Calibration method and device, system and camera device of line structured light measurement system

Abstract

The embodiment of the application provides a calibration method and device of a line structured light measurement system, a measurement system and a line structured light camera device. The calibration method comprises: obtaining input data, which comprises a fringe image formed based on structured light emitted by the line structured light camera device, a distance between the line structured light camera device and a calibration board, and intrinsic parameters of the line structured light camera device; performing first detection of the structured light fringe in the fringe image according to the input data; in response to the result of the first detection being qualified, determining calibration parameters of a structured light plane according to the input data; performing second detection of the structured light fringe according to the calibration parameters of the structured light plane; and in response to the result of the second detection being qualified, outputting the calibration parameters of the structured light plane to obtain an equation of the structured light plane. The calibration method can simply, quickly, accurately and low-costly realize calibration of the line structured light measurement system, reduce the influence of the performance of a structured light projector on the calibration accuracy, and improve the stability of the calibration result.

Description

Technical Field

[0001] This application relates to the field of structured light measurement, and more specifically, to a calibration method for a line structured light measurement system, a calibration device for a line structured light measurement system, a line structured light measurement system, and a line structured light imaging device. Background Technology

[0002] As a non-contact inspection method, line structured light measurement systems have made rapid progress in recent years and are now widely used in 3D reconstruction, 3D measurement, and non-destructive testing. Line structured light measurement systems are characterized by high inspection efficiency, high accuracy, and a large measurement range. Furthermore, the measurement accuracy of this system is directly related to the calibration of the camera device and the optical plane.

[0003] The calibration of a line structured light measurement system aims to obtain the correspondence between image pixels and three-dimensional points in the light plane space. Currently, the commonly used calibration method is line structured light sensor calibration technology based on a freely moving planar target. Specifically, by moving the target position, the equation of the light plane is calculated based on the straight lines of multiple projected light rays. Furthermore, nonlinear optimization methods are needed to obtain the optimal solution of the plane equation. In the above-mentioned commonly used calibration methods, large-area, high-precision targets are difficult to manufacture, and the calibration process is cumbersome, making it unsuitable for mass production calibration of line structured light measurement systems.

[0004] Therefore, how to obtain the plane equation of the structured light plane in the camera module coordinate system simply, quickly, accurately and economically is an urgent problem to be solved. Summary of the Invention

[0005] This application provides a calibration method and calibration device for a line structured light measurement system that can at least partially solve the above-mentioned problems existing in the related art, as well as a line structured light measurement system and a line structured light imaging device.

[0006] This application provides a calibration method for a line structured light measurement system. The calibration method includes: acquiring input data, wherein the input data includes a fringe image formed by structured light emitted from a line structured light camera, the distance between the line structured light camera and a calibration plate, and intrinsic parameters of the line structured light camera; performing a first detection of structured light fringes in the fringe image based on the input data; determining calibration parameters of a structured light plane based on the input data in response to a qualified result of the first detection; performing a second detection of the structured light fringes based on the calibration parameters of the structured light plane; and outputting the calibration parameters of the structured light plane in response to a qualified result of the second detection, thereby obtaining the equation of the structured light plane.

[0007] In one embodiment of this application, the first detection includes: curvature detection, stripe continuity detection, stripe thickness detection, and field of view detection of the structured light stripes.

[0008] In one embodiment of this application, the second detection of the structured light stripes based on the calibration parameters of the structured light plane includes: performing a parallelism detection of the structured light stripes based on the calibration parameters of the structured light plane; and performing a precision detection of the structured light stripes in response to the parallelism detection result being qualified.

[0009] In one embodiment of this application, the second detection of the structured light stripes based on the calibration parameters of the structured light plane further includes: in response to the result of the parallelism detection being unqualified, using the angle control unit of the line structured light measurement system to rotate and adjust the structured light projector of the line structured light imaging device until the result of the parallelism detection is qualified.

[0010] In one embodiment of this application, determining the calibration parameters of the structured light plane based on the input data includes: extracting the structured light stripes and selecting calibration points at N different distances based on the input data to determine the initial calibration parameters of the structured light plane, where N is a positive integer and N > 1; and optimizing the initial calibration parameters of the structured light plane to obtain the calibration parameters of the structured light plane.

[0011] In one embodiment of this application, optimizing the initial calibration parameters of the structured light plane includes: using at least one or a combination of least squares method, genetic algorithm and Bayesian estimation method to optimize the initial calibration parameters of the structured light plane.

[0012] In one embodiment of this application, the structured light stripes include at least one or a combination of: grid stripes, cross stripes, parallel line stripes, and checkerboard stripes.

[0013] In another aspect, this application provides a calibration device for a line structured light measurement system. The calibration device includes: an input unit configured to acquire input data, wherein the input data includes a fringe image formed by structured light emitted from a line structured light camera, a distance between the line structured light camera and a calibration plate, and intrinsic parameters of the line structured light camera; a detection unit configured to perform a first detection of structured light fringes in the fringe image based on the input data; and a calibration unit configured to determine calibration parameters of a structured light plane based on the input data in response to a satisfactory result of the first detection, wherein the detection unit is further configured to perform a second detection of the structured light fringes based on the calibration parameters of the structured light plane; and to output the calibration parameters of the structured light plane in response to a satisfactory result of the second detection, thereby obtaining an equation for the structured light plane.

[0014] In one embodiment of this application, the first detection includes: curvature detection, stripe continuity detection, stripe thickness detection, and field of view detection of the structured light stripes.

[0015] In one embodiment of this application, the detection unit is further configured to: perform parallelism detection of the structured light stripes according to the calibration parameters of the structured light plane; and perform accuracy detection of the structured light stripes in response to the result of the parallelism detection being qualified.

[0016] In one embodiment of this application, the detection unit is further configured to: in response to the result of the parallelism detection being unqualified, use the angle control unit of the line structured light measurement system to rotate and adjust the structured light projector of the line structured light camera device until the result of the parallelism detection is qualified.

[0017] In one embodiment of this application, the calibration unit is further configured to: extract the structured light stripes and select calibration points at N different distances based on the input data, so as to determine the initial calibration parameters of the structured light plane, where N is a positive integer and N>1; and optimize the initial calibration parameters of the structured light plane to obtain the calibration parameters of the structured light plane.

[0018] In one embodiment of this application, the calibration unit is further configured to optimize the initial calibration parameters of the structured light plane using at least one or a combination of least squares method, genetic algorithm and Bayesian estimation method.

[0019] In one embodiment of this application, the structured light stripes include at least one or a combination of: grid stripes, cross stripes, parallel line stripes, and checkerboard stripes.

[0020] In another aspect, this application provides a line structured light measurement system, the system comprising: a line structured light camera, a calibration plate, and a calibration device as described in any of the other aspects of this application.

[0021] This application provides a line structured light camera device, the camera device comprising: a structured light projector and a camera module, wherein the camera device performs a calibration method as described in any one of the claims provided in this application.

[0022] The calibration method, calibration device, and measurement system and device of the line structured light measurement system provided by at least one embodiment of this application can realize the calibration of the line structured light measurement system in a simple, fast, accurate and low-cost manner, reduce the influence of the performance of the structured light projector on the calibration accuracy, and improve the stability of the calibration results. Attached Figure Description

[0023] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings. Wherein:

[0024] Figure 1 This is a flowchart of a calibration method for a line structured light measurement system according to one embodiment of this application;

[0025] Figure 2A This is a schematic diagram of a line structured light measurement system according to one embodiment of this application;

[0026] Figure 2B This is a partial top view schematic diagram of a line structured light measurement system according to one embodiment of this application;

[0027] Figure 2C This is a partial schematic diagram of a line structured light measurement system according to one embodiment of this application;

[0028] Figure 2D This is a partial schematic diagram of a line structured light measurement system according to one embodiment of this application;

[0029] Figure 3 This is a schematic diagram of structured light stripes according to some embodiments of this application;

[0030] Figure 4 This is a schematic diagram of a calibration device for a line structured light measurement system according to one embodiment of this application;

[0031] Figure 5A This is a perspective view of a line structured light imaging device according to one embodiment of this application; and

[0032] Figure 5B This is a perspective view of a line structured light imaging device according to another embodiment of this application. Detailed Implementation

[0033] To better understand this application, various aspects of this application will be described in more detail with reference to the accompanying drawings. It should be understood that these detailed descriptions are merely illustrative of exemplary embodiments of this application and are not intended to limit the scope of this application in any way. Throughout the specification, the same reference numerals refer to the same elements. The expression "and / or" includes any and all combinations of one or more of the associated listed items.

[0034] It should be noted that in this specification, the terms "first," "second," "third," etc., are used only to distinguish one feature from another and do not imply any limitation on the features, especially not any order of precedence.

[0035] In the accompanying drawings, the thickness, dimensions, and shapes of the parts have been slightly adjusted for ease of illustration. The drawings are for illustrative purposes only and are not drawn to scale. As used herein, the terms “approximately,” “about,” and similar terms are used as expressions of approximation, not as expressions of degree, and are intended to illustrate inherent deviations in measured or calculated values ​​that will be recognized by one of ordinary skill in the art.

[0036] It should also be understood that expressions such as "comprising," "including," "having," "containing," and / or "comprising" are open-ended rather than closed-ended expressions in this specification, indicating the presence of the stated features, elements, and / or components, but not excluding the presence of one or more other features, elements, components, and / or combinations thereof. Furthermore, when expressions such as "at least one of..." appear after a list of listed features, they modify the entire list of features, not just individual elements in the list. Additionally, when describing embodiments of this application, the word "may" is used to mean "one or more embodiments of this application." And the term "exemplary" is intended to refer to examples or illustrations.

[0037] Unless otherwise specified, all terms used herein (including engineering and technical terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. It should also be understood that, unless expressly stated herein, terms defined in common dictionaries shall be interpreted as having the meaning consistent with their meaning in the context of the relevant art, and not as having an idealized or overly formalized meaning.

[0038] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. Furthermore, unless explicitly limited or contradicted by the context, the specific steps included in the methods described in this application are not limited to the order in which they are described, but can be performed in any order or in parallel. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0039] Furthermore, when the term "connection" or "linkage" is used in this application, it may indicate direct or indirect contact between the corresponding components, unless otherwise expressly defined or deduced from the context.

[0040] Figure 1 This is a flowchart of a calibration method 1000 for a line structured light measurement system according to one embodiment of this application. Figure 1 As shown, this application provides a calibration method 1000 for a line structured light measurement system, comprising:

[0041] S1, acquire input data, which includes a stripe image formed by structured light emitted by the line structured light camera, the distance between the line structured light camera and the calibration plate, and the intrinsic parameters of the line structured light camera.

[0042] S2, based on the input data, performs the first detection of structured light stripes in the stripe image.

[0043] S3, in response to the qualified result of the first test, determines the calibration parameters of the structured light plane based on the input data.

[0044] S4. Based on the calibration parameters of the structured light plane, perform the second detection of structured light fringes.

[0045] S5, in response to the passing result of the second detection, outputs the calibration parameters of the structured light plane to obtain the equation of the structured light plane.

[0046] The calibration of a line structured light measurement system aims to obtain the correspondence between image pixels and three-dimensional points in the light plane space. Currently, the commonly used calibration method is line structured light sensor calibration technology based on a freely moving planar target. Specifically, by moving the target position, the equation of the light plane is calculated based on the straight lines of multiple projected light rays. Furthermore, nonlinear optimization methods are needed to obtain the optimal solution of the plane equation. In the above-mentioned commonly used calibration methods, large-area, high-precision targets are difficult to manufacture, and the calibration process is cumbersome, making it unsuitable for mass production calibration of line structured light measurement systems.

[0047] To avoid the aforementioned problems, this application proposes a calibration method for a line structured light measurement system. This method enables the calibration of the line structured light measurement system simply, quickly, accurately, and at low cost, reducing the impact of structured light projector performance on calibration accuracy and improving the stability of calibration results. Specifically, the calibration method 1000 for the line structured light measurement system described above will be explained in detail below with reference to the accompanying drawings.

[0048] Step S1: Acquire input data, wherein the input data includes structured light emitted by the line structured light camera device. The resulting striped image, the distance between the line structured light camera and the calibration plate, and the internal parameters of the line structured light camera.

[0049] Figure 2AThis is a schematic diagram of a line structured light measurement system 2000 according to one embodiment of this application. Figure 2B This is a partial top view of a line structured light measurement system 2000 according to one embodiment of this application. Figure 2C This is a partial schematic diagram of a line structured light measurement system 2000 according to one embodiment of this application. Figure 2D This is a partial schematic diagram of a line structured light measurement system 2000 according to one embodiment of this application.

[0050] refer to Figures 1 to 2D In one embodiment of this application, the line structured light measurement system 2000 may include a line structured light camera 2001, a calibration plate 2400, and a ranging unit 2300. Optionally, the line structured light camera 2001 may include a structured light projector 2200 and a camera module 2100. Furthermore, the ranging unit 2300 may include, for example, a lifting platform with a scale (such as...). Figure 2A The distance measuring unit 2300 shown) or a graduated guide rail (such as...) Figure 2C The ranging unit 2300 is shown. A calibration plate 2400, used as a target, is mounted on the ranging unit 2300. The structured light projector 2200 is adjusted so that the structured light is projected onto the patterned area (not shown) of the calibration plate 2400, for example, in the middle area of ​​the calibration plate 2400, thereby obtaining better image quality and improving calibration accuracy. While keeping the relative positions of the various parts in the line structured light measurement system 2000 fixed, input data can be collected. This input data includes the structured light stripe image of the calibration plate 2400 at its current height position, the distance between the line structured light camera 2001 and the calibration plate 2400, and the internal parameters of the line structured light camera 2001, etc.

[0051] Specifically, the structured light projector 2200 can be used to project line structured light, and may include a light source and an optical system for adjusting the light pattern. The camera module 2100 may include an optical lens for imaging. Optionally, the camera module 2100 of the line structured light measurement system 2000 may be an infrared camera module capable of infrared imaging.

[0052] like Figures 2B to 2D As shown, in one embodiment of this application, the distance between the line structured light camera device 2001 and the calibration plate 2400 can be understood as follows: taking the camera module coordinate system XYZ of the camera module 2100 as the reference coordinate system, the ranging device 2300 measures the distance between the front surface of the lens (not shown) of the camera module 2100 and the calibration plate 2400. The camera module coordinate system XYZ can be set using a right-hand rule, with the optical center O of the lens of the camera module 2100 as the origin, the front of the lens as the Z-axis, and the right side of the lens as the X-axis. Optionally, as... Figure 2CAs shown, the structured light projector 2200 can be set parallel to the calibration plate 2400 so that the structured light emitted by the structured light projector 2200 can be projected approximately perpendicularly onto the pattern area of ​​the calibration plate 2400.

[0053] The intrinsic parameters of the line structured light imaging device 2001 may include at least the focal length, principal point position, and pixel size of the imaging module 2100. For example, as an option, the intrinsic parameters of the line structured light imaging device 2001 may include the focal length f of the imaging module 2100, the principal point coordinates (u0, v0), and the physical size of each pixel. Alternatively, the intrinsic parameters of the line structured light imaging device 2001 may also include parameters such as the intrinsic parameter matrix of the imaging module 2100, radial distortion parameters, and tangential distortion parameters, wherein the geometric relationship between the imaging module coordinate system and the image coordinate system can be determined based on the intrinsic parameter matrix, radial distortion parameters, and tangential distortion parameters of the imaging module 2100.

[0054] Optionally, before collecting input data, the calibration board 2400 should be within the working distance range designed by the structured light projector 2200. The energy output of the structured light projector 2200 should be adjusted appropriately to make the structured light stripe image as obvious as possible while ensuring the characteristic quality of the structured light (for example, the finer the linewidth of the line structured light, the better).

[0055] Figure 3 This is a schematic diagram of structured light stripes according to some embodiments of this application.

[0056] like Figure 3 As shown, in some embodiments of this application, the structured light stripes may include at least one or a combination of, for example, grid stripes, cross stripes, parallel line stripes, and checkerboard stripes, and this application does not limit them.

[0057] Step S2 involves the first detection of structured light stripes in the stripe image based on the input data.

[0058] Refer again Figure 1 and Figure 2A In one embodiment of this application, the first detection may include curvature detection, stripe continuity detection, stripe thickness detection, and field of view (FOV) detection of the structured light stripes. Based on the input data, the curvature detection, continuity detection, stripe thickness detection, and FOV detection of the structured light projector stripes are performed respectively. If any of the above items fails, the subsequent calibration steps are not performed.

[0059] Specifically, in stripe thickness detection, as an option, structured light can be projected approximately perpendicularly onto the calibration plate 2400, and a structured light stripe image can be obtained through the camera module 2100. This image, combined with the intrinsic parameters of the camera module 2100, can determine the pixels belonging to each stripe. The pixel coordinates of the stripe center can then be determined using methods such as the grayscale centroid method. Based on this, the stripe thickness can be further determined; in other words, the stripe width can be defined as several pixels extending from the stripe center's pixel coordinates to both sides of the stripe's edge.

[0060] Furthermore, when the calibration plate 2400 is placed perpendicular to the path of the structured light, the edge of the structured light beam is slightly further from the center of the beam before reaching the calibration plate 2400. Therefore, because the structured light beam diverges at this additional distance, the stripe width at the edge will be slightly larger than at the center. Optionally, the average width at different locations of each stripe can be compared with the design value for that stripe width to confirm whether the stripe thickness detection is satisfactory.

[0061] In addition, stripe continuity detection can be determined by observing the continuity of each stripe in the structured light stripe image. For example, if it is determined that the number of missing pixels in the extension direction of each stripe is less than a predetermined value, the stripe continuity can be considered qualified.

[0062] Alternatively, in stripe curvature detection, the pixel coordinates of each stripe's pixel and the stripe center can be determined using the method described above. A fitted straight line is then fitted to the stripe using the pixel coordinates of the stripe center. The offset error between each pixel and the fitted straight line is determined, and the validity of the stripe curvature detection is judged by comparing this offset error with a pre-set error threshold. If the offset error is greater than or equal to the pre-set error threshold, the stripe curvature detection is considered unqualified; conversely, if the offset error is less than the pre-set error threshold, the stripe curvature detection is considered qualified.

[0063] Alternatively, in the field of view detection of structured light stripes, the field of view of the structured light stripes can be determined by a simple formula using the structured light stripe image, the intrinsic parameters of the camera module 2100, and the distance between the camera module 2100 and the calibration plate 2400. If the field of view detection of the structured light stripes meets the design value, the field of view detection of the structured light stripes is deemed qualified.

[0064] However, those skilled in the art should understand that any suitable method can be used to perform the first detection of structured light fringes, including curvature detection, fringe continuity detection, fringe thickness detection, and field of view detection, thereby obtaining the beneficial effects described in this application.

[0065] For a structured light projector 2200 of a specific model, the light stripes on the calibration plate 2400 are relatively fixed in the image of the camera module 2100 at the same distance. By detecting the curvature, continuity, and consistency of the stripes, defective products with curved light planes or uneven laser energy distribution can be screened out. By detecting the field of view of the light stripes, it can be determined whether the structured light projector is suitable for the application scenario.

[0066] Step S3, in response to the passing result of the first detection, determines the calibration parameters of the structured light plane based on the input data.

[0067] Refer again Figure 1 , Figure 2A and Figure 2D In one embodiment of this application, in response to the qualified result of the first detection in step S2, the structured light stripe 01-1 can be extracted and the calibration point P can be selected at N different distances according to the above input data, so as to determine the initial calibration parameters of the structured light plane 01. The structured light plane 01 can be understood as the plane determined by the light path of the line structured light projected onto the calibration plate 2400. N is a positive integer and N>1.

[0068] Optionally, the structured light stripe 01-1 can be extracted and the calibration point P selected at at least three different distances to determine the initial calibration parameters of the structured light plane 01. The three different distances are three different distances between the line structured light camera device 2001 and the calibration plate 2400.

[0069] Specifically, the calibration plate 2400 can be raised or lowered at certain intervals H on the lifting platform (distance measuring unit 2300), and each height position can be recorded as position information for each measurement. Structured light fringe images at each height position are then acquired to extract structured light fringe 01-1 and select calibration point P. Furthermore, in some embodiments, the position of the calibration plate 2400 can be kept fixed, while the distance between the line structured light camera 2001 and the calibration plate 2400 can be adjusted. The relative measurement position information between the line structured light camera 2001 and the calibration plate 2400 is recorded, and structured light fringe images at different relative measurement positions are acquired. Alternatively, the positions of both the calibration plate 2400 and the line structured light camera 2001 can be set to be variable; this application does not limit this.

[0070] The initial calibration parameters of the structured light plane 01 can be determined by conventional methods, which will not be elaborated upon in this application.

[0071] In one embodiment of this application, it is assumed that the calibration parameters of the structured light plane 01 are a, b, c, and d, and satisfy the following formula (1):

[0072] The distance at the i-th distance is Z iStructured light fringe 01-1 is extracted at calibration point P, and the observed value (X) is obtained according to formula (1). i Y i Z i ),

[0073]

[0074]

[0075] Where f is the focal length of the lens of camera module 2100; u0 and v0 are the coordinates of the principal point of camera module 2100, respectively; d x d y These are the physical dimensions of the pixel in the horizontal and vertical directions, respectively; and u i v i These are the pixel coordinates of the selected calibration point P.

[0076] Substituting equation (1) into the structured light plane equation, we obtain equation (2).

[0077] aX i +bY i +cZ i +d=0 (2)

[0078] Where a, b, c, and d are the initial calibration parameters of the structured light plane 01; and (X i Y i Z i ) is the i-th distance Z i The observed values ​​of the calibration point P.

[0079] By combining the data from each calibration point and minimizing the residuals from the calibration points to the structured light plane, the initial calibration parameters of the structured light plane can be obtained.

[0080] Optionally, after obtaining the initial calibration parameters of the structured light plane, they can be optimized to obtain the final calibration parameters of the structured light plane.

[0081] Alternatively, weighting coefficients for structured light fringe images at multiple different distances can be determined based on, for example, actual results, and the initial calibration parameters of the structured light plane can be optimized based on these weighting coefficients. Furthermore, the initial calibration parameters of the structured light plane can be further optimized using at least one or a combination of least squares method, genetic algorithm, and Bayesian estimation to obtain the calibration parameters of the structured light plane. However, those skilled in the art should understand that different optimization schemes can be used to optimize the initial calibration parameters of the structured light plane based on actual results, and this application does not limit this approach.

[0082] Step S4 involves a second detection of the structured light fringes based on the calibration parameters of the structured light plane.

[0083] Refer again Figures 1 to 2D To verify the accuracy of the calibration parameters of the light plane equation and to avoid abnormal phenomena caused by incorrect calibration operations, the calibration parameters obtained in step S3 need to be verified. Theoretically, the stripes intersecting the structured light plane 01 and the calibration plate 2400 should be parallel at different distances. When the parallelism is unqualified, the structured light projector 2200 can be rotated and adjusted using the angle control unit (not shown) of the line structured light measurement system 2000 until the parallelism detection result of the structured light is qualified. In response to the qualified result of the structured light parallelism detection, the accuracy of the structured light stripes can be tested. Through the parallelism adjustment verification and accuracy verification of the structured light stripes, the required structured light plane calibration parameters can be output.

[0084] Specifically, in one embodiment of this application, the second detection of structured light stripes based on the calibration parameters of the structured light plane may include: performing parallelism detection of structured light stripe 01-1 based on the calibration parameters of the structured light plane 01; and performing accuracy detection of structured light stripe 01-1 in response to the parallelism detection result being qualified.

[0085] In the parallelism detection of structured light stripes, the imaging slopes of the intersecting lines of the structured light plane 01 and the calibration plate 2400 in the camera module 2100 can be compared at different distances, where the distance is the distance between the line structured light imaging device 2001 and the calibration plate 2400. If the slope difference is less than a preset slope threshold, the parallelism of the structured light stripe 01-1 is judged to be good; conversely, if the slope difference is greater than or equal to the preset slope threshold, the parallelism detection structure of the structured light stripe 01-1 is judged to be unqualified.

[0086] Furthermore, as an alternative, in response to a non-compliance result in the parallelism test of the structured light stripes, the real-time offset angle of structured light stripe 01-1 can be measured, and a signal can be output from the angle control unit of the line structured light measurement system 2000 to control the angle rotation unit (not shown) of the line structured light measurement system 2000 to compensate for the corresponding offset angle. Alternatively, the angle rotation unit can be fixed to the structured light projector 2200, and the angle can be adjusted using, for example, a stepper motor (not shown).

[0087] In the accuracy testing of structured light stripes, the ranging accuracy of the line structured light camera 2001 at different distances can be statistically analyzed, where the distance is the distance between the line structured light camera 2001 and the calibration plate 2400. If the ranging accuracy is less than a preset accuracy threshold, the accuracy test result of structured light stripe 01-1 is considered good; conversely, if the ranging accuracy is greater than or equal to the preset accuracy threshold, the accuracy test result of structured light stripe 01-1 is considered unqualified.

[0088] If the structured light fringe accuracy test is satisfactory, the calibration parameters of the structured light plane can be output. If the structured light fringe accuracy test is unsatisfactory, the above steps are repeated to recalibrate the structured light plane. In other words, the second test can include the parallelism test and the accuracy test of the structured light fringe. After the parallelism test of the structured light fringe is satisfactory, the accuracy test of the structured light fringe can be performed. If the accuracy test of the structured light fringe is also satisfactory, the calibration parameters of the structured light plane determined in the above steps can be confirmed as accurate and can be used to obtain the equation of the structured light plane. Conversely, if the second test is unsatisfactory, the above steps need to be repeated to recalibrate the parameters of the structured light plane until the second test is satisfactory.

[0089] Step S5, in response to the passing result of the second detection, outputs the calibration parameters of the structured light plane to obtain the structured light. Equations of the plane

[0090] Refer again Figure 1 and Figure 2A In one embodiment of this application, if the calibration parameters of the structured light plane are accurate, the equation of the structured light plane can be obtained by conventional methods.

[0091] Therefore, the calibration method provided in any embodiment of this application does not require expensive auxiliary equipment or the solution of any transformation matrix between coordinate systems. It can achieve the calibration of the line structured light measurement system in a simple, fast, accurate and low-cost manner, reduce the impact of the structured light projector performance on the calibration accuracy and improve the stability of the calibration results.

[0092] Figure 4 This is a schematic diagram of a calibration device 4000 for a line structured light measurement system according to one embodiment of this application. Figure 4 As shown, another aspect of this application provides a calibration device 4000 for a line structured light measurement system. The calibration device 4000 includes an input unit 100, a detection unit 200, and a calibration unit 300. The input unit 100 is configured to acquire input data, including a structured light fringe image, the distance between the line structured light camera and the calibration plate, and the intrinsic parameters of the line structured light camera. The detection unit 200 is configured to perform a first detection of structured light fringes based on the input data. The calibration unit 300 is configured to determine calibration parameters of the structured light plane based on the input data in response to a satisfactory result from the first detection. The detection unit 200 is further configured to perform a second detection of structured light fringes based on the calibration parameters of the structured light plane; and to output the calibration parameters of the structured light plane in response to a satisfactory result from the second detection, thereby obtaining the equation of the structured light plane.

[0093] In one embodiment of this application, the first detection may include curvature detection of structured light stripes, stripe continuity detection, stripe thickness detection, and field of view detection.

[0094] Furthermore, the detection unit 200 is further configured to perform parallelism detection of structured light stripes based on the calibration parameters of the structured light plane; and to perform accuracy detection of structured light stripes in response to the qualified result of the parallelism detection of structured light stripes.

[0095] Optionally, the detection unit 200 is further configured to, in response to a failure in the parallelism detection of the structured light stripes, use the angle control unit of the line structured light measurement system to rotate and adjust the structured light projector of the line structured light camera device until the parallelism detection result of the structured light stripes is acceptable.

[0096] Alternatively, the calibration unit 300 is further configured to extract structured light stripes and select calibration points at N different distances based on the input data to determine the initial calibration parameters of the structured light plane; and to optimize the initial calibration parameters of the structured light plane to obtain the calibration parameters of the structured light plane, where N is a positive integer and N > 1.

[0097] Optionally, structured light stripes can be extracted and calibration points selected at at least three different distances to determine the initial calibration parameters of the structured light plane. The three different distances can be understood as three different distances between the line structured light camera and the calibration plate.

[0098] Furthermore, in one embodiment of this application, the calibration unit 300 is further configured to optimize the initial calibration parameters of the structured light plane using at least one or a combination of least squares method, genetic algorithm and Bayesian estimation method.

[0099] Furthermore, in one embodiment of this application, the line structured light imaging device may include a structured light projector and an infrared camera module capable of infrared imaging.

[0100] Optionally, the structured light stripes may include at least one or a combination of: grid stripes, cross stripes, parallel line stripes, and checkerboard stripes.

[0101] Therefore, the calibration device provided in any embodiment of this application can perform simple, fast, accurate and low-cost calibration of the line structured light measurement system without the need for expensive auxiliary equipment or solving any transformation matrix between coordinate systems. This reduces the impact of the structured light projector performance on the calibration accuracy of the measurement system and improves the stability of the calibration results of the measurement system.

[0102] refer to Figures 2A to 2D ,as well as Figure 4 In another aspect, this application also provides a line structured light measurement system 2000, which may include a line structured light camera device 2001, a calibration plate 2400, and a calibration device 4000 as described in any of the embodiments above.

[0103] Specifically, the line structured light imaging device 2001 may include a structured light projector 2200 and an imaging module 2100. The structured light projector 2200 can be used to project line structured light and includes a light source and an optical system for adjusting the light pattern.

[0104] Alternatively, the camera module 2100 can be an infrared camera module capable of infrared imaging. Furthermore, the line structured light measurement system 2000 may also include a ranging unit 2300, for example, a graduated lifting platform or a graduated guide rail. A calibration plate 2400, used as a target, is mounted on the ranging unit 2300, and the structured light projector 2200 is adjusted so that the structured light is projected onto a patterned area of ​​the calibration plate 2400, for example, in the central area of ​​the calibration plate 2400, to obtain better image quality and improve calibration accuracy.

[0105] In addition, the line structured light measurement system 2000 also includes the calibration device 4000 described in any of the embodiments above, so that the line structured light measurement system 2000 can perform self-calibration simply, quickly, accurately and at low cost without the need for expensive auxiliary equipment or solving any transformation matrix between coordinate systems, thereby reducing the impact of the structured light projector performance on its calibration accuracy and improving the stability of its self-calibration results.

[0106] Figure 5A This is a three-dimensional structural schematic diagram of a line structured light imaging device 2001 according to one embodiment of this application. Figure 5B This is a perspective view of a line structured light camera device 2001 according to another embodiment of this application.

[0107] refer to Figure 5A and Figure 5B In another aspect, this application also provides a line structured light imaging device 2001, which may include a structured light projector 2200 and an imaging module 2100. The line structured light measurement device 2001 can perform the calibration method 1000 described in any of the embodiments above.

[0108] Specifically, the structured light projector 2200 can be used to project line structured light and includes a light source and an optical system for adjusting the light pattern. Alternatively, such as Figure 5AAs shown, the line structured light projector 2200 and the camera module 2100 can be arranged opposite each other; alternatively, the line structured light camera device 2001 may include two structured light projectors 2200, such as a first structured light projector 2200-1 and a second structured light projector 2200-2. However, those skilled in the art should understand that this application does not limit the number of structured light projectors, or the arrangement (e.g., relative position, angle, etc.) of the line structured light projectors and the camera module.

[0109] Alternatively, camera module 2100 can be an infrared camera module capable of infrared shooting.

[0110] The line structured light camera device provided in any embodiment of this application can perform calibration of the line structured light measurement system simply, quickly, accurately and at low cost without the need for expensive auxiliary equipment or solving any transformation matrix between coordinate systems. This reduces the impact of the structured light projector performance on the calibration accuracy of the line structured light measurement system and improves the stability of the calibration results of the line structured light measurement system.

[0111] The above description is merely an illustration of the embodiments of this application and the technical principles employed. Those skilled in the art should understand that the scope of protection involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the technical concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A calibration method for a line structured light measurement system, characterized in that, The calibration method includes: Acquire input data, wherein the input data includes a stripe image formed by structured light emitted by the line structured light camera, the distance between the line structured light camera and the calibration plate, and the intrinsic parameters of the line structured light camera; Based on the input data, a first detection of structured light stripes in the stripe image is performed, wherein the first detection includes curvature detection, stripe continuity detection, stripe thickness detection, and field of view detection of the structured light stripes; If the result of the first detection is qualified, the calibration parameters of the structured light plane are determined based on the input data; Based on the calibration parameters of the structured light plane, a second detection of the structured light stripes is performed, wherein the second detection includes parallelism detection and accuracy detection of the structured light stripes; and If the result of the second detection is qualified, the calibration parameters of the structured light plane are output to obtain the equation of the structured light plane.

2. The calibration method according to claim 1, wherein, The second detection of the structured light stripes, based on the calibration parameters of the structured light plane, includes: Based on the calibration parameters of the structured light plane, the parallelism of the structured light fringes is detected; and If the parallelism test result is satisfactory, the accuracy test of the structured light stripes is performed.

3. The calibration method according to claim 2, wherein, The second detection of the structured light stripes, based on the calibration parameters of the structured light plane, further includes: In response to the parallelism test result being unqualified, the structure light projector of the line structure light camera device is rotated and adjusted using the angle control unit of the line structure light measurement system until the parallelism test result is qualified.

4. The calibration method according to claim 1, wherein, Based on the input data, the calibration parameters of the structured light plane are determined as follows: Based on the input data, at N different distances, the structured light stripes are extracted and calibration points are selected to determine the initial calibration parameters of the structured light plane, where N is a positive integer and N > 1; and The initial calibration parameters of the structured light plane are optimized to obtain the calibration parameters of the structured light plane.

5. The calibration method according to claim 4, wherein, Optimizing the initial calibration parameters of the structured light plane includes: The initial calibration parameters of the structured light plane are optimized by using at least one or a combination of least squares method, genetic algorithm and Bayesian estimation method.

6. The calibration method according to claim 1, wherein, The structured light stripes include: At least one or a combination of the following: grid stripes, cross stripes, parallel stripes, and checkerboard stripes.

7. A calibration device for a line structured light measurement system, characterized in that, The calibration device includes: The input unit is configured to acquire input data, wherein the input data includes a stripe image formed based on structured light emitted by the line structured light camera, the distance between the line structured light camera and the calibration plate, and the intrinsic parameters of the line structured light camera. The detection unit is configured to perform a first detection of structured light fringes based on the input data, wherein the first detection includes curvature detection, fringe continuity detection, fringe thickness detection, and field of view detection of the structured light fringes; and The calibration unit is configured to determine calibration parameters of the structured light plane based on the input data in response to a pass / fail result of the first detection. The detection unit is further configured to perform a second detection of the structured light stripes based on the calibration parameters of the structured light plane, wherein the second detection includes parallelism detection and accuracy detection of the structured light stripes; and in response to the qualified result of the second detection, output the calibration parameters of the structured light plane to obtain the equation of the structured light plane.

8. The calibration device according to claim 7, wherein, The detection unit is further configured as follows: Based on the calibration parameters of the structured light plane, the parallelism of the structured light fringes is detected; and If the parallelism test result is satisfactory, the accuracy test of the structured light stripes is performed.

9. The calibration device according to claim 8, wherein, The detection unit is further configured as follows: In response to the parallelism test result being unqualified, the structure light projector of the line structure light camera device is rotated and adjusted using the angle control unit of the line structure light measurement system until the parallelism test result is qualified.

10. The calibration apparatus according to claim 7, wherein, The calibration unit is further configured as follows: Based on the input data, the structured light stripes are extracted and calibration points are selected at N different distances to determine the initial calibration parameters of the structured light plane, where N is a positive integer and N > 1; as well as The initial calibration parameters of the structured light plane are optimized to obtain the calibration parameters of the structured light plane.

11. The calibration apparatus according to claim 10, wherein, The calibration unit is further configured as follows: The initial calibration parameters of the structured light plane are optimized by using at least one or a combination of least squares method, genetic algorithm and Bayesian estimation method.

12. The calibration device according to claim 7, wherein, The structured light stripes include: At least one or a combination of the following: grid stripes, cross stripes, parallel stripes, and checkerboard stripes.

13. A line structured light measurement system, characterized in that, The measurement system includes: Line structured light imaging device, calibration plate, and calibration device according to any one of claims 7 to 12.

14. A line structured light imaging device, characterized in that, The camera device includes: Structured light projector and camera module, The camera device performs the calibration method according to any one of claims 1 to 6.

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