Laser ultrasonic inspection apparatus

Abstract

To provide a laser ultrasonic inspection device which has a small number of components and is easily miniaturized.SOLUTION: A laser interferometer that uses the second laser light to detect vibration of the subject derived from an ultrasonic wave induced in the subject by irradiation with the first laser light, the laser interferometer including a second laser light source that irradiates the subject with the second laser light, a vibrator type optical modulator that modulates a frequency of the second laser light using a vibrating element, and a photodetector that receives the second laser light having passed through the vibrator type optical modulator and the second laser light having passed through the subject; A laser ultrasonic inspection device comprising: a light receiving element that outputs a light receiving signal; and a signal processing unit that detects vibration based on the light receiving signal and a reference signal, and measures an elapsed time from when a first laser light source emits first laser light to when the vibration is detected based on the reference signal, wherein a vibration element is a signal source of the reference signal.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a laser ultrasonic inspection device. [Background technology]

[0002] Patent Document 1 discloses a laser ultrasonic flaw detection method in which pulsed ultrasonic wave generating laser light is irradiated onto a reflecting vibration plate to generate ultrasonic waves in the reflecting vibration plate, and the generated ultrasonic waves are transmitted to the test object, and ultrasonic waves reflected from a defect location in the test object are received by the reflecting vibration plate, and the vibration of the reflecting vibration plate generated at this time is detected by ultrasonic wave detecting laser light.

[0003] Furthermore, Patent Document 2 discloses a laser ultrasonic inspection device that irradiates a laser beam onto an object to be inspected to generate ultrasonic waves, and detects vibrations of the object caused by the generated ultrasonic waves with a laser interferometer. Such a laser ultrasonic inspection device can improve the distance resolution when determining the position of a defect in the object. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 04-147053 [Patent Document 2] Japanese Patent Application Publication No. 09-281085 Summary of the Invention [Problem to be solved by the invention]

[0005] In the laser ultrasonic inspection device described in Patent Document 2, when identifying the defect position using a laser interferometer, it is necessary to precisely observe the time from when the laser beam is emitted until the ultrasonic wave is detected. Patent Document 2 does not describe a method for observing this time. Also, there is known a technology for detecting the presence or absence of a defect by calculating the frequency of vibration, but in this case too, it is necessary to observe the above-mentioned time.

[0006] Generally, a reference signal (clock signal) is used to measure time. A signal generator is used to generate the reference signal, but the use of a signal generator increases the number of parts in the laser ultrasonic inspection device, hindering miniaturization.

[0007] Therefore, the challenge is to realize a laser ultrasonic inspection device that has a small number of parts and is easy to miniaturize. [Means for solving the problem]

[0008] A laser ultrasonic inspection device according to an application example of the present invention includes: a first laser light source that irradiates a subject with a pulsed first laser light; a laser interferometer that uses a second laser beam to detect vibrations of the object caused by ultrasonic waves induced in the object by irradiation with the first laser beam; Equipped with The laser interferometer comprises: a second laser light source that irradiates the subject with the second laser light; an oscillator-type optical modulator that modulates the frequency of the second laser light using an oscillator element; a light-receiving element that receives the second laser light that has passed through the oscillator-type optical modulator and the second laser light that has passed through the subject, and outputs a light-receiving signal; a signal processing unit that detects the vibration based on the light receiving signal and a reference signal, and measures, based on the reference signal, an elapsed time from when the first laser light source emits the first laser light until when the vibration is detected; and The vibration element is a signal source of the reference signal.

[0009] A laser ultrasonic inspection device according to an application example of the present invention includes: a first laser light source that irradiates a subject with a pulsed first laser light; a laser interferometer that uses a second laser beam to detect vibrations of the object caused by ultrasonic waves induced in the object by irradiation with the first laser beam; Equipped with The laser interferometer comprises: a second laser light source that irradiates the subject with the second laser light; an oscillator-type optical modulator that modulates the frequency of the second laser light using an oscillator element; a light-receiving element that receives the second laser light that has passed through the oscillator-type optical modulator and the second laser light that has passed through the subject, and outputs a light-receiving signal; a signal processing unit that detects the vibration based on the light receiving signal and a reference signal, and calculates a frequency of the vibration based on the reference signal; and The vibration element is a signal source of the reference signal. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a block diagram showing a schematic configuration of a laser ultrasonic inspection device according to a first embodiment. [Figure 2] 10 is a timing chart showing an example of a reference signal input to a signal processing unit, a displacement calculated from a light receiving signal, and a laser detection signal. [Figure 3] FIG. 10 is a schematic diagram showing the propagation of ultrasound induced by a first laser beam irradiated at two different locations, where two orthogonal axes within the surface of the object are the X-axis and Y-axis, and the axis in the depth direction is the Z-axis. [Figure 4] FIG. 10 is a block diagram showing a schematic configuration of a laser ultrasonic inspection device according to a second embodiment. [Figure 5] 1 is an example of a circuit diagram of a frequency converter including an n-ary counter. [Figure 6] FIG. 10 is a block diagram showing a schematic configuration of a laser ultrasonic inspection device according to a third embodiment. [Figure 7] FIG. 10 is a diagram showing an example of a scanning trajectory of the irradiation position of the first laser light in an orthogonal coordinate system formed by an X axis and a Y axis set on the subject, and an example of image data obtained by mapping the length of elapsed time at each position by replacing it with color density. [Figure 8]FIG. 10 is a block diagram showing a schematic configuration of a laser ultrasonic inspection device according to a fourth embodiment. [Figure 9] 10 is a diagram showing an example of a scanning locus of an irradiation position of a first laser light in an orthogonal coordinate system formed by an X axis and a Y axis set on an object. FIG. [Figure 10] FIG. 10 is a schematic diagram showing the general configuration of a laser ultrasonic inspection device according to a fifth embodiment. [Figure 11] FIG. 10 is a schematic diagram showing the general configuration of a laser ultrasonic inspection device according to a sixth embodiment. [Figure 12] 10 is a graph showing a waveform of a displacement of a subject caused by vibration. [Figure 13] FIG. 10 is a diagram showing an example of a scanning trajectory of the irradiation position of the first laser light in a Cartesian coordinate system formed by an X axis and a Y axis set on the subject, and an example of image data obtained by mapping the intensity of the frequency analysis result at each position by replacing it with color density. [Figure 14] FIG. 1 is a block diagram showing a schematic configuration of a conventional laser ultrasonic inspection device. DETAILED DESCRIPTION OF THE INVENTION

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A laser ultrasonic inspection device according to the present invention will be described in detail below with reference to the embodiments shown in the accompanying drawings.

[0012] 1. Conventional Technology First, the prior art will be described.

[0013] FIG. 14 is a block diagram showing a schematic configuration of a conventional laser ultrasonic inspection device 9. The laser ultrasonic inspection device 9 shown in FIG. 14 includes a pulsed laser irradiation unit 91 and a vibration detection unit 93 (laser interferometer).

[0014] The pulsed laser irradiation unit 91 includes a laser light source 912 , an amplifier 914 , a voltage-current converter 916 , a signal generator 918 , and a photodiode 922 .

[0015] A signal generator 918 generates a pulse control signal Sd. A voltage-to-current converter 916 converts the pulse control signal Sd, which is a pulsed voltage signal, into a current signal. An amplifier 914 amplifies the current signal and supplies it to a laser light source 912. Then, in the pulse laser irradiation unit 91, a laser light L91 emitted from the laser light source 912 is irradiated onto the test object 90. This induces ultrasonic waves US in the test object 90. The generated ultrasonic waves US propagate through the test object 90, and if there is a defect def in the test object 90, they are reflected there and reach the surface. The ultrasonic waves US that reach the surface induce vibrations VB on the surface. Furthermore, a photodiode 922 receives a portion of the laser light L91 and generates a laser detection signal S1.

[0016] The vibration detection unit 93 is a laser interferometer, and includes an acousto-optic modulator 932 (AOM), a laser light source 934, a photodiode 936, a signal generator 938, and a signal processing unit 95.

[0017] The signal generator 938 generates a drive signal Sa required to operate the acousto-optic modulator 932, and a reference signal Ss that serves as a time reference for signal processing in the signal processing unit 95. In the vibration detection unit 93, a laser beam L92 emitted from a laser light source 934 is irradiated onto the subject 90. As a result, the laser beam L92 undergoes a Doppler shift due to surface vibrations VB. The Doppler-shifted laser beam L92 and the laser beam L92 that has passed through the acousto-optic modulator 932 are received by a photodiode 936, which outputs a received light signal S2. The Doppler shift is measured using the optical interference effect, thereby electrically detecting the vibrations VB.

[0018] The signal processing unit 95 calculates the elapsed time Δt from when the laser light L91 is emitted until the vibration VB is detected, based on the laser detection signal S1 output from the photodiode 922, the light reception signal S2 output from the photodiode 936, and the reference signal Ss output from the signal generator 938. The elapsed time Δt reflects the position of the reflection point. The signal processing unit 95 determines the presence and position of a defect def based on the elapsed time Δt.

[0019] However, the signal generator 938 included in the vibration detection unit 93 increases the number of components in the laser ultrasonic inspection device 9. In particular, optical modulators such as the acousto-optic modulator 932 (AOM) and an electro-optic modulator (EOM) (not shown) are large in size and consume a lot of power. Therefore, the signal generator 938 that supplies the drive signal Sa to these modulators also inevitably increases the number of components and size, making it difficult to miniaturize the conventional laser ultrasonic inspection device 9.

[0020] Therefore, in the first embodiment described below, a vibrator-type optical modulator using a vibrating element is provided to reduce the number of parts in the vibration detection unit (laser interferometer), make it smaller, and reduce power consumption, etc. This makes it possible to realize a laser ultrasonic inspection device that is easily made smaller and has excellent portability.

[0021] 2. First embodiment Next, a laser ultrasonic inspection device according to the first embodiment will be described.

[0022] FIG. 1 is a block diagram showing a schematic configuration of a laser ultrasonic inspection device 1 according to the first embodiment.

[0023] The laser ultrasonic inspection device 1 shown in FIG. 1 includes a pulsed laser irradiation unit 11, a vibration detection unit 13 (laser interferometer), and a defect detection unit 16.

[0024] The pulsed laser irradiation unit 11 has a first laser light source 112, an amplifier 114, a voltage-current converter 116, a signal generator 118, and a photodiode 122. The pulsed laser irradiation unit 11 irradiates the test object 10 with a pulsed first laser light L11 emitted from the first laser light source 112. This induces ultrasonic waves US in the test object 10. The generated ultrasonic waves US propagate radially within the test object 10, and if there is a defect def in the test object 10, they are reflected there and reach the surface. The ultrasonic waves US that reach the surface induce vibrations VB that accompany surface displacement.

[0025] The vibration detection unit 13 is a laser interferometer and includes a vibrator-type optical modulator 132 that uses a vibration element 130, a second laser light source 134, a photodiode 136 (light receiving element), and a signal processing unit 15. In the vibration detection unit 13, the second laser light L12 emitted from the second laser light source 134 is irradiated onto the subject 10. As a result, the second laser light L12 undergoes a Doppler shift due to surface vibrations VB. The Doppler-shifted second laser light L12 is then received by the photodiode 136. This Doppler shift is measured using the interference effect of the second laser light L12, thereby electrically detecting the vibrations VB.

[0026] Specifically, the second laser light L12 emitted from the second laser light source 134 is split into two beams, for example, by a beam splitter (not shown), one of which is incident on the oscillator-type optical modulator 132 and the other of which is incident on the subject 10. The oscillator-type optical modulator 132 modulates the frequency of the second laser light L12 to generate reference light including a modulation signal. Furthermore, in the subject 10, the second laser light L12 undergoes a Doppler shift to generate object light including a surface vibration signal. These reference light and object light interfere with each other and are received by the photodiode 136. As a result, the photodiode 136 outputs a received light signal S2 including the modulation signal and the surface vibration signal. The signal processing unit 15 demodulates the surface vibration signal from the received light signal S2 to calculate the displacement and displacement speed of the surface of the subject 10.

[0027] The oscillator-type optical modulator 132 applies a modulated signal to the second laser light L12 by utilizing the vibration of the vibration element 130, and generates a reference signal Ss using the vibration element 130 as a signal source. The oscillator-type optical modulator 132 includes a vibration element oscillation circuit (not shown) that oscillates the vibration element 130. The vibration element oscillation circuit can be configured with a small number of components, so the reference signal Ss can be generated while avoiding a significant increase in the number of components. Furthermore, because the vibration element 130 can oscillate at a low voltage, the power consumption of the vibration element oscillation circuit can be kept low. Therefore, the laser ultrasonic inspection device 1 can operate not only from an external power source but also from an internal power source such as a primary battery or a secondary battery.

[0028] The signal processing unit 15 calculates the elapsed time Δt from the emission of the first laser light L11 to the detection of the vibration VB based on the laser detection signal S1 output from the photodiode 122, the light receiving signal S2 output from the photodiode 136, and the reference signal Ss output from the oscillator-type optical modulator 132.

[0029] The defect detection unit 16 detects the presence or absence of the defect def based on the elapsed time Δt, and also finds the position of the defect def, thereby enabling inspection of the inspection object 10.

[0030] In such a laser ultrasonic inspection device 1, a vibrator-type optical modulator 132 using a vibrating element 130 is provided in the vibration detection unit 13. In the vibrator-type optical modulator 132, a modulated signal is imparted to the second laser light L12 by irradiating the vibrating vibrating element 130 with the second laser light L12, thereby generating reference light. The vibrating element 130 is also used as a signal source for the reference signal Ss. Therefore, by using the vibrating element 130, a laser ultrasonic inspection device 1 that is easily miniaturized and has excellent portability can be obtained. Each part of the laser ultrasonic inspection device 1 will be described in detail below.

[0031] 2.1. Pulse laser irradiation unit 1 emits a pulsed first laser beam L11 having a predetermined repetition frequency toward the subject 10. A part of the emitted first laser beam L11 is received by a photodiode 122 to detect the timing of emission.

[0032] The first laser light source 112 emits a pulsed first laser light L11. Examples of the first laser light source 112 include an Nd:YAG laser, a CO2 laser, an Er:YAG laser, a titanium sapphire laser, an alexandrite laser, a ruby ​​laser, a dye (dye) laser, a fiber laser, an excimer laser, and a semiconductor laser. Of these, a semiconductor laser is preferably used. A semiconductor laser can contribute to reducing the size, weight, and power consumption of the first laser light source 112. Furthermore, a semiconductor laser can easily generate pulses by direct modulation, and can emit a pulsed first laser light L11 at low cost. Furthermore, the semiconductor laser may have a metal package, such as a CAN package, or a ceramic package that houses the element, as needed.

[0033] The repetition frequency of the pulsed first laser light L11 is not particularly limited, but is preferably set to be equal to or greater than 1 Hz and equal to or less than 1000 Hz.

[0034] The pulse energy of the pulsed first laser light L11 is set appropriately depending on the material of the subject 10 and is not particularly limited, but is preferably 1 μJ / pulse or more, and more preferably 10 μJ / pulse or more and 10 J / pulse or less. Furthermore, if the subject 10 is a hard object such as a concrete block or a metal block, it is preferable to select a high pulse energy of about 1 mJ / pulse, and if the subject 10 is a soft object such as resin, it is preferable to select a low pulse energy of about 1 μJ / pulse.

[0035] The amplifier 114 amplifies the current signal supplied to the first laser light source 112. The amplifier 114 may be provided as needed, and may be omitted if amplification is not required to drive the first laser light source 112.

[0036] The voltage-to-current converter 116 converts the voltage signal output from the signal generator 118 into a current signal.

[0037] Signal generator 118 outputs a voltage signal (not shown). This voltage signal is converted into a current signal by voltage-current converter 116 and supplied to first laser light source 112 via amplifier 114. In first laser light source 112, the pulse repetition period of first laser light L11 is determined based on this current signal.

[0038] The photodiode 122 receives a portion of the first laser light L11 emitted from the first laser light source 112 and outputs, for example, a current signal. This current signal is converted into a voltage signal by a current-voltage converter (not shown) and input to the signal processing unit 15 as a laser detection signal S1. The timing of emission of the first laser light L11 is detected based on the input voltage signal. Note that a phototransistor or a microphone may be used instead of the photodiode 122. The microphone detects the impact sound emitted when the first laser light L11 is irradiated onto the subject 10. This makes it possible to detect the timing of emission of the first laser light L11, similar to the case of the photodiode 122.

[0039] The pulsed laser irradiation unit 11 may be, for example, a circuit made up of discrete components, an integrated circuit, or a circuit in which both are mixed.

[0040] 2.2. Vibration detection unit 1 detects the surface vibrations VB occurring in the specimen 10 and outputs a received light signal S2 including a modulation signal and a surface vibration signal, as described above. A laser interferometer such as that disclosed in Japanese Patent Application Laid-Open No. 2022-38156 is preferably used as the vibration detection unit 13. This laser interferometer includes an oscillator-type optical modulator using an oscillator element, which contributes to miniaturization, weight reduction, and low power consumption of the vibration detection unit 13.

[0041] An example of the oscillator-type optical modulator 132 using the oscillator element 130 is the optical modulator disclosed in Japanese Patent Application Laid-Open No. 2022-38156. Examples of the oscillator element 130 include a quartz oscillator, a silicon oscillator, and a ceramic oscillator. The quartz oscillator may be an AT oscillator, a tuning fork oscillator, or other oscillators. These oscillators utilize mechanical resonance, and therefore have a high Q value, making it easy to stabilize the natural frequency. This facilitates an increase in the S / N ratio (signal-to-noise ratio) of the modulated signal imparted to the second laser light L12. Furthermore, using an oscillator with a high Q value as the oscillator element 130 can also increase the S / N ratio of the reference signal Ss generated by the oscillator-type optical modulator 132, thereby increasing the S / N ratio of various signals based on the reference signal Ss.

[0042] The laser light source disclosed in Japanese Patent Application Laid-Open No. 2022-38156 can be used as the second laser light source 134. Among these, by using a semiconductor laser such as a VCSEL (Vertical Cavity Surface Emitting Laser), the vibration detection unit 13 can be further miniaturized.

[0043] The photodiode 136 (light receiving element) receives the interference light between the reference light (the second laser light L12 that has passed through the oscillator-type optical modulator 132) and the object light (the second laser light L12 that has passed through the subject 10), and outputs a light receiving signal S2.

[0044] The oscillator-type optical modulator 132 uses the oscillator element 130 to impart a modulation signal to the second laser light L12.

[0045] As described above, the vibrator-type optical modulator 132 includes a vibrator element oscillation circuit that generates a reference signal Ss using the vibrator element 130 as a signal source (oscillating source). Examples of vibrator element oscillation circuits include an inverter-type oscillation circuit and a Colpitts-type oscillation circuit. These oscillation circuits can generate a reference signal Ss with high frequency stability by using a vibrator element 130 with a high Q value of mechanical resonance.

[0046] Furthermore, by using the vibration element 130 as a signal source, the amount of power required to generate the reference signal Ss is reduced, which contributes to lowering the power consumption of the vibration detection unit 13.

[0047] It should be noted that "using the vibration element 130 as a signal source" means vibrating the vibration element 130 and utilizing an electrical signal of a predetermined frequency that is generated based on the vibration.

[0048] The signal processing unit 15 calculates the elapsed time Δt from the emission of the first laser light L11 to the detection of the vibration VB based on the laser detection signal S1, the light reception signal S2, and the reference signal Ss.

[0049] For example, the preprocessing unit and demodulation unit disclosed in Japanese Patent Application Laid-Open No. 2022-38156 can be applied to the signal processing unit 15. The preprocessing unit performs preprocessing on the received light signal S2 based on the reference signal Ss, and the demodulation unit demodulates the surface vibration signal from the preprocessed signal based on the reference signal Ss.

[0050] When the ultrasonic waves US generated by irradiation with the first laser beam L11 are reflected by the defect def shown in FIG. 1, vibrations VB are induced on the surface of the test object 10. The vibrations VB cause changes in the displacement and displacement velocity of the surface of the test object 10. The signal processing unit 15 detects the vibrations VB by capturing the changes in the displacement and displacement velocity. The signal processing unit 15 then measures the elapsed time Δt from the emission of the first laser beam L11 to the detection of the vibrations VB. This elapsed time Δt reflects the propagation distance from the generation of the ultrasonic waves US until they are reflected by the defect def and reach the surface. The signal processing unit 15 can accurately measure the elapsed time Δt by using the reference signal Ss as a time reference. Note that this elapsed time Δt can be calculated, for example, by counting the number of pulses of the reference signal Ss. Furthermore, by detecting the vibrations VB based on the displacement and displacement velocity of the surface of the test object 10, the vibrations VB can be detected with high accuracy. As a result, the inspection accuracy of the test object 10 is improved.

[0051] FIG. 2 is a timing chart showing an example of the reference signal Ss input to the signal processing unit 15, the displacement d calculated from the light receiving signal S2, and the laser detection signal S1.

[0052] The signal processing of the displacement d and the laser detection signal S1 shown in Fig. 2 is performed based on the reference signal Ss. Specifically, the signal processing unit 15 measures, for example, the elapsed time Δt1 from the rising edge of the pulse S11 of the laser detection signal S1 shown in Fig. 2 (the timing of emission of the first laser light L11) until the displacement d1 is detected based on the reference signal Ss. Similarly, the signal processing unit 15 measures the elapsed time Δt2 from the rising edge of the pulse S12 (the timing of emission of the first laser light L11) until the displacement d2 is detected based on the reference signal Ss. This allows the elapsed times Δt1 and Δt2 to be measured accurately.

[0053] Furthermore, in this embodiment, the vibration of the vibration element 130 is used for light modulation, demodulation of the surface vibration signal, and measurement of the elapsed time Δt, which contributes to reducing the number of parts.

[0054] 2.3. Defect detection section The defect detection unit 16 detects a defect def contained in the object 10 based on the measurement result of the elapsed time Δt by the signal processing unit 15.

[0055] The difference between the elapsed time Δt1 and the elapsed time Δt2 shown in Fig. 2 reflects the relationship between the irradiation position and the position of the defect def shown in Fig. 1 when the first laser beam L11 is irradiated to different positions on the object 10. Therefore, by irradiating the first laser beam L11 while changing the irradiation position and measuring the elapsed time Δt, the position of the defect def can be identified. A specific example will be described below.

[0056] FIG. 3 is a schematic diagram showing the propagation of ultrasonic waves US1 and US2 induced by first laser beams L111 and L112 irradiated at two different locations on the surface of the object 10, where two orthogonal axes within the surface are defined as the X-axis and Y-axis, and the depth direction axis is defined as the Z-axis. When the first laser beam L111 is irradiated, the ultrasonic wave US1 propagates along multiple trajectories, including the one shown in the figure. A portion of the ultrasonic wave US1 is reflected by the defect def and reaches the surface. The ultrasonic wave US1 that has reached the surface is detected by the second laser beam L12, for example, as a surface displacement (vibration). Similarly, the first laser beam L112 induces ultrasonic waves US2 that propagate along multiple trajectories, including the one shown in the figure. A portion of the ultrasonic wave US2 is reflected by the defect def and reaches the surface. The ultrasonic wave US2 that has reached the surface is detected by the second laser beam L12, for example, as a surface displacement (vibration).

[0057] 2 is a diagram showing an example of the waveforms of a displacement d1 resulting from an ultrasonic wave US1 reflected from the defect def and a displacement d2 resulting from an ultrasonic wave US2 reflected from the defect def. Because the first laser beams L111 and L112 are irradiated at different positions, when the elapsed times Δt until the displacements d1 and d2 are detected are defined as Δt1 and Δt2, respectively, the elapsed times Δt are also different from each other. Therefore, the defect detection unit 16 may have a function of determining that a defect def exists based on a preset reference value for the elapsed time Δt, for example, if the elapsed time Δt is equal to or less than the reference value.

[0058] On the other hand, the propagation velocities of the ultrasonic waves US1 and US2 can be obtained in advance based on the material of the test object 10 or by actual measurement. Therefore, the propagation distances of the ultrasonic waves US1 and US2 can be calculated from the elapsed times Δt1 and Δt2 and the propagation velocities. When the ultrasonic wave US1 propagates over the calculated propagation distance, the defect def exists somewhere on the ellipse e1 shown in FIG. 3. Similarly, when the ultrasonic wave US2 propagates over the calculated propagation distance, the defect def exists somewhere on the ellipse e2 shown in FIG. 3. Based on this principle, the position of the defect def in FIG. 3 can be identified by irradiating three or more irradiation positions with the first laser light L11.

[0059] Since the position of the reflection point is reflected in the elapsed time Δt, the defect detection unit 16 detects the presence or absence of the defect def and identifies the position of the defect def based on the above principle. This allows the inspection of the test object 10 to be performed non-destructively. Note that the distance between the laser ultrasonic inspection device 1 and the test object 10 may be measured in advance and used to identify the position. Furthermore, the laser ultrasonic inspection device 1 may be equipped with a distance measuring unit (described later) for measuring this distance.

[0060] Examples of the constituent material of the test object 10 include concrete, metal, resin, ceramics, glass, etc. Examples of the defects def include voids, cracks, peeling, interfaces, foreign matter, modified parts, etc.

[0061] Furthermore, each function of the signal processing unit 15 and the defect detection unit 16 is realized by hardware including, for example, a CPU, a memory, and an interface. An example of such hardware is a microcomputer. The CPU is a central processing unit. Examples of the memory include any non-volatile memory element (ROM), any volatile memory element (RAM), and a removable external memory element. Examples of the interface include a digital input / output port such as a USB (Universal Serial Bus). The CPU executes a program that is preloaded in the memory, thereby realizing each function of the signal processing unit 15 and the defect detection unit 16. Note that instead of or in addition to the method in which the CPU executes a program to realize the above functions, a method in which hardware such as an FPGA (Field Programmable Gate Array), an ASIC (Application Specific Integrated Circuit), other integrated circuits, or discrete components realizes the above functions may be used.

[0062] 3. Second embodiment Next, a laser ultrasonic inspection device according to a second embodiment will be described.

[0063] FIG. 4 is a block diagram showing a schematic configuration of a laser ultrasonic inspection device 1 according to the second embodiment.

[0064] The second embodiment will be described below, focusing on the differences from the first embodiment, and omitting a description of similarities. Note that in Fig. 4, the same reference numerals are used to designate the same components as those in the first embodiment.

[0065] The laser ultrasonic inspection device 1 of the second embodiment is similar to the laser ultrasonic inspection device 1 of the first embodiment, except that the signal generator 118 is omitted from the pulse laser irradiation unit 11, and instead a reference signal Ss output from a vibrator-type optical modulator 132 is supplied to the pulse laser irradiation unit 11.

[0066] The laser ultrasonic inspection device 1 shown in FIG. 4 includes a pulsed laser irradiation unit 11, a vibration detection unit 13 (laser interferometer), and a defect detection unit 16.

[0067] The pulsed laser irradiation unit 11 shown in Fig. 4 includes a first laser light source 112, an amplifier 114, a voltage-current converter 116, and a frequency converter 124. In the pulsed laser irradiation unit 11 shown in Fig. 4, the signal generator 118 and the photodiode 122 are omitted from the pulsed laser irradiation unit 11 shown in Fig. 1, and instead, a frequency converter 124 is provided.

[0068] The frequency converter 124 converts the frequency of the reference signal Ss output from the oscillator-type optical modulator 132 to generate a pulse control signal Sd. The pulse control signal Sd controls the repetition period of the first laser light L11 emitted by the first laser light source 112. The frequency converter 124 includes, for example, a frequency divider circuit that divides the frequency of the reference signal Ss by n, an n-ary counter, etc., where n is a positive integer.

[0069] FIG. 5 is an example of a circuit diagram of the frequency converter 124 including an n-ary counter. The frequency converter 124 shown in FIG.

[0070] The first circuit 142 receives the reference signal Ss output from the oscillator-type optical modulator 132. The first circuit 142 has a function of counting pulses of the reference signal Ss and outputting the count value. The first circuit 142 also receives the pulse control signal Sd output from the second circuit as a reset signal R. The first circuit 142 has a function of resetting the count value to zero when the reset signal R is input.

[0071] The count value and the base number N are input to the second circuit 144. The base number N is set, for example, according to the desired repetition frequency of the first laser light L11. The second circuit 144 has a function of outputting a pulse when A=B, where A is the count value and the base number N is B. This pulse becomes the pulse control signal Sd. As a specific example, if the frequency of the reference signal Ss is 5 MHz and the base number N=50000, a pulse of the pulse control signal Sd is output when the count value reaches 50000. In this case, the frequency of the pulse control signal Sd is down-converted to 100 Hz.

[0072] The generated pulse control signal Sd is supplied to the first laser light source 112 via the voltage-current converter 116 and the amplifier 114. The first laser light source 112 sets a repetition period of the pulsed first laser light L11 based on the pulse control signal Sd. This pulse control signal Sd is also generated based on the reference signal Ss. Therefore, in the second embodiment, the signal generator 118 described above can be omitted. The frequency converter 124 as described above can be configured with a relatively small number of parts, which allows for a further reduction in the number of parts in the laser ultrasonic inspection device 1.

[0073] Furthermore, in this embodiment, the pulse control signal Sd output from the frequency converter 124 is input to the signal processing unit 15 as the laser detection signal S1. The signal processing unit 15 measures the elapsed time Δt from the timing of emission of the first laser light L11 reflected in the laser detection signal S1 to the detection of the vibration VB. For this reason, in the second embodiment, the photodiode 122 described above can be omitted. Furthermore, since the laser detection signal S1 is a signal input to the first laser light source 112, it accurately reflects the timing of emission of the first laser light L11. Therefore, the elapsed time Δt can be measured with greater accuracy.

[0074] In addition, the signal processing unit 15 can easily synchronize the laser detection signal S1 with the reference signal Ss, and can measure the elapsed time Δt with higher accuracy. In the second embodiment as described above, the same effects as in the first embodiment can be obtained.

[0075] In addition, in this embodiment, the vibration of the vibration element 130 is used for light modulation, demodulation of the surface vibration signal, measurement of the elapsed time Δt, and generation of the pulse control signal Sd, thereby further reducing the number of parts.

[0076] 4. Third embodiment Next, a laser ultrasonic inspection device according to a third embodiment will be described.

[0077] FIG. 6 is a block diagram showing a schematic configuration of a laser ultrasonic inspection device 1 according to the third embodiment.

[0078] The third embodiment will be described below, focusing on the differences from the second embodiment and omitting the description of the similarities. Note that in Fig. 6, the same reference numerals are used to designate the same components as those in the second embodiment.

[0079] The laser ultrasonic inspection device 1 according to the third embodiment is the same as the laser ultrasonic inspection device 1 according to the second embodiment, except that a scanning mirror 126 and a signal generator 128 are added to the pulsed laser irradiation unit 11.

[0080] The pulsed laser irradiation unit 11 shown in FIG. 6 includes a first laser light source 112, an amplifier 114, a voltage-current converter 116, a frequency converter 124, a scanning mirror 126, and a signal generator 128.

[0081] The scanning mirror 126 changes the optical path of the first laser light L11 emitted from the first laser light source 112. This causes the irradiation position of the first laser light L11 on the subject 10 to be scanned. As a result, the position of the defect def can be more easily identified. Examples of the scanning mirror 126 include a MEMS (Micro Electro Mechanical Systems) scanner and a galvano scanner. These scanning mirrors 126 change the angle of the reflecting mirror to change the reflection angle of the first laser light L11.

[0082] Among these, a MEMS mirror is preferably used. The MEMS mirror makes it easy to reduce the size, weight, and power consumption of the scanning mirror 126. The operating method of the MEMS mirror is not particularly limited, but examples include an electrostatic method, a piezoelectric method, and an electromagnetic method.

[0083] The MEMS mirror operates in either a resonant mode or a non-resonant mode. Of these, the non-resonant mode is preferably used. In the non-resonant mode, the first laser light L11 can be irradiated onto any position on the subject 10 in accordance with the mirror drive signal Sm1 input to the MEMS mirror.

[0084] Furthermore, the scanning type of scanning mirror 126 may be one-dimensional or two-dimensional. Note that two-dimensional scanning mirror 126 has two rotation axes, and changes the reflection angle of first laser light L11 by swinging the reflecting mirror around the rotation axes.

[0085] The signal generator 128 supplies a mirror drive signal Sm1 to the scanning mirror 126. In the case of a two-dimensional scanning mirror 126, the attitude of the reflecting mirror is expressed by a tilt angle (θx, θy). The signal generator 128 generates the mirror drive signal Sm1 for driving the two rotation axes so that the tilt angle (θx, θy) becomes a target value.

[0086] The scanning mirror 126 outputs a mirror attitude signal Sm2 to the signal processing unit 15. The mirror attitude signal Sm2 includes information on the tilt angle (θx, θy) of the reflecting mirror. The signal processing unit 15 can acquire, for each tilt angle (θx, θy), the elapsed time Δt from the emission of the first laser light L11 to the detection of the vibration VB. The mirror attitude signal Sm2 input to the signal processing unit 15 is, for example, an output signal from an angle sensor (not shown) provided in the scanning mirror 126.

[0087] The signal processing unit 15 may store the distance Lo between the laser ultrasonic inspection device 1 and the object 10. This distance Lo may be a value measured in advance, or may be a value measured by a distance measuring unit (not shown) provided in the laser ultrasonic inspection device 1. The signal processing unit 15 can determine the value of the irradiation position P(θx, θy, Lo) of the first laser light L11 based on the tilt angle (θx, θy) of the reflecting mirror and the distance Lo. The determined value of the irradiation position P(θx, θy, Lo) and the measured value of the elapsed time Δt are input to the defect detection unit 16.

[0088] The distance measurement unit may be, for example, a Time of Flight (ToF) distance measurement sensor or a Frequency Modulated Continuous Wave (FMCW) distance measurement sensor.

[0089] The defect detection unit 16 associates the irradiation position P(θx, θy, Lo) with the elapsed time Δt. Then, the defect detection unit 16 generates a data set of the positions of defects def and the elapsed time Δt from these values. Because this data set is point cloud data, it is possible to generate image data in which positions in the image are associated with the elapsed time Δt corresponding to those positions by using, for example, an image of the test object 10 and the point cloud data. This image data visually represents the distribution of long and short elapsed times Δt, and therefore contributes to supporting understanding of the distribution state of defects def.

[0090] 7 is a diagram showing an example of a scanning trajectory TR of the irradiation position of the first laser light L11 in an orthogonal coordinate system formed by the X-axis and the Y-axis set on the subject 10, and an example of image data Id1 obtained by mapping the length of the elapsed time Δt at each position as a color density. Fig. 7 also shows an example of waveforms of the displacement d acquired for two positions in the image data Id1 that have different color densities.

[0091] The scanning trajectory TR shown in FIG. 7 is a trajectory obtained when the irradiation position is moved back and forth in the Y-axis direction while being shifted in the X-axis direction. Furthermore, in the image data Id1 shown in FIG. 7, the color density is light when the elapsed time Δt is relatively long, and the color density is dark when the elapsed time Δt is relatively short. By creating such image data Id1, the position of the defect def can be visually indicated. This image data Id1 may be displayed in any manner. For example, it may be displayed on a monitor (not shown), or it may be projected onto the object 10.

[0092] In this embodiment, the irradiation position of the first laser light L11 is scanned, but the irradiation position of the second laser light L12 may also be scanned, or both may be scanned. In the third embodiment as described above, the same effects as in the second embodiment can be obtained.

[0093] 5. Fourth embodiment Next, a laser ultrasonic inspection device according to a fourth embodiment will be described.

[0094] FIG. 8 is a block diagram showing a schematic configuration of a laser ultrasonic inspection device 1 according to the fourth embodiment.

[0095] The fourth embodiment will be described below, focusing on the differences from the third embodiment and omitting a description of similarities. Note that in Fig. 8, the same reference numerals are used to designate the same components as those in the third embodiment.

[0096] The laser ultrasonic inspection device 1 according to the fourth embodiment is similar to the laser ultrasonic inspection device 1 according to the third embodiment, except that it includes a frequency converter 129 instead of the signal generator 128.

[0097] The pulsed laser irradiation unit 11 shown in FIG. 8 includes a first laser light source 112, an amplifier 114, a voltage-current converter 116, a frequency converter 124, a scanning mirror 126, and a frequency converter 129.

[0098] The frequency converter 129 converts the frequency of the reference signal Ss output from the oscillator circuit of the oscillator-type optical modulator 132 into a target frequency, i.e., the operating frequency of the scanning mirror 126. This allows the frequency converter 129 to generate a mirror drive signal Sm1. The frequency converter 129 includes, for example, a frequency divider circuit that divides the frequency of the mirror drive signal Sm1 by n, where n is a positive integer. An example of a frequency divider circuit is the n-ary counter shown in FIG. 5. Specifically, if the base number N in the n-ary counter shown in FIG. 5 is 10,000,000, the frequency of the mirror drive signal Sm1 output instead of the pulse control signal Sd shown in FIG. 5 can be down-converted to 0.5 Hz.

[0099] In the case of a two-dimensional scanning mirror 126, the frequency converter 129 generates a mirror drive signal Sm1 for driving the two rotation axes so that the tilt angle (θx, θy) becomes a target value. For example, if the frequency of the mirror drive signal Sm1 is 0.5 Hz and the frequency of the pulse control signal Sd is 100 Hz, the scanning mirror 126 reflects 20 pulses of the first laser light L11 during one round trip of the tilt angle θy. At this time, by shifting the phase of the signal for reciprocating the tilt angle θx (the signal for oscillating in the X-axis direction shown in FIG. 9) by 90° from the signal for reciprocating the tilt angle θy (the signal for oscillating in the Y-axis direction shown in FIG. 9), the scanning trajectory of the first laser light L11 reflected by the scanning mirror 126 becomes a circular trajectory like the scanning trajectory TR shown in FIG. 9. Then, the scanning mirror 126 reflects 20 pulses of the first laser light L11 during one round trip of the tilt angle θx.

[0100] FIG. 9 is a diagram showing an example of a scanning locus TR of the irradiation position of the first laser light L11 in an orthogonal coordinate system formed by the X-axis and Y-axis set on the object 10.

[0101] In this embodiment, a mirror drive signal Sm1 is used that is generated by utilizing the vibration of the vibration element 130. When the mirror drive signal Sm1 is input to the scanning mirror 126, the scanning locus TR of the irradiation position of the first laser light L11 becomes a circular locus as shown in Fig. 9. This allows the first laser light L11 to be scanned in a planar manner over the surface of the subject 10.

[0102] In this embodiment, the mirror attitude signal Sm2 input to the signal processing unit 15 is, for example, an output signal of an angle sensor (not shown) provided in the scanning mirror 126. In the fourth embodiment as described above, the same effects as in the third embodiment can be obtained.

[0103] In addition, in this embodiment, the vibration of the vibration element 130 is used for light modulation, demodulation of the surface vibration signal, measurement of the elapsed time Δt, generation of the pulse control signal Sd, and generation of the mirror drive signal Sm1, thereby further reducing the number of parts.

[0104] 6. Fifth embodiment Next, a laser ultrasonic inspection device according to a fifth embodiment will be described.

[0105] FIG. 10 is a schematic diagram showing the general configuration of a laser ultrasonic inspection device 1 according to the fifth embodiment.

[0106] The fifth embodiment will be described below, focusing on the differences from the first embodiment, and omitting a description of similarities. Note that in Fig. 10, the same reference numerals are used to designate the same components as those in the first embodiment.

[0107] The laser ultrasonic inspection device 1 according to the fifth embodiment is similar to the laser ultrasonic inspection device 1 according to the first embodiment, except that it is configured to inspect the thickness of the object 10 .

[0108] The laser ultrasonic inspection device 1 shown in Fig. 10 includes a signal processing unit 15 and a thickness measurement unit 17 connected thereto. In the laser ultrasonic inspection device 1 shown in Fig. 10, a first laser beam L11 is irradiated onto one surface of an object 10, and vibrations VB induced on the other surface are detected by a second laser beam L12. In this case, the elapsed time Δt from the emission of the first laser beam L11 to the detection of the vibrations VB reflects the thickness t10 of the object 10. In other words, when the propagation speed of the ultrasonic waves US is V, the thickness t10 can be calculated by the following formula (1): t10=V·Δt (1)

[0109] Alternatively, the first laser beam L11 and the second laser beam L12 may be irradiated onto the same surface of the subject 10. In this case, the ultrasound US is reflected by the surface opposite to the irradiated surface and returns to the irradiated surface. In this case, the thickness t10 can be calculated by the following formula (2). t10=V·Δt / 2 (2)

[0110] The calculation of the thickness t10 as described above can be performed by the thickness measurement unit 17 connected to the signal processing unit 15. This allows the laser ultrasonic inspection device 1 to inspect the thickness of the object 10 nondestructively. In the fifth embodiment as described above, the same effects as in the first embodiment can be obtained.

[0111] 7. Sixth embodiment Next, a laser ultrasonic inspection device according to a sixth embodiment will be described.

[0112] FIG. 11 is a schematic diagram showing the general configuration of a laser ultrasonic inspection device 1 according to the sixth embodiment.

[0113] The sixth embodiment will be described below, focusing on the differences from the third embodiment and omitting a description of similarities. Note that in Fig. 11, the same reference numerals are used to designate the same components as those in the third embodiment.

[0114] The laser ultrasonic inspection device 1 of the sixth embodiment is similar to the laser ultrasonic inspection device 1 of the third embodiment, except that the signal processing unit 15 is configured to calculate the frequency of the vibration VB based on the reference signal Ss.

[0115] 11 captures the displacement and displacement speed occurring on the surface of the object 10 in association with the vibration VB, thereby making it possible to detect the vibration VB.

[0116] 12 is a graph showing the waveform of the displacement of the test object 10 caused by the vibration VB. The horizontal axis of FIG.

[0117] 12, almost no displacement is observed during the elapsed time Δt from when the first laser light L11 is emitted until the vibration VB is detected as a displacement of the surface of the subject 10. On the other hand, after the elapsed time Δt, the amplitude of the displacement becomes large. Based on this, the vibration VB can be detected.

[0118] The signal processing unit 15 shown in FIG. 11 has a function of capturing the time waveform of the increased displacement resulting from the vibration VB shown in FIG. 12 and performing frequency analysis. Fast Fourier analysis can be used for the frequency analysis. Through the frequency analysis, the signal processing unit 15 generates a frequency analysis result fo. The frequency analysis result fo includes the intensity of each frequency component, i.e., resonance frequency information, etc. Note that since the time waveform of the displacement is generated based on the reference signal Ss, a highly accurate frequency analysis result fo can be obtained.

[0119] The value of the irradiation position P(θx, θy, Lo) calculated by the signal processing unit 15 and the value of the generated frequency analysis result fo are input to the defect detection unit 16. The defect detection unit 16 identifies the state of the defect def, i.e., the presence or absence of a void, crack, peeling, interface, foreign matter, modified area, etc., based on the frequency analysis result fo. Specifically, a specific frequency is reflected in the frequency analysis result fo depending on the state of the defect def. This allows the inspection of the specimen 10 to be performed non-destructively.

[0120] Furthermore, the defect detection unit 16 may associate the value of the irradiation position P(θx, θy, Lo) with the value of the frequency analysis result fo. In this case, the defect detection unit 16 generates a data set of the positions of the defects def and the frequency analysis results fo from these values. Because this data set is point cloud data, it is possible to generate image data in which positions in the image are associated with the frequency analysis results fo corresponding to those positions by using, for example, an image of the test object 10 and the point cloud data. This image data visually represents the distribution of the strengths of the frequency analysis results fo, and therefore contributes to supporting understanding of the distribution state of the defects def.

[0121] 13 is a diagram showing an example of a scanning trajectory TR of the irradiation position of the first laser light L11 in an orthogonal coordinate system formed by an X axis and a Y axis set on the subject 10, and an example of image data Id2 obtained by mapping the intensity of the frequency analysis result fo at each position by replacing it with color density. Fig. 13 also shows examples of frequency analysis results fo obtained for two positions in the image data Id2 that have different color densities.

[0122] 13, for example, when the intensity of a frequency around 2 kHz is below a predetermined threshold, the color density is light, and when the intensity is equal to or greater than the predetermined threshold, the color density is dark. By creating this type of image data Id2, the position of the defect def can be visually indicated.

[0123] In this embodiment, the irradiation position of the first laser light L11 is scanned, but the irradiation position of the second laser light L12 may also be scanned, or both may be scanned. In the sixth embodiment as described above, the same effects as in the third embodiment can be obtained.

[0124] In addition, in this embodiment, the vibration of the vibration element 130 is used for light modulation, demodulation of the surface vibration signal, and generation of time waveforms of displacement and displacement velocity, thereby reducing the number of parts.

[0125] 6. Effects of the above embodiment As described above, the laser ultrasonic inspection device 1 according to the embodiment includes the first laser light source 112 and the vibration detection unit 13 (laser interferometer). The first laser light source 112 irradiates the subject 10 with a pulsed first laser light L11. The vibration detection unit 13 uses the second laser light L12 to detect vibrations VB of the subject 10 resulting from ultrasound US induced in the subject 10 by irradiation with the first laser light L11. The vibration detection unit 13 also includes a second laser light source 134, a vibrator-type optical modulator 132, a photodiode 136 (light-receiving element), and a signal processing unit 15. The second laser light source 134 irradiates the subject 10 with the second laser light L12. The vibrator-type optical modulator 132 modulates the frequency of the second laser light L12 using the vibration element 130. The photodiode 136 receives the second laser light L12 that has passed through the oscillator-type optical modulator 132 and the second laser light L12 that has passed through the subject 10, and outputs a received light signal S2. The signal processing unit 15 detects the vibration VB based on the received light signal S2 and the reference signal Ss, and measures the elapsed time Δt from when the first laser light source 112 emits the first laser light L11 to when the vibration VB is detected, based on the reference signal Ss. The oscillator element 130 is the signal source of the reference signal Ss.

[0126] With this configuration, the vibration of the vibration element 130 can be used for optical modulation, demodulation of the surface vibration signal, and measurement of the elapsed time Δt. Then, the presence or absence of a defect def can be detected based on the elapsed time Δt, allowing for non-destructive inspection of the specimen 10. This makes it possible to realize a laser ultrasonic inspection device 1 that has a small number of parts and is easily miniaturized.

[0127] The laser ultrasonic inspection device 1 according to the embodiment includes a first laser light source 112 and a vibration detection unit 13 (laser interferometer). The first laser light source 112 irradiates the subject 10 with a pulsed first laser light L11. The vibration detection unit 13 uses a second laser light L12 to detect vibrations VB of the subject 10 resulting from ultrasound US induced in the subject 10 by irradiation with the first laser light L11. The vibration detection unit 13 also includes a second laser light source 134, a vibrator-type optical modulator 132, a photodiode 136 (light-receiving element), and a signal processing unit 15. The second laser light source 134 irradiates the subject 10 with the second laser light L12. The vibrator-type optical modulator 132 modulates the frequency of the second laser light L12 using a vibration element 130. The photodiode 136 receives the second laser light L12 that has passed through the oscillator-type optical modulator 132 and the second laser light L12 that has passed through the subject 10, and outputs a received light signal S2. The signal processing unit 15 detects the vibration VB based on the received light signal S2 and the reference signal Ss, and calculates the frequency of the vibration VB based on the reference signal Ss. The vibration element 130 is the signal source of the reference signal Ss.

[0128] With this configuration, the vibration of the vibration element 130 can be used for optical modulation, demodulation of the surface vibration signal, and generation of time waveforms of displacement and displacement velocity. Furthermore, by subjecting the time waveform of displacement, etc. to frequency analysis, a frequency analysis result fo including resonance frequency information, etc., can be generated. Then, the presence or absence of a defect def can be detected based on the frequency analysis result fo, allowing for non-destructive inspection of the specimen 10. This allows for the realization of a laser ultrasonic inspection device 1 with a small number of parts and easy miniaturization.

[0129] In the laser ultrasonic inspection device 1 according to the embodiment, the repetition period of the pulsed first laser light L11 is set based on a pulse control signal Sd in the first laser light source 112. The pulse control signal Sd is generated based on a reference signal Ss.

[0130] With this configuration, the vibration of the vibration element 130 can be used for optical modulation, demodulation of the surface vibration signal, measurement of the elapsed time Δt, and generation of the pulse control signal Sd, which allows for a further reduction in the number of parts of the laser ultrasonic inspection device 1.

[0131] The laser ultrasonic inspection device 1 according to the embodiment includes a scanning mirror 126. The scanning mirror 126 scans and irradiates the subject 10 with the first laser light L11.

[0132] With this configuration, it is possible to realize a laser ultrasonic inspection device 1 that can more easily identify the position of the defect def.

[0133] In the laser ultrasonic inspection device 1 according to the embodiment, the scanning mirror 126 sets the timing for scanning with the first laser light L11 based on the reference signal Ss.

[0134] With this configuration, the vibration of the vibration element 130 can be used for optical modulation, demodulation of the surface vibration signal, measurement of the elapsed time Δt, generation of the pulse control signal Sd, and generation of the mirror drive signal Sm1, thereby further reducing the number of parts in the laser ultrasonic inspection device 1.

[0135] In the laser ultrasonic inspection device 1 according to the embodiment, the signal processing unit 15 detects the vibration VB by calculating the displacement or displacement speed of the surface of the object 10 from the received light signal S2.

[0136] According to this configuration, the vibration VB can be detected based on the displacement and displacement speed of the surface of the test object 10, and therefore the vibration VB can be detected with high accuracy. As a result, the measurement accuracy of the elapsed time Δt is also improved, and ultimately the inspection accuracy of the test object 10 is improved.

[0137] The laser ultrasonic inspection device 1 according to the embodiment includes a defect detection unit 16. The defect detection unit 16 detects a defect def contained in the object 10 based on the measurement result of the elapsed time Δt.

[0138] With this configuration, the inspection object 10 can be inspected non-destructively based on the presence or absence of the defect def and its position.

[0139] The laser ultrasonic inspection device 1 according to the embodiment includes a thickness measurement unit 17. The thickness measurement unit 17 measures the thickness of the object 10 based on the measurement result of the elapsed time Δt. With this configuration, the thickness of the object 10 can be inspected non-destructively.

[0140] The laser ultrasonic inspection device 1 according to the embodiment includes a defect detection unit 16. The defect detection unit 16 detects a defect def contained in the object 10 based on the analysis result of the frequency of the vibration VB.

[0141] According to this configuration, the test object 10 can be inspected non-destructively based on the frequency analysis result fo.

[0142] Although the laser ultrasonic inspection device of the present invention has been described above based on the illustrated embodiment, the present invention is not limited to this.

[0143] For example, the laser ultrasonic inspection device of the present invention may be configured such that each part of the above-described embodiments is replaced with any component having the same function, or any component may be added to the above-described embodiments. Furthermore, the laser ultrasonic inspection device of the present invention may have a configuration that combines two or more of the above-described embodiments. [Explanation of symbols]

[0144] 1...laser ultrasonic inspection device, 9...laser ultrasonic inspection device, 10...object, 11...pulse laser irradiation unit, 13...vibration detection unit, 15...signal processing unit, 16...defect detection unit, 17...thickness measurement unit, 90...object, 91...pulse laser irradiation unit, 93...vibration detection unit, 95...signal processing unit, 112...first laser light source, 114...amplifier, 116...voltage-current converter, 118...signal generator, 122...photodiode, 124...frequency converter, 126...scanning mirror, 128...signal generator, 129...frequency converter, 130...vibration element, 132...vibrator-type optical modulator, 134...second laser light source, 136...photodiode, 142...first circuit, 144...second circuit, 912...laser light source, 914...amplifier, 916...voltage-current converter, 918...signal generator, 922...photodiode, 932...acousto-optic modulation detector, 934...laser light source, 936...photodiode, 938...signal generator, Id1...image data, Id2...image data, L11...first laser light, L111...first laser light, L112...first laser light, L12...second laser light, L91...laser light, L92...laser light, Lo...distance, N...base number, R...reset signal, S1...laser detection signal, S11...pulse, S12...pulse S..., S2...receiving signal, Sa...driving signal, Sd...pulse control signal, Sm1...mirror driving signal, Sm2...mirror position signal, Ss...reference signal, TR...scanning trajectory, US...ultrasound, US1...ultrasound, US2...ultrasound, VB...vibration, d...displacement, d1...displacement, d2...displacement, def...defect, e1...ellipse, e2...ellipse, fo...frequency analysis result, t10...thickness, Δt...elapsed time, Δt1...elapsed time, Δt2...elapsed time

Claims

1. a first laser light source that irradiates a subject with a pulsed first laser light; a laser interferometer that uses a second laser beam to detect vibrations of the subject caused by ultrasonic waves induced in the subject by irradiation with the first laser beam; Equipped with The laser interferometer comprises: a second laser light source that irradiates the subject with the second laser light; an oscillator-type optical modulator that modulates the frequency of the second laser light using an oscillator element; a light-receiving element that receives the second laser light that has passed through the oscillator-type optical modulator and the second laser light that has passed through the subject, and outputs a light-receiving signal; a signal processing unit that detects the vibration based on the light receiving signal and a reference signal, and measures, based on the reference signal, an elapsed time from when the first laser light source emits the first laser light until when the vibration is detected; and The laser ultrasonic inspection device is characterized in that the vibration element is a signal source of the reference signal.

2. a first laser light source that irradiates a subject with a pulsed first laser light; a laser interferometer that uses a second laser beam to detect vibrations of the subject caused by ultrasonic waves induced in the subject by irradiation with the first laser beam; Equipped with The laser interferometer comprises: a second laser light source that irradiates the subject with the second laser light; an oscillator-type optical modulator that modulates the frequency of the second laser light using an oscillator element; a light-receiving element that receives the second laser light that has passed through the oscillator-type optical modulator and the second laser light that has passed through the subject, and outputs a light-receiving signal; a signal processing unit that detects the vibration based on the light receiving signal and a reference signal, and calculates a frequency of the vibration based on the reference signal; and The laser ultrasonic inspection device is characterized in that the vibration element is a signal source of the reference signal.

3. the first laser light source sets a repetition period of the pulsed first laser light based on a pulse control signal, 3. The laser ultrasonic inspection device according to claim 1, wherein the pulse control signal is generated based on the reference signal.

4. 3. The laser ultrasonic inspection device according to claim 1, further comprising a scanning mirror that scans the first laser light and irradiates the object.

5. The laser ultrasonic inspection device according to claim 4 , wherein the scanning mirror sets a timing for scanning the first laser light based on the reference signal.

6. 3. The laser ultrasonic inspection device according to claim 1, wherein the signal processing unit detects the vibration by calculating a displacement or a displacement speed of the surface of the object from the received light signal.

7. 2. The laser ultrasonic inspection device according to claim 1, further comprising a defect detection unit that detects defects contained in the test object based on the measurement result of the elapsed time.

8. 2. The laser ultrasonic inspection device according to claim 1, further comprising a thickness measurement unit that measures a thickness of the object based on a measurement result of the elapsed time.

9. 3. The laser ultrasonic inspection device according to claim 2, further comprising a defect detection unit that detects defects contained in the test object based on the analysis result of the vibration frequency.

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