Defect detection device and defect detection method

Abstract

Provided is a defect detection device and a defect detection method in which a frequency suitable for defect detection can be set. The defect detection device includes: an input reception unit that receives information input by a user regarding the type and size of a defect assumed to have occurred in an object to be inspected; an excitation unit that excites an elastic wave in the object to be inspected, the frequency of the elastic wave being variable; a measurement unit that measures the vibration state of the surface of the object to be inspected generated by the elastic wave using an optical unit; a wavelength determination unit that determines the wavelength of the elastic wave generated by the excitation of the object to be inspected based on the vibration state acquired by the measurement unit; and a frequency selection unit that selects an appropriate frequency from among a plurality of frequencies based on the wavelength acquired by the wavelength determination unit for each of the plurality of frequencies by changing the frequency of the elastic wave excited by the excitation unit, and the type and size of the defect received by the input reception unit.

Description

TECHNICAL FIELD

[0001] The present application relates to a defect detection device and a defect detection method. BACKGROUND

[0002] In the past, a defect detection method using speckle interferometry or speckle shearing interferometry has been proposed (for example, refer to Patent Literature 1). Speckle interferometry branches laser light from a laser light source into illumination light and reference light, irradiates the illumination light to a test region, and obtains an interference pattern formed by light reflected from each point on the surface of a test object in the test region and the reference light. Speckle shearing interferometry irradiates laser light from a laser light source to a test region (without branching the reference light), and obtains an interference pattern formed by light reflected from two points close on the surface of a test object in the test region. In the device and method described in Patent Literature 1, an elastic wave is continuously excited to a test object by abutting a vibrator against the test object and vibrating the vibrator, and a displacement in the out-of-plane direction (direction perpendicular to the plane) of each point at a certain phase of the elastic wave (speckle interferometry) or a relative displacement in the out-of-plane direction between two points close (speckle shearing interferometry) is measured using stroboscopic illumination that repeats lighting in synchronization with the elastic wave. By performing the operation at at least three phases different from each other of the sinusoidal elastic wave, the full vibration state of the elastic wave can be reproduced, and defects in the test region can be detected with good accuracy.

[0003] In the device and method described in Patent Literature 1, the larger the amplitude of the elastic wave, the larger the displacement of each point or the relative displacement between two points close. Therefore, it is desirable to impart a vibration at a frequency close to the resonance frequency of the measurement system after combining the test object and the vibrator. However, it is difficult for the user to know such a resonance frequency in advance. Therefore, in the device and method described in Patent Literature 2, a preliminary measurement is performed in which the impedance of the vibrator is measured while changing the vibration frequency of the vibrator, and based on the data obtained by the preliminary measurement, the resonance frequency at which the amplitude of the elastic wave becomes a peak value is presented to the user as a recommended frequency. The resonance frequency depends on the size or material of the test object, and the range in which the vibration frequency is changed depends on the device, but in most cases, the measurement system can resonate at a plurality of frequencies within the range. Thus, the amplitude of the elastic wave also becomes a peak value at a plurality of frequencies, and a plurality of recommended frequencies are presented.

[0004] [Patent Literature]

[0005] [Patent Literature]

[0006] [Patent Literature 1] Japanese Patent No. 2017-219318

[0007] [Patent Literature 2] International Publication No. WO2021 / 145034 SUMMARY

[0008] [Problems to be Solved by the Invention]

[0009] If the wavelength of the elastic wave generated by the inspection object being excited is too long (the frequency is too low), sometimes the defect cannot be detected. For example, in the case where the defect is a crack, if the wavelength of the elastic wave exceeds 7 times the length of the crack, it is empirically considered that the defect cannot be accurately detected. Also, in the case where a part of a coating film implemented on the surface of the inspection object is peeled, if the coating film is also considered as a part of the inspection object, the peeled part can be considered as a defect of the inspection object. When the length of 1 / 2 times the wavelength of the elastic wave is longer than the diameter of the region where the coating film is peeled, the defect caused by the peeling of the coating film cannot be accurately detected. On the other hand, on the characteristics of a general vibrator, the shorter the wavelength of the elastic wave (the higher the frequency), the smaller the amplitude of the elastic wave that can be imparted to the inspection object. Therefore, it is desirable that the wavelength be long (the frequency be low) in a range in which the defect can be accurately detected.

[0010] As described above, in order to accurately detect a defect, the frequency of the elastic wave imparted to the inspection object must be appropriately set. However, in the device and method described in Patent Literature 2, the plurality of recommended frequencies suggested are only the frequencies at which the amplitude of the vibration of the inspection object becomes a peak value, and it is difficult for the user to determine which of these frequencies is suitable for defect detection.

[0011] The problem to be solved by the present invention is to provide a defect detection device and method in which a frequency suitable for defect detection can be set.

[0012] [Technical Means for Solving the Problem]

[0013] The defect detection device of the present invention, which is made to solve the problem, includes:

[0014] an input reception unit that receives information input by a user, the information being assumed to be a kind and a size of a defect generated in an inspection object;

[0015] an excitation unit that excites an elastic wave to the inspection object, and the frequency of the elastic wave is variable;

[0016] a measurement unit that measures a vibration state of a surface of the inspection object generated by the elastic wave using an optical member;

[0017] a wavelength determination unit that determines a wavelength of the elastic wave generated by the inspection object being excited, based on the vibration state acquired by the measurement unit; and

[0018] The frequency selection section selects an appropriate frequency from among the plurality of frequencies based on the wavelengths acquired by the wavelength determination section for each of the plurality of frequencies by varying the frequency of the elastic wave excited by the excitation section, and the kind and size of the defect accepted by the input acceptance section.

[0019] The defect detection method of the present application includes:

[0020] The vibration state acquisition step excites an elastic wave in the object under inspection, measures the vibration state of the surface of the object under inspection generated by the elastic wave using an optical member while varying the frequency of the elastic wave, and thereby acquires the vibration state of the object under inspection at a plurality of frequencies.

[0021] The wavelength acquisition step acquires the wavelength of the elastic wave generated by the excitation of the object under inspection based on the vibration state acquired in the vibration state acquisition step for each of the plurality of frequencies; and

[0022] The frequency selection step selects an appropriate frequency from among the plurality of frequencies based on the wavelengths acquired for each of the plurality of frequencies, and the kind and size of the defect assumed to be generated in the object under inspection.

[0023] [Effects of the Invention]

[0024] According to the defect detection apparatus and method of the present application, by selecting the frequency based on the wavelengths acquired by the wavelength determination section for a plurality of frequencies by varying the frequency of the elastic wave excited by the excitation section, and the kind and size of the defect assumed to be generated in the object under inspection, a frequency appropriate for defect detection corresponding to the kind and size of the defect assumed can be set.

[0025] The kind of the defect can be exemplified by a crack or peeling of a coating film generated in the object under inspection. The size of the defect input by the user can be a value of about several digits, and one value can be input, or a range of values can be input. In the case where one value is input as the size of the defect, it is desirable to select the frequency based on a range of values having a prescribed size including the value. The frequency appropriate for defect detection is determined, for example, by determining a range of frequencies by multiplying the upper limit value and the lower limit value of the range of the size of the defect assumed by a coefficient determined by the kind of the defect assumed, and selecting a frequency included in the range of frequencies from among the plurality of frequencies at which the amplitude becomes a peak value. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is a schematic configuration diagram showing a first embodiment of the defect detection apparatus of the present application.

[0027] Figure 2This is a flowchart illustrating the operation of the defect detection device and the defect detection method of the first embodiment.

[0028] Figure 3 This diagram shows an example of a setting screen displayed on the display unit in the defect detection device of the first embodiment.

[0029] Figure 4 This is a diagram illustrating a method for determining the displacement of the surface of an object being inspected in the defect detection apparatus of the first embodiment.

[0030] Figure 5 This is an example of an image showing the state of vibration on the surface of the object being inspected, obtained by the defect detection device of the first embodiment.

[0031] Figure 6 This is a schematic structural diagram illustrating a second embodiment of the defect detection device of the present invention.

[0032] Figure 7 This diagram shows an example of a setting screen displayed on the display unit in the defect detection device according to the second embodiment.

[0033] Figure 8 This is a flowchart illustrating the operation of the defect detection device and the defect detection method of the second embodiment.

[0034] Explanation of reference numerals in the attached figures

[0035] 10, 20: Defect detection device

[0036] 11: Signal Generator

[0037] 12: Vibrator

[0038] 13: Pulsed laser source

[0039] 14: Illumination Lens

[0040] 15: Speckle Shear Interferometer (Measurement Department)

[0041] 151: Beam splitter

[0042] 1521: First Reflector

[0043] 1522: Second reflecting mirror

[0044] 153: Phase shifter

[0045] 154: Condensing Lens

[0046] 155: Image Sensor

[0047] 16, 26: Measurement and Control Department

[0048] 161: input reception unit

[0049] 162, 2622: frequency control unit

[0050] 163, 263: displacement calculation unit

[0051] 164, 264: wavelength determination unit

[0052] 165, 265: frequency selection unit

[0053] 166, 266: display processing unit

[0054] 17: storage unit

[0055] 18: input unit

[0056] 19: display unit

[0057] 2611: inspected object information input reception unit

[0058] 2612: assumed defect information input reception unit

[0059] 2621: frequency candidate determination unit

[0060] 30: assumed defect information input screen

[0061] 31: defect type input area

[0062] 32: defect size input area

[0063] 33: determination button

[0064] 40: input screen

[0065] 41: inspected object shape input area

[0066] 42: inspected object material input area

[0067] 43: inspected object size input area DETAILED DESCRIPTION

[0068] Hereinafter, the use of Figures 1-8 An embodiment of a defect detection apparatus and method of the present application will be described.

[0069] (1) Structure of the defect detection apparatus of the first embodiment

[0070] The defect detection apparatus 10 of the first embodiment includes a signal generator 11, a vibrator 12, a pulsed laser light source 13, an illumination light lens 14, a speckle shearing interferometer 15, a measurement control unit 16, a storage unit 17, an input unit 18, and a display unit 19.

[0071] The signal generator 11 is connected to the vibrator 12 through a cable, generates an alternating-current electric signal, and sends it to the vibrator 12. The frequency of the alternating-current electric signal is variable, and is set by the measurement control section 16 as described later. The vibrator 12 is used in contact with the object S to be inspected, receives the alternating-current electric signal from the signal generator 11 and converts it into a mechanical vibration having the frequency, and imparts the mechanical vibration to the object S to be inspected. Thus, an elastic wave having the frequency, i.e., the frequency set by the measurement control section 16, is excited to the object S to be inspected. These signal generator 11 and vibrator 12 correspond to the excitation section.

[0072] The signal generator 11 is also connected to the pulsed laser light source 13 through a cable different from the cable connected to the vibrator 12, and sends a pulsed electric signal (pulse signal) to the pulsed laser light source 13 at a timing at which the alternating-current electric signal becomes a prescribed phase. The prescribed phase and the timing determined thereby are set by the measurement control section 16 as described later. The pulsed laser light source 13 is a light source that outputs pulsed laser light when receiving the pulse signal from the signal generator 11. The illumination light lens 14 is disposed between the pulsed 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 function of expanding the pulsed laser light from the pulsed laser light source 13 to the entire measurement region of the surface of the object S to be inspected. These pulsed laser light source 13 and illumination light lens 14 stroboscopically illuminate the measurement region of the surface of the object S to be inspected, and are included in the measurement section.

[0073] The speckle shearing interferometer 15 corresponds to the measurement section, and has a beam splitter 151, a first mirror 1521, a second mirror 1522, a phase shifter 153, a condenser lens 154, and an image sensor 155. The beam splitter 151 is a half mirror disposed at a position at which the illumination light reflected on the measurement region of the surface of the object S to be inspected is incident. The first mirror 1521 is disposed on the optical path of the illumination light reflected by the beam splitter 151, and the second 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 mirror 1521, and changes (shifts) the phase of the light passing through the phase shifter 153. The image sensor 155 is disposed on the optical path of the illumination light reflected by the first mirror 1521 after being reflected by the beam splitter 151 and transmitted through the beam splitter 151, and the illumination light reflected by the second mirror 1522 after being transmitted through the beam splitter 151 and reflected by the beam splitter 151. The condenser lens 154 is disposed between the beam splitter 151 and the image sensor 155.

[0074] The first mirror 1521 is configured such that the reflecting surface thereof forms an angle of 45° with respect to the reflecting surface of the beam splitter 151. In contrast, the second mirror 1522 is configured such that the reflecting surface thereof forms an angle slightly inclined from 45° with respect to the reflecting surface of the beam splitter 151. By these configurations of the first mirror 1521 and the second mirror 1522, in the image sensor 155, the irradiation light reflected by the point A on the surface of the object to be inspected S and the first mirror 1521 (dotted line in the figure) and the irradiation light reflected by the point B on the surface of the object to be inspected S at a position slightly shifted from the point A and the second mirror 1522 (dashed line in the figure) are incident to the same position of the image sensor 155 to interfere with each other. The image sensor 155 has a plurality of detection elements, and the light incident to the image sensor 155 from a plurality of points (the point A) on the surface of the object to be inspected S via the first mirror 1521 and the phase shifter 153 is detected by different detection elements, respectively. In the same manner with respect to the point B, the light incident to the image sensor 155 from a plurality of points via the second mirror 1522 is detected by different detection elements, respectively. Figure 1

[0075] The input section 18 is a keyboard, a mouse, a touch panel, or the like, or a combination of these, and is used for a user to input information such as the kind and size of a defect assumed to be generated in the object to be inspected S. The display section 19 is a display that displays a setting screen including a field in which the information is input, a screen indicating a measurement result, or the like.

[0076] The measurement control section 16 includes an input reception section 161, a frequency control section 162, a displacement calculation section 163, a wavelength determination section 164, a frequency selection section 165, and a display processing section 166. The measurement control section 16 is realized by hardware such as a central processing unit (CPU) and software that performs each operation. Hereinafter, each section (functional block) included in the measurement control section 16 will be described.

[0077] The input reception section 161 receives information such as the kind and size of a defect input by a user using the input section 18, and transmits the information to the frequency selection section 165.

[0078] The frequency control section 162 controls the frequency of the alternating-current signal transmitted by the signal generator 11 to the vibrator 12, that is, the frequency of the elastic wave generated by the vibrator 12 exciting the object to be inspected S. When an operation of setting a frequency appropriate for defect detection is performed, the frequency of the alternating-current signal (and thus the frequency of the elastic wave generated by the object to be inspected S being excited) is changed over a plurality of values within a prescribed range in the operation. As will be described later, after a frequency is selected by the frequency selection section 165, the frequency of the alternating-current signal is set to the selected value when measurement for defect detection is performed.​

[0079] The displacement calculating section 163 calculates the displacement in the out-of-plane direction at each point on the surface of the object S under inspection based on the detection signals obtained from each detection element of the image sensor 155 using speckle shear interference. When the operation of setting the frequency appropriate for defect detection is performed, the displacement in the out-of-plane direction at each point on the surface of the object S under inspection obtained during the period in which the frequency of the elastic wave generated by the excitation of the object S under inspection is varied by the frequency control section 162 is acquired for each frequency (time) obtained. When the measurement for defect detection is performed, the displacement in the out-of-plane direction at each point on the surface of the object S under inspection obtained at the frequency selected by the frequency selection section 165 is acquired.

[0080] The wavelength determining section 164 calculates the wavelength of the elastic wave generated by the excitation of the object S under inspection based on the displacement in the out-of-plane direction at each point on the surface of the object S under inspection acquired by the displacement calculating section 163 for each frequency when the operation of setting the frequency appropriate for defect detection is performed. The method of calculating the wavelength will be described later.

[0081] The frequency selection section 165 selects an appropriate frequency from among a plurality of frequencies based on the wavelength of the elastic wave calculated by the wavelength determining section 164 for each frequency and the kind and size of the defect assumed to be generated in the object S under inspection accepted by the input accepting section 161 when the operation of setting the frequency appropriate for defect detection is performed. For example, in the case where the kind of the defect accepted by the input accepting section 161 is a crack, a frequency whose wavelength determined by the wavelength determining section 164 is seven times or less the size of the defect accepted by the input accepting section 161 is selected from among the plurality of frequencies. In the case where the kind of the defect is caused by the peeling of a coating film, a frequency whose wavelength becomes one-half times or less the size of the defect is selected from among the plurality of frequencies. In either case of a crack or the peeling of a coating film, in the case where there are a plurality of selected frequencies, a frequency whose amplitude obtained based on the displacement at each measurement point obtained by the displacement calculating section 163 is the largest among these frequencies can be further selected as an appropriate frequency.

[0082] The display processing section 166 displays a setting screen of a column including information of a kind and a size of an input defect, or a screen indicating a measurement result, and the like on the display section 19. As the measurement result displayed on the display section 19, a measurement result indicating a displacement distribution of the out-of-plane direction at each point on the surface of the object to be inspected S in color tone on a two-dimensional map can be cited. The measurement result can display only the measurement result at one frequency selected by the frequency selection section 165, or can display the measurement results obtained at a plurality of frequencies respectively when an operation of setting a frequency suitable for defect detection is performed. In the former case, a defect can be found by generating a discontinuous portion in space in the distribution of the displacement of the out-of-plane direction displayed as the measurement result using the eyes of the user. In the latter case, the measurement result obtained at a frequency suitable for defect detection among a plurality of measurement results can be emphasized and displayed.

[0083] The storage section 17 stores measurement data such as an intensity value of a detection signal obtained from each detection element of the image sensor 155. The storage section 17 can store a value indicating a displacement of the out-of-plane direction at each point on the surface of the object to be inspected S calculated by the displacement calculation section 163 together with the measurement data (raw data), or instead of the measurement data.

[0084] (2) Action of the defect detection apparatus of the first embodiment and the defect detection method

[0085] Next, the action of the defect detection apparatus 10 of the present embodiment and the defect detection method will be described with reference to the flowchart of Figure 2 and each explanatory diagram of Figures 3-5 .

[0086] First, the user sets the object to be inspected S at a prescribed position of the defect detection apparatus 10 and brings the vibrator 12 into contact with the object to be inspected S. Then, when the user performs a prescribed operation using the input section 18, a series of actions is started.

[0087] The display processing section 166 displays a presumed defect information input screen which is a screen for inputting information of a kind and a size of a defect presumed to be generated in the object to be inspected. The user inputs this information using the input section 18 (step S1). In Figure 3An example of a hypothetical defect information input screen is shown in FIG. 10. The hypothetical defect information input screen 30 of this example has a defect type input area 31 in which the type of the hypothetical defect is input, and a defect size input area 32 in which the size of the hypothetical defect is input. In the defect type input area 31, candidates for the types of defects are displayed by a drop-down list, and the user selects from among these candidates by operating the mouse or touch screen of the input section 18. In the defect size input area 32, boxes in which the minimum and maximum values of the diameter of the hypothetical defect are respectively input are displayed, and the user inputs the values of the minimum and maximum values in these boxes using the keyboard or the like of the input section 18. In the case where the same value is input as the maximum and minimum values, one value is set instead of the range of values of the diameter of the defect.

[0088] After the input of the type and size of the defect is completed, when the user presses the OK button 33 in the hypothetical defect information input screen 30, the frequency control section 162 controls the signal generator 11 in such a manner that the AC electric signal having the frequency fi, f2,... fk (k = 1 ~ kmax) within the prescribed frequency range (20 kHz ~ 400 kHz in this embodiment, but not limited to this example) is sequentially transmitted to the vibrator 12. Here, the number of frequencies fk (k = 1 ~ kmax) is set to be equal to the number of phases k (k = 3 or more) in which the displacement of the surface of the object S is measured. h (h is an integer of 2 or more), and the signal generator 11 is controlled in such a manner that the AC electric signal having the frequency is sequentially transmitted to the vibrator 12. Here, the number of frequencies fk (k = 1 ~ kmax) is set to be equal to the number of phases k (k = 3 or more) in which the displacement of the surface of the object S is measured. h In the first embodiment, a value determined in advance is used regardless of the shape, size, material, and the like of the object S to be inspected.

[0089] First, the frequency control section 162 is set to i = 1 (step S2), and the signal generator 11 is controlled in such a manner that the AC electric signal having the frequency fi (this time, fi) is transmitted to the vibrator 12. The vibrator 12 receives the AC electric signal from the signal generator 11, and generates a vibration having the frequency fi. i The vibrator 12 is controlled in such a manner that the AC electric signal having the frequency fi is transmitted to the vibrator 12. The vibrator 12 receives the AC electric signal from the signal generator 11, and generates a vibration having the frequency fi. i The vibration of the vibrator 12 is transmitted to the object S to be inspected which is in abutment therewith, and an elastic wave having the frequency fi is excited in the object S to be inspected. i The frequency control section 162 is set to i = 1 (step S2), and the signal generator 11 is controlled in such a manner that the AC electric signal having the frequency fi, f2,... fk (k = 1 ~ kmax) within the prescribed frequency range (20 kHz ~ 400 kHz in this embodiment, but not limited to this example) is sequentially transmitted to the vibrator 12. Here, the number of frequencies fk (k = 1 ~ kmax) is set to be equal to the number of phases k (k = 3 or more) in which the displacement of the surface of the object S is measured.

[0090] In the state, the displacement in the out-of-plane direction at each point of the surface of the object S to be inspected is measured at k max phases (k max is 3 or more) which are different from each other. The k k phases (k = 1 ~ k max ) are expressed by φk = [φ0 + 2π(k-1) / k max ] using an arbitrary initial value φ0 (for example, φ0 = 0). max). First, k is set to 1 (step S4), and at every timing at which the phase of the elastic wave becomes φ1= φ0, the signal generator 11 sends a pulse signal to the pulsed laser light source 13. The pulsed laser light source 13 repeatedly outputs illumination light as pulsed laser light each time it receives the pulse signal (stroboscopic illumination). The illumination light is expanded in diameter by the illumination light lens 14, and is irradiated to the entire measurement region of the surface of the object to be inspected S (step S5).

[0091] The illumination light is reflected on the surface of the object to be inspected S, and is incident on the beam splitter 151 of the speckle shearing interferometer 15. A part of the illumination light is reflected by the beam splitter 151, passes through the phase shifter 153, is reflected by the first mirror 1521, passes through the phase shifter 153 again, and a part of it passes through the beam splitter 151 to be incident on the image sensor 155. In addition, the remaining part of the illumination light incident on the beam splitter 151 transmits through the beam splitter 151 and is reflected by the second mirror 1522, and a part of it is reflected by the beam splitter 151 to be incident on the image sensor 155. In the image sensor 155, the irradiation light reflected by a plurality of points on the surface of the object to be inspected S is detected by different detection elements, respectively.

[0092] The phase shifter 153 changes (shifts) the phase of the irradiation light passing through the phase shifter 153 (i.e., the irradiation light reflected at point A) during the period in which the illumination light as pulsed laser light is repeatedly output. Thus, the phase difference between the irradiation light reflected at point A and the irradiation light reflected at point B changes, and during the period of the change, each detection element of the image sensor 155 detects interference light in which the two irradiation lights interfere with each other, and the intensity thereof is found (step S6). In Figure 4 The upper paragraph of FIG. 8 shows an example of the intensity of the interference light detected by the detection element of the image sensor 155 with respect to the amount of phase shift of the phase shifter 153 obtained when the phase of the vibration of the vibrator 12 is φ1. In addition, the lower paragraph of FIG. 8 shows an example of the intensity of the interference light detected by the detection element of the image sensor 155 with respect to the amount of phase shift of the phase shifter 153 obtained when the phase of the vibration of the vibrator 12 is φ2. Figure 4 In the example of FIG. 8, the relationship in which the detected intensity changes in a sinusoidal wave shape with respect to the amount of phase shift is shown by a continuous curve, but actually, discrete data is observed, and a continuous sinusoidal waveform is reproduced from the observed data by the least squares method or the like. For this reason, it is necessary to detect the intensity of at least three different amounts of phase shift.

[0093] The actions of these steps S5 and S6 are also performed in the case of k = 2 to k max The actions of these steps S5 and S6 are also performed in the case of k = 2 to k max= 3, at k = 2, at every timing at which the phase of the elastic wave becomes φ2= φ0+ 2π / 3, and at k = 3, at every timing at which the phase of the elastic wave becomes φ3= φ0+ 4π / 3, the signal generator 11 sends a pulse signal to the pulsed laser light source 13 to repeatedly irradiate the illumination light to the entire measurement region of the surface of the object S under inspection, and during this period, the phase shifter 153 shifts the phase of the irradiation light passing therethrough, while the respective detection elements of the image sensor 155 detect the intensity of the interference light. In Figure 4 the case of k max = 3, at the phase φ2of the vibration of the vibrator 12 (middle section of Figure 4 ) and at the phase φ3of the vibration of the vibrator 12 (lower section of Figure 4 ), examples of the relationship between the shift amount of the phase and the intensity of the interference light.

[0094] After the actions of the step S5 and the step S6 are performed in each of the above-described cases (determination of "YES" in the step S7), the maximum output phase shift amount δφ1~ the maximum output phase shift amount δφ max are respectively found in the case of k = 1 ~ k kmax = 3, in the period during which the output of the detection element becomes maximum at the maximum output phase shift amount δφ1~ the maximum output phase shift amount δφ kmax , and further, based on the maximum output phase shift amount δφ1~ the maximum output phase shift amount δφ kmax , the difference between the maximum output phase shift amounts is found in different phases from each other. For example, in the case of k max = 3, three differences between the maximum output phase shift amounts (δφ2- δφ1), (δφ3- δφ2), and (δφ1- δφ3) are obtained. These differences between the maximum output phase shift amounts show three or more sets of data in which the phase of the vibration of the vibrator 12 is different (i.e., the time is different) with respect to the relative displacement in the out-of-plane direction of the points A and B. Based on these three or more sets of relative displacements, the values of three parameters representing the vibration state of the object S, i.e., the amplitude of the vibration, the phase of the vibration, and the center value (DC component) of the vibration at each point of the measurement region can be obtained (step S9. Corresponding to the vibration state acquisition step by frequency).

[0095] If these three parameters exist, the state of the vibration at each point can be reproduced with high accuracy. For example, as shown in the image Figure 5 , an image of the elastic wave formed in the measurement region of the surface of the object S under inspection can be generated. The wavelength determining section 164 performs image analysis based on the image of the elastic wave, and thereby finds the wavelength of the elastic wave of the frequency f i (at f1at the time point) (step S10. Corresponding to the wavelength acquisition step by frequency).

[0096] Since the value of i did not reach its maximum value h at the stated time point (no in step S11), the value of i is increased by 1 (step S12), and the frequency f is determined by repeatedly performing the operations of steps S3 to S10. i The wavelength and amplitude of the elastic wave are determined until i = h. After performing steps S3 to S10 when i = h (yes in step S11), the frequency selection unit 165 determines the wavelength and amplitude based on f1 to f2 calculated by the wavelength determination unit 164. h The wavelengths of elastic waves at various frequencies, and the types and sizes of defects received by the input receiving unit 161, from f1 to f h Then, an appropriate frequency is selected (step S13, corresponding to the frequency selection step). As described above, when the assumed defect type is a crack, the frequency at which the amplitude of an elastic wave with a wavelength less than 7 times the size of the assumed defect is maximized is selected. Furthermore, when the assumed defect type is caused by coating film peeling, the frequency at which the amplitude obtained in step S9 is maximized in an elastic wave with a wavelength less than 1 / 2 times the size of the assumed defect can be selected.

[0097] After selecting the frequency, the display processing unit 166 performs the following processing: It displays the image of the elastic wave formed in the measurement area of ​​the surface of the inspected object S, obtained at the selected frequency (a frequency suitable for defect detection), together with the value of the selected frequency, on the display unit 19 (step S14). The user can visually view the image of the elastic wave. If there are areas where the waveform of the elastic wave differs from its surroundings, or where the spatial variation of the waveform becomes discontinuous, it can be determined that a defect exists in these areas. Alternatively, defects can be detected by performing image analysis on the displayed image, and markings indicating the detected defect areas can be overlaid on the image.

[0098] Through the above operations, the defect detection device 10 and the defect detection method of this embodiment are completed.

[0099] Furthermore, when measuring multiple inspected objects that have the same type and size of assumed defects, and that have the same type of material, shape, and degree of size (described later), the operations described in steps S1 to S14 can be performed only in the measurement of the first inspected object, and in the second and subsequent inspected objects, measurements can be performed at the frequency selected in the first measurement.

[0100] According to the defect detection apparatus 10 of the present embodiment and the defect detection method of the present embodiment, by selecting the frequency with respect to the wavelength acquired by the wavelength determination section 164 for the plurality of frequencies and the kind and size of the defect assumed to be generated in the object to be inspected S, a frequency appropriate for defect detection corresponding to the kind and size of the assumed defect can be set.

[0101] (3) Defect detection apparatus and method of second embodiment

[0102] In Figure 6 A defect detection apparatus 20 as another embodiment of the present application is shown in FIG. 1. The defect detection apparatus 20 includes a measurement control section 26 having a different functional block from the measurement control section 16 in the defect detection apparatus 10 of the first embodiment. The structure other than the measurement control section 26 is the same as that of the defect detection apparatus 10 of the first embodiment, and thus detailed description is omitted.

[0103] The measurement control section 26 includes an object to be inspected information input reception section 2611, an assumed defect information input reception section 2612, a frequency candidate determination section 2621, a frequency control section 2622, a displacement calculation section 263, a wavelength determination section 264, a frequency selection section 265, and a display processing section 266.

[0104] The object to be inspected information input reception section 2611 receives parameters relating to the shape, material, and size of the object to be inspected input by the user using the input section 18. As the shape of the object to be inspected, a plate shape, a bulk shape, a pipe shape, and the like can be listed, and after they are displayed in a list form on the display section 19, the user selects them using the input section 18. The material of the object to be inspected is selected by the user using the input section 18 after various materials such as iron or concrete are displayed in a list form on the display section 19. As for the size of the object to be inspected, in the case of a plate shape, at least the value of the thickness is input, and in the case of a pipe shape, at least the outer diameter and the inner diameter (or either one of the outer diameter and the inner diameter and the wall thickness) are input.

[0105] The assumed defect information input reception section 2612 receives the kind and size of the assumed defect input by the user using the input section 18, similarly to the input reception section 161 in the defect detection apparatus 10 of the first embodiment.

[0106] The frequency candidate determination section 2621 obtains a range of frequencies presumed to be appropriate for defect detection based on the shape, material, and size of the object to be inspected S received by the object to be inspected information input reception section 2611 and the kind and size of the assumed defect received by the assumed defect information input reception section 2612, and determines candidates of a plurality of frequencies within the range.

[0107] Specifically, the speed of sound of the elastic wave generated in the object to be inspected S is calculated based on the shape and material of the object to be inspected S, and the wavelength range presumed to be suitable for defect detection is calculated based on the type and size of the assumed defect, and then the range of the frequency presumed to be suitable for defect detection is calculated from the speed of sound and the wavelength range of the elastic wave. When a plurality of candidates of the frequency are determined in the range of the frequency, the resonance frequency of the vibrator can be determined as a candidate. Thus, the frequency that makes the amplitude large by generating resonance in the measurement system is finally selected, and the detection of the defect becomes easier.

[0108] The speed of sound of the elastic wave can be calculated, for example, in the following manner. In the case where the shape of the object to be inspected S is a plate shape, the phase of the vibration in the out-of-plane direction is the same on both surfaces of the object to be inspected S in a vibration mode called A0 mode, and the speed of sound (phase velocity) of the elastic wave is calculated by solving an equation called Rayleigh-Lamb frequency equation. At this time, the speed of sound of a longitudinal wave and the speed of sound of a transverse wave (hereinafter, simply referred to as "longitudinal wave speed" and "transverse wave speed") determined by the material of the object to be inspected S, and the thickness of the plate are used as parameters without considering the shape. In the case where the shape of the object to be inspected S is a block shape, the thickness of the plate is set to be infinite in the Rayleigh-Lamb frequency equation, and the phase velocity is calculated using the longitudinal wave speed and the transverse wave speed. In the case where the shape of the object to be inspected S is a pipe shape, the phase velocity of the elastic wave is calculated by solving an equation called Gazis frequency equation in a vibration mode called F mode in which the pipe vibrates in one direction in the radial direction. At this time, the longitudinal wave speed, the transverse wave speed, and the outer diameter and the inner diameter of the pipe are used as parameters.

[0109] The frequency control section 2622, the displacement calculation section 263, the wavelength determination section 264, and the frequency selection section 265 are the same as the frequency control section 162, the displacement calculation section 163, the wavelength determination section 164, and the frequency selection section 165 in the defect detection apparatus 10 of the first embodiment.

[0110] The display processing section 266 performs processing to display a setting screen or a screen indicating a measurement result, and the like on the display section 19, like the display processing section 166 in the defect detection apparatus 10 of the first embodiment. However, in the display processing section 266 of the present embodiment, a field in which information such as the type or size of the defect input in the setting screen is displayed, and a field in which a parameter related to the shape, material, and size of the object to be inspected is input is displayed. In the case where the shape of the object to be inspected is a pipe shape, the outer diameter and the inner diameter of the pipe are displayed in the field in which the parameter is input. In the case where the shape of the object to be inspected is a block shape, the thickness of the block is displayed in the field in which the parameter is input. In the case where the shape of the object to be inspected is a plate shape, the thickness of the plate is displayed in the field in which the parameter is input. Figure 7An example of the input screen is shown in FIG. 40. The input screen 40 of this example has, in addition to the defect type input area 31 and the defect size input area 32, an inspected object shape input area 41 for inputting the shape of the inspected object S, an inspected object material input area 42 for inputting the material of the inspected object S, and an inspected object size input area 43 for inputting the size of the inspected object S.

[0111] The operation of the defect detection apparatus 20 of the second embodiment will be described with reference to the flowchart of FIG. 42. In Figure 8 the operation of the defect detection apparatus 10 of the first embodiment is performed. Figure 8 The same step numbers are assigned to the steps of performing the same operations as the flowchart of Figure 2 the operation of the defect detection apparatus 10 of the first embodiment.

[0112] When the user sets the inspected object S at a prescribed position of the defect detection apparatus 20, brings the vibrator 12 into abutment with the inspected object S, and performs a prescribed start operation using the input section 18, the display processing section 266 displays the input screen shown in FIG. 40. The user inputs information of the shape, material, and size of the inspected object and the type and size of the assumed defect using the input section 18 (step S21). Figure 7

[0113] The frequency candidate deciding section 2621 determines a range of frequencies that are presumed to be appropriate for defect detection on the basis of the shape, material, and size of the inspected object S accepted by the inspected object information input accepting section 2611 and the type and size of the assumed defect accepted by the assumed defect information input accepting section 2612, and determines a plurality of frequency candidates f i = f1, f2,... fn h in the range (step S22).

[0114] After the step S22 is performed, the operation of the steps S2 to S14 of the defect detection apparatus 10 of the first embodiment is performed to acquire an image of an elastic wave formed at an appropriate frequency in a measurement region on the surface of the inspected object S. Here, in the operations repeated in the range of i = 1 to h in the steps S2 to S12, the wavelength and amplitude of the elastic wave are determined using the plurality of frequency candidates f i = f1, f2,... fn h determined in the step S22. Thus, a more appropriate frequency can be selected from among the frequency candidates presumed to be appropriate on the basis of the shape, material, and size of the inspected object.

[0115] (4) Modification

[0116] The present application is not limited to the embodiments described above, and various modifications can be made.

[0117] ​For example, in each of the embodiments, in order to accurately reproduce the vibration state at each point on the surface of the inspected object S, three or more different (k max The out-of-plane displacement of each point was measured at one or two phases. However, since the wavelength and amplitude of the elastic wave can be determined even with lower accuracy, the out-of-plane displacement of each point can also be measured at only one or two phases. In this case, similar to the embodiment described above, the image of the elastic wave obtained by the measurement performed to select the frequency can be used directly as the image for defect detection. However, in order to perform defect detection with good accuracy, after the processing in step S13, the out-of-plane displacement of the elastic wave with the selected frequency can be measured at three or more different phases to obtain the image of the elastic wave for defect detection.

[0118] In the various embodiments described, only images of the elastic wave at the selected frequency are displayed. However, after displaying images of the elastic wave at multiple frequencies where the wavelength and / or amplitude meet the specified conditions, the user can select one of these multiple images to determine the frequency. For example, it is possible to consider displaying images of elastic waves that meet the requirement that the wavelength of the elastic wave is less than 7 times the size of the assumed defect (in the case of cracks) or less than 1 / 2 times the size of the assumed defect (in the case of paint peeling), regardless of the amplitude. Alternatively, the user can make a selection after displaying images of the elastic wave at all frequencies for which measurements have been performed.

[0119] In the embodiments described above, a speckle shear interferometer is used as the measuring unit, but other optical measuring devices may also be used. For example, a speckle interferometer using the aforementioned speckle interferometry can be used as the measuring unit in this invention. Alternatively, a scanning laser Doppler vibrator may be used as the measuring unit.

[0120] [form]

[0121] It will be clear to those skilled in the art that the exemplary embodiments described are specific examples of the following forms.

[0122] (First item)

[0123] The defect detection device in the first item includes:

[0124] The input reception department accepts information from users, presumably regarding the type and size of defects in the inspected object.

[0125] The excitation unit generates elastic waves on the object being inspected, and the frequency of the elastic waves is variable;

[0126] The measuring unit uses optical components to measure the vibration state of the surface of the object under inspection generated by the elastic wave;

[0127] a wavelength determination section that determines a wavelength of an elastic wave generated by the inspection object being excited, based on the vibration state acquired by the measurement section; and

[0128] a frequency selection section that selects an appropriate frequency from among the plurality of frequencies, based on the wavelengths acquired by the wavelength determination section for each of the plurality of frequencies by varying the frequency of the elastic wave excited by the excitation section, and the type and size of the defect accepted by the input acceptance section.

[0129] (Fifth Item)

[0130] The defect detection method of the fifth item includes:

[0131] a vibration state acquisition step of exciting an elastic wave in the inspection object, and measuring a vibration state of a surface of the inspection object generated by the elastic wave using an optical member while varying the frequency of the elastic wave, thereby acquiring a vibration state of the inspection object at a plurality of frequencies;

[0132] a wavelength acquisition step of acquiring a wavelength of an elastic wave generated by the inspection object being excited, for each of the plurality of frequencies, based on the vibration state acquired in the vibration state acquisition step by frequency; and

[0133] a frequency selection step of selecting an appropriate frequency from among the plurality of frequencies, based on the wavelengths acquired for each of the plurality of frequencies, and the type and size of the defect assumed to be generated in the inspection object.

[0134] According to the defect detection apparatus of the first item and the defect detection method of the fifth item, by selecting a frequency based on the wavelengths acquired by the wavelength determination section for a plurality of frequencies while varying the frequency of the elastic wave excited by the excitation section, and the type and size of the defect assumed to be generated in the inspection object, a frequency appropriate for defect detection corresponding to the type and size of the assumed defect can be set.

[0135] Here, the type of the defect can be exemplified by a crack or peeling of a coating film generated in the inspection object. The size of the defect input by the user can be a value of about 1, or a single value, or a range of values. In the case where a single value is input as the size of the defect, it is desirable to perform rotation of the frequency based on a range of values having a prescribed size including the value. The frequency appropriate for detecting the defect can be determined, for example, by determining a range of frequencies by multiplying an upper limit value and a lower limit value of the range of the size of the assumed defect by a coefficient determined by the type of the assumed defect, and selecting a frequency included in the range of frequencies from among the plurality of frequencies at which the amplitude becomes a peak value.

[0136] (Second Item)

[0137] The defect detection apparatus according to the first aspect, the defect detection apparatus according to the second aspect further includes:

[0138] a checked object information input receiving section that receives information of a shape, a material, and a size of the checked object input by a user; and

[0139] a frequency candidate deciding section that decides candidates of a plurality of frequencies based on the shape, the material, and the size of the checked object received by the checked object information input receiving section and the kind and the size of the assumed defect received by the input receiving section,

[0140] the frequency selecting section selects an appropriate frequency from the plurality of frequencies based on the wavelength acquired by the wavelength deciding section for each of the candidates of the plurality of frequencies and the kind and the size of the defect received by the input receiving section.

[0141] (Third aspect)

[0142] The defect detection apparatus according to the second aspect, the defect detection apparatus according to the third aspect,

[0143] the frequency candidate deciding section decides, as the candidates of the plurality of frequencies, a plurality of frequencies that are assumed to excite an elastic wave based on the kind and the size of the defect received by the input receiving section and a sound velocity in the checked object calculated based on the shape, the material, and the size of the checked object.

[0144] (Fourth aspect)

[0145] The defect detection apparatus according to the second aspect or the third aspect, the defect detection apparatus according to the fourth aspect,

[0146] the excitation section has a vibrator that imparts a vibration to the checked object,

[0147] the frequency candidate deciding section decides, as one or more of the candidates of the plurality of frequencies, a resonance frequency of the vibrator.

[0148] According to the second aspect, since the frequency candidate decision unit decides the candidates of the plurality of frequencies to be selected by the frequency selection unit based on the shape, material, and size of the object to be inspected and the type and size of the assumed defect, a more appropriate frequency can be used to detect the defect. At this time, in the third aspect, after the speed of sound of the object to be inspected is calculated based on the shape, material, and size of the object to be inspected, the candidates of the plurality of frequencies at which the elastic wave is assumed to be excited are calculated based on the speed of sound and the size of the object to be inspected, whereby the amplitude becomes large by forming the elastic wave, and thus the optimal frequency can be selected from the candidates of the frequencies at which the detection of the defect is assumed to be easier. In addition, in the fourth aspect, by deciding the resonance frequency of the vibrator possessed by the excitation unit to be one or more of the plurality of frequency candidates (here, the "plurality" can be the entire number of the plurality of frequency candidates, or can be a part of the plurality of frequency candidates), the frequency at which the amplitude becomes large due to resonance in the measurement system is selected, and the detection of the defect becomes easier.

Claims

1. A defect detection device, characterized in that, include: The input reception department accepts information from users, presumably regarding the type and size of defects in the inspected object. The excitation unit generates elastic waves on the object being inspected, and the frequency of the elastic waves is variable; The measuring unit uses optical components to measure the vibration state of the surface of the object under inspection generated by the elastic wave; The wavelength determination unit determines the wavelength of the elastic wave generated by the object under inspection when it is excited, based on the vibration state obtained by the measurement unit. as well as The frequency selection unit selects an appropriate frequency from the plurality of frequencies based on the wavelength obtained by the wavelength determination unit for each of the plurality of frequencies by changing the frequency of the elastic wave excited by the excitation unit, and the type and size of the defect received by the input receiving unit.

2. The defect detection device according to claim 1, wherein, Also includes: The inspection object information input reception department accepts information on the shape, material, and size of the inspection object input by the user; as well as The frequency candidate determination unit determines multiple frequency candidates based on the shape, material, and size of the inspected object received by the inspected object information input receiving unit, as well as the assumed type and size of defects received by the input receiving unit. The frequency selection unit selects an appropriate frequency from the plurality of frequencies based on the wavelengths obtained by the wavelength determination unit for each of the plurality of candidate frequencies and the type and magnitude of the defects received by the input receiving unit.

3. The defect detection device according to claim 2, wherein, After determining the speed of sound in the object under inspection based on its shape, material, and size, the frequency candidate determination unit determines multiple frequencies that are assumed to generate elastic waves as candidates based on the speed of sound and the size of the object under inspection.

4. The defect detection device according to claim 2, wherein, The excitation unit has a vibrator that imparts vibration to the object being inspected. The frequency candidate determination unit selects the resonant frequency of the vibrator as one or more of the candidates among the plurality of frequencies.

5. A defect detection method, characterized in that, include: The vibration state acquisition step by frequency involves exciting an elastic wave onto the object under inspection, and while changing the frequency of the elastic wave, measuring the vibration state of the surface of the object under inspection generated by the elastic wave using optical components, thereby acquiring the vibration state of the object under inspection at multiple frequencies. In the frequency-based wavelength acquisition step, for each of the plurality of frequencies, the wavelength of the elastic wave generated by the object under inspection when excited is obtained based on the vibration state obtained in the frequency-based vibration state acquisition step. as well as The frequency selection step involves selecting an appropriate frequency from the plurality of frequencies based on the wavelengths obtained for each of the plurality of frequencies and the assumed type and size of defects in the object being inspected.

Images