KR100788823B1 - Laser-Ultrasonic Apparatus and Method for Extracting Information of Surface-Breaking Crack - Google Patents

Abstract

The present invention relates to a laser-ultrasound inspection apparatus and method for extracting surface defect information, wherein the inspection apparatus generates and propagates an ultrasonic wave on the surface of an object using at least one irradiation laser beam, and measures the ultrasonic wave propagated Based on the center line of the irradiation laser beam obtained by obtaining the position information and the depth information of the defect from the ultrasonic signal information extracted by the non-contact method by irradiating the laser beam, or by taking an image of the at least one irradiation laser beam The external shape of the defect and the bottom shape of the defect can be obtained from the extracted defect shape information.

Surface defects, non-contact, ultrasonic, linear pulsed laser beam, SLS technique, shape measurement, dual wave mixed interferometer

Description

Laser-Ultrasonic Apparatus and Method for Extracting Information of Surface-Breaking Crack}

1 is a view for explaining a conventional configuration of a laser-ultrasound inspection apparatus for measuring the surface defect of the object.

2 is a block diagram illustrating a non-contact surface defect inspection apparatus according to an embodiment of the present invention.

3 is a view showing the non-contact surface defect inspection apparatus of FIG.

4 is a view showing an example of the internal configuration of the non-contact surface defect inspection apparatus according to an embodiment of the present invention.

5 is a view for explaining the principle of measuring the defect shape of the non-contact surface defect inspection apparatus according to an embodiment of the present invention.

6 is a diagram illustrating a defect shape measuring method using a linear pulsed laser beam according to an embodiment of the present invention.

FIG. 7 illustrates a detailed method for measuring the shape of the surface defect portion of FIG. 6.

8 is an example of an experimental result chart used to measure a defect location using the maximum-minimum value of an ultrasonic signal.

9 is an example of an experimental result chart used to measure a defect location using a center frequency value of an ultrasonic signal.

10 is a flowchart illustrating a non-contact surface defect inspection method according to an embodiment of the present invention.

11 is an internal block diagram of a general purpose computer device that may be employed to inspect for defects of an object in accordance with one embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

200: non-contact surface defect inspection device

1: ultrasonic induction module

2: ultrasonic signal detection module

3: Defect Shape Extraction Module

6: control / signal processing computer

The present invention relates to an apparatus and method for inspecting surface defects, and more particularly, to an apparatus and method for inspecting a specific defect on an object surface in a non-contact manner using laser-ultrasound.

Currently, surface defect inspection apparatuses for inspecting defects of materials are used in various industries or research fields, and laser-ultrasound inspection apparatus inspects surface defects by acquiring an ultrasonic signal generated by a pulsed laser beam using a laser interferometer. Device. In particular, currently widely used laser-ultrasound devices can generate and detect ultrasonic waves in a non-contact manner, compared to conventional ultrasonic transducers using contact transducers, and can also detect ultrasonic signals with a wide frequency spectrum. Research is being actively conducted because it can be generated or measured. An example of such a laser-ultrasound inspection apparatus is shown in FIG. 1.

1 is a view for explaining a conventional configuration of a laser-ultrasound inspection apparatus 1000 for measuring a surface defect of an object.

As shown in FIG. 1, the laser-ultrasound inspection apparatus 1000 is irradiated with a laser beam for irradiation from a linear pulsed laser beam irradiation focusing optical system 167 of an ultrasonic wave guide module 111, and ultrasonic waves are applied to the measurement specimen 115. Spreads on the surface In order to measure the propagated ultrasonic waves, the ultrasonic signal detection module 112 irradiates the measurement specimen 115 by using the laser beam focusing optical system 165 for measuring ultrasonic waves. The control / signal processing computer 116 analyzes the defects of the measurement specimen 115 using the measured ultrasonic signals, and thus obtains position and depth information on the surface defects of the measurement specimen 115. have.

Further, US Pat. Nos. 6,725,721 and 6,643,005 are prior art that discloses a defect inspection method by a laser-ultrasound inspection apparatus.

U.S. Patent No. 6,725,721 (Ultrasonic multi-element transducers and methods for testing) discloses a technique for measuring ultrasonic waves at several points at once by arranging several transducers used for defect detection. However, this US patent has a problem in that spatial resolution for determining a specific portion of an object to be observed or photographed is inferior, so that not only a scan can be performed to measure minute defects, but also shape information of surface defects cannot be obtained.

In addition, US Pat. No. 6,643,005 (Line sensing device for ultrafast laser acoustic inspection using adaptive optics) allows the microwave laser beams to be delayed from one another and uses a cylindrical lens to provide a linear photodiode array. As a technique for measuring the thickness of the film by detecting the shape of the furnace, there is a disadvantage that information about the shape of the surface defect cannot be obtained.

As described above, many techniques for detecting the presence of defects and extracting depth information by using ultrasonic waves have been developed, but there are limitations of information that can be obtained by simply analyzing changes in ultrasonic signals to provide defect information, and more specific defects such as shape information. There is a problem that is difficult to grasp the contents of.

The present invention has been made to solve the problems of the prior art as described above, the object of the present invention is to provide a more specific defect information by extracting the position and depth as well as the shape information for the surface defect using a laser-ultrasound To provide a non-contact surface defect inspection apparatus.

Another object of the present invention is to provide a non-contact surface defect inspection method for obtaining position, depth and shape information of surface defects of an object using a laser-ultrasound device capable of extracting a defect shape of an object.

The object surface defect inspection apparatus according to the present invention for achieving the object of the present invention as described above and to solve the above-mentioned problems of the prior art, the ultrasonic wave to generate an ultrasonic wave on the surface of the object using at least one laser beam for irradiation Induction module; An ultrasonic signal detection module irradiating a laser beam for measurement on the surface of the object through which the ultrasonic wave propagates and measuring ultrasonic waves on the surface of the object using a predetermined interferometer to extract ultrasonic signal information; And a defect shape extraction module for extracting defect shape information based on a centerline of the obtained irradiation laser beam by acquiring an image of the at least one irradiation laser beam. The position information and the depth information of the defect is obtained based on the signal information, and the outer shape of the defect and the bottom shape of the defect are obtained based on the defect shape information extracted from the defect shape extraction module.

Non-contact surface defect inspection method according to the present invention for achieving another object of the present invention as described above comprises the steps of generating an ultrasonic wave using at least one irradiation laser beam on the surface of the object; Radiating ultrasonic signal information by irradiating a surface of the object with an ultrasonic wave propagated on the surface of the object, and obtaining position information and depth information of a defect from the extracted ultrasonic signal information; And extracting defect shape information based on the centerline of the photographed irradiation laser beam by capturing an image of the at least one irradiation laser beam, and obtaining an outer shape of the defect and a bottom shape of the defect from the defect shape information. Characterized in that it comprises a step.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings and the contents described in the accompanying drawings, but the present invention is not limited or limited to the embodiments. Like reference numerals in the drawings denote like elements.

2 is a block diagram illustrating a non-contact surface defect inspection apparatus 200 according to an embodiment of the present invention.

As shown in FIG. 2, the non-contact surface defect inspection apparatus 200 includes an ultrasonic induction module 1, an ultrasonic signal detection module 2, a defect shape extraction module 3, and a control / signal processing computer 6. Include.

The non-contact surface defect inspection apparatus 200 irradiates ultrasonic waves from the ultrasonic guidance module 1 and detects the ultrasonic signals in order to measure the defects of an object (hereinafter, referred to as a test specimen) 5 to be examined for defects. The ultrasonic wave is measured in the module 2 to extract the position and depth of the defect, and the defect shape extraction module 3 extracts an object according to the irradiation laser beam of the irradiation laser device 65 through the image lens 66. It was proposed to obtain an image reflected from the surface (hereinafter referred to as an 'irradiation laser beam image') to extract the defect shape of the measurement specimen.

To this end, the non-contact surface defect inspection apparatus 200 according to an embodiment of the present invention generates an ultrasonic wave using at least one irradiation laser beam on the surface of the object, so that the ultrasonic wave propagates to the surface of the object. Ultrasound may be induced by a laser beam for irradiation (eg, a linear pulsed laser beam) using a scanning laser source (SLS) technique. Next, the propagated ultrasound beam is irradiated to the surface of the object with a measuring laser beam to extract the ultrasound signal information in a non-contact manner. In order to obtain the ultrasonic signal information, a two-wave mixing interferometer positioned at a predetermined interval may be used. Accordingly, the location information and the depth information of the micro defects can be obtained from the extracted ultrasonic signal information. In addition, the image of the at least one irradiation laser beam is taken to extract defect shape information based on the centerline of the photographed irradiation laser beam, and thus the outer shape of the defect and the bottom portion of the defect from the defect shape information. Shape can be obtained.

The ultrasonic guide module 1 generates ultrasonic waves on the surface of the object by using at least one irradiation laser beam. In other words, by irradiating a laser beam for irradiation, an ultrasonic wave having excellent directivity can be induced, and a pulsed laser beam can be used as the irradiation laser beam. The pulse laser beam may be applied to the present invention without particularly limiting the irradiation form, such as a spot or linear form. Hereinafter, the linear pulsed laser beam will be described as an example of the laser beam for irradiation. In addition, the irradiation laser beam is scanned by the scanner 4 to the area to be irradiated from the object (hereinafter, irradiated area) and the scanning operation can move one way or reciprocating, so as to scan in one or two dimensions I can move it. That is, it can be moved up and down (or left and right) and can be moved back and forth therein to allow more detailed measurement.

When the ultrasonic wave propagates on the surface of the object, the ultrasonic signal detection module 2 irradiates a surface of the object with a measuring laser beam, and thus a plurality of ultrasonic signals for which information regarding the reflected laser is guided through a certain interferometer. Extract the information. In addition, the position information and the depth information of the defect may be obtained based on the ultrasonic signal information extracted by the ultrasonic signal detection module 2. A continuous oscillation laser beam can be used as the measurement laser beam. Hereinafter, the continuous oscillation laser beam will be described as an example of the irradiation laser beam.

In addition, the ultrasonic signal detection module 2 may form a constant interferometer to measure the defect. The interferometer refers to a device for dividing the light from the same light source or the reflected laser into two or more light paths in a proper manner, and observing the interference fringes that overlap and interfere with each other. Various monochromatic light can be used as a light source. In addition, the interferometer is typically used based on the interference information between the light passing through the measurement object and the reference light not passed, and may be used for measurement of wavelength, precise comparison of length, distance, and comparison of optical distance. . In the present invention, an example of forming a two-wave mixing interferometer will be described.

In addition, the elements for forming the interferometer may include a measuring laser device 21 and a beam splitter 22 for dividing the measuring laser beam. In this case, in order to extract the ultrasonic signal information, the irradiation area may use a plurality of measuring laser beams. The laser beam for measurement may be positioned at regular intervals on the scan axis of the irradiation laser beam.

The defect shape extraction module 3 captures an image of the at least one irradiation laser beam and extracts defect shape information based on the centerline of the photographed irradiation laser beam. The outer shape of the defect and the bottom shape of the defect may be obtained based on the defect shape information extracted by the defect shape extraction module. Hereinafter, with reference to FIG. 4 to be described later.

The control / signal processing computer 6 measures and monitors the positional information and the depth information of the defect from the detected ultrasonic signal information, and the external shape of the defect and the bottom shape of the defect from the detected defect shape information. Measure and monitor. In addition, the control / signal processing computer 6 may calculate the position of the defect by judging a predetermined point of the lower portion of the lowered portion at which the amplitude or the center frequency of the detected ultrasonic signal falls from the maximum value as the start point of the defective portion. In addition, after the ultrasonic wave induced by the irradiation laser beam propagates the object, the ultrasonic wave signal detected by the interferometer measures the attenuation of the amplitude and the attenuation of the high frequency frequency component to check the defect or deterioration state of the object. Can be. The device used in the present invention can control a laser beam, signal information, movement of a specific device, analysis operation, etc., and can use a computer. Hereinafter, an example of an object defect measuring apparatus will be described with reference to FIG. 2.

3 is a diagram illustrating the non-contact surface defect inspection apparatus 200 of FIG. 2.

As shown in FIG. 3, the non-contact surface defect inspection apparatus 200 includes an ultrasonic induction module 1, an ultrasonic signal detection module 2, and a defect shape extraction module 3 and a control / signal processing computer 6. It may include. In addition, compared with the conventional laser-ultrasound inspection apparatus of FIG. 1, the defect shape extraction module 3 and the image lens 66 may be additionally used to extract the defect shape of the measurement specimen 5.

As described above, the ultrasonic induction module 1 transmits at least one linear pulsed laser beam to the surface of the measurement specimen 5 through a focusing optical system 67 for irradiating a linear pulsed laser beam (hereinafter, referred to as a focusing optical system). Irradiate to generate ultrasonic waves. In this case, the irradiation focusing optical system 67 may radiate a plurality of linear pulsed laser beams. In addition, the ultrasonic signal detection module 2 located at a predetermined distance from the irradiation focusing optical system 67 irradiates a measuring laser beam through the focusing optical system 65 to receive an ultrasonic signal propagated to the measurement specimen 5. It can be measured. The irradiation focusing optical system 67 may include a predetermined interferometer for measuring the ultrasonic signal.

In addition, the defect shape extraction module 3 separated from the irradiation focusing optical system 67 by a predetermined distance may generate an image of the irradiation laser beam irradiated onto the measurement specimen 5 by the irradiation focusing optical system 67. The imaging lens 66 can be used to acquire. The control / signal processing computer 6 also controls the ultrasonic induction module 1, the ultrasonic signal detection module 2, and the defect shape extraction module 3 as a whole, and the ultrasonic signal detection module 2 And signal processing data received from the defect shape extraction module 3 to obtain presence or absence of surface defects and depth information for the measurement specimen 5 as well as external shape and surface shape information of the surface defects and The same detailed defect information can be extracted. In addition, the scanner 4 functions to move the focusing optical system 65, the image lens 66, and the irradiation focusing optical system 67. Thus, the irradiation laser beam can scan the irradiation area from the object by the scanner 4. The detailed description of FIG. 3 will be described with reference to the example of FIG. 4.

4 is a view showing an example of the internal configuration of the non-contact surface defect inspection apparatus 200 according to an embodiment of the present invention.

As shown in FIG. 4, the non-contact surface defect inspection apparatus 200 largely includes an ultrasonic induction module 1, an ultrasonic signal detection module 2, and a defect shape extraction module 3, and includes a control / signal processing computer ( 6), and scanner 4 and the like can be used together.

The ultrasonic guidance module (or pulse laser device for linear laser beam irradiation) 1 may include a pulse laser device 11 for irradiating the laser beam for irradiation to the measurement specimen 5. The pulsed laser beam irradiated from the pulsed laser device 11 may be irradiated to the position B of the measurement specimen through a series of processes. In addition, the ultrasonic induction module 1 includes a shutter 12 for blocking or passing the pulsed laser beam as necessary to more precisely adjust the irradiated pulsed laser beam, and the intensity of the pulsed laser beam passing through the shutter. Neutral density filter 13 for adjusting the mirror, a mirror 14 for converting the angle of incidence of the pulsed laser beam passing through the neutral density filter 13 and the pulsed laser beam passing through the mirror 14 It may further include a focusing lens 15 for focusing. The focusing lens 15 focuses the pulsed laser beam into the optical fiber 62, and the irradiation focusing optical system 67 makes the pulsed laser beam passed through the optical fiber 62 into at least one linear pulsed laser beam. The surface position B of the measurement specimen 5 can be irradiated. Ultrasonic waves are generated by the irradiated at least one linear pulsed laser beam, and the generated ultrasonic waves propagate along the surface of the test specimen in the other position A, and the measuring laser interferometer 2 receives the ultrasonic waves passing through the A position. do.

The ultrasonic signal detection module (or laser interferometer device for ultrasonic measurement) 2 includes an interferometer which is guided by the focused pulsed laser beam and receives an ultrasonic signal propagated along the surface of the measurement specimen 5. And a two-wave mixing interferometer as an example of the interferometer. The interferometer may include a continuous oscillation laser device 21 for irradiating a measuring laser (continuous oscillation laser) and a beam splitter 22 for dividing the continuous oscillation laser. In addition, the half-wave plate 27 for rotating the polarization of the reflected laser beam (hereinafter referred to as a reference beam) divided by the beam splitter 22 and the beam from the half-wave plate at an angle to the photorefractive crystal 29 directly An incident mirror 28 can be used.

In addition, the ultrasonic signal detection module 2 includes a mirror 23 for converting the incident angle of the continuous oscillation laser beam (object beam) transmitted through the beam stopper 22 and the beam incident by the mirror 23. Polarization beam splitter 24 for reflecting the polarization may be included. At this time, the quarter wave plate 25 for changing the polarization state of the polarized reflected beam may be used, and the optical coupler 26 for coupling the beam from the quarter wave plate 25 with the optical fiber 63 Can be used. In addition, after collecting the light scattered from the measurement specimen (5), the polarization is rotated 90 degrees through the optical coupler 26 and the quarter wave plate 25 to pass through the polarizing beam splitter 24 and then focused The photorefractive crystal 29 may be included to receive the incident laser beam (object beam). The image lens 30 may be used to focus the interference fringes generated by the object beam passing through the photorefractive crystal 29 and the reference beam diffracted by the photorefractive crystal 29.

In addition, the ultrasonic signal detection module 2 converts the optical signal detected by the high gain optical sensor 31 and the high gain optical sensor 31 into a digital electrical signal by detecting the optical signal by receiving the focused interference fringe. A / D converter 32 to convert and a storage device 33 for storing the digital value from the A / D converter 32. The ultrasonic signal extraction device 34 extracts an ultrasonic signal portion from the data stored in the storage device 33, and thus the defect information signal processing device 35 causes the position and depth of the defect in the control / signal processing computer 6 to lie. The extracted ultrasonic signal is processed in a predetermined form so that information can be extracted. In addition, the ultrasonic signal detection module 2 focuses the continuous oscillation laser beam that has passed through the optical fiber 63 by using the focusing optical system 65 to focus the surface A phase of the measurement specimen 5 to be shifted by ultrasonic waves. Measure the surface variation at this location.

Further, in the defect shape extraction module (or shape information extraction device for surface defect measurement) 3, at least one linear pulsed laser beam image irradiated to the B position of the measurement specimen 5 ends of the optical fiber 64. Focusing is performed on the image lens 66 located at and signal processing of the image obtained thereby. The defect shape extraction module 3 includes an image acquisition device 41 for acquiring an image passing through the optical fiber 64 and the optical coupler 57, an illumination device 42 for illuminating the measurement specimen 5, Image storage devices 51 and 54 respectively store two images obtained by using the sensors 46 and 48 of the image acquisition device 41. In addition, defect shape information is collected from the centerline extraction devices 52 and 55 and the respective centerline information extracted from the centerline extraction devices 52 and 55 for extracting the centerline of the linear laser beam image portion from the respective images stored in the image storage devices 51 and 54. The defect shape information collecting apparatuses 53 and 56 are further included.

In the defect shape extraction module 3, the image acquisition device 41 is a beam splitter 43 for dividing a linear pulsed laser beam image irradiated onto a measurement specimen and a first image (hereinafter, referred to as a first image). Attenuation filter 44 for adjusting the intensity of the filter and a color filter 45 for removing noise by filtering a desired color band. In addition, the acquisition time of the constant sensor (hereinafter referred to as CCD sensor 46) that changes the image passing through the color filter 45 into an electrical signal and the linear to accurately obtain a linear pulse laser beam image on the surface of the measurement specimen 5 A time delay synchronizer 49 that matches the synchronization of the pulsed laser beam irradiation time can be used.

That is, the information according to the divided images by the beam splitter 43 is transmitted to the defect shape information collecting apparatuses 53 and 56 and collected. That is, the 3D shape information of the surface defect may be extracted based on the center line of the first image collected by the first defect shape information collecting device 53. Here, the center line of the first image is the center line of the images of the irradiation laser beam irradiated at a predetermined interval on the object surface.

In the defect shape extraction module 3, the second image (hereinafter, referred to as the second image) divided by the beam splitter 43 is thus disposed on the measurement specimen 5 after the irradiation laser beam is irradiated. As an image for obtaining the remaining marks image, the noise portion of this image can be removed by the color filter 47.

In addition, by using the time delay synchronizer 50, the acquisition time of the constant sensor (hereinafter referred to as CCD sensor 48) for converting the optical image signal passing through the color filter 47 into an electrical signal and the surface image of the measurement specimen Synchronization of the irradiation laser beam irradiation time in the form of linear pulses can be made consistent.

In addition, three-dimensional shape information of the surface defect may be extracted based on the center line of the object surface marks on the second image collected by the second defect shape information collecting device 56. Here, the center line of the object surface mark is a center line of the image of the mark of the object surface which may be left by the irradiation laser beam.

At this time, according to the synchronization of the sensors 46, 48 of the time delay synchronizers 49, 50, as well as the position and depth information of the defect, information on the outer shape of the defect and the bottom shape of the defect Extraction is possible.

In addition, the sensors 46 and 48 in the image capturing apparatus 41 mean a sensor including a charged coupled device (CCD) sensor, a complementary metal oxide semiconductor (CMOS) sensor, or another image capturing sensor. .

The CCD (Charged Coupled Device) sensors 46 and 48 are semiconductor memory devices that convert and transmit or store an image exposed to the CCD sensors 46 and 48 in an electrical form. The light received through the lens in Fig. 48 can be recognized by each sensor inside the CCD and converted into A / D converted digital data. The CCD sensors 46 and 48 measure the amount of light applied from each RGB sensor by using a filter for color recognition, convert the light into a digital signal, and electronically convert the incident light into RGB. The sensor can be separated into RGB primary colors using separate primary filters or separated into RGB primary colors. RGB sensors are arranged on the CCD in a mosaic manner, allowing each sensor to measure and record the amount of incoming light. The types of the CCD sensors 46 and 48 include a linear array (3 pass) method using the most basic CCD technology, three linear CCD (RGB) methods, a high resolution, trilinear array (1 pass) method mainly used in a scanner, Wide-spectrum Area CCD method for capturing the entire image in a short time, and CCD devices that are composed of square cells and CCD method adopted by digital cameras. Matrix).

In addition, the Complementary Metal-Oxide-Semiconductor (CMOS) sensor obtains data through continuous conversion of input light, integrates an analog signal and a digital signal processing circuit into one semiconductor, and the semiconductor device directly without a filter. It is a sensor that receives light.

In addition, when the non-contact surface defect inspection apparatus 200 needs to change the traveling direction of the irradiation laser beam or the measurement laser beam in order to implement the present invention, the incident angle of each laser beam may be changed. A mirror or the like may be appropriately disposed in a path through which the laser beam travels, and the number may be added or subtracted as necessary.

The control / signal processing computer 6 controls the scanner 4 using the scanner driver 61 and is in charge of various signal processing and system operations. The control / signal processing computer 6 comprehensively analyzes the image information received from the defect shape information collecting devices 53 and 56 and the signal information received from the defect information signal processing device 35 to the user. Can provide. In addition, the focusing optical system 65, the image lens 66, and the focusing optical system 67 for linear pulse laser beam irradiation may be configured as a single module and moved together by the scanner 4. In addition, the control / signal processing computer 6 allows the scanner 4 to operate in accordance with the scanner driver 61 and also controls the time delay synchronizers 49 and 50. In addition, the control / signal processing computer 6 may determine a predetermined point of the lowering portion at which the voltage or frequency of the detected ultrasonic signal falls from the maximum value as the starting point of the defective portion.

5 is a view for explaining the principle of measuring the defect shape of the non-contact surface defect inspection apparatus 200 according to an embodiment of the present invention.

As shown in FIG. 5, the defect shape information collecting devices 53 and 56 illustrate a principle of measuring the shape of surface defects from extracted centerline information. The linearly pulsed laser beam scanned continuously may be reflected to the measurement object. That is, when the linear pulsed laser beam is irradiated to the measurement object, the CCD sensor 46 (or 48) located at a certain observation angle θ is a magnification k (= f '/ f) (magnification of an image triangle with respect to an object triangle). A surface image can be obtained. The image triangle y 'may be obtained from an image acquired by the CCD sensor 46 (or 48), and a height H from a reference line may be obtained using Equation (1).

.......... (1)

.......... (One)

Therefore, the height of the object defect may be a value that varies depending on the incident angle of the linear pulsed laser beam or the position of the CCD sensor 46 (or 48), the image lens 66, or the like.

FIG. 6 is a diagram illustrating a defect shape measuring method using a linear pulsed laser beam according to one embodiment of the present invention, and FIG. 7 is a diagram illustrating a detailed method for measuring the shape of a surface defect portion of FIG. 6.

As shown in FIG. 6, the linearly pulsed laser beam that is continuously scanned may be reflected to the measurement object. The interval of the linear pulsed laser beam is constant d, and if there is a defect on the surface of the test specimen, a value h '(h' = d-m), which is proportional to its depth, can be obtained. , 48), so the depth information of the actual surface defects can be obtained using Eq. (1).

As shown in FIG. 6, three-dimensional shape information of an outer shape of a surface defect and a bottom shape of the surface defect may be extracted by obtaining an image of the linear pulse laser beam. In addition, the illuminating device 42 may be used to illuminate the linear pulsed laser beam after illuminating the defective position. As a result, the 3D shape information of the surface defect may be extracted by obtaining the marks image appearing on the surface of the measurement specimen 5. In this case, the image capturing device 41 may obtain a clearer image of the track due to the illumination of the lighting device 42.

FIG. 7 is an enlarged view of the dotted line portion of FIG. 6. Three laser beams of the linear pulsed laser beams pass through the defect, and the leftmost laser beam (hereinafter referred to as the first laser beam) and the adjacent laser beam (hereinafter referred to as the second laser beam) are spaced 'd' before undergoing the defect. Keep going. The distance between the first laser beam and the second laser beam is bent as the second laser beam passes through the concave portion of the defect. As a result, the distance between the first laser beam and the second laser beam inside the defect becomes 'm'. Thus, assuming that there is no defect with the second laser beam inside the defect, the distance between the traveling path of the second laser beam is h '= d-m.

8 is an example of an experimental results chart used to measure a defect location using the maximum-minimum value of an ultrasonic signal.

FIG. 8 shows the result of performing the position inspection of the defect by observing the change of the maximum-minimum value at each SLS position for the surface defect of 0.3 mm in width and 0.4 mm in depth using the non-contact surface defect inspection apparatus 200. The graph shown. Here, the linear pulsed laser beam is scanned at regular intervals, and every scan interval is measured while moving by the SLS technique at intervals of 60 μm.

The maximum-minimum value is due to the mutually constructive interference phenomenon of the ultrasonic signal directly induced by the linear pulsed laser beam and the signal reflected by the defect when the linear pulsed laser beam is located directly in front of the measurement specimen 5. The sudden increase increases the location of the defect. In addition, when the linear pulsed laser beam passes through the defect, the ultrasonic signal is attenuated and the attenuation is proportional to the depth of the defect so that the depth of the defect can be estimated.

9 is an example of an experimental result chart used to measure a defect location using a center frequency value of an ultrasonic signal.

FIG. 9 is an experimental result for extracting location information of a defect in the same method and conditions as in FIG. 8, and is an experimental result for extracting presence or absence of a defect by observing a center frequency of an ultrasonic signal at each SLS location. As in FIG. 8, when the linear pulsed laser beam is positioned immediately before the defect, the center frequency in the ultrasonic spectral signal at the moment when interference between the ultrasonic signal directly induced by the linear pulsed laser beam and the ultrasonic signal reflected from the surface defect occurs. Can rise significantly. Therefore, the position of the surface defect can be observed by observing the rising point of the center frequency, which is very effective.

Hereinafter, the non-contact surface defect inspection apparatus 200 according to the present invention described above with reference to FIGS. 2 and 4 will be described according to the steps of the operation process.

10 is a flowchart illustrating a non-contact surface defect inspection method according to an embodiment of the present invention.

First, the non-contact surface defect inspection apparatus 200 generates ultrasonic waves using at least one irradiation laser beam on the surface of the object (S1010). In this case, ultrasonic waves may be induced by using a laser beam for irradiation of a scanning laser source (SLS) technique such as a linear pulsed laser beam. The induced ultrasound propagates the surface of the object (S1020).

Next, the ultrasonic signal detection module 2 of the non-contact surface defect inspection apparatus 200 extracts ultrasonic signal information in a non-contact manner by irradiating a surface of an object to which the ultrasonic wave propagates with a laser beam for measurement. Accordingly, the position information and the depth information of the micro defects may be obtained based on the extracted ultrasonic signal information by the control / signal processing computer 6 (S1030). The ultrasonic signal detection module 2 may use a two-wave mixing interferometer located at regular intervals to obtain the ultrasonic signal information. In addition, the dual wave mixed interferometer may include a measuring laser device 21 and a beam splitter 22 for dividing the measuring laser beam, and the irradiation area may include a plurality of measuring areas to extract the ultrasonic signal information. Laser beams can be used. The control / signal processing computer 6 may calculate the position of the defect by judging a predetermined point of the lower portion of the lowered portion from which the amplitude or the center frequency of the detected ultrasonic signal rises above a predetermined value as a starting point of the defective portion. have. In addition, after the ultrasonic wave induced by the irradiation laser beam propagates the object, the interferometer may be sensed to inspect a defect or deterioration state of the object. The laser beam, signal information, movement of a specific device, analysis operation, etc. used in the present invention can be controlled, and a computer can be used.

In addition, the defect shape extraction module 3 of the non-contact surface defect inspection apparatus 200 captures an image of the at least one irradiation laser beam to extract defect shape information based on the centerline of the photographed irradiation laser beam. . Accordingly, the control / signal processing computer 6 can obtain the external shape of the defect and the bottom shape of the defect based on the defect shape information (S1040). The defect shape extraction module 3 may extract a center line of an image portion of the irradiation laser beam from the images of the irradiation laser beam, and extract shape information of the surface defect from the extracted center line information. have.

In addition, the defect shape extraction module 3 uses the beam splitter 43 to divide the image of the irradiation laser beam irradiated onto the surface of the object into a plurality of images and to obtain a plurality of divided images 41. It may include. In addition, the divided images are transmitted to the defect shape information collecting apparatuses 53 and 56 by the beam splitter 43, and images of the irradiation laser beam collected by the first defect shape information collecting apparatus 53 are obtained. Three-dimensional shape information of surface defects may be extracted based on the center line. In addition, the 3D shape information of the surface defect may be extracted based on the center line of the object surface marks collected by the second defect shape information collecting device 56.

In addition, the defect shape extraction module 3 further includes constant sensors 46 and 48 for converting images of the laser beam for irradiation into electrical signals, and obtains an image of the moment when the linear pulsed laser beam is irradiated. The time delay synchronizers 49 and 50 may be used to synchronize the irradiation time of the irradiation laser beam with the acquisition time of the constant sensor. In addition, the defect shape extraction module 3 includes a plurality of constant sensors 46 and 48, and each of the constant sensors acquires images of an irradiation laser beam irradiated onto an object surface, After the irradiation, the marks on the surface of the object can be obtained before the next irradiation laser beam is irradiated.

In addition, non-contact measurement of the irradiation focusing optical system 67, the image lens 66 of the shape information extraction device for obtaining an image of the linear pulsed laser beam irradiated on the surface of the measurement specimen (5) Focusing optical system 65 is fixed to one bar (bar) together and can be scanned.

In the non-contact surface defect inspection method according to the present invention as shown in FIG. 10, the details mentioned in the embodiments of FIGS. 2 to 9 may be applied as they are.

11 is an internal block diagram of a general purpose computer device 1100 that may be used with the control / signal processing computer 6 of FIG. 2 or 3 to check for defects in an object in accordance with one embodiment of the present invention.

The computer device 1100 includes at least one processor 1110 connected to a main memory including a random access memory (RAM) 1120 and a read only memory (ROM) 1130. The processor 1110 is also called a central processing unit (CPU). As is well known in the art, the ROM 1130 serves to transfer data and instructions to the CPU unidirectionally, and the RAM 1120 typically transmits data and instructions bidirectionally. Used to. RAM 1120 and ROM 1130 may include any suitable form of computer readable media. Mass storage 1140 is bidirectionally coupled to processor 1110 to provide additional data storage capabilities, and may be any of the computer readable recording media described above. The mass storage device 1140 is used to store programs, data, and the like, and is a secondary memory device such as a hard disk which is generally slower than the main memory device. Certain mass storage devices, such as CD ROM 1160, may also be used. The processor 1110 may include at least one input and output such as a video monitor, trackball, mouse, keyboard, microphone, touchscreen display, card reader, magnetic or paper tape reader, voice or handwriting reader, joystick, or other known computer input / output device. Is connected to the interface 1150. Finally, the processor 1110 may be connected to a wired or wireless communication network through the network interface 1170. Through this network connection, the procedure of the method described above can be performed. The apparatus and tools described above are well known to those skilled in the computer hardware and software arts.

The hardware device described above may be configured to operate as at least one software module to perform the operations of the present invention.

The non-contact surface defect inspection method according to the present invention can be implemented in the form of program instructions that can be executed by various computer means and recorded in a computer readable medium. The computer readable medium may include program instructions, data files, data structures, etc. alone or in combination. Program instructions recorded on the media may be those specially designed and constructed for the purposes of the present invention, or they may be of the kind well-known and available to those having skill in the computer software arts. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks, and magnetic tape, optical media such as CD-ROMs, DVDs, and floppy disks. Magneto-optical media, and hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. The medium may be a transmission medium such as an optical or metal wire, a waveguide, or the like including a carrier wave for transmitting a signal specifying a program command, a data structure, or the like. Examples of program instructions include not only machine code generated by a compiler, but also high-level language code that can be executed by a computer using an interpreter or the like. The hardware device described above may be configured to operate as one or more software modules to perform the operations of the present invention, and vice versa.

As described above, the present invention has been described by specific embodiments such as specific components and the like, but the embodiments and the drawings are provided only to help a more general understanding of the present invention, and the present invention is not limited to the above embodiments. For those skilled in the art, various modifications and variations are possible from such description.

Therefore, the spirit of the present invention should not be limited to the described embodiments, and all the things that are equivalent to or equivalent to the claims as well as the following claims will belong to the scope of the present invention. .

As described above, the non-contact surface defect inspection apparatus and method according to the present invention can not only extract defect information such as the position and depth of defects using ultrasonic waves, but also measure and provide the external shape of the defect and the bottom shape of the defect. As a result, it is possible to predict micro-defects and lifespan of materials and to make them widely used in various fields of industry.

Claims (12)

An ultrasonic induction module for generating ultrasonic waves on the surface of an object using at least one irradiation laser beam; An ultrasonic signal detection module irradiating a laser beam for measurement on the surface of the object through which the ultrasonic wave propagates and measuring ultrasonic waves on the surface of the object using a predetermined interferometer to extract ultrasonic signal information; And an image acquisition device for dividing the plurality of images of the irradiation laser beam irradiated onto the object surface at regular intervals using a beam splitter, and obtaining a plurality of divided images, wherein the plurality of images from the irradiation laser beam A defect shape extraction module for extracting and collecting a centerline from any one of the divided images to extract three-dimensional shape information of the surface defects; And Acquire the position information and depth information of the defect based on the ultrasonic signal information extracted by the ultrasonic signal detection module, and based on the defect shape information extracted by the defect shape extraction module, the outer shape of the defect and the bottom portion of the defect Control / Signal Processing Computer to Acquire Geometry Non-contact surface defect inspection apparatus comprising a. delete delete The method of claim 1, wherein the defect shape extraction module, Extracting 3D shape information of a surface defect by acquiring a track image of the object surface remaining by the irradiation laser beam based on the plurality of divided images and then extracting and collecting the center line of the track Non-contact surface defect inspection device, characterized in that. The method of claim 1, wherein the defect shape extraction module, An attenuation filter for adjusting the intensity of the image of the irradiation laser beam; A color filter for removing noise by filtering a predetermined color band of the image of the irradiation laser beam; And And a video storage device for storing images of the irradiated laser beam processed by the attenuation filter or the color filter. The method of claim 1, wherein the defect shape extraction module, A sensor for converting the image of the irradiation laser beam into an electrical signal; And A time delay synchronizing device that synchronizes the irradiation time of the irradiation laser beam with the acquisition time of the sensor Non-contact surface defect inspection apparatus comprising a. The method of claim 1, wherein the defect shape extraction module, A non-contact type image, wherein a mark image generated on the surface of the object after the irradiation laser beam is irradiated is obtained from the plurality of divided images obtained from the irradiation laser beam irradiated onto the object surface using the beam splitter Surface defect inspection device. The method of claim 1, wherein the defect shape extraction module, And after the irradiation laser beam is irradiated, before the next irradiation laser beam is irradiated, a non-contact surface defect inspection apparatus comprising a plurality of image acquisition sensors for obtaining a mark image of an object surface. The method of claim 1, The control / signal processing computer, Non-contact surface defect inspection apparatus, characterized in that the predetermined point of the falling portion descending from the maximum value of the amplitude or the center frequency of the extracted ultrasonic signal rises by more than a predetermined value as the starting point of the defect position. The method of claim 1, The defect shape extraction module is a non-contact surface defect inspection apparatus, characterized in that for more clearly extracting the image using a lighting device. Generating ultrasonic waves using at least one irradiation laser beam on the surface of the object; Irradiating a measuring laser beam on a surface of the object to which the ultrasonic wave propagates, measuring an ultrasonic signal, and obtaining position information and depth information of a defect from the measured ultrasonic signals; And Capturing an image of the at least one irradiation laser beam to extract defect shape information based on a centerline of the photographed irradiation laser beam, and obtaining an outer shape of the defect and a bottom shape of the defect from the defect shape information; step Non-contact surface defect inspection method comprising a. A computer-readable recording medium having recorded thereon a program for executing the method of claim 11.

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