CN110687130A - Automatic detection method for inner wall defects of micro-holes - Google Patents

Abstract

The invention relates to an automatic detection method for inner wall defects of micro-holes. The detection device used is divided into two parts, a fixed part and a rotating part, and the fixed part includes a camera and a lens, a ring light source, a connecting piece, a light-shielding cylinder and a turntable fixed part; The rotating part includes an optical information transmission part, a clamping part, a support plate and a turntable rotating part, and includes the following steps: the adopted detection device is fixed on the lifting platform, the ring light source is turned on, the optical information transmission part is controlled to enter the measured hole, and the collection An inner wall image is used to demarcate the initial direction, which is used as a benchmark to unify the direction of the collected images, which is convenient for later judgment of defect positions; the collection of panoramic images in the hole is completed by using the lift table and the turntable of the detection device; the effective area extraction is realized by using digital image processing technology , defect size and location detection.

Description

Automatic detection method for inner wall defects of micropores

technical field

The invention relates to a defect detection method, in particular to an automatic detection device for defects in the inner wall of micro-holes based on optical measurement.

Background technique

Micro holes are more and more widely used in aerospace, automotive, energy and chemical fields. In the precision casting process of automobile engine cylinder heads, aerospace vehicle heat pipes and other devices, the inner wall surface of micro holes often produces some tiny cracks , pores, pits and other defects, these defects may cause the leakage of high-pressure gas or liquid inside the components, especially the joints, resulting in the reduction of equipment performance, and even lead to safety accidents.

At present, the commonly used pipeline inner wall defect detection technologies include ultrasonic method, eddy current method, magnetic flux leakage method, etc., but they can only be used for large diameter pipe holes. For small holes below 10mm, an industrial endoscope with a small outer diameter can be used, but it can only be manually operated to determine whether there is a defect, and the size and location of the defect cannot be automatically quantitatively given. In addition, the existing measurement device based on a 360° cylindrical annular belt panoramic image optical transmission component can realize automatic detection of the inner wall defects of small holes with an inner diameter of 10 mm. On the whole, for several kinds of micro-pipe detection schemes that are relatively common at present, the light source and sensing components must all enter the inside of the pipe. Although with the development of technology and the improvement of manufacturing level, the size of optical devices and other devices can be continuously reduced, but due to the complexity of the system measurement function, the miniaturization of the pipeline under test, and the further miniaturization of the system structure, there are certain technical challenges. problem. At present, there is no automatic detection device for the inner wall defects of holes with an inner diameter of 4mm-10mm.

Relevant literature on the detection of defects on the inner surface of micro-holes (①Wu Bin, Shao Zhenyu, Zhang Yunhao. Construction and technology of defect measurement system on the inner wall of micro-pipes [J]. Optoelectronics. Laser, 2014, 25(02): 293-298; ② Zhang Yunhao. Micro-holes Research on key technologies of flexible visual inspection system for wall defects[D]. Tianjin University, 2014; ③EnHong,Hongwei Zhang,ReuvenKatz,John S.Agapiou.Non-contact inspection of internal threads of machinedparts[J].The International Journal of Advanced Manufacturing Technology, 2012,62(1-4).④EnHong,Reuven Katz,Brian Hufnagel,John Agapiou.Optical method for inspecting surface defects inside a small bore[J].MeasurementScienceandTechnology,2010,21(1). The micro-hole inner wall defect measurement device with a panoramic image optical transmission component on the face ring, but it can only measure small holes with an inner diameter of 10mm at least, and cannot meet the detection requirements of smaller tube holes generated with the development of the casting process.

SUMMARY OF THE INVENTION

In order to overcome the deficiencies of the prior art and meet the detection requirements of smaller tube holes generated with the development of the casting process, the present invention provides a method for traversing the panorama of the inner wall of the measured hole by automatically rotating and raising and lowering the optical information transmission component to achieve high-precision measurement. An automatic detection device for inner wall defects of micro-holes and a detection method are given. The technical solution is as follows:

An automatic detection method for defects on the inner wall of a micro-hole, the detection device used is divided into two parts, a fixed part and a rotating part, the fixed part includes a camera and a lens, a ring light source, a connecting piece, a light-shielding cylinder and a turntable fixed part; the rotating part includes Optical information transmission parts, clamps, pallets and turntable rotating parts, wherein,

The camera, the lens and the ring light source are fixedly connected with the fixed part of the turntable through the connector; the shading tube is fixed on the outer periphery of the lens, and the shading tube is not in contact with the optical information transmission part to prevent stray light from entering the lens;

The optical information transmission component includes a light shield, a frosted surface, a tapered light entrance surface 5, a light guide column, a plane lens, and a 45° reflector at the bottom end. The cone is arranged at the lower part of the hood. The hood and the frosted surface jointly prevent ambient light from entering the optical information transmission part from the upper end; a conical light entry surface is arranged at the lower part of the frosted surface, and the light generated by the ring light source passes through the conical light entry. The inner wall of the measured hole is illuminated along the light guide column, and the partial image of the inner wall of the measured hole is reflected to the upper end through the plane lens and the bottom 45° reflector, passes through the light-transmitting hole, enters the lens, and is imaged on the camera;

The support plate and the clamping part are fixedly connected with the rotating part of the turntable, the optical information transmission part is fastened on the rotation of the turntable by the clamping part and the support plate, and the support plate is provided with a hole allowing the light guide column to pass through.

The detection method includes the following steps:

(1) The detection device used is fixed on the lifting platform, the ring light source is turned on, the optical information transmission part is controlled to enter the measured hole, and an image of the inner wall is collected to calibrate the initial direction, which is used as a benchmark to unify the direction of the collected image, which is convenient for later stages. Determine the defect location;

(2) Use the lift table and the turntable of the detection device to complete the acquisition of the panoramic image in the hole;

(3) Using digital image processing technology to achieve effective area extraction, defect size and position detection.

The method of step (3) is as follows:

a) Convert the obtained original image from RGB image to grayscale image, use circular mean filter to preprocess the image, and use the method of histogram equalization to enhance the image contrast;

b) Perform Gaussian filtering on the preprocessed image, use the standard Canny algorithm to detect the edge of the effective area, extract the ROI area, and rotate the ROI area according to the initial direction to the same direction;

c) use Wiener filter to process the ROI area of the image, use the Suzuki algorithm to extract the defect area, calculate the number of pixels contained, and obtain the defect size;

d) According to the order of acquiring the images, number the images and correspond one-to-one with the position of the inner wall of the tested hole; combine the coordinates of the defect center on the image to obtain the position of the defect on the inner wall of the tested hole.

The invention can realize the non-contact automatic high-precision defect detection and shape measurement of the inner wall of the micro-hole of 4mm-10mm. It can meet the high-precision requirements of automatic detection of defects on the inner wall of micro-holes in aerospace, military equipment and other parts.

Description of drawings

FIG. 1 is a schematic diagram of image acquisition of an optical information transmission part of an automatic detection device for inner wall defects of a micro-hole.

FIG. 2 is a schematic diagram of the optical path transmission principle of the optical information transmission component of the automatic detection device for defects in the inner wall of the micro-hole.

FIG. 3 is a schematic diagram of the structure design of a separate lighting system of an automatic detection device for defects on the inner wall of a micro-hole.

Figure 4 is a flow chart of the automatic detection of defects on the inner wall of micropores.

1. Light hood 2. Light transmission hole 3. Frosted surface 4. Ring light source 5. Ring-shaped 45° conical light entrance surface 6. Light guide column 7. Inner wall of the measured hole 8. Flat lens 9.45° reflector 10. Camera 11. Lens 12. Connecting parts 13. Turntable fixing part 14. Shading cylinder 15. Turntable rotating part 16. Optical information transmission part 17. Clamping part 18. Supporting plate

Detailed ways

The invention provides an automatic detection device for realizing high-precision measurement of defects on the inner wall of micro-holes with a diameter of less than 10 mm by automatically rotating and raising and lowering the optical information transmission component to traverse the panorama of the inner wall of the measured hole, and provides a detection method. The automatic detection device for defects on the inner wall of a micro-hole of the present invention adopts the idea of importing an external light source and exporting an internal image to improve the resolution by locally collecting images, and then realize the image acquisition of the entire inner wall of the micro-hole through rotation and depth. The lighting system, the image acquisition device and the optical information transmission part are separated, and the optical information transmission part rotates independently. Through the reasonable design of the optical information transmission part, the external illumination light is introduced into the area to be measured in the hole, and the same optical information transmission part Optical image export of the area to be measured, combined with image information processing technology to solve technical problems such as the design of the illumination light source system in the hole, the optimal design of the transmission optical system, local area imaging, and local area image information processing, etc., to establish a micro hole with a detection accuracy of 0.01mm Inner wall defect detection system.

The present invention will be described below with reference to the embodiments.

This embodiment uses the principle of local imaging of the inner surface of the small hole by the optical information transmission component, and designs a mechanical device that traverses the inner surface of the small hole by lifting and rotating the optical information transmission component through the illumination of an external ring light source. The control program and the image processing program are used to realize the fast automatic and high-precision detection of the inner wall defects of the 4mm-10mm inner diameter micro-holes. The above technical solutions require the use of optical information transmission components (such as SP-730 from SIGHT-PIPE), ring light sources (today's optoelectronic ring machine vision light sources), cameras (such as REV-50AM industrial cameras from Yuanqi Intelligent), lenses (such as AFT) -ZL0910 microscope head), lifting table (such as Beijing Zhuoli Hanguang PSA200-11-Z high-precision electric lifting table), turntable (such as Beijing Zhuoli Hanguang RAK200 high-precision electric rotating table), and computer realization.

1. Structure of automatic detection device for inner wall defects of micro-holes:

As shown in FIG. 1 and FIG. 2 , the structure of the optical information transmission part 16 includes a light shield 1, a light-transmitting hole 2, a frosted surface 3, an annular 45° conical light entrance surface 5, a light guide column 6, a plane lens 8, and a 45° reflection surface. mirror 9. The hood 1 made of black rubber is fitted over the upper light-transmitting part of the optical information transmission member 16 , and together with the frosted surface 3 , prevents stray light from entering the optical information transmission member 16 from the upper end. The light generated by the annular light source 4 passes through the annular 45° conical light entrance surface 5 and illuminates the inner wall 7 of the hole to be measured along the light guide column 6 . The partial image of the inner wall 7 of the measured hole is reflected to the upper end through the plane lens 8 and the bottom 45° reflector 9 , passes through the light transmission hole 2 , enters the lens 11 , and is imaged in the camera 10 . Since each position can only obtain an image of a certain angle at a fixed depth of the inner wall 7 of the hole to be measured, it is necessary to rotate the optical information transmission member 16 once to obtain an image of the entire circumference at this depth.

As shown in Figure 3, the structure of the automatic detection device for micro-hole inner wall defects is divided into two parts, a fixed part and a rotating part:

The fixing part includes the camera 10 , the lens 11 , the ring light source 4 , the connecting piece 12 , the light shielding cylinder 14 and the turntable fixing part 13 . The connecting piece 12 is inserted into the interior of the turntable fixing portion 13 to be engaged with the turntable fixing portion 13 . The camera 10 and the lens 11 are connected by threads; the shading cylinder 14 and the lens 11 are connected by threads, and the shading cylinder 14 is not in contact with the optical information transmission part 16; Diameter matching, the lower end of the lens 11 is inserted into the connector 12 from above and fastened by adding a top wire on the side; the ring light source 4 is inserted into the connector 12 from below and fastened by adding a top wire on the side.

The rotating part includes an optical information transmission member 16 , a holder 17 , a pallet 18 and a turntable rotating part 15 . The supporting plate 18 is connected with the rotating part 15 of the turntable by screws, and the clamping member 17 and the supporting plate 18 are also connected by screws. The frictional force between the transmission member 16 and the holding member 17 rotates together with the turntable rotating part 15 .

First, the separation design of the fixed part and the rotating part ensures that the optical information transmission part 16 is not affected by the ring light source 4, the camera 10, and the lens 11, and maintains a good coaxiality when rotating in the inner wall 7 of the measured hole, so as to avoid it. It is dangerous to run into a wall in a narrow hole. At the same time, the stationary of the ring light source 4, the lens 11 and the camera 10 avoids the winding of the control wires.

Second, the secondary light-shielding structure includes a light-shielding cover 1 and a light-shielding cylinder 14. The light-shielding cover 1 can prevent stray light from entering the measured hole along the optical information transmission part 16 and affect the imaging effect. Light cannot be imaged.

Third, the device is installed on a lifting platform, wherein the lifting platform and the turntable are connected to the control box and controlled by the computer together with the camera 10 . Driven by the lifting table to move up and down into and out of the hole to be tested, first realize the full-length image of the hole in the same direction, and then rotate the turntable to repeat the full-length acquisition in the other direction, and so on to complete the panoramic image acquisition of the inner wall of the small hole.

2. As shown in Figure 3, the automatic detection method for defects on the inner wall of micropores includes the following steps:

(1) The installation of the automatic detection device for defects on the inner wall of the micro-hole is completed, the ring light source 4 is turned on, the control box of the turntable and the lifting table is connected to the computer, and the camera 10 is connected to the computer.

(2) Select the serial port connecting the control box of the turntable and the lifting platform with the computer to ensure that the connection with the control box is successful;

(3) Control the optical information transmission part 16 to enter the hole to be tested, and collect an image of the inner wall to demarcate the initial direction, which is used as a benchmark for unifying the direction of the collected image, which is convenient for later judgment of the defect position;

(4) Start the automatic acquisition mode, and the camera 10 collects images at a fixed frame rate while the lifting platform descends at a constant speed. After reaching the specified depth, the turntable rotates by an angle, continues to rise to collect images, and repeats this process until the acquisition of panoramic images in the hole is completed;

(5) After the image acquisition is completed, it rises and leaves the hole to be tested, and the image is uniformly transferred to the initial direction through software processing, and the technology of digital image processing is used to achieve effective area extraction, defect size, position detection and other targets. The specific implementation methods include:

a) Transform the acquired original image from RGB image to grayscale image. The image is preprocessed with a circular mean filter, and the contrast of the image is enhanced by the method of histogram equalization.

b) Perform Gaussian filtering on the image, use the standard Canny algorithm to detect the edge of the effective area, and extract the ROI area. And rotate the ROI area according to the initial direction to the same direction.

c) Use the Wiener filter to process the image, use the Suzuki algorithm to extract the defect area, calculate the number of pixels contained, and obtain the defect size.

d) According to the sequence of acquiring images, number the images to correspond one-to-one with the positions of the inner wall 7 of the measured hole. Combined with the coordinates of the defect center on the image, the position of the defect on the inner wall 7 of the hole to be tested can be obtained.

(6) Generate a test report, including the number of defects, defect size and defect coordinates.

Claims (2)

1. An automatic detection method for defects on the inner wall of micro-holes, the detection device used is divided into two parts, a fixed part and a rotating part, the fixed part includes a camera and a lens, a ring light source, a connector, a light-shielding cylinder and a turntable fixed part; The part includes an optical information transmission part, a holder, a pallet and a turntable rotating part, wherein, The camera, the lens and the ring light source are fixedly connected with the fixed part of the turntable through the connector; the shading tube is fixed on the outer periphery of the lens, and the shading tube is not in contact with the optical information transmission part to prevent stray light from entering the lens; The optical information transmission component includes a light shield, a frosted surface, a tapered light entrance surface 5, a light guide column, a plane lens, and a 45° reflector at the bottom end. The cone is arranged at the lower part of the hood. The hood and the frosted surface jointly prevent ambient light from entering the optical information transmission part from the upper end; a conical light entry surface is arranged at the lower part of the frosted surface, and the light generated by the ring light source passes through the conical light entry. The inner wall of the measured hole is illuminated along the light guide column, and the local image of the inner wall of the measured hole is reflected to the upper end through the plane lens and the bottom 45° reflector, passes through the light-transmitting hole, enters the lens, and is imaged on the camera; The support plate and the clamping part are fixedly connected with the rotating part of the turntable, the optical information transmission part is fastened on the rotation of the turntable by the clamping part and the support plate, and the support plate is provided with a hole allowing the light guide column to pass through. The detection method includes the following steps: (1) The detection device used is fixed on the lifting platform, the ring light source is turned on, the optical information transmission part is controlled to enter the measured hole, and an image of the inner wall is collected to calibrate the initial direction, which is used as a benchmark to unify the direction of the collected image, which is convenient for later stages. Determine the defect location; (2) Use the lift table and the turntable of the detection device to complete the acquisition of the panoramic image in the hole; (3) Using digital image processing technology to achieve effective area extraction, defect size and position detection. 2. method according to claim 1, is characterized in that, the method of step (3) is as follows: a) Convert the obtained original image from RGB image to grayscale image, use circular mean filter to preprocess the image, and use the method of histogram equalization to enhance the image contrast; b) Perform Gaussian filtering on the preprocessed image, use the standard Canny algorithm to detect the edge of the effective area, extract the ROI area, and rotate the ROI area according to the initial direction to the same direction; c) use Wiener filter to process the ROI area of the image, use the Suzuki algorithm to extract the defect area, calculate the number of pixels contained, and obtain the defect size; d) According to the sequence of acquiring images, number the images one-to-one with the position of the inner wall of the tested hole; combine the coordinates of the defect center on the image to obtain the position of the defect on the inner wall of the tested hole.

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