A multi-point projection device for improving the accuracy of laser ranging and its measurement method

Abstract

The present invention discloses a multi-point projection device for improving the accuracy of laser ranging and its measurement method, belonging to the technical field of laser ranging; it first emits at least three laser beams in sequence through a laser emission unit, and the laser irradiates the surface of the object to be measured at different angles in sequence through an optical scanning unit, and after being reflected by the surface of the object to be measured, it is received by a laser receiving unit through an optical receiving unit; the data processing unit obtains the ranging value of each laser beam according to the received data, and calculates the spatial coordinate data of each measurement point by combining the emission angle of each beam; constructs a Hermite matrix from the obtained spatial coordinate data to obtain the minimum eigenvalue and eigenvector, and obtains the coefficients of the plane equation according to the minimum eigenvalue and eigenvector; substitutes the obtained coefficients of the plane equation into the projection distance formula from a point to a plane to obtain the actual distance between the laser ranging device and the object to be measured; maximally eliminates external errors and improves the ranging accuracy.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser ranging, and particularly relates to a multi-point projection device for improving laser ranging accuracy and a measurement method thereof. Background Art

[0002] Laser ranging devices are commonly used measuring instruments in the prior art. The principle is to emit a very thin laser beam towards the target during operation, and calculate the round-trip time based on the echo signal received by the optoelectronic components, so as to calculate the distance from the laser ranging device to the target. Currently, common laser ranging devices use the pulse method or the phase method for distance measurement. Regardless of the measurement method used, the ranging result itself has very high accuracy. The ranging accuracy of common laser ranging devices on the market is 1 mm. This process measures the distance from point to point, and the ranging principle of common handheld laser ranging devices can ensure a ranging accuracy at the 1 mm level.

[0003] The laser ranging devices in the prior art mainly include handheld rangefinders and laser projectors. The handheld rangefinder measures the vertical distance from the handheld rangefinder to the wall in the actual working environment. However, since it is impossible to ensure that the laser beam emitted by the handheld rangefinder is completely perpendicular to the wall during the ranging process, the actual laser beam is a slant line rather than a perpendicular line relative to the wall, resulting in inaccurate measurement results. When the laser projector is working, due to the uncertain positional relationship between the wall to be projected and the laser projector, the projected image of the laser projector will be distorted. Therefore, it is necessary to perform distortion correction and refocusing on the projected image, and both the distortion correction and refocusing are based on the wall data measured by the laser projector. Therefore, how to improve the measurement reference of the laser projector is extremely important.

[0004] Regardless of the specific structure of the laser ranging device, the actual distance to be measured is the straight-line distance perpendicular to the wall to be measured. As Figure 1 shown, the actual distance to be measured by the laser ranging device is SO1 perpendicular to the wall, and its length is R. However, due to inevitable angular errors, the length actually measured by the laser ranging device is SO2, with a length of L. Usually, the measurement angle θ of the laser ranging device is about 5 - 8 degrees. Therefore, the length difference ΔR = L - R ≈ L×sinθ between SO1 and SO2. Assuming that the measurement range of the laser ranging ruler is 10 m - 60 m, the length difference ΔR can be estimated to be in the order of 20 mm to 100 mm. That is to say, although the ranging accuracy of the laser ranging device can reach the 1 mm level, the actual ranging accuracy is only 20 mm to 100 mm. Therefore, although the ranging accuracy of the laser ranging device is very high, it is difficult to obtain the projection distance perpendicular to the wall to be measured during actual use, resulting in the problem of low actual ranging accuracy of the laser ranging device. Summary of the Invention

[0005] In the prior art, during the use of a laser ranging device, angle deviation may occur, resulting in inaccurate measurement results. The purpose of the present invention is to provide a multi-point projection device and its measurement method to address the above deficiencies in the prior art. The device emits at least three lasers through the laser ranging device, and the optical scanning unit refracts them into lasers at different angles to determine the plane to be measured. By means of geometric projection, the vertical projection distance and the focusing focal length distance from the laser ranging device to the plane to be measured are calculated, maximizing the elimination of external errors, improving the measurement accuracy of the ranging device, and providing the plane equation of the surface to be projected for the laser projector, enabling the laser projector to perform automatic focusing and distortion correction.

[0006] The technical solution of the present invention is implemented as follows: A multi-point projection device for improving laser ranging accuracy includes a laser ranging device. Inside the laser ranging device, there are a data processing unit, a signal control unit, a laser emitting unit, a laser receiving unit, an optical scanning unit, and an optical receiving unit. The laser emitting unit, the laser receiving unit, and the optical scanning unit are respectively electrically connected to the signal control unit. The signal control unit and the laser receiving unit are respectively electrically connected to the data processing unit. The optical scanning unit is arranged at the output end of the laser emitting unit, and the optical receiving unit is arranged at the input end of the laser receiving unit. The optical scanning unit includes a collimating lens group, a beam multi-point modulation module, and a module controller. The collimating lens group is arranged at the output end of the laser emitting unit to convert the laser beam emitted by the laser emitting unit into a parallel beam. The beam multi-point modulation module is arranged at the output end of the collimating lens group to convert the above parallel beam into a beam at a certain angle. The module controller is respectively electrically connected to the signal control unit and the beam multi-point modulation module, and is used to adjust the angle of the beam emitted by the beam multi-point modulation module.

[0007] As a preferred solution, the beam multi-point modulation module is a MEMS galvanometer, and the module controller is a galvanometer motor drive board.

[0008] As a preferred solution, the beam multi-point modulation module includes at least one prism. The module controller is a code disk for measuring the offset angle of the prism and a driver for driving the prism to have an angular offset. The code disk and the driver are respectively connected to the data processing unit.

[0009] As a preferred solution, the beam multi-point modulation module includes a polarization grating and a liquid crystal cell. The liquid crystal cell is cascaded on the incident surface of the polarization grating. The module controller is a voltage modulation circuit board, and the voltage modulation circuit board is electrically connected to the liquid crystal cell.

[0010] A measurement method for measuring the actual distance between a laser ranging device and an object to be measured includes the following steps in sequence:

[0011] S1. The laser emission unit sequentially emits at least three laser beams. The three laser beams are sequentially irradiated onto the surface of the object to be measured at different angles through the optical scanning unit, and after being reflected by the surface of the object to be measured, they are received by the laser receiving unit through the optical receiving unit;

[0012] S2. The data processing unit respectively obtains the ranging values of each laser beam according to the data collected by the laser receiving unit, and calculates the spatial coordinate data of each measurement point by combining the emission angles of each beam;

[0013] S3. The average value data of the spatial coordinates is obtained by averaging the spatial coordinate data obtained in S2, and the Hermite matrix is constructed by subtracting the average value data from the spatial coordinate data obtained in S2. The minimum eigenvalue and eigenvector are obtained, and the coefficients of the plane equation are obtained according to the minimum eigenvalue and eigenvector;

[0014] S4. The actual distance between the laser ranging device and the object to be measured is obtained by substituting the coefficients of the plane equation obtained in S3 into the projection distance formula from a point to a plane.

[0015] As a preferred solution, the spatial coordinate data in step S2 includes data on the X-axis, Y-axis, and Z-axis; further, in step S3, the obtained spatial coordinate data is first constructed into a column vector matrix A, and then the average values in the X, Y, and Z directions are calculated and a column vector matrix B excluding the average values is reconstructed. The Hermite matrix is constructed according to the column vector matrix B, the data of each sub-item in the Hermite matrix is calculated, and the data is decomposed to obtain the eigenvalue matrix and eigenvector matrix, and the coefficients of the plane equation are calculated after calculation.

[0016] A measurement method for measuring the focal distance between a laser ranging device and an object to be measured sequentially includes the following steps:

[0017] S11. The laser emission unit sequentially emits at least three laser beams. The three laser beams are sequentially irradiated onto the surface of the object to be measured at different angles through the optical scanning unit, and after being reflected by the surface of the object to be measured, they are received by the laser receiving unit through the optical receiving unit;

[0018] S12. The data processing unit respectively obtains the ranging values of each laser beam according to the data collected by the laser receiving unit, and calculates the spatial coordinate data of each measurement point by combining the emission angles of each beam;

[0019] S13. The average value data of the spatial coordinates is obtained by averaging the spatial coordinate data obtained in S12;

[0020] S14. The Euclidean distance is obtained from the average value data of the spatial coordinates obtained in S13 to obtain the focal distance.

[0021] The beneficial effects of the present invention adopting the above structure and method are as follows: By using multiple laser beams to determine the plane equation and through the algorithm of geometric projection, the measurement errors caused by incorrect holding angles or incorrect placement angles are avoided, the external errors are eliminated to the greatest extent, the ranging accuracy is improved, and the plane equation of the surface to be projected can be provided for the laser projector, enabling the laser projector to perform automatic focusing and distortion correction. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention will be further described in detail below with reference to the embodiments in the drawings, but it does not constitute any limitation to the present invention.

[0023] Figure 1 It is a schematic diagram of the principle when the laser ranging device in the prior art measures distance;

[0024] Figure 2 It is a schematic diagram of the overall structure connection of the embodiment of the present invention;

[0025] Figure 3 It is a schematic diagram of the connection principle of the optical scanning unit in the embodiment of the present invention;

[0026] Figure 4 It is a schematic diagram of the refraction principle of polarized gratings on light in the embodiment of the present invention;

[0027] Figure 5 It is a schematic diagram of the spatial vector coordinates formed after the laser irradiates the plane in the embodiment of the present invention;

[0028] Figure 6 It is a schematic diagram of the principle when the multi-point projection device in the embodiment of the present invention measures distance;

[0029] Figure 7 It is a schematic diagram of the operation principle of the multi-point projection device in the embodiment of the present invention.

[0030] In the figure: 1 - laser ranging device, 2 - data processing unit, 3 - signal control unit, 4 - laser emitting unit, 5 - laser receiving unit, 6 - optical scanning unit, 7 - optical receiving unit, 8 - wall, 61 - collimating lens group, 62 - beam multi-point modulation module, 63 - module controller, 621 - polarized grating, 622 - liquid crystal cell. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] The embodiments of the present invention will be further described below with reference to the drawings:

[0032] As Figures 1 - 3A multi-point projection device for improving the accuracy of laser ranging is shown, including a laser ranging device 1. Inside the laser ranging device 1, there are a data processing unit 2, a signal control unit 3, a laser emitting unit 4, a laser receiving unit 5, an optical scanning unit 6 and an optical receiving unit 7. The laser emitting unit 4, the laser receiving unit 5 and the optical scanning unit 6 are respectively electrically connected to the signal control unit 3. The signal control unit 3 and the laser receiving unit 5 are respectively electrically connected to the data processing unit 2. The optical scanning unit 6 is arranged at the output end of the laser emitting unit 4, and the optical receiving unit 7 is arranged at the input end of the laser receiving unit 5. The optical scanning unit 6 includes a collimating lens group 61, a beam multi-point modulation module 62 and a module controller 63. The collimating lens group 61 is arranged at the output end of the laser emitting unit 4 to convert the laser beam scattered by the laser emitting unit 4 into a parallel beam. The beam multi-point modulation module 62 is arranged at the output end of the collimating lens group 61 to convert the above parallel beam into a beam at a certain angle. The module controller 63 is respectively electrically connected to the signal control unit 3 and the beam multi-point modulation module 62, and is used to adjust the angle of the beam emitted by the beam multi-point modulation module 62. The data processing unit 2 is used for data operation and coordinating the cooperation between each unit. The signal control unit 3 is used to send coherent synchronous control signals to the laser emitting unit 4 and the laser receiving unit 5 respectively to ensure the coherent synchronization between the laser emitting unit 4 and the laser receiving unit 5. The laser emitting unit 4 is used to generate a laser beam. The laser receiving unit 5 is used to receive the laser beam and convert the received laser beam into a data signal that can be interpreted by the data processing unit 2. The optical scanning unit 6 is used to convert the scattered laser beam emitted by the laser emitting unit 4 into a parallel laser beam. The optical receiving unit 7 is used to receive the laser beam reflected from the surface of the object to be measured and convert it into a focused laser beam, so that the laser receiving unit 5 can receive the laser. The data processing unit 2 can use an M68HC16 single-chip microcomputer or other types of single-chip microcomputers. The laser emitting unit 4 can use a laser. The laser receiving unit 5 can use a detector. The optical receiving unit 7 includes a focusing lens group. During operation, at least three laser beams are sequentially emitted by the laser emitting unit 4, and then the module controller 63 sequentially changes the refraction angle of the beam multi-point modulation module 62 to make the above laser beams emit at different angles respectively. Then, the laser receiving unit 5 sequentially receives the reflected laser beams and sends their data signals to the data processor for analysis and processing. The purpose of the present invention is to add a beam multi-point modulation module and a module controller to the existing laser ranging device 1, so that the laser ranging device 1 can sequentially emit multiple laser beams at different angles, and solve the distance from the laser ranging device 1 to the measured surface through an algorithm, thereby improving the detection accuracy of the laser ranging device 1.It should be noted that the above data processing unit 2, signal control unit 3, laser receiving unit 5, optical scanning unit 6, and optical receiving unit 7 are all prior arts and not the improvement points of the present invention. Any structure in the prior art can be adopted. The beam multi-point modulation module includes, but is not limited to, the following structures:

[0033] 1. Using the galvanometer deflection method: The beam multi-point modulation module is a MEMS galvanometer, and the module controller is a galvanometer motor driver board. The MEMS galvanometer is used to deflect the beam in the horizontal and vertical directions, emit laser at different angles for measurement, obtain the spatial point set of the plane to be measured, and then calculate its plane equation through an algorithm to obtain the projection distance from the laser ranging device 1 to the surface of the object to be measured.

[0034] 2. Using the prism deflection method: The beam multi-point modulation module includes at least one prism, and the module controller is a code disk for measuring the offset angle of the prism and a driver for driving the prism to have an angular offset. The code disk and the driver are respectively connected to the data processing unit 2. One or more prisms are used to deflect the beam, and the vector synthesis of the angles of one or more prisms is measured by the code disk to calculate the spatial deflection angle of the laser, so as to obtain the spatial point set of the plane to be measured. The subsequent algorithm processing is the same as above; the driver can adopt a deflection motor.

[0035] 3. Adopt the polarization grating method: The multi-point beam modulation module includes a polarization grating 621 and a liquid crystal cell 622. The liquid crystal cell 622 is cascaded on the incident surface of the polarization grating 621. The module controller is a voltage modulation circuit board, and the voltage modulation circuit board is electrically connected to the liquid crystal cell 622. The polarization grating 621 can diffract the left-handed incident light to the +1 order and diffract the right-handed polarized light to the -1 order. Based on this principle, a liquid crystal cell 622 can be cascaded on the incident surface of each polarization grating 621. By controlling the voltage on the liquid crystal cell 622, the left-handed and right-handed characteristics of the incident light can be regulated. Left-handed circular polarization and right-handed circular polarization. Under normal circumstances, the polarization grating 621 can diffract the left-handed circularly polarized light to the +1 order light and diffract the right-handed circularly polarized light to the -1 order light, thus generating an angular transformation. The liquid crystal structure half-wave plate (LC half-wave plate) in the liquid crystal cell 622 can modulate the left-handed and right-handed states of the polarized light. Under different voltage modulation conditions, the left-handed circularly polarized light and the right-handed circularly polarized light can be mutually transformed, so that the direction of the outgoing light can be modulated. Due to the diffraction characteristics of the polarization grating 621 itself, at the non-deflected angle, that is, the 0-order light (θ = 0) will always have light leakage. The theoretical limit of the polarization grating 621 can reduce the 0-order light to 0, but in engineering practice, the 0-order light can only be reduced very weakly and can be ignored, but it always exists; as Figure 4 Shown is a unit for modulating the outgoing direction of light. One unit can diffract a beam of light to two angles. If two modulation units are cascaded, the beam of light can be modulated to 4 angles. By voltage-modulating the liquid crystal structure half-wave plate, a mechanical-free steering of the beam of light can be achieved.

[0036] A measuring method for measuring the actual distance and the focal distance between a laser ranging device 1 and an object to be measured successively includes the following steps:

[0037] S1. The laser emission unit 4 successively emits at least three laser beams. The three beams of laser are successively irradiated onto the surface of the object to be measured at different angles through the optical scanning unit 6, and after being reflected by the surface of the object to be measured, they are received by the laser receiving unit 5 through the optical receiving unit 7;

[0038] S2. The data processing unit 2 respectively obtains the ranging values of each laser beam according to the data collected by the laser receiving unit 5, and calculates the spatial coordinate data of each measurement point by combining the emission angles of each beam of light;

[0039] S3. Average the spatial coordinate data obtained in S2 to obtain the average value data of the spatial coordinates, subtract the average value data from the spatial coordinate data obtained in S2 to construct a Hermitian matrix, obtain the minimum eigenvalue and eigenvector, and obtain the coefficients of the plane equation based on the minimum eigenvalue and eigenvector;

[0040] S4. Substitute the plane equation coefficients obtained in S3 into the projection distance formula from a point to a plane to obtain the actual distance between the laser ranging device 1 and the object to be measured; obtain the focal length distance by calculating the Euclidean distance of the average value data of the spatial coordinates obtained in S3.

[0041] The above method determines the plane to be measured by the laser ranging device 1 emitting at least three or more lasers at different angles, and then calculates the vertical projection distance of the laser ranging device 1 from the wall 8 through geometric projection, which can improve the ranging accuracy of the laser ranging device 1, avoid measurement errors caused by incorrect holding angles or incorrect placement angles, and eliminate external errors to the greatest extent.

[0042] As a preferred solution, the spatial coordinate data in step S2 includes data on the X-axis, Y-axis, and Z-axis; further, in step S3, first construct a column vector matrix A from the obtained spatial coordinate data, then calculate the average values in the X, Y, and Z directions, and reconstruct the column vector matrix B excluding the average values. Construct a Hermitian matrix based on the column vector matrix B, calculate the data of each sub-item in the Hermitian matrix, and decompose the data to obtain the eigenvalue matrix and eigenvector matrix, and calculate the coefficients of the plane equation after calculation.

[0043] The following is the calculation process in this method: In the implementation process of this solution, the signal control unit 3 controls the optical scanning unit 6 to make the laser ranging device 1 emit multiple laser lines at specified angles in sequence according to a certain method; then the signal control unit 3 controls the laser emitting unit 4 and the laser receiving unit 5 to perform ranging, and then delivers the collected data to the signal processing unit to calculate the accurate length of each laser beam in sequence. Since we know the emission angle of the laser emitting unit, the vector expression of the laser emitting unit can be known: In the formula, L i represents the column vector of laser emission, and x i , y i , z i represent the emission vector directions respectively, i represents the i-th emission, and satisfies the unit vector condition

[0044] After the i-th laser, the measured distance is a scalar R i, the following purpose is to obtain the plane equation. Therefore, a space rectangular coordinate system is established, and it is stipulated that the laser is located at the origin coordinates (0, 0, 0), and the equation is established according to the general expression of the plane ax + by + cz + d = 0. After multiple measurements, since L i is the standard vector, and the spatial vector direction of the i-th measurement is known, the measured plane spatial coordinates are Taking four emissions as an example, the spatial vector coordinates obtained after the laser irradiates the plane are as Figure 5 shown.

[0045] The following purpose is to solve the plane equation. The equation of the plane is determined by its four coefficients a, b, c, and d. Calculate the average values of the distances in the X direction, Y direction, and Z direction, which are respectively:

[0046]

[0047]

[0048]

[0049] Since at least three points determine a plane, during the measurement process, we obtained N measurement data, then N must satisfy N ≥ 3; taking the Euclidean distance of the average values in the x, y, and z directions can obtain the focal length distance from the laser ranging device 1 to the measured object as

[0050] Removing the expected values in the x, y, and z directions and re-expressing them as x i 、y i 、z i , we get:

[0051]

[0052]

[0053]

[0054] At this time, the point set coordinates are translated to be centrosymmetric about the origin. Therefore, the above data can be constructed into a positive definite quadratic form to solve the plane equation f = v T S v, where v = [a b c] T , S is a Hermitian matrix, and the respective sub-items in S are:

[0055]

[0056] Perform eigen - decomposition on matrix S to obtain eigen - vectors D and eigenvalues Λ. Since the two largest eigen - vectors are collinear with the plane, the eigen - vector corresponding to its smallest eigenvalue must be the normal direction of the plane, which is the coefficient we are solving for. Assume the k - th eigenvalue Λ kk is the smallest. Then the coefficients a, b, c, d of the straight - line equation can be expressed as:

[0057] a = D 1k , b = D 2k , c = D 3k ,

[0058] Using these coefficients, we can obtain the straight - line equation of the wall surface 8 to be measured. Then, through the point - to - straight - line distance equation, the calculated projection distance R is:

[0059]

[0060] That is, this distance is the vertical projection distance from the laser distance - measuring device 1 to the plane to be measured.

[0061] Next, take actual values as an example: As Figure 6 shown, the signal control unit 3 controls the optical scanning unit 6 to make the laser distance - measuring device 1 emit 4 laser lines at specified angles in sequence according to a certain method, which are respectively denoted as SO2, SO3, SO4, SO5. Then, the signal control unit 3 controls the laser emission unit 4 and the laser receiving unit 5 to measure the distance. Then, the collected data is handed over to the signal processing unit to calculate the accurate lengths of SO2, SO3, SO4, SO5 in sequence. Since the specified angles emitted by the laser are known, assume that the four emission angles are a normalized vector pointing from the origin to Z, and are respectively deflected by 30° to the positive and negative semi - axes of the X - axis and 30° to the positive and negative semi - axes of the Y - axis. Then the four unit spatial vectors are and which are the directions of the rays SO2, SO3, SO4, SO5. After being calculated by the signal processing unit, we measure that the four measured distances are R1 = 1.2991, R2 = 1.0186, R3 = 1.1742, R4 = 1.5633. The spatial coordinates of the plane to be measured obtained from the unit vectors are represented by the column - vector matrix as:

[0062]

[0063] Each column represents the x, y, z coordinates of a group of points, and the average values in the x, y, z directions are calculated as Then the coordinate mean point P from the laser distance - measuring device 1 to the object to be measured is:

[0064]

[0065] The focal length distance SO6 of the coordinate mean point P is the Euclidean distance from point P to the origin, that is:

[0066]

[0067] Reconstruct the coordinate system X, Y, and Z with the average values in the x, y, and z directions, expressed as: i , Y i and Z i as:

[0068]

[0069]

[0070]

[0071] Then the column vector matrix after removing the expected value is B:

[0072]

[0073] Construct the Hermitian matrix S:

[0074]

[0075] After calculation, each sub-item of matrix S is:

[0076]

[0077] Perform eigenvalue decomposition on matrix S to obtain the eigenvalue matrix Λ and the eigenvector matrix D, which are respectively:

[0078]

[0079]

[0080] Since the minimum eigenvalue is on the diagonal of matrix Λ, that is, the first one in the first row is the smallest, the corresponding eigenvector is the first column of matrix D. Therefore, the plane equation a = -0.0819, b = 0.3420, c = 0.9361, Substitute into the projection distance formula from a point to a plane to obtain:

[0081]

[0082] The true distance between the laser ranging device 1 and the wall 8 can be obtained. The algorithm implementation principle is as Figure 7 shown. The figure is the flowchart of the projection distance calculation method.

[0083] The above-mentioned embodiments are preferred embodiments of the present invention, which are only used to conveniently illustrate the present invention and do not impose any formal restrictions on the present invention. Any person with ordinary knowledge in the technical field, without departing from the technical features of the present invention, makes equivalent embodiments with partial modifications or decorations by using the technical content disclosed in the present invention, and without departing from the technical feature content of the present invention, still fall within the scope of the technical features of the present invention.

Claims

1. A measurement method for measuring the actual distance between a detection laser ranging device and an object to be measured, characterized in that: Comprising a laser ranging device (1), inside which there are provided a data processing unit (2), a signal control unit (3), a laser emitting unit (4), a laser receiving unit (5), an optical scanning unit (6) and an optical receiving unit (7). The laser emitting unit (4), the laser receiving unit (5) and the optical scanning unit (6) are respectively electrically connected to the signal control unit (3). The signal control unit (3) and the laser receiving unit (5) are respectively electrically connected to the data processing unit (2). The optical scanning unit (6) is arranged at the output end of the laser emitting unit (4), and the optical receiving unit (7) is arranged at the input end of the laser receiving unit (5); successively including the following steps: S1. The laser emitting unit (4) successively emits at least three laser beams. The at least three laser beams are successively irradiated onto the surface of the object to be measured at different angles through the optical scanning unit (6), and after being reflected by the surface of the object to be measured, are received by the laser receiving unit (5) through the optical receiving unit (7); S2. The data processing unit (2) respectively obtains the ranging values of each laser beam according to the data collected by the laser receiving unit (5), and calculates the spatial coordinate data of each measurement point by combining the emission angles of each beam; S3. The average value data of the spatial coordinates is obtained by averaging the spatial coordinate data obtained in S2, and an Hermite matrix is constructed by subtracting the average value data from the spatial coordinate data obtained in S2, the minimum eigenvalue and eigenvector are obtained, and the coefficients of the plane equation are obtained according to the minimum eigenvalue and eigenvector; S4. The actual distance between the laser ranging device and the object to be measured is obtained by substituting the coefficients of the plane equation obtained in S3 into the projection distance formula from a point to a plane.

2. A measurement method for measuring the actual distance between a measurement and detection laser ranging device and an object to be measured according to claim 1, characterized in that: The spatial coordinate data in step S2 includes data on the X-axis, Y-axis and Z-axis.

3. A measurement method for measuring the actual distance between a measurement and detection laser ranging device and an object to be measured according to claim 2, characterized in that: In step S3, first, a column vector matrix A is constructed from the obtained spatial coordinate data, then the average values in the X, Y, and Z directions are calculated, and a column vector matrix B excluding the average values is re-constructed. An Hermite matrix is constructed according to the column vector matrix B, the data of each sub-item in the Hermite matrix is calculated, and this data is decomposed to obtain an eigenvalue matrix and an eigenvector matrix, and the coefficients of the plane equation are obtained after calculation.

4. A multi-point projection device for improving the accuracy of laser ranging, including the data processing unit (2) of the measurement method according to any one of claims 1-3. The optical scanning unit (6) includes a collimating lens group (61), a beam multi-point modulation module (62) and a module controller (63). The collimating lens group (61) is arranged at the output end of the laser emitting unit (4) to convert the laser beam scattered by the laser emitting unit (4) into a parallel beam. The beam multi-point modulation module (62) is arranged at the output end of the collimating lens group (61) to convert the above parallel beam into a beam at a certain angle. The module controller (63) is respectively electrically connected to the signal control unit (3) and the beam multi-point modulation module (62) for adjusting the angle of the beam emitted by the beam multi-point modulation module (62).

5. The multi-point projection device for improving the laser ranging accuracy according to claim 4, wherein: The beam multi-point modulation module (62) is a MEMS galvanometer, and the module controller (63) is a galvanometer motor drive board.

6. The multi-point projection device for improving the laser ranging accuracy according to claim 4, wherein: The beam multi-point modulation module (62) includes at least one prism. The module controller (63) is a code disk for measuring the deflection angle of the prism and a driver for driving the prism to deflect at an angle. The code disk and the driver are respectively connected to the data processing unit (2).

7. A multi-point projection device for improving the accuracy of laser ranging according to claim 4, characterized in that: The beam multi-point modulation module (62) includes a polarization grating (621) and a liquid crystal cell (622). The liquid crystal cell (622) is cascaded on the incident surface of the polarization grating (621). The module controller (63) is a voltage modulation circuit board, and the voltage modulation circuit board is electrically connected to the liquid crystal cell (622).

8. A measurement method for measuring the focal distance between a laser ranging device and an object to be measured, including the multi-point projection device according to any one of claims 4-7, characterized in that: It sequentially includes the following steps: S11. The laser emission unit (4) sequentially emits at least three laser beams. The at least three laser beams are sequentially irradiated onto the surface of the object to be measured at different angles through the optical scanning unit (6), and after being reflected by the surface of the object to be measured, they are received by the laser receiving unit (5) through the optical receiving unit (7); S12. The data processing unit (2) respectively obtains the ranging values of each laser beam according to the data collected by the laser receiving unit (5), and calculates the spatial coordinate data of each measurement point by combining the emission angles of each beam; S13. The average value data of the spatial coordinates is obtained by averaging the spatial coordinate data obtained in S12; S14. The Euclidean distance is obtained by taking the spatial coordinate average value data obtained in S13 to obtain the focal distance.

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