A model calculation-based infrared material optical uniformity detection method

Abstract

The application discloses a kind of infrared material optical uniformity detection methods based on model calculation.Utilize spherical interferometer to build the surface shape detection light path of oblique incidence flat plate sample surface, adjust spherical mirror so that interference fringe is sparse;Again, the other surface profile of flat plate sample is measured by turning over 180°;Utilize spherical interferometer to build the optical uniformity detection light path of normal incidence flat plate sample surface, adjust spherical mirror so that interference fringe is sparse;Flat plate sample is removed from interference light path, and the cavity measurement result of interferometer and spherical mirror is measured;Establish the ray tracing model of spherical interferometer normal incidence flat plate sample, the optical uniformity of flat plate sample is characterized with polynomial, polynomial coefficient and the distance of flat plate sample to interferometer are used as the variable of iterative calculation, the wavefront data measured by spherical interferometer normal incidence flat plate sample is used as the target value of iterative calculation, and the mathematical expression of flat plate sample optical uniformity is obtained by iterative calculation.

Description

Technical Field

[0001] This application relates to the technical field of optical uniformity of infrared materials, and in particular to a method for detecting optical uniformity of infrared materials based on model calculation. Background Technology

[0002] Large-aperture infrared materials are increasingly used in space optical remote sensors, and their optical uniformity is a crucial factor affecting the imaging quality of these sensors. Employing highly uniform infrared materials, or compensating for the influence of optical uniformity through optimized optical system design, are essential means to ensure remote sensor quality. Therefore, high-precision detection of the optical uniformity of large-aperture infrared materials is of paramount importance.

[0003] Currently, the main methods used domestically and internationally for detecting the optical uniformity of optical materials include the plate method, the four-step interferometry method, and the parallel plate method. The plate method is suitable for measuring the optical uniformity of small-diameter materials, but it cannot correct for systematic errors in the measuring equipment. The method of measuring the optical uniformity of parallel plates using a wavelength-tuned phase-shifting interferometer is only applicable to parallel plate samples of visible light materials and cannot detect plate materials with wedge angles. Furthermore, all of these methods require a plane-wave interferometer with a diameter comparable to the plate sample. Due to the current lack of large-diameter infrared plane interferometers both domestically and internationally, the uniformity measurement method for large-diameter infrared materials often involves adding an additional beam expander system to the test optical path of a spherical-wave infrared interferometer to form a large-diameter collimated wavefront detection optical path. This additional beam expander system significantly increases the detection cost and requires high-precision assembly and calibration, making the detection system more complex. Another optical uniformity detection optical path uses non-collimated optical interferometry. The spherical wave output from the test arm of the infrared spherical-wave interferometer passes through the plate sample, then through a spherical mirror, and returns along the original optical path, forming interference. While this method can determine the influence of the optical homogeneity of a flat plate sample on spherical waves, it does not consider the propagation characteristics of spherical waves within the flat plate sample. Furthermore, the surface shape of the flat plate sample is coupled with the refractive index distribution, requiring an additional large interferometer to detect the sample surface shape, thus increasing the detection cost. Summary of the Invention

[0004] This application provides a model-based method for detecting the optical uniformity of infrared materials. It employs non-collimated interferometry, ray tracing model calculation, and iterative optimization calculation techniques. This method can be used for the uniformity detection of large-aperture infrared materials and has important applications in the optimization design and detection of infrared space optical remote sensors.

[0005] Firstly, a model-based method for detecting the optical uniformity of infrared materials is provided, including:

[0006] A uniformity testing platform was set up for testing, including the detection of the front and back surface shapes of the flat sample, transmission wavefront detection, and interference cavity detection.

[0007] A ray tracing model for detecting the transmitted wavefront of a flat plate sample was established using Zemax software, and simulations were performed based on the uniformity detection results.

[0008] Based on the detection results of the interference cavity and the simulation results of the ray tracing model, the optical homogeneity distribution H of the material in the flat plate sample is solved iteratively.

[0009] In conjunction with the first aspect, in some implementations of the first aspect, the uniformity detection platform includes a spherical wave interferometer, a flat sample, and a standard spherical mirror;

[0010] In the oblique incidence detection optical path of the surface shape of the flat sample, the light emitted by the spherical wave interferometer is reflected by the surface of the flat sample and then enters the standard spherical mirror. After being reflected by the standard spherical mirror, it enters the surface of the flat sample again and returns to the spherical wave interferometer.

[0011] In the detection optical path of the interference cavity, the center of the mirror coincides with the focal point of the interferometer;

[0012] In the transmission wavefront detection optical path of the flat plate sample, the light emitted by the spherical wave interferometer passes through the flat plate sample and enters the standard spherical mirror. After being reflected by the standard spherical mirror, it passes through the flat plate sample again and returns to the spherical wave interferometer.

[0013] In conjunction with the first aspect, in some implementations of the first aspect, the uniformity detection includes:

[0014] The normal direction of the flat sample surface is placed at an angle θ with the optical axis of the spherical wave interferometer, and the center of the standard spherical mirror coincides with the focal point of the interferometer. First, the surface shape of the front surface A of the flat sample is detected to obtain the measurement result W1. Then, the flat sample is rotated 180° and the surface shape of its rear surface B is detected to obtain the measurement result W2.

[0015] Remove the flat sample and build the detection optical path of the interference cavity; align the center of the standard spherical mirror with the focal point of the interferometer to perform interference cavity detection and obtain the measurement result W3;

[0016] The plate sample is placed in the detection optical path to construct the transmission wavefront detection optical path for the plate sample. The transmission wavefront of the plate sample is measured to obtain the measurement result W. t .

[0017] In conjunction with the first aspect, in some implementations of the first aspect, the angle θ is 30° to 60°.

[0018] In conjunction with the first aspect, in some implementations of the first aspect, in the ray tracing model, the front surface shape data W of the flat plate sample... A for:

[0019]

[0020] In the ray tracing model, the back surface shape data W of the flat plate sample B for:

[0021]

[0022] Where d represents the distance from the measured surface of the plate sample to the focal point of interferometer 1, θ represents the normalized coordinates of the plate sample, and x and y represent the measurement results.

[0023] In conjunction with the first aspect, in some implementations of the first aspect, the material optical homogeneity distribution H of the flat sample is characterized by a Zernike polynomial. Z i (x,y) represents the i-th Zernike polynomial, A i represents the coefficients of the Zernike polynomial.

[0024] In conjunction with the first aspect, in certain implementations of the first aspect, the optical homogeneity distribution H of the material in the flat sample is solved iteratively, including:

[0025] Based on the material optical homogeneity distribution of the flat plate sample Calculated by the ray tracing model in Zemax Figure 2 (d) shows the transmitted wavefront of the flat sample under the optical path as W. m By changing polynomial coefficients A i To change the ray tracing model result W m When the ray tracing model result W m Transmission wavefront detection results of flat plate samples W t The loop iteration ends when the difference is less than the set value ε.

[0026] In conjunction with the first aspect, some implementations of the first aspect employ a parallel gradient descent algorithm while iteratively optimizing the coefficients; A i The iterative process satisfies:

[0027] A (n+1) (n+1,i)=A (n) (n,i)-α·δ(J)·δ(A)

[0028] δ(J)=STD(Wm(A (n) +δ(A))-Wt )-STD(Wm(A (n) -δ(A))-W t )

[0029] α is the iteration coefficient; δ(A) is the value of A. i The coefficients are random variables, which are random numbers between 0 and 1; STD represents the root mean square value of the wavefront data.

[0030] In conjunction with the first aspect, in some implementations of the first aspect, α takes the value of 0.1 to 0.2.

[0031] In conjunction with the first aspect, in certain implementations of the first aspect, the material optical homogeneity of the flat sample meets the requirements, including:

[0032] The absolute value of H is less than the first preset threshold;

[0033] Z4~Z 10 The absolute values ​​of all coefficients are less than the second preset threshold.

[0034] Compared with the prior art, the solution provided in this application has at least the following beneficial technical effects:

[0035] This invention employs non-collimated light interferometry to measure the optical homogeneity of infrared materials. It obtains the surface shape of the material under test through oblique incidence of non-collimated light, and then derives the mathematical expression for the material's optical homogeneity through iterative calculation. This solves the problems of difficulty in detecting the optical homogeneity of large-aperture infrared materials and reliance on large-aperture planar interferometers, and also resolves the coupling problem between material surface shape error and optical homogeneity when detecting optical homogeneity with non-collimated light. This invention is universally applicable to the homogeneity detection of flat plate materials with different apertures and wedge angles, and offers advantages such as high precision, simple detection optical path, and low detection cost in the detection of optical homogeneity of large-aperture infrared materials. Attached Figure Description

[0036] Figure 1 This is a flowchart of the method of the present invention.

[0037] Figure 2 This is a schematic diagram illustrating the implementation of the method of the present invention.

[0038] Figure 3 This is a schematic diagram of the calculation results of the material optical uniformity of the present invention. Detailed Implementation

[0039] The present application will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0040] like Figure 1 As shown, the present invention provides a method for detecting the optical uniformity of infrared materials based on model calculation.

[0041] Step 1: Build a uniformity testing platform for testing, including material front and back surface shape testing, transmitted wavefront testing, and interference cavity testing of the flat sample.

[0042] like Figure 2 As shown, the uniformity detection platform of this invention includes a spherical wave interferometer 1, a flat plate sample 2, and a standard spherical mirror 3. In the oblique incidence detection optical path of the flat plate sample surface shape, the light emitted by the spherical wave interferometer 1 is reflected by the surface of the flat plate sample 2 and then enters the standard spherical mirror 3. After being reflected by the standard spherical mirror 3, it enters the surface of the flat plate sample 2 again and returns to the spherical wave interferometer 1. In the detection optical path of the interference cavity, the center of the mirror 3 coincides with the focal point of the interferometer 1. In the transmission wavefront detection optical path of the flat plate sample 2, the light emitted by the spherical wave interferometer 1 passes through the flat plate sample 2 and enters the standard spherical mirror 3. After being reflected by the standard spherical mirror 3, it passes through the flat plate sample 2 again and returns to the spherical wave interferometer 1.

[0043] Step 1.1: Construct an oblique incidence optical path for surface shape detection of the flat sample 2, and perform surface shape detection on the front and rear surfaces of the material. Position the normal direction of the surface of the flat sample 2 at an angle θ (30°–60°) to the optical axis of the spherical wave interferometer 1, with the center of the sphere of the reflector 3 coinciding with the focal point of the interferometer 1. First, perform surface shape detection on the front surface A of the flat sample 2 to obtain measurement result W1; then rotate the flat sample 2 180° and perform surface shape detection on its rear surface B to obtain measurement result W2.

[0044] Step 1.2: Remove the flat plate sample 2 and construct the detection optical path for the interference cavity. Align the center of the reflector 3 with the focal point of the interferometer 1 to perform interference cavity detection and obtain the measurement result W3.

[0045] Step 1.3: Place the plate sample 2 in the detection optical path, construct the transmission wavefront detection optical path for the plate sample 2, measure the transmission wavefront of the plate sample 2, and obtain the measurement result W. t .

[0046] Step 2: Using Zemax software, establish a ray tracing model of the transmitted wavefront of the plate sample 2, such as... Figure 2 As shown in (d), simulations were performed based on the uniformity detection results.

[0047] In the ray tracing model, the front surface shape data W of plate sample 2 A for:

[0048]

[0049] In the ray tracing model, the rear surface shape data W of plate sample 2 B for:

[0050]

[0051] Where d represents the distance from the measured surface of the flat plate sample 2 to the focal point of the interferometer 1, and x and y represent the normalized coordinates of the measurement results.

[0052] Step 3, the optical homogeneity distribution H of the material in plate sample 2 is characterized using Zernike polynomials as follows:

[0053]

[0054] Z i (x,y) represents the i-th Zernike polynomial, A i The coefficients of the Zernike polynomials are represented, including astigmatism, coma, triceps, and spherical aberration terms.

[0055] Step 4: Based on the interference cavity detection results and the ray tracing model simulation results, determine the material optical homogeneity distribution of plate sample 2. Perform iterative solutions.

[0056] Based on the material optical homogeneity distribution of plate sample 2 Calculated by the ray tracing model in Zemax Figure 2 (d) The transmitted wavefront of the flat sample 2 under the optical path shown is W. m By changing polynomial coefficients A i To change the ray tracing model result W m When the ray tracing model result W m The transmission wavefront detection results of plate sample 2 W t The loop iteration ends when the difference is less than the set value ε.

[0057] The calculation process is as follows Figure 1 As shown. The expression for the optical homogeneity distribution of the material in plate sample 2... polynomial coefficients A i As variables in the iterative calculation. In one embodiment, a parallel gradient descent algorithm is used to iteratively optimize each coefficient simultaneously. A i The iterative process satisfies:

[0058] A (n+1) (n+1,i)=A (n) (n,i)-α·δ(J)·δ(A)

[0059] δ(J)=STD(Wm(A (n) +δ(A))-W t )-STD(Wm(A (n) -δ(A))-Wt )

[0060] Where α is the iteration coefficient, taking values ​​such as 0.1 to 0.2; δ(A) is the value of A. i The coefficients are random variables, which are random numbers between 0 and 1; STD represents the root mean square value of the wavefront data.

[0061] When the ray tracing model result W m The transmission wavefront detection results of plate sample 2 W t The iteration ends when the difference is less than the set value ε. The final calculated result of the material optical homogeneity of the flat plate sample 2 is H=h4Z4+h5Z5+h6Z6+h7Z7+h8Z8+h9Z9+h 10 Z 10 Z4 represents the defocus term, Z5 represents the 0° phase divergence term, Z6 represents the 90° phase divergence term, Z7 represents the coma term in the X direction, Z8 represents the coma term in the Y direction, Z9 represents the triceps term, and Z... 10 This indicates the difference in sphericity.

[0062] Material optical homogeneity distribution H in Z4~Z 10 The coefficient reflects the material optical homogeneity of plate sample 2. The material optical homogeneity of plate sample 2 meets the requirements, including: the absolute value of H is less than the first preset threshold; Z4~Z 10 The absolute values ​​of all coefficients are less than the second preset threshold.

[0063] In one embodiment, ε is 0.02, and the calculated result of the material optical homogeneity of the flat plate sample 2 is H = -2.57 × 10⁻⁶. -5 Z4 -8.29×10 -5 Z5+9.82×10 -5 Z6 -1.19×10 -5 Z7+1.79×10 -5 Z8-2.2×10 - 5 Z9 -2.76×10 -5 Z 10 Optical uniformity distribution such as Figure 3 As shown.

[0064] In summary, the solution provided by this invention overcomes the limitation of non-collimated light interferometry in obtaining the optical uniformity distribution of a flat plate sample with high precision. The method provided by this invention utilizes interferometry to detect the surface shape of the flat plate sample under oblique incidence of non-collimated light, and measures the optical uniformity of the flat plate sample under normal incidence of non-collimated light. Through ray tracing and parallel gradient descent iterative calculation methods, a mathematical expression for the optical uniformity of the flat plate sample is obtained.

[0065] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope defined in the claims of the present invention.

Claims

1. A method for detecting optical uniformity of an infrared material based on model calculation, characterized in that, The application relates to a method for detecting the material optical uniformity of a flat plate sample. The method comprises the following steps: A light tracing model for detecting the transmission wave front of the flat plate sample is established by using Zemax software, and simulation is carried out according to the uniformity detection result; The material optical uniformity distribution H of the flat plate sample is iteratively solved according to the interference cavity detection result and the simulation result of the light tracing model; The uniformity detection platform comprises a spherical wave interferometer, a flat plate sample and a standard spherical mirror; In the oblique incidence detection light path of the surface profile of the flat plate sample, the light emitted by the spherical wave interferometer is reflected by the surface of the flat plate sample, enters the standard spherical mirror, is reflected by the standard spherical mirror, again enters the surface of the flat plate sample and returns to the spherical wave interferometer; In the detection light path of the interference cavity, the spherical center of the mirror is coincident with the focal point of the interferometer; In the transmission wave front detection light path of the flat plate sample, the light emitted by the spherical wave interferometer passes through the flat plate sample, enters the standard spherical mirror, is reflected by the standard spherical mirror, again passes through the flat plate sample and returns to the spherical wave interferometer; The uniformity detection comprises the following steps: The flat plate sample is placed at an angle of theta between the normal direction of the surface of the flat plate sample and the optical axis direction of the spherical wave interferometer, the spherical center of the standard spherical mirror is coincident with the focal point of the interferometer, the front surface A of the flat plate sample is detected first to obtain a measurement result W1, the flat plate sample is turned over by 180 DEG, the back surface B of the flat plate sample is detected to obtain a measurement result W2; The flat plate sample is removed, the detection light path of the interference cavity is established, the spherical center of the standard spherical mirror is coincident with the focal point of the interferometer, the interference cavity is detected to obtain a measurement result W3; Place the flat plate sample in the detection light path, build the transmission wave front detection light path of the flat plate sample, measure the transmission wave front of the flat plate sample, and obtain the measurement result W t In the ray tracing model, the front surface topography data W of the flat sample is: A W = W0 + W1 + W2 + W3 + W4 + W5 + W6 + W7 + W8 + W9 + W10 In the ray tracing model, the back surface topography data W of the flat sample is: B W = W0 + W1 + W2 + W3 + W4 + W5 + W6 + W7 + W8 + W9 + W10 Wherein, d represents the distance from the measured surface of the flat plate sample to the focal point of the interferometer, theta represents the angle, x and y represent the normalized coordinates of the measurement result; The material optical uniformity distribution H of the flat panel sample is characterized by Zernike polynomials as where Z i (x,y) represents the i-th Zernike polynomial, A i represents the coefficients of each term of the Zernike polynomials; The material optical uniformity distribution H of the flat plate sample is iteratively solved, including the following steps: Based on the material optical homogeneity distribution of the flat plate sample The transmitted wavefront of the flat plate sample under the optical path is calculated using the ray tracing model in Zemax. m By changing polynomial coefficients A i To change the ray tracing model result W m When the ray tracing model result W m Transmission wavefront detection results of flat plate samples W t The loop iteration ends when the difference is less than the set value ε. The parallel gradient descent algorithm is adopted, and each coefficient is iteratively optimized; A i The iterative process satisfies: A (n+1) (n+1,i) = A (n) (n,i) - a - d(J) - d(A) δ(J) = STD(Wm(A (n) + δ(A)) - W t )- STD(Wm(A (n) - δ(A)) - W t ) a is the iteration coefficient; δ(A) is the A i a random variable of the coefficient, a random number between 0 and 1; STD represents the root mean square value of the wavefront data.

2. The method of claim 1, wherein, The angle theta is 30 DEG to 60 DEG.

3. The method of claim 1, wherein, The value of alpha is 0.1 to 0.

2.

4. The method of claim 1, wherein, The material optical uniformity of the flat plate sample meets the requirements, including the following steps: The absolute value of H is less than a first preset threshold value; The absolute value of H is less than a first preset threshold value; Z4~Z 10 the absolute values of the coefficients of the second preset threshold.

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