conversion device 5 will be described later.

[0013] The detection unit 7 detects the light intensity distribution of the Gaussian beam or the ring beam that has passed through the bending mirror 17. In particular, in this embodiment, the case of detecting the light intensity distribution of the ring beam will be described. The detection unit 7 is configured by, for example, a CCD (Charge Coupled Device) camera. The ring beam that has passed through the bending mirror 17 is attenuated by the ND (Neutral Density) filter 21 and condensed by the imaging lens 23, and the beam profile is measured by the detection unit 7.

[0014] The storage unit 9 is a memory or database that stores data necessary for executing a process of correcting the center position of the optical element. In particular, the storage unit 9 stores the light intensity distribution of the Gaussian beam measured in advance. In addition to this, the storage unit 9 also stores the beam profile of the ring beam detected by the detection unit 7, a program for correcting the center position of the optical element, and the like.

[0015] The control unit 11 executes control to correct the center position of the optical element. In particular, the control unit 11 obtains the direction of change in which the center position of the optical element has changed and the amount of change in which the center position of the optical element has changed, and based on these amount of change and direction of change, corrects the center position of the optical element so as to coincide with the beam center of the Gaussian beam. The process of specifically correcting the center position of the optical element will be described later.

[0016] The control unit 11 is constituted by a computer having a memory, a processor such as a CPU (Central Processing Unit), and various interfaces. The memory and various interfaces are connected to the processor via a bus. By executing a program stored in the memory by the processor, the control unit 11 executes a process of correcting the center position of the optical element.

[0017] [Structure of the Mode Conversion Device] Next, with reference to FIG. 2, the specific structure of the mode conversion device 5 will be described. FIG. 2 is a cross-sectional view showing the structure of the mode conversion device 5 at a-a in FIG. 1. As shown in FIG. 2, the mode conversion device 5 includes an axicon lens 31 which is an optical element, an actuator 32, and a base frame 33. The actuator 32 is an air cylinder and is provided on the base frame 33. The actuator 32 inserts or retracts the axicon lens 31 provided at the tip of the cylinder 34 into or from the optical path of the laser beam inside the processing head 3 by moving the cylinder 34 in the X-axis direction. However, the actuator 32 may be a linear motor instead of an air cylinder.

[0018] Here, the central position of the axicon lens 31 is adjusted by the X-direction adjustment unit 35 and the Y-direction adjustment unit 36. The X-direction adjustment unit 35 is a micromotor, and under the control of the control unit 11, it moves the adjustment stopper 38 in the X-axis direction. As a result, as shown in FIG. 3, when the actuator 32 moves the cylinder 34 in the X-axis direction, the stopper 39 provided on the cylinder 34 abuts against the adjustment stopper 38, so that the central position of the axicon lens 31 in the X-axis direction is corrected.

[0019] Also, the Y-direction adjustment unit 36 is a micromotor, and under the control of the control unit 11, it moves the actuator 32 supported by the counter spring 37 in the Y-axis direction to correct the central position of the axicon lens 31 in the Y-axis direction. However, the X-direction adjustment unit 35 and the Y-direction adjustment unit 36 may be piezo elements or the like instead of micromotors.

[0020] [Method for correcting the central position of an optical element] Hereinafter, with reference to FIG. 4, a method for correcting the central position of the optical element according to the present embodiment will be described. FIG. 4 is a flowchart showing the processing procedure of the central position correction process of the optical element. As shown in FIG. 4, in step S101, the detection unit 7 measures the beam profile of the ring beam. The measured beam profile is stored in the storage unit 9 by the control unit 11. Specifically, the light intensity distribution of the ring beam detected by the detection unit 7 is shown in FIG. 5.

[0021] In step S103, the control unit 11 detects the maximum value and the minimum value of the light intensity from the light intensity distribution of the ring beam detected by the detection unit 7. First, when the control unit 11 acquires the light intensity distribution detected in step S101 from the storage unit 9, it calculates the centroid position of the light intensity distribution, and sets the calculated centroid position as the center (X0, Y0) as shown in FIG. 5.

[0022] Next, the control unit 11 divides the light intensity distribution of the ring beam at a predetermined angular interval, detects the peak value of the light intensity for each angular interval, and detects the maximum peak value among the detected peak values as the maximum value. For example, the control unit 11 divides the light intensity distribution into 120 parts at a 3° pitch centered on (X0, Y0) and obtains the light intensity of each divided cross-section. Since the light intensity of the obtained cross-section is distributed as shown in FIG. 6 with respect to the distance from the center (X0, Y0), the control unit 11 detects the peak value P. Then, when the 120 peak values P detected between 0 and 360° are plotted, the plot diagram shown in FIG. 7 is obtained, and the control unit 11 detects the maximum peak value among the peak values P as the maximum value PH of the light intensity.

[0023] Also, the control unit 11 detects the minimum peak value among the peak values of the light intensity detected for each angular interval as the minimum value. For example, the control unit 11 detects the minimum peak value among the peak values P shown in FIG. 7 as the minimum value PL of the light intensity.

[0024] In step S105, the control unit 11 detects the direction in which the maximum value PH of the light intensity is detected from the center (X0, Y0) of the light intensity distribution of the ring beam as the changing direction in which the center position of the axicon lens 31 has changed. For example, as shown in FIGS. 5 and 7, the direction θp in which the maximum value PH is detected is detected as the changing direction in which the center position of the axicon lens 31 has changed.

[0025] When the center position of the axicon lens 31 changes and deviates from the beam center of the Gaussian beam, the beam is deflected in the deviated direction, so the light intensity in the deviated direction increases. Therefore, by detecting the direction in which the light intensity is maximum, the direction in which the center position of the axicon lens 31 has changed can be detected.

[0026] Further, the changing direction of the axicon lens 31 may be detected by another method. For example, as shown in FIG. 8, the control unit 11 calculates a light intensity that is lower than the maximum value PH of the light intensity by a predetermined ratio, for example, 10%, and sets the direction at the center of the two directions θ1 and θ2 where the calculated light intensity is obtained as the changing direction θp of the axicon lens 31. That is, the control unit 11 detects θp calculated by θp = (θ1 + θ2) / 2 as the changing direction.

[0027] On the other hand, when the center position of the axicon lens 31 deviates from the beam center of the Gaussian beam, the beam is deflected in the deviated direction, so the light intensity in the direction opposite to the deviated direction decreases. Therefore, the control unit 11 may detect the light intensity in the direction opposite to the changing direction θp of the axicon lens 31 from the center (X0, Y0) of the light intensity distribution of the ring beam as the minimum value of the light intensity. For example, as shown in FIGS. 5 and 7, the peak value in the direction obtained by adding 180° in the direction opposite to the direction θp in which the maximum value PH is detected may be detected as the minimum value PL of the light intensity.

[0028] In step S107, the control unit 11 calculates the ratio of the maximum value PH and the minimum value PL of the light intensity detected in step S103 as the light intensity ratio of the ring beam. The control unit 11 calculates the light intensity ratio H = PH / PL of the ring beam from the maximum value PH and the minimum value PL of the light intensity.

[0029] In step S109, the control unit 11 calculates the amount of change in the center position of the axicon lens 31. First, the control unit 11 acquires the light intensity distribution of the Gaussian beam stored in the storage unit 9. The laser beam incident on the axicon lens 31 is in a low-order mode and is approximated by the Gaussian beam represented by Equation (1).

Equation

[0030] The light intensity distribution of the Gaussian beam represented by Equation (1) is shown in FIG. 9. Here, A is the peak intensity, σ is the standard deviation, the range of x is -R < x < R, and R is the beam radius, which is the value of x when the intensity has decreased by 86% from the peak intensity A.

[0031] Next, with reference to FIGS. 9 and 10, a method for calculating the amount of change in the central position of the axicon lens 31 will be described. FIG. 10 is a schematic diagram when the central position of the axicon lens 31 has changed by Δr from the beam center of the Gaussian beam. As shown in FIG. 10, the Gaussian beam emitted from the transmission fiber 13 is split by the axicon lens 31. The split beams are imaged on the surface of the material W via the collimating lens 15 and the focusing lens 19.

[0032] At this time, due to the amount of change Δr of the axicon lens 31, a bias occurs in the light intensity distribution of the beam on the surface of the material W. That is, when the central position of the axicon lens 31 is shifted by Δr, one of the split beams has an increased light intensity and becomes a high peak value PH, while the other has a decreased light intensity and becomes a low peak value PL. The ratio of PH to PL, that is, the light intensity ratio H (PH / PL) of the ring beam calculated in step S107, coincides with the ratio of the beams split by the axicon lens 31.

[0033] Here, as shown in FIG. 9, the Gaussian beam incident on the axicon lens 31 is split into two regions by the amount of change Δr. If the larger area is defined as S1 and the smaller area is defined as S2, Equation (2) holds between the light intensity ratio H of the ring beam.

Equation

[0034] Next, to obtain the area ratio S1 / S2, the beam profile function in Equation (1) is discretized. First, as shown in FIG. 11, the range from -R to +R of the approximate formula f(x) of the beam profile is divided into 2n parts. Then, assuming an arbitrarily divided x-coordinate is Rk (k is arbitrary) and f(Rk)=fk (where k = -n to n), as shown in FIG. 12, the beam profile function can be discretized.

[0035] Here, when the boundary between S1 and S2 is k = r (where r ≥ 0), it can be divided into region S1 and region S2 as shown in FIG. 13. Therefore, the areas of regions S1 and S2 are calculated respectively. However, fr at the boundary is included in both S1 and S2.

Number

Number

[0036] Therefore, Hr can be calculated by Equations (2) to (4).

Number

[0037] In Equation (5), Hr is calculated from r = 0 to n - 1, and the position Rr of r where Hr is closest to PH / PL becomes the change amount Δr of the center position of the axicon lens 31. In this way, in step S109, the control unit 11 calculates the change amount Δr by which the center position of the axicon lens 31 has changed.

[0038] That is, the control unit 11 divides the light intensity distribution of the Gaussian beam stored in the storage unit 9 into two regions S1 and S2 by the distance R from the beam center of the Gaussian beam, and calculates the distance Rr at which the ratio S1 / S2 of the two divided regions S1 and S2 matches the light intensity ratio H (=PH / PL) of the ring beam as the change amount Δr by which the center position of the axicon lens 31 has changed.

[0039] In step S111, based on the amount of change calculated in step S109 and the direction of change detected in step S105, the control unit 11 corrects the central position of the axicon lens 31 so as to coincide with the beam center of the Gaussian beam. As shown in FIG. 14, the central position of the axicon lens 31 is shifted by the amount of change Δr in the direction of the change direction θp. Therefore, the control unit 11 calculates the correction amounts Δx and Δy of the central position of the axicon lens 31. [Equation] [Equation]

[0040] The control unit 11 calculates a correction position (x', y') for moving the central position of the axicon lens 31 from the current position (x, y) based on the calculated correction amounts Δx and Δy. [Equation] [Equation]

[0041] The control unit 11 controls the X-direction adjustment unit 35 and the Y-direction adjustment unit 36 shown in FIG. 2 to move the central position of the axicon lens 31 from the current position (x, y) to the correction position (x', y'). Thereby, the control unit 11 can correct the central position of the axicon lens 31 so as to coincide with the beam center of the Gaussian beam. As a result, as shown in FIG. 15, the light intensity distribution of the ring beam has no bias, and a uniform light intensity can be obtained over the entire circumference of the ring beam. Thus, the central position correction process of the optical element according to the present embodiment ends.

[0042] [Modification Example] As shown in FIG. 2, the X-direction adjustment unit 35 and the Y-direction adjustment unit 36 adjust the center position of the axicon lens 31 by moving the position of the actuator 32. However, as shown in FIG. 16, the center position of the axicon lens 31 may be directly adjusted by providing the X-direction adjustment unit 35 and the Y-direction adjustment unit 36 on the lens holder 40.

[0043] In this case, the X-direction adjustment unit 35 and the Y-direction adjustment unit 36 are piezo elements, and under the control of the control unit 11, the axicon lens 31 supported by the counter springs 41 and 42 is moved in the X-axis direction and the Y-axis direction respectively to correct the center position.

[0044] [Effects of the Embodiment] As described in detail above, the laser processing machine 1 according to the present embodiment detects the maximum value and the minimum value of the light intensity from the light intensity distribution of the ring beam detected by the detection unit 7, and detects the direction in which the maximum value is detected from the center of the light intensity distribution of the ring beam as the change direction in which the center position of the optical element has changed, and calculates the ratio of the detected maximum value and minimum value as the light intensity ratio of the ring beam. The laser processing machine 1 divides the light intensity distribution of the Gaussian beam stored in the storage unit 9 into two regions by the distance from the beam center of the Gaussian beam, and calculates the distance at which the ratio of the two divided regions coincides with the light intensity ratio of the ring beam as the change amount in which the center position of the optical element has changed, and corrects the center position of the optical element so as to coincide with the beam center of the Gaussian beam based on the change amount and the change direction.

[0045] Thereby, since the center position of the optical element is corrected using the light intensity distribution of the ring beam detected by the detection unit 7, the center position of the optical element can be corrected in real time. Therefore, even if the center position of the optical element changes during processing due to heat from the laser beam or temperature changes in the external environment, etc., a decrease in processing quality can be prevented. Furthermore, since the adjustment of the center position of the optical element is always automatically performed, the alignment adjustment of the optical element becomes unnecessary, and maintenance-free can be realized.

[0046] Further, the laser processing machine 1 according to the present embodiment detects the light intensity in the direction opposite to the change direction of the optical element from the center of the light intensity distribution of the ring beam as the minimum value of the light intensity. When the center position of the optical element is displaced, the light intensity in the displaced direction becomes maximum, and the light intensity in the direction opposite to the displaced direction becomes minimum. Therefore, by detecting the light intensity in the direction opposite to the change direction of the optical element as the minimum value, the minimum value of the light intensity can be detected more accurately.

[0047] Furthermore, the laser processing machine 1 according to the present embodiment divides the light intensity distribution of the ring beam at predetermined angular intervals, detects the peak value of the light intensity for each angular interval, and detects the maximum peak value among the detected peak values as the maximum value of the light intensity. In the light intensity distribution of the ring beam, there are peak values at each angular interval. Therefore, by detecting and comparing the peak values, the maximum value of the light intensity can be detected more accurately.

[0048] Also, the laser processing machine 1 according to the present embodiment calculates a light intensity that is lower than the maximum value of the light intensity by a predetermined ratio, and detects the direction at the center between the two directions corresponding to the calculated light intensity as the change direction of the optical element. Thereby, even if there is variation in the light intensity distribution of the ring beam, an appropriate direction can be detected as the change direction of the optical element.

[0049] As described above, embodiments of the present invention have been described. However, it should not be understood that the discussions and drawings forming a part of this disclosure limit the present invention. Various alternative embodiments, examples, and operation techniques will be apparent to those skilled in the art from this disclosure.

Explanation of Reference Numerals

[0050] 1 Laser processing machine 3 Processing head 5 Mode conversion device 7 Detection unit 9 Storage unit 11 Control unit 13 Transmission fiber 15 Collimating lens 17 Bend mirror 19 Focusing lens 21 ND filter 23 imaging lens 31 axicon lens 32 actuator 33 base frame 34 cylinder 35 X-direction adjuster 36 Y-direction adjuster 37, 41, 42 counter spring 38 adjustment stopper 39 stopper 40 lens holder P peak value PH maximum value PL minimum value S1, S2 regions W material θp change direction Δr change amount

Claims

1. An optical element that converts a Gaussian beam into a ring beam, A detection unit that detects the light intensity distribution of the ring beam, A storage unit that stores the light intensity distribution of the Gaussian beam, A control unit that executes control to correct the center position of the optical element, comprising: The control unit, Detects the maximum value and the minimum value of the light intensity from the light intensity distribution of the ring beam detected by the detection unit, Detects the direction in which the maximum value is detected from the center of the light intensity distribution of the ring beam as the change direction in which the center position of the optical element has changed, Calculates the ratio of the detected maximum value to the minimum value as the light intensity ratio of the ring beam, Divides the light intensity distribution of the Gaussian beam stored in the storage unit into two regions by the distance from the beam center of the Gaussian beam, and calculates the distance at which the ratio of the two divided regions matches the light intensity ratio of the ring beam as the change amount in which the center position of the optical element has changed, Based on the change amount and the change direction, corrects the center position of the optical element so as to coincide with the beam center of the Gaussian beam Laser processing machine.

2. The control unit detects the light intensity in the direction opposite to the change direction from the center of the light intensity distribution of the ring beam as the minimum value The laser processing machine according to claim 1.

3. The control unit divides the light intensity distribution of the ring beam at predetermined angular intervals, detects the peak value of the light intensity for each angular interval, and detects the maximum peak value among the detected peak values as the maximum value The laser processing machine according to claim 1.

4. The control unit calculates the light intensity that is lower than the maximum value by a predetermined ratio, and detects the direction at the center between the two directions having the calculated light intensity as the change direction The laser processing machine according to claim 1.

5. Converts the Gaussian beam of the laser processing machine into a ring beam with an optical element, Detects the light intensity distribution of the ring beam with a detection unit, Detects the maximum value and the minimum value of the light intensity from the light intensity distribution of the ring beam detected by the detection unit, Detects the direction in which the maximum value is detected from the center of the light intensity distribution of the ring beam as the change direction in which the center position of the optical element has changed, Calculates the ratio of the detected maximum value to the minimum value as the light intensity ratio of the ring beam, The light intensity distribution of the Gaussian beam stored in the memory unit is divided into two regions by the distance from the beam center of the Gaussian beam, and the distance at which the ratio of the two divided regions matches the light intensity ratio of the ring beam is calculated as the amount of change in which the center position of the optical element has changed. Based on the amount of change and the direction of change, correct the center position of the optical element so that it coincides with the beam center of the Gaussian beam. A method for correcting the center position of an optical element.

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