A high-speed rotary table rotation angle measuring device and a measuring method thereof

Abstract

The application discloses a high-speed rotary table rotation angle measuring device and a measuring method thereof, and belongs to the technical field of optical sensing measurement. According to the technical scheme of the application, rotary table angular displacement is linearly converted into optical path variation; a rotating interference pattern is generated by using conjugate vortex light interference; a double-mode detection system in which a high-speed photoelectric detector and a camera work synchronously is adopted to perform high-speed counting on the whole period number of the interference pattern and high-precision analysis on the non-integer period rotation angle, and finally, the rotation angle is calculated by fusing data. According to the application, the angular displacement-linear displacement conversion mechanism is adopted, so that the large-angle measurement range far exceeding the traditional method is realized. Secondly, the double-mode detection scheme perfectly solves the contradiction between high-speed measurement and high-precision requirement. Finally, the conjugate light interference design effectively suppresses common-mode noise, and significantly improves the anti-interference ability and measurement stability of the device. The high-speed, high-precision, wide-range and high-robustness test of the high-speed rotary table precision is realized.

Description

Technical Field

[0001] This invention relates to the field of optical sensing and measurement technology, and more specifically, to a device and method for measuring the rotation angle of a high-speed turntable. Background Technology

[0002] A high-precision turntable is a scientific instrument with high angular position accuracy and low tilt rotation error. This equipment is widely used in many fields such as medical equipment, automobile manufacturing, satellite navigation and positioning, robotics, drones, intelligent manufacturing, agriculture, geological exploration, and marine surveying, and plays an important role in basic engineering and technological sciences, aviation, aerospace science and technology and other scientific research fields.

[0003] Current turntable accuracy testing methods primarily rely on optical measurements. Among these, autocollimators are costly and have limited measurement angles, while traditional laser interferometry is highly dependent on environmental conditions, with environmental changes significantly impacting the accuracy of the measurement results. With the deepening research into vortex beams, they have been applied to laser coherent measurements. Compared to traditional laser interferometry, vortex beam-based laser interferometry retains the inherent advantages of non-contact measurement, high resolution, and wide dynamic range. Furthermore, the unique phase structure and orbital angular momentum spectrum characteristics of vortex beams, along with the common-mode noise of conjugate vortex beams, cancel each other out during interference, greatly improving the accuracy and robustness of the measurement.

[0004] However, current turntable accuracy testing methods based on vortex light have a small measurement angle, and the measurement speed is limited due to camera acquisition frequency limitations, making it impossible to achieve high-precision and high-speed turntable accuracy testing over a wide angle range. Summary of the Invention

[0005] The purpose of this disclosure is to provide a device and method for measuring the rotation angle of a high-speed turntable, which can solve at least one of the aforementioned technical problems. The specific solution is as follows:

[0006] A device for measuring the rotation angle of a high-speed turntable, comprising:

[0007] Vortex beam generation unit, used to generate vortex beams;

[0008] A beam splitting unit is used to split the vortex beam into a first beam and a second beam.

[0009] The measuring optical path and angle-displacement conversion unit are used to convert the angular displacement of the turntable under test into the change in optical path of the first beam;

[0010] A reference optical path unit is used to receive the second beam and generate a reference beam; the reference beam is a conjugate vortex beam with the same frequency as the first beam but opposite topological charge number.

[0011] An interference beam combining unit is used to cause the first beam carrying the optical path change to interfere with the reference beam, thereby generating an interference pattern.

[0012] The dual-mode detection unit, used to synchronously acquire the interferogram, includes: a high-speed photoelectric detection subunit, an image sensing subunit, and a synchronization control subunit;

[0013] The high-speed photoelectric detection subunit is used to count the number of rotations of the interferogram over an entire cycle.

[0014] The image sensing subunit is used to acquire the interference pattern and obtain the rotation angle of a non-integer period;

[0015] The synchronization control subunit is used to send a synchronization trigger signal to the high-speed photoelectric detection subunit and the image sensing subunit to control them to start data acquisition synchronously.

[0016] The signal processing unit is used to receive the integer-cycle counting signal from the high-speed photodetector subunit and the non-integer-cycle rotation angle signal from the image sensing subunit, and calculate the rotation angle of the turntable under test according to the correspondence between the optical path change and the rotation angle of the turntable under test.

[0017] Furthermore, the high-speed photoelectric detection subunit includes N photoelectric detectors uniformly distributed on the circumference; wherein, .

[0018] Furthermore, the reference optical path unit includes a retroreflector for receiving the second beam and generating the reference beam with the opposite topological charge number.

[0019] Furthermore, the image sensing subunit is a CCD camera or a CMOS camera.

[0020] Furthermore, the measurement optical path and angle-displacement conversion unit includes a right-angle prism fixedly mounted on the turntable to be measured.

[0021] The present invention also provides a method for measuring the rotation angle of a turntable, the method comprising the following steps:

[0022] The measurement optical path and angle-displacement conversion unit are set on the turntable to be measured, and the radius of rotation is set.

[0023] The rotation of the turntable under test is controlled, and the angular displacement is converted into optical path change through the measurement optical path and the angle-displacement conversion unit.

[0024] The high-speed photoelectric detection subunit and the image sensing subunit are started synchronously by sending a trigger signal through the synchronization control subunit.

[0025] The high-speed photoelectric detection subunit counts the number of integer cycles of the interference pattern rotation;

[0026] The interference pattern is acquired by the image sensing subunit to obtain the rotation angle of a non-integer period;

[0027] The rotation angle of the turntable under test is calculated based on the number of integer cycles and the rotation angle of the non-integer cycles.

[0028] Further, the calculation of the rotation angle of the turntable under test includes:

[0029] The rotation angle of the turntable under test is calculated based on the total optical path change and the radius of rotation.

[0030] Furthermore, the expression for the total optical path change is:

[0031] ,

[0032] Wherein, s represents the total optical path change; m represents the number of integer periods; λ represents the rotation angle of a non-integer period; λ represents the wavelength of the vortex beam.

[0033] Furthermore, the expression for the rotation angle of the turntable under test is:

[0034] ,

[0035] Wherein, R represents the radius of gyration; This indicates the rotation angle of the turntable under test.

[0036] Furthermore, obtaining the rotation angle of a non-integer period includes:

[0037] Extract feature points of petals of a specific order from the interference pattern;

[0038] Establish a polar coordinate system with the center of the interference pattern as the origin, and determine the initial polar coordinate positions of the feature points;

[0039] Calculate the polar angle offset of the feature point due to the change in optical path, and obtain the rotation angle of the non-integer period.

[0040] Compared with the prior art, the above-described solutions of the present invention have at least the following beneficial effects:

[0041] 1. This invention discloses a device and method for measuring the rotation angle of a high-speed turntable. By using a measurement optical path and an angle-to-displacement conversion unit, the angular displacement of the turntable is linearly converted into an optical path change. The measurement range is no longer limited by phase ambiguity but is determined by the radius of rotation. By increasing the radius of rotation, the angle measurement range can be greatly expanded while ensuring accuracy, achieving a much larger angle measurement than traditional methods.

[0042] 2. This invention discloses a measuring device and method for measuring the rotation angle of a high-speed turntable. Through a dual-mode detection unit, a high-speed photodetector is responsible for high-speed counting, which overcomes the limitation of camera frame rate and solves the speed problem; a CCD camera or CMOS camera is responsible for high-precision subdivision, which solves the accuracy problem; the combination of the two solves the contradiction between speed and accuracy in the prior art, and is suitable for high-speed turntable testing.

[0043] 3. This invention discloses a device and method for measuring the rotation angle of a high-speed turntable. It uses a reference optical path unit to generate a conjugate vortex beam with the opposite topological charge number to the measurement beam as a reference light. When the two conjugate beams interfere, their common-mode noise, such as air jitter and platform vibration, will cancel each other out. The unique optical path change of the signal, i.e. the measurement light, is preserved, so that the device for measuring the rotation angle of a high-speed turntable can maintain stable measurement even in complex industrial environments. Attached Figure Description

[0044] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure. It is obvious that the drawings described below are merely some embodiments of this disclosure, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. In the drawings:

[0045] Figure 1 A schematic diagram of the structure of a high-speed turntable rotation angle measuring device provided in an embodiment of the present invention;

[0046] Figure 2 This is a schematic diagram of the photodetector position distribution provided in an embodiment of the present invention;

[0047] Figure 3 A flowchart illustrating a method for measuring the rotation angle of a high-speed turntable according to an embodiment of the present invention;

[0048] Figure 4 A schematic diagram illustrating the relationship between the measured angle of the turntable and the change in optical path provided in an embodiment of the present invention;

[0049] Figure 5This is a schematic diagram of a conjugate vortex optical interference pattern provided in an embodiment of the present invention.

[0050] The reference numerals in the figures include:

[0051] 1. Laser, 2. Beam expander, 3. Spiral phase plate, 4. First beam splitter, 5. Second beam splitter, 6. Right-angle prism, 7. Adapter plate, 8. Turntable under test, 9. First reflector, 10. Second reflector, 11. Retroreflector, 12. Third beam splitter, 13. Fourth beam splitter, 14. Camera, 15. Third reflector, 16. High-speed photoelectric detection subunit, 17. Synchronization control subunit, 18. Industrial control computer. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of this disclosure clearer, the disclosure will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this disclosure, and not all of them. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0053] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a product or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a product or device. Without further limitation, an element defined by the phrase "comprising one" does not exclude the presence of other identical elements in the product or device that includes that element.

[0054] The following is in conjunction with the appendix Figure 1-5 Detailed description of optional embodiments of the present invention.

[0055] like Figure 1 As shown in the figure, according to a specific embodiment of the present invention, the present invention provides a measuring device for the rotation angle of a high-speed turntable, comprising:

[0056] The vortex beam generating unit includes a laser 1, a beam expander 2, and a spiral phase plate 3, which are used to generate vortex beams.

[0057] The beam splitting unit includes a first beam splitter 4, which is used to split the vortex beam into a first beam and a second beam.

[0058] The measurement optical path and angle-displacement conversion unit includes a second beam splitter 5, a right-angle prism 6, an adapter plate 7, and a first reflector 9, used to convert the angular displacement of the turntable 8 under test into the optical path change of the first beam. The right-angle prism 6 is mounted on the turntable 8 under test via the adapter plate 7.

[0059] The reference optical path unit includes a retroreflector 11 for receiving the second beam and generating a reference beam. The reference beam is a conjugate vortex beam with the same frequency as the first beam but opposite topological charge numbers.

[0060] The interference beam combining unit includes a third beam splitter 12, which is used to cause the first beam carrying the optical path change to interfere with the reference beam to generate an interference pattern.

[0061] The dual-mode detection unit is used to synchronously acquire interferometric patterns and includes a high-speed photoelectric detection subunit 16, an image sensing subunit, and a synchronization control subunit 17.

[0062] The high-speed photoelectric detection subunit 16 includes N photoelectric detectors evenly distributed on the circumference. In this embodiment of the invention, the number of photoelectric detectors is 6, such as... Figure 2 As shown. This is used to count the number of rotations of the interference pattern over an entire cycle, where... .

[0063] The image sensing subunit, which is a CCD camera 14 or a CMOS camera 14, is used to acquire interferometric patterns and obtain non-integer rotation angles.

[0064] The synchronization control subunit 17 includes a synchronization trigger, which is used to send a synchronization trigger signal to the high-speed photoelectric detection subunit 16 and the image sensing subunit to control them to start data acquisition synchronously.

[0065] The signal processing unit includes a signal processing submodule and an industrial control computer 18. The signal processing submodule amplifies, filters, and performs A / D conversion on the signal before transmitting it to the industrial control computer 18. It receives the integer-cycle counting signal from the high-speed photoelectric detection subunit 16 and the non-integer-cycle rotation angle signal from the image sensing subunit, and calculates the rotation angle of the turntable 8 under test based on the correspondence between the optical path change and the rotation angle of the turntable 8 under test.

[0066] In this embodiment of the invention, a laser 1 with a wavelength of 632.8 nm serves as the light source for the measuring device. The laser beam emitted by the laser 1 is incident on a spiral phase plate 3, which converts the laser beam into a vortex beam. A first beam splitter 4 receives the vortex beam emitted from the spiral phase plate 3, and the vortex beam is split into a transmitted measuring beam and a reflected second beam. That is, the measuring beam is the first beam.

[0067] The first beam passes through the second beam splitter 5 and is incident on the right-angle prism 6, ensuring that the beam direction is perpendicular to the edge of the right-angle prism 6 when viewed from the side. The beam is reflected twice within the right-angle prism 6 to be reflected parallel to the incident direction. The beam exiting the right-angle prism 6 is reflected by the first reflecting mirror 9 and returns along its original path to the right-angle prism 6. Reflected by the right-angle prism 6, it reaches the second beam splitter 5, which splits it again. The beam reflected by the second beam splitter 5 is incident on the second reflecting mirror 10, and after reflection by the second reflecting mirror 10, it is incident on the third beam splitter 12. In this embodiment of the invention, the beam exiting the right-angle prism 6 is parallel to the incident beam, allowing angular displacement to be linearly converted into linear displacement.

[0068] The second beam is incident into the retroreflector 11 and generates a reference beam with the opposite topological charge number through the retroreflector 11.

[0069] The reference beam is incident on the third beam splitter 12 and interferes with the first beam at the third beam splitter 12 to generate an interference beam.

[0070] The interference beam is incident on beam expander 2, which adjusts the diameter and divergence angle of the interference beam. The adjusted interference beam is then incident on fourth beam splitter 13. After being split by fourth beam splitter 13, the reflected beam is incident on CMOS camera 14. CMOS camera 14 detects and acquires the signal and transmits the data to industrial control computer 18. The transmitted beam is incident on third reflector 15, and after reflection, it is received by high-speed photoelectric detection subunit 16. High-speed photoelectric detection subunit 16 converts the optical signal into an electrical signal and transmits the signal to signal processing submodule. Signal processing submodule amplifies, filters, performs A / D conversion, and other processing on the signal before transmitting the signal to industrial control computer 18 for subsequent calculations to obtain the rotation angle of the high-speed turntable.

[0071] In this embodiment of the invention, the expression for the electric field of the vortex beam emitted from the spiral phase plate 3 is as follows:

[0072] ,

[0073] in, Represents the electric field of a vortex beam; The amplitude is represented by the radius r and the beam width w(z). Represents the Gaussian envelope; C represents the normalization constant; Indicates azimuth; i represents imaginary number; z represents axial distance; L represents the topological charge number; ∣l∣ Represents a generalized Laguerre polynomial; exp[ l φ(r,z)] represents the Gouy phase and wavefront curvature; exp(i l θ) represents the vortex phase, carrying... The orbital angular momentum of the topological charge number.

[0074] Before the turntable 8 under test rotates, the field strength of the light beam emitted by the right-angle prism 6 The expression can be simplified as:

[0075]

[0076] in, A function representing the radial intensity distribution of a light beam.

[0077] The expression for the field strength of the beam emitted by retroreflector 11 can be simplified as follows:

[0078]

[0079] The two beams converge at the third beam splitter at point 12, and the expression for the electric field amplitude of the interference beam is:

[0080]

[0081] When the rotation angle of the turntable 8 to be measured At this time, the optical path change s, the interference beam is:

[0082]

[0083] in, The radial light intensity distribution is represented by the phase factor, which determines the distribution pattern of the interference pattern; k represents the wave number, k = 2π / λ; d represents the optical path difference between the measuring optical path and the reference optical path; λ represents the wavelength of the vortex beam. When the optical path changes by s, the phase changes by 2ks.

[0084] For the interference pattern generated by vortex optical interference, when it rotates 2π times, it represents the measured change in optical path length as λ / 2. By acquiring the rotation angle information of the interference pattern through the CMOS camera 14, the change in optical path length can be known. It is possible to identify the displacement with sub-nanometer precision, thus achieving both large-angle measurement and high-precision measurement.

[0085] When the optical path change rate is 1 mm / s, the rotation speed of the interference pattern will exceed 3000 r / s. If only the CMOS camera 14 is used for signal acquisition, this will pose a huge challenge to the sampling frequency and image processing efficiency of the CMOS camera 14.

[0086] Therefore, in actual measurement, the high-speed photodetector subunit 16 counts the rotation of the interference pattern over an integer period. In this embodiment of the invention, six photodetectors are evenly distributed along the circumference to detect the number of rotations m of the interference pattern. The non-integer rotation angle β when the interference pattern has rotated less than one revolution is recorded by the CMOS camera 14.

[0087] This invention provides a device for measuring the rotation angle of a high-speed turntable. Through conjugate vortex optical interferometry, the angular displacement of the turntable 8 under test is converted into an optical path change. After measurement by a high-speed photoelectric detection subunit 16 and a CMOS camera 14, the actual rotation angle value of the turntable is calculated and output by an industrial control computer 18. By using the measurement optical path and the angle-displacement conversion unit, the angular displacement of the turntable 8 under test is linearly converted into an optical path change. The measurement range is no longer limited by phase ambiguity but is determined by the radius of rotation. By increasing the radius of rotation, the angle measurement range can be greatly expanded while maintaining accuracy, achieving a much larger angle measurement than traditional methods. Through a dual-mode detection unit, the high-speed photoelectric detector is responsible for high-speed counting, overcoming the frame rate limitation of the CMOS camera 14 and solving the speed problem; the CCD camera 14 or the CMOS camera 14 is responsible for high-precision subdivision, solving the accuracy problem. The combination of the two resolves the contradiction between speed and accuracy in existing technologies, making it suitable for high-speed turntable testing.

[0088] This invention provides a method for measuring the rotation angle of a high-speed turntable. Laser 1 is a He-Ne laser with a wavelength of 632.8 nm. A right-angle prism 6 has a rotation radius R = 100 mm. A high-speed photodetector subunit 16 consists of six InGaAs photodetectors evenly arranged along the circumference, with TTL edge output. An image sensing subunit is a CMOS camera 14. A synchronization control subunit 17 is an FPGA that simultaneously drives the six photodetectors and the CMOS camera 14. In this embodiment, the rotation radius is the vertical distance from a specific point (such as the incident point or vertex) of the right-angle prism 6 to the turntable axis, which is the distance from the right-angle prism 6 to the center of the turntable, i.e., the rotation radius of the right-angle prism 6 when the turntable rotates it.

[0089] like Figure 3 As shown, the measurement optical path and angle-displacement conversion unit are set on the turntable 8 under test, and the rotation radius is set. The right-angle prism 6 is fixed to the table surface of the turntable 8 under test through the adapter plate 7, ensuring that the right-angle edge of the prism is parallel to the rotation axis of the turntable 8 under test, and that the distance from the vertex of the right-angle prism 6 to the rotation axis is equal to the calibration value R = 100 mm. The first reflecting mirror 9 is adjusted so that the first beam returns along the original optical path after passing the prism.

[0090] By controlling the rotation of the turntable 8 under test, the right-angle prism 6 moves around the center of rotation, which is the center of rotation of the turntable 8 under test. Figure 4 As shown, move from point P to P ， The point, that is, the change in optical path in the direction parallel to the incident light, is s.

[0091] The photodetector and CMOS camera 14 are started synchronously by sending a trigger signal through the synchronous control subunit 17.

[0092] The high-speed photoelectric detection subunit 16 counts the number of whole cycles of the interference pattern rotation.

[0093] Interference patterns are acquired through the image sensing subunit to obtain non-integer rotation angles.

[0094] For the interference pattern generated by vortex optical interference, when it rotates 2π times, it represents the measured change in optical path length as λ / 2. By acquiring the rotation angle information of the interference pattern through the CMOS camera 14, the change in optical path length can be known. It is possible to identify the displacement with sub-nanometer precision, thus achieving both large-angle measurement and high-precision measurement.

[0095] In this embodiment of the invention, the high-speed photodetector subunit 16 counts the rotation cycles of the interference pattern. Six photodetectors are evenly distributed along the circumference to detect the number of rotations *m* of the interference pattern. A CMOS camera 14 records the angle change when the interference pattern rotates less than one revolution, i.e., the non-integer rotation angle β.

[0096] like Figure 5 As shown, the rotation angle of a non-integer period is obtained, including:

[0097] Feature points of petals of a specific order in the interferogram are extracted. After the device is started, the industrial control computer 18 first uses image processing algorithms, such as threshold segmentation and connected component analysis methods in the existing technology, to automatically identify and mark the absolute value of the topological charge number within the initial zero-bit frame. l | Corresponding petals. For example l When the value is +7, the interference pattern has 14 petals. The first order petal, which is the brightest and most complete petal, is used as the tracking object.

[0098] Establish a polar coordinate system with the center of the interference pattern as the origin, and determine the initial polar coordinate positions of the feature points. With the center of the interference pattern as the origin, transform the centroid of the first-order petal into polar coordinates, and denote it as the initial polar angle.

[0099] The polar angle offset caused by the change in optical path at the feature point is calculated to obtain the rotation angle of a non-integer period. During the operation of the turntable, the real-time polar angle is obtained from each frame of the CMOS camera 14.

[0100] The rotation angle of the turntable 8 under test is calculated based on the number of integer cycles and the rotation angles of non-integer cycles. This is the difference between the current real-time polar angle and the initial polar angle, which is the rotation angle β of the non-integer cycle.

[0101] Rotation angle This can be represented as the following expression:

[0102]

[0103] In this way, the rotation angle can be obtained from the measured change in optical path length s. Compared with existing vortex optical interferometry angle measuring devices and methods, this technology greatly improves the angle measuring range.

[0104] The expression for the total optical path change is:

[0105]

[0106] Where s represents the total optical path change; m represents the number of integer periods; λ represents the rotation angle of a non-integer period; λ represents the wavelength of the vortex beam.

[0107] As can be seen from the embodiments of the present invention, the technical solution provided by the present invention converts angular displacement into linear displacement, and collects angles of integer period and non-integer period in parallel and synchronously through the high-speed photoelectric detection subunit 16 and the image sensing subunit. It can still output the angle in real time when the turntable speed is 3000 r / s and the resolution is in the sub-microradian level, and the measurement range covers a wide angle range.

[0108] Finally, it should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems or apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple, and relevant parts can be referred to the method section.

[0109] The above embodiments are only used to illustrate the technical solutions of this disclosure, and are not intended to limit it. Although this disclosure has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this disclosure.

Claims

1. A device for measuring the angle of rotation of a high-speed rotary table, characterized in that, The application relates to a measurement device and a measurement method. The application comprises: a vortex light generating unit for generating a vortex light beam; a beam splitting unit for splitting the vortex light beam into a first light beam and a second light beam; a measurement light path and angle-displacement conversion unit for converting the angular displacement of a rotary table to be measured into the optical path variation of the first light beam; a reference light path unit for receiving the second light beam and generating a reference light beam; the reference light beam is a conjugate vortex light beam with the same frequency as the first light beam and opposite topological charge number; an interference beam combining unit for making the first light beam carrying the optical path variation interfere with the reference light beam to generate an interference pattern; a dual-mode detection unit for synchronously collecting the interference pattern, which comprises a high-speed photoelectric detection subunit, an image sensing subunit and a synchronous control subunit; the high-speed photoelectric detection subunit is used for counting the whole period rotation times of the interference pattern; the image sensing subunit is used for collecting the interference pattern and acquiring the non-whole period rotation angle; the synchronous control subunit is used for sending a synchronous trigger signal to the high-speed photoelectric detection subunit and the image sensing subunit to control the two to synchronously start data collection; 2. The measuring device of claim 1, wherein, The high-speed photoelectric detection subunit comprises N photoelectric detectors uniformly distributed on a circumference; wherein, .

3. The measuring device of claim 1, wherein, a signal processing unit is used for receiving the whole period counting signal from the high-speed photoelectric detection subunit and the non-whole period rotation angle signal from the image sensing subunit, and calculating the rotation angle of the rotary table to be measured according to the corresponding relationship between the optical path variation and the rotation angle of the rotary table to be measured.

4. The measuring device of claim 1, wherein, The reference light path unit comprises a retroreflector for receiving the second light beam and generating the reference light beam with the opposite topological charge number.

5. The measuring device of claim 1, wherein, The image sensing subunit is a CCD camera or a CMOS camera.

6. A method of measuring the angle of rotation of a turret, characterized in that, The measurement light path and angle-displacement conversion unit comprises a right-angle prism fixedly arranged on the rotary table to be measured. The measurement method comprises the following steps: arranging the measurement light path and angle-displacement conversion unit on the rotary table to be measured and setting the rotation radius; controlling the rotary table to rotate and converting the angular displacement into the optical path variation through the measurement light path and angle-displacement conversion unit; sending a trigger signal through the synchronous control subunit to synchronously start the high-speed photoelectric detection subunit and the image sensing subunit; counting the whole period rotation times of the interference pattern through the high-speed photoelectric detection subunit; collecting the interference pattern through the image sensing subunit to acquire the non-whole period rotation angle; 7. The measuring method according to claim 6, characterized in that, calculating the rotation angle of the rotary table to be measured according to the whole period number and the non-whole period rotation angle. The calculation of the rotation angle of the rotary table to be measured comprises:

8. The measurement method according to claim 7, characterized in that, calculating the rotation angle of the rotary table to be measured according to the total optical path variation and the rotation radius. ， The expression of the total optical path variation is:

9. The measurement method according to claim 8, characterized in that, wherein s represents the total optical path variation, m represents the whole period number, beta represents the non-whole period rotation angle and lambda represents the wavelength of the vortex light beam. ， wherein R represents the radius of gyration; represents the angle of rotation of the turntable under test.

10. The measurement method according to claim 9, characterized in that, The expression of the rotation angle of the rotary table to be measured is: The acquisition of the non-whole period rotation angle comprises: extracting the feature points of specific order petals in the interference pattern; An polar coordinate system is established with the center of the interference pattern as the origin, and initial polar coordinate positions of the feature points are determined; An polar angle offset of the feature points caused by the optical path variation is calculated, and the non-integer period rotation angle is obtained.

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