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

Abstract

The application discloses an air refractive index self-correcting 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.The air refractive index self-correcting three-frequency laser interferometer and the interference detection method thereof can measure the optical path difference between each spatial position of a corresponding reference mirror and a to-be-detected mirror by using a frequency-doubled laser, a two-frequency-doubled laser and a four-frequency-doubled laser, can construct a correction factor determined by only the frequency-doubled laser, the two-frequency-doubled laser and the four-frequency-doubled wavelength, and can further obtain the wavefront aberration of each spatial position of the to-be-detected mirror, so that the wavefront detection of the large-aperture optical system with the air refractive index self-correcting function is realized, the detection time is short, the cost is low, the operation is simple, and the detection precision is high.

Description

TECHNICAL FIELD

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

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

[0003] In an ideal state, the refractive index is only related to the wavelength and is independent of the spatial position; therefore, the refractive index is a constant value, which can be obtained by calibration, and the physical distance of the measurement path can also be obtained by calibration, so that the optical path difference obtained by the interferometer can directly reflect the wavefront aberration of the measured mirror.

[0004] However, in actual situations, especially in large-aperture optical systems, the mirror aperture of the measured mirror is large, the measurement path is long, and the refractive index is no longer a constant value and changes constantly, so that the refractive index is also related to the spatial environment in the large-aperture optical system, resulting in that the wavefront aberration detection of the large-aperture optical system becomes a major problem to be solved in optical detection.

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

[0006] 1) By using a fan array to accelerate air circulation to make the air more uniform, and then using a multiple measurement averaging method to obtain the wavefront aberration, this method is time-consuming and can only be implemented under good environmental control, and the test precision is low and cannot accurately reflect the measured wavefront aberration.

[0007] 2) The measured optical system is placed in a vacuum tank (low pressure tank) to completely eliminate the influence of the change of air refractive index, but this method is costly, the operation process is complex, and it is difficult to debug.

[0008] 3) A dual-frequency laser is used to detect the wavefront aberration, and only the dryness of the test environment air needs to be ensured, so that the air refractive index can be self-corrected, and in the case of not too high cost (compared with the vacuum tank and the low pressure tank), the high efficiency and high precision wavefront aberration detection of the large-aperture optical system can be realized. However, the dryness of the test environment air is still a big limitation, and the air that is not dry enough will still cause a large offset to the wavefront detection of the large-aperture optical system. When the air humidity is 10%, the ratio of the wavefront aberration test error to the wavelength after correction by the dual-frequency laser is as shown in the following table, and the correction will bring a large offset error. Figure 1 SUMMARY ​

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

[0010] In order to achieve the above-mentioned purpose, the application adopts the following technical scheme:

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

[0012] The three-frequency generating module, the interference module and the signal receiving module are included.

[0013] The three-frequency generating module is used for emitting I0 direction linear polarization three-frequency combined laser formed by one frequency laser, two frequency laser and four frequency laser 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 emission end of the three-frequency generating module, the reference mirror and the second beam splitter are sequentially arranged on the transmission side light path of the second beam splitter in the direction away from the second beam splitter; the first quarter wave plate is used for arranging a to-be-detected mirror on the side away from the reference mirror; the second quarter wave plate, the grating and the polarizer array are sequentially arranged on the reflection side light path of the second beam splitter in the direction away from the second beam splitter; the second beam splitter is used for transmitting the I0 direction linear polarization three-frequency combined laser to the reference mirror, a part of which is reflected by the reference mirror, and another part of which is transmitted by the reference mirror and then rotates by the first quarter wave plate to reach the to-be-detected mirror, and then is reflected by the to-be-detected mirror, and then rotates again by the first quarter wave plate to form I1 direction linear polarization three-frequency combined laser, and then is transmitted by the reference mirror and combined with the I0 direction linear polarization three-frequency combined laser reflected by the reference mirror to form I2 direction linear polarization three-frequency combined laser, and then is reflected by the second beam splitter to the second quarter wave plate, and then is divided into a plurality of beams of I2 direction linear polarization three-frequency combined laser with different phases by the grating, and then the polarizer array changes the polarization state of each beam of I2 direction linear polarization three-frequency combined laser, and then each beam of I2 direction linear polarization three-frequency combined laser interferes respectively. 01 laser; I 01 laser is reflected by the second beam splitter to the second quarter wave plate, and then is divided into a plurality of beams of I 01 laser with different phases by the grating, and then the polarizer array changes the polarization state of each beam of I 01 laser, and then each beam of I 01 laser interferes respectively, each beam of I

[0015] The incident end of the signal receiving module corresponds to the emission end of the polarizer array, is used for receiving all one frequency interference light, two frequency interference light and four frequency interference light, and then spatially separates them, and then respectively detects them to obtain first detection information, second detection information and third detection information.

[0016] Furthermore, 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 single-frequency laser assembly is used to emit single-frequency reflected light and first single-frequency transmitted light;

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

[0019] The second second harmonic crystal and the second semiconductor amplifier are sequentially arranged along the emission direction thereof on the optical path of the first mixed light; the second second harmonic crystal is used to double the frequency of a portion of the first mixed light and leave another portion of the first mixed light to obtain a second mixed light including a second first-harmonic frequency transmitted light, a second-harmonic frequency transmitted light, and a fourth-harmonic frequency transmitted light; the second mixed light is combined with the second-harmonic frequency 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 light 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 in the I0 direction.

[0022] Furthermore, 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 to split the initial laser into a first-harmonic frequency reflected light and a first first-harmonic frequency transmitted light.

[0026] Furthermore, 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 beam splitter corresponds to the exit end of the polarizer array, and is used for receiving all the first-order frequency interference light, second-order frequency interference light and fourth-order frequency interference light, and transmitting all the first-order frequency interference light to the first detector, and reflecting all the second-order frequency interference light and fourth-order frequency interference light to the third beam splitter;

[0028] The third beam splitter is used for transmitting all the second-order frequency interference light to the second detector, and reflecting all the fourth-order frequency interference light to the third detector;

[0029] The first detector is used for acquiring first-order frequency interference graphs of different phases;

[0030] The second detector is used for acquiring second-order frequency interference graphs of different phases;

[0031] The third detector is used for acquiring fourth-order frequency interference graphs of different phases.

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

[0033] Further, the grating is a cross grating;

[0034] The laser source is a tunable narrowband laser source;

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

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

[0037] Step 1, the three-frequency generation module emits I0 direction linearly polarized three-frequency combined laser formed by first-order frequency laser, second-order frequency laser and fourth-order frequency laser to the interference module;

[0038] Step 2, the second beam splitter transmits the I0 direction linearly polarized three-frequency combined laser to the reference mirror, part of which is reflected by the reference mirror, and the other part is transmitted by the reference mirror and then reaches the to-be-detected mirror after being rotated by the first quarter wave plate, and then is reflected by the to-be-detected mirror, and then is rotated again by the first quarter wave plate to form I1 direction linearly polarized three-frequency combined laser, and then is transmitted by the reference mirror and combined with the I0 direction linearly polarized three-frequency combined laser reflected by the reference mirror to form I 01 laser; the second beam splitter reflects I 01 laser to the second quarter wave plate, and then divides it into multiple beams of I 01 light of different phases by the grating; 01 After the polarizer array changes the polarization state of each beam of I 01The spectrometer includes one frequency doubling interference light, two frequency doubling interference light and four frequency doubling interference light; the difference between the I1 direction and the I0 direction is 90°;

[0039] Step 3, the signal receiving module receives all the one frequency doubling interference light, two frequency doubling interference light and four frequency doubling interference light, and separates them in space, and then detects them respectively, and corresponding first detection information, second detection information and third detection information are obtained;

[0040] Step 4, 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 one frequency doubling interference light, the two frequency doubling interference light and the four frequency doubling interference light corresponding to the reference mirror and the mirror to be measured are calculated respectively through the first detection information, the second detection information and the third detection information, (x, y) being the plane coordinates in the direction perpendicular to the optical axis;

[0041] Step 5, the first correction factor A1 and the second correction factor A2 are obtained based on the method of steps 1-4;

[0042] Step 6, the mirror wavefront aberration W1 corresponding to the one frequency doubling laser, the mirror wavefront aberration W2 corresponding to the two frequency doubling laser and the mirror wavefront aberration W3 corresponding to the four frequency doubling laser are calculated 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] Wherein:

[0047] d1(x, y) is twice the physical distance from the reference mirror to the mirror to be measured, which is obtained by 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] Further, step 5 specifically includes:

[0050] 5.1) calculating a first theoretical correction factor A 1理 and a 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 varying with wavelength; λ1, λ2 and λ3 are 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-step 4, the N1 times of measurement of the mirror to be measured, the N1 times of measurement data obtained include the first optical path difference array containing N1 optical path difference values OPD 1i , the second optical path difference array containing N1 optical path difference values OPD 2i and the third optical path difference array containing N1 optical path difference values OPD 3i , i=1, 2, …N1, N1≥50;

[0055] 5.3), set the value range of the first correction factor A1 as [A 1min ,A 1max ], so that A 1理 ∈[A 1min ,A 1max ], take N2 equally spaced values in the value range, represented as the array A1'=A 1min :(A 1max -A 1min ) / (N2-1):A 1max , then the array A1' contains N2 values A 1j , j=1, 2, …N2, N2≥50;

[0056] Set the value range of the second correction factor A2 as [A 2min ,A 2max ], so that A 2理 ∈[A 2min ,A 2max ], take N3 equally spaced values in the value range, represented as the array A2'=A 2min :(A 2max -A 2min) / (N3-1):A 2max , then the array A2' contains N3 values A 2k , k = 1, 2, … N3, N3≥50;

[0057] 5.4), combine each value A 1j in the array A1' with each value A 2k in the array A2' to get N2 x N3 combinations, based on the N2 x 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 ) N1 times:

[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] get N1 x N2 x N3 corrected equivalent distances;

[0060] 5.5), calculate the N1 x N2 x N3 corrected equivalent distances by the formula rms(d1(i)-mean(d1(i))+d2(i)-mean(d2(i))) to get N2 x N3 non-uniformity results;

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

[0062] 5.7), expand the lower limit of the value of A 1min to A 1jmin -(A 1max -A 1min ) / (N2-1), and reduce the upper limit of the value of A 1max to A 1jmin+ (A 1max -A 1min ) / (N2-1); expand the lower limit of the value of A 2min to 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 Compare 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 single-frequency laser assembly emits single-frequency reflected light and first single-frequency transmitted light;

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

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

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

[0071] The second second harmonic crystal doubles the frequency of a portion of the first mixed light, and the remaining portion of the first mixed light is used to obtain a second mixed light including a second first-harmonic frequency transmitted light, a second second-harmonic frequency transmitted light, and a fourth-harmonic frequency transmitted light; the third mixed light is combined with the second second-harmonic frequency reflected light to form a second mixed light;

[0072] The first two-way beam splitter transmits the first doubled frequency transmitted 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] Further, step 4 is specifically:

[0075] The second beam splitter receives all the first frequency interference light, second frequency interference light and fourth frequency interference light, transmits all the first frequency interference light to the first detector, reflects all the second frequency interference light and fourth frequency interference light to the third beam splitter; the third beam splitter transmits all the second frequency interference light to the second detector, and reflects all the fourth frequency interference light to the third detector; the first detector is used for acquiring first frequency interference graphs of different phases to obtain first detection information; the second detector is used for acquiring second frequency interference graphs of different phases to obtain second detection information; and the third detector is used for acquiring fourth frequency interference graphs of different phases to obtain third detection information.

[0076] The beneficial effects of the present application are:

[0077] 1. The air refractive index self-correcting three-frequency laser interferometer and the interference detection method thereof can measure the optical path difference between the corresponding reference mirror and the to-be-measured mirror at each spatial position by measuring the first frequency laser, the second frequency laser and the fourth frequency laser, can construct a correction factor determined only by the first frequency laser, the second frequency laser and the fourth frequency wavelength, and can further obtain the wavefront aberration of each spatial position of the to-be-measured mirror, so as to realize the wavefront detection of the large-aperture optical system with air refractive index self-correction, and the detection time is short, the cost is low, the operation is simple, and the detection precision is high.

[0078] 2. The air refractive index self-correcting three-frequency laser interferometer and the interference detection method thereof can overcome the wavefront measurement error caused by the non-uniform air refractive index in the test system without accurately controlling the environmental state, which means that the high-efficiency and high-precision wavefront aberration detection of the large-aperture optical system can be realized in a harsh environment or a workshop environment, and the practicability and realizability are greatly increased. BRIEF DESCRIPTION OF DRAWINGS

[0079] Figure 1 is a wavefront aberration test error and wavelength ratio curve diagram of the present application in a 10% humidity environment, and a two-frequency correction is adopted;

[0080] Figure 2 is a structure schematic diagram of an air refractive index self-correcting three-frequency laser interferometer embodiment of the present application;

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

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

[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 following will clearly and completely describe the technical solutions of the present invention in conjunction with the accompanying drawings and embodiments. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0086] The 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 triple-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. It 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 light path of the initial laser, and is used for splitting the initial laser into a first one-fold frequency reflection light and a first one-fold frequency transmission light. The first second-harmonic crystal 5, the first semiconductor amplifier 6 and the third beam splitter 22 are sequentially arranged on the light path of the one-fold frequency reflection light along the emission direction thereof; the first second-harmonic crystal 5 is used for frequency doubling a part of the one-fold frequency reflection light to obtain a two-fold frequency reflection light; the first semiconductor amplifier 6 is used for power amplifying another part of the one-fold frequency reflection light and the two-fold frequency reflection light; the third beam splitter 22 is used for reflecting a part of the power-amplified two-fold frequency reflection light, and transmitting the first mixed light formed by superimposing another part of the power-amplified two-fold frequency reflection light and the one-fold frequency reflection light; the second second-harmonic crystal 23 and the second semiconductor amplifier 24 are sequentially arranged on the light path of the first mixed light along the emission direction thereof; the second second-harmonic crystal 23 is used for frequency doubling a part of the first mixed light to obtain a second mixed light including a second one-fold frequency transmission light, a two-fold frequency transmission light and a four-fold frequency transmission light; the second mixed light is combined with the two-fold frequency reflection 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 one-fold frequency transmission light, and is used for transmitting the first one-fold frequency transmission light to the polarizer 8, and reflecting the third mixed light to the polarizer 8; the polarizer 8 is arranged on the reflection side light path of the first two-way beam splitter 7, and is used for receiving the mixed light of the first one-fold frequency transmission light and the third mixed light, and changing the polarization state thereof to form the I0 direction linear polarization three-frequency combined laser.

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

[0090] The second beam splitter 9 corresponds to the exit end of the three-frequency generating module 19, and the reference mirror 10 and the second beam splitter 9 are sequentially arranged on the transmission side light path of the second beam splitter 9 in a direction away from the second beam splitter 9; the first quarter wave plate 11 is used for arranging the to-be-detected mirror 12 away from the side of the reference mirror 10; the second quarter wave plate 13, the grating 14 and the polarizer array 15 are sequentially arranged on the reflection side light path of the second beam splitter 9 in a direction away from the second beam splitter 9; the fast axis directions of the first quarter wave plate 11 and the second quarter wave plate 13 are (I0+I1) / 2. The second beam splitter 9 is used for transmitting the I0 direction linearly polarized three-frequency combined laser to the reference mirror 10, part of which is reflected by the reference mirror 10, and another part is transmitted by the reference mirror 10 and then rotates the light by the first quarter wave plate 11 to reach the to-be-detected mirror 12, and then is reflected by the to-be-detected mirror 12, and then rotates the light again by the first quarter wave plate 11 to form the I1 direction linearly polarized three-frequency combined laser, and then is transmitted by the reference mirror 10 to combine with the I0 direction linearly polarized three-frequency combined laser reflected by the reference mirror 10 to form the I 01 laser; I 01 The laser is reflected by the second beam splitter 9 to the second quarter wave plate 13, and then is divided into four beams of I 01 light of different phases by the grating 14; 01 After the polarizer array 15 changes the polarization state of each beam of I 01 light, each beam of I 01 light includes a frequency-doubled interference light, a two-fold frequency-doubled interference light and a four-fold frequency-doubled interference light; the difference between the I1 direction and the I0 direction is 90°.

[0091] The signal receiving module 21 includes a second two-way beam splitter 16, a third two-way 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 two-way beam splitter 16 corresponds to the exit end of the polarizer array 15, and is used for receiving all the frequency-doubled interference light, the two-fold frequency-doubled interference light and the four-fold frequency-doubled interference light, and transmitting all the frequency-doubled interference light to the first detector 25, and reflecting all the two-fold frequency-doubled interference light and the four-fold frequency-doubled interference light to the third two-way beam splitter 17; the third two-way beam splitter 17 is used for transmitting all the two-fold frequency-doubled interference light to the second detector 18, and reflecting all the four-fold frequency-doubled interference light to the third detector 26; the first detector 25 is used for acquiring frequency-doubled interference graphs of different phases; the second detector 18 is used for acquiring two-fold frequency-doubled interference graphs of different phases; and the third detector 26 is used for acquiring four-fold frequency-doubled interference graphs of different phases.

[0093] The wavefront aberration is detected by using the above-mentioned air refractive index self-correcting three-frequency laser interferometer, and 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 the other 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 power-amplified frequency-doubled reflected light, and transmit a first mixed light formed by superimposing the other part of the power-amplified frequency-doubled reflected light and the frequency-doubled reflected light; 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 triple-frequency combined laser in the I0 direction.

[0095] Step 2: After the second beam splitter 9 transmits the linearly polarized triple-frequency combined laser beam in the I0 direction to the reference mirror 10, a portion of the laser beam is reflected by the reference mirror 10, and the other portion is transmitted by the reference mirror 10 and then rotated by the first quarter-wave plate 11 before reaching the test mirror 12. After being reflected by the test mirror 12, the laser beam is rotated again by the first quarter-wave plate 11 to form the linearly polarized triple-frequency combined laser beam in the I1 direction, which is then transmitted by the reference mirror 10 and combined with the linearly polarized triple-frequency combined laser beam in the I0 direction reflected by the reference mirror 10 to form the 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, polarizer array 15 changes each beam I 01 After the polarization states of the split light are separated, they interfere with each other. Then each beam I 01 The spectroscopic results include single-harmonic interference light, double-harmonic interference light and quadruple-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, 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 first probe information, the second probe information and the third probe information corresponding to the reference mirror 10 and the mirror to be measured 12 respectively, (x, y) being the plane coordinates perpendicular to the optical axis direction;

[0098] Let the physical distance of the reference mirror 10 to the mirror to be measured 12 be d1(x, y), and the physical distance corresponding to the measured wavefront aberration be 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] Wherein: (x, y) is the plane coordinate perpendicular to the optical axis direction;

[0103] n1(x, y) is the refractive index of each point position corresponding to the first harmonic laser;

[0104] n2(x, y) is the refractive index of each point position corresponding to the second harmonic laser;

[0105] n3(x, y) is the refractive index of each point position corresponding to the fourth harmonic laser;

[0106] n1(x, y) * d2(x, y) is the measured wavefront aberration corresponding to the first harmonic laser;

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

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

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

[0110] Wherein: n is the air refractive index; a and b are coefficients varying with wavelength λ;

[0111] D1(p, T, w) and D2(p, T, w) are coefficients varying with pressure, temperature and humidity.

[0112] p(w) is a coefficient varying with humidity;

[0113] For three-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) calculating 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 varying with wavelength; λ1, λ2 and λ3 are the wavelengths of the one-frequency laser, the two-frequency laser and the four-frequency laser, respectively;

[0124] 5.2), measuring the to-be-measured mirror (12) N1 times based on the method of steps 1-4, obtaining N1 measurement data including a first optical path difference array containing N1 optical path difference values OPD 1i , a second optical path difference array containing N1 optical path difference values OPD 2i and a third optical path difference array containing 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 value range and represent them as array A1'=A 1min :(A 1max -A 1min ) / (N2-1):A 1max , j=1,2,…N2,N2≥50;

[0126] Set the value range of the second correction factor A2 to [A 2min ,A 2max ], so that A 2理 ∈[A 2min ,A 2max ], take N3 equally spaced values ​​within this range, expressed as 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] get N1×N2×N3 corrected equivalent distances;

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

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

[0133] 5.6) Get the minimum value in N2×N3 non-uniformity results corresponding to the value in the corresponding array A1' and A2', respectively recorded as A 1jmin and A 2kmin ;

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

[0135] Expand the lower limit of A 2min 's value to A 2kmin -(A 2max -A 2min ) / (N3-1), and reduce the upper limit of A 2max 's value to A 2kmin+ (A 2max -A 2min ) / (N3-1), that is, reduce 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 Compare 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, calculate the wavefront aberration W1 of the mirror to be measured corresponding to the first-harmonic frequency laser, the wavefront aberration W2 of the mirror to be measured corresponding to the second-harmonic frequency laser, and the wavefront aberration W3 of the mirror to be measured corresponding to the fourth-harmonic 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):

[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 order of 10^-6 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 and theoretical values ​​of the wavelengths of the single-harmonic laser, double-harmonic laser, and quadruple-harmonic 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 in FIG, 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 merely provides the specific implementation of the present application, but the protection scope of the present application is not limited thereto, any change or replacement within the technical range disclosed by the present application should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. An air refractive index self-correcting three-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 three-frequency generating module (19) is used to emit I0 direction linearly polarized three-frequency combined laser formed by a frequency-doubled laser, a second-harmonic laser and a fourth-harmonic laser to the interference module (20); the incident end of the signal receiving module (21) corresponds to the exit end of the polarizer array (15), which is used to receive all the first-harmonic interference light, the second-harmonic interference light and the fourth-harmonic interference light, and then separate them in space, and then detect them respectively to obtain the first detection information, the second detection information and the third detection information.

2. The air refractive index self-correcting three-frequency laser interferometer according to claim 1, characterized in that: the three-frequency generating module (19) comprises a first-harmonic laser assembly, a first second-harmonic crystal (5), a first semiconductor amplifier (6), a first two-way beam splitter (7), a polarizer (8), a third beam splitter (22), a second second-harmonic crystal (23) and a second semiconductor amplifier (24); the first-harmonic laser assembly is used to emit first-harmonic reflected light and first-harmonic transmitted light; the first second-harmonic crystal (5), the first semiconductor amplifier (6) and the third beam splitter (22) are sequentially arranged on the light path of the first-harmonic reflected light along the exit direction; the first second-harmonic crystal (5) is used to double the frequency of a part of the first-harmonic reflected light to obtain second-harmonic reflected light; the first semiconductor amplifier (6) is used to amplify the power of another part of the first-harmonic reflected light and the second-harmonic reflected light; the third beam splitter (22) is used to reflect a part of the second-harmonic reflected light after power amplification, and transmit the first mixed light formed by the other part of the second-harmonic reflected light after power amplification and the first-harmonic reflected light; the second second-harmonic crystal (23) and the second semiconductor amplifier (24) are sequentially arranged on the light path of the first mixed light along the exit direction; the second second-harmonic crystal (23) is used to double the frequency of a part of the first mixed light, and the remaining part of the first mixed light, to obtain second mixed light including second-harmonic transmitted light, second-harmonic transmitted light and fourth-harmonic transmitted light; the second mixed light is combined with the second-harmonic reflected light to form third mixed light; 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 polarizer array (15); the second beam splitter (9) corresponds to the output end of the triple-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 a mirror to be measured (12); the second quarter wave plate (13), the grating (14) and the polarizer 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 to transmit the I0 direction linearly polarized three-frequency combined beam laser to the reference mirror (10), a part of which 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 I1 direction linearly polarized three-frequency combined beam laser, and then transmitted by the reference mirror (10) and combined with the I0 direction linearly polarized three-frequency combined beam laser reflected by the reference mirror (10) to form the I 01 Laser; I 01 The laser is reflected by the second beam splitter (9) to the second quarter wave plate (13), and then is split into multiple beams of different phases by the grating (14). 01 Splitting, polarizer array (15) changes each beam I 01 After the polarization states of the split light are separated, they interfere with each other. Then each beam I 01 The spectroscopic results include single-harmonic interference light, double-harmonic interference light and quadruple-harmonic interference light; the difference between the I1 direction and the I0 direction is 90°; the first two-way beam splitter (7) is arranged at the intersection of the third mixed light and the first-harmonic transmitted light, and is used to transmit the first-harmonic transmitted light to the polarizer (8), while reflecting the third mixed light to the polarizer (8); the polarizer (8) is arranged on the reflection side light path of the first two-way beam splitter (7), and is used to receive the mixed light of the first-harmonic transmitted light and the third mixed light, and change the polarization state to form I0 direction linearly polarized three-frequency combined laser.

3. The air refractive index self-correcting three-frequency laser interferometer according to claim 2, characterized in that: the first-harmonic laser assembly comprises a laser source (3) for emitting initial laser, 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 frequency-doubled reflected light and a first frequency-doubled transmitted light. 4.The air refractive index self-correcting three-frequency laser interferometer of claim 3, wherein: The signal receiving module (21) comprises a second two-way beam splitter (16), a third two-way beam splitter (17), a first detector (25), a second detector (18), and a third detector (26); The second two-way beam splitter (16) corresponds to the exit end of the polarizer array (15), and is used for receiving all the frequency-doubled interference light, the second-order frequency-doubled interference light, and the fourth-order frequency-doubled interference light, and transmitting all the frequency-doubled interference light to the first detector (25), and reflecting all the second-order frequency-doubled interference light and the fourth-order frequency-doubled interference light to the third two-way beam splitter (17); The third two-way beam splitter (17) is used for transmitting all the second-order frequency-doubled interference light to the second detector (18), and reflecting all the fourth-order frequency-doubled interference light to the third detector (26); The first detector (25) is used for acquiring frequency-doubled interference graphs of different phases; The second detector (18) is used for acquiring second-order frequency-doubled interference graphs of different phases; The third detector (26) is used for acquiring fourth-order frequency-doubled interference graphs of different phases. 5.The air refractive index self-correcting three-frequency laser interferometer of claim 4, wherein: The first detector (25), the second detector (18), and the third detector (26) are all CCD detectors. 6.The air refractive index self-correcting three-frequency laser interferometer of any one of claims 3-5, wherein: The grating (14) is a normal grating; The laser source (3) is a tunable narrowband laser source; The fast axis direction of the first quarter-wave plate (11) and the second quarter-wave plate (13) is (I0+I1) / 2.

7. A wavefront aberration detection method using the air refractive index self-correcting three-frequency laser interferometer according to any one of claims 1-6, characterized in that, The method comprises the following steps: Step 1: The three-frequency generation module (19) emits I0 direction linearly polarized three-frequency combined laser formed by frequency-doubled laser, second-order frequency-doubled laser, and fourth-order frequency-doubled laser to the interference module (20); Step 2: After the second beam splitter (9) transmits the I0 direction linearly polarized triple-frequency combined laser beam to the reference mirror (10), a portion is reflected by the reference mirror (10), and the other portion is transmitted by the reference mirror (10) and then rotated by the first quarter wave plate (11) to reach the test mirror (12), and then reflected by the test mirror (12), and then rotated again by the first quarter wave plate (11) to form the I1 direction linearly polarized triple-frequency combined laser beam, which is then transmitted by the reference mirror (10) and combined with the I0 direction linearly polarized triple-frequency combined laser beam reflected by the reference mirror (10) to form the I 01 Laser; the second beam splitter (9) I 01 The laser is reflected to the second quarter wave plate (13) and then divided into multiple beams of different phases by the grating (14). 01 Splitting, polarizer array (15) changes each beam I 01 After the polarization states of the split light are separated, they interfere with each other. Then each beam I 01 The spectroscopic results include single-harmonic interference light, double-harmonic interference light and quadruple-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 frequency-doubled interference light, the second-order frequency-doubled interference light, and the fourth-order frequency-doubled interference light, and separates them in space, and then respectively detects them, and correspondingly obtains first detection information, second detection information, and third detection information; Step 4: 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 corresponding reference mirror (10) and the to-be-measured mirror (12) of the frequency-doubled interference light, the second-order frequency-doubled interference light, and the fourth-order frequency-doubled interference light are respectively calculated through the first detection information, the second detection information, and the third detection information, wherein (x,y) is the plane coordinate of the vertical optical axis direction; Step 5: The first correction factor A1 and the second correction factor A2 are obtained based on the method of steps 1-4. Step 6, calculating the wavefront aberration W1 of the measured mirror (12) corresponding to the first-order frequency laser, the wavefront aberration W2 of the measured mirror (12) corresponding to the second-order frequency laser and the wavefront aberration W3 of the measured mirror (12) corresponding to the fourth-order 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) respectively: 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); Wherein: d1(x, y) is twice the physical distance from the reference mirror (10) to the measured mirror (12), which is obtained by 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, wherein, Step 5 specifically includes: 5.1) calculating a first theoretical correction factor A 1理 and a 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 varying with wavelength; λ1, λ2 and λ3 are the wavelengths of the first-order frequency laser, the second-order frequency laser and the fourth-order frequency laser respectively; 5.2) Measure the test mirror (12) N1 times based on the method of step 1-step 4, and the N1 measurement data obtained include a first optical path difference array containing N1 optical path difference values OPD 1i , a second optical path difference array containing N1 optical path difference values OPD 2i , and a third optical path difference array containing N1 optical path difference values OPD 3i , i = 1, 2, … N1, N1≥50; 5.3), set the value range of the first correction factor A1 to be [A 1min ,A 1max ], so that A 1理 ∈[A 1min ,A 1max ], and take N2 equally spaced values in the value range to represent an array A1' = A 1min :(A 1max -A 1min ) / (N2-1):A 1max , wherein the array A1' contains N2 values A 1j , j = 1, 2, … N2, and N2 ≥ 50; The value range of the second correction factor A2 is set as [A 2min ,A 2max ] and A 2理 ∈[A 2min ,A 2max ]. N3 equally spaced values are taken in the value range, which is represented as an array A2' = A 2min :(A 2max -A 2min ) / (N3-1):A 2max . The array A2' contains N3 values A 2k , k = 1, 2,..., N3, and 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 the 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) The minimum value in the N2xN3 non-uniformity results is obtained, which corresponds to the values in the respective arrays A1' and A2', denoted as A 1jmin and A 2kmin ; 5.7), expanding A 1min with a lower limit of A 1jmin -(A 1max -A 1min ) / (N2-1), reducing A 1max with an upper limit of A 1jmin+ (A 1max -A 1min ) / (N2-1); expanding A 2min with a lower limit of A 2kmin -(A 2max -A 2min ) / (N3-1), reducing A 2max with an upper limit of A 2kmin+ (A 2max -A 2min ) / (N3-1); 5.8), the length A of the range of values of the first correction factor A1 and of the second correction factor A2 1max -A 1min and A 2max -A 2min are compared with a first preset threshold A3 and a second preset threshold A4, respectively: If A 1max -A 1min > A3 and / or A 2max -A 2min > A4, then return to step 5.2, otherwise output the resulting 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, wherein, Step 1 specifically is: The first-order frequency laser assembly emits first-order frequency reflected light and first-order frequency transmitted light; The first second harmonic crystal (5) doubles the frequency of a part of the first-order frequency reflected light to obtain second-order frequency reflected light; The first semiconductor amplifier (6) is used for power amplification of another part of the first-order frequency reflected light and the second-order frequency reflected light; The third beam splitter (22) is used for reflecting a part of the power amplified second-order frequency reflected light, and transmitting another part of the power amplified second-order frequency reflected light and the first-order frequency reflected light superimposed to form the first mixed light; 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, to obtain the second mixed light including the second-order frequency transmitted light, the second-order frequency transmitted light and the fourth-order frequency transmitted light; The third mixed light is combined with the second-order frequency reflected light to form the second mixed light; The first second beam splitter (7) transmits the first-order 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-order frequency transmitted light and the third mixed light to form the I0 direction linearly polarized three-frequency combined laser.

10. The wavefront aberration detection method according to claim 9, wherein, Step 4 specifically is: The second beam splitter (16) receives all the first-order frequency interference light, second-order frequency interference light and fourth-order frequency interference light, transmits all the first-order frequency interference light to the first detector (25), and reflects all the second-order frequency interference light and fourth-order frequency interference light to the third beam splitter (17); the third beam splitter (17) transmits all the second-order frequency interference light to the second detector (18), and reflects all the fourth-order frequency interference light to the third detector (26); the first detector (25) is used for acquiring first-order frequency interference images of different phases to obtain first detection information; the second detector (18) is used for acquiring second-order frequency interference images of different phases to obtain second detection information; and the third detector (26) is used for acquiring fourth-order frequency interference images of different phases to obtain third detection information.

Images