Defect detection device and defect detection method

Abstract

To provide a defect detecting device capable of setting a frequency appropriate for defect detection.SOLUTION: A defect detecting device (10) comprises: an input acceptance unit (161) which accepts information on a type and a size of a defect assumed to occur in an inspected object entered by a user; excitation units (11 and 12) which excite an elastic wave to the inspected object, a frequency of the elastic wave being variable; a measurement unit (15) which measures a vibrational state on a surface of the inspected object caused by the elastic wave by optical means; a wavelength determination unit (164) which calculates a wavelength of the elastic wave exited to the inspected object from the vibrational state acquired by the measurement unit; and a frequency selection unit (165) which selects an appropriate frequency from a plurality of frequencies on the basis of a wavelength acquired by the wavelength detection unit about each of the plurality of frequencies by changing a frequency of the elastic wave excited by the excitation unit and the type and size of the defect accepted by the input acceptance unit.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a defect detection device and a defect detection method. [Background technology]

[0002] Defect detection methods using speckle interferometry or speckle shearing interferometry have been proposed (see, for example, Patent Document 1). Speckle interferometry involves splitting a laser beam from a laser source into an illumination beam and a reference beam, irradiating an inspection area with the illumination beam, and obtaining an interference pattern between the reference beam and the light reflected from each point on the surface of the object being inspected within the inspection area. Speckle shearing interferometry involves irradiating an inspection area with laser beam from a laser source (without splitting the reference beam) and obtaining an interference pattern between the light reflected from two adjacent points on the surface of the object being inspected within the inspection area. The apparatus and method described in Patent Document 1 involve contacting a vibrator with the object being inspected and vibrating the vibrator to continuously excite elastic waves in the object being inspected, and then using a strobe light that is repeatedly lit in synchronization with the elastic waves to measure the out-of-plane displacement (perpendicular to the surface) of each point at a certain phase of the elastic waves (speckle interferometry) or the relative out-of-plane displacement (speckle shearing interferometry) between two adjacent points. By performing this operation at least three different phases of the sinusoidal elastic wave, the entire vibration state of the elastic wave can be reproduced, and defects in the inspection area can be detected with high precision.

[0003] In the device and method described in Patent Document 1, the larger the amplitude of the elastic wave, the greater the displacement at each point and the relative displacement between two adjacent points. Therefore, it is desirable to apply vibrations at a frequency close to the resonant frequency of the measurement system, which combines the object to be inspected and the vibrator. However, it is difficult for users to know such a resonant frequency in advance. Therefore, in the device and method described in Patent Document 2, a preliminary measurement is performed in which the vibrator's impedance is measured while changing its vibration frequency. Based on the data obtained from the preliminary measurement, the resonant frequency at which the amplitude of the elastic wave peaks is presented to the user as a recommended frequency. The resonant frequency depends on the size and material of the object to be inspected, and the range over which the vibration frequency is changed depends on the device. However, in many cases, the measurement system may resonate at multiple frequencies within that range. In this case, the amplitude of the elastic wave also peaks at multiple frequencies, and multiple recommended frequencies are presented. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-219318 [Patent Document 2] International Publication No. WO2021 / 145034 Summary of the Invention [Problem to be solved by the invention]

[0005] If the wavelength of the elastic wave excited in the object being inspected is too long (the frequency is too low), it may not be possible to detect the defect. For example, if the defect is a crack, experience has shown that if the wavelength of the elastic wave exceeds seven times the length of the crack, the defect cannot be accurately detected. Also, if part of the paint film applied to the surface of the object being inspected peels off, if the paint film is also considered to be part of the object being inspected, the peeled part can be considered a defect in the object being inspected. In such a defect caused by peeling of the paint film, the length of half the wavelength of the elastic wave is the same as that of the paint film. filmIf the wavelength is longer than the width of the peeled area, it cannot be detected accurately. On the other hand, due to the characteristics of a general vibrator, the shorter the wavelength (higher the frequency) of the elastic wave, the smaller the amplitude of the elastic wave that can be applied to the object being inspected. Therefore, it is desirable to have a long wavelength (low frequency) within the range in which defects can be detected accurately.

[0006] As described above, in order to accurately detect defects, the frequency of the elastic waves applied to the object to be inspected must be set appropriately. However, in the device and method described in Patent Document 2, the multiple recommended frequencies presented are merely frequencies at which the amplitude of the vibration of the object to be inspected peaks, making it difficult for the user to determine which of these frequencies is appropriate for defect detection.

[0007] An object of the present invention is to provide a defect detection apparatus and method that can set a frequency appropriate for defect detection. [Means for solving the problem]

[0008] The defect detection device according to the present invention, which is made to solve the above problems, is an input receiving unit that receives information input by a user about the type and size of defects that are expected to occur in the object to be inspected; an excitation unit for exciting elastic waves in the object to be inspected, the frequency of the elastic waves being variable; a measuring unit that measures the vibration state of the surface of the object to be inspected caused by the elastic waves by optical means; a wavelength determination unit that determines the wavelength of the elastic wave excited in the object to be inspected from the vibration state acquired by the measurement unit; a frequency selection unit that selects an appropriate frequency from the plurality of frequencies based on the wavelengths that the wavelength determination unit has acquired 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 that have been received by the input reception unit; Equipped with.

[0009] The defect detection method according to the present invention comprises: a frequency-specific vibration state acquisition step of exciting an elastic wave in the object to be inspected, and measuring the vibration state of the surface of the object to be inspected caused by the elastic wave by optical means while changing the frequency of the elastic wave, thereby acquiring the vibration state of the object to be inspected at a plurality of frequencies; a frequency-specific wavelength acquisition step of acquiring, for each of the plurality of frequencies, a wavelength of an elastic wave excited in the object to be inspected from the vibration state acquired in the frequency-specific vibration state acquisition step; a frequency selection step of selecting an appropriate frequency from the plurality of frequencies based on the wavelengths acquired for each of the plurality of frequencies and the type and size of a defect assumed to have occurred in the object to be inspected; It has. [Effects of the Invention]

[0010] According to the defect detection device and method of the present invention, by changing the frequency of the elastic wave excited by the excitation unit while selecting a frequency based on the wavelengths obtained by the wavelength determination unit for multiple frequencies and the type and size of the defect expected to occur in the object being inspected, it is possible to set a frequency appropriate for defect detection according to the type and size of the defect expected to occur.

[0011] The types of defects include cracks and paint defects that occur on the object being inspected. film Examples of such defects include peeling of the surface of the substrate. The defect size input by the user may be an approximate numerical value, and may be input as a single numerical value or as a numerical range. When a single numerical value is input as the defect size, it is desirable to select a frequency based on a numerical range having a predetermined magnitude that includes the input numerical value. The frequency appropriate for defect detection can be determined, for example, by multiplying the upper and lower limits of the range of expected defect sizes by coefficients determined depending on the expected type of defect, to determine a frequency range, and then selecting a frequency included in the frequency range from among multiple frequencies at which the measured amplitude peaks. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic configuration diagram showing a first embodiment of a defect detection device according to the present invention. [Figure 2] 4 is a flowchart showing the operation of the defect detection apparatus and the defect detection method according to the first embodiment. [Figure 3] FIG. 3 is a diagram showing an example of a setting screen displayed on a display unit in the defect detection device of the first embodiment. [Figure 4] 3A and 3B are diagrams for explaining a method for determining the displacement of the surface of an object to be inspected in the defect detection device of the first embodiment. [Figure 5] 3A and 3B are diagrams showing examples of images showing the state of vibration on the surface of an object to be inspected, obtained by the defect detection device of the first embodiment. [Figure 6] FIG. 4 is a schematic configuration diagram showing a second embodiment of a defect detection device according to the present invention. [Figure 7] FIG. 10 is a diagram showing an example of a setting screen displayed on a display unit in the defect detection device according to the second embodiment. [Figure 8] 10 is a flowchart showing the operation of the defect detection apparatus and the defect detection method according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] 1 to 8, an embodiment of a defect detection device and method according to the present invention will be described.

[0014] (1) Configuration of the defect detection device of the first embodiment The defect detection device 10 of the first embodiment includes a signal generator 11, an oscillator 12, a pulsed laser light source 13, an illumination lens 14, a speckle shearing interferometer 15, a measurement control unit 16, a memory unit 17, an input unit 18, and a display unit 19.

[0015] The signal generator 11 is connected to the vibrator 12 via a cable, and generates and transmits an AC electric signal to the vibrator 12. The frequency of this AC electric signal is variable and is set by the measurement control unit 16, as described below. The vibrator 12 is used by being brought into contact with the object S to be inspected, and receives the AC electric signal from the signal generator 11, converts it into mechanical vibrations having the frequency, and applies the mechanical vibrations to the object S to be inspected. This excites an elastic wave having the frequency, i.e., the frequency set by the measurement control unit 16, in the object S to be inspected. The signal generator 11 and vibrator 12 correspond to the excitation unit described above.

[0016] The signal generator 11 is also connected to a pulsed laser light source 13 via a cable separate from the cable connecting to the oscillator 12, and transmits a pulsed electric signal (pulse signal) to the pulsed laser light source 13 at a timing when the AC electric signal has a predetermined phase. The predetermined phase and the timing determined thereby are set by a measurement control unit 16 as described below. The pulsed laser light source 13 is a light source that outputs a pulsed laser beam when it receives a pulse signal from the signal generator 11. The illumination lens 14 is arranged between the pulsed laser light source 13 and the object S to be inspected, and is made of a concave lens. The illumination lens 14 has the role of spreading the pulsed laser beam from the pulsed laser light source 13 over the entire measurement area on the surface of the object S to be inspected. The pulsed laser light source 13 and the illumination lens 14 illuminate the measurement area on the surface of the object S to be inspected with a strobe, and are used for the aforementioned Included in the measurement section do.

[0017] The speckle shearing interferometer 15 corresponds to the measurement unit and includes a beam splitter 151, a first reflecting mirror 1521, a second reflecting mirror 1522, a phase shifter 153, a condenser lens 154, and an image sensor 155. The beam splitter 151 is a half mirror arranged at a position where illumination light reflected from a measurement region on the surface of the object S to be inspected is incident. The first reflecting mirror 1521 is arranged on the optical path of the illumination light reflected by the beam splitter 151, and the second reflecting mirror 1522 is arranged on the optical path of the illumination light passing through the beam splitter 151. The phase shifter 153 is arranged between the beam splitter 151 and the first reflecting mirror 1521 and changes (shifts) the phase of the light passing through the phase shifter 153. Image sensor 155 is disposed on the optical path of illumination light that is reflected by beam splitter 151, then reflected by first reflecting mirror 1521, and transmitted through beam splitter 151, and illumination light that is transmitted through beam splitter 151, then reflected by second reflecting mirror 1522, and then reflected back by beam splitter 151. Collecting lens 154 is disposed between beam splitter 151 and image sensor 155.

[0018] First reflecting mirror 1521 is positioned so that its reflective surface forms a 45° angle with respect to the reflective surface of beam splitter 151. In contrast, second reflecting mirror 1522 is positioned so that its reflective surface forms an angle slightly inclined from 45° with respect to the reflective surface of beam splitter 151. Due to the arrangement of first reflecting mirror 1521 and second reflecting mirror 1522, in image sensor 155, irradiation light reflected by point A on the surface of object S to be inspected and first reflecting mirror 1521 (dash-dotted line in FIG. 1) and irradiation light reflected by point B, which is slightly shifted from point A on the surface, and second reflecting mirror 1522 (dashed line in FIG. 1) enter the same position on image sensor 155 and interfere with each other. Image sensor 155 has many detecting elements, and light incident on image sensor 155 from many points on the surface of object S to be inspected (point A) through first reflecting mirror 1521 and phase shifter 153 is detected by different detecting elements. Similarly, for point B, light incident on image sensor 155 from multiple points via second reflecting mirror 1522 is detected by different detection elements.

[0019] The input unit 18 is an input device such as a keyboard, a mouse, a touch panel, or a combination thereof, which is used by the user to input information such as the type and size of defects expected to occur in the inspected object S. The display unit 19 is a display that displays a setting screen including fields for inputting the information, a screen showing the measurement results, etc.

[0020] The measurement control unit 16 includes an input receiving unit 161, a frequency control unit 162, a displacement calculation unit 163, a wavelength determination unit 164, a frequency selection unit 165, and a display processing unit 166. The measurement control unit 16 is embodied by hardware such as a CPU and software that executes each operation. Each unit (functional block) of the measurement control unit 16 will be described below.

[0021] The input receiving unit 161 receives information such as the type and size of the defect input by the user using the input unit 18 and transmits it to the frequency selecting unit 165 .

[0022] The frequency control unit 162 controls the frequency of the AC electric signal transmitted by the signal generator 11 to the vibrator 12, i.e., the frequency of the elastic waves excited in the object S to be inspected by the vibrator 12. When performing an operation to set a frequency appropriate for defect detection, the frequency of the AC electric signal (and thereby the frequency of the elastic waves excited in the object S to be inspected) is controlled to vary over a plurality of values ​​within a predetermined range during the operation. After a frequency is selected by the frequency selection unit 165 as described below, when performing measurements for defect detection, the frequency of the AC electric signal is set to the selected value.

[0023] The displacement calculation unit 163 performs an operation to determine the out-of-plane displacement at each point on the surface of the object S to be inspected based on the detection signals obtained from each detection element of the image sensor 155 using speckle shearing interference. When performing an operation to set a frequency appropriate for defect detection, the out-of-plane displacement at each point on the surface of the object S to be inspected is obtained for each obtained frequency (time) while the frequency of the elastic wave excited in the object S to be inspected is changed by the frequency control unit 162. When performing measurements for defect detection, the out-of-plane displacement at each point on the surface of the object S to be inspected is obtained at the frequency selected by the frequency selection unit 165.

[0024] The wavelength determination unit 164 determines the wavelength of the elastic wave excited in the object to be inspected S based on the out-of-plane displacement at each point on the surface of the object to be inspected S acquired by the displacement calculation unit 163 for each frequency when performing an operation to set an appropriate frequency for defect detection. The method for determining the wavelength will be described later.

[0025] The frequency selection unit 165 selects an appropriate frequency from the plurality of frequencies based on the wavelength of the elastic wave determined for each frequency by the wavelength determination unit 164 and the type and size of the defect expected to occur in the object S to be inspected, which is received by the input receiving unit 161, when setting an appropriate frequency for defect detection. For example, if the type of defect received by the input receiving unit 161 is a crack, the frequency selection unit 165 selects a frequency from the plurality of frequencies such that the wavelength determined by the wavelength determination unit 164 is no more than seven times the size of the defect received by the input receiving unit 161. If the type of defect is due to peeling of a paint film, the frequency selection unit 165 selects a frequency from the plurality of frequencies such that the wavelength determined by the wavelength determination unit 164 is no more than half the size of the defect. In both the case of a crack or peeling of a paint film, if there are multiple selected frequencies, it is preferable to select the frequency with the largest amplitude obtained based on the displacement for each measurement point obtained by the displacement calculation unit 163 as the appropriate frequency.

[0026] The display processing unit 166 performs processing to display on the display unit 19 a setting screen including fields for inputting information such as the type and size of defects, a screen showing measurement results, and the like. Examples of measurement results displayed on the display unit 19 include a two-dimensional map showing the distribution of out-of-plane displacement at each point on the surface of the object S to be inspected, using color shading or the like. When an operation to set a frequency appropriate for defect detection is performed, the measurement results may display only the measurement result at one frequency selected by the frequency selection unit 165, or may display measurement results obtained at multiple frequencies. In the former case, the user can visually use the out-of-plane displacement distribution displayed as the measurement result to find defects, for example, at locations where spatial discontinuities occur in the displacement distribution. In the latter case, it is preferable to highlight, among the multiple measurement results, those obtained at a frequency appropriate for defect detection.

[0027] The memory unit 17 stores measurement data such as the intensity values ​​of detection signals obtained from each detection element of the image sensor 155. In addition to or instead of the measurement data (raw data), the memory unit 17 may store values ​​indicating the displacement in the out-of-plane direction at each point on the surface of the object S to be inspected, calculated by the displacement calculation unit 163.

[0028] (2) Operation of the defect detection device and defect detection method of the first embodiment Next, the operation of the defect detection apparatus 10 and the defect detection method of this embodiment will be described with reference to the flowchart of FIG. 2 and the explanatory diagrams of FIGS.

[0029] First, the user places the object to be inspected S at a predetermined position in the defect detection device 10, and then brings the vibrator 12 into contact with the object to be inspected S. Then, when the user performs a predetermined operation using the input unit 18, a series of operations begins.

[0030] The display processing unit 166 displays an expected defect information input screen, which is a screen for inputting information about the type and size of defects expected to occur in the object to be inspected. The user inputs this information using the input unit 18 (step 1). FIG. 3 shows an example of the expected defect information input screen. The expected defect information input screen 30 in this example has a defect type input area 31 for inputting the type of expected defect and a defect size input area 32 for inputting the expected range of defect size. The defect type input area 31 displays multiple defect type candidates using a pull-down list, and the user selects one of these candidates by operating the mouse or touch panel of the input unit 18. The defect size input area 32 displays boxes for inputting the minimum and maximum values ​​of the expected defect's diameter, and the user inputs the minimum and maximum values ​​into these boxes using the keyboard or the like of the input unit 18. If the same value is input for the maximum and minimum values, a single value is set rather than a numerical range for the defect's diameter.

[0031] After completing the input of the type and size of the defect, when the user presses the OK button 33 in the assumed defect information input screen 30, the frequency control unit 162 calculates a plurality of frequencies f1, f2, ... f within a predetermined frequency range (20 kHz to 400 kHz in this embodiment, but not limited to this example) as follows: h (h is an integer of 2 or more) to sequentially transmit an AC electric signal having the frequency to the vibrator 12. Here, the signal generator 11 is controlled to transmit an AC electric signal having the frequency f1, f2, ...f h In the first embodiment, a predetermined value is used for (regardless of the shape, size, material, etc. of the object to be inspected S).

[0032] First, the frequency control unit 162 sets i=1 (step 2), and f i The signal generator 11 is controlled to transmit an AC electric signal of frequency f1 (in this case) to the oscillator 12. The oscillator 12 receives the AC electric signal from the signal generator 11 and converts it into a signal of frequency f2. f i The vibration of the vibrator 12 is transmitted to the object S to be inspected, and the vibration has a frequency f i An elastic wave having the following structure is excited in the object to be inspected S (step 3).

[0033] In this state, the following method is used to find different k max pieces(k max In the phase of k (3 or more), the out-of-plane displacement at each point on the surface of the object S to be inspected is measured. max The phases are calculated by dividing φ by an arbitrary initial value φ0 (for example, φ0=0). k =[φ0+2π(k-1) / k max ] (k=1~k max First, k is set to 1 (step 4), and the signal generator 11 transmits a pulse signal to the pulse laser light source 13 each time the phase of the elastic wave becomes φ1 = φ0. The pulse laser light source 13 repeatedly outputs illumination light, which is a pulse laser beam, each time it receives a pulse signal (strobe illumination). The diameter of this illumination light is expanded by the illumination lens 14, and the entire measurement area on the surface of the object S to be inspected is irradiated (step 5).

[0034] The illumination light is reflected from the surface of the object to be inspected S and enters the beam splitter 151 of the speckle shearing interferometer 15. A portion of the illumination light is reflected by the beam splitter 151, passes through the phase shifter 153, and then is reflected by the first reflecting mirror 1521. After passing through the phase shifter 153 again, a portion of the illumination light passes through the beam splitter 151 and enters the image sensor 155. The remainder of the illumination light that entered the beam splitter 151 passes through the beam splitter 151 and is reflected by the second reflecting mirror 1522, and a portion of the illumination light is reflected by the beam splitter 151 and enters the image sensor 155. In the image sensor 155, the illumination light reflected from many points on the surface of the object to be inspected S is detected by different detection elements.

[0035] While the illumination light, which is a pulsed laser beam, is repeatedly output, the phase shifter 153 changes (shifts) the phase of the illumination light passing through the phase shifter 153 (i.e., the illumination light reflected at point A). This changes the phase difference between the illumination light reflected at point A and the illumination light reflected at point B. During this change, each detection element of the image sensor 155 detects the interference light resulting from the interference of these two illumination lights, and calculates its intensity (step 6). The upper part of Figure 4 shows a graph of an example of the amount of phase shift by the phase shifter 153 and the intensity of the interference light detected by the detection elements of the image sensor 155 when the oscillation phase of the oscillator 12 is φ1. Note that in Figure 4, the relationship in which the detected intensity varies sinusoidally with the amount of phase shift is shown by a continuous curve, but what is actually observed is discrete data, and a continuous sinusoidal waveform is reproduced from the observed data using the least squares method or the like. To do this, it is necessary to detect intensities at at least three different amounts of phase shift.

[0036] These steps 5 and 6 are performed for k=2 to k max (After determining No in step 7, increase the value of k by 1 in step 8, and then execute steps 5 and 6.) For example, if k maxIn the case of k = 3, when k = 2, the signal generator 11 transmits a pulse signal to the pulse laser light source 13 at each timing when the phase of the elastic wave becomes φ2 = φ0 + 2π / 3, and when k = 3, the signal generator 11 transmits a pulse signal to the pulse laser light source 13 at each timing when the phase of the elastic wave becomes φ3 = φ0 + 4π / 3, thereby repeatedly irradiating the entire measurement area on the surface of the object S to be inspected with illumination light, and during this time, the phase shifter 153 shifts the phase of the irradiated light passing through it, while each detection element of the image sensor 155 detects the intensity of the interference light. max 4 shows an example of the relationship between the amount of phase shift and the intensity of interference light when the phase of vibration of the vibrator 12 is φ2 (middle part of FIG. 4) and φ3 (lower part of FIG. 4) in the case of φ=3.

[0037] As above, k=1~k max After executing the operations of steps 5 and 6 in each of the above (determined as YES in step 7), the phases φ1 to φ of each vibration are calculated for each detection element of the image sensor. kmax The maximum output phase shift amounts Δφ1 to Δφ at which the output of the detection element is maximized while the phase shift amount by the phase shifter 153 is changed are respectively kmax Then, based on that, calculate the difference in maximum output phase shift between different phases. For example, k max When δφ=3, the differences between the three maximum output phase shift amounts (δφ2-δφ1), (δφ3-δφ2), and (δφ1-δφ3) are obtained. These differences in the maximum output phase shift amounts indicate the relative displacement in the out-of-plane direction between point A and point B, with three or more sets of data for which the vibration phase of vibrator 12 is different (i.e., different times). Based on these three or more sets of relative displacements, the values ​​of three parameters that indicate the vibration state of object S to be inspected, namely, the vibration amplitude, vibration phase, and vibration center value (DC component) at each point in the measurement area, are obtained (step 9, which corresponds to the frequency-specific vibration state acquisition step).

[0038] With these three parameters, the vibration state at each point can be accurately reproduced. For example, as shown in FIG. 5, an image of the elastic wave formed in the measurement area on the surface of the object S to be inspected can be generated. The wavelength determination unit 164 performs image analysis based on this image of the elastic wave to determine the frequency f i The wavelength of the elastic wave (at this point f1) is determined (step 10, which corresponds to the step of obtaining wavelengths by frequency).

[0039] At this point, the value of i has not reached the maximum value h (NO in step 11), so the value of i is incremented by 1 (step 12), and the frequency f is obtained by performing steps 3 to 10. i The operation of determining the wavelength and amplitude of the elastic wave f1 to f2 is repeated until i=h. After performing the operations of steps 3 to 10 when i=h (YES in step 11), the frequency selection unit 165 determines the wavelength and amplitude of the elastic wave f1 to f2 determined by the wavelength determination unit 164. h Based on the wavelength of the elastic wave at each frequency and the type and size of the defect received by the input receiving unit 161, h From the above, an appropriate frequency is selected (step 13, which corresponds to the frequency selection step). As described above, if the type of defect expected is a crack, the frequency with the maximum amplitude is selected from among elastic waves having a wavelength that is 7 times or less the size of the expected defect. Also, if the type of defect expected is due to peeling of the paint film, the frequency with the maximum amplitude obtained in step 9 should be selected from among elastic waves having a wavelength that is 1 / 2 times or less the size of the expected defect.

[0040] After the frequency is selected in this manner, the display processing unit 166 performs processing to display on the display unit 19 an image of the elastic waves formed in the measurement region on the surface of the object to be inspected S, obtained at the selected frequency, i.e., a frequency appropriate for defect detection, together with the numerical value of the selected frequency (step 14). The user visually inspects this image of the elastic waves, and if there are any locations where the waveform of the elastic wave differs from the surroundings or where the spatial change of the waveform is discontinuous, it can be determined that defects exist in those locations. Alternatively, defects may be detected by performing image analysis on the displayed image, and symbols or the like indicating the locations where defects have been detected may be superimposed on the image.

[0041] The above operations complete the operation of the defect detection device 10 of this embodiment and the defect detection method of this embodiment.

[0042] When measurements are to be performed on multiple objects to be inspected that have the same type and size of expected defects, and that are made of the same material, have the same shape, and are of approximately the same size (described below), the above steps 1 to 14 are performed only when measuring the first object to be inspected, and measurements of the second and subsequent objects to be inspected are performed at the frequency selected for the first measurement.

[0043] According to the defect detection device 10 and the defect detection method of this embodiment, by selecting a frequency based on the wavelengths acquired by the wavelength determination unit 164 for multiple frequencies and the type and size of the defect expected to occur in the inspected object S, it is possible to set a frequency appropriate for defect detection according to the expected type and size of the defect.

[0044] (3) Defect detection device and method according to the second embodiment 6 shows a defect detection apparatus 20 according to another embodiment of the present invention. This defect detection apparatus 20 includes a measurement control unit 26 having a functional block different from the measurement control unit 16 in the defect detection apparatus 10 of the first embodiment. Since the configuration other than the measurement control unit 26 is the same as the configuration of the defect detection apparatus 10 of the first embodiment, detailed description thereof will be omitted.

[0045] The measurement control unit 26 includes an inspected object information input receiving unit 2611, a suspected defect information input receiving unit 2612, a frequency candidate determination unit 2621, a frequency control unit 2622, a displacement calculation unit 263, a wavelength determination unit 264, a frequency selection unit 265, and a display processing unit 266.

[0046] The inspection object information input receiving unit 2611 receives parameters relating to the shape, material, and size of the inspection object input by the user using the input unit 18. Shapes of the inspection object include plate-like, bulk-like, tubular, etc., which are displayed as a list on the display unit 19 and the user selects one using the input unit 18. As for the material of the inspection object, various materials such as iron and concrete are displayed as a list on the display unit 19 and the user selects one using the input unit 18. As for the size of the inspection object, if the shape is plate-like, at least the thickness value is input, and if the shape is tubular, at least the outer diameter and inner diameter (or either the outer diameter or the inner diameter and the wall thickness) are input.

[0047] The assumed defect information input receiving unit 2612 receives the type and size of an assumed defect input by the user using the input unit 18, similar to the input receiving unit 161 in the defect detection apparatus 10 of the first embodiment.

[0048] The frequency candidate determination unit 2621 determines a range of frequencies estimated to be suitable 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 receiving unit 2611, and the type and size of the expected defect received by the expected defect information input receiving unit 2612, and determines multiple frequency candidates within that range.

[0049] Specifically, the sound velocity of the elastic waves generated in the object S to be inspected is determined based on the shape and material of the object S to be inspected, and a wavelength range estimated to be suitable for defect detection is determined based on the type and size of the expected defect. Then, the frequency range estimated to be suitable for defect detection can be determined from the sound velocity and wavelength range of the elastic waves. When determining multiple candidate frequencies within the frequency range, it is advisable to determine the resonant frequency of the vibrator as the candidate. This allows the frequency that generates a large amplitude due to resonance in the measurement system to be finally selected, making defect detection easier.

[0050] The acoustic velocity of elastic waves can be calculated, for example, as follows. When the shape of the object S to be inspected is plate-shaped, the acoustic velocity (phase velocity) of elastic waves is calculated by solving an equation called the Rayleigh-Lamb frequency equation in a vibration mode called the A0 mode, in which the phase of out-of-plane vibration is the same on both the front and back surfaces. In this case, the acoustic velocity of longitudinal waves and the acoustic velocity of shear waves (hereinafter simply referred to as "longitudinal wave acoustic velocity" and "shear wave acoustic velocity"), which are determined by the material of the object S to be inspected without taking the shape into consideration, and the thickness of the plate are used as parameters. When the shape of the object S to be inspected is blocky, the phase velocity is calculated using the longitudinal wave acoustic velocity and the shear wave acoustic velocity in the Rayleigh-Lamb frequency equation, assuming the plate thickness to be infinite. When the shape of the object S to be inspected is tubular, the phase velocity of elastic waves is calculated by solving an equation called the Gazis frequency equation in a vibration mode called the F mode, in which the tube vibrates in one of the radial directions. In this case, the acoustic velocity of longitudinal waves, the acoustic velocity of shear waves, and the outer and inner diameters of the tube are used as parameters.

[0051] The frequency control unit 2622, the displacement calculation unit 263, the wavelength determination unit 264, and the frequency selection unit 265 are similar to the frequency control unit 162, the displacement calculation unit 163, the wavelength determination unit 164, and the frequency selection unit 165 in the defect detection device 10 of the first embodiment.

[0052] Similar to the display processing unit 166 in the defect detection apparatus 10 of the first embodiment, the display processing unit 266 performs processing for displaying a setting screen, a screen showing measurement results, and the like on the display unit 19. However, the display processing unit 266 of this embodiment displays a field for inputting information such as the type and size of a defect on the setting screen, as well as a field for inputting parameters related to the shape, material, and size of the object to be inspected. FIG. 7 shows an example of an input screen. In this example, an input screen 40 has, in addition to a defect type input area 31 and a defect size input area 32, an object shape input area 41 for inputting the shape of the object to be inspected S, an object material input area 42 for inputting the material of the object to be inspected S, and an object size input area 43 for inputting the size of the object to be inspected S.

[0053] The operation of the defect detection apparatus 20 of the second embodiment is shown in the flowchart of Fig. 8. In Fig. 8, the same step numbers are assigned to steps that perform the same operations as those in the flowchart of Fig. 2, which shows the operation of the defect detection apparatus 10 of the first embodiment.

[0054] When the user places the object S to be inspected at a predetermined position of the defect detection device 20, brings the vibrator 12 into contact with the object S to be inspected, and performs a predetermined start operation using the input unit 18, the display processing unit 266 displays the input screen shown in Fig. 7. Using the input unit 18, the user inputs information on the shape, material, and size of the object to be inspected, as well as the type and size of the expected defect (step 21).

[0055] The frequency candidate determination unit 2621 determines a frequency range estimated to be suitable for defect detection by the above-mentioned method based on the shape, material, and size of the object to be inspected S received by the object to be inspected information input receiving unit 2611 and the type and size of the expected defect received by the expected defect information input receiving unit 2612, and determines a plurality of frequency candidates f within the range. i =f1, f2, …f h (Step 22).

[0056] After executing step 22, step 2By performing the operations of 1 to 14, an image of the elastic wave formed in the measurement area on the surface of the object S to be inspected is obtained at an appropriate frequency. Here, in the operations repeatedly performed in steps 2 to 12 within the range of i = 1 to h, the multiple frequency candidates f obtained in step 22 are used. i =f1, f2, …f h The wavelength and amplitude of the elastic wave are calculated using the formula: This makes it possible to select a more appropriate frequency from among candidates that are assumed to be appropriate frequencies, which are determined according to the shape, material, and size of the object to be inspected.

[0057] (4) Modifications The present invention is not limited to the above-described embodiment, and various modifications are possible.

[0058] For example, in each of the above embodiments, in order to accurately reproduce the vibration state at each point on the surface of the object S to be inspected, three or more different points (k max In this example, the out-of-plane displacement of each point was measured at three or more phases, but because it is possible to determine the wavelength and amplitude of the elastic wave even if the accuracy is not very high, the out-of-plane displacement of each point may be measured at only one or two phases. In this case, as in the above embodiment, the image of the elastic wave obtained by the measurement performed to select the frequency may be used as an image for defect detection as is. However, in order to detect defects accurately, after the processing of step 13, an operation may be performed to measure the out-of-plane displacement of the elastic wave having the selected frequency at three or more different phases, and then an image of the elastic wave for defect detection may be obtained.

[0059] In the above embodiments, only the image of the elastic wave at the selected frequency is displayed, but it is also possible to display images of elastic waves at a plurality of frequencies whose wavelength and / or amplitude satisfy a predetermined condition, and then the user can select one of the images to determine the frequency. For example, the wavelength of the elastic wave may be 7 times or less (in the case of a crack) or 1 / 2 times or less (in the case of a paint) the size of the expected defect. filmIt is conceivable to display all images of elastic waves that satisfy the requirements of "in the case of peeling" regardless of the amplitude. Alternatively, images of elastic waves at all frequencies measured may be displayed and then the user may select one.

[0060] In the above embodiments, a speckle shearing interferometer is used as the measurement unit, but other optical measurement devices may also be used as the measurement unit. For example, a speckle interferometer using the above-mentioned speckle interferometry may be used as the measurement unit in the present invention. Alternatively, a scanning laser Doppler vibrometer may be used as the measurement unit.

[0061] [Aspect] It will be apparent to those skilled in the art that the above-described exemplary embodiments are examples of the following aspects.

[0062] (Section 1) The defect detection device according to paragraph 1 is an input receiving unit that receives information input by a user about the type and size of defects that are expected to occur in the object to be inspected; an excitation unit for exciting elastic waves in the object to be inspected, the frequency of the elastic waves being variable; a measuring unit that measures the vibration state of the surface of the object to be inspected caused by the elastic waves by optical means; a wavelength determination unit that determines the wavelength of the elastic wave excited in the object to be inspected from the vibration state acquired by the measurement unit; a frequency selection unit that selects an appropriate frequency from the plurality of frequencies based on the wavelengths that the wavelength determination unit has acquired 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 that have been received by the input reception unit; and Equipped with.

[0063] (Section 5) The defect detection method according to paragraph 5 is a frequency-specific vibration state acquisition step of exciting an elastic wave in the object to be inspected, and measuring the vibration state of the surface of the object to be inspected caused by the elastic wave by optical means while changing the frequency of the elastic wave, thereby acquiring the vibration state of the object to be inspected at a plurality of frequencies; a frequency-specific wavelength acquisition step of acquiring, for each of the plurality of frequencies, a wavelength of an elastic wave excited in the object to be inspected from the vibration state acquired in the frequency-specific vibration state acquisition step; a frequency selection step of selecting an appropriate frequency from the plurality of frequencies based on the wavelengths acquired for each of the plurality of frequencies and the type and size of a defect assumed to have occurred in the object to be inspected; It has.

[0064] According to the defect detection device of the first aspect and the defect detection method of the fifth aspect, by changing the frequency of the elastic wave excited by the excitation unit and selecting a frequency based on the wavelengths acquired by the wavelength determination unit for a plurality of frequencies and the type and size of a defect expected to occur in the object to be inspected, it is possible to set a frequency appropriate for defect detection according to the expected type and size of the defect.

[0065] Here, types of defects include cracks that have occurred on the object to be inspected, peeling paint, etc. The defect size input by the user may be an approximate numerical value, and may be input as a single numerical value or as a numerical range. When a single numerical value is input as the defect size, it is desirable to select a frequency based on a numerical range having a predetermined magnitude that includes that numerical value. The frequency appropriate for defect detection can be determined, for example, by multiplying the upper and lower limits of the range of expected defect sizes by coefficients determined depending on the expected type of defect, to determine a frequency range, and then selecting a frequency included in that frequency range from among multiple frequencies at which the measured amplitude peaks.

[0066] (Section 2) The defect detection device according to paragraph 2 is the defect detection device according to paragraph 1, moreover, an inspection object information input receiving unit that receives information on the shape, material, and size of the inspection object input by a user; a frequency candidate determination unit that determines a plurality of frequency candidates based on the shape, material, and size of the object to be inspected that are received by the object to be inspected information input reception unit, and the type and size of the expected defect that are received by the input reception unit; Equipped with 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 frequency candidates, and the type and size of the defect received by the input receiving unit.

[0067] (Section 3) The defect detection device according to paragraph 3 is the defect detection device according to paragraph 2, The frequency candidate determination unit determines the sound speed in the object to be inspected based on the shape, material, and size of the object to be inspected, and then determines multiple frequencies at which elastic waves are expected to be excited based on the sound speed and the size of the object to be inspected as candidates for the multiple frequencies.

[0068] (Section 4) The defect detection device according to paragraph 4 is a defect detection device according to paragraph 2 or 3, the excitation unit has a vibrator that applies vibration to the object to be inspected, The frequency candidate determination unit determines the resonant frequency of the vibrator as one or more of the plurality of frequency candidates.

[0069] According to the defect detection device of the second paragraph, the frequency candidate determination unit determines the multiple frequency candidates selected by the frequency selection unit based on the shape, material, and size of the object to be inspected, as well as the type and size of the anticipated defect, thereby enabling defects to be detected using more appropriate frequencies. In this case, the defect detection device of the third paragraph calculates the sound speed in the object to be inspected based on the shape, material, and size of the object, and then determines multiple frequencies at which elastic waves are expected to be excited based on the sound speed and the size of the object to select the optimal frequency from the frequency candidates that are expected to facilitate defect detection because the formation of elastic waves increases their amplitude. Furthermore, in the defect detection device of the fourth paragraph, the resonant frequency of the vibrator of the excitation unit is determined as one or more of the multiple frequency candidates (here, "multiple" may refer to all or some of the multiple frequency candidates), thereby selecting frequencies at which resonance occurs in the measurement system and increases the amplitude, facilitating defect detection. [Explanation of symbols]

[0070] 10, 20... Defect detection device 11...Signal generator 12...Oscillator 13...Pulse laser light source 14...Illumination lens 15...Speckle shearing interferometer (measurement unit) 151...Beam splitter 1521…1st reflector 1522…Second reflector 153...Phase shifter 154...Condenser lens 155...Image sensor 16, 26...Measurement control section 161...input reception section 162, 2622...Frequency control section 163, 263...Displacement calculation section 164, 264...Wavelength determination section 165, 265... frequency selection section 166, 266...Display processing unit 17...Storage section 18...Input section 19...Display section 2611...inspection object information input reception unit 2612…Expected defect information input reception section 2621...Frequency candidate determination unit 30...Expected defect information input screen 31...Defect type input area 32...Defect size input area 33...OK button 40...Input screen 41...Inspection object shape input area 42...Inspection object material input area 43...Inspection object size input area

Claims

1. an input receiving unit that receives information input by a user about the type and size of defects that are expected to occur in the object to be inspected; an excitation unit for exciting elastic waves in the object to be inspected, the frequency of the elastic waves being variable; a measuring unit that measures the vibration state of the surface of the object to be inspected caused by the elastic waves by optical means; a wavelength determination unit that determines the wavelength of the elastic wave excited in the object to be inspected from the vibration state acquired by the measurement unit; a frequency selection unit that selects an appropriate frequency from the plurality of frequencies based on the wavelengths that the wavelength determination unit has acquired 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 that have been received by the input reception unit; A defect detection device comprising:

2. moreover, an inspection object information input receiving unit that receives information on the shape, material, and size of the inspection object input by a user; a frequency candidate determination unit that determines a plurality of frequency candidates based on the shape, material, and size of the object to be inspected that are received by the object to be inspected information input reception unit, and the type and size of the expected defect that are received by the input reception unit; Equipped with the frequency selection unit selects an appropriate frequency from the plurality of frequencies based on the wavelength acquired by the wavelength determination unit for each of the plurality of frequency candidates and the type and size of the defect accepted by the input acceptance unit. The defect detection device according to claim 1 .

3. 3. The defect detection device of claim 2, wherein the frequency candidate determination unit determines the sound speed in the object to be inspected based on the shape, material, and size of the object to be inspected, and then determines multiple frequencies at which elastic waves are expected to be excited based on the sound speed and the size of the object to be inspected as candidates for the multiple frequencies.

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

5. a frequency-specific vibration state acquisition step of exciting an elastic wave in the object to be inspected, and measuring the vibration state of the surface of the object to be inspected caused by the elastic wave by optical means while changing the frequency of the elastic wave, thereby acquiring the vibration state of the object to be inspected at a plurality of frequencies; a frequency-specific wavelength acquisition step of acquiring, for each of the plurality of frequencies, a wavelength of an elastic wave excited in the object to be inspected from the vibration state acquired in the frequency-specific vibration state acquisition step; a frequency selection step of selecting an appropriate frequency from the plurality of frequencies based on the wavelengths acquired for each of the plurality of frequencies and the type and size of a defect assumed to have occurred in the object to be inspected; A defect detection method comprising:

Images