Roll angle measuring method, system and device based on Talbot-Moire effect

Abstract

The invention relates to the technical field of roll angle measurement, and particularly provides a roll angle measurement method, system and device based on a Talbot-Moire Effect, and the method comprises the steps: Moire fringes are imaged on the phase plane of a CCD camera, the CCD camera converts an optical signal into a digital image signal, and the digital image signal is preprocessed; according to the preprocessed digital image signal, pixels in an image are divided into two types: a stripe area and a non-stripe area; after threshold segmentation, the moire fringes are refined to extract center lines of the fringes; fitting the points of the refined moire fringes into a straight line through straight line fitting, and determining the inclination angle of the moire fringes; and the relative roll angle of the two gratings is calculated by combining the inclination angle of the moire fringes obtained through straight line fitting with the geometric parameters of the gratings, and the calculated roll angle is output. The system comprises a signal processing module, an inclination angle determination module and a roll angle output module. According to the invention, high-precision angle measurement is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of roll angle measurement, and in particular to a roll angle measurement method, system and device based on the Talber-Mohr effect. Background Art

[0002] Angle is one of the basic geometric quantities. There are many existing angle measurement methods, which are widely used in industrial production, scientific research, national defense and other fields. The three-dimensional attitude measurement of space objects relative to the geodetic coordinate system and the measurement of the three-dimensional relative rotation angle between different structures or systems of objects are important components of angle measurement. In the measurement of the three-dimensional relative rotation angle between different structures or systems of the same object, the measurement technology of relative pitch angle and yaw angle is relatively mature, such as the optical autocollimation method; for the relative roll angle, the normal of the plane where its roll vector is located coincides with the direction of the line connecting the two systems, so the measurement of the roll angle is relatively complicated.

[0003] Angle measurement is an important part of basic geometric measurement. Over the past half century, metrologists have conducted a lot of related research and invented many new angle measurement methods in the process. With the development of society, there is an urgent technical demand for angle measurement in scientific research, production, national defense and other fields. The breakthroughs in various related technologies have also given angle measurement a good development space, expanded the measurement range, improved the measurement accuracy, and made great progress in automated measurement.

[0004] The three-dimensional attitude measurement of space objects relative to the geodetic coordinate system and the measurement of the three-dimensional relative rotation angle between different structures or systems of objects are important applications of angle measurement. For example, there may be multiple reference devices or measurement systems on the base of a ship hull at the same time. Under the action of various external forces, the base may produce different degrees of deformation, resulting in three-dimensional small angle relative changes between these devices. These three-dimensional angles are represented by lateral deflection (yaw), longitudinal deflection (pitch) and torsion (roll), and are also called pitch angle, yaw angle and roll angle. The pitch angle and yaw angle are in the plane connecting the two systems, and the torsion occurs in the plane perpendicular to the line connecting the two systems. The angle generated by rotating around the x-axis is the roll angle α, the angle generated by rotating around the y-axis is the pitch angle β, and the angle generated by rotating around the z-axis is the yaw angle γ.

[0005] The measurement of deformation angles, especially the roll angle, is of great significance in rocket launches, missile azimuth aiming, and measurement of spacecraft and ship deformation. Up to now, pitch and yaw angles are relatively easy to measure, and relatively mature measurement methods have been developed. However, the roll angle is difficult to measure because its rotation axis coincides with the movement direction of common measured objects (guide rails, rockets, ships, etc.).

[0006] Over the years, as one of the most basic physical quantities, a variety of angle measurement methods have been developed in the field of angle measurement. According to different measurement principles, angle measurement technology can be roughly divided into mechanical angle measurement technology, electromagnetic angle measurement technology, optical angle measurement technology, etc.

[0007] Prior art 1, Chinese patent, application number: 202410892706.7 discloses a diffraction grating heterodyne interference roll angle measurement method and device based on a half-wave plate. The device comprises a non-polarized beam splitter combination prism arranged on the output light path of the laser light source, an acousto-optic modulator is respectively arranged on two parallel output light paths, a first non-polarized beam splitter prism is arranged on the output light path of the acousto-optic modulator, a first quarter wave plate, a first half wave plate, a first transmission grating, a first combination reflector, a second non-polarized beam splitter prism, and a third non-polarized beam splitter prism are respectively arranged on the transmission light path; a first right-angle prism, a second quarter wave plate, a second half wave plate, a second transmission grating, a second combination reflector, a second right-angle prism, a third right-angle prism, and an optical space exchanger are respectively arranged on the reflection light path, a first polarizer, a first photoelectric detector, a second polarizer, and a second photoelectric detector are respectively arranged on the output light path of the first non-polarized beam splitter prism, and detection signals of the two photoelectric detectors are compared and resolved by a phase meter, but the grating selection is not accurate enough, resulting in damage to the glass base.

[0008] Prior art 2, Chinese patent, application number: 202410892700.X discloses a high-resolution grating heterodyne interference roll angle measurement method and device. The device comprises a non-polarized beam splitting combination prism arranged on the outgoing light path of a dual-frequency laser source, a first polarized beam splitting prism arranged on the transmitted light path, a first right-angle prism, a second right-angle prism and a second polarized beam splitting prism arranged in sequence on the reflected light path; a third right-angle prism arranged on the reflected light path of the first polarized beam splitting prism; a fourth right-angle prism arranged on the reflected light path of the second polarized beam splitting prism; a quarter-wave plate, a transmission grating and a plane reflector arranged on the transmitted light path of the first polarized beam splitting prism and the reflected light path of the fourth right-angle prism; a quarter-wave plate, a transmission grating and a plane reflector arranged on the transmitted light path of the second polarized beam splitting prism and the reflected light path of the third right-angle prism; reverse corner cube prisms arranged on the reflected light paths of the first and second polarized beam splitting prisms respectively; an analyzer and a photoelectric detector arranged on the transmitted light paths of the first and second polarized beam splitting prisms; however, the fringe image processing is poor, resulting in the loss of part of the information in the fringe image processing.

[0009] Prior art three, Chinese patent, application number: 202311732477.4 belongs to the field of navigation technology, specifically relates to a method for evaluating the accuracy of roll angle measurement under ground rotation state, the method includes the following three stages: stage one: based on the rotation measurement characteristics of the ground accelerometer, construct a state equation to realize time update; stage two: based on the selected state and measurement, construct a nonlinear measurement equation to realize measurement update; stage three: based on the filter estimation result, realize roll angle estimation. In the process of testing and evaluating the roll angle accuracy of the combined navigation, the method incorporates the zero position and the equivalent lever arm into the state equation, eliminates the influence of the zero position and the equivalent lever arm, and at the same time, due to the use of the optimal estimation method, the influence of the measurement noise is weakened. The method is easy to implement in engineering, can improve the roll angle evaluation accuracy during the ground test of the combined navigation system, does not rely on the turntable synchronization function, and thus does not increase the hardware cost; however, the influence of three-dimensional angle coupling on moiré fringes is not considered, resulting in inaccurate data.

[0010] At present, the existing technologies 1, 2 and 3 have the problems of inaccurate grating selection, poor fringe image processing and failure to consider the influence of three-dimensional angle coupling on moiré fringes. Therefore, the present invention provides a roll angle measurement method, system and device based on the Talbot-Moiré effect. Summary of the invention

[0011] In order to achieve the above object, the present invention adopts the following technical scheme:

[0012] In one aspect of the present invention, a roll angle measurement method based on the Taber-Mohr effect is provided, comprising the following steps:

[0013] The moiré fringes are imaged onto the phase plane of the CCD camera, which converts the optical signal into a digital image signal, pre-processes the digital image signal, eliminates noise and retains the edge and contour of the moiré fringes;

[0014] After the preprocessed digital image signal, the moiré fringes are separated from the background by threshold segmentation, and the pixels in the image are divided into two categories: the fringe area and the non-fringe area; after the threshold segmentation, the moiré fringes are refined to extract the center line of the fringes; the refined moiré fringes are fitted into a straight line by straight line fitting to determine the inclination of the moiré fringes;

[0015] The relative roll angle of the two gratings is calculated by combining the Moire fringe inclination angle obtained by straight line fitting with the geometric parameters of the grating, and the calculated roll angle is output.

[0016] In an optional implementation manner, the process of converting the optical signal into a digital image signal by a CCD camera comprises the following steps:

[0017] The photosensitive element of the CCD camera receives the optical signal formed by the moiré fringes. The optical system accurately focuses the moiré fringes onto the phase plane of the CCD camera through a lens group. The focused optical signal triggers the photoelectric effect on the photosensitive unit of the CCD camera, converting photons into electrons. Each photosensitive unit generates a corresponding amount of charge according to the received light intensity, and the accumulation of charge is linearly related to the light intensity.

[0018] The accumulated charge is transferred row by row to the output node through the shift register inside the CCD camera; after the charge is transferred to the output node, the analog signal is converted into a digital signal through the analog-to-digital converter;

[0019] The digital image signal enters the preprocessing stage, which includes frequency domain filtering and spatial domain filtering.

[0020] In an optional implementation manner, the process of determining the inclination angle of the moiré fringes comprises the following steps:

[0021] The pre-processed digital image signal is threshold segmented by a preset grayscale threshold; the pixels in the image are divided into two categories: moiré fringe area and non-fringe area; after threshold segmentation, the width of the moiré fringe is reduced to a center line of a single pixel width by a skeletonization algorithm;

[0022] The center line of the refined moiré fringe is composed of a series of discrete pixels, which are connected into a continuous line; the pixel sequence of the center line is extracted using the eight-neighborhood tracking method;

[0023] A straight line fitting is performed on the extracted center line pixel points, and the inclination angle of the moiré fringes is calculated based on the straight line equation obtained by fitting.

[0024] In an optional implementation, the process of reducing the width of the moiré fringes to a center line of a single pixel width using a skeletonization algorithm comprises the following steps:

[0025] The grayscale feature analysis of the preprocessed digital image signal is performed, and based on the grayscale difference between the moiré fringe and the background, a dynamic grayscale threshold is set that is adaptively adjusted according to the local grayscale distribution of the image; the grayscale value of each pixel in the digital image is compared with the set threshold; the image is divided into a moiré fringe area and a non-fringe area to form a binary image;

[0026] Detect the edge of the moiré fringe area to determine the boundary position of the fringe; analyze the topological structure of the moiré fringe to identify the direction and branching of the fringe; use iterative pixel stripping to gradually remove the edge pixels of the moiré fringe area while retaining its topological structure; in each iteration, check whether each pixel is an edge pixel and determine whether its removal will affect the connectivity of the fringe; if not, strip the pixel; repeat the above process until the width of the moiré fringe area is reduced to a center line with a single pixel width;

[0027] The skeletonized center line is optimized to remove burrs or discontinuities; the center line is smoothed.

[0028] In an optional implementation, the process of gradually removing edge pixels in the moiré fringe area using iterative pixel stripping includes the following steps:

[0029] In each iteration, the edge pixels in the moiré fringe area are identified. Edge pixels are those pixels located at the junction of the moiré fringe and the background, and their characteristic is that at least one adjacent pixel belongs to the background area. By traversing all pixels in the moiré fringe area and combining the ownership of their neighboring pixels, the edge pixel set in the current iteration is identified.

[0030] For the identified edge pixels, the effect of their removal on the connectivity of the moiré fringe is analyzed; the connectivity analysis is based on the neighborhood relationship of the pixels to determine whether the pixels are key nodes for maintaining the topological structure of the moiré fringe; if removing the pixels does not lead to the breakage of the moiré fringe area or the loss of branches, the pixels are determined to be peelable; otherwise, the pixels are retained to ensure the integrity of the topological structure;

[0031] After confirming that an edge pixel can be stripped, remove it from the moiré fringe area and mark it as the background area; update the pixel set of the moiré fringe area, recalculate its edge pixel set, and prepare for the next iteration; repeat the above steps until the width of the moiré fringe area is reduced to a center line with a single pixel width.

[0032] In an optional implementation, the process of extracting the pixel point sequence of the center line using the eight-neighborhood tracking method includes the following steps:

[0033] In the center line of the refined moiré fringe, by scanning the image pixels, the pixel points located at the image boundary or with specific topological features are preferentially selected as the starting point; starting from the starting point, according to the eight-neighborhood search rule, the eight neighboring pixels of the current pixel are traversed in turn, and the neighboring pixels with the same direction as the current pixel are preferentially selected as the next tracking point;

[0034] When encountering a branch point, the optimal path is selected for tracking based on the topological features and direction information of the branch point, and other branch points are recorded as backup paths. When the tracking path reaches the image boundary or no qualified neighboring pixels can be found, the tracking of the current path is terminated and the tracking process of the backup path is started.

[0035] The pixel points extracted during the tracking process are connected in sequence to generate a continuous moiré fringe center line pixel point sequence; after the pixel point sequence is generated, the continuity and topological integrity of the sequence are verified.

[0036] In an optional implementation, the process of sequentially traversing eight neighboring pixels of the current pixel includes the following steps:

[0037] The eight neighboring pixels of the current pixel are clearly divided according to their orientation relative to the current pixel; the eight neighboring pixels are located in eight directions of the current pixel, namely, up, down, left, right, upper left, upper right, lower left, and lower right; the orientation information of each neighboring pixel is associated with the orientation information of the current pixel;

[0038] During the tracking process, the direction information of the current pixel is determined by its relative position relationship with the previous pixel; if the previous pixel is located on the left side of the current pixel, the direction information of the current pixel is from left to right, and the direction information is used as the basis for preferentially selecting neighboring pixels;

[0039] According to the direction information of the current pixel, the direction consistency of the eight neighboring pixels is judged; among the neighboring pixels with consistent direction, the optimal neighboring pixel is further selected as the next tracking point based on its topological characteristics and path continuity.

[0040] In an optional implementation, the process of calculating the relative roll angle of the two gratings comprises the following steps:

[0041] The inclination angle of the moiré fringes reflects the relative rotation relationship between the two gratings; the geometric parameters of the gratings include the grating period and the grating spacing, which are related to the moiré fringes; the relationship between the inclination angle of the moiré fringes and the relative roll angle of the two gratings is mapped through the geometric parameters of the gratings; the functional relationship between the inclination angle and the roll angle is derived using the diffraction characteristics of the gratings;

[0042] Based on the Moire fringe inclination angle and the grating geometric parameters, the calculation formula of the roll angle is derived:

[0043]

[0044] Where, φ represents the roll angle; d represents the grating period, L represents the grating spacing; θ represents the Moire fringe inclination angle;

[0045] The geometric parameters of the grating are dynamically corrected through the geometric parameter correction factor of the grating; the calculated roll angle is output for measurement or control.

[0046] Another aspect of the present invention provides a roll angle measurement system based on the Talber-Moire effect, and the roll angle measurement method based on the Talber-Moire effect is implemented, comprising:

[0047] A signal processing module is used for imaging the moiré fringes onto the phase plane of a CCD camera, the CCD camera converts the optical signal into a digital image signal, and pre-processes the digital image signal to eliminate noise and retain the edge and contour of the moiré fringes;

[0048] The inclination angle determination module is used for separating the moiré fringes from the background through threshold segmentation of the pre-processed digital image signal, and dividing the pixels in the image into two categories: the fringe area and the non-fringe area; after the threshold segmentation, the moiré fringes are thinned to extract the center line of the fringes; the points of the thinned moiré fringes are fitted into a straight line through straight line fitting to determine the inclination angle of the moiré fringes;

[0049] The roll angle output module is used to calculate the relative roll angle of the two gratings by combining the Moire fringe inclination angle obtained by straight line fitting with the geometric parameters of the grating, and output the calculated roll angle.

[0050] Another aspect of the present invention provides a roll angle measurement device based on the Talber-Moiré effect, which implements the roll angle measurement method based on the Talber-Moiré effect, comprising: a first light source, an aperture, a first beam splitter prism, a second beam splitter prism, a third beam splitter prism, an objective lens group, a grating reflector, a first CCD lens, a second light source, an autocollimation grating, a second CCD lens, a CCD camera, a lens, a Pism beam splitter, a reflective grating, a collimati on the grating, a collimator and an expander, and a laser;

[0051] Among them, the first light source is connected to the aperture, and the aperture is connected to the first beam splitter prism; the second beam splitter prism is connected to the first CCD lens and the aperture respectively; the third beam splitter prism and the second CCD lens are connected to the second beam splitter prism respectively; the objective lens group and the autocollimation grating are connected to the third beam splitter prism respectively; the second light source is connected to the autocollimation grating; the grating reflector is connected to the objective lens group; the first light source and the second light source are laser collimators; the light emitted by the laser passes through the collimation and expansion system to form a beam of parallel light, and the parallel light passes through the collimati on the grating, and a Talbot image is generated at its Talbot distance. The parallel light is reflected by the right-angle beam splitter prism and shines on the reflective grating, and the second grating is placed at the Talbot distance of the first grating, and forms moiré fringes with the Talbot image, and finally the moiré fringes image is received by the CCD camera and transmitted to the computer. When the two gratings generate an angle, the corresponding change of the moiré fringes image can be detected, and the image can be processed and analyzed by the computer to finally obtain the grating angle change, that is, the roll angle change.

[0052] In the moiré fringe imaging and preprocessing of the present invention, the moiré fringe is imaged onto the phase plane of the CCD camera, and the CCD camera converts the optical signal into a digital image signal, providing a data basis for processing; the preprocessing stage improves the image quality by eliminating noise and retaining the edge and contour of the moiré fringe, laying the foundation for accurate analysis. Threshold segmentation and fringe refinement: Through threshold segmentation, the moiré fringe is separated from the background, and the classification of the fringe area and the non-fringe area in the image is realized, providing a clear target area for processing; the refinement process extracts the center line of the fringe, further improving the clarity and accuracy of the fringe; the straight line fitting fits the center line into a straight line, determines the inclination angle of the moiré fringe, and provides a key parameter for the calculation of the roll angle. The roll angle calculation and output, combined with the geometric parameters of the grating, calculates the relative roll angle of the two gratings through the inclination angle of the moiré fringe, and realizes the accurate measurement of the angle; the calculated roll angle is output, providing data support for subsequent applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0054] Figure 1 This is a flow chart of the roll angle measurement method based on the Taber-Mohr effect provided in Example 1 of the present invention;

[0055] Figure 2 A process diagram of converting an optical signal into a digital image signal by a CCD camera provided in Embodiment 2 of the present invention;

[0056] Figure 3 A process diagram of determining the inclination angle of moire fringes provided in Embodiment 3 of the present invention;

[0057] Figure 4 A process diagram of reducing the width of the moire fringe to a center line of a single pixel width by using a skeletonization algorithm provided in Embodiment 4 of the present invention;

[0058] Figure 5 A process diagram of gradually removing edge pixels in a moiré fringe area by adopting iterative pixel stripping provided in Embodiment 5 of the present invention;

[0059] Figure 6 A process diagram of extracting a pixel point sequence of a center line using an eight-neighborhood tracking method provided in Embodiment 6 of the present invention;

[0060] Figure 7 A process diagram of sequentially traversing eight neighboring pixels of a current pixel provided in Embodiment 7 of the present invention;

[0061] Figure 8 A diagram showing a process of calculating the inclination angle of moire fringes provided in Embodiment 8 of the present invention;

[0062] Fig. 9 A diagram of a process for calculating the relative roll angle of two gratings provided in Embodiment 9 of the present invention;

[0063] Fig.10 This is a block diagram of a roll angle measurement system based on the Talber-Mohr effect provided in Embodiment 10 of the present invention;

[0064] Fig.11 A block diagram of an electronic device provided by the present invention;

[0065] Fig.12 A block diagram of a computer-readable storage medium provided in the present invention;

[0066] Fig.13 This is a schematic diagram of a roll angle measurement device based on the Taber-Mohr effect provided in Example 11 of the present invention;

[0067] Fig.14 This is a schematic diagram of the structure of the roll angle measurement based on the Talber-Mohr effect provided in Example 11 of the present invention. DETAILED DESCRIPTION

[0068] The technical solutions in the embodiments of the present invention will be described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0069] In the following, the terms "first", "second", etc. are used only for convenience of description and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0070] In the present invention, unless otherwise clearly specified and limited, the term "connection" should be understood in a broad sense, for example, "connection" can be a fixed mechanical connection, or a detachable mechanical connection, or integrated; or, "connection" can be a direct connection, or an indirect connection through an intermediate medium. In addition, unless otherwise clearly specified and limited, the term "coupling" should be understood in a broad sense, for example, "coupling" can be a direct electrical connection, such as physical contact and electrical conduction between two components, and can also be understood as electrical connection between different components in a circuit structure through physical lines such as copper foil or wires on a printed circuit board (PCB) that can transmit electrical signals to transmit electrical signals; or, "coupling" can be an indirect electrical connection between two components through an intermediate medium; or, "coupling" can be an electrical connection between two components in an air-spaced / non-contact manner, for example, two components are electrically connected by capacitive coupling to transmit electrical signals.

[0071] In the embodiments of the present invention, directional terms such as "up", "down", "left" and "right" may be defined including but not limited to the orientation relative to the schematic placement of the components in the drawings. It should be understood that these directional terms may be relative concepts, which are used for relative description and clarification, and may change accordingly according to the change of the orientation of the components in the drawings.

[0072] The embodiments of the present invention can be used in the field of aerospace: In the attitude control system of an aircraft, the accurate measurement of the roll angle is crucial to the stability and control of the aircraft. Through the method of the present invention, the roll angle change of the aircraft can be monitored in real time, thereby improving the control accuracy and safety of the aircraft. Precision manufacturing: In the process of precision machining and assembly, the measurement of the roll angle is crucial to ensure the precise alignment and assembly quality of parts. The method of the present invention can be used to detect the roll angle of mechanical parts to ensure that they meet the design requirements. Robotics: In robot motion control, the accurate measurement of the roll angle is crucial to the robot's motion trajectory and attitude control. Through the method of the present invention, the roll angle change of the robot can be monitored in real time, thereby improving the robot's motion accuracy and flexibility. Optical measurement: In an optical system, the measurement of the roll angle is crucial to ensure the alignment of optical elements and the performance of the optical system. The method of the present invention can be used to detect the roll angle of optical elements to ensure the precise alignment and performance optimization of the optical system. Automobile industry: In the process of automobile manufacturing and testing, the measurement of the roll angle is crucial to ensure the precise alignment of the body and parts. The method of the present invention can be used to detect the roll angle of automobile parts to ensure that they meet the design requirements. Medical equipment: During the manufacturing and testing of medical equipment, the measurement of the roll angle is crucial to ensure the precise alignment and performance of the equipment. The method of the present invention can be used to detect the roll angle of medical equipment to ensure that it meets the design requirements. The method of the present invention can achieve high-precision roll angle measurement, and can analyze the impact of the coupling of three-dimensional angles on the measurement, thereby improving the accuracy and reliability of the measurement. This method is not only applicable to the above-mentioned fields, but can also be extended to other application scenarios that require high-precision angle measurement.

[0073] Key technical features of the embodiments of the present invention are described as follows: The present invention introduces basic methods for angle measurement and analyzes and summarizes common methods for optical non-contact roll angle measurement. The research work of the present invention is mainly carried out around the roll angle measurement method of the Talber Moiré effect, that is, the transmission grating will produce a Talber image at its Talber distance under the irradiation of a monochromatic plane wave, and the reflection grating placed at the Talber image will produce moiré fringes with the Talber image. When the relative angle between the reflection grating and the transmission grating changes, the width and angle of the generated moiré fringes will also change accordingly.

[0074] Based on the analysis and discussion of the roll angle measurement method based on the Talbot effect, the present invention performs computational simulation analysis on the Talbot effect, and determines the scheme of the three-dimensional angle detection system combining the Talbot effect with a photoelectric autocollimator according to the design requirements; focuses on the optical path design of the system, and builds and debugs the optical path of the roll angle detection system based on the design; obtains the moiré fringe image through experiments; performs image processing on the obtained moiré fringe to obtain its inclination angle and width change, and then calculates the change of the roll angle. In the image processing process, multiple processing methods such as image preprocessing, Otus threshold segmentation, refinement, and straight line fitting are used in sequence. The influence of the coupling of three-dimensional angles on the measurement is analyzed based on simulation. The computational simulation results and experimental results show that the scheme of measuring the roll angle of an object based on the Talbot effect proposed by the present invention is feasible and can achieve high measurement accuracy and resolution; combined with the photoelectric autocollimator, the measurement of the spatial posture of the object can be effectively realized.

[0075] Embodiment 1:

[0076] like Figure 1 As shown, an embodiment of the present invention provides a roll angle measurement method based on the Talber-Mohr effect, comprising the following steps:

[0077] Step S100: The moiré fringes are imaged onto the image plane of a CCD camera, and the CCD camera converts the optical signal into a digital image signal, and pre-processes the digital image signal to eliminate noise and retain the edge and contour of the moiré fringes;

[0078] Step S200: After the preprocessed digital image signal, the moiré fringes are separated from the background by threshold segmentation, and the pixels in the image are divided into two categories: the fringe area and the non-fringe area; after the threshold segmentation, the moiré fringes are thinned to extract the center line of the fringes; the points of the thinned moiré fringes are fitted into a straight line by straight line fitting to determine the inclination of the moiré fringes;

[0079] Step S300: Calculate the relative roll angle of the two gratings by combining the Moire fringe inclination angle obtained by straight line fitting with the geometric parameters of the gratings, and output the calculated roll angle.

[0080] In the above embodiment, step S100 is moiré fringe imaging and preprocessing, where the moiré fringe is imaged onto the phase plane of the CCD camera, and the CCD camera converts the optical signal into a digital image signal, providing a data basis for processing; the preprocessing stage improves the image quality by eliminating noise and retaining the edges and contours of the moiré fringe, laying the foundation for accurate analysis. Significance: The accuracy and reliability of the measurement data are ensured. By eliminating noise, the influence of external interference on the measurement results is reduced; retaining the edges and contours provides a clear data source for subsequent fringe extraction and angle calculation. Step S200 is threshold segmentation and fringe thinning; by threshold segmentation, the moiré fringe is separated from the background, and the classification of the fringe area and the non-fringe area in the image is realized, providing a clear target area for processing; the thinning process extracts the center line of the fringe, further improving the clarity and accuracy of the fringe; the straight line fitting fits the center line into a straight line, determines the inclination angle of the moiré fringe, and provides key parameters for the calculation of the roll angle. Significance: The precise positioning and feature extraction of the moiré fringe is achieved; by threshold segmentation and thinning, the integrity and accuracy of the fringe information are ensured; the straight line fitting provides reliable geometric parameters for the subsequent calculation of the roll angle. Step S300: Roll angle calculation and output. Combined with the geometric parameters of the grating, the relative roll angle of the two gratings is calculated through the inclination of the moiré fringes, achieving accurate angle measurement; the calculated roll angle is output to provide data support for subsequent applications. Significance: The core task of the entire measurement process is completed, that is, the geometric characteristics of the moiré fringes are converted into specific roll angle values; by combining the geometric parameters of the grating, the accuracy and practicality of the measurement results are ensured, providing reliable data support for applications in related fields.

[0081] In summary, the roll angle measurement method based on the Talber-Mohr effect of this embodiment achieves high-precision angle measurement through a series of steps such as imaging, preprocessing, threshold segmentation, refinement processing and straight line fitting. Each step ensures the accuracy and reliability of the measurement results. This method has important application value in the fields of precision measurement, grating calibration, etc., and provides strong support for the development of related technologies.

[0082] Embodiment 2:

[0083] like Figure 2 As shown, based on Example 1, the process of converting the optical signal into a digital image signal by the CCD camera in step S100 provided in the embodiment of the present invention includes the following steps:

[0084] Step S101: The photosensitive element of the CCD camera receives the optical signal formed by the moiré fringes, and the optical system accurately focuses the moiré fringes onto the phase plane of the CCD camera through a lens group; the focused optical signal triggers the photoelectric effect on the photosensitive unit of the CCD camera, converting photons into electrons, and each photosensitive unit generates a corresponding amount of charge according to the received light intensity, and the accumulation of charge is linearly related to the light intensity;

[0085] Step S102: the accumulated charges are transferred row by row to the output nodes through the shift register inside the CCD camera; after the charges are transferred to the output nodes, the analog signals are converted into digital signals through the analog-to-digital converter;

[0086] Step S103: The digital image signal enters the preprocessing stage, which includes frequency domain filtering and spatial domain filtering; wherein, frequency domain filtering converts the image to the frequency domain through Fourier transform, removes high-frequency noise, and retains low-frequency fringe information; spatial domain filtering eliminates background noise and retains the key features of moiré fringes through filtering, denoising, edge enhancement and other algorithms.

[0087] Wherein, step S101 captures and converts optical signals into photoelectricity;

[0088] The focusing formula of optical signal:

[0089]

[0090] In the formula, f is the focal length of the lens, which means the distance at which the lens focuses parallel light rays to the focal point; u is the object distance, which means the distance from the object to the lens; v is the image distance, which means the distance from the imaging point to the lens; α i represents the weight coefficient of the i-th aberration, which is used to quantify the influence of the aberration on the optical path; W i (u,v) represents the wavefront error function of the i-th aberration, describing the distribution of the aberration in the optical path;

[0091] Photoelectric effect and charge accumulation formula:

[0092]

[0093] Where Q(x,y) represents the amount of charge accumulated at the position (x,y), which represents the signal intensity after photoelectric conversion; η represents the photoelectric conversion efficiency, which represents the efficiency of converting the incident light signal into charge; I(x,y,t) represents the light intensity distribution at the position (x,y) and time t; β represents the nonlinear photoelectric response coefficient, which describes the nonlinear effect in the photoelectric conversion process; N dark (x,y) represents dark current noise, which indicates charge accumulation caused by thermal effects in the absence of light;

[0094] Step S102: charge transfer and analog-to-digital conversion;

[0095] Charge transfer formula:

[0096]

[0097] In the formula, Q(x,t) represents the amount of charge at position x and time t; D represents the diffusion coefficient, which describes the diffusion characteristics of the charge during the transfer process; γ represents the charge transfer efficiency loss coefficient, which represents the loss ratio of the charge during the transfer process; J(t) represents the noise term caused by clock jitter, which describes the charge transfer error caused by the instability of the clock signal;

[0098] Analog-to-digital conversion formula:

[0099]

[0100] In the formula, S digital Represents a digital signal, which represents the discrete value of an analog signal after quantization; S analog Represents analog signal, which means continuous voltage or current signal input to ADC; Q step Represents the quantization step size, which indicates the analog signal increment corresponding to each digital value; ∈ represents the nonlinear error coefficient, which describes the nonlinear distortion in the ADC conversion process; N quant represents quantization noise, which indicates the error introduced by the quantization process;

[0101] Step S103: preprocessing of digital image signals;

[0102] Frequency domain filtering formula:

[0103]

[0104] Where G(u,v) represents the filtered frequency domain signal, which represents the distribution of the processed image in the frequency domain; F(u,v) represents the original frequency domain signal, which represents the distribution of the input image in the frequency domain; H(u,v) represents the filter transfer function, which is used to select or suppress specific frequency components; N(u,v) represents the frequency domain noise estimation, which represents the distribution of the noise in the image in the frequency domain; ∈ ′ Represents the regularization parameter, which is used to avoid the situation where the denominator is zero. It is usually a very small positive number (such as 10 -6 );η ′ Represents the Laplace operator weight coefficient, which is used to enhance the high-frequency details of the image; Represents the Laplace operator in the frequency domain, which is used to extract the high-frequency components of the image; the expression of the Laplace operator in the frequency domain is

[0105] Spatial filtering formula:

[0106]

[0107] In the formula, g(x,y) represents the filtered spatial signal, which represents the pixel value of the processed image in the spatial domain; f(x,y) represents the original spatial signal, which represents the pixel value of the input image in the spatial domain; h(m,n;x,y) represents the adaptive filter kernel, which changes with the position (x,y) and is used to dynamically adjust the filtering effect; the Gaussian filter kernel Where σ is the standard deviation; w(xm,yn) represents the edge protection weight function, which is used to protect the edge information of the image during the filtering process; the gradient-based weight function in is the image gradient; λ represents the Laplace operator weight coefficient, which is used to enhance the details and edges of the image; Represents the Laplacian operator in the spatial domain, which is used to extract high-frequency details of the image; the expression of the Laplacian operator in the spatial domain is A comprehensive description is provided for optical signal capture, photoelectric conversion, charge transfer, analog-to-digital conversion, and image preprocessing.

[0108] In the above embodiment, step S101 captures and converts optical signals to photoelectricity. The precise focusing of optical signals focuses the moiré fringes onto the phase plane of the CCD camera through the lens group, ensuring that the spatial resolution and clarity of the optical signals reach the best state; the efficient photoelectric conversion photosensitive unit converts photons into electrons, and the accumulation of charge is linearly related to the light intensity, realizing the efficient conversion of optical signals to electrical signals. Significance: It is the basis of the entire signal conversion process, ensuring the integrity and accuracy of the optical signal; through precise focusing and efficient photoelectric conversion, it provides high-quality electrical signal input for signal processing, laying a solid foundation for the accuracy of the measurement results. Step S102 charge transfer and analog-to-digital conversion, the high-fidelity transfer of charge transfers the charge line by line through the shift register, ensuring that the charge is not lost or distorted during the transfer process; the precise digitization of analog signals converts the analog signals into digital signals through the analog-to-digital converter (ADC), realizing the high-resolution digitization of the signals. Significance: It realizes the transition from analog signals to digital signals, ensuring the integrity and processability of the signals; through high-fidelity charge transfer and high-precision digitization, it provides a reliable data basis for image processing, avoiding signal distortion or information loss. Step S103: Preprocessing of digital image signals: frequency domain filtering removes high-frequency noise, converts the image to the frequency domain through Fourier transform, removes high-frequency noise, retains low-frequency fringe information, and improves the signal-to-noise ratio of the image; spatial domain filtering enhances key features: through filtering, denoising and edge enhancement algorithms, background noise is eliminated and key features of moiré fringes are retained, thus improving the clarity and analyzability of the image. Significance: The core link of image signal processing, through the comprehensive application of frequency domain and spatial domain filtering, the image quality is significantly improved. Noise interference is removed, and the key information of moiré fringes is retained, providing high-quality input data for fringe analysis and roll angle calculation, ensuring the accuracy and reliability of the measurement results.

[0109] In summary, this embodiment achieves complete conversion from optical signals to high-quality digital image signals through progressive technical means. Each step ensures the integrity, accuracy and processability of the signal during conversion and processing. It not only improves the accuracy and efficiency of roll angle measurement, but also provides reliable technical support for measurement technology based on the Talber-Mohr effect, which has important engineering application value.

[0110] Embodiment 3:

[0111] like Figure 3 As shown, based on Example 1, the process of determining the inclination angle of the moiré fringes in step S200 provided in the embodiment of the present invention includes the following steps:

[0112] Step S201: threshold segmentation is performed on the preprocessed digital image signal by a preset grayscale threshold; pixels in the image are divided into two categories: moiré fringe area and non-fringe area (background); after threshold segmentation, a skeletonization algorithm is used to reduce the width of the moiré fringe to a center line with a single pixel width;

[0113] Step S202: the center line of the thinned moiré fringe is composed of a series of discrete pixel points, and the pixel points are connected into a continuous line; the pixel point sequence of the center line is extracted using the eight-neighborhood tracking method;

[0114] Step S203: performing straight line fitting on the extracted center line pixel points, and calculating the inclination angle of the moiré fringes according to the straight line equation obtained by fitting.

[0115] In the above embodiment, step S201 is threshold segmentation and skeletonization. Threshold segmentation separates the moiré fringe area from the background area in the image through a preset grayscale threshold, thereby realizing the preliminary extraction of the fringe; it can effectively remove background noise and highlight the characteristics of the moiré fringe; the skeletonization algorithm reduces the width of the moiré fringe to a center line with a single pixel width, retains the topological structure of the fringe, and removes redundant edge pixels, providing a basis for accurate analysis. Significance achieved: Threshold segmentation and skeletonization are key steps in image processing, ensuring the clear extraction and simplification of the moiré fringe, providing high-quality data input for centerline extraction and inclination calculation; improving the accuracy and reliability of measurement, and avoiding errors caused by noise or uneven fringe width. Step S202 is centerline extraction and pixel serialization. The eight-neighborhood tracking method connects the refined discrete pixels into continuous lines and extracts the centerline pixel point sequence of the moiré fringe; it can effectively process complex fringe shapes and ensure the integrity and continuity of the centerline. Significance achieved: Centerline extraction is a key step in converting moiré fringe from a two-dimensional image to one-dimensional data. By extracting the pixel point sequence, direct data support is provided for straight line fitting; complex image information is simplified into calculable mathematical data, laying the foundation for inclination calculation. Step S203 straight line fitting and inclination calculation, straight line fitting uses the least squares method to fit the center line pixel points to obtain the straight line equation of the moiré fringes; it can effectively eliminate the influence of noise points and improve the fitting accuracy. The inclination calculation calculates the inclination of the moiré fringes through the slope based on the straight line equation obtained by fitting; the image information is converted into a specific angle value to provide key parameters for roll angle measurement. Significance achieved: Straight line fitting and inclination calculation are the core steps of the entire measurement process, which convert the results of image processing into a specific physical quantity (inclination); the conversion from image information to actual measurement values ​​is realized, providing accurate data support for roll angle calculation.

[0116] In summary, this embodiment realizes accurate measurement from image to inclination angle through threshold segmentation, skeletonization, centerline extraction, straight line fitting and inclination angle calculation; combines image processing technology and mathematical algorithms to ensure the accuracy and stability of the measurement results; converts complex moiré fringe images into quantifiable physical parameters (inclination angle), providing reliable technical support for roll angle measurement based on Talbot-Moiré effect; realizes high-precision roll angle measurement to meet the needs of precision measurement in industries, scientific research and other fields.

[0117] Embodiment 4:

[0118] like Figure 4 As shown, based on Example 3, the process of reducing the width of the moiré fringes to a center line of a single pixel width by using a skeletonization algorithm in step S201 provided in the embodiment of the present invention includes the following steps:

[0119] Step S2011: grayscale feature analysis is performed on the preprocessed digital image signal, and based on the grayscale difference between the moiré fringe and the background, a dynamic grayscale threshold is set that is adaptively adjusted according to the local grayscale distribution of the image; the grayscale value of each pixel in the digital image is compared with the set threshold; the image is divided into a moiré fringe area and a non-fringe area (background) to form a binary image;

[0120] If the pixel grayscale value is greater than or equal to the threshold, the pixel is determined to belong to the moiré fringe area;

[0121] If the pixel gray value is less than the threshold, the pixel is determined to belong to the background area;

[0122] Step S2012: Detect the edge of the moiré fringe area to determine the boundary position of the fringe; analyze the topological structure of the moiré fringe to identify the direction and branching of the fringe; use iterative pixel stripping to gradually remove the edge pixels of the moiré fringe area while retaining its topological structure; in each iteration, check whether each pixel is an edge pixel and determine whether its removal will affect the connectivity of the fringe; if not, strip the pixel; repeat the above process until the width of the moiré fringe area is reduced to a center line with a single pixel width;

[0123] Step S2013: Optimize the skeletonized center line to remove burrs or discontinuities; and smooth the center line.

[0124] In the above embodiment, step S2011 grayscale feature analysis and binarization, by performing grayscale feature analysis on the pre-processed digital image, dynamically adjusting the grayscale threshold based on the grayscale difference between the moiré fringes and the background, dividing the image into the moiré fringes area and the background area, and forming a binary image. Significance: Simplifying a complex grayscale image into a binary image, clearly distinguishing the moiré fringes area and the background; the setting of the dynamic grayscale threshold can adapt to the local grayscale distribution of the image, improve the accuracy of segmentation, and lay the foundation for skeletonization processing; through binarization, the amount of information in the image is greatly compressed, while retaining the key features of the moiré fringes. Step S2012 edge detection and iterative pixel stripping, detecting the edge of the moiré fringes area, determining the boundary position, and gradually removing the edge pixels through iterative pixel stripping, retaining the topological structure of the fringes, and finally reducing the width of the moiré fringes area to a center line with a single pixel width. Significance: Reduce the width of the moiré fringes from multiple pixels to a single pixel while keeping its topological structure unchanged; through edge detection and iterative peeling, the algorithm can accurately retain the direction and branching of the moiré fringes, avoiding information loss caused by excessive peeling. It not only simplifies the representation of the moiré fringes, but also provides a clearer structural basis for quantitative analysis. Step S2013 Centerline optimization and smoothing, optimize the skeletonized centerline, remove burrs or discontinuities, and smooth the centerline to make it more continuous and regular. Significance: Improve the quality of the centerline to make it more suitable for subsequent analysis and application. By removing burrs and discontinuities, the accuracy and reliability of the centerline are significantly improved; smoothing further improves the visual effect of the centerline, making it more in line with the needs of practical applications; the optimized centerline is not only easier to analyze, but also provides higher quality data for quantitative measurement and feature extraction.

[0125] In summary, this embodiment simplifies image information by binarizing complex grayscale images into binary images, clearly distinguishing moiré fringes from background; retains topological structure by iteratively stripping moiré fringes to a single-pixel-wide center line, while retaining its direction and branching; improves data quality by optimizing and smoothing, improving the accuracy and continuity of the center line, and providing a more reliable basis for analysis. It not only realizes the skeletonization of moiré fringes, but also provides high-quality data support for its quantitative analysis and practical application, which has important technical significance and application value.

[0126] Embodiment 5:

[0127] like Figure 5 As shown, based on Example 4, the process of using iterative pixel stripping to gradually remove edge pixels in the moiré fringe area in step S2012 provided in the embodiment of the present invention includes the following steps:

[0128] Step S20121: In each iteration, edge pixels in the moiré fringe area are identified. Edge pixels are pixels located at the junction of the moiré fringe and the background, and are characterized by at least one adjacent pixel belonging to the background area. By traversing all pixels in the moiré fringe area and combining the ownership of their neighboring pixels, a set of edge pixels in the current iteration is identified.

[0129] Step S20122: for the identified edge pixels, analyzing the effect of their removal on the connectivity of the moire fringe; the connectivity analysis is based on the neighborhood relationship of the pixels to determine whether the pixels are key nodes for maintaining the topological structure of the moire fringe; if removing the pixels does not result in the breakage of the moire fringe area or the loss of branches, then the pixels are determined to be peelable; otherwise, the pixels are retained to ensure the integrity of the topological structure;

[0130] Step S20123: after confirming that a certain edge pixel can be peeled off, remove it from the moiré fringe area and mark it as the background area; update the pixel set of the moiré fringe area, recalculate its edge pixel set, and prepare for the next iteration; repeat the above steps until the width of the moiré fringe area is reduced to a center line with a single pixel width;

[0131] The iteration termination conditions include: there are no more peelable edge pixels in the moiré fringe area; the width of the moiré fringe area has reached a single pixel width, and its topological structure is completely preserved.

[0132] In the above embodiment, step S20121 edge pixel identification and edge pixel positioning accurately identify edge pixels at the junction of the moiré fringe and the background by traversing all pixels in the moiré fringe area and combining the attribution of its neighboring pixels; dynamically update the edge pixel set in each iteration to recalculate the edge pixel set to ensure the continuity and accuracy of the refinement process. Significance achieved: edge pixel identification is the basic step of refinement processing, and its accurate positioning provides reliable data support for pixel stripping; by dynamically updating the edge pixel set, the efficiency and stability of the refinement process are ensured. Step S20122 connectivity analysis and pixel stripping determination: connectivity analysis is based on the neighborhood relationship of pixels to determine whether the edge pixel is a key node for maintaining the topological structure of the moiré fringe, ensuring that the stripping operation will not cause the breakage of the fringe area or the loss of branches; stripping determination analyzes the impact of pixel stripping on the topological structure, scientifically determines whether the edge pixel can be stripped, and avoids distortion of the refinement result due to erroneous stripping. Significance achieved: connectivity analysis and stripping determination are the core steps of refinement processing, which ensure the integrity of the moiré fringe topological structure through a scientific analysis mechanism; directly determine the accuracy and reliability of the refinement result. Step S20123: Pixel stripping and iterative update. Pixel stripping removes the edge pixels that are determined to be strippable from the moiré fringe area and marks them as the background area, gradually reducing the width of the moiré fringe; iteratively updates the pixel set in the moiré fringe area, recalculates the edge pixel set, and prepares for the next iteration to ensure the continuity and efficiency of the refinement process. Significance achieved: Pixel stripping and iterative update are the execution steps of the refinement process, which achieves the reduction of the moiré fringe width by gradually stripping the edge pixels; directly reflects the efficiency and accuracy of the refinement process. Iterative termination condition: When there are no more strippable edge pixels in the moiré fringe area, or the width of the moiré fringe area has reached a single pixel width and the topological structure is completely preserved, the iterative process is terminated; the integrity and accuracy of the refinement result are ensured by determining the termination condition. Significance achieved: The iterative termination condition is the end mark of the refinement process, which ensures the rationality of the refinement process and the reliability of the results through a scientific determination mechanism.

[0133] In summary, this embodiment achieves accurate refinement of the Moiré fringes through iterative pixel stripping, extracts a center line with a single pixel width, and provides high-quality data for inclination angle calculation; during the refinement process, the topological structure protection always protects the topological structure of the Moiré fringes, avoids fringing breakage or branch loss, and ensures the integrity of the refinement results; automated and efficient iterative processing achieves full automation of the refinement process, significantly improves processing efficiency, and reduces human intervention and errors; through the coordinated work of each step, not only high-precision processing of the Moiré fringes is achieved, but also important support is provided for the overall performance improvement of the roll angle measurement system.

[0134] Embodiment 6:

[0135] like Figure 6 As shown, based on Example 3, the process of extracting the pixel point sequence of the center line using the eight-neighborhood tracking method in step S202 provided by the embodiment of the present invention includes the following steps:

[0136] Step S2021: In the center line of the refined moiré fringe, by scanning the image pixels, a pixel point located at the image boundary or having a specific topological feature is preferentially selected as the starting point; starting from the starting point, according to the eight-neighborhood search rule, the eight neighboring pixels of the current pixel are traversed in turn, and the neighboring pixel with the same direction as the current pixel is preferentially selected as the next tracking point;

[0137] Step S2022: When a branch point is encountered, the optimal path is selected for tracking according to the topological features and direction information of the branch point, and other branch points are recorded as backup paths; when the tracking path reaches the image boundary or no neighboring pixels that meet the conditions can be found, the tracking of the current path is terminated, and the tracking process of the backup path is started;

[0138] Step S2023: connect the pixel points extracted in the tracking process in order to generate a continuous moiré fringe center line pixel point sequence; after the pixel point sequence is generated, verify the continuity and topological integrity of the sequence.

[0139] In the above embodiment, step S2021 starts point positioning and neighborhood search, and the optimization of starting point selection ensures that the starting point of the tracking process is clear and efficient by giving priority to selecting pixels located at the image boundary or having specific topological features as the starting point, avoiding redundant searches that may be caused by randomly selecting the starting point; the direction consistency search gives priority to selecting neighboring pixels that are consistent with the direction of the current pixel in the neighborhood search, reducing path branches and redundant searches, and improving tracking efficiency. Significance achieved: Improving tracking efficiency By optimizing the starting point selection and direction consistency search, the search time and computing resource consumption are significantly reduced; ensuring the continuity of the path, the direction consistency mechanism helps to generate a continuous centerline path, providing a high-quality data basis for straight line fitting. Step S2022 Branch processing and path termination, branch point optimization processing When encountering a branch point, the optimal path is selected according to the topological features and direction information, and the backup path is recorded at the same time, avoiding the path loss or redundant tracking problems that may occur at the branch point in the traditional method; path termination condition determination When the tracking path reaches the image boundary or cannot find a qualified neighborhood pixel, the current path is terminated and the backup path tracking is started, ensuring that all possible paths are fully tracked. Significance achieved: Improve path integrity. Through branch point optimization and path termination condition determination, the integrity and accuracy of centerline extraction are ensured, and path omission or breakage problems are avoided; Enhance robustness. The backup path tracking mechanism improves the algorithm's adaptability to complex topological structures and enhances the robustness of the algorithm. Step S2023: Pixel point sequence generation and integrity verification. Pixel point sequence generation connects the pixels extracted during the tracking process in sequence to generate a continuous Moire fringe centerline pixel point sequence, ensuring the continuity and consistency of the sequence; integrity verification verifies the continuity and topological integrity of the sequence after generating the pixel point sequence, further improving the reliability of the extraction results. Significance achieved: Providing a continuous pixel point sequence generated by high-quality data provides a high-quality data basis for subsequent straight line fitting and inclination calculation; Ensuring the reliability of the results through integrity verification further improves the accuracy and reliability of the centerline extraction results, avoiding errors caused by path breakage or branch loss.

[0140] In summary, this embodiment significantly improves tracking efficiency and reduces computing resource consumption through starting point optimization, direction consistency search and branch point optimization; ensures the integrity and accuracy of centerline extraction through branch point optimization, path termination condition determination and integrity verification; the backup path tracking mechanism and integrity verification enhance the algorithm's adaptability to complex topological structures and improve the robustness of the algorithm; the generated continuous pixel point sequence provides a high-quality data basis for subsequent straight line fitting and inclination calculation, ensuring the accuracy of the final result. Through the hierarchical optimization of the above steps, the eight-neighborhood tracking method not only improves efficiency and accuracy in the process of extracting the centerline pixel point sequence of moiré fringes, but also enhances the robustness and reliability of the algorithm, laying a solid foundation for the accurate calculation of the inclination of moiré fringes.

[0141] Embodiment 7:

[0142] like Figure 7 As shown, based on Example 6, the process of sequentially traversing eight neighboring pixels of the current pixel in step S2021 provided in the embodiment of the present invention includes the following steps:

[0143] Step S20211: clearly divide the eight neighboring pixels of the current pixel according to their orientation relative to the current pixel; the eight neighboring pixels are respectively located in eight directions of the current pixel: up, down, left, right, upper left, upper right, lower left, and lower right; the orientation information of each neighboring pixel is associated with the orientation information of the current pixel;

[0144] Step S20212: During the tracking process, the direction information of the current pixel is determined by its relative position relationship with the previous pixel; if the previous pixel is located on the left side of the current pixel, the direction information of the current pixel is from left to right, and the direction information is used as the basis for preferentially selecting neighboring pixels;

[0145] Step S20213: according to the direction information of the current pixel, the direction consistency of eight neighboring pixels is judged; among the neighboring pixels with consistent direction, the optimal neighboring pixel is further selected as the next tracking point according to its topological characteristics and path continuity;

[0146] The specific method for judging the direction consistency of eight neighborhood pixels is as follows:

[0147] Filtering of neighboring pixels with consistent direction: give priority to neighboring pixels with consistent direction information with the current pixel. For example, if the direction information of the current pixel is "from left to right", give priority to neighboring pixels located on the right side of the current pixel (including right, upper right, and lower right directions);

[0148] Excluding neighboring pixels with inconsistent directions: Excluding neighboring pixels with inconsistent direction information with the current pixel to reduce the possibility of redundant searches and path branching;

[0149] Select the best neighborhood pixel as the next tracking point. The specific method is as follows:

[0150] Topological feature priority: neighborhood pixels with specific topological features (such as those located near image boundaries or branch points) are prioritized to ensure the integrity and accuracy of the tracking path;

[0151] Path continuity optimization: select neighboring pixels with the best path continuity with the current pixel to avoid path breaks or redundant branches.

[0152] In the above embodiment, the orientation division of the neighboring pixels in step S20211 clearly divides the eight neighboring pixels of the current pixel according to their orientation relative to the current pixel, providing a clear basis for the direction information association and direction consistency judgment. The significance achieved: It ensures that the orientation information of the neighboring pixels can be accurately associated with the direction information of the current pixel, lays the foundation for the implementation of the direction consistency priority mechanism, and avoids the uncertainty of path selection caused by the ambiguity of the neighborhood pixel orientation in the traditional method. Step S20212 determines the direction information of the current pixel, determines the direction information by the relative position relationship between the current pixel and the previous pixel, and provides a clear basis for the priority selection of neighboring pixels. The significance achieved: It ensures the direction consistency of the tracking path, reduces the possibility of path branching, and improves the tracking efficiency; at the same time, the clarity of the direction information provides reliable data support for the subsequent direction consistency judgment. Step S20213 Direction consistency judgment and optimal neighborhood pixel selection, through direction consistency judgment, preferentially selects neighborhood pixels consistent with the direction information of the current pixel, excludes neighborhood pixels with inconsistent directions, and reduces the possibility of redundant search and path branching. Significance achieved: The continuity and consistency of the tracking path are significantly improved, avoiding the path breakage or redundant branching problems caused by random selection of neighborhood pixels in traditional methods, and providing a guarantee for high-quality centerline extraction. The optimal neighborhood pixels are selected from the neighborhood pixels with consistent directions, and the optimal neighborhood pixels are further selected based on the topological features and path continuity to ensure the integrity and accuracy of the tracking path. Significance achieved: The quality of the tracking path is further improved by prioritizing topological features and optimizing path continuity, ensuring the continuity and topological integrity of the centerline pixel sequence, and providing a high-quality data foundation for verification and application.

[0153] In summary, this embodiment improves tracking efficiency, reduces redundant searches and path branches through directional consistency judgment and optimal neighborhood pixel selection, and significantly improves tracking efficiency. Path continuity is enhanced. The directional consistency priority mechanism and path continuity optimization ensure the continuity and consistency of the tracking path, avoiding path breakage or redundant branching problems. Topological integrity is ensured. Through the priority selection of topological features, the integrity and accuracy of the tracking path are ensured, providing a guarantee for high-quality centerline extraction. A high-quality data foundation is provided*. Each step works together to generate a continuous, complete and accurate centerline pixel point sequence, providing a high-quality data foundation for verification and application. This embodiment implements the above steps in a hierarchical manner. In the process of extracting the centerline pixel point sequence, the eight-neighborhood tracking method significantly improves tracking efficiency, path continuity and topological integrity, providing reliable technical support for high-quality centerline extraction.

[0154] Embodiment 8:

[0155] like Figure 8 As shown, based on Example 2, the process of calculating the inclination angle of the moire fringes in step S203 provided in the embodiment of the present invention includes the following steps:

[0156] Step S2031: performing straight line fitting on the extracted moiré fringe center line pixel point sequence to obtain the equation of the fitted straight line, converting the discrete pixel point sequence into a continuous straight line; and obtaining the straight line equation by fitting;

[0157] Step S2032: The slope of the line equation indicates the degree of inclination of the line in the image coordinate system, which is the tangent value of the angle between the line and the positive direction of the horizontal axis of the image coordinate system; the positive or negative slope reflects the inclination direction of the line. A positive slope indicates that the line is inclined to the upper right, and a negative slope indicates that the line is inclined to the lower right;

[0158] Step S2033: According to the relationship between the slope and the inclination angle, the inclination angle is calculated by an inverse tangent function, and the slope information is converted into a specific inclination angle value.

[0159] In the above embodiment, step S2031 is straight line fitting, which converts the discrete pixel point sequence of the center line of the moiré fringe into a continuous straight line equation, thereby realizing the mathematical description of the spatial distribution of the moiré fringe; through the fitting method (such as the least squares method), the noise and error in the pixel point sequence are effectively reduced, and the accuracy of the straight line equation is improved. The significance achieved: It provides an accurate mathematical basis for slope calculation and inclination measurement; through the straight line equation, the spatial characteristic analysis of the moiré fringe is simplified. Step S2032 is slope analysis, in which the slope directly reflects the degree of inclination of the straight line in the image coordinate system, and provides a core parameter for inclination calculation; the sign of the slope (positive or negative) clarifies the inclination direction of the straight line, and provides a basis for adjusting the range of the inclination. The significance achieved: Through the relationship between the slope and the inclination, the geometric information is converted into mathematical parameters, which provides theoretical support for the inclination calculation; the sign information of the slope ensures the correctness of the inclination direction and avoids directional errors in the calculation results. Step S2033 calculates the inclination angle. The inverse tangent function is used to convert the slope information into a specific inclination angle value, thereby realizing the accurate measurement of the inclination angle of the moiré fringe. The inclination angle range is adjusted according to the sign and actual direction of the slope, thereby ensuring the intuitiveness and accuracy of the inclination angle value. The significance achieved: It provides a quantitative description of the inclination angle of the moiré fringe, providing important parameters for spatial characteristic analysis and application; through accurate inclination angle measurement, it supports the application of moiré fringe in optical measurement, image processing, industrial detection and other fields.

[0160] In summary, this embodiment realizes the precise measurement of the inclination of the moiré fringes through straight line fitting, slope analysis and inclination calculation; each step effectively reduces the influence of errors and noise, ensuring the accuracy and reliability of the calculation results. The significance achieved: It provides important mathematical tools and parameter support for the spatial characteristic analysis of moiré fringes; it supports the practical application of moiré fringes in a variety of application scenarios, such as optical measurement, image processing, industrial detection, etc.; through precise inclination measurement, it improves the technical level and application effect of related fields. The process of calculating the inclination of moiré fringes realizes the precise measurement of the inclination of moiré fringes through straight line fitting, slope analysis and inclination calculation. Each step provides important support for the spatial characteristic analysis and application of moiré fringes.

[0161] Embodiment 9:

[0162] like Fig. 9 As shown, based on Example 1, the process of calculating the relative roll angle of the two gratings in step S300 provided in the embodiment of the present invention includes the following steps:

[0163] Step S301: the inclination angle of the moiré fringes reflects the relative rotation relationship between the two gratings; the geometric parameters of the gratings include the grating period and the grating spacing, which are related to the moiré fringes; the relationship between the inclination angle of the moiré fringes and the relative roll angle of the two gratings is mapped through the geometric parameters of the gratings; the functional relationship between the inclination angle and the roll angle is derived using the diffraction characteristics of the gratings;

[0164] Step S302: Based on the Moire fringe inclination angle and the grating geometric parameters, derive a calculation formula for the roll angle:

[0165]

[0166] Where, φ represents the roll angle; d represents the grating period, L represents the grating spacing; θ represents the Moire fringe inclination angle;

[0167] Step S303: dynamically correct the geometric parameters of the grating through the geometric parameter correction factor of the grating; output the calculated roll angle for measurement or control.

[0168] In the above embodiment, step S301 establishes the mapping relationship between the inclination angle of moiré fringes and the geometric parameters of gratings, and clarifies the mathematical expression of the relative rotation relationship between the two gratings through the association between the inclination angle of moiré fringes and the geometric parameters of gratings and the grating spacing; the physical relationship between the inclination angle of moiré fringes and the roll angle is converted into a mathematical model by using the diffraction characteristics of the grating. The measurement accuracy is improved by introducing the grating geometric parameters, avoiding the limitation of relying only on the inclination angle of moiré fringes in the traditional method, and enhancing the accuracy of the measurement results. The significance achieved: provides a solid theoretical basis for the measurement of roll angle, clarifies the intrinsic connection between the inclination angle of moiré fringes and the roll angle; breaks through the limitation of the traditional linear relationship, and provides a new technical path for high-precision measurement. Step S302 derives the roll angle calculation formula, and derives the roll angle calculation formula based on the inclination angle of moiré fringes and the geometric parameters of gratings, comprehensively considering the diffraction effect of the grating and the spatial distribution characteristics of the moiré fringes, and realizing the high-precision calculation of the roll angle; the nonlinear term in the formula fully considers the geometric characteristics of the grating, and improves the accuracy of the calculation. Significance achieved: By introducing grating geometric parameters, high-precision calculation of roll angle is achieved to meet the needs of industrial detection and optical measurement. A new roll angle calculation method is provided to support the technical development of related fields. Step S303 grating geometric parameter correction and roll angle output, by introducing the correction factor of grating geometric parameters, the manufacturing error and installation deviation of the grating are dynamically corrected to further optimize the accuracy of roll angle calculation; the calculated roll angle is output in real time for measurement or control system to ensure the real-time and reliability of the measurement results.

[0169] In summary, this embodiment effectively compensates for the errors in the grating manufacturing and installation process through the correction factor, improves the reliability of the measurement results, provides high-precision roll angle data for industrial detection, optical measurement and control systems, and supports technical applications in related fields. This process provides a new technical path for roll angle measurement based on the Talber-Mohr effect, supports the application requirements in the field of high-precision optical measurement and industrial detection, and breaks through the limitations of traditional methods by introducing grating geometric parameters and correction factors.

[0170] Embodiment 10:

[0171] like Fig.10 As shown, on the basis of Embodiments 1 to 9, the roll angle measurement system based on the Taber-Mohr effect provided by the embodiment of the present invention comprises:

[0172] Signal processing module 1, used for imaging the moiré fringes onto the phase plane of the CCD camera, the CCD camera converts the optical signal into a digital image signal, pre-processes the digital image signal, eliminates noise and retains the edge and contour of the moiré fringes;

[0173] The inclination angle determination module 2 is used for separating the moiré fringes from the background through threshold segmentation of the pre-processed digital image signal, and dividing the pixels in the image into two categories: the fringe area and the non-fringe area; after the threshold segmentation, the moiré fringes are thinned to extract the center line of the fringes; the moiré fringes after thinning are fitted into a straight line by straight line fitting to determine the inclination angle of the moiré fringes;

[0174] The roll angle output module 3 is used to calculate the relative roll angle of the two gratings by combining the Moire fringe inclination angle obtained by straight line fitting with the geometric parameters of the gratings, and output the calculated roll angle.

[0175] In the above embodiment, the signal processing module 1 performs optical signal conversion and preprocessing. The optical signal conversion converts the moiré fringe optical signal captured by the CCD camera into a digital image signal, providing a data basis for subsequent processing; noise elimination removes noise interference in the image through preprocessing techniques such as filtering to ensure the clarity and integrity of the moiré fringe; edge and contour retention retains the edge and contour features of the moiré fringe while denoising, providing high-quality input for threshold segmentation and refinement processing. Significance achieved: The signal processing module is the basis of the entire system, and the high-quality digital image signal it outputs directly determines the accuracy and reliability of subsequent modules; by eliminating noise and retaining key features, the accuracy and stability of the measurement results are ensured. Inclination angle determination module 2 Moiré fringe segmentation and inclination angle calculation, threshold segmentation uses adaptive threshold segmentation technology to divide the pixels in the image into fringe areas and non-fringe areas, and realizes accurate separation of moiré fringes from the background; refinement processing refines the moiré fringe area, extracts the center line with a single pixel width, and eliminates the influence of the fringe width on the inclination angle calculation; straight line fitting and inclination angle determination Based on the refined center line, the inclination angle of the moiré fringe is calculated by straight line fitting technology, providing key parameters for roll angle calculation. Significance achieved: The inclination angle determination module is the core processing, which realizes high-precision calculation of the moiré fringe inclination angle through precise fringe segmentation, refinement processing and straight line fitting. Roll angle output module 3 Roll angle calculation and output, roll angle calculation is based on the inclination angle of the moiré fringe, combined with the geometric parameters of the grating (such as grating period, grating spacing, etc.), and the relative roll angle of the two gratings is calculated through geometric relationship; result output outputs the calculated roll angle in the form of digital or analog signal for use by users or subsequent systems. The roll angle output module is the final target realization unit. It converts the inclination angle of the moiré fringes into the actual roll angle value through precise geometric calculation, providing reliable technical support for high-precision roll angle measurement.

[0176] In summary, this embodiment achieves high-precision measurement of the roll angle through modular technical design, meeting the stringent requirements for angle measurement in industries such as industry and scientific research; it achieves fully automated processing from optical signals to roll angle output, significantly improving measurement efficiency and reducing human errors; the measurement system based on the Talber-Mohr effect has the characteristics of non-contact and high sensitivity, and can be widely used in precision machinery, optical instruments, aerospace and other fields; through the collaborative work of various modules, the system not only achieves high-precision measurement of the roll angle, but also provides important technical support for the technological development of related fields.

[0177] Fig.11 A block diagram of an exemplary electronic device suitable for implementing embodiments of the present invention is shown.

[0178] The electronic device may include a central processing unit / microprocessor / main control chip, etc. 4; a storage medium 5, coupled to the central processing unit / microprocessor / main control chip, etc. 4, and storing computer executable instructions therein, for performing the steps of each method of an embodiment of the present invention when executed by the processor.

[0179] The central processing unit / microprocessor / main control chip 4 may include but is not limited to, for example, one or more processors or microprocessors.

[0180] The storage medium 5 may include, but is not limited to, for example, random access memory (RAM), read-only memory (ROM), flash memory, EPROM memory, EEPROM memory, registers, computer storage media (such as hard disk, floppy disk, solid state drive, removable disk, CD-ROM, DVD-ROM, Blu-ray disc, etc.).

[0181] In addition, the electronic device may also include (but not limited to) a data bus 6, an input / output bus / external bus / device bus 7, a display 8, and input / output devices 9 (eg, keyboard, mouse, speaker, etc.).

[0182] The central processing unit / microprocessor / main control chip etc. 4 can communicate with external devices ( 8 , 9 etc.) through the I / O bus 7 via a wired or wireless network (not shown).

[0183] The storage medium 5 may also store at least one computer executable instruction for executing the various functions and / or method steps in the embodiments described in the present technology when executed by the central processing unit / microprocessor / main control chip 4.

[0184] In one embodiment, the at least one computer executable instruction may also be compiled into or constitute a software product, wherein one or more computer executable instructions are executed by a processor to perform the various functions and / or method steps in the embodiments described in the present technology.

[0185] Fig.12 A schematic diagram of a computer-readable storage medium according to an embodiment of the present invention is shown.

[0186] like Fig.12As shown, instructions are stored on a non-transitory computer-readable storage medium 11, and the instructions are, for example, computer-readable instructions 10. When the computer-readable instructions 10 are executed by the processor, the various methods described above can be executed. Non-transitory computer-readable storage media include, but are not limited to, for example, volatile memory and / or non-volatile memory. Volatile memory may include, for example, random access memory (RAM) and / or cache memory (cache), etc. Non-transitory non-volatile memory may include, for example, read-only memory (ROM), hard disk, flash memory, etc. For example, the non-transitory computer-readable storage medium 11 can be connected to a computing device such as a computer, and then, when the computing device runs the computer-readable instructions 10 stored on the computer-readable storage medium 11, the various methods described above can be performed.

[0187] Embodiment 11:

[0188] like Fig.13 and Fig.14 As shown, on the basis of Example 10, the roll angle measuring device based on the Talber-Mohr effect provided by the embodiment of the present invention comprises: a first light source 12, an aperture 13, a first beam splitter prism 14, a second beam splitter prism 15, a third beam splitter prism 16, an objective lens group 17, a grating reflector 18, a first CCD lens 19, a second light source 20, a self-collimating grating 21, a second CCD lens 22, a CCD camera 23, a lens 24, a Pism beam splitter 25, a reflective grid 26, a collimator 27 on the grid, a collimator and an expander 28, and a laser 29;

[0189] Among them, the first light source 12 is connected to the aperture 13, and the aperture 13 is connected to the first beam splitter prism 14; the second beam splitter prism 15 is connected to the first CCD lens 19 and the aperture 13 respectively; the third beam splitter prism 16 and the second CCD lens 22 are connected to the second beam splitter prism 15 respectively; the objective lens group 17 and the autocollimation grating 21 are connected to the third beam splitter prism 16 respectively; the second light source is connected to the autocollimation grating 21; the grating reflector 18 is connected to the objective lens group 17; the first light source 12 and the second light source 20 are laser collimators, λ=638.2nm semiconductor lasers, the spot diameter is Φ30mm, and the divergence angle; the autocollimation grating is p=20μm, Φ=15mm, one is a transmission grating as a self-collimation grating, and the other is bonded with the reflector to form a reflection grating as a moving object to provide a three-dimensional turning angle; The pixel size of the first CCD lens and the second CCD lens is 3.45μm×3.45μm, and the total number of pixels is 2448×2048, so the imaging area is 8.5mm×7.1mm; the three-dimensional angle rotation device fine-tuning polarized light right angle minimum resolution is 0.84′; the light emitted by the laser 29 passes through the collimation and expansion system to form a beam of parallel light, and the parallel light passes through the first transmission grating (Collimati27 on the grating), and a Talbot image is generated at its Talbot distance. The parallel light is reflected by the right-angle beam splitter prism and shines on the second reflection grating (reflection grating 26), and the second grating is placed at the Talbot distance of the first grating, and forms moiré fringes with the Talbot image, and finally the CCD camera 23 receives the moiré fringes image and transmits it to the computer. When the two gratings generate an angle, the corresponding change of the moiré fringes image can be detected, and the image can be processed and analyzed by the computer to finally obtain the grating angle change, that is, the roll angle change.

[0190] In the above embodiment, the position of the reflection grating G2 is adjusted so that it is exactly located at the Talbot distance of the transmission grating G1; the two grating lines are adjusted to the same direction, that is, the initial angle is zero; the fine-tuning mechanism of the reflection grating is rotated so that the grating lines of G2 and the grating lines of G1 generate a relative angle, that is, the roll angle to be measured θ; the minimum rotation angle of the fine-tuning polarizing mirror frame is 0.84′, and the moiré fringe image is collected and image processing is performed to calculate θ;

[0191] The light emitted by the laser 29 passes through the collimation and expansion system to form a beam of parallel light. The parallel light passes through the first transmission grating (Collimati27 on the grating), and a Talbot image is generated at its Talbot distance. The parallel light is reflected by the right-angle beam splitter prism and shines on the second reflection grating (reflection grating 26), and the second grating is placed at the Talbot distance of the first grating, and forms moiré fringes with the Talbot image. Finally, the CCD camera 23 receives the moiré fringes image and transmits it to the computer. When the two gratings form an angle, the corresponding change of the moiré fringes image can be detected. The image can be processed and analyzed by the computer to finally obtain the change of the grating angle, that is, the change of the roll angle.

[0192] In the several embodiments provided by the present invention, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic, for example, the division of units is only a logical function division, and there may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0193] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0194] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0195] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a number of instructions for executing all or part of the steps of the various embodiments of the method of the present invention through a computer device (which can be a personal computer, a server, or a network device, etc.). The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (full name in English: Read-Only Memory, English abbreviation: ROM), random access memory (full name in English: Random Access Memory, English abbreviation: RAM), disk or optical disk and other media that can store program codes.

[0196] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A roll angle measurement method based on the Talber-Mohr effect, characterized in that: The following steps are involved: The moiré fringes are imaged onto the phase plane of the CCD camera, which converts the optical signal into a digital image signal, pre-processes the digital image signal, eliminates noise and retains the edge and contour of the moiré fringes; After the preprocessed digital image signal, the moiré fringes are separated from the background by threshold segmentation, and the pixels in the image are divided into two categories: the fringe area and the non-fringe area; after the threshold segmentation, the moiré fringes are refined to extract the center line of the fringes; the refined moiré fringes are fitted into a straight line by straight line fitting to determine the inclination of the moiré fringes; The relative roll angle of the two gratings is calculated by combining the Moire fringe inclination angle obtained by straight line fitting with the geometric parameters of the grating, and the calculated roll angle is output.

2. The roll angle measurement method based on the Talber-Mohr effect according to claim 1, characterized in that: The process of converting optical signals into digital image signals by CCD cameras includes the following steps: The photosensitive element of the CCD camera receives the optical signal formed by the moiré fringes. The optical system accurately focuses the moiré fringes onto the phase plane of the CCD camera through a lens group. The focused optical signal triggers the photoelectric effect on the photosensitive unit of the CCD camera, converting photons into electrons. Each photosensitive unit generates a corresponding amount of charge according to the received light intensity, and the accumulation of charge is linearly related to the light intensity. The accumulated charge is transferred row by row to the output node through the shift register inside the CCD camera; after the charge is transferred to the output node, the analog signal is converted into a digital signal through the analog-to-digital converter; The digital image signal enters the preprocessing stage, which includes frequency domain filtering and spatial domain filtering.

3. The roll angle measurement method based on the Talber-Mohr effect according to claim 1, characterized in that: The process of determining the inclination angle of the moiré fringes includes the following steps: The pre-processed digital image signal is threshold segmented by a preset grayscale threshold; the pixels in the image are divided into two categories: moiré fringe area and non-fringe area; after threshold segmentation, the width of the moiré fringe is reduced to a center line of a single pixel width by a skeletonization algorithm; The center line of the refined moiré fringe is composed of a series of discrete pixels, which are connected into a continuous line; the pixel sequence of the center line is extracted using the eight-neighborhood tracking method; A straight line fitting is performed on the extracted center line pixel points, and the inclination angle of the moiré fringes is calculated based on the straight line equation obtained by fitting.

4. The roll angle measurement method based on the Talber-Mohr effect as claimed in claim 3, characterized in that: The process of using the skeletonization algorithm to reduce the width of the moiré fringes to a single-pixel wide center line includes the following steps: The grayscale feature analysis of the pre-processed digital image signal is performed, and based on the grayscale difference between the moiré fringes and the background, a dynamic grayscale threshold is set that is adaptively adjusted according to the local grayscale distribution of the image; Compare the gray value of each pixel in the digital image with the set threshold; divide the image into a moiré fringe area and a non-fringe area to form a binary image; Detect the edge of the moiré fringe area to determine the boundary position of the fringe; analyze the topological structure of the moiré fringe to identify the direction and branching of the fringe; Iterative pixel stripping is used to gradually remove edge pixels in the moiré fringe area while preserving its topological structure. In each iteration, each pixel is checked to see if it is an edge pixel and whether its removal will affect the connectivity of the fringe. If not, the pixel is stripped. The above process is repeated until the width of the moiré fringe area is reduced to a center line with a single pixel width. The skeletonized center line is optimized to remove burrs or discontinuities; the center line is smoothed.

5. The roll angle measurement method based on the Talber-Mohr effect according to claim 4, characterized in that: The process of gradually removing edge pixels in the moiré fringe area using iterative pixel stripping includes the following steps: In each iteration, the edge pixels in the moiré fringe area are identified. Edge pixels are those pixels located at the junction of the moiré fringe and the background, and their characteristic is that at least one adjacent pixel belongs to the background area. By traversing all pixels in the moiré fringe area and combining the ownership of their neighboring pixels, the edge pixel set in the current iteration is identified. For the identified edge pixels, the effect of their removal on the connectivity of the moiré fringe is analyzed; the connectivity analysis is based on the neighborhood relationship of the pixels to determine whether the pixels are key nodes for maintaining the topological structure of the moiré fringe; If removing a pixel does not result in a break in the moiré fringe region or a loss of branches, the pixel is determined to be peelable; Otherwise, the pixel is retained to ensure the integrity of the topological structure; After confirming that an edge pixel can be stripped, remove it from the moiré fringe area and mark it as the background area; update the pixel set of the moiré fringe area, recalculate its edge pixel set, and prepare for the next iteration; repeat the above steps until the width of the moiré fringe area is reduced to a center line with a single pixel width.

6. The method for measuring the rolling angle based on the Talber-Mohr effect according to claim 3, characterized in that: The process of extracting the pixel point sequence of the center line using the eight-neighborhood tracking method includes the following steps: In the center line of the refined moiré fringe, by scanning the image pixels, the pixel points located at the image boundary or with specific topological features are preferentially selected as the starting point; starting from the starting point, according to the eight-neighborhood search rule, the eight neighboring pixels of the current pixel are traversed in turn, and the neighboring pixels with the same direction as the current pixel are preferentially selected as the next tracking point; When encountering a branch point, the optimal path is selected for tracking based on the topological characteristics and direction information of the branch point, and other branch points are recorded as backup paths; When the tracking path reaches the image boundary or fails to find a neighboring pixel that meets the conditions, the tracking of the current path is terminated and the tracking process of the backup path is started; The pixel points extracted during the tracking process are connected in sequence to generate a continuous moiré fringe center line pixel point sequence; after the pixel point sequence is generated, the continuity and topological integrity of the sequence are verified.

7. The method for measuring the rolling angle based on the Talber-Mohr effect according to claim 6, characterized in that: The process of traversing the eight neighboring pixels of the current pixel in turn includes the following steps: The eight neighboring pixels of the current pixel are clearly divided according to their orientation relative to the current pixel; the eight neighboring pixels are located in eight directions of the current pixel, namely, up, down, left, right, upper left, upper right, lower left, and lower right; the orientation information of each neighboring pixel is associated with the orientation information of the current pixel; During the tracking process, the direction information of the current pixel is determined by its relative position relationship with the previous pixel; if the previous pixel is located on the left side of the current pixel, the direction information of the current pixel is from left to right, and the direction information is used as the basis for preferentially selecting neighboring pixels; According to the direction information of the current pixel, the direction consistency of the eight neighboring pixels is judged; among the neighboring pixels with consistent direction, the optimal neighboring pixel is further selected as the next tracking point based on its topological characteristics and path continuity.

8. The roll angle measurement method based on the Talber-Mohr effect according to claim 1, characterized in that: The process of calculating the relative roll angle of the two gratings includes the following steps: The inclination angle of the moiré fringes reflects the relative rotation relationship between the two gratings; the geometric parameters of the gratings include the grating period and the grating spacing, which are related to the moiré fringes; the relationship between the inclination angle of the moiré fringes and the relative roll angle of the two gratings is mapped through the geometric parameters of the gratings; the functional relationship between the inclination angle and the roll angle is derived using the diffraction characteristics of the gratings; Based on the Moire fringe inclination angle and the grating geometric parameters, the calculation formula of the roll angle is derived: Where, φ represents the roll angle; d represents the grating period, L represents the grating spacing; θ represents the Moire fringe inclination angle; The geometric parameters of the grating are dynamically corrected through the geometric parameter correction factor of the grating; the calculated roll angle is output for measurement or control.

9. A roll angle measurement system based on Talber-Moire effect, implementing the roll angle measurement method based on Talber-Moire effect as claimed in any one of claims 1 to 8, characterized in that: Include: A signal processing module is used for imaging the moiré fringes onto the phase plane of a CCD camera, the CCD camera converts the optical signal into a digital image signal, and pre-processes the digital image signal to eliminate noise and retain the edge and contour of the moiré fringes; The inclination angle determination module is used for separating the moiré fringes from the background through threshold segmentation of the pre-processed digital image signal, and dividing the pixels in the image into two categories: the fringe area and the non-fringe area; after the threshold segmentation, the moiré fringes are thinned to extract the center line of the fringes; the points of the thinned moiré fringes are fitted into a straight line through straight line fitting to determine the inclination angle of the moiré fringes; The roll angle output module is used to calculate the relative roll angle of the two gratings by combining the Moire fringe inclination angle obtained by straight line fitting with the geometric parameters of the grating, and output the calculated roll angle.

10. A roll angle measurement device based on Talber-Moire effect, implementing the roll angle measurement method based on Talber-Moire effect according to any one of claims 1 to 8, characterized in that: Including: the first light source, the aperture, the first beam splitter prism, the second beam splitter prism, the third beam splitter prism, the objective lens group, the grating reflector, the first CCD lens, the second light source, the self-collimating grating, the second CCD lens, the CCD camera, the lens, the Pism beam splitter, the reflection grid, the Collimati on the grid, the collimator and the expander, and the laser; The first light source is connected to the aperture, and the aperture is connected to the first beam splitter prism; the second beam splitter prism is connected to the first CCD lens and the aperture respectively; the third beam splitter prism and the second CCD lens are connected to the second beam splitter prism respectively; the objective lens group and the autocollimation grating are connected to the third beam splitter prism respectively; the second light source is connected to the autocollimation grating; the grating reflector is connected to the objective lens group; the first light source and the second light source are laser collimators; the light emitted by the laser forms a beam of parallel light through the collimation and expansion system, and the parallel light passes through the collimati on the grating, and a Talbot image is generated at its Talbot distance, the parallel light is reflected by the right-angle beam splitter prism and shines on the reflective grating, and the second grating is placed at the Talbot distance of the first grating, and forms moiré fringes with the Talbot image, and finally the moiré fringes image is received by the CCD camera and transmitted to the computer; when the two gratings generate an angle, the corresponding change of the moiré fringes image can be detected, and the image can be processed and analyzed by the computer to finally obtain the grating angle change, that is, the roll angle change.

Images