A method for wavefront measurement and focal plane calibration of a collimator

Abstract

The present invention relates to a wavefront measurement and focal plane calibration method, and in particular to a collimator wavefront measurement and focal plane calibration method, which is used to solve the shortcomings of existing calibration methods, which are limited by principles and technical means, making it difficult to meet the calibration requirements of high-precision and large-caliber collimators in practical applications, and provide a collimator wavefront measurement and focal plane calibration method. The collimator wavefront measurement and focal plane calibration device includes a five-dimensional adjustment frame, a beam splitter prism, a plane reflector, a one-dimensional translation stage and a CCD camera. The present invention is based on phase recovery technology and can simultaneously realize collimator wavefront measurement and focal plane calibration.

Description

Technical Field

[0001] The invention relates to a wavefront measurement and focal plane calibration method, and in particular to a parallel light tube wavefront measurement and focal plane calibration method. Background Art

[0002] Collimators are key tools in optical instruments and photoelectric detection. They are mainly used to simulate point light sources at infinity or generate parallel light. They are an important part of optical metrology instruments and are widely used in various optical experiments and tests. In recent years, with the advancement of space technology, the manufacturing level of high-precision large-aperture optical components has been significantly improved, especially in the processing and manufacturing of large-aperture optical components. The development direction of these high-precision large-aperture optical components is larger aperture and higher precision, which is crucial for high-tech fields such as astronomical optics, space optics, detection and identification of ground-based space targets, and inertial confinement fusion. In these applications, the optical system develops in the direction of large aperture and long focal length, and its aperture and focal length far exceed the applicable range of conventional collimators. Therefore, in order to calibrate these optical instruments, large-aperture collimators have gradually become essential equipment for large optical laboratories. Large-aperture collimators can provide parallel beams with infinite targets and high output parallelism, which is crucial to ensure the imaging quality of optical systems.

[0003] Commonly used collimator calibration methods include the autocollimation interference method and the pentaprism method, as follows:

[0004] (1) Self-collimation interferometry: This method is easy to debug and has high detection accuracy. It can intuitively obtain the real-time image quality (wavefront information) of the collimator. However, when the root mean square value (RMS) is used as the criterion, it can only determine whether the graticule is on the focal plane, but cannot determine whether it is in front of or behind the focus, which brings uncertainty to the adjustment. In addition, the operating conditions of the interferometer are relatively harsh. When the collimator is misaligned by a large amount, it is impossible to obtain valuable interference fringes and data to guide adjustment.

[0005] (2) Pentaprism method: This method uses the lateral movement of the pentaprism to replace the lateral swing of the human eye. When a large-aperture collimator detects full-aperture light, the scanning process is complicated and time-consuming. More importantly, this method can only determine the relative position of the point light source and the focal plane, and cannot determine the misalignment of the graticule in other directions (wavefront information), which has obvious limitations.

[0006] The existence of these technical problems is mainly due to the limitations of the principles and technical means of existing calibration methods, which makes it difficult to meet the calibration requirements of high-precision, large-aperture collimators in practical applications. Therefore, developing a calibration method that can solve the above problems, ensure accurate calibration of the wavefront measurement and focal position of the collimator, and provide high-quality parallel beams, has become a technical problem that needs to be solved urgently in the current optical detection field. Summary of the invention

[0007] The purpose of the present invention is to solve the shortcomings of existing calibration methods, which are difficult to meet the calibration requirements of high-precision and large-aperture collimators in practical applications due to limitations in principles and technical means, and to provide a collimator wavefront measurement and focal plane calibration method.

[0008] In order to solve the deficiencies of the above-mentioned prior art, the present invention provides the following technical solutions:

[0009] A collimator wavefront measurement and focal plane calibration device, the collimator comprises a laser, an optical fiber point source and a lens arranged in sequence, the output end of the laser is connected to the input end of the optical fiber point source, and the collimator comprises a five-dimensional adjustment frame, a beam splitter prism, a plane reflector, a one-dimensional translation stage and a CCD camera;

[0010] The five-dimensional adjustment frame is used to set the optical fiber point source in the collimator to adjust the azimuth and elevation of the optical fiber point source;

[0011] The beam splitter prism is arranged on the optical path between the optical fiber point source and the lens in the collimator, and is used to transmit the light emitted by the optical fiber point source to the lens; the plane reflector is arranged on the optical path after the lens, and is used to reflect the outgoing light of the lens, and the light reflected by the plane reflector is transmitted back to the beam splitter prism, and then reflected by the beam splitter prism;

[0012] The CCD camera is used to be arranged on the reflection light path of the beam splitter prism, and the CCD camera is placed on the one-dimensional translation stage, and the one-dimensional translation stage is used to move the CCD camera along the light path direction to the preset n detection positions, so that the CCD camera collects the corresponding n detection light intensities; n≥2, and is a positive integer;

[0013] The distance between two adjacent detection positions along the optical path direction is Δz, Δz∈[1, 50], in mm.

[0014] At the same time, the present invention also provides a method for measuring the wavefront of a collimator and calibrating the focal plane, which is special in that it includes the following steps:

[0015] Step 1, constructing the collimator wavefront measurement and focal plane calibration device for the collimator;

[0016] Step 2: Place the CCD camera at the preset first detection position, turn on the laser of the collimator, and let the light emitted by the optical fiber point source pass through the beam splitter prism, transmit to the lens, emit the wavefront to be measured, and then reflect it from the plane reflector, and then transmit it back to the beam splitter prism, and then reflect it into the CCD camera to obtain the detection light intensity I at the first detection position. 1 (x 1 ,y 1 ); then, the CCD camera is controlled to move to the second to nth detection positions in sequence through a one-dimensional translation stage to obtain the detection light intensity corresponding to each detection position;

[0017] Step 3, measuring the wavefront to be measured of the collimator;

[0018] Step 3.1, define the light field to be measured after the lens, and set the number of iterations num = 0;

[0019] Step 3.2, according to the light field to be measured in step 3.1, the detection light field of the first detection position is calculated by diffraction; then, the reconstructed detection light field of the next detection position is calculated by decomposing and calculating the detection light field, replacing the amplitude, and reconstructing the detection light field, until it is transmitted to the nth detection position, and the reconstructed detection light field of the nth detection position is obtained;

[0020] The method of decomposing and calculating the detection light field, replacing the amplitude, and reconstructing the detection light field is specifically as follows: the amplitude and phase are obtained according to the detection light field at the jth detection position, the amplitude is replaced by the detection amplitude calculated by the detection light intensity at the jth detection position, and the phase is kept unchanged to obtain the reconstructed detection light field at the jth detection position; j∈[1, n];

[0021] Step 3.3, according to the reconstructed detection light field of the nth detection position in step 3.2, the detection light field of the n-1th detection position is calculated by reverse diffraction; then, according to the method of decomposing and calculating the detection light field, replacing the amplitude, and reconstructing the detection light field, the reconstructed detection light field of the previous detection position is calculated in sequence until it is transmitted to the light field to be measured, so as to obtain the reconstructed light field to be measured;

[0022] Step 3.4, determine whether the RMS between the light field to be measured in step 3.1 and the reconstructed light field to be measured obtained in step 3.3 is less than or equal to a preset threshold. If so, execute step 3.5; otherwise, set the number of iterations num=num+1, replace the light field to be measured in step 3.1 with the reconstructed light field to be measured in step 3.3, and return to step 3.2;

[0023] The RMS is as follows:

[0024]

[0025] Among them, O(x 0 ,y 0) is the light field to be measured in step 3.1, O′(x 0 ,y 0 ) is the reconstructed light field to be measured described in step 3.3, (x 0 ,y 0 ) is the coordinate of the intersection of the lens optical axis and the rear surface of the lens;

[0026] Step 3.5, according to the reconstructed measured light field obtained in step 3.3, the measured light field is obtained by using the argument calculation operator, and then the measured wavefront of the parallel light tube is obtained;

[0027] Step 4. Decompose the measured wavefront of the parallel light tube obtained in step 3.5 into a linear combination of Zernike polynomials, and use the least squares method to solve the defocus coefficient q of the fourth defocus term of the Zernike polynomial; determine whether the defocus coefficient g is 0. If so, complete the calibration of the focal plane of the parallel light tube, otherwise adjust the axial distance of the optical fiber point source through the five-dimensional adjustment frame, and then return to step 2.

[0028] Furthermore, in step 3.1, the light field to be measured O(x 0 ,y 0 )=exp[iφ(x 0 ,y 0 )], where φ(x 0 ,y 0 ) is the phase corresponding to the light field to be measured, which is a set of constants or a set of random numbers.

[0029] Furthermore, the step 3.2 is specifically as follows:

[0030] Step 3.2.1, according to the light field to be measured O(x 0 ,y 0 ), calculate the detection light field U′ at the first detection position by diffraction 1 (x 1 ,y 1 ), according to the detection light field U′ at the first detection position 1 (x 1 ,y 1 ) to obtain the amplitude and phase, and use the detection light intensity I at the first detection position 1 (x 1 ,y 1 ) The detected amplitude calculated replaces the amplitude, keeping the phase unchanged, and obtains the reconstructed detected light field U′ at the first detection position. 1 (x 1 ,y 1 );(x 1 ,y 1 ) is the coordinate of the first detection position;

[0031] Step 3.2.2: Based on the detection light field U at the first detection position 1 (x 1 ,y 1 ), calculate the detection light field U of the second detection position by diffraction 2 (x 2 ,y 2 ), according to the detection light field U at the second detection position 2 (x 2 ,y 2 ) to obtain the amplitude and phase, and use the detection light intensity I at the second detection position 2 (x 2 ,y 2 ) The detected amplitude calculated replaces the amplitude, keeping the phase unchanged, and obtains the reconstructed detected light field U′ at the second detection position. 2 (x 2 ,y 2 );(x 2 ,y 2 ) are the coordinates of the second detection position;

[0032] Step 3.2.3: Based on the detection light field U at the second detection position 2 (x 2 ,y 2 ), calculate the detection light field of the next detection position by diffraction, and then obtain the amplitude and phase. According to the method of decomposing and calculating the detection light field, replacing the amplitude, and reconstructing the detection light field, the reconstructed detection light field of the next detection position is calculated in sequence until it is transmitted to the nth detection position, and the reconstructed detection light field U′ of the nth detection position is obtained. n (x n ,y n );(x n ,y n ) is the coordinate of the nth detection position.

[0033] Furthermore, in step 3.2.1, the detection light field U′ 1 (x 1 ,y 1 )as follows:

[0034] U 1 (x 1 ,y 1 )=ρ ABCD [O(x 0 ,y 0 )]

[0035] where ρ ABCD Calculated for the forward Collins diffraction;

[0036] The reconstructed detection light field U′ 1 (x 1,y 1 )as follows:

[0037]

[0038] in is the detection amplitude of the first detection position;

[0039] In step 3.2.2, the detection light field U 2 (x 2 ,y 2 )as follows:

[0040] U 2 (x 2 ,y 2 )=ρ AS [U′ 1 (x 1 ,y 1 )]

[0041] Among them, ρ AS Calculate the angular spectrum diffraction in the forward direction;

[0042] The reconstructed detection light field U′ 2 (x 2 ,y 2 )as follows:

[0043]

[0044] in is the detection amplitude of the second detection position.

[0045] Furthermore, the step 3.3 is specifically as follows:

[0046] Step 3.3.1: Calculate the reconstructed detection light field U′ at the nth detection position n (x n ,y n ) The detection light field U″ transmitted in reverse to the n-1th detection position n-1 (x n-1 ,y n-1 );According to the method of decomposing and calculating the detection light field, replacing the amplitude, and reconstructing the detection light field, the reconstructed detection light field of the previous detection position is calculated in sequence until it is transmitted to the first detection position to obtain the reconstructed detection light field U″ 1 (x 1 ,y 1 );(x n-1 ,y n-1 ) is the coordinate of the n-1th detection position;

[0047] Step 3.3.2: Calculate the detection light field U″ 1 (x 1 ,y1 ) is transmitted back to the light field to be measured, and the reconstructed light field to be measured is obtained by decomposing and calculating the detection light field, replacing the amplitude, and reconstructing the detection light field. 0 ,y 0 ).

[0048] Furthermore, in step 3.3.1, the detection light field U″ n-1 (x n-1 ,y n-1 )as follows:

[0049]

[0050] in Calculate the inverse angular spectrum of diffraction.

[0051] Furthermore, in step 3.4, the threshold is 10 -5 .

[0052] Furthermore, the step 3.5 is specifically as follows:

[0053] According to the reconstructed measured light field obtained in step 3.3, the phase φ(x 0 ,y 0 )=angle[O′(x 0 ,y 0 )], and then obtain the measured wavefront of the collimator

[0054] Further, in step 4.1, the measured wavefront of the collimator obtained in step 3.5 is decomposed into a linear combination of Zernike polynomials, and the defocus coefficient q of the fourth defocus term of the Zernike polynomials is solved by the least squares method, specifically:

[0055] The wavefront to be measured Decompose into Zernike polynomials Z k Linear combination of (x, y):

[0056]

[0057] Among them, Z k (x, y) is the kth Zernike polynomial, a k is the coefficient of the kth Zernike polynomial, and N is the order;

[0058] The defocus coefficient g of the fourth defocus term is as follows:

[0059] q=a k

[0060] By using the least squares method, the error between the wavefront data and the fitted wavefront is minimized to solve the defocus coefficient q;

[0061] Step 4.2, determine whether the defocus coefficient g is 0, if so, complete the calibration of the focal plane of the collimator;

[0062] Otherwise, according to the positive or negative value of the defocus coefficient g, it is determined whether the optical fiber point source is located before or after the focal plane. Specifically, if q>0, the optical fiber point source is located before the focal plane, and if q<0, the optical fiber point source is located after the focal plane.

[0063] Then adjust the axial distance of the optical fiber point source through the five-dimensional adjustment frame, and then return to step 2.

[0064] Compared with the prior art, the present invention has the following beneficial effects:

[0065] (1) The present invention discloses a collimator wavefront measurement and focal plane calibration device, comprising a five-dimensional adjustment frame, a beam splitter prism, a plane reflector, a one-dimensional translation stage and a CCD camera. The present invention is based on phase recovery technology and can simultaneously realize collimator wavefront measurement and focal plane calibration.

[0066] (2) Compared with the pentaprism method, the method for measuring the wavefront and calibrating the focal plane of a collimator of the present invention does not involve the complicated two-dimensional scanning process of the full aperture of the collimator, and is more advantageous for calibrating the focal plane of a large-aperture collimator, while being able to realize the measurement of the image quality (wavefront) of the collimator.

[0067] (3) Compared with the self-collimation interferometry method, the method of the present invention for measuring the wavefront of a parallel light tube and calibrating the focal plane can accurately locate the optical fiber point source in front of or behind the focal plane. In addition, it is not affected by ambient airflow disturbance and vibration. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Figure 1 It is a structural schematic diagram of an embodiment of a collimator wavefront measurement and focal plane calibration device of the present invention;

[0069] Figure 2 The present invention is a flow chart of a method for measuring the wavefront of a collimator and calibrating the focal plane.

[0070] The following are the descriptions of the reference numerals:

[0071] 01-Laser; 02-Fiber point source; 3-Five-dimensional adjustment frame; 4-Beam splitter prism; 05-Lens; 6-Plane mirror; 7-One-dimensional translation stage; 8-CCD camera; 9-Collimator; 10-Light field to be measured. DETAILED DESCRIPTION

[0072] The present invention is further described below in conjunction with the accompanying drawings and exemplary embodiments.

[0073] Reference Figure 1 A parallel light tube wavefront measurement and focal plane calibration device includes a five-dimensional adjustment frame 3, a beam splitter prism 4, a plane reflector 6, a one-dimensional translation stage 7, and a CCD camera 8.

[0074] The collimator 9 comprises a laser 01 , an optical fiber point source 02 , and a lens 05 which are arranged in sequence; the output end of the laser 01 is connected to the optical fiber point source 02 .

[0075] The beam splitter prism 4, the lens 05, the plane reflector 6 and the CCD camera 8 are sequentially arranged along the optical path;

[0076] The optical fiber point source 02 is placed on a five-dimensional adjustment frame 3 to adjust the azimuth and elevation of the optical fiber point source 02;

[0077] The CCD camera 8 is placed on a one-dimensional translation stage 7, which is used to move the CCD camera 8 to preset n detection positions (1, 2, ...j, ...n) along the optical path direction and collect corresponding n detection light intensities; n ≥ 2 and is a positive integer; the distance between two adjacent detection positions along the optical path direction is Δz, Δz∈[1, 50], and the unit is mm.

[0078] like Figure 2 As shown, a method for measuring the wavefront of a collimator and calibrating the focal plane comprises the following steps:

[0079] Step 1, constructing the collimator wavefront measurement and focal plane calibration device for the collimator 9;

[0080] Step 2: Place the CCD camera 8 at the preset first detection position, turn on the laser 01 of the collimator 9, and make the light emitted by the optical fiber point source 02 pass through the beam splitter prism 4, transmit to the lens 05, emit the wavefront to be measured, and then reflect through the plane reflector 6, transmit back to the beam splitter prism 4, reflect into the CCD camera 8, and obtain the detection light intensity I at the first detection position. 1 (x 1 ,y 1 ); then the CCD camera 8 is moved to the second to nth detection positions in sequence by the one-dimensional translation stage 7, and a total of n corresponding detection light intensities [I 1 (x 1 ,y 1 ), I 2 (x 2 ,y 2 ),......I j (x j ,y j ), ...I n (x n ,y n )];(xj ,y j ) is the coordinate of the jth detection position, j∈[1,n];

[0081] Step 3, calculating the wavefront to be measured of the collimator 9 by a phase recovery method;

[0082] Step 3.1, define the light field 10 to be measured after the lens 05 as O(x 0 ,y 0 )=exp[iφ(x 0 ,y 0 )], where φ(x 0 ,y 0 ) is the corresponding phase, which is a set of constants or a set of random numbers, (x 0 ,y 0 ) is the coordinate of the intersection of the optical axis of lens 05 and the rear surface of lens 05;

[0083] Then set the number of iterations num = 0;

[0084] Step 3.2: According to the light field 10O (x 0 ,y 0 ), calculate the detection light field of the first detection position by diffraction; then calculate the reconstructed detection light field of the next detection position in sequence according to the method of decomposing and calculating the detection light field, replacing the amplitude, and reconstructing the detection light field, until it is transmitted to the nth detection position, and the reconstructed detection light field of the nth detection position is obtained;

[0085] The method of decomposing and calculating the detection light field, replacing the amplitude, and reconstructing the detection light field is specifically as follows: the amplitude and phase are obtained according to the detection light field at the th detection position, the amplitude is replaced by the detection amplitude calculated by the detection light intensity at the th detection position, and the phase is kept unchanged to obtain the reconstructed detection light field at the th detection position;

[0086] Step 3.2.1, according to the light field to be measured 10O(x 0 ,y 0 ), calculate the detection light field U of the first detection position by diffraction 1 (x 1 ,y 1 ), according to the detection light field U at the first detection position 1 (x 1 ,y 1 ) to obtain the amplitude and phase, and use the detection light intensity I at the first detection position 1 (x 1 ,y 1 ) The detected amplitude calculated replaces the amplitude, keeping the phase unchanged, and obtains the reconstructed detected light field U′ at the first detection position. 1 (x 1 ,y1 );

[0087] U 1 (x 1 ,y 1 )=ρ ABCD [O(x 0 ,y 0 )]

[0088] where ρ ABCD Calculated for the forward Collins diffraction;

[0089]

[0090] in is the detection amplitude of the first detection position;

[0091] Step 3.2.2: Based on the detection light field U at the first detection position 1 (x 1 ,y 1 ), calculate the detection light field U of the second detection position by diffraction 2 (x 2 ,y 2 ), according to the detection light field U at the second detection position 2 (x 2 ,y 2 ) to obtain the amplitude and phase, and use the detection light intensity I at the second detection position 2 (x 2 ,y 2 ) The detected amplitude calculated replaces the amplitude, keeping the phase unchanged, and obtains the reconstructed detected light field U′ at the second detection position. 2 (x 2 ,y 2 );

[0092] U 2 (x 2 ,y 2 )=ρ AS [U′ 1 (x 1 ,y 1 )]

[0093] Among them, ρ AS Calculate the angular spectrum diffraction in the forward direction;

[0094]

[0095] in is the detection amplitude of the second detection position;

[0096] Step 3.2.3: Based on the detection light field U at the second detection position 2 (x2 ,y 2 ), calculate the detection light field of the next detection position by diffraction, and then obtain the amplitude and phase, repeatedly replace the amplitude with the detection amplitude calculated by the detection light intensity of the next detection position, keep the phase unchanged, until it is transmitted to the nth detection position, and obtain the reconstructed detection light field U′ of the nth detection position n (x n ,y n );

[0097] Step 3.3, according to the reconstructed detection light field of the nth detection position in step 3.2, the detection light field of the n-1th detection position is calculated by reverse diffraction; then, according to the method of decomposing and calculating the detection light field, replacing the amplitude, and reconstructing the detection light field, the reconstructed detection light field of the previous detection position is calculated in sequence until it is transmitted to the light field to be measured 10, and the reconstructed light field to be measured is obtained;

[0098] Step 3.3.1: Calculate the reconstructed detection light field U′ at the nth detection position n (x n ,y n ) The detection light field U″ transmitted in reverse to the n-1th detection position n-1 (x n-1 ,y n-1 );According to the method of decomposing and calculating the detection light field, replacing the amplitude, and reconstructing the detection light field, the reconstructed detection light field of the previous detection position is calculated in sequence until it is transmitted to the first detection position to obtain the reconstructed detection light field U″ 1 (x 1 ,y 1 ), at this time a cycle is completed;

[0099]

[0100] in is the inverse angular spectrum diffraction calculation, (x n-1 ,y n-1 ) is the coordinate of the n-1th detection position;

[0101] Step 3.3.2: Calculate the detection light field U″ 1 (x 1 ,y 1 ) is transmitted back to the measured light field 10 of the parallel light tube 9, and the reconstructed measured light field O′(x 0 ,y 0 );

[0102] Step 3.4: Determine whether the residual RMS between the light field to be measured 10 in step 3.1 and the light field to be measured reconstructed in step 3.3 is less than or equal to a preset threshold value 10. -5 ,as follows:

[0103]

[0104] If yes, execute step 3.5; otherwise, set the number of iterations num = num + 1, O(x 0 ,y 0 )=O′(x 0 ,y 0 ), return to step 3.2;

[0105] Step 3.5: Reconstruct the light field O′(x 0 ,y 0 ), and use the angle calculation operator angle to obtain the phase φ(x 0 ,y 0 )=angle[O′(x 0 ,y 0 )]; Due to the two reflections, the measured wavefront of the parallel light tube 9 is obtained

[0106] Step 4: Calibration of the focal plane of the collimator 9, specifically:

[0107] Step 4.1: The wavefront to be measured of the parallel light tube 9 obtained in step 3.5 Decompose it into a linear combination of Zernike polynomials, and use the least squares method to solve the defocus coefficient q of the fourth defocus term of the Zernike polynomial, which is specifically:

[0108] The wavefront to be measured Decompose into Zernike polynomials Z k Linear combination of (x, y):

[0109]

[0110] Among them, Z k (x, y) is the kth Zernike polynomial, a k is the coefficient of the kth Zernike polynomial, and N is the order;

[0111] The defocus coefficient q of the fourth defocus term is as follows:

[0112] q=a k

[0113] By using the least squares method, the error between the wavefront data and the fitted wavefront is minimized to solve the defocus coefficient q;

[0114] Step 4.2, determine whether the defocus coefficient q is 0, if so, complete the calibration of the focal plane of the collimator 9;

[0115] Otherwise, according to the positive or negative value of the defocus coefficient g, it is determined whether the optical fiber point source 02 is located before or after the focal plane. Specifically, if q>0, the optical fiber point source 02 is located before the focal plane; if q<0, the optical fiber point source 02 is located after the focal plane.

[0116] Then adjust the axial distance of the optical fiber point source 02 through the five-dimensional adjustment frame 3, and then return to step 2.

Claims

1. A method for measuring the wavefront of a collimator and calibrating the focal plane, the method being used for measuring the wavefront of a collimator and calibrating the focal plane, the collimator comprising a laser (01), an optical fiber point source (02) and a lens (05) arranged in sequence, the output end of the laser (01) being connected to the input end of the optical fiber point source (02); Features: A collimator wavefront measurement and focal plane calibration device is used, the collimator wavefront measurement and focal plane calibration device comprising a five-dimensional adjustment frame (3), a beam splitter prism (4), a plane reflector (6), a one-dimensional translation stage (7), and a CCD camera (8); The five-dimensional adjustment frame (3) is used to set the optical fiber point source (02) in the collimator (9) to achieve the adjustment of the azimuth and elevation of the optical fiber point source (02); The beam splitter prism (4) is arranged on the optical path between the optical fiber point source (02) and the lens (05) in the collimator (9) and is used to transmit the light emitted by the optical fiber point source (02) to the lens (05); the plane reflector (6) is arranged on the optical path after the lens (05) to reflect the light emitted by the lens (05); the light reflected by the plane reflector (6) is transmitted back to the beam splitter prism (4) and then reflected by the beam splitter prism (4); The CCD camera (8) is arranged on the reflection light path of the beam splitter prism (4), and the CCD camera (8) is placed on a one-dimensional translation stage (7). The one-dimensional translation stage (7) is used to move the CCD camera (8) along the light path direction to a preset detection positions so that the CCD camera (8) can collect the corresponding The detection light intensity; ≥2, and is a positive integer; The distance between two adjacent detection positions along the optical path is Δz, Δz∈[1,50], in mm; The steps include: Step 1, constructing the collimator wavefront measurement and focal plane calibration device for the collimator (9); Step 2: Place the CCD camera (8) at the preset first detection position, turn on the laser (01) of the collimator (9), and allow the light emitted by the optical fiber point source (02) to pass through the beam splitter prism (4), be transmitted to the lens (05), emit the wavefront to be measured, and then be reflected by the plane reflector (6), and then be transmitted back to the beam splitter prism (4), and then be reflected by the beam splitter prism (4) and enter the CCD camera (8), so as to obtain the detection light intensity at the first detection position. Then, the CCD camera (8) is controlled by the one-dimensional translation stage (7) to move to the first detection positions, and obtaining the detection light intensity corresponding to each detection position; Step 3, measuring the wavefront to be measured of the collimator (9); Step 3.1, define the light field to be measured (10) after the lens (05), and set the number of iterations ; Step 3.2, according to the light field to be measured (10) in step 3.1, the detection light field of the first detection position is calculated by diffraction; then, the reconstructed detection light field of the next detection position is calculated by decomposing and calculating the detection light field, replacing the amplitude, and reconstructing the detection light field, until it is transmitted to the first detection position. At the detection position, the Reconstructed detection light field at detection positions; The method of decomposing and calculating the detection light field, replacing the amplitude, and reconstructing the detection light field is specifically as follows: The amplitude and phase of the detection light field at the detection position are obtained, and the The detection amplitude calculated from the detection light intensity at the detection position replaces the amplitude, keeping the phase unchanged, and obtains the Reconstructed detection light field at detection positions; ; Step 3.3: According to step 3.2 The reconstructed detection light field at the detection position is calculated by inverse diffraction. The detection light field of the detection position is obtained; then, the reconstructed detection light field of the previous detection position is calculated in sequence according to the method of decomposing and calculating the detection light field, replacing the amplitude, and reconstructing the detection light field, until it is transmitted to the light field to be measured (10), and the reconstructed light field to be measured is obtained; Step 3.4, determine whether the RMS between the measured light field (10) in step 3.1 and the reconstructed measured light field obtained in step 3.3 is less than or equal to a preset threshold value. If so, execute step 3.5; otherwise, set the number of iterations to , after replacing the light field to be measured (10) in step 3.1 with the reconstructed light field to be measured in step 3.3, return to step 3.2; The RMS is as follows: in, is the light field to be measured (10) described in step 3.1, Reconstruct the light field to be measured as described in step 3.3, is the coordinate of the intersection of the optical axis of lens (05) and the rear surface of lens (05); Step 3.5, according to the reconstructed light field to be measured obtained in step 3.3, the light field to be measured (10) is obtained by using the argument calculation operator, and then the wavefront to be measured of the collimator (9) is obtained; Step 4: Decompose the measured wavefront of the collimator (9) obtained in step 3.5 into a linear combination of Zernike polynomials, and use the least squares method to solve the defocus coefficient of the fourth defocus term of the Zernike polynomials. ; Determine the defocus coefficient Is it 0? If so, the calibration of the focal plane of the collimator (9) is completed. Otherwise, the axial distance of the optical fiber point source (02) is adjusted through the five-dimensional adjustment frame (3), and then the process returns to step 2.

2. A method for measuring wavefront and calibrating focal plane of a collimator according to claim 1, characterized in that: In step 3.1, the light field to be measured (10) ,in is the phase corresponding to the light field (10) to be measured, which is a set of constants or a set of random numbers.

3. A method for measuring wavefront and calibrating focal plane of a collimator according to claim 2, characterized in that: The step 3.2 is specifically as follows: Step 3.2.1: According to the light field to be measured (10) , calculate the detection light field of the first detection position by diffraction , according to the detection light field at the first detection position Get the amplitude and phase, using the detection light intensity at the first detection position The calculated detection amplitude replaces the amplitude, keeping the phase unchanged, and obtains the reconstructed detection light field at the first detection position. ; is the coordinate of the first detection position; Step 3.2.2: Based on the detection light field at the first detection position , calculate the detection light field at the second detection position by diffraction , according to the detection light field at the second detection position Get the amplitude and phase, and use the detection light intensity at the second detection position The calculated detection amplitude replaces the amplitude, keeping the phase unchanged, and obtains the reconstructed detection light field at the second detection position. ; is the coordinate of the second detection position; Step 3.2.3: Based on the detection light field at the second detection position , the detection light field of the next detection position is calculated by diffraction, and then the amplitude and phase are obtained. According to the method of decomposing and calculating the detection light field, replacing the amplitude, and reconstructing the detection light field, the reconstructed detection light field of the next detection position is calculated in sequence until it is transmitted to the first At the detection position, the Reconstructed detection light field at each detection position ; For the The coordinates of the detection location.

4. A method for wavefront measurement and focal plane calibration of a collimator according to claim 3, characterized in that: In step 3.2.1, the detection light field as follows: in Calculated for the forward Collins diffraction; The reconstructed detection light field as follows: in is the detection amplitude of the first detection position; In step 3.2.2, the detection light field as follows: in, Calculate the angular spectrum diffraction in the forward direction; The reconstructed detection light field QUOTE as follows: in is the detection amplitude of the second detection position.

5. A method for measuring wavefront and calibrating focal plane of a collimator according to claim 4, characterized in that: The step 3.3 is specifically as follows: Step 3.3.

1. Calculate Reconstructed detection light field at each detection position Reverse transmission to A detection light field at a detection position; According to the method of decomposing and calculating the detection light field, replacing the amplitude, and reconstructing the detection light field, the reconstructed detection light field of the previous detection position is calculated in sequence until it is transmitted to the first detection position to obtain the reconstructed detection light field ; For the The coordinates of the detection locations; Step 3.3.2: Calculate the detection light field The light field to be measured is transmitted in reverse order (10), and the reconstructed light field to be measured is obtained by decomposing and calculating the detection light field, replacing the amplitude, and reconstructing the detection light field. .

6. A method for measuring the wavefront of a collimator and calibrating the focal plane according to claim 5, characterized in that: In step 3.3.1, the detection light field as follows: in Calculate the inverse angular spectrum of diffraction.

7. A method for wavefront measurement and focal plane calibration of a collimator according to any one of claims 1 to 6, characterized in that: In step 3.4, the threshold is 10 -5 .

8. A method for measuring the wavefront of a collimator and calibrating the focal plane according to any one of claims 1 to 6, characterized in that: The step 3.5 is specifically as follows: According to the reconstructed light field obtained in step 3.3, the angle calculation operator is used Get the phase corresponding to the measured light field (10) , and then obtain the wavefront to be measured of the collimator (9) .

9. A method for measuring wavefront and calibrating focal plane of a collimator according to claim 8, characterized in that: The step 4 is specifically as follows: Step 4.1, decompose the measured wavefront of the collimator (9) obtained in step 3.5 into a linear combination of Zernike polynomials, and use the least squares method to solve the defocus coefficient of the fourth defocus term of the Zernike polynomials. , specifically: The wavefront to be measured Decomposition into Zernike polynomials A linear combination of: in, For the Zernike polynomials, For the The coefficients of the Zernike polynomials are is the order; The defocus coefficient of the fourth defocus term ,as follows: By using the least squares method, the error between the wavefront data and the fitted wavefront is minimized to solve the defocus coefficient ; Step 4.2: Determine the defocus coefficient Is it 0? If so, the calibration of the focal plane of the collimator (9) is completed; Otherwise, according to the defocus coefficient The positive or negative value of is used to determine whether the optical fiber point source (02) is located in front of or behind the focal plane. Specifically, if , then the optical fiber point source (02) is located before the focal plane. If , then the optical fiber point source (02) is located behind the focal plane; Then, the axial distance of the optical fiber point source (02) is adjusted by the five-dimensional adjustment frame (3), and then the process returns to step 2.

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