A Three-Dimensional Measurement Method and System for Metal Workpieces Based on Adaptive Polarization Projection

Abstract

The present disclosure relates to a kind of metal workpiece three-dimensional measurement method and system based on adaptive polarization projection, comprising: obtaining the linearly polarized light projected by projector, by embedding the polarization state information of linearly polarized light into four-step phase-shifted sinusoidal fringe model, obtain global polarization encoding fringe image;Obtain uniform horizontal polarization response image, compare the gray value of each pixel in the uniform horizontal polarization response image with the set threshold value, and construct binary depolarization model according to the comparison result, map the binary depolarization model to the projector coordinate system, obtain the depolarization model under the projector coordinate system;The encoding value of corresponding pixel coordinate in global polarization encoding fringe image is modulated by depolarization model, to obtain adaptive polarization encoding image;Obtain modulated fringe image and carry out phase solution, realize the three-dimensional measurement of metal workpiece.The present disclosure method can improve the efficiency and precision of measuring complex metal workpiece while ensuring robust stability.

Description

Technical Field

[0001] This disclosure relates to the field of optical three-dimensional measurement technology, and in particular to a method and system for three-dimensional measurement of metal workpieces based on adaptive polarization projection. Background Technology

[0002] Fringe projection profilometry is an important method in modern 3D vision measurement. It projects a series of coded structured light patterns onto the surface of an object, and a camera captures the fringe images deformed by the object's height modulation. Finally, phase calculation and 3D reconstruction are used to obtain the object's surface morphology. This technology has advantages such as high precision, high speed, and non-contact operation, and is widely used in industrial inspection, quality control, and reverse engineering.

[0003] However, traditional fringe projection techniques face significant challenges when measuring the surfaces of highly reflective metal workpieces. The strong specular reflection properties of metal surfaces easily lead to camera sensor saturation, creating localized highlight (overexposed) areas in the acquired images. These overexposed areas cause the loss of phase information in the fringes, resulting in numerous holes and deformations in the final reconstructed 3D point cloud, severely compromising the integrity and accuracy of the measurement results.

[0004] To suppress specular interference, an adaptive fringe projection method has been proposed. The core idea of ​​this method is to identify overexposed areas based on image brightness information from the camera and dynamically adjust the projected grayscale values ​​in these local areas, thereby avoiding camera saturation. While this method alleviates the specular problem to some extent, it still relies on grayscale intensity modulation. This grayscale-based adjustment method is susceptible to ambient light interference and complex geometric structures of object surfaces, resulting in insufficient stability. To achieve effective suppression, iterative projection of multiple grayscale images with different intensities is often required, which significantly increases the time spent on data acquisition and processing, reduces measurement efficiency, and fails to meet the demands of efficient and high-precision measurements in industrial settings.

[0005] Therefore, there is a need for a three-dimensional profile measurement method that can effectively overcome the interference of specular highlights on metal surfaces while ensuring measurement efficiency, accuracy, and stability. Summary of the Invention

[0006] To address the issue that traditional 3D contour measurement methods are affected by the object's surface structure and ambient light, requiring an increase in the number of projected grayscale images, which leads to reduced stability and measurement efficiency, this disclosure proposes a 3D measurement method for metal workpieces based on adaptive polarization projection to solve these problems.

[0007] According to one aspect of this disclosure, a method for three-dimensional measurement of metal workpieces based on adaptive polarization projection is provided, comprising:

[0008] S10. Obtain the linearly polarized light projected by the projector, and obtain a global polarization-coded fringe image by embedding the polarization state information of the linearly polarized light into a four-step phase-shift sinusoidal fringe model. The linearly polarized light includes 0° linearly polarized light and 90° linearly polarized light.

[0009] S20. Obtain a uniform horizontal polarization response image, compare the grayscale value of each pixel in the uniform horizontal polarization response image with a set threshold, construct a binary depolarization model based on the comparison result, and map the binary depolarization model to the projector coordinate system to obtain the depolarization model in the projector coordinate system; wherein, the uniform horizontal polarization response image is obtained by projecting a uniform brightness horizontal polarization image onto the metal workpiece through the projector, and then passing it through the reflection of the metal workpiece and the polarizer filtering;

[0010] S30. Modulate the encoded values ​​of the corresponding pixel coordinates in the global polarization coded stripe image using the depolarization model to obtain an adaptive polarization coded image;

[0011] S40. Acquire the modulated stripe image, and perform phase calculation on the modulated stripe image to achieve three-dimensional measurement of the metal workpiece; wherein, the modulated stripe image is obtained by projecting the adaptive polarization coded image onto the surface of the metal workpiece.

[0012] Preferably, the global polarization-coded stripe image is represented as:

[0013] ,

[0014] In the formula, Represents a globally polarization-coded stripe image. Indicates 0° polarization coded stripes. Indicates 90° polarization coded stripes. p Indicates the projection mode. Indicates average intensity. Indicates modulation intensity. Indicates the phase value. k This is the phase shift number.

[0015] Preferably, comparing the grayscale value of each pixel in the uniform horizontal polarization response image with a set threshold includes:

[0016] If the gray value of a pixel in a uniform horizontal polarization response image is greater than a set threshold, then the pixel is a depolarized region and the corresponding pixel value is set to 1; otherwise, the pixel is a non-depolarized region and the pixel value is set to 0.

[0017] Preferably, a binary debiasing model is constructed based on the comparison results, and the binary debiasing model is expressed as follows:

[0018] ,

[0019] In the formula, This represents a binary debiasing model. Represents pixel coordinates in camera coordinates. Represents pixel coordinates in camera coordinates grayscale value, To set a threshold.

[0020] Preferably, the de-biasing model in the projector coordinate system is represented as follows:

[0021] ,

[0022] In the formula, This represents the de-polarization model in the projector coordinate system. These are the pixel coordinates in the projector coordinate system. Indicates the deflection region. This indicates the area that has not yet deviated from its original position.

[0023] Preferably, an adaptive polarization-coded image is obtained by modulating the encoded values ​​of corresponding pixel coordinates in the global polarization-coded stripe image using a depolarization model, including:

[0024] Traverse the pixel coordinates in the projector coordinate system. For each pixel coordinate, if the pixel coordinate in the projector coordinate system is identified as a de-biased region in the de-biasing model, then the encoding value of the global polarization coded stripe image at that pixel coordinate is modulated using a suppression coefficient; if the pixel coordinate in the projector coordinate system is identified as a non-de-biased region in the de-biasing model, then the encoding value remains unchanged.

[0025] Preferably, the adaptive polarization-coded image is represented as:

[0026] ,

[0027] In the formula, For adaptive polarization encoded images, For globally polarized coded stripe images, This is the suppression coefficient. This is the de-biasing model in the projector coordinate system.

[0028] According to one aspect of this disclosure, a three-dimensional measurement system for metal workpieces based on adaptive polarization projection is provided, comprising:

[0029] A global polarization-coded fringe image acquisition module acquires linearly polarized light projected by a projector. By embedding the polarization state information of the linearly polarized light into a four-step phase-shift sinusoidal fringe model, a global polarization-coded fringe image is obtained. The linearly polarized light includes 0° linearly polarized light and 90° linearly polarized light.

[0030] The depolarization model construction module acquires a uniform horizontal polarization response image, compares the grayscale value of each pixel in the uniform horizontal polarization response image with a set threshold, constructs a binary depolarization model based on the comparison result, and maps the binary depolarization model to the projector coordinate system to obtain the depolarization model in the projector coordinate system; wherein, the uniform horizontal polarization response image is obtained by projecting a uniform brightness horizontal polarization image onto the metal workpiece through the projector, and then passing it through the reflection of the metal workpiece and the polarizer filtering;

[0031] The adaptive polarization coded image calculation module modulates the coded values ​​of corresponding pixel coordinates in the global polarization coded stripe image through the depolarization model to obtain the adaptive polarization coded image.

[0032] A three-dimensional measurement module for metal workpieces acquires a modulated stripe image and performs phase calculation on the modulated stripe image to achieve three-dimensional measurement of the metal workpiece; wherein, the modulated stripe image is obtained by projecting the adaptive polarization coded image onto the surface of the metal workpiece.

[0033] According to one aspect of this disclosure, an electronic device is provided, comprising: a processor; a memory for storing processor-executable instructions; wherein the processor is configured to: perform the above-described method for three-dimensional measurement of metal workpieces based on adaptive polarization projection.

[0034] According to one aspect of this disclosure, a computer-readable storage medium is provided that stores computer program instructions thereon, which, when executed by a processor, implement the above-described method for three-dimensional measurement of metal workpieces based on adaptive polarization projection.

[0035] Compared to the prior art, the beneficial effects of this disclosure are as follows:

[0036] 1) This disclosure achieves rapid and accurate localization of highlight areas by constructing a binary depolarization model, which significantly reduces the number of image acquisitions and computational load, and improves measurement efficiency.

[0037] 2) This disclosure maps the depolarization model of the camera coordinate system to the projector coordinate system and performs local adaptive modulation on the global polarization code accordingly, which directly and specifically suppresses the light intensity in the depolarization region, avoids camera overexposure, ensures complete extraction of phase information, and improves measurement accuracy.

[0038] 3) This disclosure addresses regions with different surface characteristics (polarization / depolarization) through adaptive modulation, and can stably suppress specular highlights on complex metal surfaces and under varying exposure conditions, thereby enhancing the robustness and reliability of the measurement.

[0039] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure.

[0040] Other features and aspects of this disclosure will become clear from the following detailed description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0041] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the specification, serve to illustrate the technical solutions of this disclosure.

[0042] Figure 1 A flowchart of a three-dimensional measurement method for metal workpieces based on adaptive polarization projection is shown.

[0043] Figure 2 A visual flowchart of Example 2 is shown;

[0044] Figure 3 A schematic diagram of the uniformly coded image projected in Example 2 is shown;

[0045] Figure 4 The image captured by the camera in Example 2 and a schematic diagram of the pixel outline in row 500 are shown;

[0046] Figure 5 A schematic diagram showing the statistical results of the overexposed areas in Example 2 is displayed;

[0047] Figure 6 A schematic diagram of the measurement results of the metal workpiece in Example 2 is shown;

[0048] Figure 7 A schematic diagram showing the stability comparison results of the measurement methods in Example 2 is displayed;

[0049] Figure 8 A block diagram of a three-dimensional measurement system for metal workpieces based on adaptive polarization projection is shown. Detailed Implementation

[0050] Various exemplary embodiments, features, and aspects of this disclosure will now be described in detail with reference to the accompanying drawings. The same reference numerals in the drawings denote elements that have the same or similar functions. Although various aspects of the embodiments are shown in the drawings, they are not necessarily drawn to scale unless specifically indicated otherwise.

[0051] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments.

[0052] In this document, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A alone, A and B simultaneously, and B alone. Furthermore, the term "at least one" in this document means any combination of at least two of any one or more elements. For example, including at least one of A, B, and C can mean including any one or more elements selected from the set consisting of A, B, and C.

[0053] Furthermore, to better illustrate this disclosure, numerous specific details are set forth in the following detailed description. Those skilled in the art will understand that this disclosure can be practiced without certain specific details. In some instances, methods, means, components, and circuits well known to those skilled in the art have not been described in detail in order to highlight the main points of this disclosure.

[0054] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0055] Example 1

[0056] Based on the above ideas, this invention proposes a three-dimensional measurement method for metal workpieces based on adaptive polarization projection. Figure 1 A flowchart illustrating a three-dimensional measurement method for metal workpieces based on adaptive polarization projection is shown. The method includes:

[0057] S10. Obtain the linearly polarized light projected by the projector, and obtain a global polarization-coded fringe image by embedding the polarization state information of the linearly polarized light into a four-step phase-shift sinusoidal fringe model. The linearly polarized light includes 0° linearly polarized light and 90° linearly polarized light.

[0058] S20. Obtain a uniform horizontal polarization response image, compare the grayscale value of each pixel in the uniform horizontal polarization response image with a set threshold, construct a binary depolarization model based on the comparison result, and map the binary depolarization model to the projector coordinate system to obtain the depolarization model in the projector coordinate system; wherein, the uniform horizontal polarization response image is obtained by projecting a uniform brightness horizontal polarization image onto the metal workpiece through the projector, and then passing it through the reflection of the metal workpiece and the polarizer filtering;

[0059] S30. Modulate the encoded values ​​of the corresponding pixel coordinates in the global polarization coded stripe image using the depolarization model to obtain an adaptive polarization coded image;

[0060] S40. Acquire the modulated stripe image, and perform phase calculation on the modulated stripe image to achieve three-dimensional measurement of the metal workpiece; wherein, the modulated stripe image is obtained by projecting the adaptive polarization coded image onto the surface of the metal workpiece.

[0061] This disclosure provides a method for three-dimensional measurement of metal workpieces based on adaptive polarization projection. It replaces the traditional grayscale mode with a polarization mode, enabling accurate identification and quantification of polarization characteristics within highlight regions of a single image. This method achieves localized, highly stable, efficient, and high-precision highlight removal. While maintaining robust stability, this method improves the efficiency and accuracy of measuring complex metal workpieces. Specifically, it includes the following steps:

[0062] S10. Obtain the linearly polarized light projected by the projector, and obtain a global polarization-coded fringe image by embedding the polarization state information of the linearly polarized light into a four-step phase-shift sinusoidal fringe model. The linearly polarized light includes 0° linearly polarized light and 90° linearly polarized light.

[0063] In this embodiment, the polarization state of linearly polarized light can typically be represented by the Stokes vector. The Stokes vectors for 0° and 90° linearly polarized light can be represented as follows:

[0064] ,

[0065] The mathematical expression for the traditional four-step phase-shift sine coding can be written as:

[0066] ,

[0067] In the formula, This represents a grayscale coded stripe pattern. p Indicates the projection mode. Indicates average intensity. Indicates modulation intensity. Indicates the phase value. k This is the phase shift number.

[0068] The expressions for 0° polarization coded fringes and 90° polarization coded fringes are as follows:

[0069] ,

[0070] ,

[0071] Using 0° polarization-coded stripes to represent the white sinusoidal stripes in intensity coding, and 90° polarization-coded stripes to represent the black sinusoidal stripes in intensity coding, a global polarization-coded stripe image can be obtained, represented as:

[0072] ,

[0073] In the formula, Represents a globally polarization-coded stripe image. Indicates 0° polarization coded stripes. Indicates 90° polarization coded stripes. p Indicates the projection mode. Indicates average intensity. Indicates modulation intensity. Indicates the phase value. k This is the phase shift number.

[0074] S20. Obtain a uniform horizontal polarization response image, compare the gray value of each pixel in the uniform horizontal polarization response image with a set threshold, construct a binary depolarization model based on the comparison result, and map the binary depolarization model to the projector coordinate system to obtain the depolarization model in the projector coordinate system.

[0075] In this embodiment, the linearly polarized light, after reflection, is affected by the metal surface structure, and its Stokes vector becomes:

[0076] ,

[0077] In the formula, Indicates total light intensity. This represents the difference between horizontally polarized light and vertically polarized light. This represents the difference between 45° polarized light and 135° polarized light. This represents the difference between the left-handed and right-handed circularly polarized components of light. Indicates the degree of debiasing, with values ​​between [0,1]. r Indicates the reflection mode. It indicates the polarization direction of the reflected light.

[0078] According to the Stokes form of Malus's law, the polarization axis is... The intensity of polarized light entering the camera from the polarizer can be expressed as:

[0079] ,

[0080] Further, we can obtain

[0081] ,

[0082] It can be abbreviated as:

[0083] ,

[0084] As shown in the above equation, when the reflected light remains fully polarized, the polarizer effectively suppresses components in non-target directions, ensuring that only the modulated signal in the target direction enters the camera. This allows for the acquisition of effective structural information with maximum brightness and reduces the risk of overexposure. However, when depolarization occurs on the metal surface, the polarization state of the incident light is disrupted during reflection, significantly reducing the polarization degree of the reflected light and causing the directional components to diffuse. At this point, the polarizer's suppression of non-target direction components weakens, leading to more stray light without structural information penetrating the polarizer and entering the camera, ultimately resulting in an abnormally high image brightness. Especially in areas with high surface reflectivity, the image brightness easily exceeds the camera's dynamic range, causing local saturation and compromising phase demodulation quality. Therefore, a depolarization model suitable for 3D reconstruction of complex metal workpieces can be constructed by determining whether there are pixel regions in the image exceeding a set brightness threshold.

[0085] This disclosure proposes a depolarization region discrimination model for high-reflectivity areas of complex metal workpieces. The specific method is as follows: First, a uniformly bright horizontally polarized image is projected onto the object under test using a projector. Then, an image after reflection and filtering by a horizontal polarizer is acquired. The grayscale value of each pixel in the uniformly polarized response image is compared with a set threshold. If the grayscale value of a pixel in the uniformly polarized response image is greater than the set threshold, polarization degradation is considered to have occurred, and the pixel is considered a depolarized region, with its corresponding pixel value set to 1; otherwise, the pixel is considered a non-depolarized region, and its pixel value is set to 0.

[0086] Furthermore, a binarized debiasing model is constructed based on the comparison results. The binarized debiasing model is expressed as follows:

[0087] ,

[0088] In the formula, This represents a binary debiasing model. Represents pixel coordinates in camera coordinates. Represents pixel coordinates in camera coordinates grayscale value, To set the threshold, the influence of ambient light is taken into account. Set it to 250.

[0089] To address the impact of specular highlights caused by variations in the polarization state of complex metal workpiece surfaces, it is necessary to adaptively adjust the polarization encoding based on the established depolarization model.

[0090] Considering the debiasing model The model is constructed on the camera image plane, but subsequent pattern modulation needs to be applied to the projector output; therefore, it must be mapped to the projector coordinate system. This mapping process relies on the absolute phase information obtained from the structured light system. After system calibration, the pixel coordinates in the camera coordinate system are known. The corresponding horizontal and vertical absolute phases are respectively and Let the number of periods of the projected fringes be... T Then the mapping relationship can be expressed as:

[0091] ,

[0092] In the formula, To represent the vertical absolute phase, Indicates the horizontal absolute phase.

[0093] Will Mapped to Then, the de-polarization model in the projector coordinate system is represented as follows:

[0094] ,

[0095] In the formula, This represents the de-polarization model in the projector coordinate system. These are the pixel coordinates in the projector coordinate system. Indicates the deflection region. This indicates the area that has not yet deviated from its original position.

[0096] S30. Modulate the encoded values ​​of the corresponding pixel coordinates in the global polarization coded stripe image using the depolarization model to obtain an adaptive polarization coded image.

[0097] In this embodiment, the encoded values ​​of corresponding pixel coordinates in the global polarization coded stripe image are modulated using a depolarization model to obtain an adaptive polarization coded image. This includes: traversing the pixel coordinates in the projector coordinate system; for each pixel coordinate, if the pixel coordinate in the projector coordinate system is identified as a depolarization region in the depolarization model, then the encoding value of the global polarization coded stripe image at that pixel coordinate is modulated using a suppression coefficient; if the pixel coordinate in the projector coordinate system is identified as a non-depolarization region in the depolarization model, then the encoding value remains unchanged.

[0098] The adaptive polarization coded image is represented as follows:

[0099] ,

[0100] In the formula, For adaptive polarization encoded images, For globally polarized coded stripe images, This is the suppression coefficient. , This is the de-biasing model in the projector coordinate system.

[0101] When a complex metal depolarization region is detected, the polarization encoding of that region is adaptively adjusted using a suppression coefficient. When an undepolarized region is detected, the polarization encoding remains unchanged. In this embodiment, setting the suppression coefficient to 0.5 is sufficient to meet the requirements of most measurement scenarios.

[0102] S40. Acquire the modulated stripe image, and perform phase calculation on the modulated stripe image to achieve three-dimensional measurement of the metal workpiece; wherein, the modulated stripe image is obtained by projecting the adaptive polarization coded image onto the surface of the metal workpiece.

[0103] In this embodiment, after the projection and acquisition of the adaptive polarization-coded image are completed, the final 3D reconstruction stage begins. The core of this stage lies in acquiring the stripe image modulated by the surface of the metal workpiece and performing high-precision phase calculation and 3D point cloud reconstruction. The camera captures the modulated stripe image through a polarizer, and a multi-frequency phase-shifting method is used to perform phase calculation and unfolding on the captured stripe image. By utilizing the complementarity between stripes of different frequencies, the absolute phase distribution can be effectively recovered. Finally, based on pre-calibrated system parameters, the absolute phase is mapped to 3D spatial coordinates, thereby reconstructing a complete and accurate 3D surface contour of the metal workpiece, effectively avoiding the problems of holes and distortion caused by highlights in traditional methods.

[0104] Example 2

[0105] To verify the effectiveness of this embodiment, a structured light measurement system was constructed. This system includes a 3LCD projector (CB-FH52), a grayscale camera (FLIR BFS-U3-51S5P-C), a polarizer, and a metal workpiece to be measured. The angle between the projector and the camera is less than 10°, and the measurement system is approximately 0.6 meters away from the object. Both the projector and camera have a resolution of 1920×1080 pixels. Calibration was performed using the phase height method, and the fringe configuration used a four-step phase-shifting method with phase-shifting fringe frequencies of 70, 64, and 59. The verification steps of the three-dimensional measurement method for metal workpieces based on adaptive polarization projection in this embodiment are as follows. The visualization flowchart in this embodiment is shown below. Figure 2 As shown, where, Figure 2 (a) is a schematic diagram of a metal workpiece; Figure 2 Image (b) is a horizontally polarized encoded image; Figure 2 (c) is the polarization image captured by the camera; Figure 2 In the middle (d), the depolarization model of the polarization image is shown. Figure 2(e) in the figure represents the de-biasing model in the projector coordinate system. Figure 2 (f) in the image represents the polarization-coded stripe image; Figure 2 (g) in the image represents the adaptive polarization coded image. Figure 2 (h) in the image represents the image captured by the camera with highlights removed.

[0106] S1. Utilizing the invariance of the polarization state of linearly polarized light after reflection from a uniform metal workpiece, a global polarization-coded fringe image is obtained from the 0° and 90° polarization-coded fringes, represented as:

[0107] ,

[0108] In the formula, Represents a globally polarization-coded stripe image. Indicates 0° polarization coded stripes. Indicates 90° polarization coded stripes. p Indicates the projection mode. Indicates average intensity. Indicates modulation intensity. Indicates the phase value. k This is the phase shift number.

[0109] S2. Project a horizontally polarized image with uniform brightness onto the metal workpiece to be tested, and establish a depolarization model of the metal workpiece based on the image saturation response according to the polarization image captured by the camera.

[0110] S3, to Perform coordinate transformation to establish a de-biasing model in the projector coordinate system. According to the debiasing model By making local adjustments to the global polarization encoding, the highlights in the depolarization region can be eliminated, ensuring the accuracy of the measurement.

[0111] S4. Traditional specular removal methods are typically based on grayscale mode measurements. To evaluate the measurement efficiency of the proposed polarization mode and grayscale mode, the APPM method, a polarization mode-based measurement method, was used. A metal workpiece with a complex surface was selected for measurement. A uniform grayscale encoded image with a grayscale value of 255 and a uniform horizontal polarization encoded image were projected, respectively. Figure 3 As shown, where, Figure 3 (a) in the image is a fully white grayscale encoded image with a grayscale value of 255; Figure 3 Image (b) is a horizontally polarized encoded image. The camera exposure time was simultaneously set to 2 µs, and the overexposure threshold was set to 250. The modulated stripe image acquired by the camera is shown below. Figure 4 As shown, where, Figure 4 (a) in the image is a metal workpiece image captured by the camera under a uniform grayscale image projection with a grayscale value of 255; Figure 4 (b) in the image is an image of a metal workpiece captured by a camera under uniform horizontal polarization image projection; Figure 4 In (c), the pixel outline of the 500th row of (a) is shown. Figure 4 In the diagram, (d) represents the pixel contour of the 500th row of (b). To observe overexposure in the uniformly coded image mode, the pixel contour images of the 500th row of the modulated stripe image were extracted, as shown below. Figure 4 (c) and Figure 4 As shown in (d) in the figure.

[0112] Depend on Figure 4 (c) and Figure 4 As shown in (d), after a uniform grayscale image is projected onto a metal workpiece, a large area of ​​highlight appears on the surface without any difference. Figure 4 (b) and Figure 4 As shown in (d), after the uniformly horizontally polarized coded image is projected onto the metal workpiece, it divides the workpiece into polarized and depolarized regions. In the regular polarized region, the overexposure of the metal workpiece is effectively suppressed, while in the irregular, small-area depolarized region, highlights appear. This indicates that using linearly polarized light to measure highlight metal workpieces will be more stable.

[0113] The size of the saturated pixel area directly determines the measurement efficiency. To more accurately evaluate the measurement efficiency, the area of ​​the overexposed region was statistically analyzed under two different conditions, such as... Figure 5 As shown, where, Figure 5 (a) in the figure represents the statistics of overexposed areas in the uniform grayscale image projection mode; Figure 5 (b) Statistics of overexposed areas in uniform horizontal polarization coded image projection mode.

[0114] Depend on Figure 5 As shown in (a), in the traditional grayscale measurement mode, the overexposed area of ​​a single grayscale image reaches 15.59%. Furthermore, the traditional grayscale measurement mode typically requires processing multiple images with different grayscale values, which significantly increases the computational load and reduces measurement efficiency. Figure 5 As shown in (b), under polarization measurement mode, the highlights in the uniform region are completely eliminated, and the overexposed pixels are mainly concentrated in the small depolarization region. The highlight effect brought by the depolarization region accounts for only 2.19% of the total measurement area. The proposed method only needs to process the small depolarization region in a polarization image, thus greatly improving the measurement efficiency.

[0115] S5. To evaluate the completeness of the measurement results of the APPM method, a complex metal workpiece was reconstructed, and a comparative experiment was conducted with the traditional grayscale fringe projection profile measurement method. The results are as follows: Figure 6 As shown, where, Figure 6(a) in the image is an adaptive polarization coded image; Figure 6 (b) in the image is a polarization fringe image captured by the camera; Figure 6 (c) in the figure represents the APPM reconstruction result; Figure 6 (d) in the text represents grayscale stripe coding; Figure 6 (e) in the image is a grayscale striped image captured by the camera; Figure 6 (f) in the figure represents the reconstruction result of the grayscale stripe projection profile measurement method.

[0116] Depend on Figure 6 As can be seen in (b), APPM effectively eliminates the specular highlights in complex areas of the metal workpiece and reconstructs the three-dimensional contour of the metal workpiece relatively completely, such as... Figure 6 As shown in (c), the traditional fringe projection contour measurement method results in holes in the reconstructed 3D contour of the metal workpiece due to the influence of specular highlights, such as... Figure 6 (The red area in (f)).

[0117] S6. To verify the stability of the APPM method, a metal workpiece with higher surface complexity was selected for measurement, and the exposure time was increased to 4 ms. The experimental results are as follows: Figure 7 As shown, where, Figure 7 (a) in the image is a grayscale stripe modulated image captured by the camera; Figure 7 (b) in the image is an adaptive polarization projection modulation image captured by the camera; Figure 7 In the diagram, (c) represents the reconstruction result of (a); Figure 7 (d) in the diagram represents the reconstruction result of (b).

[0118] Depend on Figure 7 It can be seen that as the complexity of the surface stripes on the metal workpiece increases and the exposure time increases, the overexposure phenomenon of the traditional stripe projection contour measurement method becomes more serious, and the reconstruction results of the metal workpiece show large-area defects, such as... Figure 7 As shown in (c), APPM simultaneously solves the specular highlight phenomenon in both the polarization and depolarization regions, stably reconstructing the three-dimensional contour of the metal workpiece, as shown in [example]. Figure 7 As shown in (d) in the figure.

[0119] Example 3

[0120] As another aspect of the embodiments of this disclosure, a three-dimensional measurement system 100 for metal workpieces based on adaptive polarization projection is also provided, such as... Figure 8 As shown, it includes:

[0121] The global polarization-coded fringe image acquisition module 1 acquires linearly polarized light projected by the projector and obtains a global polarization-coded fringe image by embedding the polarization state information of the linearly polarized light into a four-step phase-shift sinusoidal fringe model. The linearly polarized light includes 0° linearly polarized light and 90° linearly polarized light.

[0122] Depolarization model construction module 2 acquires a uniform horizontal polarization response image, compares the grayscale value of each pixel in the uniform horizontal polarization response image with a set threshold, constructs a binary depolarization model based on the comparison result, and maps the binary depolarization model to the projector coordinate system to obtain the depolarization model in the projector coordinate system; wherein, the uniform horizontal polarization response image is obtained by projecting a uniform brightness horizontal polarization image onto the metal workpiece through the projector, and then passing it through the reflection of the metal workpiece and the polarizer filtering;

[0123] The adaptive polarization coded image calculation module 3 modulates the coded values ​​of corresponding pixel coordinates in the global polarization coded stripe image through the depolarization model to obtain an adaptive polarization coded image.

[0124] The metal workpiece three-dimensional measurement module 4 acquires a modulated stripe image and performs phase calculation on the modulated stripe image to achieve three-dimensional measurement of the metal workpiece; wherein, the modulated stripe image is obtained by projecting the adaptive polarization coded image onto the surface of the metal workpiece.

[0125] Without causing contradictions, the above-described modules in the system of the present disclosure embodiments can implement any of the above-described methods.

[0126] Based on the description of the above embodiments, it can be seen that the embodiments of this disclosure can achieve the following technical effects:

[0127] 1) The embodiments of this disclosure achieve rapid and accurate localization of the highlight area by constructing a binary depolarization model, which significantly reduces the number of image acquisitions and computational load, and improves measurement efficiency.

[0128] 2) In this embodiment, the depolarization model of the camera coordinate system is mapped to the projector coordinate system, and the global polarization code is locally adaptively modulated accordingly. This directly and specifically suppresses the light intensity in the depolarization region, avoids camera overexposure, ensures complete extraction of phase information, and improves measurement accuracy.

[0129] 3) The embodiments of this disclosure adapt to regions with different surface characteristics (polarization / depolarization) through adaptive modulation, and can stably suppress specular highlights on complex metal surfaces and under varying exposure conditions, thereby enhancing the robustness and reliability of the measurement.

[0130] This disclosure also proposes an electronic device, including: a processor; and a memory for storing processor-executable instructions; wherein the processor is configured for the aforementioned three-dimensional measurement method for metal workpieces based on adaptive polarization projection. The electronic device can be provided as a terminal, a server, or other type of device.

[0131] This disclosure also proposes a computer-readable storage medium storing computer program instructions, which, when executed by a processor, implement the aforementioned three-dimensional measurement method for metal workpieces based on adaptive polarization projection. The computer-readable storage medium may be a non-volatile computer-readable storage medium.

[0132] Those skilled in the art will understand that, in the above-described method and system for three-dimensional measurement of metal workpieces based on adaptive polarization projection in specific embodiments, the order in which each step is written does not imply a strict execution order and does not constitute any limitation on the implementation process. The specific execution order of each step should be determined by its function and possible internal logic.

[0133] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present disclosure. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of an instruction containing one or more executable instructions for implementing a specified logical function. In some alternative implementations, the functions marked in the blocks may occur in a different order than those shown in the drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, may be implemented using a dedicated hardware-based system that performs the specified function or action, or using a combination of dedicated hardware and computer instructions.

[0134] The various embodiments of this disclosure have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or technical improvements to the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for three-dimensional measurement of a metal workpiece based on adaptive polarized projection, characterized in that, The method comprises the following steps: The linearly polarized light projected by the projector is acquired, and the polarization state information of the linearly polarized light is embedded into a four-step phase-shifting sinusoidal fringe model to obtain a globally polarized encoding fringe image, wherein the linearly polarized light comprises 0° linearly polarized light and 90° linearly polarized light; A uniform horizontal polarization response image is acquired, the gray value of each pixel in the uniform horizontal polarization response image is compared with a set threshold, and a binary depolarization model is constructed according to the comparison result, the binary depolarization model is mapped to a projector coordinate system to obtain a depolarization model in the projector coordinate system; wherein the uniform horizontal polarization response image is obtained by projecting a uniform brightness horizontal polarization image on the metal workpiece by the projector, and is obtained after reflection of the metal workpiece and filtering of a polarizer; The encoding value of the corresponding pixel coordinate in the globally polarized encoding fringe image is modulated by the depolarization model to obtain an adaptive polarized encoding image; The modulated fringe image is acquired, and three-dimensional measurement of the metal workpiece is realized by phase unwrapping of the modulated fringe image; wherein the modulated fringe image is obtained by projecting the adaptive polarized encoding image onto the surface of the metal workpiece.

2. The method of claim 1, wherein, The globally polarized encoding fringe image is represented as: ， wherein represents a globally polarized encoded fringe image, represents a 0° polarized encoded fringe, represents a 90° polarized encoded fringe, p represents a projection mode, represents an average intensity, represents a modulation intensity, represents a phase value, k is a phase shift number.

3. The method of claim 1, wherein, The gray value of each pixel in the uniform horizontal polarization response image is compared with a set threshold, comprising: If the gray value of a certain pixel in the uniform horizontal polarization response image is greater than the set threshold, the pixel is a depolarization area, and the corresponding pixel value is set to 1; otherwise, the pixel is a non-depolarization area, and the pixel value is set to 0.

4. The method according to any of claims 1 or 3, characterized in that, The binary depolarization model is constructed according to the comparison result, and the binary depolarization model is represented as: ， wherein denotes the binarization de-polarization model, denotes the pixel coordinate in camera coordinates, denotes the pixel coordinate in camera coordinates the gray value of is a set threshold value.

5. The method of claim 4, wherein, The depolarization model in the projector coordinate system is represented as: ， wherein denotes a de-polarization model in the projector coordinate system, is the pixel coordinate in the projector coordinate system, denotes a de-polarized region, denotes a non-de-polarized region.

6. The method of claim 5, wherein, The encoding value of the corresponding pixel coordinate in the globally polarized encoding fringe image is modulated by the depolarization model to obtain an adaptive polarized encoding image, comprising: The pixel coordinates in the projector coordinate system are traversed, and for each pixel coordinate, if the pixel coordinate in the projector coordinate system is identified as a depolarization area in the depolarization model, the encoding value of the globally polarized encoding fringe image at the pixel coordinate is modulated by a suppression coefficient; if the pixel coordinate in the projector coordinate system is identified as a non-depolarization area in the depolarization model, the encoding value is kept unchanged.

7. The method of claim 6, wherein, The adaptive polarized encoding image is represented as: ， wherein is an adaptive polarization encoded image, is a global polarization encoded fringe image, is a suppression coefficient, is a depolarization model in the projector coordinate system.

8. A system for three-dimensional measurement of a metal workpiece based on adaptive polarized projection, characterized in that, Comprising: A globally polarized encoding fringe image acquisition module acquires linearly polarized light projected by a projector, and embeds polarization state information of the linearly polarized light into a four-step phase-shifting sinusoidal fringe model to obtain a globally polarized encoding fringe image, wherein the linearly polarized light comprises 0° linearly polarized light and 90° linearly polarized light; A de-polarization model construction module, which obtains a uniform horizontal polarization response image, compares the gray value of each pixel in the uniform horizontal polarization response image with a set threshold value, and constructs a binary de-polarization model according to the comparison result, maps the binary de-polarization model to a projector coordinate system to obtain a de-polarization model in the projector coordinate system; wherein the uniform horizontal polarization response image is obtained by projecting a uniform brightness horizontal polarization image onto a metal workpiece by a projector, and is obtained after reflection by the metal workpiece and filtering by a polarizer; An adaptive polarization encoding image calculation module, which modulates the encoding value of the corresponding pixel coordinates in the global polarization encoding fringe image by the de-polarization model to obtain an adaptive polarization encoding image; A metal workpiece three-dimensional measurement module, which obtains the modulated fringe image, and realizes three-dimensional measurement of the metal workpiece by phase unwrapping of the modulated fringe image; wherein the modulated fringe image is obtained by projecting the adaptive polarization encoding image onto the surface of the metal workpiece.

9. An electronic device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, The processor executes the computer program to realize the metal workpiece three-dimensional measurement method based on adaptive polarization projection according to any one of claims 1 to 7.

10. A computer-readable storage medium having stored thereon a computer program, characterized in that, The program is executed by the processor to realize the metal workpiece three-dimensional measurement method based on adaptive polarization projection according to any one of claims 1 to 7.

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