A differential wavefront sensing angle measurement device and measurement method based on iris diaphragm

Abstract

A differential wavefront sensing angle measurement device and method based on an iris diaphragm, belonging to the field of precision measurement technology, is intended to solve the problem of angle measurement accuracy and angle measurement linear range constraints of differential wavefront sensing technology. The invention includes a dual-frequency laser generation module, a reference light collimator, a reference photodetector, a reference reflector, No. 1, No. 2, and No. 3 non-polarized beam splitting prisms, a measuring reflector, No. 1 and No. 2 four-quadrant detectors, an iris diaphragm, and a measuring light collimator. The invention uses the No. 2 four-quadrant detector to obtain the light intensity data of each quadrant in real time according to the differential power sensing principle, and calculates the rough measurement value of the angle to be measured; adjusts the iris diaphragm to the corresponding aperture according to the rough measurement value, and realizes dynamic online adjustment of the linear range and measurement sensitivity of wavefront differential sensing measurement; finally, calculates the precise measurement value of the angle to be measured according to the differential wavefront sensing principle, and realizes coarse and precise secondary measurement, which improves the angle measurement range while ensuring the angle measurement accuracy.

Description

Technical Field

[0001] The invention belongs to the technical field of precision angle measurement, and in particular relates to a differential wavefront sensing angle measurement device and a measurement method based on an iris diaphragm. Background Art

[0002] Differential wavefront sensing measurement is an angle and displacement measurement technology based on heterodyne laser interferometry, which is widely used in space-based gravitational wave detection and laser multi-degree-of-freedom measurement systems. Its basic principle is that two laser beams with stable difference frequency are incident on a four-quadrant detector at the same time and meet the coherence condition, which will generate four beat frequency signals. The four beat frequency signals respectively record the coherent light information received by the corresponding quadrants. The phase information of the four beat frequency signals can be obtained by the phase meter. Combined with the angle measurement sensitivity, the angle measurement of the two laser beams can be realized.

[0003] Differential wavefront sensing has the advantages of high measurement accuracy, strong anti-interference ability, and low coupling, and is widely used in high-precision laser interferometry applications. However, the linear range of angle measurement of differential wavefront sensing cannot be balanced with the measurement sensitivity. Research by the University of Rochester (Yu X, Gillmer SR, Ellis JD. Beam geometry, alignment, and wave-frontaberration effects on interferometric differential wave-front sensing [J]. Measurement Science and Technology, 2015, 26 (12): 125-203.) shows that the measurement sensitivity increases with the increase of the spot size, and the measurement linear range decreases with the increase of the size of the four-quadrant detector. However, at the same time, the two restrict each other. In order to achieve higher measurement sensitivity and measurement accuracy, the measurement linear range of differential wavefront sensing will be greatly sacrificed. As mentioned above, when the measurement accuracy reaches ±1 μrad, the measurement linear range is only ±59 μrad, which undoubtedly greatly limits the further application and development of differential wavefront sensing. In subsequent work, the University of Rochester (Gillmer S R. Resolution and functionality enhancements in optical metrology [M]. University of Rochester, 2016.) proposed a compact Joo-Type differential wavefront sensing measurement scheme. There is no optical polarization device in the optical path of this scheme, which effectively reduces the nonlinear error of dual-frequency laser interferometry. At the same time, experiments show that this scheme can effectively weaken the impact of environmental noise and environmental vibration on the interference signal, significantly reduce the noise level of differential wavefront sensing measurement, and is conducive to improving measurement accuracy; however, this scheme still only has a measurement range of ±100 μrad, and measurement cannot be completed beyond this range.To this end, the Swiss Federal Institute of Technology in Zurich (Meshksar N, Mehmet M, Isleif K S, et al. Applying differential wave-front sensing and differential power sensing for simultaneous precise and wide-range test-mass rotation measurements [J]. Sensors, 2020, 21 (1): 164.) proposed combining differential wavefront sensing with differential power sensing, splitting the interference signal into two and using a lens to converge the light beam on a four-quadrant detector for differential power detection and differential wavefront sensing respectively; a measurement system for simultaneous high-precision and wide-range angle measurement was built. However, although its measurement range can reach ±5mrad, the high-sensitivity and high-precision measurement area is only ±110μrad, and only exists in the central area; at the same time, the differential power sensing unit in this structure receives both the measurement light and the reference light components, which introduces interference terms into the differential power sensing signal solution, increases the difficulty of settlement, and greatly reduces the amount of light energy received by the differential wavefront sensing unit, further reducing the measurement accuracy.

[0004] In summary, the angle measurement accuracy and angle measurement linear range of differential wavefront sensing technology restrict each other, and the two cannot be taken into account at the same time, which greatly limits the further development and application of differential wavefront sensing technology. Therefore, it is urgent to research and design a differential wavefront sensing measurement system that has a large angle measurement linear range while maintaining high measurement accuracy. Summary of the invention

[0005] The present invention aims to solve the problem that the angle measurement accuracy and the angle measurement linear range of the differential wavefront sensing technology are mutually restricted and cannot be taken into account at the same time, and proposes a differential wavefront sensing angle measurement device and measurement method based on an iris diaphragm.

[0006] To achieve the above object, the present invention is implemented through the following technical solutions:

[0007] A differential wavefront sensing angle measurement device based on an iris diaphragm comprises a dual-frequency laser, a reference light single-mode optical fiber, a reference light collimator, a reference photodetector, a No. 1 non-polarizing beam splitter prism, a reference reflector, a No. 3 non-polarizing beam splitter prism, a measuring reflector, a No. 2 four-quadrant detector, an iris diaphragm, a No. 1 four-quadrant detector, a No. 2 non-polarizing beam splitter prism, a measuring light collimator, and a measuring light single-mode optical fiber;

[0008] The dual-frequency laser is connected to a reference light single-mode optical fiber and a measurement light single-mode optical fiber respectively; the reference light single-mode optical fiber is connected to a reference light collimator, and the measurement light single-mode optical fiber is connected to a measurement light collimator;

[0009] The reference light emitted by the reference light collimator is vertically incident on the first non-polarizing beam splitter prism, and the measurement light emitted by the measurement light collimator is vertically incident on the second non-polarizing beam splitter prism; the side surfaces of the first non-polarizing beam splitter prism and the second non-polarizing beam splitter prism are bonded in parallel;

[0010] A reference photodetector is correspondingly arranged on the other side of the first non-polarizing beam splitter prism, and a reference reflector is bonded to the rear side of the first non-polarizing beam splitter prism;

[0011] An iris diaphragm is correspondingly arranged on the other side of the No. 2 non-polarizing beam splitter prism, a No. 1 four-quadrant detector is arranged on the side of the iris diaphragm, a No. 3 non-polarizing beam splitter prism is bonded to the rear side of the No. 2 non-polarizing beam splitter prism, a measuring reflector is arranged on the rear side of the No. 3 non-polarizing beam splitter prism, and a No. 2 four-quadrant detector is arranged on the side of the No. 3 non-polarizing beam splitter prism.

[0012] Furthermore, the dual-frequency laser, the reference light single-mode optical fiber, and the measurement light single-mode optical fiber constitute a dual-frequency laser generating module.

[0013] Furthermore, the reference light collimator, reference photodetector, No. 1 non-polarizing beam splitter prism, reference reflector, No. 3 non-polarizing beam splitter prism, measuring reflector, No. 2 four-quadrant detector, iris aperture, No. 1 four-quadrant detector, No. 2 non-polarizing beam splitter prism, and measuring light collimator constitute an optomechanical and electrical integrated sensing module.

[0014] Furthermore, when the movement of the measuring reflector includes both angular movement and axial displacement movement, the structure of the differential wavefront sensing angle measurement device based on the iris aperture is adjusted so that a plano-convex lens is bonded to the side of the No. 3 non-polarizing beam splitter prism, and a No. 2 four-quadrant detector is correspondingly arranged on the outer side of the plano-convex lens.

[0015] A differential wavefront sensing angle measurement method based on an iris diaphragm is implemented based on the differential wavefront sensing angle measurement device based on an iris diaphragm, and comprises the following steps:

[0016] S1. Turn on the dual-frequency laser generating module, and after the laser frequency is stable, set the measuring reflector to produce a yaw or pitch angle change, and use the No. 2 four-quadrant detector to obtain the light intensity data of each quadrant in real time according to the differential power sensing principle, and calculate the rough measurement value of the angle to be measured;

[0017] S2. Based on the rough measured value of the angle to be measured obtained in step S1, select the measurement linear range and measurement sensitivity of the differential wavefront sensor angle measurement device, and adjust the aperture of the iris diaphragm;

[0018] S3. Based on the aperture size of the iris diaphragm adjusted in step S2, use the No. 1 four-quadrant detector to collect phase data of different quadrants according to the differential wavefront sensing principle, and calculate the precise measurement value of the angle to be measured.

[0019] Furthermore, the specific implementation method of step S1 includes the following steps:

[0020] S1.1. The dual-frequency laser emits two laser beams, one for reference light and the other for measurement light;

[0021] The reference light is divided into two paths after passing through the first beam splitter prism. The transmitted light of the reference light is reflected by the reference reflector, then reflected by the first beam splitter prism and received by the reference photoelectric detector. The reflected light of the reference light is transmitted by the second beam splitter prism, passes through the iris diaphragm and is finally received by the first four-quadrant detector.

[0022] The measuring light is also divided into two paths after passing through the second beam splitter prism. The reflected light of the measuring light is transmitted through the first beam splitter prism and received by the reference photoelectric detector, forming a reference interference signal with the reference light component. The transmitted light of the measuring light is transmitted through the third beam splitter prism and then reflected by the measuring reflector and returned to the third beam splitter prism, and is divided into two paths again. The transmitted light of the measuring light is reflected by the second beam splitter prism and passed through the iris diaphragm and finally received by the first four-quadrant detector, forming a differential wavefront sensing interference signal with the reference light component. The reflected light of the measuring light is received by the second photoelectric detector to form a differential power sensing measurement signal.

[0023] S1.2. After the laser frequency is stable, set the measuring reflector to produce a deflection or pitch angle change. Set the iris diaphragm to the minimum aperture position in the initial measurement state. The second four-quadrant detector measures the light intensity of different quadrants based on the differential power sensing principle, and then calculates the rough deflection angle θ DPSx , Roughly measure the pitch angle θ DPSy , the calculation formula is:

[0024]

[0025]

[0026] Among them, P A is the light intensity of the second quadrant on the No. 2 four-quadrant detector, P B is the light intensity of the first quadrant on the second four-quadrant detector, P C is the light intensity of the fourth quadrant on the second four-quadrant detector, P Dis the light intensity of the third quadrant on the No. 2 four-quadrant detector. The quadrants are divided from A to D in a clockwise direction from the upper left corner. L DPS It is the minimum distance of light beam propagation from the front surface of the measuring reflector to the photosensitive surface of the second quadrant detector.

[0027] Furthermore, in the specific implementation method of step S2, the measurement linear range and measurement sensitivity are both corresponding characteristics of the differential wavefront sensing measurement method, and the measurement sensitivity is corrected using a quadratic curve fitting method.

[0028] Furthermore, the specific implementation method of step S3 is to use a multi-channel phase meter to measure the phase information of different quadrants on the No. 1 four-quadrant detector, and then calculate the precise measurement of the deflection angle θ DWSx 、Precisely measure the pitch angle θ DWSy , the calculation formula is:

[0029]

[0030]

[0031] Among them, φ A is the average phase of the second quadrant on the No. 1 four-quadrant detector, φ B is the average phase of the first quadrant on the No. 1 four-quadrant detector, φ C is the average phase of the fourth quadrant on the No. 1 four-quadrant detector, φ D The average phase quadrant of the third quadrant on the No. 1 four-quadrant detector is divided from A to D in a clockwise direction from the upper left corner; L x ,L y They are the measurement sensitivity of the yaw angle and the measurement sensitivity of the pitch angle respectively.

[0032] Furthermore, in step S1.2, when the laser frequency is stable, the measuring reflector is set to produce a two-dimensional angle change accompanied by an axial displacement change. The reflected light of the measuring light reflected by the measuring reflector after passing through the No. 3 non-polarized beam splitter prism first passes through a plano-convex lens and is then received by the No. 2 four-quadrant detector. When the measuring reflector produces an axial displacement and a two-dimensional deflection angle change, the iris diaphragm is set to the minimum aperture position in the initial measurement state. The No. 2 four-quadrant detector measures the light intensity of different quadrants based on the differential power sensing principle, and then calculates the rough measured roll angle and the rough measured pitch angle. The calculation formula is:

[0033]

[0034]

[0035] Where, f is the nominal focal length of the plano-convex lens;

[0036] At the same time, the axial displacement z is calculated according to the phase information of each quadrant of the No. 1 four-quadrant detector. The calculation formula is:

[0037]

[0038] Among them, L z is the axial displacement measurement sensitivity, L z It is related to the laser wavelength, optical path subdivision number and phase meter electronic subdivision number.

[0039] Beneficial effects of the present invention:

[0040] The differential wavefront sensing angle measurement device based on the iris diaphragm described in the present invention adds a third non-polarizing beam splitter prism, a second four-quadrant detector and an iris diaphragm to the traditional Joo-Type interference optical path; the differential wavefront sensing technology is combined with the differential power sensing technology to achieve coarse and fine measurements of two-dimensional angles, thereby increasing the angle measurement range of the measurement system.

[0041] The differential wavefront sensing angle measurement device based on the iris diaphragm described in the present invention can realize the dynamic adjustment of the differential wavefront sensing measurement range and measurement accuracy by using the iris diaphragm, ensure that the angle measurement to be measured is in the best measurement linear range and the highest sensitivity measurement state, and effectively improve the differential wavefront sensing angle measurement accuracy. The two-dimensional angles of pitch and yaw can be measured simultaneously, and the two-dimensional angles of pitch and yaw and the axial displacement can also be measured simultaneously by adding an optical component.

[0042] The iris diaphragm-based differential wavefront sensing angle measurement method described in the present invention is based on laser interferometry, differential wavefront sensing and differential power sensing principles, and the measurement result can be directly traced back to the laser wavelength.

[0043] The invention discloses an iris diaphragm-based differential wavefront sensing angle measurement device, wherein the optomechanical-electrical integrated sensing module is easy to disassemble and reinstall, and the optical path is bonded, thereby reducing the size and volume of the device, making it easy to use and saving costs.

[0044] The present invention discloses a differential wavefront sensing angle measurement method based on an iris diaphragm, which combines differential wavefront sensing and differential power sensing to realize coarse and fine measurements of micro-angles. An iris diaphragm is added to adjust the size of the optical aperture in real time according to the rough angle measurement value obtained by differential power sensing, and sets it close to the four-quadrant detector, which is equivalent to changing the size of the photosensitive surface of the four-quadrant detector, thereby achieving the purpose of real-time adjustment of the differential wavefront sensing measurement linear range and measurement sensitivity, ensuring that the angle precision measurement is in the best measurement linear range and the highest sensitivity measurement state, effectively improving the differential wavefront sensing angle measurement accuracy, and can be directly traced back to the laser wavelength. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a schematic structural diagram of a differential wavefront sensing measuring device capable of measuring two-dimensional angles of pitch and yaw according to the present invention;

[0046] Figure 2 The present invention is a schematic structural diagram of a differential wavefront sensing measurement device capable of measuring pitch and yaw two-dimensional angles and axial displacement. DETAILED DESCRIPTION

[0047] In order to make the purpose, technical solution and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the specific embodiments described are only part of the embodiments of the present invention, rather than all of the specific embodiments. The components of the specific embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations, and the present invention can also have other embodiments.

[0048] Therefore, the following detailed description of the specific embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents the selected specific embodiments of the present invention. Based on the specific embodiments of the present invention, all other specific embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention.

[0049] In order to further understand the content, features and effects of the present invention, the following specific implementation methods are given as examples, and the attached Figure 1 and attached Figure 2 The detailed instructions are as follows:

[0050] Embodiment 1:

[0051] A differential wavefront sensing angle measurement device based on an iris diaphragm comprises a dual-frequency laser 1, a reference light single-mode optical fiber 2, a reference light collimator 3, a reference photodetector 4, a first non-polarizing beam splitter prism 5, a reference reflector 6, a third non-polarizing beam splitter prism 7, a measuring reflector 8, a second four-quadrant detector 9, an iris diaphragm 10, a first four-quadrant detector 11, a second non-polarizing beam splitter prism 12, a measuring light collimator 13, and a measuring light single-mode optical fiber 14;

[0052] The dual-frequency laser 1 is connected to the reference light single-mode fiber 2 and the measuring light single-mode fiber 14 respectively; the reference light single-mode fiber 2 is connected to the reference light collimator 3, and the measuring light single-mode fiber 14 is connected to the measuring light collimator 13;

[0053] The reference light emitted by the reference light collimator 3 is vertically incident on the first non-polarizing beam splitter prism 5, and the measurement light emitted by the measurement light collimator 13 is vertically incident on the second non-polarizing beam splitter prism 12; the side surfaces of the first non-polarizing beam splitter prism 5 and the second non-polarizing beam splitter prism 12 are bonded in parallel;

[0054] A reference photodetector 4 is correspondingly disposed on the other side of the first non-polarizing beam splitter prism 5, and a reference reflector 6 is bonded to the rear side of the first non-polarizing beam splitter prism 5;

[0055] An iris diaphragm 10 is correspondingly arranged on the other side of the No. 2 non-polarizing beam splitter prism 12, and a No. 1 four-quadrant detector 11 is arranged on the side of the iris diaphragm 10. A No. 3 non-polarizing beam splitter prism 7 is bonded to the rear side of the No. 2 non-polarizing beam splitter prism 12, and a measuring reflector 8 is arranged on the rear side of the No. 3 non-polarizing beam splitter prism 7. A No. 2 four-quadrant detector 9 is arranged on the side of the No. 3 non-polarizing beam splitter prism 7.

[0056] Furthermore, the dual-frequency laser 1, the reference light single-mode optical fiber 2, and the measurement light single-mode optical fiber 14 constitute a dual-frequency laser generating module.

[0057] Furthermore, the reference light collimator 3, the reference photodetector 4, the first non-polarizing beam splitter prism 5, the reference reflector 6, the third non-polarizing beam splitter prism 7, the measuring reflector 8, the second four-quadrant detector 9, the iris aperture 10, the first four-quadrant detector 11, the second non-polarizing beam splitter prism 12, and the measuring light collimator 13 constitute an optomechanical and electrical integrated sensing module.

[0058] Furthermore, when the movement of the measuring reflector 8 includes both two-dimensional angular movement and axial displacement movement, the structure of the differential wavefront sensing angle measurement device based on the iris aperture is adjusted so that a plano-convex lens 15 is bonded to the side of the third non-polarizing beam splitter prism 7, and a second four-quadrant detector 9 is correspondingly arranged on the outer side of the plano-convex lens 15.

[0059] Furthermore, the splitting ratio of the first non-polarization beam splitter prism 5 and the second non-polarization beam splitter prism 12 is 50:50, and the splitting ratio of the third non-polarization beam splitter prism 7 is 90:10.

[0060] Furthermore, the third non-polarizing beam splitter prism is used to split the light reflected by the measuring reflector into two beams through the third non-polarizing beam splitter prism, and the splitting ratio is 90:10, that is, the optical power of the transmitted light: the optical power of the reflected light is 90:10, and the purpose is to make the optical power of the reference light component and the measuring light component received by the first four-quadrant detector as equal as possible;

[0061] Furthermore, the four-quadrant detector No. 1 and the iris diaphragm, the four-quadrant detector No. 1 receives the differential wavefront sensor signal as the precise measurement value of the measuring device; and the iris diaphragm can be driven by the upper computer or the lower computer to control the diaphragm size in real time, so that the photosensitive surface size of the four-quadrant detector No. 1 receiving the measuring light and the reference light can be changed in real time, thereby changing the linear measurement range and measurement sensitivity of the differential wavefront sensor signal;

[0062] Furthermore, the second four-quadrant detector receives the measurement light component reflected by the third non-polarization beam splitter prism and generates a differential power sensing signal as a rough measurement value of the measurement device;

[0063] Furthermore, the dual-frequency laser is a 633nm dual-frequency helium-neon laser, which provides a stable frequency laser signal and emits two laser beams with a fixed frequency difference.

[0064] Furthermore, the second four-quadrant detector receives the measurement light component reflected by the third non-polarized beam splitter prism, and generates a differential power sensing signal as a rough measurement value of the measurement device; when the measurement reflector simultaneously has axial displacement movement, a plano-convex lens can be bonded to the light reflecting surface of the third non-polarized beam splitter prism to achieve a rough angle measurement function;

[0065] Furthermore, the iris diaphragm can be driven by the upper computer or the lower computer to control the size of the diaphragm in real time, so that the size of the measurement light, i.e., the reference light, received by the No. 1 four-quadrant detector can be changed in real time. The No. 1 four-quadrant detector receives the differential wavefront sensor signal as the precise measurement value of the measuring device; and the iris diaphragm is used to control the size of the photosensitive surface of the No. 1 four-quadrant detector receiving the measurement light and the reference light.

[0066] Embodiment 2:

[0067] A differential wavefront sensing angle measurement method based on an iris diaphragm is implemented based on the differential wavefront sensing angle measurement device based on an iris diaphragm described in Example 1, and is characterized in that it includes the following steps:

[0068] S1. Turn on the dual-frequency laser generating module, and after the laser frequency is stable, set the measuring reflector to produce a yaw or pitch angle change, and use the No. 2 four-quadrant detector to obtain the light intensity data of each quadrant in real time according to the differential power sensing principle, and calculate the rough measurement value of the angle to be measured;

[0069] Furthermore, the specific implementation method of step S1 includes the following steps:

[0070] S1.1. The dual-frequency laser emits two laser beams, one for reference light and the other for measurement light;

[0071] The reference light is divided into two paths after passing through the first beam splitter prism. The transmitted light of the reference light is reflected by the reference reflector, then reflected by the first beam splitter prism and received by the reference photoelectric detector. The reflected light of the reference light is transmitted by the second beam splitter prism, passes through the iris diaphragm and is finally received by the first four-quadrant detector.

[0072] The measuring light is also divided into two paths after passing through the second beam splitter prism. The reflected light of the measuring light is transmitted through the first beam splitter prism and received by the reference photoelectric detector, forming a reference interference signal with the reference light component. The transmitted light of the measuring light is transmitted through the third beam splitter prism and then reflected by the measuring reflector and returned to the third beam splitter prism, and is divided into two paths again. The transmitted light of the measuring light is reflected by the second beam splitter prism and passed through the iris diaphragm and finally received by the first four-quadrant detector, forming a differential wavefront sensing interference signal with the reference light component. The reflected light of the measuring light is received by the second photoelectric detector to form a differential power sensing measurement signal.

[0073] S1.2. After the laser frequency is stable, set the measuring reflector to produce a deflection or pitch angle change. Set the iris diaphragm to the minimum aperture position in the initial measurement state. The second four-quadrant detector measures the light intensity of different quadrants based on the differential power sensing principle, and then calculates the rough deflection angle θ DPSx , Roughly measure the pitch angle θ DPSy , the calculation formula is:

[0074]

[0075]

[0076] Among them, P A is the light intensity of the second quadrant on the No. 2 four-quadrant detector, P B is the light intensity of the first quadrant on the second four-quadrant detector, P C is the light intensity of the fourth quadrant on the second four-quadrant detector, P D is the light intensity of the third quadrant on the No. 2 four-quadrant detector. The quadrants are divided from A to D in a clockwise direction from the upper left corner. L DPS is the minimum distance of light beam propagation from the front surface of the measuring reflector to the photosensitive surface of the second quadrant detector;

[0077] S2. Based on the rough measured value of the angle to be measured obtained in step S1, select the measurement linear range and measurement sensitivity of the differential wavefront sensor angle measurement device, and adjust the aperture of the iris diaphragm;

[0078] Furthermore, in the specific implementation method of step S2, the measurement linear range and measurement sensitivity are both corresponding characteristics of the differential wavefront sensing measurement method, and the measurement sensitivity is corrected using a quadratic curve fitting method;

[0079] The optimal differential wavefront sensor measurement linear range and measurement sensitivity are selected according to the rough measurement value of the angle to be measured. The selection basis is shown in Table 1 (Note: the results in the table are simulation results), and the iris diaphragm is driven to adjust the aperture to the corresponding size, which is equivalent to adjusting the size of the photosensitive surface of the four-quadrant detector (QPD); the beam waist radius in the table is determined by the characteristics of the fiber collimator, and the scale is constant during the entire measurement process; the measurement linear range and measurement sensitivity are both corresponding characteristics of the differential wavefront sensing measurement method.

[0080] Table 1:

[0081]

[0082] The measurement sensitivity calculation in the table The corresponding angular phase difference is calculated by differential wavefront sensing measurement, and the current measurement sensitivity value is corrected in real time according to the phase difference.

[0083] S3. Based on the aperture size of the iris diaphragm adjusted in step S2, use the No. 1 four-quadrant detector to collect phase data of different quadrants according to the differential wavefront sensing principle, and calculate the precise measurement value of the angle to be measured.

[0084] Furthermore, the specific implementation method of step S3 is to use a multi-channel phase meter to measure the phase information of different quadrants on the No. 1 four-quadrant detector, and then calculate the precise measurement of the deflection angle θ DWSx 、Precisely measure the pitch angle θ DWSy , the calculation formula is:

[0085]

[0086]

[0087] Among them, φ A is the average phase of the second quadrant on the No. 1 four-quadrant detector, φ B is the average phase of the first quadrant on the No. 1 four-quadrant detector, φ C is the average phase of the fourth quadrant on the No. 1 four-quadrant detector, φ D Average phase of the third quadrant on the No. 1 four-quadrant detector; the quadrants are divided from A to D in clockwise rotation from the upper left corner; L x ,L y They are the measurement sensitivity of the yaw angle and the measurement sensitivity of the pitch angle respectively.

[0088] Embodiment 3:

[0089] The difference between this embodiment and embodiment 2 is that, in step S1.2, when the laser frequency is stable, the measuring reflector is set to produce a two-dimensional angle change accompanied by an axial displacement change. The reflected light of the measuring light reflected by the measuring reflector after passing through the No. 3 non-polarized beam splitter prism first passes through a plano-convex lens and then is received by the No. 2 four-quadrant detector. When the measuring reflector produces an axial displacement and a two-dimensional deflection angle change, the iris diaphragm is set to the minimum aperture position in the initial measurement state. The No. 2 four-quadrant detector measures the light intensity of different quadrants based on the differential power sensing principle, and then calculates the rough measured roll angle and the rough measured pitch angle. The calculation formula is:

[0090]

[0091]

[0092] Where, f is the nominal focal length of the plano-convex lens;

[0093] At the same time, the axial displacement z is calculated according to the phase information of each quadrant of the No. 1 four-quadrant detector. The calculation formula is:

[0094]

[0095] Among them, L z is the axial displacement measurement sensitivity, L z It is related to the laser wavelength, optical path subdivision number and phase meter electronic subdivision number.

[0096] It should be noted that relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0097] Although the present application has been described above with reference to specific embodiments, various modifications may be made thereto and parts thereof may be replaced with equivalents without departing from the scope of the present application. In particular, as long as there is no structural conflict, the various features in the specific embodiments disclosed in the present application may be used in combination with each other in any manner, and the fact that these combinations are not exhaustively described in this specification is only for the sake of omitting space and saving resources. Therefore, the present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A differential wavefront sensing angle measurement method based on an iris diaphragm, which is realized by relying on a differential wavefront sensing angle measurement device based on an iris diaphragm, comprising a dual-frequency laser (1), a reference light single-mode optical fiber (2), a reference light collimator (3), a reference photodetector (4), a first non-polarizing beam splitter prism (5), a reference reflector (6), a third non-polarizing beam splitter prism (7), a measuring reflector (8), a second four-quadrant detector (9), an iris diaphragm (10), a first four-quadrant detector (11), a second non-polarizing beam splitter prism (12), a measuring light collimator (13), and a measuring light single-mode optical fiber (14); The dual-frequency laser (1) is respectively connected to a reference light single-mode optical fiber (2) and a measuring light single-mode optical fiber (14); the reference light single-mode optical fiber (2) is connected to a reference light collimator (3), and the measuring light single-mode optical fiber (14) is connected to a measuring light collimator (13); The reference light emitted by the reference light collimator (3) is vertically incident on the first non-polarizing beam splitter prism (5), and the measurement light emitted by the measurement light collimator (13) is vertically incident on the second non-polarizing beam splitter prism (12); the side surfaces of the first non-polarizing beam splitter prism (5) and the second non-polarizing beam splitter prism (12) are bonded in parallel; A reference photodetector (4) is correspondingly arranged on the other side of the first non-polarizing beam splitter prism (5), and a reference reflector (6) is bonded to the rear side of the first non-polarizing beam splitter prism (5); An iris diaphragm (10) is correspondingly arranged on the other side of the second non-polarizing beam splitter prism (12), a first four-quadrant detector (11) is arranged on the side of the iris diaphragm (10), a third non-polarizing beam splitter prism (7) is bonded to the rear side of the second non-polarizing beam splitter prism (12), a measuring reflector (8) is arranged on the rear side of the third non-polarizing beam splitter prism (7), and a second four-quadrant detector (9) is arranged on the side of the third non-polarizing beam splitter prism (7); It is characterized in that The steps include: S1. Turn on the dual-frequency laser generating module, and after the laser frequency is stable, set the measuring reflector to produce a yaw or pitch angle change, and use the No. 2 four-quadrant detector to obtain the light intensity data of each quadrant in real time according to the differential power sensing principle, and calculate the rough measurement value of the angle to be measured; The specific implementation method of step S1 includes the following steps: S1.

1. The dual-frequency laser emits two laser beams, one for reference light and the other for measurement light; The reference light is divided into two paths after passing through the first beam splitter prism. The transmitted light of the reference light is reflected by the reference reflector, then reflected by the first beam splitter prism and received by the reference photoelectric detector. The reflected light of the reference light is transmitted by the second beam splitter prism, passes through the iris diaphragm and is finally received by the first four-quadrant detector. The measuring light is also divided into two paths after passing through the second beam splitter prism. The reflected light of the measuring light is transmitted through the first beam splitter prism and received by the reference photoelectric detector, forming a reference interference signal with the reference light component. The transmitted light of the measuring light is transmitted through the third beam splitter prism and then reflected by the measuring reflector and returned to the third beam splitter prism, and is divided into two paths again. The transmitted light of the measuring light is reflected by the second beam splitter prism and passed through the iris diaphragm and finally received by the first four-quadrant detector, forming a differential wavefront sensing interference signal with the reference light component. The reflected light of the measuring light is received by the second photoelectric detector to form a differential power sensing measurement signal. S1.

2. After the laser frequency is stable, set the measuring reflector to produce a deflection or pitch angle change. Set the iris diaphragm to the minimum aperture position in the initial measurement state. The second four-quadrant detector measures the light intensity of different quadrants based on the differential power sensing principle, and then calculates the rough deflection angle θ DPSx , Roughly measure the pitch angle θ DPSy , the calculation formula is: Among them, P A is the light intensity of the second quadrant on the No. 2 four-quadrant detector, P B is the light intensity of the first quadrant on the second four-quadrant detector, P C is the light intensity of the fourth quadrant on the second four-quadrant detector, P D is the light intensity of the third quadrant on the No. 2 four-quadrant detector. The quadrants are divided from A to D in a clockwise direction from the upper left corner. L DPS is the minimum distance of light beam propagation from the front surface of the measuring reflector to the photosensitive surface of the second quadrant detector; S2. Based on the rough measured value of the angle to be measured obtained in step S1, select the measurement linear range and measurement sensitivity of the differential wavefront sensor angle measurement device, and adjust the aperture of the iris diaphragm; S3. Based on the aperture size of the iris diaphragm adjusted in step S2, use the No. 1 four-quadrant detector to collect phase data of different quadrants according to the differential wavefront sensing principle, and calculate the precise measurement value of the angle to be measured.

2. The method for measuring angles by differential wavefront sensing based on an iris stop according to claim 1, characterized in that: In the specific implementation method of step S2, the measurement linear range and measurement sensitivity are both corresponding characteristics of the differential wavefront sensing measurement method, and the measurement sensitivity is corrected using a quadratic curve fitting method.

3. The method for measuring angles by differential wavefront sensing based on an iris stop according to claim 2, characterized in that: The specific implementation method of step S3 is to use a multi-channel phase meter to measure the phase information of different quadrants on the No. 1 four-quadrant detector, and then calculate the precise measurement of the deflection angle θ DWSx 、Precisely measure the pitch angle θ DWSy , the calculation formula is: Among them, φ A is the average phase of the second quadrant on the No. 1 four-quadrant detector, φ B is the average phase of the first quadrant on the No. 1 four-quadrant detector, φ C is the average phase of the fourth quadrant on the No. 1 four-quadrant detector, φ D The average phase quadrant of the third quadrant on the No. 1 four-quadrant detector is divided from A to D in a clockwise direction from the upper left corner; L x ,L y They are the measurement sensitivity of the yaw angle and the measurement sensitivity of the pitch angle respectively.

4. The method for measuring angles by differential wavefront sensing based on an iris stop according to claim 3, characterized in that: Step S1.2: When the laser frequency is stable, the measuring reflector is set to produce a two-dimensional angle change accompanied by an axial displacement change. The reflected light of the measuring light reflected by the measuring reflector passes through the No. 3 non-polarized beam splitter prism and first passes through a plano-convex lens and then is received by the No. 2 four-quadrant detector. When the measuring reflector produces an axial displacement and a two-dimensional deflection angle change, the iris diaphragm is set to the minimum aperture position in the initial measurement state. The No. 2 four-quadrant detector measures the light intensity of different quadrants based on the differential power sensing principle, and then calculates the rough roll angle and the rough pitch angle. The calculation formula is: Where, f is the nominal focal length of the plano-convex lens; At the same time, the axial displacement z is calculated according to the phase information of each quadrant of the No. 1 four-quadrant detector. The calculation formula is: Among them, L z is the axial displacement measurement sensitivity, L z It is related to the laser wavelength, optical path subdivision number and phase meter electronic subdivision number.

5. The method for measuring angles by differential wavefront sensing based on an iris stop according to claim 4, characterized in that: The dual-frequency laser (1), the reference light single-mode optical fiber (2), and the measurement light single-mode optical fiber (14) constitute a dual-frequency laser generation module.

6. The method for measuring angles by differential wavefront sensing based on an iris stop according to claim 5, characterized in that: The reference light collimator (3), the reference photoelectric detector (4), the first non-polarized beam splitter prism (5), the reference reflector (6), the third non-polarized beam splitter prism (7), the measuring reflector (8), the second four-quadrant detector (9), the iris diaphragm (10), the first four-quadrant detector (11), the second non-polarized beam splitter prism (12), and the measuring light collimator (13) constitute an optomechanical and electrical integrated sensing module.

7. The method for measuring angles by differential wavefront sensing based on an iris stop according to claim 6, characterized in that: When the movement mode of the measuring reflector (8) includes both angular movement and axial displacement movement, the structure of the differential wavefront sensing angle measurement device based on the iris diaphragm is adjusted so that a plano-convex lens (15) is bonded to the side surface of the third non-polarizing beam splitting prism (7), and a second four-quadrant detector (9) is correspondingly arranged on the outer side of the plano-convex lens (15).

Images