WO2019193788A1 - 振動計測装置 - Google Patents
振動計測装置 Download PDFInfo
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- WO2019193788A1 WO2019193788A1 PCT/JP2018/045902 JP2018045902W WO2019193788A1 WO 2019193788 A1 WO2019193788 A1 WO 2019193788A1 JP 2018045902 W JP2018045902 W JP 2018045902W WO 2019193788 A1 WO2019193788 A1 WO 2019193788A1
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- wavelength
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
- G01H9/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means
- G01H9/002—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means for representing acoustic field distribution
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
- G01N21/88—Investigating the presence of flaws or contamination
- G01N21/8806—Specially adapted optical and illumination features
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B9/00—Measuring instruments characterised by the use of optical techniques
- G01B9/02—Interferometers
- G01B9/02001—Interferometers characterised by controlling or generating intrinsic radiation properties
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B9/00—Measuring instruments characterised by the use of optical techniques
- G01B9/02—Interferometers
- G01B9/02001—Interferometers characterised by controlling or generating intrinsic radiation properties
- G01B9/02012—Interferometers characterised by controlling or generating intrinsic radiation properties using temporal intensity variation
- G01B9/02014—Interferometers characterised by controlling or generating intrinsic radiation properties using temporal intensity variation by using pulsed light
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B9/00—Measuring instruments characterised by the use of optical techniques
- G01B9/02—Interferometers
- G01B9/02055—Reduction or prevention of errors; Testing; Calibration
- G01B9/02062—Active error reduction, i.e. varying with time
- G01B9/02067—Active error reduction, i.e. varying with time by electronic control systems, i.e. using feedback acting on optics or light
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B9/00—Measuring instruments characterised by the use of optical techniques
- G01B9/02—Interferometers
- G01B9/02094—Speckle interferometers, i.e. for detecting changes in speckle pattern
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B9/00—Measuring instruments characterised by the use of optical techniques
- G01B9/02—Interferometers
- G01B9/02094—Speckle interferometers, i.e. for detecting changes in speckle pattern
- G01B9/02095—Speckle interferometers, i.e. for detecting changes in speckle pattern detecting deformation from original shape
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B9/00—Measuring instruments characterised by the use of optical techniques
- G01B9/02—Interferometers
- G01B9/02097—Self-interferometers
- G01B9/02098—Shearing interferometers
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M5/00—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings
- G01M5/0033—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings by determining damage, crack or wear
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M5/00—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings
- G01M5/0041—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings by determining deflection or stress
- G01M5/005—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings by determining deflection or stress by means of external apparatus, e.g. test benches or portable test systems
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M5/00—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings
- G01M5/0066—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings by exciting or detecting vibration or acceleration
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M5/00—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings
- G01M5/0091—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings by using electromagnetic excitation or detection
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/22—Details, e.g. general constructional or apparatus details
- G01N29/24—Probes
- G01N29/2418—Probes using optoacoustic interaction with the material, e.g. laser radiation, photoacoustics
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
- G01N21/88—Investigating the presence of flaws or contamination
- G01N21/8806—Specially adapted optical and illumination features
- G01N2021/8838—Stroboscopic illumination; synchronised illumination
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2201/00—Features of devices classified in G01N21/00
- G01N2201/06—Illumination; Optics
- G01N2201/061—Sources
- G01N2201/06113—Coherent sources; lasers
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2201/00—Features of devices classified in G01N21/00
- G01N2201/06—Illumination; Optics
- G01N2201/063—Illuminating optical parts
- G01N2201/0635—Structured illumination, e.g. with grating
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/02—Indexing codes associated with the analysed material
- G01N2291/023—Solids
- G01N2291/0232—Glass, ceramics, concrete or stone
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/02—Indexing codes associated with the analysed material
- G01N2291/023—Solids
- G01N2291/0234—Metals, e.g. steel
Definitions
- the present invention relates to a vibration measuring apparatus that can be used for detecting defects in objects such as concrete and steel structures.
- the laser ultrasonic method One of the techniques for detecting defects on the surface and inside of objects such as concrete and steel structures is the laser ultrasonic method.
- the surface displacement is measured by exciting vibration of an elastic wave in an object to be inspected, irradiating the object to be inspected with laser light, and detecting reflected light with a laser interferometer. Since the displacement due to vibration changes discontinuously at the location of the defect, the defect can be detected by measuring the distribution of displacement.
- the detection laser (probe laser) of the laser interferometer is dot-like, it is necessary to scan over the entire inspection region of the object to be inspected, and there is a problem that it takes time.
- speckle interferometry laser light from a laser light source is split into illumination light and reference light, and the illumination light is used to stroboscopically illuminate the inspection area.
- the interference pattern by the light reflected by the reference light and the reference light is obtained.
- Speckle-sharing interferometry uses laser light from a laser light source (does not split reference light) to stroboscopically illuminate the inspection area and reflect it from two adjacent points on the surface of the inspected object in the inspection area. The interference pattern by the incoming light is obtained.
- Patent Document 1 in a defect detection apparatus using speckle interferometry or speckle shearing interferometry, a continuous wave of elastic waves is excited from an excitation source to an object to be inspected. Interference pattern images are captured by stroboscopic illumination from a pulse laser source in at least three different phases, and the displacement of each point (speckle interferometry) or the relative displacement between two adjacent points (speckle sharing) Measuring interferometry).
- speckle interferometry speckle interferometry
- speckle sharing speckle sharing
- a direct modulation method for controlling the laser drive current There is an external modulation system that combines a continuous wave laser and a modulator. Although the external modulation method can be applied regardless of the type of laser, the direct modulation method is more preferable in terms of downsizing of the apparatus. In particular, the direct modulation method using a semiconductor laser has an advantage of low cost. However, when a general semiconductor laser is used, there may occur an event that an interference image cannot be obtained if the surface of the inspection region has large irregularities.
- defect detection has been described as an example, but in addition to the case of detecting a defect, for example, as in the internal structure analysis of an object, vibration caused by an elastic wave excited on an object to be inspected is subjected to speckle interferometry or speckle Similar problems arise when measuring using sharing interferometry.
- the problem to be solved by the present invention is to provide a vibration measuring apparatus capable of obtaining an interference image more reliably and measuring vibration even when inspecting an inspection object having a large surface unevenness using a semiconductor laser. Is to provide.
- the vibration measuring apparatus which has been made to solve the above problems, An excitation unit that excites an elastic wave to the object to be inspected; An illumination unit that stroboscopically illuminates the measurement area of the surface of the object to be inspected using a wavelength-stabilized laser light source; A displacement measuring unit that collectively measures the displacement in the front-rear direction of each point in the measurement region by speckle interferometry or speckle-sharing interferometry.
- the speckle interferometry method uses the optical path difference between the illumination light and the reference light, and the speckle-sharing interferometry method uses an object to be inspected in the measurement area (corresponding to the inspection area in the defect inspection described above). It is necessary to make the optical path difference of light reflected from two adjacent points on the surface shorter than the coherent distance over the entire measurement region.
- the optical path difference becomes longer than the coherence distance in a part of the measurement area, and an interference image is formed in the entire measurement area. I can't get it.
- the vibration measuring apparatus by using a wavelength-stabilized laser light source as the light source of the illumination unit, it is possible to prevent the oscillation wavelength from changing during lighting, thereby preventing the coherence distance from being shortened. Can do. Thereby, since an interference image can be obtained over the whole measurement area
- wavelength-stabilized laser light sources can be used.
- an oscillation laser beam generated by a semiconductor laser is introduced into a grating provided outside the semiconductor laser (where it is not easily affected by temperature changes), and the wavelength is narrower than the wavelength band of the oscillation laser beam from the semiconductor laser.
- a laser beam that selectively emits a laser beam having a wavelength in the narrow wavelength band by repeatedly returning (feedback) the band light to the semiconductor laser by the grating is used (see, for example, Patent Document 2). be able to.
- a mechanism for controlling the temperature of the semiconductor laser and a mechanism for detecting the wavelength of the oscillation laser light generated by the semiconductor laser are provided, and the temperature of the semiconductor laser is controlled in accordance with the wavelength deviation of the oscillation laser light from a predetermined wavelength. It is also possible to use a wavelength stabilized laser light source (see, for example, Patent Document 3).
- the longitudinal displacement of each point in the area changes discontinuously at the position of the defect. Accordingly, by measuring the displacement in the front-rear direction of each point in the measurement region using the vibration measuring apparatus according to the present invention, a defect in the measurement region can be detected.
- phase shift method that changes the phase of light from two points into at least three different states can be used. Specifically, light from one of the two points is passed through a phase shifter, and the shift amount by the phase shifter is set to at least three different values. Of course, both the light from two points may be passed through the phase shifter to relatively change the phases of the two. As described above, the relative displacement between two adjacent points is measured in at least three different phases of the elastic wave in the entire measurement region.
- the displacement measuring unit controls each phase in the measurement region in at least three different phases of the elastic wave by controlling the phase of the elastic wave and the timing of the strobe illumination. It is desirable to measure the displacement in the front-rear direction.
- the displacement measuring unit has a number of phase states in the at least three phases of (2n + 1) or more, where n is a natural number of 2 or more, It is desirable to detect the nth harmonic component of the elastic wave from the longitudinal displacement of each point in the measurement region. If there is a minute defect in the object to be inspected, the discontinuous change occurring at that location may contain a lot of harmonic components. Therefore, by detecting the harmonic component in this way, The detection sensitivity for defects can be increased.
- an interference image can be obtained more reliably and vibration can be measured even when an inspection object having a large surface irregularity is inspected using a semiconductor laser.
- FIG. 1 is a schematic configuration diagram showing an embodiment of a vibration measuring apparatus according to the present invention.
- the flowchart which shows an example of the defect detection method using the vibration measuring device of this embodiment.
- the vibration measuring apparatus 10 of the present embodiment functions as a defect detection apparatus that detects a defect D (see FIG. 1) present on the surface of the inspection object S.
- the vibration measuring apparatus 10 includes a signal generator 11, a vibrator 12, a wavelength stabilized laser light source 13, an illumination light lens 14, a speckle / sharing interferometer 15, a control unit 16, and a storage unit. 17.
- the signal generator 11 is connected to the vibrator 12 with a cable, and generates an AC electric signal and transmits it to the vibrator 12.
- the vibrator 12 is used in contact with the object S to be inspected, receives an AC electric signal from the signal generator 11 and converts it into mechanical vibration, and applies the mechanical vibration to the object S to be inspected. Thereby, an elastic wave is excited in the inspected object S.
- the signal generator 11 and the vibrator 12 correspond to the above-described excitation unit.
- the signal generator 11 is also connected to the wavelength-stabilized laser light source 13 by a cable different from the cable connected to the vibrator 12, and the wavelength-stabilized laser at the timing when the AC electric signal has a predetermined phase.
- a pulsed electric signal (pulse signal) is transmitted to the light source 13.
- the wavelength-stabilized laser light source 13 uses a grating provided outside the semiconductor laser to oscillate laser light generated by the semiconductor laser, and a wavelength band narrower than the wavelength band of the oscillation laser light.
- a laser beam that emits laser light with a stable oscillation wavelength is used by performing feedback to selectively return the light to the semiconductor laser.
- VHG volume holographic grating
- the use of a volume holographic grating (VHG) produced by transferring a light interference pattern onto a medium such as silica glass or silicate glass as the grating enables high wavelength stability and high efficiency. Interference (coherence distance is 1m or more) can be obtained.
- the illumination light lens 14 is disposed between the wavelength-stabilized laser light source 13 and the object S to be inspected, and is composed of a concave lens.
- the illumination light lens 14 has a role of spreading the pulsed laser light from the wavelength stabilized laser light source 13 over the entire measurement region on the surface of the object S to be inspected.
- These wavelength-stabilized laser light source 13 and illumination light lens 14 stroboscopically illuminate the measurement region on the surface of the object S to be inspected, and correspond to the above-described illumination unit.
- the speckle / sharing interferometer 15 corresponds to the above-described displacement measuring unit, and includes a beam splitter 151, a first reflecting mirror 1521, a second reflecting mirror 1522, a phase shifter 153, a condensing lens 154, and an image sensor 155.
- the beam splitter 151 is a half mirror disposed at a position where illumination light reflected by the measurement region on the surface of the inspection object S is incident.
- the first reflecting mirror 1521 is disposed on the optical path of the illumination light reflected by the beam splitter 151, and the second reflecting mirror 1522 is disposed on the optical path of the illumination light transmitted through the beam splitter 151.
- the phase shifter 153 is disposed between the beam splitter 151 and the first reflecting mirror 1521, and changes (shifts) the phase of light passing through the phase shifter 153.
- the image sensor 155 is reflected by the beam splitter 151 and then reflected by the first reflecting mirror 1521 and transmitted through the beam splitter 151. After passing through the beam splitter 151, the image sensor 155 is reflected by the second reflecting mirror 1522 and reflected by the beam splitter. It is arranged on the optical path of the illumination light reflected at 151.
- the condenser lens 154 is disposed between the beam splitter 151 and the image sensor 155.
- the first reflecting mirror 1521 is arranged so that its reflecting surface is at an angle of 45 ° with respect to the reflecting surface of the beam splitter 151.
- the second reflecting mirror 1522 is arranged such that its reflecting surface is slightly inclined with respect to the reflecting surface of the beam splitter 151 from 45 °.
- the image sensor 155 has a large number of detection elements, and light incident on the image sensor 155 from a large number of points on the surface of the inspection object S through the first reflecting mirror 1521 and the phase shifter 153 is detected by different detection elements. To detect.
- the image sensor 155 is irradiated with a certain point A on the surface of the object S to be inspected and the first reflecting mirror 1521.
- the light (dotted line in FIG. 1), the point B at a position slightly shifted from the point A on the surface, and the irradiation light (the broken line) reflected by the second reflecting mirror 1522 are reflected by the image sensor 155. It enters the same position and interferes.
- the coherence distance becomes shorter than this optical path difference, and there is a possibility that these two irradiation lights do not interfere with each other.
- the wavelength stabilized laser light source 13 it is possible to prevent the coherence distance from being shortened and thereby cause the two irradiation lights to interfere with each other.
- the control unit 16 controls the signal generator 11 and performs data processing based on detection signals obtained from the detection elements of the image sensor 155.
- the storage unit 17 stores detection signals obtained from the respective detection elements of the image sensor 155 and data processed by the control unit 16.
- measurement of the surface displacement is performed m max ⁇ 3 times with different phases of vibration of the vibrator 12.
- “Vibration phase of the vibrator 12” is the phase of an AC electrical signal transmitted from the signal generator 11 to the vibrator 12, and the point of contact of the vibrator 12 with the elastic wave excited by the object S to be inspected. This corresponds to the phase at.
- the initial value of k is set to 1 (step S1), and an AC electrical signal is transmitted from the signal generator 11 to the vibrator 12 to start applying vibration from the vibrator 12 to the object S to be inspected. (Step S2). As a result, an elastic wave is excited in the inspection object S.
- the wavelength-stabilized laser light source 13 receives a pulse signal, it repeatedly emits illumination light, which is pulsed laser light, at a stable wavelength by feedback using the aforementioned grating.
- the illumination light is expanded in diameter by the illumination light lens 14 and irradiated to the entire measurement region on the surface of the object S to be inspected (step S3).
- the illumination light is reflected by the surface of the inspection object S and enters the beam splitter 151 of the speckle shearing interferometer 15. Part of the illumination light is reflected by the beam splitter 151, passes through the phase shifter 153, then is reflected by the first reflecting mirror 1521, passes through the phase shifter 153 again, and then partly passes through the beam splitter 151, so that the image sensor 155 is incident. Further, the remainder of the illumination light incident on the beam splitter 151 passes through the beam splitter 151 and is reflected by the second reflecting mirror 1522, and part of the illumination light is reflected by the beam splitter 151 and enters the image sensor 155. As described above, the image sensor 155 detects the irradiation light reflected at a large number of points on the surface of the inspection object S using different detection elements.
- the phase shifter 153 changes (shifts) the phase of the irradiation light that passes through the phase shifter 153 (that is, the irradiation light reflected at the point A) while the illumination light that is pulsed laser light is repeatedly output. Go.
- the phase difference between the irradiation light reflected at the point A and the irradiation light reflected at the point B changes.
- each detection element of the image sensor 155 interferes with the two irradiation lights.
- the intensity of the interference light thus detected is detected (step S4).
- the use of the wavelength-stabilized laser light source 13 prevents the coherence distance from being shortened. Can interfere.
- the phase of the vibration of the vibrator 12 is obtained when a phi 0, and the shift amount of the phase by the phase shifter 153, the intensity of the interference light detected by the detecting elements of the image sensor 155
- An example is shown in a graph.
- the relationship in which the detected intensity changes sinusoidally with respect to the phase shift amount is shown by a continuous curve, but what is actually observed is discrete data, which is observed
- the continuous sine waveform is reproduced from the data by the least square method or the like. For this purpose, it is necessary to detect the intensity at at least three different phase shift amounts.
- step S5 it is confirmed whether or not the value of k has reached m max .
- the determination in step S5 is “NO”. If “NO”, the process proceeds to step S6, and the value of k is increased by 1 to "2" (the case where the determination in step S5 is "YES" will be described later).
- the signal generator 11 transmits a pulse signal to the wavelength-stabilized laser light source 13, and the wavelength-stabilized laser light source 13 illuminates light that is pulsed laser light on the surface of the inspected object S at the timing of receiving the pulse signal. Irradiate repeatedly. Then, each detection element of the image sensor 155 is reflected at the point A and passes through the phase shifter 153 and the like while changing (shifting) the phase of the irradiation light reflected at the point A by the phase shifter 153 to at least three values. The intensity of the interference light between the irradiation light and the irradiation light reflected at the point B is detected (step S4).
- the middle diagram of FIG. 3 shows the amount of phase shift by the phase shifter 153 and the intensity of the interference light detected by the detection element of the image sensor 155 obtained when the vibration phase of the vibrator 12 is ⁇ 1. Shown in the graph.
- the middle diagram and the upper diagram in FIG. 3 are compared, the peak positions of the intensity of the interference light are shifted by ⁇ 1 - ⁇ 0 in both.
- This shift indicates that the phase difference between the optical path from the point A and the optical path from the point B has changed due to the difference in the phase of vibration of the vibrator 12 at the time of detection.
- This change in the phase difference of the optical path indicates that the relative displacement in the out-of-plane direction between point A and point B has changed.
- the relationship between the phase shift amount by the phase shifter 153 and the intensity of the interference light when the phase of the AC electrical signal is ⁇ 2 is obtained.
- step S5 since the value of k is 3 and has reached m max , “YES” is determined, and the process proceeds to step S7.
- step S7 the transmission of the AC electrical signal from the signal generator 11 to the vibrator 12 is stopped, and thereby the vibrator 12 stops vibrating.
- the vibration state (amplitude and phase) of the elastic wave at each point in the measurement region is obtained by the following operation.
- the phase shift amounts ⁇ 0 , ⁇ 1 , and ⁇ 2 are obtained (refer to the upper, middle, and lower graphs in FIG. 3). Further, differences ( ⁇ 1 - ⁇ 0 ), ( ⁇ 2 - ⁇ 1 ), and ( ⁇ 0 - ⁇ 2 ) between the maximum output phase shift amounts having different vibration phases are obtained (step S8).
- the difference between these three maximum output phase shift amounts indicates the relative displacement of point A and point B in the out-of-plane direction using two sets of data with two different vibration phases (ie, different times). ing. Based on these three sets of relative displacements, three parameter values are obtained: the amplitude of vibration, the phase of vibration, and the center value (DC component) of vibration at each point in the measurement region (step S9).
- An image is created on the basis of the vibration amplitude and phase values of each point thus obtained (step S10). For example, by increasing the luminance of the pixel corresponding to the measurement point as the amplitude of the measurement point is increased, the difference in vibration amplitude can be expressed by the difference in brightness of the image.
- the image created in this way is processed using a known image processing technique to detect a defect D on the surface of the inspection object S (step S11). For example, a point where the brightness of a pixel suddenly changes as the position on the image moves is detected as a defect.
- this defect detection may be performed by an inspector visually observing the image instead of performing image processing.
- a defect in the measurement region may be detected without detecting an image, for example, by detecting discontinuous points.
- m max 3 but by selecting m max to be larger than the number represented by [2n + 1] (n is a natural number of 2 or more), the elastic wave excited on the object S to be inspected is selected. It is possible to detect up to the nth order component (nth harmonic component). That is, since the relative displacement in the out-of-plane direction between point A and point B can be obtained by (2n + 1) or more, the fundamental wave amplitude, fundamental wave phase, second harmonic wave amplitude, second harmonic wave (2n + 1) parameter values, i.e., the amplitude of the nth harmonic, the phase of the nth harmonic, and the DC component of the elastic wave, are obtained.
- the wavelength stabilized laser light source 13 that stabilizes the wavelength by performing feedback by the volume holographic grating is used.
- a wavelength stabilized laser having other gratings may be used.
- a mechanism for controlling the temperature of the semiconductor laser and a mechanism for detecting the wavelength of the oscillation laser light generated by the semiconductor laser are provided, and the temperature of the semiconductor laser is controlled in accordance with the wavelength deviation of the oscillation laser light from a predetermined wavelength.
- a laser that stabilizes the wavelength by a method other than feedback using a grating, such as a wavelength-stabilized laser, may be used.
- the signal generator 11 and the vibrator 12, and the signal generator 11 and the wavelength-stabilized laser light source 13 are connected by a cable (wired), but they may be connected wirelessly.
- the signal generator 11 and the vibrator 12 are preferably connected wirelessly. Since the signal generator 11 and the vibrator 12 are connected wirelessly, the vibrator 12 is brought into contact with the object S to be inspected, and the constituent elements of the vibration measuring apparatus 10 other than the vibrator 12 are inspected object S. It is not necessary to prepare a long cable even if it is arranged at a position away from the cable. Such a configuration using radio is useful when inspecting a large inspected object S such as an infrastructure structure such as a bridge.
- the vibrator 12 that is used while being in contact with the surface of the inspection object S is used.
- a speaker or the like placed at a position that is not in contact with the surface of the inspection object S is used as the vibration element. It may be used. This configuration is useful when inspecting the inspection object S at a position or height where it is difficult to bring the vibrator into contact with the surface.
- the speckle sharing interferometer 15 is used, but a speckle interferometer may be used instead.
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- Remote Sensing (AREA)
- Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)
- Length Measuring Devices By Optical Means (AREA)
- Investigating Materials By The Use Of Optical Means Adapted For Particular Applications (AREA)
- Measurement Of Mechanical Vibrations Or Ultrasonic Waves (AREA)
Abstract
Description
被検査物体に弾性波を励起する励振部と、
波長安定化レーザ光源を用いて前記被検査物体の表面の測定領域にストロボ照明を行う照明部と、
スペックル干渉法又はスペックル・シェアリング干渉法により前記測定領域の各点の前後方向の変位を一括測定する変位測定部と
を備えることを特徴とする。
上記の例ではmmax=3としたが、mmaxを[2n+1](nは2以上の自然数)で表される数より大きく選ぶことにより、被検査物体Sに励起された弾性波のn次の成分(第n高調波成分)までを検出することができるようになる。すなわち、点Aと点Bの面外方向の相対的な変位が(2n+1)組以上得られることから、基本波の振幅、基本波の位相、第2高調波の振幅、第2高調波の位相、…第n高調波の振幅、第n高調波の位相、及び弾性波のDC成分、という(2n+1)個のパラメータの値が得られる。
11…信号発生器
12…振動子
13…波長安定化レーザ光源
14…照明光レンズ
15…スペックル・シェアリング干渉計
151…ビームスプリッタ
1521…第1反射鏡
1522…第2反射鏡
153…位相シフタ
154…集光レンズ
155…イメージセンサ
16…制御部
17…記憶部
Claims (5)
- 被検査物体に弾性波を励起する励振部と、
波長安定化レーザ光源を用いて前記被検査物体の表面の測定領域にストロボ照明を行う照明部と、
スペックル干渉法又はスペックル・シェアリング干渉法により前記測定領域の各点の前後方向の変位を一括測定する変位測定部と
を備えることを特徴とする振動計測装置。 - 前記変位測定部が、スペックル・シェアリング干渉法において、前記弾性波の位相と前記ストロボ照明のタイミングを制御することにより、該弾性波の互いに異なる少なくとも3つの位相において前記測定領域の各点の前後方向の変位を一括測定することを特徴とする請求項1に記載の振動計測装置。
- 前記少なくとも3つの位相における位相状態の数が(2n+1)以上であって、該nが2以上の自然数であり、前記測定領域内の各点の前後方向の変位から前記弾性波のn次の高調波成分を検出することを特徴とする請求項2に記載の振動計測装置。
- 前記波長安定化レーザが、半導体レーザと、該半導体レーザからの発振レーザ光の波長帯よりも狭い波長帯の光を選択的に半導体レーザに戻すグレーティングとを備えることを特徴とする請求項1に記載の振動計測装置。
- 前記グレーティングがボリュームホログラフィックグレーティングであることを特徴とする請求項4に記載の振動計測装置。
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US17/044,571 US20210096085A1 (en) | 2018-04-05 | 2018-12-13 | Vibration measurement device |
CN201880092070.0A CN112005086A (zh) | 2018-04-05 | 2018-12-13 | 振动测量装置 |
JP2020511594A JP7315535B2 (ja) | 2018-04-05 | 2018-12-13 | 振動計測装置 |
EP18913903.3A EP3779378B1 (en) | 2018-04-05 | 2018-12-13 | Vibration measurement device |
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EP (1) | EP3779378B1 (ja) |
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