JP2015223591A - Laser processor and laser oscillation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser processor that enables a feedback control for approximating an average output in the pulse width of a laser pulse to a target value even when a pulse repeating frequency or the pulse width is varied.SOLUTION: A laser oscillator outputs a laser beam having an average output in a pulse width corresponding to a control value given from outside. A photodetector outputs a detection value corresponding to an optical intensity when detecting a pulse laser beam outputted from the laser oscillator. The detection value is inputted from the photosensor into a laser control device. The laser control device gives a control value to the laser oscillator on the basis of an output target value and a detection value that command a target average output in a pulse width. The laser control device gives the control value to the laser oscillator so that the integral deviation of a detection value to the output target value of a period where the detection value is inputted is made small.

Description

  The present invention relates to a laser processing apparatus that performs laser processing with a pulse laser beam, and a laser oscillation method.

  The output of the carbon dioxide laser fluctuates under the influence of environmental temperature fluctuations, laser gas deterioration, and the like. If the repetition frequency and the pulse width of the pulse of the pulse laser beam are constant, feedback control can be performed based on the difference between the measurement result of the average output of the carbon dioxide laser and the target value. By performing feedback control, it is possible to suppress output fluctuations caused by environmental temperature fluctuations, laser gas degradation, and the like. The average output is obtained by integrating the pulse energy.

JP 2012-248614 A

  Laser processing may be performed by changing the pulse repetition frequency and pulse width as necessary. When the average output within the pulse width of each laser pulse is made constant and the pulse repetition frequency and pulse width are changed, the average output per unit time also changes. For this reason, it is difficult to perform feedback control using the average output per unit time.

  An object of the present invention is to provide a laser processing apparatus and a laser oscillation method capable of performing feedback control to bring an average output within the pulse width of a laser pulse closer to a target value even if the pulse repetition frequency and pulse width are changed. Is to provide.

According to one aspect of the invention,
A laser oscillator that outputs a pulse laser beam having an average output within a pulse width according to a control value given from the outside;
When detecting the pulse laser beam output from the laser oscillator, a photodetector that outputs a detection value according to the light intensity;
A laser control device that receives the detection value from the photodetector and outputs a control value to the laser oscillator based on an output target value that instructs a target average output within a pulse width and the detection value; ,
The laser control device
There is provided a laser processing apparatus for providing the control value to the laser oscillator so that an integral deviation of the detection value with respect to the output target value during a period in which the detection value is input is small.

According to another aspect of the invention,
Detecting the pulse laser beam output from the laser oscillator and generating a detection value corresponding to the light intensity of the pulse laser beam;
Multiplying an output target value for commanding an average output within a pulse width to be a target by a window function corresponding to a period during which a laser pulse of the pulse laser beam is output; and generating a comparison target value;
And a step of feeding back to the output of the laser oscillator so that an integral deviation of the detected value with respect to the target value for comparison becomes small.

  By giving a control value to the laser oscillator so that the integrated deviation of the detection value with respect to the output target value during the period in which the detection value is input becomes small, the average output within the pulse width can be brought close to the output target value. Since the output target value during the period in which the detection value is input is used as a reference for the integral deviation, it is possible to perform appropriate feedback control even if the pulse repetition frequency and pulse width vary.

FIG. 1 is a schematic diagram of an optical system and a block diagram of a control system of a laser processing apparatus according to an embodiment. FIG. 2 is a cross-sectional view of the laser oscillator. FIG. 3 is a graph illustrating an example of waveforms of various signals in the laser processing apparatus according to the embodiment. FIG. 4 is a block diagram of a laser control device used in the laser processing apparatus according to the embodiment. FIG. 5 is a graph showing examples of waveforms of various signals used for feedback control to the laser oscillator. FIG. 6A is a block diagram of a laser control device according to a modification of the embodiment shown in FIGS. 1 to 4, and FIG. 6B is an equivalent circuit diagram showing an example of a rectifier circuit used in the laser control device. FIG. 7 is a block diagram of a laser control apparatus used in a laser processing apparatus according to a modification. FIG. 8 is a block diagram of a laser control device used in a laser processing apparatus according to another embodiment. 9 shows a comparison detection value Dv1 in the laser control device shown in FIG. 8, a comparison target value Tv1 in the laser control device shown in FIG. 4, and output values Tv2, Tv3 in the laser control device shown in FIG. And the waveform of the output value Tv2 + Tv3 of the adder

  FIG. 1 shows a schematic diagram of an optical system and a block diagram of a control system of a laser processing apparatus according to an embodiment. The laser oscillator 10 includes a laser power source 11 and a discharge electrode 12. The laser power source 11 includes a DC power source 13 and a high frequency power source 14. As the laser oscillator 10, for example, a carbon dioxide laser is used. Based on a command from the processing machine control device 35, the laser control device 15 gives a control value Cv to the DC power supply 13 and gives an excitation command signal Ec to the high frequency power supply 14.

  The DC power supply 13 controls the voltage applied to the high frequency power supply 14 based on the control value Cv. The high frequency power supply 14 applies a high frequency voltage to the discharge electrode 12 based on the excitation command signal Ec. Specifically, the average output within the pulse width of the pulse laser beam is controlled by the control value Cv. Here, the “average output within the pulse width” means a value obtained by averaging the laser output during the period in which the laser pulse is output, and is equal to a value obtained by dividing the pulse energy by the pulse width. On the other hand, “unit time average output” means a value obtained by averaging laser output over unit time. Since the unit time includes a period during which the laser pulse is output and a period during which the laser pulse is not output, the unit time average output is smaller than the average output within the pulse width.

  For example, when drilling a printed circuit board or the like, the average output within the pulse width, the pulse width, the pulse repetition frequency, and the like are controlled to match the target value.

  The high frequency power supply 14 includes a switching element 14a, and switches a direct current supplied from the direct current power supply 13 to convert it into an alternating current. The switching element 14 a is on / off controlled by an excitation command signal Ec input from the laser control device 15. As an example, a MOS transistor is used as the switching element 14a, and the excitation command signal Ec is applied to the gate electrode of the MOS transistor.

  As the laser medium gas of the laser oscillator 10, for example, a mixed gas of carbon dioxide gas and nitrogen gas is used. The laser power source 11 applies a high frequency voltage Ve to the discharge electrode 12. When the high-frequency voltage Ve is applied to the discharge electrode 12, a discharge is generated between the discharge electrodes, and the pulsed laser beam Lp is output from the laser oscillator 10.

  The pulsed laser beam Lp output from the laser oscillator 10 is branched into a transmitted beam and a reflected beam by the partial reflection mirror 21. The reflected beam enters the photodetector 20. When the light detector 20 detects light, it sends a detection value Dv corresponding to the light intensity to the laser control device 15. The photodetector 20 includes, for example, a mercury cadmium tellurium (MCT) photoconductive element having sensitivity in the wavelength region of a carbon dioxide laser.

  The transmitted beam that has traveled straight through the partial reflecting mirror 21 passes through the spot position stabilizing optical system 22 and enters the aspherical lens 23. The spot position stabilizing optical system 22 includes a plurality of convex lenses, and the position of the beam spot at the position where the aspherical lens 23 is disposed even when the pulse laser beam Lp output from the laser oscillator 10 is shaken in the traveling direction. To stabilize. The aspheric lens 23 changes the beam profile of the pulsed laser beam Lp. For example, a Gaussian beam profile is changed to a top flat beam profile.

  The pulse laser beam Lp transmitted through the aspheric lens 23 is collimated by the collimator lens 24 and then enters the mask 25. The mask 25 includes a transmission window and a light shielding part, and shapes the beam cross section of the pulse laser beam Lp. The pulse laser beam Lp transmitted through the transmission window of the mask 25 is incident on the beam scanner 28 via the field lens 26 and the folding mirror 27. The beam scanner 28 scans the laser beam in a two-dimensional direction according to a command from the processing machine control device 35. As the beam scanner 28, for example, a galvano scanner is used.

  The pulsed laser beam Lp scanned by the beam scanner 28 is condensed by the fθ lens 29 and enters the workpiece 31. The workpiece 31 is held on the stage 30. The field lens 26 and the fθ lens 29 image the transmission window of the mask 25 on the surface of the workpiece 31. The stage 30 can move the workpiece 31 in a direction parallel to the surface thereof according to a command from the processing machine control device 35. At least one of the beam scanner 28 and the stage 30 functions as a moving mechanism for moving the incident position of the pulse laser beam Lp on the surface of the workpiece 31.

  The processing machine control device 35 gives the pulse output timing signal Pt and the output target value Tv to the laser control device 15. The laser control device 15 gives the excitation command signal Ec to the laser oscillator 10 during the period when the pulse output timing signal Pt is input. The average output within the pulse width of the pulse laser beam is designated by the output target value Tv.

FIG. 2 shows a cross-sectional view of the laser oscillator 10. A blower 40, a pair of discharge electrodes 12, a heat exchanger 46, and a laser medium gas are accommodated in the laser chamber 50. A discharge space 42 is defined between the pair of discharge electrodes 12. By generating a discharge in the discharge space 42,
The laser medium gas is excited. In FIG. 2, a cross section orthogonal to the length direction of the discharge electrode 12 is shown. Each of the discharge electrodes 12 includes a conductive member 43 and a ceramic member 44. The ceramic member 44 isolates the conductive member 43 and the discharge space 42.

  A circulation path from the blower 40 to the blower 40 via the discharge space 42 and the heat exchanger 46 is formed in the laser chamber 50. The heat exchanger 46 cools the laser medium gas that has become hot due to the discharge.

  A pair of terminals 51 are attached to the wall surface of the laser chamber 50. The conductive member 43 of the discharge electrode 12 is connected to the terminal 51 by an in-chamber current path 52, respectively. The terminal 51 is connected to the laser power source 11 by an out-chamber current path 55.

  FIG. 3 shows an example of waveforms of various signals in the laser processing apparatus according to the embodiment. The output target value Tv given from the processing machine control device 35 (FIG. 1) to the laser control device 15 (FIG. 1) is kept constant. The excitation command signal Ec is output in a pulse manner during a period from time t1 when the pulse output timing signal Pt rises to time t3 when it falls. A high frequency voltage Ve is applied to the discharge electrode 12 (FIG. 1) in synchronization with the excitation command signal Ec.

  When the high frequency voltage Ve is applied to the discharge electrode 12, a discharge occurs in the discharge space 42 (FIG. 2), and a discharge current Ie flows. When the application of the high-frequency voltage Ve is stopped, the discharge gradually weakens, and the discharge disappears after a certain period of time.

  The laser pulse of the pulse laser beam Lp rises at time t2 when a certain delay time has elapsed since the start of discharge. The waveform of the laser pulse is not limited to the waveform shown in FIG. 3, but depends on the characteristics of the laser oscillator. FIG. 3 shows an example in which a large peak appears at the rising point, and then a substantially flat portion continues, and the pulse intensity attenuates after time t3.

  The pulse width of the pulse output timing signal Pt is represented by T0, the pulse width of the pulse laser beam Lp is represented by T1, and the period from the rise time t2 of the laser pulse to the fall time t3 of the pulse output timing signal Pt (hereinafter, “ The main period is referred to as T2, and the period of the tail portion (hereinafter referred to as “tail period”) from the time t3 until the laser pulse disappears is expressed as T3.

  After one laser pulse falls, a subsequent laser pulse is output corresponding to the pulse of the pulse output timing signal Pt. The pulse width of the plurality of pulses of the pulse output timing signal Pt is not always constant, and the pulse interval, that is, the pulse repetition frequency is not always constant.

  FIG. 4 shows a block diagram of the laser control device 15. The detection value Dv output from the photodetector 20 is input to the non-inverting input terminal of the comparator 151. A threshold value Tt is input to the inverting input terminal of the comparator 151. The comparator 151 binarizes the detection value Dv with the threshold value Tt as a boundary, and generates a window function Wf. The threshold value Tt is set to about the noise level. The multiplier 152 generates a comparison detection value Dv1 by multiplying the detection value Dv by the window function Wf.

The multiplier 154 generates a comparison target value Tv1 by multiplying the output target value Tv output from the processing machine control device 35 by the window function Wf. The integrator 153 integrates the comparison detection value Dv1 to generate an integration detection value Dvi. The integrator 155 integrates the comparison target value Tv1 to generate an integration target value Tvi. The integration time of the integrators 153 and 155 is, for example, 1 second. That is, the integrators 153 and 155 integrate the input value over one second, and update the output to a new integration result every second.

  The subtractor 156 is referred to as a deviation Id (hereinafter referred to as an integral deviation) of the integral detection value Dvi with respect to the integral target value Tvi. ) Is generated. The integral deviation Id is amplified by the amplifier 157 and input to the adjustment unit 158. The adjustment unit 158 corrects the output target value Tv so as to reduce the integral deviation Id and outputs the control value Cv. The control value Cv is given to the laser oscillator 10.

  FIG. 5 shows examples of waveforms of various signals used in feedback control to the laser oscillator 10. The output target value Tv maintains a constant value. The pulse output timing signal Pt rises at time t1, and the pulse output timing signal Pt falls at time t3.

  The detection value Dv rises by outputting a pulse laser beam at time t2 when a certain delay time has elapsed from the rise time t1 of the pulse output timing signal Pt. The detection value Dv starts to decrease from the falling time t3 of the pulse output timing signal Pt, decreases to the threshold value Tt at time t4, and then decreases to 0. Since the threshold value Tt is set to about the noise level, it may be considered that the time t4 substantially coincides with the time when the intensity of the laser pulse becomes zero.

  A period in which the window function Wf is open (a period in which the value indicates 1) is divided into a main period T2 and a tail period T3. An overlapping portion between the period in which the window function Wf is open and the period T0 in which the pulse output timing signal Pt is given corresponds to the main period T2. Of the period in which the window function Wf is open, the part other than the main period T2 corresponds to the tail period T3.

  The window function Wf becomes 1 during the period when the detection value Dv is equal to or greater than the threshold value Tt. Since the threshold value Tt is set to about the noise level, the rise time of the window function Wf substantially coincides with the rise time t2 of the detection value Dv. Since the value of the window function Wf in the period from time t2 to t4 is 1, the comparison detection value Dv1 in the period from time t2 to t4 shows the same waveform as the detection value Dv. The comparison target value Tv1 for the period from time t2 to t4 coincides with the output target value Tv. During the period when the value of the window function Wf is 0, the comparison target value Tv1 is also 0.

  During the period when the comparison detection value Dv1 is output, that is, the period when the value of the window function Wf is 1, the integration result of the integrator 153 and the integration result of the integrator 155 monotonously increase. The integration result Dvi0 of the integrator 153 is indicated by a broken line, and the integration result Tvi0 of the integrator 155 is indicated by a broken line. The integral detection value Dvi that is the output of the integrator 153 is maintained at the value at the time of the previous reset. The slope of the integration result of the integrator 153 is proportional to the magnitude of the comparison detection value Dv1. Since the comparison target value Tv1 is constant, the slope of the integration result is also constant. During the period in which the value of the window function Wf is 0, the integration results Dvi0 and Tvi0 are maintained at a constant value.

  After time t4, the pulse of the pulse output timing signal Pt is intermittently output from the processing machine control device 35. The detection value Dv is output according to the output of the pulse output timing signal Pt, and the value of the window function Wf becomes 1. During the period when the value of the window function Wf is 1, the integration results Dvi0 and Tvi0 of the integrators 153 and 155 increase in accordance with the comparison detection value Dv1 and the comparison target value Tv1, respectively.

  At the reset time t5 of the integrators 153 and 155, the integration detection value Dvi and the integration target value Tvi are updated to new integration results. Along with this, the integral deviation Id is also updated. The adjustment unit 158 (FIG. 4) corrects the output target value Tv and outputs the control value Cv in a direction in which the integral deviation Id becomes smaller in accordance with the updated integral deviation Id.

  For example, when the average output within the pulse width is smaller than the output target value Tv, the integral detection value Dvi becomes smaller than the integral target value Tvi, and the integral deviation Id becomes positive. At this time, the adjustment unit 158 increases the control value Cv. When the control value Cv increases, the high-frequency voltage Ve applied to the discharge electrode 12 (FIG. 1) increases. As a result, the average output within the pulse width of the pulse laser beam output from the laser oscillator 10 (FIG. 1) increases.

  On the contrary, when the average output within the pulse width is larger than the output target value Tv, the integral detection value Dvi becomes larger than the integral target value Tvi, and the integral deviation Id becomes negative. At this time, the adjustment unit 158 decreases the control value Cv. When the control value Cv decreases, the high-frequency voltage Ve applied to the discharge electrode 12 (FIG. 1) decreases. As a result, the average output within the pulse width of the pulse laser beam output from the laser oscillator 10 (FIG. 1) becomes small.

  As a method for adjusting the control value Cv so that the integral deviation Id becomes small, for example, P (proportional) control, PI control, PID control, or the like can be applied.

  Generally, the pulse repetition frequency is on the order of kHz. The reset period of the integrators 153 and 155 is set to 1 second, for example. As a result, the output of the laser oscillator 10 can be feedback controlled in a cycle of 1 second. Time constants such as ambient temperature environment and laser medium gas deterioration are sufficiently longer than the reset period (for example, 1 second) of the integrators 153 and 155. For this reason, feedback control can be performed in a sufficiently short period that can follow environmental changes.

  When the pulse repetition frequency and pulse width of the pulse laser beam Lp output from the laser oscillator 10 fluctuate, the integrated detection value Dvi fluctuates even if the average output within the pulse width is constant. For this reason, even if the integral detection value Dvi is compared with the output target value Tv and the integral value, it cannot be determined whether or not the average output within the pulse width is within the allowable range.

  In the above embodiment, the output target value Tv is not integrated, but the comparison target value Tv1, which is the result of multiplying the output target value Tv by the window function Wf, is integrated. Since the output target value Tv during the period when the laser pulse is not output is not added to the integration result, the integration target value Tvi that is the integration result of the comparison target value Tv1 is used as the target value of the integration result of the comparison detection value Dv1. can do.

  By performing feedback control based on the integration target value Tvi, it is possible to appropriately perform feedback control for suppressing output fluctuation of the laser oscillator 10 even if the pulse repetition frequency and pulse width vary.

  In the embodiment shown in FIG. 4, the detection value Dv is multiplied by the window function Wf. This is to prevent the noise component from being integrated during the period when the laser pulse is not output. When the S / N ratio of the output of the photodetector 20 is sufficiently high, the detection value Dv may be directly input to the integrator 153 without being multiplied by the window function Wf.

  As shown in FIG. 6A, the detection value Dv1 output from the photodetector 20 may be rectified by a half-wave rectification circuit 159 to generate the comparison detection value Dv1. As the half-wave rectifier circuit 159, for example, a diode is used. The detected value Dv is positive during the period in which the pulse laser beam Lp is output, and the magnitude of the detected value Dv in the other periods is the noise level. When the detection value Dv is rectified by the half-wave rectification circuit 159, the comparison detection value Dv1 during a period when the detection value Dv is negative becomes zero. Thereby, the influence of noise can be reduced.

As shown in FIG. 6B, a non-inverting idealized diode circuit may be used as the half-wave rectifier circuit 159. The idealized diode circuit includes an operational amplifier, a diode, and a resistance element. When a diode is used for the half-wave rectifier circuit 159 (FIG. 6A), the comparison detection value Dv1 input to the integrator 153 (FIG. 6A) is less than the detection value Dv by the forward voltage drop of the diode. It gets smaller. If a non-inverting idealized diode circuit is used for the half-wave rectifier circuit 159, the forward voltage drop can be substantially reduced to zero.

  FIG. 7 shows a block diagram of a laser control device 15 used in a laser processing apparatus according to a modification of the above embodiment. In the embodiment shown in FIG. 4, the integration detection values Dv1 and the comparison target value Tv1 are integrated by the integrators 153 and 155 (FIG. 4), respectively, and then the integration deviation Id is obtained by the subtractor 156. In the modification shown in FIG. 7, the subtractor 156 calculates the deviation of the comparison detection value Dv1 from the comparison target value Tv1, and then integrates the deviation by the integrator 160, thereby obtaining the integral deviation Id. Also in the modification shown in FIG. 7, the same effect as the embodiment shown in FIGS. The amplifier 157 may have an integration function, and the integrator 160 may be omitted.

  Next, another embodiment will be described with reference to FIGS. Hereinafter, differences from the embodiment shown in FIGS. 1 to 5 will be described, and description of the same configuration will be omitted.

  As shown in FIG. 8, the output target value Tv is input to one input terminal of the multiplier 154A, multiplied by K, and input to one input terminal of the other multiplier 154B. Here, K is less than 1. A window function having a value of 1 in the main period T2 shown in FIG. 3 and a value of 0 in the other periods is input to the other input terminal of the multiplier 154A. A window function having a value of 1 in the tail period T3 shown in FIG. 3 and a value of 0 in the other periods is input to the other input terminal of the multiplier 154B. In the tail period T3, the laser pulse gradually attenuates.

  The output value Tv2 of the multiplier 154A and the output value Tv3 of the other multiplier 154B are added by the adder 162 and input to the integrator 155. The configuration subsequent to the integrator 155 is the same as the configuration shown in FIG.

  9 shows waveforms of the comparison detection value Dv1, the comparison target value Tv1 in the embodiment shown in FIG. 4, the output values Tv2 and Tv3 in the embodiment shown in FIG. 8, and the output value Tv2 + Tv3 of the adder 162. . In the embodiment shown in FIG. 4, the comparison target value Tv1 is maintained at a constant output target value Tv during the period T1. In the embodiment shown in FIG. 8, the output value Tv2 is maintained at the output target value Tv during the main period T2. The output value Tv3 is a value obtained by multiplying the output target value Tv by a constant K during the tail period T3.

  The output value Tv2 + Tv3 of the adder 162 is maintained at the output target value Tv during the main period T2, but is a smaller value Tv × K during the tail period T3. In the tail portion of the laser pulse, the waveform in which the comparison detection value Dv1 gradually decreases is approximated by a value Tv × K that is smaller than the output target value Tv.

  The waveform of the output value Tv2 + Tv3 of the adder 162 is closer to the waveform of the actual laser pulse than the waveform of the comparison target value Tv1 in the embodiment shown in FIG. For this reason, by adopting the configuration of the embodiment shown in FIG. 8, it is possible to perform feedback with higher accuracy than in the embodiment shown in FIG.

  In the embodiment shown in FIG. 8, the outputs of the multipliers 154 </ b> A and 154 </ b> B are added by the adder 162 and then integrated by the integrator 155. Instead of this configuration, the outputs of the multipliers 154A and 154B may be integrated and then added by an adder. In this case, the integrator 155 is omitted, and integrators are respectively inserted in the subsequent stages of the multipliers 154A and 154B.

  Further, in the embodiment shown in FIG. 8, the subtractor 156 obtains the deviation of the integral detection value Dvi from the integral target value Tvi. Instead of this configuration, the deviation of the comparison detection value Dv1 with respect to the output value Tv2 + Tv3 before integration may be obtained, and this deviation may be integrated. In this case, the integrators 153 and 155 are omitted, and one integrator is inserted after the subtractor 156. Instead of inserting an integrator in the subsequent stage of the subtracter 156, the amplifier 157 may have an integration function.

  Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

DESCRIPTION OF SYMBOLS 10 Laser oscillator 11 Laser power supply 12 Discharge electrode 13 DC power supply 14 High frequency power supply 14a Switching element 15 Laser control apparatus 20 Photodetector 21 Partial reflection mirror 22 Spot position stabilization optical system 23 Aspherical lens 24 Collimating lens 25 Mask 26 Field lens 27 Folding mirror 28 Beam scanner 29 fθ lens 30 Stage 31 Work object 35 Machine control device 40 Blower 42 Discharge space 43 Conductive member 44 Ceramic member 46 Heat exchanger 50 Chamber 51 Terminal 52 In-chamber current path 55 Out-chamber current path 151 Comparator 152 Multiplier 153 Integrator 154, 154A, 154B Multiplier 155 Integrator 156 Subtractor 157 Amplifier 158 Adjustment unit 159 Half-wave rectifier circuit 160 Integrator 162 Adder Cv Control value Dv Detection value Dv1 Comparison Detection value Dvi Integration detection value Dvi0 Integration result Ec Excitation command signal Id Integration deviation Ie Discharge current Lp Pulse laser beam Pt Pulse output timing signal Tt Threshold Tv Output target value Tv1 Comparison target value Tv2, Tv3 Output value Tvi Integration target value Tvi0 Integration Result Ve High-frequency voltage Wf Window function

Claims (8)

A laser oscillator that outputs a pulse laser beam having an average output within a pulse width according to a control value given from the outside;
When detecting the pulse laser beam output from the laser oscillator, a photodetector that outputs a detection value according to the light intensity;
A laser control device that receives the detection value from the photodetector and outputs a control value to the laser oscillator based on an output target value that instructs a target average output within a pulse width and the detection value; ,
The laser control device
A laser processing apparatus that gives the control value to the laser oscillator so that an integral deviation of the detected value with respect to the output target value during a period in which the detected value is input becomes small. The laser control device
A window function is generated by binarizing the detected value using a threshold value,
A target value for comparison is generated by multiplying the output target value by the window function,
The laser processing apparatus according to claim 1, wherein the integration deviation is obtained using the comparison target value. The laser control device generates a comparison detection value by multiplying the detection value by the window function,
The laser processing apparatus according to claim 2, wherein the integral deviation is obtained using the comparison detection value.   The laser control device obtains an integration target value obtained by integrating the comparison target value and an integration detection value obtained by integrating the comparison detection value, and the integration target value and the integration detection value are obtained. The laser processing apparatus according to claim 3, wherein the integral deviation is obtained by comparing the two. The laser oscillator is
A discharge electrode;
A laser power source that applies a high-frequency voltage having a magnitude corresponding to the control value to the discharge electrode;
The laser control device gives an excitation command signal to the laser oscillator;
5. The laser processing apparatus according to claim 2, wherein the laser power source applies the high-frequency voltage to the discharge electrode during a period in which the excitation command signal is given. The laser control device
A period in which the window function is open is divided into a main period overlapping with a period in which the excitation command signal is given, and another tail period, and the target value for comparison in the tail period is set as the main period. The laser processing apparatus according to claim 5, wherein the laser processing apparatus is smaller than the comparison target value. further,
A stage for holding a workpiece at a position where the pulse laser beam output from the laser oscillator is incident;
A beam scanner for moving the incident position of the pulsed laser beam on the surface of the workpiece held on the stage;
A processing machine control device that controls the beam scanner and gives the output target value and a pulse output timing signal to the laser control device,
The laser processing device according to claim 5, wherein the laser control device gives the excitation command signal to the laser oscillator based on the pulse output timing signal. Detecting the pulse laser beam output from the laser oscillator and generating a detection value corresponding to the light intensity of the pulse laser beam;
Multiplying an output target value for commanding an average output within a pulse width to be a target by a window function corresponding to a period during which a laser pulse of the pulse laser beam is output; and generating a comparison target value;
Feeding back to the output of the laser oscillator so that an integral deviation of the detected value with respect to the comparison target value is small.

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