JP4621781B2 - Laser ultrasonic inspection equipment - Google Patents

Description

  In the present invention, for example, a reactor bottom structure of a nuclear reactor that is difficult to contact or approach, such as a small size, high temperature, or operating part, is measured, and the measurement target is installed in an underwater environment, a dust environment, or a narrow environment. The present invention relates to a laser ultrasonic inspection apparatus capable of performing non-contact, non-destructive and high-precision inspection of cracks and defects or material evaluation.

  In recent years, for example, a laser ultrasonic method has been proposed as a technique for crack inspection of equipment and structural materials in power plants. For an overview of this technology, for example, “Yamawaki:“ Laser Ultrasound and Non-Contact Material Evaluation ”, Journal of Welding Society, Vol. 64, No. 2, P. 104-108 (issued in 1995)” (for example, non-patent It is described in documents such as Document 1).

  The laser ultrasonic method described in this document often transmits ultrasonic waves using thermal stress or vaporization reaction force generated by irradiating a material to be inspected with pulsed laser light. In this case, the receiving point is irradiated with another laser beam that continuously oscillates, and the displacement or vibration speed induced by the ultrasonic wave is received using the straightness and coherence.

  Although it is a known technique to detect a crack or intrinsic defect of a material or to evaluate a material characteristic using ultrasonic waves in this way, according to a laser ultrasonic method, these are performed in a non-contact manner. Therefore, it is expected to be applied to various material evaluation fields.

  Several different optical systems have been proposed as ultrasonic transmission / reception methods in the laser ultrasonic method, and in particular, as a receiving optical system, Michelson interferometry, Mach-Zehnder interferometry, Fabry-Perot method, phase conjugation method, A knife edge method has been proposed. Here, a block diagram of a typical conventional laser ultrasonic inspection apparatus shown in FIG. 23 is shown for an ultrasonic generation method using pulsed laser light irradiation and ultrasonic reception means using a phase conjugate method, which are closely related to the present invention. Indicates.

  As shown in FIG. 23, pulse laser light PL oscillated from an ultrasonic wave generation laser light source 1 for generating ultrasonic waves is irradiated to a predetermined position on the surface of the inspection object 3 in a predetermined beam shape via the irradiation optical system 2. Is done. Here, as the laser light source 1 for generating ultrasonic waves, a Q-switched YAG laser or the like is often used.

  When the surface of the inspection object 3 is irradiated with the pulse laser beam PL in this way, the inspection object 3 has various modes such as longitudinal wave, transverse wave, and surface wave due to the interaction between the inspection object 3 and the pulse laser light PL. The ultrasonic wave US is generated, and the ultrasonic wave US generates a phenomenon such as reflection, scattering, and change in sound speed depending on a crack or a defect included in the material 3 to be inspected or material characteristics of the material 3 to be inspected. Will not be discussed in detail. In any case, when the ultrasonic wave US propagated based on a certain propagation process reaches an arbitrary measurement point on the material 3 to be inspected, a displacement occurs at that part.

On the other hand, the laser light IL oscillated from the ultrasonic light source 4 for detecting the ultrasonic wave US is incident on the phase conjugate element 5 in the receiving optical system OP. Here, as the crystal of the phase conjugate element 5, a ferroelectric crystal (BaTiO ₃ , LiNbO ₃ etc.), a paraelectric crystal (BSO etc.), and a semiconductor (GaAs, InP, GaP etc.) are used.

  Then, the laser beam IL transmitted through the phase conjugate element 5 is incident on the first optical fiber 6 by the collimator M1, and the laser beam IL emitted from the optical fiber 6 passes through the objective lens M2 and is desired for the material 3 to be inspected. The measurement point is irradiated. Scattered light (a part of the scattered component) SL of the laser light IL irradiated to the inspection object 3 is collected by the second objective lens M3 and passes through the second optical fiber 7 and the second collimator M4. Then, it enters the phase conjugate element 5 again.

  In the normal case, when the surface of the material 3 to be inspected is optically rough, the wavefront of the scattered light SL is distorted and the interference efficiency is extremely low, so that no interference signal can be obtained. In FIG. 3, the scattered light SL interferes due to the phase conjugate effect, and the interference signal can be detected with relatively high efficiency by the photodetector 9 via the mirror 8 and the lens M5. The signal detected by the photodetector 9 is appropriately signal-processed by the signal processing device 10 and displayed and recorded.

  Here, as the photodetector 9, a PIN type photodiode (hereinafter referred to as PIN-PD) or an avalanche photodiode (hereinafter referred to as APD) is often used, and these are stationary from the first external power supply 11. It operates by applying a bias voltage. The phase conjugate element 5 also operates by applying a bias voltage on the order of several kV to several tens of orders from the second external power supply 12, and this bias voltage is applied in a pulse shape in order to suppress the drift of the phase conjugate element 5. The operation mode is set to

  Furthermore, the trigger oscillator 13 synchronizes the operation timing of the ultrasonic light generation laser light source 1 and the operation of the second external power supply 12 so as to obtain the maximum interference efficiency in the phase conjugate element 5 at the ultrasonic measurement time. To do.

  On the other hand, there is also a method in which the oscillation light PL of the ultrasonic wave generation laser light source 1 having relatively high pulse energy is incident on the optical fiber using the structure shown in FIG. In this method, the collimating lens unit CL is configured by disposing the minute lens array 15 between the first and second lens systems 14 and 16, thereby diffusing the focal point and avoiding damage to the third optical fiber 17. If this structure is used, it is possible to transmit both transmitted and received light through an optical fiber.

Yamawaki: “Laser ultrasonic waves and non-contact material evaluation”, Journal of the Japan Welding Society, Vol. 2, P.I. 104-108 (issued in 1995)

  As described above, the laser ultrasonic inspection apparatus according to the conventional method is in principle a remote non-contact inspection in which the material to be inspected 3 is difficult to contact or has poor proximity such as high temperature, high place, high radiation field, complicated shape part, etc. This is effective when the method is required, and it is also effective when the laser beam is difficult to transmit spatially by applying optical fiber technology, such as inside narrow spaces or shields. Is.

  However, the inspected material 3 is often installed in an inspection environment such as an underwater environment or a dust environment. In particular, when an inspection using surface waves is performed on the material 3 to be inspected installed in an underwater environment, a signal / noise ratio (hereinafter referred to as S / N ratio) decreases due to attenuation of the surface wave signal component. Is concerned.

  The present invention has been made in consideration of the above-described circumstances, and an object thereof is to provide a laser ultrasonic inspection apparatus capable of detecting a signal with high sensitivity in an underwater environment and efficiently reducing noise.

In order to solve the above-described problem, a laser ultrasonic inspection apparatus according to an embodiment of the present invention includes a first laser light source that oscillates a first laser beam for generating an ultrasonic wave in a material to be inspected, and the inspection object. A second laser light source that oscillates a second laser beam applied to the material to be inspected in order to receive an ultrasonic signal generated on the material; and a reflection component of the second laser light on the surface of the material to be inspected Receiving optical system for optically detecting information on the ultrasonic wave from, a signal converting means for converting an ultrasonic signal received in the receiving optical system into an electrical signal, and an output signal of the signal converting means And a signal processing device for displaying and recording information relating to ultrasonic propagation, wherein the first laser light source is a Q-switch pulse laser light source, and the pulse width of the oscillating pulse light is 100 nanometers Characterized in that from a variable pulse width variable laser light source in the range of 1 microsecond.

According to the laser ultrasonic inspection apparatus of the embodiment of the present invention, it is possible to transmit and receive an ultrasonic signal with a higher S / N ratio by irradiating a transmission laser beam having a pulse width matched to a desired frequency band. It becomes.

The laser ultrasonic inspection apparatus according to claim 1 receives a first laser light source that oscillates a first laser beam for generating ultrasonic waves in a material to be inspected, and an ultrasonic signal generated in the material to be inspected. A second laser light source that oscillates a second laser beam applied to the material to be inspected, and an irradiation / condensing mechanism that receives a reflection component of the second laser light on the surface of the material to be inspected. A receiving optical system for optically detecting information related to the ultrasonic wave from the reflected component collected by the irradiation / condensing mechanism, and an ultrasonic signal received by the receiving optical system. A signal converting means for converting the signal into the signal, a signal processing device for processing and processing the output signal of the signal converting means, and displaying and recording information relating to the propagation of the ultrasonic wave, and the ambient environment generated by the irradiation of the first laser beam. Propagating through the medium Is received by an optical system, the ultrasonic than wave signal and the reference signal amplitude measuring means for measuring the amplitude of the large amplitude signal components, the reference signal amplitude measuring means and the irradiation-condensing mechanism such that the output becomes the maximum And an optical system drive control mechanism for controlling the drive of the optical system.

According to the laser ultrasonic inspection apparatus according to claim 1, generated by irradiation of the first laser light is received by the receiving optical system to propagate the surrounding environment medium, the large amplitude signal than the ultrasonic signal By having a reference signal amplitude measuring means for measuring the amplitude of the component and an optical system drive control mechanism for driving and controlling the irradiation / condensing mechanism so that the output of the reference signal amplitude measuring means is maximized. If a signal component propagating through a large-amplitude environmental medium can be observed, it can be used as a reference, and the focus position can be adjusted so that the signal amplitude is maximized. Become.

A laser ultrasonic inspection apparatus according to an embodiment of the present invention includes a first laser light source that oscillates a first laser beam for generating an ultrasonic wave in a material to be inspected, and the first laser light as the material to be inspected. An irradiation mechanism for irradiating the inspection object; a second laser light source for oscillating a second laser light applied to the inspection material in order to receive an ultrasonic signal generated on the inspection material; An irradiation / condensation mechanism for receiving a reflection component of the laser beam on the surface of the object to be inspected, and optically detecting information on the ultrasonic wave from the reflection component condensed by the irradiation / condensation mechanism A receiving optical system, a signal converting means for converting an ultrasonic signal received by the receiving optical system into an electric signal, an output signal of the signal converting means is signal-processed, and information on ultrasonic propagation is displayed and Signal processing device to record and before A scanning unit that scans in a single axial direction on the material to be inspected while fixing a positional relationship between an irradiation mechanism and the irradiation / condensing mechanism, and scans by the scanning unit in the X-axis direction in the signal processing device. The space is displayed in two dimensions by taking time in the Y-axis direction and displaying the surface wave component, the volume wave component, and the reflection / transmission / diffraction component derived therefrom.

According to the laser ultrasonic inspection apparatus of the embodiment of the present invention, in the case of crack inspection, since the crack has a certain length and depth, the ultrasonic wave reflected, transmitted, and diffracted from the crack while scanning. Is recorded, a pattern corresponding to the crack is formed. While the noise component is random, this pattern has regularity according to the crack shape, so according to the two-dimensional display measured in this way, the signal component that has the same amplitude as the noise component is also distributed. Can be detected.

A laser ultrasonic inspection apparatus according to an embodiment of the present invention includes a plurality of channels of a reception system including the irradiation / condensing mechanism, the reception optical system, the signal conversion unit, and the signal processing device. It is characterized by that.

According to the laser ultrasonic inspection apparatus of the embodiment of the present invention, when a minute crack signal is detected, a transmitted wave (and a forward diffracted wave in some cases) and a reflected wave (and a backward diffracted wave in some cases) are detected. By detecting both, the reliability can be improved. Therefore, by providing a plurality of reception systems as in the laser ultrasonic inspection apparatus according to claim 9, it is possible to measure crack properties from many information sources and perform highly reliable crack inspection. Become.

  According to the present invention, it is possible to detect a signal with high sensitivity in an underwater environment and efficiently reduce noise.

The block block diagram which shows 1st Embodiment of the laser ultrasonic inspection apparatus which concerns on this invention. The expanded sectional view which shows the probe in FIG. (A) is the sectional view on the AA line in FIG. 2, (B) is the sectional view on the BB line in FIG. The block block diagram which shows 2nd Embodiment of the laser ultrasonic inspection apparatus which concerns on this invention. (A), (B) is explanatory drawing which shows the effect | action by the 1st modification of 2nd Embodiment of the laser ultrasonic inspection apparatus which concerns on this invention. (A), (B), (C) is explanatory drawing which shows the effect | action by the 2nd modification of 2nd Embodiment of the laser ultrasonic inspection apparatus which concerns on this invention. (A), (B) is explanatory drawing which shows the effect | action by the 3rd modification of 2nd Embodiment of the laser ultrasonic inspection apparatus which concerns on this invention. The block block diagram which shows the 4th modification of 2nd Embodiment of the laser ultrasonic inspection apparatus which concerns on this invention. The block block diagram which shows 3rd Embodiment of the laser ultrasonic inspection apparatus which concerns on this invention. The block block diagram which shows 4th Embodiment of the laser ultrasonic inspection apparatus which concerns on this invention. The block block diagram which shows 5th Embodiment of the laser ultrasonic inspection apparatus which concerns on this invention. The timing chart which shows the operation | movement of 5th Embodiment of this invention. The block block diagram which shows 6th Embodiment of the laser ultrasonic inspection apparatus which concerns on this invention. The block block diagram which shows 7th Embodiment of the laser ultrasonic inspection apparatus which concerns on this invention. The block block diagram which shows 8th Embodiment of the laser ultrasonic inspection apparatus which concerns on this invention. The block block diagram which shows 9th Embodiment of the laser ultrasonic inspection apparatus which concerns on this invention. The figure which shows the visualization result of a crack and a parallel direction regarding the 1st receiving system in 9th Embodiment of this invention. The figure which shows the visualization result of a crack and a parallel direction regarding the 2nd receiving system in 9th Embodiment of this invention. The perspective view which shows the actual crack shape of a to-be-inspected material. The figure which shows the visualization result of a crack and a perpendicular direction regarding the 1st receiving system in 9th Embodiment of this invention. The block block diagram which shows 10th Embodiment of the laser ultrasonic inspection apparatus which concerns on this invention. The figure which shows the visualization result by 10th Embodiment of the laser ultrasonic inspection apparatus which concerns on this invention. The block block diagram which shows the conventional laser ultrasonic inspection apparatus. The block diagram which shows the example which used the optical fiber for the laser beam transmission of the transmission side in the conventional laser ultrasonic inspection apparatus.

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

[First Embodiment]
FIG. 1 is a block diagram showing a first embodiment of a laser ultrasonic inspection apparatus according to the present invention. Parts that are the same as or correspond to those in the conventional configuration will be described using the same reference numerals as in FIGS.

  As shown in FIG. 1, the laser ultrasonic inspection apparatus of the present embodiment is a first laser light source that oscillates a pulsed laser light PL as a first laser light for generating an ultrasonic wave in the inspection object 3. A certain laser light source 1 for generating ultrasonic waves, a probe 18 equipped with an irradiation optical system 2 shown in FIG. 23 for irradiating the inspection target material 3 with the pulsed laser light PL, and an ultrasonic wave generated by the inspection target material 3. An ultrasonic detection laser light source 4 that is a second laser light source that oscillates a laser beam IL as a second laser beam irradiated to the material to be inspected 3 in order to receive a signal; In addition to the irradiation optical system 2, an objective lens M2 and a second objective lens M3, which are an irradiation / condensing mechanism for receiving a reflection component of the laser beam IL on the surface of the inspection object 3 are mounted.

  In addition, the laser ultrasonic inspection apparatus of the present embodiment receives for optically detecting information on the ultrasonic wave from the reflected component collected by the objective lens M2 and the second objective lens M3 in the probe 18. Optical system OP, a photodetector 9 as signal conversion means for converting an ultrasonic signal received by the receiving optical system OP into an electrical signal, and an output signal of the photodetector 9 is subjected to signal processing, And a signal processing device 10 that displays and records information related to the propagation of sound waves.

  Further, the photodetector 9 operates by applying a steady bias voltage from the first external power supply 11, and the phase conjugate element 5 provided in the receiving optical system OP is also supplied from the second external power supply 12. It operates by applying a bias voltage of several kV to several tens of orders. The trigger oscillator 13 synchronizes the operation timing of the ultrasonic wave generation laser light source 1 and the operation of the second external power supply 12.

  Therefore, the ultrasonic wave US excited on the inspection object 3 by the pulsed laser light PL is detected by the photodetector 9 using the receiving optical system OP from the reflected component of the laser light IL oscillated from the ultrasonic light source 4 for ultrasonic detection. The signal detected and detected by the light detector 9 is processed in the signal processing device 10, and the display and recording operation is the same as the operation of the configuration shown in FIGS.

  Further, in the present embodiment, the tips of the first, second and third optical fibers 6, 7, and 17 are attached to the probe 18 to which the irradiation optical system 2, the objective lens M2 and the second objective lens M3 (not shown) are attached. It is connected.

  One end of a pipe 19 is connected to the probe 18, and the other end of the pipe 19 is connected to a pump 20. The probe 18, the pipe 19, and the pump 20 constitute a replacement means, and the pump 20 is driven. The wavelength of the ultrasonic light generating laser light source 1 and the wavelength of the ultrasonic light detecting laser light source 4 are easily transmitted from the pipe 19 to the probe 18, that is, water as a transparent fluid FL having a high transmittance is contained in the medium (water) MD. The fluid FL is replaced with the propagation path of the pulsed laser light PL, the reflected light of the laser light IL, and the ultrasonic wave US.

  FIG. 2 is an enlarged sectional view showing the probe 18 in FIG. FIG. 2 shows a case where individual probes are used in each optical system, and only the irradiation system of the laser beam IL is shown.

  As shown in FIG. 2, the first optical fiber 6 that transmits the laser beam IL for reception is connected to the probe 18, and the laser beam IL is transmitted from the probe 18 by the first and second plates 21a and 21b. The material to be inspected 3 is irradiated through collimating lenses M2a and M2b that are supported and constitute the objective lens M2.

  Further, as shown in FIGS. 3A and 3B, a plurality of small holes 23 for circulating the fluid FL are formed in the first and second plates 21a and 21b in the circumferential direction. As shown in FIG. 2, a fluid pipe 19 is also inserted into the probe 18 so that the flow is substantially coaxial with the laser beam IL, and the fluid FL supplied from the pipe 19 completely passes through the probe 18. The fluid FL is sprayed from the plurality of small holes 23 onto the material 3 to be inspected.

  Further, as shown in FIG. 2 and FIGS. 3A and 3B, the first and second backflow prevention plates 22a, 22b,... Formed in a cylindrical shape are concentrically installed at the tip of the probe 18. ing.

  Next, the operation of this embodiment will be described.

  Although the transmission efficiency of ultrasonic waves to the material 3 to be inspected and the reception sensitivity of ultrasonic signals change according to the outputs of the laser light source 1 for generating ultrasonic waves and the laser light source 4 for detecting ultrasonic waves, respectively, for example, underwater with low transparency Under an environment or dust environment, loss due to scattering or the like occurs on the light propagation path, and efficient signal transmission / reception becomes impossible.

  Therefore, in the present embodiment, by driving the pump 20, the transparent fluid FL that is easily transmitted from the pipe 19 to the probe 18 with respect to the wavelength of the ultrasonic light generating laser light source 1 and the wavelength of the ultrasonic detecting laser light source 4. As the water is supplied, and the inside of the probe 18 is completely filled with the fluid FL, the fluid FL is sprayed from the plurality of small holes 23 onto the material to be inspected 3 installed in the medium (water) MD, and the pulse laser beam PL The reflected light of the laser beam IL and the propagation path of the ultrasonic wave US are replaced with the fluid FL. Thereby, highly efficient signal transmission / reception becomes possible.

  Here, depending on the flow rate of the fluid FL, the vicinity of the optical path and the ultrasonic wave propagation path are all replaced with the fluid FL, but depending on the conditions, a backflow may occur and the surrounding medium MD may be mixed into the optical path or the like. That is, when the underwater environment is replaced with gas, there is a concern that water may be involved in the flow path depending on the gas flow rate and the replacement may not be performed normally.

  Therefore, in the present embodiment, as shown in FIGS. 2 and 3A and 3B, the first and second backflow prevention plates 22a, 22b,. It is possible to sufficiently perform the replacement without being hindered by the backflow by preventing the backflow. Thus, by preventing the above entrainment with a mechanical structure or the like, it is possible to secure an optical path under a wide range of conditions.

  In addition, according to the present embodiment, since the material to be inspected 3 is installed in an underwater environment, and the transparent fluid medium is water, high efficiency is achieved without adversely affecting the environment and the material under inspection 3. Signal transmission / reception becomes possible.

  In the present embodiment, the three optical fibers 6, 7, and 17 and the three optical systems connected thereto are integrated as one probe 18, but it is also possible to use independent probes. . In this case, the pipe 19 may be connected to each probe, and depending on the flow rate, the fluid may be supplied by combining the paths of three probes from one pipe. Further, in FIG. 1, the fluid FL flows in parallel with the optical axis, but the position of the pipe 19 may be changed to flow in parallel with the material 3 to be inspected.

  In the present embodiment, the case where the medium MD is water and the fluid FL is water has been described. However, the present invention is not limited to this, and the medium MD may be water and the fluid FL may be an inert gas. . As the fluid FL in this case, if an inert gas such as nitrogen or argon is used, it is effective because no chemical action is caused even if the material of the material to be inspected 3 is a corrosive metal. Depending on the material of the inspection material 3, cheaper compressed air or the like may be used.

  That is, in this case, the inspection object 3 is installed in an underwater environment, the main ultrasonic component to be detected is a surface wave, and the medium MD of the transparent fluid FL includes the propagation path of the surface wave. Is a replaceable inert gas.

  In an underwater environment, particularly when transmitting and receiving surface waves, attenuation occurs due to the surface of the material to be inspected 3 being in contact with water. Therefore, by replacing the optical path and the propagation path of the surface wave with a clean gas, it becomes possible to form an environment with less attenuation not only in optically efficient signal transmission / reception but also in ultrasonic.

  Furthermore, in the present embodiment, the portion exposed to the environment in the optical path reaching the surface of the inspection object 3 of the laser beam IL is replaced with water. However, the present invention is not limited to this, and the inspection object 3 of the pulsed laser light PL is not limited thereto. The portion exposed to the environment in the optical path reaching the surface may be replaced with water. In short, the portion exposed to the environment in the optical path reaching the surface of at least one of the laser light IL and the pulse laser light PL to be inspected material 3. What is necessary is just to substitute the watered part with water.

[Second Embodiment]
FIG. 4 is a block diagram showing a second embodiment of the laser ultrasonic inspection apparatus according to the present invention. The same parts as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted. Only different configurations and operations will be described. The same applies to other embodiments and modifications.

  In the present embodiment, in addition to the configuration of the laser ultrasonic inspection apparatus shown in FIG. 1, the probe 18 is provided with a first photoacoustic shielding plate 24 as photoacoustic shielding means.

  That is, in the present embodiment, the irradiation position of the pulsed laser light PL as the first laser light to the inspection target material 3 and the irradiation position of the laser light IL as the second laser light to the inspection target material 3 A first photoacoustic shielding plate that is inserted in between and has an acoustic impedance significantly different from that of the surrounding environmental medium, and in which the wavelength of the ultrasonic light generation laser light source 1 and the wavelength of the ultrasonic detection laser light source 4 are not excessive 24 is provided on the probe 18.

  Next, the operation of this embodiment will be described.

  The laser ultrasonic inspection apparatus detects a weak signal reflected / scattered from the rough surface of the laser light IL in the vicinity of the pulse laser light PL having a relatively high output due to its configuration. The pulse laser beam PL is also reflected / scattered on the surface of the material 3 to be inspected, and if it is mixed into the receiving system, it may become measurement noise. In addition, there is an ultrasonic path that is generated by the irradiation of the pulsed laser light PL and reaches the receiving system without passing through the surface and the inside of the material to be inspected 3, and these become noise for measurement.

  Therefore, in the present embodiment, by having the first photoacoustic shielding plate 24 that shields them, detection of signal components can be performed more simply and with a high S / N ratio.

  In other words, in the present embodiment, the first photoacoustic shielding plate 24 is provided on the probe 18 so that the reflection component of the pulse laser light PL for transmission having a relatively high intensity is not shown. It is possible to prevent the light from entering into the receiving optical system OP and the photodetector 9 through the second objective lens M3 and the second optical fiber 7 as described above.

[First Modification]
FIGS. 5A and 5B are explanatory views showing the operation of the first modification of the second embodiment of the laser ultrasonic inspection apparatus according to the present invention.

  With respect to ultrasonic noise, a case as shown in FIG. That is, the noise component NUS propagating to the medium MD side by irradiation with the pulse laser beam PL for transmission enters the second photoacoustic shielding plate 24a, propagates inside or on the surface (NNUS in the figure), and ultrasonic waves This is a case where noise ultrasonic waves NNNNUS are radiated again at a site where a mode change or leakage may occur. This component changes the refractive index on the propagation path of the receiving laser beam IL, or directly vibrates the second objective lens M3 as an irradiation / condensing optical system, and noise is mixed in the measurement signal. There is a case.

  That is, although the ultrasonic component that becomes noise is mainly shielded by the second photoacoustic shielding plate 24a, a part of the component (NNUS) propagates through the second photoacoustic shielding plate 24a. However, depending on the shape, noise ultrasonic waves NNNUS may be re-emitted to the environment and become noise.

  Therefore, in this modified example, as shown in FIG. 5B, the third photoacoustic shielding plate 24b is formed in a smooth curved surface shape that is difficult to become a secondary sound source due to its structure, so that secondary noise ultrasonic waves are formed. It is possible to reduce the radiation of the component NNNUS and further reduce the noise.

[Second Modification]
6 (A), 6 (B), and 6 (C) are explanatory views showing the operation of the second modification of the second embodiment of the laser ultrasonic inspection apparatus according to the present invention.

  As for the noise component that propagates inside the second photoacoustic shielding plate 24a and is radiated again (see FIG. 6A), the first photoacoustic shielding plate 24 is moved to the first position as shown in FIG. 6B. The laminated structure of the first and second thin films 24c, 24d... Reflects and scatters the ultrasonic wave NNUS propagating through the inside many times, thereby reducing the emission of noise components to the receiving side.

  That is, as shown in FIG. 6A, the ultrasonic component that becomes noise is mainly shielded by the second photoacoustic shielding plate 24a, and at that time, a part of the component is the second photoacoustic shielding. It propagates inside the plate 24a, and depending on its shape, it may be re-emitted to the environment and become noise.

  Therefore, in this modification, as shown in FIG. 6B, the first photoacoustic shielding plate 24 has a laminated structure of the first and second thin films 24c, 24d. Since the sound wave component is reflected and scattered repeatedly and immediately attenuates, the noise can be further reduced.

  Moreover, in this modification, as shown in FIG.6 (C), the inside of the 1st photoacoustic shielding board 24 is formed in hollow, and the radiation | emission of the noise component to a receiving side is reduced. Here, the inside 24f of the hollow structure is sufficient if it is a medium whose acoustic impedance is significantly different from that of the structural material 24e (for example, when the structural material 24e is a metal, the inside 24f may be air). If a vacuum is applied, it is possible to completely prevent the ultrasonic component transmitted through the interior 24f.

  Therefore, in the present modification, the inside of the first photoacoustic shielding plate 24 is disposed as shown in FIG. 6C so that the ultrasonic component incident on the inside of the mechanism does not reach the back surface of the reaching surface and is re-emitted. By using a hollow structure, noise can be further reduced.

[Third Modification]
FIGS. 7A and 7B are explanatory views showing the operation of the third modification of the second embodiment of the laser ultrasonic inspection apparatus according to the present invention.

  As shown in FIG. 7A, when the ultrasonic wave component propagating through the medium near the surface of the material to be inspected 3 or the surface wave component propagating through the surface of the material to be inspected 3 becomes noise, FIG. As shown in FIG. 4, an elastic body such as rubber 24h is fixed to the tip of the fourth photoacoustic shielding plate 24g, and the rubber 24h is pressed against the material to be inspected 3 to block the propagation path in the medium MD and Surface wave components that propagate while inducing displacement can also be attenuated.

[Fourth Modification]
FIG. 8 is a block diagram showing a fourth modification of the second embodiment of the laser ultrasonic inspection apparatus according to the present invention.

  In the fourth modified example, as shown in FIG. 8, the first photoacoustic shielding plate 24 described with reference to FIG. 7B is installed in addition to the configuration of FIG. An elastic body layer such as rubber 24h shown in FIG. 7 (B) is fixed to the front end of the, and a contact sensor 25 as a contact detecting means is attached to the elastic body layer. As the contact sensor 25, an electrical resistance sensor, an optical touch sensor, an ultrasonic distance measurement touch sensor, or the like can be used.

  The first photoacoustic shielding plate 24 is driven by a motor 26 installed on the probe 18, and at that time, contact between the material to be inspected 3 and the first photoacoustic shielding plate 24 is monitored by a contact sensor 25. The contact position is controlled by a controller 27 as contact position adjusting means.

  Here, the contact position is inserted not only at the position where the material to be inspected 3 and the first photoacoustic shielding plate 24 are in contact, but also at the optimum position where the noise component is minimized by being controlled by the controller 27. Can do.

  Next, the operation of the fourth modification will be described.

  In the fourth modification, a controller 27 is provided as contact position adjusting means for adjusting the contact position of the first photoacoustic shielding plate 24. That is, in the fourth modified example, the main ultrasonic component to be detected is a volume wave, the first photoacoustic shielding plate 24 has an elastic body layer such as rubber 24h at the tip, and the material 3 to be inspected. A controller 27 for bringing the surface into contact with the rubber 24h is provided.

  The ultrasonic component and the light component that are noises are not uniquely determined by the shape of the material 3 to be inspected or the irradiation condition of the laser beam for inspection. Therefore, in order to efficiently shield the main component, By adjusting the position of one photoacoustic shielding plate 24, it becomes possible to further reduce noise.

  That is, the path of the ultrasonic component and the light component that are noises is not uniquely determined by the shape of the material 3 to be inspected or the irradiation condition of the laser beam for inspection as described above. If the propagation path of the main noise component is located near the surface of the material to be inspected 3 and the material to be inspected 3 has a curved surface shape, the first photoacoustic shielding plate 24 is a rigid structure. If this is the case, a gap is generated between the material to be inspected 3 and the first photoacoustic shielding plate 24, and noise components are easily transmitted.

  Therefore, as in the fourth modification, at least the tip of the first photoacoustic shielding plate 24 is made of an elastic body such as rubber 24h, and pressed against the material 3 to be inspected to minimize the gap, thereby further reducing noise. It becomes possible. In this case, many of the transmitted surface wave components are absorbed by the elastic body, and an effect that the volume wave can be easily observed is also obtained.

[Third Embodiment]
FIG. 9 is a block diagram showing a third embodiment of the laser ultrasonic inspection apparatus according to the present invention.

  As shown in FIG. 9, the ultrasonic signal receiving side has the same configuration and operation as the conventional apparatus described with reference to FIG. In this embodiment, a profile adjusting optical system 28 as a profile adjusting unit and an irradiation optical system 29 for adjusting an irradiation spot shape are arranged on the optical path of the pulse laser beam PL for transmission.

  With this configuration, there is no energy bias on the irradiation spot, and efficient ultrasonic transmission is possible without local ablation. Here, as the profile adjusting optical system 28 for making the profile uniform, a kaleidoscope, a micro lens array (fly eye lens), a multimode optical fiber having a relatively large core diameter, or the like is used.

  Further, it is known that the frequency and directivity of transmitted ultrasonic waves can be controlled to some extent by adjusting the irradiation spot shape and dimensions. A cylindrical lens from which a spot is obtained, a microlens array from which a one-dimensional or two-dimensional array spot is obtained, an axicon lens from which a hollow spot is obtained, or a beam expander capable of adjusting the spot size is used.

  Next, the operation of this embodiment will be described.

  In an underwater environment, a dust environment, etc., high-sensitivity measurement becomes difficult due to attenuation of ultrasonic components as signals and a decrease in ultrasonic transmission / reception efficiency by laser light. Therefore, means for increasing the energy of the pulse laser beam PL and transmitting a larger ultrasonic signal can be considered. In this case, if the pulse laser beam PL has a spatial intensity peak, a high intensity There is concern about ablation damage on the surface of the inspection object 3 at the peak position due to laser light irradiation.

  Therefore, in the present embodiment, the profile adjusting optical system 28 for uniformizing the spatial energy distribution of the pulse laser light PL as the first laser light on the optical path of the pulse laser light PL for transmission, By arranging the irradiation optical system 29 for adjusting the irradiation shape of the output light of the profile adjusting optical system 28, the spatial profile of the pulse laser light PL is made uniform and the total energy is made the same. Can be measured without ablation damage.

[Fourth Embodiment]
FIG. 10 is a block diagram showing a fourth embodiment of the laser ultrasonic inspection apparatus according to the present invention.

  As shown in FIG. 10, in this embodiment, a pulse light source 30 having a variable pulse width between 100 nanoseconds and 1 microsecond is used as the first laser light source for transmission. With this configuration, it is possible to selectively transmit ultrasonic waves in a frequency band that can be easily applied to crack inspection of about 1 MHz to 10 MHz. As a pulse light source that can be used for such a purpose, a pulse light source using a Q switch based on a photoacoustic effect can be used.

  Next, the operation of this embodiment will be described.

  In an underwater environment, a dust environment, etc., high-sensitivity measurement becomes difficult due to attenuation of ultrasonic components as signals and a decrease in ultrasonic transmission / reception efficiency by laser light. Here, the frequency component of the ultrasonic wave used for the crack inspection is generally about 1 MHz to 10 MHz, but the pulse width of the transmission laser beam capable of efficiently transmitting the frequency band is an inverse number 100. It is known to be from nanoseconds to 1 microsecond.

  Therefore, as in the present embodiment, the first laser light source is a Q-switched pulse laser light source, and the pulse as a pulse width variable laser light source whose pulse width of the oscillating pulse light is variable in the range of 100 nanoseconds to 1 microsecond. By irradiating the pulse laser beam PL for transmission having a pulse width matched with a desired frequency band from the light source 30, it is possible to transmit and receive an ultrasonic signal with a higher S / N ratio.

[Fifth Embodiment]
FIG. 11 is a block diagram showing a fifth embodiment of the laser ultrasonic inspection apparatus according to the present invention.

  As shown in FIG. 11, in the present embodiment, the first external power supply 11 in the first embodiment is used as a pulse power supply 31 that operates in a pulsed manner, and the output signal Trg2 of the trigger oscillator 13 is used as an input signal and synchronized therewith. To work.

  That is, in the present embodiment, the receiving optical system OP is a two-wave mixing interferometer using the phase conjugate element 5, and the trigger that oscillates the trigger signal at a constant timing in synchronization with the drive voltage to the phase conjugate element 5. And an oscillator 13.

  Next, the operation of the present embodiment will be described in detail with reference to FIG.

  First, the first trigger signal Trg1 oscillated from the trigger oscillator 13 is input to the second external power supply 12 that drives the phase conjugate element 5, whereby the bias voltage Ve is applied to the phase conjugate element 5 in pulses. The However, a delay time Td occurs until the phase conjugate element 5 is in a state suitable for measurement. Here, it is empirically known that the delay time Td is preferably about 2 to 5 times the element response speed which is a basic characteristic of the phase conjugate element 5.

  Therefore, after a delay time Td delayed from the first trigger signal Trg1, the second trigger signal Trg2 is input to the ultrasonic wave generation laser light source 1 which is a transmission pulse light source, and the transmission pulse laser light PL is oscillated. Here, in the conventional configuration, the bias voltage VB is steadily applied to the photodetector 9 such as an APD by the first external power supply 11, but the high bias voltage is improved while the heat due to excess current is increased. Since it increases noise or damages the thermal element, it cannot be constantly applied.

  However, in the present embodiment, the time for actually measuring the ultrasonic wave is very short (for example, the observation time required for detecting cracks in the range of about 30 cm with surface waves is at most 100 microseconds. Therefore, by applying the bias voltage VB to the photodetector 9 in a pulse manner from the pulse power supply 31 in synchronization with the second trigger signal Trg2, highly sensitive measurement is possible. Here, the time for applying the bias voltage VB to the photodetector 9 in a pulsed manner from the pulse power supply 31 is indicated by TM in FIG.

  Here, when a bias voltage is applied to the photodetector 9, a delay time TD is generated as in the case of the phase conjugate element 5. The delay time TD can be adjusted so that the light of the pulse laser PL for transmission is not detected by the photodetector 9.

  That is, in an underwater environment, a dust environment, etc., it is difficult to measure with high sensitivity due to attenuation of an ultrasonic component that is a signal and a decrease in ultrasonic transmission / reception efficiency by laser light. When the photodetector 9 as the signal conversion means is a PIN-PD or APD, the signal detection sensitivity is improved if the applied bias voltage is high, while thermal noise is generated if the high voltage is continuously applied, and further, the element itself. May be thermally damaged.

  Therefore, according to the present embodiment, a high bias voltage is applied in a pulse form from the pulse power supply 31 to the photodetector 9 in synchronization with the measurement timing of the ultrasonic wave, thereby preventing the thermal damage of the photodetector 9. It becomes possible to improve signal detection sensitivity.

[Sixth Embodiment]
FIG. 13 is a block diagram showing a sixth embodiment of the laser ultrasonic inspection apparatus according to the present invention.

  As shown in FIG. 13, in this embodiment, the probe 18 is held on the first inspection mechanism 32 by the first drive mechanism 33 in the focal direction. Of the ultrasonic signal components measured by the irradiation of the pulse laser beam PL for transmission and the laser beam IL for reception, the reference signal is the signal that is most easily detected among the surface wave component, volume wave component, and noise ultrasonic component. The first drive mechanism 33 is controlled and driven by the controller 34 so that the amplitude value is maximized. In addition, by using the same configuration and controlling so that the reference signal always takes a constant value instead of always having the maximum value, the stability of measurement can be improved.

  That is, in the present embodiment, a signal serving as a reference signal amplitude measuring unit that is generated by irradiation with the pulse laser beam PL, propagates through the medium MD in the surrounding environment, and measures the amplitude of the signal component received by the receiving optical system OP. Optical system drive control for driving and controlling the objective lens M2 and the second objective lens M3 as the irradiation / condensing mechanism of the laser beam IL for reception so that the output of the processing device 10 and the signal processing device 10 is maximized. And a controller 34 as means.

  Next, the operation of this embodiment will be described.

  In an underwater environment, a dust environment, etc., high-sensitivity measurement becomes difficult due to attenuation of ultrasonic components as signals and a decrease in ultrasonic transmission / reception efficiency by laser light. In particular, with respect to the irradiation of the laser beam IL for reception, precise alignment is important because defocusing greatly causes a decrease in sensitivity.

  Therefore, in this embodiment, when a signal component propagating through an environmental medium having a larger amplitude than the signal component can be observed, this is used as a reference, and the focal position is adjusted so that the signal amplitude is maximized. Higher sensitivity signal detection is possible.

[Seventh Embodiment]
FIG. 14 is a block diagram showing a seventh embodiment of the laser ultrasonic inspection apparatus according to the present invention.

  As shown in FIG. 14, in the present embodiment, the probe 18 is held on the first inspection mechanism 32 by the second drive mechanism 35 parallel to the material to be inspected 3. The second drive mechanism 35 is scanned one-dimensionally at an appropriate speed in an arbitrary direction by the scanning control device 36. Here, the appropriate speed depends on the measurement conditions such as the propagation time of the ultrasonic signal to be observed, the transmission pulse width, and the signal processing time, and the spatial range / size of the deterioration phenomenon to be detected. Cannot be decided. In general, the higher the speed, the shorter the inspection work, but the lower the inspection resolution.

  The current position of the second drive mechanism 35, i.e., inspection position information, is input to the first two-dimensional imaging device 37 from a position sensor (not shown) on the scanning control device 36 or the second drive mechanism 35. Then, the ultrasonic signal measured by the signal processing device 10 is also input to the first two-dimensional imaging device 37 at the same time, and the measurement signal at each inspection position is visualized.

  That is, in this embodiment, it has the 2nd drive mechanism 35 for scanning to the uniaxial direction on the to-be-inspected material 3, fixing the positional relationship of the said irradiation mechanism and the said irradiation and condensing mechanism, In the signal processing device 10, the scanning space by the second drive mechanism 35 is taken in the X-axis direction, and the surface wave component, the volume wave component, and the reflection / transmission / diffraction component derived therefrom are two-dimensionally taken in the Y-axis direction. It is trying to display.

  Next, the operation of this embodiment will be described.

  In an underwater environment or dust environment, when the reflected, transmitted, or diffracted component of the ultrasonic signal to be detected is very small due to attenuation of the ultrasonic component that is a signal or a decrease in ultrasonic transmission / reception efficiency due to laser light. Cannot be distinguished from noise components. Here, especially in the case of crack inspection, since the crack has a certain length and depth, if ultrasonic waves reflected, transmitted, and diffracted from the crack are recorded while scanning, the crack will be matched. A pattern is formed. While the noise component is random, this pattern has regularity according to the crack shape, so according to the two-dimensional display measured in this way, the signal component that has the same amplitude as the noise component is also distributed. Can be detected.

[Eighth Embodiment]
FIG. 15 is a block diagram showing the eighth embodiment of the laser ultrasonic inspection apparatus according to the present invention.

  The laser ultrasonic inspection apparatus as shown in FIG. 1 has a configuration suitable for, for example, crack detection by the pulse echo method or crack depth measurement by the surface wave transmission method. In order to perform measurement with high reliability, information should be extracted from various signal waves such as reflected waves, transmitted waves, and diffracted waves.

  Therefore, as shown in FIG. 15, in this embodiment, one transmission and two receptions (or multipoint reception) are realized instead of one transmission and one reception (conventional two-probe method). Here, the laser light source 4 for ultrasonic detection and the like may be shared by transmitting and reflecting the laser beams ILa and ILb by arranging the half mirror 38 and the mirror 8, or individually for each receiving system. You may have. Further, the probe 18 does not necessarily need to integrate all channels, and may be configured such that transmission / reception is independent or each reception system is independent.

  That is, in the present embodiment, as shown in FIG. 15, the receiving / condensing mechanism, the receiving optical systems OPa and OPb, the photodetectors 9a and 9b, and the signal processing devices 10a and 10b are included. The system has a plurality of channels. Since a plurality of receiving optical systems OPa and OPb are provided, a plurality of first optical fibers and second optical fibers are also provided as 6a, 6b, 7a and 7b.

  Next, the operation of this embodiment will be described.

  When detecting small crack signals, reliability is improved by detecting both the transmitted wave (and forward diffracted wave) and reflected wave (and possibly backward diffracted wave) of the crack. be able to.

  Thus, as described above, in the present embodiment, since the receiving system includes a plurality of channels, it is possible to measure crack properties from many information sources and perform highly reliable crack inspection.

[Ninth Embodiment]
FIG. 16 is a block diagram showing a ninth embodiment of the laser ultrasonic inspection apparatus according to the present invention.

  As shown in FIG. 16, in this embodiment, in addition to the configuration of the eighth embodiment, the probe 18 including one transmission system and two reception systems is connected to the inspection object on the second inspection mechanism 39. 3 is held by a second drive mechanism 35 parallel to the direction 3. In this case, the probe 18 may not be integrated, but in the present embodiment, it is important that the mutual positional relationship between the transmission system and each reception system does not change during a series of inspection operations.

  The scanning control device 36 controls the second driving mechanism 35 to scan in an arbitrary direction at an appropriate speed in a one-dimensional manner. Here, the appropriate speed depends on the measurement conditions such as the propagation time of the ultrasonic signal to be observed, the transmission pulse width, and the signal processing time, and the spatial range and size of the deterioration phenomenon to be detected. Cannot be decided.

  In general, the higher the speed, the shorter the inspection work, but the lower the inspection resolution. The current position of the second drive mechanism 35, that is, inspection position information, is input to the second two-dimensional imaging device 40 from a position sensor (not shown) on the scanning control device 36 or the second drive mechanism 35.

  In addition, ultrasonic signals measured by the signal processing devices 10a, 10b,... Are simultaneously input to the second two-dimensional imaging device 40, and the measurement signals at the respective inspection positions are visualized. As a visualization method, a method of visualizing each channel individually, a method of displaying three-dimensionally, and the like can be considered. The second two-dimensional imaging device 40 visualizes the position, shape, and depth distribution of a crack from the propagation time, frequency characteristic, transfer characteristic, etc. of the detected signal component.

  As described above, in this embodiment, the laser ultrasonic inspection apparatus of the eighth embodiment is used to perform a crack inspection on the inspection target material 3, and among a plurality of receiving systems, an incident surface wave to the crack and Can receive the surface wave that passes through the crack from the presence or absence and position of the crack, the propagation depth of the diffracted volume wave The crack depth is measured from the transmission surface wave received in the channel and the transmission characteristic of the incident surface wave, and the crack depth is measured from the propagation time of the diffracted volume wave.

  Next, the effect | action of this embodiment is demonstrated based on FIGS.

  The visualization result of the material 3 to be inspected by the second two-dimensional imaging device 40 is shown in FIGS. FIG. 17 shows the visualization result of the first reception system, and FIG. 18 shows the visualization result of the second reception system. The horizontal axis in FIGS. 17 and 18 represents position coordinates in the same direction as the drive direction of the second drive mechanism 35, and the vertical axis represents the measured time. The depth distribution is visualized by applying the TOFD (Time Of Flight Diffraction) method in the configuration of the laser ultrasonic inspection apparatus shown in FIG.

  The visualization results of FIGS. 17 and 18 show that the crack 41 of the material to be inspected 3 in FIG. 19 exists between the first reception system and the second reception system, and the second drive mechanism 35 is in the crack 41. It is an example in the case of moving in parallel with respect to it. Further, the actual depth of the crack 41 in the material 3 to be inspected is a shape in which the central portion becomes deeper as shown by a broken line in FIG.

  In FIG. 17, the ultrasonic transmitted wave 42 and the diffracted wave 43 with respect to the crack 41 are visualized, while in FIG. 18, the direct wave 44 by the ultrasonic wave directly propagating from the transmission system to the second reception system, and the crack An ultrasonic reflected wave 45 and a diffracted wave 43 with respect to 41 are visualized.

  Then, the visualization result by the 1st receiving system in case the 2nd drive mechanism 35 moves perpendicularly | vertically with respect to the crack 41 of the to-be-inspected material 3 is shown in FIG. In FIG. 20, the horizontal axis represents the moving distance of the second drive mechanism 35, and the vertical axis represents the measured time. In FIG. 20, the direct wave 44 by the ultrasonic wave directly propagating from the transmission system to the first reception system, and the reflected wave 45, the diffracted wave 43, and the transmitted wave 42 of the ultrasonic wave with respect to the crack 41 are visualized. The second reception system can be visualized in the same manner.

  By the way, when measuring the depth information of a minute crack, it is necessary to analyze both the transmitted wave (and forward diffracted wave) and reflected wave (and backward diffracted wave) of the crack. Thus, the reliability of the measurement depth can be improved.

  Therefore, in this embodiment, it is possible to measure the crack depth with high reliability by providing a plurality of channels for the receiving system and measuring the properties of the crack from a plurality of information obtained from the receiving system. .

[Tenth embodiment]
FIG. 21 is a block diagram showing a laser ultrasonic inspection apparatus according to the tenth embodiment of the present invention.

  As shown in FIG. 21, in this embodiment, in addition to the configuration of the ninth embodiment, the visualization information of the first and second reception systems by the second two-dimensional imaging device 40 is the second drive mechanism. The information is input to the third two-dimensional imaging device 46 together with the inspection position information such as the position 35. In this third two-dimensional imaging device 46, the propagation time, frequency characteristics, transfer characteristics, etc. of the signal components detected by the first and second receiving systems are combined to determine the crack position, shape, and depth distribution. It is to be visualized.

  That is, this embodiment is based on the laser ultrasonic inspection apparatus of the ninth embodiment, combining the measurement results of the reception system of a plurality of channels, based on the presence or absence of a reflected surface wave, the presence or absence of a crack, and the propagation time of a diffraction volume wave. The crack depth is measured from the crack depth, the transmission characteristics of the transmitted surface wave and the incident surface wave, and the crack depth is measured from the propagation time of the diffracted volume wave.

  Next, the effect | action of this embodiment is demonstrated based on FIG.

  The visualization result of the material 3 to be inspected by the third two-dimensional imaging device 46 is shown in FIG. In FIG. 22, the horizontal axis represents position coordinates in the same direction as the drive direction of the second drive mechanism 35, and the vertical axis represents the measured time. The depth distribution is visualized by applying the TOFD method in the configuration of the laser ultrasonic inspection apparatus of the ninth embodiment. The visualization result shown in FIG. 22 shows that the crack 41 of the material to be inspected 3 exists between the first receiving system and the second receiving system, and the second drive mechanism 35 moves in parallel to the crack 41. This is an example of the case. In FIG. 22, regarding the ultrasonic wave with respect to the crack 41, a transmitted wave 47 of the first receiving system, a reflected wave 48 of the second receiving system, and a direct wave 49 directly propagating to the second receiving system are visualized. In addition, the diffracted wave 50 by the first and second receiving systems is weighted and averaged by both the receiving systems with respect to the position, shape, and depth distribution of the crack.

  By the way, when measuring the depth information of a minute crack, the reliability of the measurement depth can be improved by combining the transmitted wave and the reflected wave of the crack by the receiving system of each channel. .

  Therefore, in this embodiment, it is possible to perform a highly reliable crack depth measurement by measuring a crack property from information of each channel obtained from the reception system having a plurality of channels. Become.

1 Laser light source for ultrasonic generation (first laser light source)
2 Optical system 3 Inspected material 4 Laser light source for ultrasonic detection (second laser light source)
5 Phase conjugate element 6 First optical fiber 7 Second optical fiber 8 Mirror 9 Photodetector (signal conversion means)
10 Signal processing device (reference signal amplitude measuring means)
11 First external power supply 12 Second external power supply 13 Trigger oscillator (synchronization signal generating means)
14 First lens system 15 Micro lens array 16 Second lens system 17 Third optical fiber 18 Probe (substitution means)
19 Piping (substitution)
20 Pump (replacement means)
21a 1st plate 21b 2nd plate 22a 1st backflow prevention board 22b 2nd backflow prevention board 23 Small hole 24 1st photoacoustic shielding board (photoacoustic shielding means)
24a Second photoacoustic shielding plate (photoacoustic shielding means)
24b Third photoacoustic shielding plate (photoacoustic shielding means)
24c 1st thin film 24d 2nd thin film 24e Structural material 24f Inside 24g of hollow structure 4th photoacoustic shielding board 24h Rubber 25 Contact sensor 26 Motor 27 Controller (contact position adjustment means)
28 Profile adjustment optical system (profile adjustment means)
29 Optical system for irradiation 30 Pulse light source 31 Pulse power source (synchronous pulse high voltage generating means)
32 First inspection mechanism 33 First drive mechanism 34 Controller (optical system drive control means)
35 Second drive mechanism (scanning means)
36 scanning control device 37 first two-dimensional imaging device 38 half mirror 39 second inspection mechanism 40 second two-dimensional imaging device 41 crack 42 transmitted wave 43 diffracted wave 44 direct wave 45 reflected wave 46 third Two-dimensional imaging device 47 Transmitted wave 48 of first receiving system Reflected wave 49 of second receiving system Direct wave 50 directly propagating to second receiving system 50 Diffracted wave by first and second receiving systems

Claims (1)

A first laser light source that oscillates a first laser beam for generating an ultrasonic wave on a material to be inspected;
A second laser light source that oscillates a second laser beam applied to the inspection material in order to receive an ultrasonic signal generated in the inspection material;
An irradiation / condensing mechanism for receiving a reflection component of the second laser beam on the surface of the material to be inspected;
A receiving optical system for optically detecting information on the ultrasonic wave from the reflected component condensed by the irradiation / condensing mechanism;
Signal converting means for converting an ultrasonic signal received in the receiving optical system into an electrical signal;
A signal processing device that performs signal processing on an output signal of the signal conversion means, and displays and records information on propagation of ultrasonic waves;
A reference signal amplitude measuring means that is generated by the irradiation of the first laser light, propagates through a surrounding environment medium, is received by the receiving optical system, and measures an amplitude of a signal component having a larger amplitude than the ultrasonic signal ; ,
An laser ultrasonic inspection apparatus comprising: an optical system drive control mechanism that drives and controls the irradiation / condensing mechanism so that the output of the reference signal amplitude measuring means is maximized.

Images