JP2018044881A - Crack inspection apparatus and crack inspection method - Google Patents

Abstract

A crack inspection apparatus and a crack inspection method with high inspection efficiency are provided. A crack inspection apparatus (1) measures a temperature distribution of a laser optical system (10) capable of irradiating a laser beam (L1) to different positions on the inspection object (S) and the inspection object (S) irradiated with the laser beam (L1). Measuring means. [Selection] Figure 1

Description

  Embodiments relate to a crack inspection apparatus and a crack inspection method.

  Conventionally, the presence or absence of cracks in a ceramic substrate has been inspected by image processing of photographs taken with a microscope. However, with this method, it is difficult to detect fine cracks or cracks generated inside the ceramic substrate. Therefore, a technique has been proposed in which cracks are detected by forming a temperature gradient in the ceramic substrate in the process of uniformly heating and then cooling the ceramic substrate, and detecting discontinuous lines of the temperature gradient. However, in this method, since the entire ceramic substrate is heated and then cooled, the inspection efficiency is low.

JP 2011-203163 A

  An object of the embodiment is to provide a crack inspection apparatus and a crack inspection method with high inspection efficiency.

  The crack inspection apparatus according to the embodiment includes a laser optical system capable of irradiating laser beams to mutually different positions on the object to be inspected, and measuring means for measuring a temperature distribution of the object to be inspected irradiated with the laser beam. Prepare.

  In the crack inspection method according to the embodiment, a step of irradiating a first position of an inspection object with a laser beam and measuring a temperature distribution of the inspection object; and a first position of the inspection object with a laser beam. Irradiating different second positions and measuring a temperature distribution of the object to be inspected.

It is a block diagram which shows the crack inspection apparatus which concerns on 1st Embodiment. (A)-(c) is a figure which shows the principle of the crack inspection method which concerns on 1st Embodiment. (A) And (b) is a figure which shows the principle of the crack inspection method which concerns on 1st Embodiment. (A)-(c) is a figure which shows the irradiation area | region of the laser beam in 1st Embodiment, (d) is the figure which superimposed (a)-(c). (A) And (b) is a figure which shows a to-be-inspected object, (a) shows a non-defective product, (b) shows a defective product. (A) And (b) is a figure which shows the measurement result of the temperature distribution of a to-be-inspected object, (a) shows a non-defective product, (b) shows a defective product. (A) And (b) is a graph which shows the differential value of temperature distribution, taking the value in which the position in the to-be-inspected object was taken on the horizontal axis, and the temperature was differentiated with respect to the position on the vertical axis. (B) shows a defective product, (c) shows the discontinuity of temperature distribution, with the horizontal axis representing the position on the object to be inspected and the vertical axis representing the absolute value of the differential value of the temperature. It is a graph which shows a line. It is a block diagram which shows the crack inspection apparatus which concerns on 2nd Embodiment. It is a block diagram which shows the crack inspection apparatus which concerns on 3rd Embodiment.

(First embodiment)
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, the first embodiment will be described.
FIG. 1 is a block diagram showing a crack inspection apparatus according to the present embodiment.

  As shown in FIG. 1, in the crack inspection apparatus 1 according to the present embodiment, a laser optical system 10 is provided. In the laser optical system 10, a laser light source 11, an optical element 12, and a rotation mechanism 13 are provided. The laser light source 11 is, for example, an infrared laser or QCL (Quantum Cascade Laser), and emits one laser beam L1. The optical element 12 is, for example, a DOE (Diffractive Optical Element), diffracts the laser beam L1 emitted from the laser light source 11, and branches it into a plurality of laser beams L2. The rotation mechanism 13 is an emission direction changing unit that changes the emission direction of the laser beam L2 by rotating the optical element 12.

  In the crack inspection apparatus 1, a holder 20 made of a heat insulating material is provided. The holder 20 holds the inspection object S at a position where a plurality of laser beams L2 are irradiated by the laser optical system 10. As a result, the laser optical system 10 can irradiate the laser beam L2 to different positions on the inspection object S. The inspected object S is, for example, a ceramic substrate, for example, a silicon nitride (SiN) substrate or a carbon (C) substrate used for a fuel cell.

  In the crack inspection apparatus 1, an infrared thermography 30 is provided as a measuring means. The infrared thermography 30 measures the temperature distribution of the inspection object S and images it. In the present embodiment, the infrared thermography 30 is disposed on the opposite side of the surface of the object S to be irradiated with the laser beam L2. In other words, the laser optical system 10 and the infrared thermography 30 are arranged at positions that sandwich the object S to be inspected.

  In the crack inspection apparatus 1, a control unit 40 is provided. The control unit 40 receives image data indicating the temperature distribution from the infrared thermography 30 and controls the laser light source 11 and the rotation mechanism 13. The control unit 40 may be connected to input / output means such as a display, a keyboard, and a touch panel, or may be connected to a server or the like via a network.

  In the crack inspection apparatus 1, a processing unit 50 is provided. The processing unit 50 receives image data from the control unit 40, performs image processing, detects a crack, and outputs the detection result to the control unit 40. Details of the image processing will be described later.

Next, the operation of the crack inspection apparatus according to this embodiment, that is, the crack inspection method according to this embodiment will be described.
First, the principle of the crack inspection method according to this embodiment will be described.
FIGS. 2A to 2C, FIGS. 3A and 3B are diagrams illustrating the principle of the crack inspection method according to the present embodiment.

  As shown in FIG. 2A, in the present embodiment, a laser beam is irradiated to a part of the inspection object S. As a result, the inspection object S is locally heated in the laser beam irradiation region R, and a temperature distribution is formed around it. At this time, if the crack C exists in the inspection object S, the thermal conductivity is low because there is an air layer in the crack C, and heat is not easily transmitted beyond the crack C. For this reason, in the crack C, temperature distribution becomes discontinuous. Therefore, by measuring the temperature distribution of the inspection object S, the crack C can be detected as a discontinuous line of the temperature distribution.

  However, as shown in FIG. 2B, when the laser beam irradiation region R straddles the crack C, both sides of the crack C in the inspection object S are heated, so that a discontinuous line in the temperature distribution is detected. It becomes difficult to do. In addition, as shown in FIG. 2C, when the laser beam is irradiated to the two regions R of the inspection object S, if the crack C is located near the midpoint between the two irradiation regions R, the crack Since the temperatures on both sides of C are substantially equal, discontinuous lines are difficult to detect.

  For this reason, in this embodiment, laser beam irradiation and temperature distribution measurement are performed a plurality of times, and the irradiation position of the laser beam on the inspection object S is varied for each irradiation. That is, as shown in FIG. 3A, in the first irradiation, it is assumed that the crack C1 overlaps the laser beam irradiation region R and the crack C2 is positioned near the midpoint between the two irradiation regions R. In this case, the cracks C1 and C2 are difficult to detect.

  However, as shown in FIG. 3B, in the second irradiation, when the position of the irradiation region R of the laser beam is changed with respect to the first irradiation, the irradiation region R is positioned in the vicinity of the cracks C1 and C2. there's a possibility that. In this case, cracks C1 and C2 are easily detected.

  Even in the second irradiation, there is a possibility that the crack is difficult to be detected depending on the positional relationship between the irradiation region R and the crack. In this case, the laser beam irradiation may be repeated further. Thereby, the probability that a crack is not detected decreases.

Hereinafter, the crack inspection method according to the present embodiment will be specifically described.
FIGS. 4A to 4C are diagrams showing laser beam irradiation regions in the present embodiment, and FIG. 4D is a diagram in which (a) to (c) are superimposed.

  First, as shown in FIG. 1, the inspection object S is mounted on the holder 20. Next, the control unit 40 controls the rotation mechanism 13 so that the diffraction grating of the optical element 12 has a predetermined orientation. Further, the control unit 40 controls the infrared thermography 30 and starts measuring the temperature distribution of the inspection object S.

  In this state, the control unit 40 controls the laser light source 11 and causes the laser light source 11 to emit one laser beam L1. The laser beam L1 enters the optical element 12 and is diffracted.

  At this time, as shown in FIG. 4A, for example, when the optical element 12 is an orthogonal diffraction grating, the irradiation region R1 of the laser beam L2 is dispersed in a matrix along two directions orthogonal to each other. . The infrared thermography 30 measures the temperature distribution of the inspection object S during irradiation with the laser beam L2, and outputs the measurement result to the control unit 40 as image data. Thereafter, the control unit 40 causes the laser light source 11 to stop emitting the laser beam L1.

  The control unit 40 outputs the image data input from the infrared thermography 30 to the processing unit 50. The processing unit 50 processes the image data and detects discontinuous lines in which the temperature distribution changes discontinuously. And it determines with a crack in the position where this discontinuous line appeared. In this way, the first measurement is performed.

  Next, the control unit 40 controls the rotation mechanism 13 to rotate the optical element 12. When the diffraction grating of the optical element 12 is n-fold symmetric (n is an integer of 2 or more), the rotation angle of the optical element 12 is set to an angle other than (360 / n) °. In the present embodiment, since the diffraction grating of the optical element 12 is four-fold symmetric, the rotation angle of the optical element 12 is set to an angle other than 90 °, for example, 60 °. Then, the laser light source 11 emits the laser beam L1.

  Accordingly, as shown in FIG. 4B, the irradiation region R2 of the laser beam L2 is dispersed in a matrix rotated by 60 ° with respect to the first irradiation region R1. As a result, most of the irradiation region R2 does not overlap with the irradiation region R1. In this state, the infrared thermography 30 measures the temperature distribution of the inspection object S. Thereafter, the emission of the laser beam L1 is stopped. The control unit 40 outputs the image data input from the infrared thermography 30 to the processing unit 50, and the processing unit 50 performs image processing to determine the presence or absence of a crack. In this way, the second measurement is performed.

  Next, the control unit 40 controls the rotation mechanism 13 to further rotate the optical element 12. The rotation angle at this time is also set to 60 °, for example. Then, the laser light source 11 emits the laser beam L1. The laser beam L1 is diffracted by the optical element 12, and is irradiated onto the irradiation region R3 in the inspection object S as shown in FIG. The irradiation region R3 is dispersed in a matrix rotated by 60 ° with respect to the second irradiation region R2, and most of the irradiation region R3 does not overlap with the irradiation regions R1 and R2. In this state, the infrared thermography 30 measures the temperature distribution of the inspection object S, and the processing unit 50 determines the presence or absence of cracks. In this way, the third measurement is performed.

  As shown in FIG. 4D, the irradiation regions R1, R2, and R3 are partially different from each other, but are distributed so as to be different from each other. Thereby, it can be reliably detected wherever the crack is. In this embodiment, the position of the irradiation region is changed by rotating the optical element 12, but the position of the irradiation region is changed by translating or tilting the optical element 12. Also good. Further, as the optical element 12, a diffraction grating other than the orthogonal diffraction grating may be used. For example, a hexagonal close-packed lattice may be used. An optical element other than the diffraction grating may be used as long as it is an optical element that branches one laser beam into a plurality of laser beams.

  The output of the laser beam L1 and the diameter and interval of the irradiation region R may be determined according to the characteristics of the inspection object S. For example, the interval between the irradiation regions R is larger than the width of the crack C. For example, when the object to be inspected S is a silicon nitride (SiN) substrate, the width of the crack C is, for example, about 10 to 20 μm, so that the distance between the adjacent irradiation regions R is set to be greater than 20 μm. Further, the output of the laser beam L1 and the energy density of the laser beam L2 are high enough to obtain a temperature distribution suitable for detecting the crack C, and low enough not to alter or destroy the object S to be inspected.

  Further, the output of the laser beam L1 and the distribution of the irradiation region R are also restricted by the relationship between the way heat is transmitted in the inspection object S and the imaging frame rate of the infrared thermography 30. That is, if the time for which heat input to one irradiation region R is transmitted to the midpoint between the adjacent irradiation regions R is too short compared to the frame rate of the infrared thermography 30, a temperature distribution suitable for detection of the crack C is obtained. The infrared thermography 30 may be missed. On the other hand, if the heat transfer time is too long compared to the frame rate, the inspection efficiency decreases.

Next, a specific example of a method for detecting a crack from the temperature distribution of the inspection object S will be described.
5 (a) and 5 (b) are diagrams showing the object to be inspected, where (a) shows a non-defective product and (b) shows a defective product.
FIGS. 6A and 6B are diagrams showing measurement results of the temperature distribution of the object to be inspected. FIG. 6A shows a non-defective product and FIG. 6B shows a defective product.
In FIGS. 6A and 6B, the white area has the highest temperature, the black area has the lowest temperature, and the gray area has a higher temperature in a color area closer to white.
FIGS. 7A and 7B are graphs showing differential values of the temperature distribution, with the horizontal axis representing the position on the object to be inspected and the vertical axis representing the temperature differentiated by the position. ) Shows a non-defective product, (b) shows a defective product, (c) shows the temperature distribution of the temperature distribution with the horizontal axis representing the position on the object to be inspected and the vertical axis representing the absolute value of the differential value of the temperature. It is a graph which shows a discontinuous line.
7A shows values along the line AA ′ shown in FIG. 6A, and FIG. 7B shows values along the line BB ′ shown in FIG. 6B. Show.

  As shown in FIG. 5A, it is assumed that the non-defective inspection object S has no cracks. On the other hand, as shown in FIG. 5 (b), it is assumed that the defective inspection object S has a crack C. In the actual inspection, it is unclear whether or not the inspection object S to be inspected has a crack C before the inspection, but in this specific example, the inspection object S to be inspected is for convenience of explanation. A case where the product is a defective product and is compared with a non-defective product S as a standard sample will be described.

  As shown in FIG. 6A, the temperature distribution of the non-defective product S to be inspected shows a maximum value in the irradiation region R of the laser beam and decreases as the distance from the irradiation region R decreases, but the temperature change is continuous. . On the other hand, as shown in FIG. 6B, the temperature distribution of the defective inspected object S changes discontinuously at the position of the crack C (see FIG. 5B). That is, a discontinuous line appears in the temperature distribution of the inspected object S that is defective.

  As shown in FIG. 7A, when the differential value of temperature is calculated along the A-A ′ line for a non-defective inspected object S, the absolute value of the differential value remains within a low range. On the other hand, when the differential value of the temperature is calculated along the line B-B ′ for the inspected object S that is a defective product, the absolute value of the differential value protrudes and increases at the position of the crack C.

  As shown in FIG. 7C, when calculating the absolute value of the difference between the temperature differential value shown in FIG. 7A and the temperature differential value shown in FIG. Become clear. As illustrated in FIG. 7C, the processing unit 50 determines that there is a crack C at a position U where the absolute value of the temperature differential value exceeds the reference value T.

  In the present embodiment, an example is shown in which the absolute value of the difference between the temperature distribution of the non-defective product and the temperature distribution of the defective product is calculated and then the absolute value of the difference is calculated. However, the present invention is not limited to this. For example, a difference image between an image showing a temperature distribution of a non-defective product and an image showing a temperature distribution of a defective product may be obtained, and an absolute value of a differential value of the difference image may be obtained.

Next, the effect of this embodiment will be described.
In this embodiment, the inspected object S is locally heated by irradiating a laser beam, and a discontinuous line in the temperature distribution is detected. Thereby, compared with the case where it cools after heating the whole to-be-inspected object S, the test | inspection of a crack can be performed in a short time. For this reason, the crack inspection method according to the present embodiment is highly efficient.

  Further, in the present embodiment, the temperature distribution is measured a plurality of times by changing the irradiation area of the laser beam on the inspection object S. Thereby, there is a high probability that the irradiation region R of the laser beam is in a positional relationship in which the discontinuous line of the temperature distribution is easily detected with respect to the crack C. As a result, the crack C can be detected with high accuracy.

  Further, in the present embodiment, the laser beam L1 emitted from the laser light source 11 is branched into a plurality of laser beams L2 by the optical element 12, and the object S is irradiated. Thereby, the whole inspection object S can be inspected at a time, and the inspection efficiency is high.

  Furthermore, in the present embodiment, the infrared thermography 30 is disposed on the opposite side of the laser optical system 10 when viewed from the inspection object S. Thereby, the infrared thermography 30 can be arrange | positioned in front of the to-be-inspected object S, and the focus of the infrared thermography 30 can be adjusted to the whole to-be-inspected object S accurately. As a result, the measurement accuracy of the temperature distribution is high.

(Second Embodiment)
Next, a second embodiment will be described.
FIG. 8 is a block diagram showing a crack inspection apparatus according to the present embodiment.

  As shown in FIG. 8, in the crack inspection apparatus 2 according to the present embodiment, the infrared thermography 30 is disposed on the same side as the laser optical system 10 when viewed from the inspection object S.

  According to the present embodiment, the infrared thermography 30 measures the temperature distribution on the surface of the inspection object S irradiated with the laser beam. For this reason, even if a thick object is used as the inspection object S, the temperature distribution can be measured with high accuracy. As the inspected object S having a large thickness, for example, there is a welded portion of a metal member.

In the present embodiment, the surface of the inspection object S is locally heated by the laser beam. For this reason, even if the surface of the inspection object S is not flat, a desired temperature distribution can be realized.
Other configurations, operations, and effects of the present embodiment are the same as those of the first embodiment.

(Third embodiment)
Next, a third embodiment will be described.
FIG. 9 is a block diagram showing a crack inspection apparatus according to the present embodiment.

  As shown in FIG. 9, the crack inspection apparatus 3 according to the present embodiment has a rotation mechanism 13 that rotates the optical element 12 as compared with the crack inspection apparatus 1 (see FIG. 1) according to the first embodiment described above. Instead, a difference is that a rotation mechanism 23 for rotating, tilting or moving the holder 20 is provided.

  The rotation mechanism 23 rotates, tilts, or moves the holder 20 according to a command from the control unit 40, thereby rotating, tilting, or moving the object S to be inspected. Thereby, the irradiation position of the laser beam L2 on the inspection object S relatively changes.

Also according to the present embodiment, the same effects as those of the first embodiment described above can be obtained.
Other configurations, operations, and effects of the present embodiment are the same as those of the first embodiment.

  According to the embodiment described above, a crack inspection apparatus and a crack inspection method with high inspection efficiency can be realized.

  As mentioned above, although some embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the scope of the invention described in the claims and the equivalents thereof.

  Further, the above-described embodiments can be implemented in combination with each other. For example, the first embodiment and the third embodiment described above may be combined to rotate or move both the optical element 12 and the inspected object S. Or you may test | inspect by rotating the thick to-be-inspected object S etc. combining 2nd Embodiment and 3rd Embodiment. In this case, for example, the inspection object S having a three-dimensional shape such as a welded portion can be inspected by rotating three-dimensionally.

  1, 2, 3: Crack inspection apparatus, 10: Laser optical system, 11: Laser light source, 12: Optical element, 13: Rotating mechanism, 20: Holder, 23: Rotating mechanism, 30: Infrared thermography, 40: Control unit, 50: Processing unit, C, C1, C2: Crack, L1, L2: Laser beam, R, R1 to R3: Irradiation region, S: Inspected object, T: Reference value, U: Position

Claims (5)

A laser optical system capable of irradiating laser beams to different positions on the object to be inspected;
Measuring means for measuring a temperature distribution of the object to be inspected irradiated with the laser beam;
A crack inspection device. The laser optical system is
A laser light source that emits one laser beam;
An optical element for branching the one laser beam into a plurality of laser beams;
An emission direction changing means for changing the emission direction of the plurality of laser beams by rotating, tilting or moving the optical element;
The crack inspection apparatus of Claim 1 which has these.   The crack inspection apparatus according to claim 2, wherein the optical element is a diffraction grating. Irradiating a first position of the inspection object with a laser beam and measuring a temperature distribution of the inspection object;
Irradiating a laser beam to a second position different from the first position of the inspection object, and measuring a temperature distribution of the inspection object;
A crack inspection method comprising: When irradiating the first position with the laser beam, the third position different from the first position in the inspection object is irradiated with the laser beam,
The crack inspection method according to claim 4, wherein when the second position is irradiated with the laser beam, the fourth position different from the third position in the inspection target is irradiated with the laser beam.