Striped projection-line scanning hybrid three-dimensional measurement method and system for strong reflective surface
Patent Information
- Application Number
- CN202610981846.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-07-02
- Publication Date
- 2026-10-23
AI Technical Summary
该方法因通过灰度值分布计算线特征，抵抗高反光对测量的不利影响，但其需要投影大量线图像，且计算耗时，显著降低了测量效率
本发明采用条纹投影测量技术对被测对象进行全场测量，对相机采集的条纹图中的饱和区域和非饱和区域进行划分，保留条纹投影全场覆盖、测量速度快、效率高的特点，对物体表面漫反射良好、无灰度饱和的非饱和区域快速完成三维重建，保证整体测量效率；针对高反光导致的饱和区域，采用线扫描测量技术逐线投射光条，依靠光条中心高精度提取与三角测量原理，对饱和区域快速完成三维重建，有效规避饱和失真问题，提升饱和区域的测量稳定性与精度。最后将条纹投影测量和线扫描测量得到的点云进行融合，从而得到被测对象的完整点云。本发明突破了传统条纹投影轮廓术无法测量超高反光表面的瓶颈，在不明显损失测量精度的条件下实现了对强反光表面的完整三维测量，提高实际工业场景中高反光零部件的检测效率与测量完整性。
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Figure CN122961338A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of optical three-dimensional measurement technology, and relates to a method for measuring the three-dimensional contour of a highly reflective surface, specifically a fringe projection-line scanning hybrid method and system for measuring the three-dimensional contour of a highly reflective surface. Background Technology
[0002] With the acceleration of digital transformation, the demand for 3D non-contact measurement technology is increasing. Among the many existing 3D measurement technologies, optical 3D measurement technology has been increasingly widely used in fields such as industrial component inspection and digital preservation of cultural heritage due to its advantages such as fast measurement speed, high measurement accuracy and strong scene adaptability.
[0003] For this type of measurement technology, the ideal object to be measured is a diffuse reflective surface with a relatively uniform surface reflectivity distribution. However, in actual measurements, highly reflective surfaces with large variations in surface reflectivity are often encountered, causing a significant decrease in the accuracy of 3D measurements or even 3D measurement failure. To improve the 3D measurement accuracy of highly reflective surfaces, common methods include multi-exposure methods, adaptive projection methods, and line scan measurement methods. Among them, multi-exposure methods change the camera's exposure and select different pixels from the images acquired by the camera under different exposures according to the criterion that the grayscale value is less than the saturation value and the relative maximum value is selected for fusion. For areas with high reflectivity, a projected image with a smaller exposure is used, and for areas with low reflectivity, a projected image with a larger exposure is used. This method does not require additional hardware in the measurement system. However, to ensure measurement results, the adjustment range of the camera's exposure is limited. When the camera's exposure time is adjusted to the minimum value, if there are still large saturated areas in the image acquired by the camera, this method cannot solve the problem. Adaptive projection, on the other hand, maps the saturated areas of the camera onto the projected image and adjusts the brightness of the corresponding areas to avoid grayscale saturation caused by excessively bright incident light from the camera. However, to ensure the contrast of the projected stripes, this method has a limited adjustment range and is easily affected by ambient light. It also requires the projector to perform two-dimensional pixel grayscale adjustments on the projected image, limiting the projector's selection range. Furthermore, it only changes the brightness of the projected image, without altering its form. The line scan measurement method, based on the principle of triangulation, projects linear light stripes onto the surface of the object being measured. A camera captures an image of the light stripes from another perspective. By adjusting the coordinates of the lines in the projected image, line scanning is achieved, covering the entire object and thus calculating the complete three-dimensional contour of the target. This method, by calculating line features through grayscale distribution, resists the adverse effects of high reflectivity on the measurement. However, it requires projecting a large number of line images and is computationally time-consuming, significantly reducing measurement efficiency. Summary of the Invention
[0004] To overcome the shortcomings of the aforementioned three-dimensional measurement techniques for highly reflective surfaces, this invention proposes a hybrid stripe projection-line scanning method and system for three-dimensional measurement of highly reflective surfaces. This method utilizes a projector capable of flexibly adjusting the projected image, and effectively combines the stripe projection measurement technique, which offers advantages in full-field measurement, with the line scanning measurement technique, which has strong resistance to overexposure, based on the characteristics of highly reflective surfaces. This overcomes the bottleneck of traditional stripe projection profilometry's inability to measure highly reflective surfaces, significantly improving its three-dimensional measurement performance for highly reflective surfaces while maintaining the measurement efficiency of stripe projection profilometry.
[0005] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for three-dimensional measurement of highly reflective surfaces using a hybrid stripe projection-line scanning method, comprising the following steps: Step 1: Adjust the camera and projector according to the actual measurement requirements, and perform joint calibration on the camera and projector to obtain the internal and external parameters of the measurement system composed of the camera and projector; Step 2: Generate a sine fringe pattern and project the sine fringe pattern onto the surface of the object being measured using a projector; Step 3: The camera captures the fringe pattern of the reflected light from the surface of the object being measured, obtaining the sampled fringe image; Step 4: Divide the sampled fringe image into saturated and unsaturated regions, extract the absolute phase of the sampled fringe image, and perform three-dimensional solution for the unsaturated region using the triangulation principle to obtain the three-dimensional point cloud of the unsaturated region. Step 5: Map the saturated region in the sampled stripe image to the projected image projected by the projector. The saturated region mapped to the projected image is the initial projection region of the line scan measurement. Determine the final projection region of the light stripe based on the initial projection region of the line scan measurement, and then generate multiple projected light stripe images with appropriate width that cover the entire final projection region of the light stripe. Step 6: The projector projects light stripe images onto the surface of the object to be measured from left to right, realizing the measurement of areas that cannot be accurately measured due to gray saturation in stripe projection measurement. The camera simultaneously acquires light stripe images of the surface of the object to be measured. Step 7: Extract the center coordinates of the light stripe and the parallax of the light stripe in the image captured by the camera. Based on the intrinsic and extrinsic parameters of the measurement system and the parallax of the light stripe, solve for the three-dimensional point cloud of the saturated region. Step 8: Fuse the 3D point cloud of the unsaturated region obtained in Step 4 with the 3D point cloud of the saturated region measured in Step 7 to obtain a complete 3D point cloud of the surface of the object being measured.
[0006] Furthermore, step four includes the following steps: The sampled stripe image captured by the camera is divided into saturated and unsaturated regions; The absolute phase of the sampled fringe image is extracted. Based on the absolute phase and combined with the triangulation principle, the unsaturated region is solved in three dimensions to obtain the three-dimensional coordinates of the unsaturated region in the world coordinate system. The measurement target points within the unsaturated regions are selected, and all measurement target points within the unsaturated regions constitute a three-dimensional point cloud of the unsaturated regions.
[0007] Furthermore, in step four, the saturated and unsaturated regions are divided based on whether the camera pixel grayscale value reaches the maximum camera output value. Pixels whose maximum grayscale value is less than the maximum camera output value are classified into the unsaturated region, and the remaining pixels are classified into the saturated region.
[0008] Furthermore, in step five, the initial projection area for line scan measurement is obtained by the following method: obtaining the boundary phase value of the saturated region from the absolute phase of the sampled fringe image, and using the boundary phase value of the saturated region in combination with epipolar correction to map the boundary of the saturated region in the sampled fringe image acquired by the camera to the projection image. The area in the projection image surrounded by the mapped boundary is the initial projection area for line scan measurement.
[0009] Furthermore, in step five, the specific process of generating the projected light stripe image is as follows: For each independent part of the initial projection area measured by line scanning, the width of the minimum containing rectangle is calculated from the horizontal direction of the projection image, and the height of the minimum containing rectangle is calculated from the vertical direction of the projection image. Keeping the center position of the minimum containing rectangle unchanged, the width and height are increased by a number of boundary redundant pixels to form each containing rectangle. The area where the containing rectangle is located is the final projection area of the light stripe. Light stripe encoding is performed along the direction of the sinusoidal fringe pattern in the final projection area of the light stripe to generate the projected light stripe image.
[0010] Furthermore, in step seven, the three-dimensional point cloud of the saturated region is calculated using the principle of triangulation.
[0011] Secondly, the present invention provides a fringe projection-line scanning hybrid three-dimensional measurement system for highly reflective surfaces, used to implement the method described in the first aspect of the present invention. The system includes a projector, a camera, and a host computer. The projector, camera, and host computer are connected in pairs. The host computer controls the projector to project a sinusoidal fringe pattern and a light stripe image onto the surface of the object being measured. The host computer controls the camera to simultaneously acquire the sampled fringe pattern and light stripe image of the surface of the object being measured. The sampled fringe image and light stripe image acquired by the camera are stored in the host computer. Based on the sampled fringe image and light stripe image, a complete three-dimensional point cloud of the surface of the object being measured is obtained.
[0012] Furthermore, the projector can encode and adjust the projected image as needed, enabling the projected image to change from a stripe pattern to a light bar pattern.
[0013] Compared with the prior art, the present invention has at least the following beneficial technical effects: This invention employs fringe projection measurement technology to perform full-field measurement of the object under test. It divides the saturated and unsaturated regions in the fringe pattern acquired by the camera, retaining the advantages of full-field coverage, fast measurement speed, and high efficiency of fringe projection. It rapidly completes 3D reconstruction of unsaturated regions with good diffuse reflection and no gray-scale saturation, ensuring overall measurement efficiency. For saturated regions caused by high reflectivity, line scanning measurement technology is used to project light stripes line by line. Relying on high-precision extraction of the light stripe center and the principle of triangulation, 3D reconstruction of saturated regions is rapidly completed, effectively avoiding saturation distortion and improving the measurement stability and accuracy of saturated regions. Finally, the point clouds obtained from fringe projection measurement and line scanning measurement are fused to obtain the complete point cloud of the object under test. This invention overcomes the bottleneck of traditional fringe projection profilometry in measuring ultra-high reflectivity surfaces, achieving complete 3D measurement of highly reflective surfaces without significant loss of measurement accuracy, thus improving the detection efficiency and measurement completeness of highly reflective components in practical industrial scenarios. Attached Figure Description
[0014] Figure 1a A flowchart of the three-dimensional measurement method provided by the present invention; Figure 1b This is a schematic diagram of the measuring device of the present invention; Figure 2 This is the fringe pattern used in the fringe projection measurement of the method of the present invention; Figure 3 This refers to the image captured by the camera in this invention, which projects a stripe pattern onto the highly reflective surface to be measured. Figure 4 The three-dimensional morphology of the measured object obtained by the fringe projection method in the present invention; Figure 5 For cases where the fringe projection method cannot measure due to exposure exceeding the measurement system's adjustment range. Figure 3 The area in; Figure 6 To be Figure 5 The line scan of the area to be projected is obtained by reverse mapping onto the projector plane; Figure 7 For the reason Figure 6 A one-pixel-wide projected light bar image is generated; Figure 8 For camera capture Figure 7 The light stripe image projected onto the object being measured; Figure 9 This refers to the three-dimensional morphology of a portion of the object being measured using the line scanning method in this invention. Figure 10 This refers to the complete three-dimensional shape of the object being measured using the method of this invention.
[0015] In the attached diagram: 1. Projector; 2. Camera. Detailed Implementation
[0016] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.
[0017] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.
[0018] It should be noted that when an element is referred to as being "set on" another element, it can be directly on the other element or may be interposed with another element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or may be interposed with another element. The terms "upper," "lower," "front," "rear," "left," "right," "top," "bottom," "inner," and "outer," etc., used herein to indicate orientation or positional relationships are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention.
[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.
[0020] Referring to Figure 1, a hybrid fringe projection-line scanning method for 3D measurement of highly reflective surfaces involves the following steps: First, 3D measurement of the unsaturated region of the object's surface is performed using fringe projection profilometry. Second, the spatial distribution of the saturated region is calculated, and the final projection area of the light stripe is obtained by back-mapping using the boundary phase values of the saturated region. Third, a line-scan projection light stripe image is generated using a host computer, ensuring that the projected light stripe image covers the highly reflective surface region whose morphology was not measured by fringe projection. Fourth, line scanning measurement is performed on the highly reflective region to obtain its 3D morphology. Finally, the point clouds obtained by the fringe projection method and the line scanning method are fused to obtain the complete 3D contour of the highly reflective object's surface. This invention helps to improve the 3D measurement capability of highly reflective surfaces while effectively retaining the advantages of fringe projection profilometry.
[0021] See Figure 1a and Figure 1b This invention proposes an implementation structure for a hybrid stripe projection-line scanning method for three-dimensional measurement of highly reflective surfaces, comprising a projector 1, a camera 2, and a host computer. The projector 1 and camera 2 are connected to the host computer in pairs. The host computer controls the projector to project sinusoidal fringe patterns and light stripe images onto the surface of the object being measured, and controls the camera to simultaneously acquire the fringe patterns and light stripe images from the surface of the object being measured. The sampled fringe and light stripe images acquired by the camera are then stored in the host computer.
[0022] A hybrid method for measuring highly reflective surfaces using stripe projection and line scanning includes the following steps: Step 1: Adjust camera 2 and projector 1 according to actual measurement requirements and perform joint calibration to obtain the intrinsic and extrinsic parameters of the measurement system composed of the camera and projector. The intrinsic and extrinsic parameters of the measurement system include the camera parameter matrix Mc and the projection parameter matrix Mp, where the camera parameter matrix Mc contains the camera's intrinsic parameter matrix. Rotation matrix between camera coordinate system and world coordinate system And the translation matrices of the camera coordinate system and the world coordinate system. The projection parameter matrix Mp contains the intrinsic parameter matrix of the projector. Rotation matrix between projector coordinate system and world coordinate system And the translation matrices of the projector coordinate system and the world coordinate system. ; Projector 1 can encode and adjust the projected image as needed, so that the projected image can be changed from a stripe pattern to a light bar pattern.
[0023] Step 2: Generate a sine fringe pattern and then display the sine fringe pattern (see...). Figure 2 The image is projected onto the surface of the object being measured via projector 1. Step 3: The projector triggers camera 2 to acquire a sampled stripe image of the surface reflection of the object under test (see...). Figure 3 ); Step 4: Perform fringe projection measurement: Divide the sampled fringe image acquired by camera 2 into saturated and unsaturated regions, extract the absolute phase of the fringe image, and perform 3D solution for the unsaturated region using triangulation principles to obtain the coordinates of all points in the world coordinate system corresponding to the absolute phase of the unsaturated region. Select the measurement target points within the unsaturated region. All measurement target points within the unsaturated region constitute the 3D point cloud of the unsaturated region (see...). Figure 4 ); where the absolute phase of the sampled stripe image includes the absolute phase of all pixels in the sampled stripe image.
[0024] Step 5: Obtain the boundary phase value of the saturated region from the absolute phase of the sampled fringe image extracted in Step 4. Use the boundary phase value of the saturated region in conjunction with epipolar correction to correct the saturated region in the sampled fringe image acquired by the camera (see...). Figure 5 The area mapped from the saturated region in the sampled fringe image acquired by the camera to the projected image is the initial projection area for line scan measurement (see [link]). Figure 6 Then, the host computer generates multiple projected light bar images with appropriate widths that cover the entire final projection area of the light bar (see...). Figure 7 ); Step Six: The projector projects light stripe images onto the surface of the object being measured from left to right, enabling the measurement of areas that cannot be accurately measured due to grayscale saturation in fringe projection measurement. Camera 1 acquires the light stripe image of the object's surface after being synchronously triggered (see...). Figure 8 The projector projects light stripe images onto the surface of the object being measured from left to right, enabling the measurement of areas that cannot be accurately measured due to grayscale saturation in stripe projection measurement. The camera simultaneously acquires light stripe images of the surface of the object being measured. Step 7: Extract the center coordinates and parallax of the light stripe in the image captured by the camera. Using the principle of triangulation, substitute the intrinsic and extrinsic parameters of the measurement system, as well as the column coordinates of the light stripe in the projected light stripe image corresponding to the coordinates of the target point in the light stripe image captured by the camera, and the center coordinates of the light stripe in the light stripe image captured by the camera, to obtain the 3D point cloud of the saturated area on the surface of the object that cannot be accurately measured by stripe measurement (see...). Figure 9 ); Step 8: Fuse the 3D point cloud of the unsaturated region obtained in Step 4 with the 3D point cloud of the saturated region measured in Step 7 to obtain a complete 3D point cloud of the surface of the object being measured (see...). Figure 10 In this step, the fusion method is as follows: simply add the points from the two point clouds together, then filter the fused point cloud to remove outliers. If necessary, manual selection and removal can be performed.
[0025] In step four, the saturated and unsaturated regions are divided based on whether the pixel grayscale values of the sampled fringe image acquired by camera 2 reach the maximum camera output value (e.g., for a 10-bit grayscale camera, the maximum value is 1023). The monochrome camera quantizes the light intensity received by the camera sensor into grayscale values. This measurement method uses a phase-shifting method by projecting a set of sinusoidal fringe patterns with different phase shifts for phase extraction. Therefore, the specific division method is as follows: in the sampled fringe image, pixels whose maximum grayscale value is less than the maximum camera output value are classified into the unsaturated region, and the remaining pixels are classified into the saturated region.
[0026] In step four, the selection criteria for measurement target points are: points with a modulation index greater than 10 are considered measurement target points. In the unsaturated region, the absolute phase of each pixel is calculated using the multi-frequency method and the phase-shifting method. The three-dimensional coordinates of the measurement target point P in the world coordinate system corresponding to the absolute phase are calculated using the triangulation principle. These measurement target points P constitute the point cloud of the measured object. The measured object, i.e., the measured plane, is formed by measuring several measurement target points P.
[0027] Step five involves the reverse mapping from camera pixels to projector pixels and the calculation of the initial projection area boundary for line scan measurement.
[0028] Assuming that after projecting the sinusoidal fringe pattern in step two, phase demodulation methods such as phase shifting and Fourier transform can be used to calculate the phase value of the camera plane imaging point PL corresponding to the measurement target point P, the phase value can be calculated. Then according to phase matching Obtain the encoded phase value of the projection point PR on the projector plane corresponding to the measurement target point P. The image point of the target point P corresponding to the camera plane is PL, and the projection point of the target point P corresponding to the projector plane is PR. The phase value of PL is... and PR encoding phase value The camera's calculated phase value is obtained through epipolar correction transformation. and projection-coded phase value ,according to and The camera pixel coordinates for finding matching points using epipolar correction are calculated as follows: During reverse mapping, the row coordinates of the projected pixels matched after epipolar correction are used. and the row coordinates of camera pixels used to find matching points via epipolar correction They are equal, that is, they satisfy: In the formula, and The unit is pixels. Epipolar correction uses the column coordinates of camera pixels to find matching points. By the condition of equal phase, that is In the same row of the image captured by the camera (i.e., row coordinates are...) Linear interpolation is used to calculate the column coordinates of pixels with phases equal to those of the epipolar-corrected projected pixels. The column coordinates of the epipolar-corrected projected pixels are... .because It is known that, therefore, it can be determined based on and The mapping relationship between the projection pixel coordinates and the camera pixel coordinates is established. Using this mapping relationship, the saturated region in the sampled stripe image acquired by the camera is mapped to the region of the projected image projected by the projector to obtain the initial projection area for line scan measurement.
[0029] Because the phase calculation error is large within the saturated region, unsaturated pixels surrounding the saturated region are used as boundary pixels of the initial projection region in the line scan measurement to fit the absolute phase values of the pixels in the saturated region. The coordinates of the matched projection boundary pixels of the initial projection region in the line scan measurement are calculated using the following formula: In the formula, This represents the column and row coordinates of the matched projection boundary pixels, in pixels. The inverse function of epipolar correction transforms the matched projected pixel coordinates after epipolar correction into the matched projected boundary pixel coordinates. After calculating the boundary pixel coordinates of the initial projection area of the line scan measurement, the absolute phase value of the pixels in the saturation region can be obtained by one-way linear interpolation fitting between the projection boundary pixel coordinates and the pixel coordinates inside the initial projection area of the line scan measurement.
[0030] In step five, the specific process of generating the projected light stripe image is as follows: For each independent part of the initial projection area of the line scan measurement (for a surface with multiple saturated areas, there is more than one area that needs to be measured by line scan using light stripes, and each area is independent of the others), calculate the width and height of the minimum containing rectangle (the smallest rectangle whose two sides are parallel to the horizontal and vertical axes of the image, used to contain each saturated area in the sine fringe pattern, and whose four sides have pixels coinciding with pixels in the area) in the horizontal and vertical directions of the projected image projected by the projector. Then, to avoid the adverse effects caused by phase calculation errors and system calibration errors, and to improve the stability of the algorithm, keep the center position of the minimum containing rectangle unchanged, and increase the width and height by a certain number (e.g., 5) pixels (boundary redundant pixels) to form each containing rectangle. The area where the containing rectangle is located is the final projection area of the light stripe. Light stripe encoding is performed along the direction of the sine fringe pattern in the final projection area of the light stripe to generate multiple projected light stripe images with appropriate widths that cover the entire final projection area of the light stripe. In step seven, the calculation of the center coordinates of the light stripe requires the extraction of the center coordinates of the light stripe in the light stripe image acquired by the camera. The center coordinates of the light stripe can be extracted using methods such as the Steger algorithm, gray-scale centroid method, and curve fitting method.
[0031] In step seven, the 3D point cloud of the saturated region is calculated using the principle of triangulation. By performing a 3D solution on the saturated region using the principle of triangulation, the absolute phase of the saturated region corresponds to the measurement target point in the world coordinate system. All measurement target points constitute the 3D point cloud of the saturated region. Specifically, by measuring the target point at different imaging positions in the camera and the position of the projected light stripe in the projected light stripe image, the 3D coordinates of the measurement target point are calculated inversely using the principle of two intersecting lines, through the camera parameter matrix Mc and the projection parameter matrix Mp. The intersection of the line connecting the camera optical center and the imaging point with the line connecting the projector optical center and the imaging point is the 3D coordinate (world coordinate system) of the measurement target point.
[0032] Due to the existence of light stripe parallax, the three-dimensional coordinates can be solved using the principle of triangulation. The calculation method of the triangulation principle is as follows: The transformation relationship between the camera coordinate system and the world coordinate system for measuring the target point satisfies the following formula: (1) In the formula , Indicates the location in the camera parameter matrix The value in the first row and first column. Indicates the location in the camera parameter matrix The values in the third row and fourth column, and the meanings of the other parameters, can be deduced similarly.
[0033] The transformation relationship between the projector coordinate system and the world coordinate system for measuring the target point satisfies the following formula: (2) In the formula , Indicates the location in the projection parameter matrix The value in the first row and first column. Indicates the location in the projection parameter matrix The values in the third row and fourth column, and the meanings of the other parameters, can be deduced similarly.
[0034] (3) In the formula, This represents the camera's scaling factor. This represents the scaling factor of the projector. The column coordinates represent the image position of the target point on the camera. The row coordinates representing the image position of the target point on the camera. The column coordinates represent the corresponding projected position of the measured target point on the projector. This represents the row coordinates of the projected position of the target point on the projector. K represents the intrinsic parameter matrix of the camera. P This represents the intrinsic parameter matrix of the projector. Represents the rotation matrix between the camera coordinate system and the world coordinate system. The rotation matrix representing the projector coordinate system and the world coordinate system. This represents the translation matrix between the camera coordinate system and the world coordinate system. This represents the translation matrix between the projector coordinate system and the world coordinate system. This represents the three-dimensional coordinates of the target point in the world coordinate system. Let... d represents the parallax of the light stripe. Combining equations (1) to (3) yields a system of equations. Solving this system of equations provides the three-dimensional coordinates of the target point in the world coordinate system. Typically, the world coordinate system is aligned with the camera coordinate system; in this case, we have: , Since the coordinates of the target point in the light stripe image acquired by the camera correspond to the column coordinates of the light stripe in the projected light stripe image. It is known that, will Substitution The measurement target point is mapped to the center coordinates of the light stripe in the light stripe image captured by the camera. Substitution By substituting the three parameters mentioned above into the system of equations using the principle of triangulation, the three-dimensional coordinates of the target point can be obtained. By solving for the three-dimensional coordinates of each measurement target point, the object under test is reconstructed. The three-dimensional point cloud of the saturated region of the object under test is obtained by calculating the three-dimensional coordinates of all measurement target points.
[0035] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the present invention.
Claims
1. A hybrid method for measuring three-dimensional highly reflective surfaces using stripe projection and line scanning, characterized in that, Includes the following steps: Step 1: Adjust the camera and projector according to the actual measurement requirements, and perform joint calibration on the camera and projector to obtain the internal and external parameters of the measurement system composed of the camera and projector; Step 2: Generate a sine fringe pattern and project the sine fringe pattern onto the surface of the object being measured using a projector; Step 3: The camera captures the fringe pattern of the reflected light from the surface of the object being measured, obtaining the sampled fringe image; Step 4: Divide the sampled fringe image into saturated and unsaturated regions, extract the absolute phase of the sampled fringe image, and perform three-dimensional solution for the unsaturated region using the triangulation principle to obtain the three-dimensional point cloud of the unsaturated region. Step 5: Map the saturated region in the sampled stripe image to the projected image projected by the projector. The saturated region mapped to the projected image is the initial projection region of the line scan measurement. Determine the final projection region of the light stripe based on the initial projection region of the line scan measurement, and then generate multiple projected light stripe images with appropriate width that cover the entire final projection region of the light stripe. Step 6: The projector projects light stripe images onto the surface of the object to be measured from left to right, realizing the measurement of areas that cannot be accurately measured due to gray saturation in stripe projection measurement. The camera simultaneously acquires light stripe images of the surface of the object to be measured. Step 7: Extract the center coordinates of the light stripe and the parallax of the light stripe in the image captured by the camera. Based on the intrinsic and extrinsic parameters of the measurement system and the parallax of the light stripe, solve for the three-dimensional point cloud of the saturated region. Step 8: Fuse the 3D point cloud of the unsaturated region obtained in Step 4 with the 3D point cloud of the saturated region measured in Step 7 to obtain a complete 3D point cloud of the surface of the object being measured.
2. The fringe projection-line scanning hybrid three-dimensional measurement method for highly reflective surfaces according to claim 1, characterized in that, Step four includes the following steps: The sampled stripe image captured by the camera is divided into saturated and unsaturated regions; The absolute phase of the sampled fringe image is extracted. Based on the absolute phase and combined with the triangulation principle, the unsaturated region is solved in three dimensions to obtain the three-dimensional coordinates of the unsaturated region in the world coordinate system. The measurement target points within the unsaturated regions are selected, and all measurement target points within the unsaturated regions constitute a three-dimensional point cloud of the unsaturated regions.
3. The method for three-dimensional measurement of highly reflective surfaces using a hybrid stripe projection-line scanning method according to claim 1, characterized in that, In step four, the saturated and unsaturated regions are divided based on whether the camera pixel grayscale value reaches the maximum camera output value. Pixels whose maximum grayscale value is less than the maximum camera output value are classified into the unsaturated region, and the remaining pixels are classified into the saturated region.
4. The three-dimensional measurement method for strongly reflective surfaces using a fringe projection-line scanning hybrid method according to claim 1, characterized in that, In step five, the initial projection area for line scan measurement is obtained by the following method: obtaining the boundary phase value of the saturated region from the absolute phase of the sampled fringe image, and using the boundary phase value of the saturated region in combination with epipolar correction to map the boundary of the saturated region in the sampled fringe image acquired by the camera to the projection image. The area in the projection image surrounded by the mapped boundary is the initial projection area for line scan measurement.
5. The three-dimensional measurement method for strongly reflective surfaces using a fringe projection-line scanning hybrid method according to claim 1, characterized in that, In step five, the specific process of generating the projected light stripe image is as follows: For each independent part of the initial projection area measured by line scanning, the width of the minimum containing rectangle is calculated from the horizontal direction of the projection image, and the height of the minimum containing rectangle is calculated from the vertical direction of the projection image. Keeping the center position of the minimum containing rectangle unchanged, the width and height are increased by a number of boundary redundant pixels to form each containing rectangle. The area where the containing rectangle is located is the final projection area of the light stripe. Light stripe encoding is performed along the sinusoidal fringe pattern direction in the final projection area of the light stripe to generate the projected light stripe image.
6. The fringe projection-line scanning hybrid three-dimensional measurement method for highly reflective surfaces according to claim 1, characterized in that, In step seven, the three-dimensional point cloud of the saturated region is calculated using the principle of triangulation.
7. A hybrid stripe projection-line scanning three-dimensional measurement system for highly reflective surfaces, characterized in that, The method for implementing the measurement method of claim 1 includes a projector, a camera, and a host computer. The projector, camera, and host computer are connected in pairs. The host computer controls the projector to project a sinusoidal fringe pattern and a light stripe image onto the surface of the object being measured. The host computer controls the camera to synchronously acquire the sampled fringe pattern and light stripe image of the surface of the object being measured. The sampled fringe image and light stripe image acquired by the camera are stored in the host computer. A complete three-dimensional point cloud of the surface of the object being measured is obtained based on the sampled fringe image and light stripe image.
8. The three-dimensional measurement system for strongly reflective surfaces using a hybrid stripe projection-line scanning method according to claim 7, characterized in that, The projector can encode and adjust the projected image as needed, so that the projected image can be changed from a striped pattern to a light stripe pattern.