Device and method for testing dark target detection performance and dark current of very low temperature infrared detector

Abstract

The invention provides a dark weak target detection performance and dark current testing device and method for a very low temperature infrared detector, and relates to the technical field of infrared detector detection. The testing device comprises a cooling module, an environment construction module, a detector driving and control circuit and a data analysis module, wherein the cooling module comprises a refrigerating machine, a cold head, a cold table and a vacuum tank; the environment construction module comprises a detector installation substrate, a support, a blind cold screen, a cold screen, a heat insulation layer, a black body and a black body temperature control system. The testing device is used for testing the dark target detection performance and dark current of the infrared detector. According to the invention, the very low temperature test environment covering the space-based detection requirement is constructed for the first time, and the simulation requirement of a deep-space dark weak target is met; on the basis, output data of the detector are obtained, then performance parameters and dark current parameters of the detector are calculated, and accurate testing and evaluation are carried out on the dark and weak target testing capacity of the detector in the very low temperature working state.

Description

Technical Field

[0001] The present invention relates to the field of infrared detector detection technology, and in particular to a device and method for testing the dark target detection performance and dark current of a very low temperature infrared detector. Background Art

[0002] As a core component of modern optoelectronic detection systems, the performance testing and evaluation of infrared focal plane detectors (IFPDs) are directly related to their effectiveness in cutting-edge applications such as space remote sensing and deep space exploration. Given the characteristics of weak infrared radiation and low background temperatures associated with space-based targets, medium- and long-wave infrared detectors are often used in current engineering practice to detect dim and weak space-based targets.

[0003] Within the existing technology landscape, GB / T 17444-2013, "Parameter Test Methods for Infrared Focal Plane Detectors," provides a standardized testing framework for the industry, covering test methods for key parameters such as blind pixel rate, response non-uniformity, and noise-equivalent temperature difference. However, given the demand for detecting faint targets in extremely low-temperature environments in space-based missions, traditional testing methods face the following bottlenecks under these conditions.

[0004] First, regarding operating temperature adaptability, existing test systems are generally built using liquid nitrogen refrigeration technology, with their minimum operating temperature typically limited to 77K (the standard boiling point of liquid nitrogen). Although some improved devices can extend this temperature to 60K through multi-stage refrigeration, when space-based detectors need to operate in ultra-low temperatures below 50K (such as deep space cryogenic background detection), existing technology lacks both a stable very low-temperature test environment and the corresponding performance characterization methods. This makes it difficult to quantify key parameters such as dark current characteristics and quantum efficiency changes at extremely low temperatures, severely limiting the accuracy of on-orbit performance predictions.

[0005] Secondly, regarding the ability to simulate faint targets, traditional test systems rely on blackbody radiation sources to provide target signals, but their background radiation temperature is typically above 90K. When space-based detectors need to identify faint targets with temperatures as low as 90K, existing devices are unable to generate the low-noise radiation environment that matches real-world scenarios. Excessive background radiation during testing can mask target signals, leading to overestimation of core detector specifications such as temperature resolution and signal-to-noise ratio under laboratory conditions, significantly deviating from actual application scenarios.

[0006] Crucially, in the field of ultra-low temperature dark current testing, based on the theory that dark current varies with operating temperature, the dark current parameters of detectors at ultra-low operating temperatures decrease exponentially compared to those at the conventional operating temperature of 77K. This measurement blind spot means that existing testing methods and equipment can only test and evaluate the dark current parameters of detectors at conventional operating temperatures (i.e., 77K), but cannot accurately test the dark current parameters of detectors at ultra-low temperatures. Summary of the Invention

[0007] The present invention provides a device and method for testing the dim target detection performance and dark current of a very low temperature infrared detector, which solves the problems of the dim target detection performance and dark current measurement accuracy of the infrared detector under very low temperature working conditions.

[0008] To achieve the above objectives, this application adopts the following technical solutions: In a first aspect, a device for testing the dim target detection performance and dark current of a very low temperature infrared detector is provided, comprising: A cooling module includes a refrigerator, a cold head, a cold stage, and a vacuum tank; the vacuum tank is used to provide a vacuum environment for cooling the detector, the cold head is coupled to the cold stage and is disposed within the vacuum tank, and the refrigerator is connected to the cold head to transfer cooling energy; An environmental construction module includes a detector mounting base, a bracket, a cold chain, a blind cold screen, a cold screen, an insulation layer, a black body, and a black body temperature control system. The detector mounting base is fixed by the bracket. The detector mounting base and the cold chain are used to provide a refrigeration link required to cool the detector to a very low temperature. The blind cold screen is used to cover the detector and has an opening to limit the field of view. The cold screen is used to cover part of the cold stage and the blind cold screen and has an opening corresponding to the blind cold screen. The insulation layer is used to cover the outer surface of the cold screen. The black body is a radiation source, and its relative position to the cold screen is optionally adjusted by a position adjustment mechanism. The black body temperature control system is used to adjust the black body temperature. Detector drive and control circuit, used to provide working bias voltage and timing control signal for the detector; The data analysis module includes a data acquisition card and a processor; the data acquisition card is connected to the output end of the detector to obtain an analog voltage signal, and the processor is configured with an algorithm model for converting the detector output voltage data into a performance indicator that can characterize the detector state.

[0009] In a first possible implementation of the first aspect, a multi-layer indium metal sheet is provided between the cold stage and the cold chain; A multilayer indium metal sheet is provided between the cold chain and the detector mounting substrate; A multilayer indium metal sheet is provided between the detector mounting substrate and the detector; A multi-layer indium metal sheet is provided between the connection between the cold screen and the cold stage.

[0010] In a second possible implementation of the first aspect, a first platinum resistance temperature sensor group is provided near the cold stage on the detector mounting substrate for monitoring the state of cold conduction; A second platinum resistance temperature sensor group is provided at the blind cold screen for real-time monitoring of the temperature of the blind cold screen; A third platinum resistance temperature sensor group is provided at the detector mounting substrate for monitoring the substrate temperature; A fourth platinum resistance temperature sensor group is provided at a position of the cold screen close to the black body, for monitoring the temperature of the cold screen.

[0011] In a third possible implementation manner of the first aspect, the black body is controlled to be close to the blackened surface of the cold screen; A heat insulating material is provided between the black body and the cold screen.

[0012] In a second aspect, a method for testing the dark current of a very low temperature infrared detector with a dim target is provided, wherein the dark current test is performed using the very low temperature infrared detector with a dim target detection performance and dark current test device described in the first aspect, comprising: The detector was mounted on a detector mounting base in a vacuum tank. A blind cold shield, a cold shield, and a platinum resistance temperature sensor group were installed in sequence. The cold stage and the cold shield were covered with an insulating layer. The detector input and output ports were connected to the data analysis module using a flexible transfer tape. The contact surface gaps were filled with indium metal sheets. Adjust the position of the black body so that it is close to the opening of the cold screen, and place insulation material between the black body and the opening of the cold screen; Turn on the vacuum equipment to reduce the vacuum degree in the vacuum tank to below 1E-3Pa; start the refrigerator to reduce the detector operating temperature to below 50K; Turn on the blackbody temperature control system to adjust the blackbody temperature T1; Turn on the detector drive and control circuits to provide the detector with working bias voltage and timing control signals respectively, obtain the detector output voltage through the data acquisition card, and obtain the detector dark current test results through the processor.

[0013] In a first possible implementation of the second aspect, the detector driving and control circuits are turned on to provide a working bias voltage and a timing control signal for the detector, respectively, the detector output voltage is obtained through a data acquisition card, and the detector dark current test result is obtained through a processor, specifically including: Adjust the timing control signal of the control circuit to make the detector work above the half-well state, and collect the detector output voltage under the integration time; then adjust different integration times and collect multiple sets of detector output voltages under different integration times; The detector output voltage obtained by the acquisition is subtracted from the detector output voltage when the photoelectric response is cut off to obtain the response signal at each integration time; With the integration time as the horizontal axis and the response signal as the vertical axis, the slope of the time-signal curve is fitted using the least squares method, and the detector dark current calculation result is obtained using the following formula: in, It represents the slope of the curve obtained by the least squares fitting method; Indicates the integrating capacitor used when the detector is working.

[0014] In a second possible implementation manner of the second aspect, filling the contact surface gap with the indium metal sheet specifically includes: A multi-layer indium metal sheet is provided between the cold stage and the cold chain; A multilayer indium metal sheet is provided between the cold chain and the detector mounting substrate; A multilayer indium metal sheet is provided between the detector mounting substrate and the detector; A multi-layer indium metal sheet is provided between the connection between the cold screen and the cold stage.

[0015] In a third aspect, a method for testing the dim target detection performance of a very low temperature infrared detector is provided, wherein the performance test is performed using the dim target detection performance and dark current test device of the very low temperature infrared detector described in the first aspect, comprising: The detector was mounted on a detector mounting base in a vacuum tank. A blind cold shield, a cold shield, and a platinum resistance temperature sensor group were installed in sequence. The cold stage and the cold shield were covered with an insulating layer. The detector input and output ports were connected to the data analysis module using a flexible transfer tape. The contact surface gaps were filled with indium metal sheets. Adjust the position of the black body so that it is close to the opening of the cold screen, and place insulation material between the black body and the opening of the cold screen; Turn on the vacuum equipment to reduce the vacuum degree in the vacuum tank to below 1E-3Pa; start the refrigerator to reduce the detector operating temperature to below 50K; Turn on the blackbody temperature control system to adjust the blackbody temperature T1, adjust the timing control signal of the control circuit to make the detector work in the half-well state, and collect the output level data of the infrared detector with T1 temperature; Adjust the blackbody temperature T2 and collect the output level data of the infrared detector at T2 temperature; where T2>T1; Based on the output level data of the infrared detector at temperatures T1 and T2, the detector performance indicators are calculated: quantum efficiency, response rate, noise equivalent temperature difference, response non-uniformity and detection rate.

[0016] In a first possible implementation of the third aspect, the calculation of detector performance indicators including quantum efficiency, response rate, noise equivalent temperature difference, response non-uniformity, and detection rate based on the infrared detector output level data at temperatures T1 and T2 specifically includes: Based on the output level data, static blind pixel screening is performed through response mean and noise calculation; The quantum efficiency is used to describe the ability of a detector to convert incident photons into electrons and output them, and is calculated using the following formula: in, represents quantum efficiency; represents the number of photons incident on the detector; Indicates the number of electrons converted and output by the detector; and is calculated by the following formula: in, is the blackbody radiation rate; Indicates the detector field of view, in units of sr ; Represents the photosensitive area of ​​the detector pixel, in units of cm 2 ; Indicates the detector integration time; represents the detector readout circuit integration capacitance; Indicates the detector output signal; Represents the single electron charge, and its value is ; Indicates the wavelength is , the temperature is The blackbody radiation photon energy is calculated by the following formula: ; The responsivity is used to characterize the response voltage of each pixel in the detector to unit irradiation power and is calculated by the following formula: in, represents the response rate of the pixel in the i-th row and j-th column of the detector; and represents the output voltage value of the pixel in the i-th row and j-th column of the detector at temperatures T1 and T2 respectively; represents the field of view of the detector; represents the detector pixel area; It represents the change in the irradiation power of the blackbody at T1 and T2, which is calculated by the following formula: in, represents the blackbody radiation rate of the surface source; Represents a constant whose value is ; The noise equivalent temperature difference is used to characterize the sensitivity of the infrared detector and its noise level, and is calculated by the following formula: ; The response non-uniformity is used to describe the difference in pixel output signals of infrared detectors under the same radiation power. The output voltage of each pixel is corrected by the following formula: in, It represents the output voltage of the pixel in row i and column j after correction when facing the blackbody with temperature T1; represents the correction factor; The corrected response voltage of each pixel is obtained as follows: The calculation formula for the non-uniformity of the output voltage of each pixel after correction is: in, It represents the corrected average blackbody response rate of all valid pixels in the detector component after deducting the blind pixels; The detection rate includes the detection rate of each pixel and the average detection rate of the detector, which are calculated by the following formulas: in, represents the detection rate of the pixel in the i-th row and j-th column; Indicates the integration time; represents the average detection rate of the detector; Indicates the number of blind pixels of the detector.

[0017] In a second possible implementation manner of the third aspect, filling the contact surface gap with the indium metal sheet specifically includes: The method of filling the contact surface gap with the indium metal sheet specifically includes: A multi-layer indium metal sheet is provided between the cold stage and the cold chain; A multilayer indium metal sheet is provided between the cold chain and the detector mounting substrate; A multilayer indium metal sheet is provided between the detector mounting substrate and the detector; A multi-layer indium metal sheet is provided between the connection between the cold screen and the cold stage.

[0018] The present invention has the following advantages: This application has for the first time constructed a very low temperature test environment that covers the needs of space-based detection and meets the simulation requirements of faint targets in deep space. On this basis, the detector output data is obtained and the detector performance parameters and dark current parameters are calculated to accurately test and evaluate the detector's faint target testing capabilities under very low temperature working conditions. Dark current and performance tests can be implemented under very low temperature working conditions for infrared focal plane detectors of different materials, different bands, and different specifications, which has the engineering value of efficient and accurate testing. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic flow chart of a method for testing the performance of an infrared focal plane detector at a conventional operating temperature provided in an embodiment of the present application; Figure 2 A schematic diagram of the structure of a device for testing the dim target detection performance and dark current of a very low temperature infrared detector provided in an embodiment of the present application; Figure 3 A schematic flow chart of a method for testing dark current of a dim target in a very low temperature infrared detector provided in an embodiment of the present application; Figure 4 A schematic flowchart of a method for testing the dim target detection performance of a very low temperature infrared detector provided in an embodiment of the present application. DETAILED DESCRIPTION

[0020] To further illustrate the technical means and effects of the present invention to achieve its intended purpose, the technical solutions in the embodiments of this application are clearly described. Obviously, the described embodiments are only part of the embodiments of this application, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of this application are within the scope of protection of this application.

[0021] The terms "first," "second," and the like in the specification and claims of this application are used to distinguish similar objects, and are not used to describe a specific order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate, so that the embodiments of this application can be implemented in an order other than that illustrated or described herein, and that the objects distinguished by "first," "second," and the like are generally of the same type, and do not limit the number of objects; for example, the first object can be one or more. In addition, the term "and / or" in the specification and claims represents at least one of the connected objects, and the character " / " generally indicates that the objects associated with each other are in an "or" relationship.

[0022] The description of the method flow in the specification of this application and the steps in the flowcharts in the drawings of the specification of this application do not necessarily need to be strictly executed according to the step numbers. The method steps can be executed in a different order. In addition, some steps can be omitted, multiple steps can be combined into one step, and / or one step can be decomposed into multiple steps.

[0023] As a crucial step in the infrared detector manufacturing process, performance testing is an essential quantitative measure for accurately describing the detector's operating stability and reliability. Targeted detection of space-based targets often involves weak infrared radiation and low background temperatures. Given these characteristics, current engineering practices often utilize medium- and long-wave infrared detectors for faint space-based target detection. This presents detectors with even more challenging challenges, such as operating at very low temperatures and detecting weak targets at these temperatures.

[0024] The performance testing methods currently commonly used in engineering practice are primarily based on the various indicator testing methods specified in GB / T 17444-2013, including blind pixel testing, response non-uniformity testing, and detectivity testing. These testing methods primarily target detectors operating at 77 Kelvin (hereinafter referred to as "K") and cannot accurately describe detector operation at very low temperatures. Therefore, establishing test methods that can accurately measure and evaluate detector performance parameters at very low temperatures is crucial for improving detector manufacturing processes and enhancing user experience in specific scenarios.

[0025] Furthermore, the detection and identification of low-temperature, dim targets requires detectors with higher temperature resolution and sensitivity. However, the presence of dark current significantly limits these temperature resolution and sensitivity. For medium- and long-wavelength detectors, at the same operating temperature, the longer the detection wavelength, the greater the dark current, which means lower temperature resolution and sensitivity. Based on the theory that dark current varies with operating temperature, the dark current parameter decreases exponentially at very low operating temperatures compared to the conventional operating temperature of 77K. Therefore, detectors must operate at very low temperatures (i.e., below 50K). Existing testing methods and equipment can only test and evaluate the dark current parameters of detectors at conventional operating temperatures (i.e., 77K), but cannot test the dark current parameters of detectors at very low temperatures. Therefore, accurately testing and evaluating the dark current parameters of detectors at very low operating temperatures to ensure they meet new user requirements is a pressing issue.

[0026] Figure 1This is a schematic flow chart of a performance test method for infrared focal plane detectors operating at conventional operating temperatures. The method primarily consists of a detector, a driver circuit, a control circuit, a data acquisition module, and a computer. The detector, driver circuit, control circuit, and data acquisition module constitute a complete detector test data acquisition system. The detector test data acquisition system only has detector drive and data acquisition functions, with subsequent data processing and performance calculations performed by the computer. However, existing conventional testing methods and supporting equipment are only capable of testing and evaluating detector performance at operating temperatures between 60K and 100K. They are unable to support detectors operating at very low temperatures, as low as 50K or below, and are also unable to provide blackbody radiation to simulate faint targets. To meet the requirements for testing detectors' ability to detect faint targets at very low operating temperatures, it is imperative to develop a universal, convenient, and flexible testing method.

[0027] In view of the above problems, a dim target detection performance and dark current test method for the detector at very low temperature operating temperature is proposed, which is of great significance for building a detector very low temperature working status evaluation system and improving the process status.

[0028] The present application provides a test method and equipment that can reduce the working temperature of the detector to below 50K and has performance testing, and has a supporting process method for detector installation, environment construction and performance testing, wherein the two steps of detector installation and environment construction can ensure that the detector can be reduced to an operating temperature below 50K, while suppressing the influence of its surrounding environment and improving the accuracy of the test results. Therefore, how to efficiently build a reliable test environment is one of the key technical difficulties that this method needs to overcome. In addition, on the basis of the normal operation of the detector, obtaining the output data of the detector under various working modes for evaluating the detection sensitivity and temperature resolution of the detector is another key technical difficulty that this method needs to overcome.

[0029] See Figure 2 , the embodiment of the present application provides a device for testing the dark target detection performance and dark current of a very low temperature infrared detector, such as Figure 2 Shown, including: A cooling module includes a refrigerator, a cold head, a cold stage, and a vacuum tank; the vacuum tank is used to provide a vacuum environment for cooling the detector, the cold head is coupled to the cold stage and is disposed within the vacuum tank, and the refrigerator is connected to the cold head to transfer cooling energy; An environmental construction module includes a detector mounting base, a bracket, a cold chain, a blind cold screen, a cold screen, an insulation layer, a black body, and a black body temperature control system. The detector mounting base is fixed by the bracket. The detector mounting base and the cold chain are used to provide a refrigeration link required to cool the detector to a very low temperature. The blind cold screen is used to cover the detector and has an opening to limit the field of view angle. The cold screen is used to cover part of the cold stage and the blind cold screen and has an opening corresponding to the blind cold screen. The insulation layer is used to cover the outer surface of the cold screen. The black body is a radiation source, and its relative position to the cold screen is optionally adjusted by a position adjustment mechanism. The black body temperature control system is used to adjust the black body temperature. Detector drive and control circuit, used to provide working bias voltage and timing control signal for the detector; The data analysis module includes a data acquisition card and a processor; the data acquisition card is connected to the output end of the detector to obtain an analog voltage signal, and the processor is configured with an algorithm model for converting the detector output voltage data into a performance indicator that can characterize the detector state.

[0030] Specifically, a device is provided for testing the dim target detection performance and dark current of infrared detectors under very low temperature working conditions, which mainly consists of three parts: a cooling module, an environment construction module and a data analysis module.

[0031] The cooling equipment consists of a refrigerator, a cold head, a cold stage, and a vacuum tank. The vacuum tank provides a vacuum environment for cooling the detector, suppressing the effects of moisture and impurities in the air on detector performance testing. The refrigerator lowers the temperature of the cold head, and the cold head lowers the temperature of the cold stage, thereby transferring the cooling energy to the detector and reducing its temperature.

[0032] Environmental setup involves detector substrate installation, cold shield installation, insulation coating, and blackbody position adjustment. The detector substrate and cold chain installation provide the refrigeration necessary to cool the detector to very low temperatures. The cold shield installation isolates the infrared energy radiated from the tube wall from affecting detector performance testing. The insulation coating reduces the spread of cold energy, allowing the cold plate's cooling to be concentrated on lowering the detector temperature. Blackbody position adjustment uses the extremely low-intensity infrared radiation of a blackbody to simulate the infrared radiation of a faint target. This suppresses the impact of external factors such as radiation loss and environmental interference on the accuracy of test results, providing strong support for subsequent evaluation of the detector's detection sensitivity and temperature resolution. The blackbody temperature control system includes a heater, a refrigerator, and a PDD controller, which, in conjunction with a platinum resistance thermometer on the blackbody surface, enables temperature control.

[0033] It's important to note that the blackbody should be positioned close to the blackened surface of the cold screen; insulation material is placed between the blackbody and the cold screen. During blackbody position adjustment, the blackbody should be kept as close as possible to the blackened surface of the cold screen. The blackened surface is a high-emissivity radiating surface (used to increase emissivity). Insulation material also isolates the heat transfer link between the blackbody and the cold screen, minimizing the blackbody's impact on the cold screen's temperature.

[0034] The data analysis part includes data acquisition and data processing. Data acquisition uses a data acquisition card to obtain the analog voltage signal output by the detector, and realizes analog-to-digital conversion through A / D sampling conversion, thereby supporting the computer to further process and analyze the output voltage; data processing uses self-developed data processing algorithms, including data extraction, data reconstruction, blind element screening, indicator calculation, blind element cluster screening, etc., which are used to convert the detector output voltage data into performance indicators that can characterize the detector status.

[0035] Furthermore, a multi-layer indium metal sheet is provided between the cold stage and the cold chain; A multilayer indium metal sheet is provided between the cold chain and the detector mounting substrate; A multilayer indium metal sheet is provided between the detector mounting substrate and the detector; There are multiple layers of indium metal sheets between the cold screen and the cold stage; The indium metal sheet is cut and filled on the contact surface to enhance the interfacial thermal conductivity.

[0036] Furthermore, the detector mounting substrate is provided with a first platinum resistance temperature sensor group near the cold stage for monitoring the state of cold conduction; A second platinum resistance temperature sensor group is provided at the blind cold screen for real-time monitoring of the temperature of the blind cold screen; A third platinum resistance temperature sensor group is provided at the detector mounting substrate for monitoring the substrate temperature; A fourth platinum resistance temperature sensor group is provided at a position of the cold screen close to the black body, for monitoring the temperature of the cold screen.

[0037] The purpose of this application is to address the problem that existing testing and installation methods cannot accurately evaluate the dark current and performance parameters of detectors below an operating temperature of 50K. A method for testing the dim target detection performance and dark current of infrared detectors under very low temperature working conditions is developed to achieve performance evaluation of infrared detectors and dim target detection capabilities under very low temperature working temperatures. This effectively solves the problem of failure of traditional testing methods to meet new demands, new challenges, and new technologies, and more comprehensively tests and evaluates the engineering application value of detectors. Dark current and performance tests under very low temperature working conditions can be achieved for infrared focal plane detectors of different materials, different bands, and different specifications, which has engineering value of efficient and accurate testing.

[0038] See Figure 3 The embodiment of the present application provides a method for testing dark current of a very low temperature infrared detector with a weak target. The dark current test is performed using the very low temperature infrared detector with a weak target detection performance and dark current test device of the above embodiment. Figure 3 As shown, the following steps are included: Step S10: Install the detector on the detector mounting substrate in the vacuum tank, install the blind cold shield, cold shield and platinum resistance temperature sensor group in sequence, use an insulating layer to cover the cold platform and cold shield surface, use a flexible adapter to connect the detector input port and output port to the data analysis module, and fill the contact surface gap with indium metal sheet.

[0039] In this step, the bracket supporting the detector constitutes a cold chain for transferring cold energy. The bracket and the detector mounting substrate are installed in the cold state of the vacuum tank in sequence, and then the detector is installed on the detector mounting substrate in the vacuum tank. During this process, a cut indium metal sheet needs to be placed at the connection between the bracket and the cold table, and a cut indium metal sheet needs to be placed at the connection between the substrate and the bracket.

[0040] Use transition tape to connect the detector bias input port, timing input port, and voltage output port to the connector port on the vacuum tank wall. During this process, a cut metal sheet needs to be placed at the connection between the detector and the substrate.

[0041] Install a blind cold shield and use indium metal sheet and aluminum tape to fill the gap between the blind cold shield and the detector mounting frame.

[0042] The cold screen is fastened to the cold platform with screws, and the detector, bracket, substrate and other structures are enclosed in the cold screen to isolate the high-intensity infrared rays from the external environment. During this process, a cut indium metal sheet needs to be placed at the connection between the cold screen and the cold platform.

[0043] Use aluminum tape to fix a platinum resistor at the blind cold screen to monitor the blind cold screen temperature. Use aluminum tape to fix a platinum resistor at the detector mounting base to monitor the base plate temperature. Use aluminum tape to fix a platinum resistor at the cold chain near the cold stage to monitor the cold conduction status. Use aluminum tape to fix a platinum resistor near the black body position of the cold screen to monitor the cold screen temperature.

[0044] On the periphery of the cold screen, use insulation material to cover the cold screen and the cold stage, leaving only the opening of the cold screen facing the black body, to suppress the escape of the cold stage's cooling capacity, and to avoid the influence of the high infrared radiation of the external environment on the temperature of the cold screen and the working state of the internal detector. In this process, it is necessary to pay attention to the use of additional materials to cover the opening at the transition flexible belt leading out of the detector to prevent infrared radiation from entering the opening of the transition flexible belt. Step S11 , adjusting the position of the black body so that it is close to the opening of the cold screen, and placing a heat insulating material between the black body and the opening of the cold screen.

[0045] In this step, the blackbody position is adjusted so that it is close to the cold shield opening and as close to the blackened surface of the cold shield as possible to suppress infrared radiation emitted by the external environment from entering the detector field of view through reflection from the blackbody. At the same time, low-reflectivity insulation material is placed between the blackbody and the cold shield opening to suppress the cold shield temperature increase caused by baking of the blackbody.

[0046] Step S12: Start the vacuum pumping device to reduce the vacuum degree in the vacuum tank to below 1E-3Pa; start the refrigerator to reduce the working temperature of the detector to below 50K.

[0047] Specifically, the vacuum equipment includes a roughing mechanical pump and a molecular pump. After closing the vacuum tank seal, the roughing mechanical pump and the molecular pump inside the tank are opened in turn to reduce the vacuum degree inside the tank to 1E-3Pa to prevent water molecules or other impurities in the air from adhering to the detector surface during the cooling process; after the vacuum degree reaches the standard, the refrigerator is turned on, and the cooling rate and target temperature are set.

[0048] Step S13: Start the blackbody temperature control system to adjust the blackbody temperature T1.

[0049] Step S14, start the detector driving and control circuit to provide the detector with a working bias voltage and a timing control signal, obtain the detector output voltage through the data acquisition card, and obtain the detector dark current test result through the processor.

[0050] This step further includes: Step S14a, adjust the timing control signal of the control circuit to make the detector work above the half-well state, and collect the detector output voltage under the integration time; then adjust different integration times and collect multiple groups (4-5 groups) of detector output voltages under different integration times.

[0051] After obtaining the above-mentioned infrared detector output voltage data, enter / select the data file related path, use the data reading algorithm to read the tested infrared detector output data into the system memory, and use the following calculation method of this application to process the output data to obtain the detector dark current test result. The specific data processing process is as follows: Step S14b, using the collected detector output voltage, subtracting the detector output voltage when the photoelectric response is cut off, to obtain the response signal at each integration time; In step S14c, the slope of the time-signal curve is fitted using the least squares method, with the integration time as the horizontal axis and the response signal as the vertical axis, and the calculation result of the detector dark current is obtained using the following formula: in, It represents the slope of the curve obtained by the least squares fitting method; Indicates the integrating capacitor used when the detector is working.

[0052] Furthermore, the filling of the contact surface gap by the indium metal sheet specifically includes: A multi-layer indium metal sheet is provided between the cold stage and the cold chain; A multilayer indium metal sheet is provided between the cold chain and the detector mounting substrate; A multilayer indium metal sheet is provided between the detector mounting substrate and the detector; A multi-layer indium metal sheet is provided between the connection between the cold screen and the cold stage.

[0053] See Figure 4 The embodiment of the present application provides a method for testing the performance of a very low temperature infrared detector for detecting weak targets. The performance test is performed using the very low temperature infrared detector for detecting weak targets and the dark current test device of the above embodiment. Figure 4 As shown, the following steps are included: Step S20: Install the detector on the detector mounting substrate in the vacuum tank, install the blind cold shield, cold shield and platinum resistance temperature sensor group in sequence, use an insulating layer to cover the cold platform and cold shield surface, use a flexible adapter to connect the detector input port and output port to the data analysis module, and fill the contact surface gap with indium metal sheet.

[0054] This step is the same as step S10.

[0055] Step S21 , adjusting the position of the black body to be close to the opening of the cold screen, and placing a heat insulating material between the black body and the opening of the cold screen.

[0056] This step is the same as step S11.

[0057] Step S22: Start the vacuum pumping device to reduce the vacuum degree in the vacuum tank to below 1E-3Pa; start the refrigerator to reduce the working temperature of the detector to below 50K.

[0058] This step is the same as step S12.

[0059] Step S23, start the blackbody temperature control system to adjust the blackbody temperature T1, adjust the timing control signal of the control circuit to make the detector work in a half-well state, and collect the output level data of the T1 temperature infrared detector.

[0060] Step S24, adjusting the black body temperature T2, collecting the infrared detector output level data at T2 temperature; wherein T2>T1.

[0061] Step S25 , based on the infrared detector output level data at temperatures T1 and T2 , calculate the detector performance indicators: quantum efficiency, response rate, noise equivalent temperature difference, response non-uniformity and detection rate.

[0062] After obtaining the above-mentioned infrared detector output voltage data, enter / select the data file related path, use the data reading algorithm to read the tested infrared detector output data into the system memory; use the following calculation method of this application to process the output data to obtain the detector detection performance test results. The specific data processing process is as follows: Step S25a: Based on the output level data, static blind pixel screening is performed by calculating the response mean and noise.

[0063] In the specific implementation process, based on GJB / T17444, the output level data is used to calculate the response mean and noise and other related calculation parameters, and dead pixels and overheated pixels are screened, and then a static blind pixel marking matrix is ​​generated to automatically skip the blind pixel area in subsequent data processing.

[0064] Step S25b: Quantum efficiency is used to describe the ability of the detector to convert incident photons into electrons and output them, and is calculated using the following formula: in, represents quantum efficiency; represents the number of photons incident on the detector; Indicates the number of electrons converted and output by the detector; and is calculated by the following formula: in, is the blackbody radiation rate; Indicates the detector field of view, in units of sr ; Represents the photosensitive area of ​​the detector pixel, in units of cm 2 ; Indicates the detector integration time; represents the detector readout circuit integration capacitance; Indicates the detector output signal; Represents the single electron charge, and its value is ; Indicates the wavelength is , the temperature is The blackbody radiation photon energy is calculated by the following formula:

[0065] Step S25c: The responsivity is used to characterize the response voltage of each pixel in the detector to unit irradiation power, and is calculated using the following formula: in, represents the response rate of the pixel in the i-th row and j-th column of the detector; and represents the output voltage value of the pixel in the i-th row and j-th column of the detector at temperatures T1 and T2 respectively; represents the field of view of the detector; represents the detector pixel area; It represents the change in the irradiation power of the blackbody at T1 and T2, which is calculated by the following formula: in, represents the blackbody radiation rate of the surface source; Represents a constant whose value is .

[0066] In step S25d, the noise equivalent temperature difference (NETD) is used to characterize the sensitivity and noise level of the infrared detector and is calculated using the following formula:

[0067] Step S25e: Response non-uniformity is used to describe the differences in pixel output signals of infrared detectors under the same radiation power. The output voltage of each pixel is corrected using the following formula: in, It represents the output voltage of the pixel in row i and column j after correction when facing the blackbody with temperature T1; represents the correction factor; The corrected response voltage of each pixel is obtained as follows: The calculation formula for the non-uniformity of the output voltage of each pixel after correction is: in, It represents the corrected average blackbody response rate of all valid pixels in the detector component after deducting the blind pixels.

[0068] In step S25f, the detection rate includes the detection rate of each pixel and the average detection rate of the detector, which are calculated by the following formulas: in, represents the detection rate of the pixel in the i-th row and j-th column; Indicates the integration time; represents the average detection rate of the detector; Indicates the number of blind pixels of the detector.

[0069] Furthermore, the filling of the contact surface gap by the indium metal sheet specifically includes: A multi-layer indium metal sheet is provided between the cold stage and the cold chain; A multilayer indium metal sheet is provided between the cold chain and the detector mounting substrate; A multilayer indium metal sheet is provided between the detector mounting substrate and the detector; A multi-layer indium metal sheet is provided between the connection between the cold screen and the cold stage.

[0070] Based on the above technical solution, this application expands the detector operating temperature from 77K in the existing technology to below 50K, while providing the detector with uniform background radiation and target radiation signals as low as 90K. For the first time, it constructs a very low temperature test environment covering the needs of space-based detection, ensuring that the temperature uniformity error of the detector is ≤0.5K, meeting the simulation requirements of faint targets in deep space; on this basis, the detector output data is obtained and the detector performance parameters and dark current parameters are calculated to accurately test and evaluate the detector's faint target testing capabilities under very low temperature working conditions.

[0071] It should be noted that, in this article, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device comprising the element. In addition, it should be noted that the scope of the methods and devices in the embodiments of the present application is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in the opposite order according to the functions involved. For example, the described method may be performed in an order different from that described, and various steps may also be added, omitted, or combined. In addition, the features described with reference to certain examples may be combined in other examples.

[0072] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus the necessary general hardware platform, and of course can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of the present application is essentially or the part that contributes to the prior art can be embodied in the form of a computer software product, which is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk), including a number of instructions for enabling a terminal (which can be a mobile phone, computer, server, or network device, etc.) to execute the methods described in each embodiment of the present application.

[0073] It will be appreciated that the embodiments of the present application have been described above in conjunction with the accompanying drawings, but the present application is not limited to the above-mentioned specific embodiments, which are merely illustrative and not restrictive, and those skilled in the art will appreciate that various changes or equivalent replacements may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, those of ordinary skill in the art may modify these features and embodiments to adapt to specific circumstances and materials under the inspiration or guidance of this application without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application fall within the scope protected by the present invention.

Claims

1. Very low temperature infrared detector dark target detection performance and dark current test device, characterized by: include: A cooling module includes a refrigerator, a cold head, a cold stage, and a vacuum tank; the vacuum tank is used to provide a vacuum environment for cooling the detector, the cold head is coupled to the cold stage and is disposed within the vacuum tank, and the refrigerator is connected to the cold head to transfer cooling energy; Environmental construction module, including detector mounting base plate, bracket, cold chain, blind cold shield, cold shield, insulation layer, black body and black body temperature control system; The detector mounting substrate is fixed by the bracket. The detector mounting substrate and the cold chain are used to provide the refrigeration link required to cool the detector to a very low temperature. The blind cold screen is used to cover the detector and is provided with an opening to limit the field of view angle. The cold screen is used to cover part of the cold stage and the blind cold screen and is provided with openings corresponding to the blind cold screen. The thermal insulation layer is used to cover the outer surface of the cold screen. The black body is a radiation source, and its relative position with the cold screen is optionally adjusted by a position adjustment mechanism. The black body temperature control system is used to adjust the black body temperature. Detector drive and control circuit, used to provide working bias voltage and timing control signal for the detector; The data analysis module includes a data acquisition card and a processor; the data acquisition card is connected to the output end of the detector to obtain an analog voltage signal, and the processor is configured with an algorithm model for converting the detector output voltage data into a performance indicator that can characterize the detector state.

2. The device for testing the weak target detection performance and dark current of a very low temperature infrared detector according to claim 1, characterized in that: A multi-layer indium metal sheet is provided between the cold stage and the cold chain; A multilayer indium metal sheet is provided between the cold chain and the detector mounting substrate; A multilayer indium metal sheet is provided between the detector mounting substrate and the detector; A multi-layer indium metal sheet is provided between the connection between the cold screen and the cold stage.

3. The device for testing the weak target detection performance and dark current of a very low temperature infrared detector according to claim 1, characterized in that: The detector mounting substrate is provided with a first platinum resistance temperature sensor group near the cold stage for monitoring the state of cold conduction; A second platinum resistance temperature sensor group is provided at the blind cold screen for real-time monitoring of the temperature of the blind cold screen; A third platinum resistance temperature sensor group is provided at the detector mounting substrate for monitoring the substrate temperature; A fourth platinum resistance temperature sensor group is provided at a position of the cold screen close to the black body, for monitoring the temperature of the cold screen.

4. The device for testing the weak target detection performance and dark current of a very low temperature infrared detector according to claim 1, characterized in that: Controlling the position of the black body to be close to the blackened surface of the cold screen; A heat insulating material is provided between the black body and the cold screen.

5. A method for testing dark current of a very low temperature infrared detector with a dim target, characterized in that: A dark current test is performed using the very low temperature infrared detector dim target detection performance and dark current test device according to any one of claims 1 to 4, comprising: The detector was mounted on a detector mounting base in a vacuum tank. A blind cold shield, a cold shield, and a platinum resistance temperature sensor group were installed in sequence. The cold stage and the cold shield were covered with an insulating layer. The detector input and output ports were connected to the data analysis module using a flexible transfer tape. The contact surface gaps were filled with indium metal sheets. Adjust the position of the black body so that it is close to the opening of the cold screen, and place insulation material between the black body and the opening of the cold screen; Turn on the vacuum equipment to reduce the vacuum degree in the vacuum tank to below 1E-3Pa; start the refrigerator to reduce the detector operating temperature to below 50K; Turn on the blackbody temperature control system to adjust the blackbody temperature T1; Turn on the detector drive and control circuits to provide the detector with working bias voltage and timing control signals respectively, obtain the detector output voltage through the data acquisition card, and obtain the detector dark current test results through the processor.

6. The method for testing dark current of a very low temperature infrared detector with a dim target according to claim 5, characterized in that: The detector drive and control circuit is turned on to provide the working bias voltage and timing control signal for the detector, obtain the detector output voltage through the data acquisition card, and obtain the detector dark current test result through the processor, specifically including: Adjust the timing control signal of the control circuit to make the detector work above the half-well state, and collect the detector output voltage under the integration time; then adjust different integration times and collect multiple sets of detector output voltages under different integration times; The detector output voltage obtained by the acquisition is subtracted from the detector output voltage when the photoelectric response is cut off to obtain the response signal at each integration time; With the integration time as the horizontal axis and the response signal as the vertical axis, the slope of the time-signal curve is fitted using the least squares method, and the detector dark current calculation result is obtained using the following formula: in, It represents the slope of the curve obtained by the least squares fitting method; Indicates the integrating capacitor used when the detector is working.

7. The method for testing dark current of a very low temperature infrared detector with a dim target according to claim 5, characterized in that: The method of filling the contact surface gap with the indium metal sheet specifically includes: A multi-layer indium metal sheet is provided between the cold stage and the cold chain; A multilayer indium metal sheet is provided between the cold chain and the detector mounting substrate; A multilayer indium metal sheet is provided between the detector mounting substrate and the detector; A multi-layer indium metal sheet is provided between the connection between the cold screen and the cold stage.

8. A method for testing the performance of very low temperature infrared detectors for detecting dim targets, characterized in that: The performance test of the dim target detection performance and dark current test device of the very low temperature infrared detector according to any one of claims 1 to 4 is performed, comprising: The detector was mounted on a detector mounting base in a vacuum tank. A blind cold shield, a cold shield, and a platinum resistance temperature sensor group were installed in sequence. The cold stage and the cold shield were covered with an insulating layer. The detector input and output ports were connected to the data analysis module using a flexible transfer tape. The contact surface gaps were filled with indium metal sheets. Adjust the position of the black body so that it is close to the opening of the cold screen, and place insulation material between the black body and the opening of the cold screen; Turn on the vacuum equipment to reduce the vacuum degree in the vacuum tank to below 1E-3Pa; start the refrigerator to reduce the detector operating temperature to below 50K; Turn on the blackbody temperature control system to adjust the blackbody temperature T1, adjust the timing control signal of the control circuit to make the detector work in the half-well state, and collect the output level data of the infrared detector with T1 temperature; Adjust the blackbody temperature T2 and collect the output level data of the infrared detector at T2 temperature; where T2>T1; Based on the output level data of the infrared detector at temperatures T1 and T2, the detector performance indicators are calculated: quantum efficiency, response rate, noise equivalent temperature difference, response non-uniformity and detection rate.

9. The method for testing the dim target detection performance of a very low temperature infrared detector according to claim 7, characterized in that: The detector performance indicators are calculated based on the infrared detector output level data at temperatures T1 and T2: quantum efficiency, response rate, noise equivalent temperature difference, response non-uniformity and detection rate, specifically including: Based on the output level data, static blind pixel screening is performed through response mean and noise calculation; The quantum efficiency is used to describe the ability of a detector to convert incident photons into electrons and output them, and is calculated using the following formula: in, represents quantum efficiency; represents the number of photons incident on the detector; Indicates the number of electrons converted and output by the detector; and is calculated by the following formula: in, is the blackbody radiation rate; Indicates the detector field of view, in units of sr ; Represents the photosensitive area of ​​the detector pixel, in units of cm 2 ; Indicates the detector integration time; represents the detector readout circuit integration capacitance; Indicates the detector output signal; Represents the single electron charge, and its value is ; Indicates the wavelength is , the temperature is The blackbody radiation photon energy is calculated by the following formula: ； The responsivity is used to characterize the response voltage of each pixel in the detector to unit irradiation power and is calculated by the following formula: in, represents the response rate of the pixel in the i-th row and j-th column of the detector; and represents the output voltage value of the pixel in the i-th row and j-th column of the detector at temperatures T1 and T2 respectively; represents the field of view of the detector; represents the detector pixel area; It represents the change in the irradiation power of the blackbody at T1 and T2, which is calculated by the following formula: in, represents the blackbody radiation rate of the surface source; Represents a constant whose value is ; The noise equivalent temperature difference is used to characterize the sensitivity of the infrared detector and its noise level, and is calculated by the following formula: ； The response non-uniformity is used to describe the difference in pixel output signals of infrared detectors under the same radiation power. The output voltage of each pixel is corrected by the following formula: in, It represents the output voltage of the pixel in row i and column j after correction when facing the blackbody with temperature T1; represents the correction factor; The corrected response voltage of each pixel is obtained as follows: The calculation formula for the non-uniformity of the output voltage of each pixel after correction is: in, It represents the corrected average blackbody response rate of all valid pixels in the detector component after deducting the blind pixels; The detection rate includes the detection rate of each pixel and the average detection rate of the detector, which are calculated by the following formulas: in, represents the detection rate of the pixel in the i-th row and j-th column; Indicates the integration time; represents the average detection rate of the detector; Indicates the number of blind pixels of the detector.

10. The method for testing the faint target detection performance of a very low temperature infrared detector according to claim 7, characterized in that: The method of filling the contact surface gap with the indium metal sheet specifically includes: A multi-layer indium metal sheet is provided between the cold stage and the cold chain; A multilayer indium metal sheet is provided between the cold chain and the detector mounting substrate; A multilayer indium metal sheet is provided between the detector mounting substrate and the detector; A multi-layer indium metal sheet is provided between the connection between the cold screen and the cold stage.

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