Structured light encoding and decoding method and system based on multi-helical fringe

Abstract

This invention provides a structured light encoding and decoding method and system based on multi-helical stripes, relating to the fields of 3D measurement and machine vision technology. The method includes projecting onto the object under test to generate a set of radially encoded concentric circular sinusoidal stripe phase shift maps, generating another set of concentric circular sinusoidal stripe phase shift maps at different frequencies, and generating two sets of helical stripe phase shift maps simultaneously encoded radially and circumferentially at different frequencies. A camera acquires the stripe encoding pattern modulated by the surface of the object under test. The radius phase and angular phase of points on the surface of the object under test in the camera image coordinate system are calculated. Based on the principle of triangulation, the true depth information of each point is obtained. This invention significantly improves the resolution of the angular phase by using multi-helical stripe patterns with different numbers of spirals, and reduces errors in the measurement process through improved angular phase unwrapping technology, thereby achieving high-precision 3D measurement.

Description

Technical Field

[0001] This invention relates to the fields of three-dimensional measurement and machine vision technology, specifically to a structured light encoding and decoding method and system based on multi-helix stripes. Background Technology

[0002] In the fields of 3D measurement and machine vision, structured light technology is an important non-contact measurement method. It typically involves projecting a specific optical pattern (such as stripes, grids, or dot matrix) onto a target object, and then using a camera to capture reflected images from different perspectives. By analyzing the deformation of the projected pattern on the object's surface, the object's 3D shape information can be inferred.

[0003] In traditional structured light systems, the angular phase marking accuracy in the encoding schemes used is low in practical applications. The angular phase value range is distributed in the [0, 2π] domain across the entire measurement space, and even slight jitter in the angular phase has a significant impact on the final reconstruction accuracy. Furthermore, when structured light systems encounter measurement tasks with high precision requirements, such as in precision engineering or biomedical imaging, the angular resolution of traditional fringe patterns is insufficient. Therefore, researchers urgently need to develop a new structured light encoding method to improve the resolution of the angular phase and reduce measurement errors caused by minute jitter during image acquisition.

[0004] In summary, the low angular resolution and sensitivity to dynamic errors of current structured light 3D measurement technology limit its application in high-precision measurement. Therefore, developing new encoding and decoding methods and systems to overcome these limitations is of great significance for promoting the development of 3D measurement technology. Summary of the Invention

[0005] In view of this, to improve accuracy, the range of angular phase values ​​is expanded to reduce the impact of jitter on reconstruction accuracy. This invention proposes a structured light encoding and decoding method and system based on multi-helical stripes. This method significantly improves the resolution of the angular phase by using multi-helical stripe patterns with different numbers of spirals, and reduces errors in the measurement process through improved angular phase unwrapping technology, thereby achieving high-precision three-dimensional measurement.

[0006] This invention is achieved using the following technical solution:

[0007] In a first aspect, the present invention provides a structured light encoding and decoding method based on multi-helical stripes for high-precision three-dimensional measurement, the method comprising the following steps:

[0008] Step 1. Projection Preparation:

[0009] Project the image onto the object under test to generate a set of concentric circular sinusoidal fringe phase shift maps encoded radially.

[0010] Projecting the image onto the object under test generates another set of concentric circular sinusoidal fringe phase shift maps with different frequencies;

[0011] Project the image onto the object under test to generate a set of P-helix fringe phase shift maps that are simultaneously encoded in the radial and circumferential directions;

[0012] Projecting onto the object under test generates a set of Q-spiral fringe phase shift maps that are simultaneously encoded in the radial and circumferential directions;

[0013] Step 2. Projection and Capture:

[0014] The phase shift diagrams described above are projected sequentially onto the surface of the object under test using a projector.

[0015] The striped coded pattern modulated on the surface of the object under test is captured by a camera;

[0016] Step 3. Phase Calculation

[0017] Calculate the radius phase and angular phase of the points on the surface of the object under test in the camera image coordinate system;

[0018] Step 4. 3D point cloud reconstruction:

[0019] Based on the obtained radius phase and angular phase, combined with the geometric relationship between the camera and the projector, and according to the principle of triangulation, the true depth information of each object point is obtained.

[0020] As a further aspect of the present invention, the projection onto the object under test employs an N-step phase-shifting method, performing phase shifting according to a predetermined number of steps N to obtain N phase-shifting images, with each set of stripe phase-shifting patterns including several phase-shifting states.

[0021] As a further aspect of the present invention, obtaining the radius phase and the angle phase includes the following steps:

[0022] Phase deconstruction is performed on two sets of concentric fringe patterns of different frequencies projected to obtain two truncated phase diagrams of concentric circles.

[0023] The dual-frequency heterodyne method is used to perform phase expansion processing on the first concentric circle truncated phase based on the phase difference between the two truncated phase maps, so as to obtain the radius phase covering the entire field of view.

[0024] Phase deconstruction is performed on two sets of multi-helix stripe patterns with different numbers of spirals in the projection to obtain two truncated phase diagrams of the multi-helix pattern.

[0025] The difference between two multi-helix truncated phase maps and the first concentric circle truncated phase map of the same frequency is calculated to obtain two angular phase maps that divide the field of view into several fan-shaped regions.

[0026] Based on two angular phase maps that divide the field of view into several sector regions, the first angular phase map is expanded to obtain the angular phase.

[0027] As a further aspect of the present invention, when the first angle phase diagram is unfolded, the first angle phase diagram is an angle phase diagram of a P-spiral fringe phase shift diagram, which is compared with the angle phase diagram of a Q-spiral fringe phase shift diagram to expand the range of angle phase values.

[0028] As a further aspect of the present invention, when the structured light encoding and decoding method based on multi-helical stripes performs three-dimensional measurement using the dual-frequency heterodyne method, it includes the following steps:

[0029] Starting from the origin of the camera image coordinate system, sinusoidal phase shift encoding is performed radially to generate a phase shift map;

[0030] By applying the classical phase-shifting dephase formula, the truncated phase corresponding to each pixel of the camera can be solved;

[0031] The truncated phase is unwrapped to make the phase distribution cover the entire camera field of view;

[0032] A spiral phase shift map is generated by performing sinusoidal phase shift encoding along the radial direction. Angle information is added to the principal phase value to obtain a truncated phase distribution map, which includes both radial phase and angular phase information.

[0033] By combining radius phase information, angular phase is obtained to mark the position information of all object points in the camera's field of view in the image coordinate system, reducing the number of projection frames and improving the speed of 3D measurement.

[0034] As a further aspect of the present invention, the unwrapping process of the truncated phase is performed by a dual-frequency unfolding method or a Gray code-assisted unfolding method. The dual-frequency unfolding method involves reprojecting a set of concentric circular fringes with different periods, while the Gray code-assisted unfolding method involves reprojecting a set of concentric circular Gray codes.

[0035] As a further aspect of the present invention, each object point in the camera image coordinate system has a unique radius phase value, and an object point in space is uniquely marked based on the calculated angular phase value of each object point.

[0036] As a further aspect of the present invention, angle information is added to the phase principal value, and the calculation formula is as follows:

[0037]

[0038] In the formula, P is the angle expansion factor, and the final angle phase value range will be extended to between 0 and P*2π. The generated fringe pattern is a P-spiral phase shift pattern.

[0039] As a further aspect of the present invention, the obtained truncated phase distribution map is subjected to difference processing with the truncated phase corresponding to the first group of concentric circular stripes to obtain an angular phase of 0 to 2π.

[0040] As a further aspect of the present invention, when obtaining the angle phase, the method further includes: projecting four additional multi-helix diagrams with different numbers of helices to perform a secondary expansion process on the angle phase diagram, expanding the range of angle phase values ​​to 0 to P*2π, and obtaining the angle phase diagram.

[0041] As a further aspect of the present invention, when obtaining the angular phase, four additional Q-spiral fringe patterns are projected, and a regional angular phase pattern is obtained based on the regional angular phase pattern of the P-spiral fringe phase shift pattern and the Q-spiral fringe phase shift pattern. The regional angular phase pattern of the P-spiral fringe phase shift pattern is then expanded to obtain an extended angular phase pattern covering the entire field of view.

[0042] Secondly, the present invention also includes a structured light encoding and decoding system based on multi-helix stripes for achieving high-precision three-dimensional measurement, the system comprising:

[0043] Projection module: This is a programmable projector used to generate and project concentric circle sinusoidal fringe phase shift diagrams and spiral fringe phase shift diagrams sequentially onto the surface of the object to be measured. The projected fringe pattern can be adjusted to produce fringe patterns with different frequencies and different numbers of spirals.

[0044] Image acquisition module: consisting of one or more high-resolution cameras used to capture stripe patterns modulated on the surface of the object under test.

[0045] Control and synchronization module: Used to synchronize the operation of the projector and camera, ensuring that the stripe pattern is projected and the image is acquired at the correct timing.

[0046] Data processing module: This module is used to perform phase calculation and 3D point cloud reconstruction algorithms. It receives image data acquired by the camera, calculates the radius phase and angular phase, and finally obtains the true 3D coordinates of each object point.

[0047] As a further aspect of the present invention, the system also includes:

[0048] User Interface: This interface displays measurement results and provides user interaction. Users can use this interface to configure the system, such as adjusting the projection pattern, starting the measurement process, and visually displaying the final 3D reconstruction results.

[0049] Calibration module: Used to calibrate the geometric relationship between the camera and the projector, as well as the parameters of the overall system, to ensure the accuracy of the measurement results.

[0050] In summary, the multi-helical stripe-based structured light encoding and decoding system of this invention effectively improves the accuracy and robustness of 3D reconstruction by comprehensively utilizing a combination of concentric circular stripes and helical stripes. Through precise phase calculation and efficient 3D point cloud reconstruction algorithms, the system can perform accurate 3D measurements in various application scenarios.

[0051] The present invention also includes a computer device comprising: at least one processor, and a memory communicatively connected to the at least one processor, wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to cause the at least one processor to perform the structured light encoding and decoding method based on multi-helix stripes.

[0052] The present invention also includes a computer-readable storage medium storing computer instructions for causing the computer to execute the structured light encoding and decoding method based on multi-helix stripes.

[0053] Compared with existing technologies, the structured light encoding and decoding method and system based on multi-helix stripes provided by this invention have the following advantages:

[0054] 1. Improved measurement accuracy: By using fringe phase shift maps with different frequencies and helix numbers, the method of the present invention can more accurately calculate the phase information of the object surface; where phase is the key to reconstructing three-dimensional geometry, therefore, higher phase resolution can achieve higher three-dimensional measurement accuracy.

[0055] 2. Effective handling of phase discontinuity problem: By adopting the dual-frequency heterodyne method and the multi-helical fringe strategy, the problem of phase discontinuity (phase jump) can be effectively solved. This enables the acquisition of continuous and reliable phase information on the surface of objects with complex geometries, thereby improving the stability and accuracy of the measurement.

[0056] 3. Precise acquisition of angular information: The P and Q spiral stripe method can acquire phase information not only in the radial direction but also in the angular direction, which is crucial for 3D reconstruction, especially when dealing with cylindrical or symmetrical objects, providing more comprehensive geometric information.

[0057] 4. High robustness: The use of multiple stripe patterns enhances the system's adaptability to different surface properties and lighting conditions, thus maintaining high robustness in diverse measurement environments.

[0058] 5. Highly efficient data processing: Employing advanced algorithms for phase decoding and 3D point cloud reconstruction, it can quickly process acquired image data, enabling real-time or near real-time 3D measurement, suitable for industrial online inspection and other applications requiring rapid feedback.

[0059] In summary, the structured light encoding and decoding method and system based on multi-helix stripes of the present invention provides accurate phase information and strong robustness, which improves measurement accuracy, adapts to a wider range of application scenarios, and effectively reduces operational complexity and technical barriers.

[0060] These or other aspects of the invention will become more apparent from the following description of embodiments. It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only, and are not intended to limit the invention. Attached Figure Description

[0061] To more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the accompanying drawings used in the description of the exemplary embodiments or related technologies will be briefly introduced below. The drawings are used to provide a further understanding of the present invention and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the present invention and do not constitute a limitation thereof. In the drawings:

[0062] Figure 1 This is a flowchart of a structured light encoding and decoding method based on multi-helix stripes, according to an embodiment of the present invention.

[0063] Figure 2 This is a schematic diagram illustrating the angle and phase error analysis of the single-helix scheme during the actual measurement of the standard plane.

[0064] Figure 3 This is a flowchart illustrating the acquisition of the radius phase and the extension angle phase in the structured light encoding and decoding method based on multi-helix stripes according to an embodiment of the present invention.

[0065] Figure 4 This is a schematic diagram of the phase shift map generated by the four-step phase shift method in the structured light encoding and decoding method based on multi-helix stripes according to an embodiment of the present invention.

[0066] Figure 5 This is a schematic diagram of the phase distribution and the phase trend along the radius in the fully unfolded phase distribution map of the structured light encoding and decoding method based on multi-helix stripes according to an embodiment of the present invention.

[0067] Figure 6 In the structured light encoding and decoding method based on multi-helical stripes in this embodiment of the invention, the stripe pattern generated by P=19 is a P-helical phase shift pattern.

[0068] Figure 7 This is a schematic diagram of the angular phase distribution in the structured light encoding and decoding method based on multi-helix stripes according to an embodiment of the present invention.

[0069] Figure 8This is an absolute phase distribution map related to the angle in the measurement space, which is an example of the structured light encoding and decoding method based on multi-helix stripes in this invention.

[0070] Figure 9 This is a schematic diagram illustrating the multi-helix angle phase error analysis magnified to the same scale during the actual measurement process of the structured light encoding and decoding method based on multi-helix stripes in an embodiment of the present invention.

[0071] Figure 10 This is a comparison diagram of single-helix and multi-helix structures in the structured light encoding and decoding method based on multi-helix stripes according to an embodiment of the present invention.

[0072] Figure 11 This is a structural diagram of the physical grating projection device in the structured light encoding and decoding method based on multi-helix stripes according to an embodiment of the present invention.

[0073] Figure 12 This invention relates to a structured light encoding and decoding method based on multi-helical stripes, which generates a phase shift map of concentric circles and multi-helical stripes using a multi-color physical grating. Detailed Implementation

[0074] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0075] In some of the processes described in the specification, claims, and accompanying drawings of this invention, multiple operations appearing in a specific order are included. However, it should be clearly understood that these operations may not be executed in the order they appear herein, or may be executed in parallel. The operation numbers, such as 101, 102, etc., are merely used to distinguish different operations and do not represent any execution order. Furthermore, these processes may include more or fewer operations, and these operations may be executed sequentially or in parallel. It should be noted that the descriptions such as "first," "second," etc., in this document are used to distinguish different messages, devices, modules, etc., and do not represent a sequential order, nor do they limit "first" and "second" to different types.

[0076] The technical solutions in the exemplary embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described exemplary embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0077] This invention provides a structured light encoding and decoding method and system based on multi-helix stripes, which can solve the problem of low marking accuracy of angle phase in practical applications of single-helix encoding schemes. To improve accuracy, the range of angle phase values ​​is expanded, thereby reducing the impact of jitter on reconstruction accuracy.

[0078] The technical solution of the present invention will be further described below with reference to specific embodiments:

[0079] See Figure 1 As shown, Figure 1 A flowchart illustrating a structured light encoding / decoding method based on multi-helix stripes provided by this invention. One embodiment of this invention provides a structured light encoding / decoding method based on multi-helix stripes, comprising the following steps:

[0080] Step 1: Projector Preparation

[0081] Project the image onto the object under test to generate a set of concentric circular sinusoidal fringe phase shift maps encoded radially.

[0082] Projecting the image onto the object under test generates another set of concentric circular sinusoidal fringe phase shift maps with different frequencies;

[0083] Project the image onto the object under test to generate a set of P-helix fringe phase shift maps that are simultaneously encoded in the radial and circumferential directions;

[0084] Projecting onto the object under test generates a set of Q-helix fringe phase shift maps encoded simultaneously along the radial and circumferential directions. Step 2: Projection and Capture:

[0085] The phase shift diagrams described above are projected sequentially onto the surface of the object under test using a projector.

[0086] The striped coded pattern modulated on the surface of the object to be tested is captured by a camera.

[0087] Step 3, Phase Calculation:

[0088] The radius phase and angular phase of the points on the surface of the object under test are calculated in the camera image coordinate system.

[0089] Step 4: 3D point cloud reconstruction:

[0090] Based on the obtained radius phase and angular phase, combined with the geometric relationship between the camera and the projector, and according to the principle of triangulation, the true depth information of each object point is obtained.

[0091] The structured light encoding and decoding method based on multi-helical stripes of the present invention can solve the problem of low angular phase resolution in previous helical structured light encoding schemes, such as... Figure 2 As shown, Figure 2 The results show that during actual measurement of the standard plane, the angle phase of the single-helix scheme will fluctuate, affecting the measurement accuracy. Figure 2 (a) is a schematic diagram of the angular phase distribution. The phase trend at y=400 is shown in [reference needed]. Figure 2 As shown in (b).

[0092] In step one of the present invention, the projection onto the object to be tested adopts the N-step phase shift method, and the phase shift is performed according to the predetermined number of steps N to obtain N phase shift images. Each set of stripe phase shift patterns includes several phase shift states.

[0093] In embodiments of the present invention, see Figure 3 As shown, obtaining the radius phase and angular phase includes the following steps:

[0094] Phase deconstruction is performed on two sets of concentric fringe patterns of different frequencies projected to obtain two truncated phase diagrams of concentric circles.

[0095] The dual-frequency heterodyne method is used to perform phase expansion processing on the first concentric circle truncated phase based on the phase difference between the two truncated phase maps, so as to obtain the radius phase covering the entire field of view.

[0096] Phase deconstruction is performed on two sets of multi-helix stripe patterns with different numbers of spirals in the projection to obtain two truncated phase diagrams of the multi-helix pattern.

[0097] The difference between two multi-helix truncated phase maps and the first concentric circle truncated phase map of the same frequency is calculated to obtain two angular phase maps that divide the field of view into several fan-shaped regions.

[0098] Based on two angular phase maps that divide the field of view into several sector regions, the first angular phase map is expanded to obtain the angular phase.

[0099] When expanding the first angle phase map, the first angle phase map is the angle phase map of the P spiral fringe phase shift map. It is compared with the angle phase map of the Q spiral fringe phase shift map to expand the range of angle phase values.

[0100] In some embodiments of the present invention, when the structured light encoding and decoding method based on multi-helical stripes performs three-dimensional measurement using the dual-frequency heterodyne method, it includes the following steps:

[0101] (1) Starting from the origin of the camera image coordinate system, sinusoidal phase shift encoding is performed radially to generate a phase shift map. The generated phase shift map is shown below. Figure 4 As shown.

[0102] (2) Apply the classical phase shift solution formula to solve for the truncated phase (-π to π) corresponding to each pixel of the camera.

[0103] (3) Unwrap the truncated phase to make the phase distribution cover the entire camera field of view.

[0104] In this step, the unwrapping process of the truncated phase is performed by either dual-frequency expansion or Gray code-assisted expansion. The dual-frequency expansion method involves reprojecting a set of concentric circular fringes with different periods, while the Gray code-assisted expansion method involves reprojecting a set of concentric circular Gray codes.

[0105] In this step, the phase distribution of the fully unfolded phase distribution map and the phase trend along the radius are as follows: Figure 5 As shown, each object point in the camera image coordinate system has a unique radius phase value. Based on the calculated angle phase value of each object point, an object point in space is uniquely marked.

[0106] (4) A spiral phase shift map is generated by sinusoidal phase shift encoding along the radial direction. Angle information is added to the main phase value to obtain a truncated phase distribution map, which includes both radius phase and angle phase information.

[0107] In this step, similar to the encoding method for concentric circular stripes mentioned above, sinusoidal phase-shift encoding is performed radially, starting from the origin of the camera image coordinate system. The difference is that, for each pixel, angle information is added to the phase principal value, calculated using the following formula:

[0108]

[0109] In the formula, P is the angle expansion factor, and the final angle phase value range will be extended to between 0 and P*2π, generating a P-spiral phase shift pattern. For example, with P=19... Figure 6 As shown.

[0110] Consistent with the previous method for obtaining truncated phase maps from concentric circular fringes, a truncated phase distribution map of helical fringes can be obtained. This map simultaneously contains the radius and angular phase information for each object point. Therefore, after subtracting the truncated phase from the truncated phase corresponding to the first set of concentric circular fringes, the angular phase from 0 to 2π is obtained. The angular phase distribution is as follows... Figure 7 As shown.

[0111] However, due to the multiple spirals, the angle phase cannot cover the entire field of view. Instead, it will divide the entire field of view into 19 regions from 0 to 2π. It is necessary to project four additional multi-spiral diagrams with different numbers of spirals to perform a secondary expansion process on the angle phase diagram, thereby expanding the range of angle phase values ​​to 0 to P*2π. Taking the projection of four Q spiral fringe diagrams as an example, the angle phase diagram can be obtained.

[0112] Specifically, when obtaining the angular phase, four additional Q-spiral fringe patterns are projected, and a regional angular phase pattern is obtained based on the regional angular phase pattern of the P-spiral fringe phase shift pattern and the Q-spiral fringe phase shift pattern. The regional angular phase pattern of the P-spiral fringe phase shift pattern is then expanded to obtain an extended angular phase pattern covering the entire field of view.

[0113] Similar to the dual-frequency expansion principle, based on the 19-region angular phase map and the 20-region angular phase map, the 19-region angular phase map can be expanded to obtain an extended angular phase map covering the entire field of view.

[0114] See Figure 8 As shown in the figure above right, the grayscale gradient along the Y-axis at the 1000th column position is a clear indication that the range of the angle phase is no longer limited to 0–2π, and the impact of minute jitter on accuracy during actual projection acquisition is significantly reduced. Figure 8 The results show that the multi-helix method extends the range of angular phase values ​​in the measurement space from 0 to 2π to 0 to P*2π; Figure 8 (a) is a two-dimensional distribution diagram of absolute phase related to angle, and (b) is a trend diagram of absolute phase along the x=80° direction.

[0115] See Figure 9 As shown, when magnified to the same scale during actual measurement, the angle phase of the multi-helix scheme does not exhibit jitter. Figure 9 (a) is a schematic diagram of the angular phase distribution, (b) is a phase trend diagram at y=400, and (c) is a magnified local phase trend diagram. See also Figure 10 As shown, Figure 10 In Figures (a) and (b), we see comparison images of adding a single spiral and a multi-spiral effect, respectively, representing a comparison of angular phase jitter before and after optimization. Finally, by combining the radius phase information, we obtain the angular phase to mark the position information of all object points within the camera's field of view in the image coordinate system.

[0116] The present invention provides a structured light encoding and decoding method based on multi-helix stripes. Compared with the currently proposed concentric circle combined with single-helix encoding scheme, the present invention has stronger anti-interference ability due to the expansion of the angle phase value range. Under the same experimental error conditions, the jitter of the angle phase has less impact on the accuracy.

[0117] In an embodiment of the present invention, see Figure 11 As shown, when projecting the aforementioned phase-shift map onto the surface of the object under test sequentially using a projector, a physical grating can also be used instead of DLP digital projection to obtain the phase-shift map. The physical grating projection device includes a physical light source, a collimation and homogenization assembly, a rotatable multicolor physical grating, and a projection lens group. This physical grating projection device generates a phase-shift pattern by rotating the light source and the multicolor physical grating, replacing DLP projection in generating the phase-shift map.

[0118] See Figure 12As shown, when concentric circles, P-spirals, and Q-spirals are sequentially projected onto the surface of an object using a physical grating projection device, the concentric circles, P-spirals, and Q-spirals are located in channels of different colors, projecting different colors of light. Combined with rotation, this produces multi-spiral or concentric circle phase-shifting fringes with different periods. From left to right, the images show a concentric circle grating, a P-spiral grating, and a Q-spiral grating. The method for constructing the multi-color physical grating of the physical grating projection device includes the following steps: all concentric circles are stored in the same color channel; the central grating is divided into several parts according to the number of phase-shifting steps and the fringe period; the P-spirals and Q-spirals are stored in separate color channels.

[0119] like Figure 12 The image shows an example of a phase-shifted pattern for concentric circles and multi-spiral fringes generated by a multicolor physical grating. The phase resolution of the concentric circle fringes uses a four-step phase-shifting method and a dual-frequency heterodyne method, while the phase resolution of the multi-spiral fringes uses an eight-step phase-shifting method. (The text then repeats itself, so the translation will only include the first instance.) Figure 9 The left image shows eight circular fringes with different periods and phase shift steps evenly placed in the channels of a circular grating (such as the red channel). Figure 9 The middle and right figures show P-helical and Q-helical stripes placed in the two channels (green and blue channels) of a circular grating, respectively. After each projection and acquisition of a color stripe pattern, the physical grating rotates counterclockwise. Projection acquisition. A total of 8 acquisitions were performed, with the raster rotating exactly one revolution, resulting in 8 color images. The color images were then decomposed according to the color channels, yielding 8 sets of red, green, and blue stripe patterns. The red stripe patterns were stitched together according to pre-defined region numbers to obtain 8 concentric phase-shift images; the green and blue stripes required no manipulation and corresponded to P-spiral and Q-spiral stripes with different phase-shift steps, respectively.

[0120] It should be understood that although the above description follows a certain order, these steps are not necessarily executed in that order. Unless otherwise expressly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, some steps in this embodiment may include multiple steps or multiple stages, which are not necessarily completed at the same time, but may be executed at different times. The execution order of these steps or stages is not necessarily sequential, but may be performed alternately or in turn with other steps or at least a portion of the steps or stages in other steps.

[0121] In one embodiment, the present invention provides a structured light encoding and decoding system based on multi-helix stripes for executing the above-described structured light encoding and decoding method based on multi-helix stripes, the system comprising:

[0122] Projection module: This is a programmable projector used to generate and project concentric circle sinusoidal fringe phase shift diagrams and spiral fringe phase shift diagrams sequentially onto the surface of the object to be measured. The projected fringe pattern can be adjusted to produce fringe patterns with different frequencies and different numbers of spirals.

[0123] Image acquisition module: consisting of one or more high-resolution cameras used to capture stripe patterns modulated on the surface of the object under test.

[0124] Control and synchronization module: Used to synchronize the operation of the projector and camera, ensuring that the stripe pattern is projected and the image is acquired at the correct timing.

[0125] Data processing module: This module is used to perform phase calculation and 3D point cloud reconstruction algorithms. It receives image data acquired by the camera, calculates the radius phase and angular phase, and finally obtains the true 3D coordinates of each object point.

[0126] User Interface: This interface displays measurement results and provides user interaction. Users can use this interface to configure the system, such as adjusting the projection pattern, starting the measurement process, and visually displaying the final 3D reconstruction results.

[0127] Calibration module: Used to calibrate the geometric relationship between the camera and the projector, as well as the parameters of the overall system, to ensure the accuracy of the measurement results.

[0128] The structured light encoding and decoding system based on multi-helical stripes of this invention effectively improves the accuracy and robustness of 3D reconstruction by comprehensively utilizing a combination of concentric circular stripes and helical stripes. Through precise phase calculation and efficient 3D point cloud reconstruction algorithms, the system can perform accurate 3D measurements in various application scenarios.

[0129] In this embodiment, the structured light encoding and decoding system based on multi-helix stripes adopts the steps of a structured light encoding and decoding method based on multi-helix stripes as described above. Therefore, the operation process of the structured light encoding and decoding system based on multi-helix stripes will not be described in detail in this embodiment.

[0130] In one embodiment, a computer device is also provided in the present invention, including at least one processor and a memory communicatively connected to the at least one processor, the memory storing instructions executable by the at least one processor, the instructions being executed by the at least one processor to cause the at least one processor to perform the steps of the structured light encoding and decoding method based on multi-helix stripes.

[0131] In one embodiment, the present invention also provides a computer-readable storage medium storing computer instructions for causing the computer to perform the steps of the structured light encoding and decoding method based on multi-helix stripes.

[0132] Those skilled in the art will understand that implementing all or part of the processes in the above embodiments can be accomplished by a computer program, characterized by computer instructions, instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the embodiments of the above methods. Furthermore, any references to memory, storage, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile and volatile memory.

[0133] Non-volatile memory may include read-only memory, magnetic tape, floppy disk, flash memory, or optical storage. Volatile memory may include random access memory or external cache memory. By way of illustration and not limitation, RAM can take many forms, such as static random access memory or dynamic random access memory.

[0134] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A structured light encoding and decoding method based on multi-helical stripes, characterized in that, The method includes the following steps: Step 1) Projection preparation: Project the image onto the object under test to generate a set of concentric circular sinusoidal fringe phase shift maps encoded radially. Projecting the image onto the object under test generates another set of concentric circular sinusoidal fringe phase shift maps with different frequencies; Project the image onto the object under test to generate a set of P-helix fringe phase shift maps that are simultaneously encoded in the radial and circumferential directions; Projecting onto the object under test generates a set of Q-spiral fringe phase shift maps that are simultaneously encoded in the radial and circumferential directions; Step 2) Projection and Capture: The phase shift diagrams described above are projected sequentially onto the surface of the object under test using a projector. The striped coded pattern modulated on the surface of the object under test is captured by a camera; Step 3) Phase calculation Calculate the radius phase and angular phase of the points on the surface of the object under test in the camera image coordinate system; Step 4) 3D point cloud reconstruction: Based on the obtained radius phase and angular phase, combined with the geometric relationship between the camera and the projector, and according to the principle of triangulation, the true depth information of each object point is obtained.

2. The structured light encoding and decoding method based on multi-helix stripes as described in claim 1, characterized in that, The N-step phase shift method is used to project onto the object under test. The phase shift is performed according to the predetermined number of steps N to obtain N phase shift images. Each set of stripe phase shift patterns includes several phase shift states.

3. The structured light encoding and decoding method based on multi-helix stripes as described in claim 2, characterized in that, Obtaining the radius phase and angular phase includes the following steps: Phase deconstruction is performed on two sets of concentric fringe patterns of different frequencies projected to obtain two truncated phase diagrams of concentric circles. The dual-frequency heterodyne method is used to perform phase expansion processing on the first concentric circle truncated phase based on the phase difference between the two truncated phase maps, so as to obtain the radius phase covering the entire field of view. Phase deconstruction is performed on two sets of multi-helix stripe patterns with different numbers of spirals in the projection to obtain two truncated phase diagrams of the multi-helix pattern. The difference between two multi-helix truncated phase maps and the first concentric circle truncated phase map of the same frequency is calculated to obtain two angular phase maps that divide the field of view into several fan-shaped regions. Based on two angular phase maps that divide the field of view into several sector regions, the first angular phase map is expanded to obtain the angular phase.

4. The structured light encoding and decoding method based on multi-helix stripes as described in claim 3, characterized in that, When expanding the first angle phase map, the first angle phase map is the angle phase map of the P spiral fringe phase shift map. It is compared with the angle phase map of the Q spiral fringe phase shift map to expand the range of angle phase values.

5. The structured light encoding and decoding method based on multi-helix stripes as described in claim 1, characterized in that, The structured light encoding and decoding method based on multi-helical stripes, when performing three-dimensional measurement using the dual-frequency heterodyne method, includes the following steps: Starting from the origin of the camera image coordinate system, sinusoidal phase shift encoding is performed radially to generate a phase shift map; By applying the classical phase-shifting dephase formula, the truncated phase corresponding to each pixel of the camera can be solved; The truncated phase is unwrapped to make the phase distribution cover the entire camera field of view; A spiral phase shift map is generated by performing sinusoidal phase shift encoding along the radial direction. Angle information is added to the principal phase value to obtain a truncated phase distribution map, which includes both radial phase and angular phase information. By combining the radius phase information, the angular phase is obtained to mark the position information of all object points within the camera's field of view in the image coordinate system.

6. The structured light encoding and decoding method based on multi-helix stripes as described in claim 5, characterized in that, The truncated phase is unwrapped using either a dual-frequency expansion method or a Gray code-assisted expansion method. The dual-frequency expansion method involves reprojecting a set of concentric circular fringes with different periods, while the Gray code-assisted expansion method involves reprojecting a set of concentric circular Gray codes.

7. The structured light encoding and decoding method based on multi-helix stripes as described in claim 1, characterized in that, Each object point in the camera image coordinate system has a unique radius phase value. Based on the calculated angular phase value of each object point, an object point in space is uniquely marked.

8. The structured light encoding and decoding method based on multi-helix stripes as described in claim 7, characterized in that, After the difference between the obtained truncated phase distribution map and the truncated phase corresponding to the first group of concentric circular stripes is processed, the angular phase from 0 to 2π is obtained.

9. The structured light encoding and decoding method based on multi-helix stripes as described in claim 8, characterized in that, When obtaining the angle phase, the process also includes: projecting four additional multi-helix diagrams with different numbers of helices to perform a secondary unfolding process on the angle phase diagram, expanding the range of angle phase values ​​to... Calculate the angle phase diagram.

10. A structured light encoding and decoding system based on multi-helix stripes, characterized in that, The structured light encoding and decoding system based on multi-helix stripes, used to execute any one of claims 1-9, comprises: Projection module: This is a programmable projector used to generate and project concentric circle sinusoidal fringe phase shift diagrams and spiral fringe phase shift diagrams sequentially onto the surface of the object to be measured. The projected fringe pattern can be adjusted to produce fringe patterns with different frequencies and different numbers of spirals. Image acquisition module: consisting of one or more high-resolution cameras used to capture stripe patterns modulated on the surface of the object under test; Control and synchronization module: Used to synchronize the operation of the projector and camera, ensuring that the stripe pattern is projected and the image is acquired at the correct timing. Data processing module: This module is used to perform phase calculation and 3D point cloud reconstruction algorithms. It receives image data acquired by the camera, calculates the radius phase and angular phase, and finally obtains the true 3D coordinates of each object point.

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