Line scanning optical acquisition and detection method and laser scanning acquisition and detection system

Abstract

The invention discloses a line scanning optical acquisition and detection method and a laser scanning acquisition and detection system. The acquisition method comprises the step of acquiring line-by-line image information of a detected object by line scanning in a manner that a scanning line and a scanning direction are inclined on a scanning projection plane. The detection method comprises the step of judging whether the detected object has defects based on the centring line image. The acquisition system comprises a laser projector, an area-array camera and a scanning driving unit, the linear laser projector and the area-array camera are configured to be fixed in relative position and relative angle, and the scanning driving unit is configured to be capable of moving the linear laser projector and / or the measured object so as to enable a centering line of the linear laser projector to scan on the measured object. The detection system further comprises an image processing unit and a defect judgment unit. By arranging the scanning lines inclined to the scanning direction, the detection resolution and the information amount can be ingeniously increased on the premise that the cost of existing equipment is not increased, and detection of a high-speed moving object is particularly facilitated.

Description

Technical Field

[0001] The present invention relates to optical line scanning technology, and particularly to a line scanning optical acquisition and detection method, a laser scanning acquisition and detection system. Background Art

[0002] By scanning line by line to obtain the image information of an object, compared with the technology of taking a whole picture, high-resolution images can be collected. However, in many cases, the scanning speed is restricted by the processing scenario. Sometimes, it is necessary to scan an object moving very fast, or to mount a sensing element on a high-speed moving carrier for scanning. It is difficult to reconcile the scanning accuracy and speed. Especially, without increasing costs and without changing the main parameters of the equipment, no good solution has been proposed yet.

[0003] Furthermore, in the online laser three-dimensional scanning technology, the information obtained in each step is the information on a plane. These plane information are constructed into three-dimensional information. Compared with the two-dimensional detection technology, the amount of information obtained is extremely different, and their respective limit scanning speeds are very different, resulting in the scanning speed of three-dimensional laser scanning being much lower than that of two-dimensional line scanning. This problem is particularly prominent in engineering practice. For example, when using three-dimensional laser scanning to scan railway rails, the scanning accuracy and the expected scanning speed are a pair of contradictions. Summary of the Invention

[0004] In view of the above problems, the present invention is developed, and its purpose is to provide a line scanning optical acquisition and detection method for reconciling scanning accuracy and scanning speed, and a three-dimensional laser scanning detection system.

[0005] The first aspect of the present invention provides a line scanning optical acquisition method, wherein the line scanning is performed to acquire the line-by-line image information of the object to be measured in a manner that the scanning line is inclined to the scanning direction on the scanning projection plane.

[0006] Furthermore, the scanning line is constituted by the field of view lines of a line array optical sensor; the field of view lines are stepped on the object to be measured so that the line array optical sensor acquires the line-by-line image information of the object to be measured.

[0007] Wherein, the line array optical sensor can be a line array photoelectric coupling camera. The acquisition method further includes projecting illumination on the object to be measured. In addition, the line array optical sensor can also be a line array infrared camera.

[0008] Another further, the scanning line is constituted by the projection center line of a line laser projector; the projection center line is stepped on the object to be measured, and a surface array camera with a fixed relative position and relative angle to the line laser projector takes pictures of the projection center line to obtain the line-by-line image information of the object to be measured based on the projection center line.

[0009] Specifically, the relative angle between the light projection direction of the line laser projector and the view-finding direction of the area array camera is fixed.

[0010] Furthermore, the obtaining of the line-by-line image information of the object to be measured based on the projection line includes extracting the projection line image from the captured image of the projection line.

[0011] As a transformation method for obtaining the line-by-line image information of the object to be measured based on the projection line, it may also include performing misaligned layer stacking on the captured image of the projection line in step units.

[0012] As an implementation scheme, the area array camera captures the projection line from an angle capable of collecting the three-dimensional contour of the object to be measured.

[0013] The second aspect of the present invention provides a line scanning optical detection method, wherein it is determined whether there are defects in the object to be measured based on the projection line image extracted by the above optical acquisition method. As a specific method, it can be determined whether there are defects in the object to be measured based on the contour of the projection line image.

[0014] Furthermore, the detection method further includes splicing and / or correcting the projection line image.

[0015] Specifically, the splicing includes following and connecting the projection line images line by line in step units, for example, so as to splice the line-by-line image information into the image information of the entire object to be measured. The correction includes removing abnormal data and / or rotating, stretching or compressing the contour.

[0016] The contour information of the projection line contour can be compared with the reference contour information, specifically including the comparison of the line-by-line contours and the comparison of the contour information after splicing and / or correction, and also including extracting defect features according to the line-by-line contours or the contour information after splicing and / or correction.

[0017] As an alternative or a scheme that can be combined with contour comparison, it may also include comparing the projection line image information with the reference image information, especially including comparing the spliced projection line image information with the reference image information, specifically including comparing the corrected and spliced projection line image information with the reference image information, and specifically including extracting defect features from the spliced and / or corrected image information.

[0018] The third aspect of the present invention provides a laser scanning acquisition system, including a line laser projector, a matrix camera, and a scanning drive unit. The line laser projector and the matrix camera are configured to have a fixed relative position and a fixed relative angle. The fixed relative angle is the relative angle between the light projection direction of the line laser projector and the view-finding direction of the matrix camera. The scanning drive unit is configured to be able to move the line laser projector and / or the object to be measured so that the projection line of the line laser projector scans on the object to be measured. The line laser projector is configured such that the projection line is inclined with respect to the scanning direction on the scanning projection plane. The matrix camera is configured to photograph the projection line during the scanning process from an angle capable of collecting the three-dimensional contour of the object to be measured.

[0019] The fourth aspect of the present invention provides a laser scanning detection system, including: the above-mentioned laser scanning acquisition system; an image processing unit, which is data-connected to the matrix camera of the laser scanning acquisition system and is used to receive the captured image of the projection line photographed by the matrix camera during the scanning process and extract the projection line image; a defect judgment unit, which is data-connected to the image processing unit and is used to receive the projection line image extracted by the image processing unit and judge whether there is a defect in the object to be measured based on the projection line image.

[0020] Furthermore, the image processing unit is also configured to splice and / or correct the projection line image.

[0021] The fifth aspect of the present invention provides a three-dimensional laser scanning detection system, including a line laser projector, a matrix camera, and a scanning drive unit. The line laser projector and the matrix camera are configured to have a fixed relative position and a fixed relative angle. The scanning drive unit is configured to move the line laser projector and / or the object to be measured so that the projection line of the line laser projector scans on the object to be measured. The matrix camera is configured to photograph the projection line during the scanning process from an angle capable of collecting the contour of the object to be measured. Among them, the line laser projector is configured such that the projection line is inclined with respect to the scanning direction on the scanning projection plane. It further includes an image processing unit and a defect judgment unit. The image processing unit is configured to extract the line-by-line image information of the object to be measured based on the projection line from the captured image of the projection line. The defect judgment unit is configured to judge whether there is a defect in the object to be measured at least based on the contour information in the line-by-line image information.

[0022] Furthermore, the image processing unit can also be configured to extract the image information of the projection line from the captured image of the projection line. The image processing unit can also be configured to splice and / or correct the line-by-line image information.

[0023] The sixth aspect of the present invention provides a three-dimensional scanning detection system, which includes: a linear directional light projector, an area array camera, and a scanning driving unit. The linear directional light and the area array camera are configured to have a fixed relative position and relative angle. The scanning driving unit is configured to move the linear directional light and / or the object to be measured so that the projection line of the linear directional light scans on the object to be measured. The area array camera is configured to photograph the projection line during the scanning from an angle capable of collecting the contour of the object to be measured. Among them, the linear directional light is configured so that the projection line is inclined to the scanning direction on the scanning projection plane. The system further includes an image processing unit and a defect judgment unit. The image processing unit is configured to extract the line-by-line image information of the object to be measured based on the projection line from the photographed image of the projection line. The defect judgment unit is configured to judge whether there is a defect in the object to be measured at least based on the contour information in the line-by-line image information.

[0024] The seventh aspect of the present invention provides a defect detection system based on high-speed three-dimensional laser scanning, which includes a line laser projector, an area array camera, and a scanning driving unit. The line laser projector and the area array camera are configured to have a fixed relative position and relative angle. The relative angle is fixed as the relative angle between the light projection direction of the line laser projector and the view-finding direction of the area array camera. The scanning driving unit is configured to move the line laser projector and / or the object to be measured at high speed so that the projection line of the line laser projector scans on the object to be measured. The area array camera is configured to photograph the projection line during the scanning from an angle capable of collecting the contour of the object to be measured. The line laser projector is configured so that the projection line is inclined to the scanning direction on the scanning projection plane. The system further includes an image processing unit and a defect judgment unit. The image processing unit is configured to extract the line-by-line image information of the object to be measured based on the projection line from the photographed image of the projection line. The defect judgment unit is configured to judge whether there is a defect in the object to be measured at least based on the contour information in the line-by-line image information. Specifically, the high speed is 50 - 120 Km / H.

[0025] Through the scheme of the present invention in which the scanning line is inclined to the scanning direction, it is possible to cleverly increase the detection resolution and information amount without increasing the cost of existing equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram for explaining the line scanning detection method of the present invention.

[0027] Figure 2 It is a schematic diagram for explaining the conventional scanning detection method.

[0028] Figure 3 It is an effect diagram for explaining the comparison of the information amount between the present invention and the conventional scanning scheme.

[0029] Figure 4 It is a flowchart showing an embodiment of the line scanning detection method of the present invention.

[0030] Figure 5 It is a flowchart showing another embodiment of the line scanning detection method of the present invention.

[0031] Figure 6 It is a flowchart showing still another embodiment of the line scanning detection method of the present invention.

[0032] Figure 7 It is a flowchart showing yet another embodiment of the line scanning detection method of the present invention.

[0033] Figure 8 It is a flowchart showing yet still another embodiment of the line scanning detection method of the present invention.

[0034] Figure 9 It is a schematic diagram for explaining three-dimensional laser scanning by the triangulation method.

[0035] Figure 10 It schematically shows Figure 9 the effect diagram of applying the present invention in the three-dimensional laser scanning based on the triangulation method in

[0036] Figure 11 is an effect diagram showing the experimental comparison between the present invention and the prior art, where Figure 11a is an image obtained based on vertical scanning, Figure 11b is the original image obtained based on inclined scanning, Figure 11c is the image after correction and reconstruction of the original image obtained by inclined scanning.

[0037] Figure 12a It is a schematic diagram for explaining vertical scanning of railway rails, Figure 12b It is a schematic diagram for explaining the application of the laser scanning technology based on the triangulation method of the present invention in the inspection of rail defects.

[0038] Figure 13 It is a functional schematic diagram showing an embodiment of the line scanning detection system of the present invention. Detailed implementation manners

[0039] Scanning is a traversing concept, and a certain action is successively completed in a step-by-step or continuous manner. The line scanning technology involved in the present invention means traversing the scanning area in units of lines, which is different from, for example, the area-by-area shooting and scanning of area array photoelectric sensors. When line scanning is applied for optical acquisition, it often obtains step-by-step acquisition in the form of frame rate.

[0040] The line scanning involved in the present invention is used to detect the object to be measured. Therefore, the processing actions in the line scanning process are limited to obtaining the measured information corresponding to each line of the object to be measured from the object to be measured in line units.

[0041] The scanning unit of line scanning is embodied as a scanning line in the present invention, and the following methods are listed in the embodiments of the present invention.

[0042] In one method, the scanning line corresponds to the field of view line of a line array optical sensor. A line array optical sensor is an optical sensing device that includes a single row of pixels arranged in a line array. When collecting an image, a single row of line array pixel matrix is exposed, and the image is finally constructed through the single row of pixel lines. Here, by forming the field of view lines corresponding to the pixel lines into scanning lines, the detection process of the entire scanning area is completed row by row during the scanning step.

[0043] According to some existing or foreseeable technical deformations, the pixel line may not be limited to a single row of pixels. The scanning lines formed by pixel lines composed of two or more rows of pixels and their corresponding field of view lines should still be regarded as within the definition scope of the scanning lines of the present invention.

[0044] In another method, the scanning line corresponds to the projection line projected by a line laser projector onto the object to be measured. Based on its strong directivity, the line laser projector can project a linear projection line onto the area where the object to be measured is configured. Due to the strong brightness of the laser, a diffuse reflection line that is strongly different from the surrounding area can be formed in the projected area, thereby characterizing the pattern and contour of the area to be measured. When a camera is configured at a different angle from the light projector to take a picture, the image information of the area including the projection line can be obtained, and the contour line of the object to be measured with respect to the projection line is included in this information. Here, the projection line forms a straight line on the scanning projection plane including the scanning trajectory, which is the scanning line involved in the present invention. As the scanning step progresses, the projection line traverses the object to be measured, thereby enabling the camera to continuously obtain the contour information of the entire detectable surface of the complete object to be measured.

[0045] The so-called scanning projection plane in the present invention refers to the plane that moves in the scanning direction, generally manifested as the plane where the trajectory of the movement or relative movement of the object to be measured is located.

[0046] The present invention provides a line scanning optical acquisition method for line scanning and acquiring the line-by-line image information of the object to be measured in such a way that the scanning line and the scanning direction are inclinedly configured on the scanning projection plane.

[0047] Figure 1 It is a schematic diagram for explaining the line scanning detection method of the present invention. In this figure, the shaded area represents the scanning area, and the dots represent each scanning resolution unit. Taking the line array camera scanning as an example, the dots represent the resolution density projection corresponding to each pixel. The Y-axis is the scanning direction, Ls is the step length of the line scanning, and Li is the radiation length of the scanning line on the scanning area. As shown in the figure, the scanning line and the scanning direction are inclinedly configured.

[0048] Taking the linear array camera scanning as an example, the pixel density on the scanning line depends not only on the configured height of the camera and the pixels of the linear array camera itself. When the scanning line is gradually inclined, pixel density components are added to the X-axis and Y-axis respectively, and the density of the Y-axis is also affected by the scanning step length Ls.

[0049] Through the scheme of configuring the scanning line to be inclined to the scanning direction of the present invention, it is possible to cleverly increase the detection resolution and information volume without increasing the cost of existing equipment.

[0050] The following describes the comparison between the present invention and the conventional scanning scheme.

[0051] Figure 2 It is a schematic diagram for explaining the conventional scanning detection method. Figure 2 And Figure 1 The same names and marks represent the same referents. Figure 3 It is an effect diagram for comparing the information volume between the present invention and the conventional scanning scheme.

[0052] In the traditional two-dimensional line scanning method, there is a problem in the perpendicular configuration of the scanning line and the scanning direction: when the capture speed of the camera (the number of lines captured per second) is constant, the greater the scanning travel speed, the greater the scanning step length Ls. In actual use, since the capture speed of the camera is not fast enough relative to the scanning speed, it will result in too large a scanning step length Ls, insufficient pixel density in the Y-axis direction of the image, and uneven resolution in the X and Y axes of the obtained image, that is, the resolution in the Y-axis direction is much smaller than that in the X direction.

[0053] Using the inclined scanning proposed by the present invention, it is possible to compress the scanning field of view onto the object to be measured under the same scanning speed and scanning step length conditions, and distribute it to the X-axis and Y-axis respectively, thereby increasing the information volume obtained by scanning and achieving the purpose of increasing the resolution of the image. Comparing Figure 1 It can be seen that under the condition of unchanged pixel density and unchanged scanning step length, by using inclined scanning, the pixel points scanned by the camera on the object surface increase and are more uniform.

[0054] When comparing vertical scanning and inclined scanning, when the scanning line is long enough, the information volume obtained by vertical scanning is the least. Using the length covered by the scanning line in the scanning area to represent the information volume obtained by the camera, Figure 1 where Li is the length covered during inclined scanning, representing the information volume of the object surface obtained by scanning one row during inclined scanning. Figure 2 where Lv is the length covered during vertical scanning, representing the information volume (number of pixel points) of the object surface obtained by scanning one row during vertical scanning. Let the angle between the vertical scanning line and the inclined scanning line be α, then as Figure 3 shown, the relationship between the information volumes obtained by vertical scanning and inclined scanning is:

[0055] Lv / Li = cosα.

[0056] Hereinafter, a specific example of the detection method using a line array camera for scanning will be described.

[0057] The line array optical sensor can be a line array photoelectric coupling camera or a line array infrared camera. Any line array optical sensing that obtains object surface information based on the sensing of electromagnetic waves should be recognized as the line array optical sensor of the present invention.

[0058] In the specific example of the detection method using the line array camera for scanning, the field of view line of the line array optical sensor forms the scanning line, and the field of view line is stepped and scanned on the object to be measured so that the line array optical sensor obtains the line-by-line image information of the object to be measured. Among them, the scanning line and the scanning direction are inclinedly arranged on the scanning projection plane.

[0059] Figure 4 It is a flowchart showing an embodiment of the line scanning detection method of the present invention.

[0060] In step S401, line scanning is performed to obtain the line-by-line image information of the object to be measured in such a way that the field of view line of the line array optical sensor and the scanning direction are inclinedly arranged on the scanning projection plane. In this embodiment, the field of view line of the line array optical sensor forms the scanning line, and the field of view line is stepped and scanned on the object to be measured so that the line array optical sensor obtains the line-by-line image information of the object to be measured. In step S402, the line-by-line image information is spliced into the detection image information of the object to be measured. By splicing the image information obtained line by line into the detection image information of the object to be measured, a complete detection image of the object to be measured can be obtained. Since the scheme of inclinedly arranging the field of view line and the scanning direction is adopted, a detection image with a larger amount of information can be obtained, which is beneficial to better recognition or comparison application of the obtained detection image. In step S403, the detection image information is compared with the reference image information. Thus, by comparing the detection image with a larger amount of information with the reference image, a more accurate comparison result can be obtained.

[0061] In this embodiment, it may further include projecting illumination onto the object to be measured, thereby strengthening the optical information of the object to be measured and being more conducive to the information sensing of the line array camera. For camera imaging technology, the illumination needs to maintain reasonable uniformity in the entire field of view. Almost all cameras have an internal flat-field correction function to make up for the deficiency of non-uniformity. The integration time of line scanning imaging is usually very short, so the illumination intensity usually needs to be very high. Projecting a higher intensity of light onto the object to be measured can further adapt to ensure high resolution during high-speed scanning.

[0062] Figure 5 It is a flowchart showing another embodiment of the line scanning detection method of the present invention.

[0063] In step S501, line-scanning is performed to obtain row-by-row image information of the object to be measured in such a manner that the field of view line of the line-array optical sensor is inclined with respect to the scanning direction on the scanning projection plane. In this embodiment, the field of view line of the line-array optical sensor forms the scanning line, and the field of view line is stepped-scanned on the object to be measured so that the line-array optical sensor obtains the row-by-row image information of the object to be measured. In step S502, the row-by-row image information is compared with the row-by-row reference image information. By comparing the image information obtained row by row with the row-by-row reference image information, it is possible to adapt to the rapid comparison of the object to be measured having consistent or regular information in the scanning direction, thereby quickly detecting defect problems such as flaws and wear on the object to be measured. Since the scheme of inclining the field of view line with respect to the scanning direction is adopted, a larger amount of row-by-row information can be obtained, which is beneficial for more accurate comparison and judgment.

[0064] Hereinafter, a specific example of the detection method using line laser scanning will be described.

[0065] In this specific example of the detection method using line laser scanning, the projection center line of the line laser projector forms the scanning line; the projection center line is photographed by the area array camera and the contour information is extracted based on the projection center line; the projection center line is scanned on the object to be measured so that the area array camera obtains the row-by-row contour information of the object to be measured.

[0066] Figure 6 It is a flowchart showing still another embodiment of the line-scanning detection method of the present invention.

[0067] In step S601, the projection center line of the line laser projector is scanned on the object to be measured in such a manner that the projection center line is inclined with respect to the scanning direction on the scanning projection plane, so that the area array camera for photographing the projection center line and extracting the contour information based on the projection center line obtains the row-by-row contour information of the object to be measured. In this embodiment, the projection center line of the line laser projector forms the scanning line, the projection center line is photographed by the area array camera and the contour information is extracted based on the projection center line, and the projection center line is scanned on the object to be measured so that the area array camera obtains the row-by-row contour information of the object to be measured. In step S602, the row-by-row contour information is stitched together to form the detection contour information of the object to be detected. By stitching together the contour information obtained row by row to form the detection contour information of the object to be detected, a complete contour image of the object to be measured can be obtained. Since the scheme of inclining the projection center line with respect to the scanning direction is adopted, a larger density of laser can be projected, so that the area array camera can photograph contour information with a larger amount of information, which is beneficial for better recognition or comparison application of the obtained contour information. In step S603, the detection contour information is compared with the reference contour information. Thus, by comparing the contour information with a larger amount of information with the reference information, a more accurate comparison result can be obtained.

[0068] Figure 7It is a flowchart showing another embodiment of the line scanning detection method of the present invention.

[0069] In step S701, the projection line of the line laser projector is scanned on the object to be measured in such a way that the projection line is inclined with respect to the scanning direction on the scanning projection plane, so as to obtain the row-by-row contour information of the object to be measured by a planar array camera for photographing the projection line and extracting contour information based on the projection line. In this embodiment, the projection line of the line laser projector forms the scanning line, and the planar array camera photographs the projection line and extracts contour information based on the projection line, and the projection line is scanned on the object to be measured so that the planar array camera obtains the row-by-row contour information of the object to be measured. In step S702, the row-by-row contour information is compared with the row-by-row reference contour information. By comparing the row-by-row obtained contour information with the row-by-row reference contour information, it is possible to adapt to the rapid comparison of the object to be measured with consistent or regular information in the scanning direction, so as to quickly detect defects on the object to be measured. Since the projection line and the scanning direction are inclined, a larger amount of row-by-row information can be obtained, which is beneficial to more accurate comparison and judgment.

[0070] Figure 8 It is a flowchart showing yet another embodiment of the line scanning detection method of the present invention.

[0071] In step S801, the projection line of the line laser projector is scanned on the object to be measured in such a way that the projection line is inclined with respect to the scanning direction on the scanning projection plane, so as to obtain the row-by-row contour information of the object to be measured by a planar array camera for photographing the projection line and extracting contour information based on the projection line. In this embodiment, the projection line of the line laser projector forms the scanning line, and the planar array camera photographs the projection line and extracts contour information including depth information and image information based on the projection line, and the projection line is scanned on the object to be measured so that the planar array camera obtains the row-by-row contour information of the object to be measured including depth information and image information. In step S802, the row-by-row contour information is spliced and corrected into a three-dimensional image of the object to be detected. By splicing and correcting the row-by-row contour information into a three-dimensional image of the object to be detected, a complete three-dimensional image of the object to be measured can be obtained. Since the projection line and the scanning direction are inclined, a larger density of laser can be projected, so that the planar array camera can capture more information-rich contour information, which is beneficial to better recognition or comparison application of the obtained contour information. In step S803, the three-dimensional image is three-dimensionally reconstructed to obtain a holographic image. By three-dimensionally reconstructing the three-dimensional image to obtain a holographic image, a more intuitive visualization image can be obtained.

[0072] To collect the profile information, the area array camera is configured to photograph the projection center line at an angle capable of collecting the profile of the object to be measured. Although the profile information is calculated by the area array camera in the above three examples, the present invention is not limited thereto, and it may also be implemented by a separate other image processing unit.

[0073] Although the acquisition of profile information is described in the above three examples, the present invention is not limited thereto. It is also possible to make a judgment based on pixel information, or to detect by combining pixel information and profile information. Therefore, the present invention can provide a line scan detection method. In this method, the projection center line of the line laser projector forms the scan line; the projection center line is stepped and scanned on the object to be measured, and an area array camera with a fixed relative position and relative angle to the line laser projector photographs the projection center line to extract the line-by-line image information of the object to be measured based on the projection center line. The extraction of the line-by-line image information of the object to be measured based on the projection center line can directly extract the image information of the projection center line from the photographed image of the projection center line, or can stack the photographed images of the projection center line in a misaligned layer by step unit. Although the defect judgment is performed by comparing the reference information in the above embodiments, it is also possible to make a judgment by extracting defect features from the profile information or image information, etc.

[0074] In the above embodiments, the literal concepts of image information and profile information should be determined according to the specific context. Image information may include pixel information data and position information data of each point, and profile information may also be considered to include pixel information data and position information data of each point, and may refer to position information according to the judgment use such as defects. Obtaining the line-by-line image information of the object to be measured based on the projection center line includes extracting the projection center line image from the photographed image of the projection center line. The correction and stitching processing of the projection center line image is an explanation from the visual perspective, and in the computer processing environment, it may be the correction operation and stitching operation of the data in the form of information.

[0075] In the above embodiments, the scan line and the scan direction should maintain a fixed inclination angle to ensure the accuracy of the acquired information and the stability of the information density.

[0076] For the object to be measured involved in the present invention, it may include planar structures such as plastics, fabrics, metals or papers, especially ultra-large cloths, etc., and may also include workpieces with complex shapes on the production line, railway tracks, roads, etc. Those skilled in the art can flexibly measure according to actual needs, and the present invention does not make any limitations in this regard. However, the above implementation methods are not limited to the application of obtaining two-dimensional images or three-dimensional images, because this sometimes depends on whether the image contains two-dimensional information or three-dimensional information. For example, it includes the relative position information of the pixel projection points, including the depth coordinates of the projection points on the scan line along the scan direction based on a predetermined inclination and the relative height information. The depth information of the required image can be restored through further image processing. For example, for Figure 4 andFigure 5 In an embodiment for detecting a three-dimensional shape object to be measured, three-dimensional reconstruction can be performed on planar images captured from different angles based on algorithms such as SFM and MVS. For Figures 6 - 8 the embodiment of

[0077] Figure 9 is a schematic diagram for illustrating three-dimensional laser scanning by the triangulation method.

[0078] Figure 9 Referring to an example of three-dimensional laser scanning of a toy car in the industry to introduce the three-dimensional laser scanning principle. The laser triangulation device 90 includes a scanning area formed by the space above the conveyor belt 92. Due to the complex shape structure of the toy 94 as the object to be measured, the laser triangulation method is often used to scan and detect its surface contour and image during the quality inspection process. The toy 94 is placed on the conveyor belt 92 and moves along the measurement direction M as the scanning direction.

[0079] A projector 96 including a laser source (not shown) projects a line laser 98 onto the conveyor belt 92. The line laser 98 is monitored by an imager 93, and the imager 93 includes a lens 932 and is coupled to an evaluation unit 934. The imager 93 is arranged to be separated from the projector 96, and an angle β of approximately 30° is formed at the line laser 98 between the projector 96 and the imager 93. When the object to be measured, i.e., the toy 94, moves along the measurement direction M and reaches the line laser 98, the line laser 98 is deformed. At the same time, the deformation of the line laser 98 is detected by the imager 93. According to the detected deformation of the line laser, the contour 936 of the toy 94 can be determined. The contour 936 is shown on the Figure 9 right side. As the prefabricated base 94 moves along the measurement direction M, multiple contours 936 can be determined. These contours 936 can be pieced together to form a three-dimensional model 938 of the prefabricated base 94.

[0080] This three-dimensional laser scanning by the triangulation method adopts the conventional scanning method, that is, the projector 96 projects the line laser 98 in a manner perpendicular to the measurement direction M on the conveyor belt 92.

[0081] Figure 10 is a schematic diagram showing the effect of applying the present invention to three-dimensional laser scanning based on the triangulation method. The line laser projected from the line laser 106 hits the object surface, forming an obvious diffuse reflection contour. The area containing this contour is captured by the area array camera 103 to obtain the contour line shown on the right side of the figure. In this example, the line of projection of the line laser is inclined with respect to the scanning direction on the scanning projection plane so that the line of projection scans on the object to be measured, and the area array camera for photographing the line of projection and extracting contour information based on the line of projection obtains the row-by-row contour information of the object to be measured. FromFigure 10 The collective effect of the line-by-line contours can be seen.

[0082] When the three-dimensional laser scanning technology based on the triangulation method is applied to the solution of the present invention, obvious test effects can be obtained. The present invention uses vertical scanning and inclined scanning to conduct a comparative experiment on a biscuit with a diameter of 45 mm at a step size of 0.5 mm according to the above-mentioned three-dimensional laser scanning by triangulation method. And when using laser 3D inclined scanning, the field of view angle of the camera is the same as that of vertical scanning, and the inclination angle is 76°.

[0083] Figure 11a is the image obtained by vertical scanning. Figure 11b is the original image obtained by inclined scanning, Figure 11c is the image after correction and reconstruction of the original image obtained by inclined scanning. Figure 11a and Figure 11c are compared, and it is not difficult to see that Figure 11a the resolution of is significantly improved, and the pixel points are uniform.

[0084] Applying the triangulation laser scanning technology of the present invention can bring effective applications in reality. Figure 12a is a schematic diagram for explaining vertical scanning of railway rails, Figure 12b is a schematic diagram for explaining the application of the laser scanning technology based on the triangulation method of the present invention to the inspection of rail defects. In Figure 12a 、 12b 120 represents the rail as the object to be measured, 121 is the line laser, and 122 is the area array camera. The line laser 121 and the area array camera 122 are integrated into one component.

[0085] As pointed out above, in the three-dimensional laser scanning technology based on the triangulation method, instead of capturing a single line, a frame of image is captured, and the amount of information is much larger. How many frames can be captured per second limits the application of three-dimensional laser scanning. As Figure 12a shown in the application of railway inspection, traveling at a speed of 100 Km / H and capturing one frame for every 1 mm traveled, the capture rate of the camera will reach 27.8 KHz, which is the limit of current cameras. In other words, if it is required to conduct railway inspection at a speed of 100 Km / H and capture at a rate of 27.8 KHz, the longitudinal resolution along the rail can only be 1 mm, and such scanning accuracy is not satisfactory for railway inspection products.

[0086] By using the inclined scanning proposed in this article, it is possible to increase the amount of information obtained by scanning under the conditions of the same scanning speed and scanning step size, so as to achieve the purpose of increasing the resolution of the image. As Figure 12bAs shown, the line laser projected from the line laser 121 hits the rail 120 to form a contour line. This contour line is inclined to the direction of the rail on the scanning projection plane, thereby enabling the rail contour information with greater information volume to be obtained by the area array camera 122. Through the application of the present invention, even at a speed of 100 Km / H, the longitudinal resolution can be reduced, and an acceptable detection image for defect comparison can be obtained.

[0087] The above is only an example of the application of the tilt scanning method of the present invention in reality. The application of the present invention is not limited thereto. For example, it is also applicable to the defect detection operation of workpieces on a high-speed assembly line, and the above high speed is not limited to 100 Km / H. Its application effects can be reflected at 50 - 120 Km / H, especially suitable for 80 - 110 Km / H. With the improvement of the hardware conditions affecting the resolution, the application speed range can be further increased.

[0088] Moreover, in the application of high-speed scanning, it is not limited to the composition form corresponding to the scanning line. For example, it can correspond to the scanning line formed by the field of view line of the linear array optical sensor in the above text, or it can also correspond to the projection line of the line laser projector.

[0089] Summarizing the above applications in high-speed scanning, the present invention proposes a defect detection method applied to high-speed scanning, and line-scans to obtain the line-by-line image information of the object to be measured in a manner that the scanning line is inclined to the scanning direction on the scanning projection plane.

[0090] Specifically, in the defect detection method for high-speed scanning, the line-scanning to obtain the line-by-line image information of the object to be measured in a manner that the scanning line is inclined to the scanning direction on the scanning projection plane may include: using the field of view line of the linear array optical sensor to form the scanning line; making the field of view line step-scan on the object to be measured to obtain the line-by-line image information of the object to be measured by the linear array optical sensor. The linear array optical sensor can be a linear array photoelectric coupling camera or a linear array infrared camera. The line-by-line image information can be stitched into the detection image information of the object to be measured, and then the detection image information is compared with the reference image information. It is also possible to compare the line-by-line image information with the line-by-line reference image information.

[0091] Specifically, in the defect detection method for high-speed scanning, the line-scanning to obtain the line-by-line image information of the object to be measured in the manner that the scanning line is obliquely arranged with respect to the scanning direction on the scanning projection plane may also include: using the projection center line of the line laser projector as the scanning line; photographing the projection center line by the area array camera and extracting the line-by-line image information based on the projection center line; scanning the projection center line on the object to be measured so that the area array camera can obtain the line-by-line image information of the object to be measured. The line-by-line image information can be stitched into the detection image information of the object to be detected, and then the detection image information can be compared with the reference image information. Alternatively, the line-by-line image information can be compared with the line-by-line reference graphic information. The above extraction and judgment can also be performed based on the contour information in the image information, or the contour information and pixel information can be combined. The depth information can also be converted and combined with the pixel information, and the line-by-line information can be stitched and corrected into a three-dimensional image of the object to be detected, and further, the three-dimensional image can be three-dimensionally reconstructed to obtain a holographic image.

[0092] The defect detection method based on high-speed scanning can be specifically applied Figures 4 - 9 to the specific embodiments herein. Additionally, it is preferred that the scanning line and the scanning direction maintain a fixed inclination angle.

[0093] Next, other manifestations of the present invention in terms of effects will be explained.

[0094] For example, the structural parameters of the three-dimensional laser scanning sensor mainly include the angle between the laser emission angle and the normal of the camera field of view, and the field of view angle of the camera that determines the field of view coverage. As a product, these two parameters cannot be changed arbitrarily, as they determine the scanning range and the relative position of the object to be scanned with respect to the sensor. The object to be scanned must be within the field of view range of the XYZ coordinate system. In practical applications, there are often cases where the proportion of the scanned surface contour of the object in the field of view is small, and the pixels of the sensor are not fully utilized. By using the inclined scanning scheme of the present invention, without changing the structural parameters of the sensor, the surface contour of the object to be scanned can occupy a larger proportion in the field of view, thereby obtaining more image information.

[0095] For example, compared with Figure 12a perpendicular scanning of the rail as shown, without changing the scanning step size and using the same sensor, as Figure 12b shown, by only adjusting the installation of the sensor and performing inclined scanning on the rail, more contour information can be obtained. If the same amount of image information as in perpendicular scanning is obtained, the step size of the inclined scanning can be increased accordingly to achieve the purpose of improving the scanning speed.

[0096] On the other hand, in order to ensure the imaging quality of the line-scan camera, in addition to projecting light with a relatively high intensity onto the object to be measured, the camera itself often requires extremely high sensitivity. Through the solution of the scanning line of the present invention being inclined with respect to the scanning direction, the requirement for the sensitivity of the camera itself can be alleviated to a certain extent.

[0097] Based on the same principle, the present invention also proposes a line-scan detection system.

[0098] Figure 13 is a functional schematic diagram for explaining an embodiment of the line-scan detection system of the present invention. As Figure 13 shown, the line-scan detection system 130 includes a line-array optoelectronic coupling camera 131, a first stepping driver 132, and a main controller 133.

[0099] The line-array optoelectronic coupling camera 131 is driven by the first stepping driver 132 to move uniformly along the scanning direction, and the main controller 133 is used to control the line-array optoelectronic coupling camera 131 and the first stepping driver 132 to act in unison.

[0100] The line-array optoelectronic coupling camera 131 is an optoelectronic conversion device for sensing the received optical signal and converting it into an electrical signal. The line-array optoelectronic coupling camera 131 is composed of a charge-coupled device 1311, an optoelectronic converter 1312, and a camera control main board 1313.

[0101] The charge-coupled device 1311 is a linear CCD, that is, a one-dimensional image sensor, with a width of about 10 μm. Thousands of CCD image units are arranged in parallel at intervals of 10 μm. These image units are regularly arranged in a line. When light irradiates the photosensitive surface of the image sensor, each CCD image unit receives the light irradiating thereon and generates corresponding charges according to the intensity of the sensed light.

[0102] The optoelectronic converter 1312 is used for analog / digital conversion, converting the electrical signal obtained from the charge-coupled device 1311 into a digital signal, that is, generating a row of image data. The optoelectronic converter 1312 can be coupled to the camera control main board 1313.

[0103] The functions of the camera control main board 1313 can include controlling the digital conversion of the optoelectronic converter 1312, image storage control, resolution processing, etc., and can also be used to coordinate and control the first stepping driver 132 of the line-scan detection system 130 in unison. Exemplarily, the camera control main board 1313 can include an A / D converter, a BIOS chip, an I / O control chip, and a cache (such as a Cache), etc. The main function of the BIOS chip is to perform self-check during system startup. The I / O control chip provides a connection interface and a connection channel. The cache is used to temporarily store image data to avoid data loss and image distortion.

[0104] The linear array optoelectronic coupling camera 131 may also include optical mechanisms such as a lens and a mirror, which are not limited herein.

[0105] The first stepping driver 132 is used to control the linear movement of the linear array optoelectronic coupling camera 131 along the scanning direction. For example, it may be composed of a lead screw mechanism and a stepping motor, or may be composed of a drive belt, a sliding guide rail and a stepping motor, and its specific composition method is not limited. Among them, both the lead screw mechanism and the sliding guide rail can be used to ensure the linear movement of the linear array optoelectronic coupling camera 131. The first stepping driver 132 may also have a motor controller for coordinating the control of the stepping motor to be consistent with the exposure action of the linear array optoelectronic coupling camera 131.

[0106] Here, the main controller 133 for controlling the consistent actions of the linear array optoelectronic coupling camera 131 and the first stepping driver 132 may also be omitted, and the camera control main board 1313 of the linear array optoelectronic coupling camera 131 and the motor controller of the first stepping driver 132 may be coordinated to control, or any one of them may be responsible for the overall control action, which is not limited herein.

[0107] As Figure 13 shown, the charge-coupled device 1311 of the linear array optoelectronic coupling camera 131 forms a pixel line, and this pixel line forms an inclined configuration at an angle α with the scanning direction M on the scanning projection plane S. In an actual system configuration, it can be achieved by inclining the field window of the charge-coupled device 1311 with the lead screw mechanism or the chute used to ensure the linear movement of the linear array optoelectronic coupling camera 131.

[0108] To ensure that the light of the image information is strong enough, the line scanning detection system 130 may also include a light source for increasing the light in the area where the object to be measured is located. For example, the light source may be composed of a cold cathode lamp tube to meet the requirements of color purity and intensity uniformity, which is not limited herein.

[0109] The first stepping driver 132 may also include a gear set for intermediate connection to ensure the normal operation of the mechanical equipment. However, since there will inevitably be some gaps between the teeth, in order to avoid affecting the scanning accuracy and even causing image streaks in severe cases, the micro-stepping motor technology can be used to accurately control the smooth movement of the linear array optoelectronic coupling camera 131.

[0110] In the above embodiment, the first stepping driver 132 controls the scanning direction by moving the optoelectronic coupling camera 131. However, the present invention also provides a variant of the line scanning detection system 130. As Figure 13As shown, in this modification example, a second stepper driver 134 is further included. The second stepper driver 134 can use a conveyor belt to place the object to be measured on the conveyor belt, and control the scanning direction by moving the object to be measured. In this case, the speed of the conveyor belt can be as high as 2.5 m / s. However, since the inclined configuration of the scanning lines is adopted in this embodiment, it can better meet the pursuit of high resolution under high-speed scanning than the prior art.

[0111] However, the present invention does not exclude, for example, the scenario where the first stepper driver 132 and the second stepper driver 134 act simultaneously.

[0112] The line scan detection system 130 may further include an image processing unit 135. The image processing unit 135 is, for example, a vision processor or an image acquisition card, stores the information corresponding to each pixel line through the software loaded thereon, and reconstructs the pixel data into a final image. And, for example, the image processing unit 135 can complete the functions of stitching and comparing the line-by-line image information obtained by the line scan detection system 130. For example, it may include stitching the line-by-line image information into the detection image information of the object to be measured, and comparing the detection image information with the reference image information. For example, it may include comparing the line-by-line image information with the line-by-line reference image information. The processing operations of the image processing unit 135 can be supported by a variety of operating systems (Supports Windows(WHQL Certified),Linux,Mac OS X&Other OS) and data stream modes, and have various programming language interfaces, allowing infinite possibilities for post-processing. The frame rates of various operation modes and data stream modes depend on the set integration time. In the stream mode, a constant frame rate can be achieved within an infinite time without losing any frames.

[0113] In this embodiment, although a line scan detection system using a line array optoelectronic coupled camera 131 is proposed, the line scan detection system can also be applied to a line scan detection system using a line array infrared camera.

[0114] Based on the same principle, the present invention also proposes a three-dimensional scan detection system. The system includes: a directional light projector for line-scanning and projecting a line-shaped directional light, and the projection center line of the directional light constitutes a scanning line; a scan driving unit for controlling the scanning direction to scan the projection center line of the directional light projector on the object to be measured; and a area array camera for photographing the projection center line and extracting the line-by-line information of the object to be measured based on the projection center line, wherein the scanning line and the scanning direction are inclinedly arranged on the scanning projection plane.

[0115] As an embodiment of this three-dimensional scan detection system, it includes here Figure 9 and Figure 10All the content of the examples involved. Among them, the directional light projector is preferably a line laser projector here. Therefore, it should also be understood that the directional light projector and the area array camera are configured to face the same position from different angles. It can be specifically embodied as a line laser three-dimensional detection system, including a line laser projector, an area array camera, and a scanning drive unit. The line laser projector and the area array camera are configured with a fixed relative position and relative angle. The scanning drive unit is configured to move the line laser projector and / or the object to be measured so that the projection line of the line laser projector scans on the object to be measured. The area array camera is configured to take pictures of the projection line during the scanning process from an angle capable of collecting the contour of the object to be measured. Among them, the line laser projector is configured so that the projection line is inclined to the scanning direction on the scanning projection plane. It also includes an image processing unit and a defect judgment unit. The image processing unit is configured to extract the line-by-line image information of the object to be measured from the captured image of the projection line based on the projection line. The defect judgment unit is configured to judge whether there is a defect in the object to be measured at least based on the contour information in the line-by-line image information.

[0116] As an embodiment of this three-dimensional scanning detection system, it also includes here Figure 13 All the content of the stepping driver involved in the examples. Therefore, it should also be understood that the scanning drive unit controls the scanning direction by moving the directional light projector. Different from this, the scanning drive unit also controls the synchronous movement of the area array camera and the directional light projector. In this way, for example, in a scenario of detecting railway tracks, the directional light projector and the area array camera can be fixed on the train chassis, and the scanning direction can be controlled by controlling the running speed of the train to move the directional light projector. In addition, it should also be understood that the scanning drive unit can also control the scanning direction by moving the object to be measured.

[0117] In addition, the image processing unit and the defect judgment unit are originally similar to Figure 13 the image processing unit and the defect judgment unit in, and those skilled in the art can understand their compositions. It can include an image processing unit with the same configuration as the image processing unit included in the line scanning detection system 130 involved in Figure 13 All the content. This image processing unit can complete the functions of splicing and comparing the line-by-line contour information obtained by this three-dimensional scanning detection system. For example, it can include splicing the line-by-line contour information into the detection contour information of the object to be detected, comparing the detection contour information with the reference contour information. For example, it can also include comparing the line-by-line contour information with the line-by-line reference contour information. In another embodiment, the contour information may include depth information and image information, then this image processing unit can complete splicing and correcting the line-by-line contour information into a three-dimensional image of the object to be detected, and further performing three-dimensional reconstruction on the three-dimensional image to obtain a holographic image.

Claims

1. A line scanning optical acquisition method, characterized in that: include: The line scanning is performed in such a way that the scanning line and the scanning direction are inclined on the scanning projection surface to collect the line-by-line image information of the object being measured.

2. The optical acquisition method according to claim 1, wherein: The method of collecting line-by-line image information of the object under test by line scanning in a manner that the scanning line and the scanning direction are inclined on the scanning projection surface includes: The scanning line is formed by the field of view of the linear array optical sensor; The visual field line is scanned step by step on the object to be measured so that the linear array optical sensor collects line-by-line image information of the object to be measured.

3. The optical acquisition method according to claim 1, wherein: The method of collecting line-by-line image information of the object under test by line scanning in a manner that the scanning line and the scanning direction are inclined on the scanning projection surface includes: The scanning line is formed by the projection line of the line laser projector; The center line is scanned step by step on the object to be measured, and the center line is photographed by an area array camera whose relative position and relative angle with the line laser projector are fixed, so as to obtain line-by-line image information of the object to be measured based on the center line; the relative angle is fixed as the relative angle between the light projection direction of the line laser projector and the framing direction of the area array camera.

4. The optical acquisition method according to claim 3, wherein: The step of obtaining line-by-line image information of the object to be measured based on the center line includes extracting a center line image from a captured image of the center line.

5. The optical acquisition method according to claim 3, wherein: The area array camera shoots the center line from an angle capable of capturing the three-dimensional contour of the object to be measured.

6. A line scanning optical detection method, characterized in that: Based on the center line image extracted by the optical acquisition method described in claim 5, it is judged whether the object under test has defects.

7. The optical detection method according to claim 6, characterized in that: It also includes stitching and / or correcting the center line images.

8. A laser scanning acquisition system, characterized in that: It includes a line laser projector, an area array camera and a scanning drive unit. The line laser projector and the area array camera are configured to have a fixed relative position and relative angle. The relative angle is fixed to mean that the relative angle between the light projection direction of the line laser projector and the framing direction of the area array camera is fixed; The scanning driving unit is configured to move the line laser projector and / or the object to be measured so that the center line of the line laser projector is scanned on the object to be measured; The line laser projector is configured so that the projection line and the scanning direction are inclined on the scanning projection surface; The area array camera is configured to photograph the center line during the scanning process from an angle capable of capturing the three-dimensional contour of the object being measured.

9. A laser scanning detection system, characterized in that: include: The laser scanning acquisition system according to claim 8; An image processing unit, which is connected to the area array camera data of the laser scanning acquisition system, and is used to receive the images of the center line taken by the area array camera during the scanning process and extract the center line image; The defect judgment unit is data-connected with the image processing unit, and is used to receive the center line image extracted by the image processing unit and judge whether the object under test has defects based on the center line image.

10. The scanning detection system according to claim 9, wherein: The image processing unit is further configured to stitch and / or correct the center line images.

Images