Three-channel homodyne interferometer signal processing device and method for suppressing non-orthogonal error

Abstract

The invention discloses a three-channel homodyne interferometer signal processing device and method for suppressing non-orthogonal errors. The device comprises a single-frequency laser, a polarization splitting prism A, a 1 / 4 wave plate A, a first reflector, a 1 / 4 wave plate B, a second reflector and an interference signal resolving module. Wherein the polarization splitting prism A is located at the output end of the single-frequency laser; a 1 / 4 wave plate A and a first reflector are sequentially arranged in parallel in the direction of reflected light; and a 1 / 4 wave plate B and a second reflecting mirror are sequentially arranged in parallel in the transmission light direction. On the premise of repeatedly measuring the non-orthogonal angle, the non-orthogonal error of the interference signal is corrected in the analog operation process by electrically adjusting the amplitude of the interference signal.

Description

Technical Field

[0001] The present invention relates to the field of laser measurement technology, and in particular to a three-channel homodyne interferometer signal processing device and method for suppressing non-orthogonal errors. Background Art

[0002] With the rapid development of scientific research and the rapid improvement of industrial production levels, scientific research and industrial fields have also put forward higher requirements for displacement measurement, and the minimum change in displacement measurement is also developing towards the nanometer level. Single-frequency laser interferometer is an instrument that uses the principle of laser interference to perform high-precision displacement measurement, with the advantages of non-contact and high precision. A single-frequency laser interferometer includes at least one light source that can provide a single-frequency laser; a first spectrometer that divides the single-frequency light source into a reference beam and a measurement beam; a first reflector that can reflect the reference beam; a second reflector that can reflect the measurement beam, the second reflector is usually fixed on the object to be measured and moves with the object to be measured; a second spectrometer that divides the composite beam emitted by the spectrometer into a first composite beam and a second composite beam; at least two photodetectors that can detect interference signals; and a signal processing unit, coupled to the photodetector, suitable for collecting the interference signal output by the photodetector; the reference beam and the measurement beam have the same frequency. Compared to dual-frequency laser interferometers, they are more widely used in displacement measurement due to their many advantages, including simple structure, low cost, easy circuit processing, low environmental requirements, and theoretically unlimited measurement speed. However, the processing of interference signals in practical applications, especially the nonlinear errors introduced during the processing, has always been a key issue limiting the high-precision measurement capabilities of single-frequency laser interferometers.

[0003] like Figure 1 This is a typical single-frequency laser interferometer structure at present. The single-frequency laser emitted from the laser is split into a reference beam and a measurement beam by a polarization beam splitter prism A(2); the reflected beam is reflected by a plane mirror A(4) as a reference beam and passes through a quarter wave plate A(3) twice. The transmitted beam is reflected by a plane mirror B(6) as a measurement beam and passes through a quarter wave plate B(5) twice. The reference beam and the measurement beam are transmitted and reflected by the polarization beam splitter prism A(2) respectively. Since the polarization states are vertical at this time, no interference signal is formed.

[0004] In order to identify the direction of motion and solve the detection problem under the condition of light intensity jitter, the current mainstream solutions all adopt a four-channel detection solution. Under the ideal condition of constructing the interference signal into orthogonal sinusoidal signals Ix and Iy, Ix and Iy can be expressed as follows: (P.Hu, J.Zhu, X.Guo, and J.Tan, "Compensation for the Variable Cyclic Error in Homodyne Laser Interferometers," Sensors, 2015, 15(2): 3090-3106.)

[0005]

[0006] Where R is the AC amplitude of the interference signal, and θ is the phase difference between the reference and measurement optical paths. It can be seen that Ix and Iy behave as sine and cosine functions with respect to θ. Ideally, their amplitudes are equal, their DC bias is zero, and they are orthogonal to each other. However, in practice, due to imperfections in optical components, Ix and Iy can be expressed as:

[0007]

[0008] Where p and q are DC bias errors, are the proportions of unequal amplitude errors, and α is the non-orthogonal error. It can be seen from formula (2) that Ix and Iy are actually sine and cosine functions containing the above three differences. When the above two interference signals containing the three differences are directly used for displacement calculation, a nonlinear error that changes with the displacement period will be generated. The error δθ=arctan(I' x / I' y )-arctan(I x / I y ), expand the error formula in Fourier series and ignore the higher-order terms to obtain:

[0009]

[0010] The first method for correcting nonlinear errors was proposed by Heydemann in 1981. He used the least squares method to perform elliptical fitting on interference signals greater than one period to obtain the characteristic parameters of the interference signal, thereby correcting the nonlinear error. This method is a classic approach for nonlinear error correction. Researchers have proposed various improvements based on this method, all of which can be referred to as the Heydemann correction method. This method has high correction accuracy, but its correction algorithm is time-consuming and not suitable for real-time measurement. Dai of the German Federal Institute of Physics (Bundesamt für Physik) detected the maximum and minimum values of each interference signal within one period to extract the nonlinear error parameters in real time, achieving real-time correction of the nonlinear error. This is called the extreme value correction method. When using the extreme value correction method to correct nonlinear errors in real time, it is necessary to first correct for unequal amplitude errors and DC offset errors, and then correct for non-orthogonality errors. After correcting for non-orthogonality errors, new unequal amplitude errors and DC offset errors will appear, requiring secondary correction, which increases the complexity of the system and control. The computational efficiency of the above calculation methods for suppressing nonlinear errors is greatly limited by the presence of non-orthogonality errors, significantly affecting the real-time performance of the correction process.

[0011] Wang Ke et al. proposed adding a Babinet compensator before interferometer signal detection to compensate for the non-orthogonality of the interferometer signal (Wang Ke. Periodic Nonlinear Error Suppression and Correction Techniques in Unstable Intensity Homodyne Interferometry). This method requires high device accuracy. The adjustment process is complex, and adjusting the Babinet compensator requires repeated measurement of the non-orthogonality angle of the interferometer signal, resulting in unclear adjustment indicators. Summary of the Invention

[0012] In order to solve the technical problems existing in the above-mentioned prior art, the present invention proposes a three-channel homodyne interferometer signal processing device and method for suppressing non-orthogonal errors. Under the premise of repeatedly measuring non-orthogonal angles, the interference signal amplitude is electrically adjusted to achieve the correction of non-orthogonal errors of the interference signal during the analog calculation process.

[0013] On the one hand, to achieve the above-mentioned object, the present invention provides a three-channel homodyne interferometer signal processing device for suppressing non-orthogonal errors, comprising: a single-frequency laser, a polarization beam splitter prism A, a quarter-wave plate A, a first reflector, a quarter-wave plate B, a second reflector, and an interference signal solving module;

[0014] Among them, the polarization beam splitter prism A is located at the output end of the single-frequency laser; the 1 / 4 wave plate A and the first reflector are arranged in parallel in the direction of reflected light; the 1 / 4 wave plate B and the second reflector are arranged in parallel in the direction of transmitted light; with the polarization beam splitter prism A as the axis, the interference signal solution module is arranged on the opposite side of the first reflector.

[0015] Preferably, the interference signal solution module includes a quarter wave plate C, a non-polarizing beam splitter A, a polarizer A, a non-polarizing beam splitter B, a polarizer B, a polarizer C, a photodetector A, a photodetector B, a photodetector C, a subtractor A, a subtractor B, and a displacement solution module;

[0016] Wherein, a quarter wave plate C is placed at a position where the polarization beam splitter prism A is located opposite to the second reflector, a non-polarization beam splitter A is arranged along the optical axis direction of the quarter wave plate C, a polarization plate A is arranged along the reflected light direction of the non-polarization beam splitter A, a non-polarization beam splitter B is arranged along the transmitted light direction of the non-polarization beam splitter A, a polarization plate B is arranged in the propagation direction of the reflected light of the non-polarization beam splitter B, and a polarization plate C is arranged in the propagation direction of the transmitted light of the non-polarization beam splitter B, and a photodetector A, a photodetector B, and a photodetector C are arranged behind the polarization plate A, the polarization plate B, and the polarization plate C, respectively, and the photodetector A, the photodetector B, and the photodetector C are connected to a homodyne laser interferometer signal processing unit, which inputs the processed signals into a subtractor A and a subtractor B, respectively, to obtain a signal Ix and a signal Iy, and finally the signal Ix and the signal Iy are input into a displacement solution module for displacement solution.

[0017] Preferably, the fast axis direction of the 1 / 4 wave plate A is 45° counterclockwise to the z-axis, and the fast axis direction of the 1 / 4 wave plate B is 45° clockwise to the z-axis. The transmitted light and the reflected light carry the motion information of the first reflector and the second reflector respectively, and then return to the polarization beam splitter prism A.

[0018] Preferably, the polarization direction of the polarizer A is 45° to the x-axis, the polarization direction of the polarizer B is 0° to the x-axis, and the polarization direction of the polarizer C is 90° to the x-axis.

[0019] Preferably, the homodyne laser interferometer signal processing unit includes an adjustable gain amplification module A, an adjustable gain amplification module B and an adjustable gain amplification module C, wherein the signal obtained by detection by the photodetector A is input into the adjustable gain amplification module A, the signal obtained by detection by the photodetector B is input into the adjustable gain amplification module B, and the signal obtained by detection by the photodetector C is input into the adjustable gain amplification module C. The signals processed by the adjustable gain amplification module A and the adjustable gain amplification module B are input into the subtractor A to obtain the signal Ix, and the signals processed by the adjustable gain amplification module B and the adjustable gain amplification module C are input into the subtractor B to obtain the signal Iy.

[0020] On the other hand, to achieve the above-mentioned object, the present invention further provides a three-channel homodyne interferometer signal processing method for suppressing non-orthogonal errors, which is applied to a three-channel homodyne interferometer signal processing device for suppressing non-orthogonal errors, comprising:

[0021] Polarized light of a target frequency is incident on a polarization beam splitter prism A to obtain a measuring beam and a reference beam, wherein the reference beam passes through a reference optical path and is reflected by a first reflector, and the measuring beam passes through a measuring optical path and is reflected by a second reflector carrying information of the moving target to be measured. The measuring beam and the reference beam are then combined by the polarization beam splitter prism A to form a composite beam;

[0022] The composite light beam is processed and solved by an interference signal solving module to obtain a displacement solution result.

[0023] Preferably, the composite light beam is processed by an interference signal solving module, including:

[0024] The composite light beam is sequentially split by a quarter wave plate C, a non-polarizing beam splitter A, and a non-polarizing beam splitter B to generate a first composite light beam, a second composite light beam, and a third composite light beam, respectively;

[0025] The first composite light beam forms a first interference light after passing through a polarizer A whose polarization direction is 45° to the x-axis; the second composite light beam forms a second interference light after passing through a polarizer B whose polarization direction is 0° to the x-axis; and the third composite light beam forms a third interference light after passing through a polarizer C whose polarization direction is 90° to the x-axis.

[0026] Inputting the first interference light, the second interference light, and the third interference light into photodetector A, photodetector B, and photodetector C, respectively, to obtain a first interference signal, a second interference signal, and a third interference signal;

[0027] Processing the first interference signal, the second interference signal, and the third interference signal based on a homodyne laser interferometer signal processing unit to obtain a first interference signal after AC amplitude adjustment, a second interference signal after AC amplitude adjustment, and a third interference signal after AC amplitude adjustment;

[0028] Inputting the first interference signal after AC amplitude adjustment, the second interference signal after AC amplitude adjustment, and the third interference signal after AC amplitude adjustment into subtractor A and subtractor B respectively to obtain a sine interference signal and a cosine interference signal;

[0029] Displacement calculation is performed on the sine interference signal and the cosine interference signal to obtain a final displacement calculation result.

[0030] Preferably, obtaining the first interference signal, the second interference signal and the third interference signal is specifically:

[0031]

[0032] Where I1 is the first interference signal, I2 is the second interference signal, I3 is the third interference signal, a is the AC amplitude of the interference signal, b is the DC bias of the interference signal, is the phase difference between the second interference signal and the ideal orthogonal signal.

[0033] Preferably, obtaining the first interference signal after AC amplitude adjustment, the second interference signal after AC amplitude adjustment, and the third interference signal after AC amplitude adjustment includes:

[0034] The first interference signal, the second interference signal, and the third interference signal are adjusted by the adjustable gain amplification module A, the adjustable gain amplification module B, and the adjustable gain amplification module C, respectively, to obtain the first interference signal after AC amplitude adjustment, the second interference signal after AC amplitude adjustment, and the third interference signal after AC amplitude adjustment, specifically:

[0035]

[0036] Where, I1′ is the first interference signal after AC amplitude adjustment, I2′ is the second interference signal after AC amplitude adjustment, I3′ is the third interference signal after AC amplitude adjustment, A0 is the adjusted signal AC amplitude, is the phase difference between the second interference signal and the ideal orthogonal signal, and B is the DC bias of the signal after adjustment.

[0037] Preferably, obtaining the sinusoidal interference signal and the cosine interference signal comprises:

[0038] The sine interference signal is obtained by subtracting the second interference signal after AC amplitude adjustment from the first interference signal after AC amplitude adjustment, and the cosine interference signal is obtained by subtracting the third interference signal after AC amplitude adjustment from the first interference signal after AC amplitude adjustment, specifically:

[0039]

[0040] Where, I x is a sinusoidal interference signal, I y is the cosine interference signal.

[0041] Compared with the prior art, the present invention has the following advantages and technical effects:

[0042] (1) Compared with the Heydemann or extreme value correction methods, the present invention does not require software algorithms to correct non-orthogonal errors. Instead, it adopts a reconstructed orthogonal interference signal generation scheme to suppress the non-orthogonal errors of the system based on the principle structure of orthogonal interference signal generation, thereby achieving higher correction accuracy and real-time performance.

[0043] (2) Compared with the traditional optical path, the present invention does not have too high requirements for the phase delay error of the quarter-wave plate optical device in the optical path, and more optical components such as polarizers with lower installation requirements are used, thereby reducing the processing costs of the device and optical machine;

[0044] (3) Compared with the traditional optical path, in the process of adjusting the orthogonality of the interference signal, it is necessary to repeatedly calculate the non-orthogonal angles of the two interference signals in order to adjust the phase delay. In the process of adjusting the orthogonality, the present invention only needs to confirm whether the amplitudes of the three interference signals are equal, which greatly simplifies the adjustment process of the interference measurement system, makes the adjustment result more obvious, and is more convenient for adjustment.

[0045] (4) The present invention eliminates the non-orthogonal error of the sin / cos signal pair in principle, solves the complex correction calculation introduced by the non-orthogonal error in the nonlinear correction process, and simplifies the correction process of the nonlinear error. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of this application. The exemplary embodiments and descriptions of this application are intended to explain this application and do not constitute an improper limitation on this application. In the accompanying drawings:

[0047] Figure 1 A schematic diagram of the simple structure of a laser interferometer in the background technology of the present invention;

[0048] Figure 2 Schematic diagram of an interference signal solving module according to an embodiment of the present invention;

[0049] Among them, 1. Single-frequency laser; 2. Polarization beam splitter prism A; 3. 1 / 4 wave plate A; 4. First reflector; 5. 1 / 4 wave plate B; 6. Second reflector; 7. Interference signal solution module; 8. 1 / 4 wave plate C; 9. Non-polarization beam splitter A; 10. Polarizer A; 11. Non-polarization beam splitter B; 12. Polarizer B; 13. Polarizer C; 14. Photodetector A; 15. Photodetector B; 16. Photodetector C; 17. Adjustable gain amplifier module A; 18. Adjustable gain amplifier module B; 19. Adjustable gain amplifier module C; 20. Subtractor A; 21. Subtractor B; 22. Displacement solution module. DETAILED DESCRIPTION

[0050] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0051] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0052] The present invention proposes a three-channel homodyne interferometer signal processing device for suppressing non-orthogonal errors, comprising: a single-frequency laser 1, a polarization beam splitter prism A2, a quarter-wave plate A3, a first reflector 4, a quarter-wave plate B5, a second reflector 6, and an interference signal solving module 7;

[0053] Among them, the polarization beam splitter prism A2 is located at the output end of the single-frequency laser 1; the 1 / 4 wave plate A3 and the first reflector 4 are arranged in parallel in the direction of reflected light; the 1 / 4 wave plate B5 and the second reflector 6 are arranged in parallel in the direction of transmitted light; with the polarization beam splitter prism A2 as the axis, the interference signal solution module 7 is arranged on the opposite side of the first reflector 4.

[0054] Furthermore, if Figure 2 The interference signal solving module 7 includes a quarter wave plate C8, a non-polarizing beam splitter A9, a polarizer A10, a non-polarizing beam splitter B11, a polarizer B12, a polarizer C13, a photodetector A14, a photodetector B15, a photodetector C16, a subtractor A20, a subtractor B21, and a displacement solving module 22;

[0055] Wherein, a quarter wave plate C8 is placed at a position of the polarization beam splitter prism A2 opposite to the second reflector 6, a non-polarization beam splitter A9 is arranged along the optical axis direction of the quarter wave plate C8, a polarizer A10 is arranged along the direction of reflected light of the non-polarization beam splitter A9, a non-polarization beam splitter B11 is arranged along the direction of transmitted light of the non-polarization beam splitter A9, a polarizer B12 is arranged in the propagation direction of reflected light of the non-polarization beam splitter B11, a polarizer C13 is arranged in the propagation direction of transmitted light of the non-polarization beam splitter B11, and a polarizer B14 is arranged in the propagation direction of the transmitted light of the non-polarization beam splitter B11. Photodetectors A14, B15, and C16 are arranged behind A10, polarizer B12, and polarizer C13, respectively. Photodetectors A14, B15, and C16 are connected to a homodyne laser interferometer signal processing unit. The homodyne laser interferometer signal processing unit inputs the processed signals into subtractors A20 and B21, respectively, to obtain signals Ix and Iy. Finally, signals Ix and Iy are input into a displacement solution module 22 for displacement solution.

[0056] Specifically, the fast axis direction of the 1 / 4 wave plate A3 is 45° counterclockwise to the z-axis, and the fast axis direction of the 1 / 4 wave plate B5 is 45° clockwise to the z-axis. The transmitted light and the reflected light carry the motion information of the first reflector 4 and the second reflector 6 respectively, and then return to the polarization splitter prism A2.

[0057] The polarization direction of polarizer A10 is 45° to the z-axis, the polarization direction of polarizer B12 is 0° to the x-axis, and the polarization direction of polarizer C13 is 90° to the y-axis.

[0058] Furthermore, the homodyne laser interferometer signal processing unit includes an adjustable gain amplification module A17, an adjustable gain amplification module B18 and an adjustable gain amplification module C19, wherein the signal obtained by detection by the photodetector A14 is input into the adjustable gain amplification module A17, the signal obtained by detection by the photodetector B15 is input into the adjustable gain amplification module B18, and the signal obtained by detection by the photodetector C16 is input into the adjustable gain amplification module C19. The signals processed by the adjustable gain amplification module A17 and the adjustable gain amplification module B18 are input into the subtractor A20 to obtain the signal Ix, and the signals processed by the adjustable gain amplification module B18 and the adjustable gain amplification module C19 are input into the subtractor B21 to obtain the signal Iy.

[0059] Specifically, the polarization beam splitter prism A2 is suitable for dividing a single-frequency light source into a reference beam and a measurement beam, the first reflector 4 is used to reflect the reference beam, the second reflector 6 is used to reflect the measurement beam, and the non-polarization beam splitter A9 and the non-polarization beam splitter B11 are suitable for dividing the synthetic beam of the polarization beam splitter prism A2 into a first synthetic light, a second synthetic light and a third synthetic light; the synthetic beam is obtained by combining the reference beam obtained by reflecting the first reflector 4 and the measurement beam obtained by reflecting the second reflector 6 through the polarization beam splitter prism; at least three photodetectors capable of detecting interference signals, the first interference signal is formed by the first synthetic beam passing through the polarizer A10, the second interference signal is formed by the second synthetic beam passing through the polarizer B12, and the third interference signal is formed by the interference of the third synthetic beam passing through the polarizer C13.

[0060] The homodyne laser interferometer signal processing unit includes: at least three interference signal amplitude adjustment modules, which can adjust the amplitudes of the first interference signal, the second interference signal and the third interference signal to be equal; and at least two subtraction modules, in which the signal Ix is obtained by subtracting the first interference signal from the second interference signal, and the signal Iy is obtained by subtracting the second interference signal from the third interference signal.

[0061] This embodiment further provides a three-channel homodyne interferometer signal processing method for suppressing non-orthogonality errors, including:

[0062] Linearly polarized light or circularly polarized light of a specific frequency is incident on the polarization beam splitter prism A2 to obtain a measuring beam and a reference beam. The reference beam passes through the reference optical path and is reflected by the first reflector 4. The measuring beam passes through the measuring optical path and is reflected by the second reflector 6 carrying information of the moving target to be measured. The measuring beam and the reference beam are combined by the polarization beam splitter prism A2 to form a composite beam.

[0063] The composite light beam is processed and solved by the interference signal solving module 7 to obtain the displacement solution result.

[0064] Furthermore, the composite beam is processed by the interference signal solving module 7, including:

[0065] The composite beam is sequentially split by the quarter-wave plate C8, the non-polarizing beam splitter A9, and the non-polarizing beam splitter B11 to generate a first composite beam, a second composite beam, and a third composite beam, respectively.

[0066] The first composite light beam passes through the polarizer A10, whose polarization direction is 45° to the x-axis, to form the first interference light. The second composite light beam passes through the polarizer B12, whose polarization direction is 0° to the x-axis, to form the second interference light. The third composite light beam passes through the polarizer C13, whose polarization direction is 90° to the x-axis, to form the third interference light.

[0067] The first interference light, the second interference light and the third interference light are input into the photodetector A14, the photodetector B15 and the photodetector C16 respectively to obtain the first interference signal, the second interference signal and the third interference signal;

[0068] Processing the first interference signal, the second interference signal, and the third interference signal based on a homodyne laser interferometer signal processing unit to obtain a first interference signal after AC amplitude adjustment, a second interference signal after AC amplitude adjustment, and a third interference signal after AC amplitude adjustment;

[0069] The first interference signal after AC amplitude adjustment, the second interference signal after AC amplitude adjustment, and the third interference signal after AC amplitude adjustment are input into subtractor A20 and subtractor B21 respectively to obtain a sine interference signal and a cosine interference signal;

[0070] The displacement calculation module 22 performs displacement calculation on the sine interference signal and the cosine interference signal to obtain a final displacement calculation result.

[0071] Specifically, the first interference signal, the second interference signal and the third interference signal are obtained as follows:

[0072]

[0073] Where I1 is the first interference signal, I2 is the second interference signal, I3 is the third interference signal, a is the AC amplitude of the interference signal, b is the DC bias of the interference signal, is the phase difference between the second interference signal and the ideal orthogonal signal.

[0074] Obtaining a first interference signal after AC amplitude adjustment, a second interference signal after AC amplitude adjustment, and a third interference signal after AC amplitude adjustment, including:

[0075] The first interference signal, the second interference signal, and the third interference signal are adjusted by the adjustable gain amplification module A17, the adjustable gain amplification module B18, and the adjustable gain amplification module C19, respectively, to obtain the first interference signal after AC amplitude adjustment, the second interference signal after AC amplitude adjustment, and the third interference signal after AC amplitude adjustment, specifically:

[0076]

[0077] Where, I1′ is the first interference signal after AC amplitude adjustment, I2′ is the second interference signal after AC amplitude adjustment, I3′ is the third interference signal after AC amplitude adjustment, A0 is the adjusted signal AC amplitude, is the phase difference between the second interference signal and the ideal orthogonal signal, and B is the DC bias of the signal after adjustment.

[0078] Obtain sine interference signals and cosine interference signals, including:

[0079] The sine interference signal is obtained by subtracting the second interference signal after AC amplitude adjustment from the first interference signal after AC amplitude adjustment, and the cosine interference signal is obtained by subtracting the third interference signal after AC amplitude adjustment from the first interference signal after AC amplitude adjustment. Specifically,

[0080]

[0081] Where, I x is a sinusoidal interference signal, I y is the cosine interference signal.

[0082] Specifically, when there is a non-orthogonal error introduced by an imperfect optical path device, the amplification factors of the adjustable gain amplifier module A17, the adjustable gain amplifier module B18 and the adjustable gain amplifier module C19 can be adjusted until the AC amplitudes of the three interference signals are equal, so that the output orthogonal interference signals are restored to orthogonality, and the non-orthogonal angles of the interference signals do not need to be calculated during the adjustment process.

[0083] In order to more clearly express the technical solution of the present invention, the following specific embodiments are provided to introduce the solution:

[0084] by Figure 1 Taking the bisection optical path single-frequency interferometer composed of the polarization beam splitter prism and the plane reflector as an example, the specific implementation steps of the present invention are as follows:

[0085] (1) Linearly polarized light or circularly polarized light of frequency ν is incident on a polarization beam splitter prism and is split into a measurement beam and a reference beam;

[0086] (2) The reference beam passes through the reference optical path and is reflected by the first reflector 4;

[0087] (3) The measuring beam passes through the measuring optical path, carries the information of the moving target to be measured, and is reflected by the second reflector 6;

[0088] (4) The reflected measuring beam and the reference beam are combined by the polarization beam splitter A2 to form a composite beam;

[0089] (5) After the composite beam passes through the quarter-wave plate A3, it passes through the non-polarizing beam splitter A9 and the non-polarizing beam splitter B11, and is split into the first composite beam, the second composite beam, and the third composite beam;

[0090] (6) The first composite light beam passes through the polarizer A10 whose polarization direction is 45° to the x-axis to form the first interference light. The second composite light beam passes through the polarizer B12 whose polarization direction is 0° to the x-axis to form the second interference light. The third composite light beam passes through the polarizer C13 whose polarization direction is 90° to the x-axis to form the third interference light.

[0091] (7) After the first interference light passes through the photodetector A14, a first interference signal I1 is formed. After the second interference light passes through the photodetector B15, a second interference signal I2 is formed. After the third interference light passes through the photodetector C16, a third interference signal I3 is formed.

[0092]

[0093] (8) The first, second, and third interference signals are respectively passed through the adjustable gain amplification module A17, the adjustable gain amplification module B18, and the adjustable gain amplification module C19 to adjust the AC amplitudes of the three interference signals to be equal;

[0094]

[0095] (9) The first, second and third interference signals I'1, I'2 and I'3 after AC amplitude adjustment are obtained by subtracting the second interference signal from the first interference signal to obtain the sinusoidal interference signal I x , the cosine interference signal I is obtained by subtracting the third interference signal from the first interference signal y ;

[0096]

[0097] (10) Sinusoidal interference signal I x Interference signal I yEnter the displacement solution module 22 to obtain the final displacement solution result.

[0098] The above are merely preferred embodiments of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A three-channel homodyne interferometer signal processing device for suppressing non-orthogonal errors, characterized in that: include: Single-frequency laser (1), polarization beam splitter prism A (2), quarter wave plate A (3), first reflector (4), quarter wave plate B (5), second reflector (6), interference signal solution module (7); The polarization beam splitter prism A (2) is located at the output end of the single-frequency laser (1); a quarter wave plate A (3) and a first reflector (4) are arranged in parallel in the direction of reflected light; a quarter wave plate B (5) and a second reflector (6) are arranged in parallel in the direction of transmitted light; and the interference signal resolution module (7) is arranged on the opposite side of the first reflector (4) with the polarization beam splitter prism A (2) as the axis.

2. The three-channel homodyne interferometer signal processing device for suppressing non-orthogonality errors according to claim 1, characterized in that: The interference signal calculation module (7) includes a quarter wave plate C (8), a non-polarization beam splitter A (9), a polarizer A (10), a non-polarization beam splitter B (11), a polarizer B (12), a polarizer C (13), a photodetector A (14), a photodetector B (15), a photodetector C (16), a subtractor A (20), a subtractor B (21), and a displacement calculation module (22); Wherein, a quarter wave plate C (8) is placed at a position opposite to the second reflector (6) of the polarization beam splitter prism A (2), a non-polarization beam splitter A (9) is arranged along the optical axis of the quarter wave plate C (8), a polarization plate A (10) is arranged along the direction of reflected light of the non-polarization beam splitter A (9), a non-polarization beam splitter B (11) is arranged along the direction of transmitted light of the non-polarization beam splitter A (9), a polarization plate B (12) is arranged in the propagation direction of reflected light of the non-polarization beam splitter B (11), a polarization plate C (13) is arranged in the propagation direction of transmitted light of the non-polarization beam splitter B (11), and a polarization plate A ( 10), polarizer B (12), and polarizer C (13), photodetectors A (14), B (15), and C (16) are arranged respectively. The photodetectors A (14), B (15), and C (16) are connected to a homodyne laser interferometer signal processing unit. The homodyne laser interferometer signal processing unit inputs the processed signals into a subtractor A (20) and an input subtractor B (21) respectively to obtain a signal Ix and a signal Iy. Finally, the signal Ix and the signal Iy are input into a displacement solution module (22) for displacement solution.

3. The three-channel homodyne interferometer signal processing device for suppressing non-orthogonality errors according to claim 2, characterized in that: The fast axis direction of the 1 / 4 wave plate A (3) is 45 degrees counterclockwise to the z-axis, and the fast axis direction of the 1 / 4 wave plate B (5) is 45 degrees clockwise to the z-axis. The transmitted light and the reflected light respectively carry the motion information of the first reflector (4) and the second reflector (6) and then return to the polarization beam splitter prism A (2).

4. The three-channel homodyne interferometer signal processing device for suppressing non-orthogonality errors according to claim 2, characterized in that: The polarization direction of the polarizer A (10) is 45° to the x-axis, the polarization direction of the polarizer B (12) is 0° to the x-axis, and the polarization direction of the polarizer C (13) is 90° to the x-axis.

5. The three-channel homodyne interferometer signal processing device for suppressing non-orthogonality errors according to claim 2, characterized in that: The homodyne laser interferometer signal processing unit includes an adjustable gain amplifying module A (17), an adjustable gain amplifying module B (18) and an adjustable gain amplifying module C (19), wherein the signal detected by the photodetector A (14) is input into the adjustable gain amplifying module A (17), the signal detected by the photodetector B (15) is input into the adjustable gain amplifying module B (18), and the signal detected by the photodetector C (16) is input into the adjustable gain amplifying module C (19). The signals processed by the adjustable gain amplifying module A (17) and the adjustable gain amplifying module B (18) are input into a subtractor A (20) to obtain a signal Ix, and the signals processed by the adjustable gain amplifying module B (18) and the adjustable gain amplifying module C (19) are input into a subtractor B (21) to obtain a signal Iy.

6. A three-channel homodyne interferometer signal processing method for suppressing non-orthogonal errors, applied to the three-channel homodyne interferometer signal processing device for suppressing non-orthogonal errors according to any one of claims 1 to 5, characterized in that: include: Polarized light of a target frequency is incident on a polarization beam splitter prism A (2) to obtain a measuring beam and a reference beam, wherein the reference beam passes through a reference optical path and is reflected by a first reflector (4), and the measuring beam passes through a measuring optical path and is reflected by a second reflector (6) carrying information of a moving target to be measured, and the measuring beam and the reference beam are combined through the polarization beam splitter prism A (2) to form a composite beam; The synthesized light beam is processed and solved by an interference signal solving module (7) to obtain a displacement solving result.

7. The three-channel homodyne interferometer signal processing method for suppressing non-orthogonal errors according to claim 6, characterized in that: The synthesized light beam is processed by an interference signal solving module (7), including: The composite light beam is sequentially split by passing through a quarter wave plate C (8), a non-polarizing beam splitter A (9) and a non-polarizing beam splitter B (11) to generate a first composite light beam, a second composite light beam and a third composite light beam respectively; The first composite light beam forms a first interference light after passing through a polarizer A (10) whose polarization direction is 45 degrees to the x-axis; the second composite light beam forms a second interference light after passing through a polarizer B (12) whose polarization direction is 0 degrees to the x-axis; and the third composite light beam forms a third interference light after passing through a polarizer C (13) whose polarization direction is 90 degrees to the x-axis. Inputting the first interference light, the second interference light and the third interference light into a photodetector A (14), a photodetector B (15) and a photodetector C (16) respectively to obtain a first interference signal, a second interference signal and a third interference signal; Processing the first interference signal, the second interference signal, and the third interference signal based on a homodyne laser interferometer signal processing unit to obtain a first interference signal after AC amplitude adjustment, a second interference signal after AC amplitude adjustment, and a third interference signal after AC amplitude adjustment; Inputting the first interference signal after AC amplitude adjustment, the second interference signal after AC amplitude adjustment, and the third interference signal after AC amplitude adjustment into a subtractor A (20) and a subtractor B (21), respectively, to obtain a sine interference signal and a cosine interference signal; Displacement calculation is performed on the sine interference signal and the cosine interference signal to obtain a final displacement calculation result.

8. The three-channel homodyne interferometer signal processing method for suppressing non-orthogonal errors according to claim 7, characterized in that: The first interference signal, the second interference signal, and the third interference signal are obtained, specifically: Where I1 is the first interference signal, I2 is the second interference signal, I3 is the third interference signal, a is the AC amplitude of the interference signal, b is the DC bias of the interference signal, is the phase difference between the second interference signal and the ideal orthogonal signal.

9. The three-channel homodyne interferometer signal processing method for suppressing non-orthogonal errors according to claim 7, characterized in that: Obtaining a first interference signal after AC amplitude adjustment, a second interference signal after AC amplitude adjustment, and a third interference signal after AC amplitude adjustment, including: The first interference signal, the second interference signal and the third interference signal are adjusted by the adjustable gain amplification module A (17), the adjustable gain amplification module B (18) and the adjustable gain amplification module C (19) respectively to obtain the first interference signal after AC amplitude adjustment, the second interference signal after AC amplitude adjustment and the third interference signal after AC amplitude adjustment, specifically: Where, I1′ is the first interference signal after AC amplitude adjustment, I2′ is the second interference signal after AC amplitude adjustment, I3′ is the third interference signal after AC amplitude adjustment, A0 is the adjusted signal AC amplitude, is the phase difference between the second interference signal and the ideal orthogonal signal, and B is the DC bias of the signal after adjustment.

10. The three-channel homodyne interferometer signal processing method for suppressing non-orthogonality errors according to claim 9, characterized in that: Obtaining the sinusoidal interference signal and the cosine interference signal includes: The sine interference signal is obtained by subtracting the second interference signal after AC amplitude adjustment from the first interference signal after AC amplitude adjustment, and the cosine interference signal is obtained by subtracting the third interference signal after AC amplitude adjustment from the first interference signal after AC amplitude adjustment, specifically: Where, I x is the sinusoidal interference signal, I y is the cosine interference signal.

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