High-dynamic structured light three-dimensional measurement method
By combining the three-step phase-shifting method and Gaussian filtering, the accuracy and efficiency problems of traditional structured light 3D measurement on objects with high dynamic range are solved, and efficient and accurate 3D reconstruction is achieved, which can be completed with only three images.
Patent Information
- Application Number
- CN202511908855.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-17
- Publication Date
- 2026-02-24
AI Technical Summary
Traditional structured light 3D measurement methods suffer from pixel saturation in high-dynamic-range areas and low signal-to-noise ratio in low-reflection areas when dealing with objects with high dynamic range. This results in missing 3D reconstruction data or reduced accuracy. Furthermore, existing methods struggle to balance efficiency and accuracy, leading to high system complexity.
A three-step phase-shifting method combined with Gaussian filtering and geometric constraint method is adopted to calculate the phase using three structured light fringe images. The phase is then recovered by using average intensity threshold binarization and anti-saturation compensation, combined with system calibration parameters. Finally, the three-dimensional coordinates are calculated by triangulation.
It achieves efficient and accurate 3D reconstruction, which can be completed with only three images, avoiding the inefficiency of multiple measurement fusions, improving robustness and accuracy, and reducing system complexity.
Smart Images
Figure CN121557907A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of three-dimensional measurement technology. Specifically, this invention relates to a high dynamic structured light three-dimensional measurement method. Background Technology
[0002] Structured light 3D measurement technology, due to its non-contact, high precision, and high efficiency, is widely used in modern industrial inspection, precision manufacturing, reverse engineering, cultural relic preservation, biomedicine, and smart agriculture. The basic process involves projecting an coded structured light stripe pattern onto the surface of the object being measured using a projector. A camera captures the deformed stripe image generated by the surface topography modulation, and then reconstructs the object's 3D point cloud data using algorithms such as phase calculation and stereo matching. However, when the surface of the object being measured has high dynamic range characteristics, such as the simultaneous presence of highly reflective and strongly absorbent areas, traditional structured light 3D measurement methods face significant challenges. The fundamental contradiction lies in the fact that the limited dynamic range of the camera's imaging sensor cannot adapt to the drastic changes in the object's surface reflectivity. This leads to the loss of effective phase information in high-brightness areas due to pixel saturation, while low-brightness areas introduce large phase errors due to low signal-to-noise ratios, ultimately resulting in missing 3D reconstruction data or a decrease in overall accuracy.
[0003] Existing methods mainly fall into two categories: multiple measurement fusion methods and single-best measurement methods. Multiple measurement fusion methods synthesize phase information with high dynamic range by fusing multiple images acquired at different exposure times or projection intensities. While this can extend the measurement dynamic range to some extent, it requires projecting and acquiring a large number of sequential patterns, leading to reduced measurement efficiency and making it unsuitable for industrial online inspection scenarios. Furthermore, it has high requirements for environmental stability. Single-best measurement methods aim to achieve complete 3D reconstruction through a single acquisition. For example, based on pre-calibrated adaptive projection intensity modulation, the projection light intensity can be locally adjusted according to the surface reflection characteristics. However, its performance is affected by the calibration accuracy of the camera-projector system response function, and the region boundary delineation and real-time control also face high computational complexity. While polarization-based methods can suppress specular reflection, they require the introduction of additional optical components, increasing system cost and integration complexity.
[0004] In summary, existing high dynamic range 3D measurement technologies still suffer from problems such as difficulty in balancing efficiency and accuracy, limited adaptability, system complexity, or insufficient generalization performance. There is an urgent need to develop a high dynamic range structured light 3D measurement method that is fast, accurate, and highly adaptable. Summary of the Invention
[0005] This invention provides a high dynamic structured light three-dimensional measurement method to solve the problems existing in the background art.
[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a high dynamic structured light three-dimensional measurement method, specifically including the following steps: Step S1: Build a structured light 3D imaging system, including a projector, a camera, and a computer; the projector and camera are synchronously triggered by a microcontroller to ensure that the structured light stripe pattern and the image acquisition are strictly corresponded; at the same time, there is an angle between the optical axes of the projector and the camera lenses, and the object to be measured is placed within their common field of view, and the three form a triangulation relationship. Step S2: The microcontroller sends a pulse signal to trigger the projector to sequentially project a three-step phase-shift fringe pattern onto the surface of the object under test. Simultaneously, the camera is triggered to acquire the three-step phase-shift fringe image modulated by the surface topography of the object under test during each fringe projection. These three images constitute a complete phase shift cycle; Step S3: Calculate the phase-shifted fringe image using the three-step phase-shifting method. truncated phase Simultaneously calculate the average strength Then use average strength The threshold values were used to evaluate the phase-shifting stripe images. Perform binarization processing to obtain the corresponding binary stripe image. ; Step S4: To suppress quantization noise introduced by binarization, a Gaussian filter function is used to filter the binary stripe image. Smoothing is performed to obtain a grayscale striped image. The grayscale fringe image was calculated again using the three-step phase-shifting method. truncated phase Because binarization and smoothing effectively compress the dynamic range, overexposed areas can still maintain better phase continuity. Step S5: Fuse truncated phase With truncated phase Obtain the corrected cutoff phase If the phase-shifted fringe image If the intensity of any pixel is below the saturation threshold, then that pixel is considered underexposed and the truncated phase is retained. The phase value is used; otherwise, the pixel is determined to be overexposed, and the truncated phase is retained. The phase value in the fusion strategy fully utilizes the high signal-to-noise ratio phase information in the unsaturated region, while enabling anti-saturation compensation phase in the saturated region. Step S6: Use the geometric constraint method to truncate the phase Phase unfolding to recover the absolute phase Finally, by combining the system calibration parameters, the absolute phase is mapped to three-dimensional space, and the three-dimensional coordinates of each point on the object surface are calculated using the principle of triangulation, ultimately outputting high-precision three-dimensional point cloud data.
[0007] Preferably, in step S2, the phase-shifted fringe image It can be represented as: ; In the formula: Represents phase-shifted fringe image The serial number, Represents the camera's pixel coordinates; Indicates average intensity. Indicates modulation intensity. This indicates a truncated phase.
[0008] Preferably, in step S3, the phase-shifted fringe image truncated phase The calculation formula is as follows: ; In the formula: This indicates the arctangent operation, hence the phase is truncated. The range of values is ; In step S3, the phase-shifted fringe image average intensity The calculation formula is as follows: ; Phase-shifted fringe image Corresponding binary stripe image It can be represented as: .
[0009] Preferably, in step S4, the filtered grayscale stripe image It can be represented as: ; In the formula: This represents the convolution operation. The Gaussian filter kernel can be further represented as: ; In the formula: This represents the standard deviation of the Gaussian filter kernel; the higher the value, the stronger the filtering effect.
[0010] Preferably, in step S4, the grayscale striped image truncated phase The calculation formula is as follows: ; In the formula: This indicates the arctangent operation, hence the phase is truncated. The range of values is .
[0011] Preferably, in step S5, the phase-shifted fringe image An unexposed mask can be represented as: ; In the formula: Indicates the overexposure threshold; Furthermore, phase-shifted fringe images The corresponding overexposure mask can be represented as: ; Furthermore, fusion truncated phase With truncated phase Obtain the corrected cutoff phase : .
[0012] Preferably, in step S6, the geometric constraint method can be found in Optics Express, 2016, 24(16):18445. The structured light system calibration method can be found in Optics and Lasers in Engineering, 2021, 143:106622.
[0013] The beneficial effects of adopting the above technical solutions are: 1. The present invention provides a high dynamic structured light three-dimensional measurement method that requires only three structured light stripes and does not require multiple measurement fusions. It has the advantages of high speed, high accuracy and strong robustness. Attached Figure Description
[0014] Figure 1 It is a phase-shifted fringe image Binary stripe image Grayscale striped image ; Figure 2 It is the truncated phase before and after fusion. truncated phase and truncated phase ; Figure 3 These are respectively using phase cutoff and truncated phase The reconstructed three-dimensional shape. Detailed Implementation
[0015] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings, in order to help those skilled in the art to have a more complete, accurate and in-depth understanding of the concept and technical solutions of the present invention, and to facilitate its implementation.
[0016] like Figures 1 to 3 As shown, this invention is a high-dynamic structured light three-dimensional measurement method that requires only three structured light stripes and does not require multiple measurement fusions. It has advantages such as high speed, high accuracy, and strong robustness.
[0017] The specific working method is described below using specific embodiments: Example 1: Step S1: Build a structured light 3D imaging system, including a projector, a camera, and a computer; the projector and camera are synchronously triggered by a microcontroller to ensure that the structured light stripe pattern and the image acquisition are strictly corresponded; at the same time, there is an angle between the optical axes of the projector and the camera lenses, and the object to be measured is placed within their common field of view, and the three form a triangulation relationship. Step S2: The microcontroller sends a pulse signal to trigger the projector to sequentially project a three-step phase-shift fringe pattern onto the surface of the object under test. Simultaneously, the camera is triggered to acquire the three-step phase-shift fringe image modulated by the surface topography of the object under test during each fringe projection. These three images constitute a complete phase shift period; as Figure 1 As shown in the first row of images; Step S3: Calculate the phase-shifted fringe image using the three-step phase-shifting method. truncated phase Simultaneously calculate the average strength Then use average strength The threshold values were used to evaluate the phase-shifting stripe images. Perform binarization processing to obtain the corresponding binary stripe image. ;like Figure 1 As shown in the second row of images; Step S4: To suppress quantization noise introduced by binarization, a Gaussian filter function is used to filter the binary stripe image. Smoothing is performed to obtain a grayscale striped image. ,like Figure 1 As shown in the third row of images, the grayscale fringe image is calculated again using the three-step phase-shifting method. truncated phase Because binarization and smoothing effectively compress the dynamic range, overexposed areas can still maintain better phase continuity. Step S5: Fuse truncated phase With truncated phase Obtain the corrected cutoff phase ,like Figure 2 As shown, if the phase-shifted fringe image If the intensity of any pixel is below the saturation threshold, then that pixel is considered underexposed and the truncated phase is retained. The phase value is used; otherwise, the pixel is determined to be overexposed, and the truncated phase is retained. The phase value in the fusion strategy fully utilizes the high signal-to-noise ratio phase information in the unsaturated region, while enabling anti-saturation compensation phase in the saturated region. Step S6: Use the geometric constraint method to truncate the phase Phase unfolding to recover the absolute phase Finally, by combining the system calibration parameters, the absolute phase is mapped to three-dimensional space, and the three-dimensional coordinates of each point on the object surface are calculated using the principle of triangulation, ultimately outputting high-precision three-dimensional point cloud data. Figure 3 Demonstrates the use of truncated phase and truncated phase The reconstructed three-dimensional topography clearly shows that phase truncation was used. The reconstructed 3D surface topography exhibits wavy errors, which can be addressed by using phase truncation. The reconstructed three-dimensional surface is relatively smooth, and the wavy error is greatly reduced, indicating that the method proposed in this patent can effectively correct the measurement error caused by overexposure.
[0018] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution of the present invention to other situations without modification, are all within the protection scope of the present invention.
Claims
1. A high-dynamic structured light three-dimensional measurement method, characterized in that: Specifically, the following steps are included: Step S1: Build a structured light 3D imaging system, including a projector, a camera, and a computer; the projector and camera are synchronously triggered by a microcontroller to ensure that the structured light stripe pattern and the image acquisition are strictly corresponded; at the same time, there is an angle between the optical axes of the projector and the camera lenses, and the object to be measured is placed within their common field of view, and the three form a triangulation relationship. Step S2: The microcontroller sends a pulse signal to trigger the projector to sequentially project a three-step phase-shift fringe pattern onto the surface of the object under test. Simultaneously, the camera is triggered to acquire the three-step phase-shift fringe image modulated by the surface topography of the object under test during each fringe projection. These three images constitute a complete phase shift cycle; Step S3: Calculate the phase-shifted fringe image using the three-step phase-shifting method. truncated phase Simultaneously calculate the average strength Then use average strength The threshold values were used to evaluate the phase-shifting stripe images. Perform binarization processing to obtain the corresponding binary stripe image. ; Step S4: To suppress quantization noise introduced by binarization, a Gaussian filter function is used to filter the binary stripe image. Smoothing is performed to obtain a grayscale striped image. The grayscale fringe image was calculated again using the three-step phase-shifting method. truncated phase Because binarization and smoothing effectively compress the dynamic range, overexposed areas can still maintain better phase continuity. Step S5: Fuse truncated phase With truncated phase Obtain the corrected cutoff phase If the phase-shifted fringe image If the intensity of any pixel is below the saturation threshold, then that pixel is considered underexposed and the truncated phase is retained. The phase value is used; otherwise, the pixel is determined to be overexposed, and the truncated phase is retained. The phase value in the fusion strategy fully utilizes the high signal-to-noise ratio phase information in the unsaturated region, while enabling anti-saturation compensation phase in the saturated region. Step S6: Use the geometric constraint method to truncate the phase Phase unfolding to recover the absolute phase Finally, by combining the system calibration parameters, the absolute phase is mapped to three-dimensional space, and the three-dimensional coordinates of each point on the object surface are calculated using the principle of triangulation, ultimately outputting high-precision three-dimensional point cloud data.
2. The high dynamic structured light three-dimensional measurement method according to claim 1, characterized in that: In step S2, the phase-shifted fringe image It can be represented as: ； In the formula: Represents phase-shifted fringe image The serial number, Represents the camera's pixel coordinates; Indicates average intensity. Indicates modulation intensity. This indicates a truncated phase.
3. The high dynamic structured light three-dimensional measurement method according to claim 1, characterized in that: In step S3, the phase-shifted fringe image truncated phase The calculation formula is as follows: ； In the formula: This indicates the arctangent operation, hence the phase is truncated. The range of values is ; In step S3, the phase-shifted fringe image average intensity The calculation formula is as follows: ； Phase-shifted fringe image Corresponding binary stripe image It can be represented as: 。 4. The high dynamic structured light three-dimensional measurement method according to claim 1, characterized in that: In step S4, the filtered grayscale stripe image It can be represented as: ； In the formula: This represents the convolution operation. The Gaussian filter kernel can be further represented as: ； In the formula: This represents the standard deviation of the Gaussian filter kernel; the higher the value, the stronger the filtering effect.
5. The high dynamic structured light three-dimensional measurement method according to claim 1, characterized in that: In step S4, the grayscale striped image truncated phase The calculation formula is as follows: ； In the formula: This indicates the arctangent operation, hence the phase is truncated. The range of values is .
6. The high dynamic structured light three-dimensional measurement method according to claim 1, characterized in that: In step S5, the phase-shifted fringe image An unexposed mask can be represented as: ； In the formula: Indicates the overexposure threshold; Furthermore, phase-shifted fringe images The corresponding overexposure mask can be represented as: ； Furthermore, fusion truncated phase With truncated phase Obtain the corrected cutoff phase : 。