Patent Application
20210175676
The present invention relates to a laser apparatus, a resin degradation detection method, and a detection method of an optical power, and more particularly to a method of detecting degradation of a resin that fixes an optical fiber in place, for example in a laser apparatus.
There has heretofore been known a laser apparatus having a process head that delivers a laser beam, for example, from a fiber laser to a workpiece to process the workpiece (see, e.g., Patent Literature 1). With such a laser apparatus, when a workpiece is formed of a material having a high reflectivity (for example, copper or gold), a delivered laser beam is reflected from the workpiece at a high ratio. Therefore, the reflected light may return to an interior of the laser apparatus through the process head.
If the amount of light returning to the laser apparatus increases, one or more components within the laser apparatus (e.g., an output combiner) generates heat by the optical feedback, resulting in a damaged optical fiber or a failure such as a disconnected optical path. In order to prevent such a failure, there has been proposed a method of detecting an optical feedback propagating in a laser apparatus and stopping an operation of the laser apparatus if the amount of the optical feedback exceeds a predetermined threshold.
However, if such an optical feedback repetitively returns to the laser apparatus, a portion of the optical feedback is absorbed in a resin that fixes an optical fiber or the like. Thus, the resin is degraded gradually. As a result, a failure may be caused from a portion of the resin before the amount of the optical feedback detected exceeds the aforementioned threshold.
Therefore, it is important to detect degradation of a resin that fixes an optical fiber or the like in order to prevent a failure of a laser apparatus. However, such a resin is provided at an invisible location from an outside of the structure in most cases. Thus, it is difficult to identify the degradation of the resin. Furthermore, even if the resin is visible from an outside of the structure, some type of degradation of the resin may not be recognized by visual inspection. In such a case, it is difficult to accurately detect the degradation of the resin.
Patent Literature 1: JP 2017-21099 A
One or more embodiments provide a laser apparatus and a method that can effectively detect degradation of a resin that fixes an optical fiber in place.
According to one or more embodiments, there is provided a laser apparatus capable of effectively detecting degradation of a resin that fixes an optical fiber. The laser apparatus has an optical fiber through which a laser beam propagates, a resin that fixes the optical fiber, a sound sensor configured to detect a sound produced by the resin that shrinks when a power of light propagating through the optical fiber decreases from its peak value, a storage unit configured to store a threshold (threshold value) relating to a sound produced when the resin shrinks, and a comparison determination part operable to compare a detected value representative of the sound detected by the sound sensor to the threshold stored in the storage unit and determine that the resin has been degraded when the detected value exceeds the threshold. The laser apparatus may have at least one fiber laser connected to the optical fiber.
According to one or more embodiments, there is provided a method capable of effectively detecting degradation of a resin that fixes an optical fiber. This method includes setting a certain threshold, detecting a sound produced by the resin that shrinks when a power of light propagating through the optical fiber decreases from its peak value, comparing a detected value representative of the detected sound to the threshold, and determining that the resin has been degraded when the detected value exceeds the threshold.
According to one or more embodiments, there is provided a method capable of detecting a power of light propagating through an optical fiber. This method includes detecting a sound produced when a resin that fixes an optical fiber shrinks and, based on the detected sound, detecting that a power of light propagating through the optical fiber decreases from its peak value.
Embodiments of the present invention will be described in detail below with reference to
The inventor has diligently studied a method of effectively detecting degradation of a resin that is caused by an optical feedback in order to prevent the aforementioned failure of a laser apparatus that would be caused by an optical feedback. As a result, the inventor has found that an optical feedback causes a resin to generate heat and to expand and that, when the power of the optical feedback decreases from its peak value, the resin shrinks so that a sound is produced.
As shown in
Additionally, the inventor has found that the strength of the resin shrinkage sound increases as the resin 120 is degraded. Therefore, when the strength of the resin shrinkage sound from the resin 120 that should be considered to be degraded is set as a threshold, then the degradation of the resin 120 can be determined by detecting whether or not the strength of the resin shrinkage sound produced from the resin 120 exceeds the threshold.
The frequency of a resin shrinkage sound being produced depends upon the natural frequency, which is defined by a location where the resin 120 shrinks and expands, a structure in the vicinity of the resin 120, a method of fixing the resin 120, and the like. Accordingly, if a frequency analysis is conducted on a resin shrinkage sound produced upon expansion and shrinkage of the resin 120 so as to acquire, for example, an amplitude at a specific frequency or in a specific frequency band that corresponds to the natural frequency, then the degradation of the resin 120 can be determined more accurately by comparison of the amplitude with the threshold.
Each of the fiber laser units 10 includes an optical cavity therein. Thus, each of the fiber laser units 10 is configured to output a laser beam amplified by the optical cavity. The laser beams outputted from those fiber laser units 10 propagate through the respective optical fibers 12. Those laser beams are combined by the output combiner 20 and outputted to one optical fiber 22. The combined laser beam is delivered through the optical fiber 22 to the process head 30 and directed as a focused laser beam L to a workpiece 100 by an optical system within the process head 30.
A certain length of a coating material has been removed from an end of each of the optical fibers 12 along a longitudinal direction of the optical fiber 12. Thus, claddings 12A of the optical fibers 12 are exposed. Similarly, a certain length of a coating material has been removed from an end of the optical fiber 22 along a longitudinal direction of the optical fiber 22, and a cladding 22A of the optical fiber 22 is thus exposed. Those exposed portions of the claddings 12A and the cladding 22A are located between the resin 28 and the resin 29. The diameter of the claddings 12A of the optical fibers 12 are reduced in a tapered manner so as to match the diameter of the cladding of the optical fiber 22. The tapered portion of the optical fibers 12 and the cladding 22A of the optical fiber 22 are connected to each other by fusion splice.
For example, as shown in
The sound sensor 50 is located near the resin 28 and configured to detect a sound (resin shrinkage sound) produced when the resin 28 expands and shrinks due to heat caused by the optical feedback. The sound sensor 50 is configured to detect a sound at a predetermined sampling rate and externally output the detected sound, for example, as a variation of a voltage (voltage data). Any sensor capable of detecting a resin shrinkage sound can be used for the sound sensor 50. Various kinds of sound sensors including an electrodynamic sound sensor, an electrostatic sound sensor (condenser microphone), a piezoelectric sound sensor (piezoelectric microphone), and the like may be used for the sound sensor 50.
As shown in
The processing unit 42 includes an analysis part 45 operable to perform a discrete Fourier transform on the voltage data from the sound sensor 50 for frequency analysis and a comparison determination part 46 operable to compare an amplitude (detected value) at a specific frequency in a frequency spectrum obtained by the analysis part 45 to the threshold stored in the storage unit 44. The comparison determination part 46 is configured to determine that the resin 28 has been degraded and to send a resin degradation signal S to the controller 40 when an amplitude at the specific frequency exceeds the threshold.
Now the threshold stored in the storage unit 44 will be described. The threshold may be determined and stored in the storage unit 44 before the resin 28 has been degraded. For example, the threshold is determined in the following manner.
First, a pulsed beam having a certain power is introduced into the laser apparatus 1 from the process head 30 before the resin 28 has been degraded. Thus, the resin 28 is heated so that the temperature of the resin 28 changes. Therefore, the resin 28 expands and shrinks so as to produce a resin shrinkage sound (reference sound). The sound sensor 50 detects the reference sound at a predetermined sampling rate and inputs its voltage data to the analysis part 45 of the processing unit 42. At that time, the sound sensor 50 acquires voltage data, for example, as illustrated in
The analysis part 45 of the processing unit 42 stores the voltage data as illustrated in
Now a normal operation of the laser apparatus 1 will be described.
The analysis part 45 of the processing unit 42 stores the inputted voltage data for a predetermined period of time and performs a discrete Fourier transform on the voltage data (Step S2). Some period of time may be enough for storing the voltage data. For example, the period of time for which the voltage data have been stored may be 10 milliseconds. This discrete Fourier transform provides a frequency spectrum. The comparison determination part 46 determines whether or not the amplitude of the frequency spectrum at the frequency of interest (2.1 kHz) exceeds a threshold stored in the storage unit 44 (35 mV) (Step S3). If the amplitude at the frequency of interest does not exceed the threshold, the procedure returns to the sound sampling (Step S1). If the amplitude at the frequency of interest exceeds the threshold, the comparison determination part 46 determines that the resin 28 has been degraded and sends a resin degradation signal S to the controller 40 (Step S4).
When a discrete Fourier transform is performed on the voltage data shown in
The controller 40 that has received the resin degradation signal S stops the operation of the laser apparatus 1, for example, by stopping an electric current supplied to the fiber laser units 10 (Step S5). Thus, the operation of the laser apparatus 1 can be stopped before the laser apparatus 1 experiences a failure. Furthermore, the controller 40 may decrease an electric current supplied to the fiber laser units 10 or otherwise notify an operator of degradation of the resin 28 through another user interface (e.g., a rotating lamp, a display, or means for external communication).
Thus, according to one or more embodiments, degradation of a resin can be detected by using a resin shrinkage sound. Therefore, degradation that could not be detected by visual inspection can be detected. Furthermore, even if the sound sensor 50 is located outside of the output combiner 20, the resin shrinkage sound of the resin 28 can be detected. Accordingly, even if the resin 28 is invisible from the outside of the output combiner 20, degradation of the resin 28 can be detected.
Furthermore, since a threshold that reflects a state prior to degradation of the resin 28 is used in the above embodiments, the current state can be compared to the state prior to degradation of the resin 28 when the laser apparatus 1 is operated. Accordingly, degradation of the resin can be detected more accurately.
In the above embodiments, the comparison determination part 46 compares an amplitude of the frequency spectrum at a specific frequency to the threshold. However, an integrated value of amplitudes within a specific frequency band may be used instead of an amplitude at a specific frequency. Furthermore, in the above embodiments, the analysis part 45 of the processing unit 42 performs a discrete Fourier transform on data representative of a sound detected by the sound sensor 50 (voltage data). However, the frequency analysis using a discrete Fourier transform may not be required. A detected value, such as a voltage value representative of a sound detected by the sound sensor 50, may be compared to the threshold. Moreover, the detected value representative of a sound detected by the sound sensor 50 may be any physical quantity including a voltage value and an electric current value.
Moreover, the processing unit 42, the storage unit 44, and the like as described above may be provided integrally with the controller 40, which controls an operation of the laser apparatus 1, or may be provided separately from the controller 40.
The above embodiments describe examples where degradation of resin 28 in the output combiner 20 is to be detected. Nevertheless, one or more embodiments can be applied to a resin provided at any location as long as the resin may be degraded due to the laser beam. For example, one or more embodiments can be used to detect degradation of a resin that fixes an optical fiber in a structure that removes a cladding mode.
Although only a limited number of embodiments have been described, the scope of the present invention is not limited to the aforementioned embodiments. It should be understood that various different embodiments may be devised without departing from the scope of the present invention.
As described above, according to one or more embodiments, there is provided a laser apparatus capable of effectively detecting degradation of a resin that fixes an optical fiber. The laser apparatus has an optical fiber through which a laser beam propagates, a resin that fixes the optical fiber, a sound sensor configured to detect a sound produced by the resin that shrinks when a power of light propagating through the optical fiber decreases from its peak value, a storage unit configured to store a threshold relating to a sound produced when the resin shrinks, and a comparison determination part operable to compare a detected value representative of the sound detected by the sound sensor to the threshold stored in the storage unit and determine that the resin has been degraded when the detected value exceeds the threshold. The laser apparatus may have at least one fiber laser connected to the optical fiber.
With this configuration, degradation of a resin can be detected by using a sound (resin shrinkage sound) produced by the resin that shrinks when a power of light propagating through the optical fiber decreases from its peak value. Thus, since degradation of the resin can be detected by using such a resin shrinkage sound, degradation that could not be detected by visual inspection can be detected. Furthermore, even if the laser apparatus has a structure where the resin is invisible from the outside of the structure, degradation of the resin can be detected. Moreover, since degradation of the resin can be detected, any necessary measures such as stop and alert can be taken before the laser apparatus experiences a failure.
The threshold may relate to an amplitude of a sound at a specific frequency or in a specific frequency band. The laser apparatus according to one or more embodiments may further include an analysis part operable to perform a frequency analysis on data representative of the sound detected by the sound sensor and output an amplitude at the specific frequency or in the specific frequency band as the detected value to the comparison determination part. Thus, since the comparison with the threshold employs the results obtained by a frequency analysis on data representative of the resin shrinkage sound, degradation of the resin can be detected more accurately.
One or more embodiments provide a method capable of effectively detecting degradation of a resin that fixes an optical fiber. This method includes setting a certain threshold, detecting a sound produced by the resin that shrinks when a power of light propagating through the optical fiber decreases from its peak value, comparing a detected value representative of the detected sound to the threshold, and determining that the resin has been degraded when the detected value exceeds the threshold.
According to this method, degradation of a resin can be detected by using a sound (resin shrinkage sound) produced by the resin that shrinks when a power of light propagating through an optical fiber decreases from its peak value. Thus, since degradation of the resin can be detected by using such a resin shrinkage sound, degradation that could not be detected by visual inspection can be detected. Furthermore, even if the laser apparatus has a structure where the resin is invisible from the outside of the structure, degradation of the resin can be detected.
The threshold may relate to an amplitude of a sound at a specific frequency or in a specific frequency band. In this case, a frequency analysis on data representative of the detected sound may be performed and an amplitude at the specific frequency or in the specific frequency band as the detected value may be compared to the threshold, upon the comparing the detected value to the threshold. Thus, since the comparison with the threshold employs the results obtained by a frequency analysis on data representative of the resin shrinkage sound, degradation of the resin can be detected more accurately.
Before the resin is degraded, a reference sound produced by the resin that shrinks when a power of light propagating through the optical fiber decreases from its peak value may be detected, and the threshold may be determined based on the detected reference sound. Use of such a threshold enables comparison with a state prior to degradation. Therefore, degradation of the resin can be detected more accurately.
According to one or more embodiments, there is provided a method capable of detecting a power of light propagating through an optical fiber. This method includes detecting a sound produced when a resin that fixes an optical fiber shrinks and, based on the detected sound, detecting that a power of light propagating through the optical fiber decreases from its peak value.
According to this method, the fact that a power of light propagating through an optical fiber decreases from its peak value can be detected by using a sound produced when a resin that fixes the optical fiber shrinks.
According to one or more embodiments, degradation of a resin that fixes an optical fiber can be detected by using a sound produced when the resin shrinks.
Although the disclosure has been described with respect to only a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that various other embodiments may be devised without departing from the scope of the present invention. Accordingly, the scope of the invention should be limited only by the attached claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2018-191689 | Oct 2018 | JP | national |
This is a U.S. National Stage application of International Application No. PCT/JP2019/037240 filed Sep. 24, 2019, which claims priority from Japanese patent application No. 2018-191689 filed Oct. 10, 2018. These references are incorporated herein in their entirety by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2019/037240 | 9/24/2019 | WO | 00 |
