A Shack-Hartmann wavefront sensor error evaluation method

Abstract

The present invention relates to a Shack-Hartmann wavefront sensor error evaluation method, comprising measuring a measured wavefront through a Shack-Hartmann wavefront sensor, obtaining the system parameters of the Shack-Hartmann wavefront sensor; analyzing the value ranges of different error sources of the sensor, and randomly sampling a group of error values ​​through the value ranges of each error source; constructing a Shack-Hartmann optical model, and obtaining a standard light spot array and a measured light spot array imaged on an image sensor after the standard wavefront and the measured wavefront are focused by a microlens; calculating the slope distribution of the measured wavefront, reconstructing the measured wavefront, and calculating the measurement residual; randomly sampling errors, and repeatedly performing the above steps; and evaluating the measurement uncertainty of the Shack-Hartmann wavefront sensor for the measured wavefront according to the measurement residuals under different sampling errors. Compared with the prior art, the present invention realizes the comprehensive measurement uncertainty evaluation of the Shack-Hartmann sensor through multiple error samplings, and has the advantage of evaluating any measurement wavefront error.

Description

Technical Field

[0001] The invention relates to the technical field of wavefront detection, and in particular to an error evaluation method for a Shack-Hartmann wavefront sensor. Background Art

[0002] Wavefront measurement technology can measure the phase distribution of light fields with high precision and has been widely used in biological imaging, astronomical detection, precision manufacturing, ophthalmic diagnosis and other fields. The Shack-Hartmann wavefront sensor divides the measured wavefront into a series of sub-wavefronts through a microlens array, and then maps the average slope of the sub-wavefront to the offset of the focused light spot on the image sensor, so that the measured wavefront can be reconstructed through the offset of the focused light spot. Compared with other wavefront measurement technologies based on the interference principle, the Shack-Hartmann wavefront measurement sensor has significant advantages in measurement accuracy and speed. It does not require the introduction of additional reference wavefronts, avoiding the problem of limited measurement accuracy caused by the wavefront error of the reference wavefront itself, and the information of the measured wavefront can be obtained in a single imaging. The measurement process is simple and fast.

[0003] With the continuous development of Shack-Hartmann wavefront sensors, their nominal measurement accuracy has reached the λ / 100 level. However, this nominal accuracy is only the uncertainty calibrated for a certain standard wavefront. Since the various error sources of the Shack-Hartmann sensor have different effects on different measurement wavefronts, it is not accurate to use the uncertainty of the standard wavefront to characterize the measurement residuals of the sensor for all wavefronts in general.

[0004] In order to evaluate the accuracy of Shack-Hartmann sensors, scholars have conducted relevant analysis and research on error sources such as structural error, detector error, algorithm error, and calibration error. However, the above studies only construct specific error transfer expressions for one or a few error sources in the measurement process of Shack-Hartmann sensors, making it difficult to unify the various error sources into an explicit error transfer model, and ignoring the coupling relationship between some error sources, resulting in inaccurate error analysis results. In addition, the above studies still do not take into account the impact of differences in measurement wavefront distribution on measurement accuracy. In summary, the current Shack-Hartmann sensors lack a comprehensive uncertainty assessment method that can conduct targeted analysis of different measurement wavefront distributions. Summary of the invention

[0005] The purpose of the present invention is to provide a Shack-Hartmann wavefront sensor error evaluation method in order to overcome the defect of the prior art that the existing Shack-Hartmann wavefront sensor only uses the uncertainty of a certain standard wavefront as the nominal accuracy, resulting in inaccurate evaluation results of different measured wavefront errors.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A Shack-Hartmann wavefront sensor error evaluation method comprises the following steps:

[0008] Step 1: Measure the measured wavefront Φ by using the Shack-Hartmann wavefront sensor; obtain the system parameters of the Shack-Hartmann wavefront sensor and the value ranges of different error sources;

[0009] Step 2: Randomly sample values ​​within the value range of each error source to obtain a set of error values; construct a Shack-Hartmann optical model based on the system parameters and the obtained error values, and the Shack-Hartmann optical model is used to quantify the process in which an incident wavefront passes through a microlens array and propagates to an image sensor to form an image of a light spot array;

[0010] Step 3: inputting the standard wavefront and the measured wavefront Φ into the Shack-Hartmann optical model respectively to obtain the standard spot array and the measured spot array;

[0011] Step 4: Obtain the measured wavefront slope distribution according to the difference between the standard spot array and the measured spot array, and then reconstruct the measured wavefront Φ through the wavefront reconstruction algorithm to obtain the reconstructed wavefront Φ 1 ; Calculate the reconstructed wavefront Φ 1 The measurement residual between Φ and the measured wavefront;

[0012] Step 5: Repeat steps 2 to 4 in sequence until the number of sampling reaches a preset threshold, and obtain the measurement residuals corresponding to different reconstructed wavefronts;

[0013] Step 6: Evaluate the measurement uncertainty of the Shack-Hartmann sensor for the measured wavefront Φ based on the various measurement residuals.

[0014] Furthermore, the processing of the Shack-Hartmann optical model includes:

[0015] Based on the structural parameters and error values ​​of the microlens array in the Shack-Hartmann wavefront sensor, the phase transfer function of the microlens array is calculated; and according to the phase transfer function, the convergent wavefront of the incident wavefront after passing through the microlens array is obtained;

[0016] Based on the diffraction propagation theory, a light field transfer function is established between the back of the microlens array and the imaging surface of the image sensor; and a focusing wavefront of the converging wavefront on the imaging surface of the image sensor is obtained according to the light field transfer function;

[0017] The focused wavefront is converted into a spot array image based on the imaging parameters of the image sensor.

[0018] Furthermore, the diffraction propagation theory is any one of angular spectrum diffraction propagation theory, Fresnel diffraction propagation theory or Fraunhofer diffraction propagation theory.

[0019] Further, the error sources include some or all of the following errors:

[0020] The rotation angle δ of the image sensor imaging surface relative to the x, y and z axes of the microlens array plane coordinate system α ,δ β and δ γ ; Discrete sampling error δ of image sensor discrete , quantization error δ quant and sampling noise δ noise ; The offset of the optical axis of the standard wavefront in the x- and y-axis directions of the microlens array plane coordinate system δ x ,δ y ; The angle δ between the optical axis of the standard wavefront and the xz plane and yz plane of the microlens array plane coordinate system θ , Spot array position error δ cent and the wavefront reconstruction error δ recons ;

[0021] The origin of the microlens array plane coordinate system is the center of the microlens array, the x-axis and the y-axis are parallel to the two edges of the microlens array respectively, and the z-axis is perpendicular to the microlens plane.

[0022] Furthermore, the process of acquiring the measured wavefront slope distribution is specifically as follows:

[0023] The centroid coordinates of each light spot in the standard light spot array and the centroid coordinates of each light spot in the measured light spot array are respectively obtained by a square weighted centroid calculation method;

[0024] The light spots in the standard light spot array are matched one-to-one with the light spots in the measured light spot array, and the offset of each light spot in the measured light spot array is calculated according to the centroid coordinates of the light spots;

[0025] The measured wavefront slope distribution is calculated according to the offset of each light spot in the measured light spot array and the focal length of the microlens corresponding to each light spot.

[0026] Furthermore, the wavefront reconstruction algorithm is any one of a fast Fourier transform method, an iterative solution method, a matrix vector method or a Zernike pattern wavefront reconstruction method.

[0027] Furthermore, the random sampling method of the error value is a sampling method based on any probability distribution of normal distribution, uniform distribution, triangular distribution or trapezoidal distribution.

[0028] Furthermore, the evaluation process of the measurement uncertainty of the Shack-Hartmann sensor includes:

[0029] Draw an error histogram based on the obtained measurement residuals to obtain the error distribution;

[0030] According to the error distribution, the measurement uncertainty of the measured wavefront is evaluated by any one of the standard measurement uncertainty type A evaluation method, the standard measurement uncertainty type B evaluation method or the expanded uncertainty evaluation method.

[0031] Furthermore, the measured wavefront is any one of a plane wavefront, a spherical wavefront, and a free-form wavefront.

[0032] Furthermore, the standard wavefront is any one of a plane wavefront, a quasi-plane wavefront, a spherical wavefront, and a quasi-spherical wavefront.

[0033] Compared with the prior art, the present invention has the following advantages:

[0034] (1) The present invention overcomes the problem that the existing Shack-Hartmann wavefront sensor only uses the uncertainty of a certain standard wavefront as the nominal accuracy, resulting in inaccurate evaluation results of different measured wavefront errors. By randomly sampling various error sources and constructing an end-to-end Shack-Hartmann wavefront sensor measurement model based on physical optical propagation, the present invention can respond to different wavefront distributions and has the advantage of evaluating any measured wavefront error.

[0035] This scheme can analyze the influence of various error sources such as installation error, image acquisition error, calibration error and method principle error on measurement accuracy at the diffraction effect scale, and realize the comprehensive measurement uncertainty evaluation of Shack-Hartmann sensor through multiple error sampling;

[0036] (2) The present invention can analyze the influence of different error sources on the measurement accuracy of the Shack-Hartmann sensor, which is helpful to formulate a reasonable sensor error allocation scheme in the sensor design stage. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 A schematic flow chart of a Shack-Hartmann wavefront sensor error evaluation method provided in an embodiment of the present invention;

[0038] Figure 2a A schematic diagram of a process of processing a measured wavefront through a Shack-Hartmann optical model provided in an embodiment of the present invention;

[0039] Figure 2b A schematic diagram of a convergent wavefront after a standard wavefront passes through a microlens array provided in an embodiment of the present invention;

[0040] Figure 3a A schematic diagram of measurement residuals in a group of error source sampling when a measured wavefront is a plane wavefront provided in an embodiment of the present invention;

[0041] Figure 3bA schematic diagram of measurement residuals in a group of error source sampling when the measured wavefront is a spherical wavefront provided in an embodiment of the present invention;

[0042] Figure 3c A schematic diagram of measurement residuals in a group of error source sampling when a measured wavefront is a free-form surface wavefront provided in an embodiment of the present invention;

[0043] Figure 4a It is a schematic diagram of the distribution result of the measurement residual when sampling multiple groups of error sources when the measured wavefront is a plane wavefront provided in Embodiment 1 of the present invention;

[0044] Figure 4b A schematic diagram of a measurement uncertainty evaluation result when the measured wavefront is a plane wavefront provided in Example 1 of the present invention;

[0045] Figure 5a A schematic diagram of measurement residual distribution results when sampling multiple groups of error sources when the measured wavefront is a spherical wavefront provided in Embodiment 2 of the present invention;

[0046] Figure 5b A schematic diagram of a measurement uncertainty evaluation result when the measured wavefront is a spherical wavefront provided in Example 2 of the present invention;

[0047] Figure 6a A schematic diagram of measurement residual distribution results when sampling multiple groups of error sources when the measured wavefront is a free-form surface wavefront provided in Embodiment 3 of the present invention;

[0048] Figure 6b A schematic diagram of a measurement uncertainty evaluation result when the measured wavefront is a free-form surface wavefront provided in Example 3 of the present invention;

[0049] In the figure, 1. measured wavefront, 2. microlens array, 3. image sensor, 4. measured light spot array, 5. standard light spot array, 6. standard wavefront. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0051] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0053] like Figure 1 As shown, the present invention provides a Shack-Hartmann wavefront sensor error evaluation method, comprising the following steps:

[0054] Step 1: Measure the measured wavefront Φ by using the Shack-Hartmann wavefront sensor; obtain the system parameters of the Shack-Hartmann wavefront sensor and the value ranges of different error sources;

[0055] Error sources include some or all of the following:

[0056] The rotation angle δ of the image sensor imaging surface relative to the x, y and z axes of the microlens array plane coordinate system α ,δ β and δ γ ; Discrete sampling error δ of image sensor discrete , quantization error δ quant and sampling noise δ noise ; The offset of the optical axis of the standard wavefront in the x- and y-axis directions of the microlens array plane coordinate system δ x ,δ y ; The angle δ between the optical axis of the standard wavefront and the xz plane and yz plane of the microlens array plane coordinate system θ , Spot array position error δ cent and the wavefront reconstruction error δ recons ;

[0057] The origin of the microlens array plane coordinate system is the center of the microlens array, the x-axis and the y-axis are parallel to the two edges of the microlens array, and the z-axis is perpendicular to the microlens plane.

[0058] Step 2: Randomly sample values ​​within the value range of each error source to obtain a set of error values; construct a Shack-Hartmann optical model based on the system parameters and the obtained error values, and the Shack-Hartmann optical model is used to quantify the process in which an incident wavefront passes through a microlens array and propagates to an image sensor to form an image of a light spot array;

[0059] The processing of the Shack-Hartmann optical model includes:

[0060] Based on the structural parameters and error values ​​of the microlens array in the Shack-Hartmann wavefront sensor, the phase transfer function of the microlens array is calculated; and according to the phase transfer function, the convergent wavefront of the incident wavefront after passing through the microlens array is obtained;

[0061] Based on the diffraction propagation theory, a light field transfer function is established between the back of the microlens array and the imaging surface of the image sensor; and a focusing wavefront of the converging wavefront on the imaging surface of the image sensor is obtained according to the light field transfer function;

[0062] The focused wavefront is converted into a spot array image based on the imaging parameters of the image sensor;

[0063] The diffraction propagation theory is any one of the angular spectrum diffraction propagation theory, the Fresnel diffraction propagation theory or the Fraunhofer diffraction propagation theory.

[0064] The focused wavefront is converted into a spot array image based on the imaging parameters of the image sensor;

[0065] The random sampling method of the error value is based on any probability distribution of normal distribution, uniform distribution, triangular distribution or trapezoidal distribution.

[0066] Step 3: inputting the standard wavefront and the measured wavefront Φ into the Shack-Hartmann optical model respectively to obtain the standard spot array and the measured spot array;

[0067] The measured wavefront is any one of a plane wavefront, a spherical wavefront, and a free-form wavefront.

[0068] The standard wavefront is any one of a plane wavefront, a quasi-plane wavefront, a spherical wavefront, and a quasi-spherical wavefront.

[0069] Step 4: Obtain the measured wavefront slope distribution according to the difference between the standard spot array and the measured spot array, and then reconstruct the measured wavefront Φ through the wavefront reconstruction algorithm to obtain the reconstructed wavefront Φ 1 ; Calculate the reconstructed wavefront Φ 1 The measurement residual between Φ and the measured wavefront;

[0070] The specific process of obtaining the measured wavefront slope distribution is as follows:

[0071] The centroid coordinates of each light spot in the standard light spot array and the centroid coordinates of each light spot in the measured light spot array are respectively obtained by a square weighted centroid calculation method;

[0072] The light spots in the standard light spot array are matched one-to-one with the light spots in the measured light spot array, and the offset of each light spot in the measured light spot array is calculated according to the centroid coordinates of the light spots;

[0073] The measured wavefront slope distribution is calculated according to the offset of each light spot in the measured light spot array and the focal length of the microlens corresponding to each light spot;

[0074] The wavefront reconstruction algorithm is any one of a fast Fourier transform method, an iterative solution method, a matrix vector method or a Zernike pattern wavefront reconstruction method;

[0075] Step 5: Repeat steps 2 to 4 in sequence until the number of sampling reaches a preset threshold, and obtain the measurement residuals corresponding to different reconstructed wavefronts;

[0076] Step 6: Evaluate the measurement uncertainty of the Shack-Hartmann sensor for the measured wavefront Φ based on the various measurement residuals;

[0077] The measurement uncertainty evaluation process of a Shack-Hartmann sensor includes:

[0078] Draw an error histogram based on the obtained measurement residuals to obtain the error distribution;

[0079] According to the error distribution, the measurement uncertainty of the measured wavefront is evaluated by any one of the standard measurement uncertainty type A evaluation method, the standard measurement uncertainty type B evaluation method or the expanded uncertainty evaluation method.

[0080] The solution of the present invention can be applied to the fields of biological imaging, astronomical detection, precision manufacturing, ophthalmic diagnosis, etc.

[0081] Example 1

[0082] This embodiment provides a comprehensive error evaluation method for a Shack-Hartmann wavefront sensor based on physical optics propagation, and the specific process is as follows:

[0083] In this embodiment, the measured wavefront is a plane wavefront with a wavelength λ of 532 nm, and the wavefront distribution Φ of the measured wavefront is measured by the Shack-Hartmann wavefront sensor 7;

[0084] Obtain the system parameters of the Shack-Hartmann wavefront sensor 7, including the number of microlenses N in the microlens array 2 is 1201, the microlens pitch P is 150 μm, the microlens aperture is 146 μm, the microlens thickness t is 1.2 mm, and the non-convex position thickness t of the microlens array 2 is 1 is 0.5 mm, the radius of curvature r of the microlens is 2.54 mm, the pixel size of the image sensor 3 is 2.5 μm, the bit depth of the pixel 3 of the image sensor is 8 bits, the signal-to-noise ratio of the image sensor 3 is 45.2 dB, and the distance between the microlens array 2 and the image sensor 3 is 5.2 mm;

[0085] Analyze the value range of different error sources of the sensor, including: the rotation angle δ of the image sensor imaging surface relative to the x, y and z axes of the microlens array 2 plane coordinate system α ,δ β and δ γ , respectively ±1.71mrad, ±1.71mrad and ±17.1mrad; the offset of the optical axis of the standard wavefront 6 in the x-axis and y-axis directions of the plane coordinate system of the microlens array 2 is δ x ,δ y , are ±2mm; the angle δ between the optical axis of the standard wavefront 6 and the xz plane and yz plane of the plane coordinate system of the microlens array 2 θ , Both are ±5mrad;

[0086] A set of error values ​​are randomly sampled according to uniform distribution within the range of 7 error sources, δ α ,δ β ,δ γ ,δ x ,δ y ,δ θ and The values ​​are -0.22mrad, 1.19mrad, 5.79mrad, 1.49mm, -1.38mm, 3.84mrad and -3.98mrad respectively;

[0087] The Shack-Hartmann optical model is constructed, as shown in Figure 2. According to the thin lens approximation principle, the phase modulation function M of the 1201 microlenses in the microlens array 2 is calculated. MLA (x,y) modeling:

[0088]

[0089]

[0090] in, is the wave vector, and n is a positive integer between 1 and 1201; then, the diffraction propagation process between the microlens array 2 and the imaging surface of the image sensor 3 is modeled based on the angular spectrum diffraction propagation theory: first, the spectrum distribution G of the measured wavefront with a complex amplitude distribution of g(u,v) on a parallel plane with a distance d from the rear surface of the microlens is obtained according to the calculation method of the traditional angular spectrum method. d (f u ,f v )

[0091]

[0092] According to the rotation angle δ of the imaging surface of the image sensor 3 relative to the x, y and z axes of the plane coordinate system of the microlens array 2 α ,δβ and δ γ Construct the rotation transformation matrix T and obtain the frequency distribution F(f x ,f y ):

[0093]

[0094] Finally, by x ,f y ) to obtain the complex amplitude distribution E(x,y) of the light wave on the CMOS receiving surface by inverse Fourier transform, and then calculate the square of its modulus to obtain the light intensity distribution I(x,y)

[0095]

[0096] J(f x ,f y ) is the Jacobian matrix of coordinate transformation during the integration process, F -1 is a two-dimensional inverse Fourier transform, thereby obtaining a light spot array of the measured wavefront 1 on the imaging surface of the image sensor 3;

[0097] The standard spherical wavefronts whose centers are at distances of 425mm, 452mm, 483mm, 519mm, 560mm, 609mm, 667mm, 737mm and 824mm from the microlens array 2 are Sequentially Input the constructed Shack-Hartmann optical model and obtain 9 sets of standard spherical wavefront spot arrays; obtain the centroid coordinates of each spot in the 9 sets of standard spot arrays 5 by using the square weighted centroid algorithm The 9 sets of centroid coordinates were calculated by the least squares method. Fitting is performed to estimate the centroid position of the light spot array imaged on the image sensor 3 when the standard wavefront is a standard plane wavefront This is used as the standard spot array position;

[0098] The measured wavefront 1 is input into the Shack-Hartmann optical model to obtain the measured light spot array 4; the centroid coordinates {x n ,y n}, which is used as the position of the measured light spot array;

[0099] The centroid coordinates of the standard spot array 5 The centroid coordinates of the measured spot array 4 {x n ,y n} and the structural parameters of the microlens array 2 to obtain the measured wavefront slope distribution; the measured wavefront slope distribution is reconstructed into the measured wavefront Φ by an iterative solution method.1 ; Calculate the reconstructed wavefront Φ by the root mean square error (RMSE) 1 The measured residual error e between the measured wavefront Φ 1 ,like Figure 3a As shown;

[0100] Repeat the sampling of the seven error sources 1000 times and repeat the above steps to obtain the measurement residual e 2 、e 3 ,…,e 1000 ;e 1 、e 2 ,…,e 1000 The distribution of Figure 4a As shown in the figure; the measurement uncertainty is evaluated according to the evaluation method of the expanded uncertainty of 2, and the measurement residual e is calculated 1 、e 2 ,…,e 1000 The average value is 2.89nm and the standard deviation is 0.94nm. If the measured wavefront is Figure 4a For the plane wavefront shown in the upper right corner, the measurement uncertainty of the Shack-Hartmann wavefront sensor is 2.89nm+2×0.94nm=4.77nm, as shown in Figure 4b shown.

[0101] Example 2

[0102] This embodiment is substantially the same as the first embodiment, except that the present embodiment applies the Shack-Hartmann wavefront sensor comprehensive error evaluation method based on physical optics propagation proposed by the present invention to the measurement uncertainty evaluation of a spherical wavefront to be measured. The specific method is as follows:

[0103] In this embodiment, the measured wavefront 1 is a spherical wavefront with a wavelength λ of 532 nm. Figure 5a As shown in the upper right corner, the wavefront distribution of the measured wavefront 1 is measured by the Shack-Hartmann wavefront sensor 7;

[0104] The measured wavefront 1 is input into the Shack-Hartmann optical model to obtain the measured light spot array 4; the centroid coordinates of each light spot in the measured light spot array 4 are obtained by the square weighted centroid algorithm This is used as the position of the measured light spot array;

[0105] The centroid coordinates of the standard spot array 5 The centroid coordinates of the measured light spot array 4 and the structural parameters of the microlens array 2 to obtain the measured wavefront slope distribution; the measured wavefront slope distribution is reconstructed into the measured wavefront by an iterative solution method The reconstructed wavefront is calculated by the root mean square error (RMSE) The measured residual error between the measured wavefront Φ like Figure 3b As shown;

[0106] Repeat the sampling of the seven error sources 1000 times and repeat the above steps to obtain the measurement residuals. The distribution of Figure 5a As shown; the measurement uncertainty is evaluated according to the evaluation method of the expanded uncertainty of 2, and the measurement residual is calculated The average value is 2.61nm and the standard deviation is 1.13nm. If the measured wavefront is Figure 5a For the spherical wavefront shown in the upper right corner, the measurement uncertainty of the Shack-Hartmann wavefront sensor is 2.61nm+2×1.13nm=4.81nm. Figure 5b shown.

[0107] Example 3

[0108] This embodiment is substantially the same as the first embodiment, except that the present embodiment applies the comprehensive error evaluation method of the Shack-Hartmann wavefront sensor based on physical optical propagation proposed by the present invention to the measurement uncertainty evaluation of the free-form surface wavefront to be measured. The specific method is as follows:

[0109] In this embodiment, the measured wavefront 1 is a free-form surface wavefront with a wavelength λ of 532 nm. Figure 6a As shown in the upper right corner, the wavefront distribution of the measured wavefront 1 is measured by the Shack-Hartmann wavefront sensor 7;

[0110] The measured wavefront 1 is input into the Shack-Hartmann optical model to obtain the measured light spot array 4; the centroid coordinates of each light spot in the measured light spot array 4 are obtained by the square weighted centroid algorithm This is used as the position of the measured light spot array;

[0111] The centroid coordinates of the standard spot array 5 The centroid coordinates of the measured light spot array 4 and the structural parameters of the microlens array 2 to obtain the measured wavefront slope distribution; the measured wavefront slope distribution is reconstructed into the measured wavefront by an iterative solution method The reconstructed wavefront is calculated by the root mean square error (RMSE) The measured residual error between the measured wavefront Φ like Figure 3c As shown;

[0112] Repeat the sampling of the seven error sources 1000 times and repeat the above steps to obtain the measurement residuals. The distribution of Figure 6a As shown; the measurement uncertainty is evaluated according to the evaluation method of the expanded uncertainty of 2, and the measurement residual is calculated The average value is 2.29nm and the standard deviation is 0.48nm. If the measured wavefront is Figure 6a For the free-form wavefront shown in the upper right corner, the measurement uncertainty of the Shack-Hartmann wavefront sensor is 2.29nm+2×0.48nm=3.25nm. Figure 6b shown.

[0113] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A Shack-Hartmann wavefront sensor error evaluation method, characterized in that: The following steps are involved: Step 1: Measure the measured wavefront Φ by using the Shack-Hartmann wavefront sensor; obtain the system parameters of the Shack-Hartmann wavefront sensor and the value ranges of different error sources; Step 2: Randomly sample values ​​within the value range of each error source to obtain a set of error values; construct a Shack-Hartmann optical model based on the system parameters and the obtained error values, and the Shack-Hartmann optical model is used to quantify the process in which an incident wavefront passes through a microlens array and propagates to an image sensor to form an image of a light spot array; Step 3: inputting the standard wavefront and the measured wavefront Φ into the Shack-Hartmann optical model respectively to obtain the standard spot array and the measured spot array; Step 4: Obtain the measured wavefront slope distribution according to the difference between the standard spot array and the measured spot array, thereby reconstructing the measured wavefront Φ through a wavefront reconstruction algorithm to obtain a reconstructed wavefront Φ1; calculate the measurement residual between the reconstructed wavefront Φ1 and the measured wavefront Φ; Step 5: Repeat steps 2 to 4 in sequence until the number of sampling reaches a preset threshold, and obtain the measurement residuals corresponding to different reconstructed wavefronts; Step 6: Evaluate the measurement uncertainty of the Shack-Hartmann sensor for the measured wavefront Φ based on the various measurement residuals.

2. The Shack-Hartmann wavefront sensor error evaluation method according to claim 1, characterized in that: The processing process of the Shack-Hartmann optical model includes: Based on the structural parameters and error values ​​of the microlens array in the Shack-Hartmann wavefront sensor, the phase transfer function of the microlens array is calculated; and according to the phase transfer function, the convergent wavefront of the incident wavefront after passing through the microlens array is obtained; Based on the diffraction propagation theory, a light field transfer function is established between the back of the microlens array and the imaging surface of the image sensor; and a focusing wavefront of the converging wavefront on the imaging surface of the image sensor is obtained according to the light field transfer function; The focused wavefront is converted into a spot array image based on the imaging parameters of the image sensor.

3. The Shack-Hartmann wavefront sensor error evaluation method according to claim 2, characterized in that: The diffraction propagation theory is any one of the angular spectrum diffraction propagation theory, the Fresnel diffraction propagation theory or the Fraunhofer diffraction propagation theory.

4. The Shack-Hartmann wavefront sensor error evaluation method according to claim 1, characterized in that: The error sources include some or all of the following errors: The rotation angle δ of the image sensor imaging surface relative to the x, y and z axes of the microlens array plane coordinate system α ,δ β and δ γ ; Discrete sampling error δ of image sensor discrete , quantization error δ quant and sampling noise δ noise ; The offset of the optical axis of the standard wavefront in the x- and y-axis directions of the microlens array plane coordinate system δ x ,δ y ; The angle δ between the optical axis of the standard wavefront and the xz plane and yz plane of the microlens array plane coordinate system θ ,δ φ ; Spot array position error δ cent and the wavefront reconstruction error δ recons ; The origin of the microlens array plane coordinate system is the center of the microlens array, the x-axis and the y-axis are parallel to the two edges of the microlens array respectively, and the z-axis is perpendicular to the microlens plane.

5. The Shack-Hartmann wavefront sensor error evaluation method according to claim 1, characterized in that: The process of acquiring the measured wavefront slope distribution is specifically as follows: The centroid coordinates of each light spot in the standard light spot array and the centroid coordinates of each light spot in the measured light spot array are respectively obtained by a square weighted centroid calculation method; The light spots in the standard light spot array are matched one-to-one with the light spots in the measured light spot array, and the offset of each light spot in the measured light spot array is calculated according to the centroid coordinates of the light spots; The measured wavefront slope distribution is calculated according to the offset of each light spot in the measured light spot array and the focal length of the microlens corresponding to each light spot.

6. The Shack-Hartmann wavefront sensor error evaluation method according to claim 1, characterized in that: The wavefront reconstruction algorithm is any one of a fast Fourier transform method, an iterative solution method, a matrix vector method or a Zernike mode wavefront reconstruction method.

7. The Shack-Hartmann wavefront sensor error evaluation method according to claim 1, characterized in that: The random sampling method of the error value is a sampling method based on any probability distribution of normal distribution, uniform distribution, triangular distribution or trapezoidal distribution.

8. The Shack-Hartmann wavefront sensor error evaluation method according to claim 1, characterized in that: The evaluation process of the measurement uncertainty of the Shack-Hartmann sensor includes: Draw an error histogram based on the obtained measurement residuals to obtain the error distribution; According to the error distribution, the measurement uncertainty of the measured wavefront is evaluated by any one of the standard measurement uncertainty type A evaluation method, the standard measurement uncertainty type B evaluation method or the expanded uncertainty evaluation method.

9. The Shack-Hartmann wavefront sensor error evaluation method according to claim 1, characterized in that: The measured wavefront is any one of a plane wavefront, a spherical wavefront, and a free-form wavefront.

10. The Shack-Hartmann wavefront sensor error evaluation method according to claim 1, characterized in that: The standard wavefront is any one of a plane wavefront, a quasi-plane wavefront, a spherical wavefront, and a quasi-spherical wavefront.

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