A rapid repositioning deflection measurement method and system based on guide rail motion calibration

Abstract

The application discloses a kind of fast repositioning deflection measurement methods and systems based on guide rail motion calibration.The system camera, imaging lens and display screen are fixed as pre-calibration module and installed on guide rail, and can be adjusted light path according to the curvature, aperture or measurement distance of measured element.Offline calibration, guide rail is moved to multiple positions, and the coordinates of target mark on the module under the element platform coordinate system are obtained using external space measurement equipment, and then the pose of each position module is solved, and the mapping model of guide rail position parameters and module pose is established.In actual measurement, the measured element is placed according to the platform reference, and after the module moves to the target position, only the current guide rail parameters need to be read, and the pose relationship between the camera, display screen and element can be restored according to the mapping model, and the deflection measurement is completed.The application does not need to repeat the pose of external measurement system after adjusting the light path, and significantly improves the repositioning efficiency and operation convenience of element measurement under different curvature, aperture or measurement distance.

Description

Technical Field

[0001] This invention belongs to the field of optical precision measurement technology, specifically relating to a rapid repositioning deflection measurement method and system based on guide rail motion calibration. It is particularly suitable for deflection measurement scenarios of optical components with different curvatures, different apertures, or different measurement distances. After the pre-calibrated deflection measurement module, composed of a camera, imaging lens, and display screen, adjusts the measurement optical path along the guide rail mechanism, it can quickly restore the pose relationship of the measurement module relative to the component platform coordinate system based on the guide rail position parameters. This avoids repeated external space pose measurements and quickly completes the measurement of the surface normal vector, gradient, or surface shape of the component under test. Background Technology

[0002] Phase deflection measurement is an optical surface shape detection method for reflective or specular devices under test (DUTs). This method typically utilizes a display screen to show stripes, coded patterns, or other structured light patterns. These patterns are reflected from the surface of the DUT and captured by a camera. By establishing the reflection geometry between camera pixels, display screen pixels, and points on the DUT surface, the normal vector, gradient, or surface shape of the DUT surface can be calculated. Since deflection measurement depends on the spatial geometry between the camera, display screen, and DUT, the pose relationship between the camera ray model, the spatial position of the display screen, and the coordinates of the DUT directly affects the accuracy of the measurement results.

[0003] In actual measurements, the curvature, aperture, reflection angle range, and measurement distance of different components under test (DUTs) often vary. If the relative positions of the camera, display screen, and DUT remain fixed, problems such as insufficient field of view coverage, unsuitable reflected light path, insufficient display screen stripe coverage, or limited effective measurement area may occur. Therefore, deflection measurement systems often need to adjust the measurement light path according to the geometric characteristics of the DUT and measurement requirements, such as changing the positions of the camera and display screen relative to the DUT, to obtain a suitable imaging field of view, reflection angle, and stripe coverage.

[0004] However, once the measurement optical path is adjusted, the original spatial pose relationship between the camera, display screen, and the component under test will also change. To ensure the geometric calculation accuracy of the deflection measurement, it is usually necessary to redetermine the pose relationship between the camera, display screen, and the component under test or component platform. In existing methods, key points or reference structures are often remeasured using laser trackers, coordinate measuring machines, photogrammetry equipment, or other external spatial measurement equipment to restore the adjusted system pose. This process is complex, time-consuming, and may need to be repeated every time the component type is changed, the working distance is adjusted, or the measurement optical path is changed, which is not conducive to the rapid switching measurement of multiple component specifications.

[0005] Furthermore, even if the camera and display are mounted on a guide rail, motorized slide, or other motion mechanism, the guide rail position command value, encoder reading, or motor pulse count can usually only represent the nominal position of the motion mechanism and cannot directly reflect the actual spatial pose between the camera, display, and component platform. Due to factors such as guide rail installation errors, motion direction deviations, assembly errors, and installation deviations of measuring components, relying solely on the nominal position of the motion mechanism is insufficient to meet the accuracy requirements of deflection measurement for spatial geometric relationships.

[0006] Therefore, a rapid repositioning method suitable for deflection measurement systems is still needed, so that after the camera and display screen adjust the measurement optical path according to different components under test, they can efficiently and accurately restore the spatial pose relationship between themselves and the components under test or component platform, reduce the dependence on repeated measurements by external spatial measurement equipment, and thus meet the needs of rapid and convenient deflection measurement under different curvatures, different apertures or different measurement distances. Summary of the Invention

[0007] To address the problem that existing deflection measurement systems require repeated adjustments to the measurement optical path based on the curvature, diameter, or measurement distance of the component under test, necessitating the use of laser trackers, coordinate measuring machines, photogrammetry equipment, or other external spatial measurement devices to re-determine the spatial pose relationship between the camera, display screen, and the component under test or component platform. This results in complex operations, long processing times, and hinders rapid switching between measurements of multiple component specifications. Therefore, this invention provides a rapid repositioning deflection measurement method and system based on guide rail motion calibration.

[0008] The technical problem this invention aims to solve is that deflection measurement relies on the accurate spatial relationship between camera spatial rays, display screen pixel spatial coordinates, and the geometric information of the component under test. When the measurement component, consisting of the camera, imaging lens, and display screen, is adjusted along the guide rail, the original measurement pose relationship changes accordingly. If the system pose is remeasured using external spatial measurement equipment after each adjustment, it increases the on-site operation steps and measurement preparation time. Furthermore, guide rail position command values, encoder readings, or motor pulse counts typically only characterize the nominal position of the guide rail mechanism and cannot directly reflect the actual spatial pose of the deflection measurement module relative to the component platform coordinate system. Therefore, a calibration method is needed to correlate guide rail position parameters with the actual rigid body pose of the deflection measurement module, enabling the rapid restoration of the spatial geometric relationship required for deflection measurement after the measurement optical path is adjusted.

[0009] The technical solution of the present invention is as follows:

[0010] A rapid repositioning deflection measurement method based on guide rail motion calibration includes the following steps:

[0011] S1, establish a pre-calibrated deflection measurement module, the module including a rigidly fixed camera, imaging lens, display screen and at least three non-collinear targets; obtain the camera spatial ray model, display screen pixel spatial coordinates and target coordinates in the module coordinate system {U} through pre-calibration;

[0012] S2, Establish the component platform coordinate system {W}, which is determined by the fixed measurement reference structure on the component platform;

[0013] S3, the pre-calibrated deflection measurement module is installed on the guide rail mechanism so that it can move along the guide rail. The guide rail mechanism has guide rail position parameters for characterizing the movement position of the module.

[0014] S4, offline calibration stage: move the guide rail mechanism to the position corresponding to multiple guide rail position parameters, and use external space measurement equipment to measure the coordinates of the target in the component platform coordinate system {W}.

[0015] S5. Based on the known coordinates of the target in the module coordinate system {U} and its measured coordinates in the coordinate system {W} under each guide rail position parameter, the rigid body pose of the module relative to the coordinate system {W} at each position is obtained, and a mapping model between the guide rail position parameters and the rigid body pose is established.

[0016] S6. During actual measurement, the component under test is placed on the component platform so that there is a predetermined pose relationship between the component under test and the component platform coordinate system {W}; according to the measurement requirements, the module is moved to the target guide rail position, the current guide rail position parameters are read, and the current rigid body pose of the module relative to the coordinate system {W} is restored according to the mapping model.

[0017] S7, based on the recovered current rigid body pose, transforms the camera space ray model and the display screen pixel space coordinates from the module coordinate system {U} to the component platform coordinate system {W}, and completes the deflection measurement by combining the geometric information of the component under test.

[0018] Furthermore, in step S1, the target is a spherical reflective target, a corner cone reflector, a coded marker point, or other marker structure whose spatial coordinates can be obtained through external space measurement equipment.

[0019] Further, in step S2, the component platform coordinate system {W} is established by measuring the fixed measurement reference structure on the component platform through an external space measurement device. The fixed measurement reference structure includes one or more of the following: positioning reference, positioning hole, positioning pin, reference surface, target ball seat, reference ball, or reference block.

[0020] Furthermore, the guide rail position parameters include the control panel set position, the control software input position, the motion controller target position, the servo command position, the motor pulse count, the encoder reading, or the grating ruler reading. The external space measuring device is a laser tracker, a coordinate measuring machine, a photogrammetric measuring machine, or an articulated arm measuring machine.

[0021] Further, in step S5, the rigid body pose is obtained through point set rigid body registration. Specifically, for the k-th guide rail position parameter, it is determined based on the known coordinates of the target in the module coordinate system {U}. and its measurement coordinates in the component platform coordinate system {W} The rotation matrix R is obtained by minimizing the following equation. k Translation vector t k :

[0022]

[0023] Where m≥3 Let J be the coordinates of the j-th target in the module coordinate system {U}. Let be the measured coordinates of the j-th target in coordinate system {W} under the k-th guide rail position parameters. The rigid body registration of the point set can be achieved using least squares registration, singular value decomposition, absolute orientation algorithm, or quaternion method.

[0024] In a preferred embodiment, when the motion of the guide rail mechanism is approximately a one-dimensional rigid body translation, a guide rail position parameter is selected as a reference position, and its corresponding attitude and translation vector are used as reference attitude R0 and reference translation vector t0. The guide rail motion direction a is fitted based on the translation vectors of multiple positions to establish a functional relationship between the guide rail position parameter s and the actual displacement q(s). The mapping model can be expressed as:

[0025]

[0026] Further, in step S6, the component under test is placed on the component platform through a positioning surface, positioning pin, positioning hole, limiting block, V-groove, equal height support, three-point support, kinematic positioning structure, special fixture or component tray, so that the positional relationship of the component under test relative to the component platform coordinate system {W} is determined by the design dimensions, tooling processing datum, mechanical positioning structure or pre-calibration results.

[0027] Furthermore, in step S7, the camera spatial ray is represented in the module coordinate system {U} as follows: ,

[0028] After transformation to coordinate system {W}, it can be represented as follows:

[0029]

[0030]

[0031] The spatial coordinates S of the display pixel in the module coordinate system {U} p U After transformation to coordinate system {W}, it is represented as:

[0032]

[0033] in, and This is the rotation matrix and translation vector recovered under the current guide rail position parameters s.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] 1) This invention focuses the use of external space measurement equipment in the offline calibration stage. During actual measurement, after the measurement module moves to the target guide rail position, it is only necessary to read the current guide rail position parameters to restore the current pose of the pre-calibrated deflection measurement module relative to the component platform coordinate system according to the established mapping model. There is no need to repeatedly use laser trackers, coordinate measuring machines or other external space measurement equipment to remeasure the system pose after each adjustment of the measurement optical path, thereby reducing the on-site measurement preparation steps and improving the repositioning efficiency after the measurement optical path is adjusted.

[0036] 2) This invention does not directly use the guide rail position command value, encoder reading, or motor pulse count as the spatial pose of the measurement module. Instead, it measures the actual spatial coordinates of the target module at multiple guide rail positions and establishes a mapping relationship between the guide rail position parameters and the actual rigid body pose of the measurement module through point set rigid body registration and guide rail motion model. This allows factors such as guide rail installation errors, motion direction deviations, and measurement module installation deviations to be incorporated into the offline calibration results, improving the accuracy and consistency of the deflection measurement coordinate relationship at different guide rail positions.

[0037] 3) This invention enables the pre-calibrated deflection measurement module to adjust the measurement optical path along the guide rail according to the curvature, aperture, reflection angle range, or measurement distance requirements of the component under test, so as to obtain a suitable imaging field of view, reflection angle, and display screen pattern coverage. At the same time, the guide rail motion calibration model maintains the recoverability of the spatial geometric relationship between the adjusted camera, display screen, and component under test, thereby enhancing the adaptability of the deflection measurement system to components of various specifications and different measurement distance conditions. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the repositionable deflection measurement system based on guide rail rigid body motion calibration according to the present invention.

[0039] Figure 2 This is a schematic diagram of the pre-calibration deflection measurement module;

[0040] Figure 3 This is a schematic diagram of the offline calibration process for multiple positions of the guide rail.

[0041] Figure 4 This is a schematic diagram illustrating the actual measurement principle of pose recovery and deflection measurement.

[0042] In the figure, 100-pre-calibration deflection measurement module, 200-guide rail mechanism, 300-component support platform, 101-camera, 102-imaging lens, 103-display screen, 104-rigid structure, 105-target. Detailed Implementation

[0043] The present invention will be further described below with reference to the accompanying drawings, but the scope of protection of the present invention is not limited to the following embodiments. Any equivalent substitutions or modifications made to the form of the guide rail mechanism, the type of the target, the form of the guide rail position parameters, the pose solving method, the form of the mapping model, or the form of the deflection measurement pattern based on the technical concept of the present invention shall fall within the scope of protection of the present invention.

[0044] like Figure 1 As shown, this embodiment provides a rapid repositioning deflection measurement method based on guide rail motion calibration. This method is applicable to deflection measurement systems consisting of a camera, imaging lens, and display screen. The camera, imaging lens, and display screen are mounted as a single measurement module on a guide rail mechanism, allowing adjustment of the measurement optical path along the guide rail direction according to the curvature, aperture, reflection angle range, or measurement distance requirements of the component under test. A component support platform is used to place the component under test and serves as the reference carrier for establishing the component platform coordinate system {W}.

[0045] I. Establishment of the pre-calibration deflection measurement module

[0046] like Figure 1 and Figure 2 As shown, in this embodiment, the camera 101, imaging lens 102, and display screen 103 are fixedly mounted on the same rigid structure 104, maintaining a stable rigid fixed relationship between the three to form a pre-calibrated deflection measurement module 100. The rigid structure can be a breadboard, frame structure, support beam, mounting plate, or other mechanical structure capable of maintaining the relative position stability of the camera, imaging lens, and display screen.

[0047] Establish a coordinate system {U} for the deflection measurement module. The origin and axis of the coordinate system can be flexibly selected according to actual needs. Preferably, the center point of the display screen is selected as the origin, the width direction of the display screen is selected as the X-axis, the height direction is selected as the Y-axis, and the screen normal direction is selected as the Z-axis.

[0048] At least three non-collinear targets 105 are set on the pre-calibrated deflection measurement module. In this embodiment, three non-collinear target balls are preferably used. The target balls are directly or through target ball seats fixed on the rigid mounting structure where the display screen and camera are located, and maintain a rigid fixed relationship with the camera, imaging lens and display screen.

[0049] The choice of target sphere can be determined based on the type of external space measurement equipment. When the external space measurement equipment is a laser tracker, the target is preferably a pyramidal reflector or a spherical reflector, with its reflection center coinciding with the center of the sphere, facilitating accurate measurement of the target sphere's center coordinates by the laser tracker. When the external space measurement equipment is a photogrammetric device, the target is preferably a coded point target with a specific geometric shape and contrast pattern, facilitating image processing and center extraction. When the external space measurement equipment is an articulated arm measurement device, the target is preferably a cone-and-socket or ball-and-socket structure that can mate with the articulated arm probe.

[0050] The coordinates of the center of each target ball in the coordinate system {U} of the deflection measurement module are obtained in advance using a coordinate measuring machine, laser tracker, image measuring equipment, or other metrological methods. Preferably, a coordinate measuring machine is used to perform a one-time precise measurement of the positions of all target balls on the module. During measurement, the coordinate measuring machine establishes a workpiece coordinate system consistent with the coordinate system {U} of the deflection measurement module, and then sequentially measures the coordinates of the center of each target ball, denoted as:

[0051]

[0052] in, This represents the known coordinates of the j-th target in the coordinate system {U} of the deflection measurement module, where m is the number of targets.

[0053] When the number of targets is greater than three, redundant targets can be used to improve the stability and accuracy of subsequent pose calculations. Preferably, four to eight targets are set and distributed in the four corners and the central area of ​​the module to better represent the spatial attitude of the module. The arrangement of the targets on the module should ensure that they have a large spatial distribution range relative to the module coordinate system, avoiding coplanarity or near-coplanarity, so as to reduce ill-posedness during pose calculation.

[0054] Simultaneously, the pre-calibrated deflection measurement module is internally geometrically calibrated to obtain the spatial ray model corresponding to the camera pixels and the spatial coordinates of the display screen pixels.

[0055] The spatial ray corresponding to the i-th camera pixel can be represented in the coordinate system {U} of the deflection measurement module as follows:

[0056]

[0057] in, Let {U} be the starting point of the spatial ray in the coordinate system {U} of the deflection measurement module. Let λ be the spatial ray direction vector. i For spatial ray parameters, X U It is a spatial point on a spatial ray.

[0058] The spatial coordinates of the p-th pixel on the display screen in the coordinate system {U} of the deflection measurement module are denoted as S. p U .

[0059] Therefore, the spatial coordinates of the camera ray, the spatial coordinates of the display pixel, and the coordinates of the target outside the module are all uniformly expressed in the coordinate system {U} of the deflection measurement module, providing a rigid geometric basis for subsequent guide rail motion calibration and actual measurement pose recovery.

[0060] II. Establishment of the component platform coordinate system

[0061] like Figure 1 As shown, the component carrier platform 300 is used to place the component under test and serves as the reference carrier for establishing the component platform coordinate system {W}. The component platform coordinate system {W} can be determined by the positioning reference, positioning hole, positioning pin, reference surface, target ball seat, reference ball, or other fixed measurement reference structure on the component carrier platform.

[0062] In this embodiment, a laser tracker is preferably used to establish or reproduce the component platform coordinate system {W}. Specifically, several fixed reference structures are set on the component carrier platform, such as a reference sphere, target ball seat, positioning hole, positioning pin, reference surface, or reference block. Before offline calibration, the spatial coordinates of the fixed reference structures are measured using a laser tracker, and the component platform coordinate system {W} is established based on the design coordinates, calibration coordinates, or geometric constraints of the fixed reference structures. After the component platform coordinate system {W} is established, it serves as a common coordinate system used uniformly in guide rail motion calibration and actual deflection measurement.

[0063] The component under test (DUT) is placed on the component support platform through a mechanical positioning structure, special tooling, or pre-calibrated relationship that mates with the component platform positioning datum. This allows the theoretical surface shape, design datum, nominal measurement position, or installation posture of the DUT to be expressed in the component platform coordinate system {W}. The mechanical positioning structure may include positioning surfaces, positioning pins, positioning holes, limit blocks, V-grooves, equal-height supports, three-point supports, ball-and-socket-cone-hole-plane kinematic positioning structures, special fixtures, or component trays.

[0064] It should be noted that in this embodiment, the guide rail motion calibration is used to restore the current pose of the pre-calibrated deflection measurement module relative to the component platform coordinate system {W}; the relationship between the component under test and the component platform coordinate system {W} is determined by the component platform positioning structure, the design dimensions of the special tooling, the machining datum, or the pre-calibration results.

[0065] III. Offline Calibration of Guide Rails at Multiple Positions

[0066] like Figure 3 As shown, the pre-calibrated deflection measurement module 100 is mounted on the guide rail mechanism 200, enabling it to move along the entire guide rail mechanism. The guide rail mechanism can be a linear guide rail, a lifting guide rail, an electric slide, a ball screw platform, a linear motor platform, a linear motion mechanism with an encoder, or a precision motion mechanism with grating ruler feedback.

[0067] The guide rail mechanism has a guide rail position parameter s. The guide rail position parameter s is used to characterize the target position or current position of the guide rail, and can be the position set on the control panel, the position input by the control software, the target position of the motion controller, the position of the servo command, the number of motor pulses, the encoder reading, the grating ruler reading, or other parameters that can characterize the position of the guide rail.

[0068] After establishing the component platform coordinate system {W}, the guide rail mechanism is controlled to move to positions corresponding to multiple guide rail position parameters. In this embodiment, based on the guide rail travel and measurement requirements, n calibration positions are selected, denoted as:

[0069]

[0070] Where n ≥ 2. The selection of calibration positions should cover the range of guide rail positions that may be used in actual measurements, and the spacing between adjacent calibration positions should be determined according to the required positioning accuracy. Preferably, 10 to 20 calibration positions are evenly selected within the guide rail travel range, with a spacing of 20 mm to 50 mm between adjacent positions. For applications requiring high precision, calibration can be densified near key measurement positions to improve the accuracy of the mapping model in that area.

[0071] For the k-th guide rail position parameter Using external space measurement equipment, measure the spatial coordinates of at least three non-collinear targets on the pre-calibrated deflection measurement module in the component platform coordinate system {W}, and denote them as follows:

[0072]

[0073] in, The spatial coordinates of the j-th target, measured by an external space measuring device under the k-th guide rail position parameters, are expressed in the component platform coordinate system {W}. The external space measuring device can be a laser tracker, a coordinate measuring machine, a photogrammetric device, an articulated arm measuring device, or other metrological equipment capable of measuring the coordinates of spatial points.

[0074] For each guide rail position parameter s k Based on the known coordinates P of the target in the coordinate system {U} of the deflection measurement module j Uand the measurement coordinates in the component platform coordinate system {W} The rigid body pose of the pre-calibrated deflection measurement module relative to the component platform coordinate system {W} at this position is obtained by point set rigid body registration. In offline calibration, the laser tracker target ball can be sequentially placed on each target holder of the pre-calibrated deflection measurement module, or the target fixed on the module can be directly measured; the guide rail mechanism moves sequentially to multiple calibration positions s. k After coming to a stop, record the current guide rail position parameter s. k The spatial coordinates of each target in the component platform coordinate system {W} are used to form calibration data for establishing the mapping model. The rigid body pose is determined by the rotation matrix R. k Translation vector t k This can be obtained by minimizing the following expression:

[0075]

[0076] Where m ≥ 3. The rigid body registration of the point set can be achieved using least squares registration, singular value decomposition, absolute orientation algorithm, quaternion method, or a combination thereof. When the number of targets is greater than three, redundant targets can be used to improve the stability of pose solution, and the consistency between the measurement data at the guide rail position and the rigid body assumption can be evaluated through the registration residual.

[0077] IV. Establishment of the Mapping Model between Guide Rail Position Parameters and Measurement Module Pose

[0078] Based on multiple guide rail position parameters s k The rigid body pose R obtained below k t k A mapping model is established between the guide rail position parameters s and the rigid body pose of the pre-calibrated deflection measurement module relative to the component platform coordinate system {W}. This mapping model can be obtained by fitting, interpolating, or looking up tables of the rigid body poses derived from multiple guide rail position parameters. Specifically, it can employ linear models, polynomial models, piecewise models, lookup table interpolation models, spline interpolation models, or models determined by the correspondence between encoder readings, grating ruler readings, motor pulse counts, and the rigid body pose of the module. When the mapping model includes fitting or interpolating rotational attitudes, the rotational attitudes can be represented using rotation matrices, quaternions, or rotation vectors.

[0079] In a preferred embodiment of this invention, the guide rail mechanism employs a one-dimensional translational guide rail, and the pre-calibrated deflection measurement module approximately performs a one-dimensional rigid body translational motion along the guide rail. In this case, one of the multiple guide rail position parameters, s0, is selected as the reference position. The rotation matrix and translation vector obtained from the rigid body registration of the point set at the reference position are used as the reference attitude R0 and the reference translation vector t0. Based on the translation vector t0 obtained from the rigid body registration of the point set under the multiple guide rail position parameters... k Fit the direction of the guide rail motion 'a', and based on the translation vector 't'k The projection onto the guide rail movement direction a determines the actual displacement q(s) corresponding to each guide rail position parameter. k Then, based on multiple guide rail position parameters s k and its corresponding actual displacement q(s) k Establish the functional relationship q(s) between the guide rail position parameters and the actual displacement.

[0080] When the guide rail position parameters and the actual displacement are approximately linearly related, the actual displacement can be expressed as:

[0081]

[0082] Where k is the proportionality coefficient between the guide rail position parameters and the actual displacement, and s0 is the reference guide rail position parameters. The mapping model between the guide rail position parameters and the rigid body pose of the pre-calibrated deflection measurement module can be expressed as:

[0083]

[0084] in, Let s be the rigid body transformation from the coordinate system {U} of the deflection measurement module to the coordinate system {W} of the component platform when the guide rail position parameter is s. R0 is the reference attitude of the pre-calibrated deflection measurement module relative to the coordinate system {W} of the component platform. t0 is the translation vector under the reference guide rail position. a is the unit direction vector of the guide rail motion direction under the coordinate system {W} of the component platform. q(s) is the actual displacement corresponding to the guide rail position parameter.

[0085] Under the above one-dimensional rigid body translation model, the spatial coordinates of the j-th target in the component platform coordinate system {W} can be expressed as:

[0086]

[0087] The model demonstrates that the pre-calibrated deflection measurement module maintains overall rigid constraint during guide rail movement, and its spatial position is jointly determined by the reference pose, guide rail movement direction, and the actual displacement corresponding to the guide rail position parameters. After offline calibration, the component platform coordinate system {W}, reference pose R0, reference translation vector t0, guide rail movement direction a, displacement function q(s), and related calibration parameters are stored in the data processing device. During actual measurement, external space measurement equipment does not need to participate in the pose recovery of the measurement module in real time.

[0088] V. Pose Recovery and Coordinate Transformation in Actual Measurement

[0089] like Figure 4As shown, during actual measurement, the component to be measured is first placed on the component carrier platform through a mechanical positioning structure, special tooling, or pre-calibrated relationship that matches the positioning datum of the component platform, so that the theoretical surface shape, design datum, or nominal measurement position of the component to be measured is expressed in the component platform coordinate system {W}.

[0090] Subsequently, based on the curvature, diameter, reflection angle range, or measurement distance requirements of the component under test, the pre-calibrated deflection measurement module is moved along the guide rail mechanism to the target guide rail position. The current guide rail position parameters are then read. And calculate the current rigid body pose of the pre-calibrated deflection measurement module relative to the component platform coordinate system {W} based on the mapping model established in the offline stage. When the guide rail position parameters are not exactly the same as those selected in the offline calibration stage, interpolation is performed using the mapping model or by substituting into the fitting function for calculation.

[0091]

[0092] When using a one-dimensional rigid body translation model, the current rigid body pose can be obtained from the following formula:

[0093]

[0094] Where, q( ) represents the current guide rail position parameters The corresponding actual displacement. This process only requires reading the current guide rail position parameters, without needing to recalibrate the deflection measurement module pose using a laser tracker, coordinate measuring machine, or other external space measuring equipment.

[0095] Based on the current rigid body pose, the spatial coordinates of the camera spatial rays and the display pixel spatial coordinates are transformed from the deflection measurement module coordinate system {U} to the component platform coordinate system {W}. For the spatial rays corresponding to the camera pixels:

[0096]

[0097] After transforming the current rigid body pose, the camera space ray in the component platform coordinate system {W} is obtained:

[0098]

[0099]

[0100]

[0101] Among them, R( ) and t( ) represent the current guide rail position parameters. The rotation matrix and translation vector obtained by the recovery are Oᵢ Wand dᵢ W These are the starting point and direction vector of the spatial ray in the component platform coordinate system {W}, respectively.

[0102] For the spatial coordinates S of the display pixel in the coordinate system {U} of the deflection measurement module p U After transforming the current rigid body pose, the display screen pixel space coordinates in the component platform coordinate system {W} are obtained:

[0103]

[0104] Therefore, the spatial light of the camera, the spatial coordinates of the display pixel, and the theoretical surface shape, nominal geometric position, or initial surface shape information of the component under test are all unified under the component platform coordinate system {W}.

[0105] VI. Deflection Measurement Process

[0106] After pose recovery and coordinate transformation are completed, the display screen shows the deflection measurement pattern, and the camera captures the image reflected by the component under test. The deflection measurement pattern can be a phase-shifting fringe, sinusoidal fringe, multi-frequency fringe, Gray code pattern, color-coded pattern, or other structured light pattern.

[0107] After the camera acquires the reflected image, the correspondence between camera pixels and display screen pixels is obtained through phase calculation, phase unwrapping, or pattern decoding. For the spatial ray corresponding to the camera pixel, the intersection point between the spatial ray and the surface of the device under test is determined based on the theoretical surface shape, nominal geometric position, or initial surface shape information of the device under test, and this intersection point is used as the reflection point. Then, based on the reflection relationship between the reflection point, the camera spatial ray, and the corresponding display screen pixel spatial coordinates, the deflection measurement is completed to obtain the surface normal vector, gradient, or surface shape of the device under test.

[0108] This process demonstrates that the guide rail motion calibration in this embodiment is not a separate mechanical motion calibration, but rather a means to restore the current spatial pose of the pre-calibrated deflection measurement module relative to the component platform coordinate system {W} after the measurement optical path is adjusted. After the component under test is connected to the component platform coordinate system {W} through the component platform positioning reference, the camera spatial light, display pixel spatial coordinates, and the theoretical surface shape, nominal geometric position, or initial surface shape information of the component under test required for deflection measurement can be unified into the same coordinate system for calculation.

[0109] In a specific application, the pre-calibrated deflection measurement module is mounted on a vertical lifting guide rail, and the reflector under test is placed on a component support platform with positioning pins and equal-height supports. In the offline phase, a laser tracker measures the spatial coordinates of the module target ball in the component platform coordinate system {W} at multiple guide rail height positions. A mapping model between the guide rail position parameters and the measurement module pose is established through point set rigid body registration and guide rail motion direction fitting. When actually measuring reflectors with different curvatures or diameters, the target guide rail position is input according to the measurement requirements, and the guide rail control system drives the pre-calibrated deflection measurement module to move to the corresponding position. The data processing device reads the current guide rail position parameters, substitutes them into the established mapping model, restores the current pose of the measurement module relative to the component platform coordinate system {W}, and unifies the coordinates of the camera spatial rays, display pixel spatial coordinates, and the surface shape information of the component under test, thereby completing the deflection measurement.

[0110] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, any equivalent substitutions or modifications made to the number of targets, the arrangement of targets, the form of the guide rail mechanism, the form of the guide rail position parameters, the method of establishing the coordinate system of the component platform, the positioning method of the component under test, the form of the displacement function, the pose recovery algorithm, the coordinate transformation method, or the form of the deflection measurement pattern without departing from the technical concept of the present invention shall fall within the protection scope of the present invention.

Claims

1. A rapid repositioning deflection measurement method based on guide rail motion calibration, characterized in that, Includes the following steps: S1, establish a pre-calibrated deflection measurement module, the module including a rigidly fixed camera, imaging lens, display screen and at least three non-collinear targets; obtain the camera spatial ray model, display screen pixel spatial coordinates and target coordinates in the module coordinate system {U} through pre-calibration; S2, Establish the component platform coordinate system {W}, which is determined by the fixed measurement reference structure on the component platform; S3, the pre-calibrated deflection measurement module is installed on the guide rail mechanism so that it can move along the guide rail. The guide rail mechanism has guide rail position parameters for characterizing the movement position of the module. S4, offline calibration stage: move the guide rail mechanism to the position corresponding to multiple guide rail position parameters, and use external space measurement equipment to measure the coordinates of the target in the component platform coordinate system {W}. S5. Based on the known coordinates of the target in the module coordinate system {U} and its measured coordinates in the coordinate system {W} under each guide rail position parameter, the rigid body pose of the module relative to the coordinate system {W} at each position is obtained, and a mapping model between the guide rail position parameter and the rigid body pose is established. S6. During actual measurement, the component under test is placed on the component platform so that there is a predetermined pose relationship between the component under test and the component platform coordinate system {W}; according to the measurement requirements, the module is moved to the target guide rail position, the current guide rail position parameters are read, and the current rigid body pose of the module relative to the coordinate system {W} is restored according to the mapping model. S7, based on the recovered current rigid body pose, transforms the camera space ray model and the display screen pixel space coordinates from the module coordinate system {U} to the component platform coordinate system {W}, and completes the deflection measurement by combining the geometric information of the component under test.

2. The method according to claim 1, characterized in that, In step S1, the target is a spherical reflective target, a corner cone reflector, a coded marker point, or other marker structure whose spatial coordinates can be obtained through external space measurement equipment.

3. The method according to claim 1, characterized in that, In step S2, the component platform coordinate system {W} is established by measuring the fixed measurement reference structure on the component platform. The fixed measurement reference structure includes one or more of the following: positioning reference, positioning hole, positioning pin, reference surface, target ball seat, reference ball or reference block.

4. The method according to claim 1, characterized in that, The guide rail position parameters refer to the control parameters used to characterize the target position or current position of the guide rail, including the control panel set position, the control software input position, the motion controller target position, the servo command position, the number of motor pulses, the encoder reading, the grating ruler reading, or other parameters that can characterize the guide rail position.

5. The method according to claim 1, characterized in that, The external space measurement device is a laser tracker, a coordinate measuring machine, a photogrammetric machine, an articulated arm measuring machine, or other metrology equipment capable of measuring the coordinates of spatial points.

6. The method according to claim 1, characterized in that, In step S5, firstly, under each guide rail position parameter, based on the known coordinates of the at least three non-collinear targets in the deflection measurement module coordinate system {U} and the measured coordinates in the component platform coordinate system {W}, the rigid body pose of the pre-calibrated deflection measurement module relative to the component platform coordinate system {W} is obtained by point set rigid body registration. Then, based on the rigid body poses under multiple guide rail position parameters, a mapping model between the guide rail position parameters and the rigid body pose of the pre-calibrated deflection measurement module is established.

7. The method according to claim 6, characterized in that, The rigid body registration of the point set is obtained by minimizing the rotation matrix and translation vector by the following formula: Where m≥3, P j U Let {j} be the known coordinates of the j-th target in the coordinate system {U} of the deflection measurement module. Let R be the spatial coordinates of the j-th target measured by an external space measuring device under the k-th guide rail position parameters, expressed in the component platform coordinate system {W}. k and t k These are the rotation matrix and translation vector of the pre-calibrated deflection measurement module relative to the component platform coordinate system {W} under the k-th guide rail position parameters, respectively; the rigid body registration of the point set is achieved by least squares registration, singular value decomposition, absolute orientation algorithm, quaternion method or a combination thereof.

8. The method according to claim 6, characterized in that, Select one of the multiple guide rail position parameters, s0, as the reference position, and use the rotation matrix and translation vector obtained by rigid body registration of the point set at the reference position as the reference attitude R0 and the reference translation vector t0; or determine the reference attitude R0 and the reference translation vector t0 by averaging, fitting, or optimization based on the rotation matrix and translation vector obtained by rigid body registration of the point set at multiple guide rail position parameters.

9. The method according to claim 8, characterized in that, The translation vector t obtained from rigid body registration of point set under multiple guide rail position parameters. k Fit the direction of the guide rail motion 'a', and based on the translation vector 't' k The projection onto the guide rail movement direction a determines the actual displacement q(s) corresponding to each guide rail position parameter. k Then, based on multiple guide rail position parameters s k and its corresponding actual displacement q(s) k Establish the functional relationship q(s) between the guide rail position parameters and the actual displacement.

10. The method according to claim 9, characterized in that, When the motion of the guide rail mechanism is approximately a one-dimensional rigid body translation, the mapping model between the guide rail position parameters and the rigid body pose of the pre-calibrated deflection measurement module is expressed as: Where s is the guide rail position parameter, T {U}→{W} (s) represents the rigid body transformation from the coordinate system {U} of the deflection measurement module to the coordinate system {W} of the component platform when the guide rail position parameter is s. R0 is the reference attitude of the pre-calibrated deflection measurement module relative to the coordinate system {W} of the component platform. t0 is the translation vector under the reference guide rail position. a is the unit direction vector of the guide rail motion direction under the coordinate system {W} of the component platform. q(s) is the actual displacement corresponding to the guide rail position parameter.

11. The method according to claim 10, characterized in that, When the actual displacement is a linear function of the guide rail position parameters, q(s) = k(s - s0), where k is the proportionality coefficient between the guide rail position parameters and the actual displacement, and s0 is the reference guide rail position parameters; under the guide rail rigid body translation model, the spatial coordinates of the j-th target in the component platform coordinate system {W} are expressed as: in, Let {j} be the known coordinates of the j-th target in the coordinate system {U} of the deflection measurement module. Let s be the spatial coordinates of the target in the component platform coordinate system {W} when the guide rail position parameter is s.

12. The method according to claim 1, characterized in that, In step S6, the component under test is placed on the component platform through a positioning surface, positioning pin, positioning hole, limiting block, V-groove, equal height support, three-point support, ball-and-socket-cone-plane kinematic positioning structure, special fixture or component tray, so that the positional relationship of the component under test relative to the component platform coordinate system {W} is determined by the design dimensions, tooling processing datum, mechanical positioning structure or pre-calibration results.

13. The method according to claim 1, characterized in that, In step S7, the spatial ray corresponding to the camera pixel is represented in the coordinate system {U} of the deflection measurement module as follows: After restoring the current rigid body pose through step S6, the camera space ray in the component platform coordinate system {W} is obtained: ; ;in, and These represent the starting point and direction vector of the spatial ray in the coordinate system {U} of the deflection measurement module, respectively. and Let $\mathbf$ be the origin and direction vector of the spatial ray in the coordinate system {W} of the component platform, respectively; where, and Let U and Z represent the rotation and translation transformation matrices of the coordinate system {U} of the deflection measurement module relative to the coordinate system {W} of the component platform under the guide rail position parameter s, respectively.

14. The method according to claim 1, characterized in that, In step S7, the spatial coordinates of the display pixel in the coordinate system {U} of the deflection measurement module are S. p U After a rigid body transformation from the coordinate system {U} of the deflection measurement module to the coordinate system {W} of the component platform, the pixel space coordinates of the display screen in the component platform coordinate system {W} are obtained: 。 15. A rapid repositioning deflection measurement system based on guide rail motion calibration, characterized in that, include: A pre-calibrated deflection measurement module includes a camera, an imaging lens, and a display screen. The camera, imaging lens, and display screen are fixedly mounted on the same rigid structure. At least three non-collinear targets are provided on the rigid structure. The targets maintain a fixed spatial positional relationship with the camera, imaging lens, and display screen. The guide rail mechanism includes a pre-calibrated deflection measurement module mounted on it, enabling it to move along the entire guide rail mechanism. The guide rail mechanism has guide rail position parameters, which characterize the target position or current position of the guide rail. A component platform is used to place the component to be tested. The component platform is provided with a fixed measurement reference structure for establishing the component platform coordinate system {W}. An external space measurement device is used to measure the spatial coordinates of the target in the component platform coordinate system {W} during the offline calibration phase; A data processing device, communicatively connected to the camera, display screen, guide rail mechanism and external space measurement equipment, performs the calculation steps in the method as described in any one of claims 1 to 14.

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