JP4649280B2 - Laser ultrasonic receiving apparatus and laser ultrasonic receiving method - Google Patents

Description

The present invention relates to a laser ultrasonic wave receiving apparatus and a laser ultrasonic wave receiving method, and in particular, has an apparatus state monitoring function and an apparatus state optimizing function suitable for use in the field, and is in a stable state over a long period of time. The present invention relates to a laser ultrasonic receiving apparatus and a laser ultrasonic receiving method capable of high-accuracy flaw detection operations.

(Description of known technology)
Ultrasonic technology is an extremely effective technique for detecting cracks and internal defects generated on the material surface or analyzing material properties. In a normal detection operation, ultrasonic reception is performed by bringing a receiving element such as a piezoelectric element into contact with an ultrasonic propagation medium, but this can be replaced by using laser light and a receiving optical system. Yes (for example, see Non-Patent Document 1).

  The ultrasonic reception method using laser light is non-contact in principle, and the object to be measured is in a high temperature state, placed at a high place, placed in a high radiation field, or small and has a complicated shape. Therefore, it is expected to be applied to various industrial technical fields such as a case where it is difficult to contact an inspection instrument, or a part where the proximity is poor and a remote non-contact measurement method is required.

  The ultrasonic reception technology by laser irradiates the receiving laser beam with a sufficiently long pulse compared to continuous wave or ultrasonic propagation time, and is induced by ultrasonic waves using its straightness and coherence. This is a technique for detecting the surface displacement or vibration speed of the receiving point (see, for example, Non-Patent Document 2).

  As an optical system used in the laser ultrasonic wave reception method, a Michelson interferometry method, a Mach-Zehnder interferometry method, a Fabry-Perot method, a two-wave mixing method using a phase conjugate element, a knife edge method, and the like have been proposed (for example, (See Patent Document 3). However, the Fabry-Perot method is expected to be applied from an industrial point of view.

  Here, a conventional typical laser ultrasonic wave receiving method and apparatus combining a pulse laser beam and the Fabry-Perot method will be described below. FIG. 7 is a block diagram showing a configuration of a conventional typical laser ultrasonic wave receiving apparatus.

  In FIG. 7, it is assumed that the ultrasonic signal US based on an arbitrary generation process or propagation process reaches an arbitrary point P on the surface of the object TP to be measured, and generates a vibration at that point. Here, the reception pulse laser light source PDL oscillates the pulse laser light IL in synchronization with the ultrasonic signal US appropriately.

  The seed laser light oscillated from the seed laser 1 installed in the received pulse laser light source PDL is incident on an optical amplifier 2 (MOPA: Master Oscillator Pulsed Amplifier) via an optical isolator 5a and total reflection mirrors M1 and M2, and is pulsed. The output is amplified in a shape. Here, as the seed laser 1, a continuous wave Nd: YAG laser light source having a frequency stabilization function with an output of about 10 mW to 1 W is used. The MOPA excites the optical amplification medium with a flash lamp or a semiconductor laser that is driven by the power source 3 and is cooled by the cooling water W returning from the cooling water inlet Win to the cooling water outlet Wout.

  The amplified received pulse laser beam IL is incident on the first optical fiber 4 by the collimator lens L1, and is irradiated to the measurement point P on the object TP to be measured by the first objective lens L2 installed in the irradiation head H. The Here, when the reflected light reflected by the end face of each optical element enters the seed laser 1 or the optical amplifier 2, optical noise is generated, so that it is possible to prevent the reflected light from being mixed into the seed laser 1 or the optical amplifier 2. In some cases, optical isolators 5a and 5b are installed at the positions. In some cases, an optical attenuator 6 for adjusting the light output irradiated to the object TP to be measured is installed.

  As shown in FIG. 8, the irradiated laser beam IL is modulated to its optical frequency by the surface vibration caused by the ultrasonic signal US by ± vd (Doppler shift), and a part SL of the scattered component is irradiated by the irradiation head H. The light is collected by the second objective lens L3 installed inside and enters the Fabry-Perot interferometer FP via the second optical fiber 7 and the collimator lens L4. Here, a part of the laser light SL incident on the Fabry-Perot interferometer FP is reflected by the partial transmission mirror PM1, and the light quantity thereof is measured by the reference photodetector 8.

  The Fabry-Perot interferometer FP is a resonator composed of two partially reflecting mirrors CPM1 and CPM2 that often have a confocal point, and is between the optical frequency of incident light and the transmitted light intensity. Holds the relationship shown in FIG. Here, the horizontal axis of FIG. 8 indicates the optical frequency v, and the vertical axis indicates the transmitted light intensity I. As shown in FIG. 8, the Fabry-Perot interferometer FP operates as a narrow-band optical frequency filter in which the transmitted light intensity I has a peak at a specific optical frequency and quickly attenuates before and after that. The optical frequency giving the peak can be changed by adjusting the resonator length of the Fabry-Perot interferometer FP (ie, the distance between the mirrors CPM1 and CPM2). Therefore, from the measured values of the incident light amount and transmitted light amount of the Fabry-Perot interferometer FP, the optical frequency at which the slope of the curve shown in FIG. 8 is maximum (for example, point A in FIG. 8) matches the optical frequency of the pulsed laser light IL. As described above, if the mirror CPM1 or CPM2 is driven and controlled by the piezoelectric element 9, the change ± vd of the optical frequency due to the ultrasonic signal US can be converted into the change ± Id of the relatively large transmitted light intensity.

  The optical signal transmitted through the Fabry-Perot interferometer FP is detected by the photodetector 10 through the lens L5 and processed by a frequency filter (in many cases, using a high-pass filter) 11 corresponding to the ultrasonic frequency US. Thus, an electrical signal corresponding to the ultrasonic signal US can be obtained. The detected electrical signal is appropriately subjected to signal conversion, signal processing, display, and recording by the signal processing device 12. Here, as the photodetectors 8 and 10, a photodiode (PD), a PIN photodiode (PIN-PD), or an avalanche photodiode (APD) is often used.

  Note that the output signal of the photodetector 10 is branched, processed by a frequency filter (in many cases, a low-pass filter) 13 for observing a change in the amount of transmitted light, and input to the piezoelectric element drive control device 14. Supplied with long control.

  In addition, for the sake of simplicity, the above description has been made by paying attention to the transmitted light of the Fabry-Perot interferometer FP. However, the reflected light of the Fabry-Perot interferometer FP is also detected by the similar operation. It is possible (for example, refer nonpatent literature 4).

  Further, as shown in FIG. 9, the measured object TP is irradiated with the received laser beam IL using one objective lens L6 and one optical fiber 15 installed in the irradiation head H, and the measured object TP. A structure for condensing the scattering component SL on the surface is already known (see, for example, Patent Document 1). In this case, the scattered light SL transmitted from the object to be measured TP side to the Fabry-Perot interferometer FP by the optical fiber 15 is branched from the optical path of the receiving laser light IL by the beam splitter 16, and then the coupling lens L 7, the optical fiber 17 to the Fabry-Perot interferometer FP. In order to efficiently branch the scattered light SL and the ultrasonic receiving laser light IL, branch control by deflection using a deflection control optical element such as a wavelength plate and a deflection beam splitter may be employed.

In the above conventional laser ultrasonic wave receiver, since the inspection instrument is in principle non-contact, the object to be measured is in a high temperature state, placed in a high place, placed in a high radiation field, or compact. Therefore, it is expected to be applied to various technical fields, such as when it is difficult to contact an inspection instrument with a complicated shape portion, or when the proximity is poor and a remote non-contact measurement method is required. In addition, a known method and apparatus for receiving a laser ultrasonic wave has been established as a basic principle, and can be sufficiently applied in a prepared environment such as a laboratory environment or in a short time.
JP 2001-318081 A Monchalin, J. -P., Et al., “Optical detection of ultrasound,” IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 33, 1986, pp. 485-499. Choquet, M., et al., “Laser-ultrasonic inspection of the composite structure of an aircraft in a maintenance hanger,” Review of Progress in Quantitative Nondestructive Evaluation, vol.14, 1995, pp. 545-552. Yamawaki: “Laser Ultrasound and Non-contact Material Evaluation”, Journal of the Japan Welding Society, Vol. 64, No. 2, P.104-108 (1995) Dewhurst, RJ, et al., “Modeling of confocal Fabry-Perot interferometer for the measurement of ultrasound,” Meas. Sci. Technol. 5 (1994) pp. 655-662.

  However, when the conventional laser ultrasonic receiving method and apparatus as described above are used for a long time for ultrasonic flaw detection and measurement work in a field environment such as a power plant or a production line, the temperature change in the apparatus installation environment Due to the displacement of the optical element due to vibration and vibration, the amount or temperature change of the cooling water used in the apparatus, and the deterioration of the flash lamp for exciting the receiving laser used in the laser ultrasonic receiving method and apparatus, Deterioration was raised.

(1) Decreased output of seed laser beam or abnormal oscillation (2) Reduced output of pulsed laser beam or generation of waveform distortion (3) Increased optical fiber coupling loss (4) Inability to control resonator length of Fabry-Perot interferometer Stable or uncontrollable

  That is, there has been a fatal problem that the flaw detection operation becomes unstable due to the deterioration of the apparatus state as described above and the flaw detection accuracy is lowered. Further, in order to ensure a constant device state for a long time, it is necessary to frequently adjust the operating conditions, so that the operation operation becomes complicated and the flaw detection cost is greatly increased. In order to enable a highly accurate flaw detection operation over a long period of time in a more stable state, it is necessary to appropriately monitor the apparatus state and reset it to optimum conditions as necessary.

The present invention has been made to solve the above-described problems, and has a device state monitoring function and a device state optimization function suitable for use in the field, and is highly stable over a long period of time in a stable state. An object of the present invention is to provide a laser ultrasonic wave receiving apparatus and a laser ultrasonic wave receiving method capable of performing an accurate flaw detection operation.

In order to achieve the above object, a laser ultrasonic wave receiving apparatus according to the present invention includes a seed laser oscillation unit that oscillates a seed laser beam that irradiates a surface of an object to be measured for detecting an ultrasonic signal, and the seed laser oscillation unit. A laser oscillation means configured to amplify the oscillation light in the form of pulses, an optical interference means for extracting an ultrasonic signal from the signal light reflected and scattered by the surface of the object to be measured, and A signal processing means for processing an output signal of the optical interference means, a state detecting means for detecting a state of the laser oscillating means, and an optical fiber for transmitting the laser light emitted from the laser oscillating means to the object to be measured. And end face reflection detecting means for detecting backscattered / reflected light from the optical fiber, and whether the incident state result of the laser light detected by the end face reflection detecting means is within a preset allowable range. When deviating a control drive means for controlling the incident position of the said optical fiber of said laser beam, display and record the incident state of the detected laser beam by said state detecting means the end surface reflection detection means In addition, when the incident state result of the end surface reflection detection means does not return to the allowable range even by driving of the control drive means, it is estimated that there is an abnormality on the transmission path of the laser light. .

In the laser ultrasonic wave receiving apparatus according to the present invention, the state detection unit detects an oscillation state of the seed laser oscillation unit.

Furthermore, the laser ultrasonic wave receiving apparatus according to the present invention is characterized in that the state detection unit detects a state of laser light pulse-oscillated from the optical amplification unit.

The laser ultrasonic wave receiving apparatus according to the present invention further includes a cooling water supply unit that supplies cooling water to an excitation light source that excites an optical amplification medium included in the optical amplification unit and cools, and the state detection unit includes the cooling unit. At least one of an operation for detecting the state of the cooling water supplied from the water supply means and an operation for controlling the state of the cooling water is executed.

Furthermore, a laser ultrasonic wave receiving apparatus according to the present invention includes a seed laser oscillating unit that oscillates a seed laser beam that irradiates the surface of an object to be measured for detecting an ultrasonic signal, and pulses the oscillation light of the seed laser oscillating unit. A laser oscillation means comprising an optical amplification means for amplifying the light, an incident light quantity detection means for detecting the incident light quantity, and an output light quantity detection means for detecting the output light quantity. A Fabry-Perot interferometer for extracting an ultrasonic signal from the signal light reflected and scattered by the optical signal, a signal processing means for processing an output signal of the optical interference means, an output signal of the incident light quantity detection means, and the output light quantity And a state detecting means for displaying and recording at least one of the output signals of the detecting means simultaneously with the ultrasonic signal of the signal processing means.

Furthermore , a laser ultrasonic wave receiving apparatus according to the present invention includes an optical fiber that transmits a laser beam applied to the object to be measured from the laser oscillation unit, an image sensor that detects an incident end surface of the optical fiber, and the image sensor. The image processing means for detecting the incident state of the laser light to the optical fiber from the detection result of the laser, and the incident state of the laser light to the optical fiber are controlled from the incident state result of the laser light detected by the image processing means And a state driving means for displaying and recording the incident state of the laser beam detected by the image processing means.

Further, the laser ultrasonic wave receiving apparatus according to the present invention includes an optical fiber that transmits a laser beam applied to the object to be measured from the laser oscillation unit, and an end surface reflection that detects backscattered / reflected light from the optical fiber. Detection means, and control drive means for controlling the incident state of the laser light into the optical fiber from the result of the incident state of the laser light detected by the end surface reflection detection means, the state detection means being the end face The incident state of the laser beam detected by the reflection detecting means is displayed and recorded.

The laser ultrasonic wave receiving apparatus according to the present invention further comprises pulse power supply means for driving an excitation light source for exciting an optical amplification medium included in the optical amplification means, and the state detection means indicates an oscillation state of the pulse power supply means. At least one of an operation to detect and an operation to control the oscillation state is executed.

Further , the laser ultrasonic wave receiving apparatus according to the present invention includes a data storage means for storing a part or all of the output signal of the state detection means or the feature amount in the apparatus, and one of the signals stored in the data storage means. And communication means for reading all or part of the data or transmitting a control signal.
The laser ultrasonic wave receiving method according to the present invention includes a seed laser oscillating unit that oscillates a seed laser beam that irradiates the surface of an object to be measured for detecting an ultrasonic signal, and pulses the oscillation light of the seed laser oscillating unit. A laser oscillation means comprising an optical amplification means that amplifies the laser signal, and an ultrasonic signal is extracted by optical interference means from the signal light reflected and scattered by the surface of the object to be measured; The output signal is processed by the signal processing means, the state of the laser oscillating means is detected by the state detecting means, and the laser light irradiated from the laser oscillating means to the object to be measured is transmitted by an optical fiber. The back scattered / reflected light is detected by the end surface reflection detecting means, and the incident state result of the laser beam detected by the end surface reflection detecting means is within a preset allowable range. When the laser beam is removed, the incident position of the laser beam on the optical fiber is controlled by the control driving unit, and the state detection unit displays and records the incident state of the laser beam detected by the end surface reflection detection unit, and the control When the incident state result of the end surface reflection detecting means does not return to the allowable range even by driving of the driving means, it is estimated that there is an abnormality on the transmission path of the laser light .

  According to the laser ultrasonic wave receiving apparatus according to the present invention having the above configuration, the state quantity of the laser ultrasonic receiving apparatus is appropriately monitored and detected, and even when a fluctuation due to disturbance occurs, the state quantity is always an appropriate value. Therefore, the flaw detection operation can be performed with high accuracy over a long period of time in a more stable state.

  Embodiments of a laser ultrasonic wave receiving apparatus according to the present invention will be specifically described below with reference to the accompanying drawings.

[Example 1]
FIG. 1 is a block diagram illustrating a configuration of a laser ultrasonic wave receiving apparatus according to the present embodiment. In addition, the same code | symbol is attached | subjected to the element same as the basic component in the conventional laser ultrasonic wave receiver shown in FIG. In the figure, TP is an object to be measured, US is an ultrasonic signal, and H is an irradiation head of received laser light.

  The laser light oscillated from the seed laser 1 in the reception pulse laser light source PDL is pulse-amplified by the optical amplifier 2 and enters the optical fiber 4 through the coupling lens L1. The output light IL of the optical fiber 4 is irradiated to the irradiation point P of the object TP to be measured by the objective lens L2 in the irradiation head H. Here, the output light IL of the optical fiber 4 irradiated on the surface of the object TP to be measured undergoes a frequency shift due to surface vibration caused by the ultrasonic signal US, and is reflected and scattered by the surface to be collected by the objective lens L3. The The condensed scattered light SL is guided to the receiving interferometer DOP via the optical fiber 7.

  A part of the scattered light SL is reflected by the partial reflection mirror PM1 and detected by the photodetector 8. On the other hand, the light component transmitted through the partial reflection mirror PM1 is incident on the Fabry-Perot interferometer FP whose resonator length is controlled by the piezoelectric element 9, and the transmitted light is input to the photodetector 10 by the lens L5. It is converted into an electrical signal corresponding to the ultrasonic signal US. On the other hand, the ultrasonic signal converted into the electric signal becomes a drive signal for the piezoelectric element 9 that drives and controls the resonator length of the Fabry-Perot interferometer FP via the frequency filter 13 and the drive control device 14. On the other hand, the ultrasonic signal converted into the electric signal is extracted through the frequency filter 11 and is appropriately converted, signal processed, displayed, and recorded by the signal processing device 12.

  Here, the first feature in the present embodiment is that the partial reflection mirror PM2 that reflects a part (in many cases, 10% or less) of the output light of the seed laser light source 1 and the photodetector 15 for measuring it. When the signal output from the light detector 15 deviates from the specified value, the state monitoring device 19 appropriately records signal conversion, signal processing, real-time numerical display or trend display, and records that fact. Is to output a warning signal or a stop signal to the apparatus. The output signal of the photodetector 15 is optical power (optical energy), optical frequency (wavelength), and the like.

  With the configuration described above, the seed laser light source 1 is monitored for changes in the seed laser light source 1 over time or abnormalities, a decrease in output of the seed laser light due to contamination of the seed laser light source 1 due to end face reflection due to optical element positional deviation, or an oscillation abnormality. At the same time, when any abnormality occurs in the apparatus, it can be fed back to the apparatus operation appropriately and quickly.

  The second feature of the present embodiment is that a part (in many cases, 10% or less) of the received laser light IL amplified in pulses by the optical amplifier 2 and adjusted to an appropriate power by the optical attenuator 6 is reflected. A partial reflection mirror PM3 and a photodetector 16 for measuring the partial reflection mirror PM3. The state monitoring device 19a appropriately converts the output signal of the photodetector 16 into signal conversion, signal processing, real-time numerical display or trend display, In addition to recording, when the output signal deviates from a specified value, a warning to that effect or a stop signal to the apparatus is output. The output signal of the photodetector 16 is a time waveform of pulsed light, optical power (optical energy), optical frequency (wavelength), pulse width, oscillation frequency, and the like.

  With the above-described configuration, the output pulse laser beam is reduced in output or waveform distortion due to temporal changes or abnormalities in the optical amplifier 2, deterioration of the flash lamp over time, end-face reflection due to optical element misalignment, and the like. Can be monitored, and when any abnormality occurs in the apparatus, it can be fed back to the apparatus operation appropriately and quickly.

  A third feature of the present embodiment is that the optical amplifier 2 that amplifies the received laser light in a pulse form includes a cooling water measuring device 17 that measures a state quantity of the cooling water system W for cooling the excitation source, The output signal of the cooling water measuring instrument 17 is appropriately signal-converted, signal-processed, real-time numerical value display or trend display and recorded by the state monitoring device 19a, and if the signal deviates from the specified value, a warning to that effect, Alternatively, a stop signal is output to the apparatus. Here, the output signal of the cooling water measuring instrument 17 is the flow rate and temperature of the cooling water.

  By configuring as described above, it is possible to monitor the operation under an abnormally high temperature condition that leads to a decrease in the output power of the received pulse laser beam due to an abnormality in the amount and temperature of the cooling water or a deterioration / failure of the apparatus. By adjusting the operation or opening degree of the valve V that adjusts the cooling water using the output signal and the valve control drive device 18, if any abnormality occurs in the cooling water system, it can be fed back to the device operation appropriately and quickly. it can.

  The fourth feature of the present embodiment is that the two output signals of the photodetector 8 and the frequency filter 13 are appropriately subjected to signal conversion, signal processing, real-time numerical display or trend display, and recorded by the state monitoring device 19a. If the signal deviates from the specified value, a warning to that effect or a device stop signal is output. The ratio of the two output signals of the photodetector 8 and the frequency filter 13 is a constant value if the apparatus is healthy, but the output value of the frequency filter 13 fluctuates if the resonator length control becomes unstable for some reason. However, the ratio of the two output signals changes. Therefore, by constantly monitoring the ratio of the two signals in this way, the stability of the resonator control of the Fabry-Perot interferometer due to environmental temperature changes and environmental vibrations is monitored, and if the control becomes unstable It is possible to feed back the apparatus operation control appropriately and quickly.

  Further, by displaying and recording at least one output signal shown in the present embodiment and an ultrasonic signal subjected to signal conversion or signal processing in the signal processing device 12 with the state monitoring device 19a simultaneously, It is possible to grasp the state of the apparatus when each waveform of the ultrasonic signal continuously collected is measured.

[Example 2]
Next, a second embodiment of the laser ultrasonic wave receiving apparatus according to the present invention will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the component same as Example 1, and the overlapping description is abbreviate | omitted.

  The feature of this embodiment is that the imaging optical system L8 and the CCD camera 20 for observing the incident end face of the optical fiber 4 on which the reception laser beam IL is incident, and the reception laser from the image information obtained by the CCD camera 20 An image processing device 21 that detects an incident position of the light IL to the optical fiber 4 and generates a control signal for controlling the incident position to an appropriate position in the core of the end face of the optical fiber 4, and the optical fiber 4 And a moving mechanism 22 for moving the end face position to the proper position described above.

  When the incident end face of the optical fiber 4 is observed in a two-dimensional image, for example, as shown in FIG. 3, the incident end face (center: C1) of the optical fiber 4 and the incident position (center: C2) of the received laser light IL are simultaneously displayed. Observe. Here, the amount of deviation (C1-C2) is quantitatively measured by the image processing device 21 shown on the left side of FIG. 3, and the amount of deviation is measured by the moving mechanism 22 at both centers as shown on the right side of FIG. By correcting so that (C1, C2) match, a constant optical fiber coupling performance can always be obtained. As the moving mechanism 22, a moving mechanism having a degree of freedom in two horizontal and vertical axes or a moving mechanism having a degree of freedom in the rotation direction can be used. It is also possible to control and drive the incident position of the received laser beam IL with respect to the end face of the fixed optical fiber 4 instead of the end face position of the optical fiber 4 as described above using an optical system (not shown).

  By configuring as described above, it is possible to monitor an increase in optical fiber coupling loss due to a positional deviation of the optical element due to a temperature change or vibration of the apparatus installation environment, and when the positional deviation exceeds a preset allowable range, It becomes possible to return the position appropriately and quickly.

  It is to be noted that the signal for positional deviation correction is appropriately signal-converted, signal-processed, real-time numerical value display or trend display, and recorded by the state monitoring device 19b, and if the signal deviates from the specified value, a warning to that effect, Alternatively, an apparatus stop signal can be output.

[Example 3]
Next, a third embodiment of the laser ultrasonic wave receiving apparatus according to the present invention will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the component same as Examples 1-2, and the overlapping description is abbreviate | omitted.

  The characteristic configuration in the present embodiment is light detection for measuring the amount of light reflected and scattered backward in the direction of the optical amplifier 2 from the optical fiber 4 on which the received laser beam IL is incident (hereinafter referred to as “end surface reflected light amount”). 23, a control device 24 for generating a control signal for controlling the incident position of the received laser beam IL to an appropriate position in the core of the end face of the optical fiber 4 so as to keep the output signal at a constant value, and an optical fiber 4 is provided with a moving mechanism 22 for moving the end face position of 4 to the above-described proper position. As the moving mechanism 22, a moving mechanism having a degree of freedom in two horizontal and vertical directions or a moving mechanism having a degree of freedom in the rotational direction can be used.

  While the reception laser beam IL propagates from the optical fiber 4 to the irradiation head H, a part of the reception end surface of the optical fiber 4 (for example, the material of the optical fiber is quartz glass). Assuming that the installation environment is in the air, about 3 to 5% of the light is scattered and reflected backward. These scattering / reflection amounts are numerical values that should always be constant if the state of the apparatus is steady. Here, by correcting the coupling of the optical fiber 4 by the moving mechanism 22 so that the end surface reflected light amount is held at a constant value by the control device 24, a constant optical fiber coupling performance can be always obtained. It is also possible to control and drive the incident position of the received laser beam IL with respect to the end face of the fixed optical fiber 4 instead of the end face position of the optical fiber 4 using an optical system (not shown).

  By configuring as described above, it is possible to monitor an increase in optical fiber coupling loss due to a positional shift of the optical element due to a temperature change or vibration of the apparatus installation environment, and when the positional shift exceeds a preset allowable range, It is possible to return to the proper position appropriately and quickly. If the output signal of the light detector 23 does not return to a normal value due to the operation of the moving mechanism 22, there is some abnormality in the transmission path of the received laser light IL (the optical fiber 4 and the objective lens L2 in FIG. 4). It can also be estimated.

  In addition, the signal of the photodetector 23 is appropriately signal-converted, signal-processed, real-time numerical value display or trend display, and recorded by the state monitoring device 19c, and if the signal deviates from the specified value, a warning to that effect Alternatively, it is possible to output a device stop signal. Further, the soundness of the optical fiber 4 or 7 or the irradiation head H is obtained by observing and recording this signal and the output signal of the photodetector 8 indicating the output of the scattered light SL incident on the receiving interferometer. Can also be estimated.

[Example 4]
Next, Embodiment 4 of the laser ultrasonic wave receiving apparatus according to the present invention will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the component same as Examples 1-3, and the overlapping description is abbreviate | omitted.

  The characteristic configuration of this embodiment includes a power supply monitoring control device 25 that measures and controls the oscillation state of the power supply 3 of the optical amplifier 2 that pulse-amplifies the laser light oscillated from the seed laser light source 1. The state monitoring device 19c appropriately records the signal conversion, signal processing, real-time numerical value display or trend display, and records the output signal when the signal deviates from the specified value, or stops to the device. It is to output a signal. The output signal of the power supply monitoring control device 25 is the oscillation frequency, peak voltage, number of oscillation pulses, etc. of the pulse power supply.

  With the configuration described above, deterioration with time of the pumping flash lamp can be monitored, and when the oscillation output of the received laser light IL is reduced, the power supply 3 is not used without depending on the optical attenuator 6 as shown in FIG. Therefore, it is possible to narrow down the oscillation output and extend the life of the power supply 3 and the flash lamp.

[Example 5]
Next, a laser ultrasonic receiving apparatus according to a fifth embodiment of the present invention will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the same component as the said Examples 1-4, and the overlapping description is abbreviate | omitted.

  The characteristic configuration of the present embodiment is such that at least one of the reception pulse laser light source PDL and the reception interferometer DOP outputs a part of the output signal of each monitoring / control function described in the first to fourth embodiments or a feature amount thereof. Alternatively, the data storage device 25 for storing all of the data and the interfaces 26a and 26b for reading out the data are provided, and the data is appropriately read out by using the interfaces 26a and 26b in the state monitoring device 19d, and converted into signals. In addition to signal processing, real-time numerical display or trend display, and recording, when the signal deviates from a specified value, a warning to that effect or a stop signal to the apparatus is output. As the interfaces 26a and 26b, any combination of wired, wireless analog format, and digital format can be considered. Further, a control signal is transmitted from the state monitoring device 19d to the reception pulse laser light source PDL and to the reception interferometer DOP, and the operation of the drive mechanism 22, the opening of the valve V, and the oscillation state by the power supply monitoring control device 25 are controlled remotely. It is also possible to do.

The block diagram which shows the structure of the 1st Example of the laser ultrasonic wave receiver which concerns on this invention. The block diagram which shows the structure of the 2nd Example of the laser ultrasonic wave receiver which concerns on this invention. Sectional drawing which shows the incident state of the received laser beam to an optical fiber. The block diagram which shows the structure of the 3rd Example of the laser ultrasonic wave receiver which concerns on this invention. The block diagram which shows the structure of 4th Example of the laser ultrasonic wave receiver which concerns on this invention. The block diagram which shows the structure of 5th Example of the laser ultrasonic wave receiver which concerns on this invention. The block diagram which shows the structure of the conventional laser ultrasonic wave receiver. Explanatory drawing which shows operation | movement of a Fabry-Perot interferometer. The block diagram which shows the other structural example of the conventional laser ultrasonic wave receiver.

DESCRIPTION OF SYMBOLS 1 Seed laser light source 2 Optical amplifier 3 Power supply 4, 7, 15, 17 Optical fiber 8, 10, 15, 16, 23 Photo detector 11, 13 Frequency filter 12 Signal processing device 17 Cooling water measuring device 18 Valve control drive device 19 , 19a, 19b, 19c, 19d State monitoring device 20 CCD camera 21 Image processing device 22 Incident state adjustment drive mechanism TP Inspected object V Cooling water adjustment valve PDL Reception pulse laser light source DOP Reception interferometer H Irradiation head US Sound wave signal W Cooling water FP Fabry-Perot interferometer PM1, PM2 Partial reflection mirror L Lens (or lens group)
M mirror

Claims (4)

A laser comprising a seed laser oscillating means that oscillates a seed laser beam that irradiates the surface of an object to be measured for detecting an ultrasonic signal, and an optical amplifying means that amplifies the oscillation light of the seed laser oscillating means in a pulsed manner. Oscillation means;
Optical interference means for extracting an ultrasonic signal from signal light reflected and scattered by the surface of the object to be measured;
Signal processing means for processing an output signal of the optical interference means;
State detection means for detecting the state of the laser oscillation means;
An optical fiber that transmits a laser beam applied to the object to be measured from the laser oscillation unit;
End face reflection detection means for detecting backscattered / reflected light from the optical fiber;
Control drive means for controlling the incident position of the laser light on the optical fiber when the result of the incident state of the laser light detected by the end face reflection detection means deviates from a preset allowable range; With
The state detection means displays and records the incident state of the laser beam detected by the end face reflection detection means, and the incident state result of the end face reflection detection means returns to the allowable range by driving the control drive means. If not, it is estimated that there is an abnormality on the laser light transmission path . A laser comprising a seed laser oscillating means that oscillates a seed laser beam that irradiates the surface of an object to be measured for detecting an ultrasonic signal, and an optical amplifying means that amplifies the oscillation light of the seed laser oscillating means in a pulsed manner. Oscillation means;
A Fabry for detecting an incident light quantity and an output light quantity detecting means for detecting an output light quantity, and for extracting an ultrasonic signal from the signal light reflected and scattered by the surface of the object to be measured.・ Perot interferometer,
Signal processing means for processing an output signal of the optical interference means;
At least one of the output signal of the output signal and the output light amount detecting means of the incident light amount detecting means and a state detecting means for displaying and recording with a ultrasonic signal and simultaneity of the signal processing means, said state detecting means A laser ultrasonic wave reception that outputs a warning or a stop signal when at least one of an output signal of the incident light amount detection means and an output signal of the output light amount detection means to display and record deviates from a specified value apparatus. Data storage means for storing a part or all of the output signal of the state detection means or the feature amount in the apparatus;
3. The laser ultrasonic wave receiving apparatus according to claim 1, further comprising a communication unit for reading out part or all of the signal stored in the data storage unit or transmitting a control signal. The laser oscillation means comprises: a seed laser oscillation means that oscillates a seed laser beam that irradiates the surface of the object to be measured for detecting an ultrasonic signal; and an optical amplification means that amplifies the oscillation light of the seed laser oscillation means in a pulse shape. Configure
  From the signal light reflected and scattered by the surface of the object to be measured, an ultrasonic signal is extracted by optical interference means,
Processing the output signal of the optical interference means by a signal processing means;
The state of the laser oscillation means is detected by a state detection means,
Transmitting the laser beam irradiated from the laser oscillation means to the object to be measured through an optical fiber,
The back-scattered / reflected light from this optical fiber is detected by the end face reflection detection means,
When the incident state result of the laser beam detected by the end surface reflection detection unit deviates from a preset allowable range, the incident position of the laser beam to the optical fiber is controlled by the control driving unit,
The state detecting means displays and records the incident state of the laser beam detected by the end face reflection detecting means, and the incident state result of the end face reflection detecting means does not return to the allowable range even when the control driving means is driven. In this case, it is estimated that there is an abnormality on the transmission path of the laser beam.

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