JP6050607B2 - Laser processing apparatus and laser output calibration method - Google Patents

Description

  The present invention relates to a laser processing apparatus, and more particularly to a technique for calibrating a laser output of a laser processing apparatus.

  Laser processing is a non-contact thermal process that instantaneously melts or evaporates the material to be processed with high-density laser energy by condensing coherent laser light into a minute spot and irradiating the processing point. Almost all kinds of work materials such as non-ferrous metals, ceramics, plastics, and papers can be processed such as drilling, welding, cutting, and surface treatment.

  In general, if the laser wavelength is constant, the melting or evaporation of the processing point increases as the laser output increases, and decreases as the laser output decreases. In laser processing, the laser output is the most important processing condition that affects the processing capability of the laser, and is always under the control of the user.

  In the laser processing apparatus, the laser output of the laser beam applied to the workpiece must be in accordance with the setting of the user, both in terms of quality control of laser processing and reliability of the apparatus performance. However, the laser output characteristics of the laser processing apparatus fluctuate due to a change with time of the laser oscillation unit, a deviation of the optical axis, deterioration or contamination of the laser transmission optical system, and the like. Therefore, it is necessary to calibrate the laser output between the operations of the laser processing apparatus or periodically.

  Usually, in a laser processing apparatus, an optical power meter is used for calibration of laser output. There are two types of usage forms of the optical power meter: a form incorporated in the apparatus and a form in which the optical power meter is arranged at the machining position separately from the laser machining apparatus.

  In the case of the built-in type, a partial reflection mirror (beam splitter) or a total reflection mirror (folding mirror) is arranged or inserted on the laser transmission path so as to guide the laser light output by oscillation to the optical power meter. The partial reflection mirror is generally arranged fixedly on a laser transmission path, branches a part of the laser beam oscillated and output as monitor light, and transmits the remaining laser light as processing laser light. However, normally, laser processing is not performed when the laser output is calibrated, and the processing laser light transmitted through the partial reflection mirror is incident on a damper (absorber) instead of the workpiece. Yes. On the other hand, the total reflection mirror is inserted on the laser transmission path only when the laser output is calibrated, and reflects all of the laser light incident from the laser oscillation unit toward the optical power meter. Therefore, no damper is required.

  In the case of the separate stand-alone type, the laser light emitted from the laser processing apparatus is incident on the optical power meter at the processing position, so that neither a partial reflection mirror or a total reflection mirror for calibration nor a damper is required. However, manual operation of the user is required in handling (installation and removal) of the optical power meter.

JP2011-142187A

  In a laser processing apparatus, a conventional laser output calibration method using an optical power meter uses a continuous wave (CW) laser beam for calibration, and takes a long time of about 1 to 3 minutes. For this reason, when the laser output is calibrated routinely or frequently, especially when the laser output is calibrated at the start-up of the apparatus, it is redundant and inconvenient.

  In addition, when a partial reflection mirror is incorporated for calibration of laser output, the reflectance and transmittance of the partial reflection mirror change depending on the polarization and wavelength of the laser beam, which may impair calibration accuracy and reliability.

  On the other hand, in the total reflection mirror built-in type and the separation independent type, continuous oscillation laser light is incident on the optical power meter for a long time without branching, so that a large amount of laser energy is input to the optical power meter. For this reason, in a kW class laser processing apparatus such as a fiber laser, a large optical power meter having a water cooling type cooling mechanism must be used. In the case of the total reflection mirror built-in type, it is difficult to reduce the size and space of the apparatus by installing such a large optical power meter. In the case of the separate stand-alone type, it takes a lot of time and effort to set such a large optical power meter at the processing position, and it is difficult to set it correctly, and the calibration results easily vary by the operator.

  Even when the partial reflection mirror built-in type is adopted, in the kW class laser processing apparatus, it is necessary to provide the damper with a cooling mechanism such as a water cooling type, and when the branching ratio of the branching laser light (monitoring light) is large. A large optical power meter provided with a cooling mechanism is used.

  The present invention solves the problems of the prior art as described above. Regardless of whether the laser output is high or low, the laser output can be calibrated accurately in a short time using a simple and compact optical power meter. Provided are a laser calibration method and a laser processing apparatus which can be used.

A laser calibration method according to a first aspect of the present invention is a laser output calibration method for calibrating a laser output in a laser processing apparatus, and a step of setting a peak output and a pulse width of pulsed laser light in the laser processing apparatus. A step of generating a single pulse laser beam by a laser generation unit of the laser processing apparatus on the condition of the set peak output and pulse width, and an optical power meter for the pulse laser beam generated by the laser generation unit And measuring the laser energy of the pulse laser beam with the optical power meter, and making the pulse laser beam generated by the laser generator incident on a photodiode capable of high-speed response, Measuring the pulse width of the pulse laser beam based on the output signal of A normalized laser output measurement corresponding to a laser energy measurement value or an average peak output measurement value per unit time related to the pulse laser beam from the laser energy measurement value and the pulse width measurement value related to the pulse laser beam A step of obtaining a value, and a step of calibrating the laser output characteristics of the laser generator so that a deviation between the normalized laser output measurement value and the set peak output is zero.

A laser processing apparatus according to a first aspect of the present invention includes a condition setting unit that sets a peak output and a pulse width of a pulse laser beam, and a single pulse laser that uses the peak output and the pulse width set by the condition setting unit as conditions. A laser generator that generates light, an optical power meter that receives the pulsed laser light generated by the laser generator and measures the laser energy of the pulsed laser light, and the pulses generated by the laser generator A fast-response photodiode that receives laser light and generates an electrical signal corresponding to the light intensity of the pulsed laser light, and a pulse width that measures the pulse width of the pulsed laser light based on the output signal of the photodiode From the measurement unit, the measured value of the laser energy obtained from the optical power meter, and the photodiode From the measured value of the pulse width is, a calculator for calculating a normalized laser power measurement value corresponding to the laser energy measurement or an average peak measured output value per unit time of the pulsed laser beam, the laser generating unit A calibration unit that calibrates the laser output characteristic so that a deviation between the measured value of the normalized laser output and the set peak output is zero ;

  In the laser processing method or apparatus according to the first aspect, since the laser output is calibrated using a single pulse laser beam having a short duration, the time required for the calibration process can be greatly shortened and the optical power meter can be used. Very low heat input. Therefore, even if the optical power meter does not include a cooling mechanism, the optical power meter can stably perform the measurement operation. Even if the rising edge and the falling edge of the pulse laser beam for calibration generated by the laser generator have an indefinite time delay, the optical power meter only needs to accurately measure the laser energy of the pulse laser beam. . Instead, the photodiode accurately detects the rising edge and the falling edge of the pulse laser beam with a high-speed response, and obtains a highly accurate measurement value regarding the pulse width of the pulse laser beam. With such a combination of an optical power meter and a photodiode, it is possible to acquire highly reliable monitor information for laser output calibration. A simple and small optical power meter can be used.

A laser calibration method according to a second aspect of the present invention is a laser output calibration method for calibrating a laser output in a laser processing apparatus, and includes a peak output, a pulse width, and a repetition frequency of repetitively pulsed laser light in the laser processing apparatus. A step of generating a pulse laser beam repeatedly by the laser generator of the laser processing apparatus on the condition of the set peak output, pulse width and repetition frequency, and the repetition generated by the laser generator A step of making a pulse laser beam incident on an optical power meter, measuring a laser output of the repetitive pulse laser beam by the optical power meter, and a photo capable of high-speed response of the repetitive pulse laser beam generated by the laser generator. Make it incident on the diode, The step of measuring the duty of the repetitive pulsed laser light based on the force signal, the measured value of the laser output related to the repetitive pulsed laser light, and the measured value of the duty when the duty is replaced with 100% A step of obtaining a normalized laser output measurement value corresponding to the laser output of the repetitively pulsed laser light, and a difference between the normalized laser output measurement value and the set peak output is set to zero in the laser output characteristics of the laser generator. And a step of applying calibration such as

A laser processing apparatus according to a second aspect of the present invention includes a condition setting unit that sets a peak output, pulse width, and repetition frequency of a repetitively pulsed laser beam, and a peak output, pulse width, and repetition frequency that are set by the condition setting unit. A laser generating unit that repeatedly generates pulsed laser light on the condition, an optical power meter that receives the repeated pulsed laser beam generated by the laser generating unit and measures the laser output of the repeated pulsed laser beam, and the laser A fast-response photodiode that receives the pulse laser beam generated by the generator and generates an electrical signal corresponding to the light intensity of the pulse laser beam, and the repetitive pulse laser based on the output signal of the photodiode A duty measurement unit that measures the duty of light and the optical power meter Normalized laser output measurement corresponding to the laser output of the repetitively pulsed laser light when the duty is replaced with 100% from the measured value of the laser output obtained and the measured value of the duty obtained from the duty measuring unit. A calculation unit that calculates a value; and a calibration unit that calibrates a laser output characteristic of the laser generation unit so that a deviation between the normalized laser output measurement value and the set peak output is zero .

  In the laser processing method or apparatus according to the second aspect, since the laser output is calibrated using repetitively pulsed laser light, the time required for the calibration process can be shortened and the heat input to the optical power meter is small. Therefore, even if the optical power meter does not include a cooling mechanism, the optical power meter can stably perform the measurement operation. Further, since the normalized laser output measurement value averaged over a large number of continuous pulse laser beams is obtained, the laser output can be calibrated accurately or stably.

  According to the laser calibration method and the laser processing apparatus of the present invention, the laser output calibration can be performed in a short time using a simple and small optical power meter regardless of the level of the laser output. It can be done accurately.

It is a block diagram which shows the structure of the laser processing apparatus in 1st Example of this invention. It is a figure which shows the waveform of each part in the calibration mode of the said laser processing apparatus. FIG. 3 is a diagram showing a comparison between a conventional technique (CW method), a first example (single pulse method), and a second example (repetitive pulse method) with respect to laser light (laser output waveform) for laser output calibration. . It is a block diagram which shows the structure of the fiber laser processing apparatus in a 3rd Example. It is a block diagram which shows the structure of the fiber laser processing apparatus in a 4th Example.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.
[Example 1]

  FIG. 1 shows the configuration of a laser processing apparatus according to the first embodiment of the present invention. This laser processing apparatus has, as a basic configuration, a laser oscillation unit 10 that can generate continuous oscillation or pulse oscillation laser light, a laser power supply unit 12 that supplies laser oscillation power to the laser oscillation unit 10, A control unit 14 that controls each unit in the apparatus and the entire apparatus, an operation panel 16 for man-machine interface, and an optical power monitor unit 18 for laser output calibration are provided.

  The control unit 14 includes one or a plurality of microcomputers. Functionally, the control unit 14 holds various setting values input by the user via the display unit 16a and the input unit 16b of the operation panel 16, and A laser control unit 22 for controlling the laser power source unit 12 according to a predetermined set value given from the setting unit 20, a mode control unit 24 for controlling or switching each unit according to the operation mode of the apparatus, and an optical power monitor unit And a calibration unit 26 that calibrates functions related to the laser output of the laser generation unit 25 based on the monitor information from 18. The laser generation unit 25 in this embodiment is configured by the laser oscillation unit 10, the laser power source unit 12, and the control unit 14 (particularly the laser control unit 22). The calibration unit 26 includes a function (calculation unit) that performs computation or signal processing necessary for calibration of the laser output.

  In this embodiment, the control unit 14 is shown as one control unit, but a plurality of control units may share the functions of the control unit 14 in parallel or hierarchically.

  The optical power monitor unit 18 includes an optical power meter 28 and a PIN photodiode 30, and is attached, for example, inside the apparatus main body or externally. In this embodiment, a movable total reflection mirror (folding mirror) 32 is provided on a laser transmission path 35 for propagating the laser beam LB emitted from the laser oscillation unit 10 in the air. The total reflection mirror 32 optically connects the laser oscillation unit 10 and the optical power monitoring unit 18 when the laser output is calibrated by the mirror actuator 34 under the control of the control unit 14 (mode control unit 24). When the laser output is not calibrated, it is retracted from the laser transmission path 35.

When the total reflection mirror 32 is inserted into the laser transmission path 35, a laser beam from the laser oscillation unit 10, that is, a single pulse laser beam LB _S for calibration, which will be described later, is totally reflected by the total reflection mirror 32 and passes through the optical path. It is bent and enters the light receiving surface of the optical power meter 28. An output terminal of the optical power meter 28 is connected to the control unit 14.

  The optical power meter measures the voltage or current proportional to the number of incident photons using a photoelectric conversion element and a thermal conversion type that absorbs laser light with an absorber and converts it into heat to measure temperature change. There are two types of photoelectric conversion type. As the optical power meter 28 used in this embodiment, a heat conversion type having a wide light energy measurement range is preferable, but a photoelectric conversion type can also be used. In this embodiment, as will be described later, even if the optical power meter 28 is not provided with a cooling mechanism, highly reliable calibration can be performed for a laser output having a high kW class. Therefore, a simple and small optical power meter can be used as the optical power meter 28 regardless of whether it is a thermal conversion type or a photoelectric conversion type.

The PIN photodiode 30 is arranged near the optical power meter 28 so as to receive the pulsed laser light LB _S as the light ΔLB _S scattered on the light receiving surface of the optical power meter 28. The output terminal of the PIN photodiode 30 is connected to the control unit 14.

A sensitive position for the PIN photodiode 30 to receive the scattered light ΔLB _S from the optical power meter 28 is a distance from the light receiving surface of the optical power meter 28 of 100 mm to 200 mm, and the optical path of the pulse laser beam LB _S It is a place where the distance from is within 50 mm. However, the function required for the PIN photodiode 30 is to accurately detect the rising and falling edges of the laser output waveform (pulse waveform) in the pulsed laser light LB _S with a high response speed, that is, a short response time (preferably 10 ns or less). Whether or not the above arrangement condition is satisfied is not so important (that is, the accuracy of sensitivity may be low).

  When laser processing is performed, the mirror actuator 34 retracts the total reflection mirror 32 from the laser transmission path 35 under the control of the control unit 14 (mode control unit 24). Thereby, the processing laser beam LB emitted from the laser oscillation unit 10 is incident on the workpiece W at the processing position without being guided to the optical power monitor unit 18.

  Next, the operation when the laser output is calibrated in this laser processing apparatus will be described. In this embodiment, the control unit is instructed when the user instructs the apparatus through the operation panel 16 to set the laser output calibration mode, when the apparatus is started by turning on the power switch, or periodically (for example, at a fixed time every day). 14 switches to the laser output calibration mode. The control unit 14 executes a processing procedure (sequence) for laser output calibration under a predetermined control program.

In the laser output calibration mode, a single pulse laser beam LB _S as shown in FIG. The peak output P _S and the pulse width T _S of the pulse laser beam LB _S are set as defaults by the user through the operation panel 16 or in the control unit 14, and are given from the setting unit 20 to the laser control unit 22 and calibrated. Also given to part 26.

The waveform of the pulse laser beam LB _S may be arbitrary, but a rectangular pulse waveform is usually selected. Here, the pulse width T _S is not particularly limited, but considering the general performance of the optical power meter 28, the range of 0.1 ms to 100 ms is preferable. The peak output P _S of the pulse laser beam LB _S is set according to the specification of the laser processing apparatus, that is, the rated output. For example, the rated output of the laser machining apparatus when a 6 kW, the peak output P _S is also set to 6 kW. Therefore, when the pulse width T _{S is set} to 10 ms and the peak output P _S is set to 6 kW, the laser energy (set value) of the pulse laser beam LB _S is 60 J (joules). Of course, the peak output P _S of the pulse laser beam LB _S can be set to a value other than the rated output value (6 kW), for example, a power value actually used (for example, 5 kW).

The laser control unit 22 starts up the pulse laser beam LB _S from the base output (zero watts) to the peak output P _S at _a predetermined time point ta on the condition of the set peak output P _S and the pulse width T _S. At time t _b (t _b = t _a + T _S ), the laser power supply unit 12 is controlled so that the pulse laser beam LB _S falls from the peak output P _S to the base output (zero watts). However, the time delay of the electrical control system in the laser control unit 22 and the laser power supply unit 12 and the delay of the pulse oscillation operation in the laser oscillation unit 10 (particularly the time delay related to the inversion distribution state) are added. The rising edge time t _a ′ and the falling edge time t _b ′ of the pulse laser beam LB _S actually emitted from the laser oscillation unit 10 are the rising edge time t _a and the rising edge expected by the laser control unit 20. Delayed by δt _α and δt _β from the time t _{b of the} falling edge, respectively. The time delays δt _α and δt _β of the rising edge and the falling edge vary depending on individual laser processing apparatuses (so-called machine differences or individual differences) even in the same model, and various types of laser processing apparatuses also have various delays. It varies depending on factors (temperature characteristics, changes over time, etc.). In addition, an error δP can also occur between the set peak output P _S and the actual peak output P _S ′, and correcting (removing) this error δP is also the purpose of laser output calibration.

In the optical power monitor 18, the optical power meter 28 receives the single pulse laser beam LB _S emitted from the laser oscillation unit 10 through the total reflection mirror 32, and receives the laser energy ELB _S of the pulse laser beam LB _S. taking measurement. In this case, since the optical power meter 28 measures the laser energy ELB _S corresponding to the area of the pulse waveform of the pulse laser beam LB _S (shaded portion in FIG. 2), the rising edge and the falling edge of the pulse laser beam LB _S A net laser energy measurement value [ELB _S ] with high accuracy reflecting the time delays δt _α and δt _β is obtained. The laser energy measurement value [ELB _S ] acquired by the optical power meter 28 is sent to the calibration unit 26 of the control unit 14.

On the other hand, the PIN photodiode 30 receives the pulse laser beam LB _S as the scattered light ΔLB _s from the optical power meter 28 and outputs an output signal having a pulse waveform corresponding to the light intensity of the pulse laser beam LB _S , that is, the laser output waveform. Occur. Here, the PIN photodiode 30 can detect the laser output waveform of the received pulsed laser beam LB _S at high speed and with high sensitivity, but, as shown in FIG. 2C, the base level and the peak level of the output signal. Is likely to be mixed with large noise (generally white noise). For this reason, the output signal of the PIN photodiode 30 is not suitable as monitor information for directly measuring the laser output of the pulsed laser light LB _S. However, the rising edge and the falling edge of the output signal of the PIN photodiode 30 are not affected by noise, and clearly and faithfully represent the rising edge and the falling edge of the received pulse laser beam LB _S.

In this embodiment, using such output characteristics of the PIN photodiode 30, the calibration unit 26 of the control unit 14 converts the output signal of the PIN photodiode 30 into a pulse shaping circuit (eg, a comparator having a predetermined threshold value TH). 2), a binary signal as shown in FIG. 2D, that is, a pulse width measurement signal is obtained. The pulse width [T _S ′] of this pulse width measurement signal corresponds to the pulse width of the output signal of the PIN photodiode 30, and as a result, the pulse width (t _S of the pulse laser light LB _S actually emitted from the laser oscillation unit 10. _a ′ to t _b ′).

Next, the calibration unit 26 divides the measured laser energy value [ELB _S ] taken from the optical power meter 28 by the measured pulse width value [T _S ′], thereby measuring the measured laser energy value per unit time (T Joule / s) or normalized laser power measurement MP _s corresponding to the average peak power measurement (watts) is obtained. Here, MP _s = [ELB _S ] / [T _S '].

Next, the calibration unit 26 uses the normalized laser output measurement value MP _s related to the actual pulsed laser light LB _S acquired as described above, and the laser output reference related to the pulsed laser light LB _S set in the setting unit 20. compared to P _S (laser energy per or unit time) value, i.e. peak power, a deviation [delta] P. Here, a δP = MP _s -P _S or δP = P _S -MP _s.

When the deviation δP is zero, the normalized laser output measurement value MP _s matches the reference value P _S. Therefore, the laser output characteristic of the laser generator 25 is in a normal state, and the calibration unit 26 determines that correction (calibration) is unnecessary. In this case, the calibration of the laser output by the calibration unit 26 is not performed in the laser control unit 22 and / or the laser power source unit 12.

However, when the deviation δP is a significant value, the normalized laser output measurement value MP _s is deviated from the reference value P _S. In this case, the calibration unit 26 applies correction (calibration) to the laser output characteristic of the laser generation unit 25 so that the deviation δP becomes zero through the laser control unit 22 and / or the laser power source unit 12. For example, the laser power supply unit 12 calibrates the amplification factor of an amplification circuit for amplifying current, voltage, or power supplied to the laser oscillation unit 10. Alternatively, the laser control unit 22 calibrates the control amount for the laser power supply unit 12. It is also possible to repeat the automatic calibration operation using the single pulse laser beam LB _S as described above until the deviation δP matches or approximates zero.

As described above, in this first embodiment, since the laser output is calibrated using the single pulse laser beam LB _S having a short duration, continuous oscillation (CW) as shown in FIG. Compared with the conventional laser output calibration method using the above laser beam, the time required for the calibration process is greatly reduced and the heat input to the optical power meter 28 is very small. Therefore, even if the optical power meter 28 does not include a cooling mechanism, the optical power meter 28 can stably perform the measurement operation. Further, even if the rising edge and the falling edge of the calibration pulse laser beam LB _S generated by the laser generator 25 have an indefinite time delay, the optical power meter 28 accurately determines the laser energy of the pulse laser beam LB _S. Just measure it. Alternatively, PIN Photodiode 30 is a rising edge and a falling edge of the pulsed laser beam LB _S accurately detected at high speed response, obtain measurements of high accuracy with respect to the pulse width T _S 'of the pulsed laser beam LB _S. As a result, it is possible to acquire highly reliable monitor information for laser output calibration in the entire optical power monitor unit 18 (optical power meter 28 and PIN photodiode 30). For this reason, a simple and small optical power meter can be used as the optical power meter 28. Therefore, even if the total reflection mirror built-in type is adopted, there is no problem in making the device compact and saving space.

[Example 2]

In the first embodiment described above, the laser output was calibrated using the single pulse laser beam LB _S. According to the present invention, as shown in FIG. 3C, it is also possible to use repetitive (continuous) pulsed laser beams LB _S1 , LB _{S2 ,.} is there.

In this case as well, the waveform of the pulse laser beam LB _S may be arbitrary, but a rectangular pulse waveform is usually selected. Here, the pulse width T _S is not particularly limited, but considering the general performance of the optical power meter 28, the pulse width T _S is in the range of 0.1 ms to 100 ms as in the first embodiment (single pulse system). preferable. Individual pulsed laser beam _{LB Si (i = 1,2, ··} ) the peak output P _S of may be set according to the rated output of the laser processing apparatus. The repetition frequency of the continuous pulse is preferably in the range of 10 ppm to 10 kppm in consideration of the general performance of the optical power meter 28. For example, when the pulse width T _{S is set} to 1 ms, the peak output P _S is set to 6 kW, and the repetition frequency is set to 10 pps, the laser output (set value) of the repeated pulse laser beams LB _S1 , LB _S2 ,. The duty D is 1%.

When the second embodiment (repetitive pulse method) is applied to the laser processing apparatus (FIG. 1) instead of the first embodiment (single pulse method), the optical power meter 28 of the optical power monitor unit 18 is The laser outputs of the repetitively pulsed laser beams LB _S1 , LB _S2 ,... Are measured. For example, repeated pulsed laser beam LB _S1, LB _S2 per unit time (1 sec), the laser energy ... measured may be the laser energy measurement value per unit time and the laser output measured value mP _S. In that case, even if the optical power meter 28 cannot accurately detect (or ignore) the time of the rising edge and the falling edge of each pulse laser beam LB _Si , the pulse laser beams LB _S1 and LB are repeatedly detected. _S2, it is possible to obtain a high measurement value mP _S precision for the laser output.. (laser energy per unit time).

On the other hand, PIN Photodiode 30, the pulsed laser beam LB _S1 repeated as scattered light DerutaLB _s from the optical power meter 28, LB _S2, receives ..., their repetition of the pulse laser beam LB _S1, LB _S2, · · An output signal having a pulse waveform corresponding to the light intensity waveform, that is, the laser output waveform is generated. As in the first embodiment, the rising edge and the falling edge of the output signal of the PIN photodiode 30 are not affected by noise, and the rising edge of the received repetitive pulsed laser beams LB _S1 , LB _S2 ,. And the falling edge is clearly and faithfully represented.

The calibrating unit 26 of the control unit 14 repeatedly detects the time points of the rising edge and the falling edge of the pulse laser beams LB _S1 , LB _S2 ,. The average value (or representative value) of _s and period T _c is measured, and duty D is measured. Here, when the measured value of the duty D is MD (%), MD = 100 × T _s / T _c .

Next, from the calibration unit 26, repetitive pulse laser light LB _S1, LB _S2, the duty measurements MD obtained through laser output measured value mP _S and PIN photodiode 30 which is acquired by the power meter 28 for ..., Normalized laser output measurement value corresponding to the laser output of the repetitively pulsed laser beams LB _S1 , LB _S2 ,... When the duty is replaced with 100% (that is, the laser output when converted to the continuous wave laser beam LB). MP _S is calculated. Here, MP _S = 100 × mP _S / MD. Therefore, for example, when mP _S = 58 W and MD = 0.98, MP _S = 5.92 kW.

Next, the calibration unit 26 sets the normalized laser output measurement value MP _s related to the actual repetitive pulsed laser beams LB _S1 , LB _S2 ,. The deviation δP is obtained by comparison with a reference value, that is, a peak output or a rated value P _S. Here, a δP = MP _s -P _S or δP = P _S -MP _s. As in the first embodiment, when the deviation δP is a significant value, the deviation δP is set to zero in the laser output characteristics of the laser generation unit 25 through the laser control unit 22 and / or the laser power supply unit 12. Apply such correction (calibration).

As described above, in the second embodiment, since the laser output is calibrated using the repetitively pulsed laser beams LB _S1 , LB _S2 ,..., The conventional laser output using the continuous wave (CW) laser beam is used. Compared to the calibration method, although not as much as in the first embodiment, the time required for the calibration process is greatly shortened and the heat input to the optical power meter 28 is small. Therefore, also in the second embodiment, the simple and small optical power meter 28 can be used regardless of the level of the laser output (particularly even if the laser output is kW class). Further, the normalized laser output measurement value MP _S averaged for a large number of continuous pulsed laser beams LB _S1 , LB _S2 ,... Is obtained, so that the laser is obtained by one calibration process (usually within 10 seconds). The output can also be calibrated accurately.

In this embodiment, the calibration unit 26 in the control unit 14 also functions as a calculation unit and a duty measurement unit. However, these functions can be separated and independent.

[Example 3]

  FIG. 4 shows an embodiment (third embodiment) in which the present invention is applied to a general fiber laser processing apparatus. In the figure, parts having the same configuration or function as those of the first or second embodiment described above are denoted by the same reference numerals.

  A laser oscillation unit 10 of this fiber laser processing apparatus includes an oscillation optical fiber (hereinafter referred to as “oscillation fiber”) 40 and electro-optical excitation that irradiates one end surface of the oscillation fiber 40 with pumping excitation light MB. And a pair of optical resonator mirrors 44 and 46 that are optically opposed to each other via the oscillation fiber 40. The electro-optical excitation unit 42 includes a laser diode (LD) 48 as an excitation light source and a condensing optical lens 50.

To measure the LD drive current I _D supplied to the laser power source 12 from the LD 30, a current sensor 52 and the LD current measurement circuit 54 are provided. The current sensor 52 is composed of, for example, a Hall element, and detects the LD drive current _ID without contact. LD current measurement circuit 54 inputs the output signal of the current sensor 52 a current measuring value of the LD drive current I _D (eg, current effective value) is calculated M _ID. The current measurement value M _ID obtained by the LD current measurement circuit 54 is given to the laser power source 12 as a feedback signal.

The processing laser beam LB (or the calibration pulse laser beam LB _S ) emitted from the laser oscillation unit 10 enters the laser incident unit 58 through the partial reflection mirror (beam splitter) 56.

The partial reflection mirror 56 reflects a part (for example, 1%) of the incident laser beam LB (or pulsed laser beam LB _S ) toward a predetermined direction, that is, the PIN photodiode 60 for power monitoring, and the remaining most (99 %) Straight. A condensing lens 62 that condenses the reflected light or the branched light ΔLB (ΔLB _s ) from the partial reflection mirror 56 is disposed in front of the PIN photodiode 60.

The PIN photodiode 60 photoelectrically converts the branched light ΔLB (ΔLB _s ) from the partial reflection mirror 56, and an electric signal (laser output measurement) representing the light intensity or laser output of the laser light LB (or pulsed laser light LB _S ). Signal). The laser output measurement circuit 64 obtains the laser output measurement value MP _s of the laser beam LB (or the pulsed laser beam LB _S ) by analog signal processing based on the output signal of the PIN photodiode 60. The laser output measurement value MP _s obtained by the laser output measurement circuit 64 is given to the laser power source 12 as a feedback signal.

  In this embodiment, the PIN photodiode 60 also serves as the PIN photodiode 30 of the optical power monitor unit 18. When the laser output is calibrated, the output signal of the PIN photodiode 60 is the control unit 14 (calibration unit 26). It is supposed to be taken in.

The laser beam LB (or pulsed laser beam LB _S ) that has passed straight through the partial reflection mirror 56 and entered the laser incident portion 58 is first folded in a predetermined direction by the vent mirror 66, and then the condenser lens in the incident unit 68. The light is condensed by 70 and is incident on one end face of a transmission optical fiber (hereinafter referred to as “transmission fiber”) 74 of the fiber transmission system 72. The transmission optical fiber 74 is made of, for example, an SI (step index) type fiber, and transmits the laser beam LB (or pulsed laser beam LB _s ) incident in the incident unit 68 to the emission unit 76 of the laser emission unit. The emission unit 76 arranges the collimating lens 78 for collimating the pulsed laser beam FB emitted from the end face of the transmission fiber 74 into parallel light, and the paralleled laser beam LB (or pulsed laser beam LB _s ) at a predetermined processing position. And a condensing lens 80 for condensing light on the workpiece W.

In this fiber laser processing apparatus, when the laser output is calibrated, an optical power meter 28 is arranged at the processing position instead of the workpiece W. As in the first or second embodiment described above, the single-shot pulse laser beam LB _S as shown in FIG. 3B or the (c) of FIG. 3 is used as the calibration laser beam. The repetitive pulsed laser beams LB _S1 , LB _S2 ,... LB _S as shown in FIG.

Calibration single-shot pulsed laser light LB _S (or repetitively pulsed laser light LB _S1 , LB _S2 ,...) Emitted from the laser oscillation unit 10 is incident on the partial reflection mirror 56 and branched light ΔLB _S (1 %) Is incident on the PIN photodiode 60, and the remaining (99%) is incident on the optical power meter 28 at the processing position through the laser incident part 58, the fiber transmission system 72, and the laser emitting part 75.

  The optical power meter 28 may be a simple and small one that does not include a cooling mechanism, has the same configuration or function as in the case of the first embodiment or the second embodiment, and performs the same measurement operation. The PIN photodiode 60 (30) also has the same configuration or function as in the first or second embodiment, and performs the same light detection or photoelectric conversion operation.

  Also in the control unit 14, the calibration unit 26 has the same configuration or function as in the case of the first embodiment or the second embodiment, and performs the same calibration (calculation, determination, correction, etc.) processing. In particular, in this embodiment, an amplification circuit (not shown) for amplifying the sensor signal or the feedback signal is provided in the LD current measurement circuit 54 of the current feedback loop and the laser output measurement circuit 64 of the power feedback loop. . The calibration unit 26 can adjust the amplification factors of these amplifier circuits in order to apply correction (calibration) to the laser output characteristics of the laser generation unit 25 so that the deviation δP becomes zero.

In the third embodiment, the same function and effect as in the first embodiment or the second embodiment can be obtained. In particular, regardless of the level of the laser output (especially kW class laser output), a simple, small and inexpensive optical power meter 28 can be used. Further, when the stand-alone type is adopted, the handling of the optical power meter 28 is easy, and anyone can set the optical power meter 28 at the processing position with the correct posture and orientation.

[Example 4]

  FIG. 5 shows an embodiment (fourth embodiment) in which the present invention is applied to a MOPA (Master Oscillator Power Amplifier) type fiber laser processing apparatus. In the figure, parts having the same configuration or function as those of the first, second, or third embodiments are denoted by the same reference numerals.

  This MOPA type fiber laser processing apparatus includes a seed light generation unit 100, first and second amplification optical fibers (hereinafter referred to as “active fibers”) 102 and 104, and a laser irradiation unit 106, and isolators 108, 110, and 112, and Optically cascaded through optical couplers 114 and 116.

  The seed light generation unit 100 is a seed laser diode (hereinafter referred to as “seed LD”) 118 and a seed that drives the seed LD 118 with a pulse waveform or continuous wave (CW) current to generate pulse oscillation or continuous oscillation. And an LD power supply circuit 120. The seed LD 118 is configured as a fiber coupling LD.

  The optical coupler 114 provided between the seed light generating unit 100 and the first active fiber 102 includes a plurality of, for example, three input ports 114IN (1), 114IN (2), 114IN (3) and one output port 114OUT. And have. A seed LD 118 is connected to the first input port 114IN (1) through an isolator 108. An excitation LD (hereinafter referred to as “pump LD”) 122 for exciting the core of the first active fiber 102 is connected to the second input port 114IN (2). The third input port 114IN (3) is an expansion port, and another pump LD 122 (not shown) can be connected to the third input port 114IN (3). The input port of the active fiber 102 is connected to the output port 114OUT.

  The seed light generation unit 100, the isolator 108, and the optical coupler 114 constitute a seed light injection unit for the first active fiber 102. The pump LD 122 and the optical coupler 114 constitute an excitation light injection unit for the first active fiber 102.

  The first active fiber 102 has a core made of quartz to which at least Yb ions are added and a clad made of, for example, quartz surrounding the core coaxially, and the total length (fiber length) is selected to be, for example, 3 to 15 m. It is. The gain of the first active fiber 102 (first stage amplifier) can be adjusted, for example, in the range of 10 to 40 dB by the total output of the pump LD 122.

  The optical coupler 116 provided between the first active fiber 102 and the second active fiber 104 includes a plurality of, for example, seven input ports 116IN (1), 116IN (2) to 116IN (7) and one output port. 116OUT. The output terminal of the first active fiber 102 is connected to the first input port 116IN (1) through the isolator 110. Pumps LD 124 for exciting the core of the second active fiber 104 are connected to the second to fifth input ports 116IN (2) to 116IN (5), respectively. The sixth and seventh input ports 116IN (2) and 116IN (7) are vacant ports, but a pump LD can be added as necessary. The input port of the second active fiber 104 is connected to the output port 116OUT.

  Similarly to the first active fiber 102, the second active fiber 104 also has a core made of quartz to which at least Yb is added and a clad made of, for example, quartz that surrounds the core coaxially. For example, 3-15 m. The gain of the second active fiber 104 (second stage amplifier) can be adjusted, for example, in the range of 10 to 40 dB by the total output of the pump LD124.

  The pumps LD 122 and 124 used for pumping the first and second active fibers 102 and 104 are driven by a pump LD power supply circuit 134 in accordance with a control signal PC from the control unit 14. The pump LD power supply circuit 134 and the seed LD power supply unit 120 constitute the laser power supply unit 12.

  The laser irradiation unit 106 receives the processing laser beam LB extracted from the output end of the second active fiber 104 via an optical transmission system such as the collimator 130 and the vent mirror 132, and the received laser beam LB is processed. The work piece W arranged in FIG.

A PIN photodiode 30 is attached near the exit of the laser irradiation unit 106. The PIN photodiode 30 receives scattered light ΔLB _S from the optical power meter 28 disposed at the processing position when the laser output is calibrated.

  In the MOPA type fiber laser processing apparatus, when the laser output is calibrated, the optical power meter 28 is disposed at the processing position instead of the workpiece W. The optical power meter 28 may be a simple and small one that does not include a cooling mechanism, has the same configuration or function as in the case of the first embodiment or the second embodiment, and performs the same measurement operation.

As in the first or second embodiment described above, the single-shot pulse laser beam LB _S as shown in FIG. 3B or the (c) of FIG. 3 is used as the calibration laser beam. The repetitive pulsed laser beams LB _S1 , LB _S2 ,... LB _S as shown in FIG. In this case, if the seed LD 118 is pulse-oscillated, the pulse width is as short as about 200 nsec. Therefore, in this embodiment, the seed LD 118 is continuously oscillated. Instead, the pump LDs 122 and 124 are pulse-oscillated with a pulse width of about 0.1 msec to 10 msec, for example, so that the single-pulse laser beam LB _S for calibration or the repetitive pulse laser beams LB _S1 , LB _S2 ,. Generate LB _S

  Also in the control unit 14, the calibration unit 26 has the same configuration or function as in the first embodiment, the second or third embodiment, and performs the same calibration (calculation, determination, correction, etc.) processing. Do. In particular, in this embodiment, the pump LD power supply circuit 134 and the seed LD power supply unit 120 are provided with an amplifier circuit (not shown) for adjusting the LD drive current. The calibration unit 26 can adjust the amplification factors of these amplifier circuits in order to apply correction (calibration) to the laser output characteristics of the laser generation unit 25 so that the deviation δP becomes zero.

In the fourth embodiment, the same function and effect as in the first, second, or third embodiment can be obtained. In particular, regardless of the level of the laser output (especially kW class laser output), a simple, small and inexpensive optical power meter 28 can be used. Further, when the stand-alone type is adopted, the handling of the optical power meter 28 is easy, and anyone can set the optical power meter 28 at the processing position with the correct posture and orientation.

[Other Examples or Modifications]

  As mentioned above, although preferred embodiment of this invention was described, embodiment mentioned above does not limit this invention. Those skilled in the art can make various modifications and changes in specific embodiments without departing from the technical idea and technical scope of the present invention.

For example, in the first or second laser processing apparatus (FIG. 1), the total reflection mirror 32 can be replaced with a partial reflection mirror. In this case, when the laser output is calibrated, the damper is disposed at the machining position instead of the workpiece W. According to the present invention, the single pulse laser beam LB _{S having} a short duration or the repetitive pulse laser beams LB _S1 , LB _S2 ,... LB _S is incident (heat input) on the damper, so that the damper has a cooling mechanism. There is no need to provide it.

Further, the PIN photodiode 30 only needs to be able to detect the pulse waveform of the calibration pulse laser beam LB _S (LB _S1 , LB _S2 ,...), So that the pulse laser leaks or scatters on the laser transmission path of the laser processing apparatus. The light LB _S (LB _S1 , LB _S2 ,...) Can be arranged at an arbitrary position where the pulse laser beam can be received.

  Of course, a large power meter having a cooling mechanism can be used as the optical power meter 28.

  In addition, a fiber laser oscillator having a fiber Bragg grating (FBG) or a fiber laser oscillator having a combiner (optical coupler) is used as the laser oscillation unit 10 in the third embodiment (FIG. 4) according to the fiber laser processing apparatus. Is also possible.

DESCRIPTION OF SYMBOLS 10 Laser oscillation part 12 Laser power supply part 14 Control part 18 Optical power monitor part
DESCRIPTION OF SYMBOLS 20 Setting part 22 Laser control part 26 Calibration part 28 Optical power meter 30 PIN photodiode 32 Total reflection mirror 54 LD current measurement circuit 60 PIN photodiode 64 Laser output measurement circuit 120 Seed LD power supply circuit 134 Pump LD power supply circuit

Claims (19)

A laser output calibration method for calibrating laser output in a laser processing apparatus,
A step of setting a peak output and a pulse width of the pulse laser beam in the laser processing apparatus;
A step of generating a single pulse laser beam by a laser generation unit of the laser processing apparatus on the condition of the set peak output and pulse width;
Making the pulse laser beam generated by the laser generator incident on an optical power meter, and measuring the laser energy of the pulse laser beam with the optical power meter;
Making the pulse laser beam generated by the laser generator incident on a photodiode capable of high-speed response, and measuring a pulse width of the pulse laser beam based on an output signal of the photodiode;
A normalized laser output measurement corresponding to a laser energy measurement value or an average peak output measurement value per unit time related to the pulse laser light from the laser energy measurement value and the pulse width measurement value related to the pulse laser light. A process for determining a value;
A method of calibrating the laser output characteristics of the laser generating unit so as to make a deviation between the normalized laser output measurement value and the set peak output zero.   The laser output calibration method according to claim 1, wherein the pulse laser beam has a rectangular pulse waveform, and a pulse width thereof is set to 0.1 ms to 100 ms. A laser output calibration method for calibrating laser output in a laser processing apparatus,
A step of setting a peak output, a pulse width and a repetition frequency of a repetitively pulsed laser beam in the laser processing apparatus;
A step of repeatedly generating a pulsed laser beam by a laser generating unit of the laser processing apparatus on the condition of the set peak output, pulse width and repetition frequency;
Making the repetitive pulse laser beam generated by the laser generator incident on an optical power meter, and measuring the laser output of the repetitive pulse laser beam by the optical power meter; and
Making the repetitive pulsed laser light generated by the laser generator incident on a photodiode capable of high-speed response, and measuring the duty of the repetitive pulsed laser light based on the output signal of the photodiode;
A normalized laser output measurement value corresponding to the laser output of the repetition pulse laser beam when the duty is replaced with 100% is obtained from the measurement value of the laser output and the measurement value of the duty related to the repetition pulse laser beam. Process,
A method of calibrating the laser output characteristics of the laser generating unit so as to make a deviation between the normalized laser output measurement value and the set peak output zero.   4. The laser output calibration method according to claim 3, wherein each pulse laser beam constituting the repetitive pulse laser beam has a rectangular pulse waveform, and the pulse width is set to 0.1 ms to 100 ms.   The laser output calibration method according to claim 3 or 4, wherein a repetition frequency of the repetitive pulsed laser light is set to 10 pps to 10 kpps.   The laser power calibration method according to claim 1, wherein the optical power meter receives the pulsed laser light from the laser generation unit via a total reflection mirror or a partial reflection mirror.   6. The laser output calibration method according to claim 1, wherein the optical power meter receives the pulsed laser light at a position where a workpiece is subjected to laser processing by the laser processing apparatus.   The laser output calibration method according to claim 1, wherein the photodiode receives the pulsed laser light scattered from a light receiving surface of the optical power meter.   The laser output calibration method according to claim 1, wherein the photodiode receives the pulsed laser light from the laser generation unit via a partial reflection mirror.   The laser output calibration method according to any one of claims 1 to 7, wherein the photodiode receives the pulsed laser light leaked or scattered on a laser transmission path of the laser processing apparatus.   The laser output calibration method according to claim 1, wherein the photodiode is a PIN photodiode. A condition setting unit for setting the peak output and pulse width of the pulse laser beam;
A laser generator that generates a single pulse laser beam on the condition of the peak output and the pulse width set by the condition setting unit;
An optical power meter that receives the pulse laser beam generated by the laser generator and measures the laser energy of the pulse laser beam; and
A photodiode capable of high-speed response that receives the pulsed laser light generated by the laser generator and generates an electrical signal according to the light intensity of the pulsed laser light;
A pulse width measuring unit that measures the pulse width of the pulsed laser light based on the output signal of the photodiode;
From the measured value of the laser energy obtained from the optical power meter and the measured value of the pulse width obtained from the photodiode, it corresponds to a measured value of laser energy or an average peak output value per unit time of the pulsed laser light. A calculation unit for calculating a normalized laser output measurement value;
The laser processing apparatus which has a calibration part which calibrates the laser output characteristic of the said laser production | generation part so that the deviation of the said normalized laser output measured value and the said set peak output may be set to zero. A condition setting unit for setting the peak output, pulse width and repetition frequency of the repetitive pulse laser beam;
A laser generator that repeatedly generates pulsed laser light on condition that the peak output, the pulse width, and the repetition frequency set by the condition setting unit;
An optical power meter that receives the repetitive pulse laser beam generated by the laser generator and measures the laser output of the repetitive pulse laser beam; and
A photodiode capable of high-speed response that receives the pulsed laser light generated by the laser generation unit and generates an electrical signal corresponding to the light intensity of the pulsed laser light;
A duty measuring unit that measures the duty of the repetitively pulsed laser light based on an output signal of the photodiode;
A normal value corresponding to the laser output of the repetitively pulsed laser light when the duty is replaced with 100% from the measured value of the laser output obtained from the optical power meter and the measured value of the duty obtained from the duty measuring unit. A calculation unit for calculating the measured laser output measurement value;
The laser processing apparatus which has a calibration part which calibrates the laser output characteristic of the said laser production | generation part so that the deviation of the said normalized laser output measured value and the said set peak output may be set to zero. The laser generation unit controls the laser power supply unit, a laser oscillation unit that generates laser light upon receiving power supply, a laser power supply unit that supplies power for continuous oscillation or pulse oscillation to the laser oscillation unit, and the laser power supply unit A laser control unit,
The calibration unit calibrates an amplification factor of an amplification circuit that amplifies current, voltage, or power supplied to the laser oscillation unit in the laser power source unit.
The laser processing apparatus of Claim 12 or Claim 13. The laser generation unit receives a supply of electric power to generate a laser beam, a laser power supply unit that supplies electric power for continuous oscillation or pulse oscillation to the laser oscillation unit, and the laser power supply unit A laser control unit for controlling the current value of the driving or excitation current supplied to the oscillation unit;
The laser processing apparatus according to claim 12, wherein the calibration unit calibrates a control amount given from the laser control unit to the laser power supply unit. The laser control unit controls the laser power supply unit using a current feedback loop, and detects a current for driving or excitation, and a current of the current based on an output signal of the current sensor. A current measurement circuit that generates a feedback signal representing a measurement value, and an amplification circuit provided in the current measurement circuit to amplify the feedback signal;
The calibration unit calibrates the amplification factor of the amplifier circuit;
The laser processing apparatus according to claim 15. The laser control unit is configured to receive a part of the laser beam generated from the laser generation unit and control the laser power source unit using a power feedback loop, and represents an electric signal representing the laser output of the laser beam. A laser output measuring circuit for generating a feedback signal representing a laser output measurement value of the laser light based on an output signal of the photoelectric conversion element, and the laser output for amplifying the feedback signal An amplifier circuit provided in the measurement circuit,
The calibration unit calibrates the amplification factor of the amplifier circuit;
The laser processing apparatus according to claim 15.   13. A total reflection mirror or a partial reflection mirror that is movable between a first position for optically coupling the laser generator and the optical power meter and a second position for retraction is provided. The laser processing apparatus as described in any one of -17.   The laser processing apparatus according to claim 12, wherein the photodiode is a PIN photodiode.

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