JP2010188368A - Optical fiber transmission monitoring system, and laser beam machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To instantaneously perform safety measures without any substantial time delay with a simple configuration and in high monitoring precision and reliability in the occurrence of abnormality of an optical fiber transmission system in a laser beam machine of an optical fiber transmission system. <P>SOLUTION: The laser beam machining apparatus comprises, in a simultaneous bisected optical fiber transmission system, a laser generator 12, a branching unit 14, an incident unit 16, optical fibers 18(1), 18(2), exit units 20(1), 20(2), and a controller 22, comprising in addition an optical fiber transmission monitoring section 24 that performs normal monitoring and abnormality detection of the optical fiber transmission system including the optical fibers 18(1), 18(2). The optical fiber transmission monitoring section 24 is composed of a monitoring light source 50, an optical superimposing unit 52, optical separating units 54(1), 54(2), optical detectors 56(1), 56(2), and an interlocking mechanism 58. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a laser processing apparatus that performs desired laser processing by irradiating a workpiece with laser light, and in particular, an optical fiber transmission type laser that transmits laser light through an optical fiber from a laser generator to an emission unit. It relates to a processing apparatus.

  As a basic configuration, a laser processing apparatus includes a laser generation unit that generates a processing laser beam, an emission unit that focuses and irradiates the processing laser beam toward a workpiece, and a laser beam from the laser generation unit to the emission unit. A laser transmission optical system.

  An optical fiber transmission system that uses an optical fiber in a laser transmission optical system can be installed or placed at any place in the laser oscillation section and the emission unit, so it can be flexibly adapted to various production lines and applications of laser processing. There is an advantage.

  In general, an optical fiber for transmission used in laser processing of an optical fiber transmission system is covered with a flexible protective tube such as a metal spiral tube, but the optical fiber can be arbitrarily used in a factory or a work place. It may be bent or receive external force or impact to cause breakage or damage. Of course, if the optical fiber is broken or damaged, the laser beam for processing output from the laser generator is not normally transmitted to the emission unit, and the desired laser processing cannot be performed. However, what is more important than that is that the laser beam for processing leaks from the breakage or breakage of the optical fiber and heats the protective tube. In the worst case, the risk of leaking out of the protective tube is completely prevented. It is to be. Particularly in recent laser processing, since high-power processing laser light has been frequently used, safety measures against breakage and breakage of an optical fiber for laser transmission have become one of the most important items.

  Accordingly, when the optical fiber for laser transmission is broken or damaged during the operation of the laser processing apparatus, the laser output operation of the laser generator is immediately stopped, and the optical fiber is disconnected while the operation of the laser processing apparatus is suspended. A monitoring or safety device is required to stop the laser output operation of the laser generator when it breaks or breaks.

  Initially, this type of monitoring apparatus includes a photodetector that photoelectrically converts reflected light or leakage light of a processing laser beam generated from an optical lens or the like in an emission unit, and the amount of light received by the photodetector is electrical. If the optical reference level is equal to or higher than the reference level, it is determined that the optical fiber is not broken. If the amount of light received by the photodetector is equal to or lower than the electric reference level, the optical fiber is determined to be broken. However, in this method, when the output of the processing laser beam is considerably low, the optical fiber breaks if the amount of light received by the photodetector is below the reference level even if the optical fiber is not actually broken. The monitoring accuracy and reliability were low.

  Nowadays, it is a common practice to use monitor light dedicated to breakage detection separately from the processing laser light. The optical fiber breakage inspection apparatus using monitor light is a first method (for example, Patent Document 1) in which a dedicated optical fiber is provided along with the original optical fiber for transmitting the processing laser light, or monitor light. Is superposed on the laser beam for processing and propagated in the optical fiber for laser processing (for example, Patent Document 2).

  In the first method, a monitor light source and a photodetector are used to check whether the monitor light propagates normally in the optical fiber dedicated to the monitor. It is assumed that the optical fiber is broken together with the optical fiber for laser processing.

  In the conventional inspection apparatus that employs the second method, the monitor light is superimposed on the processing laser light to propagate through the optical fiber, and the monitor light immediately before entering the one end surface of the optical fiber is the first light. While the photoelectric conversion is performed by the detector, the monitor light immediately after coming out from the other end face of the optical fiber is photoelectrically converted by the second photodetector. Then, the comparison / determination unit calculates the ratio of both detection signals from the first and second photodetectors, compares the calculation result with a reference value, and the comparison error is within an allowable range. It is determined that the optical fiber is not broken, and if the comparison error is outside the allowable range, it is determined that the optical fiber is broken. Then, based on the determination result obtained by the comparison determination unit, when the optical fiber is not broken, the control unit operates the power source of the processing laser oscillation unit normally or as planned, and the optical fiber is broken. Sometimes, the operation of the laser power source is stopped or stopped.

JP2000-422771 JP-A-2-258185

  In the conventional optical fiber breakage inspection apparatus, the first method has a large and complicated installation of the monitor-dedicated optical fiber, and the monitor-dedicated optical fiber and the laser processing optical fiber are not always broken together. In addition, low monitoring reliability is a major practical disadvantage.

  On the other hand, the conventional apparatus adopting the second method has a simple configuration because it does not require a monitor-dedicated optical fiber, and has high monitoring accuracy because it directly detects the breakage of the processing optical fiber. However, when the optical fiber breaks, a time corresponding to the arithmetic processing of the comparison determination unit and the command processing of the control unit from when the output signal of the second photodetector changes until the operation of the laser power supply is stopped. Therefore, there is a certain time delay (usually several μs or more), and the processing laser light may leak from the broken portion of the optical fiber during this time delay. That is, there is a problem in the operation speed as a safety device. In addition, there is a risk that the comparison / determination unit or the control unit may malfunction or run away due to the influence of noise or the like received from the outside or the outside, and there is also one aspect that absolute reliability and reliability as a safety device are low.

  The present invention has been made in view of the above-described problems of the prior art. In an optical fiber transmission system, the configuration is simple, the monitoring accuracy and reliability are high, and the optical fiber transmission system is substantially effective when an abnormality occurs. An object of the present invention is to provide a high optical fiber transmission system monitoring apparatus and a laser processing apparatus capable of instantaneously performing a safety measure operation without a significant time delay.

  In order to achieve the above object, an optical fiber transmission system monitoring apparatus according to the first aspect of the present invention transmits a processing laser beam output from a laser generator to an emission unit through an optical fiber, An optical fiber transmission system monitoring apparatus that performs normal monitoring and abnormality detection of an optical fiber transmission system in a laser processing apparatus that performs desired laser processing by condensing and irradiating the workpiece with the laser beam from an emission unit, A monitor light source for generating monitor light having a wavelength different from that of the laser light for light, a light superimposing device for superimposing the monitor light from the monitor light source on the laser light for processing and making it incident on an incident end face of the optical fiber, and the light A light separator that separates at least a part of the monitor light emitted from the output end face of the fiber from the processing laser light; and a photoelectric converter that receives light from the light separator. A light detection unit that outputs an electrical signal, outputs a first monitor signal when the amount of received light is higher than a predetermined threshold, and outputs a second monitor signal when the amount of received light is lower than the threshold; The laser is electrically connected to the output terminal of the light detection unit, and the first monitor signal is output from the light detection unit while the monitor light source is generating the monitor light. An interlock mechanism for permitting or continuing the laser output operation of the generator, and prohibiting or stopping the laser output operation of the laser generator when the second monitor signal is output from the light detector And have.

  An optical fiber transmission system monitoring device according to a second aspect of the present invention transmits a processing laser beam output from a laser generator operating under the control of a controller through an optical fiber to an emission unit, An optical fiber transmission system monitoring apparatus that performs normal monitoring and abnormality detection of an optical fiber transmission system in a laser processing apparatus that performs desired laser processing by condensing and irradiating the workpiece with the laser beam from an emission unit, A monitor light source for generating monitor light having a wavelength different from that of the laser light for light, a light superimposing device for superimposing the monitor light from the monitor light source on the laser light for processing and making it incident on an incident end face of the optical fiber, and the light A light separator that separates at least a part of the monitor light emitted from the output end face of the fiber from the processing laser light; and photoelectric conversion by receiving light from the light separator A light detection unit that converts the signal into an electrical signal, outputs a first monitor signal when the amount of received light is higher than a predetermined threshold, and outputs a second monitor signal when the amount of received light is lower than the threshold; The laser is electrically connected to the output terminal of the light detection unit, and the first monitor signal is output from the light detection unit while the monitor light source is generating the monitor light. The control of the generation unit is left to the control unit, and when the second monitor signal is output from the light detection unit, the laser output operation of the laser generation unit is forcibly prohibited in preference to the control unit. Or an interlock mechanism for stopping.

  A laser processing apparatus according to a third aspect of the present invention includes a laser generating unit that generates a processing laser beam, and an optical fiber for transmitting the processing laser beam generated by the laser generating unit to a laser processing site. An emission unit that is installed or arranged at the laser processing location and that condenses and irradiates the workpiece with the processing laser light emitted from the output end face of the optical fiber, and monitor light having a wavelength different from that of the processing laser light. A monitor light source for generating light, an optical superimposer for superimposing the monitor light from the monitor light source on the laser beam for processing and entering the incident end face of the optical fiber, and the monitor exiting from the exit end face of the optical fiber A light separator that separates at least a part of the light from the processing laser light; and the light from the light separator is received and converted into an electrical signal by photoelectric conversion; A first monitor signal is output when the value is higher than the threshold value, and a second monitor signal is output when the amount of received light is lower than the threshold value. The light detection unit is electrically connected directly to the output terminal of the light detection unit. During the period when the monitor light source is generating the monitor light, the laser generation operation is permitted or continued when the first monitor signal is output from the light detection unit. And an interlock mechanism for prohibiting or stopping the laser output operation of the laser generator when the second monitor signal is output from the light detector.

  A laser processing apparatus according to a fourth aspect of the present invention includes a laser generator that generates a laser beam for processing, a control unit that controls the operation of the laser generator, and the laser generator generated by the laser generator. An optical fiber for transmitting the processing laser beam to the laser processing site, and the processing laser beam installed or arranged at the laser processing site and emitted from the emission end face of the optical fiber is focused and irradiated on the workpiece. An emission unit, a monitor light source that generates monitor light having a wavelength different from that of the processing laser light, and light that is incident on the incident end face of the optical fiber by superimposing the monitor light from the monitor light source on the processing laser light A superimposer, a light separator for separating at least a part of the monitor light emitted from the output end face of the optical fiber from the processing laser light, and receiving light from the light separator; Photodetector that converts an electrical signal by photoelectric conversion, outputs a first monitor signal when the amount of received light is higher than a predetermined threshold, and outputs a second monitor signal when the amount of received light is lower than the threshold And when the first monitor signal is output from the light detection unit while the monitor light source is generating the monitor light, and is electrically connected directly to the output terminal of the light detection unit. The control of the laser generation unit is left to the control unit, and when the second monitor signal is output from the light detection unit, the laser generation operation of the laser generation unit is forcibly given priority over the control unit. And an interlock mechanism for prohibiting or stopping.

  In the optical fiber break inspection apparatus or laser processing apparatus of the present invention, monitor light having a wavelength different from that of the processing laser light is superimposed on the processing laser light and passed through the optical fiber, and is monitored by the optical separator on the output unit side. Is separated from the processing laser beam. The light detection unit receives the light separated by the light separator and outputs a first monitor signal when the amount of received light is higher than a predetermined threshold, and the second when the amount of received light is lower than the threshold. Output monitor signal.

  The interlock mechanism is in an operable state during a period in which the monitor light source is generating monitor light, and when the first monitor signal is output from the light detection unit in response to the output signal of the light detection unit. When the laser output operation of the laser generator is permitted or continued (or the control of the laser generator is left to the controller) and the second monitor signal is output from the light detector, the laser output of the laser generator The operation is prohibited or stopped (or the laser output operation of the laser generation unit is forcibly prohibited or stopped in preference to the control unit).

  The interlock mechanism is connected to a power source (preferably a primary power source) of the laser generating unit and / or a driving unit of the optical shutter in order to forcibly prohibit or stop the laser output operation of the laser generating unit.

  As described above, when an abnormality occurs in the optical fiber transmission system, typically, when the optical fiber is broken or broken, the interlock mechanism operates in response to the output signal (second monitor signal) of the light detection unit. The laser output operation of the laser generator is stopped. The time delay associated with the interlock operation is substantially only the interlock mechanism or the switching time in the laser generator, and does not involve the processing of the controller (arithmetic processing, command processing, etc.). Therefore, when an abnormality occurs, it is possible to perform the operation of the safety measure instantaneously without causing a substantial time delay, and the risk of processing laser light leaking from the broken part of the optical fiber is sufficiently prevented or It can be avoided.

  Further, since the interlock mechanism of the present invention does not include an electronic circuit or software for performing comparison operation processing or instruction processing, there is no risk of malfunction or runaway due to noise or the like, and a highly reliable safety device is provided. .

  According to a preferred aspect of the present invention, an aperture for limiting the beam diameter of the monitor light to a desired aperture is disposed between the light separator and the light detection unit. This aperture extracts the portion near the optical axis that propagates through the core of the optical fiber, preferably the central portion where the power density is concentrated, out of the light bundle of the monitor light separated by the light separator, and receives the light at the light detecting portion. Have a role to let you. The aperture diameter is usually most preferably the same as the core diameter of the optical fiber, and smaller apertures are also preferred.

  Thus, by providing the above-described pinhole aperture between the light separator and the light detection unit, when the optical fiber transmission system is normal, the light flux of the monitor light extracted from the light separator is reduced. Of these, only the central portion where the power density is concentrated can be received by the light detection unit. Then, the amount of light received by the light detection unit at that time is adjusted so as to slightly exceed the threshold, that is, the minimum light receiving sensitivity. In order to adjust the light amount, a configuration in which an optical attenuator for attenuating the light intensity of the light separated by the optical separator is disposed between the optical separator and the light detection unit is also preferable.

  According to this configuration, for example, when the optical fiber is broken, the amount of light received by the light detection unit instantaneously and reliably divides the threshold value, so that the output signal of the light detection unit is changed from the first monitor signal to the second monitor signal. In response to this, the interlocking mechanism interlocks the laser generator to forcibly prohibit or stop the laser output operation.

  In another preferred embodiment, the interlock mechanism includes a relay having an input circuit connected to the output terminal of the photodetector and an output circuit connected to the power supply of the laser oscillation unit. In this case, the relay is preferably an electromagnetic relay, an electromagnetic coil is provided in the input circuit, and a contact portion is provided in the output circuit.

  In another preferred embodiment, a predetermined power supply voltage is simultaneously supplied to the monitor light source and the interlock mechanism while the main power switch of the laser processing apparatus is on.

  According to the optical fiber transmission system monitoring apparatus or laser processing apparatus of the present invention, with the above-described configuration and operation, in the optical fiber transmission system, the configuration is simple and the monitoring accuracy and reliability are high. When an abnormality occurs, the operation of the safety measure can be instantaneously performed without a substantial time delay.

It is a block diagram which shows the structure of the optical fiber transmission system monitoring apparatus and laser processing apparatus in one Embodiment of this invention. It is a side view which shows the suitable Example of the optical system around the photodetector in the apparatus of embodiment. It is a circuit diagram which shows one Example of the photodetector and interlock mechanism in the apparatus of embodiment. It is a circuit diagram which shows another Example of the photodetector and interlock mechanism in the apparatus of embodiment.

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

  FIG. 1 shows the configuration of a laser processing apparatus incorporating an optical fiber transmission system monitoring apparatus according to an embodiment of the present invention. This laser processing apparatus uses a simultaneous multi-branch, for example, a simultaneous two-branch optical fiber transmission system, to perform two simultaneous operations on two processing stages 10 (1) and 10 (2) installed at a desired laser processing location. A multi-point simultaneous machining type system configuration is employed in which the same or the same kind of laser processing, for example, laser welding, is performed on the workpieces W (1) and W (2).

  The laser processing apparatus mainly includes a laser generator 12, a branch unit 14, an incident unit 16, optical fibers 18 (1) and 18 (2), emission units 20 (1) and 20 (2), and a controller 22. In addition, an optical fiber transmission system monitoring unit 24 that performs normal monitoring and abnormality detection of the optical fiber transmission system including the optical fibers 18 (1) and 18 (2) is provided.

The laser generation unit 12 includes an electro-optic conversion unit 26 that generates an original laser beam LB for processing by electro-optic conversion, and a laser power source 28 that supplies a drive current I _LD to the electro-optic conversion unit 26. The electro-optic conversion unit 26 is made of, for example, a fiber coupling LD, and includes an LD unit 30 and an optical fiber 32 for extracting laser light. The LD unit 30 has one or a plurality of LD arrays, and is supplied (injected) with a required LD drive current I _LD from the laser power supply 28. For example, a high-power LD light having a wavelength of 915 nm is processed as an original laser light. Generate as LB. The extraction optical fiber 32 is, for example, a step index (SI) type optical fiber, and emits the original laser beam LB from its emission end face. The original laser beam LB emitted from the emission end face of the extraction optical fiber 32 with a constant spread angle is collimated into parallel light by the collimating lens 34 and then enters the branch unit 14.

  In the illustrated configuration example, an optical shutter 33 is provided in the middle of the take-out optical fiber 32 of the laser generator 12. The optical shutter 33 is driven to open and close by a shutter drive unit 35.

  The branching unit 14 includes a first-stage partially reflecting / transmitting mirror or beam splitter 36 having a branching ratio of about 50/50, and a next-stage total reflecting mirror or folding mirror 38. The beam splitter 36 has a coating film having a transmittance of about 50% and a reflectance of about 50% with respect to the wavelength of the original laser beam LB, and is 45 degrees on the extension of the optical axis of the optical fiber 32 for extraction. It is arranged with the inclination of. Of the original laser beam LB incident on the beam splitter 36 from the collimator lens 34, about half LB (1) passes through and passes straight through, and the remaining half LB (2) reflects there to reflect the optical path at a right angle. Bend.

  The transmitted light, that is, the first branched laser beam LB (1) passes through the first condenser lens 40 of the incident unit 16 and is condensed and incident on one end face (incident end face) of the first optical fiber 18 (1). . On the other hand, the reflected light, that is, the second branched laser beam LB (2) is totally reflected by the folding mirror 38, and the optical path is made parallel to the optical path of the first branched laser beam LB (1). Through the condensing lens 42 and converges and enters one end face (incident end face) of the second optical fiber 18 (2).

  The first and second optical fibers 18 (1) and 18 (2) are, for example, of the SI type, have an arbitrary length, and the first and second processing stages 10 (1), 10 (1), The first and second emission units 20 (1) and 20 (2) respectively disposed above 10 (2) are terminated.

  The first and second emission units 20 (1), 20 (2) are arranged at predetermined positions in a cylindrical casing with collimating lenses 44 (1), 44 (2) and condenser lenses 46 (1), 46 ( 2) are provided, and the laser emission ports are arranged facing the processing stages 10 (1) and 10 (2). In these emission units 20 (1) and 20 (2), the branched laser beam LB (1) for processing emitted from the other end face (outgoing end face) of the optical fibers 18 (1) and 18 (2) at a constant divergence angle. ) And LB (2) are collimated into parallel light by collimating lenses 44 (1) and 44 (2), respectively, and then exit from the laser exit through condensing lenses 46 (1) and 46 (2). Then, the light is focused and incident on the processing points of the workpieces W (1) and W (2) placed on the processing stages 10 (1) and 10 (2), respectively.

  In this laser processing apparatus, for example, when laser welding is performed, the laser generator 12 outputs the original laser beam LB having a pulse waveform. The original laser beam LB having this pulse waveform is divided into two branch laser beams LB (1) and LB (2) by the branch unit 14, and these branch laser beams LB (1) and LB (2) are optical fibers 18. (1) and 18 (2) are respectively transmitted to the output units 20 (1) and 20 (2) at the laser processing site, and the processing units 10 (1) and 20 (2) are processed by the output units 20 (1) and 20 (2). The workpieces W (1) and W (2) on 10 (2) are respectively focused and irradiated. At the processing point (laser irradiation part) of the workpieces W (1) and W (2), the workpiece is melted by the energy of the pulse laser beams LB (1) and LB (2), and solidifies after the pulse irradiation ends. Each nugget is formed.

  The control unit 22 is composed of, for example, a microcomputer and controls each unit (laser power supply unit 28, shutter drive unit 35, etc.) in the apparatus in order to execute desired laser processing, as well as an input unit (not shown) and Input / output processing such as setting of machining conditions and monitor display is performed through the display unit 48.

  In this laser processing apparatus, two workpieces W (1), W (2) are simultaneously processed at two laser processing locations arbitrarily selected within the range where the optical fibers 18 (1), 18 (2) can reach. ) Can be subjected to the same or similar laser processing. However, as a problem inherent to the optical fiber transmission system, one or both of the optical fibers 18 (1) and 18 (2) are arbitrarily bent in the factory or at the work place, or are broken or damaged due to external force or impact. Can be. Even if the optical fibers 18 (1) and 18 (2) are accommodated in the protective tube, if the protective tube breaks or breaks together, the optical fiber 18 (1) and 18 (2) are broken or broken. There is a risk that the high-power processing laser beams LB (1) and LB (2) may leak out. Also, due to ambient vibration or atmosphere, the optical axis alignment of the optical fiber transmission system may be defective due to some other cause, or the optical lenses (40, 42, 20 (1), 20 (2)) may be damaged or dirty. Sometimes.

  In this embodiment, when the above-described abnormality occurs in the optical fiber transmission system during operation of the laser processing apparatus, the laser output operation of the laser generator 12 is forcibly (ie, controlled) in preference to the controller 22. If an abnormality occurs while the laser processing apparatus is not in operation, the laser output operation of the laser generator 12 is forcibly (prioritized over the controller 22). And an optical fiber transmission system monitoring unit 24 to be stopped.

  The configuration and operation of the optical fiber transmission system monitoring unit 24 in this embodiment will be described below.

  In FIG. 1, the optical fiber transmission system monitoring unit 24 includes a monitor light source 50, an optical superimposing device 52, optical separators 54 (1) and 54 (2), optical detectors 56 (1) and 56 (2), and an interface. The lock mechanism 58 is used.

  The monitor light source 50 is composed of, for example, a high-intensity LED, and outputs an original monitor light (for example, 650 nm) MB for monitoring an optical fiber transmission system having a wavelength different from that of the processing laser light LB at a constant power. The original monitor light MB is sent to an optical superimposer 52 provided between the branch unit 14 and the incident unit 16.

  The optical superimposer 52 has a beam splitter 60 and a folding mirror 62. Here, the beam splitter 60 is arranged at an inclination of 45 degrees on the optical path of the first processing branched laser beam LB (1) between the beam splitter 36 of the branch unit 14 and the condenser lens 40 of the incident unit 16. Has been. On the other hand, the folding mirror 62 is disposed at an inclination of 45 degrees on the optical path of the second processing branched laser beam LB (2) between the folding mirror 38 of the branch unit 14 and the condenser lens 42 of the incident unit 16. ing.

  The original monitor light MB from the monitor light source 50 first enters the beam splitter 60 at an incident angle of 45 degrees from the direction orthogonal to the optical path of the branched laser light LB (1). The beam splitter 60 has a reflectivity of about 50% and a transmittance of about 50% for the wavelength of the monitor light MB (650 nm), and a reflectivity of about a wavelength of the processing laser beam LB (915 nm). It has a coating film with 0% and transmittance of about 100%.

  Accordingly, about half MB (1) of the original monitor light MB incident on the beam splitter 60 is reflected there, and the optical path is bent at a right angle to be superimposed on the first branched laser beam LB (1). And enters the incident end face of the first optical fiber 18 (1). The remaining half MB (2) passes straight through the beam splitter 60, is totally reflected by the folding mirror 62, bends the optical path at a right angle, and is superimposed on the second branched laser beam LB (2). Then, the light enters the incident end face of the second optical fiber 18 (2). The folding mirror 62 has a reflectance of about 100% and a transmittance of about 0% for the wavelength of the monitor light MB, and a reflectance of about 0% for the wavelength of the processing laser beam LB. A membrane with a transmittance of about 100% is coated.

  Thus, the first and second branch monitor lights MB (1) and MB (2) are superimposed on the first and second processing branch laser lights LB (1) and LB (2), and both optical fibers 18 are overlapped. (1) and 18 (2), respectively, and after exiting at a certain divergence angle from the exit end faces of both optical fibers 18 (1) and 18 (2) in the exit units 20 (1) and 20 (2). The light enters the first and second light separators 54 (1) and 54 (2) through the collimating lenses 44 (1) and 44 (2), respectively.

  The light separators 54 (1) and 54 (2) are arranged on the optical path of the laser light / monitor light between the collimating lenses 44 (1) and 44 (2) and the condenser lenses 46 (1) and 46 (2). Are configured as beam splitters arranged at an inclination of 45 degrees. These beam splitters 54 (1) and 54 (2) have a reflectance of about 100% and a transmittance of about 0% with respect to the wavelength of the monitor light MB, and with respect to the wavelength of the processing laser light LB. The coating film has a reflectance of about 0% and a transmittance of about 100%.

  Accordingly, in the first emission unit 20 (1), the first processing branched laser beam LB (1) and the first laser beam LB (1) incident on the first light separator 54 (1) through the collimator lens 44 (1) and the first laser beam LB (1). Among the one branch monitor light MB (1), the first processing branch laser light LB (1) is transmitted straight without changing the optical path, and the first branch monitor light MB (1) is totally reflected to be the optical path. Bend sideways at a right angle. The first branch monitor light MB (1) separated by the first light separator 54 (1) in this way is the first photodetector 56 (1) attached to the inner wall of the emission unit 20 (1). ).

  Further, in the second emission unit 20 (2), the second branched laser beam LB (2) for processing and the second laser beam LB (2) incident on the second light separator 54 (2) through the collimator lens 44 (2) and the second laser beam LB (2). Of the two branch monitor lights MB (2), the second processing branch laser light LB (2) is transmitted straight without changing the optical path, and the second branch monitor light MB (2) is totally reflected to be the optical path. Bend sideways at a right angle. The second branch monitor light MB (2) separated by the second light separator 54 (2) in this way is the second photodetector 56 (2) attached to the inner wall of the emission unit 20 (2). ).

  FIG. 2 shows a preferred embodiment of the optical system around each photodetector 56 (i) (i = 1, 2). As shown in the figure, an aperture 64 (i) and an attenuator 66 (i) are disposed on the optical path between the light separator 54 (i) and the light receiving surface of the photodetector 56 (i).

The aperture 64 (i) is an aperture stop for limiting the beam diameter of the monitor light MB (i) separated by the light separator 54 (i) to a desired diameter φ _b , and the size of the aperture diameter φ _b is set. preferably 0.5 times to about 1 times the core diameter phi _a of the optical fiber 18 (i) (normal most preferred ratio is 1 fold) are choosing the size of the. This aperture 64 (i) has passed through the central axis part near the core optical axis, preferably the core center part of the optical fiber, among the light beams of the monitor light MB (i) separated by the optical separator 54 (i). It is responsible for extracting the partial CMB (i) in a limited manner and causing the photodetector 56 (i) to receive light.

  That is, the processing laser light LB (i) and the monitor light MB (i) propagating in the optical fiber 18 (i) are schematically shown in FIG. 2 regardless of whether they are single mode or multimode. In addition, the respective power densities are concentrated in the core center portion of the optical fiber 18 (i), and this profile is maintained even after exiting from the exit end face of the optical fiber 18 (i). The monitor light MB (i) extracted from the optical separator 54 (i) enters the aperture 64 (i), and the central portion CMB (i) near the optical axis where the power density is concentrated in the monitor light MB (i). ) Passes through the opening of the aperture 64 (i) and enters the light receiving portion of the photodetector 56 (i).

  The attenuator 66 (i) is composed of, for example, an ND filter, and is used for optimizing the adjustment of the amount of light (light intensity) of the monitor light MB (i), that is, under the normal condition of the optical fiber transmission system. It is provided to adjust the light amount (light intensity) of the monitor light CMB (i) incident on (i) to a level slightly exceeding the threshold value of the photodetector 56 (i), that is, the minimum light receiving sensitivity. If the optimization of such light amount adjustment can be achieved with only the aperture 64 (i), the attenuator 66 (i) can be omitted.

  Note that, among the light beams of the monitor light MB (i) extracted by the optical separator 54 (i), not only the light beam that propagates through the core of the optical fiber 18 (i) but also the light beam that propagates through the cladding. There are some things. Such clad propagation light is not only low in power density but also indefinite, and easily spreads after exiting from the fiber exit end face. Further, since the collimating lens 44 (i) is designed according to the wavelength of the branching laser beam LB (i) for processing, the clad propagation light does not become parallel light even if it passes through the collimating lens 44 (i). Continue to expand. However, such clad propagation light is shielded by the aperture 64 (i) and is not received by the photodetector 56 (i).

  When an abnormality occurs in the optical fiber transmission system that transmits the processing laser beam LB (i) and the monitor light MB (i), for example, when the optical fiber 18 (i) is broken or damaged, the light diffuses at the failure location, It becomes difficult for the laser beam LB (i) and the monitor beam MB (i) to propagate through the transmission path ahead (the latter stage) of the failure location. As a result, in the output unit 20 (i), the power density distribution of the light emitted from the output end face of the optical fiber 18 (i) is schematically shown by alternate long and short dash lines LB (i) ′, MB (i) ′ in FIG. As shown in FIG. 4, the profile is a collapsed profile in which there is no power concentrated portion (central peak portion). As a result, the amount of light received by the light separator 54 (i) decreases stepwise and falls below the threshold value (minimum light sensitivity) instantaneously and reliably, and the light receiving sensor receives the light amount (power) to perform the sensing operation. As a result, the output of the light separator 54 (i) changes in a binary manner.

  FIG. 3 shows a preferred embodiment of the photodetectors 56 (1) and 56 (2) and the interlock mechanism 58.

Both photodetectors 56 (1) and 56 (2) have the same circuit configuration. That is, each photodetector 56 (i) has a photoelectric conversion element 70 (i), an amplifier circuit 72 (i), and an output transistor 74 (i). The photoelectric conversion element 70 (i) is made of a photodiode, for example, and is applied with a voltage in the reverse direction from the amplifier circuit 72 (i). When the amount of received light exceeds a threshold value (minimum light receiving sensitivity), a current or photocurrent greater than a certain value is generated. Amplifier circuit 72 (i), when the dark current in the photoelectric conversion elements 70 (i) flows generates an output voltage A _L of the reference level or less without amplification effect (logical value L), the photoelectric conversion element 70 (i) when the photocurrent is flowing current - higher than a reference level by performing the voltage conversion and amplification action is adapted to generate an output voltage a _H (logical value H). The output terminal of the amplifier circuit 72 (i) is connected to the base electrode (or gate electrode) of the output transistor 74 (i).

Both photodetectors 56 (1) and 56 (2) are electrically connected to the interlock mechanism 58 via paired cables 68 (1) and 68 (2), respectively. In particular, the output transistor 74 (1) of the first photodetector 56 (1) has a collector (or drain) electrode whose power supply voltage is within the interlock mechanism 58 via the forward path of the first pair cable 68 (1). The V _DD terminal is connected, and the emitter (or source) electrode is connected to the return path of the first pair cable 68 (1) and the first drive conversion circuit 75 (1) in the interlock mechanism 58 and the first first stage relay. It is connected to the ground potential V _SS terminal through a 76 (1) electromagnetic coil L (1).

On the other hand, the output transistor 74 (2) of the second photodetector 56 (2) has a collector (or drain) electrode whose power supply voltage is within the interlock mechanism 58 via the forward path of the second pair cable 68 (2). The V _DD terminal is connected, and the emitter (or source) electrode has the return path of the first pair cable 68 (2) and the second drive conversion circuit 75 (2) in the interlock mechanism 58 and the second first stage relay. It is connected to the ground potential V _SS terminal via the 76 (2) electromagnetic coil L (2).

In the interlock mechanism 58, the contact portion S (1) of the first first-stage relay 76 (1), the contact portion S (2) of the second first-stage relay 76 (2), and the electromagnetic coil L (3 of the next-stage relay 78 ) Are connected in series between the power supply voltage V _DD terminal and the ground potential V _SS terminal.

  Here, in the first first-stage relay 76 (1), when the current flows through the electromagnetic coil L (1), the contact portion S (1) is closed (turned on), and the current flows through the electromagnetic coil L (1). When there is no contact, the contact portion S (1) is opened (turned off). Further, in the second first-stage relay 76 (2), when the current flows through the electromagnetic coil L (2), the contact portion S (2) is closed (turned on), and no current flows through the electromagnetic coil L (2). At times, the contact portion S (2) is opened (turned off).

  The next-stage relay 78 interlocks (connects) the two contact portions S (3a) and S (3b) to the electromagnetic coil L (3), and both current contact portions when the current flows through the electromagnetic coil L (3). When S (3a) and S (3b) are closed (turned on) and no current flows through the electromagnetic coil L (3), both contact portions S (3a) and S (3b) are opened (turned off). ing.

  One contact portion S (3a) of the next-stage relay 78 is connected to the laser power source 28 as a forced on / off switch. The laser power source 28 includes, for example, a primary power source 80 composed of a commercial AC power source, a rectifier circuit (not shown) for converting commercial AC power from the primary power source 80 to DC, and direct current obtained from the rectifier circuit at a desired level. A switching power supply circuit (not shown) for converting or adjusting to a direct current voltage is included, and a contact portion S (3a) is incorporated as a breaker of the primary power supply 80.

When the contact portion S (3a) is in the on state, the laser power source 28 operates as usual under the control of the control portion 22 and supplies the drive current I _LD to the LD unit 30. However, since the primary power supply 80 is cut off when the contact portion S (3a) is turned off, the laser power supply 28 is configured to stop the output of the drive current _ILD or to be in an output impossible state.

  The other contact portion S (3b) of the next-stage relay 78 is a control switch 22 serving as a monitor switch that gives a kind of status information about the state of the optical transmission system around the optical fibers 18 (i) and 18 (2) or whether there is an abnormality. It is connected to the. The control unit 22 recognizes that there is no abnormality such as fiber breakage in the optical transmission system around the optical fibers 18 (i) and 18 (2) when the contact portion S (3a) is in the on state. When the contact part S (3a) is in the OFF state, it is recognized that an abnormality has occurred in one of the optical transmission systems around the optical fibers 18 (i) and 18 (2). Necessary monitor output is performed through the unit 48.

In this laser processing apparatus, while the main power switch is on, a required power supply voltage is supplied to each part of the apparatus from a power supply circuit (not shown), and both photodetectors 56 (1) and 56 (2). Is supplied with the power supply voltage V _DD via the interlock mechanism 58 and the forward path of the electric cables 68 (1) and 68 (2), and at the same time, the monitor light source 50 is supplied with the power supply voltage V _DD for driving or another power supply voltage. Is fed.

  Thus, regardless of whether or not the laser generator 12 is performing a laser output operation, the original monitor light MB is output from the monitor light source 50 during the period when the main power switch is on, that is, during operation of the apparatus. Both photodetectors 56 (1) and 56 (2) are activated. Therefore, if both of the optical transmission systems around both optical fibers 18 (1) and 18 (2) are normal, the two branch monitor lights MB (1), derived from the original monitor light MB via the optical superimposer 52, MB (2) passes through the optical transmission systems around the optical fibers 18 (i) and 18 (2), respectively, and the light detector 56 (1) in the emission units 20 (1) and 20 (1). ) And 56 (2), respectively.

In this case, in the first photodetector 56 (1), the photodiode 70 (1) sets the center extraction unit CMB (1) of the first branch monitor light MB (1) slightly with a threshold (minimum light receiving sensitivity). received by the light receiving quantity greater than the output voltage a _H logic value H from the output terminal of the amplifier circuit 72 (1) is output, the output transistor 74 (1) is kept in the oN state. The first drive conversion circuit 75 (1) in the interlock mechanism 58 responds to the ON state of the output transistor 74 (1) via the first electric cable 68 (1), and the first relay 76 (1 ) To the electromagnetic coil L (1) with the input (primary) circuit. As a result, the contact portion S (1) is turned on in the output (secondary) circuit of the first relay 76 (1).

In the second photodetector 56 (2), the photodiode 70 (2) receives light that slightly exceeds the threshold (minimum light receiving sensitivity) of the center extraction unit CMB (2) of the second monitor light MB (2). The output voltage _AH having a logical value H is output from the output terminal of the amplifier circuit 72 (2), and the output transistor 74 (2) is kept on. The second drive conversion circuit 75 (2) in the interlock mechanism 58 responds to the ON state of the output transistor 74 (2) via the second electric cable 68 (2), and the second relay 76 (2 ) To the electromagnetic coil L (2) through the input (primary) circuit. As a result, the contact portion S (2) is turned on in the output (secondary) circuit of the second relay 76 (2).

  Thus, when the contact portions S (1) and S (2) of the first and second relays 76 (1) and 76 (2) are both turned on, the electromagnetic coil L ( A current flows through 3), and the contact portions S (3a) and S (3b) of the third relay 78 are kept on. Therefore, the laser generator 12 performs a laser output operation under the control of the controller 22 as usual without receiving interference from the interlock mechanism 58.

However, an abnormality occurs in one of the optical transmission systems around the optical fibers 18 (i) and 18 (2) for some reason during the period when the main power switch is on, that is, during operation of the apparatus. It is assumed that the optical fiber 18 (2) in FIG. In this case, at the same time when the optical fiber 18 (2) is broken, the amount of light received by the photodiode 70 (2) in the second photodetector 56 (2) instantaneously and reliably falls below the threshold (minimum light receiving sensitivity), An output voltage A _L having a logical value L is output from the output terminal of the amplifier circuit 72 (2), and the output transistor 74 (2) is turned off. As a result, in the interlock mechanism 58, no current flows through the electromagnetic coil L (2) of the second relay 76 (2), and the contact portion S (2) is switched from the previous on state to the off state. . Then, no current flows through the electromagnetic coil L (3) of the third relay 78, and the contact portions S (3a) and S (3b) of the output circuit are switched from the previous on state to the off state.

When the contact portion S (3a) is switched from the on state to the off state in the interlock mechanism 58, the primary power source 80 of the laser power source 28 is cut off, and the laser power source 28 immediately stops the output of the LD drive current I _LD. Or cancel. Accordingly, when the laser generator 12 is in the process of outputting the processing laser beam LB, the laser beam LB is immediately generated when the interlock is applied even during the laser duration (for example, pulse time). Output stops. Further, when the interlock is applied between the outputs of the laser beams LB, the subsequent laser output operation is stopped.

  As described above, when the second optical fiber 18 (2) is broken, the relays 76 (2) and 78 of the interlock mechanism 58 are moved by the laser generator 12 in response to the output signal of the photodetector 56 (2). The laser output operation is stopped. The time delay associated with this interlock operation is substantially only the switching time of relays 76 (2) and 78 (usually well below 1 μsec), and the laser beam for processing starts from the broken portion of optical fiber 18 (2). The risk of leakage of LB (2) can be completely prevented or avoided.

  When the first optical fiber 18 (1) is broken for some reason while the main power switch is on, that is, during operation of the apparatus, the output signal of the first photodetector 56 (1) is the same as above. In response, the relays 76 (1) and 78 of the interlock mechanism 58 stop the laser output operation of the laser generator 12. Also in this case, the time delay associated with the interlock operation is substantially only the switching time of the relays 76 (1) and 78, and the processing laser beam LB (1) leaks from the broken portion of the optical fiber 18 (1). Can be reliably prevented or avoided.

In addition, during the period when the main power switch is off, that is, when the apparatus is not operating, an abnormal situation occurs in one of the optical transmission systems around the optical fibers 18 (i) and 18 (2) for some reason. There is also a possibility. In this case, immediately after the main power switch is turned on and the supply of the power supply voltage V _DD to each part of the apparatus is started, while the control unit 22 is performing initialization, the optical fiber transmission system monitoring unit 24 The laser generator 12 is interlocked by the same operation as described above. As a result, the laser generator 12 enters an operation halt state and does not perform any laser output operation until it is reset, even if it receives a command from the controller 22.

  FIG. 4 shows another embodiment of the interlock mechanism 58. In this embodiment, the next-stage relay (78) is omitted, and instead, two contact portions S (1a) and S (1b) are provided in the output circuit of the first relay 76 (1), and the second relay 76 ( The output circuit 2) is also provided with two contact portions S (2a) and S (2b).

  One contact portion S (1a) of the first relay 76 (1) and one contact portion S (2a) of the second relay 76 (2) are connected to each other as a forcible on / off switch connected in series. 28.

  The other contact portion S (1b) of the first relay 76 (1) and the other contact portion S (2b) of the second relay 76 (2) are individually connected to the laser power supply 28 as independent monitor switches. It is connected.

  When both the optical transmission systems around the optical fibers 18 (1) and 18 (2) are normal during operation of the apparatus, the first and second relays 76 (1) and 76 (2) Current flows through the coils L (1) and L (2), and the contact portions S (1a), S (1b), S (2a), and S (2b) of the output circuit are all turned on. Therefore, the laser generator 12 performs a laser output operation under the control of the controller 22 as usual without receiving interference from the interlock mechanism 58. The control unit 22 also recognizes that the optical transmission system around both the optical fibers 18 (1) and 18 (2) is normal, and executes the laser processing sequence as planned.

  For example, when the second optical fiber 18 (2) is broken during the operation of the apparatus, the current that has been flowing to the electromagnetic coil L (2) of the input circuit in the second relay 76 (2) stops. The contact portions S (2a) and S (2b) of the output circuit are switched from the previous on state to the off state.

  When the contact portion S (2a) is turned off, the laser generator 12 immediately stops the laser output operation in response to this. Then, the laser output operation is paused until reset. Further, when the contact portion S (2b) is turned off, the control unit 22 recognizes that an abnormality has occurred in the optical transmission system around the second optical fiber 18 (2), and outputs the monitor through the display unit 48.

  When the first optical fiber 18 (1) is broken during the operation of the apparatus, the same operation as described above is performed except that the operations of the first and second relays 76 (1) and 76 (2) are switched. The laser generator 12 immediately stops the laser output operation, and the controller 22 recognizes that an abnormality has occurred in the optical transmission system around the first optical fiber 18 (2) and performs a required process.

  Most of the abnormalities in the optical fiber transmission system detected by the optical fiber transmission system monitoring unit 24 of this embodiment are the breakage or breakage of the optical fiber, but the optical axis alignment is defective, the optical lens is dirty or deteriorated, etc. Can be detected.

  Although not shown in FIGS. 3 and 4, a relay in the interlock mechanism 58 may be connected to the shutter drive unit 33, and an optical transmission system around the optical fibers 18 (1) and 18 (2). When an abnormality is detected in any of the above, it is possible to forcibly close the optical shutter 31 by interlocking the shutter drive unit 33.

  In the present invention, only the photodetector 56 (1) provided in the emission unit 20 (i) photoelectrically converts the monitor light MB (i) passed through each optical fiber 18 (i). A photodetector that photoelectrically converts the monitor light MB (i) immediately before entering the optical fiber 18 (i) is unnecessary. This is particularly advantageous in the simultaneous multi-branch optical fiber transmission system as in the above embodiment, and the greater the number of branches, the greater the advantage.

  Of course, the present invention can also be applied to a configuration without branching, that is, a single optical fiber transmission system.

  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 above embodiment, an SI type optical fiber is used as an optical fiber for laser transmission, but other types of optical fibers such as a GI type can also be used. The configuration of the laser generator 12 can be modified in various ways. In particular, the electro-optic converter 26 is not limited to the fiber coupling LD, and other forms of LD are possible, or a fiber laser oscillator, a YAG laser oscillator, etc. There may be. The circuit configuration of the photodetection unit can be modified in various ways. For example, the configuration in which the amplifier circuit 72 (i) is a simpler photodiode output circuit, the output transistor 74 (i) is connected in an open collector, and the collector A configuration in which the potential (on / off state of the transistor) is read in a binary manner via a clamp circuit is also possible. The circuit configuration in the interlock mechanism can be arbitrarily modified. For example, a semiconductor relay or a photocoupler may be used instead of the electromagnetic relay.

  The laser processing apparatus of the present invention is not limited to laser welding as long as it employs an optical fiber transmission system, and can be applied to other laser processing such as drilling, cutting, and marking.

DESCRIPTION OF SYMBOLS 12 Laser generator 14 Branch unit 16 Incident unit 18 (1), 18 (2) Optical fiber 20 (1), 20 (2) Output unit 22 Control part 24 Optical fiber transmission system monitoring part 26 Electro-optic conversion part 28 Laser power supply 50 Monitor light source 52 Optical superimposer 54 (1), 54 (2) Optical separator 56 (1), 56 (2) Photo detector 58 Interlock mechanism 64 (i) Aperture 66 (i) Optical attenuator 75 (1) 75 (2) Drive conversion circuit 80 Primary power supply

Claims (22)

A laser processing apparatus for transmitting a processing laser beam output from a laser generator through an optical fiber to an output unit, and condensing and irradiating the workpiece with the laser beam from the output unit to perform a desired laser processing An optical fiber transmission system monitoring device for performing normal monitoring and abnormality detection of an optical fiber transmission system in
A monitor light source that generates monitor light having a wavelength different from that of the processing laser light;
A light superimposing unit that superimposes the monitor light from the monitor light source on the laser beam for processing and makes it incident on an incident end face of the optical fiber;
An optical separator that separates at least a part of the monitor light emitted from the emission end face of the optical fiber from the processing laser light;
The light from the light separator is received and converted into an electrical signal by photoelectric conversion, and when the amount of received light is higher than a predetermined threshold, a first monitor signal is output, and when the amount of received light is lower than the threshold A light detection unit for outputting a second monitor signal;
The laser is electrically connected to the output terminal of the light detection unit, and the first monitor signal is output from the light detection unit while the monitor light source is generating the monitor light. An interlock mechanism for permitting or continuing the laser output operation of the generator, and prohibiting or stopping the laser output operation of the laser generator when the second monitor signal is output from the light detector And an optical fiber transmission system monitoring device. The laser beam for processing output from the laser generator operating under the control of the control unit is transmitted to the emission unit through the optical fiber, and the laser beam is focused and irradiated on the workpiece from the emission unit. An optical fiber transmission system monitoring apparatus that performs normal monitoring and abnormality detection of an optical fiber transmission system in a laser processing apparatus that performs desired laser processing,
A monitor light source that generates monitor light having a wavelength different from that of the processing laser light;
A light superimposing unit that superimposes the monitor light from the monitor light source on the laser beam for processing and makes it incident on an incident end face of the optical fiber;
An optical separator that separates at least a part of the monitor light emitted from the emission end face of the optical fiber from the processing laser light;
The light from the light separator is received and converted into an electrical signal by photoelectric conversion, and when the amount of received light is higher than a predetermined threshold, a first monitor signal is output, and when the amount of received light is lower than the threshold A light detection unit for outputting a second monitor signal;
The laser is electrically connected to the output terminal of the light detection unit, and the first monitor signal is output from the light detection unit while the monitor light source is generating the monitor light. The control of the generation unit is left to the control unit, and when the second monitor signal is output from the light detection unit, the laser output operation of the laser generation unit is forcibly prohibited in preference to the control unit. Or an optical fiber transmission system monitoring device having an interlock mechanism to be stopped.   3. The optical fiber transmission system monitoring apparatus according to claim 1, further comprising an aperture disposed between the optical separator and the light detection unit in order to limit a beam diameter of the monitor light to a desired aperture. .   The optical fiber transmission system monitoring apparatus according to claim 3, wherein the aperture has a diameter that is substantially the same as a core diameter of the optical fiber.   The optical fiber transmission system monitoring apparatus according to claim 3, wherein the aperture has an aperture smaller than a core diameter of the optical fiber.   The optical attenuator disposed between the light separator and the light detection unit in order to attenuate the light intensity of the light separated by the light separator. Optical fiber transmission system monitoring device.   The optical fiber transmission system monitoring device according to any one of claims 1 to 6, wherein the light detection unit has the threshold value near a lower limit of a received light amount at which the first monitor signal can be output by photoelectric conversion.   The interlock mechanism includes a first relay having an input circuit connected to an output terminal of the light detection unit and a first output circuit connected to a power source of the laser generation unit. The optical fiber transmission system monitoring device according to any one of claims 7 to 9. An optical shutter is provided on the laser beam path of the laser generator,
The optical fiber transmission system monitoring apparatus according to claim 8, wherein the interlock mechanism includes a second relay having a second output circuit connected to the driving unit of the optical shutter.   The optical fiber transmission system monitoring device according to claim 8 or 9, wherein the relay is an electromagnetic relay having an electromagnetic coil provided in the input circuit and a contact portion provided in the output circuit.   The predetermined power supply voltage is simultaneously supplied to the monitor light source and the interlock mechanism during a period in which the main power switch of the laser processing apparatus is turned on. Optical fiber transmission system monitoring device. A laser generator for generating laser light for processing;
An optical fiber for transmitting the laser beam for processing generated by the laser generator to a laser processing location;
An emission unit that is installed or arranged at the laser processing location and that condenses and irradiates the workpiece with the processing laser light emitted from the emission end face of the optical fiber;
A monitor light source that generates monitor light having a wavelength different from that of the processing laser light;
A light superimposing unit that superimposes the monitor light from the monitor light source on the laser beam for processing and makes it incident on an incident end face of the optical fiber;
An optical separator that separates at least a part of the monitor light emitted from the emission end face of the optical fiber from the processing laser light;
The light from the light separator is received and converted into an electrical signal by photoelectric conversion, and when the amount of received light is higher than a predetermined threshold, a first monitor signal is output, and when the amount of received light is lower than the threshold A light detection unit for outputting a second monitor signal;
The laser is electrically connected to the output terminal of the light detection unit, and the first monitor signal is output from the light detection unit while the monitor light source is generating the monitor light. An interlock mechanism for permitting or continuing the laser output operation of the generator, and prohibiting or stopping the laser output operation of the laser generator when the second monitor signal is output from the light detector And a laser processing apparatus. A laser generator for generating laser light for processing;
A controller for controlling the operation of the laser generator;
An optical fiber for transmitting the laser beam for processing generated by the laser generator to a laser processing location;
An emission unit that is installed or arranged at the laser processing location and that condenses and irradiates the workpiece with the processing laser light emitted from the emission end face of the optical fiber;
A monitor light source that generates monitor light having a wavelength different from that of the processing laser light;
A light superimposing unit that superimposes the monitor light from the monitor light source on the laser beam for processing and makes it incident on an incident end face of the optical fiber;
An optical separator that separates at least a part of the monitor light emitted from the emission end face of the optical fiber from the processing laser light;
The light from the light separator is received and converted into an electrical signal by photoelectric conversion, and when the amount of received light is higher than a predetermined threshold, a first monitor signal is output, and when the amount of received light is lower than the threshold A light detection unit for outputting a second monitor signal;
The laser is electrically connected to the output terminal of the light detection unit, and the first monitor signal is output from the light detection unit while the monitor light source is generating the monitor light. The control of the generation unit is left to the control unit, and when the second monitor signal is output from the light detection unit, the laser output operation of the laser generation unit is forcibly prohibited in preference to the control unit. Or a laser processing device having an interlock mechanism for stopping.   14. The laser processing apparatus according to claim 12, further comprising an aperture disposed between the light separator and the light detection unit in order to limit a beam diameter of the monitor light to a desired aperture.   The laser processing apparatus according to claim 14, wherein the aperture has a diameter substantially the same as a core diameter of the optical fiber.   The laser processing apparatus according to claim 14, wherein the aperture has a diameter smaller than a core diameter of the optical fiber.   The optical attenuator disposed between the optical separator and the light detection unit in order to attenuate the light intensity of the light separated by the optical separator. Laser processing equipment.   The laser processing apparatus according to any one of claims 12 to 17, wherein the light detection unit has the threshold value in the vicinity of a lower limit of an amount of received light that can output the first monitor signal by photoelectric conversion.   The interlock mechanism includes a first relay having an input circuit connected to an output terminal of the light detection unit and a first output circuit connected to a power source of the laser generation unit. The laser processing apparatus according to any one of 18. An optical shutter is provided on the laser beam path of the laser generator,
The laser processing apparatus according to claim 19, wherein the interlock mechanism includes a second relay having a second output circuit connected to a drive unit of the optical shutter.   21. The laser processing apparatus according to claim 19, wherein the relay is an electromagnetic relay having an electromagnetic coil provided in the input circuit and a contact portion provided in the output circuit.   The laser processing apparatus according to any one of claims 12 to 21, wherein a predetermined power supply voltage is simultaneously supplied to the monitor light source and the interlock mechanism during a period in which the main power switch is on.

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