Low-stress non-adhesive elastic supporting structure of profound hypothermia lens

Abstract

A low-stress non-adhesive elastic supporting structure for a profound hypothermia lens comprises a lens frame, a pre-tightening spring, a rubber mat, an adjusting gasket, a bottom plate and an elastic pressing plate. The pre-tightening springs are installed on the inner side of the mirror frame and evenly distributed in the circumferential direction, and adjusting gaskets are arranged between the pre-tightening springs and the mirror frame. The rubber mat is trimmed into a required shape and is adhered to the contact surface of the pre-tightening spring and the lens, meanwhile, the rubber mat is also adhered to the bottom plate for axially supporting the lens, and the bottom plate is mounted on the lens frame after curing; the lens is arranged on the lens frame, is supported by the bottom plate and is compressed and fixed through the pre-tightening spring in the radial direction; the elastic pressing plate is installed on the lens frame to achieve axial positioning of the lens in the lens frame. Positioning of the lens in the lens frame is achieved through pretightening force provided by preloading deformation of the low-rigidity elastic unit, the gravity of ground adjustment testing and acceleration overload force in the launching process are overcome, thermal stress unloading introduced by thermal deformation difference is achieved through rigidity design of the elastic unit, and the surface shape precision of the lens at the low temperature is guaranteed.

Description

Technical Field

[0001] The invention relates to a low-stress, non-adhesive elastic supporting structure for a deep cryogenic lens, and belongs to the technical field of cryogenic optics. Background Art

[0002] With the development of space infrared remote sensors, their spectrum covers from near infrared (about 1μm) to far infrared (about 240μm), and even submillimeter spectrum (670μm). However, since the development of infrared detection devices has approached or reached the background limit detection, the detection sensitivity and dynamic range of infrared remote sensors are mainly limited by the size of the radiation noise in the observation background. Even after good external stray light suppression, its detection ability is greatly affected because the internal radiation of the optical lens components has become the main source of background radiation noise. Therefore, in order to reduce the internal thermal radiation of the system, reduce the background noise of the infrared detector, and effectively improve the detection sensitivity and spatial resolution of the infrared remote sensor, a low-temperature optical system for cooling the lens must be used.

[0003] When the cryogenic optical system is converted from room temperature (manufacturing, assembly, and adjustment) to cryogenic working temperature, for transmission-type infrared remote sensors, there is generally a large difference in the coefficient of thermal expansion (CTE) of the lens and the supporting structure. The different coefficients of thermal expansion (CTE) between different materials cause structural distortion and deformation, affecting the positioning and surface accuracy of the optical components, resulting in image quality degradation, or even damage to the optical components. Therefore, in addition to meeting the high rigidity requirements, the design of the transmission-type cryogenic lens support structure also needs to consider the thermal effects of the lens in the low-temperature environment on orbit. How to meet the mechanical and thermal properties of the cryogenic lens is the focus of the support structure design, especially when the operating temperature is reduced by about 100K, the adhesive properties of the lens and the supporting structure need to be considered.

[0004] The commonly used transmission type cryogenic lens support solution relies on radial flexible structure to unload excess stress, and is bonded with bonding technology. The design of cryogenic lenses at home and abroad adopts similar design concepts, that is, reasonable design and adjustment to meet the mechanical and thermal performance of cryogenic lenses at the same time. However, for materials with poor surface hardness (such as ZnSe), micro-damage is easy to be left on the surface after optical processing. The maximum allowable working stress at the micro-damage is difficult to estimate. When bonded with low temperature glue, the bonding surface is easily subjected to stress and stress concentration occurs at the micro-damage, resulting in damage. The preload force provided by the preload deformation of the low-rigidity elastic unit is now used to achieve the positioning of the lens in the frame, replacing the adhesive positioning, and overcoming the gravity and acceleration overload force of the launch process during the ground assembly and adjustment test.

[0005] The Near Infrared Spectrometer and Photometer (NISP) of ESA's Euclid space telescope uses a flexible cantilever support structure using bonding technology. However, the resulting bonding stress seriously damaged the surface level of the lens and caused partial cracks in the lens.

[0006] An infrared low-temperature lens structure released by Chinese invention patent CN105005132B can only solve the support of low-temperature lenses at a temperature of about 273K. It is fixed by gluing and the thermal deformation difference between the lens and the supporting structure is compensated by designing the thickness of the glue. However, the design of the glue thickness has certain limitations. When the glue is too thick, the strength will deteriorate and the lens will not be able to play a positioning role. Therefore, it is only suitable for the case where the thermal deformation difference between the lens and the structure is small, and it is not applicable to the lens support with a temperature difference of more than 20K.

[0007] A dual-material infrared low-temperature lens structure released by China's invention patent CN116107053A adopts a combination of a low-rigidity structure and a thermal matching structure to achieve thermal deformation compensation for a temperature difference of 150K. However, it still needs to be fixed by gluing. At an operating temperature of around 100K, it poses a high processing difficulty for materials with poor surface hardness such as ZnSe. There is a risk of breakage due to stress concentration at micro-damages caused by stress on the bonding surface at low temperatures. Summary of the invention

[0008] The technical problem solved by the present invention is: to overcome the shortcomings of the existing technology and provide a low-stress, adhesive-free elastic support structure for deep-cryogenic lenses, to solve the support and positioning of transmission lenses in low-temperature environments, and to be used for low-stress support and positioning of brittle lens materials in deep-cryogenic environments.

[0009] The technical solution adopted by the present invention is:

[0010] A low-stress, non-adhesive elastic support structure for a deep cryogenic lens, comprising: a lens frame, a preload spring, a rubber pad, an adjustment pad, a bottom plate and an elastic pressure plate;

[0011] The lens frame is used to install the lens and provide an external interface. The preload spring is installed inside the lens frame and evenly distributed along the circumference. An adjustment gasket is provided between the preload spring and the lens frame.

[0012] The rubber pad is trimmed into a desired shape and glued to the contact surface between the preload spring and the lens. At the same time, the rubber pad is also glued to the bottom plate used for axially supporting the lens. After curing, the bottom plate is installed on the frame.

[0013] The lens is placed in the frame, supported by the bottom plate, and radially compressed and fixed by a preloaded spring; an elastic pressure plate is installed on the frame to realize axial positioning of the lens in the frame.

[0014] Furthermore, the preload spring is used to fix the lens and achieve radial thermal stress unloading.

[0015] Furthermore, the elastic pressure plate is used to fix the lens to achieve axial thermal stress unloading.

[0016] Furthermore, by adjusting the thickness of the adjusting gasket, the radial preload force provided by the preload spring is adjusted.

[0017] Furthermore, before installing the adjustment gasket, the rubber pad has been glued to the contact surface between the preload spring and the lens. By measuring the distance between the rubber pad and the axis of the frame fitting, the thickness of the adjustment gasket that needs to be installed between the preload spring and the frame is calculated, and the adjustment gaskets and adjustment springs of different thicknesses are installed on the lens frame one by one.

[0018] Furthermore, the process of placing the lens in the frame is as follows:

[0019] Fix the mirror frame with the adjustment gasket, adjustment spring and bottom plate installed on the support base, use the adjustment table to pull the adjustment spring outwards and fix the position;

[0020] Put the lens into the frame, place it on the bottom plate, and use a feeler gauge to adjust the distance between the positioning boss in the frame and the outer circle of the lens to ensure that the lens is placed in the center;

[0021] Slowly loosen the adjustment stages one by one to make the adjustment springs compressed around the lens;

[0022] After installing the lens and the adjustment spring, install the elastic pressure plate on the lens frame to ensure the axial positioning of the lens in the lens frame.

[0023] Furthermore, the force on each adjustment spring mounting point on the lens is F n :

[0024] F n =k[ξ+δcos(n*φ)]

[0025] Where k is the spring stiffness, ξ is the initial compression of the spring when it is installed, δ is the displacement of the lens under the action of gravity or overload, φ is the installation angle between two adjacent springs, and n is the number of the spring, n = 1, 2, 3...N, N is the number of springs.

[0026] Furthermore, for a lens with a mass of m, n uniformly distributed springs are used for radial support. When the friction between the spring and the lens is not considered, the resultant force of the radial support and the force on the lens are in a state of equilibrium, that is,

[0027] During the ground installation test, g is the acceleration due to gravity;

[0028] In the transmitting state, F overload Indicates the overload force that the lens is subjected to during launch.

[0029] Furthermore, the minimum value of the spring stiffness k min Calculated as follows:

[0030]

[0031] The δ value is selected according to the lens eccentricity tolerance.

[0032] Furthermore, in the mechanical test simulating the launch process, it is necessary to consider the static overload force to ensure that the lens and the spring always maintain contact. At this time, δ≤ξ, and the minimum preload force provided by the spring during the launch overload is:

[0033]

[0034] Furthermore, the spring adopts a beam structure with fixed ends, and the spring stiffness k is calculated by the following formula:

[0035]

[0036] Where E is the elastic modulus of the material, h is the thickness of the beam unit section, b is the width of the beam unit section, L is the length of the beam unit, and C is the correction coefficient;

[0037] When selecting spring materials, the spring stiffness k ≥ k calculated according to the above formula min .

[0038] The advantages of the present invention compared with the prior art are:

[0039] (1) The present invention uses the preload force provided by the preload deformation of the low-rigidity elastic unit to realize the positioning of the lens in the frame, overcome the gravity in the ground adjustment test and the acceleration overload force in the launch process, and realize the unloading of the thermal stress introduced by the thermal deformation difference by designing the stiffness of the elastic unit, thereby ensuring the surface accuracy of the lens at low temperatures.

[0040] (2) The present invention uses spring preload support to achieve glue-free lens support, thereby avoiding the risk of lens breakage due to excessive bonding stress.

[0041] (3) The present invention is applicable to supporting lenses with large temperature differences below 150K.

[0042] (4) The present invention is applicable to low-temperature support of lens materials with poor surface hardness. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a diagram of a low-stress, non-adhesive elastic support structure component of a deep cryogenic lens of the present invention;

[0044] Figure 2 This is a schematic diagram of the thick support structure for adding a bottom plate;

[0045] Figure 3 It is a schematic diagram of the radial force state of the lens of the present invention;

[0046] Figure 4 It is a schematic diagram of the relative positions of the preload spring and the rubber pad of the present invention;

[0047] Figure 5 This is a schematic diagram of the relative positions of the bottom plate and the rubber pad of the present invention;

[0048] Figure 6 is a schematic diagram of an elastic pressure plate; DETAILED DESCRIPTION

[0049] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0050] like Figure 1 and Figure 2 As shown, the present invention proposes a low-stress, non-adhesive elastic support structure for a deep cryogenic lens, comprising: a lens frame 1, a preload spring 2, a rubber pad 3, an adjustment gasket 4, a bottom plate 5 and an elastic pressure plate 6;

[0051] The lens frame 1 is used to install the lens and provide an external interface. The preload spring 2 is installed inside the lens frame 1 and is evenly distributed along the circumference. An adjustment gasket 4 is provided between the preload spring 2 and the lens frame 1.

[0052] like Figure 4 As shown, the rubber pad 3 is trimmed into a desired shape and glued to the contact surface between the preload spring 2 and the lens. At the same time, the rubber pad 3 is also glued to the bottom plate 5 for axially supporting the lens. After curing, the bottom plate 5 is installed on the frame 1. Figure 4 and Figure 5 As shown;

[0053] The lens is placed in the frame 1, supported by the bottom plate, and radially compressed and fixed by the preload spring 2; the elastic pressure plate 6 is installed on the frame 1 to realize the axial positioning of the lens in the frame, such as Figure 6 shown.

[0054] The preload spring is used to fix the lens and unload the radial thermal stress. The elastic pressure plate is used to fix the lens and unload the axial thermal stress. The radial preload force provided by the preload spring 2 is adjusted by adjusting the thickness of the adjusting gasket 4. Figure 3 Shown is a schematic diagram of the radial force state of the lens of the present invention.

[0055] Before installing the adjustment gasket 4, the rubber pad 3 has been glued to the contact surface of the preload spring 2 and the lens. By measuring the distance between the rubber pad and the axis of the frame fitting, the thickness of the adjustment gasket that needs to be installed between the preload spring and the frame is calculated, and the adjustment gaskets and adjustment springs of different thicknesses are installed on the lens frame one by one.

[0056] The process of placing the lens in the frame is as follows: fix the frame with the adjustment gasket, adjustment spring and bottom plate installed on the support base, use the adjustment table to pull the adjustment spring outward and fix the position;

[0057] Put the lens into the frame, place it on the bottom plate, and use a feeler gauge to adjust the distance between the positioning boss in the frame and the outer circle of the lens to ensure that the lens is placed in the center;

[0058] Slowly loosen the adjustment stages one by one to make the adjustment springs compressed around the lens;

[0059] After installing the lens and the adjustment spring, install the elastic pressure plate on the lens frame to ensure the axial positioning of the lens in the lens frame.

[0060] The force on each adjustment spring installation point on the lens is F n :

[0061] F n =k[ξ+δcos(n*φ)]

[0062] Where k is the spring stiffness, ξ is the initial compression of the spring when it is installed, δ is the displacement of the lens under the action of gravity or overload, φ is the installation angle between two adjacent springs, and n is the number of the spring, n = 1, 2, 3...N, N is the number of springs.

[0063] For a lens with a mass of m, n uniformly distributed springs are used for radial support. When the friction between the spring and the lens is not considered, the resultant force of the radial support and the force on the lens are in equilibrium, that is,

[0064] During the ground installation test, g is the acceleration due to gravity;

[0065] In the transmitting state, F overload Indicates the overload force that the lens is subjected to during launch.

[0066] Minimum spring stiffness k min Calculated as follows:

[0067]

[0068] The δ value is selected according to the lens eccentricity tolerance.

[0069] The present invention ensures that the lens and the spring always maintain contact under the action of static overload, and can provide a minimum preload force when the launch overload occurs. The preload force value must meet the mechanical resistance performance while ensuring the lens surface accuracy.

[0070] The mechanical test simulating the launch process needs to consider the static overload force to ensure that the lens and the spring are always in contact. At this time, δ≤ξ, and the minimum preload force provided by the spring during the launch overload is:

[0071]

[0072] The spring adopts a beam structure with fixed ends, and the spring stiffness k is calculated by the following formula:

[0073]

[0074] Where E is the elastic modulus of the material, h is the thickness of the beam unit section, b is the width of the beam unit section, L is the length of the beam unit, and C is the correction coefficient;

[0075] When selecting spring materials, the spring stiffness k ≥ k calculated according to the above formula min .

[0076] Example:

[0077] The elastic support structure of the present invention is assembled in the following order:

[0078] 1. Trim the rubber pad into the required shape and glue it to the contact surface between the spring and the lens;

[0079] 2. Install the spring on the frame, measure the distance between the rubber pad and the axis of the frame using three-dimensional coordinates, and calculate the thickness of the adjustment gasket between the spring and the frame based on the size. Install the gaskets and spring assemblies of different thicknesses on the lens frame one by one;

[0080] 3. Glue the rubber pad to the base plate, and install the base plate to the lens frame after curing;

[0081] 4. Fix the frame with the gasket, spring and bottom plate installed on the support base, use the adjustment table to pull the spring outward and fix the position; gently put the lens into the frame and place it on the bottom plate, use the feeler gauge to adjust the distance between the positioning boss in the frame and the outer circle of the lens to ensure that the lens is placed in the center; then slowly loosen the adjustment table in turn, so that the spring is in a compressed state around the lens;

[0082] 5. After installing the lens and spring, install the elastic pressure plate on the frame to ensure the axial positioning of the lens in the frame.

[0083] Parts of the present invention that are not described in detail belong to common knowledge among those skilled in the art.

Claims

1. A low-stress, non-adhesive elastic support structure for a deep cryogenic lens, characterized in that include: Mirror frame (1), preload spring (2), rubber pad (3), adjustment pad (4), bottom plate (5) and elastic pressure plate (6); The lens frame (1) is used to install the lens and provide an external interface. The preload spring (2) is installed inside the lens frame (1) and is evenly distributed along the circumference. An adjustment gasket (4) is provided between the preload spring (2) and the lens frame (1). The rubber pad (3) is trimmed into a desired shape and glued to the contact surface between the preload spring (2) and the lens. At the same time, the rubber pad (3) is also glued to the bottom plate (5) used for axially supporting the lens. After curing, the bottom plate (5) is installed on the lens frame (1); The lens is placed in the lens frame (1), supported by a bottom plate, and radially compressed and fixed by a preload spring (2); an elastic pressure plate (6) is installed on the lens frame (1) to realize axial positioning of the lens in the lens frame.

2. The low-stress, non-adhesive elastic support structure for a deep cryogenic lens according to claim 1, characterized in that: The preload spring is used to fix the lens and achieve radial thermal stress unloading.

3. The low-stress, non-adhesive elastic support structure for a deep cryogenic lens according to claim 1, characterized in that: The elastic pressure plate is used to fix the lens to achieve axial thermal stress unloading.

4. The low-stress, non-adhesive elastic support structure for a deep cryogenic lens according to claim 1, characterized in that: The radial preload force provided by the preload spring (2) is adjusted by adjusting the thickness of the adjusting gasket (4).

5. The low-stress, non-adhesive elastic support structure for a deep cryogenic lens according to claim 4, characterized in that: Before installing the adjustment gasket (4), the rubber pad (3) has been glued to the contact surface between the preload spring (2) and the lens. By measuring the distance between the rubber pad and the axis of the frame, the thickness of the adjustment gasket to be installed between the preload spring and the frame is calculated, and the adjustment gaskets and adjustment springs of different thicknesses are installed on the lens frame one by one.

6. The low-stress, non-adhesive elastic support structure for a deep cryogenic lens according to claim 1, characterized in that: The process of placing the lens in the frame is as follows: Fix the mirror frame with the adjustment gasket, adjustment spring and bottom plate installed on the support base, use the adjustment table to pull the adjustment spring outwards and fix the position; Put the lens into the frame, place it on the bottom plate, and use a feeler gauge to adjust the distance between the positioning boss in the frame and the outer circle of the lens to ensure that the lens is placed in the center; Slowly loosen the adjustment stages one by one to make the adjustment springs compressed around the lens; After installing the lens and the adjustment spring, install the elastic pressure plate on the lens frame to ensure the axial positioning of the lens in the lens frame.

7. The low-stress, non-adhesive elastic support structure for a deep cryogenic lens according to claim 1, characterized in that: The force on each adjustment spring installation point on the lens is F n : F n =k[ξ+δcos(n*φ)] Where k is the spring stiffness, ξ is the initial compression of the spring when it is installed, δ is the displacement of the lens under the action of gravity or overload, φ is the installation angle between two adjacent springs, and n is the number of the spring, n = 1, 2, 3...N, N is the number of springs.

8. The low-stress, non-adhesive elastic support structure for a deep cryogenic lens according to claim 7, characterized in that: For a lens with a mass of m, n uniformly distributed springs are used for radial support. When the friction between the spring and the lens is not considered, the resultant force of the radial support and the force on the lens are in equilibrium, that is, During the ground installation test, g is the acceleration due to gravity; In the transmitting state, F overload Indicates the overload force that the lens is subjected to during launch.

9. The low-stress, non-adhesive elastic support structure for a deep cryogenic lens according to claim 7, characterized in that: Minimum spring stiffness k min Calculated as follows: The δ value is selected according to the lens eccentricity tolerance.

10. The low-stress, non-adhesive elastic support structure for a deep cryogenic lens according to claim 9, characterized in that: The mechanical test simulating the launch process needs to consider the static overload force to ensure that the lens and the spring are always in contact. At this time, δ≤ξ, and the minimum preload force provided by the spring during the launch overload is:

11. The low-stress, non-adhesive elastic support structure for a deep cryogenic lens according to claim 9, characterized in that: The spring adopts a beam structure with fixed ends, and the spring stiffness k is calculated by the following formula: Where E is the elastic modulus of the material, h is the thickness of the beam unit section, b is the width of the beam unit section, L is the length of the beam unit, and C is the correction coefficient; When selecting spring materials, the spring stiffness k ≥ k calculated according to the above formula min .

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