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CN-121994142-A - Nanometer displacement real-time compensation measurement method and system based on double-frequency laser interference

CN121994142ACN 121994142 ACN121994142 ACN 121994142ACN-121994142-A

Abstract

The invention discloses a nanoscale displacement real-time compensation measurement method and system based on double-frequency laser interference, and belongs to the technical field of precision measurement. Aiming at the problems that three error sources of environmental drift, periodic nonlinear error and dynamic vibration are mutually coupled and the real-time requirement is high in dual-frequency laser interferometry, the invention constructs a multi-source error unified state space model comprising measured positions, air refractive index parameters, nonlinear error parameters and vibration disturbance quantity. And an extended Kalman filter with a grouping updating strategy is adopted, a high-dimensional state vector is divided into a displacement-refractive index group and a nonlinear parameter group, the displacement-refractive index group and the nonlinear parameter group are updated alternately in a pipelining parallel mode, nonlinear parameters are identified in real time by combining an online recursive least square algorithm, and the state of the filter is corrected through a state coupling injection mechanism. The real-time compensation of the end-to-end delay of less than 80 mu s is realized, the residual error of displacement measurement is controlled within +/-0.3 nm under the condition of composite disturbance, and the method is suitable for the precise assembly of the optical components of the intelligent glasses.

Inventors

  • WANG XING

Assignees

  • 柔博(上海)科技有限公司

Dates

Publication Date
20260508
Application Date
20260212

Claims (10)

  1. 1. The nano-scale displacement real-time compensation measurement method based on double-frequency laser interference is characterized by comprising the following steps of: Acquiring a measured beat frequency signal carrying measured displacement information and a reference beat frequency signal serving as a phase reference by using a dual-frequency laser interference optical unit, and converting the measured beat frequency signal into two paths of orthogonal electric signals by using an orthogonal signal detection unit; Establishing a multisource error unified state space model, defining a high-dimensional state vector containing measured real displacement, displacement speed, air refractive index deviation change rate, periodic nonlinear error harmonic parameters and external mechanical vibration disturbance quantity, and establishing a state transition equation describing the state vector evolution along with time and an observation equation describing the nonlinear mapping relation between a phase observation value and the state vector; And in each sampling period, firstly, uniformly predicting all state components according to a state transition equation, then dividing the state vectors into a first state group and a second state group, sequentially carrying out grouping update on the first state group and the second state group by using a phase observation value, and extracting a measured real displacement component from the updated state vectors to serve as a compensated displacement value for output.
  2. 2. The method for measuring the nanoscale displacement real-time compensation based on the dual-frequency laser interference according to claim 1, wherein the high-dimensional state vector specifically comprises 9 state components, namely measured real displacement, displacement speed, air refractive index deviation change rate, cosine amplitude of a first-order periodic nonlinear error, sine amplitude of a first-order periodic nonlinear error, cosine amplitude of a second-order periodic nonlinear error, sine amplitude of a second-order periodic nonlinear error and external mechanical vibration disturbance quantity.
  3. 3. The method for real-time compensation measurement of nanoscale displacement based on dual-frequency laser interference according to claim 2 is characterized in that the specific process of dividing a state vector into a first state group and a second state group and sequentially updating the first state group and the second state group by using a phase observation value comprises the steps of defining the first state group to comprise measured real displacement, displacement speed, air refractive index deviation change rate and external mechanical vibration disturbance quantity, defining the second state group to comprise cosine amplitude values and sine amplitude values of first-order and second-order periodic nonlinear errors, calculating a jacobian submatrix corresponding to the first state group, calculating a first Kalman gain by using the phase observation value and a current prediction value, updating a state estimation value and a covariance matrix of the first state group, synchronously updating a cross covariance matrix between the first state group and the second state group, calculating a jacobian corresponding to the second state group, calculating an observation residual by using the phase observation value, the updated first state group estimation value and the second state group prediction value, and calculating an observation residual, and updating a second Kalman gain estimation value and a state covariance matrix of the second state group.
  4. 4. The method for measuring nanoscale displacement real-time compensation based on double-frequency laser interference according to claim 3, wherein the method further comprises a state coupling injection step, namely running an online recursive least square parameter identification algorithm in parallel, utilizing Lissajous elliptic fitting residual errors of the two paths of orthogonal electric signals to identify periodic nonlinear error parameters in real time, judging whether the difference between a parameter identification value output by the recursive least square algorithm and a current estimated value of a second state group in a packet updating extended Kalman filter exceeds a preset threshold, and injecting the parameter identification value into state estimation of the second state group in a weighted mode when the difference exceeds the preset threshold, and correspondingly increasing a covariance matrix value of the second state group.
  5. 5. The method for measuring the nanoscale displacement real-time compensation based on the dual-frequency laser interference according to claim 4, wherein the online recursive least square parameter identification algorithm adopts a recursive mechanism with a forgetting factor, and the value range of the forgetting factor is 0.98-0.995, so that the error parameter can be quickly converged to a new nonlinear error parameter when the light path condition changes.
  6. 6. The method for measuring the nanoscale displacement real-time compensation based on the double-frequency laser interference according to claim 2, further comprising the auxiliary updating step of environment observation, wherein an air refractive index deviation observation value is calculated by using a modified Edl en formula according to the temperature, air pressure and humidity data, and independent Kalman updating modification is carried out on the air refractive index deviation and the change rate component of the air refractive index deviation in the high-dimensional state vector by using the air refractive index deviation observation value.
  7. 7. The method for measuring the nanoscale displacement real-time compensation based on the dual-frequency laser interference according to claim 2, wherein the nonlinear mapping relation between the phase observation value and the state vector in the observation equation is specifically expressed as that the phase observation value is equal to the real displacement phase containing refractive index deviation correction plus the additional phase deviation introduced by nonlinear error, and the real displacement phase term represents the product coupling relation between the refractive index deviation and the total displacement containing vibration disturbance.
  8. 8. The method for compensating and measuring the displacement of the nanometer level based on the double-frequency laser interference in real time according to claim 4 is characterized in that the method is operated on an FPGA and ARM heterogeneous computing platform, wherein the FPGA is responsible for executing digital phase demodulation, unified state prediction and grouping update operation of a first state group and a second state group, each step is executed in parallel in a pipeline mode, and the ARM is responsible for executing environment parameter Edl en formula calculation, an online recursion least square parameter identification algorithm and state coupling injection logic judgment.
  9. 9. The method for measuring the nanoscale displacement real-time compensation based on the dual-frequency laser interference according to claim 1 is applied to a precise assembly production line of an intelligent glasses diffraction optical waveguide or a micro-display array, and the compensated displacement value is used for closed-loop position feedback control of a nanometer positioning workbench.
  10. 10. The nano-scale displacement real-time compensation measurement system based on the dual-frequency laser interference is characterized by comprising a dual-frequency laser interference optical unit, an environment parameter sensing unit and a signal processing and calculating platform, wherein the dual-frequency laser interference optical unit is used for generating dual-frequency laser and forming an interference light path, outputting a measurement beat frequency signal and a reference beat frequency signal, and outputting orthogonal electric signals through orthogonal detection, the environment parameter sensing unit is used for collecting temperature, air pressure and humidity data of an optical path environment, and the signal processing and calculating platform comprises an FPGA coprocessor and an ARM processor and is configured to execute the nano-scale displacement real-time compensation measurement method based on the dual-frequency laser interference according to any one of claims 1 to 9.

Description

Nanometer displacement real-time compensation measurement method and system based on double-frequency laser interference Technical Field The invention relates to the technical field of precise measurement, in particular to a nano-scale displacement real-time compensation measurement method and system based on double-frequency laser interference for an intelligent glasses optical component precise assembly scene. Background The dual-frequency laser interferometry technology becomes a mainstream scheme of nanoscale precise displacement measurement by virtue of the high resolution and wide-range characteristics, and is widely applied to the fields of semiconductor lithography, precise machining, optical element assembly and the like. Particularly, in the production and manufacturing process of intelligent glasses, the assembly precision requirements of the diffraction optical waveguide, the micro display array and the free-form surface optical lens reach submicron or even nanometer level, which puts high requirements on the real-time performance and the environmental adaptability of a displacement measurement system. However, in a practical nanoscale assembly environment, dual-frequency laser interferometry suffers from common interference of multiple source errors, namely wavelength drift caused by air refractive index along with temperature, humidity and pressure fluctuation, frequency drift and non-orthogonal errors of dual-frequency signals output by a laser, periodic nonlinear errors caused by non-ideal polarization splitting of an optical element, and high-frequency mechanical vibration in the environment. In the prior art, an independent compensation scheme is generally adopted for the errors, for example, a low-frequency off-line correction environment parameter is performed by using a Edl en formula, or an off-line calibration lookup table method is adopted for correcting nonlinear errors. However, the prior art mainly has the following problems that firstly, algorithms such as environment drift compensation, nonlinear error correction, dynamic vibration suppression and the like are usually executed independently and serially, so that overall compensation delay superposition is caused, often exceeds 1ms, the strict requirement of an intelligent glasses diffraction optical waveguide precise attaching process on control loop response time being smaller than 100 mu s cannot be met, secondly, coupling effects among error sources are ignored in serial compensation, compensation residual errors are accumulated mutually under complex working conditions with multiple source errors, sub-nanometer measurement accuracy is difficult to achieve, and finally, nonlinear error compensation based on off-line calibration lacks self-adaptive capacity, and once optical path conditions are changed due to optical element switching, original calibration parameters fail, so that production is interrupted. Disclosure of Invention In order to achieve the above purpose, the present invention provides a method for measuring nanoscale displacement real-time compensation based on dual-frequency laser interferometry, which comprises the following steps: Acquiring a measured beat frequency signal carrying measured displacement information and a reference beat frequency signal serving as a phase reference by using a dual-frequency laser interference optical unit, and converting the measured beat frequency signal into two paths of orthogonal electric signals by using an orthogonal signal detection unit; Establishing a multisource error unified state space model, defining a high-dimensional state vector containing measured real displacement, displacement speed, air refractive index deviation change rate, periodic nonlinear error harmonic parameters and external mechanical vibration disturbance quantity, and establishing a state transition equation describing the state vector evolution along with time and an observation equation describing the nonlinear mapping relation between a phase observation value and the state vector; The method comprises the steps of estimating the high-dimensional state vector in real time by adopting a grouping update extended Kalman filter, uniformly predicting all state components according to a state transfer equation in each sampling period, dividing the state vector into a first state group and a second state group, and sequentially carrying out grouping update on the first state group and the second state group by utilizing a phase observation value; and extracting the measured real displacement component from the updated state vector to be used as a compensated displacement value for output. As a preferable technical scheme of the invention, the high-dimensional state vector specifically comprises 9 state components, namely measured real displacement, displacement speed, air refractive index deviation change rate, cosine amplitude of a first-order periodic nonlinear error, sine amplitude of a first-orde