CN116793257B - Three-dimensional measurement system and method - Google Patents
Three-dimensional measurement system and method Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
- G01B11/245—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures using a plurality of fixed, simultaneously operating transducers
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/002—Measuring arrangements characterised by the use of optical techniques for measuring two or more coordinates
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/22—Measuring arrangements characterised by the use of optical techniques for measuring depth
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Abstract
The invention relates to the technical field of positioning, and particularly discloses a three-dimensional measurement system and a three-dimensional measurement method, wherein the three-dimensional measurement system and the three-dimensional measurement method are characterized in that a monocular camera is calibrated with position parameters of a laser scanning ranging module, an image of a target to be measured is obtained by the monocular camera, meanwhile, depth information of a current scanning point of the target to be measured is obtained by the laser scanning ranging module, and three-dimensional information of the current scanning point is obtained according to pixel coordinates of image points and by combining the depth information and the calibration parameters; and obtaining three-dimensional measurement information of all points of the target to be measured through continuous scanning, and outputting a three-dimensional point cloud image. The three-dimensional measuring system provided by the invention avoids the problem that the measuring precision of the scanning laser radar depends on an angle measuring device, achieves pixel-level precision in the two-dimensional plane direction, and has the precision in the depth direction equivalent to that of a laser ranging module.
Description
Technical Field
The invention relates to the technical field of positioning, in particular to a three-dimensional measurement system and method.
Background
Laser three-dimensional measurement has been greatly developed and various methods have been developed, such as the most common scanning type laser radar, but the measurement accuracy is highly dependent on a high-accuracy angle measurement device, and the measurement accuracy is often low, and a complicated and expensive high-accuracy angle measurement device is required to improve the measurement accuracy. The university of Zhejiang proposes a pixel-level target positioning method based on fusion of laser and monocular vision, wherein a monocular camera is used for acquiring an environmental image to determine the pixel coordinates of a target to be positioned, then a laser ranging module is used for acquiring distance information of the target to be positioned, and the three-dimensional coordinates of the target point to be positioned are obtained by combining the relative position calibration parameters of the monocular camera and the laser ranging module, so that the pixel-level target positioning is realized. However, this method is only a single point positioning method, and three-dimensional image information cannot be obtained.
In the existing laser three-dimensional scanning measurement, the adopted laser collimation scanning optical system is too simple in structure and function, is only suitable for synchronous scanning of a light source and the collimation scanning optical system, and cannot be suitable for the condition that only the light source scans along an arc, such as a collimation lens disclosed in JP4208209B2, CN103472570A and the like; or the structure is too complex and the focal length cannot be adjusted, which is not suitable for the accurate control in the measurement field, such as the projection objective and the scanning display device disclosed in CN113495357 a.
In addition, conventional point light source collimation systems such as JP4208209B2, JPH112758a and linear light source collimation systems such as CN103472570A, CN108227149a are not applicable due to the wobbling effect of the light source spot. Although a collimating projection objective with an arc light source 01 is disclosed in the prior art CN113495357a, the number of lenses is as large as 11, the structure is complex and the volume is large, and the manufacturing and the assembly between the lens and the light source are difficult. The existing collimation scanning optical system often adopts an aspheric lens to adjust the collimation of marginal rays, and the complexity of the optical system structure is increased. In addition, since the laser source and the collimating optical system are fixed by glue after being aligned, the alignment performance may be deteriorated during the assembly and fixation process or after long-term use, and when the ambient temperature changes, the lens and the lens barrel may expand with the temperature, resulting in the change of parameters of the collimating optical system and the decrease of the collimation. On the one hand, the varifocal collimating lens is adopted, so that the position of the lens can be adjusted to compensate the degradation caused by the assembly and fixing process and long-term use, and the focal length can be adjusted to compensate the temperature drift.
Based on the problems, the invention provides a three-dimensional measurement system and a three-dimensional measurement method, and provides a collimation scanning optical system which is composed of four spherical lenses and can be focused, so that the whole structure is simplified.
Disclosure of Invention
Aiming at the technical problems, the invention provides a three-dimensional measurement system and a three-dimensional measurement method, designs a matched collimation scanning optical system aiming at the system and the method, not only avoids the problem that the three-dimensional measurement precision of the scanning laser radar depends on a high-precision angle measurement device, but also realizes the precise three-dimensional measurement with pixel-level precision in the two-dimensional plane direction and equivalent to the laser ranging precision in the depth direction, and the matched collimation scanning optical system is suitable for scanning only a light source along an arc, has a simple structure and has the function of adjusting the focal length.
The three-dimensional measurement system comprises a monocular camera, a laser scanning ranging module and a data processing unit, wherein the data processing unit comprises relative position calibration parameters of the monocular camera and the laser scanning ranging module, the monocular camera acquires an image of a target to be measured, the laser scanning ranging module acquires depth information of a current scanning point of the target to be measured, the data processing unit processes the image to obtain pixel coordinates of an image point corresponding to the current scanning point of the laser scanning ranging module, and three-dimensional information of the current scanning point of the laser scanning ranging module is obtained by combining the depth information and the calibration parameters. And completely scanning all points of the target to be detected through the laser scanning ranging module to obtain complete three-dimensional measurement information of the target to be detected, and inputting the three-dimensional point cloud.
The laser scanning ranging module comprises a laser source, a collimation scanning optical system and a receiving ranging unit. The collimating scanning optical system comprises a first lens, a second lens, a third lens and a fourth lens which are sequentially arranged from a light source side to a projection side; the collimating scanning optical system comprises four lenses, and spherical lenses are adopted; during zooming, the second lens moves from the light source side to the projection side along the optical axis, and the third lens moves from the projection side to the light source side; wherein:
the first lens is a positive lens, the object side surface is a concave surface, and the image side surface is a concave surface;
the second lens is a positive lens, the object side surface is a convex surface, and the image side surface is a concave surface;
the third lens is a positive lens, the object side surface is a concave surface, and the image side surface is a concave surface;
the fourth lens element is a positive lens element, and has a concave object-side surface and a concave image-side surface.
Further, the collimator scanning optical system satisfies the following conditional expression:
1.1<f1/EFL<1.2；1.5<f2/EFL<1.6；38<f3/EFL<40；10<f4/EFL<12；10<TTL/EFL<12；
wherein EFL is the total focal length of the collimating scanning optical system, TTL is the total length of the collimating scanning optical system on the optical axis, f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, and f4 is the focal length of the fourth lens.
Further, the collimator scanning optical system satisfies the following conditional expression:
0.5<(R1-R2)/(R1+R2)<0.6；4<(R3-R4)/(R3+R4)<6；
-1<(R5-R6)/(R5+R6)<1；-1<(R7-R8)/(R7+R8)<-1；
wherein, R1 and R2 are the radii of curvature of the first lens object-side surface and the image-side surface, R3 and R4 are the radii of curvature of the second lens object-side surface and the image-side surface, R5 and R6 are the radii of curvature of the third lens object-side surface and the image-side surface, and R7 and R8 are the radii of curvature of the fourth lens object-side surface and the image-side surface, respectively.
Further, the collimator scanning optical system preferably satisfies the following conditional expression:
0.02<D1/TTL<0.03；0.02<D3/TTL<0.025；
0.03<D5/TTL<0.04；0.02<D7/TTL<0.025；
wherein D1 represents the thickness of the first lens on the optical axis, D3 represents the thickness of the second lens on the optical axis, D5 represents the thickness of the third lens on the optical axis, and D7 represents the thickness of the fourth lens on the optical axis.
Further, the collimator scanning optical system preferably satisfies the following conditional expression:
0.005<D2/TTL<0.02；0.03<D4/TTL<0.15；0.01<D6/TTL<0.12；
where D2 denotes an interval on the optical axis of the first lens and the second lens, D4 denotes an interval on the optical axis of the second lens and the third lens, and D6 denotes an interval on the optical axis of the third lens and the fourth lens.
Further, the collimator scanning optical system preferably satisfies the following conditional expression:
-0.1.ltoreq.R0/EFL.ltoreq.0.05; wherein R0 is the curvature radius of the scanning path of the laser source.
Further, the collimator scanning optical system preferably satisfies the following conditional expression:
FOV is more than or equal to 15 degrees and less than or equal to 20 degrees; wherein the FOV is the full field angle of the quasi-straight scanning optical system.
The invention also discloses a three-dimensional measurement method, which comprises the following steps:
step one: installing a monocular camera and a laser scanning ranging module, calibrating the relative positions of the monocular camera and the laser scanning ranging module, and obtaining the spatial position relation of the monocular camera and the laser scanning ranging module to obtain calibration parameters;
step two: the data processing unit acquires the calibration parameters, and the monocular camera acquires an image of a target to be detected;
step three: the data processing unit processes the image, acquires pixel coordinates of an image point in the image, and acquires a real point on a target to be detected according to the image point;
step four: aligning a laser scanning ranging module to the real point of the target to be measured, and measuring the distance of the real point, wherein the distance is depth information of a corresponding image point;
step five: the three-dimensional information of the real point is obtained by combining the pixel coordinates of the image point and the depth information and the calibration parameters;
step six: and driving the collimation scanning optical system to scan the next point of the target to be detected, repeating the steps three to five until the collimation scanning optical system finishes scanning, processing the three-dimensional information of all points of the target to be detected, and outputting a three-dimensional point cloud.
Compared with the prior art, the invention has the beneficial effects that:
1. according to the three-dimensional measurement system and method for fusion of laser and monocular vision, the problem that the three-dimensional measurement precision of a scanning laser radar depends on a high-precision angle measurement device is avoided, pixel-level precision is achieved in a two-dimensional plane direction, precise three-dimensional measurement equivalent to laser ranging precision in a depth direction is achieved, and a three-dimensional point cloud image is finally obtained;
2. the collimation scanning optical system is suitable for a system in which only a light source scans along an arc, has a simple structure and a function of adjusting focal length, and can offset assembly errors and temperature drift.
Drawings
Fig. 1 is a three-dimensional measurement system of the present invention.
Fig. 2 is an optical block diagram of a collimator scanning optical system employed in the present invention.
FIG. 3 is an exemplary optical block diagram of a collimating scanning optical system employed in the present invention in different zoom states, wherein (a), (b), and (c) represent diagrams of different zoom positions, respectively.
Fig. 4 is a light trace of the light exit surface (i.e., the image side surface of the last lens) of the collimating scanning optical system.
Wherein, 1, a monocular camera, 2, a laser source, 3, a collimation scanning optical system, 4, a virtual arc line, 5, an object to be measured, 0, a light source surface, L1, a first lens, L2, a second lens, L3, a third lens, L4 and a fourth lens, S0-S8 sequentially represent serial numbers of each surface from the light source surface to the image side surface of the last lens, and half-view field HFOV respectively takes 0 DEG, -8 DEG and 10 deg.
Detailed Description
The three-dimensional measurement system and method of the present invention are described in detail below in conjunction with fig. 1-4.
The three-dimensional measurement system of the invention shown in fig. 1 comprises a monocular camera 1, a laser scanning ranging module and a data processing unit, wherein the data processing unit comprises relative position calibration parameters of the monocular camera 1 and the laser scanning ranging module, the monocular camera acquires an image of a target 5 to be measured, the laser scanning ranging module acquires depth information of a current scanning point of the target 5 to be measured, the data processing unit processes the image to obtain pixel coordinates of an image point corresponding to the current scanning point of the laser scanning ranging module, and three-dimensional information of the current scanning point of the laser scanning ranging module is obtained by combining the depth information and the calibration parameters. The three-dimensional information is three-dimensional coordinate point information under a camera coordinate system. And (3) completely scanning all points of the target 5 to be detected through the laser scanning ranging module to obtain complete three-dimensional measurement information of the target 5 to be detected, and inputting a three-dimensional point cloud.
The laser scanning ranging module comprises a laser source 2, a collimation scanning optical system 3 and a receiving ranging unit. The existing laser scanning mainly comprises transmission type scanning and reflection type scanning, the reflection type scanning realizes the scanning of a tested video field through a rotary reflecting mirror unit, and the transmission type scanning comprises two modes: only the wobble light source or the light source is wobbled together with the collimating optical system. The light source and the collimating optical system swing together to have lower performance requirements on the collimating optical system, but the swinging device has large volume, high energy consumption and higher control precision requirements because the light source and the collimating optical system need to swing simultaneously; the proposal of only swinging the light source greatly reduces the volume of the swinging device, is easier to control accurately and has low energy consumption, but has higher requirement on aligning the optical system. The invention therefore preferably employs a manner of only swinging the light source. In fig. 1, a dashed arc 4 represents a wobble path of the outgoing spot of the laser source 2, which is abbreviated as a laser source scanning path. Because the light source light-emitting point swings along the virtual arc line 4, the traditional point light source collimation system cannot be applied; in order to meet the use requirement of the invention, an optical design is specially carried out, and a collimating scanning optical system with adjustable focus is formed by adopting four spherical lenses, so that the integral structure is simplified.
Fig. 2 is an optical structure diagram of a collimating scanning optical system according to the present invention, which includes a first lens L1, a second lens L2, a third lens L3, and a fourth lens L4, S0 being a sequence number of the surface of a light source surface 0, which are sequentially arranged from the light source side to the projection side. In addition, the object side surface of the first lens is used as a diaphragm surface, so that the structure can be further simplified; of course, an additional diaphragm may be added separately. The collimating scanning optical system comprises four lenses, and all the lenses adopt spherical surfaces; during zooming, the second lens L2 moves from the light source side to the projection side along the optical axis, while the third lens L3 moves from the projection side to the light source side; wherein:
the first lens element L1 has a concave object-side surface S1 and a concave image-side surface S2;
the second lens element L2 has a convex object-side surface S3 and a concave image-side surface S4;
the third lens element L3 with a concave object-side surface S5 and a concave image-side surface S6;
the fourth lens element L4 has a concave object-side surface S7 and a concave image-side surface S8.
The collimator scanning optical system of the present embodiment satisfies the following conditional expression (1):
1.1<f1/EFL<1.2；1.5<f2/EFL<1.6；38<f3/EFL<40；10<f4/EFL<12；10<TTL/EFL<12 （1）
wherein EFL is the total focal length of the quasi-straight scanning optical system; TTL represents the total length of the collimating scanning optical system on the optical axis, i.e. the distance from the object side surface S1 of the first lens L1 to the image side surface S8 of the fourth lens L4; f1 denotes a focal length of the first lens L1, f2 denotes a focal length of the second lens L2, f3 denotes a focal length of the third lens L3, and f4 denotes a focal length of the fourth lens L4.
The condition (1) reasonably distributes the focal power and the surface shape of each lens by selecting the basic structure of the system, so that the system is easy to form a collimation zoom system, and if the focal length and the surface shape are distributed unreasonably, the system can not perform zooming under the condition that collimation is difficult to realize, and the system can not complete collimation zooming only through spherical lenses. And meanwhile, the ratio of the total length to the total focal length is limited, so that the system is miniaturized and the structure is simplified.
The collimator scanning optical system of the present embodiment satisfies the following conditional expression (2):
0.5<(R1-R2)/(R1+R2)<0.6；4<(R3-R4)/(R3+R4)<6；
-1<(R5-R6)/(R5+R6)<1；
-1<(R7-R8)/(R7+R8)<-1； （2）
wherein, R1 and R2 are the radii of curvature of the first lens object-side surface and the image-side surface, R3 and R4 are the radii of curvature of the second lens object-side surface and the image-side surface, R5 and R6 are the radii of curvature of the third lens object-side surface and the image-side surface, and R7 and R8 are the radii of curvature of the fourth lens object-side surface and the image-side surface, respectively; and (R1-R2)/(R1+R2) is defined as the surface form factor of the first lens, (R3-R4)/(R3+R4) is defined as the surface form factor of the second lens, (R5-R6)/(R5+R6) is defined as the surface form factor of the third lens, and (R7-R8)/(R7+R8) is defined as the surface form factor of the fourth lens.
Conditional expression (2) enables the system to maintain a large angle of view while zooming by further defining the surface form factor of each lens.
The collimator scanning optical system of the present embodiment preferably satisfies the following conditional expression (3):
0.02<D1/TTL<0.03；0.02<D3/TTL<0.025；
0.03<D5/TTL<0.04；
0.02<D7/TTL<0.025 （3）
wherein D1 represents the thickness of the first lens L1 on the optical axis, D3 represents the thickness of the second lens L2 on the optical axis, D5 represents the thickness of the third lens L3 on the optical axis, and D7 represents the thickness of the fourth lens L4 on the optical axis.
Conditional expression (3) makes it easy for the system to obtain a smaller overall volume by further defining the thickness distribution of each lens.
The collimator scanning optical system of the present embodiment preferably satisfies the following conditional expression (4):
0.005<D2/TTL<0.02；0.03<D4/TTL<0.15；0.01<D6/TTL<0.12 （4）
wherein D2 represents the interval on the optical axis of the first lens L1 and the second lens L2, that is, the intervals of S2 to S3 on the optical axis; d4 denotes an interval on the optical axis of the second lens L2 and the third lens L3, that is, intervals on the optical axis of S4 to S5; d6 denotes an interval on the optical axis of the third lens L3 and the fourth lens L4, that is, intervals on the optical axis of S6 to S7. By reasonably limiting the moving distance of the zoom lens, the good collimation performance of the system during zooming is ensured.
The collimator scanning optical system of the present embodiment preferably satisfies the following conditional expression (5):
-0.1≤R0/EFL≤-0.05 （5）
wherein R0 is the curvature radius of the scanning path of the laser source. By reasonably setting the ratio of the curvature radius of the laser source scanning path to the total focal length, the system is easy to adapt to the scanning laser source.
The collimator scanning optical system of the present embodiment preferably satisfies the following conditional expression (6):
15°≤FOV≤20° （6）
and the condition (5) limits the angle of the field of view, so that the projected collimated light beam can have a larger scanning range and has wider application scene.
Table 1 shows a specific set of data for a collimator scanning optical system, with the object aperture NA of the system set to 0.1.
TABLE 1 (Length Unit: mm)
The distance (thickness) T of the surface S8 is freely set according to the actual projection distance.
FIG. 3 is an exemplary optical block diagram of a collimating scanning optical system employed in the present invention in different zoom states, wherein (a), (b), and (c) represent diagrams of different zoom positions, respectively. In the zooming process, the second lens L2 moves from the light source side to the projection side along the optical axis, while the third lens L3 moves from the projection side to the light source side, only the middle two lenses move, and the first lens L1 and the fourth lens L4 are fixed, so that the total length of the whole optical system can be kept unchanged in zooming. See table 2 for specific zoom data.
TABLE 2 (Length Unit: mm)
As can be seen from table 2 above, as the second lens L2 and the third lens L3 move, the total focal length of the system becomes smaller and then becomes larger, so that when focal length adjustment is performed, there are two lens positions corresponding to the same focal length value, and one of the two lens positions can be selected as required, so that adjustment is easier.
Tables 3 and 4 show some of the optical conditional parameters of this example.
TABLE 3 (Length Unit: mm)
TABLE 4 (Length Unit: mm)
The meaning of each label is as follows: NA is the aperture of the object space of the collimating scanning optical system, and EFL is the total focal length of the collimating scanning optical system; TTL represents the total length of the collimating scanning optical system on the optical axis, i.e. the distance from the object side surface S1 of the first lens L1 to the image side surface S8 of the fourth lens L4; FOV is the full field angle of the collimated scanning optical system, HFOV is the half field angle; f1 to f4 respectively represent focal lengths of the first lens L1 to the fourth lens L4; d1 denotes a thickness of the first lens L1 on the optical axis, D3 denotes a thickness of the second lens L2 on the optical axis, D5 denotes a thickness of the third lens L3 on the optical axis, and D7 denotes a thickness of the fourth lens L4 on the optical axis; d2 denotes an interval on the optical axis of the first lens L1 and the second lens L2, that is, an interval S2 to S3 on the optical axis, D4 denotes an interval on the optical axis of the second lens L2 and the third lens L3, that is, an interval S4 to S5 on the optical axis, D6 denotes an interval on the optical axis of the third lens L3 and the fourth lens L4, that is, an interval S6 to S7 on the optical axis, and T denotes a projection distance; r0 is the curvature radius of the scanning path of the laser source, R1 and R2 are the curvature radius of the first lens object side surface and the image side surface respectively, R3 and R4 are the curvature radius of the second lens object side surface and the image side surface respectively, R5 and R6 are the curvature radius of the third lens object side surface and the image side surface respectively, and R7 and R8 are the curvature radius of the fourth lens object side surface and the image side surface respectively; and (R1-R2)/(R1+R2) is defined as the surface form factor of the first lens, (R3-R4)/(R3+R4) is defined as the surface form factor of the second lens, (R5-R6)/(R5+R6) is defined as the surface form factor of the third lens, and (R7-R8)/(R7+R8) is defined as the surface form factor of the fourth lens.
Fig. 4 is a plot of the light exit surface (i.e., the image side surface of the last lens) of a collimating scanning optical system, with half field angles of 0 deg., -8 deg., and 10 deg., respectively. The light spots of the light rays corresponding to the three half fields of view on the light-emitting surface can be seen to be very uniform.
The invention also discloses a three-dimensional measurement method, which comprises the following steps:
step one: installing a monocular camera 1 and a laser scanning ranging module, calibrating the relative positions of the monocular camera 1 and the laser scanning ranging module, and obtaining the spatial position relation of the monocular camera 1 and the laser scanning ranging module to obtain calibration parameters;
step two: the data processing unit acquires the calibration parameters, and the monocular camera 1 acquires an image of the target 5 to be measured;
step three: the data processing unit processes the image, acquires the pixel coordinate of one image point in the image, and acquires the real point on the target 5 to be detected according to the image point;
step four: aligning a laser scanning ranging module to the real point of the target to be measured, and measuring the distance of the real point, wherein the distance is depth information of a corresponding image point;
step five: the three-dimensional information of the real point is obtained by combining the pixel coordinates of the image point and the depth information and the calibration parameters;
step six: and driving the collimation scanning optical system to scan the next point of the target to be detected, repeating the steps three to five until the collimation scanning optical system finishes scanning, processing the three-dimensional information of all points of the target to be detected, and outputting a three-dimensional point cloud.
In the second step of the method, the monocular camera 1 can acquire the complete image of the target 5 to be measured at one time, and then the laser scanning ranging module scans each point on the image to acquire depth information, so that the image shooting time and the storage space can be saved; the method can also be used for shooting each real point of the target 5 to be detected once to acquire an image, and then taking the center point of the image as a pixel point to acquire depth information, so that the monocular camera 1 has the advantages that the measurement precision of coordinates can be improved by taking the center point of the image as the pixel point due to edge phase difference, the whole precision of three-dimensional measurement is greatly improved, the required resolution and the required angle of view of the monocular camera can be relatively reduced, but each shooting needs to take time and occupy storage space.
The three-dimensional measurement system and the method for fusing laser and monocular vision not only solve the problem that the three-dimensional measurement precision of the scanning laser radar depends on a high-precision angle measurement device, realize precise three-dimensional measurement which reaches pixel-level precision in the two-dimensional plane direction and is equivalent to laser ranging precision in the depth direction, but also are suitable for scanning only a light source along an arc, have a simple structure and have the function of adjusting focal length by matching with a designed collimation scanning optical system.
The above-described embodiments are provided for ease of description and understanding only, and it will be readily appreciated by those skilled in the art that modifications and variations may be made thereto without departing from the spirit and scope of the present disclosure as defined by the appended claims.
Claims (7)
1. The three-dimensional measurement system comprises a monocular camera (1), a laser scanning ranging module and a data processing unit, and is characterized in that: the laser scanning ranging module comprises a laser source (2), a collimation scanning optical system (3) and a receiving ranging unit; the data processing unit comprises relative position calibration parameters of a monocular camera (1) and a laser scanning ranging module, the monocular camera (1) acquires an image of a target to be measured, the laser scanning ranging module acquires depth information of a current scanning point of the target to be measured, the data processing unit processes the image to acquire pixel coordinates of an image point corresponding to the current scanning point of the laser scanning ranging module, and three-dimensional information of the current scanning point of the laser scanning ranging module is acquired by combining the depth information and the calibration parameters; the method comprises the steps of completely scanning all points of a target to be detected through a laser scanning ranging module to obtain complete three-dimensional measurement information of the target to be detected, and inputting three-dimensional point clouds;
the collimating scanning optical system (3) comprises a first lens, a second lens, a third lens and a fourth lens which are sequentially arranged from a light source side to a projection side; the collimating scanning optical system (3) has four lenses, and all the lenses adopt spherical lenses; during zooming, the second lens moves from the light source side to the projection side along the optical axis, and the third lens moves from the projection side to the light source side; wherein:
the first lens is a positive lens, the object side surface is a concave surface, and the image side surface is a concave surface;
the second lens is a positive lens, the object side surface is a convex surface, and the image side surface is a concave surface;
the third lens is a positive lens, the object side surface is a concave surface, and the image side surface is a concave surface;
the fourth lens is a positive lens, the object side surface is a concave surface, and the image side surface is a concave surface;
the collimator scanning optical system (3) satisfies the following conditional expression:
1.1<f1/EFL<1.2；1.5<f2/EFL<1.6；38<f3/EFL<40；10<f4/EFL<12；10<TTL/EFL<12；
wherein EFL is the total focal length of the collimating scanning optical system, TTL is the total length of the collimating scanning optical system on the optical axis, f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, and f4 is the focal length of the fourth lens.
2. The three-dimensional measurement system of claim 1, wherein: the collimating scanning optical system (3) satisfies the following conditional expression:
0.5<(R1-R2)/(R1+R2)<0.6；4<(R3-R4)/(R3+R4)<6；
-1<(R5-R6)/(R5+R6)<1；-1<(R7-R8)/(R7+R8)< -1；
wherein, R1 and R2 are the radii of curvature of the first lens object-side surface and the image-side surface, R3 and R4 are the radii of curvature of the second lens object-side surface and the image-side surface, R5 and R6 are the radii of curvature of the third lens object-side surface and the image-side surface, and R7 and R8 are the radii of curvature of the fourth lens object-side surface and the image-side surface, respectively.
3. The three-dimensional measurement system of claim 1, wherein: the collimating scanning optical system (3) satisfies the following conditional expression:
0.02<D1/TTL<0.03；0.02<D3/TTL<0.025；
0.03<D5/TTL<0.04；0.02<D7/TTL<0.025；
wherein D1 represents the thickness of the first lens on the optical axis, D3 represents the thickness of the second lens on the optical axis, D5 represents the thickness of the third lens on the optical axis, and D7 represents the thickness of the fourth lens on the optical axis.
4. The three-dimensional measurement system of claim 1, wherein: the collimating scanning optical system (3) satisfies the following conditional expression:
0.005<D2/TTL<0.02；0.03<D4/TTL<0.15；0.01<D6/TTL<0.12；
where D2 denotes an interval on the optical axis of the first lens and the second lens, D4 denotes an interval on the optical axis of the second lens and the third lens, and D6 denotes an interval on the optical axis of the third lens and the fourth lens.
5. The three-dimensional measurement system of claim 1, wherein: the collimating scanning optical system (3) satisfies the following conditional expression:
-0.1≤R0/EFL≤-0.05；
wherein R0 is the curvature radius of the scanning path of the laser source.
6. The three-dimensional measurement system of claim 1, wherein: the collimating scanning optical system (3) satisfies the following conditional expression:
15°≤FOV≤20°
wherein the FOV is the full field angle of the quasi-straight scanning optical system.
7. A three-dimensional measurement method employing the three-dimensional measurement system according to any one of claims 1 to 6, comprising the steps of:
step one: installing a monocular camera (1) and a laser scanning ranging module, calibrating the relative positions of the monocular camera (1) and the laser scanning ranging module, and obtaining the spatial position relation of the monocular camera (1) and the laser scanning ranging module to obtain calibration parameters;
step two: the data processing unit acquires the calibration parameters, and the monocular camera (1) acquires an image of a target to be detected;
step three: the data processing unit processes the image, acquires pixel coordinates of an image point in the image, and acquires a real point on a target to be detected according to the image point;
step four: aligning a laser scanning ranging module to the real point of the target to be measured, and measuring the distance of the real point, wherein the distance is depth information of a corresponding image point;
step five: the three-dimensional information of the real point is obtained by combining the pixel coordinates of the image point and the depth information and the calibration parameters;
step six: and driving the collimation scanning optical system (3) to scan the next point of the target to be detected, repeating the steps three to five until the collimation scanning optical system (3) finishes scanning, processing the three-dimensional information of all points of the target to be detected, and outputting a three-dimensional point cloud.
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