JP2008008896A - Laser ultrasonic transmission method and transmitter of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To generate ultrasonic waves within an object to be measured through utilization of an ablation phenomenon by means of laser light irradiation, to transmit the ultrasonic waves without impairing a remote operability and a noncontact properties, and to eliminate the influence on the surface of the object to be measured due to transmission laser light irradiation. <P>SOLUTION: An ultrasonic transmitter 10 comprises: a transmission laser light source 12 for outputting a transmitted laser light GL for irradiating the surface of the object 11 to be measured; a laser irradiation optical system 13 for irradiating the surface of the object 11 to be measured with the transmitted laser light GL outputted from the transmission laser light source 12 on the desired light collection conditions, generating ultrasonic waves within the object 11 to be measured by ablation phenomenon, and transmitting the ultrasonic waves; and a fluid jetting apparatus 11 for running an oxidation-resistant fluid F that is inert against surface oxidation, to an irradiation location of the transmitted laser light GL irradiated to the surface of the object 11, to be measured through the irradiation optical system 13 or its vicinity. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a laser ultrasonic transmission technology, and in particular, a laser ultrasonic transmission that generates and transmits an ultrasonic wave inside a measurement object using an ablation phenomenon that occurs when laser light is irradiated on the surface of the measurement object. The present invention relates to a method and a transmission apparatus thereof.

  Ultrasound technology leads to medical diagnosis from nondestructive inspection of intrinsic defects such as surface cracks and nests that occur in materials (objects to be measured), analysis of material characteristics, or measurement of plate thickness, flow rate, water level, temperature, etc. It is used in a wide range of technical fields.

  In normal ultrasonic technology, transmission / reception of ultrasonic signals is performed by bringing a contact sensor such as a piezoelectric element or an ultrasonic probe into contact with an object to be measured via an ultrasonic propagation medium. There has also been proposed a laser ultrasonic method that is replaced by a laser technology for transmission and reception (for example, Non-Patent Document 1). Laser ultrasonic method can measure in principle without contact with the object to be measured. If the object to be measured is difficult to contact, such as high temperature, high place, high radiation field, small size, complicated shape part, etc. It is expected to be applied to various fields such as parts that require non-contact measurement techniques.

  For ultrasonic reception by a laser, the surface displacement or vibration velocity of the reception point induced by the ultrasonic wave is detected using the straightness and coherence of the laser beam for receiving the ultrasonic wave (hereinafter referred to as reception laser light). Technology is used. As an optical system for ultrasonic signal detection, Michelson interferometry, Mach-Zehnder interferometry, confocal Fabry-Perot interferometer, interferometer using a phase conjugate optical element, knife edge method, etc. have been proposed (for example, Non-patent document 2).

On the other hand, ultrasonic transmission by a laser is performed by irradiating a measurement object with laser light (hereinafter referred to as transmission laser light) that is temporally pulsed or intensity-modulated. For example, even in a medium-scale laser light source with an average output of about 10 W, the laser oscillation is temporally controlled in a pulse form on the order of several hundred microseconds (μs) to nanoseconds (ns), and the laser light irradiation spot is spatially controlled. If it is narrowed down to the millimeter order, GW / cm ² can be realized as the power applied to the condensing point.

  When such a laser beam is irradiated onto the object to be measured, the effect of heating the entire material of the object to be measured is very small because the incident power is only about 10 W in the medium-scale laser source. It is sufficiently possible to heat a very small area on the surface of a material, or to plasma several atomic layers from the material surface.

  When the power density of the laser beam is small, thermal stress is generated by the rapid heating-rapid cooling process of the surface micro-region, and the generated thermal stress becomes the strain source of the material and an ultrasonic signal is generated (thermal strain mode). ). On the other hand, when the power density is large, several atomic layers on the target surface of the object to be measured are turned into plasma, and pressure is applied to the material (object to be measured) as a reaction force of plasma expansion to generate vibration (ablation mode).

By combining this laser technology with ultrasonic transmission / reception technology, it is possible to realize a laser ultrasonic method that can be remotely operated and is a remote / non-contact ultrasonic transmission / reception method. In particular, when attention is focused on ultrasonic transmission by laser, not only the advantage of remote / non-contact, but also the laser ultrasonic transmission method has the following advantages.
・ Can generate ultrasonic waves with a wide frequency band,
・ Various ultrasonic modes such as surface waves propagating on the material surface, longitudinal and transverse waves propagating inside, and plate waves propagating through the thin plate portion of the material can be generated.
・ Dependence on the surface shape and roughness of the target is small (the intensity, directivity, mode, etc. of the generated ultrasonic waves depend on the irradiation conditions and are not easily affected by the incident angle of the transmitting laser)
・ It is possible to set the irradiation spot minutely, and it can be applied to small parts, complex shapes, narrow spaces, etc.
・ Ultrasonic sound sources can be regarded as “points” and measurement with high spatial resolution is possible.
There are features such as.

  The ultrasonic transmission technology using laser is not only useful for laser ultrasonic reception, but also has a great merit when used in combination with a reception technology such as a normal piezoelectric element or electromagnetic ultrasonic probe.

  Such a laser ultrasonic transmission method has been established as a basic principle, and industrial use has already started.

  However, in the conventional laser ultrasonic transmission method, when an ultrasonic signal having a higher intensity is to be transmitted, it is necessary to use an ablation mode. When this ablation mode is used, the surface of the object to be measured becomes plasma, and there is a concern about the influence on the material of the surface of the object to be measured.

  As a laser ultrasonic transmission technique using an ablation mode, an ultrasonic generator described in Patent Document 1 is known.

  In the laser ultrasonic transmission technique described in Patent Document 1, as shown in FIGS. 15A and 15B, the influence on the material of the surface of the object to be measured a is “surface damage” and the surface layer is several μm or less. In order to avoid this “damage of the surface of the object to be tested due to ablation”, a thin plate b having a thickness equal to or less than the wavelength of the ultrasonic wave to be used is placed in contact with the surface of the object to be measured. The thin plate b is irradiated with the transmission laser light d from the pulse laser light source c (FIG. 15).

According to this laser ultrasonic transmission technology, generation of ultrasonic waves, that is, plasma generation occurs on the thin plate b, so that the surface of the object to be measured is not damaged by the transmission laser beam d, and ultrasonic waves are transmitted during propagation of the thin plate b. It is possible to generate a strong ultrasonic wave with respect to the object to be measured a without being attenuated.
Japanese Patent Laid-Open No. 10-128236 CB Scruby and LE Drain; “Laser Ultrasonics Technique and Applications” Adam Hilger, Bristol, Philadelphia and New York, (1990) 447p. Yamawaki: “Laser Ultrasound and Non-contact Material Evaluation”, Journal of the Japan Welding Society, Vol. 64, No. 2, P.104-108 (1995)

  In the laser ultrasonic transmission technique described in Patent Document 1, the thin plate b and the object to be measured a must be brought into ultrasonic contact, and the remote operation and non-contact characteristics that are the greatest features of the laser ultrasonic method are provided. There is a risk that it will be damaged or lost at all.

  The present invention has been made in consideration of the above-described circumstances, and does not impair the remote operability and non-contact property of the laser ultrasonic transmission method. In addition, the effect of the transmission laser light irradiation on the surface of the object to be measured is substantial. It is an object of the present invention to provide a laser ultrasonic transmission method and a transmission apparatus thereof that are not suitable.

  In order to solve the above-described problems, a laser ultrasonic transmission method according to the present invention is a laser that generates an ultrasonic signal on an object to be measured using an ablation phenomenon that occurs when the surface of the object to be measured is irradiated with laser light. In the ultrasonic transmission method, the laser superposition is characterized in that the laser light is irradiated to the position where the ablation occurs on the surface of the object to be measured and the vicinity thereof, and an anti-oxidation fluid which is inactive against surface oxidation is flowed. This is a sound wave transmission method.

  In order to solve the above-described problem, a laser ultrasonic transmission apparatus according to the present invention transmits a transmission laser light source that outputs a transmission laser beam irradiated on the surface of an object to be measured, and a transmission laser beam output from the transmission laser light source. Is irradiated onto the surface of the object under desired focusing conditions, an ultrasonic wave is generated in the object to be measured by an ablation phenomenon, and an ultrasonic signal is transmitted. The irradiation position of the transmission laser beam irradiated on the surface of the object to be measured and its vicinity are composed of a fluid ejection device for flowing an antioxidant fluid which is inactive against surface oxidation.

  In the laser ultrasonic transmission method and the transmission apparatus according to the present invention, it is possible to prevent oxidation of the transmission laser light irradiation point of the object to be measured without impairing the remote operability and non-contact property.

  Embodiments of a laser ultrasonic transmission method and a transmission apparatus thereof according to the present invention will be described with reference to the accompanying drawings.

[First Embodiment]
FIG. 1 is a configuration diagram for explaining a first embodiment of a laser ultrasonic wave transmitting apparatus according to the present invention.

  This laser ultrasonic transmitter 10 guides and irradiates the surface of the object 11 to be measured, which is an inspection object, with the transmission laser light GL output from the transmission laser light source 12 as a laser generator, and scans the laser. An optical system 13, a fluid ejection device 14 that sprays an antioxidant fluid F onto the surface of the object to be measured 11 at and near an irradiation position where the transmission laser beam GL is irradiated, and a fluid ejected and sprayed from the fluid ejection device 14 And a fluid recovery device 15 that recovers F.

  The transmission laser light source 12 outputs a pulsed or intensity-modulated transmission laser light GL, and the output transmission laser light GL is spatially transmitted to form a laser irradiation optical system 13 comprising a mirror lens scanning optical system. The measurement object 11 is irradiated via. The transmission laser light GL irradiated to the object to be measured 11 is irradiated onto the object to be measured 11 so that it can be scanned one-dimensionally or two-dimensionally with the focusing condition appropriately determined by the objective lens 17 or the like.

  In addition, the fluid ejection device 14 uses a substance that has a high transmittance of the transmission laser light GL and is inactive against surface oxidation. This substance includes an inert gas such as He gas, Ne gas, Ar gas, a gas such as nitrogen gas or a mixed gas of these gases, or a liquid that does not contain a substance that contributes to the surface oxidation of the object to be measured 11. There is a prevention fluid F, which is stored in the liquid source 18. The antioxidant fluid F stored in the fluid source 18 passes through a fluid supply pipe or hose 19 as a fluid transmission means, and is irradiated or irradiated with the transmission laser light GL of the object to be measured 11 from a fluid ejection nozzle (fluid ejection means) 20. It is ejected toward the part or its vicinity.

  In the middle of the fluid supply pipe 19, a filter 21 for removing foreign substances such as dust and fine particles that can become scatterers or substances contributing to oxidation during propagation of a transmission laser beam and a fluid pump (not shown) are provided as necessary. ) Is installed. The fluid source 18 may be pressurized instead of the fluid pump. When the antioxidant fluid F is an inert gas such as helium gas or nitrogen gas, it may be a blow duct instead of the fluid jet nozzle 20.

  The fluid ejection device 14 basically includes an antioxidant fluid storage function, a fluid transmission function, and a fluid ejection function. If necessary, fine particles that can become a scatterer when propagating laser light, substances that contribute to oxidation, and the like A filtration function is provided. When the antioxidant fluid is a gas, specific examples of the filtering function include not only a so-called filter but also a drying function for removing moisture that is a substance contributing to surface oxidation. The fluid source 18 may be configured by a fluid source 18 that is pressurized and self-injected, and a flow rate control function as a fluid control means for controlling the ejection, or a fluid drive function such as a fluid pump. And a fluid source 18 may be used.

  The antioxidant fluid F ejected from the fluid ejection nozzle or the ejection duct 20 is recovered by a fluid recovery device 15 provided as necessary. The supply and recovery of the antioxidant fluid F may adopt a circulation form of the antioxidant fluid F instead of the flow path form shown in FIG. 1 so that the antioxidant fluid F draws a circulation cycle.

  When an inert gas such as helium gas and a material having a large thermal conductivity are selected as the antioxidant fluid F, not only the surface of the object to be measured 11 is prevented from oxidation but also the fluctuation of the optical path due to the propagation of the transmission laser beam GL. Can be prevented. When the ambient atmosphere in which the object to be measured 11 is installed is air, when argon (Ar) gas is selected, Ar gas is easily retained in the vicinity of the light irradiation point by utilizing the density difference, and an inert atmosphere is formed and maintained. There is an advantage that it is easy to do. Further, when the environmental atmosphere is air, if nitrogen gas is selected, there is an advantage that there is no need for recovery and there is no difference in density, so that the change in optical refractive index is small.

On the other hand, the laser irradiation condition of the transmission laser light GL irradiated to the object to be measured 11 by the laser irradiation optical system 13 is set as laser condition 1 as an example.
[Laser condition 1]
Transmission laser light wavelength: 532 nm
Transmission laser beam pulse width: 5 to 10 ns
Transmitting laser light pulse energy: about 30mJ

  The transmission laser beam GL is irradiated a plurality of times while scanning the surface of the object to be measured 11 one-dimensionally or two-dimensionally (planar scanning). The influence on the surface of the DUT 11 when the transmission laser beam GL is irradiated a plurality of times is analyzed. The transmission laser beam GL is a pulse laser beam, and the pulse width of the pulse laser beam may be set within a range of 1 ns to 10 ns, and the pulse energy may be set within a range of 100 μJ to 1 J (laser beam condition 2).

  When, for example, a stainless steel plate, which is a representative metal material, is selected as the object to be measured 11, [Laser Condition 1] is a standard condition for obtaining a good laser ultrasonic signal.

The influence of the transmission laser beam GL applied to the surface of the object to be measured is
・ Appearance change ・ Surface roughness ・ Metal structure observation (micro observation)
・ Hardness measurement (Depth direction distribution of measured object)
-Analyzed from each viewpoint of metal composition analysis, and the analysis results are displayed as shown in FIGS.

  As shown in FIG. 2, a rectangular (m * n dimension), for example, 50 mm × 20 mm irradiation region 23 is set on the surface of a rectangular plate-shaped object 11 having a vertical and horizontal l * m dimension, for example, 100 mm × 50 mm, The irradiation region 23 is irradiated with the transmission laser beam GL from the transmission laser light source 12 under, for example, [Laser beam condition 1] to perform two-dimensional scanning (planar scanning). By irradiation with the transmission laser beam GL, the irradiation region 23 of the object to be measured 11 is blackened by an oxidation reaction, and the surface is oxidized.

  Further, as shown in FIGS. 3 to 5, the surface roughness, the metal structure in the vicinity of the surface, and the hardness distribution on the surface of the measurement object 11 irradiated with [Laser Condition 1] are different from those of the irradiated region 23. There is no significant change between the irradiated region 24 and the irradiated region 24. This change is seen in the metal structure as shown in FIGS. 6 (A) and 6 (B). In particular, it can be seen that the metal structure is oxidized in the range of about 500 nm in the depth direction from the surface layer of the object to be measured 11 by irradiation with the transmission laser beam GL, and from FIG. 6A, the degree of this oxidation is 100 nm from the surface layer. It can be seen that the depth range is large.

  It is estimated that the influence of the change in the metal composition on the order of nm on the strength, function, etc. of the material of the DUT 11 is extremely small. On the other hand, the color change of the surface of the object to be measured 11 is not a problem in the structural material or the like, but is a problem in the appearance of the object to be measured 11.

  When the laser ultrasonic wave transmitting device 10 irradiates the surface of the object to be measured 11 with the transmission laser light GL, the influence of the irradiation of the transmission laser light GL causes an ablation phenomenon on the surface layer of the object to be measured 11, thereby transmitting laser light. The ultrasonic wave US can be generated in the object to be measured 11 from the GL irradiation unit, and laser ultrasonic transmission can be realized.

  In the laser ultrasonic transmission device 10 shown in FIG. 1, the antioxidant fluid F is ejected from the fluid ejection device 14 to the surface of the object 11 to prevent oxidation that causes a black change in the surface of the object 11. . The anti-oxidation fluid F does not contain a substance that contributes to surface oxidation, and the anti-oxidation fluid F having a high light transmittance with respect to the wavelength of the transmission laser beam GL is ejected, and the irradiation point of the transmission laser beam GL (ablation occurs) It is possible to prevent oxidation at the irradiation position and its vicinity).

  Next, the operation of the laser ultrasonic transmission device will be described.

  When the laser transmission device 10 activates the transmission laser light source 12, the transmission laser light source 12 outputs a transmission laser beam GL that is pulsed or intensity-modulated. The output transmission laser beam GL is appropriately condensed by the laser irradiation optical system 13 and irradiated on the surface of the object 11 to be measured, and two-dimensional (planar) scanning is performed on this surface.

  On the other hand, an anti-oxidation fluid F, for example, an inert gas such as helium gas (He), is supplied from the fluid source 18 of the fluid ejection device 14 toward the irradiation point of the transmission laser beam GL on the object to be measured 11, the irradiation unit, and the vicinity thereof. It blows out and prevents the irradiation point of the transmission laser beam GL from being oxidized.

  The condition set in [Laser Condition 1] is used as an example of the irradiation condition of the transmission laser beam GL irradiated on the surface of the DUT 11. Various modes of irradiation conditions for the surface of the DUT 11 can be considered.

  By irradiating the object to be measured 11 with the transmission laser beam GL, an ablation phenomenon is generated on the surface layer of the object to be measured 11 to generate an ultrasonic wave, and this ultrasonic wave US is transmitted radially into the object to be measured 11. .

  In this laser ultrasonic transmission device 10, various irradiation conditions of the transmission laser beam GL irradiated to the object to be measured 11 can be considered, and an ablation phenomenon occurs on the surface layer of the object to be measured 11 due to the irradiation of the transmission laser beam GL. Any irradiation condition can be used as long as it can be used.

  Specifically, not only the Nd: YAG laser second harmonic light source having a wavelength of 532 nm as the transmission laser light source 12, but also a solid laser light source, an excimer laser light source, a carbon dioxide gas laser such as a carbon dioxide gas laser, and a pulse laser. The present invention can also be applied to a case where any laser light source that generates an ablation phenomenon on the surface of the object to be measured 11 such as a light source or a semiconductor laser light source is used.

  In addition, regarding the pulse width of the transmission laser beam GL, not only a Q-switch oscillation of 5 to 10 ns, but also an ultrashort pulse laser light source of picosecond or femtosecond oscillation, a long pulse laser light source of several hundred nanoseconds to several hundred microseconds Can also be applied to the prevention of surface oxidation when an ablation phenomenon occurs on the surface of the object to be measured 11.

  With this configuration, the laser ultrasonic transmission device 10 realizes laser ultrasonic transmission in an ablation mode that has a very small influence on the material of the object to be measured 11 while maintaining the features of remote scanning and non-contact. It becomes possible to do.

[Second Embodiment]
A second embodiment of the laser ultrasonic transmitter according to the present invention will be described with reference to FIGS.

  FIG. 7 is a configuration diagram illustrating a second embodiment of the laser ultrasonic transmission apparatus. The laser ultrasonic wave transmitting device 10 </ b> A transmits the transmission laser light GL output from the transmission laser light source 12 through the optical fiber 25 and is guided to the laser irradiation optical system 27. In the laser irradiation optical system 27, a lens optical system 29 is incorporated in a cylindrical lens holder 28 to which an optical fiber 25 is connected, and the transmission laser light GL is once expanded by the lens optical system 29 to become parallel light. After that, the surface of the object to be measured 11 is appropriately squeezed under a condensing condition and irradiated.

  On the other hand, the laser irradiation optical system 27 is stored in the cylindrical main body 34 of the fluid ejection nozzle 33. The cylindrical lens holder 28 of the laser irradiation optical system 27 is held substantially concentrically in a hollow fluid ejection nozzle 33 by fixing means such as a bar-shaped support bridge 35 having a cross shape in plan view as shown in FIG. .

  On the other hand, the fluid ejection nozzle 33 is connected to the pressurized fluid source 18 via a fluid transmission hose 37 to constitute a fluid ejection device 38. The antioxidant fluid F supplied from the pressurized fluid source 18 is guided to the fluid ejection nozzle 33 and ejected from the nozzle port 39 to the surface of the object to be measured 11. The cross-sectional area of the fluid ejection nozzle 33 has a tapered structure that becomes smaller (squeezed) in accordance with the flow direction of the antioxidant fluid F.

The nozzle port 39 of the fluid ejection nozzle 34 has a tip extending from the tip of the laser irradiation optical system 27 to a position close to the object to be measured 11 by a length L. The nozzle shape of the fluid ejection nozzle 33 may be a structure that is narrowed toward the tip such that the diameter φ ₁ of the cylindrical body 34 finally becomes the diameter φ ₂ of the nozzle port 39 (φ ₁ > φ ₂ ).

  In this laser ultrasonic transmission apparatus 10A, the example in which the transmission laser light GL output from the transmission laser light source 12 is cable-transmitted by the optical fiber 25 has been shown. However, an appropriate optical window (transmission window) is provided in the fluid ejection nozzle 33. In this way, the transmission laser light GL may be replaced with a cable transmission and a spatial transmission without using an optical fiber.

  Next, the operation of the laser ultrasonic transmission apparatus 10A shown in FIGS. 7 and 8 will be described.

  In this laser ultrasonic transmission apparatus 10A, when the transmission laser light source 12 is oscillated, the transmission laser light GL output from the transmission laser light source 12 is transmitted through the optical fiber incident optical system 30 and the optical fiber 25. The light is guided to the irradiation optical system 27, and the laser irradiation optical system 27 irradiates the measurement object 11 under appropriate condensing conditions.

  On the other hand, the laser irradiation optical system 27 is housed in a hollow fluid ejection cable 33, and the antioxidant fluid F from the fluid source 18 pressurized in the cylindrical body 34 of the fluid ejection nozzle 33 is used as a fluid transmission hose. The antioxidant fluid F supplied via the (fluid supply pipe) 37 and supplied to the cylindrical main body 34 is blown out from the nozzle port 39 toward the irradiation part of the transmission laser light GL of the object to be measured 11, and the irradiation part Is covered with an antioxidant fluid F to prevent the surface of the object to be measured 11 from being oxidized.

  Further, the laser irradiation optical system 27 irradiates the surface of the measurement object 11 with the transmission laser light GL, and the transmission laser light GL is scanned one-dimensionally or two-dimensionally on the surface of the measurement object 11 as necessary. When the transmission laser beam GL is irradiated onto the object to be measured 11, the influence of the irradiation of the transmission laser beam GL reaches the surface of the object to be measured 11 and causes an ablation phenomenon on the surface layer of the object to be measured 11. An ultrasonic signal is generated in the object 11. The generated ultrasonic wave is transmitted as an ultrasonic signal in the object to be measured 11 radially to the center.

  At this time, the laser irradiation optical system 27 is concentrically accommodated in the fluid ejection nozzle 33 so as to have a common axis, and the antioxidant fluid F is coaxial with the transmission laser light GL and passes through the nozzle port 39 without taking extra space. The irradiated portion of the transmission laser beam GL and the vicinity of the irradiation point are covered with an antioxidant fluid, and oxidation of the irradiation point can be efficiently prevented. The fluid ejection device 38 shares at least a part of the propagation path of the transmission laser light GL and the laser irradiation optical system 27 and ejects the antioxidant fluid F in the same direction as the irradiation direction of the transmission laser light GL.

  Further, the cross-sectional shape of the crossbar support bridge 35 serving as a fixing means for holding the laser irradiation optical system 27 accommodated in the fluid ejection nozzle 33 is configured as a wing structure or a fin shape, and the downstream side of the laser irradiation optical system 27. The anti-oxidant fluid F may generate a turbulent flow, a rotating flow, or a helical flow. Furthermore, the nozzle port 39 of the fluid ejection nozzle 33 may be branched into a plurality of parts, and the antioxidant fluid F may be blown out from each nozzle port in a linear or ring shape.

[Third Embodiment]
A third embodiment of the laser ultrasonic transmitter according to the present invention will be described with reference to FIG.

  FIG. 9 is a configuration diagram illustrating a third embodiment of the laser ultrasonic transmission apparatus 10B. The laser ultrasonic transmission device 10B shown in this embodiment differs from the laser ultrasonic transmission device 10A shown in the second embodiment in the fluid ejection structure of the fluid ejection nozzle 40, and other configurations are not substantially different. Therefore, the same components are denoted by the same reference numerals and description thereof is omitted.

  The fluid ejection nozzle 40 includes a chamber box 41 that covers the object to be measured 11 on the nozzle opening side, and a fluid retention chamber 44 that forms an atmosphere of the antioxidant fluid F is formed in the chamber box 41. The chamber box 41 has a fluid retention structure at the tip of the fluid ejection nozzle 40, and the antioxidant fluid F is retained at and near the irradiation position of the transmission laser light GL by the chamber box 41.

  Also in the laser ultrasonic wave transmitting apparatus 10B, when the transmission laser light source 12 is oscillated, the transmission laser light GL output from the transmission laser light source 12 is transmitted through the optical fiber incident optical system 30 and the optical fiber 25. The light is guided to the irradiation optical system 40, and the laser irradiation optical system 40 irradiates the object to be measured 11 under appropriate light collecting conditions. Here, the laser irradiation optical system 40 is installed inside the hollow fluid ejection nozzle 40 and connected to the fluid source 18 pressurized by the fluid transmission hose 37.

  On the other hand, the fluid ejection nozzle 40 is provided with a chamber box 41 on the outlet (nozzle port) side so as to partially cover the surface of the object 11 to be measured, and constitutes a retention chamber 44 in which the antioxidant fluid F is retained. The anti-oxidation fluid F is retained to some extent so as to cover the irradiation light of the transmission laser beam GL by the nozzle opening side chamber structure (fluid retention structure) of the fluid ejection nozzle 40, and effectively oxidizes the irradiation point. It is preventing.

  In the laser ultrasonic transmitting apparatus 10B shown in the third embodiment, an example in which the transmission laser light GL from the transmission laser light source 12 is cable-transmitted using the optical fiber 25 has been shown. However, an optical suitable for the fluid ejection nozzle 40 is shown. By providing the window, it is possible to perform spatial transmission without using an optical fiber, and the same effect can be obtained with respect to spatially transmitted transmission laser light.

  This laser ultrasonic transmitter 10B can blow out the antioxidant fluid F supplied from the fluid source 18 near the irradiation point of the transmission laser beam GL irradiated on the surface of the object 11 to be measured. The oxidation of the product 11 can be effectively and effectively prevented.

(First embodiment)
As a first example of the third embodiment, a laser ultrasonic transmitting apparatus 10B ₁ of the nozzle opening of the fluid jetting nozzle 40A of the chamber box 41A provided in (outlet) side asymmetrically with respect to the optical axis of the transmitted laser light GL By shaping and making the stay chamber 44A formed in the chamber box 41A asymmetric with respect to the optical axis, the flow of the antioxidant fluid F in the stay chamber 44A also becomes asymmetric. Rather than the arrangement in which the irradiation point of the transmission laser beam GL is the central position of the staying chamber 44A, the vortex or swirl of the antioxidant fluid F is generated more actively in the staying chamber 44A, and the irradiation point of the transmission laser beam GL and Oxidation in the vicinity of the vicinity can be efficiently prevented.

  Since the other configuration is not different from the configuration and operation of the laser ultrasonic transmitting apparatus 10B shown in FIG. 9, the same components are denoted by the same reference numerals and description thereof is omitted.

(Second embodiment)
As a second example of the third embodiment, there is a laser ultrasonic transmitting apparatus 10B ₂ shown in FIG. 11.

The laser ultrasonic transmission device 10B ₂ has a nozzle port sealing means 46 provided with the elastic sealing member in the chamber box 41 that is formed on the (outlet) side of the fluid jetting nozzle 40 is provided, the object to be measured by the sealing means 46 The space containing 11 is configured in a sealed structure.

  In this case, the DUT 11 is covered with the chamber box 41 in an airtight (or liquid-tight) manner, and the staying chamber 44A in the chamber box 41 is configured in an airtight manner. With the airtight residence chamber 44A, the antioxidant fluid F can be retained more efficiently without supplying a large amount of the antioxidant fluid F into the residence chamber 44A, and the laser on the surface of the object to be measured 11 can be retained. Oxidation can be effectively prevented with a small amount of the antioxidant fluid F at and around the light irradiation point.

  In the second embodiment, the measurement object 11 is stored in the chamber box 41 of the fluid ejection nozzle 40. However, when the surface of the measurement object is large, the fluid ejection nozzle 40 is measured. It is good also as an airtight structure mounted on the thing 11 in airtight (or liquid-tight).

[Fourth Embodiment]
FIG. 12 is a block diagram showing a fourth embodiment of the laser ultrasonic wave transmitting apparatus according to the present invention.

  A laser ultrasonic transmission apparatus 10C shown in this embodiment includes a fluid jet nozzle 50 having a double cylinder structure, and is configured to forcibly circulate the antioxidant fluid F in the irradiation region of the measurement object 11. However, unlike the laser ultrasonic transmission apparatus 10A shown in the second embodiment, other configurations are not substantially different, and thus the same components are denoted by the same reference numerals and detailed description thereof is omitted.

  The fluid ejection nozzle 50 is concentrically arranged so that the outer cylinder 51 and the inner cylinder 52 have a common axis, and is configured in a multiple cylinder structure, for example, a double cylinder structure. A laser irradiation optical system is provided in the inner cylinder 52. 27 is accommodated. The laser irradiation optical system 27 is held in the inner cylinder 52 through fixing means such as a crossbar-shaped support bridge 35. The fluid ejection nozzle 50 forms a triple cylinder structure including the cylindrical lens holder 28 of the laser irradiation optical system 27.

  The inner cylinder 52 of the fluid ejection nozzle 50 passes through the top of the outer cylinder 51 and protrudes upward in FIG. 12, and a fluid recovery pipe 53 is connected to the protrusion. The other end of the fluid recovery pipe 53 is connected to the fluid recovery device 15.

  On the other hand, a fluid transmission hose (liquid supply pipe) 37 connected to the pressurized fluid source 18 is connected to the outer cylinder 51 of the fluid ejection nozzle 50. Antioxidant fluid supplied from the fluid source 18 through the fluid transmission hose 37 to the fluid ejection nozzle 50 passes through an annular or sleeve-like outer fluid flow path 54 between the outer cylinder 51 and the inner cylinder 52, and the outer nozzle port 55. The antioxidant fluid F thus blown off is changed in the flow direction on the surface of the object to be measured 11 and reversed and sucked into the inner nozzle port 56. . The fluid sucked into the inner nozzle port 56 rises through an annular or sleeve-like inner fluid channel 57 between the inner cylinder 52 and the cylindrical lens holder 28, and the fluid recovery pipe 53 from the top of the inner fluid channel 57. Then, it is sucked into the fluid recovery device 15 and forcibly recovered.

  Further, the optical axis of the transmission laser beam GL that is focused and irradiated from the laser irradiation optical system 27 toward the surface of the object to be measured 11 has a common axis with the nozzle ports 55 and 56 of the fluid jet port 50. Concentric.

  Further, the fluid ejection nozzle 50 may be configured such that the air outlet side and the air inlet side of the nozzle ports 55 and 56 are reversed, and the air jet nozzle 50 blows out from the inner nozzle port 56 and sucks in from the outer nozzle port 55.

  Next, the operation of the laser ultrasonic transmitter 10C will be described.

  When the laser ultrasonic transmission device 10 </ b> C drives the transmission laser light source 12, the transmission laser light GL is oscillated from the transmission laser light source 12. The transmission laser light GL output from the transmission laser light source 12 is guided to the laser irradiation optical system 27 via the optical fiber incident optical system 30 and the optical fiber 25, and an appropriate condensing condition is obtained by the laser irradiation optical system 27. Then, the light is focused on the surface of the object 11 to be measured.

  On the other hand, the laser irradiation optical system 27 is accommodated in the inner cylinder 52 of the fluid ejection nozzle 50. An antioxidant fluid F is guided from the pressurized fluid source 18 through the fluid transmission pipe 37 into the outer cylinder 51 of the fluid ejection nozzle 50, and the fluid F is interposed between the outer cylinder 51 and the inner cylinder 52. It blows out from the annular outer fluid flow path 54 through the outer nozzle port 55. The blown antioxidant fluid F is reversed by changing the flow path on the surface of the object to be measured 11 and sucked from the inner nozzle port 56.

  At that time, the outer fluid channel 54 and the inner fluid channel 57 formed in the inner cylinder 52 are concentrically formed independently of each other, and pass through the outer (outer ring) fluid channel 54 of the object to be measured 11. It is blown out at and near the irradiation point of the transmission laser beam GL. On the other hand, the inner fluid flow path 57 is connected to the fluid recovery device 15 via the fluid recovery pipe 53, and the fluid F sprayed to the irradiation point of the transmission laser light GL and its vicinity by the suction force of the fluid recovery function. Is sucked into the inner fluid flow path 57 and recovered by the fluid recovery device 15.

  A structure in which the antioxidant fluid F is blown out and sucked in by the outer fluid channel 54 and the inner fluid channel 57, and a structure in which the antioxidant fluid F is blown out to the irradiation point region of the transmission laser light GL, Then, the antioxidant fluid F can be blown out near the irradiation point.

  The structure is suitable when it is not desired to release the antioxidant fluid F to the surrounding environment.

  Further, an ablation phenomenon is caused on the surface layer of the measurement object 11 due to the irradiation of the transmission laser light GL at the vicinity of the irradiation point of the transmission laser light GL irradiated from the laser irradiation optical system 27 and the vicinity thereof. The ultrasonic wave US can be generated radially from the irradiation point as a point and transmitted to the inside of the object to be measured 11.

  If the laser ultrasonic transmission apparatus 10C is configured as described above, laser ultrasonic transmission is performed in an ablation mode that has a very small influence on the material of the object to be measured 11 while maintaining the feature of non-contact by remote operation. be able to.

  Further, the laser ultrasonic transmission device 10C has a double flow path structure of an outer (outer ring) fluid flow path 54 and an inner fluid flow path 57 in the fluid ejection nozzle 50, and one is used for the forward path and the other for the return path. showed that. You may use a double flow path structure as two ejection flow paths with a flow velocity difference. In this way, the slow fluid flow ejected from the inside is confined by the fast fluid flow on the outside, and it becomes possible to more effectively prevent oxidation near the irradiation point of the transmission laser light GL and the vicinity thereof.

[Fifth Embodiment]
FIG. 13 is a configuration diagram for explaining a fifth embodiment of the laser ultrasonic wave transmitting apparatus according to the present invention.

  The laser ultrasonic transmission apparatus shown in this embodiment includes a control device 61 that controls and drives the fluid control means 60 based on the oscillation timing of the transmission laser light source 12, and other configurations and operations are the first embodiment. Since it is not different from the laser ultrasonic transmission apparatus 10 described in the embodiment, the same components are denoted by the same reference numerals and description thereof is omitted.

  The laser ultrasonic transmission device 10D shown in FIG. 13 is covered with an antioxidant fluid F ejected from the fluid source 18 of the fluid ejection device 14 to prevent oxidation at the irradiation point and in the vicinity thereof.

  The transmission laser light GL is oscillated and output by the transmission laser light source 12, is appropriately focused under a focusing condition via the laser irradiation optical system 13, is irradiated on the surface of the object to be measured 11, and is scanned. The irradiated laser beam GL causes an ablation phenomenon on the surface of the object to be measured 11, and laser ultrasonic transmission in an ablation mode having a very small influence on the material of the object to be measured 11 can be performed.

  The laser ultrasonic transmission device 10D shown in the fifth embodiment includes a fluid control means 60 for controlling the flow of the antioxidant fluid to the fluid transmission hose 37, for example, a flow control valve, an electromagnetic, etc. A valve is provided, and the operation of the fluid control means 60 is controlled by the control device 61 based on the transmission timing signal of the transmission laser light GL output from the transmission laser light source 12.

  Specifically, when the transmission laser light GL oscillates in a pulse form from the transmission laser light source 12, the transmission laser light is synchronized with the timing at which the ablation phenomenon occurs on the measurement object 11 due to the irradiation of the transmission laser light GL. The flow of the antioxidant fluid F is ON / OFF controlled or adjusted by the fluid control means 60 so that the antioxidant fluid is blown out to the irradiation point area of the GL, so that the antioxidant fluid F can be used efficiently and effectively. It is something that can be done.

[Sixth Embodiment]
FIG. 14 is a block diagram for explaining a sixth embodiment of the laser ultrasonic transmitting apparatus according to the present invention.

  The laser ultrasonic transmission device 10E shown in this embodiment shows a usage example in which a laser ultrasonic transmission function and a laser ultrasonic reception function are combined, and includes a laser ultrasonic reception device 63. Other configurations and operations are not substantially different from those of the laser ultrasonic transmission apparatus 10D shown in the fifth embodiment, and therefore the same components are denoted by the same reference numerals and description thereof is omitted.

  The laser ultrasonic transmission apparatus 10E shown in the sixth embodiment is provided with a laser ultrasonic reception apparatus 63, and both apparatuses 10E and 63 are used in combination.

  The laser ultrasonic wave receiving device 63 has a reception laser light source 64 that works in conjunction with the transmission laser light source 12, and the received laser light DL oscillated from the reception laser light source 64 and outputted via the reception irradiation optical system 65. The object lens 66 is appropriately condensed and irradiated on the surface of the object to be measured 11. The reflected / scattered component of the received laser beam DL irradiated on the surface of the object to be measured 11 is condensed by causing the objective lens 66 to function as a condenser lens. The collected reflected / scattered component is input to an optical interferometer 68 by a beam splitter 67 such as a half mirror, and the ultrasonic interferometer 68 receives and detects the ultrasonic signal component.

  On the other hand, the transmission laser beam GL output from the transmission laser light source 12 is focused and irradiated on the surface of the object to be measured 11 via the laser irradiation optical system 13, and an ablation phenomenon occurs near the surface layer of the object to be measured 11. Cause it to occur. By utilizing the ablation phenomenon due to the irradiation effect of the transmission laser beam GL, the ultrasonic wave US is generated inside the measured object 11, and the generated ultrasonic signal is transmitted through the measured object 11.

  The laser ultrasonic wave transmitting device 10E is used in combination with the laser ultrasonic wave receiving device 63, so that the object to be measured is caused by the ablation phenomenon caused by the transmission laser light GL irradiated from the laser irradiation optical system 13 to the surface of the object 11 to be measured. The ultrasonic waves generated in 11 are transmitted radially in the object to be measured 11. The transmitted ultrasonic wave affects the reflected / scattered component of the received laser beam DL emitted from the received irradiation optical system 65, condenses the reflected / scattered component of the received laser beam DL, and converts the reflected / scattered component into the reflected / scattered component. It is detected by measuring with an optical interferometer 68.

  By using the laser ultrasonic transmission device 10E shown in the sixth embodiment in combination with the laser ultrasonic receiving device 63 provided together, the influence on the material of the object to be measured 11 in a non-contact manner by a complete remote operation. The laser ultrasonic wave transmission / reception can be performed by the ablation mode having a small value. By analyzing the propagation state of the ultrasonic wave generated by the ablation phenomenon inside the object to be measured 11 by laser ultrasonic transmission / reception, the surface defect of the material to be measured 11 is not contacted by remote operation such as a surface crack or nest. Can be non-damaged.

BRIEF DESCRIPTION OF THE DRAWINGS The block diagram explaining 1st Embodiment of the laser ultrasonic transmitter which concerns on this invention. The figure which shows an example of the irradiation area | region of the to-be-measured object irradiated with a laser beam. The figure which shows an example of the to-be-measured object surface roughness change at the time of laser irradiation. The figure which shows an example of the metal structure phase change of the to-be-measured object surface at the time of laser irradiation. The figure which shows an example of the depth distribution change of the to-be-measured object hardness at the time of laser irradiation. The figure which shows an example of the depth distribution change of a to-be-measured object composition at the time of irradiating a laser with the said laser ultrasonic transmitter, comparing an irradiation area | region and an unirradiated area | region. The block diagram which shows 2nd Embodiment of the laser ultrasonic wave transmitter which concerns on this invention. FIG. 8 is a plan sectional view taken along line VIII-VIII in FIG. 7. The block diagram which shows 3rd Embodiment of the laser ultrasonic transmission apparatus in connection with this invention. The block diagram which shows the 1st Example of 3rd Embodiment of the laser ultrasonic transmitter which concerns on this invention. The block diagram which shows the 2nd Example of 3rd Embodiment of the laser ultrasonic transmitter which concerns on this invention. The block diagram which shows 4th Embodiment of the laser ultrasonic transmitter which concerns on this invention. The block diagram which shows 5th Embodiment of the laser ultrasonic wave transmitter which concerns on this invention. The block diagram which shows 6th Embodiment of the laser ultrasonic wave transmitter which concerns on this invention. The figure which shows the conventional laser ultrasonic transmitter.

Explanation of symbols

10, 10A, 10B, 10B ₁ , 10B ₂ , 10C, 10D, 10E Laser ultrasonic transmitter 11 Object to be measured (inspection object)
12 Transmitting laser light source (pulse laser light source)
13 Laser irradiation optical system (for transmission laser)
14 Fluid ejection device 15 Fluid recovery device 17 Objective lens 18 Fluid source 19 Fluid supply pipe (hose, duct)
20 Fluid jet nozzle (Blowout duct)
21 Filtration device 23 Irradiation area 24 Non-irradiation area 25 Optical fiber 27 Laser irradiation optical system 28 Cylindrical lens holder 29 Lens optical system 30 Optical fiber incidence optical system 33 Fluid ejection nozzle 34 Cylindrical body 35 Support bridge 37 Fluid transmission hose ( Fluid supply pipe)
38 Fluid ejection device 39 Nozzle port 40 Fluid ejection nozzle 41, 41A Chamber box 44, 44A Residence chamber 50 Fluid ejection nozzle 51 Outer cylinder 52 Inner cylinder 53 Fluid recovery pipe 54 Outer fluid channel 55 Outer nozzle port 56 Inner nozzle port 57 Inside Fluid flow path 60 Fluid control means 61 Controller 63 Laser ultrasonic wave receiver 64 Reception laser light source 65 Reception optical system for reception (for reception laser)
66 Objective lens (Condenser lens)
67 Beam splitter 68 Optical interferometer

Claims (13)

In a laser ultrasonic transmission method for generating an ultrasonic signal in a measurement object using an ablation phenomenon generated by irradiation of a laser beam on the measurement object surface,
A laser ultrasonic transmission method, wherein the laser beam is irradiated to the position where the ablation occurs on the surface of the object to be measured and the vicinity thereof, and an anti-oxidation fluid which is inactive against surface oxidation is flowed. 2. The laser ultrasonic transmission method according to claim 1, wherein the antioxidant fluid is any one of an inert gas such as helium gas, neon gas, and argon gas, nitrogen gas, or a mixed gas of these gases. A transmission laser light source for outputting a transmission laser beam irradiated on the surface of the object to be measured;
Laser irradiation that irradiates the surface of the object to be measured with a desired condensing condition from the transmission laser light source, and generates an ultrasonic wave in the object to be measured by an ablation phenomenon to transmit an ultrasonic signal. Optical system,
The irradiation position of the transmission laser beam irradiated to the surface of the object to be measured by the irradiation optical system and its vicinity are composed of a fluid ejection device for flowing an antioxidant fluid that is inactive against surface oxidation. Laser ultrasonic transmitter. The fluid ejection device includes a fluid source for holding an antioxidant fluid;
Fluid transmission means for transmitting an antioxidant fluid flowing out of the fluid source;
4. The laser ultrasonic transmission device according to claim 3, further comprising fluid ejection means for ejecting the antioxidant fluid transmitted by the fluid transmission means to and near the irradiation position of the transmission laser light. 5. The laser ultrasonic transmission device according to claim 4, wherein the fluid ejecting device includes a filtering unit that removes at least one of fine particles that can be a scatterer and a substance that contributes to oxidation during propagation of the transmission laser light. The fluid ejection device includes a hollow fluid ejection nozzle having at least a part of the transmission path of the transmission laser light and the laser irradiation optical system, and ejecting an antioxidant fluid substantially in the same direction as the irradiation direction of the transmission laser light. The laser ultrasonic transmitter according to claim 3, further comprising: 7. The laser superstructure according to claim 6, wherein the fluid ejection nozzle has a fluid retention structure that retains the antioxidant fluid at and near the irradiation position of the transmission laser beam at the tip in the flow direction of the antioxidant fluid. Sonic transmitter. The laser ultrasonic transmission apparatus according to claim 7, wherein the fluid retention structure is formed in an asymmetric shape with respect to an optical axis of the transmission laser light. The laser ultrasonic transmission apparatus according to claim 7, wherein the fluid retention structure has a sealed structure that forms a space that encloses the object to be measured. 10. The laser ultrasonic transmission device according to claim 3, further comprising fluid recovery means for recovering the antioxidant fluid ejected at and near the irradiation position of the transmission laser light. 7. The laser super-jet according to claim 6, wherein the fluid ejection nozzle has a double fluid flow path structure in which one is connected to the fluid source and the other is connected to a fluid recovery means for recovering the fluid. Sonic transmitter. 7. The laser ultrasonic transmission device according to claim 6, wherein the fluid ejection nozzle has a double channel structure for ejecting the antioxidant fluid flowing out from the fluid source with a flow velocity difference. The fluid control means for controlling the outflow of the fluid from the fluid source, and the control device for controlling the operation of the fluid control means based on the oscillation timing of the transmission laser light. The laser ultrasonic transmitter according to any one of the above.

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