JP2017062159A - Defect inspection device and defect inspection method - Google Patents

Abstract

A defect inspection apparatus capable of reducing the time required for defect inspection of a workpiece having a curved surface shape. A defect inspection apparatus 1 generates a laser light source that emits laser light, generates object light and reference light from the laser light, irradiates the object light toward the inspection target surface, and reflects it from the inspection target surface. Interference caused by interference, an interference optical system that causes interference between the light and the reference light, an optical member that changes the direction of the optical axis of the object light, and makes the object light incident on the curved inspection target surface from a plurality of different directions An imaging device that acquires the fringes as imaging data and a control device 8 that calculates the shape of the inspection target surface based on the imaging data are provided. [Selection] Figure 1

Description

  The present invention relates to a defect inspection apparatus that inspects a defect on a workpiece surface using holographic interference.

On the surface of a work such as a spoiler or a handle, there may be a case where minute irregularities and steps called bokeh or sink mark are generated by painting. Such irregularities and steps are detected as defects when the height exceeds the allowable tolerance.

  Holographic interferometry is known as a technique for detecting such a workpiece defect. The holographic interferometry method irradiates a workpiece with object light, causes the object light reflected from the workpiece to interfere with a reference light that does not irradiate the workpiece, and images a hologram (interference fringes) caused by the interference with a CCD camera or the like. Record as data. Then, by analyzing the imaging data with a computer, the shape of the workpiece can be restored by numerical calculation, and a defect can be detected.

  Patent Document 1 discloses a method for measuring a tooth surface shape of a gear using a holographic interferometry method. In this measurement method, incident angle data of object light is acquired from a theoretical tooth surface simulation image, and a measurement error due to a difference in incident angle is calculated. For this reason, it is possible to accurately measure the shape of a tooth surface having a curved surface with different incident angles at each portion.

JP-A-4-258709

  According to the measurement method of Patent Document 1, it is possible to measure the shape of a workpiece having a curved surface. However, since interference fringes are densely formed on a surface having a large curvature, a plurality of interference fringes may be recognized by the camera as one interference fringe. In such a case, it is necessary to divide the measurement site, change the incident angle of the object light, and shoot the image in multiple times, which takes time.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a defect inspection apparatus capable of shortening the time required for defect inspection of a workpiece having a curved surface shape.

  The defect inspection apparatus according to the present invention generates a laser light source that emits laser light, and generates object light and reference light from the laser light, irradiates the object light toward the inspection target surface, and from the inspection target surface. An interference optical system that causes interference between the reflected light of the object and the reference light, and an optical member that changes the direction of the optical axis of the object light and causes the object light to enter the curved inspection target surface from a plurality of different directions. And an imaging device that acquires interference fringes caused by the interference as imaging data, and a control device that calculates the shape of the inspection target surface based on the imaging data.

  The defect inspection method according to the present invention includes a step of emitting laser light from a laser light source, a step of generating object light and reference light from the laser light, irradiating the object light toward an inspection target surface, and the object Changing the direction of the optical axis of light, causing the object light to enter the curved inspection target surface from a plurality of different directions, and causing the reflected light from the inspection target surface to interfere with the reference light And acquiring the interference fringes generated by the interference as imaging data, and calculating the shape of the inspection target surface based on the imaging data.

  According to the present invention, since the direction of the optical axis of the object light is changed and the object light is incident on the curved inspection target surface from a plurality of different directions, the number of imaging required for the inspection can be reduced. Therefore, it is possible to shorten the time required for defect inspection of a workpiece having a curved shape.

It is the schematic of the defect inspection apparatus which concerns on 1st Embodiment of this invention. It is a block diagram of a control device concerning a 1st embodiment of the present invention. It is a schematic diagram of the interference measurement sensor which concerns on 1st Embodiment of this invention. It is a figure for demonstrating the imaging data which concern on 1st Embodiment of this invention. It is a figure for demonstrating the relationship between the interference fringe and camera pixel which concern on 1st Embodiment of this invention. It is a schematic diagram of the revolver which concerns on 1st Embodiment of this invention. It is a schematic diagram which shows the cross section of the revolver which concerns on 1st Embodiment of this invention. It is a figure for demonstrating the lens structure which concerns on 1st Embodiment of this invention. It is a schematic diagram of the revolver which concerns on 1st Embodiment of this invention. It is a figure for demonstrating the inspection area of the workpiece | work which concerns on 1st Embodiment of this invention. It is a figure for demonstrating the image processing which concerns on 1st Embodiment of this invention. It is a flowchart which shows the defect inspection method which concerns on 1st Embodiment of this invention. It is a flowchart which shows the defect inspection method which concerns on 1st Embodiment of this invention. It is a schematic diagram which shows the cross section of the revolver which concerns on 2nd Embodiment of this invention. It is a figure for demonstrating the lens structure which concerns on 2nd Embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic diagram of a defect inspection apparatus 1 according to the present embodiment. The defect inspection apparatus 1 includes an interference measurement sensor 3, a revolver 4, a robot arm 5, a rotary stage 6, a robot controller 7, and a control device 8. In the following description, the interference measurement sensor 3 and the revolver 4 are collectively referred to as an inspection head 2.

  The interference measurement sensor 3 is a sensor using holographic interference, and can image a hologram (interference fringe) of an inspection object (hereinafter also referred to as a workpiece) 9 and obtain it as imaging data. A disc-shaped revolver 4 is attached to the interference measurement sensor 3, and the interference measurement sensor 3 irradiates the workpiece 9 with laser light and receives reflected light from the workpiece 9 through the revolver 4. The revolver 4 includes an optical member or the like, and can change the direction of the optical axis of the laser beam passing therethrough.

  The robot arm 5 is an articulated arm type robot, and the inspection head 2 is attached to the tip of the robot arm 5. The robot arm 5 can freely move the inspection head 2 by changing the posture of the arm. A workpiece 9 is held on the rotary stage 6. The rotary stage 6 includes a drive motor and the like, and the front and back of the workpiece 9 can be reversed by rotating the stage. By combining the movements of the robot arm 5 and the rotary stage 6, the inspection head 2 can be brought close to a desired measurement site of the workpiece 9.

  A robot controller 7 is connected to the robot arm 5 and the rotary stage 6. The robot controller 7 can sequence control the operations of the robot arm 5 and the rotary stage 6 according to a predetermined program.

  The control device 8 is a computer including a CPU, a memory, a storage device, and the like, and is connected to the interference measurement sensor 3, the revolver 4, and the robot controller 7. The control device 8 controls the operations of the interference measurement sensor 3, the revolver 4, and the robot controller 7, and has a function of storing and analyzing imaging data acquired by the interference measurement sensor 3. These functions are realized by the CPU executing a predetermined program stored in the memory.

  The workpiece 9 is a metal or resin member, and minute irregularities on the surface of the workpiece 9 are to be inspected. The surface of the workpiece 9 is divided into a plurality of inspection target surfaces, and the measurement by the defect inspection apparatus 1 is sequentially performed for each inspection target surface. Although the workpiece 9 has a quadric surface shape, the surface shape of each inspection target surface can be regarded as a primary curved surface or a flat surface. In the subsequent drawings, for convenience, the workpiece 9 is shown in a primary curved surface shape (semi-cylindrical shape).

  FIG. 2 is a block diagram of the control device 8 according to the present embodiment. The control device 8 includes a sensor control unit 81, a revolver control unit 82, a robot control unit 83, a storage unit 84, an image processing unit 85, and a display unit 86.

  The sensor control unit 81 outputs a control signal to the interference measurement sensor 3, and controls the timing at which the interference measurement sensor 3 irradiates laser light and the timing at which an interference fringe is imaged. The revolver control unit 82 outputs a control signal to the revolver 4 and controls the timing at which the revolver 4 switches the optical member.

  The robot control unit 83 outputs a drive command to the robot controller 7. The robot controller 7 drives the robot arm 5 and the rotary stage 6 based on the drive command from the robot control unit 83 to move the inspection head 2 to a predetermined measurement position.

  The storage unit 84 stores the imaging data acquired by the interference measurement sensor 3. The image processing unit 85 analyzes the imaging data stored in the storage unit 84 and generates shape data of the workpiece 9. The shape data includes a relative height displacement with respect to the reference surface for each inspection target surface. Furthermore, the image processing unit 85 determines the quality of the workpiece 9 by extracting defects from the generated shape data. The image processing unit 85 stores inspection results such as shape data and defect information in the storage unit 84.

  The display unit 86 is a display, a printer, or the like, and can display analysis data from the image processing unit 85, for example, various information such as the shape data of the workpiece 9, the presence / absence and position of defects, and the like.

  FIG. 3 is a schematic diagram of the interference measurement sensor 3 according to the present embodiment. The interference measurement sensor 3 includes a laser light source 301, an optical isolator 302, convex lenses 303, 305, 309, 311, pinholes 304 and 310, beam splitters 306 and 308, a reflection mirror 307, a beam splitter (beam combiner) 312, and a camera 313. I have.

  The laser light source 301 is, for example, a YAG laser having an oscillation wavelength of 532 nm, and emits coherent laser light. As the laser light source 301, a He—Ne laser, a semiconductor laser, or the like may be used. Laser light emitted from the laser light source 301 enters the convex lens 303 via the optical isolator 302. The optical isolator 302 blocks the return light to the laser light source 301.

  The convex lens 303 condenses the laser light incident from the optical isolator 302 and passes it through the pinhole 304. The pinhole 304 is disposed at the condensing position of the convex lens 303 and removes unnecessary diffraction components from the laser light. The convex lens 305 converts the laser light passing through the pinhole 304 into parallel light having a predetermined beam diameter for measurement and makes it incident on the beam splitter 306.

  The beam splitter 306 branches the laser light incident from the convex lens 305 into object light passing through the beam splitter 306 (solid arrow) and reference light reflected by the beam splitter 306 by 90 degrees (dotted arrow). The object light enters the reflection mirror 307, and the reference light enters the beam splitter 312. The reflection mirror 307 changes the optical path of the object light incident from the beam splitter 306 and emits the light toward the work 9. The object light emitted toward the workpiece 9 passes through the beam splitter 308 and is irradiated onto the workpiece 9 via the revolver 4.

  The object light applied to the workpiece 9 via the revolver 4 is reflected by the surface of the workpiece 9 (hereinafter referred to as reflected light), and is received by the beam splitter 308 via the revolver 4 again. The beam splitter 308 reflects the reflected light from the workpiece 9 by 90 degrees and makes it incident on the convex lens 309.

  The convex lens 309 collects the reflected light incident from the beam splitter 308 and passes it through the pinhole 310. The pinhole 310 is disposed at the condensing position of the convex lens 309 and removes unnecessary diffraction components from the reflected light. The convex lens 311 converts the reflected light passing through the pinhole 310 into parallel light having a predetermined beam diameter for imaging and makes it incident on the beam splitter 312.

  The beam splitter 312 passes the reflected light incident from the convex lens 311. Further, the beam splitter 312 reflects the reference light incident from the beam splitter 306 by 90 degrees, and enters the camera 313 so as to overlap the reflected light passing through the beam splitter 312. That is, the beam splitter 312 causes the object light and the reference light to interfere with each other and causes the interference light to enter the camera 313.

  The camera 313 is a CCD camera or a CMOS camera, and has an imaging surface 313a with high resolution (for example, 3000 × 3000 pixels). Interference light enters the imaging surface 313a of the camera 313 vertically, and interference fringes are formed. The camera 313 can image interference fringes formed on the imaging surface 313a and output it as imaging data.

  FIG. 4A is a diagram for describing imaging data according to the present embodiment. 4A (a) is an example of interference fringes formed on the imaging surface 313a of the camera 313. FIG. In FIG. 4A (a), two interference fringes 901 and 902 are formed. Since the interval between the interference fringes 901 and 902 is equal to the half wavelength of the object light irradiated on the work 9, the depth of the work 9 that can be measured by one imaging (the length in the direction perpendicular to the surface of the work 9). Is the number of interference fringes × the wavelength of the laser light to be used / 2.

  4A (b) is imaging data acquired by imaging the interference fringes of FIG. 4A (a) with the camera 313, and the luminance values of the interference fringes in the CC line section of FIG. 4A (a) are shown in a graph. Has been. The interference fringes imaged by the camera 313 are recorded as luminance values corresponding to the pixels of the camera 313. As shown in FIG. 4A (b), the recorded brightness value is a relative value based on the brightness value at the position of each interference fringe.

  FIG. 4B is a diagram for explaining the relationship between interference fringes and camera pixels according to the present embodiment. FIG. 4B (a) schematically shows interference fringes formed on the imaging surface 313a of the camera 313, and a part of the pixels constituting the imaging surface 313a is enlarged. Each square portion corresponds to one pixel, a pixel having a large luminance value is represented by a white square (bright), and a pixel having a small luminance value is represented by a black square (dark).

  Since the combination of a pair of bright pixels and dark pixels is a theoretical limit for recognizing one interference fringe, the number of interference fringes that can be recorded as imaging data depends on the number of pixels on the imaging surface 313a. That is, when the number of pixels on the imaging surface 313a corresponding to the measurement depth (the number of pixels in the X-axis direction in FIG. 4A) is N, the theoretical maximum number of fringes is N / 2. Therefore, for example, when the wavelength of the object light is 532 nm and the number of pixels in the X-axis direction of the imaging surface 313a is 3000, the depth of (3000/2) × (532/2) = 0.399 mm is obtained by one imaging. The shape of the workpiece 9 can be measured.

  As shown in FIG. 4B (b), when the object light of parallel light is irradiated onto the workpiece 9 having a curved shape, the outer peripheral portion (surrounded by a dotted line) having a large curvature, that is, a large shape change in the Z-axis direction. Interference fringes are densely formed in the portion). At this time, two or more interference fringes may be formed in one pixel on the imaging surface 313a of the camera 313 or continuously on adjacent pixels (see FIGS. 4C and 4D). In such a case, since the camera 313 cannot recognize a plurality of interference fringes, accurate measurement cannot be performed. That is, the size of the area that can be measured by one imaging is limited by the resolution of the camera 313.

  The revolver 4 according to the present embodiment includes an optical member, and the optical member changes the direction of the optical axis of the object light applied to the workpiece 9 in a direction perpendicular to the curved surface of the workpiece 9. For this reason, in the present embodiment, interference fringes are less likely to be dense even in a curved surface portion having a large curvature, and the above-described limitation can be relaxed. Hereinafter, the revolver 4 will be described in detail.

  FIG. 5 is a schematic diagram of the revolver 4 according to the present embodiment, and the curved surface portion of the work 9 is an object to be imaged. The revolver 4 includes a rotating shaft 401, through holes 402 and 403, a lens holder 410, two prism lenses 411, and three cylindrical lenses 412.

  The revolver 4 is a disk-shaped member, and is attached to the interference measurement sensor 3 by a rotation shaft 401 provided at the center. The revolver 4 is formed with a circular through hole 402 and a rectangular through hole 403. The revolver 4 rotates the rotation shaft 401 in accordance with the drive signal from the revolver control unit 82, and selectively arranges the through hole 402 or 403 on the optical path of the object light. That is, the object light emitted from the interference measurement sensor 3 is irradiated to the workpiece 9 through the through hole 402 or 403.

  The sizes of the through holes 402 and 403 are designed according to the beam diameter of the object light. For example, the beam diameter of the object light, the diameter of the through hole 402, and the length of one side of the through hole 403 can be set to 100 mm. The shape and number of the through holes 402 and 403 are not limited to the example of the present embodiment.

  A box-shaped lens holder 410 is mounted below the rectangular through hole 403 (on the work 9 side). The upper and lower surfaces of the lens holder 410 are open, and two prism lenses 411 and three cylindrical lenses 412 are held inside the lens holder 410. These lenses refract the object light incident on the through hole 403 and change the direction of the optical axis to irradiate the work 9. Similarly, these lenses refract the reflected light from the work 9 and change the direction of the optical axis to enter the interference measurement sensor 3.

  On the other hand, an optical member such as a lens is not attached to the circular through hole 402. The object light and the reflected light incident on the through hole 402 simply pass through the revolver 4 without changing the direction of the optical axis and enter the work 9. Similarly, the reflected light from the workpiece 9 enters the interference measurement sensor 3 as it is without changing the direction of the optical axis.

  The revolver control unit 82 of the control device 8 can switch the through holes 402 and 403 arranged on the optical path of the object light by rotating the revolver 4. Therefore, it is selected whether to irradiate the work 9 directly with the object light emitted from the interference measurement sensor 3 or to irradiate the work 9 with the optical axis of the object light changed via the prism lens 411 and the cylindrical lens 412. It is possible.

  FIG. 6 is a schematic diagram showing a cross section of the revolver 4 according to the present embodiment. A prism lens 411 and a cylindrical lens 412 are arranged on the optical path of the object light irradiated to the work 9 by the revolver 4. The broken line arrows indicate the directions of the optical axes of the object light and the reflected light.

  6A is a cross-sectional view taken along line AA in FIG. The prism lens 411 is a triangular prism, and the column axis of the lens is arranged perpendicular to the optical axis of the object light. The cylindrical lens 412 is a semi-cylindrical lens, and the column axis of the lens is arranged perpendicular to the optical axis of the object light. These lenses are arranged in the order of the prism lens 411 and the cylindrical lens 412 when viewed from the interference measurement sensor 3 side (laser light source side), and the column axes of the lenses face the same direction (Y-axis direction). .

  6B is a cross-sectional view taken along line BB in FIG. The prism lens 411 is arranged such that the side surface (triangular surface) of the prism is parallel to the optical axis of the object light and the curvature direction of the workpiece 9 (XZ plane). The cylindrical lens 412 is arranged such that the side surface (semicircular surface) of the lens is parallel to the optical axis of the object light and the curvature direction of the workpiece 9 (XZ plane). In the two prism lenses 411, the two prisms are spaced apart and arranged in parallel in a direction perpendicular to the optical axis of the object light. In the three cylindrical lenses 412, one lens is arranged perpendicular to the optical axis of the object light, and two lenses are arranged in parallel in an arc shape on both sides thereof. The two cylindrical lenses 412 on both sides are arranged to face the two prism lenses 411, respectively.

  As described above, the prism lens 411 and the cylindrical lens 412 are arranged so as to refract the passing object light and reflected light in a plane (XZ plane) along the primary curved surface of the work 9. In other words, the object light and the reflected light do not change in the optical axis in the plane (YZ plane) different from the primary curved surface direction of the workpiece 9 (FIG. 6A), but follow the primary curved surface of the workpiece 9. In the plane (XZ plane), the optical axis changes (FIG. 6B). Therefore, these lens configurations have a function of converting the object light applied to the work 9 from a plane wave to a curved wave, and increasing the incident angle of the object light with respect to the curved surface of the work 9.

  FIG. 7 is a diagram for explaining a lens configuration according to this embodiment. FIG. 7A shows a cross-sectional view taken along line BB in FIG. For convenience, the revolver 4 and the lens holder 410 are not shown. FIG. 7B also shows a cross-sectional view taken along line BB in FIG. 5, but the shape of the workpiece 9 is different from that in FIG.

  As described above, object light is incident on the two prism lenses 411 and the three cylindrical lenses 412 from the interference measurement sensor 3. The object light at the time of incidence is a parallel light beam, and the beam diameter Φ of the object light is, for example, 100 mm. The workpiece 9 has a primary curved surface with a radius of curvature r centered on the origin R. The size of the workpiece 9 is, for example, a width of 250 mm, a length of 1200 mm, and a curvature radius of 20 mm.

  The two prism lenses 411 have the same refractive index, and are arranged with a central portion of the through hole 403 therebetween. Therefore, the two prism lenses 411 refract only the light beam of the outer part of the object light incident on the through-hole 403 and enter the two cylindrical lenses 412 facing each other.

  The three cylindrical lenses 412 have the same focal length f and are arranged in an arc shape so that all the focal positions coincide. The two cylindrical lenses 412 on both sides are angled with respect to the refractive angle of the prism lens 411 with respect to the central cylindrical lens 412. The focal length f is, for example, 34.05 mm. The distance between the three cylindrical lenses 412 and the workpiece 9 is adjusted so that the focal point thereof coincides with the origin R of the workpiece 9.

  The portion of the object light that is refracted by the prism lens 411 is perpendicularly incident on the plane surface of the corresponding cylindrical lens 412. The light beam in the central portion of the object light is directly incident on the plane surface of the cylindrical lens 412 disposed in the center perpendicularly. Therefore, all the light rays of the object light are collected by the corresponding cylindrical lens 412 with the origin R of the curved surface of the workpiece 9 as a focal point, and are irradiated from the vertical direction on the curved surface of the workpiece 9.

  The object light irradiated on the curved surface of the work 9 is received by the interference measurement sensor 3 along a path opposite to that at the time of incidence. That is, the reflected light diffused from the workpiece 9 is converted into parallel light by the cylindrical lens 412, and the direction of the optical axis is aligned by the prism lens 411 and then incident on the interference measurement sensor 3.

  When the lens configuration of the present embodiment is used, the curved surface portion of the workpiece 9 corresponding to the total light collection angle (hereinafter referred to as measurement angle θ) of the three cylindrical lenses 412 can be measured at a time. 9a. For example, when three cylindrical lenses 412 having a condensing angle of 28 degrees are used, the measurement angle θ of the inspection target surface 9a is 84 degrees.

  The size (surface area) of the inspection target surface 9a of the workpiece 9 varies depending on the distance WD between the cylindrical lens 412 and the workpiece 9. The distance WD is determined based on the focal length f of the cylindrical lens 412 and the curvature radius r of the workpiece 9. For example, when the curvature radius r of the workpiece 9 is large, the distance WD is set small, and when the curvature radius r of the workpiece 9 is small, the distance WD is set large. The setting data of the distance WD is stored in advance in the robot controller 7 in association with each inspection target surface 9a. At the time of measurement, the robot controller 7 can move the robot arm 5 to adjust the distance WD.

  As shown in FIG. 7B, the lens configuration of the present embodiment can be applied even when the workpiece 9 has a concave curved surface. That is, the distance WD is set for the concave inspection target surface 9 a so that the focal point of the cylindrical lens 412 is located between the inspection target surface 9 a and the cylindrical lens 412.

  Note that the number and arrangement of the prism lens 411 and the cylindrical lens 412 are not limited, and can be appropriately selected according to the performance of the lens, the shape of the workpiece, and the like.

  FIG. 8A is a schematic diagram of the revolver 4 according to the present embodiment, and a plane portion of the work 9 is an object to be imaged. FIG. 8B is a cross-sectional view taken along line AA in FIG. The broken line arrow indicates the optical axis of the object light, and the circular through hole 402 is arranged on the optical path of the object light. The object light emitted from the interference measurement sensor 3 passes through the through hole 402, is irradiated perpendicularly to the plane portion of the workpiece 9, and is reflected toward the interference measurement sensor 3. The direction of the optical axis of the object light does not change via the revolver 4.

  FIG. 9 is a diagram for explaining the inspection target surface 9a of the workpiece 9 according to the present embodiment. FIG. 9A is a side view of the revolver 4 and the workpiece 9, and FIG. 9B is a top view (front side) of the revolver 4 and the workpiece 9. Object light is irradiated from above the work 9 through the revolver 4 and imaging is performed. In the following description, only the front side of the work 9 will be described as the inspection target surface, but the same applies to the back side of the work 9.

  The shape of the workpiece 9 is classified into a flat surface portion 91 and a curved surface portion 92. The flat surface portion 91 may be a substantially flat surface, and a predetermined radius of curvature (for example, 145 mm) may be determined as a threshold value, and a surface larger than the threshold value may be determined as the flat surface portion 91 and a surface smaller than the threshold value as the curved surface portion 92. .

  Each of the flat surface portion 91 and the curved surface portion 92 of the workpiece 9 is divided into a plurality of inspection target surfaces 9a. The inspection target surface 9a is a range measured by one imaging (one shot), and the measurement is sequentially performed by the inspection head 2. Each of the sections in FIG. 8B corresponds to the inspection target surface 9a. In the figure, for the sake of convenience, reference numerals of the inspection target surface 9a are given to only some sections.

  The number of inspection target surfaces 9a (outlined sections) of the flat portion 91 can be determined based on the beam diameter Φ of the object light. Further, the number of inspection target surfaces 9a (shaded areas) of the curved surface portion 92 can be determined by dividing the spread angle φ of the curved surface portion 92 of the work 9 by the measurement angle θ of the lens. The overall shape of the workpiece 9 can be acquired from a three-dimensional measuring machine, design data, or the like.

  Data such as the overall shape of the workpiece 9, the position information of the inspection target surface 9a, and the measurement order are registered in advance in the robot controller 7 in the form of three-dimensional coordinates or the like. Alternatively, the information may be stored in the storage unit 84 of the control device 8 so that the control device 8 appropriately transmits necessary information to the robot controller 7.

  FIG. 10 is a diagram for explaining image processing according to the present embodiment. The image processing is performed by the image processing unit 85 of the control device 8, and for example, bottom hat processing is applied to the shape data. 10A to 10D schematically show an example of bottom hat processing. For convenience, a cross-sectional image (two-dimensional image) of the workpiece 9 is shown as shape data, but a three-dimensional image can be processed similarly.

  In the bottom hat process, first, a derate (expansion) process is performed on the original shape data (FIG. 10A) (FIG. 10B). For example, the luminance value of the shape data is replaced with the maximum luminance value of the surrounding pixels. That is, by expanding the shape data, minute irregularities in the contour portion are deleted (filled).

  Next, an erosion (shrinkage) process is performed on the shape data after the derating process (FIG. 10C). For example, the luminance value of the shape data is replaced with the minimum luminance value of the surrounding pixels. That is, the part that was not deleted by the derate process is returned to the original state. Therefore, the shape data after the erode process is obtained by deleting only minute irregularities from the original shape data. Therefore, by obtaining the difference between the shape data after erosion and the original shape data, it is possible to extract the minute irregularities included in the original shape data (FIG. 10D).

  11A and 11B are flowcharts showing the defect inspection method according to the present embodiment. The processing performed by the control device 8 is realized by the CPU of the control device 8 executing a predetermined inspection program stored in the storage unit 84.

  First, the operator sets the workpiece 9 on the rotary stage 6 (step S101). Next, when the operator activates the defect inspection apparatus 1, the control apparatus 8 starts executing the inspection program (step S102). That is, the robot control unit 83 of the control device 8 transmits a drive command to the robot controller 7 to cause the robot controller 7 to start controlling the robot arm 5.

  The robot controller 7 controls the robot arm 5 to move the inspection head 2 to a predetermined imaging position with respect to the first inspection target surface 9a (step S103). The imaging position is a position away from the inspection target surface 9a by a distance WD.

  When the movement of the robot arm 5 is started, the revolver control unit 82 of the control device 8 moves the revolver 4 based on the shape data of the inspection target surface 9a stored in the storage unit 84 in advance, for example, three-dimensional CAD data. Rotate (step S104). That is, the revolver control unit 82 selects the through hole 403 in which the lens holder 410 is mounted for the inspection target surface 9a of the curved surface portion 92, and the lens for the inspection target surface 9a of the flat surface portion 91. The through hole 402 to which no is attached is selected.

  Next, the image processing unit 85 of the control device 8 determines whether or not unprocessed imaging data (interference fringes) remains in the storage unit 84 (step S105). If unprocessed imaging data exists (YES in step S105), the image processing unit 85 calculates shape data of the inspection target surface 9a from the imaging data, and performs image processing on the obtained shape data (step). S106).

  Specifically, the image processing unit 85 of the control device 8 extracts a minute unevenness included in the shape data by applying a bottom hat process to the calculated shape data. Next, the image processing unit 85 compares the size of the extracted minute unevenness with a predetermined threshold, and determines whether the minute unevenness is a defect. Further, the image processing unit 85 generates an enhanced image in which the uneven portion determined to be a defect is emphasized with a predetermined color on the inspection target surface 9 a and stores the enhanced image in the storage unit 84.

  Subsequently, the control device 8 displays the determination result by the image processing unit 85, that is, the presence or absence (OK, NG) of the defect in the inspection target surface 9a on the display unit 86 (step S107). Further, the control device 8 may display an enhanced image of the inspection target surface 9a. The processing from step S105 to step S107 by the image processing unit 85 is executed in parallel with the processing of step S103, that is, the movement of the robot arm 5 by the robot controller 7.

  If unprocessed imaging data does not exist in the storage unit 84 of the control device 8 (NO in step S105), the processes in steps S106 and S107 are skipped.

  Next, the control device 8 determines whether or not the robot arm 5 is stopped (step S108). That is, it is determined whether or not the movement of the robot arm 5 started in step S103 is completed and the inspection head is located at a predetermined imaging position. If the robot arm 5 is still moving (NO in step S108), the control device 8 waits until the movement of the robot arm 5 is completed and the robot arm 5 stops. When the robot arm 5 is stopped (YES in step S108), the sensor control unit 81 of the control device 8 controls the interference measurement sensor 3 to emit laser light from the laser light source 301 (step S109). .

  Subsequently, the sensor control unit 81 of the control device 8 controls the interference measurement sensor 3, and images the interference fringes with the camera 313 (step S110). Further, the sensor control unit 81 receives the image data captured from the interference measurement sensor 3 and stores it in the storage unit 84. When the imaging is completed, the sensor control unit 81 controls the interference measurement sensor 3 to stop the oscillation of the laser light from the laser light source 301 (step S111).

  Next, the control device 8 determines whether or not the imaging of all the inspection target surfaces 9a on the front side of the workpiece 9 has been completed (step S112). When the inspection target surface 9a that has not been imaged remains on the front side (NO in step S112), the control device 8 executes the processing after step S103. That is, the robot controller 7 drives the robot arm 5 to move the inspection head 2 to the imaging position of the next inspection target surface 9a (step S103), and the control device 8 executes the processing from step S104 to step S111 again. To do.

  When imaging of all the inspection target surfaces 9a on the front side of the work 9 is completed (YES in step S112), the control device 8 determines whether imaging of all the inspection target surfaces 9a on the back side of the work 9 is completed. Is determined (step S113). When the inspection target surface 9a that has not been imaged remains on the back side (NO in step S113), the control device 8 determines whether or not the work 9 set on the rotary stage 6 faces the back side ( Step S114).

  If the workpiece 9 is facing the front side (NO in step S114), the robot control unit 83 of the control device 8 transmits a drive command to the robot controller 7 so that the workpiece 9 faces the back side. The rotary stage 6 is rotated (step S115).

  After the work 9 is reversed to the back side, or when the work 9 is facing the back side (YES in step S114), the flowchart returns to step S103. That is, the robot controller 7 drives the robot arm 5 to move the inspection head 2 to the imaging position of the next inspection target surface 9a (step S103), and the control device 8 performs the processing from step S104 to step S111. Try again.

  When imaging of all the inspection target surfaces 9a on the back side of the workpiece 9 is completed (YES in step S113), the robot control unit 83 of the control device 8 transmits a drive command to the robot controller 7, and the robot arm 5, The rotary stage 6 is returned to the origin position (step S116).

  In addition, the image processing unit 85 of the control device 8 performs image processing on the imaged data of the inspection target surface 9a that was imaged last (step S117). This is the same process as the process in step S106.

  Finally, the control device 8 acquires data such as the presence / absence of defects on all the inspection target surfaces 9a and the emphasized image from the storage unit 84, and performs comprehensive determination of the workpiece 9 (step S118). For example, the control device 8 displays, on the display unit 86, the number and position of defects for each inspection target surface 9a, a determination result of whether the workpiece 9 is a good product or a defective product, and the like.

  As described above, the defect inspection apparatus according to the present embodiment has a lens configuration including a prism lens and a cylindrical lens. This lens configuration refracts the laser light applied to the object to be inspected and converts the wavefront of the object light from a flat surface to a curved surface and from a curved surface to a flat surface. By irradiating the curved surface portion of the object to be inspected with curved wave object light, it is possible to enlarge the area that can be measured by one imaging (one-direction image) limited by the resolution of the camera. Therefore, it is possible to reduce the number of times of imaging required for the inspection, reduce the movement time of the robot arm accompanying the imaging, and shorten the time required for the inspection.

(Second Embodiment)
Subsequently, a defect inspection apparatus according to the second embodiment of the present invention will be described. Since the defect inspection apparatus according to the present embodiment is configured in the same manner as the defect inspection apparatus according to the first embodiment, differences from the first embodiment will be mainly described.

  FIG. 12 is a schematic diagram of the revolver 4 according to the present embodiment. The revolver 4 includes a rotation shaft 401, through holes 402 and 403, a lens holder 410, two prism lenses 413, and two reflection mirrors 414.

  A rectangular tube-shaped lens holder 410 is attached to the lower part (workpiece 9 side) of the rectangular through hole 403. Two prism lenses 413 and two reflection mirrors 414 are held inside the lens holder 410. These lenses and mirrors refract the object light incident on the through hole 403 and change the direction of the optical axis to irradiate the work 9. Similarly, these lenses refract the reflected light from the work 9 and change the direction of the optical axis to enter the interference measurement sensor 3.

  FIG. 13 is a schematic diagram showing a cross section of the revolver 4 according to this embodiment, and is a cross-sectional view taken along the line BB in FIG. The broken line arrows indicate the directions of the optical axes of the object light and the reflected light.

  The reflection mirror 414 is held by the lens holder 410 by the adjustment member 414a. The adjustment member 414a can rotate the reflection mirror 414 around the Y-axis direction and move it in the X-axis direction. Therefore, the angle and position of the optical axis of the object light applied to the workpiece 9 can be arbitrarily adjusted in the XZ plane.

  The prism lens 413 and the reflection mirror 414 are arranged so that the object light and the reflected light that have passed through and incident are refracted in the plane (XZ plane) along the primary curved surface of the work 9 and the optical axis is changed. These lens configurations have a function of irradiating object light onto the curved surface of the work 9 from a plurality of different directions and increasing the incident angle of the object light with respect to the curved surface of the work 9.

  Thus, the defect inspection apparatus according to the present embodiment has a lens configuration including a prism lens and a reflection mirror. This lens configuration refracts laser light to be irradiated on the inspection object, and simultaneously irradiates object light from a plurality of different directions. By adjusting the reflecting mirror and increasing the incident angle of the object light with respect to the curved surface portion of the object to be inspected, the area that can be measured by one imaging (one-direction image) limited by the resolution of the camera is expanded. Can do. Therefore, it is possible to reduce the number of times of imaging required for the inspection, reduce the movement time of the robot arm accompanying the imaging, and shorten the time required for the inspection.

  The present invention is not limited to the above-described embodiment, and can be modified without departing from the spirit of the present invention. For example, in the present invention, an aspherical lens may be used for the lens configuration, or a plurality of lens configurations having different revolvers may be switched.

DESCRIPTION OF SYMBOLS 1 Defect detection apparatus 2 Inspection head 3 Interference measurement sensor 301 Laser light source 313 Camera 313a Imaging surface 4 Revolver 411 Prism lens 412 Cylindrical lens 5 Robot arm 6 Rotating stage 7 Robot controller 8 Control device 9 Work 9a Inspection object surface 91 Flat surface 92 Curved surface 901, 902 interference fringes

Claims (7)

A laser light source for emitting laser light;
An interference optical system that generates object light and reference light from the laser light, irradiates the object light toward the inspection target surface, and causes interference between reflected light from the inspection target surface and the reference light;
An optical member that changes the direction of the optical axis of the object light and makes the object light incident on the curved inspection target surface from a plurality of different directions;
An imaging device that acquires interference fringes generated by the interference as imaging data;
A control device that calculates the shape of the inspection target surface based on the imaging data;
A defect inspection apparatus comprising:   The defect inspection apparatus according to claim 1, further comprising a revolver that holds the optical member and selectively arranges the optical member on an optical path of the object light.   The defect inspection apparatus according to claim 1, wherein the plurality of different directions are directed to a center of curvature of the inspection target surface.   The defect inspection apparatus according to claim 1, wherein the optical member includes a prism lens and a cylindrical lens. The prism lens includes two prism lenses arranged in parallel and spaced apart in a direction perpendicular to the optical axis of the object light,
The cylindrical lens includes one cylindrical lens arranged perpendicular to the optical axis of the object light, and two cylindrical lenses arranged in parallel in an arc shape on both sides of the one cylindrical lens. Including
The defect inspection apparatus according to claim 4, wherein each of the two cylindrical lenses is disposed on the inspection target surface side of the prism lens so as to face the two prism lenses.   The optical member is provided at a distal end portion of a robot arm, and the robot arm changes a distance between the optical member and the inspection target surface according to a radius of curvature of the inspection target surface. The defect inspection apparatus in any one of thru | or 5. Emitting laser light from a laser light source;
Generating object light and reference light from the laser light and irradiating the object light toward a surface to be inspected;
Changing the direction of the optical axis of the object light, and causing the object light to be incident on the curved inspection target surface from a plurality of different directions;
Causing the reflected light from the surface to be inspected to interfere with the reference light;
Obtaining interference fringes caused by the interference as imaging data;
Calculating the shape of the inspection target surface based on the imaging data;
A defect inspection method.

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