JP6957113B2 - Laser control device - Google Patents

Description

The present invention relates to a laser control device.

Processing technology using pulsed laser light is used for drilling holes in printed wiring boards. Patent Document 1 discloses a laser processing apparatus capable of outputting a pulsed laser beam having a desired pulse width. In this laser processing device, after turning on the pulse control power supply that outputs the pulsed laser beam to the laser resonator, the pulse is based on the output timing and pulse width command of the pulsed laser beam actually output from the laser resonator. Turn off the control power. Even if the time from turning on the pulse control power supply to the actual output of the pulsed laser light varies, the pulse width can be maintained at the commanded value.

International Publication No. 2014/010046

When processing using a pulsed laser beam, it is important to keep the energy per pulse (pulse energy) constant. According to the evaluation experiments of the inventors of the present application, it has been found that even if the pulse width is maintained at the commanded value, the effect of suppressing the variation in the pulse energy may not be sufficient.

An object of the present invention is to provide a laser control device capable of suppressing variations in pulse energy.

According to one aspect of the invention
The build-up time, which is the elapsed time from the start of excitation of the laser oscillator that outputs the pulsed laser beam to the rise of the laser pulse, is calculated and used as the measured value.
The command value is calculated so that the command value of the pulse width of the laser pulse output from the laser oscillator becomes longer as the measured value of the build-up time becomes longer.
Provided is a laser control device that controls the laser oscillator so that the pulse width of the laser pulse output at the present time becomes the calculated command value.

According to the measurement value of the build-up time is longer, the longer you Rukoto the command value of the pulse width of the laser pulses being output from the laser oscillator, less variation in pulse energy as compared with the case where the pulse width constant can do.

FIG. 1 is a schematic view of a laser processing apparatus equipped with a laser control apparatus according to an embodiment. FIG. 2 is a graph showing waveforms of an oscillation command signal S0 transmitted from the laser control device to the laser oscillator according to the embodiment and a detection signal S1 given to the laser control device from the photodetector. FIG. 3A is a graph showing the relationship between the discharge voltage and the pulse energy under a condition where the pulse width is constant, FIG. 3B is a graph showing the relationship between the discharge voltage and the build-up time, and FIG. 3C is a pulse. It is a graph which shows the relationship between the build-up time and the pulse energy under the condition of a constant width. FIG. 4A is an example of a block diagram of the laser control device according to the embodiment, and FIG. 4B shows the measured value of the build-up time and the command value of the pulse width stored in the storage unit of the laser control device according to the embodiment. It is a figure which shows the correspondence relationship by a graph. FIG. 5 is a flowchart of processing executed by the laser control device according to the embodiment. FIG. 6 is a flowchart showing the process of step SA4 (FIG. 5). FIG. 7A is a graph showing the relationship between the measured value of the build-up time and the measured value of the pulse energy when the pulse width is constant regardless of the build-up time, and FIG. 7B shows the laser control device according to the embodiment. It is a graph which shows the relationship between the measured value of the build-up time and the measured value of the pulse energy when used. FIG. 8A is a block diagram of the laser control device according to another embodiment, and FIG. 8B is a graph showing the correspondence between the measured value of the average output and the command value of the discharge voltage. FIG. 9 is a flowchart of a process in which the laser control device according to the embodiment shown in FIG. 8A controls the discharge voltage. FIG. 10 is a flowchart of step SA4 (FIG. 5) according to the embodiment shown in FIG. 8A. FIG. 11 shows an example of a time change of the command value of the discharge voltage, the measured value of the average output of the laser oscillator 20, the measured value of the build-up time, and the command value of the pulse width when the reference value of the build-up time is unchanged. It is a graph which shows. FIG. 12 shows the command value of the discharge voltage, the measured value of the average output of the laser oscillator, the measured value of the build-up time, and the time of the command value of the pulse width when the laser control device according to the embodiment shown in FIG. 8A is used. It is a graph which shows an example of a change.

The laser control device according to the embodiment will be described with reference to FIGS. 1 to 7B.

FIG. 1 is a schematic view of a laser processing device equipped with a laser control device 30 according to an embodiment. The laser oscillator 20 receives an oscillation command signal S0 from the laser control device 30 and outputs a pulsed laser beam. As the laser oscillator 20, various pulse laser oscillators, for example, a carbon dioxide laser oscillator that oscillates in pulses can be used. The laser oscillator 20 includes an optical resonator, a discharge electrode, a discharge electrode drive circuit, and the like.

The pulsed laser beam output from the laser oscillator 20 passes through the first optical system 21, is reflected by the bending mirror 22, passes through the second optical system 23, and is incident on the workpiece 25 held by the stage 24. do. The object to be processed 25 is, for example, a printed wiring board, and drilling is performed by a pulsed laser beam.

A part of the pulsed laser beam incident on the bending mirror 22 passes through the bending mirror 22 and is incident on the photodetector 26. The photodetector 26 detects an incident laser pulse and outputs a detection signal S1 which is an electric signal corresponding to the light intensity of the laser pulse. As the photodetector 26, an infrared sensor having a response speed capable of following a change in the pulse waveform, for example, a mercury cadmium tellurized mercury sensor (MCT sensor) or the like can be used. The photodetector 26 may be arranged immediately after the laser emission port of the laser oscillator 20.

The first optical system 21 includes a beam expander, an aspherical lens, an aperture, and the like. The beam expander changes the beam diameter and spread angle of the laser beam. The aspherical lens changes the beam profile from a Gaussian shape to a top flat shape. The aperture shapes the cross-sectional shape of the beam.

The second optical system 23 includes a beam scanner, an fθ lens, and the like. The beam scanner includes, for example, a pair of galvanometer mirrors, and scans the laser beam in a two-dimensional direction according to a command from the laser control device 30. The fθ lens focuses the laser beam scanned by the beam scanner on the surface of the object to be processed 25. The position of the aperture may be reduced and projected onto the surface of the object to be processed 25.

The stage 24 can hold the work object 25 on a horizontal holding surface, for example, and move the work object 25 in two directions in a horizontal plane. The laser control device 30 controls the movement of the stage 24. For the stage 24, for example, an XY stage is used.

The laser control device 30 adjusts the pulse width of the pulsed laser beam output from the laser oscillator 20 for each laser pulse so that the pulse energy becomes constant, based on the detection signal S1 of the laser pulse by the light detector 26. do.

FIG. 2 shows an oscillation command signal S0 transmitted from the laser control device 30 (FIG. 1) to the laser oscillator 20 (FIG. 1), and is given to the laser control device 30 (FIG. 1) from the light detector 26 (FIG. 1). It is a graph which shows the waveform of the detection signal S1.

When the oscillation command signal S0 rises at time t0, the laser oscillator 20 starts supplying high-frequency power to the discharge electrode. By starting the supply of high-frequency power to the discharge electrode, the excitation of the laser medium of the laser oscillator 20 is started. That is, the rising edge of the oscillation command signal S0 corresponds to the oscillation start command of the laser oscillator 20, and the rising point of the oscillation command signal S0 corresponds to the excitation start time of the laser oscillator 20.

The laser pulse rises at time t1 after the excitation start time t0. The detection signal S1 also rises in response to the rise of the laser pulse. The elapsed time from the excitation start time t0 to the laser pulse rise time t1 is referred to as the build-up time BU. At the rising edge of the laser pulse, a very short peak waveform due to gain switching appears, after which a nearly constant light intensity is maintained. The portion where a substantially constant light intensity is maintained is referred to as the main portion of the pulse waveform.

When the oscillation command signal S0 falls at time t2, the laser oscillator 20 stops supplying high-frequency power to the discharge electrode. When the supply of high-frequency power to the discharge electrode is stopped, the laser medium of the laser oscillator 20 is not excited. That is, the falling edge of the oscillation command signal S0 means a command to stop the excitation of the laser oscillator 20. When the excitation of the laser oscillator 20 is stopped, the intensity of the laser pulse output from the laser oscillator 20 drops sharply.

The value obtained by integrating one pulse waveform of the detection signal S1 with time is determined by the energy per pulse (pulse energy). In the present specification, this integrated value determined by pulse energy is referred to as "pulse energy-dependent physical quantity".

Since the time width of the extremely short peak waveform due to gain switching is sufficiently shorter than the overall pulse width, the integrated value of the portion of the pulse waveform excluding the extremely short peak waveform due to gain switching is the pulse energy-dependent physical quantity. May be adopted as. Further, the time width of the tail portion after the excitation is stopped is also sufficiently shorter than the pulse width of the laser pulse, and the light intensity of the tail portion sharply decreases with the passage of time. The integrated value may be adopted as a pulse energy-dependent physical quantity. In this way, the integrated value of the main part of the pulse waveform may be adopted as the pulse energy-dependent physical quantity.

FIG. 3A is a graph showing the relationship between the discharge voltage and the pulse energy of the laser oscillator 20 under the condition that the pulse width is constant. As the discharge voltage increases, the high-frequency power applied to the laser oscillator 20 increases. As the discharge voltage increases and the high frequency power applied increases, the laser medium is excited more strongly. As a result, the pulse energy becomes high. Therefore, the discharge voltage, high-frequency power, and the like can be referred to as excitation intensities.

FIG. 3B is a graph showing the relationship between the discharge voltage and the build-up time. The higher the discharge voltage, the faster the excited state of the laser medium reaches the oscillation threshold, which shortens the build-up time.

FIG. 3C is a graph showing the relationship between the build-up time and the pulse energy under the condition that the pulse width is constant. From the relationship between the discharge voltage and the pulse energy shown in FIG. 3A and the relationship between the discharge voltage and the build-up time shown in FIG. 3B, it can be seen that the pulse energy decreases as the build-up time increases. Conversely, the shorter the build-up time, the larger the pulse energy.

Although FIGS. 3A to 3C show an example in which the build-up time changes depending on the discharge voltage, the discharge voltage is not the only factor that changes the build-up time. Although the build-up time changes depending on other factors, under the condition that the pulse width is constant, the pulse energy usually tends to decrease as the build-up time increases, as shown in FIG. 3C.

FIG. 4A is an example of a block diagram of the laser control device 30 according to the embodiment. The laser control device 30 includes a laser pulse detection unit 31, a signal transmission unit 32, a pulse width adjustment unit 33, and a storage unit 34.

The laser pulse detection unit 31 receives the detection signal S1 from the photodetector 26 and detects the rise time of the laser pulse. The signal transmission unit 32 transmits the oscillation command signal S0 to the laser oscillator 20.

The storage unit 34 stores the correspondence between the measured value of the build-up time and the command value of the pulse width.

FIG. 4B is a graph showing the correspondence between the measured value of the build-up time stored in the storage unit 34 and the command value of the pulse width. When the measured value of the build-up time is the reference value BU _ref , the command value of the pulse width is associated with the _{reference value PW ref.} As the measured build-up time _{becomes longer than the reference value BU ref} , the command value of the pulse width becomes longer than the reference value PW _ref , and as the measured value of the build-up time _{becomes shorter than the reference value BU ref} , the pulse width PW The correspondence between the two is defined so that the command value is _{shorter than the reference value PW ref.}

The pulse width adjusting unit 33 (FIG. 4A) acquires information indicating the rising time of the oscillation command signal S0 (t0 in FIG. 2) from the signal transmitting unit 32, and the laser pulse detecting unit 31 obtains information indicating the rising time of the laser pulse (FIG. 2). The information indicating t1) of the above is acquired. The pulse width adjusting unit 33 obtains the build-up time (FIG. 2) from the acquired information and uses it as a measured value of the build-up time. Further, the command value of the pulse width of the laser pulse is calculated based on the measured value of the build-up time and the correspondence relationship stored in the storage unit 34.

The signal transmission unit 32 acquires the command value of the pulse width calculated by the pulse width adjustment unit 33. Further, the signal transmission unit 32 lowers the oscillation command signal S0 (FIG. 2) transmitted to the laser oscillator 20 so that the pulse width of the currently output laser pulse matches the command value of the pulse width. .. As a result, the pulse width of the laser pulse output from the laser oscillator 20 substantially matches the command value.

FIG. 5 is a flowchart of the process executed by the laser control device 30 (FIG. 4A) according to the embodiment.
The signal transmission unit 32 transmits an oscillation start command to the laser oscillator 20 (step SA1). Specifically, the oscillation command signal S0 (FIG. 2) is launched. As a result, the laser pulse output from the laser oscillator 20 rises. The laser pulse detection unit 31 (FIG. 4) acquires the detection signal S1 (FIG. 2) and detects the rise of the laser pulse (step SA2).

When the rising edge of the laser pulse is detected, the pulse width adjusting unit 33 calculates the measured value of the build-up time (step SA3). Further, the pulse width adjusting unit 33 calculates the command value of the pulse width based on the measured value of the build-up time with reference to the correspondence stored in the storage unit 34 (step SA4). After that, the signal transmission unit 32 transmits an oscillation stop command to the laser oscillator 20 so that the pulse width of the current laser pulse matches the command value (step SA5). Specifically, the oscillation command signal S0 (FIG. 2) is turned off.

The processing from step SA1 to step SA5 is repeated until the laser machining is completed (step SA6).

FIG. 6 is a flowchart showing the process of step SA4 (FIG. 5). First, the pulse width adjusting unit 33 compares the measured value of the build-up time with the reference value BU _ref (FIG. 4B) (step SA41). Further, the pulse width adjusting unit 33 calculates the command value of the pulse width based on the comparison result and the correspondence relationship stored in the storage unit 34 (step SA42).

Next, the excellent effect obtained by controlling the laser processing device with the laser control device 30 according to the above embodiment will be described.

In a pulse laser oscillator such as a carbon dioxide laser oscillator, as shown in FIG. 3C, even if the pulse width is constant, the pulse energy tends to decrease as the build-up time becomes longer. In the embodiment, as shown in FIG. 4B, as the measured value of the build-up time becomes longer, the command value of the pulse width of the currently output laser pulse is lengthened to compensate for the decrease in pulse energy. ing. Therefore, the variation in pulse energy can be reduced as compared with the case where the pulse width is controlled to be constant.

Next, with reference to FIGS. 7A and 7B, the result of confirming the effect obtained by using the laser control device 30 according to the above embodiment by the evaluation experiment will be described.

FIG. 7A is a graph showing the relationship between the measured value of the build-up time and the measured value of the pulse energy when the pulse width is constant regardless of the build-up time. The horizontal axis represents the build-up time in an arbitrary unit, and the vertical axis represents the pulse energy in an arbitrary unit. The measured value for one laser pulse is represented by one circle symbol. It can be seen that the pulse energy tends to decrease as the build-up time increases.

FIG. 7B is a graph showing the relationship between the measured value of the build-up time and the measured value of the pulse energy when the laser control device 30 according to the above embodiment is used. The standard deviation of the pulse energy distribution at this time is smaller than the standard deviation of the pulse energy shown in FIG. 7A. It was confirmed that the variation in pulse energy was reduced by using the laser control device 30 according to the embodiment.

Next, the laser control device according to another embodiment will be described with reference to FIGS. 8A to 12. Hereinafter, the description of the configuration common to the laser control device according to the embodiment shown in FIGS. 1 to 7B will be omitted. In this embodiment, not only the pulse width of the laser pulse but also the excitation intensity given to the laser oscillator 20 is changed. In order to change the excitation intensity, for example, the magnitude of the discharge voltage applied to the discharge electrode may be changed, or the duty of the high frequency current supplied to the discharge electrode may be changed. In the following description, the excitation intensity is changed by changing the discharge voltage.

FIG. 8A is a block diagram of the laser control device 30 according to this embodiment. The laser control device 30 according to this embodiment has an average output calculation unit 35 and an average output adjustment unit 36 in addition to the respective parts of the laser control device 30 according to the embodiment shown in FIG. 4A. Further, the storage unit 34 stores the correspondence between the measured value of the average output and the command value of the excitation intensity.

FIG. 8B is a graph showing the correspondence between the measured value of the average output and the command value of the discharge voltage. When the measured value of the average output is the reference value _Pref , the command value of the discharge voltage corresponds to the _{reference value Vref.} As the measured value of the average output _{becomes higher than the reference value Pref} , the command value of the discharge voltage tends to decrease. On the contrary, as the measured value of the average output _{becomes lower than the reference value Pref} , the command value of the discharge voltage tends to increase.

The average output calculation unit 35 (FIG. 8A) calculates the average output for a certain period based on the detection signal S1 (FIG. 2) from the photodetector 26, and uses it as a measured value of the average output. The average output can be calculated by dividing the total value of the integrated values of the pulse waveforms acquired in a certain period by the length of the certain period.

The average output adjusting unit 36 calculates a command value of the discharge voltage based on the measured value of the average output and the correspondence relationship (FIG. 8B) stored in the storage unit 34. For example, as the measured value of the average output _{becomes larger than the reference value Pref} , the command value of the discharge voltage _{is made smaller than the reference value V ref} , and as the measured value of the average output _{becomes smaller than the reference value Pref} , the command value of the discharge voltage is commanded. _{Make the} value larger than the reference value V ref.

The signal transmission unit 32 transmits a signal S2 that commands the discharge voltage to the laser oscillator 20 based on the command value of the discharge voltage obtained by the average output adjustment unit 36. The laser oscillator 20 applies the discharge voltage commanded by the signal S2 to the discharge electrode when the laser medium is excited.

FIG. 9 is a flowchart of a process in which the laser control device 30 (FIG. 8A) according to the present embodiment controls the discharge voltage.

When the laser control device 30 is activated, the command value of the discharge voltage is set to the reference value V _ref (step SB1). When outputting the laser pulse, the laser oscillator 20 is excited based on the command value of the current discharge voltage (step SB2). The command value of the discharge voltage is fixed for a certain period of time. The fixed period in which the command value of the discharge voltage is fixed is referred to as the "discharge voltage fixed period". Even during the discharge voltage fixed period, the pulse width is adjusted for each laser pulse based on the build-up time shown in FIG.

When the discharge voltage fixed period elapses after setting the discharge voltage command value, the average output calculation unit 35 (FIG. 8A) calculates the average output during the discharge voltage fixed period and uses it as the measured value of the average output (step SB3). ). The average output adjusting unit 36 (FIG. 8A) updates the command value of the discharge voltage based on the measured value of the average output and the correspondence relationship (FIG. 8B) stored in the storage unit 34 (step SB4). The signal transmission unit 32 transmits the updated command value to the laser oscillator 20. The processing from step SB2 to step SB4 is repeated until the laser machining is completed (step SB5).

FIG. 10 is a flowchart of step SA4 of FIG. Step SA41 and step SA42 are the same as the corresponding steps of the embodiment shown in FIG. In the example shown in FIG. 6, the reference value BU _ref of the build-up time was unchanged. In this embodiment, the reference value BU _ref of the build-up time is periodically updated to the measured value of the build-up time. For example, after calculating the command value of the pulse width, when the _{update cycle elapses from the update immediately before the reference value BU ref} of the build-up time (step SA43), the reference value BU _ref of the build-up time is set in the immediately preceding one cycle. Update to the average laser pulse build-up time. After updating the build-up time reference value BU _ref , step SA5 (FIG. 5) is executed.

Next, before explaining the excellent effect obtained by adopting the laser control device 30 according to the embodiment of FIGS. 8A to 10, when the reference value of the build-up time is made unchanged with reference to FIG. That is, a case where step SA43 and step SA44 (FIG. 10) are not executed will be described.

FIG. 11 shows the time change of the discharge voltage command value, the measured value of the average output of the laser oscillator 20, the measured value of the build-up time, and the command value of the pulse width when _{the reference value BU ref of the build-up time is unchanged.} It is a graph which shows an example. The measured value of the build-up time and the command value of the pulse width change for each laser pulse, but FIG. 11 shows the average value for each update cycle _{of the reference value BU ref of the build-up time.} In the initial state, the command value of the discharge voltage _{is set to the reference value V ref} , and the command value of the pulse width is set to the reference value PW _ref . Measurements of the average output is substantially equal to the reference value P _ref, measurement of the build-up time is to be approximately equal to the reference value BU _ref.

When the measured value of the average output _{falls below the reference value Pref for} some reason (t10), control is performed to increase the command value of the discharge voltage (t11) (step SB4 in FIG. 9). When the command value of the discharge voltage rises, the output of the laser oscillator 20 increases, so that the measured value of the average output rises (t12) and the measured value of the build-up time becomes short (t13).

When the measured value of the build-up time _{becomes shorter than the reference value BU ref,} the control to make the command value of the pulse width _{shorter than the reference value PW ref} is performed (t14) (step SA4 in FIG. 5). Shortening the command value of the pulse width acts to reduce the average output. Therefore, the measured value of the average output decreases (t15). When the measured value of the average output decreases, the command value of the discharge voltage increases as at the time t10 (t16). As a result, the measured value of the average output is returned to the reference value _{P ref} (t17). Since the increase in the discharge voltage acts in the direction of shortening the build-up time, the measured value of the build-up time is further shortened (t18). When the measured value of the build-up time is shortened _{, the difference between the reference value BU ref} of the build-up time and the measured value is widened, so that the command value of the pulse width is further shortened (t19).

By continuously executing the process of shortening the command value of the pulse width in this way, the command value of the pulse width reaches the _{permissible lower limit value PW min.} After the command value of the pulse width _{reaches the allowable lower limit value PW min} , the command value of the pulse width is fixed to the _{allowable lower limit value PW min.} As described above, even if the adjustment of the discharge voltage and the adjustment of the pulse width are used in combination, the function of adjusting the pulse width may not work. This is because the gain from the change in the discharge voltage to the change in the pulse energy through the change in the build-up time and the adjustment of the pulse width is larger than the change in the pulse energy due to the change in the discharge voltage. If the function for adjusting the pulse width does not work, the effect of suppressing the variation in pulse energy cannot be obtained.

FIG. 12 shows the time change of the command value of the discharge voltage, the measured value of the average output of the laser oscillator 20, the measured value of the build-up time, and the command value of the pulse width when the laser control device 30 according to the present embodiment is used. It is a graph which shows an example. The time change of the discharge voltage command value from time t10 to t17, the measured value of the average output of the laser oscillator 20, the measured value of the build-up time, and the command value of the pulse width is the same as the example shown in FIG. ..

As the discharge voltage rises (t16), the build-up time measurement becomes shorter (t21). At this time, the reference value BU _ref of the build-up time is updated to the average value of the measured values in the immediately preceding cycle (step SA44). In FIG. 12, the reference value BU _ref of the build-up time is shown by a broken line. Since the reference value _{BU ref} buildup time is updated, for example, the difference between the measured value of the build-up time and the reference value _{BU ref} at time t21, the measurement of the build-up time at the time t13 and the reference value _{BU ref} Is almost equal to the difference. Therefore, the command value of the pulse width does not substantially change (t22).

When the update cycle of the build-up time reference value BU _ref elapses from the time t21, the build-up time reference value BU _ref is updated (t23), and the measured value of the build-up time is almost the same as the _{build-up time reference value BU ref.} Become equal. Therefore, control is performed to return the command value of the pulse width to substantially the reference value PW _ref (t24) (step SA4). Since the control for increasing the pulse width acts in the direction of increasing the average output, the measured value of the average output increases (t25).

When the measured value of the average output rises, control is performed to lower the command value of the discharge voltage (t26) (step SB4 in FIG. 9). When the command value of the discharge voltage decreases, the measured value of the average output decreases (t27) and the measured value of the build-up time becomes long (t28). Since the build-up time reference value BU _ref is updated to the average value of the build-up time measurement values of the immediately preceding cycle, the build-up time measurement value becomes longer than the _{reference value BU ref.} Therefore, control is performed to lengthen the command value of the pulse width (t29) (step SA42 in FIG. 10).

When the command value of the pulse width becomes long, the measured value of the average output becomes large (t30) as at the time t24, and then the control to lower the command value of the discharge voltage is performed (t31). As a result, the measured value of the average output decreases (t32), and the measured value of the build-up time becomes long (t33). Since the build-up time reference value BU _ref is updated to the average value of the build-up time measurement values of the immediately preceding cycle, _{the difference between the build-up time measurement value and the reference value BU ref} is the build at time t28. It is almost equal to the difference between the measured value of the up time and the reference value BU _ref. As a result, the command value of the pulse width does not change substantially (t34).

As described above, in this embodiment, since the reference value BU _ref of the build-up time is updated based on the measured value, it is possible to prevent _{the command value of the pulse width from being fixed to the allowable lower limit value PW min.} .. Therefore, even when the adjustment of the discharge voltage and the adjustment of the pulse width are used in combination, the function of adjusting the pulse width can be effectively used. Therefore, both the effects of stabilizing the output and reducing the variation in pulse energy can be obtained.

It goes without saying that each of the above embodiments is exemplary and the configurations shown in different examples can be partially replaced or combined. Similar effects and effects due to the same configuration of a plurality of examples will not be mentioned sequentially for each example. Furthermore, the present invention is not limited to the above-mentioned examples. For example, it will be obvious to those skilled in the art that various changes, improvements, combinations, etc. are possible.

20 Laser oscillator 21 1st optical system 22 Bending mirror 23 2nd optical system 24 Stage 25 Processing object 26 Photodetector 30 Laser control device 31 Laser pulse detection unit 32 Signal transmission unit 33 Pulse width adjustment unit 34 Storage unit 35 Average output Calculation unit 36 Average output adjustment unit

Claims (6)

The build-up time, which is the elapsed time from the start of excitation of the laser oscillator that outputs the pulsed laser beam to the rise of the laser pulse, is calculated and used as the measured value.
The command value is calculated so that the command value of the pulse width of the laser pulse output from the laser oscillator becomes longer as the measured value of the build-up time becomes longer.
A laser control device that controls the laser oscillator so that the pulse width of the laser pulse output at the present time becomes the calculated command value. The laser control device according to claim 1, further adjusting the excitation intensity of the laser oscillator based on the measured value of the average output of the pulsed laser beam output from the laser oscillator. When calculating the command value of the pulse width of the laser pulse, the measured value of the build-up time is compared with the reference value of the build-up time, and the command value of the pulse width of the laser pulse is calculated based on the comparison result. The laser control device according to claim 1 or 2. The laser control device according to claim 3, wherein when calculating the command value of the pulse width of the laser pulse, the reference value of the build-up time is updated based on the measured value of the build-up time. The laser according to claim 4, wherein the reference value of the build-up time is periodically updated, and the reference value of the build-up time is updated to the average value of the period immediately before the measured value of the build-up time of the laser pulse. Control device. When calculating the command value of the pulse width of the laser pulse, the command value of the pulse width of the laser pulse becomes longer than the reference value of the pulse width as the measured value of the build-up time becomes longer than the reference value of the build-up time. Then, as the measured value of the build-up time becomes shorter than the reference value of the build-up time, the command value of the pulse width of the laser pulse is made shorter than the reference value of the pulse width according to any one of claims 1 to 5. The laser control device described.

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