Device and method for testing low-temperature background performance of refrigeration type infrared detector

Abstract

The invention discloses a device and method for testing the low-temperature background performance of a refrigeration type infrared detector, and the device comprises the steps: arranging an isolation disc, forming a small hole in the isolation disc, communicating the interior of a cold cover with a sealing cavity, reducing a heat conduction medium in the air through vacuumizing, and arranging a double-layer structure with the cold cover as an outer layer and a cold shield as an inner layer, thereby achieving the testing of the low-temperature background performance of the refrigeration type infrared detector. Heat radiation during operation of the refrigerating machine is effectively shielded, a second baffle is arranged to shield the Dewar and heat radiation during operation of the refrigerating machine, the heat radiation is conducted into the cold cover through small holes in an isolation disc, and the heat radiation is absorbed through a blackening layer, so that the device can reach a lower temperature in the testing process, the influence caused by the heat radiation is reduced, and the testing efficiency is improved. And the test accuracy is improved.

Description

Technical Field

[0001] This invention belongs to the field of performance testing of cooled infrared detectors, and specifically relates to an apparatus and method for testing the low-temperature background performance of cooled infrared detectors. Background Technology

[0002] Large-area cooled infrared detectors, due to their high detection sensitivity and high resolution, are widely used in space applications such as astronomical observation, environmental monitoring, and resource exploration. These applications typically use deep space as the observation background, with targets at great distances (hundreds to thousands of kilometers) or at low temperatures, resulting in very weak signals received by the infrared detectors. For the optomechanical system at the front end of the infrared detector, thermal background noise caused by its own thermal radiation is a significant factor affecting the detector's sensitivity. Therefore, to maximize the sensitivity of the infrared detector, the optomechanical system usually adopts a fully cryogenic optical system design. The core of this design is to comprehensively consider the detector's own performance, the infrared radiation characteristics of the target object and the optomechanical system to determine the detector's permissible limits for background radiation noise. This allows for the rational design of the optical system's cooling temperature, the satellite payload's energy supply, and ultimately ensures that all parameters of the optical system meet the system's performance requirements.

[0003] To provide data references for the rational design and development of cryogenic optical systems, infrared detectors need to undergo performance testing under cryogenic conditions. Typical testing equipment includes... Figure 1 As shown, the device consists of five parts: an infrared detector connected to an infrared detector performance testing system, which can provide power to the infrared detector chip, control it, and perform signal processing and data acquisition and processing; a cooling power supply that can power the infrared detector cooling unit to cool the infrared detector device to its operating temperature; and a surface source blackbody and its temperature control module that can control the temperature of the blackbody to a specific temperature as needed.

[0004] However, the temperature control range of surface source blackbody is quite limited: to achieve low-temperature background performance testing of infrared detectors, the blackbody temperature usually needs to be controlled to -173℃ or even lower. The temperature control range of conventional surface source blackbody is 0~100℃, which cannot meet the testing requirements.

[0005] Furthermore, the thermal background noise caused by the infrared detector's own thermal radiation was not effectively suppressed. Figure 1 The metal Dewar radiator of the packaged infrared detector chip is at ambient temperature. When testing low-temperature background performance, the Dewar radiates a large amount of heat, which will seriously affect the accuracy of the test results.

[0006] The basic method for testing the performance of a cooled infrared detector is as follows: First, power is supplied to the cooling unit until the infrared detector reaches its operating temperature; second, a specific voltage is applied to the detector through the test unit, and the output voltage data of each pixel of the device is continuously collected at blackbody temperatures T1 and T2; finally, the detector's responsivity, detectivity, and other performance parameters are calculated based on the collected data.

[0007] CN108168705A discloses a variable temperature testing unit, comprising: a background support body, a first housing, a first cold finger cylinder, a blackbody plane, a first cooling device, a chip support body, a second housing, a second cold finger cylinder, a cold screen, a second cooling device, and a vacuum interface. The main shortcomings of the aforementioned prior art are:

[0008] On the one hand, although the first and second shells are airtightly connected, the shells themselves and the external environment emit a lot of heat when testing low-temperature background performance, which will affect the test results.

[0009] On the other hand, a very small amount of heat radiation generated by the refrigeration unit's outer casing may enter the sealed cavity through the pipes, affecting the test results in the context of low temperature.

[0010] To address the shortcomings of existing technologies where the housing itself emits thermal radiation and the refrigeration unit's radiation enters the sealed cavity through the gas path, affecting testing under extremely low temperature backgrounds, a device and method for testing the low-temperature background performance of a cooled infrared detector are proposed. Summary of the Invention

[0011] To address the aforementioned issues, this invention has made improvements and innovations, aiming to provide a device and method for testing the low-temperature background performance of cooled infrared detectors. The device and method are simple in structure, easy to install, and highly versatile, applicable to the low-temperature background performance testing of most area array infrared detectors. By setting up a sealed connection between the housing and the Dewar, using a vacuum pump to create a vacuum inside the cavity, and using a cooling machine to reduce the influence of the heat radiation generated by the Dewar itself on the test results.

[0012] By setting up a cold cover, a two-layer structure is formed together with the cold shield, and the cold cover is sealed to the second-stage cold finger of the second refrigeration unit, which effectively shields and reduces the heat radiation generated by the Dewar shell itself and the first and second refrigeration units during operation, thus reducing the impact on the test.

[0013] By opening small holes in the isolation plate and sealing it with the cold cover, the inner cavity of the cold cover is connected to the sealed cavity between the first and second refrigeration units. Under the action of the vacuum pump, a vacuum environment is jointly formed, reducing convective heat transfer in the air and providing a vacuum environment for subsequent cooling.

[0014] Specifically, the present invention is implemented as follows: a device for testing the low-temperature background performance of a cooled infrared detector, comprising an infrared detector, a blackbody system, a power supply, a vacuum pump, a temperature controller, and an infrared detector performance testing unit. The infrared detector includes a detector chip, a cold screen, a Dewar flare, and a first refrigerator. The first refrigerator is equipped with a cold finger. The blackbody system is equipped with a second refrigerator. The second refrigerator is equipped with a primary cold finger, and a ring-shaped secondary cold finger extends from the sidewall of the primary cold finger. The device also includes:

[0015] An isolation plate, the isolation plate being generally disc-shaped with a circular hole in its center, through which the isolation plate is fitted onto the cold finger of the first refrigeration unit;

[0016] The cold cover has one end sealed to the isolation plate and the other end sealed to the secondary cold finger of the second refrigerator. A non-sealed cavity is formed between the isolation plate and the secondary cold finger, forming a two-layer wrapping structure for the detector chip, with the cold cover as the outer layer and the cold screen as the inner layer.

[0017] The outer edge of the isolation disk is sealed to the cold cover and a gap is left between it and the detector chip fixing base plate. The isolation disk is provided with several small holes to allow the inside and outside of the cold cover to communicate. A vacuum environment is formed in the sealed cavity and inside the cold cover by a vacuum pump.

[0018] The inner wall of the cold cover is provided with several annular second baffles to shield the heat radiation conducted from the Dewar side through the small holes of the isolation plate into the cold cover.

[0019] Furthermore, the Dewar is fitted onto the cold finger of the first refrigerator, and the cold finger is connected to the detector chip; the blackbody system also includes a blackbody and a housing, and the first-stage cold finger of the second refrigerator is connected to the blackbody; wherein, one end of the Dewar is sealed to the side wall of the first refrigerator, and the other end is sealed to one end of the housing, and the other end of the housing is sealed to the side wall of the second refrigerator, forming a sealed cavity between the first and second refrigerators, and the side wall of the housing is provided with a connection port for use with a vacuum pump to evacuate the sealed cavity.

[0020] Furthermore, the inner wall of the cold cover, the inner and outer walls of the cold screen, and the second baffle are all coated with a blackening layer with an emissivity of 0.95, which is used to absorb thermal radiation.

[0021] Furthermore, the cold screen is a cup-shaped structure with a larger diameter at one end and a smaller diameter at the other end. Its inner wall is provided with several annular first baffles. The large opening end of the cold screen is connected to the detector chip fixing base plate, and the small opening end is provided with an opening so that the detector chip is opposite to the blackbody. The inner wall of the cold screen is provided with several annular first baffles for shielding thermal radiation.

[0022] Furthermore, the detector chip is electrically connected to the infrared detector performance testing device; the blackbody is electrically connected to the temperature controller; and the first refrigerator, the second refrigerator, and the vacuum pump are all electrically connected to the power supply.

[0023] Furthermore, the second refrigeration unit is a GM refrigeration unit, including a primary cooling finger and a secondary cooling finger. The secondary cooling finger is a ring-shaped structure extending from the sidewall of the primary cooling finger, and its diameter matches that of the cooling shroud. The primary cooling finger is connected to the blackbody and provides cooling to the blackbody, with a minimum temperature drop to -253°C. The secondary cooling finger is sealed to the cooling shroud and provides cooling to the cooling shroud, with a minimum temperature drop to -243°C and a temperature control accuracy of 0.1°C.

[0024] Furthermore, the connection port is a KF25 vacuum interface.

[0025] Furthermore, the length of the second baffle on the inner wall of the cold cover matches the cup-shaped structure of the cold screen, so that there is a gap between the longitudinal end of the second baffle and the side wall of the cold screen.

[0026] A method for testing the low-temperature background performance of a cooled infrared detector using an apparatus includes the following steps:

[0027] S1. Start the vacuum pump until a vacuum environment is formed in both the sealed cavity and the inside of the cold cover. The inside of the cold cover is connected to the sealed cavity through the small hole on the isolation plate. Under the action of the vacuum pump, a vacuum environment is formed together to reduce convective heat transfer in the air and achieve better cooling conditions.

[0028] S2. Start the first and second refrigerators. At this time, the first refrigerator cools the detector chip through the cold finger, and the second refrigerator cools the blackbody through the first-stage cold finger and the cold cover through the second-stage cold finger, forming a non-sealed low-temperature cavity with the cold cover as the outer layer and the cold screen as the inner layer, until the infrared detector reaches the working temperature.

[0029] S3. During the continuous cooling process, the Dewar itself, the first refrigeration unit and the second refrigeration unit generate heat radiation during the cooling process. The two-layer structure formed by the cold cover and the cold screen can effectively shield it. The heat radiation conducted from the small hole to the inside of the cold cover is effectively shielded by the second baffle inside the cold cover, and the heat radiation is absorbed by the blackening layer.

[0030] S4. The first baffle inside the cold shield provides secondary shielding against the heat radiation conducted through the small hole to the inside of the cold cover, and absorbs the heat radiation through the blackening layer on the inner wall of the cold shield, reducing the impact of heat radiation on the testing process, so that the temperature at the blackbody can be reduced to a minimum of -253°C and the temperature at the cold cover can be reduced to a minimum of -243°C, which is closer to absolute zero.

[0031] S5. Start the performance testing unit for the temperature controller and infrared detector;

[0032] S6. Perform performance testing on the infrared detector.

[0033] Working principle:

[0034] In existing technologies such as Figure 1 As shown, the metal Dewar assembling the infrared detector chip is at ambient temperature and is connected to the detector chip only through the cooling coil of the refrigerator. When testing low-temperature background performance, the Dewar itself emits significant heat radiation, and the refrigerator itself also emits heat during operation. These factors severely affect the accuracy of the test results due to background heat radiation. Furthermore, testing low-temperature background performance requires controlling the blackbody temperature to -173℃ or even lower, while the standard blackbody temperature control range is 0~100℃, which cannot meet the testing requirements.

[0035] In addressing the issue of heat radiation from the Dewar 13, the first refrigerator 14, and the second refrigerator 23, this invention first designs a cold cover 4, combining the cold cover 4 and the cold shield 12 into a double-layered cavity. A small hole 31 is opened on the isolation plate 3 to connect the inside and outside of the cold cover 4. A vacuum pump 7 creates a vacuum environment within the sealed cavity 5 formed by the Dewar 13 and the shell 22. The design of the small hole 31 also creates a vacuum environment inside the cold cover 4, removing heat radiation from the air and providing conditions for cooling. During the cooling process, the first refrigerator 14 and the second refrigerator 23 generate heat radiation. The second refrigerator 23's secondary cooling index 232 continuously cools the inside of the cold cover. The double-layered structure formed by the cold cover 4 and the cold shield 12 effectively shields the external heat radiation from the cold cover 4. The heat radiation from one side of the Dewar 13 and the first refrigerator 14 is... The heat radiation is conducted into the cold cover 4 through the small hole 31. At this time, a second baffle 41 is set inside the cold cover 4 to shield the heat radiation entering the cold cover 4. The heat radiation is further shielded by the first baffle 121 inside the cold screen 12. The heat radiation is absorbed by the blackening layer 42 plated on the inner and outer surfaces of the cold screen 12, the first baffle 121 and the second baffle 41 inside the cold cover 4. The emissivity of the blackening layer is 0.95. For the temperature control of the blackbody 21, the first-stage cooling finger 231 of the second refrigerator 23 cools the blackbody 21. The second-stage cooling finger 232 of the second refrigerator 51 continuously cools the inside of the cold cover 4, reducing the residual heat radiation inside the cold cover 4. The temperature at the blackbody 21 can be reduced to a minimum of -253°C, and the temperature inside the cold cover 4 can be reduced to a minimum of -243°C, which is closer to absolute zero, significantly reducing the impact of heat radiation on the test results.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] This invention provides a cold shield between the isolation plate and the secondary cold finger of the second refrigerator, forming a double-layer cavity with the cold shield and the cold shield. The secondary cold finger further cools the inside of the cold shield, and the cold shield shields the heat radiation generated during the operation of the second refrigerator, providing a better low-temperature background and ensuring the accuracy of the test results.

[0038] This invention provides support for the cold cover by setting up an isolation plate and opening small holes in the isolation plate, forming a cavity structure. The small holes also connect the sealed cavity formed between the first and second refrigeration units, so that during the vacuuming process, the small holes provide a gas path for evacuating the inside of the cold cover, creating a vacuum condition inside the cold cover and the cold screen.

[0039] The present invention provides several second baffles on the inner wall of the cold cover to isolate the heat radiation generated by the first refrigeration unit during operation and the Dewar itself, and to coat all the inner and outer surfaces of all components inside the cold cover with a blackening layer to absorb heat radiation.

[0040] The present invention provides a method to shield and absorb heat radiation conducted from the small holes of the isolation disk into the cold cover by setting several first baffles inside the cold screen and coating the inner wall of the cold screen with a blackening layer.

[0041] This invention creates a sealed cavity between the first and second refrigeration units by setting a Dewar and sealing it with the housing. By setting a connection port on the side wall of the housing to connect with a vacuum pump, a vacuum environment is created inside the cavity, providing a vacuum environment for subsequent refrigeration.

[0042] This invention utilizes a GM refrigerator, which includes two cooling stages. The first stage provides cooling to the blackbody, with a minimum temperature drop of -253°C, while the second stage provides cooling to the cold cover, with a minimum temperature drop of -243°C. The temperature control accuracy is 0.1°C. This refrigerator can be used for both blackbody cooling and cold cover cooling, while also shielding against external heat radiation. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the overall structure of the device in the background art;

[0044] Figure 2 This is a schematic diagram of the overall structure of Example 1;

[0045] Figure 3 This is a schematic diagram of the double-layer structure formed by the cold screen 12 and the cold cover 4 in Example 1;

[0046] Figure 4 A schematic diagram showing the shielding and absorption of thermal radiation by the first baffle 121 and blackening layer 42 inside the cold screen;

[0047] Figure 5 These are two sets of two-dimensional arrays of F frames in Example 2.

[0048] The reference numerals in the figure are as follows: 1-infrared detector, 11-detector chip, 12-cold screen, 13-dewar, 14-first refrigerator, 111-base plate, 121-first baffle, 141-cold finger;

[0049] 2-Blackbody system, 21-Blackbody, 22-Shell, 221-Connection port, 23-Second refrigerator, 231-Primary cooling index, 232-Secondary cooling index;

[0050] 3-Isolation plate, 31-Small hole;

[0051] 4-Cooling cover, 41-Second baffle, 42-Blackening layer;

[0052] 5-Sealed cavity;

[0053] 6-Power supply;

[0054] 7-Vacuum pump;

[0055] 8-Temperature controller;

[0056] 9-Infrared detector performance testing unit. Detailed Implementation

[0057] To make the technical means, inventive features, and achieved objectives and effects of the present invention readily understood, the technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0058] Example 1

[0059] like Figure 2-4 As shown, this embodiment provides an apparatus for testing the low-temperature background performance of a cooled infrared detector, including an infrared detector 1, a blackbody system 2, a power supply 6, a vacuum pump 7, a temperature controller 8, and an infrared detector performance testing unit 9. The infrared detector 1 includes a detector chip 11, a cold screen 12, a Dewar 13, and a first refrigerator 14. The first refrigerator 14 is provided with a cold finger 141. The blackbody system 2 is provided with a second refrigerator 23. The second refrigerator 23 is provided with a primary cold finger 231, and an annular secondary cold finger 232 extends from the sidewall of the primary cold finger 231. The apparatus also includes:

[0060] The isolation plate 3 is generally disc-shaped with a circular hole in its center. The isolation plate 3 is then fitted onto the cold finger 141 of the first refrigeration unit through the circular hole.

[0061] The cold cover 4 has one end sealed to the isolation plate 3 and the other end sealed to the secondary cold finger 232 of the second refrigeration unit. A non-sealed cavity is formed between the isolation plate 3 and the secondary cold finger 232, forming a two-layer wrapping structure of the detector chip 11 with the cold cover 4 as the outer layer and the cold screen 12 as the inner layer.

[0062] The outer edge of the isolation disk 3 is sealed to the cold cover 4 and a gap is left between it and the base plate of the detector chip 11. The isolation disk 3 is provided with several small holes 31 to allow the inside and outside of the cold cover 4 to communicate. The vacuum pump 7 makes the sealed cavity 5 and the inside of the cold cover 4 form a vacuum environment.

[0063] The inner wall of the cold cover 4 is provided with several annular second baffles 41, which are used to shield the heat radiation conducted from the small hole 31 of the isolation plate to the inside of the cold cover 4 from the side of the Dewar 13.

[0064] Specifically, a sealed cavity 5 is formed between the Dewar 13 and the housing 22, and a vacuum operation is performed to reduce the heat transfer medium, thus providing conditions for subsequent cooling and precise temperature control.

[0065] Specifically, the isolation plate 3 not only provides support for the cold cover 4 and forms a cavity structure together with the secondary cold finger 232, but also connects the sealed cavity between the first refrigeration unit 14 and the second refrigeration unit 23 through the small hole 31, so that the air path provided by the small hole 31 during the vacuuming process can create a vacuum condition inside the cold cover 4 and the cold screen 12.

[0066] Furthermore, the Dewar 13 is mounted on the cold finger 141 of the first refrigerator 14, and the cold finger 141 is connected to the detector chip 11; the blackbody system 2 also includes a blackbody 21 and a housing 22, and the first-stage cold finger 231 of the second refrigerator 23 is connected to the blackbody 21; wherein, one end of the Dewar 13 is sealed to the side wall of the first refrigerator 14, and the other end is sealed to one end of the housing 22, and the other end of the housing 22 is sealed to the side wall of the second refrigerator 23, forming a sealed cavity 5 between the first refrigerator 14 and the second refrigerator 23, and the side wall of the housing 22 is provided with a connection port 221, which cooperates with the vacuum pump 7 to evacuate the sealed cavity 5.

[0067] Furthermore, the inner wall of the cold cover 4, the inner and outer walls of the cold screen 12, and the second baffle 41 are all coated with a blackening layer 42, which has an emissivity of 0.95 and is used to absorb thermal radiation.

[0068] Furthermore, the cold screen 12 is a cup-shaped structure with a large diameter at one end and a small diameter at the other end. Its inner wall is provided with several annular first baffles 121. The large end of the cold screen 12 is connected to the base plate of the detector chip 11, and the small end is provided with an opening so that the detector chip 11 is opposite to the blackbody 21. The inner wall of the cold screen 12 is provided with several annular first baffles 121 for shielding thermal radiation.

[0069] The above-described device for testing the low-temperature background performance of a cooled infrared detector involves the following steps before use: First, the operator connects the first refrigerator 14, the second refrigerator 23, the vacuum pump 7 to the power supply 6; connects the blackbody 21 to the temperature controller 8; connects the detector chip 11 to the infrared detector performance testing unit 9; and then, the Dewar 13 is fitted onto the cold finger 141 of the first refrigerator 14, with one end of the Dewar 13 sealed to the outer wall of the first refrigerator 14. Next, the isolation plate 3 is fitted onto the cold finger 141 of the first refrigerator 14, and the detector chip 11 is connected to the end of the cold finger 141. The large-diameter end of the cold screen 12 is connected to the base plate fixing the detector chip 11. At this point, the first refrigerator 14, the cold finger 141, the Dewar 13, the isolation plate 3, the detector chip 11, and... The centers of the cold shield 12 are all on the same axis. The second stage cold finger 232 of the second refrigerator 23 is sealed and connected to one end of the cold cover 4. At this time, the first stage cold finger 231 of the second refrigerator 23 passes into the cold cover 4 and is connected to the blackbody 21. The centers of the first stage cold finger 231, the blackbody 21, and the detector chip 11 are on the same axis. The other end of the cold cover 4 is sealed and connected to the isolation plate 3 to form a non-sealed cavity structure. The wing-shaped protrusions of the Dewar 13 and the wing-shaped protrusions of the housing 22 are aligned and sealed using bolts and rubber rings. The other end of the housing 22 is sealed and connected to the side wall of the second refrigerator 23. At this time, the Dewar 13 and the housing 22 between the first refrigerator 14 and the second refrigerator 23 together form a sealed cavity. The side wall of the housing 22 is provided with a connection port 221, through which the vacuum pump 7 is connected. Figure 2 As shown, the assembly of the device is completed.

[0070] During operation, the operator turns on the power to supply power to the vacuum pump 7 and evacuates the sealed cavity formed by the Dewar 13 and the housing 22 through the connection port 221. At this time, due to the small hole 31, the inside of the cold cover 4 is connected to the sealed cavity, creating a vacuum environment under the action of the vacuum pump 7. Power is supplied through the first refrigerator 14 and the second refrigerator 23. At this time, the first refrigerator 14's cooling finger 141 cools the detector chip 11, and the second refrigerator 23's first-stage cooling finger 231 cools the blackbody 21, and the second-stage cooling finger 232 cools the cold cover 4, forming a non-sealed low-temperature cavity inside the cold cover 4. Then, power is supplied to the vacuum pump 7, and the inside of the cold cover 4 is connected to the sealed cavity 5 through the small hole 31 on the isolation plate 3. Figure 3As shown, under the action of vacuum pump 7, a vacuum environment is formed inside the cold cover 4 and the sealed cavity 5. At this time, because the cold cover 4 and the cold screen 12 together form a double-layer structure, and the second-stage cooling finger 232 of the second refrigerator 23 cools the inside of the cold cover 4, the heat radiation generated during the operation of the second refrigerator 23 is effectively reduced and isolated outside the cold cover 4. By setting a second baffle 41 inside the cold cover 4, when the heat radiation generated by the Dewar 13 itself and the first refrigerator 14 during operation is conducted to the inside of the cold cover 4 through the small hole 31, it is shielded by the second baffle 41. The heat radiation is further shielded by the first baffle 121 set inside the cold screen 12. And all the inner and outer surfaces of all components inside the cold cover 4 are coated with a blackening layer 42, such as Figure 3 As shown, the blackening layer 42 has an emissivity of 0.95, which absorbs the heat radiation entering the cold cover 4. The secondary cooling finger 232 continuously cools the inside of the cold cover 4, reducing the heat radiation at this location, making the lowest temperature at the blackbody 21 -253℃ and the lowest temperature inside the cold cover 4 -243℃. Finally, the temperature controller and infrared detector performance testing unit 9 are activated. The temperature of the blackbody 21 is adjusted to T1 and T2 by the temperature controller 8. The output voltage data of each pixel of the F-frame device is continuously collected by the infrared detector performance testing unit. At this time, F≥100. The detector's responsivity, detectivity and other performance are calculated based on the collected data.

[0071] Furthermore, the detector chip 11 is electrically connected to the infrared detector performance testing device 8; the blackbody 21 is electrically connected to the temperature controller 8; and the first refrigerator 14, the second refrigerator 23, and the vacuum pump 7 are all electrically connected to the power supply 6.

[0072] Furthermore, the second refrigeration unit 23 is a GM refrigeration unit, including a primary cooling finger 231 and a secondary cooling finger 232. The secondary cooling finger 232 is an annular structure extending from the side wall of the primary cooling finger 231, and its diameter matches that of the cooling cover 4. The primary cooling finger 231 is connected to the blackbody 21 and provides cooling to the blackbody 21, with a minimum temperature drop to -253°C. The secondary cooling finger 232 is sealed to the cooling cover 4 and provides cooling to the cooling cover 4, with a minimum temperature drop to -243°C and a temperature control accuracy of 0.1°C.

[0073] Furthermore, the connection port 221 is a KF25 vacuum interface.

[0074] Furthermore, the length of the second baffle 41 provided on the inner wall of the cold cover 4 matches the cup-shaped structure of the cold screen 12, so that there is a gap between the longitudinal end of the second baffle 41 and the side wall of the cold screen 12.

[0075] Specifically, the length of the second baffle 41 set on the inner wall of the cold cover 4 matches the cup-shaped structure of the cold screen 12, so that there is a gap between the longitudinal end of the second baffle 41 and the side wall of the cold screen 12. This can more effectively shield and absorb the heat radiation conducted to the cold cover 4 from the small hole 31, and prevent the heat radiation from affecting the detector chip 11 and the blackbody 21, which would lead to inaccurate test results.

[0076] Example 2

[0077] This embodiment 2 describes the method for testing the infrared focal plane array parameters of the infrared detector performance testing unit 9 in embodiment 1. The following tests are conducted according to the People's Republic of China National Standard GB / T17444—2013:

[0078] 1. Testing Principle

[0079] The test of responsivity can be reduced to the test of response voltage under two different blackbody irradiation conditions: signal voltage test under blackbody temperature T0 irradiation and signal voltage test under blackbody temperature T irradiation, referred to as response voltage test. After measuring the response voltage, characteristic parameters such as responsivity can be calculated according to the definition.

[0080] 2. Test Conditions

[0081] a) The blackbody temperature is stable, and the output is not modulated; the blackbody radiation should ensure uniform irradiation of each pixel on the focal plane.

[0082] b) When using a surface source blackbody for testing, the recommended blackbody temperatures T0 and T for mid-wave and long-wave infrared focal plane array devices are 293K and 308K, respectively. For short-wave infrared focal plane array devices, the specified temperatures T0 and T should be used.

[0083] 3. Testing Procedures

[0084] a) Configure the system.

[0085] b) Adjust the test system and apply the specified voltage to the device under test to bring it into normal working condition.

[0086] c) At blackbody temperature T0 and blackbody temperature T, continuously acquire F frames of data (F≥100 is recommended) respectively (if the device under test is a linear focal plane, then continuously acquire F rows of data), and obtain the following results: Figure 5 The two sets of F-frame two-dimensional arrays are shown. Under the conditions of temperature T0 and T, the F-frame two-dimensional arrays measured are VDS[(i,j),T0,f] and VDS[(i,j),T,f], respectively.

[0087] d) When measured as Figure 5After the two sets of F-frame two-dimensional arrays shown, the voltage responsivity and responsivity non-uniformity can be calculated according to the definition.

[0088] The subsequent calculation methods are standard procedures for those skilled in the art, and the specific calculation process is based on pages 6 to 16 of the People's Republic of China National Standard GB / T17444—2013.

[0089] Example 3

[0090] This embodiment 3 describes a method for testing the low-temperature background performance of a cooled infrared detector using the apparatus described in embodiment 1, comprising the following steps:

[0091] S1. Start the vacuum pump 7 until a vacuum environment is formed inside both the sealed cavity 5 and the cold cover 4. The cold cover 4 is connected to the sealed cavity 5 through the small hole 31 on the isolation plate 3. Under the action of the vacuum pump 7, a vacuum environment is formed together, reducing convective heat transfer in the air and achieving better cooling conditions.

[0092] S2. Start the first refrigerator 14 and the second refrigerator 23. At this time, the first refrigerator 14 cools the detector chip 11 through the cold finger 141, and the second refrigerator 23 cools the blackbody 21 through the first-stage cold finger 231 and the cold cover 4 through the second-stage cold finger 232, forming a non-sealed low-temperature cavity with the cold cover 4 as the outer layer and the cold screen 12 as the inner layer, until the infrared detector 1 reaches the working temperature.

[0093] In this invention, the double-layer structure formed by the cold cover 4 and the cold screen 12 effectively shields the external environment and the heat radiation generated during the operation of the second refrigeration unit 23.

[0094] S3. During the continuous cooling process, the Dewar 13 itself, the first refrigeration unit 14 and the second refrigeration unit 23 generate heat radiation during the cooling process. The two-layer structure formed by the cold cover 4 and the cold screen 12 can effectively shield it. The second baffle 41 inside the cold cover 4 effectively shields the heat radiation conducted from the small hole 31 to the inside of the cold cover 4, and absorbs the heat radiation through the blackening layer 42.

[0095] In this invention, the thermal radiation generated during the operation of the first refrigerator 14 and the thermal radiation of the Dewar 13 itself are conducted into the cold cover 4 through the small hole 31. The thermal radiation is effectively shielded by the setting of the second baffle 41, and the thermal radiation is absorbed by the blackening layer 42 to prevent the thermal radiation from affecting the detector chip 11 and the blackbody 21.

[0096] S4. The first baffle 121 inside the cold screen 12 provides secondary shielding against the heat radiation conducted from the small hole 31 to the inside of the cold cover 4, and absorbs the heat radiation through the blackening layer 42 on the inner wall of the cold screen 12, reducing the impact of heat radiation on the test process, so that the temperature at the blackbody 21 can be reduced to a minimum of -253°C and the temperature at the cold cover 4 can be reduced to a minimum of -243°C, which is closer to absolute zero.

[0097] In this invention, some thermal radiation is still conducted into the interior of the cold shield 12. The first baffle 121 is set to shield this part of the thermal radiation again, and the radiation is absorbed by the blackening layer 42. During the process of the secondary cold finger 232 continuously cooling the interior of the cold cover 4, the impact of thermal radiation on the blackbody 21 and the detector chip 11 is reduced.

[0098] S5. Start the performance testing unit 8 for the temperature controller and the infrared detector;

[0099] S6. Perform performance testing on infrared detector 1.

[0100] In this invention, under the condition that the temperature of the blackbody 21 is adjusted to T1 and T2, the output voltage data of each pixel of the F-frame device is continuously collected by the infrared detector performance test unit 9, where F≥100, and the performance of the infrared detector 1, such as the responsivity and detectivity, is calculated based on the collected data.

[0101] Figure 2 The difference between having and not having a cooling cover 4: With cooling cover 4, the dark current test result for infrared detector chip 11 is 0.2~0.5pA, while without cooling cover 4, the test result is 200~500pA, a difference of 4 orders of magnitude. The dark current calculation formula is as follows:

[0102] I = (CΔU) / ΔT

[0103] In the formula: C: capacitance;

[0104] ΔU: The signal difference measured at integration times T1 and T2 is ΔU = U2 - U1;

[0105] ΔT: The time difference between the two tests, ΔU = T2 - T1.

[0106] The above examples illustrate the present invention only to aid in understanding it and are not intended to limit the scope of the invention. Those skilled in the art can make various simple deductions, modifications, or substitutions based on the principles of this invention.

Claims

1. An apparatus for testing the low-temperature background performance of a cooled infrared detector, comprising an infrared detector (1), a blackbody system (2), a power supply (6), a vacuum pump (7), a temperature controller (8), and an infrared detector performance testing unit (9), wherein the infrared detector (1) comprises a detector chip (11), a cold screen (12), a Dewar (13), and a first refrigerator (14), the first refrigerator (14) having a cold finger (141), the blackbody system (2) having a second refrigerator (23), the second refrigerator (23) having a primary cold finger (231), and the primary cold finger (231) having an annular secondary cold finger (232) extending from its sidewall; characterized in that, Also includes: Isolation plate (3), the isolation plate (3) is in the shape of a disc, and a circular hole is provided in the center of the disc. The isolation plate (3) is sleeved on the cold finger (141) of the first refrigeration unit through the circular hole; The cold cover (4) is sealed to the isolation plate (3) at one end and sealed to the secondary cold finger (232) of the second refrigerator at the other end. A non-sealed cavity is formed between the isolation plate (3) and the secondary cold finger (232), forming a two-layer wrapping structure of the detector chip (11) with the cold cover (4) as the outer layer and the cold screen (12) as the inner layer. The outer edge of the isolation disk (3) is sealed to the cold cover (4) and there is a gap between it and the base plate of the detector chip (11). The isolation disk (3) has several small holes (31) to make the inside and outside of the cold cover (4) connected. The vacuum environment is formed in the sealed cavity (5) and the cold cover (4) by the vacuum pump (7). The inner wall of the cold cover (4) is provided with several annular second baffles (41) to shield the heat radiation from the Dewar (13) side conducted from the small hole (31) of the isolation plate into the cold cover (4).

2. The apparatus for testing the low-temperature background performance of a cooled infrared detector according to claim 1, characterized in that, The Dewar (13) is fitted onto the cold finger (141) of the first refrigerator (14), and the cold finger (141) is connected to the detector chip (11); the blackbody system (2) also includes a blackbody (21) and a housing (22), and the first-stage cold finger (231) of the second refrigerator (23) is connected to the blackbody (21); wherein, one end of the Dewar (13) is sealed to the side wall of the first refrigerator (14), and the other end is sealed to one end of the housing (22), and the other end of the housing (22) is sealed to the side wall of the second refrigerator (23), forming a sealed cavity (5) between the first refrigerator (14) and the second refrigerator (23), and the side wall of the housing (22) is provided with a connection port (221), which cooperates with the vacuum pump (7) to evacuate the sealed cavity (5).

3. The apparatus for testing the low-temperature background performance of a cooled infrared detector according to claim 1, characterized in that, The inner wall of the cold cover (4), the inner and outer walls of the cold screen (12), and the second baffle (41) are all coated with a blackening layer (42). The blackening layer (42) has an emissivity of 0.95 and is used to absorb thermal radiation.

4. The apparatus for testing the low-temperature background performance of a cooled infrared detector according to claim 3, characterized in that, The cold screen (12) is a cup-shaped structure with a large diameter at one end and a small diameter at the other end. Its inner wall is provided with several annular first baffles (121). The large end of the cold screen (12) is connected to the base plate of the detector chip (11), and the small end is provided with an opening so that the detector chip (11) is opposite to the blackbody (21). The inner wall of the cold screen (12) is provided with several annular first baffles (121) for shielding thermal radiation.

5. The apparatus for testing the low-temperature background performance of a cooled infrared detector according to claim 1, characterized in that, The detector chip (11) is electrically connected to the infrared detector performance testing device (8); the blackbody (21) is electrically connected to the temperature controller (8); the first refrigerator (14), the second refrigerator (23) and the vacuum pump (7) are all electrically connected to the power supply (6).

6. The apparatus for testing the low-temperature background performance of a cooled infrared detector according to claim 1, characterized in that, The second refrigeration unit (23) is a GM refrigeration unit, including a primary cooling finger (231) and a secondary cooling finger (232). The secondary cooling finger (232) is an annular structure extending from the side wall of the primary cooling finger (231), and its diameter matches that of the cooling cover (4). The primary cooling finger (231) is connected to the blackbody (21) to provide cooling to the blackbody (21), with a minimum temperature drop to -253°C. The secondary cooling finger (232) is sealed to the cooling cover (4) to provide cooling to the cooling cover (4), with a minimum temperature drop to -243°C and a temperature control accuracy of 0.1°C.

7. The apparatus for testing the low-temperature background performance of a cooled infrared detector according to claim 1, characterized in that, The connection port (221) is a KF25 vacuum interface.

8. The apparatus for testing the low-temperature background performance of a cooled infrared detector according to claim 3, characterized in that, The length of the second baffle (41) provided on the inner wall of the cold cover (4) matches the cup-shaped structure of the cold screen (12), so that there is a gap between the longitudinal end of the second baffle (41) and the side wall of the cold screen (12).

9. A method for testing using the apparatus for testing the low-temperature background performance of a cooled infrared detector as described in claim 1, characterized in that... Includes the following steps: S1. Start the vacuum pump (7) until a vacuum environment is formed inside both the sealed cavity (5) and the cold cover (4). The cold cover (4) is connected to the sealed cavity (5) through the small hole (31) on the isolation plate. Under the action of the vacuum pump (7), a vacuum environment is formed together, reducing convective heat transfer in the air and achieving better cooling conditions. S2. Start the first refrigerator (14) and the second refrigerator (23). At this time, the first refrigerator (14) cools the detector chip (11) through the cold finger (141), and the second refrigerator (23) cools the blackbody (21) with the first-level cold finger (231) and the second-level cold finger (232) cools the cold cover (4), forming a non-sealed low-temperature cavity with the cold cover (4) as the outer layer and the cold screen (12) as the inner layer, until the infrared detector (1) reaches the working temperature. S3. During the continuous cooling process, the Dewar (13) itself, the first refrigeration unit (14) and the second refrigeration unit (23) generate heat radiation during the cooling process. The two-layer structure formed by the cold cover (4) and the cold screen (12) can effectively shield it. The heat radiation conducted from the small hole (31) to the inside of the cold cover (4) is effectively shielded by the second baffle (41) inside the cold cover (4), and the heat radiation is absorbed by the blackening layer (42). S4. The first baffle (121) inside the cold screen (12) provides secondary shielding against the heat radiation transmitted from the small hole (31) to the inside of the cold cover (4), and absorbs the heat radiation through the blackening layer (42) on the inner wall of the cold screen (12), reducing the influence of heat radiation on the test process, so that the temperature at the blackbody (21) can be reduced to a minimum of -253°C and the temperature at the cold cover (4) can be reduced to a minimum of -243°C, which is closer to absolute zero. S5. Start the temperature controller (8) and infrared detector performance test unit (9); S6. Perform performance testing on the infrared detector (1).

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