Air refractive index self-correction three-frequency laser interferometer and wavefront aberration detection method

Abstract

The invention discloses an air refractive index self-correction three-frequency laser interferometer and an interference detection method thereof, and solves the problems of long time consumption and high measurement cost of a wavefront aberration detection method for a large-aperture optical system. According to the air refractive index self-correction three-frequency laser interferometer and the interference detection method thereof provided by the invention, the optical path differences between the spatial positions of the reference mirror and the mirror to be measured are measured by the first-frequency-doubled laser, the second-frequency-doubled laser and the fourth-frequency-doubled laser respectively; according to the wavefront detection method, the correction factor determined only by the first-frequency-doubled laser, the second-frequency-doubled laser and the quadruplicated frequency wavelength can be constructed, then the wavefront aberration of each spatial position of the to-be-detected mirror is obtained, large-aperture optical system wavefront detection with the air refractive index self-correction function is achieved, and the wavefront detection method is short in detection time, low in cost, easy and convenient to operate and high in detection precision.

Description

Technical Field

[0001] The invention relates to an interferometer and an interference detection method thereof, and in particular to an air refractive index self-correcting three-frequency laser interferometer and an interference detection method thereof. Background Art

[0002] The basic principle of laser interferometer is to obtain the optical path difference between the target position of the mirror to be measured and the reference mirror through the interference of laser. The optical path difference is the sum of the optical path difference introduced by the measuring optical path and the wavefront aberration of the mirror to be measured. The optical path difference introduced by the measuring optical path can be directly obtained by multiplying the physical distance of the measuring optical path by the refractive index.

[0003] Under ideal conditions, the refractive index is only related to the wavelength and has nothing to do with the spatial position; therefore, the refractive index is a constant value and can be obtained through calibration. The physical distance of the measured optical path can also be obtained through calibration. At this time, the optical path difference obtained by the interferometer can directly reflect the wavefront aberration of the mirror to be measured.

[0004] However, in actual situations, especially in large-aperture optical systems, the mirror aperture of the measured mirror is large, the measuring optical path is long, and the refractive index is no longer a constant value but is constantly changing. As a result, the refractive index in large-aperture optical systems is also related to the spatial environment, causing wavefront aberration detection of large-aperture optical systems to become a major problem that needs to be solved urgently in optical detection.

[0005] The existing detection methods mainly include the following:

[0006] 1) By disturbing the air field in the measurement optical path (such as using a fan array to speed up air circulation), the air is made more uniform, and then the wavefront aberration is obtained by averaging multiple measurements. This method is time-consuming and can only be achieved under better environmental control. In addition, the test accuracy is low and it cannot accurately reflect the measured wavefront aberration.

[0007] 2) Place the optical system under test in a vacuum tank (low-pressure tank) to completely eliminate the influence of changes in the refractive index of air. However, this method is costly, has a complicated operation process, and is difficult to debug.

[0008] 3) Using dual-frequency laser to detect wavefront aberration, it is only necessary to ensure the dryness of the test environment air, so that the air refractive index can be self-corrected. Under the condition of not too high cost (compared with vacuum tanks and low-pressure tanks), high-efficiency and high-precision wavefront aberration detection of large-aperture optical systems can be achieved. However, keeping the test environment air dry is still a major limitation. Air that is not dry enough will still cause a large offset in the wavefront detection of large-aperture optical systems. When the air humidity is 10%, the ratio of the wavefront aberration test error to the wavelength using dual-frequency laser correction is as follows: Figure 1 As shown, the correction will bring about a large offset error. Summary of the invention

[0009] In order to solve the technical problems of long time consumption, high measurement cost, low measurement accuracy and complicated operation process for wavefront aberration detection methods of large-aperture optical systems, the present invention provides an air refractive index self-correcting three-frequency laser interferometer and its interference detection method.

[0010] In order to achieve the above object, the present invention adopts the following technical solution:

[0011] An air refractive index self-correcting triple-frequency laser interferometer, which is special in that:

[0012] It includes a three-frequency generating module, an interference module and a signal receiving module;

[0013] The triple-frequency generation module is used to emit a linearly polarized triple-frequency combined laser beam in the I0 direction formed by combining a single-frequency laser, a double-frequency laser and a quadruple-frequency laser beam to the interference module;

[0014] The interference module includes a second beam splitter, a reference mirror, a first quarter wave plate, a second quarter wave plate, a grating and a polarizer array; the second beam splitter corresponds to the output end of the three-frequency generating module, and the reference mirror and the second beam splitter are sequentially arranged on the transmission side optical path of the second beam splitter in a direction away from the second beam splitter; the side of the first quarter wave plate away from the reference mirror is used to set the mirror to be measured; the second quarter wave plate, the grating and the polarizer array are sequentially arranged on the reflection side optical path of the second beam splitter in a direction away from the second beam splitter; the second beam splitter is used to transmit the linearly polarized three-frequency combined beam laser in the I0 direction to the reference mirror, a part of which is reflected by the reference mirror, and the other part is transmitted by the reference mirror and then rotated by the first quarter wave plate to reach the mirror to be measured, and then reflected by the mirror to be measured, and then rotated again by the first quarter wave plate to form a linearly polarized three-frequency combined beam laser in the I1 direction, and then transmitted by the reference mirror and combined with the linearly polarized three-frequency combined beam laser in the I0 direction reflected by the reference mirror to form I 01 Laser; I 01 The laser is reflected by the second beam splitter to the second quarter-wave plate, and then split into multiple beams of different phases by the grating. 01 Splitting, polarizer array changes each beam I 01 The polarization states of the split light interfere with each other, so each beam I 01 The split light includes the first-harmonic interference light, the second-harmonic interference light and the fourth-harmonic interference light; the difference between the I1 direction and the I0 direction is 90°;

[0015] The incident end of the signal receiving module corresponds to the output end of the polarizer array, and is used to receive all the first-harmonic interference light, the second-harmonic interference light and the fourth-harmonic interference light, separate them spatially, and then detect them respectively to obtain the first detection information, the second detection information and the third detection information.

[0016] Further, the triple-frequency generation module includes a frequency-doubled laser component, a first second harmonic crystal, a first semiconductor amplifier, a first dichroic beam splitter, a polarizer, a third beam splitter, a second second harmonic crystal and a second semiconductor amplifier;

[0017] The one-time frequency laser assembly is used to emit one-time frequency reflected light and first one-time frequency transmitted light;

[0018] The first second harmonic crystal, the first semiconductor amplifier and the third beam splitter are sequentially arranged on the optical path of the first-frequency reflected light along the emission direction thereof; the first second harmonic crystal is used to double the frequency of a part of the first-frequency reflected light to obtain the second-frequency reflected light; the first semiconductor amplifier is used to power amplify another part of the first-frequency reflected light and the second-frequency reflected light; the third beam splitter is used to reflect a part of the second-frequency reflected light after power amplification, and transmit a first mixed light formed by superposition of another part of the second-frequency reflected light and the first-frequency reflected light after power amplification;

[0019] The second second harmonic crystal and the second semiconductor amplifier are sequentially arranged on the optical path of the first mixed light along the emission direction thereof; the second second harmonic crystal is used to double the frequency of a part of the first mixed light, and to keep another part of the first mixed light, so as to obtain a second mixed light including a second first-harmonic transmission light, a second second-harmonic transmission light and a fourth-harmonic transmission light; the second mixed light is combined with the second-harmonic reflected light to form a third mixed light;

[0020] The first two-way beam splitter is arranged at the intersection of the third mixed light and the first doubled frequency transmitted light, and is used to transmit the first doubled frequency transmitted light to the polarizer, and reflect the third mixed light to the polarizer;

[0021] The polarizer is arranged on the reflection side optical path of the first dichroic beam splitter, and is used to receive the mixed light of the first doubled frequency transmitted light and the third mixed light, and change its polarization state to form a linearly polarized triple-frequency combined laser beam in the I0 direction.

[0022] Further, the frequency-doubled laser assembly includes a laser source for emitting an initial laser, an optical frequency comb, an atomic clock and a first beam splitter;

[0023] The laser source is phase-locked to an optical frequency comb;

[0024] The optical frequency comb is phase-locked to an atomic clock;

[0025] The first beam splitter is arranged on the optical path of the initial laser, and is used for splitting the initial laser into a first-doubled frequency reflected light and a first first-doubled frequency transmitted light.

[0026] Further, the signal receiving module includes a second dichroic beam splitter, a third dichroic beam splitter, a first detector, a second detector and a third detector;

[0027] The second dichroic beam splitter corresponds to the output end of the polarizer array, and is used to receive all the first-harmonic interference light, the second-harmonic interference light, and the fourth-harmonic interference light, and transmit all the first-harmonic interference light to the first detector, and reflect all the second-harmonic interference light and the fourth-harmonic interference light to the third dichroic beam splitter;

[0028] The third two-way beam splitter is used to transmit all the doubled frequency interference light to the second detector and reflect all the quadruple frequency interference light to the third detector;

[0029] The first detector is used to obtain a frequency-doubled interference pattern with different phases;

[0030] The second detector is used to obtain frequency doubled interference patterns of different phases;

[0031] The third detector is used to obtain quadruple frequency interference patterns with different phases.

[0032] Furthermore, the first detector, the second detector and the third detector are all CCD detectors.

[0033] Further, the grating is an orthogonal grating;

[0034] The laser source is a tunable narrow-band laser source;

[0035] The fast axis directions of the first quarter wave plate and the second quarter wave plate are (I0+I1) / 2.

[0036] A wavefront aberration detection method, using the above-mentioned air refractive index self-correcting triple-frequency laser interferometer, is special in that it includes the following steps:

[0037] Step 1: The triple-frequency generation module emits a linearly polarized triple-frequency combined laser beam in the I0 direction formed by combining a single-frequency laser, a double-frequency laser and a quadruple-frequency laser beam to the interference module;

[0038] Step 2: After the second beam splitter transmits the I0 direction linearly polarized three-frequency combined beam laser to the reference mirror, a part of it is reflected by the reference mirror, and the other part is transmitted by the reference mirror and then rotated by the first quarter wave plate to reach the mirror to be measured, and then reflected by the mirror to be measured, and then rotated again by the first quarter wave plate to form the I1 direction linearly polarized three-frequency combined beam laser, which is then transmitted by the reference mirror and combined with the I0 direction linearly polarized three-frequency combined beam laser reflected by the reference mirror to form I 01 Laser; the second beam splitter I 01 The laser is reflected to the second quarter wave plate and then divided into multiple beams of different phases by the grating. 01 Splitting, polarizer array changes each beam I 01 The polarization states of the split light interfere with each other, so each beam I 01The split light includes the first-harmonic interference light, the second-harmonic interference light and the fourth-harmonic interference light; the difference between the I1 direction and the I0 direction is 90°;

[0039] Step 3, the signal receiving module receives all the first-harmonic interference light, the second-harmonic interference light and the fourth-harmonic interference light, separates them spatially, and then detects them respectively, and obtains the first detection information, the second detection information and the third detection information accordingly;

[0040] Step 4, respectively calculate the first optical path difference OPD1(x, y), the second optical path difference OPD2(x, y) and the third optical path difference OPD3(x, y) of the reference mirror and the mirror to be measured corresponding to the first-harmonic interference light, the second-harmonic interference light and the fourth-harmonic interference light through the first detection information, the second detection information and the third detection information, where (x, y) is the plane coordinate in the direction perpendicular to the optical axis;

[0041] Step 5, obtaining a first correction factor A1 and a second correction factor A2 based on the method of steps 1 to 4;

[0042] Step 6, calculate the wavefront aberration W1 of the mirror to be measured corresponding to the first-time frequency laser, the wavefront aberration W2 of the mirror to be measured corresponding to the second-time frequency laser, and the wavefront aberration W3 of the mirror to be measured corresponding to the fourth-time frequency laser respectively through the first optical path difference OPD1(x, y), the second optical path difference OPD2(x, y), and the third optical path difference OPD3(x, y):

[0043] W1=d2(x,y). / (d1(x,y)+d2(x,y)).*OPD1(x,y);

[0044] W2=d2(x,y). / (d1(x,y)+d2(x,y)).*OPD2(x,y);

[0045] W3=d2(x,y). / (d1(x,y)+d2(x,y)).*OPD3(x,y);

[0046] in:

[0047] d1(x,y) is twice the physical distance from the reference mirror to the mirror to be measured, obtained through calibration;

[0048] d2(x,y)=OPD1(x,y)-A1*(OPD1(x,y)-OPD2(x,y))-A2*(OPD1(x,y)-OPD3(x,y))-d1(x,y).

[0049] Furthermore, step 5 specifically includes:

[0050] 5.1) Calculate the first theoretical correction factor A 1理 and the second theoretical correction factor A 2理 :

[0051] A 1理 =(a(λ1)*(b(λ1)-b(λ3))-b(λ1)*(a(λ1)-a(λ3)) / ((a(λ1)-a(λ2)*(b(λ1)-b(λ3))-(b(λ1)-b(λ2))*(a(λ1)-a(λ3));

[0052] A 2理 =(-a(λ1)*(b(λ1)-b(λ2))+b(λ1)*((a(λ1)-a(λ2)) / ((a(λ1)-a(λ2))*(b(λ1)-b(λ3))-(b(λ1)-b(λ2))*(a(λ1)-a(λ3));

[0053] Wherein, a and b are coefficients that vary with wavelength; λ1, λ2 and λ3 are the wavelengths of the first-harmonic laser, the second-harmonic laser and the fourth-harmonic laser, respectively;

[0054] 5.2) Based on the method of step 1 to step 4, the mirror to be tested is measured N1 times, and the obtained N1 measurement data includes N1 optical path difference values ​​OPD 1i The first optical path difference array contains N1 optical path difference values ​​OPD 2i The second optical path difference array contains N1 optical path difference values ​​OPD 3i The third optical path difference array, i = 1, 2, ... N1, N1 ≥ 50;

[0055] 5.3) Set the value range of the first correction factor A1 to [A 1min ,A 1max ], so that A 1理 ∈[A 1min ,A 1max ], take N2 equally spaced values ​​within this range and represent them as array A1'=A 1min :(A 1max -A 1min ) / (N2-1):A 1max , then array A1' contains N2 values ​​A 1j , j=1,2,…N2,N2≥50;

[0056] The value range of the second correction factor A2 is set to [A 2min ,A 2max ], so that A 2理 ∈[A 2min ,A 2max ], take N3 equally spaced values ​​within this range, represented by the array A2'=A 2min :(A 2max -A 2min) / (N3-1):A 2max , then array A2' contains N3 values ​​A 2k , k=1,2,…N3,N3≥50;

[0057] 5.4) Set the N2 values ​​A in array A1' 1j and the N3 values ​​A in array A2' 2k Perform pairwise combinations to obtain N2×N3 combinations. Based on the N2×N3 combinations and the N1 measurement data in step 5.2, calculate the corrected equivalent distance d1(i, A 1j ,A 2k )+d2(i,A 1j ,A 2k ):

[0058] d1(i,A 1j ,A 2k )+d2(i,A 1j ,A 2k )=OPD 1i -A 1j *(OPD 1i -OPD 2i )-A 2k *(OPD 1i -OPD 3i )

[0059] Obtain N1×N2×N3 corrected equivalent distances;

[0060] 5.5) Calculate N1×N2×N3 corrected equivalent distances by the formula rms(d1(i)-mean(d1(i))+d2(i)-mean(d2(i))) to obtain N2×N3 non-uniformity results;

[0061] 5.6) Obtain the minimum value among the N2×N3 non-uniformity results corresponding to the values ​​in the corresponding arrays A1' and A2', which are respectively denoted as A 1jmin and A 2kmin ;

[0062] 5.7) Expand A 1min The lower limit of the value is A 1jmin -(A 1max -A 1min ) / (N2-1), reduce A 1max The upper limit of the value is A 1jmin+ (A 1max -A 1min ) / (N2-1); expand A 2min The lower limit of the value is A 2kmin -(A 2max -A 2min) / (N3-1), reduce A 2max The upper limit of the value is A 2kmin+ (A 2max -A 2min ) / (N3-1);

[0063] 5.8) Set the value range length A of the first correction factor A1 and the second correction factor A2 1max -A 1min and A 2max -A 2min Compared with the first preset threshold value A3 and the second preset threshold value A4 respectively:

[0064] If A 1max -A 1min >A3 and / or A 2max -A 2min >A4, then return to step 5.2, otherwise output the final values ​​of the first correction factor A1 and the second correction factor A2;

[0065] Where 0<A3<10 -4 ,0<A4<10 -4 .

[0066] Furthermore, step 1 is specifically as follows:

[0067] The one-time frequency laser assembly emits one-time frequency reflected light and the first one-time frequency transmitted light;

[0068] The first second harmonic crystal doubles the frequency of a portion of the first-harmonic reflected light to obtain a second-harmonic reflected light;

[0069] The first semiconductor amplifier is used to amplify the power of another part of the first-time frequency reflected light and the second-time frequency reflected light;

[0070] The third beam splitter is used to reflect a portion of the double frequency reflected light after power amplification, and transmit a first mixed light formed by superposition of another portion of the double frequency reflected light and the single frequency reflected light after power amplification;

[0071] The second second harmonic crystal doubles the frequency of a part of the first mixed light, and another part of the first mixed light remains, so as to obtain a second mixed light including a second first-harmonic transmission light, a second second-harmonic transmission light and a fourth-harmonic transmission light; the third mixed light is combined with the second second-harmonic reflected light to form a second mixed light;

[0072] The first two-way beam splitter transmits the first doubled frequency transmission light to the polarizer, and reflects the third mixed light to the polarizer;

[0073] The polarizer changes the polarization state of the mixed light of the first doubled frequency transmitted light and the third mixed light to form a linearly polarized triple-frequency combined laser beam in the I0 direction.

[0074] Furthermore, step 4 is specifically as follows:

[0075] The second two-way beam splitter receives all the first-harmonic interference light, the second-harmonic interference light and the fourth-harmonic interference light, and transmits all the first-harmonic interference light to the first detector, and reflects all the second-harmonic interference light and the fourth-harmonic interference light to the third two-way beam splitter; the third two-way beam splitter transmits all the second-harmonic interference light to the second detector, and reflects all the fourth-harmonic interference light to the third detector; the first detector is used to obtain the first-harmonic interference pattern of different phases to obtain the first detection information; the second detector is used to obtain the second-harmonic interference pattern of different phases to obtain the second detection information; the third detector is used to obtain the fourth-harmonic interference pattern of different phases to obtain the third detection information.

[0076] Beneficial effects of the present invention:

[0077] 1. The present invention provides an air refractive index self-correcting triple-frequency laser interferometer and its interference detection method, which respectively measures the optical path difference between the corresponding reference mirror and the mirror to be measured at each spatial position using the single-frequency laser, double-frequency laser and quadruple-frequency laser to measure, and can construct a correction factor determined only by the wavelengths of the single-frequency laser, double-frequency laser and quadruple-frequency laser, and then obtain the wavefront aberration of each spatial position of the mirror to be measured, thereby realizing the wavefront detection of a large-aperture optical system with self-correction of air refractive index, and the detection time is short, the cost is low, the operation is simple and the detection accuracy is high.

[0078] 2. The present invention provides an air refractive index self-correcting three-frequency laser interferometer and its interference detection method, which can overcome the wavefront measurement error caused by the uneven air refractive index in the test system without the need to accurately control the environmental conditions. This means that high-efficiency and high-precision wavefront aberration detection of large-aperture optical systems can be achieved in harsh environments or workshop environments, greatly increasing practicality and feasibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0079] Figure 1 It is a curve diagram of the ratio of the wavefront aberration test error to the wavelength using dual-frequency correction in a 10% humidity environment of the present invention;

[0080] Figure 2 It is a structural schematic diagram of an embodiment of an air refractive index self-correcting triple-frequency laser interferometer of the present invention;

[0081] Figure 3 is a curve diagram of the ratio of the wavefront aberration test error corrected by the theoretical correction factor to the wavelength in an embodiment of the present invention;

[0082] Figure 4 3 is a curve diagram of the ratio of the wavefront aberration test error corrected by the first correction factor A1 and the second correction factor A2 to the wavelength in an embodiment of the present invention.

[0083] Figure Number:

[0084] 1. Atomic clock, 2. Optical frequency comb, 3. Laser source, 4. First beam splitter, 5. First second harmonic crystal; 6. First semiconductor amplifier, 7. First dichroic beam splitter, 8. Polarizer, 9. Second beam splitter, 10. Reference mirror, 11. First quarter wave plate, 12. Mirror to be measured, 13. Second quarter wave plate, 14. Grating, 15. Polarizer array, 16. Second dichroic beam splitter, 17. Third dichroic beam splitter, 18. Second detector, 19. Triple frequency generation module, 20. Interference module, 21. Signal receiving module, 22. Third beam splitter, 23. Second second harmonic crystal, 24. Second semiconductor amplifier, 25. First detector, 26. Third detector. DETAILED DESCRIPTION

[0085] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0086] An embodiment of the present invention provides an air refractive index self-correcting triple-frequency laser interferometer, such as Figure 2 As shown, the interferometer includes a three-frequency generating module 19 , an interference module 20 and a signal receiving module 21 .

[0087] The triple-frequency generation module 19 includes a laser source 3 for emitting an initial laser, an optical frequency comb 2, an atomic clock 1 and a first beam splitter 4, and also includes a first second harmonic crystal 5, a first semiconductor amplifier 6, a first dichroic beam splitter 7, a polarizer 8, a third beam splitter 22, a second second harmonic crystal 23 and a second semiconductor amplifier 24; the laser source 3 is a tunable narrow-band laser source.

[0088] The laser source 3 is phase-locked to the optical frequency comb 2; the optical frequency comb 2 is phase-locked to the atomic clock 1; the first beam splitter 4 is arranged on the optical path where the initial laser is located, and is used to split the initial laser into a first-frequency reflected light and a first first-frequency transmitted light. The first second harmonic crystal 5, the first semiconductor amplifier 6 and the third beam splitter 22 are arranged in sequence on the optical path where the first-frequency reflected light is located along its emission direction; the first second harmonic crystal 5 is used to double the frequency of a part of the first-frequency reflected light to obtain a second-frequency reflected light; the first semiconductor amplifier 6 is used to power amplify another part of the first-frequency reflected light and the second-frequency reflected light; the third beam splitter 22 is used to reflect a part of the second-frequency reflected light after power amplification, and transmit a first mixed light formed by superposition of another part of the second-frequency reflected light and the first-frequency reflected light after power amplification; the second second harmonic crystal 23 and the second semiconductor amplifier 24 are arranged in sequence on the optical path where the first mixed light is located along its emission direction; The second second harmonic crystal 23 is used to double the frequency of a part of the first mixed light, and the other part of the first mixed light remains, so as to obtain a second mixed light including a second first-doubled frequency transmitted light, a doubled frequency transmitted light and a quadruple frequency transmitted light; the second mixed light is combined with the doubled frequency reflected light to form a third mixed light; the first two-way beam splitter 7 is arranged at the intersection of the third mixed light and the first first-doubled frequency transmitted light, and is used to transmit the first first-doubled frequency transmitted light to the polarizer 8, and reflect the third mixed light to the polarizer 8 at the same time; the polarizer 8 is arranged on the reflection side optical path of the first two-way beam splitter 7, and is used to receive the mixed light of the first first-doubled frequency transmitted light and the third mixed light, and change its polarization state to form a linearly polarized three-frequency combined laser in the I0 direction.

[0089] The interference module 20 includes a second beam splitter 9, a reference mirror 10, a first quarter wave plate 11, a second quarter wave plate 13, a grating 14 and a polarizer array 15; the grating 14 is an orthogonal grating.

[0090] The second beam splitter 9 corresponds to the output end of the three-frequency generating module 19; the reference mirror 10 and the second beam splitter 9 are sequentially arranged on the transmission side optical path of the second beam splitter 9 in the direction away from the second beam splitter 9; the side of the first quarter wave plate 11 away from the reference mirror 10 is used to set the test mirror 12; the second quarter wave plate 13, the grating 14 and the polarizer array 15 are sequentially arranged on the reflection side optical path of the second beam splitter 9 in the direction away from the second beam splitter 9; the fast axis direction of the first quarter wave plate 11 and the second quarter wave plate 13 is (I0+I1) / 2. The second beam splitter 9 is used to transmit the linearly polarized three-frequency combined beam laser in the I0 direction to the reference mirror 10, and then a part of it is reflected by the reference mirror 10, and the other part is transmitted by the reference mirror 10 and then rotated by the first quarter wave plate 11 to reach the mirror to be measured 12, and then reflected by the mirror to be measured 12, and then rotated again by the first quarter wave plate 11 to form the linearly polarized three-frequency combined beam laser in the I1 direction, and then transmitted by the reference mirror 10 and combined with the linearly polarized three-frequency combined beam laser in the I0 direction reflected by the reference mirror 10 to form I 01 Laser; I 01 The laser is reflected by the second beam splitter 9 to the second quarter wave plate 13, and then split into four beams of different phases by the grating 14. 01 Splitting, polarizing array 15 changes each beam I 01 The polarization states of the split light interfere with each other, so each beam I 01 The spectroscopic light includes first-harmonic interference light, second-harmonic interference light and fourth-harmonic interference light; the difference between the I1 direction and the I0 direction is 90°.

[0091] The signal receiving module 21 includes a second dichroic beam splitter 16, a third dichroic beam splitter 17, a first detector 25, a second detector 18 and a third detector 26; the first detector 25, the second detector 18 and the third detector 26 are all CCD detectors.

[0092] The second dichroic beam splitter 16 corresponds to the output end of the polarizer array 15, and is used to receive all the first-harmonic interference light, the second-harmonic interference light and the fourth-harmonic interference light, and transmit all the first-harmonic interference light to the first detector 25, and reflect all the second-harmonic interference light and the fourth-harmonic interference light to the third dichroic beam splitter 17; the third dichroic beam splitter 17 is used to transmit all the second-harmonic interference light to the second detector 18, and reflect all the fourth-harmonic interference light to the third detector 26; the first detector 25 is used to obtain the first-harmonic interference pattern of different phases; the second detector 18 is used to obtain the second-harmonic interference pattern of different phases; the third detector 26 is used to obtain the fourth-harmonic interference pattern of different phases.

[0093] The wavefront aberration detection is performed using the above-mentioned air refractive index self-correcting triple-frequency laser interferometer, which specifically includes the following steps:

[0094] Step 1, a frequency-doubled laser component emits a frequency-doubled reflected light and a first frequency-doubled transmitted light; the first second harmonic crystal 5 doubles the frequency of a part of the frequency-doubled reflected light to obtain a frequency-doubled reflected light; the first semiconductor amplifier 6 is used to power amplify another part of the frequency-doubled reflected light and the frequency-doubled reflected light; the third beam splitter 22 is used to reflect a part of the frequency-doubled reflected light after power amplification, and transmit a first mixed light formed by superposition of another part of the frequency-doubled reflected light and the frequency-doubled reflected light after power amplification; the second second harmonic crystal 23 doubles the frequency of a part of the first mixed light, and the remaining part of the first mixed light obtains a second mixed light including a second frequency-doubled transmitted light, a frequency-doubled transmitted light and a frequency-quadrupled transmitted light; the third mixed light is combined with the frequency-doubled reflected light to form a second mixed light; the first two-way beam splitter 7 transmits the first frequency-doubled transmitted light to the polarizer 8, and reflects the third mixed light to the polarizer 8 at the same time; the polarizer 8 changes the polarization state of the mixed light of the first frequency-doubled transmitted light and the third mixed light to form a linearly polarized three-frequency combined laser in the I0 direction.

[0095] Step 2, after the second beam splitter 9 transmits the linearly polarized three-frequency combined beam laser in the I0 direction to the reference mirror 10, a part of it is reflected by the reference mirror 10, and the other part is transmitted by the reference mirror 10 and then rotated by the first quarter wave plate 11 to reach the mirror to be measured 12, and then reflected by the mirror to be measured 12, and then rotated again by the first quarter wave plate 11 to form the linearly polarized three-frequency combined beam laser in the I1 direction, and then transmitted by the reference mirror 10 and combined with the linearly polarized three-frequency combined beam laser in the I0 direction reflected by the reference mirror 10 to form I 01 Laser; the second beam splitter 9 will I 01 The laser is reflected to the second quarter wave plate 13 and then divided into four beams of I with different phases by the grating 14. 01 Splitting, polarizing array 15 changes each beam I 01 The polarization states of the split light interfere with each other, so each beam I 01 The split light includes the first-harmonic interference light, the second-harmonic interference light and the fourth-harmonic interference light; the difference between the I1 direction and the I0 direction is 90°;

[0096] Step 3, the second dichroic beam splitter 16 receives all the first-harmonic interference light, the second-harmonic interference light and the fourth-harmonic interference light, and transmits all the first-harmonic interference light to the first detector 25, and reflects all the second-harmonic interference light and the fourth-harmonic interference light to the third dichroic beam splitter 17; the third dichroic beam splitter 17 transmits all the second-harmonic interference light to the second detector 18, and reflects all the fourth-harmonic interference light to the third detector 26; the first detector 25 is used to obtain the first-harmonic interference pattern of different phases to obtain the first detection information; the second detector 18 is used to obtain the second-harmonic interference pattern of different phases to obtain the second detection information; the third detector 26 is used to obtain the fourth-harmonic interference pattern of different phases to obtain the third detection information.

[0097] Step 4, respectively calculate the first optical path difference OPD1(x, y), the second optical path difference OPD2(x, y) and the third optical path difference OPD3(x, y) of the reference mirror 10 and the mirror to be measured 12 corresponding to the first detection information, the second detection information and the third detection information, where (x, y) is the plane coordinate in the direction perpendicular to the optical axis;

[0098] The physical distance from the reference mirror 10 to the measured mirror 12 is d1(x, y), and the physical distance corresponding to the measured wavefront aberration is d2(x, y); then:

[0099] OPD1(x,y)=n1(x,y).*d1(x,y)+n1(x,y).*d2(x,y);

[0100] OPD2(x,y)=n2(x,y).*d1(x,y)+n2(x,y).*d2(x,y);

[0101] OPD3(x,y)=n3(x,y).*d1(x,y)+n3(x,y).*d2(x,y);

[0102] Where: (x, y) is the plane coordinate perpendicular to the optical axis;

[0103] n1(x,y) is the refractive index of each point in space corresponding to the frequency-doubled laser;

[0104] n2(x,y) is the refractive index of each point in space corresponding to the frequency doubled laser;

[0105] n3(x,y) is the refractive index of each point in space corresponding to the quadruple frequency laser;

[0106] n1(x,y).*d2(x,y) is the measured wavefront aberration corresponding to the frequency-doubled laser;

[0107] n2(x,y).*d2(x,y) is the measured wavefront aberration corresponding to the double frequency laser;

[0108] n3(x,y).*d2(x,y) is the measured wavefront aberration corresponding to the quadruple frequency laser;

[0109] The empirical formula for air refractive index is: n-1 = a(λ)*D1(p,T,w)+b(λ)*p(w)*D2(p,T,w);

[0110] Where: n is the refractive index of air; a and b are coefficients that vary with wavelength λ;

[0111] D1(p,T,w) and D2(p,T,w) are coefficients that vary with pressure, temperature, and humidity;

[0112] p(w) is the coefficient that varies with humidity;

[0113] For triple-frequency laser,

[0114] n1(x,y)-1=a(λ1)*D1(p,T,w)+b(λ1)*p(w)*D2(p,T,w);

[0115] n2(x,y)-1=a(λ2)*D1(p,T,w)+b(λ2)*p(w)*D2(p,T,w);

[0116] n3(x,y)-1=a(λ3)*D1(p,T,w)+b(λ3)*p(w)*D2(p,T,w);

[0117] Step 5, obtaining the first correction factor A1 and the second correction factor A2 based on the method of steps 1-4; specifically comprising:

[0118] 5.1) Calculate the first theoretical correction factor A 1理 and the second theoretical correction factor A 2理 :

[0119] A 1理 =(a(λ1)*(b(λ1)-b(λ3))-b(λ1)*(a(λ1)-a(λ3)) / ((a(λ1)-a(λ2)*(b(λ1)-b(λ3))-

[0120] (b(λ1)-b(λ2))*(a(λ1)-a(λ3));

[0121] A 2理 =(-a(λ1)*(b(λ1)-b(λ2))+b(λ1)*((a(λ1)-a(λ2)) / ((a(λ1)-a(λ2))*(b(λ1)-b(λ3))-

[0122] (b(λ1)-b(λ2))*(a(λ1)-a(λ3));

[0123] Wherein, a and b are coefficients that vary with wavelength; λ1, λ2 and λ3 are the wavelengths of the first-harmonic laser, the second-harmonic laser and the fourth-harmonic laser, respectively;

[0124] 5.2) Based on the method of steps 1 to 4, the mirror to be measured (12) is measured N1 times, and the obtained N1 measurement data include N1 optical path difference values ​​OPD 1i The first optical path difference array contains N1 optical path difference values ​​OPD 2i The second optical path difference array contains N1 optical path difference values ​​OPD 3iThe third optical path difference array, i = 1, 2, ... N1, N1 ≥ 50;

[0125] 5.3) Set the value range of the first correction factor A1 to [A 1min ,A 1max ], so that A 1理 ∈[A 1min ,A 1max ], take N2 equally spaced values ​​within this range and represent them as array A1'=A 1min :(A 1max -A 1min ) / (N2-1):A 1max , j=1,2,…N2,N2≥50;

[0126] The value range of the second correction factor A2 is set to [A 2min ,A 2max ], so that A 2理 ∈[A 2min ,A 2max ], take N3 equally spaced values ​​within this range, represented by the array A2'=A 2min :(A 2max -A 2min ) / (N3-1):A 2max , k=1,2,…N3,N3≥50;

[0127] In this embodiment, A is preferred 1min =A 1理 -50, A 1max =A 1理 +50, A 2min =A 2理 -50, A 2max =A 2理 +50, its purpose is to ensure the first theoretical correction factor A 1理 and the second theoretical correction factor A 2理 , must be able to be in the value range [A 1min ,A 1max ] and [A 2min ,A 2max ] can be obtained.

[0128] 5.4) Set the N2 values ​​A in array A1' 1j and the N3 values ​​A in array A2' 2k Perform pairwise combinations to obtain N2×N3 combinations. Based on the N2×N3 combinations and the N1 measurement data in step 5.2, calculate the corrected equivalent distance d1(i, A 1j ,A 2k )+d2(i,A 1j ,A2k ):

[0129] d1(i,A 1j ,A 2k )+d2(i,A 1j ,A 2k )=OPD 1i -A 1j *(OPD 1i -OPD 2i )-A 2k *(OPD 1i -OPD 3i )

[0130] Obtain N1×N2×N3 corrected equivalent distances;

[0131] 5.5) Calculate N1×N2×N3 corrected equivalent distances by the formula rms(d1(i)-mean(d1(i))+d2(i)-mean(d2(i))) to obtain N2×N3 non-uniformity results;

[0132] That is, N1×N2×N3 corrected equivalent distances are input into the formula rms(d1(i)-mean(d1(i))+d2(i)-mean(d2(i))), and N2×N3 non-uniformity results are output.

[0133] 5.6) Obtain the minimum value among the N2×N3 non-uniformity results corresponding to the values ​​in the corresponding arrays A1' and A2', which are respectively denoted as A 1jmin and A 2kmin ;

[0134] 5.7) Expand A 1min The lower limit of the value is A 1jmin -(A 1max -A 1min ) / (N2-1), reduce A 1max The upper limit of the value is A 1jmin+ (A 1max -A 1min ) / (N2-1), that is, narrowing the value range of the first correction factor A1;

[0135] Expand A 2min The lower limit of the value is A 2kmin -(A 2max -A 2min ) / (N3-1), reduce A 2max The upper limit of the value is A 2kmin+ (A 2max -A 2min ) / (N3-1), that is, narrowing the value range of the second correction factor A2;

[0136] 5.8) Set the value range length A of the first correction factor A1 and the second correction factor A2 1max -A 1min and A 2max -A 2min Compared with the first preset threshold value A3 and the second preset threshold value A4 respectively:

[0137] If A 1max -A 1min >A3 and / or A 2max -A 2min >A4, then return to step 5.2, otherwise output the final values ​​of the first correction factor A1 and the second correction factor A2;

[0138] Where 0<A3<10 -4 ,0<A4<10 -4 .

[0139] Step 6, respectively calculate the wavefront aberration W1 of the mirror to be measured corresponding to the first-time frequency laser, the wavefront aberration W2 of the mirror to be measured corresponding to the second-time frequency laser, and the wavefront aberration W3 of the mirror to be measured corresponding to the fourth-time frequency laser through the first optical path difference OPD1(x, y), the second optical path difference OPD2(x, y), and the third optical path difference OPD3(x, y):

[0140] W1=d2(x,y). / (d1(x,y)+d2(x,y)).*OPD1(x,y);

[0141] W2=d2(x,y). / (d1(x,y)+d2(x,y)).*OPD2(x,y);

[0142] W3=d2(x,y). / (d1(x,y)+d2(x,y)).*OPD3(x,y);

[0143] from Figure 3 It can be seen that the wavefront aberration test error corrected by the theoretical correction factor is close to the 10^-6 order of magnitude of the wavelength, which meets the requirements for precise measurement of wavefront aberrations in large-aperture optical systems; however, if there is an offset between the actual value and the theoretical value of the wavelength of the single-frequency laser, double-frequency laser, and quadruple-frequency laser, or if the empirical refractive index formula used is not accurate enough, the theoretical correction factor will also have an error. At this time, the wavefront aberration test error will have a large offset, affecting the precise measurement of wavefront aberrations in large-aperture optical systems. Figure 4 As shown, the ratio of the wavefront aberration test error corrected by the correction factors A1 and A2 calculated by the method provided by the present invention to the wavelength. At this time, the order of magnitude of the wavefront aberration test error is on the order of 10^-5 of the wavelength, indicating the effectiveness of the method provided in this embodiment.

[0144] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. An air refractive index self-correcting triple-frequency laser interferometer, characterized in that: It comprises a three-frequency generating module (19), an interference module (20) and a signal receiving module (21); The triple-frequency generation module (19) is used to emit a triple-frequency combined laser beam with linear polarization in the I0 direction formed by combining a single-frequency laser beam, a double-frequency laser beam and a quadruple-frequency laser beam to the interference module (20); The interference module (20) comprises a second beam splitter (9), a reference mirror (10), a first quarter wave plate (11), a second quarter wave plate (13), a grating (14) and a polarizing plate array (15); the second beam splitter (9) corresponds to the output end of the three-frequency generating module (19); the reference mirror (10) and the second beam splitter (9) are sequentially arranged on the transmission side optical path of the second beam splitter (9) in a direction away from the second beam splitter (9); a side of the first quarter wave plate (11) away from the reference mirror (10) is used to arrange the test mirror (12); the second quarter wave plate (13), the grating (14) and the polarizing plate array (15) The optical paths of the reflection side of the second beam splitter (9) are sequentially arranged in a direction away from the second beam splitter (9); the second beam splitter (9) is used for transmitting the linearly polarized three-frequency combined beam laser in the I0 direction to the reference mirror (10), a part of which is reflected by the reference mirror (10), and another part of which is transmitted by the reference mirror (10) and then rotated by the first quarter wave plate (11) to reach the mirror to be measured (12), and then reflected by the mirror to be measured (12), and then rotated again by the first quarter wave plate (11) to form the linearly polarized three-frequency combined beam laser in the I1 direction, and then transmitted by the reference mirror (10) and combined with the linearly polarized three-frequency combined beam laser in the I0 direction reflected by the reference mirror (10) to form the I 01 Laser; I 01 The laser light is reflected by the second beam splitter (9) to the second quarter wave plate (13), and then is split into a plurality of beams of different phases by the grating (14). 01 Splitting, the polarizer array (15) changes the 01 The polarization states of the split light interfere with each other, so each beam I 01 The split light includes the first-harmonic interference light, the second-harmonic interference light and the fourth-harmonic interference light; the difference between the I1 direction and the I0 direction is 90°; The incident end of the signal receiving module (21) corresponds to the output end of the polarizing plate array (15), and is used to receive all the first-harmonic interference light, the second-harmonic interference light and the fourth-harmonic interference light, separate them spatially, and then detect them respectively to obtain first detection information, second detection information and third detection information.

2. The air refractive index self-correcting triple-frequency laser interferometer according to claim 1, characterized in that: The triple-frequency generation module (19) comprises a frequency-doubled laser component, a first second harmonic crystal (5), a first semiconductor amplifier (6), a first dichroic beam splitter (7), a polarizing plate (8), a third beam splitter (22), a second second harmonic crystal (23) and a second semiconductor amplifier (24); The one-time frequency laser assembly is used to emit one-time frequency reflected light and first one-time frequency transmitted light; The first second harmonic crystal (5), the first semiconductor amplifier (6) and the third beam splitter (22) are sequentially arranged on the optical path of the first-frequency reflected light along its emission direction; the first second harmonic crystal (5) is used to double the frequency of a portion of the first-frequency reflected light to obtain the second-frequency reflected light; the first semiconductor amplifier (6) is used to amplify the power of another portion of the first-frequency reflected light and the second-frequency reflected light; the third beam splitter (22) is used to reflect a portion of the second-frequency reflected light after power amplification, and transmit a first mixed light formed by superposition of another portion of the second-frequency reflected light and the first-frequency reflected light after power amplification; The second second harmonic crystal (23) and the second semiconductor amplifier (24) are sequentially arranged on the optical path of the first mixed light along the emission direction thereof; the second second harmonic crystal (23) is used to double the frequency of a portion of the first mixed light and to leave another portion of the first mixed light to obtain a second mixed light including a second first-time frequency transmission light, a second second-time frequency transmission light and a fourth-time frequency transmission light; the second mixed light is combined with the second second-time frequency reflected light to form a third mixed light; The first two-way beam splitter (7) is arranged at the intersection of the third mixed light and the first doubled frequency transmitted light, and is used to transmit the first doubled frequency transmitted light to the polarizer (8) and reflect the third mixed light to the polarizer (8); The polarizer (8) is arranged on the reflection side optical path of the first dichroic beam splitter (7) and is used to receive the mixed light of the first doubled frequency transmitted light and the third mixed light and change its polarization state to form a linearly polarized triple-frequency combined laser beam in the I0 direction.

3. The air refractive index self-correcting triple-frequency laser interferometer according to claim 2, characterized in that: The frequency-doubled laser assembly comprises a laser source (3) for emitting initial laser light, an optical frequency comb (2), an atomic clock (1) and a first beam splitter (4); The laser source (3) is phase-locked to the optical frequency comb (2); The optical frequency comb (2) is phase-locked to the atomic clock (1); The first beam splitter (4) is arranged on the optical path of the initial laser and is used for splitting the initial laser into a first-doubled frequency reflected light and a first first-doubled frequency transmitted light.

4. The air refractive index self-correcting triple-frequency laser interferometer according to claim 3, characterized in that: The signal receiving module (21) comprises a second dichroic beam splitter (16), a third dichroic beam splitter (17), a first detector (25), a second detector (18) and a third detector (26); The second dichroic beam splitter (16) corresponds to the output end of the polarizer array (15), and is used to receive all the first-frequency interference light, the second-frequency interference light, and the fourth-frequency interference light, and transmit all the first-frequency interference light to the first detector (25), and reflect all the second-frequency interference light and the fourth-frequency interference light to the third dichroic beam splitter (17); The third dichroic beam splitter (17) is used to transmit all the doubled frequency interference light to the second detector (18), and reflect all the quadruple frequency interference light to the third detector (26); The first detector (25) is used to obtain a frequency-doubled interference pattern with different phases; The second detector (18) is used to obtain frequency doubled interference patterns with different phases; The third detector (26) is used to obtain quadruple frequency interference patterns with different phases.

5. The air refractive index self-correcting triple-frequency laser interferometer according to claim 4, characterized in that: The first detector (25), the second detector (18) and the third detector (26) are all CCD detectors.

6. The air refractive index self-correcting triple-frequency laser interferometer according to any one of claims 3 to 5, characterized in that: The grating (14) is an orthogonal grating; The laser source (3) is a tunable narrow-band laser source; The fast axis directions of the first quarter wave plate (11) and the second quarter wave plate (13) are (I0+I1) / 2.

7. A wavefront aberration detection method, using the air refractive index self-correcting triple-frequency laser interferometer according to any one of claims 1 to 6, characterized in that: The following steps are involved: Step 1, the triple-frequency generating module (19) emits a triple-frequency combined laser beam linearly polarized in the I0 direction formed by combining a single-frequency laser beam, a double-frequency laser beam and a quadruple-frequency laser beam to the interference module (20); Step 2, after the second beam splitter (9) transmits the linearly polarized three-frequency combined laser beam in the I0 direction to the reference mirror (10), a part of the laser beam is reflected by the reference mirror (10), and the other part of the laser beam is transmitted by the reference mirror (10) and then rotated by the first quarter wave plate (11) to reach the mirror to be measured (12), and then reflected by the mirror to be measured (12), and then rotated again by the first quarter wave plate (11) to form the linearly polarized three-frequency combined laser beam in the I1 direction, and then transmitted by the reference mirror (10) and combined with the linearly polarized three-frequency combined laser beam in the I0 direction reflected by the reference mirror (10) to form I 01 The second beam splitter (9) 01 The laser is reflected to the second quarter wave plate (13), and then is divided into multiple beams of different phases by the grating (14). 01 Splitting, polarizer array (15) changes each beam I 01 The polarization states of the split light interfere with each other, so each beam I 01 The split light includes the first-harmonic interference light, the second-harmonic interference light and the fourth-harmonic interference light; the difference between the I1 direction and the I0 direction is 90°; Step 3, the signal receiving module (21) receives all the single-frequency interference light, the double-frequency interference light and the quadruple-frequency interference light, separates them spatially, and then detects them respectively, and obtains first detection information, second detection information and third detection information accordingly; Step 4, respectively calculating the first optical path difference OPD1(x, y), the second optical path difference OPD2(x, y) and the third optical path difference OPD3(x, y) of the reference mirror (10) and the mirror to be measured (12) corresponding to the first-harmonic interference light, the second-harmonic interference light and the fourth-harmonic interference light through the first detection information, the second detection information and the third detection information, where (x, y) is the plane coordinate in the direction perpendicular to the optical axis; Step 5, obtaining a first correction factor A1 and a second correction factor A2 based on the method of steps 1 to 4; Step 6, respectively calculate the wavefront aberration W1 of the mirror to be measured (12) corresponding to the first-time frequency laser, the wavefront aberration W2 of the mirror to be measured (12) corresponding to the second-time frequency laser, and the wavefront aberration W3 of the mirror to be measured (12) corresponding to the fourth-time frequency laser through the first optical path difference OPD1 (x, y), the second optical path difference OPD2 (x, y), and the third optical path difference OPD3 (x, y): W1=d2(x,y). / (d1(x,y)+d2(x,y)).*OPD1(x,y); W2=d2(x,y). / (d1(x,y)+d2(x,y)).*OPD2(x,y); W3=d2(x,y). / (d1(x,y)+d2(x,y)).*OPD3(x,y); in: d1(x, y) is twice the physical distance from the reference mirror (10) to the mirror to be measured (12), which is obtained through calibration; d2(x,y)=OPD1(x,y)-A1*(OPD1(x,y)-OPD2(x,y))-A2*(OPD1(x,y)-OPD3(x,y))- d1(x,y).

8. The wavefront aberration detection method according to claim 7, characterized in that: Step 5 specifically includes: 5.1) Calculate the first theoretical correction factor A 1理 and the second theoretical correction factor A 2理 : A 1理 =(a(λ1)*(b(λ1)-b(λ3))-b(λ1)*(a(λ1)-a(λ3)) / ((a(λ1)-a(λ2)*(b(λ1)-b(λ3))- (b(λ1)-b(λ2))*(a(λ1)-a(λ3)); A 2理 =(-a(λ1)*(b(λ1)-b(λ2))+b(λ1)*((a(λ1)-a(λ2)) / ((a(λ1)-a(λ2))*(b(λ1)-b(λ3))- (b(λ1)-b(λ2))*(a(λ1)-a(λ3)); Wherein, a and b are coefficients that vary with wavelength; λ1, λ2 and λ3 are the wavelengths of the first-harmonic laser, the second-harmonic laser and the fourth-harmonic laser, respectively; 5.2) Based on the method of steps 1 to 4, the mirror to be measured (12) is measured N1 times, and the obtained N1 measurement data include N1 optical path difference values ​​OPD 1i The first optical path difference array contains N1 optical path difference values ​​OPD 2i The second optical path difference array contains N1 optical path difference values ​​OPD 3i The third optical path difference array, i = 1, 2, ... N1, N1 ≥ 50; 5.3) Set the value range of the first correction factor A1 to [A 1min ,A 1max ], so that A 1理 ∈[A 1min ,A 1max ], take N2 equally spaced values ​​within this value range and represent them as array A1'=A 1min :(A 1max -A 1min ) / (N2-1):A 1max , then array A1' contains N2 values ​​A 1j , j=1,2,…N2,N2≥50; The value range of the second correction factor A2 is set to [A 2min ,A 2max ], so that A 2理 ∈[A 2min ,A 2max ], take N3 equally spaced values ​​within this range, represented by the array A2'=A 2min :(A 2max -A 2min ) / (N3-1):A 2max , then array A2' contains N3 values ​​A 2k , k=1,2,…N3,N3≥50; 5.4) Set the N2 values ​​A in array A1' 1j and the N3 values ​​A in array A2' 2k Perform pairwise combinations to obtain N2×N3 combinations. Based on the N2×N3 combinations and the N1 measurement data in step 5.2, calculate the corrected equivalent distance d1(i, A 1j ,A 2k )+d2(i,A 1j ,A 2k ): d1(i,A 1j ,A 2k )+d2(i,A 1j ,A 2k )=OPD 1i -A 1j *(OPD 1i -OPD 2i )-A 2k *(OPD 1i -OPD 3i ) Obtain N1×N2×N3 corrected equivalent distances; 5.5) Calculate N1×N2×N3 corrected equivalent distances by the formula rms(d1(i)-mean(d1(i))+d2(i)-mean(d2(i))) to obtain N2×N3 non-uniformity results; 5.6) Obtain the minimum value among the N2×N3 non-uniformity results corresponding to the values ​​in the corresponding arrays A1' and A2', which are denoted as A 1jmin and A 2kmin ; 5.7) Expand A 1min The lower limit of the value is A 1jmin -(A 1max -A 1min ) / (N2-1), reduce A 1max The upper limit of the value is A 1jmin+ (A 1max -A 1min ) / (N2-1); expand A 2min The lower limit of the value is A 2kmin -(A 2max -A 2min ) / (N3-1), reduce A 2max The upper limit of the value is A 2kmin+ (A 2max -A 2min ) / (N3-1); 5.8) Set the value range length A of the first correction factor A1 and the second correction factor A2 1max -A 1min and A 2max -A 2min Compared with the first preset threshold value A3 and the second preset threshold value A4 respectively: If A 1max -A 1min >A3 and / or A 2max -A 2min >A4, then return to step 5.2, otherwise output the final values ​​of the first correction factor A1 and the second correction factor A2; Where 0<A3<10 -4 ,0<A4<10 -4 .

9. The wavefront aberration detection method according to claim 8, characterized in that: Step 1 is as follows: The one-time frequency laser assembly emits one-time frequency reflected light and the first one-time frequency transmitted light; The first second harmonic crystal (5) doubles the frequency of a portion of the first-harmonic reflected light to obtain a second-harmonic reflected light; The first semiconductor amplifier (6) is used to amplify the power of the other part of the first-frequency reflected light and the second-frequency reflected light; The third beam splitter (22) is used for reflecting a part of the double frequency reflected light after power amplification, and transmitting a first mixed light formed by superposition of another part of the double frequency reflected light and the single frequency reflected light after power amplification; The second second harmonic crystal (23) doubles the frequency of a part of the first mixed light and leaves another part of the first mixed light to obtain a second mixed light including a second first-time frequency transmission light, a second second-time frequency transmission light and a fourth-time frequency transmission light; the third mixed light is combined with the second second-time frequency reflected light to form a second mixed light; The first two-way beam splitter (7) transmits the first doubled frequency transmitted light to the polarizer (8), and reflects the third mixed light to the polarizer (8); The polarizer (8) changes the polarization state of the mixed light of the first doubled frequency transmitted light and the third mixed light to form a linearly polarized triple-frequency combined laser beam in the I0 direction.

10. The wavefront aberration detection method according to claim 9, characterized in that: Step 4 is as follows: The second dichroic beam splitter (16) receives all the first-harmonic interference light, the second-harmonic interference light and the fourth-harmonic interference light, transmits all the first-harmonic interference light to the first detector (25), and reflects all the second-harmonic interference light and the fourth-harmonic interference light to the third dichroic beam splitter (17); the third dichroic beam splitter (17) transmits all the second-harmonic interference light to the second detector (18), and reflects all the fourth-harmonic interference light to the third detector (26); the first detector (25) is used to obtain the first-harmonic interference pattern of different phases to obtain the first detection information; the second detector (18) is used to obtain the second-harmonic interference pattern of different phases to obtain the second detection information; the third detector (26) is used to obtain the fourth-harmonic interference pattern of different phases to obtain the third detection information.

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