A 3D measurement method based on a wide spectrum light source

Abstract

The application discloses a 3D measurement method based on a wide-spectrum light source, which comprises the following steps: firstly, a triangular laser measurement model is established; a calibration object is placed into the triangular laser measurement model, and the object plane coordinates (x, z) of the calibration object are measured by means of a measuring instrument; a plurality of sets of object plane coordinates of the calibration object and corresponding image plane coordinates are obtained by moving the calibration object for multiple times, and a binary first-order function relationship formula is obtained; finally, a measured object is placed into the triangular laser measurement model, the image plane coordinates (u, v) of the object plane of the measured object are acquired by an imaging detector, the z coordinate of the object plane of the measured object is calculated through the function relationship formula, the y coordinate is measured by moving the measured object in the vertical direction of the focusing beam optical axis by a displacement movement mechanism, the object plane profile (x, z) in the displacement distance is spliced, the whole object plane profile of the measured object is obtained, and the 3D size of the whole measured object is obtained. The application has the characteristics of large tolerance angle, high compatibility and high measurement precision, and greatly reduces the volume and cost.

Description

Technical Field

[0001] This invention belongs to the field of optical measurement technology, and in particular refers to a 3D measurement method based on a broadband light source. Background Technology

[0002] Triangulation laser measurement and spectral confocal imaging measurement are the most common 3D optical measurement methods. From a cost and efficiency perspective, triangulation laser measurement is superior. However, it has high requirements for the light source, using collimated lasers (narrow spectrum, spectral width less than 10nm). The beam divergence angle is very small, and the reflected light energy is highly sensitive to angle changes, leading to poor imaging of specular reflective objects. In contrast, spectral confocal imaging measurement is superior. It uses a focused beam instead of a collimated beam, resulting in better angle compatibility and image quality. Furthermore, the receiving and transmitting lenses of the spectral confocal sensor are identical, compensating for the dispersion of the transmitting lens. Then, a spectrometer analyzes the spectrum of the reflected light to calculate the height of the reflecting object. Figure 1 As shown. However, the spectral confocal model uses a scheme of dispersive confocal combined with spectral measurement, which is very complex in terms of optical path. The spectrometer setup also results in a large size and high cost. The price of a typical spectral confocal product is more than three times that of a triangular laser, thus increasing the purchase cost.

[0003] Broad spectrum, usually refers to a spectrum with a spectral width greater than 10 nm. In contrast to narrow spectrum with a width less than 10 nm, broad spectrum is easier to obtain. Therefore, based on the above-mentioned shortcomings, the inventors propose a triangular laser 3D measurement technology based on broad spectrum. Summary of the Invention

[0004] The purpose of this invention is to provide a 3D measurement method based on a broadband light source, which has the characteristics of large tolerance angle, high compatibility and high measurement accuracy, and greatly reduces volume and cost.

[0005] To achieve the above objectives, the solution of the present invention is: a 3D measurement method based on a broadband light source, comprising the following steps: S1 Model Establishment: A triangular laser measurement model is set up in the dispersive region. This model includes a broadband light source, a dispersive lens, a displacement mechanism, the object surface to be measured, a high-resolution imaging lens, an imaging detector, and a data processing system. The broadband light source emits a diverging beam. The dispersive lens focuses different colors of light from the diverging beam onto different heights of the object surface to form a focused beam. The object surface reflects the focused beam at an angle to the high-resolution imaging lens. The displacement mechanism is used to place the object to be measured and move it. The direction of movement is perpendicular to the optical axis of the focused beam. The displacement mechanism is connected to the data processing system. The high-resolution imaging lens focuses the reflected beam onto the imaging detector to form an image. The imaging detector and data processing system are used to convert the optical signal into an electrical signal and generate the data required for 3D measurement. S2 uses a calibration object: First, the calibration object is placed in the triangular laser measurement model instead of the object being measured and a three-dimensional coordinate system is set. Then, the object plane coordinates (x, z) of the calibration object are measured with the help of a high-precision measuring instrument. The x coordinate represents the coordinate of the focused beam direction and the z coordinate represents the vertical coordinate. Then, the image plane coordinates (u, v) of the imaging detector are obtained. The u is the element corresponding to the x coordinate and the v is the element corresponding to the z coordinate. Within the dispersive region, by moving the calibration object, a mapping relationship between the object plane coordinates and the image plane coordinates can be established, generating a two-variable linear function relationship for calculation: x0 = au + bv + δ1 (1) z0=cu+dv+δ2(2) Where a, b, c, d, δ1, and δ2 are all coefficients. By moving the calibration object multiple times, multiple sets of object plane coordinates and corresponding image plane coordinates of the calibration object are obtained. Then, these multiple sets of object plane coordinates and image plane coordinates are substituted into formulas (1) and (2) to obtain the values ​​of a, b, c, d, δ1, and δ2, and finally, the bivariate linear function relationship with determined coefficients is obtained. S3 measures the 3D dimensions of the object under test: The object under test is placed in a triangular laser measurement model. The x and z coordinates of each point on the surface of the object under test are calculated using u, v values ​​and a linear function relationship. n points form a line, and n lines form a surface, thus obtaining the contour of the surface of the object under test. At the same time, the displacement motion mechanism drives the object under test to move in the direction perpendicular to the optical axis of the focused beam, i.e., the direction of movement is set as the y direction. The displacement motion mechanism is divided into multiple motion units in the y direction. In this way, the motion units of the object surface contour from the beginning of its appearance in the image plane coordinates to the end of its disappearance in the image plane coordinates are recorded. Finally, the recorded motion units are added together to obtain the y coordinate of the object under test. The object surface contour (x, z) within each motion unit is then combined to obtain the entire surface contour of the object under test, thus obtaining the 3D dimensions of the entire object under test, including the x, y, and z coordinates of any point on the object under test, and thus obtaining the depth or height of defects on the surface of the object under test.

[0006] Further, step S3 is replaced by: placing the object to be measured into a triangular laser measurement model, calculating the x and z coordinates of each point on the surface of the object using u, v values ​​and a linear function relationship, forming a line from n points, and a surface from n lines, thus obtaining the contour of the object surface. At the same time, the displacement mechanism drives the object to move in the direction perpendicular to the optical axis of the focused beam, i.e., the direction of movement is set to the y direction. A stepper motor is set in the displacement mechanism, the step distance of the stepper motor is set first, and then the pulse quantity of the object surface contour from the moment it appears in the image plane coordinates until it disappears in the image plane coordinates is recorded. Finally, the pulse quantity is converted into the displacement distance to obtain the y coordinate of the object. Similarly, the object surface contours (x, z) within the displacement distance are combined to obtain the entire object surface contour, thus obtaining the 3D dimensions of the entire object, including the x, y, and z coordinates of any point on the object, and thus obtaining the depth or height of defects on the object surface.

[0007] Furthermore, the broadband light source is a point spectrum, and the imaging detector is a linear array detector.

[0008] Furthermore, the broadband light source is a multi-point spectrum, and the imaging detector is a multi-linear array detector.

[0009] Furthermore, the broadband light source is a line light source, and the imaging detector is an area array detector.

[0010] Furthermore, the dispersive lens disperses the light emitted by the broadband light source, while the high-resolution imaging lens is a conventional imaging lens that does not contain dispersive light.

[0011] Furthermore, the object surface under test is located between the dispersive lens and the high-resolution imaging lens.

[0012] Furthermore, the imaging detector and data processing system are located at the focal plane of the high-resolution imaging lens.

[0013] After adopting the above scheme, the gain effect of the present invention is as follows: By using a broadband light source, emitted light waves can be decomposed into converging beams of different wavelengths, forming converging wavelengths at different heights. The main wavelength reflected by the object is this converging wavelength, so the beam does not change much at different heights. This solves the problem of beam widening in the defocused state, allowing the measurement model to maintain good measurement accuracy over a wide height range.

[0014] In existing technologies, the receiving and transmitting lenses of spectral confocal sensors are identical. Compensation for the chromatic aberration of the transmitting lens is required, followed by analysis of the reflected light spectrum using a spectrometer to calculate the 3D dimensions of the reflecting object. However, this invention uses a triangular laser receiving lens, eliminating the need for chromatic aberration compensation, allowing direct imaging, and simplifying the optical path without the need for a spectrometer. Furthermore, the overall system structure is simpler, significantly reducing size and cost, thus achieving superior measurement accuracy. The dispersive lens described in this invention can focus light of different wavelengths from the broadband light source to different heights on the object surface. For the focused beam, the reflected light has a certain divergence angle, improving the model's tolerance to the tilt of the object's surface and enhancing measurement accuracy. Therefore, the model of this invention can measure specularly reflective objects such as metal and glass, as well as objects with curved or stepped surfaces, such as 3D glass, grooves, welds, etc.

[0015] Compared with the prior art, the advantages of the present invention are as follows: Broadband beams possess a certain divergence angle, meaning that even with specular reflection from the target surface, the reflected beam retains a divergence angle, reducing the angular sensitivity of the measurement model and enhancing its detection capability for specularly reflective targets. For diffusely reflective targets, this broadband illumination method still offers advantages, namely improved detection capabilities for curved and tilted surfaces. Compared to line laser systems, this system offers a larger tolerance angle and higher measurement accuracy. Compared to spectral confocal systems, this system significantly reduces size and cost. Therefore, broadband beam systems overcome the shortcomings of both line laser and spectral confocal systems while combining their advantages, effectively expanding the application scenarios and scope of the measurement system. Attached Figure Description

[0016] Figure 1 This is a schematic diagram illustrating the principle of the existing spectral confocal model; Figure 2 This is a schematic diagram of the structure of a 3D measurement model based on a broadband light source, as described in this embodiment. Figure 1 ; Figure 3 This is a schematic diagram of the structure of a 3D measurement model based on a broadband light source, as described in this embodiment. Figure 2 (Imaging changes); Figure 4 This is a schematic diagram illustrating the principle of a 3D measurement model based on a broadband light source, according to an embodiment. Figure 5 This is a schematic diagram illustrating the imaging relationship between image plane coordinates and object plane coordinates according to the present invention.

[0017] Labeling explanation: 1. Spectral light source; 2. Dispersion lens; 3. Surface of the object being measured; 4. High-resolution imaging lens; 5. Imaging detector; 6. Displacement mechanism. Detailed Implementation

[0018] In the following description, embodiments of the invention will be described more fully. The invention may have various embodiments, and adjustments and changes may be made therein. However, it should be understood that there is no intention to limit the scope of the invention to the specific embodiments disclosed herein, but rather the invention should be understood to cover all modifications, equivalents, and / or alternatives falling within the spirit and scope of the various embodiments of the invention.

[0019] This invention relates to a 3D measurement model based on a broadband light source, such as... Figure 4 As shown, it includes a broadband light source 1, a dispersive lens 2, the surface of the object being measured 3, a high-resolution imaging lens 4, an imaging detector 5, a data processing system, and a displacement mechanism 6.

[0020] The broadband light source 1 emits a diverging light beam. The broadband light source 1 is located in front of the dispersive lens 2. The dispersive lens 2 disperses the light from the broadband light source 1. The dispersive lens 2 focuses different colors of light from the diverging beam onto different heights of the object surface 3 to form a focused beam. The displacement mechanism 6 is used to place the object and move it, with the movement direction perpendicular to the optical axis of the focused beam. The object surface is located between the dispersive lens and the high-resolution imaging lens. The object surface 3 reflects the focused beam onto the high-resolution imaging lens 4, which then focuses the reflected beam onto the imaging detector 5. The imaging detector and data processing system are located at the focal plane of the high-resolution imaging lens. Figure 2 and Figure 3 The diagram shows that when there are defects such as dents on the surface of the object being measured, the reflected light beam changes, which in turn changes the image on the imaging detector 5. The imaging detector 5 converts the light signal into an electrical signal and sends it to the data processing system. The data processing system generates the data required for 3D measurement. The displacement motion mechanism 6 is connected to the data processing system. The displacement motion mechanism 6 described in this case can be a conveyor belt, a conveyor plate, or other mechanism capable of generating displacement motion.

[0021] This invention relates to a 3D measurement method based on a broadband light source. The data processing system can achieve 3D measurement through the following measurement method, specifically including the following steps: S1 Model Establishment: Arrange the above-mentioned triangular laser measurement model in the dispersive region; S2 uses a calibration object: First, the calibration object is placed in the triangular laser measurement model instead of the object being measured and a three-dimensional coordinate system is set. Then, the object plane coordinates (x, z) of the calibration object can be measured with the help of a high-precision measuring instrument (such as an infrared laser rangefinder, interferometer, etc.). The x-coordinate represents the coordinate of the focused beam direction and the z-coordinate represents the vertical coordinate. Then, the image plane coordinates (u, v) of the imaging detector are obtained, where u is the element corresponding to the x-coordinate and v is the element corresponding to the z-coordinate. Within the dispersive region, by moving the calibration object, a complete relationship between the object plane coordinates and the image plane coordinates can be established, generating a "uv-xz lookup table" or a two-variable linear function relationship for calculation: x0 = au + bv + δ1 (1) z0=cu+dv+δ2(2) Where a, b, c, d, δ1, and δ2 are all coefficients. By moving the calibration object multiple times, multiple sets of object plane coordinates and corresponding image plane coordinates of the calibration object are obtained. Then, these multiple sets of object plane coordinates and image plane coordinates are substituted into formulas (1) and (2) to obtain the values ​​of a, b, c, d, δ1, and δ2. Finally, a binary linear function relationship with determined coefficients is obtained. The more sets there are, the more accurate the fitting is. S3 measures the 3D dimensions of the object being measured: The object is placed into a triangular laser measurement model. The x and z coordinates of the object's surface are calculated by consulting a UV-XZ lookup table or using a linear function. Specifically, the object's surface coordinates (x, z) for each point are detected using the u and v values. For example... Figure 5 As shown, the coordinates of the point (40, 30) in the image plane coordinate system on the left are 40 and 30 respectively. The x and z values ​​of the point mapped to the object plane coordinate system on the right are 4000 and 3000 respectively, which means the coordinates of the point in the object plane coordinate system are (4000, 3000). Thus, n points form a line, and n lines form a surface, obtaining the contour of the object being measured. Simultaneously, the displacement mechanism drives the object being measured to move in the direction perpendicular to the focused beam, i.e., the direction of movement is set as the y-direction. The displacement mechanism is divided into multiple motion units in the y-direction. The denser the number of motion units, the more accurate the data. In this way, the motion units of the object's surface contour are recorded from the moment it appears in the image plane coordinates until it disappears from the image plane coordinates. Finally, the recorded motion units are added together to obtain the y-coordinate of the object being measured. The object's surface contour (x, z) within each motion unit is then combined to obtain the entire surface contour of the object being measured, thereby obtaining the 3D dimensions of the entire object being measured, including the x, y, and z coordinates of any point on the object being measured. This allows the depth or height of defects on the surface of the object to be obtained. The higher the density of motion units, the finer the 3D dimensions, and the higher the accuracy of the measured defects.

[0022] Alternatively, a stepper motor can be set in the displacement motion mechanism. First, the step distance of the stepper motor is set, and then the pulse quantity of the object surface contour from the beginning of its appearance in the image plane coordinates to the end of its disappearance in the image plane coordinates is recorded. Finally, the pulse quantity is converted into displacement distance to obtain the y coordinate of the object. Similarly, the object surface contour (x, z) within the displacement distance is stitched together to obtain the entire object surface contour, thereby obtaining the 3D size of the entire object, including the x, y, z coordinates of any point on the object, and thus obtaining the depth or height of defects on the surface of the object.

[0023] The calibration object can be any shape, such as a calibration block or calibration plate.

[0024] The broadband light source described in this invention can be a single-point spectrum, thus obtaining a single-point measurement model; it can be a multi-point spectrum, thus obtaining a multi-point measurement model; or it can be a line light source, thus obtaining a line measurement model. Correspondingly, the imaging detector can be a linear array detector, a multi-linear array detector, or a planar array detector. Depending on the measurement requirements, scanning can obtain the target's cross section, multi-section, surface contour, or multi-layer structure.

[0025] The dispersive lens described in this invention can focus light of different wavelengths from a broadband light source to different heights on the object surface. For the focused beam, the reflected light has a certain divergence angle, which improves the model's tolerance to the tilt of the object's surface and also improves measurement accuracy. Therefore, the model of this invention can measure specularly reflective objects such as metal and glass, as well as objects with curved or stepped surfaces, such as 3D glass, grooves, welds, etc.

[0026] The high-resolution imaging lens described in this invention is a conventional imaging lens that corrects for chromatic aberration, relying on measuring the height of the focused beam rather than its color. Since color differentiation is unnecessary, the subsequent spectral measurement model is eliminated, thus saving significant cost and space. Therefore, this model offers higher accuracy than conventional triangular laser measurement models and better cost-effectiveness than spectral confocal models.

[0027] The imaging detector and data processing system described in this invention comprises two parts: an imaging detector and a data processing system. Depending on the light source, the imaging detector can be a single-line, multi-line, or area array, thus forming a single-point, multi-point, or line measurement model. The data processing system converts the signals detected by the imaging detector into data information and stores it, possessing high-speed signal processing and transmission capabilities.

[0028] This invention utilizes a broadband light source that emits a convergent beam after dispersion by a dispersive lens. Different wavelengths of light converge at different heights, resulting in a convergent wavelength at each height. The dominant wavelength reflected by the object is this convergent wavelength. Because beams of different wavelengths exhibit convergence, the beam width remains relatively constant across different heights. This solves the problem of beam widening when the convergent beam is defocused, allowing the system to maintain good measurement accuracy over a wide height range. At the receiving end, a triangular laser receiving lens is used instead of a spectral measurement method. This simplifies the system structure, significantly reducing size and cost. This structure combines the advantages of spectral confocal light and triangular laser light while overcoming their disadvantages, expanding the application scenarios and scope of the measurement system.

[0029] The foregoing has provided a detailed description of a triangulation laser measurement system using a broadband light source provided in the embodiments of this patent. Specific examples have been used to illustrate the principles and implementation methods of this patent. The descriptions of the embodiments above are only for the purpose of helping to understand the method and core ideas of this patent. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this patent. Therefore, the content of this specification should not be construed as a limitation of this patent.

Claims

1. A 3D measurement method based on a broadband light source, characterized in that: Includes the following steps: S1 Model Establishment: A triangular laser measurement model is set up in the dispersive region. This model includes a broadband light source, a dispersive lens, a displacement mechanism, the object surface to be measured, a high-resolution imaging lens, an imaging detector, and a data processing system. The broadband light source emits a diverging beam. The dispersive lens focuses different colors of light from the diverging beam onto different heights of the object surface to form a focused beam. The object surface reflects the focused beam at an angle to the high-resolution imaging lens. The displacement mechanism is used to place the object to be measured and move it. The direction of movement is perpendicular to the optical axis of the focused beam. The displacement mechanism is connected to the data processing system. The high-resolution imaging lens focuses the reflected beam onto the imaging detector to form an image. The imaging detector and data processing system are used to convert the optical signal into an electrical signal and generate the data required for 3D measurement. S2 uses a calibration object: First, the calibration object is placed in the triangular laser measurement model instead of the object being measured and a three-dimensional coordinate system is set. Then, the object plane coordinates (x, z) of the calibration object are measured with the help of a high-precision measuring instrument. The x coordinate represents the coordinate of the focused beam direction and the z coordinate represents the vertical coordinate. Then, the image plane coordinates (u, v) of the imaging detector are obtained. The u is the element corresponding to the x coordinate and the v is the element corresponding to the z coordinate. Within the dispersive region, the mapping relationship between object plane coordinates and image plane coordinates is established by moving the calibration object, generating a "uv-xz lookup table" or a two-variable linear function relationship for calculation: x0 = au + bv + δ1 (1) z0=cu+dv+δ2(2) Where a, b, c, d, δ1, and δ2 are all coefficients. By moving the calibration object multiple times, multiple sets of object plane coordinates and corresponding image plane coordinates of the calibration object are obtained. Then, these multiple sets of object plane coordinates and image plane coordinates are substituted into formulas (1) and (2) to obtain the values ​​of a, b, c, d, δ1, and δ2, and finally, the bivariate linear function relationship with determined coefficients is obtained. S3 measures the 3D dimensions of the object under test: The object under test is placed in a triangular laser measurement model. The x and z coordinates of each point on the surface of the object are calculated using u and v values ​​and a linear function relationship or by referring to the "uv-xz lookup table". n points form a line, and n lines form a surface, thus obtaining the contour of the surface of the object under test. At the same time, the displacement motion mechanism drives the object under test to move in the direction perpendicular to the optical axis of the focused beam, i.e., the direction of movement is set as the y direction. The displacement motion mechanism is divided into multiple motion units in the y direction. In this way, the motion units of the object surface contour from the beginning of its appearance in the image plane coordinates to the end of its disappearance in the image plane coordinates are recorded. Finally, the recorded motion units are added together to obtain the y coordinate of the object under test. The object surface contour (x, z) within each motion unit is then combined to obtain the entire object surface contour, thus obtaining the 3D dimensions of the entire object under test, including the x, y, and z coordinates of any point on the object under test, and thus obtaining the depth or height of defects on the surface of the object under test.

2. The 3D measurement method based on a broadband light source as described in claim 1, characterized in that: Step S3 is replaced by: placing the object to be measured into the triangular laser measurement model, calculating the x and z coordinates of each point on the surface of the object using the u and v values ​​and the linear function relationship, forming a line from n points, and a surface from n lines, thus obtaining the contour of the object surface. At the same time, the displacement mechanism drives the object to move in the direction perpendicular to the optical axis of the focused beam, i.e., the direction of movement is set to the y direction. A stepper motor is set in the displacement mechanism, and the step distance of the stepper motor is set first. Then, the pulse quantity of the object surface contour from the moment it appears in the image plane coordinates until it disappears in the image plane coordinates is recorded. Finally, the pulse quantity is converted into the displacement distance to obtain the y coordinate of the object. Similarly, the object surface contours (x, z) within the displacement distance are stitched together to obtain the entire object surface contour, thus obtaining the 3D dimensions of the entire object, including the x, y, and z coordinates of any point on the object, and thus obtaining the depth or height of the defects on the object surface.

3. The 3D measurement method based on a broadband light source as described in claim 1, characterized in that: The broadband light source is a point spectrum, and the imaging detector is a linear array detector.

4. The 3D measurement method based on a broadband light source as described in claim 1, characterized in that: The broadband light source is a multi-point spectrum, and the imaging detector is a multi-linear array detector.

5. The 3D measurement method based on a broadband light source as described in claim 1, characterized in that: The broadband light source is a line light source, and the imaging detector is an area array detector.

6. The 3D measurement method based on a broadband light source as described in claim 1, characterized in that: The dispersive lens disperses the light emitted by the broadband light source, while the high-resolution imaging lens is a conventional imaging lens that does not contain dispersive light.

7. The 3D measurement method based on a broadband light source as described in claim 1, characterized in that: The object being measured is located between the dispersive lens and the high-resolution imaging lens.

8. The 3D measurement method based on a broadband light source as described in claim 1, characterized in that: The imaging detector and data processing system are located at the focal plane of the high-resolution imaging lens.

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