Infrared target simulator with rapid refrigeration and self-temperature control and refrigeration method thereof

Abstract

The application provides a quick refrigeration and self-temperature-control infrared target simulator and a refrigeration method thereof, and is used for solving the essential conflict between a traditional low-temperature refrigeration scheme and a dynamic and accurate temperature control infrared target simulator, and the technical problems of low refrigeration efficiency, poor energy utilization rate, asynchronous refrigeration, and possible complete loss of precise mechanical performance and optical performance of the whole optical system due to heat management failure. The quick refrigeration and self-temperature-control infrared target simulator adopts a collaborative design of a distributed cold source and a multi-branch flexible cold chain based on heat capacity matching, and multiple cold sources are reasonably arranged to avoid single-point supercooling and cooling blind area, so that the problems of asynchronous refrigeration and thermal stress of the infrared target simulator caused by heat inertia difference are fundamentally solved, the dynamic refrigeration synchronism of different heat inertia components is ensured, and the generation of thermal stress is effectively inhibited.

Description

Technical Field

[0001] This invention relates to an infrared target simulator and its cooling method, and more particularly to an infrared target simulator with rapid cooling and self-temperature control and its cooling method. Background Technology

[0002] With the development of infrared detection technology, cryogenic optics has become a major technical means to reduce background noise and improve infrared detection capabilities. Traditional cryogenic cooling solutions mainly include mechanical cooling and liquid nitrogen storage cooling, which have formed relatively mature solutions for dealing with traditional miniaturized, lightweight, and static or micro-moving (millimeter-level stroke) optical components. The core design concept of mechanical cooling and liquid nitrogen storage cooling can be summarized as follows: by using a point cold source (a single small cold source) or a static surface cold source (the wall of the liquid nitrogen tank), supplemented by simple temperature homogenization measures, such as graphite film, effective and uniform cooling and temperature control of the target can be achieved. However, when the target to be cooled is upgraded to a large-size (>1.8m), large-mass (≥50kg) optical system with integrated large-stroke moving parts, existing cryogenic cooling technologies will expose a series of fundamental and irreconcilable contradictions and performance bottlenecks, making them completely unable to meet application requirements.

[0003] Currently, infrared target simulators are widely used large-size, high-mass optical systems with integrated long-stroke moving parts. They are mainly used for testing the extreme detection capabilities and sensitivity of infrared systems. However, traditional cryogenic cooling solutions for infrared target simulators typically have the following problems:

[0004] (i) Mechanical refrigeration presents a contradiction between point cold sources and large-size, large-mass refrigeration targets.

[0005] The cooling capacity of a single small cold source is woefully inadequate for a cooling target exceeding 50kg. Even more serious is the fact that the enormous size makes the transfer of cooling energy from the point cold source to the distant end extremely difficult, resulting in a huge temperature gradient of tens of Kelvin (e.g., >20K). At this point, traditional temperature homogenization methods such as surface-mounted graphite films are negligible, the cooling dead zone is drastically amplified, and optical components experience deformation and stress due to temperature unevenness, failing to meet the ±1K or even higher temperature uniformity requirements typically required for precision optical systems.

[0006] (ii) There is a contradiction between static refrigeration and the dynamic control requirements of refrigeration target in storage-type liquid nitrogen refrigeration.

[0007] Storage-type liquid nitrogen refrigeration is essentially a passive, slow, and imprecisely controllable process. Its cooling rate relies entirely on natural heat conduction and radiation, resulting in an extremely slow cooling speed that cannot meet the urgent need for rapid cooling. For example, the literature (Shen Mangzuo, Ma Wenli, Liao Sheng, et al. Development of a low-temperature optical system [J]. Acta Optica Sinica, 2001, (02): 202-205.) discloses a low-temperature optical system that takes about 9 hours to cool an optical system weighing only 2.5 kg to a stable state. The literature (Xu Bing, Ma Long, Li Xiaoman. Development of an infrared background simulator for a low-temperature vacuum environment [J]. Spacecraft Environmental Engineering, 2012, 29 (04): 430-436.) discloses an infrared background simulator for a low-temperature vacuum environment that takes about 16 hours to cool a 600 mm × 600 mm × 3 mm cold aperture from its initial temperature to 90 K. Therefore, it can be deduced that the time required to cool a target weighing 50 kg is far from meeting the need for rapid cooling.

[0008] Furthermore, the cooling temperature and operating mode of storage-type liquid nitrogen refrigeration cannot be adjusted in real time and flexibly according to actual needs. Once the system starts cooling, it continuously consumes liquid nitrogen at a near-fixed power level, without being able to pause or reduce the power. When moving parts suddenly begin to move, the liquid nitrogen cannot offset this sudden increase in heat load by accelerating or increasing power, leading to a runaway rise in system temperature. This open-loop, uncontrollable cooling characteristic is completely contrary to the dynamic control requirements of real-time thermal management and precise temperature control.

[0009] (iii) Uneven heat capacity in the cooling area leads to asynchronous cooling.

[0010] The infrared target simulator has a complex internal structure, with significant differences in heat capacity across different regions due to variations in structure, mass, and materials. These differences in heat capacity result in varying thermal inertia during the cooling process. When a uniform cold source is applied, regions with high heat capacity cool down slowly, while regions with low heat capacity cool down quickly. This dynamically asynchronous cooling process prolongs the overall system stabilization time and generates significant thermal stress within the infrared target simulator during cooling, potentially leading to device deformation or damage. Furthermore, asynchronous cooling results in temperature unevenness, failing to meet the requirements of high-precision testing.

[0011] In summary, there is an inherent conflict between traditional cryogenic cooling solutions and dynamic, precise temperature-controlled infrared target simulators. This not only results in low cooling efficiency, extremely poor energy utilization, and asynchronous cooling, but may also lead to the complete loss of the precision mechanical and optical properties of the entire optical system due to thermal management failure. Summary of the Invention

[0012] The purpose of this invention is to solve the technical problems of the inherent conflict between traditional cryogenic cooling schemes and dynamic, precise temperature-controlled infrared target simulators, which result in low cooling efficiency, extremely poor energy utilization, asynchronous cooling, and the complete loss of the precision mechanical and optical properties of the entire optical system due to thermal management failure. The invention provides a rapid cooling and self-temperature-controlled infrared target simulator and its cooling method.

[0013] To achieve the above objectives, the technical solution provided by the present invention is as follows:

[0014] A rapid cooling and self-temperature-controlled infrared target simulator is characterized by comprising an optical housing, a primary mirror, a secondary mirror, a target, a movable light shield, an exit pupil light shield, a cooling unit, and a control unit.

[0015] The optical housing has a light inlet and a light outlet diagonally arranged on two opposite side walls; both the primary mirror and the secondary mirror are off-axis aspherical mirrors, with the primary mirror mounted on the side wall of the optical housing on the same side as the light inlet and the secondary mirror mounted on the side wall of the optical housing on the same side as the light outlet; the primary mirror and the secondary mirror are diagonally arranged, and the line connecting their centers intersects the projection of the line connecting the centers of the light inlet and the light outlet on the horizontal plane;

[0016] The target has at least one light-passing hole, which is located on the outside of the optical box directly opposite the light-entry hole; one end of the movable light shield is located on the outside of the optical box corresponding to the light-exit hole, and the exit pupil light shield is connected to the other end of the movable light shield.

[0017] The cooling unit includes five cooling channels, each including a flexible cold chain and a cold source mounted on the flexible cold chain. The flexible cold chain can be a multi-branch structure or a single-branch structure. The branches of the first flexible cold chain are respectively connected to the side wall of the optical housing and the back of the primary and secondary mirrors. The branches of the second flexible cold chain are respectively connected to the side wall of the optical housing. The branches of the third flexible cold chain are connected to the target. The branches of the fourth flexible cold chain are respectively connected to the side wall of the movable light shield. The branches of the fifth flexible cold chain are respectively connected to the side wall of the exit pupil light shield. The thermal resistance of each flexible cold chain is designed to match the thermal capacity of the structure it is connected to.

[0018] At least one heater is provided on the outer surface of the branch ends of the multiple flexible cold chains and on the outer wall of the optical box, target, movable light shield, and exit pupil light shield, corresponding to the position of each flexible cold chain; at least one temperature sensor is provided on the optical box, primary mirror, secondary mirror, target, movable light shield, and exit pupil light shield, respectively.

[0019] The control unit is electrically connected to multiple heaters and multiple temperature sensors respectively, and is used to control the working state of the corresponding heaters according to the temperature signals fed back by the temperature sensors at different locations, so as to realize closed-loop temperature control.

[0020] Furthermore, it also includes a two-dimensional moving platform for the light shield and a two-dimensional moving platform for the target;

[0021] The movable light shield is set on a two-dimensional moving platform for the light shield, and is used to drive the movable light shield to move in a direction perpendicular to the optical axis in the horizontal plane through the two-dimensional moving platform.

[0022] The target is set on a two-dimensional target moving platform, which is used to drive the target to move in the horizontal plane along a direction perpendicular to the optical axis.

[0023] Furthermore, the flexible cold chains in the five refrigeration pathways are respectively the first flexible cold chain, the second flexible cold chain, the third flexible cold chain, the fourth flexible cold chain, and the fifth flexible cold chain; the second flexible cold chain and the fourth flexible cold chain in the five refrigeration pathways share a cold source, and the four cold sources are respectively referred to as the first cold source, the second cold source, the third cold source, and the fourth cold source;

[0024] The first flexible cold chain has a multi-branch structure, which includes a first mounting plate and five first L-shaped branches connected to the first mounting plate;

[0025] The second flexible cold chain has a multi-branch structure, which includes a second mounting plate and three second L-shaped branches connected to the second mounting plate;

[0026] The third flexible cold chain is a single-branch structure, which includes a third mounting plate and a first U-shaped branch connected to the third mounting plate;

[0027] The fourth flexible cold chain has a multi-branch structure, including a fourth mounting plate, a second U-shaped branch connected to one end of the fourth mounting plate, a first intermediate connecting plate connected to the other end of the second U-shaped branch, and two third L-shaped branches connected to the first intermediate connecting plate.

[0028] The fifth flexible cold chain is a multi-branch structure, which includes a fifth mounting plate, two fourth L-shaped branches connected to one end of the fifth mounting plate, two second intermediate connecting plates respectively connected to the other end of the two fourth L-shaped branches, and two fifth L-shaped branches respectively connected to the two second intermediate connecting plates.

[0029] The ends of the first L-shaped branch, the second L-shaped branch, the first U-shaped branch, the third L-shaped branch, and the fifth L-shaped branch are respectively provided with connecting plates;

[0030] The connecting plates at the ends of the three first L-shaped branches are respectively connected to the front, rear, and left side walls of the optical housing; the connecting plates at the ends of the other two first L-shaped branches are respectively connected to the back of the primary and secondary mirrors; the connecting plates at the ends of the three second L-shaped branches are respectively connected to the top, bottom, and right side walls of the optical housing; the connecting plate at the end of the first U-shaped branch is connected to the target; the connecting plates at the ends of the two third L-shaped branches are respectively connected to the top and bottom side walls of the movable light shield; the connecting plates at the ends of the two fifth L-shaped branches corresponding to one of the second intermediate connecting plates are respectively connected to the top and bottom side walls of the front end of the exit pupil light shield; the connecting plates at the ends of the two fifth L-shaped branches corresponding to another second intermediate connecting plate are respectively connected to the top and bottom side walls of the rear end of the exit pupil light shield.

[0031] The second mounting plate and the fourth mounting plate are stacked together to form a stacked mounting plate; the first cold source is mounted on the first mounting plate, the second cold source is mounted on the stacked mounting plate, the third cold source is mounted on the third mounting plate, and the fourth cold source is mounted on the fifth mounting plate.

[0032] Furthermore, the first mounting plate, the second mounting plate, the third mounting plate, the fourth mounting plate, the fifth mounting plate, the first intermediate connecting plate, the second intermediate connecting plate, and each connecting plate are all made of hard aluminum alloy or oxygen-free copper material.

[0033] The first L-shaped branch, the second L-shaped branch, the third L-shaped branch, the fourth L-shaped branch, the fifth L-shaped branch, the first U-shaped branch, and the second U-shaped branch are all made of flexible graphite film or metal braided tape.

[0034] Furthermore, the bends of the first L-shaped branch, the second L-shaped branch, the third L-shaped branch, the fourth L-shaped branch, the fifth L-shaped branch, the first U-shaped branch, and the second U-shaped branch are all designed with rounded transitions.

[0035] Furthermore, it also includes an optical platform and thermal insulation support;

[0036] The optical enclosure is mounted on the optical platform via thermal insulation supports;

[0037] The two-dimensional moving platform for the light shield and the two-dimensional moving platform for the target are mounted on the optical platform.

[0038] Furthermore, the outer surfaces of the optical housing, primary mirror, secondary mirror, target, movable light shield, exit pupil light shield, flexible cold chain, heater, temperature sensor, optical platform, heat insulation support, two-dimensional movable platform of light shield, and two-dimensional movable platform of target are all covered with heat insulation components; the heat insulation components include M layers of heat insulation film, 1≤M≤40.

[0039] Furthermore, the optical housing, primary mirror, and secondary mirror are made of the same thermally conductive metal material.

[0040] Furthermore, the heater is a thin-film heater;

[0041] The control unit is a temperature controller.

[0042] In addition, the present invention also provides a cooling method for the above-mentioned rapid cooling and self-temperature-controlled infrared target simulator, which is characterized by including the following steps:

[0043] Step 1: Activate multiple cold sources and distribute cooling to the optical housing, primary mirror, secondary mirror, target, movable light shield, and exit pupil light shield through corresponding flexible cold chains;

[0044] Step 2: The temperature of the optical housing, primary mirror, secondary mirror, target, movable light shield, and exit pupil light shield is monitored in real time by multiple temperature sensors and transmitted to the control unit. The control unit controls the working status of the heaters on the optical housing, primary mirror, secondary mirror, target, movable light shield, and exit pupil light shield according to the temperature signals fed back by the temperature sensors at different locations, so as to compensate for the cooling and achieve rapid cooling.

[0045] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0046] 1. This invention provides an infrared target simulator with rapid cooling and self-temperature control. It creatively adopts a collaborative design of distributed cold sources and a multi-branch flexible cold chain based on thermal capacity matching. Thermal capacity matching is introduced as a complete and quantitative design criterion into the cooling and temperature control of the infrared target simulator. At the same time, multiple cold sources are reasonably arranged to avoid single-point overcooling and cooling blind spots. According to the thermal capacity of each component of the infrared target simulator, the thermal resistance of each flexible cold chain branch is precisely matched and designed. This fundamentally solves the problem of asynchronous cooling and thermal stress caused by the difference in thermal inertia in large-size and high-mass infrared target simulators. It ensures the dynamic cooling synchronization of components with different thermal inertia and effectively suppresses the generation of thermal stress.

[0047] 2. The infrared target simulator provided by this invention is a rapid cooling and self-temperature controlled infrared target simulator. Through the closed-loop control strategy consisting of a control unit, a temperature sensor and a heater, the infrared target simulator system can achieve continuous and precise temperature regulation in a wide temperature range of 100K~180K. The temperature control accuracy (better than ±0.1K) and uniformity are significantly improved. The time from room temperature to 170K does not exceed 5 hours, which meets the needs of high-end testing.

[0048] 3. The infrared target simulator provided by this invention features a multi-branch flexible cold chain that efficiently transfers cold energy for dynamic cooling. Its flexibility also provides additional advantages such as vibration isolation, displacement compensation, and ease of installation, greatly ensuring the system reliability and temperature stability of the moving light shield and target during long-stroke movement.

[0049] 4. The present invention provides a cooling method for an infrared target simulator with rapid cooling and self-temperature control. After the cooling test is completed, the system can be rapidly restored from a low temperature state to a normal temperature by actively turning on the heater. Compared with the design without active temperature recovery, the temperature recovery efficiency of the present invention is increased by tens of times, which greatly shortens the test interval and significantly improves the utilization rate and economic benefits of the equipment. Attached Figure Description

[0050] Figure 1 This is a first-view structural schematic diagram of an embodiment of an infrared target simulator with rapid cooling and self-temperature control according to the present invention;

[0051] Figure 2 This is a second-view structural schematic diagram of an embodiment of an infrared target simulator with rapid cooling and self-temperature control according to the present invention;

[0052] Figure 3 This is a schematic diagram of the structure of the first flexible cold chain in an embodiment of the present invention;

[0053] Figure 4 This is a schematic diagram of the structure of the second flexible cold chain in an embodiment of the present invention;

[0054] Figure 5 This is a schematic diagram of the third flexible cold chain in an embodiment of the present invention;

[0055] Figure 6 This is a schematic diagram of the fourth flexible cold chain in an embodiment of the present invention;

[0056] Figure 7 This is a schematic diagram of the fifth flexible cold chain in an embodiment of the present invention;

[0057] Figure 8 This is a schematic diagram of the cooling curve of the primary mirror in an embodiment of the present invention;

[0058] Figure 9 This is a schematic diagram of the cooling curve of the secondary mirror in an embodiment of the present invention;

[0059] Figure 10 This is a schematic diagram of the cooling curves of the optical housing and the movable light shield in an embodiment of the present invention;

[0060] Figure 11 This is a schematic diagram of the cooling curve of the target in an embodiment of the present invention;

[0061] Figure 12 This is a schematic diagram of the cooling curve of the exit pupil light shield in an embodiment of the present invention.

[0062] The attached figures are labeled as follows:

[0063] 1-Optical housing; 101-Light entrance aperture; 2-Primary mirror; 3-Secondary mirror; 4-Target; 5-Moving light shield; 6-Exit pupil light shield; 7-Control unit; 81-First flexible cold chain; 811-First mounting plate; 812-First L-shaped branch; 82-Second flexible cold chain; 821-Second mounting plate; 822-Second L-shaped branch; 83-Third flexible cold chain; 831-Third mounting plate; 832-First U-shaped branch; 84-Fourth flexible cold chain; 841-Fourth mounting plate; 842-Second U-shaped branch Support, 843-First intermediate connecting plate, 844-Third L-shaped branch, 85-Fifth flexible cold chain, 851-Fifth mounting plate, 852-Fourth L-shaped branch, 853-Second intermediate connecting plate, 854-Fifth L-shaped branch, 800-Connecting plate; 91-First cold source, 92-Second cold source, 93-Third cold source, 94-Fourth cold source; 10-Heater; 11-Temperature sensor; 12-Optical platform; 13-Heat insulation support; 14-Light shield two-dimensional moving platform; 15-Target two-dimensional moving platform. Detailed Implementation

[0064] To make the advantages and features of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0065] like Figure 1 , Figure 2 As shown, an infrared target simulator with rapid cooling and self-temperature control includes an optical housing 1, a primary mirror 2, a secondary mirror 3, a target 4, a movable light shield 5, an exit pupil light shield 6, a cooling unit, a control unit 7, multiple heaters 10, multiple temperature sensors 11, an optical platform 12, a heat-insulating support 13, a two-dimensional moving platform for the light shield 14, and a two-dimensional moving platform for the target 15. In this embodiment, the total mass of the infrared target simulator is ≥50kg, and the overall dimensions are 1837*1260*587mm.

[0066] The optical housing 1 is mounted on the optical platform 12 via a heat-insulating support 13. Optical housing 1 has a light inlet 101 and a light outlet 101 diagonally arranged on two opposite sidewalls. The primary mirror 2 and secondary mirror 3 are both off-axis aspherical mirrors. The primary mirror 2 is mounted on the sidewall of optical housing 1 on the same side as the light inlet 101, and the secondary mirror 3 is mounted on the sidewall of optical housing 1 on the same side as the light outlet 101. The primary mirror 2 and secondary mirror 3 are diagonally arranged, and the projection of the line connecting the centers of the primary mirror 2 and secondary mirror 3 onto the horizontal plane intersects the projection of the line connecting the centers of the light inlet 101 and the light outlet 101. The optical housing 1, primary mirror 2, and secondary mirror 3 are made of the same thermally conductive metal material.

[0067] Because the moving light shield 5 needs to be displaced by ±400mm in the horizontal plane along a direction perpendicular to the optical axis during the calibration of the low-temperature infrared simulator, the moving light shield 5 is mounted on the two-dimensional moving platform 14, with one end located outside the optical housing 1 directly opposite the light exit hole. The two-dimensional moving platform 14 is mounted on the optical platform 12 and is used to move the moving light shield 5 in the horizontal plane along a direction perpendicular to the optical axis. The exit pupil light shield 6 serves as the exit pupil end and is detachably connected to the other end of the moving light shield 5.

[0068] The target 4 has multiple light-transmitting holes. When the low-temperature infrared simulator finishes calibration and switches to normal operation mode, the target 4 needs to be displaced by ±80mm in the horizontal plane along the direction perpendicular to the optical axis. Therefore, the target 4 is set on the target two-dimensional moving platform 15 and located on the outside of the optical housing 1 at the position corresponding to the light-entry hole 101. The target two-dimensional moving platform 15 is fixed on the optical platform 12 and is used to drive the target 4 to move in the horizontal plane along the direction perpendicular to the optical axis.

[0069] Infrared light emitted from an external infrared light source enters the optical housing 1 through the light-passing hole on the target 4 and the light-entry hole 101 on the optical housing 1. It is then reflected by the secondary mirror 3 to reach the surface of the primary mirror 2, and after further reflection by the primary mirror 2, exits sequentially through the light-exiting hole, the movable light-shielding cover 5, and the exit pupil light-shielding cover 6. In this invention, the optical housing 1 is used as an example; the direction corresponding to the light-entry hole 101 on the optical housing 1 is designated as "front," and the direction corresponding to the light-exiting hole on the optical housing 1 is designated as "back."

[0070] The key points of this invention are a multi-cold source synergistic refrigeration strategy based on heat capacity matching and a composite temperature control strategy based on a high-precision control unit.

[0071] I. A multi-cold source collaborative refrigeration strategy based on heat capacity matching, namely, a distributed multi-cold source layout combined with a multi-branch flexible cold chain.

[0072] Considering the structure and distributed internal heat load of the infrared target simulator, multiple cold sources are strategically placed to avoid single-point overcooling and cooling blind spots. Simultaneously, to achieve efficient and synchronous heat transfer, a multi-branch flexible cold chain is designed based on a heat capacity matching mechanism to achieve synchronized cooling of all components of the infrared target simulator. Each flexible cold chain branch is designed as a parallel network structure to reduce overall thermal resistance and improve cold chain efficiency. The heat capacity matching mechanism calculates the equivalent heat capacity of the target cooling area precisely, uses this as input to deduce the thermal resistance requirements of each flexible cold chain branch, and then optimizes the physical structural parameters of each flexible cold chain branch based on these requirements, including but not limited to the cross-sectional area and equivalent length of the heat conduction path of each flexible cold chain branch.

[0073] The design calculation process for each flexible cold chain branch is as follows:

[0074] The object to be cooled, namely the infrared target simulator, is divided into multiple regions, and the heat capacity C of each region is calculated using the following formula:

[0075] C = c·m

[0076] Where m is the mass of the region corresponding to the object being refrigerated, in kg, and c is the specific heat capacity of the region corresponding to the object being refrigerated, in J / (kg·K).

[0077] Within a specified time, the area corresponding to the object to be cooled will be reduced from its initial temperature T. i Cool down to the target temperature T t The amount of cold P that the corresponding area of ​​the object to be cooled needs to absorb during the cooling process is calculated using the following formula:

[0078] P=Q / t=C·(T i -T t ) / t

[0079] Where Q is the total heat released in the area corresponding to the object being refrigerated, in J / K, and t is the cooling time, in h.

[0080] The cooling capacity provided by the cold source needs to overcome the thermal resistance along the heat transfer path in order to cool the corresponding area of ​​the object to the required target temperature. The thermal resistance R of each flexible cold chain branch is calculated using the following formula:

[0081] R=(T e -T t ) / P

[0082] Among them, T e The temperature of the cold source is expressed in °C.

[0083] Once the required thermal resistance for each flexible cold chain branch is determined, the physical structure of each branch can be designed using the following heat transfer formula:

[0084] R = L / (λ·A)

[0085] Where L is the equivalent length of each flexible cold chain branch in meters (m), λ is the thermal conductivity of each flexible cold chain branch in W / (m·K), and A is the cross-sectional area of ​​each flexible cold chain branch in square meters (m²). 2 .

[0086] In this embodiment, the refrigeration unit includes five refrigeration paths, each consisting of a flexible cold chain and a cold source. The flexible cold chains in the five refrigeration paths are designated as the first flexible cold chain 81, the second flexible cold chain 82, the third flexible cold chain 83, the fourth flexible cold chain 84, and the fifth flexible cold chain 85. Preferably, in this embodiment, the second flexible cold chain 82 and the fourth flexible cold chain 84 share a single cold source, designated as the first cold source 91, the second cold source 92, the third cold source 93, and the fourth cold source 94. In this embodiment, the first cold source 91, the second cold source 92, the third cold source 93, and the fourth cold source 94 are all refrigerators. In other embodiments of the present invention, liquid nitrogen, JT refrigerators, or other cold sources may also be used; no specific limitation is made here.

[0087] like Figure 3 As shown, the first flexible cold chain 81 has a multi-branch structure, including a first mounting plate 811 and five first L-shaped branches 812 connected to the first mounting plate 811. Figure 4 As shown, the second flexible cold chain 82 also has a multi-branch structure, including a second mounting plate 821 and three second L-shaped branches 822 connected to the second mounting plate 821. Figure 5 As shown, the third flexible cold chain 83 has a single-branch structure, which includes a third mounting plate 831 and a first U-shaped branch 832 connected to the third mounting plate 831. Figure 6 As shown, the fourth flexible cold chain 84 has a multi-branch structure, including a fourth mounting plate 841, a second U-shaped branch 842 connected at one end to the fourth mounting plate 841, a first intermediate connecting plate 843 connected to the other end of the second U-shaped branch 842, and two third L-shaped branches 844 connected to the first intermediate connecting plate 843. Figure 7As shown, the fifth flexible cold chain 85 has a multi-branch structure, which includes a fifth mounting plate 851, two fourth L-shaped branches 852 connected to the fifth mounting plate 851 at one end, two second intermediate connecting plates 853 respectively connected to the other end of the two fourth L-shaped branches 852, and two fifth L-shaped branches 854 respectively connected to the two second intermediate connecting plates 853. The ends of the first L-shaped branch 812, the second L-shaped branch 822, the first U-shaped branch 832, the third L-shaped branch 844, and the fifth L-shaped branch 854 are respectively provided with connecting plates 800. The first mounting plate 811, the second mounting plate 821, the third mounting plate 831, the fourth mounting plate 841, the fifth mounting plate 851, the first intermediate connecting plate 843, the second intermediate connecting plate 853, and each connecting plate 800 are all made of hard aluminum alloy. The first L-shaped branch 812, the second L-shaped branch 822, the third L-shaped branch 844, the fourth L-shaped branch 852, the fifth L-shaped branch 854, the first U-shaped branch 832, and the second U-shaped branch 842 are all made of flexible graphite film. In other embodiments of the present invention, the first mounting plate 811, the second mounting plate 821, the third mounting plate 831, the fourth mounting plate 841, the fifth mounting plate 851, the first intermediate connecting plate 843, the second intermediate connecting plate 853, and each connecting plate 800 may also be made of other hard materials with good thermal conductivity, such as oxygen-free copper. The first L-shaped branch 812, the second L-shaped branch 822, the third L-shaped branch 844, the fourth L-shaped branch 852, the fifth L-shaped branch 854, the first U-shaped branch 832, and the second U-shaped branch 842 may also be made of flexible thermally conductive materials such as metal braided strips. Preferably, the bends of the first L-shaped branch 812, the second L-shaped branch 822, the third L-shaped branch 844, the fourth L-shaped branch 852, the fifth L-shaped branch 854, the first U-shaped branch 832, and the second U-shaped branch 842 are all rounded.

[0088] The connecting plates 800 at the ends of the three first L-shaped branches 812 are respectively connected to the front, rear, and left side walls of the optical housing 1 by screws; the connecting plates 800 at the ends of the other two first L-shaped branches 812 are respectively connected to the back of the primary mirror 2 and the secondary mirror 3 by screws; the connecting plates 800 at the ends of the three second L-shaped branches 822 are respectively connected to the top, bottom, and right side walls of the optical housing 1 by screws; the connecting plate 800 at the end of the first U-shaped branch 832 is connected to the target 4 by screws; two The connecting plates 800 at the ends of the third L-shaped branch 844 are respectively connected to the top and bottom side walls of the movable light shield 5 by screws; the connecting plates 800 at the ends of the two fifth L-shaped branches 854 corresponding to one of the second intermediate connecting plates 853 are respectively connected to the top and bottom side walls of the front end of the exit pupil light shield 6 by screws; the connecting plates 800 at the ends of the two fifth L-shaped branches 854 corresponding to the other second intermediate connecting plate 853 are respectively connected to the top and bottom side walls of the rear end of the exit pupil light shield 6 by screws.

[0089] Since the second flexible cold chain 82 and the fourth flexible cold chain 84 share a common cold source, the second mounting plate 821 and the fourth mounting plate 841 are stacked together to form a stacked mounting plate. The first cold source 91 is mounted on the first mounting plate 811 with screws, the second cold source 92 is mounted on the stacked mounting plate with screws, the third cold source 93 is mounted on the third mounting plate 831 with screws, and the fourth cold source 94 is mounted on the fifth mounting plate 851 with screws.

[0090] Preferably, each connection interface between the connecting plate 800 and the infrared target simulator, and each connection interface between the cold source and the corresponding flexible cold chain are provided with thermally conductive silicone grease to reduce the contact thermal resistance between the corresponding connection interfaces.

[0091] In addition, each flexible cold chain also serves as a vibration isolation mechanism, effectively suppressing the transmission of vibrations generated by the cold source to the infrared target simulator and preventing interference with infrared imaging. In particular, the third flexible cold chain 83 and the fourth flexible cold chain 84 also provide large displacement compensation for the target 4 and the moving light shield 5. On the basis of vibration isolation, they can also absorb the huge displacements of ±80mm and ±400mm caused by moving parts, ensuring smooth movement of moving parts without jamming throughout the low-temperature process.

[0092] II. Composite temperature control strategy based on high-precision control unit.

[0093] For objects with large mass and heat capacity, achieving rapid cooling requires a high-capacity cold source (≥100W@100K). However, high-capacity cold sources cannot achieve closed-loop temperature control, meaning they cannot provide continuously adjustable cooling temperatures. Therefore, this invention employs an intelligent composite temperature control strategy of "cooling as the foundation, heating as an auxiliary measure." The control unit 7 controls the heating circuit based on the temperature signal from the temperature sensor 11 to ensure closed-loop temperature control of the infrared target simulator. The control unit 7 dynamically monitors the temperature and precisely offsets excess cooling by controlling the power of the heater 10. Temperature setting is no longer limited by the fixed cooling capacity of the cold source, achieving continuous adjustable and controllable cooling temperatures within the range of 100K~180K. This invention, through closed-loop temperature control, resists environmental fluctuations and changes in heat load, stabilizing the temperature at the set point to achieve high temperature control accuracy and stability (accuracy better than 0.1K). After the cooling test, the heating circuit is activated, allowing the infrared target simulator to quickly return from a low-temperature state to a normal temperature state. Compared to a design without a heating circuit, the recovery rate is increased by tens of times. In this embodiment, the control unit 7 is a temperature controller. In other embodiments, a general-purpose controller such as a PLC can also be used to achieve the same temperature control logic.

[0094] Specifically, in this embodiment, heaters 10 are respectively installed on the outer walls of the connecting plates 800 of the five flexible cold chains, and on the outer walls of the optical housing 1, the movable light shield 5, and the exit pupil light shield 6 at positions corresponding to each flexible cold chain. Preferably, thin-film heaters are used in this embodiment. Meanwhile, multiple temperature sensors 11 are respectively installed on the optical housing 1, the primary mirror 2, the secondary mirror 3, the target 4, the movable light shield 5, and the exit pupil light shield 6. The control unit 7 is electrically connected to the multiple heaters 10 and the multiple temperature sensors 11, and is used to control the working state of the corresponding heater 10 according to the temperature signals fed back by the temperature sensors 11 at different positions, so as to achieve closed-loop temperature control.

[0095] Preferably, in order to ensure the cooling effect, in this embodiment, the outer surfaces of the optical housing 1, primary mirror 2, secondary mirror 3, target 4, movable light shield 5, exit pupil light shield 6, flexible cold chain, heater 10, temperature sensor 11, optical platform 12, heat insulation support 13, light shield two-dimensional moving platform 14 and target two-dimensional moving platform 15 are all covered with heat insulation components, wherein the heat insulation components are formed by stacking 30 layers of heat insulation film.

[0096] The cooling method for the aforementioned rapid cooling and self-temperature-controlled infrared target simulator specifically includes the following steps:

[0097] Step 1: Activate the first cold source 91, the second cold source 92, the third cold source 93 and the fourth cold source 94, and perform distributed cooling on the optical box 1, the primary mirror 2, the secondary mirror 3, the target 4, the movable light shield 5 and the exit pupil light shield 6 through the first flexible cold chain 81, the second flexible cold chain 82, the third flexible cold chain 83, the fourth flexible cold chain 84 and the fifth flexible cold chain 85 based on heat capacity matching;

[0098] Step 2: Multiple temperature sensors 11 monitor the temperatures of the optical housing 1, primary mirror 2, secondary mirror 3, target 4, movable light shield 5, and exit pupil light shield 6 in real time, and transmit the data to the control unit 7. The control unit 7 determines whether the average temperature of the corresponding component has reached the corresponding cooling target temperature range based on the temperature signals fed back by the temperature sensors 11 at different locations. When the average temperature of the corresponding component reaches the corresponding cooling target temperature range, the heaters 10 on the optical housing 1, primary mirror 2, secondary mirror 3, target 4, movable light shield 5, and exit pupil light shield 6 are activated to gradually control the temperature of each component within the target temperature threshold range and stabilize it, thereby compensating for the cooling load and stabilizing the temperature of the infrared target simulator within the target set value of 100K~180K, thus completing rapid cooling.

[0099] The cooling curves of each component in the rapid cooling and self-temperature-controlled infrared target simulator of this embodiment are as follows: Figures 8-12 As shown. Among them. Figure 8 This is a schematic diagram of the cooling curve for main mirror 2. Figure 9 This is a schematic diagram of the cooling curve of mirror 3. Figure 10 This is a schematic diagram of the cooling curves for the optical housing 1 and the movable light shield 5. Figure 11 This is a schematic diagram of the cooling curve for target 4. Figure 12 This is a schematic diagram of the cooling curve of the exit pupil shield 6. It can be seen that the time required for the primary mirror 2, secondary mirror 3, and optical housing 1 to cool from room temperature to the target temperature (170K) and reach a stable state is 4.5h, 4.4h, and 4.7h, respectively. The time required for the exit pupil shield 6 to cool from room temperature to the target temperature (160K) and reach a stable state is 5.4h, and the time required for the target 4 to cool from room temperature to the target temperature (170K) and reach a stable state is 3.5h. It can be seen that the average cooling rate is approximately 0.5℃ / min, indicating that the infrared target simulator body has highly synchronized temperature control consistency, effectively avoiding deformation and stress caused by differences in thermal inertia.

[0100] Therefore, the infrared target simulator with rapid cooling and self-temperature control in this embodiment takes a maximum of 5.4 hours to cool from room temperature to the target temperature and reach a stable state. The cooling time meets the requirements of rapid cooling. The cooling time and cooling rate of each component are shown in Table 1.

[0101] Table 1 Cooling time and cooling rate of each component

[0102]

[0103] The above description is only used to illustrate the technical solutions of the present invention, and is not intended to limit them. For those skilled in the art, modifications can be made to the specific technical solutions described in the above embodiments, or equivalent substitutions can be made to some of the technical features. However, these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions protected by the present invention.

Claims

1. An infrared target simulator with rapid cooling and self-temperature control, characterized in that: It includes an optical housing (1), a primary mirror (2), a secondary mirror (3), a target (4), a movable light shield (5), an exit pupil light shield (6), a cooling unit, and a control unit (7). The optical housing (1) has a light inlet (101) and a light outlet on two opposite side walls. The primary mirror (2) and the secondary mirror (3) are both off-axis aspherical mirrors. The primary mirror (2) is mounted on the side wall of the optical housing (1) on the same side as the light inlet (101), and the secondary mirror (3) is mounted on the side wall of the optical housing (1) on the same side as the light outlet. The primary mirror (2) and the secondary mirror (3) are diagonally arranged, and the line connecting their centers intersects the projection of the line connecting the centers of the light inlet (101) and the light outlet on the horizontal plane. The target (4) has at least one light-transmitting hole, which is located on the outside of the optical box (1) directly opposite the light-inlet hole (101); one end of the movable light shield (5) is located on the outside of the optical box (1) corresponding to the light-outlet hole, and the exit pupil light shield (6) is connected to the other end of the movable light shield (5). The cooling unit includes five cooling channels, each of which includes a flexible cold chain and a cold source mounted on the flexible cold chain. The flexible cold chain is a multi-branch structure or a single-branch structure. The ends of each branch of the first flexible cold chain are respectively connected to the side wall of the optical housing (1) and the back of the primary mirror (2) and the secondary mirror (3). The ends of each branch of the second flexible cold chain are respectively connected to the side wall of the optical housing (1). The ends of each branch of the third flexible cold chain are connected to the target (4). The ends of each branch of the fourth flexible cold chain are respectively connected to the side wall of the movable light shield (5). The ends of each branch of the fifth flexible cold chain are respectively connected to the side wall of the exit pupil light shield (6). The thermal resistance of each flexible cold chain is designed based on the thermal capacity of the structure to which it is connected. At least one heater (10) is provided on the outer surface of the branch ends of the multiple flexible cold chains and on the outer wall of the optical box (1), target (4), movable light shield (5), and exit pupil light shield (6) corresponding to the position of each flexible cold chain; at least one temperature sensor (11) is provided on the optical box (1), primary mirror (2), secondary mirror (3), target (4), movable light shield (5), and exit pupil light shield (6). The control unit (7) is electrically connected to multiple heaters (10) and multiple temperature sensors (11) respectively, and is used to control the working state of the corresponding heater (10) according to the temperature signal fed back by the temperature sensor (11) at different positions, so as to realize closed-loop temperature control.

2. The infrared target simulator with rapid cooling and self-temperature control according to claim 1, characterized in that: It also includes a two-dimensional moving platform for the light shield (14) and a two-dimensional moving platform for the target (15). The movable light shield (5) is set on the two-dimensional moving platform (14) of the light shield, and is used to drive the movable light shield (5) to move in the horizontal plane in a direction perpendicular to the optical axis through the two-dimensional moving platform (14). The target (4) is set on the target two-dimensional moving platform (15) and is used to drive the target (4) to move in the horizontal plane in a direction perpendicular to the optical axis through the target two-dimensional moving platform (15).

3. The infrared target simulator with rapid cooling and self-temperature control according to claim 2, characterized in that: The five flexible cold chains in the refrigeration pathways are the first flexible cold chain (81), the second flexible cold chain (82), the third flexible cold chain (83), the fourth flexible cold chain (84), and the fifth flexible cold chain (85); the second flexible cold chain (82) and the fourth flexible cold chain (84) in the five refrigeration pathways share a cold source, and the four cold sources are respectively denoted as the first cold source (91), the second cold source (92), the third cold source (93), and the fourth cold source (94); The first flexible cold chain (81) has a multi-branch structure, which includes a first mounting plate (811) and five first L-shaped branches (812) connected to the first mounting plate (811). The second flexible cold chain (82) has a multi-branch structure, which includes a second mounting plate (821) and three second L-shaped branches (822) connected to the second mounting plate (821). The third flexible cold chain (83) is a single-branch structure, which includes a third mounting plate (831) and a first U-shaped branch (832) connected to the third mounting plate (831). The fourth flexible cold chain (84) is a multi-branch structure, which includes a fourth mounting plate (841), a second U-shaped branch (842) connected to the fourth mounting plate (841) at one end, a first intermediate connecting plate (843) connected to the other end of the second U-shaped branch (842), and two third L-shaped branches (844) connected to the first intermediate connecting plate (843). The fifth flexible cold chain (85) is a multi-branch structure, which includes a fifth mounting plate (851), two fourth L-shaped branches (852) connected to the fifth mounting plate (851) at one end, two second intermediate connecting plates (853) respectively connected to the other end of the two fourth L-shaped branches (852), and two fifth L-shaped branches (854) respectively connected to the two second intermediate connecting plates (853). The ends of the first L-shaped branch (812), the second L-shaped branch (822), the first U-shaped branch (832), the third L-shaped branch (844), and the fifth L-shaped branch (854) are respectively provided with connecting plates (800). The connecting plates (800) at the ends of the three first L-shaped branches (812) are respectively connected to the front side wall, rear side wall and left side wall of the optical housing (1), and the connecting plates (800) at the ends of the other two first L-shaped branches (812) are respectively connected to the back of the primary mirror (2) and the secondary mirror (3); the connecting plates (800) at the ends of the three second L-shaped branches (822) are respectively connected to the top side wall, bottom side wall and right side wall of the optical housing (1); the connecting plate (800) at the end of the first U-shaped branch (832) is connected to the target (4); The connecting plates (800) at the ends of the two third L-shaped branches (844) are respectively connected to the top and bottom side walls of the movable light shield (5); the connecting plates (800) at the ends of the two fifth L-shaped branches (854) on one of the second intermediate connecting plates (853) are respectively connected to the top and bottom side walls of the front end of the exit pupil light shield (6); the connecting plates (800) at the ends of the two fifth L-shaped branches (854) on the other second intermediate connecting plate (853) are respectively connected to the top and bottom side walls of the rear end of the exit pupil light shield (6). The second mounting plate (821) and the fourth mounting plate (841) are stacked together to form a stacked mounting plate; the first cold source (91) is mounted on the first mounting plate (811), the second cold source (92) is mounted on the stacked mounting plate, the third cold source (93) is mounted on the third mounting plate (831), and the fourth cold source (94) is mounted on the fifth mounting plate (851).

4. The infrared target simulator with rapid cooling and self-temperature control according to claim 3, characterized in that: The first mounting plate (811), the second mounting plate (821), the third mounting plate (831), the fourth mounting plate (841), the fifth mounting plate (851), the first intermediate connecting plate (843), the second intermediate connecting plate (853), and each connecting plate (800) are all made of hard aluminum alloy or oxygen-free copper material. The first L-shaped branch (812), the second L-shaped branch (822), the third L-shaped branch (844), the fourth L-shaped branch (852), the fifth L-shaped branch (854), the first U-shaped branch (832), and the second U-shaped branch (842) are all made of flexible graphite film or metal braided tape.

5. The infrared target simulator with rapid cooling and self-temperature control according to claim 4, characterized in that: The bends of the first L-shaped branch (812), the second L-shaped branch (822), the third L-shaped branch (844), the fourth L-shaped branch (852), the fifth L-shaped branch (854), the first U-shaped branch (832), and the second U-shaped branch (842) are all set to be rounded transitions.

6. The infrared target simulator with rapid cooling and self-temperature control according to claim 5, characterized in that: It also includes an optical platform (12) and a thermal support (13); The optical housing (1) is mounted on the optical platform (12) by means of a heat-insulating support (13); The two-dimensional moving platform (14) for the light shield and the two-dimensional moving platform (15) for the target are mounted on the optical platform (12).

7. The infrared target simulator with rapid cooling and self-temperature control according to claim 6, characterized in that: The outer surfaces of the optical housing (1), primary mirror (2), secondary mirror (3), target (4), movable light shield (5), exit pupil light shield (6), flexible cold chain, heater (10), temperature sensor (11), optical platform (12), heat insulation support (13), light shield two-dimensional moving platform (14), and target two-dimensional moving platform (15) are all covered with heat insulation components; the heat insulation components include M layers of heat insulation film, 1≤M≤40.

8. The infrared target simulator with rapid cooling and self-temperature control according to claim 1, characterized in that: The optical housing (1), primary mirror (2), and secondary mirror (3) are made of the same thermally conductive metal material.

9. The infrared target simulator with rapid cooling and self-temperature control according to claim 8, characterized in that: The heater (10) is a thin-film heater; The control unit (7) is a temperature controller.

10. A method of refrigeration for a fast-cooling and self-regulating temperature infrared target simulator according to any one of claims 1-9, characterized in that, Includes the following steps: Step 1: Activate multiple cold sources and distribute cooling to the optical housing (1), primary mirror (2), secondary mirror (3), target (4), movable light shield (5), and exit pupil light shield (6) through corresponding flexible cold chains; Step 2: The temperature of the optical housing (1), primary mirror (2), secondary mirror (3), target (4), movable light shield (5) and exit pupil light shield (6) is monitored in real time by multiple temperature sensors (11) and transmitted to the control unit (7); The control unit (7) controls the working status of the heaters (10) on the optical housing (1), primary mirror (2), secondary mirror (3), target (4), movable light shield (5) and exit pupil light shield (6) according to the temperature signals fed back by the temperature sensors (11) at different positions, so as to compensate for the cold and achieve rapid cooling.

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