JP2011089826A - Internal surface defect inspection apparatus of screw hole or hole - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inspection apparatus for precisely inspecting internal surface defects of holes without inserting an inspection head into screw holes or holes. <P>SOLUTION: When an internal surface of the screw hole 32 is imaged by a camera 16, a wide-angle lens 12 having a wide visual field angle as an objective lens is disposed away from the opening of the screw hole by a prescribed distance. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an inspection apparatus for inspecting a surface defect inside a screw hole or a hole.

  When forming a screw hole or hole in a casting by cutting, a cast hole appears on the inner surface of the screw hole or hole, or cutting chips remain in the screw hole or hole as a foreign object. May cause internal surface defects.

  There is one that automatically performs such an internal surface defect using an image processing technique instead of a visual inspection by a person (for example, see Patent Document 1).

JP 2009-014347 A

  However, since the probe that is the inspection head is inserted into the screw hole, if there is residual chips other than the cast hole, the probe and the residual chips come into contact with each other, resulting in displacement of the probe and the inside of the screw hole. There is a problem that surface defects cannot be detected stably.

  The present invention has been made in view of the above problems, and provides an internal surface defect inspection apparatus capable of accurately inspecting internal surface defects of a hole without inserting an inspection head into the screw hole or the inside of the hole. Objective.

  The first problem-solving means of the present invention includes a wide-angle lens as an objective lens, a relay lens, a half mirror, an eyepiece lens, a camera for imaging an object to be imaged, and an object to be imaged via the half mirror. An inspection head having a light source that irradiates light, an illumination power source that supplies power to the light source, an image processing device that is connected to the camera and processes an image captured by the camera, the illumination power source, and the image In a screw hole or hole internal surface defect inspection apparatus having a control device for controlling a processing device, the wide-angle lens is screw hole or hole opening when the inside of the screw hole or hole is imaged by the camera. The internal surface defect inspection apparatus is characterized by being separated by a predetermined distance.

  The second problem-solving means is characterized in that the camera images a screw hole or an inner surface of the hole so that the pixels of the image are in a square lattice arrangement, and the image processing device transmits orthogonal coordinates sent from the camera. System image information is converted into polar coordinate system image information and recorded as original image information, and the polar coordinate system image information is converted again into orthogonal coordinate system image information to develop a screw hole or a hole internal surface image. The depth difference in the depth direction is corrected based on the image information in the orthogonal coordinate system of the screw hole or the internal surface image of the hole, and the wavy distortion of the image caused by the center shift of the wide-angle lens is corrected. It is to correct.

  A third problem solving means is that the viewing angle of the wide-angle lens is 100 degrees or more.

  Furthermore, a fourth problem solving means is that the inspection head is fixed to an arm of a robot, and a robot controller controlled by the control device controls the movement of the robot.

  In the present invention, since a wide-angle lens having a large viewing angle is used as an objective lens, the inside of the screw hole or hole can be imaged by a camera at a predetermined distance from the opening of the screw hole or hole, and the inspection head is inside the screw hole or hole. Therefore, the inspection head and the residual chips come into contact with each other, so that the inspection head is not displaced, and screw holes and holes can be detected stably.

  In addition, the image processing apparatus converts the orthogonal coordinate system image information sent from the camera into the polar coordinate system image information to extract the inspection area as the original image information, and then converts it again into the orthogonal coordinate system image information. Thus, since the screw hole or the inner surface image of the hole is processed so as to become a developed image, the inner surface image can be taken and image processing can be performed without inserting the inspection head into the screw hole or hole. In addition, in order to correct the perspective difference in the depth direction of the inner surface image of the screw hole or hole, that is, the perspective difference that appears closer to the bottom even with the same dimension compared to the dimensions of the screw hole or hole opening, The size of internal surface defects can also be accurately detected. Furthermore, it corrects image wavy distortion caused by misalignment of the center of the wide-angle lens, that is, cutting traces that should be a set of diagonal straight lines and wavy lines in the thread valleys, eliminating noise components in image information that are not necessary for detection. , Can detect internal surface defects stably.

  In addition, since the viewing angle of the wide-angle lens is 100 degrees or more, it is possible to irradiate the screw hole or the entire inner surface of the hole, and an image without uneven brightness can be obtained.

  Further, since the inspection head is fixed to the robot arm and the robot controller controlled by the control device controls the movement of the robot, the inspection head is automatically and accurately positioned, and an image with less distortion is obtained.

It is a block diagram of the internal surface defect inspection apparatus of a screw hole. It is a schematic diagram which shows an inspection head. It is a graph which shows changing the exposure time of a camera, and the irradiation light quantity of high-intensity spot illumination according to the characteristic of a screw hole or a hole. It is the image of the screw hole imaged with constant brightness. It is the image of the screw hole which imaged by adjusting the exposure time of a camera and the irradiation light quantity of high-intensity spot illumination according to the characteristic of a screw hole. It is the captured image and processed image in each process of an internal surface defect inspection of a screw hole. It is a flowchart which shows the internal surface defect inspection procedure of a screw hole. It is a schematic diagram explaining "wave-like distortion".

  Hereinafter, embodiments of the present invention will be described in detail.

  FIG. 1 is a configuration diagram of an internal surface defect inspection apparatus for screw holes according to the present invention, and FIG. 2 is a diagram schematically showing an inspection head.

  As shown in FIGS. 1 and 2, the internal surface defect inspection apparatus 1 according to the present invention includes a wide-angle lens 12 whose optical axis is parallel to the axis of a screw hole (object to be imaged) 32 of a work 31, and high accuracy. An inspection head 11 comprising a relay lens 13 comprising a combination of lenses, a high-intensity spot illumination (light source) 17, a half mirror 14 that bends light from the high-intensity spot illumination 17 and irradiates the screw holes 32, and a camera 16; The robot 6 that moves the inspection head 11 away from the opening of the screw hole 32 by a predetermined distance, the robot controller 5 that controls the robot, the image processing device 3 that processes the imaged internal surface of the screw hole 32, and the high It comprises an illumination power source 4 that supplies power to the luminance spot illumination 17, and a controller 2 that controls the robot controller 5, the image processing device 3, and the illumination power source 4. .

  The light emitted from the high-intensity spot illumination 17 is bent by a half mirror, passes through the high-precision relay lens 13 and the wide-angle lens 12, and uniformly illuminates the inner surface of the screw hole 32. The reflected light from the screw hole 32 passes through the wide-angle lens 12, the high-precision relay lens 13, and the half mirror 14 and enters the camera, and the camera captures an internal surface image of the screw hole 32.

  The inspection head 11 is held away from the opening of the screw hole 32 by a predetermined distance L, and images the inner surfaces of the plurality of screw holes while moving to the position (teaching position) previously taught on the screw hole 32. To do. That is, when the robot controller moves and stops the inspection head 11 attached to the tip of the robot arm 6a to each teaching point according to a command from the control device 2, and the inspection head 11 stops at the teaching point, the high-intensity spot illumination 17 The internal surface of the screw hole irradiated in step S is imaged by the camera 16 based on the command of the image processing apparatus 3.

  When the imaging is completed, the robot controller 5 moves the inspection head 11 to the next teaching point, and the image processing apparatus 3 determines the presence or absence of an internal surface defect in the imaged area while the inspection head 11 is moving. The determination result is transmitted to the control device 2. When the imaging of all the screw holes 32 to be inspected is completed, the control device 2 displays a teaching point having an internal surface defect.

  Since the viewing angle of the wide-angle lens 12 is 100 degrees or more, the entire inner surface of the screw hole 32 can be irradiated uniformly, and an image without uneven brightness can be obtained. Note that the viewing angle θ is one of the specifications of the wide-angle lens 12 and is an angle of how much incident light that is incident in parallel is spread and emitted. In the present embodiment, the viewing angle θ is 100 degrees. As above.

  In addition, as shown in the graph of FIG. 3, the exposure time of the camera 16 and the amount of irradiation light of the high-intensity spot illumination 17 are adjusted according to the characteristics of the screw hole 32 (through screw hole or bag screw hole, screw inner diameter difference). Thus, as shown in FIG. 5, the contrast between the normal surface and the internal surface defect f is good regardless of whether it is a cap screw hole (FIG. 5A) or a through screw hole (FIG. 5B). Large images can be obtained, and defects such as cast holes and residual chips can be easily identified. FIG. 4 shows a case where an image is captured at a constant brightness without adjusting the amount of irradiation light. In the through screw hole (FIG. 4B), the screw valley 32b becomes too dark and the internal surface defect f. The contrast of

  Next, the procedure for detecting the internal surface defect f of the screw hole 32 will be described based on the captured image and processed image of FIG. 6 and the flowchart of FIG.

  In step S <b> 1, the image captured by the camera 16 (FIG. 6A) is taken into the image processing device 3 and used as an original image. At this time, the coordinates of the pixels of the image are displayed in polar coordinates.

  Steps Sa to Se are steps in which the characteristics of the screw holes 32 are determined, and the exposure time of the camera 16 is adjusted and the light intensity of the high-intensity spot illumination is automatically adjusted.

  First, in step Sa, it is determined from the captured original image whether the contour of the hole is closed or helical, and it is determined whether the object to be imaged is a screw hole or a hole (this embodiment is a body for inspecting a screw hole). Although this is the case, the present invention has this step because it can be applied to ordinary holes that are not screw holes).

  Next, in step Sb, the screw hole or the inner diameter of the hole is specified. In the case of a screw hole, the image is scanned horizontally so as to pass through the center of the image, and the inner diameter and center coordinates are calculated from the positions of the left and right ends of the contour. Similarly to the horizontal direction, the vertical and diagonal directions (45-degree oblique direction) are similarly scanned to calculate the inner diameter and the center coordinates, and the average inner diameter and the average center coordinates are calculated from the inner diameter and the center coordinates. In the case of a hole, the inner diameter and the center coordinate are calculated from the contour coordinates of the hole by the least square method.

  Next, in step Sc, the average luminance near the center of the screw hole 32 obtained in step Sb is obtained. If it is a cap screw hole, light is reflected and the brightness near the center is increased, and if it is a through screw hole, the light is transmitted and the brightness is lowered, so it is determined whether it is a cap screw hole or a through screw hole. .

  In step Sd, the exposure time of the camera 16 and the irradiation light quantity of the high-intensity spot illumination 17 are determined based on the graph of FIG. 3, and the internal surface of the screw hole 32 is imaged again in step Se.

  If the screw hole type (cap screw hole, through screw hole) and screw hole diameter are input as known information to the control device based on the drawing information or the like, the image processing device controlled by the control device is the camera 16. Since the exposure time and the irradiation light amount of the high-intensity spot illumination 17 are automatically determined, the process from step Sa to step Se may be omitted.

  Next, in step S2, an inspection area is extracted (FIG. 6B).

  In step 3, the pixel coordinates are converted from a polar coordinate system to an orthogonal coordinate system to generate a developed image of the inner surface of the so-called screw hole (FIG. 6C).

  In step S4, perspective correction is performed to correct that the opening side of the screw hole 32 is imaged larger than the bottom side even if the dimensions are the same, and a perspective correction image is generated (FIG. 6D).

  Next, in step S5, the wave-like noise (wave-like distortion) in the threads of the screw is removed. The wavy noise is that the optical axis of the wide-angle lens 12 deviates from the center of the screw hole 32 in a cutting trace, a screw thread 32a, and a screw thread 32b that should originally be a set of oblique straight lines (FIG. 8A). In this step, the undulation is corrected (FIG. 6 (e), FIG. 6 (f), and FIG. 6 (g)).

  Next, in step S6, dynamic binarization is performed in which the defect contrast is divided into two values according to a predetermined luminance threshold value (FIG. 6 (h)).

  In step S7, an internal surface defect candidate fk (not shown; the same applies hereinafter) is extracted.

  In step S8, the feature amount of the inner surface defect candidate fk extracted in step S7 (the major and minor diameters of the equivalent ellipse inscribed by the inner surface defect candidate fk, the area, the detection position, etc.) is calculated.

  In step S9, the inspection standard information recorded in advance and the feature quantity of the internal surface defect candidate fk are compared to determine whether the internal surface defect candidate fk is the internal surface defect part f or the normal surface. In the case of the internal surface defect portion f, the teaching point number, the internal surface defect position, and the feature amount are displayed on the display unit of the control device 2.

  Next, in step S10, an image obtained by converting image data that has been subjected to image processing in the orthogonal coordinate system into data in the polar coordinate system is generated again, and it is confirmed whether or not the original image is returned.

  In step S11, the completion of the inspection of all inspection parts is confirmed and the inspection is terminated.

  According to this embodiment, since the wide-angle lens 12 having a large viewing angle is used as the objective lens, the internal surface of the screw hole 32 can be imaged by the camera 16 at a predetermined distance L from the opening of the screw hole 32, and the inspection head 11 is Since it is not inserted into the screw hole 32, the position of the inspection head 11 due to contact between the inspection head 11 and residual chips does not occur, and the internal surface defects of the screw hole 32 can be detected stably.

  Further, after the image processing apparatus 3 converts the image information of the orthogonal coordinate system sent from the camera 16 into the image information of the polar coordinate system and extracts the inspection area as the original image information, the image information of the orthogonal coordinate system is again obtained. Therefore, the inner surface image of the screw hole 32 is processed to be a developed image, so that the inner surface image can be captured and image processed without inserting the inspection head 11 into the screw hole 32. In addition, in order to correct the perspective difference in the depth direction of the internal surface image of the screw hole 32, that is, the perspective difference in which the same size appears closer to the bottom than the dimensions of the opening of the screw hole 32, the inner surface is corrected. The size of the defect f can also be accurately detected. In addition, the image distortion caused by misalignment of the center of the wide-angle lens 12, that is, the waviness of the cutting trace and the thread crest line that should be a set of oblique straight lines, is corrected. The internal surface defect f can be detected stably.

  In addition, since the viewing angle of the wide-angle lens 12 is 100 degrees or more, it is possible to irradiate the entire inner surface of the screw hole 32, and an image without uneven brightness can be obtained.

  Further, since the inspection head 11 is fixed to the arm 6a of the robot and the robot controller 5 controlled by the control device 2 controls the movement of the robot 6, the inspection head 1 is automatically and accurately positioned, and the image is less distorted. Is obtained.

DESCRIPTION OF SYMBOLS 1 Internal surface defect inspection apparatus 2 Control apparatus 3 Image processing apparatus 4 Power supply for illumination 5 Robot controller 6 Robot 6a Arm 11 Inspection head 12 Wide-angle lens 13 Relay lens 14 Half mirror 15 Eyepiece 16 Camera 17 High-intensity spot illumination (light source)
31 Work 32 Screw hole (Target to be imaged)
32a Screw thread 32b Screw valley f Internal surface defects

Claims (4)

  An inspection head having a wide-angle lens as an objective lens, a relay lens, a half mirror, an eyepiece lens, a camera that images an object to be imaged, and a light source that emits light to the object to be imaged via the half mirror, in order from the object to be imaged side An illumination power source that supplies power to the light source, an image processing device that is connected to the camera and processes an image captured by the camera, and a control device that controls the illumination power source and the image processing device. In addition, the wide-angle lens is separated from the opening of the screw hole or hole by a predetermined distance when the inside of the screw hole or hole is imaged by the camera. Internal surface defect inspection device.   The camera images a screw hole or an inner surface of the hole so that the pixels of the image are in a square lattice arrangement, and the image processing device converts the orthogonal coordinate system image information sent from the camera into polar coordinate system image information. Is recorded as original image information, the image information of the polar coordinate system is converted again to image information of the orthogonal coordinate system, and the screw hole or the inner surface image of the hole is processed to be a developed image, 2. A perspective difference in a depth direction is corrected based on image information of an orthogonal coordinate system of an inner surface image of a hole, and a wave-like distortion of an image caused by a center shift of the wide-angle lens is corrected. The internal surface defect inspection apparatus described in 1.   3. The internal surface defect inspection apparatus according to claim 1, wherein a viewing angle of the wide-angle lens is 100 degrees or more.   The internal surface defect inspection according to any one of claims 1 to 3, wherein the inspection head is fixed to a robot arm, and a robot controller controlled by the control device controls movement of the robot. apparatus.

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