Symmetrical prism center deviation testing device

Abstract

The application discloses a symmetric prism center deviation testing device, and belongs to the technical field of optical element detection. The device comprises a testing assembly and an auxiliary clamp. The testing assembly comprises a CCD camera, a photoelectric centering instrument and a stage arranged coaxially. The auxiliary clamp comprises a positioning mechanism arranged on the periphery of the stage and an auxiliary mechanism. The positioning mechanism is provided with a V-shaped positioning groove, and the auxiliary mechanism is clamped on the opposite sides of the prism to be tested. The auxiliary mechanism drives the prism to be tested to rotate at a constant speed, and the photoelectric centering instrument synchronously captures the center deviation signals at each rotation angle. The application also discloses a corresponding testing method. The geometric deviation parameters of the actual rotation axis are fitted by collecting calibration data, and the original measurement data is compensated by coordinate transformation. The application has the advantages of simple structure, convenient operation, high detection precision, controllable cost and suitability for batch production and detection of symmetric prisms.

Description

Technical Field

[0001] This application relates to a symmetrical prism center deviation testing device, which belongs to the field of optical component testing technology and can be widely used in the mass production testing of symmetrical prisms in optical manufacturing, precision instruments, aerospace and other fields. Background Technology

[0002] As optical manufacturing technology rapidly advances towards higher precision, miniaturization, and higher integration, the performance ceiling of optical systems directly depends on the manufacturing precision of core components. Consequently, the accuracy requirements for detecting the center deviation of symmetrical prism surfaces are continuously increasing. During the fabrication of symmetrical prisms, factors such as machine tool positioning errors in the edge grinding and polishing processes of the prism blank material, mechanical clamping deviations during centering assembly, and micro-deformation of materials caused by changes in environmental temperature and humidity can all lead to the normal at the centering vertex of the symmetrical prism's optical surface not coinciding with the reference axis. This phenomenon is defined as the center deviation of the symmetrical prism.

[0003] The negative impact of center deviation on optical systems is both conductive and amplified: even slight deviations can cause abnormal light refraction angles, leading to image point shift, coma, and spherical aberration, directly resulting in blurred images, reduced resolution, and decreased contrast at the edge of the field of view. In high-precision applications, eccentricity can also cause stray light interference, disrupting the system's energy concentration. Especially with the current development trend in the optical manufacturing industry, the aperture of symmetrical prisms is gradually increasing, their thickness is continuously decreasing, and the curvature of their working surfaces is becoming increasingly complex. The performance degradation effect caused by center deviation is further amplified, and the precision control requirements for deviation have gradually increased from the traditional tens of micrometers to the sub-micrometer or even nanometer level.

[0004] Currently, the detection of center deviation in symmetrical prisms mainly relies on two types of equipment: one is general-purpose high-precision optical inspection equipment, which integrates the detection functions of multiple types of optical components and achieves high-precision detection through a complex air-bearing rotary table and laser interferometry module. However, it suffers from problems such as structural redundancy, cumbersome operation, and high equipment cost. The other is a simple manual inspection device, which uses manual positioning and rotation of the prism, judging the deviation by visually observing the spot displacement. This not only has low detection efficiency but also heavily relies on the operator's experience level, resulting in poor accuracy and stability. Neither of these two types of equipment can meet the core requirements of high efficiency, accuracy, and low cost for mass production of symmetrical prisms, becoming a key bottleneck restricting the improvement of production capacity and quality control in the optical manufacturing industry.

[0005] As a fundamental core unit of an optical system, the center deviation of a symmetrical prism directly affects the subsequent assembly accuracy and overall imaging quality. Existing testing equipment has significant adaptation deficiencies, specifically: First, general-purpose equipment has a complex structure and cumbersome operation procedures. When testing a single type of symmetrical prism component, redundant functions lead to wasted equipment costs, and the testing efficiency is difficult to match the needs of mass production. Second, simple testing equipment can only achieve a rough measurement of the overall deviation, with a testing error ≥0.01mm, which cannot meet the quality requirements of high-precision application scenarios. Third, traditional testing methods have not optimized the clamping structure for the thin and curved characteristics of symmetrical prisms, which easily leads to prism clamping deformation, and a single test takes ≥2 minutes, making it difficult to adapt to the efficient testing requirements of mass production of symmetrical prisms. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the core objective of this invention is to provide a symmetrical prism center deviation testing device that is structurally simple, easy to operate, accurate in detection, and cost-controllable, thus solving the technical problems of poor adaptability, insufficient accuracy, low efficiency, and excessive cost of existing equipment. The specific solution is as follows: A symmetrical prism center deviation testing device, the testing device comprising a testing component and an auxiliary fixture; The test components include a CCD camera, a photoelectric centering device, and a stage arranged from top to bottom, and the CCD camera, photoelectric centering device, and stage are coaxially arranged. The CCD camera is used to acquire the light spot image formed by the photoelectric centering instrument, which corresponds to the center deviation of the symmetrical prism under test, in order to obtain the original measurement data of the center deviation. The photoelectric centering instrument moves up and down to focus the detection optical axis at the center of the sphere of the symmetrical prism detection surface; The auxiliary clamp includes a positioning mechanism and an auxiliary mechanism disposed around the periphery of the stage; The positioning mechanism is provided with a V-shaped positioning groove on the side facing the platform; The V-shaped positioning groove and the auxiliary mechanism are respectively clamped on opposite sides of the prism to be tested; The auxiliary mechanism has a driven wheel that is opposite to the V-shaped positioning groove. The outer circumferential surface of the driven wheel is used to make frictional contact with the outer circular side surface of the symmetrical prism to be tested. The auxiliary mechanism is clamped on the other side of the prism to be tested. The auxiliary mechanism drives the prism to be tested, which is placed on the stage, to rotate at a constant speed through its own drive, so as to realize that the photoelectric centering instrument can synchronously capture the center deviation signal at each rotation angle.

[0007] Preferably, the testing device further includes a drive mechanism for driving the photoelectric centering instrument to move up and down; The drive mechanism includes a column and a drive assembly; The column is located on one side of the platform; The drive assembly is located on the side of the column facing the platform, and the drive assembly includes a matching guide rail and a slider. The guide rail is provided on the side of the column facing the platform, along the extension direction of the column; The slider is slidably connected to the guide rail; The photoelectric centering device is mounted on the slider and moves up and down along the guide rail as the slider slides.

[0008] Preferably, the center lines of the guide rail, the column, and the platform are arranged in the same plane.

[0009] Preferably, the positioning mechanism includes a first adjusting seat and a positioning element located on top of the first adjusting seat; The positioning component has a V-shaped positioning groove on the side facing the stage, and the positioning component is installed on the top of the first adjustment seat.

[0010] Preferably, a fastening assembly is provided between the top of the first adjusting seat and the positioning member; The fastening assembly includes a limiting groove and a clamping element disposed on the positioning element; The limiting groove is disposed at one end of the positioning member located at the top of the first adjusting seat, and the limiting groove is disposed along the extending direction of the positioning member; At least two clamping components are provided. One end of the clamping component presses against the top of the positioning component, and the other end of the clamping component passes through the limiting groove and is threaded to the top of the first adjusting seat.

[0011] Preferably, the auxiliary mechanism includes a second adjusting seat, a pulley assembly located on top of the second adjusting seat and matched therewith, and a drive motor located on top of the pulley assembly; The drive wheel and driven wheel of the pulley assembly are horizontally arranged at their end faces. The drive wheel and driven wheel are rotatably mounted on the top of the second adjusting seat. The driven wheel is located on the side of the drive wheel facing the platform. The drive motor is located on top of the drive wheel, and the output end of the drive motor is connected to the drive wheel.

[0012] Preferably, the testing device is further equipped with a data acquisition module and a processing module; The acquisition module is located on one side of the stage. The acquisition module is used to acquire the number of axial movements, the displacement of each axial movement, and the rotation angle of the symmetrical prism under test within one rotation cycle. The processing module is electrically connected to the drive motor, the acquisition module, and the CCD camera, respectively, and performs the following operations: Based on the calibration dataset acquired by the acquisition module within a calibration cycle, and the coordinates of feature points in the spot image synchronously acquired by the CCD camera, the geometric deviation parameter of the actual rotation axis of the symmetrical prism under test relative to the ideal measurement coordinate system is determined by fitting; and in subsequent formal measurements, the geometric deviation parameter is used to perform coordinate transformation compensation on the coordinates of the original spot image acquired by the CCD camera to eliminate the systematic error introduced by the spatial position deviation of the rotation axis.

[0013] Preferably, the processing module is configured as follows: S1, while driving the symmetrical prism under test to rotate in actual rotation, acquire the symmetrical prism under test within at least one uniform calibration rotation cycle, the angles of multiple calibration rotation surfaces, the calibration axial displacement measurement values ​​corresponding to each calibration rotation surface angle, and the coordinates of the feature points of the spot image synchronously acquired by the CCD camera, so as to establish a calibration dataset. S2, Based on the calibration dataset, determine the deflection angle and translation of the actual rotation axis relative to the ideal measurement coordinate system, as a geometric deviation parameter; S3, during formal scanning and measurement, based on the current rotation angle and geometric deviation parameters acquired in real time by the acquisition module, the coordinates of the original spot image acquired by the CCD camera at the same moment are transformed into spatial coordinates to obtain the compensated accurate coordinates. S4 calculates the center deviation of the symmetrical prism under test using the compensated accurate coordinates, and uses it as the final measurement value.

[0014] Preferably, the error compensation method specifically includes: The processing module controls the drive motor to rotate the symmetrical prism under test for calibration, and uses the acquisition module to synchronously acquire the calibration dataset. The calibration dataset includes the axial displacement of the symmetrical prism under test at different rotation angles, the corresponding rotation plane angles, and the coordinates of the feature points of the spot image synchronously acquired by the CCD camera. Based on the calibration dataset, the geometric deviation parameters describing the spatial position deviation of the actual rotation axis of the symmetrical prism under test are solved by data fitting. During formal multi-angle scanning measurement, the coordinate transformation of the original spot image coordinates corresponding to the current rotation angle acquired by the CCD camera in real time and the geometric deviation parameters is performed based on the current rotation angle acquired by the acquisition module in real time, in order to compensate for the systematic error caused by the deviation of the actual rotation axis, and the center deviation is output as the final measurement data.

[0015] Preferably, the geometric deviation parameters include at least the angle between the actual axis of rotation and the Z-axis of the ideal measurement coordinate system, as well as the offsets in the X-axis and Y-axis directions; The ideal measurement coordinate system has the center of the top surface of the stage as its origin, the detection optical axis of the photoelectric centering instrument as its Z-axis, and two mutually orthogonal directions within the top surface of the stage as its X-axis and Y-axis. The coordinate transformation process satisfies the following coordinate transformation relationship: ; Where Pm is the coordinate vector of the original spot image in the ideal measurement coordinate system; T=(Δx,Δy,0) T The vectors representing the offset of the actual axis of rotation in the X and Y directions on the reference plane where the top surface of the stage is located; Ra is the rotation matrix that transforms the actual rotation axis to coincide with the Z-axis of the ideal measurement coordinate system; Rz( () represents the current rotation angle around the Z-axis. rotation matrix; Pc is the compensated, precise coordinate vector. The beneficial effects of this application are as follows: The positioning mechanism of this application has a V-shaped positioning groove on the side facing the symmetrical prism to be tested, forming an automatic centering structure of the V-shaped positioning groove. This will not cause the symmetrical prism to deform during the clamping process. The auxiliary mechanism is set on the other side of the symmetrical prism to be tested. On the one hand, it forms two opposite clamping points with the positioning mechanism, and on the other hand, it drives the symmetrical prism to be tested to rotate on the stage. The positioning mechanism adjusts the height by rotating the fine-tuning screws at the bottom of the first and second adjusting seats in both forward and reverse directions. By using the limiting groove and clamping parts on the positioning parts, when the cross-sectional size of the symmetrical prism to be tested changes, the distance between the positioning parts and the symmetrical prism to be tested can be adjusted to adapt to the clamping of symmetrical prisms with different cross-sectional sizes. Generally, it can be adapted to spherical / aspherical symmetrical prisms with a diameter of φ2-100mm, which solves the problem of narrow compatibility of traditional equipment. In this application, by simplifying the air-bearing rotary table, the complex laser interference module and the high-end computing unit, and by adopting a combination of low-cost stepper motor and ordinary CCD camera, the manufacturing cost of the equipment is greatly reduced. In this application, by utilizing the stable transmission design of the motor and synchronous belt, and in conjunction with the real-time data acquisition function of the photoelectric centering instrument, the single detection time is ≤40s and the detection accuracy can reach 0.001mm / 0.001°. This not only meets the high-efficiency detection requirements of mass production of symmetrical prisms, but also achieves sub-micron level accuracy standards, thus resolving the contradiction between high efficiency and accuracy in existing equipment. In this application, the testing device described herein can automatically perform testing after leveling, placing the part, and pressing it. No professional technicians are required to operate it. Operators can quickly get started after simple training, which reduces labor costs and the operating threshold. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of a symmetrical prism center deviation testing device described in this application; Figure 2 This is a schematic diagram of the auxiliary fixture in a symmetrical prism center deviation testing device described in this application; List of components and reference numerals: The components include: 1. Lifting guide rail; 2. Centering instrument clamping seat; 3. Photoelectric centering instrument; 4. Reinforcing plate; 5. Stage; 6. Stepper motor; 7. Synchronous pulley; 8. Belt; 9. Base; 10. Support foot; 11. Spiral clamping component; 12. Positioning component; 13. Light source; 14. First adjusting component; 15. Second adjusting component; 16. V-shaped positioning groove; 17. Driven wheel; 18. Limiting groove. Detailed Implementation

[0017] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0018] Reference Appendix Figure 1 and 2 This application provides a test device for the center deviation of a symmetrical prism, the test device including a test component and an auxiliary fixture; The test components include a CCD camera, a photoelectric centering device, and a stage arranged from top to bottom, and the CCD camera, photoelectric centering device, and stage are coaxially arranged. The CCD camera is used to acquire the light spot image formed by the photoelectric centering instrument 3 corresponding to the center deviation of the symmetrical prism under test, so as to obtain the original measurement data of the center deviation; the photoelectric centering instrument 3 moves up and down to focus the detection optical axis on the curvature center position of the detection surface of the symmetrical prism under test; for aspherical detection surfaces, it focuses on the curvature center or the best-fit sphere center position at the vertex of the detection surface.

[0019] The auxiliary clamp includes a positioning mechanism and an auxiliary mechanism disposed around the periphery of the stage; The positioning mechanism is provided with a V-shaped positioning groove 16 on the side facing the platform 5; The V-shaped positioning groove 16 and the driven wheel of the auxiliary mechanism are respectively clamped on opposite sides of the prism to be tested; The auxiliary mechanism has a driven wheel 17 disposed opposite to the V-shaped positioning groove 16, and the outer peripheral surface of the driven wheel 17 is used for frictional contact with the outer circular side surface of the symmetrical prism to be tested.

[0020] The auxiliary mechanism is clamped on the other side of the prism to be tested. The auxiliary mechanism drives the driven wheel 17 to rotate through its own drive, so as to drive the symmetrical prism to be tested placed on the stage 5 to rotate at a constant speed, so that the photoelectric centering instrument 3 can synchronously capture the center deviation signal at each rotation angle.

[0021] It should be noted that: V-shaped positioning groove outer circle positioning module: The core adopts a fixed V-shaped positioning groove 16. Utilizing the automatic centering principle of the inclined surface of the V-shaped positioning groove, it can achieve precise positioning of the outer circle of the symmetrical prism without the need for multi-jaw synchronous adjustment. It can be achieved by manually tightening the screw. The contact surface between the stage 5 and the symmetrical prism is made of hard plastic and polished, which effectively prevents scratches on the surface of the symmetrical prism while ensuring reliable centering. The stage does not require an air-bearing structure or complex bearings, only ensuring basic coaxiality, significantly reducing processing and assembly costs. This structure is the core protection point. The groove angle of the V-shaped positioning groove 16 can be adaptively adjusted according to the shape and specifications of the symmetrical prism. As long as the core principle of automatic centering of the inclined plane is maintained, the same positioning effect can be achieved.

[0022] A common CCD camera is used as the image acquisition element to acquire the light spot image formed by the photoelectric centering instrument 3. The data processing is simplified to basic trajectory extraction and fixed coefficient aberration correction. No complex computing unit is required, and the cost of electronic components is effectively controlled while ensuring detection accuracy.

[0023] In one embodiment of this application, the test component and the auxiliary fixture are respectively mounted on the base 9; Among them, the base 9 is a load-bearing integrated base structure, with at least three adjustable screw-type support feet 10 evenly distributed on its bottom. By rotating the support feet 10, the overall horizontal calibration of the base 9 can be achieved, providing a stable benchmark for testing.

[0024] The stage 5 is mounted on the top surface of the base 9 and is located within the detection range of the photoelectric centering instrument 3. The top of the stage 5 is provided with a mounting groove that matches the symmetrical prism, so that the symmetrical prism is placed in the mounting groove and can rotate within the mounting groove.

[0025] Furthermore, the testing device also includes a drive mechanism for driving the photoelectric centering instrument to move up and down; The drive mechanism includes a column and a drive assembly; The column is located on one side of the platform; The drive assembly is located on the side of the column facing the platform, and the drive assembly includes a matching guide rail and a slider. The guide rail is provided on the side of the column facing the platform, along the extension direction of the column; The slider is slidably connected to the guide rail; The photoelectric centering device is mounted on the slider and moves up and down along the guide rail by sliding the slider.

[0026] The column is vertically fixed to the top surface of the base 9. The column is reinforced and connected to the base 9 through the reinforcing plate 4 to form the load-bearing frame of the device and ensure the structural stability. The slider slides along the guide rail 1 via a lifting drive mechanism, which is installed on the top of the column. The output end of the lifting drive mechanism is connected to the slider. The slider slides in cooperation with the lifting guide rail 1 with a small gap, which can ensure the linearity and positioning accuracy of the lifting motion. The photoelectric centering instrument 3 is fixed to the slider via the centering instrument holder 2 and mounting plate, and moves vertically up and down synchronously with the slider. The photoelectric centering instrument 3 includes an internal beam splitter and imaging lens group. The detection beam emitted by the light source 13 is reflected by the beam splitter and then incident downward along the detection optical axis onto the detection surface of the symmetrical prism to be tested. The detection beam reflected back from the detection surface returns upward along the detection optical axis, passes through the beam splitter, and is imaged onto the photosensitive surface of the CCD camera at the light outlet above the photoelectric centering instrument 3 by the imaging lens group, forming a light spot image corresponding to the center deviation. After the CCD camera acquires the light spot image, the processing module extracts the center deviation from the coordinates of the light spot image, providing a data basis for deviation calculation. Furthermore, the center lines of the guide rail, the column, and the stage are coplanar.

[0027] Furthermore, the positioning mechanism includes a first adjusting seat and a positioning element located on top of the first adjusting seat; The positioning member 12 is provided with a V-shaped positioning groove 16 on the side facing the platform, and the positioning member is installed on the top of the first adjustment seat.

[0028] The positioning component 12 has a V-shaped positioning groove 16 on its side, which guides the symmetrical prism to the outer geometric center using the principle of automatic centering of the inclined plane; the V-shaped positioning groove 16 is equipped with a manual spiral clamping component 11, which is used to press the symmetrical prism into the V-shaped positioning groove 16 to prevent displacement during rotation.

[0029] Furthermore, a fastening assembly is provided between the top of the first adjusting seat and the positioning member; The fastening assembly includes a limiting groove 18 and a clamping member 11 disposed on the positioning member 12; The limiting groove 18 is arranged along the extension direction of the positioning member 12 at one end of the positioning member 12 located at the top of the first adjusting seat, on the center line of the positioning member 12, and is opened at one end facing away from the platform 5. At least two clamping members 11 are provided. One end of the clamping member presses against the top of the positioning member, and the other end of the clamping member passes through the limiting groove and is threadedly connected to the top of the first adjusting seat 14.

[0030] Furthermore, the auxiliary mechanism includes a second adjusting seat 15, a pulley assembly located on top of the second adjusting seat and matched therewith, and a drive motor located on top of the pulley assembly; The drive wheel and driven wheel of the pulley assembly are horizontally arranged at their end faces. The drive wheel and driven wheel are rotatably mounted on the top of the second adjusting seat. The driven wheel is located on the side of the drive wheel facing the platform. The drive motor is located on top of the drive wheel, and the output end of the drive motor is connected to the drive motor.

[0031] It should be noted that: The pulley in this application comprises a transmission mechanism consisting of a synchronous pulley 7 and a rubber synchronous belt 8, wherein the synchronous pulley 7 includes a drive pulley and a driven pulley 17. By optimizing the transmission ratio design, the rotation speed of the symmetrical prism under test is ensured to be uniform and stable, replacing the traditional manual rotation method, which not only improves the accuracy of trajectory acquisition but also reduces the labor intensity of operators; the rotation speed can be adjusted by a simple knob to adapt to the testing requirements of symmetrical prisms of different specifications. This transmission scheme is a key protection point.

[0032] The drive motor in this application can be either a stepper motor or a servo motor. The synchronous belt drive in the transmission structure is replaced with a gear drive, which can further improve the speed stability and transmission accuracy, and is suitable for inspection with higher precision requirements.

[0033] The power output of the drive motor 6 is connected to the symmetrical prism under test on the stage 5 via the drive wheel in the synchronous pulley 7 and the belt 8, so as to drive the symmetrical prism under test to rotate at a constant speed: In one embodiment of this application, the first adjusting seat 14 and the second adjusting seat 15 are bases with a mounting platform at the top and a fine-tuning screw at the bottom. The mounting platform is fixed to the top of the fine-tuning screw, and the fine-tuning screw is threaded to the top surface of the base 9. The height of the two can be adjusted by forward and reverse rotation. The first adjusting seat 14 and the second adjusting seat 15 are distributed below the V-shaped positioning groove 16 and below the rotating mechanism, and are used to finely adjust the horizontal position of the V-shaped positioning groove 16 and the synchronous wheel 7 to ensure the initial positioning accuracy of the prism.

[0034] Furthermore, the testing device is also equipped with a data acquisition module and a processing module; The acquisition module is located on one side of the stage. The acquisition module is used to acquire the number of axial movements, the displacement of each axial movement, and the rotation angle of the symmetrical prism under test within one rotation cycle. The processing module is electrically connected to the drive motor 16, the acquisition module, and the CCD camera, respectively. The processing module performs the following operations: Based on the calibration dataset acquired by the acquisition module within a calibration cycle, and the coordinates of feature points in the spot image synchronously acquired by the CCD camera, the geometric deviation parameter of the actual rotation axis of the symmetrical prism under test relative to the ideal measurement coordinate system is determined by fitting; and in subsequent formal measurements, the geometric deviation parameter is used to perform coordinate transformation compensation on the coordinates of the original spot image acquired by the CCD camera to eliminate the systematic error introduced by the spatial position deviation of the rotation axis.

[0035] Furthermore, the processing module is configured as follows: S1, while driving the symmetrical prism under test to rotate in actual rotation, obtain the number of calibrations of axial displacement of the symmetrical prism under test in at least one uniform calibration rotation cycle, the angles of multiple calibration rotation surfaces, and the calibration axial displacement measurement values ​​corresponding to the calibration rotation surface angles, so as to establish a calibration dataset. S2, Based on the calibration dataset, determine the deflection angle and translation of the actual rotation axis relative to the ideal measurement coordinate system, as a geometric deviation parameter; S3, during formal scanning and measurement, based on the current rotation angle and geometric deviation parameters acquired in real time by the acquisition module, the original coordinates of the surface contour or feature points of the symmetrical prism to be measured acquired by the CCD camera at the same time are transformed into spatial coordinates to obtain the compensated accurate coordinates. S4 uses the compensated, precise coordinates as the final measurement value.

[0036] The fitting and compensation process of the processing module is specified in three steps: calibration data acquisition, deviation parameter fitting, and real-time coordinate transformation compensation.

[0037] Furthermore, the error compensation method specifically includes: The processing module controls the drive motor to rotate the symmetrical prism under test for calibration, and uses the acquisition module to synchronously acquire the calibration dataset, which includes the axial displacement of the symmetrical prism under test at different rotation angles. Based on the calibration dataset, the geometric deviation parameters describing the spatial position deviation of the actual rotation axis of the symmetrical prism under test are solved by data fitting. During formal multi-angle scanning measurement, the original measurement data obtained by the CCD camera corresponding to the current rotation angle is transformed according to the current rotation angle collected in real time by the acquisition module and the geometric deviation parameters, in order to compensate for the systematic error caused by the deviation of the actual rotation axis, and output the compensated final measurement data.

[0038] Furthermore, the geometric deviation parameters include at least the angle between the actual rotation axis and the Z-axis of the ideal measurement coordinate system, as well as the offset in the X-axis and Y-axis directions; that is, the actual rotation axis is established as an inclined straight line in space, so as to solve the deflection angle and translation of the straight line relative to the ideal measurement coordinate system. The coordinate transformation process specifically includes: projecting the original measurement data obtained based on the ideal coordinate system in reverse to the object coordinate system with the actual rotation axis as the reference; The object coordinate system is rotated according to the current rotation angle, and the transformed data is projected back into the ideal measurement coordinate system to obtain the compensated accurate coordinates. Specifically: First, the original measurement data obtained based on the ideal coordinate system is projected in reverse to the object coordinate system with the actual rotation axis as the reference, that is, the coordinates of the original data points measured by the CCD camera are obtained. Assuming the position of this point when the prism rotates around the ideal axis, using the known geometric deviation parameters, through a reverse translation and rotation, that is, the inverse transformation of the coordinate transformation, this point is placed back onto the body of the symmetrical prism that it truly belongs to, which rotates around the actual axis.

[0039] Then, in the object coordinate system, a correct rotation transformation is performed based on the current rotation angle; that is, in the object coordinate system, the prism rotates around its own actual axis to the current angle. Finally, the transformed data is projected back into the ideal measurement coordinate system to obtain the compensated, accurate coordinates. The coordinates of the point after correct rotation are then mapped back into the ideal measurement coordinate system of the CCD camera through a positive coordinate transformation (defined by the geometric deviation parameter), yielding the correct coordinates of this point that should be measured, eliminating the influence of axis deviation.

[0040] The processing module stores or outputs the compensated coordinates as the final measurement result. Through the above calibration and compensation mechanism, the systematic error introduced by the spatial deviation between the actual rotation axis of the symmetrical prism under test and the ideal measurement coordinate system can be effectively eliminated, thereby improving the accuracy and repeatability of multi-angle scanning measurements.

[0041] During testing, the symmetrical prism is placed on the stage and clamped to opposite sides by V-shaped positioning grooves and auxiliary mechanisms. The photoelectric centering device 13, mounted on a guide rail on a column via a slider, can move vertically to focus the detection optical axis at the center of the prism's detection surface. The light source 13 is positioned in the detection optical path of the photoelectric centering device 3 to project a detection beam onto the detection surface of the symmetrical prism under test. The photoelectric centering device 3 receives the detection beam reflected back from the detection surface and forms a light spot image. A CCD camera acquires this light spot image. The drive motor 6 is started, driving the symmetrical prism under test to rotate via the drive wheel, belt 8, and driven wheel 17.

[0042] The acquisition module obtains axial displacement and rotation angle data within the calibration period, and the processing module uses this data to fit the geometric deviation parameters of the actual rotation axis. Specifically: Within the calibration rotation period, the axial displacement Δzi corresponding to multiple rotation angles φi is recorded, along with the coordinates (xi, yi) of the feature points in the spot image synchronously acquired by the CCD camera. This data constitutes the calibration dataset. In the calibration dataset, the change in axial displacement with rotation angle reflects the deflection between the actual rotation axis and the Z-axis of the ideal measurement coordinate system; the trajectory of the feature point coordinates in the spot image reflects the offset of the actual rotation axis in the X and Y directions. By fitting the sequence of axial displacement changes with rotation angle to a sine function, and fitting the sequence of feature point coordinates in the spot image to a circular trajectory, the deflection components θx and θy of the actual rotation axis relative to the ideal measurement coordinate system, as well as the offsets Δx and Δy, can be obtained.

[0043] During the formal measurement, the processing module performs coordinate transformation compensation on the coordinates of the original spot image acquired by the CCD camera at the same moment, based on the current rotation angle φ collected in real time by the acquisition module and the aforementioned geometric deviation parameters. The coordinate transformation satisfies the following relationship: ; Among them, P m The coordinate vector of the original spot image in an ideal measurement coordinate system; T=(Δx,Δy,0) T The actual axis of rotation lies on the reference plane where the top surface of the stage is located. X-axis and Y-axis offset vectors; Ra is the rotation matrix that transforms the actual rotation axis to coincide with the Z-axis of the ideal measurement coordinate system; Rz( () is the rotation matrix that rotates around the Z-axis by the current rotation angle φ; Pc is the compensated, precise coordinate vector.

[0044] The ideal measurement coordinate system has its origin at the center of the top surface of the stage and is centered by the photoelectric centering. The detection optical axis of the instrument is the Z-axis, and the two mutually orthogonal directions within the top surface of the stage are the X-axis and Y-axis.

[0045] The compensated light spot image coordinates are used to calculate the center deviation of the symmetrical prism under the rotation angle. The calculation method is to multiply the compensated light spot image coordinates by the displacement conversion coefficient corresponding to the optical magnification of the photoelectric centering instrument to obtain the center deviation.

[0046] Through the above calibration and compensation mechanism, the systematic error introduced by the spatial deviation between the actual rotation axis of the symmetrical prism under test and the ideal measurement coordinate system can be effectively eliminated, thereby improving the accuracy and repeatability of multi-angle scanning measurement.

[0047] The acquisition module specifically includes an axially arranged laser displacement sensor for measuring axial displacement, and a coaxially mounted encoder or another angle sensor for measuring rotation angle. The axial displacement sensor is aligned with the end face or side face of the symmetrical prism under test to acquire its displacement change along the theoretical axis. The rotation angle sensor is coupled to the output shaft of the drive motor or the rotation shaft of the symmetrical prism under test to achieve synchronous monitoring of the actual motion information of the symmetrical prism under test in a non-ideal state during rotation, i.e., actual axial movement and actual rotation angle, through an independent acquisition module. Simultaneously, a CCD camera is fixed to the side to acquire the light spot image formed by the photoelectric centering instrument 3. All data are converged to the processing module, which executes algorithms for deviation parameter calculation and measurement data correction.

[0048] The processing module uses this monitoring data to reverse-engineer the geometric deviation parameters that cause the actual rotation axis in space. In subsequent formal measurements, the system uses these geometric deviation parameters as correction values, performing real-time or post-processing corrections on each original measurement point of the CCD camera through coordinate transformation, thereby correcting systematic errors such as axis instability. This achieves axis stabilization without relying on increasing the mechanical precision of the clamping components and rotating wheels, allowing for deviations within a certain range, which are then eliminated using this method. This overcomes the axis drift problem caused by rotation axis instability.

[0049] In one embodiment of the application, the processing module is an embedded controller or an industrial computer; the axial displacement sensor is specifically any one of a laser triangulation rangefinder or a contact probe, used to continuously record the minute axial movement of the symmetrical prism under test as it rotates, recording the sequence of displacement changes with time or rotation angle; the rotation angle sensor is specifically any one of a photoelectric encoder or a rotary transformer, used to record the actual rotation angle of the symmetrical prism under test at each moment, thereby obtaining axial movement and angle feedback, providing a high-quality, quantifiable input data basis for the subsequent processing module to perform accurate deviation parameter fitting.

[0050] A laser displacement sensor is mounted on the side of the worktable, its beam striking one end face of the prism perpendicularly. The encoder can be directly mounted on the rear end of the drive motor, or mounted on the main shaft supporting the prism via a coupling. The processing module synchronously reads the signals from both sensors and the coordinates of the light spot image from the CCD camera via a data acquisition card.

[0051] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A symmetrical prism center deviation testing device, characterized in that, The testing device includes testing components and auxiliary fixtures; The test components include a CCD camera, a photoelectric centering device, and a stage arranged from top to bottom, and the CCD camera, photoelectric centering device, and stage are coaxially arranged. The CCD camera is used to acquire the light spot image formed by the photoelectric centering instrument, which corresponds to the center deviation of the symmetrical prism under test, in order to obtain the original measurement data of the center deviation. The photoelectric centering instrument moves up and down to focus the detection optical axis at the center of the sphere of the symmetrical prism detection surface; The auxiliary fixture includes a positioning mechanism and an auxiliary mechanism disposed around the periphery of the stage; The positioning mechanism is provided with a V-shaped positioning groove on the side facing the platform; The V-shaped positioning groove and the auxiliary mechanism are respectively clamped on opposite sides of the prism to be tested; The auxiliary mechanism has a driven wheel that is opposite to the V-shaped positioning groove. The outer circumferential surface of the driven wheel is used to make frictional contact with the outer circular side surface of the symmetrical prism to be tested. The auxiliary mechanism is clamped on the other side of the prism to be tested. The auxiliary mechanism drives the prism to be tested, which is placed on the stage, to rotate at a constant speed through its own drive, so as to realize that the photoelectric centering instrument can synchronously capture the center deviation signal at each rotation angle.

2. The symmetrical prism center deviation testing device according to claim 1, characterized in that, The testing device also includes a drive mechanism that drives the photoelectric centering instrument to move up and down. The drive mechanism includes a column and a drive assembly; The column is located on one side of the platform; The drive assembly is located on the side of the column facing the platform, and the drive assembly includes a matching guide rail and a slider. The guide rail is provided on the side of the column facing the platform, along the extension direction of the column; The slider is slidably connected to the guide rail; The photoelectric centering device is mounted on the slider and moves up and down along the guide rail as the slider slides.

3. The symmetrical prism center deviation testing device according to claim 2, characterized in that, The center lines of the guide rail, the column, and the platform are arranged in the same plane.

4. The symmetrical prism center deviation testing device according to claim 1, characterized in that, The positioning mechanism includes a first adjusting seat and a positioning element located on top of the first adjusting seat; The positioning component has a V-shaped positioning groove on the side facing the stage, and the positioning component is installed on the top of the first adjustment seat.

5. The symmetrical prism center deviation testing device according to claim 4, characterized in that, A fastening assembly is provided between the top of the first adjusting seat and the positioning member; The fastening assembly includes a limiting groove and a clamping element disposed on the positioning element; The limiting groove is disposed at one end of the positioning member located at the top of the first adjusting seat, and the limiting groove is disposed along the extending direction of the positioning member; At least two clamping components are provided. One end of the clamping component presses against the top of the positioning component, and the other end of the clamping component passes through the limiting groove and is threaded to the top of the first adjusting seat.

6. The symmetrical prism center deviation testing device according to claim 4, characterized in that, The auxiliary mechanism includes a second adjusting seat, a pulley assembly located on top of the second adjusting seat and matched therewith, and a drive motor located on top of the pulley assembly; The drive wheel and driven wheel of the pulley assembly are horizontally arranged at their end faces. The drive wheel and driven wheel are rotatably mounted on the top of the second adjusting seat. The driven wheel is located on the side of the drive wheel facing the platform. The drive motor is located on top of the drive wheel, and the output end of the drive motor is connected to the drive wheel.

7. The symmetrical prism center deviation testing device according to claim 6, characterized in that, The testing device is also equipped with a data acquisition module and a processing module; The acquisition module is located on one side of the stage. The acquisition module is used to acquire the number of axial movements, the displacement of each axial movement, and the rotation angle of the symmetrical prism under test within one rotation cycle. The processing module is electrically connected to the drive motor, the acquisition module, and the CCD camera, respectively, and performs the following operations: Based on the calibration dataset acquired by the acquisition module within a calibration cycle, and the coordinates of feature points in the spot image synchronously acquired by the CCD camera, the geometric deviation parameter of the actual rotation axis of the symmetrical prism under test relative to the ideal measurement coordinate system is determined by fitting; and in subsequent formal measurements, the geometric deviation parameter is used to perform coordinate transformation compensation on the coordinates of the original spot image acquired by the CCD camera to eliminate the systematic error introduced by the spatial position deviation of the rotation axis.

8. The symmetrical prism center deviation testing device according to claim 7, characterized in that, The processing module is configured as follows: S1, while driving the symmetrical prism under test to rotate in actual rotation, acquire the symmetrical prism under test within at least one uniform calibration rotation cycle, the angles of multiple calibration rotation surfaces, the calibration axial displacement measurement values ​​corresponding to each calibration rotation surface angle, and the coordinates of the feature points of the spot image synchronously acquired by the CCD camera, so as to establish a calibration dataset. S2, Based on the calibration dataset, determine the deflection angle and translation of the actual rotation axis relative to the ideal measurement coordinate system, as a geometric deviation parameter; S3, during formal scanning and measurement, based on the current rotation angle and geometric deviation parameters acquired in real time by the acquisition module, the coordinates of the original spot image acquired by the CCD camera at the same moment are transformed into spatial coordinates to obtain the compensated accurate coordinates. S4 calculates the center deviation of the symmetrical prism under test using the compensated accurate coordinates, and uses it as the final measurement value.

9. A symmetrical prism center deviation testing device according to claim 7 or 8, characterized in that, The error compensation method specifically includes: The processing module controls the drive motor to rotate the symmetrical prism under test for calibration, and uses the acquisition module to synchronously acquire the calibration dataset. The calibration dataset includes the axial displacement of the symmetrical prism under test at different rotation angles, the corresponding rotation plane angles, and the coordinates of the feature points of the spot image synchronously acquired by the CCD camera. Based on the calibration dataset, the geometric deviation parameters describing the spatial position deviation of the actual rotation axis of the symmetrical prism under test are solved by data fitting. During formal multi-angle scanning measurement, the coordinate transformation of the original spot image coordinates corresponding to the current rotation angle acquired by the CCD camera in real time and the geometric deviation parameters is performed based on the current rotation angle acquired by the acquisition module in real time, in order to compensate for the systematic error caused by the deviation of the actual rotation axis, and the center deviation is output as the final measurement data.

10. A symmetrical prism center deviation testing device according to claim 7, characterized in that, The geometric deviation parameters include at least the angle between the actual axis of rotation and the Z-axis of the ideal measurement coordinate system, as well as the offsets in the X and Y axes. The ideal measurement coordinate system has the center of the top surface of the stage as its origin, the detection optical axis of the photoelectric centering instrument as its Z-axis, and two mutually orthogonal directions within the top surface of the stage as its X-axis and Y-axis. The coordinate transformation process satisfies the following coordinate transformation relationship: ； Where Pm is the coordinate vector of the original spot image in the ideal measurement coordinate system; T=(Δx,Δy,0) T The vectors representing the offset of the actual axis of rotation in the X and Y directions on the reference plane where the top surface of the stage is located; Ra is the rotation matrix that transforms the actual rotation axis to coincide with the Z-axis of the ideal measurement coordinate system; Rz( The current rotation angle is the rotation around the Z-axis. rotation matrix; Pc is the compensated, precise coordinate vector.

Images