KR20190092254A - Laser control apparatus - Google Patents

Abstract

A laser control apparatus capable of suppressing a deviation in pulse energy is provided. The laser control apparatus obtains a measured value by calculating build-up time, which is elapsed time from a start of excitation of a laser oscillator outputting a pulse laser beam to operation of a laser pulse. Based on the measured value of the build-up time, a command value of a pulse width of the laser pulse outputted from the laser oscillator is calculated. The laser oscillator is controlled for the pulse width of the laser pulse outputted at the present time to be the calculated command value.

Description

Laser control apparatus

This application claims the priority based on Japanese Patent Application No. 2018-013218 for which it applied on January 30, 2018. The entire contents of that application are incorporated herein by reference.

The present invention relates to a laser control apparatus.

For punching processing of printed wiring boards, a processing technique using pulsed laser light is used. Patent Document 1 discloses a laser processing apparatus capable of outputting pulsed laser light having a desired pulse width. In this laser processing apparatus, after turning on the pulse control power supply for outputting the pulsed laser light to the laser resonator, the pulse control power supply is turned off based on the output timing and pulse width command of the pulsed laser light actually output from the laser resonator. . Even if there is a deviation in the time from turning on the pulse control power supply until the pulse laser light is actually output, the pulse width can be maintained at the commanded value.

Patent Document 1: International Publication No. 2014/010046

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

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

According to one aspect of the present invention,

The build-up time, which is the elapsed time from the start of the excitation of the laser oscillator that outputs the pulsed laser beam to the start of the laser pulse, is obtained and measured as

Based on the measured value of the buildup time, a command value of the pulse width of the laser pulse output from the laser oscillator is calculated,

A laser controller for controlling the laser oscillator is provided so that the pulse width of the laser pulse output at the present time becomes a calculated command value.

By changing the pulse width command value of the laser pulse output from the laser oscillator based on the measured value of the buildup time, the variation in pulse energy can be reduced as compared with the case where the pulse width is made constant.

1 is a schematic diagram of a laser processing apparatus equipped with a laser control apparatus according to an embodiment.
2 is a graph showing waveforms of the oscillation command signal S0 transmitted from the laser control device to the laser oscillator according to the embodiment, and the detection signal S1 applied from the photodetector to the laser control device.
In Fig. 3, (a) is a graph showing the relationship between the discharge voltage and the pulse energy under the condition that the pulse width is constant, (b) is a graph showing the relationship between the discharge voltage and the buildup time, ( c) is a graph showing the relationship between the buildup time and the pulse energy under the condition that the pulse width is constant.
In FIG. 4, (a) is an example of the block diagram of the laser control apparatus which concerns on an Example, (b) is the measured value and pulse of the buildup time memorize | stored in the memory | storage part of the laser control apparatus which concerns on an Example. It is a figure which shows the correspondence relationship of the width | variety command value with a graph.
5 is a flowchart of processing executed by the laser control apparatus according to the embodiment.
FIG. 6 is a flowchart showing the process of step SA4 (FIG. 5).
In FIG. 7, (a) is a graph which shows the relationship between the measured value of a buildup time, and the measured value of a pulse energy when a pulse width is made constant regardless of a buildup time, (b) is an Example Is a graph showing the relationship between the measured value of the build-up time and the measured value of the pulse energy when a laser control device is used.
In FIG. 8, (a) is a block diagram of the laser control apparatus which concerns on another Example, (b) is a graph which shows the correspondence relationship between the measured value of average output, and the command value of discharge voltage.
FIG. 9 is a flowchart of a process in which the laser controller 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.
11 shows the time 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 buildup time, and the command value of the pulse width when the reference value of the buildup time is invariant. It is a graph showing an example of change.
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 buildup time, and the pulse width when the laser control apparatus according to the embodiment shown in Fig. 8A is used. This is a graph showing an example of the time change of the command value.

With reference to FIGS. 1-7, the laser control apparatus by an Example is demonstrated.

1 is a schematic diagram of a laser processing apparatus equipped with the laser control apparatus 30 according to the embodiment. The laser oscillator 20 receives the oscillation command signal SO from the laser control device 30 and outputs a pulsed laser beam. As the laser oscillator 20, various pulsed laser oscillators, for example, a pulsed carbon dioxide laser oscillator, can be used. The laser oscillator 20 includes an optical resonator, a discharge electrode, a discharge electrode driving circuit, and the like.

The processing of 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 held by the stage 24. It enters into the object 25. The object to be processed 25 is, for example, a printed wiring board, and is punched out 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 enters the photodetector 26. The photodetector 26 detects the 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 the change in the pulse waveform, for example, a cadmium mercury telluride sensor (MCT sensor) or the like can be used. However, the photodetector 26 may be disposed immediately after the laser injection 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 the diffusion angle of the laser beam. The aspherical lens changes the beam profile from the Gaussian shape to the top flat shape. The aperture forms a beam cross-sectional shape.

The second optical system 23 includes a beam scanner, an fθ lens, and the like. The beam scanner includes, for example, a pair of galvano mirrors, and scans the laser beam in a two-dimensional direction by an instruction from the laser controller 30. The f? lens focuses the laser beam scanned by the beam scanner on the surface of the object to be processed 25. However, the position of the aperture may be reduced in size on the surface of the object to be processed 25.

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

The laser controller 30 sets the pulse width of the pulsed laser beam output from the laser oscillator 20 to be constant based on the detection signal S1 of the laser pulse by the photodetector 26, Adjust for each laser pulse.

2 shows the oscillation command signal S0 transmitted from the laser controller 30 (FIG. 1) to the laser oscillator 20 (FIG. 1), and the laser controller 30 from the photodetector 26 (FIG. 1). Fig. 1 is a graph showing the waveform of the detection signal S1 applied to (Fig. 1).

When the oscillation command signal S0 is activated (or generated) 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, excitation of the laser medium of the laser oscillator 20 is started. That is, the start of the oscillation command signal S0 corresponds to the oscillation start command of the laser oscillator 20, and the start point of the oscillation command signal S0 corresponds to the start point of excitation of the laser oscillator 20.

Delayed from time t0 at the start of excitation, the laser pulse is started at time t1. In response to the start of the laser pulse, the detection signal S1 is also started. The elapsed time from the time t0 at the start of the excitation to the time t1 at the start of the laser pulse is assumed to be the buildup time BU. At the start of the laser pulse, a very short time peak waveform by gain switching appears, and then a substantially constant light intensity is maintained. The portion where the substantially constant light intensity is maintained is called a main portion of the pulse waveform.

When the oscillation command signal SO is finished at time t2, the laser oscillator 20 stops supplying the high frequency power to the discharge electrode. When the supply of the high frequency power to the discharge electrode is stopped, excitation of the laser medium of the laser oscillator 20 is not performed. That is, the end of the oscillation command signal S0 means the command of the excitation stop 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 rapidly.

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 this specification, this integral value determined by pulse energy shall be called "pulse energy dependent physical quantity".

Since the time width of a very short time peak waveform by gain switching is sufficiently short compared with the entire pulse width, the integral value of the pulse waveform from the gain waveform except the very short time peak waveform by the gain switching is obtained. It may be employed as. Also, since the time width of the tail portion after the excitation stop is sufficiently short compared to the pulse width of the laser pulse, and the light intensity of the tail portion decreases rapidly with time, the integral value of the pulse waveform excluding the tail portion is reduced. You may employ | adopt as a pulse energy dependent physical quantity. In this manner, the integral value of the main portion of the pulse waveform may be employed 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 input to the laser oscillator 20 increases. When the discharge voltage is high and the high frequency power input is large, the laser medium is more strongly excited. As a result, the pulse energy is increased. For this reason, discharge voltage, high frequency electric power, etc. can be called excitation intensity.

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

FIG. 3C is a graph showing the relationship between the buildup time and the pulse energy under the condition where 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, the pulse energy decreases as the build up time becomes longer. It can be seen that. On the contrary, when the buildup time is shortened, the pulse energy is increased.

In Figs. 3A to 3C, as an example, an example in which the buildup time changes with the discharge voltage is shown. However, not only the discharge voltage is a factor that changes the buildup time. Although the buildup time changes depending on other factors, under conditions where the pulse width is constant, as shown in FIG. 3C, the pulse energy tends to decrease as the buildup time becomes longer.

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 detector 31, a signal transmitter 32, a pulse width adjuster 33, and a storage 34.

The laser pulse detector 31 receives the detection signal S1 from the photodetector 26 and detects the start time of the laser pulse. The signal transmitter 32 transmits the oscillation command signal SO to the laser oscillator 20.

In the storage unit 34, the correspondence relationship between the measured value of the buildup time and the command value of the pulse width is stored.

FIG. 4B is a graph showing the correspondence relationship between the measured value of the buildup time stored in the storage unit 34 and the command value of the pulse width. When the measured value of the buildup time is the reference value BU _ref , the command value of the pulse width corresponds to the reference value PW _ref . As the measured value of the buildup time is longer than the reference value BU _ref , the pulse as the command value of the pulse width is longer than the reference value PW _ref , and the measured value of the buildup time is shorter than the reference value BU _ref . The correspondence relationship between the two is defined such that the command value of the width PW is shorter than the reference value PW _ref .

The pulse width adjusting unit 33 (FIG. 4A) acquires information indicating the starting point of the oscillation command signal S0 (t0 in FIG. 2) from the signal transmitting unit 32, and the laser pulse detecting unit 31 Information indicating the start point of the laser pulse (t1 in FIG. 2) is obtained from the data. The pulse width adjusting unit 33 obtains the buildup time (FIG. 2) from the acquired information, and sets it as a measured value of the buildup time. Further, the command value of the pulse width of the laser pulse is calculated based on the measured value of the buildup time and the correspondence relationship stored in the storage unit 34.

The signal transmitter 32 acquires the command value of the pulse width calculated by the pulse width adjuster 33. The signal transmitter 32 ends the oscillation command signal S0 (FIG. 2) transmitted to the laser oscillator 20 so that the pulse width of the laser pulse currently output corresponds to the pulse width command value. do. As a result, the pulse width of the laser pulse output from the laser oscillator 20 substantially coincides with the command value.

5 is a flowchart of processing executed by the laser control device 30 (FIG. 4A) according to the embodiment.

The signal transmitter 32 transmits an oscillation start command to the laser oscillator 20 (step SA1). Specifically, the oscillation command signal S0 (Fig. 2) is started. As a result, the laser pulse output from the laser oscillator 20 is activated. The laser pulse detection unit 31 (FIG. 4) acquires the detection signal S1 (FIG. 2), and detects the start of the laser pulse (step SA2).

When the start of the laser pulse is detected, the pulse width adjusting unit 33 calculates the measured value of the buildup time (step SA3). In addition, the pulse width adjusting unit 33 calculates the command value of the pulse width by referring to the corresponding relationship stored in the storage unit 34 based on the measured value of the build-up time (step SA4). Thereafter, the signal transmitter 32 transmits the oscillation stop command to the laser oscillator 20 so that the pulse width of the laser pulse at the present time matches the command value (step SA5). Specifically, the oscillation command signal SO (figure 2) ends.

The processing from step SA1 to step SA5 is repeated until the laser processing 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 buildup time with the reference value BU _ref (FIG. 4B) (step SA41). In addition, the pulse width adjusting unit 33 calculates a command value of the pulse width based on the comparison result and the correspondence stored in the storage unit 34 (step SA42).

Next, the excellent effect obtained by controlling a factory value by the laser control apparatus 30 by the said Example is demonstrated.

In a pulsed 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 buildup time becomes longer. In the embodiment, as shown in (b) of FIG. 4, as the measured value of the build-up time becomes longer, the decrease in pulse energy is compensated by increasing the command value of the pulse width of the laser pulse currently being output. have. For this reason, the variation of pulse energy can be reduced compared with the case where it controls so that a pulse width may become constant.

Next, with reference to FIGS. 7A and 7B, the results obtained by evaluation experiments of the effects obtained by using the laser control device 30 according to the embodiment 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 made constant regardless of the build up time. The horizontal axis represents the buildup time in arbitrary units, and the vertical axis represents the pulse energy in arbitrary units. The measured value with respect to one laser pulse is shown with one circle symbol. It is understood that the pulse energy tends to be lowered as the build up time becomes longer.

FIG. 7B is a graph showing the relationship between the measured value of the buildup time and the measured value of the pulse energy when the laser control device 30 according to the 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. By using the laser control device 30 according to the embodiment, it was confirmed that the variation in pulse energy is reduced.

Next, with reference to FIGS. 8-12, the laser control apparatus by other Example is demonstrated. Hereinafter, the description common to the laser control apparatus according to the embodiment shown in FIGS. 1 to 7 will be omitted. In this embodiment, not only the pulse width of the laser pulse but also the excitation intensity applied to the laser oscillator 20 are 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.

8A is a block diagram of the laser control device 30 according to the present embodiment. The laser control device 30 according to the present embodiment includes, in addition to the respective parts of the laser control device 30 according to the embodiment shown in FIG. 4A, the average output calculating unit 35 and the average output adjusting unit 36. Has The storage unit 34 also stores a correspondence relationship between the measured value of the average output and the command value of the excitation intensity.

8B is a graph showing a correspondence relationship 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 P _ref , the command value of the discharge voltage corresponds to the reference value V _ref . As the measured value of average output becomes higher than the reference value P _ref , the command value of discharge voltage shows the tendency to fall. On the contrary, as the measured value of the average output becomes lower than the reference value P _ref , the command value of the discharge voltage tends to increase.

The average output calculation unit 35 (FIG. 8A) calculates an average output of a certain period of time based on the detection signal S1 (FIG. 2) from the photodetector 26, Measured value is used. The average output can be calculated by dividing the total value of the integral values of the pulse waveforms acquired in a certain period by the length of the predetermined period.

The average output adjustment 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 P _ref , 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 P _ref . The command value of the discharge voltage is made larger than the reference value V _ref .

The signal transmitter 32 transmits a signal S2 for commanding the discharge voltage to the laser oscillator 20 based on the command value of the discharge voltage determined by the average output adjuster 36. The laser oscillator 20 applies the discharge voltage commanded by the signal S2 to the discharge electrode when the laser medium is excited.

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 a laser pulse, the laser oscillator 20 is excited based on the command value of the discharge voltage at this time (step SB2). The command value of the discharge voltage is fixed for a certain period of time. A certain period during which the command value of the discharge voltage is fixed is called "discharge voltage fixed period". Even during the discharge voltage fixed period, pulse width adjustment based on the buildup time shown in FIG. 4 is performed for each laser pulse.

When the discharge voltage fixed period elapses after setting the command value of the discharge voltage, the average output calculation unit 35 (Fig. 8 (a)) calculates the average output of the discharge voltage fixed period, and the measured value of the average output. (Step SB3). The average output adjustment unit 36 (FIG. 8A) converts the command value of the discharge voltage into the measured value of the average output and the corresponding relationship (FIG. 8B) stored in the storage unit 34. Update based on the step (step SB4). The signal transmitter 32 transmits the updated command value to the laser oscillator 20. The process from step SB2 to step SB4 is repeated until laser processing is complete (step SB5).

FIG. 10 is a flowchart of step SA4 of FIG. 5. Step SA41 and step SA42 are the same as the corresponding step of the embodiment shown in FIG. In the example shown in FIG. 6, the reference value BU _ref of the buildup time was unchanged. In this embodiment, the reference value BU _ref of the buildup time is periodically updated to the measured value of the buildup time. For example, after calculating a command value of the pulse width, when the refresh cycle from the update of the previous reference value (BU _ref) of the build-up time has elapsed (step SA43), build a reference value of the up time (BU _ref), just before the The average value of the build-up time of the laser pulses in one cycle is updated. After updating the reference value BU _ref of the buildup time, step SA5 (Fig. 5) is executed.

Next, before explaining the excellent effect obtained by employing the laser control apparatus 30 according to the embodiment of FIGS. 8 to 10, the reference value of the build-up time is invariant with reference to FIG. The case where SA43 and step SA44 (FIG. 10) are not implemented is demonstrated.

11 shows the command value of the discharge voltage, the measured value of the average output of the laser oscillator 20, the measured value of the buildup time, and the pulse width when the reference value BU _ref of the buildup time is invariant. It is a graph showing an example of time change of the command value. In addition, although the measured value of a buildup time and the command value of a pulse width change every laser pulse, in FIG. 11, the average value for every update period of the reference value BU _ref of a buildup time is shown. 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 . It is assumed that the measured value of the average output is approximately equal to the reference value P _ref , and the measured value of the build-up time is approximately equal to the reference value BU _ref .

If the measured value of average output falls below the reference value P _ref by some factor (t10), control to raise the command value of discharge voltage is performed (t11) (step SB4 of 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 buildup time is shortened (t13).

If the measured value of the buildup time is shorter than the reference value BU _ref , control is performed to make the pulse width command value shorter than the reference value PW _ref (t14) (step SA4 in FIG. 5). Shortening the command value of the pulse width acts in a direction of decreasing the average output. For this reason, the measured value of average output falls (t15). When the measured value of average output falls, the command value of a discharge voltage will rise similarly to the time t10 (t16). As a result, the measured value of the average output returns to the reference value P _ref (t17). Since the rise of the discharge voltage acts in the direction of shortening the buildup time, the measured value of the buildup time is shorter (t18). When the measured value of the buildup time is shortened, the difference between the reference value BU _ref and the measured value of the buildup time is increased, so that the command value of the pulse width becomes shorter (t19).

In this way, the process of shortening the pulse width command value is continuously executed, whereby the pulse width command value reaches the 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 . Thus, even if the adjustment of the discharge voltage and the adjustment of the pulse width are used together, 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 buildup time and the pulse width is larger than the change in the pulse energy due to the change in the discharge voltage. When the function of adjusting the pulse width does not work, the effect of suppressing the variation of the pulse energy is not obtained.

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

When the discharge voltage rises (t16), the measured value of the buildup time is shortened (t21). At this time, the reference value BU _ref of the buildup time is updated to the average value of the measured values of the immediately preceding cycle (step SA44). In FIG. 12, the reference value BU _ref of the buildup time is indicated by a broken line. Since the reference value BU _ref of the build-up time is updated, for example, the difference between the measured value of the build-up time at the time t21 and the reference value BU _ref is determined from the measured value of the build-up time at the time t13. It is approximately equal to the difference of the reference value BU _ref . For this reason, the command value of the pulse width does not substantially change (t22).

When the update period of the reference value (BU _ref) of the build-up time has elapsed from the time t21, to build the reference value (BU _ref) of the up-time and updated (t23), build a reference value of the up-time measure the build-up time (BU _ref Approximately the same as). For this reason, control which returns a command value of a pulse width to the reference value PW _ref substantially is performed (t24) (step SA4). Since the control to lengthen the pulse width acts in the direction of increasing the average output, the measured value of the average output rises (t25).

When the measured value of average output rises, control to reduce the command value of discharge voltage is performed (t26) (step SB4 of FIG. 9). When the command value of the discharge voltage decreases, the measured value of the average output falls (t27), and the measured value of the build-up time becomes long (t28). Since the reference value BU _ref of the buildup time is updated to an average value of the measured values of the buildup time of the immediately preceding cycle, the measured value of the buildup time is longer than the reference value BU _ref . For this reason, control which lengthens the command value of a pulse width is performed (t29) (step SA42 of FIG. 10).

When the command value of the pulse width becomes long, the measured value of the average output becomes large (t30) as in the time t24, and then the control for lowering the command value of the discharge voltage is performed (t31). As a result, the measured value of average output falls (t32), and the measured value of a buildup time becomes long (t33). Since the reference value BU _ref of the buildup time is updated to the average value of the measured values of the buildup time of the previous cycle, the difference between the measured value of the buildup time and the reference value BU _ref is the buildup at time t28. It is approximately equal to the difference between the measured value of time and the reference value BU _ref . As a result, the command value of the pulse width does not substantially change (t34).

As described above, in the present 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 lower limit value PW _min . For this reason, even when the adjustment of the discharge voltage and the adjustment of the pulse width are used together, the function of adjusting the pulse width can be made effective. This obtains both effects of stabilization of the output and reduction of the variation in pulse energy.

Each embodiment mentioned above is an illustration, It goes without saying that partial substitution or combination of the structure shown by another embodiment is possible. The same operation and effect by the same configuration of the plurality of embodiments is not separately mentioned for each embodiment. In addition, the present invention is not limited to the above-described embodiment. For example, it will be apparent to those skilled in the art that various changes, improvements, combinations, and the like are possible.

20 laser oscillators
21 First Optical System
22 bending mirror
23 Second optical system
24 stage
25 Object
26 Photodetector
30 Laser Control
31 Laser pulse detector
32 Signal Transmitter
33 pulse width adjusting part
34 memory
35 Average output calculation unit
36 Average output adjuster

Claims (6)

The build-up time, which is the elapsed time from the start of the excitation of the laser oscillator that outputs the pulsed laser beam to the start of the laser pulse, is obtained,
Based on the measured value of the buildup time, a command value of the pulse width of the laser pulse output from the laser oscillator is calculated,
And a laser control device for controlling the laser oscillator so that the pulse width of the laser pulse output at the present time becomes a calculated command value. The method of claim 1,
And an excitation intensity of the laser oscillator on the basis of the measured value of the average power of the pulsed laser beam output from the laser oscillator. The method according to claim 1 or 2,
When calculating the pulse width command value of the laser pulse, the laser control for comparing the measured value of the build-up time with the reference value of the build-up time, and calculating the command value of the pulse width of the laser pulse based on the comparison result. Device. The method of claim 3,
And a reference value of the build-up time is updated based on the measured value of the build-up time when the command value of the pulse width of the laser pulse is calculated. The method of claim 4, wherein
And periodically updating the reference value of the build-up time, and updating the reference value of the build-up time to an average value of a period immediately preceding the measured value of the build-up time of a laser pulse. The method according to claim 1 or 2,
When calculating the pulse width command value of the laser pulse, as the measured value of the build-up time becomes longer than the reference value of the build-up time, the command value of the pulse width of the laser pulse is made longer than the reference value of the pulse width, and And a command value of the pulse width of the laser pulse is shorter than the reference value of the pulse width as the measured value of the build-up time is shorter than the reference value of the build-up time.

Images