Method for obtaining internal stray radiation of an infrared optical system

Abstract

This invention provides a method for acquiring internal stray radiation from infrared optical systems. This method addresses the problem of calculating internal stray radiation energy during cold optics implementations of infrared optical systems. Compared to existing simulation methods, this method can rapidly calculate internal stray radiation from infrared systems. The primary source of internal stray radiation from infrared optical systems is spontaneous infrared radiation from the inner wall of the lens barrel, the lens frame, and the pressure ring. Based on radiation transmission theory, this invention establishes a corresponding model. By establishing a coordinate system for the inner wall of the lens barrel, the lens frame, and the pressure ring relative to the detector focal plane, a corresponding algorithm model is established to calculate internal stray radiation. This acquisition method provides rapid calculations and relatively accurate results.

Description

Technical Field

[0001] The present invention relates to the field of infrared photoelectric imaging, and in particular to a method for acquiring stray radiation inside an infrared optical system. Background Art

[0002] Since all objects other than absolute zero will generate spontaneous radiation in the infrared band, the optical-mechanical system itself will generate strong internal stray radiation, and the internal stray radiation will be received by the focal plane of the detector, which will reduce the signal-to-noise ratio of the instrument. In severe cases, the target signal may even be completely overwhelmed by the internal stray radiation. Therefore, it is necessary to analyze and calculate the internal stray radiation.

[0003] Existing methods for analyzing and testing internal stray radiation in infrared optical systems primarily rely on simulation analysis. These methods utilize computer software to model and analyze internal stray radiation. Software analysis methods are primarily based on Monte Carlo and ray tracing methods. While these methods offer relatively accurate simulation results, their accuracy is positively correlated with computer performance, simulation time, and modeling sophistication. Therefore, achieving accurate results requires detailed modeling of the infrared optical system and significant computational effort.

[0004] Based on this, the relevant fields urgently need a method for obtaining internal stray radiation with fast calculation and relatively accurate results to replace the simulation analysis method. Summary of the Invention

[0005] In order to solve the problem that when using existing simulation analysis methods to test and analyze the internal stray radiation of infrared optical systems, in order to obtain accurate results, it is necessary to finely model the infrared optical system and spend a lot of time on simulation calculations, the present invention proposes a method for obtaining the internal stray radiation of infrared optical systems.

[0006] The specific contents of the present invention are as follows:

[0007] A method for obtaining internal stray radiation of an infrared optical system, which has the following characteristics:

[0008] Step 1) establishing a radiation transmission model for the infrared optical system;

[0009] Step 2) determining the internal stray radiation sources of the radiation transfer model and the number of internal stray radiation sources M, M ≥ 1;

[0010] The types of internal stray radiation sources include the inner wall of the lens barrel, the lens frame and the pressure ring;

[0011] The inner wall of the lens barrel includes the inner wall of a cylindrical lens barrel and the inner wall of a conical lens barrel;

[0012] Step 3) establishing a coordinate system based on the relative positional relationship between the internal stray radiation source and the focal plane of the detector obtained in step 2), and calculating the radiation flux generated by each internal stray radiation source at the focal plane of the detector based on the coordinate data of the radiation source in its respective coordinate system.

[0013] Furthermore, in step 3), when the internal stray radiation source is the inner wall of the cylindrical lens barrel, the radiation flux acquisition process is:

[0014] Step 3.1.1) In the coordinate system of the radiation transfer model, take the center of the detector focal plane as the coordinate origin, and the Y axis of the coordinate system is parallel to the optical axis; the X axis of the coordinate system is parallel to the long direction of the detector focal plane, and the Z axis of the coordinate system is parallel to the wide direction of the detector focal plane;

[0015] Step 3.1.2) Take any infinitesimal element s on the inner wall of the cylindrical tube 21 , the coordinates are (x1, y1, z1); the radiation generated by the inner wall of the cylindrical tube is incident on a microelement s on the focal plane of the detector 11 superior;

[0016] Set the infinitesimal element s 11 and infinitesimal s 21 The areas of ds are 11 and ds 21 ;Micro element s 11 To infinitesimal s 21 The distance of the path is r1; the infinitesimal element s 11 With infinitesimal s 21 The angles between the surface normal direction and the path between the two are θ 11 and θ 21 ;

[0017] Step 3.1.3) In the infinitesimal element s 21 The circular section of the cylindrical lens barrel is intercepted at the position, and the circular section coincides with or is parallel to the xoz plane, and the infinitesimal element s 21 Located on the circular cross section;

[0018] s on the circumference of a circular cross section 21 The length of the arc formed by the vertex of the circular section is l1, and the coordinate origin is the projection point of the circular section to the infinitesimal element s on the inner wall of the lens barrel. 21 The distance is c1; the vertex of the circular section is the intersection of the circular section and the positive direction of the Z axis;

[0019] Step 3.1.4) Calculate the internal stray radiation flux P1 of the inner wall of the cylindrical lens barrel using the following formula based on the data obtained in steps 3.1.2) and 3.1.3);

[0020]

[0021]

[0022] in,

[0023] Where: 11 ,λ 12 They are the upper and lower limits of the spectral range in which the infrared optical system operates, respectively;

[0024] y 11 is the Y-axis coordinate value of the inner end of the cylindrical lens barrel;

[0025] y 12 is the Y-axis coordinate value of the inner wall end of the cylindrical lens barrel;

[0026] T1 is the temperature of the infrared optical system;

[0027] M1(λ1, T1) is the radiation flux density of a black body at wavelength λ1 and temperature T1;

[0028] ε 11 is the infinitesimal element s 11 Absorption rate, ε 21 is the infinitesimal element s 21 Absorption rate;

[0029] R1 is the radius of the cylindrical lens barrel, and a1 is the distance from the coordinate origin to the optical axis.

[0030] Furthermore, when the internal stray radiation source in step 3) is the inner wall of the conical lens barrel, the radiation flux acquisition process is:

[0031] Step 3.2.1) In the coordinate system of the radiation transfer model, the center of the detector focal plane is taken as the coordinate origin, the Y axis of the coordinate system is parallel to the optical axis, the X axis of the coordinate system is parallel to the length of the detector focal plane, and the Z axis of the coordinate system is parallel to the width of the detector focal plane;

[0032] Step 3.2.2) Take any infinitesimal element s on the inner wall of the conical tube 22 , the coordinates are marked as (x2, y2, z2), and the radiation generated by the inner wall of the conical tube is incident on a microelement s on the focal plane of the detector 12 superior;

[0033] Set the infinitesimal element s 12 and infinitesimal s 22 The areas of ds are 12 and ds 22 ;Micro element s 12 To infinitesimal s 22 The distance of the path is r2; the infinitesimal element s 12 With infinitesimal s 22 The angles between the surface normal direction and the path between the two are θ 12and θ 22 ;

[0034] Step 3.2.3) In the infinitesimal element s 22 The position plane intercepts the circular section of the conical lens barrel, which coincides with or is parallel to the xoz plane, and the infinitesimal element s 22 Located on the circular cross section;

[0035] s on a circular cross section 22 The length of the arc formed by the vertex of the circular section is l2, the maximum radius of the circular section of the conical lens barrel is R0, and the radius of the circular section of the conical lens barrel is R2, where R0≧R2;

[0036] The center of the circular cross section of the conical tube is O, and the inner wall of the conical tube has a microelement s. 22 The intersection of the normal and the axis is O1, the angle between the conical barrel surface and the optical axis is α, the distance from OO1 is d, and the infinitesimal element s 22 The distance from the origin to O1 is b, the distance from the origin to the optical axis is a1, the distance from the origin to O1 is e, and the distance from the origin to the projection point of the circular cross section of the conical lens barrel to the infinitesimal element s is 22 The distance is c2;

[0037] Step 3.2.4) Calculate the internal stray radiation flux P2 of the inner wall of the conical tube using the data obtained in steps 3.2.2) and 3.2.3) using the following formula;

[0038]

[0039] in,

[0040]

[0041] Where: 21 ,λ 22 They are the upper and lower limits of the spectral range in which the infrared optical system operates, respectively;

[0042] y 21 is the Y-axis coordinate value corresponding to the starting point of the inner wall of the conical barrel;

[0043] y 22 is the Y-axis coordinate value of the end of the inner wall of the conical tube;

[0044] T2 is the temperature of the infrared optical system;

[0045] M2(λ2, T2) is the radiation flux density of a black body at wavelength λ2 and temperature T2;

[0046] ε 12 and ε 22 are respectively the infinitesimal elements s 12 and infinitesimal s 22 absorption rate.

[0047] Furthermore, when the internal stray radiation source in step 3) is a mirror frame or a pressure ring, the process of obtaining the radiation flux is:

[0048] Step 3.3.1) In the coordinate system of the radiation transfer model, the center of the mirror frame or pressure ring is used as the coordinate origin. The Y axis of the coordinate system is parallel to the optical axis, the X axis is parallel to the length of the detector focal plane, and the Z axis is parallel to the width of the detector focal plane.

[0049] Step 3.3.2) Take the microelement s on the detector focal plane 13 , the coordinates are marked as (0, y 30 , z 30 ); Take any infinitesimal element s on the frame or the pressure ring 23 , the coordinates are marked as (x3, 0, z3);

[0050] Set the infinitesimal element s 13 and infinitesimal s 23 The areas of ds are 13 and ds 23 ;Micro element s 13 To infinitesimal s 23 The distance of the path is r3; the infinitesimal element s 13 With infinitesimal s 23 The angles between the surface normal direction and the path between the two are θ 13 and θ 23 ;Micro element s 13 and s 23 The absorption rates are ε 13 , ε 23 ;

[0051] Step 3.3.3) In the infinitesimal element s 23 The xoz surface cuts off the circular cross section of the frame or the pressing ring; the circular cross section coincides with the xoz surface, and the infinitesimal element s 23 Located on the circular cross section;

[0052] Step 3.3.4) Calculate the internal stray radiation flux P3 of the frame or pressure ring based on the data obtained in step 3.3.2) using the following formula;

[0053]

[0054]

[0055] in,

[0056]

[0057] Where: 31 ,λ32 They are the upper and lower limits of the spectral range in which the infrared optical system operates, respectively;

[0058] x 31 、x 32 is the coordinate value of the pressing ring or frame surface corresponding to the X axis;

[0059] z 31 、z 32 x 31 、x 32 The corresponding Z-axis coordinate value;

[0060] R l 、R S are the size radius of the circular cross-section of the frame or the pressing ring respectively;

[0061] T3 is the temperature of the infrared optical system;

[0062] M3(λ3, T3) is the radiation flux density of a black body at wavelength λ3 and temperature T3. The beneficial effects of the present invention are:

[0063] (1) The present invention proposes for the first time a method for calculating stray radiation inside an infrared optical system other than the simulation analysis method.

[0064] (2) The present invention classifies the structural components that mainly generate radiation in the optical system into corresponding types according to their different characteristics, which is convenient for scientific researchers to calculate.

[0065] (3) The present invention proposes a universal method for obtaining radiation flux based on the different types of structural components that generate radiation.

[0066] (4) The present invention proposes a universal acquisition method for the internal stray radiation of any infrared optical system, which greatly reduces the calculation process and calculation time and has high accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 Schematic diagram of the optical-mechanical structure of a medium-wave infrared spectrometer in an embodiment of the present invention;

[0068] Figure 2 is a coordinate relationship diagram for calculating internal stray radiation of a cylindrical lens barrel in an embodiment;

[0069] Figure 3 is a coordinate relationship diagram for calculating internal stray radiation of the conical lens barrel in the embodiment;

[0070] Figure 4 is a coordinate relationship diagram for calculating internal stray radiation of the lens frame and the pressure ring in the embodiment;

[0071] The reference numerals are as follows:

[0072] 1-first cylindrical lens barrel, 2-first pressure ring lens barrel, 3-second cylindrical lens barrel, 4-third cylindrical lens barrel, 5-second pressure ring lens barrel, 6-conical lens barrel, 7-fourth cylindrical lens barrel, 8-lens frame. DETAILED DESCRIPTION

[0073] The present invention will be described in detail below with reference to the embodiments:

[0074] This embodiment provides a method for obtaining internal stray radiation of an infrared optical system. Figure 1 Take the optical path multiplexing type medium-wave infrared grating spectrometer shown as an example.

[0075] The optical path multiplexing medium-wave infrared grating spectrometer includes a lens barrel, a lens frame, a pressure ring, and optical components installed inside the lens barrel. Since the internal stray radiation of the infrared optical system mainly comes from the spontaneous radiation of the structural components, it can be divided into cylindrical lens barrel type, conical lens barrel type, lens frame and pressure ring type according to the shape of the structural components. Figure 1 The optical path multiplexing type medium-wave infrared grating spectrometer shown can be specifically divided into:

[0076] Cylindrical lens barrel type: the first cylindrical lens barrel 1, the second cylindrical lens barrel 3, the third cylindrical lens barrel 4, and the fourth cylindrical lens barrel 7 are cylindrical in shape.

[0077] Conical lens barrel type: The conical lens barrel 6 has a conical shape.

[0078] Mirror frame and pressure ring type: the first pressure ring type lens barrel 2, the second pressure ring type lens barrel 5, and the mirror frame 8 are in the shape of a circular ring.

[0079] Step 1) Establish a radiation transmission model for the optical path multiplexing medium-wave infrared grating spectrometer.

[0080] Step 2) Determine the internal stray radiation sources of the radiation transfer model and the number of internal stray radiation sources M (M ≥ 1). The types of internal stray radiation sources include the inner wall of the lens barrel, the lens frame, and the pressure ring; the inner wall of the lens barrel is divided into a cylindrical inner wall of the lens barrel and a conical inner wall of the lens barrel.

[0081] Since the internal stray radiation of the infrared optical system is mainly contributed by the structural elements of the optical system, the internal stray radiation of the medium-wave infrared spectrometer in this example mainly comes from the first cylindrical lens barrel 1, the first pressure ring lens barrel 2, the second cylindrical lens barrel 3, the third cylindrical lens barrel 4, the second pressure ring lens barrel 5, the conical lens barrel 6, the fourth cylindrical lens barrel 7, and the lens frame 8.

[0082] Step 3) Establish a coordinate system based on the relative positional relationship between the internal stray radiation source and the focal plane of the detector obtained in step 2), and establish coordinate systems for the eight internal stray radiation sources, namely, the first cylindrical lens barrel 1, the second cylindrical lens barrel 3, the third cylindrical lens barrel 4, the fourth cylindrical lens barrel 7, the conical lens barrel 6, the first pressure ring lens barrel 2, the second pressure ring lens barrel 5, and the lens frame 8. Calculate the radiation flux generated by each internal stray radiation source at the focal plane of the detector based on the coordinate data of each internal stray radiation source in its respective coordinate system and the radiation transmission model.

[0083] According to the reciprocity theorem, the transmission of radiation energy between two Lambertian radiation sources follows the following formula:

[0084] P=N1 cosθ1dA1dΩ1=N2 cosθ2dA2dΩ2

[0085] Where: P is the radiation flux;

[0086] N is the radiation brightness of the microelement;

[0087] dA1 and dA2 are the areas of the two Lambertian radiation sources respectively;

[0088] dΩ1 and dΩ2 are the solid angles between the two surface sources;

[0089] θ1 and θ2 are the angles between the two surface source normals and the transmission direction;

[0090] By transforming the radiation energy transmission formula between two Lambertian radiation sources, we can derive the radiation flux P received by the detector focal plane at the optomechanical element as follows:

[0091]

[0092] Where: L1 is the radiation brightness of the optomechanical element;

[0093] dS1 is the area of the optomechanical element;

[0094] dS2 is the infinitesimal area of the detector focal plane;

[0095] ε1 and ε2 are the absorptivity of the detector focal plane and optomechanical components, respectively.

[0096] Step 3.1) When the internal stray radiation source in step 3) is the inner wall of the cylindrical lens barrel;

[0097] Calculate the internal stray radiation of the first cylindrical lens barrel 1, the second cylindrical lens barrel 3, the third cylindrical lens barrel 4, and the fourth cylindrical lens barrel 7. Taking the first cylindrical lens barrel 1 as an example, the coordinate system is as follows: Figure 2 shown.

[0098] Step 3.1.1) In the coordinate system of the radiation transfer model, the center of the detector focal plane is taken as the coordinate origin, the Y axis of the coordinate system is parallel to the optical axis, the X axis of the coordinate system is parallel to the length of the detector focal plane, and the Z axis of the coordinate system is parallel to the width of the detector focal plane;

[0099] Step 3.1.2) Take a microelement s on the inner wall of the cylindrical tube in the coordinate system 21 (x1, y1, z1); the radiation generated by the inner wall of the cylindrical tube is incident on the focal plane of the detector, a microelement s 11 Up, micro-yuan s 11 and infinitesimal s 21 The areas of ds are 11 and ds 21 ;Micro element s 11 To infinitesimal s 21 The distance of the path is r1; the infinitesimal element s 11 With infinitesimal s 21 The angles between the surface normal direction and the path between the two are θ 11 and θ 21 ;

[0100] Step 3.1.3) In the infinitesimal element s 21 The xoz surface cuts off the circular section of the cylindrical barrel, which coincides with or is parallel to the xoz surface, and the infinitesimal element s 21 Located on the circular cross section;

[0101] s on a circular cross section 21 The length of the arc formed by the vertex of the circular section is l1, and the coordinate origin is the projection point of the circular section to the infinitesimal element s on the inner wall of the lens barrel. 21 The distance is c1; the vertex of the circular section is the intersection of the circular section and the positive direction of the Z axis;

[0102] Step 3.1.4) Calculate the internal stray radiation flux P1 of the inner wall of the cylindrical lens barrel using the following formula based on the data obtained in steps 3.1.2) and 3.1.3);

[0103]

[0104]

[0105] in,

[0106] Where: 11 ,λ 12 They are the upper and lower limits of the spectral range in which the infrared optical system operates, respectively;

[0107] y 11 is the Y-axis coordinate value of the inner end of the cylindrical lens barrel;

[0108] y 12 is the Y-axis coordinate value of the inner wall end of the cylindrical lens barrel;

[0109] T1 is the temperature of the infrared optical system;

[0110] M1(λ1, T1) is the radiation flux density of a black body at wavelength λ1 and temperature T1;

[0111] ε 11 is the infinitesimal element s 11 Absorption rate, ε 21 is the infinitesimal element s 21 Absorption rate;

[0112] R1 is the radius of the cylindrical lens barrel, and a1 is the distance from the coordinate origin to the optical axis.

[0113] According to the calculation formula for the internal stray radiation of the inner wall of the cylindrical lens barrel provided in this embodiment, calculations are performed for the cases when T = 140K and T = 120K respectively. The corresponding radiation flux is calculated according to the calculation formula and finally converted into radiation illuminance. The calculation results of the internal stray radiation of the inner walls of the first cylindrical lens barrel 1, the second cylindrical lens barrel 3, the third cylindrical lens barrel 4 and the fourth cylindrical lens barrel 7 are shown in Table 1.

[0114] Step 3.2) Calculate the internal stray radiation of the inner wall of the conical lens barrel. In this embodiment, the conical lens barrel 6 is taken as an example. Figure 3 shown.

[0115] Step 3.2.1) In the coordinate system of the radiation transfer model, the center of the detector focal plane is taken as the coordinate origin, the Y axis of the coordinate system is parallel to the optical axis, the X axis of the coordinate system is parallel to the length of the detector focal plane, and the Z axis of the coordinate system is parallel to the width of the detector focal plane;

[0116] Step 3.2.2) Take a microelement s on the inner wall of the conical tube in the coordinate system 22 , then s 22 The coordinates are (x2, y2, z2), and the radiation generated by the inner wall of the conical tube is incident on the focal plane of the detector, a microelement s 12 Up, micro-yuan s 12 and infinitesimal s 22 The areas of ds are 12 and ds 22 ;Micro element s 12 To infinitesimal s 22 The distance of the path is r2; the infinitesimal element s 12 With infinitesimal s 22 The angles between the surface normal direction and the path between the two are θ 12 and θ 22 ;

[0117] The radiation flux density of the black body is M2, and the infinitesimal element s 12 and infinitesimal s 22 The absorption rates are ε 12 and ε 22 ,

[0118] Step 3.2.3) In the infinitesimal element s 22 The xoz surface intercepts the circular section of the conical lens barrel, and the circular section s 22 The length of the arc formed by the vertex of the circular section is l2, the radius of the circular section of the conical tube is R2, the maximum radius of the circular section of the conical tube is R0, the center of the circular section of the conical tube is O, and the infinitesimal element s of the inner wall of the conical tube is 22 The intersection point of the normal lines is O1, the angle between the conical barrel surface and the optical axis is α, the distance from O to O1 is d, and the infinitesimal element s 22 The distance from the origin to O1 is b, the distance from the origin to the optical axis is a1, the distance from the origin to O1 is e, and the distance from the origin to the projection point of the circular cross section of the conical lens barrel to the infinitesimal element s 22 The distance is c2;

[0119] Step 3.2.4) Calculate the internal stray radiation flux P2 of the inner wall of the conical tube using the data obtained in steps 3.2.2) and 3.2.3) using the following formula;

[0120]

[0121] in,

[0122]

[0123] Where: 21 ,λ 22 They are the upper and lower limits of the spectral range in which the infrared optical system operates, respectively;

[0124] y 21 is the Y-axis coordinate value corresponding to the starting point of the inner wall of the conical barrel;

[0125] y 22 is the Y-axis coordinate value of the end of the inner wall of the conical tube;

[0126] T2 is the temperature of the infrared optical system;

[0127] M2(λ2, T2) is the radiation flux density of a black body at wavelength λ2 and temperature T2.

[0128] According to the calculation formula for the internal stray radiation of the inner wall of the conical lens barrel provided in this embodiment, the conical lens barrel 6 is calculated respectively under the conditions of T = 140K and T = 120K. The corresponding radiation flux is calculated according to the calculation formula and finally converted into radiation illuminance. The calculation results of the internal stray radiation of the inner wall of the conical lens barrel 6 are shown in Table 1.

[0129] Step 3.3) Calculate the internal stray radiation of the lens frame and the pressure ring, that is, in this embodiment, calculate the internal stray radiation of the first pressure ring type lens barrel 2, the second pressure ring type lens barrel 5 and the lens frame type 8. Take the first pressure ring type lens barrel 2 as an example, as shown in FIG. Figure 4 shown.

[0130] Step 3.3.1) In the coordinate system of the radiation transfer model, the center of the mirror frame or pressure ring is used as the coordinate origin. The Y axis of the coordinate system is parallel to the optical axis. The X axis of the coordinate system is parallel to the length of the detector focal plane. The Z axis of the coordinate system is parallel to the width of the detector focal plane.

[0131] In step 3.3.2) coordinate system, take a microelement s on the focal plane of the detector 13 , then the coordinates of the infinitesimal element s1 are (0, y 30 , z 30 ), take a microelement s on the frame or pressure ring 23 , then the infinitesimal element s 23 The coordinates are (x3, 0, y3), the infinitesimal s 13 and infinitesimal s 23 The areas of ds are 13 and ds 23 .

[0132] micro-units 13 To infinitesimal s 23 The distance of the path is r3; the infinitesimal element s 13 With infinitesimal s 23 The angles between the surface normal direction and the path between the two are θ 13 and θ 23 ; The radiation flux density of the black body is M3, and the infinitesimal element s 13 and s 23 The absorption rates are ε 13 , ε 23 ;

[0133] Step 3.3.3) In the infinitesimal element s 23 The xoz surface cuts off the circular cross section of the frame or the pressing ring; the circular cross section coincides with or is parallel to the xoz surface, and the infinitesimal element s 23 Located on the circular cross section;

[0134] Step 3.3.4) Calculate the internal stray radiation flux P3 of the frame and the pressure ring based on the data obtained in step 3.3.2) using the following formula;

[0135]

[0136]

[0137] in,

[0138]

[0139] Where: 31 ,λ 32 They are the upper and lower limits of the spectral range in which the infrared optical system operates, respectively;

[0140] x 31 、x 32 is the coordinate value of the pressing ring or frame surface corresponding to the X axis;

[0141] z 31 、z 32 x 31 、x 32 The corresponding Z-axis coordinate value;

[0142] R l 、R S are the size and radius of the circular cross-section of the frame or the pressing ring respectively;

[0143] T3 is the temperature of the infrared optical system;

[0144] M3(λ3, T3) is the radiation flux density of a black body at wavelength λ3 and temperature T3.

[0145] In this embodiment, calculations are performed for the two cases of T = 140K and T = 120K respectively;

[0146] According to the calculation formula for the internal stray radiation of the lens frame and the pressure ring provided in this embodiment, the corresponding radiation flux is calculated according to the calculation formula and finally converted into radiation illuminance. The calculation results of the internal stray radiation of the first pressure ring type lens barrel 2, the second pressure ring type lens barrel 5 and the frame type 8 are shown in Table 1.

[0147] To verify the accuracy of the acquisition method provided in this embodiment, a simulation analysis method was simultaneously used to calculate the internal stray radiation of the optical path multiplexing medium-wave infrared grating spectrometer in this embodiment. The optical-mechanical structure of the optical path multiplexing medium-wave infrared grating spectrometer was modeled in TracePro simulation software, and its material and surface properties were defined. The first cylindrical lens barrel 1, the first pressure ring lens barrel 2, the second cylindrical lens barrel 3, the third cylindrical lens barrel 4, the second pressure ring lens barrel 5, the conical lens barrel 6, the third cylindrical lens barrel 4, and the frame 8 were set as gray-body light sources. The Monte Carlo method was then used to simulate and calculate the background radiation at T = 140K and T = 120K, respectively. The calculation results are shown in Table 1.

[0148] Table 1

[0149]

[0150]

[0151] Comparing the calculation results with the simulation results, it can be seen that the calculation values are basically consistent with the simulation values. Therefore, the method for obtaining internal stray radiation of an infrared optical system provided in this embodiment is correct and effective.

Claims

1. A method for acquiring internal stray radiation of an infrared optical system, characterized by: Step 1) establishing a radiation transmission model for the infrared optical system; Step 2) determining the internal stray radiation sources of the radiation transfer model and the number of internal stray radiation sources M, M ≥ 1; The types of internal stray radiation sources include the inner wall of the lens barrel, the lens frame and the pressure ring; The inner wall of the lens barrel includes the inner wall of a cylindrical lens barrel and the inner wall of a conical lens barrel; Step 3) establishing a coordinate system based on the relative positional relationship between the internal stray radiation source and the focal plane of the detector obtained in Step 2), and calculating the radiation flux generated by each internal stray radiation source at the focal plane of the detector based on the coordinate data of the radiation source in its respective coordinate system; According to the reciprocity theorem, the transmission of radiation energy between two Lambertian radiation sources follows the following formula: P=N1 cosθ1dA1dΩ1=N2 cosθ2dA2dΩ2 Where: P is the radiation flux; N1 is the radiant brightness of Lambertian body 1, N2 is the radiant brightness of Lambertian body 2; the radiant brightness of the microelement; dA1 and dA2 are the areas of the two Lambertian radiation sources respectively; dΩ1 and dΩ2 are the solid angles between the two surface sources; θ1 and θ2 are the angles between the two surface source normals and the transmission direction; By transforming the radiation energy transmission formula between two Lambertian radiation sources, we can derive the radiation flux P received by the detector focal plane at the optomechanical element as follows: Where: L1 is the radiation brightness of the optomechanical element; dS1 is the area of the optomechanical element; dS2 is the infinitesimal area of the detector focal plane; ε1 and ε2 are the absorptivity of the detector focal plane and optomechanical components, respectively; λ is the wavelength of the stray radiation inside the radiation source; T is the temperature of the radiation source; dλ is the differential of the wavelength; M is the blackbody radiation flux density; r is the distance of the radiation transmission path between the radiation source and the detector.

2. The method for acquiring internal stray radiation of an infrared optical system according to claim 1, characterized in that: In step 3), when the internal stray radiation source is the inner wall of the cylindrical lens barrel, the radiation flux acquisition process is: Step 3.1.1) In the coordinate system of the radiation transfer model, take the center of the detector focal plane as the coordinate origin, and the Y axis of the coordinate system is parallel to the optical axis; the X axis of the coordinate system is parallel to the long direction of the detector focal plane, and the Z axis of the coordinate system is parallel to the wide direction of the detector focal plane; Step 3.1.2) Take any infinitesimal element s on the inner wall of the cylindrical tube 21 , the coordinates are (x1, y1, z1); the radiation generated by the inner wall of the cylindrical tube is incident on a microelement s on the focal plane of the detector 11 superior; Set the infinitesimal element s 11 and microelement s 21 The areas of ds are 11 and ds 21 ;Micro element s 11 To infinitesimal s 21 The distance of the path is r1; the infinitesimal element s 11 With infinitesimal s 21 The angles between the surface normal direction and the path between the two are θ 11 and θ 21 ; Step 3.1.3) In the infinitesimal element s 21 The circular section of the cylindrical lens barrel is intercepted at the position, and the circular section coincides with or is parallel to the xoz plane, and the infinitesimal element s 21 Located on the circular cross section; s on the circumference of a circular cross section 21 The length of the arc formed by the vertex of the circular section is l1, and the coordinate origin is the projection point of the circular section to the infinitesimal element s on the inner wall of the lens barrel. 21 The distance is c1; the vertex of the circular section is the intersection of the circular section and the positive direction of the Z axis; Step 3.1.4) Calculate the internal stray radiation flux P1 of the inner wall of the cylindrical lens barrel using the following formula based on the data obtained in steps 3.1.2) and 3.1.3); in, Where: 11 ,λ 12 They are the upper and lower limits of the spectral range in which the infrared optical system operates, respectively; y 11 is the Y-axis coordinate value of the inner end of the cylindrical lens barrel; y 12 is the Y-axis coordinate value of the inner wall end of the cylindrical lens barrel; T1 is the temperature of the infrared optical system; M1(λ1, T1) is the radiation flux density of a black body at wavelength λ1 and temperature T1; ε 11 is the infinitesimal element s 11 Absorption rate, ε 21 is the infinitesimal element s 21 Absorption rate; l1 is the circumference of the circular cross section 21 The length of the arc enclosed by the vertices of the circular section; r1 is the infinitesimal element s 11 To infinitesimal s 21 The distance of the path; dl1 is the differential of the arc length l1; dy1 is the differential of the y coordinate in the length direction of the tube; ds 11 The area of the microelement s11 is ds11; dλ1 is the differential of the wavelength of the internal stray radiation of the inner wall of the cylindrical lens barrel; R1 is the radius of the cylindrical lens barrel, and a1 is the distance from the coordinate origin to the optical axis.

3. The method for acquiring internal stray radiation of an infrared optical system according to claim 1, characterized in that: When the internal stray radiation source in step 3) is the inner wall of the conical lens barrel, the radiation flux acquisition process is: Step 3.2.1) In the coordinate system of the radiation transfer model, the center of the detector focal plane is taken as the coordinate origin, the Y axis of the coordinate system is parallel to the optical axis, the X axis of the coordinate system is parallel to the length of the detector focal plane, and the Z axis of the coordinate system is parallel to the width of the detector focal plane; Step 3.2.2) Take any infinitesimal element s on the inner wall of the conical tube 22 , the coordinates are marked as (x2, y2, z2), and the radiation generated by the inner wall of the conical tube is incident on a microelement s on the focal plane of the detector 12 superior; Set the infinitesimal element s 12 and infinitesimal s 22 The areas of ds are 12 and ds 22 ;Micro element s 12 To infinitesimal s 22 The distance of the path is r2; the infinitesimal element s 12 With infinitesimal s 22 The angles between the surface normal direction and the path between the two are θ 12 and θ 22 ; Step 3.2.3) In the infinitesimal element s 22 The position plane intercepts the circular section of the conical lens barrel, which coincides with or is parallel to the xoz plane, and the infinitesimal element s 22 Located on the circular cross section; s on a circular cross section 22 The length of the arc formed by the vertex of the circular section is l2, the maximum radius of the circular section of the conical lens barrel is R0, and the radius of the circular section of the conical lens barrel is R2, where R0≧R2; Set the center of the circular cross section of the cone-shaped lens barrel as O, and the inner wall of the cone-shaped lens barrel as the infinitesimal element s. 22 The intersection point of the normal and the axis is O1, the angle between the conical barrel surface and the optical axis is α, the distance from O to O1 is d, and the infinitesimal element s 22 The distance from the origin to O1 is b, the distance from the origin to the optical axis is a1, the distance from the origin to O1 is e, and the distance from the origin to the projection point of the circular cross section of the conical lens barrel to the infinitesimal element s is 22 The distance is c2; Step 3.2.4) Calculate the internal stray radiation flux P2 of the inner wall of the conical tube using the data obtained in steps 3.2.2) and 3.2.3) using the following formula; in, Where: 21 ,λ 22 They are the upper and lower limits of the spectral range in which the infrared optical system operates, respectively; y 21 is the Y-axis coordinate value corresponding to the starting point of the inner wall of the conical barrel; y 22 is the Y-axis coordinate value of the end of the inner wall of the conical tube; T2 is the temperature of the infrared optical system; M2(λ2, T2) is the radiation flux density of a black body at wavelength λ2 and temperature T2; ε 12 and ε 22 are respectively the infinitesimal elements s 12 and microelement s 22 Absorption rate; l2 is the length of the arc formed by s22 and the vertex of the circular section; r2 is the distance from the infinitesimal element s12 to the infinitesimal element s22; d l2 is the differential of the arc length formed by s22 and the vertex of the circular section; dy2 is the differential of the y coordinate in the length direction of the lens barrel; ds 12 The area of the infinitesimal element s12 is ds12; dλ2 is the differential of the wavelength of the internal stray radiation on the inner wall of the conical barrel.

4. The method for acquiring internal stray radiation of an infrared optical system according to claim 1, wherein: When the internal stray radiation source in step 3) is the mirror frame or the pressure ring, the radiation flux acquisition process is as follows: Step 3.3.1) In the coordinate system of the radiation transfer model, the center of the mirror frame or pressure ring is used as the coordinate origin. The Y axis of the coordinate system is parallel to the optical axis, the X axis is parallel to the length of the detector focal plane, and the Z axis is parallel to the width of the detector focal plane. Step 3.3.2) Take the microelement s on the detector focal plane 13 , the coordinates are marked as (0, y 30 , z 30 ); Take any infinitesimal element s on the frame or the pressure ring 23 , the coordinates are marked as (x3, 0, z3); Set the infinitesimal element s 13 and infinitesimal s 23 The areas of ds are 13 and ds 23 ;Micro element s 13 To infinitesimal s 23 The distance of the path is r3; the infinitesimal element s 13 With infinitesimal s 23 The angles between the surface normal direction and the path between the two are θ 13 and θ 23 ;Micro element s 13 and s 23 The absorption rates are ε 13 , ε 23 ; Step 3.3.3) In the infinitesimal element s 23 The xoz surface cuts off the circular cross section of the frame or the pressing ring; the circular cross section coincides with the xoz surface, and the infinitesimal element s 23 Located on the circular cross section; Step 3.3.4) Calculate the internal stray radiation flux P3 of the frame or pressure ring based on the data obtained in step 3.3.2) using the following formula; in, Where: 31 ,λ 32 They are the upper and lower limits of the spectral range in which the infrared optical system operates, respectively; x 31 、x 32 is the coordinate value of the pressing ring or frame surface corresponding to the X axis; z 31 、z 32 x 31 、x 32 The corresponding Z-axis coordinate value; R l 、R S are the size radius of the circular cross-section of the frame or the pressing ring respectively; T3 is the temperature of the infrared optical system; M3(λ3, T3) is the radiation flux density of a black body at wavelength λ3 and temperature T3; r3 is the infinitesimal element s 13 To infinitesimal s 23 The distance of the path; dz3 is the infinitesimal s 23 Differential of the z coordinate; ds 13 is the infinitesimal element s 13 The area of the lens frame; dλ3 is the differential of the wavelength of the internal stray radiation of the lens frame or pressure ring.

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