阅读说明：本技术 一种旋转扫描获得完整外表面3d轮廓的装置和方法 (Device and method for obtaining complete outer surface 3D contour through rotary scanning ) 是由 董仕 吴先哲 秦海宁 赵学渝 于 2019-09-18 设计创作，主要内容包括：本发明公开了一种旋转扫描获得完整外表面3D轮廓的装置和方法,装置包括由动圈和静圈构成水平的回转平台,静圈的中心设有两面平整透明且上下表面与回转轴垂直的工件载台；动圈上固定有相机组支架,相机组支架穿过静圈并可转动180°以上；相机组支架上设有两个相对的一字线结构光光源,以及两台相机和两个平行光线的平行光背光源；同一侧的相机和一字结构光源位于工件载台的同一方,平行光背光源与相机相对位于另一方；一字结构光中心线与回转平台的轴心线重合,且一字线方向与相机的图像传感器的水平线平行；相机的镜头轴线与水平面呈20°～70°倾斜。测试方法基于前述装置实施。本发明的有益效果是,装置为消除盲区和快速检测提供了保障；方法操作性强,能够获得精准、完整的3D轮廓数字模型。(The invention discloses a device and a method for obtaining a complete outer surface 3D contour by rotary scanning, wherein the device comprises a horizontal rotary platform consisting of a moving coil and a static coil, and a workpiece carrying platform with two flat and transparent surfaces and upper and lower surfaces vertical to a rotary shaft is arranged at the center of the static coil; a camera group bracket is fixed on the movable ring, penetrates through the stationary ring and can rotate for more than 180 degrees; the camera group bracket is provided with two opposite linear structured light sources, two cameras and two parallel light backlight sources of parallel light rays; the camera and the linear structure light source on the same side are positioned on the same side of the workpiece carrying platform, and the parallel light backlight source and the camera are positioned on the other side oppositely; the center line of the linear structured light is superposed with the axis line of the rotary platform, and the direction of a word line is parallel to the horizontal line of the image sensor of the camera; the lens axis of the camera is inclined at 20-70 degrees with the horizontal plane. The testing method is implemented based on the device. The invention has the advantages that the device provides guarantee for eliminating blind areas and fast detection; the method is strong in operability, and an accurate and complete 3D contour digital model can be obtained.)

1. A device for obtaining a complete outer surface 3D contour through rotary scanning is characterized by comprising a rotary platform, wherein the rotary platform horizontally rotates and consists of a moving coil (1) and a static coil (2), a transparent workpiece carrying platform (3) used for carrying a workpiece to be detected is arranged at the center of the static coil (2) of the rotary platform, the workpiece carrying platform (3) is in relatively fixed connection with the static coil (2) through a connecting arm, and a C-shaped through groove is formed between the periphery of the workpiece carrying platform (3) and the inner wall of the static coil (2); the camera set support (4) is fixedly connected to the moving coil (1), and the camera set support (4) comprises a connecting part penetrating through the C-shaped through groove and two extending parts extending up and down from the connecting part; the camera set bracket (4) is provided with two opposite linear structured light sources (5), two cameras (6) and two parallel light backlight sources (7) of parallel light rays; the two cameras (6) are distributed on the two extending parts, each camera (6) corresponds to one word line structured light source (5) and one parallel light backlight source (7), and the parallel light backlight sources (7) are positioned on the other extending part opposite to the extending part where the camera (6) is positioned; the linear structured light center lines of the two linear structured light sources (5) are superposed with the axis line of the rotary platform, and the direction of one linear line is parallel to the horizontal line of the image sensor of the camera (6); the lens axis of the camera (6) and the horizontal plane form an included angle of 20-70 degrees.

2. The device according to claim 1, characterized in that the lens axes of the two cameras (6) intersect perpendicularly.

3. The device according to claim 2, characterized in that the axis of the camera (6) is at an angle of 45 ° to the horizontal.

4. The device according to claim 1, characterized in that the lens axis of the camera (6) intersects the swivel axis of the swivel platform.

5. The device according to claim 1, characterized in that the moving coil (1) of the rotary platform is driven to rotate by a first motor and a synchronous belt transmission structure; the first motor is a stepping motor or a servo motor.

6. The device according to any one of claims 1 to 5, characterized in that the camera set bracket (4) is provided with a lifting slipway (9) driven by a second motor (8) to lift; a camera (6), a linear structured light source (5) and a parallel light backlight source (7) which are positioned above the workpiece carrying platform (3) are arranged on the lifting sliding table (9); or the camera group bracket (4) is provided with a lifting sliding table (9) driven by a second motor (8) to lift and a tilting moving sliding table driven by a third motor; a linear structured light source (5) and a parallel light backlight source (7) which are positioned above the workpiece carrying platform (3) are arranged on the lifting sliding table (9); the camera (6) positioned above the workpiece carrier (3) is arranged on the inclined moving sliding table, and the axis of the camera (6) is consistent with the moving direction of the inclined moving sliding table; and the optical axis of the parallel light backlight source (7) is kept coincident with or parallel to the axial lead of the lens of the corresponding camera (6).

7. A method for obtaining a 3D contour of a complete outer surface of a workpiece through rotary scanning, which is implemented by the device of any one of claims 1-6, and comprises the following steps:

first, test preparation: the method comprises the steps of placing a workpiece to be measured on a workpiece carrying platform, and enabling the center of the workpiece to be measured to be close to or coincide with the rotation center of a rotation platform;

secondly, shooting frame by frame: rotating the moving coil by a set angle in the same rotating direction, and shooting once after each rotation is finished; repeating the rotating and shooting process of the moving coil, and stopping shooting after the moving coil rotates by an angle not less than 180 degrees;

thirdly, data processing: denoising the digital image information obtained by shooting to obtain the image digital information close to a real object;

fourthly, establishing a 3D contour model: and according to the processed data, constructing and obtaining a complete outer surface 3D contour digital model of the measured workpiece through a pre-established mathematical model.

8. The method according to claim 7, characterized in that before or during the placement of the workpiece to be tested, the method further comprises the steps of adjusting the height of an upper parallel light backlight, a linear structured light source and a camera of a lifting sliding table (9) in the device through a second motor (8); or the height of an upper parallel light backlight source and a horizontal line structured light source (5) is adjusted on a lifting sliding table (9) in the device through a second motor (8), and the object distance of a camera (6) is adjusted by driving an inclined sliding table to move through a third motor; to obtain the optimum working distance.

9. The method as claimed in claim 7, wherein in the step of frame-by-frame photographing, after completing one photographing for rotating the moving coil in a set direction, further comprising performing next frame-by-frame photographing in a rotation manner opposite to that of the previous photographing; and/or in the step of shooting frame by frame, the rotating angles of the moving coil between adjacent frames comprise equal angles and unequal angles; when the unequal-angle rotation is adopted, the method also comprises the step of recording the rotation angle position information during snapshot as a parameter for contour reconstruction.

10. The method according to claim 7, characterized in that, during the shooting process, the upper and lower cameras (6) adopt a time-sharing exposure shooting mode, that is, when the upper camera (6) is exposed, the upper word line structured light source (5) and the lower parallel light backlight source (7) are lighted up under the trigger of a camera flash signal; the camera (6) below and the line structured light source (5) below and the parallel light backlight (7) above are disabled; accordingly, when the lower camera (6) is in operation, the upper camera (6) and the upper one-line structured light source (5) and the lower parallel light backlight (7) are disabled.

Technical Field

The invention relates to the technical field of computer vision measurement, in particular to a device and a method for obtaining a complete outer surface 3D contour through rotary scanning.

Background

The 3D contour measuring instrument which is mainstream in the market at present is mainly realized in a structured light detection mode and generally divided into two types, one type is that workpiece thickness/height contour information is obtained one by one on the basis of raster scanning through a triangulation principle, then contour lines are associated under a unified coordinate system to form point cloud data of a 3D contour of a workpiece, and information such as the external dimension, the surface roughness and the like of the workpiece can be obtained through inherent parameters of equipment and the point cloud data; the other type is a scanning mode which adopts single-line structured light and takes mechanical motion as profile information acquisition, and then 3D profile information of a workpiece is obtained. The difference between the two methods is mainly efficiency and cost, the former has higher efficiency and expensive cost, and the latter has lower efficiency but low price, but the measurement precision is not very different. However, the two aforementioned contour scanning detection methods may generate a detection blind area or a detection error area due to light projection, reflection, transmission, refraction, or the like, so that a raster scanning 3D contour detection technology combining mechanical movement and spectral adjustment (color conversion) appears, but the overall cost of the device is more expensive due to the need of spatial coordinate conversion and the use of precision machinery.

Although these devices have the capability of 3D contour reconstruction, they are essentially partial contour reconstruction, accounting for less than 3/4 of the overall surface contour of the workpiece, which is still insufficient for applications requiring complete contour information of the workpiece for inspection. For example, the detection of an optical lens blank needs to simultaneously measure various parameters such as the center thickness, the curved surface rise, the roundness, the diameter, the thickness difference, the chamfer angle and the like of the lens, the convex and concave shape of a workpiece is uncertain, and the workpiece does not have an ideal reference datum due to the addition of the shape tolerance, so that the detection is almost impossible to realize for the traditional machine vision detection equipment, the single jig and the clamp are difficult to rapidly clamp the workpiece in place, and the traditional schemes are almost not feasible compared with the detection requirements of the shape size of tens of hundreds of millimeters, the wire-level precision and the second-level detection efficiency.

Moreover, the above-mentioned devices still do not allow to obtain the complete contour information of the workpiece, since the light rays propagate along a straight line to form a projected occlusion zone; the workpiece also generally requires physical support to form an interface between the support and the workpiece, thereby forming an undetectable zone. A solution is to establish a spatial correlation characteristic mark outside a workpiece, turn the workpiece at a certain angle after the scanning is finished, scan the workpiece again, and obtain complete 3D contour point cloud data of the workpiece to be measured by ensuring the correlation of the characteristic mark and then by spatial coordinate transformation, thereby providing enough information support for further measurement. However, the method is time-consuming and labor-consuming in setting the characteristic marks, and the surfaces of some workpieces do not have mark setting positions, so that the application range of the method is greatly limited.

Other methods such as three-coordinate detection, scanning probe, point scanning, etc. also have the problems of small information amount, high price, low efficiency, etc., so that at present, no better scheme or product is provided for solving the problems.

Especially for on-line inspection in industrial production, the need for complete inspection of thousands or even tens of thousands of pieces per day is often required, and these apparatuses and methods are not feasible in principle. Such as the inspection of optical lens blanks, is desirable and subject to surface-unstable optical quality and internal uncertain scattering characteristics, which conventional visual inspection devices, along with the acquisition of basic information, become very difficult. Therefore, there is a need for improvements to existing inspection apparatus and methods to quickly and accurately obtain a 3D profile of the complete outer surface of a workpiece under inspection.

Disclosure of Invention

The invention aims to overcome the defects of low measurement efficiency and incapability of acquiring complete contour information at one time in the existing computer vision measurement technology, and provides a device for acquiring a complete outer surface 3D contour by rotary scanning. A second object of the present invention is to provide a method for obtaining a complete 3D profile of an external surface by means of a rotational scan, which is implemented on the basis of the aforementioned device, so as to significantly improve the detection efficiency.

In order to achieve the first object, the invention adopts the following technical scheme.

A device for obtaining a complete outer surface 3D contour through rotary scanning comprises a rotary platform which is horizontally rotated and consists of a moving coil and a static coil, wherein a transparent workpiece carrying platform used for bearing a workpiece to be detected is arranged at the center of the static coil of the rotary platform, the workpiece carrying platform is in relatively fixed connection with the static coil through a connecting arm, and a C-shaped through groove is formed between the periphery of the workpiece carrying platform and the inner wall of the static coil; the camera group bracket is fixedly connected to the moving ring and comprises a connecting part passing through the C-shaped through groove and two extending parts extending up and down from the connecting part; the camera group bracket is provided with two opposite linear structured light sources, two cameras and two parallel light backlight sources of parallel light rays; the two cameras are distributed on the two extension parts, each camera corresponds to one word line structured light source and one parallel light backlight source, and the parallel light backlight sources are positioned on the other extension part opposite to the extension part where the camera is positioned; the upper surface and the lower surface of the carrier are flat and parallel, the plane of the carrier is vertical to the rotation axis, the linear structured light center lines of the two linear structured light sources are superposed with the axis line of the rotation platform, and the direction of one linear line is parallel to the horizontal line of the image sensor of the camera; the lens axis of the camera and the horizontal plane form an included angle of 20-70 degrees.

The device adopting the technical scheme comprises the steps that two straight line structure light rays are respectively irradiated on the upper surface and the lower surface of a workpiece to form upper and lower surface positive outline images, two parallel light backlight sources of parallel light rays are irradiated on the upper and lower side surfaces of the workpiece to form high-contrast rear projection negative outline images, and rotary scanning is formed by utilizing an electronic photographing technology through successive rotary transformation of the transmission position of the light source on the workpiece to obtain complete 3D outline data of the workpiece. Because the camera lens of shooing is the slope setting, can eliminate the sheltering from nature projection blind area of concave surface, the camera lens axis is bigger with horizontal plane inclination, can adapt to the degree of depth that detects the depressed surface more deeply. This scheme adopts rotatory mode can avoid the detection blind area on the shady plain noodles and the quadrature face of work piece, normal direction structure light and between the normal direction and the tangential camera of slope installation can avoid the projection detection blind area of spill structure work piece. And then, restoring the surface sampling point space coordinate point cloud data of the workpiece through positive and negative projection information acquired by the upper and lower groups of cameras and a certain algorithm according to the inherent spatial relationship of the two groups of cameras, and then solving attitude information, size information and surface quality information of the workpiece based on the point cloud characteristics. Compared with the prior art, when the device provided by the invention is used for detecting the workpiece, the workpiece only needs to be placed on the carrying platform, clamping is not needed, shielding is avoided in all directions, and the complete 3D contour data of the workpiece can be obtained by rotating the light source and the camera after the workpiece is placed on the carrying platform, so that the detection efficiency is obviously improved. The method is not only suitable for sampling inspection of products produced in batch, but also suitable for full inspection, and has wide application range. The upper linear structure light source and the lower parallel light backlight source are controlled by a synchronous signal of the upper camera to take a snapshot, the upper camera starts the snapshot and is triggered according to the synchronous signal of the servo driver, and the servo motor sends a trigger signal to take a snapshot for one frame when rotating at a fixed angle. The method can be used for capturing at equal angles and can also be used for capturing at unequal angles, the rotation angle is required to be recorded, and the contour space coordinate of the workpiece is calculated based on the variable; the lower linear structure light source and the upper parallel light backlight source are controlled by the synchronous signal of the lower camera to perform snapshot, the starting snapshot of the lower camera is triggered according to the synchronous signal given by the servo driver, however, the synchronous signal has to keep a certain phase difference with the synchronous signal of the upper camera, and the exposure overlapping of the upper camera and the lower camera is avoided. In order to obtain lower background noise, the in-line structured light and the parallel light backlight source can be kept in an alternating working state.

Preferably, the lens axes of the two cameras are vertically intersected. So as to eliminate the blind area to the maximum extent when the minimum precision loss is ensured.

Further preferably, the camera axis forms an angle of 45 ° with the horizontal plane. The detection precision is guaranteed, the workload of subsequent data processing is reduced, the complexity of the system is reduced, the running speed of the system is increased, and the detection efficiency is improved.

Preferably, the lens axis of the camera intersects with the rotation axis of the rotating platform. The method and the device have the advantages that the workload of subsequent data processing is reduced, the complexity of the system is reduced, the running speed of the system is increased, and the detection efficiency is improved.

Preferably, the moving coil of the rotary platform is driven to rotate by a first motor and a synchronous belt transmission structure; the first motor is a stepping motor or a servo motor. So as to realize automatic control, improve detection efficiency, ensure to detect the precision.

Preferably, the camera group bracket is provided with a lifting sliding table driven to lift by a second motor; the camera, the linear structured light source and the parallel light backlight source which are positioned above the workpiece carrying platform are arranged on the lifting sliding table; or the camera group bracket is provided with a lifting sliding table driven by a second motor to lift and a tilting moving sliding table driven by a third motor; a linear structured light source and a parallel light backlight source which are positioned above the workpiece carrying platform are arranged on the lifting sliding table; a camera positioned above the workpiece carrying platform is arranged on the inclined moving sliding table, and the axis of the camera is consistent with the moving direction of the inclined moving sliding table; and the optical axis of the parallel light backlight source is kept coincident with or parallel to the axial lead of the lens of the corresponding camera. So that the synchronous adjustment of the height of the upper camera, the height of the horizontal line structured light and the height of the parallel light backlight source can be carried out through the lifting sliding table according to the height or thickness change of the workpiece to be detected; or, the height of the horizontal line structured light and the height of the parallel light backlight source are synchronously adjusted through the lifting sliding table, and the object distance of the camera is adjusted through the movement of the inclined sliding table, so that the optimal working distance is obtained, and the application range is effectively widened. The third motor and the inclined moving sliding table can be arranged on the lifting sliding table or can be directly arranged on the camera set bracket.

In order to achieve the second object, the invention adopts the following technical scheme.

A method for obtaining a 3D contour of the complete outer surface of a workpiece by means of a rotational scan, carried out on the basis of a device for achieving the first object, comprising the following steps:

first, test preparation: the method comprises the steps of placing a workpiece to be measured on a workpiece carrying platform, and enabling the center of the workpiece to be measured to be close to or coincide with the rotation center of a rotation platform;

secondly, shooting frame by frame: rotating the moving coil by a set angle in the same rotating direction, and shooting once after each rotation is finished; repeating the rotating and shooting process of the moving coil, and stopping shooting after the moving coil rotates by an angle not less than 180 degrees;

thirdly, data processing: denoising digital image information obtained by shooting to obtain image digital information close to a real object;

fourthly, establishing a 3D contour model: and according to the processed data, constructing and obtaining a complete outer surface 3D contour digital model of the measured workpiece through a pre-established mathematical model.

The method of the invention adopting the scheme is implemented by utilizing the device, and the complete outer surface 3D contour digital model of the measured workpiece can be rapidly obtained. In the implementation process, the upper linear structure light source and the lower parallel light backlight source are controlled by a synchronous signal of the upper camera to carry out snapshot, and when a frame is snapshot through a fixed angle every time the frame rotates, the angular snapshot can be carried out at equal angles, the angular snapshot can also be carried out at unequal angles, the rotation angle is required to be recorded, and the contour space coordinate of the workpiece is calculated based on the variable; the lower linear structure light source and the upper parallel light backlight source are controlled by the synchronous signal of the lower camera to take a snapshot. To achieve lower background noise, the in-line structured light and the parallel light backlight may be operated alternately. Generally, the upper and lower phase units also need to adopt a time-sharing exposure mode, namely, when the upper phase unit is exposed, the upper word line structured light source and the lower parallel light source are triggered to be lightened by a camera flash signal of the servo driver; the lower camera, the next word line structured light source and the upper parallel light source are in forbidden states; similarly, when the lower camera works, the upper camera, the upper word line structured light source and the lower parallel light source are in an forbidden state; in order to eliminate interference of scattered, reflected and transmitted signals.

Preferably, before or during the placement of the workpiece to be detected, the device further comprises a second motor for adjusting the height of an upper parallel light backlight source, a linear structured light source and a camera on a lifting sliding table in the device; or the height of an upper parallel light backlight source and a horizontal line structured light source of a lifting sliding table in the device is adjusted through a second motor, and the object distance of the camera is adjusted by driving an inclined sliding table to move through a third motor; to obtain the optimum working distance. So as to adapt to the height or thickness change requirement of the measured workpiece, thereby obtaining the optimal working distance and widening the application range.

Preferably, in the step of frame-by-frame shooting, after completing one shooting of rotating the moving coil in a set direction, the next frame-by-frame shooting is further performed in a reverse rotation mode next to the previous shooting; and/or the rotating angles of the moving coil between the adjacent frames comprise equal angles and unequal angles; when the unequal-angle rotation is adopted, the method also comprises the step of recording the rotation angle as a parameter for contour reconstruction. So as to obtain the contour information repeatedly or repeatedly, and obtain more accurate contour information through comprehensive operation and the like; and/or, under the condition that the processing means guarantee capacity is high enough, the shooting times are reduced, and the detection efficiency is improved.

Preferably, in the shooting process, the upper and lower cameras adopt a time-sharing exposure shooting mode, that is, when the upper camera is exposed, the upper one-line structured light source and the lower parallel light backlight source are triggered to be lighted up by a camera flash signal; the camera below and the light source of the word line structure below and the parallel light backlight source above are forbidden; accordingly, when the lower camera is in operation, the upper camera and the upper one-line structured light source and the lower parallel light backlight are disabled. To eliminate interference signals due to reflection and transmission.

The invention has the beneficial effects that: the device provides guarantee for eliminating blind areas and fast detection; the method is strong in operability, and an accurate and complete 3D contour digital model can be obtained.

Drawings

FIG. 1 is a schematic front view of the structure of the apparatus of the present invention.

FIG. 2 is a schematic side view of the structure of the apparatus of the present invention.

FIG. 3 is a schematic top view of the structure of the apparatus of the present invention.

FIG. 4 is a schematic diagram of the position relationship between the stationary ring and the carrier in the apparatus of the present invention.

The above figures also serve to illustrate the process of the invention.

Detailed Description

The present invention will be further described with reference to the following drawings, which are illustrative only for the purpose of disclosing and explaining the present invention so as to fully understand the present invention, and not to limit the present invention within the scope of the described embodiments.