JP2010109195A - Laser oscillator, and laser beam machine using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To precisely detect the occurrence of abnormal conditions in a laser oscillator which emits laser pulses. <P>SOLUTION: The light intensity of the laser pulse emitted at a predetermined frequency is compared with a plurality of threshold intensities which have been set in advance, for counting a frequency at which the light intensity exceeds a threshold intensity, for each threshold intensity. The intensity range (minimum peak intensity range) in which the minimum value of peak intensity of laser pulse is present and the intensity range (maximum peak intensity range) in which the maximum value of peak intensity is present are detected, based on the number of emission pulses obtained for each of the threshold intensities as well as the number of reference pulses which is normally expected. Presence of abnormal operation of the laser oscillator is determined based on the fact whether they are within a predetermined intensity range. With this configuration, the information about a minimum value and maximum value of peak intensity and also the information about width of variation of peak intensity can be reflected, thereby the presence of abnormal operation of the laser oscillator is precisely determined. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a technique for stably generating laser light using a laser oscillator, and more particularly to a technique for stably generating pulsed laser light at a constant frequency.

  Unlike general light, laser light has a great feature that the wavelength and phase of light are uniform. For this reason, not only the directivity and coherence (coherence) of light are high, but it is also possible to focus on an extremely small area using an optical system. Therefore, utilizing such properties, laser light is used in many fields such as communication, measurement technology, medical field, and processing technology. In addition to continuous emission of laser light, it is also possible to emit pulsed laser light (hereinafter sometimes referred to as “laser pulse”) at a constant frequency. By using laser pulses emitted at a constant frequency in this way, high-speed communication can be realized, various phenomena can be measured with high time resolution, and even the difficult-to-work materials can be affected by heat. It is possible to further expand the possibilities of laser light, such as being able to process with a minimum.

  Here, since the laser light is based on the principle of light amplification by optical resonance, in order to stably emit the laser light, the predetermined oscillation condition must be properly satisfied in the laser oscillator. It becomes important. In addition, there are various methods for generating a laser pulse with a constant frequency, such as a method using a so-called Q switch and a method using a mode lock. Regardless of which method is used, a stable laser pulse can be generated. In order to emit light, it is assumed that the oscillation conditions in the laser oscillator are correctly satisfied. Therefore, if the oscillation condition in the laser oscillator is no longer satisfied by monitoring the amount of laser light, or by monitoring the amount of laser light and the input power, this is immediately detected. Techniques have been proposed (for example, Patent Document 1, Patent Document 2, Patent Document 3, etc.).

JP-A-10-190103 Japanese Patent Application Laid-Open No. 2002-076506 JP 2003-224316 A

  However, when emitting pulsed laser light at a constant frequency, it is difficult to determine abnormal operation of the laser oscillator with sufficient accuracy by the conventional method as proposed, and as a result, the oscillation conditions of the laser oscillator Although it is satisfied, it is erroneously determined that an abnormality has occurred, or conversely, it is erroneously determined that it is operating stably even though the oscillation conditions are unstable. There was a problem that sometimes.

  The present invention has been completed in view of the above circumstances, and an object of the present invention is to accurately detect the presence or absence of an operation abnormality in a laser oscillator that emits pulsed laser light at a constant frequency. It is in providing technology.

In order to solve at least a part of the problems described above, the laser oscillator of the present invention employs the following configuration. That is,
In a laser oscillator that emits a laser pulse that is a pulsed laser beam at a predetermined frequency,
A light receiving means for receiving the laser pulse;
Based on the light intensity of the received laser pulse, an emission pulse number detecting means for detecting the number of emission pulses of the laser pulse by counting the number of pulses of the laser pulse within a predetermined counting time;
By comparing the number of reference pulses determined by the predetermined frequency of the laser pulse and the counting time with the number of emitted pulses obtained based on different light intensity levels of the laser pulse, the number of pulses obtained within the counting time is obtained. An abnormality determination for determining whether or not the laser oscillator is abnormal by determining whether or not the minimum value and the maximum value of the peak intensity of the laser pulse are within a predetermined reference range respectively determined And means.

  In such a laser oscillator of the present invention, when laser light (laser pulse) emitted in a pulse shape at a predetermined frequency is received, the number of pulses within a predetermined counting time is counted based on the light intensity of the received laser pulse. By doing so, the number of laser pulses emitted is detected. Thus, if the number of outgoing pulses obtained for different light intensity levels is compared with the reference pulse number, the minimum value of the peak intensity of the laser pulse within the counting time is within the predetermined reference range defined for the minimum value. It can be determined whether or not the maximum value of the peak intensity of the laser pulse is within a predetermined reference range defined for the maximum value. Here, the reference pulse number is the number of pulses emitted from a laser pulse emitted at a predetermined frequency during a predetermined counting time, and can be determined immediately if the frequency and the counting time are known. If the minimum value and the maximum value of the peak intensity are within the predetermined reference range, it is determined that the operation of the laser oscillator is normal. Conversely, if the peak intensity is not within the predetermined reference range, the operation is abnormal. Judge.

  In this way, not only the information on the minimum or maximum peak intensity, but also the information on the variation width of the peak intensity of each laser pulse can be reflected to determine whether there is an abnormal operation of the laser oscillator. It is possible to accurately determine whether there is an abnormality.

  In the above-described laser oscillator of the present invention, when the deviation between the minimum value and the maximum value of the peak intensity detected based on the number of outgoing pulses at each light intensity level is larger than a predetermined reference value, the laser It may be determined that the operation of the oscillator is abnormal.

  When the operation of the laser oscillator that emits a laser pulse becomes abnormal, the variation in the peak intensity of each laser pulse increases. Therefore, if the deviation between the minimum value and the maximum value of the peak intensity obtained within the predetermined counting time exceeds the predetermined reference value, it is possible to accurately determine the abnormal operation of the laser oscillator if it is determined as abnormal. It becomes possible.

  Further, in the laser oscillator of the present invention described above, the number of outgoing pulses at different light intensity levels may be detected as follows. That is, the number of emitted pulses at different light intensity levels may be detected by changing the light intensity level at the time of detecting the number of emitted pulses step by step for each predetermined counting time.

  In this way, it is possible to detect the number of outgoing pulses having different light intensity levels. Also, since the pulse width of the laser pulse is very short and the frequency at which the laser pulse is emitted is high, it is not so easy to simultaneously count the number of emitted pulses at different light intensity levels. On the other hand, if the number of outgoing pulses is detected while changing the light intensity level when detecting the number of outgoing pulses step by step for each predetermined counting time, the number of outgoing pulses at different light intensity levels can be detected simultaneously. This is preferable because there is no need to do this.

  Further, the above-described laser oscillator of the present invention may be incorporated as a laser light source of a so-called laser processing machine.

  In a laser processing machine that performs processing using laser pulses, if the operation of a laser oscillator that emits laser pulses becomes abnormal, the intensity of each laser pulse may vary, or laser pulses may be emitted at a constant frequency. It becomes impossible to cause deterioration of processing quality. On the other hand, the laser oscillator according to the present invention described above is preferable because it is possible to accurately determine an abnormal operation, and it is possible to prevent the processing quality of the object to be processed from being lowered.

Further, the laser oscillator of the present invention described above can be grasped in the following manner. That is,
In a laser oscillator that emits a laser pulse that is a pulsed laser beam at a predetermined frequency,
A light receiving means for receiving the laser pulse;
By comparing the light intensity of the received laser pulse with a plurality of preset threshold intensities, and counting the number of times the light intensity of the laser pulse exceeds the threshold intensity during a predetermined counting time , An emission pulse number detecting means for detecting the number of emission pulses of the laser pulse for each threshold intensity;
There is a minimum value of the peak intensity of the laser pulse by comparing the reference pulse number determined by the predetermined frequency of the laser pulse and the counting time with the number of emitted pulses obtained for each threshold intensity. A minimum peak intensity range detecting means for detecting a minimum peak intensity range which is an intensity range;
A maximum peak intensity range detecting means for detecting a maximum peak intensity range which is an intensity range in which a maximum value of the peak intensity of the laser pulse exists, based on the number of emitted pulses obtained for each threshold intensity;
An abnormality determining means for determining whether the laser oscillator is abnormal by determining whether the minimum peak intensity range and the maximum peak intensity range are within predetermined intensity ranges, respectively. It is also possible to grasp as a laser oscillator.

  Further, the abnormality determination means in the laser oscillator according to the present invention ascertained in such a manner allows the laser oscillator to operate when the deviation between the minimum peak intensity range and the maximum peak intensity range is larger than a predetermined reference value. It is good also as determining with it being abnormal.

Hereinafter, in order to clarify the contents of the present invention described above, examples will be described in the following order.
A. Device configuration:
B. Judgment principle of abnormal operation:
C. First embodiment:
D. Second embodiment:
E. Variation:
E-1. First modification:
E-2. Second modification:

A. Device configuration :
FIG. 1 is an explanatory diagram showing a configuration of a laser processing machine 10 equipped with a laser oscillator 100 of the present embodiment. The laser processing machine 10 of the present embodiment includes a laser oscillator 100 that emits laser light, an optical system 200 that guides the emitted laser light to the workpiece W, and operations of the laser oscillator 100 and the optical system 200. The control unit 300 is configured to be controlled. A pulsed laser beam (laser pulse) is emitted from the laser oscillator 100 at a predetermined frequency, and the laser pulse emitted from the laser oscillator 100 is reflected by the reflection mirror 12 and guided to the optical system 200. The optical system 200 includes a plurality of optical lenses, and the focal position of the laser pulse can be moved along the optical axis direction by adjusting the distance between the lenses. Then, the laser pulse whose focal position is adjusted by the optical system 200 is irradiated on the surface of the workpiece W through the emission lens 14. Further, if a galvano scanner is incorporated in the optical system 200, the irradiation position of the laser pulse can be scanned on the surface of the workpiece W.

  FIG. 2 is an explanatory diagram showing the internal structure of the laser oscillator 100 of this embodiment. FIG. 2 also conceptually shows various functions provided in the control unit 300 for controlling the operation of the laser oscillator 100. As shown in FIG. 2, the laser oscillator 100 includes a pair of reflecting mirrors 102 and 104 provided to face each other, a laser medium 106 that can take a special energy state called inversion distribution, and a laser medium 106. An excitation light source 108 that generates an inversion distribution state by excitation, a modulator 110 that emits laser light in pulses at a predetermined frequency, a photodetector 112 that detects the light intensity of the laser light, and the like. .

  When emitting laser light, first, the laser medium 106 is irradiated with excitation light from the excitation light source 108. Then, a part of the laser medium 106 becomes a special energy state called inversion distribution. This inversion distribution is an unstable state in which the existence probability of a state having a high energy level is higher than the existence probability of a state having a low energy level. For this reason, in order to shift to a more stable energy distribution state, a transition is made from a high energy level state to a low energy level state, and at this time, light having a wavelength corresponding to the energy level difference is emitted. . The light emitted in this way triggers a transition from a high energy level to a low energy level, a stronger light is emitted, which further promotes the transition of the energy level. . Note that irradiating the laser medium 106 with excitation light to create an inverted distribution state in the laser medium 106 is called “pumping”. In the laser oscillator 100 of the present embodiment, the pumping light source driving unit provided in the control unit 300 drives the pumping light source 108 to pump the laser medium 106.

  A pair of reflecting mirrors 102 and 104 are provided opposite to each other on both sides of the laser medium 106. If the distance between the reflection mirrors 102 and 104 is adjusted to an integral multiple of the wavelength of the light emitted by the transition of the energy level, the light emitted from the laser medium 106 is changed between the reflection mirrors 102 and 104. Can be stored in the form of standing waves.

  In this way, while an inversion distribution is formed in the laser medium 106 by the excitation light from the excitation light source 108, light of a predetermined wavelength is emitted in an attempt to return to a more stable energy distribution state. As a result, the emitted light is stored in the form of a standing wave between the reflecting mirrors 102 and 104. Finally, part of the light passes through the reflecting mirror 102 on the output side and is emitted as laser light. Is done. Such a phenomenon can be considered as a kind of resonance phenomenon that occurs between the reflecting mirrors 102 and 104 facing each other.

  The modulator 110 is used for shaping the laser beam into a pulse shape. There are various methods for generating a pulsed laser beam (laser pulse). Typical methods include a method called “Q switch” and a method called “mode lock”. . In a method called a Q switch, a modulator 110 that can be modulated from the outside is provided between the reflection mirrors 102 and 104, and a condition in which resonance does not occur between the reflection mirrors 102 and 104 while no laser pulse is emitted. The modulator 110 is modulated in advance. As a result, the inversion distribution state is accumulated inside the laser medium 106. When the laser pulse is emitted, the modulation by the modulator 110 is canceled and the condition for causing resonance between the reflection mirrors 102 and 104 is restored. Then, the energy stored in the laser medium 106 as an inverted distribution state is released at a stretch, and a very strong laser pulse is emitted in an extremely short time.

  In a method called mode lock, a laser pulse is generated by utilizing the fact that a plurality of resonance modes can be generated in the reflection mirrors 102 and 104. That is, a plurality of standing waves having different numbers of nodes can be considered as standing waves that can exist between the reflecting mirrors 102 and 104. Further, since the wavelength of light is very short compared to the size of the resonator formed between the reflection mirrors 102 and 104, a standing wave in a direction perpendicular to the axis of the reflection mirrors 102 and 104 may be considered. it can. The actual laser oscillator 100 has a plurality of resonance modes as described above, and has a slightly different resonance frequency (wavelength) for each mode. In a method called mode lock, the phases of the plurality of modes are adjusted to a certain condition. For example, if an optical switch that can be controlled from the outside is provided between the reflecting mirrors 102 and 104, and the modes are oscillated simultaneously by opening the optical switch for a moment, the phases of a plurality of modes can be aligned. Alternatively, a special absorber (saturable absorber) having a property of absorbing weak light but transmitting light when the light intensity becomes a certain level or more may be provided between the reflection mirrors 102 and 104. Since the light of each mode alone is weak, it is absorbed by the saturable absorber, but when the phases of the modes are aligned, the light becomes stronger and passes through the saturable absorber. As a result, the phase of each mode can be finally aligned. In such a state in which the phases of a plurality of modes are aligned, the condition that the light of each mode is intensified every certain time period is established, and each time a strong laser pulse is generated for a very short time. Become.

  The method of generating the laser pulse is not limited to the above-described Q switch method or mode lock method. For example, only when the laser pulse is emitted, the “resonator damping” is used to reduce the transmittance of the reflection mirror 102 on the emission side. There are various methods such as a method called “method”. In the laser oscillator 100 of the present embodiment, any method can be adopted.

  As the laser oscillator 100, impurities such as a gas laser using a gas such as argon gas, helium gas or carbon dioxide gas as the laser medium 106, a dye laser using a liquid in which an organic solvent is dissolved as the laser medium 106, and impurities are added. Various types of laser oscillators such as a solid-state laser using a transparent solid medium (ruby or the like) as the laser medium 106 and a semiconductor laser using a light-emitting diode as the laser medium 106 can be used. Alternatively, an optical fiber to which a rare earth element such as Er (erbium), Y (yttrium), or Yb (ytterbium) is added can be used as the laser medium 106.

B. Judgment principle of abnormal operation:
When the laser oscillator 100 is operating normally, it is possible to stably emit a laser pulse having a constant light intensity at a constant time interval. Therefore, by monitoring the light intensity of the laser light and confirming whether or not a laser pulse having a certain light intensity or more is emitted at a certain time interval, it is determined whether or not the laser oscillator 100 is operating normally. Can be judged. The presence or absence of abnormal operation of a laser oscillator that emits a laser pulse has been determined based on this concept.

  FIG. 3 is an explanatory diagram showing a method of determining an operation abnormality that has been employed in a conventional laser oscillator. FIG. 3A shows a state where the laser oscillator is operating normally. When the laser oscillator operates normally, as illustrated in FIG. 3A, laser pulses with uniform peak intensities are emitted at regular time intervals. Accordingly, a threshold light intensity (threshold intensity) Eth having a slight margin is set with respect to the peak intensity at the time of shipment of the laser oscillator (or an ideally adjusted state), and the light of the laser light is set. The number of times that the intensity exceeds the threshold intensity Eth is counted. The number of pulses emitted from the laser pulse counted during the predetermined counting time t0 is calculated from the predetermined frequency at which the laser oscillator should emit the laser pulse and the counting time of the laser pulse (reference pulse number). If it matches, it is determined that the laser oscillator is operating normally. For example, in the example shown in FIG. 3A, if the number of pulses counted during the measurement time t0 is four, it is determined that the laser oscillator is operating normally.

  On the other hand, when the laser oscillator is not operating normally, the peak intensity of the laser pulse varies as illustrated in FIG. For example, when the laser pulse is generated using the above-described Q switch, the inversion distribution state generated between the time when the laser pulse is emitted and the time when the next laser pulse is emitted varies. The peak intensity of the laser pulse may vary. In addition, when laser pulses are generated using mode lock, when a plurality of modes formed between the reflecting mirrors 102 and 104 are not as designed (for example, a certain mode is missing or For example, when the intensity distribution of the mode is distorted, the peak intensity of each laser pulse may vary.

  As described above, when variations occur in the peak intensity of each laser pulse, as illustrated in FIG. 3B, a pulse whose peak intensity does not exceed the threshold intensity Eth is generated. The reference pulse number to be counted is not reached. For this reason, it is possible to detect that the laser oscillator is not operating normally.

  However, in such a method that has been conventionally employed, even if the laser oscillator is still operating normally, it may be erroneously determined that the operation is abnormal. For example, consider a case where the operation as an oscillator is normal, but the output peak is slightly deteriorated due to a change over time due to long-term use. In this case, as shown in FIG. 3 (c), a laser pulse is output at a reference frequency and with a stable peak intensity, and although it is considered that the laser oscillator is operating normally, a predetermined frequency is obtained. Since the number of outgoing pulses counted at the measurement time t0 does not reach the reference pulse number, it may be erroneously determined as an operation abnormality.

  Of course, in the case illustrated in FIG. 3C, erroneous determination can be avoided by slightly lowering the setting of the threshold strength Eth. However, when the threshold intensity Eth is lowered, as illustrated in FIG. 3D, it may be determined that the operation is normally normal even when it should be determined as an abnormal operation. That is, in the example shown in FIG. 3D, the threshold strength is lowered from “Eth” to “Eth ′”. Therefore, if the threshold strength is set to “Eth”, it is correctly determined that the operation is abnormal. Even if it is performed (see FIG. 3B), it is erroneously determined to be normal.

  In the laser oscillator 100 of the present embodiment, it is possible to accurately determine an abnormal operation of the laser oscillator 100 by counting the number of emitted laser pulses with a plurality of threshold intensities. Hereinafter, an operation abnormality determination method used in the laser oscillator 100 of this embodiment will be described.

C. First Example:
FIG. 4 is an explanatory diagram showing a rough circuit configuration for counting the number of outgoing pulses in the laser oscillator 100 of the first embodiment. These circuit configurations are incorporated in the control unit 300 as an output pulse number counting unit 302 as shown in FIG. Then, it receives a signal from the photodetector 112 provided in the laser oscillator 100 and counts the number of outgoing pulses.

  FIG. 4A shows the configuration of the emission pulse number counting unit 302 formed using an analog circuit. As shown in the drawing, the signal of the light intensity detected by the photodetector 112 is divided into a plurality of (here, four) paths and input to analog comparators provided in the respective paths. Further, different threshold strengths Eth0, Eth1, Eth2, and Eth3 (where Eth0> Eth1> Eth2> Eth3) are set in each analog comparator. Each analog comparator outputs a pulse signal every time the light intensity received from the photodetector 112 exceeds the threshold intensity set for each, and the pulse signal is counted by a counter provided for each analog comparator. To do. The count value obtained by each counter is output as the number of outgoing pulses for each threshold intensity while resetting each counter at a certain count time t0. FIG. 4A shows the number of outgoing pulses N0 for the threshold strength Eth0, the number of outgoing pulses N1 for the threshold strength Eth1, the number of outgoing pulses N2 for the threshold strength Eth2, and the number of outgoing pulses for the threshold strength Eth3. The state in which N3 is output is shown. In the present embodiment, the number of set threshold strengths is described as four. However, any number of threshold strengths may be set as long as there are a plurality of threshold strengths. .

  Alternatively, similar processing may be realized using software. That is, as shown in FIG. 4B, the waveform data of the light intensity detected by the photodetector 112 is temporarily stored in the waveform memory. It is sufficient that the waveform data to be stored is at least as long as the measurement time t0. A plurality of threshold strengths are set in advance in the memory. Then, the waveform data is analyzed, the number of times that the threshold intensity is exceeded during the measurement time t0 is obtained, and the number of outgoing pulses for each threshold intensity may be output.

  The number of outgoing pulses N0, N1, N2, N3 obtained for the plurality of threshold intensities Eth0, Eth1, Eth2, Eth3 in this way is a peak intensity range detector provided in the controller 300 (see FIG. 2). ) To detect the range in which the peak intensity of the laser pulse exists. Then, the detection result is supplied to an abnormality determination unit (see FIG. 2), and the presence / absence of an operation abnormality of the laser oscillator 100 is determined.

  FIG. 5 is an explanatory diagram showing a state in which the presence / absence of abnormal operation of the laser oscillator 100 is determined based on the number of emitted pulses obtained for a plurality of threshold intensities. FIG. 5A illustrates a waveform of the light intensity detected by the photodetector 112 and a plurality of threshold intensities Eth0 to Eth3. As shown in the figure, the highest threshold intensity Eth0 is set slightly lower than the ideal (or shipped) peak intensity of the laser pulse of the laser oscillator 100. The other threshold strengths Eth1 to Eth3 are set lower than the threshold strength Eth0 and at substantially equal intervals. In this embodiment, the threshold strengths Eth0, Eth1, Eth2, and Eth3 are described as being set at equal intervals. However, these threshold strengths need to be set at equal intervals. There is no.

  In the waveform shown in FIG. 5A, since the peak intensity of each laser pulse exceeds the threshold intensity Eth1, Eth2, Eth3, the number of emitted pulses N1, N2 counted at the measurement time t0 with the respective threshold intensity. N3 are both "4". Here, it is assumed that the number of pulses (reference pulse number) to be emitted by the laser oscillator 100 during the measurement time t0 is also “4”. For the highest threshold intensity Eth0, the number of outgoing pulses N0 is “0”.

  FIG. 5B collectively shows the number of outgoing pulses N0 to N3 obtained for each threshold intensity. For the threshold intensity Eth1 to the threshold intensity Eth3, the same number of outgoing pulses as the reference pulse number is counted. Therefore, all the laser pulses emitted at the counting time t0 are considered to have a peak intensity higher than the threshold intensity Eth1. In addition, the number of outgoing pulses counted at a threshold intensity Eth0 that is one step higher than the threshold intensity Eth1 does not reach the reference pulse number. From this, it can be considered that the peak intensity (minimum peak intensity) of the pulse having the smallest light intensity among the laser pulses emitted at the counting time t0 exists in the intensity range of the threshold intensity Eth1 to the threshold intensity Eth0. .

  On the other hand, since the number N0 of emitted pulses obtained for the highest threshold intensity Eth0 is “0”, there is a pulse having a peak intensity higher than the threshold intensity Eth0 among the laser pulses emitted at the counting time t0. I understand that it is not. In addition, since the number N1 of emitted pulses obtained at a threshold intensity Eth1 that is one step lower than the threshold intensity Eth0 is not "0", there are laser pulses having a peak intensity exceeding the threshold intensity Eth1. From this, it can be considered that the peak intensity (maximum peak intensity) of the pulse having the highest light intensity among the laser pulses emitted at the counting time t0 exists in the intensity range of the threshold intensity Eth1 to the threshold intensity Eth0. . FIG. 5B shows an intensity range in which the maximum peak intensity exists (maximum peak intensity range) based on the number of outgoing pulses N0 to N3 obtained for each threshold intensity Eth0 to Eth3 in this way, and the minimum A state in which an intensity range in which peak intensity exists (minimum peak intensity range) is obtained is shown.

  Further, in the case shown in FIG. 3C where the operation of the laser oscillator 100 is erroneously determined to be abnormal, the number of emitted pulses N0 to N3 as shown in FIG. 5C can be obtained. Even in such a case, the intensity range in which the maximum peak intensity exists and the intensity range in which the minimum peak intensity exists can be obtained in the same manner as in FIG. There is no laser pulse whose peak intensity exceeds the threshold intensity Eth1 (because the number of outgoing pulses N1 corresponding to the threshold intensity Eth1 is “0”), but there is a laser pulse that exceeds the threshold intensity Eth2 which is lower by one level. (Because the number N2 of outgoing pulses corresponding to the threshold intensity Eth2 is not "0"). Therefore, it can be considered that the intensity range in which the maximum peak intensity exists is in the range of the threshold intensity Eth1 to the threshold intensity Eth0. Further, the number of outgoing pulses equal to the reference pulse number is obtained at the threshold intensity Eth2, but the obtained outgoing pulse number N1 does not reach the reference pulse number at the threshold intensity Eth1 that is higher by one level. Therefore, it can be considered that the intensity range in which the minimum peak intensity exists is in the range of the threshold intensity Eth1 to the threshold intensity Eth0. In the “peak intensity range detection unit” (see FIG. 2) of the control unit 300 mounted on the laser oscillator 100 of the present embodiment, the maximum number is obtained from the number of emitted pulses obtained at each threshold intensity as described above. A range in which the peak intensity exists (maximum peak intensity range) and a range in which the minimum peak intensity exists (minimum peak intensity range) are detected.

  An “abnormality determination unit” (see FIG. 2) provided in the control unit 300 determines whether there is an abnormal operation of the laser oscillator 100 based on the maximum peak intensity range and the minimum peak intensity range thus obtained. For example, in the example shown in FIG. 5B, since the minimum peak intensity range is in the intensity range of the threshold intensity Eth1 to the threshold intensity Eth0, the laser pulse has sufficient light intensity, and the pulse has a desired frequency. Is emitted. Further, since the maximum peak intensity range and the minimum peak intensity range are not separated (in the illustrated example, they are the same), the output variation of the laser pulse is small. From these things, it can be determined that the laser oscillator 100 is operating normally. Similarly, in the example shown in FIG. 5C, the minimum peak intensity range is in the intensity range of threshold intensity Eth2 to threshold intensity Eth1, and the maximum peak intensity range and the minimum peak intensity range are not separated from each other. 100 can be determined to be operating normally.

  FIG. 6 is an explanatory diagram illustrating a case where the operation of the laser oscillator 100 is determined to be abnormal. In FIG. 6A, the waveform of the light intensity detected by the photodetector 112 is shown together with the respective threshold intensities Eth0 to Eth3. If the number of outgoing pulses N0, N1, N2, N3 at each threshold intensity is obtained for such a waveform, the result shown in FIG. 6B can be obtained.

  In the result shown in FIG. 6B, the number of outgoing pulses N3 obtained with the threshold intensity Eth3 is the same as the number of reference pulses, but the number of outgoing pulses N2 obtained with the threshold intensity Eth2 is the reference pulse. The number has not been reached. Therefore, it can be considered that the minimum peak intensity exists in the range of the threshold intensity Eth3 to the threshold intensity Eth2. The number N0 of outgoing pulses obtained at the highest threshold intensity Eth0 is “0”, but the number N1 of outgoing pulses obtained at the threshold intensity Eth1 is not “0”, so the maximum peak intensity is the threshold intensity Eth1. It can be considered that it exists in the range of ~ threshold strength Eth0. In this case, since there is a large gap between the intensity range in which the minimum peak intensity exists and the intensity range in which the maximum peak intensity exists, the intensity of the laser pulse varies greatly, and the laser oscillator 100 operates normally. It can be determined that it is not operating.

  In the example shown in FIG. 6B, the intensity range in which the minimum peak intensity exists is also low, from threshold intensity Eth3 to threshold intensity Eth2. In such a case, as shown in FIG. 6C, even when the intensity range of the minimum peak intensity and the intensity range of the maximum peak intensity are not separated from each other, the output abnormality can be correctly determined.

  As described above, in the laser oscillator 100 according to the present embodiment, the presence / absence of the operation abnormality of the laser oscillator 100 can be accurately determined by detecting the existence range of the minimum peak intensity and the existence range of the minimum peak intensity. . In the determination, an allowable existence range of the minimum peak intensity and an allowable existence range of the maximum peak intensity are set in advance, and the existence range of the minimum peak intensity and the existence range of the maximum peak intensity are within the respective allowable existence ranges. It is possible to determine that the operation of the laser oscillator 100 is abnormal when any of them exceeds the allowable existence range.

  Alternatively, the presence / absence of an abnormal operation of the laser oscillator 100 may be determined based on an allowable deviation between the minimum peak intensity and the maximum peak intensity. In other words, the existence range of the minimum peak intensity and the existence range of the maximum peak intensity are obtained from the number of outgoing pulses. Then, a deviation between the existence range of the minimum peak intensity and the existence range of the maximum peak intensity is obtained, and it is determined whether or not the deviation is within a preset allowable range. As a result, if the deviation is within the allowable range, it is confirmed whether the previously obtained minimum peak intensity existing range is not too low or the maximum peak intensity existing range is not too high. Any one of the lower limit value of the minimum peak intensity and the upper limit value of the maximum peak intensity may be set in advance, and the set condition may be confirmed. And the deviation between the existence range of the minimum peak intensity and the existence range of the maximum peak intensity is within the allowable range, and the existence range of the minimum peak intensity is not less than the lower limit value, or the existence range of the maximum peak intensity is If it is less than or equal to the upper limit value, it may be determined that the laser oscillator 100 is operating normally, and otherwise, it may be determined that the operation is abnormal.

  As described in detail above, in the laser oscillator 100 of the first embodiment, the presence or absence of abnormal operation of the laser oscillator 100 is determined easily and accurately by obtaining the number of emitted pulses for each of a plurality of threshold intensities. It becomes possible.

D. Second embodiment:
In the first embodiment described above, the number of outgoing pulses for each threshold intensity is obtained from the same waveform detected by the photodetector 112. On the other hand, the number of outgoing pulses of each threshold intensity may be obtained by time division. By doing so, it is not necessary to count a plurality of outgoing pulses at the same time, so that outgoing pulses can be easily counted, and the operation determination of the laser oscillator 100 can be easily executed. Hereinafter, such a second embodiment will be described.

  FIG. 7 is an explanatory diagram showing a rough circuit configuration for counting the number of outgoing pulses in the laser oscillator 100 of the second embodiment. In the first embodiment described above with reference to FIG. 4A, a plurality of analog comparators are connected in parallel, and the signal waveform of the light intensity detected by the photodetector 112 is distributed to each analog comparator. Had been supplied. On the other hand, in the second embodiment, the signal waveform from the photodetector 112 is input to one analog comparator. Further, the output of the digital-analog converter (DAC) is input to the threshold value of the analog comparator. In the second embodiment, the DAC output has a staircase waveform that switches from “threshold strength Eth3 → threshold strength Eth2 → threshold strength Eth1 → threshold strength Eth0” every counting time t0. That is, one analog comparator is time-divided for each counting time t0 and compared with a different threshold intensity within each divided time.

  Then, the output pulses of the analog comparator are counted with a counter. At this time, by resetting the counter each time the threshold intensity is switched, the number of times that the waveform of the light intensity exceeds the threshold time within each division time is counted and output. In this way, in synchronism with the timing at which the threshold intensity switches from “threshold intensity Eth3 → threshold intensity Eth2 → threshold intensity Eth1 → threshold intensity Eth0”, “number of output pulses N3 → number of output pulses N2 → number of output pulses N1 → The number of outgoing pulses at each threshold intensity can be obtained by repeating "number of outgoing pulses N0".

  FIG. 8 is an explanatory diagram showing how the number of outgoing pulses at a plurality of threshold intensities is obtained in a time division manner in the laser oscillator 100 of the second embodiment. FIG. 8A illustrates a case where the laser oscillator 100 is operating normally, and FIG. 8B illustrates a case where the laser oscillator 100 is not operating normally. In either case, every time a certain counting time t0 elapses, the threshold intensity is switched from “threshold intensity Eth3 → threshold intensity Eth2 → threshold intensity Eth1 → threshold intensity Eth0” to obtain “number of output pulses N3 → output. The number of emitted pulses can be determined in the order of the number of pulses N2 → the number of emitted pulses N1 → the number of emitted pulses N0. As a result, for example, with the waveform illustrated in FIG. 8A, the same result as the number of outgoing pulses shown in FIG. 5B can be obtained, so that the operation of the laser oscillator 100 can be determined to be normal. Further, for the waveform illustrated in FIG. 8B, the same result as in FIG. 6B can be obtained, so that it can be determined that the operation is abnormal. As a result, also in the second embodiment, as in the first embodiment, it is possible to easily and accurately determine whether or not the laser oscillator 100 is operating abnormally.

  Further, in the second embodiment described above, the following may be performed. First, by repeating the setting of the threshold intensity over a plurality of periods as “threshold intensity Eth3 → threshold intensity Eth2 → threshold intensity Eth1 → threshold intensity Eth0 → threshold intensity Eth3”, “the number of emitted pulses N3 → the number of emitted pulses N2 → The number of emitted pulses repeated over a plurality of cycles is counted as “number of emitted pulses N1 → number of emitted pulses N0 → number of emitted pulses N3”. The average number of output pulses Nav3, average number of output pulses Nav2, average number of output pulses Nav, number N2 of output pulses, number of output pulses N1, and number of output pulses N0 counted over a plurality of periods are averaged. The number of outgoing pulses Nav1 and the average number of outgoing pulses Nav0 are calculated. The existence range of the minimum peak intensity and the existence range of the maximum peak intensity may be obtained based on the average number of outgoing pulses Nav thus obtained for each threshold intensity. By doing so, it is not affected by measurement variations, so that it is possible to determine the presence or absence of abnormal operation of the laser oscillator 100 with higher accuracy.

  Of course, similarly in the first embodiment described above, it is also possible to obtain the average number of emitted pulses at each threshold intensity by repeating counting of the number of emitted pulses a plurality of times and averaging the counted values. By doing so, also in the first embodiment, it is possible to determine the presence or absence of abnormal operation of the laser oscillator 100 with higher accuracy by eliminating the influence of measurement variations.

E. Modified example:
Several modifications can be considered for the first and second embodiments described above. Hereinafter, these modified examples will be briefly described.

E-1. First modification:
In the first embodiment or the second embodiment described above, the interval between the threshold strengths is not particularly mentioned. However, it is desirable to set the intervals between the threshold strengths as follows. Generally, the maximum value of the allowable variation is determined for the peak intensity of the laser pulse. Here, the maximum allowable variation is referred to as “peak variation allowable width”. It is desirable to set the interval between the threshold intensities to be an interval narrower than the peak variation allowable width. In this way, it is possible to immediately detect that the variation in the peak intensity of the laser pulse has exceeded the peak variation tolerance for the following reasons. As a result, it is possible to determine the operation abnormality of the laser oscillator 100 with higher accuracy.

  FIG. 9 is an explanatory diagram showing how to determine whether or not the laser oscillator 100 is operating abnormally in the first modification. FIG. 9A shows a case where the interval between the threshold strengths is set slightly narrower than the peak variation allowable width. FIG. 9B shows a case where the interval between the threshold strengths is set to half of the peak variation allowable width. In both FIG. 9A and FIG. 9B, the light intensity waveform is a laser pulse waveform in which variation in peak intensity is within the allowable limit.

  In the example shown in FIG. 9A, the intensity range having the minimum peak intensity is a range from threshold intensity Eth2 to threshold intensity Eth1, and the intensity range having the maximum peak intensity is threshold intensity Eth1 to threshold intensity Eth0. . When the interval between the threshold intensities is set slightly narrower than the peak variation allowable width, the existence range of the minimum peak intensity and the maximum peak intensity of the laser pulse at the variation limit is as shown in FIG. , Detected across two adjacent intensity ranges. In the example shown in FIG. 9A, the detection is performed across the intensity range of the threshold intensity Eth2 to the threshold intensity Eth1 and the intensity range of the threshold intensity Eth1 to the threshold intensity Eth0 adjacent thereto. On the contrary, when the peak intensity of the laser pulse is at the variation limit, the existence range of the minimum peak intensity and the maximum peak intensity cannot be detected across three or more intensity ranges. Accordingly, when the existence range of the minimum peak intensity and the maximum peak intensity is detected over three or more intensity ranges, the laser pulse may determine that the peak intensity variation exceeds the peak variation allowable range. it can.

  The same is true in FIG. 9B in which the interval between the threshold strengths is set to half the allowable peak variation width. In the example shown in FIG. 9B, the existence range of the minimum peak intensity is a range from the threshold intensity Eth3 to the threshold intensity Eth2, and the intensity range having the maximum peak intensity is the threshold intensity Eth1 to the threshold intensity Eth0. When the interval between the threshold intensities is set to be half of the allowable peak variation width, the minimum peak intensity and the maximum peak intensity existing range of the laser pulse at the variation limit are three intensity ranges across one intensity range. Detected across. In the example shown in FIG. 9B, an intensity range one level higher than the lower intensity range (threshold intensity Eth3 to threshold intensity Eth2) with the intensity range of threshold intensity Eth2 to threshold intensity Eth1 in between. It is detected across three intensity ranges from (threshold intensity Eth1 to threshold intensity Eth0). Accordingly, when the existence range of the minimum peak intensity and the maximum peak intensity is detected over four or more intensity ranges, the laser pulse may determine that the peak intensity variation exceeds the peak variation allowable range. it can.

  In this way, if the interval between the threshold intensities is set to an interval that is at least narrower than the peak variation allowable width, it can be immediately detected that the variation in the peak intensity of the laser pulse has exceeded the allowable limit. As a result, it is possible to determine the operation abnormality of the laser oscillator 100 with higher accuracy. 9A and 9B, as the interval between the threshold intensities becomes narrower, it is more accurate that the variation in the peak intensity of the laser pulse exceeds the allowable limit. It is possible to detect well.

E-2. Second modification:
Further, in the various embodiments and modifications described above, the setting of the lowest threshold strength among the threshold strengths (the minimum threshold strength, which corresponds to the threshold strength Eth3 in the above-described embodiments) is not particularly mentioned. . However, it is desirable that the minimum threshold intensity is set to an allowable lower limit value of the peak intensity of the laser pulse. By doing so, it is possible to immediately detect that the peak intensity of the laser pulse has fallen beyond the allowable limit for the following reason, so that it is possible to accurately determine an abnormal operation of the laser oscillator 100.

  FIG. 10 is an explanatory diagram showing a state in which the presence or absence of abnormal operation of the laser oscillator 100 is determined in the second modification. FIG. 10A shows the waveform of a laser pulse in which the peak intensity is reduced to near the allowable lower limit (EthL). The lowest threshold intensity Eth3 of each threshold intensity is set to the allowable lower limit value EthL of the peak intensity. In the case illustrated in FIG. 10A, the peak intensity of the laser pulse barely exceeds the allowable lower limit value EthL. For this reason, when the number of outgoing pulses for each threshold intensity is counted, a result as shown in FIG. 10B can be obtained. If the minimum threshold intensity Eth3 is set to the allowable lower limit value EthL of the peak intensity, when the result shown in FIG. 10B is obtained, “the operation of the laser oscillator 100 is normal, but the output level Can be correctly determined.

  After that, while the laser oscillator 100 continues to be used, if the result of counting the number of emitted pulses at each threshold intensity becomes the result shown in FIG. 10C, the output level of the laser pulse is below the allowable limit. It can be determined that it has dropped.

  As described above, in the second modification, since the minimum threshold intensity Eth3 is set to the allowable lower limit value EthL of the peak intensity, it is possible to immediately detect that the peak intensity of the laser pulse has decreased to the allowable limit or more. Therefore, it is possible to accurately determine an operation abnormality of the laser oscillator 100.

  While various embodiments of the present invention have been described above, the present invention is not limited thereto, and is not limited to the wording of each claim unless it departs from the scope described in each claim. Improvements based on the knowledge that a person skilled in the art normally has can also be added as appropriate to the extent that those skilled in the art can easily replace them.

It is explanatory drawing which showed the structure of the laser processing machine 10 carrying the laser oscillator 100 of a present Example. It is explanatory drawing which showed the internal structure of the laser oscillator 100 of a present Example. It is explanatory drawing which showed the determination method of the operation abnormality employ | adopted with the conventional laser oscillator. It is explanatory drawing which showed the rough circuit structure for counting the number of emitted pulses in the laser oscillator 100 of 1st Example. It is explanatory drawing which showed a mode that the presence or absence of operation abnormality of the laser oscillator 100 was determined based on the number of the emitted pulses obtained about several threshold intensity | strength. 6 is an explanatory diagram illustrating a case where the operation of the laser oscillator 100 is determined to be abnormal. FIG. It is explanatory drawing which showed the rough circuit structure for counting the number of emitted pulses within the laser oscillator 100 of 2nd Example. It is explanatory drawing which showed a mode that the laser oscillator 100 of 2nd Example calculates | requires the emitted pulse number by several threshold intensity | strength by a time division. It is explanatory drawing which showed a mode that the presence or absence of operation abnormality of the laser oscillator 100 in the 1st modification was determined. It is explanatory drawing which showed a mode that the presence or absence of the operation abnormality of the laser oscillator 100 in the 2nd modification was determined.

Explanation of symbols

10 ... Laser beam machine, 12 ... Reflection mirror, 14 ... Outgoing lens,
100 ... laser oscillator, 102,104 ... reflecting mirror,
106 ... Laser medium, 108 ... Excitation light source, 110 ... Modulator,
DESCRIPTION OF SYMBOLS 112 ... Photodetector 200 ... Optical system 300 ... Control part 302 ... Output pulse number counting part, W ... Work target object

Claims (4)

In a laser oscillator that emits a laser pulse that is a pulsed laser beam at a predetermined frequency,
A light receiving means for receiving the laser pulse;
Based on the light intensity of the received laser pulse, an emission pulse number detecting means for detecting the number of emission pulses of the laser pulse by counting the number of pulses of the laser pulse within a predetermined counting time;
By comparing the number of reference pulses determined by the predetermined frequency of the laser pulse and the counting time with the number of emitted pulses obtained based on different light intensity levels of the laser pulse, the number of pulses obtained within the counting time is obtained. An abnormality determination for determining whether or not the laser oscillator is abnormal by determining whether or not the minimum value and the maximum value of the peak intensity of the laser pulse are within a predetermined reference range respectively determined And a laser oscillator. The laser oscillator according to claim 1, wherein
The abnormality determining means is means for determining that the operation of the laser oscillator is abnormal when a deviation between the minimum value and the maximum value of the peak intensity is larger than a predetermined reference value. Laser oscillator. The laser oscillator according to claim 1, wherein
The emitted pulse number detecting means is means for detecting the emitted pulse number while gradually changing the light intensity level for detecting the emitted pulse number for each counting time. Laser oscillator.   A laser processing machine comprising the laser oscillator according to any one of claims 1 to 3.

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