TW201933706A - Laser control device capable of suppressing deviation of pulse energy - Google Patents

Abstract

The present invention discloses a laser control device capable of suppressing deviation of pulse energy. The laser control device may calculate the elapsed time from the beginning of excitation of laser oscillator for outputting pulse laser beam until the rising of laser pulse, i.e. the accumulated time, and the result will be set as a measuring value. According to the measuring value of the accumulated time, the instruction value for the pulse width of the laser pulse outputted from the laser oscillator is calculated to become the instruction value for calculating the pulse width of the laser pulse that is outputted currently and thus controlling the laser oscillator.

Description

Laser control device

The invention relates to a laser control device.

A processing technique using pulsed laser light is used in drilling processing of a printed wiring board or the like. Patent Document 1 discloses a laser processing apparatus capable of outputting pulsed laser light having a desired pulse width. In the laser processing apparatus, after the pulse control power source that outputs the pulsed laser light to the laser resonator is turned on, the pulse control power source is turned off according to the output timing and the pulse width command of the pulsed laser beam actually outputted from the laser resonator. . Even if the time from the on-pulse control power supply to the actual output of the pulsed laser beam is varied, the pulse width can be maintained at the indicated value.
[Previous Technical Literature]
[Patent Literature]

[Patent Document 1] International Publication No. 2014/010046

[Questions to be solved by the invention]

When processing with a pulsed laser beam, it is important to set the energy (pulse energy) of each pulse to be constant. According to the evaluation experiment by the inventors of the present invention, it is clarified that even if the pulse width is maintained at the indicated value, the effect of suppressing variations in pulse energy is insufficient.

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

[Means for solving the problem]

According to an aspect of the present invention, a laser control apparatus is provided, wherein
Obtaining the elapsed time from the start of the excitation of the laser oscillator that outputs the pulsed laser beam to the rise of the laser pulse, that is, the cumulative time, and setting it as the measured value;
Calculating a command value of a pulse width of a laser pulse outputted from the laser oscillator according to the measured value of the accumulated time;
The laser oscillator is controlled so as to be a command value for calculating the pulse width of the currently output laser pulse.

[Effect of the invention]

The command value of the pulse width of the laser pulse output from the laser oscillator is changed in accordance with the measured value of the accumulated time, whereby the variation in pulse energy can be reduced as compared with the case where the pulse width is made constant.

A laser control apparatus according to an embodiment will be described with reference to Figs. 1 to 7B.

FIG. 1 is a schematic view of a laser processing apparatus equipped with a laser control device 30 according to an embodiment. The laser oscillator 20 receives the oscillation command signal S0 from the laser control device 30 and outputs a pulsed laser beam. As the laser oscillator 20, various pulsed laser oscillators can be used, for example, a carbon dioxide laser oscillator that performs pulse oscillation. 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 is reflected by the mirror 22 through the first optical system 21, and is incident on the object 25 held by the stage 24 by the second optical system 23. The object to be processed 25 is, for example, a printed wiring board, and is drilled by a pulsed laser beam.

A portion of the pulsed laser beam incident on the mirror 22 is incident on the photodetector 26 through the mirror 22. The photodetector 26 detects the incident laser pulse and outputs a signal corresponding to the light intensity of the laser pulse, that is, the detection signal S1. As the photodetector 26, an infrared sensor having a response speed following a change in the pulse waveform, such as a cadmium telluride mercury sensor (MCT sensor) or the like can be used. In addition, the photodetector 26 can be disposed immediately after the laser exit of the laser oscillator 20.

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

The second optical system 23 includes a beam scanner, an fθ lens, and the like. The beam scanner, for example, includes a pair of current mirrors that are scanned in a two dimensional direction by commands from the laser control device 30. The fθ lens condenses the laser beam scanned by the beam scanner on the surface of the object 25. Further, a configuration may be adopted in which the position of the orifice is reduced and projected on the surface of the object 25 to be processed.

The stage 24 can hold the object 25 on the horizontal holding surface, for example, and move the object 25 in two directions in the horizontal plane. The laser control device 30 controls the movement of the stage 24. Regarding 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 according to the laser pulse based on the detection signal S1 of the laser pulse of the photodetector 26 in a manner that the pulse energy is constant. .

2 is a view showing an oscillation command signal S0 transmitted from the laser control device 30 (FIG. 1) to the laser oscillator 20 (FIG. 1) and from the photodetector 26 (FIG. 1) to the laser control device 30 (FIG. 1). A graph of the waveform of the detection signal S1 given.

At time t0, when the oscillation command signal S0 rises, the laser oscillator 20 starts supplying high frequency power to the discharge electrode. The laser medium that excites the laser oscillator 20 is started by starting to supply high frequency power to the discharge electrode. That is, the rise of the oscillation command signal S0 corresponds to the oscillation start command of the laser oscillator 20, and the rising time point of the oscillation command signal S0 corresponds to the time point at which the excitation of the laser oscillator 20 starts.

At time t1, the laser pulse is delayed from the time t0 at which the excitation starts. The detection signal S1 also rises in response to the rise of the laser pulse. The elapsed time from the time t0 at which the excitation starts to the time t1 at which the laser pulse rises is referred to as the accumulation time BU. When the laser pulse rises, a peak waveform based on the gain switch for a very short time occurs, and then a substantially constant light intensity is maintained. The portion that maintains a substantially constant light intensity is set as the main portion of the pulse waveform.

At time t2, when the oscillation command signal S0 falls, the laser oscillator 20 stops supplying high frequency power to the discharge electrode. When the supply of the high-frequency power to the discharge electrode is stopped, the excitation of the laser medium of the laser oscillator 20 cannot be performed. That is, the falling of the oscillation command signal S0 indicates an instruction 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 is drastically lowered.

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

Compared with the overall pulse width, the time interval of the peak waveform based on the extremely short time of the gain switch is very short, and the integral value of the portion of the peak waveform based on the extremely short time of the gain switch can be removed from the pulse waveform as the pulse energy dependent physical quantity. And adopted. Further, the time interval of the tail portion after the energization is stopped is also very short compared to the pulse width of the laser pulse, and the light intensity of the tail portion is drastically lowered with the passage of time, so that the integral of the pulse waveform of the tail portion can be removed. The value is used as the pulse energy dependent physical quantity. In this way, the integral value of the main portion of the pulse waveform can be used as the pulse energy dependent physical quantity.

Fig. 3A is a graph showing the relationship between the discharge voltage of the laser oscillator 20 and the pulse energy under the condition that the pulse width is constant. When the discharge voltage is increased, the high-frequency power input to the laser oscillator 20 is increased. When the discharge voltage becomes high and the input high-frequency power becomes large, 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 intensity.

Fig. 3B is a graph showing the relationship between the discharge voltage and the accumulation time. If the discharge voltage becomes high, the excitation state of the laser medium reaches the oscillation threshold earlier, and thus the accumulation time becomes shorter.

Fig. 3C is a graph showing the relationship between the accumulation 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 accumulation time shown in FIG. 3B, it is understood that the pulse energy is lowered as the accumulation time becomes longer. Conversely, if the accumulation time becomes shorter, the pulse energy becomes larger.

In FIGS. 3A to 3C, an example in which the accumulation time changes due to the discharge voltage is shown as an example. However, the factor that changes the accumulation time is not only the discharge voltage. The accumulation time is also changed by other factors, but under the condition that the pulse width is constant, generally, as shown in Fig. 3C, the tendency of the pulse energy to decrease as the accumulation time becomes longer is shown.

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 detecting unit 31, a signal transmitting unit 32, a pulse width adjusting unit 33, and a memory unit 34.

The laser pulse detecting unit 31 receives the detection signal S1 from the photodetector 26 and detects the rising timing of the laser pulse. The signal transmitting unit 32 transmits the oscillation command signal S0 to the laser oscillator 20.

The memory unit 34 stores a correspondence relationship between the measured value of the accumulated time and the command value of the pulse width.

4B is a graph showing the correspondence relationship between the measured value of the accumulated time stored in the memory unit 34 and the command value of the pulse width. When the measured value of the accumulated 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 value of the accumulation 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 becomes shorter than the reference value BU _ref as the measured value of the cumulative time becomes shorter, the pulse width The command value of the PW becomes shorter than the reference value PW _ref , and the correspondence between the two is defined.

The pulse width adjusting unit 33 (FIG. 4A) acquires information indicating the rising time point (t0 of FIG. 2) of the oscillation command signal S0 from the signal transmitting unit 32, and acquires the rising time point indicating the laser pulse from the laser pulse detecting unit 31. (t1 of Figure 2) information. The pulse width adjustment unit 33 obtains the accumulation time (FIG. 2) from the acquired information, and sets it as the measurement value of the accumulation time. Then, the command value of the pulse width of the laser pulse is calculated based on the measured value of the accumulated time and the correspondence relationship stored in the memory unit 34.

The signal transmitting unit 32 acquires the command value of the pulse width calculated by the pulse width adjusting unit 33. Further, the signal transmitting 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 coincides with the command value of the pulse width. Thereby, the pulse width of the laser pulse output from the laser oscillator 20 substantially coincides with the command value.

FIG. 5 is a flow chart of the processing performed by the laser control device 30 (FIG. 4A) based on the embodiment.
The signal transmitting unit 32 transmits an oscillation start command to the laser oscillator 20 (step SA1). Specifically, the oscillation command signal S0 (Fig. 2) is raised. Thereby, the laser beam output from the laser oscillator 20 rises. The laser pulse detecting unit 31 (Fig. 4) acquires the detection signal S1 (Fig. 2) and detects the rise of the laser pulse (step SA2).

When the rise of the laser beam is detected, the pulse width adjustment unit 33 calculates the measured value of the accumulation time (step SA3). Further, the pulse width adjusting unit 33 calculates a command value of the pulse width by referring to the correspondence relationship stored in the memory unit 34 based on the measured value of the accumulated time (step SA4). Thereafter, the signal transmitting unit 32 transmits an oscillation stop command to the laser oscillator 20 such that the pulse width of the current laser pulse coincides with the command value (step SA5). Specifically, the oscillation command signal S0 (Fig. 2) is lowered.

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

Fig. 6 is a flow chart showing the processing of step SA4 (Fig. 5). First, the pulse width adjustment unit 33 compares the measured value of the accumulated time with the reference value BUref (FIG. 4B) (step SA41). Further, the pulse width adjustment unit 33 calculates a command value of the pulse width based on the comparison result and the correspondence relationship stored in the storage unit 34 (step SA42).

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

As shown in FIG. 3C, in a pulsed laser oscillator such as a carbon dioxide laser oscillator, it is shown that even if the pulse width is constant, the pulse energy tends to decrease as the accumulation time becomes longer. In the embodiment, as shown in FIG. 4B, the decrease in the pulse energy is compensated by lengthening the command value of the pulse width of the currently output laser pulse as the measured value of the accumulation time becomes longer. Therefore, the variation of the pulse energy can be reduced as compared with the case where the control is performed such that the pulse width becomes constant.

Next, the results obtained by using the laser control device 30 according to the above embodiment will be confirmed by an evaluation experiment with reference to FIGS. 7A and 7B.

FIG. 7A is a graph showing the relationship between the measured value of the accumulated time and the measured value of the pulse energy when the pulse width is made constant regardless of the accumulation time. The horizontal axis represents the accumulation time in arbitrary units, and the vertical axis represents the pulse energy in arbitrary units. The measured value associated with one laser pulse is indicated by one circle mark. It can be seen that as the accumulation time becomes longer, the pulse energy tends to decrease.

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

Next, a laser control device according to another embodiment will be described with reference to Figs. 8A to 12 . Hereinafter, the description of the same structure as that of the laser control device according to the embodiment shown in FIGS. 1 to 7B will be omitted. In the present embodiment, not only the pulse width of the laser pulse is changed 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, and the energy rate (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 based on the present embodiment. The laser control device 30 according to the present embodiment has an average output calculation unit 35 and an average output adjustment unit 36 in addition to the respective portions of the laser control device 30 according to the embodiment shown in FIG. 4A. Further, the memory unit 34 stores a correspondence relationship between the measured value of the average output and the command value of the excitation intensity.

Fig. 8B is a graph showing the 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 . It is shown that the measured value of the average output is higher than the reference value P _ref and the command value of the discharge voltage is lowered. Conversely, it is shown that the measured value of the discharge voltage becomes higher as the measured value of the average output becomes lower than the reference value P _ref .

The average output calculation unit 35 (Fig. 8A) calculates the average output of a certain constant period based on the detection signal S1 (Fig. 2) from the photodetector 26, and sets it as the measured value of the average output. The total value of the integrated values of the pulse waveforms acquired during the constant period is divided by the length of the constant period, whereby the average output can be calculated.

The average output adjustment unit 36 calculates a command value of the discharge voltage based on the correlation between the measured value of the average output and the memory (34B) stored in the memory 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 discharge is made The command value of the voltage is larger than the reference value V _ref .

The signal transmitting unit 32 transmits a signal S2 indicating the discharge voltage to the laser oscillator 20 based on the command value of the discharge voltage obtained by the average output adjusting unit 36. When the laser oscillator 20 excites the laser medium, the discharge voltage indicated by the signal S2 is applied to the discharge electrode.

Fig. 9 is a flow chart showing the process of controlling the discharge voltage by the laser control device 30 (Fig. 8A) according to the present embodiment.

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 the laser beam is output, the laser oscillator 20 is excited in accordance with the command value of the current discharge voltage (step SB2). The command value of the discharge voltage is fixed during a constant period. The constant period in which the command value of the discharge voltage is fixed is referred to as "discharge voltage fixed period". During the period in which the discharge voltage is fixed, the adjustment of the pulse width based on the accumulation time shown in FIG. 4 is also performed in accordance with the laser pulse.

When the discharge voltage is fixed after the command value of the discharge voltage is set, the average output calculation unit 35 (FIG. 8A) calculates the average output of the discharge voltage constant period, and sets it as the average output measurement value (step SB3). The average output adjustment 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 memory unit 34 (step SB4). The signal transmitting unit 32 transmits the updated command value to the laser oscillator 20. Until the end of the laser processing, the processing from step SB2 to step SB4 is repeated (step SB5).

FIG. 10 is a flowchart of step SA4 of FIG. 5. Steps SA41 and SA42 are the same as the steps corresponding to the embodiment shown in FIG. 6. In the embodiment shown in Fig. 6, the reference value BU _{ref of the} accumulation time does not change. In the present embodiment, the reference value BU _ref of the accumulation time is periodically updated to the measured value of the accumulation time. For example, after the command value of the pulse width is calculated, if the update period is passed from the previous update of the reference value BU _ref of the accumulation time (step SA43), the reference value BU _{ref of the} accumulation time is updated to the mine of the previous cycle. The average of the cumulative time of the shot pulses. After the reference value BU _{ref of} the accumulation time is updated, step SA5 (Fig. 5) is performed.

Next, before describing the excellent effects obtained by using the laser control device 30 based on the embodiment of FIGS. 8A to 10, referring to FIG. 11, the case where the reference value of the accumulation time is set to be unchanged, That is, the case where step SA43 and step SA44 (FIG. 10) are not performed will be described.

11 is a timing chart showing a command value of a discharge voltage when the reference value BU _{ref of the} accumulation time is constant, a measured value of the average output of the laser oscillator 20, a measured value of the accumulated time, and a command value of the pulse width. An example of a chart. Further, the measured value of the accumulated time and the command value of the pulse width are changed by the laser pulse. However, in FIG. 11, the average value of each update period of the reference value BU _ref of the accumulated 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 as the reference value PW _ref . The measured value of the average output substantially coincides with the reference value P _ref , and the measured value of the accumulated time substantially coincides with the reference value BU _ref .

When the measured value of the average output is lowered to be lower than the reference value P _ref by some factors (t10), control (t11) of increasing the command value of the discharge voltage is performed (step SB4 of FIG. 9). When the command value of the discharge voltage rises, the output of the laser oscillator 20 becomes high, so that the measured value of the average output rises (t12), and the measured value of the accumulated time becomes short (t13).

When the measured value of the accumulated time becomes shorter than the reference value BU _ref , the control (t14) of making the command value of the pulse width shorter than the reference value PW _ref is performed (step SA4 of FIG. 5 ). The pulse width command value becomes shorter and will act to reduce the direction of the average output. Therefore, the measured value of the average output is lowered (t15). When the measured value of the average output decreases, the command value of the discharge voltage rises in the same manner as at time t10 (t16). As a result, the measured value of the average output returns to the reference value _Pref (t17). The rise of the discharge voltage acts in the direction of shortening the accumulation time, so the measured value of the accumulation time is further shortened (t18). When the measured value of the accumulated time is shortened, the difference between the reference value BU _{ref of} the accumulated time and the measured value is expanded, and therefore the command value of the pulse width is further shortened (t19).

Thus, the processing performed by continuously shortening the pulse width of the command value, the command pulse width value reaches the allowable lower limit PW _min. After the pulse width command value reaches the allowable lower limit PW _min, the pulse width of the command value is fixed at the allowable lower limit value PW _min. As a result, even if the discharge voltage is adjusted and the pulse width is adjusted, the function of adjusting the pulse width may not function. This is because the gain of the pulse energy due to the change in the discharge voltage is larger from the change in the discharge voltage to the change in the pulse energy through the change in the accumulation time and the adjustment of the pulse width. If the function of adjusting the pulse width does not work, the effect of suppressing variations in pulse energy cannot be obtained.

Fig. 12 is a view showing temporal changes of a command value of a discharge voltage, a measured value of an average output of the laser oscillator 20, a measured value of an accumulated time, and a command value of a pulse width when the laser control device 30 according to the present embodiment is used. An example of a chart. 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 cumulative time, and the command value of the pulse width is the same as the example shown in FIG.

When the discharge voltage rises (t16), the measured value of the accumulation time becomes shorter (t21). At this time, the reference value BU _{ref of the} accumulation time is updated to the average value of the measured values of the previous cycle (step SA44). In Fig. 12, the reference value BU _{ref of the} accumulation time is indicated by a broken line. Update the accumulated value of the time reference BU _ref, and thus, for example, the measured value of the reference cumulative time difference between the time t21 BU _ref value of the cumulative time difference between the time t13 BU _ref of the measured value and the reference value are substantially equal. Therefore, the command value of the pulse width does not substantially change (t22).

When the update period of the reference value BU _ref of the accumulation time elapses from the time t21, the reference value BU _{ref of} the accumulation time is updated (t23), and the measured value of the accumulation time becomes substantially equal to the reference value BU _{ref of the} accumulation time. Therefore, control (t24) of substantially returning the command value of the pulse width to the reference value PW _ref is performed (step SA4). The control of the extended pulse width acts to increase the direction of the average output, so the measured value of the average output rises (t25).

When the measured value of the average output rises, control of the command value for decreasing the discharge voltage is performed (t26) (step SB4 of FIG. 9). When the command value of the discharge voltage is lowered, the measured value of the average output is lowered (t27), and the measured value of the accumulated time becomes long (t28). The reference value BU _ref of the accumulation time is updated to the average value of the measured values of the accumulation time of the previous cycle, and thus the measured value of the accumulation time becomes longer than the reference value BU _ref . Therefore, control of the command value for lengthening the 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 larger as in the case of time t24 (t30), and thereafter, the control value of the discharge voltage is controlled (t31). As a result, the measured value of the average output is lowered (t32), and the measured value of the cumulative time becomes long (t33). The reference value BU _ref of the accumulation time is updated to the average value of the measured values of the accumulation time of the previous cycle, and therefore the difference between the measured value of the accumulated time and the reference value BU _ref and the measured value and the reference value of the accumulated time at the time t28 The difference between BU _ref becomes approximately equal. 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} accumulation 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 discharge voltage is adjusted and the pulse width is adjusted in combination, the function of adjusting the pulse width can be effectively made effective. Therefore, it is possible to obtain two effects of stable output and reduced deviation of pulse energy.

The various embodiments described above are illustrative, and of course, a partial substitution or combination of the configurations shown in the different embodiments. The same effects of the plural embodiments based on the same configuration will not be mentioned in every embodiment. Moreover, the invention is not limited to the above embodiments. For example, various changes, modifications, combinations, and the like can be made, which will be apparent to those of ordinary skill in the art to which the invention pertains.

20‧‧‧Laser oscillator

21‧‧‧1st optical system

22‧‧‧Mirror

23‧‧‧2nd optical system

24‧‧‧ stage

25‧‧‧Processing objects

26‧‧‧Photodetector

30‧‧‧Road control unit

31‧‧‧Laser pulse detection unit

32‧‧‧Signal Transmission Department

33‧‧‧ Pulse width adjustment unit

34‧‧‧Memory Department

35‧‧‧Average Output Calculation Department

36‧‧‧Average Output Adjustment Department

Fig. 1 is a schematic view showing a laser processing apparatus equipped with a laser control device according to an embodiment.

2 is a graph showing waveforms of an oscillation command signal S0 transmitted from a laser control device according to an embodiment to a laser oscillator and a detection signal S1 supplied from a photodetector to a laser control device.

3] FIG. 3A is a graph showing the relationship between the discharge voltage and the pulse energy under the condition that the pulse width is constant, FIG. 3B is a graph showing the relationship between the discharge voltage and the accumulation time, and FIG. 3C is a graph showing the condition that the pulse width is constant. A graph of the relationship between cumulative time and pulse energy.

4A is an example of a block diagram of a laser control apparatus according to an embodiment, and FIG. 4B is a graph showing measured values and pulse widths of accumulated time stored in a memory section of the laser control apparatus according to the embodiment. A diagram of the correspondence between the command values.

Fig. 5 is a flowchart of processing performed by a laser control apparatus according to an embodiment.

Fig. 6 is a flow chart showing the processing of step SA4 (Fig. 5).

7A is a graph showing a relationship between a measured value of an accumulated time and a measured value of pulse energy when the pulse width is constant irrespective of the accumulation time, and FIG. 7B is a view showing a laser using the embodiment. A graph showing the relationship between the measured value of the accumulated time and the measured value of the pulse energy when the device is controlled.

8] Fig. 8A is a block diagram of a laser control apparatus according to another embodiment, and Fig. 8B is a graph showing a correspondence relationship between a measured value of an average output and a command value of a discharge voltage.

9] FIG. 9 is a flowchart of a process of controlling a discharge voltage by a laser control apparatus according to the embodiment shown in FIG. 8A.

FIG. 10 is a flow chart based on step SA4 (FIG. 5) of the embodiment shown in FIG. 8A.

[Fig. 11] Fig. 11 is a view showing a command value of a discharge voltage when the reference value of the accumulation time is constant, a measured value of the average output of the laser oscillator 20, a measured value of the accumulated time, and a command value of the pulse width. A chart of an example of time change.

[Fig. 12] Fig. 12 is a view showing a command value of a discharge voltage, a measured value of an average output of a laser oscillator, a measured value of an accumulated time, and a pulse width when a laser control device based on the embodiment shown in Fig. 8A is used. A graph of an example of the time change of the command value.

Claims (6)

A laser control device, wherein Obtaining the elapsed time from the start of the excitation of the laser oscillator that outputs the pulsed laser beam to the rise of the laser pulse, that is, the cumulative time, and setting it as the measured value; Calculating a command value of a pulse width of a laser pulse outputted from the laser oscillator according to the measured value of the accumulated time; The laser oscillator is controlled so as to be a command value for calculating the pulse width of the currently output laser pulse. a laser control device as claimed in claim 1, wherein The excitation intensity of the aforementioned laser oscillator is also adjusted in accordance with the measured value of the average output of the pulsed laser beam output from the aforementioned laser oscillator. a laser control device according to claim 1 or 2, wherein When calculating the command value of the pulse width of the laser pulse, the measured value of the accumulated time is compared with the reference value of the accumulated time, and the command value of the pulse width of the laser pulse is calculated based on the comparison result. a laser control device as claimed in claim 3, wherein When the command value of the pulse width of the laser pulse is calculated, the reference value of the aforementioned accumulation time is updated based on the measured value of the accumulated time. a laser control device as claimed in claim 4, wherein The reference value of the aforementioned accumulation time is periodically updated, and the reference value of the aforementioned accumulation time is updated to the average value of the previous period of the measurement value of the aforementioned accumulation time of the laser pulse. a laser control device according to claim 1 or 2, wherein When the command value of the pulse width of the laser pulse is calculated, the measured value of the pulse width of the laser pulse is made longer than the reference value of the pulse width as the measured value of the accumulated time becomes longer than the reference value of the accumulated time. As the measured value of the aforementioned accumulation time becomes shorter than the reference value of the aforementioned accumulation time, the command value of the pulse width of the laser pulse is made shorter than the reference value of the pulse width.