JP2010038880A - Device and method for laser ultrasonography - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser ultrasonic technique in which a cheaper image pickup device of high-frequency response is available, or the one which can detect any optical intensity variation from a large level to small level even by using such a cheaper image pickup device with low resolution. <P>SOLUTION: The device for laser ultrasonography includes a laser light source 2, a laser light branching mechanism 3 for branching laser beam into irradiation laser light Ii and laser light for reference Ir, a laser irradiation mechanism 30 for irradiating an inspecting object surface 1 with the irradiation laser light, a laser focusing mechanism 31 for collecting irradiation laser light reflected on the inspecting object surface 1, a photorefractive crystal 6 which receives both the irradiation laser light and the laser light for reference to measure interference, a wavelength conversion mechanism 14 for converting wavelength of the laser beam interfered by the photorefractive crystal 6, and a light-receiving mechanism 13 for receiving the laser beam with wavelength converted. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a laser ultrasonic inspection apparatus and a laser ultrasonic inspection method for irradiating a surface to be inspected with a laser beam and inspecting a defect on the surface to be inspected nondestructively.

  Ultrasonic flaw detection is an example of a non-destructive inspection method. Ultrasonic flaw detection is widely used in various fields because it can detect material characteristics and deterioration. Examples of means for performing ultrasonic flaw detection include a method using a piezoelectric element, a method using an electromagnetic, and a laser. When inspecting a certain object using these methods, in many cases, it is often required not to measure only one point, but to inspect widely over a certain region or the entire surface of the object. For this reason, in general, a method of scanning one sensor or an array of sensors to deal with a wide range of inspections.

  In recent years, a two-dimensional measurement method using a laser beam has been proposed as an ultrasonic detection method in which such a method is further advanced. As an example of a two-dimensional measurement method using laser light, a measurement method using speckle is known (Patent Document 1). This is due to the propagation of ultrasonic waves by measuring speckles that occur when the target is irradiated with laser light, measuring the speckles again when ultrasonic waves are generated, and taking the difference between the two speckles. This is a technique that enables measurement of changes in speckle, that is, the influence of physical properties, deterioration, etc., on an ultrasonic wave.

Also, a two-dimensional interference measurement method using laser light using a photorefractive effect has been proposed (Patent Document 2). As shown in FIG. 11, the laser light emitted from the laser light source 2 is branched into the irradiation laser light Ii and the reference laser light Ir by the laser light branching mechanism 3, and the irradiation laser light Ii is emitted from the inspection object 1. Laser light Is reflected on the surface and containing an ultrasonic component and two laser lights obtained by modulating the reference laser light Ir by the phase modulator 4 are incident on the photorefractive crystal 6. As a result, a diffraction grating is formed inside the photorefractive crystal 6, thereby performing interference measurement. The laser light I after the interference can be measured by the light receiving mechanism 13 while maintaining the two-dimensional shape image irradiated on the surface of the inspection object 1. In this way, the distribution state of the two-dimensional ultrasonic signal can be measured.
JP 2004-101189 A US Patent No. 6,175,411

  Since the technique proposed in the above-mentioned Patent Document 1 needs to use data before exciting ultrasonic waves, there is a problem that inspection cannot be performed by one ultrasonic transmission. On the other hand, the method disclosed in Patent Document 2 is a method of detecting an ultrasonic signal itself as in a general ultrasonic inspection.

  In the measurement apparatus shown in FIG. 11, a photorefractive crystal that enables interference measurement to detect an ultrasonic signal is a BSO (Bismuth Silicon Oxide) crystal. This crystal is characterized in that it can operate with respect to visible light. Therefore, it is possible to measure the interference signal with an inexpensive CCD (Charge Coupled Device) camera. However, the BSO crystal has a problem that the response time for forming a diffraction grating in the photorefractive element is slow because of interference. This limits the frequency of ultrasonic signals that can be measured when performing interference measurement.

  For this purpose, the phase modulator 4 in FIG. 11 modulates the phase of the reference laser beam Ir so that the difference frequency from the modulation by the ultrasonic signal that is actually desired to be measured is reduced. Sound wave measurement is possible. However, many phase modulators are expensive, may be damaged by laser light, and require that the frequency of the ultrasonic signal to be measured needs to be determined to some extent in advance.

  Further, since the BSO crystal is an optically active crystal, there is a feature that the polarized light is rotated when the laser beam is transmitted through the crystal. Therefore, it is necessary to adjust the polarization state in order to efficiently generate the photorefractive effect in the BSO crystal. Therefore, the arrangement of optical elements increases, the apparatus becomes complicated, and an optical loss occurs, leading to a decrease in detection sensitivity.

  Despite these problems, the BSO crystal is used for the following reason. That is, other photorefractive crystals with a fast time constant include InP, GaAs, and quantum well semiconductors, all of which have a photorefractive effect for near infrared wavelengths and are difficult to use with visible light. Because. Invisibility makes it difficult to adjust the optical system and causes problems for the detector. Many general-purpose CCD cameras and C-MOS (Complementary Metal Oxide Semiconductor) cameras are designed so that visible light can be detected efficiently, and the detection performance of CCD cameras deteriorates for near-infrared wavelengths. To do. In addition, the near-infrared CCD camera not only has poor performance, but is also expensive and disadvantageous compared to a visible light CCD camera.

  Accordingly, a first object of the present invention is to provide a laser ultrasonic inspection method having a high frequency response and capable of using a visible light CCD or the like.

  On the other hand, CCD cameras and C-MOS cameras are promising candidates for the light receiving mechanism, but they have a problem of dynamic range. CCD and C-MOS have high pixel resolution and can record signals in real time with hundreds of thousands to millions of photodetectors, but the dynamic range for light intensity is a general photodiode. There is a problem that it is worse than when using. Further, when an optical signal is converted into an electrical signal and then output as a digital signal, many CCDs are converted with an 8-bit resolution, that is, with a light resolution of 256 gradations relative to full scale. Therefore, it is difficult to detect from dark light to bright light at once.

  This causes a problem in the inspection method as shown in FIG. Assuming that the inspection object 1 is viewed from above, when the ultrasonic wave is excited at the ultrasonic wave excitation point G, the generated ultrasonic wave propagates concentrically. In this case, the ultrasonic amplitude is the largest in the vicinity of the ultrasonic excitation point G, and as the propagation proceeds, the attenuation of the distance and the scattering / attenuation due to the material characteristics occur, so the ultrasonic amplitude becomes smaller. That is, the light intensity change becomes smaller. Therefore, the dynamic range of the detected light intensity is greatly different between the vicinity of the ultrasonic excitation point G and a distant place. Therefore, if the sensitivity of the CCD is adjusted to detect the light intensity change in the vicinity of the ultrasonic excitation point, the light intensity change at a location far from the ultrasonic excitation point has a low CCD resolution, so the detection resolution of the light intensity change is low. There is a problem of lowering.

  Therefore, a second problem of the present invention is to provide a laser ultrasonic inspection method capable of detecting from a large light intensity change to a small light intensity change even in a CCD having a low resolution.

  The present invention solves the first or second problem, and an object of the present invention is to provide a laser ultrasonic inspection method capable of using an image pickup device such as a CCD having a high frequency response and a low cost, or an inexpensive low resolution. It is to provide a laser ultrasonic inspection method capable of detecting from a large light intensity change to a small light intensity change even if an image pickup device such as a CCD is used.

  In order to achieve the above object, one aspect of a laser ultrasonic inspection apparatus according to the present invention includes a laser light source that generates a laser beam, a laser beam emitted from the laser light source, a laser beam that is irradiated, and a reference laser beam. A laser beam splitting unit that splits the target laser beam, a laser irradiation unit that irradiates the surface to be inspected with the irradiation laser light, a laser condensing unit that condenses the irradiation laser light reflected by the surface to be inspected, and the laser collector A photorefractive crystal for receiving interference laser light passing through the optical means and the reference laser light and performing interference measurement; and wavelength converting means for converting the wavelength of the laser light subjected to interference by the photorefractive crystal; And a light receiving means for receiving the laser light whose wavelength is converted by the wavelength converting means.

  Another aspect of the laser ultrasonic inspection apparatus according to the present invention is a laser light source that generates laser light, and a laser that splits the laser light generated by the laser light source into irradiation laser light and reference laser light. A light branching means, a laser irradiation means for irradiating the surface to be inspected with the irradiation laser light, a laser condensing means for condensing the irradiation laser light reflected by the surface to be inspected, and a laser condensing means. A photorefractive crystal for performing interference measurement by receiving the irradiated laser beam and the reference laser beam, profile control means for changing a profile of the laser beam that has received interference by the photorefractive crystal, and the profile control And a light receiving means for receiving the laser light whose profile has been changed by the means.

  In one aspect of the laser ultrasonic inspection method according to the present invention, a laser beam is generated, the laser beam is branched into an irradiation laser beam and a reference laser beam, and the irradiation laser beam is applied to a surface to be inspected. Irradiating and reflecting, condensing the irradiation laser light reflected by the surface to be inspected, receiving the collected irradiation laser light and the reference laser light with a photorefractive crystal, and performing interference measurement, Converting the wavelength of the laser beam that has received interference by the photorefractive crystal, and receiving the laser beam having the converted wavelength.

  In another aspect of the laser ultrasonic inspection method according to the present invention, a laser beam is generated, the laser beam is branched into an irradiation laser beam and a reference laser beam, and the irradiation laser beam is inspected. Irradiate the surface and reflect it, condense the irradiated laser beam reflected by the surface to be inspected, and receive the collected irradiated laser beam and the reference laser beam with a photorefractive crystal to measure interference And changing the profile of the laser beam that has been interfered with by the photorefractive crystal, and receiving the laser beam having the changed profile.

  According to the present invention, a laser ultrasonic inspection method that can use an inexpensive image pickup device such as a CCD with a high frequency response, or an inexpensive image pickup device such as a low-resolution CCD can use a small light intensity change. A laser ultrasonic inspection method capable of detecting even a change in light intensity can be provided.

  Hereinafter, embodiments of a laser ultrasonic inspection apparatus according to the present invention will be described with reference to FIGS. Here, the same or similar parts are denoted by common reference numerals, and redundant description is omitted.

(First embodiment)
A first embodiment of a laser ultrasonic inspection apparatus according to the present invention will be described with reference to FIG. Here, FIG. 1 is a longitudinal sectional view schematically showing the laser ultrasonic inspection apparatus of the first embodiment.

  The laser ultrasonic inspection apparatus of the first embodiment includes a laser light source 2, a laser beam branching mechanism 3, a laser irradiation mechanism 30, a laser condensing mechanism 31, a polarizer 11, a photorefractive crystal 6, and a wavelength. A conversion element 14 and a light receiving mechanism 13 are included.

  The laser light source 2 is for irradiating the surface of the inspection object 1 with the laser light Ii, and emits laser light in the near infrared region having a wavelength of 1064 nm, for example. In addition, the wavelength of other laser light having a wavelength operable with respect to the photorefractive crystal 6 is also conceivable. The laser light source 2 can use not only continuous light but also pulsed laser light having a high peak power.

  The laser light emitted from the laser light source 2 enters the laser light branching mechanism 3 and is branched into the irradiation laser light Ii and the reference laser light Ir.

  The irradiated laser beam Ii branched by the laser beam splitting mechanism 3 is changed to an arbitrary shape by the laser irradiation mechanism 30 so that the two-dimensional region to be observed is irradiated with the laser beam, and is irradiated on the surface of the inspection object 1. Is done. The laser irradiation mechanism 30 includes, for example, an optical lens 7 and a reflecting mirror 8.

  When the irradiation laser beam Ii is irradiated onto the surface of the object 1 to be inspected, the irradiation laser beam Ii is affected by the ultrasonic vibration of the surface, and is reflected as the irradiation laser beam Is including the ultrasonic component. The irradiation laser light Is including the ultrasonic component is condensed by the laser condensing mechanism 31. The laser condensing mechanism 31 includes, for example, optical lenses 9 and 10. The laser condensing mechanism 31 can use an imaging fiber or the like (not shown) that can transfer an image using a fiber in addition to a mechanism that combines lenses.

  The irradiated laser light Is emitted from the laser condensing mechanism 31 passes through the polarizer 11 and is incident on the photorefractive crystal 6. On the other hand, the reference laser beam Ir branched by the laser beam branching mechanism 3 is incident on the photorefractive crystal 6 as it is. The photorefractive crystal 6 causes the irradiation laser beam Is containing the ultrasonic component to interfere with the laser beam Ir. That is, when the laser beam Ir and the laser beam Is are irradiated onto the photorefractive crystal 4, a diffraction grating is formed inside the photorefractive crystal by the two laser beams. By this diffraction grating, Is that is affected by the ultrasonic vibration receives interference, and becomes the laser beam I that is affected by the interference.

  Crystals that can be used as the photorefractive crystal 6 include GaAs, GaP, InP-based (for example, InP: Fe), CdTe-based (for example, CdTe: V), and elements having a quantum well structure (for example, AlGaAs / GaAs). .

  The laser beam I that has received interference by the photorefractive crystal 6 passes through the wavelength conversion element 14 and is converted into a laser beam Iw having a wavelength that provides the optimum sensitivity of the light receiving mechanism 13. The wavelength conversion element 14 is preferably an element that can be converted into a laser beam having a visible light wavelength, such as a BiBO crystal, a BBO crystal, a KTP crystal, an LBO crystal, or a LiNbO crystal. Other crystals are also conceivable.

  The laser beam Iw wavelength-converted by the wavelength conversion element 14 is received by the light receiving mechanism 13. The light receiving mechanism 13 is a CCD camera, a C-MOS camera, a photodiode array, another mechanism that can measure light two-dimensionally, or a mechanism that can measure light one-dimensionally, such as a linear array sensor. Since the laser beam Iw has a spatial profile, the light receiving mechanism 13 measures the state of the ultrasonic wave on the surface of the object 1 to be inspected one-dimensionally or two-dimensionally instead of general point measurement. Is possible.

  Next, effects of the embodiment described above will be described.

  In general, when a crystal that operates with visible light, such as a BSO crystal, is used as a photorefractive element, adjustment of an optical system is easy because laser light can be visually confirmed. In addition, when a CCD camera or C-MOS camera is used for the light receiving mechanism 13 that can be used, since these devices are often assumed to be used under visible light, they have functions optimized for visible light. From the standpoints of various functions and costs, CCDs and C-MOS cameras that operate with visible light are excellent, and thus crystals that operate with visible light are suitable.

  On the other hand, the BSO crystal operating with visible light has a problem that the response speed for forming the diffraction grating is slow. Therefore, since the time for forming the diffraction grating is delayed, it is not suitable for measuring ultrasonic waves having a high frequency. Further, the optical activity of the BSO crystal changes the polarization of the laser light propagating inside the crystal. This complicates the arrangement of the optical elements.

  On the other hand, GaAs crystals, InP crystals, CdTe crystals, etc., which can be operated mainly with laser light having a wavelength of 900 nm to 1500 nm, have a faster response speed and no optical activity. Measurement of ultrasonic waves having a high frequency is facilitated, and the arrangement of optical elements can be simplified.

  Therefore, a laser light source having a near-infrared wavelength (900 nm to 1500 nm) capable of operating the above crystal is used as the laser light source 2 and a crystal such as a GaAs crystal, an InP crystal, or a CdTe crystal is used. It can be an interferometer having a response speed. Laser light I after interference has a near-infrared wavelength as it is, but by converting this into laser light Iw having a visible light wavelength by a wavelength conversion mechanism, a high-function, high-sensitivity CCD for visible light A camera or a C-MOS camera can be applied. As described above, according to the present embodiment, it is possible to provide a laser ultrasonic inspection method which is a first problem in the present invention and has a high frequency response and can use a visible light CCD.

(Second Embodiment)
A second embodiment of the laser ultrasonic inspection apparatus according to the present invention will be described with reference to FIG. Here, FIG. 2 is a longitudinal sectional view schematically showing the laser ultrasonic inspection apparatus of the second embodiment. This embodiment is a modification of the first embodiment (FIG. 1), and before the reference laser beam Ir branched by the laser beam branching mechanism 3 is incident on the photorefractive crystal 6, the phase modulator 4. Is configured to pass through. Even with this configuration, it is possible to obtain the same operations and effects as in the first embodiment.

(Third embodiment)
A third embodiment of the laser ultrasonic inspection apparatus according to the present invention will be described with reference to FIG. Here, FIG. 3 is a longitudinal sectional view schematically showing a laser ultrasonic inspection apparatus according to the third embodiment.

  The laser ultrasonic inspection apparatus of the third embodiment includes a laser light source 2, a laser beam branching mechanism 3, a laser irradiation mechanism 30, a laser condensing mechanism 31, a polarizer 11, a photorefractive crystal 6, and a wavelength. In addition to having the conversion element 14 and the light receiving mechanism 13, it has an isolator 19, an optical lens 37, and a reflecting mirror 38.

  The laser light emitted from the laser light source 2 is incident on the laser light branching mechanism 3 through the isolator 19 and branched into the irradiation laser light Ii and the reference laser light Ir.

  The irradiated laser beam Ii branched by the laser beam branching mechanism 3 is changed by the laser irradiation mechanism 30 into an arbitrary shape so that the two-dimensional region to be observed is irradiated with the laser beam and irradiated on the surface of the inspection object 1. The In this embodiment, the laser irradiation mechanism 30 includes the optical lens 7, the polarization beam splitter 17, and the quarter wavelength plate 18. The irradiated laser beam Ii branched by the laser beam branching mechanism 3 passes through the optical lens 7, the polarization beam splitter 17, and the ¼ wavelength plate 18 in this order, and is irradiated onto the inspection object 1. In this embodiment, the irradiation laser beam Ii is incident perpendicularly to the surface of the inspection object 1.

  The irradiation laser light irradiated on the surface of the inspection object 1 is affected by the ultrasonic vibration and reflected as irradiation laser light Is including an ultrasonic component. The irradiation laser light Is including the ultrasonic component is incident again on the polarization beam splitter 17 through the quarter-wave plate 18, where the direction is changed, and the light is condensed by the laser condensing mechanism 31. The laser condensing mechanism 31 is composed of, for example, an optical lens.

  The irradiated laser light Is emitted from the laser condensing mechanism 31 passes through the polarizer 11 and is incident on the photorefractive crystal 6. On the other hand, the reference laser beam Ir branched by the laser beam branching mechanism 3 is incident on the photorefractive crystal 6 through the optical lens 37 and the reflecting mirror 38. The photorefractive crystal 6 causes the irradiation laser beam Is containing the ultrasonic component to interfere with the laser beam Ir. As a result, Is that is affected by the ultrasonic vibration receives interference, and becomes the laser light I that is affected by the interference.

  The laser light I passes through the wavelength conversion element 14 and is converted into laser light Iw having a wavelength that provides the optimum sensitivity of the light receiving mechanism 13. The laser beam Iw wavelength-converted by the wavelength conversion element 14 is received by the light receiving mechanism 13.

  According to this embodiment, it is possible to irradiate a laser beam with the object 1 to be inspected facing directly.

(Fourth embodiment)
A fourth embodiment of the laser ultrasonic inspection apparatus according to the present invention will be described with reference to FIG. Here, FIG. 4 is a longitudinal sectional view schematically showing a laser ultrasonic inspection apparatus of the fourth embodiment.

  The fourth embodiment is a modification of the second embodiment (FIG. 2), and has a visible light source 15, and the visible light V emitted from the visible light source 15 is irradiated with laser light Ii by the laser light branching mechanism 3. Is superimposed. It is desirable to use a light source having a wavelength as close as possible to the wavelength of the laser light used in the laser light source 2 as the visible light source 15 because the influence of aberrations and the like received by each optical element is small.

  In the second embodiment, when the laser light source 2 is changed from a laser light having a visible light wavelength to a laser light source having a near infrared wavelength capable of operating the photorefractive crystal 6 having a fast response time, the laser light is In many cases, it cannot be seen with the eyes. Therefore, it is difficult to adjust the position of the optical element used at various places on the surface of the object 1 to be inspected, or to confirm the image obtained by the light receiving mechanism 13. .

  In the fourth embodiment, the visible light V is emitted from the visible light source 15 and adjusted so that the optical path is substantially the same as that of the laser light Ii, so that these problems can be solved. Moreover, it is possible to provide a laser ultrasonic inspection method that has a high frequency response, which is the first problem described above, and that can use a CCD for visible light.

(Fifth embodiment)
A fifth embodiment of the laser ultrasonic inspection apparatus according to the present invention will be described with reference to FIG. Here, FIG. 5 is a longitudinal sectional view schematically showing a laser ultrasonic inspection apparatus of the fifth embodiment.

  The fifth embodiment is a modification of the second embodiment (FIG. 2), in which a profile control mechanism 16 is arranged instead of the wavelength conversion element 14 of the second embodiment. Here, the profile control mechanism 16 can change the profile of the laser beam I, such as an ND (Neutral Density) filter (deceleration filter), a Fourier lens, a diffraction grating, or the like. The laser beam I affected by the interference is changed by the profile control mechanism 16 to the laser beam I ′ after interference whose profile has been shaped.

  The laser beam I measured by interference in the photorefractive crystal 6 has an intensity profile according to the measured ultrasonic profile. Therefore, the profile can be changed by transmitting the laser beam I having a profile to the profile control mechanism 16. For example, when the profile obtained by the ultrasonic signal has a concentric wave shape as shown in FIGS. 7 and 8, if the profile control mechanism 16 is a mechanism having a transmission amount as shown by the solid line 40 in FIG. The profile of the laser beam I can be made as shown in FIG.

  Further, when the Fourier lens is used as the profile control mechanism 16, when the laser beam I has a profile having a regular periodicity, the profile of the laser beam I is obtained as a two-dimensional frequency conversion result corresponding to the spatial frequency. Will be converted.

  In general, for example, in FIG. 8, the dynamic range of the CCD camera must be set to R1, but in this case, the intensity change in the R2 portion must be measured at a low resolution portion, so measurement is performed at a low SN. There is a problem that must be done. On the other hand, according to the present embodiment, the profile of the laser beam I can be changed by the profile control mechanism 16 that can change the amount of transmission of the laser beam as shown in FIG. 10 is converted. Since the profile of the converted laser beam I can be made uniform with only a certain dynamic range R3, the measurement can be performed without causing a decrease in sensitivity depending on the location of the profile.

  Further, when the profile control mechanism 16 is a Fourier lens, a profile change due to a regular ultrasonic waveform outputs a laser beam profile change that is different from the usual when the regularity is broken. Even a slight change can be converted into a large profile change.

  As described above, the present embodiment provides a laser ultrasonic inspection method capable of detecting a large light intensity change to a small light intensity change even in a CCD having a low resolution, which is a second problem in the present invention. It is possible.

(Sixth embodiment)
A sixth embodiment of the laser ultrasonic inspection apparatus according to the present invention will be described with reference to FIG. Here, FIG. 6 is a longitudinal sectional view schematically showing a laser ultrasonic inspection apparatus according to the sixth embodiment.

  The sixth embodiment is a modification of the first embodiment (FIG. 1) or a modification of the fifth embodiment (FIG. 5), and between the wavelength conversion element 14 and the light receiving mechanism 13 of the first embodiment. In this configuration, the same profile control mechanism 16 as in the fifth embodiment is inserted. It can also be said that the phase modulator 4 is omitted from the configuration of the fifth embodiment. With this configuration, it is possible to obtain the same operations and effects as in the fifth embodiment.

(Other embodiments)
Each embodiment described above is merely an example, and the present invention is not limited thereto.

  For example, as a modification of the sixth embodiment, the profile control mechanism 16 can be disposed in front of the wavelength conversion element 14.

  Further, the photorefractive crystal 6 of the third or fourth embodiment is replaced with a profile control mechanism 16, or the profile control mechanism 16 is added in front of or behind the photorefractive crystal 6 of the third or fourth embodiment. It is also possible to combine the features of the embodiments in various ways.

1 is a longitudinal sectional view schematically showing a first embodiment of a laser ultrasonic inspection apparatus according to the present invention. The longitudinal cross-sectional view which shows typically 2nd Embodiment of the laser ultrasonic inspection apparatus which concerns on this invention. The longitudinal cross-sectional view which shows typically 3rd Embodiment of the laser ultrasonic inspection apparatus which concerns on this invention. The longitudinal cross-sectional view which shows typically 4th Embodiment of the laser ultrasonic inspection apparatus which concerns on this invention. The longitudinal cross-sectional view which shows typically 5th Embodiment of the laser ultrasonic inspection apparatus which concerns on this invention. The longitudinal cross-sectional view which shows typically 6th Embodiment of the laser ultrasonic inspection apparatus which concerns on this invention. It is a figure for demonstrating the effect of 5th Embodiment of the laser ultrasonic inspection apparatus which concerns on this invention, Comprising: The graph which shows the two-dimensional distribution of the intensity | strength of an ultrasonic signal as distribution of brightness. The graph which shows the profile of the intensity distribution along the VIII-VIII line of FIG. The graph which shows the transmission amount characteristic of the profile control apparatus in 5th Embodiment of the laser ultrasonic inspection apparatus which concerns on this invention. The graph which shows the profile of intensity distribution after transmitting the signal shown in FIG. 8 to the profile control apparatus which has the characteristic of FIG. 9 in 5th Embodiment of the laser ultrasonic inspection apparatus which concerns on this invention. The longitudinal cross-sectional view which shows an example of the conventional laser ultrasonic inspection apparatus typically.

Explanation of symbols

1: Object to be inspected 2: Laser light source 3: Laser beam branching mechanism 4: Phase modulator 5: Polarizer 6: Photorefractive crystal 7: Optical lens 8: Reflector 9: Optical lens 10: Optical lenses 11 and 12: Polarizer 13: Light receiving mechanism 14: Wavelength converting element 15: Visible light source 16: Profile control mechanism 17: Polarizing beam splitter 18: 1/4 wavelength plate 19: Isolator 30: Laser irradiation mechanism 31: Laser condensing mechanism 37: Optical lens 38: Reflector

Claims (13)

A laser light source for generating laser light;
A laser beam branching means for branching the laser beam generated by the laser light source into an irradiation laser beam and a reference laser beam;
Laser irradiation means for irradiating the surface to be inspected with the irradiation laser light; and
Laser condensing means for condensing the irradiation laser light reflected by the surface to be inspected;
A photorefractive crystal for performing interference measurement by receiving the irradiation laser light and the reference laser light that have passed through the laser focusing means;
Wavelength converting means for converting the wavelength of the laser light that has received interference in the photorefractive crystal;
A light receiving means for receiving the laser light whose wavelength has been converted by the wavelength converting means;
A laser ultrasonic inspection apparatus characterized by comprising:   The laser beam generated by the laser light source is a near-infrared wavelength laser beam, and the wavelength converting means converts the laser beam having a wavelength in the infrared region into a laser beam having a wavelength in the visible light region. The laser ultrasonic inspection apparatus according to claim 1.     3. The laser ultrasonic inspection according to claim 1, further comprising profile control means for changing a profile of laser light before being incident on the light receiving means due to interference by the photorefractive crystal. 4. apparatus. A laser light source for generating laser light;
A laser beam branching means for branching the laser beam generated by the laser light source into an irradiation laser beam and a reference laser beam;
Laser irradiation means for irradiating the surface to be inspected with the irradiation laser light; and
Laser condensing means for condensing the irradiation laser light reflected by the surface to be inspected;
A photorefractive crystal for performing interference measurement by receiving the irradiation laser light and the reference laser light that have passed through the laser focusing means;
Profile control means for changing the profile of the laser beam that has received interference in the photorefractive crystal;
A light receiving means for receiving laser light whose profile has been changed by the profile control means;
A laser ultrasonic inspection apparatus characterized by comprising:   The laser ultrasonic inspection apparatus according to claim 3 or 4, wherein the profile control means includes an ND filter.   The laser ultrasonic inspection apparatus according to claim 3 or 4, wherein the profile control means includes a Fourier lens.   7. The laser ultrasonic inspection apparatus according to claim 1, wherein the laser light source is a pulse laser light source.   8. The method according to claim 1, further comprising phase modulation means for performing phase modulation on the irradiated laser light branched by the laser light branching means and causing the photorefractive crystal to receive light. Laser ultrasonic inspection equipment. The laser irradiation means includes a polarization beam splitter,
9. The irradiation laser light reflected by the surface to be inspected is configured to be incident on the laser condensing unit through the polarization beam splitter. The laser ultrasonic inspection apparatus according to item.   10. The light source according to claim 1, further comprising a visible light source that irradiates the surface to be inspected with visible light superimposed on the irradiated laser light through the laser beam branching unit and the laser irradiation unit. The laser ultrasonic inspection apparatus according to item.   The laser ultrasonic inspection apparatus according to any one of claims 1 to 10, wherein the light receiving means includes a visible light CCD camera or a C-MOS camera. Generate laser light,
The laser beam is branched into an irradiation laser beam and a reference laser beam,
Irradiate and irradiate the irradiated laser light to the surface to be inspected,
Condensing the irradiation laser light reflected by the surface to be inspected,
The focused irradiation laser beam and the reference laser beam are received by a photorefractive crystal to perform interference measurement,
Converting the wavelength of the laser beam that has received interference in the photorefractive crystal,
Receiving laser light having the wavelength converted;
A laser ultrasonic inspection method characterized by comprising: Generate laser light,
The laser beam is branched into an irradiation laser beam and a reference laser beam,
Irradiate and irradiate the irradiated laser light to the surface to be inspected,
Condensing the irradiation laser light reflected by the surface to be inspected,
The focused irradiation laser beam and the reference laser beam are received by a photorefractive crystal to perform interference measurement,
Changing the profile of the laser beam that has been interfered with by the photorefractive crystal;
Receiving a laser beam whose profile has changed,
A laser ultrasonic inspection method characterized by comprising:

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