A cryogenic optical system

Abstract

The present invention relates to the field of detection technology, and discloses a cryogenic optical system, wherein the optical system is used to be installed inside a dewar cavity of an infrared detection system, and the optical system is used to be movably connected to a cold source of the infrared detection system, and the optical system includes a focusing device, and the focusing device includes a rotating arm, a first end of the rotating arm is detachably connected to the optical system, and a second end of the rotating arm passes through the dewar cavity and is movably connected to the dewar cavity. The present invention provides a cryogenic optical system, which takes into account that a certain degree of defocusing will occur after lowering the temperature of the optical system, and adjusts the cryogenic optical system by setting a focusing device so that focusing can be performed at low temperatures to ensure image quality at low temperatures.

Description

Technical Field

[0001] The present invention relates to the field of detection technology, and in particular to a low-temperature optical system. Background Art

[0002] With the development of infrared detection technology, high-sensitivity infrared detection has become one of the main research directions, and has broad application prospects in the fields of thermal infrared hyperspectral imaging, long-distance detection of weak targets, infrared astronomical observation, etc. Since the target temperature is near room temperature, its corresponding peak infrared radiation signal overlaps with the infrared signal emitted by the optical system which is also at room temperature, making it difficult to achieve long-distance detection of the target. By lowering the temperature of the optical system itself, the radiation noise of the optical system itself can be effectively reduced, which is a necessary means to achieve high-sensitivity infrared detection.

[0003] Most of the existing low-temperature optical systems have optical-mechanical structures that are directly used at low temperatures after being assembled and adjusted at room temperature. Optical systems assembled and adjusted at room temperature will have a certain degree of defocus at low temperatures, affecting the image quality at low temperatures. The focusing device at room temperature actively controls the position of one or more optical parts through a driving device, but conventional focusing devices cannot be directly used in low-temperature and vacuum environments. Summary of the invention

[0004] An embodiment of the present invention provides a cryogenic optical system, which is used to solve or partially solve the problem that the optical-mechanical structure of the existing cryogenic optical system will be defocused to a certain extent at low temperatures, thereby affecting the imaging quality at low temperatures.

[0005] An embodiment of the present invention provides a low-temperature optical system, which is used to be installed inside a Dewar cavity of an infrared detection system, and the optical system is used to be movably connected to a cold source of the infrared detection system. The optical system includes a focusing device, and the focusing device includes a rotating arm. The first end of the rotating arm is detachably connected to the optical system, and the second end of the rotating arm passes through the Dewar cavity and is movably connected to the Dewar cavity.

[0006] Based on the above scheme, the optical system includes a lens barrel and a plurality of optical devices arranged inside the lens barrel, the outer side of the lens barrel is provided with a conductive sleeve, and the lens barrel and the conductive sleeve are movably connected, and the conductive sleeve is connected to a cold source.

[0007] Based on the above solution, a threaded connection section is provided between the lens barrel and the conductive sleeve, the Dewar chamber includes a connected Dewar shell and a Dewar front cover, and the second end of the rotating arm is used to be rotatably connected to the Dewar front cover.

[0008] Based on the above scheme, a protrusion is provided on the outer wall of the lens barrel along the circumference, and the protrusion is provided with at least one notch along the circumference of the lens barrel, and the first end of the rotating arm is connected to a fork corresponding to the notch, and the fork is inserted into the notch.

[0009] Based on the above solution, the protrusion is located between the end surface of the conductive sleeve and the first end surface of the rotating arm, and there is a distance between the protrusion and the conductive sleeve and between the protrusion and the first end surface of the rotating arm.

[0010] Based on the above solution, there is a distance between the shift fork and the outer wall surface of the lens barrel; and the width of the notch is greater than the width of the shift fork.

[0011] On the basis of the above scheme, an opening is provided on the Dewar front cover, the inner wall of the opening has a step surface, and a convex edge is provided on the outer wall of the second end of the rotating arm, one side of the convex edge is connected to the step surface, and the other side of the convex edge is connected to the pressure ring, and the pressure ring is connected to the Dewar front cover.

[0012] Based on the above solution, a sealing structure is provided between the second end of the rotating arm and the Dewar housing.

[0013] Based on the above solution, the second end of the rotating arm is detachably connected to a focusing wrench.

[0014] Based on the above solution, thermal grease is provided between the outer wall of the lens barrel and the inner wall of the conductive sleeve at a position other than the threaded connection section.

[0015] A low-temperature optical system provided by an embodiment of the present invention takes into account that a certain degree of defocusing may occur after lowering the temperature of the optical system. A focusing device is provided to adjust the low-temperature optical system so that focusing can be performed at low temperatures to ensure image quality at low temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 It is a cross-sectional schematic diagram of an optical system arranged in a Dewar cavity in an embodiment of the present invention;

[0018] Figure 2 is a cross-sectional schematic diagram of an optical system in an embodiment of the present invention;

[0019] Figure 3 is an external schematic diagram of an optical system in an embodiment of the present invention;

[0020] Figure 4 It is a schematic diagram of the end face of the Dewar front cover in an embodiment of the present invention;

[0021] Figure 5 Schematic diagram of the connection cross section between the optical system and the focusing wrench in an embodiment of the present invention;

[0022] Figure 6 The figure is an overall schematic diagram of the arrangement of the focusing wrench in the embodiment of the present invention.

[0023] Description of reference numerals:

[0024] Among them, 1. infrared detector; 2. conductive sleeve; 3. dewar housing; 4. lens barrel; 5. threaded connection section; 6. rotating arm; 7. dewar front cover; 8. focusing wrench; 9. dewar window; 10. pressure ring; 11. optical lens group; 12. fork; 13. notch; 14. convex edge; 15. cold source contact surface; 16. bump; 17. sealing structure. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0027] refer to Figure 1 The embodiment of the present invention provides a cryogenic optical system, wherein the optical system is used to be installed inside the Dewar cavity of the infrared detection system, and the optical system is used to be movably connected to the cold source of the infrared detection system. The optical system includes a focusing device, and the focusing device includes a rotating arm 6, a first end of the rotating arm 6 is detachably connected to the optical system, and a second end of the rotating arm 6 passes through the Dewar cavity and is movably connected to the Dewar cavity.

[0028] The present embodiment provides an optical system suitable for a low-temperature infrared detection system. The present embodiment places the optical system into the Dewar cavity of the detection system, and connects the optical system to a cold source, so that the optical system can obtain the coldness of the cold source, thereby placing the optical system in a low-temperature environment, which can effectively reduce noise and improve detection sensitivity. Furthermore, the present embodiment takes into account that the optical system generally includes a germanium lens, which has a large temperature refractive index coefficient and is very sensitive to temperature changes. After the optical system is debugged at room temperature, a certain degree of defocus will occur after the temperature of the optical system is lowered; the present embodiment proposes to set a focusing device to adjust the low-temperature optical system, so that focusing can be performed at low temperatures to ensure image quality at low temperatures.

[0029] The infrared detector 1 in the infrared detection system is generally fixedly connected to the cold source in the Dewar cavity. In this embodiment, the optical system is arranged to be movable relative to the cold source, so that the relative distance between the optical system and the infrared detector 1 can be adjusted by moving the optical system to achieve the effect of focusing. The rotating arm 6 is the main component of the focusing device. The rotating arm 6 passes through the Dewar cavity and is movably connected to the Dewar cavity, so that the optical system can be driven to move by moving the rotating arm 6 outside the Dewar cavity for focusing.

[0030] A low-temperature optical system provided in this embodiment addresses the difficulty of detecting weak targets at long distances in space. By lowering the temperature of the optical system and reducing the background noise of the optical system, the sensitivity of the entire system is improved, thereby improving the signal-to-noise ratio of the detection system, thereby achieving infrared detection of weak targets. In addition, considering that a certain degree of defocusing will occur after lowering the temperature of the optical system, a focusing device is provided to adjust the low-temperature optical system so that focusing can be achieved at low temperatures to ensure image quality at low temperatures.

[0031] Furthermore, the low-temperature optical system provided in this embodiment has a stable working temperature, is not affected by changes in the external environment temperature, and reduces the non-uniformity correction of the system; the optical system and the infrared detector 1 share a cold source, and the traditional Dewar cold screen can also be eliminated. The optical system is not affected by the cold screen F number, has a large field of view, and has the characteristics of compact structure. Among them, the cold source is not limited to low-temperature refrigerants (cryogenic liquids such as liquid nitrogen, liquid oxygen, and liquid helium), but also includes low-temperature refrigerators (Stirling refrigerators, pulse tube refrigerators, GM refrigerators, etc.), which are not specifically limited.

[0032] Furthermore, in this embodiment, the first end of the rotating arm 6 is detachably connected to the optical system. In this embodiment, the optical system is connected to the cold source and is in a low temperature state, and the second end of the rotating arm 6 passes through the Dewar cavity and extends into the surrounding environment so that the rotating arm 6 is in a normal temperature state. If the rotating arm 6 is always connected to the optical system, it will inevitably affect the low temperature state of the optical system. Then, when focusing is required, the rotating arm 6 can be connected to the optical system for focusing; and when focusing is not required, the rotating arm 6 can be disconnected from the optical system, thereby preventing the rotating arm 6 from affecting the low temperature of the optical system and ensuring the low temperature state of the optical system.

[0033] On the basis of the above embodiments, further, referring to Figure 1 In this embodiment, the optical system includes a lens barrel 4 and a plurality of optical devices arranged inside the lens barrel 4. A conductive sleeve 2 is provided on the outer side of the lens barrel 4, and the lens barrel 4 and the conductive sleeve 2 are movably connected, and the conductive sleeve 2 is connected to a cold source. The lens barrel 4 conducts heat transfer with the cold source through the conductive sleeve 2, and the optical devices and the lens barrel 4 also conduct heat transfer, thereby achieving low temperature of the optical system. The lens barrel 4 is connected to the first end of the rotating arm 6. The conductive sleeve 2 can be fixedly connected to the cold source, so that by moving the lens barrel 4, the lens barrel 4 is moved relative to the conductive sleeve 2, and the lens barrel 4 is moved relative to the cold source to achieve focusing. The optical system is driven to move by moving the lens barrel 4 as a whole. Reference Figure 2 , the conductive sleeve 2 is connected to the cold source contact surface 15; the infrared detector 1 is also installed on the cold source contact surface 15 (it can be a conventional connection method, not specifically shown in the figure); the conductive sleeve 2 can be a hollow structure, and the infrared detector 1 is arranged inside the conductive sleeve 2, and the two are not in contact with each other and are respectively connected to the cold source. The infrared detector 1 and the conductive sleeve 2 are installed on the same cold source, which can be liquid nitrogen, a mechanical refrigerator, or other refrigeration forms that can obtain low temperatures.

[0034] Further, refer to Figure 2 This embodiment provides a transmissive optical system. The optical system includes an optical lens group 11 connected to the inside of the lens barrel 4 in sequence along the axial direction of the lens barrel 4; the optical lens group 11 may include multiple lenses, filters, pupils, etc. The transmissive optical system has a compact structure and a large field of view, and is easy to package and integrate with the infrared detector 1. The optical lens group 11 is fixed to the lens barrel 4 by gluing.

[0035] The optical system may also be other optical systems, which are not specifically limited; preferably, the optical system is an optical system that is convenient for packaging and integration, so that the optical system can be driven to move and achieve focusing through the rotating arm 6.

[0036] On the basis of the above embodiments, further, referring to Figure 1 and Figure 2A threaded connection section 5 is provided between the lens barrel 4 and the conductive sleeve 2, the Dewar chamber includes a connected Dewar housing 3 and a Dewar front cover 7, and the second end of the rotating arm 6 is used to be rotatably connected to the Dewar front cover 7. The lens barrel 4 can move axially relative to the conductive sleeve 2 by rotating. The rotation of the lens barrel 4 can be achieved by rotating the rotating arm 6. Since the conductive sleeve 2 is fixed, the rotation of the lens barrel 4 can achieve the front and back adjustment of the focal length. By rotating the lens barrel 4, the front and back movement of the lens barrel 4 can be achieved, so that the relative distance between the optical lens group 11 and the infrared detector 1 can be changed, thereby achieving the purpose of focusing.

[0037] Furthermore, the movable connection between the optical system and the cold source may also be other structures, for example, a guide rail or track may be provided to be connected to the cold source, and the optical system may be movably connected to the guide rail or track, etc. In this case, the second end of the rotating arm 6 may be slidably connected to the Dewar front cover 7. In addition, the movable connection between the lens barrel 4 and the conductive sleeve 2 may also be realized without threaded connection, and the movable connection between the lens barrel 4 and the conductive sleeve 2 may also be realized through structures such as guide rails or tracks; the specific connection structure between the optical system and the cold source is not limited.

[0038] Furthermore, the rotating arm 6 can also extend out of the Dewar housing 3 and be rotatably connected to the Dewar housing 3 to drive the lens barrel 4 to rotate to adjust the focal length.

[0039] On the basis of the above embodiment, further, thermal conductive grease is provided between the outer wall of the lens barrel 4 and the inner wall of the conductive sleeve 2 at a position other than the threaded connection section 5. Figure 1 and Figure 2 A threaded connection section 5 is provided between the front end of the lens barrel 4, i.e., the end close to the Dewar front cover 7, and the conductive sleeve 2. The middle and rear ends of the lens barrel 4 are in sliding contact with the conductive sleeve 2, and the contact interface is filled with thermal grease to ensure good thermal contact. At the same time, the lens barrel 4 can rotate at low temperatures.

[0040] In order to effectively conduct the coldness of the low-temperature cooling source to the optical device, the heat conduction efficiency between the two must be ensured, and the heat conduction efficiency between the two is mainly determined by the thermal contact between the conductive sleeve 2 and the low-temperature cooling source, the thermal contact between the conductive sleeve 2 and the lens barrel 4, and the thermal contact between the lens barrel 4 and the optical device. The lens barrel 4 and the conductive sleeve 2 are in sliding contact outside the threaded connection section 5, and thermal grease is added on the contact surface to ensure heat conduction between the two.

[0041] On the basis of the above embodiments, further, referring to Figure 1 , a protrusion 16 is provided on the outer wall of the lens barrel 4 along the circumferential direction, referring to Figure 3, and the projection 16 is provided with at least one notch 13 along the circumference of the lens barrel 4, and the first end of the rotating arm 6 is connected with a shift fork 12 corresponding to the notch 13, and the shift fork 12 is inserted into the notch 13. The shift fork 12 is a shift block or a shift piece connected to the first end of the rotating arm 6, and the shift fork 12 is inserted into the notch 13, so that by rotating the rotating arm 6, the shift fork 12 can cooperate with the notch 13 to drive the lens barrel 4 to rotate.

[0042] In order to enable the lens barrel 4 to rotate, a rotating arm 6 is designed, and a shift fork 12 is designed on the rotating arm 6 to cooperate with the notch 13 on the lens barrel 4, such as Figure 3 As shown, rotating the rotating arm 6 can drive the lens barrel 4 to rotate through the fork 12, and rotating the rotating arm 6 left and right can realize the front and back movement of the lens barrel 4, realize the change of the distance between the optical lens group 11 and the infrared detector 1, and thus realize the adjustment of the focal length.

[0043] On the basis of the above embodiments, further, referring to Figure 3 The projection 16 is located between the end surface of the conductive sleeve 2 and the first end surface of the rotating arm 6, and there is a spacing between the projection 16 and the conductive sleeve 2 and between the projection 16 and the first end surface of the rotating arm 6. Thus, a space is provided for the lens barrel 4 to move in two axial directions, so that the lens barrel 4 can move in two directions, and the flexibility of focal length adjustment is improved.

[0044] refer to Figure 2 , the front end of the conductive sleeve 2 may be open, the lens barrel 4 may be inserted into the conductive sleeve 2 from the front end of the conductive sleeve 2, and the threaded connection section 5 is threadedly connected to the conductive sleeve 2, and a spacing is provided between the protrusion 16 and the front end face of the conductive sleeve 2 in the axial direction of the lens barrel 4. The first end of the rotating arm 6 is connected with a shift fork 12, and the shift fork 12 is inserted into the notch 13 on the protrusion 16. The setting of the shift fork 12 should not affect the axial movement of the lens barrel 4; and the shift fork 12 should have a certain length to ensure that it can always cooperate with the notch 13 during the rotation of the lens barrel 4. Therefore, the rotating arm 6 only needs to rotate to adjust the position of the lens barrel 4, and the rotating arm 6 does not need to move along the axial direction of the lens barrel 4. The difficulty of connecting the rotating arm 6 and the Dewar front cover 7 can be reduced, and the connection between the rotating arm 6 and the Dewar front cover 7 can be easily achieved.

[0045] On the basis of the above embodiments, further, referring to Figure 3, there is a gap between the fork 12 and the outer wall of the lens barrel 4; the width of the notch 13 is greater than the width of the fork 12. That is, the width of the notch 13 along the circumference of the lens barrel 4 is greater than the width of the fork 12 along the circumference of the lens barrel 4. By rotating the rotating arm 6, the fork 12 can be completely out of contact with the lens barrel 4 and the protrusion 16. A detachable connection structure between the rotating arm 6 and the lens barrel 4 is realized. When the focusing is completed, the rotating arm 6 can be rotated so that the fork 12 is located in the middle of the notch 13, and both sides of the fork 12 are not in contact with the protrusions 16 on both sides. At the same time, the fork 12 is also not in contact with the outer wall of the lens barrel 4, thereby disconnecting the connection between the rotating arm 6 and the lens barrel 4, achieving thermal decoupling, and ensuring the temperature stability of the optical system.

[0046] Since the rotating arm 6 is at room temperature and the lens barrel 4 is at a low temperature, the rotating arm 6 and the lens barrel 4 will only come into contact when the focal length adjustment is required, and the two should be disconnected after the adjustment is completed. Therefore, during the design, it is ensured that the rotating arm 6 fork 12 does not contact the outer wall surface of the lens barrel 4, that is, the two do not contact in the radial direction; the fork 12 can leave a 1.5 mm gap on the left and right sides with the protrusion 16 in the notch 13; when the focal length adjustment is completed, the rotating arm 6 is rotated at a certain angle to disconnect the rotating arm 6 and the lens barrel 4, thereby achieving thermal insulation between the two.

[0047] On the basis of the above embodiments, further, referring to Figure 1 and Figure 4 An opening is provided on the Dewar front cover 7, and the inner wall of the opening has a step surface. A convex edge 14 is provided on the outer wall of the second end of the rotating arm 6, one side of the convex edge 14 is connected to the step surface, and the other side of the convex edge 14 is connected to the pressure ring 10, and the pressure ring 10 is connected to the Dewar front cover 7.

[0048] The rotating arm 6 is axially fixed on the Dewar front cover 7 by the pressing ring 10. The two are only the limit of the rotating arm 6 in the axial direction, and the two can slide against each other in the circumferential direction. The convex edge 14 of the rotating arm 6 is arranged between the step surface in the opening of the Dewar front cover 7 and the pressing ring 10. The convex edge 14 and the step surface and the pressing ring 10 do not need to be connected, so that the rotating arm 6 can rotate freely between the step surface and the pressing ring 10. The pressing ring 10 can be connected to the Dewar front cover 7 by gluing or screws, etc., to realize the limit fixation of the rotating arm 6 in the axial direction.

[0049] On the basis of the above embodiments, further, referring to Figure 1, a sealing structure 17 is provided between the second end of the rotating arm 6 and the Dewar housing 3. Specifically, a sealing structure 17 such as a sealing ring can be provided between the convex edge 14 at the second end of the rotating arm 6 and the step surface in the opening of the Dewar front cover 7 to ensure the vacuum environment of the Dewar chamber. Specifically. An O-ring groove is designed at the second end of the rotating arm 6, and a dynamic seal is achieved between the convex edge 14 on the rotating arm 6 and the step surface of the Dewar front cover 7 to ensure that the entire Dewar does not leak when the rotating arm 6 rotates. Furthermore, a lubricating material layer can be provided between the convex edge 14 and the step surface and between the convex edge 14 and the pressure ring 10 to ensure the smooth rotation of the rotating arm 6.

[0050] On the basis of the above embodiments, further, referring to Figure 1 and Figure 4 The second end of the rotating arm 6 is open, and the second end of the rotating arm 6 is connected to the Dewar window 9. The Dewar window 9 can be fixed to the opening of the second end of the rotating arm 6 by gluing or other means. Further, the first end of the rotating arm 6 can also be provided with an opening, and the first end of the rotating arm 6 can be sleeved on the outside of the lens barrel 4. This can ensure the smooth passage of light.

[0051] refer to Figure 1 The front end of the Dewar housing 3 and the Dewar front cover 7 can be detachably fixedly connected by screws, etc. The rear end of the Dewar housing 3 can be connected to a cold source.

[0052] On the basis of the above embodiments, further, referring to Figure 5 and Figure 6 , the second end of the rotating arm 6 is detachably connected with a focusing wrench 8. It is convenient to apply force to the rotating arm 6 for focusing. Specifically, a matching concave-convex structure can be set between the second end of the rotating arm 6 and the focusing wrench 8 to realize the transmission connection between the two and facilitate disassembly. For example, a matching concave-convex structure can be set between the second end face of the rotating arm 6 and the end face of the focusing wrench 8, and the second end face of the rotating arm 6 can be set flush with the end face of the Dewar front cover 7; the second end face of the rotating arm 6 can also be set to extend out of the Dewar front cover 7, and the focusing wrench 8 is sleeved on the second end of the rotating arm 6, and a matching concave-convex structure can be set between the outer wall of the second end of the rotating arm 6 and the inner wall of the focusing wrench 8. The connection structure between the rotating arm 6 and the focusing wrench 8 is not limited, with the purpose of realizing the transmission connection between the two and facilitating disassembly. Rotating the rotating arm 6 by the focusing wrench 8 can realize the forward and backward movement of the lens barrel 4 at vacuum and low temperature, change the distance between the optical lens group 11 and the infrared detector 1, and thus realize the adjustment of the focal length.

[0053] On the basis of the above embodiments, further, this embodiment provides a low-temperature focusing device, which can realize real-time adjustment of the focal length of a transmission-type infrared low-temperature optical system at low temperatures. The transmission-type low-temperature optical focusing device includes a dewar housing 3, a dewar front cover 7, a dewar window 9, a rotating arm 6, a pressure ring 10, an optical lens group 11, a lens barrel 4 and a conductive sleeve 2.

[0054] As the optical part of the refrigerated infrared detection system, the transmission type low temperature optical system needs to work at low temperature (below 120K temperature) like the infrared detector 1. In order to reduce the volume of the system, the infrared detector 1 and the optical system adopt a common cold source design. The detector can be fixed on the substrate, and the substrate is in direct contact with the low temperature cold source. The optical lens barrel 4 is connected to the cold source contact surface 15 through the conductive sleeve 2. The conductive sleeve 2 is fixedly installed with the low temperature cold source. The low temperature cold source cools the optical system to a low temperature while cooling the infrared detector 1. In addition, in order to ensure that the detector and the optical system do not fog up due to low temperature during operation, both need to work in a vacuum low temperature environment.

[0055] The complexity of adjusting the focal length of the system is considered during the optical design. By adjusting the back intercept, the defocus of the system can be compensated to achieve better image quality. For this reason, the transmission type low-temperature optical low-temperature focusing needs to solve the problem that the optical lens barrel 4 can realize the forward and backward movement between the focal plane of the detector in a vacuum and low-temperature environment. The method adopted is to process a section of thread at the front end of the lens barrel 4 and the conductive sleeve 2 respectively, and the threads of the two form a thread pair, which can rotate with each other. In order to enable the lens barrel 4 to rotate with each other, a rotating arm 6 is designed. The rotating arm 6 has a shift fork 12, and there is a notch 13 on the outside of the lens barrel 4. The rotation of the rotating arm 6 can realize the rotation of the lens barrel 4. In order to ensure real-time focusing at low temperatures, it is necessary to ensure good vacuum sealing and good thermal conductivity conditions. An O-ring sealing groove is designed on the rotating arm 6, and the dynamic sealing of the rotating arm 6 and the Dewar front cover 7 is realized by the O-ring to ensure the vacuum condition during focusing. After the focusing is completed, the heat leakage of the system should be minimized as much as possible. At this time, the rotating arm 6 is rotated at a certain angle to disconnect the thermal connection between the rotating arm 6 and the lens barrel 4 to ensure the temperature stability of the optical system.

[0056] In view of the fact that most existing cryogenic optical systems lack an adaptive focusing device, this embodiment provides a focusing device that can be used in cryogenic optical systems. Because the refractive index of infrared lens materials is very sensitive to temperature, the focusing of existing cryogenic systems is mostly a case of installing at room temperature and adjusting at low temperature. There will be certain errors in actual use, and the accuracy of the focal length at low temperatures cannot be guaranteed. The purpose of this embodiment is to solve the problem of low-temperature focusing of a transmission-type cryogenic optical system and ensure the optical performance of the optical system at low temperatures.

[0057] The low-temperature optical system focusing device can be used in vacuum and low-temperature environments; it can realize real-time adjustment of the focal length of the transmission-type low-temperature optical system; after completing the focusing, the focusing device can be thermally decoupled from the low-temperature optical system without affecting the temperature distribution of the optical system, thereby maintaining the stability of the optical focal plane.

[0058] On the basis of the above embodiments, further, this embodiment provides an infrared detection system based on transmission-type cryogenic optics, which can realize high-sensitivity infrared detection of weak targets at long distances in space. According to the blackbody radiation law, the radiation energy is related to the fourth power of temperature. Therefore, this embodiment can greatly reduce the thermal noise of the optical system by lowering the temperature of the optical system, thereby improving the signal-to-noise ratio of the detection system, thereby improving the detection sensitivity and realizing effective detection of weak targets. This embodiment belongs to the field of infrared detection, and relates to a high-sensitivity infrared detection system suitable for long-wave and very long-wave infrared detection in space.

[0059] The infrared detection system provided in this embodiment uses a mechanical refrigerator as a cold source to cool the optical system to a low temperature while cooling the infrared detector 1 and ensure its imaging quality at low temperatures, thereby achieving effective detection of weak targets by reducing the thermal noise of the optical system.

[0060] Specifically, an infrared detection system based on transmission-type cryogenic optics includes a refrigerated infrared detector 1, a cryogenic cold source, a conductive sleeve 2, an optical window, a transmission-type cryogenic optical system, a vacuum pump, and a detector electrical lead interface. A cryogenic cold source, such as a cryogenic refrigerant (liquid nitrogen), a mechanical refrigerator, or the like, can provide cryogenic cold energy to cool the infrared detector 1 to a temperature of 80K or below by heat conduction. The cold source transfers the cold energy to the optical system through the conductive sleeve 2, so that the optical system is cooled to a low temperature. The vacuum pump (not shown in the figure) is provided on the Dewar housing 3 or the Dewar front cover 7, and is used to achieve the vacuum of the Dewar cavity. The detector electrical lead interface (not shown in the figure) is used to power the infrared detector 1.

[0061] The cryogenic optical system consists of a transmission optical system, a lens barrel 4, a cold mass transmission device, namely a conductive sleeve 2, and a cryogenic focusing device. The optical system and the detector share a common cold source design, and the optical system is cooled to a low temperature while cooling the detector. According to the blackbody radiation law, when the temperature of the optical system is reduced, its own radiation will be greatly reduced, which will help reduce the noise of the detection system and improve the signal-to-noise ratio.

[0062] The cold source can be connected to the substrate. The infrared focal plane detector is installed on the low-temperature cold source substrate, and the cold conduction sleeve 2 is installed on the low-temperature cold source substrate. The optical lens assembly is installed on the lens barrel 4, and then the entire optical assembly is installed on the cold conduction sleeve 2, and the back intercept of the optical system is maintained at the designed value. The vacuum dewar shell 3, the vacuum dewar front cover 7, the light window and the focusing device are installed as a whole. The connection between each component has an O-ring as a sealing structure 17, which can ensure the vacuum sealing of the entire structure. The focusing device is aligned with the notch 13 of the lens barrel 4 to install the vacuum dewar shell 3 assembly on the vacuum interface of the low-temperature cold source.

[0063] The transmission optical system is installed inside the dewar and shares a cold source with the detector. The target signal passes through the window and then passes through the optical system and converges on the infrared focal plane detector. During operation, the inside of the dewar is in a vacuum state, and the infrared detector 1 and the optical system are cooled to a low temperature at the same time. Due to the optical system, the self-noise is greatly reduced after the temperature is lowered, so that the signal-to-noise ratio of the entire system can be improved, and high-sensitivity detection can be achieved. Since the transmission optical system is different at low temperature and room temperature, the focal length of the optical system will change when it works at low temperature. At this time, the low-temperature focusing device is used to focus at low temperature. When the focal length of the optical system is adjusted to a suitable position, the focusing device and the optical system are disconnected. At this time, the low-temperature optical system can clearly image at low temperature. The infrared detection system based on transmission-type low-temperature optics is not only for the optical system listed in this embodiment.

[0064] The infrared detection system based on the transmission type low temperature optical system is designed with a common cold source for the detector and the optical system, and has the characteristics of low noise and high sensitivity. The transmission type low temperature optical system has a compact structure and a large field of view, which solves the problem of transmission type low temperature imaging. It has the function of real-time focusing at low temperatures. It can realize the effective detection of faint targets, has a compact structure and a large field of view, and is suitable for fields with limited volume and weight but requiring high-sensitivity infrared detection.

[0065] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A cryogenic optical system, characterized in that: The optical system is used to be installed inside the Dewar cavity of the infrared detection system, and the optical system is used to be movably connected to the cold source of the infrared detection system. The optical system includes a focusing device, and the focusing device includes a rotating arm. The first end of the rotating arm is detachably connected to the optical system, and the second end of the rotating arm passes through the Dewar cavity and is movably connected to the Dewar cavity; the optical system includes a lens barrel and a plurality of optical devices arranged inside the lens barrel, the outer side of the lens barrel is provided with a conductive sleeve, and the lens barrel is movably connected to the conductive sleeve, and the conductive sleeve is connected to the cold source; a threaded connection section is provided between the lens barrel and the conductive sleeve, the Dewar cavity includes a connected Dewar shell and a Dewar front cover, and the second end of the rotating arm is used to be rotatably connected to the Dewar front cover; a convex block is provided on the outer wall of the lens barrel along the circumferential direction , and the protrusion is provided with at least one notch along the circumference of the lens barrel, the first end of the rotating arm is connected with a shift fork corresponding to the notch, and the shift fork is inserted into the notch; the protrusion is located between the end face of the conductive sleeve and the first end face of the rotating arm, and there is a spacing between the protrusion and the conductive sleeve and between the protrusion and the first end face of the rotating arm respectively; there is a spacing between the shift fork and the outer wall surface of the lens barrel; the width of the notch is greater than the width of the shift fork; an opening is provided on the Dewar front cover, and the inner wall of the opening has a step surface, and a convex edge is provided on the outer wall of the second end of the rotating arm, one side of the convex edge is connected to the step surface, and the other side of the convex edge is connected to a pressure ring, and the pressure ring is connected to the Dewar front cover; a sealing structure is provided between the second end of the rotating arm and the Dewar outer shell.

2. The cryogenic optical system according to claim 1, characterized in that: The second end of the rotating arm is detachably connected with a focusing wrench.

3. The cryogenic optical system according to claim 1, characterized in that: Thermal grease is provided between the outer wall of the lens barrel and the inner wall of the conductive sleeve at a position other than the threaded connection section.

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