JP6568691B2 - Flaw detection system and flaw detection method for detecting internal defect of flaw detection object - Google Patents

Description

  The present invention relates to a flaw detection technique for detecting defects such as scratches and peeling occurring inside a flaw detection object by measuring the temperature of the flaw detection object.

  An infrared thermography method is one of the methods for detecting defects generated inside the inspection object by nondestructive inspection. In this infrared thermography method, the surface of a test object is heated by a heat source, and the subsequent surface temperature is measured by an infrared camera or the like. When there is a defect inside, the flow of heat propagating to the inside changes, so that a local temperature change occurs on the surface. By detecting this temperature change, it is possible to detect a defect occurring inside the flaw detection object.

  For example, in the flaw detection method described in Patent Document 1, a defect of a flaw detection object (inspection object) is detected and displayed by the following procedure. First, the surface of the flaw detection target is pulse-heated, and the surface temperatures of a plurality of portions of the flaw detection target after heating are detected at a set sampling frequency for a set time. As a result, data indicating the relationship between the elapsed time after heating and the surface temperature is acquired for each cell (for each pixel). Although it is possible to detect and inspect defects from changes in the thermal image of the surface, the acquired data is further subjected to Fourier transform to convert it into data indicating the relationship between frequency and phase. From the converted data, a phase value for each cell with respect to the frequency determined by the measured time and the sampling frequency is obtained. A phase image for each frequency obtained by the Fourier transform is generated from the phase value and displayed on the display unit. In this phase image, the phase value changes depending on the presence / absence of defects inside the flaw detection object, so that defects inside the flaw detection object can be detected and displayed based on the phase image. And it can be made into an image with fewer deep defects and less noise than a thermal image.

JP 2011-247718 A

  The flaw detection method described in Patent Document 1 targets a stationary flaw detection object. Therefore, when applied to a moving flaw detection object, there is a problem that phase analysis cannot be performed due to an increase in unnecessary signals and noise, such as picking up the surface temperature of not only the part where the surface temperature is to be detected but also the adjacent part.

  The present invention has been made in view of such circumstances, and an object of the present invention is to be able to display internal defects of a flaw detection object even when the flaw detection object relatively moves.

In order to achieve the above-described object, a flaw detection system according to the present invention includes a heating unit that continuously heats a flaw detection object that moves relatively at a predetermined speed at a predetermined heating position, and a downstream side in the relative movement direction from the heating position. to be spaced intervals, vertical or horizontal direction of the imaging range with respect to a first direction perpendicular to the relative movement direction is installed so as to be parallel, the flaw object periodically shooting An infrared camera that acquires a plurality of thermal images representing a distribution of heat, and at least one same column along the first direction of the plurality of thermal images taken by the infrared camera, A control unit that extracts a linear heat quantity group in the first direction of each of a plurality of thermal images, and generates a panoramic image by linking the linear heat quantity groups in the orthogonal direction in time series for each of the same columns. And equipped with .

Preferably, the flaw detection system further includes a display unit, and the control unit displays the generated panoramic image on the display unit.

In the above inspection system, the flaw object to be moved, can be displayed inside defect depth from the surface are different.

Further, after heating (i.e., after the lapse of the heating position fixed time) panoramic image image showing a heat flaw object is obtained. By this panoramic image, the flaw object to be moved, can be displayed defects approximate depth aliquot.

Further, the flaw detection method according to the present invention includes a heating step of continuously heating a flaw detection object relatively moving at a predetermined speed at a predetermined heating position, and an interval from the heating position to the downstream side in the relative movement direction. In addition, the flaw detection object is periodically imaged by an infrared camera installed so that the vertical direction or the horizontal direction of the imaging range is parallel to the first direction orthogonal to the relative movement direction. The acquisition step of acquiring a plurality of thermal images representing the distribution of heat quantity, and at least one same row along the first direction of the plurality of thermal images taken by the infrared camera A generation process for extracting a linear heat quantity group in the first direction of each thermal image and generating a panoramic image by connecting the linear heat quantity groups in the orthogonal direction in time series in the same row. Tsu including and up, the.

Preferably, the flaw detection method further includes a display step of causing the display unit to display the panoramic image generated in the generation step.

  According to the present invention, it is possible to detect an internal defect of a flaw detection object even when the flaw detection object moves relatively.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows one Embodiment of the flaw detection system which concerns on this invention, (a) is the schematic which shows the whole system, (b) is explanatory drawing which shows the memory area provided in a memory | storage part. It is a top view with which it uses for description of the visual field of the X direction of an infrared camera, and the moving direction of a test target. It is explanatory drawing which shows the thermal image (frame) acquired by imaging | photography. It is explanatory drawing which shows the relationship between a thermal image and a cell (pixel). It is a flowchart which shows the flaw detection processing procedure in the flaw detection system of FIG. It is a figure explaining the heating range by the halogen light with respect to a test object, and the imaging | photography range by an infrared camera. It is a figure explaining a heating position and a calorie | heat amount acquisition position. It is a figure with which it uses for description of heat quantity acquisition in case a flaw detection target object is installed perpendicularly | vertically with respect to the camera axis of an infrared camera, (a) is a schematic which shows the extraction point which moves within the visual field of the infrared camera in a heat quantity acquisition position FIG. 4B is a graph showing the temperature change of the amount of heat at the extraction point, and FIG. 4C is a schematic diagram showing the positional relationship between the infrared camera and the flaw detection object and the extraction point moving within the visual field at that time. It is a figure with which it uses for description of the calorie | heat amount acquisition when a flaw detection target object is installed diagonally with respect to the camera axis of an infrared camera, (a) is a schematic which shows the extraction point which moves within the visual field of the infrared camera in a calorie | heat amount acquisition position FIG. 4B is a graph showing the temperature change of the amount of heat at the extraction point, and FIG. 4C is a schematic diagram showing the positional relationship between the infrared camera and the flaw detection object and the extraction point moving within the visual field at that time. It is a conceptual diagram which shows the relationship between the superimposition image showing the locus | trajectory of the extraction point in the visual field of an infrared camera, the some thermal image which comprises a superimposition image, and the temperature change of an extraction point. It is a figure explaining the flaw detection process in other embodiment, (a) is a conceptual diagram which shows the calorie | heat amount group acquired in a calorie | heat amount acquisition position, (b) is a schematic diagram which shows the continuous isotherm by the temperature of the said calorie | heat amount group. is there. It is a figure explaining the flaw detection process in other embodiment, (a) is a conceptual diagram which shows the calorie | heat amount group acquired in several calorie | heat amount acquisition positions, (b) shows the continuous isotherm by the temperature of the said each calorie | heat amount group. It is a schematic diagram.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. A flaw detection system 10 shown in FIG. 1A includes an infrared camera 11, a halogen light 12, and a control device 13.

  The infrared camera 11 is a device for photographing a subject such as the flaw detection target Z, detecting infrared energy emitted from the surface of the subject, and visualizing it as a thermal image FL (see FIGS. 3 and 4). . The data of the thermal image FL output from the infrared camera 11 is input to the control device 13, the amount of heat is obtained by the control unit 16, and converted into the surface temperature. The data of the thermal image FL corresponds to the amount of heat generated from the flaw detection object Z. For this reason, the infrared camera 11 constitutes a heat quantity acquisition unit together with the control unit 16 of the control device 13. Further, the control unit 16 analyzes the phase of the extraction point P1 (see FIG. 7, FIG. 8, etc.) arbitrarily set on the flaw detection target Z with the relative movement of the flaw detection target Z, details of which will be described later. It also functions as a phase analysis unit.

  In the illustrated infrared camera 11, infrared energy within the field of view (shooting range) is collected by the optical system and input to the infrared detection element. The infrared detection element converts the input infrared energy into an electrical signal corresponding to the intensity and outputs the electrical signal. That is, the infrared detection element divides the field of view into a matrix (matrix), and outputs an electrical signal for each division unit (cell) as data of the thermal image FL. Here, as the amount of heat emitted from the subject increases, infrared radiation emitted from the surface of the subject increases, and the value (for example, voltage value) of the electrical signal output from the infrared detection element increases.

Here, as shown in FIGS. 2 and 4, the moving speed of the test object Z is V, the distance from the infrared camera 11 to the test object Z is L, the imaging frequency of the infrared camera 11 is F, and the infrared camera 11 is used. The field angle in the moving direction of the flaw detection object Z (X direction in the visual field) is θ, the visual field in the X direction in the infrared camera 11 is A ₀ , the number of pixels in the X direction in the visual field A ₀ is N, and the Y direction orthogonal to the X direction B ₀ , the number of cells in the X direction (number of pixels) in the field of view B ₀ is N, and the number of cells in the Y direction (number of pixels) is M.

In this case, the visual field A _{0 in the} X direction can be expressed by 2 × L × tan (θ / 2). Since the cell C is square, the visual field B _{0 in the} Y direction can be expressed as A ₀ / N × M. The field of view (detection width) Δ per cell C can be expressed as A ₀ / N. The infrared camera 11 can acquire time-series thermal images FL as shown in FIG. 3 at a speed of, for example, 50 images per second (imaging frequency F = 50 Hz; intervals of 0.02 seconds).

  As shown in FIG. 4, in the thermal image FL, the cells C are arranged in a matrix, and a color corresponding to the temperature (heat amount) is set for each cell C. The display of the thermal image FL on the infrared camera 11 or the display unit 18 is performed by coloring each cell C according to the output of the cell C indicating a value corresponding to the amount of heat. In the infrared camera 11 of this embodiment, a thermal image FL in which N (for example, 320) cells in the X direction and M (for example, 240) cells C are arranged in the Y direction is taken. The number of cells (number of pixels) constituting the thermal image FL and the imaging frequency F of the infrared camera 11 can be set as appropriate.

  As shown in FIG. 1A, the halogen light 12 corresponds to a heating unit, and heats the surface of the flaw detection object Z by, for example, continuous light emission. Specifically, in this embodiment, a case where the halogen light 12 having a rated output of 1 kW is used will be described, but the present invention is not limited to this. Since the light emitted from the halogen light 12 heats the flaw detection object Z from the surface, a light source (xenon lamp, laser light, etc.) other than the halogen light 12 may be used as the heating unit. The light emission control of the halogen light 12 and other types of light sources may be performed by the control device 13 or manually. A continuous emission xenon lamp having a narrow pulse interval can also be used.

  The control device 13 controls the operation of the infrared camera 11 and the halogen light 12, and processes and displays the data of the thermal image FL from the infrared camera 11. The control device 13 is configured by a personal computer, for example, and includes a CPU (Central Processing Unit) 14, a control unit 16 having a storage unit 15, and an input unit 17 configured by a mouse, a touch panel, a keyboard, and the like. And a display unit 18 composed of various displays.

  The CPU 14 reads the computer program stored in the storage unit 15 and operates according to the computer program and an operation signal from the input unit 17. By the operation of the CPU 14, the control unit 16 controls the operation of the infrared camera 11, performs various calculations based on the data of the thermal image FL, and displays the calculation result on the display unit 18.

  The storage unit 15 is a part that stores computer programs and various data, and uses a storage element capable of writing and reading such as an HDD (Hard Disk Drive), a solid state drive, a RAM (Random Access Memory), and a flash memory. It is done.

  As shown in FIG. 1B, a partial area of the storage unit 15 includes a program storage area 15a, a flaw detection program storage area 15b, a parameter storage area 15c, a thermal image storage area 15d, a superimposed image storage area 15e, a time- It is used as a temperature data storage area 15f, a frequency-phase data storage area 15g, and a phase image storage area 15h.

  The program storage area 15a stores a computer program for causing the set of the infrared camera 11, the halogen light 12, and the control device 13 to function as the flaw detection system 10. The flaw detection program storage area 15b stores a computer program required when the control unit 16 automatically performs inspection and determination by referring to a determination condition based on a thermal image FL described later. Yes.

Various parameters required in the flaw detection process are stored in the parameter storage area 15c. For example, the distance L to the subject, the visual field A _{0 in the} X direction, the visual field B _{0 in the} Y direction, the moving speed V of the flaw detection object Z, the number N of cells in the X direction, the number M of cells in the Y direction, the imaging frequency F, The field of view Δ per cell is stored. At this time, the moving speed V includes an angle formed with the camera axis at the time of photographing by the infrared camera 11. Further, the resolution (N, M) at the time of photographing with the infrared camera 11 and the operation content of the halogen light 12 (light emission time and intensity, heating condition of the flaw detection object Z) are also stored. In the thermal image storage area 15d, a time-series thermal image FL output from the infrared camera 11 is stored. Furthermore, if the movement trajectory of the arbitrarily set extraction point in the camera visual field is also known in advance, it is stored (the movement trajectory of the extraction point P1 can also be obtained by image analysis).

  Although details will be described later, the superimposed image storage area 15e stores a superimposed image in which time-series thermal images FL are sequentially superimposed. The time-temperature data storage area 15f stores data indicating the relationship between time and temperature for each cell C acquired for the superimposed image. The frequency-phase data storage area 15g stores frequency-phase data indicating the relationship between frequency and phase, which is obtained by Fourier transforming time-temperature data. In the phase image storage area 15h, a phase image generated based on the frequency-phase data (a phase image based on an equiphase image at a set frequency) is stored.

  Here, the infrared camera 11 and the control unit 16 serving as the heat quantity acquisition unit shoot the shooting range MV including the heat quantity acquisition position at a predetermined time interval based on the set shooting frequency F, so that the inside of the shooting range MV is captured. The amount of heat of the entire imaging range MV in the moving flaw detection target Z that moves is acquired as a plurality of thermal images FL showing the time series. Further, the control unit 16 as the phase analysis unit is obtained based on a plurality of thermal images FL, and is coordinate data indicating a trajectory in which the extraction point P1 arbitrarily set on the flaw detection target Z moves within the imaging range MV. And the temperature data at each point in the locus of the extraction point P1 and the time-series temperature change data accompanying the movement of the extraction point P1 obtained from the Fourier transform, and the temperature and time of the extraction point P1 on the flaw detection object Z The frequency-phase data indicating the change in the frequency is acquired. And the display part 18 displays the defect which exists in the inside of the flaw detection target Z by the image of the equal temperature value in the locus | trajectory of the extraction point P1, or the image of an equal phase value based on the frequency-phase data.

  Next, flaw detection processing in the flaw detection system 10 having the above-described configuration will be described with reference to the flowchart of FIG. In the flaw detection process described below, an extraction point P1 for calorimetric measurement is arbitrarily set on the flaw detection target Z, and phase analysis is performed on the extraction point P1 based on the thermal image FL photographed by the infrared camera 11. Monitor the amount of heat continuously. Thereby, the defect existing inside can be displayed with respect to the flaw detection target Z that moves relatively, but this is an example and the present invention is not limited thereto. For example, the extraction point P1 may be plural (extraction points P1, P2). Further, instead of the extraction point P1, the amount of heat is measured in a line extending in the vertical direction (Y direction in FIG. 6) perpendicular to the relative movement direction (X direction in FIG. 6) using a line sensor described later. You may make it do.

  First, in the flaw detection system 10, parameters are first set (S1). In this setting process, the operator sets the resolution at the time of photographing with the infrared camera 11, the photographing frequency F, the output of the halogen light 12, and the like. For example, a screen prompting input of these parameters is displayed on the display unit 18, and necessary parameters are input by operating the input unit 17. The set parameters are stored in the parameter storage area 15c of the storage unit 15. If the moving direction and speed of the flaw detection object Z are unknown, the speed and direction are recognized from the movement in the image at the initial stage of movement or read by a detector different from the infrared camera 11. .

  When the necessary parameters are set, the surface of the flaw detection object Z is heated (S2). In this case, the moving flaw detection object Z is continuously heated by the heat released by the light emission of the halogen light 12. Specifically, as shown in FIG. 6, the surface of the flaw detection object Z that is moving at a speed V is heated by irradiating the predetermined heating range HT with continuous light from the halogen light 12. As shown in the figure, the heating range HT is set at a predetermined distance from the imaging range MV of the infrared camera 11 to the upstream side in the moving direction of the flaw detection object Z.

Since the flaw detection object Z has moved, as shown in FIG. 7, the extraction point P1 heated at time T0 moves downstream by the interval W1 at time T1, and the infrared camera 11 moves in the X direction. it reaches the position of the upstream end of the field a _0. The extraction point P1 moves downstream by the interval W2 at time T2, and reaches the center position (A _0/2 ) of the visual field A ₀ in the X direction in the infrared camera 11. Furthermore, the extraction point P1 moves to the downstream side at time T3 by a distance W3, reaches the position of the downstream end of field A ₀ of the infrared camera 11.

When the flaw detection object Z is heated, a thermal image FL acquisition / storage process is performed (S3). In this process, the infrared camera 11 performs imaging at the imaging frequency F to generate a thermal image FL in the imaging range MV in time series. As a result, time-series thermal images FL (t1) to FL (tn) determined by the imaging frequency F are acquired as shown in FIGS. In these thermal images FL (t1) to FL (tn), it can be seen that each time the thermal image FL is acquired, the extraction point P1 on the flaw detection object Z moves in the X direction at a predetermined movement pitch. Further, the control unit 16 receives the thermal images FL sequentially transmitted from the infrared camera 11 and stores them in the thermal image storage area 15 d of the storage unit 15. In this thermal image FL acquisition / storage process, as shown in FIG. 8A, the extraction point P1, which is the inspection target portion of the flaw detection object Z, passes through the imaging range MV (the visual field A _{0 of the} infrared camera 11). It continues until it is done.

  When the thermal images FL are acquired and stored for the extraction points P1 and P2 of the flaw detection target Z, the control unit 16 superimposes the stored thermal images FL according to the captured time series, so that FIG. (C) and a superimposed image as shown in FIG. 10 are acquired and stored in the superimposed image storage area 15e of the storage unit 15 (S4). This process is performed by the control unit 16. Therefore, the control unit 16 corresponds to a superimposed image acquisition unit that acquires a superimposed image.

  When the superimposed image is stored, the control unit 16 causes the display unit 18 to display the superimposed image (thermal images FL (t1) to FL (tn)). Thereby, an operator of the flaw detection system 10 can visually recognize the heat storage state of the flaw detection object Z on the display unit 18. If there is a defect inside the flaw detection object Z, the color of the portion is displayed differently from the color of the other portion, so that the operator can determine the presence or absence of the defect. Specifically, when a defect exists inside the flaw detection object Z, heat released from the halogen light 12 is accumulated at the position of the defect. For this reason, the amount of heat increases in the defect portion as compared with the portion where the defect does not exist. Therefore, the defect in the flaw detection object Z can be displayed based on the change in the amount of heat. Moreover, the presence or absence of a defect | deletion can be determined.

Next, a series of processing (flaw detection processing) for detecting defects existing inside the flaw detection object Z is performed based on the superimposed image. This flaw detection process consists of the process of S5-S10 demonstrated below. In this flaw detection process, first, a movement locus calculation process is performed (S5). In this process, the control unit 16 reads the superimposed image from the superimposed image storage area 15e, and based on the superimposed image, the extraction point P1 is the imaging range MV on the flaw detection target Z (the field of view A _{0 of the} infrared camera 11). The coordinate data indicating the trajectory that has moved in is obtained. At this time, the coordinate data is obtained from a superimposed image representing the entire fields of view A ₀ and B ₀ as the imaging range MV as shown in FIG. 10, and position data and time data indicating the locus of the extraction point P1 in the image. Consists of

  Next, the control unit 16 performs time-temperature data acquisition / storage processing associated with the movement of the extraction point P1 (S6). In this process, the control unit 16 determines the time and temperature for each of the cells C (see FIG. 4) constituting the superimposed image based on the calculated coordinate data and the temperature data at each point in the locus of the extraction point P1. Is obtained as time-series temperature change data. This temperature change data includes a temporal change in the amount of heat at an arbitrary extraction point P1 on the flaw detection object Z. Then, temperature change data indicating the relationship between time and temperature for all the cells C is stored in the time-temperature data storage area 15f of the storage unit 15 as time-temperature data.

  Here, based on the time-temperature data, the heat quantity of the flaw detection object Z is indicated by an analog continuous curve as shown in FIG. This curve is generated for each point in the locus of the extraction point P1. At this time, it is assumed that the extraction point P1 is set to a position where the surface of the flaw detection object Z has a defect, and the extraction point P2 is set to a position where there is no defect. In this case, in the graph based on the time-temperature data, fluctuation appears in the curve of the extraction point P1 having a defect, and the curve of the extraction point P2 having no defect is shown as a smooth attenuation curve. And the calorie | heat amount of a corresponding position is computable from the coordinate value of the X direction in the produced | generated curve. Here, the coordinate value in the X direction is selected as a value that matches the display mesh of the display unit 18. Furthermore, the control part 16 performs the above process with respect to all the curves. As a result, a thermal image FL that can be displayed on the display unit 18 is obtained and displayed on the display unit 18. Thus, even when the test object Z is moving, the internal defect of the test object Z can be detected.

  When the time-temperature data is stored, Fourier transform is performed on the time-temperature data (S7). By this Fourier transform, the time-temperature data is converted into frequency-phase data indicating the relationship between frequency and phase. This Fourier transform is performed by the control unit 16. Therefore, the control unit 16 functions as a data conversion unit. It should be noted that the Fourier transform is prepared as a subroutine, and when there is a required request from the time series, the time-temperature data is sent to the subroutine and Fourier-transformed to provide frequency-phase data. Also good. Here, since the time-temperature data in this embodiment is discrete, discrete Fourier transform is performed.

The discrete Fourier transform is performed according to the following equations (1) and (2).

Here, F _n represents a conversion result (frequency component, complex intensity) at a frequency n times the value obtained by dividing the sampling frequency f _s by 2 times the number of acquired data DN. Re _n represents the real part of the conversion result, and Im _n represents the imaginary part of the conversion result. T is the temperature of the kth sampling. A _n represents the phase value of the frequency K of the conversion result. In the discrete Fourier transform, the frequency range after the transformation is determined by the sampling frequency and the number of acquired data (time). The minimum value f _min and the maximum value f _max of the converted frequency are expressed by the following equations (3) and (4) using the sampling frequency f _s and the number of acquired data DN.

The phase-frequency data obtained by the above Fourier transform and the data of the minimum frequency f _min and the maximum value f _max after the conversion are stored in the frequency-phase data storage area 15g of the storage unit 15. Thereafter, a phase image is generated and stored (S9). In the phase image generation process, the inspection frequency is set to a discrete arbitrary frequency that is not less than the aforementioned minimum value f _{min and not} more than the maximum value f _max , and uses the phase value of the determined inspection frequency. A phase image is generated.

In the phase image generation process, the number of data DN calculated at a frequency of 1 / T between f _min = 1 / T, 2 / T, 3 / T... Fs / 2 (= N / 2T) Then, f _max = f / 2 (= (N / 2) / T), and half phase images of the number N of cells C constituting the acquired thermal image FL are generated.

The inspection frequency can be arbitrarily determined at an interval of 1 / T as long as it is in the range of the minimum value f _min or more and the maximum value f _max or less. For example, it can be set to a frequency determined from the capturing time of the thermal image FL and the capturing time interval.

  The generation of the phase image is performed by the control unit 16. For this reason, the control unit 16 also functions as a phase image generation unit. Then, the generated phase image is stored in the phase image storage area 15 h of the storage unit 15. Moreover, the internal state from which the depth from the surface differs can be confirmed by changing a test | inspection frequency. The inspection frequency can be set by the operator via the input unit 17.

  When the phase image is generated and stored, the phase image and the inspection result are displayed (S10). In this display process, the phase image stored in the phase image storage area 15 h is read out by the control unit 16, converted into a video signal, and displayed on the display unit 18. The display unit 18 also displays the inspection result.

  As described above, according to the flaw detection system 10 of the present embodiment, the pair of the infrared camera 11 and the control unit 16 (heat amount acquisition unit) at the heat amount acquisition position that is spaced from the heating range by a predetermined interval causes the flaw detection target Z to be heated. The amount of heat is acquired in time series. Inside the flaw detection target Z, the amount of heat in the part with the defect changes significantly from the amount of heat in the part without the defect, so the flaw detection target Z that moves relatively by acquiring the amount of heat continuously at the heat amount acquisition position. Can display internal defects.

In such a flaw detection system 10, a superimposed image showing a trajectory in which the extraction point P1 arbitrarily set on the flaw detection target Z moves within the same imaging range MV can be acquired, so that the flaw detection target is within the visual fields A ₀ and B ₀ . Even when the object Z moves, the thermal image FL of the flaw detection object Z can be displayed on the display unit 18 and the defects existing inside the flaw detection object Z can be recognized. This flaw detection method is suitable for individual inspection of a mass-produced object that is moving, and can capture and inspect the thermal image FL during the time required to move within the visual fields A ₀ and B ₀ . Moreover, it is useful when detecting a big defect rapidly.

  Further, in this flaw detection system 10, frequency-phase data indicating the relationship between frequency and phase is obtained by performing Fourier transform on the time-temperature data indicating the relationship between time and temperature in the superimposed image, and obtained from the frequency-phase data. Based on the obtained phase image, a defect existing inside the flaw detection object Z is detected. In this flaw detection system 10, since the defect which exists in the inside of the flaw detection target Z is detected based on the phase image obtained from frequency-phase data, the defect in the deep place from the surface can also be detected (S5-S10).

  Further, in the flaw detection system 10, the control unit 16 (phase analysis unit) detects a defect present inside the flaw detection target Z based on the phase image obtained by the equiphase image at the set frequency. In this flaw detection system 10, it is possible to detect a defect at a location having a different depth from the surface by setting the frequency. This frequency can be arbitrarily determined. For example, since it can be determined to a frequency determined from the capturing time of the thermal image FL and the time interval of capturing, the high frequency is 1/2 of the capturing frequency of the thermal image FL, and the low frequency is 1 / T (capturing time). Any frequency with a frequency interval of 1 / T until T) can be selected.

  The above description of the embodiment is for facilitating the understanding of the present invention, and does not limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and the present invention includes equivalents thereof. For example, you may comprise as follows.

In the above-described embodiment, the case where the infrared camera 11 is fixed and the flaw detection target Z moves in the X direction in the field of view A ₀ and B _{0 of the} infrared camera 11 has been described as an example. It is not limited. The halogen light 12 and the infrared camera 11 may be moved with respect to the fixed flaw detection target Z.

  In the above-described embodiment, the case where the flaw detection object Z moves in the X direction (the horizontal direction of the thermal image FL) has been described. However, the case where the flaw detection object Z moves in the Y direction (the vertical direction of the thermal image FL). Can be applied similarly. In addition, the present invention can be similarly applied to the case where the flaw detection object Z moves in each of the X direction and the Y direction (the oblique direction of the thermal image FL).

  At this time, if the trajectory of the arbitrary extraction point P1 on the flaw detection object Z is obtained within the field of view of the infrared camera 11, the time-temperature data of the extraction point P1 can be obtained. Even if the object moves away from or approaches, the inspection can be performed in the same manner.

  In the above-described embodiment, time-temperature data and frequency-phase data are acquired for one cell C. However, the present invention is not limited to this configuration. For example, time-temperature data and frequency-phase data may be acquired with an average value of a plurality of cells C.

  In the above-described embodiment, the case where the infrared camera 11 is installed with the camera axis perpendicular to the flaw detection target Z has been described. However, the present invention is not limited to this. For example, as shown in FIG. 9C, when the infrared camera 11 is installed with the camera axis tilted with respect to the flaw detection target Z, the flaw detection target Z is shown in FIG. As shown, the moving direction side located on the right side of the drawing with respect to the shooting range MV is narrow. At this time, it is assumed that the extraction point P1 is set to a position where the surface of the flaw detection object Z has a defect, and the extraction point P2 is set to a position where there is no defect. In this case, as shown in FIG. 9B, in the graph based on the time-temperature data, fluctuation appears in the curve of the extraction point P1 having a defect, and fluctuation does not appear in the curve of the extraction point P2 having no defect. Shown as a smooth decay curve. For this reason, as in the above-described embodiment, even when the flaw detection target Z is moving, an internal defect of the flaw detection target Z can be detected.

  In the above-described embodiment, the heat quantity of the flaw detection target Z is approximated by a curve. However, the heat quantity of adjacent measurement points may be approximated by a fine straight line such as linear interpolation. Further, if the amount of heat acquired at each measurement point can be displayed on the display unit 18 as it is, approximation may not be performed.

  In this flaw detection system 10, the heat quantity of the flaw detection object Z is acquired using the image from the infrared camera 11, but it is sufficient that the heat quantity in the Y direction at the heat quantity acquisition position can be acquired in time series. For this reason, it may replace with the infrared camera 11 and may use the line sensor which acquires the calorie | heat amount in a calorie | heat amount acquisition position.

  That is, the infrared camera 11 and the control unit 16 make a vertical direction (Y substantially orthogonal to the relative movement direction (X direction) with respect to the flaw detection target Z that moves relatively at the heat quantity acquisition position based on the set imaging frequency F. The heat amount of the flaw detection target Z after heating may be acquired as a plurality of thermal images FL showing the time series in a line extending in the direction) at predetermined time intervals. At this time, each thermal image FL is shown as a linear heat quantity group acquired at the heat quantity acquisition position.

More specifically, as shown in FIG. 11 (a), the time T1 (i.e., the center position of the visual field A ₀ of the X-direction in FIG. 6 (A _0/2)) obtains the amount of heat groups as heat acquisition position You may make it do. In the figure, the vertical axis in the imaging range MV indicates the position of each cell (measurement point in the Y direction) at the heat amount acquisition position, and the horizontal axis indicates the measurement timing in the X direction. As shown in this figure, in the above-described thermal image acquisition process (S3), the amount of heat is acquired at intervals of the visual field Δ per cell C in the Y direction. On the other hand, in the X direction, the amount of heat is acquired at every movement pitch p determined by the imaging frequency F of the infrared camera 11 and the moving speed V of the flaw detection object Z, that is, at an interval determined by the moving speed V / imaging frequency F.

  Then, as shown by the hatched frame in FIG. 11A, a heat amount group in the Y direction belonging to a certain cell C (measurement point) in the X direction is extracted, the heat amount on the vertical axis, and the X direction on the horizontal axis. When the movement amount is plotted, for example, a panoramic image of a continuous isotherm as shown in FIG. 11B is obtained. That is, a heat quantity group having a size Δ and a moving pitch p is obtained. Then, the combination of the amount of heat and the measurement point in the X direction shown in FIG. 11B is acquired for each cell C (measurement point) in the Y direction.

  Here, when a defect exists inside the flaw detection object Z, the heat released from the heating unit is accumulated at the position of the defect. For this reason, the amount of heat increases in the defect portion as compared with the portion where the defect does not exist. Therefore, the defect in the flaw detection object Z can be displayed based on the change in the amount of heat. Moreover, the presence or absence of a defect | deletion can be determined.

Incidentally, in this case, it has been acquired in time series heat flaw object Z after heating at the position of the center of the visual field A ₀ of the X direction (A _0/2). Here, the position in the X direction in the visual field A ₀ defines the elapsed time from the heating as described above. Then, since the heat absorbed in the flaw detection target Z is gradually released from the surface of the flaw detection target Z, the elapsed time from the heating defines the detection depth of the defect in the flaw detection target Z. . Accordingly, as shown in FIG. 12 (a), the heat quantity acquisition position is moved in the X direction, and the heat quantity of the flaw detection target Z after heating is time-sequentially at a plurality of heat quantity acquisition positions having different intervals from the heating position. get. As a result, a panoramic image of a continuous isotherm as shown in FIG. 12B is obtained from the heat quantity group at time T1, and a continuous isotherm panorama as shown in FIG. 12C from the heat quantity group at time T2. By obtaining an image, it is possible to detect the presence or absence of defects having different depths from the surface.

That is, in the flaw detection system 10, as shown in FIG. 7, can be selected heat acquisition position in a range from the upstream end in the field A ₀ of the X-direction to the downstream end. When the upstream end of the visual field A ₀ that has moved downstream from the heating range by the interval W1 is selected as the heat amount acquisition position, the heat amount of the flaw detection target Z is acquired when a predetermined time (T1-T0) has elapsed since the heating by the heating unit. it can. Further, when the downstream end of field A ₀ which is moved to the downstream side distance W3 from the heating range be selected heat acquisition position, obtaining the amount of heat of a predetermined time from the heating by the heating section (T3-T0) probe at the elapsed point scratches object Z it can. Thus, the defect which exists in the inside of the flaw detection target Z from which the depth from the surface differs can be displayed on the display part 18 by selection of a calorie | heat amount acquisition position.

  The moving speed V of the flaw detection object Z can be acquired by various methods. For example, the control unit 16 can also obtain the pattern feature points drawn on the surface of the flaw detection target Z by referring to a plurality of thermal images FL having different imaging timings and calculating the movement amount thereof. When the moving speed V of the flaw detection object Z is known in advance, the moving speed V may be input by the operator in the parameter setting process (S1). Then, the acquired moving speed V is stored in the parameter storage area 15 c of the storage unit 15.

  In the above-described embodiment, the phase image is acquired from the frequency-phase data, and the scratch existing in the flaw detection object Z is searched for by the phase image. However, the present invention is not limited to this configuration. For example, a defect existing inside the flaw detection object Z may be detected directly from the time-temperature data in the superimposed image.

DESCRIPTION OF SYMBOLS 10 ... Flaw detection system, 11 ... Infrared camera, 12 ... Halogen light, 13 ... Control apparatus, 14 ... CPU, 15 ... Storage part, 15a ... Program storage area, 15b ... Flaw detection program storage area, 15c ... Parameter storage area, 15d ... Thermal image storage area, 15e ... superimposed image storage area, 15f ... time-temperature data storage area, 15g ... frequency-phase data storage area, 15h ... phase image storage area, 16 ... control unit, 17 ... input unit, 18 ... Display unit, Z ... flaw detection object, V ... flaw detection object moving speed, FL ... thermal image, L ... distance from the infrared camera to the flaw detection object, F ... infrared camera imaging frequency, θ ... infrared camera X direction angle of, a ₀ ... X direction of the field of view of the infrared camera, B ₀ ... infrared camera Y direction of the field, N ... field a X direction number of cells at _0, the M ... field B ₀ Contact Movement pitch of that Y-direction number of cells, p ... flaw detection object

Claims (4)

A heating unit that continuously heats the flaw detection object relatively moving at a predetermined speed at a predetermined heating position;
It is arranged at an interval from the heating position on the downstream side in the relative movement direction, and is set so that the vertical direction or the horizontal direction of the imaging range is parallel to the first direction orthogonal to the relative movement direction, An infrared camera that acquires a plurality of thermal images representing the distribution of heat by periodically imaging the flaw detection object;
The linear heat quantity group in the first direction of each of the plurality of thermal images is extracted for each of at least one same row along the first direction of the plurality of thermal images taken by the infrared camera. A control unit that generates a panoramic image by linking the linear heat quantity group in the orthogonal direction in time series for each of the same columns;
A flaw detection system. A display unit;
The flaw detection system according to claim 1, wherein the control unit displays the generated panoramic image on the display unit. A heating step of continuously heating a flaw detection object relatively moving at a predetermined speed at a predetermined heating position;
It is arranged at an interval downstream from the heating position in the relative movement direction, and is set so that the vertical direction or the horizontal direction of the photographing range is parallel to the first direction orthogonal to the relative movement direction. An acquisition step of acquiring a plurality of thermal images representing a distribution of heat quantity by periodically imaging the flaw detection object with an infrared camera;
The linear heat quantity group in the first direction of each of the plurality of thermal images is extracted for each of at least one same row along the first direction of the plurality of thermal images taken by the infrared camera. A generation step of generating a panoramic image by linking the linear heat quantity group in the orthogonal direction in time series in the same row;
Flaw detection methods including. The flaw detection method according to claim 3 , further comprising a display step of displaying the panoramic image generated in the generation step on a display unit.

Images