CN105547188A - Three-dimensional scanning system and three-dimensional scanning method for measuring volume of loose sediment block sample - Google Patents

Abstract

The invention relates to a three-dimensional scanning method for measuring the volume of loose sediment block samples, comprising the following steps: obtaining standard black and white checkerboard optical information through a projector and a camera, encoding the optical information, and performing triangulation The three-dimensional information of the edge point is obtained, and three-dimensional reconstruction is performed according to the three-dimensional information of the edge point; according to the above three-dimensional reconstruction, the coordinate position of the axis center of the turntable in the coordinate system of the projector and the camera system is obtained by calculation; the position of the turntable is obtained according to the calculation The coordinate position of the axis in the coordinate system of the projector and camera system is used for automatic registration of 3D data from different angles. The invention also relates to a three-dimensional scanning system for measuring the volume of bulk samples of loose sediments. The invention does not damage the physical or chemical structure of the sample to be tested, and improves the measurement accuracy and three-dimensional scanning efficiency.

Description

Three-dimensional scanning system and method for measuring the volume of bulk samples of loose sediments

technical field

The invention relates to a three-dimensional scanning system and method for measuring the volume of loose sediment bulk samples.

Background technique

With the rapid development of science and technology today, it is more and more common to use high-tech equipment and means to solve traditional problems in basic disciplines such as geology and environment. At present, most researches on the geological environment are inseparable from high-precision measurement and processing, conversion of theoretical problems and practical models, and advanced experimental environments.

The density and volume of loose sediments and soil samples are very important parameters for some basic researches such as reconstruction of paleoenvironment. But for a long time, there have been technical limitations and barriers on how to solve such a seemingly simple problem. From the point of view of the existing means of measuring bulk density, contact measurement is the main method, based on Archimedes principle, the sample to be tested is placed in a medium with a fixed volume and known density, such as water, sand, oil etc. By calculating the volume of the excluded object, the volume of the measured object can be obtained indirectly, and then the density of the entire sample can be calculated through the mass. In addition, through optical methods such as laser irradiation or ray scanning, the local density of the object or the solid density excluding voids can also be known.

However, the existing technical methods and means often cannot meet the current scientific research needs. Due to the complex internal structure of loose sediments and soils, which have the characteristics of void development, semi-consolidation, and easy dispersion, the local density or solid density obtained by laser projection and other methods cannot represent the actual density of sediment samples. In many studies It cannot reflect the corresponding scientific truth and solve the targeted scientific problems, and the laser projection through the whole mineral will also cause certain irreversible damage to the sample. The results obtained by contact measurement are accurate, but they will damage the sample itself and its internal structure. For example, water will wash away and absorb, and sand will adhere to the surface, which is not conducive to other experiments and storage of samples; for loose sediment samples, whether it is easy to absorb and disperse, whether reliable The measurements are all subject to considerable controversy. If some inert gas medium is selected, the medium itself and the particularity of the measurement method will increase the cost a lot. At the same time, the increase of the filling pressure of the medium will also make the measurement result tend to be close to the solid density, and the error will increase or be unavailable. Corresponding research .

The rapid development of 3D scanning technology has been applied to many fields and industries such as industrial inspection, design, animation and film special effects production, 3D display, virtual surgery, and reverse engineering. From the point of view of the existing 3D scanning technology, laser 3D scanning and projection structured light 3D scanning technology are the main technologies. The laser 3D scanning system projects laser lines or dot arrays, captures the projected laser features with a camera, and restores 3D through triangulation. Depth information, but the main disadvantage of this point-by-point and line-by-line scanning method is the slow speed; in the projector-based structured light 3D scanning system, it uses structured light coding technology to realize one-time measurement of the entire surface, which has a fast speed And the obvious advantages of high precision, so the projection-based structured light 3D scanning technology has become the current mainstream technology.

All in all, the existing technology has different defects and disadvantages, and cannot meet the needs of geological and environmental first-line scientific research for the measurement of the bulk density of different samples. The main problems are as follows: 1) only the local density or solid density of the sample to be tested can be obtained, It cannot replace the actual density of the sample; 2) If the measurement result is accurate, expensive media and tools must be used, and the measurement cost will increase; 3) The measurement method is in contact with the object to be measured, which will change the physical or chemical structure of the object to be measured, which is not conducive to Preservation and reuse of test objects.

Contents of the invention

In view of this, it is necessary to provide a three-dimensional scanning system and method for measuring the volume of loose sediment bulk samples.

The invention provides a three-dimensional scanning system for measuring the volume of bulk samples of loose sediments. The system includes a projector, a camera and a turntable respectively connected to a computer. There is a plane for placing a sample to be measured on the turntable, and the The computer includes a three-dimensional reconstruction module, a coordinate position calculation module and an automatic registration module, wherein: the three-dimensional reconstruction module is used to obtain the optical information of a standard black and white checkerboard through a projector and a camera, encode the optical information, and perform triangulation The three-dimensional information of the edge point is measured, and the three-dimensional reconstruction is performed according to the three-dimensional information of the edge point; the coordinate position calculation module is used to calculate and obtain the axis of the turntable in the coordinate system of the projector and the camera system according to the above three-dimensional reconstruction coordinate position; the automatic registration module is used to perform automatic registration of three-dimensional data at different angles according to the calculated coordinate position of the axis of the turntable in the coordinate system of the projector and the camera system.

Wherein, the three-dimensional reconstruction module is specifically used to: obtain the internal and external parameters of the projector and the camera, so as to facilitate the depth calculation of subsequent triangulation; and according to the internal and external parameters of the projector and camera obtained above, to project The resulting structured light stripes are encoded.

The coordinate position calculation module is specifically used to: scan the plane to obtain its three-dimensional data P1; rotate the turntable at a certain angle, scan the plane again, and obtain the three-dimensional data P2 after it rotates at a certain angle; and calculate according to P1 and P2 The axis of rotation L of the turntable.

The automatic registration module is specifically used for: controlling each rotation angle A of the turntable, rotating 360/A times, completing a comprehensive scan of the turntable, and obtaining 360/A group of three-dimensional scanning data; and according to the rotation angle A of the turntable and The rotation axis L is based on the first group of three-dimensional scanning data, and the registration of the 360/A group of three-dimensional scanning data obtained above is completed.

The invention provides a three-dimensional scanning method for measuring the volume of a loose sediment block sample, the method comprising the following steps: a. Obtaining the optical information of a standard black and white checkerboard through a projector and a camera, and encoding the optical information , obtain the three-dimensional information of the edge point through triangulation, and perform three-dimensional reconstruction according to the three-dimensional information of the edge point; b. According to the above three-dimensional reconstruction, calculate the coordinate position of the axis of the turntable in the coordinate system of the projector and camera system ; c. According to the calculated coordinate position of the axis of the turntable in the coordinate system of the projector and camera system, automatic registration of three-dimensional data from different angles is performed.

Wherein, said a specifically includes: a1. Obtaining the internal and external parameters of the projector and camera, so as to facilitate the depth calculation of subsequent triangulation; and a2. According to the internal and external parameters of the projector and camera obtained above, Code the projected structured light stripes.

The b specifically includes: scanning the plane to obtain its three-dimensional data P1; rotating the turntable at a certain angle, scanning the plane again to obtain the three-dimensional data P2 after it rotates at a certain angle; and calculating the turntable according to P1 and P2 The axis of rotation L.

The c specifically includes: controlling the rotation angle A of the turntable each time, rotating 360/A times, completing a comprehensive scan of the turntable, and obtaining 360/A groups of three-dimensional scanning data; and according to the rotation angle A and the rotation axis L of the turntable, Based on the first group of three-dimensional scanning data, the registration of the 360/A group of three-dimensional scanning data obtained above is completed.

The three-dimensional scanning system and method for measuring the volume of bulk samples of loose sediments provided by the present invention does not require manual participation and contact measurement operations, and can automatically complete the scanning of the entire model, thereby eliminating the destruction of the sample by the measurement method , while improving the accuracy of measurement, greatly simplifying the operational complexity of the entire three-dimensional scanning process, and significantly improving the efficiency of three-dimensional scanning.

Description of drawings

Fig. 1 is the operating environment schematic diagram of the three-dimensional scanning system that the present invention is used for measuring the volume of bulk sample of loose sediment;

Fig. 2 is the hardware architecture figure of computer 5 of the present invention;

Fig. 3 is the flow chart of the three-dimensional scanning method that the present invention is used for measuring loose sediment block sample volume;

Fig. 4 is the detailed flowchart of step S1 of the present invention;

Fig. 5 is the detailed flowchart of step S11 of the present invention;

Fig. 6 is the detailed flowchart of step S12 of the present invention;

Fig. 7 is the detailed flowchart of step S2 of the present invention;

FIG. 8 is a detailed flowchart of step S3 of the present invention.

detailed description

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

Referring to FIG. 1 , it is a schematic diagram of the operating environment of the three-dimensional scanning system for measuring the volume of loose sediment bulk samples according to the present invention. The system includes a projector 1, a camera 2, and a turntable 3 electrically connected to a computer 5, respectively. Wherein, the plane 4 is placed on the turntable 3 for placing the object to be measured. The computer 5 can respectively control the projector 1 to project, the camera 2 to take pictures and the turntable 3 to rotate.

Please also refer to FIG. 2 , the computer 5 includes: a three-dimensional reconstruction module, a coordinate position calculation module and an automatic registration module.

The three-dimensional reconstruction module is used to obtain the optical information of the standard black and white checkerboard through the projector 1 and the camera 2, encode the optical information, obtain the three-dimensional information of the edge point through triangulation, and obtain the three-dimensional information of the edge point according to the three-dimensional information of the edge point Perform 3D reconstruction. Wherein, the three-dimensional information of the edge points is the data of the three-dimensional point cloud. in particular:

The three-dimensional reconstruction module obtains the internal and external parameters of the projector 1 and the camera 2, so as to facilitate the depth calculation of subsequent triangulation; and

The three-dimensional reconstruction module encodes the projected structured light stripes according to the acquired internal and external parameters of the projector 1 and the camera 2 .

Wherein, the three-dimensional reconstruction module obtains the internal and external parameters of the projector 1 and the camera 2, so as to facilitate the depth calculation of the subsequent triangulation, specifically including:

Paste a standard black and white checkerboard picture on a flat object, the size and number of checkerboards are known;

The checkerboard is placed in front of the camera 2, and a photo of the checkerboard is taken;

Keep the checkerboard position still, turn on projector 1, project a black and white checkerboard pattern onto the calibration board, and control camera 2 to take a picture;

Changing the position or posture of the checkerboard plane, repeating the above camera shooting and projector projection steps; and

According to the photos acquired by the camera 2, the calibration of the internal and external parameters of the projector 1 and the camera 2 is completed.

Wherein, the three-dimensional reconstruction module encodes the projected structured light stripes according to the internal and external parameters of the projector 1 and camera 2 obtained above, specifically including:

Firstly, 11 Gray code pictures are projected, and according to the definition of Gray code, 2 ¹⁰ =1024 regions of the whole image are uniquely encoded through the 11 Gray code pictures, that is, Gray code global encoding. Wherein, the code value of the gray code global encoding is 1 to 1020;

Use black and white stripes with a width of 4 pixels, and then move it by 1 pixel each time, and move it 3 times in total, and get 4 images with stripes in total. Through the edge detection technology, detect the edge of the stripe after each movement, and The edge pixels of the stripes are encoded with four encoding values of 1-2-3-4, that is, local unique encoding, and the code values of the Gray code global encoding are 1 to 4;

According to the local unique coding and Gray code global coding, the global unique coding of edge pixels is completed, and the code value of the global unique coding is 1 to 1024; and

According to the epipolar line constraints in the calibration stage and the globally unique code, the matching of the edge points of the projector 1 and the camera 2 is completed, and then the three-dimensional information of the edge points is obtained through triangulation, and the 3D reconstruction is realized according to the three-dimensional information of the edge points .

The coordinate position calculation module is used to calculate the coordinate position of the axis of the turntable 3 in the system coordinate system of the projector 1 and the camera 2 according to the above three-dimensional reconstruction. in particular:

The coordinate position calculation module places a plane 4 on the surface of the turntable 3, and scans the plane 4 to obtain its three-dimensional data P1;

The coordinate position calculation module rotates the turntable 3 by a certain angle, scans the plane 4 again, and obtains the three-dimensional data P2 rotated by a certain angle; and

The coordinate position calculation module calculates the rotation axis L of the turntable 3 according to P1 and P2. Specifically, the reconstruction simulation is performed according to the above-mentioned three-dimensional data P1 and P2, and the rotation axis L of the turntable 3 is calculated.

In this embodiment, the three-dimensional data P1 and P2 are reconstructed to simulate the intersecting part of the middle planes of S21 and S22 to form a cylinder or cone, and the central axis of the cylinder or cone is the turntable 3 The axis L of rotation is the axis of the turntable 3 in the system coordinate system of the projector 1 and the camera 2 .

The automatic registration module is used to perform automatic registration of three-dimensional data from different angles according to the calculated coordinate position of the axis of the turntable 3 in the system coordinate system of the projector 1 and the camera 2 . in particular:

The automatic registration module controls the rotation angle A of the turntable 3 each time, rotates 360/A times, completes the comprehensive scan of the turntable 3, and obtains 360/A group of three-dimensional scanning data; and

The automatic registration module completes the registration of the 360/A group of 3D scan data obtained above according to the rotation angle A and the rotation axis L of the turntable 3 and based on the first group of 3D scan data.

Referring to FIG. 3 , it is a flow chart of a preferred embodiment of the three-dimensional scanning method for measuring the volume of loose sediment bulk samples according to the present invention.

In step S1, the optical information of the standard black and white checkerboard is obtained by the projector 1 and the camera 2, and the optical information is encoded, and the three-dimensional information of the edge points is obtained through triangulation, and the three-dimensional reconstruction is performed according to the three-dimensional information of the edge points. Wherein, the three-dimensional information of the edge points is the data of the three-dimensional point cloud. The details are as follows, please refer to Figure 4:

In step S11, the internal and external parameters of the projector 1 and the camera 2 are obtained, so as to facilitate the depth calculation of the subsequent triangulation. For details, please refer to Figure 5:

Step S111, pasting a standard black and white checkerboard picture on the plane object. Wherein, the size and number of squares of the checkerboard are known.

Step S112, place the checkerboard in front of the camera 2, and take a photo of the checkerboard.

Step S113, keep the checkerboard position still, turn on the projector 1, project a black and white checkerboard pattern onto the calibration board, and control the camera 2 to take a picture.

Step S114, changing the position or posture of the checkerboard plane. In this embodiment, the above step S112 to step S114 are repeated about 20 to 30 times.

Step S115 , completing the calibration of the internal and external parameters of the projector 1 and the camera 2 according to the photos acquired by the camera 2 . In this embodiment, the calibration of internal and external parameters of the projector 1 and the camera 2 is completed according to 20 to 30 pairs of photos acquired by the camera 2 .

Step S12 , according to the acquired internal and external parameters of the projector 1 and the camera 2 , encode the projected structured light stripes. For details, please refer to Figure 6:

Step S121 , first project 11 Gray code pictures, and according to the definition of Gray code, 2 ¹⁰ =1024 regions of the whole image are uniquely coded through the 11 Gray code pictures, that is, Gray code global coding. Wherein, the code value of the Gray code global encoding is 1 to 1020.

Step S122, using black and white stripes with a width of 4 pixels, and moving them by 1 pixel at a time, moving them 3 times in total, and obtaining 4 images with stripes in total. The edge of the stripe after each movement is detected by the edge detection technology, and the edge pixels of the stripe are encoded with four encoding values of 1-2-3-4, that is, local unique encoding. Wherein, the code value of the Gray code global encoding is 1 to 4.

Step S123, complete the globally unique encoding of the edge pixels according to the local unique encoding and the global gray code encoding. Wherein, the code value of the globally unique code is 1 to 1024.

Step S124, complete the matching of the edge points of the projector 1 and the camera 2 according to the epipolar line constraints in the calibration stage and the globally unique code, and then obtain the three-dimensional information of the edge points through triangulation, and according to the three-dimensional information of the edge points Realize 3D reconstruction.

Step S2, according to the above-mentioned three-dimensional reconstruction, the coordinate position of the axis of the turntable 3 in the system coordinate system of the projector 1 and the camera 2 is calculated. The details are as follows, please refer to Figure 7:

Step S21, placing a plane 4 on the surface of the turntable 3, and scanning the plane 4 to obtain its three-dimensional data P1;

Step S22, rotating the turntable 3 by a certain angle, scanning the plane 4 again, and obtaining the three-dimensional data P2 after it is rotated by a certain angle;

Step S23, calculating the rotation axis L of the turntable 3 according to P1 and P2. Specifically, the reconstruction simulation is performed according to the above-mentioned three-dimensional data P1 and P2, and the rotation axis L of the turntable 3 is calculated.

In this embodiment, the three-dimensional data P1 and P2 are reconstructed to simulate the intersecting part of the middle planes of S21 and S22 to form a cylinder or cone, and the central axis of the cylinder or cone is the turntable 3 The axis L of rotation is the axis of the turntable 3 in the system coordinate system of the projector 1 and the camera 2 .

Step S3 , according to the calculated coordinate position of the axis center of the turntable 3 in the system coordinate system of the projector 1 and the camera 2 , automatic registration of three-dimensional data from different angles is performed. The details are as follows, please refer to Figure 8:

Step S31 , control the turntable 3 to rotate by an angle A each time, and rotate 360/A times to complete a comprehensive scan of the turntable 3 to obtain 360/A sets of three-dimensional scanning data.

In this embodiment, if A=30 degrees, then a total of 12 rotations are performed, that is, the full scan of the turntable 3 is completed, assuming that the three-dimensional scanning data obtained by the first scan is D1, and so on, then D1...D12 is obtained , a total of 12 sets of 3D scanning data;

In step S32 , according to the rotation angle A and the rotation axis L of the turntable 3 , the registration of the 360/A group of 3D scan data obtained above is completed based on the first group of 3D scan data.

In this embodiment, the relative spatial positions of the projector 1, the camera 2, and the turntable 3 will not change during the rotation process. According to the rotation angle A and the rotation axis L of the turntable 3, and based on the first set of three-dimensional scanning data D1, the D2 rotates A degrees around the rotation axis L to complete the precise registration of D2 and D1, and so on, taking the first set of 3D scan data as the reference of D1, and the subsequent scan data revolves around the rotation axis L and reversely rotates (N-1)×30 Degree, complete the registration of 12 sets of data.

After the above registration is completed, the ruler and reference objects are determined for the subsequent measurement of the block sample. When measuring the volume of the block sample, the block sample can be quickly scanned and reconstructed in three dimensions according to the determined position.

The present invention is based on a structured light three-dimensional scanning device composed of a projector and a camera, adding a programmable turntable, placing the sample to be tested on the platform, controlling the turntable to rotate several angles through software, and performing three-dimensional scanning at the same time, thereby realizing automatic multi-angle For the scanning of three-dimensional data, since the precision turntable rotates strictly around one axis, the three-dimensional data scanned at different angles can be rotated by calculating the rotation axis of the turntable, combined with the known rotation angle of the turntable, and realizing automatic multi-dimensional data scanning. Angular 3D data registration and fusion. The advantages are as follows: 1) It does not need to contact with the object to be tested, and will not damage the physical or chemical structure of the sample to be tested; 2) It can measure the entire volume of the object and obtain the overall density; 3) It can be recycled, with high precision and low cost; 4 ) Fully automatic 360-degree three-dimensional scanning of objects; 5) No need for existing auxiliary registration operations such as manual labeling, and the registration method using spatial rotation axis calculation is simpler and more accurate.

Although the present invention has been described with reference to the current preferred embodiments, those skilled in the art should understand that the above-mentioned preferred embodiments are only used to illustrate the present invention, and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and scope of principles shall be included in the protection scope of the present invention.

Claims (8)

1. A three-dimensional scanning system for measuring the bulk sample volume of loose deposits, the system includes a projector, a camera and a turntable connected to a computer respectively, the turntable has a plane for placing the sample to be measured, it is characterized in that , the computer includes a three-dimensional reconstruction module, a coordinate position calculation module and an automatic registration module, wherein: The three-dimensional reconstruction module is used to obtain the optical information of the standard black and white checkerboard through the projector and the camera, encode the optical information, obtain the three-dimensional information of the edge points through triangulation, and perform three-dimensional reconstruction according to the three-dimensional information of the edge points. reconstruction; The coordinate position calculation module is used to calculate the coordinate position of the axis of the turntable in the coordinate system of the projector and camera system according to the above three-dimensional reconstruction; The automatic registration module is used to perform automatic registration of three-dimensional data at different angles according to the calculated coordinate position of the axis of the turntable in the coordinate system of the projector and camera system. 2. The system according to claim 1, wherein the three-dimensional reconstruction module is specifically used for: Acquiring the internal and external parameters of the projector and camera to facilitate the depth calculation of the subsequent triangulation; and According to the internal and external parameters of the projector and the camera obtained above, encoding processing is performed on the projected structured light stripes. 3. The system according to claim 2, wherein the coordinate position calculation module is specifically used for: Scanning the plane to obtain its three-dimensional data P1; Rotate the turntable by a certain angle, scan the plane again, and obtain the three-dimensional data P2 rotated by a certain angle; and The rotation axis L of the turntable is calculated according to P1 and P2. 4. The system according to claim 3, wherein the automatic registration module is specifically used for: Control the rotation angle A of the turntable each time, rotate 360/A times, complete the comprehensive scanning of the turntable, and obtain the 360/A group of three-dimensional scanning data; and According to the rotation angle A and the rotation axis L of the turntable, the registration of the 360/A group of three-dimensional scanning data obtained above is completed based on the first group of three-dimensional scanning data. 5. A three-dimensional scanning method for measuring the bulk sample volume of loose sediment, it is characterized in that, the method comprises the steps: a. Obtain the optical information of the standard black and white checkerboard through the projector and the camera, encode the optical information, obtain the three-dimensional information of the edge points through triangulation, and perform three-dimensional reconstruction according to the three-dimensional information of the edge points; b. According to the above three-dimensional reconstruction, calculate the coordinate position of the axis of the turntable in the coordinate system of the projector and camera system; c. According to the calculated coordinate position of the axis of the turntable in the coordinate system of the projector and camera system, automatic registration of three-dimensional data from different angles is performed. 6. the method for claim 5 is characterized in that, described a specifically comprises: a1. Obtain the internal and external parameters of the projector and camera, so as to facilitate the depth calculation of subsequent triangulation; and a2. According to the internal and external parameters of the projector and camera obtained above, encode the projected structured light stripes. 7. The method according to claim 6, wherein said b specifically comprises: Scanning the plane to obtain its three-dimensional data P1; Rotate the turntable by a certain angle, scan the plane again, and obtain the three-dimensional data P2 rotated by a certain angle; and The rotation axis L of the turntable is calculated according to P1 and P2. 8. The method according to claim 7, wherein said c specifically comprises: Control the rotation angle A of the turntable each time, rotate 360/A times, complete the comprehensive scanning of the turntable, and obtain the 360/A group of three-dimensional scanning data; and According to the rotation angle A and the rotation axis L of the turntable, the registration of the 360/A group of three-dimensional scanning data obtained above is completed based on the first group of three-dimensional scanning data.