Infrared detector test evaluation method for cold background point target application

Abstract

The invention discloses a cold background point target application-oriented infrared detector test evaluation method, which comprises the following steps of: according to radiation characteristics of an actual background and a target, camera parameters and infrared detector test system parameters, enabling a cold background and a cold background superposition point target to be equivalent to a surface source black body temperature tested by an infrared detector; and the performance of the infrared detector is tested and evaluated in the cold background infrared detector test cold cabin. The cold cabin is connected with the focal plane refrigeration and temperature measurement and control module, the black body refrigeration and temperature measurement and control module, the acquisition module and the vacuum pump, and can provide high-vacuum low-background test conditions for extremely low dark current and various photoelectric properties of the high-sensitivity infrared detector. The infrared detector performance parameters obtained by the method can provide test data support for actual performance evaluation of the cold background point target detection camera.

Description

Technical Field

[0001] This invention relates to a testing and evaluation method for infrared detectors used in cold background point target applications, belonging to the field of aerospace remote sensing infrared detector technology. Background Technology

[0002] An infrared detector is a sensor that can detect and respond to infrared radiation. Due to its advantages such as high detection sensitivity, strong atmospheric penetration in the infrared spectrum, and good environmental adaptability, it plays a vital role in the aerospace field.

[0003] Conventional infrared detector testing and evaluation is based on the national standard "GB / T 17444-2013 Infrared Focal Plane Array Parameter Test Method". The background and target temperatures are equivalent to a blackbody at room temperature of 20℃ and 35℃, respectively, and the response voltage is tested. Then, characteristic parameters such as responsivity are calculated according to the definition.

[0004] However, deep space exploration missions target extremely low-temperature backgrounds and dark, weak targets, which results in very low photocurrents for infrared detectors. The detection spectrum needs to be extended from near-infrared to long-wave and very long-wave infrared. Normal-temperature background and target testing methods are no longer suitable for practical application scenarios.

[0005] To ensure consistent performance across different environments for infrared detectors, the detection scenario should be clearly defined first, including target intensity, distance, and background radiance. Then, the key performance indicators for the infrared detector should be derived from the camera system's mission requirements, such as dark current and quantum efficiency. Finally, infrared detector testing methods adapted to the actual application of the camera system should be developed to accurately test and evaluate the key performance characteristics of the actual infrared detector.

[0006] Current testing and evaluation methods for infrared detectors are geared towards applications with normal temperature backgrounds and cannot be applied to the evaluation needs of point targets in deep space with cold backgrounds. Summary of the Invention

[0007] The technical problem solved by this invention is to overcome the shortcomings of the prior art and provide an infrared detector testing and evaluation method for cold background point target applications, which can meet the evaluation requirements for deep space cold background point target applications.

[0008] The technical solution of this invention is as follows: Firstly, an infrared detector testing system for applications targeting cold background point targets is provided, comprising: a cold background infrared detector testing chamber, a focal plane cooling and temperature control module, a blackbody cooling and temperature control module, a data acquisition module, and a vacuum pump; the cold background infrared detector testing chamber is referred to as the cold chamber, and the cold chamber includes: the infrared detector chip to be tested, a filter, a cold platform, a cold screen, a platinum resistance thermometer, an electrical connector, a surface source blackbody, and a slide rail; wherein:

[0009] The infrared detector chip under test is mounted on a cold platform; a filter is packaged in the direction of light incidence of the infrared detector chip;

[0010] The cold shield is installed on the cold platform; the focal surface cooling and temperature control module outside the cold chamber is connected to the cold platform to regulate the temperature of the cold platform, infrared detector, filter and cold shield inside the cold chamber.

[0011] The surface-source blackbody is mounted on a slide rail and can be moved to the front of the cold screen via the slide rail;

[0012] The blackbody cooling and temperature control module outside the cold chamber is connected to the surface source blackbody to regulate the temperature of the surface source blackbody inside the cold chamber.

[0013] Platinum resistance thermometers are attached to both the cold screen and the cold platform to measure their temperatures in real time. The electrical signal lines of the platinum resistance thermometers are connected to the coke surface cooling and temperature control system via electrical connectors on the cold chamber walls.

[0014] The electrical leads of the infrared detector chip are connected to the acquisition module through electrical connectors on the wall of the cold chamber; the vacuum pump is connected to the cold chamber to provide a vacuum environment for the cold chamber.

[0015] Secondly, a testing and evaluation method for infrared detectors used in cold background point target applications is provided, including:

[0016] S1. Based on the detection capability of the infrared detector under cold background point target application, decompose the maximum allowable dark current value I of the infrared detector. dark Calculate the operating temperature T of the infrared detector under test. work ;

[0017] S2. Calculate the equivalent surface source blackbody temperature T0 of the background to be measured, and the equivalent surface source blackbody temperature T1 of the target at the superposition point of the background to be measured.

[0018] S3. The infrared detector chip is packaged in a cold background infrared detector test chamber;

[0019] S4, The vacuum level of the cold chamber tested by the cold background infrared detector reached 1×10⁻⁶. -5 After Pa, the focal surface cooling and temperature control module is activated to perform closed-loop cooling and temperature control on the infrared detector chip and the cold screen.

[0020] S5. Start the blackbody cooling and temperature control module to perform closed-loop cooling and temperature control on the surface source blackbody;

[0021] S6, the infrared detector chip, cold screen, and surface source blackbody temperatures are all stable at T. work Then, the imaging data of the infrared detector under the M-level integration time is collected, with N frames collected each time;

[0022] S7. Calculate the measured dark current value I of the infrared detector based on the M sets of data collected in step S6. d ′ ark ;

[0023] S8. Calculate the half-trap integration time t;

[0024] S9, Maintain the infrared detector chip and cold screen temperature at T work Once the surface source blackbody temperature stabilizes at T0 and T1 respectively, N frames of imaging data are collected for the infrared detector at each temperature state with a half-trap integration time t.

[0025] S10. Calculate the performance of the infrared detector based on the two sets of imaging data collected in S9, including the average response voltage of the pixels. Average response rate of a pixel Blind pixel rate (BR), response rate nonuniformity (UR), and average quantum efficiency (QE) of a pixel.

[0026] Preferably, the maximum permissible dark current value I of the decomposed infrared detector in S1 dark Calculate the operating temperature T of the infrared detector under test. work The specific method is as follows:

[0027] S1-a. Starting from the overall camera specifications, to meet the signal-to-noise ratio requirement for point target detection, the maximum allowable dark current noise voltage V of the infrared detector is decomposed. dark ;

[0028] S1-b, Calculate the maximum permissible dark current value I from the maximum dark current noise voltage of the infrared detector. dark :

[0029]

[0030] Among them, C int Let t be the integrating capacitor, t′ be the camera's main integration time, and e be the charge of one electron.

[0031] S1-c. Based on rule 07 and the material and manufacturing process of the infrared detector under test, calculate the maximum operating temperature T of the infrared detector under test. work .

[0032] Preferably, in S2, the equivalent blackbody temperature T0 of the background to be measured and the equivalent blackbody temperature T1 of the target at the superposition point of the background to be measured are calculated as follows:

[0033] S2-a, Based on the simulation results of background radiance L in the actual detection scene within the detection spectrum band λ1~λ2, and the camera F-number F... camera Camera optical system efficiency η camera Calculate the total illuminance E of the background radiation reaching the image plane.b :

[0034]

[0035] S2-b, Based on the simulation results I of the actual target radiation intensity at the detection point within the detection spectrum band λ1~λ2, the camera entrance pupil area Φ, detection distance d, energy concentration R, and pixel area A d Calculate the illuminance E of the point target radiation reaching the image plane. t :

[0036]

[0037] S2-c and the equivalent surface source blackbody temperature T0 of the background to be measured satisfy:

[0038]

[0039] T0 is obtained by inverse calculation using the above formula; where h is Planck's constant, c is the speed of light, k is Boltzmann's constant, λ is the specific spectral segment in the detection spectrum, and λ1 and λ2 are the minimum and maximum values ​​of the detection spectrum, respectively; F detector For testing infrared detectors, the cold screen F-number, η detctor E represents the total transmittance of the filter. l The simulation results show the illuminance of the image plane reached by optomechanical thermal radiation.

[0040] S2-d, the equivalent surface source blackbody temperature T1 of the target at the background superposition point satisfies:

[0041]

[0042] T1 can be obtained by inverse calculation using the above formula.

[0043] Preferably, in S3, the infrared detector chip is packaged in a cold background infrared detector test chamber, specifically as follows:

[0044] S3-a. Open the cold background infrared detector test chamber and install the infrared detector chip, which is encapsulated with a filter with a transmission spectrum of λ1 to λ2, and the cold screen on the cold platform inside the chamber.

[0045] S3-b, Connect the electrical leads of the infrared detector chip to the electrical connector on the bulkhead and connect it to the acquisition module;

[0046] S3-c, Attach the temperature measuring platinum resistance thermometer to the cold screen and cold platform, connect the electrical signal line of the platinum resistance thermometer to the electrical connector on the bulkhead, and connect it to the focal surface cooling and temperature control module.

[0047] S3-d: Move the blackbody to the vicinity of the front of the cold screen via the slide rail, so that the blackbody covers the entire opening of the cold screen, and connect the blackbody to the blackbody cooling and temperature measurement and control module;

[0048] S3-e: Turn off the cold background infrared detector and test the cold chamber, then start the vacuum pump to evacuate the vacuum chamber.

[0049] Preferably, in step S4, the temperature range that the infrared detector chip and the cold screen can achieve includes the operating temperature value T of the infrared detector under test. work ;

[0050] In step S5, the temperature range achievable by the surface source blackbody includes the operating temperature value T of the infrared detector under test. work .

[0051] Preferably, in step S6, when the temperature of the cold screen and the blackbody does not exceed the chip's operating temperature, the effect of the number of radiated photons on the chip's dark current test can be ignored. Therefore, the temperature of the cold screen and the blackbody is less than or equal to T. work Therefore, the steps for acquiring imaging data from the infrared detector at the M-mode integration time are as follows:

[0052] S6-a. Gradually increase the integration time until the average pixel response reaches 90% full well. The integration time is t5.

[0053] S6-b, Between 0 and t5, four integration time values ​​are taken at equal intervals, for a total of five integration time values, namely t1, t2, t3, t4, and t5;

[0054] S6-c: Imaging data is acquired for the infrared detector at integration times t1, t2, t3, t4, and t5, with N frames acquired at each integration time.

[0055] Preferably, in step S7, the measured dark current value I of the infrared detector is... d ′ ark The specific method for performing the calculation is as follows:

[0056] During the integration time t n Below, the average voltage of N frames for pixel (i,j) in the i-th row and j-th column. for:

[0057]

[0058] Where f represents the number of frames;

[0059] Average voltage of the entire array across N frames for:

[0060]

[0061] The infrared detector has a pixel size of X×Y;

[0062] With t n The x-axis is... Using the ordinate as the vertical axis, the slope is obtained by linear fitting using the least squares method. The measured dark current value I of the infrared detector d ′ ark for

[0063]

[0064] Among them, C int It is an integrating capacitor.

[0065] Preferably, in step S8, the method for calculating the half-trap integration time t is as follows: based on the I obtained in step S7... d ′ ark The T0 obtained in step S2, and the half-trap integration time t satisfy:

[0066]

[0067] t can be obtained by reverse calculation using the above formula;

[0068] Among them, A d Let V be the pixel area, Q be the predicted quantum efficiency, and V be the value of the pixel. sat For saturation voltage, I d ′ ark η is the measured dark current value of the infrared detector. detctor F represents the total transmittance of the filter. detector Here, F-number is the cold screen number used for testing the infrared detector, h is Planck's constant, c is the speed of light, k is Boltzmann's constant, T0 is the equivalent surface source blackbody temperature of the background to be measured, and C is... int For integrating capacitor, V sat λ is the saturation voltage, e is the charge of an electron, λ is the specific spectral segment in the detection spectrum, and λ1 and λ2 are the minimum and maximum values ​​of the detection spectrum, respectively.

[0069] Preferably, in step S10, the method for calculating the performance of the infrared detector is as follows:

[0070] Given the equivalent blackbody temperature T0 of the background under test, and the equivalent blackbody temperature T1 of the target at the superposition point of the background under test and T0, the average N-frame voltage of pixel (i,j) is as follows:

[0071]

[0072] Where f represents the number of frames;

[0073] When the infrared detector is in positive output mode, the response voltage V of pixel (i,j) is... s (i,j) is:

[0074]

[0075] Mean response voltage of all pixels for:

[0076]

[0077] Wherein, dead represents the number of dead blind pixels, i.e., the number of pixels with a response lower than half the mean; hot represents the number of overheat blind pixels, i.e., the number of pixels with noise higher than twice the mean; the pixel size of the infrared detector is X×Y.

[0078] The blind cell rate BR is:

[0079]

[0080] The response rate R(i,j) of pixel (i,j) is:

[0081]

[0082] Average response rate of all pixels for:

[0083]

[0084] in, F detector For testing infrared detectors, the cold screen F-number, A d Let σ be the area of ​​a pixel, and σ be the Stephan constant.

[0085] The response rate nonuniformity UR is:

[0086]

[0087] Wherein, dead represents the number of dead blind pixels, which is the number of pixels with a response lower than half of the mean; hot represents the number of hot blind pixels, which is the number of pixels with noise higher than twice the mean.

[0088] The average quantum efficiency (QE) of all pixels is:

[0089]

[0090] Where h is Planck's constant, c is the speed of light, k is Boltzmann's constant, t is the half-trap integration time, and C int For the integrating capacitor, η detctor F represents the total transmittance of the filter. detector λ is the F-number of the cold screen used for testing the infrared detector, λ is the specific spectral segment in the detection spectrum, and λ1 and λ2 are the minimum and maximum values ​​of the detection spectrum, respectively.

[0091] Compared with the prior art, the present invention has the following advantages:

[0092] (1) In the test and evaluation of infrared detectors for cold background point targets, this invention, based on the radiation characteristics of the actual background and target, as well as the camera parameters and infrared detector test system parameters, equates the cold background and cold background superimposed point targets to the surface source blackbody temperature of the infrared detector test, thereby testing and evaluating the performance of the infrared detector; the infrared detector performance parameters obtained by this method can provide test data support for the actual performance evaluation of the camera.

[0093] (2) The cold background infrared detector test cold chamber mentioned in this invention is connected to the focal plane cooling and temperature control module, the blackbody cooling and temperature control module, the acquisition module, and the vacuum pump. It can provide high vacuum and deep low temperature working conditions for the infrared detector chip, and provide cold background test conditions for the extremely low dark current of the high-sensitivity infrared detector, as well as indicators such as quantum efficiency and response non-uniformity. Attached Figure Description

[0094] Figure 1 This is a schematic diagram comparing the paths of optical signal transmission to the camera focal plane and the photosensitive surface of the infrared detector in this invention;

[0095] Figure 2 This is a block diagram of the infrared detector testing system in this invention;

[0096] Figure 3 This is a model diagram of the cold chamber used for testing the cold background infrared detector in this invention. Detailed Implementation

[0097] The present invention solves the above-mentioned technical problem through the following technical solution:

[0098] A testing and evaluation method for infrared detectors used in applications targeting point targets against a cold background, the method comprising the following steps:

[0099] (1) Based on the camera's detection capability for cold background point targets, decompose the maximum allowable dark current value I of the infrared detector. dark Calculate the operating temperature T of the infrared detector under test. work ;

[0100] (2) Calculate the equivalent surface source blackbody temperature T0 of the background to be measured and the equivalent surface source blackbody temperature T1 of the target at the superposition point of the background to be measured.

[0101] (3) The infrared detector chip is packaged in a cold background infrared detector test chamber;

[0102] (4) The vacuum degree reaches 1×10 -5 After Pa, the focal surface cooling and temperature control module is activated to perform closed-loop cooling and temperature control on the infrared detector and the cold screen.

[0103] (5) Start the blackbody cooling and temperature control module to perform closed-loop cooling and temperature control on the surface source blackbody;

[0104] (6) Wait until the temperatures of the infrared detector chip, cold screen, and blackbody source are all stable at T work Then, the imaging data of the infrared detector at the M-level integration time (M≥5) is collected, and N frames are collected each time (N≥100);

[0105] (7) Fit the measured dark current value I of the infrared detector based on the M sets of data collected in step (6). d ′ ark Perform calculations;

[0106] (8) Calculate the half-trap integration time t;

[0107] (9) Maintain the infrared detector chip and cold screen temperature at T work After the surface source blackbody temperature stabilizes at T0 and T1, N frames (N≥100) of imaging data of the infrared detector are collected at the half-well integration time t.

[0108] (10) Calculate the performance of the infrared detector based on the two sets of imaging data collected in step (9).

[0109] The infrared detector testing system for cold background point target applications includes: a cold background infrared detector testing chamber, a focal plane cooling and temperature control module, a blackbody cooling and temperature control module, a data acquisition module, and a vacuum pump. The cold background infrared detector testing chamber contains: the infrared detector chip under test, a filter, a cold platform, a cold screen, a platinum resistance thermometer (PTT), an electrical connector, a blackbody, and a slide rail. The connection method includes: the infrared detector chip is mounted on the cold platform; the filter is encapsulated in the direction of light incidence of the infrared detector chip; the cold screen is mounted on the cold platform; the cold platform is connected to the focal plane cooling and temperature control module outside the chamber; the blackbody is mounted on the slide rail; the blackbody is connected to the blackbody cooling and temperature control module outside the chamber; platinum resistance thermometers are attached to both the cold screen and the cold platform, and the electrical signal lines of the platinum resistance thermometers are connected to the focal plane cooling and temperature control system through electrical connectors on the chamber wall; the electrical leads of the infrared detector chip are connected to the data acquisition module through electrical connectors on the chamber wall; and the cold chamber is connected to the vacuum pump.

[0110] The aforementioned focal plane cooling and temperature control module is used to regulate the temperature of the cold platform, infrared detector, filter, and cold screen inside the chamber; the aforementioned slide rail is used to move the surface source blackbody to the vicinity of the front of the cold screen; the aforementioned blackbody cooling and temperature control module is used to regulate the temperature of the surface source blackbody inside the chamber; the aforementioned platinum resistance thermometer is used to measure the temperature of the cold screen and cold platform in real time; and the aforementioned vacuum pump is used to provide a vacuum environment for the cold chamber.

[0111] In the above-mentioned infrared detector testing and evaluation method for cold background point target applications, in step (1), the maximum permissible dark current value I of the infrared detector is decomposed. dark Calculate the operating temperature T of the infrared detector under test. work The steps are as follows: (a) Starting from the overall camera specifications, in order to meet the signal-to-noise ratio of point target detection, the maximum allowable dark current noise voltage V of the infrared detector is decomposed. dark (b) Calculate the maximum allowable dark current value from the maximum dark current noise voltage of the infrared detector. Among them, C int (c) Based on rule 07 and the material and manufacturing process of the infrared detector under test, calculate the maximum operating temperature T of the infrared detector under test. work .

[0112] In the above-mentioned infrared detector test and evaluation method for cold background point targets, in step (2), the steps for calculating the equivalent blackbody temperature T0 of the background to be tested and the equivalent blackbody temperature T1 of the point target superimposed on the background to be tested are as follows: (a1) Based on the simulation results of background radiance L and camera F number F in the actual detection scene within the detection spectrum λ1~λ2. camera Camera optical system efficiency η camera Calculate the total illuminance of background radiation reaching the image plane. (b1) Based on the simulation results I of the actual detected point target radiation intensity in the detection spectrum λ1~λ2, the camera entrance pupil area Φ, the detection distance d, and the energy concentration R, calculate the illuminance of the point target radiation reaching the image plane. Where h is Planck's constant, c is the speed of light, and k is Boltzmann's constant; (c1) The equivalent surface source blackbody temperature T0 of the background to be measured satisfies T0 is obtained by reverse calculation, where the F-number of the cold screen used for infrared detector testing is F. detector The total transmittance of the filter (window) is η. detctor The simulation result for the illuminance of the image plane reached by optomechanical thermal radiation is E. l (d1) The equivalent surface source blackbody temperature T1 of the target at the background superposition point satisfies T1 is obtained by reverse calculation.

[0113] In the above-mentioned infrared detector testing and evaluation method for cold background point target applications, in step (3), the infrared detector testing system includes: a cold background infrared detector testing chamber, an infrared detector chip, a filter, a cold screen, a cold platform, a surface source blackbody, a slide rail, a focal plane cooling and temperature control module, a blackbody cooling and temperature control module, an acquisition module, and a vacuum pump. The steps for encapsulating the infrared detector chip in the cold chamber for testing the cold background infrared detector are as follows: (a3) ​​Open the cold chamber for testing the cold background infrared detector, and install the infrared detector chip, which is encapsulated with a filter with a transmission spectrum of λ1 to λ2, and the cold screen on the cold platform inside the chamber; (b3) Connect the electrical leads of the infrared detector chip (including the signal lines of the chip temperature-sensing diode) to the electrical connector on the chamber wall and connect it to the acquisition module; (c3) Attach the temperature-sensing platinum resistance thermometer to the cold screen and the cold platform, connect the electrical signal lines of the platinum resistance thermometer to the electrical connector on the chamber wall, and connect it to the focal plane cooling and temperature control module; (d3) Move the blackbody to the vicinity of the front of the cold screen via the slide rail, so that the blackbody covers the entire opening of the cold screen, and connect the blackbody to the blackbody cooling and temperature control module; (e3) Close the cold chamber for testing the cold background infrared detector and start the vacuum pump to evacuate the vacuum.

[0114] In the above-mentioned infrared detector testing and evaluation method for cold background point target applications, in step (4), the temperature range that the infrared detector chip and the cold screen can achieve includes T work .

[0115] In the above-mentioned infrared detector testing and evaluation method for cold background point target applications, in step (5), the temperature range that the surface source blackbody can achieve includes T work .

[0116] In the above-mentioned infrared detector testing and evaluation method for cold background point target applications, regarding step (6), it should be noted that, through theoretical calculation, when the temperatures of the cold screen and the blackbody do not exceed the chip's operating temperature, the influence of the number of radiated photons on the chip's dark current test can be ignored. Therefore, the temperatures of the cold screen and the blackbody do not need to exceed T. work The steps for acquiring imaging data of the infrared detector at integration time M (M≥5) are as follows: (a4) Gradually increase the integration time until the average pixel response reaches 90% full-well, and record the integration time as t5; (b4) Between 0 and t5, take four integration time values ​​at equal intervals, for a total of five integration time levels, namely t1, t2, t3, t4, and t5; (c4) Acquire imaging data of the infrared detector at integration times t1, t2, t3, t4, and t5 respectively, acquiring N frames each time (N≥100).

[0117] In the above-mentioned infrared detector testing and evaluation method for cold background point targets, in step (7), the measured dark current value I of the infrared detector is... d ′ark The calculation method is as follows: during the integration time t n Below, the average voltage of the N-frame pixel (i,j) in the i-th row and j-th column is The average voltage of the entire array across N frames is (The infrared detector has a pixel size of X×Y). Using t n The x-axis is... Using the ordinate as the vertical axis, the slope is obtained by linear fitting using the least squares method. The measured dark current value of the infrared detector is

[0118] In the above-mentioned infrared detector testing and evaluation method for cold background point targets, the method for calculating the half-well integration time t in step (8) is as follows: based on I obtained in step (7) dark The T0 obtained in step (2) and the half-trap integration time t satisfy: t is obtained by reverse calculation. Where, A d Let V be the pixel area, Q be the predicted quantum efficiency, and V be the value of the pixel. sat For saturation voltage, I d ′ ark η is the measured dark current value of the infrared detector. detctor F represents the total transmittance of the filter. detector Here, F-number is the cold screen number used for testing the infrared detector, h is Planck's constant, c is the speed of light, k is Boltzmann's constant, T0 is the equivalent surface source blackbody temperature of the background to be measured, and C is... int For integrating capacitor, V sat λ is the saturation voltage, e is the charge of an electron, λ is the specific spectral segment in the detection spectrum, and λ1 and λ2 are the minimum and maximum values ​​of the detection spectrum, respectively.

[0119] In the above-mentioned infrared detector test and evaluation method for cold background point target applications, the method for calculating the performance of the infrared detector in step (10) is as follows: at blackbody temperatures T0 and T1, the average voltage of pixel (i,j) in N frames is respectively... and The response voltage of pixel (i,j) is (Assuming the infrared detector is a positive output), then the response rate of pixel (i,j) is Dead blind pixels are pixels with a response below half the mean, and their number is "dead"; overheated blind pixels are pixels with noise levels above twice the mean, and their number is "hot". The blind pixel rate is then calculated. The mean response voltage of all pixels is then... The average response rate of all pixels is then in σ represents the Stirpan constant; the non-uniformity of the response rate is... The average quantum efficiency of all pixels is:

[0120]

[0121] Where h is Planck's constant, c is the speed of light, k is Boltzmann's constant, t is the half-trap integration time, and C int For the integrating capacitor, η detctor F represents the total transmittance of the filter. detector The F-number of the cold screen used for testing infrared detectors.

[0122] The parameters obtained from the tests in this invention that are ultimately used to evaluate the infrared detector are:

[0123] Measured dark current value I of the infrared detector d ′ ark Average response voltage of pixels Average response rate of a pixel Blind pixel rate (BR), response rate nonuniformity (UR), and average quantum efficiency (QE) of a pixel.

[0124] Example:

[0125] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0126] In this embodiment, the infrared detector test and evaluation focuses on the application of a camera to detect a target against a cold background. The known parameters of the actual detection scenario are: the simulated background radiance L within the detection spectral band is 6.30 × 10⁻⁶. -5 W / sr / m 2 The simulated radiation intensity of the point target is I = 19 W / sr, and the detection range d = 2000 km. Known camera parameters: detection spectral range 6–10 μm, camera F-number F... camera The efficiency η of the camera optical system is 1.3. camera The value is 0.7, and the entrance pupil area Φ is 0.023m². 2 The energy concentration R is 0.65, and the simulation result for the illuminance of the image plane reached by the optomechanical thermal radiation is E. l 1.31×10 -4 W / m 2 Given the parameters of the infrared detector testing system: the cold screen used for infrared detector testing has an F-number (F). detector The total transmittance of the filter (window) is η, which is 1.5. detctor The value is 0.9, the pixel size is 640×512, and the integrating capacitor C int 50fF, pixel area A d It is 6.25×10 -10 m 2 saturation voltage V sat The voltage is 2.8V, and the predicted quantum efficiency Q is 40%. Figure 1This is a schematic diagram comparing the paths of light signals transmitted to the camera's focal plane and the photosensitive surface of the infrared detector.

[0127] Based on the overall camera specifications, and to meet the point target detection signal-to-noise ratio requirements, and considering the control levels of camera photon noise, optomechanical thermal noise, and electronic noise, the allowable infrared detector dark current noise voltage is determined to be ≤0.5mV. Therefore, the maximum allowable dark current value is... Given a current of 0.1 pA, and based on rule 07 and the material and manufacturing process of the infrared detector under test, calculate the maximum operating temperature T of the infrared detector under test. work It is 50K.

[0128] Based on the actual detection scene parameters, camera parameters, and infrared detector test system parameters, the total illuminance of background radiation reaching the image plane is calculated. 1.31×10 -4 W / m 2 Illuminance of a point target reaching the image plane It is 7.84×10 -5 W / m 2 The equivalent surface source blackbody temperature T0 of the background to be measured satisfies The inverse calculation yields T0 as 107.7 K; the equivalent surface source blackbody temperature T1 of the target at the background superposition point satisfies... The reverse calculation yields T1 as 110.7K.

[0129] Follow these steps to encapsulate the infrared detector chip and cold screen in the cold background infrared detector test chamber and start the test. The test system block diagram is shown below. Figure 2 As shown.

[0130] (1) Open the cold background infrared detector test chamber and install the infrared detector chip, which is encapsulated with a filter with a transmission spectrum of 6-10μm, and the cold screen on the cold platform inside the chamber.

[0131] (2) Connect the electrical leads of the infrared detector chip (including the signal line of the chip temperature measuring diode) to the electrical connector on the bulkhead and connect it to the acquisition module.

[0132] (3) Attach the temperature measuring platinum resistance thermometer to the cold screen and cold platform, connect the electrical signal line of the platinum resistance thermometer to the electrical connector on the bulkhead, and connect it to the coke surface cooling and temperature control module.

[0133] (4) Move the blackbody to the vicinity of the cold screen via a slide rail, so that the blackbody covers the entire opening of the cold screen, and connect the blackbody to the blackbody cooling and temperature control module, such as... Figure 3 As shown.

[0134] (5) Turn off the cold background infrared detector to test the cold chamber and start the vacuum pump to evacuate.

[0135] (6) The vacuum degree reaches 1×10 -5 After Pa, the focal surface cooling and temperature control module is activated to perform closed-loop cooling and temperature control on the infrared detector and the cold screen; the infrared detector chip and the cold screen can achieve a temperature range of 40K to 308K.

[0136] (7) Start the blackbody cooling and temperature control module to perform closed-loop cooling and temperature control on the surface source blackbody; the temperature range that the surface source blackbody can achieve is 40K~308K.

[0137] (8) After the chip, cold screen and blackbody temperature are all stable at 50K, the average response of the infrared detector pixel reaches 90% and the full-well integration time is about 1300ms. Therefore, imaging data at five integration times of 260ms, 520ms, 780ms, 1040ms and 1300ms are collected, with 100 frames collected each time.

[0138] The processing results of the imaging data acquired at five integration times in (8) are shown in the table below. (Using t...) n The x-axis is... Using the vertical axis as the ordinate, a least-squares linear fit yields a slope k of 1.885. Therefore, the measured dark current value I of the infrared detector is... d ′ ark =C int k is 0.094 pA.

[0139]

[0140] Given T0 = 107.7K, I d ′ ark Substituting 0.094pA into the following formula:

[0141]

[0142] The calculated half-trap integration time t is 68 ms.

[0143] (9) Keep the chip and cold screen temperature at 50K. After the surface source blackbody temperature stabilizes at T0 and T1, collect 100 frames of imaging data from the infrared detector at an integration time of 68ms.

[0144] The processing results of the two sets of imaging data collected in step (9) are shown in the table below.

[0145]

[0146] In this embodiment, when testing and evaluating the infrared detector, based on the radiation characteristics of the actual background and target, as well as the camera parameters and infrared detector test system parameters, the cold background and the cold background superimposed point target are equivalent to the surface source blackbody temperature of the infrared detector test, thereby testing and evaluating the infrared detector. The results obtained by this method, such as dark current, quantum efficiency, and response rate non-uniformity, can be used as a reference for evaluating the dark current noise voltage, point target detection signal-to-noise ratio, and non-uniformity correction effect of a camera for detecting a point target against a cold background. In this embodiment, the cold chamber for testing the infrared detector against the cold background is connected to the focal plane cooling and temperature control module, the blackbody cooling and temperature control module, the acquisition module, and the vacuum pump, which can provide high vacuum and deep low temperature operating conditions for the infrared detector chip, and provide cold background test conditions for the extremely low dark current, quantum efficiency, response non-uniformity, and other indicators of the high-sensitivity infrared detector.

[0147] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

[0148] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

Claims

1. An infrared detector testing system for applications targeting point targets against a cold background, characterized in that... include: The test chamber for the cold background infrared detector includes a focal plane cooling and temperature control module, a blackbody cooling and temperature control module, a data acquisition module, and a vacuum pump. The cold background infrared detector test chamber is referred to as the cold chamber, which includes: the infrared detector chip under test, a filter, a cold platform, a cold screen, a platinum resistance thermometer, an electrical connector, a blackbody, and a slide rail; wherein: The infrared detector chip under test is mounted on a cold platform; a filter is packaged in the direction of light incidence of the infrared detector chip; The cold shield is installed on the cold platform; the focal surface cooling and temperature control module outside the cold chamber is connected to the cold platform to regulate the temperature of the cold platform, infrared detector, filter and cold shield inside the cold chamber. The surface-source blackbody is mounted on a slide rail and can be moved to the front of the cold screen via the slide rail; The blackbody cooling and temperature control module outside the cold chamber is connected to the surface source blackbody to regulate the temperature of the surface source blackbody inside the cold chamber. Platinum resistance thermometers are attached to both the cold screen and the cold platform to measure their temperatures in real time. The electrical signal lines of the platinum resistance thermometers are connected to the coke surface cooling and temperature control system via electrical connectors on the cold chamber walls. The electrical leads of the infrared detector chip are connected to the acquisition module through electrical connectors on the wall of the cold chamber; the vacuum pump is connected to the cold chamber to provide a vacuum environment for the cold chamber.

2. A method for testing and evaluating infrared detectors for cold background point targets using the infrared detector testing system of claim 1, characterized in that... include: S1. Based on the detection capability of the infrared detector under cold background point target application, decompose the maximum allowable dark current value I of the infrared detector. dark Calculate the operating temperature T of the infrared detector under test. work ; S2. Calculate the equivalent surface source blackbody temperature T0 of the background to be measured, and the equivalent surface source blackbody temperature T1 of the target at the superposition point of the background to be measured. S3. The infrared detector chip is packaged in a cold background infrared detector test chamber; S4, The vacuum level of the cold chamber tested by the cold background infrared detector reached 1×10⁻⁶. -5 After Pa, the focal surface cooling and temperature control module is activated to perform closed-loop cooling and temperature control on the infrared detector chip and the cold screen. S5. Start the blackbody cooling and temperature control module to perform closed-loop cooling and temperature control on the surface source blackbody; S6, the infrared detector chip, cold screen, and surface source blackbody temperatures are all stable at T. work Then, the imaging data of the infrared detector under the M-level integration time is collected, with N frames collected each time; S7. Calculate the measured dark current value I of the infrared detector based on the M sets of data collected in step S6. d ′ ark ; S8. Calculate the half-trap integration time t; S9, Maintain the infrared detector chip and cold screen temperature at T work Once the surface source blackbody temperature stabilizes at T0 and T1 respectively, N frames of imaging data are collected for the infrared detector at each temperature state with a half-trap integration time t. S10. Calculate the performance of the infrared detector based on the two sets of imaging data collected in S9, including the average response voltage of the pixels. Average response rate of a pixel Blind pixel rate (BR), response rate nonuniformity (UR), and average quantum efficiency (QE) of a pixel.

3. The infrared detector testing and evaluation method for cold background point target applications according to claim 1, characterized in that: The maximum permissible dark current value I of the decomposed infrared detector in S1 dark Calculate the operating temperature T of the infrared detector under test. work The specific method is as follows: S1-a. Starting from the overall camera specifications, to meet the signal-to-noise ratio requirement for point target detection, the maximum allowable dark current noise voltage V of the infrared detector is decomposed. dark ; S1-b, Calculate the maximum permissible dark current value I from the maximum dark current noise voltage of the infrared detector. dark : Among them, C int Let t be the integrating capacitor, t′ be the camera's main integration time, and e be the charge of one electron. S1-c. Based on rule 07 and the material and manufacturing process of the infrared detector under test, calculate the maximum operating temperature T of the infrared detector under test. work .

4. The infrared detector testing and evaluation method for cold background point target applications according to claim 1, characterized in that: In S2, the equivalent blackbody temperature T0 of the background to be measured and the equivalent blackbody temperature T1 of the target at the superposition point of the background to be measured are calculated as follows: S2-a, Based on the simulation results of background radiance L in the actual detection scene within the detection spectrum band λ1~λ2, and the camera F-number F... camera Camera optical system efficiency η camera Calculate the total illuminance E of the background radiation reaching the image plane. b : S2-b, Based on the simulation results I of the actual target radiation intensity at the detection point within the detection spectrum band λ1~λ2, the camera entrance pupil area Φ, detection distance d, energy concentration R, and pixel area A d Calculate the illuminance E of the point target radiation reaching the image plane. t : S2-c and the equivalent surface source blackbody temperature T0 of the background to be measured satisfy: T0 is obtained by inverse calculation using the above formula; where h is Planck's constant, c is the speed of light, k is Boltzmann's constant, λ is the specific spectral segment in the detection spectrum, and λ1 and λ2 are the minimum and maximum values ​​of the detection spectrum, respectively; F detector For testing infrared detectors, the cold screen F-number, η detctor E represents the total transmittance of the filter. l The simulation results show the illuminance of the image plane reached by optomechanical thermal radiation. S2-d, the equivalent surface source blackbody temperature T1 of the target at the background superposition point satisfies: T1 can be obtained by inverse calculation using the above formula.

5. The infrared detector testing and evaluation method for cold background point target applications according to claim 2, characterized in that: In S3, the infrared detector chip is packaged in a cold background infrared detector test chamber, specifically: S3-a. Open the cold background infrared detector test chamber and install the infrared detector chip, which is encapsulated with a filter with a transmission spectrum of λ1 to λ2, and the cold screen on the cold platform inside the chamber. S3-b, Connect the electrical leads of the infrared detector chip to the electrical connector on the bulkhead and connect it to the acquisition module; S3-c, Attach the temperature measuring platinum resistance thermometer to the cold screen and cold platform, connect the electrical signal line of the platinum resistance thermometer to the electrical connector on the bulkhead, and connect it to the focal surface cooling and temperature control module. S3-d: Move the blackbody to the vicinity of the front of the cold screen via the slide rail, so that the blackbody covers the entire opening of the cold screen, and connect the blackbody to the blackbody cooling and temperature measurement and control module; S3-e: Turn off the cold background infrared detector and test the cold chamber, then start the vacuum pump to evacuate the vacuum chamber.

6. The infrared detector testing and evaluation method for cold background point target applications according to claim 1, characterized in that: In step S4, the temperature range that the infrared detector chip and the cold screen can achieve includes the operating temperature value T of the infrared detector under test. work ; In step S5, the temperature range achievable by the surface source blackbody includes the operating temperature value T of the infrared detector under test. work .

7. The infrared detector testing and evaluation method for cold background point target applications according to claim 1, characterized in that: In step S6, when the temperatures of the cold screen and the blackbody do not exceed the chip's operating temperature, the effect of the number of radiated photons on the chip's dark current test is negligible. Therefore, the temperatures of the cold screen and the blackbody are less than or equal to T. work Therefore, the steps for acquiring imaging data from the infrared detector at the M-mode integration time are as follows: S6-a. Gradually increase the integration time until the average pixel response reaches 90% full well. The integration time is t5. S6-b, Between 0 and t5, four integration time values ​​are taken at equal intervals, for a total of five integration time values, namely t1, t2, t3, t4, and t5; S6-c: Imaging data is acquired for the infrared detector at integration times t1, t2, t3, t4, and t5, with N frames acquired at each integration time.

8. The infrared detector testing and evaluation method for cold background point target applications according to claim 1, characterized in that: In step S7, the measured dark current value I of the infrared detector is... d ′ ark The specific method for performing the calculation is as follows: During the integration time t n Below, the average voltage of N frames for pixel (i,j) in the i-th row and j-th column. for: Where f represents the number of frames; Average voltage of the entire array across N frames for: The infrared detector has a pixel size of X×Y; With t n The x-axis is... Using the ordinate as the vertical axis, the slope is obtained by linear fitting using the least squares method. The measured dark current value I of the infrared detector d ′ ark for Among them, C int It is an integrating capacitor.

9. The infrared detector testing and evaluation method for cold background point target applications according to claim 1, characterized in that: In step S8, the method for calculating the half-trap integration time t is as follows: based on I obtained in step S7... d ′ ark The T0 obtained in step S2, and the half-trap integration time t satisfy: t can be obtained by reverse calculation using the above formula; Among them, A d Let V be the pixel area, Q be the predicted quantum efficiency, and V be the value of the pixel. sat For saturation voltage, I d ′ ark η is the measured dark current value of the infrared detector. detctor F represents the total transmittance of the filter. detector Here, F-number is the cold screen number used for testing the infrared detector, h is Planck's constant, c is the speed of light, k is Boltzmann's constant, T0 is the equivalent surface source blackbody temperature of the background to be measured, and C is... int For integrating capacitor, V sat λ is the saturation voltage, e is the charge of an electron, λ is the specific spectral segment in the detection spectrum, and λ1 and λ2 are the minimum and maximum values ​​of the detection spectrum, respectively.

10. The infrared detector testing and evaluation method for cold background point target applications according to claim 1, characterized in that: In step S10, the method for calculating the performance of the infrared detector is as follows: Given the equivalent blackbody temperature T0 of the background under test, and the equivalent blackbody temperature T1 of the target at the superposition point of the background under test and T0, the average N-frame voltage of pixel (i,j) is as follows: Where f represents the number of frames; When the infrared detector is in positive output mode, the response voltage V of pixel (i,j) is... s (i,j) is: Mean response voltage of all pixels for: Wherein, dead represents the number of dead blind pixels, i.e., the number of pixels with a response lower than half the mean; hot represents the number of overheat blind pixels, i.e., the number of pixels with noise higher than twice the mean; the pixel size of the infrared detector is X×Y. The blind cell rate BR is: The response rate R(i,j) of pixel (i,j) is: Average response rate of all pixels for: in, F detector For testing infrared detectors, the cold screen F-number, A d Let σ be the area of ​​a pixel, and σ be the Stephan constant. The response rate nonuniformity UR is: Wherein, dead represents the number of dead blind pixels, which is the number of pixels with a response lower than half of the mean; hot represents the number of hot blind pixels, which is the number of pixels with noise higher than twice the mean. The average quantum efficiency (QE) of all pixels is: Where h is Planck's constant, c is the speed of light, k is Boltzmann's constant, t is the half-trap integration time, and C int For the integrating capacitor, η detctor F represents the total transmittance of the filter. detector λ is the F-number of the cold screen used for testing the infrared detector, λ is the specific spectral segment in the detection spectrum, and λ1 and λ2 are the minimum and maximum values ​​of the detection spectrum, respectively.

Images